• 대한의용생체공학회:의공학회지
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• 제14권2호
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• pp.163-167
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• 1993

We developed a ventricular assist device(VAD) to be used as a bridge to heart transplantation or a circulatory assist device for patients with end-stage heart disease or poor myocardial function after cardiac surgery. It is a pneumatic and diaphragm-type VAD and its stroke volume is 90 cc. The upper housing and diaphragm is made of a segmented polyurethane and the lower back plate is made of a polycarbonate. Two Carbomedics$^R$ mechanical valves are used as inlet and outlet valves. It was tested in vitro and the cardiac output of the VAD was 7 L/min at a heart rate of 70 bpm. The line pressure from a pressure transducer inserted in the pneumatic line was recorded and compared with the ideal pressure tracing.

• 설비공학논문집
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• 제20권4호
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• pp.274-279
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• 2008

In the perspective of saving energy in buildings, high performance of insulation and air tightness for improving the heating and the cooling efficiency has brought the positive effect in an economical view. However, these building energy saving technologies cause the lack of ventilation, which is the direct cause of increasing the indoor contaminants, and it is also very harmful to residents because they spend over 90% of their time in the indoor area. Therefore, the ventilation is important to keep indoor environment clean and it can also save energy consumption. In this study, a HEPA type breathing wall is designed as a passive ventilation system to collect airborne particles and to supply fresh outdoor air. To make fine porous structures, polymer nano fibers which were made by electro spinning method are used as a precursor. The nano fibers are coated with SiO2 nano particles and finally the HEPA type breathing wall is made by sintering in the electric furnace at $300\sim500^{\circ}C$. The pressure drops of nano ceramic structure are 8.2, 25.5 and 44.9 mmAq at the face velocity of 2.0, 5.9 and 8.8 cm/s, respectively. Also the water vapor permeability is $3.6g/m^2{\cdot}h{\cdot}mmHg$. In this research, the porous nano ceramic structures are obtained and the possibility for the usage of a material for HEPA type breathing wall can be obtained.

• 한국자동차공학회논문집
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• 제18권6호
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• pp.53-62
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• 2010

An airbag is composed of housing assembly, door assembly, cushion assembly, and an inflator. The inflator is the essential part that generates gas for airbag. When an airbag is activated, it effectively absorbs the crash energy of the passenger by inflating a cushion. In this study, tank tests were performed with newly synthesized propellants with various compositions, and the results are compared with the numerical results. In the simulation of inflator, a zonal model has been adopted which consisted of four zones of flow regions: combustion chamber, filter, gas plenum, and discharge tank. Each zone was described by the conservation equations with specified constitutive relations for gas. The pressure and temperature of each zone of the inflator were calculated and analyzed and the results were compared with the tank test data. In the zone of discharge tank the pressure quickly rose, the pattern of pressure curve was very similar to the pressure curve of real test. And in zone 1 & 2 & 3 the mass of products was increased and decreased with time. In zone 4, the mass of products was increased with time like real inflator. From the similarity of pressure curve in zone 4 and closed bomb calculation the modeled results are well correlated with the experimental values.

• 한국주거학회논문집
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• 제23권2호
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• pp.25-36
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• 2012

The purpose of this study is to find out the commercialization characteristics of 2nd class residential district in innercity railway station area as basic research to protect urban residential area against the pressure of commercialization. Through the research that are based on literature, field survey and urban planning map, it analysed the commercialization characteristic of selected three sites under similar urban condition; to be a nearby subway station and to be a famous commercial street in site, etc. The consequences of this study are summarized as follows; First it finds the commercialized lots in all blocks that adjoin blocks of upper class zoning. Second it is in inverse proportion between the commercialization of lots and the distance from subway station to residential block. Third, the corner lot of a block and the access road directly connected collector road are very important factors to spread commercialization to residential area. Finally, it finds the difference of the commercialization degree of 2nd class residential zone according to arrange main commercial street and the 2nd class residential block; vertical arrangement and horizontal arrangement.

• 한국환경과학회지
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• 제12권7호
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• pp.705-713
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• 2003

In mid-August 2002, under clear summer pressure patterns, we carried out an intensive meteorological observation to examine the warming effects due to artificial constructions in a large housing complex. We set an automatic weather system(AWS) at two places in a bare soil surface within a limited development district and an asphalt surface within a large apartment residence area, respectively. As a result of observation, it became clear that the difference of the surface air(ground) temperature between the bare soil surface and its peripheral asphalt area reached about 4$^{\circ}C$(13$^{\circ}C$) at the maximum from diurnal variation of surface temperatures on AWS data. Through the heat balance analysis using measurement data, it became clear that the thermal conditions at two places are dependent on the properties of surface material. The latent heat flux over the bare soil surface reached to about 300 W/㎡, which is more than a half of net radiation during the daytime. On the other hand, it was nearly zero over the asphalt surface. Hence, the sensible heat flux over the asphalt surface was far more than that of the bare soil surface. The sensible heat flux over the asphalt surface showed about 20∼30 W/㎡ during the night. It was released from asphalt surface which have far more heat capacity than that of bare soil surface.

• 가정과삶의질연구
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• 제33권1호
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• pp.1-17
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• 2015

This study investigated how variables of internalizing and externalizing problematic behaviors change according to gender and as time passes by and how the variables influence adolescent problematic behaviors. The variables selected for the analysis are personal variables, parent variables, peer and school variables, and community variables. longitudinal data collected for 4 years from the Korea Youth Panel Survey(KYPS) were utilized for the analysis. Data were collected initially from 2,707 fifth grade elementary students in 2005 and they were traced until 2008. The final respondents were 2,448 students. The findings are as follows. Frist, the statistical significance was found in changes of problematic behavioral variables in terms of the gender difference. Second, variables, such as self-esteem and self-control are negatively correlated to the problematic behaviors and stress level is strongly positively correlated to the behaviors. Third, the study pressure and peer attachment level are correlated to the initial value of internalizing problematic behaviors. In conclusion, given that more statistical significances were found at initial values than the change rates among variables, early intervention is important in addressing adolescent problematic behaviors.

• 한국해양공학회지
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• 제22권6호
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• pp.64-74
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• 2008

The flaw around a ROV (Remotely Operated Vehicle) has been numerically investigated to improve resistance performance by modifying the hull form of the ROV. For the base hull form considered in this study, the form drag rather than the friction drag is dominant to the total drag Subsequently, the surfaces on which the local pressure highly acts have been modified to produce the streamlined-shape. Based on the surface modification, seven different hull forms have been chosen as candidates for drag reduction. Among the candidates, the semi-sphericalized housing and the streamlined-bow achieved greatest drag reduction comparing with the others. Consequently, the hull form combined with the semi-sphericalized housing and the streamlined-bow gave approximately 17% drag reduction at the design velocity of 3 knots.

• 가정과삶의질연구
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• 제9권1호통권17호
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• pp.95-112
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• 1991

This study is planned to provide the basic idea to seek for the appropriate Time Management Strategies and to investigate the Time Management Strategies and household work time of wives. For these research tasks, the data are collected through the questionnaire rand 479 respondents were housewives in seoul. Their data are analyzed using Frequency, ANOVA, Pearson's Correlation Analysis, Simple Regression Analysis, Multiple Regression Analysis. The Major findings of this study were as follows ; 1) There are significant differences in the time management strategies according to housewife's age, education level, and employment status, children's number, the type of housing, the type family, income and sex role attitude. 2) There are significant differences in the household work time according to housewife's age, education level, employment status, family size, children's number, type of housing, income, sex role attitude and time pressure perceptibility. 3) The Household work time is found to be negatively correlated to the Time Management Stategies except the adjustment of leisure and sleep time. 4) The Household work time is significantly related to housewife's employment status and the adjustment of leisure and sleep time.

• Advances in Automotive Engineering
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• 제1권1호
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• pp.21-39
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• 2018

Clutch energy is the thermal energy dissipated on the clutch disc, and it reaches its highest level during drive-off as a result of the difference between the angular speeds of the flywheel and clutch disc, and the torque transmitted. The thermal energy dissipated effects the clutch life. This study presents a new drive-off and thermal model to calculate the clutch energy for a rear wheel driven heavy-duty vehicle and to analyze the effects of clutch energy on temperatures of clutch pressure plate, flywheel and clutch housing. Three different driver profiles are used, based on the release of the clutch pedal in modulation zone: i) the pedal travels with the same speed all the way, ii) the travel speed of the pedal increases, iii) the travel speed of the pedal decreases. Vehicle test is performed to check the accuracy of the model. When compared to a simpler model that is widely used in the literature to calculate the clutch energy, the model used in this study calculates the clutch energy and angular speed behaviors of flywheel and transmission input shaft in better agreement with experimental results. Clutch wear and total clutch life are also estimated using the mean specific friction power.

• 한국주조공학회지
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• 제20권6호
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• pp.400-406
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• 2000

Computer simulation for the predictions of casting defects is very important to produce high quality castings with less cost. Complicate shaped Al solenoid housing part was selected to be cold chamber die cast and a numerical simulation technique was applied for the optimization of the chill vent position and gating. A first design led to insufficient central flow. This flow left the last filled areas falling into the inner portion of the part. And last filled area did not fit the chill vent position. So these resulted in a high possibility of air entrapment in the casting and the design was not proper for the part. The design was improved by using a proper gating system, a more chill vent and proper overflow positions. New design provided a homogenous mold filling pattern and the last filled areas that being located at the overflow and chill vent. Casting plan which produce good quality solenoid housing part was established by using the computer simulation.