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  • Public defence: 2018-11-28 13:00 Kappa, Västerås
    Musonda, John
    Mälardalen University, School of Education, Culture and Communication. University of Zambia.
    Reordering in Noncommutative Algebras, Orthogonal Polynomials and Operators2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main object studied in this thesis is the multi-parametric family of unital associative complex algebras generated by the element $Q$ and the finite or infinite set $\{S_j\}_{j\in J}$ of elements satisfying the commutation relations $S_jQ=\sigma_j(Q)S_j$, where $\sigma_j$ is a polynomial for all $j\in J$. A concrete representation is given by the operators $Q_x(f)(x)=xf(x)$ and $\alpha_{\sigma_j}(f)(x)=f(\sigma_j(x))$ acting on polynomials or other suitable functions. The main goal is to reorder arbitrary elements in this family and some of its generalizations, and to study properties of operators in some representing operator algebras, including their connections to orthogonal polynomials. For $J=\{1\}$ and $\sigma(x)=x+1$, the above commutation relations reduce to the famous classical Heisenberg--Lie commutation relation $SQ-QS=S$. Reordering an element in $S$ and $Q$ means to bring it, using the commutation relation, into a form where all elements $Q$ stand either to the left or to the right. For example, $SQ^2=Q^2S+2QS+S$. In general, one can use the commutation relation $SQ-QS=S$ successively and transform for any positive integer $n$ the element $SQ^n$ into a form where all elements $Q$ stand to the left. The coefficients which appear upon reordering in this case are the binomial coefficients. General reordering formulas for arbitrary elements in noncommutative algebras defined by commutation relations are important in many research directions, open problems and applications of the algebras and their operator representations. In investigation of the structure, representation theory and applications of noncommutative algebras, an important role is played by the explicit description of suitable normal forms for noncommutative expressions or functions of generators. Further investigation of the operator representations of the commutation relations by difference type operators on Hilbert function spaces leads to interesting connections to functional analysis and orthogonal polynomials.

     

    This thesis consists of two main parts. The first part is devoted to the multi-parametric family of algebras introduced above. General reordering formulas for arbitrary elements in this family are derived, generalizing some well-known results. As an example of an application of the formulas, centralizers and centers are computed. Some operator representations of the above algebras are also described, including considering them in the context of twisted derivations. The second part of this thesis is devoted to a special representation of these algebras by difference operators associated with action by shifts on the complex plane. It is shown that there are three systems of orthogonal polynomials of the class of Meixner--Pollaczek polynomials that are connected by these operators. Boundedness properties of two singular integral operators of convolution type connected to these difference operators are investigated in the Hilbert spaces related to these systems of orthogonal polynomials. Orthogonal polynomials are used to prove boundedness in the weighted spaces and Fourier analysis is used to prove boundedness in the translation invariant case. It is proved in both cases that the two operators are bounded on the $L^2$-spaces and estimates of the norms are obtained. This investigation is also extended to $L^p$-spaces on the real line where it is proved again that the two operators are bounded.

  • Public defence: 2018-11-29 13:00 Delta, Västerås
    Rooth, Hetty
    Mälardalen University, School of Health, Care and Social Welfare, Health and Welfare.
    All Parents in Focus: Governing parents and children in universal parenting training2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thesis deals with power and control in public health interventions in Sweden using structured parental support programs. The aim is to visualize how parents and children's relationships are described and discussed in manuals and courses intended for all parents with children between the ages of 0 and 17 and how the children themselves describe in their family.

    By using theories of power and governing, the thesis aims to study how the parent-child relationship is regulated through normative discourses and power processes in selected parenting courses (Connect and ABC). The thesis also wants to give children a voice about their position in the family. The interest of the thesis is how preventive work, through structured courses, currently used in universal parenting training, can contribute to promote children’s health.

    Previous research on universal parenting training in Sweden is based primarily on health economic calculations and quantitative assessments of behavioural changes in children and parents. This thesis instead wants to study the values ​​and methodology of parenting training programs and the children's experiences in their family when parents have participated in parenting courses. With a children´s rights perspective, the thesis also wishes to highlight the parenting support in relation to the children's situation.

    The thesis contains four qualitative studies. Two are conducted with discourse analysis (Study I and III) and two use content analysis (Study II and IV). Study I examines two public investigations from 1947 and 2008, both of which deal with child rearing, parenting and parenting education. Study II explores the contents of the course manuals of the Canadian Connect program and Swedish All Children in Focus (ABC) in relation to the UN Convention on the Rights of the Child. Study III examines how principles ​​about parental skills and children’s actions are reflected in the parenting courses. Study IV describes children's experiences of being children in the families where the parents have participated in a parenting course.

    The findings in study I show that society's views on parents' relational ability in both investigations creates the prerequisite for acting politically for universal parenting training. The children's position is subordinate to adults in the investigations. Furthermore, in Study II, it appears that the content of both program manuals (Connect and ABC) is in accordance with Swedish public health policies, where parental ability can be seen as a protective factor for children's development. The study also shows that the courses can both restrain and promote children's participation. Study III shows that leaders at course meetings encourage parents to improve their parenting through self-control and conflict management. Parental capacity is seen as a determinant for children's development and health. In study IV, with children´s interviews, the children´s relate their views on the relationship with their parents and the children´s own relational ability.

    Throughout the thesis the findings show how an adult perspective is used to deal with conflicts and stabilize relationships in the family. An adult ambition to understand children and promote good relationships within the family is hampered by the concern of both society and parents for the parental child rearing ability. This concern can contribute to an uneven balance of power between adults and children. Preventive manual-based parenting training offers limited scope for children's influence in a health-promoting public health context. Children's experiences should thus be captured when society provides parenting support.

  • Public defence: 2018-12-03 09:30 Kappa, Västerås
    Jaradat, Omar
    Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Contracts-Based Maintenance of Safety Cases2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Safety critical systems are those systems whose failure could result in loss of life, significant property damage, or damage to the environment. System safety is a major property that shall be adequately assured to avoid any severe outcomes in safety critical systems. Safety assurance should provide justified confidence that all potential risks due to system failures are either eliminated or acceptably mitigated. System developers in many domains (e.g., automotive, avionics, railways) should provide convincing arguments regarding the safe performance of their systems to a national or international regulatory authority and obtain approvals before putting the system into service.  Building 'Safety cases' is a proven technique to argue about and communicate systems' safety and it has become a common practice in many safety critical system domains. System developers use safety cases to articulate claims about how systems meet their safety requirements and objectives, collect and document items of evidence, and construct a safety argument to show how the available items of evidence support the claims.

    Safety critical systems are evolutionary and constantly subject to preventive, perfective, corrective or adaptive changes during both the development and operational phases. Changes to any part of those systems can undermine the confidence in safety since changes can refute articulated claims about safety or challenge the supporting evidence on which this confidence relies. Hence, safety cases need to be built as living documents that should always be maintained to justify the safety status of the associated system and evolve as these systems evolve. However, building safety cases are costly since they require a significant amount of time and efforts to define the safety objectives, generate the required evidence and conclude the underlying logic behind the safety case arguments. Safety cases document highly dependent elements such as safety goals, assumptions and evidence. Seemingly minor changes may have a major impact. Changes to a system or its environment can necessitate a costly and painstaking impact analysis for systems and their safety cases. In addition, changes may require system developers to generate completely new items of evidence by repeating the verification activities. Therefore, changes can exacerbate the cost of producing and maintaining safety cases.  

    Safety contracts have been proposed as a means for helping to manage changes. There have been works that discuss the usefulness of contracts for reusability and maintainability. However, there has been little attention on how to derive them and how exactly they can be utilised for system or safety case maintenance.

    The main goal of this thesis is to support the change impact analysis as a key factor to enhance the maintainability of safety cases. We focus on utilising safety contracts to achieve this goal. To address this, we study how safety contracts can support essential factors for any useful change management process, such as (1) identifying the impacted  elements  and  those  that  are  not  impacted, (2) minimising the number of impacted  safety  case  elements, and (3) reducing the  work  needed  to  make  the  impacted  safety  case  elements valid again. The preliminary finding of our study reveals that using safety contracts can be promising to develop techniques and processes to facilitate safety case maintenance. The absence of safety case maintenance guidelines from safety standards and the lack of systematic and methodical maintenance techniques have motivated the work of this thesis. Our work is presented through a set of developed and assessed techniques, where these techniques utilise safety contracts to achieve the overall goal by various contributions. We begin by a framework for evaluation of the impact of change on safety critical systems and safety cases. Through this, we identify and highlight the most sensitive system components to a particular change. We propose new ways to associate system design elements with safety case arguments to enable traceability. How to identify and reduce the propagation of change impact is addressed subsequently.  Our research also uses safety contracts to enable through-life safety assurance by monitoring and detecting any potential mismatch between the design safety assumptions and the actual behaviour of the system during its operational phase. More specifically, we use safety contracts to capture thresholds of selected safety requirements and compare them with the runtime related data (i.e., operational data) to continuously assess and evolve the safety arguments.

    In summary, our proposed techniques pave the way for cost-effective maintenance of safety cases upon preventive, perfective, corrective or adaptive changes in safety critical systems thus helping better decision support for change impact analysis.

  • Public defence: 2018-12-04 13:30 Kappa, Västerås
    Abbaspour Asadollah, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Concurrency Bugs: Characterization, Debugging and Runtime Verification2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Concurrent software has been increasingly adopted in recent years, mainly due to the introduction of multicore platforms. However, concurrency bugs are still difficult to test and debug due to their complex interactions involving multiple threads (or tasks). Typically, real world concurrent software has huge state spaces. Thus, testing techniques and handling of concurrency bugs need to focus on exposing the bugs in this large space. However, existing solutions typically do not provide debugging information to developers (and testers) for understanding the bugs.

    Our work focuses on improving concurrent software reliability via three contributions: 1) An investigation of concurrent software challenges with the aim to help developers (and testers) to better understand concurrency bugs. We propose a classification of concurrency bugs and discuss observable properties of each type of bug. In addition, we identify a number of gaps in the body of knowledge on concurrent software bugs and their debugging. 2) Exploring concurrency related bugs in real-world software with respect to the reproducibility of bugs, severity of their consequence and effort required to fix them. Our findings here is that concurrency bugs are different from other bugs in terms of their fixing time and severity, while they are similar in terms of reproducibility. 3) A model for monitoring concurrency bugs and the implementation and evaluation of a related runtime verification tool to detect the bugs. In general, runtime verification techniques are used to (a) dynamically verify that the observed behaviour matches specified properties and (b) explicitly recognize understandable behaviors in the considered software. Our implemented tool is used to detect concurrency bugs in embedded software and is in its current form tailored for the FreeRTOS operating system. It helps developers and testers to automatically identify concurrency bugs and subsequently helps to reduce their finding and fixing time.

  • Public defence: 2018-12-10 13:00 Filharmonin, Eskilstuna
    Norouzilame, Farhad
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Coordination of international manufacturing networks2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to globalisation, many companies have established or acquired production plants worldwide in order to capture the market opportunities that lay beyond their national borders. This has resulted in the emergence of international manufacturing networks (IMNs), which consist of multiple, interdependent production plants with different characteristics within a single organisation.

    Coordination of such networks consisting of multiple plants in different countries is not a simple management task. That is why some companies struggle with it, and turn their global production into a function that hinders their agility and performance; while others turn it into a formidable advantage. Coordination of an IMN requires a company to link and integrate its plants to support its strategic business objectives. A proficient coordination of activities, across multiple plants of an international manufacturing company, leads to competitive advantages.

    Despite its significance, the coordination aspect of IMN management has not been studied sufficiently. Operations leaders in today’s complex manufacturing world require a common language, tailored tools and frameworks for the management of their network. The research area of international manufacturing lacks empirical evidence of how industrial companies are (or could be) coordinated. Therefore, the overall aim of this research is to develop knowledge that improves the coordination of an IMN.

    The data in this study were acquired from case studies carried out on the IMNs of four global manufacturing companies where the majority of data was gathered from a global contract manufacturer headquartered in Sweden. The findings reveal a set of challenges, which influence the coordination of an IMN as one of the main aspects of its management.

    In order to improve IMN coordination, a framework has been developed from the results of the studies performed in this research project, as well as the results of previous research related to IMN management. It is composed of two distinctive parts: (1) preparatory steps, and (2) executional mechanisms.

    The first part of the framework discusses, and provides an insight into, the strategic relevance of coordination, the establishment of an autonomy balance among plants in an IMN, and mapping an IMN. The second part of the framework contains three mechanisms for conducting coordination in an IMN.

    The full text will be freely available from 2018-11-19 06:15
  • Public defence: 2018-12-14 13:00 Delta, Västerås
    Hosain, Md Lokman
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Fluid Flow and Heat Transfer Simulations for Complex Industrial Applications: From Reynolds Averaged Navier-Stokes towards Smoothed Particle Hydrodynamics2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optimal process control can significantly enhance energy efficiency of heating and cooling processes in many industries. Process control systems typically rely on measurements and so called grey or black box models that are based mainly on empirical correlations, in which the transient characteristics and their influence on the control parameters are often ignored. A robust and reliable numerical technique, to solve fluid flow and heat transfer problems, such as computational fluid dynamics (CFD), which is capable of providing a detailed understanding of the multiple underlying physical phenomena, is a necessity for optimization, decision support and diagnostics of complex industrial systems. The thesis focuses on performing high-fidelity CFD simulations of a wide range of industrial applications to highlight and understand the complex nonlinear coupling between the fluid flow and heat transfer. The industrial applications studied in this thesis include cooling and heating processes in a hot rolling steel plant, electric motors, heat exchangers and sloshing inside a ship carrying liquefied natural gas. The goal is to identify the difficulties and challenges to be met when simulating these applications using different CFD tools and methods and to discuss the strengths and limitations of the different tools.

    The mesh-based finite volume CFD solver ANSYS Fluent is employed to acquire detailed and accurate solutions of each application and to highlight challenges and limitations. The limitations of conventional mesh-based CFD tools are exposed when attempting to resolve the multiple space and time scales involved in large industrial processes. Therefore, a mesh-free particle method, smoothed particle hydrodynamics (SPH) is identified in this thesis as an alternative to overcome some of the observed limitations of the mesh-based solvers. SPH is introduced to simulate some of the selected cases to understand the challenges and highlight the limitations. The thesis also contributes to the development of SPH by implementing the energy equation into an open-source SPH flow solver to solve thermal problems. The thesis highlights the current state of different CFD approaches towards complex industrial applications and discusses the future development possibilities.

    The overall observations, based on the industrial problems addressed in this thesis, can serve as decision tool for industries to select an appropriate numerical method or tool for solving problems within the presented context. The analysis and discussions also serve as a basis for further development and research to shed light on the use of CFD simulations for improved process control, optimization and diagnostics.

    The full text will be freely available from 2018-11-23 08:00
  • Public defence: 2018-12-21 13:15 Lambda, Västerås
    Tahvili, Sahar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. RISE SICS Västerås.
    Multi-Criteria Optimization of System Integration Testing2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optimizing software testing process has received much attention over the last few decades. Test optimization is typically seen as a multi-criteria decision making problem. One aspect of test optimization involves test selection, prioritization and execution scheduling. Having an efficient test process can result in the satisfaction of many objectives such as cost and time minimization. It can also lead to on-time delivery and a better quality of the final software product. To achieve the goal of test efficiency, a set of criteria, having an impact on the test cases, need to be identified. The analysis of several industrial case studies and also state of the art in this thesis, indicate that the dependency between integration test cases is one such criterion, with a direct impact on the test execution results. Other criteria of interest include requirement coverage and test execution time. In this doctoral thesis, we introduce, apply and evaluate a set of approaches and tools for test execution optimization at industrial integration testing level in embedded software development. Furthermore, ESPRET (Estimation and Prediction of Execution Time) and sOrTES (Stochastic Optimizing of Test Case Scheduling) are our proposed supportive tools for predicting the execution time and the scheduling of manual integration test cases, respectively. All proposed methods and tools in this thesis, have been evaluated at industrial testing projects at Bombardier Transportation (BT) in Sweden. As a result of the scientific contributions made in this doctoral thesis, employing the proposed approaches has led to an improvement in terms of reducing redundant test execution failures of up to 40% with respect to the current test execution approach at BT. Moreover, an increase in the requirements coverage of up to 9.6% is observed at BT. In summary, the application of the proposed approaches in this doctoral thesis has shown to give considerable gains by optimizing test schedules in system integration testing of embedded software development.