传动销齿故障时间分布定量化建模及应用

为确保飞机调向转盘装置执行调运任务的成功率,对其关键部件传动销齿的故障时间分布规律进行研究.采用基于极大似然估计和相关系数拟合优度检验建立可靠的传动销齿故障时间分布函数,并应用于飞机调向转盘装置的使用和维护,最后进行实例分析.分析结果表明:建立的传动销齿故障时间分布函数对飞机调向转盘装置的使用和维护具有一定的指导意义,能够确保飞机调向转盘装置执行调运任务的成功率.     

环境·意境·心境——基于城市意象理论的风景名胜区规划方法

近年来,风景名胜区的特色流失和风貌趋同现象越发明显,急需探索一套能够增强风景名胜区特色的规划方法。文章通过对城市意象理论的深入研究和风景名胜区规划实践的系统分析,将城市意象理论引入风景名胜区规划,提出了道路等级化与景观化、边界层级化与刚性化、区域空间联动一体化、节点人性化与场域化、标志物特色化与符号化等规划策略,并结合广西壮族自治区灵山县六峰山—三海岩风景名胜区总体规划进行分析,以期为其他风景名胜区规划提供借鉴。     

Seismic Data‐Driven Identification of Linear Models for Building Structures Using Performance and Stabilizing Objectives

A two‐stage dual‐objective structural identification method is presented in this article. The complexity of the identification of story‐level physical models for large‐scale building structures is first addressed through a comparative study. A stiffness variation‐based stabilizing objective is proposed to be necessarily incorporated into iterative optimization with the classical performance objectives to improve the model feasibility, and an area‐type evaluation index is subsequently proposed for the stopping criteria. Accordingly, a two‐stage differential evolution‐based dual‐objective optimization framework is presented for the computation of Pareto fronts for nondominated candidate solutions. Then, the proposed method is investigated using two illustrative examples, including a nine‐story benchmark structure, and a real‐world seven‐story reinforced concrete structure. A series of condensed models are identified from the nondominated solutions on the Pareto front. The prediction performance of the single‐objective optimal model and the dual‐objective acceptable models is compared using the overall discrepancies of acceleration, interstory drift, and modal properties, within both estimation and validation cases. Incorporation of the noise effect into the method is finally studied and discussed.     

Optimizing Location and Capacity for Multiple Types of Locomotive Maintenance Shops

Thousands of locomotives run in the North America railroad network and each of them must receive periodic maintenance service; meanwhile, the locomotives may break down during shipment operations and demand repair. Maintenance shops are characterized by the types of locomotives they can handle and the level of service they can provide. This article formulates a mixed‐integer program model to optimize location and capacity of locomotive maintenance shops. The objective is to minimize the sum of the costs for building new (or shutting down existing) maintenance shops, the costs for capacity expansion (or reduction), and the costs for shipping broken locomotives to a suitable shop. A Lagrangian‐relaxation‐based heuristic algorithm is proposed to solve the shop location and capacity planning problem. The model and solution techniques are applied to a full‐scale real‐world case study, while the computational results show that the current maintenance shops are overly built and recommend that two maintenance shops should be closed and an amount of capacities should be reduced from the existing shops. A series of numerical sensitivity analyses are also conducted to draw managerial insights.     

无底柱分段崩落法斜壁边界条件放矿实验

为了研究无底柱分段崩落法斜壁边界条件下矿石散体的移动规律,开展了斜壁边界条件下的底部放矿实验。按照1∶25的几何相似比,制作了无底柱分段崩落法斜壁边界条件下底部放矿模型,根据矿山现场矿石块度级配,制备了对应级配的矿石散体材料及流动性与散体材料一致的标志颗粒。在实验数据的基础上,绘制了各水平层标志颗粒放出量曲线图,分析了矿体厚度和上下盘边壁对散体流动规律的影响。结果表明,矿体厚度对散体流动规律影响较小,在上下盘边壁的约束作用下,同一水平层,越靠近上盘的散体越先被放出。结果对无底柱分段崩落法放矿工艺的研究和应用具有一定指导意义。     

基于光伏逆变器无功调节的低压配电网多模式电压控制

针对大规模户用光伏接入引起的低压配电网电压越限问题,以逆变器无功控制为手段,提出了一种多模式逆变器控制策略,以提高低压配电网对光伏的消纳能力。基于电压灵敏度理论,定义了虚拟注入有功功率的概念,实现了节点有功和无功功率之间的折算。根据节点虚拟注入功率将光伏发电的并网分为过电压抑制、欠电压抑制以及网损和功率因数的优化三种模式。当网络出现过电压(欠电压)运行风险时,以风险的抑制为目标调节逆变器无功功率;当网络运行无风险时,则以网损和功率因数的优化作为逆变器的无功调节依据。此外,为了实现就地的协调控制,结合全网电压灵敏度矩阵建立了不同节点光伏逆变器控制参数的优化模型,实现网络无通信条件下的协调电压控制。仿真结果表明,所提的多模式电压控制方法可以有效地抑制网络电压越限,同时使网络损耗和功率因数也得到优化。     

NoC中负载均衡的AVOQ路由器设计

针对片上网络中使用虚拟输出队列(VOQ)机制的路由器在网络拥塞时存在的头阻塞问题,提出负载均衡的AVOQ路由器架构。首先,输入缓冲区仍使用VOQ机制来处理头阻塞问题。其次,在路由计算模块自适应地选择输出端口,确保数据从较不拥塞的端口输出;在单个虚通道内自适应地读取数据包,确保下游不拥塞的流量能够在网络里流通。实验结果表明,相较于虚通道路由器和VOQ路由器,AVOQ路由器平均延时最多减少83.2%和57.1%,吞吐率最多增加72.7%和33.3%,功耗和面积开销可接受。该方案通过两个层级的自适应均衡全网的流量分布,缓解拥塞,进而降低头阻塞出现的可能性,并在头阻塞出现时消除其影响,提升网络性能。     

Vulnerability Mitigation of Multiple Spatially Localized Attacks on Critical Infrastructure Systems

Recently, many studies have analyzed critical infrastructure vulnerability under spatially localized attack (SLA), which is modeled as the failure of a set of infrastructure components, distributed in a spatially localized area, due to malicious attacks, while other components outside of the area do not directly fail. However, existing studies have only considered one single attack area, and multiple SLAs (MSLAs) with more than one attack area have been seldom investigated. This article addresses this issue and studies vulnerability mitigation of critical infrastructure systems (CISs) against the worst‐case MSLAs. The problem is mathematically formulated as a tri‐level defender‐attacker‐defender model, the exact solution of which is solved by a proposed decomposition algorithm. Case studies on the adapted IEEE 24 bus system and the power transmission systems in Shelby County and Harris County, U.S., indicate that (1) system vulnerability under 2*M localized attack areas might be much larger than two times of the vulnerability under M localized attack areas; (2) small preevent defense investment might mitigate the worst‐case vulnerability by more than 40%; and (3) MSLAs might cause larger vulnerability than nonproximity‐based malicious attacks.     

智慧城市发展对城市规划的影响评述

当前,智慧城市作为新型的城市发展理念与范式,迅速成为全球城市发展与规划领域关注的焦点。研究在分析智慧城市缘起、内涵及发展态势的基础上,根据智慧城市的发展特征,将全球范围内的智慧城市划分为美国、欧洲和亚太地区三个分布区,并将智慧城市应用体系划分为强应用、弱应用和开拓应用三大领域。智慧城市发展与规划对城市规划领域产生了显著的影响,包括对传统城市规划内容的补正与革新,对城市规划类型的创新,对城市规划体系的扩充与完善;对城市规划编制单位业务类型的拓展;对城市规划师的业务水平和专业素质提出更高的要求。     

我国自然公园旅游规划中存在的问题--以北京青龙峡旅游度假区为例

本文以北京青龙峡旅游度假区为例,从规划分区、活动设施、细节设置等几方面,列举了目前我国旅游规划中常见的规划误区和实际影响,反映出了我国自然公园旅游规划中存在的问题。