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- 저자 : Sangwha Lee (검색결과 10 건)
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Mass Transfer Effect on the Photocatalytic Activity of UV/TiO₂ Packed-Bed System
Lee, Sangwha,Lee, Kisay 한국공업화학회 2004 Journal of Industrial and Engineering Chemistry Vol.10 No.3
Effects of mass transfer on photocatalytic activity were investigated using a recirculated feed solution (20 - 500 mL/min) in a UV/Ti0₂ packed-bed photoreactor. The rate of phenol disappearance was significantly increased as the recirculation rate was raised up to 300 mL/min and reached a plateau beyond 400 mL/min. We confirmed that the degradation rate was influenced by the convective mass transfer of phenol from the bulk solution to the external surface of the catalysis particles. Other factors, such as solution pH and initial concentration, exhibited clear influences on the photocatalytic activity of the UV/TiO₂ packed-bed system. Assumin a constant intrinsic kinetic coefficient, the ratio of effective catalyst surface area to reactor volume, aexp (㎠/㎤), was estimated to be on the order of by the resistance-in-series model of rate constants. The obtained low a values indicate that only a small fraction of the surface area was effectively illuminated by the radiant source in the present reactor configuration and that improving the a value should be considered as one of the parameters for optimizing photoreactor design.
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The Patriarchy in China : An Investigation of Public and Private Spheres
Lee, Sangwha Ewha Womans University Press 1999 Asian Journal of Women's Studies(AJWS) Vol.5 No.1
This study is a historical and conceptual investigation into how the division of public and private spheres is significant in the development of Chinese patriarchy. The distinctive characteristics of the concepts, public and private, in Confucian traditions are found in the ideal of jiaguo tonggou and the rule of nei / wai (inside / outside). The political ideal of jiaguo tonggou literally means that the family and the state have the same structure. Furthermore, the principle of nei / wai (inside / outside) is a rule that rigorously classified people's everyday activities, roles, and living space according to sex. This inside-outside dichotomy appears to be analogous to the public-private opposition in Western feminist thought. With this dichotomy, the lives of women and men were separated within their families and women were consistently excluded from the public sphere in ancient China. After the Communist revolution, however, China has made remarkable strides. The revolutionary shift, however, had its own limitations insofar as the new democratic patriarchal system that emerged was a mixture of socialist ideas and a deep-rooted traditional patriarchy that it was unable to rid itself of. There is evidence that in the recent social discourse of "women return home," emerging after the reform eras of the 1980s, the state has sought to sought to restructure society according to the principles of a socialist market economy and send women back to the domestic sphere. Perhaps the question of the separation between public and private spheres in itself is less important than the questions of whether women are active agents of reform, whether they are empowered enough in the process, and whether they are free to make choices about their activities. However, the current controversy over "women return home" in China is still evolving, and these questions need to be explored further in the future.
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[멀티미디어] 뉴로 네트워크에서 코사인 모듈화 된 가우스함수의 다항식과 계단함수의 근사
이상화(Sangwha Lee) 大韓電子工學會 2012 電子工學會論文誌-CI (Computer and Information) Vol.49 No.2
본 논문에서는 CosGauss라고 하는 코사인함수로 모듈화 된 가우시안 활성화함수가 뉴로 네트워크에서 다항식과 계단함수의 근사에 사용될 수 있음을 증명한다. CosGauss 함수는 시그모이드, 하이퍼볼릭 탄젠트, 가우시안 활성화 함수보다 더 많은 범프(bump)를 구성 할 수 있다. 이 함수를 캐스케이드 코릴레이션 뉴로 네트워크 학습에 사용하여 벤치마크 문제인 Tic-Tac-Toe 게임과 아이리스(iris) 식물 문제와 실험하고 여기에서 얻어진 결과를 다른 활성화 함수를 사용한 결과와 비교 분석한다. We present here a new class of activation functions for neural networks, which herein will be called CosGauss function. This function is a cosine-modulated gaussian function. In contrast to the sigmoidal-, hyperbolic tangent- and gaussian activation functions, more ridges can be obtained by the CosGauss function. It will be proven that this function can be used to aproximate polynomials and step functions. The CosGauss function was tested with a Cascade-Correlation-Network of the multilayer structure on the Tic-Tac-Toe game and iris plants problems, and results are compared with those obtained with other activation functions.
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Studies of NO Adsorption on Proton-Irradiated MgO Surfaces
Jeonggil Lee,Jae-yong Kim,Jae-Kyun Jeon,Kyeryung Kim,Sang-pil Youn,Sangwha Lee,Youn Man Lee,Jeongha Kim,신관우 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3
Recently, adsorption studies of gases for various adsorbents have been intensive because they are useful in probing the fine structure of the surface. Meso-sized MgO(100) powder was irradiated by a proton beam with a high energy of 35 MeV. Transmission electron microscope (TEM) investigations revealed no structural change of the MgO powders after irradiating with the proton beam. After proton beam irradiation, NO gas isotherm adsorption data were recorded from the same sample below the triple point (109.8 K). The results revealed that there was no hint of multi-isotherm step formation, which indicates the creation of an atomic layer of NO molecules. Instead, only a monolayer of NO molecules was obtained. It is understood that pre-existing unwanted impurities, such as water and carbon-related organic gases, hinder the formation of atomic layers in a regular fashion on the MgO powder surface. By comparing NO adsorption data from the pure and the proton-irradiated MgO samples, we were able to calculate the surface-related thermodynamic characteristics, including the 2-dimensional compressibility and the heat of adsorption. Recently, adsorption studies of gases for various adsorbents have been intensive because they are useful in probing the fine structure of the surface. Meso-sized MgO(100) powder was irradiated by a proton beam with a high energy of 35 MeV. Transmission electron microscope (TEM) investigations revealed no structural change of the MgO powders after irradiating with the proton beam. After proton beam irradiation, NO gas isotherm adsorption data were recorded from the same sample below the triple point (109.8 K). The results revealed that there was no hint of multi-isotherm step formation, which indicates the creation of an atomic layer of NO molecules. Instead, only a monolayer of NO molecules was obtained. It is understood that pre-existing unwanted impurities, such as water and carbon-related organic gases, hinder the formation of atomic layers in a regular fashion on the MgO powder surface. By comparing NO adsorption data from the pure and the proton-irradiated MgO samples, we were able to calculate the surface-related thermodynamic characteristics, including the 2-dimensional compressibility and the heat of adsorption.
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Bu, Yanru,Lee, Sangwha American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.8
<P>Gold (Au), silver (Ag), and Ag<SUB>core</SUB>Au<SUB>shell</SUB> nanoparticles (NPs) were explored as optical sensing agents for the sensitive detection of dopamine (DA) neurotransmitters in surface-enhanced Raman scattering (SERS) measurements. In these colloidal systems, dopamine (DA) molecules played as a cross-linker between M NPs (Au or Ag NPs), allowing them to reside in the confined junctions (i.e., hot spots) between aggregated NPs. The progressive addition of DA molecules (from 1 × 10<SUP>–6</SUP> to 1 × 10<SUP>–3</SUP> M) consequently decreased a primary absorption peak attributed to the characteristic M NPs and generated a secondary absorption peak at longer wavelengths attributed to heavily aggregated M NPs formed by molecular bridging effects of DA molecules at high concentrations. The aggregation degree of M NPs was also dependent on the surface states of Au and Ag NPs, i.e., DA molecules with positive amine groups induced more aggregations of Au NPs in comparison to Ag NPs with less negative charges. As the final outcome, Au NPs demonstrated higher sensitivity in SERS detection of DA at low concentrations (1 × 10<SUP>–7</SUP> to 1 × 10<SUP>–5</SUP> M), whereas Ag NPs exhibited the stronger Raman signals of DA molecules at high concentrations (1 × 10<SUP>–4</SUP> to 1 × 10<SUP>–3</SUP> M). Besides, Ag<SUB>core</SUB>Au<SUB>shell</SUB> NPs with the lowest surface coverage of Au shell exhibited more sensitive and stronger SERS activity for DA molecules than that of singular Au NPs, probably due to the combined contribution by Ag core with strong SERS intensity and Au shell with high SERS sensitivity.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-8/am300750s/production/images/medium/am-2012-00750s_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am300750s'>ACS Electronic Supporting Info</A></P>
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The optical properties of gold nanoparticles with dopamine at different hydrogen ion concentration.
Bu, Yanru,Lee, Sangwha American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.6
<P>In this work, gold nanoparticles (Au NPs) were prepared by citrate reduction method, and the Surface-Enhanced Raman Scattering (SERS) intensities of these colloidal solutions with dopamine (DA) were compared at different hydrogen ion concentration (pH). The charged states of Au NPs and DA molecules at different pH were critical factors for the SERS intensity by affecting NPs aggregation degree via DA bridging-effect. The results showed that the SERS enhancement was strongest at intermediate pH ranges (pH 7-9), in which the Au NPs was sufficiently stable and the electrostatic interaction between the Au NPs and the DA molecules was appropriate, together with a slightly aggregating.</P>
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촉매의 종류에 따른 lactic acid의 에스테르화 반응의 연구
한지윤,김종화,이상화 한국공업화학회 2003 응용화학 Vol.7 No.2
Esterification of lactic acid with butanol catalyzed by Amberlyst-type ion exchange resin and sulfuric acid was carried out in a batch reactor under temperature ranges of 100∼130℃. The reaction rate was significantly influenced by water contents (wt%), alcohol/lactic acid mole ratio, kinds of catalysts and reaction temperature. Esterification of the lactic acid with butanol is promoted by removing residual water continuously using recycle reactive distillation(above 100℃). The presence of water strongly inhibits the conversion of lactic acid to butyl lactate due to equilibrium-limited reaction. Other operation parameters were also investigated in terms of lactic acid conversion.
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