高寒冻融环境下隧道结构服役性能预测模型

为分析高寒大温差冻融环境对公路隧道衬砌结构长期服役性能的影响, 采用现场测试方法得到了姜路岭隧道洞口温度变化规律, 基于室内冻融循环试验拟合了冻融环境下衬砌混凝土力学性能劣化计算公式, 应用荷载结构法建立了高寒冻融环境下衬砌结构服役性能的时空预测模型。研究结果表明: 铺设厚度为5cm、导热系数为0.03 W·(m·℃)^-1的保温层后, 姜路岭隧道1年内经历的等效室内冻融循环次数从8下降为0.32;无保温层且混凝土饱水条件下, 5、10、15、20年后拱脚处截面安全系数相对于刚服役时分别降低了0.6%、23.7%、41.1%、69.8%, 二次衬砌服役20年后安全系数已不能满足结构承载的要求; 铺设厚度为5cm、导热系数为0.03 W·(m·℃)^-1的保温层后, 二次衬砌服役100年后安全系数仍能够满足承载要求。可见冻融循环的剧烈程度对衬砌结构长期服役性能影响显著, 保温层能有效改善混凝土的冻融环境。     

DBD型低温等离子体放电功率影响因素研究

为深入理解介质阻挡放电特性,提高其运行效率,采用Q-VLissajous图形法对介质阻挡放电功率P进行测量,研究了外加激励峰值电压V、放电频率f、放电气隙lg、介质厚度ld等因素对介质阻挡放电功率的影响。试验结果表明,P随V的增大而增大;相同V时,提高f可增大P,且采用较大f的P随V的增长速度较快;P随lg的增加而提高,但lg不宜太大,否则热损耗增加,且易造成介质击穿;减小ld可提高P,为避免介质击穿,ld也不宜太小。     

刮水/洗涤器试验装置

介绍长丰汽车公司自制的刮水/洗涤器试验装置的功能和构成,论述其上位机、下位机和水路系统的工作原理。     

轻型载货汽车车外噪声分析与控制

用声强扫描法对国产某轻型载货汽车车外噪声源进行了识别,确定了其车外主要噪声源。开发了材料声学特性测量系统,并对多种车用吸声、隔声材料进行了测试与分析。根据被试轻型载货汽车车外主要噪声源的特性合理地选择吸声、隔声材料和噪声控制方案,对其进行了降噪处理。通过对降噪前、后该车车外噪声进行测试分析表明,采取降噪措施后,被试车辆车外动态加速噪声由84dB(A)下降到78dB(A),能够满足国家标准GB1495—2002对该类车辆车外动态加速噪声限值的要求。     

超薄沥青混合料室内试验方法研究

超薄沥青混凝土面层是一种摊铺厚度为1.5～2.5cm之间的细粒式沥青面层,其主要目的是用于旧路的功能性恢复以及新建公路表面功能层。在大量室内试验的基础上,探索了超薄沥青混合料室内试验评价方法。     

钢纤维掺量及规格对桥梁用超高性能混凝土性能影响的研究

为了探究钢纤维掺量及规格对桥梁用超高性能混凝土施工性能和力学性能的影响,通过设置不同钢纤维掺量(0％、0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％)和长径比(65、80、90、100)进行对照试验,分别得到试件的扩展度、抗压强度、抗折强度.试验结果表明:当钢纤维长径比为65时,随着掺量的增加,超高性能...     

Two Bandwidth Packing Algorithms for the Centralized Wireless Network and Their Average-case Analysis

This paper presents a detail analysis of two bandwidth packing algorithms, used for processing connection requests in the centralized wireless network. Each call comes with a specific bandwidth request. A request can be satisfied only if there is sufficient bandwidth available during resource scheduling and allocation. Unsatisfied requests were held in a queue. The metric of bandwidth utilization ratio was used to quantify the performance of our algorithms. By theoretical analysis, our algorithms can improve the average bandwidth usage ratio significantly, about 8%~10% without adding much computation complexity. Moreover, our algorithms outperform next fit with fragmentation (NFF) algorithm when the bandwidth resource is scarce. In this paper, the contributions follows: Introducing bandwidth packing problem into wireless network; Proposing two new bandwidth packing algorithms for wireless network where the complicate scheduling algorithms are prohibited; Studying the average performance of our algorithms mathematically, which agree well with the simulation results.     

高性能钢在日本及欧洲的研发与应用

随着对桥梁结构在荷载等级、跨度等方面提出了更高的要求,设计对材料的要求也越来越高,高性能钢的研发可以满足这一工程需求,系统介绍了日本、欧洲在这一领域的最新研究进展。     

Multi-objective optimization for asphalt pavement maintenance plans at project level: Integrating performance,cost and environment

Traditionally, asphalt pavement maintenance mainly considers pavement performance and cost and largely ignores the environment while substantial amount of environmental burdens are released in the process. In this study, a multi-objective optimization model was developed integrating the three elements in order to optimize the asphalt pavement maintenance plans at the project level. Pavement performance element was decided as the multiplier of pavement serviceability index and traffic volume. Cost element was represented by the net present value, including components of agency cost, vehicle operation cost and salvage value. Environmental element, integrating energy consumption, global warming potential, acidification potential and respiratory effects potential, was measured by the life cycle assessment model. A hypothetic asphalt pavement maintenance case study was conducted using the developed multi-objective optimization model and harvested 103 sets of feasible combinations of maintenance plans, each of which is non-dominated by the others. Trade-offs analysis was performed among the three objectives and visualized in both two- and three-dimension forms. It is found there is an opportunity of reducing the cost and environmental impacts to 80.3% and 77.8% and increasing the pavement performance to 146.6% compared to the base case. However, they are mutually compromised and cannot be reached simultaneously. The developed model reveals the quantitatively interactive relationship of the three objectives and helps optimize the asphalt pavement maintenance plans.     

Environmental and transport effects of warehouse relocationing: evidence from Norway

Reducing traffic volumes and CO2-emissions from freight transport has proven difficult in many countries. Although the increasing suburbanization of warehouses is seen as a relevant land use trend, comprehensive analyses of their impact remain scarce. This study uses real data in modeling transport, costs, environmental and modal effects from warehouse relocations around Oslo and Trondheim (Norway). Results indicate that for Oslo, traffic performance (ton-km), CO2-emissions, and transport costs increase following warehouse suburbanization. For Trondheim, transport performance and CO2-emissions increase less, while transport costs decrease marginally. We conclude that specific case characteristics (geography and trade patterns) are important in determining the strength and direction of effects, and expect that common concomitant developments (warehouse centralization and consolidation) would lead to more pronounced results. Our findings confirm some, but challenge other, findings from the relatively scarcely literature available. Finally, the study's more general insights and observations can help advance similar analyses beyond Norway.