• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1597-1602
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• 2003

Numerical analysis is carried out to assess the temperature distribution on the mixing tee line of Residual Heat Removal System (RHRS). In RHRS, hot and cold fluids of main and bypass piping are mixed and unmixed by the flow rate or piping layout. Thermal stratification phenomenon is a cause of major degradation on RHRS piping. According to the analysis for each operation modes, maximum temperature difference between top and bottom of piping were evaluated about 60K when the flow rate of main and bypass lines is same. Temperature difference will be decreased at the elbow on RHRS piping if the length of vertical piping is increased.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2010년도 춘계학술논문발표회 논문집
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• pp.289-296
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• 2010

This study is aiming at analyzing correlation between flashover's time and maximum smoke production rate's time on sandwich panel specimens. For this analysis, KS F ISO 137481-1 has been performed for 23 kinds of sandwich panels which mainly consist of EPS, PIR, PUR, Glass wool and so on. KS F ISO 13784-1 represents real scale reaction-to-fire test and focuses on measuring flashover phenomenon rather than other tests as like ISO 5660-1 and SBI.

• 한국통신학회논문지
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• 제40권10호
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• pp.1976-1985
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• 2015

비디오 스트리밍 수신기의 재생 버퍼에 있는 패킷량은 네트워크 상태에 따라 변화되며 지연 및 지터의 영향으로 인해 포화 및 고갈 현상이 일어날 수 있다. 특히, 유입되는 비디오 트래픽의 양이 재생 버퍼의 최대 양을 넘으면 버퍼 오버플로우(buffer overflow)문제가 발생된다. 버퍼 오버플로우는 화질의 열화를 발생시키고 스킵(skip) 현상으로 인해 재생의 불연속성을 발생시킨다. 또한 네트워크 혼잡으로 인하여 패킷의 유입이 늦어지면 버퍼 언더플로우(buffer underflow) 문제에 의한 버퍼링에 의해 영상의 멈춤 현상이 일어날 수 있다. 상기 문제들을 해결하기 위하여 본 논문에서는 토큰버킷(Token Bucket)의 주요 파라미터인 토큰 발생률 파라메타와 버킷의 최대 용량 파라미터를 각각의 비디오 패킷들의 패턴에 따라서 자동적으로 설정하는 토큰버킷 기법을 장착한 비디오 스트리밍 수신기를 제안한다. NS-2(Network Simulator-2)와 JSVM(Joint Scalable Video Model)을 이용하는 시뮬레이션 결과는 제안하는 토큰버킷 파라메타 자동설정 기법이 기존의 수동설정 기법보다 3개의 시험 비디오 시퀀스들에 대해 오버플로우/언더플로우 횟수와 패킷 손실 비율 및 PSNR(Peak Signal to Noise Ratio)측면에서 우수한 성능을 제공함을 확인 할 수 있었다.

• Journal of Biosystems Engineering
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• 제31권3호
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• pp.146-152
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• 2006

Most upland in Korea have irregular field shapes. Boom sprayers working alone winding row will show considerable differences of spraying amount per unit area between left and right booms. If flow rates of both booms are equal. This phenomenon becomes significant as steering radius of sprayer decreases. This study was performed to seek a method which reduce the difference of the spray amount between left, right and center booms while spraying along curvy rows. A flow rate control method for keeping application rate of each boom section constant was proposed and experimentally proved using a boom sprayer attached to a cultivating tractor. The flow rate control device was composed of 3 ball valves and a rotary angle sensor. The rotary angle sensor showed a symmetric voltage output with respect to steering radius. The spray overlapping was happened in a boom nearby the steering center when steering radius of the sprayer was less than 5.2 m. Flow rates for left, right and center booms were regulated using ball valves based on the steering radius and spraying areas ration of right/left boom. The Maximum spraying area ratio ($S_{LR}$) of left to right boom section was 1:3.6 at the steering radius of 5.2 m. However, The Maximum achieved right and left spraying flow ratio was 1:2.7.

• 전자공학회논문지CI
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• 제38권2호
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• pp.16-26
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• 2001

본 논문에서는 주어진 필터와 구현 복잡도에 대하여 최대 코딩이득을 내는 부 주파수 분활을 가진 서브밴드 부호화기를 구축하는 고속 알고리듬을 제안한다. 이를 위하여 본 논문에서는 직교 기저 및 비 직교 기저와 임의의 부 주파수 분할에 대하여 적용할 수 있는 통합적인 코딩이득의 식을 유도한 다음, 부 주파수 대역수에 대하여 코딩이득이 단순 증가 함수임을 증명한다, 이를 바탕으로 복잡도에 대하여 최대 코딩이득을 내는 최적화 된 부 주파수 분할을 찾아내기 위하여 그 단순 증가 함수를 부 주파수 대역 수에 따른 왜곡 함수로 다룬다. 이 왜곡 함수을 목적함수로 두고 Lagrange 방법에 근거하여 최적화 된 해를 고속으로 제공하는 알고리듬을 개발한다.

• 한국환경보건학회지
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• 제22권3호
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• pp.56-63
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• 1996

The results of the water purification studies using water parsley (Oenanthe javanica) were obtained as follows. The removal rate of nutrient salts increased with longer plant growth periods. The results of this study use the assumption, log(T+1) = $K(C_0-C)^A$, based on Prakish's Theory. The initial concentration was calculated from experimental data. A and K are closely related to the initial concentration. It is possible to model the concentration of residual salts, as time goes by, if concentration is constant. It was observed that water parsley neutralizes acid and alkali substances promptly. The maximum suitable neutralization period is 48 hours. But water parsley withered up in strong acid and alkali solutions within a week. The removal efficiency of Cd progresses in 2 steps, which are unrelated to the initial concentration of Cd. The first part of the curve shows the concentration rapid rate of Cd removal, followed by a levelling off. The removal rate of $NO_x-N$ in the sample water tank containing 0.5 ppm Cd was between 50~80% but the removal rate was less than 20% for the higher concentration. On the other hand, increased amounts of $PO_4-P$ in the sample water tank from the third day on suspected that $PO_4-P$ was desorbed from the water parsley. The accumulation efficiency of Cd in plant was increased in proportion to the initial concentration of Cd. The accumulation phenomenon was observed in the tanks more than 50~100 times.

• 설비공학논문집
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• 제29권12호
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• pp.628-637
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• 2017

This study was conducted to present an effective control method for the common duct system to uniformly discharge volume flow rate exhausted from the kitchen and bathroom of each household in an apartment regardless of the position of household. Since the common duct system is installed vertically and the ventilator is installed in the terminal, the static pressure of each household decreases when vertical height increases. Therefore, the volume flow rate exhausted from each household is different. In order to improve such a phenomenon, a constant air volume damper shall be installed in a branch duct coupled with a common vertical duct system. The selected ventilator should also be able to handle the maximum volume flow rate considering diversity factor. Therefore, a uniform volume flow rate must be exhausted from all households where the hood is operated. This paper mainly focuses on suggestion of an optimum exhaust control method by comparing exhaust performance of each household according to the presence or absence of a constant air volume damper.

• 한국생산제조학회지
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• 제24권1호
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• pp.69-74
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• 2015

This study examined the fluid flow characteristics of a hydraulic retarder adapted as an auxiliary brake for heavy vehicles. The commercial computational fluid dynamics (CFD) software STAR-CCM+ was used to investigate the torque performance and flow characteristics of the hydraulic retarder. The numerical results showed that the pressure distribution was higher near the inner wall surface of the rotor and stator. The pressure of the working fluid increased in the radial direction of the rotor and stator. The variation in the fluid velocity intensity showed a similar trend to that of the fluid pressure, but the maximum velocity appeared near the outer wall surface of the rotor and stator interface. The numerical results showed that increasing the revolution speed of the retarder greatly increased the rate of torque generation.

• Design & Manufacturing
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• 제14권1호
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• pp.1-7
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• 2020

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gate size of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores are laser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigidity than the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set to minimize the deformation of the core during the injection process. The resin used in the injection molding test is a PP material. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. The runner diameter used was ∅3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 ㎟, respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away from the gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tends to decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thickness shrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holding pressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to the over-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded due to the high pressure generation. It was confirmed that precise packing process control is necessary because over-packing phenomenon may occur.

• KSBB Journal
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• 제4권2호
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• pp.191-196
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• 1989

초기 당농도 50, 79, 110, 190 및 250g/l 각 각에 대한 S, cervisiae SIV-89이 돼지감자 알콜발효특성(비생장속도, 비생성속도, 알콜생성율, 균체생성율, 알콜전환율, 알콜농도의 영향)을 시간의 함수로 규명하여 보았다. 최대 비증식속도 및 최대 알콜 비생성속도는 초기당농도 70내지 80g/l까지는 증가하여 최대값 0.35와 1.98을 나타내었으나 그 이상에서는 감소하였다. 또한 최대 비증식속도 및 최애 알콜 비생성속도가 나타나는 시간은 초기 당농도 증가에 따라 점차로 지연되는 현상을 나타내었다. 균체생성율 $Y_x/_s$알콜생성을$Y_p/_s$의 최대값은 0.15, 0.45이였으며 초기 당농도 증가에 따라 감소 겨향을 나타내었다, 당의 알콜 전환율은 당농도의 증가에 따라 감소하여 당농도 190g/l 이상에서는 70%이하로 떨어졌다. 또한 발효기질 내의 알콜농도가 증가하면 균주의 대사활동이 감퇴되어 알콜농도 70내지 80g/l에 이르게 되며 잔여당농도에 관계없이 균체의 성장 및 알콜 생성이 완전히 중지되는 현상을 나타내었다.