• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1249-1258
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• 1994

Titanium carbide was synthesized by reacting the prepared titanium powder and carbon black using SHS method sustains the reaction spontaneously, utilizing heat generated by the exothermic reaction itself. In this process, the effect of the particle size of titanium powder on combustion temperature and combustion wave velocity was investigated. By controlling combustion temperature and combustion wave velocity via mixing Ti and C powder with TiC, the reaction kinetics of TiC formation by SHS method was considered. Without reference to the change of combustion temperature and combustion wave velocity, TiC was easily synthesized by combustion reaction. As the particle size of titanium powder was bigger, or, as the amount of added diluent(TiC) increased, combustion temperature and combustion wave velocity were found to be decreased. The formation of TiC by combustion reaction in the Ti-C system seems to occur via two different mechanisms. At the beginning of the reaction, when the combustion temperatures were higher than 2551 K, the reaction was considered to be controlled by the rate of dissolution of carbon into a titanium melt with an apparent activation energy of 148 kJ/mol. For combustion temperatures less than 2551 K, it was considered to be controlled by the atomic diffusion rate of carbon through a TiC layer with an apparent activation energy of 355 kJ/mol. The average particle size of the synthesized titanium carbide was smaller than that of the starting material(Ti).

• Journal of ILASS-Korea
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• v.3 no.3
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• pp.33-41
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• 1998

In recently, a study on the lean combustion is investigated intensively, because it is expected that this method may decrease the harmful exhaust gas and improve fuel economy in gasoline engine. The problems of lean combustion system in gasoline engine are ignition difficulty, misfire and instability of combustion. The investigation on the optimization of fuel metering and the control of mixing gas flow may be critical to improve the performance of lean combustion. In the fuel injection gasoline engine, the formation of mixture influences strongly on the engine performance such that the importance of fuel metering system becomes apparent. First of all, a study on the fuel breakup characteristics of gasoline fuel injector was carried out in this paper. Fuel injectors are pintle and 4hole-2spray type. The purpose of this study is to clarify the atomization mechanism of spray injected into atomosphere field through electronic controlled-fuel injectors, and to analyze spray characteristics such as drop size distribution and mean drop diameter produced at fuel injector. In this paper, the spray development is observed by taking photograps using 80mm still-camera system, and drop sizes are measured by PMAS. From these experiment, spray pattern injected from gasoline fuel injectors was investigated clearly. Also, it was found that SMD and drop size distribution of injected fuel spray from gasoline fuel injectors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.625-632
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• 2011

The ignition characteristics of a $CH_4$/hot air counterflow diffusion flame were investigated numerically using a flame-controlling continuation method. For the chemical reactions, the GRI-v1.2 reaction mechanism was used in the simulation. The maximum flame temperature was presented in the space of the inverse global strain rate, and showed S-curve-type behavior. The flame temperatures and velocities of the upper and middle branches were compared for different global strain rates. In addition, the global strain rate was compared with the local strain rates defined at the flame surface and the boundaries of the fuel and oxidizer sides of the fuel/air mixing layer. These local strain rates correlated well with the global strain rate.

• Wind and Structures
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• v.23 no.2
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• pp.157-169
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• 2016

The structural integrity of tube bundles represents a major concern when dealing with high risk industries, such as nuclear steam generators, where the rupture of a tube or tubes will lead to the undesired mixing of the primary and secondary fluids. Flow-induced vibration is one of the major concerns that could compromise the structural integrity. The vibration is caused by fluid flow excitation. While there are several excitation mechanisms that could contribute to these vibrations, fluidelastic instability is generally regarded as the most severe. When this mechanism prevails, it could cause serious damage to tube arrays in a very short period of time. The tubes are therefore stiffened by means of supports to avoid these vibrations. To accommodate the thermal expansion of the tube, as well as to facilitate the installation of these tube bundles, clearances are allowed between the tubes and their supports. Progressive tube wear and chemical cleaning gradually increases the clearances between the tubes and their supports, which can lead to more frequent and severe tube/support impact and rubbing. These increased impacts can lead to tube damage due to fatigue and/or wear at the support locations. This paper presents simulations of a loosely supported multi-span U-bend tube subjected to turbulence and fluidelastic instability forces. The mathematical model for the loosely-supported tubes and the fluidelastic instability model is presented. The model is then utilized to simulate the nonlinear response of a U-bend tube with flat bar supports subjected to cross-flow. The effect of the support clearance as well as the support offset are investigated. Special attention is given to the tube/support interaction parameters that affect wear, such as impact and normal work rate.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.29-35
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• 1999

Inductively coupled plsama etching of platinum thin film was studied using $O_2$ addition to $Cl_2$/Ar gas plasma. In this study, Pt etching mechanism was investigated with Ar/$Cl_2$ /$O_2$ gas plasma by using XPS and QMS. Ion current density was measured with Ar/$Cl_2$ /$O_2$ gas plasma by using single Langmuir probe. It was confirmed by using QMS and single Langmuir probe that Cl and Ar species rapidly decreased and ion current density was also decreased with increasing $O_2$ gas ratios. These results implied that the decrease of Pt etch rate is due to the decrease of reactive species ans ion current density with increasing $O_2$ gas mixing ratios. A maximum etch rate of 150nm/min and the oxide selectivity of 2.5 were obtained at Ar/$Cl_2$ /$O_2$ flow rate of 50 seem, RF power of 600 W, dc bias voltage of 125 V, and the total pressure of 10 mTorr.

• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.352-359
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• 1990

The synergistic effect of glucoamylase and a -amylase on the hydrolysis of raw corn starch in an agitated bead reaction system was studied by investigating the changes of sugar profiles, the granular structure, particle size distribution, and X-ray diffraction pattern of residual raw corn starch. The enzymatic hydrolysis of raw corn starch was greatly enhanced by synergistic effect of glucoamylase and $\alpha$ -amylase. Even though the sugar profiles were mainly determined by the mixing ratio of glucoamylase and $\alpha$-amylase; raw starch was mainly converted to glucose directly without accumulation of any significant amount of oligosaccharides. The cavity formation and fragmentation phenomena of raw corn starch granule subjected to enzyme reaction were analyzed by means of SEM and the particle size distribution. The X-ray diffraction pattern of raw starch was not changed at the initial stage of reaction but slightly changed at the late stage of hydrolysis, which may be caused by the preferential degradation of amorphous region by enzymatic reaction, not by the destruction of microcrystalline structure of raw corn starch.

• Journal of Science and Technology Studies
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• v.12 no.2
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• pp.117-157
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• 2012

This paper investigated the biomedical medicalization of "depression"which is growing fast in Korea in terms of the treatment mechanism. Depression has been regarded as a mental disease that occurs with mixing various causations because what was the cause of this disease was not clarified until a recent date. Thus, as depression treatment, the medicine and the psycho-socio therapy have been used. However, from 1990s, as the brain science was introduced in the western society, and the high-tech diagnostic equipment of the brain disease and new drugs for the mental disease were developed, depression was rapidly redefined as 'the brain nerve system illness'that is easy to be taken and is able to obtain the permanent relief with the regular care. Under the influence of the redefinition of depression and the new treatment of it, recently, 8% of depression patients per year emerge as the aggressive cure subjects in the Korean psychiatric circle. However, according to the Korean psychiatric circle's unofficial calculation, it is estimated that only 10% of depression patients are receiving the accurate treatment but over 80% of the patients are not. If so, what does this estimation mean? Based on this question, this paper critically investigated the biomedical medicalization of depression.

• Macromolecular Research
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• v.14 no.1
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• pp.66-72
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• 2006

The purpose of this study is to develop novel nanoparticles based on polyion complex formation between low molecular weight water-soluble chitosan (LMWSC) and all-trans retinoic acid (atRA). LMWSC nanoparticles encapsulating atRA based on polyion complex were prepared by mixing of atRA into LMWSC aqueous solution using ultrasonication. In FTIR spectra, the carbonyl group of atRA at 1690 $cm^{-1}$ disappeared or decreased when ion complexes were formed between LMWSC and atRA. In ${1}^H$ NMR spectra, specific peaks of atRA disappeared when atRA-encapsulated LMWSC (RAC) nanoparticles were reconstituted into $D_{2}O$ while specific peaks both of atRA and LMWSC appeared in $D_{2}O$/DMSO (1/3, v/v) mixture. XRD patterns also showed that the crystal peaks of atRA were disappeared by encapsulation into LMWSC nanoparticles. LMWSC nanoparticles encapsulating atRA have spherical shapes with particle size below 200 nm. The mechanism of encapsulation of atRA into LMWSC nanoparticles was thought to be an ion complex formation between LMWSC and atRA. LMWSC nanoparticles showed high atRA loading efficiency over 90$\%$ (w/w). AtRA was continuously released from nanoparticles over 10 days. In in vitro cell cytotoxicity test, free atRA showed higher cytotoxic effect against CT 26 colon carcinoma cell line on 1 day. However, RAC nanoparticles showed similar cytotoxicity against CT 26 cells on 2 day. These results suggest the potential for the introduction of LMWSC nanoparticles into various biomedical fields such as drug delivery.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.826-830
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• 2013

In this paper, we carried out the investigations of both etch characteristics and mechanisms for the $SnO_2$ thin films in $O_2/BCl_3/Ar$ plasma. The dry etching characteristics of the $SnO_2$ thin films was studied by varying the $O_2/BCl_3/Ar$ gas mixing ratio. We determined the optimized process conditions that were as follows: a RF power of 700 W, a DC-bias voltage of - 150 V, and a process pressure of 2 Pa. The maximum etch rate was 509.9 nm/min in $O_2/BCl_3/Ar$=(3:4:16 sccm) plasma. From XPS analysis, the etch mechanism of the $SnO_2$ thin films in the $O_2/BCl_3/Ar$ plasma can be identified as the ion-assisted chemical reaction while the role of ion bombardment includes the destruction of the metal-oxide bonds as well as the cleaning of the etched surface form the reaction products.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.298-303
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• 2003

Bi$_4$-$_{x}$EU$_{x}$Ti$_3$O$_{12}$ (BET) thin films were etched by inductively coupled CF$_4$/Ar plasma. We obtained the maximum etch rate of 78 nm/min at the gas mixing ratio of CF$_4$(10%)/Ar(90%). The variation of volume density for F and Ar atoms are measured by the optical emission spectroscopy. As CF$_4$increased in CF$_4$/Ar plasma, the emission intensities of F increase, but Ar atoms decrease, which confirms our suggestion that emission intensity is proportional to the volume density of atoms. From X-ray photoelectron spectroscopy, the intensities of the Bi-O, the Eu-O and the Ti-O peaks are changed. By pure Ar plasma, intensity peak of the oxygen-metal (O-M : TiO$_2$, Bi$_2$O$_3$, Eu$_2$O$_3$) bond was seemed to disappear while the intensity of pure oxygen peak showed an opposite tendency. After the BET thin films was etched by CF$_4$/Ar plasma, the peak intensity of O-M bond increase slowly, but more quickly than that of peak belonged to pure oxygen atoms due to the decrease of Ar ion bombardment. Scanning electron microscopy was used to investigate etching Profile. The Profile of etched BET thin film was over 85$^{\circ}$./TEX>.