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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Elektromagnetiska fälts påverkan hos personer i dess närhet

Svärd, Erik January 2017 (has links)
No description available.
2

Theory and applications of tri-axial electromagnetic field measurements /

Karlsson, Roger, January 2005 (has links)
Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 8 uppsatser.
3

Transient response of grounding systems caused by lightning : modelling and experiments /

Liu, Yaqing, January 2004 (has links)
Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 11 uppsatser.
4

Measurements and analysis of electromagnetic interferences in the Swedish railway systems /

Niska, Stefan, January 2008 (has links)
Diss. (sammanfattning) Luleå : Luleå tekniska universitet, 2008. / Härtill 5 uppsatser.
5

Extremely low frequency magnetic fields and breast cancer /

Forssén, Ulla, January 2003 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.
6

Etiological and clinical aspects of skin sensitivity /

Lonne-Rahm, Sol-Britt, January 2003 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.
7

Occupational exposure to electromagnetic fields and chronic diseases /

Håkansson, Niclas, January 2003 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.
8

Sökande efter radiovågor från skärzonen vid svarvning

Firoz, Safdari, Yonas, Woldegiorgis January 2021 (has links)
Adhesive wear occurs when small surfaces of the cutting tool due to friction are micro-welded to the chips and removed from the tool surface. A hypothesis as to whywelding occurs is that an electric potential field arises which initiates a chemical reaction and then welding of the work material and the tool takes place in the cuttingzone. The electric potential field results in a fluttering magnetic field, which in turngenerates electromagnetic issues. The waves should be around and above 1 MHz.The aim of this work is thus to investigate the presence of electromagnetic wavesfrom the cutting zone. The purpose is to compare sound and electromagnetic wavesduring the adhesive process. Previous research shows that the adhesive mechanism is a transient vibration thatmanifests itself as a cluster of waves with a stochastic duration, including a feedbacksystem restricted by the plastic deformation within the chip. Furthermore, the cutting speed is the most important cutting parameter in tool wear and the main wearmechanism at cutting speeds around 200 m/min is the adhesive wear. Several studies showed the emission of electromagnetic waves during plastic deformation ofmetals during tensile test. Frequency ranges for radiations are between 1 and 1000MHz. To investigate the hypothesis, axial turning was performed with a cutting speed190–200 (m/min) and one steel grade, SS2541 was used as a work material. Thedepth of cut and feed were set to 1 mm and 0,196 mm/rev. Detection and measurement of electromagnetic waves was performed with a spectrum analyzerMT8221B with four different signal receivers. A reference measurement was madewhen the turning machine was on without the workpiece being machined and then ameasurement was made during the turning process. The results of measurementsshowed a source of electromagnetic radiation within the frequency range 0–5 MHz.This result was achieved with copper plate as an antenna. To find out how signalsfrom acoustic emission and electromagnetic waves develop during the adhesive wearprocess, sound measurements were performed with microphones during the turningprocess. Results of sound measurement showed that the frequency at which adhesivewear occurs decreases and the amplitude increases as the insert wears. To be able toanalyze how electromagnetic radiation develops with the wear process, measurements must be performed in a shielded space from ambient disturbances, as in aworkshop there are many sources of noise that can affect the accuracy of the measurement. An antenna can be designed so that the measurement can take place asclose to the cutting zone as possible.
9

Assessment of Exposure to Electromagnetic Fields from Distributed MIMO Antennas / Bedömning av elektromagnetisk exponering från distribuerade MIMO antenner

Nyberg Zou, Frans January 2022 (has links)
Research on 6G telecommunication networks has been initiated. Among all potential technology components, the distributed multi-input multioutput (D-MIMO) technology is one of the promising enablers. Due to the new technology solutions, additional methodologies for assessment of electromagnetic field (EMF) exposure need to be developed. This study provides methodologies and results for EMF exposure from D-MIMO operating at 3.5 GHz in an indoor industrial environment using CST Studio Suite®. The D-MIMO access points (APs) are mounted on the 7 m ceiling. The EMF exposure is statistically evaluated in a subvolume that extends up to 2.5 m above the floor, using receiving antennas that are pseudorandomly distributed over space. The resulting EMF exposure levels of DMIMO were compared to those of a ceiling-mounted reference massive MIMO array, considering different receiving antenna orientations and AP densities. The results from zero forcing (ZF) precoding were compared to those based on maximum ratio transmission (MRT) precoding. For a total radiated power of 1 W, the 99th-percentile power density values in the D-MIMO deployment are found to be 2.9 mW/m2 or lower, in all studied cases using the MRT-based precoding. This is about 0.03 % of the EMF exposure limits for the general public specified in international guidelines. The corresponding results from the reference massive MIMO array are found to be 7.7 mW/m2 or lower. In the ZF precoding case, the total radiated power and the EMF exposure levels are reduced and the reduction in the D-MIMO deployment is found greater than the reduction in the massive MIMO array. At the 99th-percentile, the power density value is found to be 0.090 mW/m2 in one of the cases of D-MIMO deployment and 5.1 mW/m2 in the corresponding case with the massive MIMO array. The effects of receiving antenna orientations and AP density on the EMF exposure levels are found to be small. This work benefits further studies by providing estimates of realistic EMF exposure and by demonstrating a simulation method for EMF exposure assessment for D-MIMO. / Forskning inom 6G har påbörjats. Bland de möjliga teknologierna för 6G är distribuerad multi-input multi-output (D-MIMO) ett lovande koncept som möjliggör 6G. På grund av den nya teknologin förväntas nya metoder behövas för bedömning av exponering för elektromagnetiska fält. I denna studie utvecklades och användes metoder för simulering av elektromagnetisk exponering från D-MIMO på frekvensen 3.5 GHz i en industriell inomhusmiljö i CST Studio Suite®. En statistisk behandling av exponeringsnivåer utfördes för pseudoslumpmässiga fördelningar av mottagarantenner. Antennerna i nätverket var placerade intill taket på 7 meters höjd och exponeringsnivån mättes i en delvolym som sträcker sig från golvet till 2.5 m höjd. Jämförelser gjordes med massiv MIMO som referens, och mellan olika vinklar hos mottagarantenner och tätheter av uppkopplingspunkter i nätverket. Antennloberna riktades med zero forcing (ZF) och en metod baserad på maximum ratio transmission (MRT). Med MRT och en total utsänd effekt på 1 W, var 99th-percentilen för elektromagnetisk fältintensitet från D-MIMO 2.9 mW/m2 eller lägre i alla studerade fall, vilket är 0.03 % av den internationella referensnivån för elektromagnetisk exponering. Motsvarande nivå för massiv MIMO var 7.7 mW/m2 eller lägre. Med ZF reducerades den totala utsända effekten och reduktionen i exponeringsnivån var större för D-MIMO än för massiv MIMO. I ett av de studerade fallen var 99th-percentilen från D-MIMO 0.090 mW/m2 , och motsvarande nivå för massivt MIMO var 5.1 mW/m2 eller lägre, Effekterna av vinklar hos mottagarantenner och tätheter av uppkopplingspunkter var liten. Detta arbete bidrar till framtida studier inom ämnet genom att ange uppskattningar av realistiska exponeringsnivåer och genom att demonstrera en metod för simulering av exponeringsnivåer för D-MIMO.
10

High-Performance Beamforming for Radar Technology : A Comparative Study of GPU Beamforming Algorithms / Högpresterande beamforming för radarteknologi : En jämförande studie av beamforming-algoritmer på GPU

Lindgren, Oscar January 2022 (has links)
Radar technology is widely used in today´s society, whether it is the localisation and identification of aircraft in air traffic control systems, ships in harbour management systems, or the weather forecast presented on the news. In military applications, such as in fighter jets or missile lock-on systems, the speed at which the radar processes incoming data is essential to ensure a successful outcome. These applications need more powerful execution platforms, such as Application-Specific Integrated Circuits (ASICs) or Field-Programmable Gate Array (FPGAs) to run at the required speed. Radar technology manufacturers face both high development costs and long development cycles when designing, redesigning and developing these powerful execution platforms. A solution to these problems could be to design and develop the system in software before implementing it on the specialised ASIC and FPGA ships. As a step toward creating a software-based processing chain for radar systems, this thesis amide to investigate whether General-Purpose Graphical Processing Units (GPUs) could be used to develop and run beamforming applications in real-time at a sample rate of 100 MHz. To achieve this goal, the Bartlett and MVDR Beamforming algorithms were analysed and implemented in the Computer Unified Device Architecture (CUDA) programming framework on an NVIDIA GeForce RTX 2080 super GPU. The algorithms´ parallelisable elements were considered before implementation, and then implemented to fit with the CUDA programming model. In the end, both beamformers´ primary acceleration methods is using the cuBLAS library for linear algebra operations. The results of this study show that beamforming in real-time is not possible on a GPU when processing a signal sampled at 100 MHz. However, the GPU used just passed its third anniversary since release, and NVIDIA has released subsequent generations of GPUs with significant (>100%) performance increases. Future work on this area could include trying the implementations on more recent GPUs or implementing other beamforming algorithms on GPUs. / Radarteknik används inom flera områden idag. Bland annat för lokalisering och identifiering av flygplan och fartyg i flyglednings- och hamnledningssystem, eller för att skapa väderprognosen som presenteras på nyheterna. För militära tillämpningar, till exempel i stridsflygplan eller missillåsningssystem, är behandlingshastigheten av inkommande data avgörande för att korrekt information ska visas. Dessa användningsområden kräver kraftfulla chip, såsom ASICs eller FPGAer, för att uppnå den exekveringshastighet, kompakthet och energieffektivitet som krävs. Såväl höga utvecklingskostnader som långa utvecklingscykler uppstår för radartillverkare när de designar och utvecklar dessa kraftfulla chip. En lösning på de långa cyklerna och höga kostnaderna kan vara att designa och utveckla systemet i mjukvara på en högre abstraktionsnivå innan det implementeras på de specialiserade ASIC- och FPGA-chipen. I ett steg mot att skapa en mjukvarubaserad signalbehandligsskedja gör radarsystem, syftar detta examensarbete till att undersöka om GPUer skulle kunna användas för att utveckla och exekvera beamformingapplikationer i realtid med en samplingsfrekvens på 100 MHz. För att uppnå detta mål analyserades och  implementerades beamformingalgoritmerna Bartlett och MVDR i CUDA på en NVIDIA GeForce RTX 2080 Super GPU. De element av algoritmerna som går att parallellisera undersöktes, följt av implementation i CUDAs programmeringsmodell. Den primära accelerationsmetoden för båda beamformingalgoritmerna är att använda cuBLAS-biblioteket för linjär algebraoperationer. Resultaten av denna studie visa att beamforming i realtid inte är möjligt på en GPU vid behandling av en signal samplad i 100 MHz. Den GPU som användes har nyligen passerat sin tredje årsdag sedan lansering, och NVIDA har släppt efterföljande GPU-generationer med avsevärda (>100%) prestandaökningar- I framtida arbeten på området föreslås att testa implementationerna på nyare GPUer, implementera beamformers i t.ex. OpenGL, implementera andra beamformingalgoritmer i CUDA.

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