Asymptotic field of mode Ⅱ dynamic growing crack in visco-elastic material

A mechanical model of visco-elastic material is established in order to investigate viscous effect in dynamic growing crack-tip field of mode Ⅱ. It is shown that in stable creep growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, the stress and strain have the same singularity, namely, (σε) ∝r^-1/(n-1). The asymptotic solutions of separatied variables of stress, stain and displacement in crack-tip field are obtained by asymptotic analysis, and the results of numerical value of stress and strain in crack-tip field are obtained by shooting method. Through numerical calculation, it is shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. By the asymptotic analysis to the crack-tip field, the fracture criterion of mode Ⅱ dynamic growing crack of visco-elastic materials is put forward from the point of view of strain.     

胶州湾地貌特征及海床演变分析

为判明胶州湾海床冲淤演变趋势 ,在地貌调查及有关资料整理的基础上 ,对胶州湾的形成和演变进行了分析 ,从沉积特征与泥沙来源上对海床稳定性的影响进行了探讨 ,认为海床处于稳定状态 ,并将延续这种演变趋势。     

Dynamic Obstacle Avoidance for Application of Human-Robot Cooperative Dispensing Medicines

For safety reasons,in the automated dispensing medicines process,robots and humans cooperate to accomplish the task of drug sorting and distribution.In this dynamic unstructured environment,such as a human-robot collaboration scenario,the safety of human,robot,and equipment in the environment is paramount.In this work,a practical and effective robot motion planning method is proposed for dynamic unstructured environments.To figure out the problems of blind zones of single depth sensor and dynamic obstacle avoidance,we first propose a method for establishing offline mapping and online fusion of multi-sensor depth images and 3D grids of the robot workspace,which is used to determine the occupation states of the 3D grids occluded by robots and obstacles and to conduct real-time estimation of the minimum distance between the robot and obstacles.Then,based on the reactive control method,the attractive and repulsive forces are calculated and transformed into robot joint velocities to avoid obstacles in real time.Finally,the robot's dynamic obstacle avoidance ability is evaluated on an experimental platform with a UR5 robot and two KinectV2 RGB-D sensors,and the effectiveness of the proposed method is verified.     

高等级公路养护机械设备的维护与管理

结合对高速公路养护机械设备维保要求的提高,从设备类型、机械配置、管理方式、人员素质等角度论述当前高速公路养护机械设备的维护与管理中存在的问题,并提出有针对性的解决措施。     

基于Web GIS的公路施工管理系统研究

基于Web从组织机构和功能两个方面分析公路施工管理系统的实际需求,分析公路施工管理系统中主要模块之间的关系,并据此设计基于Web的公路施工管理系统的总体结构。该系统利用GIS、图形显示等技术,为施工管理搭建了一个地图可视化平台,在电子图库、三维分析、工程量计算等方面进行了一定的探索。     

Is the curb 80% full or 20% empty? Assessing the impacts of San Francisco’s parking pricing experiment

The city of San Francisco is undertaking a large-scale controlled parking pricing experiment. San Francisco has adopted a performance goal of 60–80% occupancy for its metered parking. The goal represents an heuristic performance measure intended to reduce double parking and cruising for parking, and improve the driver experience; it follows a wave of academic and policy literature that calls for adjusting on-street parking prices to achieve similar occupancy targets. In this paper, we evaluate the relationship between occupancy rules and metrics of direct policy interest, such as the probability of finding a parking space and the amount of cruising. We show how cruising and arrival rates can be simulated or estimated from hourly occupancy data. Further, we evaluate the impacts of the first two years of the San Francisco program, and conclude that rate changes have helped achieve the City’s occupancy goal and reduced cruising by 50%.     

房地产开发项目如何确定目标成本探讨

房地产开发项目,其投资包括的费用内容较多,不仅有建安工程费、配套设施费、拆迁费等概预算编制规定的各项费用,还有获取土地价款等有关费用。此文在阐述项目成本费用组成的基础上,重点阐述如何合理确定和控制目标成本,即建立目标成本管理机制、分阶段确定目标成本、推行限额设计加强设计管理、提高造价管理水平等,以达到有效控制目标成本和售后利润的目标。     

和谐管理理论在施工企业二次经营中的应用

为提高施工企业二次经营水平，对二次经营的概念和范围的界定进行详细阐述，并就和谐管理理论引入到二次经营工作中。在二次经营阶段通过确定项目和谐主题，建立谐则机制和和则机制并进行有效结合，使项目参建人员通过学习相关知识，提高认识，积极开展施工方案优化，有效控制项目成本，优质的完成所承建的工程任务，取得业主和监理单位的认同，为二次经营创造条件。并就开展二次经营组织机构的建立，相关制度、管理办法、管理措施的制定进行阐述。     

强夯法在下卧深层软基处治中的应用

结合工程实例，分析强夯法处理软弱路基机理，总结强夯法形成硬壳层在处理下卧深层软基的新思路，对类似公路的建设具有借鉴作用。     

A competing Markov model for cracking prediction on civil structures

Cracks on the surface of civil structures (e.g. pavement sections, concrete structures) progress in several formations and under different deterioration mechanisms. In monitoring practice, it is often that cracking type with its worst damage level is selected as a representative condition state, while other cracking types and their damage levels are neglected in records, remaining as hidden information. Therefore, the practice in monitoring has a potential to conceal with a bias selection process, which possibly result in not optimal intervention strategies. In overcoming these problems, our paper presents a non-homogeneous Markov hazard model, with competing hazard rates. Cracking condition states are classified in three types (longitudinal crack, horizontal crack, and alligator crack), with three respective damage levels. The dynamic selection of cracking condition states are undergone a competing process of cracking types and damage levels. We apply a numerical solution using Bayesian estimation and Markov Chain Monte Carlo method to solve the problem of high-order integration of complete likelihood function. An empirical study on a data-set of Japanese pavement system is presented to demonstrate the applicability and contribution of the model.