Predicting the engineering and transport properties of soils using fractal equivalent circuit model: Laboratory experiments

Geophysics ◽  
2011 ◽  
Vol 76 (5) ◽  
pp. F329-F338 ◽  
Author(s):  
Fred Kofi Boadu
Keyword(s):  
Hydraulic Conductivity ◽  
Transport Properties ◽  
Equivalent Circuit ◽  
Void Ratio ◽  
Equivalent Circuit Model ◽  
Circuit Model ◽  
Dry Density ◽  
Electrical Measurements ◽  
Intergranular Void Ratio ◽  
Intergranular Void

Frequency-dependent electrical measurements of soils contain useful information about their texture and structure that can be linked to their engineering and transport properties. We performed frequency-dependent electrical measurements on 29 natural soils with wide variability in physical and textural properties in a laboratory environment at a constant stress level and in the frequency range of 0.01 Hz–10 kHz. The engineering and hydraulic properties of these soils, that is, the hydraulic conductivity [Formula: see text], void ratio [Formula: see text], fines content [Formula: see text], intergranular void ratio [Formula: see text] and the dry density [Formula: see text] are concurrently measured. The electrical behaviors of the soils are modeled with an equivalent circuit model, which are described by six circuit parameters. Relationships between the circuit parameters and the soil properties (geotechnical engineering and hydraulic) are investigated. Crossplots of frequency exponent [Formula: see text] and resistivity [Formula: see text] and that of [Formula: see text] and grain percent resistivity [Formula: see text] clusters soils with high and low values of hydraulic conductivity, whereas crossplots of relaxation time [Formula: see text] and [Formula: see text] clusters soils with high and low intergranular void ratio. Regression models are developed using the parameters [Formula: see text] and [Formula: see text] to predict the hydraulic conductivity with [Formula: see text]; [Formula: see text] and [Formula: see text] to predict the intergranular void ratio with [Formula: see text] and [Formula: see text] and [Formula: see text] to predict the dry density with [Formula: see text].

scholarly journals Gallium Nitride Electrical Characteristics Extraction and Uniformity Sorting

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Shyr-Long Jeng ◽  
Chih-Chiang Wu ◽  
Wei-Hua Chieng
Keyword(s):  
Gallium Nitride ◽  
Equivalent Circuit ◽  
Field Effect Transistors ◽  
Equivalent Circuit Model ◽  
Circuit Model ◽  
Electrical Characteristics ◽  
Electrical Measurements ◽  
Power Transistors ◽  
High Power Output ◽  
The Difference

This study examined the output electrical characteristics—current-voltage (I-V) output, threshold voltage, and parasitic capacitance—of novel gallium nitride (GaN) power transistors. Experimental measurements revealed that both enhanced- and depletion-mode GaN field-effect transistors (FETs) containing different components of identical specifications yielded varied turn-off impedance; hence, the FET quality was inconsistent. Establishing standardized electrical measurements can provide necessary information for designers, and measuring transistor electrical characteristics establishes its equivalent-circuit model for circuit simulations. Moreover, high power output requires multiple parallel power transistors, and sorting the difference between similar electrical characteristics is critical in a power system. An isolated gate driver detection method is proposed for sorting the uniformity from the option of the turn-off characteristic. In addition, an equivalent-circuit model for GaN FETs is established on the basis of the measured electrical characteristics and verified experimentally.

Assessing Relations Between Electrical and Geotechnical Properties of Sand-Clay Mixtures Using Jonscher Fractal Power Law Model

2019 ◽  
Vol 24 (1) ◽  
pp. 77-85
Author(s):  
Fred Kofi Boadu ◽  
Samuel Ampadu
Keyword(s):  
Water Content ◽  
Effective Stress ◽  
Power Law ◽  
Void Ratio ◽  
Geotechnical Properties ◽  
Dry Density ◽  
Power Law Model ◽  
Stress Levels ◽  
Intergranular Void Ratio ◽  
Intergranular Void

The geotechnical properties of unconsolidated geo-materials such as soils are influenced by modifications of their micro-structure, texture, mineralogy, water content and imposed effective stress levels. Fundamental relations between the characteristic electrical parameters describing the electrical responses soils based on a fractal power law model with scaling properties, and parameters influencing their geotechnical behavior are investigated. Low frequency electrical conductivity laboratory measurements were performed on sand and clay mixtures subjected to varying effective stress levels with concurrent measurements of their geotechnical properties. The conductivity spectra of the mixtures were described using a Jonscher fractal power law model characterized with three characteristic parameters, the dc conductivity ( σ dc ), the characteristic frequency ( f c ) and an exponent ( n). Changes in effective stress, water content, clay content, and other engineering properties of the mixture such as dry density, porosity, pore size and intergranular void ratio are discussed with respect to changes in the electrical parameters. The dc conductivity and characteristic frequency decrease with an increase in effective stress levels. The exponent, however, has the opposite behavior and increases with an increase in effective stress. As the water content increases, σ dc and f c increase while n decreases for all mixtures. With increasing stress levels, the average pore size of the mixtures decreases which results in a decrease in σ dc and f c but an increase in the values of the exponent. An increase in dry density of the mixtures leads to a decrease in σ dc and f c whilst n increases. Both σ dc and f c increase with increase in the intergranular void ratio of the mixture whilst the exponent values decrease with an increase in the intergranular void ratio. This study serves as a contribution to our quest in utilizing electrical geophysical methods, to assess and monitor non-invasively, the geotechnical properties of the subsurface in a less expensive and faster manner.

An Equivalent Circuit Model for Vertical Comb Drive MEMS Optical Scanner Controlled by Pulse Width Modulation

2012 ◽  
Vol 132 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Satoshi Maruyama ◽  
Muneki Nakada ◽  
Makoto Mita ◽  
Takuya Takahashi ◽  
Hiroyuki Fujita ◽  
...  
Keyword(s):  
Equivalent Circuit ◽  
Pulse Width ◽  
Pulse Width Modulation ◽  
Equivalent Circuit Model ◽  
Circuit Model ◽  
Comb Drive ◽  
Optical Scanner

scholarly journals A Novel, Improved Equivalent Circuit Model for Double-Sided Linear Induction Motor

Electronics ◽  
2021 ◽  
Vol 10 (14) ◽  
pp. 1644
Author(s):  
Qian Zhang ◽  
Huijuan Liu ◽  
Tengfei Song ◽  
Zhenyang Zhang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Equivalent Circuit ◽  
Skin Effect ◽  
Equivalent Circuit Model ◽  
Element Model ◽  
Circuit Model ◽  
End Effects ◽  
3D Finite Element ◽  
Linear Induction

A novel, improved equivalent circuit model of double-sided linear induction motors (DLIMs) is proposed, which takes the skin effect and the nonzero leakage reactance of the secondary, longitudinal, and transverse end effects into consideration. Firstly, the traditional equivalent circuit with longitudinal and transverse end effects are briefly reviewed. Additionally, the correction coefficients for longitudinal and transverse end effects derived by one-dimensional analysis models are given. Secondly, correction factors for skin effect, which reflects the inhomogeneous air gap magnetic field vertically, and the secondary leakage reactance are derived by the quasi-two-dimensional analysis model. Then, the proposed equivalent circuit is presented, and the excitation reactance and secondary resistance are modified by the correction coefficients derived from the three analytical models. Finally, a three-dimensional (3D) finite element model is used to verify the proposed equivalent circuit model under varying air gap width and frequency, and the results are also compared with that of the traditional equivalent circuit models. The calculated thrust characteristics by the proposed equivalent circuit and 3D finite element model are experimentally validated under a constant voltage–frequency drive.

Mesh Dependency on a Partial Element Equivalent Circuit Model for an NI HTS Coil

2021 ◽  
Vol 31 (5) ◽  
pp. 1-5
Author(s):  
Chaemin Im ◽  
Geonyoung Kim ◽  
Jeseok Bang ◽  
Kibum Choi ◽  
Soobin An ◽  
...  
Keyword(s):  
Equivalent Circuit ◽  
Equivalent Circuit Model ◽  
Circuit Model ◽  
Mesh Dependency ◽  
Partial Element Equivalent Circuit ◽  
Partial Element
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