新一代天气雷达产品共享平台的设计与实现   总被引：1，自引：0，他引：1       下载免费PDF全文

郜凌云  曲晓波  陈传雷 《气象与环境学报》2006,22(2):67-68

为将新一代天气雷达产品自动、实时传输到各级气象部门,根据辽宁已有的雷达产品显示终端和通信条件,依托省—市—县的2 M数字电路,采用FTP协议,建立新一代天气雷达资料全省共享平台,实现了雷达产品信息资料的共享。  相似文献   

Effects of modified gravity black holes on the bounds of greybody factor     

《New Astronomy》2022

The study of greybody factor helps us to understand the quantum nature of the black hole. Gravitational potentials and bounds on the greybody factors for some well known black holes are developed and we investigate the influence of Born–Infeld and massive gravity parameters on them. It is observed that greybody factor bounds depend on the shape of effective potential. For higher values of effective potential, it becomes difficult for the waves to transmit and hence reduces the greybody factor bounds. It is also worthwhile to mention here that charge works as barrier and cosmological constant increases the emission rate of Hawking radiation. It is also observed that the energy of emitted particles increases which results in the enhancement of the greybody factor bound. We also discuss the relationship of transmission probability and reflection probability.  相似文献   

多单体雷暴的形变与列车效应传播机制   总被引：20，自引：7，他引：13       下载免费PDF全文

孙继松  何娜  郭锐  陈明轩 《大气科学》2013,37(1):137-148

本文利用变分多普勒雷达分析系统(Variational Doppler Radar Analysis System,简称VDRAS)基础上构建的四维变分(4 Dimensional Variational assimilation,简称4DVar)低层热、动力反演系统,针对发生在北京地区的几次多单体雷暴系统演变过程,研究了线性多单体对流系统传播过程中发生的形变过程、强弱变化和“列车效应”等现象的物理机制.结果表明:(1)对于雷暴单体的传播方向与雨带的移动方向基本一致的多单体雷暴系统(如飑线系统),单体的传播速度不同最终造成多单体雷暴在形态上发生变化(如由直线形回波演变为“弓”形回波等),以及雷暴单体传播过程中的强弱变化等,是雷暴单体传播过程与低层环境大气相互作用的结果:如果雷暴前端的入流本身是暖湿的,并存在较强的水汽辐合现象时,雷暴单体发展更旺盛,传播速度更快,反之则趋于减弱,传播速度减慢.因此,对飑线系统的临近预报而言,需要特别关注多单体雷暴系统传播方向与近地面层中尺度水汽通量辐合带的交叉区域,该区域的雷暴单体“移动”速度更快、发展更为强烈.(2)对于“列车效应”多单体雷暴而言,其传播环境、传播机制与上述多单体雷暴系统几乎完全不同:“列车效应”一般发生在低空暖湿气流或低空急流附近,环境大气表现为条件性静力不稳定.雷暴单体的传播机制可能是惯性重力波的激发、传播的结果,由于西南暖湿气流或急流是一支暖湿气流输送带,惯性重力波由假相当位温θ_se的高值区向低值区传播,重力波将从背景场中不断获得能量而发展.因此,雷暴传播过程中不断增强的现象造成波动排列的多单体雷暴形成的最大降水中心往往出现在波列的前端.  相似文献   

Google Earth在线路勘测设计中的应用分析     

周冬梅 《北京测绘》2014,(4):42-44

通过分析Google Earth在电力线路勘测及输电线路基建管理中的应用,提出了一种简单可行的构建三维输电线路GIS系统的方法。  相似文献   

GPS精密轨道插值误差及方差估计     

钟剑龙  花向红  邱卫宁  龚子桢 《测绘信息与工程》2011,36(4):4-6

分析了影响GPS精密轨道插值传播误差精度的因素,给出了IGS精密星历误差在多项插值中的传播模型及传播误差的方差分量计算方法,为评定GPS插值轨道的精度提供了量化的客观依据,并用算例证明了卫星插值轨道的传播误差精度与精密星历误差精度在同一量级。  相似文献   

基于Ganley理论含有衰减特性零偏VSP正演研究及修正          下载免费PDF全文

武银婷  朱光明  刘伊克  常旭 《地球物理学报》2011,54(9):2368-2374

含有衰减的VSP资料能够提供丰富的地下岩层和岩性信息,本文根据Ganley理论对其进行了正演计算.引入品质因子Q值,考虑界面发生反射和透射,对震源位于地表及地下某一深度进行讨论,分别计算水平层状介质中的下行波和上行波.与不含有衰减特性的正演记录及其时频分析对比可以看出,高频成分的吸收、主频的降低、较多的能量衰减揭示了地...  相似文献   

Wave interaction with a wave absorbing double curtain-wall breakwater   总被引：3，自引：0，他引：3  

Yong Liu  Yu-cheng Li 《Ocean Engineering》2011,38(10):1237-1245

This study examines the hydrodynamic performance of a wave absorbing double curtain-wall breakwater. The breakwater consists of a seaward perforated wall and a shoreward impermeable wall. Both walls extend from above the seawater to some distance above the seabed. Then the below gap allows the seawater exchange, the sediment transport and the fish passage. By means of the eigenfunction expansion method and a least square approach, a linear analytical solution is developed for the interaction of water waves with the breakwater. Then the reflection coefficient, the transmission coefficient and the wave forces acting on the walls are calculated. The numerical results obtained for limiting cases agree very well with previous predictions for a single partially immersed impermeable wall, the double partially immersed impermeable walls and the bottom-standing Jarlan-type breakwater. The predicted reflection coefficients for the present breakwater also agree reasonable with previous experimental results. Numerical results show that with appropriate structure parameters, the reflection and transmission coefficients of the breakwater may be both below 0.5 at a wide range of the relative water depth. At the same time, the magnitude of wave force acting on each wall is small. This is significant for practical engineering.  相似文献   

Dynamic analysis of wave energy converter by incorporating the effect of hydraulic transmission lines   总被引：1，自引：0，他引：1  

Limin Yang  Torgeir Moan 《Ocean Engineering》2011,38(16):1849-1860

A heaving-buoy wave energy converter equipped with hydraulic power take-off is studied in this paper. This wave energy converter system is divided into five subsystems: a heaving buoy, hydraulic pump, pipelines, non-return check valves and a hydraulic motor combined with an electric generator. A dynamic model was developed by considering the interactions between the subsystems in a state space form. The transient pressures caused by starting/stopping the buoy or closing/opening the check valves were predicted numerically using the established model. The simulation results show that transmission line dynamics play a dominant role in the studied wave energy converter system. The length of the pipeline will not only affect the amplitude of the transient pressures but also affect the converted power. The variation of the time-averaged converted electric power with the pipeline length is estimated using the simulation method for the buoy exposed to one irregular sea state. Finally, it is suggested how reduced power efficiency due to the pipelines may be ameliorated.  相似文献   

闭环极点与开环零极点的一种关系式     

邱伟光 《广东海洋大学学报》2002,22(6):54-57

根据控制系统的特征方程和开环传递函数的关系 ,推导出闭环极点与开环零极点之间的关系式 ,并举例说明其应用 ,该公式简单且具有通用性和实用性。  相似文献   

马氏珠母贝外套膜培养细胞的电镜观察     

王爱民  阎冰  苏琼  叶力 《海洋科学》2002,26(10):4-9

运用扫描电镜和透射电镜对马氏珠母贝（Pinctada martensii D0外套膜组织培养过程中各种细胞的生长变化和活动状况的研究，重点是对上皮细胞分泌活动的观察。最初从外套膜组织迁出的上皮细胞为圆球形，细胞表面近似光滑，但有走向规则细而浅的花纹；培养到第4天，上皮细胞形态上发生了较大的变化，分成A型和B型两种细胞，A型上皮细胞内颗粒物少，是处于合成分泌物的早期阶段或尚未开始合成分泌物，B型上皮细胞处于旺盛的分泌物合成阶段，细胞内粗面内质网和线粒体丰富。培养到15－16天的B型上皮细胞体积明显变大，细胞合成并聚集了大量单层膜包裹的颗粒物，培养到第31天的B型上皮细胞分泌活动减弱，上皮细胞逐渐失去分泌功能，进入衰老，死亡，胞体明显萎缩变小，整个培养过程持续了65d。  相似文献