• 한국응용과학기술학회지
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• 제34권4호
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• pp.1112-1120
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• 2017

석유제품은 다양한 형태의 탄화수소화합물로 구성되어진 화합물로, 다른 종류의 액체류와 마찬가지로 온도변화에 따른 밀도와 부피의 변화가 발생한다. 액상에서 석유제품의 밀도를 측정하는 방법은 분별 증류된 각 석유제품에 대해 주로 얻어진 실험 데이터를 기반으로 한다. 본 연구에서는 등유와 자동차용 경유의 온도변화에 따른 밀도와 부피변화를 실제 측정하여 온도변화에 따른 변화추이를 분석하고, 국제규격인 ASTM에서 제시하는 밀도부피 환산표를 이용한 환산값을 계산하고 두 값을 비교분석하였다. 또한, 국내 계량 관련법에서 규정하고 있는 온도변화에 대한 기준과 실측값과의 상호 비교를 통해 차이점을 분석하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.127-128
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• 2021

Rigid urethane foam is widely applied because it is light and has superior insulation performance compared to insulation materials such as EPS or glass wool. However, it has the disadvantage of being vulnerable to fire. Therefore, in this study, before proceeding with the research to improve the fire resistance of the rigid polyurethane foam, we would like to investigate the change in density and thermal conductivity of the rigid polyurethane foam according to the change in the mixed weight of the main material and the curing agent. It was found that the density increased as the mixed weight increased. The thermal conductivity showed similar values overall. As for the density distribution, the central part was low and the outer part was high.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1201-1206
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• 2004

This paper deals with the numerical analysis of natural convection flow induced by the density inversion effect of water inside horizontal pipe. The numerical method is based on SIMPLE/PWIM in general coordinate for its wide applicabilities. The numerical tool was validated through the comparison with the previous results concerning the density inversion effect of water It is shown that the developed numerical tool could predict the flow pattern and the heat transfer phenomena qualitatively And it is also found that the density inversion effect of water has significant effects on the flow pattern.

• 접착 및 계면
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• 제3권2호
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• pp.30-39
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• 2002

실리카로 보강된 천연고무 가황물에서 가황촉진제의 양이 열노화에 의한 가교밀도의 변화에 미치는 영향에 대해 연구하였다. 또한 실란커플링제의 영향도 조사하였다. 가황촉진제로는 N-tert-butyl-2-benzothiazole sulfenamide(TBBS)를 실란 커플링제로는 bis-(3-(triethoxysilyl)-propyl)-tetrasulfide(TESPT)를 사용하였다. 가황물을 열노화 시키면 가교밀도는 증가하였고 노화 온도가 높을수록 그 변화 정도는 컸다. 실란 커플링제가 포함되지 않은 가황물의 가교밀도 변화가 실란 커플링제를 포함한 것에 비해 더 크게 나타났다. 실란 커플링제가 포함되지 않은 가황물의 경우에는 가교밀도의 변화에 대한 활성화 에너지가 가황촉진제의 함량이 증가할수록 순차적으로 낮아지는 경향을 보였다.

• Journal of Periodontal and Implant Science
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• 제39권2호
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• pp.185-192
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• 2009

Purpose: The aim of this study was to examine the correlation of the subjective and the objective evaluation of edentulous ridge bone quality, and to evaluate the change of the dental implant stability in each bone density group for early healing period after implant installation. Methods: Sixty-seven implants(Osstem implant$^{(R)}$, Seoul, Korea) were included in this study. We evaluated the bone density by 2 methods. The one was the subjective method which was determined by practitioner s tactile sense, the other was the objective bone type was based on Hounsfield units. The implant stability in each bone type group was assessed by resonance frequency analyzer(Osstell mentor$^{(R)}$). Data were analyzed for the change of the implant stability, and they were compared to verify the difference of groups at the time of installation, 2, 6, 10, 14 weeks postoperatively. Spearman's correlation was used to demonstrate the correlation between the subjective and the objective evaluation of the bone density, and analysis of variance(ANOVA) was used to analyze the differences of implant stability at each time point. Results: There was no close relation between the subjective and the objective evaluation of the bone density(r=0.57). In the subjective groups, there was statistically significant difference between the type 1 and 3 at 10 weeks and between the type 2 and 3 at 14 weeks. In the objective groups, there was no statistically significant difference between the D 1, 2, 3, 4, and 5 group with regard to RFA from baseline to 14 weeks(P>0.1). Conclusions: The implant stability increased over time during the study, and it was improved with bone density proportionally after 2weeks postoperatively. It is recommended that the decision of bone density is base on Hounsfield unit for implant loading time.

• 핵의학기술
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• 제27권2호
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• pp.95-98
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• 2023

Purpose: The precision error of a bone density meter reflects the equipment and reproducibility of results by an examiner. Precision error values can be expressed as coefficient of variation (CV), CV%, and root mean square-SD (RMS-SD). The International Society for Clinical Densitometry (ISCD) currently recommends using RMS-SD as the precision error value. When a 95% confidence interval is applied, the least significant change (LSC) value is calculated by multiplying the precision error value by 2.77. Exceeding the LSC value reflects a significant difference in measured bone density. Therefore, the LSC value of a bone density equipment is an essential factor for accurately determining a patient's bone density. Accordingly, we aimed to calculate the LSC value of a bone density meter (Lunar iDXA, GE) and compare it with the value recommended by the ISCD. We also assessed whether the value measured by the iDXA equipment was below the LSC value recommended by ISCD. Material and Methods: The bone densities of the lumbar spine and thighs of 30 participants were measured twice, and the LSC values were calculated using the precision calculation tool provided by the ISCD (http://www.iscd.org). To check the reproducibility of the measurement, patients were asked to completely dismount from the equipment after the first measurement; the patient was then repositioned before proceeding with the second measurement. Results: The LSC values derived using the CV% values recommended by the ISCD were 5.3% for the lumbar spine and 5.0% for the thigh. The LSC values measured using our bone density equipment were 2.47% for the lumbar spine and 1.61% for the thigh. The LSC value using RMS-SD was 0.031 g/cm² for the lumbar spine and 0.017 g/cm² for the thigh. Conclusion: that the findings confirm that the CV% value measured using our bone density meter and the LSC value using RMS-SD were maintained very stably. This can be helpful for obtaining accurate measurements during bone density follow-up examinations.

• 한국콘텐츠학회논문지
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• 제12권9호
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• pp.250-256
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• 2012

골밀도 감소에 의해서 발생되는 골감소증, 골다공증 등은 폐경 후 여성에게 유병률이 높은 질환이며, 골다공증 골절에 따른 사회적 의료비 상승으로 의학적 관심이 급증하고 있다. 신부전환자는 체내에 비타민D 합성 능력이 저하되어 칼슘 흡수가 감소하여 뼈의 섬유화가 발생되고, 골밀도가 감소하는 현상이 나타난다. 따라서 신부전환자는 신장 기능 장애로 그치지 않고, 골다공증과 같은 골밀도 감소에 따른 합병증에 노출되어 있다. 본 연구에서는 치료 중에 있는 신부전환자들의 골밀도 변화를 관찰하였고, 신장이식 전후에서 발견되는 골밀도 변화를 분석하였다. 조사대상은 부산 B종합병원 신장내과 내원환자 중 신부전환자 214명을 신장이식의 유무에 따라 골밀도의 변화를 세대별, 성별로 나누어 분석했다. 분석결과 신장이식 환자군에서는 골밀도가 유지되거나 개선되었지만, 비신장이식 환자군에서는 골밀도가 꾸준히 나빠지는 결과를 보였다. 신부전환자는 신장이식을 받는 것이 최선의 치료책으로 사료되며, 신장이식을 통해서 골밀도의 개선이 가능함을 확인하였다. 이는 추가적으로 예상되는 합병증을 예방하기 위한 자료로도 활용할 수 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제28권6호
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• pp.962-971
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• 2004

This paper has dealt with thermo-physical properties of microencapsulated phase change material slurry as a latent heat storage material having a low melting point. The measured results of the thermo-physical properties of the test microencapsulated phase change material slurry, those are, density, specific heat, thermal conductivity and viscosity, were discussed for the temperature region of solid and liquid phases of the dispersion material (paraffin). The measurements of these properties of microencapsulated phase change material slurry have been carried out by using a specific-gravity meter, a water calorimeter, a differential scanning calorimeter(DSC), a transient hot wire method and rotating type viscometer, respectively. It was clarified that the additional properties law could be applied to the estimation of the density and specific heat of microencapsulated phase change material slurry and also the Euckens equation could be applied to the estimation of the thermal conductivity of this slurry.

• 아동학회지
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• 제22권1호
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• pp.97-107
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• 2001

This study argues the nature of the microgenetic method in respect to child development research and explores its merits and limitations. The microgenetic method focuses on observations that span the entire period from the beginning of developmental change to the time it reaches a relatively stable state. This produces a high density of observations relative to the rate of change in the phenomenon. In this way, observed behavior may be used in intensive trial-by-trial analysis. The microgenetic method is superior to other methods in the possibilities for observing developmental changes as they occur, examining various aspects of change, detecting variability in behavior, and flexibility in application regardless of theoretical perspectives. Limitations of this method include reliability problems due to repeated observations, artificiality relative to the natural situation, inconsistency of short-and long-term change, and demands on children's motivation for participation in research.

• 대한한의학회지
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• 제29권2호
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• pp.116-132
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• 2008

Objective: This study investigated the effects of Bimanbang-1 (肥滿1號方: here in after referred to BMB-1) on the obese gene and obese inhibitory. Methods: C57BL/6 mice were induced by high fat diet. Mice were divided into three groups (normal, high fat diet with control, high fat diet with BMB-1 extract) and fed for 15 weeks. Items of this experimental study are as follows: body weight change, final body weight, the weight change of the adipocytes in body, the level change of LFT, NEFA and creatinine, the expression of ${\beta}3AR$ and leptin gene in primary adipocytes, the production change of leptin in primary adipocytes, the expression of ${\beta}3AR$, leptin and $TNF-{\alpha}$ in adipocytes tissue. Result: 1. All experimental groups showedthat the weight change decreased considerably and the high density group showedthat the final weight decreased considerably. 2. The high density group showed that the amount of the adipocyte in weight decreased considerably. 3. All experimental groups showedthat the amount of ALT decreased considerably, and AST decreased in the high density group. However, the amount of creatinine and glucose did not increase considerably. 4. All experimental groups showed that the amount of total cholesterol, LDL-cholesterol, triglyceride, and NEFA decreased, and HDL-cholesterol increased considerably. 5. The high density groups showedthat the amount of leptin decreased considerably. 6. All experimental groups showed that the revelation of ${\beta}3AR$ in primary adipose cell and 3T3-L1 cell increased considerably, and that the revelation of leptin and $TNF-{\alpha}$ in primary adipose cellsand 3T3-L1 cells decreased considerably. 7. All experimental groups showed that the size of adipocyte in adipocytes tissue decreased. 8. All experimental groups showed that the adipose vacuoles in liver tissue decreased considerably. Conclusion: The findings suggest that Bimanbang-1 causes weight loss and histological change, thus it may be effective to treat obesity.