• Applied Science and Convergence Technology
• /
• v.27 no.3
• /
• pp.47-51
• /
• 2018

We fabricated an anode-type ion beam source and studied its driving characteristics of the initial extraction of ions using two driving mechanisms: a diffusion phenomenon and a charge repulsion phenomenon. For specimen exposed to the ion beam in two methods, the surface impurity element was investigated by using X-ray photoelectron spectroscopy. Upon Ar gas injection for plasma generation the ion beam source was operated for 48 hours. We found a Fe 2p peak 5.4 at. % in the initial ions by the diffusion mechanism while no indication of Fe in the ions released in the charge repulsion mechanism. As for a long operation of 200 min, the temperature of ion beam sources was measured to increase at the rate of ${\sim}0.1^{\circ}C/min$ and kept at the initial value of $27^{\circ}C$ for driving by diffusion and charge repulsion mechanism, respectively. In this study, we confirmed that the ion beam source driven by the charge repulsion mechanism was very efficient for a long operation as proved by little electrode damage and thermal stability.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.6
• /
• pp.743-748
• /
• 2022

The initial operation stability of hydrogen-fueled, solid oxide fuel cell with Ni thin-film anode fabricated by direct current sputtering was evaluated in terms of electrochemical properties such as peak power density, open circuit voltage, overpotential, and alternating current impedance at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1455-1458
• /
• 2008

Amorphous silicon (a-Si:H) thin-film transistors (TFTs) are fabricated on flexible organic polymer foil substrates. As-fabricated performance, electrical bias-stability at elevated temperatures, electrical response under mechanical flexing, and prolonged mechanical stability of the TFTs are studied. TFTs made on plastic at ultra low process temperatures of $150^{\circ}C$ show initial electrical performance like TFTs made on glass but large gate-bias stress instability. An abnormal saturation of the instability against operation temperature is observed.

• Proceedings of the KIEE Conference
• /
• 2002.07a
• /
• pp.96-98
• /
• 2002

A 765kV Transmission line system plays an important role in delivering the electric power produced at mid-western in Korea. This system will be constructed and operated normally on 2002. By doing the number of test operation in a given time, the reliability on the operation of 765kV transmission system could be secured.

• Proceedings of the KIEE Conference
• /
• 2002.11b
• /
• pp.227-230
• /
• 2002

A 765kV Transmission line system plays an important role in delivering the electric power produced at mid-western in Korea. This system will be constructed and operated normally on 2002. By doing the number of test operation in a given time, the reliability on the operation of 765kV transmission system could be secured.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.39 no.1
• /
• pp.1-9
• /
• 1990

The structure of A matrix of one machine connected to the infinite bus is described for a full model. The A matrix can be partitioned to submatrices which depend on the initial operating point and do not depend on it. When the dynamic properties for several different operating points are desired, those submatrices can be obtained through simple column operation. Furthermore, the elements of A matrix can be directly calculated from the manufacturer's data. RMS quantities of the state variables for the initial operating point are used. This approach can save the labor for calculating the elements of A matrix for the dynamic stability analysis.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.18 no.3
• /
• pp.321-327
• /
• 2009

This paper studied the influences of the main design parameter-the expansion angle and the material properties of the self-expansion anterior cruciate ligament fixation device on the contact condition with the bone and the initial stability of the device. Using finite element analysis, the stress distributions of the ring part of the device and the wall of the bone tunnel were calculated. And the micro-migration of the device by the pull-out force was calculated. From the analysis results, it was found that when designing the self-expansion type anterior cruciate ligament fixation device, it is desirable to use the material having higher Young's modulus and to design the fixation device that all wedges uniformly maintain contact with bone to obtain initial stability after operation.

• New & Renewable Energy
• /
• v.3 no.1 s.9
• /
• pp.60-67
• /
• 2007

Catalyst coated membrane [CCM] type and catalyst coated substrate [CCS] type of membrane electrode assembly [MEA] were manufactured and evaluated their performance. Degradation test were conducted to find the difference of long term stability in two types of MEA and the factor for performance degradation problem occurred. Performance degradation test of single cell in two different types of MEA were carried out when current density was $200mA/cm^{2}$. The degradation test had proceeded for 230 hours and performance degradation was checked by I-V curve and impedance measurement at regular intervals. Also, MEA before/after operation and changes of catalyst layer were characterized by SEM, TEM, and XRD. Maximum power density of CCM type was higher than that of CCS type. Meanwhile, an increase of particle size of catalyst and an increase of impedance resistance after long term operation were observed. In the case of using CCM type MEA, the performance was deteriorated 38% of initial performance. In the case of using CCS type MEA, the performance was deteriorated 43% of initial performance. In consideration of difference of initial performance, performance of CCM type is higher than that of CCS type but both types had similar problems during degradation test.

• Wind and Structures
• /
• v.32 no.2
• /
• pp.169-177
• /
• 2021

This study investigates the effects of blade configuration and solidity of Darrieus wind turbine on the starting torque characteristics. Generally, the configuration of Darrieus wind turbine is divided into Troposkien, parabola, Catenary, Sandia, modified-parabola and straight types. A numerical analysis has been carried out using Multiple Stream Tube (MST) method to investigate the effect of blade configuration and solidity of Darrieus wind turbine on the starting torque under the initial low range of rotational speed. The simulation results show that the starting torque of Darrieus wind turbine varies considerably depending on the blade configuration. The initial starting torque was larger with Troposkien, Parabola, Catenary, and Sandia configurations than with modified parabola or straight types. The increase in solidity with increasing number of blades raised the starting torque and improved the dynamic stability during the initial operational speed of Darrieus wind turbine. Additionally, these torque results represent basic data for fluid-structure interaction (FSI) simulation of the steady-dynamic operation of the turbine.

• Journal of Yeungnam Medical Science
• /
• v.18 no.1
• /
• pp.101-111
• /
• 2001

Background: We analyze the functional evaluation, posterior stability after surgery of acute injuries in the femoral detachment and tibial avulsion fracture of posterior cruciate ligament. Materials and Methods: Twenty two patients who underwent primary repair were followed more than one year after operation (mean follow-up 33.7 months). The patients were evaluated with KT 2000 arthrometer and posterior stress test for posterior stability. Lysholm knee score was used for knee function. Results: Lysholm score revealed 85.3 in femoral detachment group and 91.1 in tibial avulsion fracture group (P<0.05). Posterior displacement of the posterior stress test showed 17.2 mm at initial injury and 8.6 mm at last follow up in femoral detachment group, 16.8 mm at initial injury and 7.1 mm at last follow up in tibial avulsion fracture group. There revealed the tendency of the improved posterior stability of the tibial avulsion group compared with femoral detachment group, but there showed no statistical significance in KT 2000 arthrometer and posterior stress x-ray. Conclusion: Functional results of tibial avulsion fracture group revealed the better outcome compared with femoral detachment group, but the degree of posterior stability in tibial avulsion fracture group showed no statistical significance in posterior stability.