• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.11
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• pp.1929-1945
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• 2011

RFID technologies have attracted a lot of attention in recent years because of their cost/time-effectiveness in large-scale logistics, supply chain management (SCM) and other various potential applications. One of the most important issues of the RFID-based systems is how quickly tags can be identified. Tag collision arbitration plays a more critical role in determining the system performance especially for passive tag-based ones where tag collisions are dealt with rather than prevented. We present a novel tag collision arbitration protocol called Optimum Frame-Slotted Aloha (OFSA). The protocol has been designed to achieve time-optimal efficiency in tag identification through an analytic study of tag identification delay and tag number estimation. Results from our analysis and extensive simulations demonstrate that OFSA outperforms other collision arbitration protocols. Also, unlike most prior anti-collision protocols, it does not require any modification to the current standards and architectures facilitating the rollout of RFID systems.

• Journal of Korea Multimedia Society
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• v.15 no.10
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• pp.1212-1220
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• 2012

In this paper, a collision-free resource reservation scheme for WUSB (Wireless Universal Serial Bus) networks with WiMedia D-MAC (Distributed Medium Access Control). Since distributed characteristic of the WiMedia D-MAC supporting DRP (Distributed Reservation Protocol) scheme may cause lots of conflicts, overall performances of the WUSB with WiMedia D-MAC can be deteriorated. In addition, when we consider multi-hop environment, "mobile" hidden node problem due to mobility of WUSB devices can be happened, and it is a critical problem to mobile WUSB devices transceiving real-time QoS (Quality of Service) traffic. To tackle the problem, we propose a new DRP reservation mechanism to prevent DRP conflicts for multi-hop mobility support in WUSB networks with WiMedia D-MAC and show its improved performance via simulation results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2684-2690
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• 2009

The existing mobile learning service is the method that provides data packets in real time. It has some problems of much data packet cost and delay to provide the mobile learning service. In this paper, to solve the problems, we suggest to implementation of the mobile learning system of the new method using serial communication.

• Journal of the Korean Society of Systems Engineering
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• v.7 no.2
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• pp.21-30
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• 2011

The contractor management for the effective defense project is essential factor in the modern defense acquisition project. The occurrence of Improper Businessman causes the reason in which defense acquisition project is unable to be reasonably fulfilled and setback to the deployment of defense weapon system. In this paper, we develop a prediction model for the effective defense project by using the Discriminant Analysis, the Logistic Regression & Artificial Neural Network and analyse the core variables that determine the Improper Businessman in many variables. It is expected that our model can be used to improve the project management capability of defense acquisition and contribute to the establishment of efficient procurement procedure through entry of the reliable domestic manufacturer.

• Asian Journal of Business Environment
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• v.3 no.1
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• pp.5-16
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• 2013

Purpose - Micro-finance institutions (MFIs) are critical to Vietnam's quest for poverty alleviation among the poor in the rural and agrarian communities. The current study attempts to investigate the impact of microfinance outreach programs undertaken by formal and semi-formal MFIs in Vietnam targeting the poor rural and agrarian communities. Research design, data, methodology - An enquiry was made as to whether the poor and rural communities accessed the micro credit offered by Government supported MFIs and NGOs through their microfinance outreach programs. Furthermore, the current study attempted to explore if the current mode of operations adopted by MFIs in Vietnam is sustainable. Results -The findings indicate that significant progress has been made in Vietnam to alleviate poverty among the poor rural communities through micro finance outreach programs. Conclusions - There are also pointers of MFIs sustainability in Vietnam. However, it still remains to be seen if the current sustainability pointers are long lasting without government subsidies or some international organizations financial support to microfinance outreach programs.

• Journal of Distribution Science
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• v.10 no.12
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• pp.19-24
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• 2012

Purpose - This paper discusses the heterogeneous fixed fleet vehicle routing problem with pick-up and delivery (HFFVRPPD), for vehicles with different capacities, fixed costs, and travel costs. Research Design, data, methodology - This paper made nine assumptions for establishing a mathematical model to describe HFFVRPPD. It established a practical mathematical model, and because of the non-deterministic polynomial-time hard (NP-hard), improved the traditional simulated annealing algorithm and tested a new algorithm using a certain scale model. Result - We calculated the minimum cost of the heterogeneous fixed fleet vehicle routing problem (HFFVRP) with a single task and, on comparing the results with the actual HFFVRP for the single task alone, observed that the total cost of HFFVRPPD reduced significantly by 46.7%. The results showed that the new algorithm provides better solutions and stability. Conclusions - This paper, by comparing the HFFVRP and HFFVRPPD results, highlights certain advantages of using HFFVRPPD in physical distribution enterprises, such as saving distribution vehicles, reducing logistics cost, and raising economic benefits.

• Journal of Navigation and Port Research
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• v.33 no.4
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• pp.263-270
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• 2009

Busan North port is facing crisis due to the opening of the New port. The North Port and NewPort are competing for a limited volume of cargoes and this competition is leading after all to price competition, lowering cargo work fee that may result in the failure of both This paper proposed the balanced development plans, which are the strategies of business tie-up and activation between the North Port and NewPort by introducing the strategy of "co-opetition" and the analysis for the success factor of co-opetition: to solve this operational problems on Busan port. It is found out that activation strategy is more successful co-opetition strategy than business tie-up strategy. The execution for the two co-opetition strategies will lead Busan Port to the balanced development as well as the enhanced competitiveness and will leap Busan port into global hub port as well.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.162-163
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• 2011

This paper presents the system dynamics methodology for modeling and control the production/inventory system. Under system dynamics point of view, we can apply some production/inventory policies as if we use the control laws for dynamics systems, then the behavior of system is analyzed and evaluated to improve the performance of production/inventory system. We also utilize the hybrid modeling method for the dynamic of production system with the combination of Matlab/Simulink and Matlab/Sateflow. Finally, the numerical simulation results are carried out in Matlab/Simulink environment and compare with the results from other works. It is shown that our approach can obtain some good performances (such as operational cost, stability of inventory, customer service level).

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.83-89
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• 2001

This paper provides a short description of the COMPASS-model which is a concept for the simulation of multiway systems. The focus of the COMPASS-model is to offer an opportunity to investigate the effects of redistribution strategies on logistic and monetary values in a system of returnable transport items (RTI). The modeling concept consists of five modules: topology, system load, distribution, redistribution, cost. It includes the integration of highly sophisticated evolutionary algorithms for the optimal solving of complex capacitated vehicle routing problems (CVRP) which are typical for RTI-systems. The results of first experiments with a COMPASS-based prototype are repeated. They reveal some basic regularities in RTI-systems.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.48
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• pp.263-268
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• 1998

An efficient agricultural marketing system is very important to producers and consumers to keep the reasonable prices. In these days, the main policy for the efficient agricultural marketing system is to enlarge the direct transaction market. But it is not easy to enlarge the direct transaction market in a few years. This paper proposes a new efficient agricultural marketing system that gives a similar effect with the direct market. The proposed system is mainly composed of three associations; producers', consumers' and retailers'association, and the function of the system is devided into material affairs and commercial affairs. The structure of the system also can be simplified as two to three steps. So the system can reduce the cost of logistics and keep the reasonable prices for both producers and consumers.