Optimization model of number of scheduled freight train formation cars
The determination of the number of formation cars is an important part of making a scheduled freight train plan, and it also has a large influence on the benefits of railway freight transportation. First, the influences that affect the number of formation cars are analyzed. Secondly, taking the maximum freight transport benefits as an objective, and comprehensively considering the primary factors that include service frequency of freight trains, section traction weight, effective length of arrival-departure tracks, and so on, this paper establishes the optimization model of the number of scheduled freight train formation cars. Finally, the solving method for the model is presented, and a case is given to show the solution process. It provides a reference for decision-makers of railway freight transportation.
The Programming of Freight Train Departure Timetable in the Mode of Accumulation with Fixed Time in Marshalling Station
Under the mode of freight trains accumulation with fixed time in marshalling station,it is a periodic event scheduling problem to end car group accumulation and to schedule different trains.According to the theory of Periodic Event Scheduling Problem(PESP),fully considering station operation capability and line carrying capability constraints,departing time of each train and periodic constraints between them are illustrated by periodic constraint graph.Based on the actual working requirements,the model of fixed-time-departure timetable of freight trains is established with benefiting locomotive operating and distributing departing times as evenly as possible as the objective functions.The model genetic algorithm is designed and solved by selecting proper spanning tree of periodic constraint graph and according to the sufficient and necessary condition of PESP.Taking the car flow in Beijing-Guangzhou direction in Fengtai West Marshalling Station as an example,the solution is obtained by the designed genetic algorithm.Calculation result demonstrates that it is probable to get a fixedtime-departure timetable of trains by selecting proper spanning tree to construct fundamental circle basis to help reduce the complexity of solving the model.The sufficient and necessary condition is added to get the feasible solution,which can efficiently save the time of solving the model to get freight train departure timetable at fixed time,the average accumulation hour and the average formation number of departure trains.
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.