Application of CSDG Mosfet based active high pass filter in communication systems.

Masters Degree. University of KwaZulu-Natal, Durban.This research work looks at the design of three active high pass filters. These filters have been designed for (i) robotic system, (ii) sensing device and (iii) satellite communication system. In this research work a high pass filter has been designed with a Cylindrical Surrounding Double Gate (CSDG) MOSFET. A CSDG MOSFET is a continuation of DG MOSFET technology. It is formed by rotation of a DG MOSFET with respect to its reference point to form a hollow cylinder. It consists of 2 gates, a drain and a source. Electronic robotic systems have a section of transmitter and receiver. For the receiver, to provide the required selectivity of frequencies, a filter is used. There is a wide variety of these filters that can be used within the Radio Frequency (RF) range. Radio frequencies range from 3 kHz to 300 GHz. This particular filter is designed and simulated at a cutoff frequency of 100 GHz (0.1 THz). It makes use both an operational amplifier and a transistor. This circuit was compared to a circuit that made use of 2 operational amplifiers and the results are discussed. In addition a CSDG MOSFET which makes use of a Silicon Dioxide dielectric is connected to the output of the transistor circuit to see what effect it has on the circuit. Using this model of filter a fine signal (command) can be given to robotic system. The second filter is designed for remote sensing devices. These devices continuously send/receive signals and these signals or radio waves are transmitted/received via a transmission line to/from a receiver/transmitter which has a filter that selectively sorts out the signals and only passes a desired range of signals. The CSDG MOSFET being a capacitive model allows for better filtering of low frequencies and passes through a frequency range of 200 GHz (0.2 THz) efficiently. By placing the capacitors in parallel, the design requires smaller capacitance values to be used. In addition the desired range of frequencies can be achieved from the inversely proportional relationship between frequency and capacitance. Finally a filter has been designed to use in satellite communication systems. These systems consist of various subsystems to allow it to function efficiently. These subsystems require a number of electronic devices. In this research work, a CSDG MOSFET is added to the output of the transistor circuit and operates within the EHF band (0.3 THz). The CSDG MOSFET makes use of Hafnium Silicate (HfSiO4) as a dielectric material due to its wide band-gap and lower dielectric constant makes it ideal for this design. The gain and other parameters of the three designed filters are analyzed. In conclusion, it has been demonstrated that the third order active high pass filters performs better with the CSDG MOSFET

An assessment of modified systematic sampling designs in the presence of linear trend.

Doctor of Philosophy in Statistics. University of KwaZulu-Natal, Durban, 2017.Sampling is used to estimate population parameters, as it is usually impossible to study a whole population, due to time and budget restrictions. There are various sampling designs to address this issue and this thesis is related with a particular probability sampling design, known as systematic sampling. Systematic sampling is operationally convenient and efficient and hence is used extensively in most practical situations. The shortcomings associated with systematic sampling include: (i) it is impossible to obtain an unbiased estimate of the sampling variance when conducting systematic sampling with a single random start; (iii) if the population size is not a multiple of the sample size, then conducting conventional systematic sampling, also known as linear systematic sampling, may result in variable sample sizes. In this thesis, I would like to provide some contribution to the current body of knowledge, by proposing modifications to the systematic sampling design, so as to address these shortcomings. Firstly, a discussion on the measures used to compare the various probability sampling designs is provided, before reviewing the general theory of systematic sampling. The per- formance of systematic sampling is dependent on the population structure. Hence, this thesis concentrates on a specific and common population structure, namely, linear trend. A discussion on the performance of linear systematic sampling and all relative modifica- tions, including a new proposed modification, is then presented under the assumption of linear trend among the population units. For each of the above-mentioned problems, a brief review of all the associated sampling designs from existing literature, along with my proposed modified design, will then be explored. Thereafter, I will introduce a modified sampling design that addresses the above-mentioned problems in tandem, before providing a comprehensive report on the thesis. The aim of this thesis is to provide solutions to the above-mentioned disadvantages, by proposing modified systematic sampling designs and/or estimators that are favourable over its existing literature counterparts. Keywords: systematic sampling; super-population model; Horvitz-Thompson estimator; Yates' end corrections method; balanced modified systematic sampling; multiple-start balanced modified systematic sampling; remainder modified systematic sampling; balanced centered random sampling

Oral health-related quality of life of paediatric patients with AIDS

<p>Abstract</p> <p>Background</p> <p>Children with Acquired Immune Deficiency Syndrome (AIDS) exhibit impaired dental status, which can affect their quality of life. This study assessed the oral health-related quality of life of these patients and associated factors.</p> <p>Methods</p> <p>The "Child Perceptions Questionnaire 11-14", rating overall and domain-specific (oral symptoms, functional limitations, emotional well being, and social well being) oral health-related quality of life (OHR-QoL) was completed by 88 children with AIDS assisted in the Child Institute, Sao Paulo, Brazil. Parents or guardians provided behavioural and socio-demographic information. The clinical status was provided by hospital records. OHR-QoL covariates were assessed by Poisson regression analysis.</p> <p>Results</p> <p>The most affected OHR-QoL subscale concerned oral symptoms, whose rate was 23.9%. The direct answer for oral health and well being made up a rate of 47.7%. Brushing the teeth less than two times a day and viral load exceeding 10,000 HIV-RNA copies per millilitre of plasma were directly associated (p < 0.05) with a poorer oral health-related quality of life.</p> <p>Conclusions</p> <p>Children with more severe AIDS manifestations complained of poorer status of oral symptoms, functional limitations, emotional and social well being related to their oral health. Recognizing the factors that are associated with poorer OHR-QoL in children with AIDS may contribute to the planning of dental services for this population.</p