• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.923-928
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• 1986

A set of measurements has been made for the thermal conductivity of the pure paraffin in liquid and solid phases and for the effective thermal conductivity of the paraffin with metal scrap with the aid of the heat flux meter. Ther thermopile-type heat flux meter has been designed by steady state method and the functional relation between the temperature difference of both sides and heat flux has been obtained. The measured values of thermal conductivity are compared with the existing data for the pure paraffin and with the predicated values from the suggested model in which only one empirical constant is contained. The comparison within ten percent of the volume fraction of the metal scrap in the paraffin is satisfactory.

• Microbiology and Biotechnology Letters
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• v.14 no.2
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• pp.199-203
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• 1986

A tubular tormentor was prepared by packing the wood chips and pumping the yeast solution of Saccharomyces formosensis in a tubular column. Investigations to characterize the ethanol fermentation in the immobilized cell tubular fermentor and to compare such a fermentors with other type fermentors were undertaken. Ethanol productivity of 24.4g EtOH/$\ell$.hr has been obtained from glucose substrate. This productivity is higher or compared favourably with that reported in immobilized bio-reactors.

• Journal of the Korean Ceramic Society
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• v.38 no.6
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• pp.575-581
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• 2001

세라믹/금속기지 복합재료에서 횡방향의 단축인장하중을 받는 경우, 복합재료의 특성에 관한 시뮬레이션 결과이다. 세라믹과 금속기지간 계면에 강한 결합이 존재하는 복합재와, 계면에서의 결합이 약한 복합재의 두 경우에 대하여 횡방향 평균응력과 평균변형율에 대한 관계를 계산하였다. 복합재료의 미시역학적개념과 유한요소해석법을 적용하여 세라믹체적분율의 변화에 따라 각기 해석되었다. 본 연구에서 계산된 횡방향 탄성계수는 문헌에 알려져 있는 미시역학개념으로 유도된 식에 의한 횡방향탄성계수값과 잘 일치되었다. 계면에서 강한 결합이 있는 복합재와는 달리, 약한 결합의 복합재는 인장하중에 의하여 세라믹/금속계면에서 금속재료와 세라믹간의 분리가 발생된다. 이 분리는 전체복합재의 강성을 감소시키며, 금속의 부피분율이 감소될수록 (즉, 세라믹의 부피분율이 증가할수록) 횡방향 평균응력의 평균변형율에 대한 감소로 나타났다. 미시역학의 개념을 적용한 유한요소해석기법을 통하여, 이미 알고 있는 복합재 각 성분의 특성으로부터 복합재료의 계면특성과 횡방향특성을 예측할 수 있다.

• Journal of the Korean GEO-environmental Society
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• v.22 no.2
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• pp.25-33
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• 2021

This study was conducted to understand the deposition characteristics of debris flow and to analyze the reduction effect of debris flow damage by installing a berm. Flume experiments were performed in consideration of various channel slope and volumetric sediment concontration. In order to analyze the reduction effect of debris flow damage by installing a berm, the cases of not installing a berm and the cases of installing a berm were compared. In this study, the runout distance, total travel distance, and mobility ratio were analyzed among the deposition characteristics of debris flow. First, the deposition characteristics of debris flow according to the change of the channel slope were analyzed, and the deposition characteristics of debris flow due to the change of volumetric sediment concentration were analyzed. In addition, the change rate of debris flow deposition characteristics when a berm was installed was calculated based on the case when a berm was not installed. As a result of the experiments, it was confirmed that the channel slope and volumetric sediment concentration had a significant effect on the deposition characteristics of debris flow. In addition, when a berm is installed on the slope, the runout distance and mobility ratio of debris flow are greatly decreased, and the total travel distance is increased. This means that installing a berm delays the movement of debris flow and reduces the potential mobility of debris flow. The results of this study will provide useful information for understanding the deposition characteristics of debris flow. Furthermore, it is expected to help in the design of a berm.

• Bulletin of Food Technology
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• v.25 no.2
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• pp.116-128
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• 2012

식품동결에 의한 품질손상에 있어 크게 영향을 미치는 인자 중의 하나가 체적변화에 의한 조직 파괴이므로 식육 및 과채류의 냉동시 내부압력에 따른 조직파괴를 방지하기 위한 기초연구로 다양한 동결방법에 따른 내부압력 변화에 대하여 조사한 결과, 급속 및 완만동결시 우육의 내부압력 변화 경향은 동결 직전에 급격히 상승한 후 동결 초기부터 최대빙결정생성대를 통과하는 동안은 급격히 감소하다가 다시 온도가 내려감에 따라 압력변화는 증가와 감소를 반복하여 상승하는 경향을 보여 주었고, 동결시의 내부압력 크기는 약 8~10 psig 수준이며, 내부압력의 변화 경향은 정지공기식보다 침지식에서 약 1 psig 정도 크게 나타났다. 냉동냉장시에 일어나는 내부압력의 상하변화는 돈육의 품온차가 ${\pm}1^{\circ}C$일 때, 시료중량에 따라 1.84~2.32 psig 정도의 내부압력 차가 반복적으로 발생됨을 알 수 있었다. 또한, 돈육의 해동시 내부압력은 해동 개시 후 급격히 상승하여 5분 이내에 최고압력에 도달한 이후에는 서서히 하강하였으며, 해동시에 발생한 내부압력의 값은 동결시의 내부압력 값보다도 대부분 크게 나타났다. 또한, 균온처리한 우육의 동결시 내부압력 값은 약 1~4 psig 수준으로 균온처리하지 않은 우육에 비하여 매우 적게 나타났으며, 동결소요시간도 약 10~20% 정도 짧게 나타났다. 그리고 균온처리 및 다양한 동결방법에 따른 동결식육의 조직과 냉동냉장 중의 품질변화를 비교 검토한 결과, 동결방법에 따른 드립손실율은 우육의 경우 정지공기식으로 처리한 시료는 타 처리구에 비해 계속 높게 나타났으며, 돈육은 우육에 비해 상대적으로 드립손실량이 적게 나타났으나 송풍식으로 처리한 시료에서 저장 40일째, 7.39%로 가장 높게 나타났다. 동결 우육 및 돈육의 pH변화는 뚜렷한 차이를 나타내지 않았으며, VBN 및 TBA값에 있어서는 균온 처리한 시료가 완만 및 급속동결 처리한 타 시료에 비해 저장 200일까지 가장 변화가 없었다. 동결저장온도의 상하변동에 있어서는 온도변동 횟수가 증가할수록 pH 및 수분함량은 뚜렷한 변화가 없었으나 드립손실율, VBN 및 TBA값은 온도 변동횟수가 증가할수록 서서히 증가하는 경향을 보여 주었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.2
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• pp.125-130
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• 2005

This study was peformed to investigate the phase change temperature, the supercooling, the maintenance time of liquid phase and the change rate of volume of TMA 30 $wt\% clathrate compound with additives. TMA 30 $wt\% clathrate compound with additive was cooled at heat source temperature of $-6^{circ}C$. The additives are ethylene glycol and chloroform. Their concentration are 0.1$wt\% respectively. The experimental results showed that the phase change temperature was not affected by additives and this was average $5.3^{circ}C$. Also the supercooling and the maintenance time of liquid phase were decreased by additives. Especially, the average value of supercooling showed by $8.8^{circ}C$ and the maintenance time of liquid phase was by 19 minutes in the case of chloroform 0.1$wt\%. Additionally, the average change rate of volume showed by $1.26{\~}1.31\%$ according to additives and the volume was decreased by the phase change from liquid to solid.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1183-1189
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• 2004

An experimental investigation is conducted to measure phase change temperature and supercooling when acetone is added to TMA 30 wt% clathrate during cooling process in heat source. Also rate of volume change is investigated when acetone is added to TMA 30 wt% clathrate during the cooling process in heat source -8$^{\circ}C$. The results show that phase change temperature is about 4.5～5.5$^{\circ}C$ when acetone is added to TMA 30 wt% clathrate during the cooling process for heat sink temperature of -6, -7$^{\circ}C$ and -8$^{\circ}C$. Supercooling is repressed about 2～1$0^{\circ}C$ when 0.08 wt% acetone is added to it and rate of volume change is decreased about 2.9% when 0.1 wt% acetone is added for the heat sink temperature of -8$^{\circ}C$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.6
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• pp.351-356
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• 2022

In this paper, we present the regression analysis and design optimization for improving the permeability of 3D woven materials based on numerical analysis data. First, the parametric analysis model is generated with variables that define the gap sizes between each directional wire of the woven material. Then, material properties such as bulk modulus, thermal conductivity coefficient, and permeability are calculated using numerical analysis, and these material data are used in the polynomial-based regression analysis. The Pareto optimal solution is obtained between bulk modulus and permeability by using multi-objective optimization and shows their trade-off relation. In addition, gradient-based design optimization is applied to maximize the fluid permeability for 3D woven materials, and the optimal designs are obtained according to the various minimum bulk modulus constraints. Finally, the optimal solutions from regression equations are verified to demonstrate the accuracy of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.875-882
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• 2011

In the present study, the imbalance in the axial-thrust and variation in the volumetric efficiency that occurred during the trimming of impeller diameter were investigated. The present study was focused on low-specific-speed multistage centrifugal pumps with a balancing piston as the balancing mechanism. The effects of impeller trimming on the axial-thrust balance in multistage pumps with horizontal and vertical axes were compared. The results showed that impeller trimming resulted in an additional axial-thrust acting in direction of pump inlet. The axial-thrust imbalance due to impeller trimming was more severe in the vertical-axis pumps than in the horizontal-axis pumps. The rate of increase in the diameter of the balancing piston, which was proportional to the rate of impeller trimming, was evaluated to maintain the axial-thrust balance. Furthermore, a simultaneous increase in the piston length and piston diameter was more effective for reducing the axial-thrust imbalance along with the volumetric efficiency drop.

• Journal of the Korean Wood Science and Technology
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• v.35 no.3
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• pp.45-52
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• 2007

The anatomical characteristics of Quercus variabilis woods carbonized at 310 to $350^{\circ}C$ were examined with an optical and scanning electron microscopy, and an X-ray diffraction analysis. Dimensional change and weight loss were also investigated. Volume of wood samples decreased with increasing the carbonization temperature, and checks were developed along with radial direction. Vessel diameter in tangential direction showed higher shrinkage than that in radial direction. Weight loss of samples increased with increasing carbonization temperature. Especially, the weight loss rapidly increased at the temperature ranging from 330 to $340^{\circ}C$. SEM study presented that the cell walls of samples carbonized at below $320^{\circ}C$ showed the layering structure. However, it was revealed that the layering structure was disappeared at $330^{\circ}C$ and over and showed an amorphous-like structure without cell wall layering. Interestingly, the existence of cellulose crystalline substance at $340^{\circ}C$ was confirmed by X-ray diffraction analysis and it was not detected at $350^{\circ}C$. Consequently, it is considered that the critical temperature for carbonization of wood was around $350^{\circ}C$.