• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.226-231
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• 2001

The purpose of this paper is to propose the experimental method of thermal properties of Phase Change Materials (PCMs) by using T-history method. As far, in order to measure the heat of fusion and specific heat of PCMs, conventional thermal analysis methods such as DSC and DTA have been used. Because these methods test very small samples, thermal properties of samples are usually different from those of materials consisting of several components. For these reasons, T-history method, the simple measurement method of the heat of fusion and specific heat of PCMs have been performed. In this paper, we investigated the thermal properties of low temperature PCMs(below $0^{\circ}C$) under the charging process by using T-history method. The results are compared to those of DSC method. The T-history method will be useful for selection of the best PCM from lots of candidates and development of new PCMs.

• 설비공학논문집
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• 제13권12호
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• pp.1223-1229
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• 2001

Though conventional calorimetry methods such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA) are used generally in measuring heat of fusion, T-history method has the advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermal properties of inhomogeneous phase change materials (PCMs) in sealed tubes. However, random criteria (a degree of supercooling) used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권1호
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• pp.32-39
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• 2003

Though conventional calorimetry methods such as differential scanning calorimetry and differential thermal analysis are used generally in measuring heat of fusion, T-history method has advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermophyical properties of in-homogeneous phase change materials in sealed tubes. However, the degree of supercooling used in selecting a range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• 설비공학논문집
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• 제15권8호
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• pp.652-660
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• 2003

T-history method, measuring heat-of-fusion of phase change material (PCM) in sealed tubes, has the advantages of a simple experimental device and no requirements in sampling process. However, a degree of supercooling used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion in the original method, which has been improved in order to predict better results by us. In the present study, the modified method was applied to a variety of PCM such as paraffin and lauric acid having very small or no supercooling with a satisfactory precision. Also the selection of inflection point and temperature measurement position was fumed out not to affect the accuracy of heat-of-fusion significantly. As a result, the method can provide an appropriate means to assess a new developed PCM by cycle test even if a very accurate value cannot be obtained.

• 설비공학논문집
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• 제17권3호
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• pp.223-231
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• 2005

When test tubes for PCM with melting point lower than a room temperature are installed vertically as the T-history method proposes, there exists a temperature distribution in the longitudinal direction by natural convection, which lowers the precision of measured heat-of-fusion. The purpose of the present work is to improve the precision by arranging the test tubes horizontally, while maintaining the simplicity and convenience. Assuming that the amount of heat transfer is very small through the vapor space formed in the upper part of the tubes by volumetric change, the obtained value by the T-history method using the latent heat period bounded by two inflection points is in good agreement with that of the literature. Also, the scattering of measured values by the proposed method decreases markedly compared to that of vertical positioning.

• Korean Chemical Engineering Research
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• 제48권1호
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• pp.93-97
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• 2010

본 연구에서는 수정된 T-history 법을 사용하여 백신 또는 의약품들의 수송 시 냉매로 사용될 수 있는 $0{\sim}15^{\circ}C$의 상전이 온도를 갖는 유기 상전이 소재들과 이중 두 물질의 혼합물들의 열용량, 잠열, 비열과 같은 열 물성을 측정하였다. 순수한 파라핀들을 측정한 결과, 각 물질들의 상전이 온도를 고려하여 최적의 냉각 속도를 유지하며 측정을 하는 것이 열물성의 신뢰성을 향상시킬 수 있음을 알 수 있었고, 특히 혼합물의 열 물성 측정에 적용할 경우, 수정된 T-history 법의 사용은 기존의 DSC 분석에 사용하는 시료의 양이 소량이므로 유발될 수 있는 결과의 부정확성 등의 문제점을 해결하는데 기여할 수 있음을 알 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2003년도 하계학술대회 논문집
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• pp.90-90
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• 2003

• 한국수학사학회지
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• 제15권2호
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• pp.49-68
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• 2002

One of the characteristics of modem mathematics is to use algebra in every fields of mathematics. But we don't have the exact definition of algebra, and we can't clearly define algebraic thinking. In order to solve this problem, this paper investigate the history of algebra. First, we describe some of the features of proportional Babylonian thinking by analysing some problems. In chapter 4, we consider Greek's analytical method and proportional theory. And in chapter 5, we deal with Diophantus' algebraic method by giving an overview of Arithmetica. Finally we investigate Viete's thinking of algebra through his ‘the analytical art’. By investigating these history of algebra, we reach the following conclusions. 1. The origin of algebra comes from problem solving(various equations). 2. The origin of algebraic thinking is the proportional thinking and the analytical thinking. 3. The thing that plays an important role in transition from arithmetical thinking to algebraic thinking is Babylonian ‘the false value’ idea and Diophantus’ ‘arithmos’ concept.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권4호
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• pp.206-213
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• 2004

Cycle test for developed phase change material (PCM) is necessary in order to assess the variation of latent heat, which decreases with time by deterioration. T-history method and measurement using heat-flux meter are appropriate for the cycle test in a tube filled with PCM because they do not need an extraction of sample in measuring heat of fusion. In the present study, these methods were applied to a PCM having a melting point below a room temperature, different to the past studies for PCMs melting above a room temperature. As a result of experiment using pure water as specimen, we can obtained rea-sonable values for heat of fusion.

• 한국의사학회지
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• 제18권2호
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• pp.245-255
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• 2005

The researcher categorized the acupuncture methods mentioned in DongUiBoGam according to the form, and examined how to select and use the acupuncture points explained in the Acupuncture/Moxibustion prescription. By comparing the original text to the Acupuncture/Moxibustion prescriptions, it was established that the various acupuncture points in these Acupuncture/Moxibustion prescriptions all had individual meaning. Also, it showed that DongUiBoGam didn't indicate a particular acupuncture point but allowed a possibility for selection according to the patient's condition and the skill of the practitioner.