共查询到20条相似文献,搜索用时 92 毫秒
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分析共振因素,探讨影响共振的重要因素,对夹具设计的基本要求,一般夹具的选材和基本形式、夹具设计中应注意的问题和设计技巧以及夹具设计理论与实际应用中的差距。 经过振动试验的产品,其结果是否能够正确地反映产品经受试验后的结论,除了振动设备和测量仪器及方法的因素外,振动试验用的夹具设计是否能够满足试验条件的要求及合理性,起着决定性的因素。振动夹具的设计,涉及的问题很多,而且从理论设计到实际应用,还存在一个实验和修正的问题。 鉴于目前国家尚未就力学振动试验中所用夹具的设计及应用制定统一标准,本文仅就电子元器件振动夹具的设计及试验中有关共振的问题,谈一点粗浅的看法,供有关方面参考,并希望经过讨论,对此问题给予足够的重视。 相似文献
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一.控制随机振动的必要性 许多产品在使用时,或者在运输过程及生产过程中都承受振动。因此很有必要确定产品是否经受得住振动及是否工作可靠。当然,有时还需确定产品在实用环境中的寿命。 很自然,在设计既要求精度高、重量轻、成本低,又要求在苛刻条件下使用的高级技术产品时,这些问题显得非常重要。例如,在航天工业中,一般产品结构都极其复杂,造价都很高,在进行产品试验时很值得考虑其可靠性和安全性。 另一方面,为了保证产品的包装能有效地经受住运输过程的冲击和振动,也需要进行振动试验。 相似文献
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随着科技日益发展,客户对产品的交付周期与质量要求越来越高。尤其是军工装备产品,需通过试验保证其可靠性。这些试验通常耗时、开销大。在装备修理中,环境试验常被用来筛选产品的可靠性。主要包含高低温试验与振动试验。本文针对振动试验,设计了一种可用于多种产品参数、复杂产品种类的振动状态检测验证算法。在振动试验时,不同种产品的重量不同,振动工装夹具也不同,产品的振动频谱复杂多变。因此自动化振动试验状态判断不易实现。本文提出一种基于SVM算法的振动状态检测方法,并对不同产品、不同试验状态进行试验状态验证算法的研究。 相似文献
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A sample of 873 residents of Accra, Ghana, stratified by type of neighborhood was gathered in order to measure the association of poor neighborhood quality with neighborhood problems and residents' personal characteristics. Strong associations were found with poor schools, physical blight, rowdy and criminal behavior, ethnic differences, and environmental problems. In addition, poor neighborhood quality was strongly associated with mistrust of authority and a feeling of a lack of control over neighborhood activities. Respondents identified road, street, drainage, sewage, and other infrastructure deficiencies as priorities to address, even though these were not prominent discriminators of neighborhood quality ratings. Many of these findings are common to counterparts in the US, but some findings appear to reflect cultural and differences in urbanization. 相似文献
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Sarah Ewing 《Journal of the American Water Resources Association》1999,35(3):663-673
ABSTRACT: Australia's ‘Landcare’ program is a community-based participatory program established by government to tackle the problem of land degradation. Landcare involves thousands of Australians working together in locally based groups, tackling problems of common concern. Government and community are now looking to ‘scale up’ the Landcare idea to a regional level. State and territory governments have moved to create regional (often watershed-based) frameworks for land management planning and resource conservation, in accordance with the concept of integrated watershed management. Growing out of the success of community involvement in Landcare, many of these approaches involve the community. However scaling up of the Landcare idea introduces problems of both time and space. There have been a number of problems experienced in the implementation of Landcare and integrated watershed management. These problems include the equitable delineation of membership on decision-making bodies; the raising of sufficient funds for program implementation; and the coordination of a diversity of governmental layers, planning processes and management programs. This paper reviews how the State of Victoria has responded to these challenges and suggests what challenges remain. 相似文献
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David T. Fractor 《Journal of the American Water Resources Association》1988,24(2):405-412
ABSTRACT: While most inquiries into improving the efficiency of ground water allocation have focused upon various schemes involving centralized management, recently the focus has shifted towards exploring private property solutions to these problems. However, most of these studies, when modeling ground water use, have equated behavior under private property to that under common property conditions. This leads to the possibly mistaken conclusion that private property rights do not promote more efficient ground water use, because these models assume that producers ignore the future effects of current pumping. This paper attempts to correct this deficiency by formally modeling ground water use under common property, central management, and private property scenarios. Moreover, there are many ways that property rights can be defined over ground water, some establishing more exclusivity over the resource than others. Four specifications of property rights are analyzed for their likely effects on allocative efficiency: full stock-flow, partial stock-flow, limited stock-flow, and pure flow rights. 相似文献
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John R. Labadie 《Environmental management》1984,8(6):489-494
Local governments (county and city) take the most active role in responding to natural and manmade disasters, yet very little is understood about the role of the emergency manager-the administrator who organizes and coordinates the emergency response of a community. This article describes the more common organizational niches that emergency managers are placed into, and it examines some of the political, institutional, and budgetary constraints that hinder the emergency manager's operations. Finally, it suggests strategies for solving these problems and identifies areas for further research. 相似文献
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WICKED WATER PROBLEMS: SOCIOLOGY AND LOCAL WATER ORGANIZATIONS IN ADDRESSING WATER RESOURCES POLICY1
David M. Freeman 《Journal of the American Water Resources Association》2000,36(3):483-491
ABSTRACT: Water policy problems are wicked, not in an ethically deplorable sense, but in the sense that they present us with especially difficult challenges of becoming more effective in our interdisciplinary collaboration, of integrating two very different types of knowledge, of working across several socio‐political units of analysis simultaneously, and of better organizing water as a common property resource. Sociology, as a discipline, does not have a particularly rich history of successful interdisciplinary collaboration on water resources research and teaching, but it potentially has a most useful contribution to make by focusing on the analysis of local common property resource organizations that operate in the interface between individual resource users and State‐Federal entities. These organizations (e.g., water user associations, mutual companies, irrigation districts, acequias, conservancy districts) have been the orphans of water policy discourse but their operations are critical to undertaking more effective 21st century social analysis, research work, and action programs. Sociologists who work to better comprehend the operations of, and constraints upon, these organizations build a sociology that can better collaborate with other water‐related disciplines in addressing the challenges posed by the wickedness of our water problems. 相似文献
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随着能力验证计划活动的广泛应用,能力验证活动的组织者在设计与实施能力验证计划方案过程中会遇到一些问题,本文试着从对一些共性问题进行分析及探讨,以期为今后的能力验证工作提供参考. 相似文献
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NII ALLOTEY ODUNTON 《Natural resources forum》1977,1(3):285-297
The deep ocean floor represents the latest frontier of knowledge about global mineral resources. The ocean environment poses unique problems for mineral resource development - problems of resource assessment, adaptation of mining technology, and management of resources common to all of mankind. In the first of three related articles on the mineral resources of the ocean, Mr. Odunton assesses the current state of knowledge about the nature and extent of marigenous minerals. He examines the processes of formation, the composition, and the regional distribution of ferromanganese nodules, which represent the most promising of these minerals at present. Attention is also given to the considerations involved in the location, evaluation and exploitation of nodule deposits. Future articles will review ocean mining technology and the economic and policy issues involved in the development of ocean mineral resources. 相似文献