1,721,165 research outputs found
An optimal production run length in deteriorating production processes
No full textThis paper presents an EMQ model which determines an optimal production run length in a deteriorating production process. It is assumed that the process is subject to a random deterioration from an in-control state to an out-of-control state with an arbitrary distribution and, thus, produces some proportion of defective items. An optimal production run length and a minimum average cost are derived in three deteriorating processes: constant, linearly increasing, and exponentially increasing. Several different results from those of previous research are obtained and discussed. A numerical experiment is carried out to see the behavior of the proposed model depending on the cost and process parameters. Some interesting behaviors are observed. (C) 1999 Elsevier Science B.V. All rights reserved.X1194sciescopu
A stock rationing policy in a (s,S)-controlled stochastic production system with 2-phase Coxian processing times and lost sales
No full textThis paper analyzes a (sS)-controlled stochastic production system with multi-class demands and lost sales. Demands in each class are assumed to arrive according to a Poisson process, and the time required to process an item is assumed to follow a 2-phase Coxian distribution. For each class, a stock rationing level is set. When customers arrive, if the inventory level is lower than the predetermined rationing level, the demands are lost for future demands with higher priorities. A behavior of the production system is modeled as a continuous time Markov chain, and an efficient algorithm to calculate the steady-state probability distribution of the system is proposed. The average operating cost under the stock rationing policy is compared with the one without stock rationing. Numerical experiment shows that the proposed stock rationing policy reduces the average operating cost significantly, depending on the system parameters. (C) 2002 Elsevier Science B.V. All rights reserved.X1110sciescopu
An extended EMQ model for a failure prone machine with general lifetime distribution
No full textThis paper presents an EMQ model which determines an optimal lot size in a failure prone machine. It is assumed that time between failures of a machine is generally distributed, and a machine is repaired instantaneously when it fails. Depending on various types of failure rate function of a machine, it is discussed how to determine an EMQ and prove its uniqueness. Variations of an EMQ depending on repair cost are also examined. Through numerical experiments, extensive investigations are carried out on the effects of repair cost and setup cost to an EMQ as well as average cost, and some interesting behaviors are observed.X1131sciescopu
Production planning and control in major industries in Korea
No full textThis paper presents an extensive survey on many application research activities in production planning, scheduling and control in major industries in Korea. The four largest manufacturing industries in terms of total revenue; steel industry, automobile industry, semiconductor and electronic industry, and shipbuilding industry are selected for review, and the research reviewed is limited to the work on rather practical applications than theoretical ones. The present research progress in production planning and control in Korean industries is discussed, and future research directions in the area are proposed for major manufacturing industries in Korea in order to be more competitive in the international business market.X11sciescopu
Channel coordination through a revenue sharing contract in a two-period newsboy problem
No full textThis paper studies channel coordination through revenue sharing contract between a single retailer and a single wholesaler in a two-period newsboy problem. Two models are discussed, a single-buying-opportunity model and a two-buying-opportunity model. We discuss how the revenue sharing ratio and the wholesale prices are to be determined in order to achieve channel coordination and a win-win outcome. We find that the wholesale prices are set to be lower than the retail prices and the optimal revenue sharing ratio is linearly increasing in the wholesale prices. The proposed revenue sharing contract has more flexibility than price protection, in that the optimal revenue sharing ratio can be settled reasonably through negotiation between the retailer and wholesaler. (C) 2008 Elsevier B.V. All rights reserved.X1179sciescopu
THE ANALYSIS OF A PRODUCTION LINE WITH UNRELIABLE MACHINES AND RANDOM PROCESSING TIMES
No full textThis paper develops an efficient analytical method for the analysis of an n-machine production line with unreliable machines and random processing times. The behavior of the n-machine line is approximated by the behaviors of the (n - 1) two-machine lines based on the decomposition. Simulation and numerical experiment show that the analytical method works well and is very efficient.X1115sciescopu
Joint economic procurement - production-delivery policy for multiple items in a single-manufacturer, multiple-retailer system
No full textThis paper proposes an analytical model to effectively integrate and synchronize the procurement, production and delivery activities in a supply chain consisting of a single raw material supplier, a single manufacturer and multiple retailers. The manufacturer produces multiple items on a single facility utilizing common raw material under a common rotation cycle policy of not incurring shortages at any retailers. This problem is formulated as a variant of the classical economic lot scheduling problem. The objective is to find the production sequence of multiple items, the common production cycle length, and the delivery frequencies and quantities that minimize the average total cost. An efficient heuristic algorithm is presented to solve the proposed problem. Through numerical tests, we show that the proposed heuristic gives quite satisfactory solutions. (c) 2005 Elsevier B.V. All rights reserved.X1161sciescopu
Analysis of a batch machine fed by an unreliable discrete machine
No full textThis paper analyses the behaviour of a manufacturing line consisting of two machines in series where the first machine processes lots one at a time, and is subject to failure and takes a random amount of time to repair when it fails, and the second machine is a perfectly reliable batch machine. A control limit policy is adopted to determine lot sizes for the batch machine. When the batch machine completes processing, if the number of lots in the buffer is greater than or equal to the critical number ( Q ), all the lots in the buffer are loaded immediately, otherwise the batch machine waits until Q lots are accumulated. An embedded discrete time Markov-chain approach is proposed, and recursive approaches are developed to derive necessary performance measures. A numerical example explains how to obtain the optimal value of a critical number minimizing the cost functions.X111sciescopu
A laterally driven symmetric micro-resonator for gyroscopic applications
No full textConventional microgyroscopes of the vibrating type require resonant frequency tuning of the driving and sensing modes to achieve high sensitivity These tuning conditions depend on each microgyroscope fabricated, even though the microgyroscopes are identically designed. A new micromachined resonator, which is applicable to microgyroscopes with self-tuning characteristics, is presented. Since the laterally driven two-degrees-of-freedom resonator was designed as a symmetric structure with identical stiffness in two orthogonal axes, the resonator is applicable to vibrating microgyroscopes, which do not need mode tuning. A dynamic model of the resonator was derived considering gyroscopic applications. The dynamic model was evaluated by experimental comparison with fabricated resonators. The resonators were fabricated using a simple process of a single polysilicon layer deposited on an insulator layer. The feasibility of the resonator as a vibrating microgyroscope with self-tuning capability is discussed. The fabricated resonators of a particular design have process-induced non-uniformities that cause different resonant frequencies. For several resonators, the standard deviations of the driving and sensing resonant frequencies were as high as 1232 and 1214 Hz, whereas the experimental average detuning frequency was 91.75 Nz. The minimum detuned frequency was 68 Hz with 0.034 mV s(-1) sensitivity. The sensitivity of the microgyroscope was low due to process-induced non-uniformity; however, the angular rate bandwidth was wide. This resonator could be successfully applicable to a vibrating microgyroscope with high sensitivity, if improvements in uniformity of the fabrication process are achieved. Further developments in improved integrated circuits are expected to lower the noise level even more
An efficient scheduling algorithm for the hot coil making in the steel mini-mill
No full textThis paper investigates and suggests an efficient solution to the problem of scheduling the steel making line in the Mini Steel Mill, which consists of three major processes: molten steel making, continuous slab casting, and hot charged rolling. Careful synchronization of these processes is a key productivity factor, since a very limited amount of work-in-process inventory is allowed. Since each process must run in batch, the schedule for the Mini-Mill consists of grouping and sequencing of lots for each process. However, each process has its own criteria for judging the quality of its lot grouping, which often conflicts with other processes. An efficient scheduling algorithm for the Mini-Mill is proposed. Numerical experiments with real world data suggest that the proposed algorithm yield satisfactory schedules very efficiently. The algorithm is currently used for the actual scheduling of a Mini-Mill in Korea.X1111sciescopu
- …
