• 설비공학논문집
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• 제17권7호
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• pp.649-658
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• 2005

Flow condensation heat transfer coefficients (HTCs) of R22, R410, Propane (R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of $0.1\~0.9$ at mass flux of $200\~400kg/m^2s$ and heat flux of $7.3\~7.7kW/m^2$ at the saturation temperature of $40^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within $25\%$ deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than $20\%$ for all data.

• 한국치위생학회지
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• 제9권4호
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• pp.659-669
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• 2009

Objectives : The degree of depression in dental hygienist was analyzed to reveal the various factors related to them. Methods : The self-administered questionnaires were filled out from 202 dental hygienist in Daejeon City. The survey items included subjects' socio-demographic and job-related characteristics, health-related behaviors, depression. Chi-Square analysis and Pearson's correlation coefficient was put into survey results, in which a degree of depression was dependent variable and others were independent variable. Results : 1. The distribution for depression degree has shown the rate as 80.2% in normal range group and 19.8% in depression group. 2. As for depression, long working hours(p=0.042), poor sense satisfaction in work(p=0.000), not fit to the job(p=0.003), low personal relation with peer works or supervisors(p=0.039), without alcohol drinking(p=0.048), poor subjective condition of health(p=0.000) than their respective counterparts. 3. Concerning correlation between depression and various factors, poor sense satisfaction in work(r=-0.332, p=0.000), not fit to the job(r=-0.353, p=0.000), low personal relation with peer works or supervisors(r=-0.215, p=0.002), without alcohol drinking(r=-0183, p=0.009), poor subjective condition of health(r=-0.333, p=0.000). Conclusions : These results showed that depression state could be influenced by various factors, which include socio-demographic, job-related characteristics and health-related behaviors. Therefore, in order to reduce depression state of dental hygienists, development and application of programs to manage and research for them are required to be revitalized as well as socio-demographic and job-related characteristics and health-related behaviors.

• The Korean Journal of Physiology
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• 제25권1호
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• pp.69-79
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• 1991

To evaluate the acute and chronic effects of potassium on aldosterone response to different amounts of sodium intake, two series of experiments were conducted. In the first series of experiments, when the plasma K level was increased acutely by KCI infusion $(20\;{\mu}g/kg/min\;for\;20 min)$, plasma aldosterone concentration increased in both low Na and high Na groups. However, the aldosterone response to K infusion was significantly greater in the low Na than in the high Na groups. In the second series of experiments, rats fed a high K diet chronically showed a significantly higher plasma K level than those fed a low K diet. However, plasma Na level was maintained relatively constant independent of the Na intake. Both the plasma renin activity (PRA) and aldosterone levels were inversely related to the Na intake. There was a highly positive correlation between aldosterone level and PRA over a wide range of sodium intakes. However, the slope of the correlation line was distinctly steeper in the K-repleted than in the K-depleted rats. The above results indicate that the adrenotropic action of acute K load was augmented in the presence of high plasma renin levels. However, when plasna K level was elevated chronically by a high-K diet, aldosterone secretion was markedly stimulated, although the plasma lenin levels were suppressed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.249-255
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• 2005

Flow condensation heat transfer coefficients(HTCs) of R22, R4IO, Propane(R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53 m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of 0.1 ${\sim}$ 0.9 at mass flux of $200{\sim}400$ $kg/m^2s$ and heat flux of $7.3{\sim}7.7$ $kW/m^2$ at the saturation temperature of $4^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within 25% deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than 20% for all data.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.513-520
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• 2018

본 논문은 포신의 길이 및 발사되는 탄약의 압력에 따른 포신 내부 및 배연기의 유동 특성에 대한 연구 내용이다. 탄약 설계 전 포신길이 및 탄약 압력에 따른 배연기의 유동 특성을 분석함으로서 탄약 운용 간 발생할 수 있는 Flareback 현상을 사전에 예방 할 수 있으며, 기존 탄약의 설계 요소인 속도, 정확도, 관통성능, 사거리 외에 운용성 향상을 위한 포신과 탄약의 호환성이 탄약 설계의 주요 요소임을 추가로 도출하였다. 유동 해석 수행 결과 포신 길이가 길고, 사격되는 탄약의 압력이 낮을수록 포신의 배연기 작동시간이 느려져 전투차량 내부로 추진제 가스가 들어올 확률이 높아짐을 확인하였다. 따라서, 본 연구를 통해 확인 된 포신 길이 및 탄약 압력에 의한 배연기 유동 특성 상관관계 해석 기법은 신규 탄약 설계 시 운용성 향상을 위한 주요 요소로 고려되어 탄약의 무게 결정과 추진제 압력 선택에 활용이 가능 할 것으로 판단된다.

• 한국지반환경공학회 논문집
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• 제23권5호
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• pp.15-24
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• 2022

준설 매립지반의 경우 공학적, 물리적 조건이 열악하여 매립현장에서 이를 개량하기 위한 시간과 비용이 많이 든다. 또한 국내 실정에 적합한 관중혼합 이송처리 공법의 적용사례가 없고 공법 적용성 및 효과에 관하여 불확실할 뿐 아니라 실제 현장과 실내실험 간의 차이가 발생할 수 있다. 이러한 문제점을 해결하기 위해 개질재(표준사+입도조절재)가 혼합된 준설토를 대상으로 실내 특성실험을 통해 개질재의 적정한 입도분포 및 함수비 범위를 결정하였다. 그 결과 단계투기 시 침강압밀계수가 증가하고 분리침강에 대한 개선효과가 있는 것으로 확인되었다. 실험결과 회귀분석을 통해 개질 처리토의 함수비에 따른 비배수전단강도를 도출하고, 이를 활용하여 배합비를 결정할 수 있는 상관식을 제시하였다.

• Environmental Engineering Research
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• 제13권4호
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• pp.184-191
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• 2008

Long term monitoring was conducted to investigate a surface runoff of pollution from urban highway. The monitoring data was collected for 18 rainfall events and was used to correlate pollution load to various parameters, such as rainfall intensity, antecedent dry days and total discharge flow. Runoff coefficient and seasonal variation were also evaluated. The mean runoff coefficient of the highway was 0.823(range; $0.4687{\sim}0.9884$), and wash-off ratio for $COD_{Mn}$ and SS loads was 72.6% and 64.3%, respectively. For the initial rainfall event, the runoff EMC of $COD_{Mn}$ was high in summer and the EMC of SS was high in autumn season. However the seasonal variation of T-N and T-P was not significant. The discharged $COD_{Mn}$-EMC was $147.6\;mg/L{\sim}9.0\;mg/L$ on the generated $COD_{Mn}$-EMC of $98.8\;mg/L{\sim}8.9\;mg/L$. While the generated EMC of SS was in $285.7\;mg/L{\sim}20.0\;mg/L$ and its discharged EMC was in $190.4\;mg/L{\sim}8.0\;mg/L$. EMC of pollutants was not directly related to the first flush rainfall intensity and the antecedent dry days. But the correlation was relatively high between EMC and cumulative runoff flow volume. The trend of EMC was reduced with the cumulative runoff flow volume.

• 한국소음진동공학회논문집
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• 제22권5호
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• pp.480-488
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• 2012

The aircrafts with high aspect ratio wings made by a composite material have been developed, which enable high energy efficiency and long-term flight by reducing air resistance and structural weight. However, they have difficulties in securing the aeroelastic stability such as the flutter because of their long and flexible wings. The flutter is unstable self-excited-vibration caused by interaction between the structural dynamics and the aerodynamics. It should be verified analytically prior to first flight test that the flutter does not happen in the range of flight mission. Normally, the finite element model is used for the flutter analysis. So it is important to construct the finite element model representing dynamic characteristics similar to those of a real aircraft. Accordingly, in this research, to acquire dynamic characteristics experimentally the modal test of the aircraft with high aspect ratio composite wings was conducted. And then the modal parameters from the finite element analysis(FEA) were compared with those from the modal test. To make analysis results closer to test results, the finite element model was updated by means of the sensitivity analysis on variables and the optimization. Finally, it was proved that the updated finite element model is reliable as compared with the results of the modal test.

• Biomolecules & Therapeutics
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• 제15권4호
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• pp.266-272
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• 2007

A rapid analytical method was developed to quantify very long-chain fatty acids (VLCFAs, C22:0, C24:0, C26:0) in human plasma with good sensitivity and specificity using tert-butyldimethylsilyl (TBDMS) derivatization and stable isotope GC-MS selective ion monitoring (GC-MS/SIM). Two-hundred and fifty ${\mu}L$ of plasma was fortified with deuterated stable isotope internal standards (d3-C22:0, d3-C24:0, d3-C26:0) and standard mixtures of chloroform and methanol, and then extracted with hexane and acetonitrile. To upper layer of liquid-liquid-extraction, N-(t-Butyldimethylsilyl)-N-methyltrifluoroacetamide was added and then heated to $60^{\circ}C$ for 30 min to produce the TBDMS derivatives. Derivatives of VLCFAs were analyzed by GC-MS/SIM. Calibration curves showed a linear relationship for the target compounds in the concentration range of $10^{-4}{\sim}2{\times}10^3\;{\mu}g/mL$ with the correlation coefficient ranging from 0.996 to 0.999. The limit of quantification for the plasma was $10^{-4}{\sim}2{\times}10^{-4}\;{\mu}g/mL$ (S/N=3). When applied to the plasma specimens of patients with peroxisomal disorder, X-linked adrenoleucodystropy (ALD, Mckusick 202370), the method clearly differentiated normal subjects from ALD patients. The C24:0/C22:0 and C26:0/C22:0 ratios were significantly elevated in the plasma of patients with X-linked ALD compared to normal subjects. The new developed method might be useful for a rapid and sensitive diagnosis of X-linked ALD and other peroxisomal disorders.

• BLOOD RESEARCH
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• 제53권4호
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• pp.320-324
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• 2018

Background Recent studies have devoted much attention to non-protein-coding transcripts in relation to a wide range of malignancies. MALAT1, a long non-coding RNA, has been reported to be associated with cancer progression and prognosis. Thus, we here determined MALAT1 gene expression in chronic lymphocytic leukemia (CLL), a genetically heterogeneous disease, and explored its possible relationships with cytogenetic abnormalities. Methods MALAT1 expression level was evaluated using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) on blood mononuclear cells from 30 non-treated CLL patients and 30 matched healthy controls. Cytogenetic abnormalities were determined in patients by fluorescence in situ hybridization (FISH). Results MALAT1 expression level was up-regulated in the CLL group compared to healthy controls (P=0.008). Del13q14, followed by Del11q22, were the most prevalent cytogenetic abnormalities. We found no association between the FISH results and MALAT1 expression in patients. Conclusion Altered expression of MALAT1 is associated with CLL development. Further investigations are required to assess the relationship between this long non-coding RNA and CLL patient survival and prognosis.