• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.252-257
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• 1991

This paper proposed that the eddy-current measurement method can be used a means of in-process measuring the hardening depth in Laser surface treatment process. Also, this paper deal with the numerical analysis of magnetic flux distribution and experimental result of measurement. In Laser heat treatment process of steels, a thin layer of the substrate is rapidly heated to austenitizing temperature and subsequently cooled at a very fast rate due to the self-quenching by heat conduction into the bulk body, to produce a martensite structure which have low magnetic permeability. The eddy-current measurement method depends on the properties of material to be measured such as electric conductivity, magnetic permeability and geometry. In this paper, the hardening depth was measured by detecting relevant magnetic permeability changes caused by heat treatment of steels.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.40.1-40.1
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• 2017

Massive early-type galaxies (ETG) have been spectroscopically confirmed up to z>3 which, together with their ages and abundances at z>1.5, implies that their progenitors must have converted gas into stars on short timescales. The termination of star formation in these galaxies can occur through several channels, but they remain largely conjectural, in part due to the current lack of direct measurements of the amount of residual gas in high redshift ETGs. Here I will present constraints on the star formation rate and dust/gas content of z=1.4-2.5 ETGs. These galaxies, close to their epoch of quenching, contained more than 2 orders of magnitude more dust than their local counterparts, which suggests the presence of substantial amounts of gas and a low star formation efficiency.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.26-33
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• 1994

A new reliable method to prediet the axial vapor fraction distribution from the measured probability density of the liquid bulk temperature is suggested in this paper. And also the actual quality of the subcooled boiling flow is easily calculated from the liquid bulk temperature. When the heat generating rate is reached to the CHF value, the sharp wall temperature increasing by the wall temperature fluctuation is occurred under the CHF condition. This paper presents the simple wall temperature fluctuation model of transition boiling by the repeating process of overheating and quenching, when the coalescent bubble passes slowly near the wall. Experiments for the subcooled R-113 flow are carride-out in the range of(0.9399~4.461)${\times}10^6$kg/$m^2$hr mass velocity and 10~3$0^{\circ}C$ intel subcooling condition.

• Transactions of Materials Processing
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• v.14 no.3 s.75
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• pp.215-223
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• 2005

A numerical analysis program is developed by FDM scheme for the prediction of microstructural transformation during heat treatment of steels. In this study, multi-phase model was used fur description of diffusional austenite transformations in low-alloy hypoeutectoid steels during cooling after austenitization. A fundamental property of the model consisting of coupled differential equations is that by taking into account the rate of austenite grain growth, it permits the prediction of the progress of ferrite, pearlite, and bainite transformations simultaneously during quenching and estimate the amount of martensite also by using K-M eq. In order to simulate the microstructural evolution during tempering process, another Avrami-type eq. was adopted and method for vickers hardness prediction was also proposed. To verify the developed program, the calculated results are compared with experimental ones of casting product. Based on these results, newly designed heat treatment process is proposed and it was proved to be effective for industry.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.119-122
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• 2003

We report a dramatic increase in the photo-stability of a blue-emitting polymer, poly(9,9-dioctylfluorene), achieved by the addition of gold nanoparticles to the polymer. The optical absorption band of gold nanoparticles is tuned to resonate the triplet exciton-ground state band gap energy of the polymer. The photo-oxidation rate of poly(9,9-dioctylfluorene) was drastically reduced by doping the polymer with a very small amount ($10^{-6}-10^{-5}$ volume fraction) of gold nanoparticles. The gold nanoparticles used herein act as the quenching agent of the triplet states and can be directly applied to various blue light emitting polymer thin film ( < 100 nm ) devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.248-248
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• 2010

We have demonstrated new functionalities of Ag-doped chalcogenide glasses based on their capabilities as solid electrolytes. The influence of silver on the properties of the newly formed materials is regarded in terms of diffusion kinetics, and Ag saturation is related to the composition of the hosting material. Silver saturated in chalcogenide glass has been used in the formation of solid electrolyte, which is the active medium in the programmable metallization cell (PMC) device. In this paper, we investigated the optical properties of Ag-doped chalcogenide thin film by He-Ne laser beam exposure, which is concerned with the Ag-doping effect of PMCs before or after annealing. Chalcogenide bulk glass was fabricated by a conventional melt quenching technique. Amorphous chalcogenide and Ag thin films were prepared by e-beam evaporation at a deposition rate of about $4\;{\AA}/sec$. As a result of resistance change with laser beam exposure, the resistance abruptly dropped from the initial value of $1.4\;M{\Omega}$ to the saturated value of $400\;{\Omega}$.

• Journal of Photoscience
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• v.5 no.3
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• pp.125-129
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• 1998

Occurrence of an electron (or H atom equivalent to one electron plus H+) transfer from $\alpha$- tocopherol $\alpha$(TOH) to a number of photosensitizers in theri triplet states were investigated by monitoring the ESR signal of $\alpha$-chromaoxyl radical ($\alpha$(TO.) in ethanolic solutions of $\alpha$TOH and the sensitizers under continuous illumination. Every sensitizer molecule examined, such as protocholorophyllide (Pchl), hematoporphyrin and rose bengal which are generally regarded as efficient type II photosensitizers and thus have long-lived triplet states, was found to actively participate in an electro transfer reaction with $\alpha$TOH even under air-saturation conditions, generating $\alpha$TOH complex as an intermediate in a fashion of Michaelis-Menten type of reaction. For the reaction of $\alpha$TOH with triplet Pchl, the rate law was derived by applying the steady approximation for the binary complex, triplet Pchl-$\alpha$TOH , which turned out to be well consistent with the kinetic data.

• Transactions of Materials Processing
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• v.16 no.3 s.93
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• pp.193-200
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• 2007

Simulations of the thermally-induced residual stresses and birefringence in freely quenched plates of polycarbonate were performed by using the linear viscoelastic and photoviscoelastic constitutive equations for the mechanical and optical properties, respectively, and the first order rate equation for volume relaxation. The predictions for the birefringence showed good agreement with experimental measurements. However, for initial temperature close to the glass transition temperature, some differences existed around the surface layer. Based on the simulation, the influences of various cooling conditions on the residual stress and birefringence in plates were investigated. The residual stress and birefringence increased with increasing initial temperature, decreasing coolant temperature and increasing heat transfer coefficient of coolants.

• Journal of Korea Foundry Society
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• v.11 no.5
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• pp.406-413
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• 1991

Ductile cast iron(DCI) with a multi-phase(ferrite-bainite-martensite) structures was produced by various special heat treatment. Intercritical heat treatment(I. C.), intermediate heat treatment(I. M.) and step quenching(S. Q.) were used to strengthen and toughen the fracture initiation sites such as graphite-marix interfaces and eutectic cell boundaries in DCI. The purpose of this study was to investigate of DCI by the special heat treatment. (I. C., I. M., and S. Q.) At a result, bainite nucleation rate at higher temperature was higher than that of at lower temperature, and shapes of bainite and martensite became bar /spheroidal type with increase of isothermal transformation time.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.107-114
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• 2007

Underwater wet arc welds were experimentally performed on 11mm thick SS400 mild steel plate as base metal by using six different types of flux coated electrodes of 4.0mm diameter; KSKR, KSKT, USBL, JPUW, UWEA, and UWEB. As results, the developed flux coated underwater electrode had a good weldability compared with other domestic terrestrial electrodes. By rapid cooling rate, the hardness value of HAZ were increased by quenching effects. Mechanical properties for the multi-pass butt-welding specimen are also tested experimentally. The feasibility of the developed underwater electrode was experimentally studied and the results achieved in this wet arc welds have shown that the developed wet welding electrode UWEB can have a degree of integrity.