Papers by Jik-chang Leong
E3S Web of Conferences
The National Pingtung University of Science and Technology was established as an agricultural ins... more The National Pingtung University of Science and Technology was established as an agricultural institution in 1924. Since then, this educational institution has been one of the key role players in developing the agricultural advancement in Taiwan. For years, the university has seriously planned and carried out projects that strengthen her identity, “being green”. Under the scope of university’s uniqueness and responsibility, measures taken in the university directly involves administrative affairs, such as teaching, research, university development, student welfare, etc. As a matter of fact, initiating new policies, measures, and projects is only the beginning of everything. Without proper planning, enforcement, and funding, any one of these policies, measures, and projects may end up going nowhere. In other words, sustainability is absolutely the most critical element that dictates the success of the policies, measures, and projects. This sustainability covers financial allocation, ...
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Applied Mechanics and Materials, Dec 12, 2013
In this study, an elastic-plastic finite element model is used to simulate the thermal affected b... more In this study, an elastic-plastic finite element model is used to simulate the thermal affected bone (TAZ) during bone drilling process under the condition of constant applied drilling force. Various drilling times and measurement depths are investigated to explore the size of TAZ and stress distributions within the bone. The results indicate that the maximum TAZ occurs at the interface of cortical bone and cancellous bone. The maximum diameter of TAZ is found to be 3.5 mm in this study.
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Advanced Materials Research, 2011
This work employs FDS to simulate the heating process of a tunnel-type dryer and visualizes the c... more This work employs FDS to simulate the heating process of a tunnel-type dryer and visualizes the computational results using Smokeview. The inappropriate design of a tunnel-type dryer in a factory has motivated this work. This poorly designed dryer not only has caused terrible fuel consumption but also produced parts some of which are under- or over-cooked. These are caused by the terribly uneven temperature distribution within the dryer. In order to improve the evenness of temperature distribution, this work simulates and investigates the effects of various ventilation schemes. Based on the results, it is found that the hot air intake vent should be placed at the bottom whereas the cold air outtake vent at the top. The flow rate through the intake vents does not have a very significant effect on the temperature distribution after 40 s.
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Journal of Applied Mathematics, 2014
The steady-state problem of a magnetic fluid filling a porous annulus between two cylindrical wal... more The steady-state problem of a magnetic fluid filling a porous annulus between two cylindrical walls under the influence of a nonuniform radially outward magnetic field has been investigated. The cylindrical walls are either electrically perfectly insulated or electrically perfectly conducting. The permeability of the porous annulus increases with its radial location. The governing partial differential equations were derived carefully and closed form solutions for the profiles of the velocity component and the induced magnetic component were obtained. The effect of the strength of the externally applied magnetic field, the permeability of the porous annulus, and the conductivity of the cylindrical walls were examined through the angular velocity components, as well as the induced magnetic field.
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Applied Mathematical Modelling, 2015
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Heat Transfer: Volume 1, 2003
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Key Engineering Materials, 2011
ABSTRACT This paper uses a femtosecond laser scriber to perform the direct-writing ablation of gl... more ABSTRACT This paper uses a femtosecond laser scriber to perform the direct-writing ablation of glass substrate for the development of microfluidic biochips. The surface quality of the ablated microchannels was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurement techniques. The developed femtosecond laser ablation system provides a versatile and economic approach for the fabrication of glass-base microfluidic chips. In the laser writing process, the desired microfluidic patterns are designed using commercial computer software and are then transferred to the laser scriber to ablate the trenches. The results show that a very smooth channel wall can be achieved through the annealing process at the temperature 650°C and 5 hours. The system provides an economic and powerful means of rapid glass microfluidic biochips development.
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Journal of Porous Media, 2013
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Journal of Heat Transfer, 2001
The feasibility of using a lumped system approach in the heat transfer analysis of a layered poro... more The feasibility of using a lumped system approach in the heat transfer analysis of a layered porous cavity is numerically investigated in this paper. Two layered cavities are considered; in one case the sublayers are perpendicular to the imposed temperature gradient while in the other case they are parallel to the imposed temperature gradient. Numerical calculations have covered a wide range of parameters (i.e., 10⩽Ra1⩽1000,0.01⩽K1/K2⩽100, and L1/LH1/H=0.25, 0.5 and 0.75). The results are presented in term of the effective Rayleigh number which is defined based on the effective permeability. Two averaging techniques are used for the evaluation of the effective permeability; one is arithmetic average and the other is harmonic average. The results show that the lumped system approach can provide a fairly accurate prediction in heat transfer if the permeability is correctly characterized. Also found is that the effective permeability of a layered porous cavity is strongly dependent on ...
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Japanese Journal of Applied Physics, 2007
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International Journal of Heat and Mass Transfer, 2006
ABSTRACT Analytical solutions obtained through perturbation method and Fourier transform are pres... more ABSTRACT Analytical solutions obtained through perturbation method and Fourier transform are presented for natural convection in concentric cylinders with a porous sleeve. The porous sleeve is press-fitted to the inner surface of the outer cylinder. Both the inner and outer cylinders are kept at constant temperatures with the inner surface at a slightly higher temperature than that of the outer. The main objective of the present study is to investigate the buoyancy-induced flow as affected by the presence of the porous layer. A parametric study has been performed to investigate the effects of Rayleigh number, Darcy number, porous sleeve thickness, and relative thermal conductivity on the heat transfer results.
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Applied Mechanics and Materials, 2013
This work simulates the steady-state flow field in a magnetohydrodynamic journal bearing. A unifo... more This work simulates the steady-state flow field in a magnetohydrodynamic journal bearing. A uniform magnetic field is applied in the axial direction across the bearing. Current results indicate that a crescent-shape secondary flow will develop at E = 0.8. The velocity profiles at the location of the minimum and maximum film thickness are almost independent of the strength of the external magnetic field unless the eccentricity ratio is relatively small and magnetic field is strong. There exists an eccentric dependent threshold Ha beyond which the shear stress on the journal increases with Ha while that on the bearing decreases.
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Applied Mechanics and Materials, 2013
This work obtained an analytical solution for a steady cylindrical MHD Couette flow in a porous m... more This work obtained an analytical solution for a steady cylindrical MHD Couette flow in a porous medium between two perfectly conducting rotating cylinders under the influence of a non-uniform radial magnetic field. Since part of the analytical solution is expressed in terms of the integral of the Modified Bessel function of the first and second kinds of variable order, numerical integration was performed. Current results indicate that the flow may become more uniform when the strength of the external magnetic field is increased. The magnetic fluid tends to slow down if the permeability of the porous medium decreases. If the porous annulus is thick, the momentum of the flow is more difficult to propagate from the outer cylinder into the inner part of the annulus. If both the inner and outer cylinders rotate, the shear effect the inner cylinder imposes is only relatively influential in the region close to it. A decrease in Da no less than 10-2 may increase the amount of magnetic field...
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Applied Mechanics and Materials, 2013
In this study, an elastic-plastic finite element model is used to simulate the thermal affected b... more In this study, an elastic-plastic finite element model is used to simulate the thermal affected bone (TAZ) during bone drilling process under the condition of constant applied drilling force. Various drilling times and measurement depths are investigated to explore the size of TAZ and stress distributions within the bone. The results indicate that the maximum TAZ occurs at the interface of cortical bone and cancellous bone. The maximum diameter of TAZ is found to be 3.5 mm in this study.
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Applied Mathematical Modelling, 2013
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Applied Mathematical Modelling, 2011
... Although their JASMINE results only agreed quite satisfactorily with the measurements of loca... more ... Although their JASMINE results only agreed quite satisfactorily with the measurements of local temperature, CO 2 , O 2 , and fuel concentration recorded at ... ideal gases in the presence of energy and mass sources can be given in the forms of continuity, Navier–Stokes, and heat ...
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International Communications in Heat and Mass Transfer, 2005
... For mixed convection in a lid-driven cavity, the stability of convective flow has been analyz... more ... For mixed convection in a lid-driven cavity, the stability of convective flow has been analyzed by Mohamad and Viskanta [1]. Based on their analysis, there exist two critical wave numbers depending on whether the dominant driving force is buoyancy or shear. ...
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Key Engineering Materials, 2011
ABSTRACT This paper presents a novel simple Y-type micromixer based on stable water suspensions o... more ABSTRACT This paper presents a novel simple Y-type micromixer based on stable water suspensions of magnetic nanoparticles (i.e. ferrofluids). An electromagnet driven by an AC power source is used to induce transient interactive flows between a ferrofluid and DI water. The alternative magnetic field causes the ferrofluid to expand significantly and uniformly toward DI water associated with a great number of extremely fine fingering structures on the interface in the microchannel. Different magnetic strengths of the electromagnet were applied by adjusting the magnitude of AC supplied power at frequency of 45 Hz. The results show, due to the magnetic fields, two fluids mix with each other efficiently (mixing ratio can be as high as 95%). When the magnetic field is high enough, the labyrinthine fingering instability take place. This phenomenon is favorable for the fluid mixing. In addition, the increasing magnetic field enhances the efficiency of the mixing apparently.
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ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer, Volume 1, 2009
ABSTRACT In this paper, a microflow cytometer for particles/cells passive focusing, fluorescence ... more ABSTRACT In this paper, a microflow cytometer for particles/cells passive focusing, fluorescence detection, and sizing is demonstrated with a convergent geometry of 50 μm detection gate channel and a pair of external optic fibers on poly-dimethylsiloxane (PDMS) microchip. A laser (635 nm) is used for fluorescent excitation. The amplitudes of the backward fluorescence signal and forward scattered light signal indicate the corresponding fluorescent intensity and size of the detected fluorescent particles and labeled white blood cells, respectively. In the experiment, the uniform fluorescent light intensity was measured by focusing the fluorescent particles in a 200×50×30μm detection gate channel. However, the emitted fluorescence and forward scattered light intensity of different size particles/cells are also measured simultaneously by external optic fibers.
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Papers by Jik-chang Leong