An enhanced security mechanism through blockchain for E-polling/counting process using IoT devices

Wireless Networks - One of the biggest challenges in political mayhem is visible during the election process where no stone is kept unturned in order to gain the power. Further, due to poll...     

A trust computed framework for IoT devices and fog computing environment

Wireless Networks - In this paper, we have demoralized the transmission processing concerns of fog nodes and IoT device layer attack during the handoff (mobility) of IoT devices in the fog...     

Perturbation-Based Stochastic Modeling of Nonlinear Circuits

This paper presents a general model for a nonlinear circuit, in which, the circuit parameters (e.g. resistance and capacitance) are subject to random fluctuations due to noise, which vary with time. The fluctuating amplitudes of these parameters are assumed to be Ornstein–Uhlenbeck (O.U.) processes and not the white noise owing to temporal correlations. The nonlinear circuit is represented by a system of nonlinear differential equations depending upon a set of parameters that fluctuate slowly with time. To model these fluctuations, we use the theory of Ito’s stochastic differential equations (SDEs). Then the driving force of the circuit dynamics is in accordance with the general perturbation theory decomposed into the sum of a strong linear component and a weak nonlinear component by the introduction of a small perturbation parameter. The circuit states are expanded in the powers of this small perturbation parameter and recursive solutions to the various approximates obtained. Finally, the approximate expressions for the output states are obtained as stochastic integrals with respect to Brownian motion processes. The proposed method is applied to a half-wave rectifier circuit which is built out of a diode, a resistor and a capacitor. The diode is represented by nonlinear voltage–current equation, and resistance and capacitance are subject to random fluctuations due to noise, which vary slowly with time. The results, obtained using the proposed method, are compared with those obtained via the conventional perturbation-based deterministic differential equations model for a nonlinear circuit. Hence, the noise process component, present at the output, is obtained.     

Perturbation-Based Fourier Series Analysis of Transistor Amplifier

A perturbation-based Fourier series model is proposed to approximate the nonlinear distortion in weakly nonlinear circuits. This general model is applicable to any set of multi-variable state equations that completely describe a nonlinear circuit. This model is applied to a common emitter amplifier circuit wherein the transistor is represented by Ebers–Moll nonlinear current equations. Appropriate state variables are defined, then the linear and nonlinear parts of the Ebers–Moll current equations are separated, and a small perturbation parameter is incorporated into the nonlinear part. Now these current equations are incorporated into the set of KCL, KVL equations defined for the circuit and the state variables are perturbatively expanded. Hence, multi-variable state equations are obtained from these equations. The state variables are approximated up to first order through Fourier series expansion, as described in the proposed model. The main advantage of the proposed model is that it is simple and straightforward approach to analyze weakly nonlinear circuits, as it involves matrix computations and the calculations of exponential Fourier coefficients.     

Image restoration in computed tomography: estimation of the spatially variant point spread function

An indirect method for determining the point-spread-function (PSF) in computed tomography (CT) is described. Unlike experimental techniques in which a resolution phantom is scanned to obtain the system PSF, the approach estimates the parameters of a model which describes the two-dimensional X-ray beam profile at each point as a convolution of the appropriately scaled focal spot intensity and detector sensitivity distributions. The model was validated by experimental measurement of the focal spot intensity distribution. Using known X-ray beam profiles, the PSF of a CT scanner can be derived by simulating the data collection process and applying conventional image reconstruction techniques. Visual comparison of directly measured and computed PSFs reveals an asymmetry resulting from misregistration of the phantom wires and the image grid.     

Aggregation of a peptide antibiotic alamethicin at the air-water interface and its influence on the viscoelasticity of phospholipid monolayers

The aggregation properties of an antibiotic membrane-active peptide alamethicin at the air-water interface have been studied using interfacial rheology and fluorescence microscopy techniques. Fluorescence microscopy of alamethicin monolayers revealed a coexistence of liquid expanded (LE) and solid phases at the surface concentrations studied. Interfacial oscillatory shear measurements on alamethicin monolayers indicate that its viscoelastic properties are determined by the area fraction of the solid domains. The role of zwitterionic phospholipids dioleoylphosphatidyl choline (DOPC) and dioleoylphosphatidyl ethanolamine (DOPE) on the peptide aggregation behavior was also investigated. Fluorescence microscopy of alamethicin/phospholipid monolayers revealed an intermediate phase (I) in addition to the solid and LE phase. In mixed monolayers of phospholipid (L)/alamethicin (P), with increase in L/P, the monolayer transforms from a viscoelastic to a viscous fluid with the increase in area fraction of the intermediate phase. Further, a homogeneous mixing of alamethicin/lipid molecules is observed at L/P > 4. Our studies also confirm that the viscoelasticity of alamethicin/phospholipid monolayers is closely related to the alamethicin/phospholipid interactions at the air-water interface.     

Capacitance-voltage analysis of a high-k dielectric on silicon

正Device characteristics of TiO_2 gate dielectrics deposited by a sol-gel method and DC sputtering method on a P-type silicon wafer are reported.Metal-oxide-semiconductor capacitors with Al as the top electrode were fabricated to study the electrical properties of TiO_2 films.The films were physically characterized by using X-ray diffraction,a capacitor voltage measurement,scanning electron microscopy,and by spectroscopy ellipsometry.The XRD and DST-TG indicate the presence of an anatase TiO_2 phase in the film.Films deposited at higher temperatures showed better crystallinity.The dielectric constant calculated using the capacitance voltage measurement was found to be 18 and 73 for sputtering and sol-gel samples respectively.The refractive indices of the films were found to be 2.16 for sputtering and 2.42 for sol-gel samples.     

A Review of Recent Progress in Solid State Fabrication of Composites and Functionally Graded Systems Via Friction Stir Processing

Friction stir processing (FSP) is a rapidly emerging newer solid-state technique for composite fabrication. It involves surface modification which in turn enables successful adaptation of surface properties through plastic deformations in solid state. During initial years of FSP inception, it was primarily employed in development of metal matrix composites of light metal alloys like aluminum. However, recently, it has gained an alluring role in fabrication of composites of various nonferrous and ferrous metal alloys as well as of polymers. In addition to composite fabrication, FSP has evolved as a revolutionary technique in developing functionally graded systems/surfaces (FGS) of metal matrix. This article covers all aspects of FSP in which reinforcement particles are embedded in the base matrix to develop composites and FGS. It presents a critical review on domains of recent developments, effects of different types of reinforcement particles and properties enhancement of composites, and FGS fabrication. In addition to this, various issues, challenges, and future work that demand attention are systematically addressed.     

Image restoration in computed tomography: the spatially invariant point spread function

Image restoration to deblur smoothing caused by the finite-size X-ray beam profile for a simulated computed tomography (CT) system is presented. Three simple image restoration methods are compared when the point-spread-function (PSF) is spatially invariant. In the first restoration method, an iterative least squares solution, regularized with the image norm and constrained by the boundary of the object, is obtained from the projection data. In the second method, a Wiener filter, designed using the power spectrum of CT noise, is applied to the reconstructed CT image. The third method obtains a weighted least-squares solution, by iteration, from the reconstructed CT image; the solution is regularized with the weighted image norm. Restored images were compared with the image obtained using filtered backprojection method. Differences between these images were evaluated qualitatively.