Fluctuating Demand-Oriented Optimization of Train Line Planning Considering Carriage Resources Transfer under Flexible Compositions

Line planning is an important part of service management of Railway. Using the minimum operating cost as objective function, an integer linear programming model for line planning problem of intercity railway is established in this paper. Different alternative line set are constructed according to different train stopping patterns of intercity railways to investigate the impact of different train stopping strategies on rail line capacity utilization and passenger service level. A case study is carried out with Guangzhou-Zhuhai intercity railway as a background. The results show, train stopping pattern plays an important role at the stage of line planning and it will affect a train line plan from interval, equilibrium and other aspects of service quality.

In a railway network, making a line plan is a critical optimization problem that determines the daily transportation capacity of the network, aiming at aligning it with passenger demand while minimizing the operational cost. However, the inherent uncertainty in passenger demand often makes the determined line plan infeasible to cover. Meanwhile, additional adjustments to the line plan due to fluctuating demand in the complex railway system can cause unexpected costs. To obtain a robust line plan, we propose a distributionally robust chance-constrained (DRCC) line planning model based on a type-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\infty $ </tex-math></inline-formula> Wasserstein ambiguity set, aiming to generate a line plan that remains feasible with a pre-specified probability while accommodating a given distribution deviation tolerance. We present an equivalent tractable reformulation for the proposed DRCC model by explicitly characterizing the worst-case probability distribution. Furthermore, we develop valid inequalities and a warm start strategy tailored to this model to enhance computational efficiency. The proposed model and solution method are validated through numerical experiments conducted on the Wuhan-Guangzhou high-speed railway corridor. Results demonstrate the effectiveness of the solution acceleration techniques and underscore the advantage of the DRCC model over the robust optimization model and conventional chance-constrained model in reducing operational costs. Note to Practitioners—The motivation for this paper stems from the need to provide a daily line plan for the railway to meet the uncertain passenger demand with a pre-specified probability. We assume that an estimated probability distribution of the demand is available and characterized by finite scenarios with weights, but we do not need the estimation to be perfect/accurate. We propose a distributionally robust chance-constrained line planning model to maintain robustness under the deviation/inaccurate probability distribution. To solve the model efficiently, we develop a warm start method to quickly find a partial initial solution and design valid inequalities where adding them as constraints can shorten the solving procedure by reducing the feasible region of the model’s continuous relaxation. The produced line plan requires less operational cost than the robust optimization model to cover the same amount of demand by the benefits of leveraging the distributional information.

Beijing-Tianjin Intercity Railway is the first high-speed railway in China. It is an important part of the inter-city railway transit network in the Bohai Rim. High-speed railway has the requirements of high smoothness and high stability to the subgrade. However, in recent years, due to the development of the city, ground subsidence caused by overexploitation of groundwater has caused serious threat to the safe operation of high-speed railway. Therefore, it is significant to conduct continuous observation and analysis for the deformation of high-speed railway and the environment along it.In this paper, TerraSAR-X data is mainly used to study the Beijing Tianjin inter-city railway（Beijing section）, and the Interferometric point targets analysis (IPTA) technique is applied to process the SAR data, so as to accurately estimate the ground deformation in this region. In addition, the results are verified by combining with the second-level leveling results in the range of the region, and the results obtained by this method have a better estimation of the deformation.The Maximal Information-based Nonparametric Exploration method is used to explore the relationship between the various influencing factors and the deformation of high-speed railway. The reasons of uneven settlement along the high-speed railway are analyzed synthetically by combining the results of deformation with the data of groundwater, geological strata, fault zone, aquifer system and precipitation in the area. This method can quantitatively describe the relationship between the above factors and the settlement point, more intuitive understanding its impact on the settlement of high-speed railway. The results show that during the observation period, serious spatiotemporal non-uniform settlement of the high-speed railway has occurred along it. Then the results of InSAR time series deformation and second-level leveling results are combined, the time series segmentation characteristics of deformation point is studied. Ground subsidence and the decrease of groundwater level has a better response. The increase of the groundwater exploitation quantity, resulting in the decrease of underground water level, leading to the settlement of the area increased. At the same time, the land subsidence has a certain relationship with the compressible layer thickness in this area. Through statistical analysis, the correlation between settlement and various factors are summed up to determine the key areas for settlement monitoring. Provide important decision support for the safe operation of high-speed railway.

The development of inter-city railway in China will greatly facilitate people’s travel between cities. Accessibility is a fundamental concept in transportation analysis and planning. Typically, the accessibility of an inter-city railway station means an ease level from an origin to the railway station that can be used to evaluate the service performance of an inter-city railway station. Therefore, the inter-city railway station must have relatively good accessibility in order to reflect the railway’s advantage of travel time compared with other traffic modes in terms of four indexes: time, cost, level of comfort and reliability. In this paper, we calculated these four indexes by evaluating the costs of travel time, travel fare and discomfort. This paper mainly discusses the accessibility level depending on groups of people and distances based on each travel mode.

With the rapid development of intercity railways in China, issues such as wheel rail wear and excessive lateral forces during the negotiation of small-radius curved tracks have emerged. This paper proposed a method of integrating Electro-Hydrostatic Actuator (EHA)-based active radial steering dynamic modeling. The method integrates vehicle dynamic modeling, fractional-order Proportional-Integral (PI) control, and wear analysis. An EHA model integrating permanent magnet synchronous motors, gear pumps, and hydraulic cylinders was developed in Simulink. To address the poor curve-negotiation performance of conventional passive bogies, two EHA configuration schemes (longitudinal and lateral arrangements) were proposed based on theoretical analysis. Parameter analysis has been conducted, and the longitudinal EHA configuration has been demonstrated to be superior in the simulation environment. The results show that active radial steering technology significantly improves curve-negotiation performance through optimized wheelset alignment, with the longitudinal EHA configuration achieving superior reductions in attack angles, wear, and lateral forces. The longitudinal EHA arrangement demonstrates superior performance in suppressing wheelset attack angle and comprehensive wear control. Under standard conditions, it reduces wheelset attack angle by 35% and wear number by 30% in a small radius curved track. This technology enhances operational safety and reduces maintenance costs, providing critical technical support for efficient intercity railway operations.

Maximum fluctuations in mass demand for service at public facilities

Simply supported pre-stressed concrete box-girder bridges are the most common bridge type found on high-speed railway and urban rail transit lines in China. A field experiment has been conducted on the Pixian Viaduct of the Chengdu–Dujiangyan Intercity Railway, where two kinds of simply supported pre-stressed concrete box-girder bridges with a standard span of 32 m are used, one single track and the other double track. Characteristics of the noise underneath the box-girder, far from the bridge, and near the bridge gap were measured and analyzed in the time and frequency domains during high-speed train passage, as was the vibration of the box-girder’s bottom plate. The variations of noise with distance and train speed at locations 1.5 and 9 m above ground level were measured and fitted using mathematical formulae. A simplified formula to predict near-field bridge-borne noise was proposed and verified. The peak bridge-borne noise frequency and its tonal characteristic at 50 and 63 Hz for the double-track and single-track box-girders, respectively, were interpreted in terms of bridge vibration and sound radiation efficiency, respectively. The vibration/noise transfer function and coherence were evaluated, showing that vibration resonance is more significant than acoustic coincidence and that the former is more important in terms of noise reduction.

With the development of high-speed railway (HSR) systems, high-speed rail express delivery (HSReD) is currently the growing trend in railway cargo transport. The decisions on line planning and freight flow allocation are two of the main problems for the practical operation of HSReD. This paper focuses on integrating the above issues, considering differentiated transportation modes and products. A collaborative optimisation model is developed to maximise the benefits of freight transport. Numerical experiments are conducted based on the Beijing-Shanghai HSR. The results show that the collaborative optimisation model gets a 7.96% higher freight-demand fulfilment rate and an 18.64% increase in the profit rate, compared with the two-stage model under the same network conditions and parameter settings. Some operational implications are also obtained based on the sensitivity analysis, which is potentially useful for optimising the daily operation management of HSReD.

Optimal selection of energy efficiency measures for energy sustainability of existing buildings

Diversified customer demands are raising importance of just-in-time and agile manufacturing much more than before. Accordingly, introduction of mixed-model assembly lines becomes popular to realize the small-lot-multi-kinds production. Since it produces various kinds on the same assembly line, a rational management is of special importance. With this point of view, this study focuses on a sequencing problem of mixed-model assembly line including a paint line as its preceding process. By taking into account the paint line together, reducing work-in-process (WIP) inventory between these heterogeneous lines becomes a major concern of the sequencing problem besides improving production efficiency. Finally, we have formulated the sequencing problem as a bi-objective optimization problem to prevent various line stoppages, and to reduce the volume of WIP inventory simultaneously. Then we have proposed a practical method for the multi-objective analysis. For this purpose, we applied the weighting method to derive the Pareto front. Actually, the resulting problem is solved by a meta-heuristic method like SA (Simulated Annealing). Through numerical experiments, we verified the validity of the proposed approach, and discussed the significance of trade-off analysis between the conflicting objectives.

Introduction: To date, a variety of studies have been published on the topic of long term energy system transition. Most studies on future energy systems, however, have a shorter time frame or adopt a supranational focus (e.g. the Energy Roadmap, 2011 or the World Energy Outlook, 2015). It then constitutes a sincere challenge to perform a national energy system transition study with as time horizon 2050 and covering a far-reaching transformation of the energy system. VITO, together with the FPB (Federal Planning Bureau) and ICEDD, performed a study to scrutinise the transition of the Belgian national energy system towards a future mix entirely based on renewable energy sources. The focus on renewable energy sources and on building a national energy system completely running on renewable energy can be traced back to three main concerns: – Climate change: Renewable energy sources (RES) are a major instrument in the fight against climate change as RES do not release (net) greenhouse gas emissions. – Security...

Production plans based on Material Requirement Planning (MRP) frequently fall short in reflecting actual customer demand and coping with demand fluctuations, mainly due to the rising complexity of the production environment and the challenge of making precise predictions. At the same time, MRP is deficient in effective adjustment strategies and has inadequate operability in plan optimization. To address material management challenges in a volatile supply-demand environment, this paper creates a make-to-stock (MTS) material production planning model that is based on customer demand and the demand-driven production planning and control framework. The objective of the model is to optimize material planning output under resource constraints (capacity and storage space constraints) to meet the fluctuating demand of customers. To solve constrained optimization problems, the demand-driven material requirements planning (DDMRP) management concept is integrated with the grey wolf optimization (GWO) algorithm and proposed the DDMRP-GWO algorithm. The proposed DDMRP-GWO algorithm is used to optimize the inventory levels, shortage rates, and production line capacity utilization simultaneously. To validate the effectiveness of the proposed approach, two sets of customer demand data with different levels of volatility are used in experiments. The results demonstrate that the DDMRP-GWO algorithm can optimize the production capacity allocation of different types of parts under the resource constraints, enhance the material supply level, reduce the shortage rate, and maintain a stable production process.

This paper is devoted to designing a mixed-integer linear programming to solve the simultaneous line planning and timetabling problem. A directed graph is first constructed to represent the combinational travel network for both candidate trains and passengers. Through this graph, it is easy to simultaneously describe trains’ operation choices, passengers’ travel choices, and their restrictive relations. Based on it, a mixed-integer linear programming model with many binary and non-negative integer decision variables is built to simultaneously optimize the line plan, timetable, and passenger travel choices, which can be efficiently solved using commercial solver CPLEX for small-scale network, while a decomposition strategy is required to combine with CPLEX for large-scale network. A set of numerical experiments are carried out to analyse the impacts of flow sub-units, number of candidate trains, and weight factors. Finally, we conduct two case studies for testing the practicability of our proposed method.

Joint distribution of wind speed and direction over complex terrains based on nonparametric copula models

This paper briefly discusses the inventory management of coal in a cement industry. The cement company uses coal as fuel in the production process. Continuous production process must be maintained, thus the coal supply must be met to the production demand. In this study, we develop a dynamic simulation of coal inventory control system. We implemented periodic review system (P system) and continuous review system (Q system) method. Our simulation scenario consider some decision variables such as supply, variation of demand, and fluctuation of demand in order to understand the behaviour of the proposed model. This method is expected to provide recommendations for improve the inventory control policies in determining the optimum amount of coal in the warehouse and the optimal interval between orders with a minimum total inventory cost at uncertainty demand condition of product clinker and cement.