• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.219-220
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• 2006

To understand the effect of powder characteristics on the thermal debinding behavior, PIM parts produced with powders with different particle sizes and particle shapes were examined to determine their weight losses during thermal debinding. The results show that the average diameter of the pore channel in the compact increased when the temperature increased and when coarse powders were used. However, the weight loss rates did not increase proportionally with the pore size. This suggests that the different powders that are frequently used in PIM parts do not affect the thermal debinding rate significantly. This is because the pore size is much larger than the mean free path of the decomposed gas molecules. Thus, the diffusion rates of the gases are not rate-controlling in thermal debinding. The controlling mechanism of the thermal debinding rate is the decomposition of the backbone binder in the PIM parts.

• Journal of the Korean Chemical Society
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• v.18 no.6
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• pp.447-452
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• 1974

A mechanistic possibility for the initiation of the thermal polymerization reactions are envisaged theoretically. As result of the considerations, it is assumed that the thermal polymerization reactions take place via the pseudo molecular complex which has been supposed to be an intermediate in the transition state of Diels-Alder reactions.

• Journal of Welding and Joining
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• v.12 no.2
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• pp.39-48
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• 1994

In comparison to the conventional brazing, laser welding of ceramics has advantages of direct bonding without filler material, which causes the thermal stress due to the differences of thermal expansion coefficients. In pulse-mode, laser welding of dispersion ceramic having high thermal resistance is possible at relatively low preheating temperature of $1300^{\circ}C$ In CW-mode, alumina can be welded at high preheating temperature $1500^{\circ}C$ under the condition of low feed rate of 500 mm/min, respectively. Further studies on developing mechanism of pores in the bead during laser welding of ceramics is required.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.602-613
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• 2015

As one of the mission payloads to be verified through the cube satellite mission of Cube Laboratory for Space Technology Experimental Project (STEP Cube Lab), we developed a hinge driving separation nut-type holding and releasing mechanism. The mechanism offers advantages, such as a large holding capacity and negligible induced shock, although its activation principle is based on a nylon cable cutting mechanism triggered by a nichrome burn wire generally used for cube satellite applications for the purpose of holding and releasing onboard appendages owing to its simplicity and low cost. The basic characteristics of the mechanism have been measured through a release function test, static load test under qualification temperature limits, and shock measurement test. In addition, the structural safety and operational functionality of the mechanism module under launch and on-orbit environments have been successfully demonstrated through a vibration test and thermal vacuum test.

• Journal of the Korean Ceramic Society
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• v.15 no.3
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• pp.135-139
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• 1978

Sintering oxide which was prepared by sintering at $1200^{\circ}C$ the mixture of ${\gamma}$-$Fe_2O_3$ and $Sb_2O_3$ in 2 : 1 mol ratio, showed 1st electrical switching and stable 2nd switching when D.C. voltage was applied. This electrical switching mechanism was known to be thermal mechanism from dependence of environmental temperature of threshold Voltage(Vm), Current(Im) and the conductivity of the current filament of the sintering oxide.

• Journal of Photoscience
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• v.9 no.2
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• pp.51-54
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• 2002

We propose a novel mechanism (Twist Sharing Mechanism) for the cis-trans photoisomerization of rhodopsin, based on the molecular dynamics (MD) simulation study. New things devised in our simulations are (1) the adoption of Mt. Fuji potentials in the excited state for twisting of the three bonds C9=C10, C11=C12 and C13=14 which are modeled using the detailed ab initio quantum chemical calculations and (2) to use the rhodopsin structure which was resolved recently by the X-ray crystallographic study. As a result, we found the followings: Due to the intramolecular steric hindrance between 20-methyl and 10-H in the retinal chromophore, the C12-C13 and C10-C11 bonds are considerably twisted counterclockwise in rhodopsin, allowing only counterclockwise rotation of the C11 =C12 in the excited state. The movement of 19-methyl in rhodopsin is blocked by the surrounding three amino acids, Thr 118, Met 207 and Tyr 268, prohibiting the rotation of C9=C10. As a result only all-trans form of the chromophore is obtainable as a photoproduct. At the 90$^{\circ}$ twisting of C11=C12 in the course of photoisomerization, twisting energies of the other bonds amount to about 20 kcal/mol. If the transition state for the thermal isomerization is assumed to be similar to this structure, the activation energy for the thermal isomerization around C11=C12'in rhodopsin is elevated by about 20 kcal/mol and the thermal isomerization rate is decelerated by 10$\^$-14/ times than that of the retinal chromophore in solution, protecting photosignal from the thermal noise.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.146-153
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• 2007

The detailed chemistry with reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions, have been numerically conducted to investigate the flame structure and NO emission characteristics in a non-premixed counterflow flame of blended fuel of $H_2/CO_2/Ar$. The combination of $H_2,\;CO_2$, and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of $CO_2$. Radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. All mechanisms including thermal, $NO_2,\;N_2O$, and Fenimore are also taken into account to separately evaluate the effects of $CO_2$ addition on NO emission characteristics. The increase of added $CO_2$ quantity causes flame temperature to fall since at high strain rates diluent effect is prevailing and at low strain rates the breakdown of $CO_2$ produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the ratio of the contribution by Fenimore mechanism to that by thermal mechanism in the total mole production rate becomes much larger with increase in the $CO_2$ quantity and strain rate, even though the absolute quantity of NO production is deceased. Consequently, as strain rate and $CO_2$ quantity increase, NO production by Fenimore mechanism is remarkably augmented.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.342.2-342
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• 2001

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2160-2164
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• 2007

In this study, the mechanism of enhanced thermal conductivity is elucidated on the bases of both electric double layer (EDL) and kinetic theory. A novel expression for the thermal conductivity of nanofluids is proposed and verified by applying to $Al_2O_3$ nanofluids with regard to various temperatures, volume fractions and particle sizes. In dilute nanofluids, the effects of Brownian motion and particle interaction on enhancing the thermal conductivity of nanofluids are quite comparable while the effect of particle interaction due to EDL is more prominent in dense nanofluids. The model presented in this paper shows that particle interaction due to the electrical double layer is the most responsible for the enhancement of thermal conductivity of nanofluids.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.61-64
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• 2002

Fiber reinforced metal laminate(FRML) consists of alternations layers of metal and fiber reinforced composite. The difference in the coefficients of thermal expansion between metal and composite layer produces remarkable amount of thermal residual stresses between layers. Generally, FRML shows a tensile stress in metal layers, a compressive stress in composite layers after curing. In this study, the thermal residual stresses of several types of FRML are investigated to get the best combination of metal and composite which can reduce the thermal residual stresses. The residual stress level is compared with the strength of each layers to explain the fracture mechanism of FRML.