Interval analysis of mode shapes to identify damage in beam structures

Various damage detection methods have been proposed by several researchers in the past few decades. Amongst them, the efficiency of mode shapes in detecting damage has been demonstrated by many researchers when further processed. In most cases, the processing involves expansion or reduction of the mode shape data. However, vital information that are damage-prints are often lost during processing of the mode shape data. In addition, most of these processes involve long and complex computation, thus, leading to inaccurate damage identification. In this study, a simple and fast damage identification technique is proposed to identify damage in beam structures. Interval analysis is applied to the mode shapes of a beam structure in the damaged and undamaged states. The interval situations of each of the beam's segment via mode shape are derived to obtain the upper and lower bounds and the derived bounds are compared. To establish a relationship for identify the damaged point, a possibility of damage existence is defined for each segment of the beam structure. The mode shape increment is defined as the increase in the mode shape value. Furthermore, a damage measure index that provide enhance damage information is obtained as the product of the possibility of damage existence and mode shape increment. A numerical model of a simply supported steel beam is applied to demonstrate this method by imposing damage through thickness reduction of elements in segments. In addition, a parametric analysis is carried out to evaluate noise effect by considering varying damage severities and different noise levels. The results showed that this method is simple and provides considerable accurate results.     

观察的可能性——风景园林视角感知空间的设计基础教学探索

设计学的核心离不开对场所和空间的感知能力，以广州美术学院建筑艺术设计学院设计基础课程——观察与记录为研究对象，该课程在设计类多学科老师的共同参与中进行，其中风景园林学作为人居环境学重要的学科之一，对于户外空间营造有举足轻重的作用。选取“观察的可能性”作为讨论核心，从风景园林学的视角出发探讨感知空间的观察途径和方法，培养学生对场所空间观察的策略意识。     

An efficient method for estimating time-dependent failure possibility by combining adaptive Kriging with adaptive truncated fuzzy simulation

Time-dependent failure possibility (TDFP) can measure the structural safety level for a time interval of interest under fuzzy uncertainty, but its calculational cost is unaffordable by using fuzzy simulation (FS) due to a required large size of FS candidate sampling pool (CSP). Although time-dependent adaptive Kriging model (T-AK) combined with FS (T-AK-FS) was presented to reduce the number of calling performance function, a large FS CSP still makes training T-AK time-consuming. To improve its efficiency, an adaptive truncated FS (ATFS) with T-AK (T-AK-ATFS) is proposed by CSP size reduction approach. By T-AK-ATFS, the largest safety hypercube in fuzzy standard space is adaptively searched, in which the samples are in safety states and can be removed from the FS CSP. Moreover, T-AK is adaptively trained to search the largest safety hypercube and estimate TDFP simultaneously. In adaptively searching process, the FS CSP is divided into several sub-CSPs, on which training T-AK is more time-saving. Overall, strategies of T-AK-ATFS include proposing ATFS to reduce the FS CSP, adaptively searching the largest safety hypercube, estimating the TDFP with the same T-AK and training T-AK in the sub-CSPs sequentially. Verified by examples, these strategies make T-AK-ATFS more efficient than existing FS and T-AK-FS.     

可持续发展的商业步行环境——对商业步行街设计的几点思考

对商业步行环境的可持续发展规律作了初步探讨 ,结合设计实践提出了开放的功能体系 ,生态式的环境艺术等二个大的设计原则与方法。以期在微观层面上把握住可持续发展的时代课题     

浅谈离心式压缩机在浮法玻璃生产中的应用前景

采用废热锅炉产生蒸汽驱动汽轮机来带动离心式压缩机,为浮法玻璃生产服务,从而节约动力投资,降低产品成本,为玻璃厂在节能降耗方面进行大胆尝试提供一个发展方向.     

雷电诱发500kV变电站5台电流互感器故障分析

为分析某500 kV变电站5台电流互感器故障是否可能因雷电过电压激发而产生,针对故障时站内避雷器放电计数器均未动作的情况,分析了避雷器的动作特性,搭建了线路及变电站雷电过电压计算模型,研究了雷击导线及杆塔时可触发避雷器放电计数器动作的最小雷电流幅值与传导距离的关系,计算了雷击杆塔时传导至变电站各故障点的过电压幅值。研究结果表明:雷击导线及杆塔时,可触发变电站避雷器放电计数器动作的最小雷电流幅值与传导距离基本都呈线性关系;雷击杆塔时,导线上感应到的过电压难以触发变电站避雷器放电计数器动作,而相比之下,绕击导线时则容易的多;当雷击杆塔时,雷击处三相导线均感应出过电压,传导至变电站时,即使线路间隔装设有避雷器,故障电流互感器承受的过电压最高仍可高达666 kV。如果5台故障设备此前均已存在绝缘缺陷时,有可能在此过电压的激发下加速故障过程。     

An approach to multiplicative linguistic group decision making based on possibility degrees

In order to compare two uncertain multiplicative linguistic variables, a possibility degree formula has been developed and its properties are also studied. Then a possibility degree matrix (also considered as a reciprocal preference relation) is constructed to compare a collection of uncertain multiplicative linguistic variables. Two models are further provided to derive the priority vector from the possibility degree matrix based on the additive consistency and multiplicative consistency. Especially, if the parameters are assigned specific values, then the models reduce to the existing ones. A group decision making method has been developed to deal with the situations where the preferences on alternatives are expressed by uncertain multiplicative linguistic variables. In this method, the possibility degree matrix is first constructed, from which the priority of alternatives is obtained using the developed models. At the end, an example is given to illustrate the proposed method.     

UNCERTAINTY IN THE DEMPSTER-SHAFER THEORY: A CRITICAL RE-EXAMINATION

Measures of two types of uncertainty that coexist in the Dempster-Shafer theory are overviewed. A measure of one type of uncertainty, which expresses nonspecificity of evidential claims, is well justified on both intuitive and mathematical grounds. Proposed measures of the other types of uncertainty, which atlempt to capture conflicts among evidential claims, are shown to have some deficiencies. To alleviate these deficiencies, a new measure is proposed. This measure, which is called a measure of discord, is not only satisfactory on intuitive grounds, but has also desirable mathematical properties. A measure of total uncertainty, which is defined as the sum of nonspecificity and discord, is also discussed. The paper focuses on conceptual issues. Mathematical properties of the measure of discord are only slated; their proofs are given in a companion paper.¹⁵     

基于生产可能性边界的安全投入优化方法研究

安全也是生产力,安全投入的比例不协调、数额不足或投入过量等,对安全投入的经济效益乃至整个企业正常的生产运作都会产生影响。本文主研究经济学中的生产可能性边界在安全投入方法的优化中的应用。文章以中交第四公路工程局有限公司的一个工程项目为案例进行定量分析,将安全费用分为安全设备费用和安全预防费用两大类,构建坐标系,通过安全投入分布图及实际经济条件拟合边界曲线,构建安全投入可能性边界模型。最后根据企业的实际经济情况与运作模式,通过Matlab构建合适的隶属度函数,引入隶属度来验证安全投入决策的合理性,使得企业安全投入决策得到优化。     

A fuzzy screening model for multiple attribute decision-making

A method for the screening of multiple attribute decision-making problems is presented. The model assists the decision-maker in eliminating inferior alternatives and insignificant attributes prior to a detailed evaluation. A preliminary evaluation of the alternatives provides the information necessary for the reduction of the decision problem. The procedure calculates maximum preference factors on which the decision-maker can base his screening decisions. These factors assess the role of alternatives in the final ranking by estimating their potential to become superior to other alternatives. Since screening tasks are carried out early in decision-making, the information available is generally uncertain. Uncertainty is represented in the model using fuzzy sets. This framework permits the handling of both imprecise and precise (crisp) estimates of impacts and provides a possibil-istic assessment of the risk associated with screening decisions.