• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.36-43
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• 2018

A great deal of difficulty is encountered in the thermo-mechanical analyses of nozzle assemblies for solid propellant rocket motors. The main issue in this paper is the modeling of the boundary conditions and the connections between the various components-gaps, relative movements of the components, contacts, friction, etc. This paper evaluates the complex phenomena of nozzle assemblies during burning time with co-simulations that include fluid, thermal surface reaction/ablation, and structural analysis. The validity of this approach is verified via comparison of analysis results with measured strains.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2494-2499
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• 2007

Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. The high-current simulation provides information about the mixing process of the hot PTFE cloud with $SF_6$ gas which is difficult to access for measurement. But it is also hard to simulate flow phenomenon because the flow in interrupter with high current, $SF_6$-PTFE mixture vapor and complex physical behavior including radiation, calculation of electric field. Using a commercial computational fluid dynamics(CFD) package, the conservation equation for the gas and temperature, velocity and electric fields within breaker can be solved. Results show good agreement between the predicted and measured pressure rise in the thermal chamber.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.181-188
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• 2010

Metal surface decontamination characteristics were investigated by using a laser ablation method. A second harmonic generation of a Q-switched Nd:YAG laser with a wave length of 532 nm, a pulse energy of 150 mJ and a pulse width of 5 ns was employed to assess the decontamination performance for metal surfaces contaminated with $CsNO_3$, $Co(NH_4)_2(SO_4)_2$, $Eu_2O_3$ and $CeO_2$. The ablation behavior was investigated for the decontamination variables such as a number of laser shots, laser fluence and an irradiation angle. Their optimum values were found to be 8, 13.3 J/$cm^2$ and $30^{\circ}$, respectively. The decontamination efficiency was different depending on the kinds of the contaminated ions, due to their different melting and boiling points and was in the order: $CsNO_3>Co(NH_4)_2(SO_4)_2>Eu_2O_3>CeO_2$. We also evaluated a correlation between the metal ablation thickness and the number of laser shots for the different laser fluences.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.10
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• pp.438-442
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• 2005

Si nanocrystal (Si NC) memory device has several advantages such as better retention, lower operating voltage, reduced punch-through and consequently a smaller cell area, suppressed leakage current. However, the physical and electrical reasons for this behavior are not completely understood but could be related to interface states of Si NCs. In order to find out this effect, we characterized electrical properties of Si NCs embedded in a SiO$_{2}$ layer by scanning probe microscopy (SPM). The Si NCs were generated by the laser ablation method with compressed Si powder and followed by a sharpening oxidation. In this step Si NCs are capped with a thin oxide layer with the thickness of 1$\~$2 nm for isolation and the size control. The size of 51 NCs is in the range of 10$\~$50 m and the density around 10$^{11}$/cm$^{2}$ It also affects the interface states of Si NCs, resulting in the change of electrical properties. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift due to the trapped charges were monitored. The results were compared with C-V characteristics of the conventional MOS capacitor structure.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.5-8
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• 2013

The ignition of aluminum particles under high pressure and temperature conditions is studied. The laser ablation method is used to generate aluminum particles exposed to pressures ranging between 0.35 and 2.2 GPa. A continuous wave $CO_2$ laser is then used to heat surface of the aluminum target until ignition is achieved. We confirm ignition by a spectroscopic analysis of AlO vibronic band of 484 nm wavelength. The radiant temperature is measured with respect to various pressures for tracing of required heating energy for ignition. Then the ignition temperature is deduced from the radiant temperature using the thermal diffusion equation. The established ignition criteria for corresponding temperature and pressure can be used in the modeling of detonation behavior of heavily aluminized high explosives or solid propellants.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.2
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• pp.67-73
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• 2016

The degradation behaviors of TiN coating layers under thermo-mechanical stress were investigated in terms of comparison of finite element analysis (FEA) and experimental data. The coating specimen was designed to quarter cylinder model, and the pulsed laser ablation was assumed as heat flux condition. The FEA results showed that heat accumulation at the center of the laser-ablated spot occurred and principle stress was concentrated at the lower region of the coating layer. The microstructural observation revealed that surface melting and decrease of the coating thickness occurred in the TiN/Inconel 617 and the interfacial cracks formed in the TiN/Si. The delamination was caused by the mechanical stress from the center to the outside of the ablated spot as the FEA results expected. It was considered that the improvement of the thermal shock resistance was attributed to higher thermal conductivity of Si wafer than that of Inconel 617.

• BMB Reports
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• v.49 no.9
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• pp.457-458
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• 2016

Recent studies have strongly implicated postsynaptic scaffolding proteins such as SAPAP3 or Shank3 in the pathogenesis of various mood disorders, including autism spectrum disorder, bipolar disorder (BD), and obsessive-compulsive disorders. Neural Abelson-related gene-binding protein 2 (nArgBP2) was originally identified as a protein that interacts with SAPAP3 and Shank3. Recent study shows that the genetic deletion of nArgBP2 in mice leads to manic/bipolar-like behavior resembling symptoms of BD. However, the function of nArgBP2 at synapse, or its connection with the synaptic dysfunctions, is completely unknown. This study provides compelling evidence that nArgBP2 regulates the spine morphogenesis through the activation of Rac1/WAVE/PAK/cofilin pathway, and that its ablation causes a robust and selective inhibition of excitatory synapse formation, by controlling actin dynamics. Our results revealed the underlying mechanism for the synaptic dysfunction caused by nArgBP2 downregulation that associates with analogous human BD. Moreover, since nArgBP2 interacts with key proteins involved in various neuropsychiatric disorders, our finding implies that nArgBP2 could function as a hub linking various etiological factors of different mood disorders.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.523-527
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• 2013

Ti-based coatings following laser ablation were studied to compare degradation behaviors by thermomechanical stress. TiN, TiCN, and TiAlN coatings were degraded by a Nd:YAG pulsed laser with an increase in the laser pulses. A decrease in the hardness was identified as the pulses increased, and the hardness levels were in the order of TiAlN > TiCN > TiN. The TiN showed cracks on the surface, and cracks with pores formed along the cracks were observed in the TiCN. The dominant degradation behavior of the TiAlN was surface pore formation. EDS results revealed that diffusion of substrate atoms to the coating surface occurred in the TiN. Delamination occurred in the TiN and TiCN, while the TiAlN which has higher thermal stability than the TiN and TiCN maintained adhesion to the substrate. It was considered that the decrease in the hardness of the Ti-based hard coatings is attributed to surface cracking and the diffusion of substrate atoms.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.67-69
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• 2003

The magnetic properties of single- and poly-crystalline $La_{0.7}Sr_{0.3}MnO_3/Pr_{0.65}Ca_{0.35}MnO_3$ multilayered (ML) films, and composite (CP) $(La_{0.7}Sr_{0.3})_{0.5}(Pr_{0.65}Ca_{0.35}_{0.5}MnO_3$ films, prepared by laser ablation, have been investigated in a wide temperature range. It was shown that the transformation from an incoherent to a coherent interface in the ML films leads to an enhancement of the ferromagnetic coupling between layers and to a single-phase magnetic transition. The amorphous CP films demonstrate a paramagnetic behavior of the magnetization with a sharp peak at $T_{G}\approx$45 K, which was interpreted as the formation of Griffiths phase. A short-term annealing at $750^{\circ}C$ induced the complete crystallization of film, and a recovery of the ferromagnetic and the metal-insulator transitions.

• Korean journal of applied entomology
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• v.52 no.3
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• pp.249-253
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• 2013

The adzuki pod worm, Matsumuraeses phaseoli (Matsumura) is an insect pest that attacks the flowers and pods of Vigna angularis. The circadian rhythms of eclosion and mating, and the effects of age and antenna ablation on mating success, were investigated. With a photoperiodic regime of 16:8 (Light:Dark) h, most adult eclosion was observed within 4 h after lights-on. Most adult mating was observed during the scotophase, although some occurred within 2 h after lights-on. However, the adults did not copulate on the day of emergence. The mating rate increased with adult age: being higher in the 4-d-old adult pairs than pairs of lower age. Most of the antennectomized males or females did not copulate with normal individuals of the opposite sex.