• Journal of Biosystems Engineering
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• 제36권6호
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• pp.444-452
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• 2011

In this study the characteristics of natural ventilation of Venlo-type greenhouse with continuous roof vents were analyzed using commercial computational fluid dynamics (CFD) code. Developed CFD simulation model was verified by comparison with experimental data. Simulation errors were 1.9-46.0% for air velocity and 1.7-11.2% for air temperature at each measurement point. CFD simulations were conducted to estimate the effect of roof vents opening direction, opening angle, outside wind velocity and wind directions on ventilation rate and climate condition in greenhouse. The results of this study showed that ventilation rate of the present greenhouse was increased linearly in proportion to the increase of roof vent opening angle and outside wind velocity over 2.0 m/s. According to the analysis on the effects of different roof vent opening direction, simultaneous opening of wind and leeward vents showed the highest ventilation rate and lowest mean temperature in greenhouse.

• 한국강구조학회 논문집
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• 제24권3호
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• pp.245-256
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• 2012

본 연구는 SC 벽체의 구조적 성능에 개구부가 주는 영향을 평가하는 목적으로 하였다. SC구조의 실험체는 개구부가 있는 실험체와 없는 실험체로 구분하였으며 개구부형상은 정사각형으로 개구부 주변의 보강과 비보강 그리고 슬리브두께를 변수로 계획하였다. 실험체의 공통된 파괴양상은 강판의 좌굴이 스터드와 스터드 사이에서 발생한 후 콘크리트의 균열이 진행되는 형태이며 개구부의 파괴형태는 수직 슬리브 벽이 개구부 안쪽으로 좌굴되는 파괴형태를 보여주었다. 또한 개구부의 슬리브 유무에 따라 강판좌굴 하중은 비슷하지만 최대압축강도는 슬리브가 있는 것이 크게 나타났다.

• 한국수소및신에너지학회논문집
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• 제29권4호
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• pp.370-377
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• 2018

Ball valve has been widely used in the field of high-pressure gas pipeline as an important component because of its low flow resistance and good leakage performance. The present paper focuses on the flow nature at the downstream of the ball valve used for gas pipelines according to valve opening rates. Steady 3-D RANS equations, SC/Tetra, have been introduced to analyze the flow characteristics inside the ball valve. Numerical boundary conditions at the inlet and outlet of the valve system are imposed by mass flow-rate and pressure, respectively. Velocity distributions obtained by numerical simulation are compared with respect to the valve opening rates of 30, 50, and 70%. Cavity distributions, asymmetry flow velocity and the flow stabilization point at each opening rate are also compared. When the valve opening rates are 30 and 50%, the flow stabilization requires the sufficient length of 10D or more due to the influence of the recirculation flow at the downstream of the valve.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.315-320
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• 2004

Swing check valves are the most common type of check valve in nuclear power plant and need to be operated property to perform their functions and to keep the valve internals stable. However, for a swing check valve disc to remain stable, the opening characteristics should be identified and the upstream flow velocity should be enough to hold the disc fully open and without motion. Thus it is necessary to develop a model for predicting the flow velocity for a given disc opening. In the present study, the disc positions with mean flow velocity were measured for 3 inch and 6 inch swing check valves. Comparison of the measurements with the existing models showed that the models underestimate the mean flow velocity for a given disc position. Therefore, the existing model for predicting swing check valve disc position was improved with the realistic disc impingement area perpendicular to the flow stream and the experimental data. The result showed that the improved model with the best estimate of kb = 0.04 predicts well the disc openings of 6 inch swing check valve, especially in the low velocity region. For better prediction of the disc opening at high flow velocity, however, it is recommended to develop a kb correlation with the disc angle.

• 말소리와 음성과학
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• 제15권1호
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• pp.19-24
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• 2023

This study investigated acoustic (VOT) and articulatory characteristics of Korean velar stops in monosyllabic CV structures to examine how the three-way distinction is realized in the laryngeal and supralaryngeal domains and how the distinction is manifested in male versus female speakers' speech production. EMA data were collected from 22 speakers. In line with previous studies, male speakers preserved the three-way differentiation of velar stops (/k^*/</k/</k^h/) in terms of VOT while female speakers showed only a two-way distinction (/k^*/</k/=/k^h/). As for the kinematic characteristics, a clear three-way distinction was found only in male speakers' peak velocity measure in the C-to-V opening movement (/k^h/</k/</k^*/). For the other kinematic measures (i.e., articulatory closure duration, deceleration duration of the opening movement and the entire opening movement duration), male speakers showed only a two-way distinction between fortis and the other two stops. Female speakers did not show a three-way contrast in any kinematic measure. They showed a two-way distinction between lenis and the other two stops in C-to-V deceleration duration (/k^*/=/k^h/</k/), and a two-way distinction between fortis and lenis stops in the opening movement duration. An overall comparison of VOT and articulatory analyses revealed that the lenis-aspirated kinematic distinction is diminishing, driven by female speakers, in line with the loss of the lenis-aspirated distinction in VOT that could influence supralaryngeal articulation.

• 한국치위생학회지
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• 제11권6호
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• pp.901-911
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• 2011

Objectives : This study was conducted during the period from August 30 to September 9, 2011 in order to survey difference in the general perception of medical market opening and factors related to the choice of foreign hospitals among dental hygiene and nursing students at universities in Seoul. Methods : For this purpose, 438 students were surveyed using a questionnaire and collected data were analyzed using SPSSWIN 18.0. Conclusions drawn from this study are as follows. Results : 1. With regard to dental hygiene and nursing students' perception of medical market opening according to general characteristics, significant difference was not observed according to gender, experience in working at a hospital, medical institution used, and the frequency of using medical institutions, but significant difference was observed according to department, and interest in healthcare-related news. 2. There was significant difference in dental hygiene and nursing students'pro/con attitude toward medical market opening, but not in gender, experience in working at a hospital, medical institution used, and the frequency of using medical institutions. 3. With regard to intention to visit and revisit foreign hospitals, there was significant difference between dental hygiene and nursing students in intention to visit but not in intention to revisit. Conclusions : The results of this study suggest that more research on the medical market opening portion dental hygiene and nursing students' perception and attitude did not differ significantly, so the more accurate and open markets for a variety of medical education and school education and a variety of materials through hands-on experience be grasped should allow. Furthermore, students' acquisition of accurate prior knowledge about medical market opening is expected to be helpful to activate their employment in overseas.

• 산업경영시스템학회지
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• 제40권1호
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• pp.1-10
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• 2017

The difficulties in opening and closing a sport utility vehicle (SUV) tailgate is important aspect of JD (James David) power's Initial Quality Survey (IQS) assessment, and affective quality has a big impact on the the success of thesedays products. The purpose of this study is to evaluate the perceived difficulty and satisfaction of customers by the opening and closing of the tailgate and to grasp the relationship between them and the opening and closing reaction force. The mechanical force required to open and close 42 domestic and overseas SUV tailgates was measured with the help of an auto company. In the experiment, 100 male drivers in their 20s to 50s evaluated perceived difficulty and satisfaction with opening and closing the tailgate. The results of the analysis showed that perceived difficulty and satisfaction were statistically different depending on the vehicle, but did not depend on the personal characteristics of the participants. The perceived difficulty and satisfaction regression model of tailgate opening and closing was developed by mechanical force variables and had a relatively high adjusted $R^2$ ranging from 0.62 to 0.73. The models showed that the the initial close and open force, the difference between initial and maximum close force and the difference between initial and auto-fall angle should be small for the low perceived exertion and high satisfaction. In addition, the correlation analysis between IQS score of tailages and perceived difficulty and satisfaction showed that the IQS scores were more related to the perceived difficulty and satisfaction of closing than those of opening. The results of the study will be helpful to design and test mechanical open and close structure of SUV tailgates.

• 한국유체기계학회 논문집
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• 제17권1호
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• pp.5-11
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• 2014

The purpose of this paper is to investigate an analytical approach for opening performance evaluation of the nuclear pressure safety valve based on standard codes such as ASME or KEPIC. It is well-known that safety valve is considered as one of pressure relief valves for protecting a boiler or pressure vessel from exceeding the maximum allowable working pressure. When pressure in a container reaches its set pressure, the safety valve commences discharging the internal fluid by a sudden opening called as popping. Safety valve is usually evaluated by set pressure, full open, blow-down, leakage and flow capacity. The test procedure and technical requirement for performance evaluation is described in international code of ASME code such as BPVC. The opening characteristics of steam safety valve can be analyzed by computational fluid dynamics (CFD) and steam shaft dynamics. First, the flow analysis along opening process is simulated by running the CFD models of the ten types of opening steps from 0 to 100%. As a analysis result, the various CFD outputs of flow pattern, pressure, forces on the disc and mass flow at each simulation step is demonstrated. The lift force is calculated by using the forces applied on disc from static pressure and secondary flow. And, the effect of huddle chamber or control chamber is studied by dynamic analysis based on CFD simulation results such as lift force. As a result, dynamics analysis shows opening features according to the sizes of control chamber.

• 약학회지
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• 제42권2호
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• pp.196-204
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• 1998

The blood-brain barrier (BBB) of rats was modificated opening reversibly by infusing a hyperosmotic solution of arabinose (1.6 molal) into the right external carotid artery. Pre vious studies demonstrated that permeability was increased maxmmally in the first 15 min and remained slightly elevated at 1 hr. As control reference, saline was used. In the present study, to evaluate the effects of osmotic BBB opening on the BBB trasport according to hydrophilic or hydrophobic characteristics of drugs. And the differences of the uptakes of these compounds to right (treated osmotic opening) and left (untreated) hemispheres in same rats were compared each other following injection of 8 mCi per rat of $^{99m}Tc$-ethylene triamine pentaacetic acid (DTPA) as hydrophilic drug or 5mg/kg of phenytoin as hydrophobic drug mto the right external carotid artery of rats between two groups (1.6 molal arabinose vs saline). The uptakes of $^{99m}Tc$-DTPA and phenytoin in the right cerebral hemispheres were increased to about thirty three times and twice rather than those in the left cerebral heimspheres, respectively. And PAs (permeability X capillary surface area) were also increased from a control mean of 2.11${\times}10^{-4}$ (Untreated) to 6.98${\times}10^{-3}\;sec^{-1}$ (treated osmotic opening for $^{99m}Tc$-DTPA and 0.29 to 0.17 $sec^{-1}$ for phenytoin, respectively. From the results of present study, it is noted that osmotic opening of BBB is more effective in the brain delivery of hydrophilic drugs rather than that of hydrophobic drugs.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.687-708
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• 2020

Openings in steel plate shear walls (SPSWs) are usually used for decorative designs, crossing locations of multiple utilities and/or structural objectives. However, earlier studies showed that generating an opening in an SPSW has a negative effect on the cyclic performance of the SPSW. Therefore, this study proposes tripling or doubling the steel-sheet-plate (SSP) layer and stiffening the opening of the SPSW to provide a solution to undesirable opening effects, improve the SPSW performance and provide the infill option of potential strengthening measures after the construction stage. The study aims to investigate the impact of SSP doubling with a stiffened opening on the cyclic behaviour, expand the essential data required by structural designers and quantify the SPSW performance factors. Validated numerical models were adopted to identify the influence of the chosen parameters on the cyclic capacity, energy dissipation, ductility, seismic performance factors (SPF) and stiffness of the suggested method. A finite Element (FE) analysis was performed via Abaqus/CAE software on half-scale single-story models of SPSWs exposed to cyclic loading. The key parameters included the number of SSP layers, the opening size ratios corresponding to the net width of the SSP, and the opening shape. The findings showed that the proposed assembly method found a negligible influence in the shear capacity with opening sizes of 10, 15, 20%. However, a deterioration in the wall strength was observed for openings with sizes of 25% and 30%. The circular opening is preferable compared with the square opening. Moreover, for all the models, the average value of the obtained ductility did not show substantial changes and the ultimate shear resistance was achieved after reaching a drift ratio of 4.36%. Additionally, the equivalent sectional area of the SSP in the twin and triple configuration of the SPSWs demonstrated approximately similar results. Compared with the single SSP layer, the proposed configuration of the twin SSP layer with a stiffened opening suggest to more sufficiency create SSP openings in the SPSW compared to that of other configurations. Finally, a tabular SPF quantification is exhibited for SPSWs with openings.