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251.
252.
为了快速、准确地检测出钻井船供电系统中的基波和谐波电流,本文提出一种基于FBD的改进谐波检测算法.该算法利用移动窗算法取代传统FBD的低通滤波器(LPF),通过对正序电流畸变率和直流分量响应时间2个指标进行分析,验证改进FBD在谐波电流检测的速度和精度.为了验证改进的算法在钻井船电网工作状态下的效果,本文加入了动态负载验证改进FBD算法.利用Matlab在稳态和动态负载下对正序电流畸变率和直流分量响应时间分别进行仿真,根据实验结果分析,表明算法具有良好的动态响应、检测精度高、易实现等特点.最后用改进的FBD电流检测配合PR控制方式对钻井船复杂电力系统进行补偿,通过观察谐波电流畸变率可知谐波电流补偿的效果,验证了改进FBD的可行性. 相似文献
253.
Analysis of household activity scheduling has to date been limited to one-day periods. This paper extends the study of household
task allocation to a one-week period. Using a one-week time use survey held under couples in The Netherlands in 2003, the
paper proposes indicators for measuring task allocation on a daily and weekly scale and investigates to what extent role expectations,
work status and indicators of time pressure influence task allocation patterns. The outcomes suggest that egalitarian role
expectations and higher female work status lead to a more balanced allocation of work and households tasks between spouses.
More traditional role views and increased time pressure lead to more specialisation and inequality between spouses. Interestingly,
households under time pressure apply day-to-day specialisation to arrive at balanced weekly allocation totals.
相似文献
Tanja van der LippeEmail: |
254.
In this paper techniques for scheduling additional train services (SATS) are considered as is train scheduling involving general time window constraints, fixed operations, maintenance activities and periods of section unavailability. The SATS problem is important because additional services must often be given access to the railway and subsequently integrated into current timetables. The SATS problem therefore considers the competition for railway infrastructure between new services and existing services belonging to the same or different operators. The SATS problem is characterised as a hybrid job shop scheduling problem with time window constraints. To solve this problem constructive algorithm and meta-heuristic scheduling techniques that operate upon a disjunctive graph model of train operations are utilised. From numerical investigations the proposed framework and associated techniques are tested and shown to be effective. 相似文献
255.
256.
大跨度连续梁桥摩擦摆支座布置及参数研究 总被引:2,自引:2,他引:0
《铁道标准设计通讯》2016,(11):70-76
以1座(71+83+123.5+240+123.5+83+71)m大跨度连续梁桥作为研究对象,研究摩擦摆支座的布置方式以及支座的力学参数取值对结构的地震响应的影响。分析结果表明:采用摩擦摆隔震支座体系的大跨度连续梁,在E2地震作用下,能大幅降低原固定墩的受力,使得各墩内力分布更加均匀,同时降低墩顶的位移;综合考虑可以仅在主跨的主墩上布置摩擦摆支座;摩擦摆支座摩擦系数的变化对结构地震反应影响很大,摩擦系数的增大虽然使支座耗能能力增加,但是过大的摩擦力不能有效地阻断墩梁间惯性力的传递,不能充分发挥隔震支座的耗能作用,建议摩擦系数采用0.02~0.03;摩擦摆支座半径的变化对结构地震反应影响很小,建议根据支座竖向承载力采用相应的曲率半径。 相似文献
257.
Vortex-induced vibration (VIV) of flexible risers with both internal and external flows has received much attention recently. Hence, VIV dynamics of a fluid-conveying flexible riser subjected to external shear current is investigated. The effect of internal flow velocity and fluid density on VIV response is mainly examined and analyzed. A time domain model is introduced and elaborated. Then the finite element method is adopted to discretize the governing equations. Firstly, the model is validated based on the comparison between the numerical and experimental results. Then the influence of the internal flow velocity and fluid density on VIV dynamics is studied. The results show that multi-frequency response occurs when the flexible riser with various internal flow velocities and densities is subjected to external shear current. Under same shear current velocity, the IL mean deflection is enlarged with the increase of the internal flow velocity and fluid density. In addition, the internal flow velocity and fluid density have an evident effect on the vibrating frequency and the root mean square (RMS) displacement in both in-line (IL) and cross-flow (CF) directions. Moreover, mode and frequency transitions can be observed under different internal flow velocities and fluid densities. 相似文献
258.
Installation of floating wind turbines at the offshore site is a challenging task. A significant part of the time efficiency and costs are related to the installation methods which are sensitive to weather conditions. This study investigates a large floating dock concept, which can be used to shield a floating wind turbine during installation of tower, nacelle, and rotor onto a spar foundation. In this paper, the concept is described in detail, and a design optimisation is carried out using simple design constraints. Hydrodynamic analysis and dynamic response analysis of the coupled system of the optimum dock and spar are conducted. Two spars of different sizes are considered, and the motion responses of the spars with and without the dock in irregular waves are compared. Through analysis of the motion spectra and response statistics, dynamic characteristics of the coupled system is revealed. The present design of the dock reduces the platform-pitch responses of the spars and potentially facilitates blade mating, but may deteriorate the heave velocity of the spars in swell conditions. Finally, future design aspects of the floating dock are discussed. 相似文献
259.
This paper studies a vehicle routing problem with time-dependent and stochastic travel times. In our problem setting, customers have soft time windows. A mathematical model is used in which both efficiency for service as well as reliability for customers are taken into account. Depending on whether service times are included or not, we consider two versions of this problem. Two metaheuristics are built: a Tabu Search and an Adaptive Large Neighborhood Search. We carry out our experiments for well-known problem instances and perform comprehensive analyses on the numerical results in terms of the computational time and the solution quality. Experiments confirm that the proposed procedure is effective to obtain very good solutions to be performed in real-life environment. 相似文献
260.
This paper proposes an Interactive Multiple Model-based Pattern Hybrid (IMMPH) approach to predict short-term passenger demand. The approach maximizes the effective information content by assembling the knowledge from pattern models using historical data and optimizing the interaction between them using real-time observations. It can dynamically estimate the priori pattern models combination in advance for the next time interval. The source demand data were collected by Smart Card system along one bus service route over one year. After correlation analysis, three temporal relevant pattern time series are generated, namely, the weekly, daily and hourly pattern time series. Then statistical pattern models are developed to capture different time series patterns. Finally, an amended IMM algorithm is applied to dynamically combine the pattern models estimations to output the final demand prediction. The proposed IMMPH model is validated by comparing with statistical methods and an artificial neural network based hybrid model. The results suggest that the IMMPH model provides a better forecast performance than its alternatives, including prediction accuracy, robustness, explanatory power and model complexity. The proposed approach can be potentially extended to other short-term time series forecast applications as well, such as traffic flow forecast. 相似文献