新加坡地铁C855标盾构隧道开挖面稳定性分析及泥水压力设定

复合地层中盾构隧道开挖面稳定性一直是盾构隧道工程技术难点之一。新加坡地铁环线属于典型的复合地层,并首次大规模采用泥水平衡盾构施工。文章结合地铁环线C855标段,对复合地层泥水平衡盾构施工中开挖面的稳定性分析与泥水压力设定等问题进行了探讨,基于Anagnostou和Kovari提出的楔形体模型,引进稳定数Ns概念,对沿线开挖面的泥水压力进行了分析计算,综合考虑设备性能、周边环境条件、现场组织与实施等因素给出了泥水压力设定表;并针对工程实施过程中遇到的问题,如开挖面坍塌、泥水逃逸以及降水等情况进行了分析,成果可为其它类似工程提供借鉴与参考。     

基于粘弹性阻尼层随机性的自由阻尼层板的振动和阻尼分析

本文基于粘弹性阻尼层的随机性用Monte Carlo直接抽样法对自由阻尼层板的振动和阻尼进行了分析研究。分析中随机变量取正态分布。针对不同的阻尼层厚度分别考察了复弹性模量的实部、虚部、材料的损耗因子的影响。考察了整体性和局部单元性阻尼导厚度的影响。结果表明,粘弹性材料弹性模量的随机性对结构固有频率的影响不大,对模态损耗因子影响较大;不论是整体的还是局部单元的,阻尼层厚度的随机性对模态损耗因子的影响很显著。因此粘弹性阻尼层的随机性对抑制结构共振响应和声辐射的影响是较大的。阻尼层厚度局部单元随机性影响表明了对阻尼结构采用随机分析的必要性。     

Studying travel-related individual assessments and desires by combining hierarchically structured ordinal variables

Ordinal measures are frequently encountered in travel behavior research. This paper presents a new method for combining them when a hierarchical structure of the data can be presumed. This method is applied to study the subjective assessment of the amount of travel by different transportation modes among a group of French clerical workers, along with the desire to increase or decrease the use of such modes. Some advantages of this approach over traditional data reduction technique such as factor analysis when applied to ordinal data are then illustrated. In this study, combining evidence from several variables sheds light on the observed moderately negative relationship between the personal assessment of the amount of travel and the desire to increase or decrease it, thus integrating previous partial (univariate) results. We find a latent demand for travel, thus contributing to clarify the behavioral mechanisms behind the induced traffic phenomenon. Categorizing the above relationship by transportation mode shows a desire for a less environmental-friendly mix of modes (i.e., a greater desire to use heavy motorized modes and a lower desire to use two-wheeled modes), whenever the respondents do not feel to travel extensively. This result, combined with previous theoretical investigations concerning the determinants of the desire to alter trips consumption levels, shows the importance of making people aware of how much they travel.

Toll product preferences and implications for alternative payment options and going cashless

There has been a great deal of research on deriving estimates of the value of travel time savings (VTTS) as a way of converting travel time benefits of toll roads relative to free routes into monetary units, the major user benefit in the development of forecasts of traffic and hence revenue streams. By contrast there has been almost no consideration given to identifying the role that various tollroad products play in establishing preferences for toll routes over non-tolled routes. Increasingly tollroads give users the option to pay by cash at a toll booth, by electronic tolling or by a pre- or post-paid debit and credit account system involving vehicle identification. The efficiency gained by electronic tolling for both the users and the operator have resulted in moves in many jurisdictions to eliminate cash collection entirely (or not introduce it when introducing a new tolled road facility), and to introduce a range of pre- and post-payment options. This has been accompanied by a growing move to distance-based charging in some contexts which is more cumbersome to structure with a cash option. This paper investigates current and potential travellers’ preferences for a range of toll products and how much individual’s are willing to pay for very specific toll products. Data from a stated choice experiment is used in a mixed logit model to establish the role that toll products play in the context of offered times and costs of alternative routes, in choosing between alternative ways of paying for the use of tolled routes.

A copula-based approach to accommodate the dependence among microscopic traffic variables

Developing microscopic traffic simulation models requires the knowledge of probability distributions of microscopic traffic variables. Although previous studies have proposed extensive mathematical distributions for describing traffic variables (e.g., speed, headway, vehicle length, etc.), these studies usually consider microscopic traffic observations to be independent variables and distributions for these variables are investigated separately. As a result, some traditional approaches consider microscopic traffic variables as independent inputs to the traffic simulation process and these methods may ignore the possible dependence among different traffic variables.The objectives of this paper are to investigate the dependence structure among microscopic traffic variables and to examine the applicability of the copula approach to the joint modeling of these variables. Copulas are functions that relate multivariate distribution functions of random variables to their one-dimensional marginal distribution functions. The concept of copulas has been well recognized in the statistics field and recently has been introduced in transportation studies. The proposed copula approach is applied to the 24-h traffic data collected on IH-35 in Austin, Texas. The preliminary data analysis indicates that there exists dependence among microscopic traffic variables. Moreover, the modeling and simulation results suggest that copula models can adequately accommodate and accurately reproduce the dependence structure revealed by the traffic observations. Overall, the findings in this paper provide a framework for generating multiple microscopic traffic variables simultaneously by considering their dependence.     

基于混合Logit模型的旅客对短途高速铁路列车选择行为

以南京到上海和南京到杭州的短途高速铁路客流为背景,应用行为调查法与意向调查法开展客流调查,获取客流数据.基于选择行为理论,以旅客对列车的选择作为因变量,旅客个体特征、出行特征、列车服务水平作为白变量,基于多项式Logit模型构建混合Logit模型,拟合客流调查数据.结果 表明:混合Logit模型的拟合优度高于多项式Lo...     

城市轨道交通快慢车运营模式综合评价体系研究

为满足长途客流的快速直达需求,我国城市轨道交通已经开始快慢车混跑运营模式的尝试。而快慢车运营模式,与传统的轨道交通系统相比具有其显著的特点,需建立一套比较客观、科学的评价体系对拟采用的快慢车运营模式进行客观、中肯地评估,以判定其运营效果,为前期项目决策提供依据。根据快慢车运营模式的特点,提出4个主要影响因素,包括对车站投资、车辆相关投资、运营能耗、出行时间的影响,并运用层次分析法建立快慢车运营模式综合评价指标体系,最终确定快慢车运营模式综合评价值。若快慢车运营模式综合评价值大于零,则说明快慢车运营模式社会效益良好,若快慢车运营模式综合评价值小于等于零,则说明需进一步采取措施优化方案,重新进行项目运营模式论证。     

Blind Detection of LSB Steganography in Grayscale Images

There are many detectors for the least significant bit(LSB)steganography which is broadly used in hiding information in the digital images.The length of the hidden information is one of the most important parameters in detecting steganographic information.Using 2-D gradient of a pixel and the distance between variables the proposed method gives the length of hidden information in natural grayscale images without original image.Extensive experimental results show good performance even at low embedding rate compared with other methods.Furthermore,the proposed method also works well disregarding the status of the embedded information.     

浅谈高速公路绿化设计及养护管理

通过对沈大高速公路绿地生态及地形特点的分析,提出高速公路绿地规划的原则,并从植物选择与配植以及养护管理中的一些技术问题,与同行进行探讨。     

深穗中跨珠江口通道选用盾构法隧道方案的风险及对策

长大深水底隧道面临着复杂地质、环境保护、港口产业、航道交通、空域交通、异常气象等风险,盾构法隧道作为一种环境友好型工法,具有自身独特的优势去克服以上风险。文章针对深圳、广州至中山跨珠江口通道工程的特点,基于广州地铁在类同复合地层盾构工程的大规模实践成果,同时结合国内外大直径、高水压、长距离推进等盾构施工关键技术的突破和经验,对施工方案进行了综合研究,认为盾构法三隧洞方案"功能齐备、质量保障、经济合理、风险可控等优势明显,为本工程最优方案,并进一步分析了本盾构隧道工程的风险及对策。