• International Journal of Highway Engineering
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• v.15 no.5
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• pp.101-110
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• 2013

PURPOSES : The purpose of this study is to evaluate the durability of ternary blended concrete mixtures adding ultra fine admixture. METHODS : From the literature review, crack was considered as the main distress failure criterion on concrete bridge deck pavement. To reduce the initial crack development due to drying shrinkage, CSA expansion agent and shrink reduction agent were used to ternary blended concrete mixtures as a admixture. Laboratory tests including chloride ion penetration test, surface scaling test, rapid freeze & thaw resistance test, non restrained drying shrinkage and restrained drying shrinkage test were conducted to verify the durability of ternary blended concrete mixtures. RESULTS : Based on the test results, proposed mixtures were verified as high qualified durable materials. Expecially initial drying shrinkage crack was not occurred in ternary blended concrete mixtures with CSA expansion agent. CONCLUSIONS : It is concluded that the durability of proposed ternary blend concrete mixture was acceptable to apply for the concrete bridge deck pavement.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.570-576
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• 2005

Powder Injection Molding(PIM) has recently been recognized as an advanced manufacturing technology for low-cost mass production of metal or ceramic parts of complicated geometry With this regards, design technology of dental scaler tip PIM mold, which has complex shape and small core pin (diameter=0.6mm), with the help of computer-aided analysis of powder injection molding process was developed. Computer-aided analysis for dental scaler tip mold was implemented by finite element method with non-Newtonian fluid, modified Cross model viscosity, PvT data of powder/binder mixture. Compter-aided analysis results, such as filling pattern, weldline formation, air vent position prediction were compared with experimental result, and eventually have been shown good agreement. The core pin (diameter=0.6mm) deflection analysis of dental scaler tip PIM mold during PIM filling process was also investigated before mold fabrication.

• Structural Engineering and Mechanics
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• v.67 no.2
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• pp.175-183
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• 2018

This research deals with the wave dispersion analysis of functionally graded double-layered nanobeam systems (FG-DNBSs) considering the piezoelectric effect based on nonlocal strain gradient theory. The nanobeam is modeled via Euler-Bernoulli beam theory. Material properties are considered to change gradually along the nanobeams' thickness on the basis of the rule of mixture. By implementing a Hamiltonian approach, the Euler-Lagrange equations of piezoelectric FG-DNBSs are obtained. Furthermore, applying an analytical solution, the dispersion relations of smart FG-DNBSs are derived by solving an eigenvalue problem. The effects of various parameters such as nonlocality, length scale parameter, interlayer stiffness, applied electric voltage, relative motions and gradient index on the wave dispersion characteristics of nanoscale beam have been investigated. Also, validity of reported results is proven in the framework of a diagram showing the convergence of this model's curve with that of a previous published attempt.

• Bulletin of the Korean Chemical Society
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• v.11 no.1
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• pp.54-58
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• 1990

Acid-base equilibria and spectroscopic properties of diazepam and chlorodiazepoxide were investigated in sodium dodecyl sulfate (SDS) micellar solutions as functions of pH. The results were compared with the behaviors in homogeneous aqueous media. The presence of SDS increased the $pK_a$ of chlorodiazepoxide to 6.3 from 4.7, while it has little effect on the $pK_a$ of diazepam. The acidic protonated form of diazepam was moderately fluorescent when the solution was excited at 350 nm, and emissnion intensity of the species was enhanced about 5 fold by the presence of SDS. On the other hand, the acidic solution of chlorodiazepoxide was non-fluorescent, but the neutral solution of the compound was fluorescent upon excitation at 350 nm. The emission peak of the neutral chlorodiazepoxide shifted to shorter wavelength region without significant change in the emission intensity upon the addition of SDS. Procedures for assay of the individual drugs from their mixture by the use of SDS micelle were discussed.

• Korean Journal of Remote Sensing
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• v.21 no.5
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• pp.417-423
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• 2005

A fuzzy approach using an EM algorithm for image classification is presented. In this study, a double compound stochastic image process is assumed to combine a discrete-valued field for region-class processes and a continuous random field for observed intensity processes. The Markov random field is employed to characterize the geophysical connectedness of a digital image structure. The fuzzy classification is an EM iterative approach based on mixture probability distribution. Under the assumption of the double compound process, given an initial class map, this approach iteratively computes the fuzzy membership vectors in the E-step and the estimates of class-related parameters in the M-step. In the experiments with remotely sensed data, the MRF-based method yielded a spatially smooth class-map with more distinctive configuration of the classes than the non-MRF approach.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.449-453
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• 1991

The degree of electrophilic interference on the solvolytic reactions of model substrates has been studied in fluorinated alcohol solvent mixtures. With variation of solvent composition of 1,1,1,3,3,3-hexafluoro-2-propanol(HFP) and 2-propanol (PrOH) mixtures, the magnitude of electrophilic solvent assistance was changed inversely with the degree of nucleophilic solvent assistance. The contribution of electrophilic interference for 2-adamantyl tosylate showed higher than tert-butyl chloride in HFP-PrOH mixtures. Through a correlation of nucleophilic solvent assistance and electrophilic solvent assistance based on the method of double differences, HFP-PrOH mixture showed a big discrepancy from non-fluorinated alcohol systems.

• Bulletin of the Korean Chemical Society
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• v.18 no.12
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• pp.1291-1295
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• 1997

The catalytic dehydrocoupling of di-n-butylstannane n-Bu2SnH2 by the Cp2MCl2/Red-Al (M = Ti, Zr, Hf) and M(CO)6/Red-Al in situ combination catalysts yielded a mixture of two kinds of catenated products: one is a cross-linked insoluble solid, and the other is a non-cross-linked soluble solid (≒Sn5) or viscous oil (≒Sn2). The soluble oligostannanes could be produced by simple dehydrocoupling of n-Bu2SnH2, whereas the insoluble polystannanes could be obtained via disproportionation/dehydrocoupling combination process of n-Bu2SnH2. The disproportionation/dehydrocoupling combination process may initially produce a low-molecular-weight oligostannane with partial backbone Sn-H bonds which could then undergo an extensive cross-linking reaction of backbone Sn-H bonds, resulting in the formation of an insoluble polystannane.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.11
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• pp.964-969
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• 2003

The objective of this study is to investigate the effect of surfactant on the onset of Marangoni convection adapting a non-linear surface equation of state. The surface tension gradient with respect to the absorbate concentration, ${\gamma}$, is linearly related to the surface concentration of a surfactant with a coeffcient $x_{A}$. The numerical results show that the role of the initial surfactant concentration to Marangoni instability changes from the stabilizer to the destabilizer depending on the change of the sign of $x_{A}$ from negative to positive. It is concluded that for $x_{A}$>0 there is a critical modified Marangoni number of surfactant $M_{Ac}$ $^{*}$ above which liquid layer is always unstable against long wave disturbances.rbances.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.445-452
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• 2019

Shear thickening is an intriguing phenomenon in the fields of chemical engineering and rheology because it originates from complex situations with experimental and numerical measurements. This paper presents results from the numerical modeling of the particle-fluid dynamics of a two-dimensional mixture of colloidal particles immersed in a fluid. Our results reveal the characteristic particle behavior with an application of a shear force to the upper part of the fluid domain. By combining the lattice Boltzmann and discrete element methods with the calculation of the lubrication forces when particles approach or recede from each other, this study aims to reveal the behavior of the suspension, specifically shear thickening. The results show that the calculated suspension viscosity is in good agreement with the experimental results. Results describing the particle deviation, diffusivity, concentration, and contact numbers are also demonstrated.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.73-77
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• 2019

Isothermal (vapor + liquid) equilibrium data measurements were undertaken for the binary mixtures of (propylene oxide + 1-pentanol) system at three different temperatures (303.15, 318.15, and 333.15) K. The Peng-Robinson-Stryjek-Vera equation of state (PRSV EOS) was used to correlate the experimental data. The van der Waals one-fluid mixing rule was used for the vapor phase and the Wong-Sandler mixing rule, which incorporates the non-random two liquid (NRTL) model, the universal quasi-chemical (UNIQUAC) model and the Wilson model, was used for the liquid phase. The experimental data were in good agreement with the correlation results.