• Fire Science and Engineering
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• v.22 no.5
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• pp.55-60
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• 2008

In this study, we conducted an FDS numerical simulation for the purpose of carrying out a basic assessment of the usefulness of the water spray for fire extinguishing. We analyzed the effect of securing the stability in temperature and smoke density in case of fire according to fire intensities (20MW, 50MW) and changes in wind speed. When there was no wind speed in tunnels, it was effective in securing the safety of people because the cooling effect of the water spray system had an excellent effect on reducing temperatures and smoke densities there. The higher a fire intensity is, the less effect it has on reducing smoke flows. When an air current exists in tunnels, its cooling effect disturbs the smoke stratification and lowers the visibility degree during evacuation. Therefore, the water spray for fire extinguishing should be put into action only after people take shelter during fire.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.507-513
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• 2021

This study examined the final stop position and posture of both vehicles, the damaged part of the vehicle, the road surface, the specifications of the vehicle, and the angle of impact, centering on the case of a collision in which no surface trace was found. As a result of the simulation, the impact velocity of an SM5 and Lexus was 131 km/h and 74 km/h, respectively, and the impact angle of the SM5 and Lexus was 0.91° and -161.07°, respectively. The cause of the accident was that the SM5 passed through the intersection exceeding the maximum speed limit of 61 km/h and entered the Lexus' left turn lane. Lexus collided during the evacuation to avoid the collision. The collision trajectory error rate of the simulation was approximately 1.4%. Of the subjective experience of accident investigators, the collision dynamics and vehicle engineering aspects and simulations were actively utilized to provide close-to-fact cause identification.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.533-537
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• 2003

Compared to sintered polycrystalline diamond (PCD), the deposited thin film diamond has a great advantage on the fabrication of cutting tools with complex geometries such as drills. Because of high performance in high speed machining non-ferrous difficult-to-cut materials in the field of automobiles industry, aeronautics and astronautics industry, diamond-coated drills find large potentialities in commercial applications. However, the poor adhesion of the diamond film on the substrate and high surface roughness of the drill flute adversely affect the tool lift and machining quality and they become the main technical barriers for the successful development and commercialization of diamond-coated drills. In this paper, diamond thin films were deposited on the commercial WC-Co based drills by the electron aided hot filament chemical vapor deposition (EACVD). A new multiple coating technology based on changing gas pressure in different process stages was developed. The large triangular faceted diamond grains may have great contribution to the adhesive strength between the film and the substrate, and the overlapping ball like blocks consisted of nanometer sized diamond crystals may contribute much to the very low roughness of diamond film. Adhesive strength and quality of diamond film were evaluated by scanning electron microscope (SEM), atomic force microscope (AFM), Raman spectrum and drilling experiments. The ring-block tribological experiments were also conducted and the results revealed that the friction coefficient increased with the surface roughness of the diamond film. From a practical viewpoint, the cutting performances of diamond-coated drills were studied by drilling the SiC particles reinforced aluminum-matrix composite. The good adhesive strength and low surface roughness of flute were proved to be beneficial to the good chip evacuation and the decrease of thrust and consequently led to a prolonged tool lift and an improved machining quality. The wear mechanism of diamond-coated drills is the abrasive mechanical attrition.

• Fire Science and Engineering
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• v.30 no.2
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• pp.81-86
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• 2016

Recently, frequent traffic congestion has occurred in domestic urban roads. As a solution for downtown traffic congestion in domestic urban roads, plans for great depth underground double-deck tunnels have been made. Great depth underground double-deck tunnels that have been planned for passenger cars, has the structure of a network type; the entry of vehicles is carried out in the underground space. In these network great depth underground double-deck tunnels, the cross section and the height of the tunnel are smaller than the general road tunnel, and the smoke of a fire will propagate faster than the evacuation of tunnel passengers by the action of the traffic-ventilation and casualties are expected. Therefore, in the present study, an attempt was made to prevent the delay system for fire smoke diffusion at the time of a fire in a domestic network great depth underground double-deck tunnel according to the area of the tunnel block during the operation of the delay system for fire smoke diffusion to analyze the effects of reducing the inflow velocity. When the area of the tunnel block was not less than 50%, the effect of reducing about 21% of the wind speed acting on the tunnel was significant. If the area is more than 50%, the diffusion rate of fire smoke was reduced by approximately 21%, which will be useful for a safe evacuation.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.395-408
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• 2021

In this study, we investigated the effects of wind speed and direction on building fires using GIS and a CFD model. We conducted numerical simulations for a fire event that occurred at an apartment in Ulsan on October 8, 2020. For realistic simulations, we used the profiles of wind speeds and directions and temperatures predicted by the local data assimilation and prediction system (LDAPS). First, using the realistic boundary conditions, we conducted two numerical simulations (a control run, CNTL, considered the building fire and the other assumed the same conditions as CNTL except for the building fire). Then, we conducted the additional four simulations with the same conditions as CNTL except for the inflow wind speeds and direction. When the ignition point was located on the windward of the building, strong updraft induced by the fire had a wide impact on the building roof and downwind region. The evacuation floor (15th floor) played a role to spread fire to the downwind wall of the building. The weaker the wind speed, the narrower fire spread around the ignition point, but the higher the flame above the building reaches. When the ignition point was located on the downwind wall of the building, the flame didn't spread to the upwind wall of the building. The results showed that wind speed and direction were important for the flow and temperature (or flame) distribution around a firing building.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.1
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• pp.95-108
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• 2022

The increase in the use time of tunnel users due to the lengthening of the road tunnel may increase the evacuation time in case of fire, resulting in a large number of casualties. In order to reduce the casualties caused by fire, the "Road Tunnel Design Manual, Part 6 Tunnel" and "Road Tunnel Disaster Prevention Facility Installation and Management Guidelines" stipulate that ventilation facilities should be installed along with the extension of the tunnel. The ventilation system design factor considers the wind speed of the external natural wind to be at least 2.5 m/s, and it is applied upward according to the characteristics of the tunnel. As a result of analyzing the five-minute average wind speed data in the Daegwallyeong region for the past 6 years, it was analyzed that 15.8% of the windy days were winds of 10 m/s or more, and the maximum was 20 m/s. Therefore, in this study, when a fire occurs in a tunnel, the pattern of natural wind flowing into the tunnel and the backlayering distance of the tunnel fire smoke according to the maximum wind speed were analyzed. As a result, it was analyzed that a backflow of up to 490 m occurs when a gust of 20 m/s blows.

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.85-94
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• 2006

In this study, scaled model tests were carried out to decide the optimal critical velocity, to prevent back layering in the case of fire in a long traffic tunnel. Realistic estimates were made for the time required for people to escape ken the tunnel and far the time required by the ventilation operator to increase the system speed to full capacity. The analysis, predicts that the emergency ventilation will start about 240 seconds after the tunnel fire. It was also found that prevention of back layering would occur within 4 minutes after fan operation. To find out optimal critical velocity, a 1/50 scaled model tunnel(diameter : 0.2 m and length : 20 m) based on the Froude similarity technique was constructed. Changing $\beta$ values in the Tetzner's equation, smoke propagation was observed. From the experiment, it was concluded that using a $\beta$ value of 0.5 to prevent back layering successfully allowed time for safe evacuation.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.6
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• pp.925-932
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• 2007

This study was designed to measure the effect of regrowth age of Digitaria decumbens (D. decumbens) on the intake and dynamics of digesta in the rumen of rams. Six Black-belly rams (mean liveweight: 51.6 (s.d. 0.68) kg) fitted with rumen cannulae were fed twice daily a 14-, 28-, 42- and 56-day old fresh D. decumbens successively for 4 experimental periods. The daily dry matter intake decreased curvilineary from 75.2 to 48.5 (s.e. 2.0) g/kg $BW^{0.75}$ as the age of the D. decumbens grass increased from 14 to 56 days. Dry matter intake for the first 3 h after the morning meal was 863.6, 598.3, 576.4 and 401.5 (s.e. 55.6) g for the 14-, 28-, 42- and 56-day old grasses respectively. The pool of NDF in the rumen at the end of the 3-h feeding period did not vary significantly among the four diets. Twelve hours after the beginning of the morning meal, the pool of NDF increased with the forage regrowth age. Within the total pool of NDF, the pool of large particles tended to increase with the regrowth age. It was concluded that high intake was associated with fast evacuation of NDF from the rumen. Moreover, digestion (cellulolysis) rate and degree of particle reduction by rumination are highly correlated, though speed of physical degradation of forage seems to be the driving force behind intake.

• Journal of Sasang Constitutional Medicine
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• v.19 no.3
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• pp.144-155
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• 2007

1. Objectives The purpose of this study was to find the difference of ordinary and pathological symptoms according to Sasang Constitution. 2. Methods We recruited 418 subjects in the five oriental hospitals and researched normal symptoms and illness ones through a paper, who were diagnosed by the Sasang Constitution specialist in oriental hospital, who had remarkable improvement in their chief complain after Sasang Constitution medication. 3. Results 1) In ordinary symptoms, amount, speed and appetite items of Digestion are significantly different according to Sasang Constitution statistically(p<0.05). Feeling after evacuation of Feces, feeling after urination and yellow color of Urine, amount, feeling after sweat, location in hand/feet of Sweat, and in the others, Tireness in head, Drinking water, sensitivity, coldness in hand/feet, warmness in belly of Coldness/Warmness are also significantly different(p<0.05). 2) In pathological symptoms, palpitation, swelling and lack of appetite items are significantly different according to Sasang Constitution statistically(p<0.05). 3) In diseases, Hypertension and DM items are significantly different according to Sasang Constitution statistically(p<0.05). 4. Conclusions There were significantly difference items in ordinary, pathological symptoms and diseases according to Sasang Constitution.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.52-58
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• 2009

When a fire breaks out, it is frequent that large sized miserable death is happened by seriousness of poisonous gas and peculiarity of space because the building construction is recently more complex and diverse. So early countermeasure in preparation for evacuation escape linked directly with a loss of lives is pressing. Because escape light that mark fixing one-way of existing way is not efficiently extricated refugees from dangers when a fire breaks out, construction of system that can extricate refugees from dangers and suppress early a fire by grasping correctly fire point is required urgently. When a fire breaks out, all escape lights connected with fire sensor and reception group which have ill aiming in these point will lead people to safe emergency entrance of opposite direction of place that a fire is broken out after being calculated the direction and speed of flame and smoke. There is the purpose of my research in development of artificial intelligent directional escape light that can mark direction to most suitable pull-out and assist in early extinguishing a fire.