• Journal of the Korean earth science society
• /
• v.34 no.1
• /
• pp.59-68
• /
• 2013

Focal mechanism solutions in the southwestern region of the Korean Peninsula ($34^{\circ}N-36^{\circ}N$, $126^{\circ}E-128^{\circ}E$) were obtained from the analysis of the recent 22 earthquakes ($M{\geq}2.0$) occurred from January, 2005 to March, 2011. The spatial differences between the epicenters recalculated by this study and those by KMA (Korea Meteorological Administration) and KIGAM (Korea Institute of Geoscience and Mineral Resources) are less than $0.05^{\circ}$, indicating a small deviation. However, they become a little bit larger in the coastal area due to a biased arrangement of seismic stations. Redetermined depths of hypocenters show a difference less than 12.7 km by comparison with the depth data announced by KIGAM. Most epicenters in inland area are located closely to the lineaments. Fault plane solutions were obtained from the analysis of P and SH wave polarities, and SH/P amplitude ratios. They show strike-slip faulting or strike-slip faulting with reverse components dominantly. The P-axes trends are mainly ENE-WSW or E-W directions. The direction of fault plane and auxiliary plane with 'NNE-SSW and WNW-ESE' or 'NE-SW and NW-SE' are dominant and almost parallel to the general trends of lineaments in the study area.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.35 no.2
• /
• pp.112-119
• /
• 2015

Photoacoustic microscopy is capable of providing high-resolution molecular images, and its spatial resolution is typically determined by ultrasonic transducers used to receive the photoacoustic signals. Therefore, ultrasonic transducers for photoacoustic microscopy (PAM) should have a high operating frequency, broad bandwidth, and high signal-reception efficiency. Polyvinylidene fluoride (PVDF) is a suitable material. To take full advantage of this material, the selection of the backing material is crucial, as it influences the center frequency and bandwidth of the transducer. Therefore, we experimentally determined the most suitable backing material among EPO-TEK 301, E-Solder 3022, and RTV. For this, three PVDF high-frequency single-element transducers were fabricated with each backing material. The center frequency and -6 dB bandwidth of each transducer were ascertained by a pulse-echo test. The spatial resolution of each transducer was examined using wire-target images. The experimental results indicated that EPO-TEK 301 is the most suitable backing material for a PAM transducer. This material provides the highest signal magnitude and a reasonable bandwidth because a large portion of the energy propagates toward the front medium, and the PVDF resonates in the half-wave mode.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2000.11a
• /
• pp.11-11
• /
• 2000

이동통신기술의 급격한 발달로 고주파회로의 packaging과 interconnect 기술의 고성능화 와 저가격화에 대한 새로운 도전이 요구되고 있다‘ 대부분 기존의 무선통신 부품은 P PCB(Printed Wiring Board)기술을 활용하고 있으나 이러한 기술이 점차로 고주파화되는 경 향을 만족시킬수 없어 새로운 고주파 부품기술이 요구되고 있는 실정이다 .. RF 회로를 구성 하기 위하여 PCB소재의 환경적, 치수안정성 문제를 극복하기 위하여 L TCC(Low T Temperature Cofired Ceramics)기술이 최근 주목을 받고 있다. 차세대 이동통신 기술은 수십 GHz 이상의 고주파특성이 우수하고, 고성능의 초소형의 부품을 저가격으로 제조할수 있으며, 시장의 변화에 기민하게 대처할수 있는 기술이 요구되 고 있으며, 이러한 기술적 필요성에 부합할수 있도록 LTCC 기술이 제안되었다. 이러한 C Ceramic Interconnect 기술은 높은 신뢰성을 바탕으로 fine patterning 기술과 저가의 m metallizing 기술로 가능하게 되었다. 초고주파 통신부품기술은 미국과 유럽 등을 중심으로 G GHz 대역또는 mm wave 대역의 기술에 대하여 치열한 기술개발 경쟁을 벌이고 있으며, 이 러한 고주파 패키징 기술을 바탕으로 미래의 군사, 항공, 우주 및 이동통신 기술에 지대한 영향을 미칠수 있는 기반기술로 자리잡을 전망이다. L LTCC 기술은 기존의 후막혼성기술에 비하여 공정이 단순하고 대량생산이 가능하고 가 격이 비교적 저렴하다. 또한 다층구조로 제작할수 있고, 수동소자를 내장할수 있어 회로의 소형화와 고밀도화가 가능하다. 특히 무선으로 초고속 정보를 처리하기 위하여 이동통신기 기의 고주파화가 빠르게 진행됨에 따라서 고분자재료에 비하여 고주파특성이 우수할뿐아니 라 환경적, 치수안정성이 우수한 세라믹소재플 사용함으로써 고주파 손실율을 저감할 수 있 다 .. LTCC 기술은 후막회로 기술과 tape dielectric 기술이 결합된 기술이다. 표준화된 소재 와 공정기술을 활용하여 저가격으로 고성능소자플 제작할 수 있으며, 전극재료로서 높은 전 도도를 갖고 있는 Ag, Cu, Au 및 Pd! Ag릎 사용함으로써 고주파 손실을 저감시킬 수 있다. L LTCC 기술이 최종적으로 소형화, 고기능 고주파 부품기술로 지속적으로 발전하기 위하여 무수축(Zero shrinkage) 소성기술, 광식각 후막기술 등이 원천기술로서 확립될 수 있어야 하 며, 특히 국내의 이동통신 기술에 대한 막대한 투자에도 불구하고 차세대 이동통신 부품기 술에 대한 개발은 상대적으로 미흡한 실정이므로 국내에 LTCC 관련 소재공정 및 부품소자 기술에 대한 개발투자가 시급히 이루워져야 할 것으로 판단된다. 본 발표에서는 지금까지 국내외 LTCC 기술의 발전과정을 정리하였고, 현재 이 기술의 응용과 소재와 공정을 중심으로한 개발현황에 대하여 조사하였으며, 앞으로 LTCC가 발전 해야할 방향을 제시하고자 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.1
• /
• pp.7-14
• /
• 2008

In this paper, we propose VATL(Voltage-controlled Artificial Transmission Line) employing periodically loaded diodes for application to on-chip matching components on MMIC. Compared with conventional microstrip line, the VATL showed a much shorter wave length due to periodic capacitance of diodes, and the characteristic impedance of the VATL was easily controlled bγ changing supplied voltage. Concretely, the characteristic impedance of the VATL was changed from $80{\sim}20{\Omega}$ in a range of $0{\sim}1.05V$ and the VATL showed a wavelength of 1.5mm at 20GHz, while conventional microstrip line showed a wavelength of 5.3mm at the same frequency. Using the VATL, a ${\lambda}/4$ impedance transformer was fabricated on GaAs MMIC for application to on-chip matching components on MMIC. Using the ${\lambda}/4$ impedance transformer made it possible to perform impedance matching between RF components with various characteristic impedance of $30{\sim}100{\Omega}$ by adjusting applied Voltage.

• Journal of the Korean Magnetics Society
• /
• v.7 no.1
• /
• pp.38-43
• /
• 1997

For amorphous $Co_{1-x}Ti_x$(X=0.13, 0.16, 0.21 at.%) thin films deposited by DC magnetron sputtering method ferromagnetic resonance experiments have been used to investigate the dependence of surface magnetic properties according to annealing temperature (150~225 $^{\circ}C$). Spin wave resonance spectra for all annealing temperatures consist of several volume modes and one(or two) surface mode. It is suggested that both surfaces of the film have a perpendicular hard axis to the film plane(negative surface anisotropy). Also, the surface anisotropy $K_{s2}$ at substrate film interface is varied slowly from -0.11 to -0.25 erg/ $\textrm{cm}^2$ and the surface anisotropy $K_{s1}$ at film-air interface is varied from 0.16 to -0.53 erg/ $\textrm{cm}^2$ with increasing annealing temperature. We conjecture that the variation of surface anisotropy $K_{s1}$ is due to the increase of Co concentration resulted from Ti oxidation for low temperature annealing(150~200 $^{\circ}C$) and the diffusion of Co atoms near the film surfaces for high temperature annealing(225~250 $^{\circ}C$).

• Korean Journal of Remote Sensing
• /
• v.27 no.3
• /
• pp.235-258
• /
• 2011

The purpose of this study is to investigate climatological variations from the temporal and spatial surface particulate organic carbon (POC) estimates based on SeaWiFS spectral radiance, and to determine the physical mechanisms that affect the distribution of pac in the Gulf of Mexico. 7-year monthly mean values of surface pac concentration (Sept. 1997 - Dec. 2004) were estimated from Maximum Normalized Difference Carbon Index (MNDCI) algorithm using SeaWiFS data. Synchronous 7-year monthly mean values of remote sensing data (sea surface temperature (SST), sea surface wind (SSW), sea surface height anomaly (SSHA), precipitation rate (PR)) and recorded river discharge data were used to determine physical forcing factors. The spatial pattern of POC was related to one or more factors such as river runoff, wind-derived current, and stratification of the water column, the energetic Loop Current/Eddies, and buoyancy forcing. The observed seasonal change in the POC plume's response to wind speed in the western delta region resulted from seasonal changes in the upper ocean stratification. During late spring and summer, the low-density river water is heated rapidly at the surface by incoming solar radiation. This lowers the density of the fresh-water plume and increases the near-surface stratification of the water column. In the absence of significant wind forcing, the plume undergoes buoyant spreading and the sediment is maintained at the surface by the shallow pycnocline. However, when the wind speed increases substantially, wind-wave action increases vertical motion, reducing stratification, and the sediment were mixed downward rather than spreading laterally. Maximum particle concentrations over the outer shelf and the upper slope during lower runoff seasons were related to the Loop Current/eddies and buoyancy forcing. Inter-annual differences of POC concentration were related to ENSO cycles. During the El Nino events (1997-1998 and 2002-2004), the higher pac concentrations existed and were related to high runoffs in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico. During La Nina conditions (1999-2001), low Poe concentration was related to normal or low river discharge, and low PM/nutrient waters in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico.

• Journal of Chest Surgery
• /
• v.36 no.5
• /
• pp.329-334
• /
• 2003

Backgound: Cryoablation and radiofrequency ablation have been used to treat the atrial fibrillation. Some reports insisted that the microwave ablation Is a better method for a deep and extensive lesion. Material and Method: From December 2001 to July 2002, we peformed 8 microwave ablations in patients who needed mitral valve surgery (7 MVR, 1 MVR+AVR). There were 3 men and 5 women, and their mean age was 43.4$\pm$8.3 years and mean follow up period was 5.6$\pm$2.4 months respectively. The microwave was applied on endocardium or epicardium by Lynx (Afx, inc.) using a power of 45 watts for 25 seconds. We studied the left atrial dimension, the left atrial function and the sinus conversion with echocardiography and electro-cardiography at three times; 1) before the operation, 2) immediately after the operation, and 3) 6 months after the operation. Result: There was no complication and no mortality. The mean aortic clamping time was 104.6$\pm$25.0 minutes, and the mean total bypass time was 130.5$\pm$28.7 minutes. The rate of sinus conversion was 75%, A wave across the mitral valve was a mean of 77.0$\pm$24.8 cm/sec, and the AVE was a mean of 0.46$\pm$0.17 at 5.6 months postoperatively Conclusion: There was no difference in the early result of microwave ablation compared to other methods. The microwave ablation was an acceptable method due to its convenient application especially in beating heart.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.478-478
• /
• 2012

Recently, there are many researches in order to increase the deposition rate (D/R) and improve film uniformity and quality in the deposition of microcrystalline silicon thin film. These two factors are the most important issues in the fabrication of the thin film solar cell, and for the purpose of that, several process conditions, including the large area electrode (more than 1.1 X 1.3 (m2)), higher pressure (1 ~ 10 (Torr)), and very high frequency regime (VHF, 40 ~ 100 (MHz)), have been needed. But, in the case of large-area capacitively coupled discharges (CCP) driven at frequencies higher than the usual RF (13.56 (MHz)) frequency, the standing wave and skin effects should be the critical problems for obtaining the good plasma uniformity, and the ion damage on the thin film layer due to the high voltage between the substrate and the bulk plasma might cause the defects which degrade the film quality. In this study, we will propose the new concept of the large-area multi-electrode (a new multi-electrode concept for the large-area plasma source), which consists of a series of electrodes and grounds arranged by turns. The experimental results with this new electrode showed the processing performances of high D/R (1 ~ 2 (nm/sec)), controllable crystallinity (~70% and controllable), and good uniformity (less than 10%) at the conditions of the relatively high frequency of 40 MHz in the large-area electrode of 280 X 540 mm2. And, we also observed the SEM images of the deposited thin film at the conditions of peeling, normal microcrystalline, and powder formation, and discussed the mechanisms of the crystal formation and voids generation in the film in order to try the enhancement of the film quality compared to the cases of normal VHF capacitive discharges. Also, we will discuss the relation between the processing parameters (including gap length between electrode and substrate, operating pressure) and the processing results (D/R and crystallinity) with the process condition map for ${\mu}c$-Si:H formation at a fixed input power and gas flow rate. Finally, we will discuss the potential of the multi-electrode of the 3.5G-class large-area plasma processing (650 X 550 (mm2) to the possibility of the expansion of the new electrode concept to 8G class large-area plasma processing and the additional issues in order to improve the process efficiency.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
• /
• v.11 no.1
• /
• pp.11-28
• /
• 2005

Spasticity has been defined as "a motor disorder characterized by a velocity-dependent increased in tonic stretch reflexes with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as one components of the upper motorneuron syndrome". Spasticity is one of the common symptoms of stroke patients and frequently interferes with the motor functions such as gait, posture and activities of daily living. Therefore, its management is becoming a major issue in physical therapy. The purpose of this study was to determined the effects of reciprocal inhibition by isometric contraction of pre-tibia muscle on spasticity in hemiplegic patients through Hoffmann reflex. The subjects were consisted 45 patients who had hemiplegia due to stroke. All subjects randomly assigned to 3 group: manual reciprocal inhibition program group(manual group), neuromuscular electrical stimulation group(NMES group) and control group. The manual group received voluntary isometric contraction of pre-tibia muscle. The NMES group received neuromuscular electrical stimulation on tibialis anterior. The control group was not received any therapeutic intervention. Before and after experiments, Hoffmann reflex, M-wave and Modified Ashworth scale was measure in all patients. The data of 30 patients who complete experimental course were statistically analysed. Modified Ashworth scale were significantly decreased after experiment in manual group(p<.01). The Hmax/Mmax ratios were significantly decreased after experiment in manual group(p<.o1). There were no statistical difference between pre-test and post-test with modified Ashworth scale in NMES group(p>.01). There were no statistical difference between pre-test and post-test with Hmax/Mmax ratios in NMES group(p>.01). There were no statistical difference between pre-test and post-test with modified Ashworth scale in control group(p>.01). There were no statistical difference between pre-test and post-test with Hmax/Mmax ratios in control group(p>.01). The present results revealed that reciprocal inhibition which produced by voluntary isometric contraction of pre-tibia muscle can be reduce spasticity of gastrocnemius. Therefore, reciprocal inhibition is useful to improve functional activities in hemiplegic patient. Further study should be done to analyse the effects of intervention duration of reciprocal inhibition, appropriate muscle contraction, optimal time to apply the reciprocal inhibition in more long period.

• Korean Journal of Optics and Photonics
• /
• v.31 no.3
• /
• pp.142-147
• /
• 2020

In this paper, we report highly efficient second harmonic generation of continuous-wave Yb fiber lasers incorporating a periodically poled LiTaO₃ device (MgO:PPSLT) as a frequency converter. The seed laser output from a Yb fiber master oscillator using a Fabry-Perot feedback cavity was amplified in a Yb fiber amplifier stage, yielding 28.5 W of linearly polarized output at 1064 nm in a beam with beam quality, M², of ~1.07. Second harmonic generation was achieved by passing the laser beam through MgO:PPSLT. Under optimized conditions, we obtained 11.1 W of green laser output at 532 nm for an incident signal power of 25.0 W at 1064 nm, corresponding to a conversion efficiency of 44.4%. The detailed investigation to find the optimized operating conditions and prospects for further improvement are discussed.