998 resultados para Compósito W-Cu
Resumo:
A road safety audit was conducted for a seven-mile section of County Road W-55 in Washington County, Iowa. In 2006, the average annual daily traffic on this roadway was found to be 1,290 vehicles per day. Using crash data from 2001 to 2007, the Iowa Department of Transportation (Iowa DOT) has identified this roadway as being in the top 5% of Iowa secondary rural roads with the highest density of serious (fatal and major injury) crashes for single-vehicle run-off-road incidents. Considering these safety data, the Washington County Engineer requested that a road safety audit be conducted to identify areas with safety concerns and to recommend low-cost mitigation to address those concerns. Staff and officials from the Iowa DOT, Iowa State Patrol, Governor’s Traffic Safety Bureau, Federal Highway Administration, Institute for Transportation, and local law enforcement and transportation agencies met to review crash data and discuss potential safety improvements to this segment of W-55. This report outlines the findings and recommendations of the road safety audit team to address the safety concerns on this W-55 corridor and explain several selected mitigation strategies.
Resumo:
On October 20–21, 2009, two road safety audits were conducted in Lee County, Iowa: one for a 6 mile section of County Road X-23 from IA 2 to the south corporate limits of West Point and one for a 9.7 mile section of County Road W-62 from US 218 to IA 27. Both roads have high severe crash histories for the years of 2001 through 2008. Using these crash data, the Iowa Department of Transportation (Iowa DOT) has identified County Road X-23 as being in the top 5 percent of similar roads for run-off-road crashes. The Iowa DOT lists County Road W-62 as a high-risk rural road that has above-average crash numbers and is eligible for funding under the Federal High-Risk Rural Road Program. Considering these issues, the Lee County Engineer and Iowa DOT requested that road safety audits be conducted to address the safety concerns and to suggest possible mitigation strategies.
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[Qaddich]
Resumo:
We present results from both, calorimetric and dilatometric studies of the isothermal ordering process taking place in a Cu-Zn-Al shape memory alloy after quenches from Tq temperatures ranging from 350 K to 1200 K. The dissipated energy and the length variations of the system are obtained during the process. The change of these quantities in the whole process have been compared with the difference [MATH] between Ms, measured after the relaxation and Ms measured just after the quench. We obtain that these three quantities present, as a function of Tq, the same qualitative behaviour. These changes are then associated with changes of the L21 ordering after the quench in the system. The relaxational process does not follow a single exponential decay. Instead, a continuous slowing down is observed. A relaxation time [MATH] has been defined to characterize the relaxation rate. We show that [MATH] depends on both the annealing and the quenching (Tq [MATH] 800 K) temperatures through an Arrhenius law.
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In this work the adsorption mechanisms of atomic and molecular oxygen on Cu(100) surface are studied using ab initio simulation methods. Through the atomistic scale under-standing of the elementary oxidation processes we can further understand the large-scale oxidation. Copper is a material widely used in industry which makes it an interesting subject, and also understanding the oxidation of copper helps us understand the oxidation mechanism of other metals. First we have a look on some theory on surface alloys in general and behaviour of Ag on Cu(100) surface. After that the physical background there is behind the methods of density functional calculations are discussed, and some methods, namely potential energy surfaces and molecular dynamics, are introduced. Then there is a brief look on the numerical details used in the calculations, and after that, the results of the simulations are exhibited.
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In this work annealing and growth of CuInS2 thin films is investigated with quasireal-time in situ Raman spectroscopy. During the annealing a shift of the Raman A1 mode towards lower wave numbers with increasing temperature is observed. A linear temperature dependence of the phonon branch of ¿2 cm¿1/100 K is evaluated. The investigation of the growth process (sulfurization of metallic precursors) with high surface sensitivity reveals the occurrence of phases which are not detected with bulk sensitive methods. This allows a detailed insight in the formation of the CuInS2 phases. Independent from stoichiometry and doping of the starting precursors the CuAu ordering of CuInS2 initially forms as the dominating ordering. The transformation of the CuAu ordering into the chalcopyrite one is, in contrast, strongly dependent on the precursor composition and requires high temperatures.
Resumo:
Tässä työssä on tutkittu kuparin (510)-askelpinnan reaktiivisuutta käyttäen apuna kvanttimekaanisia ab initio laskentamenetelmiä. Tutkimus on toteutettu laskemalla happiatomin adsorptioenergia ja tilatiheys erilaisissa potentiaalisissa adsorptiopaikoissa pinnalla. Myös happimolekyylin adsorptiota ja hajoamista ontarkasteltu laskemalla pintaa lähestyvälle molekyylille potentiaalienergiapintoja. Energiapintojen tuloksia on myös täydennetty kvanttimekaanisilla molekyylidynamiikkalaskuilla. Metallisia askelpintoja pidetään yleisesti sileitä pintoja reaktiivisempina happea kohtaan, johtuen askeleen reunan pienentävästä vaikutuksesta molekyylin hajoamisen tiellä olevaan energiavaliin. On kuitenkin olemassa myös tuloksia, jotka osoittavat hapen tarttumisprosessin olevan hallitseva juuri terassialueella, askeleen reunan sijasta. Tässä työssä on todettu hapen adsorboituvan Cu(510)-pinnalla tehokkaimmin juuri terassilla olevaan hollow-paikkaan. Myös adsorptioenergiat ovat tällä pinnalla pienempiä kuin sileällä (100)-pinnalla. Potentiaalienergiapintojen perusteella Cu(510)-pinnan todetaan myös olevan vähemmän reaktiivinen kuin askelpintojen yleisesti odotetaan olevan, vaikka askeleen reunan todetaankin pienentävän happiatominhajoamisen esteenä olevaa energiavallia.