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  • 1.
    Aalbers, Anouschka
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science.
    Öberg, Linn
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science.
    Agil Kravprioritering: En kvalitativ studie om prioriteringsprocesser inom agil mjukvaruutveckling hos Monitor ERP System AB2021Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Prioritizing requirements is one of the most important and influential steps in the creation of a software product. The process is iterative; it takes place during the entire agile software development. Through prioritizing requirements, it is decided which requirements are to be developed, in which order, and why. 

    The aim of this study is to investigate how companies that design software prioritize requirements and to identify which prioritization methods they might use during this process. The purpose of this study is to gain an understanding for why a well-balanced prioritization is important, which specific prioritization factors give value to a product, as well as identifying how these factors are related to the result. The purpose is also to investigate the difficulties that exist in a prioritization process, and to create an overview of some of the most used prioritization methods in agile software development. 

    This study is conducted in collaboration with the software company Monitor ERP in order to analyze the company's prioritization processes used to develop their business management system Monitor. The method used is a qualitative study that consists of observations of meetings about prioritization processes, and semi-structured interviews. Processing of collected material was done by organizing, analyzing, and compiling results according to concepts and categories that emerged from the literature study. The results documents work processes, common goals, prioritization aspects and challenges in the requirements prioritization at Monitor ERP. 

    A well-balanced prioritization proved to be important to be able to deliver the right functionality on time and to be able to provide dependable estimates of development, which in turn leads to customers gaining confidence in both the product and the company. A number of prioritization factors that give value to the Monitor software were identified, many of which contribute to increasing customer satisfaction and product quality. Monitor ERP does not use any specific prioritization methods, but the development philosophy Minimum Viable Product is used as a basis for their prioritization choices. During the prioritization process, challenges such as limited resources, unpredictable tasks, difficulties with time estimation, and a challenge in balancing customer value and customer focus were experienced.

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    Agil_Kravprioritering_Aalbers_Öberg
  • 2.
    Abad, Shayan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science.
    Gholamy, Hassan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science.
    Evaluation of machine learning models for classifying malicious URLs2023Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Millions of new websites are created daily, making it challenging to determine which ones are safe. Cybersecurity involves protecting companies and users from cyberattacks. Cybercriminals exploit various methods, including phishing attacks, to trick users into revealing sensitive information. In Australia alone, there were over 74,000 reported phishing attacks in 2022, resulting in a financial loss of over $24 million. Artificial intelligence (AI) and machine learning are effective tools in various domains, such as cancer detection, financial fraud detection, and chatbot development. Machine learning models, such as Random Forest and Support Vector Machines, are commonly used for classification tasks. With the rise of cybercrime, it is crucial to use machine learning to identify both known and new malicious URLs. The purpose of the study is to compare different instance selection methods and machine learning models for classifying malicious URLs.

    In this study, a dataset containing approximately 650,000 URLs from Kaggle was used. The dataset consisted of four categories: phishing, defacement, malware, and benign URLs. Three datasets, each consisting of around 170,000 URLs, were generated using instance selection methods (DRLSH, BPLSH, and random selection) implemented in MATLAB. Machine learning models, including SVM, DT, KNNs, and RF, were employed. The study applied these instance selection methods to a dataset of malicious URLs, trained the machine learning models on the resulting datasets, and evaluated their performance using 16 features and one output feature.

    In the process of hyperparameter tuning, the training dataset was used to train four models with different hyperparameter settings. Bayesian optimization was employed to find the best hyperparameters for each model. The classification process was then conducted, and the results were compared. The study found that the random instance selection method outperformed the other two methods, BPLSH and DRLSH, in terms of both accuracy and elapsed time for data selection. The lower accuracies achieved by the DRLSH and BPLSH methods may be attributed to the imbalanced dataset, which led to poor sample selection.

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    Evaluation of machine learning models for classifying malicious URLs
  • 3.
    Abad, Shayan
    et al.
    Department of Computer and Geo-Spatial Sciences, University of Gävle, 801 76 Gävle, Sweden.
    Gholamy, Hassan
    Department of Computer and Geo-Spatial Sciences, University of Gävle, 801 76 Gävle, Sweden.
    Aslani, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Computer Science.
    Classification of Malicious URLs Using Machine Learning2023In: Sensors, E-ISSN 1424-8220, Vol. 23, no 18, article id 7760Article in journal (Refereed)
    Abstract [en]

    Amid the rapid proliferation of thousands of new websites daily, distinguishing safe ones from potentially harmful ones has become an increasingly complex task. These websites often collect user data, and, without adequate cybersecurity measures such as the efficient detection and classification of malicious URLs, users’ sensitive information could be compromised. This study aims to develop models based on machine learning algorithms for the efficient identification and classification of malicious URLs, contributing to enhanced cybersecurity. Within this context, this study leverages support vector machines (SVMs), random forests (RFs), decision trees (DTs), and k-nearest neighbors (KNNs) in combination with Bayesian optimization to accurately classify URLs. To improve computational efficiency, instance selection methods are employed, including data reduction based on locality-sensitive hashing (DRLSH), border point extraction based on locality-sensitive hashing (BPLSH), and random selection. The results show the effectiveness of RFs in delivering high precision, recall, and F1 scores, with SVMs also providing competitive performance at the expense of increased training time. The results also emphasize the substantial impact of the instance selection method on the performance of these models, indicating its significance in the machine learning pipeline for malicious URL classification

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  • 4.
    Abbassi, Selma
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Engström, Rickard
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Algoritm för lokalisering av referensnoder med Indoor Positioning System2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Indoor Positioning Systems lokaliserar människor och objekt inomhus med hjälp av minst tre kända referenspunkter. System för inomhuspositionering som använder kända referenspunkter kallas anchor-based lokalisering medan de som beräknar deras positioner själva kallas anchor-free lokalisering. Syftet med detta arbete är att utveckla en algoritm som är anpassad efter ett anchor-free lokaliseringssystem. Den ska vara oberoende av nätverksuppkopplingen, hårdvaran och hur avstånden mellan mottagare och sensorer beräknats. Utgångspunkten för algoritmen är enbart avstånd mellan en mottagare och tre sensorer vilket kan beskrivas som arbetets huvudsakliga problem.

    Algoritmen implementerades i Java med en simulering som återspeglar positioneringen i en perfekt miljö och sedan testas på en Android-applikation. Simuleringen tillåter användaren att rita ut flera mätpunkter som skapar en rutt. Dessa mätpunkter utnyttjas för att dynamiskt lokalisera referenspunkterna och mätpunkterna genom att hitta ett minsta avstånd mellan sensorerna. Dessa avstånd kan beskrivas som sidorna för en referenstriangel som möjliggör att ett koordinatsystem kan spännas upp.

    Resultatet av den empiriska studien visade en felmarginal mellan 0,3-6 m utan signalstörningar, vilket inte var tillräckligt noggrant. Efter att algoritmen implementerats lades fokus på en korrigering som kan itereras igenom för att uppskatta bättre mätvärden för referenstriangeln. Korrigeringen gav positiva resultat med lägre felmarginal. Arbetet kan vidareutvecklas genom att implementeras i ett verkligt IPS-system och algoritmen kan förbättras genom att skapa utökade funktioner som kan hantera fler än tre beacons.

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  • 5.
    Abd Nikooie Pour, Mina
    et al.
    Linköpings universitet.
    Algergawy, Alsayed
    University Jena, Germany.
    Amardeilh, Florence
    Elzeard.co, Paris, France.
    Amini, Reihaneh
    Data Semantics (DaSe) Laboratory, Kansas State University, United States.
    Fallatah, Omaima
    Information School, University Of Sheffield, Sheffield, United Kingdom.
    Faria, Daniel
    Faculdade De Cîencias, Universidade De Lisboa, Lasige, Portugal.
    Fundulaki, Irini
    Institute Of Computer Science-FORTH, Heraklion, Greece.
    Harrow, Ian
    Pistoia Alliance Inc., United States.
    Hertling, Sven
    University Of Mannheim, Germany.
    Hitzler, Pascal
    Data Semantics (DaSe) Laboratory, Kansas State University, United States.
    Huschka, Martin
    Fraunhofer Institute For High-Speed Dynamics, EMI, Germany.
    Ibanescu, Liliana
    AgroParisTech, Umr MIA-Paris/INRAE, France.
    Jiménez-Ruiz, Ernesto
    University Of London, City, United Kingdom; Department Of Informatics, University Of Oslo, Norway.
    Karam, Naouel
    Fraunhofer Fokus, Berlin, Germany; Institute For Applied Informatics (InfAI), University Of Leipzig, Germany.
    Laadhar, Amir
    Department Of Computer Science, Aalborg University, Denmark.
    Lambrix, Patrick
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Linköpings universitet.
    Li, Huanyu
    Linköpings universitet.
    Li, Ying
    Linköpings universitet.
    Michel, Franck
    University Ĉote d'Azur, CNRS, Inria, France.
    Nasr, Engy
    University Of Freiburg, Freiburg Galaxy Team, Germany.
    Paulheim, Heiko
    University Of Mannheim, Germany.
    Pesquita, Catia
    Faculdade De Cîencias, Universidade De Lisboa, Lasige, Portugal.
    Portisch, Jan
    University Of Mannheim, Germany.
    Roussey, Catherine
    Inrae Centre Clermont-ARA, Laboratoire Tscf, France.
    Saveta, Tzanina
    Institute Of Computer Science-FORTH, Heraklion, Greece.
    Shvaiko, Pavel
    Trentino Digitale SpA, Trento, Italy.
    Splendiani, Andrea
    Pistoia Alliance Inc., United States.
    Trojahn, Cássia
    Irit and Université Toulouse II, Toulouse, France.
    Vatascinová, Jana
    Prague University Of Economics And Business, Czech Republic.
    Yaman, Beyza
    Adapt Centre, Dublin City University, Ireland.
    Zamazal, Ondrej
    Prague University Of Economics And Business, Czech Republic.
    Zhou, Lu
    Data Semantics (DaSe) Laboratory, Kansas State University, United States.
    Results of the Ontology Alignment Evaluation Initiative 20212021In: Proceedings of the 16th International Workshop on Ontology Matching co-located with the 20th International Semantic Web Conference (ISWC 2021), Virtual conference, October 25, 2021 / [ed] Shvaiko P., Euzenat J., Jimenez-Ruiz E., Jimenez-Ruiz E., Hassanzadeh O., Trojahn C., CEUR-WS.org , 2021, p. 62-108Conference paper (Refereed)
    Abstract [en]

    The Ontology Alignment Evaluation Initiative (OAEI) aims at comparing ontology matching systems on precisely defined test cases. These test cases can be based on ontologies of different levels of complexity and use different evaluation modalities (e.g., blind evaluation, open evaluation, or consensus).The OAEI 2021 campaign offered 13 tracks and was attended by 21 participants.This paper is an overall presentation of that campaign. 

  • 6.
    Abd Nikooie Pour, Mina
    et al.
    Linköping University.
    Li, Huanyu
    Linköping University.
    Armiento, Rickard
    Linköping University.
    Lambrix, Patrick
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Linköping University.
    A First Step Towards a Tool for Extending Ontologies2021In: Proceedings of the Sixth International Workshop on the Visualization and Interaction for Ontologies and Linked Data: co-located with the 20th International Semantic Web Conference (ISWC 2021) / [ed] Patrick Lambrix, Catia Pesquita, Vitalis Wiens, CEUR Workshop proceedings , 2021, p. 1-12Conference paper (Refereed)
    Abstract [en]

    Ontologies have been proposed as a means towards making data FAIR (Findable, Accessible, Interoperable, Reusable). This has attracted much interest in several communities and ontologies are being developed. However, to obtain good results when using ontologies in semantically-enabled applications, the ontologies need to be of high quality. One of the quality aspects is that the ontologies should be as complete as possible. In this paper we propose a first version of a tool that supports users in extending ontologies using a phrase-based approach.  To demonstrate the usefulness of our proposed tool, we exemplify the use by extending the Materials Design Ontology.

  • 7.
    Abdulkadir, Hassan Bisri
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences.
    Undersökning av användbarheten hos ett tidsrapporteringssystem2022Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In our everyday life, we as users encounter many different interfaces, therefore it is of great importance that they work well and have clear instructions for how to use them, i.e., that they have a good usability. Through the increased digitization, people today can work or study remotely, which is something that has been of great help recently during the covid pandemic. Since remote work and education has become common, it is important that we can also do our usability tests remotely.

    The purpose of this work is to investigate the usability of the time reporting system Tidig and to compare different test tools to see which tool is best suited for future usability tests on Tidig. The tests will be of the type URUT (Unmoderated Remote Usability Testing), which means that usability tests are unmoderated and done remotely for easier data collection. With the given data the result is expected to give a better picture of the usability of time reporting systems for future improvement work as well as which tool should be used in future usability tests.

    The results of the usability tests have shown that the time reporting system Tidig has a high usability. During the usability tests, the participants did not have a major difficulty in solving most of the tasks. The questions that were asked showed that the participants were satisfied with the system but would like small improvements to be made on certain parts of the time reporting system. The comparison of the tools shows that the tool best suited for future usability tests on Tidig is the Loop11 test tool. Loop11 offers a variety of functions to collect quantitative and qualitative data, the test tool also provides statistics on tasks, questions and the questionnaires.

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  • 8.
    Abens, Maria
    University of Gävle, Department of Mathematics, Natural and Computer Sciences.
    Outdoor Education in Mathematics: Can it be implemented?2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study examines outdoor education in mathematics at an international school under the IB PYP curriculum. Students spend most of their time indoors with the exception of lunch recess. Outdoor education provides a new and different way for both teachers and students to get fresh air. Research indicates that children who spend more time outdoors suffer less from allergies and other health problems. In the study, teachers and parents were given questionnaires, and three mathematics lessons were conducted outdoors.  Students were later interviewed in groups. Most parents and teachers were positive to the idea of academic outdoor lessons in any subject. Teachers saw some difficulties implementing it because of time, weather and behavioural problems with students outside. Furthermore, they agreed that children should spend more time outside and that the children’s health might benefit. Most of the students enjoyed the outdoor mathematics lessons. They were positive towards outdoor education in any subject.

  • 9.
    Abgaryan, Garnik V.
    et al.
    Department of Applied Mathematics and Artificial Intelligence, Institute of Computational Mathematics and Information Technology, Kazan Federal University, Kremlevskaya Street 35, Kazan 420008, Russia.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics. Russian Technological University MIREA, Moscow 119454, Russia.
    TE-Polarized Electromagnetic Wave Diffraction by a Circular Slotted Cylinder2023In: Mathematics, E-ISSN 2227-7390, Vol. 11, no 9, article id 1991Article in journal (Refereed)
    Abstract [en]

    The problem of diffraction of a TE-polarized electromagnetic wave by a circular slotted cylinder is investigated. The boundary value problem in question for the Helmholtz equation is reduced to an infinite system of linear algebraic equations of the second kind (SLAE-II) using integral summation identities (ISI). A detailed study of the matrix operator of the problem is performed and its Fredholm property in the weighted Hilbert space of infinite sequences is proven. The convergence of the truncation method constructed in the paper for the numerical solution of SLAE-II is justified and the results of computations are presented and discussed, specifically considering the determination of resonance modes.

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    fulltext
  • 10.
    Abid, Rabia
    et al.
    University Lahore, Pakistan.
    Iwendi, Celestine
    University of Bolton, UK.
    Javed, Abdul Rehman
    Air University, Islamabad, Pakistan.
    Rizwan, Muhammad
    University Lahore, Pakistan.
    Jalil, Zunera
    Air University, Islamabad, Pakistan.
    Anajemba, Joseph Henry
    Hohai University,Changzhou, China.
    Biamba, Cresantus
    University of Gävle, Faculty of Education and Business Studies, Department of Educational sciences, Educational science.
    An optimised homomorphic CRT-RSA algorithm for secure and efficient communication2023In: Personal and Ubiquitous Computing, ISSN 1617-4909, E-ISSN 1617-4917, Vol. 27, p. 1405-1418Article in journal (Refereed)
    Abstract [en]

    Secure and reliable exchange of information between devices is crucial for any network in the current digital world. This information is maintained on storage devices, routing devices, and communication over the cloud. Cryptographic techniques are used to ensure the secure transmission of data, ensuring the user’s privacy by storing and transmitting data in a particular format. Using encryption, only the intended user possessing the key can access the information. During data or essential transmission, the channel should be secured by using robust encryption techniques. Homomorphic Encryption (HE) techniques have been used in the past for this purpose. However, one of the flaws of the conventional HE is seen either in its slow transmission or fast key decryption. Thus, this paper proposes an optimized Homomorphic Encryption Chinese Remainder Theorem with a Rivest-Shamir-Adleman (HE-CRT-RSA) algorithm to overcome this challenge. The proposed Technique, HE-CRT-RSA, utilizes multiple keys for efficient communication and security. In addition, the performance of the HE-CRT-RSA algorithm was evaluated in comparison with the classical RSA algorithm. The result of the proposed algorithm shows performance improvement with reduced decryption time. It is observed that the proposed HE-CRT-RSA is 3–4% faster than the classical Rivest-Shamir-Adleman (RSA). The result also suggests that HE-CRT-RSA effectively enhances security issues of the cloud and helps to decrease the involvement of intruders or any third party during communication or inside the data/server centers.

  • 11. Aboul-Ata, E
    et al.
    Aboul-Ata, Ahmad
    El Attar, K
    Soliman, Ahmad M
    Rezk, Adel A
    Wright, Sandra A. I.
    Università degli studi di Molise (Unimol).
    Mazyad, Hamed M
    Harandi, Ali
    Olsson, Olof
    Gene expression and gene suppression mechanisms for human and plant virus-infection control in Egypt: HCV, HSV-2, PVX-Eg2 and TYLCV2009In: BIOSPECTRUM 2009, International symposium on, Second Green Revolution: Priorities, Programs, Social and Ethical Issues, 2009, p. 12-13Conference paper (Other academic)
  • 12.
    Abraham, David
    et al.
    Lunds Universitet.
    Ryrholm, Nils
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Witzell, Håkan
    Lunds Universitet.
    Scoble, Malcolm
    British Museum of Natural History.
    Holloway, Jeremy
    British Museum of Natural History.
    Löfstedt, Christer
    Lunds Universitet.
    Molecular phylogeny of the subfamilies in Geometridae (Geometroidea: Lepidoptera.)2001In: Molecular Phylogenetics and Evolution, ISSN 1055-7903, E-ISSN 1095-9513, Vol. 20, p. 65-77Article in journal (Refereed)
  • 13.
    Abrahamsson, Emil
    University of Gävle, Department of Mathematics, Natural and Computer Sciences.
    Digitalt arkiv2008Student paper second term, 10 points / 15 hpStudent thesis
    Abstract [sv]

    Grunden för detta arbete har varit att förenkla hantering och sökning bland ritningar och förteckningar i ett ritningsarkiv. Lösningen har blivit ett webbaserat datasystem som bygger på en databas där all information lagras och är sökbar. Resultatet har blivit ett system som man oavsett var man befinner sig inom företagets nätverk ha tillgång till alla ritningar och förteckningar på ett snabbt och effektivt sätt.

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    FULLTEXT01
  • 14.
    Abrehdary, M.
    et al.
    Royal Inst Technol KTH, Div Geodesy & Satellite Positioning, S-10044 Stockholm, Sweden..
    Sjöberg, L. E.
    Royal Inst Technol KTH, Div Geodesy & Satellite Positioning, S-10044 Stockholm, Sweden..
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Royal Inst Technol KTH, Div Geodesy & Satellite Positioning, S-10044 Stockholm, Sweden..
    Modelling Moho depth in ocean areas based on satellite altimetry using Vening Meinesz-Moritz' method2016In: Acta Geodaetica et Geophysica, ISSN 2213-5812, Vol. 51, no 2, p. 137-149Article in journal (Refereed)
    Abstract [en]

    An experiment for estimating Moho depth is carried out based on satellite altimetry and topographic information using the Vening Meinesz-Moritz gravimetric isostatic hypothesis. In order to investigate the possibility and quality of satellite altimetry in Moho determination, the DNSC08GRA global marine gravity field model and the DTM2006 global topography model are used to obtain a global Moho depth model over the oceans with a resolution of 1 degrees x 1 degrees. The numerical results show that the estimated Bouguer gravity disturbance varies from 86 to 767 mGal, with a global average of 747 mGal, and the estimated Moho depth varies from 3 to 39 km with a global average of 19 km. Comparing the Bouguer gravity disturbance estimated from satellite altimetry and that derived by the gravimetric satellite-only model GOGRA04S shows that the two models agree to 13 mGal in root mean square (RMS). Similarly, the estimated Moho depths from satellite altimetry and GOGRA04S agree to 0.69 km in RMS. It is also concluded that possible mean dynamic topography in the marine gravity model does not significantly affect the Moho determination.

  • 15.
    Abrehdary, Majid
    et al.
    Department of Environment and Life Sciences, Geomatics Section, University of Karlstad, Karlstad,Sweden; Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Lars, Sjöberg
    Division of Geodesy and Satellite Positioning, Royal Institute of Technology(KTH), Sweden.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Sampietro, Daniele
    GReD s.r.l., Como, Italy.
    Towards the Moho depth and Moho density contrast along with their uncertainties from seismic and satellite gravity observations2017In: Journal of Applied Geodesy, ISSN 1862-9016, E-ISSN 1862-9024, Vol. 11, no 4, p. 231-247Article in journal (Refereed)
    Abstract [en]

    We present a combined method for estimating a new global Moho model named KTH15C, containing Moho depth and Moho density contrast (or shortly Moho parameters), from a combination of global models of gravity (GOCO05S), topography (DTM2006) and seismic information (CRUST1.0 and MDN07) to a resolution of 1° × 1° based on a solution of Vening Meinesz-Moritz’ inverse problem of isostasy. This paper also aims modelling of the observation standard errors propagated from the Vening Meinesz-Moritz and CRUST1.0 models in estimating the uncertainty of the final Moho model. The numerical results yield Moho depths ranging from 6.5 to 70.3 km, and the estimated Moho density contrasts ranging from 21 to 650 kg/m3, respectively. Moreover, test computations display that in most areas estimated uncertainties in the parameters are less than 3 km and 50 kg/m3, respectively, but they reach to more significant values under Gulf of Mexico, Chile, Eastern Mediterranean, Timor sea and parts of polar regions. Comparing the Moho depths estimated by KTH15C and those derived by KTH11C, GEMMA2012C, CRUST1.0, KTH14C, CRUST14 and GEMMA1.0 models shows that KTH15C agree fairly well with CRUST1.0 but rather poor with other models. The Moho density contrasts estimated by KTH15C and those of the KTH11C, KTH14C and VMM model agree to 112, 31 and 61 kg/m3 in RMS. The regional numerical studies show that the RMS differences between KTH15C and Moho depths from seismic information yields fits of 2 to 4 km in South and North America, Africa, Europe, Asia, Australia and Antarctica, respectively.

  • 16.
    Abrehdary, Majid
    et al.
    Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Sjöberg, Lars E.
    Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Combined Moho parameters determination using CRUST1.0 and Vening Meinesz-Moritz model2015In: Journal of Earth Science, ISSN 1674-487X, E-ISSN 1867-111X, Vol. 26, no 4, p. 607-616Article in journal (Refereed)
    Abstract [en]

    According to Vening Meinesz-Moritz (VMM) global inverse isostatic problem, either the Moho density contrast (crust-mantle density contrast) or the Moho geometry can be estimated by solving a non-linear Fredholm integral equation of the first kind. Here solutions to the two Moho parameters are presented by combining the global geopotential model (GOCO-03S), topography (DTM2006) and a seismic crust model, the latter being the recent digital global crustal model (CRUST1.0) with a resolution of 1A(0)x1A(0). The numerical results show that the estimated Moho density contrast varies from 21 to 637 kg/m(3), with a global average of 321 kg/m(3), and the estimated Moho depth varies from 6 to 86 km with a global average of 24 km. Comparing the Moho density contrasts estimated using our leastsquares method and those derived by the CRUST1.0, CRUST2.0, and PREM models shows that our estimate agrees fairly well with CRUST1.0 model and rather poor with other models. The estimated Moho depths by our least-squares method and the CRUST1.0 model agree to 4.8 km in RMS and with the GEMMA1.0 based model to 6.3 km.

  • 17.
    Abrehdary, Majid
    et al.
    Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Sjöberg, Lars E.
    Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    The spherical terrain correction and its effect on the gravimetric-isostatic Moho determination2016In: International Journal of Geophysics, ISSN 1687-885X, E-ISSN 1687-8868, Vol. 204, no 1, p. 262-273Article in journal (Refereed)
    Abstract [en]

    In this study, the Moho depth is estimated based on the refined spherical Bouguer gravity disturbance and DTM2006 topographic data using the Vening Meinesz-Moritz gravimetric-isostatic hypothesis. In this context, we compute the refined spherical Bouguer gravity disturbances in a set of 1° × 1° blocks. The spherical terrain correction, a residual correction to each Bouguer shell, is computed using rock heights and ice sheet thicknesses from the DTM2006 and Earth2014 models. The study illustrates that the defined simple Bouguer gravity disturbance corrected for the density variations of the oceans, ice sheets and sediment basins and also the non-isostatic effects needs a significant terrain correction to become the refined Bouguer gravity disturbance, and that the isostatic gravity disturbance is significantly better defined by the latter disturbance plus a compensation attraction. Our study shows that despite the fact that the lateral variation of the crustal depth is rather smooth, the terrain affects the result most significantly in many areas. The global numerical results show that the estimated Moho depths by the simple and refined spherical Bouguer gravity disturbances and the seismic CRUST1.0 model agree to 5.6 and 2.7 km in RMS, respectively. Also, the mean value differences are 1.7 and 0.2 km, respectively. Two regional numerical studies show that the RMS differences between the Moho depths estimated based on the simple and refined spherical Bouguer gravity disturbance and that using CRUST1.0 model yield fits of 4.9 and 3.2 km in South America and yield 3.2 and 3.4 km in Fennoscandia, respectively.

  • 18. Adams, Robin
    et al.
    Fincher, Sally
    Pears, Arnold
    Börstler, Jürgen
    Boustedt, Jonas
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Dalenius, Peter
    Eken, Gunilla
    Heyer, Tim
    Jacobsson, Andreas
    Lindberg, Vanja
    Molin, Bengt
    Moström, Jan-Erik
    Wiggberg, Mattias
    What is the word for 'Engineering' in Swedish: Swedish students conceptions of their discipline2007Report (Other academic)
    Abstract [en]

    Engineering education in Sweden – as in the rest of the world – is experiencing a decline in student interest. There are concerns about the ways in which students think about engineering education, why they join an academic programme in engineering, and why they persist in their studies. In this context the aims of the Nationellt ämnesdidaktiskt Centrum för Teknikutbildning i Studenternas Sammanhang project (CeTUSS) is to investigate the student experience and to identify and support a continuing network of interested researchers, as well as in building capacity for disciplinary pedagogic investigation.

    The Stepping Stones project brings together these interests in a multi-researcher, multi-institutional study that investigates how tudents and academic staff perceive engineering in Sweden and in Swedish education. The first results of that project are reported here. As this study is situated uniquely in Swedish education, it allows for exploration of “a Swedish perspective” on conceptions of engineering. The Stepping Stones project was based on a model of research capacity-building previously instantiated in the USA and Australia (Fincher & Tenenberg, 2006).

  • 19.
    Adamsson, Maria
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Undersökande arbetssätt: inom naturvetenskap och teknik i årskurs 4-62020Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Syftet med denna studie är att söka kunskap om hur lärare och elever arbetar med undersökande arbetssätt, inom ämnena naturvetenskap och teknik i årskurs 4-6. I studien deltog en lärare och elever i årskurs 5 på en kommunal grundskola i Mellansverige. Kvalitativa metoder används i undersökningen samt i analysen och materialet har samlats in genom klassrumsobservationer. Resultatet av studien visar att eleverna, i alla fall till viss del, arbetar med undersökande arbetssätt men att de skulle gynnas av att träna mer på de olika momenten för att sedan själva kunna genomföra egna undersökningar. Kopplingen till det naturvetenskapliga området behöver också göras tydligare, det är lätt att få uppfattningen att det enbart är undersökningar som ingår i arbetssättet. Att tydliggöra de olika delarna i undersökande arbetssätt skulle kunna göra det lättare för lärare att undervisa i ämnet och ge eleverna mer likvärdiga kunskaper i naturvetenskap och teknik, oavsett lärare och skola.

     

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  • 20.
    Agha Karimi, Armin
    et al.
    KTH.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Huremuz, Milan
    KTH.
    Multidecadal sea level variability in the Baltic sea and its impact on acceleration estimations2021In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 8, article id 702512Article in journal (Refereed)
    Abstract [en]

    Multidecadal sea level variation in the Baltic Sea is investigated from 1900 to 2020 deploying satellite and in situ datasets. As a part of this investigation, nearly 30 years of satellite altimetry data are used to compare with tide gauge data in terms of linear trend. This, in turn, leads to validation of the regional uplift model developed for the Fennoscandia. The role of North Atlantic Oscillation (NAO) in multidecadal variations of the Baltic Sea is also analyzed. Although NAO impacts the Baltic Sea level on seasonal to decadal time scales according to previous studies, it is not a pronounced factor in the multidecadal variations. The acceleration in the sea level rise of the basin is reported as statistically insignificant in recent studies or even decelerating in an investigation of the early 1990s. It is shown that the reason for these results relates to the global warming hiatus in the 1950s−1970s, which can be seen in all eight tide gauges used for this study. To account for the slowdown period, the acceleration in the basin is investigated by fitting linear trends to time spans of six to seven decades, which include the hiatus. These results imply that the sea level rise is accelerated in the Baltic Sea during the period 1900–2020.

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  • 21.
    Agrell, Jenny
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    ”Det de gör med händerna, det minns de”: En intervjustudie om laborativt material i årskurs 1–32023Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Syftet med denna studie är att förstå lärares resonemang om användningav laborativt material inom aritmetik i årskurs 1–3. Arbetet syftar även till att undersöka hur lärare resonerar kring vad som har betydelse för deras aritmetikundervisning med avseende pålaborativt material. För att uppnå syftet har semistrukturerade intervjuer med sju lärare genomförts. De data som samlats in har analyserats med hjälp av en tematisk analys och tolkats med den sociokulturella teorin som teoretiskt ramverk. Studiens resultat visar att lärarna använder laborativa material i olika syften där att underlätta för att eleverna ska gå från konkret till abstrakt förståelse är mest framträdande. Det som har högst betydelse i lärarnas aritmetikundervisning med laborativa material visar sig vara influenser från andra lärare och från internet. Slutsatserna som kan dras är att lärare kan ha svårt att veta hur de ska gå vidare från det laborativa materialet med elever som har svårt för aritmetik. Lärarna önskar även mer utbildning i hur de kan använda laborativa material med sina elever.

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  • 22.
    Ahlenius, Milla
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science.
    Hur mycket är klockan?: Lågstadieelevers kunskaper om att avläsa och mäta tid2023Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Syftet med studien är att skapa förståelse för lågstadieelevers kunskaper inom ämnesområdet mätning av tid. Studien baseras på ett skriftligt kvantitativt klocktest som 13 elever i årskurs 2 och 5 elever i årskurs 3 har genomfört, samt kvalitativa elevintervjuer som fyra elever i respektive årskurs har genomfört. Klocktesten har analyserats numeriskt och elevintervjuerna har analyserats tematiskt. Den teoretiska utgångspunkten är den sociokulturella teorin med inslag av lösningsstrategier. Studiens resultat indikerar att lågstadieelever har bättre kunskaper om den analoga klockan, jämfört med den digitala klockan. När eleverna har löst uppgifter om avläsning och mätning av tid har de främst använt strategin räkna uppåt. Slutsatsen som kan dras utifrån det är att lågstadieelever har kunskaper om klockan, men det finns kunskapsskillnader mellan de olika klocktyperna och mellan eleverna. Samtliga elever kunde redogöra för minst en lösningsstrategi som användes vid klockuppgifterna men strategierna fungerade olika bra. 

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  • 23.
    Ahlmén, Caroline
    University of Gävle. University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Hemligheten bakom populära animerade karaktärer2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Vad gör en framgångsrik animerad karaktär? Homer Simpson, Svampbob Fyrkant och Eric Cartman kommer att analyseras och jämföras för att hitta vad som gör just dem så populära. Därefter kommer de psykologiska aspekterna att granskas. Varför tilltalar dessa karaktärer människor? Riktlinjer för hur man skapar en populär animerad karaktär kommer att utvecklas utifrån resultatet av utredningen.

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  • 24.
    Ahmed, Dolovan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Fadul, Mohammed Erik Jamal
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Utsläpp från svenska reningsverk till Östersjön: Granskning av Henriksdals reningsverk, Ryaverket, Sjölunda reningsverk, Kungssängsverket och Duvbackens reningsverk2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    From domestic and industrial waste water will have to be cleaned before it can be released into lakes and streams again. This purification takes place through various stages of treatment plants. Wastewater contains many substances that are harmful to the environment as well as human and animal health, so it is important that the purification that is done is done in an efficient and thoughtful manner. The steps that are common in Swedish cleaning plants are mechanical, biological and chemical purification. These purification steps ensure that larger particles do not come out to the open water, convert nitrogen into nitrogen through the activation process, and that by chemical treatment, the emission of phosphorus is reduced. All of these purification steps can be designed differently and vary from purification plants to purification plants. Therefore, the degree of purification and emissions can distinguish between different treatment plants. Because there are many factors involved in the processes at Swedish waste treatment plants, it is important to carry out annual audits to detect problems that can lead to environmental damage.If cleaning does not work, exercise can increase in lakes and seas, which causes people and animals to suffer. Bottom dead and acid deficiency are already a major problem for the Baltic Sea. In order to reduce the negative environmental effects, emissions of nutrients are drastically reduced. This concerns the release of nutrients from all countries around the Baltic Sea.This study focuses on nitrogen and phosphorus purification from 5 wastewater treatment plants, Henriksdal's purification plant (Stockholm), Ryaverket (Gothenburg), Sjölunda purification plant (Malmö), Kungssängsverket (Uppsala) and Duvbacken purification plant (Gävle). Information about its activities has been obtained through interviews and works own reports.The purification plants use different technical solutions, and all treatment plants meet today's requirements for purification. The biggest difference is the degree of nitrogen purification. All wastewater treatment plants have a history of changes in technical solutions to improve treatment. Cleaning wastewater from households and industries costs a lot of money for the treatment plants, so it's always a challenge for the wastewater treatment plants to clean the water in the best possible way without costing too much.It is expected that the cleaning requirements will be tightened and all treatment plants should continue to develop to increase efficiency. Current purification requirements are designed to suit the recipient's sensitivity. If the EU's idea of ​​the same degree of purification across the country is transformed into requirements, Duvbacken will need to significantly improve the nitrogen treatment at the waste water treatment plant.

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  • 25.
    Ahonen-Jonnarth, Ulla
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Odelstad, Jan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Simulation as a tool for the evaluation of forest management treatments2010In: ESM'2010 - The 2010 European Simulation and Modelling Conference / [ed] Gerrit K. Janssens, Katrien Ramaekers and An Caris, Ghent: EUROSIS-ETI , 2010, p. 426-433Conference paper (Refereed)
    Abstract [en]

    Cleaning of young forest stands is a multicriteria problem with conflicting goals. This kind of forest management treatment is performed by human beings but it is possible that this work may be performed by artificial agents in the future. The artificial agents need detailed information about how to clean a forest stand and/or what are the goals for cleaning. One problem in development of cleaning rules for artificial cleaning agents is that explicit knowledge about good cleaning results is not detailed. In this paper we present a tool for developing and testing rules and judging evaluation functions for cleaning. We illustrate this tool by presenting examples of some ways to clean forest stands in a computer environment and we present how the cleaning results can be evaluated. In order to obtain material for experiments it is also possible to simulate forest stands using this tool.

  • 26.
    Ahonen-Jonnarth, Ulla
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Van Hees, P. A. W.
    Lundström, U. S.
    Finlay, R. D.
    Organic acids produced by mycorrhizal Pinus sylvestris exposed to elevated aluminium and heavy metal concentrations2000In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 146, no 3, p. 557-567Article in journal (Refereed)
    Abstract [en]

    A cultivation method was developed to enable exposure of ectomycorrhizal plants with intact extramatrical mycelium to solutions containing different concentrations of aluminium or heavy metals. Pinus sylvestris seedlings colonized by Suillus variegatus (two isolates), Rhizopogon roseolus or Paxillus involutus (two isolates) were used. Seedlings were transferred to Petri dishes containing glass beads and exposed to elevated concentrations of Al, Cd, Cu, or Ni in two ways: immediately following transfer; and after allowing mycorrhizal seedlings to develop an extraradical mycelium that colonized the interface between the upper surface of the beads and the metal-containing solution. Production of organic acids in mycorrhizal and non-mycorrhizal systems was measured by withdrawing samples from the solution and analyzing by HPLC. In most experiments, levels of oxalic acid were significantly higher in mycorrhizal treatments than in non-mycorrhizal controls. The measured levels of organic acids were variable, but the results obtained suggest that production of oxalic acid is stimulated by exposure to elevated Al in mycorrhizal seedlings colonized by S. variegatus and R. roseolus. Elevated Al concentrations also increased oxalic acid production by non-mycorrhizal seedlings significantly in two of four Al experiments performed, but the measured concentrations were significantly lower than in corresponding mycorrhizal treatments in both cases. Malonic acid was found in the culture solution of non-mycorrhizal had P. involutus-colonized seedlings, but only trace amounts were found in S. variegatus or R. roseolus-infected seedlings. Citric, shikimic, lactic, acetic, propionic, fumaric, formic, iso-butyric and butyric acid were found in variable concentrations. Production of oxalic acid by seedlings ColoniZed by S. variegatus BL or P. involutus was not stimulated by exposure to 0.44 μM Cd or 17 μM Ni. Exposure to 0.157 mM CU in two separate experiments using P. involutus 87.017 and two strains of S. variegatus (BL and 159) appeared to stimulate production of oxalic acid irrespective of mycorrhizal status or species.

  • 27.
    Ahrné, Karin
    et al.
    SLU.
    Bengtsson, Bengt Åke
    Björklund, Jan-Olof
    Cederberg, Björn
    Eliasson, Claes
    Hydén, Nils
    Jonasson, Jan
    Lindeborg, Mats
    Lst Kalmar Län.
    Ohlsson, Anders
    Palmqvist, Göran
    Ryrholm, Nils
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Biology.
    Rödlista över fjärilar Lepidoptera2015In: Rödlistade arter i Sverige 2015 / [ed] Westling, Anna, Uppsala: ArtDatabanken SLU , 2015, p. 98-112Chapter in book (Other academic)
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  • 28.
    Airey, John
    et al.
    Uppsala universitet, Fysikundervisningens didaktik.
    Eriksson, Urban
    Uppsala universitet, Fysikundervisningens didaktik.
    Fredlund, Tobias
    Uppsala universitet, Fysikundervisningens didaktik.
    Linder, Cedric
    Uppsala universitet, Fysikundervisningens didaktik.
    On the Disciplinary Affordances of Semiotic Resources2014In: IACS-2014 Book of abstracts, 2014, p. 54-55Conference paper (Refereed)
    Abstract [en]

    In the late 70’s Gibson (1979) introduced the concept of affordance. Initially framed around the needs of an organism in its environment, over the years the term has been appropriated and debated at length by a number of researchers in various fields. Most famous, perhaps is the disagreement between Gibson and Norman (1988) about whether affordances are inherent properties of objects or are only present when they are perceived by an organism. More recently, affordance has been drawn on in the educational arena, particularly with respect to multimodality (see Linder (2013) for a recent example). Here, Kress et al. (2001) have claimed that different modes have different specialized affordances. Then, building on this idea, Airey and Linder (2009) suggested that there is a critical constellation of modes that students need to achieve fluency in before they can experience a concept in an appropriate disciplinary manner. Later, Airey (2009) nuanced this claim, shifting the focus from the modes themselves to a critical constellation of semiotic resources, thus acknowledging that different semiotic resources within a mode often have different affordances (e.g. two or more diagrams may form the critical constellation).

    In this theoretical paper the concept of disciplinary affordance (Fredlund et al., 2012) is suggested as a useful analytical tool for use in education. The concept makes a radical break with the views of both Gibson and Norman in that rather than focusing on the discernment of one individual, it refers to the disciplinary community as a whole. Put simply, the disciplinary affordances of a given semiotic resource are determined by those functions that the resource is expected to fulfil by the disciplinary community. Disciplinary affordances have thus been negotiated and developed within the discipline over time. As such, the question of whether these affordances are inherent or discerned becomes moot. Rather, from an educational perspective the issue is whether the meaning that a semiotic resource affords to an individual matches the disciplinary affordance assigned by the community. The power of the term for educational work is that learning can now be framed as coming to discern the disciplinary affordances of semiotic resources.

    In this paper we will briefly discuss the history of the term affordance, define the term disciplinary affordance and illustrate its usefulness in a number of educational settings.

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  • 29.
    Aktan, Mikael
    University of Gävle, Department of Mathematics, Natural and Computer Sciences.
    Dynamic hair effects2007Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [en]

    Creating three dimensional hair is still one of the hardest elements when creating characters. Problems occur because of the constant changes in the software every few years. A major goal is to create as realistic hair as possible in Autodesk Maya and to supply this detailed information on to other 3D artist. Techniques are researched and reviewed on how different hair systems are created, as well as how dynamic effects react on the moving hair.

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  • 30.
    Al-Asadi, Hind
    University of Gävle, Faculty of Education and Business Studies, Department of Culture Studies, Religious Studies and Educational Sciences.
    Hur elever med matematiksvårigheter kan få stöd genom alternativa undervisningsmetoder: En studie gjorde med hjälp av dataprogrammet GeoGebra i ett sociokulturellt sammanhang2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
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  • 31.
    Al-Asadi, Yousif
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences.
    Streit, Jennifer
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences.
    Identifiering av UNO-kort: En jämförelse av bildigenkänningstekniker2023Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Engaging in the social game of UNO represents a form of social interaction aimed atpromoting enjoyment. Each UNO card deck consists of five different colors (blue,red, green, yellow and joker) and various symbols. However participating in such agame can be frustrating for individuals with color vision impairment. Since a substantial portion of the game relies on accurately identifying the color of each card.The overall purpose of this research is to develop a prototype for object recognitionof UNO cards to support individuals with color vision impairment. This thesis involves comparing object recognition methods, namely Convolutional Neural Network (CNN) and Template Matching (TM). Each method will be compared with respect to color and symbol recognition both separately and combined.  

    The development of such a prototype will be through creating and training two different CNN models, where the first model focuses on solely symbol recognitionwhile the other model incorporates both color and symbol recognition. These models will be trained though an algorithm called YOLOv5 which is considered state-ofthe-art (SOTA) with fast execution. At the same time, two models of TM inspiredmethods, hue template test and binary template test, will be developed with thehelp of OpenCV and by creating templates for the cards. Each template will be usedas a way to compare the detected card in order to classify it. Additionally, the KNearest Neighbor (KNN) algorithm, a machine learning algorithm, will be developed specifically to identify the color of the cards. Finally a comparative analysis ofthese methods will be conducted by evaluating performance metrics such as accuracy, precision, recall and latency. The comparison will be carried out in betweeneach method using a confusion matrix for color and symbol in respective models.

    The study’s findings revealed that the model combining CNN and KNN demonstrated the best performance during the validation of the different models. Furthermore, the study shows that template tests are faster to implement than CNN due tothe training that a neural network requires. Moreover, the execution time showsthat there is a difference between the different models, where CNN achieved thehighest performance.

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    Identifiering av UNO-kort - En jämförelse av bildigenkänningstekniker
  • 32.
    Alatalo, Juha M.
    et al.
    Qatar University, Doha, Qatar.
    Dai, Junhu
    Institute Of Geographic Sciences And Natural Resources Research, Beijing, China.
    Pandey, Rajiv
    Indian Council Of Forestry Research And Education, Dehradun, India.
    Erfanian, Mohammad Bagher
    Ferdowsi University Of Mashhad, Mashhad, Iran.
    Ahmed, Talaat
    Qatar University, Doha, Qatar.
    Bai, Yang
    Xishuangbanna Tropical Botanical Garden, Mengla, China.
    Molau, Ulf
    University Of Gothenburg, Gothenburg, Sweden.
    Jägerbrand, Annika
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Impact of ambient temperature, precipitation and seven years of experimental warming and nutrient addition on fruit production in an alpine heath and meadow community2022In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 836, article id 155450Article in journal (Refereed)
    Abstract [en]

    Alpine and polar regions are predicted to be among the most vulnerable to changes in temperature, precipitation, and nutrient availability. We carried out a seven-year factorial experiment with warming and nutrient addition in two alpine vegetation communities. We analyzed the relationship between fruit production and monthly mean, maximum, and min temperatures during the fall of the pre-fruiting year, the fruiting summer, and the whole fruit production period, and measured the effects of precipitation and growing and thawing degree days (GDD & TDD) on fruit production. Nutrient addition (heath: 27.88 ± 3.19 fold change at the end of the experiment; meadow: 18.02 ± 4.07) and combined nutrient addition and warming (heath: 20.63 ± 29.34 fold change at the end of the experiment; meadow: 18.21 ± 16.28) increased total fruit production and fruit production of graminoids. Fruit production of evergreen and deciduous shrubs fluctuated among the treatments and years in both the heath and meadow. Pre-maximum temperatures had a negative effect on fruit production in both communities, while current year maximum temperatures had a positive impact on fruit production in the meadow. Pre-minimum, pre-mean, current mean, total minimum, and total mean temperatures were all positively correlated with fruit production in the meadow. The current year and total precipitation had a negative effect on the fruit production of deciduous shrubs in the heath. GDD had a positive effect on fruit production in both communities, while TDD only impacted fruit production in the meadow. Increased nutrient availability increased fruit production over time in the high alpine plant communities, while experimental warming had either no effect or a negative effect. Deciduous shrubs were the most sensitive to climate parameters in both communities, and the meadow was more sensitive than the heath. The difference in importance of TDD for fruit production may be due to differences in snow cover in the two communities. © 2022 The Authors

  • 33.
    Alatalo, Juha M.
    et al.
    Qatar University, Doha, Qatar.
    Erfanian, Mohammad Bagher
    Ferdowsi University of Mashhad, Mashhad, Iran.
    Molau, Ulf
    Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
    Chen, Shengbin
    Chengdu University of Technology, Chengdu, China.
    Bai, Yang
    Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences, Mengla, China.
    Jägerbrand, Annika
    Högskolan i Halmstad, Centrum för innovations-, entreprenörskaps- och lärandeforskning (CIEL).
    Changes in plant composition and diversity in an alpine heath and meadow after 18 years of experimental warming2022In: Alpine Botany, ISSN 1664-2201, E-ISSN 1664-221X, Vol. 132, no 2, p. 181-193Article in journal (Refereed)
    Abstract [en]

    Global warming is expected to have large impacts on high alpine and Arctic ecosystems in the future. Here we report effects of 18 years of experimental warming on two contrasting high alpine plant communities in subarctic Sweden. Using open-top chambers, we analysed effects of long-term passive experimental warming on a heath and a meadow. We determined the impact on species composition, species diversity (at the level of rare, common and dominant species), and phylogenetic and functional diversity. Long-term warming drove differentiation in species composition in both communities; warmed plots, but not control plots, had distinctly different species composition in 2013 compared with 1995. Beta diversity increased in the meadow, while it decreased in the heath. Long-term warming had significant negative effects on the three orders of phylogenetic Hill diversity in the meadow. There was a similar tendency in the heath, but only phylogenetic diversity of dominant species was significantly affected. Long-term warming caused reductions in forbs in the heath, while evergreen shrubs increased. In the meadow, deciduous and evergreen shrubs showed increased abundance from 2001 to 2013 in warmed plots. Responses in species and phylogenetic diversity to experimental warming varied over both time (medium (7 years) vs long-term (18 years)) and space (between two neighbouring plant communities). The meadow community was more negatively affected in terms of species and phylogenetic diversity than the heath community. A potential driver for the changes in the meadow may be decreased soil moisture caused by long-term warming. © 2021

  • 34. Alatalo, Juha M.
    et al.
    Jägerbrand, Annika
    Chen, Shengbin
    Molau, Ulf
    Responses of lichen communities to 18 years of natural and experimental warming2017In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 120, no 1, p. 159-170Article in journal (Refereed)
    Abstract [en]

    Background and Aims 

    Climate change is expected to have major impacts on high alpine and arctic ecosystems in the future, but empirical data on the impact of long-term warming on lichen diversity and richness are sparse. This study report the effects of 18 years of ambient and experimental warming on lichens and vascular plant cover in two alpine plant communities, a dry heath with sparse canopy cover (54 %) and a mesic meadow with a more developed (67 %) canopy cover, in sub-arctic Sweden.

    Methods 

    The effects of long-term passive experimental warming using open top chambers (OTCs) on lichens and total vascular plant cover, and the impact of plant cover on lichen community parameters, were analysed.

    Key Results 

    Between 1993 and 2013, mean annual temperature increased about 2 °C. Both site and experimental warming had a significant effect on cover, species richness, effective number of species evenness of lichens, and total plant canopy cover. Lichen cover increased in the heath under ambient conditions, and remained more stable under experimental warming. The negative effect on species richness and effective number of species was driven by a decrease in lichens under experimental warming in the meadow. Lichen cover, species richness, effective number of species evenness were negatively correlated with plant canopy cover. There was a significant negative impact on one species and a non-significant tendency of lower abundance of the most common species in response to experimental warming.

    Conclusions 

    The results from the long-term warming study imply that arctic and high alpine lichen communities are likely to be negatively affected by climate change and an increase in plant canopy cover. Both biotic and abiotic factors are thus important for future impacts of climate change on lichens.

  • 35.
    Alatalo, Juha M.
    et al.
    Department of Biological and Environmental Sciences, Qatar University, Doha, Qatar; Environmental Science Center, Qatar University, Doha, Qatar.
    Jägerbrand, Annika
    Högskolan i Halmstad, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS).
    Dai, Junhu
    Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China; CAS-HEC, Islamabad, Pakistan.
    Mollazehi, Mohammad D.
    Qatar University, Doha, Qatar.
    Abdel-Salam, Abdel-Salam G.
    Qatar University, Doha, Qatar.
    Pandey, Rajiv
    Indian Council of Forestry Research and Education, Dehradun, India.
    Molau, Ulf
    Göteborgs Universitet, Gothenburg, Sweden.
    Effects of ambient climate and three warming treatments on fruit production in an alpine, subarctic meadow community2021In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 108, no 3, p. 411-422Article in journal (Refereed)
    Abstract [en]

    Premise: Climate change is having major impacts on alpine and arctic regions, and inter-annual variations in temperature are likely to increase. How increased climate variability will impact plant reproduction is unclear. Methods: In a 4-year study on fruit production by an alpine plant community in northern Sweden, we applied three warming regimes: (1) a static level of warming with open-top chambers (OTC), (2) press warming, a yearly stepwise increase in warming, and (3) pulse warming, a single-year pulse event of higher warming. We analyzed the relationship between fruit production and monthly temperatures during the budding period, fruiting period, and whole fruit production period and the effect of winter and summer precipitation on fruit production. Results: Year and treatment had a significant effect on total fruit production by evergreen shrubs, Cassiope tetragona, and Dryas octopetala, with large variations between treatments and years. Year, but not treatment, had a significant effect on deciduous shrubs and graminoids, both of which increased fruit production over the 4 years, while forbs were negatively affected by the press warming, but not by year. Fruit production was influenced by ambient temperature during the previous-year budding period, current-year fruiting period, and whole fruit production period. Minimum and average temperatures were more important than maximum temperature. In general, fruit production was negatively correlated with increased precipitation. Conclusions: These results indicate that predicted increased climate variability and increased precipitation due to climate change may affect plant reproductive output and long-term community dynamics in alpine meadow communities. © 2021 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America

  • 36.
    Alatalo, Juha M.
    et al.
    Qatar University, Doha, Qatar.
    Jägerbrand, Annika
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Erfanian, Mohammad Bagher
    Ferdowsi University of Mashhad, Mashhad, Iran.
    Chen, Shengbin
    Chengdu University of Technology, Chengdu, China.
    Sun, Shou Qin
    Institute Of Mountain Hazards And Environment, Chengdu, China.
    Molau, Ulf
    University Of Gothenburg, Gothenburg, Sweden.
    Bryophyte cover and richness decline after 18 years of experimental warming in alpine Sweden2020In: AoB Plants, E-ISSN 2041-2851, Vol. 12, no 6, article id plaa061Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to affect alpine and Arctic tundra communities. Most previous long-term studies have focused on impacts on vascular plants, this study examined impacts of long-term warming on bryophyte communities. Experimental warming with open-top chambers (OTCs) was applied for 18 years to a mesic meadow and a dry heath alpine plant community. Species abundance was measured in 1995, 1999, 2001 and 2013. Species composition changed significantly from original communities in the heath, but remained similar in mesic meadow. Experimental warming increased beta diversity in the heath. Bryophyte cover and species richness both declined with long-term warming, while Simpson diversity showed no significant responses. Over the 18-year period, bryophyte cover in warmed plots decreased from 43 % to 11 % in heath and from 68 % to 35 % in meadow (75 % and 48 % decline, respectively, in original cover), while richness declined by 39 % and 26 %, respectively. Importantly, the decline in cover and richness first emerged after 7 years. Warming caused significant increase in litter in both plant communities. Deciduous shrub and litter cover had negative impact on bryophyte cover. We show that bryophyte species do not respond similarly to climate change. Total bryophyte cover declined in both heath and mesic meadow under experimental long-term warming (by 1.5-3 °C), driven by general declines in many species. Principal response curve, cover and richness results suggested that bryophytes in alpine heath are more susceptible to warming than in meadow, supporting the suggestion that bryophytes may be less resistant in drier environments than in wetter habitats. Species loss was slower than the decline in bryophyte abundance, and diversity remained similar in both communities. Increased deciduous shrub and litter cover led to decline in bryophyte cover. The non-linear response to warming over time underlines the importance of long-term experiments and monitoring. © 2020 The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company.

  • 37. Alatalo, Juha M.
    et al.
    Jägerbrand, Annika
    Calluna AB, Nacka, Sweden.
    Juhanson, Jaanis
    Michelsen, Anders
    Ľuptáčik, Peter
    Impacts of twenty years of experimental warming on soil carbon, nitrogen, moisture and soil mites across alpine/subarctic tundra communities2017In: Scientific Reports, E-ISSN 2045-2322, Vol. 7Article in journal (Refereed)
    Abstract [en]

    High-altitude and alpine areas are predicted to experience rapid and substantial increases in future temperature, which may have serious impacts on soil carbon, nutrient and soil fauna. Here we report the impact of 20 years of experimental warming on soil properties and soil mites in three contrasting plant communities in alpine/subarctic Sweden. Long-term warming decreased juvenile oribatid mite density, but had no effect on adult oribatids density, total mite density, any major mite group or the most common species. Long-term warming also caused loss of nitrogen, carbon and moisture from the mineral soil layer in mesic meadow, but not in wet meadow or heath or from the organic soil layer. There was a significant site effect on the density of one mite species, Oppiella neerlandica, and all soil parameters. A significant plot-scale impact on mites suggests that small-scale heterogeneity may be important for buffering mites from global warming. The results indicated that juvenile mites may be more vulnerable to global warming than adult stages. Importantly, the results also indicated that global warming may cause carbon and nitrogen losses in alpine and tundra mineral soils and that its effects may differ at local scale.

  • 38.
    Alatalo, Juha M
    et al.
    Uppsala Universitet, Campus Gotland.
    Jägerbrand, Annika
    Statens väg- och transportforskningsinstitut.
    Molau, Ulf
    Göteborg Universitet.
    Climate change and climatic events: Community-, functional- and species-level responses of bryophytes and lichens to constant, stepwise, and pulse experimental warming in an alpine tundra2014In: Alpine Botany, ISSN 1664-2201, E-ISSN 1664-221X, Vol. 124, no 2, p. 81-91Article in journal (Refereed)
    Abstract [en]

    We experimentally imposed three different kinds of warming scenarios over 3 years on an alpine meadow community to identify the differential effects of climate warming and extreme climatic events on the abundance and biomass of bryophytes and lichens. Treatments consisted of (a) a constant level of warming with open top chambers (an average temperature increase of 1.87 °C), (b) a yearly stepwise increase of warming (average temperature increases of 1.0; 1.87 and 3.54 °C, consecutively), and (c) a pulse warming, i.e., a single first year pulse event of warming (average temperature increase of 3.54 °C only during the first year). To our knowledge, this is the first climate change study that attempts to distinguish between the effects of constant, stepwise and pulse warming on bryophyte and lichen communities. We hypothesised that pulse warming would have a significant short-term effect compared to the other warming treatments, and that stepwise warming would have a significant mid-term effect compared to the other warming treatments. Acrocarpous bryophytes as a group increased in abundance and biomass to the short-term effect of pulse warming. We found no significant effects of mid-term (third-year) stepwise warming. However, one pleurocarpous bryophyte species, Tomentypnum nitens, generally increased in abundance during the warm year 1997 but decreased in control plots and in response to the stepwise warming treatment. Three years of experimental warming (all treatments as a group) did have a significant impact at the community level, yet changes in abundance did not translate into significant changes in the dominance hierarchies at the functional level (for acrocarpous bryophytes, pleurocarpous bryophytes, Sphagnum or lichens), or in significant changes in other bryophyte or lichen species. The results suggest that bryophytes and lichens, both at the functional group and species level, to a large extent are resistant to the different climate change warming simulations that were applied.

  • 39.
    Alatalo, Juha M.
    et al.
    Qatar University.
    Jägerbrand, Annika
    Statens väg- och transportforskningsinstitut.
    Molau, Ulf
    Göteborgs Universitet.
    Impacts of different climate change regimes and extreme climatic events on an alpine meadow community2016In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, article id 21720Article in journal (Refereed)
    Abstract [en]

    Climate variability is expected to increase in future but there exist very few experimental studies that apply different warming regimes on plant communities over several years. We studied an alpine meadow community under three warming regimes over three years. Treatments consisted of (a) a constant level of warming with open-top chambers (ca. 1.9 °C above ambient), (b) yearly stepwise increases in warming (increases of ca. 1.0, 1.9 and 3.5 °C), and (c) pulse warming, a single first-year pulse event of warming (increase of ca. 3.5 °C). Pulse warming and stepwise warming was hypothesised to cause distinct first-year and third-year effects, respectively. We found support for both hypotheses; however, the responses varied among measurement levels (whole community, canopy, bottom layer, and plant functional groups), treatments, and time. Our study revealed complex responses of the alpine plant community to the different experimentally imposed climate warming regimes. Plant cover, height and biomass frequently responded distinctly to the constant level of warming, the stepwise increase in warming and the extreme pulse-warming event. Notably, we found that stepwise warming had an accumulating effect on biomass, the responses to the different warming regimes varied among functional groups, and the short-term perturbations had negative effect on species richness and diversity.

  • 40.
    Alatalo, Juha M.
    et al.
    Uppsala Universitet.
    Jägerbrand, Annika
    Statens väg- och transportforskningsinstitut.
    Molau, Ulf
    University of Gothenburg.
    Seven years of experimental warming and nutrient addition causes decline of bryophytes and lichens in alpine meadow and heath communitiesManuscript (preprint) (Other academic)
    Abstract [sv]

    Global change is predicted to have large and rapid impact on polar and alpine regions. Bryophytes and lichens increase their importance in terms of biomass, carbon/nutrient cycling, cover and ecosystem functioning at higher latitudes/altitudes. Here we report from a seven year factorial experiment with nutrient addition and warming on the abundance of bryophytes and lichens in an alpine meadow and heath community. Treatments had significant negative effect on relative change of total abundance bryophytes and lichens, the largest decline to the nutrient addition and the combined nutrient addition and warming treatments, bryophytes decreasing most in the meadow, lichens most in the heath. Nutrient addition, and the combined nutrient addition and warming brought rapid decrease in both bryophytes and lichens, while warming had a delayed negative impact. Of sixteen species that were included the statistical analyses, we found significant negative effects on seven species. We show that impact of simulated global change on bryophytes and lichens differ in in time and magnitude among treatments and plant communities. Our results underscore the importance of longer-term studies to improve the quality of climate change models, as short-term studies are poor predictors of longer-term responses of bryophytes and lichens, similar to what have been shown for vascular plants. Species-specific responses may differ in time, and this will likely cause changes in the dominance structures of bryophytes and lichens over time.

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  • 41.
    Alatalo, Juha M
    et al.
    Uppsala universitet, Växtekologi och evolution.
    Jägerbrand, Annika
    VTI, Swedish Natl Rd & Transport Res Inst, S-10215 Stockholm, Sweden..
    Molau, Ulf
    Univ Gothenburg, Dept Biol & Environm Sci, SE-40530 Gothenburg, Sweden..
    Testing reliability of short-term responses to predict longer-term responses of bryophytes and lichens to environmental change2015In: Ecological Indicators, ISSN 1470-160X, E-ISSN 1872-7034, Vol. 58, p. 77-85Article in journal (Refereed)
    Abstract [en]

    Environmental changes are predicted to have severe and rapid impacts on polar and alpine regions. At high latitudes/altitudes, cryptogams such as bryophytes and lichens are of great importance in terms of biomass, carbon/nutrient cycling, cover and ecosystem functioning. This seven-year factorial experiment examined the effects of fertilizing and experimental warming on bryophyte and lichen abundance in an alpine meadow and a heath community in subarctic Sweden. The aim was to determine whether shortterm responses (five years) are good predictors of longer-term responses (seven years). Fertilizing and warming had significant negative effects on total and relative abundance of bryophytes and lichens, with the largest and most rapid decline caused by fertilizing and combined fertilizing and warming. Bryophytes decreased most in the alpine meadow community, which was bryophyte-dominated, and lichens decreased most in the heath community, which was lichen-dominated. This was surprising, as the most diverse group in each community was expected to be most resistant to perturbation. Warming alone had a delayed negative impact. Of the 16 species included in statistical analyses, seven were significantly negatively affected. Overall, the impacts of simulated warming on bryophytes and lichens as a whole and on individual species differed in time and magnitude between treatments and plant communities (meadow and heath). This will likely cause changes in the dominance structures over time. These results underscore the importance of longer-term studies to improve the quality of data used in climate change models, as models based on short-term data are poor predictors of long-term responses of bryophytes and lichens.

  • 42.
    Alatalo, Juha M
    et al.
    Qatar University.
    Jägerbrand, Annika
    Statens väg- och transportforskningsinstitut.
    Čuchta, Peter
    Academy of Science of the Czech Republic.
    Collembola at three alpine subarctic sites resistant to twenty years of experimental warming2015In: Scientific Reports, E-ISSN 2045-2322, Vol. 5, article id 18161Article in journal (Refereed)
    Abstract [en]

    This study examined the effects of micro-scale, site and 19 and 21 years of experimental warming on Collembola in three contrasting alpine subarctic plant communities (poor heath, rich meadow, wet meadow). Unexpectedly, experimental long-term warming had no significant effect on species richness, effective number of species, total abundance or abundance of any Collembola species. There were micro-scale effects on species richness, total abundance, and abundance of 10 of 35 species identified. Site had significant effect on effective number of species, and abundance of six species, with abundance patterns differing between sites. Site and long-term warming gave non-significant trends in species richness.

    The highest species richness was observed in poor heath, but mean species richness tended to be highest in rich meadow and lowest in wet meadow. Warming showed a tendency for a negative impact on species richness. This long-term warming experiment across three contrasting sites revealed that Collembola is capable of high resistance to climate change. We demonstrated that micro-scale and site effects are the main controlling factors for Collembola abundance in high alpine subarctic environments. Thus local heterogeneity is likely important for soil fauna composition and may play a crucial role in buffering Collembola against future climate change.

  • 43.
    Alatalo, Juha M.
    et al.
    Uppsala universitet, Växtekologi och evolution.
    Little, Chelsea J.
    Uppsala universitet, Växtekologi och evolution.
    Jägerbrand, Annika
    VTI, Swedish National Road and Transport Research Institute, Stockholm, Sweden.
    Molau, Ulf
    Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
    Dominance hierarchies, diversity and species richness of vascular plants in an alpine meadow: contrasting short and medium term responses to simulated global change2014In: PeerJ, E-ISSN 2167-8359, Vol. 2, article id 406Article in journal (Refereed)
    Abstract [en]

    We studied the impact of simulated global change on a high alpine meadow plant community. Specifically, we examined whether short-term (5 years) responses are good predictors for medium-term (7 years) changes in the system by applying a factorial warming and nutrient manipulation to 20 plots in Latnjajaure, subarctic Sweden. Seven years of experimental warming and nutrient enhancement caused dramatic shifts in dominance hierarchies in response to the nutrient and the combined warming and nutrient enhancement treatments. Dominance hierarchies in the meadow moved from a community being dominated by cushion plants, deciduous, and evergreen shrubs to a community being dominated by grasses, sedges, and forbs. Short-termresponses were shown to be inconsistent in their ability to predict medium-term responses for most functional groups, however, grasses showed a consistent and very substantial increase in response to nutrient addition over the seven years. The non-linear responses over time point out the importance of longer-term studies with repeated measurements to be able to better predict future changes. Forecasted changes to temperature and nutrient availability have implications for trophic interactions, and may ultimately influence the access to and palatability of the forage for grazers. Depending on what anthropogenic change will be most pronounced in the future (increase in nutrient deposits, warming, or a combination of them both), different shifts in community dominance hierarchies may occur. Generally, this study supports the productivity-diversity relationship found across arctic habitats, with community diversity peaking in mid-productivity systems and degrading as nutrient availability increases further. This is likely due the increasing competition in plant-plant interactions and the shifting dominance structure with grasses taking over the experimental plots, suggesting that global change could have high costs to biodiversity in the Arctic.

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  • 44.
    Alatalo, Juha M.
    et al.
    Uppsala universitet, Växtekologi och evolution.
    Little, Chelsea J.
    Uppsala universitet, Växtekologi och evolution.
    Jägerbrand, Annika
    Statens väg- och transportforskningsinstitut, Samhälle, miljö och transporter, SAMT, Miljö, MILJÖ.
    Molau, Ulf
    Vascular plant abundance and diversity in an alpine heath under observed and simulated global change2015In: Scientific Reports, E-ISSN 2045-2322, Vol. 5, article id 10197Article in journal (Refereed)
    Abstract [en]

    Global change is predicted to cause shifts in species distributions and biodiversity in arctic tundra. We applied factorial warming and nutrient manipulation to a nutrient and species poor alpine/arctic heath community for seven years. Vascular plant abundance in control plots increased by 31%. There were also notable changes in cover in the nutrient and combined nutrient and warming treatments, with deciduous and evergreen shrubs declining, grasses overgrowing these plots. Sedge abundance initially increased significantly with nutrient amendment and then declined, going below initial values in the combined nutrient and warming treatment. Nutrient addition resulted in a change in dominance hierarchy from deciduous shrubs to grasses. We found significant declines in vascular plant diversity and evenness in the warming treatment and a decline in diversity in the combined warming and nutrient addition treatment, while nutrient addition caused a decline in species richness. The results give some experimental support that species poor plant communities with low diversity may be more vulnerable to loss of species diversity than communities with higher initial diversity. The projected increase in nutrient deposition and warming may therefore have negative impacts on ecosystem processes, functioning and services due to loss of species diversity in an already impoverished environment.

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  • 45.
    Alekseev, Gennady
    et al.
    Institute of Applied Mathematics FEB RAS, Vladivostok, Russia; School of Natural Sciences, Far Eastern Federal University, Vladivostok, Russia .
    Tereshko, Dmitri
    Institute of Applied Mathematics FEB RAS, Vladivostok, Russia.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Mathematics.
    Optimization approach for axisymmetric electric field cloaking and shielding2021In: Inverse Problems in Science and Engineering, ISSN 1741-5977, E-ISSN 1741-5985, Vol. 29, no 1, p. 40-55Article in journal (Refereed)
    Abstract [en]

    In this paper we study inverse problems of electric conductivity that arise in the design of spherical shielding or cloaking shells and other functional devices used to control static electric fields. The shells are considered consisting of a finite number of layers filled with homogeneous isotropic or anisotropic medium. The inverse problems under study are reduced to control problems with the layers electric conductivities taken as controls. A different choice of minimized functionals allows us to solve a wide range of design problems using one approach. A numerical algorithm to solve these problems is based on particle swarm optimization. Various results of numerical experiments are discussed in order to find the most effective designs. The findings obtained in this study describe a broad set of specific easy-to-manufacture structures that have the highest cloaking or shielding performance in the class of layered shells.

  • 46.
    Alfredsson, Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. frastructure, Geodata Division, Lantmäteriet , Gävle , Sweden.
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Department of Geodetic Infrastructure, Geodata Division, Lantmäteriet , SE-80182 Gävle , Sweden.
    A first step towards a national realisation of the international height reference system in Sweden with a comparison to RH 20002023In: Journal of Geodetic Science, ISSN 2081-9919, E-ISSN 2081-9943, Vol. 13, no 1, article id 20220156Article in journal (Refereed)
    Abstract [en]

    The International Height Reference System (IHRS) was defined by the International Association of Geodesy in 2015. Since then, the international geodetic community has been working on the specification and establishment of its realisation, the International Height Reference Frame (IHRF). This frame will primarily be realised by geopotential numbers (or physical heights) in a sparse global reference network. In Sweden, only one such global station is planned. Regional and national realisations (or densifications) computed in accordance with the IHRS definition are needed to enable the best possible unification of height datums. The main purpose of this article is to make a case study for Sweden regarding the national realisation of IHRS and to investigate in what way preliminary IHRF differs from the current Swedish levelling-based realisation of the European Vertical Reference System, RH 2000. The two different quasigeoid models that we consider best over Sweden at the present time are used to compute the preliminary IHRS realisations in the study. The realisations are compared to each other and to RH 2000. It is shown that a very significant part of the difference to RH 2000 is due to the different postglacial land uplift epochs, permanent tide concepts, and zero levels. The standard deviation for the difference between one of the preliminary national IHRS realisations and RH 2000 is reduced from 75.5 to 19.2 mm after correction of the postglacial land uplift and permanent tide effects. The corresponding mean differences are –208.5 and –454.7 mm, respectively. The magnitude of the mean difference thus increases when the corrections in question are applied.

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  • 47.
    Alfredsson, Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Department of Geodetic Infrastructure, Geodata Division, Lantmäteriet, Gävle, Sweden.
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Department of Geodetic Infrastructure, Geodata Division, Lantmäteriet, Gävle, Sweden.
    Olsson, Per-Anders
    Department of Geodetic Infrastructure, Geodata Division, Lantmäteriet, Gävle, Sweden.
    A Comparison of Pointwise and Levelling Assisted Regional Realisations of IHRS with a Case Study over Sweden2023In: International Association of Geodesy Symposia / [ed] Jeffrey T Freymueller, Springer Berlin/Heidelberg, 2023Chapter in book (Refereed)
    Abstract [en]

    The International Height Reference System (IHRS) was defined by the International Association of Geodesy (IAG) in 2015. The global International Height Reference Frame (IHRF) should provide access to the IHRS in a broad sense. To provide high accuracy local access, regional (or national) realisations will also be needed. This study aims at evaluating different approaches to compute a denser regional realisation of IHRS in case a high accuracy levelling network is available. Using Sweden as a case study region, a GNSS (Global Navigation Satellite System) and geoid based pointwise realisation is compared with three types of levelling assisted realisations. The latter are made by applying least squares adjustments of the precise levelling observations with fixed potential value(s) from either the global IHRF station in Sweden or the pointwise potentials of a larger number of stations. It is concluded that making a minimum constraint adjustment with one station fixed is not the best option. It is favourable to fix a reasonable number of pointwise stations at an internal distance over which the relative uncertainty of levelling is significantly lower than the relative uncertainty of the pointwise solution. The investigation is made using levelling data from the third precise levelling of Sweden, the NKG2015 quasigeoid model and the NKG2016LU postglacial land uplift model.

  • 48.
    Ali, Arshad
    et al.
    East China Normal University.
    Molau, Ulf
    Göteborgs Universitet.
    Bai, Yang
    Chinese Academy of Sciences.
    Jägerbrand, Annika
    Statens väg- och transportforskningsinstitut.
    Alatalo, Juha M.
    Qatar University.
    Diversity-productivity dependent resistance of an alpine plant community to different climate change scenarios2016In: Ecological research, ISSN 0912-3814, E-ISSN 1440-1703, Vol. 31, no 6, p. 935-945Article in journal (Refereed)
    Abstract [en]

    Here we report from a experiment imposing different warming scenarios [control with ambient temperature, constant level of moderate warming for 3 years, stepwise increase in warming for 3 years, and one season of high level warming (pulse) simulating an extreme summer event] on an alpine ecosystem to study the impact on species diversity–biomass relationship, and community resistance in terms of biomass production.

    Multiple linear mixed models indicate that experimental years had stronger influence on biomass than warming scenarios and species diversity. Species diversity and biomass had almost humpback relationships under different warming scenarios over different experimental years. There was generally a negative diversity–biomass relationship, implying that a positive diversity–biomass relationship was not the case.

    The application of different warming scenarios did not change this tendency. The change in community resistance to all warming scenarios was generally negatively correlated with increasing species diversity, the strength of the correlation varying both between treatments and between years within treatments. The strong effect of experimental years was consistent with the notion that niche complementarity effects increase over time, and hence, higher biomass productivity over experimental years. The strongest negative relationship was found in the first year of the pulse treatment, indicating that the community had weak resistance to an extreme event of one season of abnormally warm climate.

    Biomass production started recovering during the two subsequent years. Contrasting biomass-related resistance emerged in the different treatments, indicating that micro sites within the same plant community may differ in their resistance to different warming scenarios.

  • 49.
    Ali, Fadi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Urban classification by pixel and object-based approaches for very high resolution imagery2015Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Recently, there is a tremendous amount of high resolution imagery that wasn’t available years ago, mainly because of the advancement of the technology in capturing such images. Most of the very high resolution (VHR) imagery comes in three bands only the red, green and blue (RGB), whereas, the importance of using such imagery in remote sensing studies has been only considered lately, despite that, there are no enough studies examining the usefulness of these imagery in urban applications. This research proposes a method to investigate high resolution imagery to analyse an urban area using UAV imagery for land use and land cover classification. Remote sensing imagery comes in various characteristics and format from different sources, most commonly from satellite and airborne platforms. Recently, unmanned aerial vehicles (UAVs) have become a very good potential source to collect geographic data with new unique properties, most important asset is the VHR of spatiotemporal data structure. UAV systems are as a promising technology that will advance not only remote sensing but GIScience as well. UAVs imagery has been gaining popularity in the last decade for various remote sensing and GIS applications in general, and particularly in image analysis and classification. One of the concerns of UAV imagery is finding an optimal approach to classify UAV imagery which is usually hard to define, because many variables are involved in the process such as the properties of the image source and purpose of the classification. The main objective of this research is evaluating land use / land cover (LULC) classification for urban areas, whereas the data of the study area consists of VHR imagery of RGB bands collected by a basic, off-shelf and simple UAV. LULC classification was conducted by pixel and object-based approaches, where supervised algorithms were used for both approaches to classify the image. In pixel-based image analysis, three different algorithms were used to create a final classified map, where one algorithm was used in the object-based image analysis. The study also tested the effectiveness of object-based approach instead of pixel-based in order to minimize the difficulty in classifying mixed pixels in VHR imagery, while identifying all possible classes in the scene and maintain the high accuracy. Both approaches were applied to a UAV image with three spectral bands (red, green and blue), in addition to a DEM layer that was added later to the image as ancillary data. Previous studies of comparing pixel-based and object-based classification approaches claims that object-based had produced better results of classes for VHR imagery. Meanwhile several trade-offs are being made when selecting a classification approach that varies from different perspectives and factors such as time cost, trial and error, and subjectivity.

          Classification based on pixels was approached in this study through supervised learning algorithms, where the classification process included all necessary steps such as selecting representative training samples and creating a spectral signature file. The process in object-based classification included segmenting the UAV’s imagery and creating class rules by using feature extraction. In addition, the incorporation of hue, saturation and intensity (IHS) colour domain and Principle Component Analysis (PCA) layers were tested to evaluate the ability of such method to produce better results of classes for simple UAVs imagery. These UAVs are usually equipped with only RGB colour sensors, where combining more derived colour bands such as IHS has been proven useful in prior studies for object-based image analysis (OBIA) of UAV’s imagery, however, incorporating the IHS domain and PCA layers in this research did not provide much better classes. For the pixel-based classification approach, it was found that Maximum Likelihood algorithm performs better for VHR of UAV imagery than the other two algorithms, the Minimum Distance and Mahalanobis Distance. The difference in the overall accuracy for all algorithms in the pixel-based approach was obvious, where the values for Maximum Likelihood, Minimum Distance and Mahalanobis Distance were respectively as 86%, 80% and 76%. The Average Precision (AP) measure was calculated to compare between the pixel and object-based approaches, the result was higher in the object-based approach when applied for the buildings class, the AP measure for object-based classification was 0.9621 and 0.9152 for pixel-based classification. The results revealed that pixel-based classification is still effective and can be applicable for UAV imagery, however, the object-based classification that was done by the Nearest Neighbour algorithm has produced more appealing classes with higher accuracy. Also, it was concluded that OBIA has more power for extracting geographic information and easier integration within the GIS, whereas the result of this research is estimated to be applicable for classifying UAV’s imagery used for LULC applications.

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  • 50.
    Ali, Rafef
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Matematik och estetiska lärprocesser: en studie om ämnesintegration av estetiska verktyg i matematikundervisning.2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Syftet med undersökningen var att observera hur lärarna arbetar med matematik i årskurserna F-3, med fokus på hur estetiska verktyg används i matematikundervisningen. Studien är baserad på klassobservationer i två årskurser i de tidigare skolåren F-3 samt elev- och lärarintervjuer och ämnade lyfta estetiska lärprocesser samt hur de spelar in på elevernas upplevelser vad gäller ämnesintegration i matematikundervisning. Resultaten visar att estetiska verktyg används mer med yngre elever och mindre ju äldre eleverna blir. Lärarna i denna studie påpekade att ett ämnesövergripande arbetssätt och att blanda in olika sinnen främjar elevernas inlärning. Majoriteten av de intervjuade lärarna betonade att det gäller att hitta en balans mellan olika metoder för att skapa en varierad undervisning. 

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