Yu-Ching Yang

Kun Shan University, 臺南市, Taiwan, Taiwan

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Publications (81)178.21 Total impact

  • Wen-Lih Chen · Yu-Ching Yang · Jose Leon Salazar
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    ABSTRACT: An in-house CFD code has been applied to a low-temperature-differential (LTD) γ-type Stirling engine to understand the effects posed by several geometrical and operational parameters on engine performance. The results include variations of pressure, temperature, and heat transfer rates within an engine cycle as well as variations of engine's power and efficiency versus these parameters. It is found that power piston stroke and radius influence engine performance very similarly, and power and efficiency both increase as these two parameters increase. In fact, the effects of the two parameters can be assimilated into those by the parameter of compression ratio. The stroke of displacer is observed to affect strongly on heat input but weakly on power, thus causing the efficiency to decrease as it increases. As expected, both power and efficiency increase as temperature difference between the hot and cold ends increases. Lastly, engine speed is observed to pose strong positive effects on power but exert weak effects on efficiency. This study reveals the effects produced by several important parameters on engine performance, and such information is very useful for the design of new LTD Stirling engines.
    No preview · Article · Dec 2015 · Energy Conversion and Management
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    ABSTRACT: To accommodate the micro-structural effect, this work applies the dual-phase-lag (DPL) heat transfer model to explore the transient heat transfer for a moving finite medium under the effect of a time-dependent laser heat source. Laser heating is modeled as an internal heat source. A numerical scheme has been developed to overcome the mathematical difficulties in dealing with the hyperbolic heat conduction equation. Comparison between present numerical results and the analytic solutions for the non-Fourier case is made to verify the accuracy of the present numerical method. Additionally, the effects of different medium parameters, for example, moving velocity, phase lags values of the heat flux and temperature gradient, on the behavior of heat transfer have been examined. It is found that there exists clear phase shifts in the temperature distributions due to the medium moving velocity. The heat-flux phase lag tends to induce thermal waves with sharp wave-fronts in the medium, the inclusion of temperature-gradient phase lag smoothens the sharp wave-fronts by promoting conduction into the medium, resulting in non-Fourier diffusion-like conduction.
    No preview · Article · Dec 2015 · Applied Mathematical Modelling
  • Win-Jin Chang · Yu-Ching Yang · Haw-Long Lee
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    ABSTRACT: The vibration analysis of an atomic force microscope (AFM) cantilever with an arbitrary number of cracks during the nanomachining process is studied based on the modified couple stress theory. The cantilever with p cracks is divided into p + 1 segments by the cracks and a rotational spring is used to simulate each crack. An analytical expression for the vibration frequency and displacement of the cracked cantilever is derived. According to the analysis, in addition, the displacement increases with an increase in the number of cracks and crack flexibilities. For nanomachining, the displacement of the cantilever tip is related to the depth of cut. The area under the displacement-time curve implies the material removal rate. The present study is useful for the design of an AFM-based nanomachining cantilever with cracks.
    No preview · Article · Nov 2015 · Modern Physics Letters B
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    ABSTRACT: In this study, the dual-phase-lag (DPL) heat conduction model is applied to study the non-Fourier heat transfer in a thermal barrier coating (TBC) structure subjected to heat flux on the exterior of the coating. An efficient numerical scheme involving the hybrid application of the Laplace transform and control volume methods in conjunction with hyperbolic shape functions is used to solve the hyperbolic heat conduction equations in the linearized form of DPL model. The transformed nodal temperatures are inverted to the physical quantities using numerical inversion of the Laplace transform. Parametric studies of properties of the substrate and the coating on the temperature distributions in the TBC are performed. A comparison between the present study and other work in the literature using the thermal wave model is also made. The results also show that the phase lag of heat flux tends to induce thermal waves with sharp wave fronts separating heated and unheated zones in the structure, while the phase lag of temperature gradient results in non-Fourier diffusion-like conduction and smooths the sharp wave fronts by promoting conduction into the medium.
    No preview · Article · Aug 2015 · Journal of the Brazilian Society of Mechanical Sciences and Engineering
  • Songhao Wang · Syun-Cheng Lin · Yu-Ching Yang
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    ABSTRACT: The aim of this study is to solve an inverse geometry heat conduction problem (shape identification problem) to estimate the unknown geometry of the inner surface in a furnace wall which is made of functionally graded materials (FGMs). The inner surface geometry is estimated from the temperatures of measured points within the furnace wall. The inverse algorithm used in the study is based on the conjugate gradient method (CGM) and the discrepancy principle. The effect of measurement errors and measurement locations on the estimation accuracy is also investigated. Two different examples are discussed. Results show that the unknown geometry of the inner wall surface can be predicted precisely by using the present approach.
    No preview · Article · Jun 2015 · International Communications in Heat and Mass Transfer
  • Tser-Son Wu · Haw-Long Lee · Win-Jin Chang · Yu-Ching Yang
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem with the dual-phase-lag heat transfer model in estimating the unknown boundary pulse heat flux in an infinitely long solid cylinder from the temperature measurements taken within the medium. An efficient numerical scheme involving the hybrid application of the Laplace transform and control volume methods in conjunction with hyperbolic shape functions is used to solve the hyperbolic direct problem. The inverse solutions will be justified based on the numerical experiments in which two different heat flux distributions are to be determined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent pulse heat flux can be obtained for the test cases considered in this study.
    No preview · Article · Nov 2014 · International Communications in Heat and Mass Transfer
  • Haw-Long Lee · Yu-Ching Yang · Win-Jin Chang

    No preview · Article · Aug 2014 · Microscopy and Microanalysis
  • Haw-Long Lee · Yu-Ching Yang · Win-Jin Chang

    No preview · Article · Aug 2014 · Microscopy and Microanalysis
  • Win-Jin Chang · Haw-Long Lee · Yu-Ching Yang

    No preview · Article · Aug 2014 · Microscopy and Microanalysis
  • Haw-Long Lee · Wen-Lih Chen · Win-Jin Chang · Yu-Ching Yang
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown time-dependent surface heat flux in a skin tissue, which is stratified into epidermis, dermis, and subcutaneous layers, from the temperature measurements taken within the medium. Subsequently, the temperature distributions in the tissue can be calculated as well. The concept of finite heat propagation velocity is applied to the modeling of the bioheat transfer problem. The inverse solutions will be justified based on the numerical experiments in which two different heat flux distributions are to be determined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors on the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent surface heat flux can be obtained for the test cases considered in this study.
    No preview · Article · Jun 2014 · Computer Methods in Biomechanics and Biomedical Engineering
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to simultaneously estimate the unknown boundary heat flux and convective heat transfer coefficient in a curved plate cooled by an impinging slot jet from the knowledge of temperature measurements taken within the plate. Subsequently, the distributions of temperature in the plate can be determined. It is assumed that no prior information is available on the functional forms of the heat flux and convective heat transfer coefficient; hence the procedure is classified as the function estimation in inverse calculation. The temperature data obtained from the direct problem are used to simulate the temperature measurements, and the effect of the errors and locations in these measurements upon the precision of the estimated results is also considered. Results show that an excellent estimation on the heat flux and convective heat transfer coefficient and temperature distributions can be obtained for the two test cases considered in this study.
    No preview · Article · May 2014 · Numerical Heat Transfer Applications
  • Haw-Long Lee · Wen-Lih Chen · Win-Jin Chang · Yu-Ching Yang
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem with a dual-phase-lag model to estimate the unknown space- and time-dependent energy absorption rate in a thin metal film exposed to short-pulse laser heating from the temperature measurements taken within the medium. Subsequently, the temperature distributions in the metal film can be determined as well. The inverse solutions are justified based on the numerical experiments in which two different energy absorption rates are estimated. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the laser energy absorption rate can be obtained for the test cases considered in this study.
    No preview · Article · Apr 2014 · Applied Thermal Engineering
  • Wen-Lih Chen · Huann-Ming Chou · Haw-Long Lee · Yu-Ching Yang
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown space- and time-dependent base heat flux of a cylindrical pin fin from the knowledge of temperature measurements taken within the medium. The inverse solutions have been justified based on the numerical experiments in which three specific cases to determine the unknown base heat flux are examined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the space- and time-dependent base heat flux can be obtained for the test cases considered in this study.
    No preview · Article · Mar 2014 · International Communications in Heat and Mass Transfer
  • Win-Jin Chang · Haw-Long Lee · Yu-Ching Yang
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    ABSTRACT: This article theoretically analyzes the cutting depth and material removal rate of an atomic force microscope (AFM) cantilever during nanomachining. An analytical expression for the vibration frequency and displacement of the cantilever has been obtained by using the modified couple stress theory. The theory includes one additional material length scale parameter revealing the micro-scale effect. According to the analysis, the results show that the effect of size-dependent on the vibration behavior of the AFM cantilever is obvious. The maximum displacement of nanomachining with the AFM cantilever represents the cutting depth. The area under the displacement-time curve is related to the material removal rate. When the excitation frequency is closer to the nature frequency of the cantilever, a larger material removal rate is obtained.
    No preview · Article · Feb 2014 · Journal of Physics Conference Series
  • Win-Jin Chang · Yu-Ching Yang · Haw-Long Lee
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    ABSTRACT: A modified couple stress theory is used to analyse the dynamic displacement of an atomic force microscope (AFM) cantilever during nanomachining. According to the analysis, the results show that the effect of size-dependence on the vibration behaviour of the AFM cantilever is obvious. The displacement obtained based on the modified couple stress theory is lower than that based on the classical beam theory. The maximum displacement of nanomachining with the AFM cantilever represents the cutting depth. When the excitation frequency is closer to the natural frequency of the cantilever, a larger material removal rate is obtained.
    No preview · Article · Nov 2013 · Micro & Nano Letters
  • Wen-Lih Chen · Huann-Ming Chou · Yu-Ching Yang
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to estimate the unknown space-dependent thermal conductivity of a functionally graded hollow cylinder. Two different boundary condition types are discussed. The results show that boundary condition type is very crucial to the success of the inverse method. For the case studied here, the inverse method works in conjunction with heat flux specified at the inner wall and convective heat transfer condition at the outer wall but not with constant temperatures specified at both inner and outer walls. The effect of measurement error and sensor number on the estimation accuracy is also investigated. The method can be developed into an accurate, simple, and inexpensive technique for the quality control during the manufacture of functionally graded materials.
    No preview · Article · Jul 2013 · Composites Part B Engineering
  • Yu-Ching Yang · Win-Jin Chang · Haw-Long Lee
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    ABSTRACT: In the paper, the coupled equation of motion for the dynamic displacement of a C-60 fullerene moving in a (10,10) single-walled carbon nanotube (SWCNT) is derived using nonlocal Timoshenko beam theory, including the effects of rotary inertia and shear deformation. The effects of confined stiffness between the C-60 fullerene and nanotube, foundation stiffness, and nonlocal parameter on the dynamic behavior are analyzed using the Runge-Kutta Method. The numerical solution is in agreement with the analytical result for the special case. The numerical results show that increasing the confined stiffness and foundation stiffness decrease the dynamic displacement of SWCNT. However, the dynamic displacement increases with increasing the nonlocal parameter. In addition, result using the Euler beam theory and the Timoshenko beam theory are compared. It can be found that ignoring the effects of rotary inertia and shear deformation leads to an underestimation of the displacement.
    No preview · Article · Jun 2013 · Journal of Computational and Theoretical Nanoscience
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown time-dependent inner-wall heat flux of a hollow cylinder from the knowledge of temperature measurements taken within the medium. The inverse solutions have been justified through the numerical experiments in two specific cases to determine the unknown heat flux. Temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors upon the precision of the estimated results is also investigated. Results show that excellent estimation on the time-dependent heat flux can be obtained for the test cases considered in this study. Once heat flux variation is accurately estimated, the evolution of temperature, displacement, and stress distributions can be calculated in great precision.
    No preview · Article · May 2013 · International Journal of Heat and Mass Transfer
  • Haw-Long Lee · Win-Jin Chang · Shang-Chen Wu · Yu-Ching Yang
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    ABSTRACT: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown time-dependent base heat flux of an annular fin from the knowledge of temperature measurements taken within the fin. The inverse solutions will be justified based on the numerical experiments in which two specific cases to determine the unknown base heat flux are examined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent base heat flux can be obtained for the test cases considered in this study. (c) 2013 Elsevier Ltd. All rights reserved.
    No preview · Article · May 2013 · International Communications in Heat and Mass Transfer
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    ABSTRACT: In this study, the dual phase lag (DPL) heat transfer model is applied to investigate the transient heat transfer in a thin metal film exposed to short-pulse laser heating. An efficient numerical scheme involving the hybrid application of the Laplace transform and control volume methods in conjunction with hyperbolic shape functions is used to solve the hyperbolic heat conduction equation in the linearized form of DPL model. The transformed nodal temperatures are inverted to the physical quantities by using numerical inversion of the Laplace transform. Comparison between the numerical results and the analytic solution for a short-pulse laser heating with the Gaussian temporal profile evidences the accuracy of the present numerical results. Effect of different phase lags values of the heat flux and the temperature gradient on the behavior of heat transfer is also investigated. The results show that the phase lag of the heat flux tends to induce thermal waves with sharp wave-fronts separating heated and unheated zones in the metal film, while the phase lag of the temperature gradient destroys the waveforms and increases the thermally disturbed zone.
    No preview · Article · Apr 2013 · Applied Thermal Engineering