造船项目贷款风险识别与评估方法研究

由于影响项目贷款风险的各要素之间有主次、轻重之分,评价的主体和客体也具有模糊性,因而本文试图运用模糊数学方法研究贷款风险识别评估问题,提出了基于Fuzzy集合论和AHP结合的模糊综合评判法,并引用造船项目贷款案例进行实证分析.     

VIV response of a flexible cylinder with varied coverage by buoyancy elements and helical strakes

Many significant engineering challenges have emerged as the petroleum industry has moved their field development and production activities into increasingly deeper water depths. The design of deepwater marine risers presents the combined challenges to minimize top tensioning requirements, mitigate any flow-induced vibrations, and if possible to increase the expected fatigue life of these slender structural members. As part of the design process to achieve these goals external buoyancy modules and strakes have been employed. To gain insight into the complex multi-mode response behavior a recent experimental study was performed and the analysis of selected data sets is presented. In the experiments a horizontal cylinder with a length to diameter ratio of 263 was fitted with a variety of strake and buoyancy element configurations. The models were towed at uniform speeds ranging from 0.4 to 2.0 m/s and fiber optic strain gages were used to measure both in-line and cross-flow strain response. The resulting time series information was processed utilizing the method of time domain decomposition formulated for strain data input and the introduction of modal assurance criterion to resolve the modal strain information that included frequency, mode shape, and critical damping ratio information. The pre-tensioned cylinder without appendages was used as a base case and the results were basically consistent with expectations. In the case of 0.8 m/s low-tension test, multiple closely spaced non-overlapping peaks were observed in both in-line and cross-flow directions and were identified as being of the same mode with mode shapes distorted away from purely sinusoidal behavior. The test data for the 100% coverage by helical stakes demonstrated the effectiveness of that suppression device over the range of current velocities investigated. The most interesting case was that of a staggered combination of helical strakes and buoyancy element whose total for each type of coverage was equal. This effective asymmetric VIV suppression approach is presented and discussed in detail.     

长江电子航道图航道要素脱密处理方法

长江电子航道图中涵盖了多种要素及其属性,是指导船舶安全航行的必备重要信息.但根据相关保密法律法规中的规定,部分要素及其属性属于涉密内容,不能对外公开.为了既保证数据的规范性又保证数据的安全性,在充分分析相关保密法律法规和航道要素及其属性的基础上,对长江电子航道图航道要素密级及脱密处理方法进行研究,规定涉密要素及其属性的取舍情况.在保证对外发布数据安全性的同时,确保长江电子航道图能够正确指导船舶用户安全航行.     

我国现代玩具设计融入传统吉祥图案的思考

中国传统吉祥图案是中华文化的重要组成部分,应用领域非常广泛,包括现代玩具设计。文章从现代玩具设计的特点出发,探讨现代玩具设计融入传统文化符号的必要性和可行性,同时以传统吉祥图案为案例,结合吉祥图案中的动物图案元素,分析现代玩具设计如何融入这些文化符号,希望对我国的现代玩具设计产生一定的启示。     

Structural behavior and design of high-strength steel welded tubular connections under extreme loading

The present work is motivated by the increasing need for cost-efficient solutions in offshore structural systems for wind energy production and for improvement of their structural performance. The structural behavior and design of high-strength steel welded tubular connections (yield strength higher than 700 MPa) subjected to monotonic and strong cyclic loading is investigated. In the first part of the paper, an experimental investigation is presented on high-strength steel tubular X-joints subjected to monotonic and cyclic loading far beyond the elastic limit of the material, leading to weld fracture. Two grades of weld metal material are employed in the welding process of the specimens. The experimental results indicate that the weld material grade has a significant influence on the deformation capacity of the welded connection under monotonic loading conditions, and its low-cycle fatigue life. The experimental procedure is simulated using advanced finite element models, elucidating several features of joint behavior and complementing the experimental results. Overall, a good agreement is found between numerical simulations and experimental results, in terms of both global response and local strains at the vicinity of the welds. Furthermore, the structural performance of the welded tubular joints under consideration is assessed using available design methodologies in terms of both ultimate strength and low-cycle fatigue resistance, in an attempt to validate an efficient design methodology for low-cycle fatigue. The results from this research effort are aimed at developing the necessary background for the possible use of high-strength steel in tubular steel lattice structures, particularly in offshore platforms for renewable energy production. They can also be used as a basis for the possible amendment of relevant design specifications and recommendations for including special provisions for high-strength steel structural systems.     

基于改进EEMD和WVD联合时频分析的车轮多边形状态识别方法

为了准确识别高速列车车轮多边形状态以及磨耗幅值,提出了一种改进的聚合经验模态分解(EEMD)与魏格纳-威尔分布(WVD)相结合的随机振动信号联合时频分析方法;利用相关系数法和频谱分析来评估筛选轴箱振动加速度信号经EEMD分解后的变量,然后进行WVD计算,在保持WVD高时频分辨率的同时可有效抑制交叉干扰项;应用该方法分析了周期性车轮多边形磨耗与现场实测随机车轮多边形磨耗引起的轴箱振动加速度信号。研究结果表明：利用EEMD-WVD二维时频谱的主频率可识别车轮多边形状态,利用EEMD-WVD三维时频能量谱的能量幅值分布可评估车轮多边形磨耗幅值,最大误差为0.3%;将改进EEMD和WVD联合时频分析方法的识别结果与短时傅里叶变换、小波分解、WVD传统时频分析方法进行对比,表明此方法应用时无需改变任何参数,自适应强,保留了WVD高时频分辨率的特点,而且可有效抑制EEMD产生的模态混叠现象和WVD产生的交叉干扰项,验证了所提出联合时频分析方法的有效性及其优势,为高速动车组车轮多边形识别和评估提供了新的技术途径。     

大跨度钢筋混凝土箱拱极限承载力的复合非线性分析

基于大跨度箱形拱桥的几何非线性及材料非线性耦合分析方法,采用平面杆系对钢筋混凝土箱拱进行非线性有限元分析的方法,及编制的计算程序．对于大跨度钢筋混凝土箱拱极限承载力的复合非线性分析有所助益。     

地震作用下顺层岩质边坡变形破坏坡面效应

地震作用下,坡面形态对岩质边坡的变形破坏过程存在一定影响。文中以汶川地区公路沿线具有典型坡面形态的顺层岩质边坡为例,采用离散元UDEC软件,模拟4种坡面形态下边坡的变形破坏过程,并监测坡体关键位置处的位移和坡体应力场。通过模拟结果,对比分析不同坡型边坡变形破坏的动力响应时间、边坡的破坏位置,以及边坡破坏的程度和模式,总结出地震作用下该类顺层岩质边坡变形破坏的坡面效应,最后通过应力场分析引起坡面效应的原因。     

混凝土泵车底盘的专用化设计要素探讨

根据混凝土泵车的作业特点,介绍了混凝土泵车底盘与通用重卡底盘设计的区别,并对混凝土泵车底盘总体布置、动力系统、传动系统、行驶系统、电器系统的专用化设计进行了介绍,便于设计人员掌握混凝土泵车底盘的设计要素。     

盾构掘进破坏孤石诱发地层塌陷的灾变机制研究

孤石地层因勘察、施工处理困难,使得隧道穿越该地层时面临风险。针对因盾构掘进破碎孤石后造成地层空洞,并最终引发地层塌陷的现象,利用研发的随机多边形生成方法,在离散元软件PFC2D中建立隧道孤石地层开挖模型,研究隧道掘进破碎孤石诱发地层塌陷的灾变机制及其影响范围。研究结果表明： 根据孤石所在不同方位可以定性判断地表突然塌陷位置; 当孤石粒径大于临界粒径或隧道埋深小于临界埋深后,孤石切削不当将引发地层塌穿型坍塌; 在相同孤石粒径时,孤石形状的改变对地层位移影响甚微。