• Polymer(Korea)
• /
• v.26 no.1
• /
• pp.80-87
• /
• 2002

A comparative study using electron-beam(EB) and thermal curing techniques was carried out to determine the effect of cure behavior and thermal stability of epoxy resins. In this work, benzylquinoxalinium hexafluoroantimonate(BQH) was used as a latent cationic catalyst for an epoxy resin. According to the thermogravimetric analysis(TGA), the decomposed activation energy based on Coats-Redfern method was higher in the case of thermal curing technique. This could be interpreted in terms of slow thermal diffusion rate resulted from high crosslink density of the thermally cured epoxy resin. However, the increase of hydroxyl group in the epoxy resin cured by EB technique was observed in near-infrared spectroscopy(NIRS) measurements, resulting in improving the stable short aromatic chain structure, integral procedural decomposition temperature, and finally ductile properties for high impact strengths.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.11
• /
• pp.914-922
• /
• 2002

Thermo-acoustic waves can be thermally generated in a compressible flow field by rapid heating and cooling, and chemical reaction near the boundary walls. This mechanism is very important in the space environment in which natural convection does not exist. Also this may be a significant factor for heat transfer when the fluids are close to the thermodynamic critical point. In this study, the generation and transmission characteristics of thermo-acoustic waves in an air-filled confined domain with two-step pulsed heating are studied numerically. The governing equations are discretized using control volume method, and are solved using PISO algorithm and second-order upwind scheme. For the purpose of stable solution, time step was set to the order of $1\times10_-9s,\;and\;grids\;are\;50\times2000$. Results show that temperature and pressure distributions of fluid near the boundary wall subjected to a rapid heating are increased abruptly, and the induced thermo-acoustic wave propagates through the fluid until it decays due to viscous and heat dissipation. Pressure waves have sharp front shape and decay with a long tail in the case of step heating, but these waves have sharp pin shape in the case of pulsed heating.

• Journal of the Optical Society of Korea
• /
• v.10 no.1
• /
• pp.1-10
• /
• 2006

Optical transparency and high diffraction efficiency are two essential factors for high performance of the photopolymer. Optical transparency mainly depends on the miscibility between polymer binder and photopolymerized polymer, while diffraction efficiency depends on the refractive index modulation between polymer binder and photopolymerized polymer. For most of organic materials, the large refractive index difference between two polymers accompanies large structural difference that leads to the poor miscibility and thus poor optical quality via light scattering. Therefore, it is difficult to design a high-performance photopolymer satisfying both requirements. In this work, first, we prepared a new phase-stable photopolymer (PMMA) with large refractive index modulation and investigated the optical properties. Our photopolymer is based on modified poly (methyl methacrylate) as a polymer binder, acryl amide as a photopolymerizable monomer, triethanolamine as initiator, and yellow eosin as a photosensitizer at 532 nm. Diffraction efficiency over 85% and optical transmittance over 90% were obtained for the photopolymer. Second, Organic-inorganic nanocomposite films were prepared by dispersing an aromatic methacrylic monomer and a photo- initiator in organic-inorganic hybrid sol-gel matrices. The film properties could be controlled by optimizing the content of an organically modified silica precursor (TSPEG) in the sol-gel matrices. The photopolymer film modified with the organic chain (TSPEG) showed high diffraction efficiency (> 90%) under an optimized condition. High diffraction efficiency could be ascribed to the fast diffusion and efficient polymerization of monomers under interference light to generate refractive index modulation. The TSPEG modified photopolymer film could be successfully used for holographic memory.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.4
• /
• pp.560-566
• /
• 2015

The self-consistent simulation based on the drift-diffusion approximation with anisotropic transport coefficients was performed. The RHCP-wave propagation was observed in MICP and this wave was refracted toward the high-density region. The calculated impedance seen from the antenna terminal shows that resistance component of MICP is a higher than that of ordinary ICP. Because of a higher resistance, the power transfer efficiency was improved to 95%. This property is practically important for large-size, low-pressure plasma sources because high resistance corresponds to high power-transfer efficiency and stable impedance matching characteristics.

• Journal of Digital Convergence
• /
• v.5 no.1
• /
• pp.55-68
• /
• 2007

It soaks but 2001 July information communication base step law enforcement and the Enforcement Ordinance are published to follow, in order to support the establishment of evaluation and protective measure in order the vulnerability analysis against the facility of the agency which manages an important information communication base hour opinion to designate information protection specialty enterprise. As information protection specialty enterprise being revealed evacuation laboratory back 12 enterprises from information communication department become designation as the consulting enterprise and they do an enterprise activity actively. It follows in diffusion of the IT and information reconciliation level the other side where our country belongs in the world-wide first group, the research against the disfunction plan of preparation comparison the fact that law it is come negligently all actuality. The network as it will give management coat fatal effect even at obstacle occurrence hour of instant for of case and IT facility of the cyber transactions which leads, in the future there to be to corporate management, there is a possibility the stable civil official of information Facilities for communications very seeing in the portion which is important. Present condition and important propulsion contents of information communication base step law enforcement after, against a vulnerability analysis of information protection relation field and evaluation consulting methodological application situation to sleep it researches from the dissertation which it sees consequently and it does.

• Journal of computational fluids engineering
• /
• v.14 no.4
• /
• pp.13-22
• /
• 2009

A two-phase (gas and liquid) flow analysis solver, named CUPID, has been developed for a realistic simulation of transient two-phase flows in light water nuclear reactor components. In the CUPID solver, a two-fluid three-field model is adopted and the governing equations are solved on unstructured grids for flow analyses in complicated geometries. For the numerical solution scheme, the semi-implicit method of the RELAP5 code, which has been proved to be very stable and accurate for most practical applications of nuclear thermal hydraulics, was used with some modifications for an application to unstructured non-staggered grids. This paper is concerned with the effects of interpolation schemes on the simulation of two-phase flows. In order to stabilize a numerical solution and assure a high numerical accuracy, the second-order upwind scheme is implemented into the CUPID code in the present paper. Some numerical tests have been performed with the implemented scheme and the comparison results between the second-order and first-order upwind schemes are introduced in the present paper. The comparison results among the two interpolation schemes and either the exact solutions or the mesh convergence studies showed the reduced numerical diffusion with the second-order scheme.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.3
• /
• pp.342-349
• /
• 2011

The purpose of this paper is to describe experimental results about the butt welding and bead on plate welding of the high power Continuous Wave (CW) Fiber laser for Ultra-low carbon Interstitial Free(IF) steel plate for gear part of car. After being welded of the gear parts by the fiber laser and electron beam Microstructures of melting zone had been mixed acicular, granular bainitic, quasi-polygonal and widmanstatten ferrite because of a radical thermal diffusion after welding, difference of critical volume and grain size. As a result of experiment, when gear parts were welded by the fiber laser and electron beam, the fiber laser welding has been stable properties without internal defects more than the electron beam welding. Therefore it has the very advantages of welding high quality and productivity more than conventional melting method. The optimal welding processing parameters for gear parts were as follows : the laser power and welding speed were 3kWatt, 30mm/sec respectively. At this time heat input was $21.2{\times}10^3J/cm^2$.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1999.07a
• /
• pp.27-30
• /
• 1999

Poly(phenylene oxide)s were used to prepare flat, integrally skinned self-supporthed asymmetric membranes by dry-wet phase separption. The intrinsic ideal gas selectivity of poly- (2,6-dimethy-1,4-phenylene oxide) (PMPO) was retained in the membranes, and improved by a coating with silicone rubber. Polymers of the same class were coated of UF supports with a silicon rubber gutter layer, yielding composite membranes with high flux but lower selectivity. The effect of th glutaraldehyde cross-linking of sodium alginate (SA) membranes on the mobility of water and ethanol has been studied with pfg nmr. Crosslinking reduces water self-diffusion, and does not seem to be stable on the timescale of weeks.

• Proceedings of the Membrane Society of Korea Conference
• /
• 2004.05a
• /
• pp.19-24
• /
• 2004

ED method is employed to effectively remove the organic acid salts in actual PDO fermentation broth. The lower electrical potential is selected to avoid the serious membrane fouling so as to ensure a stable and durative desalination process. Under the selected operation conditions, about 90% of organic acids salts are removed from PDO fermentation broth successfully by ED process. To reduce the loss of PDO product due to the diffusion, the operation time should be considered carefully. And based on mass balance equation and irreversible thermodynamics approach, a mathematical model is developed to describe the desalination process of an aqueous solution containing neutral solute by ED method. While the influence of concentration polarization is reflected by decreasing the conductivity of membrane, the model is verified well to describe the ED processes under varied operation conditions. Through the model, ED process of actual PDO fermentation broth is simulated to get a suitable scope of initial concentration in concentrated compartment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.369-372
• /
• 2004

The characteristics of antimony implants are relatively well-known. Antimony has lower diffusion coefficient, shorter implantation range, and smaller scattering as compared with conventional dopants such as phosphorous and arsenic. It has been commonly used in the doping of buried layer in Bi-CMOS process. In this paper, characteristics and appropriate condition of monitoring in antimony implant beam tuning using $Sb_2O_3$ were investigated to get a reliable process. TW(Thema Wave) and Rs(Sheet Resistance) test were carried out to set up condition of monitoring for stable operation through the periodic inspection of instruction condition. The monitoring was progressed at the point that the slant of Rs varied significantly to investigate the variation of instruction accurately.