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The prediction of ship stability during the early stages of the design process is very important from the point of a vessel's safety. Hence, in this study, a formula is presented to estimate cross curves of fishing vessels to predict initial stability at the preliminary design stage. For this purpose, 175 fishing vessel forms have been generated from Doust trawler hull series. The predictive technique is established by regression analysis of systematically varied fishing vessel series data. The mathematical model is constructed as a function of main design parameters such as length to beam ratio LWL/BWL, beam to draft ratio BWL/T, moulded depth to draft ratio D/T and block coefficient CB. This prediction is also used to determine the effect of specific hull form parameters and load conditions on the stability of the fishing vessel. Some basic considerations on how the proposed method can be applied to a new fishing vessel are presented. 相似文献
93.
南极冰川的流速在南极物质平衡研究中有着重要的作用。将SIFT算子的旋转参数引入传统的基于归一化互相关(NCC)的冰川流速提取方法,使其拥有旋转不变的特性。利用此方法,基于Landsat 8 OLI数据对东南极的极记录冰川流速进行了提取,并通过利用模拟影像和NASA发布的MEa SUREs冰川流速结果对该方法的精度进行了验证。结果表明,改进的NCC算法能够在冰川流速方向改变区域提取更多的流速信息,极记录冰川流速最大可达870m·a~(-1),提取结果与MEa SUREs结果相比,平均偏差为23.9 m·a~(-1)。 相似文献
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The hydrologic response of a catchment is sensitive to the morphology of the drainage network. Dimensions of bigger channels are usually well known, however, geometrical data for man-made ditches is often missing as there are many and small. Aerial LiDAR data offers the possibility to extract these small geometrical features. Analysing the three-dimensional point clouds directly will maintain the highest degree of information. A longitudinal and cross-sectional buffer were used to extract the cross-sectional profile points from the LiDAR point cloud. The profile was represented by spline functions fitted through the minimum envelop of the extracted points. The cross-sectional ditch profiles were classified for the presence of water and vegetation based on the normalized difference water index and the spatial characteristics of the points along the profile. The normalized difference water index was created using the RGB and intensity data coupled to the LiDAR points. The mean vertical deviation of 0.14 m found between the extracted and reference cross sections could mainly be attributed to the occurrence of water and partly to vegetation on the banks. In contrast to the cross-sectional area, the extracted width was not influenced by the environment (coefficient of determination R2 = 0.87). Water and vegetation influenced the extracted ditch characteristics, but the proposed method is still robust and therefore facilitates input data acquisition and improves accuracy of spatially explicit hydrological models. 相似文献
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This paper presents an experimental investigation on the seismic behavior of H‐beam to circular tubular column connections stiffened by an outer ring diaphragm. An innovative three‐dimensional (3D) connection subassembly testing system was first described. Specimens representative of two‐dimensional (2D) interior columns, 3D interior and exterior columns in a steel building frame were then tested to failure under unidirectional or bidirectional cyclic loads. Various specimen parameters are used to evaluate their effects on connection behavior. Test results indicate significantly different failure modes for 2D and 3D weak panel connections, with panel shear buckling and local distortion of outer diaphragm occurring only for 3D connections. The weak beam connections unexceptionally exhibited final fracture at the junction between diaphragm and beam flange. In contrast with weak beam connections, weak panel connections demonstrated better seismic performance and ductility. As a result, a seismic design philosophy considering panel zone yielding before beam flexural yielding is proposed. Based on experiment observations, small diaphragm width and simplified fillet welding are found to be feasible especially for weak beam connections, improving architectural appearance and facilitating construction. Strength evaluations also suggest that current AIJ design provisions may be appropriate when applied to panel zones in 3D connections. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
Priyanka Bangalore Nagaraj Mohan Kumar Mandalagiri Subbarayappa Vouillamoz Jean-Michel Johan Hoareau 《水文研究》2021,35(10):e14395
Estimation of hydraulic parameters is essential to understand the interaction between groundwater flow and seawater intrusion. Though several studies have addressed hydraulic parameter estimation, based on pumping tests as well as geophysical methods, not many studies have addressed the problem with clayey formations being present. In this study, a methodology is proposed to estimate anisotropic hydraulic conductivity and porosity values for the coastal aquifer with unconsolidated formations. For this purpose, the one-dimensional resistivity of the aquifer and the groundwater conductivity data are used to estimate porosity at discrete points. The hydraulic conductivity values are estimated by its mutual dependence with porosity and petrophysical parameters. From these estimated values, the bilinear relationship between hydraulic conductivity and aquifer resistivity is established based on the clay content of the sampled formation. The methodology is applied on a coastal aquifer along with the coastal Karnataka, India, which has significant clayey formations embedded in unconsolidated rock. The estimation of hydraulic conductivity values from the established correlations has a correlation coefficient of 0.83 with pumping test data, indicating good reliability of the methodology. The established correlations also enable the estimation of horizontal hydraulic conductivity on two-dimensional resistivity sections, which was not addressed by earlier studies. The inventive approach of using the established bilinear correlations at one-dimensional to two-dimensional resistivity sections is verified by the comparison method. The horizontal hydraulic conductivity agrees with previous findings from inverse modelling. Additionally, this study provides critical insights into the estimation of vertical hydraulic conductivity and an equation is formulated which relates vertical hydraulic conductivity with horizontal. Based on the approach presented, the anisotropic hydraulic conductivity of any type aquifer with embedded clayey formations can be estimated. The anisotropic hydraulic conductivity has the potential to be used as an important input to the groundwater models. 相似文献
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100.