Dispersion and Deposition of Spherical Particles from Point Sources in a Turbulent Channel Flow

The dispersion and deposition of particles from a point source in a turbulent channel flow are studied. An empirical mean velocity profile and the experimental data for turbulent intensities are used in the analysis. The instantaneous turbulence fluctuation is simulated as a continuous Gaussian random field, and an ensemble of particle trajectories is generated and statistically analyzed. A series of digital simulations for dispersion and deposition of aerosol particles of various sizes from point sources at different positions from the wall is performed. Effects of Brownian diffusion on particle dispersion are studied. The effects of variation in particle density and particle-surface interaction are also discussed.     

Thermo-elastic/plastic semi-analytical solution of incompressible functionally graded spherical pressure vessel under thermo-mechanical loading

In this paper, numerical solutions to assess partially plastic and fully plastic deformation behavior of a functionally graded spherical pressure vessel are presented. The modulus of elasticity of the material is assumed to vary nonlinearly in the radial direction and axisymmetric displacements and stresses in the functionally graded spherical vessel subjected to thermal loading and uniform internal pressure are determined using plasticity theory. Tresca??s yield criterion and its associated flow rule are used to formulate different plastic regions for an ideal FG material. In this way, the material property varies by Young??s modulus that may be an arbitrary function of the radial coordinate. Therefore, the material is assumed to be functionally graded in the radial direction. Hence, the general analytical solutions of such equations are not available, the numerical method (semi-analytical) is applied and a new collection of equilibrium equations with small deflections is presented. Accordingly, the radial domain is divided into some virtual sub-domains in which the power-law distribution is used for the thermomechanical properties of the elemental components. By considering the necessary continuity conditions between adjacent sub-domains, jointly with the global boundary conditions, a set of linear differential equations is obtained. Solution of the linear differential equations yields the thermoelastic responses for each sub-domain as exponential functions of the radial coordinate. Subsequently, attributed to centrifugal force, results for the stress, strain, and displacement components along the radius in elastic and plastic area are presented.     

Metaheuristics for fuzzy dynamic facility layout problem with unequal area constraints and closeness ratings

Dynamic facility layout problem deals with the problem of arranging and rearranging the layout plan of a system throughout several periods. In each period, the material handling costs are different from the past period due to the change in the market demand and product mix. In this paper, the uncertainty that exists in transportation values’ forecast is modeled by fuzzy theory. In this paper, departments have unequal areas. This means that in each period, departments can be placed only in certain places due to different spacing requirements. In addition, closeness rating matrix is considered in order to model the goodness of different layout plans with regard to qualitative factors according to decision maker. Accordingly, fuzzy dynamic facility layout problem with unequal areas and closeness rating matrix is considered that aims to minimize the uncertain material handling costs as well as the shifting costs, and maximize closeness rating with regard to space requirements of unequal area departments. A number of fuzzy algorithms are developed in order to deal with the problem. A number of ranking criteria from the literature are implemented in order to compare the performance of the developed algorithms.     

A miniaturised monopole antenna for ultra-wide band applications with band-notch filter

This study presents a new miniaturised printed monopole antenna. The size of the antenna is 18 x 18 mm². First simple design rules are given to arrive at an initial design for the antenna, then the antenna parameters are optimised for utilisation in ultra wide band (UWB) applications. The performance parameters like voltage standing wave ratio (VSWR) of the single antenna as well as transmission function, group delay and the fidelity factor of a two-antenna system are calculated and measured. It is shown that the band-notched performance can be obtained from the designed antenna by introducing simple p-shape or V-shape slots in its radiating element. Good agreements between simulated and measured results are observed.     

Influence of solvent on thermodynamic parameters and stability of some multicomponent polymer complexes involving an acrylic polymer,poly (ethylene imine) and poly (vinyl pyrrolidone)

Summary Stability constant and thermodynamic parameters (e.g. ΔH⁰ and ΔS⁰) have been determined at several temperatures for some multicomponent complexes of varying composition involving poly (acrylic acid) (PAA), poly (vinyl pyrrolidone) (PVP) and poly (ethylene imine) (PEI) in aqueous medium and water-DMSO mixture. It has been observed that the stability constant and thermodynamic parameters of the interpolymer complexes change due to presence of organic solvent in the medium. Some of these observations have been attributed to the change in the degree of solvation of component polymers, reduced hydrophobic interaction and dielectric constant of the medium.     

Restoration of images degraded by compound noise sources using Markov random field models

The main theme of this paper is the derivation of a new algorithm for restoring digitized images degraded by both additive and multiplicative noise sources. In order to keep the derivation sufficiently general, the authors also include degradation caused by blur and a class of nonlinearities. The images under consideration are modeled as Markov random fields, while the additive and multiplicative noise sources are assumed to be Gaussian processes with known means and variances. Blurring of images is accomplished by a shift-invariant point-spread function. Test results with degraded images indicate that the algorithm is effective in restoring images degraded by high levels of additive and multiplicative noise.     

Flexible Prime‐Field Genus 2 Hyperelliptic Curve Cryptography Processor with Low Power Consumption and Uniform Power Draw

This paper presents an energy‐efficient (low power) prime‐field hyperelliptic curve cryptography (HECC) processor with uniform power draw. The HECC processor performs divisor scalar multiplication on the Jacobian of genus 2 hyperelliptic curves defined over prime fields for arbitrary field and curve parameters. It supports the most frequent case of divisor doubling and addition. The optimized implementation, which is synthesized in a 0.13 μm standard CMOS technology, performs an 81‐bit divisor multiplication in 503 ms consuming only 6.55 μJ of energy (average power consumption is 12.76 μW). In addition, we present a technique to make the power consumption of the HECC processor more uniform and lower the peaks of its power consumption.     

Classification of acoustic emission signals collected during tensile tests on unidirectional ultra high molecular weight polypropylene fiber reinforced epoxy composites using principal component analysis

The objective of this study is to utilize a mathematical procedure for the evaluation of damage mechanism in ultra high molecular weight polypropylene/epoxy composite (UHMWPP/epoxy) specimen with different configuration based on the analysis of the AE signals of presented. Principal component analysis (PCA) is powerful tool, which utilized for the classification of the monitored AE transients. We worked on epoxy L160 resin, UHMWPP fiber bundle and UHMWPP/epoxy unidirectional specimens, subjected to tensile loading. Using model specimens exhibiting a predominant damage mechanism, correlations were established between the observed damage growth mechanisms and the AE parameter variances result in PCA. Outputs from this study revealed that the PCA is an effective tool for identifying damage modes such as matrix cracking, fibre/matrix debonding, fibre breakage and fibre pull-out in the UHMWPP/epoxy composites. The presence of damage modes in UHMWPP/epoxy composites was proven with scanning electron microscopy (SEM) images.     

Evaluation of patient dose in some mammography centres in Iran

High diagnostic sensitivity and specificity while maintaining the least dose to the patient is the ideal mammography. The objective of this work was to evaluate patient dose and image quality of mammograms to propose corrective actions. The image quality for 1242 patient in 7 mammography facilities in Tehran city was evaluated based on selected image quality criteria using a three-point scale. Clinical image quality, the entrance surface air kerma, the average glandular dose and optical density of films for standard PMMA phantom of 4.5 cm thickness were evaluated. The results showed that up to 72 % of mammograms were in good condition to be diagnosed, and only about 3.4 % of the images were unacceptable or with suboptimal quality. The entrance surface air kerma values were in the range of 3.8-10.5 mGy, average glandular dose 0.5-1.8 mGy and optical density of films 0.74-2.03. The image quality evaluation after correction actions, periodic image quality evaluation and using the correct equipment certainly will improve patient dose.     

An integrated approach based on acoustic emission and mechanical information to evaluate the delamination fracture toughness at mode I in composite laminate

This paper addresses a new method based on the combination of mechanical behavior and acoustic emission (AE) information of composite materials during mode I delamination. The method is based on a special purpose function, called sentry function, which is defined as the logarithm of the ratio between mechanical energy and acoustic energy (f = Ln(E_s/E_a)). The sentry function is used to study the delamination process and to evaluate the delamination fracture toughness in mode I. The relationship between cumulative fracture toughness energy release rate (G_I) and the integral of the sentry function during crack propagation showed a transition point with two sensitive regions below and above it. This behavior can be followed to obtain the critical strain energy release rate value (G_Ic). Results obtained by means of the sentry function are compared with results obtained by a methodology proposed by other authors.