18,007 research outputs found
Institutionalized Discrimination in the Legal System: A Socio-Historical Approach
Despite many of the social, political, and economic changes of the 1960s, discrimination is still prevalent in the United States. Increasingly, evidence of discrimination can be seen in our nation\u27s courts, institutions of higher education, in public policy decisions, and every social, political and economic institution. The question of how this can be in these days of ethnic and cultural diversity has aroused considerable interest among social scientists, as well as among the general public. One area that has been the target of considerable research is the criminal justice system. Wilbanks[1] has suggested that it is a myth that the criminal justice system is racist and discriminates against blacks and other minorities. This paper argues to the contrary. It is suggested that Wilbanks has inappropriately applied a microlevel analysis to a macrolevel phenomenon. Examining the historical-structural nature of the legal systems points to great disparities in the status quo of US jurisprudence
Appraisal of digital terrain elevation data for low-altitude flight
The use of terrain elevation databases in advanced guidance and navigation systems has greatly expanded. However, the limitations and accuracies of these databases must be considered and established prior to safe system flight evaluation. A simple approach to quantify reasonable flight limits is presented and evaluated for a helicopter guidance system dependent on a terrain database. The flight test evaluated involved a helicopter equipped with a Global Positioning System (GPS) receiver and radar altimeter, and a ground station GPS receiver which provided improved helicopter positioning. The precision navigation and radar altimeter data was acquired while flying low-altitude missions in south-central Pennsylvania. The aircraft-determined terrain elevations were compared with the terrain predicted by the Defense Mapping Agency (DMA) Level 1 terrain elevation data for the same area. The results suggest a safe set clearance altitude of 220 ft for flight testing of a DMA-based guidance avionic in the same area
Modeling Light Trapping in Nanostructured Solar Cells
The integration of nanophotonic and plasmonic structures with solar cells offers the ability to control and confine light in nanoscale dimensions. These nanostructures can be used to couple incident sunlight into both localized and guided modes, enhancing absorption while reducing the quantity of material. Here we use electromagnetic modeling to study the resonances in a solar cell containing both plasmonic metal back contacts and nanostructured semiconductor top contacts, identify the local and guided modes contributing to enhanced absorption, and optimize the design. We then study the role of the different interfaces and show that Al is a viable plasmonic back contact material
Photographic Study of Liquid-Oxygen Boiling and Gas Injection in the Injector of a Chugging Rocket Engine
High-speed motion pictures were taken of conditions in the injector liquid-oxygen cavity of an RL-10 rocket engine during throttled engine operation. Photographs were taken during operation of the engine in the chugging region as the helium gas was injected to stabilize combustion, during operation at rated thrust, and during transition into chugging conditions as the gas injection was discontinued. Results of the investigation indicate that, during chugging rocket operation of the RL-10 engine, a high population of fairly large bubbles formed and collapsed within the liquid-oxygen cavity at the same frequency as the chamber pressure oscillations. When gaseous helium was injected into the liquid-oxygen cavity, a fog rapidly spread over the entire field of view, and the system immediately became stable. The injection of gaseous helium at rated conditions produced a very slight increase in engine performance but not enough to produce a net gain in a typical mission payload with the extra equipment needed. The inherent low-frequency system instability associated with the fuel system at low thrust levels was reduced by injecting either gaseous helium or hydrogen. Complete stabilization was achieved in some cases, and a reduction in the severity of the oscillations in others. This was apparently due to the anchoring of the phase change front to the location of the gas injection
A Systems Theory Perspective
Aktualisierung: Am 12. Oktober 2018 wurde die digitale Version des Buchbeitrags um den fehlenden Teil (Seiten 53-66) ergänzt
Comparative study of evolution of residual stress state by local mechanical tensioning and laser processing of ferritic and austenitic structural steel welds.
Complex thermal stresses generated in welded structures are undesirable but inevitable in fusion welding. The presence of residual stresses can be detrimental to the integrity of a welded joint. In this research, redistribution of residual stress magnitude and profile was studied and compared in two multi-pass welded structural alloys (API X100 and 304L stainless steel) after cold rolling and laser processing. The residual stress field was studied by neutron diffraction using the SALSA strain scanner at their reactor neutron source at ILL, Grenoble. In addition to a complex distribution of residual stress state, multi-pass welds also forms dendritic grain structure, which are repeatedly heated, resulting in segregation of alloying elements. Dendritic grain structure is weaker and segregation of alloying elements may result in formation of corrosion microcells as well as reduction in overall corrosion prevention due to depletion of alloying elements in certain areas. The modification of as-welded residual stress state was done by cold rolling which was followed by laser processing to create a recrystallized microstructure to minimise segregation. The main objective of this study is to understand the suitability of this novel manufacturing technique to create a stress free weldment with recrystallised grain structure. Hardness evolution in the welded structures was scanned following welding, post weld cold rolling and cold rolling followed by laser processing. Hardness distribution in both the structural alloys showed a significant evidence of plastic deformation near the cap pass of the weld metal. Residual stress redistribution was observed up to 4 mm from the capping pass for ferritic steel, while in austenitic steel weld, post weld cold rolling was effective in modifying the residual stress redistribution throughout the entire thickness. Laser processing in both cases reinstated the as-welded residual stress distribution and resulted in softening of the strained area
Innovative Stormwater Treatment Technologies: Best Management Practices Manual
Urban stormwater carries a number of pathogens, nutrients, heavy metals, sediment, and other contaminants as surface runoff flows over land. The increase in impervious or paved surfaces associated with development in urban areas reduces the natural infiltration of precipitation into the ground. With impervious cover, precipitation collects and carries contaminants before draining into nearby surface waters. Stormwater runoff from paved surfaces in developed areas can degrade downstream waters with both contaminants and increased volumes of water. This publication aims to make information on innovative stormwater treatment technologies more available to New Hampshire’s urban planners, developers, and communities. Traditional runoff management techniques such as detention basins and infiltration swales may be preferable, but are not always practical for treating urban stormwater. Lack of space for natural solutions is often a problem in existing developed areas, making innovative treatment technologies an attractive alternative. Mostly designed for subsurface installation, urban “retrofits” use less space than conventional methods to treat stormwater. This manual provides information on the innovative stormwater “retrofit” technologies currently available for use in developed areas in New Hampshire
Collision integrals and high temperature transport properties for N-N, O-O, and N-O
Accurate collision integrals are reported for the interactions of N(4 S 0) + N(4 S 0), O(3 P), and N(4 S 0) + O(3 P). These are computed from a semiclassical formulation of the scattering using the best available representations of all of the potential energy curves needed to describe the collisions. Experimental RKR curves and other accurate measured data are used where available; the results of accurate ab initio electronic structure calculations are used to determine the remaining potential curves. The high-lying states are found to give the largest contributions to the collision cross sections. The nine collision integrals, needed to determine transport properties to second order, are tabulated for translational temperatures in the range 250 K to 100,000 K. These results are intended to reduce the uncertainty in future predictions of the transport properties of nonequilibrium air, particularly at high temperatures. The viscosity, thermal conductivity, diffusion coefficient, and thermal diffusion factor for a gas composed of nitrogen and oxygen atoms in thermal equilibrium are calculated. It was found that the second order contribution to the transport properties is small. Graphs of these transport properties for various mixture ratios are presented for temperatures in the range 5000 to 15000 K
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