Stochastic seat allocation models for passenger rail transportation under customer choice

We study the seat allocation problem for passenger rail revenue management, in which a rail operator attempts to determine the optimal quantity of seats to be allocated to each cabin class for each train service. We formulate the problem with single-stage and multi-stage decisions as two stochastic programming models that incorporate passengers’ choice behavior. We transform the stochastic models into equivalent deterministic mathematical programs that are easy to solve. Then, we form a variety of seat allocation polices from the optimal solutions to the seat allocation models. A number of simulation tests are offered to test the policies.     

城市土地利用碳排放系统动力学仿真研究——以武汉市为例

研究目的:从系统角度分析土地、人口、社会、经济、能源对碳排放的影响作用,并对武汉市2017—2030年不同政策情景下的土地利用碳排放进行模拟,为其低碳发展战略和低碳土地利用规划提供决策依据。研究方法:系统动力学方法。研究结果:(1)建立的城市土地利用碳排放系统动力学模型是有效的;(2)按照目前的发展趋势,武汉市的碳排放总量将保持逐年攀升的趋势;(3)经济的快速发展对武汉市土地利用碳排放量的增加具有显著的影响作用;(4)调整土地利用结构、调整产业结构以及提高能源利用效率都能够有效的减少武汉市土地利用碳排放量,其中调整土地利用结构和调整产业结构的作用效果相对来说更加明显。研究结论:转变经济增长方式、升级产业结构、调整土地利用结构和积极研发先进的低碳科学技术是武汉市低碳发展的重要途径。     

极软表土层支护技术研究

通过对回风斜井的围岩性质及巷道破坏原因分析,结合数值模拟,提出了U型钢支架与短锚杆全长锚固巷道底角加锚索并喷射混凝土封闭围岩支护治理方案。经实验表明,上述方案的实施取得了良好的支护效果。     

随机数在随机事件与概率教学中的应用探索

本文对在随机事件与概率中的常见问题提出了一种新的借助于计算机实现的解决思路,即通过机器自动产生随机数后构建相应的数学模型,再通过编程计算得到最后结果。该方法既为概率论的教学带来了创新性思维,也为当前的教师提出了新的挑战。     

Simulating Price-Taking

In this article, the author presents a price-takers’ market simulation geared toward principles-level students. This simulation demonstrates that price-taking behavior is a natural result of the conditions that create perfect competition. In trials, there is a significant degree of price convergence in just three or four rounds. Students find this simulation to be a fun, educational experience that adds value to their understanding of competitive markets.     

Selecting make-to-stock and postponement policies for different products in a chemical plant: A case study using discrete event simulation

We present a guideline for selecting the inventory management policy for a specialty chemical plant that produces products with limited shelf life, by producing multiple grades of bulk chemical and packaging them into a large variety of bottles. The policy for each product was selected based on a cost-benefit analysis, using the multiple objectives of maximizing the on time order fulfillment, minimizing the production (cleaning and shelf life expiration) and inventory costs. To generate realistic cost estimates, we developed a discrete event simulation model that included demand variability, planning and scheduling policies, and operational details. We evaluated three different policies: make-to-stock (MTS), postponement, and combined MTS/postponement. We also evaluated different storage media and optimized the number of storage units for products selected for postponement. A combined MTS/postponement policy, in which postponement is applied to products with low to medium demand and high expiration provided lowest costs without significantly impacting the customer on time order fulfillment. For all other products, a MTS policy is applied to maximize order fulfillment on time, reduce cleaning costs and to reduce number of storage units.     

网络安全综合评价方法的应用研究

文章分析了计算机网络运行存在的风险;并从分段技术、加密技术、防火墙技术和抗病毒技术方面探讨了如何防范安全风险。     

艺术类高职学院计算机基础教学模式的探索与思考

深化高职计算机基础教学的改革,必须首先从高职计算机基础教学模式和教材模式改革入手。本文简要阐述了关于艺术类高职学院计算机基础教学模式的思考。     

急诊实践教学方法探讨:PBL联合模拟教学法

急诊医学作为一门临床综合学科,其医学的范畴涉及多个专科,具有急迫性、综合性、实践性、复杂性等特点,实践教学难度较大。我院在急诊医学实践教学中,采用以问题为基础的教学法(PBL)联合模拟教学法,显著提高学生的学习主动性,有效地建立急诊临床思维,培养学生实践能力及知识运用能力,促进急诊医学理论知识的深入掌握,提高教学效果。     

上部覆盖层下伏页岩一类潜在滑坡演化变形机制分析

为研究上部覆盖层下伏页岩这一类型的滑坡失稳变形,需要确定其变形的潜在影响因素,从定量角度上分析这一类型滑坡灾害的变形演化问题。以容县六王镇西流河潜在滑坡为研究对象,借助钻孔勘探、室内试验和地质调绘,详细分析了西流河滑坡的工程地质概况,并推测其可能的变形演化机制,然后利用Geostudio数值软件建立西流河滑坡的渗流模型,模拟其在不同降雨工况下的渗流规律。研究发现:西流河滑坡在持续降雨过程中稳定性系数从1.224逐步降低至1.09,稳定性系数不断下降,滑坡体内由垂直入渗逐步转化沿滑动带稳定渗流;当遭遇极端暴雨情况(50年重现期)时,滑坡体内稳定渗流场显著增厚,饱和滑带土增多,滑坡安全储备达到极限。由此可以得出:上部覆盖层下伏页岩一类滑坡变形演化过程主要分滑坡体上部覆盖层堆积阶段,垂直入渗至页岩富水软化阶段和稳定渗流至潜在滑动带软化蠕变这3个阶段;其中上部覆盖层的高渗透性和下伏页岩的隔水特征是导致页岩风化带软化蠕变和稳定渗流场形成的关键因素。研究结果为上部覆盖层下伏页岩这一类滑坡影响因素的研究提供了一些证据,对研究滑坡演化变形机制具有借鉴意义。