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排序方式: 共有510条查询结果,搜索用时 18 毫秒
1.
Chou Y.C. Leung D. Lai R. Grundbacher R. Barsky M. Kan Q. Tsai R. Wojtowicz M. Eng D. Tran L. Block T. Liu P.H. Nishimoto M. Oki A. 《Electron Device Letters, IEEE》2003,24(6):378-380
The authors have investigated the reliability performance of G-band (183 GHz) monolithic microwave integrated circuit (MMIC) amplifiers fabricated using 0.07-/spl mu/m T-gate InGaAs-InAlAs-InP HEMTs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel on 3-in wafers. Life test was performed at two temperatures (T/sub 1/ = 200 /spl deg/C and T/sub 2/ = 215 /spl deg/C), and the amplifiers were stressed at V/sub ds/ of 1 V and I/sub ds/ of 250 mA/mm in a N/sub 2/ ambient. The activation energy is as high as 1.7 eV, achieving a projected median-time-to-failure (MTTF) /spl ap/ 2 /spl times/ 10/sup 6/ h at a junction temperature of 125 /spl deg/C. MTTF was determined by 2-temperature constant current stress using /spl Delta/G/sub mp/ = -20% as the failure criteria. The difference of reliability performance between 0.07-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel and 0.1-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with In/sub 0.6/Ga/sub 0.4/As channel is also discussed. The achieved high-reliability result demonstrates a robust 0.07-/spl mu/m pseudomorphic InGaAs-InAlAs-InP HEMT MMICs production technology for G-band applications. 相似文献
2.
3.
Comments on an article by Bushman and Anderson (see record 2001-17729-001). We are concerned that Bushman and Anderson's article on media violence contains data that are incorrect or irreproducible. This is a serious issue; the article has already been referenced by numerous other formal papers according to a Google scholarly article search as well as in a statement to the U.S. Senate, in legal proceedings, and in California State law (Assembly Bill 1179 in 2005). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
J Norris L Harnack S Carmichael T Pouane P Wakimoto G Block 《Canadian Metallurgical Quarterly》1997,87(5):740-746
OBJECTIVES: This study examined US trends in nutrient intake, using almost identical methods and nutrient databases in two time periods. METHODS: An extensive dietary intake questionnaire was included in supplements to the 1987 and 1992 National Health Interview Surveys. Dietary data from approximately 11,000 persons in each of those years were analyzed. RESULTS: The total and saturated fat intake and the percentage of energy from fat declined among Whites and Hispanics, but only minimal changes were seen in Black Americans. The changes in fat intake were attributable principally to behavioral changes in frequency and type of fat-containing foods consumed rather than to the increased availability of leaner cuts of meat. Dietary cholesterol showed one of the largest declines of the nutrients examined. Less desirable changes were also seen. Cereal fortification played an important role in the observed changes in several micronutrients. CONCLUSIONS: Educational campaigns on dietary fat and cholesterol have been moderately effective, but not in all racial/ethnic groups. Future campaigns should emphasize maintaining or increasing micronutrient intake. 相似文献
5.
Thirty-four heifers (24 Holstein, 8 Ayrshire, 2 Jersey) and 12 Holstein steer calves were grouped into 23 blocks of 2 animals each according to breed, sex, and body weight. Animals in each block were randomly assigned to control or treated groups. The treated group received an anthelmintic bolus containing morantel tartrate before they were permitted access to pasture. A 2.6 ha pasture was divided in half with a double fence; the resulting two pastures had separate feed and water troughs. Steer calves were slaughtered upon termination of the trial to ascertain gastrointestinal parasite burdens. Two worm-free tracer calves were placed on each pasture every 2 mo and slaughtered after 4 wk of grazing to determine parasite infectivity of pastures. Herbage samples were obtained monthly and analyzed for infective larvae. The trial was conducted for 141 d during the grazing season. Treatment resulted in 90% reduction in infective larvae on pasture, 74% reduction in fecal worm-eggs, 91% reduction in adult worm burdens, and a trend toward reduced worm burdens in tracer calves by 52%. An overall average daily gain of .68 and .88 kg was obtained for control and treated animals. Reproductive data for the heifers remaining in the herd from the trial showed that treatment resulted in 44 less days to first breeding. 相似文献
6.
Steel production is an energy- and water-intensive process: large quantities of water are used for cooling, process and environmental-technical
applications. In the mid-1990s, Arcelor Gent, a large integrated carbon steel producing company in Flanders (Belgium), started
a number of water-related projects: the existing water infrastructure was adapted: the water from the coke plant was biologically
treated; canal water was demineralised using reverse osmosis; waste water from the blast furnaces was neutralised with alkaline
water from the steel plant. As a result of these projects, the quantity of discharged waste water was reduced by a factor
of 2 (water recycling doubled from a factor of 10 to a factor of 20), and the discharge of pollutants decreased. Also resource
consumption decreased: lime used in the steel plant, could be recovered to precipitate Zn in the waste water of the blast
furnaces.
Arcelor Gent obtained for these projects several Environmental Awards. 相似文献
7.
In 1675, English scientist Robert Hooke discovered “the true... ...manner of arches for building,” which he summarized with
a single phrase: “As hangs the flexible line, so but inverted will stand the rigid arch.” In the centuries that followed,
Hooke’s simple idea has been used to understand and design numerous important works. Recent research at MIT on the interactive
analysis of structural forces provides new graphical tools for the understanding of arch behavior, which are useful for relating
the forces and geometry of masonry structures. The key mathematical principle is the use of graphical analysis to determine
possible equilibrium states. 相似文献
8.
Huei Wang Kwo Wei Chang Tran L.T. Cowles J.C. Block T.R. Lin E.W. Dow G.S. Oki A.K. Streit D.C. Allen B.R. 《Solid-State Circuits, IEEE Journal of》1996,31(10):1419-1425
A family of millimeter-wave sources based on InP heterojunction bipolar transistor (HBT) monolithic microwave/millimeter-wave integrated circuit (MMIC) technology has been developed. These sources include 40-GHz, 46-GHz, 62-GHz MMIC fundamental mode oscillators, and a 95-GHz frequency source module using a 23.8-GHz InP HBT MMIC dielectric resonator oscillator (DRO) in conjunction with a GaAs-based high electron mobility transistor (HEMT) MMIC frequency quadrupler and W-band output amplifiers. Good phase noise performance was achieved due to the low 1/f noise of the InP-based HBT devices. To our knowledge, this is the first demonstration of millimeter-wave sources using InP-based HBT MMIC's 相似文献
9.
Global cerebral ischemia leads morphologically to selective neuronal damage in the CA1 sector of the hippocampus and in the striatum and functionally to a deficit in spatial learning and memory in the water maze. The results of earlier studies which examined the relationship between neuronal damage and the deficits in the water maze were not clear cut. It has been observed, however, that neuroprotection reduces both the deficits in the water maze as well as the neuronal damage. The present study therefore approached the relationship between the neuronal damage and the deficits in water maze using pharmacological means. Global cerebral ischemia was induced in male Wistar rats by four-vessel occlusion for 20 min. Ischemic rats were treated with the N-methyl-D-aspartate receptor antagonist dextromethorphan, 50 mg/kg, with the calcium antagonist levemopamil, 30 mg/kg, with the radical scavenger EPC-K1, 10 mg/kg, or with solvent. Treatment with dextromethorphan or levemopamil reduced the deficit in spatial learning by limiting the increase in swim distance due to ischemia. Both substances also reduced the deficit in spatial memory by minimizing the ischemia-induced reduction in time spent in the quadrant of the former platform position during the probe trial. EPC-K1 had no influence on the ischemia-induced behavioural changes. Group comparisons demonstrated that the swim speed and the percentage of the swimming path along the sidewall were affected neither by ischemia nor by any of the treatments. Histological examination revealed neuronal damage in the hippocampus and in the striatum in all of the ischemic rats. Treatment with dextromethorphan or levemopamil reduced the hippocampal damage by 32% and 36%, respectively. In addition, dextromethorphan diminished the striatal damage about 78%. Correlation analysis demonstrated a correlation between the cumulative swim distance of all 20 escape trials and hippocampal damage (r = 0.65, P < 0.001) but not between swim distance and striatal damage (r = 0.14, P = 0.364). No correlation was found between quadrant time of the probe trial and either hippocampal damage (r = -0.21, P = 0.19) or striatal damage (r = -0.02, P = 0.889). The average percentage of the swimming path along the side wall related to the hippocampal damage (r = 0.28, P = 0.035) but not to the striatal damage (r = 0.05, P = 0.381). With respect to the average swim speed a correlation to striatal damage was observed (r = -0.69, P < 0.001) but not to hippocampal damage (r = -0.15, P = 0.168). These results clearly demonstrate that using the pharmacological approach it is possible to uncover certain correlations between functional deficits in the water maze and neuronal damage which are both due to global cerebral ischemia. 相似文献
10.
JW Erdman AJ Thatcher NE Hofmann JD Lederman SS Block CM Lee S Mokady 《Canadian Metallurgical Quarterly》1998,128(11):2009-2013
The algae Dunaliella bardawil and Dunaliella salina naturally contain large concentrations of all-trans and 9-cis beta-carotene (betaC). The purpose of this study was to compare the relative serum and tissue accumulation of all-trans and 9-cis betaC in ferrets fed different ratios of all-trans/9-cis betaC derived from two commercial sources, D. bardawil or D. salina (Betatene). Male ferrets (7 wk old) were fed carotene-free, pelleted diets for 27 d. Beginning on d 18, groups of ferrets (n = 6 or 7) received daily, one of six oral supplements varying in ratios of 9-cis and all-trans betaC mixed with approximately 1.0mL of Ensure. Four supplements containing 5.2-8.3 micromol total betaC were prepared from a 20% Betatene preparation, D. bardawil, a high-cis Betatene preparation, and Betatene further enriched in 9-cis betaC with all-trans betaC/9-cis betaC ratios of 2.2, 1.5, 0.6 and 0.4, respectively. Two control supplements, high and low betaC, were prepared from commercial betaC beadlets. The high control supplement had an all-trans/9-cis ratio of 19.0, whereas 9-cis betaC was not detected in the low supplement. On d 27, serum and tissues were obtained for HPLC analysis of betaC and its isomers. Analysis of livers showed that all-trans betaC was the primary isomer present, but 9-cis and other isomers were also detected in all groups. The hepatic all-trans/9-cis ratios were 5.9, 4.9, 2.5, 1.4, 52.2 and47.5, respectively, for the groups listed above. Lower amounts of all-trans and 9-cis betaC were found in kidneys compared with the liver, but ratios of all-trans/9-cis were not different among groups. Only trace amounts of 9-cis betaC were found in serum. These results demonstrate that the algae D. bardawil and D. salina provide a bioavailable source of betaC isomers, but, as in humans, absorption of 9-cis betaC is poor and any 9-cis betaC absorbed is apparently cleared by the liver. 相似文献