Showing papers by "Ming-Jyi Jang published in 2007"

Bifurcation and nonlinear dynamic analysis of a flexible rotor supported by relative short gas journal bearings

Abstract: This paper studies the bifurcation and nonlinear behaviors of a flexible rotor supported by relative short gas film bearings. A time-dependent mathematical model for gas journal bearings is presented. The finite difference method with successive over relation method is employed to solve the Reynolds’ equation. The system state trajectory, Poincare maps, power spectra, and bifurcation diagrams are used to analyze the dynamic behavior of the rotor and journal center in the horizontal and vertical directions under different operating conditions. The analysis reveals a complex dynamic behavior comprising periodic and subharmonic response of the rotor and journal center. This paper shows how the dynamic behavior of this type of system varies with changes in rotor mass and rotational velocity. The results of this study contribute to a further understanding of the nonlinear dynamics of gas film rotor-bearing systems.

An enhanced common path interference optic measurement system for refractive indices and thickness

Abstract: This study proposes a common path interference optical system for the measurement of refractive indices and thickness of uniaxial crystal material The measurement system comprises an accurate Mach–Zehnder laser interferometer, a single-axis rotary stepping motor, and a computer The laser interferometer is composed of a single-frequency He–Ne laser, two-beam splitters and two reflectors The Mach–Zehnder laser interferometer measures the optical length difference by using its linear measurement accuracy The proposed solution procedure enables both the refractive indices and the thickness of the optical waveplate to be obtained The proposed design differs from conventional designs in that it does not use a heterodyne modulator with a lock-in technique It is shown that the refractive indices and thickness of the tested optical elements can be measured rapidly and accurately

A Study of Manufacturing Micro-Nano Particles of Green Tea by Rapid Expansion of Supercritical Solutions Method

Abstract: One of the most important areas of research in the material science field is the manufacture of fine particles. Small particles have an improved dissolution rate and are therefore more easily absorbed into biological in-vivo tissue or the skin surface layer. This study investigates the effects of temperature and pressure on the particle size of green tea powder manufactured via the rapid expansion supercritical solution method. The dissolution rate of the green tea extract in the supercritical carbon dioxide solution is enhanced via the addition of a modest quantity of ethyl alcohol. The size of the particles produced under different temperature and pressure conditions is analyzed using a laser particle size analyzer. The results show that under constant temperature conditions, a higher pressure causes the particle size decreased. Meanwhile, for a constant pressure, both the particle size and the volume of powder produced reduce as the temperature is increased. Overall, the results show that a minimum particle size of 58 nm is obtained at a pressure of 2000 psi and a temperature of 45°C.Copyright © 2007 by ASME

Determining the Thickness and Refractive Index of a Birefringence by Using an Improved Accurate Measurement System

Abstract: This paper presents a high-precision, non-destructive measurement system for determining the thickness and refractive indices of birefringent optical wave plates. Significantly, the proposed method enables the two refractive indices of the optical sample to be measured simultaneously. The performance of the proposed system is verified using a commercial quartz optical wave plate with known refractive indices of 1.5518 e n = and 1.5427 o n = , respectively, and a thickness of 452.1428 μm. The experimentally determined values of the refractive indices are found to be 1.55190 e n = and 1.54281 o n = , respectively, while the thickness is found to be 452.189 μm, corresponding to an experimental error of approximately 0.046 μm. The measurement resolution of the proposed system exceeds that of the interferometer hardware itself and provides a simple yet highly accurate means of measuring the principal optical parameters of birefringent glass wave plates.

Qualitative Analysis of Surface Energy Using Atomic Force Microscopy Approach

Abstract: This paper performs a qualitative analysis of the surface energy of copper (Cu), aluminum (Al), carbon steel (S45C) and alloy steel (SKD11) by analyzing the variation in the resonant frequency of the cantilever beam (Si3N4 ) of an atomic force microscope following repeated contacts with the specimen surface. In a pure material (Cu, Al and S45C), it is found that the adhesive mass on the tip of the cantilever beam saturates following repeated contacts with the surface. Since the adhesive mass is determined by the difference between the surface energy of the cantilever beam material and that of the test material, the surface energies of the cantilever beam and the pure materials can be qualitatively compared. However, for the alloy steel (SKD11), the adhesive mass varies after each contact and hence no conclusions can be made regarding its surface energy. The present results indicate that the surface energies of the cantilever beam and the pure materials can be ranked as follows: Cu>Si3N4 >Al>S45C. It has been shown that the surface energy of a rigid material (S45C) is less than that of a soft material (Cu).

Quasi-periodic and subharmonic analysis of a spherical aerodynamic bearing system

Abstract: This paper employs a hybrid numerical method combining the differential transformation method and the finite difference method to study the nonlinear dynamic behavior of a flexible rotor supported by a spherical aerodynamic journal bearing system. The analytical results reveal a complex dynamic behavior comprising periodic, sub-harmonic, and quasi-periodic responses of the rotor center and the journal center. Furthermore, the results reveal the changes which take place in the dynamic behavior of the bearing system as the rotor mass and rotational velocity are increased. The proposed method provides an effective means of gaining insights into the nonlinear dynamics of spherical gas film rotor-bearing systems.

Effect of the Adhesive Mass at the Cantilever Beam Tip Position

Abstract: This study employs finite element simulations to investigate the relationship between the equivalent mass and the real mass of end masses adhered to the tip of the cantilever beam of an atomic force microscope. The equivalent mass was determined by analyzing the variation in the resonant frequency of the cantilever beam caused by the addition of the end mass. The analysis considered five different adhesive mass materials, namely copper, aluminum, S45C steel, titanium alloy and magnesium alloy. Furthermore, the analysis also considerd the effect of the position of the adhesive mass on its equivalent mass value. The numerical results indicate that the equivalent adhesive mass is less than the real adhesive mass. The ratio of the equivalent adhesive mass to the real adhesive mass is approximately constant for a given adhesive position and adhesive material and has a value of approximately 0.6361 for a high-density material. Finally, the results show that an offset of the adhesive mass from the tip position causes a slight change in the value of the equivalent mass to real mass ratio.

Nonlinear Analysis of Large Deflections of Isotropic Rectangular Clamped Plate using Hybrid Method

Abstract: This paper analyses the large deflections of an isotropic rectangular clamped thin plate A hybrid method which combines the finite difference method and the differential transformation method is employed to reduce the partial differential equations describing the large deflections of the plate to a set of algebraic equations The simulation results indicate that significant errors are present in the numerical results obtained for the deflections of the plate in the transient state when a step force is applied The magnitude of the numerical error is found to reduce, and the deflection of the plate to converge, as the number of sub-domains considered in the solution procedure increases The load-deflection curves converge as the aspect ratio of the plate is reduced The current modeling results confirm the applicability of the proposed hybrid method to the solution of the large deflections of a rectangular isotropic clamped plate

An Enhanced Common Path Interference Measurement Method for Optical Refractive Indices

Abstract: This study presents an enhanced common path interference system designed to measure the refractive index of crystal optical components. The proposed system is based on the classic Michelson interferometer and comprises a frequency stabilized helium-neon (He-Ne) laser, a beam splitter, a fixed mirror, an adjustable mirror, and a light detection system. The waveplate of interest was clamped to a rotatory motor and positioned between the beam splitter and the fixed mirror. The refractive index of the waveplate was then derived from the change in rotational angle of the waveplate as it moved from one position of minimum interference to the next. The measurement system proposed in this study is simple in construction, straightforward in operation, and robust to the effects of experimental noise. Furthermore, the system is a non-contact measurement system, and hence does not damage the optical component of interest. The experimental results are found to be in good agreement with the theoretical results. Therefore, the proposed system provides a viable means for the rapid experimental evaluation of the optical characteristics of quartz components.

Design and Manufacture of Novel MEMS-based Dielectrophoretic Biochip

Abstract: This study designs and fabricates a novel biochip for electroporation applications. Dielectrophoretic forces are used to separate the host cells from the sample stream. The cells are then absorbed in the reaction region of the biochip and subjected to a high-intensity electrical pulse. In the resulting electroporation effect, the outer membrane of the cell is temporarily ruptured, allowing the introduction of a foreign gene, a drug, and so on, into the host cell. The biochip is fabricated using conventional micro-electro mechanical systems (MEMS) techniques and features a unique 3D stacked electrode arrangement. Using water to simulate a reaction medium, the distribution and formation of bubbles on the surfaces of electrodes of different widths are observed following the application of an electro-impulse and during a dielectrophoretic test, respectively. In general, the biochip presented in this study has the advantages of a reduced sample and reagent consumption, an enhanced detection efficiency, improved sensitivity and reliability, and a greater protection of the cells from the effects of thermal heating and environmental contamination.

Design and Fabrication of In-Vitro Electroporation Chip for Gene Transfection

Abstract: This paper presents the design and fabrication of an array-type bio-chip with a novel 3D electrode structure for gene delivery. The bio-chip enables the processes of gene delivery and cell culturing to be performed in a single device. The genes are introduced into the host cell via a process of electroporation induced by the application of a transient electric field to the electrodes of the bio-chip. The 3D electrode structure for gene delivery can cause the position of the positive and negative electrode is different. When the position of the positive and negative electrode is different, the electroporation and electrophoretic forces are applied at the same time. The bio-chip comprises three major components, namely a reaction chamber, a cell accommodating structure, and a 3D interdigitated electrode arrangement. The chip is fabricated using conventional micro-electro mechanical systems (MEMS) techniques. The study establishes two different types of foundation plates the array type gene delivery to breed the chip, and use electricity pulse electric field test, may effectively improve strengthens the electric field power, enhances the chip transformation to breed the function. This result indicates that the efficiency of 3D structure bio-chip is high than the plane structure by using water testing.