Damage alarming for bridge expansion joints using novelty detection technique based on long-term monitoring data

Damage alarming and safety evaluation using long-term monitoring data is an area of significant research activity for long-span bridges. In order to extend the research in this field, the damage alarming technique for bridge expansion joints based on long-term monitoring data was developed. The effects of environmental factors on the expansion joint displacement were analyzed. Multiple linear regression models were obtained to describe the correlation between displacements and the dominant environmental factors. The damage alarming index was defined based on the multiple regression models. At last, the X-bar control chart was utilized to detect the abnormal change of the displacements. Analysis results reveal that temperature and traffic condition are the dominant environmental factors to influence the displacement. When the confidence level of X-bar control chart is set to be 0.003, the false-positive indications of damage can be avoided. The damage sensitivity analysis shows that the proper X-bar control chart can detect 0.1 cm damage-induced change of the expansion joint displacement. It is reasonably believed that the proposed technique is robust against false-positive indication of damage and suitable to alarm the possible future damage of the expansion joints.     

边界条件对尾流自导鱼雷攻击的影响

针对尾流自导鱼雷攻击水面目标的技术特点,阐述了影响尾流自导鱼雷攻击使用的边界条件范围及分类,一方面分析尾流自导鱼雷在边界条件下攻击的影响因素,另一方面从鱼雷的命中概率仿真数据入手,以确保在边界条件下尾流自导鱼雷攻击的效果为目的,完善尾流自导鱼雷在特定战场态势下攻击的灵活性措施,进而发挥武器装备应有的作战效能.     

基于D-S证据理论的变电站设备状态监测模型

为了提高变电站设备的供电可靠性,根据已有的设备状态监测方法,利用小波分析方法和D-S证据理论,提出了一种变压器状态监测模型,通过对变电站设备特征量的分析来实现对变电站设备状态的实时监测.     

冲积河流系统特性与河流反应的研究

取一小流域为典型,从系统角度分析了冲积河流系统的基本结构特征及水沙、河流演变特性。同时研究了水电工程对河流水沙条件的影响特点,以及冲积河流系统河流反应的特点、发展趋向性。对一些水库修建后,下游河道的河性、河床形态变化进行了分析,指出了河流系统的良性循环与水电开发建设的可持续发展必须协调起来。     

Application of Short Fourier-Transform in Detection of Early Fault Rolling-Element Bearing

0INTRODUCTIONRollingelementbearingiswidelyusedinallkindsofrotatingmachinesandtheconditionmonitorsystemforitsworkingstateisveryimPOrlantforrotatingmachines.SoresearchonthetechniqUeofearl}rfaultrolling-elementbearingdetectionhasagreatsignificanceinengineering.TheachievementofthetechniqUehasindicatethat:thedetectionmethodthroughvibrationmonitoringtechniqUeisthemostPOweifulandreliableanalySistoolfordeducingmechanicalfaultS.Theearlyfailureofrollingelementhearingpresentssomepittings,brinelli…     

A Note on Diophantine Equation Ax~4+ 1 = By~2 and Erds'''' Conjecture on Combinatorial Number

oINTRODUCT1ONLetNbethesetofpositiveintegers.LetA,BeNwithgcd(A,B)=l,B>landBissquarefree.Thereweremanypaperscon-cernedwiththeequationAx4+l=By',x,yeN(1)writtenbyLjunggren,Cohn,KeandSun,andtheauthoretc.(seell]).LjunggrenI']provedthatifA=land(l)hassolution(x,y),thenX2+yJB=n',(2)wheren=uo+v,Inisthefundamentalsolu-tionofPell'sequationu2-Bv2=-l,uo=dut,d,u,eN,dissquarefree.Infact,repeatingthemethodof[3]com-pletely,wecanproveTheoremlTheequation(l)hassolution(x,y)ifandonlyiftheequationAu2…     

瓦斯突出的气体介质条件

在研究瓦斯突出中的作用机理、煤的瓦斯吸附特性和煤的瓦斯放散特性的基础上,论述了瓦斯突出的气体介质条件,为认识瓦斯动力现象的本质提供了科学依据．     

FL25／30型塔式起重机的结构特点及测试分析

通过对ＦＩ２５／３０型塔式起重机的结构强度测试,并与ＱＴ８０型塔式起重机相应位置的自重应力,实际尖力相比较,说明ＦＩ２５／３０型塔式起重机的主要特点及两种没机型的实际受力情况。     

时域有限差分法的优化吸收边界条件

基于单向波算子,给出了一个形式简洁的Ｎ阶优化吸收边界条件,给出了确定其参量的方法．数值结果表明,对于特定电磁问题,适当选择参量,优化吸收边界条件优于同阶Ｍｕｒ吸收边界条件．