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61.
极地海区等距离正圆柱投影平面上等角航线的展绘方法 总被引:1,自引:0,他引:1
墨卡托投影由于其纬度渐长的特性导致在极地海区投影存在严重的长度变形,无法在南北纬80°以外高纬度海区航海图中较好地应用。将长度变形程度明显低于墨卡托投影的等距离正圆柱投影作为极地海区的海图投影,研究了该投影平面中等角航线在极地海区的展绘方法。建立了等距离正圆柱投影平面上等角航线方程并对其曲率进行了分析,推导了绘制一般曲线形态的"以直代曲"公式;最后提出了一种可满足给定精度要求的等角航线展绘算法。实验结果表明:该算法简单易行,可在海图编绘规范规定的误差范围内,实现等角航线的精确展绘。 相似文献
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63.
通过现场工程试验研究,进一步论证了水泥粘结基材替代化学粘结基材的岩质边坡绿化技术的可行性;同时提出了岩质边坡工程绿化应按"循序渐进"来进行植被恢复的理念. 相似文献
64.
新疆鄯善康古尔塔格蛇绿岩及其大地构造意义 总被引:4,自引:1,他引:4
康古尔塔格蛇绿岩的岩石组合为变质橄榄岩-堆晶橄榄岩-辉长岩-斜长花岗岩-辉绿岩-玄武岩。方辉橄榄岩(蛇纹岩)、蛇纹石化辉石岩、蚀变辉长岩与特罗多斯蛇绿岩中同类型岩石类似,岩石总体低钾。变质橄榄岩MgO/(MgO+TFeO)为0.834~0.866,TiO,(wt%)为0.02%,为SSZ型蛇绿岩的变质橄榄岩。玄武岩的构造环境判别显示其形成于边缘海盆。放射虫硅质岩的Al2O3/(Al2O3+Fe2O3)值平均为0.047,MnO/TiO2比值平均为0.93,Ce具负异常,Ce/Ce^*=0.548,Lan/Cen=1.661.表明放射虫硅质岩的形成环境与洋中脊有密切关系。该蛇绿岩位于塔里木板块和哈萨克斯坦-准噶尔板块的艾比湖-康古尔塔格缝合线上,为一套无序产出的古生代北天山洋在该区的古洋壳残片。 相似文献
65.
导线覆冰大跨越输电塔-线体系动力特性分析 总被引:2,自引:0,他引:2
大跨越输电塔-线体系对导线覆冰等环境荷载反应敏感,容易发生动态倒塌破坏。目前对线路覆冰下输电塔的振动问题虽然取得了一定的研究成果,但是线路覆冰下输电塔的动力特性规律尚需进一步研究。本文以实际工程为例,建立了大跨越输电塔-线体系数值分析模型,分析了导线划分精度对输电塔-线体系动力特性的影响,并在此基础上分析了导线覆冰对输电塔-线体系动力特性的影响。研究结果表明:导线划分精度对输电塔振动影响较大;导线覆冰不仅影响输电塔振动频率,而且对输电塔振型也有较大影响,尤其是对输电塔横担的振动影响更大。 相似文献
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67.
From 1989 to 1992, systematic cetacean surveys were carried out twice weekly along a trans‐regional fixed transect in the Central Tyrrhenian Sea, utilising passenger ferries as research platforms. Using the same protocol and supervised by the same investigators, the research restarted in 2007, providing the opportunity to compare consistent data over a long 20‐year period. The monitored transect (Civitavecchia‐Golfo Aranci) runs along a strategic area just outside the southeastern border of the Pelagos Sanctuary. Over the last two decades, an increasing trend of temperature and salinity, in the deep and intermediate layers, has been documented in the region, as well as general changes over the Mediterranean basin. These changes, together with the increasing impact of some pressures (e.g. maritime traffic) may have led to changes in oceanographic and anthropogenic features and, subsequently, in cetacean presence and distribution. The research aimed to verify whether any changes occurred in the pattern of cetacean occurrence over the 20‐year period along the representative transect in the Central Tyrrhenian Sea. Data from 90 summer weekly runs undertaken in the 1990s were compared with data obtained from 95 runs undertaken in the 2000s. Each ferry run was considered an independent statistical unit: the encounter rate (ER = number of sightings per hour spent on effort) was calculated to compare relative abundance between periods, years and months. Spatial analysis was performed on geographical data using Kernel analysis to map the distribution of sightings. Logistic regression (GLM) was performed to compare habitat preference. Total encounter rate in the 1990s (ER = 0.59 ± CI 0.08) was significantly lower (P < 0.01) compared with the 2000s (ER = 0.94 ± CI 0.15). The same seven out of eight species known for their regular presence in the Mediterranean Sea were sighted in both the investigated periods. The most common species were striped dolphin (Stenella coeruleoalba), fin whale (Balaenoptera physalus) and common bottlenose dolphin (Tursiops truncatus). Neither the pilot whale nor any other rare or occasional species were sighted during the 6 years of the study. Despite the time span, no dramatic changes were observed for any species, bar fin whale, in terms of distribution, relative abundance, group size or habitat preference. Sightings of fin whale have surprisingly increased (+300%, P< 0.001), and their spatial and temporal distribution and habitat preference showed a radical difference between the two periods. The 2000s surveys confirmed the existence of high density areas of cetaceans, especially of fin whale, and the consequent necessity of specific legislative acts for cetacean conservation. 相似文献
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69.
N. Schartel 《Astronomische Nachrichten》2006,327(10):941-942
“Variable and Broad Iron Lines around Black Holes” was the topic of the first scientific workshop organized by the XMMNewton Science Operations Centre. This foreword gives a brief introduction to the history of black hole research, which motivated the workshop's scientific topic. The organizing committees are listed and the meeting is shortly outlined. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
70.
G. A. Athanasopoulos 《Geotechnical and Geological Engineering》1994,12(2):122-132
Summary A review is presented of conceptual approaches that are currently in use for interpreting the operation of reinforced soil.
The concepts of enhanced confining pressure and of reduced normal tensile strains are found to be closely related to current
experimental and theoretical investigations as well as to the design methodologies available at present for reinforced soil
applications. Focusing on the enhanced confining pressure concept, analytical expressions are developed that allow the estimation
of the value of equivalent confining stress increase when the properties of soil and reinforcement and the state of stresses
acting on a cylindrical reinforced soil element are known. The derived expressions can also be utilized for estimating the
soil-reinforcement friction angle from the results of triaxial tests on cylindrical samples reinforced with horizontal layers
of reinforcement. 相似文献