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.

Performance Analysis and Optimization of a Dual Warhead System

2012 ◽  
Vol 13 (1) ◽  
Author(s):  
Xiao-Jun Guo ◽  
He-Ming Wen
Keyword(s):  
Experimental Data ◽  
Performance Analysis ◽  
Analytical Model ◽  
Present Model ◽  
Shaped Charge ◽  
Weapon Systems ◽  
Model Predictions ◽  
Modern Warfare ◽  
Good Agreement ◽  
Concrete Target

AbstractIn modern warfare earth penetrating weapons are often used to defeat enemy’s hardened and deeply buried targets such as aircraft shelters and bunkers. A dual warhead system (DWS) is one of such weapons composed of a forward shaped charge (FSC) and a following through warhead (FTW). In this paper, an analytical model is first proposed to analyze the penetration of an FTW into concrete targets with pre-drilled holes and a DWS is then optimized in order to achieve its best penetration performance. The effects of various parameters on the performance of a dual warhead system penetrating a concrete target are delineated. It transpires that the present model predictions are in good agreement with available experimental data and that the results obtained may be useful for designing such weapon systems.

An Analytical Model for Vocs Emission from Porous Building Materials

2010 ◽  
Vol 113-116 ◽  
pp. 1861-1864 ◽  
Author(s):  
Lian Ying Cao ◽  
Jun Shen
Keyword(s):  
Analytical Model ◽  
Laplace Transformation ◽  
Building Materials ◽  
Present Model ◽  
Medium Density ◽  
Porous Building Materials ◽  
Volatile Organic ◽  
Airtight Chamber ◽  
Vocs Emission ◽  
Good Agreement

This paper presented a new analytical model of partial differential equations (pde) for volatile organic compounds (vocs) emission from porous building materials. By applying Laplace transformation the representations for vocs concentration in the chamber and in the porous building material were given. The emission curves and average concentrations of some porous building materials Medium Density Fiberboards (mdf) in an airtight chamber were obtained. Result of the present model shows a good agreement with the experimental data.

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.

Performance Analysis and Optimization of a Dual Warhead System

2012 ◽  
Vol 13 (1) ◽  
Author(s):  
Xiao-Jun Guo ◽  
He-Ming Wen
Keyword(s):  
Experimental Data ◽  
Performance Analysis ◽  
Analytical Model ◽  
Present Model ◽  
Shaped Charge ◽  
Weapon Systems ◽  
Model Predictions ◽  
Modern Warfare ◽  
Good Agreement ◽  
Concrete Target

AbstractIn modern warfare earth penetrating weapons are often used to defeat enemy’s hardened and deeply buried targets such as aircraft shelters and bunkers. A dual warhead system (DWS) is one of such weapons composed of a forward shaped charge (FSC) and a following through warhead (FTW). In this paper, an analytical model is first proposed to analyze the penetration of an FTW into concrete targets with pre-drilled holes and a DWS is then optimized in order to achieve its best penetration performance. The effects of various parameters on the performance of a dual warhead system penetrating a concrete target are delineated. It transpires that the present model predictions are in good agreement with available experimental data and that the results obtained may be useful for designing such weapon systems.

scholarly journals A semi-analytical model for diffuse reflectance in marine and inland waters

2015 ◽  
Vol 12 (4) ◽  
pp. 1893-1912 ◽  
Author(s):  
J. D. Pravin ◽  
P. Shanmugam ◽  
Y.-H. Ahn
Keyword(s):  
Optical Properties ◽  
Water Column ◽  
Analytical Model ◽  
Diffuse Reflectance ◽  
Present Model ◽  
Open Ocean ◽  
Inherent Optical Properties ◽  
Wide Range ◽  
Good Agreement

Abstract. A semi-analytical model for predicting diffuse reflectance of coastal and oceanic waters is developed based on the water-column optical properties and illumination conditions. Diffuse reflectance (R) is an apparent optical property that is related to the Gordon's parameter (bb/(a+bb)) through a proportionality factor "f". The conventional assumption of "f" as a constant (0.33) yields large errors in case of turbid and productive coastal waters and a predictive model based on this assumption is generally restricted to open-ocean waters (low chlorophyll case). In this paper, we have sorted the dependent factors that influence "f" values in the water column. Here, the parameter "f" is modeled as a function of wavelength, depth, inherent optical properties (IOPs) and illumination conditions. This work eliminates the spectral constants (KChl and KSS) associated with our previous model and constrains the present model to be solely dependent on the IOPs and illumination conditions. Data used for parameterization and validation are obtained from in situ measurements in different waters within coastal environments. Validation shows good agreement between the model R and in situ R values with the overall mean relative error of less than a few percent. The model is valid for a wide range waters within coastal and open-ocean environments.

A Numerical Method for Predicting Thermoelastic Damping in Micromechanical Resonators

2008 ◽  
Author(s):  
Yang Xu ◽  
Zhili Hao
Keyword(s):  
Numerical Method ◽  
Thermal Field ◽  
Elastic Field ◽  
Complex Frequency ◽  
Thermoelastic Damping ◽  
Structural Geometry ◽  
Micromechanical Resonators ◽  
Beam Resonator ◽  
Modeling Software ◽  
Parameter Measuring

This paper presents a numerical method for predicting thermoelastic damping (TED) in micromechanical resonators with any arbitrary structural geometry. In this numerical method, TED is interpreted as the generation of thermal energy per cycle of vibration from the viewpoint of thermal field. Consequently, TED is mathematically expressed in terms of entropy — a parameter measuring the irreversibility in heat conduction, and then numerically calculated in ANSYS/Multiphysics. The validity of this numerical method has been verified using the well-known solution to TED in a beam resonator and experimental data in the literature. Compared to the commonly used interpretation of TED in the elastic field-complex frequency, this numerical method does not involve complex values and thus offers the advantages of simplicity and compatibility with finite element modeling software.

A Compact Model for Spherical Rough Contacts

2004 ◽  
Author(s):  
M. Bahrami ◽  
M. M. Yovanovich ◽  
J. R. Culham
Keyword(s):  
Pressure Distribution ◽  
Entire Range ◽  
Present Model ◽  
Numerical Solutions ◽  
Contact Radius ◽  
Bulk Deformation ◽  
Dimensional Parameters ◽  
Maximum Contact ◽  
Good Agreement ◽  
Key Parameter

The contact of rough spheres is of high interest in many tribological, thermal, and electrical fundamental analyses. Implementing the existing models is complex and requires iterative numerical solutions. In this paper a new model is presented and a general pressure distribution is proposed that encompasses the entire range of spherical rough contacts including the Hertzian limit. It is shown that the non-dimensional maximum contact pressure is the key parameter that controls the solution. Compact expressions are proposed for calculating the pressure distribution, radius of the contact area, elastic bulk deformation, and the compliance as functions of the governing non-dimensional parameters. The present model shows the same trends as those of the Greenwood and Tripp model. Correlations proposed for the contact radius and the compliance are compared with experimental data collected by others and good agreement is observed.

Thermoelastic damping in GaAs micromechanical resonators

2008 ◽  
Vol 5 (9) ◽  
pp. 2920-2922 ◽  
Author(s):  
Hajime Okamoto ◽  
Daisuke Ito ◽  
Koji Onomitsu ◽  
Hiroshi Yamaguchi
Keyword(s):  
Thermoelastic Damping ◽  
Micromechanical Resonators
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