• Membrane Journal
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• v.10 no.3
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• pp.155-162
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• 2000

The reverse osmosis membrane housing(HY) was developed for excellent distribution of a feed solution, and the separation performance was compared with the commercialized Rochem(RC) system. The permeation flux of HY system was a little lower than that of RC system. On the other hand, the NaCl rejection ra4io was generally higher. Also, the permeation flux and rejection ratio for type A, B and C modules(disc plate and frame type) were measured using NaCl, sucrose and butanol solutions. The separation performance of type C module for NaCL and sucrose solutions was the most effective, and then those of type A and B were followed, respectively. However, the separation performance for butanol solution was type B, C and A order. The flux improvement ratio of type B to A increased as butanol concentration decreased or operating pressure increased up to 28 bar.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.80-85
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• 2011

The crystallization behavior and microstructural change of the glass-ceramics were analyzed as a function of concentration and etching time of the HF solution in order to enhance the degree of crystallinity induced by heterogeneous nucleation of glass of bottom ash containing 15 wt% $Li_2O$. The nucleation site seemed to be generated where the Si ion was eluted. The main crystal phases in the glass-ceramics fabricated in this study were $\beta$-spodumene and $Li_2SiO_3$. The specimens etched with HF of 0.5 vol% within 0~60 seconds showed increased crystalline peak intensities in XRD pattern with etching time compared to no-etched one. Also the crystal size and crystal occupancy in the glass matrix observed by SEM were increased with etching time. For the glass-ceramics etched with 1.0 and 2.0 vol% HF solution, the etching time over 10 s was not effective to increase the crystallinity. From this study, it was found that the glass-ceramics with the higher crystallinity could be obtained by HF-etching followed by heat treatment process, even though the nucleating agent or 2-stages thermal treatment process were not used.

• BMB Reports
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• v.33 no.3
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• pp.268-275
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• 2000

In contrast to the pyrimidine (6-4)pyrimidone photoproduct [(6-4) adduct], its Dewar valence isomer (Dewar product) is low mutagenic and produces a broad range of mutations with a 42 % replicating error frequency. In order to determine the origin of the mutagenic property of the Dewar product, we used experimental NMR restraints and molecular dynamics to determine the solution structure of a Dewar·lesion DNA decamer duplex, which contains a mismatched base pair between the 3'-T residue and an opposed G residue. The 3'-T of the Dewar lesion forms stable hydrogen bonds with the opposite G residue. The helical bending and unwinding angles of the DW/GA duplex, however, are much higher than those of the DW/AA duplex. The stable hydrogen bonding of the G 15 residue does not increase the thermal stability of the overall helix. It also does not restore the distorted backbone conformation of the DNA helix that is caused by the forming of a Dewar lesion. These structural features implicate that no thermal stability, or conformational benefits of G over A opposite the 3'-T of the Dewar lesion, facilitate the preferential incorporation of an A. This is in accordance with the A rule during translesion replication and leads to the low frequent $3'-T{\rightarrow}C$ mutation at this site.

• Toxicological Research
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• v.13 no.3
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• pp.223-228
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• 1997

Quinones have been reported to undergo nonenzymatic reaction with thiols to generate reactive oxygens. It is therefore possible that the nonenzymatic reaction of quinones with thiols in plasma could lead to potentJared cellular toxicity or disease. When 1 mM menadione was added in plasma under pH 11.2, 7.4 and 5.0, the increase in oxygen consumption rate was the order of pH 11.2 > pH 7.4 > pH 5.0. In addition, oxygen consumption rates under plasma anticoagulated with trisodium citrate solution (pH 7.85) was significantly higher than those with acid-citrate-dextrose solution (pH 6.87). SOD and catalase reduced the rate of oxygen consumption induced by menadione in plasma. Taken together, these results suggest that the menadione-induced increased oxygen consumption was due to nonenzymatic reaction of menadione with thiols in the plasma. The presence of plasma has an additive effect on the increased oxygen consumption rates induced by the menadione treatments on our model tissue, platelets, as compared between washed platelet (WP) and platelet rich plasma (PRP). Cytotoxicity, as determined by LDH release, are well correlated with the oxygen consumption rates observed in each system and strongly suggest that menadione-induced cytotoxicity can be increased with the presence of blood plasma.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.658-667
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• 2006

Fractional derivative models, which are used to describe the viscoelastic behavior of material, have received considerable attention. Thus it is necessary to put forward the analysis solutions of dynamic systems containing a fractional derivative. Although previously reported such kind of fractional calculus-based constitutive models, it only handles the particularity of rational number in part, has great limitation by reason of only handling with particular rational number field. Simultaneously, the former study has great unreliability by reason of using the complementary error function which can't ensure uniform real number. In this paper, a new approach is proposed for an analytical scheme for dynamic system of a spring-mass-damper system of single-degree of freedom under general forcing conditions, whose damping is described by a fractional derivative of the order $0<{\alpha}<1$ which can be both irrational number and rational number. The new approach combines the fractional Green's function and Laplace transform of fractional derivative. Analytical examples of dynamic system under general forcing conditions obtained by means of this approach verify the feasibility very well with much higher reliability and universality.

• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.3
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• pp.67-78
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• 1992

MODM (multiobjective decision-making) problem is very complex system for the analyst. The problem is more complex if the goals of each of the objective functions are expressed imprecisely. It requires suitable MODM method to deal with imprecisions. Therefore, we present a new interactive fuzzy decision making method for solving multiobjective nonlinear programming problems by assuming that the decision maker (DM) has imprecise goals that assume fuzzy linguistic variable for each of the objective functions. The imprecise goals of the DM are quantified by eliciting corresponding membership functions through the interactive with the DM out of six membership functions. After determining membership functions, in order to generate the compromise or satisficing solution which is .lambda.-pareto optimal, .lambda.-max problem is solved. The higher degree of membership is chosen to satisfy imprecise goals of all objective functions by combining the membership functions. Then, the values are the compromise or satisficing solution. On the basis of the proposed method, and interactive computer programming is written to implement man-machine interactive procedures. Our programming is a revised version of sequential unconstrained minimization technique. Finally, a numerical example illustrates various aspects of the results developed in this paper.

• Environmental Engineering Research
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• v.20 no.2
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• pp.181-189
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• 2015

A composite material was tested to eliminate phenol in aqueous solution combining adsorption on activated carbon and photocatalysis with $TiO_2$ in two different ways. A first implementation involved a sequential process with a loop reactor. The aim was to reuse this material as adsorbent several times with in situ photocatalytic regeneration. This process alternated a step of adsorption in the dark and a step of photocatalytic oxidation under UV irradiation with or without $H_2O_2$. Without $H_2O_2$, the composite material was poorly regenerated due to the accumulation of phenol and intermediates in the solution and on $TiO_2$ particles. In presence of $H_2O_2$, the regeneration of the composite material was clearly enhanced. After five consecutive adsorption runs, the amount of eliminated phenol was twice the maximum adsorption capacity. The phenol degradation could be described by a pseudo first-order kinetic model where constants were much higher with $H_2O_2$ (about tenfold) due to additional ${\bullet}OH$ radicals. The second implementation was in a continuous process as with a fixed bed reactor where adsorption and photocatalysis occurred simultaneously. The results were promising as a steady state was reached indicating stabilized behavior for both adsorption and photocatalysis.

• The Mathematical Education
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• v.48 no.2
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• pp.149-167
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• 2009

This study was aimed to examine problem-solving ability of fifth graders on two types of mathematical essay problems, and to analyze the process of mathematical justification in solving the essay problems. For this purpose, a total of 14 mathematical essay problems were developed, in which half of the items were single tasks and the other half were data-provided tasks. Sixteen students with higher academic achievements in mathematics and the Korean language were chosen, and were given to solve the mathematical essay problems individually. They then were asked to justify their solution methods in groups of 4 and to reach a consensus through negotiation among group members. Students were good at understanding the given single tasks but they often revealed lack of logical thinking and representation. They also tended to use everyday language rather than mathematical language in explaining their solution processes. Some students experienced difficulty in understanding the meaning of data in the essay problems. With regard to mathematical justification, students employed more internal justification by experience or mathematical logic than external justification by authority. Given this, this paper includes implications for teachers on how they need to teach mathematics in order to foster students' logical thinking and communication.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.845-854
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• 1998

Following the approach of Ebersole (1985), water wave transformation is predicted using the eikonal equation and transport equation for wave energy which are reduced from the extended mild-slope equation of Massel (1993), and also the irrotationality of wave number vectors. The higher-order bottom effect terms, i.e., squared bottom slope and bottom curvature, are neglected in the study of Ebersole but are included in the present study. It was expected that, if these terms are included in this study, the approach would give more accurate solution in the case of rapidly varying topography. But, the expectation was frustrated. It is probably because, in the case of rapidly varying topography, the diffraction effect which is included in the eikonal equation does not work well and thus the solution is deteriorated.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.83-91
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• 1991

In this paper the dynamic analysis of the multi-span beam on elastic foundation, which include discrete transnational and rotational springs, was performed. Furthermore, the effects of the intermediate supports were investigated. As a solution method, first the orthogonal polynomial functions which satisfy both the geometric and dynamic boundary conditions are obtained by imposing the orthogonality conditions. Then, the Galerkin's method is used to obtain the natural frequencies of the system. From numerical tests for various constraint and boundary conditions, it was found that the higher order orthogonal polynomial functions obtained by the present method can be used to get the accurate solution.