Research on Analytical Method of Fatigue Characteristics of Soft Yoke Mooring System Based on Full-Scale Measurement

By focusing on the vulnerability of the structure of marine equipments, together with considering the randomness of meta-ocean load in statistics, a kind of analytical method of fatigue characteristics of marine structure based on full- scale and actual measurement of prototype is proposed. On the basis of short-term field measurement results of structural response, research is carried out on the fatigue analysis of hinge joints at the upper part of the Soft Yoke single point Mooring System （SYMS） by simultaneously monitoring the environmental load and considering the design criteria of offshore structure. Through analysis of finite element modeling, the time-histories of typical stress response are obtained, and then the assessment of fatigue damage at key hinge joints is conducted. The simulation results indicate that the proposed method can accurately analyze the fatigue damage of offshore engineering structure caused by the effect of wave load. The present analytical method of fatigue characteristics can be extended on other offshore engineering structures subjected to meta-ocean load.

Scaled radar cross section measurement method for lossy targets via dynamically matching reflection coefficients in THz band

In the terahertz band,the dispersive characteristic of dielectric material is one of the major problems in the scaled radar cross section(RCS)measurement,which is inconsistent with the electrodynamics similitude deducted according to the Maxwell’s equations.Based on the high-frequency estimation method of physical optics(PO),a scaled RCS measurement method for lossy objects is proposed through dynamically matching the reflection coefficients according to the distribution of the object facets.Simulations of the model of SLICY are conducted,and the inversed RCS of the lossy prototype is obtained using the proposed method.Comparing the inversed RCS with the calculated results,the validity of the proposed method is demonstrated.The proposed method provides an effective solution to the scaled RCS measurement for lossy objects in the THz band.

Numerical simulation and parameter optimization of Coriolis force scale measurement process based on DEM

The Coriolis force method is a recently developed and highly regarded direct measurement technique that enables high-precision measurement of bulk materials.The operational parameters and variations thereof directly influence the measurement accuracy of the equipment.In this study,a measurement correction coefficient is introduced to improve the calculation method for mass flow rate of the materials.The DEM is employed to simulate the motion of particle groups within the Coriolis force scale under different parameters,and the effects of various structural and operational parameters on the measurement results are compared.The research findings indicate that a lower rotational speed leads to more stable instantaneous measurement results,although the measurement error is relatively large.When the rotational speed exceeds 300 rpm,the measurement error remains within 15%.For materials with a radius of 1–2 mm,the variation range of precision error is approximately 0.4%.Among the structural parameters,the radius of the measurement wheel has the most significant impact on the measurement results,wherein a larger measurement wheel radius corresponds to a smaller measurement error.The horizontal angle of the blades follows as the next influential parameter,with a clockwise rotation and a horizontal angle of 30°resulting in a measurement error below 2%.

The design philosophy and bridge＇s technical innovation of Hong Kong- Zhuhai-Macao Bridge

This article introduces the project overview, construction goal and design philosophy of Hong Kong- Zhuhai-Macao Bridge. Based on large scale, factory production, standardization and assemble line, the innova- tive concept is taken as the general principle for design with the emphasis on description of the new material, new technology, new construction method and new equipment used in the design. The application of innovative technology has provided a solid foundation and favorable guarantee for project quality and design service

Three-Dimensional Thermo-Elastic-Plastic Finite Element Method Modeling for Predicting Weld-Induced Residual Stresses and Distortions in Steel Stiffened-Plate Structures

The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.

Computational multiscale methods for granular materials

The fine-scale heterogeneity of granular material is characterized by its polydisperse microstructure with randomness and no periodicity. To predict the mechanical response of the material as the microstructure evolves, it is demonstrated to develop computational multiscale methods using discrete particle assembly-Cosserat continuum modeling in micro- and macro- scales,respectively. The computational homogenization method and the bridge scale method along the concurrent scale linking approach are briefly introduced. Based on the weak form of the Hu-Washizu variational principle, the mixed finite element procedure of gradient Cosserat continuum in the frame of the second-order homogenization scheme is developed. The meso-mechanically informed anisotropic damage of effective Cosserat continuum is characterized and identified and the microscopic mechanisms of macroscopic damage phenomenon are revealed. c 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi： 10.1063/2.1301101]

大口径管道烟气流量测量方法综述

2021年全国碳市场开启,为了提高碳交易的准确性,需要做到碳排放数据的可测量、可报告、可核查。在这种背景下,烟气在线监测系统作为一种碳排放量化方法得到了重视。其有效工作的基础是烟气流量的准确测量。但电厂烟囱尺寸大,内部烟气流动特性复杂,烟气流量难以准确测量。重点分析了皮托管流量计和气体超声波流量计在大口径管道流量测量中的研究现状,详细介绍了大口径管道气体流量测量技术。此外,还介绍了一种独立的流量测量方法—示踪气体稀释法,探讨其发展现状及作为一种流量标定方法的潜力。

飞机装配准确度快速评价方法及典型应用

飞机大部件数字化对接中的装配准确度是指部件气动力外形准确度、部件内部组合件及零件的位置准确度和部件间相对位置的准确度。数字化测量模型的构建及数据的准确分析为装配准确度的评价提供了高效、可靠的新方法。在数字化测量环境下,通过构建飞机测量模型,将飞机装配相对位置准确度评价转化为计算飞机装配特征点之间的相对位置关系,从而实现孔、槽、型面、边缘等相对位置准确度关系评价。同时,基于工程实际对该方法的应用进行了分析。

基于显微镜标尺法的碳纤维复合材料孔隙率测量不确定度评定

使用显微镜标尺法对碳纤维复合材料孔隙率试验结果进行测量不确定度评定,对不确定度来源进行分析,对各个不确定度分量进行计算。结果表明:影响不确定度的主要因素是孔隙格子数的测量重复性。

差值换算法在端头装配工艺中的研究

一些航天飞行器的前舱为端头和舱体组合结构,无防护层试装后分解,通过分别粘接防护层再次进行装配,装配中需保证对接面台阶值符合要求。针对端头已粘接防护层但舱体未粘接防护层,装配中无法保证对接面台阶值的问题,根据端头结构和扫描精测数据,建立了端头坐标轴,设计了测量数据差值换算法和台阶值判断合格的方法,在舱体装配替代端头测量台阶值,计算得到原端头理论台阶值,进而可以进行合格性指标判断和制定修磨措施,解决了非常规工序下端头装配中如何保证台阶值的问题。通过端头装配试验验证了方法有效,可以保证对接面台阶值符合要求,并且提出了本研究分别在产品研制阶段、批产阶段、类似结构产品装配中的推广价值。

TG328A光电分析天平的横梁不等臂检测与调修

TG328A光电分析天平属于等臂杠杆天平,即支点位于力点和重点连线的正中间。由于理论上要求左臂与右臂需完全相等,但实际使用中无法做到。因此,天平检定员、修理人员和使用者需具有检测天平的不等臂程度及相应的调修能力。

Stressed portfolio optimization with semiparametric method

Tail risk is a classic topic in stressed portfolio optimization to treat unprecedented risks,while the traditional mean–variance approach may fail to perform well.This study proposes an innovative semiparametric method consisting of two modeling components:the nonparametric estimation and copula method for each marginal distribution of the portfolio and their joint distribution,respectively.We then focus on the optimal weights of the stressed portfolio and its optimal scale beyond the Gaussian restriction.Empirical studies include statistical estimation for the semiparametric method,risk measure minimization for optimal weights,and value measure maximization for the optimal scale to enlarge the investment.From the outputs of short-term and long-term data analysis,optimal stressed portfolios demonstrate the advantages of model flexibility to account for tail risk over the traditional mean–variance method.

Re-measuring International Short-term Capital Flow into China with Varying Methods

This paper.fi＇rst conducts a systematic review of domestic and foreign scholars＇ approaches to predicting short-term capital flows, then employs a combination of both direct and indirect methods to carry out its analysis. Three kinds of indicators, both specific and general, are applied in both methods. Thorough consideration is given to short-term international capital inflow from trade, other current account items, capital account, and errors and omissions, as well as other channels through which short term capital might accrue to a nation＇s balance. Based on a comprehensive comparison of year-on-year data, this paper also estimates monthly data using a simplified, indirect calculation approach. Estimates show that, despite a degree of difference in results between methods, most estimates are highly consistent for a given period. Based on monthly estimates, we conclude that turbulence in international financial markets （i.e., the United States subprime mortgage crisis and the European sovereign debt crisis） has had a major impact on China ＇s short-term capital flow.

房地产开发企业视角下发展装配式建筑意愿的影响因素研究

近年来,在建筑业的转型升级背景下,出现了政府积极鼓励房地产企业开发装配式建筑,而房地产企业开发的积极性不高的局面,严重阻碍了装配式建筑的发展。通过对房地产企业开发装配式建筑的相关文献研究,结合专家问卷调查的结果从房地产企业开发意愿因素的成本、政策、市场和技术四个方面选取了九个影响因素,通过运用AHP法对各因素的相对影响程度进行测算,分析出四种主要的影响因素。基于对各因素相对影响程度的测算结果及相关分析提出相对应的优化措施来提高房地产企业发展装配式的意愿。

面向装配对接的双视觉测量试验系统优化标定方法

针对航空航天、轨道交通零部件装配对接测量与定位过程,为解决测量视场范围大、多种测量设备组合使用步骤烦琐等问题,对面向装配对接的双视觉测量系统标定方法进行了研究。通过构建双视觉测量系统模型,分析系统间各相机参数的关系,在单个双目系统中引入闭环约束,结合LM算法对单个双目系统中的相机参数进行优化,另外采用改进的EPnP算法对双视觉系统进行标定,并结合自行设计的双面一维靶标完成了双视觉系统的全局标定和坐标转换。模拟对接试验的结果表明,该优化标定算法在精度上优于传统算法,并在使用过程中简化测量步骤,提高测量效率。

立板机动臂翻转结构优化设计与研究

针对现今装配式建筑预制墙板的安装问题,设计了一种新型墙板立板机,通过动臂翻转机构实现末端抓取装置俯仰位姿调节,进而实现预制墙板定位安装作业。其中,动臂翻转机构属于液动连杆机构,通过力学仿真分析发现,动臂起落机构属于主要承力机构,驱动油缸负载最大。为此,针对动臂起落机构建立尺度优化模型,以驱动油缸的最大负载最小为目标函数,基于复合形法优化算法求得动臂翻转机构最优尺度参数,优化后驱动油缸最大负载降低36%左右,驱动油缸性能显著提升;通过Creo软件建立虚拟样机,进行了刚体动力学仿真分析,验证了机构尺度优化模型的可行性;最后,进行样机研制及其施工试验,动臂翻转机构工作性能符合设计要求。

船体冰载荷的反演确定法

由于船体结构受到的外部载荷及载荷承受能力决定了船体结构的损伤程度,因此船舶在冰区海域航行的安全性与其受到的冰载荷直接相关。本文根据极地科考补给船S.A. Agulhas II的原型测量数据,给出了两种艉肩部冰载荷的反演确定方法:一种为根据试验建立的影响系数矩阵法来确定肋骨处受到的冰载荷,另一种为利用Tikhonov正则化建立的三种离散方式来确定外板区域受到的冰载荷。计算结果表明,这两种方法均能克服数据处理过程中的病态性并得到船体结构的冰载荷。

不同比例尺下单波束测深数据的插值方法精度分析

以某内河航道局部航段作为试验区域,对不同比例尺单波束测深数据采用空间插值方法进行格网化,同时与多波束测深系统的实测数据进行对比,统计插值方法精度特征指标。结果表明,不同比例尺水深源数据密度对空间插值方法影响显著,随着测量比例尺不断减小,空间插值方法的内插精度下降明显;对于比例尺大于1:500的水深数据源,克里金插值法、最小曲率法和线性插值三角网法3种插值方法的精度基本相当,反距离加权插值法不满足插值精度要求;综合考虑内插精度特征参数,在类似区域建议采用线性插值三角网法。

Modeling, measurement and simulation of the disturbance torque generated via solar array drive assembly

The disturbance torque generated via solar array drive assembly(SADA) can significantly degrade the key performance of satellite.The discussed SADA is composed of a two-phase hybrid stepping motor and a set of two-stage straight gear reducer. Firstly, the vibration equation of the two-phase hybrid stepping motor is established via simplifying and linearizing the electromagnetic torque.Secondly, based on the vibration equation established, the disturbance torque model of SADA is created via force analysis and force system simplification. Thirdly, for precisely ground measuring the disturbance torque aroused by SADA, a measurement system,including a strain micro-vibrations measurement platform(SMMP) and a set of gravity unloading device(GUD), is designed.Fourthly, the proposed disturbance torque model is validated by measuring and simulating the disturbance torque produced via SADA driving rigid load through GUD. The results indicate that, the proposed disturbance torque model holds the ability to describe the disturbance torque caused by SADA with high precision. Finally, the disturbance torque emitted by SADA driving a flexible load, designed to simulate solar array, is modeled and simulated via using fixed-interface mode synthesis method(FIMSM). All the conclusions drawn from this article do have a meaningful help for studying the disturbance torque produced by SADA driving solar array on orbit.

基于长尺度测量法的纯电动客车暗电流系统性分析与验证

为了准确评估纯电动客车的暗电流,避免车辆因蓄电池电量不足无法起动,选取2款纯电动客车,对其车载电气设备的供电模式及整车暗电流进行系统性分析,在总结常规暗电流测量方法的基础上提出长尺度测量法,采用电功率测试仪及测量模块设计检测方案记录暗电流并完成实车测试。理论分析与试验数据对比结果表明:长尺度测量法能够准确评估纯电动客车暗电流并将其控制在合理范围内,进而计算车辆的停运时长。