Non-uniform Parameters Research Articles

An Optimal Parametrization Scheme for Path Generation Using Fourier Descriptors for Four-Bar Mechanism Synthesis

Fourier descriptor (FD)-based path synthesis algorithms for generation of planar four-bar mechanisms require assigning time parameter values to the given points along the path. An improper selection of time parameters leads to poor fitting of the given path and suboptimal four-bar mechanisms while also ignoring a host of mechanisms that could be potentially generated otherwise. A common approach taken is to use uniform time parameter values, which does not take into account the unique harmonic properties of the coupler path. In this paper, we are presenting a nonuniform parametrization scheme in conjunction with an objective function that provides a better fit, leverages the harmonics of the four-bar coupler, and allows imposing additional user-specified constraints.

MHD natural convection and entropy generation of ferrofluids in a cavity with a non-uniformly heated horizontal plate

Numerical analysis has been performed to study natural convection heat transfer combined with entropy generation of ferrofluid in a square cavity with a non-uniformly heated centered horizontal plate under the influence of inclined uniform magnetic field. The vertical borders of the enclosure are kept at constant low temperatures while the horizontal walls are adiabatic. The centrally located heated plate has a linear changed temperature along the plate. Basic equations formulated in dimensionless primitive variables have been solved by the finite difference method. The impacts of governing parameters such as Hartmann number (Ha = 0–100), magnetic field inclination angle (γ = 0°–90°), dimensionless temperature difference (Ω = 0.001–0.1), nanoparticles volume fraction (ϕ = 0.01–0.04) and plate non-uniformity parameter (λ = 0 and 1) on the flow structures, thermal transmission characteristics and entropy generation parameters have been investigated. Computational results have shown that a growth of the Hartmann number decreases the average Nusselt number and average entropy generation. In addition, it is observed that an inclusion of nanoparticles leads to the rise of the heat transfer rate and average entropy generation.

Wall Properties and Slip Consequences on Peristaltic Transport of a Casson Liquid in a Flexible Channel with Heat Transfer

Abstract In this paper, the peristaltic wave propagation of a Non-Newtonian Casson liquid in a non-uniform (flexible)channel with wall properties and heat transfer is analyzed. Long wavelength and low Reynolds number approximations are considered. Analytical solution for velocity, stream function and temperature in terms of various physical parameters is obtained. The impact of yield stress, elasticity, slip and non-uniformity parameters on the peristaltic flow of Casson liquidare observed through graphs and discussed. The important outcome is that an increase in rigidity, stiffness and viscous damping force of the wall results in the enhancement of the size and number of bolus formed in the flow pattern.

Effects of Slip, Brownian Motion and Thermophoresis on Peristaltic Pumping of Nano Fluid in an Asymmetric Channel with Porous Medium

This paper deals with peristaltic motion of electrically conducting nanofluid in a tapered asymmetric channel through a porous medium in presence of heat and mass transfer under the effect of slip conditions. The problem is reduced mathematically by a set of nonlinear partial differential equations which describe the conservation of mass, momentum, energy and concentration of nanoparticles. The non-dimensional form of these equations is simplified under the assumption of long wavelength and low Reynolds number. The coupled governing equations are solved analytically. The expressions for velocity, stream function, temperature and concentration are derived. The results have been presented graphically for the various interested emerging parameters and the obtained results are discussed in detail. It is observed that the magnitude of the velocity decreases in the middle of the channel while it increases near the channel walls with an increase in the non-uniform parameter It is also noticed that the nanoparticle temperature increases with increasing thermal slip parameter . The present result coincides with the findings of Kothandapani and Prakash [19].

Effect of mutually orthogonal heated plates on buoyancy convection flow of micropolar fluid in a cavity

PurposeThe main purpose of this study is to investigate the natural convection of micropolar fluid in a square cavity with two orthogonal heaters placed inside. The study of natural convection in a two-dimensional enclosure determines the effect of non-uniform heated plate on certain micropolar fluid flows which are found in many engineering applications. Therefore, because of its practical interest in the engineering fields such as building design, cooling of electronic components, melting and solidification process, solar energy systems, solar collectors, liquid crystals, animal blood, colloidal fluids and polymeric fluids, the topic needs to be further explored.Design/methodology/approachThe dimensionless governing equations have been solved by finite volume method of the second-order central difference and upwind scheme.FindingsThe effects of the Rayleigh number, nonuniformity parameter and vortex viscosity parameter on fluid flow and heat transfer have been analyzed. The rate of heat transfer increases with an increase in the aspect ratio of the heated plates for all the values of Rayleigh number and vortex viscosity parameter. The heat transfer rate is reduced with an increase in the vortex viscosity parameter. It is predicted that the non-uniform of the baffle gives better heat transfer than uniform heating.Originality/valueThe present numerical results were tested against the experimental work. The present results have an excellent agreement with the results obtained by the previous experimental work.

Digital imaging devices as sensors for iron determination

Portable, sensitive and cost-effective sensors represent an unmet need, especially in resource-limited settings and locally deprived communities. Digital imaging devices can fill the gap. Thus, we have tested a desktop scanner, a digital camera and a smartphone to determine iron using three standard colour reactions. Images of reacting solutions were analysed to obtain the RGB (red, green and blue) non-uniform colour space parameters. To improve the calibration linearity, sensitivity, and detection limit, we converted the RGB intensities into six uniform colour space values and two colour differences attributes. The converted signals surpassed the RGB signals and compared well with reference spectrophotometric signals. The simplicity and sensitivity of this approach make digital imaging devices as excellent competitors to field-monitoring instruments and sophisticated spectrophotometers. Our approach was successfully applied to the assessment of iron in Nile river water, soils, plant materials and meat and liver samples.

Effect of Inclusions on Magnetostriction in Superconducting Cylinder with Exponential Distribution of Critical-Current Density

The magnetoelastic behaviour subjected to the electromagnetic body force induced by flux pinning is studied with Kim model for zero-field cooling (ZFC) magnetization process, in which the non-uniform parameter η is considered for inclusion-superconducting matrix system. For superconducting composites, the effect of inhomogeneous distribution of critical current density on effective magnetostriction is also obtained based on the plane strain approach. The results show that the exponential distribution of critical-current density will lead to a larger trapped field and magnetostriction inside the inhomogeneous sample, which also means that it is worthwhile to investigate the magnetoelastic problem of bulk superconductors with inhomogeneous distribution of critical-current density.

MHD stagnation point slip flow due to a non-linearly moving surface with effect of non-uniform heat source

AbstractIn this paper, we have studied the heat transfer characteristics of stagnation point flow of an MHD flow over a non-linearly moving plate with momentum and thermal slip effects in presence of non-uniform heat source/sink. The governing differential equations are transformed into the ordinary differential equations using suitable similarity transformations. These equations which are BVPs’ and are solved using a numerically by fourth order Runge-Kutta method using MAPLE computing software. The effects of governing parameters are studied on flow, velocity and heat distributions and are discussed in detail. It is observed that the non-uniform heat source parameters enhance the temperature distribution. Our results are agreed well with previously published results for some limiting conditions, which validate our present results are correct.

Electromagnetic Field Inhomogeneity in Artificial Crystals with Ferrimagnetic Particles

An algorithm for estimating the inhomogeneity of the microwave electromagnetic field is proposed for micro- and nano-heterogeneous media in a magnetic field. It is shown that the nonuniformity parameter for the microwave field in an artificial crystal containing ferrimagnetic particles depends significantly on the constant magnetic field, and the minimal value of the nonuniformity parameter corresponds approximately to the field of ferromagnetic resonance.

Convective–radiative heat transfer in a cavity filled with a nanofluid under the effect of a nonuniformly heated plate

PurposeThe purpose of this study is to examine the radiation effect on the natural convective heat transfer of an alumina–water nanofluid in a square cavity in the presence of centered nonuniformly heated plate.Design/methodology/approachThe square cavity filled with alumina–water nanofluid has a nonuniformly heated plate placed horizontally or vertically at its center. The plate is heated isothermally with linearly varying temperature. The vertical walls are cooled isothermally with a constant temperature, while the horizontal walls are insulated. The governing equations have been discretized using finite volume method on a uniformly staggered grid system. Simulations were carried out for different values of the heated plate nonuniformity parameter (λ = –1, 0 and 1), the nanoparticles solid volume fraction (Φ = 0.01 − 0.04) and the radiation parameter (Rd = 0 – 2) at the Rayleigh number of Ra = 1e+07.FindingsIt is found that the total heat transfer rate is enhanced with an increase in the radiation parameter for both the horizontal and vertical plates. The role of nanoparticles addition to the base fluid can have dual effects on the heat transfer rate by augmenting and dampening for the absence of radiation while it dampens the heat transfer rate for the presence of radiation.Originality/valueThe originality of this work is to analyze steady natural convection in a square cavity filled with a water-based nanofluid in the presence of centered nonuniformly heated plate. The results would benefit scientists and engineers to become familiar with the analysis of convective heat and mass transfer in nanofluids, and the way to predict the properties of nanofluid convective flow in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

Systematic Evaluation of Non-Uniform Sampling Parameters in the Targeted Analysis of Urine Metabolites by 1H,1H 2D NMR Spectroscopy

Non-uniform sampling (NUS) allows the accelerated acquisition of multidimensional NMR spectra. The aim of this contribution was the systematic evaluation of the impact of various quantitative NUS parameters on the accuracy and precision of 2D NMR measurements of urinary metabolites. Urine aliquots spiked with varying concentrations (15.6–500.0 µM) of tryptophan, tyrosine, glutamine, glutamic acid, lactic acid, and threonine, which can only be resolved fully by 2D NMR, were used to assess the influence of the sampling scheme, reconstruction algorithm, amount of omitted data points, and seed value on the quantitative performance of NUS in 1H,1H-TOCSY and 1H,1H-COSY45 NMR spectroscopy. Sinusoidal Poisson-gap sampling and a compressed sensing approach employing the iterative re-weighted least squares method for spectral reconstruction allowed a 50% reduction in measurement time while maintaining sufficient quantitative accuracy and precision for both types of homonuclear 2D NMR spectroscopy. Together with other advances in instrument design, such as state-of-the-art cryogenic probes, use of 2D NMR spectroscopy in large biomedical cohort studies seems feasible.

Seismic bearing capacity of non-uniform soil slopes using discretization-based kinematic analysis considering Rayleigh waves

This study aims to present a procedure for predicting the bearing capacity of a soil slope under seismic loading. The emphasis is on the variations of soil strength parameters. In order to account for soil profile with varying friction angles in the generation of a potential collapse mechanism, the discretization technique is introduced. The kinematically admissible failure surface is gradually formed by ‘point-to-point’ method. The modified pseudo-dynamic approach is employed to represent seismic accelerations and forces, with considerations to the Rayleigh wave apart from the primary and shear waves. The upper bound solution of limiting surcharge is formulated from the work rate-based balance equation. The results obtained from the discretization-based kinematic analysis are compared with those computed with the conventional upper bound analysis using the pseudo-static approach. In order to better understand the implication of non-uniform strength parameters on the ultimate bearing capacity and the extent of critical failure surface, a parametric study is carried out to encompass a range of spatial variations of soil strength parameters.

Optimization of highly efficient random grating thin-film solar cell using modified gravitational search algorithm and particle swarm optimization algorithm

A design of hydrogenated amorphous silicon (a-Si:H) solar cell (SC) based on one-dimensional subwavelength grating with nonuniform distribution is proposed and optimized using modified hybrid gravitational search algorithm and particle swarm optimization (GSA-PSO). The reported structure consists of nine gratings with different widths, positions, and heights that can enhance the light trapping through the SC. The nonuniform grating positions and geometrical parameters of the proposed design are optimized in terms of absorption, ultimate efficiency, and short circuit current density. The absorption inside the active layer is enhanced by 67.5% over the conventional thin-film SC. Further, the exposed area caused by forward nanotexturing surface is increased. Moreover, the nonuniform grating parameters and distribution support better light absorption than the periodic grating distribution by increasing the optical path length of the incident light through the active layer. Therefore, the suggested SC achieves a broadband absorption improvement. The enhanced absorption in the active layer is reported using three-dimensional finite-difference time-domain method. In addition, the performance of the suggested SC using different active layer materials, i.e., crystalline silicon, a-Si:H, and gallium arsenide is studied. The hydrogenated amorphous silicon-based design shows high ultimate efficiency of 38.73%, short-circuit current density (JSC) of 34.69 mA / cm2, open-circuit voltage of 1.0393 V, and power conversion efficiency of 35.4%. The modified GSA-PSO algorithm shows also high potential for the design and optimization of different types of solar cells.

New Method for Determining the Thermoemission Nonuniformity Parameters of Cathode Materials for Microwave Devices

A new method developed here for studying the thermoemission nonuniformity parameters of cathode materials makes it possible to determine the temperature dependences of the average size of the thermoemission centers on the cathode surface, the average distance between thermoemission centers, the relative area of the emission-active surface of the cathodes, and the true value of the work function for emissionactive centers on the cathode surface by processing the current–voltage characteristics. The method is tested on nickel oxide, agglomerated nickel oxide, and impregnated cathodes.

Calculation of dose volume parameters and indices in plan evaluation of HDR interstitial brachytherapy by MUPIT in carcinoma cervix.

Evaluation of a HDR- interstitial brachytherapy plan is a challenging job. Owing to the complexities and diversity of the normalization and optimization techniques involved, a simple objective assessment of these plans is required. This can improve the radiation dose coverage of the tumour with decreased organ toxicity. To study and document the various dose volume indices and parameters required to evaluate a HDR interstitial brachytherapy plan by Volume normalization and graphical optimization using MUPIT (Martinez Universal Perineal Interstitial Template) in patients of carcinoma cervix. Single arm, retrospective study. 35 patients of carcinoma cervix who received EBRT and HDR brachytherapy using MUPIT, were selected. The dose prescribed was 4 Gray/Fraction in four fractions (16Gy/4) treated twice daily, at least 6 hours apart. CTV and OARs were delineated on the axial CT image set. Volume normalization and graphical optimization was done for planning. Coverage Index (CI), Dose homogeneity index (DHI), Overdose index (OI), Dose non-uniformity ratio (DNR), Conformity Index (COIN) and dose volume parameters i.e. D2cc, D1cc, D0.1cc of rectum and bladder were evaluated. SPSS version 16 was used. CI was 0.95 ± 1.84 which means 95% of the target received 100% of the prescribed dose. The mean COIN was 0.841 ± 0.06 and DHI was 0.502 ± 0.11. D2cc rectum and bladder was 3.40 ± 0.56 and 2.95 ± 0.62 respectively which was within the tolerance limit of this organs. There should be an optimum balance between these indices for improving the quality of the implant and to yield maximum clinical benefit out of it, keeping the dose to the OARs in limit. Dose optimization should be carefully monitered and an institutional protocol should be devised for the acceptability criteria of these plans.

Modeling and Simulation of Transverse Free Vibration Analysis of a Rectangular Plate with Cutouts Using Energy Principles

A modeling method is proposed for the vibration characteristics of rectangular plates with cutouts having variable size. Different from the existing modeling method by considering the cutout as an extremely thin part of the plate, the energy principles in conjunction with Rayleigh‐Ritz solution technique are employed for the modeling of the structure. Under this theoretical framework, the effect of the cutout is taken into account by subtracting the energies of the cutout domains from the total energies of the whole plate with arbitrary boundary conditions. The displacement of the rectangular plate with nonuniform physic parameters is expressed as the combination of a two‐dimensional trigonometric cosine series and supplementary terms introduced to ensure the uniform convergence of the solution over the entire solution domain including the cutouts boundary. The effectiveness and reliability of the eigenmodes of the rectangular plate with cutouts are checked against the results obtained by the finite element method (FEM). The cutout number, position, and size are varied to illustrate the effect of the cutouts on the vibration characteristics of the rectangular plate with cutouts.

QuickSun 830A module solar simulator. Study of mini PV modules

QS830A module solar simulator is applied to measure electrical parameters of standard PV modules based on mono/polycrystalline silicon solar cells, large format photovoltaic (PV) modules 150 cm x 220 cm, with effective measurements time of 2 ms / 4 ms, flush pulse duration 3 ms / 10 ms (one flash tube / two flash tubes), and non-uniformity less than 2%. In order to comply with the Class AAA tolerances of the standard IEC 60904-9 Edition 2.0 of QuickSun 830A simulators (Endeas Oy, Finland), proprietary optical system behind the light source filament has been developed for filtering spectrum and improving irradiance nonuniformity simultaneously. Non-uniformity parameter for 14% of total modules testing area, i.e. 0.65 m2, will be appointed in this work.

Development of an Airline Model with Non-Uniform Parameters for Coordination Studies of Isolation

Development of an Airline Model with Non-Uniform Parameters for Coordination Studies of Isolation

Non-uniform interpolatory subdivision surface

This paper presents an interpolatory subdivision scheme with non-uniform parametrization for arbitrary polygon meshes with arbitrary manifold topology. This is the first attempt to generalize the non-uniform four point interpolatory curve subdivision to surface with extraordinary points. The scheme is constructed from the inspiration of the relation between the non-uniform four-point interpolatory subdivision scheme and the non-uniform B-spline refinement rule. Numerical examples and comparisons with the uniform interpolatory subdivision schemes indicate that the quality of the limit surface can be improved by using non-uniform parameter values for non-uniform initial data.

Revisiting crown stability of tunnels deeply buried in non-uniform rock surrounds

A kinematic analysis procedure is presented to investigate the crown stability of deep-buried tunnels in non-uniform rock strata. The non-uniformity of rock properties is considered using the discretized approach with finite thickness layers. In the realm of upper bound theory, kinematic analysis is briefly presented for a single layer so as to provide basis for multi-layer analysis. A 2D collapse mechanism is postulated to depict the potential falling block with an arbitrary tunnel cross-section, although rectangular tunnels are considered in the 3D kinematic analysis for ease of calculation. An impending collapse is likely to occur, provided that the width of the excavation is no less than the collapse width. In order to reflect the nonlinear characteristics of rock materials at failure, the Hoek-Brown criterion is employed for tightly interlocked and very poor rock masses, with its form expressed by normal and shear stresses to facilitate calculations of internal energy dissipation rate. Based on the variational principle and power-based balance equation, the effective collapse mechanism is derived in closed form. Comparison is carried out to verify the robustness of the proposed approach. Sensitivity analysis is performed to depict the influence of each non-uniform rock strength parameter on crown stability. As expected, such a discretized approach incorporated into kinematic analysis enables one to account for non-uniformity of rock surrounds, which would fill the knowledge and design gap of similar tunnelling issues much needed at present state of practice.