• Journal of the Korean Chemical Society
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• v.64 no.3
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• pp.175-188
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• 2020

The purpose of this study was to analyze chemistry textbooks and teachers' guidebooks from the perspective of 'Ignorance', one of the important features of model. This is because the emphasis is on developing modeling capabilities for students in the 2015 Revised Curriculum. For this, Arrhenius model and Brønsted-Lowry model were selected as acid and base models in neutralization reaction which are important contents in chemistry curriculum. The analysis criteria of this study were extracted by analyzing previous studies and four general chemistry textbooks dealing with 'Ignorance' related to acid and base neutralization reaction. Based on the analysis criteria, we analyzed nine chemistry I textbooks and teacher's guides and six chemistry II textbooks and teacher's guides of the 2015 revised curriculum. In addition, we analyzed contents of four chemistry I textbooks and teacher's guides and three chemistry II textbooks and teacher's guides in the 2009 revised curriculum for comparison according to revised curriculums. We analyzed the contents related to the concept of 'neutralization reaction', 'neutrality', 'quantitative relation of neutralization reaction', 'degree of ionization', and 'ionization constant'. Based on the results of this study, we proposed a way to present 'Ignorance' of the models in teachers' guidebooks that chemistry teachers can understand 'Ignorance' of model and teach modeling capabilities for students.

• Journal of Mechanical Science and Technology
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• v.19 no.9
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• pp.1695-1705
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• 2005

Reaction wheels and thrusters are commonly used for the satellite attitude control. Since satellites frequently need fast maneuvers, the minimum time maneuvers have been extensively studied. When the speed of attitude maneuver is restricted due to the wheel torque capacity of low level, the combinational use of wheel and thruster is considered. In this paper, minimum time optimal control performances with reaction wheels and thrusters are studied. We first identify the features of the maneuvers of the satellite with reaction wheels only. It is shown that the time-optimal maneuver for the satellite with four reaction wheels in a pyramid configuration occurs on the fashion of single axis rotation. Pseudo control logic for reaction wheels is successfully adopted for smooth and chattering-free time-optimal maneuvers. Secondly, two different thrusting logics for satellite time-optimal attitude maneuver are compared with each other: constant time-sharing thrusting logic and varying time-sharing thrusting logic. The newly suggested varying time-sharing thrusting logic is found to reduce the maneuvering time dramatically. Finally, the hybrid control with reaction wheels and thrusters are considered. The simulation results show that the simultaneous actuation of reaction wheels and thrusters with varying time-sharing logic reduces the maneuvering time enormously. Spacecraft model is Korea Multi-Purpose Satellite (KOMPSAT)-2 which is being developed in Korea as an agile maneuvering satellite.

• Journal of Life Science
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• v.16 no.2 s.75
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• pp.323-327
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• 2006

The Formation of acrylamide was studied in Maillard model reaction systems based on asparagine-glucose. The mixture of asparagine and glucose in equal molar ratio, and then heated at 125, 150, 175 and $200^{\circ}C$ for 10, 20 and 30 minute, respectively. The reaction products were extracted with ethyl acetate and methanol, and then isolated and detected on FFAP capillary column and HP-5MS 5% phenyl methyl siloxane column by using GC/MS. Acrylamide was detected only from methanol extracts and on FFAP capillary column, at retention time 23.53 min., and the detection limit was 4.6 ng. Acrylamide content mainly increased with increasing temperature and processing time till $175^{\circ}C$, therefore, maximal acrylamide formation occurred at $175^{\circ}C$ for 10 minute ($116{\mu}g/g$), while, above $175^{\circ}C$, higher temperatures or prolonged processing times caused a decrease of acrylamide levels, finally disappeared at $200^{\circ}C$ for 30 minute. Three major compounds were identified as 1,3-dihydroxypropanone, 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyrane-4-one and 5-hydroxymethylfurfural, and three minor compounds also as 5-methylfurfural, 2-acetylpyrrole and N,N-dimethylcyclohexamine, from ethyl acetate or methanol extracts on FFAP or HP-5MS capillary column.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.387-393
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• 1995

Diffusion coefficients of moisture and solid, reaction rate constants of carotene destruction, and the fitness of drying models for moisture transfer were determined to study the characteristics of mass transfer during osmotic dehydration. Moisture loss and solid gain were increased with increase of temperature and concentration; temperature had higher osmotic effect than concentration. Diffusion coefficient showed similar trend with osmotic effect. Diffusion coefficients of solids were larger than those of moisture because the movement of solid was faster than that of moisture at the high temperature. Reaction rate constants were affected to the greater extent by concentration changes than by temperature changes. Arrhenius equation was applied to determine the effect of temperature on diffusion coefficients and reaction rate constants. Moisture diffusion required high activation energy in $20^{\circ}Brix$, while relatively low in $60^{\circ}Brix$. To predict the diffusion coefficients and reaction rate constants, a model was established by using the optimum functions of temperature and concentration. The model had high $R^2$ value when applied to diffusion coefficients, but low when applied to reaction rate constants. Quadratic drying model was most fittable to express moisture transfer during drying. In conclusion, moisture content of carrots could be predictable during the osmotic dehydration process, and thereby mass transfer characteristics could be determined by predicted moisture content and diffusion coefficient.

• Journal of Korea Multimedia Society
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• v.10 no.4
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• pp.527-536
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• 2007

This paper proposes a 3D fashion design system that generates a 3D clothes model by using 2D patterns of clothes and drapes the 3D clothes model on a 3D human model. In the proposed system, 2D patterns of clothes are designed by selecting comer points of 2D mesh. After designing 2D patterns, a 3D clothes model is designed by describing the control points to be connected between 2D patterns. The proposed system reads a 3D human body model file and the designed 3D clothes model and creates a 3D human model putting on the clothes by using the mass-spring model based physical simulation. It calculates collision and reaction between the triangles of human body model and those of clothes for realistic simulation. Because the number of triangles is very large, the collision and reaction processing need a lot of time. To solve this problem, the proposed system decreases the number of collision and reaction processing by using the Octree space subdivision technique. It took a few seconds for generating a 3D human model putting on the designed 3D clothes.

• The KIPS Transactions:PartA
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• v.13A no.4 s.101
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• pp.371-380
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• 2006

This paper utilizing model picture of finished clothes in fashion design field various material (textile fabrics) doing Draping directly can invent new design, and do not produce direction sample or poetic theme width and confirm clothes work to simulation. Also, construct database about model and material image and embodied system that can confirm Mapping result by real time. And propose clothes simulation system to dress to 3D human body model of imagination because using several cloth pieces first by process to do so that can do simulation dressing abstracted poetic theme width to 3D model here. Proposed system creates 3D model who put clothes by physical simulation that do fetters to mass-spring model after read 3D human body model file and 2D foundation pattern file. System of this treatise examines collision between triangle that compose human body model for realistic simulation and triangle that compose clothes and achieved reaction processing. Because number of triangle to compose human body is very much, this collision examination and reaction processing need much times. To solve this problem, treatise that see could create realistic picture by method to diminish collision public prosecutor and reaction processing number, and could dress clothes to imagination human body model within water plant taking advantage of Octree space sharing techniques.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.168-176
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• 1989

Theoretical analysis of HF chemical laser models are performed through chemical reaction kinetics, gain process and stimulated emission process. A chemical laser of F+$H_2$ nonchain reaction is investigated through V-R transitions of excited HF for vibrational levels up to v = 3 and rate equations including nonchain pumping and deactivation. On this analysis, harmonic and anharmonic vibrational levels are considered separately and the results of the corresponding power calculations are showed very small difference between the two. Output powers are calculated with variation of temperature and initial concentrations of $H_2$. A HF chemical laser of $H_2$+$F_2$ chain reaction is also simulated with a premixed initial condition. Results of present model calculations are satisfactory through comparison with detailed calculations reported by others.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.125-132
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• 2006

Transient kinetics of $NH_3$ adsorption/desorption and of SCR(selective catalytic reduction) of NO with $NH_3$ were studied over vanadium based catalysts, such as $V_2O_5/TiO_2$ and $V_2O_5-WO_3/TiO_2$. In the present catalytic reaction process, NO adsorption is neglected while $NH_3$ is strongly chemisorbed on the catalytic surface. Accordingly, it is ruled out the possibility of a reaction between strongly adsorbed $NH_3$ and NO species in line with the hypothesis of an Eley-Rideal mechanism. The present kinetic model assumes; (1) non-activated $NH_3$ adsorption, (2) Temkin-type $NH_3$ coverage dependence of the desorption energy, (3) non-linear dependence of the SCR reaction rate on the $NH_3$ surface coverage. Thus, the surface heterogeneity for adsorption/desorption of $NH_3$ is taken into account in this model. The present study extends the pure chemical kinetic model based on a powdered-phase catalytic system to the chemico-physical one applicable to a realistic monolith reactor.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.385-395
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• 2002

A stochastic model using FOEA(First-Order Error-Analysis) and Monte Carlo Method is developed to predict water quality variation in a river. A sensitivity analysis using influential matrix is performed to determine the significant reaction coefficients. Also the BFGS (Broyden-Fletcher-Goldfarb-Shanno) optimization method is applied to estimate the optimal values of the major reaction coefficients. The developed stochastic model is applied to the real study reach and the results are agreed well with those of deterministic analysis. The process for analyzing the uncertainties of the discharge, water quality and reaction coefficients of headwater and tributaries is included in the model to estimate the influence on the water quality variation at downstream. The extents of contribution of the uncertainties influencing on the total uncertainty can be evaluated from the results of the model.

• The Korean Journal of Pain
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• v.20 no.2
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• pp.92-99
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• 2007

Background: A correlation between a T-type voltage activated calcium channel (VACC) and pain mechanism has not yet been established. The purpose of this study is to find out the effect of ethosuximide and mibefradil, representative selective T-type VACC blockers on postoperative pain using an incisional pain model of rats. Methods: After performing a plantar incision, rats were stabilized on plastic mesh for 2 hours. Then, the rats were injected with ethosuximide or mibefradil, intraperitoneally and intrathecally. The level of withdrawal threshold to the von Frey filament near the incision site was determined and the dose response curves were obtained. Results: After an intraperitoneal ethosuximide or mibefradil injection, the dose-response curve showed a dose-dependent increase of the threshold in a withdrawal reaction. After an intrathecal injection of ethosuximide, the threshold of a withdrawal reaction to mechanical stimulation increased and the increase was dose-dependent. After an intrathecal injection of mibefradil, no change occurred in either the threshold of a withdrawal reaction to mechanical stimulation or a dose-response curve. Conclusions: The T-type VACC blockers in a rat model of postoperative pain showed the antihyperalgesic effect. This effect might be due to blockade of T-type VACC, which was distributed in the peripheral nociceptors or at the supraspinal level. Further studies of the effect of T-type VACC on a pain transmission mechanism at the spinal cord level would be needed.