• Journal of the Korean Society for Heat Treatment
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• v.14 no.5
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• pp.282-285
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• 2001

Based on the mass balance of anion and cation fluxes, the parabolic rate constant ($K_p$) of oxide grown during the high-temperature oxidation of metal is theoretically calculated. It is assumed that the diffusion of oxygen anion and metal cation through oxide scale obeys the Fick's 1st law, the growth of oxide is controlled by the diffusion of ions, electrical potential gradient as driving force for diffusion of ions is ignored, and oxidation occurs within an existing oxide layer. Then, the parabolic rate constant can be expressed by $K_p=[2{\rho}_{MmOn}{M^2}_{MmOn}(mD_oC_o{^e}+nD_MC_M{^e})/nm]$.

• Korean Journal of Materials Research
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• v.14 no.3
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• pp.163-167
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• 2004

TiAl(La)N thin films were oxidized in vacuum of about 7 Pa to reduce the oxidation of WC-Co as a substrate. The oxidation rate constants of the thin films were quantified by an assumption of parabolic oxidation. Increasing AI content significantly decreased the parabolic oxidation rate constant. A simultaneous addition of AI and La was more effective to reduce the oxidation rate. The parabolic oxidation rate constant of $Ti_{0.66}$ $Al_{0.32}$ $La_{ 0.02}$N thin film at 1273 K showed about ten times lower than that of TiN. The addition of a small amount of La with Al induced the preferential formation of dense $\alpha$ $-Al_2$$O_3$ film in oxide film, leading to the abrupt reduction of oxidation rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.237-244
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• 2003

This paper presents the design of a QPSK/16-QAM downstreams receiver chip. The proposed chip consists of a blind equalizer, a timing recovery block and a carrier recovery block. The blind equalizer uses a DFE sturucture using CMA(Constant Module Algorithm). The symbol timing recovery uses the modified parabolic interpolator. The decision-directed carrier recovery is used to remove the carrier frequency offset, phase offset and phase jitter. The implemented LMDS receiver can support four data rates, 10, 20, 30 and 40 Mbps and can accommodate the symbol rate up to 10 Mbaud. This symbol rate is faster than existing QAM receivers.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.449-452
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• 1998

We have studied the oxidatio nrte of $Si_{1-x}Ge_{x}$ epitaxial layer grown by MBE(molecular beam epitaxy). Oxidation were performed at 700.deg. C, 800.deg. C, 900.deg. C, and 1000.deg. C. After the oxidation, the results of AES(auger electron spectroscopy) showed that Ge was completely rejected out of the oxide and pile up at $SiO_{2}/$Si_{1-x}Ge_{x}$ interface. It is shown that the presence of Ge at the $SiO_{2}$/$Si_{1-x}Ge_{x}$ interface changes the dry oxidation rate. The dry oxidation rate was equal to that of pure Si regardless of Ge mole fraction at 700.deg. C and 800.deg.C, while it was decreased at both 900.deg. C and 1000.deg.C as the Ge mole fraction was increased. The ry oxidation rates were reduced for heavy Ge concentration, and large oxidation time. In the parabolic growth region of $Si_{1-x}Ge_{x}$ oxidation, The parabolic rate constant are decreased due to the presence of Ge-rich layer. After the longer oxidation at the 1000.deg.C, AES showed that Ge peak distribution at the $SiO_{2}$/$Si_{1-x}Ge_{x}$ interface reduced by interdiffusion of silicon and germanium.

• Journal of the Mineralogical Society of Korea
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• v.9 no.1
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• pp.1-6
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• 1996

Woolastonite from Susan occurs as intercalations in limestone beds of Lower Paleozoic Joseon Supergroup. It is a thermal metamorphic product of impure limestone. Electron microprobe analysis shows that it is considerably pure wollastonite. It has triclinic cell with a=7.932$\AA$, b=7.328$\AA$, c=7.069$\AA$, $\alpha$=89.995$^{\circ}$, $\beta$=$95.255^{\circ}$, and $ \Upsilon=103.367^{\circ}$.Dissolution behaviors of wollastonite have been studied conducting three different dissolution experiments; two different reactions with HC1 (one batch and one re-initialization experiment) and one traction with distilled water. In the batch type powder wollastonite-HCl reaction, pH of solution rapidly increases in the early stage and then its rate of increase slows down to reach plateau resulting in parabolic relationship with time. It is represented by the early rapid rise and fall in pH giving a sharp pH-edge and succeeding slow rise in the re-initialization experiment. The early rapid rise in pH is due to the rapid sorption of H- in solution to oxygens on the reactive surface of wollastonite and the fall in pH means that all reactive surface sites are occupied by H- ions and no more H- adsorption occurs. The slow rise in pH following the pH- edge is due to the dissolution of wollastonite as evidenced by the correlation of pH variation and cation concentration. Dissolution of powder wollastonite in HCl shows linear trend with time. Si is dissolved predominantly over Ca at a constant rate. Ca is dissolved predominantly in the very early stage. Dissolution rate of coarse-grained wollastonite fragments in distilled water is parabolic with times howing a rapid reaction in the early stage and a slow reaction in the advanced stage. The Ca/Si ratio in solution is high in the case of coarse-grained wollastonite fragment as compared with powder wollastonite. The coarse-grained wollastonite fragment-water (acid) reaction resulted in the solution with an elevated constant pH value (alkaline) giving an important significance on the environmental view point.

• Journal of Power System Engineering
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• v.21 no.2
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• pp.14-19
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• 2017

The corrosion characteristics of Al-Si-Mg alloy were investigated in $O_2$ and $H_2S/H_2$ environments at high temperature. The weight gain and the reaction rate constant of the Al-Si-Mg alloy were measured in the oxygen and hydrogen sulfide environments at 773K. The weight gain of Al-Si-Mg alloy was showed parabolic increase in the oxygen and hydrogen sulfide environments. The reaction rate constants were confirmed to be $1.45{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the oxygen environment and $6.19{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the hydrogen sulfide environment respectively. As a result of XPS analysis on the specimen surface, $Al_2O_3$ and MgO compounds were detected in oxygen environment and $Al_2(SO_4)_3$ sulfate was detected in the hydrogen sulfide environment. Corrosion rate of Al-Si-Mg alloy was about 4.3 times faster in hydrogen sulfide environment than oxygen environment.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.236-241
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• 2016

The common ice plant (Mesembryanthemum crystallinum L.) has some medicinal uses and recommended plant in closed-type plant factory. The objective of this study was to estimate the cardinal temperatures for seed germination of the common ice plant using bilinear, parabolic, and beta distribution models. Seeds of the common ice plant were germinated in the dark in a growth chamber at four constant temperatures: 16, 20, 24, and $28^{\circ}C$. For this, four replicates of 100 seeds were placed on two layers of filter paper in a 9-cm petri dish and radicle emergence of 0.1 mm was scored as germination. The times to 50% germination were 4.3, 2.5, 2.0, and 1.8 days at 16, 20, 24, and $28^{\circ}C$, respectively, indicating that the germination of this warm-weather crop increased with temperature. Next, the time course of germination was modeled using a logistic function. For the selection of an accurate model, seeds were germinated in the dark at constant temperatures of 6, 12, 32, and $36^{\circ}C$. Germination started earlier and increased rapidly at temperatures above $20^{\circ}C$. The minimum, optimal, and maximum temperatures were estimated by regression of the inverse of time to 50% germination rate, as a function of the temperature gradient. The different functions estimated differing minimum, optimal and maximum temperatures, with 5.7, 27.7, and $36.5^{\circ}C$, respectively for the bilinear function, 13.4, 25.0, and $36.6^{\circ}C$, respectively, for the parabolic function and 7.8, 25.9, and $36.0^{\circ}C$, respectively, for the beta distribution function. The models estimated that the inverse of time to 50% germination rate was 0 at 6 and $36^{\circ}C$. The observed final germination rates at 12 and $32^{\circ}C$ were 62 and 97%, respectively. Our data show that a beta distribution function provides a useful model for estimating the cardinal temperatures for germination of seed from the common ice plant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1080-1086
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• 2005

We have studied the Ge redistribution after dry oxidation and the oxide growth rate of $Si_{1-x}Ge_x$ epitaxial layer. Oxidation were performed at 700, 800, 900, and $1,000\;^{\circ}C$. After the oxidation, the results of RBS (Rutherford Back Scattering) & AES(Auger Electron Spectroscopy) showed that Ge was completely rejected out of the oxide and pile up at $Si_{1-x}Ge_x$ interface. It is shown that the presence of Ge at the $Si_{1-x}Ge_x$ interface changes the dry oxidation rate. The dry oxidation rate was equal to that of pure Si regardless of Ge mole fraction at 700 and 800$^{\circ}C$, while it was decreased at both 900 and $1,000^{\circ}C$ as the Ge mole fraction was increased. The dry of idation rates were reduced for heavy Ge concentration, and large oxiidation time. In the parabolic growth region of $Si_{1-x}Ge_x$ oxidation, the parabolic rate constant are decreased due to the presence of Ge-rich layer. After the longer oxidation at the $1,000^{\circ}C$, AES showed that Ge peak distribution at the $Si_{1-x}Ge_x$ interface reduced by interdiffusion of silicon and germanium.

• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.371-377
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• 1995

Silicon oxide films were grown on single-crystal silicon substrates at low temperatures (25~205$^{\circ}C$) in a low pressure electron cyclotron resonance (ECR) oxygen plasma. The growth rate of the silicon oxide film increased as the temperature increased or the pressure decreased. Also, the thickness of the silicon oxide film increased at negative bias voltage, but not changed at positive bias voltage. The growth law of the silicon oxide film was approximated to the parabolic form. Capacitance-voltage (C-V) and current density-electric field (J-E) characteristics were studied using Al/SiO2/p-Si MOS structures. For a 10.2 nm thick silicon oxide film, the leakage current density at the electric field of 1 MVcm-1 was less than 1.0$\times$10-8Acm-2 and the breakdown field was higher than 10 MVcm-1. The flat band voltage of Al/SiO2/p-Si MOS capacitor was varied in the range of -2~-3 V and the effective dielectric constant was 3.85. These results indicate that high quality oxide films with properties that are similar to those of thermal oxide film can be fastly grown at low temperature using the ECR oxygen plasma.

• Journal of the Korean Ceramic Society
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• v.31 no.7
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• pp.753-758
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• 1994

(100) Si and 4$^{\circ}$off (100) Si were oxidized in dry oxygen, and the differences in thermal oxidation behavior and electrical characteristics between two specimens were investigated. Ellipsometer measurements of the oxide thickness produced by oxidation in dry oxygen from 1000 to 120$0^{\circ}C$ showed that the oxidation rates of the 5$^{\circ}$ off (100) Si were more rapid than those of the (100) Si and the differences between them decreased as the oxidation temperature increased. The activation energies based on the parabolic rate constant, B for (100) and 4$^{\circ}$off (100) Si were 25.8, 28.6 kcal/mol and those on the linear rate constant, B/A were 56.8, 54.9 kcal/mol, respectively. Variation of C-V characteristics with the oxidation temperature showed that the flat band voltages were shifted positively and surface state charge densities decreased as the oxidation temperature increased, and the surface state charge density of the 4$^{\circ}$off (100) Si was lower than that of the (100) Si. Also considerable decrease in the density of oxidation induced stacking faults (OSF) for the 4$^{\circ}$off (100) Si was observed through optical microscopy after preferentially etching off the oxide layer.