• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.12 s.105
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• pp.1416-1421
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• 2005

This paper presents an analytical approach for the vibration characteristics of a piezoelectric disc for torsional vibration transducers. The characteristic equation of the piezoelectric annular disc has been derived from Gibbs' free energy equations and mechanical and electrical equilibrium. With an anisotropic material properties of the disc, the characteristic equation has yielded resonance frequencies. Numerically-calculated results have been compared with the results obtained by the finite element analysis and experiments and have confirmed the validity of the theoretical analysis.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.802-805
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• 1988

The objective of the present study was to manufacture the piezoelectric composites of Lead Zirconate Titanate (PZT) - polymer for applications such as ultrasonic medical diagnosis and hydrophone. The PZT rod-polymer composites have been prepared with 4.5 to 57 volume percent PZT using 1.5 mm rod, so the connectivity pattern of the two phase is 1-3 type. The electromechanical coupling factors of radial mode ($k_{p}$) and thickness mode ($k_{t}$) were nearly independent of the volume percent PZT, which were 0.3 and 0.65, respectively. The acoustic impedance of the piezoelectric composites was measured by the resonance technique in the frequency range 50 KHz-1.5 MHz, which was in the range of 3.8 - 60 Mrayl.

• KSBB Journal
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• v.17 no.1
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• pp.1-13
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• 2002

Label-free optical methods for the monitoring of interactions between biological molecules have become increasingly popular within the last decade. A rising number of publications have demonstrated the benefits of direct biomolecular interaction analysis(BIA) for biology and biochemistry, such as antigen-antibody Interactions, receptor-ligand interactions, protein-DNA, DNA- intercalator, and DNA-DNA interactions. This article gives an overview of the historical development, principle and application of label-free optical biosensor to examine the functional characteristics of biospecific interaction, such as kinetics, affinity, and binding position of biomolecular between an immobilized species at the transducer surface and its dissolved binding partner.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.263-267
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• 2011

Ultrasonic metal welding can be used to weld different metals together safely and precisely, without solder, flux and special preparation. Ultrasonic metal welding machine consists of a power supply, a transducer, a booster and a horn. This paper designed the horn needed for Ultrasonic metal welding. The horn has to be designed and manufactured accurately, because measurements such as the shape, length, mass and etc. have effects on the resonant frequency and the vibration mode. The designed horn has the feature of 40,000Hz of nature frequency, and maximizes vibration range in the Tip by resonance in the frequency of ultrasonic wave machine. In this paper, we calculated and analyzed the natural frequency to find the optimal design of the horn that had the amplitude about $12{\mu}m$ by the modal analysis and harmonic analysis using ANSYS. And we analyzed FFT analysis of the manufactured horn.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.3
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• pp.1-10
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• 1986

This paper describes a new, effective method developed at the National Research Council Canada for rolling element bearing incipient failure detection. This method can detect not only outer race damage, previously published, but also inner race damage with a 100% detection rate based on a sample size of 32. The prediction of the exact angular location of the damage spot along the raceway is illustrated and experimental confirmation is presented. For the first time, a statically measurable parameter for inner and outer race damage is introduced as a means of verifying other techniques which do not offer absolute proof, but resort only to "overwhelming evidence". A brief comparison with other methods such as Shock Pulse Method, Kurtosis Analysis and High Frequency Resonance Technique is presented. A computerized automatic monitoring system utilizing the new method is described and experimental results are presented.presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.1
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• pp.13-23
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• 2015

The paper experimentally deals with the radial in-plane vibration characteristics of disk-shaped piezoelectric transducers. The radial in-plane motion, which is induced due to Poisson's ratio in the piezoelectric disk polarized in the thickness direction, was measured by using an in-plane laser vibrometer, and the natural frequencies were measured by using an impedance analyzer. The experimental results have been compared with theoretical predictions obtained by simplified theoretical and finite-element analyses. It appears that the fundamental mode of a piezoelectric disk transducer is a radial mode and its radial displacement distribution from the center to the perimeter is not monotonic but shows maximum slightly apart from the perimeter. The theoretically-calculated fundamental frequencies agree well with the finite-element results for small thickness-to-diameter ratio, and they are accurate within 7 % error for the ratio up to 0.4.

• 전자공학회논문지 IE
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• v.48 no.2
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• pp.40-46
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• 2011

In this study, PZT-5A green sheet were prepared by using tape casting technique, and the piezoelectric properties of PZT-5A by variation of sintering temperature was investigated. After, design and piezoelectric properties of 2-2 piezocomposite ultrasonic transducers by menas of the FEA. The acoustic impedance and piezoelectric charge constant of the 2-2 type piezocomposite transducer decreased proportionally due to the density decrease caused by the PZT volume fraction decrease. The piezocomposite acoustic impedance were 7~3 MRayl between 0.6 and 0.2 allowing it to be used for a ultrasonic transducer. The resonance characteristics and the electro-mechanical coupling factor were the best when the volume fraction PZT was 0.6. The PZT volume fraction shows the fixed value, 0.6~0.65, approximately within the range between 0.2 and 0.6 while it is increased to decreased over the range. The result of the experiment above confirmed that the 2-2 piezoelectric composites could be used as the ultrasonic transducers.

• The Journal of Advanced Prosthodontics
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• v.1 no.1
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• pp.31-36
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• 2009

PURPOSE. To determine the change in stability of single-stage, three different design of implant systems in humans utilizing resonance frequency analysis for early healing period(24 weeks), without loading. MATERIAL AND METHODS. Twenty-five patients were included into this study. A total of 45 implants, three different design of implant systems(group A,C,R) were placed in the posterior maxilla or mandible. The specific transducer for each implant system was used. ISQ(implant stability quotient) reading were obtained for each implant at the time of surgery, 3, 6, 8, 10, 12, 24 weeks postoperatively. Data were analyzed for different implant type, bone type, healing time, anatomical locations. RESULTS. For each implant system, a two-factor mixed-model ANOVA demonstrated that a significant effect on ISQ values(group A=0.0022, C=0.017, R=0.0018). For each implant system, in a two-factor mixed model ANOVA, and two-sample t-test, the main effect of jaw position(P > .005) on ISQ values were not significant. CONCLUSIONS. All the implant groups A, C and R, the change patterns of ISQ over time differed by bone type. Implant stability increased greatly between week 0 and week six and showed slow increase between week six and six months(plateau effect).

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.80-86
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• 2007

We have investigated on the development of 2-2 type piezocomposites that have better piezoelectric activity and lower acoustic impedance than those of conventional piezoceramics. In this study, we have investigated the piezoelectric and acoustic properties of 2-2 type piezocomposites sensor which was fabricated using dice-and-fill technique for the different volume fraction of PZT. The specific acoustic impedance of 2-2 type piezocomposites decreased linearly when PZT volume fraction was decreased. The resonance characteristics measured by an impedance analyzer(HP4194A) were similar to the analysis of finite element method (FEM). The resonance characteristics and the electromechanical coupling factor were the best when the volume fraction PZT was 0.6. It also showed the highest result from the standpoint of sensitivity, bandwidth and ring-down property and so on at the same condition. The specific characteristics show that the 2-2 type piezocomposites turned out to be superior to the ultrasonic sensor composed by single phase PZT.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.197-205
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• 2004

Most of gas turbines is operated by the type of dry premixed combustion to reduce NOx emission and economize fuel consumption. However this type operation, combustion induced instability brought failure problems cause by high pressure and heat release fluctuations. Though there has been lots of studies since Lord Rayleigh to understand this instability mechanism and control the instabilities, none of them made matters clear. In order to understand the instability phenomena, a simple experimental study with dump combustor was conducted at the moderate pressure and ambient temperature conditions. From this model gas turbine combustor self-excited instabilities at the resonance mode(200Hz) and bulk mode(10Hz) were occurred and observed at the three points of view; pressure, heat release and equivalence ratio which are acquired by peizo-electric transducer, HICCD camera and acetone LIF respectively. From this results we could see the instability mechanism clear with the account of time scale analysis which explained by the propagation of pressure wave to the upward of mixture stream and convectional transfer of the equivalence ratio fluctuation by this pressure fluctuation.