• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.11
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• pp.5489-5511
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• 2019

The performance of evolutionary algorithms can be seriously weakened when constraints limit the feasible region of the search space. In this paper we present a constrained multi-objective optimization algorithm based on adaptive ε-truncation (ε-T-CMOA) to further improve distribution and convergence of the obtained solutions. First of all, as a novel constraint handling technique, ε-truncation technique keeps an effective balance between feasible solutions and infeasible solutions by permitting some excellent infeasible solutions with good objective value and low constraint violation to take part in the evolution, so diversity is improved, and convergence is also coordinated. Next, an exponential variation is introduced after differential mutation and crossover to boost the local exploitation ability. At last, the improved crowding density method only selects some Pareto solutions and near solutions to join in calculation, thus it can evaluate the distribution more accurately. The comparative results with other state-of-the-art algorithms show that ε-T-CMOA is more diverse than the other algorithms and it gains better in terms of convergence in some extent.

• Bulletin of the Korean Chemical Society
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• v.25 no.1
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• pp.79-84
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• 2004

The existing technological schemes for processing rhenium-containing raw materials involve the recovery of Re from solutions, which can be effectively achieved by anion exchange method. The application of anion exchange also allows to study rhenium state in aqueous solutions and to develop analytical control methods. The present work is focused on investigation of ion exchange equilibrium in the analytical system Re(VII)-HCl-$SnCl_2$-KSCN-anion exchanger by means of sorption-desorption method as well as by electron, IR- and diffuse reflection spectroscopy. It was shown that rhenium can be quantitatively recovered from this system. It is proposed to use the sorption-spectroscopic method for Re(VII) determination in aqueous solutions. The calibration curve is linear in the concentration range of 0.5-20.0 mg/L (sample volume is 25.0 mL) and the detection limit is 0.05 mg/L. The presence of Mo(VI), Cu(II), Fe(II, III), Ni(II), Zn(II) as well as $K^+,\;Na^+$ do not hinder the solid-phase determination of rhenium. Rhenium (VII) determination by diffuse reflection spectroscopy was carried out in model solutions as well as in samples of river-derived water and in solutions obtained after the dissolution of spent catalysts.

• Journal of the Chungcheong Mathematical Society
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• v.27 no.1
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• pp.17-27
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• 2014

In order to study the propagation of singularities for solutions to second order quasilinear strictly hyperbolic equations with boundary, we have to consider the regularity of solutions of first order nonlinear equations satisfied by a characteristic hyper-surface. In this paper, we study the regularity compositions of the form v(${\varphi}$(x), x) with v and ${\varphi}$ assumed to have limited Sobolev regularities and we use it to prove the regularity of solutions of the first order nonlinear equations.

• Bulletin of the Korean Mathematical Society
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• v.51 no.4
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• pp.933-942
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• 2014

We give a representation of the component of solutions with characteristic multiplier 1 in a periodic linear inhomogeneous continuous system. It follows from this representation that asymptotic behaviors of the component of solutions to the system and to its associated homogeneous system are quite different, though they are similar in the case where the characteristic multiplier is not 1. Moreover, the representation is applicable to linear discrete systems with constant coefficients.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.12 no.4
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• pp.201-202
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• 2008

Because of the importance of suction or injection in the fields of aerodynamics, space science and many other industrial applications, our present study is motivated. The effect of natural convection on MHD flow past a vertical plate with suction or injection is studied. We have tried to solve the dimensionless governing equations by using finite difference scheme. To ensure the validity of our numerical solutions, we have compared our numerical solutions for temperature and velocity for the case of suction and injection for unit Prandtl number with the available exact solutions in the literature. The corresponding codes were written in Mathematica 5.0 for calculating numerical solutions for temperature and velocity and the comparison between the exact and numerical solutions. For the purpose of discussing the results some numerical calculations are carried out for non-dimensional temperature T, velocity u, skin friction ${\tau}$ and the Nusselt number $N_u$, by making use of it, the rate of heat transfer is studied.

• International Journal of Highway Engineering
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• v.18 no.3
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• pp.21-32
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• 2016

PURPOSES : In this paper, the analytical solutions suggested to simulate the behavior of rheological fluids were rigorously re-derived and investigated for fixed conditions to evaluate the applicability for the solutions on a mini-cone slump test of cement paste. The selected solutions with proper boundary conditions can be used as reference solutions to evaluate the performance of numerical simulation approaches, such as the discrete element method. METHODS : The slump, height, and spread radius for the given boundary and yield stress conditions that are determined by five different analytical solutions are compared. RESULTS : The analytical solution based on fluid mechanics for pure shear flow shows similar results to that for intermediate flow at low yield stresses. The fluid mechanics-based analytical solution resulted in a very similar trend to the geometry-based analytical solution. However, it showed a higher slump at high yield stress and lower slump at low yield stress ranges than the geometry-based analytical model. The analytical solution based on the mini-cone geometry was not significantly affected by the yield criteria, such as von Mises and Tresca. CONCLUSIONS : Even though differences among the analytical solutions in terms of slump and spread radius existed, the difference can be considered insignificant when the solutions were used as reference to evaluate the appropriateness of numerical approaches, such as the discrete element method.

• Journal of the Korean Ceramic Society
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• v.31 no.2
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• pp.220-226
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• 1994

The hydrolysis and condensation reactions in the mixed alkoxide solutions of Si(OC2H5)4 and Zr(O-nC3H7)4 with various water contents (1, 2, 4, and 8 in molar ratio to alkoxide, r) and catalysts were examined by rheological measurements and the number average molecular weight in order to explain the shape of the polymer in the mixed alkoxide solutions. It was found that fibers could be drawn in the viscosity range of 1∼100P from the acid-catalyzed solutions with lower water contents of the mole ratio H2O/alkoxide, r 2. On the other hand, crack free bulk gel was formed from the acid-catalyzed solutions including a large amount of water (r 4), and the base-catalyzed solutions. The relation between the intrinsic viscosity [{{{{ eta }}] and the number average molecular weight n, namely [{{{{ eta }}]=Knα, has shown that the acid-catalyzed spinnable solutions (r=1 and 2) have linear polymers and the exponent α's are about 0.56 and 0.81, whereas non-spinnable solutions (r=4 and 8) have three dimensional network polymers or spherical particles and the exponent α's are 0.41∼0.51 and 0.35.

• The Journal of the Acoustical Society of Korea
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• v.17 no.3E
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• pp.35-42
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• 1998

Transient acoustic and elastic wave propagation in inhomogeneous media are studied by using the Fourier method. It is known that the fourier method has advantages in memory requirements and computing speed over conventional methods such as FDM and FEM, because the Fourier method needs less grid points for achieving the same accuracy. To verify the proposed numerical scheme, several examples having analytic solutions are considered, where two different semi-infinite media are in contact along a plane boundary. The comparisons of numerical results by the Fourier method and analytic solutions show good agreements. In addition, the fourier method is applied to a layered half-plane, in which an elastic semi-infinite medium is covered by an elastic layer of finite thickness. It is showed how to derive the analytic solutions by using the Cagniard-de Hoop method. The numerical solutions are in excellent agreements with analytic results.

• Korean Management Science Review
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• v.29 no.2
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• pp.143-155
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• 2012

The purpose of this study is to formulate and solve the scheduling problem to heat-treatment process in forging process and apply it to industries. Heat-treatment is a common process in manufacturing heavy forged products in ship engines and wind power generators. Total complete time of the schedule depends on how to group parts and assign them into heat furnace. Efficient operation of heat-treatment process increases the productivity of whole production system while scheduling the parts into heat-treatment furnace is a combinatorial problem which is known as an NP-hard problem. So the scheduling, on manufacturing site, relies on engineers' experience. To improve heat-treatment process schedule, this study formulated it into an MIP mathematical model which minimizes total complete time. Three methods were applied to example problems and the results were compared to each other. In case of small problems, optimal solutions were easily found. In case of big problems, feasible solutions were found and that feasible solutions were very close to lower bound of the solutions. ILOG OPL Studio 5.5 was used in this study.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.370-378
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• 2009

Kinetic studies on the ligand substitution reactions of cyanocomplexes were performed in several micellar solutions. It showed the observed rate constants was found to be independent of the entering ligand concentration at high concentration of cyanopyridine and pyrazinecarboxylate. We could see also that in nonionic and anionic micellar solutions no influence of changes in the surfactant concentration on the observed rate constants was found. Taking into account the hydrophilic nature of the cobalt complex, the cobalt complex molecule was expected to be located in the aqueous phase of the micellar systems, where the reaction would take place. In cationic micellar solutions, a small increase in the observed rate constant was found when the cationic surfactant concentration increased. After reaching a maximum, the rate constant decreased on increasing surfactant concentration and subsequently it reached a plateau, where the observed rate constant was independent of changes in the surfactant concentration.