<p>A technique is presented for assessing the relative performance of various signal processors of the surface detected electromyographic signal (EMG) in the gross skeletal muscles of man. A minicomputer is used to sample, store, and to later process the EMGs for agonists of the upper arm for various net forces, as measured at the wrist, under a condition of isometric tension. A two dimensional analysis of the flexor and extensor EMGs is performed for each force level. The number of force levels from which distinct, high confidence, control signals may be derived is used as a figure of merit to determine the superior of the signal processors studied and the superior of various electrode sites considered. For prosthetic use it is often desirable to maximize the number of control signals per muscle site.</p> / Master of Engineering (ME)

<p>The gastroduodenal junction coordination was studied by conducting experiments on six dogs. The electrical and mechanical signals in the gastroduodenal area were recorded by surgically implanting electrodes and strain gauges. Recordings were made on an analog tape recorder for about 30 minutes in the fasted state and for about 45 minuted after food or with intravenous infusion of pentagastrin. The recorded signals were later fed into Data General Nova 830 Minicomputer for subsequent analysis. In analysing these signals frequency is of prime importance as interaction could result in the argumentation of the proximal duodenal electrical/mechanical signal at antral frequency. The application of spectral analysis techniques for this purpose is described. The programs are developed for the following purposes:</p> <p>1) To accept the analog data and convert them into discrete digital data.</p> <p>2) To display any segment of data for visual observation of recorded signals.</p> <p>3) To compute the auto and cross power spectral density.</p> <p>The results of the analysis are presented in the form of tables. It is concluded that there exists a coordination. The possible mechanism could be myogenic, since coordination in the electrical activity is evident when atropine was given.</p> / Master of Engineering (ME)

No description available.

<p>Effektförstärkare för radiofrekvensapplikationer utgör fortfarande ett av de största problemen i trådlösa kommunikationssystem. Detta beror på att dessa förstärkare är ickelinjära, har låg energieffektivitet och ger mycket distortioner. Bättre verktyg för att förstå och korrigera dessa beteenden är nödvändiga. Ett sådant verktyg är beteendemodellering. En beteendemodell kan ses som en svart låda med insignal(er) och utsignal(er). In detta fall är dessa signaler samplade basbandssignaler och den svarta lådan är en matematisk relation mellan en insignal och en utsignal.</p><p>Avhandlingen behandlar några krav för beteendemodellering av nämnda system genom att presentera metoder för utvärdering och förbättring av modellernas prestanda. Detta åstadkoms genom att betrakta ett frekvensviktat felkriterium. Ett högpresterande mätsystem är också nödvändigt för experimenten. Prestandan hos det tillgängliga systemet jämförs med prestandan hos ett allmänt erkänt mätsystem, en s.k. storsignalsnätverksanalysator, genom att betrakta prestandan hos beteendemodellerna som extraheras och valideras med data från respektive mätsystem. Resultatet visar att det existerande mätsystemet har god prestanda.</p><p>Ett stort problem vid beteendemodellering är att kunna sampla med tillräckligt hög hastighet. Genom att använda Zhu-Franks generaliserade samplingsteorem vid beteendemodellering kan en del av detta problem undvikas. Teoremet medför att man kan sampla med en väsentligt lägre samlingsfrekvens än vad Nyquistteoremet säger. Modeller extraheras och prestandan utvärderas genom att använda kriteriet normalized mean square error (NMSE).</p><p>För stabil prediktion och korrektion av utsignalen måste robustheten hos de använda modellerna verifieras. En sådan studie som berör robustheten mot variationer i lastimpedansen har genomförts. Prestandan på direkta modeller försämras med 7 dB mätt som adjacent channel error power ratio (ACEPR). Prestanda på inversmodellen, implementerad som digital predistortion, försämras med upp till 13 dB mätt som adjacent channel power ratio (ACPR).</p> / <p>Radio frequency (RF) power amplifiers (PA) are still the most troublesomepart of a wireless system due to their inherent nonlinearity, low powerefficiency and high distortions. Better tools are needed to understand and correct the undesirable behavior. Some of these tools are behavioral models. A behavioral model is often thought of as a black box with some inputs andsome outputs. In the case here these inputs are sampled signals which meansthat the modeling amounts to finding a mathematical relationship betweenthe input signal(s) and the output signal(s).</p><p>This thesis considers some requirements for behavioral modeling of said systems by presenting methods for general performance evaluation and improvement by considering a frequency weighted error criterion.</p><p>A high performance measurement system is also needed. The performance of the available system is compared to the performance of a well recognized system, the largesignal network analyzer (LSNA). The results show that the existing measurementsystem can extract behavioral models with the same performance as the LSNA and can give lower performance validation errors.</p><p>Still the need for higher bandwidths drives the measurement systems to the limits, especially the digital parts. By utilizing the so called Zhu-Frank generalized sampling theorem, behavioral modeling of a PA is done by using data acquired at a sampling rate lower than the Nyquist rate. Models of a PA are extracted and the performance is evaluated using the normalized meansquare error (NMSE) criterion. For prediction and correction of the output signals the stability of the models regarding changes must be investigated. One such study considering controlled variations on the output load of the PA is done and both the predictive and corrective capabilities of the models are evaluated. The predictive capability gets up to 7 dB worse measured as adjacent channel error powerratio (ACEPR) and the corrective, as digital predistortion, gets up to 13 dB worse measured as adjacent channel power ratio (ACPR).</p>

<p>In line with the quality awareness of good prevention of pressure sores and in treatment of those sores already developed, evaluation of antidecubitus mattresses plays an important role. However, there are shortages in the evaluations performed today, since often interface pressure is the only parameter regarded. Since ischaemia in the tissue is the primary cause of pressure sore, the focus in this thesis is on blood flow measurements in tissue exposed external loading. To study the tissue blood flow would give a better and more direct indication on the mattress effectiveness in minimizing the negative effects on the tissue viability.</p><p>The results presented in this thesis reveal that the superficial blood flow in areas prone to pressure sore development, is affected by increased skin temperature and external loading of the tissue. Both the effects from pressure and shear stress have been studied.</p><p>Measurements of the tissue blood flow is interesting to relate to the two theories about at which tissue layer the pressure sores start to develop. To achieved more knowledge about the pressure sore etiology and also be able to non-invasively measure the tissue blood flow for evaluations of antidecubitus mattresses an optical sensor has been developed. The sensor combines the two optical methods, laser Doppler flowmetry and photoplethysmography. With the design of the sensor, measurements of the superficial skin blood flow and the deeper blood flow, even the muscle blood flow, can be performed. Measurement depths of 2 mm, 8 mm, and 20 mm into the tissue is assumed.</p><p>Preliminary result from measurements performed with the optical sensor in four test subjects, revealed great individual differences in blood flow, but also different response to the same external loading at different measurement depths, in the same individual. This new optical sensor is likely to be of great value in future studies of pressure sore etiology and in future evaluations of antidecubitus mattresses.</p>

<p>In this thesis, digit-serial implementation of recursive digital filters is considered. The theories presented can be applied to any recursive digital filter, and in this thesis we study the lossless discrete integrator (LDI) allpass filter. A brief introduction regarding suppression of limit cycles at finite wordlength conditions is given, and an extended stability region, where the second-order LDI allpass filter is free from quantization limit cycles, is presented.</p><p>The realization of digit-serial processing elements, i.e., digit-serial adders and multipliers, is studied. A new digit-serial hybrid adder (DSHA) is presented. The adder can be pipelined to the bit level with a short arithmetic critical path, which makes it well suited when implementing high-throughput recursive digital filters.</p><p>Two digit-serial multipliers which can be pipelined to the bit level are considered. It is concluded that a digit-serial/parallelmultiplier based on shift-accumulation(DSAAM) is a good candidate when implementing recursive digital systems, mainly due to low latency. Furthermore, our study shows that low latency will lead to higher throughput and lower power consumption.</p><p>Scheduling of recursive digit-serial algorithms is studied. It is concluded that implementation issues such as latency and arithmetic critical path are usually required before scheduling considerations can be made. Cyclic scheduling using digit-serial arithmetics is also considered. It is shown that digit-serial cyclic scheduling is very attractive for high-throughput implementations.</p>

There is a demand for compact, low profile, and wideband antennas for modem wireless devices. The purpose of this dissertation is to develop two such antennas. A method of moments and finite difference time domain method are used for the design and analysis of the antennas. A new microstrip antenna is designed which has more than 90 % bandwidth. The operation of the antenna is explained and design equations are developed. The antenna is integrated with electromagnetic band gap structures (EBG) to examine if performance enhancement is possible. The simulation results are verified by limited measurements. A wideband loop antenna is also integrated with EBGs and significant perfbrrnance improvement is achieved.

Up until the 1980s, conventional radar systems consisted primarily of analog circuits, which are costly to build and compatible only to a narrow band of operations. Modern digital technology offers increasing capabilities at a lower cost making it attractive for modern radar application. The Direct Digital Synthesizer (DDS) is one such example of digital technology that is now routinely found in newer radar system designs. The DDS characteristics that most attract radar-system designers are precision frequency tuning, phase offset control, and linear "chirp" capability. This study discusses the option of incorporating DDS for use in a digital pulsed and/or frequency modulated continuous wave (FMCW) radar, and examined the necessary adaptations such as up-converting baseband signals from DDS to a radar transmission frequency, viable transmit and receive waveforms and the synchronization problem relating to synchronizing the many radiating elements that could range from a few to possibly thousands.

Electricity is a critical component in our daily life. Because it is almost always available, we take it for granted. However, given the proper conditions, blackouts do happen every once in a while and can cause discomfort at a minimum, and a catastrophe in rare circumstances. The largest blackouts typically include cascading failures, which are sequences of interdependent outages. Although timely and effective operator intervention can often prevent a cascade from spreading, such interventions require ample situational awareness. The goals of this dissertation are twofold: to provide power system operators with insight into the risk of blackouts given the space of potential initiating outages, and to evaluate control systems that might mitigate cascading failure risk. Accordingly, this dissertation proposes a novel method to estimate cascading failure risk. It is shown that this method is at least two orders of magnitude faster in estimating risk, compared with a traditional Monte-Carlo simulation in two test systems including a large-scale real power grid model. This method allows one to find critical components in a system and suggests ideas for how to reduce blackout risk by preventive measures, such as adjusting initial dispatch of a system. In addition to preventive measures, it is also possible to use corrective control strategies to reduce blackout sizes. These methods could be used once the system is under stress (for example if some of the elements are overloaded) to stop a potential cascade before it unfolds. This dissertation focuses on a distributed receding horizon model predictive control strategy to mitigate overloads in a system, in which each node can only control other nodes in its local neighborhood. A distributed approach not only needs less communication and computation, but is also a more natural fit with modern power system operations, in which many control centers manage disjoint regional networks. In addition, a distributed controller may be more robust to random failures and attacks. A central controller benefits from perfect information, and thus provides the optimal solution. This dissertation shows that as long as the local neighborhood of the distributed method is large enough, distributed control can provide high quality solutions that are similar to what an omniscient centralized controller could achieve, but with less communication requirements (per node), relative to the centralized approach.

M.Sc. / Please refer to full text to view abstract