• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.535-547
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• 2021

A policy to expand the hydrogen economy has been established in Korea and the supply of FCEV is being expanded to realize a hydrogen society. Therefore, the supply of FCEV is expected to increase rapidly, and a solution to respond to accidents of FCEV is required. In this study, an experimental study was conducted to analyze the effect of the hydrogen jet flame generated by a FCEV on the inner wall of the tunnel and the characteristics of the internal radiant heat. For the experiment, the initial pressure of hydrogen tank was set to 700 bar, and the injection nozzle diameter was set to 1.8 mm in order to make the same as the conditions generated in the FCEV. In addition, a tunnel fire resistance test specimen having the same strength as the compressive strength of concrete applied to general tunnels of 40 MPa was manufactured and used in the experiment. The results were analyzed for the separation distance (2 m and 4 m) between the hydrogen release nozzle and the tunnel fire resistance test concrete. As the result, the maximum internal temperature of the test concrete was measured to 1,349.9℃ (2 m separation distance), and the radiant heat around the jet flame was up to 39.16 kW/m².

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.347-353
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• 2009

The qualitative factors influencing the ingress of chloride ion into concrete are water-binder (W/B) ratio, cement type, age, chloride ion concentration of given environment, wet and dry conditions, etc. Thus, an objective of this experimental research is to investigate the effects of cement types and environmental conditions on the chloride ion diffusion characteristics in concrete through the chloride ion diffusion test. For this purpose, the diffusion coefficients for chloride ion in concrete with three types of cement such as ordinary portland cement (OPC), binary blended cement (BBC), and ternary blended cement (TBC), were measured for the concrete specimens with W/B ratios of 32%, 38%, and 43%, respectively. The diffusion coefficients for chloride ion were also measured for the concrete specimens with W/B ratio of 43%, which were subjected to standard curing and field exposure conditions. It was observed from the test results that the resistance against chloride ion penetration increased with decreasing W/B ratio and those of BBC and TBC concretes were greater than that of OPC concrete. Therefore, it was revealed that the use of these cements containing mineral admixtures is required to extend the service life of RC structures exposed to chloride environment. On the other hand, it was noted that the resistance against chloride ion penetration of field exposure test specimens was slightly lower than that of standard curing test specimens due to the penetration of chloride ion under the irregular ambient temperature, splash of wave, and cycle of wet and dry.

• The Journal of the Convergence on Culture Technology
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• v.10 no.2
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• pp.419-427
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• 2024

This study assessed the potential impact of gas leakage resulting from accidental damage to buried urban gas pipelines during perforating operation near subway construction sites. The risk of explosions due to ignition sources such as static electricity, arising from gas infiltrating the subway construction site through storm sewers and sewage pipes, was evaluated using the ALOHA program. The results of the threat zone calculation, which input various parameters of urban gas pipelines such as length, diameter, and pressure, indicated that the flammable area within the vapor cloud extended from 1.2 to 1.4 km (red zone), the blast area ranged from 0.8 to 1.0 km (yellow zone), and the jet fire extended from 45 to 61 m (red zone). This study demonstrates that within the flammable area of the vapor cloud, a specific combination of concentration and conditions can increase flammability. The blast area may experience explosions with a pressure of 1.0 psi, sufficient to break glass windows. In the event of a jet fire, high temperatures and intense radiant heat exposure lead to rapid fire propagation in densely populated areas, posing a high risk of casualties. The findings are presented in terms of the sphere of influence and threat zone ranges.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.9
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• pp.1499-1512
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• 2013

The purpose of this study was to compare the coffee shop visits of Koreans and Mongolians, and to determine the quality attributes that should be managed by Importance-Performance Analysis (IPA). The survey was conducted in Seoul and the Gyeonggi Province of Korea, and at Ulaanbaatar in Mongolia from April to May 2012. The questionnaire was distributed to 380 Koreans and 380 Mongolians, with 253 and 250 responses from the Koreans and Mongolians, respectively, used for statistical analyses. From the results, Koreans visited coffee shops more frequently than Mongolians, with both groups mainly visiting a coffee shop with friends. Koreans also spent more time in a coffee shop than Mongolians. In addition, they generally used a coffee shop, regardless of time. In terms of coffee preference, Koreans preferred Americano and Mongolians preferred Espresso. The most frequently stated purpose of Koreans for visiting a coffee shop was to rest, while Mongolians typically visited to drink coffee. The general price range respondents spent on coffee was less than 4~8 thousand won for the Koreans and 2~4 thousand won for the Mongolians. Both Koreans and Mongolians obtained information about coffee shops from recommendations. According to the IPA results of 20 quality attributes of coffee shops, the selection attributes with high importance but low satisfaction were quality, price, and kindness for Koreans, but none of the attributes was found for Mongolians.

• Geotechnical Engineering
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• v.13 no.3
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• pp.101-122
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• 1997

A spiting reinforcement system is composed of a series of radially installed reinforcing spites along the perimeter of the tunnel opening ahead of excavation. The reinforcing spill network is extended into the in-situ soil mass both radially and longitudinally The sailing reinforcement system has been successfully used for the construction of underground openings to reinforce weak rock formations on several occasions. The application of this spiting reinforcement system is currently extended to soft ground tunneling in limited occasions because of lack of reliable analysis and design methods. A method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground is presented. The shape of the potential failure wedge for the case of smile-reinforced shallow tunnel is assumed on the basis of the results of three dimensional finite element analyses. A criterion to differentiate the spill-reinforced shallow tunnel from the smile-reinforced deep tunnel is also formulated, where the tunnel depth, soil type, geometry of the tunnel and reinforcing spites, together with soil arching effects, are considered. To examine the suitability of the proposed method of threedimensional stability analysis in practice, overall stability of the spill-reinforced shallow tunnel at facing is evaluated, and the predicted safety factors are compared with results from twotimensional analyses. Using the proposed method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground, a parametric study is also made to investigate the effects of various design parameters such as tunnel depth, smile length and wadial spill spacing. With slight modifications the analytical method of threeiimensional stability analysis proposed may also be extended for the analysis and design of steel pipe reinforced multi -step grouting technique frequently used as a supplementary reinforcing method in soft ground tunnel construction.

• Journal of the Korean earth science society
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• v.21 no.1
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• pp.59-66
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• 2000

In Kyeongsang basin, there were very dynamic magmatic activities, resulting to form volcanic and plutonic rocks. A plutonic recycle appeared in this region. Presumption of the pressure for hornblende-bearing granitic rock among the plutonic rocks, can support important informations for the emplacement depth of Cretaceous Bulgugsa granites in Kyeongsang basin. $Al^T$(Al total) contents of hornblende is related to the pressure, oxygen fugacity, and compositions of other minerals having the solid solution. So we apply the $Al^T$ content of hornblende to several empirical and experimental geobarometer systems to presume the pressure and to determine the emplacement depth of Cretaceous Bulgugsa granites in Kyeongsang basin from the inferred pressure. With the result that we applied the $Al^T$ contents of hornblende to the various geobarometers, there was a positive relationship between the pressure and $Al^T$. The minimum pressure value ranges from 0.73 to 1.70kbar in Kyeongju and the maximum value from 2.02 to 3.16kbar in Kimhae. And then the tectonic setting in Kyeongsang basin has no relation to the emplacement depth of Cretaceous granites and means variations with the movement of vertical component in each area. As we suppose that the density of earth's crust is $2.8g/cm^3$, the average values of the emplacement depth ranges in each area range from 2.6 to 11.4km. These data confirm the previous idea about the emplacement depth of Cretaceous granites in Kyeongsang basin, and these geobarometers using the $Al^T$ contents of hornblende is available though they have much limits. Therefore Cretaceous Bulgugsa granites in Kyeongsang basin was the shallow depth intrusive rut and the exposed granites was the shallow depth crust.

• Economic and Environmental Geology
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• v.17 no.3
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• pp.179-195
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• 1984

The Jurassic Daejeon and Nonsan granitoids are "S-type" syntectonic calc-alkaline two-mica monzogranite and granodiorite, respectively. With evidences of high CaO, $Al_2O_3$, LIL/HFS elements, total REE, (Ce/Yb)N and initial ($^{87}Sr/^{88}Sr$) ratio, and no significant Eu anomaly, the primary magmas for the Daejeon and Nonsan granitic rocks are derived from partial melting of the Precambrian granulite (e.g. grey gneisses). But those Jurassic granitoids crystallised from different chemical characteristics of parental magmas which is mainly due to varying degree of partial melting of the granulite (crustal anatexis). The absence of significant anomalous Eu($Eu/Eu^*=O.82{\sim}1.00$) in the Daejeon and Nonsan granitoids could indicate that feldspars, mainly plagioclase, did not separate from the magmas. The parental hydrous magmas could not rise appreciably above their source region before crystallisation. The Jurassic granitoids may be resulted by closing-collision situation and belong to the Hercynotype (Pitcher 1979) such as compressive ductile regime of an intracontinental orogen.

• Nuclear Engineering and Technology
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• v.22 no.4
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• pp.337-350
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• 1990

A post-irradiation annealing study was conducted with use of reactor pressure vessel(RPV) steel A533B Cl.1 base metal irradiated to a dose of 4.84$\times$10$^{18}$ n/$\textrm{cm}^2$ at about 38$0^{\circ}C$. Microhardness and positron annihilation (PA) methods were used to obtain better understanding of the recovery of radiation hardening. Isochronal anneal experiments indicated that two recovery processes occur during annealing of irradiated specimens. The first recovery process occurs in the temperature range of 280-3O5$^{\circ}C$, Michrohardness and positron annihilation (PA) methods were used to obtain better understanding of the recovery of radiation hardening. Isochronal anneal experiments indicated that two recovery processes occur during annealing of irradiated specimens. The first recovery process occurrs in the temperature range of 280-305$^{\circ}C$. The variations of Ip, Iw and R parameters indicated that the formation of vacancy clusters by vacancy agglomeration and the annihilation of monovacancies are the first recovery process. The second recovery process occurs in the range of 405-49$0^{\circ}C$ and positron annihilation parameters measured indicated that the dissolution of carbon atoms decorated around vacancy-type defects and possible precipitates, and the annihilation of monovacancies give rise to the second recovery process. It was further indicated that radiation anneal hardening (RAH) in the range of 305-405$^{\circ}C$ between the temperature ranges for the two processes occurs due to the formation of carbon-decorated vacancy clusters and precipitates. The activation energies, orders of reaction and other characteristics of recovery processes were determined by the Meechan-Brinkman method. The activation energy for the first recovery process was determined as 1.76 eV and that for the second recovery process as 2.00eV. These values are lower than those obtained by other workers. This difference may be attributed to the lower copper content of the RPV steel used in the present study. The order of reaction for the first recovery process was determined as 1.78, while that for the second recovery process as 1.67 Non-integer orders of reaction for recovery processes seem to be attributed to the fact that several mechanisms for the first order and the second order of reaction are compounded in one process. This result also supports for the above conclusions from measurements of PA parameters.

• Korean Business Review
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• v.13
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• pp.49-66
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• 2000

Despite the fact that understanding customers satisfaction with transportation services is a subject of great importance, authors, so far, found no systematic researches referred to that issue. From this point, studying the satisfaction with subways services can be extremely useful. Empirical study of key factors in the satisfaction with subway services is the departure point, which holds as objectives, and we believe, will contribute to overall increasing in the number of subways services used and in the amount of public benefits derived from that usage. In order to achieve these goals: First, several items referred to some key factors in the satisfaction of subway usage were systemized. Second, a research of specific weights attached to those key factors by subway passengers was conducted. Knowledge of the satisfaction variables system can provide deep insights into ones perceptual experience when using a subway. The results were as follows: Various interrelated factors compose a passengers satisfaction with subway services. People do not just use subway passively; a number of key factors, like physical and personal services, exact timing, easiness to access etc. determine the passengers satisfaction with subway. In order to find out specific weights of these key factors multiple regression analysis was employed. Results showed that satisfaction with subway is determined by (in order of importance) easiness to access, quality of physical services, friendliness of working stuff and timing exactness. According to the findings, passengers do not use subway as a simple mean of transportation, rather they perceive it as a complex combination of environmental elements and overall satisfaction depends on these various factors. Therefore, to learn passengers satisfaction with subways services, passengers subway experience must be thoroughly studied and analyzed, and this is where papers value resides.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.61-71
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• 2000

When irradiate the power ultrasound into the aqueous solutions, water vapor is decomposed by the heat of very high temperature in the cavitation bubble to produce OH (hydroxyl radical) and H (hydrogen radical), and these radicals play a role in decomposing the substances in aqueous solution by oxidation and/or reduction, and in producing the hydrogen peroxide. Accordingly it is possible to predict that the quantity of hydrogen peroxide produced may correlate with the sonolysis mechanism of the substance in aqueous solution. Thus to confirm this prediction, the quantities of hydrogen peroxide produced from each of the air saturated distilled water and three aqueous solutions of TCE, benzene, and 2,4-DCP that are prepared by dissolving them into distilled water are measured. As a result, it showed that the quantity of hydrogen peroxide produced from the distilled water and three aqueous solutions are increased in order of distilled water>TCE solution>2,4-DCP solution>benzene solution, and decrease with decrease in concentration of organic substance, which coincide with the sonolysis mechanisms reported that TCE in aqueous solution is decomposed directly by the pyrolysis in and around the cavitation bubbles when its concentration is high and by the radical reaction when low, however, benzene and 2,4-DCP are decomposed not only by the pyrolysis but also by the radical reactions. Effects of such experimental parameters as the acoustic frequency and power and as the concentration showed that the higher the acoustic frequency and the lower the acoustic power, the less the quantity of hydrogen peroxide was produced. This result coincide with the theory of ultrasound for the relation between the cavitation that is the energy source of the power ultrasound in aqueous solution and these experimental parameters.