• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.525-530
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• 2013

In this study, the generator engine of training ship M/S "HAE RIM" of Kunsan National University which is being operated for 20 years was used in the experiment. The experiment was carried out under the engine speed of 1200rpm, then the load was varied 30 kW intervals from 0 to 90 kW and the injection timing was varied $2^{\circ}$CA intervals from BTDC $19^{\circ}$ to $23^{\circ}$CA. In the case of advancing fuel injection timing from BTDC $21^{\circ}$CA to $23^{\circ}$CA, specific fuel consumption is decreased by 1.37%, NOx is increased by 11.59 %, soot is decreased by 23.5 % and $SO_2$ is decreased by 2.8 %. Accoring to the analysis of effects of fuel injection timing on combustion & exhaust emissions characteristics on an old marine diesel engine, it is proved that the optimum fuel injection timing is BTDC $23^{\circ}$ which is $2^{\circ}$ faster than that of original injection timing.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.141-147
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• 2019

Recently, the biggest issue in the electricity industry is the increase in renewable energy, and various technologies are being developed to ensure the capacity of the power system. In addition, super-grids linking power systems are being pushed to utilize eco-friendly energy between countries and regions worldwide. The HVDC transmission technology is required to link the power network between regions with different characteristics of the power system such as frequency and voltage. Until now, Korea has applied HVDC transmission technology that connects mainland and Jeju Island with submarine cables. But, the HVDC transmission technology is still developing for long-distance high-capacity power transmission from power parks on the east coast to load-tight areas near the metropolitan area. Considering the high population density and mountainous domestic environment, it is pushing for commercialization of the design technology of the ${\pm}500kV$ Double Bipole with metallic return wire transmission line to transmit large-scale power of 8 GW using minimal right of ways. In this paper, the insulation characteristics were studied for the design of double-bipole transmission tower with metallic return wire, which is the first time in the world. And the air insulation characteristics resistant to the various overvoltage phenomena occurring on transmission lines were verified through a full-scale impulse voltage test.

• Journal of Chest Surgery
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• v.36 no.7
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• pp.523-526
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• 2003

A 44-year-old man had been admitted for dyspnea on exertion and abdominal distension. The echocardiography revealed abnormal mass in right atrium and tricuspid valve stenosis with right ventricular obliteration. The operation was performed with mass removal, enlargement of tricuspid valve opening, and right ventricular endocardiectormy. And then, atrial septal defect was made due to inadequate right ventricular volume. The patient's symptom was improved and he discharged without events. The endomyocardial fibrosis was diagnosed with microscopic examination. Eighteen months later, the patient was readmitted due to aggravated dyspnea and cyanosis. The right ventricular obliteration was progressed and pulmonary blood flow was severely decreased in follow up echocardiography. Palliative bidirectional cave-pulmonary shunt was performed due to functional single ventricle. The dyspnea and cyanosis was markedly improved. Bidirectional cavo-pulmonary shunt for advanced and isolated right ventricular endomyocardial fibrosis provided effective palliation at early postoperative period, However, long-term follow up is mandatory.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.86-97
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• 2006

For the design of DC traction power supply system at new Light Rail Transit(LRT) construction, it is very important to determine system configuration, location and power capacity of substation. However, a LRT system consists of a number of subsystems such as train movement, power supply and traction drives, which inevitably contains many complexities and diversities. The objective of this paper is to clarify and systematize the design procedure and its assessment for the electrification system of a LRT line. This paper discusses in detail our approach to system design and its assessment. The whole DC-feeding network configuration, characteristics of a train, and design method of substation arrangements is thoroughly investigated for the design. As a result of the investigations, the design procedure is clarified and systematized and a computer program for the design and evaluation of the system is developed using the most suitable iterative method with nodal equation. To verify the proposed design and its assessment procedure, case studies for the DC traction power supply system of a planed Korean LRT line are performed.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.9
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• pp.327-336
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• 2015

Mobile game servers usually execute frequent dynamic memory allocation for generating the buffers that deal with clients requests. It causes to deteriorate the performance of game servers since it increases system workload and memory fragmentation. In this paper, we propose fixed-sized memory pool management method. Memory pool for the proposed method has a sequential memory structure based on circular linked list data structure. It solves memory fragmentation problem and saves time for searching the memory blocks which are required for memory allocation and deallocation. We showed the efficiency of the proposed method by evaluating the performance of dynamic memory allocation, through the proposed method and the memory pool management method based on boost open source library.

• Journal of the Ergonomics Society of Korea
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• v.36 no.5
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• pp.579-587
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• 2017

Objective: The purpose of this study is to measure the workload of Korea coastal ship crew members, to investigate whether they are following work-break time regulations and to identify the main causes of their workload. Background: According to the US Coast Guard, about 33% of human casualties are reported to be due to fatigue, and 30% of marine casualties reported by the British Marine Accident Investigation Agency (MAIB) are attributed to crew fatigue. But the coastal ship are not managed for business hours and breaks despite the harsh environment. Method: The workload of duty crew members on the 100 domestic coastal vessels was measured. It was also investigated whether they are following domestic and international work-break time regulations. Finally, the marine accidents resulted from the fatigue of the crew was analyzed. Results: As a result of workload analysis, the workload on the 42~62% of the vessels exceeded the standard of working time on the related regulation. The workload increased with the number of inbound and outbound ports. Especially, in the system where there are two seafarers, the workload exceeded the working time requirement. As a result of the marine accidents analysis on 100 vessels, it was found that collision and grounding occurred due to fatigue, workload and drowsiness in 7 marine accidents out of 30 marine accidents. Conclusion: It is necessary for the shipping companies to introduce an operation management manual for the management of the crews' workload and reasonable crew arrangement. It is also required for crew members to easily record work times and for shipping companies to manage the record. It would be possible to prevent many marine accidents by providing adequate rest to the crews and flexibly adjusting their working hours. Application: The results of this study can be used as fundamental data to manage crews' fatigue and to make job management manuals.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.51-55
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• 2007

Generally, PLC (Power Line Communication) based home automation devices such as wall switch, walt socket, gas controller, etc, must maintain wake-up status at all time to control other electronic devices and monitor their on/off status whether they are in service or not. In order to reduce the unnecessary energy consumption during the standby mode, the new power-saving PLC 2 ports wall switch has been developed, separating PLC communication part and controller part and introducing sleep mode. In addition, to expand life cycle of PLC product and to reduce the rate of product failure in active mode, the instant controlling method in controlling process is adopted instead of the maintenance controlling method. In comparison to the earlier model, the new 2 ports PLC wall switch has reduced power by 0.95[W] less in standby mode and 3.2[W] less in active mode than the previous one.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.1
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• pp.69-76
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• 2020

Bridges which are components of road network consume large amounts of resources such as concrete and steel materials, which have large environmental impacts during construction. This causes a great environmental burden. In order to reduce the environmental impact caused by the construction of the bridge, the environmental impact should be reviewed based on reasonable data in the early design stage. The purpose of this study is to provide basic data for LCA-based environmental impact assessment in the process of selecting bridge type in the early design stage. For this purpose, design data for four types of PSC bridges (general PSC girder, IPC girder, e-Beam, DR girder) were collected and LCA was performed to analyze the basic unit value and impact factors of environmental load. The results of the analysis showed that the environmental impact of IPC girder was the smallest, and the environmental impact of e-Beam was 133.7% higher than that of IPC girder. In addition, concrete, reinforcement, PC strand, square timber, sheath pipe, and steel plate were derived as the main factors that generate 98.5% of the overall environmental impact of PSC girder.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8576-8584
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• 2015

Load forecasting is needed to make supply and demand plan for a stable supply of electricity. It is also necessary for optimal operational plan of the power system planning. In particular, in order to ensure stable power supply, long-term load forecasting is important. And regional load forecasting is important for tightening supply stability. Regional load forecasting is known to be an essential process for the optimal state composition and maintenance of the electric power system network including transmission lines and substations to meet the load required for the area. Therefore, in this paper we propose a forecasting method using SARIMA during the 12 months (long-term/mid-term) load forecasting by 16 regions of the South Korea.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.7
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• pp.384-393
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• 2002

A Parallel file system is normally used to support excessive file requests from parallel applications in a cluster system, whereas prefetching is useful for improving the file system performance. This paper proposes a new prefetching method, Fips(dynamic File Prefetching Scheme based on file access patterms), that is particularly suitable for parallel scientific applications and multimedia web services in a parallel file system. The proposed prefetching method introduces a dynamic prefetching scheme to predict data blocks precisely in run-time although the file access patterns are irregular. In addition, it includes an algorithm to determine whether and when the prefetching is performed using the current available I/O bandwidth. Experimental results confirmed that the use of the proposed prefetching policy in a parallel file system produced a higher file system performance.