• Fire Science and Engineering
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• v.17 no.2
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• pp.62-69
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• 2003

The smoke control system in subway platform is not only using for smoke exhaust facility but also using ventilation system. For this reason, smoke vent effectiveness is depending on its position, ventilating volume capacity and the vent method. In this study, the passenger's evacuation time was calculated for the case of fire on sloped subway train vehicle in subway platform. In order to recommend the mechanical smoke exhaust operation mode, SES (Subway Environmental Simulation) was used to predict the airflow of the inlet and outlet tunnel for the subway station. Fire dynamics Simulator(FDS) was used the SES's velocity boundary conditions to calculate the smoke density and temperature under the condition of fire on stopped subway train vehicle at the platform. We compared smoke density and temperature distributions for each 6 types of smoke exhaust systems to clarify the characteristics of smoke and hot air exhaust effectiveness from the result of fire simulation.

• Journal of Biomedical Engineering Research
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• v.14 no.1
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• pp.89-96
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• 1993

During high frequency ventilation (HFV), mean alveolar pressure has been measured to increase with mean airway opening pressure controlled at a constant level in both humans and experimental animals. Since this phenomenon could potentiate barotrauma limiting advantages of HFV, the present study theoretically predicted the difference between menu alveolar and airway opening pressures ($MP_{alv}$). In a Weibel's trumpet airway model, approximated formula for $MP_{alv}$ was derived based on momentum conservation assuming a uniform velocity profile. The prediction, equation was a func pion of gas density($\rho$), mean flow rate(Q), and diameter of the airway opening where the pressure measurement was made($D_0$) : $MP_{alv}=4{\rho}(Q/D_0^{2})^2$. This was a result of the difference in crosssectional area between the alveoli and the airway opening. A simple aireway model experiment was performed and the results well fitted to the prediction, which demonstrated the validity of the present analysis. Previously reported $MP_{alv}$ data from anesthetized dogs in supine position were comparable to the predicted values, indicating that the observed dissociation between mean alveolar and airway opening pressures during HFV can be explained by this innate geometric (or cross-sectional area) asymmetry of the airways. In lateral position, however, the prediction substantially underestimated the measurements suggesting involvement of other important physiological mechanisms.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.1
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• pp.36-44
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• 2005

A push pull hood system is frequently applied to control contaminants evaporated from an open surface tank in recent years. Efficiency of push pull hood system is affected by various parameters, such as cross draft, vessel shapes, size of tanks surface, liquid temperature, and so on. Among these, velocity of cross draft might be one of the most influencing factor for determining the ventilation efficiency. To take account of the effect of cross draft velocities over 0.38m/s, a flow adjustment of ${\pm}$20% should be considered into the push and +20% into the pull flow system Although there are many studies about the efficiency evaluation of push pull hood system based on CFDs(Computational Fluid Dynamics) and experiments, there have been no reports regarding the influence of velocities and direction of cross-draft on push-pull hood efficiency. This study was conducted to investigate the influence of cross draft direction and velocities on the capture efficiency of the push-pull ventilation system. Smoke visualization method was used along with mock-up of push-pull hood systems to verify the ventilation efficiency by experiments. When the cross-draft blew from the same origins of the push flows, the efficiency of the system was in it's high value, but it was decreased significantly when the cross-draft came from the opposite side of push flows Moreover, the efficiency of the system dramatically decreased when the cross-draft of open surface tank was faster than 0.4m/s.

• Journal of the Korean Solar Energy Society
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• v.36 no.5
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• pp.31-50
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• 2016

To develope a greenhouse fog cooling system to control the temperature and relative humidity simultaneously to the target value, a theoretical analysis and experiments were done. The control process includes the measuring of environmental variables, setting and coding of the water and heat balance equations to maintain the target temperature and relative humidity in greenhouse, calculating of the open level of the greenhouse roof window that governs the natural ventilation and spray water quantity, and operating of the motor to open/close the roof window and pump to spray for water. The study results were shown to be very good because the average air temperature in the greenhouse was kept to be about $28.2^{\circ}C$ with the standard deviation of about $0.37^{\circ}C$ compared to the target temperature of $28^{\circ}C$ and the average relative humidity was about 75.2% compared to the target relative humidity was 75% during the experiments. The average outside relative humidity was about 41.0% and the average outside temperature was $27.2^{\circ}C$ with the standard deviation of about $0.54^{\circ}C$. The average solar intensity in the greenhouse was 712.9 W. The wind velocity of outside greenhouse was 0.558 m/s with the standard deviation of 0.46 m/s.

• Journal of computational fluids engineering
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• v.18 no.3
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• pp.72-78
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• 2013

The turbulent flow behavior of air supply and exhaustion in the Shin-gum-ho subway station is analyzed for ordinary and emergency state. The depth of Shin-gum-ho station is 43.6m which consists of the island-type platform(8th floor in underground) and a two-story lobby (first & second floor in underground). An emergency stairway connects between the platform and the lobby. Ventilation operation mode for ordinary state is set up as a combination of air supply and exhaustion in the lobby and platform, while for emergency state it is set up as a full air supply in the lobby and a full exhaustion in the platform. The entire station is covered for simulation. The ventilation diffusers are modeled as 95 square shapes of $0.6m{\times}0.6m$ in the lobby and as 222 square shapes of $0.6m{\times}0.6m$ and 4 rectangular shapes of $1.2m{\times}0.8m$ in the platform. The total of 7.5million grids are generated and whole domain is divided to 22 blocks for MPI efficiency of calculation. Large eddy simulation(LES) is applied to solve the momentum equation and Smagorinsky model($C_s$=0.2) is used as SGS(subgrid scale) model. The time-averaged velocity fields are compared to experimental data and show a good agreement with it.

• Mycobiology
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• v.31 no.3
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• pp.145-150
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• 2003

This study investigated the morphological differences of P. ostreatus grown in the artificial environmental conditions such as humidity, temperature, ventilation, and watering. Oyster mushroom, which was cultivated on artificial environmental condition, was shown to have different morphology of fruitbodies. The optimum $CO_2$ concentration for good morphology of P.ostreatus was 0.3%. But most fruitbody showed the morphologically low qualities in more than 0.5% of $CO_2$ concentration. In the humidity in excess of 80% at $13{\sim}16^{\circ}C$, the best morphology of P. ostreatus was investigated. The growth of fruitbodies of P. ostreatus in the ventilation system was good at the wind velocity ranging from $0.2{\sim}0.5$ fpms and expouring type. In other conditions, P. ostreatus generally showed the morphology closing to malformation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.4
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• pp.325-334
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• 2006

Understanding the airflow characteristics within the canopy structure installed between closely adjacent tunnels either for light adaptation or for protection from snow hazards is required for the normal ventilation as well as safety system design. Grade, horizontal alignment, cross-sectional area and shape are known to substantially influence the fire smoke behavior and their influences raise great concern for the safety design. This paper aims at studying the effects of tunnel geometrical characteristics and canopy installation on the ventilation and fire propagation through CFD analysis. In the case of 145m long canopy, 50% opening ratio is preferred with respect to the airflow pattern and ventilation efficiency. When a 20MW fire occurs in a 1.8km-long tunnel and four 1250mm reversible jet fans are instantly turned on, smoke concentration at 40m downstream of the fire decrease 13% for the upgrade tunnel with 2% gradient and increases 20% for -2% gradient, compared to the standard horizontal tunnel. Backlayering is observed within 45m-long segment toward the entrance in 2% down-graded tunnel. In a rectangular tunnel, there is no significant difference of smoke concentration as well as velocity profile from the standard crown tunnel. Three-laned tunnel shows lower level of both profiles and backlayering is detected up to 50m upstream of the fire, while the risky situation rapidly disappears thereafter.

• Journal of Animal Environmental Science
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• v.18 no.1
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• pp.1-8
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• 2012

The study was conducted to investigate the effects of climate on indoor environment of a swine house with natural. This study was tested in the beef swine stall at Young-in, Kyung-ki do. The test was experimented for the effect of interior environment by the outdoor environment and the interior-pan. The results are as follows. 1. In test 1 ($T_{out}$ : $25.7^{\circ}C$, without fan), an indoor air flow pattern was showed that entered from sidewall winch-curtain to went out of a indoor by the ridge winch-curtain. And the velocity of a section of the center was measured two times as large as the velocity of the floor. It is the acceleration of the velocity by thermal buoyancy. And, the entered air was rapidly dissipated by flow energy. So that in the swain livestock with sidewall winch-curtain is effected by thermal buoyancy. And the air temperature of the indoor was distributed more higher as compared with the outdoor temperature. This result is caused by the sensible heat from swine and the ventilation is restricted. 2. In test 2 (($T_{out}$ : $25.7^{\circ}C$, with fan), the velocity of a section of the center was measured more higher as compared with the test 1. And the variance of air velocity was distributed higher as compared with the test 1. This result is showed dead region of air flow with a fan operation. And, the variance of gas density was distributed lower as compared with the test 1.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.405-421
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• 2018

In most of cases, the wall friction coefficients applied for local tunnel design are quoted directly from foreign data or local design guideline. In the previous studies, the wall friction coefficient was estimated using the velocity decay method. However, it is difficult to estimate the wall friction coefficient when the convergence wind velocity in the tunnel is negative (-) or if there is a change in the natural wind. Therefore, in this study, the wall friction coefficient is estimated by applying the dynamic simulation technique in addition to the conventional the velocity decay method. As a result of the analysis, the coefficient of wall friction in the tunnels for the total of 9 tunnels (18 tubes both directions) was 0.011~0.025, and the mean value was estimated to be 0.020. In addition, the wall friction coefficient obtained quantitatively through this study was compared with the current design criteria.

• Journal of Korean Society of Transportation
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• v.28 no.5
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• pp.55-64
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• 2010

In order to prepare an efficient solution for PM10 reduction in underground stations, the authors measured PM10 concentration levels every 30 minutes in the concourse, platform, and tunnel of Gaehwasan Station of Seoul's subway line 5. Through a correlation analysis of each changing pattern of PM10 concentration, the direction and velocity of diffusion in underground stations were estimated. The PM10 concentration levels were highest in the tunnel, followed by the platform and concourse. PM10 concentrations in the tunnel, platform, and concourse showed a pattern of increasing in the rush hours and decreasing in the non-rush hours. According to the statistical analysis of PM10 concentrations and changing patterns in each location, the higher PM10 concentration in the tunnel expanded to the platform, and some from the platform expanded to the concourse. Therefore, to efficiently reduce PM10 concentrations, it is essential to detect the centralized generation, diffusion factor, expanding route, expanding measure, and other variables and to remove or reduce the diffusion factor and level. Through operating the ventilation system in the right time frame while the PM10 concentration level increases, the power consumption and peak power consumption can be reduced.