Nonlinear Resistance Research Articles

Effects of non-linear resistance training and curcumin supplementation on the liver biochemical markers levels and structure in older women with non-alcoholic fatty liver disease

BackgroundWith increasing age, non-alcoholic fatty liver disease is very common among women with low levels of physical activity. Nonlinear resistance training is one of the new methods to help patients who have low levels of physical activity. Curcumin is an herbal supplement that has anti-inflammatory effects. The present study aimed to examine the effects of nonlinear resistance training and curcumin supplementation on the liver structure and biochemical markers in obese older women with non-alcoholic fatty liver disease. MethodsForty-five obese women with non-alcoholic fatty liver disease were randomly assigned into resistance training (RT), curcumin supplement (C), resistance training with curcumin supplement (RTC), and placebo (P) groups. The RT and RTC groups received 12-weeks of nonlinear resistance training while the C and P groups had a normal sedentary lifestyle. Daily, the C and RTC groups received a curcumin capsule while the P and RT groups were given a placebo capsule. Blood sampling and ultrasonography were taken before and after the protocol. ResultsAlanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels significantly decreased in the RT and RTC groups (P ≤ 0.05) but not in the C and P groups (P > 0.05). Alkaline phosphatase (ALP), total bilirubin (TB) levels, platelet counts (PLT), and liver structure did not significantly change in all groups (P > 0.05). Resistance training alone and with curcumin supplementation could significantly improve liver function while taking curcumin alone did not have any significant effect on it. Conclusion12-week non-linear resistance training has beneficial effects on non-alcoholic fatty liver disease in older obese women.

Enhancing the efficiency of kW-class vanadium redox flow batteries by flow factor modulation: An experimental method

The paper presents a control method of the electrolyte flow factor in kW-class Vanadium Redox Flow Batteries that minimizes transport losses without affecting the battery's electrical performance. This method uses experimental data acquired on a 9 kW/27 kWh test facility at varying operating conditions. The effects of overpotentials on the polarization curves are then modeled as non-linear electrical resistances that vary with the stack current, state of charge and electrolyte flow rates. Our analysis of these variables shows that the optimal performance is found if the flow factor is modulated during operation according to stack current and the battery state, so as to minimize the overall flow-dependent losses. The optimal profiles have been identified as functions of the battery's operating conditions. Based on these results, a dynamic control for the electrolyte flow rates has been implemented at a software level (i.e. without modifying the hardware of the test facility), which is capable of maximizing the round-trip efficiency and exceeds the performance achieved with a constant flow factor strategy, as proposed in previous literature. The implementation of the optimal flow rate control requires a preliminary test campaign to collect performance data, which are then used in the control protocol to manage the battery's operation. This scheme is easily implementable at a software level in other industrial redox flow batteries.

Nonlinear Spark Resistance and Capacitive Circuit Models of Electrostatic Discharge

Over the past century, several models of spark discharge have been developed that approximate the effect of a spark channel in a circuit as a nonlinear resistance. In this article, we review the physical derivations of a set of spark models, and give analytical and numerical solutions to spark discharges in simple capacitive circuits. In electrostatic discharge (ESD), we find the drop in spark resistance is limited by the initial stored charge in the system. For a simpler ESD model (spark resistance in series with the electrode capacitance), we obtain the analytical solutions for a spark resistance model of a general integral form, consisting of the time integral of the current raised to an arbitrary power. We also consider a circuit with an additional fixed “victim” resistance in series with the spark resistance, and capacitance. Here, although the general case requires numerical solution, it is possible to find asymptotic limits for the case of the Rompe and Weizel spark model. Our analysis provides insights into system response that can, for example, be used to evaluate risk zones of parameter space for ESD protection.

Axial and lateral resistance coupling in the analysis of large-diameter drilled shafts

Pier foundations subjected to lateral loads are commonly designed using beam on nonlinear Winkler foundation (BNWF) models. This form of soil-structure interaction (SSI) modeling typically involves load transfer between structural members (e.g., drilled shafts) and surrounding soil via nonlinear soil resistance springs, which are distributed along the centerline of beam-column elements. Physically, soil resistance develops at the shaft-soil interface, and special considerations may be warranted regarding coupling between axial and lateral resistance when modeling large-diameter drilled shafts. Presented in this paper are side (t-z) and lateral (p-y) soil-resistance relationships for Florida limestone, obtained from centrifuge tests, and moment-rotation springs associated with coupling of axial and lateral resistances of laterally loaded drilled shafts. Using the coupled approach, BNWF models are developed that: 1) Capture physically measured lateral load responses of shafts founded in a range of soil/rock types; and, 2) Are suitable for large-diameter shafts at variable embedment lengths. This study highlights the need for such analyses in cases when relatively stiff soil/rock materials exist at shallow depths and/or when shafts undergo significant rotations. Use of coupled analysis is found to reduce computed maximum values of shaft bending moment and deflection up to 12% and 19%, respectively, compared to uncoupled analysis.

Effects of glycyrrhizic acid supplementation during nonlinear resistance training on inflammatory markers and muscular damage indices in overweight young men

ObjectivesThe purpose of this study was to investigate the effects of glycyrrhizic acid supplementation during nonlinear resistance training on inflammatory markers and muscular damage indices in overweight young men. MethodsForty eight overweight young men participated voluntarily in the study and were randomly divided into six groups including nonlinear resistance training + placebo (NRT-P), NRT + glycyrrhizic acid (250 mg) (NRT-GA1), NRT + glycyrrhizic acid (500 mg) (NRT-GA2), glycyrrhizic (250 mg) acid (GA1), glycyrrhizic acid (500 mg) (GA2) and control + placebo (C-P). The training protocol was progressive circuit resistance training (3 session/week, 8 weeks). Blood samples were collected 48 h before exercise and 48 h after the last session. The data were analyzed using two-way repeated measures analysis of variance (P < 0.05 was considered as significant). ResultsResistance training caused a significant decrease in serum TNF-α, IL-6, IL-1β, hs-CRP, LDH and CK. Both doses of glycyrrhizic acid improved TNF-α, IL-6, IL-1β, hs-CRP, LDH and CK than C-P group. Combination of NRT and GA significantly decreased serum TNF-α, IL-6, IL-1β, hs-CRP, LDH and CK but more reduction in the NRT-GA2 group was observed. ConclusionsCombination of resistance training with 500 ml g of glycyrrhizic acid supplement could be useful to decrease some inflammatory and muscle damage markers as well as body weight and body fat percentage.

Compact Modeling of the I-V Characteristics of ZnO Nanowires Including Nonlinear Series Resistance Effects

This letter deals with the compact modeling of the I-V characteristics of single crystalline ZnO nanowires (NW) attached to two metal electrodes (Pt and Ag). Starting from the standard model of electron transport in these structures based on the series combination of two back-to-back Schottky diodes, three different approaches which account for the role played by the NW series resistance are presented. The first approach considers a fixed potential drop across the NW, the second one involves the solution to the problem of a diode with linear and nonlinear series resistances using the Lambert W function, and the third one consists in a behavioral model with continuous first derivative suitable for circuit simulation environments. In the three cases, the proposed solutions are consistent with the observed electrical constraints both at low (linear I-V relationship) and high (current saturation) voltages.

Genetic-based optimization of a multi insulator tunneling diode for THz energy harvesting

AbstractThe deployment of multi-insulator tunneling diodes has recently had more attention to be used as rectifiers in energy harvesting rectennas with good potentiality for a millimeter and terahertz range. However, with the rather complicated math to obtain the current–voltage relation, it is difficult to evaluate the design figures of merit (FOM)s such as asymmetry, nonlinearity, responsivity, and dynamic resistance and monitor the impact of changing physical parameters on them. This complicates the decision-making process for the required physical parameters. In this work, a heuristic optimization framework using genetic algorithm is suggested using the transfer matrix method to find the combination of physical parameters which satisfies the minimum required FOM set by users and weighted by their preference.

A Novel Linearizing Signal Conditioner for Half-Bridge Based TMR Angle Sensor

This paper proposes a novel signal conditioning circuit for half-bridge topology based Tunneling Magneto-Resistance (TMR) angle sensor. The resistances of TMR angle sensor vary as a sine/cosine function of the shaft angle. The proposed circuit employs an enhanced dual-slope technique to process these non-linear resistance variations and render a linear digital output for full-circle range. The circuit uses easily available and low-cost circuit components, and a novel linearization logic in its architecture. It possesses low dependence on many circuit and sensor non-idealities. Further, a novel algorithm is proposed to reduce the measurement error due the mismatch in nominal resistances of the TMR sensor. The working of the circuit is verified using simulation as well as experimental studies. The maximum non-linearity in the circuit output, observed with expected sine/cosine characteristic, is 0.038 %. Later, a shaft angle sensing unit, employing AAT003-10E half-bridge TMR angle sensor IC, is designed, built, and characterized. The interfacing studies showcase the capability of the developed signal conditioning circuit for linearizing practical TMR angle sensors. The efficacy of the compensation algorithm is also proved in the experimentation.

Coupled Simulation of Current Flow and Residual Thermal Stress in ZnO Varistors

An electromechanically coupled modeling framework for the simulation of electric current flow in ZnO varistors is developed. The model is based on an equivalent circuit representation of the varistor microstructure with grain boundaries represented by nonlinear resistor branches of the circuit. This approach extends on previous circuit models by including the effect of mechanical stress on grain boundary conductivity. In this article, we consider, in particular, the effect of residual thermal stress in polycrystalline structures on electrical conductivity. The distribution of this stress throughout the material is computed by finite element method (FEM) simulations. Then, each grain boundary conductivity is determined by applying a self-consistent model for the trapped interface charge induced by piezoelectric polarization. Finally, the electric current flow patterns and the bulk conductivity of the material are computed using the nonlinear circuit model. The simulated I–V characteristics reveal a significant sensitivity of the electrical conductivity to internal thermal stress within the material. Furthermore, for realistic ZnO microstructures, the simulations demonstrate the effect of current concentration along thin conducting paths depending on the mechanical stress condition of the material.

Experimental Study of Electrical Contact Nonlinearity and its Passive Intermodulation Effect

In this article, the single-point electrical contact nonlinearity of the oxidation enhanced copper and its induced passive intermodulation (PIM) effect were systematically investigated. First, based on the composition analysis of the intentionally oxidized copper samples and the pristine ones, the electron potential barrier model across the contact interface was built. Then, based on an equivalent circuit model concluding a linear and nonlinear resistance, a total current equation based on the thermal emission mechanism was deduced and verified by performing a series of I–V measurements. When an oxide film is integrated, the linear current and the nonlinear current are comparable; when the oxide film was broken under an external force, the nonlinear current changes lightly, while the linear current increases sharply by more than two orders of magnitude. Therefore, we observed the transition process from the obvious nonlinear I–V characteristics to the dominant linear curves. Finally, the induced PIM behavior of the pristine and thermal oxidized single-point copper joints was investigated utilizing a specially designed near-field coupling PIM test system. As the pressure increases, the PIM level decrease with the joint pressure increases because both the contact resistance and the nonlinear current decrease. The measured PIM results are consistent with the obtained linear–nonlinear relation from the contact characteristics experiments. Experimentally, the total nonlinear current as the function of voltage drop across the contact interface, which is caused by the linear current, determines the induced PIM level.

A computational approach to evaluate the nonlinear and noisy DC electrical response in carbon nanotube/polymer nanocomposites near the percolation threshold

This paper presents a percolating network model to determine the electrical behavior of carbon nanotube (CNT)/polymer nanocomposites, especially near the percolation threshold. In this extended model, we considered a voltage-dependent tunneling resistance at the CNT junctions, based on Simmons’ formulation. This assumption led to an electrical resistor network containing both linear and nonlinear resistance elements. We focused on extracting the continuous current-voltage (I-V) response of the nanocomposites through a recursive calculation to show the ability of the model to simulate the nonlinear and noisy behavior of the I-V curve in CNT/polymer systems. The effects of CNT diameter, length, concentration, and intrinsic conductance, as well as the tunneling gap at the junctions and matrix dielectric constant, were also investigated and discussed. Our results revealed that the nonlinearity in I-V curves near the percolation threshold is related to the voltage-dependent nature of the tunneling resistance. The number of junctions and equivalent CNT length in the percolation pathway are two effective parameters controlling the electrical behavior of CNT/polymer nanocomposites. The results obtained are also in good agreement with our previous experimental data on CNT/epoxy nanocomposite and confirmed that the proposed model can efficiently predict the I-V characteristic curves for CNT/polymer composites.

The prediction of nonlinear resistance and distortion for a miniature loudspeaker with vented cavities.

The nonlinear resistance and its influence on the total harmonic distortion of a miniature loudspeaker with vented cavities are investigated. A method for the prediction of nonlinear resistance is described. In the model, the nonlinear resistance caused by the magnetic gap and the orifices in the back cover of the miniature loudspeaker is taken into account. The nonlinear acoustic resistance is estimated through the electric analogy method, and then it is transformed into the equivalent nonlinear resistance of the vibrating diaphragm. The estimated nonlinear resistance is verified through the Klippel Analyzer measurement. The influence of the nonlinear resistance, mechanical stiffness and force factor on the total harmonic distortion is calculated and compared with the measurements.

Generating Multi-Scroll Chua’s Attractors via Simplified Piecewise-Linear Chua’s Diode

High implementation complexity of multi-scroll circuit is a bottleneck problem in real chaos-based communication. Especially, in multi-scroll Chua's circuit, the simplified implementation of piecewise-linear resistors with multiple segments is difficult due to their intricate irregular breakpoints and slopes. To solve the challenge, this paper presents a systematic scheme for synthesizing a Chua's diode with multi-segment piecewise-linearity, which is achieved by cascading even-numbered passive nonlinear resistors with odd-numbered ones via a negative impedance converter. The traditional voltage mode op-amps are used to implement nonlinear resistors. As no extra DC bias voltage is employed, the scheme can be implemented by much simpler circuits. The voltage-current characteristics of the obtained Chua's diode are analyzed theoretically and verified by numerical simulations. Using the Chua's diode and a second-order active Sallen-Key high-pass filter, a new inductor-free Chua's circuit is then constructed to generate multi-scroll chaotic attractors. Different number of scrolls can be generated by changing the number of passive nonlinear resistor cells or adjusting two coupling parameters. Besides, the system can be scaled by using different power supplies, satisfying the low-voltage low-power requirement of integrated circuit design. The circuit simulations and hardware experiments both confirmed the feasibility of the designed system.

Self-sensing capabilities of cement-based sensor with layer-distributed conductive rubber fibres

Piezoresistive-based cementitious composites have unique advantages compared with other sensors for structural health monitoring. A novel cement-based sensor incorporating conductive rubber was explored in this study, including its raw materials, manufacturing process, electrical conductivity, self-sensing efficiency, repeatability and compressive strength. Different water to binder (w/b) ratios of composites and loading stress magnitudes were also investigated. The results show that the conductive rubber fibres had capacity to improve the electrical conductivity of cementitious composite, with percolation threshold approximately from 60–100 rubber fibres (0.96–1.6 vol.% to specimen). The higher w/b ratio, the lower resistivity and the more inconspicuous percolation the composite was. Furthermore, the composites at w/b ratio of 0.38 were provided with best piezoresistivity, whose fractional changes of resistivity reached 25% under stress magnitude of 10 MPa when reinforced by 80 rubber fibres (1.28 vol.%). The sensitive coefficient proposed could describe piezoresistive sensitivity in different stress magnitudes, because of the non-linear resistivity changes with increased stress amplitude. As for the mechanical properties, satisfactory compressive strength of 36 MPa was obtained for the composite filled with 80 rubber fibres (1.28 vol.%) at w/b ratio of 0.38. Therefore, the conductive rubber embedded cementitious composites have great application potential as new cement-based sensors for concrete structural health and pavement traffic monitoring.

A Novel Empirical Model for CMOS Schottky Diodes up to 67 GHz

A novel empirical model capable of predicting dc current and RF capacitance characteristics for CMOS Schottky diodes is first proposed. The model is developed upon a physical-based equivalent circuit and a set of closed-form formulas. Different current transport mechanisms including thermionic emission, tunneling, and carrier velocity saturation are counted by nonlinear resistances in the intrinsic model, while stray and substrate parasitic effects are also included in the parasitic model. A systematic procedure is built up to directly extract all the model parameters from measurements. The model is validated in 65- and 130-nm CMOS technology, and the modeled results show an excellent agreement with the measured data up to 67 GHz, which is the highest modeling frequency reported up till now.

Identification of transformer equivalent circuit parameters for transients simulation

The paper deals with experimental identification of transformer equivalent circuit parameters for simulation purpose. Dependences of transformer voltage and power from primary winding current in open circuit configuration were measured. Current to voltage characteristic of magnetic losses nonlinear resistor, flux to current characteristic of magnetic core, resistance and leakage inductance of primary and secondary windings of one-phase transformer were calculated from the measured parameters. Equivalent circuit of the transformer allowing calculation of transformer transients, such as inrush and overload, was obtained as a result.

A Dual-Parameter Oscillation Method for Eddy Current Testing With the Aid of Impedance Nonlinearity

The ferrite core of a sensing coil enhances its magnetic field, thereby improving its detection sensitivity in eddy current testing (ECT). Due to the hysteresis caused by the ferrite core, the lumped impedance of a coil–target system is essentially nonlinear. In this article, the impedance nonlinearity is used and a dual-parameter oscillation method for ECT is proposed. By utilizing the nonlinear impedance of the coil–target system in the oscillating circuit, a self-oscillation signal can be generated. Subsequently, the dual parameters of oscillation, i.e., the amplitude and the frequency are obtained by the detection circuit. The amplitude reflects the nonlinear resistance of the coil–target system, while the frequency reflects the nonlinear inductance. A negative resistor is used to ensure the oscillation and adjust the amplitude to the appropriate range and a capacitor is used to adjust the frequency. This method is capable of real-time defect detection. The correlation of dual parameters is analyzed and used, and a synthesis parameter is proposed to suppress the lift-off effect and noise, therefore the performance of detection for small defects is enhanced. The proposed dual-parameter maps provide a graphical observation of the location and the depth of defects in real-time scanning. The proposed method is applied to detect the surface and subsurface defects of the metal sample as well as of a ferromagnetic target behind the nonferromagnetic shield.

Finite-Difference Time-Domain Simulation of a Lightning-Impulse-Applied ZnO Element

The voltage across a zinc oxide (ZnO) element, in which a lightning impulse current is injected, and the temperature distribution in the ZnO element have been computed using the finite-difference time-domain (FDTD) method. The ZnO element having a length of 36 mm and a radius of 16 mm is represented with many 2 mm × 2 mm × 4 mm rectangular cells, each of which has a nonlinear resistivity in each of the x, y, and z directions dependent on the electric field in each direction and the temperature in each cell. Waveforms of the voltage across the ZnO element and maximum temperatures, computed using the FDTD method, for lightning impulse currents having magnitudes of about 30-65 kA, have been compared with those measured by the authors. Furthermore, the voltage across a 66- or 77-kV transmission-line surge arrester, composed of nine stacked ZnO elements, and the distribution of temperature in the arrester have been computed for a 50-kA lightning impulse current.

Nonlinear Resistivity in Epoxy Composites Containing ZnO Particles and Secondary Particles

Nonlinear Resistivity in Epoxy Composites Containing ZnO Particles and Secondary Particles

Analysis and electronic implementation of an absolute memristor autonomous Van der Pol-Duffing circuit

In this paper, a memristor-based chaotic circuit is built by replacing the nonlinear resistor of a unified Van der Pol-Duffing circuit by an ideal and active flux-controlled memristor with an absolute value nonlinearity. The equilibrium points of the mathematical model describing the proposed absolute memristor Van der Pol-Duffing circuit are determined and their stabilities are analyzed thank to the Routh-Hurwitz criteria. The numerical simulations reveal that the proposed absolute memristor circuit exhibits reverse period-doubling to chaos, bistable one-scroll chaotic attractors, double-scroll chaotic attractor, bistable periodic attractors and antimonotonicity phenomenon. Moreover the proposed absolute memristor circuit is implemented in PSIM software package. The results found using the PSIM software package have a good qualitative agreement with those found during the numerical simulations.