Decreasing power consumption in small devices such as handhelds, cell phones and high-performance processors is now one of the most critical design concerns. On-chip cache memories dominate the chip area in microprocessors and thus arises the need for power efficient cache memories. Cache is the simplest cost effective method to attain high speed memory hierarchy and, its performance is extremely critical for high speed computers. Cache is used by the microprocessor for channeling the performance gap between processor and main memory (RAM) hence the memory bandwidth is frequently a bottleneck which can affect the peak throughput significantly. In the design of any cache system, the tradeoffs of area/cost, performance, power consumption, and thermal management must be taken into consideration. Previous work has mainly concentrated on performance and area/cost constraints. More recent works have focused on low power design especially for portable devices and media-processing systems, however fewer research has been done on the relationship between heat management, Leakage power and cost per die. Lately, the focus of power dissipation in the new generations of microprocessors has shifted from dynamic power to idle power, a previously underestimated form of power loss that causes battery charge to drain and shutdown too early due the waste of energy. The problem has been aggravated by the aggressive scaling of process; device level method used originally by designers to enhance performance, conserve dissipation and reduces the sizes of digital circuits that are increasingly condensed. This dissertation studies the impact of hotspots, in the cache memory, on leakage consumption and microprocessor reliability and durability. The work will first prove that by eliminating hotspots in the cache memory, leakage power will be reduced and therefore, the reliability will be improved. The second technique studied is data quality management that improves the quality of the data stored in the cache to reduce power consumption. The initial work done on this subject focuses on the type of data that increases leakage consumption and ways to manage without impacting the performance of the microprocessor. The second phase of the project focuses on managing the data storage in different blocks of the cache to smooth the leakage power as well as dynamic power consumption. The last technique is a voltage controlled cache to reduce the leakage consumption of the cache while in execution and even in idle state. Two blocks of the 4-way set associative cache go through a voltage regulator before getting to the voltage well, and the other two are directly connected to the voltage well. The idea behind this technique is to use the replacement algorithm information to increase or decrease voltage of the two blocks depending on the need of the information stored on them.

OBJECTIVES: To evaluate in vitro the coronal leakage of endodontically treated teeth sealed with temporary restorative materials with or without coating sealants, and subjected to brushing and thermocycling. MATERIALS AND METHODS: One hundred two extracted human premolars and molars, were endodontically accessed, and restored with 3 types of temporary restorations: 1. Cavit (3M ESPE), 2. Ketac Molar (3M ESPE), 3. Riva Light Cure GlC (SDI). Each type of restoration had one subgroup with a coating (Cavit-Ketac Glaze, Ketac Molar- Ketac Glaze, Riva Light Cure GIC – Riva Coat) and the other without coating. Restored teeth were placed in artificial saliva at 37°C for 24 hours. Teeth were divided into 3 treatment subgroups: Group A: No treatment, soaked at 37° C artificial saliva; Group B: Teeth underwent thermocycling; Group C: teeth underwent both thermocycling and brushing. Thermocycling included 500 cycles between 5°C to 55°C. Tooth brushing was simulated in a brushing machine using 190g weight applied to 16,800 linear strokes. The control group was not exposed to thermocycling or brushing. Leakage was detected by immersion of specimens in 2% methylene blue dye for 24 hours. Specimens were epoxy embedded and sectioned longitudinally. The leakage scores were evaluated from photographs by longitudinal dye penetration depth scored 0 for no leakage and 4 for maximum leakage to the bottom of restoration. Statistical analysis was done to examine the effect of coating and post-treatment on leakage scores. RESULTS: All tested temporary restorative materials with coating had lower leakage than without coating in all experimental groups. CONCLUSIONS: The leakage of temporary restorative materials can be reduced by surface coating, however, thermocycling and brushing treatment can still generate some leakage. / 2020-06-28T00:00:00Z

Orientador: Marco antonio Bottino / Banca: Nelson Luiz de Macedo / Banca: Francisco Fernando Todescan / Banca: Diego Klee de Vasconcellos / Resumo: O objetivo nesta pesquisa foi avaliar a infiltração bacteriana in vitro na interface entre o pilar e o implante, comparando-se três tipos de conexões protéticas: Hexágono Externo (HE), Hexágono Interno Indexado (HII) e Cone Morse (CM). Sob condições estéreis, foi inoculada colônia de Escherichia coli na porção apical do parafuso do pilar. Após, os pilares foram fixados aos implantes com torque de 20 N/cm. Foram descartadas as amostras que apresentaram contaminação externa imediata. As amostras foram colocadas em tubos de ensaios contendo 2 ml de caldo TSB estéril. Em acompanhamento diário, por 7 dias, os caldos que se apresentaram turvos foram semeados em placa de petri com TSA e incubados em estufa bacteriológica à 37oC por 24 horas, para a observação de crescimento bacteriano. Coloração Gram foi realizada tanto no caldo quanto na colônia resultante da semeadura, para comprovação da presença de E. coli (Gram-negativo). Ao final do período, todas as amostras foram separadas, o conteúdo interno foi coletado com cone de papel e solução salina e semeado em placas de petri contendo TSA, levadas à estufa bacteriológica a 37º C por, 24 horas para verificar a viabilidade das bactérias. As amostras que não continham E.coli viáveis no seu interior foram descartadas do resultado final. Após os descartes por contaminação externa e inviabilidade, obtiveram-se os seguintes números de amostra: 38 (HE), 40 (HII) e 41 (CM). Os resultados, em % de amostras com infiltração bacteriana, foram submetidos ao teste de comparações múltiplas de proporções. As curvas de sobrevivência foram analisadas pelo método de Kaplan-Meyer e comparadas pelo teste estatístico de Log-Rank. Não houve diferença entre HE (10,53%), HII (4,88%) e CM (7,50%). As curvas de sobrevivência não diferiram entre si. A infiltração bacteriana ocorreu de modo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to evaluate, in vitro, the bacterial leakage between implant and abutment comparing three kinds of implantabutments connections: extern hexagon (EH), indexed intern hexagon (IIH) and morse-taper (MT). Under sterile controlled conditions, the tip of the abutment screw was inoculated with Escherichia coli culture and then the abutment was placed in position and tightened (20N/cm). The specimen was discarded if an external contamination of the outer surface was observed. Each specimen was incubated in a glass tube containing 2mL of sterile TSB medium at 37oC. The growth of E. Coli in the medium was registered every 24h. Once the sample showed cloudy broth, it was individually plated on TSA plates and incubated in an anaerobic chamber at 37oC for 24h, in order to observe the bacterial growth. Gram test was performed both in the medium and in the culture to certify the presence of E. Coli (Gram negative). After 7 days, each test specimen was sampled using a sterile paper point which was incubated in TSA plates and incubated in anaerobic chamber at 37oC for 24h, to verify bacterial viability. Samples that did not show bacterial viability in the end of the study were eliminated from the final results. After that, there were 38 EH samples, 40 IIH samples and 41 CM samples. The results, in %, of bacterial leakage, were statistically evaluated by multiple comparisons for proportion. The survival curves were analyzed by Kaplan-Meyer method and compared by statistical test of Log-Rank. There was no statistical difference among EH (10,53%), IIH (4,88%) e MT (7,50%). The three survival curves did not differ (p>0.005). It was conclude that the bacterial leakage occurred in a similar way for the three kinds of implant-abutment interface, no matter the assembly configuration. / Doutor

M.Ing. / With an ever-increasing population and a decrease in availability of fresh water, the sustainable and secure supply of fresh water is a growing concern worldwide, and particularly so in South Africa. Plumbing systems have a significant impact on both the efficient use of water and water losses because high quality plumbing components can reduce wastage and leakage, while inferior components increase the risk of failures and leakage and can even have health impacts in case of leaching of toxic elements or contamination of drinking water. In recent years, South Africa has seen a plethora of imported and pirated plumbing components introduced onto the local market. While South African legislation requires that only plumbing components approved by the South African Bureau of Standards or Water Services Authorities (municipalities) shall be installed, it does not explicitly prohibit the importation and sale of non-compliant components. The availability of non-compliant components on the market combined with insufficient enforcement of legislation, have created a situation where many non-compliant components are installed, although the extent of this problem was not known at the start of the project. The study aimed to quantify the extent of non-compliant plumbing components installed in South Africa, as well as the impact this will have on future water demands and losses. Various research methods were used including literature reviews, surveys and interviews with role players, search of available plumbing components for sale in South Africa, on-site visits and analysis of some case studies. The study found that about 50% of plumbing components installed in South Africa do not comply with legal requirements. Because these components are of poor quality, they hurt the local industry whose components cost more in order to comply with SABS standards. Therefore, they suffer from reduced market share and lower profit margins, and South African job losses occur in the sector. In general, compliant Summary components are up to 135% more expensive than non-compliant components. This study also found that even plumbers who are IOPSA members, and therefore bound by a code of conduct to use only compliant components, install non-compliant components. The site visits to some government low-cost housing developments showed that less than 10% of the plumbing components installed were compliant, and a major problem with non-compliant components was leakage. Therefore if the situation does not change, on-site water leaks will remain a great concern in South Africa. In order to address this situation the main suggestions are better enforcement of legislation, better training and control of plumbers and restrictions on the importation of non-compliant components.

M.Tech. / The Water Services Authorities in South africa are currently responsible for the management and operation of rural water supply in the country.Many of these comunity water supply schemes are in poor conditions due to lack of proper operation, maintenance, poor design and/or poor construction with the result that they experience serious water losses through physical losses(leakage)and apparent losses, and often fail to meet the consumer's demand during peak periods.Indications are that substantial quantities of water are lost in the systems due to leakage, wasteful use, illegal connections and meter errors. As a result of these problems, the levels of service delivery are often very poor leading to low cost recovery resulting in water services institutions becoming ineffective and inefficient businesses. The investigation attempted to identify effective techniques and/or strategies for water loss reduction in Dinokana Village (Central District Municipality). The study identified and defined various procedures/methodologies for managing Non Revenue Water in community water supply schemes. Some of the strategies developed from the findings of this research have been implemented with a view of quantitatively verifying their effectiveness.

No description available.

Water leakages and subsequent water shortages is an occurrence that causes inconveniences to many people around the world. Expanding population groups have the potential to stimulate urban development rates which in turn leads to an increase in water demand. This places more pressure on water suppliers and the infrastructure involved in water distribution systems causing pipe bursts and water leakages to occur more frequently. Water resources are thus wasted, leading to costs associated with the impact of the pipe burst and water shortage for both water suppliers and consumers. This study focuses largely on the identification, causes, impacts and quantification of losses through water leakages and the subsequent cost associated with the leakage. The study area that was chosen is Vorna Valley, which is in the region of Midrand and falls within the Gauteng province. Midrand is rapidly expanding spatially and population rates are on the rise. To achieve the objectives of this study, residents, water suppliers and key informants were consulted through questionnaires and the results were statistically analysed. The Economic Model for Leakage Management, that is specifically aimed at determining when a water supplier should invest in active leakage control for a specific, zoned metered area, was applied. The model established the costs of leakages and pipe bursts and the appropriate interval for active leakage control by the municipality for the study area. Results from the Economic Model for Leakage Management suggests that an active leakage control interval of 6 months is best as the cost due to water loss is at its lowest. In the study region, 83,1% of residents experience burst pipes over 6 months. Findings of this study could benefit water suppliers when choosing the best mitigation method to apply during water leakages and water shortages. / Dissertation (MSc (Environment and Society))--University of Pretoria, 2020. / National Research Foundation / Geography, Geoinformatics and Meteorology / MSc (Environment and Society) / Restricted

PhD Thesis / Recently, gallium nitride high electron mobility transistor [GaN HEMT] has evolved as a promising device in the field of power electronics. It has excellent material qualities such as high bandgap, high saturation velocity, and good thermal stability which is expected to give superior device performances compared to its Si counterparts. One of the major challenges in GaN technology is to achieve enhancement operation (or normally off mode) due to the presence of its inherent two-dimensional electron gas[2DEG]. Among many methods developed to realize this, pGaN HEMT has emerged as the most encouraging technique for power GaN technology due to its high threshold voltage and good reliability. However, one of the major issues in pGaN HEMTs is that it suffers from high gate leakage current which limits their device performance. In this thesis, we have made a detailed study of the gate leakage process in pGaN HEMTs in terms of modeling, TCAD simulations, and alternative methods being used to reduce gate leakage in pGaN devices. A numerical model has been developed to model the gate leakage in pGaN HEMTs as a function of gate bias and temperature. This model is validated against 5 devices with different contact metals, geometries, and process conditions. A single model with a consistent set of parameters can fit the experimental data for all these 5 devices without the need to invoke multiple mechanisms to explain the gate leakage process. The numerical model relied on some simplifications, such as ignoring series resistance, using the compact diode model, and using a simplified expression to describe trap-assisted tunneling. Using commercial TCAD simulations, can address these limitations since the simulator computes the electric field distribution throughout the structure. Furthermore, using TCAD some of the trap levels have been identified which accounts for leakage at low bias. We were able to calibrate our TCAD simulations against published data for the drain current and then used the calibrated simulation environment to accurately simulate gate leakage using parameters that closely correspond to the physical phenomena described, including interface trap parameters, which we identify with known trap levels in GaN. Finally, we have examined different strategies that have been implemented so far to reduce leakage current. The pGaN layer is important in the whole device operation. Its doping concentration and thickness affect the leakage characteristics. Three modified structures have been studied through TCAD simulations which decrease gate leakage current. In each case, we used our calibrated TCAD model to study the impact on the drain current as well as the leakage current. Our results closely fit published experimental results and therefore provide confidence on the simulated dependence of leakage and drive current behavior on process modifications. The specific results, and our model overall, are expected to be of benefit to device designers in optimizing device structures for leakage while maintaining the required drive current. / Thesis / Doctor of Philosophy (PhD)

Leakage current and process variations are two primary hurdles in modern VLSI design. It depends exponentially on process and environmental parameters and hence small variations in these result in a large spread in leakage current of manufactured dies. Traditionally, Exponential Quadratic(EQ) models have been used to model leakage current as a function of process parameters which can model limited non-linearity and hence become inaccurate for large process variations. Artificial Neural Networks (ANN) have shown great promise in modeling circuit parameters for CAD applications. We model leakage with ANN models which perform better than the EQ models for increased process variations. However, the complex nature of the ANN model, with the standard sigmoidal activation functions, does not allow analytical expressions for its mean and variance for the case of Gaussian process variations. We propose the use of a new activation function that allows us to derive an analytical expression for the mean and a semi-analytical expression for the variance of the ANN based leakage model. To the best of our knowledge this is the first result in this direction. All existing SLA frameworks are closely tied to the EQ leakage model and hence fail to work with sophisticated ANN models. We therefore set up an SLA framework that can efficiently work with these ANN models. Results show that the CDF of leakage current of ISCAS'85 circuits can be predicted accurately with the error in mean and standard deviation, compared to Monte Carlo based simulations, being less than 1\% and 2\% respectively across a range of voltage and temperature values. The complexity of our framework is similar to existing SLA frameworks yet more accurate over a larger range of variations. Ignoring the thermal profile of the chip leads to a gross error of nearly 50\% in the prediction of leakage yield. Our neural network model also includes the voltage and temperature as input parameters, thereby enabling voltage and temperature aware statistical leakage analysis (SLA). Similarly leakage CDF can be predicted across a range of supply and body voltages since they are both part of the model. Our framework used analytical techniques to account for local variations and Monte Carlo techniques for global variations and hence it can also be used for Non-Gaussian global variations.

The main function of a water distribution system is to supply water in sufficient quantity at appropriate pressure with an acceptable quality and as economically as possible. Water leakage in distribution networks may account from 5% to 50% and even larger of the total water delivered. The amount of leakage in a network is directly related to system service pressure. Therefore, reductions in high service pressures will result in considerable reductions in leakage. A methodology for leakage reduction has been presented in context of a developed computer program, LEAKSOL with two sub-programs. The first code, CODE I, provides solution by using optimization techniques with defined pressure-leakage and pressure-demand relations in order to find optimal flow control valve settings minimizing water leakage. The second one, CODE II, makes hydraulic analysis of the network in order to solve the system and to compute the amount of leakage and the amount of water consumed, by using different combinations of isolation valves generated according to the number of valves given and employing the relationships among pressure, leakage and consumption. Computer program application was performed for different scenarios in a sample network previously used in literature and also in N8-3 pressure zone of Ankara Municipal Water Supply System. Leakage reduction up to 10 % has been achieved in N8-3 pressure zone for eight valves located at the entrances of sub-zones, depending on the defined pressure-leakage relationship.