丁腈橡胶在燃气介质中的老化性能测试研究

基于烘箱热空气老化试验方法,建立了一种能让试验样品处于流通气氛冲刷的闭合试验装置,对橡胶材料进行燃气环境中老化性能测试。选用丁腈橡胶为试样,测试其在不同温度、不同气氛下的老化性能,预测其使用时间。测试结果显示,采用空气气氛方法进行丁腈橡胶加速老化试验,预测的使用时间结果与实际使用时间的偏差在80%以上;燃气气氛冲刷环境下,丁腈橡胶在老化速率是热空气老化的2倍左右,且燃气气氛下的加速老化使用时间的预测结果与实际的偏差在±20%之内。     

服务型政府下的城乡规划管理市场化改革

顺应我国经济、政治和社会的发展,政府必然从经济上的建设型政府、管理上的管制型政府向以公共管理为主的服务型政府转型。城乡规划作为政府的一项重要公共政策,一直是以主动、全面管理为主。如何顺应服务型政府在职能上的需求,通过市场化改革,逐步放权,以更好地发挥市场在城市建设中的资源调节作用,加强市场竞争对城市发展的促进作用,是我国需要探讨的重要问题。研究通过分析我国经济发展趋势、服务型政府主要特色及现有城乡规划管理审批、决策、评价等面临的主要问题,分析市场化改革的特色、目标与多样性,从渐进式、突变式两方面探讨了市场化改革实施路径。     

生活圈视角下的中小城市公共服务规划对策研究

传统城市规划对公共服务配套重视 不足,一定程度上影响了中小城市公共服务 的完善程度,也对生活圈的构建提出了新的 挑战。本文以重庆市潼南区为例,通过研究 中小城市居民生活的行为特征、对公共服务 的需求以及城市服务配套现状,从生活圈尺 度、边界、设施配套等方面提出了中小城市 公共服务规划对策,以期为生活圈时代的中 小城市公共服务规划提供参考,丰富生活圈 研究内容。     

Labelling accuracy in Tasmanian seafood: An investigation using DNA barcoding

Mislabelling of seafood products has been documented in numerous countries for over three-quarters of a century. With a trend towards increased consumption of seafood, the informed consumer demands accurately labelled products that provide full disclosure of composition. DNA barcoding can be used to accurately identify a seafood product to species based on its genetic signature, and so provides a means to test the authenticity and accuracy of seafood labelling. This can be especially useful for products such as fillets which have few or no unambiguous identifying characters, and can easily be mislabelled. We investigated labelling accuracy in seafood retailers in Tasmania, Australia. Thirty-eight seafood products were obtained from seafood retailers, sequenced for the barcoding gene region cytochrome oxidase subunit 1(CO1), and subsequently identified to species level by querying GenBank and Barcode of Life Data Systems (BOLD) DNA sequence records. Results were compared with standard fish names (SFN) prescribed under the Australian Fish Names Standard (AFNS) and FishBase. Of the 38 samples, none were deemed to have been mislabelled under Australian regulation, although in some cases naming discrepancies and ambiguity may cause confusion for some consumers. Our work, while reflecting high standards in Tasmanian seafood, highlights the need for mandatory standard labelling across all seafood products so as to eliminate any possible misrepresentation.     

定向穿越管道的挤毁失效及其防护装置的设计

定向穿越敷管技术由于其特殊优势,被越来越多地应用于油气管道敷设,但复杂的地质条件又极易导致穿越管道挤毁失效,对油气输送安全造成严重威胁。为此,针对复杂地层中穿越管道的挤毁失效行为,分析了其失效原因,主要是由孔壁失稳、地层沉降和地下水渗流等所导致的。进而基于管材非线性及管土耦合作用,建立了无缺陷和凹陷穿越管道的挤毁数值计算模型,并对其挤毁行为进行了研究。结果表明:①无缺陷管道与凹陷管道的挤毁失效模式不同,完整穿越管道的挤毁过程可分为6个阶段,管道横截面经历了椭圆形、"新月"形、"葫芦"形及"8"字形变化过程;②而凹陷管道的挤毁过程可分为5个阶段,管道横截面经历了"心"形、"新月"形、"葫芦"形及"8"字形变化过程;③围土压力越大,管道的挤毁失效后果越严重。最后,设计了一种结构简单、易于操作且具有自主知识产权的定向穿越管道用防护装置,可以有效降低管道发生凹陷、挤毁等失效的概率,延长管道使用寿命,可用于穿越危险地层的油气管道防护。     

Performance evaluation of two-worker operations in a worker-to-cell order assorting system

This paper studies an order assorting system (OAS) composed of multiple-parallel order assorting aisles (OAAs) in a retailer’s order fulfillment center. We evaluate two worker-assignment policies for a worker-to-part OAA: a dedicated-assignment policy and a shared-assignment policy. Our analytical models evaluate the mean value and variance of worker process time including assorting time, walk time, empty walk time, and blocking time when single-line products arrive randomly. From the worker process time, we identify the system flow time of product lines per each worker-assignment policy using G/G/1 and G/G/2 queuing models. We find that the shared-assignment policy performs better compared to the dedicated-assignment policy in spite of workers’ productivity losses incurred by blocking delays over high sort probability, slow walk speed, and high magnitude and variations of inter-arrival times. At the worker-centric break-even point of worker process time, where worker process time suggests selecting either policy, system flow time always suggests selecting the shared-assignment policy.     

System for augmented human–robot interaction through mixed reality and robot training by non-experts in customer service environments

Human–robot interaction during general service tasks in home or retail environment has been proven challenging, partly because (1) robots lack high-level context-based cognition and (2) humans cannot intuit the perception state of robots as they can for other humans. To solve these two problems, we present a complete robot system that has been given the highest evaluation score at the Customer Interaction Task of the Future Convenience Store Challenge at the World Robot Summit 2018, which implements several key technologies: (1) a hierarchical spatial concepts formation for general robot task planning and (2) a mixed reality interface to enable users to intuitively visualize the current state of the robot perception and naturally interact with it. The results obtained during the competition indicate that the proposed system allows both non-expert operators and end users to achieve human–robot interactions in customer service environments. Furthermore, we describe a detailed scenario including employee operation and customer interaction which serves as a set of requirements for service robots and a road map for development. The system integration and task scenario described in this paper should be helpful for groups facing customer interaction challenges and looking for a successfully deployed base to build on.     

Development of strategic hydrogen refueling station deployment plan for Korea

The Republic of Korea government has set yearly targets of hydrogen cars and buses and plans to install hydrogen refueling stations nationwide. This paper proposes a methodology for developing a strategic deployment plan with three mathematical models. For a given target, future refueling demand locations and amount from general road and expressway are systematically estimated. First, the required number of refueling stations to satisfy the target covering ratio of the total demand set by the government is determined by the Station number determination model. Next, the locations of the capacitated stations and the allocation of demand to the stations are determined by the second Max cover and the third p-median models. Since the max covering is more important than minimizing the travel time, the two models are used sequentially. The nationwide hydrogen station deployment plan for the years 2022–2040 obtained by the proposed methodology is reported.     

A maritime inventory routing problem with stochastic sailing and port times

This paper describes a stochastic short sea shipping problem where a company is responsible for both the distribution of oil products between islands and the inventory management of those products at consumption storage tanks located at ports. In general, ship routing and scheduling is associated with uncertainty in weather conditions and unpredictable waiting times at ports. In this work, both sailing times and port times are considered to be stochastic parameters. A two-stage stochastic programming model with recourse is presented where the first stage consists of routing, loading and unloading decisions, and the second stage consists of scheduling and inventory decisions. The model is solved using a decomposition approach similar to an L-shaped algorithm where optimality cuts are added dynamically, and this solution process is embedded within the sample average approximation method. A computational study based on real-world instances is presented.     

Simulation studies of methods to delay corrosion and increase service life for cracked concrete exposed to chlorides

The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosion and eventually compromises a structure’s integrity. To extend its service life and improve safety, it is crucial to develop sound repair strategies for our nation’s infrastructure. In this paper, results are presented for numerical simulations to study the effectiveness of fillers for repair of cracks in concrete, so as to delay the onset of corrosion in reinforcing steel. Concretes without cracks and with either a 50 μm or 500 μm wide crack located directly above the steel reinforcement are simulated, with the addition of silica fume, a corrosion inhibitor, or epoxy-coated reinforcement being considered as additional scenarios. The effectiveness of the crack filler depends not only on its inherent diffusivity with respect to chloride ions, but also on its ability to penetrate and fill the damaged zone or interface between the open crack region and the bulk concrete. Additional simulations indicate that using continuum models instead of models that include details of the rebar placement can lead to underestimating the chloride concentration and overestimating the service life. Experiments are needed to study the ingress of chlorides in damaged (interfacial) regions adjacent to the crack or at the reinforcement surface, as the local transport properties of these regions can significantly influence service life predictions.