• 대한금속재료학회지
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• 제48권3호
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• pp.241-247
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• 2010

In order to develop the vacuum distillation process of magnesium alloy scrap, a fundamental study on the evaporation behavior of magnesium alloy (AM50) scrap melt was carried out. Melt temperature, pressure, reaction time, and initial specific surface area of melt were considered as experimental variables. The evaporation rate of magnesium increased with the increase of melt temperature and initial specific surface area of melt, and with the decrease of the pressure. The activation energy of magnesium evaporation reaction calculated by an Arrhenius plot decreased with the decrease of the pressure and with the increase of the initial specific surface area of melt. An empirical equation was derived for the evaporation rate of magnesium from AM50 alloy melt.

• Advances in concrete construction
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• 제13권5호
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• pp.361-365
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• 2022

The objective of this study is to simulate the two-phase flow in pipes with various two-fluid models and determinate the shear stress. A hyperbolic shear deformation theory is used for modelling of the pipe. Two-fluid models are solved by using the conservative shock capturing method. Energy relations are used for deriving the motion equations. When the initial conditions of problem satisfied the Kelvin Helmholtz instability conditions, the free-pressure two-fluid model could accurately predict discontinuities in the solution field. A numerical solution is applied for computing the shear stress. The two-pressure two-fluid model produces more numerical diffusion compared to the free-pressure two-fluid and single-pressure two-fluid models. Results show that with increasing the two-phase percent, the shear stress is reduced.

• 생명과학회지
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• 제28권2호
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• pp.187-194
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• 2018

표고버섯으로부터 유래한 eritadenine (EA)은 혈중 low density lipoprotein (LDL), triglyceride (TG), phospholipid를 감소시키는 물질이다. 최근 저희 연구팀은 in vitro 연구에서 EA가 angiotensin converting enzyme (ACE)의 활성을 저해함을 밝혔다. 본 연구에서는 EA와 EA 함유한 표고버섯균사체 고체배양 효소추출물(EA-LEMCEE)이 본태성 고혈압 쥐 SHR의 혈압을 낮추었음을 보고한다. EA 및 EA-LEMSCEE는 인체 탯줄 혈관내피세포 EA.hy926 세포의 ACE 활성을 억제하였다. EA-LEMSCEE는 SHR의 수축기 및 이완기 혈압을 Control 처리구에 비해 유의성 있게 낮추어 처리 5주에는 Positive control인 captopril (CP) 처리와 비슷한 혈압감소 효과를 나타내었다. EA-LEMCE는 LEMSCEE에 비해 수축기 및 이완기 혈압을 감소시켰지만 유의성은 없었다. EA- LEMSCEE는 renin과 ACE 활성을 Control 처리에 비해 유의성 있게 억제하였고, angiotensin II (Ang II) 함량을 감소시켜, 처리 5주 후에 이러한 CP의 효과와 유사하였다. 또한 EA-LEMCEE는 LEMCEE에 비해 유의성 있게 renin 및 ACE 활성을 억제하였고 및 Ang II 함량을 감소시켰다. 이와 같은 결과는 EA 및 EA-LEMCEE는 본태성 고혈압 SHR의 renin과 ACE 활성을 억제하여 혈압을 낮추었고, EA 및 EA-LEMSCEE는 인체 고혈압을 낮출 수 있음을 의미한다.

• 분석과학
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• 제34권1호
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• pp.23-35
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• 2021

In order to measure the volatile organic compounds (VOCs) of a sample which is too large to use commercially available chamber, a stainless steel vacuum chamber (VC) (with an internal diameter of 205 mm and a height of 50 mm) was manufactured and the temperature of the chamber was controlled using an oven. After concentrating the volatiles of the sample in the chamber by helium gas, it was made possible to remove residual volatile substances present in the chamber under reduced pressure ((2 ± 1) × 10-2 mmHg). The chamber was connected to a purge & trap (P&T) using a 6 port valve to concentrate the VOCs, which were analyzed by gas chromatography-mass spectrometry (GC-MS) after thermal desorption (VC-P&T-GC-MS). Using toluene, the toluene recovery rate of this device was 85 ± 2 %, reproducibility was 5 ± 2 %, and the detection limit was 0.01 ng L-1. The method of removing VOCs remaining in the chamber with helium and the method of removing those with reduced pressure was compared using Korean drinking water regulation (KDWR) VOC Mix A (5 μL of 100 ㎍ mL-1) and butylated hydroxytoluene (BHT, 2 μL of 500 ㎍ mL-1). In case of using helium, which requires a large amount of gas and time, reduced pressure ((2 ± 1) × 10-2 mmHg) only during the GC-MS running time, could remove VOCs and BHT to less than 0.1 % of the original injection concentration. As a result of analyzing volatile substances using VC-P&T-GC-MS of six types of cell phone case, BHT was detected in four types and quantitatively analyzed. Maintaining the chamber at reduced pressure during the GC-MS analysis time eliminated memory effect and did not affect the next sample analysis. The volatile substances in a cell phone case were also analyzed by dynamic headspace (HT3) and GC-MS, and the results of the analysis were compared with those of VC-P&T-GC-MS. Considering the chamber volume and sample weight, the VC-P&T configuration was able to collect volatile substances more efficiently than the HT3. The VC-P&T-GC-MS system is believed to be useful for VOCs measurement of inhomogeneous large sample or devices used inside clean rooms.

• 한국생활과학회지
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• 제16권4호
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• pp.837-848
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• 2007

The literature suggested that a small reduction in overall blood pressure can have a large effect on overall prevalence of hypertension, and therefore, the affect of taste preferences of the population on salt intake should be considered for long-term blood pressure intervention programs. The purpose of this study is to investigate the influence of salt taste preference and salt taste sensitivity on salt intake behavior as risk factors for high blood pressure. We collected information on blood pressure, diet and lifestyle behaviors, salt taste preference and salt taste sensitivity from 540 respondents from Suseo-dong, Seoul. Salt taste sensitivity was assessed by administering a 1% NaCl solution to the subject's tongue and measuring the perceived intensity on 10 level scale. Salt intake behavior was classified into 3 categories: frequency of high-sodium foods, practice of salt-reducing behavior and frequency of vegetable and fruit intake. Salt taste preference showed a significant relation to the subjects' blood pressure, i.e. subjects with a higher salt preference had higher blood pressure. Salt taste sensitivity did not show a significant relation to blood pressure. However, there was a positive correlation between salt taste preference and salt taste sensitivity. Among the 3 indicators used to measure salt intake behavior, the practice of salt-reducing behavior remained significantly correlated to blood pressure. Moreover, salt-reducing behavior and salt taste preference showed a significant correlation, i.e. people who do not like salty foods tend to practice more salt-reducing behavior, leading to reduced levels in blood pressure. In a population, a small reduction in overall blood pressure can have large effects in overall prevalence of hypertension, in contrast to clinical studies where achievement of an individual's normal blood pressure is emphasized. Therefore, taste preference of the population should be considered for long-term blood pressure intervention programs.

• 복식문화연구
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• 제20권6호
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• pp.799-810
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• 2012

A girdle is a body-shaping article of clothing. The garment pressure of the girdle is considered an indispensable factor. The purpose of this study was to identify changes in body size and distribution of garment pressure after donning the girdle. The changes of body size and garment pressure were analyzed by body types. Korean women (n=19) in their 20s participated in the experiment. Their body types were classified according to four factors: the index value(hip girth-waist girth), and waist, hip, and thigh girths. The garment pressure was measured at 12 points. The results of this study showed that the hip and thigh girths were reduced mostly after donning the girdle. These values were 2.0~2.8cm and 1.7~2.3cm, respectively. The garment pressure was high at the waist band, the hip joint, and the gluteal furrow region at the back. The subjects whose waists, thighs, or hips were well developed showed great garment pressure in the hip area, but their hip girth decreased very little. The subjects with less developed or slim thighs or hips showed a slimming effect, with moderate pressure in the hip and thigh regions. These results show that the hip and thigh can be slimmed with moderate pressure by donning a thigh-length girdle. High garment pressure is not necessary for the girdle's body shaping effect. The hip area is hard to get body slimming effect with high garment pressure. The current girdle sizing system needs to be revised in order to lower garment pressure in the hip region. The researchers suggest using 3cm size intervals rather than 6cm size intervals for hip girth.

• Journal of Biosystems Engineering
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• 제42권3호
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• pp.136-146
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• 2017

Purpose: This paper presents an appropriate wrapping method by analyzing the pressure distribution applied to a bale surface, along with the change in pressure according to an increase in the number of film layers in rice straw bales, which account for 74% of the total bulky feed supply in Korea. Methods: A model with the shape of an actual bale was fabricated to analyze the distribution of surface pressure in bale wrapping, and the pressure was measured. Experiments were conducted to analyze the pressure using eight different layer numbers (2, 4, 6, 8 10, 12, 14, and 16 layers) at five wrapping speeds (27, 29, 31, 33, and 35 rpm). Results: The maximum pressure applied to a circular bale by the film occurred at the center of the end of the bale, whereas the minimum pressure occurred at the center of the bale side. An extreme value ratio between the minimum and maximum pressures was distributed as 8.5-56.6%, which was improved with an increase in rotation speed. The an uneven pressure distribution occurred because the number of film overlaps was 8.24-times greater at the center of the bale's end than at the center of the ba le side. At a level 5 rotation speed, the minimum pressure was $P_{LV5-M1}=0.0625{\sigma}^2+36.173{\sigma}-36.753$ ($R^2=0.9845$) at $M_1$, and the maximum pressure was $P_{LV5-M6}=5.5552{\sigma}^2+41.05{\sigma}-39.071$ at $M_2$, revealing a correlation of $R^2=0.9983$. Conclusions: To replace four layers with six layers, 2-4 layers were added only to the side of the bale, and the minimum pressure at $M_1$ was then improved from that at four layers to that at six layers, and the amount of film consumed for 4-6 layers was reduced by 84.6%.

• 대한통합의학회지
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• 제7권1호
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• pp.75-80
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• 2019

Purpose : This study investigated the effect of bamboo stepping exercises on the blood pressure of the elderly. This study was performed for 8 weeks. Methods : The study participants included 25 people aged 65 and over. Of the participants, 16 were in the hypertensive elderly group and 9 were in the normal blood pressure elderly group. The participants stepped on semicircular bamboo for 20 minutes 3 times a week for 8 weeks. The participants' blood pressure was measured 3 times before and after 8 weeks of exercise. The mean values of the 3 before and after measurements were compared and analyzed statistically. Results : The systolic blood pressure of the hypertensive elderly group decreased significantly from $134.6{\pm}21.1mmHg$ to $119.9{\pm}18.1mmHg$ (p<.05). The diastolic blood pressure of the hypertensive elderly group decreased from $70.2{\pm}10.5mmHg$ to $66.1{\pm}9.8mmHg$, but the difference was not significant. The systolic blood pressure of the normal blood pressure elderly group decreased significantly from $127.2{\pm}18.7mmHg$ to $115.5{\pm}19mmHg$ (p<.05). The diastolic blood pressure of the normal blood pressure elderly group decreased from $72.6{\pm}11.3mmHg$ to $68.2{\pm}12mmHg$, but the decrease was not significant. Conclusion : After completing 8 weeks of the bamboo stepping exercises, the elderly participants' systolic blood pressure was effectively reduced. Today, lifestyle modifications, such as daily exercise, are necessary to control the blood pressure of the elderly. We hope that the bamboo stepping exercises, which are easy to perform and are not restricted by place and time, will become part of the elderly health policy.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2393-2399
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• 2011

In the case where the bottom of railroad is penetrated by non-excavation construction method, the design is performed based on the assumption that there is no displacement and no change of stress However, measurement data showed that reduction of earth pressure and relaxation of stress take place by the displacement. In this study, we investigated the earth pressure on the structure under the railroad constructed by a non-excavation method and the stress relaxation region. The design based on earth pressure is non-economical because it is an over design. Relaxation of stress may lead to road base settlement and rail irregularly due to the reduced railroad supporting stiffness, to ballast crack in the case of concrete roadbed. The result showed that it is reasonable to set the stress on the structures as active earth pressure not as earth pressure at rest. Additionally, the study on the stress relaxation region identified the regions that should be supported in future construction by a non-excavation method.

• 설비공학논문집
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• 제18권1호
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• pp.38-46
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• 2006

The characteristics about the pressure drop in microtubes have been investigated. The test tubes are the circular, seamless, stainless steel tubes with an inner diameter of 0.244, 0.430, and 0.792 mm, respectively. R-l34a was used as a test fluid. Early flow transition which has been reported in some previous studies is not found in single-phase flow pressure drop tests. The conventional theory between friction factor and Reynolds number predicted the experimental friction factors within an absolute average deviation of $8.9\%$. The two-phase flow pressure drop increases for higher quality and mass flux, and for reduced inner diameter. The existing correlations fail to predict the experimental data. A new correlation to predict the two-phase flow pressure drop is developed in the form of the Lockhart-Martinelli correlation. The effects of the tube diameter and the surface tension were considered, and the correlation predicted the experimental data within an average absolute deviation of $8.1\%$.