• Journal of Internet Computing and Services
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• v.9 no.4
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• pp.21-27
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• 2008

TCP receivers deliver ACK packets to senders for reliable end-to-end transfer. When ACK packets are not transferred properly because of network congestion, the performance of TCP degrades. This paper proposes a reverse congestion warning mechanism and a congestion handling mechanism in heterogeneous networks with heavy background traffic in the backward direction. Help from TCP receivers or hardware such as routers and gateways other than the ACK packets themselves is not necessary. TCP senders compare the arrival intervals of ACK data passed from receivers and the difference in t imestamp values echoed by receivers. According to the simulation results using the NS-2 network simulator, the proposed scheme shows a performance elevation of 20% greater than Reno, 150% greater than New Reno, and 450% greater than Westwood, respectively, under heterogeneous networks and that the error rate of the radio link is 1% when the backward network is congested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.963-969
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• 2015

Bicycle is one of the most popular mode of transport due to the increase of interest in the well-being and environment pollution. Before fabricating a continuously variable transmission that is applied to the actual bicycle, for reducing the problems in the early stage, the reliable simulation program has been applied and the financial problem can be solved. In this paper, in order to confirm the design factor, the stress analysis has been applied. In all models, each link and the joint portion are assumed to be a major design factors, and impact of each link and joints received stress during the operation and it is confirmed by using the CAE. Also, for the analysis region, the special code has been developed to calculate pulsation phenomenon through appropriate mathematical modeling.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2642-2647
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• 2007

This study represents numerical study on the thermal and fluid flow characteristics of exhaust gas in a motorcycle muffler. The reference engine was used 124.cc small displacement. Numerical analysis with computational fluid dynamics(CFD) was carried out to investigate the exhaust gas that flow into a motorcycle muffler. The STAR-CD S/W used to three dimensional steady state CFD analysis in a muffler. And than We got the information of static pressure it is used to structural analysis ant the first baffle plate using the commercial CAE code ANSYS workbench. Exhaust gas flow third chamber from frist chamber and running second chamber. A simulation result shows that each chamber of muffler temperature is about 460 K, 445 and 463K and pressure is about 22,000 Pa, 16,000 Pa and 10,000 Pa.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.90-96
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• 2009

Injection molding process is one of the most important methods to produce plastic parts with high efficiency and low cost. Today, injection molded parts have been increased dramatically the demand for high strength and quality applications. This report investigates that the optimum injection molding condition for minimum of shrinkage. Molding shrinkage is occurred by several reasons such as thermal shrinkage, a hardening process and compressibility. This report concentrate on shrinkage by a hardening process. As Change a holding pressure and holding time, checked deflections of X, Y, Z directions by shrinkage based on same condition. In conclusion, it was found that holding pressure is stronger and holding time is longer, the deflection by shrinkage is smaller because injection molding needs enough time for cooling and high density. The FEM Simulation CAE tool. Moldflow, is used for the analysis of injection molding process.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.159-165
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• 2002

So far, an alternator pulley has been formed by cold forging and casting with a metal due to the necessity of its high strength. Various advantages such as the light weight, the low cost, and the high productivity can be obtained by the injection molding process using engineering plastics. Engineering plastics have an excellent performance in the characteristics off strength vs. weight, a good forming ability and a productivity. The object of this study is to develop an alternator pulley, which has been made with a metal, using the injection molding process based on Taguchi methods. A sink mark is considered as a characteristic parameter to improve the quality. The FEM Simulation CAE tool, Moldflow, is used for the analysis of injection molding process.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.1
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• pp.91-96
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• 2002

Recently industry has moved towards automated operations with the goal of achieving better product quality greater productivity and reliability The pump design in characterized by extensive utilization of the related database which contains performance data. The inputs to the system are through interactive dialogue sessions and the basic input consist of flow rate, head, of fluid efficiency and the customer special requirements. These basic inputs along with the numerous rules in the knowledge bases and the mathematical modeling enable the effective design of the pump industry This paper represents the development of an automatic pump design system that was composed of a main program the data input module the drawing module the drawing edit module and was programed by the AutoLISP language under the Auto CAD program The developed system ultimately generates the design for a pump through the AutoCAD language.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.111-114
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• 1992

과거 사출금형 설계 및 성형은 대부분의 단편적인 경험에 의존하여 왔으며 이는 단납기, 고품질화에의 대응에 있어서 가장 큰 문제점중의 하나로 인식되어 왔다. 그러나 최근에는 컴퓨터의 성능이 급격히 향상되고 보편화되면서 대기업을 선두로 한 컴퓨터 시뮬레이션이 활발히 응용되고 있으며 이는 앞으로 더욱 활성화될 전망이다. 본 연구에서는 사출성형 자동평가 시스템을 개발하였으며 이는 전처리 모듈, CAE해석 모듈 및 자동분석 모듈, 후처리 모듈등으로 구성되어 있다. 본 시스템에서는 주입장치 설계 표준 DATA BASE가 구축되어 있으며 특히 설계자가 설계 및 성형조건에 대한 기준만 정의하면 그 이후의 모든 평가 및 최적조건이 자동으로 계산, 도출될 수 있도록 하였다. 이번에 개발한 시스템에서의 핵심기술은 수치해석을 응용한 고분자 가공공정해석기술, 최적화 기술, DATA BASE구축기술 그리고 컴퓨터 그래픽 기술 등으로 위에서 언급한 바와 같은 사용시스템이 갖고 있는 현장 활용시 문제점들을 근본적으로 해결하여 차별화 시킨 것이다.

• Design & Manufacturing
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• v.12 no.2
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• pp.57-62
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• 2018

In diabetics, daily blood glucose testing is generally required at home, and thus, performing blood collection several times a day using a blood line is essential. Blood collection in the home and in the hospital is a source of pain and is the second most common cause of infection. In blood collecting device generally consists of four major parts: inner-case, outer case, main shaft and triger, and the most import part among those for necessary functionality is the main shaft. Filling time and injection pressure, filling balance, strain-rate analysis of change based on availability of the product. The Moldflow of FEM simulation is used for the analysis of injection molding process. In this study, aims to create a technique for injection molding and manufacturing of a main shaft of a high-performance blood-collecting apparatus capable of automatically extracting a lancet to relieve pain through depth control of the lancet.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.83-88
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• 2011

워터스크린(이하 W/S)에 의한 화재방화시스템은 도로터널에 화재가 발생시, 공간에 수막을 사용하여 구획화하고, 열 연기의 확산을 억제하며 유해 부유입자를 세정함으로서 인간의 안전을 확보 및 구조물의 피해를 극소화 하는 시스템이다. 이 W/S에 의한 구획의 성능을 평가하기 위해, 1/2의 터널 모형에 의한 공간 내 열 성장 파악을 위한 화재 실험을 분석하였고, 그 결과, 천정 근방 온도 및 방사수열량으로서는 발열 속도의 크기, 풍속의 대소에 의하지 않고 약 80%의 저감율을 나타냈다. 또, 발생한 유해 부유입자 농도에 대해서는 약 60%, 화원 성질과 상태로서 발열 속도는 약30%의 W/S에 의한 저감 효과를 나타내었다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.28-31
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• 2011

최근 산불과 같은 불티로 인한 2차화재의 발생 비율이 높아지고 있는 추세이다. 그러나 이를 불티로 인한 화재 성상을 CFD로 해석하기 위해서는 불티에 가해지는 유체력을 평가하여야 연소모델을 적용할 수 있다. 따라서 본 연구에서는 기존 풍속에 의한 불티 확산실험의 결과를 토대로 FDS에 적용 할 수 있는 연소모델을 구축하고 위하여 수리 모델 및 수치 해법에 대해 정리하고 이를 FDS 연소모델에 적용을 실시하였다.