Power consumption of VLSI (Very Large Scale Integrated) circuits has been growing at an alarmingly rapid rate. This increase in power consumption, coupled with the increasing demand for portable/hand-held electronics, has made power consumption a dominant concern in the design of VLSI circuits today. Traditionally dynamic (switching) power has dominated the total power consumption of VLSI circuits. However, due to process scaling trends, leakage power has now become a major component of the total power consumption in VLSI circuits. This dissertation explores techniques to reduce leakage, as well as techniques to exploit leakage currents through the use of sub-threshold circuits. This dissertation consists of two studies. In the first study, techniques to reduce leakage are presented. These include a low leakage ASIC design methodology that uses high VT sleep transistors selectively, a methodology that combines input vector control and circuit modification, and a scheme to find the optimum reverse body bias voltage to minimize leakage. As the minimum feature size of VLSI fabrication processes continues to shrink with each successive process generation (along with the value of supply voltage and therefore the threshold voltage of the devices), leakage currents increase exponentially. Leakage currents are hence seen as a necessary evil in traditional VLSI design methodologies. We present an approach to turn this problem into an opportunity. In the second study in this dissertation, we attempt to exploit leakage currents to perform computation. We use sub-threshold digital circuits and come up with ways to get around some of the pitfalls associated with sub-threshold circuit design. These include a technique that uses body biasing adaptively to compensate for Process, Voltage and Temperature (PVT) variations, a design approach that uses asynchronous micro-pipelined Network of Programmable Logic Arrays (NPLAs) to help improve the throughput of sub-threshold designs, and a method to find the optimum supply voltage that minimizes energy consumption in a circuit.

Endotoxin (lipopolysaccharide, LPS), is a constituent of the outer membrane of Gram-negative bacteria, activates macrophages to release cytokines that can cause local or systemic inflammatory responses. Plasma leakage and polymorphonuclear leukocyte infiltration are characteristic features of inflammation. This study examined the effect of LPS to induce subcutaneous inflammatory lesions, including time course of changes in plasma extravasation and level of leukocyte influx into the tissue interstitium. To investigate LPS-induced plasma leakage in the skin, LPS (500 £gg/site) was administered by subcutaneous injection in the hindpaw skin. India ink (1 ml/kg) was used as tracer dye to measure the area density of ink-labeled leaky blood vessels. Our results showed that the postcapillary venules were leaking immediately at five minutes after LPS. The area density of India ink-labeled leaky vessels was 33.9 %¡Ó5.6 % (n=5) after the administration of LPS. The magnitude of plasma leakage was 2 times as the value of saline control (16.6 %¡Ó1.8 %, n=5). Plasma leakage peaked at 30 min (42.5 %¡Ó2.5 %, n=11) after LPS. Staining of the microvasculature by silver nitrate showed endothelial gap formation in venules and indicated the positive relevance to plasma leakage. Leukocytes (neutrophils and eosinophils) in hindpaw skin whole mounts were stained by a histochemical reaction for myeloperoxidase and the numbers of leukocytes quantified. LPS caused a severe response in leukocyte adhesion and accumulation. The number of leukocytes after LPS was 5 times as the number after saline. It is concluded that local injection of LPS in the skin caused formation of endothelial gaps and leukocyte infiltration that resulted in an increase in local vascular permeability.

In this thesis, novel technology for manufacturing high-performance hydrogenated amorphous silicon (a-Si:H) TFT is developed . In the bottom gate light-shied a-Si:H TFT structure, the side edge of a-Si:H island is capped with extra deposition of heavily phosphorous-doped a-Si layer. The new structure a-Si:H TFT process steps is almost unchanged. The masksteops of fabrication new structure TFT are the same as the inverter-staggered TFT. Such an ingenuity can effectively eliminate the leakage path between the parasitic contacts between source/drain metal and a-Si:H at the edge of a-Si:H island. a-Si:H is a well-known photosensitivity material. For driving LCD the TFT must be operated with illuminated environment. It will cause the leakage current. The new TFT structure is similar to the light-shield TFT proposed by Akiyama in 1989. So the new structure TFT can not only reduce the schoktty emission leakage current but also the photo-leakage current. In addition, electrical performance of the novel a-Si:H TFT device exhibits superior effective carrier mobility, as high as 1.05 cm2/Vsec due to the enormous improvement in parasitic resistance. The impressively high performance provides the potential of our proposed a-Si:H TFT to apply for AMLCD and AMOLED technology.

Cryogenic composites find critical application in the manufacture of fuel tanks for reusable launch vehicles due to significant reduction in overall structural weight of the tank. These fuel tanks contain pressurized cryogen such as hydrogen at cryogenic temperatures. Exposure to varying temperatures and mechanical loads resulting from flight cycle, containment of pressurized cryogen causes thermo-mechanical loading of the composite. The thermo-mechanical loading cycles combined with anisotropy of the composite and mismatch in the thermal and mechanical properties of fibers and matrix lead to transverse matrix cracks (TMC) in each ply. TMC in adjacent plies intersect in localized regions at ply interfaces called crack junctions, which open up due to delamination on application of thermo-mechanical load. TMC and crack junctions usually form a network of leakage paths that assists leakage of cryogen through the composite. In this study, the volumetric flow rate of cryogen leaking through a damaged cross-ply composite with five plies is determined by estimating the effective conductance of the leakage paths. For a given damage state and applied load, crack junction and TMC openings are obtained by finite element analysis. A computational fluid dynamics model is first used to estimate the effective conductance of a leakage path to hydrogen leakage and then a simplified analytical model is used to compute the effective conductance from individual conductances of each crack junction and TMC through a series-parallel combination. A single phase flow model is considered for the numerical analysis of hydrogen flow through TMC and crack junctions. The simulations are carried out using a commercial computational fluid dynamics software, FLUENT. Parametric studies are carried out to investigate the dependence of leak rate of hydrogen on the irregularities of the TMC geometry and TMC, crack junction openings. The simplified model predictions of the effective conductance for the five ply composite show good comparison with numerical simulations.

Reducing secondary leakage is a common challenge in numerous machines, particularly in steam and gas turbines. Too large leakage in seals produces a substantial loss in efficiency and power delivery with an increase in specific fuel consumption. Various seal types exist, each with unique advantages and disadvantages as per leakage, power loss, and wear. Labyrinth seals are most common due to their simple design and low cost. Their main drawback is a too high leakage due to enlarged (worn) clearances when a rotor vibrates. More complicated seal types, such as brush seals can withstand rotor excursions and ensure lower leakage rates than with labyrinth seals. Brush seals utilize a bristle bed which contacts the rotor and wears out thereby reducing leakage performance. The HALOTM seal, an all-metal seal with flexibly supported shoes, is engineered as a clearance control seal to reduce leakage even more, in particular for operation with high pressure differentials and with high surface rotor speeds. Static leakage tests with hot air at a high temperature (max. 300°C) conducted in a test rig holding a labyrinth seal and a novel all-metal seal (HALOTM seal), both of the same diameter, length and clearance, show the novel seal leaks ~1/5 the flow of a labyrinth seal for pressure ratios (Ps/Pa) > 3.5. The savings in leakage are maximized during operation at high pressure differentials. Leakage measurements with a rotor spinning to a maximum speed of 2,700 rpm (surface speed = 23.6 m/s) produce a slight decrease in leakage with increasing rotor speed. The research product is a reliable leakage data base enabling the application of a state of the art sealing technology that increases system efficiency by reducing leakage and extends maintenance intervals by eliminating wear of components.

Study of a database of 350 giant oilfields show these to be dynamic short lived phenomena, with a median age of 35 Ma. A third show evidence of post-entrapment destructive processes, particularly erosion, fault leakage and gas flushing. Biodegradation is a destructive process most active during oil entrapment. Re-entrapment of oil released from spilling or breached traps is common. These processes are illustrated with case examples from SE Asia and throughout the world. The main controls on oilfield preservation are post-entrapment tectonism and seal type, with temperature and hydrodynamic regimes being secondary factors. Destructive processes are concentrated in shallow and deep zones and in seepage-prone traps such as compressional anticlines. Such factors strongly influence the distribution of preserved light oilfields, with preservation potential maximised in tectonically quiescent basins with evaporite or thick mudstone seals e.g. the Middle East and the Permian Basin, or in basin centres distant from inverted or uplifted zones e.g. Central Sumatra. More attention is required in prospect and regional evaluations to models involving post-entrapment leakage and re-migration.

Side channel attacks, where an attacker learns some physical information about the state of a device, are one of the ways in which cryptographic schemes are broken in practice. "Provably secure" schemes are subject to these attacks since the traditional models of security do not account for them. The theoretical community has recently proposed leakage resilient cryptography in an effort to account for side channel attacks in the security model. This thesis provides an in-depth look into what security guarantees public key leakage resilient schemes provide in practice.

Thesis (Ph. D.)--Michigan State University. Electrical and Computer Engineering Department, 2006. / Title from PDF t.p. (viewed on June 19, 2009) Includes bibliographical references (p. 87-89). Also issued in print.

Thesis (M.S.)--University of MIchigan, Ann Arbor, 1963. / Typescript (photocopy). Includes bibliographical references (leaves 56-60). Also issued in print.

Thesis (M.S.)--University of MIchigan, Ann Arbor, 1963. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 56-60).