• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.434-434
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• 2011

가뭄은 홍수와는 달라서 정확한 발생시점, 지속시간, 피해반경 등을 정의하기 어렵다. 가뭄은 가뭄지수를 통해서 정의되며 정해진 지속시간에 따라서 가뭄의 특성을 평가하는 것이 일반적이다. 이러한 가뭄의 심도를 평가하기 위해서 많이 사용되는 지수로 표준강수지수(standardized precipitation index)가 있다. 본 연구에서는 6개월 지속시간에 SPI 지수를 대상으로 연구를 수행하였다. 최근 가뭄연구에서 시공간적 거동을 평가하는 연구가 중요한 연구주제로 자리 잡고 있다. 가뭄은 홍수와는 달리 공간적으로 전이되는 특성을 가지고 있어서 가뭄의 시작점과 영역반경을 평가하는 것은 가뭄을 예측하는데 있어서 기본적으로 선결되어야 한다. 그러나 상대적으로 가뭄의 시공간적 분석 연구는 많이 진행되지 않았다. 본 연구에서는 질량모멘트 개념을 도입하여 가뭄의 중심과 영역을 평가하는 기법을 개발하였다. 가뭄의 중심(centroid)은 1차모멘트를 통해서 추정되며 가뭄의 영역은 2차모멘트 즉, x방향의 공분산, y방향의 공분산, xy의 공분산을 통해서 타원(ellipse)형태로 수치적 접근이 가능하다. 다음 그림과 같이 가뭄의 중심을 1차모멘트로 추정하게 되면 +형태로 표시될 수 있으며 분산을 타원체로 표현하여 가뭄의 영역을 정의할 수 있다. 1, 2차모멘트를 추정하는데 있어서 Threshold 로 -2.0 이하의 값만을 이용하였으며 각 격자별 SPI 강도를 가중인자로 이용하였다. 그림과 같이 가뭄이 서해안에서 시작되어 시간에 따라 중동부로 퍼져나가는 것을 정량적으로 확인할 수 있다. 본 모형을 통해서 추출된 1, 2차 모멘트 정보를 활용하여 가뭄의 특성을 범주화하고 이를 기상학적 특성과 연결시키면 기상특성을 고려한 가뭄 예측모형으로의 개발도 가능할 것으로 판단된다.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.17 no.1
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• pp.3-9
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• 2006

Objectives: Obesity is one of risk factors for psychological and social adjustment problems (depression, low self esteem, low school function etc). Quality of life(QOL) is comprehensive and multidimensional construct including physical, emotional, social and school functioning. Some authors reported that child and adolescent obesity is associated with impaired QOL. This study was to examine the association between QOL and body mass index (BMI) in middle school students. Methods : Cross sectional analysis of 471 adolescents between the ages of 13 and 14 years ($mean{\pm}SD,\;13.4{\pm}0.6$), who attended one of middle schools in Seoul, Korea. Participants' QOL were scored by using Korean version of pediatric QOL inventory generic score scale ($PedsQL^{TM}$ 4.0). Participants had a $mean{\pm}SD\;BMI\;of\;21.3{\pm}4.0$. Self reports and parent proxy reports using $PedsQL^{TM}$ 4.0 were administered to measure participant's QOL. Participants were divided into four groups by BMI (Male: obesity group >26.5, at risk group 23.2-26.5, normal weight group 15.8-23.1, underweight group <15.8, Female : obesity group >25.2, at risk group 22.9-25.2, normal weight group 16.0-22.8, underweight group <16.0). Results : Compared with other groups, obese adolescents reported significantly(p<0.01) love. QOL in all domains. Obese adolescents were more likely to have impaired QOL than normal weight adolescents (Odds Ratio, 8.3, 95% confidence interval, 4.0-16.7). Conclusion : Obese adolescents have lower QOL than normal weight adolescents. Psychiatrist, parents, and teachers need to be informed of the risk fur impaired QOL in obese adolescents to target interventions that could enhance health outcomes.

• The Korean Journal of Rehabilitation Nursing
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• v.14 no.2
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• pp.129-135
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• 2011

Purpose: This study was done to examine the effects of Tai Chi exercise program on BMI, positive and negative psychiatric symptoms in patient with schizophrenia. Methods: The participants were patient with schizophrenia in S psychiatric hospital in D city. Twenty five patients were assigned to experimental group, and 26 patients were assigned to control group. Data were collected from May 9, to July 8, 2011. The Tai Chi exercise program was conducted with a duration of 60 minutes, 2 times a week for 8 weeks (a total 8 times). Measures were BMI, positive and negative psychiatric symptoms. Data were analyzed using descriptive statistics, chi-square test and t-test with SPSS/WIN 19.0 version. Result: The experimental group received Tai Chi exercise program had a significant changes in BMI, positive and negative psychiatric symptoms. Conclusion: The results of this study indicate that Tai Chi exercise program is an effective intervention program to improve the BMI, positive and negative psychiatric symptoms of patients with schizophrenia.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.39-45
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• 2004

Experiments were performed in a two-phase swirling spray facility that has been described elsewhere. Measurements of spray transport and drop size distribution are analyzed over wide ranges of air to liquid mass flow ratios, utilizing four different internal mixing pneumatic nozzles. The spatial distributions of mean velocities. fluctuating velocities, and velocity-diameter correlation were quantitatively analyzed. Also, the exponential correlation curves were obtained with ALR along the spray centerline, which indicated an approximately identical formulation regardless of ALR. It indicated that the atomization characteristics were remarkably superior in the case of 30o of swirl angle with higher ALR. Among other things. nozzle configuration is one of the significant parameters affecting spray phenomena from an internal mixing nozzle. Turbulence intensities are increasingly degenerated with an increase of nozzle configuration, allowing a rapid increment of drop size distribution.

• Journal of Gastric Cancer
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• v.7 no.4
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• pp.242-247
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• 2007

Purpose: We assumed that an obese patient has a high rate of postoperative wounds, but there is no objective data showing the relationship between the body mass index (BMI) and the rate of postoperative wounds in Korea. We describe the relationship of BMI and rates of postoperative wound complications. Materials and Methods: From September 2005 to February 2006, 772 patients undergoing elective gastrectomy surgery due to gastric cancer were enrolled in a retrospective study to measure postoperative wound complications. A preoperative history, physical examination and daily progress notes were reviewed retrospectively from the medical records. Postoperative wound complications were detected from the elective medical record and from a doctor in charge statement. Results: The total number of patients was 772, the mean age of the patients was $57{\pm}11.2$ years and the sex ratio (male/female) was 1.82:1. Postoperative wound complication rates were different among the BMI groups (BMI < $20\;kg/m^2$ vs $20{\leq}BMI{\leq}25\;kg/m^2$ vs >$25\;kg/m^2$), and patients with a BMI>$25\;kg/m^2$ that underwent gastrectomy had a significantly higher wound complication rate (4.6%) than underweight and normal weight patients (0.9% and 1.6%, respectively) (P=0.038). Conclusion: Overall, there was a statistical correlation between BMI and the postoperative wound complication rate. Overweight (BMI>$25\;kg/m^2$) patients that underwent gastrectomy had a higher wound complication rate than normal body weight ($BMI{\leq}25\;kg/m^2$) patients. Further studies will be required with a larger population and prospectively designed study considering other factors that affect the wound complication rate.

• Journal of the Korea Society of Computer and Information
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• v.26 no.8
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• pp.209-220
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• 2021

The effect of body composition such as lean mass and fat mass on bone mineral density (BMD) is complex and still controversial. In this study, we investigated the relationship between body composition and bone mineral density using nation-wide data from 2008 to 2011 Korea National Health and Nutrition Examination Survey (KNHANES) in 2,139 men and 2,193 postmenopausal women aged 50 years or older. Subjects with history of medication for osteoporosis or with diseases or malignancy affecting bone metabolism were excluded. Data of anthropometric measurements and demographic characteristics were collected by trained examiner. Fasting blood sample was obtained for blood chemistry analysis. BMD of the lumbar spine, total femur, and femoral neck, and body composition such as total lean mass (TLM), total fat mass (TFM), truncal fat mass (TrFM) were measured using dual-energy X-ray absorptiometry (DXA). There were significant positive correlations between body composition indices such as lean mass and fat mass with BMD. In multiple regression analysis, TLM was positively associated with BMD after adjusting age, body mass index, monthly house income, education level, physical activity, daily calcium intake and vitamin D concentration in both men and postmenopausal women. BMD at lumbar spine and femur in lowest quartile of TLM was significantly lower than other quartiles after adjusting those confounding factors in both gender. TrFM was negatively associated with total femur BMD in male and femur neck BMD in postmenopausal women after adjusting confounding factors. In conclusion, TLM is very important factor in maintaining BMD in subjects aged 50 years or older in men and postmenopausal women.

• Polymer(Korea)
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• v.39 no.2
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• pp.346-352
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• 2015

Polyalphaolefin (PAO) is a synthetic lubricant that is superior to mineral-based lubricants in the terms of physical and chemical characteristics such as low pour point, high viscosity index (VI), and thermal and oxidation stability. Several kinds of PAOs have been synthesized by using 1-pentene, 1-hexene, 1-octene, or 1-dodecene as monomer with three kinds of aluminum-based Lewis acid catalysts via cationic polymerization. The control of the catalytic performance and physical properties of PAO such like molecular weight, kinematic viscosity, pour point, and viscosity index was done by changing polymerization parameters. The alkyl aluminum halide-based catalysts show better catalytic activity than that of the conventional $AlCl_3$ catalyst. The microstructure of PAO was investigated by means of TOF-MS (time of flightmass spectroscopy) analysis in order to elucidate the correlation between the performances of the lubricant (VI, pour point) and the molecular structure of PAO. The VI of PAO increases with increases in the carbon number of ${\alpha}$-olefin. In other words, the performances of PAO as a lubricant strongly depended on the branch length of PAO.

• Fire Science and Engineering
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• v.25 no.3
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• pp.57-62
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• 2011

The combustion characteristic was evaluated for Pinus densiflora, used as a building material in Hanok, which were treated with two different flame retardant method. The specimen was brushed with flame retardant liquid two or three times and then let the specimen dehydrated during 24 h for spreaded treating. And the other specimen was soaked in the liquid for 72 h. The test methods were inflammability test using meker burner and heat release rate test using cone calorimeter. As a result for the tests, flame retardant treated specimens met the requirements of the inflammability and the spreaded treated method was more efficient than immersed method. The spreaded treated specimen had lower combustive properties than immersed specimen in TTI (time to ignition), PHRR (peak heat release rate), MLR (mass loss rate) and THR (total heat release).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.635-643
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• 2015

In this study, the experimental test results are given to confirm the control efficiency of the linear control algorithm used for designing the active mass dampers(AMD) which are supposed to be installed at Incheon international airport control tower. The comparison between the results from test and numerical analysis is conducted and it was observed that the AMD showed the control performance expected by the numerical model. The effects of the gain scheduling and constant-velocity signal added to the control signal calculated by the algorithm is identified through the observation that the AMD always show behavior within the given stroke limit without any loss of the desired control performance. The phase difference between the accelerations of the structure and the AMD were almost close to 90 degree, which implies that the AMD absorbed the structural energy effectively.

• Elastomers and Composites
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• v.37 no.3
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• pp.159-169
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• 2002

The improvement of flame retardancy of the foams based on NBR/GTR compounds was conducted by formulating various materials i.e. NBR, GTR, inorganic and phosphorus containing flame retardants, foaming agent, cross-linking agent and activator. The foaming properties, morphology, smoke density and flame retardancy of the specimens were investigated using SEM, LOI tester, smoke density control system and cone calorimeter. The phosphorus containing flame retardant reduces heat release rate, increases the limiting oxygen index and a char formation. The inorganic flame retardant increases the limiting oxygen index and reduces heat release rate with an increased CO yield by char formation, and smoke suppressing effect. The formed char seemed to intercept the oxygen transport and heat transfer into the core area. When the composition ratios of the compounds of NBR/GTR were $100{\sim}80/0{\sim}20 wt.%$, and the ratios of the rubbers/flame retardants were $1/1.55{\sim}3.60 wt.%$, we could developed foams with low heat release rate, high limiting oxygen index($28.0{\sim}39.3$), closed or semi-closed cell of uniformity and reasonable expandability($225{\sim}250 %$).