Power Conservative Thevenin-Norton and Norton-Thevenin Transformations

A power conservative Thevenin-Norton and Norton-Thevenin transformations are proposed in this letter. The transformations introduce a voltage and a current generators for which parameters depend on the loading impedance value.

Dynamic analysis of submerged microscale plates: the effects of acoustic radiation and viscous dissipation

The aim of this paper is to study the dynamic characteristics of micromechanical rectangular plates used as sensing elements in a viscous compressible fluid. A novel modelling procedure for the plate–fluid interaction problem is developed on the basis of linearized Navier–Stokes equations and no-slip conditions. Analytical expression for the fluid-loading impedance is obtained using a double Fourier transform approach. This modelling work provides us an analytical means to study the effects of inertial loading, acoustic radiation and viscous dissipation of the fluid acting on the vibration of microplates. The numerical simulation is conducted on microplates with different boundary conditions and fluids with different viscosities. The simulation results reveal that the acoustic radiation dominates the damping mechanism of the submerged microplates. It is also proved that microplates offer better sensitivities (Q-factors) than the conventional beam type microcantilevers being mass sensing platforms in a viscous fluid environment. The frequency response features of microplates under highly viscous fluid loading are studied using the present model. The dynamics of the microplates with all edges clamped are less influenced by the highly viscous dissipation of the fluid than the microplates with other types of boundary conditions.

A High-PSRR Low Dropout Regulator for LNB Using the First-Stage Reference-Included Coarse-Filtering Technique

A high-PSRR low dropout regulator using the first-stage reference-included coarse-filtering technique is presented, for the reduced output ripple of the low noise block (LNB) power supply in the satellite set-top box. Compared with the conventional system, the regulator with the technique is characterized by the two successive negative feedback loops, so as to alleviate the output ripple of the power supply caused by the preceding DC–DC converter's modulation signal. With the technique, the ripple near to the frequency of the LNB supply voltage tuning signal (22 kHz) can be significantly alleviated. To further enhance the PSRR performance without the reference-by-pass capacitor, the bipolar-loop buffer amplifier and the reference-included coarse-filtering regulator are proposed. The circuits are extracted from the LDO layout and simulated with a 0.35 μm BCD process in Cadence. With the typical 16.3 V input supply voltage and loading current 100 mA, the line regulation corresponding to the DC supply voltage is achieved at -72 dB; the PSRR performance of the supply voltage ripple up to the frequency (100 kHz) is better than -70 dB; Moreover, the quiescent current without the loading impedance is less than 153 μA.

Investigations on Pulsation-Reduction Characteristics of Hydraulic Attenuator Based on Experimental Method

Three types of hydraulic attenuators are designed and investigated to study the pulsation-reduction characteristics in hydraulic system. Attenuator test rig is established to obtain pressure signals in time domain and frequency domain (5 Hz to 1200 Hz), respectively. Influences of changing source impedance and loading impedance to the attenuation rate (Ka) and pressure ratio of inlet and outlet (Pio) are discussed. Experiment results show that expansion chamber attenuator (ECA) is a better choice for a wide frequency range of pulsation reduction. Two types of perforated tube attenuators (PTA) have better performances in some certain frequency range. The performance of PTA can have further improvements by designing the damping holes diameters. The performance of the attenuator is mainly influenced by pump character and rotating speed. The system loading has limited influence on the performance comparing to source impedance.

Analysis of lung parenchyma as a parametric porous medium

The dynamic behavior of the lung in health and disease depends on its viscoelastic properties. To better understand these properties, several mathematical models have been utilized by many investigators. In the present work, we present a new approach that characterizes the dynamics of gas flow into a viscoelastic porous medium that models the lung structure. This problem is considered in terms of the lung input impedance on a macro level and parenchymal tissue impedance on the level of an alveolar wall. We start from a basic theoretical analysis in which macroscopic tissue deformations are represented in accordance with the linearized Navier-Stokes equations. This approach has strong theoretical underpinnings in other situations but has not been applied to analyze the impedance of the inflated lung. Our analysis provides a theoretical basis for analyzing the interaction between flow into the lungs as a biophysical diffusion process and parenchymal viscoelasticity described phenomenologically, within the frameworks of standard viscoelasticity and structural damping. This lung impedance incorporates parameters of porosity, permeability, and viscoelasticity on micro and macro levels of parenchymal tissue. The analysis shows the theoretical basis of the transformation from the impedance of alveolar walls or isolated tissue strips to that of the intact parenchyma. We also show how the loading impedance at the lung boundary may have a significant impact on the dynamic behavior of whole lung viscoelasticity. Our analysis may be useful in directing specific tests of different models and for analyzing experimental measurements of viscoelastic parameters of lung material under normal and pathological conditions.