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81.
Van Wyk J.D. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(8):1164-1193
The historical development of power electronic converters to control electrical machines is traced up to the present state of the technology. The fundamental possibilities to control average power in a switching mode are considered and the concepts switching function, converter topology and converter structure defined. A systematic approach to developing more complicated topologies and structures for singular and composite converters is discussed and application to motion control systems given. A functional classification of motion control converters is also related to the switching nature of the power processing, illustrating the fundamental dilemma of this kind of highly efficient power control. The different control possibilities of using power electronic converters with electrical machines in motion control applications (DC drives, AC drives) are reviewed systematically. The paper does not attempt to compile a comprehensive list of all possible converter circuits and variations but focusses on generic issues and technologies. The switching technology in converters and its limitations is related to snubberless, snubbed, and resonant transition-type operation, with reference also to switch drive and converter protection technology. Some future generic possibilities related to electromagnetic integration of switching converters are discussed, also in relation to a motion control application 相似文献
82.
Bellens R. de Schrijver E. Van den Bosch G. Groeseneken G. Heremans P. Maes H.E. 《Electron Devices, IEEE Transactions on》1994,41(3):413-419
A continued fast interface trap generation is observed in n-channel MOS transistors after termination of the hot-carrier stress. The magnitude of this post-stress effect is strongly dependent on the conditions of the preceding stress, on the post-stress conditions and on the process parameters. For measurements at 293 K, a simple model is proposed which is based on the release of hydrogen by the thermal detrapping of holes, and which can explain the observed dependencies. The importance of the post-stress Dit-generation is illustrated for the case of dynamic stress conditions where it can lead to an apparently deviating degradation behavior 相似文献
83.
Van Eupen M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1994,40(1):193
Optimal ternary linear codes with parameters [29,5,18], [34,5,21], [43,5,27], [61,5,39], and [31,6,18] have been found. Codes with these parameters were not known until now 相似文献
84.
G. Coudenys I. Moeeman G. Vermeire F. Vermaerke Y. Zhu P. Van Daele P. Demeester E. Maayan B. Elsner J. Salzman E. Finkman 《Journal of Electronic Materials》1994,23(2):225-232
The shadow masked growth technique is presented as a tool to achieve thickness and bandgap variations laterally over the substrate
during metalorganic vapor phase epitaxy. Lateral thickness and bandgap variations are very important for the fabrication of
photonic integrated circuits, where several passive and active optical components need to be integrated on the same substrate.
Several aspects of the shadow masked growth are characterized for InP based materials as well as for GaAs based materials.
Thickness reductions are studied as a function of the mask dimensions, the reactor pressure, the orientation of the masked
channels and the undercutting of the mask. The thickness reduction is strongly influenced by the mask dimensions and the reactor
pressure, while the influence of the orientation of the channels and the amount of undercutting is only significant for narrow
mask windows. During shadow masked growth, there are not only thickness variations but also compositional variations. Therefore,
we studied the changes in In/Ga and As/P ratios for InGaAs and InGaAsP layers. It appears that mainly the In/Ga-ratio is responsible
for compositional changes and that the As/P-ratio remains unchanged during shadow masked growth. 相似文献
85.
The levels of bacterial blood endotoxin, antiendotoxin antibodies and the overall immunity were studied in 48 females with inflammatory genital diseases complicated by pelvioperitonitis. The severest pelvioperitonitis-complicated abnormality was shown to characterized by high concentrations of endotoxin and low levels of antibodies. Endotoxinemia was found to be of diagnostic and prognostic value. 相似文献
86.
Hanssen M.; Krabbendam L.; Vollema M.; Delespaul P.; Van Os J. 《Canadian Metallurgical Quarterly》2006,115(1):5
It is unknown to what degree dimensions of schizotypy (subclinical psychosis) show independent, family-specific variation in the general population. Psychologists administered the Community Assessment of Psychic Experiences, the Structured Interview for Schizotypy-Revised (SIS-R), and the Brief Psychiatric Rating Scale to 257 subjects pertaining to 82 general population families. All 3 instruments showed family-specific variation for positive and negative subclinical psychosis dimensions with between-families proportions of total variance between 10% and 40%. However, only the SIS-R showed family-specific variation of the negative dimension independent of its correlation with the positive dimension. The positive dimension of subclinical psychosis shows familial-specific variation in samples unselected for psychiatric disorder, suggesting dimensional liability in the population. The SIS-R additionally captures family-specific variation in the negative domain. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Verbrugge Sara; Dieussaert Kristien; Schaeken Walter; Van Belle William 《Canadian Metallurgical Quarterly》2004,58(2):106
Evidence from reasoning tasks shows that promises and threats both tend to receive biconditional interpretations. They also both display high speaker control. On the face of it, the only difference seems to be the positive or negative signing of the consequent. In a promise, the speaker tries to persuade the hearer to do something by holding out the prospect of a particular reward; in a threat, the speaker tries to refrain the hearer from doing something by holding out the prospect of a particular punishment. This paper investigates the respects in which conditional promises and threats differ further by means of an inference task. The credibility of the consequent was manipulated in order to examine whether the acceptability ratings of inferences based on promises and on threats would be equally affected. The results of the inference task and an analysis of the reasons people give for their answers suggest that the credibility of promises is less affected by the use of excessive consequents than the credibility of threats. In other words, promise remains debt, whereas threat is another matter. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
Insulin-like growth factor I activates the invasion suppressor function of E-cadherin in MCF-7 human mammary carcinoma cells in vitro 总被引:1,自引:0,他引:1
ME Bracke BM Vyncke EA Bruyneel SJ Vermeulen GK De Bruyne NA Van Larebeke K Vleminckx FM Van Roy MM Mareel 《Canadian Metallurgical Quarterly》1993,68(2):282-289
The calcium-dependent cell-cell adhesion molecule E-cadherin has been shown to counteract invasion of epithelial neoplastic cells. Using three monoclonal antibodies, we have demonstrated the presence of E-cadherin at the surface of human MCF-7/6 mammary carcinoma cells by indirect immunofluorescence coupled to flow cytometry and by immunocytochemistry. Nevertheless, MCF-7/6 cells failed to aggregate in a medium containing 1.25 mM CaCl2, and they were invasive after confrontation with embryonic chick heart fragments in organ culture. Treatment of MCF-7/6 cells with 0.5 microgram ml-1 insulin-like growth factor I (IGF-I) led to homotypic aggregation within 5 to 10 min and inhibited invasion in vitro during at least 8 days. The effect of IGF-I on cellular aggregation was insensitive to cycloheximide. However, monoclonal antibodies that interfered with the function of either the IGF-I receptor (alpha IR3) or E-cadherin (HECD-1, MB2) blocked the effect of IGF-I on aggregation. The effects of IGF-I on aggregation and on invasion could be mimicked by 1 microgram ml-1 insulin, but not by 0.5 microgram ml-1 IGF-II. The insulin effects were presumably not mediated by the IGF-I receptor, since they could not be blocked by an antibody against this receptor (alpha IR3). Our results indicate that IGF-I activates the invasion suppressor role of E-cadherin in MCF-7/6 cells. 相似文献
89.
A Cuschieri S Shimi S Banting G Van Velpen P Dunkley 《Canadian Metallurgical Quarterly》1993,1(5-6):303-305
New coaxial curved and bayonet instruments have been designed which permit controlled dissection and directional change of the functional tip, blunt dissection and lift retraction. The instruments are introduced into the peritoneal and thoracic cavities through flexible re-usable metal cannulae. The excellent ergonomic properties of the new instruments have been confirmed by their use in major laparoscopic and thoracoscopic operations. Coaxial instruments enhance the scope of minimal access surgery and have distinct advantages over the traditional straight instruments. 相似文献
90.
The construction of a small solid oxide fuel cell laboratory is described in terms of required materials, measuring techniques and equipment design. Details of various electrode deposition techniques and ways of making contacts to the electrodes are also outlined. 相似文献