• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.3
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• pp.113-121
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• 1994

Since it is difficult to expect the normal production of plants in greenhouses during hot summer season in Korea, certain provisions on the control of extreme environmental factors in summer should be considered for the year-round cultivation in greenhouses. This study was carried out to find a method to suppress the temperature rising of nutrient solution by cooling, which is able to contribute to the improvement of the plant growth environment in hydroponic greenhouse during hot summer season. A mechanical cooling system using the counter flow type with double pipe was developed for cooling the nutrient solution efficiently. Also the heat transfer characteristics of the system was analysed experimentally and theoretically, and compared with the existing cooling systems of nutrient solution. The cooling capacities of three different Systems, which used polyethylene tube in solution tank, stainless tube in solution tank, and the counter flow type with double pipe, were evaluated. The performance of each cooling system was about 41 %, 70% and 81 % of design cooling load in hydroponic greenhouse of 1 ,000m$^2$ on the conditions that the flow rate of ground water was 2m$^3$/hr and the temperature difference between two liquids was 10 ˚C According to the results analysed as above, the cooling system was found to have a satisfactory cooling capability for regions where ground water supply is available. Fer the other regions where ground water supply is restricted, more efficient cooling System should be developed.

• Journal of Korean Society of Forest Science
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• v.81 no.4
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• pp.383-392
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• 1992

The objective of this study is to evaluate the impacts on the domestic timber supply potential of forest resources management policies such as the extention of forest management infrastruture and setting aside more forest lands for the provision of environmental goods. To this end, the domestic timber supply functions were estimated using time series data for the period 1970-1990 and were used to predict the future trends in timber production in the Republic of Korea. For this purpose, a set of scenarios based on the forest road density and forest inventory growth were designed for the next 40 years. The timber supply behavior in Korea was found to be different by species group : domestic supply of softwood roundwood is inelastic with respect to its ovum price while that of hardwood elastic. The effect of forest road construction on the domestic timber production seems to be insignificant yet. The model simulation aided by policy scenarios revealed that the future timber supply potential will be largely restricted if the policy option with emphasis on the provision of environmental goods from the forest resources were adopted.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.672-678
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• 2020

The parallel-feeding operation of an AC traction power supply system has the advantages of extending the power supply section and increasing the power supply capacity by reducing the voltage drop and peak demand caused by a train operation load. On the other hand, the parallel-feeding operation is restricted because of the circulating power flow induced from the phase difference between substations. Moreover, the power supply capacity is limited because of the unbalanced substation load depending on the trainload distribution, which can be changed by the train operation along the railway track. This paper suggests a Thyristor-controlled Phase Angle Regulator (TCPAR) to reduce the circulating power flow and the unbalanced substation load, which depends on the phase difference and the trainload distribution and provides a feasibility study. A dedicated control model of TCPAR is also provided, which uses substation power supplies as the input to control the circulating power flow and an unbalanced substation load depending on the phase difference and the trainload distribution. Simulation studies using PSCAD/EMTDC shows that the proposed TCPAR control model can reduce the circulating power flow and the unbalanced substation load depending on the phase difference and the trainload distribution. The proposed TCPAR can extend the parallel-feeding operation of an AC traction power system and increase the power supply capacity.

• Journal of the military operations research society of Korea
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• v.34 no.3
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• pp.1-12
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• 2008

Design of supply chain network (SCN) is required to optimize every factor in SCN and to provide a long-term and strategic decision-making. A mathematical model can not reflect the real world because design of SCN contains variables and stochastic factors according to status of its system. This paper presents the designing methodology of military SCN using the mathematical model and the simulation model. It constructs SCN to minimize its total costs using the Mixed Integer Programming (MIP) model. And we solve problems of a vehicle assignment and routing through adaptation of experiment parameters repeatedly in the simulation model based on the results from the MIP model. We implement each model with CPLEX and AutoMod, and experiment to reconstruct SCN when the Logistic Support Unit is restricted to support military units. The results from these experiments show that the proposed method can be used for a design of military SCN.

• Fashion & Textile Research Journal
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• v.24 no.2
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• pp.206-216
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• 2022

This study sought to examine the sustainability criteria found in the global sourcing practices of global fashion retailers. Sustainable supply chain management, with a particular focus on the sustainability criteria of global sourcing, was analyzed. This qualitative study was based on a focus group interview and corporate social responsibility (CSR) annual reports. Eight master categories, 18 middle categories, and 37 bottom categories were extracted. The key categories and their middle categories were as follows: (1) Social compliance (working conditions, employment, safety); (2) Environment concerns (environmental pollution management, eco-friendly production, supply chain environment); (3) Energy efficiency (energy saving program, store environment); (4) Consumer protection (restricted substances management, consumer product safety improvement); (5) Management system (code of conduct, triangle audit system); (6) Community social activities (local community service, voluntary activities, charitable activities); (7) External stakeholder engagement (media & non-governmental organization management, maintenance of relationship with local authority); (8) Brand protection (respect for companies' intellectual property). The findings of this study offer academically significant insights into the sustainability criteria that can be encountered by companies under diverse global sourcing scenarios, revealing that global sourcing by fashion retailers is not merely a means of reducing costs, but a way of generating new jobs and making a social contribution to developing countries. The study's findings also have practical significance, offering guidelines for general CSR activities in the global sourcing process.

• Journal of Information Technology Applications and Management
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• v.21 no.4_spc
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• pp.449-462
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• 2014

As mobile traffic is growing, the demand for spectrum is increasing but the deficiency of spectrum becomes serious as the supply is restricted essentially. For resolving the issue, spectrum sharing system is discussed from the technical and regulatory point of view, where multiple radio users occupy same frequency. In this paper, the policies and adoptions of spectrum sharing system in some countries are analyzed with a focus on TV white space and licensed shared access, which are based on unlicensed and licensed spectrum usage respectively. Some legal and regulatory plans to adopt and activate spectrum sharing in the Radio Waves Act system of Korea are proposed as well.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1249-1254
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• 2013

A torque control algorithm suitable for detecting an open circuit failure in which one of the three phases is unable to supply power to a motor in the permanent magnet synchronous motor is presented in this paper. When the failure occurs in the inverter, the output torque of motor is restricted. A new method which is implemented by using only a processor algorithm internally without any hardware redundancy circuit is proposed. A simulation and experimental study is carried out with a three phase inverter system to show the validity of the proposed method.

• Journal of the Korean Operations Research and Management Science Society
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• v.35 no.1
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• pp.111-124
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• 2010

In the last decade, traveling purchaser problem (TPP) has received some attention of the researchers in the operational research area. TPP is a generalization of the well-known traveling salesman problem (TSP), which has many real-world applications such as purchasing the required raw materials for the manufacturing factories and the scheduling of a set of jobs over some machines, and many others. In this paper we suggest heterogeneous multiple traveling purchaser problem with budget constraint (HMTPP-B) which looks for several cycles starting at and ending to the depot and visiting a subset at a minimum traveling cost and such that the demand for each product is satisfied and the cost spent for purchasing the products does not exceed a given budget threshold. All the past studies of TPP are restricted on a single purchaser. Therefore we randomly generated some instances. CPLEX is used for getting optimal solutions in these experiments.

• Journal of the Korean Professional Engineers Association
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• v.28 no.4
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• pp.21-32
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• 1995

Tideland Reclamation Projects, which have played a significant role in selfsuffficieny of food in Korea, are being greatly restricted nowadays in their implementation due to their demands of big amount of construction costs and their severe malfunctioning of contaminat-ing the marine environment. Under the situation, this paper was prepared not only to stimulate the Government to continue the imlementation of new tideland reclamation projects, but also to contribute to the development of tideland reclamation technology by which the construction costs and rnalfunctionings could be minimized. Eventhough, the functioning of filters is considered to be important for the safety of seadikes, their planning and design are being made unreasonably In view point of construc-tion cost and strutural safety. Therefore, a reliable planning and design method for filters is presented in this paper on the basis of filter theory. In this way, we professional engineers corncerned should endeavor to develop more ad-vanced technology, by which the Government would implement the tideland reclamation projects continuously to supply the land and water more steadily in time.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.100-105
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• 1998

Along with fusion energy, photovoltaic solar energy conversion has long been considered as one of the few sustainable options for large scale energy supply in the future. In the past, commercial use has been restricted largely to remote area applications where conventional electricity is expensive. However, 1998 marked a year of transition where the major application of the cells changed to become generation of residential electricity in urban areas already supplied by the conventional grid. The current state of the technology is discussed as are major overseas programs to accelerate the urban residential use of photovoltaics, particularly in Japan, Europe and the United States, includng the "million roof" program in the latter. Finally, the planned use of photovoltaics in the Sydney 2000 Olympics is described, where the technology will be used to provide most of the electricity requirements of the 665 residences which will be a legacy of the Olympic Village.