• 대한전기학회:학술대회논문집
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• 대한전기학회 1986년도 하계학술대회논문집
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• pp.591-594
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• 1986

An asymptotic solution of electro-magnetic waves diffracted by a dielectric wedge of the angle larger than $180^{\circ}$ is obtained in case of the incidence of a E-polarized plane wave. Based on the dual integral equation in the spectral domain, physical optics approximation is supplemented by correction currents distributed along the interfaces. Those currents are expanded in a series of Bessel functions, known as Neumann's expansion of which fractional order is chosen to satisfy the static edge condition as the limiting value of dynamic case. Numerical results of edge diffraction patterns and field patterns are presented for some typical cases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.521-524
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• 2002

In the present study, kinetic energy of laminar steady flow in the exit region connected to the square-sectional $180^{\circ}$curved duct was investigated experimentally. The experimental study for air flows was conducted to measure kinetic energy distributions by using the Particle Image Velocimetry(PIV) system with the data acquisition and processing system of Cactus 2000 software. The results obtained from experimental studies are summarized as follows : (1) The critical Reynolds number for a change from laminar steady flow to transitional steadt flow was about 1910, in the 50 region of dimensionless axial position (x/Dh) whirh was considered as a fully developed flow region. (2) Maximum kinetic energy of laminar steady flow was gradually increased as the Reynolds number increased.

• 설비공학논문집
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• 제16권9호
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• pp.804-810
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• 2004

This paper reports the characteristics of the three dimensional turbulent flow by numerical method in the 180 degree bends with increasing cross-sectional area. Calculated pressure and velocity, Reynolds stress distributions are compared to the experimental data. Turbulence model employed are low Reynolds number $textsc{k}$-$\varepsilon$ model and algebraic stress model(ASM). The results show that the main vortex generated from the inlet part of the bend maintained to outlet of the bend and vortices are continually developed at the inner wall region. The distribution of turbulent kinetic energy along the bend are increase up to 120$^{\circ}$ because of increment of cross-sectional area. Secondary flow strength of the flow is lower about 60% than that of square duct flow.

• 대한방사선기술학회지:방사선기술과학
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• 제42권2호
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• pp.113-117
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• 2019

The purpose of this study was to investigate the FA value which can produce the best T2-weighted images by measuring the signal intensity and noise according to the FA value change in the brain image and the abdominal image of the mouse using micro-MRI. Brain imaging and abdominal imaging of BALB / C mice weighing 20g were performed using 4.7T (Bruker BioSpin MRI GmbH) micro-MRI equipment, Turbo RARE-T2 (spin echo-T2) images were scanned at TR 3500 msec and TE 36 msec. The changes of the FA values were $60^{\circ}$, $80^{\circ}$, $100^{\circ}$, $120^{\circ}$, $140^{\circ}$, $160^{\circ}$ and $180^{\circ}$. We measured signal intensity according to FA values of ventricle and thalamus in brain imaging, The signal intensity of kidney and muscle around the kidney was measured in abdominal images. To obtain SNR and CNR, we measured the background signals of two different parts, not the tissue. In the brain (thalamus) image, the signal intensity of FA $100^{\circ}$ was 7,433 and SNR (6.49) was the highest. In the abdominal (kidney) image, the signal intensity was highest at 16,523 when FA was $120^{\circ}$, and the highest SNR was 8.54 when FA was $140^{\circ}$. The CNR value of the brain image was 1.38 at FA $60^{\circ}$ and gradually increased to 8.29 at FA $180^{\circ}$. The CNR value of the muscle adjacent to the kidney gradually increased from 2.36 when the FA value was $60^{\circ}$ and the highest value was 4,57 at the FA value $180^{\circ}$.

• 한국수산과학회지
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• 제31권4호
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• pp.483-488
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• 1998

고등어와 꽁치를 온도와 시간을 달리하여 배소한 것과 배소한 시료를 저온 ($5\pm2^{\circ}C$)에서 저장한 후 단계적으로 가열처리했을 때 발생하는 지질산화에 heme 화합물이 미치는 영향을 알아보았다. Heme 화합물 중 myoglobin 함량은 고등어나 꽁치모두 $180^{\circ}C$에서 20분간 어피 제거육의 상태로 배소한 것이 가장 감소폭이 컸으며 가열. 재가열에 의해서도 지속적으로 감소하였다. 특히 $180^{\circ}C$에서 어피 제거육의 상태로 20분간 배소한 것은 생시료에 비해 myoglobin 함량이 약 $62\%$ 정도 감소하였다 Myoglobin의 감소에 의한 metmyoglobin 함량은 고등어와 꽁치 모두 점차증가하는 경향이였으며, 배소온도가 낮을수록 그리고 어피를 제거한 경우가 metmyoglobin의 생성이 가장 많았다. 총철 함량은 배소온도와 시간을 달리하여 처리하여도 두 어종 모두 생시료와는 함량 차이가 거의 없었다. 비heme 철은 고등어의 경우 총철 함량에 비해 약 $28\%$의 비heme 철이 함유되어 있었으며. $180^{\circ}C$에서 20분간 어피 제거육의 상태로 배소했을 경우 생시료에 비해 약 $96\%$ 정도 비heme 철 함량이 증가하였다. 꽁치는 생시료에는 건물당으로 약 1.6mg/100g 함유되어 있었으며, $220^{\circ}C$에서 10분 배소시에는 총철 함량에 대해 약$40\%$. $200^{\circ}C$에서 15분 배소시에는 $41\~43\%$ 그리고 $180^{\circ}C$에서 20분 배소시에는 약 $48\%$의 비heme 철이 생성되었다. Heme 철 함량은 고등어와 꽁치 모두 비heme철의 증가에 반비례해서 감소하는 경향이였으며 또한 배소시간이 길수록 그리고 어피 잔존육보다는 어피 제거육의 감소폭이 더 컸다.

• 한국식품영양과학회지
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• 제10권1호
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• pp.17-25
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• 1981

국내산(國內産) 해바라기 종자유(種子油)를 사용(使用)하여 가열산화(加熱酸化)에 의(依)한 변화(變化)를 검토(檢討)하기 위하여 지방산조성(脂肪酸組成) 및 중성지질성분(中性脂質成分)의 변화(變化)와 특성(特性)을 측정(測定)한 결과(結果)는 다음과 같다. 종자유(種子油) 중에는 중성지질(中性脂質), 당지질(糖脂質) 및 인지질(燐脂質)의 함량(含量)은 각각(各各) 94.1%, 3.2% 및 2.7%였다. 지방산조성(脂肪酸組成)은 채유직후(採油直後) oleic acid가 59.84%로 가장 많고 linoleic acid는 29.48%로 그 다음으로 많으며 palmitic 및 stearic acid가 각각(各各) 6.21% 및 4.50%였다. 이는 외국(外國)에서 생산(生産)되는 종자유(種子油)와 비교(比較)하면 linoleic acid가 $20{\sim}30%$ 낮은 반면(反面)에 oleic acid는 $20{\sim}30%$정도 높았다. 처리후(處理後) linoleic acid 함량(含量)은 $100^{\circ}C$, $180^{\circ}C$에서 각각(各各) 1.48%, 5.32% 감소(減少)되었으나, oleic, palmitic 및 stearic acid는 상대적(相對的)으로 증가(增加)하였다. 또한 중성지질(中性脂質) 성분(成分)은 triglyceride, diglyceride 및 free fatty acid등(等)의 함량순(含量順)으로 6개(個)의 성분(成分)을 확인 하였고 처리후(處理後)에 있어서는 triglyceride는 감소(減少)한 반면(反面)에 diglyceride 및 monoglyceride는 증차증가(漸次增加)하였다. 또한 free fatty acid는 $100^{\circ}C$에서 점차(漸次) 증가(增加)하였으나 $180^{\circ}C$ 16시간(時間) 이후(以後)에는 약간의 감소(減少)를 보였다. 옥도가(沃度價)는 처리후(處理後) 감소(減少)하였으며, 과산화물가(過酸化物價)는 $100^{\circ}C$에서 점차(漸次) 계속 증가(增加)하였으나. $180^{\circ}C$에서는 16시간(時間) 까지는 증가(增加)하였으나 그이후(以後) 감소현상(減少現象)을 나타내었다.

• 대한기계학회논문집
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• 제18권5호
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• pp.1203-1217
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• 1994

In the present study, in order to analyze a turbulent flow in a square sectiond 180.deg. bend, Kim's low Reynolds number second moment turbulence closure is adopted. In this model, turbulence model constants in the wall region are modified as functions of turbulent Reynolds number by use of near wall turbulent universal properties based on Laufer's experimental results of Reynolds stress distriburions. Algebraic stress model and Reynolds stress equation model are used to verify the low Reynolds number second moment closure. The application of the present low Reynolds number algebraic stress model to the prediction of a square sectioned 180.deg. bend flow gives improved velocities and Reynolds stresses profiles compared with those obtained by using the van Driest mixing length model and present low Reynolds number Reynolds stress equation model.

• 대한기계학회논문집
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• 제16권2호
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• pp.290-301
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• 1992

An experimental study has been performed to investigate the characteristics of forced convective heat transfer in a rectangular duct with a 180.deg. bend. The Nusselt number of outer wall has maximum value near 105.deg. at which secondary flow is most active and the Nusselt number of inner wall has maximum value near the inlet of a duct. Near the outlet of a duct, the Nusselt number of outer wall decreases, the Nusselt number of inner wall increases and so those access each other through the influence of a straight duct attached to the end of a duct with a 180.deg. bend. Results of this experimental study would be the fundamental data when streamline curvature correction models are developed in the numerical study for forced convective heat transfer in a curved duct.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.386-391
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• 2005

An experimental study was conducted to analyze the thermal stability and to estimate the lifetime of refrigerating lubricants. PAG and POE oil are considered as a test fluids in this study. The viscosity of PAG and POE oil was measured by the vibration type viscometer while temperature is varied periodically in the range of $0^{\circ}C{\sim}100^{\circ}C$. The results indicate that the reduction rates of viscosity of PAG and POE oil were less than 5% after 510 cycles. In order to estimate lifetime of PAG and POE oil with temperature, the viscosity was measured while the temperature of oils was maintained at 180, 200 and $220^{\circ}C$. It is found that the lifetimes of PAG oil were shown to be 244, 177 and 89 hours at the temperature of 180, 200 and $220^{\circ}C$, respectively. Also the lifetimes of POE oil were estimated to be 1,744, 1,007 and 334 hours at the temperature of 180, 200 and $220^{\circ}C$, respectively. The lifetime correlations of PAG and POE oil are suggested in this paper.

• 한국전자파학회논문지
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• 제16권8호
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• pp.835-841
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• 2005

본 논문에서는 소형화된 CPW(Coplanar Waveguide) 발룬을 제안한다. 제안된 발룬에는 신호선-접지선 교차구조가 CPW전송 선로의 중앙 신호선과 양쪽 접지면 사이에 존재하여 180도의 위상차를 만들어 준다 따라서 물리적 길이가 $3{\lambda}/4$인 전송 선로가 ${\lambda}/4$의 길이로 줄어들어도 전기적 길이는 270도를 유지하므로 회로의 소형화가 가능하다. 이것은 종래에 제안된 월킨슨 분배기 구조의 발룬이 월킨슨 분배기 구조를 구성하기 위하여 한쪽 단자 방향으로 $3{\lambda/4$ 길이의 전송 선로를 필요로 하였다는 사실과 비교될 수 있다. 본 논문에서는 또한 CPW 선로의 신호선-접지선 교차 구조가 지니는 180도의 위상차를 측정으로 확인하고 그 결과를 함께 제시한다.