学术英语ppt

introduction
✓ The Periodic Event-Scheduling Problem (PESP), introduced by Serafini and Ukovich (1989), can be used for scheduling a number of periodically recurring events. Railway operators use the PESP model to develop cyclic timetables. The usual PESP model for cyclic railway timetables uses fixed rolling stock and passenger connections to develop the timetable.
✓ Using the well-known method for translating pairs of disjunctive constraints in a PESP model into pairs of conjunctive constraints, we described the rolling stock and passenger connections in a flexible way so that the model can choose between the different options.
content
abstract
✓ In this paper we describe how rolling stock and passenger connections in a cyclic railway timetable can be modeled in a flexible way within the model for the Periodic EventScheduling ProLeabharlann Baidulem (PESP). Usually, PESP models assume that the constraints for rolling stock or passenger connections specify in detail which trains should connect with each other.
✓ 此外，当最小化三个目标中的任何一个时，另外的几个目 标就考虑赋给它们很小的权值以最小化他们，得到主要目 标的最小值。
Long sentences 3
✓ Now we want to find an expression for the total connection time between the arrivals and departures that connect with each other in station B if the connections in station B are still to be determined.
✓ 在本章，我们依据每个方向有两列车的案例的约束图中特 定圈的圈变量介绍以整数线性方式编制列车时刻表所需要 的动车组数量。
Long sentences 2
✓ Furthermore, when minimizing either of the three objectives, the other objectives are taken into account with a tiny weight in order to minimize them, given the minimal value of the main objective.
✓ 运用常用的方法将PESP模型中的单个约束转换成连续的约 束，我们用一种灵活的方式描述动车组交路和旅客接续使 得模型可以有不同的选择。
Summary and conclusions
✓ For the case of two trains per hour in both directions, we expressed the number of train compositions needed to operate the timetable in terms of the cycle variables of certain cycles in the constraint graph. For the more general case, we expressed the total connection time in a matching of the arriving and departing trains in terms of certain process time variables, based on the method described by Villumsen (2006). This can then be used to determine the number of train compositions needed to operate the timetable.
✓ 然而，本文中所提出的灵活性允许模型去选择在动车组交 路接续和旅客接续中列车的接续。依据特定过程的时间变 量得到最小到发列车配对，我们用它来表达接续时间。
abstract
✓ We also describe an abstract framework demonstrating that, under certain conditions, the extra flexibility can be modeled purely in terms of PESP constraints. The concept of flexible rolling stock and passenger connections is illustrated by an example based on three intercity lines of Netherlands Railways.
Sentences pattern
✓ Note that … 注意… （表示解释说明） ✓ With respect to 关于，至于 ✓ In terms of 依据，根据 ✓ For the sake of clarity，…. 清晰起见，….
Summary and conclusions
✓ In this paper we illustrated that a priori fixing the rolling stock or passenger connections in a PESP model may lead to suboptimal solutions if the involved trains are operated more than once per hour. It may even lead to infeasibility for instances where a feasible solution would exist if the connections were selected in the right way. These results were illustrated by a case based on three intercity lines of Netherlands Railways, the largest operator of passenger trains in the Netherlands.
Long sentences 1
✓ In this section we express the number of train compositions needed to operate the timetable in an integer linear way in terms of the cycle variables of certain cycles of the constraint graph for the case that there are two trains in each direction.
✓ However, in this paper we describe how the rolling stock and passenger connections can be modeled in a flexible way within the PESP model, thereby leading to better timetables with respect to passenger connection times, running and dwell times, or the number of train compositions required to operate the timetable.
✓ 现在我们想要找到一个，如果B站的衔接还待定时，在B 站连接到达和出发列车的总衔接时间的表达。
Sentences pattern
This paper is structured as follows : ✓In §2 we describe … ✓Section 3 deals with ... ✓ Section 4 focuses on … ✓Next, in §5 we describe … ✓ Section 6 presents the case involving … ✓ The paper is finished with … in §7.
✓ Serafini 和 Ukovich 在 1989 年 提 出 的 周 期 时 间 规 划 问 题 （PESP），是用来规划一系列周期复现事件。铁路运营者 用PESP模型编制周期性列车时刻表。通常周期性铁路列车 时刻表的PESP模型都采用固定动车组交路和旅客接续来编 制时刻表。
introduction
§2 general properties of PESP models §3 deal with rolling stock connections and counting the number of train compositions needed to operate a timetable §4 passenger connections §5 the general framework for the flexible connections §6 presents the case involving the three intercity lines of Netherlands Railways §7 conclusions
✓ 文章中我们举例说明了PESP模型中，如果一小时开行一列以上列车 的话，一个提前固定的动车组交路和旅客接续可能导致次优解。而 且在存在最优解且接续选择正确的情况下，在案例中有可能导致不 可行解。这些结果在案例中得到验证，案例是基于荷兰铁路的三条 城际线路，荷兰铁路是荷兰最大的旅客列车运营商。
Summary and conclusions
✓ 我们也描述一个简明的框架证明，在特定情况下，可以只 依据PESP约束表示出其他额外的灵活性。关于灵活的动车 组交路接续和旅客接续概念，我们用一个基于荷兰铁路三 条城际线路的例子来说明。
Key words
✓ cyclic railway timetabling; ✓ rolling stock and passenger connections; ✓ PESP
✓ 然而，本文描述动车组交路接续和旅客接续如何用一种灵 活的方式在PESP模型中建模，这样的灵活性会引导生成在 旅客接续时间、运行时间、停站时间或者时刻表所需的动 车组运用数量等方面更优的时刻表。
introduction
introduction
structures
This paper is structured as follows
✓ 本文描述了周期性列车时刻表中动车组交路和旅客接续如 何用一种灵活的方式在PESP模型中建模。通常，PESP模型 假设动车组和旅客的接续约束是确定的。
abstract
✓ However, the flexibility described in this paper allows the model to choose which trains should connect with each other in a rolling stock or passenger connection. We express the connection times in a minimum matching of arriving and departing trains in terms of certain process time variables.