• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.489-494
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• 2004

In this paper, we investigated impurities content and thermal properties showing by changing the content of carbon black which is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICP-AES(Inductively Coupled Plasma Atomic Emission Spectrometer), and density of specimens were measured by density meter. And then heat capacity(${\Delta}H$) and melting temperature(Tm), specific heat(Cp) were measured by DSC(Differential Scanning Calorimetry). The dimension of measurement temperature was $0[^{\circ}C]\;to\;200[^{\circ}C]$, and rising temperature was $4[^{\circ}C/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result also density was increased according to these properties. Specially, impurities content values of the A1 and A2 of existing resins were measured more than 4000[ppm]. Heat capacity, melting temperature, and specific heat from the DSC results were simultaneously decreased according to increasing the content of carbon black. Because metallic impurities of carbon black having Fe, Co, Mn, A1 and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• Journal of Surface Science and Engineering
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• v.32 no.3
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• pp.312-316
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• 1999

The interfacial structure of duplex treated AISI 4140 consisting of iron nitride and TiN layer was characterized by optical microscope, SEM and XRD. A black layer was formed from the decomposition of iron nitride during Ti ion bombardment. The black layer was characterized as an a-Fe phase transformed from the iron nitride by XRD. In order to identify the formation mechanism of the black layer, a thermal analysis of iron nitride undertaken by DSC method. As an iron nitride was mostly consisted of ${\gamma}$'-Fe$_4$N and $\varepsilon$-$Fe_3$N phase after plasma nitriding, in this study, a ${\gamma}$'$-Fe_4$N and $\varepsilon$-$Fe_3$N powders were separately prepared by the different processing conditions of gas nitriding of iron powder in the fluidized bed. From the DSC thermal analysis, the phase transformation of ${\gamma}$'$-Fe_4$N, $\varepsilon$-$Fe_3$N was followed the path of transformation; $ \Upsilon{'}-Fe_4$Nlongrightarrow${\gamma}$-Felongrightarrowa-Fe and of $\varepsilon$-$Fe_3$Nlongrightarrow$\varepsilon$-$Fe_{2.5}$ /N+${\gamma}$'$-Fe_4$Nlongrightarrow${\gamma}$'-Fe$_4$Nlongrightarrow${\gamma}$longrightarrowFelongrightarrowalongrightarrowFe, respectively. It explains the reason why the $\varepsilon$ $-Fe_3$N phase disappeared in the first time and then ${\gamma}$'-Fe$_4$N in the formation of the black layer in the duplex coating.

• Preventive Nutrition and Food Science
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• v.1 no.1
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• pp.75-79
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• 1996

The purpose of this study was to investigate the effect of vitamin {TEX}$B_{6}${/TEX} deficiency on the utilization and recuperation of stored fuel in exercising rats. Thirty six rats were fed either a vitamin {TEX}$B_{6}${/TEX} deficient diet(-{TEX}$B_{6}${/TEX}) or a control diet(+{TEX}$B_{6}${/TEX}) for 5 weeks, then subdivided into 3 group: non-exercise group(NE), exercise group(EX), exercise and recuperation group(EX). EX group were exercised in treadmill({TEX}$10^{o}${/TEX}, 0.5~0.8km/h)for 2 hours and ER group were recuperated three days with the respective diet after exercise. Glucose(GLU), glycogen(GLY), protein(PRO), trigyceride(TG) and free fatty acid(FFA) were compared in plasma(P), liver(L) and skeletal muscle(M) of rats. Compared to +{TEX}$B_{6}${/TEX} rats, in NE group, the level of L-GLY of -{TEX}$B_{6}${/TEX} rats was higher, M-TG, L-PRO of -{TEX}$B_{6}${/TEX} rats were lower and there were no differences in P-PRO, P-FFA, P-TG, M-GLY, M-PRO and L-TG. In EX group, the levels of P-FFA, L-PRO of -{TEX}$B_{6}${/TEX} rats were higher. P-TG, L-TG of -{TEX}$B_{6}${/TEX} rats were lower and there was no difference in L-GLY. In EG group, the levels of P-GLU, P-PRO, P-RG, L-PRO of -{TEX}$B_{6}${/TEX} rats were lower and there were no differences in L-GLY, L-TG, M-TG and M-GLY. these results suggest that a lowered intake of vitamin {TEX}$B_{6}${/TEX} may impair the recuperation of aminals after exercise related to exercise fuel stores although there is a compensation among stored fuel utilization during exercise.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.331-337
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• 2012

Electrical properties as a function of composition in silicon nitride ($SiN_x$) films grown at low temperatures ($<200^{\circ}C$) were studied for applications to photonic devices and thin film transistors. Both silicon-rich and nitrogen-rich compositions were successfully produced in final films by controlling the source gas mixing ratio, $R=[(N_2\;or\;NH_3)/SiH_4]$, and the RF plasma power. Depending on the film composition, the dielectric and optical properties of $SiN_x$ films varied substantially. Both the resistivity and breakdown field strength showed the maximum value at the stoichiometric composition (N/Si = 1.33), and degraded as the composition deviated to either side. The electrical properties degraded more rapidly when the composition shifted toward the silicon-rich side than toward the nitrogen-rich side. The composition shift from the silicon-rich side to the nitrogen-rich side accompanied the shift in the photoluminescence characteristic peak to a shorter wavelength, indicating an increase in the band gap. As long as the film composition is close to the stoichiometry, the breakdown field strength and the bulk resistivity showed adequate values for use as a gate dielectric layer down to $150^{\circ}C$ of the process temperature.

• Animal Bioscience
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• v.35 no.11
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• pp.1666-1674
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• 2022

Objective: Letrozole, a potent aromatase inhibitor, is known to have the potential to modify male reproductive function by altering sex hormone levels. This study aimed to evaluate the semen and testicular characteristics and hormonal profile of aged Mrakhoz bucks (Capra hircus) treated with letrozole. Methods: Twelve Markhoz male goats, aged between 4.5 to 5.5 years with an average body weight (BW) of 61.05±4.97 kg were used for the study. Animals were randomly divided into two equal groups and subcutaneously received either 0.25 mg/kg BW of letrozole or a control every week for 2 months. The semen collections were performed every 10 days, and blood samples and testicular biometric records were collected at 20 days intervals. Results: Letrozole causes increased testosterone and follicle-stimulating hormone levels, testosterone to estradiol ratio, semen index and reaction time during the period from 20th to 60th days (p<0.05). Furthermore, letrozole-treated bucks had higher semen volume, sperm concentration, and total sperm per ejaculate from 30th to 60th days (p<0.05). However, no differences occurred between the groups in scrotal circumference, relative testicular volume, semen pH, abnormality, acrosome integrity, and membrane integrity of sperm during the study (p>0.05). The serum luteinizing hormone levels, sperm viability, motility, and progressive motility increased, and estradiol levels decreased after 40th to 60th days of letrozole treatment (p<0.05). Conclusion: Letrozole application to aged Markhoz bucks provokes reproductive hormonal axis which, in turn, induces enhancement of semen production and quality.

• Journal of Periodontal and Implant Science
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• v.53 no.1
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• pp.2-19
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• 2023

Purpose: Surgical techniques in orthodontics have received widespread attention in recent years. Meanwhile, biomaterials with high molecular content have been introduced, such as platelet concentrates (PCs), which may accelerate orthodontic tooth movement (OTM) and reduce periodontal damage. The present systematic review aimed to answer the following PICO question: "In patients in whom orthodontic surgical techniques are performed (P), what is the effectiveness of using PCs over the surgical site (I) when compared to not placing PCs (C) to achieve faster tooth movement (O)?" Methods: A search was performed in 6 databases. The criteria employed were those described in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses declaration. The present review included studies with a control group that provided information about the influence of PCs on the rate of OTM. Results: The electronic search identified 10 studies that met the established criteria. Conclusions: The included studies were very diverse, making it difficult to draw convincing conclusions. However, a tendency was observed for OTM to be accelerated when PCs were used as an adjuvant for canine distalization after premolar extraction when distalization was started in the same session. Likewise, studies seem to indicate an association between PC injection and the amount of canine retraction. However, it is not possible to affirm that the use of PCs in corticotomy shortens the overall treatment time, as this question has not been studied adequately.

• The Korean Journal of Physiology and Pharmacology
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• v.70 no.1
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• pp.121-133
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• 2019

Dexamethasone inhibits mucin secretion considering the primary option for treating acute asthma exacerbation. However, the mechanism underlying dexamethasone-induced decreased in mucosecretion is unclear. Recent studies have reported that dexamethasone exerts an inhibitory effect on mucosecretion in the lung by modulating the expression of calcium processing genes. However, the expression of the calcium processing genes in the trachea is not examined yet. Thus, the present study is the first to report the localization of calcium processing proteins such as transient receptor potential vanilloid-4 (Trpv4), transient receptor potential vanilloid-6 (Trpv6), calbindin-D_9k (CaBP-9k) and plasma membrane Ca²⁺-ATPase 1 (Pmca1) in the mouse trachea and their glucocorticoid-induced response. In this study, mice were subcutaneously injected with dexamethasone for 5 days, and their tracheal samples were collected by dividing the trachea into the cervical, and thoracic sections based on its anatomical structure. The localization of TRPV4, TRPV6, CaBP-9k, and PMCA1 proteins was detected in the tracheal epithelium, submucosal glands, cartilages and muscles. Dexamethasone treatment downregulated the mRNA expression of the four calcium processing genes and mucin producing genes. The dexamethasone-induced decrease in the secretion of mucosubstances in the trachea was determined by performing Alcian blue-periodic acid-Schiff staining. Thus, the findings of the present study suggest that glucocorticoids simultaneously can regulate the expression of calcium processing genes and tracheal mucosecretion.

• Journal of Ceramic Processing Research
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• v.21
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• pp.47-52
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• 2020

Graphene was synthesized using rapid thermal chemical vapor deposition (RT-CVD) equipment designed to produce largearea graphene at high speed. The effects of methane (CH₄), argon (Ar), and hydrogen (H₂) gases were investigated between 800 ℃ and 1,000 ℃ during heating and cooling in the graphene synthesis process. The findings reveal that multilayer domains increased due to hydrogen pretreatment with increase in temperature. Furthermore, when pretreated with the same gas, it was confirmed that the post-argon-treated sample cooled from 1,000 ℃ to 800 ℃ had a higher I_D/I_G value than that of the other samples. This result was consistent with the sheet resistance properties of graphene. The sample prepared in methane atmosphere maintained during both the pre-treatment and post-treatment demonstrated the lowest sheet resistance of 787.49 Ω/sq. Maintaining the methane gas atmosphere in the high-temperature region during graphene synthesis by RT-CVD reduced the defects and improved the electrical property.

• Journal of Practical Agriculture & Fisheries Research
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• v.4 no.1
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• pp.110-118
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• 2002

This study was conducted to investigate the physiology of optimal reproductive age in Hanwoo for protection to decrease of reproductivity and improvement of production of offspring. Thirty two cows were devided into 4 groups of treatments : T1(12 months of age and 0.5kg daily gain), T2(12 months of age and 0.8kg daily gain), T3(15 months of age and 0.5kg daily gain) and T4(18 months of age and 0.5kg daily gain). The days of the first heat of treated cows were 263.3±6.4 days and average weight was 181.1±11.3kg. The conception rates of first insemination were 25%(T1) and 75%(T4), and the number of insemination of T3 and T4(both 1.5) was lower than those of T1 and T2(2.3 and 2.4), respectively. With regard to estrus return after the first parturition, T1, T2, T3 and T4 showed 66.2,76.7, 62.4 and 68.5 days, respectively, indicating the average days of estrus return was 65.7. Plasma progesterone(P4) concentration was nearly the same during the observation periods of treated cows and P4 began to be detected after 12months. Only 5(15.6%) out of 32cows showed normal estrus cycle and ovulation before 12 months. During the peri-parturition period, P4 concentration was rapidly decreased and there was no detection of P4 from parturition to 40 days after milking. P4 would be released again on 45 day after parturition. The results imply that the optimal reproductive age of Hanwoo heifers would be around at the 14 months of age, 110cm height and 265kg weight.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.372-381
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• 2015

The effect of preparation method on the catalytic activities of the $Ni/Al_2O_3$ catalysts on steam reforming of ethylene glycol was investigated. The catalysts were prepared with various preparation methods such as an incipient wetness impregnation, wet impregnation, and coprecipitation method. In the case of coprecipitation method, various precipitants such as KOH, $K_2CO_3$, and $NH_4OH$ were compared. The prepared catalysts were characterized by using $N_2$ physisorption, inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, temperatureprogrammed reduction, pulsed $H_2$ chemisorption, temperature-programmed oxidation, scanning electron microscopy, and thermogravimetric analysis. Among the catalysts reduced at 773 K, the $Ni/Al_2O_3$ catalyst prepared by a coprecipitation with KOH or $K_2CO_3$ as precipitants showed the best catalytic performance. The preparation method affected the particle size of Ni, reducibility of nickel oxides, catalytic performance (activity and stability), and types of coke formed during the reaction. The $Ni/Al_2O_3$ catalyst prepared by a coprecipitation with KOH showed the increasing catalytic activity with an increase in the reduction temperature from 773 to 1173 K because of an increase in the reduction degree of Ni oxide species even though the particle size of Ni increased with increasing reduction temperature.