• 한국항공우주학회지
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• 제36권9호
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• pp.907-915
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• 2008

하이드라진(N2H4) 아크젯 추력기의 열화학 유동장 해석을 위한 전산유체해석을 수행하였다. 열복사와 전기장이 고려된 압축성 유동해석을 위해서 RANS 방정식을 수정하여 사용하였다. 로렌츠 힘과 Ohm 가열효과를 고려한 Maxwell 방정식이 유동방정식과 결합되어 전기 방전으로 인한 전기장해석을 위해 이용되었다. 아크젯 추력기 내부에서 유동장은 충분히 고온상태이기에 화학평형 해석이 이용되었으며, 광학 두께를 이용한 열복사 모델이 유동방정식에 적용되었다. 계산 결과들은 아크젯 추력기유동이 동결유동에 비해 추력은 180%증가되며, 비추력은 200%가까이 상승됨을 보여준다. 또한 유동장 해석 결과들은 아크젯 추력기 내부의 열적 물리적 특성에 대한 이해를 돕는다.

• Reproductive and Developmental Biology
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• 제35권3호
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• pp.295-300
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• 2011

The objective of this study was to evaluate efficiency of methyl-beta-cyclodextrin (MBCD) in the sperm preservation of bull. For this study, the freezing of diluted semen were added with Triladyl containing 20% egg-yolk and/or 0, 1, 5, 10 and 20 mM MBCD before freezing process. Analysis of viability in frozen-thawed sperm was estimated by SYBR14/PI double stain, hypoosmotic swelling test(HOST) and acrosome damage with FITC-PNA, and mitochondria activation with Rhodamin123 by flow-cytometry. The sperm viability was significantly in 0 mM and 5 mM concentrations of MBCD than other groups (p<0.05). However, the HOST was significantly lower at 20 mM concentration of MBCD than other concentrations (p<0.05). In addition, acrosome damage and mitochondria activation rates were significantly lower at 20 mM concentration of MBCD than other groups (p<0.05). In conclusion, the viability of sperm was not significantly different among concentrations of MBCD 0, 5 and 10 mM, but MBCD 20 mM was significantly lower than other groups. In addition, as concentrations of MBCD was high, HOST, acrosome damage and mitochondria activation rates had a negative effect in bull sperm.

• Geomechanics and Engineering
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• 제8권3호
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• pp.391-414
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• 2015

In this paper, stabilities of a plane slide rock slope under different hydraulic distributions were studied based on the nonlinear Barton-Bandis (B-B) failure criterion. The influence of various parameters on the stability of rock slopes was analyzed. Parametric analysis indicated that studying the factor of safety (FS) of planar slide rock slopes using the B-B failure criterion is both simple and effective and that the effects of the basic friction angle of the joint (${\varphi}_b$), the joint roughness coefficient (JRC), and the joint compressive strength (JCS) on the FS of a planar slide rock slope are significant. Qualitatively, the influence of the JCS on the FS of a slope is small, whereas the influences of the ${\varphi}_b$ and the JRC are significant. The FS of the rock slope decreases as the water in a tension crack becomes deeper. This trend is more significant when the flow outlet is blocked, a situation that is particularly prevalent in regions with permafrost or seasonal frozen soil. Finally, the work is extended to study the reliability of the slope against plane failure according to the uncertainty from physical and mechanics parameters.

• Journal of Nutrition and Health
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• 제19권1호
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• pp.3-15
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• 1986

This study was intended to investigate the rheological properties of the development formula of infant foods and the results are summarized as follow ; 1) Consistency of starch solutions measured by Brabender Anylograph and Brookfield viscometer showed that waxy rice and riece with malt had lower consistency and more rheological stability.The flow type of tested raw materials and formula was found to ？ pseudoplastic, as judged by n-value of 0.332 -0.692, and no yield value. 2) The influenced of temperature on consistency could be accounted for by the equation, In (n) = K(1/T) + const. this relationship indicated that consistency of tested sample increased as temperature decreased. The consistency of waxy rice, rice with malt and formula A were less affected by the temperature change. 3) Infant foods with malt(formula A ) ad with waxy rice maintained better freeze-thaw stability in terms of consistency and starch aggregation indicating that this infant food could be stored for a long term in the freezer section of the home refrigeratory without adverse effect on the product quality. 4) From the above experiments, it would necessarily follow that infant food can be easily made at home the food-stuffs generally available around us, and that the easiest and safest way to store them lies in making them into semisolid state, and in keeping them in frozen state.

• 대한기계학회논문집A
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• 제23권7호
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• pp.1094-1103
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• 1999

Ice-plugging of tube in nuclear power plant has been widely used for the purpose of preventing flow of the tube temporarily like a valve. Most common plugging method employs Liquid Nitrogen Gas of $-196^{\circ}C$. According to the change of tube materials and its dimension, the thermal stress caused from the application of the frozen gas can be varied. In this research, a series of experiments have been carried out to inspect the effect of tube geometry on thermal stresses induced due to ice-plugging. Two typical dimension of stainless and mild steels of 3 and 6 inch diameters were used for the experiments. Each critical spots were checked using strain rosette gages. Another inspection was made on the pressure and temperature of the fluid. It is shown that significant thermal stress level which can cause plastic deformation of failure has not been noticed in this series of experiments.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.45-54
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• 2012

In order to predict trailing edge noise from a flat plate more effectively and accurately, the prediction algorithm based on semi-analytic model for point pressure spectrum is proposed. The semi-analytic model consists of empirical models for point pressure spectra and theoretical model to determine the boundary layer characteristics needed for the empirical models. The proposed methods are applied to predict the trailing edge noise of the flat plate located in the mean flow of speed 38 m/s, for which the measured data are available. In present study, six empirical models for point pressure spectra are utilized for the predictions of trailing edge noise and their prediction results are compared to the measured data. Through the analysis of these comparisons, it is revealed that the present method based on non-frozen formula using Efimtsov model and Smol'yakov-Tkachenko model can provide more accurate and efficient predictions of trailing edge noise.

• 한국소음진동공학회논문집
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• 제22권6호
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• pp.524-534
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• 2012

In order to predict trailing edge noise from a flat plate more effectively and accurately, the prediction algorithm based on semi-analytic model for point pressure spectrum is proposed. The semi-analytic model consists of empirical models for point pressure spectra and theoretical model to determine the boundary layer characteristics needed for the empirical models. The proposed methods are applied to predict the trailing edge noise of the flat plate located in the mean flow of speed 38 m/s, for which the measured data are available. In present study, six empirical models for point pressure spectra are utilized for the predictions of trailing edge noise and their prediction results are compared to the measured data. Through the analysis of these comparisons, it is revealed that the present method based on non-frozen formula using Efimtsov model and Smol'yakov-Tkachenko model can provide more accurate and efficient predictions of trailing edge noise.

• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.456-465
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• 1988

The performance of the cold latent heat storage is investigated by experiment and by a simplified analytic approach. The heat storage tank has eight horizontal circular tubes and one path of refrigerant evaporating tube. The phase change material in the heat storage tank is water which is frozen by evaporating refrigerant of refrigeration system and melts by the warm air in the heat storage tank. In the experiment, the performance has been studied by the various conditions including the initial water temperature on solidification and flow rate and temperature of air. The rate of recovered heat has been simulated by a simplified model and the results shows a good agreement. In solidification process, initial water temperature causes time delay corresponding to the sensible heat and it is found that the shape of evaporator is important. In melting process, the recovered heat rate from the heat storage tank is proportional to $Re^{0.8}(T_{bi}-T_f)$ of air where $T_{bi}$ and $T_f$ indicate temperatures of inlet air and phase change, respectively. And the deminishing rate of the recovered heat is higher for the higher heat rate.

• 한국가축번식학회지
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• 제23권2호
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• pp.165-174
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• 1999

본 연구는 동결융해 후 정자의 생존성에 영향을 미치는 요인을 찾기 위하여 수행하였다. 동결융해 후 생존성에 대한 요인으로써 동결보존액, 동해보호제, 예비동결법 및 동결소요시간을 비교하였다. 동결과정중 정액의 질을 평가하기 위하여 활력, NAR 및 생존율을 조사한 결과는 다음과 같다. 돼지정액을 BF5, LYE, Soejima 및 modified Soejima 보존액으로 동결하였을 때 동결융해 후 정자활력은 M-Soejima 보존액이 44.5$\pm$6.4%로 다소 높았다. M-Soejima 보존액의 2차 회석액에 caffeine(2mM), heparin(l00 ${\mu}\ell$/$m\ell$) 및 caffeine＋heparin 를 첨가하였을 때 동결융해 후 활력은 caffeine 첨가구가 61.7% 로 가장 높았으며, 단독 혹은 혼합첨가가 첨가하지 않은 대조구보다 유의적으로 높은 활력을 나타내었다 (p＜0.05). M-Soejima 보존액에 동해보호제로서 glycerol(Gly), ethylene glycol(EG), propylene glycol(GP), Gly＋EG 및 Gly＋PG을 첨가하였을 때 동결융해 후 활력 및 NAR 율은 Gly＋PG의 혼합첨가시 (31.3%/39.5%) 가 다른 첨가구보다 다소 높았으며 생존율은 Gly＋EG 첨가구가 21.2% 로 다른 첨가구보다 다소 높았다. BE5와 M-Soejima 보존액으로 straw 및 pellet 동결법으로 동결하는 동안 dry ice-pellet, dry ice-straw 및 L$N_2$vapor-straw 법으로 예비동결하였을 때 각각 22.8, 47.5, 52.5% 및 42.5, 47.5, 57.5% 의 활력을 나타내었다. 또한 M-Soejima 보존액의 straw 법으로 l차 희석부터 동결완료까지 소요되는 시간을 2, 5 및 7시간으로 하였을 때 동결융해 후 활력 및 생존율은 처리간에 큰 차이가 없었으나, NAR 율은 처리시간이 길어질수록 다소 높은 경향을 나타내었다. 이러한 결과로 미루어 볼 때 동결융해 후 활력, NAR 및 생존율을 높이기 위해서는 caffeine 이 첨가된 M-Soejima 보존액에 동해보호제로 glycerol과 propylene glycol 또는 ehtylene glycol 을 사용하여 2시간 동안 빠르게 동결처리된 정액이 다소 유리할 것으로 사료되었다.

• 한국식품위생안전성학회지
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• 제29권2호
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• pp.79-84
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• 2014

본 연구는 비가열 섭취 냉동 당근주스의 HACCP (Hazard Analysis Critical Control Point)시스템 구축을 위하여 생물학적 위해요소분석을 위한 목적으로 2013년 6월 21일~2014년 3월 30일까지 약 270일간 제주도 제주시 구좌읍 소재에 있는 구좌농협에서 수행하였다. 일반적인 과채주스 제조업체의 제조공정을 참고로 하여 공정도를 작성하였으며, 원료 농산물(당근), 용수와 포장재료 입고, 보관, 세척, 분쇄, 착즙, 냉각, 내포장, 금속검출, 외포장, 보관 및 출하공정에 대하여 Fig. 1과 같이 작성하였다. 원료 당근의 세척 전, 세척 후의 Coliform group, Staphylococcus aureus, Salmonella spp., Bacillus cereus, Listeria Monocytogenes, 장출혈성대장균수를 측정한 결과 Bacillus cereus 는 세척 전 $4.70{\times}10^4CFU/g$이었으나, 세척 후 $1.02{\times}10^2CFU/g$ 검출되었으며, 나머지 병원성균은 검출되지 않았다. 자외선살균공정에서 당근주스의 유속를 변화시키면서 미생물의 변화를 시험한 결과 유속 4 L/min을 한계기준으로 결정하였다. 작업장별 공중낙하균(일반세균수, 대장균, 진균수) 시험결과 세척실의 미생물수는 20 CFU/Plate가 검출되었다. 작업자 손 세척 전후 시험결과 세척 전 일반세균수가 $6{\times}10^4CFU/cm^2$로 높게 나타났으나 손 세척 후에는 검출되지 않아 손 세척 및 소독에 대한 중요성을 교육하고 훈련해야 할 것이다. 제조설비 및 기구의 표면오염도를 검사한 결과 모든 시료에서 대장균군은 검출되지 않았고, 일반세균은 포장기 노즐에서 가장 많은 $8.5{\times}10^4CFU/cm^2$ 검출되었다. 위해분석 결과 병원성미생물을 예방, 감소 또는 제거할 수 있는 자외선살균 공정이 CCP-B (Biological)로 관리되어야 하고, 한계기준은 유속 4 L/min로 결정하였다. 따라서 Kwon의 유산균을 함유한 녹즙의 HACCP에 관한 연구에서와 같이 자외선살균 공정의 한계기준 및 이탈시 조치방법, 검증방법, 교육 훈련과 기록관리 등 철저한 HACCP 관리계획이 필요할 것으로 생각된다.