浅谈公路环评解译工作中遥感影像的选择

对目前公路环评解译工作中常用的TM、SPOT5、QUICK BIRD等影像在分辨率、波谱特征和经济性等方面进行了对比,得知TM影像在分辨率、波谱特性、价格方面均满足公路环评工作的需要,是适合公路环评工作的卫星影像。并以神池至河曲高速公路所在地区的TM影像为例,运用Chavezetal提出的最佳指数法得到了该区域解译的最优波段组合。     

Port privatization under Cournot vs. Bertrand competition: a third-market approach

By incorporating port competition into a third-market model consisting of two exporting firms and one importing country, we demonstrate the endogenous choice of port structures (i.e. privatization or public ownership) under either Bertrand or Cournot competition. In contrast to previous studies on port competition, we analyze the port strategy in view of all trading countries (i.e. importing country and exporting countries). We find that regardless of transport cost, the port ownership strategy alters according to exporting firm’s competition mode. Under Bertrand competition, the choice of port ownership structure depends on the degree of imperfect substitutability. However, under Cournot competition, all trading countries choose same ownership structures of each port. By comparing equilibrium of each competition mode, we show that welfare of exporting country under Cournot competition is higher than under Bertrand competition if goods are sufficiently substitutes. In contrast, importing country prefers Bertrand competition to Cournot competition when the competitive pressure is sufficiently high.     

Cape结构路用性能调查和试验研究

通过现场调查得出Cape结构试验路的主要病害,并根据调查结果确定试验内容,分别研究了Cape结构的防水性、低温抗裂性、高温抗车辙性和层间粘结性能。试验结果表明:Cape结构防水性能良好,但用规范关于稀浆封层渗水系数的标准检测过于严格;Cape结构低温抗裂性能较沥青混凝土差,与沥青碎石相近,SBR改性剂可明显改善其低温抗裂性能;Cape结构高温抗车辙性能良好,层间粘结性能随温度的升高而下降,并且与基层表面处理措施密切相关,当温度较高时容易发生剪切破坏。     

一维固结变形理论参数的试验分析

通过对原状土样及重塑土样的一维固结及渗透试验分析,对一维固结变形理论中的有关试验参数进了系统试验分析。探索了土体侧压力系数在固结过程中的变化规律,发现对正常固结土存在一临界固结压力,当固结压力大于该值时,土体的变形以次固结变形为主;通过对渗透系数的变化进行分析,表明土体结构对渗透系数有较大影响,且提出了渗透系数的计算公式;同时利用割线模量法给出了地基沉降的计算公式。在此基础上,对固结系数的算法进行了有益的尝试,并将之与传统方法进行对比,提出了一种固结沉降计算新方法。最后,通过工程实例,验证了研究成果的可靠性。     

双掺增钙渣、增钙粉煤灰水泥混凝土路用性能试验分析

首先对新型废料——增钙渣和增钙粉煤灰进行了物理化学性能分析,证明其活性优于普通混凝土。采用正交试验方法对双掺该材料的水泥混凝土的力学强度试验结果进行了极差和方差分析,得出了影响强度性能的因素。采用快冻法等规定的试验方法验证了双掺混凝土的抗冻、收缩、抗磨耗等路用耐久性能。对双掺混凝土的强度和耐久性机理进行了级配调整、改善界面性能、孔结构等3方面的理论分析。对比试验结果表明:双掺增钙渣、增钙灰混凝土的抗压、抗折强度、抗折弹性模量等力学指标达到重交通等级公路要求,抗冻性能、收缩性能与普通砂混凝土相当,抗磨耗性能超过了普通砂混凝土,证明双掺此种材料的水泥混凝土可以满足公路建设的需要,而且还可以减少环境污染,社会意义重大。     

冷铣刨机金属探测技术研究

随着冷铣刨机在路面养护施工中的大量使用,铣刨机金属探测技术的应用显得越来越重要。介绍了金属探测技术方法的选择和金属探测器的应用情况,并通过实验确定了金属探测器安装在铣刨机上的最佳数量、位置和高度。     

汽车实验模态分析微机系统的开发及应用

本文介绍了自行开发的适用于汽车工程的实验模态分析微机系统。在阐述适合微机的模态分析理论基础上,展示了该系统的组成结构、软件开发及特点。最后介绍了应用该系统对SC-110汽车驾驶室和车架总成的实验模态分析。     

引气粉煤灰混凝土的氯离子扩散系数

基于盐碱寒冷地区的工程环境与混凝土的配制特点,模拟配制了SA溶液,采用正交方案试验研究了水灰比、含气量和粉煤灰掺量3个参数对引气粉煤灰混凝土氯离子扩散系数的影响,建立了氯离子扩散系数计算模型,并采用游程检验法对计算模型进行了检验,结果表明该模型表征的相关关系显著,预测值与实测值无显著差异。     

级配碎石裂缝缓解层防裂机理及足尺疲劳试验

反射裂缝是旧水泥混凝土路面沥青加铺层的主要病害之一,目前尚无理想的解决方法,针对这一问题,提出了采用级配碎石作为裂缝缓解层的方法。对级配碎石层的防裂机理进行了分析,采用大型反射裂缝试验台架进行了设置级配碎石层及其他对比结构层的加铺层疲劳破坏试验,模拟了沥青加铺层荷载型及温度型反射裂缝的产生、发展过程。结果表明,级配碎石防裂效果最好,玻纤格栅和土工布的防裂效果次之,普通沥青混凝土加铺层防裂效果最差。     

Analysing Demand for Suburban Trips: A Mixed RP/SP Model with Latent Variables and Interaction Effects

We analyse mode choice behaviour for suburban trips in the Grand Canary island using mixed revealed preference (RP)/stated preference (SP) information. The SP choice experiment allowed for interactions among the main policy variables: travel cost, travel time and frequency, and also to test the influence of latent variables such as comfort. It also led to discuss additional requirements on the size and sign of the estimated model parameters, to assess model quality when interactions are present. The RP survey produced data on actual trip behaviour and was used to adapt the SP choice experiment. During the specification searches we detected the presence of income effect and were able to derive willingness-to-pay measures, such as the subjective value of time, which varied among individuals. We also studied the systematic heterogeneity in individual tastes through the specification of models allowing for interactions between level-of-service and socio-economic variables. We concluded examining the sensitivity of travellers’ behaviour to various policy scenarios. In particular, it seems that contrary to political opinion, in a crowded island policies penalising the use of the private car seem to have a far greater impact in terms of bus patronage than policies implying direct improvements to the public transport service.