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排序方式: 共有1519条查询结果,搜索用时 17 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
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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
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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
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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
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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
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There is now considerable evidence suggesting that alterations in the DNA methylating machinery play an important role in tumorigenesis and tumour progression. For example, focal hypermethylation and generalised genomic demethylation are features of many different types of neoplasms. It is thought that tumorigenesis and tumour progression may be caused by hypermethylation induced mutational events and silencing of genes which control cellular proliferation and/or demethylation induced reactivation of genes which may only be required during embryological development. Consequently, we have begun to investigate the role of DNA methylation and developmental genes in malignant lymphoproliferative diseases. Previously, in all cases of non-Hodgkins lymphoma and leukemia studied, we have shown that the myogenic developmental gene Myf-3 is abnormally hypermethylated. In this review we discuss the possible significance of these findings since in vitro studies suggest that Myf-3 may play an important role in control of the cell cycle and therefore lymphomagenesis. In vitro and in vivo evidence suggests that PAX genes may also have oncogenic potential. The PAX family of developmental genes are involved in cellular differentiation, proliferation and cell migration. Expression of PAX3 in particular is associated with cellular mobility. Our previous studies have indicated that alternate regional expression of PAX genes may be controlled by DNA methylation. Therefore, we have proposed that abnormal methylation profiles of PAX3 may be associated with neoplastic transformation and/or metastatic potential. Results thus far reveal that the paired box of PAX3 is abnormally hypermethylated and the homeobox abnormally hypomethylated in lymphomas and leukemias. These new findings are consistent with our postulate and support the idea that inappropriate methylation induced activation or inactivation of developmental genes such as Myf-3 and PAX3 play an important role in lymphomagenesis and disease progression and that inspection of the methylation status of other developmental genes is warranted. 相似文献
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