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211.
212.
Lessons in precaution: The International Whaling Commission experience with precautionary management
The precautionary principle (PP) only represents a new approach to managing uncertainty in so far that it requires proponents of an activity or substance to provide evidence that the activity/substance is harmless, as opposed to the more traditional “trial and error” approach that has instead placed the burden of proof that something is harmful on its opponents. This article critiques the PP as a policy making tool for managing uncertainty, focusing on the epistemological problems it raises, before then using the International Whaling Commission's experience with precautionary approaches to wildlife management to demonstrate the principle's limits and weaknesses when applied in a highly politicised policymaking environment. The article concludes that while the PP offers some benefits for managing uncertainty, its vagueness and openness to broad interpretation can also result in its application creating, rather than limiting, risks and uncertainty. 相似文献
213.
In this paper, an exact analytical method is developed for the problem of wave radiation by a uniform cylinder in front of a vertical wall. Based on the image principle, the hydrodynamic problem of a cylinder in front of a vertical wall is transformed into the equivalent problem of double cylinders in unbounded fluid domain. Consequently, an analytical method of eigenfunction expansion is adopted to calculate the radiation of the cylinder due to the motion in surge, sway, roll and pitch, respectively. Moreover, numerical analysis has been carried out in detail in order to discuss the influences of the distance between the cylinder and the vertical wall and water depth on the added mass and radiation damping of the cylinder. It is shown that added mass and damping of the cylinder in front of a vertical wall are evidently different from those in case of the cylinder in unbounded fluid domain from the numerical results. It is also found that the added mass and radiation damping oscillate with wave number, and the oscillating frequency increases with the increasing of the distance between the cylinder and the wall. 相似文献
214.
Victor Brumberg 《Celestial Mechanics and Dynamical Astronomy》2007,99(3):245-252
The half-century old idea of Infeld to use the variational principle of the general relativity field equations is reminded
to show that the commonly employed EIH (Einstein–Infeld–Hoffman) equations of motion may be derived from the linearized (weak-field)
metric alone. Based on it, the linearized metric might be sufficient for post-Newtonian celestial mechanics and astrometry
enabling one to derive the post-Newtonian equations of motion and rotation of celestial bodies as well as the post-Newtonian
equations of light propagation within the general relativity framework. 相似文献
215.
针对现有地下流体观测仪器单一、结构分散,稳定性较差、故障多,功耗大、运行成本高,有线通信方式网络故障率高,易遭雷击等诸多问题,设计了一体化的数字地下水动态观测系统, 并介绍该系统的组成和系统的基本工作原理。 相似文献
216.
铌主要应用于钢铁的生产,含铌钢材广泛应用于航空航天、海洋工程、汽车与交通、能源化工及工程机械等高端制造领域。中国是当前世界第一大铌资源消费国,供需矛盾极为突出,严重依赖国外资源。为保障中国铌资源供应安全与钢铁产业结构调整提供依据,本文基于恒等式原理构建了钢铁工业铌资源需求预测模型,参考发达国家钢铁工业铌资源消费经验,对中国钢铁工业铌需求进行了定量预测。研究结果表明:(1)中国铌工业和钢铁工业现代化程度明显落后于发达国家;(2)典型发达国家含铌钢产量占粗钢产量比例从最低值增长至最高值呈现出一定的规律性;(3)到2030年,中国钢铁工业铌资源需求将持续增长,2025年钢铁工业铌资源需求为3.3~5.2万t、2030年为4.0~7.1万t,中国铌资源供应安全面临严峻挑战。为此,本文建议持续扩大中国铌资源海外权益产量、提高国内储量、加强铌资源提取和二次资源回收技术研发来保障国内外铌资源稳定的供应,同时推进国内铌相关产业建设。 相似文献
217.
系统有线性和非线性之分.线性系统有统一的描述形式,非线性系统因类别无数,不可能有统一描述.线性参数系统是一类特殊的非线性系统,它在参数空间上呈现线性特征,介于线性系统与非线性系统之间.针对伪线性参数系统,讨论了基于辅助模型的多新息辨识方法、基于滤波的辅助模型多新息辨识方法、基于模型分解的辅助模型多新息辨识方法、基于滤波的分解多新息辨识方法,并给出了几个典型辨识算法的计算量、计算步骤和流程图. 相似文献
218.
219.
国际河流公平合理利用原则:回顾、反思与消解 总被引:1,自引:0,他引:1
公平合理利用原则是国际水法的一项基本原则,它的适用对保护国际河流水资源及协调国际河流水资源利用冲突具有重要的意义。但伴随全球淡水资源日益匮乏,水资源利用冲突频发,公平合理利用原则的局限性也日益凸显。要摆脱公平合理利用原则难以具体运用于实践的困境,一方面需在国际法律文件中对"公平合理利用"进一步界定和完善,另一方面,需结合实际情况缔结国际河流水资源公平合理利用条约并设置相应的配套措施,以保障国际河流水资源公平合理利用原则得以真正实现。 相似文献
220.
《Experimental Astronomy》2009,23(2):611-649
In response to ESA’s Call for proposals of 5 March 2007 of the COSMIC VISION 2015–2025 plan of the ESA science programme,
we propose a M-class satellite mission to test of the Equivalence Principle in the quantum domain by investigating the extended free fall of matter waves instead of macroscopic bodies as in the case of GAUGE, MICROSCOPE
or STEP. The satellite, called Matter Wave Explorer of Gravity, will carry an experiment to test gravity, namely the measurement of the equal rate of free fall with various isotopes
of distinct atomic species with precision cold atom interferometry in the vicinity of the earth. This will allow for a first
quantum test the Equivalence Principle with spin polarised particles and with pure fermionic and bosonic atomic ensembles. Due to the
space conditions, the free fall of Rubidium and Potassium isotopes will be compared with a maximum accelerational sensitivity
of 5·10 − 16 m/s2 corresponding to an accuracy of the test of the Equivalence Principle of 1 part in 1016. Besides the primary scientific goal, the quantum test of the Equivalence Principle, the mission can be extended to provide
additional information about the gravitational field of the earth or for testing theories of fundamental processes of decoherence
which are investigated by various theory groups in the context of quantum gravity phenomenology. In this proposal we present
in detail the mission objectives and the technical aspects of the proposed mission. 相似文献