• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.134-141
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• 2002

The ER fluid can be one of efficient materials in ultraprecision polishing for optics, ceramics and semiconductors because of electrically controllable apparent viscosity. To finish small 3 dimensional structures such as the aspherical surface in optical elements, the possible arrangement of a tool, workpiece and auxiliary electrode is described. We examined the influence of the addition of a few abrasive particles on the performance of the ER fluid by measuring yield stress, and observed the behavior of abrasive particles in the ER fluid by a CCD camera, which is also theoretically predicted from the electromechanical principles of particles. On the basis of the above results, the steady flow analysis around the rotating micro tool is worked out considering the non-uniform electric field. Finally, Pyrex glass is polished using the mixture of the ER fluid and abrasive particles, and the effect of the electric field strength is evaluated.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.305-306
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• 2009

This study is on basic experimental methods of easily verifying the fiber content in non-spalling concrete at construction sites. As a result, fiber content in a mixture can be effectively measured by using 15$\ell$ of water for dilution of specimens, dry bit trowel for tool, and microwave for drying.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.401-411
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• 1990

Deposition of diamond films on Si(100) from the mixtures of methane and hydrogen were investigated using hot W filament CVD method. The nucleation density could be increased thousandfold by surface treatment with SiC powder. Upon oxygen addition to the mixture, crystal facets became developed more clearly by selectively removing non-diamond carbons, but the film growth rate generally decreased. However, at a very high methane content(e.g. 10%), a small amount of oxygen addition has resulted in an increase in the film deposition rate presumably by promotion of methane decomposition. When the gas pressure was varied, the growth rate exhibited a maxiumum at around 20torr and the film crystallinity steadily improved with the pressure increase. The observed variation of the growth rate by oxygen addition was discussed in terms of its role in the pyrolysis and the subsequent gas phase reactions.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.3
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• pp.258-261
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• 2006

The addition of zeolite particles enhances the stability of mRNA molecules in a cell-free protein synthesis system. When $20{\mu}g/{\mu}L$ of zeolite (Y5.4) is added to a reaction mixture of cell-free protein synthesis, a substantial increase in protein synthesis is observed. The stabilizing effect of zeolite is most dearly observed in an in vitro translation reaction directed by purified mRNA, as opposed to a coupled transcription and translation reaction. Upon the addition of zeolite in the in vitro translation reaction, the life span of the mRNA molecules is substantially extended, leading to an 80% increase in protein synthesis. The effect of zeolite upon the mRNA stability appears be strongly related to the cation exchange (potassium to sodium) reaction. Our results demonstrate the possibility of modifying this biological process using heterogeneous, non-biological substances in a cell-free protein synthesis system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.384-384
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• 2010

The surface reaction characteristics of Zinc Oxide (ZnO) in $Cl_2/BCl_3$/Ar gas ratio using inductively coupled plasma system were investigated. It was found that ZnO etch rate shows a non-monotonic behavior with increasing both Ar fraction in $Cl_2/BCl_3$ plasma, RF power, and gas pressure. The maximum ZnO etch rate of 53 nm/min was obtained for $Cl_2$(3 sccm)/$BCl_3$(16 sccm) /Ar(4 sccm) gas mixture. The chemical state of etched surfaces was investigated with X-ray diffraction (XRD) and the etched surface was investigated to the rms by atomic force microscopy (AFM). From these data, the suggestions on the ZnO etch mechanism were made by secondary ion mass spectrometery (SIMS).

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.938-946
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• 2008

Fe-base amorphous alloy and two crystalline phases composite were fabricated. The effect of temperature and strain rate on mechanical properties was evaluated utilizing compression test. Mixture of non-crystalline and crystalline phases were found using X-ray diffraction (XRD) and differential thermal analysis (DTA) tests. Based on glass transition temperature and crystallization temperature. compression tests were performed in the temperature ranging from $560^{\circ}C$ to $700^{\circ}C$ with $20^{\circ}C$ interval. Relationship between microstructure, including fracture surface morphology, and mechanical behavior was studied. The peak stress of Fe-base amorphous alloy was over 2GPa and expected to have a good wear resistance, but it is expected hard to deform because of low ductility. The peak stress and elongation of two crystalline phases composite was over 1GPa and about 20%, therefore it is possible to deform high strength wear resistant materials such as engine valve.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1193-1202
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• 2000

The paper describes the use of genetic algorithms (GA's) to the minimum weight design of stiffened composite panels for buckling constraints. The proposed design problem is characterized by mixture of continuous and discrete design variables corresponding to panel elements and stacking sequence of laminates, respectively. Design space is multimodal and non-convex, thereby introducing the need for global search strategies. Advanced strategies in GA's such as directed crossover, multistage search and separated crossover are adopted to improve search ability and to save computational resource requirements. The paper explores the effectiveness of genetic algorithms and their advanced strategies in designing stiffened composite panels under various uniaxial compressive load conditions and the linrlit on stacking sequence of laminates.

• Archives of Plastic Surgery
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• v.40 no.4
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• pp.327-329
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• 2013

As a technically demanding skill, microsurgery is taught in the lab, in the form of a course of variable length (depending on the centre). Microsurgical training courses usually use a mixture of non-living and live animal simulation models. In the literature, a plethora of microsurgical training models have been described, ranging from low to high fidelity models. Given the high costs associated with live animal models, cheaper alternatives are coming into vogue. In this paper we describe the use of the chicken aorta as a simple and cost effective low fidelity microsurgical simulation model for training.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.663-668
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• 1996

A two-dimensional continuum model for the prediction of the hydrogen mixing phenomena in the containment compartment under the severe accident conditions is developed. The model could predict well the distribution of time-dependent hydrogen concentration for selected HEDL Experiment. For a simulation of these experiments, the hydrogen is mixed uniform over the test compartment. To predict the extent of non-uniform distribution, the dominant factors such as the geometrical shape of obstacle and velocity of source injection in mixing phenomena are investigated. If the obstacle disturbing the flow of gas mixture exists in the compartment, the uniform distribution of hydrogen may be not guaranteed. The convective circulation of gas flow is separately formed up and down of the obstacle position, which makes a difference of hydrogen concentration between the upper and lower region of the compartment. The recirculation flow must have a considerable mass flow rate relative to velocity of the source injection to sustain the well-mixed conditions of hydrogen.

• Textile Coloration and Finishing
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• v.10 no.2
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• pp.18-28
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• 1998

in order to overcome disadvantage of the conventional two bath dyeing method of polyester/cotton blends, it had prompted significant effort to the development of the one bath dyeing method which can accomplish sayings in time, energy and water usage. Also, when dyeing polyester/cotton blends by the one bath dyeing method, the high salt concentrations needed for the reactive dye can cause particles of disperse dye, used for the polyester component, to aggregate. A supplementary problem that can occasionally be happened is the change of hue that occurs on dyed polyester in an alkaline dyebath. To improve dyeing property of polyester/cotton blends, cotton component was pretreated with epichlolohydrine-trimethylamine hydrochloride in aqueous solution of sodium hydroxide to produce a cationized cotton that can be dyed under neutral conditions with reactive dye in a non-electrolytic or il little electrolytic dyebath. The one bath dyeing method of polyester/cationized cotton blends with disperse dye/reactive dye mixture resulted in a satisfactory dyeing property and color yield in comparison with ordinary two bath dyeing method.