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Hydraulic Tests of Fuel Pump for 75-ton class Liquid Rocket Engines (75톤급 로켓엔진용 연료펌프의 수력성능시험)

  • Kim, Dae-Jin;Hong, Soon-Sam;Choi, Chang-Ho;Noh, Jun-Gu;Kim, Jin-Han
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.78-81
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    • 2009
  • A series of hydraulic tests of a fuel pump are performed using water at a room temperature. The pump is under development for 75-ton class liquid rocket engines of the open-loop gas generator type. According to the test results, the fuel pump satisfies its design requirement and its head and efficiency at the design flowrate are higher than the expected value by the computational analysis. Also, it is found that the pressure at the rear bearing outlet is higher than expected because the inlet of bypass pipe line is narrow. Furthermore, the flowrate of the secondary flow is estimated using the pressure difference of the elbow of the bypass pipe line.

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A Study on the Problem Analysis and Improvement Plan for the Korean Railways Communication Networks (국내 철도 통신망의 문제점 분석 및 개선방안 연구)

  • Kim, Kyung-Hee;Kim, Yong-Kyu;Park, Duk-Kyu
    • Journal of the Korean Society for Railway
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    • v.16 no.6
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    • pp.534-539
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    • 2013
  • The research about the Korean integrated wireless network for railways is in progress. The network integrates and complements the various railway functions. In addition, the network is trying to change from wire communication to radio communication. The activities for the railway frequency acquisition are also in progress for the implementation of the network. This paper analyzes the problems for the Korean railway communication networks. The problems revolve around the dispersed network structure, the limited functions, the different communication methods, the technology limitation for the communication methods, and the usage of the non-licensed band. Subsequently, we explain the current state and trend for the foreign communication of the railways. This paper suggests improvement plans for the problems and also explains the expected efficiency for the improvement plans.

Rules of Three Untrained Workers' Assignment Optimization in Reset Limited-Cycled Model with Multiple Periods

  • Song, Peiya;Kong, Xianda;Yamamoto, Hisashi;Sun, Jing;Matsui, Masayuki
    • Industrial Engineering and Management Systems
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    • v.14 no.4
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    • pp.372-378
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    • 2015
  • In labor-intensive enterprise, such as garment factory, assembly line is widely used as a manufacturing process for reducing costs and production time. However, for the sake of the various working capacity of worker, idle or delay may happen and influence the rear processes. If these unforeseeable delay happened continuously, it may influence the whole manufacturing process and a model, which is called limited-cycle model with multiple periods (LCMwMP), is assumed to evaluate the influence risk. In order to minimize the risk, the assignment of the workers is focused on. In this paper, we deal with an assembly line as LCMwMP model when two kinds of workers exist, whose efficiency is assumed to two different groups. We consider an optimization problem for finding an assignment of workers to the line that minimizes total expected risk, which is exchanged to expected cost by reset model of LCMwMP. First, reset model as a simple model of LCMwMP is introduced. Then, some hypotheses of the rules of the optimal worker assignment are proposed and some numerical experiments are researched assuming the processing time as Erlang distribution. Finally, the other rules on other certain conditions are discussed.

Pressure sensor placement method for real-time operation efficiency of water transmission mains (도·송수관로의 실시간 운영효율화를 위한 수압계 설치위치 선정 방안)

  • Kim, Seong Han;Choi, Doo Yong;Kim, Kyoung Pil;Lee, Sang Cheol
    • Journal of Korean Society of Water and Wastewater
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    • v.30 no.5
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    • pp.491-500
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    • 2016
  • Pressure monitoring is expected to be expanded in a water distribution system according to accelerated development of smart water network management technologies caused by appearances of affordable digital infrastructures like computing, storage and bandwidth. However, the placement of pressure sensors has been determined by engineer's technical decisions since there is no well-defined criteria for deciding a suitable location of pressure sensor. This study presents a placement method of pressure sensors based on the consideration of allowable error in calibrating water network analysis modeling. The proposed method is to find a minimum set of pressure sensors for achieving a reliable management of water transmissions main and increasing the efficiency of their real-time operation. In the case study in Y area's transmission main, the proposed method shows equally distributed pressure sensors in terms of hydraulics. It is expected that the proposed method can be used to manage transmission mains stably and construct a robust real-time network analysis system as a minimal criteria.

Evaluating C-RAN Fronthaul Functional Splits in Terms of Network Level Energy and Cost Savings

  • Checko, Aleksandra;Avramova, Andrijana P.;Berger, Michael S.;Christiansen, Henrik L.
    • Journal of Communications and Networks
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    • v.18 no.2
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    • pp.162-172
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    • 2016
  • The placement of the complete baseband processing in a centralized pool results in high data rate requirement and inflexibility of the fronthaul network, which challenges the energy and cost effectiveness of the cloud radio access network (C-RAN). Recently, redesign of the C-RAN through functional split in the baseband processing chain has been proposed to overcome these challenges. This paper evaluates, by mathematical and simulation methods, different splits with respect to network level energy and cost efficiency having in the mind the expected quality of service. The proposed mathematical model quantifies the multiplexing gains and the trade-offs between centralization and decentralization concerning the cost of the pool, fronthaul network capacity and resource utilization. The event-based simulation captures the influence of the traffic load dynamics and traffic type variation on designing an efficient fronthaul network. Based on the obtained results, we derive a principle for fronthaul dimensioning based on the traffic profile. This principle allows for efficient radio access network with respect to multiplexing gains while achieving the expected users' quality of service.

Brief Review of Silicon Solar Cells (실리콘 태양전지)

  • Yi, Jun-Sin
    • Journal of the Korean Vacuum Society
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    • v.16 no.3
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    • pp.161-166
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    • 2007
  • Photovoltaic (PV) technology permits the transformation of solar light directly into electricity. For the last five years, the photovoltaic sector has experienced one of the highest growth rates worldwide (over 30% in 2006) and for the next 20 years, the average production growth rate is estimated to be between 27% and 34% annually. Currently the cost of electricity produced using photovoltaic technology is above that for traditional energy sources, but this is expected to fall with technological progress and more efficient production processes. A large scale production of solar grade silicon material of high purity could supply the world demand at a reasonably lower cost. A shift from crystalline silicon to thin film is expected in the future. The technical limit for the conversion efficiency is about 30%. It is assumed that in 2030 thin films will have a major market share (90%) and the share of crystalline cells will have decreased to 10%. Our research at Sungkyunkwan University of South Korea is confined to crystalline silicon solar cell technology. We aim to develop a technology for low cost production of high efficiency silicon solar cell. We have successfully fabricated silicon solar cells of efficiency more than 16% starting with multicrystalline wafers and that of efficiency more than 17% on single crystalline wafers with screen printing metallization. The process of transformation from the first generation to second generation solar cell should be geared up with the entry of new approaches but still silicon seems to remain as the major material for solar cells for many years to come. Local barriers to the implementation of this technology may also keep continuing up to year 2010 and by that time the cost of the solar cell generated power is expected to be 60 cent per watt. Photovoltaic source could establish itself as a clean and sustainable energy alternate to the ever depleting and polluting non-renewable energy resource.

A Study of Analysis for Domestic Airport Efficiency Considering Undesirable Output (유해산출물을 고려한 국내 공항 효율성 측정에 관한 연구)

  • Kang, Dalwon;Jeong, Donghun;Jeon, Seungjoon
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.26 no.4
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    • pp.27-35
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    • 2018
  • Recently, Intense competition is expected to bring about continuous change with the rapid global aviation industry. In particular, domestic passenger demand has been steadily increasing over the past five years, with domestic and international shipments growing at a CAGR of 8.4% and 10.0%, respectively. In addition to the economic value of the airport, social interest due to greenhouse gas emissions is also rising. In this study, we analyzed the efficiency of airport operation by using DEA model(Directional Technology Distance Function) considering undesirable output for 14 airports in Korea. As a result of analysis, all airports except Gimhae, Yangyang, Cheongju and Yeosu were analyzed as efficient airports. However, only Gimpo, Gimhae, Jeju, Muan, Daegu and Gwangju were analyzed as efficient airports considering the undesirable output.

Recent Developments and Policy Directions in Fisheries Finance in Korea (IMF 이후 한국수산금융의 현황과 정책방향)

  • 김경호
    • The Journal of Fisheries Business Administration
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    • v.32 no.2
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    • pp.1-22
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    • 2001
  • In recent years Korea fisheries have been much more influenced than ever before by domestic and foreign environmental changes such as market liberalization, sustainability, efficiency and effectiveness of domestic fisheries, fisher's welfare etc. Under the wide range of environmental changes, government is carrying out various fisheries policies. However, it seems insufficient to accomplish policy goals under the existing policy instruments. The main focus of the paper is to investigate structural changes and policy directions of fisheries finance in Korea after asian economic crisis. The results of the study are as follows; Fisheries sector in whole economy has been lowering in its proportion. To survive in emerging global competition, fisheries sector is needed structural reformation. In particular the strategy that increases operative efficiency and effectiveness on government financial policy in fisheries sector is much expected. Also, it is necessary to minimize costs, to reform institution and management for increasing efficiency and effectiveness.

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A study on Design for Multi-step Filter to improve the Efficiency of Insulating Oil (절연오일의 효율을 향상하기 위한 다단계 필터 설계에 관한 연구)

  • 권병무;기현철;정우성;최창주;김태성
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.155-158
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    • 1999
  • Because the traditional filters have many demerits, multi-step electric oil filter have manufactured the efficiency of insulating oil to improve. Therefore, the function of oil filter to improve based on my experience and know-how about my job. Through this study have obtained many merits. The efficiency of insulating oil is improved. The waste oil reused in repair works of the damaged transformer. Multi-step filter is shortening the working time and safety. it is handy for use and movement. This study lengthen the expected life span of filter. The improvement of oil filter bring about elevation of productivity.

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Machining Technology of Scroll shape by Feed control method (이송속도 제어를 통한 스크롤 형상의 가공기술)

  • 심상우;강명창;김정석;정현출
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.123-127
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    • 1999
  • This paper suggests the establishment of high-accuracy and high-efficiency machining method of scroll shape workpiece by using the feed control method. The cutting paths for machining the inside and outside surfaces of the scroll-shape workpiece are calculated, and the calculation method of the cutting chip areas based on the coordinate of the base circle is shown. A feed control method is proposed for a constant cutting area and cutting force. By machining test of scroll shape workpiece, The machined accuracy of wrap, tool wear, and surface roughness are evaluated. By this method, Reduction of the machining time and large increase of the efficiency can be expected.

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