Numerical parametric study on the influence of location and inclination of large-scale asperities on the shear strength of concreterock interfaces of small buttress dams

When assessing the sliding stability of a concrete dam,the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by current dam assessment guidelines.However,these asperities can potentially improve the load capacity of a concrete dam in terms of sliding stability.Although their influence in a sliding plane has been thoroughly studied for direct shear,their influence under eccentric loading,as in the case of dams,is unknown.This paper presents the results of a parametric study that used finite element analysis(FEA)to investigate the influence of large-scale asperities on the load capacity of small buttress dams.By varying the inclination and location of an asperity located in the concrete-rock interface along with the strength of the rock foundation material,transitions between different failure modes and correlations between the load capacity and the varied parameters were observed.The results indicated that the inclination of the asperity had a significant impact on the failure mode.When the inclinationwas 30and greater,interlocking occurred between the dam and foundation and the governing failure modes were either rupture of the dam body or asperity.When the asperity inclination was significant enough to provide interlocking,the load capacity of the dam was impacted by the strength of the rock in the foundation through influencing the load capacity of the asperity.The location of the asperity along the concrete-rock interface did not affect the failure mode,except for when the asperity was located at the toe of the dam,but had an influence on the load capacity when the failure occurred by rupture of the buttress or by sliding.By accounting for a single large-scale asperity in the concrete-rock interface of the analysed dam,a horizontal load capacity increase of 30%e160%was obtained,depending on the inclination and location of the asperity and the strength of the foundation material.

Study on the method of optimal location on explosion events at near-source site

IntroductionEarthquake location is one of the inverse problems in seismology. The accurate earthquake source location is the basis of studies of earthquake images, the relation analysis between seismicity and tectonics, and the important parameters of earthquakes. It is also the basic data used to study the space distribution of aftershocks after a strong earthquake. The earthquake location accuracy mainly depends on reliability of the velocity models for the earth￠s crust, the reasonable design of the seismograph network, the accuracy of arrival time, and the location method used (ZHAO, 1983; ZHU, ZHAO, 1997; LI, et al, 1999). The reliability of the velocity model directly influences loca-tion results. The reasonable seismograph network design can improve the location accuracy; otherwise it will in-troduce ill-conditioned equations and large location error. If arrival time is not accurate, for example, if the seismic phase is wrongly identified or the time service is inaccurate, large arrival time error will be produced, and the location results and real hypocenters will be discordant. Different location algorithms adopted will produce differ-ent location errors. The residual criterion chosen has influence on location results. Besides, whether the event is correctly associated also influences the location quality. In practice, it can often be seen that large location devia-tion introduced by wrong event association.

Stabilization of CSTR w ith Self-tuning Sliding Mode Controller Using T-S Fuzzy Linearization

A self-tuning reaching law based sliding mode control(SMC)theory is proposed to stabilize the nonlinear continuous stirred tank reactor(CSTR).T-S fuzzy logic is used to build a global fuzzy state-space linear model.Combing the traits of SMC and CSTR,three fuzzy rules can meet the requirements of controlled system.The self-tuning switch control law which can drive the state variables to the sliding surface as soon as possible is designed to ensure the robustness of uncertain fuzzy system.Lyapunov equation is applied to proving the stability of the sliding surface.The simulations show that the proposed approach can achieve desired performance with less chattering problem.

Influences of Al and Si Powders on Microstructure and Hot Mechanical Properties of Al_2O_3-C Slide Plates

The basic formulation of Al2O3- C slide plates was65%（ in mass,the same hereinafter） white fused corundum particles,25% white fused corundum fines,6% active α-Al2O3 micropowder,4% carbon black and flake graphite, and additional 4% phenolic resin.Based on this formulation,3% Al powder,3% Si powder,and 3% Al ＋ 3% Si powder were used to substitute equivalent white corundum fines to improve the hot mechanical properties of Al2O3- C slide plates. The specimens with dimensions of 140 mm × 25 mm × 25 mm were pressed at 150 MPa,dried at 200 ℃ for 24 h,and hot treated at 1 400 ℃ for 3 h in carbon embedded condition. Then hot modulus of rupture and thermal shock resistance of the specimens were tested and the phase compositions and microstructure were analyzed. The results show that specimen with 3% Al powder has the higher hot modulus of rupture but lower residual modulus of rupture after thermal shock than the specimen with3% Si powder; the specimen with 3% Al ＋ 3% Si powders exhibits the highest hot modulus of rupture and the best thermal shock resistance; the change of mechanical property is closely related with the in-situ formed nonoxides： AlN in the form of bars is formed in specimens with Al powder; fibrous SiC whiskers are formed in specimens with Si powder; in the specimens with both Al and Sipowders,besides AlN and SiC whiskers,hexagonal tabular SiAlON is in-situ synthesized,which interlocks with each other.

基于轨迹修正的曲面抛光机器人终端滑模导纳控制

针对传统抛光机器人力控制算法在位置内环控制上稳定性差的问题,同时为减小力/位控制算法相互切换导致的抛光轨迹误差,提出一种基于轨迹修正的终端滑模导纳控制方法。在抛光过程中,将力传感器反馈的参数与期望力的差值作用于导纳模型产生位置修正量,设计了终端滑模控制模型作为位置内环控制环节,并通过实时反馈位置修正量进行轨迹跟踪。通过实际轨迹信息修正规划轨迹来减小抛光力误差,达到高精度抛光的效果。仿真实验表明,终端滑模导纳控制效果良好,在对轨迹进行修正后抛光力误差相对于修正前有明显改善。利用该模型抛光后表明,轮廓算数平均偏差达到0.035μm,抛光质量得到明显提高。

六自由度机械手轨迹位置跟踪控制策略研究

针对六自由度机器人轨迹的位置控制,设计了带有滑动扰动观测器的滑模控制方法(SMCSPO)和积分滑模控制(ISMC)两种不同的控制方法。SMCSPO对由非线性、参数不确定性和外部干扰组成的扰动具有较强的鲁棒性,但不易辨识系统参数。ISMC在多自由度机器人的位置控制方面,不需要推导多自由度机器人的运动方程或进行系统辨识,能够通过控制输入的开关增益实现了扰动的补偿。与SMCSPO相比,ISMC具有较高的轨迹位置跟踪精度。两种控制方法均在MATLAB/Simulink中进行了模拟仿真,结果表明ISMC的跟踪误差均小于SMCSPO的跟踪误差,且具有较好的收敛速度。

基于双重滑模观测器的MMC开关管开路故障诊断与定位策略

作为柔性直流输电系统的核心设备,模块化多电平换流器(MMC)由于子模块数量多,发生故障的概率也较高。文中分析了基于子模块电容电压滑模观测器的MMC开关管开路故障检测及定位时间问题,通过对所有子模块电容电压进行分组形成新的观测子单元,提出了一种基于子单元电压滑模观测器与桥臂电流滑模观测器的故障交叉诊断与定位方法,实现了单子模块故障时的精确定位。在此基础上,通过对观测子单元进行重构进一步实现了多管开路故障诊断以及故障开关管的精确定位。最后,通过在MATLAB/Simulink中搭建相关仿真模型,验证了所提方法的可行性。

一种新型滑套开关工具及配套技术应用研究

介绍了一种新的滑套开关工具,通过连续油管带光纤设备连接井下工具串,能够精确定位滑套位置并实时监测井下负载、压力、温度等参数,通过在地面对测量数据进行处理、解释,可准确判断井下情况,实现滑套的可靠开关操作;并通过CCL曲线变化确定滑套是否操作到位,节约因操作失误导致的大量后期作业成本和时间。

Fault plane parameters of Sanhe-Pinggu M8 earthquake in 1679 determined using present-day small earthquakes

The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method. Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows： the strike is 38.23°, the dip angle is 82.54°, the slip angle is -156.08°, the fault length is about 80 km, the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 kin. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault, southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earth-quake and seismic-wave velocity profile in the focal area all verified our study result.

基于Green-Ampt模型的多层结构边坡降雨入渗改进计算方法及稳定性影响研究

降雨作用下,边坡土体的饱和度及含水率升高,基质吸力减小。随着降雨历时的增长,雨水入渗深度对坡体的稳定性产生影响。然而传统多层结构边坡的入渗计算方法并未考虑随入渗深度不断变化的基质吸力与层间积水点的形成,且忽略饱和层内沿坡体层面流动的部分雨水对入渗过程的影响,亦未考虑潜在滑动面位置随降雨历时的变化。将入渗过程分解为若干个子过程,并基于Green-Ampt(G-A)入渗模型对传统多层结构边坡的入渗计算方法进行改进,以对每个子过程进行求解,最后将其合并为整体入渗过程的解。在此基础上对层间积水点的形成时刻进行计算,进而分析雨水入渗深度与时间的关系,并研究降雨强度与雨水入渗深度对边坡不同位置处(湿润锋、饱和层)稳定系数和滑动面位置的影响。研究表明:(1)基于G-A模型的改进计算方法所得结果比传统多层结构边坡入渗计算方法所得结果更接近于数值模拟结果。(2)对于多层结构土质边坡,其安全系数随着雨水入渗深度的增加不断降低,并且在层间积水点形成时产生突变现象。(3)随着降雨历时和降雨强度的增大,边坡中潜在滑动面位置会产生变化,前期潜在滑动面位置出现在湿润锋处,后期则出现在饱和层交界面处。该方法提高了多层结构边坡传统降雨入渗计算方法的精度,更加全面的对多层结构边坡的稳定性进行评价,其工程应用范围亦得到进一步扩大。

Compact Model for the Obnoxious <i>p</i>-Median Problem

Obnoxious facilities are those crucial to human living, yet antagonistic to the public or environment. However, the interactions between obnoxious facilities and their clients have been less frequently investigated. A state-of-the-art model for this problem involves numerous 0 - 1 variables, rendering it difficult to solve. This study aims at removing most of these 0 - 1 variables to enhanced model efficiency. A compact model is presented in this study, with the equivalence between the new and original models proved. Additionally, numerical tests were conducted to show that the proposed compact model is more efficient than the original one.

Comparison of two earthquake early warning location methods

According to earthquake catalog records of Fujian Seismic Network, the Tnow method and the fourstation continuous location method put forward by Jin Xing are inspected by using P-wave arrival information of the first four stations in each earthquake. It shows that the fourstation continuous location method can locate more seismic events than the Tnow method. By analyzing the results, it is concluded that the reason for this is that the Tnow method makes use of information from stations without being triggered, while some stations failed to be reflected in earthquake catalog because of discontinuous records or unclear records of seismic phases. For seismic events whose location results can be given, there is no obvious difference in location results of the two methods and positioning deviation of most seismic events is also not significant. For earthquakes outside the network, the positioning deviation may amplify as the epicentral distance enlarges, which may relate to the situation that the seismic stations are centered on one side of epicenter and the opening angle between seismic stations used for location and epicenter is small.

3D Track-keeping Method for Autonomous Underwater Vehicle

In this paper, 3D track-keeping control method for autonomous underwater vehicle (AUV) with and without the influence of ocean current is investigated. Because the system to be controlled is highly nonlinear and strong coupled, an approach is used to divide it into two subsystems. One is to control the heading and the track error on the horizontal plane. The other is to control the pitch and the track error on the vertical plane. The results of computer simulation show that the autopilot works properly, it can capture the current waypoint and turns to track the next path automatically.

LOCATIONAL DISTRIBUTION AND SPATIAL DIFFUSION OF FOREIGN DIRECT INVESTMENTS FROM HONGKONG AND MACAO IN MAINLAND OF CHINA

Foreign direct investments (or FDIs) have been employed since the early 1980s and they have become more and more immportant in Chinese economic development. However, the roles of FDIs are very different between regions, partly due to the different locational preference of various source countries. Some facts show that FDIs from Hongkong - Macao indicate a strong locational preference. Therefore, this paper attempts to make an empirical research on the locational preference of Hongkong - Macao’s FDIs and their spatial diffusion under the support of statistical data with regrereion analysis. In this paper, three statistical models, including the special location model, the general location model and the spatial diffusion model, are created. The results show that this kind of analysis is successful. The major conclusions are as follows. (1) The optimum location for FDIs from Hongkong - Macao lies in the coastal area, especially Guangdong, Hainan, Jiangsu, Shandong, Fujian provinces. Besides, Hubei Province is also an important radon. (2) The FDIs from HongkongMacao in China have diffused gradually from the coastal provinces to the inland regions, the northem and the metropolis and from the locations that had attracted a large number of investments to their vicinities since the 1990s. (3) The special location factors, such as the herder effect, the unique social and kinship ties are the key factors determining the special locational distribution. (4) The general location and spatial diffusion of Hongkong - Macao’s FDIs are the results of interplay of several economic factors. They are the economic scale and advantage, the growth rate, the laier force and economic extrovert etc.

Thermo-mechanical Properties of In-situ Formed Al_2O_3-SiC-SiAION Composites

Al2 O3 - SiC - SiAION composite specimens have been prepared using fused alumina, ultra fine α-Al2O3, Si and Al powders as starting materials and liquid phenol formaldehyde resin as binder and firing at 1 500 ℃ for 3 h in carbon embedded condition. Thermo-mechanical properties of Al2 O3 - SiC - SiAlON composites have been studied. The results show ： （ 1 ） Al2 O3 - SiC - SiAION composites can be prepared and sintered at 1 500 ℃ under carbon embedded condition. When Si/Al ratio is 8/0 and 7/1, the prepared composite is Al2O3 - SiC - O＇ -SiAlON; when Si/Al ratio is 5/3 and 3/5, the pre- pared composite is Al2 O3 - SiC - β-SiAION. （ 2 ） The composites possess high temperature strength properties. Hot modulus of rupture at 1 400 ℃ is 10 - 30 MPa. They are in elastic range up to 1 000 ℃, after which plastic deformation is observed; even at 1 400 ℃, amount of deformation is relatively low. （3） The com- posites possess good thermal shock resistance, their resid- ual strength ratio （AT = 1 100 ℃ ） is 65% - 80%. （4） The marked improvement in thermo-mechanical properties of Al2O3 - SiC - SiAlON composites may be at- tributed to the in-situ formation of SiC, SiAlON and AIN, the fibrous SiC, columnar SiAlON and tabular-like AlN fill in the corundum skeleton structure creating strengthening and toughening effects.

Climatic Change in Qinghai-Tibet Plateau and the Surrounding Areas in 130 Years

[ Objective] The research aimed to study climatic change in Qinghai -Tibet Plateau and the surrounding areas from 1880 to 2011. [ Method] Based on GISS temperature grid data, by using change rules of the annual and monthly anomaly temperatures, sliding t-test and wavelet analysis, periodicity and tendency of the atmospheric temperature change in Qinghai -Tibet Plateau and the surrounding areas were analyzed. [ Re- sult] Both annual and monthly anomaly temperatures in Qinghai -Tibet Plateau in recent 130 years presented rise tendency. Since the 1990s, tem- perature rose evidently, and it presented temperature-rise tendency of winter 〉 autumn 〉 spring 〉 summer. Rise velocity of the temperature had spatial difference. Rise velocity of the temperature in west Inner Mongolia was the highest, followed by west Sichuan and east Tibet. Rise velocity of the temperature in some areas of Xinjiang was the slowest. Abrupt change of the temperature happened in the 1930s, and main period of the wavelet analysis was 10 years. [ Conclusion] The research could lay foundation for discussinq Qlobal climate change.

基于运动平台的多普勒频移无源定位算法

无源定位能力是现代电磁频谱战的要素之一,侦察设备实现对雷达辐射源的高精度快速定位,是保障作战致胜的重要环节。基于运动平台的无源侦察设备,提出了一种多普勒频移算法,深入研究了相对运动时信号多普勒频率与目标位置的变化特性,对雷达目标进行定位。该算法兼顾了定位时效性与雷达扫描周期等因素,能够提高截获数据利用率,提升对目标雷达的定位精度。

一种用于智能空间的多目标跟踪室内定位系统

定位系统是智能空间位置感知计算的基础部件,它不仅要能较精确定位多目标,而且在方向性、可携带性等方面也要满足要求.文中设计了一种室内定位系统Cicada,该系统基于射频和超声波到达时间差来测量距离,并采用滑窗滤波和卡尔曼滤波的方法计算位置.实验表明它对静止和移动目标都能提供平均5cm的定位精度,拥有全向型的工作区域,便于携带,具有较好的规模伸缩度以及易部署性,能较全面地满足智能空间定位的需求.

沉入式抗滑桩优化设计研究

沉入式抗滑桩是根据普通抗滑桩受力特点改进而成的一种新型抗滑桩,它能大幅度降低工程造价。作为一种新型边坡支护结构,由于设计理论不完善,严重影响其工程应用。其中合理沉入深度和最优设置位置是沉入式抗滑桩设计的关键,如果沉入深度过大可能导致上部坡体发生越顶破坏,形成新的次级滑动,沉入深度过小则起不到降低工程投资的目地。采用极限上限定理,在假设滑面为通过坡趾下端的对数螺旋曲线基础上,研究确保边坡稳定抗滑桩所需提供的最小抗力;在抗滑桩设置位置和沉入深度优化分析中,采用基于极限分析的扇形条分法,对可能出现的次级滑面形状及其稳定性进行预测研究。结合算例,分析沉入式抗滑桩设置位置、沉入深度对边坡稳定性及其抗力的影响,从而为沉入式抗滑桩的优化设计提供一种理论方法。

岩体离层对锚固体荷载影响的弹塑性分析

巷道围岩由于变形不协调而产生离层,离层对锚杆产生附加应力。在已有弹性分析的基础上,根据岩层相对移动时拉拔载荷对锚杆的作用机制,建立了离层进一步扩展、锚固体界面进入弹塑性阶段的锚杆受力模型。通过选取二阶段线性函数剪切滑移模型,确定了离层左右两侧的滑移范围,并得出锚固体的应力分布形式。总结出离层作用下锚固体的受力过程一般分为4个阶段:弹性阶段、单侧进入弹塑性阶段、离层两侧均进入弹塑性阶段和一侧全部滑移、另一侧滑移范围增大阶段。通过对不同离层值和离层位置的参数分析得出:在相同离层位置条件下,离层值越大,离层对锚杆产生的附加应力就越大;在相同离层值条件下,弹塑性阶段基本趋势和弹性阶段相同,表现为锚杆中心处应力最小,越靠近边缘离层产生的附加应力越大。