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Dae Ryook Yang,Seungjong Yeom,Huichan Yun 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.10
L-glutamic acid can be crystallized as metastable α-form and stable β-form crystal. The α-form is desired because of its prismatic shape. Production of α-form of L-glutamic acid by cooling crystallization is not well-defined and α-form solid is commercially not available. In this study, an optimal cooling strategy to selectively produce large and narrowly distributed α-crystals is found by modeling and optimizing the crystallization and polymorphic transformation of L-glutamic acid. The optimal temperature profile is found to be cooling-heating-cooling concept where short nucleation period is followed by growth period in metastable zone. The obtained α-form of L-glutamic acid by optimal strategy had improved mean size, distribution, and purity compared to constant cooling.
Improving Dynamics of Glass pH Electrodes
Dae Ryook Yang,Seungjae Lee,Su Whan Sung,Jietae Lee IEEE 2009 IEEE Sensors Journal Vol.9 No.12
<P>The glass pH electrode has a very large internal resistance and an internal capacitance, exhibiting a relatively large response time. For some applications, the response time needs be shortened. For this purpose, a method to reduce the response time of glass pH electrodes and to diagnose its performance is proposed.</P>
Dae Sung Lee,Dae Ryook Yang,In-Beum Lee,Kun Soo Chang 대한전자공학회 1992 대한전자공학회 학술대회 Vol.1992 No.10
In order to achieve stable and efficient use of energy at iron and steel works, a model for the prediction of supply and demand of electric power system is developed on the basis of the information on operation and particular patterns of electric power consumption. The optimal amount of electric power to be purchased and the optimal fuel allocation for the in-house electric power plants are also obtained by a mixed-integer linear programming(MILP) and a nonlinear programming(NLP) solutions, respectively. The validity and the effectiveness of the proposed model are investigated by several illustrative examples. The simulation results show the satisfactory energy saving by the optimal solution obtained through this reseach.
Jung, Heon,Yang, Dae-Ryook,Joo, Oh-Shim,Jung, Kwang-Deog Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.5
Ternary Cu/ZnO/$Al_2O_3$ catalysts were prepared by a co-precipitation method. The precursor structures were monitored during the aging. The first precipitate structure was amorphous georgeite, which transformed into the unknown crystalline structure. The transition crystalline structure was assigned to the crystalline georgeite, which was suggested with elemental analysis, IR and XRD. The final structure of precursors was malachite. The Cu surface area of the resulting Cu/ZnO/$Al_2O_3$ was maximized to be 30.6 $m^2$/g at the aging time of 36 h. The further aging rapidly decreased Cu surface areas of Cu/ZnO/$Al_2O_3$. ZnO characteristic peaks in oxide samples almost disappeared after 24 h aging, indicating that ZnO was dispersed in around bulk CuO. TOF of the prepared catalysts of the Cu surface area ranges from 13.0 to 30.6 $m^2/g_{cat}$ was to be 2.67 ${\pm}$ 0.27 mmol/$m^2$.h in methanol synthesis at the condition of $250^{\circ}C$, 50 atm and 12,000 mL/$g_{cat}$. h irrespective of the XRD and TPR patterns of CuO and ZnO structure in CuO/ZnO/$Al_2O_3$. The pH of the precipitate solution during the aging time can be maintained at 7 by $CO_2$ bubbling into the precipitate solution. Then, the decrease of Cu surface area by a long aging time can be prevented and minimize the aging time to get the highest Cu surface area.
CCL4 DECOMPOSITION BY GLIDING ARC PLASMA: ROLE OF C2 COMPOUNDS ON PRODUCTS DISTRIBUTION
Indarto, Antonius,Yang, Dae Ryook,Choi, Jae-Wook,Lee, Hwaung,Song, Hyung Keun Taylor Francis 2007 Chemical engineering communications Vol.194 No.8
<P> The goal of this work is to investigate the role of existing C2 compounds in the plasma reactions of carbon tetrachloride (CCl4) decomposition. The experiment of CCl4 decomposition was carried out by gliding arc plasma. The decomposition products were dominated by CO, CO2, and Cl2. The conversion of CCl4 into Cl2 and (CO + CO2) reaches ∼ 50% and ∼ 40%, respectively. Other chlorinated compounds were suspected to be produced, such as COCl, COCl2, and C2 compounds. In order to prove the existence of those compounds, for example, chlorinated C2 compounds, a kinetic simulation was performed and cross-checked with the experimental results to clarify the reactions mechanism.</P>
Lee, Jietae,Lee, Yongjeh,Yang, Dae Ryook,Edgar, Thomas F. American Chemical Society 2018 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.57 No.8
<P>Many methods are available to tune proportional integral (PI) controllers for first order plus time delay (FOPTD) models of overdamped processes. The two asymptotes for small and large ratios of time delays over time constants are easily calculated. These two asymptotes can be used to evaluate and provide guidelines for the performance and application ranges of PI controller tuning rules. By matching these two asymptotes, a simple analytic tuning rule is suggested. For some overdamped processes whose transfer functions have large zero terms, half-order plus time delay (HOPTD) models are found to yield better results than the FOPTD models. Applying the technique of matching two asymptotes, a simple analytic PI controller tuning rule has also been proposed for the HOPTD models. To apply these tuning rules to high order processes with known transfer functions, model reduction methods to obtain the FOPTD and HOPTD models are investigated. Simulation results for empirical and full models of processes show the performances of the proposed model reduction methods and tuning rules.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/iecred/2018/iecred.2018.57.issue-8/acs.iecr.7b03966/production/images/medium/ie-2017-039664_0009.gif'></P>