• Elastomers and Composites
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• 제33권2호
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• pp.75-82
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• 1998

The purpose of this experimental study was to investigate the effects of vulcanization condition on the properties of reinforced rubbers. Rubber reinforcing ability of carbon black was more efficient than other fillers, but tensile properties were not affected by vulcanization condition while vulcanization condition affected the physical properties of rubber compounds with silica and silane treated slica. It was found that silica and silane treated silica filled rubber compounds showed good dynamic properties, rebound, heat build-up, 0 and $60^{\circ}C$ tan $\delta$ compared with carbon black filled rubber compounds. Carbon black filled rubber compounds were higher than silica and silane treated silica filled rubber compounds in total crosslinking density by vulcanization condition. By analysis of crosslinking type, polysulfide crosslinking was the highest in the carbon black filled rubber compounds with decreasing the ratio of sulfur to accelerator, monosulfide crosslinking was the highest in the silane treated silica filled compounds with in-creasing the ratio of sulfur to accelerator.

• Journal of Magnetics
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• 제2권4호
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• pp.130-134
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• 1997

The amorphous Co-based alloy Co66Fe4Ni1B15Si14 (Metglas 2714A) is a suitable magnetic core material for high frequency operation. Appreciable reduction of the coercive force can be achieved by proper heat treatment. In this study, samples annealed at wide temperature range were analyzed using differential scanning calorimetry, high frequency B-H loop tester, X-ray diffractometer and resistivity meter. The results show that coercive force at 10 kHz decreases with in-creasing annealing temperature up to 773 K, but dramatically increases above this temperature. The squareness shows that the magnetic anisotropy on longitudinal direction of the as-cast state remains up to 773 K. Above this temperature, it decreases down to 0.5 that represents random distribution of magnetic domains. The crystallization abruptly occurs between 781 K and 783 K.

• 한국응용과학기술학회지
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• 제9권1호
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• pp.55-61
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• 1992

This study was performed observe the effect of edible oil on the serum lipid of 0.5% cholesterol-fed rats. In this experiment, male rats of Sprague-Dawley strain were used. The rats were divided into 5groups which were fed differently eigher for 8 weeks : basal diet, 20% sunflower oil diet, 20% soybean oil diet, 20% rapeseed oil diet, 20% coconut oil diet. The followings are the results of this experiment. 1. The total chol., free chol., TG, PL level in the serum were showed tendency of decrease with in creasing of P/S ratios. 2. HDL-chol. level was increased with increasing of P/S ratios but LDL-chol. level was decreased. 3. GOT, GPT, TBA level in the serum were increased with increasing of P/S ratios.

• Elastomers and Composites
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• 제34권4호
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• pp.332-340
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• 1999

Hydrogenations of BR and NR performed by a noncatalytic method using p-toluenesulphonylhydrazide were carried out by reactive processing. The experimental procedures for carrying out the reaction were established. Two steps comprising premixing of the rubber with TSH followed by hydrogenation in compression mould were proved to be suitable. The percentages of hydrogenation attained by reactive processing were higher than those of the reaction carried out in solution at the same [TSH]/[C=C] ratio, reaction temperature and time. In-creasing the reaction temperature and reaction time resulted in increases of the percentage of hydrogenation. For BR, the maximum percentage of hydrogenation obtained was 36% at [TSH]/[C=C]=1/1.5. For NR, the highest percentage of hydrogenation was 34% at [TSH]/[C=C]=1/1.5. Cis-trans isomerisation was also observed to occur during hydrogenation of both BR and NR. Thermal stabilities of the hydrogenated BR and NR were shown to improve over those or the unhydrogenated counterparts.

• 한국안전학회지
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• 제7권3호
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• pp.66-72
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• 1992

An experimental study was carried out to analyse the explosion characteristics of flammable gas-air mixtures. Used flammable gases were hydrogen, methane, acethylene, ethylene and pro-pane, explosion Pressure, explosoin pressure rising rate, and flame propagation velocity were measured experimentaly. The maximum explosion pressure and rising rate of flammmalbe gas air mixtures were appeared at the range of slightly higher concentration than the stoichiometric concentration. Initial pressure before explosion was controlled from 0.6 to 2.0kg/cm absolutly. Explosion pressure was increased with increment of the initial pressure, and the relationship between initial pressure and explosion pressure was Pe = KPi. The effect of vessel size on explosion characteristics was also analysed In this experiment. Explosion pressure was increased with in-creasing the vessel size, otherwise explosion pressure rising rate was decreased. When we locate a dummy material in vessel explosion pressure was decreased with increasing the dummy volume but exlosion pressure rising rate was increased.

• 한국표면공학회지
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• 제26권5호
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• pp.245-254
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• 1993

The effects of pulse current electrolysis conditions on the composition and the microstructure of Ag-Sn alloy were studied by using a pyrophosphate bath. Both cathode current efficiency and throwing power of alloy deposits formed under pulse plating conditions, decreased with increasing mean current density, and lower than those under D.C. electrolysis condition. Tin content of Ag-Sn alloy decreased noticebly with in-creasing the mean current density, while it increased with the increase of On-time from 1 to 10 ms. The pre-ferred orientation of Ag-Sn alloy changed with increasing cathode overpotential in the sequence of (100)longrightarrow(100)+(111)longrightarrow(111) at $20^{\circ}C$ and (110)longrightarrow(111)longrightarrow(111)+(100) at $30^{\circ}C$. The effective crystal grain size of the alloy was decreased by decreasing temperature from $30^{\circ}C$ to $20^{\circ}C$ and the surface structure of them was related to the preferred orientation.

• 한국표면공학회지
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• 제32권1호
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• pp.31-42
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• 1999

The effect was investigated that aluminium in the zinc bath has on the coating adhesion of Hot-rolled Galvanized Iron(HGI) manufactured without pickling process. It is thought that the coating adhesion of HGI manufactured without pickling process is good due to the fact that increasing aluminium content in the zinc bath makes zinc and aluminium diffuse to the cracks or pores in the scale formed through the reduction heat treatment, and Fe-Zn-Al compound with good ductility is formed in the scale layer and plays a role of anchor between zinc coating and substrate. It is possible that HGI with the good coating adhesion was produced without pickling treatment in the zinc bath with more that 3wt% of Al content even at the $550^{\circ}C$ of conventional reduction heating temperature. In creasing the temperature of heating section and aluminium content in the zinc bath prevents the Zn-Fe alloy. The corrosion resistance of HGI manufactured without pickling process is excellent because of the mixed reaction of zinc sacrifice and aluminium passivity film.

• 대한치과기공학회지
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• 제7권1호
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• pp.13-18
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• 1985

Casting alloys, both precious and non-precious, were by heat in order to observe the change in HB and the results were : 1. The hard treatment showed 1.4 - 1.5 times as high as the soft treatment in HB. 2. The experiment shows that Au-Pt should be contained more than 75% to prevent color change. 3. Cu by hard teatment played the greatect part in creasing the solidity of Ag-Cu alloy. 4. Casting Co-Cr alloys showed little difference of HB in heat treatment.

• 설비공학논문집
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• 제14권12호
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• pp.1078-1083
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• 2002

The objectives of this paper are to measure the concentration of $H_2$O/LiBr solution by measuring the electrical conductivity and to study the effect of the solution temperature and the concentration on the electrical conductivity of the solution. The solution temperature ranges $20^{\circ},\;40^{\circ},\;and\; 60^{\circ}$ for a fixed concentration during the experiment. The valid ranges of the concentration are two regions, low concentration region (1~20% of LiBr) and high concentration region (55~66% of LiBr). The results show that the conductivity of the solution increases linearly with increasing the solution temperature while it increases without creasing the concentration lower than about 35% of LiBr and decreases with increasing the concentration higher than 35%. This paper proposes experimental correlations for the concentration as functions of the solution temperature and the concentration with error band of $\pm7$% for the low concentration region and $\pm1$% for the high concentration region, respectively. The experimental correlation can be practically used in the on-line measurement without any sampling of solution from the closed system.

• 에너지공학
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• 제13권2호
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• pp.166-172
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• 2004

The activated carbon was produced from Sancheong bamboo by steam and carbon dioxide gas activation methods. The carbonization of raw material was conducted at 90$0^{\circ}C$ and gas activation reactions were conducted with respect to various conditions. -activation temperature 750-90$0^{\circ}C$, the flow rate of steam 0.5-2g-$H_2O$/g-char$.$hr, the flow rate of carbon dioxide 5-30$m\ell$-$CO_2$/g-char-min and activation time 1-5 hr. The prepared activated carbons were measured yield, the adsorption capacity of iodine and methylene blue, BET specific surface area and pore size distribution. The adsorption capacity of iodine (680.5-1526.1 mg/g) and methylene blue (18.3-221.5 mg/g) increased with creasing activation temperature and activation time. The adsorption capacity of iodine and methylene blue increased with the activation gas quantity in the range of 0.5-1.5g-$H_2O$/g-charㆍhr, 5-18.9$m\ell$-Co$_2$/g-charㆍmin. But those decreased over those range due to the pore shrinkage. The steam activation method was superior in efficiency to carbon dioxide activation method.