• Journal of the Korean Chemical Society
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• v.64 no.6
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• pp.327-333
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• 2020

Performance of a portable GC that can be utilized for the real time determination of volatile organic compounds in air was evaluated. It employs purified/compressed ambient air as the carrier gas eliminating the need for high pressure gas tanks. The compact system with dimensions of 35 × 26 × 15 ㎤ and weight of 5 kg is powered by either a 24 V DC external adapter or battery pack. Chromatograms of the mixture sample including benzene, toluene, ethylbenzene, and oxylene at concentrations of 1 ppmv and 20 ppmv represent a good reproducibility: 3.79% and 0.48% relative standard deviations (RSDs) for peak area variations; 0.40% and 0.08% RSDs for retention times. The method detection limit was 0.09 ppmv. A 30 m long, 0.28 mm I.D. column operated at an optimal condition yielded a peak capacity of 61 with good resolution for a 10 min isothermal analysis. The relative standard deviations (RSD) of the peak area variations and retention times during consecutive measurements over 27 h were less than 2.4%RSD and 0.5%RSD, respectively. Thus, this instrument makes it suitable for continuous and field analysis of low-concentration VOC mixtures in the indoor/outdoor environment as well as the spillage accident of hazardous chemicals.

• Fire Science and Engineering
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• v.31 no.5
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• pp.53-62
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• 2017

Electric power which is the energy source of economy and industries requires long distance transportation due to regional difference between its production and consumption, and it is supplied through the multi-loop transmission and distribution system. Prior to its actual use, electric power flows through several transformations by voltage transformers in substations depending on the characteristics of each usage, and a transformer has the structure consisting of the main body, winding wire, insulating oil and bushings. A transformer fire that breaks out in substations entails the primary damage that interrupts the power supply to houses and commercial facilities and causes various safety accidents as well as the secondary economic losses. It is considered that causes of such fire include the leak of insulating oil resulting from the destruction of bottom part of bushings, and the chain reaction of fire due to insulating oil that reaches its ignition point within 1 second. The smoke detector and automatic fire extinguishing system are established in order to minimize fire damage, but a difficulty in securing golden time for extinguishing fire due to delay in the operation of detector and release of gas from the extinguishing system has become a problem. Accordingly, this study was carried out according to needs of active mechanism to prevent the spread of fire and block the leak of insulating oil, in accordance with the importance of securing golden time in extinguishing a fire in its early stage. A bushings fireproof structure was developed by applying the high temperature shape retention materials, which are expanded by flame, and mechanical flame cutoff devices. The bushings fireproof structure was installed on the transformer model produced by applying the actual standards of bushings and flange, and the full scale fire test was carried out. It was confirmed that the bushings fireproof structure operated at accurate position and height within 3 seconds from the flame initiation. It is considered that it could block the spread of flame effectively in the event of actual transformer fire.

• Journal of the Korean Institute of Gas
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• v.8 no.2 s.23
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• pp.15-27
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• 2004

The purpose of this paper is to improve the performance of Polymer electrolyte fuel cell(PEMFC) by studying the channel dimension of bipolar plates using commercial CFD program 'Fluent'. Simulations are done ranging from 0.5 to 3.0mm for different size in order to find the channel size which shoves the highst hydrogen consumption. The results showed that the smaller channel width, land width, channel depth, the higher hydrogen consumption in anode. When channel width is increased, the pressure drop in channel is decreased because total channel length Is decreased, and when land width is increased, the net hydrogen consumption is decreased because hydrogen is diffused under the land width. It is also found that the influence of hydrogen consumption is larger at different channel width than it at different land width. The change of hydrogen consumption with different channel depth isn't as large as it with different channel width, but channel depth has to be small as can as it does because it has influence on the volume of bipolar plates. however the hydrogen utilization among the channel sizes more than 1.0mm which can be machined in reality is the most at channel width 1.0, land width 1.0, channel depth 0.5mm and considered as optimum channel size. The fuel cell combined with 2cm${\times}$2cm diagonal or serpentine type flow field and MEA(Membrane Electrode Assembly) is tested using 100W PEMFC test station to confirm that the channel size studied in simulation. The results showed that diagonal and serpentine flow field have similarly high OCV and current density of diagonal (low field is higher($2-40mA/m^2$) than that of serpentine flow field under 0.6 voltage, but the current density of serpentine type has higher performance($5-10mA/m^2$) than that of diagonal flow field under 0.7-0.8 voltage.

• Journal of Microbiology and Biotechnology
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• v.19 no.4
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• pp.391-396
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• 2009

The chemical compositions, and antibacterial and antifungal effects of essential oils extracted from three coniferous species, Pinus densiflora, Cryptomeria japonica, and Chamaecyparis obtusa, were investigated. Gas chromatography mass analysis of the essential oils revealed that the major components and the percentage of each essential oil were 16.66% $\beta$-phellandrene and 14.85% $\alpha$-pinene in P. densiflora; 31.45% kaur-16-ene and 11.06% sabinene in C. japonica; and 18.75% bicyclo [2,2,1] heptan-2-ol and 17.41% 2-carene in Ch. obtusa. The antimicrobial assay by agar disc diffusion method showed that $2.2{\mu}g$ of Ch. obtusa oil inhibited most effectively the growth of Escherichia coli ATCC 33312 and Klebsiella oxytoca ATCC 10031, whereas the C. japonica oil gave weak antimicrobial activity. The minimal inhibitory concentration(MIC) values for bacterial strains were in the range of 5.45-21.8 mg/ml depending on essential oils, but most Gram-negative bacteria were resistant even at 21.8 mg oil/ml. P. densiflora oil showed the most effective antifungal activity and the MIC values for Cryptococcus neoformans B42419 and Candida glabrata YFCC 062CCM 11658 were as low as 0.545 and 2.18 mg/ml, respectively. Cryp. neoformans B42419 was the most sensitive to all essential oils in the range of 0.545-2.18 mg/ml. Our data clearly showed that the essential oils from the three conifers had effective antimicrobial activity, especially against fungi.

• Journal of the Korea Institute of Building Construction
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• v.17 no.6
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• pp.507-515
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• 2017

This study is to develop a high quality lightweight foamed concrete that can be applied in the field using EXFG by cracking reducing agent combined with FGD and ALS. First, to increase the volume of foam, the flow and density of the mixture was increased and decreased, respectively. At this time, the effect of substitution ratio of EXFG on fluidity was negligible. The fraction of foam was the highest at EXFG 1%, and the settlement was found to be prevented by the expansion reaction at EXFG 1%. At this time, the ratio of foam was 65%. In the compressive strength, the strengths were similar or decreased when the substitution ratio of EXFG was more than 1%. The apparent density satisfied the KS 0.5 type at the bubble contents was 65%. In case of EXFG substitution, dry shrinkage was decreased by about 10%. As the substitution ratio of EXFG increased, the thermal conductivity increased proportionally.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.989-999
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• 2012

An ejector is a fluid transportation device that operates based on the principle that a high-pressure fluid is spouted through a driving pipe and the pressure of a low-pressure fluid is increased through exchange of momentum with a low-pressure gas. Steam-steam ejectors have been widely used for suction, mixture, and dehydration. They can be easily used in places where fluid moves and expenses are reasonable. In addition, such ejectors are a semi-permanent fluid device that requires little maintenance. In this study, we present an optimized design by analyzing what cannot be obtained through experiments in order to improve the device performance, analyze general contents of a flow by acquiring exact test data on specific and interpretative areas using more advanced experimental techniques, and identify the flow characteristics of a branch pipe by examining the validity of experiments using computer hydrodynamics simulations.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.19-27
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• 2016

The flow analyses through a porous hydraulic fractures is among the most important tasks in recently developed shale reservoirs but is rendered difficult by non-Darcy effects and geometric changes in the hydraulic fractures during production. In this study, several Computational Fluid Dynamics(CFD) models of hydraulic fractures, with a simple shape such as that of parallel plates, filled with proppants were built. Direct Numerical Simulation(DNS) analyses were then carried out to examine the flow loss characteristics of the fractures. The hydraulic diameters for the simulation models were calculated using the DNS results, and then they were compared with the results from Kozeny's definition of hydraulic diameter which is most widely used in the flow analysis field. Also, the characteristic parameters based on both hydraulic diameters were estimated for the investigation of the flow loss variation features. Consequently, it was checked in this study that the hydraulic diameter based on Kozeny's definition is not accordant to the results from the DNS analyses, and the case using the CFD results exhibits f Re robustness like general pipe flows, whereas the other case using Kozeny's definition doesn't. Ultimately, it is expected that discoveries reported in this study would help further porous flow analyses such as hydraulic fracture flows.

• Land and Housing Review
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• v.2 no.3
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• pp.307-313
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• 2011

This study was aimed to suggest a management strategy of GHG emissions for the public organizations in land and housing costruction sector. As public organizations' businesses are characterized as 'public' and 'comprehensive', these characteristics should be considered in scoping emissions, setting-up reduction target, building GHG inventory, and establishing management system. Since public organizations' activities in construction sector involve a wide range of social infrastructure construction projects, it is not easy to account their actions to reduce GHG emissions quantitatively. Therefore, this study suggested that a twofold approach is suitable for public organizations in construction area, classifying the measurable reductions and the immeasurable actions according to the their business characteristics. To give a concrete example, a GHG emission management system for the Korea Land and Housing Corporation (LH) was proposed.

• Journal of Welding and Joining
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• v.28 no.5
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• pp.45-50
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• 2010

The fatigue crack growth characteristics of base metal and weld joint of 9% Ni steel for LNG storage tank was carried out using CT specimen at room temperature and $-162^{\circ}C$. Fatigue crack growth rate of base and weld metals at RT and $-162^{\circ}C$ was coincided with a single line independent of the change of stress ratio and temperature. In the region of lower stress intensity factor range, fatigue crack growth rate at $-162^{\circ}C$ was slower than that at RT, and the slop of fatigue crack growth rate at $-162^{\circ}C$ increased sharply with propagating of fatigue crack, fatigue crack growth rate at RT and $-162^{\circ}C$ was intersected near the region of $2{\times}10-4\;mm$/cycle, and after the intersection region, fatigue crack growth rate at $-162^{\circ}C$ was faster than that at RT. The micro-fracture mechanism using SEM shows the ductile striation in the stable crack growth region. Also the defects of weld specimen after fatigue testing were detected using the A scan of ultrasonic apparatus.

• Journal of Energy Engineering
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• v.28 no.4
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• pp.29-34
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• 2019

In this study, a quantitative risk assessment was carried out for a hydrogen complex station. The complex fueling station to be evaluated was hydrogen-LPG, and the components of each station were analyzed and the risk was evaluated. The final risk is assessed by individual and societal risks, taking into account the impact of damage and the frequency of accidents. As a result of individual risk calculation for the hydrogen-LPG fueling station that is the subject of this study, the hydrogen-LPG type fueling station does not show the unacceptable hazardous area (> 1 × 10E-3) proposed by HSE. The level of individual risk for both the public and the worker is within acceptable limits. In societal risk assessment, the model to be interpreted shows the distribution of risks in an acceptable range(ALARP, As Low As Reasonably Practicable). To ensure improved safety, we recommend regular inspections and checks for high-risk hydrogen reservoirs, dispensers, tube trailer leaks, and LPG vapor recovery lines.