Separation of Q-factors for tubular microstructure with point imperfections

Kim, Jung-Hwan,Kim, Ji-Hwan Elsevier 2018 Applied mathematical modelling Vol.64 No.-

<P><B>Abstract</B></P> <P>In this paper, thermoelastic damping (TED) effect on the vibration of cylindrical shell with point masses is investigated in order to correlate the deviation of Q-factors as compared with the uniform shell model. The simplification of the governing equations is based on Donnell–Mushtari–Vlasov (DMV) approach. To obtain the eigenfrequencies of the imperfect structure, the shell model is analyzed based on the receptance method. Then, the isothermal frequencies of the model are obtained with the matching point of both receptances of the uniform shell and point masses. Furthermore, one dimensional heat transfer equation is considered to evaluate the dissipation in the modeling of heat conduction for high-frequency vibration. Using the results of temperature profile, TED effects are estimated by the quality factors (Q-factors) of the tubular microstructure with point masses. For the verification of this work, previous literatures are compared with the present data. Specifically, amounts of Q-factor splits result in the deviation of the magnitude as well as location of imperfections in the structures. Moreover, the numerical data are summarized with respect to the size of the shell model and magnitude of lumped mass.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermoelastic damping (TED) effect is considered on the vibration of cylindrical shell with point masses. </LI> <LI> The simplification of the governing equations are based on Donnell–Mushtari–Vlasov (DMV) approach. </LI> <LI> The model is considered as the receptances of the shell and point masses. </LI> <LI> Quality factor (Q-factor) depends on the TED effects. </LI> <LI> Q-factor split is the function of magnitude and location of imperfect masses. </LI> </UL> </P>

Analytical Study of Noise Spectral Density in -controlled Atomic Force Microscopy

이만희,안상민,제원호 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.3

Q-controlled atomic force microscopy utilizes an oscillating probe with an adjustable qualityfactor, which is done by adding a variable damping interaction to the probe. While the Q-controlcan enhance the probe sensitivity by increasing the Q-factor, the applied interaction increases thenoise of the probe motion as well. Thus, the signal-to-noise ratio (SNR) associated with the probesensitivity varies accordingly. Here, we analytically derive the noise spectral density of the tipmotion, and theoretically investigate the SNR in Q-controlled atomic force microscopy. We showthat both the overall tip-motion signal and the noise monotonically increase with the effective Qfactorunder control, whereas the SNR exhibits a global minimum near the original Q value andasymptotically scales as the square root of the effective Q-factor. Therefore, in general, the Qcontroltechnique can be used to alter the quality factor, the magnitudes of signal and noise, andthe probe sensitivity in amplitude-modulation atomic force microscopy.

Extraction of Fundamental Component in Power Quality Application using Tunable-Q Wavelet Transform

G.Ravi Shankar Reddy,Rameshwar Rao 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.8

Application of a Tunable-Q Wavelet Transform based technique is proposed in this paper for the extraction of Fundamental frequency component in Power Quality Disturbances. The TQWT filters are designed to extract the fundamental frequency component from the complete voltage (or) current signal. This is achieved by tuning the Q-factor and redundancy of the wavelet by primarily investigating the presence of interharmonics near the fundamental frequency. To test the effectiveness of the proposed scheme, the system is verified with various Power Quality Disturbances as per IEEE standards encountered in power system are considered here.

공진 주파수 변환 마이크로 캔티레버 진동의 노이즈 스펙트럼 밀도 이론

이만희 한국물리학회 2018 New Physics: Sae Mulli Vol.68 No.7

원자 힘 현미경에서 마이크로 캔티레버의 공진 주파수 및 Q-factor 변환 기술은 다양한 조건에서 이미징 성능을 향상시키는데 널리 사용된다, 이러한 전기적인 변환기술로 캔티레버의 공진 특성을 원하는 대로 조절할 수 있는 반면, 전기적 기작으로 인해 시스템의 노이즈는 증가한다. 결과적으로 캔티레버의 공진 주파수와 Q-factor를 제어하면, 캔티레버 진동의 `신호 대 잡음 비'가 변하게 되지만, 이러한 현상을 기술하는 이론은 아직 개발되지 못했다. 본 연구에서는 마이크로 캔티레버의 공진 주파수와 Q-factor 변환에 따른 캔티레버의 진폭 시그널 그리고 노이즈 스펙트럼 밀도를 이론적으로 예측한다. Q-factor가 증가하거나 감소할 때, 대부분 영역에서 신호 대 잡음 비는 증가한다. 이와는 다르게 공진 주파수가 증가할 때 신호 대 잡음 비는 감소하는 반면, 공진 주파수가 감소하면 신호 대 잡음 비는 비선형적으로 증가함을 보인다. 캔티레버의 신호 대 잡음 비는 센서의 감도에 중요한 요소이므로, 본 연구는 원자 힘 현미경을 이용한 이미징 및 상호작용 측정 연구에서 중요하게 사용될 수 있다. We analytically derive the noise spectral density and the associated signal-to-noise ratio for micro-cantilevers under the resonance frequency and quality factor control, taking into account the measurement noise, as well as the thermal noise. We show that the signal-to-noise ratio increases with increasing or decreasing the quality factor for a given resonance frequency. On the other hand, when the resonance frequency is altered, the signal-to-noise ratio exhibits a nonlinear behavior; it shows a local maximum near the original resonance frequency and diverges as the resonance frequency is reduced to zero. This analytical theory can be applied to enhance the probe sensitivity in atomic force microscopy, which is directly related to the noise of the cantilever's motion signal.

Splitting of quality factors for micro-ring with arbitrary point masses

Kim, J.H.,Kang, S.J.,Kim, J.H. Elsevier [etc.] 2017 Journal of sound and vibration Vol.395 No.-

<P>A ring resonator model with mass imperfections can be represented by a circular ring with irregularly distributed point masses. In this paper, in-plane vibration of the micro ring is to be investigated. Also, the ThermoElastic Damping (TED) effect is considered in the structures. In order to get the temperature profile for the thermal flow, one-dimensional heat conduction equation is employed. Using the assumed mode shapes for the inextensional vibration of the imperfect micro-ring with TED, analytical expressions for the natural frequencies with concentrated masses are determined by the equations of motion. Then, the split of the natural frequencies are determined according to the effect of distributed point masses. Finally, imperfect micro-ring with TED is presented with the variations of Quality-factors (Q-factors) for lower and higher modes. Based on the verification of the present work, more parametric studies are performed for the ring with mass imperfections. (C) 2017 Published by Elsevier Ltd.</P>

Thermoelastic dissipation of rotating imperfect micro-ring model

Kim, Jung-Hwan,Kim, Ji-Hwan Elsevier 2016 International journal of mechanical sciences Vol.119 No.-

<P><B>Abstract</B></P> <P>Present work considers the investigation of rotating micro-ring gyro resonator model with arbitrary imperfect point masses. Equation of motion of the ring is used to obtain the natural frequency with the effect of thermoelastic damping (TED) induced by the high-frequency vibration. In this regard, the temperature profile through the radial thickness of the model is obtained using the one dimensional heat-conduction equation. And then, the inextensional assumption of the model is employed in terms of displacement fields based on harmonic vibration. In order to express the lower and higher modes of the imperfect model, a sum of density function with respect to angular position is adopted. Also, the rotating speed is discussed including unbalance of the ring and the split of the two modes defined as forward and backward directions. Finally, numerical data for TED effect are obtained as Quality factors (Q-factors), and compared with previous results to verify present work. Moreover, parametric studies are presented for the rotating imperfect micro-ring model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The rotational speed is important factor to consider the vibration of the micro-ring model. </LI> <LI> The rotational speed of the model should be controlled to the proper value due to the impovement of the stability behavior and efficiency. </LI> <LI> The amount of imperfect mass should be smaller to keep the higher Q-factor for lower energy dissipation. </LI> <LI> The dissipation is lower when the ambient temperature of the surrounding is lower. </LI> <LI> The attached or eliminated point masses and rotating concepts can be applied into the frequency trimming and controlling. </LI> </UL> </P>

Prediction of shelf-life and changes in the quality characteristics of semidried persimmons stored at different temperatures

최지영,이현정,조정석,이영민,우진호,문광덕 한국식품과학회 2017 Food Science and Biotechnology Vol.26 No.5

This study was performed to investigate changes in the quality characteristics and shelf-life of semidried persimmons stored at different temperatures using acceleration experiments. In order to estimate quality changes in the samples, we evaluated the physicochemical properties, microbiological changes, and sensory features of the samples periodically after storage at −20, −10, 0, and 10 °C. At all storage temperatures, CIE L * a * b * values decreased significantly. Based on the results of this study, regression equations are set up. L * had the highest correlation and were therefore used to determine quality factor. The activation energy, which was calculated using the Arrhenius equation, was found to be 12.98 kcal/mol, and the Q10-values were 3.81, 2.07, and 2.06 at −20 to −10 °C, −10 to 0 °C, and 0 to 10 °C, respectively. Therefore, the expected expiration dates of the semidried persimmons were estimated to be 203.83, 53.46, 22.00, and 8.71 days at −20, −10, 0, and 10 °C.

BiFe₃첨가에 따른 저온소결 PSN-PZT세라믹스의 유전 및 압전 특성

류주현,정광현,정영호 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.5

In this study, (0.96 -x)(PSN-PZT)-xBF-0.04 PNW+0.3wt%MnO$_2$+0.6wt%CuO ceramics were fabricated with the variations of the amount of BiFeO$_3$substitution and sintering temperature for the development of modified ceramics which can be sintered in the low temperature($\leq$100$0^{\circ}C$ ), and their microstructural, dielectric and piezoelectric characteristics were investigated. As the amount of BiFeO$_3$ substitution was increased, the density, mechanical quality factor(Q$_{m}$) and electromechanical coupling factor(k$_{p}$) showed the maximum value at each of sintering temperature. At sintering temperature of 98$0^{\circ}C$ and BiFeO$_3$substitution of 2 mol%, the density, dielectric constant and electromechanical coupling factor(k$_{p}$) showed the maximum value of 7.84 g/㎤, 1415 and 0.49, respectively. And at sintering temperature of 95$0^{\circ}C$ and BiFeO$_3$substitution of 3mol%, mechanical quality factor showed the maximum value of 1062. 1062.

GEANT4-based Monte Carlo Simulation of Beam Quality Correction Factors for the Leksell Gamma Knifer PerfexionTM

Schaarschmidt Thomas,Taehoon Kim,Yong Kyun Kim,Hye Jeong Yang,Hyun-Tai Chung 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.12

With the publication of TRS-483 in late 2017 the IAEA has established an international code of practice for reference dosimetry in small and non-standard fields based on a formalism first suggested by Alfonso et al. in 2008. However, data on beam quality correction factors (kfmsr;fref Qmsr;Q0 ) for the Leksell Gamma Knifer PerfexionTM is scarce and what little data is available was obtained under conditions not necessarily in accordance with the IAEA's recommendations. This study constitutes the first systematic attempt to calculate those correction factors by applying the new code of practice to Monte Carlo simulation using the GEANT4 toolkit. kfmsr;fref Qmsr;Q0 values were determined for three common ionization chamber detectors and five different phantom materials, with results indicating that in most phantom materials, all chambers were well suited for reference dosimetry with the Gamma Knifer. Similarities and differences between the results of this study and previous ones were also analyzed and it was found that the results obtained herein were generally in good agreement with earlier PENELOPE and EGSnrc studies.

RF-MEMS 스위치용 마이크로 외팔보의 감쇠특성

이진우(Lee, Jin-Woo) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.6

A theoretical approach is carried out to predict the quality factors of flexible modes of a microcantilever on a squeeze-film. The frequency response function of an inertially-excited microcantilever beam is derived using an Euler-Bernoulli beam theory. The external force due to squeeze-film phenomenon is developed from the Reynolds equation. Slip boundary conditions are employed at the interfaces between the fluid and the structure to consider the gas rarefaction effect, and pressure boundary condition at both ends of fluid analysis region is enhanced to increase the exactness of predicted quality factors. To the end, an approximate equation is derived for the first bending mode of the microcantilever. Using the approximate equation, the quality factors of the second and third bending modes are calculated and compared with experimental results of previously reported work. The comparison shows the feasibility of the current approach.