Affected by the outbreak of COVID-2019,the international shipping market oscillated down,and the volume of new shipbuilding orders decreased significantly worldwide.China's shipbuilding completion and hand-held sh...Affected by the outbreak of COVID-2019,the international shipping market oscillated down,and the volume of new shipbuilding orders decreased significantly worldwide.China's shipbuilding completion and hand-held ship orders decreased year-on-year(YOY),and due to the lower base in the same period last year,China's new ship orders increased YOY.Major economic indicators such as the total industrial output value of key monitored enterprises declined YOY.展开更多
Based on the second order hydroelasticity theory of ships, the numerical methods and the calculated results of the non-linear hydroelastic responses of a ship traveling in rough seas were investigated. The non-linear ...Based on the second order hydroelasticity theory of ships, the numerical methods and the calculated results of the non-linear hydroelastic responses of a ship traveling in rough seas were investigated. The non-linear hydrodynamic actions induced by the rigid body rotations and the variations of instantaneous wetted surface area were included in the second order analysis. The first order wave potentials and responses, which are sure to make the major contributions to the second order hydrodynamic actions, were obtained by employing the translating and pulsating source Green function and the Kelvin steady wave flow solution based on the linear three-dimensional hydroelasticity theory. The influences of the forward speed and the steady wave flow on the responses, and the differences of the predicted non-linear responses were illustrated by the numerical examples of a SWATH ship traveling with forward speed of 12 kn in irregular waves.展开更多
A three-dimensional high-order panel method based on non-uniform rational B-spline(NURBS) is developed for predicting the hydrodynamic interaction forces on a moored ship induced by a passing ship in shallow water. An...A three-dimensional high-order panel method based on non-uniform rational B-spline(NURBS) is developed for predicting the hydrodynamic interaction forces on a moored ship induced by a passing ship in shallow water. An NURBS surface is used to precisely represent the hull geometry. Velocity potential on the hull surface is described by B-spline after the source density distribution on the boundary surface is determined. A collocation approach is applied to the boundary integral equation discretization. Under the assumption of low passing speed, the effect of free surface elevation is neglected in the numerical calculation, and infinite image method is used to deal with the finite water depth effect. The time stepping method is used to solve the velocity potential at each time step. Detailed convergence study with respect to time step, panel size and Green function is undertaken. The present results of hydrodynamic forces are compared with those obtained by slender-body theory to show the validity of the proposed numerical method. Calculations are conducted for different water depths and lateral distances between ships, and the detail results are presented to demonstrate the effects of these factors.展开更多
乾隆四十二年《各国夷船入口货总簿》为笔者在英国利兹大学布劳瑟顿图书馆发现的清代广州贸易中文档案。现将档案全文与英国东印度公司档案BL:IOR/G/12/62,Imports Canton 1777进行勘比,进而对上述中文档案的有关史料进行考证和笺注。...乾隆四十二年《各国夷船入口货总簿》为笔者在英国利兹大学布劳瑟顿图书馆发现的清代广州贸易中文档案。现将档案全文与英国东印度公司档案BL:IOR/G/12/62,Imports Canton 1777进行勘比,进而对上述中文档案的有关史料进行考证和笺注。经过比对,笔者推断乾隆四十二年《各国夷船入口货总簿》与英国东印度公司档案中公布的1777年“各欧洲国家进口广州货物记录”均系抄自粤海关的原始数据,二者有共同来源。此外,这份中文档案不仅能完整反映乾隆四十二年广州进口贸易的具体情况,还能为研究西文商品名称的汉译提供绝佳参照。展开更多
针对短相干积累时间(coherent integration time,CIT)引起的多普勒分辨率低,无法从强大海杂波中检测出舰船目标的问题,提出了基于高阶奇异值分解(higher order singular value decomposition,HOSVD)的海杂波抑制算法。首先利用相邻单元...针对短相干积累时间(coherent integration time,CIT)引起的多普勒分辨率低,无法从强大海杂波中检测出舰船目标的问题,提出了基于高阶奇异值分解(higher order singular value decomposition,HOSVD)的海杂波抑制算法。首先利用相邻单元内海杂波的相干性,将毗邻距离单元和方位单元的多脉冲接收数据应用三阶张量表示,然后采用HOSVD方法求解三阶张量的海杂波子空间和目标子空间的投影矩阵,最后利用投影矩阵将三阶张量映射到目标子空间以抑制海杂波。该方法与现有子空间类海杂波抑制方法相比,提高了信干噪比(signal to clutter plus noise ratio,SCNR)和峰值旁瓣电平比(peak sidelobe level ratio,PSLR),解决了目标谱峰偏移问题。展开更多
文摘Affected by the outbreak of COVID-2019,the international shipping market oscillated down,and the volume of new shipbuilding orders decreased significantly worldwide.China's shipbuilding completion and hand-held ship orders decreased year-on-year(YOY),and due to the lower base in the same period last year,China's new ship orders increased YOY.Major economic indicators such as the total industrial output value of key monitored enterprises declined YOY.
文摘Based on the second order hydroelasticity theory of ships, the numerical methods and the calculated results of the non-linear hydroelastic responses of a ship traveling in rough seas were investigated. The non-linear hydrodynamic actions induced by the rigid body rotations and the variations of instantaneous wetted surface area were included in the second order analysis. The first order wave potentials and responses, which are sure to make the major contributions to the second order hydrodynamic actions, were obtained by employing the translating and pulsating source Green function and the Kelvin steady wave flow solution based on the linear three-dimensional hydroelasticity theory. The influences of the forward speed and the steady wave flow on the responses, and the differences of the predicted non-linear responses were illustrated by the numerical examples of a SWATH ship traveling with forward speed of 12 kn in irregular waves.
基金the National Natural Science Foundation of China(Nos.51179019 and 51309152)
文摘A three-dimensional high-order panel method based on non-uniform rational B-spline(NURBS) is developed for predicting the hydrodynamic interaction forces on a moored ship induced by a passing ship in shallow water. An NURBS surface is used to precisely represent the hull geometry. Velocity potential on the hull surface is described by B-spline after the source density distribution on the boundary surface is determined. A collocation approach is applied to the boundary integral equation discretization. Under the assumption of low passing speed, the effect of free surface elevation is neglected in the numerical calculation, and infinite image method is used to deal with the finite water depth effect. The time stepping method is used to solve the velocity potential at each time step. Detailed convergence study with respect to time step, panel size and Green function is undertaken. The present results of hydrodynamic forces are compared with those obtained by slender-body theory to show the validity of the proposed numerical method. Calculations are conducted for different water depths and lateral distances between ships, and the detail results are presented to demonstrate the effects of these factors.
文摘乾隆四十二年《各国夷船入口货总簿》为笔者在英国利兹大学布劳瑟顿图书馆发现的清代广州贸易中文档案。现将档案全文与英国东印度公司档案BL:IOR/G/12/62,Imports Canton 1777进行勘比,进而对上述中文档案的有关史料进行考证和笺注。经过比对,笔者推断乾隆四十二年《各国夷船入口货总簿》与英国东印度公司档案中公布的1777年“各欧洲国家进口广州货物记录”均系抄自粤海关的原始数据,二者有共同来源。此外,这份中文档案不仅能完整反映乾隆四十二年广州进口贸易的具体情况,还能为研究西文商品名称的汉译提供绝佳参照。
文摘针对短相干积累时间(coherent integration time,CIT)引起的多普勒分辨率低,无法从强大海杂波中检测出舰船目标的问题,提出了基于高阶奇异值分解(higher order singular value decomposition,HOSVD)的海杂波抑制算法。首先利用相邻单元内海杂波的相干性,将毗邻距离单元和方位单元的多脉冲接收数据应用三阶张量表示,然后采用HOSVD方法求解三阶张量的海杂波子空间和目标子空间的投影矩阵,最后利用投影矩阵将三阶张量映射到目标子空间以抑制海杂波。该方法与现有子空间类海杂波抑制方法相比,提高了信干噪比(signal to clutter plus noise ratio,SCNR)和峰值旁瓣电平比(peak sidelobe level ratio,PSLR),解决了目标谱峰偏移问题。
