网络地图服务传输机制的研究     

陈应东  陈毓芬  卢晨琰 《测绘学院学报》2006,(3)

就目前网络地图服务过程中所涉及的信息传输机制问题进行了研究。传统的地图传输模式主要偏向于信息的表达和获取之间的关系,特别是地图符号化以及使用者对地图表达的认识能力。在此基础上,提出网络地图服务传输的基本框架,探讨了网络地图服务传输的新模式。认为它们必须经过服务请求和服务响应两个过程,以及需求信息到数据描述语言的转换、需求描述到服务描述的转换、数据描述语言到地图数据提供的转换等3种信息转换。  相似文献   

沙尘暴资料传输系统   总被引：1，自引：2，他引：1  

孙林花  陈旭辉  崔永红  邵亮  杨菊梅 《干旱气象》2006,24(2):84-88

本系统采用C BUILDER 6.0面向对象的软件开发工具,通过提供灵活的参数配置接口,可完成W INDOW S操作系统下沙尘暴等各类气象数据的定时自动传输和手工传输。在SCO UNIX操作系统下,用C完成了资料二次传输软件的开发,主要解决省到国家局沙尘暴等各类数据的定时自动传输,解决了9210业务应用软件无法解决长文件名的传输问题。  相似文献   

Ambiguous reflection coefficients for anelastic media     

B.O. Ruud 《Studia Geophysica et Geodaetica》2006,50(3):479-498

The calculation of reflection and transmission coefficients of plane waves at a plane interface between two homogeneous anelastic media may become ambiguous because it is not always obvious how to determine the sign of the vertical component of the slowness vector of the scattered waves. For elastic media, the sign is determined by applying so-called radiation condition when the slowness vector is complex-valued, but it has long been known that this approach does not work satisfactorily for anelastic media. Other approaches have been suggested, e.g., by requiring that the reflection and transmission coefficients should vary continuously with increasing incident angles, or by relating the sign to the direction of the energy flux. In the present paper, it is shown that these approaches may give different results, and that the results can be inconsistent with the elastic case even for weak attenuation. Instead, it is demonstrated that the ambiguity in the reflection coefficient can be resolved by expressing the seismic response of a point source over an interface as a superposition of plane waves and their reflection coefficients, and solving the resulting integral by the saddle point approximation. Although the saddle point itself (point of stationary phase) does not provide new insight, the ambiguity is removed by considering the steepest descent path through the point. Ray synthetic seismograms computed by this method compare well with synthetics computed by the reflectivity method, which does not suffer from the above-mentioned ambiguity since the integration path is taken along the real axis. This paper concentrates on the isotropic case, but it is discussed how the result may be extended to layered transversely isotropic media. The suggested approach, derived for a point source and plane layers, does not directly apply to 2-D or 3-D laterally inhomogeneous media, or to media of general anisotropy. A generalization of the result found is that the sign of the vertical slowness components should be chosen according to the energy flux direction for subcritical incidence and according to the radiation condition for supercritical incidence, even if this creates a discontinuity in the coefficients at the critical incidence angle. Such a discontinuity is sometimes necessary to get results which are consistent with the elastic case. It is discussed how the generalized result can be obtained by applying certain continuity criteria for the sub-and supercritical angle intervals, but the validity of this approach for general models remains to be proved.  相似文献   

Seismic reflection and transmission coefficients at an air-water interface of saturated porous soil     

周新民  夏唐代徐平 邹振轩 《地震学报(英文版)》2006,19(4):397-405

Based on the modified Biot＇s theory of two-phase porous media, a study was presented on seismic reflection and transmission coefficients at an air-water interface of saturated porous soil media. The major differences between air-saturated soils and water-saturated soils were theoretically discussed, and the theoretical formulas of reflection and transmission coefficients at an air-water interface were derived. The characteristics of propagation and attenuation of elastic waves in air-saturated soils were given and the relations among the frequency, the angle of incidence and the reflection, transmission coefficients were analyzed by using numerical methods. Numerical results show that the propagation characteristic of the wave in air-saturated soils is great different from that in water-saturated soils. The frequency and the angle of incidence can have great influences on the reflection and transmission coefficients at interface. Some new cognition about the wave propagation is obtained and the study suggests that we may carefully pay attention to the influence of air on the dynamic analysis of seismic wave.  相似文献   

探讨气象短信的发展之路   总被引：24，自引：0，他引：24  

袁丽军  粟华林 《广西气象》2006,27(3):49-50,64

通过对气象短信的定制模式和广告宣传方面的探讨，认识到气象短信服务是目前气象部门传播气象预警信号一个重要的现代通信手段，能使气象灾害预警服务更具时效性；气象短信的发展壮大关系到方方面面。  相似文献   

SARS空间传播模式及其在疫情监控信息系统设计中的应用   总被引：4，自引：0，他引：4  

阎守邕  刘亚岚  李小文  曹春香  金水高 《遥感学报》2003,7(4):266-272

在中国控制SARS(Severe Acute Respiratory Syndrome)疫情扩散与蔓延的大量科学实践活动基础上，从人地系统科学的理论和观点出发，提出了各种致病因子在人地互动过程中转移路径的逻辑模型，进而又提出了控制SARS疫情发展的人地互动逻辑模型。从后一个模型出发，把中国SARS疫情的发展规律归纳为5种传播模式，即异类病毒转移传播模式、家庭和社区接触传播模式、医院和门诊感染传播模式、市内随机扩散传播模式和飞点跳跃跨区传播模式。其中，跨区传播模式的影响最广泛、危害最巨大、控制起来最艰巨、复杂，是建立中国突发公共卫生事件应急机制、增强应急能力需要解决的主要问题和关键内容。为此，作者对中国的疫情控制应急机制及其实现提出了一些具体的看法和建议，包括对现有疫情系统进行技术改造和创新的建议，在全新运作机制和高技术基础上建立应急疫情监测控制信息系统的概念结构等内容。  相似文献   

关于PDF与跨平台发行文件的解决方案   总被引：3，自引：0，他引：3  

张砚  闪永强 《测绘学院学报》2003,20(1):62-64

PDF是Adobe公司开发的一种可以跨平台的文件格式。文中主要探讨了PDF文件格式的特点与应用，将其与PostScript进行了对比说明，并介绍了PDF的工具软件与PDF的制作和网上发布方法，以及如何利用PDF跨平台发行文件。  相似文献   

青海省数字地震数据准实时传输研究     

王海功  沙成宁吴哲 《高原地震》2003,15(2):44-48

通过对青海省“九五”新、改建数字地震台地震数据传输方式的研究，用X．25组建数字地震台网广域网，可方便地实现数字地震数据的准实时传输，其组建简单，台站终端设备接入方便，运行成本低；同时，数字地震台网广域网也可用DDN、RF组建，使“九五”已建台站和“十五”待建台站数据传输良好地衔接。  相似文献   

大气降尘TEM观察及其环境矿物学意义   总被引：10，自引：5，他引：10       下载免费PDF全文

陈天虎  徐惠芳 《岩石矿物学杂志》2003,22(4):425-428

在X射线衍射等分析研究基础上，进一步用透射电镜对半封闭室内长期沉积的大气降尘进行观察，提供了合肥地区大气降尘物相组成和各种物相形貌特征信息，揭示合肥地区大气污染物来源占第1位的是地表扬尘，以粘土矿物为标志；占第2位的是来源于大气化学次生气溶胶，主要和SO2、CO2、NOx等气态污染物排放有关，以石膏、碳酸盐和易溶盐类为标志；占第3位的是来源于汽车尾气排放的烟尘，以炭球为标志；占第4位的是来源于燃煤烟尘排放，以球形玻璃珠为特征。TEM调查不仅为合肥地区大气气溶胶颗粒成因、城市大气污染物来源和污染控制对策提供准确资料和依据，而且为确定大气颗粒物来源提供了有效研究方法和物源判别标志。  相似文献   

动测法桩基检测过程中弹性波能量在桩体界面上的反射和透射     

刘金俊 《物探与化探》1998,22(4):295-299

本文分别就(1)变阻抗桩(2)变截面桩(3)阻抗截面均有变化的桩阐述了在动测过程中弹性波能量的传输过程,即弹性波能量在截面上的入射、反射和透射的关系及分配特性。  相似文献