• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 4758
  • 1081
  • 621
  • 336
  • 65
  • 4
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 7493
  • 7493
  • 6557
  • 5919
  • 3310
  • 3310
  • 2753
  • 2688
  • 2584
  • 2584
  • 2584
  • 2584
  • 2584
  • 995
  • 987
  • 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.

Development of a monitoring and data logging system for a multi-line telephone console

Molnar, Andras Mathys Zsigmond January 1991 (has links)
Thesis (Masters Diploma (Electrical Engineering)) -- Cape Technikon, Cape Town, 1991 / This thesis describes the design, development and implementation of a monitoring and data logging system for a multi-line telephone console as required by the Account Enquiry section of the Department of Posts and Telecommunications.

A remote radio transmission system to record the physiological phenomena of an equine athlete

Myburgh, WT January 1991 (has links)
Thesis (Masters Diploma(Technology) -- Cape Technikon, Cape Town, 1991 / The call for the system design in this book came from a field that grew to be a part of millions of lives in this country. It is a sport which has developed to have a major infrastructure, with large sums of money involved. In fact, the money involved has made it one of the largest tax earners country wide. Due to its high development, competition has become furious and breeders will do their utmost to produce a competitor which would have the slightest edge on the next one. As most people would know by now, the discussion is about the Horse Racing Industry. During the years, owners have relied on various exercising programs and breeding of proven winners to produce new ones. To give the animal the necessary training and simply run it on experience is no longer sufficient. A more scientific approach has become necessary. There exists a need for a system whereby one could monitor certain physiological aspects of the animal. This would not only allow the physical condition of each horse to be monitored, but also allow a more effective and specialized exercise program for each individual animal to be developed, thereby not only improving its ability, but saving on time as well. Tests that were considered included ECG, temperature, and speed measurements. Existing equipment performing the first two tests require the animal to be stationary. This defeats the object of the exercise, as information should be relevant to the animal when under strain. During test periods, the ideal situation would be to allow the horse to perform its exercise routine around the track without any interference. This could best be done by monitoring all the.necessary data via a radio link and having most of the analyzing apparatus in a small and light as possible package on the animal itself.

Electronic in-circuit PCB testers & identifier PCB tester

Kotze, WP January 1989 (has links)
Thesis (Masters Diploma(Electrical Engineering)) -- Cape Technikon, Cape Town,1989 / various types of electronic card test equipment are freely available today for different types of electronic printed circuit boards. A company certainly wants to pick the most suitable tester to suit their needs, and more importantly a tester that will fit into their bUdget. Today a company can easily import in-circuit testers that will cost well in the reglon of six figures. The cheaper the equipment go, the less features one can expect from the equipment. Like all other big decisions in life, this might also be a tough one for a company. Part one of this thesis will consider most of these questions, and will also give more insight on what type of specifications to look for. This section will also explain the different types of faults that occur, the repair costs involved, different types of card testers available and some of their features. Advanced in-circuit testing techniques will also be explained. Part two of this thesis describes the design and development of the Identif ier Card Tester. The" Program Control and Impulse Sender Card", (referred to as "Identifier Card") is one of the cards used in a system called "Electronic Identifier". The electronic identifier was developed to enable a subscriber directory number, a line or equipment numbers, or in general, the origin of information and classes-of-service to be determined by way of an existing connection within a telephone exchange. The system was designed for the purpose of incorporating it into the existing public exchanges where no identifier wires are available. It operates on the principle of a switching circuit (line) tester. The identification pulses are evaluated with the aid of 6 mm bistable magnetic ring cores according to the current steering principle. The program control and the output circuit uses a transistor, a magnetic core/transistor or a magnetic core/thyristor circuit. The electronic identifier is mostly used with "Routiners" in Electra-mechanical exchanges. The biggest percentage of failures on these systems are caused by the Identifier Card and hence the request for the development of a "Identifier Card Tester".

The development of a 100 KHZ switched-mode power supply

Gartner, Andy Michael January 1991 (has links)
Thesis (Masters Diploma (Electricity Engineering) -- Cape Technikon, Cape Town,1991 / At the time of the design the maximum allowable operating frequency for an output power of between 200 and 250 watts was 100 kHz. Although a 600 kHz operating frequency could have been achieved, it would only be at a very low output power level. To maximise the current components available, a 210 watt 100 kHz direct-off-line switched-mode power supply was developed. The design presented can be used to power any compatible IBM XT/AT personal computer. The prototype was tested. An overall efficiency of 61% was achieved. The final prototype required 1 521 cm3 and weighed approximately 980 g, representing a power to volume ratio of 0.14 W/cm3 (2.26 W/inch3). Detailed procedures are also presented to help with the design and selection of the reactive components. Special design features include the half-bridge push-pull topology, MOSFETS as power switches, digital current limiting, primary power limiting, multiple outputs and fault counting to name but a few.

A permittivity measurement system for high frequency laboratories

Marais, Johannes Izak Frederik 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / The open-ended coaxial probe is revisited as a broadband measurement system for general high frequency permittivity measurements. Three coaxial probes were developed that are suited for the measurement of both liquids and solids. The components of a permittivity measurement system were investigated and improvements were made to the coaxial probe where needed. This includes the development of a full wave code with great calculation time improvements without sacrificing accuracy. This code allows measurements to be performed in a high frequency laboratory and the permittivity extracted without any mentionable delay. A capacitance model that better describes the impedance of an open-ended coaxial line is also suggested that can be used for real-time permittivity extraction over a limited frequency range. Calibration formed a vital part of the project and great time was spent developing a TRL and a SOLT calibration set for the coaxial probe geometry. The combination of the TRL and SOLT standards also allows measurement of the residual errors after calibration and is used in an uncertainty analysis of the extracted permittivity. Well known materials such as PTFE, PVC, methanol and water were measured to test the probes. The measured dielectric constants are all within 3% of values quoted in literature. The loss term of the samples are also in good agreement with the expected values.

Parameter extraction of superconducting integrated circuits

Lotter, Pierre 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / Integrated circuits are expensive to manufacture and it is important to verify the correct operation of a circuit before fabrication. Efficient, though accurate, parameter extraction of post-layout designs are required for estimation of circuit success rates. This thesis discusses electrical netlist and fast parameter extraction techniques suited for both intraand inter-gate connections. This includes the use of extraction windows and look-up tables (LUTs) for accurate inductance and capacitance estimation. These techniques can readily be implemented in automated layout software where fast parameter extraction is required for timing analysis and gate placement.

Real-time simulator studies and model development for time-down voltage stability analysis.

Makasa, Joseph Kangombe. January 2006 (has links)
Problems of voltage stability and voltage collapse have become a major concern in power system planning and operation in recent years, often as a result of power systems being operated under much more stressed conditions than was usual in the past. Factors that are responsible for this trend include: environmental pressures on transmission expansion; increased electricity consumption in concentrated heavy loads where installation of new generation is not feasible; new system loading patterns. Voltage stability problems are characterised by either slow or sudden voltage drops, sometimes escalating further to a collapse in voltage, leading, in some cases, to system wide blackouts. The power engineering community has devoted significant effort to developing new analysis tools and methods to control this type of instability. The main methods that have been developed and used for analysis of voltage stability are steady-state methods (power flow: analysis via PV and Q-V curves); dynamic analysis (time-domain simulations); modal analysis of system jacobian matrices and optimization (special optimal power flow). This thesis investigates the use of a particular tool, real time simulation, as a method for voltage stability analysis and testing of voltage control strategies. The particular simulator used is the Real-Time Digital Simulator (RTDS) from RTDS Technologies. The real-time simulator software environment provides generalized models of generation, transmission, distribution plant and loads that can be used to develop accurate models of power systems for analysis in real-time. The broad objectives of this thesis are to assess the suitability of the RTDS as a tool for time domain voltage stability analysis and to develop additional real-time models of particular power system controllers that are known to playa key role in voltage stability phenomena. In particular the thesis considers development of custom real-time models of a transformer on-load tap changer (OLTC) controller, detailed generator excitation controls (automatic voltage regulators), a static var compensator (SVC) controller and a synchronous condenser reactive output controller. The thesis then describes the development of real-time models of two benchmark systems for the voltage stability studies: a well known II-bus voltage stability benchmark system and a smaller (4-bus) benchmark system. These two benchmark systems are used to establish the validity and correctness of the custom real-time models and to investigate simple compensation and control strategies for voltage stabilization. In particular the thesis considers the following stabilizing techniques on the II-bus system: switched shunt capacitor compensation, voltage control using a synchronous condenser and finally the use of an SVc. Finally, the thesis demonstrates the ability of RTDS to investigate the performance of actual hardware controllers on the plant in the real-time model of the 11 bus system in a full closed loop arrangement. The custom-developed real-time software model of the OLTC controller in the II-bus benchmark system is replaced with an actual external hardware controllers connected in closed loop with the real-time simulation. This thesis has successfully confirmed the known characteristics of individual power system plant using the models provided in the RTDS environment and developed additional customized software models of controllers for voltage stability studies on the RTDS. The results of the RTDS simulations of voltage stability benchmark systems have been found to agree with documented results of these systems. The thesis has shown that the RTDS provides a suitable platform on which time-domain voltage stability studies can be conducted. The thesis has also shown that real-time digital simulation is a practicable technique for the analysis and investigation of control strategies for voltage stability, particularly when interactions between real hardware controllers and their impact on system stability are of concern. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006

Quality of service for voice over next generation networks.

Perumal, Eugene Govindhren. January 2004 (has links)
The Global communications transformation is currently in progress. Packet switched technology has moved from data - only applications into the heart of the network to take up the functions of traditional circuit - switched equipment. Voice over A TM(VoATM) and voice over IP(VoIP) are the two main alternatives for carrying voice packets over NGN' s. A TM offers the advantage of its built in quality of service mechanisms. IP on the other hand could not provide QoS guarantees in its traditional form. IP QoS mechanisms evolved only in recent years. There are currently no QoS differences between Next Generation Networks based on VoATM or VoIP. However non QoS agreements are more in favour of VoIP instead of VoA TM. This gives VoIP the leading edge bet the Voice over packet technologies. In this thesis the E - Model was optimized and used to study the effects of delay, utilization and coder design on voice quality. The optimization was used to choose a coder and utilization levels given certain conditions. An optimization algorithm formed through the E - Model was used to assist with the selection of parameters important to VoIP networks. These parameters include the link utilization, voice coder and allowable packet loss. This research also shows us that different utilization, voice coder and packet loss levels are optimal in different situations. A remote and core VoIP Network simulation model was developed and used to study the complex queuing issues surrounding VoIP networks. The models look at some of the variables that need to be controlled in order to minimize delay. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2004.

Video object segmentation and tracking.

Murugas, Themesha. 31 March 2014 (has links)
One of the more complex video processing problems currently vexing researchers is that of object segmentation. This involves identifying semantically meaningful objects in a scene and separating them from the background. While the human visual system is capable of performing this task with minimal effort, development and research in machine vision is yet to yield techniques that perform the task as effectively and efficiently. The problem is not only difficult due to the complexity of the mechanisms involved but also because it is an ill-posed problem. No unique segmentation of a scene exists as what is of interest as a segmented object depends very much on the application and the scene content. In most situations a priori knowledge of the nature of the problem is required, often depending on the specific application in which the segmentation tool is to be used. This research presents an automatic method of segmenting objects from a video sequence. The intent is to extract and maintain both the shape and contour information as the object changes dynamically over time in the sequence. A priori information is incorporated by requesting the user to tune a set of input parameters prior to execution of the algorithm. Motion is used as a semantic for video object extraction subject to the assumption that there is only one moving object in the scene and the only motion in the video sequence is that of the object of interest. It is further assumed that there is constant illumination and no occlusion of the object. A change detection mask is used to detect the moving object followed by morphological operators to refine the result. The change detection mask yields a model of the moving components; this is then compared to a contour map of the frame to extract a more accurate contour of the moving object and this is then used to extract the object of interest itself. Since the video object is moving as the sequence progresses, it is necessary to update the object over time. To accomplish this, an object tracker has been implemented based on the Hausdorff objectmatching algorithm. The dissertation begins with an overview of segmentation techniques and a discussion of the approach used in this research. This is followed by a detailed description of the algorithm covering initial segmentation, object tracking across frames and video object extraction. Finally, the semantic object extraction results for a variety of video sequences are presented and evaluated. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005

Integrating sensors and actuators for robotic assembly

Johnson, David Gary January 1986 (has links)
This thesis addresses the problem of integrating sensors and actuators for closed-loop control of a robotic assembly cell. In addition to the problems of interfacing the physical components of the work-cell, the difficulties of representing sensory feedback at a high level within the robot control program are investigated. A new level of robot programming, called sensor-level programming, is introduced. In this, the movements of the actuators are not given explicitly, but rather are inferred by the programming system to achieve new sensor conditions given by the programmer. Control of each sensor and actuator is distributed through a master-slave hierarchy, with each sensor and actuator having its own slave controller. A protocol for information interchange between each controller and the master is defined. If possible, the control of the kinematics of a robot arm is achieved through the manufacturer's existing control system. Under these circumstances, the actuator slave would be acting as an interface between the generic command codes issued from the central controller, and the syntax of the corresponding control instructions required by the commercial system. Sensor information is preprocessed in the sensor slaves and a set of high-level descriptors, called attributes, are sent to the central controller. Closed-loop control is achieved on the basis of these attributes. The processing of sensor information which is corrupted by noise is investigated. Sources of sensor noise are identified and new algorithms are developed to quantify the noise based on information obtained from the closed-loop servoing. Once the relative magnitudes of the system and measurement noise have been estimated, a Kalman filter is used to weight the sensor information and hence reduce the credibility given to noisy sensors; in the limit ignoring the information completely. The improvements in system performance by processing the sensor information in this way are demonstrated. The sensor-level representation and automatic error processing are embedded in a software control system, which can be used to interface commercial systems as well as purpose-built devices. An'industrial research project associated with the lay-up of carbon-fibre provides an example of its operation. A list of publications resulting from the work in this thesis is given in Appendix E.

Page generated in 0.1499 seconds