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排序方式: 共有1997条查询结果,搜索用时 15 毫秒
31.
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Powertrain hybridization as well as electrical energy management are imposing new requirements on electrical storage systems in vehicles. This paper characterizes the associated vehicle attributes and, in particular, the various levels of hybrids. New requirements for the electrical storage system are derived, including: shallow-cycle life, high dynamic charge acceptance particularly for regenerative braking and robust service life in sustained partial-state-of-charge usage. Lead/acid, either with liquid or absorptive glass-fibre mat electrolyte, is expected to remain the predominant battery technology for 14 V systems, including micro-hybrids, and with a cost-effective battery monitoring system for demanding applications. Advanced AGM batteries may be considered for mild or even medium hybrids once they have proven robustness under real-world conditions, particularly with respect to cycle life at partial-states-of-charge and dynamic charge acceptance. For the foreseeable future, NiMH and Li-ion are the dominating current and potential battery technologies for higher-functionality HEVs. Li-ion, currently at development and demonstration stages, offers attractive opportunities for improvements in performance and cost. Supercapacitors may be considered for pulse power applications. Aside from cell technologies, attention to the issue of system integration of the battery into the powertrain and vehicle is growing. Opportunities and challenges for potential “battery pack” system suppliers are discussed. 相似文献
33.
PB DePetrillo 《Canadian Metallurgical Quarterly》1997,68(5):1863-1869
Calcium-activated neutral protease activity was determined in PC12 cells exposed to ethanol for 96 h using a fluorescence-based assay with N-succinyl-Leu-Tyr 7-amido-4-methylcoumarin as the substrate. Stimulated activity was measured at high (1,400 microM) or low (140 microM) Ca2+ concentrations in the presence of 20 microM ionomycin. Kinetic parameters were derived by fitting a model relating fluorescence intensity to time: F(t) = F(final)*(1 - e(-k(obs)t). Cell extracts were subjected to nondenaturing gel electrophoresis and casein zymography with quantification of the activity of the two calpain isoforms. Exposure to ethanol significantly decreased whole cell calpain activity measured by k(obs) beginning at 20 mM, to 27.8% of control at 1,400 microM Ca2+ and 29.2% of control at 140 microM Ca2+ in the presence of 20 microM ionomycin. No changes in mu-calpain or m-calpain activities were found in cell extracts from cells exposed to 20 mM ethanol, whereas at 40 and 80 mM ethanol, significant decreases in both mu-calpain and m-calpain activities were discovered. 相似文献
34.
Aortic valve endocarditis commonly leads to the formation of a root abscess, but fistulae are uncommon. The echocardiographic findings in a patient with Streptococcus viridans endocarditis of a prosthetic aortic valve associated with a fistula between the aorta and the left atrium are presented. The diagnosis was made by transthoracic echocardiography, although the transesophageal study gave higher resolution views and allowed a more confident exclusion of mitral valve involvement. 相似文献
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36.
Teleoperation is frequently performed with misalignments between operator or camera viewing direction and controller orientation. Examples of this occur in endoscopic surgery and in teleoperation with multiple camera views. The objective of this study was to find a method to automatically compensate for those misalignments so that human operators performing tasks under such scenarios could achieve levels of performance comparable to aligned conditions without additional training requirements. In this paper we report on a set of experiments conducted to test a method developed for that purpose. Participants were asked to track a randomly moving target on a computer display using a cursor controlled with a joystick. Performance was recorded under various visual-motor misalignments with and without automated compensation. Results indicated significant improvements in operator performance through use of automatic compensation only under certain types of misalignment. Actual or potential applications of this research include teleoperation and endoscopic surgery. 相似文献
37.
JC Clouse M Rogers RC Reba JL Littlefield PB Schneider M Pollycove 《Canadian Metallurgical Quarterly》1998,39(7):11N-13N, 27N, 30N
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39.
We have analyzed X-chromosome inactivation patterns in lymphocytes of 264 females from 38 families not known to have any genetic disease. Quantitative measures of X-inactivation showed strong sister-sister correlation in the degree of departure from equal numbers of cells having each X chromosome active, suggesting heritability of this phenotype. Strong sister-sister correlation was also observed for the fraction of cells having the same parent's X chromosome active, consistent with the possibility that this trait might be controlled by a cis-acting, X-linked gene. We used a sib-pair approach to determine whether X-inactivation phenotype was linked to loci in any region of the X chromosome. Both quantitative and discrete measures of X-inactivation phenotype showed evidence of linkage to markers in the region of the X inactivation center (XIC). The quantitative measure of X-inactivation phenotype used in our study also showed linkage to loci at Xq25-q26. This study provides the first evidence for X-linked inheritance of X chromosome inactivation phenotype derived from linkage analysis in phenotypically normal human families. 相似文献
40.