• Title/Summary/Keyword: Surface acoustic wave

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Heat and Mass Transfer Enhancement of a pendant droplet on heated horizontal surface by acoustic resonance (가열된 평판위에 매달려 있는 액적의 음향공진에 의한 열 및 물질 전달 촉진에 관한 연구)

  • Moon, Jong-Hoon
    • Proceedings of the SAREK Conference
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    • 2005.11a
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    • pp.335-340
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    • 2005
  • Nonlinear and forced oscillations of supported viscous droplet were focused in the present study. The droplet has a free contact line with solid plate and inviscid fluid. Natural frequencies of a pendant droplet have been investigated experimentally by imposing the acoustic wave while the frequency is being increased at a fixed amplitude. The evaporation was observed at atmosphere pressure. The droplet was recorded throughout the entire evaporation process and transient variations of the volume was measured. The evaporation process of oscillating droplet with thermofoil has been also observed to investigate analyzing the resonance effect on the thermal characteristics of droplet. It is found that a pendant droplet shows the resonant behaviors at each mode similar to the theoretical analysis. During imposing the acoustic wave, the pendant droplet makes a rotating motion in its longitudinal axis which is a new shape oscillation mode. The evaporation rate of a pendant droplet at resonant frequency is significantly enhanced.

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Application of GC-SAW(Surface Acoustic Wave) Electronic Nose to Classification of Origins and Blended Commercial Brands in Roasted Ground Coffee Beans (GC-SAW(Surface Acoustic Wave) 전자코를 활용한 볶은 커피의 원산지 및 배합 커피의 상품별 분류)

  • Seo, Han-Seok;Kang, Hee-Jin;Jung, Eun-Hee;Hwang, In-Kyeong
    • Korean journal of food and cookery science
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    • v.22 no.3 s.93
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    • pp.299-306
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    • 2006
  • The numerous varieties of coffee beans contain a wide range prices and qualities. While the varieties of green coffee beans can generally be distinguished by their appearance, this visual criterion is impossible after the roasting process. Therefore, we need to develop a classification method or device. In this study, the potential of a new type of electronic nose, fast gas chromatography based on a surface acoustic wave sensor(SAW), was evaluated for the classification of origins and blended commercial brands in roasted coffee beans. Eight blended commercial brands and the origins of four similarly roasted ground coffee beans(with no significant difference of color) were rapidly(90 sec/sample) classified. The reproductive results were easily understandable over the aroma image pattern by $VaporPrint^{TM}$. In conclusion, GC-SAW electronic nose can be applied to the classification of origins and commercial brands in roasted ground coffee beans and to e evaluation of the similarities and differences of volatile pattern between samples.

Surface Acoustic Wave Characteristics of Piezoelectric Materials and Protein Immobilization (압전 재료의 탄성표면파 특성과 단백질의 고정화)

  • Chong, Woo-Suk;Hong, Chul-Un;Kim, Gi-Beum
    • Korean Chemical Engineering Research
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    • v.44 no.2
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    • pp.166-171
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    • 2006
  • In this study, in using a piezoelectric material of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ (PMN-PT), which has a high electromechanical coupling coefficient, we have tried to study about this material can be practically available as a new biosensor to detect protein by using surface acoustic wave (SAW). As the results, the filtering of the center frequency of the PMN-PT substrate is a superior result to that of the $LiTaO_3$ (LT) substrate, but the result was not completely satisfactory. Also this study attempts to develop a sensing method to detect mismatched DNA in order to diagnose cancer. We could directly immobilize the MutS to the NTA using the EDC solution. But, we immobilized MutS using nickel and it is judged that is more effective method to detect mismatched DNA.

B-Scan Image Processing Technique by Using Ultrasonic Microscope System (초음파 현미경 시스템에 의한 B-스캔 영상처리 기술)

  • 고대식;전계석
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.12
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    • pp.1889-1893
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    • 1990
  • In this paper, ultrasonic microscope system has been constructed with the small aperturre acoustic lens and the angle controller, and the new type of B-scanultransonic imaging has been analyzed. The system with small aperture lens was used to detect flaw existing within the thick specimen and its resolution was in the range of one wavelength at interior plane of sample. The anle controller was used to excited surface acoustic wave or shear wave. In order to obtain B-scan image of the flaw existig at interior of solids, shear wave has been excited and backscattering signals from the flaw have been processed. In experimental results, B-scan ultransonic images have been obtain from the flaws of varable shape and measured flaw size from the images has been in good agreement with practical size in the range of 10% error.

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Interactions of Spherical Acoustic Shock Waves with a Spherical Elastic Shell near a Free-Surface (자유표면 근처에서의 구형 셸과 충격파의 비정상 유체-구조물 상호작용 해석)

  • Lee, Min-Hyung;Lee, Beom-Heon;Lee, Seung-Yop
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.6
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    • pp.1143-1148
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    • 2002
  • This paper analyses the transient response of a spherical elastic shell located near fee surface and impinged by spherical step-exponential acoustic shock waves. The problem is solved through extension of a method (Huang, 1969) previously formulated for the excitation in an infinite domain, which employs the classical separation of variables, series solutions, and Laplace transform technique The effect of the free surface reflection is taken into account using the image source method. The reflection of the incident wave has been treated by the same image formulation. If the reflection of the pressure field scattered and radiated by the shell is considered, the problem becomes that of multiple scattering by two spheres. However, this is in general negligible considering errors inherent from other sources and that the scattered and radiated pressure waves emanating from the shell are small. Thus, the problem is reduced to that of a structure immersed in an infinite fluid and impinged upon the origin and the image incident.

Inspection of Ceramic Coatings Using Nanoindentation and Frequency Domain Photoacoustic Microscopy

  • Steen, T.L.;Basu, S.N.;Sarin, V.K.;Murray, T.W.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.6
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    • pp.390-402
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    • 2006
  • The elastic properties and thickness of mullite environmental barrier coatings grown through chemical vapor deposition (CVD) on silicon carbide substrates were measured using frequency domain photoacoustic microscopy. In this technique, extremely narrow bandwidth surface acoustic waves are generated with an amplitude modulated laser source. A photorefractive crystal based interferometer is used to detect the resulting surface displacement. The complex displacement field is mapped as a function of source-to-receiver distance in order to extract the wavelength of the surface acoustic wave at a given excitation frequency, and the phase velocity is determined. The coatings tested exhibited spatial variations in thickness and mechanical properties. The measured surface wave dispersion curves were used to extract an effective value for the elastic modulus and the coating thickness. Nanoindentation was used to validate the measurements of the effective elastic modulus. The average elastic modulus measured through the coating thickness using nanoindentation is compared to the effective modulus found using the photoacoustic system. Optical microscopy is used to validate the thickness measurements. The results indicate that the photoacoustic microscopy technique can be used to estimate the effective elastic properties in coatings exhibiting spatial inhomogeneities, potentially providing valuable feedback for the optimization of the CVD growth process.

Study on Smart Cooling Technology by Acoustic Streaming Generated by Ultrasonic Vibration Using 3D PIV (3차원 PIV를 활용한 초음파 진동에 의해 발생된 음향 유동을 이용한 스마트 냉각법 연구)

  • Lee, Dong-Ryul;Loh, Byoung-Gook;Kwon, Ki-Jung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.11
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    • pp.1078-1088
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    • 2010
  • In order to analyze the quantitative characteristics of acoustic streaming, experimental setup of 3-D stereoscopic PIV(particle imaging velocimetry) was designed and quantitative ultrasonic flow fields in the gap between the ultrasonic vibrator and heat source were measured. Utilizing acoustic streaming induced by ultrasonic vibration, surface temperature drop of cooling object was also measured. The study on smart cooling method by acoustic streaming induced by ultrasonic vibration was performed due to the empirical relations of flow pattern, average flow velocity, different gaps, and enhancement on cooling rates in the gap. Average velocity fields and maximum acoustic streaming velocity in the open gap between the stationary cylindrical heat source and ultrasonic vibrator were experimentally measured at no vibration, resonance, and non-resonance. It was clearly observed that the enhancement of cooling rates existed owing to the acoustic air flow in the gap at resonance and non-resonance induced by ultrasonic vibration. The ultrasonic wave propagating into air in the gap creates steady-state secondary eddy called acoustic streaming which enhances heat transfer from the heat source to encompassing air. The intensity of the acoustic streaming induced by ultrasonic vibration experimentally depended upon the gap between the heat source and ultrasonic vibrator. The ultrasonic vibration at resonance caused the increase of the acoustic streaming velocity and convective heat transfer augmentation when the flow fields by 3D stereoscopic PIV and temperature drop of the heat source were measured experimentally. The acoustic streaming velocity of air enhancement on cooling rates in the gap is maximal when the gap agrees with the multiples of half wavelength of the ultrasonic wave, which is specifically 12 mm.