Sensor nodes in a wireless sensor network (WSN) have a small, non-rechargeable power supply. Each message transmission or reception depletes a sensor node’s energy. Many WSN applications are ad-hoc deployments where a sensor node is only aware of its immediate neighbours. The lack of a predefined route path and the need to restrict the amount of communication that occurs within the application area impose constraints on WSNs not prevalent in other types of networks. An area of active research has been how to notify the central sink (or monitoring hub) about an event in real-time by utilising the minimum number of messages to route a message from a source node to the destination sink node. In this thesis, strategies to limit communication within a WSN application area, while ensuring that events are reported on and responded to in real-time, is presented. A solution based on modelling a WSN as a small world network and then transmitting an initialisation message (IM) on network start-up to create multiple route paths from any sensor node to one or more sinks is proposed. The reason for modelling a WSN as a small world network is to reduce the number of nodes required to re-transmit a message from a source sensor node to a sink. The purpose of sending an IM at network start-up is to ensure that communication within the WSN is minimised. When routing a message to a static sink, the nodes closest to the static sink receive a disproportionate number of messages, resulting in their energy being consumed earlier. The use of mobile sinks has been proposed but to our knowledge no studies have been undertaken on the paths these mobile sinks should follow. An algorithm to determine the optimum path for mobile sinks to follow in a WSN application area is described. The purpose of an optimum path is to allow more equitable usage of all nodes to transfer an event message to a mobile sink. The idea of using multiple static sinks placed at specific points in the small world model is broadened to include using multiple mobile sinks called actors to move within a WSN application area and respond to an event in real-time. Current coordination solutions to determine which actor(s) must respond to the event result in excessive message communication and limit the real-time response to an event. An info gap decision theory (IGDT) model to coordinate which actor or set of actors should respond to the event is described. A comparison of the small world routing (SWR) model against routing using flooding and gossiping shows that the SWR model significantly reduces the number of messages transmitted within the network. An analysis of the number of IMs transmitted and received at individual node level shows that prudent selection of the hop count (number of additional nodes required to route a message to sink) to a sink node will result in a reduced number of messages transmitted and received per node within the network. The use of the IGDT model results in a robust decision on the actor(s) chosen to respond to an event even when uncertainty about the location and available energy of other actor(s) exists. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

In order to remove the local openings for contacting PERC Solar cells, one has to introduce passivating contacts. The Al₂O₃-TiOₓ double layer stack is an attractive candidate for this purpose. This study will guide a way to enhance the conductivity of those contacts by doping TiO x with a. Additionally, it is shown, that major parts of the stacks are deposited by sputtering. This demonstrates a higher feasibility for industrial applications than atomic layer deposition as reported earlier [1], [2].

This thesis deals with the design of LED matrix array contains 150 LEDs. In the first part, the thesis identifies source of light like OLED and LED and provide an overview of their lifetime, reliability and basic principle of design systems with LEDs. The thesis then describe design of LED matrix array, deals with power supply of this LED array and with cooling of LED. Finally the thesis describes a software for contol of LED matrix array.

The lifetime of plastic pipes for water supply and other applications is demanded to exceed at least 50 years. Such a long lifetime is difficult to prove by standard testing methods like the hydrostatic pres-sure test. However, it is possible to calculate an estimation of the lifetime, as the most frequently oc-curring mechanism of failure of plastic pipes is the creep crack propagation and subsequent failure. The method is based on describing the crack propagation by parameters of the linear-elastic fracture mechanics. An important part of this method is a finite element simulation of crack propagation in a pipe loaded by various types of loads. Residual stress, a side product of solidification after extrusion, is one of these loads. This thesis begins with an introductory part and literature review of the relevant topics – most of all the typical material properties of the pipe materials, mechanisms of failure, methods of residual stress determination suitable for plastic pipes and their results, methods of testing the materials and calculating lifetime. After the introduction, the problems to be solved are defined. The description of the residual stress state in the wall of various plastic pipes is the main topic. Both tangential (hoop) and axial residual stress in pipes of different dimensions and materials are determined using a combination of experiments and numerical simulations. Also, a simplified method of tangential residual stress is designed that can provide a sufficiently precise description of the tangential resid-ual stress state and is not difficult to carry out. A method to include the residual stress in the lifetime calculations and its influence on the lifetime is also dealt with. Apart from residual stress, the influence of soil loads in case of a buried pipe is studied. The residual stress can also influence the experimental determination of crack growth rate. If the CRB (cracked round bar) test is used to measure the crack growth rate, the crack can propagate asymmetrically due to the presence of residual stress in the specimens, which affects the results. Based on a finite element simulation of crack propagation in a CRB specimen, the severity of the influence is assessed.

This work deals with method for characterization of photovoltaic solar cells based on evaluation of solar cell response to fast transients. The voltage of the cell in both forward and reverse polarisation was controlled by current pulse exciting. Real reverse breakdown voltage and exact value of serial resistance of the cell can be obtained easily by evaluation of the transient curves recorded by digital osciloscope. By negotiation of the time constants of the cell response to excitation in forward polarisation the lifetime of minority carriers in semiconductor bulk can be estimated.

The lead-acid batteries used in hybrid electronic vehicles HEV operate in high-rate mode in a state of partial charge PSoC. It occurs when the degradation mechanisms related to irreversible sulphation and negative electrodes are a limiting factor in the life of lead-acid batteries. The electrode system was applied to experimental pressure cells of different sizes. Exp. cells were subjected to measurement and evaluation of potential negative electrode, a negative active mass resistance, contact resistance of transition collector - the active mass with the evaluation and measurement of pressure fluctuations within four PSoC runs.

This thesis is focused on analysis of production facilities utilization and maintenance in the company RAMET C.H.M. a.s. located in Kunovice. In this thesis, there is performed the analysis of present property condition, machinery and equipment used within radar antenna production. Within property maintenance, there are introduced planned and unplanned processes of servicing activities and machine and equipment repair. In a part of proposal for solution, there are recommended processes for keeping up production capabilities based on extensive analysis of size property influence on production volume. The method for reliability estimation of production chain is described for the antenna production, related to limiting production capability and costs to maintain service availability of production facilities.

The diploma project is focused on investigating the reliability of multi-state technical systems. A summary of the basic conception of renewal theory and stochastic processes is given in this paper. The possibility of solving multi-state systems reliability by using Markov models or simulation is shown. The software Reliab. S. M. S. O. 1.0 was created for solving non-homogeneous series, parallel, series-parallel and parallel-series systems. Outputs of this software are described in chapter 10. This work also contains $\beta$-factor method and theory of common-cause failures. The diploma project was supported by project from MSMT of the Czech Republic no. 1M06047 "Centre for Quality and Reliability of Production" and by grant from Grant Agency of the Czech Republic (Czech Science Foundation) reg. no. 103/08/1658 "Advanced optimum design of composed concrete structures".

A new methodology of polymer pipe lifetime estimation taking into account residual stresses is described in this thesis. Engineering equations derived based on numerical simulations of a hydrostatic pressure test are proposed. Residual lifetime calculations were performed for different loading conditions using experimental data of a creep crack propagation in studied material and stress distribution in the pipe wall. The effects which significantly influence lifetime estimation were quantified with special focus on residual stresses.

This master´s thesis is focused on the comparison of selected methods that the use for evaluation real property type flat. Thesis defines the basic notions connected with valuation and describes the methods of valuation. Valuated flats are situated in Písek and surrounding. Work includes description given to areas and maps local situation in the marketplace with flat unit. Flats were selected with different layout.