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Recent construction projects involving the building of extremely tall and large structures have increased the demand for various major equipment, including tower cranes (TCs). However, most lifting plans for TCs at construction sites are performed based on the experience and intuition of the site manager as opposed to a systematic process of rational work. This study presents a framework for scheduling TCs using sequential characteristics of a dependency structure matrix (DSM) to efficiently improve the lifting plan of TCs. In this research, a real world construction case study involving a TC in charge of three buildings was examined. The results of the case study indicated that the scheduling of TC using sequential DSM was useful in leveling the TC lifting plan in terms of ease of use, especially in the typical floor cycle lifting planning. Therefore, the TC lifting plan based on sequential DSM presents a more precise and systematic TC lifting plan. Key words: tower crane, dependency structure matrix, lifting plan, frame construction, typical floor. Les projets de construction recents impliquant la realisation de tres hautes et imposantes structures ont fait augmenter la demande pour divers equipements majeurs, y compris les grues a tour (GT). Cependant, la plupart des plans de levage de GT sur les chantiers sont executes en fonction de l'experience et de l'intuition du directeur de chantier et non en fonction d'un processus systematique de travail rationnel. Cette etude presente un cadre pour la planification de l'utilisation des GT selon des caracteristiques sequentielles d'une structure matricielle de dependance (SMD) afin d'ameliorer de maniere efficace le plan de levage de GT. Dans le cadre de cette recherche, une etude de cas reel dans le domaine de la construction impliquant une GT utilisee pour trois constructions a ete examinee. Les resultats de l'etude de cas ont indique que la planification de la GT a l'aide d'une SMD sequentielle etait efficace au niveau de la repartition du plan de levage de la GT en ce qui a trait a la facilite, particulierement dans la planification de levage pour les cycles d'etage types. Donc, le plan de levage de la GT fonde sur la SMD sequentielle constitue un plan plus precis et systematique. [Traduit par la Redaction] Mots-cles : grue a tour, structure matricielle de dependance (SMD), plan de levage, construction de l'ossature, etage type., Introduction Recent construction projects involve enormous and tall structures, given the high densification of cities and the rapid development of construction technologies. The increasing size of structures has led to [...]

The research conducted to find out a new approach called the Reentrant Shop Decentralised Scheduling (RESDES), to comply all the most innovative trends in reentrant shop scheduling using the concept of decentralised decision making is presented. The performance and robustness and real life suitability of the approach is analyzed through the extensive test conducted based on the real data in two cases belonging to semiconductors and metalworking businesses.

ABSTRACT Rescheduling of open orders has played an important part in manufacturing systems to deal with production uncertainty, such as machine breakdowns or scraps. To be responsive to the needs [...]

In this paper, we study a problem Central to crossdocking that aims to eliminate or minimize storage and order picking activity using JIT scheduling. The problem is modelled naturally as a machine scheduling problem. As the problem is NP-hard, and for real-time applications, we designed and implemented two heuristics. The first uses Squeaky Wheel Optimization embedded in a Genetic Algorithm and the second uses Linear Programming within a Genetic Algorithm. Both heuristics offer good solutions in experiments where comparisons are made with the CPLEX solver. Keywords: crossdock: machine scheduling: just-in-time scheduling: heuristics

We consider a scheduling problem in which N products are processed on M identical parallel machines. Each product comprises two components. Because the components of a product are processed in a fixed order, one is conveniently called as first-component and the other is as second-component. First-components are fabricated in batches, each of which is initiated with a set-up. As for second-components, they are manufactured individually. Two components of a product are restrictedly processed on the same machine. A product is completed when both its two components have been completed and are available. We propose two heuristics to build up near-optimal schedules with respect to minimizing the total completion time of products. The performances of both heuristics are compared with a lower bound. Especially, within the experimental range, one heuristic not only dominates over the other all the time but also is much more timesaving. Keywords: Two-component product; Scheduling; Setup, 1. Introduction This study tackles the scheduling problem of component fabrication for N two-component products on M identical parallel machines. Baker [1] makes a pioneering investigation on the single-machine scheduling [...]

Delta Air Lines periodically trains its cockpit crew members to maintain their flight qualifications. The negotiation of the new pilot working agreement (PWA) in June 2001 introduced a short and [...]

A case study of one trucking firm's experience in adopting a traffic optimization model is presented. The executives of the trucking firm were faced with the challenge of balancing the need to improve traffic scheduling while keeping drivers happy. The executives responded by coordinating decision-making regarding the adoption of a real-time routing and scheduling model. After considering the firm's problems, the executives agreed to acquire an advance scheduling system, a move that would help the trucking firm increase profitability while improving customer service and decreasing driver turnover.

The material flow process in the dashboard area and the mechanic area of an automated automobile assembly facility was characterized as part of a cost benefit analysis of several dynamic dispatching rules. Consequently, simulation experiments under varying production conditions were performed using WITNESS. The results demonstrated the superiority of the matching rule over the push rule with respect to work-in-process minimization.

The Daewoo Shipbuilding Scheduling (DAS) system for integrated production planning and scheduling was jointly developed by the shipbuilder and Korea Advanced Institute of Science and Technology. Consisting of several subsystems, it is based on a combination of operations research and artificial intelligence methods such as hierarchical architecture, constrained directed graph search and neural network estimation.

Computational experiments were performed to schedule the assignment of locomotives to train segments for a large railroad network. The nonlinear integer programming problem, which was characterized as a multi-commodity network flow problem and decomposed into many subproblems, was solved using a branch-and-bound procedure involving Dantzwig-Wolfe decomposition. The results indicated an improvement of seven percent over existing solutions using actual data from Canadian National North America.

A nonlinear multi-commodity network flow model and a branch-and-bound procedure based on Dantzig-Wolfe decomposition were employed to reformulate and solve France's crew pairing problem within a set partitioning problem, respectively. This approach, which used resource constrained shortest path subproblems to generate all feasible pairings, produced significant improvements over solutions generated by an expert system being used by the airline.

Computational experiments involving that of scheduling the shutdown of nuclear power plant for refueling and maintenance activities are discussed. Single-site and multi-site problems were considered under site and demand constraints. The problem, which becomes difficult to solve as the number of reactors increases, may be solved using a branch-and-bound search, a price-directed decomposition method and other mixed-integer programming techniques.

The computational complexity of the scheduling problem of minimizing either the maximum tardiness or minimizing the number of tardy jobs in semiconductor burn-in operations was analyzed. The two problems, which are NP-hard with agreeable release times and due dates of the jobs, were found to be amenable to solutions in polynomial time when the processing times, release times and due dates of the jobs are agreeable to each other.

The problem of scheduling the manufacture of multiple components and their assembly into final products of a single type on a single machine is considered. Specifically, an iterative batching and sequencing procedure that generates a repetitive schedule for minimizing the total production cost by optimizing the batch size and production sequence repetitive schedule is described.

An optimal heuristic for scheduling jobs sequences in manufacturing cells containing input and output buffers with a minimum total blocking time is proposed. The heuristic, which reduces the incidence of a job's blocked entry into the automated manufacturing module, provides optimal to near optimal solutions in polynomial time. Hence, it is superior to dynamic programming solutions because the latter becomes computationally intractable with large data sizes.

A new method for security-constrained corrective rescheduling of real power using the Hopfield neural network is presented. The proposed method is based on solution of a set of differential equations obtained from transformation of an energy function. Results from this work are compared with the results from a method based on dual linear programming formulation of the optimal corrective rescheduling. The minimum deviations in real power generations and loads at buses are combined to form the objective function for optimization. Inclusion of inequality constraints on active line flow limits and equality constraint on real power generation load balance assures a solution representing a secure system. Transmission losses are also taken into account in the constraint function. Keywords: Feedback ANN, Real power optimal dispatch, corrective strategy, security enhancement.

Scheduling of pumped-storage units at Taiwan Power Company (TPC) is investigated in this work. In addition to economic considerations, oscillatory stability of the system as affected by the operation of pumped-storage units is of major concern. To achieve a secure as well as economical dispatching schedule for the pumped-storage units, differential dynamic programming is first employed to reach a preliminary schedule in which total fuel cost of the thermal units over the study period is minimized. Oscillatory stability analysis of the system under the preliminary schedule is then performed by computing the eigenvalues and eigenvectors for all electromechanical modes. Sensitivities of the eigenvalues for the poorly-damped inter-area mode with respect to individual generator outputs are evaluated. Then a systematic approach based on linear programming is presented to refine the preliminary schedule in order to improve the damping for the inter-area mode. The effectiveness of the proposed approach is demonstrated by short term operational planning of Taiwan power system. keyword: power system operational planning, hydro scheduling, pumped-storage unit, oscillatory stability, low frequency oscillations, linear programming

The problem of scheduling n dependent tasks represented by out-forest/in-forest precedence graphs on a system of m identical processors in the presence of communication delays was examined. Specifically, several polynomial time algorithms for generating optimal schedules for cases where m is a bounded variable of the problem and both computational and communication delay are of unit time duration were presented. Their evaluation shows that scheduling problems may preserve their polynomial time complexity property even when communication delays are present.

A new integer programming approach that optimizes the scheduling of work shifts with multiple breaks and multiple disjoint break windows is introduced. Unlike set-covering methods, the new scheme reduces the number of integer variables by assigning a set of break variables for each shift-break type combination 'at the expense of an additional constraint for every shift-break combination' for generating the break schedules. It is applicable to situations involving both 24-hr. and less-than-24-hr. continuous operations as well as cases of part-time, full-time and split shifts. The results of its implementation on 40 test problems requiring between 1,728 and 8,640 shift variations showed that it produces optimal results.

This paper presents a new methodology for maintenance scheduling that takes into account the uncertain constraints of the unit maintenance problem. If the spinning reserve is enough, this model can obtain an optimal solution based on reliability or cost concerned. Since the power development is more difficult than ever before, scheduling the unit maintenance under tight spinning reserve is a difficult task. In such a situation, treating various constraints, such as the spinning reserve, duration of maintenance, the maintenance crew, etc., as soft constraints, a fuzzy 0-1 integer programming model is adopted to find the minimum violation solution. In order to verify this model can be implemented in the real system, a case study of the Taiwan Power System is carried out using the algorithm. Index Terms--0-1 integer programming, crisp model, fuzzy model, maintenance scheduling, spinning reserve.

Research into hot rolling production scheduling at Shanghai Baoshan Iron & Steel Complex is presented. A strategy to simultaneously schedule multiple turns in the same shift is considered.