Enhancement of Thermo-Electric Energy Conversion Using Graphene Nano-platelets Embedded Phase Change Material

유정빈,윤재륜,송영석 한국고분자학회 2021 Macromolecular Research Vol.29 No.8

Phase change materials (PCMs) containing graphene nano-platelets (GNPs) were fabricated and utilized for efficient thermo-electric energy harvesting during the phase transition process. A system composed of two different PCMs at opposite positions can absorb or release large amounts of thermal energy while remaining in a nearly isothermal condition. Based on the Seebeck effect, the energy harvesting system generates electrical current from temperature differences. The increase in the thermal conductivity of the PCMs can create isothermal fields and enhance thermoelectric energy conversion efficiency. In this study, two different PCM composites were found to exhibit higher thermal conductivity with increasing the amount of GNPs filler. The thermal conductivity of the two composites clearly increased to 0.5858 W/mK and 0.4974 W/mK, while the heating and cooling thermo-electric conversion efficiencies were also enhanced to 55.59% and 33.33%. Furthermore, the thermo-electric energy profiles were numerically modeled using the finite element method (FEM) to compare with the experimental results.

표본조사에서의 품질측정방법에 관한 연구

유정빈 서원대학교 미래창조연구소 2004 과학과 문화 Vol.1 No.1

As the utilization of official statistics has been recently increased, the necessity of objective quality measurement also has been increased. Since mean square error(MSE) and response rate, which have been considered as representative quality measurement indicators in the past, may have the limits of use, it has been demanded to develop new quality measurement indicators which are able to reflect the various requirements of users and many processes in official statistics production. Generally speaking, there are two approaches for improving survey quality. The one is a process-oriented approach and the other is a output-oriented approach. The aim of process-oriented quality characteristics is to gain from an insight into important parts of the process. And the output-oriented quality characteristics can be made from the end products of survey research. This paper introduces the quality index of Booleman and Brakel(1999) in Statistics Netherlands, which uses 'the results of a survey research'. And new quality index is suggested, which is a form of the well-known loss function.

수중 외발젓기 운동 시 수심과 속도에 따른 주동근 근전도 반응에 미치는 영향

유정빈,최종인,김기홍 한국스포츠학회 2022 한국스포츠학회지 Vol.20 No.2

The purpose of this study was to analyze muscle activity of lower extremity and trunk muscles according to water depth and speed during single leg swing aquatic exercise, and to provide a mechanism for intermuscular coordination to maintain balance and basic data for balance training in water. The subjects of this study were 9 males with more than 6 months of resistance training experience, and a total of 9 experiment were performed according to 3 water depths and speed conditions. EMG was measured during exercise and the measured variables were analyzed with Repeated measurements two-way ANOVA. As a result, as the speed of rowing foot increased, the muscle activity was significantly higher in the lower extremity and trunk muscles(p=.001), (p=.019, p=.001). On the other hand, the lower the water depth, the higher the calf muscle activity of the stepping foot(p=019, p=.001), and the higher the rectus abdominis muscle activity at the waist(p=.043). Therefore, this study is thought to be able to control intensity of exercise by increasing the speed during exercise to improve balance in water, and in the water depth condition, it is appropriate to gradually lower the water depth for training the muscles around the ankle, and it is judged that the waist depth is the most suitable for training the trunk muscles. 이 연구는 수중 외발젓기 운동 시 수심과 속도에 따른 하지근과 몸통근의 근활성도를 분석하여 균형을 유지하기 위한 근육 간 협응 기전과 수중에서 평형성 훈련 시 기초자료를 제공하고자 하였다. 연구대상자는 저항운동 경력 6개월 이상의 남자 대학생 9명을 선정하였으며, 3가지 수심과 속도조건에 따라 수중 외발젓기 운동을 총 9회 실시하였다. 운동 중 하지근과 몸통근의 근전도를 측정하였으며, 측정된 변인들은 반복측정 이원변량분석으로 분석하였다. 그 결과 젓는발의 속도가 빨라질수록 하지근과 몸통근에서 근활성도가 유의하게 높게 나타났으며(p=.001), (p=.019, p=.001), 한편 수심 조건에서는 수심이 낮아질수록 디딤발 종아리 근육의 근활성도가 유의하게 높게 나타났고(p=019, p=.001), 배곧은근은 허리수심에서 근활성도가 유의하게 높게 나타났다(p=.043). 따라서 이 연구는 수중에서 평형성 향상을 위한 운동 시 동작의 속도를 증가시켜 운동의 강도를 조절할 수 있을것으로 판단되며, 한편 수심에 따라서는 발목 주변 근육의 강화를 위해 단계적으로 수심을 낮추는 것이 효과적이고, 몸통 주변 근육의 강화를 위해서는 허리수심이 가장 적합할 것으로 판단된다.

6-Sigma 경영전략의 국가통계품질측정에 대한 적용 가능성에 대한 고찰

유정빈 서원대학교 응용과학연구소 2003 응용과학연구 Vol.12 No.1

As the utilization of official statistics has been recently increased, the necessity of objective quality assessment also has been increased. Since mean square error(MSE) and response rate, which have been considered as representative quality assessment indicators in the past, may have the limits of use, it has been demanded to develop new quality assessment indicators which are able to reflect the various requirements of users and many processes in official statistics production. This paper is shown that the well-known 6-sigma strategies are well applied to the quality assessment of the procedures of official statistics production. Of course, there are many further topics to be studied.

임업총조사 자료로부터 층화절사추출법을 이용한 표본크기 결정 방법

유정빈 서원대학교 응용과학연구소 2002 응용과학연구 Vol.11 No.1

In this paper, a sample design is studied for 2000 forestry management survey of five types forestry ; tree felling gathering of pine mushroom, growing of nut trees, growing of wild flowers, and lumbering industry. I introduce population stratificatin and a modified stratified cut-off sampling which deal with determination of sample size.

Dual Reponse System에서 손실함수를 이용한 최적화방법

유정빈 서원대학교 응용과학연구소 2000 응용과학연구 Vol.9 No.1

A method is proposed for the dual response systems that depend on the same set of controllable variables and are adequately represented by a quadratic response surface model. This new optimizing method is a sort of general minimax criterion. That is, the degree of loss with respect to the mean and dispersion can be modeled by the functions which increase monotonically from 0 at the target value T to 1 and the general loss functions. First of all, the proposed method achieves a better balance between bias and variance compared to the existing methods. Secondly, this method is flexible in that it allows the decision makers to incorporate they preference into the model.

비대칭 모집단을 두 개의 층으로 나누는 절사점에 대한 연구

유정빈 서원대학교 응용과학연구소 2001 응용과학연구 Vol.10 No.1

In extremely non-symmetric distribution it is very difficult to design the sampling method. Cut-off sampling is a proper method in this situation. In this method it is not easy to decide the cut-off point which devide two strata. A criterion of deciding the cut-off point which devide two strata will be suggested by using population-ratio of a specific item, sampling number and MSE.

다구찌 품질 공학에 관한 연구

유정빈 서원대학교 응용과학연구소 1992 응용과학연구 Vol.1 No.1

This paper considers the philosophy and methods proposed by Professor G. Taguchi. He has emphasized the use of designed experiments in several novel and important applications. And the use of statistical experimental designs is accomplished by designing products to be robust to environmental conditions. The engineering concept of robust product design is very important since it is frequently impossible to control sources of variation due to environmental conditions. Robust product design enables the experimenter to discover how to nodify the design of the product to minimize the effect due to variation from environmental sources. In the present paper the many criticisms and improved propositions which are discussed from 1985 to 1991 contain. In particular the uses of crossed-product orthogonal arrays in the parameter designs, of the ANOVA by SN-ratios and of the accumulation analysis are discussed. And as the process optimization going beyond Taguch Methods, the response surface methods (RSM) are introduced.

반응표면 분석에서 다중반응의 동시 최적화

유정빈 서원대학교 응용과학연구소 1994 응용과학연구 Vol.3 No.1

A method is developed for the simultaneous optimization of several response functions that depend on the same set of controllable variables and are adequately represented by a response surface model of the same degree. This algorithm is developed under the condition that individual response has the target value. In order to use Box-Draper estimation the data are first checked for linear dependencies among the responses by eigenvalue analysis. Thus a set of responses among which no linear functional relationships exist is chosen and used in developing a functions that measures the distance of the vector of estimated responses from the target values.

선형회귀모형에서 다중공선성이 존재할 때 결정계수에 대한 연구+

유정빈 서원대학교 응용과학연구소 1996 응용과학연구 Vol.5 No.1

The coefficient of determination R²is a very useful measure in linear regression analysis. But if the independent variables are correlated, many problems are produced in ordinary linear regression analysis. One of them is (수식입력불가). Sometimes under what conditions the sum is less than (수식입력불가). This topic was discussed in Park and Lee(1995). But the sufficient conditions that they founded for k=3 are ambiguous. In addition, examples to be proposed are not available. In this paper the new method to find the conditions for (수식입력불가) and for k=2 and 3 the new examples to be available in most practical cases are proposed.