• KSTLE International Journal
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• v.4 no.1
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• pp.8-13
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• 2003

Abrasion in fretting wear mechanism is studied experimentally with the specimens of two different shapes of spacer grid spring and fuel tubes of a nuclear fuel. Reciprocating sliding wear test has been carried out in the environment of air and water at room temperature. Especially, third body abrasion is referred to for explaining the wear region expansion found during the slip displacement increase with constant normal contact farce. It is found that the expansion behaviour depends on the contact shape. The small clearance between the tube and spring seems to be the preferable region of the wear particle accumulation, which causes third body abrasion of the non-contact area. Even in water environment the third body abrasion occurs apparently. Since the abrasion on the clearance contributes wear volume, the influence of the contact shape on the severity of third body abrasion should be considered to improve the grid spring design in the point of restraining wear damage of a nuclear fuel.

• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.13-19
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• 2006

The micro-gas sensor based on carbon nanotubes (CNTs) was fabricated and its gas sensing characteristics on nitrogen dioxide ($NO_{2}$) have been investigated. The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_{2}$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• Journal of the Korean Home Economics Association
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• v.30 no.3
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• pp.101-117
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• 1992

Effects of gamma irradiation(2.5∼20kGy) on water absorption property was studied for a local variety of black soybeans. In water absorption patterns of black soybeans, the time to reach a fixed moisture content was reduced depending on the increment of water soaking temperature and irradiation dose. Irradiation at 2.5∼10kGy resulted in the reduction of soaking time of black soybeans by about 1∼3 hours and the increase of hydration capacity by 10∼20%, respectively, compared to the nonirradiated control black soybean. The water uptake rate constant of the irradiated black soybean difinitely increased with the increase of dose levels and water soaking temperature. The activation energy for water absorption and z-value were lower in the irradiated black soybeans than in the nonirradiated control black soybean. The efficacy of water absorption property in the irradiated black soybeans was also recognized after one year of storage at room temperature.

• Journal of Radiation Protection and Research
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• v.38 no.4
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• pp.185-188
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• 2013

Heating method using electric heater was used to reduce water content in fingernail clippings. Authors found that low water content is helpful to measure EPR signal of fingernail sample with enhanced variability. Generally, natural dehydration happens in normal room condition at least one month and needs much time for using in experiment. So, artificial heating method is applied in this study for time savings. Fingernail samples were tested to find effect of water content to the EPR signal on microwave power levels for dosimetry. Low water content in fingernail reduced variability of EPR signal and makes it possible to measure accurate EPR signal. It also made it possible to measure constant movement of EPR signals on several microwave power levels. Although this method was difficult to apply directly in fingernail/EPR dosimetry, we, authors, believe that this heating method would be useful to differentiate MIS2 and RIS which are generally located at the same g-factor and almost impossible to be identified with each other.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.101-109
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• 1996

The mechanical propertieso f sintered AlN with the addition of alumina were investigated The flexural strength of the AlN dispersed ALON specimens was higher than that of ALON and fracture toughness showed similar tendency. The high-temperature flexural strength of specimens which 50 and 64.3 mol% alumina was added to AlN was constant up to 100$0^{\circ}C$ with about 290 and 420 MPa respectively but abruptly decreased at 120$0^{\circ}C$ In the specimens which contained 5 and 30mol% alumina the flexural strength increased to about 14% at 100$0^{\circ}C$ and did not decrease at 120$0^{\circ}C$ compared to at room temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1038-1042
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• 2005

We have investigated dielectric properties depending on bias voltage in organic light-emitting diodes using 8-hydroxyquinoline aluminum $(Alq_3)$ as an electron transport and emissive material. We analyzed the dielectric properties of organic light-emitting diodes using impedance of characteristics. Impedance characteristics was measured complex impedance Z and phase $\theta$ in the frequency range of 40 Hz to $10^8$ Hz. We obtained complex electrical conductivity, dielectric constant, and loss tangent $(tan\delta)$ of the device at room temperature. From these analyses, we are able to interpret a conduction mechanism and dielectric properties contributed by an interfacial and orientational polarization.

• Journal of the Korea Furniture Society
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• v.14 no.1
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• pp.79-89
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• 2003

Today's aesthetics and design orientations seem to be: flexibility, mobility, multi-functionality required front user's new needs. Our spaces have changed increasingly contain the needs of constant mobility and ability to adapt to a wide variety of situations. For efficient use, a modular system in furnishing can manage the spaces with components which are easy to assemble and disassemble. The function comes from spacial technological structure that is an 'union' formed by units to joint each other. The repeated module is tailored to unchanging environmental conditions. On the other hand, the structure defined by change reacts flexibility to a dynamic environment. In decision-making, it is flexible and able to adapt. Their ability to be positioned freely anywhere in the room allows individual tasks to be carried out by different people, and their almost endless variety of uses create distinctive spaces for living.

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1053-1059
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• 1997

The dynamic fatigue behavior of alumina ceramics was observed at room temperature using four point bending system. The dynamic fatigue fracture strength and the dynamic fatigue lifetime were observed as a function of crosshead speed and the notch length. The notched specimen showed the smaller deviation in dynamic fatigue fracture strength than the unnotched specimen. The crack growth exponent n and the material constant A of the notched specimen could be represented as functions of the notch length. Fracture strength of the specimen calculated from the notch length, when the notch length was regarded as the crack size, was in good agreement with the measured 4 point bending strength. Fracture surface of the specimen showed the different fracture modes according to the crosshead speed. The four point flexural strength, fracture toughness, Young's modulus and Weibull modulus of the alumina were measured as 360 MPa, 3.91 MPa.m1/2, 159GPa, 17.64, respectively.

• Journal of Magnetics
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• v.4 no.1
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• pp.13-16
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• 1999

Magnetic viscosities of a commercialized metal evaporated tape were measured as a function of sweeping rate in VSM at room temperature. Within several seconds in the viscosity measurement, curves are downward concave and more concave with increasing sweeping rate when magnetization were plotted as a logarithmic function of time. However, magnetization varied as a logarithmic function of time after several seconds. Magetic viscosity coefficient gradually increased with increasing sweeping rate and then kept a constant value at a rate faster than 61.5 Oe/s. It was supposed that magnetic viscosity occurs during field sweeping, which was in good agreement with Sharrock's model qualitatively. Activation volume decreased with increasing sweeping rate, which was due to the fact that magnetic viscosity coefficients increased with sweeping rate while irreversible susceptibilities were not affected by sweeping rate.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.37-44
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• 2000

High velocity, gas-assisted liquid drop trajectories were investigated under well-controlled experimental conditions at elevated gas densities and room temperature. A monodisperse stream of drops which are generated by a vibrating-orifice drop generator were injected into a transverse high velocity gas stream. The gas density and air jet velocity were adjusted independently to keep the Weber numbers constant. The Weber numbers studied were 72, 148, 270, 532. The range of experimental conditions included studied the three drop breakup regimes previously referred as bag, stretching/thinning and catastrophic breakup regimes. High-magnification photography and conventional spray field photographs were taken to study the microscopic breakup mechanisms and the drop trajectories in high velocity gas flow fields, respectively. The parent drop trajectories were affected by the gas density and the gas jet velocities and do not show similarity with respect to the either Weber or the Reynolds number, as expected.