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  • 1. 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).

  • 2.
    Ahonen-Jonnarth, Ulla
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Dynamic web interface for metabolic pathways2002In: Promote IT 2002, 2002Conference paper (Other academic)
  • 3.
    Ahonen-Jonnarth, Ulla
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Göransson, A
    Finlay, R
    Growth and nutrient uptake of ectomycorrhizal Pinus sylvestris seedlings treated with elevated Al concentrations and decreased levels of base cations2003In: Tree Physiology, ISSN 0829-318X, E-ISSN 1758-4469, Vol. 23, no 3, p. 157-167Article in journal (Other academic)
    Abstract [en]

    Models of the effects of elevated concentrations of aluminum (Al) on growth and nutrient uptake of forest trees frequently ignore the effects of mycorrhizal fungi. In this study, we present novel data indicating that ectomycorrhizal mycelia may prevent leaching of base cations and Al. Mycorrhizal and non-mycorrhizal Pinus sylvestris L. seedlings were grown in sand obtained from the B-horizon of a local forest. In Experiment 1, non-mycorrhizal seedlings and seedlings inoculated with Hebeloma cf. longicaudum (Pers.: Fr.) Kumm. ss. Lange or Laccaria bicolor (Maire) Orton were provided with nutrient solution containing 2.5 mM Al. Aluminum did not affect growth of non-mycorrhizal seedlings or seedlings inoculated with L. bicolor. Seedlings colonized by H. cf. longicaudum had the highest biomass production of all seedlings grown without added Al, but the fungus did not tolerate Al. Shoots of seedlings colonized by L. bicolor had the lowest nitrogen (N) concentrations but the highest phosphorus (P) concentrations of all seedlings. The treatments had small but significant effects on shoot and root Al concentrations. In Experiment 2, inoculation with L. bicolor was factorially combined with the addition of a complete nutrient solution, or a solution lacking the base cations K, Ca and Mg, and solutions containing 0 or 0.74 mM Al. Seedling growth decreased in response to 0.74 mM Al, but the effect was significant only for non-mycorrhizal seedlings. Mycorrhizal seedlings generally had higher P concentrations than non-mycorrhizal seedlings. Aluminum reduced P uptake in non-mycorrhizal plants but had no effect on P uptake in mycorrhizal plants. Mycorrhizal colonization increased the pH of the soil solution by about 0.5 units and addition of Al decreased the pH by the same amount. We conclude that the presence of ectomycorrhizal mycelia decreased leaching of base cations and Al from the soil.

  • 4.
    Ahonen-Jonnarth, Ulla
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Odelstad, Jan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Evaluation of simulations with conflicting goals with application to cleaning of young forest stands2006In: Proceedings of ISC 2006 (Forth International Industrial Simulation Conference), 2006, p. 498-503Conference paper (Other academic)
  • 5.
    Ahonen-Jonnarth, Ulla
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Odelstad, Jan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Simulation of cleaning of young forest stands2005Report (Other academic)
  • 6.
    Ahonen-Jonnarth, Ulla
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Roitto, M
    Markkola, A M
    Ranta, H
    Neuvonen, S
    Effects of Nickel and Copper on Growth and Mycorrhiza of Scots Pine Seedlings Inoculated with Gremmeniella abietina2004In: Forest Pathology, ISSN 1437-4781, E-ISSN 1439-0329, Vol. 34, no 6, p. 337-348Article in journal (Other academic)
    Abstract [en]

    Scots pine (Pinus sylvestris) seedlings were planted in soil originating from two localities with different background levels of nickel and copper. In addition, some of the seedlings were exposed to additional nickel (20.5 mg Ni/l of soil) or copper (63.5 mg Cu/l of soil), or a combination of both Ni and Cu, via soil without direct shoot exposure during their second growing period. The seedlings were either irrigated with spring water (pH 6) or got only natural rain during the whole field experiment. All seedlings were inoculated with conidia of a shoot-pathogen Gremmeniella abietina during their third growing season, and harvested the following spring. Lengths of shoots of different year-classes were used as growth estimates. In roots, the proportion of fungal (assumedly mycorrhizal) biomass was estimated by measuring ergosterol concentration. Guajacol peroxidase activity was measured. Short roots were classified into two groups according to their condition and the composition of the mycorrhizal community was expressed as a proportion of morphotypes in the roots. The seedlings exposed to additional Ni had higher shoot growth than the seedlings in the other treatments. The mean Ni concentration in the roots of seedlings exposed to additional Ni was 79 p.p.m. and in other seedlings 16 p.p.m. Additional Ni also decreased the frequency of clearly senescent short roots and the proportion of the mycorrhizal morphotype with the thinnest mantle. These results indicate that the Ni exposure levels used in this experiment had some positive effects on the seedlings. The relative fungal biomass was about 6% lower (p = 0.0981) in the fine roots of seedlings treated with additional Cu. The mean Cu concentration in the roots of seedlings exposed to additional Cu was 256 p.p.m. and in other seedlings 29 p.p.m. Peroxidase activity, which was used as a general stress indicator in this study, was not affected by any of the treatments. The shoot growth and the relative biomass of fungi in the fine roots were positively correlated in all seedlings, and this correlation was stronger in seedlings exposed to additional Ni that were not irrigated compared with seedlings not exposed to additional Ni that were irrigated. The frequency of asymptomatic infections of G. abietina was positively correlated with the proportion of senescent short roots in the irrigated seedlings but not in not-irrigated seedlings. The general condition of seedlings may be an important factor for infection by G. abietina when moisture is high enough for the fungi to infect seedlings by conidia.

  • 7. Andersson, B
    et al.
    Bergholtz, M
    Grégoire, B
    Johannesson, P
    Schmitt, M
    Zdravkovic, Jelena
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    From Business to Process Models: a Chaining Methodology2006In: Proceedings of the 18th International Conference on Advanced Information Systems and Engineering (CAiSE’06), 2006Conference paper (Other academic)
    Abstract [en]

    In this paper we discuss the problem of how to go from a business model to a process model in a systematic way. Business models are economic models used for business analysis, while process models capture low-level business activities and their coordination. We propose a method that starts with a business model where the main actors and their relationships are identified. This forms a basis for design of a final process model. Processes are described in terms of patterns stored in a pattern library.

  • 8.
    Andersson, Sebastian
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Karaktärsdesign: från koncept till färdig spelkaraktär2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Denna rapport innefattar skapandeprocessen för en spelkaraktär. Vilka metoder som används i dagens industri och vilka verktyg som artisterna använder för att en 3dkaraktär till next-gen spel. Den undersöker även vilka slags tekniker som används för att skapa en personlighet och ett utseende som gör karaktären minnesvärd. Vilka metoder som kan användas för att skapa en viss känsla hos karaktärer. Rapporten går också igenom en av alla de olika vägarna man kan ta för att skapa en karaktär från koncept till färdig spelkaraktär. Detta med hjälp av välkända program och tekniker som används.

  • 9. Barerra, Tony
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, Ewert
    An Alternative Model for Real-Time Rendering of Diffuse Light for Rough Materials2005In: SCCG '05 Proceedings II, 2005, p. 27-28Conference paper (Other academic)
  • 10.
    Barreby, Martin
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    When is it Necessary to Use Muscle Systems to Enhance 3D Animation?2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

     

    To build muscles to enhance the animation of a 3D character takes more time and effort than the standard character rig. In some cases, the muscles will not be noticeable and therefore are unnecessary. This research tried to find the moments when the muscles did or did not make a difference. The new Maya Muscle System is also explored and the procedure to create muscles for a standard rig is explained. The test that was performed showed that the muscles are more noticeable in all cases.

     

  • 11. Barrera, T
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, E
    A Fast All-Integer Ellipse Discretization Algorithm2003In: Graphics Programming Methods / [ed] Jeff Lander, Hingham, Mass.: Charles River Media , 2003, p. 121-132Chapter in book (Other academic)
  • 12. Barrera, T
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, E
    A Fast and Simple All-Integer Parametric Line2003In: Graphics Programming Methods / [ed] Jeff Lander, Hingham, Mass.: Charles River Media , 2003Chapter in book (Other academic)
  • 13. Barrera, T
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, E
    Fast Near Phong-Quality Software Shading2006In: WSCG'06, 2006Conference paper (Refereed)
    Abstract [en]

    Quadratic shading has been proposed as a technique giving better results than Gouraud shading, but which is substantially faster than Phong shading. Several techniques for fitting a second order surface to six points have been proposed. We show in this paper how an approximation of the mid-edge samples can be done in a very efficient way. An approximation of the mid-edge vectors are derived. Several advantages are apparent when these vectors are put into the original formulation. First of all it will only depend on the vertex vectors. Moreover, it will simplify the setup and no extra square roots are necessary for normalizing the mid-edge vectors. The setup will be about three times faster than previous approaches. This makes quadratic shading very fast for interpolation of both diffuse and specular light, which will make it suitable for near Phong quality software renderings.

  • 14. Barrera, T
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, E
    Faster shading by equal angle interpolation of vectors2004In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 10, no 2, p. 217-223Article in journal (Refereed)
    Abstract [en]

    In this paper, we show how spherical linear interpolation can be used to produce shading with a quality at least similar to Phong shading at a computational effort in the inner loop that is close to that of the Gouraud method. We show how to use the Chebyshev's recurrence relation in order to compute the shading very efficiently. Furthermore, it can also be used to interpolate vectors in such a way that normalization is not necessary, which will make the interpolation very fast. The somewhat larger setup effort required by this approach can be handled through table look up techniques.

  • 15. Barrera, T
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, E
    Incremental Spherical Linear Interpolation2004In: Sigrad 2004, 2004, p. 7-10Conference paper (Refereed)
  • 16. Barrera, T
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, E
    Surface Construction with Near Least Square Acceleration based on Vertex Normals on Triangular Meshes2002In: Proceedings from Sigrad 2002, 2002, p. 43-48Conference paper (Refereed)
  • 17. Barrera, Tony
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, Ewert
    Connected Minimal Acceleration Trigonometric Curves2005Conference paper (Refereed)
    Abstract [en]

    We present a technique that can be used to obtain a series of connected minimal bending trigonometric splines that will intersect any number of predefined points in space. The minimal bending property is obtained by a least square minimization of the acceleration. Each curve segment between two consecutive points will be a trigonometric Hermite spline obtained from a Fourier series and its four first terms. The proposed method can be used for a number of points and predefined tangents. The tangent length will then be optimized to yield a minimal bending curve. We also show how both the tangent direction and length can be optimized to give as smooth curves as possible. It is also possible to obtain a closed loop of minimal bending curves. These types of curves can be useful tools for 3D modelling, etc.

  • 18. Barrera, Tony
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, Ewert
    Minimal Acceleration Hermite Curves2005In: Game programming gems 5 / [ed] Kim Pallister, Hingham, Massachusetts: Charles River Media, inc. , 2005, p. 225-231Chapter in book (Other (popular science, discussion, etc.))
  • 19. Barrera, Tony
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, Ewert
    Trigonometric Splines2008In: Game Programming Gems 7, Boston: Charles River Media , 2008, p. 191-198Chapter in book (Refereed)
  • 20. Barrera, Tony
    et al.
    Spångberg, Daniel
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, Ewert
    Vectorized table driven algorithms for double precision elementary functions using Taylor expansions2009In: APLIMAT 8th international conference, 2009, p. 231-246Conference paper (Refereed)
    Abstract [en]

    This paper presents fast implementations of the inverse square root and arcsine, both in double precision. In single precision it is often possible to use a small table and one ordinary Newton-Raphson iteration to compute elementary functions such as the square root. In double precision a substantially larger table is necessary to obtain the desired precision, or, if a smaller table is used, the additional Newton-Raphson iterations required to obtain the precision often requires the evaluation of other expensive elementary functions. Furthermore, large tables use a lot of the cash memory that should have been used for the application code.

    Obtaining the desired precision using a small table can instead be realised by using a higher order method than the second order Newton-Raphson method. A generalization of Newton's method to higher order is Householder's method, which unfortunately often results in very complicated expressions requiring many multiplications, additions, and even divisions.

    We show how a high-order method can be used, which only requires a few extra additions and multiplications for each degree of higher order. The method starts from the Taylor expansion of the difference of the value of the elementary function and a starting guess value for each iteration. If the Taylor series is truncated after the second term, ordinary Newton iterations are obtained. In several cases it is possible to algebraically simplify the difference between the true value and the starting guess value. In those cases we show that it is advantageous to use the Taylor series to higher order to obtain the fast convergent method. Moreover, we will show how the coefficients of a Chebyshev polynomial can be fitted to give as little error as possible for the functions close to zero and in the same time reduce the terms in the Taylor expansion.

    In the paper we benchmark two example implementations of the method on the x86_64 architecture. The first is the inverse square root, where the actual table (to 12 bit precision) is provided by the processor hardware. The inverse square root is important in many application programs, including computer graphics, and explicit particle simulation codes, for instance the Monte Carlo and Molecular Dynamics methods of statistical mechanics. The other example is the arcsine function, which has a slow converging Taylor expansion and where no tables are provided by the hardware. The vectorized versions of the implementations of the inverse square root are 3.5 times faster than compiled code on the Athlon64 and about 5 times faster on the Core 2. The scalar version of the arcsine function is, depending on order and table size, between 2 and 3 times faster than the compiled code, and the vectorized version is between 3 and 4 times faster on the Athlon64, while it is between 4 and 5 times faster than the compiled version on the Core 2.

  • 21. Barrera, Tony
    et al.
    Spångberg, Daniel
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Bengtsson, Ewert
    Vectorized table driven algorithms for double precision elementary functions using Taylor expansions2009In: Aplimat - Journal of Applied Mathematics, ISSN 1337-6365, Vol. 2, no 3, p. 171-188Article in journal (Refereed)
    Abstract [en]

    This paper presents fast implementations of the inverse square root and arcsine, both in double precision. In single precision it is often possible to use a small table and one ordinary Newton-Raphson iteration to compute elementary functions such as the square root. In double precision a substantially larger table is necessary to obtain the desired precision, or, if a smaller table is used, the additional Newton-Raphson iterations required to obtain the precision often requires the evaluation of other expensive elementary functions. Furthermore, large tables use a lot of the cash memory that should have been used for the application code.

    Obtaining the desired precision using a small table can instead be realised by using a higher order method than the second order Newton-Raphson method. A generalization of Newton's method to higher order is Householder's method, which unfortunately often results in very complicated expressions requiring many multiplications, additions, and even divisions.

    We show how a high-order method can be used, which only requires a few extra additions and multiplications for each degree of higher order. The method starts from the Taylor expansion of the difference of the value of the elementary function and a starting guess value for each iteration. If the Taylor series is truncated after the second term, ordinary Newton iterations are obtained. In several cases it is possible to algebraically simplify the difference between the true value and the starting guess value. In those cases we show that it is advantageous to use the Taylor series to higher order to obtain the fast convergent method. Moreover, we will show how the coefficients of a Chebyshev polynomial can be fitted to give as little error as possible for the functions close to zero and in the same time reduce the terms in the Taylor expansion.

    In the paper we benchmark two example implementations of the method on the x86_64 architecture. The first is the inverse square root, where the actual table (to 12 bit precision) is provided by the processor hardware. The inverse square root is important in many application programs, including computer graphics, and explicit particle simulation codes, for instance the Monte Carlo and Molecular Dynamics methods of statistical mechanics. The other example is the arcsine function, which has a slow converging Taylor expansion and where no tables are provided by the hardware. The vectorized versions of the implementations of the inverse square root are 3.5 times faster than compiled code on the Athlon64 and about 5 times faster on the Core 2. The scalar version of the arcsine function is, depending on order and table size, between 2 and 3 times faster than the compiled code, and the vectorized version is between 3 and 4 times faster on the Athlon64, while it is between 4 and 5 times faster than the compiled version on the Core 2.

  • 22. Bergholtz, M
    et al.
    Grégoire, B
    Johannesson, P
    Schmit, M
    Wohed, P
    Zdravkovic, Jelena
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Integrated Methodology for Linking Business and Process Models with Risk Mitigation2005In: Proceedings of the INTEROP REBNITA’05 Workshop, 2005Conference paper (Other academic)
  • 23.
    Bergsten, Marcus
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
     Visualisering av multidimensionella data med hjälp av parallella koordinater2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Problem består ofta av flera variabler som behöver sammanvägas för att vi ska kunna fatta ett beslut om vilket alternativ som är bäst. Detta gör vi var och varannan dag. Med detta arbete görs ett försök att skapa en integrerad webblösning som hämtar information och visualiserar den på ett sätt som förenklar ett beslutsfattande. Till hjälp för detta användes parallella koordinater.

  • 24.
    Björklund, Niklas
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Acting in animation2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    It is important to remember actors and animators are similar in many respects, but also very different in some. They both frame and provide life to a character, through thoughts and feelings. To obtain a better understanding of how professional animators work and what methods they use, this thesis contains general background information on animation and the Principles in Animation, as well as the analysis of acting and the different acting concepts. By studying these methods and utilizing them in my own work, a short animation was developed to visualize a characters personality through his actions. The result was then applied to a questionnaire to determine if the audience could pick out the characters personality only through the animation without dialog, music, or sound. According to the interviewed audience, they could feel some of the characters emotions and pick out some of the inner thoughts and feelings from the animation.

  • 25.
    Boustedt, Jonas
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    A methodology for exploring students’ experiences and interaction with large-scale software through role-play and phenomenography2008In: ICER '08: proceedings of the fourth international workshop on Computing education research, New York: ACM , 2008, p. 27-38Conference paper (Refereed)
    Abstract [en]

    Traditional interview methods within qualitative research often capture the purely academic perspective on phenomena. To address this problem, an innovative research method, combining role-playing with phenomenography is proposed. The approach suggested in this paper aims to stimulate participants to widen their perspectives by encouraging them to a deeper engagement with a specific activity, thereby enabling them to reflect actively on their actions and on concepts involved in a specific situated context. In the outlined strategy, the role-playing involved realistic work with large-scale software. This was immediately followed by a debriefing using phenomenographic research interviews when the participants still had the experience fresh in mind. The phenomenographic analysis of the interview transcripts confirmed that the method was successful. The subjects frequently expressed their understanding of theoretical concepts in relation to their experiences from working with the software. The more advanced ways to experience the phenomena was often expressed – and sometimes inspired – by the software’s way to take advantage of the concepts. The specific use of the described method resulted in empirical insights into how students experience object-oriented concepts in software engineering, such as the Java Interface.

  • 26.
    Boustedt, Jonas
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Automated Analysis of Dynamic Web Services2002Report (Other academic)
    Abstract [en]

    For a web application test-engineer, it would be convenient to have a map, in form of a graph, describing the functional topology of the application. In that way, it would be possible to analyse the possible paths which can be navigated to discover redundancies and circularities for example. A web spider tool can automate the construction of such a graph. The spider can request a document from the application, find all references to other documents in it, and explore them recursively until all the references have been analysed. However, web services often produce dynamic responses which means that the content cannot be distinctly represented by its reference, i.e., the responses must be classified in a way that matches the users perception. The main problem is to find suitable criteria for this classification. This study describes how to make such a tool and it surveys ideas for how to create a classifying identifier for dynamic responses. The implemented spider was used to make experiments on selected web services, using different models for web node identification. The result is a proposal of suitable criteria for classification of dynamic responses, coming from web applications. These criteria are implemented in algorithms which use the parse structure and the set of internal references as the dominant terms of identification.

  • 27.
    Boustedt, Jonas
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Students' Understanding of the Concept of Interface in a Situated Context2009In: Computer Science Education, ISSN 0899-3408, E-ISSN 1744-5175, Vol. 19, no 1, p. 15-36Article in journal (Refereed)
    Abstract [en]

    The paper describes an empirical study with the aim of producing insights about how students experience programming and software engineering. The research aims to investigate the students’ world, and hence, we have chosen a phenomenographic approach. Our questions focus on the students’ experience of concepts related to a realistic programming task in an extensive software system, particularly the Java Interface. The results show that there is a distinct variation of descriptions spanning from a concrete to-do list to a more advanced description where the interface plays a crucial role in order to produce dynamic and adaptive systems. We interpret the results and suggest how they can be used in teaching to provide an extended and varied understanding for how to work with advanced software.

  • 28.
    Boustedt, Jonas
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Students working with a large software system: experiences and understandings2007Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This monograph describes an empirical study with the overall aim of producing insights about how students experience the subject Computer Science and its learning environments, particularly programming and software engineering.

    The research takes a start in the students' world, from their perspective, using their stories, and hence, we have chosen a phenomenographic approach for our research. By interpreting the students' descriptions and experiences of various phenomena and situations, it is possible to gain knowledge about which different conceptions students can have and how teaching and the learning environment affect their understanding. In this study, we focus specifically on students' conceptions of aspects of object-oriented programming and their experiences of problem solving situations in connection with object-oriented system development.

    The questions posed enlighten and focus on the students' conceptions of both tangible and abstract concepts; the study investigates how students experienced a task concerning development in a specific software system, how they conceived the system itself, and how the students describe the system's plugin modules. Academic education in programming deals with abstract concepts, such as interfaces in the programming language Java. Hence, one of the questions in this study is how students describe that specific abstract concept, in a context where they are conducting a realistic software engineering task.

    The results show that there is a distinct variation of descriptions, spanning from a concrete to-do list, to a more advanced description where the interface plays a crucial role in order to produce dynamic and adaptive systems. The discussion interprets the results and suggests how we can use them in teaching to provide an extended and varied understanding, where the educational goal is to provide for and strengthen the conditions for students to be able to learn how to develop and understand advanced software.

  • 29.
    Boustedt, Jonas
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Eckerdal, Anna
    McCartney, Robert
    Moström, Jan Erik
    Ratcliffe, Mark
    Sanders, Kate
    Zander, Carol
    Threshold concepts in computer science: do they exist and are they useful?2007In: SIGCSE Bulletin inroads, ISSN 0097-8418, Vol. 39, no 1, p. 504-508Article in journal (Other academic)
    Abstract [en]

    Yes, and Yes.

    We are currently undertaking an empirical investigation of “Threshold Concepts” in Computer Science, with input from both instructors and students. We have found good empirical evidence that at least two concepts—Object-oriented programming and pointers—are Threshold Concepts, and that there are potentially many more others.

    In this paper, we present results gathered using various experimental techniques, and discuss how Threshold Concepts can affect the learning process.

  • 30.
    Boustedt, Jonas
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    McCartney, Robert
    Department of Computer Science and Engineering, University of Connecticut, United States.
    Deibel, Katherine
    Department of Computer Science and Engineering, University of Washington, Seattle, United States.
    Huggins, Jim
    Department of Computer Science, Kettering University, United States.
    Simon, Beth
    Department of Computer Science and Engineering, University of California San Diego, San Diego, United States.
    Westbrook, Suzanne
    Department of Computer Science, University of Arizona, Tucson, United States.
    It seemed like a good idea at the time2009In: SIGCSE '09: Proceedings of the 40th ACM technical symposium on Computer science education, New York, NY, USA: ACM , 2009, p. 265-266Conference paper (Refereed)
    Abstract [en]

    We often learn of successful pedagogical experiments, but we seldom hear of the the ones that failed. For this special session we solicited submissions from the SIGCSE membership, selected the best from among these, and will have presentations at the session by the selected authors. Our contributions describe pedagogical approaches that seemed to be good ideas but turned out as failures. At the session, contributors will describe their pedagogical experiment, the rationale for the experiment, evidence of failure, and lessons learned.

  • 31.
    Boustedt, Jonas
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    McCartney, Robert
    University of Conneticut.
    Tenenberg, Josh
    University of Washington, Tacoma, United States.
    Anderson, Scott D.
    Wellesley College.
    Eastman, Caroline M.
    University of South Carolina.
    Garcia, Daniel D.
    University of California, Berkeley, United States.
    Gestwicki, Paul V.
    Ball State University.
    Menzin, Margaret S.
    Simmons college.
    It seemed like a good idea at the time2008In: SIGCSE '08: Proceedings of the 39th ACM Technical Symposium on Computer Science Education, 2008, p. 528-529Conference paper (Other academic)
    Abstract [en]

    We often learn of successful pedagogical experiments, but we seldom hear of the the ones that failed. For this special session we solicited submissions from the SIGCSE membership, selected the best from among these, and will have presentations at the session by the selected authors. Our contributions describe pedagogical approaches that seemed to be good ideas but turned out as failures. Contributors will describe their pedagogical experiment, the rationale for the experiment, evidence of failure, and lessons learned.

  • 32.
    Boustedt, Jonas
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    McCartney, Robert
    University of Connecticut.
    Tenenberg, Josh
    University of Washington, Tacoma, USA.
    Winters, Titus
    University of California, Riverside, USA.
    Edwards, Stephen
    Virginia Tech (VPI and SU), USA.
    Morrison, Briana B.
    So. Polytechnic St. University.
    Musicant, David R.
    Carleton College.
    Utting, Ian
    University of Kent, Canterbury, United Kingdom.
    Zander, Carol
    University of Washington, Bothell, USA.
    It seemed like a good idea at the time2007In: SIGCSE '07: Proceedings of the 38th SIGCSE technical symposium on Computer science education, 2007, p. 346-347Conference paper (Other academic)
    Abstract [en]

    We often learn of successful pedagogical experiments, but we seldom hear of the the ones that failed. From an epistemological point of view, learning from failures can be at least as effecitive as learning from good examples. This special session has a structure similar to that of Parlante’s Nifty Assignments, i.e. we solicited submissions from the SIGCSE membership, selected the best from among these, and have presentations at the session by the selected authors. Our contributions describe pedagogical approaches that seemed to be good ideas but turned out as failures. Contributors will describe their pedagogical experiment, the rationale for the experiment, evidence of failure, and lessons learned.

  • 33.
    Christiansson, Kajsa
    University of Gävle. University of Gävle, Department of Mathematics, Natural and Computer Sciences. University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Walk-A-Way: A Maya Plug-in for Walk Cycle Automation2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In 3D and 2D animations walk cycles of characters appear very frequently and are an important way of expressing various aspects of the story told. However walk cycles are tedious and time consuming to animate. In this work an Autodesk MAYA plug-in has been developed, that aims at automating this process. The walk cycle plug-in can be highly beneficial for animators when creating convincing walk cycles in a fast and simple way. The plug-in calculates the right values for each phase in the walk cycle. The GUI of the plug-in makes it easy to provide the required input parameters. In addition, the plug-in allows the animation of a character to walk along a chosen path.

  • 34. Crnkovic, I
    et al.
    Hnich, B
    Jonsson, Torsten
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Kiziltan, Z
    Basic Concepts in CBSE2002In: Building Reliable Component-Based Software Systems / [ed] Ivica Crnkovic, Magnus Larsson, Boston: Artech House Publishers , 2002Chapter in book (Other academic)
  • 35. Crnkovic, Ivica
    et al.
    Hnich, Brahim
    Jonsson, Torsten
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Kiziltan, Zeynep
    Specification, implementation, and deployment of components2002In: Communications of the ACM, ISSN 0001-0782, E-ISSN 1557-7317, Vol. 45, no 10, p. 35-40Article in journal (Refereed)
  • 36.
    Dogantimur, Erkan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    A method to generate modern city buildings with the aid of Python-scripting2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    It takes time to model buildings in a 3D city environment, for example in a game. Time is usually something very constricted in a production stage of anything, whether it is a personal project at home, at school or more occurring; in the 3D industry. This report will bring forth a method to quickly generate detailed buildings with the help of Python scripting, integrated in Maya 2009. The script will be working with modules that will be assembled together to create a modern city type of building. A comparison will be made between this script and a couple other scripts that offer the same solution but in different ways.

  • 37. Ericsson, Martin
    et al.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Nyström, Ingela
    Interactivity, Quality and Usability: Three-Dimensional Image Studio for Uppsala2008In: SIGRAD, 2008, p. 79-80Conference paper (Refereed)
  • 38.
    Eriksson, Lars-Peter
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Effektsekvens på hal is2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Detta examensarbete handlar ”Verklighetstrogen Effektskomposition”. Målet med arbetet är att undersöka och utnyttja alla de olika aspekterna som gör att en film med specialeffekter känns så verklighetstrogen som möjligt. Arbetet handlar om de olika delarna i en filmproduktionsfas så som pre-production,production och post-production. Filmen som skapas är en specialeffektsbaserad hemmavideo som har som syfte att vara så chockande som möjligt i förhållande till vad man förväntar sig när man börjar kolla. Arbetets fokus ligger mycket på tracking i en svårtrackad miljö där detta problem kommer att lösas.

  • 39.
    Forsberg, Ann-Kristin
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    How to Create a More Efficient User Interface in the Harvester2003In: Proceedings of the 2nd Forest Engineering Conference, 2003: Decision support system/tools, 2003, p. 113-124Conference paper (Other academic)
  • 40.
    Forsberg, Ann-Kristin
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Winkler Pettersson, Lars
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Linden, Elisabet
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    An augmented-reality approach to co-located visual exploration of indoor climate data in real rooms2005In: Indoor Air 2005: Proceedings of the 10th International Conference on Indoor Air Quality and Climate, 2005, p. 2860-2860Conference paper (Other academic)
    Abstract [en]

    We live in two spaces, the visible space and the non-visible but otherwise sensed space. Both spaces must satisfy our needs and there is a relation between them. If parts of the room are too cold this will lead to a restriction of the use of the room. We cannot endure draft for any longer time. Draft caused by a ventilation supply frequently leads to blockage of the supply device, which in turn gives rise to a reduction of the ventilation rate. The final result may be a deterioration of the air quality. Therefore, to be able to guarantee the air quality it is necessary to make the invisible thermal climate visible. In this paper a novel method based on Augmented Reality for presenting die thermal climate is presented and discussed. The data, e.g. temperatures and velocities, are shown on a lightweight display. Several people can walk around in a real room and see on a screen where the hot and/or cold spots may appear. Different ventilation solutions could in that way be compared in a dialogue between different actors in the building process.

  • 41. Forsell, C
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Lind, M
    Simple 3D Glyphs for Spatial Multivariate Data2005In: Proceedings of the IEEE Symposium on Information Visualization – Infovis 2005, 2005, p. 119-124Conference paper (Other academic)
    Abstract [en]

    We present an effort to evaluate the possible utility of a new type of 3D glyphs intended for visualizations of multivariate spatial data. They are based on results from vision research suggesting that our perception of metric 3D structure is distorted and imprecise relative to the actual scene before us (e.g., [1]); only a class of qualitative properties of the scene is perceived with accuracy. These properties are best characterized as being invariant over affine but not Euclidean transformations. They are related, but not identical to, the non-accidental properties (NAPs) described by Lowe [2] on which the notion of geons is based [3]. A large number of possible 3D glyphs for the visualization of spatial data can be constructed using such properties. One group is based on the local sign of surface curvature. We investigated these properties in a visualization experiment. The results are promising and the implications for visualization are discussed.

  • 42. Forsell, C
    et al.
    Seipel, Stefan
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Lind, M
    Surface Glyphs for Efficient Visualization of Multivariate Data2006In: Information Visualization, ISSN 1473-8716, E-ISSN 1473-8724, Vol. 5, no 2, p. 112-124Article in journal (Other academic)
    Abstract [en]

    We present a first effort to evaluate the possible utility of a new type of surface glyphs intended for visualizations of multivariate spatial data. The glyphs are based on results from vision research suggesting that our perception of metric 3D structure is distorted and imprecise relative to the actual scene before us; only a class of qualitative properties of the scene is perceived with accuracy. These properties are best characterized as being invariant over affine but not Euclidean transformations. A large number of possible 3D glyphs for the visualization of spatial data can be constructed using such properties. One group of such glyphs is based on the local sign of surface curvature. We investigated this group in two visualization experiments. The results show that available sources of 3D structural information were sufficient for our subjects to make fast and accurate judgments. Some implications for visualization are also discussed.

  • 43.
    Granskog, Karl-Adam
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Integrerad video och digital grafik med fokus på postproduktion2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I detta examensarbete beskrivs kombinationen av video och digital grafik vid filmproduktion. Jag kommer att förklara filmproduktionens olika stadier med fokus på postproduktionen. Jag behandlar frågor som förklarar vad postproduktion är, hur det går till samt olika tekniker inom den digitala postproduktionen för att kombinera video och digital teknik. Målet med arbetet är att undersöka och beskriva det digitala arbetssättet inom modern filmproduktion genom att förklara metoder och tekniska lösningar generellt samt i ljuset av ett mindre videoprojekt.Nyckelord: examensarbete, postproduktion, redigering, digital postproduktion, keying, keyframing, tracking, mask, matte, färgkorrigering, video.

  • 44.
    Gustafsson, Pär
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Digital compositing i 3D-miljö2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I dagens visuella effekter är digital compositing en av de viktigaste processerna. Från att uteslutande ha utförts i 2D har digital compositing dock kommit att innebära en alltmer tredimensionell process. Det här arbetet reder ut begreppet 3D-compositing och sammanställer vilka 3D-compositingtekniker som är vanligt förekommande. Ett urval av dessa tekniker tillämpas sedan i en egen effektsekvens. Slutsatsen blir att det är kombinationen av 3D-funkionalitet och 2D-compositing i samma program som är styrkan med digital compositing i 3D-miljö.

  • 45.
    Haglund, Håkan
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Andersson, Mattias
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Snow Accumulation in Real-time2002In: Proceedings from SIGRAD 2002, 2002, p. 11-15Conference paper (Refereed)
    Abstract [en]

    Whenever real-time snowfall is animated in computer games, no snow accumulation is simulated, as far as we know. Instead, so-called zero thickness is used, which means that the blanket of snow does not grow when the snowflakes reach the ground. In this paper we present a method for simulation of snow accumulation, which simulates the different stages, starting with a snow free environment and ending with a totally snow covered scene, all in real-time. The main focus is not on the physical properties of snow but on speed and visual result.

  • 46. Harjula, Erkki
    et al.
    Ala-Kurikka, Jussi
    Howie, Douglas
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Ylianttila, Mika
    Analysis of Peer-to-Peer SIP in a Distributed Mobile Middleware System2006In: 49th IEEE Global Telecommunications Conference, 2006Conference paper (Refereed)
    Abstract [en]

    The seamless and flexible interconnection of the existing and emerging protocols and networks is essential to the success of the new generation mobile applications and services. For exploiting the functional diversity, we have developed a middleware for mobile devices called the Plug-and-Play Application Platform (PnPAP). We have previously studied the Session Initiation Protocol (SIP) as an interconnecting protocol for the PnPAP nodes. In this paper, we analyze the usage of a new variant of SIP called Peer-to-Peer SIP (P2P SIP) for this purpose. Our interconnection architecture utilizes layered (hierarchical) P2P SIP to establish a self-organizing, failure tolerant overlay signaling network between PnPAP nodes. Signaling latency and scalability of the layered P2P SIP signaling is compared in a simulation environment with both the traditional client-server SIP and fully distributed P2P SIP. Simulation results illustrate the benefits of the layered P2P SIP solution where only the supernodes participate to the DHT management, enabling light-weight peer node implementation for mobile nodes.

  • 47.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    A Model for Anisotropic Shading of Fibers with varying Topology2006In: SCCG'06, 2006Conference paper (Refereed)
  • 48.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    An Alternative Model for Shading of Diffuse Light for Rough Materials2008In: Game Programming Gems 7 / [ed] Scott Jacobs, Boston: Charles River Media , 2008, p. 191-198Chapter in book (Other (popular science, discussion, etc.))
  • 49.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Elementary Predicates for Continuous Collision Detection,2008In: Proceedings of the 13th International Conference on Geometry and Graphics, Dresden: Technische Universität , 2008, p. 1-10Conference paper (Refereed)
  • 50.
    Hast, Anders
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Geometry of fibers with varying topology2006In: Extended abstract in Proceedings of the 9th Conference “Geometry and Computer”, 2006, p. 25-26Conference paper (Other academic)
    Abstract [en]

    Anisotropic shading techniques can be used for materials like hair and silk. Such materials have a surface consisting of very small fibers having a main direction. Geometrically each fiber can be viewed as a cylinder. Poulin and Fournier proposed an illumination model for such materials using a flat topology only. In the paper a model using a varying topology is described. The varying topology is a more correct model and visible differences are clearly apparent.

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