• 한국염색가공학회지
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• 제19권3호
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• pp.26-36
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• 2007

This study was carried out to treat the aqueous solutions containing reactive dyes(RB19, RR120 and RY179) by the Ozone demand flask method and adsorption process using activated carbon fiber(ACF) which are one of the main pollutants in dye wastewater. Ozone oxidation of three kinds of the reactive dyes was examined to investigate the reactivity of dyes with ozone, competition reaction and ozone utilization on various conditions for single- and multi-solute dye solution. Concentration of dyes was decreased continuously with increasing ozone dosage in the single-solute dye solutions. Competition quotient values were calculated to investigate the preferential oxidation of individual dyes in multi-solute dye solutions. Competition quotients(CQi) and values of the overall utilization efficiency, ${\eta}O_3$, were increased at 40mg/l of ozone dosage in multi-solute dye solutions. ACF(A-15) has much larger specific surface area$(1,584m^2/g-ACF)$ in comparison with granular activated carbon adsorbent (F400, $1,125m^2/g-GAC$), which is commonly used, and most of pores were found to be micropores with pore radius of 2nm and below. It was found that RB19 was most easily adsorbed among the dyes in this study. In the case of PCP (p-chlorophenol) and sucrose, which are single component adsorbate, adsorption capacities of ACF(A-15) were in good agreement with the batch adsorption measurement, and saturation time predicted of ACF columns for these components was also well agreed with practically measured time. But in the case of reactive dyes, which have relatively high molecular weight and aggregated with multi-components, adsorption capacities or saturation time predicted were not agreed with practically measured values.

• Advanced Composite Materials
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• 제18권4호
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• pp.381-394
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• 2009

The kinetics of centrifugal infiltration of fibrous tubular preform is built theoretically, and simulations are conducted to study the effects of various casting conditions on infiltration kinetics and macrosegregation by combining with the energy, mass and kinetic equations. A similarity way is used to simplify the one-dimensional model and the parameter is ascertained by an iterative method. The results indicate that the increase of superheat, initial preform temperature, porosity tends to enlarge the remelting region and decrease copper solute concentration at the infiltration front. Higher angular velocity leads to smaller remelting region and solute concentration at the tip. The pressure in the infiltrated region increase significantly when the angular velocity is much higher, which requires a stronger preform. It is observed that the pressure distribution is mainly determined by the angular velocity, and the macrosegregation in the centrifugal casting is greatly dependent on the superheat of inlet metal matrix, initial temperature and porosity of the preform, and the angular velocity.

• Journal of Welding and Joining
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• 제17권4호
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• pp.60-68
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• 1999

The previously developed two dimensional model was modified in order to predict more accurately the degree of microsegregation and eutectic fraction on in weld metal whose solidification rate is very fast. The model employed the same assumptions with previous model but considered of a tip undercooling. The previously predicted microsegregation and eutectic fraction has the discrepancies between simulated and examined results in the weld metal solidification. The experiments for the weld metal solidification of 2024 A1 and Fe-Ni alloy were carried out in order to examine the reasonability and feasibility of this modified model. The concentration profile of the solute and eutectic fraction predicted by the simulation agreed well with those found from experimental works. According to the results, it was believed that the dendrite tip undercooling considered in the modified model be reasonable for predicting the degree of microsegregation more accurately in weld metla solidification. In the GTA welds, degree of dendrite-tip undercooling increases with increasing solidification rage(welding speed). This serves to increase the concentration of dendrite core and thus result in reducing the degree of segregation. And solid state diffusion(back diffusion) during solidification is very low in the weld metal solidification so that little additional homogenization of solute occurs during solidification. With consideration of tip undercooling this modified model can predict exactly degree of microsegregation and eutectic fraction from slow solidification(casting) to fast solidification(welding).

• 한국결정성장학회지
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• 제9권3호
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• pp.286-288
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• 1999

When concentration of vacancies in a CZ silicon crystal is defined by molar fraction $X_{B}$, the degree for supersaturation $\sigma$ is given by $[X_{B}-X_{BS}]/X_{BS}=X_{B}/X_{BS}-1=ln(X_{B}/X_{BS})$ because $X_{B}/X_{BS}$ is nearly equal to unity. Here, $X_{BS}$ is the saturated concentration of vacancies in a silicon crystal and $X_{B}$ is a little larger than $X_{BS}$. According to Bragg-Williams approximation, the chemical potential of the vacancies in the crystal is given by ${\mu}_{B}={\mu}^{0}+RT$ ln $X_{B}+RT$ ln ${\gamma}$, where R is the gas constant, T is temperature, ${\mu}^{0}$ is an ideal chemical potential of the vacancies and ${\gamma}$ is and adjustable parameter similar to the activity of solute in a solute in a solution. Thus, ${\sigma}(T)$ is equal to $({\mu}_{B}-{\mu}_{BS})/RT$. Driving force of nucleation for the vacancy agglomeration will be proportional to the chemical potentialdifference $({\mu}_{B}-{\mu}_{BS})/RT$ or ${\sigma}(T)$, while growth of the vacancy agglomeration is proportaional to diffusion of the vacancies and grad ${\mu}_{B}$.

• 한국식품영양과학회지
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• 제24권6호
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• pp.984-989
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• 1995

The concentration-efficiencyh of blue dextran solution in the progressive freeze-concentration was related to the freezing conditions such as the freezing speed and the stirring speed in the solution phase. From the theoreticla balance equation of heat and mass transfer at freezing front, the relationship between the freezing conditions and the ice structure at freezing front was drived. A high freeze-concentration efficiency was obtained under the operating conditions represented by a low speed of freezing and a high speed of stirring. The operating conditions were related to a smooth solid-liquid interface and these results were well explained by the theoretical equation. Effect of the solute component size on the concentration efficiency in the progressive freezeconcentration was also tested. The concentration efficiency of latex particles showed a lower value than that of blue dextran, however, its difference was insignificant.

• 한국표면공학회지
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• 제34권3호
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• pp.247-257
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• 2001

In an effort to improve the dent resistance of exterior body panels at a reduced steel thickness, the bake hardenable steels added Ti or Nb with tensile strength of 35Kgf/$\textrm{mm}^2$ were investigated. The bake hardenability increased with the annealing temperature and solute carbon content. Bake hardening of 3 to 5Kgf/$\textrm{mm}^2$ was obtained in steels with a controlled solute carbon concentration range from 6 to 10ppm. The galvannealing temperature and time had little influence on the bake hardenability. The Fe-Zn alloying reaction of 35Kgf/$\textrm{mm}^2$ BH steel was remarkably retarded due to a 0.07%P addition. The optimum galvannealing temperatures of 35Kgf/$\textrm{mm}^2$ BH steel were ranged from 520 to 56$0^{\circ}C$ in view of the Fe content and powdering resistance. The cross-section and planar views of the galvannealed coatings to characterize morphology development were discussed.

• 대한치과보철학회지
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• 제9권1호
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• pp.41-45
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• 1969

A major disadvantage of Dental cements is their solubility. So it is very important to measure the exact amount of solubility to select clinically suitable materials. The most common laboratory test for solubility is the measurement of disintegration in distilled water, as outlined in A.D.A. Specifications 8 and 9, In addition to the possible factors influencing the solubility, the experiments were all conducted in compliance with A.D.A. Specifications. The solubility of 2 Zinc Phosphate cements and 1 Silicate cement in time of dissolution, concentration of solute in dissolving medium, and type of dissolving medium were investigated. The following results were obtained. 1. Generally the materials were more soluble in organic acids than in distilled water. 2. The dissolution cements tends be minimized by tests utilizing prolonged storage in the same media. 3. In Acetic acid solution, Zinc Phosphate cements were more soluble than Silicate cement, and in Citric acid solution both were markedly more soluble. 4. Solubility was increased by continually presenting fresh liquid, unsaturated with solute, to the cement-water interface.

• 물과 미래
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• 제23권2호
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• pp.213-225
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• 1990

본 연구는 불규칙한 단면을 가지면서 완곡을 이루는 일반하천에서 공장이나 가정으로부터 방류되는 오염물질의 횡확산현상을 예측하기 위한 수치모형을 제안하였다. 이 수치모형은 자연좌표계와 누적유량개념을 도입하였으며 여기에 필요한 여러가지 요소들을 직접측정하지 않고 컴퓨터 프로그래밍을 통하여 간단히 결과를 얻을수 있는 효율적인 방법을 개발하여 실험결과와 비교검토하므로서 본수치모형의 현지적용성을 검토하였다.

• 대한의용생체공학회:의공학회지
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• 제5권1호
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• pp.9-14
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• 1984

The asymptotic solution using the Tailor series has been given explicit form for the solute concentration and overall solute removal in hemodiafilter using one dimensional model. The numerical solutions have been calculated within 0.001% error by the Romberg integration method. Compared with the numerical solutions, the oneterm asymptotic solutions were found to be within 3% error for the condition > 3.0 and three-terms asymtotic solutions were required for the condition >0.7 where denotes measure of convection over diffusional transport and a the ratio of blood flow rate over dialysate flow rate.

• 대한전기학회논문지
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• 제41권1호
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• pp.56-62
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• 1992

The GaAs bulk crystals are grown by the Synthesis Solute Diffusion(SSD) method and its properties are investigated. The crystal growth rate at optimum condition is 0.28 cm/day and their temperature dependence is R(T) = 2.92 x 10S04T exp(-1.548eV/kS1BTT) [cmS02T/day.K]. Etch pits density distribution along radial direction is order of 10S04TcmS0-2T and 10S03TcmS0-2T at the edge and middle of the wafers, respectively, and it increased exponentially along vertical direction of ingot. Moreover,it is uniformly distributed as order of 10S03TcmS0-2T in radial direction of In doped GaAs. The carrier concentration and mobilities are measured to 0.34-2.1 x 10S016T cmS0-3T and 2.3-3.3x10S03T cmS02T/V.sec, respectively.