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Several methods exist to estimate the fracture energy for adhesive joints using the double cantilever beam specimen and linear elastic fracture mechanics. Since the mechanical properties of all adhesives are non-linear, errors are generated. By use of an exact solution experiments are simulated. These are evaluated with eight different methods. The influence of the constitutive parameters is systematically studied. This influence is small for most methods. The error due to the choice of evaluation method is considerably larger. One of the commonly used methods gives accurate results; the error is less than 3%. However, most methods yield substantial errors. 相似文献
54.
As a result of recent advances in signal processing technology and standards for video compression systems there has been a dramatic increase in interest in commercial applications. This paper reviews the current broadcasting situation from a number of viewpoints relevant to the future development of the available technologies. After a review of the context, which includes alternative new broadcasting technologies as well as alternative media capable of competing with satellite, digital technology is given a wide ranging assessment with particular attention paid to the direct broadcasting to the home by satellite application currently receiving considerable attention world-wide. The possible system architectures and subsystem design features are highlighted with the European Baseline Satellite Broadcasting specification developed by the European Digital Video Broadcasting Project gaining special attention. For completeness a brief review of the digital audio broadcasting system (DAB) is also given. In addition to the applications for direct broadcasting, applications in the professional domain for distributing television signals from studios to terrestrial transmitters, satellite up-link sites or cable heads or for satellite news gathering (SNG) are examined. Features of existing commercially available hardware to support these services are described briefly. 相似文献
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Simple Knowledge Organization System (SKOS) provides a data model and vocabulary for expressing Knowledge Organization Systems (KOSs) such as thesauri and classification schemes in Semantic Web applications. This paper presents the main components of SKOS and their formal expression in Web Ontology Language (OWL), providing an extensive account of the design decisions taken by the Semantic Web Deployment (SWD) Working Group of the World Wide Web Consortium (W3C), which between 2006 and 2009 brought SKOS to the status of W3C Recommendation. The paper explains key design principles such as “minimal ontological commitment” and systematically cites the requirements and issues that influenced the design of SKOS components.By reconstructing the discussion around alternative features and design options and presenting the rationale for design decisions, the paper aims at providing insight into how SKOS turned out as it did, and why. Assuming that SKOS, like any other successful technology, may eventually be subject to revision and improvement, the critical account offered here may help future editors approach such a task with deeper understanding. 相似文献
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LED城市照明示范工程应注意的问题 总被引:1,自引:0,他引:1
该文主要介绍了半导体(LED)在城市照明示范工程应用中应该注意的一些问题。论文包含有LED的性能和特点、科技部十城万盏半导体照明示范工程的要求及内容、示范工程应遵循的设计标准、LED照明器具应满足的技术要求等。 相似文献
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This article describes the ethical challenges that psychologists face when doing international humanitarian aid work. It is based on personal experience and uses the framework of the Canadian Code of Ethics for Psychologists to reflect on the unique challenges when doing such work. The article is organized around themes of ethical challenges under the following headings: limitation of resources, local political pressure, local cultural and social realities, challenges to confidentiality, problems in obtaining consent, sequelae of colonial history, individual versus population interests, and tolerance of differences in standards. Examples illustrate these points. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
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Cultivation theory suggests that society holds very different body standards for men versus women, and research indicates that the consequences of defying these social norms may not be linear. To test these notions in the employment context, we examined the relationship between weight and income and the degree to which the relationship varies by gender. For women, we theorized a negative weight–income relationship that is steepest at the thin end of the distribution. For men, we predicted a positive weight–income relationship until obesity, where it becomes negative. To test these hypotheses, we utilized 2 longitudinal studies, 1 German and 1 American. In Study 1, weight was measured over 2 time periods, and earnings were averaged over the subsequent 5 years. Study 2 was a multilevel study in which weight and earnings were within-individual variables observed over time, and gender was a between-individual variable. Results from the 2 studies generally support the hypotheses, even when examining within-individual changes in weight over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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本文以新经济革命为基点,论述了可持续消费的内涵、特征及建立模式的原则,分析了国内目前实施可持续消费的障碍,阐明了可持续消费必须以技术标准为基础,建立可持续消费技术标准体系是实现可持续消费的前提,并提出了可持续生产和可持续消费的有效对策和具体措施。 相似文献
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Janine Fischer Daniel PröfrockNorbert Hort Regine WillumeitFrank Feyerabend 《Materials Science and Engineering: B》2011,176(11):830-834
Metallic magnesium (Mg) and its alloys are highly suitable for medical applications as biocompatible and biodegradable implant materials. Magnesium has mechanical properties similar to bone, stimulates bone regeneration, is an essential non-toxic element for the human body and degrades completely within the body environment. In consequence, magnesium is a promising candidate as implant material for orthopaedic applications. Protocols using the guideline of current ISO standards should be carefully evaluated when applying them for the characterization of the cytotoxic potential of degradable magnesium materials. For as-cast material we recommend using 10 times more extraction medium than recommended by the ISO standards to obtain reasonable results for reliable cytotoxicity rankings of degradable materials in vitro. In addition primary isolated human osteoblasts or mesenchymal stem cells should be used to test magnesium materials. 相似文献