scholarly journals Entropy Generation and Thermoelastic Damping in the In-plane Vibration of Microring Resonators

Entropy ◽  
2019 ◽  
Vol 21 (7) ◽  
pp. 631 ◽  
Author(s):  
Yongpeng Tai ◽  
Pu Li ◽  
Yan Zheng ◽  
Jie Tian
Keyword(s):  
Analytical Model ◽  
Entropy Generation ◽  
Critical Issue ◽  
Ring Resonators ◽  
Thermoelastic Damping ◽  
Ambient Temperatures ◽  
Plane Vibration ◽  
Radial Thickness ◽  
Complex Temperature ◽  
Very High

Thermoelastic damping is a critical issue for designing very high quality factor microresonators. This paper derives the entropy generation, associated with the irreversibility in heat conduction, that is used for ring resonators in in-plane vibration and presents an analytical model of thermoelastic damping according to heat increments calculated by entropy theory. We consider the heat flow only in radial thickness of the ring and obtain a complex temperature field that is out of phase with the mechanical stress. The thermoelastic dissipation is calculated in the perspective of heat increments that appear due to entropy generation. The analytical model is validated by comparing with an LR (Lifshitz and Roukes) model, finite-element method and measurement. The accuracy of the present model is found to be very high for different ambient temperatures and structures. The effects of structure dimensions and vibration frequencies on entropy generation and thermoelastic damping is investigated for ring resonators under in-plane vibration.

An Analytical Model for Thermoelastic Damping in Microresonators Based on Entropy Generation

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Yongpeng Tai ◽  
Pu Li
Keyword(s):  
Analytical Model ◽  
Entropy Generation ◽  
Present Model ◽  
Stress Fields ◽  
Accurate Estimation ◽  
Solution Technique ◽  
Thermoelastic Damping ◽  
Micromechanical Resonators ◽  
Parameter Measuring ◽  
Good Agreement

This paper presents an analytical model for thermoelastic damping (TED) in micromechanical resonators, which is based on entropy generation, a thermodynamic parameter measuring the irreversibility in heat conduction. The analytical solution is derived from the entropy generation equation and provides an accurate estimation of thermoelastic damping in flexural resonators. This solution technique for estimation of thermoelastic damping is applied in beams and plates resonators. The derivation shows that the analytical expression for fully clamped and simply supported plates is similar to that for beams, but not the same as the latter due to different strain and stress fields. The present model is verified by comparing with Zener's approximation and the LR (Lifshitz and Roukes) method. The effect of structural dimensions on entropy generation corresponding to thermoelastic damping is investigated for beam resonators. The results of the present model are found to be in good agreement with the numerical and experimental results.

An Entropy Based Analytical Model for Thermoelastic Damping in Micromechanical Resonators

2012 ◽  
Vol 159 ◽  
pp. 46-50 ◽  
Author(s):  
Yong Peng Tai ◽  
Pu Li ◽  
Wan Li Zuo
Keyword(s):  
Quality Factor ◽  
Analytical Model ◽  
Entropy Generation ◽  
Accurate Estimation ◽  
Thermoelastic Damping ◽  
Small Vibration ◽  
Micromechanical Resonators ◽  
Thin Beam ◽  
Parameter Measuring ◽  
Linear Thermoelasticity

In this paper, we present an analytical model for thermoelastic damping (TED) in micromechanical resonators, which is based on entropy generation, a thermodynamic parameter measuring the irreversibility in heat conduction. The temperature field of thin beam with small vibration is obtained by solving governing equations of linear thermoelasticity. The analytical solution is derived from the entropy generation equation. This method of entropy generation can provide an accurate estimation of the quality factor in flexural resonators. The results are compared with Zener’s approximation and LR (Lifshitz and Roukes) method. It is shown that the analytical model described in this paper is valid to estimate the quality factor due to thermoelastic damping.

Intersubject viability in growth hormone time course during different types of work

1983 ◽  
Vol 55 (6) ◽  
pp. 1682-1687 ◽  
Author(s):  
J. Raynaud ◽  
A. Capderou ◽  
J. P. Martineaud ◽  
J. Bordachar ◽  
J. Durand
Keyword(s):  
Growth Hormone ◽  
Time Course ◽  
Intermittent Exercise ◽  
Muscular Activity ◽  
Human Growth ◽  
Submaximal Exercise ◽  
Similar Time ◽  
Ambient Temperatures ◽  
Type Of Exercise ◽  
Very High

This study addresses the question of variability of immunoreactive human growth hormone (IRHGH) response to the following types of muscular exercise. 1) One hour of submaximal exercise with restarting for 30 min after 20 min of recovery. Three types of responses were observed: a rise of [IRHGH] occurred in response to muscular activity; [IRHGH] was maintained at rest level during the first bout and then rose in the second bout; or [IRHGH] rose during the first bout and was no longer modified by the restarting. 2) Thirty minutes of heavy exercise. In some subjects [IRHGH] change was almost linear with time, reaching very high values and dropping as soon as exercise had stopped, whereas in others peak values were similar to those of submaximal exercise but, in contrast, plateaued during recovery. 3) One hour of exercise performed either continuously or with alternate sequences of 30-s exercise and 30-s pause. In intermittent exercise, some subjects displayed a similar time course of [IRHGH] as in continuous exercise and others displayed markedly high values. 4) One hour of submaximal exercise at three different intensities carried out at ambient temperatures of 24 and 33 degrees C. At 33 degrees C, in some subjects, [IRHGH] time course at the three intensities was unchanged at 33 degrees C compared with that at 24 degrees C, whereas the maximal value increased in another subject up to 150 ng X ml-1. A significant intrasubject consistency to a given type of exercise was evident over several months. The study emphasizes that caution should be used in drawing definite conclusions from averaged results with high variability.

Negative Refractive Index of Meta-materials at Optical Frequencies

2006 ◽  
Vol 964 ◽  
Author(s):  
S. Anantha Ramakrishna ◽  
Sangeeta Chakrabarti
Keyword(s):  
Refractive Index ◽  
Negative Refractive Index ◽  
Magnetic Activity ◽  
Ring Resonators ◽  
Split Ring ◽  
Complex Behaviour ◽  
High Frequencies ◽  
Displacement Currents ◽  
Very High Frequencies ◽  
Very High

ABSTRACTScaling the performance of metamaterials to obtain negative refractive index at optical frequencies has been of great interest. One of the great barriers to the scaling is that real currents cannot be driven at very high frequencies and one is more dependent on displacement currents to generate negative magnetic permeability. Moreover to keep the dimensions of the metamaterials physically accessible, the structural lengthscales of the metamaterials begin approach the wavelength of the radiation in free space and homogenisation is often questionable. Here we will show that metamaterials such as Split ring resonators in these high frequency limits exhibit complex behaviour. Magnetic activity and Negative refractive index behaviour can, indeed, be obtained at optical frequencies but will need to be interpreted very carefully. The plasmonic nature of the metallic system and excitation needs to be considered in detail.

Sign in / Sign up

Export Citation Format

Share Document