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281.
针对城市轨道交通客流预测问题,采用离散一维Daub4,小波分析方法对某一时间段的原始客流时间序列数据进行分解;以分解得到的高频分量和低频分量为样本数据,对最小二乘支持向量机进行训练,确定最小二乘支持向量机的核参数σ,以及系数a和b.利用训练后的最小二乘支持向量机预测未来一段时间客流时间序列数据的高频分量和低频分最,然后再利用Daub4小波分析方法对预测的高频分量和低频分量进行数据重构,从而得到预测的未来一段时间客流时间序列数据.与历史平均预测法和灰色预测法进行比较,结果表明,基于小波分析的支持向量机客流预测方法用于轨道交通短期客流预测具有更好的精度. 相似文献
282.
主要介绍了德黑兰地铁12号线的ATP系统,它能够控制司机对列车的操作,具有故障-安全特性。该系统是ATC(Automatic Train Control)系统的子系统,用于保障行车安全,避免行车事故的发生。当司机不遵守列车运行指令而盲目驾驶的时候,ATP系统能够向司机报警并自动开启制动,降低列车行驶速度。重点介绍德黑兰地铁12号线ATP系统的安装、调试运行情况。目前德黑兰地铁的车载ATP还没有安装数据记录系统,主要对此进行了探讨并提出了相关解决方案。 相似文献
283.
LKJ数据换装施工实行属地管理,在感受其安全及时、节省资源等有利面时,也应客观分析其存在的弊端。结合LKJ数据属地换装实际,针对如何存利去弊,完善LKJ数据换装施工属地管理,谈谈个人的一些建议与看法。 相似文献
284.
285.
To efficiently solve the materialized view selection problem, an optimal genetic algorithm of how to select a set of views to be materialized is proposed so as to achieve both good query performance and low view maintenance cost under a storage space constraint. First, a pre-processing algorithm based on the maximum benefit per unit space is used to generate initial solutions. Then, the initial solutions are improved by the genetic algorithm having the mixture of optimal strategies. Furthermore, the generated infeasible solutions during the evolution process are repaired by loss function. The experimental results show that the proposed algorithm outperforms the heuristic algorithm and canonical genetic algorithm in finding optimal solutions. 相似文献
286.
城市综合交通枢纽评价能否客观有效,将对城市综合交通系统的规划和发展产生重大影响。因此,本文重新整合数据包络分析法(DEA),在传统CCR模型基础上,补充决策单元(DMU)排序方法,使其不但能够指出各决策单元是否有效及无效的原因和程度,同时得到各决策单元的优先排序。并将该方法应用到城市综合交通枢纽评价领域,不仅得到各枢纽或同一枢纽的不同规划方案的排序值,而且找到DEA无效枢纽或方案所存在的症结和改进的方向。最后,通过实例验证了该方法的可行性。 相似文献
287.
道路上的交通流数据通常是以20-30秒间隔采集并传递到交通管理中心的,为了使这些数据能够广泛地运用于各种交通用途,必须采用合理高效的集成方法对其进行处理。传统的数据集成方法基于数理统计的理论,该方法不能有效地去除数据中的噪音。近年来迅速发展的基于小波变换的交通流数据集成方法克服了这一缺点,通过对交通流数据的频率特性进行详细分析能够使集成更加高效,准确满足不同的交通用途对集成的需求。但该方法尚未作进一步的灵敏度分析,本文通过对数据集成中小波函数和数据样本量这两个重要参数的分析,从理论的角度探讨了这两个参数变化对数据集成的影响。然后以北京市三环上的交通流数据为例,计算得到了数据集成建议采用的小波族和小波阶数,以及合理的最小样本量。该结论对数据集成在将来的实际应用具有指导意义。 相似文献
288.
Powder segregation induced by mold filling is an important phenomenon that affects the final quality of metal injection molding (MIM). The prediction of segregation in MIM requires a bi-phase flow model to describe distinctly the flows of metallic powder and polymer binder. Viscous behaviors for the flows of each phase should hence be determined. The coefficient of interaction between the flows of two phases should also be evaluated. However, only viscosity of the mixed feedstock is measurable by capillary tests. Wall sticking is supposed in the traditional model for capillary tests, while the wall slip is important to be taken into account in MIM injection. Objective of the present paper is to introduce the slip effect in bi-phase simulation, and search the suitable way to determine the viscous behaviors for each phase with the consideration of wall slip in capillary tests. Analytical and numerical methods were proposed to realize such a specific purpose. The proposed method is based on the mass conservation between the capillary flows in mono-phase model for the mixed feedstock and in bi-phase model for the flows of two phases. Examples of the bi-phase simulation in MIM were realized with the software developed by research team. The results show evident segregation, which is valuable for improving the mould designs. 相似文献
289.
Taxing vehicle emissions has been advocated as an effective measure to solve the smog and haze problems in China. This paper investigates the effects of vehicle emission taxes on residential segregation in a model of a monocentric city with two income classes. The proposed model explicitly considers the interactions among three types of stakeholders, namely the authority, property developers and heterogeneous households in terms of income level. The properties of the proposed model are analytically explored and the optimal vehicle emission taxes that maximize the social welfare of the urban system are determined. The conditions under which either the rich or the poor lives in the urban central area while the other class in the suburb are identified. The findings show that (i) a high emission tax can drive the low-income households to migrate from suburbs to urban central areas, and the high-income households to migrate from urban central areas to suburbs; (ii) the implementation of the vehicle emission taxes can effectively reduce the air pollution cost and increase the total social welfare of the urban system; and (iii) the emission tax policy may incur inequity issue in terms of change in utility levels of different income classes before and after introducing the vehicle emission taxes. 相似文献
290.
The public transport networks of dense cities such as London serve passengers with widely different travel patterns. In line with the diverse lives of urban dwellers, activities and journeys are combined within days and across days in diverse sequences. From personalized customer information, to improved travel demand models, understanding this type of heterogeneity among transit users is relevant to a number of applications core to public transport agencies’ function. In this study, passenger heterogeneity is investigated based on a longitudinal representation of each user’s multi-week activity sequence derived from smart card data. We propose a methodology leveraging this representation to identify clusters of users with similar activity sequence structure. The methodology is applied to a large sample (n = 33,026) from London’s public transport network, in which each passenger is represented by a continuous 4-week activity sequence. The application reveals 11 clusters, each characterized by a distinct sequence structure. Socio-demographic information available for a small sample of users (n = 1973) is combined to smart card transactions to analyze associations between the identified patterns and demographic attributes including passenger age, occupation, household composition and income, and vehicle ownership. The analysis reveals that significant connections exist between the demographic attributes of users and activity patterns identified exclusively from fare transactions. 相似文献