一种适用于对流层干延迟的新的几何映射函数   总被引：1，自引：0，他引：1  

殷海涛  熊永良  黄丁发 《测绘科学》2006,31(1):46-48

本文提出了一种新的对流层干延迟映射函数,此模型形式简洁,精度较高,是完全应用几何方法得出的,模型只与大气的有效高度有关,不包含任何气象因素,适用于动态定位及导航。文中通过实验在不同高度角、不同纬度与目前最常用的CFA2·2和Niell映射函数进行了比较,结果表明,在高度角大于6度时此函数与这两种模型精度相当,得到了非常理想的效果。  相似文献   

Experimental analysis of compaction of concrete and mortar     

Nicolas Burlion  Gilles Pijaudier‐Cabot  Noël Dahan 《国际地质力学数值与分析法杂志》2001,25(15):1467-1486

Compaction of concrete is physically a collapse of the material porous microstructure. It produces plastic strains in the material and, at the same time, an increase of its bulk modulus. This paper presents two experimental techniques aimed at obtaining the hydrostatic response of concrete and mortar. The first one is a uniaxial confined compression test which is quite simple to implement and allows to reach hydrostatic pressures of about 600 MPa. The specimen size is large enough so that concrete with aggregate sizes up to 16 mm can be tested. The second one is a true hydrostatic test performed on smaller (mortar) specimens. Test results show that the hydrostatic response of the material is elasto‐plastic with a stiffening effect on both the tangent and unloading bulk moduli. The magnitude of the irreversible volumetric strains depends on the initial porosity of the material. This porosity can be related in a first approximation to the water/cement ratio. A comparison of the hydrostatic responses obtained from the two testing techniques on the same material show that the hydrostatic response of cementitious materials cannot be uncoupled from the deviatoric response, as opposed to the standard assumption in constitutive relations for metal alloys. This feature should be taken into account in the development of constitutive relations for concrete subjected to high confinement pressures which are needed in the modelling of impact problems. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

构造附加静水压力及构造物理化学在地质研究中的应用     

吕古贤  王义强  郭涛  孙丰月 《国土资源》1999,(3)

“构造附加静水压力”概念认为，地壳任一点静水压力部分是由重力所附加的静水压力和由构造作用力所附加的静水压力叠合而成的。构造叠加致使同一地壳深度的水平面上静水压力值不相等，这种压力梯度是流体及油气长距离水平运移的主要原因。建立岩石矿床形成深度的构造校正测算方法，得出胶东“玲珑－ 焦家式”金矿成矿深度仅３ ｋｍ 左右的数据，进而测得大别超高压变质带含柯石英榴辉岩形成深度仅≥３２ ｋｍ ，它们可能是壳内构造物理化学过程的产物； 逐步形成构造通过影响物理化学环境的方式影响成岩成矿地球化学过程， 即构造物理化学成矿的新认识， 探讨应用构造物理化学场结构分析与界面成矿的观点进行预测未知区隐伏矿床。  相似文献   

重力异常对静力水准系统测量精度的影响   总被引：3，自引：2，他引：1  

何晓业 《大地测量与地球动力学》2006,26(2):124-127

讨论了在大距离范围中使用静力水准系统应注意的问题,根据地球潮汐理论,着重分析了由于附近巨大物体以及月球和太阳的作用引起的测量范围内的重力异常对系统测量精度的影响和相应的修正办法,并推导出了改正量公式。  相似文献   

热带气旋的螺旋度特性   总被引：18，自引：1，他引：18  

陈华  谈哲敏 《热带气象学报》1999,15(1):81-85

将螺旋度的概念引入热带气旋，对热带气旋螺旋度的结构特征及其在热带气旋发展过程中的演变过程进行了研究。结果表明，热带气旋这种具有较强螺旋性的天气系统，其发展过程也就是螺旋度增强的过程。螺旋度对热带气旋稳定过程的维持及其长久的生命期具有重要的作用。  相似文献   

静水压法人工诱导牙鲆(♀)×圆斑星鲽(♂)杂交三倍体的探索     

刘金相  王旭波  刘聪辉  高金宁  王忠凯  王文基  王志刚  于海洋  齐洁 《中国海洋大学学报(自然科学版)》2014,44(2)

开展了牙鲆(Paralichthys olivaceus)(♀)和圆斑星鲽(Verasper variegatus)(♂)杂交,通过静水压抑制受精卵第二极体的释放来诱导杂交三倍体,设计单因素分析实验,筛选出当前试验条件下的最佳诱导条件。结果表明:静水压法可成功诱导出杂交三倍体,诱导率主要受到受精后处理起始时刻、处理压强和压强处理时间3个因素的影响。静水压法的最佳诱导条件为:海水温度(15.0±0.2)℃,受精后3 min起,以70 MPa压力处理6 min。此时相对孵化率为(24.06±1.10)%,利用倍性分析仪对其进行倍性鉴定,三倍体率为(26.67±6.67)%。染色体分析表明,三倍体胚胎的染色体数目为71条,对照组二倍体胚胎的染色体数目为47条。还发现有少量染色体数目为24条的单倍体胚胎。研究结果为鲆鲽鱼类异源多倍体的培育提供了参考。  相似文献   

Effect of tropical cyclone intensity and instability on the evolution of spiral bands     

Hong Huang  Yongqiang Jiang  Zhongyi Chen  Jian Luo  Xuezhong Wang 《大气科学进展》2014,31(5):1090-1100

The evolution of spiral-band-like structures triggered by asymmetric heating in three tropical-cyclone-like vortices of different intensities is examined using the Three-Dimensional Vortex Perturbation Analyzer and Simulator （3DVPAS） model. To simulate the spiral bands, asymmetric thermal perturbations are imposed on the radius of maximum wind （RMW） of vortices, which can be considered as the location near the eyewall of real tropical cyclones （TCs）. All the three vortices experience a hydrostatic adjustment after the introduction of thermal asymmetries. It takes more time for weaker and stable vortices to finish such a process. The spiral-band-like structures, especially those distant from the vortex centers, form and evolve accompanying this process. In the quasi-balance state, the spiral bands are gradually concentrated to the inner core, the wave behavior of which resembles the features of classic vortex Rossby （VR） waves. The unstable vortices regain nonhydrostatic features after the quasi-balance stage. The spiral bands further from the vortex center, similar to distant spiral bands in real TCs, form and maintain more easily in the moderate basic-state vortex, satisfying the conditions of barotropic instability. The widest radial extent and longest-lived distant bands always exist in weak and stable vortices. This study represents an attempt to determine the role of TC intensity and stability in the formation and evolution of spiral bands via hydrostatic balance adjustment, and provides some valuable insights into the formation of distant spiral rainbands.  相似文献   

Extensions of GAP‐tree and its implementation based on a non‐topological data model     

Changxiu Cheng  Fangqu Niu  Jun Cai  Yanlu Zhu 《International journal of geographical information science》2013,27(6):657-673

This paper discusses extensions of GAP‐trees from three aspects and its implementation based on non‐topological structure in order to enhance access to large vector data sets. First of all, we apply cartographic generalization rules to build a generalization procedure of the GAP‐tree, which makes coarse representations more consistent with human cognition. Second, we replace the three‐dimensional (pseudo‐) Reactive‐tree index with a 2D R‐tree index and a B‐tree index to improve the system efficiency. Finally, we compress a binary GAP‐tree into multi‐way GAP‐trees in order to reduce data redundancy. The shallower multi‐way GAP‐trees not only eliminate redundant data but also accelerate the system's response time. The extensions have been successfully implemented in PostgreSQL. A test of Beijing's land‐use data at the 1:10 000 scale demonstrates that the extended GAP‐trees are efficient, compact, and easy to implement.  相似文献   

Non‐hyperbolic common reflection surface     

Sergey Fomel  Roman Kazinnik 《Geophysical Prospecting》2013,61(1):21-27

The method of common reflection surface (CRS) extends conventional stacking of seismic traces over offset to multidimensional stacking over offset‐midpoint surfaces. We propose a new form of the stacking surface, derived from the analytical solution for reflection traveltime from a hyperbolic reflector. Both analytical comparisons and numerical tests show that the new approximation can be significantly more accurate than the conventional CRS approximation at large offsets or at large midpoint separations while using essentially the same parameters.  相似文献   

北太平洋夏季的两个典型层积云区与海温和大气低层热力过程的关系     

章丽娜  王必正  曾庆存 《气候与环境研究》2005,10(3):626-637

比较ISCCP D2层积云云量的季节平均图后发现:除了大洋东部常年有层积云外,北太平洋夏季也存在一片大值区.在副热带东北太平洋和中纬度西北太平洋各取一个10°×10°的区域,分别记为NEP和NWP.利用OI-SST、NCEP/NCAR再分析资料和ERBE资料,通过相关和气候分析,提出了新的物理意义明确的稳定度判据,比较了NEP和NWP两个区的夏季层积云云量与海温、大气热力过程的异同.结果表明:夏季,NEP和NWP都有正的稳定度,有利于层积云的形成和维持.NEP区和NWP区夏季的海气温差、感热通量、潜热通量有明显的差异.从海温和夏季层积云云量的相关分析发现:在NEP区,海温滞后于层积云云量,其相关于滞后3个月时有最大负值,这可能是由于海洋有较大的热惯性,对层积云遮蔽太阳辐射而导致洋面降温的响应需要3个月;而在NWP区,则是海温超前于层积云云量,其相关于超前1个月时有最大负值,这可能是由于从5月份开始海温低于气温,且有暖空气平流,有利于随后层积云、层云和雾的形成.  相似文献