• 한국국방경영분석학회지
• /
• 제15권1호
• /
• pp.95-111
• /
• 1989

A mixted integer non-linear programming model which has the object function as minimizing building costs, and constraints with the functions for carrying capacity and service level of queueing time is developed. By using the proposed model, the most adequate on a building and the most economical elevator's specifications could be determined by sequential search method like complex method.

• 한국산업융합학회 논문집
• /
• 제4권1호
• /
• pp.41-49
• /
• 2001

This study developed signal optimization algorithm by analyzing vehicle arrival patterns. The major principle of signal optimization is dissipate all queueing vehicle in 1cycle and assign delay time uniformly for all approaches. For this, this study used optimal green time and surplus green time. Optimal green time calculated by estimated traffic volume from vehicle arrival model. Surplus green time defined as the gap of optimal green time and queue dissipated time. And alternative cycle has minimum surplus green time was selected as the optimal cycle. Finally, total delay and average delay per vehicle can be calculated by using queueing theory.

• 산업경영시스템학회지
• /
• 제25권5호
• /
• pp.31-38
• /
• 2002

In this paper, we model a two-server queueing system with priority, to which we put a restriction on the number of servers for each customer class. customers are divided into two different classes. Class 1 customers have non-preemptive priority over class 2 customers. They are served by both servers when available but class 2 customers are served only by a designated server. We use a method of generating function depending on the state of servers. We find the generating function of the number of customers in queue, server utilization, mean queue length and mean waiting time for each class of customers.

• 품질경영학회지
• /
• 제17권2호
• /
• pp.142-148
• /
• 1989

In order to determine the level of service which minimizes the total of expected cost of service and the expected cost of waiting for that service, the important considerations are to evaluate the distance traveled to and from a service facility (D) and the expected number of mechanics in queueing system (L). The travel-time models are very useful when the servers must travel to the customer from the service facility. Thus, in this paper we studied on the determination of the optimal service level by the travel-time models. In order to decide the optimal service level, (D) has been introduced as a uniform distribution and (L) has been introduced as M/M/S model of queueing theory.

• 품질경영학회지
• /
• 제31권3호
• /
• pp.114-125
• /
• 2003

In this paper, we deal with the problem of modeling of agent-based robot manufacturing cell. Its role is becoming increasingly important in automated manufacturing systems. For Object Oriented & Queueing Petri Nets (OO&QPNs), an extended formalism for the combined quantitative and qualitative analysis of different systems is used for structure and performance analysis of mobile robotic cell. In the case study, the OO&QPN model of a mobile robotic cell is represented and analyzed, considering multi-class parts, non-preemptive priority and alternative routing. Finally, the comparison of performance values between Shortest Process Time (SPT) rule and First Come First Serve (FCFS) rule is suggested. In general, SPT rule is most suitable for parts that have shorter processing time than others.

• 산업공학
• /
• 제11권3호
• /
• pp.55-63
• /
• 1998

In this study we consider a CONWIP system in which the processing times at each station follow an exponential distribution and the demands for the finished products arrive according to a compound Poisson process. The demands that are not satisfied instantaneously are assumed to be lost. We assume that the lot size at each station is greater than one. For this system we develop an approximation method to obtain the performance measures such as steady state probabilities of the number of parts at each station, average number of parts at each station and the proportion of lost demands. For the analysis of the proposed CONWIP system, we model the CONWIP system as a closed queueing network with a synchronization station and analyze the closed queueing network using a product form approximation method. A recursive technique is used to solve the subnetwork in the application of the product-form approximation method. To test the accuracy of the approximation method, the results obtained from the approximation method were compared with those obtained by simulation. Comparisons with simulation have shown that the accuracy of the approximate method is acceptable.

• 한국경영과학회지
• /
• 제29권4호
• /
• pp.175-187
• /
• 2004

We consider the simultaneous selection of part routes for multiple part types in Flexible Manufacturing Systems (FMSs). Using an optimization framework we investigate two alternative route assignment policies. The one, called routing mix policy in the literature, specifies the optimal proportion of each part type to be produced along its alternative routes, assuming that the proportions can be kept during execution. The other one, which we propose and call pallet allocation policy, partitions the pallets assigned to each part type among the routes. The optimization framework used is a nonlinear programming superimposed on a closed queueing network model of an FMS which produces multiple part types with distinct repeated visits to certain workstations. The objective is to maximize the weighted throughput. Our study shows that the simultaneous use of multiple routes leads to reduced bottleneck utilization, improved workload balance, and a significant increase in the FMS's weighted throughput, without any additional capital investments. Based on numerical work, we also conjecture that pallet allocation policy is more robust than routing mix policy, operationally easier to implement, and may yield higher revenues.

• 산업경영시스템학회지
• /
• 제27권3호
• /
• pp.26-30
• /
• 2004

We consider an AS/RS(Automated Storage/ Retrieval System) which performs both of single and dual commands. The service times of single and dual commands are assumed to be differently distributed. Steady-state probabilities at the service completion epochs are calculated. Then, we transform the arrival rates of storage and retrieval commands into those of single and dual commands. Using this, we propose a non-preemptive queueing model with priority for the performance analysis of an AS/RS, and obtain approximated means of queue lengths and waiting times.

• Management Science and Financial Engineering
• /
• 제12권2호
• /
• pp.1-18
• /
• 2006

We consider an $M^x/G/1$ queueing system with Bernoulli vacation schedule under multiple vacation policy. where after each vacation completion or service completion the server takes sequence of vacations until a batch of new customer arrive. This generalizes both $M^x/G/1$ queueing system with multiple vacation as well as M/G/1 Bernoulli vacation model. We carryout an extensive analysis for the queue size distributions at various epochs. Further attempts have been made to unify the results of related batch arrival vacation models.

• Management Science and Financial Engineering
• /
• 제15권2호
• /
• pp.1-21
• /
• 2009

We consider an $M^x/G/1$ queueing system with a random setup time under Bernoulli vacation schedule, where the service of the first unit at the completion of each busy period or a vacation period is preceded by a random setup time, on completion of which service starts. However, after each service completion, the server may take a vacation with probability p or remain in the system to provide next service, if any, with probability (1-p). This generalizes both the $M^x/G/1$ queueing system with a random setup time as well as the Bernoulli vacation model. We carryout an extensive analysis for the queue size distributions at various epochs. Further, attempts have been made to unify the results of related batch arrival vacation models.