• Journal of the Korean Society for Railway
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• v.16 no.2
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• pp.79-84
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• 2013

The definition and classification of shunting, which involves the process of sorting rolling stock into complete train sets inside station yard, are not clearly specified in Korean domestic safety regulations for railway operations. As a result, collisions during shunting occur rather frequently compared with other types of accidents in railway operations. Therefore, new systematic safety principles are proposed in this paper to improve operation safety during shunting. The improvements in safety and efficiency derived from the newly proposed approach are analyzed and verified in field application.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.37-43
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• 2015

A Beta-type Stirling engine is developed and tested on the operation stability and cycle performance. The flow rate for cooling water ranges from 300 to 1500 ml/min, while the temperature of heat source changes from 300 to $500^{\circ}C$. The internal pressure, working temperatures, and operation speed are measured and the engine performance is estimated from them. In the experiment, the rise in the temperature of heat source reduces internal pressure but increases operation speed, and overall, enhances the power output. The faster coolant flow rate contributes to the high temperature limit for stable operation, the cycle efficiency due to the alleviated thermal expansion of power piston, and the heat input to the engine, respectively. The experimental Stirling engine showed the maximum power output of 12.1 W and the cycle efficiency of 3.0 % when the cooling flow is 900 ml/min and the heat source temperature is $500^{\circ}C$.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.1
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• pp.40-48
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• 2019

Hybrid electric propulsion systems (H-EPSs) are an intermediate step for integrated full electric propulsion warships. H-EPSs are a dynamic combination of mechanical and electrical propulsion systems to achieve the required mission performances. The system modes could adapt to meet the requirement of the various operation conditions of a warship. This paper presents a configuration and operating modes of H-EPSs considering the operation conditions of a destroyer class warship. The system has three propulsion modes, namely, motoring mode, generating mode [power take off (PTO) mode], and mechanical mode. The PTO mode requires a careful fuel efficiency analysis because the fuel consumption rate of propulsion engines may be low compared with the generator's engines depending on the loading power. Therefore, the calculation of fuel consumption according to the operating modes is performed in this study. Although the economics of the PTO mode depends on system cases, it has an advantage in that it ensures the reliability of electric power in case of blackout or minimum generator operation.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.4
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• pp.132-144
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• 2022

In response to the recent surge in aviation demand, major airport and aviation authorities continue to make efforts to formulate arrival procedures that take into account efficient aircraft separation, noise and environmental issues related to carbon (CO₂) emissions. In order to ensure efficient traffic control and environmental issues, as a result, a new concept Trombone, Point Merge, etc. have been introduced and widely used. However, these new concept incisions are becoming a factor that hinders operational efficiency and stability due to the restricted domestic airspace such as military airspace and excessive constraints of altitude, speed, etc. which do not reflect the concept of continuous descent operation and eventually needs to be modified to make continuous descent operation as feasible as possible. We herewith analyze and propose the way of improving flight safety and efficiency in the arrival operation procedure by supplementary modification which consequently contribute to the aviation industry international competitiveness.

• The Journal of Information Technology
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• v.6 no.4
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• pp.125-134
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• 2003

This paper is to measure the sensitivity of relations in communication network operation. In order to procure an important adequacy in the network operation and quality improvement, it is necessary to increase network operation efficiency and analyze the characteristic of network operation. Finally, we analyze costing appropriate operation, propose profit increase scheme and apply realistic business. First of all it's important to improve and estimate a proper operating cost thoroughly and comprehensively. Because the important issue of this process is quality process and this quality process occurs customers' satisfaction, therefore, to make a mutual relation in-between individual change of each element is to analyze a reasonable standard. So, for this reason we study on structuring nice models for network operation and estimating many scenarios for measuring efficiency. Especially those in economic and sensitivity based.

• Journal of the Korean Solar Energy Society
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• v.34 no.5
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• pp.109-115
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• 2014

The supply rate of renewable energy has been increasing under the influence of an energy scarcity. Government has supported the use of renewable energy by government subsidies. The operation of renewable may not been operating appropriately, although increasing the use of renewable energy. We found out some problems of the operation of renewable energy and offered some improvements. This research proposes the efficient operation method for the solar thermal system, and proposed operation method was compared and evaluated with existing operation strategy after selecting one building installed solar thermal system. Recently, the interest to renewable energy has increased because of the environmental issues and energy crisis. However the utilization of the renewable energy system is low because of the use of renewable energy system and existing renewable energy system independently, although supply rate of renewable system is increasing. Especially, in the case of solar thermal system heating load is not responsible for the load of hot water supply in many cases. Therefore, suggesting efficient operation plans and evaluations of the energy consumption and efficiency of a solar thermal system is needed.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.861-868
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• 2010

As CAS, X-ATK, and INT models considered as the most typical Air-to-Ground operation models in ROKAF are mainly designed as the voice-centered system between aircraft and ground control facilities, it is critical to newly develop the Link-16 based model for the ROK-US combined operation between F-15K, AWACS, M-SAM, and KDX-III equipped with Link-16. Former studies had been limited to the CAS operation, and they had mainly focused on reducing the voice transmission time to exchange the information between each mission step with maintaining existing operation steps. Therefore, this paper makes up the weak point in former studies, thereby designing new Air-to-Ground operation model for CAS, X-ATK, INT mission using Enterprise Architecture OV6c, which enables both aircraft and ground control facilities or between aircraft to obtain the real-time information on the location, identification, armament and the real-time image data through the broadcasting function. Based on the analysis of new operation model, we come to a conclusion that by simultaneously exchanging the information on mission between nodes concerned through the broadcasting function of Link-16. It is possible to cut down superfluous steps among the mission steps, and to reduce the mission time. It is clear that it gives rise to improve the battle efficiency and the decision-making tempo as well as the battlefield situational awareness.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.6 no.4
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• pp.137-152
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• 2011

The purpose of this study is to estimate efficiency of agricultural business corporations using Data Envelopment Analysis. A proposed method employs a bootstrapping approach to generate efficiency estimates through Monte Carlo simulation re-sampling process. The technical efficiency, pure technical efficiency, and scale efficiency measure of the corporations is 0.749 0.790, 0.948 respectively. Among the 692 agricultural business corporations, the number of Increasing Returns to Scale (IRS)-type corporations was analyzed to be 539(77.9%). The number of Constant Returns to Scale (CRS)-type corporations was 108(15.6%), and that of Decreasing Returns to Scale (DRS)-type corporations was 45(6.5%). Since an increase in input is lower than an increase in output in IRS, an increase in input factors such as new investments is required. The Tobit model suggests that the type of corporation, capital level, and period of operation affect the efficiency score more than others. The positive coefficient of capital level and period of operation variable indicates that efficiency score increases as capital level and period of operation increases.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.64-69
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• 2001

Energy recovery in the regenerative region is very important when SRM is used in traction drive, This is to reduce en-ergy loss during mechanical braking and/or to have a high efficiency drive during braking To control excitation voltage in motor operation and regenerative voltage in the generator operation in the SRM multi-level voltage control is effective The paper sug-gests multi-level inverter which is useful for motoring and regenerative operation in SRM

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1171-1176
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• 2010

Because of global warming, the new environment energy policy was already announced. The role of Green-railways is increasing in the field of railway. The government announced a policy direction of science & technology basic plan. The field of railway transportation proposed various railway transportation policy and plans. In this paper, I presented technical trend analysis for railway policy and railway operation field. Technical trend analysis at home and overseas are classified into railway industry technology, railway transportation system technology, railway operation efficiency technology, railway logistics technology.