• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.4
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• pp.292-300
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• 1993

Acoustical imaging has made brilliant progress in the medical science field, and has also made much progress in the nondestructive testing and under water acoustics applications since doctor Dussik brother has studied about possibilities of making images of brain by recording variations in the intensity of ultrasonic beam from head in 1937. In this paper an acoustical image is reconstructed with the power spectra analysed by impulse ultrasound wave generated by electrodynamic transducer(EDT). The EDT generates the impulse ultrasound of 77KHz in center frequency and 120KHz in bandwidth at -20dB by 1200V exciter in this experiment. The impulse ultrasound has the dominant frequency components of 47KHz, 177KHz, 110KHz and 155KHz. The U shape object is adopted in making an acoustical image. The resulted spectral acoustical images are different from the optical view of the U shape object. However the image reconstructed from 110KHz spectrum is very similar to the original optical shape of the object. Even KHz level impulse sound of 70$\mu$sec pulse width is found to be useful in reconstructing acoustical imaging improvement.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.111-116
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• 2022

In the paper, A prototype Fetal Heart Monitor, mini - size, was designed and produced for pre-mothers to measure the rate and rhythm of their features's heart at home.Pre-mothers could listen fetal heart rhythm through an inner bluetooth speaker ant the monitor. LED colors show the frequency of fetal heart rate variability on the monitor. All measured health information, by ultrasonic resonator and bluetooth speaker, is linked to a mother's smart phone. A test verified this simple measuring device helps users discover the symptoms of fetal health. Patients using at home devices usefully prevent sudden cardiac death and myocardial infraction by discovering symptoms.

• Ocean and Polar Research
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• v.35 no.1
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• pp.15-26
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• 2013

The toxic, Harmful Algal Blooms (HABs) caused by the Cochlodinium polykrikoides have a serious impact on the coastal waters of Korea. In this study, the acoustic detection system was developed for rapid HABs detection, based on the acoustic backscattering properties of the C. polykrikoides. The developed system was mainly composed of a pulser-receiver board, a signal processor board, a control board, a network board, a power board, ultrasonic sensors (3.5 and 5.0 MHz), an environmental sensor, GPS, and a land-based control unit. To evaluate the performance of the system, a trail was done at a laboratory, and two in situ trials were conducted: (1) when there was no red tide, and (2) when there was red tide. In the laboratory evaluation, the system performed well in accordance with the number of C. polykrikoides in the received level. Second, under the condition when there was no red tide in the field, there was a good correlation between the acoustic data and sampling data. Finally, under the condition when there was red tide in the field, the system successfully worked at various densities in accordance with the number of C. polykrikoides, and the results corresponded with the sampling data and monitoring result of NFRDI (National Fisheries Research & Development Institute). From the laboratory and field evaluations, the developed acoustic detection system for early detecting HABs has demonstrated that it could be a significant system to monitor the occurrence of HABs in coastal regions.

• The Journal of the Korean dental association
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• v.55 no.11
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• pp.789-799
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• 2017

Ultrasound images are noninvasive, can be observed in real time, have no radiation exposure, do not cause pain, and are not restricted in use depending on the patient's prosthetic implant or medical condition. Since the use of ultrasound in the dental field was first applied for tooth preparation in 1957, the use of diagnostic ultrasound for the first time in 1963 has been reported. Currently, it is used in the diagnosis of soft tissue lesions such as malignant tumor or salivary gland disease, fine needle aspiration test, temporomandibular joint disease, lymph node metastasis, measurement of muscle thickness and inflammatory diseases, differentiation of periapical cyst and granulation tissue, measurement of periodontal tissue thickness. The ultrasound image can be visualized in real time. The clinician can explain the structure to the patient while consulting the patient and consult the patient. When injecting the drug into a specific site or aspirating a specific site or substance, So that it can be confirmed and practiced. Recently, ultrasonic equipment specialized in the dental field has been developed and marketed, and it is expected that the use of ultrasonic waves will become active in the dentistry. In the future, development of popular equipment with size and frequency suitable for dental diagnosis and various researches on maxillofacial ultrasonic anatomy. If clinical studies are continuously carried out to demonstrate efficacy, ultrasound is expected to aid in accurate diagnosis and treatment throughout the dentistry.

• The Journal of the Acoustical Society of Korea
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• v.34 no.4
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• pp.264-273
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• 2015

Improvement of the radiation beam profile of a medical ultrasonic transducer has been researched in this paper. In order to improve the beam profile, a new transducer structure has been devised that includes both a shaded electrode and a multi-focus lens. For a linear sound source, the beam profile was investigated through finite element analysis, and then the optimal design of the devised structure was carried out by considering such performances as sidelobe level, focal range and beamwidth simultaneously. In the process, the optimal dimension of the devised structure was derived by using the ratio of the focal range to the minimum beamwidth as a performance index. As a result, the beam profile has been improved to have a lower sidelobe level at -20.2 dB and a consistent narrow beamwidth from 30 mm to 160 mm depth with the minimum beamwidth at 2.04 mm. Further, a prototype transducer was fabricated to have the devised structure, and its performance was measured and compared with the analysis results to confirm the validity of the devised transducer structure.

• Journal of Radiation Industry
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• v.9 no.2
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• pp.91-102
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• 2015

The iridium disc, generally used in industrial radiography, is examined to find the fracture morphology and fine particles remaining on the shear blank surface. Randomly selected 1,200 discs were observed under a scanning electron microscope tilted more than $45^{\circ}$. Fracture surfaces are classified into three groups: (1) surface fall-out, (2) fracture on the edge and (3) multi-step brittle fracture, which shows the mutual relationship between the fracture morphology and remaining particles. Fracture particles were removed by cleaning the discs in a ultrasonic bath with acetone and collected at the bottom. Removed number of the particles were counted for each different group of fracture surfaces. Followings are conclusions: (1) About 80.5% of discs (966/1,200), have sound plastic shear surfaces with particles remained. (2) About 2% discs accompany surface fall-out's having large particles tens of ${\mu}m$, which is stable not to be pulled out even after the considerably long time of ultrasonic cleaning. (3) About 5% discs contain the fractures on the edge and the particles are removed thoroughly within 30 minutes. (4) 234 discs out of 1,200 discs have multi-step fracture surfaces whose particles never removed in a short period of time but come out very slowly. Such a disc having multiple-step fracture is attributed to the promate cause to the 'leaker'. It is noted here that the discs having mutiple-step fractures should be treated separately with special care, and it is need to study how to treat them.

• Journal of Energy Engineering
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• v.22 no.3
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• pp.287-293
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• 2013

This study was carried out to diminish the formation of scale in boilers which is one of the defect elements when they are operating. The defect relating to scale can cause a fatal impact on the explosion of boilers due to the overheating of their tubes, or it can affect the flow of water inside boilers with its bad circulation and result in a disparity of water inside the equipment. Heat transfer in the scale is low comparing to the boiler material, so it can lead to energy losses and has also impact on the global warming. In 2005, the Korean government introduced a system which requires boiler users to install the equipment which can prevent or eliminate the formation of scale to improve the management of water quality in boilers. The study on the techniques for preventing or eliminating the formation of scale started in 1821 and since then subsequently there have been lots of similar studies. The first one was about the scale reduction using potato starch. Since an ultrasonic scale preventer developed by a scientist from a Russian acoustic institute was introduced in1993, a variety of equipment of this kind have been disseminated in Korea. There has been a need to demonstrate the condition for the best performances of such equipment. Boilers are mostly composed of the main body and 288 the tube with a circular curved surface. I carried out a demonstration study on a circular tube which affects the scale defect the most among the boiler components. As a result of it, I found out the fact that the ultrasonic wave needs to reach a certain level of sound pressure and frequency to affect the formation of scale.

• The Journal of the Acoustical Society of Korea
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• v.38 no.4
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• pp.459-466
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• 2019

When a laser pulse is irradiated on a CNT (Carbon Nanotube) and PDMS (Poly dimethylsiloxane) composite coated on a transparent PMMA (Poly methyl methacrylate) substrate, a strong ultrasonic wave is generated due to the thermoelastic effect. In this paper, the thermoacoustic theory related to the wave generation by the CNT/PDMS composite was established. The waveforms of ultrasonic waves when a laser pulse having a Gaussian waveform is irradiated on the composite with a thickness of $20{\mu}m$ were numerically simulated. From the results, it was confirmed that ultrasonic shock waves can be generated from the CNT/PDMS composite and the waveforms are changed little even if the physical properties of the composite are changed by ${\pm}20%$. It was found that the peak positive and negative pressures increase as the thermal expansion coefficient increases, or as density, heat capacity and sound speed decreased. However, those changes were not so sensitive with thermal conductivity. In addition, the physical properties of the CNT/PDMS composite fabricated in this study were estimated from the comparison of the measurement and simulation results.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.361-367
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• 2024

Ultrasound in the air is widely used in industry as a measurement technique to prevent abnormalities in the machinery. Recently, the use of airborne ultrasound imaging techniques, which can find the location of abnormalities using an array transducers, is increasing. A beamforming method that uses the phase difference for each sensor is used to visualize the location of the ultrasonic sound source. We exploit a random sparse ultrasonic array and obtain beamforming power distribution on the source in a certain distance away from the array. Conventional beamforming methods inevitably have limited spatial resolution depending on the number of sensors used and the aperture size. A high-resolution ultrasound imaging technique was implemented by applying functional beamforming as a method to overcome the geometric constraints of the array. The functional beamforming method can be expressed as a generalized beam forming method mathematically, and has the advantage of being able to obtain high-resolution imaging by reducing main-lobe width and side lobes. As a result of observation through computer simulation, it was verified that the resolution of the ultrasonic source in the air was successfully increased by functional beamforming using the ultrasonic sparse array.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.185-190
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• 2018

The Tonpilz transducer was implemented using the structural module of COMSOL which is a FEM simulation tool. In order to compare the sound pressure characteristics of the transducer with the simulated results, the spacial distribution of the sound pressure level (SPL) was simulated by the acoustic module of COMSOL and then compared with the SPL distribution measured by a microphone. As a result, the resonance frequency and the peak in SPL for the simulation were predicted to be 28 kHz and 163.5 dB, respectively. And the resonance frequency and the peak in SPL for the actual transducer were measured to be 28.84 kHz and 137.8 dB, respectively. It is also confirmed that the simulated SPL distribution and the actually measured one are formed in a similar pattern.