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排序方式: 共有1338条查询结果,搜索用时 15 毫秒
1.
共反射面元(CRS)叠加借助于菲涅耳带的理念,可以最大限度地提高信噪比。在CRS叠加中,叠加效果取决于波场运动学参数,因此对参数的搜索尤为重要,而一些局部优化算法效果受限于参数初值的选取。本文采用粒子群(PSO)算法实现对二维CRS参数的搜索,在不影响叠加效果的基础上,提高了参数搜索效率,大大缩短了计算时间。模型和实际数据处理结果验证了方法的有效性。  相似文献   
2.
赵华 《现代矿业》2019,35(1):215-218
以红海矿区11031工作面为研究区域,通过对其设置地表移动变形观测站,实地观测得到数据资料,然后对数据资料进行分析处理,求得了各种角量参数(边界角、移动角、裂缝角)、动态参数(起动距、超前影响角、超前影响距等)、预计参数(下沉系数q、主要影响角正切tanβ、拐点移动距S、开采影响传播角θ)。结合岩移参数,采用概率积分法进行了地表沉陷预计,得到了动态预计参数和下沉盆地预计的可视化模型。在此基础上,分析出其主要造成了塌陷地和地表裂缝等土地破坏现象。为采空区下降区地表恢复提供指导。  相似文献   
3.
The United Nations Watercourses Convention entered into force on 17 August 2014, following a long and complex journey that dates back to 1970 when the UN referred the matter to its legal arm, the International Law Commission. This article follows the Convention through that long and turbulent road, examines its main provisions and analyses the reasons for the delay of its entry into force. It concludes by answering the question of why entry into force of the Convention should indeed matter.  相似文献   
4.
In this article, two novel kinds of focusing elements as reflectors are analyzed and compared. One is the grooved Fresnel zone plate reflector with continuous phase‐correcting. The other called subzone paraboloid reflector, has the profile that consists of a series of paraboloids. Their diffraction efficiencies and bandwidths are described. The two elements still preserve the advantages of Fresnel zone plates, namely, low profile, high efficiency, and simple fabrication. Two dual‐reflector antennas using the proposed focusing elements as the main reflectors are simulated and the results show that these antennas have good radiation performances. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:101–108, 2015.  相似文献   
5.
能源行业法律法规设置了“没收违法所得”行政处罚方式,但违法所得这一概念还存在很多模糊认识,具体认定方式也需要进一步明确。在不同行政机关对违法所得的法律概念存在较大分歧时,能源监管领域应遵循违法所得固有含义和立法原意,结合能源行业的基本特点,采取利润说观点定义违法所得概念,并以全部收人扣减合理支出方式进行计算。  相似文献   
6.
This study proposes a fiber-optic temperature sensor with a single-mode fiber tip covered with a thermo-sensitive polymer resin. The temperature is sensed by measuring the Fresnel reflection from the optical fiber/polymer interface. Because the thermo-optic coefficients differ between the optical fiber and the polymer, the in situ temperature can be measured even in curing composite materials. In initial experiments, the proposed sensor successfully measured and recovered the temperature information. The measured sensor data were linearly correlated, with an R2 exceeding 0.99. The standard deviation in the long-term measurements of constant temperature was 2.6%. The durability and stability of the sensor head material in long-term operation was validated by Fourier transform infrared spectroscopy and X-ray diffraction analysis. In further experiments, the suggested miniature temperature sensor obtained the internal temperatures of curing composite material over a wide range (30–110 °C).  相似文献   
7.
ABSTRACT

In spite of groundwater’s growing importance, the 2008 Draft Articles on the Law of Transboundary Aquifers have yet to be fully adopted by the international community. As states contemplate the future of the draft articles, this article aims to reassess them through the lens of the legal principle of reciprocity. To do so, this article provides a framework for the analysis of law via reciprocity, followed by its application to the draft articles. Although this article primarily finds that they follow a reciprocal structure, it also identifies areas to be revisited, including sovereignty and recharge zone states.  相似文献   
8.
刘振  王丽玲 《当代化工》2014,(1):114-117
试验结果表明,超声波技术在集输管线和计量站应用中,能够满足在线运行的工况要求,具有很好的防垢与除垢效果。近些年,我国在超声波防垢和除垢技术领域取得显著的成就,该技术具有重要的科研价值和应用前景。其中,超声波的空化效应、活化效应、剪切效应可以有效的除垢防垢。近年来,研究超声波对碳酸钙结垢影响规律的文献比较多,但是超声波对硫酸钡结垢影响规律的研究较少,文章通过称重法和电镜粒度分析法研究超声波对硫酸钡结垢影响规律,为油气田有效的除去硫酸钡污垢提供一定的理论基础。  相似文献   
9.
Humans not only structure the landscape through their activities, but their perceptions of nature are affected by the spatial and temporal arrangements (structure) in the landscape. Our understanding of these interactions, however, is limited. We explored the relationship between landscape structure and peoples’ perceptions of nature in the Chicago, IL, USA, suburbs of Riverside and Berwyn because they offer contrasting paradigms of an urban landscape. Designed in the 1800s by Frederick Law Olmsted, Riverside has several unique design elements (curvilinear streets, ample setbacks, parkways of variable width with mowed grass and naturalistic groupings of trees) that define the structure and composition of this landscape. The urban forest was the keystone of Olmsted's desire to create a harmonious community characterized by “refined sylvan beauty”. In contrast, the adjacent community of Berwyn has right-angled streets with small lots and narrow setbacks for houses. Differences in landscape structure between the two communities produced differences in the diversity, size, and composition of woody vegetation. As measured by patch-size distribution, Riverside had greater diversity in landscape structure than Berwyn, and in turn, Riverside had greater diversity in the composition and size of the woody vegetation compared to Berwyn. Riverside tended toward a “natural” appearance with vegetation, while yards in Berwyn tended to be trimmed and edged. Significant differences between the mean ratings of Riverside and Berwyn respondents were found for six of seven community attribute categories. Riverside participants reported receiving greater benefit from the visual and nature-related features of the urban forest than did Berwyn respondents. Berwyn residents ranked social atmosphere for the community and locomotion (wayfinding) highest among the seven community attribute categories. Despite differences between the two communities, residents valued the green residential environment provided by vegetation. However, the more diverse urban landscape as measured by built structures, woody vegetation, and lot size and shape proved to be more satisfying to the residents of these two communities. The design concepts developed and implemented by Olmsted more than century ago in Riverside are still relevant to city planners striving to develop living environments that are satisfying to urban and suburban residents.  相似文献   
10.
美国国家公园的法律基础   总被引:5,自引:3,他引:5  
李如生 《中国园林》2002,18(5):6-12
始于黄石公署的国家公园的建立,是美国人在历史上的创举。美国国会的立法、决议以及相关政策的制定伴随着美国国家公园发展的全过程。这一系列法律、法规和相关政策始终强调这样一个理念:必须把国家公园的资源和价值完整地留给了子孙后代,让他们共享这些资源和价值。  相似文献   
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