• 비파괴검사학회지
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• 제28권2호
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• pp.131-136
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• 2008

정재초음파를 이용하면 유체에 잠겨 있거나 유체를 따라서 흐르는 미세 입자의 조작이 가능하다. 정재초음파 장이 입자에 힘을 작용하여 입자를 음압마디 또는 반음압마디로 이동시킨다. 본 연구에서는 정재초음파의 주파수를 조정함으로써 유동 중 미세 입자의 위치를 제어하는 방법을 제안하고자 한다. 이를 위해 먼저 수침형 초음파 트랜스듀서를 이용하여 폭 수 밀리미터의 미세 채널을 가지는 정재초음파 발생시스템을 구성하였다. 제안한 발생시스템을 이용하여 주파수 2 MHz부터 2.5 MHz까지 영역에서 정재초음파 장을 발생시키고, 물을 따라 흐르는 수 마이크로미터 내외의 탄화규소 입자가 음압 마디로 잘 이동함을 확인하였다. 이때, 미세 채널의 폭과 주파수가 입자의 거동에 미치는 영향을 관찰하였으며, 주파수가 미세입자의 이동 위치를 결정하는 중요한 파라미터임을 확인하였다. 결과적으로, 초음파의 주파수를 조정함으로써 입자의 이동 위치를 제어할 수 있음을 실험을 통해 확인하였으며 최대 범위는 약 261 마이크로미터이다. 본 연구로부터 유체내의 입자 조작에 있어서 정재초음파의 다양한 응용 가능성을 확인할 수 있었다.

• The Journal of Korean Physical Therapy
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• 제18권2호
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• pp.47-58
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• 2006

Purpose: The study to pulsed ultrasound effects of diabetes mellitus fracture model in rat. Methods: We used 36 Sprague-Dawely rats which were divided into 3 groups; the animals were divided into group of 4 rats each 4th, 14th and 28th days. All animal was induced diabetes mellitus model to used streptozotocin with 45 mg/kg. Pulsed wave were divided into $50\;mW/cm^2$ and $100\;mW/cm^2$. Results: T-ALP value was significantly change from group II, III on 14th, 28th days (p<0.05). Especially T-ALP value to between groups was significantly change from group II on 14th days (p<0.05). Osteocalcin value was significantly change from group II on 28th days(p<0.05). At fracture site, osteoblast, osteoclast expression was observed from 4th days after treatment and it reached its maximum intensity at 28th days. At fracture site, $TGF-{\beta}_1$ expression was observed from 4th days after treatment and it reached maximum intensity at 14th days. Conclusion: According to this study, diabetes mellitus fracture model to the more effective is divided into $50m\;W/cm^2$ pulsed ultrasound.

• 한국환경과학회지
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• 제19권3호
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• pp.379-387
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• 2010

Sediments of Little Scioto (LS) River in Ohio was contaminated by poor disposal of creosote from Baker Wood Creosoting Facility. Among the primary compounds of creosote, Polycyclic Aromatic Hydrocarbons (PAHs) are the most common ingredient PAHs are known for toxic, carcinogenic and mutagenic compounds. There are many difficulties to remove the PAHs in nature environment because their characteristics are having a less water-solubility, volatile and low mobility properties as increasing the molecular weight. The generation of hydroxyl radicals (${\cdot}OH$) and hydrogen peroxide ($H_2O_2$) forms as well as high temperature (5000 K) and pressure (1000 atm) by a physico-chemical effects of ultrasound during a cavitation collapse can promote the degradation and desorption of PAHs in sediment And it can also produces shock wave and microjets which are able to change the size and surface of particle in solid-liquid system as one of physical effects. Therefore, we explored to understand the role of particle size, the effect of elimination for PAHs concentration by ultrasound and optimize the conditions for ultrasonic treatment. The condition of various size of particles (> $150{\mu}m$, < $150{\mu}m$) and solid-liquid ratio (12.5g/L, 25g/L) for the treatment was considered and ultrasonic power (430 W/L) with liquid - hexane extraction and microwave extraction method were applied after ultrasound treatment.

• Nuclear Engineering and Technology
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• 제39권5호
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• pp.637-646
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• 2007

An UET (ultrasound excited thermography) has been used for several years for a remote non-destructive testing in the automotive and aircraft industry. It provides a thermo sonic image for a defect detection. A thermograhy is based On a propagation and a reflection of a thermal wave, which is launched from the surface into the inspected sample by an absorption of a modulated radiation. For an energy deposition to a sample, the UET uses an ultrasound excited vibration energy as an internal heat source. In this paper the applicability of the UET for a realtime defect detection is described. Measurements were performed on two kinds of pipes made from a copper and a CFRP material. In the interior of the CFRP pipe (70mm diameter), a groove (width - 6mm, depth - 2.7mm, and length - 70mm) was engraved by a milling. In the case of the copper pipe, a defect was made with a groove (width - 2mm, depth - 1mm, and length - 110 mm) by the same method. An ultrasonic vibration energy of a pulsed type is injected into the exterior side of the pipe. A hot spot, which is a small area around the defect was considerably heated up when compared to the other intact areas, was observed. A test On a damaged copper pipe produced a thermo sonic image, which was an excellent image contrast when compared to a CFRP pipe. Test on a CFRP pipe with a subsurface defect revealed a thermo sonic image at the groove position which was a relatively weak contrast.

• 비파괴검사학회지
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• 제27권3호
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• pp.231-238
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• 2007

Ultrasonic inspection of austenitic steel weldments is a truly difficult task due to complicated wave propagation phenomena such as beam skewing, splitting and distortion. In order to understand these phenomena and design proper inspection procedures, simulation is increasingly paid more attention to. This article addresses a ray tracing based approach to determine incident angle and position of optimal wave mode ultrasonic beam for flaw detection in anisotropic and inhomogeneous austenitic steel weldments. Specially, the optimal mode of ultrasonic wave wave is selected by ray tracing simulation, and an optimization approach based on ray tracing and bi-section search is proposed in order to find the ray path connecting two given points in weldments. With help of this approach, the optimal incident angle and position of ultrasonic beam can be determined for a given flaw position.

• 비파괴검사학회지
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• 제35권6호
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• pp.389-397
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• 2015

Recently, wave propagation imaging based on laser scanning-generated elastic waves has been intensively used for nondestructive inspection. However, the proficiency of the conventional software based system reduces when the scan area is large since the processing time increases significantly due to unavoidable processor multitasking, where computing resources are shared with multiple processes. Hence, the field programmable gate array (FPGA) was introduced for a wave propagation imaging method in order to obtain extreme processing time reduction. An FPGA board was used for the design, implementing post-processing ultrasonic wave propagation imaging (UWPI). The results were compared with the conventional system and considerable improvement was observed, with at least 78% (scanning of $100{\times}100mm^2$ with 0.5 mm interval) to 87.5% (scanning of $200{\times}200mm^2$ with 0.5 mm interval) less processing time, strengthening the claim for the research. This new concept to implement FPGA technology into the UPI system will act as a break-through technology for full-scale automatic inspection.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 추계종합학술대회
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• pp.835-838
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• 2002

동작되고 있는 고전압 기기는 전기의 독특한 특성 때문에 초음파 방출을 유발하는 특유한 소리를 방출한다. 초음파 방출이란 아킹, 코로나, 트래킹과 같은 전기적변화에 의해서 발생된다 고전압 전력 설비에서 아킹, 코로나, 트래킹은 여러 가지 장애를 일으킬 뿐만 아니라 인체에도 매우 치명적인 손상을 야기한다. 고전압 기기의 장애 요소를 방지하고 사전에 진단하기 위해 초음파 측정이 주목받게 되었지만 아직까지 기초적인 측정 데이터가 충분히 제시되어 있지 않은 실정이다. 본 논문에서는 변압기 설비에서 발생하는 초음파 이상음을 분석하고 분석한 자료를 표준 데이터화 하는데 그 목적을 둔다.

• 비파괴검사학회지
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• 제36권1호
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• pp.9-17
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• 2016

The elastic modulus of a 3D-printed Kelvin foam plate is investigated by measuring the acoustic wave velocity of 1 MHz ultrasound. An isotropic tetrakaidecahedron foam with 3 mm unit cell is designed and printed layer upon layer to fabricate a Kelvin foam plate of 14 mm thickness with a 3D CAD/printer using ABS plastic. The Kelvin foam plate is completely filled with paraffin wax for impedance matching, so that the acoustic wave may propagate through the porous foam plate. The acoustic wave velocity of the foam plate is measured using the time-of-flight (TOF) method and is used to calculate the elastic modulus of the Kelvin foam plate based on acousto-elasticity. Finite element method (FEM) and micromechanics is applied to the Kelvin foam plate to calculate the theoretical elastic modulus using a non-isotropic tetrakaidecahedron model. The predicted elastic modulus of the Kelvin foam plate from FEM and micromechanics model is similar, which is only 3-4% of the bulk material. The experimental value of the elastic modulus from the ultrasonic method is approximately twice as that of the numerical and theoretical methods because of the flexural deformation of the cell edges neglected in the ultrasonic method.

• 비파괴검사학회지
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• 제30권2호
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• pp.126-131
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• 2010

본 연구에서는 유도초음파를 이용하여 다양한 온도에서 사용되어지는 항공기 복합재료의 건전성에 대하여 평가하였다. 항공기가 지상과 비행고도에서 운행할 때의 온도편차나, 반복되어지는 열주기 횟수와 같이, 항공기가 운행되어지는 온도와 관련하여 복합재료의 건전성에 결정적인 영향을 미치는 요소에 관한 연구는 항공기 안전에 있어서 매우 중요한 요소가 되고 있다. 본 연구에서는 유도초음파를 이용하여 항공기의 운행환경과 유사한 환경 하에서 열피로가 가해진 항공기의 복합재료 시편을 평가하였다. 유도초음파의 분산선도 곡선은 서로 다른 열피로가 가해진 시편에 대한 민감성을 나타내기 위해 최적의 모드를 선택하는데 사용되었다. 현재 제시된 접근법 또한 항공기의 건전성을 평가하는데 있어서 하나의 도구로 구현될 수 있다.

• 대한전자공학회논문지
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• 제27권12호
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• pp.1916-1924
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• 1990

In this paper attenuation effect on the measurement and the tomography of nonlinear parameter is discussed. We perform computer simulation with the method using harmonic components and the method using secondary wave components, and then estimate attenuation effect through the results and compare two measurement techniques. According to simulation result the attenuation effect is more intensive as large n and \ulcorner, and the degree of the attenuation effect is represented as error functions. In the aspect of measuremnet techniques, the method using secondary wave components is more insensitive to attenuation effect than the method using harmonic compnents. We obtain the same result in the nonlinear tomography, and show that the attenuation compensive filter is required because the whole tomogram is affected by frequency dependent attenuation(or nonlinear attenuation)