• Macromolecular Research
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• v.13 no.1
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• pp.45-53
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• 2005

In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacryl­amide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N'-methylenebis­acrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g­PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-poly­methacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the Alg-g-PMAM or the H-Alg-g-PMAM was characterized by FTIR spectroscopy. The effects of the grafting variables (i.e., concentration of MBA, MAM, and APS) and the alkaline hydrolysis conditions (i.e., NaOH concentration, hydrolysis time, and temperature) were optimized systematically to achieve a hydrogel having the maximum swelling capacity. Measurements of the absorbency in various aqueous salt solutions indicated that the swelling capacity decreased upon increasing the ionic strength of the swelling medium. This behavior could be attributed to a charge screening effect for monovalent cations, as well as ionic cross-linking for multivalent cations. Because of the high swelling capacity in salt solutions, however, the hydrogels might be considered as anti-salt superabsorbents. The swelling behavior of the superabsorbing hydrogels was also measured in solutions having values of pH ranging from 1 to 13. Furthermore, the pH reversibility and on/off switching behavior, measured at pH 2.0 and 8.0, suggested that the synthesized hydrogels were excellent candidates for the controlled delivery of bioactive agents. Finally, we performed preliminary investigations of the swelling kinetics of the synthesized hydrogels at various particle sizes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.325-325
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• 2007

The perovskites in the $LaAlO_3-BaZrO_3$ system (i.e., $(1-x)LaAlO_3-xBaZrO_3$ were fabricated by a solid state reaction and their dielectric properties were investigated. For the compositions of x=0.1~0.9, the mixture of $LaAlO_3$ with a rhombohedral structure and $BaZrO_3$ with a cubic was observed when the sintering was conducted at $1500^{\circ}C$, indicating that the solubility of constituent elements was very low and a narrow solid solution region might exist. The large difference of ionic radii between $La^{3+}$ ion (0.136nm, C.N.=12) and $Ba^{2+}$ ion (0.161nm) or $Al^{3+}$ ion (0.0535nm, C.N.=6) and $Zr^{4+}$ ion (0.072nm) might hinder the mutual substitution. Within the compositions of x=0~0.7, the dielectric constant of the mixture increased with the amount of $BaZrO_3$, i.e., x value, which was in good agreement with the logarithmic mixing rule (In $_{r,i}={\Sigma}v_iln\;_{r,i}$). The increase in $BaZrO_3$ doping decreased $Q{\times}f$ value significantly due to the low $Q{\times}f$ value of $BaZrO_3$ itself, a poor microstructure of the mixture with an increased grain boundary area per volume, and defects in the cation and oxygen sub-lattices which were respectively caused by the evaporation of barium during the sintering process and the substitution of Ba on La-site or Al on Zr-site.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.723-731
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• 1995

P $b_2$S $r_2$( $Y_{1-x}$ C $a_{x}$)C $u_3$ $O_{8+}$$\delta$/ samples were prepared with x=0.4~0.6 and small $\delta$. To minimize the extent of oxidative decomposition reaction which occurs during the preparation of this phase, two annealing steps were adopted : First, sintered samples of P $b_2$S $r_2$( $Y_{1-x}$ C $a_{x}$)C $u_3$ $O_{8+}$$\delta$/ are oxygenated under 100% $O_2$, which leads to a large $\delta$(e.g., $\delta$=1.8). Second, the resulting samples are deoxygenated under 0.1~1.0% $O_2$in $N_2$, lowering $\delta$ to desired values. This two-step annealing procedure minimized the extent of oxidative decomposition. However, even with the two-step annealing procedure, the oxidative decomposition of P $b_2$S $r_2$( $Y_{1-x}$ C $a_{x}$)C $u_3$ $O_{8+}$$\delta$/ cannot be completely suppressed if $\delta$ is to be reduced to maximize $T_{c}$. Electrical resistivity data show that $T_{c}$(onset) is a function of hole concentration in the Cu $O_2$layer, and the optimum hole concentration for the maximum $T_{c}$ is achieved when $Ca^{2+}$is substituted for $Y^{3+}$between 0.5 and 0.6 A $T_{c}$(onset)=80K has been observed for one such sample, and this is the highest $T_{c}$(onset) yet reported for this compound.ed for this compound.nd.

• Progress in Superconductivity and Cryogenics
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• v.19 no.1
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• pp.42-46
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• 2017

The effects of the heat treatment temperature ($600^{\circ}C-1050^{\circ}C$) on the formation of $MgB_2$ and the superconducting properties have been examined. The self-synthesized $MgB_4$ and commercial Mg powders were used as raw materials for the formation of $MgB_2$. The superconducting critical temperatures ($T_cs$) of $MgB_2$ bulk superconductors prepared at $600^{\circ}C-850^{\circ}C$ were as high as 37-38 K regardless of the heat treatment temperature. However, because $MgB_4$ is more stable than $MgB_2$ at above $850^{\circ}C$, no superconducting signals were detected in the susceptibility-temperature curves of the samples prepared above $850^{\circ}C$. As for the critical current density ($J_c$), the sample heat-treated at a low temperature ($600^{\circ}C$) for a prolonged period (40 h) showed a Jc higher than those prepared at $650^{\circ}C-850^{\circ}C$ for a short period (1 h). The FWHM (full width at half maximum) result showed that the grain size of $MgB_2$ of the $600^{\circ}C$ sample was smaller than that of the other samples. The high $J_c$ of the $600^{\circ}C$sample is attributed to the presence of large numbers of grain boundaries, which can act as flux pinning centers of $MgB_2$.

• Journal of Practical Agriculture & Fisheries Research
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• v.23 no.2
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• pp.63-70
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• 2021

In order to compare and investigate the growth rates of each of the various soils, the soil mixing ratios were varied to four soils (Pitmos, Pearlite, Masato, General Soil, and Cocopeat). Ten were selected for each soil ratio and the average length and weight were compared. As a result, in the ratio of No. 1 pitmos 6.5: Perlite 2: Masato 1.5, it was measured as 16.36cm, 0.60g. In the ratio of No. 2 pitmos 10, 13.74cm, 0.41g. In the ratio of No. 3 general clay 10, it was measured as 12.43cm, 0.26g. 4 general clay 8, 0.39g. The growth rate of each soil was measured to be superior to that of other soil growth environments in the ratio of pitmos 6.5: pearlite 2: masato 1.5 soil. For ginseng plant analysis, 30 ginseng plants grown in the average length and weight of each soil at a ratio of 6.5: pearlite 2: masato 1.5 and relatively low-result general soil were selected and analyzed. As a result, 1,040ppm of nitrite nitrogen(NO₃-N) was higher in ginseng plants grown in general soil. There was no significant difference in phosphoric acid(P), potassium(K), and magnesium(Mg). Ginseng is characterized by poor growth when it exceeds 300ppm by combining ammonia tae (NH₄-N) and nitrate tae (NO₃-N) nitrogen. In addition, nitric acid produced in a part of this nitrite makes the pH reaction of the soil acidic, and the nitrite remaining in the soil evaporates into gas.

• Journal of Energy Engineering
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• v.19 no.4
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• pp.215-220
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• 2010

Hydrogen is a clean and efficient energy source and is expected to take an important role in future energy demand. A possibly good route to produce hydrogen is by using biomass and organic wastes as a source through thermo-chemical conversion technology. In this study, pyrolysis of wood Pellet(Oregon pine) has been carried out in batch type fixed-bed reactor in $N_2$ atmosphere during 20 minutes to determine the optimum hydrogen generating conditions. At the influence of temperature, hydrogen yield was increased with increasing temperature. For the influence of Steam/Biomass Ratio(SBR), hydrogen yield was increased by steam addition at low temperature condition. However, effect of steam addition was insignificant over at SBR = 1. The hydrogen yield was increased with increasing SBR at high temperature condition. From result of $H_2$/CO and $H_2/CH_4$ ratio, dominant reaction was steam reforming in this experimental condition. The optimum condition for hydrogen production was determined as follows: $H_2$ yield = 38.3 vol.% (56.01 L/min kg) at $900^{\circ}C$, SBR=3.

• Journal of Nutrition and Health
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• v.40 no.7
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• pp.639-649
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• 2007

This study was performed to investigate the effects of very low calorie diet (VLCD) using meal replacements that contain the wild grass extracts based on Samul-tang ingredients on psychological factors and quality of life in the obese women $(BMI{\geq}25kg/m^2)$ for four weeks. Seventy five women $(20{\leq}age<26)$ participated in this experiment. Subjects were randomly classified three groups: 1) General diet group (GD roup, n=27) consumed 3 regular meals within 600 kcal/day 2) Meal replacements group (MR group, n=27) consumed 1 regular meal and 2 meal replacements within 600 kcal/day 3) Herbal Meal replacements group (HMR group, n=27) consumed 1 regular meal and 2 meal replacements within 600 kcal/day. Physical factors (weight, BMI, fat (%)) of the HMR group significantly decreased more than those of GD and MR groups. Moreover, binge eating habit and environmental factors (surrounding support, emotional reaction, expression of opinion) of the HMR group significantly decreased more than those of GD and MR groups. Psychological factor and quality of life were no significant differences among three groups during the experimental period, because both were significantly decreased in all groups after 4 weeks. Therefore, very low calorie diet using meal replacements that contain the wild grass extracts based on Samul-tang ingredients for 4 weeks was effective on improvement of psychological factor and quality of life as well as weight reduction in the obese premenopausal women.

• Journal of Veterinary Clinics
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• v.40 no.5
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• pp.336-340
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• 2023

A dog (2-year old, female, Shih-Tzu) presented with hyperthermia and right-sided facial paralysis characterized by the inability to close the right eye and drooling from the right side of the mouth after H3N2 influenza vaccination [A/Canine/Korea/01/07(H3N2) strain; Caniflu-Max, Bionote, Hwaseong, Gyeonggi-do, ROK]. To determine the cause of the fever and neurological symptoms, physical examination, ophthalmic examination, thoracic and abdominal radiography, abdominal ultrasonography, complete blood counts, serum chemistry values, and electrolyte levels were determined. In addition, Cerebrospinal fluid analysis, antinuclear antibody test, fever of unknown origin polymerase chain reaction (PCR) panel, tick-borne pathogen PCR panel were performed. As a result, hyperthermia, leukocytosis, and elevated C-reactive protein were confirmed. In addition, neurological examination revealed decreased right eyelid reflexes, corneal reflexes, threat response, and facial sensation, it was possible to suspect problems with the trigeminal and facial nerves of the cranial nerve. Magnetic resonance imaging revealed a lesion suggestive of myositis in the right muscular lesion at atlanto-occipital junction level on site of vaccine injection. Therefore, right-sided facial paralysis was tentatively determined to be a secondary cause of nerve damage caused by myositis. The patient was treated with immunosuppressants such as prednisolone and mycophenolate mofetil. After 3 months of immunosuppressant therapy, the patient's symptoms improved.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.2
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• pp.249-257
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• 2006

In this work, the adsorptive and desorptive behavior of reduced sulfur compounds (RSC) was investigated using the combination of the Peltier cooling (PC)/thermal desorption (TD) unit with the gas chromatographic (GC) detection technique. To examine the adsorptive characteristics of RSC on clothing materials, a total of nine experiments were conducted in a stepwise manner. Once small towel pieces are exposed to significant quantities of RSC standards with high concentrations (10 ppm), the desoprtion stage was then induced by deloading RSC with ultrapure $N_2$ at three different flow rates (FR) of 20, 40, and 60 mL/min. At each FR, the total deloading volume of 400, 800, and 1,600 mL were maintained. These results were then compared in terms of odoring efficiency by dividing the total amount of desorption with the total amount used for exposition or RSC loading. The results indicated that desorption reaction of certain compounds ($CH_3SH$ and DMS) can be influenced significantly with the reducing FR, while they are not affected directly by the total deloading volume. In addition, when the extent of adsorption was compared for most S compounds by the odoring efficiency term, the extent of absorption generally occurred at approximately 1/1000 level of original exposition.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.113-117
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• 2005

Multiferroic $HoMnO_3$ single crystal was prepared using 4-point focused floating zone furnace, and polycrystalline $HoMn_{1-x}\;^57Fe_xO_3$ (x=0.00, 0.01, 0.02, 0.05) powders have been prepared by solid state reaction. Their magnetic and crystallographic properties are studied using MPMS, PPMS, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structure found to be a hexagonal and a magnetic easy-axis is (110) direction. As the external applied magnetic field increases, temperature of the dielectric constant anomaly is decreased. $HoMn_{0.95}\;^{57}Fe_{0.05}O_3$ shows huge quadrupole splitting value from the $M\ddot{o}ssbauer$ spectra.