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금속관 내부의 음압유량 향상을 위한 기하학적 디자인 및 SLIPS 윤활
김동근(Dong Geun Kim),장창환(Changhwan Jang),김성재(Seong Jae Kim),김대겸(Daegyoum Kim),김산하(Sanha Kim) 한국트라이볼로지학회 2021 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.37 No.6
Metal pipes are used in a wide range of applications, from plumbing systems of large construction sites to small devices such as medical tools. When a liquid is enforced to flow through a metal pipe, a higher flow rate is beneficial for higher efficiency. Using high pressures can enhance the flow rate yet can be harmful for medical applications. Thus, we consider an optimal geometrical design to increase the flow rate in medical devices. In this study, we focus on cannulas, which are widely used small metal pipes for surgical procedures, such as liposuction. We characterize the internal flow rate driven by a negative pressure and explore its dependence on the key design parameters. We quantitatively analyze the suction characteristics for each design variable by conducting computational fluid dynamics simulations. In addition, we build a suction performance measurement system which enables the translational motion of cannulas with pre-programmed velocity for experimental validation. The inner diameter, section geometry, and hole configuration are the design factors to be evaluated. The effect of the inner diameter dominates over that of section geometry and hole configuration. In addition, the circular tube shape provides the maximum flow rate among the elliptical geometries. Once the flow rate exceeds a critical value, the rate becomes independent of the number and width of the suction holes. Finally, we introduce a slippery liquid-infused nanoporous surface (SLIPS) coating using nanoparticles and hydrophobic lubricants that effectively improves the flow rate and antifouling property of cannulas without altering the geometrical design parameter.
초임계 CO2 유체 추출법으로 얻은 탈지 유채박 중 표면활성 물질의 유화 성질 연구
김정원 ( Jeong Won Kim ),정용선 ( Yong Seon Jeong ),이의석 ( Eui Seok Lee ),길나영 ( Na Young Gil ),김산성 ( San Seong Kim ),김현효 ( Hyun Hyo Kim ),김태영 ( Tae Young Kim ),이영화 ( Yong Hwa Lee ),장영석 ( Young Seok Jang ),이기 한국유화학회 2013 한국응용과학기술학회지 Vol.30 No.4
This study was carried out to investigate the emulsifying properties of surface-active substances from defatted rapeseed cake by supercritical CO2 extraction. Based on the interfacial tension data, a supercritical fluid extract (SFE) with the lowest value of 14.16 mN/m was chosen for evaluation which was obtained from No. 2 extraction condition (150 bar, 65℃, 250 g). For emulsions with SFE, some physicochemical properties (i.e., fat globule size, creaming stability, zeta potential etc) were investigated according to changes in SFE concentration, pH, and NaCl addition in an emulsion. It was found that fat globule size was decreased with increasing SFE concentration in emulsion, with showing a critical value at 0.5 wt%, thereby resulting in less susceptibility to creaming behavior. The SFE emulsion also showed instability at acidic conditions (pH<7.0) as well as by NaCl addition. This was coincided with zeta potential data of emulsion. In addition, SSL (sodium stearoyl lactylate) found to be suitable as a co-surfactant, as it helped considerably in decreasing fat globule size in emulsions and its optimum concentration to be over 0.03 wt%, based on 0.1 wt% SFE in emulsion.
기하학적 설계 변수에 따른 의료용 지방흡입 기기의 성능 분석
김동근(D. G. Kim),김성재(S. J. Kim),장창환(C. Jang),김대겸(D. Kim),김산하(S. Kim) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
의료용 흡입 기기는 기초 수술 분야 및 지방흡입 분야에서 널리 사용되고 있다. 조직과 직접 접촉하는 캐뉼라는 다양한 형상으로 그 특성에 따라 다목적으로 사용되고 있다. 하지만 캐뉼라의 정량적인 연구가 존재하지 않아 현재 사용되고 있는 캐뉼라 디자인이 흡입 성능에 어떤 영향을 미치는지에 대한 이해가 부족하며, 성능 개선을 위한 디자인 최적화에 어려움이 있다. 본 연구에서는 의료현장에서 실제 사용되는 캐뉼라 기기의 기하학적 특성을 분석하였고, 그에 따른 흡입 성능에 대한 정량적인 데이터를 획득하였다. 먼저, 캐뉼라의 제작 방법에 따른 외경과 내경, 팁끝 반경, 거칠기 등 기하학적 특성 데이터를 분석하였다. 지방 흡입 성능의 정량적 획득을 위해서 지방흡입 수술을 모사한 자동화 흡입 실험 시스템을 구축함으로써 캐뉼라의 기하학적 특성에 따른 흡입 성능을 평가하였다. 또한 전산 유체 역학에 따른 시뮬레이션을 통해 실험 결과와 흡입 성능을 비교 검증하였으며, 추가적인 주요 디자인 변수의 영향을 시뮬레이션을 통해 예측하였다. 캐뉼라의 지름이 커짐에 따라 단조적으로 흡입량이 증가하는 것을 확인하였고, 같은 지름에서 펌프와 근접한 상부에 흡입 구멍이 위치하는 것이 효율적임을 확인하였다. 캐뉼라의 단면 형상이 원일 때 가장 우수한 성능을 보였으며, 둘레 방향의 홀 가공은 흡입 성능과 큰 영향이 없어 목적에 맞게 유연한 디자인을 제공할 수 있음을 확인하였다. 마지막으로 흡입 기기의 성능을 향상시키고 세척 과정의 수월성을 높이기 위해 캐뉼라 내부에 나노다공성 윤활 코팅 방법을 제안하였다. 해당 코팅 방식은 액적에 의한 표면 오염을 줄이며 적절한 음압 조건 하에서 흡입 성능을 개선할 수 있을 것으로 기대된다.
스위칭 엑티비티를 최소화한 저전력 DCT 아키텍쳐 구현
김산,박종수,이용주,이용석,Kim San,Park Jong-Su,Lee Yong-Joo,Lee Yong-Surk 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.6C
저전력 설계는 시스템의 소모전력을 줄임으로써 에너지 절약과 함께 휴대용 장치의 배터리 수명을 극대화시킴에 있어 직면한 가장 중요한 문제이다. 본 논문에서는 개량형 CSHM을 이용하여 저전력 DCT 구조를 제안하였다. 제안된 구조는 Computation Sharing Multiplication 연산 과정 중 불필요한 비트에 대한 연산을 수행하지 않는다. 실험 결과, 기존의 DCT 알고리즘과 동일한 연산 결과를 보이면서도 최대 약 9%의 소모전력이 감소하였다. 따라서 제안된 저전력 DCT 구조는 저전력 및 고성능으로 DCT 알고리즘을 처리해야하는 휴대용 멀티미디어 시스템에 적용이 가능하다. Low-power design is one of the most important challenges encountered in maximizing battery life in portable devices as well as saving energy during system operation. In this paper we propose a low-power DCT (Discrete Cosine Transform) architecture using a modified Computation Sharing Multiplication (CSHM). The overall rate of Power consumption is reduced during DCT: the proposed architecture does not perform arithmetic operations on unnecessary bits during the Computation Sharing Multiplication calculations. Experimental results show that it is possible to reduce power dissipation up to about $7\sim8%$ without compromising the final DCT results. The proposed low-power DCT architecture can be applied to consumer electronics as well as portable multimedia systems requiring high throughput and low-power.
김산옥(San-Og Kim),정명선(Myung-Sun Chung) 전남대학교 생활과학연구소 1992 生活科學硏究 Vol.2 No.-
The purpose of this study was to find out the relationship between needs(need for abasement, autonomy, exhibitionism, sex, achievement, emotion) and criteria of clothing evaluation(aesthics, status symbolism, modesty, economy, fashion) of college males, and to find out the relationship between criteria of clothing evaluation and demographic variables. (college, proportion of female in department, income.) For this study, the quetionnaire were administered to 386 college males. The data were analyzed by using Pearson’s correlation, F-test, Partial correlation. The results of this study were as follows: 1) Need for achivement was strongest and need for exhibitionism, need for sex was generally strong among college males. 2) There were not significant differences in criteria of clothing evaluation according to proportion of female in department, and college too. But there were significant differences in criteria of clothing evaluation according to the income. 3) Significant positive correlation were found among the three criteria of clothing evaluation: aesthics, status symbolism, fashion. And modesty correlated significantly with economy at the .001 level. 4) There were significant positive correlation between need for abasement and modesty(p<0.001), economy(p<0.001). But there were negative correlation between need for abasement and fashion. Need for exhibitionism, need for sex positively correlated with aesthics, status symbolism, fashion. While need for sex negatively correlated with modesty. And need for achievement positively correlated with aesthics. 5) When status symbolism and fashion were controlled, need for exhibitionism and need for achievement positively correlated with aesthics at the .001 level. While need for sex not significantly correlated with aesthics when fash ion was controlled. When aesthics was controlled, need for exhibitionism significant positively correlated fashion at the .001 level. When aesthics and fashion were controlled, need for sex correlated significantly with status symbolismat at the .01 level. After status symbolism and aesthics were controlled, need for sex correlated significantly with fashion at the .01 level and need for abasement negatively correlated with fashion at the .001 level. When fashion and status symbolism were controlled, need for exhibitionism and need for achievement significantly correlated with aesthics at the .001 level.