The use of renewable energy is promoted worldwide to be less dependent on fossil fuels and nuclear energy. Therefore research in the field is driven to increase efficiency of renewable energy systems. This study aimed to develop a wind turbine for low wind speeds in South Africa. Although there is a greater tendency to use solar panels because of the local weather conditions, there are some practical implications that have put the use of solar panels in certain areas to an end. The biggest problem is panel theft. Also, in some parts of the country the weather is more suitable to apply wind turbines. Thus, this study focused on the design of a new concept to improve wind turbines to be appropriate for the low wind speeds in South Africa. The concept involves the implementation of a concentrator and diffuser to a wind turbine, to increase the power coefficient. Although the wind turbine was not tested for starting speeds, the implementation of the shroud should contribute to improved starting of the wind turbine at lower wind speeds. The configuration were not manufactured, but simulated with the use of a program to obtain the power production of the wind turbine over a range of wind speeds. These values were compared to measured results of a open wind turbine developed for South Africa. The most important matter at hand when dealing with a shrouded wind turbine is to determine if the overall diameter or the blade diameter of the turbine should be the point of reference. As the wind turbine is situated in a shroud that has a larger diameter than the turbine blades, some researchers believe that the overall diameter should be used to calculate the efficiency. Theory was revised to determine the available energy in the shroud after initial calculations showed that the power coefficients should have been higher than the open wind turbine with the same total diameter. A new equation was derived to predict the available energy in a shroud. The benefits of shrouded wind turbines are fully discussed in the dissertation content. / MSc (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

The use of renewable energy is promoted worldwide to be less dependent on fossil fuels and nuclear energy. Therefore research in the field is driven to increase efficiency of renewable energy systems. This study aimed to develop a wind turbine for low wind speeds in South Africa. Although there is a greater tendency to use solar panels because of the local weather conditions, there are some practical implications that have put the use of solar panels in certain areas to an end. The biggest problem is panel theft. Also, in some parts of the country the weather is more suitable to apply wind turbines. Thus, this study focused on the design of a new concept to improve wind turbines to be appropriate for the low wind speeds in South Africa. The concept involves the implementation of a concentrator and diffuser to a wind turbine, to increase the power coefficient. Although the wind turbine was not tested for starting speeds, the implementation of the shroud should contribute to improved starting of the wind turbine at lower wind speeds. The configuration were not manufactured, but simulated with the use of a program to obtain the power production of the wind turbine over a range of wind speeds. These values were compared to measured results of a open wind turbine developed for South Africa. The most important matter at hand when dealing with a shrouded wind turbine is to determine if the overall diameter or the blade diameter of the turbine should be the point of reference. As the wind turbine is situated in a shroud that has a larger diameter than the turbine blades, some researchers believe that the overall diameter should be used to calculate the efficiency. Theory was revised to determine the available energy in the shroud after initial calculations showed that the power coefficients should have been higher than the open wind turbine with the same total diameter. A new equation was derived to predict the available energy in a shroud. The benefits of shrouded wind turbines are fully discussed in the dissertation content. / MSc (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / In order to meet the high-speed and high-density recording requirements for today's development and testing environments, we are seeking to merge the cutting edge technologies of tiny, high-performance disk drives and field programmable gate arrays (FPGAs) to build a high-speed compact disk recorder (CHSDR). Specifically, we designed, built, and tested a multi-drive controller that handles the interleaving of data to eight inexpensive IDE drives. These drives and controller comprise a "cell" capable of transferring data at 2.45 MB/sec (4 to 5 times the rate of a single drive). Furthermore, these "cells" can be run in parallel (with a single controller interleaving data between the cells). This "tree" effect multiplies the data rate by the number of cells employed. For example, 8 cells (of 8 drives each) can reach nearly 20 MB/second (sustained) and can be built for less than $30,000. The drives we used are the size of match boxes (the Hewlett Packard KittyHawk). These tiny drives hold 42 megabytes each and can withstand 150 Gs while operating. The cell controller is a Xilinx 4005 FPGA. Furthermore, we've designed a 120 MB/sec RAM FIFO to buffer data entering the system (to account for unavoidable drive seek latencies). In short, the compact high-speed disk array is a small, relatively low cost recording solution for anyone requiring high data speed but modest data volume. Missile shots, nuclear tests, and other short-term experiments are good examples of such requirements.

published_or_final_version / abstract / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

No description available.

A consequence of high speed rail transportation is the generation of elevated ground borne vibrations. This thesis presents several original contributions towards the prediction of these vibrations. Firstly, a new three dimensional finite element model capable of vibration prediction was developed. Its main feature was its ability to model complex track geometries while doing so through a fully coupled vehicle-tracksoil system. Model output was compared to experimental results obtained during this thesis and also to independent data sets. It was shown to predict velocity time histories, vibration frequency spectrums and international vibration descriptors with high accuracy. An appraisal of the suitability of a finite difference time domain modelling approach for railway vibration prediction was also undertaken. This resulted in the development of a new ‘higher order’ perfectly matched layers absorbing boundary condition. This condition was found to offer higher performance in comparison to current alternative absorbing boundary conditions. Field work was then undertaken on high speed lines with varying embankment conditions in Belgium and England. Vibration data was recorded up to 100m from each track and geophysical investigations were performed to determine the underlying soil properties. The results were used for numerical model validation and also to provide new insights into the effect of various embankment conditions on vibration propagation. It was found that embankments generate higher frequency excitation in comparison to nonembankment cases and that cuttings generate higher vibration levels than noncuttings. Once validated the finite element model was used to provide new insights into the effect of train speed, embankment constituent materials and railway track type on vibration levels. It was found that the shape and magnitude of ground vibration increased rapidly as the train’s speed approached the Rayleigh wave speed of the underlying soil. It was also found that ballast, slab and metal tracks produced similar levels of vibration and that stiffer embankments reduced vibration levels at distances near and far from the track. Two vibration mitigation techniques were also explored through numerical simulation. Firstly, an analysis was undertaken to determine the ability of a new modified ballast material to actively isolate vibration within the track structure. Secondly, wave barrier geometries were investigated to optimise their performance whilst minimising cost. It was found that barrier depth was the most influential parameter, whereas width had little effect. Additionally, geometry optimisation was found to result in a 95% cost saving in comparison to a base case. Using a vast array of results generated using the previously developed finite element model, a new empirical prediction model was also developed, capable of quickly assessing vibration levels across large sections of track. Unlike currently available empirical models, it was able to account for soil properties in its calculation and could predict a variety of international vibration metrics. It was shown to offer increased prediction performance in comparison to an alternative empirical model.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / There are many applications for High-speed photography, and most rely on film as the primary medium of data acquisition. One such application of interest to the military services is the study of stores separation from aircraft. This type of testing has traditionally used high-speed film to gather data, however, there are many disadvantages to using film, such as the high cost of raw film, as well as the high processing expense after it has been exposed. In addition, there is no way to review data from film until it has been processed, nor is there any way to preview in real-time other conditions such as lighting which may affect the outcome of a test event. This paper discusses the characteristics of television systems with respect to motion picture systems, the challenges of recording and transmitting pictures, as well as the nature of what the first and eventual desired systems might be.

In the past few years, increased penetration of wind energy has made more disturbances into electrical power systems. The proper integration of wind turbine models within power system simulations is of great importance for analysis of wind energy penetration and power system performance. This thesis analyzes the impacts of the connection of wind turbines on the operations of weak electric distribution systems. Using an actual feeder located in a rural area, the effects on the voltage profile caused by variable-speed wind turbines are compared to those caused by fixed-speed wind turbines. Simulations are conducted by using the developed models in Matlab/Simulink Keywords: Wind energy, Variable-speed turbines, Fixed-speed turbines

The multi-speed drive hub mainly makes for change speed with planetary gear trains. It has some advantages such as small, change the shelf steadily to move and difficult to receive external environmental impact. So the multi-speed drive hub has already become the focal point that every bicycle's factory researches and develops gradually. The purpose of this work is to develop a system methodology for the computer-aided design of multi-speed bicycle drive hubs. First, analyzing multi-speed drive hub patents to identify the basic characteristics and requirement of multi-speed drive hub, and using a systematized method synthesizes the feasible gear trains. Second, a method is proposed to determine the feasible multi-speed sequence tables for each planetary gear train. Third, a method is formulated to find the gear ratios and gear teeth according to the feasible multi-speed sequence tables. Fourth, a method is to design and dispose the governors of multi-speed drive hubs easily. Finally, using Visual Basic 6.0 procedure language develop a computer software easy to use by utilizing the above-mentioned procedures, and the results of this work will be benefit to the development and design of multi-speed bicycle drive hubs.

Overuse of the Interstate and National Highway Systems has led many urban freeways to suffer from recurrent congestion and high crash rates. One method of ameliorating these problems is through the use of Active Traffic Management (ATM). Within ATM, the practice of speed harmonization is well suited to improving safety and reducing delay. In this study, speed harmonization is applied to a segment of Interstate Highway 35, just south of downtown Austin, Texas. First, the need for congestion and safety improvements will be established. Then, the framework of a speed harmonization system will be developed through a synthesis of speed harmonization best practice. Next, the speed harmonization framework will be evaluated for its impact on efficiency through the development of before and after micro-simulation models. Finally, the trajectory files generated from simulation will be analyzed using surrogate safety measures to assess the safety impact of the proposed speed harmonization system. / text