• 펄프종이기술
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• 제40권4호
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• pp.66-73
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• 2008

When coated paperboard is printed, pressed into a groove with a creasing rule and folded, white line cracking occurs along the crease due to intensive mechanical pressure. The cracking will deteriorates product quality and waste resources. Effects of creasing pressure and ink dosage on the foldability of coated board were investigated. It was shown that applying an optimum pressure is important during creasing. When the pressure was too low, the crease formed was not sufficiently deep enough to enable precise folding. When an excess pressure was applied, fiber bonding was destroyed, resulted in unsatisfactory cracking. When the coated board was folded in machine direction (MD), long cracks were formed along MD. When it folded in cross direction (CD), the cracks were shorter and formed perpendicular to CD. Printing promoted cracking due to the decrease in flexibility of coated board. In addition, uneven ink film layer on the coating layer caused worse cracking.

• 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.

• 한국정밀공학회지
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• 제5권3호
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• pp.81-90
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• 1988

In recent, the requirement of remote control of hychaulic system is in- creasing. The actuator unit whose output position is proportional to input electrical signal needs a pressure reducer and a dump valve. The pressure reducer provides a constant regulated pressure and filters contaminants. The dump valve supplies proper pressure to the pressure reducer and unloads when the system is not operated. In this thesis, dump valve and pressure reducer with auxiliary function are studied. The choke in the pressure reducer prevents actuator from supplying higher pressure than necessary pressure at beginning, and the spring constant affects on the dynamic characterisics. In dump valve, it is proved that diameter of servo-slide hold and choke diameter of dump plunger affects on damping response.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1657-1659
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• 1997

Electron temperature and electron density were measured in a radio-frequency inductively coupled plasma (RFICP) using a probe measurements. Measurement was conducted in an argon discharge for pressures from 10 [mTorr] to 40 [mTorr] and input rf power from 100 [W] to 800 [W], Ar flow rate from 5 [sccm] to 30 [sccm], Spatial distribution electron temperature and electron density were measured for discharge with same aspect ratio (R/L=2). Electron temperature and electron density were discovered depending on both pressure and power, Ar flow rate. Electron density was increased with increasing input power and in creasing pressure, increasing Ar flow rate. Radial distribution of the electron density was peaked in the plasma center. Normal distribution of the electron density was peaked in the center between quartz plate and substrate. From these results, We found out the generation mechanism of Radio-Frequency Inductively Coupled Plasma.

• Nuclear Engineering and Technology
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• 제27권6호
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• pp.825-832
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• 1995

SA508 Cl.3 원자로 압력용기강에서 하중변수와 온도가 공기 중에서 피로 균열성장률에 미치는 영향에 대하여 조사하였다. 피로 균열성장률 시험은 12.7mm 두께의 CT(compact tension) 시편을 이용하였으며, 균열길이 추정은 컴플라이언스 방법을 사용하였다. 시험은 0.1, 0.5 하중비와 1, 10Hz의 하중주파수로 상온에서 40$0^{\circ}C$ 까지 온도를 변화시키면서 수행하였다. 12$0^{\circ}C$ 이하의 비교적 낮은 온도에서는 피로균열전파속도는 하중주파수와 온도에 영향을 받지 않았지만, 12$0^{\circ}C$이상의 경우 피로 균열성장률은 온도가 높을수록, 하중주파수가 낮을수록 증가하였다. 이러한 피로균열진전속도의 빨라짐은 균열선단에서의 산화속도의 증가로 인한것으로 생각된다. 또한 하중비의 영향으로 균열닫힘과 산화의 상호작용으로 피로 균열성장률은 상온에서 두드러졌다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.155-160
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• 2002

Metal matrix composites had generated a lot of interest in recent times because of significant in specific properties. It was also highlighted as the materials of frontier industry because strength, heat-resistant, corrosion-resistant, wear-resistant were superiored. In this study the strength properties of $Al_{18}B_4O_{33}/AC4CH$ were represented mixing the binder of $Al_2O_3$ and $TiO_2$. It was also fabricated by squeeze casting. $Al_{18}B_4O_{33}/AC4CH$ was fabricated at the melt temperature of $760^{\circ}C$ the perform temperature of $700^{\circ}C$ and mold temperature of $200^{\circ}C$ under the pressure of 83.4MPa and observed SEM. Fatigue crack growth rate tests on compact tension specimen(half-size) of thickness 12.5mm were conducted by using sinusoidal waveform. Compact tension specimens(half-size) were used and fatigue crack growth rate da/dN and stress intensity factor range ${\Delta}K$ were analyzed concerning to the R value of 0.1 and 0.05. In order to find out the value of ${\Delta}K$, load amplitude constant method was applied by the standard fatigue testing method describes in ASTM E647-95a. As the results of this study, Fatigue crack growth rate increased with in creasing the load ratio, Consequently, At equivalent stress intensity factors, the fatigue crack growth rates in MMC were faster than those of AC4CH alloy. then the fatigue life and the fatigue crack growth rate was investigated using scanning election microscopy(SEM)

• 한국농공학회지
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• 제17권4호
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• pp.3980-3990
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• 1975

This study was carried out to develop a method of grain drying ststem that can be done by forcing the heated-air directly into the grains within the sack. The air duct was pushed into the central position of the grain-deposited sack and the heated-air was forced to flow in the radial direction. The system is referred here as the unit sack drying system. At a first step of this study, an air flow resistance tester was constructed to measure the resistance of air flow to grains in cooperated with some different sack materials, the sack materials, the tested were rice-straw bag, sack of polyethylene film, and jute sack In addition, unit sack drying system was constructed to investigate the drying characteristics of the dryer. on this dryer, two kind of terminal air ducts were attached and tested to examine its effects on uniform drying, and also, aseries of drying test was performed to trace the effect of increasing air flow rate on uniform drying. The results are as follows: 1) Resistance of air flow for each sack material was increased almost proportional to the increasing rate of air flow. Experimental data showed little significant differences of the air flow resistance among the materials. 2) From the comparison with air flow resistance of sack material and that of roughrice, it was indicated that airflow resistance of sack material was much higher than that of rice rough Therefore, in the unit sack drying sysle in which air flow is destined to face the sach material after leaving the grain, it was suggested that air flow would be inuniform to each part of grain within sack because of much higher air flow resistance of sack material than that of grain, and the fact would results inuniform grain drying. 3) Drying test on the unit sack drying system in cooperated with different type of terminal air ducts showed that high speed air is better for uniform drying than in high pressure. with the drying system which was assembled with the air ducts delivering higher speed air, there also involved a problem of significant inuniform drying. Therefore, any means to improve the inuniform drying should be undertaken for practical use. 4) A series of drying test with in creasing air flow rate resulted that increasing air flow rate in the unitsack drying system gave little effect on uniform drying, therefore, it is recommened to change its drying system for drying grain uniformly.