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• An ALO algorithm is developed for tuning the FOPI regulators of a grid connected DFIG turbine system. • The fractional order controllers with frequency and time response analysis are presented. • The various performance parameters of the grid connected DFIG Wind Turbine System with PI, FOPI, PSO-FOPI, and ALO-FOPI regulators are compared and analysed using the bode plot. • The proposed algorithm shows superior performance compared to conventional controllers. The wind velocities are unpredictable, and generating power with persistent speed is difficult which comprises mechanical stress at the rotor that leads to poor efficiency. So, variable wind power speed generation has ample significance with the Doubly Fed Induction Generator (DFIG). For a grid-connected DFIG, the governing of power is done conventionally by employing vector-controlled PI regulators. Yet, the performance of PI regulators depends on system parameters, which motivates the adoption of Fractional Order PI (FOPI) regulators. Presently FOPI regulators are seizing a lot of applications with the assistance of additional tuning parameters. However, tuning FOPI regulators by conventional methods is challenging. So, initially, the Particle Swarm Optimization (PSO) method was used for tuning FOPI regulators, but the disadvantages are low convergence rate, falling into local elucidation, entailing more variables to attune, and requiring a large number of iterations. Thus, this motivates introducing the Ant Lion Optimization (ALO) algorithm in this article due to its better performance and eligibility to overcome the limitations of conventional methods. Furthermore, in the validation of the proposed algorithm, the performance parameters like DC coupling capacitor voltage, rotor Speed, active power, and reactive power with PI, FOPI, PSO-FOPI, and ALO-FOPI regulators are compared and analysed using the bode plot are presented. The time response analysis of all the controllers with PI, FOPI, PSO-FOPI, and ALO-FOPI controllers were also observed with a voltage dip. Finally, the fractional order controllers with frequency response and time response analysis show superior performance in distributed generation with advanced heuristic controllers when compared to conventional controllers. The complete work has been simulated via MATLAB/ Simulation platform. [ABSTRACT FROM AUTHOR]

This paper presents a vibration analysis method and an example of its application to evaluate the influence of mass parameters on torsional vibration frequencies in the steering system of a motorcycle. The purpose of this paper is to analyze to what extent vibration frequencies can change during their daily operation. These changes are largely due to the ratio of vehicle weight to driver and load. The complex dynamics make it very difficult to conduct research using simple models. It is difficult to observe the influence of individual parameters because they are strongly interrelated. This paper provides a description of the vibration analysis method, and the results are presented in the form of Bode diagrams and tables. On this basis, it was found that the driver, deciding on the way of using the vehicle and introducing modifications in it, influences the resonant frequencies of the steering system. Typical exploitation factors, on the other hand, do not cause significant changes, although they may contribute to increasing the sensitivity of the system to vibrations. The conducted analysis also showed some nonlinear changes in the dynamics of the system with linear changes of the parameter values.

In this paper we have reported the synthesis of graphene by a novel and facile thermal exfoliation process of Allium cepa (Onion) and was characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy to investigate the morphological and structural properties and chemical networks present on it. The AFM and SEM images revealed the formation of thin strip-like layered structure of graphene with the thickness of 1.1 nm. The electrochemical properties of graphene were characterized by cyclic voltammeter, impedance spectroscopy, Tafel plot, Nyquist plot, Bode plot, and voltage-dependent impedance using 0.5 M H2SO4 electrolyte as an illustrative standard material. The cyclic voltammetric curve of graphene electrodes determined a quasi-reversible electrochemical behavior under linear diffusion control square shape at higher process temperature. The ratio of atomic % C-to-O varied from 7.57 to 24.04 indicating a decrease in the oxygen content for the graphene processed at higher temperature. The areal capacitance and voltage-dependent impedance varied from 8.59 × 10− 5 to 18.8 × 10− 5 F/cm2 and 15.79 to 7.7 Ohm, respectively, with the process temperature varying from 600 to 1000 °C. The corrosion potential (Ecorr) and corrosion current density (Icorr) values are − 0.12 V and − 9.1A/cm2, respectively, for the graphene processed at 1000 °C. [ABSTRACT FROM AUTHOR]

Multiple loops have been used extensively to enhance the system performance in various applications. However, the increasing complexity of multi-loop systems also makes them much more difficult to analyze and implement. In this paper, a new methodology to analyze multi-loop system is proposed. In the proposed framework, multi-loop systems are regarded to be built upon of sub-modules of cascade, parallel adding, and feedback units, and then, they are simplified following a certain procedure based on the correlation of the Bode characteristics of the segmented sub-modules. Applying this methodology, the Bode plot and the transfer function of the system can be easily obtained with the system properties of gains, zeros, and poles. Two examples are provided as demonstrators, including a multi-loop low-dropout regulator (LDO) from literature, and a newly designed multi-loop LDO aiming at enhancing the stability over a wide load range, which show that the Bode plot and the transfer function can be obtained more intuitively and rapidly. Excellent agreements among theory, simulations, and measurements are confirmed, which verify the proposed method. It can help designers to gain more intuitions and insights on multi-loop systems from both circuit and device perspectives, which is also an effective tool for both stability analysis and circuit design. [ABSTRACT FROM AUTHOR]

Abstract The present work focuses on synthesis and characterization of novel polymeric based smart coatings containing various amount of titania nanotubes (TiO 2) encapsulated with dodecylamine (DOC). The novelty of the current research work resides on the fact that the encapsulation of TiO 2 nanotubes with DOC and its inhibition effect in polymeric smart coatings have not been previously reported. Towards this direction, TiO 2 nanotubes with an average size of ⁓10–15 nm (as confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis) were synthesized through a hydrothermal process and were then impregnated with DOC. Various contents of the encapsulated TiO 2 nanotubes (1, 3 and 5 wt%) were thoroughly dispersed into the epoxy matrix and the resulting composites were then applied on a cleaned steel substrate using doctor blade technique to develop smart coatings. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the impregnation of TiO 2 nanotubes with DOC. The encapsulated amount of DOC in TiO 2 nanotubes was estimated by the thermogravimetric analysis (TGA). The UV–vis spectroscopy study demonstrates time dependent self-release of encapsulated DOC from the TiO 2 nanotubes in response to pH change of the corrosive medium. TGA and FTIR analyses also indicate that different amounts of encapsulated TiO 2 nanotubes dispersed into smart coatings do not degrade their structural and thermal properties. Moreover, a decrease in the corrosion rate of smart coatings with increasing amount of encapsulated TiO 2 nanotubes in the EIS analysis confirms their superior anticorrosive performance. This improvement in corrosion resistance can be attributed to the efficient and high amount of DOC released from the encapsulated TiO 2 nanotubes. A decent improvement of corrosion resistance make these smart coatings attractive for industrial applications. [ABSTRACT FROM AUTHOR]

This paper proposes a small-signal modeling method for building an LLC half-bridge resonant converter. In recent years, the LLC half-bridge resonant converter has attracted the attention of many researchers because of its high-power conversion efficiency and high-power density. Generally, the LLC half-bridge resonant converter consists of many passive components, including stray and parasitic elements, resulting in a high-order system. Because the fundamental harmonic approximation (FHA) method for an LLC resonant converter only considers the fundamental harmonic and neglects higher harmonics, it is not accurate and introduces large errors in a higher-order system. In this paper, according to the operation principle of the LLC half-bridge resonant converter, a small-signal model is established. Based on the small-signal model, the input-to-output and control-to-output transfer function is derived. The experimental result verified that the proposed model yields a high accuracy, thereby highlighting the usefulness and versatility of the proposed model over other existing models. [ABSTRACT FROM AUTHOR]

This paper presents a novel robust model reference adaptive system (MRAS) technique for rotor speed estimation of direct torque control (DTC) of an induction motor drive used for solar PV powered water pumping. The maximum power point tracking (MPPT) of PV array is assured by a proposed P&O algorithm, which has improved tracking time without deviation during insolation change. Moreover, an additional loop is incorporated in the MPPT control, which provides an additional feature of derating the panel, which consequently controls the flow rate. The effect of parameter variation e.g. change in rotor resistance, stator resistance and the rotor time constant on the stability of overall system, is analysed and tested. The MRAS involves fluxes estimation and uses the same machine parameters which are involved in DTC. The elimination of speed sensor and parameters adaptation make the overall induction motor drive (IMD) suitable for such application. The stability of the system is assured by Lyapunov's stability criterion and the stability of parameters adaptation is shown by Bode plot and well‐known Popov's stability criterion. Therefore, the reduced sensors (voltage and current sensors) based proposed system with deviation‐free MPPT technique and with flow rate controller, is modeled, simulated, and experimentally verified. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the corrosion rates and porosity of industrial paints used for car body coating. Seven types of industrial paints were used for car body structuresincluded 2K clear coat (Lacquers), Auto Paint 2K top coat, TS 16949 (Easi coat), Clear coat (Palinal), National Numix top coat, DENSO and ICI 2K solvent based (Tinters P420) were tested and studied using the electrochemical impedance spectroscopic (EIS) method. The liquefaction potable water solution was used as electrolyte for test. The obtained results showed that the Palinal paint has high impendence and lower porosity while TS 16949 (Easi coat) shows lower impedance and high porosity. Other types showed moderates values. Microscopic inspection of the surface coatings after EIS test showed that most paints had pitting corrosion except Auto paint shows blisters.

Bioelectric impedance spectroscopy (BIS) has been widely used to study the electrical properties of biological tissue based on the characteristics of the complex electrical impedance dispersions. One of the problems in using the BIS method is the length of time required for the data acquisition process and possibly data analysis as well. In this research, a compact and work rapidly BIS instrumentation system has been developed at a low cost. It is designed to work in the frequency range of 100 Hz to 100 kHz, which is generally used in the fields of biophysics and medical physics. The BIS instrumentation system is built using several integrated modules. The modules are an AC current source to produce a selectable injection current; a data acquisition system to measure voltage, current, and phase difference rapidly and simultaneously; and software to calculate and display measurement results in the form of Bode and Nyquist plots in real time. The developed BIS system has been validated using a simple RC circuit as the sample being tested. The average time needed in the process of data acquisition and analysis until the formation of impedance dispersion curves in the form of Bode and Nyquist plots, for 54 sample frequencies, is less than one minute. The system is able to identify R and C values of the sample with a maximum error of 1.5%. In addition, some simple application examples are also presented in this paper.

A method for the performance design of analog amplifier circuits based on nullors is discussed. It covers the design of AC parameters of the amplifier viz. input and output resistance, gain and bandwidth. Fixator-norator pair, which is a combination of nullor and sources, is the key element in this method. The complete performance design is considered as a two step process. Fixator-norator pair along with the linear equivalent model of the target circuit together does the first step, which is the design for input and output resistance and gain. The second step performs the design for bandwidth, i.e., mainly the cut-off frequencies. This is based on Bode plot analysis, which requires a reference circuit having the same frequency response as that of the desired one. The reference circuit is required only for simulation and it can be removed after the final design is met. Four examples are worked out for better understanding of the method. [ABSTRACT FROM AUTHOR]

In this paper, a modified small signal state space average model is proposed to analyze the pulse width modulated converter operating in discontinuous conduction mode (DCM). It is based on a unique correction matrix (Mc) and new duty ratio constrain which is derived on the basic properties of inductor current. A 12 volt, 5 watt power supply based on Cuk converter is designed to demonstrate this proposed methodology. Transfer functions (input-to-output and control-tooutput) of this power supply are calculated theoretically with the help of proposed modelling procedure. Bode plots of those transfer function are achieved using MATLAB toolboxes. To validate the proposed model, a simulation is also performed in MATLAB and frequency response is captured at run time using linearization technique. Bode plots from proposed model are very much in line with simulation results and offer improved predictions for high frequency dynamics of converter operating in DCM. The validity of presented work is reconfirmed by experimental set-up. The presented work is also compared with conventional small signal modelling on the basis of frequency analysis. [ABSTRACT FROM AUTHOR]

Gel polymer electrolytes (GPEs) have demonstrated a greater potential to be used as electrolytes for various applications such as batteries, super capacitors, electrochromic devices and dye sensitised solar cells. They consist of a salt and a mixture of solvents trapped in a polymer matrix. In this study, optimisation and characterisation of a GPE consisting of polyvinylidene fluoride, ethylene carbonate, propylene carbonate and sodium iodide and its application in a redox capacitor with two polypyrrole electrodes was studied. GPE shows a conductivity of 9.69 × 10-3 Scm-1 at room temperature (28 °C) with good mechanical stability. The corresponding composition is 1.13 PVdF : 2.5 EC : 2.5 PC : 0.4 NaI (by weight). The variation of conductivity with temperature follows Arhenius behaviour suggesting that the conductivity mechanism takes place via hopping of ions. Conductivity is purely ionic in nature. Properties of the redox capacitors were studied by the cyclic voltammetry (CV) technique, electrochemical impedance spectroscopy (EIS) technique and galvanostatic charge-discharge (GCD) test. The CV results showed the dependency of specific capacitance on the scan rate. The EIS results showed that capacitive behaviour becomes dominant only at low frequency range. The resulting specific capacitance was 3.19 Fg-1. It was found that the redox capacitor exhibits an average discharge specific capacitance of 5.93 Fg-1 while having a specific energy density of 0.03 Whkg-1 and a specific power density of 0.42 Wkg-1. [ABSTRACT FROM AUTHOR]