| 1. |
- Abbaspour, Sara, 1984-
(författare)
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Proposing Combined Approaches to Remove ECG Artifacts from Surface EMG Signals
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electromyography (EMG) is a tool routinely used for a variety of applications in a very large breadth of disciplines. However, this signal is inevitably contaminated by various artifacts originated from different sources. Electrical activity of heart muscles, electrocardiogram (ECG), is one of sources which affects the EMG signals due to the proximity of the collection sites to the heart and makes its analysis non-reliable. Different methods have been proposed to remove ECG artifacts from surface EMG signals; however, in spite of numerous attempts to eliminate or reduce this artifact, the problem of accurate and effective de-noising of EMG still remains a challenge. In this study common methods such as high pass filter (HPF), gating method, spike clipping, hybrid technique, template subtraction, independent component analysis (ICA), wavelet transform, wavelet-ICA, artificial neural network (ANN), and adaptive noise canceller (ANC) and adaptive neuro-fuzzy inference system (ANFIS) are used to remove ECG artifacts from surface EMG signals and their accuracy and effectiveness is investigated. HPF, gating method and spike clipping are fast; however they remove useful information from EMG signals. Hybrid technique and ANC are time consuming. Template subtraction requires predetermined QRS pattern. Using wavelet transform some artifacts remain in the original signal and part of the desired signal is removed. ICA requires multi-channel signals. Wavelet-ICA approach does not require multi-channel signals; however, it is user-dependent. ANN and ANFIS have good performance, but it is possible to improve their results by combining them with other techniques. For some applications of EMG signals such as rehabilitation, motion control and motion prediction, the quality of EMG signals is very important. Furthermore, the artifact removal methods need to be online and automatic. Hence, efficient methods such as ANN-wavelet, adaptive subtraction and automated wavelet-ICA are proposed to effectively eliminate ECG artifacts from surface EMG signals. To compare the results of the investigated methods and the proposed methods in this study, clean EMG signals from biceps and deltoid muscles and ECG artifacts from pectoralis major muscle are recorded from five healthy subjects to create 10 channels of contaminated EMG signals by adding the recorded ECG artifacts to the clean EMG signals. The artifact removal methods are also applied to the 10 channels of real contaminated EMG signals from pectoralis major muscle of the left side. Evaluation criteria such as signal to noise ratio, relative error, correlation coefficient, elapsed time and power spectrum density are used to evaluate the performance of the proposed methods. It is found that the performance of the proposed ANN-wavelet method is superior to the other methods with a signal to noise ratio, relative error and correlation coefficient of 15.53, 0.01 and 0.98 respectively.
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| 2. |
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| 3. |
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| 4. |
- Afshar, Sara
(författare)
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Lock-Based Resource Sharing in Real-Time Multiprocessor Platforms
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded systems are typically resource constrained, i.e., resources such as processors, I/O devices, shared buffers or shared memory can be limited for tasks in the system. Therefore, techniques that enable an efficient usage of such resources are of great importance.In the industry, typically large and complex software systems are divided into smaller parts (applications) where each part is developed independently. Migration towards multiprocessor platforms has become inevitable from an industrial perspective. Due to such migration and to efficient use of system resources, these applications eventually may be integrated on a shared multiprocessor platform. In order to facilitate the integration phase of the applications on a shared platform, the timing and resource requirements of each application can be provided in an interface when the application is developed. The system integrator can benefit from such provided information in the interface of each application to ease the integration process. In this thesis, we have provided the resource and timing requirements of each application in their interfaces for applications that may need several processors to be allocated on when they are developed.Although many scheduling techniques have been studied for multiprocessor systems, these techniques are usually based on the assumption that tasks are independent, i.e. do not share resources other than the processors. This assumption is typically not true. In this thesis, we provide an extension to such systems to handle sharing of resources other than processor among tasks. Two traditional approaches exist for multiprocessor systems to schedule tasks on processors. A recent scheduling approach for multiprocessors has combined the two traditional approaches and achieved a hybrid more efficient approach compared to the two previous one. Due to the complex nature of this scheduling approach the conventional approaches for resource sharing could not be used straight forwardly. In this thesis, we have modified resource sharing approaches such that they can be used in such hybrid scheduling systems. A second concern is that enabling resource sharing in the systems can cause unpredictable delays and variations in response time of tasks which can degrade system performance. Therefore, it is of great significance to improve the resource handling techniques to reduce the effect of imposed delays caused by resource sharing in a multiprocessor platform. In this thesis we have proposed alternative techniques for resource handling that can improve system performance for special setups.
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| 5. |
- Agerskans, Natalie
(författare)
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Digital Technologies for Enabling Smart Production : Examining the Aspects of Selection and Integration
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the development towards Industry 5.0, manufacturing companies are developing towards smart production. In smart production, data is used as a resource to interconnect different elements in the production system to learn and adapt to changing production conditions. Common objectives include human-centricity, resource-efficiency, and sustainable production. To enable these desired benefits of smart production, there is a need to use digital technologies to create and manage the entire flow of data. To enable smart production, it is essential to deploy digital technologies in a way so that collected raw data is converted into useful data that can be applied by equipment or humans to generate value or reduce waste in production. This requires consideration to the data flow within the production system, i.e., the entire process of converting raw data into useful data which includes data management aspects such as the collection, analysis, and visualization of data. To enable a good data flow, there is a need to combine several digital technologies. However, many manufacturing companies are facing challenges when selecting suitable digital technologies for their specific production system. Common challenges are related to the overwhelming number of advanced digital technologies available on the market, and the complexity of production system and digital technologies. This makes it a complex task to understand what digital technologies to select and the recourses and actions needed to integrate them in the production system.Against this background, the purpose of this licentiate thesis is to examine the selection and integration of digital technologies to enable smart production within manufacturing companies. More specifically, this licentiate thesis examines the challenges and critical factors of selecting and integrating digital technologies for smart production. This was accomplished by performing a qualitative-based multiple case study involving manufacturing companies within different industries and of different sizes. The findings show that identified challenges and critical factors are related to the different phases of the data value chain: data sources and collection, data communication, data processing and storage, and data visualisation and usage. General challenges and critical factors that were related to all phases of the data value chain were also identified. Moreover, the challenges and critical factors were related to people, process, and technology aspects. This shows that there is a need for holistic perspective on the entire data value chain and different production system elements when digital technologies are selected and integrated. Furthermore, there is a need to define a structured process for the selection and integration of digital technologies, where both management and operational level are involved.
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| 6. |
- Ahl, Linda, 1970-
(författare)
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Approaching Curriculum Resources : Examining the potential of textbooks and teacher guides to support mathematics learning and teaching
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The driving forces of conducting the two studies presented in this thesis are: the strong position of curriculum resources in the mathematics classroom in general; teachers’ faith in curriculum resources to convey the intentions and goals of mathematics education; and the expected benefits to mathematics education through expanding the knowledge base of research in the area of curriculum resources in general, and teacher guides in particular. This thesis builds upon two studies conducted in Sweden. The first is a study on how teachers use teacher guides. The results of this study could be seen as one piece in the building of a theoretical understanding of how teachers use their tools in planning and enacting teaching. The data for Study I were collected through semi-structured interviews with five early-years mathematics teachers. In advance, the teachers were asked to copy the pages from the teacher guide they had used the week before the interview. The analysis of the interviews shows that less experienced teachers desire a wider scope of content in their teacher guide. More experienced teachers desire support from teaching activities, in the design of teaching in classroom practice. Another interesting result was that all teachers in our study, regardless of prior experience, knowledge, beliefs, etc., want the teacher guide to offer connections between theory and practice. The second study investigates what content is represented in Swedish textbooks. The results of this study map the terrain over how the most commonly used textbooks in Sweden construct the topic of proportion and proportional reasoning. My choice of textbooks is based on a questionnaire among all compulsory school mathematics teachers in the sixth largest municipality in Sweden, revealing that two curriculum resources together covered 97% of the classrooms in Grades 7-9. The study provides insights into the strengths and weaknesses in the presented structure regarding proportional reasoning in the most commonly used textbooks in Swedish lower secondary school. Teachers could use these insights when making decisions about how to use their textbooks, and to possibly reconsider how to organize the enactment of the national curriculum in order to develop deep understanding. The analyses could provide authors of teacher guides and textbooks with valuable information to consider regarding structure and design.
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| 7. |
- Ahlskog, Mats, 1970-
(författare)
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Supporting pre-development of new manufacturing technologies
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In today’s tough industrial environment, efficient development of new products and new manufacturing solutions is necessary to stay competitive on a global market. Manufacturing companies use substantial money and development resources to develop new products. However, the resources spent on finding and implementing emerging manufacturing technologies are much more limited. This is often the case even though it is well known that a way of competing on a global market is through the introduction of new manufacturing technologies that can improve product quality as well as contribute to reducing manufacturing time, resulting in reduced product price and in the end increased profit.When introducing new manufacturing technologies, different challenges arise such as lack of knowledge, involvement of an external equipment supplier, etc. In addition, time-to-volume is critical when introducing new manufacturing technologies in a manufacturing context. To be able to have a fast ramp-up, manufacturing technology needs to be mature enough and at the same time meet all requirements. Efficient introduction of new manufacturing technologies requires that pre-development activities have been performed in advance.Previous research in this area highlights a lack of knowledge and solutions regarding pre-development of new manufacturing technologies. Such pre-development is important in order to have a successful introduction, fast time-to-volume and production system development. Based on these challenges, the objective of the research presented in this thesis is to develop support for pre-development of new manufacturing technologies.The research is based on literature reviews and three empirical case studies, carried out over a two-year period of time. The first empirical case study was an exploratory case study in the manufacturing industry. The purpose of that research study was to identify critical factors forcing manufacturing companies to improve the development of manufacturing technologies.The second study was a longitudinal embedded case study in the manufacturing industry with the purpose of identifying factors that affect evaluation of new manufacturing technologies during new product development. Particular attention was given to the product development process and how it has affected the evaluation of new manufacturing technologies.Finally, the third study was a single case study in the manufacturing industry with the purpose of analysing and discussing the assessment of the maturity level of a manufacturing technology.
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| 8. |
- Akbari, Keramatollah, 1961-
(författare)
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Impact of Radon Ventilation on Indoor Air Quality and Building Energy saving
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Industrial living is caused much people do live and work in closed and confined places; offices and residential buildings. This is why in this new world more fresh air which is generally provided by forced ventilation plays a vital role in living of human being. Furthermore because of many different indoor pollutants, like radon and artificial pollutants, the amount of fresh air and in turn the energy consumption has increased. This energy consumption related to ventilation has reached up to about 30 percent of energy used of building section. So making interaction between indoor air quality (IAQ) and optimization of energy saving is a necessary work. Radon as a natural pollutant is occurred in environment and in many countries threatens people health whereas is called the second causes of cancer. For reducing radon concentration in residential building at the acceptable level forced ventilation is used usually. Ventilation can improve IAQ but in the other side would increase the energy consumption in building sector and just now the contribution of ventilation exceeds up 50 percent of building sector's share. The aim of this thesis is to study the impact of ventilation on indoor radon by using Computational Fluid Dynamics (CFD) to achieve indoor air quality and energy efficiency. Application of CFD as a new technology, because of its cost and time savings, and on the other side, of its flexibility and precision is increasingly grown and can be used as a very important and valuable tool for the prediction and measurement of radon distribution in a ventilated building . Currently, measurement techniques and proposed standards and regulations of indoor pollutants and ventilation, particularly related to indoor radon cannot be able to provide a secure, safe and energy efficient indoor climate. This is why the indoor airflow distribution is very complex and with changing building geometry and operation condition, the treatment of air flow pattern, substantially would be changed, whereas the rules are usually independent of the buildings features. Furthermore, the indoor standards and regulations are based on average amount of pollutants in a room, whereas the pollutant distributions aren't identical and are varied throughout the room. Then the current techniques aren't so exactly valuable and acceptable. From different methods which is privilege to control pollutants, ventilation method is applicable in existing buildings. Designing effective ventilation can reduce radon concentration to very level low with regarding energy conservation remarks. This thesis presents results from simulation studies on ventilation and radon mitigation in residential buildings, in view points of indoor air quality and energy savings. The CFD technique is applied to predict, visualize and calculate of mixture radon-air flow. The distribution of indoor radon concentration, air velocity and room temperature also have considered together for achieving indoor air quality and energy saving. The results are also compared with the experimental data and related previous works. It was found that with increasing ventilation rate, the radon concentration is decreased, but the location of ventilation system is also important. From the simulation results, it is observed that within the ventilated room, there are some zones, which are good for living and somewhere is more polluted. The traditional radon detectors basically show the average value of radon content in 1m3 of air. That is why detector measuring is not exact and safe. Simulation results proved that floor heat can be supported ventilation effect and speed up the mixture movement. Floor heating reinforces the buoyancy effect, which is useful to reduce radon content in the floor (seating area) and then lower ventilation rate can be applied.
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| 9. |
- Andersson, Anna, 1974-
(författare)
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A framework supporting the collaboration between the logistics- and the product development process
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the competitive environment of today’s global markets, the demands of customers are increasing. They expect to get the best product at the lowest price with immediate availability. Logistics, including transportation, inventory maintenance, order processing, purchasing, warehousing, materials handling, packaging, customer service standards, and product scheduling must continuously be developed to meet the challenges of the market. The globalization, with longer distances to customers and suppliers, and the progressing trend of outsourcing are examples of why the importance of logistics has increased over the last few years.A considerable part of the final product cost is frozen during the early product development phases. In the early phases of the product development process, the cost of making design changes is low compared to making changes later in the product development process. The product development decisions made in the early phases of the product development process have considerable impact on future manufacturing and logistics activities as well.The objective of this research project is to develop a framework supporting the collaboration between the logistics- and the product development process. To do this, it has been essential to analyze which parameters influence the efficiency of the logistics process and the interface between the logistics- and the product development process. Also, to investigate how the logistics department can be integrated earlier in the product development process has been of interest. This has been done through both a theoretical review and also through a number of case studies.The result and conclusion of this project is a framework that gives support for what to focus on, how to collaborate, in which phases collaboration is meaningful, and which persons need to be involved in the different product development phases. Working as the framework suggests will, hopefully, give closer collaboration between the logistics- and the product development process than without this supportive framework. The expectation of the collaboration is an earlier integration of the logistics department in the product development process and through this influence and increase the efficiency of the logistics process.
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| 10. |
- Andersson, Carina, 1970-
(författare)
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Upplevelser av budskap : Fallstudier av hur användare upplever och förstår information i användargränssnitt
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- När användbarheten studeras av den information som presenteras i ett användargränssnitt på en datorskärm kan det framkomma vad som fungerar effektivt och korrekt. I sådana sammanhang förs sällan någon diskussion om hur den information som presenteras kommunicerar med en användare.Syftet med detta forskningsprojekt är att på ett generellt plan öka kunskapen om olika analytiska perspektiv för att studera den information som presenteras i ett användargränssnitt på en datorskärm, som ett led till att skapa begriplig information för människor. Mer preciserat är syftet att få en djupare förståelse för hur en informationslämnare kan kommunicera med en informationsanvändare genom den information som presenteras i ett användargränssnitt. Målet med forskningsprojektet är att presentera ett antal relevanta analytiska perspektiv som kan användas för att beskriva hur presenterad information i ett användargränssnitt kan kommunicera med en användare. Forskningsresultatet bidrar med ett ramverk som kan ligga till grund för ett analysstöd. Forskningsresultatet bidrar även med en ansats för framtida forskning inom området.Forskningsprojektet bygger på fyra fallstudier. Analysobjekten i fallstudierna utgörs av fyra olika användargränssnitt på datorskärm, vilka används inom olika myndigheter, organisationer och företag. Vartdera användargränssnittet och dess informationsdesign studeras med hänsyn till: informationslämnarnas önskemål och intentioner, informationsanvändarnas upplevelse och förståelse av information och kontexters påverkan.De slutsatser som dras är bland annat att informationsdesign i ett användargränssnitt på datorskärm upplevs och förstås av användare i samklang med inre, när och yttre kontext. Dessa kontexter kan studeras utifrån tre olika perspektiv, ett semiotiskt, ett retoriskt och ett narrativt perspektiv. En sådan analys kan framhäva den kommunikation som sker mellan de budskap som informationslämnaren vill berätta, hur den presenterade informationen i användargränssnittet arrangeras och komponeras och hur olika kontexter påverkar användarnas upplevelse och förståelse av den information som presenteras.
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| 11. |
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| 12. |
- Andersson, Mona, 1948-
(författare)
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Botvids väg till rätt vård : Planering av ett interorganisatoriskt vårdkedjeprojekt
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The patient Botvid´s way to right care. The planning process of an inter-organizational care pathway project.A general problem in an elderly patient’s care – and rehabilitation process, which involves different care providers, is that there is no one single staff that is responsible for the whole “production process” i.e. from diagnosis to completed treatment. All too often care providers focus on their own part of the process with insufficient communication with other providers, resulting in low quality of care. Poor co-operation also leads to increased demand for check-ups, unproductive waiting time, duplication of work and other inefficiencies. A solution to these co-ordination problems can be to introduce process orientation (integrated care pathways). A process view requires the concerned staff to look at their own work with other eyes. The process view implies that they need to change focus to what is best from the patient’s point of view.Experiences from earlier reforms, that were centrally initiated and managed, show that the concerned staff (doctors, nurses etc.) had too little influence during the planning and implementation phases. Several official reports therefore call attention to the need for broad participation from all of the different staff categories in organizational development.In this thesis a qualitative case study of the planning process of an inter-organizational project between primary care, hospital treatment and municipality care is presented. The aim of the project was to develop an organization that could support a process view among the care providers. The focus of the thesis is on how the project management acted to shape the necessary conditions for a process view to enable the professional staff to participate, and on the role that the change strategy played in this connection.The results show that the professional staff had an active role in the management of the project. The initiator was a doctor, who managed the project team of 50 care staff together with a project leader. This team had a series of meetings and conferences during ten months. By exchanging ideas and experiences they found solutions to the operative problems that were the starting points for the project. They developed an action plan in consensus, with prioritized activities, which is now to be implemented.
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| 13. |
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| 14. |
- Ashjaei, Mohammad, 1980-
(författare)
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Multi-Hop Real-Time Communication over Switched Ethernet Technology
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Switched Ethernet technology has been introduced to be exploited in real-time communication systems due to its features such as its high throughput and wide availability, hence being a cost-effective solution. Many real-time switched Ethernet protocols have been developed, preserving the profits of traditional Ethernet technology, to overcome the limitations imposed by using commercially available (COTS) switches. These limitations mainly originate from the non-deterministic behavior of the Ethernet switches inherent in the use of FIFO queues and a limited number of priority levels. In our research we focus on two particular real-time communication technologies, one based on COTS Ethernet switches named the FTT-SE architecture and the other using a modified Ethernet switch called the HaRTES architecture. Both architectures are based on a master-slave technique supporting different and temporally isolated traffic types including real-time periodic, real-time sporadic and non-real-time traffic. Also, they provide mechanisms implementing adaptivity as a response to the requirements imposed by dynamic real-time applications. Nevertheless, the two mentioned architectures were originally developed for a simple network consisting of a single switch, and they were lacking support for multi-hop communication. In industrial applications, multi-hop communication is essential as the networks comprise a high number of nodes, that is far beyond the capability of a single switch. In this thesis, we study the challenges of building multi-hop communication using the FTT-SE and the HaRTES architectures. We propose different architectures to provide multi-hop communication while preserving the key characteristics of the single-switch architecture such as timeliness guarantee, resource efficiency, adaptivity and dynamicity. We develop a response time analysis for each proposed architecture and we compare them to assess their corresponding benefits and limitations. Further, we develop a simulation tool to evaluate the solutions.
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| 15. |
- Ask, Andréas, 1977-
(författare)
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Factory-in-a-Box : an Enabler for Flexibility in Manufacturing Systems
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AT PRESENT, many markets are characterized by a fast pace of change, as well as a high internationally enlarged competition. Since the conception of Mass Customization emerged in the late 1980´s, many companies within the manufacturing industry have been striving to fulfill this vision by increasing the flexibility within their manufacturing system. However, although there are many manufacturing theories that describe theoretical solutions to mass customization, but there is still a lack of practical enablers that can realize the conception.In January 2005, the Swedish Foundation for Strategic Research started the project Factory-in-a-Box. There, the key characteristic is to realize is the concept of modular production units that are flexible, mobile and quick to ramp-up. This licentiate thesis is a part of the Factory-in-a-Box project, and its objective is to investigate if and how the Factory-in-a-box concept is an enabler to realize flexibility in manufacturing systems.The outcome of this research work indicates that the Factory-in-a-Box concept is a plausible solution that goes in line with previous research and future challenges within the manufacturing industry. The Factory-in-a-Box concept offers possibilities for a more flexible and responsive manufacturing system, which also unwrap new business possibilities, increased automation, and entering new markets. To succeed in implementing the Factory-in-a-Box concept in a manufacturing system some key generic requirements have been identified.The research project concludes that mobile manufacturing systems in general and the Factory-in-a-Box concept in particular offer new possibilities to the manufacturing industry. Also, the concept is not limited to the manufacturing industry, there are a wide range of applications where the concept could be useful, for example within the construction industry.
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| 16. |
- Badasjane, Viktorija
(författare)
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Coordinating Digital Transformation in International Manufacturing Networks
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Manufacturing companies have adapted to globalisation and collected their globally dispersed factories into factory networks, known as international manufacturing networks (IMNs). This requires coordination to access the associated competitive advantages, synchronise the factories, and exploit the capabilities inherent in those individual factories. However, when IMNs introduce digital transformation into the factories, the coordination is often hindered by uncertainty and complexity, as digital transformation requires an extensive adjustment that affects everything from the organisational structure to ways of working. Different parts of the network that are dependent on one another, for example, may be difficult to track and foresee the consequences of digital transformation. Hence, due to the respective challenges, complexities, and uncertainties, the coordination of digital transformation in IMN is paramount to examine. This licentiate thesis begins with exploring coordination mechanisms to increase the understanding of existing research and shape it into a comprehensive overview. Moreover, through case studies, this thesis explores the challenges in and enablers for coordinating digital transformation in IMNs. Altogether, the challenges and enablers are analysed within the dimensions and categories of coordination mechanisms, i.e., they are collected into an overview and described within the case study context. The most significant findings of this thesis are related to the organisational structure, which enables the coordination of digital transformation. However, plenty of challenges remain, foremost connected to the formalisation of the organisational structure, e.g., balancing the rules and guidelines for digital transformation but providing space for people performing the activities to explore and investigate digital technologies. This thesis further contributes to the existing body of research by untangling the complexity of coordination itself and, specifically, the coordination of digital transformation in IMNs, explicitly adding to the operations management field and the management of global operations. Practical contributions are also made, i.e., this thesis promotes practitioners’ increased understanding by providing specific examples and descriptions of the findings within their context. Based on the findings, this thesis offers multiple paths for future research, keeping in mind that coordination is not static but evolving, depending on the context in which it is performed.
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| 17. |
- Bakhshi Valojerdi, Zeinab, 1986-
(författare)
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Persistent Fault-Tolerant Storage at the Fog Layer
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Clouds are powerful computer centers that provide computing and storage facilities that can be remotely accessed. The flexibility and cost-efficiency offered by clouds have made them very popular for business and web applications. The use of clouds is now being extended to safety-critical applications such as factories. However, cloud services do not provide time predictability which creates a hassle for such time-sensitive applications. Moreover, delays in the data communication between clouds and the devices the clouds control are unpredictable. Therefore, to increase predictability an intermediate layer between devices and the cloud is introduced. This layer, the Fog layer, aims to provide computational resources closer to the edge of the network. However, the fog computing paradigm relies on resource-constrained nodes, creating new potential challenges in resource management, scalability, and reliability. Solutions such as lightweight virtualization technologies can be leveraged for solving the dichotomy between performance and reliability in fog computing. In this context, container-based virtualization is a key technology providing lightweight virtualization for cloud computing that can be applied in fog computing as well. Such container-based technologies provide fault tolerance mechanisms that improve the reliability and availability of application execution. By the study of a robotic use-case, we have realized that persistent data storage for stateful applications at the fog layer is particularly important. In addition, we identified the need to enhance the current container orchestration solution to fit fog applications executing in container-based architectures. In this thesis, we identify open challenges in achieving dependable fog platforms. Among these, we focus particularly on scalable, lightweight virtualization, auto-recovery, and re-integration solutions after failures in fog applications and nodes. We implement a testbed to deploy our use-case on a container-based fog platform and investigate the fulfillment of key dependability requirements. We enhance the architecture and identify the lack of persistent storage for stateful applications as an important impediment for the execution of control applications. We propose a solution for persistent fault-tolerant storage at the fog layer, which dissociates storage from applications to reduce application load and separates the concern of distributed storage. Our solution includes a replicated data structure supported by a consensus protocol that ensures distributed data consistency and fault tolerance in case of node failures. Finally, we use the UPPAAL verification tool to model and verify the fault tolerance and consistency of our solution.
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| 18. |
- Baumgart, Stephan, 1979-
(författare)
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Incorporating Functional Safety in Model-based Development of Product Lines
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Product lines in industry are often based on an engineer’s focus on fast and feasible product instantiation rather than a precise product line development method and process as described in literature. When considering functional safety, we need a precise model that includes evidence for the safety of each variant of the product.Functional safety standards provide guidance to develop safety critical products and require that evidence is collected to prove the safety of the product. But today’s functional safety standards do not provide guidance on how to achieve functional safety in product lines. At the same time arguments need to be collected during development so that each product configuration is safe and is fulfilling the requirements of the standards. Providing these arguments requires tracing safety-related requirements and dependencies through the development process taking the impact of variability in different development artifacts into consideration.In this thesis, we study the challenges of developing safety critical products in product lines. We explore industrial practices to achieve functional safety standard compliance in product lines by interviewing practitioners from different companies and by collecting the reported challenges and practices. This information helps us to identify improvement areas and we derive requirements that a product line engineering method needs to fulfill. Based on these findings we analyze variability management methods from the software product line engineering research domain to identify potential candidate solutions that can be adapted to support safety critical products. We provide an approach for capturing functional safety related characteristics in a model-based product line engineering method. We apply our method in an industrial case demonstrating the applicability.
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| 19. |
- Beckinghausen, Aubrey, 1991-
(författare)
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Investigation of nitrogen recovery from concentrated wastewater
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nitrogen recovery from wastewater treatment for fertilizers is a research topic that exists at the intersection of multiple topics important to the future of sustainable society. First, nitrogen recovery from wastewater implies a departure from the current methods of nitrogen mitigation, which involve nitrogen removal by conversion of various aqueous species to inert nitrogen gas. Secondly, by recovering nitrogen from wastewater specifically, there is the opportunity to begin a circular economy where value added products can be obtained from material that has historically been seen as a “waste”. Current wastewater treatment involves nitrogen removal through the biological transformation of aqueous nitrogen species to inert nitrogen gas. This process is energy intensive and risks the production of air pollutants such as N2O as intermediates in the biological transformation. If this nitrogen can be captured in a form that can be reused, a valuable product can be achieved with the potential reduction of both the energy required at the wastewater treatment plant as well as the carbon footprint. Finally, by recovering nitrogen in a form that can be used in agriculture as a fertilizer, additional environmental benefits can be realized by reducing reliance on Haber-Bosch based ammonia production, which is also energy intensive and contributes harmful emissions to the atmosphere.The work described in the following licentiate aims to consider the current status of nitrogen recovery from wastewater for fertilizers as a research topic. Literature was analytically examined to compare different techniques in terms of energy requirements, cost for fertilizer production, market for final fertilizer product, and technological readiness. The most interesting findings from this review were that there seems to be a disconnect between the fertilizer product produced by nitrogen recovery techniques and the market, which will become a challenge if these techniques are implemented at a large scale. The attitude of the farmers with regards to fertilizers from waste was overall positive, with their concerns mainly focused on the performance ability and cost of the product. Additionally, many techniques such as microbial fuel cells and microbial electrolysis cells have been unable to move past the laboratory phase despite being researched for many years. This indicates there are cost and technological barriers that are preventing the further scale up and implementation of these techniques. Energy and cost analyses will be crucial to motivate investment into these processes, and these are missing for many of the techniques found around this topic.To contribute to this field, experimental work was also included to assess the potential for ammonium adsorption from concentrated wastewater for fertilizer production. The experimental work focused on the utilization of the solid product of pyrolysis of sewage sludge (biochar) for adsorption and explored the potential enhancement of the char with various chemical treatments. The char with the best ammonium adsorption performance was found to be using a treatment of HNO3 followed by and NaOH, with an adsorption capacity of 4 mg NH4/g biochar. This char was compared with commercially activated carbon and clinoptilolite for full scale applications. It was found that even with this increased adsorption capacity, the use of chemically enhanced sewage sludge biochar for full scale applications is not realistic. The amount of raw material required for the complete recovery of ammonium from reject water at the municipal wastewater treatment plants exceeds the total amount of sewage sludge generated. Therefore it is recommended that the goal of incorporating sewage sludge biochar with wastewater treatment is to produce a solid fertilizer product loaded with ammonium (which would provide ammonium-N and phosphorus for plant growth, as well as carbon and other minerals for soil amendment) rather than having the goal be complete ammonium recovery from the wastewater stream.
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| 20. |
- Behnam, Moris
(författare)
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Hierarchical Real Time Scheduling and Synchronization
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Hierarchical Scheduling Framework (HSF) has been introduced to enable compositional schedulability analysis and execution of embedded software systems with real-time constraints. In this thesis, we consider a system consisting of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF provides CPU-time to the subsystems and it guarantees that the individual subsystems respect their allocated CPU budgets. However, if subsystems are allowed to share logical resources, extra complexity with respect to analysis and run-time mechanisms is introduced. In this thesis we address three issues related to hierarchical scheduling of semi-independent subsystems. In the first part, we investigate the feasibility of implementing the hierarchical scheduling framework in a commercial operating system, and we present the detailed figures of various key properties with respect to the overhead of the implementation. In the second part, we studied the problem of supporting shared resources in a hierarchical scheduling framework and we propose two different solutions to support resource sharing. The first proposed solution is called SIRAP, a synchronization protocol for resource sharing in hierarchically scheduled open real-time systems, and the second solution is an enhanced overrun mechanism. In the third part, we present a resource efficient approach to minimize system load (i.e., the collective CPU requirements to guarantee the schedulability of hierarchically scheduled subsystems). Our work is motivated from a tradeoff between reducing resource locking times and reducing system load. We formulate an optimization problem that determines the resource locking times of each individual subsystem with the goal of minimizing the system load subject to system schedulability. We present linear complexity algorithms to find an optimal solution to the problem, and we prove their correctness
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| 21. |
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| 22. |
- Berg, Benita, 1976-
(författare)
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Lgr11 – stöd eller begränsning? : Lärares röster om styrdokument och reformens påverkan på deras matematikundervisning
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis examines teachers’ voices on the latest curriculum reform and how teachers experience the impact of the reform on their teaching. The aim of this study is to contribute to knowledge about the conditions of the implementation of a new reform and how the reform controls and empowers teachers’ teaching. I examine the issue using the concepts from curriculum theory and implementation theory as well as visible and invisible pedagogy. Primary school teachers, Grades 1-3 (n=224) within an entire municipality responded to an extensive questionnaire concerning their relation to the reform. The questionnaire was developed from qualitative interviews and questionnaires with open questions. The new curriculum reform tends towards increased control but the results show that the majority of teachers consider both the curriculum and the national examinations for Grade 3 as a support in their teaching and assessment. Most teachers express that the recent curriculum increases their professionalism. Yet there is a tension between positive and negative experiences of the reform, as some teachers express that the new curriculum and the national tests limit their professional freedom while other teachers express that they would like even more detailed support and guidance. There are also teachers who think it is too early to introduce goals, in the form of knowledge requirements and national tests, because it violates the students’ right to develop at their own pace based on their prerequisites. Further, most teachers in the study state that they have been affected by the goals and the national tests, but at a school level a common plan in mathematics and routines to discuss the goals of mathematics education is often lacking. The study also shows that national tests are not used in order to improve the mathematics results of the whole school. The factor analysis shows that there are differences between teachers’ voices depending on their age, their teaching experience, and if they are graduated before or after the reform of 1994. The different expressions can be linked to teachers’ voices of teacher professionalism, of student learning and maturity. The results of the study are of interest for various actors at different educational levels like politicians, curriculum authors and principals. By taking part of the study they have the opportunity to gain more knowledge of how to create good conditions to support teachers to enact the curriculum in their classrooms.
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| 23. |
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| 24. |
- Bilic, Damir
(författare)
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Managing Variability in SysML Models of Automotive Systems
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organizations developing software-intensive systems inevitably face increasing complexity of developed products, mainly due to rapid advancements in all domains of technology. Many such organizations are considering model-based systems engineering (MBSE) practices to cope with the increasing complexity. The use of models, as a central role during product design, promises to provide benefits such as enhanced communication among system stakeholders, continuous verification, improved design integrity, traceability between requirements and system artifacts and many more. Additionally, products are often built in many variants. That is especially obvious in the automotive domain, where customers have the ability to configure vehicles with hundreds of configuration options. To deal with the variability, a product line engineering approach is often used. It allows the development of a family of similar software-intensive systems that share a common base while being adapted to individual customer requirements.In this thesis, the overall goal is to evaluate and facilitate the combination of the two mentioned approaches, model-based systems engineering and product line engineering, in an industrial environment. To achieve the main thesis goal, it was divided into three separate research goals.The first goal was to identify challenges when applying an annotation-based approach for variant management in SysML models on a use case provided by Volvo Construction Equipment. The aim was to identify and understand challenges when using existing tool support to manage variants in implementation artifacts of existing products. The second research goal was to identify reuse-related challenges in the ``clone-and-own'' based development process of Volvo CE. Moreover, we assess the effects of model-based product line engineering on the identified challenges. Lastly, the third research goal was to develop an approach for consistency checking between variability- and SysML system models. To achieve that, we develop an integrated tool chain for model-based product line engineering that allows the integration of variable artifacts, which are not documented in system models, into the development process. Secondly, we define and develop an approach for consistency checking between variability models that describe the system in terms of features and implementation models that describe how variability is implemented in the product itself, since such support does not exist in current state of the art tools.In conclusion, based on the results from the results of case studies at Volvo CE, it was shown that model-based product line engineering has the potential to improve communication and highlight implications of variability to stakeholders (e.g. to non-technical staff), improve traceability between variability in requirements and variability in design and implementation, improve consistency through constraints between variants and automate repetitive activities.In other words, it shows potential for improving product quality while reducing the development lead time. However, the evaluation and measurement of improvement will be left for future work as measuring the product quality and lead time requires an organizational roll out of model-based product-line engineering.
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| 25. |
- Björnander, Stefan, 1968-
(författare)
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Methods and Tool Support for Analyzing Architectural Models of Embedded Systems
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded systems are ubiquitous in the modern world. They are microcomputers most often included incomplete devices consisting of software and hardware. Embedded systems range from small devices to large systems monitoring and controlling complex processes. Design and development of such systems is a complex task, since embedded systems often need to fulfill extra-functional requirements, on top of functional ones, within constrained amounts of platform resources. Some embedded systems are mission critical; hence, they are not allowed to fail during the mission. One way to ensure that a system works in accordance to its specification is to define the system in an Architecture Description Language (ADL) and apply formal verification methods. The Architecture Design and Analysis Language (AADL) has become popular in the avionic and automobile industry, and is equipped with several annexes, among them the Behavior Annex. However, AADL still misses a formal semantics, which prevents the possibility to prove correctness of architecture features by performing model checking on AADL models. Moreover, AADL does not support time annotations, which prevents modeling of real-time systems in AADL.In this thesis, we address these issues by presenting a formal analysis framework including a denotationalsemantics for a subset of the AADL and its Behavior Annex, which evaluates properties defined in Computation Tree Logic (CTL) by providing model checking. Model checking is a formal verification method that has proved to be powerful as well as effective. Our AADL-semantics is supported by a tool with an implementation of the semantics in Standard ML, which in turn is encapsulated in an Eclipse plugin.We also present a time annotation extension of AADL, implemented in a tool translating time annotated AADL and its Behavior Annex into the Timed Abstract State Machine (TASM) for simulation of real-time features. Another closely related problem is how to achieve optimal component distribution; in order to address this issue we have developed a tool that perform near-optional component distribution in regard to a series of parameters.The research results, which have been validated thought case studies, provides the possibility for a system engineer to model a system and prove its correctness. The research has been conducted in the context of the PROGRESS research center, for predictable embedded software systems.
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