| 1. |
- Forsström, Stefan, 1984-, et al.
(författare)
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Specialanpassade kurser för yrkesverksamma ingenjörer : Erfarenheter och upplevelser
- 2023
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Ingår i: Bidrag från den 9:e utvecklingskonferensen för Sveriges ingenjörsutbildningar. - : Mälardalens universitet. - 9789174856200 ; , s. 348-353
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- I dagens samhälle blir det allt viktigare att fortbilda sig under hela sitt yrkesverksamma liv. För att möta efterfrågan på det livslånga lärandet har Mittuniversitetet utvecklat och genomfört ett antal kurser som riktar sig mot yrkesverksamma ingenjörer. Detta arbete presenterar våra erfarenheter av att ge dessa kurser, med en tyngdpunkt på studenternas upplevelser. Syftet med detta är att bygga upp en vetenskaplig bas för vad vi gör som är bra, men även vad som kan förbättras och förändras. Målsättningen är att göra dessa specialanpassade kurser riktade mot yrkesverksamma ingenjörer så givande och flexibla som möjligt. Våra initiala resultat visar bland annat att studenternas negativa upplevelser ofta var kopplade till antagningsförfarandet och det praktiska genomförandet av kurserna. Man hade svårigheter med att hitta hur man skulle registrera sig på kursen och att tidsramen för registrering kunde vara ett problem. Läroplattformen uppfattades som svår att överblicka och det förekom även viss otydlighet gällande var undervisningen skulle äga rum. Den positiva responsen i utvärderingarna gällde främst det faktiska kursinnehållet, då man ansåg att uppgifter och kursmaterial var givande. Vidare uppskattades kursupplägget, att man kunde kombinera studierna med arbete. Framledes kommer vi att fortsätta med dessa utvärderingar i takt med att kurserna ges, och därefter anpassa vårt mottagande och kommunikationen med studenterna. Även kursupplägget ses över kontinuerligt via den återkoppling vi mottar.
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| 2. |
- Ahmad, Jawad, 1985-, et al.
(författare)
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A Proposal of Implementation of Sitting Posture Monitoring System for Wheelchair Utilizing Machine Learning Methods
- 2021
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Ingår i: Sensors. - : MDPI. - 1424-8220. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a posture recognition system aimed at detecting sitting postures of a wheelchair user. The main goals of the proposed system are to identify and inform irregular and improper posture to prevent sitting-related health issues such as pressure ulcers, with the potential that it could also be used for individuals without mobility issues. In the proposed monitoring system, an array of 16 screen printed pressure sensor units was employed to obtain pressure data, which are sampled and processed in real-time using read-out electronics. The posture recognition was performed for four sitting positions: right-, left-, forward- and backward leaning based on k-nearest neighbors (k-NN), support vector machines (SVM), random forest (RF), decision tree (DT) and LightGBM machine learning algorithms. As a result, a posture classification accuracy of up to 99.03 percent can be achieved. Experimental studies illustrate that the system can provide real-time pressure distribution value in the form of a pressure map on a standard PC and also on a raspberry pi system equipped with a touchscreen monitor. The stored pressure distribution data can later be shared with healthcare professionals so that abnormalities in sitting patterns can be identified by employing a post-processing unit. The proposed system could be used for risk assessments related to pressure ulcers. It may be served as a benchmark by recording and identifying individuals’ sitting patterns and the possibility of being realized as a lightweight portable health monitoring device.
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| 3. |
- Ahmad, Jawad, 1985-
(författare)
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Development and Characterization of Large Area Pressure Sensors and Sitting Posture Monitoring Systems
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the emergence of the Internet and rapid development of science and technology over the past few decades, many individuals worldwide now rely on the Internet to conduct daily activities ranging from education, business and creativity to communication and shopping. As we tend to spend more and more time on the Internet and engage less in physical activities, this persistent behaviour could result in some health-related issues within a relatively short period of time. This behaviour, known as sedentary lifestyle, may be related to a higher risk of cardiovascular disease, osteoporosis, obesity, anxiety, pressure ulcers and many other illnesses. As a consequence, there has been great interest in developing non-invasive and unobtrusive measurement techniques for a variety of health care-monitoring applications, such as for blood oxygen saturation, stress levels, electrocardiograms and glucose monitoring. In such systems, wearable and flexible electronics technologies may enable monitoring of vital signs, offering significant potential for early screening as well as long-term behaviour modelling.In this thesis, large area pressure sensors based on non-conventional materials are proposed and realised by screen printing technique for monitoring sitting postures. The developed pressure sensing system measures distributed pressure when an individual sits on a chair equipped with a pressure sensor array. This technology could provide grounding for the advancement of health-related monitoring systems for both able-bodied and disabled individuals and inform them of their sitting time and sitting posture, and this could be used to establish a sitting pattern. To accomplish this, pressure sensors have been designed using non-conventional flexible electronics. A blend of non-conductive and low-resistance ink is used as pressure-sensitive material to enable the realization of screen-printed sensors. To characterise the performance of the suggested pressure sensor, several tests, such as repeatability, drift and flexibility, are conducted. The sensor has also been exposed to different humidity and temperature conditions in a climate chamber to examine its functionalities.A graphical user interface was developed for real-time demonstration of data from distributed pressure points in the form of a pressure map to display the pressure values. Four sitting postures are identified: forward, backward, left, and right leaning. Furthermore, a stretchable pressure sensor is proposed that could follow slight stretching with regard to changes in the shape of the human skin. Machine learning algorithms have been employed to further enhance the sitting posture identification, and accuracy of 99.03% is attained. A standalone embedded system capable of illustrating real-time pressure data has been developed with the potential to be used in portable health monitoring systems. In summary, this work provides a promising framework for measuring pressure distribution and identifying irregular sitting postures that may help to reduce the potential risks of developing health-related issues associated with prolonged sitting time.
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| 4. |
- Ahmad, Jawad, 1985-, et al.
(författare)
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Stretchable Pressure Sensor Using Thermoplastic Polyurethane and Conductive Inks
- 2021
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Ingår i: Proceedings of IEEE Sensors. - : IEEE. - 9781728195018
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Konferensbidrag (refereegranskat)abstract
- The development of wearable health devices is an emerging technology, and pressure sensors have been widely used in several of these applications. Plenty of research within pressure sensors is focused on tactile sensing and artificial skin. In this paper, a highly flexible and stretchable pressure sensor is presented. The sensor comprises stretchable thermoplastic polyurethane (TPU) film as substrate and stretchable conductive inks as electrodes and sensing material. Screen printing is used to fabricate electrodes and pressure sensing components on TPU sheets. Electrical and mechanical properties of the fabricated sensors indicate good mechanical and electrical stability while retaining pressure sensing properties and marginal deterioration even after 100 elongation cycles. The findings show that the presented stretchable pressure sensor has a great potential for usage on surfaces where bending and stretching will occur while retaining nearly all of its electrical and mechanical capabilities. The proposed sensor may be employed as a wearable device to detect human movements.
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| 5. |
- Li, Xiaotian
(författare)
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Towards Large-Area Electronic Systems Using Non-Conventional Substrate and Conductor Materials
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Flexible circuits, also known as flexible printed circuit boards, were originally developed in the 1950s for interconnection between multiple electronic devices when flexibility and movement were required. Nowadays, flexible circuits can be used for implementing electronic systems much more complicated than just interconnections. A commonly seen material combination of flexible circuits is copper foils laminated on polyimide substrates, although these solutions are both expensive and environmentally hazardous. With developments in printed electronics, many non-conventional materials can be used in fabricating flexible circuits that have advantages such as increased flexibility, low cost, a small environmental impact, etc. In addition, fast and efficient manufacturing methods can produce flexible electronics in large volumes. This opens a window of opportunity to create electronic systems over geometrically large areas. This thesis proposes methods and guidelines for how to implement largearea electronic devices using non-conventional flexible materials and technologies. The thesis specifically focuses on electronic systems that integrate both digital and analogue signals. Further, it demonstrates and provides examples of how signals in the microwave frequencies, commonly requiring expensive materials, can be handled with non-conventional materials and technologies. Several conductor-substrate material combinations are used, which are fabricated using industrial processes. The conductor materials include conductive inks, copper foils, and aluminium foils, while the substrate materials comprise papers, a nonwoven fabric, and a polyimide. In particular, methods are investigated in order to achieve a low DC resistance in printed conductiveink-based tracks, which opens the possibilities for them to be used in highcurrent applications. Several surface mounting techniques are developed for incorporating surface mount devices within the fabricated flexible circuits, including the use of low-temperature solder paste, isotropic conductive adhesives, and anisotropic conductive adhesives. Some of the techniques have achieved sufficiently low contact resistance and adequate component bonding strengths, and thus can be used in implementing hybrid electronic systems. In addition, most of the techniques have the potential to be used in automated component assembly lines. As demonstrators, two antenna systems for commercial RFID readers operating at high frequency (13.56 MHz) and ultra-high frequency (867 MHz) iv Abstract bands are implemented, which comprise both digital and analogue signals. The two antenna systems are designed as part of SP4T switching networks using standard antenna elements as the loads of the network. It is shown in the results that both antenna systems have low RF attenuations, the potential to perform passive RFID tag positioning, and the possibility to be expanded to larger areas. Based on the characterisations to the two antenna systems, discussions are made about how large the antenna system areas can be as well as how many antenna elements can be achieved in a single antenna system. This thesis provides a material-to-system approach and demonstrates that non-conventional flexible materials and printed electronic technologies are suitable choices for large-area electronics.
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| 6. |
- Persson, Johan, et al.
(författare)
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Geometrical Optimization of Jetting Duct
- 2020
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Ingår i: 2020 8th International Electrical Engineering Congress (iEECON). - : IEEE. - 9781728130767 ; , s. 1-3
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Konferensbidrag (refereegranskat)abstract
- This paper presents and evaluates three new designs of fibre optic cable ducts for jetting. The three designs are longitudinal ridges with square, triangular and semicircular geometries. The effects of the geometries are evaluated with regards to electrostatic force, fluid drag force and jetting length with limited push force. An optimal design is suggested, with triangular longitudinal ridges on the inner surface of the duct.
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| 7. |
- Akram, Shazad, et al.
(författare)
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Battery powered inductive welding system for electrofusion joints in optical fiber microducts
- 2021
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Ingår i: Electronics. - : MDPI AG. - 2079-9292. ; 10:6
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Tidskriftsartikel (refereegranskat)abstract
- Optical fiber microducts are joined together by mechanical joints. These mechanical joints are bulky, require more space per joint, and are prone to air pressure leakage and water seepage during service. A battery powered electrofusion welding system with a resistive-type joint has been recently developed to replace mechanical joints. These resistive-type electrofusion joints require physical connectors for power input. Due to a different installation environment, the power input connectors of resistive optical fiber microduct joints may corrode over time. This corrosion of connectors will eventually cause water seepage or air pressure leakage in the long run. Moreover, due to connector corrosion, resistive-type optical fiber microduct joints cannot be re-heated in future if the need arises. In this study, an inductively coupled electrofusion-type joint was proposed and investigated. This inductive-type electrofusion joint is not prone to long-term corrosion risk, due to the absence of power connectors. Inductive-type electrofusion joints can be re-heated again for resealing or removal in the long run, as no metal part is exposed to the environment. The battery powered inductive welding system can be easily powered with a 38 volts 160 watt-hour battery. The inductive-type electrofusion joint was welded within one second, and passed a 300-newton pull strength test and a 10-bar air pressure leakage test. It was demonstrated that the power input requirement for inductive electrofusion joints is 64% higher than that of resistive electrofusion joints. However, these inductive joints are relatively easy to manufacture, inexpensive, have no air leakage, and no water seepage risk in highly corrosive environments.
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| 8. |
- Akram, Shazad, et al.
(författare)
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Design and Development of a Battery Powered Electrofusion Welding System for Optical Fiber Microducts
- 2020
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Ingår i: IEEE Access. - 2169-3536. ; 8, s. 173024-173043
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Tidskriftsartikel (refereegranskat)abstract
- At present, optical fiber microducts are coupled together by mechanical types of joints. Mechanical joints are thick, require a large space, and reduce the installation distance in multi-microduct installation. They may leak or explode in the blown fiber installation process. Mechanical joints are subjected to time dependent deterioration under long service times beneath the earth's surface. It may start with a small leakage, followed by damage due to water freezing inside the optical fiber microduct. Optical fiber microducts are made up of high-density polyethylene, which is considered most suitable for thermoelectric welding. For thermoelectric welding of two optical fiber microducts, the welding time should be one second, and should not cause any damage to the inner structure of the microducts that are being coupled. To fulfill these requirements, an LTspice simulation model for the welding system was developed and validated. The developed LTspice model has two parts. The first part models the power input to joule heating wire and the second part models the heat propagation inside the different layers of the optical fiber microduct and surrounding joint by using electro-thermal analogy. In order to validate the simulation results, a battery powered prototype welding system was developed and tested. The prototype welding system consists of a custom-built electrofusion joint and a controller board. A 40 volt 4 ampere-hour Li-Ion battery was used to power the complete system. The power drawn from the battery was controlled by charging and discharging of a capacitor bank, which makes sure that the battery is not overloaded. After successful welding, a pull strength test and an air pressure leakage test were performed to ensure that the welded joints met the requirements set by the mechanical joints. The results show that this new kind of joint and welding system can effectively replace mechanical joints in future optical fiber duct installations.
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| 9. |
- Bakar, Muhammad Abu, 1969-
(författare)
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Wide Range Isolated Power Converters
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Power electronics technology is rapidly growing in most industrialapplications. There is an increasing demand for efficient and low profilepower converters in the industry like automotive, power grids, renewableenergy systems, electric rail systems, home appliances, and informationtechnology. In some applications, there is an increasing demand for powerconverters showing a stable performance over a wide variation in inputvoltage, whereas in others the demand is for converters showing a stableperformance over a wide variation of output voltage. In this regard, not somuch work has been done to combine both requirements into one solution;this is the primary focus of the dissertation. It presents a unique solution tothe industry, which addresses both requirements. The technique can beapplied in a one size fits all solution which not only extends the range of theline voltage and the output voltage but also provides the flexibility to adjustthe required set of line/output voltage. The variation in line voltage severelydegrades the performance of power converters because of the extendedfreewheeling interval, more circulating current, narrow range of zero voltageswitching and increased EMI. To overcome this, the converter consists of tworeconfigurable modes on the input side that can be configured following thevariation in line voltage to maintain a stable performance. In addition, itproposes three reconfigurable steps for the output voltage, which can be usedto adjust the output voltage from base level X to 2X and 4X in discrete stepsand/or from X - 4X volt while showing stable performance. This makes theproposal a 2x3 reconfigurable modes power converter, which means that thegain of the proposed converter can be raised to 4 or 8. Furthermore, theflexibility in the reconfigurable structure simplifies the implementation of theproposed single solution in a range of applications. Each concept proposed inthe thesis is verified analytically, experimentally and modelling it into aSPICE simulation. Then the whole concept is confined into a single entity,which is applied in an example application of a phase shifted full bridgeconverter. The full converter is characterized for input voltage 100-400Vdc, theoutput voltage 24-96Vdc, and up to the load power of 1kW.
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| 10. |
- Du, Yijun, et al.
(författare)
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Design of ultra-wideband antenna with high-selectivity band notches using fragment-type etch pattern
- 2020
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Ingår i: Microwave and optical technology letters (Print). - : Wiley. - 0895-2477 .- 1098-2760. ; 62:2, s. 912-918
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Tidskriftsartikel (refereegranskat)abstract
- By specifying objective functions defining the two bands to be notched with high roll-off criteria (ROCs), optimization searching for the best fragment-type etch pattern on ultra-wideband (UWB) antenna is implemented by using multi-objective optimization. The optimization with too many objective functions requires special treatment to improve the searching efficiency. In this design, two slits are preset on appropriate positions on different sides of the UWB radiator to constrain the decision space for etch pattern searching and yield two initial notched bands to speed up the optimization. For demonstration, a UWB patch antenna is designed with dual-band notches of ROC = 0.63 at WiMAX band and ROC = 0.65 at WLAN band. Both the simulation and measurement results indicate that there is significant improvement of the selectivity of the dual-band notches.
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