• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.402-411
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• 2000

This study investigates the method to measure the viscoelastic properties of asphalt cement, one of the viscoelastic materials, using the ultrasound. The wave speed and attenuation were measured from $-20^{\circ}C$ to $60^{\circ}C$ at the frequency of 2.25MHz. Then, the storage and loss longitudinal moduli, loss tangent storage and loss longitudinal compliances were found depending on the temperatures based on the linear viscoelastic theory. Stress relaxation, creep, and viscosity were predicted using Maxwell and Voigt-Kelvin viscoelastic models. The validity of superposition principle and shift factor were verified by comparing the present results to the data reported in the literatures.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.217-220
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• 2016

Phytoestrogens are one of quasi-estrogens which are not generated within the endocrine system, but consumed by intaking phytoestrogenic plants. Phytoestrogens, also called as "dietary estrogens", are various botanic chemical compound groups naturally occurring nonsteroidal plant compounds of spontaneous generation. Due to their structural similarities to estrogone, they may provide desirable health benefits for reducing the menopausal symptoms. In this paper, various phytoestrogens were extracted from sophora root, pomegranate and kudzu by ultrasonic extraction process. In this study, the amount of extracted phytoestrogens at various ultrasonic power strengths and extraction times were compared, which could be used as basic data in the study of biology and chemistry related to natural products.

• 전기의세계
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• v.32 no.3
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• pp.142-149
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• 1983

지금까지 알려진 내부마찰측정방법으로는 자유감쇄법(free decay method), 강제진동법(forced vibration method), 비공진강제진동법(non-resonance forced vibration method) 및 초음파법(ultrasoni method) 등이 있다. 이상의 모든 내부마찰실험방법에 관한 실험장치는 그 기계의 동작특성에 따라 실험주파수가 극히 한정되어 있어 연속적인 변화를 시킬 수 없으므로 완화효과를 연속적으로 추적하기 위하여 온도를 변화시키는 방법이 널리 사용되고 있다. 이상에서 소개한 방법들중 본인들이 국산제작실험에 성공한 바 있는 장치는 자유감쇄법에 속하는 염회진자장치(torsion pendulum device) 이므로 이 장치를 중심으로 내부마찰측정원리와 그의 장치에 관하여 소개하고저 한다.

• Journal of Adhesion and Interface
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• v.14 no.1
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• pp.21-27
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• 2013

Cellulose-based rayon fibers or fabrics can be thermally decomposed very fast within a narrow temperature window during stabilization process. Therefore the stabilization stage is critically important for producing rayon-based carbon fibers. Consequently, in the present study the effects of isothermal stabilization and ultrasonic cleaning on the weight loss, chemical composition, microstructure, and fabric texture of cellulose-based rayon fabrics were explored. The temperature of the isothermal stabilization process performed in the range of $200{\sim}240^{\circ}C$ influenced the processing time, carbon and oxygen contents, cellulose structural change, and fabric texture. The ultrasonic cleaning, which was conducted prior to the stabilization process, played a role in shortening the stabilization time, increasing the carbon contents, decreasing the oxygen contents, and changing the XRD pattern. Also, it was considered that the ultrasonic cleaning contributed to retarding the weight loss, to reducing the thermal shrinkage, and further to reducing the fast physical change of rayon fabrics.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.4
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• pp.268-274
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• 2015

Weld overlay was first used in power plants in the US in the early 1980s as an interim method of repairing the welds of flawed piping joints. Weld overlaid piping joints in nuclear power plants must be examined periodically using ultrasonic examination technology. Portable phased array ultrasonic technology has recently become available. Currently, the application of preemptive weld overlays as a mitigation technique and/as a method to improve the examination surface condition for more complex configurations is becoming more common. These complex geometries may require several focused conventional transducers for adequate inspection of the overlay, the original weld, and the base material. Alternatively, Phased array ultrasonic probes can be used to generate several inspection angles simultaneously at various focal depths to provide better and faster coverage than that possible by conventional methods. Thus, this technology can increase the speed of examinations, save costs, and reduce radiation exposure. In this paper, we explain the general sequence of the inspection of weld overlay and the results of signal analysis for some PAUT (phased array ultrasonic testing) signals detected in on-site inspections.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.550-555
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• 2000

Nonlinear oscillation of a microbubble under ultrasound was investigated theoretically. The bubble radius-time curves calculated by the Rayleigh-Plesset equation with a polytropic index and by the Keller-Miksis equation with the analytical solution for the Navier-Stokes equations of the gases were compared with the observed results by the light scattering method. This study has revealed that the bubble behavior such as the expansion ratio and the bouncing motion after the first collapse under ultrasound depends crucially on the retarded time of the bubble motion to the applied ultrasound.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.916-920
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• 2007

ADCP(Acoustic Doppler Current Profiler)는 유수의 흐름을 방해하지 않으면서 물 속으로 일정 주파수의 초음파를 전송하고, 부유하는 입자들에 의해 산란되어 돌아오는 반향을 수집, 도플러효과를 이용하여 유속을 측정하는 장비이다. ADCP는 하천을 횡단하면서 순간적인 유속을 측정하므로 시간평균한 평균유속과의 차이가 발생하지만 1초에 1회 이상의 빠른 속도로 연직유속분포를 수집하면서 이를 공간적으로 평균함으로써 순간유속이 갖는 변동성을 완화시키는 특징을 갖는다. 본 연구에서는 ADCP를 활용하여 사행하천에서 수평방향 2차원 유속분포를 측정하고자 하였다. 만곡부가 교호적으로 나타나는 사행하천의 흐름구조는 매우 복잡하다. 특히 주 흐름의 수직인 단면에 나선형의 2차류가 관찰되는데, 이는 원심력과 횡방향의 수면경사 및 난류의 상호작용으로 발생된다. 주 흐름의 유속과 다른 분포를 나타낸다. 본 연구에서는 이찬주 등(2005)이 제시한 공간평균기법과 이동경로 수정을 통하여 측선별 2차원 유속분포를 측정하여 기 개발된 RAMS(서울대학교, 2007)를 적용하고 이를 검증하기 위한 자료를 확보하고자 하였다.

• Journal of the Korean Orthopaedic Association
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• v.55 no.3
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• pp.229-236
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• 2020

Purpose: This study examined the utility of preliminary magnetic resonance imaging (MRI) measurements in the ultrasound-guided L4 selective nerve root block. Materials and Methods: As a retrospective study, 71 patients, who met the criteria for outpatient visits from March 2016 to December 2017, were included. From March 2016 to February 2017, 31 patients who underwent an L4 nerve root block without MRI were classified as group A, and 40 patients who underwent an L4 nerve root block through MRI measurements from March 2017 to December 2017 were classified as group B. Group A was injected under ultrasound-guidance through the pararadicular approach without a pre-interventional MRI evaluation, and group B was injected under ultrasound-guidance according to the preliminary MRI measurements. The results were assessed using the numeric rating scale scores before, three hours, and two, six, and 12 weeks after the procedure. Results: At three hours after the procedure, the proportion of patients better than good results were 51.6% in group A and 67.5% in group B. At two weeks after the procedure, the proportion of patients with better than good results were 48.4% and 70.0% in groups A and B, respectively; 58.1% and 62.5% of patient of groups A and B, respectively, showed better than good results after six weeks. In 12 weeks after the procedure, the results of group A and B were 67.7% and 62.5%, respectively. At three hours and two weeks after the procedure, group B showed significant symptom improvement than group A (p<0.05). The procedures were repeated 2.8 and 1.7 times in groups A and B, respectively, between two and six weeks for satisfactory pain relief (p<0.05). Conclusion: A pre-interventional MRI evaluation might improve pain relief within the initial two weeks after ultrasound-guided L4 selective nerve root block by improving the success rate of the procedure.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.3 no.1
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• pp.21-25
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• 2010

Purpose: To evaluate efficacy of ultrasound guided prolotherapy in patients with persistant symptoms after rotator cuff repair. Materials and Methods: Between January and December of 2008, 90 patients who had persistant pain and shoulder adhesion 4 weeks after rotator cuff repair were treated with ultrasound guided prolotherapy. The mean age was 55.2 years. Visual analogue scale (VAS) and range of motion (ROM) before and after the procedure, complications related to the procedure were analyzed. Results: The average VAS score at 4 weeks follow up decreased to $2.5{\pm}2.304$ from $6.3{\pm}1.25$ before prolotherapy and forward flexion range at 4 weeks follow up increased to $143{\pm}26.63$ from $106{\pm}21.64.$ Four weeks after the ultrasound guided prolotherapy, 74 cases(82%) reported of improved pain and ROM, 13 cases(14%) reported of improvement after 2~5 days of the procedure and 3 cases(4%) had no improved in pain and ROM. No complications were encountered. Conclusion: The authors believe that ultrasound guided prolotherapy in repaired rotator cuff tear patients theoretically increased possibilities of healing and with relieving the pain of the patients results in increased possibility of rehabilitation effect.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.4 no.2
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• pp.77-83
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• 2011

Purpose: We compared with USG-guided steroid injection group and blind steroid injection group for the treatment of calcific tendinitis to evaluate the effectiveness of the treatment modalities. Materials and Methods: We reviewed two groups of calcific tendinitis treated with steroid injection and follow up upto 6 month after injection. Group I was blind injection for 88 patient with average age of 53years old and female gender in 77%. Group II was USG- guided injection for 102 patients with average age of 54years old and female gender in 85%. We compared follow up results according to age, gender, size of tendon involvement, initial VAS score, and phase of the calcific tendinitis between two groups. Results: At 6 month's follow up period, USG-guided injected group was more prevalent compared to blind injection group with 92%(94/102) and 72%(64/88) (P<0.05). In Group I, 77%(49/64) patients have improved symptom. And in Group II, 92%(86/94) patients have improved symptom in formative or resorptive phase. Despite of symptom improvement, calcium deposit is remained 47%(30/64) in Group I, and 20%(19/94) in Group II. Conclusion: Conservative treatment of Shoulder calcific tendinitis patients through USG-guided injection is more effective than Blind injection in pain relief & calcium decrease. The patients USG-guided injected group was more prevalent in follow up at outpatient clinic, throughout more accurate injection with improved confidence.