• 산업경영시스템학회지
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• 제34권1호
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• pp.1-8
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• 2011

Controlling industrial vehicle operated by human in warehouse was not simple since the information transfer for controlling the vehicle was not easy. However, as the technology for the WMS (Warehouse Management System) has been advanced and the PDA (Personal Digital Assistant) has come into wide use in a workplace, the control of man-operated vehicle became less difficult as do to AGVS (Automated Guided Vehicle System). This study examines the ways to improve the efficiency of warehouse operation through introducing rule of task assignment for the vehicles, particularly forklift. This study, basically, refer to AGV operation policy because a great number of studies for AGV dispatching rule have been done and the mechanism for the controlling vehicles is very similar. The workers in field prefer to simple dispatching rules such as Shortest Retrieval Time First (SRTF), Shortest Travel Time First (STTF), and Longest Waiting Time First (LWTF). However, these rules have potential disadvantage. Thus, several rules made up by combining rules mentioned above are introduced and these new rules use threshold value or evaluation formula. The effectiveness of these new rules are tested by simulation and the results are compared. This study proposes favorable dispatching rules for forklift in warehouse for the efficiency of the vehicle operation and stability of service level.

• 대한산업공학회지
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• 제21권1호
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• pp.85-101
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• 1995

Automated Guided Vehicles(AGVs) are widely used in computer integrated manufacturing(CIM) systems for material handling purposes. Although automated guided vehicles provide higher levels of flexibility and computer integrability, the installations are limited in number and one of the critical reasons lies in the complexity involved in the operation. The main objective of this research is to alleviate this problem by proposing efficient integrated operational control methods for AGV-based CIM systems. Particularly, this research is concerned with the mixed problem of dispatching automated guided vehicles and scheduling machines operation. The proposed dynamic heuristic algorithm uses various priority schemes and relevant information concerning the load of the system, the status of queues, and the position of AGVs in the scheduling process. The scheduling decision process is hierarchical in the sense that different decision criteria are applied sequentially to identify the most appropriate part to be served. This algorithm consists of two sections, the section of part selection by AGVs for the next service whenever an AGV completes the current assignment, and the section of part selection by machines for next service whenever a machine completes the current operation. The proposed algorithm has been compared with other scheduling schemes using the performance measure of mean flow-time and mean tardiness. Simulation results indicate that the proposed algorithm can reduce the mean flow-time and mean tardiness significantly.

• Architectural research
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• 제19권3호
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• pp.71-77
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• 2017

Dynamic pricing refers to a system in which a tariff varies, according to a level of charging and applied time depending on time change. The power billing system used in the Korean Electric Power Corporation (KEPCO) is based on time of use (TOU) pricing, which is one of the dynamic pricing systems. This paper aimed to determine the operational results of a variable refrigerant flow system, to which a new control algorithm was applied, in order to respond to dynamic pricing, in summer and the utility of the new control. To do this, real measured data was acquired from a VRF system installed in a building for educational purposes, where dynamic pricing was applied for about 100 days during summer time. At the maximum load operation time period in TOU, the new control minimized operation within the indoor comfort range, an increase in refrigerant evaporation temperature in the indoor unit and the number of revolutions in a compressor in the outdoor unit was limited. As a result, power usage was decreased by 11%, and the operational cost by 14.6%. Furthermore, measurement results using the Predicted Mean Vote (PMV) model, that represented satisfaction of thermal environment, showed that 82.8% to 90.4% of the occupants of the building were satisfied during operation when the new control was applied.

• 교육시설 논문지
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• 제25권4호
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• pp.3-9
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• 2018

In recent years, schools in the urban areas are also showing their interest in the integrated school and considering adapting the actual operation method. That is why decline of the school-age population is not limited to rural areas any more, and decreasing number of students in urban schools is raised as a social issue to reconsider the continuation of schools. To solve the problems of the small-scale schools in the urban area, the integrated school is being considered as an alternative. Furthermore, the newly built schools in the urban development areas are also planned as the integrated school. Accordingly, the purpose of this study is to examine the cases of integrated schools in urban area of developed countries and to analyze their architectural planning considerations in practice.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.618-622
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• 2007

In the present study, the cooling and heating operation characteristics of a multi-heat pump have been experimentally investigated for the number of the indoor units(A, B, C) and the operating conditions. The heat pump was controlled by an inverter scroll compressor. The performance of the heat pump was measured by the multi-calorimeter of an air enthalpy method. Cooling and heating capacities and COPs were obtained at the cooling and heating temperature conditions and the setting temperatures of an indoor unit. With increasing the operation frequency of the compressor, the cooling and heating capacities of the heat pump increased linearly. The operation frequency region of the compressor was different as the combination of the indoor unit and the cooling/ heating condition.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.91-98
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• 2007

This paper presents the induced mathematical modeling equations for evaluating the operation stability with automatic transmission of heavy duty vehicle. This theoretical approach indicates that linearized governing equations of system can be converted into eigen-value problems. if the eigen-value has positive number, we can predict the engine operating point locates an unstable operating region. To be a stable state, the unstable operating point diverges toward a stable point which is able to maintain uniform velocity. Based on the previous theoretical analysis, we carry out dynamic simulation to show the behavior of engine operating point and torque converter in transient state. As a result of the dynamic simulation, the suggested theoretical method is found to be reasonable for evaluating the operation stability of a torque converter. In addition, the numerical results explain the engine stops and fluctuating phenomenon in reality.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.338-346
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• 2016

In order for the optimal solution of generators’ annual maintenance scheduling to be applicable to the actual power system it is crucial to incorporate the constraints related to the equivalent operation hours (EOHs) in the optimization model. However, most of the existing researches on the optimal maintenance scheduling are based on the assumption that the maintenances are to be performed periodically regardless of the operation hours. It is mainly because the computation time to calculate EOHs increases exponentially as the number of generators becomes larger. In this paper an efficient algorithm based on demand grouping method is proposed to calculate the approximate EOHs in an acceptable computation time. The method to calculate the approximate EOHs is incorporated into the optimization model for the maintenance scheduling with consideration on the EOHs of generators. The proposed method is successfully applied to the actual Korean power system and shows significant improvement when compared to the result of the maintenance scheduling algorithm without consideration on EOHs.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제25권4호
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• pp.93-104
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• 2019

Purpose: To establish the building guidelines and to analyze the function of Regional Public Hospitals, the survey was conducted primarily on the current status focusing on the location and relationship of the department, area composition ratio, area per bed, and area per operating room. Methods: The research methods of this paper are as follows. 1) A literature survey on the function of the operating and related departments, 2) A drawing analysis for spatial composition and net area calculation. Results: The area of the Operation Department in the Regional Public Hospitals with 200 to 300 beds are as follows. Area ratio: 3.35%, area per Bed: 2.53㎡/bed, the number of beds per operating room: 64.37bed, area per operating room: 146.46㎡/n, area per operating room by plan type: integration corridor 133.84㎡/n, separation corridor 184.82㎡/n. Implications: This paper analyzed data on the current state of Operation Departments for setting up the function and role for the Regional Public Hospital. In the future, it is also required to provide size that takes into account user behavior and the user's psychological aspect in order to suggest appropriate area.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.947-956
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• 2005

In this paper, I scrutinize what Korea has achieved from the KTX(Korea Train Express) project for the past one year of operation since it was open to public in April 2004 while looking into some improvement measures for better services in the future. I tried to compare the clements with those of the Tokaido Shinkasen in Japan. As things may turn at its premier operation, the KTX has been suffering from a small number of passengers, low in demand. However, when I compared the previous year with the post KTX operation of one year, demand of the passenger has increased $40\%$ on Kyong-bu line. I figured the first one year of the KTX operation pretty much followed in the footstep of the Tokaido Shinkansen's. For example, the rate of the each train to be on time as the timetable was equivalent while KTX went through less technical problems than the Tokaido Shinkansen. I have come up with some ideas for improvement, which I believe will lead to the development growth of KTX. First, I suggest that we complete the construction of laying new rails on Kyong-bu line at the earliest possible time. Second, we need to extend the high speed network as well as the rail modernization. Last, I have no doubt that we should secure high technology before we forge in the overseas markets.

• 설비공학논문집
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• 제16권4호
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• pp.311-317
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• 2004

In the present study, the cooling characteristics of the multi-air conditioner (A/C) using an inverter scroll compressor are experimentally investigated for the number of the indoor units and the operating conditions (2$0^{\circ}C$, 24$^{\circ}C$, 26$^{\circ}C$) under the cooling standard conditions by KS C 9306. In the case of the simultaneous operation for 3 indoor units, the cooling capacity, the mass flow rate and the input power have a decreasing trend and COP has an increasing trend, with decreasing the difference in the operating temperature of the indoor unit and the room temperature. In the case of the simultaneous operation for 2 indoor units, the COP of the indoor unit with large cooling capacity is high when the operating temperature is high, but the COP of the indoor unit with low cooling capacity is high when the operating temperature is low. In the case of the single operation for one unit, when the large cooling capacity of the indoor unit is less than 50％ the compressor operates at the minimum operation frequency region and the COP decreases.