• KSBB Journal
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• v.5 no.1
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• pp.59-67
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• 1990

Enzymatic hydrolysis of insoluble cellulose was performed in a bubble column with tangential flow ulrafiltration membrane unit. The reactor was operated in a batch mode as well as semi-continuous and continuous with continuous removal of products through the tangential flow ultrafiltration membrane. The optimum superficial gas velocity was 1-3cm / sec so as to avoid bubble coalescence and enzyme denaturation. In continuous and selni-cotinuous process, the conversion was gradually increased but the total reduced sugar concentration was drcastically dereased with the dilution rate. It was concluded that the bubble column attaching tangential flow ultrafiltration membrane unit was effective on continuous hydrolysis of cellulose and recovery of enzyme.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.77-77
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• 2003

산업화에 따라 각종 산업분야에서 유기 용제의 사용이 증가하게 되었고 대기오염, 수질오염 등의 상태가 심각해져가고 있는 실정이다 그러나 다양해진 오염물질을 처리하는 데 있어서 기존의 산화처리방법은 한계에 달하였고 새로운 처리공정으로 최근 고급산화법(AOP : Advanced Oxidation Process)에 대한 연구가 활발하게 진행되고 있다. 이에 본 연구에서는 대기환경 및 인체에 심각한 영향을 주는 VOCs(Voletail Organic compounds)중 BTEX(Benzene, Toluene, Ethylbenzene, Xylene)를 다양한 형태의 광촉매제를 이용하여 기상 광분해한 후 이에 대한 최적의 분해 조건과 분해율을 비교하고자 하였다. 순환식의 자체 제작한 기상광반응장치를 이용하여, CVD법으로 TiO$_2$ 입자를 알루미나 비드위에 코팅한 볼과 같은 방법으로 유리기판위에 코팅한 판상의 광촉매제 그리고 결정성이 각기 다른 루틸상과 아나타제 그리고 아나타제/루틸 혼합상의 TiO$_2$ 분말을 직접 이용하여 VOCs 농도와 종류, 광원의 종류 및 세기를 변화시켜 PID(Photo ionization Detector)방식의 순환식 VOCs 측정기를 이용하여 광분해율을 실시간으로 측정하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.26-33
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• 1994

A new reliable method to prediet the axial vapor fraction distribution from the measured probability density of the liquid bulk temperature is suggested in this paper. And also the actual quality of the subcooled boiling flow is easily calculated from the liquid bulk temperature. When the heat generating rate is reached to the CHF value, the sharp wall temperature increasing by the wall temperature fluctuation is occurred under the CHF condition. This paper presents the simple wall temperature fluctuation model of transition boiling by the repeating process of overheating and quenching, when the coalescent bubble passes slowly near the wall. Experiments for the subcooled R-113 flow are carride-out in the range of(0.9399~4.461)${\times}10^6$kg/$m^2$hr mass velocity and 10~3$0^{\circ}C$ intel subcooling condition.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.7-12
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• 2013

As emission regulation for vehicle has been reinforced, many researches carried out for HCNG(hydrogen-natural gas blends) fuel to the conventional compressed natural gas (CNG) engine. However, abnormal combustion such as backfire, pre-ignition or knocking can be caused due to high combustion speed of hydrogen and it can result in over heating of engine or reduction of thermal efficiency and power output. In the present study, improvement of combustion performance was observed with HCNG fuel since it can extend a flammability limit. Knocking characteristics for CNG and HCNG fuel were investigated. Feasibility of HCNG fuel was evaluated by checking the knock margin according to excess air ratio. The operation of engine with HCNG was stable at minimum advance for best torque(MBT) spark timing and knock phenomena were not detected. However, it is necessary to prepare higher knock tendency since possibility of knock is higher with HCNG fuel.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.56-56
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• 2022

벌개미취(Aster koraiensis Nakai)는 국화과에 속하는 우리나라 자생종으로 어린잎은 식용하고, 항비만 및 고지혈증 예방 등의 연구 결과가 보고되어 이용 가치가 높다고 알려져 있다. 또한 주로 조경소재로 이용되고 있으며, 생태복원을 위한 소재식물로 벌개미취를 이용하려는 시도가 이루어지고 있다. DMZ 남방한계선 철책 주변에는 군의 경계작전을 위해 반복적으로 식생을 제거한 지역(불모지)이 형성되어 있어 이를 복원할 필요가 있다. 생태복원에 있어 가장 기본적인 종 선정 방법은 자생종 또는 인접 지역종을 이용하는 것이다. 벌개미취는 DMZ 일원에 자생할 뿐만 아니라, 건조한 환경은 물론 습윤한 지역에서도 생육한다. 본 연구에서는 토성에 따른 벌개미취의 발아 특성과 광조건에 따른 광합성 반응을 조사하여 DMZ 불모지와 유사한 환경에서의 생육이 건전한지 살펴보고자 하였다. 이를 위해 벌개미취의 기내발아 검정(15℃, 12/12h)과 토성(마사토, 상토, 혼합토)에 따른 종자 발아율을 비교하였고, 차광(0, 50, 75 및 95%)처리에 따른 엽면적당 건중량, 엽록소 함량, 광-광합성 반응을 조사하였다. 벌개미취의 발아율은 기내(79%), 마사토(74%), 상토(82%) 그리고 혼합토(77%)로 나타나 각 처리구간 유의한 차이가 나타나지 않았다. 벌개미취의 엽면적당 건중량은 차광수준이 높을수록 감소하였고, 엽록소 a와 b 함량은 차광수준이 높을수록 감소하였으나 a/b는 통계적으로 차이가 없었다. 광-광합성 반응을 통해 산출한 벌개미취의 광포화점과 광합성 최대속도는 차광수준이 높을수록 감소하는 경향이 나타났고, 순양자수율은 증가하는 경향이 나타났다. 벌개미취는 전천광보다 낮은 광도에서 생장 시 광합성 능력이 감소하는 것으로 보이며, 광이 제한되지 않는 불모지 환경에서 생육이 유리할 것으로 생각한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.304-304
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• 2007

고주파 모률에서 사용되는 기판소재는 저유전율과 낮은 loss 특성을 요구함으로 지속적인 연구를 필요로 한다. 지금까지의 ceramic/glass composite 에서 주로 사용된 ceramic filler는 Al2O3로 낮은 유전률을 구현에 한계가 있었다. Cordierite는 낮은 유전율 (${\varepsilon}_r$ < 4)을 나타내는 filler로서 그 가능성이 높지만 아직까지 보고된 결과들이 미흡한 실정이다. 따라서 본 연구에서는 cordierite filler와 SiO2-B2O3-Al2O3-RO (R : Zn, Sr, Ba, Ca)계의 glass를 혼합하여 LTCC용 기판소재로서의 가능성을 확인하고자 저온 동시소성이 가능한 소결온도인 $850^{\circ}C{\sim}1.000^{\circ}C$ 사이에서 소재의 소결실험을 진행하였다. 소결온도에 따른 상변화, 유전특성을 확인한 결과 filler로 사용된 cordierite상만이 관찰 되었으며 소결조건에 따라 5.0~5.5의 낮은 유전율과 1.000~1,500의 Q를 나타내는 것을 확인 하였다.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.75-86
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• 2002

This paper presents sedimentation and consolidation characteristics of dredged soils mixed with sand materials through the self-weight consolidation tests adopting stepwise filling method. After completely throwing away dredged soils daily by flour kinds of S-C, which is the quantity of sand contained, results fi:om laboratory tests are compared with those from a new method using hyperbolic, which considers stage settling and consolidating characteristics, and those from the existing analyzing method. Liquid limit up to 65% had a large effect on consistency properties. Assuming that the settlement occurred only by clay content of dredged soils, it is shown that the clay void ratio is less than 2 and 4 respectively in case S-C is 0% and 50%. In the applied hyperbolic method, reinitialized curve has a linear behavior of a coefficient of correlation of almost 1, and the coefficient of slope and intercept except fur the specimen with the height of 10cm and 20cm had a tendency to fellow exponent function and a shape of zone settling and dispersing settling. The results computed by the applied hyperbolic method rather than the existing analyzing method coincide with those of laboratory tests. It is shown that the former is more suitable than the latter for the area considering the influence, of sand materials.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.9
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• pp.1339-1346
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• 2015

In a previous study, baekseolgi with xylitol or sucralose was comparable to baekseolgi with sugar in terms of all sensory characteristics. However, the hardness of sucralose baekseolgi increased considerably during storage while that of xylitol baekseolgi remained unchanged. To improve the physical limitations observed in sucralose baekseolgi, a combination of sucralose and xylitol were substituted for sugar when preparing baekseolgi (SL0~SL100, SLn; baekseolgi where sugar was replaced with n% sucralose and 100-n% xylitol based on relative sweetness to sugar). All SLn baekseolgi samples were not significantly different from sugar baekseolgi in terms of sensory properties. The moisture content was not different between sugar and xylitol baekseolgi (SL0), but decreased significantly as the amount of sucralose increased (P<0.01), which correlated with cohesiveness of baekseolgi. Texture profile analysis revealed that hardness of SLn baekseolgi increased without any noticeable change in moisture content after storage at $4^{\circ}C$ for 7 days. In addition, the hardness after storage was the highest in sucralose baekseolgi (SL100), which was comparatively lower in SL0~SL80 containing xylitol presumably due to the hygroscopic characteristics of xylitol. In particular, SL20 was found to be comparable to sugar baekseolgi in terms of moisture and cohesiveness during storage. The results showed that the combination of xylitol and sucralose could be a potential sugar substitute in terms of not only sensory characteristics but also physicochemical properties.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.5
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• pp.262-268
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• 2015

This study established an analytical method to simultaneously determine six organophosphorous pesticides [methyldemetone-S, diazinon, fenitrothion, parathion, phentoate, and O-ethyl O-(4-nitrophenyl) phenylphosphonothioate (EPN)] and carbaryl in water using a gas chromatography/mass spectrometry (GC/MS) system coupled with on-line micro extraction by packed sorbent (MEPS) and programmed temperature vaporizer (PTV) injector. Polystyrene divinylbenzene (PDVB) was used as a sorbent of MEPS. The effects of elution solvents, pH, elution volume and draw-eject cycles of samples on sample pretreatment process were investigated. Also, quality assurance and quality control (QA/QC) and the recovery of the pesticides in environmental samples were evaluated. The elution was performed using $30{\mu}L$ of a mixed solvent (acetone : dichloromethane = 80 : 20 (v/v)). Sample pretreatment processes were optimized with seven cycles of draw-eject of sample (1 mL) spiking an internal standard and sulfuric acid. At lower pH, the analytical sensitivity of diazinon decreased, but that of carbaryl increased. The method detection limit and the limit of quantification for this method were 0.02~0.18 and $0.08{\sim}0.59{\mu}g/L$, respectively. The method precision and accuracy were 1.5~11.5% and 83.3~129.8%, respectively, at concentrations of $0.5{\sim}5.0{\mu}g/L$. The recovery rates for all the pesticides except carbaryl in various environmental samples ranged 75.7~129.3%. The recovery rate of carbaryl in effluent sample was over 200% whereas carbaryl in drinking water, groundwater, and river water were in the acceptable range.

• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.61-66
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• 2014

The various recycling methods of mixed coal ash have been developed considerably and it's recycling quantity has been increased. However, the more relatively finer grain content of coal ash in ash pond is increased the more it's quantity is increased in recycling as products for drainage in soft ground etc. Accordingly, the geotechnical properties of mixed coal ash in ash pond would be inferior and it's recycling rate should reach the limitations in increase. In this study, to recycle mixed coal ash contained fine grain in considerably amount as products for strength, etc. By adding binder to it and manifesting, it's compressive strength is stronger than the criteria, these are suggested; 1) the variety of compressive strength test performed on mixed coal ash of various grain distributions as main material, 2) the kind of binder, it's mixing quantity and the optimum content rate range of fine grain coal ash that the compressive strength stronger than a certain compressive strength is manifested. Cement is more excellent than quicklime as binder in manifesting stronger compressive strength and the sieve type to sort it is #40 sieve in order to recycle all mixed coal ash in ash pond efficiently as products for drainage as well as products for strength, etc. And, it could increase insufficient compressive strength remarkably that content of pure sand is more in the rate as pure sand and the part of mixed coal ash in ash pond to pass through #40 sieve is mixed in the ratio of 2 to 8.