• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.419-424
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• 2001

We intended to evaluate the Young's modulus of trabecular bone of a human distal femur by spherical Indentation test and CT images and to quantify relationships between the direction of load, density. and Young's modulus. The specimens were scanned at 1 mm intervals on CT scanner After scanning the bones were sectioned with diamond saw. producing 8mm cubes of trabecular bone. The tubes were mechanically tested in inferior-superior(IS), anterior-posterior(AP). and medial-lateral(ML) direction with custom-made device. After testing, the real apparent density of specimens were measured. The results of this study showed that the IS modulus was significant1y greater than both the AP and ML modulus and the AP modulus was also greater than ML modulus significantly(p〈0.01) A significant Power relationship between the apparent density and the modulus was also found.

• Korean Journal of Materials Research
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• v.10 no.9
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• pp.624-628
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• 2000

As a power durable-electrode in SAW filter, Al-1%Cu/tungsten nitride multi-layer thin film was fabricated by magnetron sputtering process. Tungsten nitride films had the amorphous phase at the nitrogen ratio, R, ranging from 10~40%. The amorphization could be controlled by nitrogen ratio, R= $N_2$/($N_2$+Ar) as a sputtering process parameter. Residual stress in tungsten nitride abruptly decreased with the formation of amorphous phase. Al-1%Cu thin film was deposited on the amorphous tungsten nitride. After the multi-layed thin film was annealed for 4 hours at 453K, the resistivity decreased as $3.6{\mu}{\Omega}-cm$, which was due to grain growth reduced crystal defects.

• Journal of IKEEE
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• v.8 no.1 s.14
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• pp.152-159
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• 2004

In this study, we design the one-chip PWM IC with high voltage power switch (300V class LDMOSFET) for SMPS (Switching Mode Power Supply) application. Reference circuits generate constant voltage(5V) in the various of power supply and temperature condition. Error amp. is designed with large DC gain $({\simeq}65dB)$, unity frequency $({\simeq}190kHz)$ and large $PM(75^{\circ})$. comparator is designed with 2 stage. Saw tooth generators operate with 20kHz oscillation frequency. Also, we optimize drift concentration & drift length of n-LDMOSFET for design of high voltage switching device. It is shown that simulation results have the breakdown voltage of 350V. (using ISE-TCAD Simulation tool). PWM IC with power switching device is designed with 2um design rule and Bi-DMOS technology.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.393-400
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• 2012

In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.1
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• pp.103-111
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• 2020

Pulling-type cutting devices, which use a diamond wire saw, have been used generally for cutting concrete structures. In this study, a pushing-type cutting device with a collection cover was developed by overcoming the disadvantages of pulling-type devices. In this device, dry or liquid methods can be selected to cool frictional heat. Operation and leakage tests of the dust generated during the dismantling of a concrete structure were carried out, confirming the suitable operation of the fabricated cutting device; the leakage rate was approximately 1.7%. For a conservative evaluation, the internal dose of workers was estimated in dismantling the core center part of biological shield concrete with a specific activity of 99.5 Bq·g^-1. The committed effective dose per worker was 0.25 mSv. The developed cutting device contributed to reducing radioactive concrete waste and minimizing worker exposure due to its easy installation. Therefore, it can be utilized as a cutting apparatus for dismantling not only reinforced concrete structures but also radioactive biological shield concrete in nuclear power plant decommissioning efforts.

• Journal of Chest Surgery
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• v.37 no.6
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• pp.467-473
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• 2004

Background: The sinus conversion rate after the maze procedure in chronic atrial fibrillation using radiofrequency energy is lower than with either conventional 'cut and saw' technique or cryothermia. The creation of incomplete transmural lesions due to poor tissue-catheter contact is thought to be the main cause. To address this problem, the current study was aimed to evaluate the effectiveness of a specially constructed compression device designed to enhance tissue catheter contact during unipolar radiofrequency catheter ablation. Material and Method: Circum-ferential right auricular epicardial lesions were created with a linear radiofrequency catheter in 10 anesthetized pigs. A device specially designed to increase contact by compression of the catheter to the atrial wall was used in 5 pigs (study group). This device was not used in the control group (5 pigs). Conduction block across the right auricular lesion was assessed by pacing, and the transmurality of the lesions were confirmed by microscopic examination. Result: Conduction block was observed in a total of 8 pigs; 5 in study group and 3 in control group. Transmural injury was confirmed microscopically by the accumulation of acute inflammatory cells and loss of elastic fibers in the endocardium. In two pigs with failed conduction block, microscopic examination of the endocardium appeared normal. Conclusion: Failed radiofrequency ablation is strongly related to non-transmural energy delivery. The specially constructed compression device in the current study was successful in creating firm tissue-catheter contact and thereby generating transmural lesions during unipolar radiofrequency ablation.

• Journal of IKEEE
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• v.14 no.2
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• pp.90-97
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• 2010

The high efficiency power management IC(PMIC) with DTMOS(Dynamic Threshold voltage MOSFET) switching device and DTMOS Error Amplifier is presented in this paper. PMIC is controlled with PWM control method in order to have high power efficiency at high current level. Dynamic Threshold voltage CMOS(DT-CMOS) with low on-resistance is designed to decrease conduction loss. The control parts in Buck converter, that is, PWM control circuits consist of a saw-tooth generator, a band-gap reference circuit, an DT-CMOS error amplifier and a comparator circuit as a block. the proposed DT-CMOS Error Amplifier has 72dB DC gain and 83.5deg phase margin. also Error Amplifier that use DTMOS more than CMOS showed power consumption decrease of about 30%. DC-DC converter, based on Voltage-mode PWM control circuits and low on-resistance switching device is achieved the high efficiency near 96% at 100mA output current. And DC-DC converter is designed with Low Drop Out regulator(LDO regulator) in stand-by mode which fewer than 1mA for high efficiency.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.175-185
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• 2004

Rotating disks are used in various machines such as data storage device, gyroscope, circular saw, etc. Transverse vibration of a rotating disk is very important for the performance of these machines. This work proposes a method to suppress transverse vibration of a very flexible rotating disk in non-contacting manner. A system considered in this study is a very flexible rotating disk with a thrust bearing pad which is located underneath the rotating disk. The pressure force generated in the gap between the rotating disk and the thrust pad pushes the rotating disk in the direction of axis of rotation while the centrifugal force and the elastic recovery force push the rotating disk in reverse direction. The balance between these forces suppresses the transverse vibration of the rotating disk. A coupled disk-fluid system is analyzed numerically. The finite element method is used to compute the pressure distribution between the thrust pad and the rotating disk while the finite difference method is used to compute the transverse vibration of a rotating disk. Results show that the transverse vibration of the rotating disk can be suppressed effectively for certain combination of air bearing and operating parameters.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.706-713
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• 2002

In the multi-pass welding of pressure vessels or ships, the mechanical touch sensor system is generally used together with a manipulator to measure the gap and depth of the narrow gap to perform seam tracking. Unfortunately, such mechanical touch sensors may commit measuring errors caused by the eterioration of the measuring device. An automation system of narrow gap multi-pass welding using a laser vision system which can track the seam line of narrow gap and which can control welding power has been developed. The joint profile of the narrow gap, with 250mm depth and 28mm width, can be captured by laser vision camera. The image is then processed for defining tracking positions of the torch during welding. Then, the real-time correction of lateral and vertical position of the torch can be done by the laser vision system. The adaptive control of welding conditions like welding Currents and welding speeds, can also be performed by the laser vision system, which cannot be done by conventional mechanical touch systems. The developed automation system will be adopted to reduce the idle time of welders, which happens frequently in conventional long welding processes, and to improve the reliability of the weld quality as well.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.565-566
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• 2008

The high efficiency power management IC(PMIC) for Moblie application is proposed in this paper. PMIC is controlled with PWM control method in order to have high power efficiency at high current level. The saw-tooth generator is made to have 1.2 MHz oscillation frequency and full range of output swing from ground to supply voltage(VDD:3.3V). The comparator is designed with two stage OP amplifier. And the error amplifier has 70dB DC gain and $64^{\circ}$ phase margin. DC-DC converter, based on Voltage-mode PWM control circuits, achieved the high efficiency near 95% at 100mA output current. DC-DC converter is designed with LDO in stand-by mode which fewer than 1mA for high efficiency.