Revisiting the Parallel Strategy for DOACROSS Loops

Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front...     

交变拉伸载荷下油管丝扣密封性能研究

针对高压注入井油管在服役环境下长期承受交变拉伸载荷作用存在泄漏风险的问题，通过搭建交变拉伸载荷下油管丝扣密封性能测试试验平台、优选试验设备及制定合理的试验步骤，对平扣、BGT扣、FOX扣油管试样在10~50 t拉伸交变载荷下的密封性能进行了模拟。模拟结果显示:对3种扣型油管试样施加同等拉伸载荷，其密封性能随交变次数增加而降低，降低幅度为平扣>BGT扣>FOX扣；50 t拉伸载荷施加5次后，3种扣型油管试样的密封性能分别为5.67 MPa、32.69 MPa、73.67 MPa。研究表明，平扣无法满足注入井的密封要求，BGT扣及FOX扣具有较好的适用性。研究结果为注入井油管扣型选择提供了依据。     

硬孔攻丝用高性能先端丝锥的设计及应用

热后硬孔攻丝螺纹变形量小、尺寸稳定、强度高。该工艺方法对刀具强度要求较高,使用普通高速钢丝锥和螺纹铣刀加工时,普通高速钢丝锥无法承受热后硬孔攻丝所产生的大扭矩而频繁折断,报废率较高,同时螺纹铣刀成本高,不适合大批量生产。针对热后硬孔攻丝工艺复杂、成本高的问题,专门设计了硬孔攻丝用高性能先端丝锥,解决硬孔攻丝难题,并与其他种类丝锥进行了切削力对比。     

Integer programming methods for large-scale practical classroom assignment problems

In this paper we present an integer programming method for solving the Classroom Assignment Problem in University Course Timetabling. We introduce a novel formulation of the problem which generalises existing models and maintains tractability even for large instances. The model is validated through computational results based on our experiences at the University of Auckland, and on instances from the 2007 International Timetabling Competition. We also expand upon existing results into the computational difficulty of room assignment problems.     

Survey on Passivity Based Control of Induction Machine

Induction machines (IM) constitute a theoretically interesting and practically important class of nonlinear systems. They are frequently used as wind generators for their power/cost ratio. They are described by a fifth‐order nonlinear differential equation with two inputs and only three state variables available for measurement. The control task is further complicated by the fact that IM are subject to unknown (load) disturbances and the parameters can be of great uncertainty. One is then faced with the challenging problem of controlling a highly nonlinear system, with unknown time‐varying parameters, where the regulated output, besides being unmeasurable, is perturbed by an unknown additive signal. Passivity‐based control (PBC) is a well‐established structure‐preserving design methodology which has shown to be very powerful to design robust controllers for physical systems described by Euler‐Lagrange equations of motion. PBCs provide a natural procedure to "shape" the potential energy yielding controllers with a clear physical interpretation in terms of interconnection of the system with its environment and are robust vis á vis to unmodeled dissipative effects. One recent approach of PBC is the Interconnection and Damping Assignment Passivity‐Based Control (IDA‐PBC) which is a very useful technique to control nonlinear systems assigning a desired (Port‐Controlled Hamiltonian) structure to the closed‐loop. The aim of this paper is to give a survey on different PBC of IM. The originality of this work is that the author proves that the well known field oriented control of IM is a particular case of the IDA‐PBC with disturbance.     

Integrated order acceptance and supply chain scheduling problem with supplier selection and due date assignment

The importance, benefits, and impact of integration of decisions within supply chains have long been investigated by many researchers. Order acceptance and supplier selection are two of the most critical decisions for supply chain managers. Throughout the process of order acceptance, a manufacturer has to decide which orders to be accepted and processed and based on the accepted orders, the volume of required raw material is determined. On the other hand, a manufacturer aims to choose one or several suppliers among all possible choices to provide sufficient raw material for the accepted orders, subject to different criteria such as list price, transportation cost, etc. This paper addresses an integrated framework for profit maximization in an integrated supplier selection, order acceptance and scheduling problem in a single-machine environment with multiple customers. There is substantial literature on the problems of supplier selection and order acceptance; however, to the best of our knowledge, this paper is the first research that integrates these essential decisions in the form of a mathematical model to maximize the total profit. The problem is NP-hard in nature; therefore, solving to optimality is not practically possible for problems with medium and large size. For that purpose, we developed a Heuristic Algorithm (HA) to solve the problem above in a reasonable time, with proper accuracy. Results from this heuristic algorithm are compared with that of a commercial solver (GAMS) and the well-known Genetic Algorithm (GA) and Variable Neighborhood Search (VNS). Computational experiments demonstrate that the developed heuristic algorithm is more efficient in comparison with other tested methods.     

Airline planning and scheduling: Models and solution methodologies

The airline industry is a representative industry with high cost and low profitability. Therefore, airlines should carefully plan their schedules to ensure that overall profit is maximized. We review the literature on airline planning and scheduling and focus on mathematical formulations and solution methodologies. Our research framework is anchored on three major problems in the airline scheduling, namely, fleet assignment, aircraft routing, and crew scheduling. General formulation, widely used solution approaches, and important extensions are presented for each problem and integrated problems. We conclude the review by identifying promising areas for further research.     

南海高温高压气田尾管回接管柱改进及入井质量控制

南海西部海域高温高压条件苛刻,气井开发将准177.8 mm尾管回接至井口并全井段封固作为井筒完整性保障的技术措施之一。由于常规回接工具插入回接筒困难、密封能力有限,不能满足高温高压气井的要求,同时回接尾管材质软,采用特殊螺纹设计,入井质量要求高,因此优化改进了尾管回接工具及管柱结构,包括节流带孔碰压浮箍、4道密封件以及顶部封隔器+防上顶卡瓦的设计;开展了特殊螺纹上扣准确度控制技术研究,基于螺纹密封脂的摩擦因数修正了套管上扣扭矩计算公式,总结了上扣曲线可接受度的关键判断方法,提出了上卸扣速度精细化调整建议。上述工具和技术在6口高温高压开发井进行了应用,尾管回接作业提效20%,并有效提高了套管入井质量和井筒完整性。     

Heuristics for solving continuous berth allocation problem considering periodic balancing utilization of cranes

This study investigates a berth allocation problem considering the periodic balancing utilization of quay cranes in container terminals. The proposed model considers that the quay cranes allocated to a work shift should be fully used and other real-world considerations, such as the continuous quay line, the penalties for early arrivals and departure delays. To solve the model, several heuristics are developed: the model for large problems is decomposed into sub-models that are solved by rolling-horizon heuristics; neighborhood search heuristics are used for optimizing a berthing order of vessels; parallel computing is used to improve the algorithmic performance. The method performs well when applied to real-world large-scale instances with promising computation time that is linearly related to the number of vessels.