• Korean Chemical Engineering Research
• /
• v.50 no.5
• /
• pp.766-771
• /
• 2012

PC (polycarbonate) is one of the widely used engineering plastics. Polycarbonate (PC) is traditionally produced by the reaction of phosgene and bisphenol-A. This phosgene process has the disadvantage as the high toxicity and corrosiveness of phosgene. The main point of focus to overcome the disadvantage of phosgene based process has been a route through dimethyl carbonate (DMC) to diphenyl carbonate (DPC). In this paper, for the DPC synthesis reaction using PBO as a catalyst, the effect of reaction temperature, reactant ratio, catalyst concentration on the reaction yield was investigated. A kinetic model for the DPC synthesis reaction was proposed and kinetic parameters for the proposed model was determined from batch reactor experiments. The predicted results by the proposed model were in good agreement with the experimental results.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1994.04a
• /
• pp.238-238
• /
• 1994

녹용의 알려진 약리작용 중에서 녹용의 상용량 투여에 의해 나타나는 것은 강장작용과 창상치유작용이므로 이러한 작용이 진정한 녹용의 효능으로 간주될 수 있으나 이러한 작용을 생물활성 검색법으로 활용하여 녹용의 유효성분을 검색하기에는 재현성과 간편성이라는 면에서 어려운 점이 없지 않다. 녹용의 효능이 생체의 질소평형이 음의 방향으로 진행되었을 때 이를 정상 수준으로 복귀시키는 생물활성에 기인할 것이라는 가정하에서, 실험적으로 생체내 질소편형을 음의 방향으로 전환시킬 수 있는 급성기 반응 (acute-phase responce)을 야기시킨 다음 녹용의 효과를 연구하였다. 흰쥐의 급성기 반응물질 (acute-phase reactants, APR) 중에 서 positive ARP인 ceruloplasmin, $\alpha$-cysteine pretense inhibitor(= T-kininogen)는 비색정량법으로 간편하게 측정될수 있음에 착안하여 이 단백질을 지표로 삼아 turpentine oil로 급성 염증을 유발시킨 전후에 녹용 물추출액의 효과를 측정하였다. 그 결과 녹용의 상용량에서 괴소 4일 이상 경구투여한 흰쥐에서 급성 염증유발 후 4일에서 ceruloplasmin 의 혈중농도가 현저히 감소함을 알수 있었다. 급성 염증 유발후 녹용의 경구투여한 실험에서는 적어도 녹용 상용량의 3배 이상을 투여하여야 만 ceruloplasmin 혈중 농도를 감소시킬 수 있었다. 본 연구에서 수립된 생물활성을 이용하여 녹용의 유효 성분을 단리할 계획이다.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2007.05a
• /
• pp.370-374
• /
• 2007

난분해성 유기물 처리에 적절한 불용성 전극을 선정하고 성능을 평가하기 위하여 1-3 성분계 전극을 이용하여 양이온 염료인 Rhodamine B (RhB)의 전기분해 처리에서 다음의 결론을 얻었다. 1) 반응 2분 후 RhB 농도를 고찰한 결과 RhB 농도감소는 Ru-Sn-Ti/Ti ${\fallingdotseq}$ Ru-Sn-Sb/Ti > Ir-Sn-Sb/Ti > Sn-Sb/Ti > Ru/Ti > Ir/Ti > Pt/Ti의 순서로 나타나 3성분계 > 2성분계 > 1성분계 전극의 순서로 나타났다. Ru를 사용한 전극이 Ir을 사용한 전극보다 1성분계와 3성분계 모두 성능이 우수한 것으로 나타났다. 기존 전극으로 가장 많이 사용되고 있는 Pt 전극의 성능은 가장 떨어지는 것으로 나타났다. 2) RhB 초기 농도감소 속도는 전극 간격이 좁은 것이 유리한 것으로 나타났으나 최종 농도는 비슷하였다. 전극 간격이 좁을수록 전력 면에서 유리한 것으로 나타났다. 면적이 큰 전극이 초기 반응이 빠르고 나타났고 최종농도도 약간 낮은 것으로 나타났으나 차이는 크지 않았다. 면적이 좁은 경우 반응면적이 적지만 전류밀도가 높기 때문에 성능의 차이는 크지 않으나 면적이 적은 전극의 경우 요구 전력량이 높기 때문에 적절한 크기의 전극이 필요한 것으로 사료되었다.

• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.770-775
• /
• 2001

Numerical calculation has been performed to investigate the fluid flow, heat transfer and local mass fraction of chemical species in the MOCVD (metalorganic chemical vapor deposition) manufacturing process. The mixing of reactants (trimethylgallium with hydrogen gas and ammonia) was presented by the concentration of each reactants to predict the uniformity of film growth. Effects of inlet size, location, mass flow rate and susceptor/cold wall tilt angle on the concentration were reported. The newly developed reactor, that precursors were supplied at separated inlet to prevent from premixing, was investigated to obtain the quantitative verification. As a results, the optimum mass flow rate, wall tilt angle and inlet conditions were proposed.

• JOURNAL OF ELECTRICAL WORLD
• /
• s.271
• /
• pp.63-68
• /
• 1999

오존(Ozone) 이용의 역사는 19세기의 음료수 살균으로 거슬러 올라간다. 그후 선택적 화학반응을 이용한 화학합성, 1970년대의 공해대책시대의 배수(排水)탈색(脫色)$\cdot$탈취(脫臭), 수질 유지로 진전되어 왔다. 최근에는 특히 여러 가지 제품의 제조프로세스 등에서 환경부하가 적고 생산성이 좋은 프로세스가 요청되고 있어, 그러한 관점에서도 분해 후 무해한 산소로 되돌아가는 산화제인 오존의 활용이 기대를 모으고 있다. 기술면에서는 오존 단독처리에 더하여 과산화수소나 자외선과의 병용에 의한 촉진산화처리, 생물처리와의 병용처리 등 반응속도의 향상, 비처리물질의 확대를 겨냥한 새로운 반응기술, 대용량$\cdot$고농도 오조나이저(Ozonizer), 클린 오조나이저 등, 적용분야의 확대를 가능케 하는 오존발생기술, 하드웨어 기술의 진보가 현저하다. 최근에는 이 최신기술과 다른 기술과의 복합에 의한 새로운 제안도 많이 나오고 있으며, 수처리를 중심으로 신(新)프로세스에 더하여, 예를 들면 펄프 표백(漂白) 프로세스와 반도체 제조프로세스 등에의 적용이 급속하게 확대되는 경향이 있어, 바야흐로 새로운 분야를 개척하게 됨으로써 고객의 요구가 다시 신기술을 일으키는 쪽으로 돌아가고 있다고 할 수 있다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.4
• /
• pp.480-492
• /
• 1996

AZO (Aluminum doped Zinc Oxide) transparent conducting thin films were fabricated by reactive DC mangnetron sputtering method using zinc target containing 2 wt% of Al. Transition range with optimum transmittance and conductivity was obtained by contrlling partial pressure of reactive oxygen gas. Sputtering condition for this transition range could be kept stable by regulating the target voltage. According to XRD analysis, there was only one peak for (002) plane in AZO films and the films deposited in transition range.

• Journal of radiological science and technology
• /
• v.32 no.2
• /
• pp.205-212
• /
• 2009

The response correction factor ( h) is a factor to convert the response of the chamber in solid phantom to the response in water. In RW3 solid phantom, the dependency of beam quality and depth for high energy X-rays are known characteristics, however the dependency of field size, SSD, and chamber type are unknown. In this work we have studied the unknown characteristics on the dependency of response correction factor. The farmer type chamber (FC65G) and small chamber (CC13) were used and two beam qualities of 6 and 15 MV were evaluated. The measured response correction factors at the depth of 5 cm and 10 cm were h = 1.015 and 1.021 for 6 MV X-rays, and h = 1.024 and 1.029 for 15 MV X-rays. In conclusion the response correction factor did not depend on the field size and SSD while depending on the beam quality and depth. In the chambers, there are small differences between the two chambers used in this study but we think additional study for more chambers should be required. The results in this study can be used for analyzing the measured values from ionization chamber dosimetry in RW3.

• Journal of Life Science
• /
• v.24 no.12
• /
• pp.1364-1370
• /
• 2014

Ascorbic acid (AA) is a multifunctional metabolite in plants that is essential for plant development and growth. We examined the effect of AA, an antioxidant, on the gravitropic response of primary roots in maize. The application of $10^{-3}$ M AA to the elongation zone did not affect the gravitropic response and slightly inhibited the root growth. However, treatment with both $10^{-5}$ M and $10^{-3}$ M AA at the root tip increased the gravitropic response and inhibited root growth. Differences in indole-3- acetic acid (IAA) activity between the upper and lower hemispheres of the root resulted in differential elongation along the horizontal root. Roots are extremely sensitive to IAA, and increasing the amount of IAA in the lower hemisphere of the root inhibited elongation. Therefore, we examined the effect of IAA in the presence of AA. The inhibitory effect of AA on the gravitropic response was greater in combination with IAA. To understand the role of AA in the regulation of root growth and the gravitropic response, we measured ethylene production in the presence of AA in the primary roots of maize. AA stimulated ethylene production via the activation of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene, which regulates the conversion of ACC to ethylene. These results suggest that AA alters the gravitropic response of maize roots through modification of the action of ethylene.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.2
• /
• pp.135-146
• /
• 2020

To define an interface in a conventional level-set method, an analytical function must be revealed for an interfacial geometry. However, it is not always possible to define a functional form of level sets when interfaces become complex in a Cartesian coordinate system. To overcome this difficulty, we have developed a new level-set formalism that discriminates the interior from the exterior of a CAD modeled interface by parameterizing the stereolithography (STL) file format. The work outlined here confirms the accuracy and scalability of the hydrodynamic reactive solver that utilizes the new level set concept through a series of tests. In particular, the complex interaction between shock and geometrical confinements towards deflagration-to-detonation transition is numerically investigated. Also, a process of flame spreading and damages caused by point source detonation in a real-sized plant facility have been simulated to confirm the validity of the new method built for reactive hydrodynamic simulation in any complex three-dimensional geometries.

• Journal of Intelligence and Information Systems
• /
• v.29 no.4
• /
• pp.69-90
• /
• 2023

The purpose of this study is to evaluate the service attributes and consumer reactions of telemedicine apps in South Korea and visualize their differentiation by constructing positioning maps. We crawled 23,219 user reviews of 6 major telemedicine apps in Korea from the Google Play store. Topics were derived by BERTopic modeling, and sentiment scores for each topic were calculated through KoBERT sentiment analysis. As a result, five service characteristics in the application attribute category and three in the medical service category were derived. Based on this, a two-dimensional positioning map was constructed through principal component analysis. This study proposes an objective service evaluation method based on text mining, which has implications. In sum, this study combines empirical statistical methods and text mining techniques based on user review texts of telemedicine apps. It presents a system of service attribute elicitation, sentiment analysis, and product positioning. This can serve as an effective way to objectively diagnose the service quality and consumer responses of telemedicine applications.