A hybrid denoising algorithm based on shearlet transform method and Yaroslavsky’s filter

In this paper, we have proposed a hybrid denoising algorithm based on combining of the shearlet transform method, as a pre-processing step, with the Yaroslavsky’s filter, as a kernel smoother, on a wide class of images with various properties such as thin features and textures. In the other word, proposed algorithm is a two-step algorithm, where in the first step the image is filtered by shearlet transform method and in the second step the weighted Yaroslavsky’s filter is applied on result of first step. The weight coefficients of the Yaroslavsky’s filter are achieved by pixel similarities in the denoised image from the first step. The theoretical results are confirmed via simulations for 2D images corrupted by additive white Gaussian noise. Experimental results illustrate that proposed hybrid method has good effect on suppressing the pseudo-Gibbs and shearlet-like artifacts can obtain better performance in terms of mean square error (MSE), peak signal to noise ratio (PSNR) and structural similarity (SSIM) index rather than existing state-of-the-art methods.     

Multi-objective optimization of a hatchback rear end utilizing fractional factorial design algorithm

Air flow has significant effects on fuel consumption, performance, and comfort. Decreasing drag coefficient enhances fuel consumption and vehicle performance. Moreover, omitting or reducing the power of aerodynamic noise sources provides passengers comfort. In this paper, optimization of a hatchback rear end is conducted considering drag and aerodynamic noise objectives. To this end, five geometrical parameters of the hatchback rear end are chosen as design variables in two levels. Numerical simulation is applied to survey air flow features around the models in the wind tunnel. To reduce the number of runs, fraction factorial design algorithm is applied to generate layout of the simulations which decreased the number of case studies to half. Main and interaction effects of these factors on drag coefficient and acoustic power of the rear end source are derived using analysis of variance. Optimum level for each parameter is chosen considering simultaneous drag and noise goals. Finally, characteristics of air flow and acoustic power around optimum model are discussed.

     

Pulsatile flow of blood using a modified second-grade fluid model

We study the unsteady pulsatile flow of blood in an artery, where the effects of body acceleration are included. The blood is modeled as a modified second-grade fluid where the viscosity and the normal stress coefficients depend on the shear rate. It is assumed that the blood near the wall behaves as a Newtonian fluid, and in the core as a non-Newtonian fluid. This phenomenon is also known as the Fahraeus–Lindqvist effect. The equations are made dimensionless and solved numerically.     

Effect of the Hierarchical Structure in Poly(propylene)/Clay Composites on their Thermal Stability: From Single‐ to Multi‐Step Degradation Processes

Composites with several hierarchical structures were prepared by using different clays, compatibilizers, and PPs. TGA showed that the thermal stability of the composites can be strongly improved, under either inert or thermo‐oxidative conditions, depending on the type of clay and its morphology. Drastic increases in the temperature of the maximum rate of weight loss (ΔT_peak ≈ 170 °C) under thermo‐oxidative conditions were observed depending on the clay dispersion. Furthermore, some composites had a complex multi‐step degradation behavior instead of a single‐step process related with different clay morphologies that can be present simultaneously. Finally, it was concluded that the TGA has a higher sensitivity toward the composite morphology than the mechanical properties.

     

Nickel-lithium oxide alloy transparent conducting films deposited by spray pyrolysis technique

In this research, nickel oxide (NiO) transparent semiconducting films are prepared by spray pyrolysis technique on glass substrates. The effect of Ni concentration in initial solution and substrate temperature on the structural, electrical, thermoelectrical, optical and photoconductivity properties of NiO thin films are studied. The results of investigations show that optimum Ni concentration and suitable substrate temperature for preparation of basic undoped NiO thin films with p-type conductivity and high optical transparency is 0.1 M and 450 °C, respectively. Then, by using these optimized deposition parameters, nickel-lithium oxide ((Li:Ni)O_x) alloy films are prepared. The XRD structural analysis indicate the formation of the cubic structure of NiO and (Li:Ni)O_x alloy films. Also, in high Li doping levels, Ni₂O₃ and NiCl₂ phases are observed. The electrical measurements show that the resistance of the films decreases with increasing Li level up to 50 at%. For these films, the optical band gap and carrier concentration are obtained to be 3.6 eV and 10¹⁵-10¹⁸ cm⁻³, respectively.     

Tool path accuracy enhancement through geometrical error compensation

Kinematic and geometric errors of CNC machine tools, introduce large deviations in the real path traveled by the cutting tool. Tool path deviation reduces geometrical and dimensional accuracy of the machined features of the component. Tool path modification is an effective strategy to increase accuracy of the machined features. An improved error estimation model based on kinematic transformation concepts has been developed and used to calculate the volumetric overall error. These calculations are applicable for each arbitrary target positions of the machine's work space. Also a NC Program editor software has been developed in order to manage the calculations, modifications and to generate the new compensated NC program. The compensation procedure includes: fragmentation of nominal tool path to small linear elements, translating nominal position of elements to real positions using the Kinematics error model, finding compensated positions using the error compensation algorithm, converting newly generated elements to new tool paths using the packing algorithms and finally editing old NC program using NC code generator algorithm. Experimental tests showed 4-8 times accuracy improvement for linear, and S-pline tool paths deviations.     

Experimental and finite element analysis of EDM process and investigation of material removal rate by response surface methodology

In this study, thermal modeling and finite element simulation of electrical discharge machining (EDM) has been done, taking into account several important aspects such as temperature-dependent material properties, shape and size of the heated zone (Gaussian heat distribution), energy distribution factor, plasma flushing efficiency, and phase change to predict thermal behavior and material removal mechanism in EDM process. Temperature distribution on the cathode has been calculated using ANSYS finite element code, and the effect of EDM parameters on heat distribution along the radius and depth of the workpiece has been obtained. Temperature profiles have been used to calculate theoretical material removal rate (MRR) from the cathode. Theoretically calculated MRRs are compared with the experimental results, making it possible to precisely determine the portion of energy that enters the cathode for AISI H13 tool steel. Also in this paper, the effect of EDM parameters on MRR has been investigated by using the technique of design of experiments and response surface methodology. Finally, a quadratic polynomial regression model has been proposed for MRR, and the accuracy of this model has been checked by means of analysis of residuals.     

Plasma surface modification and characterization of collagen‐based artificial cornea for enhanced epithelialization

Argon plasma treatment enhanced the attachment of epithelial cells to a collagen‐based artificial cornea crosslinked using glutaraldehyde (GA) and glutaraldehyde‐polyethylene oxide dialdehyde (GA‐PEODA) systems. The epithelialization of untreated and treated surfaces was evaluated by the seeding and growth of human corneal epithelial cells. Characterization of polymer surface properties such as surface hydrophilicity and roughness was also made by contact angle measurement and atomic force microscopy, respectively. Contact angle analysis revealed that the surface hydrophilicity significantly increased after the treatment. In addition, AFM characterization showed an increase in surface roughness through argon plasma treatment. Based on the biological and surface analysis, argon plasma treatment displays promising potential for biocompatibility enhancement of collagen‐based artificial corneas. It was also found that the cell attachment to artificial cornea surfaces was influenced by the combined effects of surface chemistry (i.e., surface energy), polymer surface morphology (i.e., surface roughness), and polar interactions between functional groups at the polymer surface and cell membrane proteins. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007