基于能量原理的Park & Ang损伤模型简化计算方法

Park＆Ang损伤模型综合考虑了结构最大变形和累积滞回耗能的耦合作用,具有一定的先进性,被国内外研究者广泛采用;但由于该模型中参数的计算困难,尤其涉及结构滞回耗能的计算问题时,该模型的应用受到了一定的限制;文中从能量的关系入手,寻找出结构滞回耗能与结构最大位移的关系,利用该关系可方便求解出结构的滞回耗能,从而为该模型的计算提供了一种简便方法;最后,例题分析证明本文的方法简便可行,计算效率高。     

基于"山西2015速度模型"的定位方法对比研究

为了确定山西台网基于“山西2015速度模型”的相对固定的定位方法,选择2010~2016年最大空隙角小于45°、参与定位台站数大于40的103个地震事件,分别采用单纯形法、Hypo2000、Hyposat结合PTD等3种方法重新测定。结果显示,单纯形法和Hyposat结合PTD测定的残差以及网缘地震的震中距两方面均优于Hypo2000;在震源深度方面,Hyposat结合PTD的结果较为可信。综合分析认为,基于“山西2015速度模型”定位地震时,山西台网应固定使用Hyposat结合PTD的方法。     

视频对象分割及跟踪方法研究

讨论和分析了视频对象全自动提取及后续帧中的跟踪过程及采用的方法,对其算法、分割性能和结果进行了比较和评述。并结合Hausdorff和Snake跟踪器,对初始对象轮廓进行跟踪。结果证明,这种跟踪方法能有效地解决对象被遮挡和形变以及背景移动的问题。     

一个湍能封闭模型对风暴潮海底底应力的应用研究

将一个三维湍能封闭模型应用于开阔海区的风暴潮，通过数值计算探讨了Ｔａｙｌｏｒ底摩擦二次率的拖曳系数随空间的分布及拖曳系数与水深、海底粗糙度、风向和风速等因素的关系。本文对底摩擦二次率的可靠性做了评价。     

红板岩材料隐式本构模型的建立及其应用研究

针对红板岩材料在岩土工程中所表现的大量模糊的和不确定的因素等特点,基于人工神经网络的学习能力,借助于室内岩石力学试验,进行了对该材料的力学本构特性进行了神经网络模拟研究,提出了隐式本构模型的思想和方法,并通过该方法对该岩石的流变试验结果进行学习,获得了以网络权值结构保存的力学特性知识,由此得到了表征红板岩应力应变本构关系的隐式本构模型。应用结果表明,该方法对岩土类材料本构关系的模拟研究具有很好的应用前景。     

THE APPLICATION OF IMAGE-BASED MODELING IN PALEOEARTHQUAKE TRENCH STUDY

The geological structure exposed by paleoearthquake trenches is the key material to the right cognition of fault activity and paleoearthquake. However, paleoearthquake trenching inevitably destroys active tectonic geomorphic evidence and trench exposures are usually difficult to reserve. The conventional process of recording the delicate geological information, manually constructing photomosaics by image-editing software, is time-consuming and produces undesirable artificial distortions. Herein, we explored the process of constructing trench orthophotomosaics and the 3D image model using the Image-based Modeling technology and applied it to the Liutiaohe trench across the Tianqiaogou-Huangyangchuan Fault, Gansu Province. Based on the 3D image modeling and orthophotomosaic, we firstly constructed the control points and scale bars on cleaned trench walls and collected photos of all sections of the trench with a digital camera in the field, and then reconstructed the 3D model of the trench through the Agisoft PhotoScan, an efficient image-based modeling software, and finally yielded the 3D image model of the trench and othophotomasaics of the trench exposures. The results show that the automated workflow can produce seamless, sub-millimeter-level high-resolution photomosaics more quickly, with precision in the centimeter range, and the 3D image model is of great help to identify strata and geological structures in trenches with much lower capital and labor costs and low expertise levels compared with LiDAR, meanwhile, the 3D archive benefits the share and communication and even allows future reinterpreting the site using new insights.     

Tropospheric Ozone in a Global-Scale Three-Dimensional Lagrangian Model and Its Response to NOX Emission Controls

A three-dimensional Lagrangian tropospheric chemistry modelis used toinvestigate the impact of human activities on the tropospheric distributionofozone and hydroxyl radicals. The model describes the behaviour of 50 speciesincluding methane, carbon monoxide, oxides of nitrogen, sulphur dioxide andnineorganic compounds emitted from human activities and a range of other sources.Thechemical mechanism involves about 100 chemical reactions of which 16 arephotochemical reactions whose diurnal dependence is treated in full. The modelutilises a five minute chemistry time step and a three hour advection timestepfor the 50,000 air parcels. Meteorological data for the winds, temperatures,clouds and so on are taken from the UK Meteorological Office global model for1994 onwards. The impacts of a 50% reduction in European NO_Xemissions onglobal ozone concentrations are assessed. Surface ozoneconcentrations decrease in summertime and rise in wintertime, but to differentextents.     

基于投影变换的线阵旋转扫描相机标定方法

针对线阵旋转扫描相机标定数据难以获取及模型解算不稳定的问题,提出了一种基于投影变换的线阵旋转扫描相机标定方法。首先构建了一种新的线阵旋转扫描相机成像模型,该模型可以根据相机旋转平台参数、线阵旋转扫描相机成像平面与其切平面的位置关系将旋转扫描图像投影为框幅式图像;然后根据构建出的成像模型,采用直接线性变换法和非线性优化方法进行相机标定和参数优化。试验结果表明,此方法简单易行,具有较高的精度。     

Under‐ice salinity and stable isotope distribution of Saroma‐ko Lagoon,Hokkaido, northern Japan

In winter, lakes and lagoons at high altitudes or high latitudes have interesting hydrological cycles that differ from those in other seasons or in other regions, because water surfaces are covered with ice. Hydrological balances of lakes and lagoons are complex dynamic systems, and to elucidate them, isotopic tracers of water have been used as effective tools along with observations of precipitation, evaporation, inflows, and outflows. Here, to understand hydrological processes during freezing periods in the brackish Saroma‐ko Lagoon, Hokkaido, northern Japan, we examined horizontal and vertical distributions of salinity and isotope compositions of lagoon water and ice in 2005 and 2006. Horizontal and vertical gradients of salinity and isotope compositions were observed from the river mouth to the sea channel, and factors determining these distributions were considered. The mixing of freshwater and seawater and a freezing effect were presumed to be factors in relationships between salinity and isotopes and in relationships between surface waters and ice just above the water. A simple box model for water balance was constructed based on these putative factors to reproduce the distributions of salinity and isotope compositions of surface waters and ice. An evaluation of the model revealed that this hydrological system is controlled primarily by horizontal advection of the epilimnion, freshwater influx, and the ice growth rate. Copyright © 2009 John Wiley & Sons, Ltd.     

Lateral tidal mixing in the Antarctic marginal seas

Tidal mixing plays an important role in the modification of dense water masses around the Antarctic continent. In addition to the vertical (diapycnal) mixing in the near-bottom layers, lateral mixing can also be of relevance in some areas. A numerical tide simulation shows that lateral tidal mixing is not uniformly distributed along the shelf break. In particular, strong mixing occurs all along the Ross Sea and Southern Weddell Sea shelf breaks, while other regions (e.g., the western Weddell Sea) are relatively quiet. The latter regions correspond surprisingly well to areas where indications for cross-shelf exchange of dense water masses have been found. The results suggest that lateral tidal mixing may account for the relatively small contribution of Ross Sea dense water masses to Antarctic Bottom Water.