• Polymer(Korea)
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• v.24 no.2
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• pp.182-193
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• 2000

Molar cyclization equilibrium constant (K$_{x}$) of poly(alkylene terephthalate) (PAT) cyclics was calculated by the Monte Carlo simulation on the basis of rotational isomeric state (RIS) model. The experimental $K_{x}$ of PAT cyclics, which was not clearly explained by the Jacobson-Stockmayer theory and the method of Flory, Suter, and Mutter however, was explained well by the direct computational method with the reaction radius ${\gamma}$=0.5 < ${\gamma}^{2}$> $^{1/2}$. The effect of PAT conformation on $K_{x}$ of PAT cyclics was investigated by changing its statistical weight parameters, ${\sigma}_{1}$ and ${\sigma}_{2}{\cdot}K_{x}$ of PAT cyclics obtained by the direct computation method with various radii and the radius ${\gamma}$=0.5 < ${\gamma}^{2}$> $^{1/2}$ was slightly changed with ${\sigma}_{1}$ and ${\sigma}_{2}$. Consequently, it was concluded that $K_{x}$ of PAT cyclics is strongly dependent on the configuration of each PAT and affected by the change of its conformation to some extent.

• Journal of the Korea Computer Graphics Society
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• v.7 no.4
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• pp.9-18
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• 2001

There was much previous work to represent effects which are used in the real world paintings. In case of Western paintings like as watercolor or oil painting, largely conversion techniques from photo images were researched. However, in case of Oriental paintings, the development of a conversion technique is not easy because a few strokes are used to represent objects. Then, model-based approach was studied to draw Oriental paintings. In this paper, a model-based approach for Oriental paintings is described. In our model, to represent the diffusion effects, LEM(Local Equilibrium Model) is proposed. LEM is a method to calculate the movement of water and ink effectively. Also, a layer model for paper is proposed to discriminate wet or dry state. And a brush model to draw strokes is described.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.285-291
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• 2014

This paper is related to the improvement of efficiency for high performance centrifugal pumps by reducing leakage loss, which is achieved by applying the grooved seal as a non-contact seal to the pumps. Various combinations of grooved seal types, including the spiral and the parallel groove in the rotor and/or in the stator, were tested by the experiment. And the corresponding hydraulic performance and the magnitude of axial thrust were measured and calculated for ten cases. From the results, the type with the spiral groove(spiral angle : $0.98^{\circ}$) in both the rotor and the stator was found to be most effective. In this case, the head and the efficiency were improved from the original design by 2.1% and 2.3% respectively at design capacity($340m^3/h$), and the axial thrust was decreased by 10%.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1222-1228
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• 2020

The adsorption and ion exchange properties of tin phosphate were studied in an aqueous solution of KCl, varing the pH and metal ion concentration in the solution. The data were explained on the basis of chemical equilibrium. Tin phosphate behaved as an acidic ion exchanger and had an adsorption selectivity toward the bivalent transition metal ions in the following order : Cu⁺² > Co⁺² > Ni⁺². As in the case of a weekly acidic exchanger, the change in hydration of metal ions played the dominant role in determining the selectivity of tin phosphate. In all cases the extent of adsorption increased with an increase in temperature and concentration. The apperance of irregular kinks in the titration curves justified the presence of several exchangeable adsorption sites with different pKa values.

• Journal of the Korean Society of Food Science and Nutrition
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• v.11 no.1
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• pp.37-43
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• 1982

Constant rate period, falling rate period and diffusion coefficient using filefish fillet as sample during drying in hot air drier were determined under controlled conditions of temperature, humidity and air velocity. Drying rate curve consisted of a short period of constant rate and two stages of falling rate period. When 1 to 3m/see of air velocities were applied, diffusion coefficients were in the range of 1.9130 to $2.6187\;{\times}\;10^{-6}\;\textrm{cm}^2/sec$ at $50^{\circ}C$. 2.4806 to $3.5342\;{\times}\;10^{-6}\;\textrm{cm}^2/sec$ at $60^{\circ}C$ and 4.3405 to $5.3042\;{\times}\;10^{-6}\;\textrm{cm}^2/sec$ at $70^{\circ}C$, respectively. Available lysine content was decreased by 15%. 16% and 20% in the fillet dried at $50^{\circ}C$, $60^{\circ}C$ and $70^{\circ}C$, respectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.1 no.1
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• pp.81-92
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• 2003

In order to predict the dynamic behaviors of uranium and cobalt in a fixed bed at various influent pH values of liquid waste, the adsorption system is regarded as a multi-component adsorption between each ionic species in the solution. Langmuir isotherm parameters of each species were extracted by incorporating equilibrium data with the solution chemistry of the uranium and cobalt using IAST. Prediction results were in good agreement with the experimental data, except for a high concentration and pH. Although there was some limitations in predicting the cobalt adsorption, this method may be useful in analyzing a complex adsorption system where various kinds of ionic species exist in a solution.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.174-179
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• 1992

Reaction of aniline and iodine in$CHCl_3,\;CH_2Cl_2 : CHCl_3$(1 : 1), and $CH_2Cl_2$ has been studied kinetically by using conductivity method, Pseudo first-order rate constants ($k_{obs}$) and second-order rate constants ($k_{obs}$/[aniline]) are dependent on the aniline concentration. Second-order rate constants obtained were increased with increasing aniline concentration. We analysed these results on the basis of formation of charge transfer complex as reaction intermediate. From the construction of react ion scheme and derivation of rate equation, we calculated equilibrium constants and activation parameters for the formation and transformation of charge transfer complex. The equilibrium constants were decreased by an increase in the dielectric constant of the solvent and the value is 1.7-3.7$M^{-1}$. The rate of transformation are markedly affected by the solvent polarity. ${\Delta}H^{\neq}$ is about 14.2kJ/mol, and ${\Delta}S^{\neq}$ is large negative value of -243J/mol K.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1337-1348
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• 1990

Estimations of the thermodynamic properties are made for the selected binary non-azeotropic refrigerant mixtures including R13B1/R114, R22/R114, R12/R114, R152a/R114, R13B1/R152a and R13B1/R12 using the Peng-Robinson equation of state and mixing rules. In this study, we find that the binary interaction coefficients for the above mixtures have an effect upon the vapor-liquid equilibria and the thermodynamic properties. As the binary interaction coefficient becomes larger, the deviation from the idealized model, say, Raoult`s rule, is obvious. A correlation is proposed to relate the binary interaction coefficient to the difference between the dipole moments op each pure refrigerant. Vapor-liquid equilibrium are also accurately estimated using the binary interaction coefficient. Pressure-enthalpy and temperature-entropy relations are plotted for a certain composition ratio of each refrigerant mixture. Results show that the estimating method in this study can be applied to the investigation of the thermodynamic properties for the binary non-azeotropic refrigerant mixtures.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.180-180
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• 2013

반도체, 디스플레이와 같이 저압, 극청정 조건에서 진행되는 공정에서 발생한 오염입자는 수 율에 큰 영향을 미친다. 따라서 공정 중에 발생한 오염입자를 실시간으로 모니터링할 수 있는 장비에 대한 연구가 활발히 진행되고 있다. Particle Beam Mass Spectrometer (PBMS)는 저압에서 실시간으로 나노 입자의 크기를 측정할 수 있는 대표적인 장비 중 하나이다. 입자를 포함한 가스 유동이 PBMS로 유입되면, 우선 입자를 입자빔의 형태로 집속하는 공기역학렌즈를 통과하게 된다. 집속된 입자는 노즐에 의해서 가속되며, 이로 인해 충분한 관성을 가지게 된 입자는 양극과 음극, 필라멘트로 구성된 electron gun에서 전자충돌에 의해 포화상태로 하전된다. 하전한 입자는 electrostatic deflector에서 크기에 따라 분류되어 Faraday detector와 electrometer에 의해 측정된다. 그러나 공기역학렌즈는 입자의 크기가 작아질수록 집속 효율이 급격히 낮아진다는 문제점을 지니고 있다. 이는 입자가 작아질수록 점성에 의한 영향이 관성에 의한 영향보다 커짐으로써 나타나는 현상이다. 최근 이러한 문제점을 해결하기 위해 사중극자를 사용하여 입자를 집속시키는 방법이 대안으로 제시되었다. 사중극자는 서로 마주보는 쌍곡선 형태의 전극구조에 AC 전기장을 인가하는 방식을 사용한다. 사중극자의 중심은 정확히 평형점을 가지게 되며 입자는 사중극자 내에서 진동을 반복하며 평형점을 향해 모이게 된다. 입자의 크기가 작을수록 전기력에 의한 영향을 크게 받으므로 사중극자를 이용한 입자집속 방법은 나노입자의 집속에 있어 공기역학렌즈를 이용한 집속에 비해 이점을 지닌다. 또한 집속 하고자 하는 입자 대상이 바뀔 경우 구조를 바꿔야 하는 공기역학렌즈와 달리 사중극자를 이용한 방법은 AC 전기장을 조절하는 것 만으로 제어가 가능하다. 본 연구에서는 저압 조건에서 나노입자를 집속하기 위한 사중극자의 전극 구조를 이론적인 계산을 통하여 구하였다. 그 결과 0.1 torr의 압력 조건하에서 5~100 nm 범위의 기본 입자를 AC 전압과 진동수를 조절하여 집속할 수 있는 사중극자 형태를 설계하였다.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.25-28
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• 2010

The need for multiband RF front-end in modern communication system is growing rapidly. For example, satellite system always uses a complex arrangement of frequency plans and consequently needs filters for each communication channel and it will be ideal to have a single filter module that does jobs of all those channel filters to reduce the size and payload of the system. In this paper, a new method to transform four-port self-feedback balanced dual-band bandpass filter into two-port is proposed. The two-port balanced dual-band bandpass filter which has baluns at the input and output ports and the fundamental frequency at 2.5 GHz and the first harmonic frequency at 5.7 GHz is fabricated and measured. Good agreement between measured and simulated results was achieved.