Applied Voltage Ratio Research Articles

Nonlinear electromechanical bending of bi-modular piezoelectric laminated beams

In this paper, the nonlinear electromechanical bending of a bi-modular piezoelectric laminated beam is studied based on the principle of minimum potential energy and the Adomian decomposition method. The different tensile-compressive Young’s modulus of the core and piezoelectric layers, and the different tensile-compressive piezoelectric coefficients are considered. The electromechanical governing equations and related boundary conditions are obtained by using the principle of minimum potential energy. The deflection, neutral layer and interlaminar stresses of the beam are solved by the Adomian decomposition method and the iterative method, and verified by the finite element model and Galerkin's method. Results show that the applied voltage and the bi-modular characteristics affect the position of the neutral layer and the interlaminar stresses. Compared with the bi-modular properties of the core layer, the influences of the bi-modular properties of the piezoelectric layer on the neutral layer are relatively unobvious. In addition, the interlaminar stresses between the piezoelectric layer and core layer can be increased or decreased, depending on the relative magnitude of the applied voltage ratio and the bi-modular ratio. The results obtained are helpful for the analysis of the electromechanical coupling mechanism and design of piezoelectric composites and structures with bi-modular characteristics.

Standards for the characterization of high intensity nonlinear ultrasound fields and power generated by therapeutic systems

The emerging field of high intensity therapeutic ultrasound (HITU) presents multiple challenges. Early attempts to characterize high pressure fields fried both hydrophones and force balances originally designed for diagnostic ultrasound. Working Group 6 of International Electrotechnical Commission (IEC) Technical Committee 87 initially sought out methods employing current validated measurement technology. Technical Specification 62256 focused on two field characterization approaches for water. The first was using conventional calibrated hydrophones in the linear range and a scaling up of field pressure values by the applied voltage ratio. The other method involved a finely sampled 2D scan near the transducer face as input data to linear projection algorithms to recreate the entire pressure field. This computed field could then be scaled up the previously described voltage ratio. An additional benefit of the second approach was that the same scan data could be used to predict pressure and thermal levels in simulated tissue media representing clinical scenarios. Technical standard 62255 described HITU power measurements with scaling and a novel buoyancy method. Current efforts are directed at the direct measurement of high pressure fields with new technologies and the data-based nonlinear simulation of fields and bioeffect end points in water and tissues.

Evaluating and improving color washout of vertical aligned liquid crystal display

We demonstrated an optimized 8-domain vertical aligned (VA) liquid crystal display (LCD) by minimizing its color washout. The index G is adopted to analyze the degree of color washout through simulation. By using linearly and circularly polarized incident light, the optimized regime of the area and applied voltage ratios of sub-pixels is obtained. In the experiments with the circularly polarized light, the images are sensuously improved in a coupled capacity type LCD by applying the simulated applied voltage ratio of two sub-pixels.

The Optimal Control of Geometry and Voltage Parameters on Electrokinetic Transport to Avoid Sample Leakage in Microfluidic Chips

Computer simulation is used to investigate sample transport phenomena of cross microfluidic chips. In this study, Kirchhoff circuit theory is employed to calculate the electric field strength and approximate electroosmotic flow. It is apparent from the results that both the simulation and the theoretical data show similar trends in the electroosmosis of cross microchips. The main target in this study is to summarize the optimal controlling parameter values for avoiding sample leakage in the transport process. The effects of the applied voltage ratio, the geometry ratio and the zeta potential were simulated using a computational fluid dynamics and multiphysics solver software package (CFD-ACE+). Under our designed conditions, two major conclusions were reached: (1) for high-voltage ratios, the sample leakage can be avoided as the geometry ratio is large enough at 0.5 or greater, and (2) for small geometries, maintaining a smaller voltage ratio, 0.3 or less, is essential for avoiding sample leakage. The key is to govern the sample velocity in the upstream faster than that in the downstream. Although real experimental conditions can be further fine tuned under microscopy monitoring, these conclusions are helpful to design the proper channel geometry and set up suitable voltage parameters to avoid sample leakages in one cross-channel chip.

DESIGN OF AN ELECTROSTATIC IMMERSION LENS USING THE CHARGE DENSITY METHOD

A computational investigation has been carried out in the field of non-relativistic chargedparticle optics using the charge density method as a boundary value problem with the aid of a personal computer under the absence of space-charge effects. This work has been concentrated on designing a two-electrode electrostatic immersion lens whose electrodes are cylindrical in shape separated by an air gap. The variable parameters of the two electrodes are the applied voltage ratio and the radii of the two cylindrical electrodes. The axial potential distribution of an electrostatic immersion lens has been computed by taking into consideration the distribution of the charge density due to the voltages applied on the two cylindrical electrodes. Potentials have been determined anywhere in space by using Coulomb s law. The optical properties of the immersion lens have been investigated under finite and zero magnification conditions.

Effect of Adding Coils to Dual-Input Twin-T Quartz Circuit

We derived an exact frequency equation and examined the behaviors of the effective Q factor and effective resistance for the case in which coils are added to a dual-input twin-T quartz circuit whose null frequency can be changed by adjusting the applied voltage ratio. In the circuit construction, two sets of T-circuits are used in which a quartz resonator is placed in the shunt branch and the output of each circuit settles in one terminal. The changeable frequency range exceeds the limit determined by the electromechanical coupling factor of the piezoelectric resonator used without any decrease in the effective Q factor and any increase in the effective resistance, within the entire changeable-frequency range when the resonance frequency of a coil and a capacitor in the series branch of the twin-T circuit is set to almost the same value as the resonance frequency of the resonators used in the twin-T circuit. The derived null-frequency equation and effective Q factor agreed with the experimental results for AT-cut quartz resonators.

Transmission performance of 10-Gb/s optical duobinary transmission systems considering adjustable chirp of nonideal LiNbO/sub 3/ Mach-Zehnder modulators due to applied voltage ratio and filter bandwidth

We investigate interplay between the residual and applied chirp of optical duobinary modulated signals in order to improve transmission performance. To find the best performance for 10-Gb/s optical duobinary transmission systems, we consider the residual chirp accompanying from the finite extinction ratio, the applied chirp adjusted by the applied voltage ratio (the chirp parameter) between two electrodes of LiNbO/sub 3/ modulators, and the bandwidth of electrical low-pass filters used in duobinary transmitters. The simulation results suggest that nearly zero chirp during the mark ('1') period and large peak chirp at the middle of the space ('0') provide the best transmission performance. This zero chirp around marks and high peak chirp at the middle of each space can be controlled by the applied voltage ratio between two electrodes of modulator and the filter bandwidth, respectively.