Shaking table tests on dome‐roof adobe houses

This paper presents the results of an experimental work in order to evaluate the performance of a novel proposed retrofitting technique on a typical dome‐roof adobe building by shaking table tests. For this purpose, two specimens, scaled 2:3, were subjected to a total of nine shaking table tests. The unretrofitted specimen, constructed by common practice, is designed to evaluate seismic performance and vulnerability of dome‐roof adobe houses. The retrofitted specimen, exactly duplicating the first specimen, is retrofitted based on the results obtained from unretrofitted specimen tests, and the improvement in seismic behavior of the structure is investigated. Zarand earthquake (2005) Chatrood Station is selected as the input ground motion that was applied consecutively at 25, 100, 125, 150 and 175% of the design‐level excitation. At 125% excitation level, the roof of the unretofitted specimen collapsed due to the walls' out‐of‐plane action and imbalanced forces. The retrofitting elements consist of eight horizontal steel rods drilled into the walls, passed through the specimen and bolted on the opposite wall surfaces. To improve walls in‐plane seismic performance, welded steel mesh without using mortar, covered less than half area of walls on the external face of the walls, is used. In addition to strain gauges for recording steel rod responses, several instrumentations including acceleration and displacement transducers are implemented to capture response time histories of different parts of the specimens. The corresponding full‐scaled retrofitted prototype tolerated peak acceleration of 0.62 g almost without any serious damage. Copyright © 2016 John Wiley & Sons, Ltd.     

基于非结构双网格的2D RMT双参数同步反演研究

Radio-magnetotelluric(RMT)是以无线电发射机为信号源的一种地球物理勘探方法,近年来被广泛应用于数米至数十米内的近地表工程和环境地球物理勘探.目前,各类电磁资料的反演均是以寻求满足目标拟合差的地下介质电阻率分布为目的.然而,对于勘探频率为10~300kHz的RMT数据,由介电常数所引起的波动场在总场中的比例可达20%以上,在这种情况下,忽略介电常数,仅通过电阻率参数的反演来进行数据拟合势必降低反演资料解释的准确性.为解决这一问题,本文研究了基于电阻率-介电常数的双参数同步反演算法.构建了一个全新的双参数目标函数,并推导了双参数反演迭代方程组;通过灵敏度分析,研究了电阻率和介电常数对正演响应的影响,并据此提出相对电导率的概念,统一了反演参数的灵敏度;通过理论模型分析了参考频率、双参数正则化因子对反演结果的影响,并给出了一般性的参数优选方案.此外,为了能够灵活处理复杂地形,本文采用非结构的正反演双网格进行模型离散,并通过局部加密技术保证反演的速度和精度.最后,对一带地形的理论模型分别进行了单参数和双参数反演,结果表明单参数反演无法正确反映出地电信息,而双参数反演能够准确得到异常的分布,验证了本文所开发的双参数反演程序的有效性.     

A body-force model for waterjet pump simulation

The role of waterjet pump is to generate thrust by increasing the flow head. Details of the flow inside waterjet pump are important when pump performance is of the main interest. However, in waterjet self-propulsion, pump induced effects are of the main interest rather than the details of the flow inside the pump. This permits simplification of pump models when using numerical methods for simulating the flow. In order to find a robust and yet accurate pump model suitable for Computational Fluid Dynamics based methods, models of different sophistication level are studied in this paper. First, a Sliding Mesh approach, which is capable of capturing the flow details, is validated against a set of cavitation tunnel measurements. Then a series of simpler models, i.e. Moving Reference Frame technique and three different body-force models, are studied and their results are compared to the ones obtained from the Sliding Mesh approach. The results indicate that one of the body-force models which takes the guide vanes as well as the impeller induced flow swirl into account has the best compromise between the robustness and accuracy among the investigated pump models.     

地球空间网格编码技术分析

地球空间网格是将地球空间区域剖分成不同尺度单元的空间参考系统。网格编码利用地理空间位置的结构化索引表达技术,将代码分配给地球空间网格系统的每个网格单元,实现网格位置的统一标识。对照统一规则递归剖分形成的多层次、多分辨率全球的地球空间网格系统编码的要求,本文在分析当前地球空间索引标识技术方法的基础上,探讨地球空间网格编码方案,以实现地球空间网格单元的统一标识,并可通过代码描述网格单元空间位置,反映网格单元间的空间关系。     

一种倾斜摄影模型精细融合方法

现有三维模型融合方法多采用对原有三角面片顶点重新构网的方式,容易导致原有模型几何特征丢失及纹理失真等。本文针对倾斜摄影模型自身特点,提出了一种模型精细融合方法。首先,以一个模型作为中心模型,并以另一模型与中心模型外轮廓的空间关系计算融合区域;然后,以中心模型外轮廓作为约束,对原始模型三角面片进行精细剖分;最后,基于精细剖分的三角面片进行纹理坐标的插值计算。以实际倾斜摄影数据进行试验的结果表明,本文方法融合后的网格模型拓扑结构正确,融合边界不存在漏洞、裂缝和错位等情况,而且纹理过渡自然,颜色无明显差异。     

基于裤式拖网法的虾拖网网囊网目选择性试验与分析

为研究虾拖网网囊网目对主要渔获种类的选择性,于2017年9月在南海区采用裤式拖网法进行选择性试验。在SELECT模型框架下,使用极似然估算法,结合单网次和联合网次的数据,同时考虑网次间差异,估算网囊对主要渔获种类的平均选择性。共完成14网次作业,其中对照网囊之间的渔获性能比较试验4次,试验网囊的选择性试验10次。研究表明:对照网囊的位置对其渔获性能无显著影响;试验网囊对刀额新对虾(Metapenaeus ensis)的网次50%选择体长(L 50)为78.84~92.09 mm,平均为82.38 mm,网次选择范围(SR)为5.01~11.32 mm,平均为6.39 mm,网次相对作业强度(p)为0.44~0.71,平均为0.52;试验网囊对黄斑蓝子鱼(Siganus oramin)的网次L 50为59.20~76.80 mm,平均为71.17 mm,网次SR为5.30~16.87 mm,平均为14.20 mm,网次p为0.43~0.71,平均为0.63。试验网囊对刀额新对虾的网次和平均L 50值均大于其首次性成熟体长(80 mm),可见试验网囊对刀额新对虾的资源利用是合理的。本试验的裤式拖网法和数据处理方法可为今后拖网选择性研究提供参考。     

基于VOF模型的浮式消波海流机性能优化

针对浮式消波海流机样机测试时出现的问题,对其吃水深度线和叶片安装角度进行优化。根据装置结构特点,用Gambit建立了装置横截面的二维网格模型。根据浮式消波海流机实际工作环境,利用Fluent流体仿真软件,使用VOF(volume of fluid)两相流模型,分配空气相与液态水相在流域中的不同比例,来确定不同的吃水深度线。并且结合k-epsilon紊流模型建立模拟仿真环境。先对3种水线进行仿真分析,然后进行实验验证。通过分析对比装置的3种不同吃水深度线的模拟与实验结果,得到装置的最优吃水深度线为1/3水线。基于最优吃水深度线,分别对叶片的4种安装角度在相同的仿真环境中进行模拟仿真。利用仿真得到的扭矩数据,计算扭矩系数、功率系数,分析对比仿真数据以及仿真过程中扭矩趋势图得出4种叶片安装角度的最优角度是90°。吃水深度线决定了装置的消波能力,并且为叶片获能提供条件,叶片安装角度直接影响着装置的获能效率,所以最优的吃水深度线和叶片安装角度对海流机的消波能力和获能效率具有重要意义。     

电阻率法探测黄土滑坡滑动面(带)的试验研究

根据滑体与滑床土的结构差异特性,其中电阻率特性也有显著不同,利用WDJD-1型多功能数字直流激电仪和改进的探测电极装置,分别在滑坡后壁原状黄土地层、探槽及钻孔中测试黄土滑坡滑面上下各层土的电阻率值。试验结果显示电阻率测试曲线在滑动带位置出现异常跃变现象,而曲线在未滑动过的黄土地层之间变化差异不明显。这一异常突变特性,在实践中可作为鉴别滑动面位置的特征标志。该探测方法充分利用现有的勘探技术条件,操作简便,试验结果直观,可在黄土滑坡勘察实践中推广使用。     

长江口自适应网格的构造与水流和泥沙冲淤的数值模拟的初步研究

随着沿海经济带的开发利用,河口海岸动力学问题,如航道淤积、河口演变、港湾建设及污染物的排放和扩散等,日益引起人们的重视.数值模拟方法是研究这些海岸环境问题的理想工具之一,但由于河口区域的海岸线和河岸线的形状非常复杂,加上众多的岛屿,给模式网格的划分造成很大的困难.为此,我们将自适应网格的生成方法应用于河口港湾的数值模拟研究,以长江口和杭州湾的水动力学模拟为例,该法较好地克服了均匀网格拟合边界的困难,得到了较合理的计算结果.