• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.04a
• /
• pp.151-154
• /
• 2003

The synthesis and luminescent properties of trivalent europium activated gadolinium oxide red phosphors by sol-gel process have been investigated. Aqueous metal nitrate solution was mixed with EDTA which was chosen by the most suitable material of sol-gel formation as chelating agents. We noticed that the samples when are heated with EDTA at a temperature of $100^{\circ}C$ for lhrs, produced brownish and crisp powders due to condensation reaction on decomposition, dehydration and formation of sol-gel. Hence, when the powder pre-heated at about $100^{\circ}C$ was then heated at $1200^{\circ}C$ for 3hrs in atmosphere, the luminescence properties of resultant $Gd_{2}O_{3}:Eu^{3+}$ phosphor was measured by SEM, FT-IT and brightness intensity was shown 20% higher than those prepared by conventional method and by other chelating agent.

• Applied Chemistry for Engineering
• /
• v.20 no.6
• /
• pp.670-674
• /
• 2009

3-Chromonealdehyde(2,2-disubstituted)hydrazone derivatives were synthesized by dehydration condensation. They are green-emitting materials for organic light emitting device (OLED) composed of electron acceptor of 3-chromonealdehydes and electron donor of 2,2-disubstituted hydrazones by a conjugated structure. The structural properties of reaction products were analyzed FT-IR and $^1H-NMR$ spectroscopy. The thermal stabilities and reactivities were measured by melting points and yields. The UV-visibles and PL properties can be determined by excitation spectra and emission spectra, respectively.

• Korean Journal of Veterinary Research
• /
• v.33 no.3
• /
• pp.419-427
• /
• 1993

Thirteen strains of Clostridium perfringens were isolated from the pigs with hemorrhagic enteritis. The characteristics of the outbreaks, clinical signs and lesions were examined. The biochemical properties, type of toxin and susceptibility to antimicrobial agents of the isolates were investigated. The results could be summarized as follows ; 1. Almost of the pigs affected with hemorrhagic enteritis, 17 cases examined from 1989 to 1992, were piglets less than 7 day old. 2. The average mortality rate of piglet less than 7 day old affected with hemorragic and necrotic enteritis was 48.5%. 3. The clinical signs of pigs with hemorrhagic enteritis were depression, hemorrhagic diarrhea, anemia and dehydration. Necropsy of the infected pigs showed typical hemorrhage of upper intestine and necrosis of mucosal membrane. 4. The characteristic biochemical properties of the isolates were 2-band hemolysis, positive reaction of reverse CAMP test and formation of LV precipitate in egg yolk medium. 5. The toxin type of the 13 isolates, investigated by mouse inoculation test, was all type C strains of Clostridium perfringens. 6. In susceptibility test to antimicrobial agents, 13 isolates of Clostridium perfringens were highly sensitive to ampicillin, enrofloxacin(Baytril), cephalothin, penicillin and trimethoprim-sulfamethoxazole.

• Journal of Veterinary Clinics
• /
• v.17 no.2
• /
• pp.464-469
• /
• 2000

An epizootic of calf diarrhea occurred in a Korean native cattle farm located in Chonbuk province. The calves that had either bloody or watery diarrhea were 1 to 30 days old. Some of these animals died during the acute course of the disease. Five calves with predominant clinical signs were examined in more detail. Hematological and serum chemical findings were suggestive of dehydration and nutritional insufficiency. Fecal material from the calve was cultured on/in brilliant green agar (BGA), xylose-lysine deoxycholate (XLD) medium, MacConkey agar, eosin methylene blue (EMB) agar and triple sugar iorn (TSI) A bacteria was isolated. which was subsequently identificed as belonging to Salmonella spp. To differentiate Salmoenlla serotype, rfbs gene of S. dublin was amli- find (720 bp) by multiplex (PCR). The rfbS gene sequences of S, dublin ficld isolate(SDC-1) was com- pared with that off S. dublin(S-37) S, dublin(Ahn et al, 1996), S enteritidis(Ahn et al 1996)and S. typhi (Generbak accession No M29682). The identities of nucleotide sequences were 100%. 99.6%, 99.6%, 97.5% respectively.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.4
• /
• pp.374-381
• /
• 2015

This study is investigating the fire resistant finishing materials composed of fly ash and glass forming light weight aggregate has the high temperature thermal stability. High temperatures such as a fire, cementitious materials beget dehydration and micro crack of cement matrix. From the test result, developed fire resistant finishing materials showed good stability in high temperatures. These high temperature stability is caused by the ceramic binding and low thermal conductivity of glass forming light weight aggregate. Also, alkali activation reaction of fly ash and meta kaolin not showing the decomposition of calcium hydrates. Thus, this result indicates that it is possible to fire resistant finishing light weight mortars.

• Journal of the Korean Chemical Society
• /
• v.57 no.5
• /
• pp.533-539
• /
• 2013

The electrochemical corrosion and passivation of Ni rotating disk electrod in borate buffer solution was studied with potentiodynamic and electrochemical impedance spectroscopy. The mechanisms of both the active dissolution and passivation of nickel and the hydrogen evolution in reduction reaction were hypothetically established while utilizing the Tafel slope, impedance data, the rotation speed of Ni-RDE and the pH dependence of corrosion potential and current. Based on the EIS data, an equivalent circuit was suggested. In addition, carefully measured were the electrochemical parameters for specific anodic dissolution regions. It can be concluded from the data collected that the $Ni(OH)_2$ oxide film, which is primarily formed by passivation, is converted to NiO by dehydration under the influence of an electrical field.

• Journal of the Korean Society of Safety
• /
• v.11 no.2
• /
• pp.67-78
• /
• 1996

Gas sensing element, $\gamma-Fe_2O_3$was synthesized by dehydration, reduction, and oxidation of $$${\gamma}$-FeOOH, which was synthesized with $FeSO_4\;{\cdot}\;7H_2O$ and NaOH. They were produced as a bulk-type, a thick film-type. Then, their responses and mechanisms of response to the gas of liquefied-petroleum were studied. The qualities of gas sensing elements are decided by the structure and the relative surface area. In the process of $\alpha-FeOOH $synthesis, the effects of reaction conditions as the equivalent ratio, on the structure and the relative surface area of gas sensing element were observed. The changes of the structure were measured with XRD, SEM, TG-DTA and BET. The resistance changes of the synthesized gas sensor in the air were measured. The response ratio were also measured for the changes of working temperature and gas concentration. As a result of analysis with XRD, it was confirmed that the the best conditions for the synthesis of $\alpha -FeOOH$ were equivalent ratio 0.65. The thick film-type element of $\gamma-Fe_2O_3$responded more quickly than the bulk-type did. The structure and the relative surface area of the $\alpha-FeOOH $were confirmed as the important factors deciding gas response charcteristics.

• Journal of the Korean Magnetic Resonance Society
• /
• v.10 no.2
• /
• pp.141-154
• /
• 2006

A solid-state reaction of $V_2O_5$ with AlMCM-41 followed by calcinations generated $V^{5+}$ species in the mesoporous materials. Dehydration results in the formation of a vanadyl species, $VO^{2+}$, that can be characterized by electron spin resonance (ESR). The chemical environment of the vanadium centers in V-AlMCM-41 was investigated by XRD, EDX, diffuse reflectance UV-VIS, ESR, $^{29}Si,\;^{27}Al,\;and\;^{51}V$ NMR. It was found that the vanadium species on the wall surface and inside the wall of the hexagonal tubular wall of the V-AlMCM-41 were completely oxidized to tetrahedral $V^{5+}$ and transformed to square pyramidal by additional coordination to water molecules upon hydration. The oxidized $V^{5+}$ species on the wall surfaces and inside the wall were also reversibly reduced to $VO^{2+}$ species or lower valences by thermal process.

• The Journal of the Korea Contents Association
• /
• v.8 no.10
• /
• pp.301-308
• /
• 2008

The purpose of this study was to investigate the change of physical fitness, MDA, SOD after short-term weight reduction through exercise, food restriction and exhalation of sweat among Taekwondo players. The subjects ten male collage Taekwondo players with excellent practical skills, and more than seven years of experiences. They were asked to reduce about 5% of their body weight in seven days. Physical fitness levels were analyzed through grip strength, muscle endurance, flexibility, power, agility, balance, reaction time and MDA and SOD through blood test. The results of this study were as follows; First, there was no significant change in physical fitness due to short-term weight reduction in muscle strength, muscle endurance, flexibility, power, agility, balance and reaction time. Second, The change of MDA and SOD, resulting from short-term weight reduction did not show significant difference statistically. Therefore, the results of this study indicate that the Taekwondo players' short-term weight reduction of 5% of their body weight did not influence on their athletic performance and physiological capacity. Therefore athletes and coaches should endeavor to take exercise, dietary, and dehydration into consideration when conducting 5% of their body weight reduction in a week.

• Journal of the Korean Applied Science and Technology
• /
• v.8 no.1
• /
• pp.59-67
• /
• 1991

The reactions of semicarbazide hydrochloride with aliphatic and alicyclic ketones were studied kinetically at 15, 25, 35 and 45$^{\circ}C$ in 20% ethanol solution buffered at pH 2.9. The rate of cyclohexanone semicarbazone formation is 5.5 times as fast as that of cyclopentanone semicarbazone, while 3-pentanone semicarbazone is 4.7 times as slow as that of 2-pentanone, The activation energy of cyclohexanone, 2-pentanone, 2 hexanone, cyclopentanone, 4-methyl-2-pentanone and 3-pentanone semicarbazone formation are calculated 5.08, 7.52, 8.79, 9.59, 9.49, 11.59, respectively. It is concluded from the effect of ionic strength that the reaction is affected by not ion but neutral molecules being progressed hydrogen bond between oxygen atom of carbonyl group and hydrogen atom of acid-catalyst and concerted nucleophilic attack of free base on the carbonly compound. Dependence on pH of the rate of 2-pentanone semicarbozone formation is linear relationship below pH 4.60 and above pH 5.60. As a result of studing citric acid catalysis, second order constants increase linearly with citric acid concentration. As the catalyst concentration is varied from 0.025 to 0.10 mol/1 at pH 2.90, the rate constants increase 1.4 times, but slight increase is observed at pH 5.60. Conclusively, the rate-determining step is formation of tetrahedral interemediate below pH 4.65 and dehydration between pH 5.60 and pH 7.11. It is concluded that the formation reaction of cyclohexanone semicarbazone is faster than cyclopentanone semicarbazone due to the steric strain in the process of forming tetrahedral intermediate.