• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.338-343
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• 2006

The effects of lead-borosilicate glass frits on the sintering behavior and microwave dielectric properties of ceramic-glass composites were investigated as functions of glass composition of glass addition ($10{\sim}50vol%$), softening point (Ts) of the glass, and sintering temperature of the composites ($500{\sim}900^{\circ}C$ for 2 h). The addition of 50 vol% glass ensured successful sintering below $900^{\circ}C$. Sintering characteristics of the composites were well described in terms of Ts. PbO addition in to the glass enhanced the reaction with $Al_{2}O_3$ to form liquid phase and $PbAl_{2}Si_{2}O_8$, which was responsible to lower Ts. Dielectric constant(${\epsilon}_r$), $Q{\times}f_0$ and temperature coefficient of resonant frequency (${\tau}_f$) of the composite with 50 vol% glass contents ($B_{2}O_{3}:PbO:SiO_{2}:CaO:Al_{2}O_3$ = 5:40:45:5:5) demonstrated 8.5, 6,000 GHz, $-70\;ppm/^{\circ}C$, respectively, which is applicable to substrate requiring a low dielectric constant. When the same glass composition was applied sinter $MgTiO_3\;and\;TiO_2,\;at\;900^{\circ}C$ (50 vol% glass in total), the properties were 23.8, 4,000 GHz, $-65ppm/^{\circ}C$ and 31.1, 2,500 GHz, $+80ppm/^{\circ}C$ respectively, which is applicable to filter requiring an intermidiate dielectric constant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.808-812
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• 2006

In this dissertation, Ru-Zr metal gate electrode deposited on two kinds of dielectric were formed for MOS capacitor. Sample co-sputtering method was used as a alloy deposition method. Various atomic composition was achieved when metal film was deposited by controlling sputtering power. To study the characteristics of metal gate electrode, C-V(capacitance-voltage) and I-V(current-voltage) measurements were performed. Work function and equivalent oxide thickness were extracted from C-V curves by using NCSU(North Carolina State University) quantum model. After the annealing at various temperature, thermal/chemical stability was verified by measuring the variation of effective oxide thickness and work function. This dissertation verified that Ru-Zr gate electrodes deposited on $SiO_{2}\;and\;ZrO_{2}$ have compatible work functions for NMOS at the specified atomic composition and this metal alloys are thermally stable. Ru-Zr metal gate electrode deposited on $SiO_{2}\;and\;ZrO_{2}$ exhibit low sheet resistance and this values were varied with temperature. Metal alloy deposited on two kinds of dielectric proposed in this dissertation will be used in company with high-k dielectric replacing polysilicon and will lead improvement of CMOS properties.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.19-19
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• 2002

Perovskite-type titanate dielectrics have attracted much attention in memory devices such as DRAMs or FeRAMs due to their high dielectric constants. However, low volatility of the Ba, Sr, Pb or Zr precursors with only thd ligands has limitations in obtaining high quality thin films by liquid source metal organic chemical vapor deposition (LS-MOCVD) processes. To improve the volatility of these precursors, many attempts have been made such as adding polyether ligands to satisfy the coordinative saturation. We report the synthesis of new precursors Ba(thd)₂(tmeea) and Sr(thd)₂(tmeea), where tmeea = tris[2-(2-methoxyethoxy)ethyl]amino, and LS-MOCVD of barium strontium titanate (BSTO) thin films using these precursors. Due to increased basicity of amines compared with ethers, it is expected that the nitrogen-donor ligand will make a strong bond to a metal than an analogous oxygen-donor ligand, consequently improving the volatility and thermal behavior of these precursors. Thin films of BSTO were grown on Pt(111)/SiO₂/Si(100) substrates by LS-MOCVD using a cocktail source consisting of the conventional Ti precursor Ti(thd)₂(O/sup i/Pr), and these new Ba and Sr precursors. As-grown films were characterized by XPS, SEM, XRD, XRF, and C-V and I-V measurements. BSTO films grown at 420℃ were stoichiometric barium strontium titanate with very smooth surface morphology and their dielectric constants were found to be as targe as 450. Dependence of the composition, microstructure and the electrical properties of the BSTO films on the growth temperature, annealing temperature, working pressure, and the composition of the cocktail source will be discussed.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.9 no.1
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• pp.33-54
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• 2003

The aim of this study was to develop a model that could be used in the design of modified atmosphere packaging (MAP) for peaches. Respiratory data at 5, 10, $20^{\circ}C$ for peaches were gathered and altered for create useful respiration model. Packaging materials were conventional low density polyethylene and polypropylene with anti-fog, and anti-fungi treatments, and thickness was $30{\mu}m$ and $50{\mu}m$ each. Permeability tests were performed to find their oxygen, carbon dioxide, water vapor transmission rate as increases in temperature. Test results were then converted to logarithm format for MAP modeling. The maximum rate of oxygen uptake increased with increasing temperature. Optimum gas composition in the package system for fruits were set according to literature and upper or lower limits of oxygen and dioxide established. To predict gas composition at certain storage time, weight of fruits, film thickness, film type, and other variables, respiration rate was studied at various storage conditions. The results of tests were used to calculate Cameron's model and converted to a cubic estimation equation. The validity of the model was tested experimentally by observing actual atmospheric changes inside packages. This result of study may be useful for designing dynamic gas exchange MAP systems for similar agricultural products.

• Korean Journal of Agricultural Science
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• v.46 no.2
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• pp.239-256
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• 2019

The quality of tomatoes drastically changes according to storage conditions, such as temperature, humidity, and air composition. High storage temperatures result in the degradation of the firmness and color of tomatoes and in decay by bacteria, whereas chilling injury and softening can be caused by storage at low temperatures. The gas composition in the storage and packaging are other parameters that influence the quality and shelf life of tomatoes by preventing excessive transpiration and respiration. In addition, tomato quality is dependent on the degree of maturity and harvest season. Because there are many quality parameters, it is necessary to systemically establish an optimal standard, and this approach requires collecting and reviewing various data on storage conditions. The aim of this review was to provide basic information by comparing and analyzing studies on the changes in tomato quality (firmness, color, lycopene content, and acidity of tomatoes) during storage and to describe a few models that can assess the quality parameters. Many studies have provided results from experiments on the effects of postharvest control (e.g., storage temperature, packaging film, and gas treatment, as reviewed above) on tomato quality including firmness, soluble solids content, and lycopene content. However, it is still necessary to conduct an overall analysis of the published conditions and to determine the best method for preserving the quality of tomatoes as well as other fruits.

• Korean Journal of Metals and Materials
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• v.46 no.2
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• pp.69-79
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• 2008

A composition consisting of 10 nm-Ni/1 nm-Pd/(30 nm or 70 nm-poly)Si was thermally annealed using rapid thermal for 40 seconds at $300{\sim}1100^{\circ}C$ to improve the thermal stability of conventional nickel monosilicide. The annealed bilayer structure developed into $Ni(Pd)Si_x$, and the resulting changes in sheet resistance, microstructure, phase, chemical composition, and surface roughness were investigated. The silicide, which formed on single crystal silicon, could defer the transformation of $NiSi_2$, and was stable at temperatures up to $1100^{\circ}C$. It remained unchanged on polysilicon substrate compared with the sheet resistance of conventional nickel silicide. The silicides annealed at $700^{\circ}C$, formed on single crystal silicon and 30 nm polysilicon substrates exhibited 30 nm-thick uniform silicide layers. However, silicide annealed at $1,000^{\circ}C$ showed preferred and agglomerated phase. The high resistance was due to the agglomerated and mixed microstructures. Through X-ray diffraction analysis, the silicide formed on single crystal silicon and 30 nm polysilicon substrate, showed NiSi phase on the entire temperature range and mixed phases of NiSi and $NiSi_2$ on 70 nm polysilicon substrate. Through scanning probe microscope (SPM) analysis, we confirmed that the surface roughness increased abruptly until 36 nm on 30 nm polysilicon substrate while not changed on single crystal and 70 nm polysilicon substrates. The Pd-inserted nickel monosilicide could maintain low resistance in a wide temperature range and is considered suitable for nano-thick silicide processing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.33-33
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• 2007

In PDP industry, the dielectrics and barrier ribs have been required with low dielectric constant, low melting point and Pb-free composition due to the low power consumption, low signal delay time and the environment restriction. We were studied with $B_2O_3-Al_2O_3$-SrO glass systems about optical, thermal and dielectric properties. The glass forming region of the $B_2O_3-Al_2O_3$-SrO glass systems was narrow due to the amount of the glass former $(B_2O_3)$. The glass transition temperature (Tg) of the glasses was at $550{\sim}590^{\circ}C$. The glasses have 6~8 for the dielectric constant. Furthermore, the transmittance of the glasses was over 80% on the range of the visible ray. From the results, the glasses of the $B_2O_3-Al_2O_3$-SrO glass systems should enable to be a good candidate of the PDP devices for information display with low dielectric constant. The aim of this study is to give a fundamental result of new glass system for low dielectric constant in the information display.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1058-1063
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• 1998

As a series of study on the hygienization and long-term storage of dried red pepper and red pepper powder using gamma irradiation, water activity and fatty acid composition were monitored for stored samples. In proximate composition of dried pepper, moisture contents were 21.75 % in pericarp and 9.30% in seed, and crude fats were 7.20% (fresh wt.) in pericap and 22.50% in seed, respectively. Proximate components were stable against irradiation up to 10 kGy. Moisture contents and water activity of packaged samples in PE (0.1mm)/polycloth (whole pepper) and in nylon $15\;{\mu}m/PE\;100\;{\mu}m$ (pepper powder) were not remarkably changed during storage for 9 months under room temperature $(3{\sim}30^{\circ}C,\;RH\;50{\circ}95%,\;whole\;pepper,\;powder)$ and low temperature $(5{\sim}10^{\circ}C,\;pepper\;powder)$, respectively. Fatty acids of dried red pepper were mainly composed of linoleic acid, oleic acid, palmitic acid and linolenic acid. Particularly higher composition of unsaturated fatty acids were observed in seed $(84{\sim}85%)$ than in pericarp $(73{\sim}76%)$, and which showed negligible changes during post irradiation period for 6 months.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.5
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• pp.665-674
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• 2019

Objective: In tropical regions, as in temperate regions where seasonality of forage production occurs, well-preserved forage is necessary for animal production during periods of forage shortage. However, the unique climate conditions (hot and humid) and forage characteristics (high moisture content and low soluble carbohydrate) in the tropics make forage preservation more difficult. The current study used natural ensiling of tropical forage as a model to evaluate silage characteristics under different temperatures ($28^{\circ}C$ and $40^{\circ}C$). Methods: Four tropical forages (king grass, paspalum, white popinac, and stylo) were ensiled under different temperatures ($28^{\circ}C$ and $40^{\circ}C$). After ensiling for 30 and 60 days, samples were collected to examine the fermentation quality, chemical composition and microbial community. Results: High concentrations of acetic acid (ranging from 7.8 to 38.5 g/kg dry matter [DM]) were detected in silages of king grass, paspalum and stylo with relatively low DM (ranging from 23.9% to 30.8% fresh material [FM]) content, acetic acid production was promoted with increased temperature and prolonged ensiling. Small concentrations of organic acid (ranging from 0.3 to 3.1 g/kg DM) were detected in silage of white popinac with high DM content (50.8% FM). The microbial diversity analysis indicated that Cyanobacteria originally dominated the bacterial community for these four tropical forages and was replaced by Lactobacillus and Enterobacter after ensiling. Conclusion: The results suggested that forage silages under tropical climate conditions showed enhanced acetate fermentation, while high DM materials showed limited fermentation. Lactobacillus and Enterobacter were the most probable genera responsible for tropical silage fermentation.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.66.3-67
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• 2021

Low-mass stars form by the gravitational collapse of dense molecular cores. Observations and theories of low-mass protostars both suggest that accretion bursts happen in timescales of ~100 years with high accretion rates, so called episodic accretion. One mechanism that triggers accretion bursts is infalling fragments from the outer disk. Such fragmentation happens when the disk is massive enough, preferentially activated during the embedded phase of star formation (Class 0 and I). Most observations and models focus on the gas structure of the protostars undergoing episodic accretion. However, the dust and ice composition are poorly understood, but crucial to the chemical evolution through thermal and energetic processing via accretion burst. During the burst phase, the surrounding material is heated up, and the chemical compositions of gas and ice in the disk and envelope are altered by sublimation of icy molecules from grain surfaces. Such alterations leave imprints in the ice composition even when the temperature returns to the pre-burst level. Thus, chemical compositions of gas and ice retain the history of past bursts. Infrared spectral observations of the Spitzer and AKARI revealed a signature caused by substantial heating, toward many embedded protostars at the quiescent phase. We present the AKARI IRC 2.5-5.0 ㎛ spectra for embedded protostars to trace down the characteristics of accretion burst across the evolutionary stages. The ice compositions obtained from the absorption features therein are used as a clock to measure the timescale after the burst event, comparing the analyses of the gas component that traced the burst frequency using the different refreeze-out timescales. We discuss ice abundances, whose chemical change has been carved in the icy mantle, during the different timescales after the burst ends.