Getting Charlie off the MTA: a multiobjective optimization method to account for cost constraints in public transit accessibility metrics     

Matthew Wigginton Conway  Anson F. Stewart 《International journal of geographical information science》2019,33(9):1759-1787

Most analyses of accessibility by public transit have focused on travel time and not considered the cost of transit fares. It is difficult to include fares in shortest-path algorithms because fares are often path-dependent. When fare policies allow discounted transfers, for example, the fare for a given journey segment depends on characteristics of previous journey segments. Existing methods to characterize tradeoffs between travel time and monetary cost objectives do not scale well to complex networks, or they rely on approximations. Additionally, they often require assumed values of time, which may be problematic for evaluating the equity of service provision. We propose a new method that allows us to find Pareto sets of paths, jointly minimizing fare and travel time. Using a case study in greater Boston, Massachusetts, USA, we test the algorithm’s performance as part of an interactive web application for computing accessibility metrics. Potential extensions for journey planning and route choice models are also discussed.  相似文献   

An Analytical Solution for the Run-Out of Submarine Debris Flows     

Yi Rui 《Marine Geodesy》2019,42(3):246-262

Submarine debris flows have a significant impact on offshore and coastal facilities. The unique characteristics of submarine debris flows involve large mass movements and long travel distances over very gentle slopes. To improve our insight and knowledge of the basic mechanism behind submarine debris flows, an analytical model was derived for the mobility of submarine debris flows. This model takes into account the mass change of debris flows induced by deposition, stagnation pressure, and the topography of the depositional area. One case study on the Palos Verdes debris flow proves its ability to predict the run-out distance of a submarine debris flow to a reasonable level of accuracy. On the gentle slopes, the submarine debris flow progressively loses mass due to deposition, which in turn influences the flow velocity. In addition, the results show that the slope angle and spreading angle of the debris depositional zone play important roles in the sliding process.  相似文献   

Analytical approach for circular-jointed shield tunnel lining based on the state space method     

Jinchang Wang  Weiming Huang  Riqing Xu  Zhongxuan Yang  Rongqiao Xu 《国际地质力学数值与分析法杂志》2020,44(5):575-595

This paper presents a new analytical solution to the circular segmental tunnel lining subjected to overburden and surrounding earth pressures. The governing equations are derived by adopting the curved Euler beam theory and the principle of minimum potential energy. Based on the state space method, the displacements and the relevant energy-conjugated internal forces are treated as the fundamental unknown state vector and can be obtained by solving the state function. The inter-segment joints on the lining are modeled by a set of linear springs, including shear, compression, and rotation. The presented method allows for the arbitrary distribution of the segmented joints and loads along the circumferential direction. The most striking advantages of the proposed method include the rigid body displacement treatment, lining-displacement-dependent soil reaction, and internal force direction dependency of the joint stiffness. Using this method, the displacements and internal forces of the entire lining can be obtained conveniently and simultaneously under the arbitrary loading and joint distribution conditions. The verification of the analytical solutions is provided by several examples.  相似文献   

基于遍历搜索算法的水文地质参数优化求解     

邱淑伟  吴亚敏  柯昱琪  闫佰忠 《吉林大学学报(地球科学版)》2020,50(6):1854-1861

为了解决传统的Theis配线法在求参过程中无法利用全部抽水试验数据、手动配线效率较低、求参过程受人为主观因素影响较大等问题，利用抽水试验数据，以Theis公式和叠加原理为理论基础，以理论计算降深与实测降深的Nach-Sutcliffe效率系数值达到最大为目标函数，基于Matlab软件编程，再利用遍历搜索算法对导水系数（T）、贮水系数（S）在其对应范围内进行遍历，实现了水文地质参数的自动精确求解。将遍历搜索算法应用于2个抽水试验实例的水文地质参数求解，并与传统求参方法的计算结果进行比较分析。结果表明：利用遍历搜索算法求参的计算结果与传统求参方法的计算结果相近，表明利用遍历搜索算法求解水文地质参数有效可靠；2个抽水实例利用遍历搜索算法得到的参数对应的理论计算降深与实测降深的Nach-Sutcliffe效率系数值分别为0.996 5、0.970 8，且相比传统的求参方法而言更接近1.000 0，说明其拟合程度更好。  相似文献   

BDS/GPS双差解算库的嵌入式开发及性能分析     

邹进贵  陈春莹 《大地测量与地球动力学》2018,38(4):366-369

主要开发同时具有BDS、GPS基线解算功能的ATL COM组件和DLL动态链接库，将其嵌入到网页开发中，并对不同观测时长、不同基线长度的多组实验数据进行处理与分析。结果表明，该基线解算库具有良好的封装性、嵌入性及普适性，且可以大幅度减少开发时间。  相似文献   

Cavity expansion in strain hardening frictional soils under drained condition          下载免费PDF全文

S.L. Chen  Y.N. Abousleiman 《国际地质力学数值与分析法杂志》2018,42(1):132-142

  相似文献   

随机模型对BDS/GPS长基线解算精度的影响     

吴康良  罗晨曦  杨菂 《大地测量与地球动力学》2018,38(4):386-389

利用四川CORS网中ZHIJ、QLAI两个测站数据探讨常用的等权模型、高度角模型以及Helmert验后方差估计模型对BDS/GPS长基线解算精度的影响。结果表明：1）BDS/GPS组合系统可以实现长基线高精度解算；2）Helmert验后方差估计随机模型解算精度最高， BDS/GPS组合系统140 km长基线解算精度在水平向和垂向分别优于8 mm和10 mm；3）等权随机模型、高度角随机模型对BDS/GPS长基线解算性能基本相当。  相似文献   

纳滤法用于铝锂分离的初步研究          下载免费PDF全文

高琳  王怀有  赵有璟  王敏 《盐湖研究》2020,28(2):79-90

本文探讨了纳滤分离Al³⁺和Li⁺的可行性,研究了含盐量和铝锂比对分离效率的影响,提出了从锂云母浸出液中分离回收锂的新方法。实验结果表明,纳滤膜对Al³⁺和Li⁺的截留率随含盐量的升高而降低,其中Li⁺始终呈现负浓度梯度扩散的趋势,而Al³⁺的截留率始终稳定在99%以上。当含盐量为45 g/L时,铝锂分离因子最高可达248.33,膜面相应Zeta电位的绝对值达到最大。随着溶液中铝锂比的变化,Al³⁺和Li⁺的截留率分别在不同铝锂比的条件下出现拐点,溶液的pH呈现先下降后上升最后下降的复杂趋势。本实验研究发现,DK膜能够在酸性环境下实现高效的铝锂分离和锂的浓缩,从而为锂云母浸出液中锂的提取提供新的思路。  相似文献   

Theoretical and Experimental Study on the Acoustic Wave Energy After the Nonlinear Interaction of Acoustic Waves in Aqueous Media     

兰朝凤  李凤臣  陈欢  卢迪  杨德森  张梦 《海洋工程》2015,29(4):611-621

Based on the Burgers equation and Manley?Rowe equation, the derivation about nonlinear interaction of the acoustic waves has been done in this paper. After nonlinear interaction among the low-frequency weak waves and the pump wave, the analytical solutions of acoustic waves’ amplitude in the field are deduced. The relationship between normalized energy of high-frequency and the change of acoustic energy before and after the nonlinear interaction of the acoustic waves is analyzed. The experimental results about the changes of the acoustic energy are presented. The study shows that new frequencies are generated and the energies of the low-frequency are modulated in a long term by the pump waves, which leads the energies of the low-frequency acoustic waves to change in the pulse trend in the process of the nonlinear interaction of the acoustic waves. The increase and decrease of the energies of the low-frequency are observed under certain typical conditions, which lays a foundation for practical engineering applications.  相似文献   

TBC5.0软件在GPS控制网基线解算中的性能评估     

吴宜桐 《测绘地理信息》2021,46(2):55-58

针对天宝公司新研发的TBC5.0软件在大型GPS控制网基线解算中的可行性问题,以某航道工程GPS控制网作为研究对象,对TBC(Trimble Business Center)5.0软件在长基线解算中的性能进行评估,并对比分析新版本TBC5.0软件较旧版本TBC3.5软件在模糊度固定方面的不同。结果表明,新版本TBC5.0软件在长基线解算方面的能力得到了较大提高,在1200 km范围内搭载精密星历以及1000 km范围内搭载广播星历时,解算GPS控制网可以得到固定解。基线水平与垂直精度、基线矢量中误差、基线重复率共3个方面的计算结果均表明800 km范围内TBC5.0软件搭载精密星历解算的基线具有较高的稳定性和准确性,且不受精密星历种类的限制。  相似文献