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排序方式: 共有435条查询结果,搜索用时 46 毫秒
121.
Rainer Dudek Reinhard Pufall Bettina Seiler Bernd Michel 《Microelectronics Reliability》2012,52(7):1255-1265
Thermal cycling induced failure in power packages has been studied comparing thermal cycling (TC) with thermal shock (TS) tests by thermo-mechanical analyses. The major question for the time reduction is if the failure mechanism changes and if it depends on loading type and duration. These questions were addressed by theoretical analyses including coupled transient thermal–mechanical analyses and interface fracture mechanics applying the cohesive zone approach. By the latter, critical states for delamination failures could be derived. Finally, critical interface fracture parameters of the package were compared with results from the button shear test. 相似文献
122.
123.
Jette Oddershede Bettina Camin Søren Schmidt Lars P. Mikkelsen Henning Osholm Sørensen Ulrich Lienert Henning Friis Poulsen Walter Reimers 《Acta Materialia》2012,60(8):3570-3580
The stress field around a notch in a coarse grained Mg AZ31 sample has been measured under tensile load using the individual grains as probes in an in situ high energy synchrotron diffraction experiment. The experimental set-up, a variant of three-dimensional X-ray diffraction microscopy, allows the position, orientation and full stress tensor of each illuminated grain to be determined and, hence, enables the study of evolving stress fields in coarse grained materials with a spatial resolution equal to the grain size. Grain resolved information like this is vital for understanding what happens when the traditional continuum mechanics approach breaks down and fracture is governed by local heterogeneities (e.g. phase or stress differences) between grains. As a first approximation the results obtained were averaged through the thickness of the sample and compared with an elastic–plastic continuum finite element simulation. It was found that a full three-dimensional simulation was required to account for the measured transition from the overall plane stress case away from the notch to the essentially plane strain case observed near the notch tip. The measured and simulated stress contours were shown to be in good agreement except at the highest applied load, at which stress relaxation at the notch tip was observed in the experimental data. This stress relaxation is attributed to the initiation and propagation of a crack. Finally, it was demonstrated that the measured lattice rotations could be used as a qualitative measure of the shape and extent of the plastic deformation zone. 相似文献
124.
This research is concerned with the ecological performance of electrical consumer products. It examines the influence of design-based measures on various ecological performance parameters and the relationship of user variables and performance. In the experimental scenario, 40 users were asked to clean a room with a vacuum cleaner under different conditions. In a multi-factorial design, the following independent variables were employed: on-product information, enhanced display-control labelling and proximity of controls. Measures of user variables (environmental concern, knowledge, habits) of ecological behaviour were also taken. The results showed that enhanced display-control labelling improved ecological performance but only when the label was placed close to the user. On-product information only resulted in behavioural change when it was in close spatial proximity to the control device. A positive effect on ecological performance was also observed when controls were in a proximal rather than distal position. Among user variables, habits were found to have an influence on behaviour shown in experimental scenarios. A practical implication of the findings for environmentally friendly design of consumer products is that there should be a stronger focus on system-based measures rather than information-based measures. Finally, the article discusses the theoretical implications of using operational scenarios rather than the information display board paradigm. 相似文献
125.
R package flexmix provides flexible modelling of finite mixtures of regression models using the EM algorithm. Several new features of the software such as fixed and nested varying effects for mixtures of generalized linear models and multinomial regression for a priori probabilities given concomitant variables are introduced. The use of the software in addition to model selection is demonstrated on a logistic regression example. 相似文献
126.
Analysis of navigation behaviour in web sites integrating multiple information systems 总被引:6,自引:0,他引:6
Bettina Berendt Myra Spiliopoulou 《The VLDB Journal The International Journal on Very Large Data Bases》2000,9(1):56-75
Abstract. The analysis of web usage has mostly focused on sites composed of conventional static pages. However, huge amounts of information
available in the web come from databases or other data collections and are presented to the users in the form of dynamically
generated pages. The query interfaces of such sites allow the specification of many search criteria. Their generated results
support navigation to pages of results combining cross-linked data from many sources. For the analysis of visitor navigation
behaviour in such web sites, we propose the web usage miner (WUM), which discovers navigation patterns subject to advanced
statistical and structural constraints. Since our objective is the discovery of interesting navigation patterns, we do not
focus on accesses to individual pages. Instead, we construct conceptual hierarchies that reflect the query capabilities used
in the production of those pages. Our experiments with a real web site that integrates data from multiple databases, the German
SchulWeb, demonstrate the appropriateness of WUM in discovering navigation patterns and show how those discoveries can help
in assessing and improving the quality of the site.
Received June 21, 1999 / Accepted December 24, 1999 相似文献
127.
Bettina Fazzinga Giorgio Gianforme Georg Gottlob Thomas Lukasiewicz 《Journal of Web Semantics》2011,9(4):453-473
Many experts predict that the next huge step forward in Web information technology will be achieved by adding semantics to Web data, and will possibly consist of (some form of) the Semantic Web. In this paper, we present a novel approach to Semantic Web search, called Serene, which allows for a semantic processing of Web search queries, and for evaluating complex Web search queries that involve reasoning over the Web. More specifically, we first add ontological structure and semantics to Web pages, which then allows for both attaching a meaning to Web search queries and Web pages, and for formulating and processing ontology-based complex Web search queries (i.e., conjunctive queries) that involve reasoning over the Web. Here, we assume the existence of an underlying ontology (in a lightweight ontology language) relative to which Web pages are annotated and Web search queries are formulated. Depending on whether we use a general or a specialized ontology, we thus obtain a general or a vertical Semantic Web search interface, respectively. That is, we are actually mapping the Web into an ontological knowledge base, which then allows for Semantic Web search relative to the underlying ontology. The latter is then realized by reduction to standard Web search on standard Web pages and logically completed ontological annotations. That is, standard Web search engines are used as the main inference motor for ontology-based Semantic Web search. We develop the formal model behind this approach and also provide an implementation in desktop search. Furthermore, we report on extensive experiments, including an implemented Semantic Web search on the Internet Movie Database. 相似文献
128.
Statistical data associated with geographic regions is nowadays globally available in large amounts and hence automated methods to visually display these data are in high demand. There are several well-established thematic map types for quantitative data on the ratio-scale associated with regions: choropleth maps, cartograms, and proportional symbol maps. However, all these maps suffer from limitations, especially if large data values are associated with small regions. To overcome these limitations, we propose a novel type of quantitative thematic map, the necklace map. In a necklace map, the regions of the underlying two-dimensional map are projected onto intervals on a one-dimensional curve (the necklace) that surrounds the map regions. Symbols are scaled such that their area corresponds to the data of their region and placed without overlap inside the corresponding interval on the necklace. Necklace maps appear clear and uncluttered and allow for comparatively large symbol sizes. They visualize data sets well which are not proportional to region sizes. The linear ordering of the symbols along the necklace facilitates an easy comparison of symbol sizes. One map can contain several nested or disjoint necklaces to visualize clustered data. The advantages of necklace maps come at a price: the association between a symbol and its region is weaker than with other types of maps. Interactivity can help to strengthen this association if necessary. We present an automated approach to generate necklace maps which allows the user to interactively control the final symbol placement. We validate our approach with experiments using various data sets and maps. 相似文献
129.
Luis M. Montao Bettina Sommer Hctor Solís-Chagoyn Bianca S. Romero-Martínez Arnoldo Aquino-Glvez Juan C. Gomez-Verjan Eduardo Calixto Georgina Gonzlez-Avila Edgar Flores-Soto 《International journal of molecular sciences》2022,23(2)
The health scourge imposed on humanity by the COVID-19 pandemic seems not to recede. This fact warrants refined and novel ideas analyzing different aspects of the illness. One such aspect is related to the observation that most COVID-19 casualties were older males, a tendency also noticed in the epidemics of SARS-CoV in 2003 and the Middle East respiratory syndrome in 2012. This gender-related difference in the COVID-19 death toll might be directly involved with testosterone (TEST) and its plasmatic concentration in men. TEST has been demonstrated to provide men with anti-inflammatory and immunological advantages. As the plasmatic concentration of this androgen decreases with age, the health benefit it confers also diminishes. Low plasmatic levels of TEST can be determinant in the infection’s outcome and might be related to a dysfunctional cell Ca2+ homeostasis. Not only does TEST modulate the activity of diverse proteins that regulate cellular calcium concentrations, but these proteins have also been proven to be necessary for the replication of many viruses. Therefore, we discuss herein how TEST regulates different Ca2+-handling proteins in healthy tissues and propose how low TEST concentrations might facilitate the replication of the SARS-CoV-2 virus through the lack of modulation of the mechanisms that regulate intracellular Ca2+ concentrations. 相似文献
130.