• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.1
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• pp.28-34
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• 1985

This paper describes that the characteristic of movement and the performance of the directional system of the liquid magnetic compass analyze and investigate in the kinds of compass and the coefficient of viscosity of the liquid of compass, which the horizontal magnetic field of the geo-magnetic is varied from the equator to the polar region (0.39 gauss-0.03 gauss) by use of apparatus generating artificial magnetic fields. The results are as follows; 1. It is confirmed that the measured values and the calculated values on the characteristic of damping curve by the type of compass and coefficient of viscosity has almost agree with one another. 2. As the horizontal magnetic force geo-magnetic field approaches around the equator (0.39 gauss), the horizontal magnetic field get near the polar region (0.03 gauss), its period is to be longer and the compass card prove not to be more stabilized. 3. The coefficient of viscosity of the liquid in the A, B, C, D and E compasses used in the experiment is estimated 0.03 poises, 0.02 poises, 0.02 poises, 0.015 poises and 0.048 poises respectively by computer simulation.

• Computers and Concrete
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• v.8 no.3
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• pp.279-292
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• 2011

The main purpose of this study includes investigation of the rheological properties of fresh self consolidating cement paste containing chemical and mineral additives using Artificial Neural Network (ANN) model. In order to develop the model, 200 different mixes are cast in the laboratory as a part of an extensive experimental research program. The data used in the ANN model are arranged in a format of fourteen input parameters covering water-binder ratio, four different mineral additives (calcium carbonate, metakaolin, silica fume, and limestone), five different superplasticizers based on the poly carboxylate and naphthalene and four different Viscosity Modified Admixtures (VMAs). Two common output parameters including the mini slump value and flow cone time are chosen for measuring the rheological properties of fresh self consolidating cement paste. Having validated the model, the influence of effective parameters on the rheological properties of fresh self consolidating cement paste is investigated based on the ANN model outputs. The output results of the model are then compared with the results of previous studies performed by other researchers. Ultimately, the analysis of the model outputs determines the optimal percentage of additives which has a strong influence on the rheological properties of fresh self consolidating cement paste. The proposed ANN model shows that metakaolin and silica fume affect the rheological properties in the same manner. In addition, for providing the suitable rheological properties, the ANN model introduces the optimal percentage of metakaolin, silica fume, calcium carbonate and limestone as 15, 15, 20 and 20% by cement weight, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.2
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• pp.245-255
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• 1994

A two-dimensional Lagrangian finite-difference computer program is developed for the wave propagation analysis of impact phenomena. The numerical scheme is the standard method originally proposed by Von Neuman and Richtmyer, using artificial viscosity to smooth shock fronts. The material model used in the study is the standard hydrodynamic-elastic-plastic relations with Von-Mises yield criterion. A test configuration consisted of a target and a projectile were calculated to understand the response of a colliding event. However, the computer code is in plane strain, the calculations were intended for generating the qualitative features of the model behaviors. Nevertheless, the computational results were consistent with the experimental observations and provided a rational basis to interpret the modes of failures.

• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.41-46
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• 2004

The formation of rust on metallic substrate is known to cause the damages and destructions of raw materials, which is one of the leading reasons of sturctural collapses and many kind of hazards in modern industry. Polymer gels with rust removing effects were compounded in this study by employing various kinds of acids like hydrochloric acid, phosphoric acid, gluconic acid, oxalic acid as the rust removing ingredients. TEA(Triethanolamine) as dispersant and hydrophilic chemical were used for effective gelation of acids. Also corrosion inhibitor was added to enable the coating effect and to improve rust removing effect on metallic surface. In order to investigate the rust properites on metallic substrate, artificial rusts were prepared in salt solution, using iron, copper, aluminium and brass as the base metals. The properties of gel compounds were checked by gelation, pH, viscosity, morphology property and rust removing test. Developed gel compounds in this study have a good rust removing property, showing a strong adhesion on horizontal and vertical metallic surface, and can be easily rinsed off by water.

• 보존과학연구
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• s.20
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• pp.139-154
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• 1999

We tested to obtain the excellent Epoxy resins on the property of matter. Existing Epoxy resins is tested to regulate the viscosity, color and hardening time etc. Benzen-ring structure of Bisphenol A type (AY 103) is replaced by Hydrogenated B.P.A type. And hardener is replaced by Polyoxyalkylene Amine. So we are developed into the two resins(L-30, L-40).To know if this Epoxy resins was fitted to repairing and restoration of stone cultural properties. Three kinds of Epoxy resins (AY 103, L-30, L-40) are tested on the artificial weathering test, freezing-melting test, exposure test etc. As a result of test, L-30 is less the discoloration than that of other Epoxy resins and was superior to the excellent property of matter.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.3
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• pp.638-651
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• 2014

Main aim of this paper is to find the best combination of numerical schemes for 2-D SPH simulation of wedge water entry. Diffusion term is considered as laminar, turbulent, and artificial viscosity. Density filter that seriously affects the pressure distribution is investigated by adopting no filter, first order filter, and second order filter. Validation of the results indicates that turbulent model and first order density filter can lead to more reasonable solutions. This simulation was then conducted for wedge water entry with wide range of deadrise angles including 10 degrees, 20 degrees, 30 degrees, 45 degrees, 60 degrees and 81 degrees, with extreme deadrise angles of 10 degrees, 60 degrees and 81 degrees being considered. Comparison of SPH results with BEM solutions has displayed favorable agreement. In two particular cases where experimental data are available, the SPH results are shown to be closer to the experiments than BEM solution. While, accuracy of the obtained results for moderate deadrise angles is desirable, numerical findings for very small or very large deadrise angles are also very reasonable.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.3
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• pp.110-122
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• 1996

Finite element analysis tool was developed to analyze the casting process. Generally, casting process consists of mold filling and solidification. Both filling and solidication process were simulated simultaneously to investigate the effects of process variables and to predict the defect. At filling process, thermal coupling was especially considered to investigate thermal history of material during the filling stage. And thermal condition at the final stage of filling is used as the initial conditions in a solidification process for the exact simullation of the actual casting processes. At mold filling process, Lagragian-type finite element method with automatic remeshing scheme was used to find the material flow. A perturbation method with artificial viscosity is adopted to avoid numerical instability in low viscous fluid. At solidification process, enthalpy-based finite element method was used to solove the heat transfer problem with phase change. And elastic stress analysis has been performed to predict the thermal residual stress. Through the FE analysis, solidification time, position of solidus line, liquidus line and thermal residual stress are found. Through the study, the importance of combined analysis has been emphasized. Finite element tools developed in this study will be used process design of casting process and may be basic structure for total CAE system of castings which will be constructed afterward.

• Elastomers and Composites
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• v.58 no.3
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• pp.112-120
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• 2023

Herein, we propose a facile water-processible method to develop an eggshell membrane (ESM)-embedded waterborne polyurethane (WPU)-based bio-degradable and bio-compatible coating material that exhibits attractive tactile properties. Virgin ESM is not dispersible in water. Hence, to develop the ESM-based WPU composite, soluble ESM (S-ESM) was first extracted by de-crosslinking the ESM. The extracted S-ESM at different concentrations (0, 0.5, 1.0, 1.5 wt %) was mixed with WPU. Compared to virgin WPU, the viscosity of S-ESM/WPU dispersion and the in-plane coefficient of friction (COF) of the composite film surfaces decreased with an increase in the S-ESM content. In addition, an increase in the S-ESM content improved the tribo-positive characteristics of the film. Different good touch-feeling biomaterials, such as fur, feather, and human skin exhibit tribo-positivity. Thus, the enhanced tribo-positive characteristics of the S-ESM/WPU and the decrease in their COF owing to an increase in the S-ESM content imply the enhancement of its touch-feeling performance. The S-ESM embedded WPU composites have potential applications as coating materials in various fields, including automobile interiors and artificial leather.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.119-127
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• 2003

We measured the effect of wettability of six MPSs for RGP lens. The used MPSs(multipurpose solutions) were OPTI-SOAK(ALCON), SOLO care hard(CIBA Vision), Total care(ALLERGAN), Simplicity(BOSTON). Wetting and Soaking Sol.(Bausch & Lomb) and Aquas-multi(Saehan). These MPSs keeps hydrophilic property of lens surface and increase the effect of cleaning or increase the effect of preservative effect. To compare with the effect of wettability we followed the way of contact angle measurement which was general way to measure wettability and compared lens which was conducted by each MPS made by different companies. As a control, 0.9% NaCl solution and artificial tears were used. The degree of the effect of wettability was decided by contact angle. It is hydrophilic property nearby $0^{\circ}$ of contact angle and it is closed by hydrophobic property as it increases. To compare with the effect of wettability we followed the way of contact angle measurement which was general way to measure wettability and compared lens which was conducted by each MPS made by different companies. As a control, 0.9% NaCl solution and artificial tears were used. The degree of the effect of wettability was decided by contact angle. It is hydrophilic property nearby $0^{\circ}$ of contact angle and it is closed by hydrophobic property as it increases. The results showed that every lens was nearby hydrophilic property within $25^{\circ}{\sim}36^{\circ}$. Also, it was differed by various factors. The surface tension showed various differences between 19.8 and 31.3(mN/m). In the viscosity, MPSs represented the highest viscosity between $4^{\circ}C$ and $20^{\circ}C$. It was much higher than compared with the viscosity of soft lens MPS. This experiment could be used to grasping the interaction between solutions used to MPS and the natural endowments of lens and to considering the relations of different factors effecting the wettability.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.1
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• pp.47-53
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• 2011

The artificial aggregates (AAs) were manufactured from the parent batch powders consisting of bottom ash containing excess unburned carbon and dredged soil, 7 : 3 weight ratio by direct sintering method and those physical properties were evaluated. Especially, the effects of waste glass or frit (NWG) which was made by addition of 5 wt% $Na_2O$ to the waste glass upon the bloating phenomenon of AAs were analyzed. The AAs manufactured from the parent batch powders showed a lower specific gravity than that of specimens containing waste glass or NWG due to excess u$Na_2O$nburned carbon which usually obstructs a sintering process. But, the waste glass added on parent batch powders promoted the sintering and densification thus increased the specific gravity of AAs. Also the specific gravity of AAs added with 5 wt% NWG, was lowered compared to that of AAs added with as-received waste glass. This is because of bloating of shell which captures gases owing to the lowered viscosity of liquid formed at the specimen surface caused by $Na_2O$ addition. In conclusion, the AAs sintered at above $1100^{\circ}C$ in this study showed characters of lightweight aggregate of specific gravity 1.15~1.34 and water absorption 11~19 %, and the bloating phenomenon of AAs was occurred at the shell rather black core part.