• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.1-11
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• 1987

Comprehensive laboratory experiments including digestion failures were conducted to identify differences between mesophilic and thermophilic digestion. Critical HRT was found to be near 10days for mesophilic and near 5days for thermophilic digestion. Inhibition occurred rapidly when operated below critical HRT. However, inhibition at mesophilic condition was much greater than that at thermophilic condition. Although digester performances were similar above critical HRT of mesophilic digestion, thermophilic digestion was considerably advantageous below this HRT. Thermophilic digestion produced smaller amount of sludges which had significantly higher settling velocity and lower specific resistance. Reaction rates also clearly demonstrated temperature and HRT effects on digestion. It was also found that gas production rates increased linearly with increasing reaction rates regardless of temperature and their relationships were almost identical at mesophilic and thermophilic temperature.

• The Korean Journal of Food And Nutrition
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• v.11 no.2
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• pp.150-158
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• 1998

Limit dextrin of Korean beer(3 brands) and Japanese beer(21 brands) were separated by ethanol fractionation. Limit dextrin of Korean and Japanese beer was estimated to be 1.1%. 1H-NMR analysis revealed that the limit dextrin showed both signal of $\alpha$-1, 4- and $\alpha$-1, 6- glucosidic linkage with its estimation ratio of average 5.5:1. Limit dextrin was hydrolyzed to glucose with the yield of 57.22% by Aspergillus awamori $\alpha$-glucosidase(24.7 unit) plus human salivay $\alpha$-amylase(2.4 unit) in 100${mu}ell$ of 0.043M acetate buffer at 37$^{\circ}C$ for 5 hour. Among them, limit dextrin of Korean beer showed the highest hydrolysis rate of 76%. Small size sugars (64.8%) removed by ethanol fractionation and limit dextrin(21.4%) hydrolyzed by amylases that is digestable sugar. Non hydrolyzed limit dextrin(13.8%) by the amylases which can be a growth factor of Bifidobacterium in human intestine.

• Fire Science and Engineering
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• v.28 no.3
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• pp.20-28
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• 2014

Effect of radiation models on the suppression limits in counterflow $CH_4$/air diffusion flame was numerically investigated with fundamental experiments for the numerical validation. $N_2$ and $CO_2$ were considered as extinguishing agents. The differences in extinguishing concentration between OTM and SNB radiation models which have different accuracy levels were examined. As a result, there is no considerable difference in extinguishing concentration for the $N_2$ dilution as the radiation models with different accuracy levels were used. As the $CO_2$ having strong radiative effect was diluted in the low strain flames, however, the radiation model with high predictive accuracy such as SNB should be used. In particular, the $CO_2$ dilution in fuel stream leads to the significant difference in extinguishing concentration between OTM and SNB models. Therefore, it is necessary that the radiation model should be reasonably chosen with the consideration of numerical accuracy and computational time for the prediction of extinguishing concentration.

• 방재와보험
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• s.92
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• pp.36-39
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• 2002

우리는 지금 이제껏 우리가 사용해 오던 재래식 포소화약제를 버리고 새로운 대안을 찾아야 하는 갈림길에 서 있다. 미래에도 예전처럼 소화능력에 대한 우리의 신뢰를 저버리지 않으면서 친환경적인 포는 과연 어떤 것이어야 하나? 미래형 포소화약제의 선택 방향과 그 한계를 알아보고 소비자들의 판단 기준을 짚어보기로 한다.

• Proceedings of the Korean DIstribution Association Conference
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• 2000.10a
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• pp.151-162
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• 2000

철도소화물 부문의 택배시스템 도입은 원가절감이 가능하고, 경쟁력을 갖출 수 있는 장점을 갖추고 있으므로, 현실적으로 매우 필요하다. 택배시스템 도입은 철도청에서 제3자에게 위탁 운영케 하든지, 직접 운영하든지, 별도법인을 만들 수도 있다. 그러나 본고에서는 이러한 내용은 별도의 연구가 있어야할 것으로 보이므로 생략한다. 본고에서는 환경ㆍ제도적인 측면과 운영ㆍ시스템 측면에서 택배시스템을 도입하기 위한 대책방안 만을 강구한다. 본고는 철도소화물시장이 독점적으로 정부의 관할 하에 있기 때문에 철도소화물에 대한 연구가 국내에서 여러 전문가에 의하여 다양하게 전개되지 못하였다는 점이 취약점이다. 따라서 본고도 이러한 환경에서 폭넓은 연구사례를 제기하지 못한다는 한계가 있다. 그러나 설문조사나 인터뷰, 실증자료와 관련 기업과 단체의 내부자료를 통하여 이 문제를 극복하고자 노력하였다.

• Journal of Korea Technology Innovation Society
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• v.3 no.3
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• pp.1-17
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• 2000

This paper shows the institutional limits of technological innovation at the railway package service, that is the limits of introducing the package express system. The railway package service, owned by government and operated by D company, has been suffered severe operating loss since early 1990's. The package express system supported by information network and co-working with inner city quick service might be an solution for the railway package service. But there are several obstacles such as labor union and the rigidities of the Korean National Railroad of government agency.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.194-199
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• 2008

현재 일반화재 및 산림화재에 따른 목조건축물 및 문화재 등에 화재가 확산 될 경우 일반 소화기 및 옥내 및 외소화전으로는 약제의 날림 및 다량의 물로 인한 수손피해 등으로 한계가 있으며, 이를 개선하기 위한 적합한 소화설비가 구비되지 못한 관계로 많은 어려움이 있으며, 이로 인하여 초기진화에 실패함으로 많은 인적 물적 피해가 발생되고 있다. 따라서 이러한 문제점들을 보완하기 위한 해결 방안으로 개인 휴대가 용의하고 간편한 청정 친환경소화시스템을 연구 하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.9 s.240
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• pp.997-1005
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• 2005

The extinction characteristics of low strain rate normal gravity (1-g) nonpremixed methane-air flames were studied numerically and experimentally. A time-dependent axisymmetric two-dimensional (2D) model considering buoyancy effects and radiative heat transfer was developed to capture the structure and extinction limits of 1-g flames. One-dimensional (1D) computations were also conducted to provide information on 0-g flames. A 3-step global reaction mechanism was used in both the 1D and 2D computations to predict the measured extinction limit and flame temperature. A specific maximum heat release rate was introduced to quantify the local flame strength and to elucidate the extinction mechanism. Overall fractional contribution by each term in the energy equation to the heat release was evaluated to investigate the multi-dimensional structure and radiative extinction of 1-g flames. Images of flames were taken for comparison with the model calculation undergoing extinction. The two-dimensional numerical model was validated by comparing flame temperature profiles and extinction limits with experiments and ID computation results. The 2D computations yielded insight into the extinction mode and flame structure of 1-g flames. Two combustion regimes depending on the extinction mode were identified. Lateral heat loss effects and multi-dimensional flame structure were also found. At low strain rates of 1-g flame ('Regime A'), the flame is extinguished from the weak outer flame edge, which is attributed to multi-dimensional flame structure and flow field. At high strain rates, ('Regime B'), the flame extinction initiates near the flame centerline due to an increased diluent concentration in reaction zone, which is the same as the extinction mode of 1D flame. These two extinction modes could be clearly explained with the specific maximum heat release rate.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.2
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• pp.13-18
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• 2019

Sewage sludge treatment is increasing every year due to improvement of living and urbanization. However, interest in anaerobic digestion which is one of the recycling technology. There is anaerobic digestion of increasing due to limitations of ocean dumping and final disposal. But, the limit of anaerobic digestion efficiency due to the advanced treatment of sewage has been limited, and studies for solubilization technology have been actively conducted. Therefore, in this study, we aimed to investigate the variation of generation of scum and the solubilization efficiency in the application of pre-treatment of ozone reaction and the change of properties of digested sludge with wet milling. There are results of VS/TS increased by 4.4% and $SCOD_{cr}/TCOD_{cr}$ increased by 9.4% by wet milling alone. In addition, the increase of the specific surface area due to which the reduction of the particle size of the solid content of the sludge in the ozone reaction caused by wet milling decreased the generation rate of scum at 14.3% and increased VS/TS at 2.1%, compared with the ozone reaction alone. From these results, it is expected that the application of wet milling can be increased the contact efficiency with solids in the sludge during ozone reaction with suppress scum and increase the efficiency of the subsequent process in anaerobic digestion.

• Fire Science and Engineering
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• v.17 no.4
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• pp.28-35
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• 2003

To analyze the transfer characteristics of $CO_2$ extinguishant when extinguishant is injected into a closed space similar to a marine engine room, a numerical simulation was performed. Flow and Concentration fields are calculated according with the variation of the fire plume,s location. The results show that tile variation of fire plumes, location greatly effected on the flow patterns and the characteristics of $CO_2$ extinguishant transfer. In case of the fire plume located at left region of the 2nd floor center in the engine room consisted of first and second floor, The effects similar to the air curtain is found and cut off the mass transfer. In the characteristics with hight, the iso-concentration line below the extinguishable limit is formed in the left region of the 1st and 2nd floor center after the $CO_2$ extinguishant is completely injected. therefore I think that the results of this study are considered to arrange the $CO_2$ injection nozzles for the $CO_2$ fire fighting equipments.