• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.894-903
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• 2014

Insertion loss prediction of large acoustical enclosures using Statistical Energy Analysis (SEA) method is presented. The SEA model consists of three elements: sound field inside the enclosure, vibration energy of the enclosure panel, and sound field outside the enclosure. It is assumed that the space surrounding the enclosure is sufficiently large so that there is no energy flow from the outside to the wall panel or to air cavity inside the enclosure. The comparison of the predicted insertion loss to the measured data for typical large acoustical enclosures shows good agreements. It is found that if the critical frequency of the wall panel falls above the frequency region of interest, insertion loss is dominated by the sound transmission loss of the wall panel and averaged sound absorption coefficient inside the enclosure. However, if the critical frequency of the wall panel falls into the frequency region of interest, acoustic power from the sound radiation by the wall panel must be added to the acoustic power from transmission through the panel.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.390-396
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• 2010

An 80MHz surface acoustic wave (SAW)-based gyroscope utilizing a progressive wave was developed on a piezoelectric substrate. The developed sensor consists of two SAW oscillators in which one is used for sensing element and has metallic dots in the cavity between input and output IDTs. The other is used for a reference element. Coupling of mode (COM) modeling was conducted to determine the optimal device parameters prior to fabrication. According to the simulation results, the device was fabricated and then measured on a rate table. When the device was subjected to an angular rotation, oscillation frequency differences between the two oscillators were observed because of the Coriolis force acting on the metallic dots. Depending on the angular rate, the difference of the oscillation frequency was modulated. The obtained sensitivity was approximately 52.35 Hz/deg.s within the angular rate range of 0~1000 deg/s. The performances of devices with three IDT structures for two kinds of piezoelectric substrates were characterized. Good thermal stability was also observed during the evaluation process.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.24-30
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• 1998

A directly coupled Boundary Element and Finite Element Model was applied to the dynamic analysis of a coupled acoustic silencer with vibratory wall. In this cupled BEM-FEM muffler model, the BEM model was used to discretize the acoustic cavity and the FEM model was used to discretize the vibratory wall structure. Then the BEM model was coupled with the FEM model. The results of the coupled BEM-FEM model for the dynamic analysis of the simple expansion type reactive muffler configurations with flexible walls were verified by comparing the predicted results to analytical solutions. In order to investigate the effects of the muffler's structural flexibility on its transmission loss(TL) characteristics, the results of the coupled BEM-FEM model in conjunction with the four-pole parameter theory were utilized. The muffler's TL characteristics using the BEM-FEM coupled model with flexible walls as compared to other muffler configurations was studied. Finally the muffler's TL values with respect to different wall's thickness are predicted and compared.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1430-1435
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• 2007

We developed a 440MHz surface acoustic wave (SAW) microsensor integrated with pressure-temperature sensors and ID tag. Two piezoelectric substrates were bonded, in which ${\sim}150\;{\mu}m$ cavity was structured. Four sides were completely sealed by JSR photoresist (PR). Pressure sensor was placed on the top substrate, whereas ill tag and temperature sensor were placed on the bottom substrate. Using network analyzer, the developed microsensor was wirelessly tested. Sharp reflection peaks with high S/N ratio, small signal attenuation, and small spurious peaks were observed. All the reflection peaks were well matched with the coupling of mode (COM) simulation results. With a 10mW RF power from the network analyzer, a ${\sim}1$ meter readout distance was observed. Eight sharp ON reflection peaks were observed for ID tag. Temperature sensor was characterized from $20^{\circ}C$ to $200^{\circ}C$. A large phase shift per unit temperature change was observed. The evaluated sensitivity was ${\sim}10^{\circ}/^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2203-2208
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• 2011

This study was to examine the change of vowel acoustic characteristics of the temporomandibular joint disorder patients by maintaining normal vocalization pattern of the temporomandibular joint through increasing the range of motion, that was, the oral cavity sonorant cavity of the temporomandibular joint, related to vowel articulation through temporomandibular training using the physical therapy. The subjects of this study were 3 male adults in 20-30s that were diagnosed with temporomandibular joint disorder. As a result of conducting temporomandibular training program using the physical therapy, the $1^{st}$ Formant Frequency(F1), $2^{nd}$ Formant Frequency(F2), and Fundamental Frequency(F0) of the temporomandibular joint disorder patients were increased compared to before and this showed the change of the $1^{st}$ Formant Frequency(F1) related to the open mouth grade of a vowel, as well as the $2^{nd}$ Formant Frequency(F2), and Fundamental Frequency(F0) related to the front-back of a vowel which shows the relationship between the temporomandibular joint, vowels and voice calculation.

• Clinical and Experimental Reproductive Medicine
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• v.25 no.2
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• pp.153-160
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• 1998

The objective of this retrospective study was to evaluate whether the transvaginal ultrasonographic analysis of endometrial pattern and thickness could predict the stage of menstrual cycle. Endometrial pattern and thickness were observed in those patients receiving infertility work up from April, 1994 to July, 1998 at Seoul National University Hospital. The study group was 185 patients with normal regular menstrual cycles. Among them, 44 patients received endometrial biopsy, and the date of endometrium was compared with the observed endometrial pattern and thickness. The observed endometrial pattern was presence or absence of central cavity echogenicity, triple line sign, endometrial hypoechogenicity, ring sign, endometrial hyperechogenicity and posterior acoustic sonic enhancement. The results were as follows; Central cavity echogenicity was seen throughout menstrual cycle. Triple line sign was observed in 81.1% of patients during early secretory phase. However, in mid to late secretory phase, triple line sign was appeared in only 6.8%. The percentage of positive endometrial hypoechogenicity was highest in early secretory phase. In contrast to hypoechogenicity, positive endometrial hyperechogenicty was highest in mid to late secretory phase. Ring sign was observed in 73.5% of the patients during early secretory phase with peak incidence. Posterior acoustic enhancement was seen in 72.7% of the patients during late secretory phase. The sensitivity and specificity of being a secretory phase if the patients showed hyperechogenic endometrium, were 84.2%, 83.3% respectively. The sensitivity and specificity of being a secretory phase if the patients showed posterior acoustic enhancement were 93.8%, 58.3% respectively. Endometrial thickness was not correlated with endometrial dating. In conclusion, transvaginal ultrasonographical delineation of the endometrial pattern might be useful tool in predicting endometrial status during normal menstrual cycle. But, endometrial thickness could not predict the endometrial dating.

• Archives of Craniofacial Surgery
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• v.18 no.2
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• pp.82-88
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• 2017

Background: Turbinate hypertrophy is one of the common causes of chronic nasal obstruction. In principle, therapeutic guidelines recommend medical treatment. Failure to treat turbinate thickening despite drug therapy may indicate the need for surgery. The main aim of this study was to determine the effect of radiofrequency surgery, among various other surgical procedures, on people with both nasal septal deviation and turbinate hypertrophy. Methods: Among people with nasal deviation who visited the subject hospital between July 2008 to July 2014, 21 people with nasal septal deviation and severe turbinate hypertrophy before their surgery had undergone septoplasty with turbinoplasty using radiofrequency combined with septoplasty. The degree of the turbinate's hypertrophy was appraised in all the patients before and after the surgery using the rhinoscopy, and acoustic rhinometry was objectively carried out. The subjective effect of the turbinoplasty using radiofrequency was explored through the visual analog scale (VAS) score. Results: The degree of contraction of the nasal mucosa after the rhinoscopy changed from Grades 3 and 4 (100%) to Grades 1 and 2 (95.2%) and Grades 3 (4.8%). The minimal cross-sectional area significantly increased from $0.44{\pm}0.07$ to $0.70{\pm}0.07cm^2$ (p<0.05). The nasal cavity volume increased from $4.79{\pm}0.49$ to $6.76{\pm}0.55cm^2$ (p<0.05). The subjective symptoms evaluated with VAS score a year after the surgery significantly improved (p<0.05). Conclusion: Turbinoplasty using Coblator with septoplasty is an effective treatment method because it expands nasal cavity, has a low incidence of complications, subjectively improves symptoms, and has short treatment duration.

• Journal of Energy Engineering
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• v.15 no.1 s.45
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• pp.35-44
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• 2006

This study experimentally investigates effect of boiling heat transfer when ultrasonic vibration was applied. Under the wall temperature condition, temperature distribution in a cavity was measured during the boiling process and heat transfer coefficient of convection, sub-tooled boiling and saturated boiling states were measured with and without ultrasonic vibration, respectively. Also, the profiles of the pressure distribution in acoustic field measured by a hydrophone were compared with the augmentation ratios of heat transfer calculated by local heat transfer coefficient. Result of this study, heat transfer coefficient and augmentation ratio of heat transfer is higher with ultrasonic waves than without one. Especially, augmentation ratio of heat transfer is more increased the convection state than sub-cooled boiling and saturated boiling states. Acoustic pressure is relatively higher near ultrasonic transducer than other points where is no installed it and affects the augmentation ratio of heat transfer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.169-174
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• 2011

Acoustic emission (AE) signals were detected and analyzed in real time during the polymerization shrinkage of composite resin restoration in an artificial dental ring with a class I cavity. Most AE hit events were observed in the initial curing period of the 1st region with high contraction rate. The range of the $2^{nd}$ region for the stainless steel specimen was shorter than that for the PMMA specimen but longer than that for the human dentin specimen. AE hit events showed a blast-type signal having an amplitude in the range of 25.45 dB and a frequency band of 100.200 kHz or 240.300 kHz. These values of amplitude and frequency indicated the fracture of resin or of the adhesive layer.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.7
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• pp.604-611
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• 2004

It is well known that wall impedance essentially determines how sound wave transmits from one place to another. The wall impedance is related with its dynamic properties : for example, the mass, stiffness, and damping characteristics. It is noteworthy, however, that the wall impedance is also function of spatial characteristics of two spaces that is separated by the wall. This is often referred that the wall is not locally reacting. In this paper, we have attempted to see how the acoustic characteristics of the two spaces is affected by various structure parameters such as density, applied tension, and a normalized length of the wall. Calculations are conducted for two different modally reacting boundary conditions by modal expansion method. The variation of the Helmholtz mode and the structural-dominated mode are analyzed as the structure parameters vary. The displacement distribution of the structure, pressure and active intensity of the inside and outside cavity are presented at the Helmholtz mode and the structure-dominated mode. It is shown that the frequency characteristics are governed by both structure-and fluid-dominated mode. The results exhibit that the density of the structure is the most sensitive design parameter on the frequency characteristics for the coupling system as we could imagine in the beginning. The Helmholtz mode frequency decrease as density increases. However. it increases as applied tension and an opening size increase. The bandwidth of the Helmholtz mode is mainly affected by density of the structure and its opening size.