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排序方式: 共有1340条查询结果,搜索用时 15 毫秒
1.
Adama Ouedraogo Ladifata Mogmenga Nbon Bado Thierry Sikoudouin Maurice Ky Dieudonn Joseph Bathiebo 《SILICON》2020,12(8):1831-1837
The present paper is about an experimental evaluation of the terrestrial silicon single-crystalline solar PV module behavior under low gamma radiation. The 相似文献
2.
An important feature of database technology of the nineties is the use of parallelism for speeding up the execution of complex queries. This technology is being tested in several experimental database architectures and a few commercial systems for conventional select-project-join queries. In particular, hash-based fragmentation is used to distribute data to disks under the control of different processors in order to perform selections and joins in parallel. With the development of new query languages, and in particular with the definition of transitive closure queries and of more general logic programming queries, the new dimension of recursion has been added to query processing. Recursive queries are complex; at the same time, their regular structure is particularly suited for parallel execution, and parallelism may give a high efficiency gain. We survey the approaches to parallel execution of recursive queries that have been presented in the recent literature. We observe that research on parallel execution of recursive queries is separated into two distinct subareas, one focused on the transitive closure of Relational Algebra expressions, the other one focused on optimization of more general Datalog queries. Though the subareas seem radically different because of the approach and formalism used, they have many common features. This is not surprising, because most typical Datalog queries can be solved by means of the transitive closure of simple algebraic expressions. We first analyze the relationship between the transitive closure of expressions in Relational Algebra and Datalog programs. We then review sequential methods for evaluating transitive closure, distinguishing iterative and direct methods. We address the parallelization of these methods, by discussing various forms of parallelization. Data fragmentation plays an important role in obtaining parallel execution; we describe hash-based and semantic fragmentation. Finally, we consider Datalog queries, and present general methods for parallel rule execution; we recognize the similarities between these methods and the methods reviewed previously, when the former are applied to linear Datalog queries. We also provide a quantitative analysis that shows the impact of the initial data distribution on the performance of methods.
Recommended by: Patrick Valduriez 相似文献
3.
D.W. McKee 《Carbon》1985,23(6)
The behavior of a number of rare earth oxides as catalysts for the oxidation of graphite in air has been investigated by the methods of thermal analysis. Of the oxides studied, only CeO2 showed significant activity in accelerating the gasification of graphite by oxygen between 500 and 1000°C. Cerium salts, which decompose to a finely dispersed oxide phase at low temperatures, e.g. Ce (III) nitrate and ammonium Ce (IV) nitrate, were found to be very active catalysts. The catalytic effect may be due to a redox process involving the cyclic conversion of the oxide from the Ce (IV) to the Ce (III) oxidation state, or the oxide particles may provide sites for the dissociative chemisorption of oxygen. 相似文献
4.
Maurice Kamen-Kaye 《Journal of Petroleum Geology》1985,8(3):323-329
Exploratory drilling on the Seychelles Bank, in a sector west of outcrop granite on Mahé Island, has revealed the presence of substantial Mesozoic colums. Their thicness approaches 3,000m; and total Phanerozoic down to true basement probably exceeds 4,500m. Still greater depths are possible, not only in this drilled NW-most sector of the island arc of the Mascarene Ridge, but also elsewhere along the arc, whose total cross-latitudinal dimension is more than 2,000km. Volcanics, like those in the African borderlands, repeatedly enter the Phanerozoic column of the Seychelles. The young "basaltic basement" of geodynamic theory, consequently, cannot exist on the Seychelles Bank. The same negative may hold true for the whole arc of the Mascarene Ridge and for its marginal waters westward as far back as the African borderlands themsleves. In the domain of exploration, the prime parameter of sedimentary volume is acceptable along much of the Mascarene Ridge, for which reason wells drilled to true basement merit consideration in future drilling. Such wells in central and southern sectors might recover basement rocks whose petrology could offer a strong challenge to present concepts of paleogeography in the whole back-arc area of the western Indain Ocean. 相似文献
5.
Izard Carroll E.; Fantauzzo Christina A.; Castle Janine M.; Haynes O. Maurice; Rayias Maria F.; Putnam Priscilla H. 《Canadian Metallurgical Quarterly》1995,31(6):997
Four studies examined aspects of the differential emotions theory (DET) hypothesis of expressive behavior development. In Study 1, facial-expressive movements of 108 2.5–9-mo-old infants were video recorded in positive and negative mother–infant interactions (conditions). As expected, Max-specified full-face and partial expressions of interest, joy, sadness, and anger were morphologically stable between the 2 ages. Studies 1 and 2 confirmed predicted differential responding to mother sadness and anger expressions and to composite positive and negative conditions. Discrete negative expressions exceeded negative blends, and the amount of both expression types remained stable across ages. Studies 3 and 4 provided varying degrees of support for the social validity of Max-specified infant negative affect expressions. Conclusions include revisions and clarifications of DET. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
The aim of this randomized cross-over trial was to evaluate the dose effect and systemic absorption of epinephrine nebulized at 2 and 5 mg in comparison with salbutamol (5 mg). Thirteen asthmatic patients (29 +/- 15 years, 4 men and 9 women) were randomly assigned to receive one nebulization of each of the three treatment regimens at 24 h interval. The evaluation concerned forced expiratory volume in 1 second (FEV1), heart rate, respiratory rate and arterial pressure. All measurements were done at baseline, every 15 minutes during the first hour, and hourly thereafter until return to baseline FEV1. Serum potassium was measured at baseline (T0) and sixty minutes after (T60). Plasma levels of epinephrine were measured at T0, T20, T60. Fifteen minutes after the beginning of nebulization FEV1 improved significantly over baseline in the three groups. These changes were similar in the three groups until T45, while FEV1 improvement was significantly greater in A5 and S groups than A2 group (+640 +/- 470 ml, +721 +/- 349 ml, +406 +/- 306 ml in A5, S and A2 groups respectively, p < 0.01). Bronchodilation lasted significantly longer with salbutamol than with epinephrine (p < 0.05). No side effects were recorded in spite of substantial and dose-dependent systemic absorption of epinephrine. CONCLUSION: Increasing epinephrine doses produces greater bronchodilation without additional side effects. However this bronchodilation lasts shorter than with salbutamol. 相似文献
7.
GR McKee 《Canadian Metallurgical Quarterly》1995,76(2):427-434
Legal responsibility for acts presumes that a person's behavior is rationally intentional and under voluntary control. Automatism, a type of insanity defense, contends that the person's conscious, voluntary control of behavior has been impaired by a mental disorder. In a recent case in South Carolina, automatism was offered as a defense to adultery, an at-fault grounds to divorce. On appeal, the State Supreme Court recognized the novel application of mental impairment defenses in domestic litigation and remanded the case for rehearing. Implications of the ruling for clinical and forensic practice in family court are discussed. 相似文献
8.
Meta-accuracy, knowing how others view the self, was examined using the Social Relations Model. 15 groups of 4–6 acquainted individuals gave self-ratings, perceptions of other group members, and estimated others' perceptions of self (metaperceptions) on the Big Five and Interesting. Individuals also rated liking and metaperceptions of liking. Trait perceptions were consensual, and self–other agreement emerged for most traits. Affect judgments were entirely relational; individuals differentiated among targets. Trait metaperceptions were dominated by perceiver variance. Individuals differed in the impression they believed others generally held about them. Affect metaperceptions, however, were relational in nature. Correlations between perceptions and metaperceptions assessed 2 types of meta-accuracy. Generalized meta-accuracy was obtained for some trait ratings. Affect judgments revealed significant dyadic meta-accuracy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Lullo G. McKee A. McLean C.J. Bryce A.C. Button C. Marsh J.H. 《Electronics letters》1994,30(19):1623-1625
Electroabsorption optical modulators have been fabricated on GaInAs/GaInAsP multiquantum well structures whose bandgap had been increased by laser photoabsorption-induced disordering. Modulation depths of 20 dB have been obtained in material which has been bandgap blue shifted by as much as 120 nm, while samples shifted by 80 nm gave depths as high as 27 dB 相似文献
10.
Crook Thomas H.; Youngjohn James R.; Larrabee Glenn J.; Salama Maurice 《Canadian Metallurgical Quarterly》1992,6(2):123
Performance on computer-simulated, everyday memory tasks was found to deteriorate with age in 434 Belgian (aged 14–88 yrs) and 434 American Ss matched on gender and age. This age-related memory decline was reasonably consistent across samples. Difficulties in cross-cultural research and the advantages of ecologically valid measurement instruments are discussed. Instruments included a grocery list selective reminding test, the Wechsler Memory Scale, the Benton Visual Retention Test, and the Wechsler Adult Intelligence Scale (WAIS). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献