• Geosciences Journal
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• 제22권6호
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• pp.1027-1039
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• 2018

Seismic attributes are often used to identify lithology and evaluate reservoir properties. However, interpretation based only on structural attributes and without knowledge of the Vp/Vs ratio can limit the ability to evaluate changes in heavy oil reservoirs. These limitations are often due to less obvious impedance differences. In order to investigate pieces of evidence of a heavy-oil shaly-sand reservoir from seismic data, besides geochemistry, we studied seismic attributes and characterized the reservoir using seismic stack data and well logging data. The study area was the Muglad rift basin in South Sudan. We conducted a seismic complex analysis to evaluate the target reservoir. To delineate the frequency responses of the different lithological units, we applied the spectral decomposition method to the target reservoir. The most unexpected result was continuous bands of strong seismic reflectors in the target reservoir, which extended across the borehole. Spectral decomposition analysis showed that the low-frequency zone of 25 Hz dominant frequency was consistent with instantaneous attributes. This approach can identify lithology, reveal frequency anomalies, and filter the stacked section into low- and high-frequency bands. The heavy-oil reservoir zones exhibited velocity attenuation and the amplitude was strongly frequency dependent.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.643-646
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• 2005

The gas hydrate exploration using seismic reflection data, the detection of BSR(Bottom Simulating Reflector) on the seismic section is the most important work flow because the BSR have been interpreted as being formed at the base of a gas hydrate zone. Usually, BSR has some dominant qualitative characteristics on seismic section i.e. Wavelet phase reversal compare to sea bottom signal, Parallel layer with sea bottom, Strong amplitude, Masking phenomenon above the BSR, Cross bedding with other geological layer. Even though a BSR can be selected on seismic section with these guidance, it is not enough to conform as being true BSR. Some other available methods for verifying the BSR with reliable analysis quantitatively i.e. Interval velocity analysis, AVO(Amplitude Variation with Offset)analysis etc. Usually, AVO analysis can be divided by three main parts. The first part is AVO analysis, the second is AVO modeling and the last is AVO inversion. AVO analysis is unique method for detecting the free gas zone on seismic section directly. Therefore it can be a kind of useful analysis method for discriminating true BSR, which might arise from an Possion ratio contrast between high velocity layer, partially hydrated sediment and low velocity layer, water saturated gas sediment. During the AVO interpretation, as the AVO response can be changed depend upon the water saturation ratio, it is confused to discriminate the AVO response of gas layer from dry layer. In that case, the AVO modeling is necessary to generate synthetic seismogram comparing with real data. It can be available to make conclusions from correspondence or lack of correspondence between the two seismograms. AVO inversion process is the method for driving a geological model by iterative operation that the result ing synthetic seismogram matches to real data seismogram wi thin some tolerance level. AVO inversion is a topic of current research and for now there is no general consensus on how the process should be done or even whether is valid for standard seismic data. Unfortunately, there are no well log data acquired from gas hydrate exploration area in Korea. Instead of that data, well log data and seismic data acquired from gas sand area located nearby the gas hydrate exploration area is used to AVO analysis, As the results of AVO modeling, type III AVO anomaly confirmed on the gas sand layer. The Castagna's equation constant value for estimating the S-wave velocity are evaluated as A=0.86190, B=-3845.14431 respectively and water saturation ratio is $50\%$. To calculate the reflection coefficient of synthetic seismogram, the Zoeppritz equation is used. For AVO inversion process, the dataset provided by Hampson-Rushell CO. is used.

• Smart Structures and Systems
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• 제26권5호
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• pp.619-629
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• 2020

Solar towers, which often has a large aspect ratio and low fundamental natural frequency, were extremely prone to large amplitude of wind-induced vibrations, especially Vortex-Induced Vibration (VIV). A tiny Tuned Mass Damper (TMD) with conveniently adjustable eddy current damping was specially designed and manufactured for elastic wind tunnel tests of a solar tower. A series of numerical simulations by using the COMSOL software were conducted to determine three key parameters, including the thickness of the back iron plate and the conductive plate (T_b and T_c), the distance between the magnet and the conductive plate (T_d). Based on the results of numerical simulations, a tiny TMD was manufactured and its structural parameters were experimentally identified. The optimized values of the tiny TMD can be conveniently realized. The tiny TMD was installed at the top of the elastic test model of a 243-meter-high solar tower, and a series of wind tunnel tests were carried out to examine the effectiveness of the TMD in suppressing wind-induced responses of the test model. The results showed that the wind-induced responses could be obviously reduced by the TMD, especially in the cross-wind direction. The cross-wind RMS and peak responses at the critical wind velocity can be reduced by about 86% and 75%, respectively. However, the maximum reduction of the responses at the design wind velocity is about 45%, obviously less than that at the critical wind velocity.

• 대한정형도수물리치료학회지
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• 제22권1호
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• pp.17-25
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• 2016

Purpose: This study was aimed to determine the effects of thoracic spine thrust manipulation on muscle activities of the scapular upward rotators and middle deltoid, active range of motion (AROM), shoulder pain, and rounded shoulder posture in young adults with rounded shoulder. Methods: The subjects were 30 young adults (14 males, 16 females) with rounded shoulder. Thirty subjects were randomly assigned to an experimental (manipulation) and control (placebo) groups of fifteen subjects respectively. The manipulation group received the manipulation (high velocity, low amplitude), which was performed by a physical therapist with the subject in the supine position and with the arms crossed over the chest and hands passed over the shoulders. For the sham group, the same procedure was performed, with the exception that the high-velocity thrust was not applied. Measurements were taken before and after the intervention. Muscle activity of upper and lower trapezius, serratus anterior, middle deltoid was measured using surface electromyography. Visual analog scale (VAS) was used for shoulder pain. Goniometry was used for shoulder abduction active range of motion (AROM). Straight edge was used for supine rounded shoulder posture (RSP) distance. Results: The muscle activity of the upper trapezius, lower trapezius and middle deltoid muscle increased significantly after the intervention (p<.05). However, no significant difference was observed in serratus anterior muscle (p>.05). The VAS was significantly decreased and AROM significantly increased after the intervention (p<.05). The distance of RSP were not significant (p>.05). The control group showed no differences before and after the intervention (p>.05). Conclusion: The results of this study suggest that thoracic spine thrust manipulation can be an effective component of treatment plan to improve pain and function.

• 한국소음진동공학회논문집
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• 제14권6호
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• pp.528-535
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• 2004

Ultrasonic Vibrator is designed to achieve the maximum vibration amplitude at 30 kHz by in-cluding a horn (diameter, 40 mm), mechanical vibration amplifier at the top of the ultrasonic vibrator in the system and making the complete system resonate. In addition, it is experimentally visualized by particle imaging velocimetry (PIV) that the acoustic streaming velocity in the gap is at maximum when the gap between the ultrasonic vibrator and stationary plate agrees with the multiples of half-wavelength of the ultrasonic wave. This fact results from the resonance of the sound wave and the theoretical analysis of that is also accomplished and verified by experiment. It is observed that the magnitude of the acoustic streaming dependent upon the gap between the ultrasonic vibrator and stationary plate possibly changes due to the measurement of the average velocity fields of the acoustic streaming induced by the ultrasonic vibration at resonance and non-resonance. There exists extremely small average velocity at non-resonant gaps while the relatively large average velocity exists at resonant gaps compared with non-resonant gaps. It also reveals that there should be larger axial turbulent intensity at the hub region of the vibrator and at the edge of it in the resonant gap where the air streaming velocity is maximized and the flow phenomena is conspicuous than that at the other region. Because the variation of the acoustic streaming velocity at resonant gap is more distinctive than that at non-resonant gap, shear stress increases more in the resonant gap and is also maximized at the center region of the vibrator except the local position of center (r〓0). At the non-resonant gap there should be low values of vorticity distribution, but in contrast to the non-resonant gap, high and negative values of it exist at the center region of the vibrator with respect to the radial direction and in the vicinity of the middle region with respect to the axial direction. Acoustic streaming is noise-free due to the ultrasonic vibration and maintenance-free because of the absence of moving parts. Moreover, the proposed method by acoustic streaming can be utilized to the nano and micro-electro mechanical systems as a driving mechanism in addition to the augmentation of the streaming velocity.

• 한국지진공학회논문집
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• 제11권3호
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• pp.53-62
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• 2007

이 연구에서는 작용하는 하중특성에 따라 적절한 감쇠력을 발휘할 수 있는 복합감쇠기(complex damper)를 제안하고 그 유용성을 장대교량의 지진응답해석을 통하여 검토하였다. 제안한 복합감쇠기는 두개 이상의 탄소성감쇠기(elasto-plastic damper)와 오일 감쇠기(oil damper)의 조합에 의하여 구성되며, 탄소성감쇠기의 변위의존적인 특성과 오일감쇠기의 속도의존적인 특성을 적절히 결합함으로서 효율적인 감쇠시스템의 구성이 가능하게 하였다. 중소형의 지진이나 작은 진폭의 진동에서는 오일감쇠기가 주로 진동을 흡수하며, 발생 빈도가 낮으나 규모가 큰 지진 등에 대해서는 탄소성 감쇠기가 진동에너지를 흡수한다. 이와 같이 복합감쇠기는 두 가지 종류의 감쇠기 역할을 잘 구분시켜 경제적이고 제진효율성이 뛰어난 설계를 가능하게 한다. 복합감쇠장치의 수학적 모델을 정립하였고, 수치모사를 통하여 응답특성과 효율성을 평가하였다. 수치모사 결과, 복합감쇠기는 단일의 수동형감쇠기를 이용하는 경우보다 뛰어난 감쇠효과를 더욱 경제적으로 구현할 수 있으며 내진성능을 크게 향상시킬 수 있는 것으로 나타났다.

• 한국분무공학회지
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• 제18권3호
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• pp.126-131
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• 2013

This paper describes the effect of ultrasonic frequency(f) on the atomization and deformation characteristics of single water droplet in an acoustic levitation field. To achieve this, the ultrasonic levitator that can control sound pressure and velocity amplitude by changing frequency was installed, and visualization of single water droplet was conducted with high resolution ICCD and CCD camera. At the same time, atomization and deformation characteristics of single water droplet was studied in terms of normalized droplet diameter($d/d_0$), droplet diameter(d) variation and droplet volume(V) variation under different ultrasonic frequency(f) conditions. It was revealed that increase of ultrasonic frequency reduces the droplet diameter. Therefore, it is able to levitate with low sound pressure level. It also induces the wide oscillation range, large diameter and volume variation of water droplet. In conclusion, the increase of ultrasonic frequency(f) can enhance the atomization performance of single water droplet.

• 대한정형도수물리치료학회지
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• 제22권1호
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• pp.59-64
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• 2016

Background: This study was to investigate the effect of cervical HVLA technique and mulligan MWM technique on patients with lateral epicondylitis. Methods: 36 participants were randomly allocated to the two groups; group I involved high velocity low amplitude (HVLA) cervical mobilization technique, mulligan mobilizations with movement (MWM) technique (n=18). group II mulligan MWM (n=18). Patient attended for three times a week for six weeks. Results: The change of visual analogue scale (VAS) was statistically and significantly decreased in both of the group I and the group II. The change of patients rated tennis elbow evaluation (PRTEE) was statistically and significantly decreased in both of the group I and the group II. The change of pressure pain threshold (PPT) was statistically and significantly increased in both of the group I and the group II. Nevertheless, There is no statistical differences between group I and group II. Conclusion: After experiment, pressure pain threshold and visual analogue scale, patients rated tennis elbow evaluation were improved in both group. But Cervical HVLA group does not showed the change better than mulligan MWM group.

• 천문학회지
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• 제47권2호
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• pp.69-76
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• 2014

We report the detection of an exoplanet candidate in orbit around ${\sigma}$ Persei from a radial velocity (RV) survey. The system exhibits periodic RV variations of $579.8{\pm}2.4$ days. The purpose of the survey is to search for low-amplitude and long-period RV variations in giants and examine the origin of the variations using the fiber-fed Bohyunsan Observatory Echelle Spectrograph installed at the 1.8-m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We present high-accuracy RV measurements of ${\sigma}$ Per made from December 2003 to January 2014. We argue that the RV variations are not related to the surface inhomogeneities but instead a Keplerian motion of the planetary companion is the most likely explanation. Assuming a stellar mass of $2.25{\pm}0.5$ $M_{\odot}$, we obtain a minimum planetary companion mass of $6.5{\pm}1.0$ $M_{Jup}$, with an orbital semi-major axis of $1.8{\pm}0.1$ AU, and an eccentricity of $0.3{\pm}0.1$ around ${\sigma}$ Per.

• 한국전문물리치료학회지
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• 제3권2호
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• pp.95-105
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• 1996

지금까지의 내용을 요약하면 먼저, 인체의 각 관절 주위에는 관절의 움직임과 위치를 파악하는 감지기 역할을 하는 기계적 감수기가 있다. 이러한 감수기는 크게 네가지로 구분되어지는데 대개 I형 감수기, II형 감수기 등의 용어를 사용한다. 각각의 감수기의 특성(표 2.)을 알아보면, 루피니(Ruffini)감각기와 유사한 모양을 하고 있는 I형 관절감수기는 주로 운동의 속도(speed)와 방향(direction)을 감지(detection) 하며, 파시니안(Pacinian)감각기와 유사한 형태를 하고 있는 II형 관절감수기는 매우 작은 움직임에 대한 감지를 하는데, 예를 들어 속도가 가속(acceleration)되는 것과 같은 움직임 등을 알아낸다. 이외에 골지건과 비슷한 모습을 하고 있는 III형 관절감수기는 운동의 자세(position)와 방향에 대한 정보를 전달하게 된다 (Carpanter, 1990). 관절의 자세 유지 혹은 안정성 즉, 정적(static) 운동에 주로 관여하는 I형 관절감수기와, 역동적(dynamic)인 운동에 감지를 주로 하는 II형 관절감수기는 진동(oscillation)자극에 잘 촉진된다. 이러한 자극은 동통이 심하게 발생된 관절에 나타나는 근육의 과긴장(hypertonicity)과 동통을 경감시킬 수 있다. III형 관절감수기는 억제 (inhibitory)감수기라 할 수 있는데, 골지건(golgi tendon organ)의 기능과 매우 관련이 깊다. 이 감수기는 관절의 가동범위를 기계적인 자극으로 증가시키기 위해 관절의 가동 끝범위에서 강한 신장(strong strectch)이나 thrust 기술로 감수기를 촉진할 수 있다. 이러한 자극은 결국 근육에 이완을 얻게 할 수 있다. 위에서 언급한 관절 주위의 조직에 분포한 특별한 기계적 감지를 환자들의 임상 증상에 따라 선택적으로 자극하는 치료를 적용할 수 있다면, 현재 물리치료사들이 적용하고 있는 관절 가동운동을 좀더 전문적인 수준으로 수행할 수 있을 것이다.