• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.2
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• pp.268-273
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• 1994

The quality of Kimchi was investigated under airtight and ventilating conditions. At 2$0^{\circ}C$ and 4$^{\circ}C$ fermentation, there were no significantly difference in pH, acidity and vitamin C of Kimchi between airtight and ventilating conditions. The contents of $CO_2$ , the number of lactic acid bacteria and the sensory score of carbonated taste under airtight condition were higher than those values under ventilating condition. While , the number of aerobic bacteria under airtight condition was lower than those under ventilating condition.

• Journal of Welding and Joining
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• v.19 no.1
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• pp.27-32
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• 2001

This paper is studied about welding conditions and weldability of seam welding for galvanized steel sheet of automotive. The fuel tank of automobile is made by seam welding to be required of airtight or oiltight. This method have required a short time for welding, simplicity operation progress and little HAZ. Especially, it has more less residual stress and transformation than different welding progress. So, this study is for decreasing the leakage occurrence rate and to make standard operating condition table anyone can operate easily. Therefore, this study is analyzed the optimum conditions of seam welding for making the automobile with galvanized steel sheets by means of observing the microstructure and configuration back projection, RT, tensile-shear strengths test and SEM. Optimum conditions of seam welding obtained as follows, current 17.2-17.6kA speed 1.0m/min weld time 4:10:6 and current 16.5-17.4kA, speed 0.83m/min, weld time 4:10:4 at t1.0, and current, 18.5-18.9kA, speed 0.8m/min, weld time 4:10:4 and current 16.5-17.4kA, speed 0.68m/mi, weld time 4:10:2 at t1.6.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.12
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• pp.477-482
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• 2016

Airtight containers have been widely used in many industries and household. They need a packing for sealing between the inside and outside. Previous packing materials have some drawbacks like stench, stickiness, and difficulty of applying to automated manufacturing systems. So, a new packing material which is harmless and suitable for automation is needed. This study performed a hot plate welding process of thermoplastic elastomer (TPE) as the packing material. The hot plate welding process included a phase change process of solidification and melting. The porosity-enthalpy method was adopted in order to simulate phase change problems. The TPE showed non-Newtonian fluid characteristics during the melting process. Since properties of SEBS are not well-defined, we established TPE properties by observing the melting behavior of TPE. In order to find an optimized condition, a parametric study including packing thickness, shapes, hot plate temperature, and thermal resistance, was conducted.

• Agribusiness and Information Management
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• v.10 no.2
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• pp.18-27
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• 2018

This study aims to confirm the appropriateness of fruit and vegetable sales at military commissaries, with the purpose of enhancing the physical health and morale of military personnel. In order to achieve this objective, we examined the actual conditions of fruit and vegetable sales at military commissaries and analyzed the soldiers' awareness of fruit and vegetable sales through questionnaire surveys. The conclusions of this study are as follows: Firstly, fresh fruits and vegetables were not sold at military commissaries. Secondly, soldiers acknowledged the need for the consumption of fruits and vegetables and strongly expressed the desire for these fresh food products to be sold at military commissaries. Although the ROK Navy privatized military commissaries for the purposes of increasing management efficiency of national defense and strengthening combat power by transferring PX salesclerk soldiers to join combat personnel, this effort produced a negative effect of price increase. The following are proposals for improving this condition: fruit and vegetable products should be introduced to military commissaries through military welfare funds; fresh food markets should be established by closely cooperating with the local community's agricultural producers; processed fruit and vegetable product (dry, frozen, airtight packaged, etc.) sales should be increased; and the privatization of the navy commissaries should be abolished.

• Horticultural Science & Technology
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• v.28 no.5
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• pp.864-870
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• 2010

This study was conducted to determine the effects of foliage plants on reducing indoor carbon dioxide ($CO_2$). Five foliage plants such as $Hedera$ $helix$ L., $Ficus$ $benjamina$ L., $Pachira$ $aquatica$, $Chamaedorea$ $elegans$, and $Ficus$ $elastica$ were selected and cultivated in two different growth medium (peatmoss and hydroball). Each plant was placed in an airtight chamber and then treated with the combinations of two different $CO_2$ concentrations (500 or 1,000 ppm) and two different light intensities (50 or $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$). The change of $CO_2$ concentration (ppm) in the airtight chamber during day and night was measured and then converted into the photosynthetic rate (${\mu}mol\;CO_2{\cdot}m^{-2}{\cdot}s^{-1}$). As the results, each foliage plant reduced $CO_2$ level in the airtight chamber for one hour by photosynthesis. $Pachira$ $aquatica$ and $Ficus$ $elastica$ absorbed $CO_2$ more effectively compared to the other plants. The plants exposed to higher $CO_2$ concentration (1,000 ppm) and higher light intensity ($200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) showed more effective $CO_2$ elimination rate and photosynthetic rate. The plants that have wide leaves and big leaf areas such as $Pachira$ $aquatica$, $Hedera$ $helix$ L.,and $Ficus$ $elastica$ showed higher photosynthetic rate than the other plants that have smaller leaves. Released $CO_2$ concentration by respiration of the plants during the night was very low compared to the absorbed $CO_2$ concentration by photosynthesis during the day. There was no significant difference between peatmoss and hydroball medium on reducing $CO_2$ concentration and increasing photosynthetic rate. In conclusion, this study suggested that foliage plants can effectively eliminate indoor $CO_2$. Optimum environmental control in relation to photosyntheis and usage of right indoor foliage plants having lots of leaves and showing active photosynthesis even under low light intensity like indoor light condition would be required to increase the elimination capacity of indoor $CO_2$.

• Journal of the Korea Institute of Building Construction
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• v.3 no.1
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• pp.107-114
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• 2003

This study aims to find methods that prevents aging of buildings paint coating and that limits defects in construction. Defects in painting can occur in four stages: pure paint, during painting, after the paint coating has dried, and after some period of time has passed after coating. Paint may become bad due to precipitation of pigments, formation of membranes, and seeding during manufacturing. Therefore, it is important that the paint is well mixed and kept airtight at a cool, dark place. Indents, paint brush strokes, orange peel, separation of colors, and paint running and spreading during the paint work process can be prevented by using high quality materials and applying a high-level of construction method. After the paint coating has dried, boiling, yellowing, poor drying, poor bonding, and/or glen deficiency may occur. These are influenced by the levels of cleanness of the dried product, drying temperature and hydration. Then, when the coating has been left dried for some period of time, cracking, peeling, scaling, swelling, discoloring, and/or rusting may develop due to the ultraviolet and contaminants in the air. Since these defects occur due to inappropriate construction schedule and/or hot and humid condition, one must use weatherproof materials. Furthermore, poor paint color may be caused by contamination in the sample plate, discoloration, and/or discrepancies in colors which are due to material differences, level of glossiness, degree of dispersion, dual color property of metallic colors, precipitation of pigments, etc. One should achieve reduction in construction cost and effectiveness in paint work by limiting contaminations in the construction site and strictly observing to construction regulations.

• Journal of the Korea Safety Management & Science
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• v.9 no.1
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• pp.197-211
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• 2007

The power of semiconductor, Korea is continuously constructing semiconductor production line for keeping a front-runner status. however, studies and data about potential risks in semiconductor factory are still short. If fire does not initially suppressed, the fire causes a great damage. To decrease fire risk factors, in addition to fire fighting safety equipment, more important thing is how to design and construct fire protection system. The current fire protection codes about semiconductor factory come under functional law, and this law is short of consideration about particularity of factory. The existing prescriptive fire codes depending on experience compose without evident engineering verifications, thus equipments which is created by the current prescriptive fire code may bring about a variety of problems. For example, the design under the current regulation can not cope with the excessive investments, low efficiencies, and the diversifying construction designs and be applied to the quick changes of new technologies. Ergo, an optimal design for fire protection is to equip fire protection arrangements with condition and environment of production field. Manufacturing factory of semiconductors is a windowless airtight space. And for cleanliness, there exists strong flow of cooperation. Therefore, there is a need for fire safety design that meets the characteristic of a clean room. Accordingly, we are to derive smoke flow according to cooperation process within a clean room and construction plan of an optimal sensor system. In this study, in order to confirm the performance of proposed smoke-exhaust equipment and suggest efficient smoke exhaust device when there is a fire of 1MW of methane in the clean room of company H, we have implemented fire simulation using fluid dynamics computation.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.309-314
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• 2009

When a train enters into a tunnel, a compression wave is generated by a front nose and a expansion wave is generated by a rear tail respectively. The interaction between pressure waves and the train makes the internal and external pressure of the train change dramatically. In this paper, we had measured the internal and external pressure variations of TTX and analyzed the pressure variations as the tunnel length. Also, the rate of internal pressure variations were investigated with the current airtight condition of TTX. In short tunnels, the internal and external pressure variation were not large because the superposition of pressure waves was not happened. In long tunnels, however, the rapid and large pressure variations were shown because of the superpositions between the same sort of pressure waves, such as expansion wave and expansion wave or compression wave and compression wave. In specific length tunnels, the pressure variation and the pressure variation rates were largely lessened because the compression wave and expansion wave were superposed.

• Tribology and Lubricants
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• v.35 no.4
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• pp.222-228
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• 2019

As rubber products such as O-rings, which are also known as packings or toric joints, come in regular, long term contact with liquid fuel, they can eventually swell, become mechanically weakened, and occasionally crack; this diminishes both their usefulness and intrinsic lifetime and could cause leaks during the steady-state flow condition of the fuel. In this study, we evaluate the lifetime of such products through compression set tests of FKM, a family of fluorocarbon elastomer materials defined by the ASTM international standard D141; these materials have great compression, sunlight, and ozone resistance as well as a low gas absorption rate. In this process, O-rings are immersed in the liquid fuel of airtight containers that can be expressed as a compression set, and the liquid fuel leakage in a flow rig tester at variable temperatures over 12 months is investigated. Using the Power Law model, our study determined a theoretical O-ring lifetime of 2,647 years, i.e. a semi-permanent lifespan, by confirming the absence of liquid fuel leakage around the O-ring assembled fittings. These results indicate that the FKM O-rings are significantly compatible for fuel tests to evaluate long-term sealing conditions.

• Journal of Biomedical Engineering Research
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• v.39 no.6
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• pp.243-249
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• 2018

The indoor radon concentration was measured in the lecture room of the university and the radon concentration was converted to the amount related to the radon exposure using the dose conversion convention and compared with the reference levels for the radon concentration control. The effect of indoor radon inhalation was evaluated by estimating the life effective dose and the risk of exposure. To measure the radon concentration, measurements were made with a radon meter and a dedicated analysis Capture Ver. 5.5 program in a university lecture room from January to February 2018. The radon concentration measurement was carried out for 5 consecutive hours for 24 hours after keeping the airtight condition for 12 hours before the measurement. Radon exposure risk was calculated using the radon dose and dose conversion factor. Indoor radon concentration, radon exposure risk, and annual effective dose were found within the 95% confidence interval as the minimum and maximum boundary ranges. The radon concentration in the lecture room was $43.1-79.1Bq/m^3$, and the maximum boundary range within the 95% confidence interval was $77.7Bq/m^3$. The annual effective dose was estimated to be 0.20-0.36 mSv/y (mean 0.28 mSv/y). The life-time effective dose was estimated to be 0.66-1.18 mSv (mean $0.93{\pm}0.08mSv$). Life effective doses were estimated to be 0.88-0.99 mSv and radon exposure risk was estimated to be 12.4 out of 10.9 per 100,000. Radon concentration was measured, dose effective dose was evaluated using dose conversion convention, and degree of health hazard by indoor radon exposure was evaluated by predicting radon exposure risk using nominal hazard coefficient. It was concluded that indoor living environment could be applied to other specific exposure situations.