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排序方式: 共有4773条查询结果,搜索用时 15 毫秒
1.
Nicholas Biery Marc De Graef Jack Beuth Rafel Raban Andrew Elliott Tresa M. Pollock Curt Austin 《Metallurgical and Materials Transactions A》2002,33(10):3127-3136
Tensile experiments have been performed on specimens of four different investment-cast TiAl-based alloys with variations in
casting conditions. The average ductilities obtained in these experiments vary between approximately 0.8 to 2.0 pct plastic
strain to failure in tension. By using the three-parameter form of the Weibull relation, with the 0.2 pct offset yield strength
as the minimum failure strength, the resulting variability in the data can be quantified and is found to be similar for those
alloys with similar microstructural scale (grain size). Large variations in lamellar volume fraction, segregation, and phase
distribution have a minor influence on property variability, compared to changes in the scale of the grain structure caused
by either variations in cooling rate during casting or the addition of grain refiners. 相似文献
2.
Jean‐Marc Aldric Philippe Thonart 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1401-1408
BACKGROUND: In the framework of biological processes used for waste gas treatment, the impact of the inoculum size on the start‐up performance needs to be better evaluated. Moreover, only a few studies have investigated the behaviour of elimination capacity and biomass viability in a two‐phase partitioning bioreactor (TPPB) used for waste gas treatment. Lastly, the impact of ethanol as a co‐substrate remains misunderstood. RESULTS: Firstly, no benefit of inoculation with a high cellular density (>1.5 g L?1) was observed in terms of start‐up performance. Secondly, the TPPB was monitored for 38 days to characterise its behaviour under several operational conditions. The removal efficiency remained above 63% for an inlet concentration of 7 g isopropylbenzene (IPB) m?3 and at some time points reached 92% during an intermittent loading phase (10 h day?1), corresponding to a mean elimination capacity of 4 × 10?3 g L?1 min?1 (240 g m?3 h?1) for a mean IPB inlet load of 6.19 × 10?3 g L?1 min?1 (390 g m?3 h?1). Under continuous IPB loading, the performance of the TPPB declined, but the period of biomass acclimatisation to this operational condition was shorter than 5 days. The biomass grew to approximately 10 g L?1 but the cellular viability changed greatly during the experiment, suggesting an endorespiration phenomenon in the bioreactor. It was also shown that simultaneous degradation of IPB and ethanol occurred, suggesting that ethanol improves the biodegradation process without causing oxygen depletion. CONCLUSION: A water/silicone oil TPPB with ethanol as co‐substrate allowed the removal of a high inlet load of IPB during an experiment lasting 38 days. Copyright © 2008 Society of Chemical Industry 相似文献
3.
Developing T cells in the thymus are subject to a screening process, through interactions with thymic stromal cells, from which T cells with appropriate T-cell receptors are selected. The recent generation of T-cell receptor transgenic mice and mice homozygous for disrupted T-cell receptor genes have now supplied tools that improve the prospect for a better understanding of the molecular mechanisms of this thymic selection process. In addition these model systems appear to indicate a role for a, not yet fully characterized, pre-T cell receptor complex in survival and further differentiation of pre-T cells. 相似文献
4.
Neben der Gestaltung technischer Systeme zur Unterstützung des Wissensmanagements ist die Ausgestaltung organisatorischer
Ma?nahmen gleichbedeutend wichtig. 相似文献
5.
The accuracy of the prediction of criminal violence may be improved by combining psychopathy with other variables that have been found to predict violence. Research has suggested that assessing intelligence (i.e., IQ) as well as psychopathy improves the accuracy of violence prediction. In the present study, the authors tested this hypothesis by using a contemporary measure of psychopathy, the Psychopathy Checklist-Revised (R. D. Hare, 2003), in a sample of 326 European American and 348 African American male offenders. The postdictive power of psychopathy was evident for both ethnic groups and robust across most changes in the operationalization of violence and the analysis conducted, whereas the postdictive power of IQ was not. No Psychopathy x IQ interactions were identified. Implications of these results for violence prediction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
This study examines the links between antecedents and consequences of Gabonese teachers' (N= 152) work motivation. The theoretical underpinnings are based on the Motivational Model of Job Burnout (MMJB) which is grounded in Self-Determination Theory (SDT) and states that the more supervisors satisfy an employee's need for self-determination, competence, and relatedness, the more self-determined is the latter's work motivation. The level of self-determined motivation has an impact on job satisfaction, which in turn determines life satisfaction. Higher levels of self-determined motivation also buffer emotional exhaustion and psychological distress. The model was confirmed via structural equation modeling and provides support for the validity and generalizability of the MMJB and SDT. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
J Valla A Leguerrier H Corbineau B Sevray T Langanay H Le Couls M Sellin C Rioux Y Logeais 《Canadian Metallurgical Quarterly》1995,49(9):816-823
From 1978 to 1992, 121 cases of postinfarction left ventricular aneurysm (99 males, 22 females, mean age 60 years) were operated on. The authors insist on a high rate of clinical arhythmogenicity (31.4%) and associated mechanical complications (21%). 76% of patients were in functional NYHA class III or IV. Resection was performed in 90% of patients, plication in 10%. 58% underwent coronary artery bypass grafting (1.7 graft/patient), 16% encircling ventriculotomy, 8% mitral valve replacement and 13% closure of ventricular septal defect. Operative mortality was 14.9% (10% when other mechanical complications where excluded). 5-year survival is 67.9%. Late cardiac deaths are as follow: left ventricular failure (1.8% A/P), Sudden death (1.4% A/P), Myocardial infarction (0.6% A/P). 82% of survivals are in functional NYHA class I or II. Only functional class NYHA III or IV is predictive of late death. We conclude that postinfarction left ventricular aneurysm remains a high risk complication especially when associated with other mechanical complications. When arhythmogenicity is present we suggest rhythmologic surgery and in all cases, complete revascularization. 相似文献
8.
Huseyin Selcuk Jeosadaque J Sene Marc A Anderson 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(9):979-984
This study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV254 removal and the degradation of color (Vis400) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10?1 min?1, 8.3 × 10?2 min?1 and 2.49 × 10?2 min?1 (R2 > 0.97) for UV254 degradation and 1.7 × 10?1 min?1, 6.5 × 10?2 min?1 and 2.0 × 10?2 min?1 for color removal from 5 mg dm?3, 10 mg dm?3 and 25 mg dm?3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm?3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV254 removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry 相似文献
9.
A family of energy/economic/environmental (E3) models is presented as a mechanism for analysing national policy issues. The family consists of discrete models which are designed to be run in an integrated manner. The outputs of certain models provide the inputs to the next. This structure allows the analyst to readily incorporate an understanding of regional factors such as local energy prices, concerns over air quality, water availability, or attitudes towards construction of new energy facilities, into national assessments of energy policies. This paper reviews the analytic framework within which energy policy issues are currently addressed. The initial family of E3 models is described with the emphasis on the data linkages and feedback which are provided when these models are run sequentially. The ongoing MITRE research programme with the E3 family of models is presented and plans and opportunities for future work are outlined. 相似文献
10.
Thermodynamic analysis of solar photovoltaic cell systems 总被引:1,自引:0,他引:1
Ahmet Duran Sahin Ibrahim Dincer Marc A. Rosen 《Solar Energy Materials & Solar Cells》2007,91(2-3):153-159
The thermodynamic characteristics of solar photovoltaic (PV) cells are investigated from a perspective based on exergy. A new efficiency is developed that is useful in studying PV performance and possible improvements. Exergy analysis is applied to a PV system and its components, and exergy flows, losses and efficiencies are evaluated. Energy efficiency is seen to vary between 7% and 12% during the day. In contrast, exergy efficiencies, which incorporate the second law of thermodynamics and account for solar irradiation exergy values, are lower for electricity generation using the considered PV system, ranging from 2% to 8%. Values of “fill factors” are determined for the system and observed to be similar to values of exergy efficiency. 相似文献