• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.227-234
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• 2020

One of the most important operational goals in container terminals is to maximize the quay side productivity by minimizing the turnaround times of the vessels, for which the operations of the quay cranes (QC) to load/unload containers onto/from the vessels should be conducted efficiently without delays. This paper suggests using a policy-based dispatching method for YTs (Yard Tractor) that deliver containers between QCs and the storage yard. The goal of using such a dispatching policy is to maximize the efficiency of the YT operation and accordingly to minimize the QC delays because of late arrivals of the YTs. In particular, in this paper, we modified the previously proposed policy for its application to real container terminal and verified the effect through simulation experiments using real terminal data.

• Journal of Korean Society for Quality Management
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• v.12 no.2
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• pp.33-36
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• 1984

This paper is concerned with the optimal replacement policy of auto-scale with increasing error-variance. This optimization model is to minimize the sum of the cost of defective and excess weight allowance for a target value. The numerical example for the proposed problem is solved by Golden-Section Search and Simpsons's rule.

• Journal of applied mathematics & informatics
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• v.6 no.2
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• pp.539-552
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• 1999

An order-level inventory model for a perishable product with a time-dependent demand is developed for a fixed planning pe-riod allowing backlogging in all cycles within the said period. The market demand is assumed to decrease exponentially as time elapses. The average system cost is derived and its optimization procedure is illustrated with a numerical example. Sensitivity of the optimal so-lution to changes in the values of different parameters of the system is also analysed.

• IE interfaces
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• v.14 no.1
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• pp.30-38
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• 2001

Logistics network management has become one of the most important sources of competitive advantage regarding logistics cost and customer service in numerous business segments. Logistics network simulation is a powerful analysis method for designing and planning the logistics network optimally in an integrated way. This paper introduces a logistics network simulator, LONSIM, developed by author. LONSIM deploys a mix of simulation and optimization functions to model and analysis logistics network issues such as facility location, inventory policy, manufacturing policy, transportation mode, warehouse assignment, supplier assignment, order processing priority rule, and vehicle routes. LONSIM is built with AweSim 2.1 and Visual Basic 6.0, and executed in windows environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.5
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• pp.1238-1259
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• 2024

Previous studies on joint optimization of computation offloading and service caching policies in Mobile Edge Computing (MEC) have often neglected the impact of dependency-aware subtasks, edge server resource constraints, and multiple users on policy formulation. To remedy this deficiency, this paper proposes a many-objective joint optimization dependency-aware task offloading and service caching model (MaJDTOSC). MaJDTOSC considers the impact of dependencies between subtasks on the joint optimization problem of task offloading and service caching in multi-user, resource-constrained MEC scenarios, and takes the task completion time, energy consumption, subtask hit rate, load variability, and storage resource utilization as optimization objectives. Meanwhile, in order to better solve MaJDTOSC, a many-objective evolutionary algorithm TSMSNSGAIII based on a three-stage mating selection strategy is proposed. Simulation results show that TSMSNSGAIII exhibits an excellent and stable performance in solving MaJDTOSC with different number of users setting and can converge faster. Therefore, it is believed that TSMSNSGAIII can provide appropriate sub-task offloading and service caching strategies in multi-user and resource-constrained MEC scenarios, which can greatly improve the system offloading efficiency and enhance the user experience.

• Korean Management Science Review
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• v.28 no.3
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• pp.15-29
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• 2011

In this paper, we consider a system working at both primary service and secondary service. A server can switch between the primary service and the secondary service or it can be assigned to secondary service as a dedicated server. A service policy is characterized by the number of servers dedicated to the secondary service and a rule for switching the remaining servers between two services. The primary service system is modelled as a Markovian queueing system and the throughput is a function of the number of servers, buffer capacity, and service policy. And the secondary service system has a service level requirement strategically determined to perform the service assigned. There is a revenue obtained from throughput and costs due to servers and buffers. We study the problem of simultaneously determining the optimal total number of servers, buffers, and service policy to maximize profit of the system subject to both an expected customer waiting time constraint of the primary service and a service level constraint of the secondary service and develop an algorithm which can be successfully applied with the small number of computations.

• Journal of the Korean Operations Research and Management Science Society
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• v.37 no.3
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• pp.69-78
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• 2012

Reduction of power consumption has been a major issue and an interesting challenge to maximize the lifetime of wireless sensor networks. We investigate the practical meaning of N-policy in queues as a power saving technique in a WSN. We consider the N-policy of a finite M/M/1 queue. We formulate the optimization problem of power consumption considering the packet loss probability. We analyze the trade-off between power consumption and the packet loss probability and demonstrate the operational characteristics of N-policy as a power saving technique in a WSN with various numerical examples.

• Proceedings of the Korean Statistical Society Conference
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• 2005.11a
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• pp.73-78
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• 2005

This paper considers a preventive maintenance policy following the expiration of renewing warranty, Most preventive maintenance models assume that each PM costs a fixed predetermined amount regardless of the effectiveness of each PM. However, it seems more reasonable to assume that the PM cost depends on the degree of effectiveness of the PM activity. In this paper we consider a periodic preventive maintenance policy following the expiration of renewing warranty when the PM cost is an increasing function of the PM effect. The optimal number and period for the periodic PM policy with effect dependent cost that minimize the expected cost rate per unit time over an infinite time span are obtained.

• Journal of the Korea Society for Simulation
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• v.8 no.3
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• pp.67-76
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• 1999

The study of the optimization of operating policy of AGV system, which is used in many factory automation environments has been proceeded by many researchers. The major operating policy of AGV system consists of routing and scheduling policy. AGV routing is composed with collision avoidance and minimal cost path find algorithm. To allocate jobs to the AGV system, AGV scheduling has to include AGV selection rules, parking rules, and recharging rules. Also in these rules, the key time parameters such as processing time of the device, loading/unloading time and charging time should be considered. In this research, we compare and analyze several operating policies of multiple loop-multiple AGV system by making a computer model and simulating it to present an appropriate operating policy.

• International Journal of Industrial Entomology and Biomaterials
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• v.17 no.1
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• pp.109-113
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• 2008

Realizing the scope of utilizing by-products of silk cocoons by applying appropriate methods is the immediate crave to optimize returns. The nutritive value of pupae suits for human diet, feed for poultry, carps, fish, rabbits, piggery and dogs. The pupal skin, fat, oil, cocoon palade have applications in oleo chemical, soap, glycerin, cosmetic, artificial fibres, membranes and n-triacontanol isolation. The pupal proteins Chitin, Shinki fibroin, Serrapeptidase, glucosamine are latent precursors of post surgical, anti-carcinogenic, anti-inflammative, anti-bacterial, anti-histaminic, gastric, hepatitis, pancreatitis, leukocytopenia, neurological, ophthalmic, blood pressure, cardiac and diabetic medicines and for preparation of vitamins A, E and K. The silk and its proteins sericin and fibroin are potentially used for wound healing, diabetes, impotence, sinusitis, arthritis, edema, cystitis, epididymitis, tissue regeneration, cancer, post-surgical trauma and used as anti-oxidatives, bio-adhesives, ultra violet screens and bio-active textiles. The waste cocoons can be used in making art crafts like garlands, carpets, overcoats, decoratives and greeting cards. The in-depth research towards utility optimization and make aware this reality to sericulturists, reelers, weavers, traders, entrepreneurs, policy makers etc., is the upright want of the today's Sericulture industry.