• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.123-134
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• 2019

This study presents dynamic responses of circular pipe models as a part of fundamental studies on dynamic stability monitoring of the large circular steel pipe cofferdam with the ship collision. Small-scaled laboratory experiments are performed with a single and bolted circular steel pipes with a diameter, thickness, and height of 30, 0.4, 90 cm, respectively. The bolted circular steel pipe is configured with three segments of 30 cm in height. Circular steel pipe models are embedded in a soil tank, all 1 m in length, width, and height. The thickness of soil in the soil tank is set at 23 cm. The ship collision is simulated with a hammer impacting. The dynamic responses are investigated with different water levels of 25, 40, 55, and 70 cm. Experimental results show that a signal energy decreases with increasing water level. More sensitive reduction in the energy appears for the bolted circular steel pipe. A predominant frequency decreases with increasing water level for both single and bolted steel pipes. The minor reduction in the frequency appears for the bolted circular steel pipe under the water level of 70 cm. This study suggests that the signal energy and frequency response is useful for the dynamic stability monitoring of the large circular steel pipe cofferdam.

• Korean Journal of Food Science and Technology
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• v.32 no.4
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• pp.860-866
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• 2000

The efforts were made to develop persimmon leaf beverages on the basis of the results of sensory evaluation. The result of sensory evaluation for the development of persimmon leaf beverages showed that when the concentration of extracts was 10%, the aroma and flavor of persimmon leaves was best. The optimum concentration of sugar was 4.5% and apple juice was 15%. The change of pH had the tendency to keep stable range(3.82-3.71) during the period of 30 days and free-sugar had little change according to the temperature and time of preservation. The preservation of the change of ascorbic acid revealed that the range of decrease in the case of preservation at $4^{\circ}C$ was a bit narrower than in the case of preservation at $25^{\circ}C$. Nonvolatile organic acids were four kinds of acids, oxalic acid, levulinic acid, malic acid, and citric acid, among which levulinic acid was on the increase for the first 10 days during the preservation period and then on the decrease regardless of the temperature of preservation. The browning of beverages was on the slight increase.

• KSBB Journal
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• v.23 no.4
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• pp.350-354
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• 2008

Magnetically separable immobilized trypsin was developed and their biocatalytic activity was evaluated for the different immobilization media. The activity, recyclability, pH effect, and stability of immobilized enzymes were evaluated for the different supporting media. The biocatalytic activity of immobilized trypsin was highest with magnetically separable polyaniline (PAMP), and Vm and Km of PAMP were 0.169 mM/min and 0.263 mM respectively. With increasedpH, the biocatalytic activity increased for all supporting materials used. Immobilized enzymes were recycled and recycle activities were over 90% of their original activity after ten times reuse. The operational stabilities of enzymes were greatly improved with enzyme immobilization.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.163-170
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• 2008

The aeroelastic stability analysis of a soft-in-plane, composite hingeless rotor blade in hover and in forward flight has been performed by combining the mixed beam method and the aeroelastic analysis system that is based on a moderate deflection beam approach. The aerodynamic forces and moments acting on the blade are obtained using the Leishman-Beddoes unsteady aerodynamic model. Hamilton's principle is used to derive the governing equations of composite helicopter blades undergoing extension, lag and flap bending, and torsion deflections. The influence of key structural modeling issues on the aeroelastic stability behavior of helicopter blades is studied. The issues include the shell wall thickness, elastic couplings and the correct treatment of constitutive assumptions in the section wall of the blade. It is found that the structural modeling effects are largely dependent on the layup geometries adopted in the section of the blade and these affect on the stability behavior in a large scale.

• Journal of Life Science
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• v.8 no.5
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• pp.497-503
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• 1998

Cyclodextrinase from B. stearothemophilus KJ16 that can produce both cyclodextrin(CD) glucanotransferase and cyclodextrinase was purified 87.6-fold with 7% yield by ammonium sulfate precipitation, DEAE-cellulose chromatog-raphy, Sephadex G-100 chromatography, and FPLC. The molecular weight of the purified enzyme was about 68,000 dalton by SDS-PAGE. The optimal pH and temperature were 6.0 and 55$^{\circ}C$, respectively. The enzyme was stable at 5$0^{\circ}C$ for 2 hr in the pH range of 5.5 and 8.5. The enzyme activity was inhibited strongly by mercaptoethanol, di-thiothreitol, p-chloromercuribenzoate, N-bromosuccinimide, $Cu^{+2}$and $Hg^{+2}$. The purified enzyme hydrolyzed CDs with$\gamma$-CD>$\beta$-CD>$\alpha$-CD. The enzyme also hydrolyzed linear maltodextrins and polysaccharides, but the rates of hyd-rolysis for such substrates were slow as compared to that for $\gamma$-CD. The final degradation products with all substrates were maltose and glucose. Maltose was not further hydrolyzed.

• Microbiology and Biotechnology Letters
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• v.26 no.4
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• pp.323-330
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• 1998

Cyclodextrin glucanotransferase (CGTase) was purified from the culture broth of the Bacillus firmus var. alkalophilus, using ultrafiltration, starch adsorption/desorption, ion-exchange chromatography on DEAE-cellulose and gel filtration on Sephacryl HR-100. The molecular weight of the purified enzyme was determined as 77,000 by SDS-PAGE. The optimum pH and temperature for the CD synthesis were 6.0 and 5$0^{\circ}C$, respectively. The activity of this enzyme was stably kept at the range of pH 6.0～9.5 and up to 5$0^{\circ}C$. However, in the presence of $Ca^{2+}$, the optimum temperature for CD synthesis was shifted 55~6$0^{\circ}C$ and this enzyme was stable up to 6$0^{\circ}C$ because of the stabilizing effect of $Ca^{2+}$. The purified CGTase produced CDs with high conversion yields of 45~51% from sweet potato starch, com starch and amylopectin as substrate, especially, and the product ratio of $\beta$-CD to ${\gamma}$-CD was obtained at range of from 5.8:1 to 8.4:1 according to the kind of substrate. The purified enzyme produced mainly $\beta$-CD without accumulation of $\alpha$-CD during enzyme reaction using various starches as the substrate, indicating that the purified enzyme is the typical $\beta$-CGTase. The purified CGTase produced 25 g/l of CDs from 5.0% (w/v) liquefied com starch and the conversion yield of CDs was 50%, and the content of $\beta$-CD was 84% of total CDs after 8 hours under the optimum reaction condition.ion.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.45-50
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• 2021

As the difficulty of flip chip products increases, there is a growing interest in the material of flux, which is safe from the solder wetting and reliability. In the case of no clean flux, there is merit in terms of process efficiency because there is no cleaning process. But Cu migration and delamination can be occurred if the residue remains after the reflow process. In this study, major element materials, solvent and activator, are changed and confirmed effect of non-wet and reliability in the package environment. Stability of materials were secured through storage stability evaluation, and we found out non-wet zero materials through the application of two types of solvent and activator with different boiling point and the increase of activator content. After reliability test, no delamination was found in the plane analysis, which secured the final composition of low residue flux.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.421-421
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• 2021

도시화, 산업화로 인해 하수처리장 유입하수 내 질소 농도가 증가하면서 그에 따른 부영양화 발생, 수생태계에 독성을 미치는 등의 악영향 또한 증가하게 되었다. 하수 내 고농도 질소를 처리하기 위해 1990년 초 연구가 시작되어 현재 보편적으로 사용되고 있는 생물학적 질소 제거 공정은 산소공급과 외부탄소원 보충 과정에서 상당한 비용이 소요된다. 이와 같은 문제점이 대두됨에 따라 고도의 질소 제거 공정이 요구되면서, 경제적으로 개선이 이루어져 기존의 질산화·탈질 공정보다 효율적인 혐기성 암모늄 산화 공정(ANaerobic AMMonium OXidation, ANAMMOX)이 제안되었다. ANAMMOX 공정은 혐기성 조건 아래 전자공여체와 전자수용체로써 암모니아성 질소와 아질산성 질소를 이용해 질소가스 형태로 질소를 제거하는 공정이다. 질산화·탈질 공정과 비교했을 때, 폭기과정에서의 산소요구량 감소, 외부탄소원 불필요, 질소 제거 과정 단축 등의 장점을 가진다. 본 연구는 수처리공정에서의 ANAMMOX 공정의 적용 가능성을 확인하고, 암모니아성 질소대비 아질산성 질소 비율에 따른 Mainstream ANAMMOX 공정의 효율 비교를 통해 공정의 안정성과 높은 제거효율을 확보할 수 있는 NH₄⁺ 대비 NO₂^- 비율을 도출하는데 목적이 있다. 실험실 규모의 Mainstream ANAMMOX 반응조에 적용한 비율은 선행연구를 비롯한 화학양론식에서 제시된 비율을 바탕으로 산정하였다. 1.00부터 1.30의 전체적인 비율을 Initial과 Advanced 2개의 구간으로 나누어 운전한 결과, 각 구간의 NH₄⁺ 제거효율은 각각 58~86%, 94~99%였다. NH₄⁺ 대비 NO₂^- 비율이 증가함에 따라 공정의 안정성이 확보되고, NH₄⁺ 및 총질소(TN) 제거효율이 증가하는 경향이 나타났다. 본 연구의 결과는 수처리공정에서의 안정적인 ANAMMOX 공정 적용을 유도하고, ANAMMOX 공정의 성능개선을 도모하는 연구의 기초로 활용될 수 있다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.147-147
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• 2017

$TiO_2$는 의료기기, 광촉매, 태양전지 등의 여러 분야에 응용이 가능하여 많은 연구가 진행되어 왔다. 그 중 양극산화를 통하여 수직으로 잘 정렬된 나노튜브는 넓은 반응면적, 높은 전자 전도성 등의 장점으로 그 성능을 더욱 향상 시킬 수 있어 많은 연구자들이 이용하고 있다. 양극산화의 특성상 Ti 기판 위에 형성된 나노튜브의 효용성을 높이기 위하여 기판에서 분리하여 membrane의 형태로 이용하기도 한다. 이런 $TiO_2$ 나노튜브 멤브레인의 이용은 주로 오염물의 분해를 위한 광촉매, 염료감응 태양전지의 전극으로 이용되고 있다. 본 연구는 $TiO_2$ 나노튜브 멤브레인에 기체 동위 원소 분리에 이용되는 HKUST-1, ZIF-8 등과 같은 Metal Organic Frame Work (MOF)을 충진 시켜 극저온에서 수소 동위 원소를 분리 하고 자 하는데 있다. 하지만 MOF를 충진하기 위해서는 기존의 $TiO_2$ 나노 튜브 멤브레인보다 더 넓은 내경과 안정성이 요구되는 바이다. 이를 위하여 본 연구에서는 내경을 수백 나노미터 이상으로 확장하기 위한 전해질, 전류(전압) 조건 등에 대하여 연구 하였다. 또한 멤브레인의 안정적인 제조를 위하여 2-step 양극산화 조건, 열처리 조건 등의 변화를 통하여 그 목적을 달성 하고자 하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.237-237
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• 2012

반도체 소자를 취급하는 반도체 산업은 여러 산업 중에서도 부가가치율이 높은 것의 하나이다. 반도체 공정은 산화막과 질화막은 각각 다양한 두께와 방법으로 제조되고 있으며 CVD, PEALD 이용한 증착 공정을 기반으로 하고 있다. 하지만 양산에서의 많은 문제 요소를 가지고 있다. 첫째, 양적인 실시간과 전구체의 정상상태를 확인 할 수 없으므로 인한 질 적인 저하등을 요소를 가지고 있으며 둘째, 양산 후 남은 전구체를 외관상의 변색, 점도 변화를 통해 변질을 확인하고 전구체를 교체함으로써 엄청난 경제적인 손실과 안정적인 공급에 어려움이 있다. 그러므로 본 연구에서는 reference 전구체와 공정에서 사용된 전구체를 이용하여 Vapor Pressure 측정과 FT-IR (Fourier transform-infrared), QMS을 이용하여 개발된 전구체의 기상 안정성 및 반응성을 실시간으로 진단하여 기존의 전구체와의 차별성을 확인하고 우수한 전구체를 선별하기 위한 연구를 진행하였다. 또한 변화에서의 분자 상태 변형을 진담함으로 인해 기업의 양산의 경제적인 손실을 줄일 수 있을 뿐만 아니라 성장 조건에 따라 전구체 박막 특성을 논의 할 수 있을 것이다.