In this thesis, we propose a new thin-film transistor with trenched body and airgap-insulated structure (AITFT) for one-transistor dynamic random access memory (1T-DRAM) applications and investigate the influence of different materials on the sensing current window and retention time. Its basic operation mechanisms are based on the impact ionization and floating body effects. Due to the generated holes storing in the pseudo neutral region, the threshold voltage (Vth) is lower, resulting in a high drain current for state ¡§1¡¨. So we can recognize the data by sensing the difference of the drain current. According to the ISE TCAD 10.0 simulations, owing to the design of trench and airgap-isolation structure, the AITFT can enhance about 212% sensing current window and 42% retention time compared with the conventional TFT at the channel length of 150 nm and temperature of 300K conditions. Also, owing to the source/drain-tie, the generated heat can be dissipated quickly from the source/drain to the substrate thus the thermal instability is improved. In other words, the AITFT can improve the thermal reliability but without losing control of the short-channel effects.

In this thesis, we propose a simple trench oxide layer polysilicon thin-film Transistor (TO TFT) process and the self-heating effects can be significantly reduced because of its structural advantages. According to the ISE-TCAD simulation results, our proposed TO TFT structure has novel features as follows: 1. The buried oxide and the isolation oxide are carried out simultaneously in order to achieve a goal of simple process. 2. The trench design is used to improve both the sensing current windows (~ 84%) and the retention time (~ 57%). 3. The thermal stability is drastically improved by its naturally formed source/drain tie. The above mentioned features help our proposed device structure to demonstrate the desired characteristics that are better than that of a conventional TFT. Additionally, the thermal instability is drastically improved which is good for long-term device operation.

The patterns and rates of forest regeneration on a critical wildlife winter range on the floor of the trench, known locally as Premier Ridge were examined in this study. A nearby western wall of the trench was also investigated to ascertain the effect of elevation on forest regeneration and understory productivity. Forest regeneration in a community which has remained unforested for several as years has pronounced effects on the floristic dynamics and productivity of the understory. On Premier Ridge the greatest floristic change was a rapid increase in pinegrass and a. corresponding decrease in the abundance of all other grass species as the forest regeneration progressed. Forbs varied widely in abundance while shrubs were slower to react to changes in the overstory. Similar trends were observed on Estella Mountain. Productivity of the grass component on the unforested sites was four times that of the forested sites. The production of forbs and some species of shrubs also declined as forest regrowth began. One species, bearberry, increased under light forest canopies. The reduction in productivity and the changes in species composition of-the understory which occur in regenerating forest communities, appear to be detrimental to foraging populations of wild and domestic ungulates. Cattle seem to prefer to graze the open, unforested areas, and as regeneration proceeds, the acreage which they will readily use diminishes. Since there have been few reductions in stock numbers to compensate for this range shrinkage, local overgrazing has become more widespread. The regrowth of the forest reduces the grass, both in terms of quality and quantity. This is the most important component in the diet of cattle and most of the wildlife species using the Premier Ridge area. In addition, bitterbrush, used in the summer by cattle and during the winter by big game species, is quickly eliminated by forest regeneration. Bearberry, which may be used by wildlife to some extent, increases under forest cover. This component does not approach in value or usefulness, the losses that the other components represent to grazing animals. The trees of the south and southwestern aspects are characterized by relatively slow growth rates. Forage production on these slopes is modest; if grazing animals are deemed desirable in the future economy of the East Kootenay, these areas should remain treeless. Growth rates are more favourable on the north and northeast aspects, which are less frequently used as foraging areas by winter wildlife, but may be used as shelter or bedding areas. / Land and Food Systems, Faculty of / Graduate

With the sampling limitations for the study of the hadopelagic environment, an alternative in the use of sediment eDNA is utilized in one of the world’s most productive ecosystems: The Atacama Trench. Having a history of overfishing events and effects of ENSO of differing intensities, five sites were sampled through sediment cores at depths going from 2400 to nearly 8000m. As layers of sediment are formed over time, within each layer are fragments of eDNA deposited by the pelagic fauna that inhabited at that time. For this study, the sediment layers were dated and the community composition for the years in which they inhabited was determined utilizing metabarcoding with the Euka02 and 18SMini primers. The communities identified for both primers are mainly composed of chordates and members of the recently established Chromista kingdom, and through further beta-diversity analyses, are shown to not be too distinct from one another. Alphadiversity was calculated for all sites in intervals of 15 years, and it became clear that there was a drop in biodiversity from 1977 to 2002. This is attributed to human influence, as the extensive fishing efforts in this period of time combined with the escape of salmonids from farms and adverse ENSO events contributed to the reduction of diversity, warning that although diversity is currently back at previous levels, anthropogenic impacts must be limited for conservation purposes. Overall, it is shown that sediment eDNA is a valuable emerging tool not only for research on the current state of communities in pelagic environments, but also as a snap-shot of the past that allows for comparisons within an ecosystem.

The study of soldier’s experience is important to understanding the effect that wars have on society. In the latter part of the 19th century the experience of warfare changed due to advances in weapons technology. The defensive tactic of trench warfare gained new importance. The most prolific use of trench warfare occured on the Western Front in the First World War, but it was during the siege of Petersburg in the American Civil War that extensive trenches were first used with technologically advanced weapons. By comparing the siege of Petersburg with the Western Front, it is clear that similar conditions elicited similar emotional reactions from soldiers. The most common reactions were fraternization and war neurosis. Fraternization was more prevelant during the siege of Petersburg than at other times during the war. Fraternization was also common on the Western Front. The reasons for this vary, but are all linked to the nature of trench warfare. War neurosis was also caused by the conditions of the trenches. It was a bigger problem at Petersburg and on the Western Front than it was for soldiers in other conflicts. Trench warfare created these emotional reactions. / Master of Arts

No description available.

Increases in impervious surfaces associated with urbanization change stream hydrology by increasing peak flow rates, storm-flow volumes and flood frequency, and degrade water quality through increases in sediment, nutrient, and bacteria concentrations. In response to water quality and quantity issues within the Stroubles Creek watershed, the Town of Blacksburg and Virginia Tech designed and constructed two innovative stormwater best management practices (BMPs). The goal of this project was to evaluate the effectiveness of a bioretention cell and a CU-Structural Soil™ infiltration trench. BMP construction was completed in July 2007. Twenty-nine precipitation events were monitored over a period of five months between October 2007 and March 2008. For each storm, inflow and outflow composite samples were collected for each BMP and analyzed for suspended sediment, total nitrogen, total phosphorus, fecal coliform bacteria and E-coli bacteria. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were then compared to evaluate how well each BMP reduces stormwater flows, decrease peak runoff rates and improves water quality of stormwater runoff. Results for the bioretention cell indicate average reductions in stormwater quantity, sediment, total nitrogen, total phosphorus and fecal coliform bacteria that exceeded 99% by mass. The CU-Structural Soil™ infiltration trench produced reductions in stormwater quantity, total phosphorus and sediment that averaged 60%, 45% and 51%, respectively. Preliminary bacteria results indicated that both BMPs served as sources of E-coli, and the infiltration trench served as a source of fecal coliform bacteria. / Master of Science

Atualmente a otimização e redução de custos verificados na fabricação de tubulações está caminhando para um limite. Toda e qualquer modificação no processo produtivo exige grandes investimentos com retorno a prazos cada vez maiores. Assim, a possibilidade de poder contar com técnicas que permitam a redução de esforços sobre tubulações enterradas traz sem dúvida uma importante contribuição. Este trabalho estuda o uso da trincheira como forma de reduzir os esforços que atuam sobre condutos enterrados, utilizando duas séries de ensaios denominados \"A\" e \"B\". Cada série é composta basicamente de quatro combinações diferentes, com variações geométricas da relação de altura relativa (h/B) e largura relativa (b/B). A série B teve a posição relativa (H/B) da camada flexível modificada em relação à série A. Os ensaios realizados no Departamento de Geotecnia da Escola de Engenharia de São Carlos apresentam como resultado uma redução dos esforços da ordem de 44% a 86% em relação ao ensaio de referência montado sem o uso da camada indutora. / Nowadays the optimization and the reduction of costs verified in the pipes production are walking for a limit. All and whatever modification on the productive process demands great investments with larger time return. Thus, the possibility of taking account with techniques that allows reduction efforts on buried pipes bring without any doubt, an important contribution. This work studies the induced trench to reduce the efforts that act over buried conduits, using two series, \"A\" and \"B\", with four treatments each one. The A series is composed with four different combinations. These combinations have geometric variation between relative height (h/B) and relative width (b/B) of flexible layers, were built directly over the trap door. The \"B\" series is composed with the same geometric flexible layer used in series \"A\", and they have their relative position (H/B) modified. The treatments were conducted at the \"Departamento de Geotecnia\" da \"Escola de Engenharia de São Carlos\". The results obtained were a reduction of the 44 to 86% on the efforts in relation to the reference treatment built without the use of an induced layer.

Atualmente a otimização e redução de custos verificados na fabricação de tubulações está caminhando para um limite. Toda e qualquer modificação no processo produtivo exige grandes investimentos com retorno a prazos cada vez maiores. Assim, a possibilidade de poder contar com técnicas que permitam a redução de esforços sobre tubulações enterradas traz sem dúvida uma importante contribuição. Este trabalho estuda o uso da trincheira como forma de reduzir os esforços que atuam sobre condutos enterrados, utilizando duas séries de ensaios denominados \"A\" e \"B\". Cada série é composta basicamente de quatro combinações diferentes, com variações geométricas da relação de altura relativa (h/B) e largura relativa (b/B). A série B teve a posição relativa (H/B) da camada flexível modificada em relação à série A. Os ensaios realizados no Departamento de Geotecnia da Escola de Engenharia de São Carlos apresentam como resultado uma redução dos esforços da ordem de 44% a 86% em relação ao ensaio de referência montado sem o uso da camada indutora. / Nowadays the optimization and the reduction of costs verified in the pipes production are walking for a limit. All and whatever modification on the productive process demands great investments with larger time return. Thus, the possibility of taking account with techniques that allows reduction efforts on buried pipes bring without any doubt, an important contribution. This work studies the induced trench to reduce the efforts that act over buried conduits, using two series, \"A\" and \"B\", with four treatments each one. The A series is composed with four different combinations. These combinations have geometric variation between relative height (h/B) and relative width (b/B) of flexible layers, were built directly over the trap door. The \"B\" series is composed with the same geometric flexible layer used in series \"A\", and they have their relative position (H/B) modified. The treatments were conducted at the \"Departamento de Geotecnia\" da \"Escola de Engenharia de São Carlos\". The results obtained were a reduction of the 44 to 86% on the efforts in relation to the reference treatment built without the use of an induced layer.

The following is a thesis project involving investigation of applicability of trench type IGBTs in present and future VSC based HVDC convertors. The work involves three major sections – theoretical loss evaluation of adoption of Trench technology (both IGBT and BIGT) for HVDC Light® applications, testing the Trench IGBT prototype with existing gate units and finalizing with a hypothesis and a practical solution for unexplained turn-on phenomenon observed during testing. The thesis concludes with the suggestion of suitable driving mechanisms (e.g. reduced number of current sources and removal of active gate snubbers) which shall result in both simpler and more cost effective driving compared to the present employed methods. / Följande avhandling är en studie om tillämpligheten av trench type IGBTer i nuvarande och framtida VSC baserade HVDC konverterare. Arbetet omfattar tre övergripande delar – teoretisk förlustberäkning vid tillämpning av trench teknologi (både IGBT och BIGT) till HVDC Light applikationer, prov av Trench IGBT prototyp med befintliga gate enheter och slutligen en hypotes och praktisk lösning till oförklarliga turn-on fenomen som observerats under prövning. Avhandlingen avslutas med en sammanfattning över lämpliga drivningsmekansimer (t.ex om antal strömkällor och borttagning av aktiv snubber vid gate enheten) som torde resultera både i enklare och kostnadseffektivare drivning jämfört metoder som tillämpas idag