带孔洞面域间的拓扑关系的组合推理

空间对象间拓扑关系是GIS中空间要素间最基本也是最重要的关系之一,是进行空间查询和分析的基础,因而空间对象间拓扑关系一直是研究的热点之一。目前,对拓扑关系模型的研究主要集中在简单对象间拓扑关系方面,而对于带空洞的复杂面域间的空间拓扑关系的研究则相对较少,因而对它的进一步研究具有较重要的理论意义。本文在文献[11]的基础上,根据点集拓扑学理论,对带孔面域进行了定义。通过分析简单对象间拓扑关系的演变过程,提出一种能描述带一个孔的面域间的空间拓扑关系的方法,并用该方法详细推导了带一个孔的面域间有意义的拓扑关系。通过实验验证,证明该方法在理论上是可行的,对提高GIS对现实世界的建模和分析能力可提供一定的理论依据。     

Delaunay三角网关键技术探讨

利用计算机技术,基于实际测量数据,利用逐点插入法,在不建立格网索引的情况下,提出一种高效的Delaunay三角网构建方法,与建立格网索引法搜索点所在的三角形相比,具有较高的执行效率.     

线实体候选匹配集的优化方法研究

地图数据合并是地理空间数据集成的基本途径,同名实体匹配是其中的重点与难点。本文根据线实体的形状将其分为简单线实体与复杂线实体,提出针对前者以线实体端点与中点为发生元生成的Voronoi图所得到的邻近对应关系为依据、针对后者以基于线实体缓冲区重叠度构造的相似性测度指标为依据优化候选匹配集的思路,并设计与实现了相关算法。实证研究表明,该算法能够适应不同比例尺与不同时相的城市道路网地图数据同名实体匹配。     

混合单元模型在道路工程土方量计算中的运用

通过综合规则格网和不规则三角网的特点,构建了混合单元模型运用于道路勘察设计的土方量计算中,采用蒙特卡罗积分方法进行体积计算.通过工程实例对比,验证了此方法可行性,为土方量计算提供新模式.     

中外烈度表“人的感觉”和“器物的反应”对比研究

随着震害经验的积累以及人们对地震认识的深化,不断修改烈度标准,使烈度评定更加客观与科学是地震工程界一直所追求的.人的感觉和器物的反应都是评定一次地震时相应烈度的宏观标志,是烈度表的重要组成部分.鉴于此,本文简要介绍了中国历代地震烈度表(《新的中国地震烈度表》、《中国地震烈度表(1980)》、《中国地震烈度表( 1999...     

Wind-induced drift of objects at sea: The leeway field method

A method for conducting leeway field experiments to establish the drift properties of small objects (0.1-25 m) is described. The objective is to define a standardized and unambiguous procedure for condensing the drift properties down to a set of coefficients that may be incorporated into existing stochastic trajectory forecast models for drifting objects of concern to search and rescue operations and other activities involving vessels lost at sea such as containers with hazardous material.An operational definition of the slip or wind and wave-induced motion of a drifting object relative to the ambient current is proposed. This definition taken together with a strict adherence to a 10 m wind speed allows us to refer unambiguously to the leeway of a drifting object. We recommend that all objects if possible be studied using what we term the direct method, where the object’s leeway is studied directly using an attached current meter.We establish a minimum set of parameters that should be estimated for a drifting object for it to be included in the operational forecast models used for prediction of search areas for drifting objects.We divide drifting objects into four categories, depending on their size. For the smaller objects (less than 0.5 m), an indirect method of measuring the object’s motion relative to the ambient current must be used. For larger objects, direct measurement of the motion through the near-surface water masses is strongly recommended. Larger objects are categorized according to the ability to attach current meters and wind monitoring systems to them.The leeway field method proposed here is illustrated with results from field work where three objects were studied in their distress configuration; a 1:3.3 sized model of a 40-foot Shipping container, a World War II mine and a 220 l (55-gallon) oil drum.     

Experimental researches on reflective and transmitting performances of quarter circular breakwater under regular and irregular waves

A series of regular and irregular wave experiments are conducted to study the reflective and transmitting performances of quarter circular breakwater (QCB) in comparison with those of semi-circular breakwater (SCB). Based on regular wave tests, the reflection and transmission characteristics of QCB are analyzed and a few influencing factors are investigated. Then, the wave energy dissipation as wave passing over the breakwater is discussed based on the hydraulic coefficients of QCB and SCB. In irregular wave experiments, the reflection coefficients of QCB and their spectrums are studied. Finally, the comparisons between the experimental results and numerical simulations for QCB under regular and irregular wave conditions are presented.     

Fault-Growth Pattern of the South Margin Normal Fault of the Yuguang Basin in Northwest Beijing and its Influencing Factors

Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the evolution of the Yuguang Basin South Margin Fault (YBSMF) in northwest Beijing was carried out. We found that the propagation and growth of faults most often occurred often at two locations: the fault overlapping zone and the uneven or rough fault segment. Through detailed observation and analysis of all cropouts of faults along the YBSMF from zone a to zone i, we identified three major factors that dominate or affect fault propagation and growth. First, the irregularity of fault geometry determine the propagation and growth of the fault, and therefore, the faults always propagate and grow at such irregular fault segments. The fault finally cuts off and eliminates its irregularity, making the fault geometry and fault plane smoother than before, which contributes to the slipping movement of the half-graben block in the basin. Second, the scale of the irregularity of the fault geometry affects the result of fault propagation and growth, that is, the degree of the cutting off of fault irregularity. The degree of cutting off decreases as irregularity scale increases. Third, the maximum possible slip displacement of the fault segment influences the duration of fault propagation and growth. The duration at the central segments with a large slip displacement is longer than that at the end segments with a smaller slippage value.     

Radon变换在非规则观测系统中波场分离的应用

Radon变换是数据处理中广泛应用的一种方法技术.本文介绍了Radon变换在规则及其非规则观测系统中波场分离中应用,讨论了Radon变换的公式、实现方法和有关计算参数的选择.通过理论模型的试算,阐明了Radon变换在缺失道、道距变化情况下依然可以高精度的分离波场,并对线性、抛物Radon变换进行了比较,对隧道超前预报反射波资料进行了处理,给出了隧道超前预报处理流程中提取反射波的算例.     

航道对多方向波传播影响

应用Boussinesq方程对不同入射角、不同方向集中度的波浪与航道的相互作用进行模拟,得到了航道的折射影响规律以及不同入射角、不同方向集中度的波浪对航道作用的差别.结果对试验研究及工程实践有指导意义.