• Journal of the Korean Magnetics Society
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• v.14 no.2
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• pp.76-82
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• 2004

Crystallographic and magnetic properties for Brownmillerite-type oxides $Ca_{1-x}$Sr$_{x}$FeO$_{2.5}$ (x = 0, 0.3, 0.5, 0.7, 1.0) were investigated using x-ray diffraction (XRD) and Mossbauer spectroscopy. Polycrystalline samples were prepared by conventional solid-state reaction method. Information on exact crystalline structures, lattice parameters, bond lengths and bond angles were obtained by refining their XRD profiles using a Rietveld method. The crystal structures were found to be all orthorhombic with space group Icmm (x = 0, 0.3) and Icmm (x = 0.5, 0.7, 1.0) The lattice parameters increased monotonically with increasing Sr concentration. Both the tetrahedral and the octahedral sites were considerably distorted and elongated along b-axis. While bond lengths and bond angles O-Fe-O tend to increase minutely with the increase of Sr content, bond angles Fe-O-Fe decreased accordingly. The Mossbauer spectra showed two sets of sharp sextets originating from ferric ions occupying the tetrahedral and the octahedral sites under the magnetic transition temperature T$_{N}$. Regardless of the compositions x, the electric quadrupole splittings were -0.3 mm/s and 0.4 mm/s for the octahedral and the tetrahedral site, respectively. Above T$_{N}$, the Mossbauer spectra showed the paramagnetic doublets whose electric quadrupole splittings were about 1.6 mm/s, irrespective of compositions x. T$_{N}$ was found to decrease monotonically with the increase of Sr concentration. Ratios of absorption area for the two sites were almost 1:1 up to as high as 0.95 T$_{N}$ for all x. The result of the Debye temperature indicated that the inter-atomic binding force for the Fe atoms in the tetrahedral site was stronger than that for the octahedral site.hedral site.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.294-300
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• 2015

Objectives: The aim of this study is to identify physicochemical properties such as chemical composition, size, shape and crystal structure of powder byproducts generated from a metallization process and its 1st scrubber in the semiconductor industry. Methods: Powder samples were collected from inner chambers during maintenance of the W-plug process equipment (using tungsten hexafluoride as a precursor material) and its 1st scrubber. The chemical composition, size and shape of the powder particles were determined by field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with an energy dispersive spectroscope (EDS). The crystal structure of the powders was analyzed by X-ray diffraction (XRD). Results: From the SEM-EDS and TEM-EDS analyses, O and W were mainly detected, which indicates the powder byproducts are tungsten trioxide ($WO_3$), whereas Al, F and Ti were detected as low peaks. The powder particles were spherical and nearly spherical, and the particle size collected from the process equipment and its 1st scrubber showed 10-20 nm (agglomerates: 55-90 nm) and 16-20 nm (agglomerates: 80-120 nm) as primary particles, respectively. The XRD patterns of the yellow powder byproducts exhibit five peaks at $23.8^{\circ}$ $33.9^{\circ}$ $41.74^{\circ}$ $48.86^{\circ}$ and $54.78^{\circ}$ which correspond to the (200), (220), (222), (400), and (420) planes of cubic $WO_3$. Conclusions: We elucidated the physicochemical characteristics of the powder byproducts collected from W-plug process equipment and its 1st scrubber. This study should provide useful information for the development of alternative strategies to improve the working environment and workers' health.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.5
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• pp.534-544
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• 2011

The secondary aerosol forming potential of ambient air was first measured with the Potential Aerosol Mass(PAM) chamber at Gosan supersite on Jeju island from October 22 to November 5, 2010. PAM chamber is a small flowthrough photo-oxidation chamber with extremely high OH and $O_3$ levels. The OH exposure in the PAM chamber was $(2{\pm}0.4){\times}10^{11}{\sim}(6{\pm}1.2){\times}10^{11}$ molecules $cm^{-3}$ s and was similar to 2 to 5 days of aging in the atmosphere. By periodically turning on and off UV lamps in the PAM chamber, ambient aerosol and newly formed aerosol (e.g. called as PAM aerosol) was alternately measured. Aerosol number and mass concentration in the range of 10~487 nm in diameter was measured by SMPS 3034. With UV lamps on, the nucleation mode particles smaller than 50 nm in diameters were formed. Their number concentration was greater than 105 $cm^{-3}$, leading to increase in aerosol mass by 0~8 ${\mu}gm^{-3}$. The variations of PAM and ambient aerosols were greatly dependent on characteristics of air masses such as precursor concentrations and degree of aging. This preliminary results suggests that PAM chamber is useful to assess the aerosol formation potential of air mass and its impact on the air quality. The further analysis of data with gaseous and particulate measurements will be done.

• Journal of Microbiology and Biotechnology
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• v.25 no.4
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• pp.496-502
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• 2015

Polyketide secondary metabolites share common precursor pools, acyl-CoA. Thus, the effects of engineering strategies for heterologous and native secondary metabolite production are often determined by the measurement of pikromycin in Streptomyces venezuelae. It is hard to compare the effectiveness of engineering targets among published data owing to the different pikromycin production media used from one study to the other. To determine the most important nutritional factor and establish optimal culture conditions, medium optimization of pikromycin from Streptomyces venezuelae ATCC 15439 was studied with a statistical method, Plackett-Burman design. Nine variables (glucose, sucrose, peptone, (NH₄)₂SO₄, K₂HPO₄, KH₂PO₄, NaCl, MgSO₄·7H₂O, and CaCO₃) were analyzed for their effects on a response, pikromycin. Glucose, K₂HPO₄, and CaCO₃ were determined to be the most significant factors. The path of the steepest ascent and response surface methodology about the three selected components were performed to study interactions among the three factors, and the fine-tune concentrations for maximized product yields. The significant variables and optimal concentrations were 139 g/1 sucrose, 5.29 g/l K₂HPO₄, and 0.081 g/l CaCO₃, with the maximal pikromycin yield of 35.5 mg/l. Increases of the antibiotics production by 1.45-fold, 1.3-fold, and 1.98-fold, compared with unoptimized medium and two other pikromycin production media SCM and SGGP, respectively, were achieved.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.3
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• pp.1-8
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• 2002

In order to study electric properties of (Pb$\_$0.9/La$\_$0.1/)Ti$\_$0.975/O$_3$(PLT (10)) films with varying excess lead concentration (7.5, 10, 12.5, 15 ㏖% excess lead), the PLT films were deposited by sol-gel process. DTA analyses reveal that the crystallization temperature of the precursor powers decreased with increasing amount of excess lead. XRD patterns of PLT reveal pure perovskite structure and the preferred orientation increased with increasing Pb content in the films. With increasing amount of excess P$\_$b/, the relative permittivity ($\xi$$\_$r/) increased and leakage current density at 100 ㎸/cm transformed 4.01$\times$10$\^$-5/, 2.42$\times$10$\^$-6/, 1.27$\times$10$\^$-6/, 1.56$\times$10$\^$-6/A/㎠ respectively. In the results of hysteresis loops measured at 166 kV/cm, the remanent polarization (P$\_$r/) and the coercive field (E$\_$c) are 6.36$\mu$C/cm and 58.7 ㎸/cm, respectively (at 12.5 ㏖% excess P$\_$b/) With increasing amount of excess Pb, the remanent polarization for PLT thin film degraded to about 44%, 27%, 15%, 16% of the initial value after 10$\^$9/ cycles./TEX>) With increasing amount of excess Pb, the remanent polarization for PLT thin film degraded to about 44%, 27%, 15%, 16% of the initial value after $10^{9}$ cycles.

• Journal of the Korean Electrochemical Society
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• v.20 no.1
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• pp.7-12
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• 2017

Using a precursor of $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ as a starting material, a surface-modified cathode material was obtained by coating with KCl, where the added KCl reduces residual Li compounds such as $Li_2CO_3$ and LiOH, on the surface. The resulting electrochemical properties were investigated. The amounts of $Li_2CO_3$ and LiOH decreased from 8,464 ppm to 1,639 ppm and from 8,088 ppm to 6,287 ppm, respectively, with 1 wt% KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ that had been calcined at $800^{\circ}C$. X-ray diffraction results revealed that 1 wt% of KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ did not affect the parent structure but enhanced the development of hexagonal crystallites. Additionally, the charge transfer resistance ($R_{ct}$) decreased dramatically from $225{\Omega}$ to $99{\Omega}$, and the discharge capacity increased to 182.73mAh/g. Using atomic force microscopy, we observed that the surface area decreased by half because of the exothermic heat released by the Li residues. The reduced surface area protects the cathode material from reacting with the electrolyte and hinders the development of a solid electrolyte interphase (SEI) film on the surface of the oxide particles. Finally, we found that the introduction of KCl into $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ is a very effective method of enhancing the electrochemical properties of this active material by reducing the residual Li. To the best of our knowledge, this report is the first to demonstrate this phenomenon.

• Korean Journal of Poultry Science
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• v.34 no.3
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• pp.173-180
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• 2007

This study was conducted to evaluate conjugated linoleic acid (CLA) precursor and produce supplementation on egg production, egg quality and blood immunological parameters in laying hens. The total of 252 (32-wk) Hy-line brown commercial hens were used for 5 weeks. Dietary treatments included 1) CON (basal diet + oat 1% + soybean oil 1%), 2) WOS (basal diet + whey 0.5% + oat 0.5% + soybean oil 1%), 3) WS (basal diet+ whey 1% + soybean oil 1%), 4) WOCLA (basal diet + whey 0.5% + oat 0.5% + CLA produce 1%), 5) WCLA (basal diet + whey 1% + CLA produce 1%) and 6) FOCLA (basal diet + Fish oil 0.5% + oat 1% + CLA produce 0.5%). For 4 weeks egg shell thickness was higher in WOS and FOCLA treatments than WOCLA and WCLA treatments (P<0.05). Egg weight was significantly increased (P<0.05) in WOS and FOCLA treatments compared to WS and WCLA treatments for 4 weeks. From 4 to 5 weeks yolk high, yolk color and haugh unit were significantly higher in FOCLA treatment than CON treatment (P<0.05). IgG concentration of blood was increased in WOS and FOCLA treatments compared to CON, WS and WOCLA treatments(P<0.05). In conclusion, fish oil, CLA produce and oat supplementation in laying hens diet improve egg shell thickness, yolk high, yolk color and haugh unit, also, CLA precursor supplementaion in laying hens diet improve IgG concentration of blood higher than CON treatment.

• Journal of Soil and Groundwater Environment
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• v.25 no.3
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• pp.74-83
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• 2020

Since fine dust (PM₁₀) has a significant influence on soil and groundwater composition during dry and wet deposition processes, it is of a vital importance to understand the fate and transport of aerosol in geological environments. Fine dust is formed after the chemical reaction of several precursors, typically observed in short intervals within a few hours. In this study, deep learning approach was applied to predict the fate of fine dust in an urban area. Deep learning training was performed by combining convolutional neural network (CNN) and recurrent neural network (RNN) techniques. The PM₁₀ concentration after 1 hour was predicted based on three-hour data by setting SO₂, CO, O₃, NO₂, and PM₁₀ as training data. The obtained coefficient of determination value, R², was 0.8973 between predicted and measured values for the entire concentration range of PM₁₀, suggesting deep learning method can be developed into a reliable and viable tool for prediction of fine dust concentration.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.3
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• pp.1247-1250
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• 2015

Background: Psoriasis, a common cutaneous disorder characterized by inflammation and abnormal epidermal proliferation with a prevalence of 2-3% in the general population, may be linked to certain types of cancer. Several studies have reported an association between interleukin 10 (IL-10) variant polymorphisms and inflammatory diseases such as psoriasis vulgaris although the results vary according to the population studied. No studies have been performed in the Saudi population. The present study concerned novel variants and other genetic polymorphisms of the promoter and exonic regions of the IL10 gene in patients with moderate to severe psoriasis and potential differences in genotype compared to a group of healthy volunteers. Materials and Methods: Patients with moderate to severe psoriasis and healthy controls with no personal or family history of psoriasis were selected from the central region of Saudi Arabia. Polymorphisms of the IL 10 gene of both groups were genotyped. Results: We observed two novel variants in 5'UTR region of the promoter precursor with higher prevalence of the genotype with both wild-type alleles in patients compared to the healthy control group. The differences at positions -377 and -150 were significantly associated with disease, both the variants conferred strong protection against psoriasis in Saudi patients. Conclusions: This observation provides further support for the importance of the part that IL10 plays in the pathophysiology of this disease. Confirmation of our findings in larger populations of different ethnicities would provide evidence for the role of IL-10 in psoriasis.

• Polymer(Korea)
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• v.26 no.1
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• pp.18-27
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• 2002

Poly(ο-hydroxyamide)s as polybenzoxazoles precursors were synthesized by polycondensation from 2,2'-bis(3-amino-4-hydroxyphenyl) hexafluoropropane and various bis-acids. And the polymers were modified to acid-sensitive polyamides by introducing tetrahydropyran in order to impart photosensitivity. A study of optical transmittance at 365 nm, according to the chemical structure of bis-acid, revealed that the polymer derived from 4,4'-oxydibenzoic acid showed better optical transparency than those from other bis-acids. This tendency of optical transmittance could be explained by formation of charge transfer complex. In case of the polymer derived from 4,4'-oxydibenzoic acid, the electron accepting characteristic of bis-acid is reduced by introduction of electron donating group, -O-. Thus, optical transmittance increased due to the diminished formation of intramolecular charge transfer complex. In addition, the optical transmittance increased with increasing the THP content in the polymer. This is attributed to the reduced intermolecular interaction by the loosening of the packing density of the polymer chain.