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51.
52.
航天动力学环境的最新进展与技术展望 总被引:6,自引:6,他引:0
总结了近年来航天动力学分析、试验方面的最新成果。按照航天飞行器寿命期不同阶段的特点,对动力学试验与理论建模、分析预示、试验技术、测量方法,特别是地面气候复合以及高速飞行热结构动力学分析与试验方面的工作进行归纳,并指出存在的不足,以及未来发展的方向。通过工程研制中的分析与数据积累修正,在建模分析预示、条件制定以及测量技术等方面取得显著成果,但由于飞行器复杂,在准确精细预示方法、热结构预示与试验技术方面以及气候复合状态下的分析与试验方面尚需大量研究。应坚持理论与试验、工程研制与研究相结合的方式,不断完善持续改进,实现动力学精细化预示与天地一致性试验。 相似文献
53.
Carranza ML Acosta AT Stanisci A Pirone G Ciaschetti G 《Environmental monitoring and assessment》2008,140(1-3):99-107
Many recent developments in coastal science have gone against the demands of European Union legislation. Coastal dune systems
which cover small areas of the earth can host a high level of biodiversity. However, human pressure on coastal zones around
the world has increased dramatically in the last 50 years. In addition to direct habitat loss, the rapid extinction of many
species that are unique to these systems can be attributed to landscape deterioration through the lack of appropriate management.
In this paper, we propose to use of an ecosystem classification technique that integrates potential natural vegetation distribution
as a reference framework for coastal dune EU Habitats (92/43) distribution analysis and assessment. As an example, the present
study analyses the EU Habitats distribution within a hierarchical ecosystem classification of the coastal dune systems of
central Italy. In total, 24 land elements belonging to 8 land units, 5 land facets, 2 land systems and 2 land regions were
identified for the coastal dunes of central Italy, based on diagnostic land attributes. In central Italy, coastal dune environments
including all the beach area, mobile dunes and all the fixed-dune land elements contain or could potentially hold at least
one EU habitat of interest. Almost all dune slack transitions present the potentiality for the spontaneous development of
EU woodlands of interest. The precise information concerning these ecosystems distribution and ecological relationships that
this method produces, makes it very effective in Natura 2000 European network assessment. This hierarchical ecosystem classification
method facilitates the identification of areas to be surveyed and eventually bound, under the implementation of EU Habitat
directive (92/43) including areas with highly disturbed coastal dune ecosystems. 相似文献
54.
易高翔 《中国安全生产科学技术》2009,5(6):147-150
在重大危险源信息系统长期实践的基础上,针对SQL server 2000+Tomcat系统,探讨了提高系统稳定性、保证系统安全的方法。一方面从数据设计保证系统规范合理,研究SQL server数据性能优化,数据库安全配置,数据库备份与日志管理;另一方面讨论应用系统部署,通过对Tomcat服务器的外部环境和自身进行优化,防止了内存泄露和不稳定现象的发生,并分析Tomcat入侵途径,探讨了预防黑客攻击的方法。这些方法在很多实践中取得了满意的效果,并对一般信息系统建设也有很强指导意义。 相似文献
55.
Irene Bouwma Duncan Liefferink Rob Van Apeldoorn Bas Arts 《Journal of Environmental Policy & Planning》2016,18(2):214-233
This article reviews the influence of two specific European Union (EU) laws, the Birds and Habitats Directives, on the choice of national policy instruments by Member States. Both Directives leave the choice for policy instruments to manage the sites designated under the Directives to the Member States. Using path dependency as a leading concept, this article analyses the continuity or changes in policy instruments due to the implementation of the Directives in 15 countries. This article shows that the tendency to use existing instruments to implement EU policy is limited, as in almost all countries new instruments were developed. Yet, states do tend to choose instruments from their predominant policy instrument mix and preferred implementation style to address the management requirements of the Directives. Additionally, in Central and Eastern European countries where the implementation of EU policy coincided with a process of transition to a market economy, new instruments were introduced outside the existing implementation style. The introduction of new policy instruments is the result of historical turns, domestic pressure and a shift to new modes of governance. National case studies are needed to shed more light on the interaction between EU policy and domestic factors during the process of instrument choice. 相似文献
56.
用SQLServer 7.0分布式数据库管理系统管理图书数据 ,并利用ASP(AcrtiveServerPages)网页设计技术、及IIS4 0信息服务建立局域网内部Intranet网 ,通过浏览器的形式管理和使用数据图书数据。 相似文献
57.
Matches and mismatches between conservation investments and biodiversity values in the European Union
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David Sánchez‐Fernández Pedro Abellán Pedro Aragón Sara Varela Mar Cabeza 《Conservation biology》2018,32(1):109-115
Recently, the European Commission adopted a new strategy to halt the loss of biodiversity. Member states are expected to favor a more effective collection and redistribution of European Union (EU) funds under the current Multiannual Financial Framework for 2014–2020. Because of the large spatial variation in the distribution of biodiversity and conservation needs at the continental scale, EU instruments should ensure that countries with higher biodiversity values get more funds and resources for the conservation than other countries. Using linear regressions, we assessed the association between conservation investments and biodiversity values across member states, accounting for a variety of conservation investment indicators, taxonomic groups (including groups of plants, vertebrates, and invertebrates), and indicators of biodiversity value. In general, we found clear overall associations between conservation investments and biodiversity variables. However, some countries received more or less investment than would be expected based on biodiversity values in those countries. We also found that the extensive use of birds as unique indicators of conservation effectiveness may lead to biased decisions. Our results can inform future decisions regarding funding allocation and thus improve distribution of EU conservation funds. 相似文献
58.
本文详细解读了GMW 3205:2000汽车内饰材料中气味散发测试方法以及SAE J1351绝缘材料气味散发测试方法之间的差异.介绍了汽车内饰件材料气味测试原理.以及气味试验的定义与实际使用中的意义等方面对GMW 3205:2000和SAE J1351气味测试标准进行差异分析. 相似文献
59.
60.
Dieter M. Imboden 《Integrated Assessment》2000,1(4):321-330
Macroeconomic models predict that the global primary energy demand will increase by a factor of 2–4 by the year 2050. In contrast,
climate analyses made by the IPCC claim that CO2 emissions in 2050 should not exceed the values of 1990 or even be 20% lower. By 2100 emissions should be reduced to one third
of the present value. The common wisdom to deal with these opposing trends is the concept of de-carbonization, i.e., the continuous
decrease of the carbon emission per unit energy utilization. De-carbonization rates needed to compensate for the growing demand
while keeping the CO2-emissions constant should at least be 2% per year compared to actual values of 0.3%. The potential of different de-carbonization
rate measures is analyzed. It is argued that the goal can only be met if per capita energy utilization in the industrialized
countries is significantly reduced from their typical level of 5000–10 000 W. As a realistic target we suggest 2000 Watt per
capita, the present global average. This would leave expansion capacity for the developing countries which presently have
per capita demand between 300 and 1000 W. Based on the example of Switzerland it is shown that the two key issues to attain
this goal are the quality of buildings and the demand for mobility. It is concluded that the conversion of the present energy
system into a 2000 W system is neither limited by technology nor by finances but by the acceptance of a new life style in
which energy is used more efficiently and more intelligently than today.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献