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  • 1. Adams, R
    et al.
    Lindberg, Vanja
    What is the word for engineering in Swedish: students conception of their discipline2007Other (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 students 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. Alexandrova, A. A.
    et al.
    Ibragimov, Nail
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Lukashchuk, V. O.
    Group classification and conservation laws of nonlinear filtration equation with a small parameter2014In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 19, no 2, 364-370 p.Article in journal (Refereed)
    Abstract [en]

    Group classification of the perturbed nonlinear filtration equation is performed assuming that the perturbation is an arbitrary function of the dependent variable. The nonlinear self-adjointness of the equation under consideration is investigated. Using these results, the approximate conservation laws are constructed.

  • 3. Avdonina, Elena D.
    et al.
    Ibragimov, Nail H.
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Heat conduction in anisotropic media: Nonlinear self-adjointness and conservation laws2012In: Discontinuity, Nonlinearity and Complexity, ISSN 2164-6376, Vol. 1, no 3, 237-251 p.Article in journal (Refereed)
    Abstract [en]

    Nonlinear self-adjointness of the anisotropic nonlinear heat equation is investigated. Mathematical models of heat conduction in anisotropic media with a source are considered and a class of self-adjoint models is identified. Conservation laws corresponding to the symmetries of the equations in question are computed.

  • 4. Avdonina, Elena D.
    et al.
    Ibragimov, Nail H.
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Khamitova, Raisa
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Exact solutions of gasdynamic equations obtained by the method of conservation laws2013In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 18Article in journal (Refereed)
    Abstract [en]

    In the present paper, the recent method of conservation laws for constructing exact solutions for systems of nonlinear partial differential equations is applied to the gasdynamic equations describing one-dimensional and three-dimensional polytropic flows. In the one-dimensional case singular solutions are constructed in closed forms. In the threedimensional case several conservation laws are used simultaneously. It is shown that the method of conservation laws leads to particular solutions different from group invariant solutions.

  • 5.
    AWOMEWE, Alaba-Femi
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Monitoring the volatility in a process which reflects trading in the financial market2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Recently, the financial market has become an area of increased research interest for mathematician and statisticians. The Black and Scholes breakthrough in this area triggered a lot of new research activity. Commonly the research concerns the log returns of assets (shares, bond, foreign exchange, option). The variation in the log returns is called volatility and it is widely studied and because of its relevance for applications in the financial world. The volatility is mostly used for measuring the risk and also for forecasting future prices. In this research work a process of trading activities is considered. It is assumed that at a random time-point a parameter change in the laws of the trading occurs, indicating changed trading behaviour. For inferential matters about the process it is of vital importance to be able to state that such change has occurred quickly and accurately. The methods used to this end are called stopping rules which signal alarm as soon as some statistics based on-line observations goes beyond some boundary. The model considered for this process of log returns is the family of Autoregressive Conditional Heteroskedastic (ARCH) model. It is widely accepted that this well describes a lot of phenomena in the financial market. In this work statements about this process will be derived, the stopping rule will be defined, evaluated and their properties discussed.

  • 6.
    Ayub, Muhammad
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Choquet and Sugeno Integrals2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In real word many problems, most of criteria have interdependent or interactive characteristics, which cannot be evaluated by additive measures exactly. For the human subjective evaluation processes it will be more better to apply Choquet and Sugeno integrals model together with the definition of lambda − fuzzy measure, in which the property of additivity is not necessary. My thesis presents the application of fuzzy integrals as tool for criteria aggregation in the decision problems. Finally, this research gives the examples of evaluating medicine with illustrations of hierarchicalstructure of lambda− fuzzy measure for Choquet and Sugeno integrals model.

  • 7.
    AZIZ, YASSAR
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    ASLAM, MUHAMMAD NAEEM
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Traffic Engineering with Multi-Protocol Label Switching, Performance Comparison with IP networks2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Traffic Engineering (TE) is the stage which deals with geometric design planning and traffic operation of networks, network devices and relationship of routers for the transportation of data. TE is that feature of network engineering which concentrate on problems of performance optimization of operational networks. It involves techniques and application of knowledge to gain performance objectives, which includes movement of data through network, reliability, planning of network capacity and efficient use of network resources. This thesis addresses the problems of traffic engineering and suggests a solution by using the concept of Multi-Protocol Label Switching (MPLS). We have done simulation in Matlab environment to compare the performance of MPLS against the IP network in a simulated environment. MPLS is a modern technique for forwarding network data. It broadens routing according to path controlling and packet forwarding. In this thesis MPLS is computed on the basis of its performance, efficiency for sending data from source to destination. A MATLAB based simulation tool is developed to compare MPLS with IP network in a simulated environment. The results show the performance of MPLS network in comparison of IP network.

  • 8. Baikov, V. A.
    et al.
    Ibragimov, Nail
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Zheltova, I. S.
    Yakovlev, A. A.
    Conservation laws for two-phase filtration models2014In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 19, no 2, 383-389 p.Article in journal (Refereed)
    Abstract [en]

    The paper is devoted to investigation of group properties of a one-dimensional model of two-phase filtration in porous medium. Along with the general model, some of its particular cases widely used in oil-field development are discussed. The Buckley-Leverett model is considered in detail as a particular case of the one-dimensional filtration model. This model is constructed under the assumption that filtration is one-dimensional and horizontally directed, the porous medium is homogeneous and incompressible, the filtering fluids are also incompressible. The model of "chromatic fluid" filtration is also investigated. New conservation laws and particular solutions are constructed using symmetries and nonlinear self-adjointness of the system of equations.

  • 9. Ballal, Tarig
    et al.
    Grbic, Nedelko
    Mohammed, Abbas
    Blind Source Separation of Speech Mixtures using a Simple and Computationally Efficient Time-Frequency Approach2007Conference paper (Refereed)
  • 10. Berglund, Johan
    Association of diagnosis of ischaemic heart disease, diabetes mellitus and heart failure with cognitive function in the elderly population.2006In: European Journal of General Practice, ISSN 1381-4788, E-ISSN 1751-1402, Vol. 12, no 3, 114-119 p.Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: The aim of this study was to describe the association between ischaemic heart disease (IHD), diabetes mellitus (DM) and heart failure (HF) and the prevalence of cognitive impairment. METHODS: In a cross-sectional, community-based study in Karlskrona, Sweden, 1402 participants of the Swedish National Study on Ageing and Care (60-96 y) underwent a medical examination and psychological testing including the Mini Mental State Examination (MMSE). Of these, 58% stated that they were treated for hypertension, IHD, DM or HF, or had ECG abnormalities (positive screen). RESULTS: The prevalence of cognitive impairment (MMSE score < 24) in patients treated for IHD, DM or HF was 28.5% compared to 16.1% in the population with a negative screen without cardiovascular disease or DM. After stratification by age, the difference was seen to be due to a higher prevalence of cognitive impairment in the age group 70-79 y, where 68.8% of the cognitively impaired came from the group treated for IHD, DM or HF. The odds ratio for cognitive impairment in this age group was 4.4 (95% CI 1.7-11.4), when compared to those with a negative screen as baseline. CONCLUSION: This study has shown that the patient group treated for IHD, DM or HF has a higher prevalence of cognitive impairment and a higher risk of developing early cognitive impairment between the ages of 70 and 79 y. Although this study has not provided conclusive evidence that cardiovascular disease and DM are associated with the early development of cognitive impairment, it provides incentive for further studies.

  • 11. Berglund, Johan
    et al.
    Stjernberg, Louise
    Ornstein, Katharina
    Tykesson/Joelsson, Katarina
    Walter, Hallstein
    5-y follow-up study of patients with neuroborreliosis2002In: Scandinavian Journal of Infectious Diseases, ISSN 0036-5548, E-ISSN 1651-1980, Vol. 34, no 6, 421-425 p.Article in journal (Refereed)
    Abstract [en]

    The objective of this follow-up study was to determine the long-term outcome of strictly classified cases of neuroborreliosis treated with antibiotics. A one-year prospective population-based survey of Lyme borreliosis was conducted in southern Sweden, between 1992 and 1993. A total of 349 identified cases with suspected neuroborreliosis were followed up 5 years later. Medical records were reviewed and all participants filled in a questionnaire. Of those classified with definite neuroborreliosis 114/130 completed the follow-up, of whom 111 had completed the initial antibiotic treatment. Of the 114 patients followed up, 86 (75%) had recovered completely and 70 (61%) had recovered within 6 months. Residual neurological symptoms such as facial palsy, concentration disorder, paresthesia and/or neuropathy were reported by 28/114. No significant differences between different antibiotic treatments were observed in terms of occurrence of sequelae. To conclude, we found that 25% (95% confidence interval 17-33%) of the patients suffered from residual neurological symptoms 5 years post-treatment. However, the clinical outcome of treated neuroborreliosis is favourable as only 14/114 (12%) of the patients had sequelae that influenced their daily activity post-treatment. Early diagnosis and treatment would seem to be of great importance in order to avoid such sequelae.

  • 12. Bergman, Karl
    Gränslandet: Från Roskildefreden till Maastricht. En historisk reflektion2005Other (Other academic)
    Abstract [sv]

    Artikel: Gränslandet : Från Roskildefreden till Maastricht. En historisk reflektion" Rötter och Vingar 2005, Blekinge Museum 7 s pdf-format

  • 13.
    Berner, Jessica
    et al.
    Blekinge Institute of Technology, School of Health Science.
    Rennemark, Mikael
    Blekinge Institute of Technology, School of Health Science.
    Jogréus, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Berglund, Johan
    Blekinge Institute of Technology, School of Health Science.
    Distribution of personality, individual characteristics and internet usage in Swedish older adults2012In: Aging and Mental Health, ISSN 1360-7863 , Vol. 16, no 1, 119-126 p.Article in journal (Refereed)
    Abstract [en]

    Objectives: This paper investigated factors associated with internet usage in the Swedish older adults ranging in age from 60 to 96. Personality traits and individual characteristics have been previously noted to influence internet usage, where older adults have not been the focus population. In this study the relationships between personality, individual characteristics and internet usage were investigated. Methods: A descriptive analysis of the personality tests of a total of 1402 subjects included in the Swedish National Study on Aging and Care (SNAC) was conducted. Three variables were controlled for: sex, age and education. Descriptive statistics, Mann-Whitney and Kruskal-Wallis tests, chi square tests and a logistic regression were used in order to detect the relationships with internet usage. Results: Men differ significantly from women in the personality traits analysis. Those with higher education were more open and neuroticism was lower in the oldest older adults. Internet usage declined significantly with age and those with middle to higher education were using the internet the most. No other associations with internet use were found Conclusion: Personality traits and individual characteristics do not seem to influence the Swedish older adult and their internet usage. What one needs to account for is the age and education of the person. The more educated and the youngest cohorts were using the internet more frequently.

  • 14.
    Berner, Jessica
    et al.
    Blekinge Institute of Technology, School of Health Science.
    Rennemark, Mikael
    Blekinge Institute of Technology, School of Health Science.
    Jogréus, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Berglund, Johan
    Blekinge Institute of Technology, School of Health Science.
    Factors associated with change in Internet usage of Swedish older adults (2004-2010)2013In: Health Informatics Journal, ISSN 1460-4582, E-ISSN 1741-2811, Vol. 19, no 2, 152-162 p.Article in journal (Refereed)
    Abstract [en]

    The increased reliance on Internet use in social functions has presumably left out a part of the population: the oldest-older adults. These are people who have not kept themselves up to date with the technological developments for various reasons. There are, however, exceptions from whom we have something to learn. This study investigates the older people in Sweden who started to use the Internet over a period of 6 years. Cognition, extraversion, openness, functional disability, household economy, sex, age and education were investigated in relation to starting to use the Internet. A chi-square test, Spearman correlation and a logistic regression analysis were conducted. It was found that higher cognition, being male and being between the ages of 60 and 80 years were determining factors in starting to use the Internet for the Swedish older adult. Our results indicate that the oldest-older adults are slow to adapt to using the Internet and more attention should be paid on how to support this group.

  • 15. Bozhkov, Y.
    et al.
    Dimas, S.
    Ibragimov, Nail H.
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Conservation laws for a coupled variable-coefficient modified Korteweg–de Vries system in a two-layer fluid model2013In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, E-ISSN 1878-7274, Vol. 18Article in journal (Refereed)
    Abstract [en]

    We find the Lie point symmetries of a coupled variable-coefficient modified Korteweg–de Vries system in a two-layer fluid model. Then we establish its quasi self-adjointness and corresponding conservation laws.

  • 16. Bruzon, MS
    et al.
    Gandarias, ML
    Ibragimov, Nail H.
    Self-adjoint sub-classes of generalized thin film equations2009In: Journal of Mathematical Analysis and Applications, ISSN 0022-247X, E-ISSN 1096-0813, Vol. 357, no 1, 307-313 p.Article in journal (Refereed)
    Abstract [en]

    In this work we consider a class of fourth-order nonlinear partial differential equation containing several tin-specified coefficient functions of the dependent variable which encapsulates various mathematical models used, e.g. for describing the dynamics of thin liquid films. We determine the subclasses of these equations which are self-adjoint. By using a general theorem on conservation laws proved by one of the authors (NHI) we find conservation laws for some of these partial differential equations without Classical Lagrangians.

  • 17. Bunikis, Jonas
    et al.
    Tsao, J.
    Garpmo, Ulf
    Berglund, Johan
    Fish, Durland
    Barbour, AG
    Typing of Borrelia relapsing fever group strains.2004In: Emerging Infectious Diseases, ISSN 1080-6040, E-ISSN 1080-6059, Vol. 10, no 9, 1661-1664 p.Article in journal (Refereed)
    Abstract [en]

    Partial sequencing of the 16S-23S rDNA intergenic spacer showed two to four genotypes each for Borrelia hermsii and B. turicatae, both relapsing fever agents transmitted by argasid ticks, and for B. miyamotoi and B. lonestari, transmitted by ixodid ticks. Field surveys of Ixodes ticks in Connecticut and Sweden showed limited local diversity for B. miyamotoi.

  • 18. Carlsson, Bengt
    et al.
    Johansson, Stefan J.
    Boman, Magnus
    Generous and greedy strategies1999In: Complexity International, ISSN 1320-0682, Vol. 6Article in journal (Refereed)
    Abstract [en]

    We introduce generous, even-matched, and greedy strategies ÊÊas concepts for analyzing games. A two person prisoner's dilemma Êgame is described by the four outcomes (C,D), (C,C), (D,C), and (D,D). In a generous strategy the proportion of (C,D) is larger than that of (D,C), i.e. the probability of facing a defecting agent is larger than the probability of defecting. An even-matched strategy has the (C,D) proportion approximately equal to that of (D,C). A greedy strategy is an inverted generous strategy. The basis of the partition is that it is a zero-sum game given that the sum of the proportions of strategies (C,D) must equal that of (D,C). In a population simulation, we compare the prisoner's dilemma (PD) game with the chicken game Ê(CG), given complete as well as partial knowledge of the rules for moves in the other strategies. In a traffic intersection example, we expected a co-operating generous strategy to be successful when the cost for collision was high in addition to the presence of uncertainty. The simulation indeed showed that a generous strategy was successful in the CG part, in which agents faced uncertainty about the outcome. If the resulting zero-sum game is changed from a PD game to a CG, or if the noise level is increased, it will favor generous strategies rather than an even-matched or greedy strategies.

  • 19. Dorodnitsyn, Vladimir
    et al.
    Ibragimov, Nail
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    An extension of the Noether theorem: Accompanying equations possessing conservation laws2014In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 19, no 2, 328-336 p.Article in journal (Refereed)
    Abstract [en]

    It is shown that the Noether theorem can be extended for some equations associated (accompanying) with Euler-Lagrange equation. Each symmetry of Lagrangian yields a class of accompanying equations possessing conservation law (first integral). The generalization is done for canonical Hamiltonian equations as well.

  • 20. Ekelin, Annelie
    “What’s Up Over There?” Reflections of development of e-government in the States of California and Washington2005Other (Other academic)
    Abstract [en]

    Some highlights in this report could be summarized as follows: there are several examples of extensive investment of human and economical resources into security improvement and security related planning currently going on in the United States, coupled with a strong focus on implementing best practice frameworks and advanced interoperability. Other important aspects are the ongoing re-engineering of both governmental leadership structures as well as organisational work practice, where technological systems are to be seen both as something that cause issues, but also as an important part when solving those problems in the future. In the US, and particularly in the Seattle area, mobile government is developing fast. The state portal has also got a very prominent “sister portal”, called the Democracy portal with its own local TV-channel, Seattle Channel working actively on promotion of state actions. www.seattlechannel.org/videos/browseVideos.asp?topic=community This initiative is not new, but is nevertheless interesting since it has been developing more and more towards greater interactivity. It is in some sense an extension of the state portal, but also, according to Laurie Kraft, functions well as a ”window to government”, where the public is offered possibilities of interaction and participation in processes of general local decision-making. A working group recently worked out new guidelines on how to expand the interactive web format. New sections such as ”Tell me more” gives the public possibilities to learn more about for example the preparation of the budget estimates or having the opportunity to deepen their argumentation about local issues such as the debate about the local monorail expansion. In another section they are offered suggestions on how to proceed if they want to get involved in different matters, or find an answer to the question: How do I engage? Further developmental work is going to concentrate on how to tackle the occurrence of new digital divides, considering additional opportunities to reach those who rarely participates such as youths, non-native English speakers, and others who feel disenfranchised from the democratic process and the society. A well-thought strategy on ho to stimulate people to broaden their knowledge and take the opportunity to learn more about local decision-making. California is the fifth largest economic engine in the world with a fast expanding economy after a recession. In the annual survey of Digital Counties (2005), conducted by the Centre for Digital Government, a national research and advisory institute on Information technology policies and best practices in state and local government, several Californian counties appear on the list. In the survey, which focuses on how the county governments are deploying information technology to advance their services to citizens, San Diego County occupies the second place in the category of counties with a population of more than 500 000. In the smaller categories, covering less populated counties, California appears as number 10, and in the category of the counties with a population less than 150.000, Nevada County, Napa County and Sutter County cluster themselves in second, third and fourth place.

  • 21. Ekström, Magnus
    et al.
    Jogreus, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Ström, Kerstin
    Comorbidity and Sex-Related Differences in Mortality in Oxygen-Dependent Chronic Obstructive Pulmonary Disease2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 4Article in journal (Refereed)
    Abstract [en]

    Background: It is not known why survival differs between men and women in oxygen-dependent chronic obstructive pulmonary disease (COPD). The present study evaluates differences in comorbidity between men and women, and tests the hypothesis that comorbidity contributes to sex-related differences in mortality in oxygen-dependent COPD. Methods: National prospective study of patients aged 50 years or older, starting long-term oxygen therapy (LTOT) for COPD in Sweden between 1992 and 2008. Comorbidities were obtained from the Swedish Hospital Discharge Register. Sex-related differences in comorbidity were estimated using logistic regression, adjusting for age, smoking status and year of inclusion. The effect of comorbidity on overall mortality and the interaction between comorbidity and sex were evaluated using Cox regression, adjusting for age, sex, Pa-O2 breathing air, FEV1, smoking history and year of inclusion. Results: In total, 8,712 patients (55% women) were included and 6,729 patients died during the study period. No patient was lost to follow-up. Compared with women, men had significantly more arrhythmia, cancer, ischemic heart disease and renal failure, and less hypertension, mental disorders, osteoporosis and rheumatoid arthritis (P<0.05 for all odds ratios). Comorbidity was an independent predictor of mortality, and the effect was similar for the sexes. Women had lower mortality, which remained unchanged even after adjusting for comorbidity; hazard ratio 0.73 (95% confidence interval, 0.68-0.77; P<0.001). Conclusions: Comorbidity is different in men and women, but does not explain the sex-related difference in mortality in oxygen-dependent COPD.

  • 22. Elovaara, Pirjo
    et al.
    Mörtberg, Christina
    Design of Digital Democracies – Staging and Performing Citizenship, Gender and Information Technology2006Conference paper (Other academic)
    Abstract [en]

    The aim of the project is to explore how the ideas of democracy, citizenship, agency and gender can be connected to the notion of design of information technology. One of the reasons to focus on democracy and citizenship is to be found in the growing interest in e-government that is currently launched, politically and technologically, not only in Europe, but world wide. IT policies on a national as well as EU level express wishes to create an information society for all. How are then relations between democracy/citizenship and IT articulated in different practices? How are relations performed by the citizens as users and how is the staging of democracy/citizenship being inscribed in the design by systems designers? The intention of firs empirical part of the study is to investigate a number of spaces/places and practices for (re)negotiating democracy, citizenship, gender and IT. By spaces/places and practices we mean heterogeneous sociomaterial relations between human and non-human actors. Neither citizenship, gender and IT thus understood as fixed or closed categories, but are constantly reinforced, reshaped and (re)produced. Our initial research questions are: - How are dreams and visions of the good democratic lives articulated in a variety of spaces/places and practices by heterogeneous actors? Meanings connected to democracy, citizenship, gender and IT – how are they performed - What are the tensions and contradictions to be founded? - What are the dominating discourses and what are the concurring ones? The second part of the study focuses on the issue of design. Possible research questions to be addressed are: Are the multiple voices kept alive in the design process? How could they be kept alive in the whole design process from an idea to a product - artefact or running the IT-system? Do some methodologies and methods support heterogeneity better than others? Why and how do some perspectives win over others in design processes? How do asymmetrical power relations (gender, ethnicity, age, sexuality etc) intervene in designers definitions of actors involved in systems design? How do designers inscribe their visions of the worlds in the artefacts and systems? We are interested to see if the study can find methodological inspiration and support from a combination of various systems design approaches (participatory design, experimental design), feminist technoscience and Actor-Network-Theory.

  • 23. Enflo, Bengt
    et al.
    Hedberg, Claes
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    On the evolution of a spherical short pulse in nonlinear acoustics2012Conference paper (Refereed)
    Abstract [en]

    Planar wave propagation in nonlinear acoustics is modeled by the Burgers equation, which is exactly soluble. Spherical wave propagation is modeled by a generalized Burgers equation, in which the dissipative parameter of the plane wave Burgers equation is replaced by an exponentially growing function of the variable symbolizing the travelled length of the wave. A procedure previously used in 1998 by B.O. Enflo [1] on cylindrical short pulses is now used on spherical short pulses, which are originally N-waves. The procedure consists of the four steps: 1) A shock solution of the generalized Burgers equation is found by asymptotic matching. The shock fades in the region where the nonlinear term in the equation can be neglected. 2) The linear equation in step 1) is rescaled. It is identically solved by an integral representation containing an unknown function. 3) The integral representation found in step 2) is evaluated by the steepest descent method in the fading shock region introduced in step 1). The unknown function introduced in step 2) is determined by comparing the result of this evaluation with the fading shock solution found in step 1). 4) The integral representation with the unknown function determined is evaluated approximately asymptotically for large values of the original length (or time) variables in the original generalized Burgers equation (old-age regime). The result of this procedure is an old-age solution, controlled by numerical calculations. Curves of analytical and numerical solutions are given

  • 24.
    Eriksson, Mattias
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Radiation processes in the Seyfert galaxy NGC 41512012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 547Article in journal (Refereed)
    Abstract [en]

    Aims. The main aim of this work was to investigate if the radiative process photoexcitation by accidental resonance (PAR) is producing Fe II lines in the UV region of NGC 4151. At the same time I searched for collisionally excited Fe II emission. While doing so, the broad line region (BLR), intermediate line region (ILR) and narrow line region (NLR) contributions to the Mg II resonance doublet were also investigated. Methods. The focus was on the 2000 to 3000 Å wavelength region, in which decay from both the collisionally and PAR excited Fe II levels would form emission lines. I examined three archived Space Telescope Imaging Spectrograph (STIS) spectra of NGC 4151. Theoretical spectra based on calculated ranges for possible fluxes of the collisionally excited lines and pumping rates through the Fe II channels were then fitted to the observed spectra Results. I show that the UV region is influenced by PAR and that the Fe II fluorescence lines are clearly needed to explain the spectrum between 2000 to 3000 Å. The best fit of the theoretical spectra to the STIS spectra was obtained by assuming a similar radiation power of Fe+ ions and Mg+ ions. Conclusions. The PAR is active in the BLR of NGC 4151 and the total power of the Fe II fluorescence is a significant fraction of the total emission in the 2000 to 3000 wavelength region. Therefore it is important to incorporate this in models of NGC 4151 and possibly also in models of other active galactic nuclei. There are also many collisionally excited Fe II lines that are blended by each other and are therefore not individually observable in the NGC 4151 spectra.

  • 25. Feldt, Robert
    et al.
    Torkar, Richard
    Angelis, Lefteris
    Samuelsson, Maria
    Towards Individualized Software Engineering: Empirical Studies Should Collect Psyhometrics2008Conference paper (Refereed)
  • 26. Fiedler, Markus
    et al.
    Chevul, Stefan
    Radtke, Olaf
    Tutschku, Kurt
    Binzenhöfer, Andreas
    The Network Utility Function: A practicable concept for assessing network impact on distributed services2005Conference paper (Refereed)
    Abstract [en]

    Based on the need for distributed end-to-end quality management for next generation Internet services, this paper presents a ready-to-deploy quality assessment concept for the impact of the network on the service performance. The proposed Network Utility Function (NUF) combines the observed network utility at the inlet and the outlet. Thus, it captures the damping effect of the network onto user-perceived quality from an end-to-end perspective. As opposed to incomprehensible QoS parameters such as delay and loss, the NUF is highly intuitive due to its mapping to a simple value between 0 and 1. We demonstrate the capabilities of the proposed concept for a special NUF, the Throughput Utility Function (TUF) by realistic simulation.

  • 27.
    Fiedler, Markus
    et al.
    Blekinge Institute of Technology, School of Computing.
    Hackbarth, Klaus
    Hlavacs, Helmut
    Socio-economic issues in Future Generation Internet2008In: Journal of universal computer science (Online), ISSN 0948-695X, E-ISSN 0948-6968, Vol. 14, no 5, 612-614 p.Article in journal (Refereed)
  • 28. Gainetdinova, A.
    et al.
    Ibragimov, Nail
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Meleshko, Sergey
    Group classification of ODE y‴ = F (x, y, y′)2014In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 19, no 2, 345-349 p.Article in journal (Refereed)
    Abstract [en]

    In his extensive work of 1884 on the group classification of ordinary differential equations Lie performed, inter alia, the group classification of the particular type of the second-order equations y″ = F (x, y). In the present paper we extend Lie's classification to the third-order equations y‴ = F (x, y, y′).

  • 29. Galiakberova, L. R.
    et al.
    Ibragimov, Nail
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Nonlinear self-adjointness of the Krichever-Novikov equation2014In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 19, no 2, 361-363 p.Article in journal (Refereed)
    Abstract [en]

    It is known that the classification of third-order evolutionary equations with the constant separant possessing a nontrivial Lie-Bäcklund algebra (in other words, integrable equations) results in the linear equation, the KdV equation and the Krichever-Novikov equation. The first two of these equations are nonlinearly self-adjoint. This property allows to associate conservation laws of the equations in question with their symmetries. The problem on nonlinear self-adjointness of the Krichever-Novikov equation has not been solved yet. In the present paper we solve this problem and find the explicit form of the differential substitution providing the nonlinear self-adjointness.

  • 30. Gandarias, ML
    et al.
    Ibragimov, Nail H.
    Equivalence group of a fourth-order evolution equation unifying various non-linear models2008In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 13, no 2, 259-268 p.Article in journal (Refereed)
    Abstract [en]

    A fourth-order non-linear evolutionary partial differential equation containing several arbitrary functions of the dependent variable is considered. This equation arises as a generalization of various non-linear models describing a non-linear heat diffusion, the dynamics of thin liquid films, etc. Equivalence transformations give more flexibility to the unified model. We determine the generators of the equivalence group and use them for specifying certain types of arbitrary functions when the model equation has additional symmetries, and hence admits non-trivial group invariant solutions. (c) 2006 Elsevier B.V. All rights reserved.

  • 31. Gazizov, Rafail
    et al.
    Ibragimov, Nail
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Rudenko, Oleg
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Effect of resonant absorption in viscous and dry vibrating contact: Mathematical models and theory connected with slow dynamics and friction welding2014In: Communications in nonlinear science & numerical simulation, ISSN 1007-5704, Vol. 19, no 2, 337-344 p.Article in journal (Refereed)
    Abstract [en]

    Process of heating of thin layer located between two vibrating surfaces is studied. Energy loss goes on due to viscous or dry friction. Optimal quantities of shear viscosity and friction corresponding to maximum energy loss are determined. Resonant behavior of loss must be taken into account in the description of "slow dynamics" of rocks and materials exposed to high-intensity seismic or acoustic irradiation as well as in various technologies. Bonding of materials by linear friction welding, widely used in propulsion engineering, can exemplify such a technology.

  • 32. Gazizov, Rafail K.
    et al.
    Ibragimov, Nail H.
    Lukashchuk, Veronika O.
    Integration of ODE with a small parameter via approximate symmetries: reduction of approximate symmetry algebra to a canonical formMay 27Conference paper (Refereed)
    Abstract [en]

    The simplest method of integration of second-order differential equations using the Lie's canonical forms of two-dimensional algebras is well-known. We propose a generalization of this method on a case of integration of second-order differential equation with a small parameter having two approximate symmetries. The solution of such problem is reduced to the followings: 1) to classify approximate Lie algebras with two essential operators. As a result, seven different types of such Lie algebras have been obtained; 2) to construct canonical form of basic operators of non-similar algebras of every types for their realization in R2; 3) to set up general forms of invariant equations and formulas of their approximate solutions. The similar problems are solved for systems of two ordinary differential equations with two approximate symmetries. On this way we have constructed representation of non-similar approximated Lie algebras in R3.

  • 33. Gazizov, Rafail K.
    et al.
    Ibragimov, Nail H.
    Lukashchuk, V.O.
    Integration of ordinary differential equation with a small parameter via approximate symmetries: Reduction of approximate symmetry algebra to a canonical form2010In: Lobachevskii Journal of Mathematics, ISSN 1995-0802, Vol. 31, no 2, 141-151 p.Article in journal (Refereed)
    Abstract [en]

    Method of integration of second-order ordinary differential equations with twodimensional Lie symmetry algebras by reducing basic symmetries to canonical forms is extended to second-order equations with a small parameter for their approximate integration using two essential approximate symmetries. Canonical forms of basic operators of corresponding approximate Lie algebras Lr, r = 2, 3, 4, as well as general forms of invariant differential equations and their solutions are presented. The similar problems are also solved for systems of two first-order ordinary differential equations with two approximate symmetries.

  • 34.
    Gomez, Aldo Fabricio Gutierrez
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Mathematical Analysis of Financial Markets2006Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Basic mathematic analysis of how financial markets work and different valuation models such as the Stochastic Market Price Estimator, valuation model created by the author.

  • 35. Grigoriev, Yurii
    et al.
    Ibragimov, Nail H.
    Kovalev, Vladimir
    Meleshko, Sergey
    Delay differential equations2010In: Lecture Notes in Physics, ISSN 0075-8450, Vol. 806, 251-292 p.Article in journal (Refereed)
    Abstract [en]

    In this chapter, applications of group analysis to delay differential equations are considered. Many mathematical models in biology, physics and engineering, where there is a time lag or aftereffect, are described by delay differential equations. These equations are similar to ordinary differential equations, but their evolution involves past values of the state variable. For the sake of completeness the chapter is started with a short introduction into the theory of delay differential equations. The mathematical background of these equations is followed by the section which deals with the definition of an admitted Lie group for them and some examples. The purpose of the next section is to give a complete group classification with respect to admitted Lie groups of a second-order delay ordinary differential equation. The reasonable generalization of the definition of an equivalence Lie group for delay differential equations is considered in the next section. The last section of the chapter is devoted to application of the developed theory to the reaction-diffusion equation with a delay.

  • 36. Grigoriev, Yurii
    et al.
    Ibragimov, Nail H.
    Kovalev, Vladimir
    Meleshko, Sergey
    Introduction to group analysis and invariant solutions of integro-differential equations2010In: Lecture Notes in Physics, ISSN 0075-8450, Vol. 806, 57-111 p.Article in journal (Refereed)
    Abstract [en]

    In this chapter an introduction into applications of group analysis to equations with nonlocal operators, in particular, to integro-differential equations is given. The most known integro-differential equations are kinetic equations which form a mathematical basis in the kinetic theories of rarefied gases, plasma, radiation transfer, coagulation. Since these equations are directly associated with fundamental physical laws, there is special interest in studies of their solutions. The first section of this chapter contains a retrospective survey of different methods for constructing symmetries and finding invariant solutions of such equations. The presentation of the methods is carried out using simple model equations of small dimensionality, allowing the reader to follow the calculations in detail. In the next section, the classical scheme of the construction of determining equations of an admitted Lie group is generalized for equations with nonlocal operators. In the concluding sections of this chapter, the developed regular method of obtaining admitted Lie groups is illustrated by applications to some known integro-differential equations.

  • 37. Grigoriev, Yurii
    et al.
    Ibragimov, Nail H.
    Kovalev, Vladimir
    Meleshko, Sergey
    Introduction to group analysis of differential equations2010In: Lecture Notes in Physics, ISSN 0075-8450, Vol. 806, 1-55 p.Article in journal (Refereed)
    Abstract [en]

    The first chapter is a brief, but a sufficiently comprehensive introduction to the methods of Lie group analysis of ordinary and partial differential equations. The chapter presents basic concepts from the theory: continuous transformation groups, their generators, Lie equations, groups admitted by differential equations, integration of ordinary differential equations using their symmetries, group classification and invariant solutions of partial differential equations. New trends in modern group analysis such as the theory of Lie-Bäcklund transformations groups and approximate groups are also reflected. The intention of the chapter is to give the basic ideas of classical and modern group analysis to beginner readers and provide useful materials for advanced specialists

  • 38. Grigoriev, Yurii
    et al.
    Ibragimov, Nail H.
    Kovalev, Vladimir
    Meleshko, Sergey
    Plasma kinetic theory: Vlasov-maxwell and related equations2010In: Lecture Notes in Physics, ISSN 0075-8450, Vol. 806, 145-208 p.Article in journal (Refereed)
    Abstract [en]

    This chapter is devoted to a group analysis of the Vlasov-Maxwell and related type equations. The equations form the basis of the collisionless plasma kinetic theory, and are also applied in gravitational astrophysics, in shallow-water theory, etc. Nonlocal operators in these equations appear in the form of the functionals defined by integrals of the distribution functions over momenta of particles. In the beginning sections the plasma kinetic theory equations are introduced and the way of looking at the symmetries of nonlocal equations is described. Much of the importance of the approach used in this chapter for calculating symmetries stems from the procedure of solving determining equations using variational differentiation. The set of symmetries obtained in the sections that follow comprises symmetries for the Vlasov-Maxwell equations of the non-relativistic and relativistic electron and electron-ion plasmas in both one- and three-dimensional cases, and symmetries for Benney equations. In the concluding sections of this chapter the procedure for symmetry calculation and the renormalization group algorithm go hand in hand to present illustrations from plasma kinetic theory, plasma dynamics, and nonlinear optics, which demonstrate the potentialities of the method in construction of analytic solutions to nonlocal problems of nonlinear physics.

  • 39. Grigoriev, Yurii
    et al.
    Ibragimov, Nail H.
    Kovalev, Vladimir
    Meleshko, Sergey
    Symmetries of stochastic differential equations2010In: Lecture Notes in Physics, ISSN 0075-8450, Vol. 806, 209-250 p.Article in journal (Refereed)
    Abstract [en]

    This chapter deals with applications of the group analysis method to stochastic differential equations. These equations are often obtained by including random fluctuations in differential equations, which have been deduced from phenomenological or physical view. In contrast to deterministic differential equations, only few attempts to apply group analysis to stochastic differential equations can be found in the literature. It is worth to note that this theory is still developing. Before defining an admitted symmetry for stochastic differential equations an introduction into the theory of this type of equations is given. The introduction includes the discussion of a stochastic integration, a stochastic differential and a change of the variables (Itô formula) in stochastic differential equations. Applications of the Itô formula are considered in the next section which deals with the linearization problem. The Itô formula and the change of time in stochastic differential equations are the main tools of defining admitted transformations for them. After introducing an admitted Lie group and supporting material of the introduced definition, some examples of applications of the given definition are studied.

  • 40. Grigoriev, Yurii
    et al.
    Ibragimov, Nail H.
    Kovalev, Vladimir
    Meleshko, Sergey
    The Boltzmann kinetic equation and various models2010In: Lecture Notes in Physics, ISSN 0075-8450, Vol. 806, 113-144 p.Article in journal (Refereed)
    Abstract [en]

    The chapter deals with applications of the group analysis method to the full Boltzmann kinetic equation and some similar equations. These equations form the foundation of the kinetic theory of rarefied gas and coagulation. They typically include special integral operators with quadratic nonlinearity and multiple kernels which are called collision integrals. Calculations of the 11-parameter Lie group G 11 admitted by the full Boltzmann equation with arbitrary intermolecular potential and its extensions for power potentials are presented. The found isomorphism of these Lie groups with the Lie groups admitted by the ideal gas dynamics equations allowed one to obtain an optimal system of admitted subalgebras and to classify all invariant solutions of the full Boltzmann equation. For equations similar to the full Boltzmann equation complete admitted Lie groups are derived by solving determining equations. The corresponding optimal systems of admitted subalgebras are constructed and representations of all invariant solutions are obtained.

  • 41. Gustavsson, Ingvar
    A Flexible Remote Electronics Laboratory for Engineering Education2006Conference paper (Other academic)
    Abstract [en]

    The overall goal of engineering education is to prepare students to practice engineering and, in particular, to deal with the forces and materials of nature. Thus, from the earliest days of engineering education, instructional laboratories have been an essential part of undergraduate programs. However, during the last decades the author and others have noted a trend towards increased use of simulations replacing physical experiments in electrical engineering education. One obvious reason is the fact that instructional laboratories are expensive to maintain. Another possible reason is the persistence of the belief that simulations can replace physical experiments. However, physical experiments are indispensable for developing skills to deal with physical processes and instrumentation. The Internet provides new possibilities for universities and other teaching organizations to share laboratories. Blekinge Institute of Technology (hereafter referred to as BTH) in Sweden has opened a traditional electronics laboratory for remote operation 24-7 and fitted the laboratory with a unique virtual interface where the students on the computer screen recognize the desktop instruments and the breadboard they have already used in the local laboratory. The fact that teachers in different countries can use existing teaching material in their own language is also unique for this laboratory. Instrument manuals can be downloaded from the web sites of the manufacturers. The activities started 1999 at BTH and the amount of work spent so far is approximately 12 man-years. The BTH design and has been awarded a Best Paper Award at the ASEE (American Society for Engineering Education) Annual Conference in Montreal 2002. Most remote electronics laboratories elsewhere offer fixed experiments but in this one, students around the world can simultaneously wire circuits much like they do in the local laboratory. The BTH laboratory is a client/server application and the Internet is used as the communication infrastructure. The equipment provided comprises a dual channel oscilloscope, a digital multi-meter a triple DC power supply, a circuit wiring robot, and component sets selected by the teachers who have written the lab instruction manuals for the courses. The laboratory staff has mounted these component sets in the circuit assembly robot in the equipment server at BTH and photographs of the components in a set will be displayed in a component box on the client PC screens. Thus a certain set of components is provided for each lab session. The current laboratory supports only instrument models used at BTH. Other universities have other models and a virtual equipment shelf containing other instruments from different manufacturers will be added. The performance of the provided hardware matches most instrument models used in undergraduate education. Students use the mouse to wire instruments and components from the component box to form a circuit on the breadboard displayed on each client PC. They thus control the robot by means of the wiring on the virtual breadboard, Figure 1. The robot is not a mechanical device but a switching matrix consisting of relays, sockets for components, and instrument connectors. Virtual instrument front panels are used to control and read the computer-based instruments by means of remote control, Figure 2. Most of the instruments in the equipment server are manufactured by National Instruments. To avoid damage to components and/or instruments, the teachers define maximum source voltages and all permitted current loops. However, harmless mistakes are allowed. A virtual instructor routine checks each desired circuit and acknowledges the circuit when the voltage levels are not too high and it only contains permitted current loops. Thus, if a user damages a component or an instrument the teacher is to blame not the user. A description of the laboratory can be found in: I. Gustavsson, J. Zackrisson, H. Åkesson, L. Håkansson, "A Flexible Remote Electronics Laboratory", Proceedings of the 2005 REV symposium, Brasov, Romania, June 30 - July 1, 2005. Figure 1. An operational amplifier (μA741) circuit wired on the virtual breadboard. Figure 2. The oscilloscope virtual front panel displaying the slew rate of the uA741 operational amplifier in the circuit on the breadboard illustrated in Figure 1. Access to the laboratory is restricted by a reservation system. The main items of this system are students, courses, and lab sessions in order to fit the traditional university system. The teacher of a course makes time reservations for regular supervised lab sessions of the course and specifies also the sets of components to be used in the sessions. Only students enrolled in the course are permitted to perform experiments using the component sets belonging to the lab sessions of that course. However, there are two guest courses open to the public. In each of the guest courses there is a lab session and a set of components. Only a 56 kbit/s modem and a web browser are required to access these experimental resources. The laboratory is always open and can be used by registered students and guest users around the world. The time-sharing scheme used allows simultaneous access with acceptable response time for 8 client PCs. The address of the laboratory web site is http://distanslabserver.its.bth.se/. Universities and other teaching organizations are invited to let their students conduct experiments and to provide regular lab sessions using their own components and learning material in the language of their choice. Expensive laboratory equipment can be provided for students with no time or space limitations. Apart from the fact that each student or team of students using a client computer works in a virtual environment with no face-to-face contact with the instructor or other students in the laboratory, the difference between a lab session in the laboratory presented here and a session in a local laboratory is that it is not possible for users to manipulate the components and the wires with their fingers in a remote laboratory. However, the latter constitutes a new educational tool which is ready for use in undergraduate education and in secondary schools as well as in vocational training and life-long learning. Remote experiments will not replace local lab sessions but supplement them and make experiments more accessible, especially for inexperienced or less confident people requiring more time. It may be possible to compensate for the reduction in the number of traditional lab sessions during the past few decades and even improve electronics courses without incurring any increase in cost. New more effective teaching methods may emerge. Experiments can, for example, easily be integrated into lectures. How about opening a laboratory containing mechanical components? In most cases sound and/or video image transmission will be required. A remote vibration analysis laboratory is being set up at BTH and will provide a platform for an evaluation of the feasibility of remote vibration experiments using the same concept. A dynamic signal analyzer, Agilent 35670A, connected to a server and traditional vibration sensors and actuators for experimental vibration analysis will be used. As a first example this setup will enable estimation of the important quantities in experimental vibration analysis based on measurements on a boring bar. Such bars are responsible for the majority of vibration problems in turning. The intention is to provide the students with vibration experiments related to an authentic important vibration problem in the industry. The research field has wider implications. Engineering education is not as popular today as it should be given the spread of technology in society. However, it is not so exciting to disassemble a modern digital alarm clock as grandmother’s one! Technical devices in our everyday life are no longer transparent. It has been reported that most teachers in, for example, nursery schools influencing our children have no technical courses whatsoever in their own professional training. The ultimate goal for the research at BTH is ubiquitous physical experimental resources accessible 24-7 for everyone to inspire and encourage children, young people and others to study engineering and become good professionals or to be used as means for long life learning of teachers and other professionals.

  • 42. Gustavsson, Ingvar
    A General Framework for a Module Based Distributed Online-Lab Network/Grid based on Open Source Technologies2006Conference paper (Other academic)
    Abstract [en]

    In order to combine theoretical knowledge and practice, many Universities and Schools have setup online laboratories, allowing students to deepen their theoretical knowledge and to gain some practical experience by attending online experiments over the Internet. Especially in the field of engineering and sciences, laboratories in Universities as well as in SMEs are an essential part of education and have demonstrated their success. The fundamental idea of this project is to build-up a self-growing Online-Lab-Grid consisting of different online laboratories all around the world which will bring together scientists, learners and pedagogues from all over Europe and overseas. The open remotely controllable laboratories at Blekinge Institute of Technology (hereafter referred to as BTH) in Sweden are examples of a module based laboratory designed to be distributed. They are used in regular courses for both distant learning students and campus students. The electronics laboratory is equipped with a unique virtual interface enabling students to recognize on their own computer screen the desktop instruments and the breadboard they have already used in the local laboratory. This is a way to increase opportunities for students to perform physical experiments and to compensate for the reduced number of such activities in undergraduate education during the last decades without incurring any increase in cost. The laboratories consist of modules communicating with xml based protocols. The goal is an international standard, enabling research teams worldwide to jointly expand and develop this and other powerful approaches by using standardized open source software and shared equipment platforms. The Carinthia Tech Institute is developing a software-based Web portal for online laboratories, which enables an interconnection of different online laboratories on different places all around the world. This Web portal offers the opportunity to share online laboratories within a common framework and thus increasing the network capability over all.

  • 43. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Åkesson, Henrik
    Håkansson, Lars
    A Flexible Remote Electronics Laboratory2005Conference paper (Refereed)
    Abstract [en]

    The Internet provides new possibilities for universities and other teaching organizations to share laboratories equipped with expensive instruments. A remotely operated electronics laboratory has been set up by Blekinge Institute of Technology in Sweden. The laboratory is a client/server application and the Internet is used as the communication infrastructure. In the new version presented in this paper security problems are solved and an authentic appearance of instruments and components are provided. Most remote electronics laboratories elsewhere offer fixed experiments but in this one, students can simultaneously assemble circuits and conduct experiments much like they do in a traditional university laboratory. The laboratory is always open and can be used by registered students and guest users around the world.

  • 44. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Åkesson, Henrik
    Håkansson, Lars
    Experimentera hemma med utrustningen i universitetens övningslaboratorier2006Conference paper (Other academic)
    Abstract [sv]

    Blekinge Tekniska Högskola, BTH, har öppnat ett övningslaboratorium för ellära och elektronik för fjärrstyrning och håller på att öppna ett fjärrstyrbart signalbehandlingslaboratorium för vibrationsanalys. Ett unikt användargränssnitt gör det möjligt att från valfri plats styra och manövrera experimentutrustningen på samma sätt som i laboratorielokalerna. Allt som behövs är Internetansluten PC med standardprogramvara. Denna forskning är inriktad mot vad som upplevs som den största utmaningen dvs. att ge studenterna en så genuin upplevelse som möjligt oaktat bristen på direkt kontakt med den fysikiska experimentutrustningen. BTH bjuder in andra lärosäten både nationellt och internationellt att delta i pedagogisk utvärdering av detta komplement till att experimentera i laboratoriesal och att delta i vidareutvecklingen mot en internationell standard.

  • 45. Haan, Jan Mark de
    Filter bank design for digital speech signal processing: methods and applications2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Adaptive filter theory is an important subject in the field of signal processing and has numerous applications in speech processing, telecommunications and mechanical engineering. Examples in speech processing include suppression of background noise, echo cancellation and dereverberation (acoustic path equalization). Examples in telecommunications include channel equalization and interference cancellation. Subband filter banks are introduced in the area of adaptive filtering in order to improve the performance of time domain adaptive filters. The main performance improvements are faster convergence speed and reduction of computational complexity due to shorter adaptive filters in the subbands. The thesis deals with design and analysis of subband adaptive systems using subband filter banks, with applications in speech enhancement. Multirate subband filter banks often introduce signal degradations. Some of these degradations are inherent from the multirate building blocks and some are due to improperly designed analysis and synthesis filters. Filter banks need to be designed in such a way, that the benefits are sustained while degradations due to the multirate processing are minimized. The presented design methods in this thesis aim to address two important filter bank properties, transmission delay and aliasing distortions caused by multi-rate building blocks. Aliasing distortions appear in the subband signals and in the reconstructed output signal, and have great impact on the performance of the speech enhancement algorithms as well as on the quality of the output enhanced speech. The main contributions in this thesis are design methods for uniform and nonuniform filter banks for adaptive filtering applications. The proposed methods are compared with conventional methods, and performance aspects of different filter bank designs are compared in different speech processing applications. These applications include acoustic echo cancellation, speech enhancement, and subband beamforming. Real speech signals are used in evaluations and results show that properly designed filter banks play an important role in the quality of the output enhanced speech. Another important contribution is the convergence analysis of certain types of delayless subband adaptive filters. The analysis leads to design requirements for improved convergence speed of such adaptive filters.

  • 46. Haikola, Lars
    et al.
    Ibragimov, Nail H.
    Louise Petrén and her generalization of Laplace’s methodMay 27Conference paper (Refereed)
    Abstract [en]

    Louise Petrén is an interesting person in the history of Swedish mathematics. In her PhD thesis defended in Lund in 1911, she extended to higher-order equations Laplace’s method of integration of second-order linear hyperbolic equations with two independent variables. It is interesting to consider her results from point of view of invariants of differential equations and compare with the theory of the Laplace invariants. However, L. Petrén’s research was not known until recently among mathematicians working in group analysis. The aim of our talk is to introduce Louise Petrén as a person and to discuss her generalization of Laplace’s method. Lars Haikola will contribute with a family background of Louise Petrén.

  • 47.
    Hansen, Rickard
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Pilot study: Modeling of Wildfires2008Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    There is presently no wildfire model developed for Swedish conditions, only a fire danger rating system (FWI) has been developed for Swedish conditions. The demand for a wildfire model has not been great in the past in Sweden but the climate changes now taking place increases the risk of large and intensive wildfires in Sweden. The need for additional and better tools for sizing-up wildfires will be in great demand in the future. This pre-study is aimed at: - Presenting what has been done in the wildfire modeling field during the years and mainly the last twenty years. - Giving recommendations on the continued work with developing a Swedish wildfire model. The method that was used was literature and article survey. The study also looks into the required input data for a wildfire model and the input data available at the moment. This issue is highly crucial as the quality of the output of a wildfire model is depending upon the quality of the input data. During the study, a primitive wildfire model was constructed and refined in order to get an insight in the complexities and problems with developing an operational model. The following characterization of wildfire models was used during the study: - Statistical models: based primarily on statistics from earlier or experimental fires. They do not explicitly consider the controlling physical processes. - Semi-empirical models: based on physical laws, but enhanced with some empirical factors, often by lumping all physical mechanisms for heat transfer together. - Physical models: based on physical principles and distinguishing between physical mechanisms for heat transfer. The statistical models make no attempt to involve physical processes, as they are merely a statistical description of test fires. Thus the lack of a physical basis means that statistical models must be used carefully outside the test conditions. Semi-empirical models are often based on conservation of energy principles but do not make any difference between conduction, convection and radiation heat transfer. The semi-empirical model has low computational requirements and includes variables that are generally easy to measure in the field. So despite the issue with limited accuracy, the speed and simplicity of these models make them useful for operational use. Physical models have the advantage that they are based on known relationships and thus facilitating their scaling. Thus we can expect that physical models would provide the most accurate predictions and have the widest applicability. But the work on physical models is suffering of for example the lack of understanding of several processes, such as the characterization of the chemical processes taking place during combustion, the resulting flame characteristics and the isolation and quantification of physical processes governing heat transfer. The input data available today are generally not detailed enough for physical models. As a result, a very detailed physical model will still only give imprecise predictions. As better and more detailed input will be available, the use of physical models will be more justified. A semi-empirical model is recommended being developed in Sweden. This conclusion is based upon the following factors: - The accuracy of a semi-empirical model is generally much better than for a statistical model, also the use of a semi-empirical model is much wider than the use of a statistical model. - The amount of work required for developing a semi-empirical model will not differ much from the amount of work required for a statistical model. In both cases a number of test fires will have to be conducted to define and calibrate a number of fuel models representative of Sweden. - Presently the performance and application of physical models is not at an acceptable level (due to for example the complexity which they are to model and the computational capabilities of the PC’s of today) for operational use. The semi-empirical model for Sweden is recommended to be built upon Swedish conditions (i.e. built upon the type of vegetation found in Sweden) instead of trying to retrofit the local Swedish conditions into an existing model. This would most likely give the best output for Swedish conditions. A system for better input data - weather and fuel data – should be worked on as well. This could for example take advantage of the results of the very promising “Alarm”-project that is being conducted in western part of Sweden. Regarding the issue on better fuel data, new technology for satellite images or aerial photos and image classification techniques must be monitored as one major problem to be solved is distinguishing between the canopy fuel and the ground fuel. For more specific conclusions and reflections, please see the analysis and discussion, and conclusions sections of this report.

  • 48. Hansson, Christina
    et al.
    Dittrich, Yvonne
    Gustavsson, Björn
    Zarnaak, Stefan
    How agile are industrial software development practices?2006In: Journal of Systems and Software, ISSN 0164-1212, Vol. 79, no 9Article in journal (Refereed)
    Abstract [en]

    Representatives from the agile development movement claim that agile ways of developing software are more fitting to what is actually needed in industrial software development. If this is so, successful industrial software development should already exhibit agile characteristics. This article therefore aims to examine whether that is the case. It presents an analysis of interviews with software developers from five different companies. We asked about concrete projects, both about the project models and the methods used, but also about the real situation in their daily work. Based on the interviews, we describe and then analyze their development practices. The analysis shows that the software providers we interviewed have more agile practices than they might themselves be aware of. However, plans and more formal development models also are well established. The conclusions answer the question posed in the title: It all depends! It depends on which of the different principles you take to judge agility. And it depends on the characteristics not only of the company but also of the individual project.

  • 49.
    Hedberg, Claes
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Andersson, Sara
    Haller, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Deflection dynamics of rock beam caused by ultrasound2013In: Mechanics of time-dependant materials, ISSN 1385-2000, E-ISSN 1573-2738, Vol. 17, no 4, 597-604 p.Article in journal (Refereed)
    Abstract [en]

    A new method for monitoring the time dependent dynamics of materials is proposed and implemented. By completely separating the conditioning (here ultrasound), the probing (here gravity), and the material state indicator (here deflection), the details of this dynamic process becomes apparent. The method allows both continuous monitoring of the material state without cross-interaction by the measuring process on the results, as well as complete freedom of conditioning and probing. It was successfully tested for sensitivity and repeatability when applied on a horizontally suspended beam of gabbro rock, which was observed to sag when subjected to ultrasound. These introductory tests have given new insights. The beam rises back, against the force of gravity, after the ultrasound is turned off. The deflection motions are fast both at the onset and at the termination of ultrasound, with the subsequent continuations being much slower. This new method is able to provide the higher accuracy needed for the advancement of the theoretical framework for material property time dependent dynamics.

  • 50.
    Holmgren, Johan
    et al.
    Blekinge Institute of Technology, School of Computing.
    Dahl, Mattias
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Davidsson, Paul
    Person, Jan A.
    Agent-based simulation of freight transport between geographical zones2013Conference paper (Refereed)
    Abstract [en]

    We present TAPAS-Z, which is an agent-based freight transport analysis model for simulation of decision-making and transport activities. TAPAS-Z is a further development of a simulation model called TAPAS, and it has improved support for simulation of transport in large geographical regions. It is based on the principles that shipments are simulated for chosen supplier-consumer relations in a geographic region, and that the geographic locations of suppliers and consumers are randomly varied for each shipment. In TAPAS-Z, one supplier represents all real-world suppliers in a geographic zone, and one consumer represents all real-world consumers in a zone. In that way, TAPAS-Z is able to capture some of the diversity in freight transport that is caused by the varying geographic locations of senders and receivers, and which is important when assessing the impact of transport policy and infrastructural measures.

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