• Korea Trade Review
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• v.46 no.2
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• pp.213-228
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• 2021

In recent year, US government requires local investment ,unlike in the past, when import restrictions and tariff were imposed. In this situation, many companies are considering new investment in the US and entering the local market. However, research on the optimal investment plan along with the case analysis on trade regulation is extremely limited and more research needs to be conducted. Accordingly, this study aims to suggest the implications and countermeasure of the SCM and logistical perspective by studying the optimal measures for the new investment of each company due to trade regulation. As a research method, the gravity location model, Mixed Integer Linear Programming Model were used to select the optimal automobile manufacturing factory considering each state's population. This study will be implication of SCM and logistics perspective not only for companies considering new investment in the US but also for the government to conduct trade negotiations. In the future, it is expected that the US trade pressure will increase and affect Korea in many ways. Therefore, in order to cope with such difficult situation in a timely manner, continuous research considering various possibilities is needed in the future.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.9
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• pp.681-688
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• 2013

Several problems caused by inevitable increment of airplane have been issued. The most effective solution to solve the issues is considered as establishing appropriate Air Traffic Management (ATM) that reduces aircraft's delay at an airport and intensify the airport's capacity. The purpose of this paper is to produce the optimum aircraft schedules that maximize the aircraft throughput by smooth air traffic flow near terminal area of an airport In this paper, mathematical formulations of the scheduling problem are firstly specified. Based on the mathematical modelling, an Optimization-Based Flight Scheduler that provides the optimum flight schedules for arriving aircraft is developed by introducing the Mixed Integer Linear Programming(MILP) and the Genetic Algorithms(GA). With this scheduler, we calculated the optimum schedules to compare to real schedule data from an Incheon Airport. As a result, it is validated that aircraft throughput produced by the optimum schedule is much better than that of the schedule from the Incheon airport. The optimization-based flight scheduler is expected to deal with problems due to the aircraft saturation in near future.

• Journal of Navigation and Port Research
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• v.39 no.4
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• pp.353-360
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• 2015

The offshore oil production requires a huge amount of cost and time accompanied by multiple variables due to the peculiar nature of 'offshore'. And every process concerned is controlled by elaborate series of plans for reducing loss of lives, environment and property. This paper treats an optimization problem for offshore oil production and transportation. We present an offshore production and transportation network to define scope of the problem and construct a mixed integer linear programming model to tackle it. To demonstrate the validity of the optimization model presented, some computational experiments based on hypothetical offshore oil fields and demand markets are carried out by using MS Office Excel solver. The downstream of the offshore production and transportation network ends up with the maritime transportation problem distributing the crude oil produced from offshore fields to demand markets. We used MoDiSS(Model-based DSS in Ship Scheduling) which was built to resolve this maritime transportation problem. The paper concludes with the remark that the results of the study might be meaningfully applicable to the real world problems of offshore oil production and transportation.

• Journal of Korea Water Resources Association
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• v.54 no.6
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• pp.443-452
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• 2021

The authors obtained the discrete hedging rule for a reservoir's water supply operation by applying mixed-integer programming to save more water by earlier rationing of water supply for a drought period. The 'water supply adjustment guide' is the current operational method applied to the multipurpose reservoirs, and it was derived by a simulation method. Applying the two rules to the Hapcheon multipurpose dam's reservoir simulations with the inflow record from 2003 to 2018, the water supply deficit occurred for the long drought from 2015 to 2018. Especially, the no water supply or intermittent water supply persisted for the second half of 2017. The water supply adjustment guide had the 'normal water supply recovery threshold on storage,' which resulted in the water supply being unavailable in July 2017; then, the water supply suspension occurred until January 2018, when the reservoir storage was greater than the normal water supply recovery threshold. Despite the storage increasing due to the inflow of water into the reservoir, the suspension occurrence needs to be improved in practice. The current water supply adjustment guide and the discrete hedging rule for a reservoir's water supply operation are useful and realistic as the reservoir operation guide, which shows the concept of reducing water supply during the drought phase as scientific figures. However, to improve the reservoir simulation results, which do not provide any or intermittent water for several months, it is necessary to increase the current water supply reduction for drought phases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.601-605
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• 1999

$LiCoO_2$and $LiCo_{1-x}$$Ni_x$$O_2$ solid solutions were fabricated by the solid state reaction process. The structural cation mixing phenomena were investigated using XRD, SEM, particle size analysis and $^7$Li NMR,The synthesized LiCoO$_2$ and $LiCo_{1-x}Ni_XO_2$ microcrystallines showed the hexagonal layered structures. Mean particle sizes were increased with the increase of the amount of nickel in the solid solutions. The cation mixing effects were increased as increasing the fraction of nickel(x), x = 0.3, 0.5, 0.7. the peak frequency of $^7$Li NMR was shifted to the higher frequency and the line width increased as increasing the amount of nickel in the solid solutions.

• The Journal of Society for e-Business Studies
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• v.18 no.1
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• pp.71-95
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• 2013

This study aims to validate the cost of building the infrastructure to commercialize online electric vehicles. For that purpose, we probe the cost to construct the necessary infrastructure for online electric vehicles regarding Seoul area public bus transit. OLEV and PEV are considered as alternative electric vehicle schemes, and each of them has their own cons and pros in terms of rechargeable battery cost and charger cost. An optimization model which minimizes the cost to install online electric bus feeding devices is proposed in order to compare the total costs of the two alternative schemes. We developed a Mixed Integer Programming model to locate the feeding devices of several different lengths at each bus stops. Furthermore, we implemented a computer simulator to obtain the parameters which will be used in the MIP model and a Web-based system which determines the optimal location of infrastructure for the whole city area from a result of the MIP model. The cost comparison result shows that the total cost of OLEV is cheaper than that of PEV considering the real data of Seoul area public transit, and, as a result, confirms the feasibility of the commercialization of OLEV.

• Clinical and Experimental Pediatrics
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• v.48 no.5
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• pp.518-522
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• 2005

Purpose : To evaluate the effect of inhaled hypertonic saline solution in hospitalized infants with bronchiolitis. Methods : A randomized double blind trial was performed from October 2003 to May 2004. A total of eighty patients <1 year of age with a clinical diagnosis of acute viral bronchiolitis were enrolled and assigned to receive either of the following : inhalation of 2 mL(0.5 mg) fenoterol added to 2 mL of 0.9 percent saline solution(group 1; n=40) or 2 mL(0.5 mg) fenoterol added to 2 mL of 3 percent saline solution(group 2; n=40). This therapy was repeated at six hours interval after admission. They were evaluated daily just before and 20 minutes after nebulization. The outcome measures included changes in clinical severity score(based on respiratory rate, presence of wheezing, retraction, and general condition) after nebulization and duration of hospitalization. Results : In the clinical severity score, a significant improvement was observed during the 72 hours of hospitalization in both groups(P<0.05). The basic clinical severity scores before inhalation were decreased significantly faster in group 2 as compared to group 1 on each day of treatment(P<0.05). The mean duration of hospital stay was significantly reduced in group 2 than group 1($5.9{\pm}1.9days$ versus $7.4{\pm}2.0days$, P<0.05). No adverse effects were associated with inhaled therapy. Conclusion : These results suggest that a nebulized 3 percent saline solution plus 0.5 mg fenoterol may be more effective than a 0.9 percent saline solution plus 0.5 mg fenoterol in accelerating the clinical recovery of infants with viral bronchiolitis.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.150-159
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• 1996

In this paper, an A-team(Asynchronous Team ) based approach for Reactive power and volage control considering static security assessment in a power system with infrastructural deficiencies is proposed. Reactive power and voltage control problem is the one of optimally establishing voltage level given several constraints such as reactive generation, voltage magnitude, line flow, and other switchable reactive power sources. It can be formulated as a mixed-integer linear programming(MILP) problem without deteriorating of solution accuracy to a certain extent. The security assessment is to estimate the relative robustness of the system in Its present state through the evaluation of data provided by security monitoring. Deterministic approach based on AC load flow calculations is adopted to assess the system security, especially voltage security. A security metric, as a standard of measurement for power system security, producting a set of discrete values rather than binary values, is employed. In order to analyze the above two problems, reactive power/voltage control problem and static security assessment problem, in an integrated fashion for real-time operations, a new organizational structure, called an A-team, is adopted. An A-team is an organization for agents which ale all autonomeus, work in parallel and communicate asynchronously, which is well-suited to the development of computer-based, multi-agent systems for operations. This A-team based approach, although it is still in the beginning stage, also has potential for handling other difficult power system problems.

• Journal of Intelligence and Information Systems
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• v.19 no.4
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• pp.55-79
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• 2013

In this paper, we propose a hybrid genetic algorithm (HGA) approach to effectively solve the reverse logistics network with centralized centers (RLNCC). For the proposed HGA approach, genetic algorithm (GA) is used as a main algorithm. For implementing GA, a new bit-string representation scheme using 0 and 1 values is suggested, which can easily make initial population of GA. As genetic operators, the elitist strategy in enlarged sampling space developed by Gen and Chang (1997), a new two-point crossover operator, and a new random mutation operator are used for selection, crossover and mutation, respectively. For hybrid concept of GA, an iterative hill climbing method (IHCM) developed by Michalewicz (1994) is inserted into HGA search loop. The IHCM is one of local search techniques and precisely explores the space converged by GA search. The RLNCC is composed of collection centers, remanufacturing centers, redistribution centers, and secondary markets in reverse logistics networks. Of the centers and secondary markets, only one collection center, remanufacturing center, redistribution center, and secondary market should be opened in reverse logistics networks. Some assumptions are considered for effectively implementing the RLNCC The RLNCC is represented by a mixed integer programming (MIP) model using indexes, parameters and decision variables. The objective function of the MIP model is to minimize the total cost which is consisted of transportation cost, fixed cost, and handling cost. The transportation cost is obtained by transporting the returned products between each centers and secondary markets. The fixed cost is calculated by opening or closing decision at each center and secondary markets. That is, if there are three collection centers (the opening costs of collection center 1 2, and 3 are 10.5, 12.1, 8.9, respectively), and the collection center 1 is opened and the remainders are all closed, then the fixed cost is 10.5. The handling cost means the cost of treating the products returned from customers at each center and secondary markets which are opened at each RLNCC stage. The RLNCC is solved by the proposed HGA approach. In numerical experiment, the proposed HGA and a conventional competing approach is compared with each other using various measures of performance. For the conventional competing approach, the GA approach by Yun (2013) is used. The GA approach has not any local search technique such as the IHCM proposed the HGA approach. As measures of performance, CPU time, optimal solution, and optimal setting are used. Two types of the RLNCC with different numbers of customers, collection centers, remanufacturing centers, redistribution centers and secondary markets are presented for comparing the performances of the HGA and GA approaches. The MIP models using the two types of the RLNCC are programmed by Visual Basic Version 6.0, and the computer implementing environment is the IBM compatible PC with 3.06Ghz CPU speed and 1GB RAM on Windows XP. The parameters used in the HGA and GA approaches are that the total number of generations is 10,000, population size 20, crossover rate 0.5, mutation rate 0.1, and the search range for the IHCM is 2.0. Total 20 iterations are made for eliminating the randomness of the searches of the HGA and GA approaches. With performance comparisons, network representations by opening/closing decision, and convergence processes using two types of the RLNCCs, the experimental result shows that the HGA has significantly better performance in terms of the optimal solution than the GA, though the GA is slightly quicker than the HGA in terms of the CPU time. Finally, it has been proved that the proposed HGA approach is more efficient than conventional GA approach in two types of the RLNCC since the former has a GA search process as well as a local search process for additional search scheme, while the latter has a GA search process alone. For a future study, much more large-sized RLNCCs will be tested for robustness of our approach.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.6
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• pp.248-252
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• 2008

To get a fine $LiFePO_4$ powder with high electrical conductivity, the influences of doping of aliovalent elements(Cr+B and Cr+Al) on electrical conductivity and of heat treatment conditions on particle size of the doped powders were studied. Two kinds of the doped powders $LiFe_{0.965}Cr_{0.03}B_{0.005}PO_4$ and $LiFe_{0.065}Cr_{0.03}Al_{0.005}PO_4$ were synthesized using mechanochemical milling and subsequent heat treatment at $675{\sim}750^{\circ}C$ for $5{\sim}10\;h$. The doping enhanced grain growth and electrical conductivity. The electrical conductivity at $30^{\circ}C$ was $1{\times}10^{-8}S/cm$ in the doped with Cr and Al, and $5{\times}10^{-10}S/cm$ in the undoped one.