A new consideration on reinforcement distribution in the different planes of nanostructured metal matrix composite sheets prepared by accumulative roll bonding (ARB)

Recently, a number of novel methods based on accumulative roll bonding (ARB) have been introduced to produce particulate metal matrix composites. Nonetheless, the microstructure uniformity from the reinforcement distribution viewpoint in the different planes of ARBed composite sheets has not been focused up to date. This paper aims to compare the evolution of the B₄C particles distribution in nanostructured Al-10 vol.% B₄C composites prepared by ARB in the rolling direction-normal direction (RD-ND) and transverse direction-normal direction (TD-ND) planes. From optical microscopic evaluations quantified by the radial distribution function analysis, it is realized that the homogeneity in the RD-ND planes is in excess of the TD-ND planes. In addition, transmission electron microscopy reveals the development of nanostructures in the Al matrix after seven ARB passes.     

A simplified analysis method for correlating rotary atomizer performance on droplet size and coating appearance

The dominant method of atomizing automotive paint is through the use of rotating bell sprayers. For this class of atomizer, the problem of paint thickness across the bell has been theoretically solved on a representative geometry that includes factors such as fluid flow rate, bell speed, bell cup radius, and fluid properties. It was assumed that the paint film eventually forms uniform ligaments at the bell cup edge that break due to hydrodynamic stability during the paint spray process; thus, creating a characteristic particle size distribution for the spray. These particle size distributions will vary as the spray parameters, specifically fluid flow rate, bell speed, and bell cup radius, vary. The theoretical model that has been developed strongly correlates to the literature data available for paint droplet size from rotary bell atomizers. Expansion of the correlation of the theoretical model to paint appearance wavelength measurements, Wc and Wd, in place of droplet size provides further understanding of the effect of paint spray parameters on paint appearance. Use of these correlations can help to optimize paint appearance and improve paint spray simulation results.     

Effect of process variables on product yield distribution in thermal catalytic cracking of naphtha to light olefins over Fe/HZSM-5

The effect of temperature, WHSV and Fe loading over HZSM-5 catalyst in thermal-catalytic cracking (TCC) of naphtha for the production of light olefins has been studied. The response surface defined by three most significant parameters is obtained from Box-Behnken design method and the optimal parameter set is found. The results show that ethylene increases with temperature, while propylene shows an optimum at 650 °C. Moderate WHSV is favorable for maximum production of light olefins. Addition of Fe to HZSM-5 has a favorable effect on the production of light olefins up to 6% of loading. Excess amount of loading decreases the conversion of naphtha, which leads to a drop in light olefin yields. The yield of light olefins (ethylene and propylene) at 670 °C, 44 hr⁻¹ and 6 wt% Fe has been increased to 5.43 wt% compared to the unmodified HZSM-5 and reaches to 42.47 wt%.     

Using weighted pseudo‐inverse method for reconstruction of reflectance spectra and analyzing the dataset in terms of normality

Most of spectral estimation methods are based on improving the learning‐based procedures which mainly modify the training sets used by the basic methods. In this article, a new method is developed for analyzing of superiority of these modified processes to the basic methods in terms of normality of datasets. Hence, two qualitative terms, named generality and similarity are introduced to interpret the recovery achievements of different databases and their roles as training and testing sets. Also, a simple technique based on dataset modification of pseudo‐inverse method is introduced for the recovery of reflectance spectra of samples from their corresponding colorimetric data. The method modifies the training dataset according to the color specifications of test sample. In fact, different weighting matrices are employed as dynamic modifiers to improve the pseudo‐inverse estimation as a simple recovery method. The employed datasets are examined in the self as well as cross test conditions and the results are spectrally and colorimetrically evaluated. The root mean square errors between the reconstructed and actual spectra along with the corresponding color difference values under different illuminants decrease by employing the suggested modification method in comparison to classical pseudo‐inverse technique as well as the recently improved version named optimized adaptive Wiener method. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010     

Development of a new analytical tool to design hierarchical truss beams for natural frequency

A set of recursive equations are introduced for optimum design of a wide range of hierarchical truss beams to satisfy a minimum required natural frequency. The design equations are based on a general analytical solution, which are derived based on a critical dimensional analysis. A practical example is examined in both 2D and 3D spaces, which promises substantial mass reduction, as much as 99%, when using high order hierarchical truss beams. The results are verified by numerical evaluation of three case studies. The approach looks also very promising to design nanostructures when it comes to the problems associated with vibration.     

A hybrid model of fuzzy goal programming and grey numbers in continuous project time,cost, and quality tradeoff

The purpose of this paper is to develop current mathematical models of cost, time, and quality tradeoffs in conditions that parameters of project activities are estimated uncertainly by grey numbers. In some projects like construction projects, activities can be done within a much shorter time by increasing in the resources, while project's cost may rise at the same time. In such situations, managers are usually required to determine the best combination of cost, time, and quality parameters of the activities, although their information regarding these parameters is limited and rather incomplete. The greyness of these parameters in the proposed method can aid managers to deal with these conditions. The most important aspect of the proposed model is that it considers uncertainty of the project planning data in the form of grey numbers. A combination of fuzzy goal programming and grey linear programming is also developed to solve the proposed model. Finally, this model will provide the managers with a stronger ability to face with uncertainty in project management and planning. The application of this model is examined in a numerical example. As its major finding, the model determines an optimal range in which the project managers can respond to intrinsic changes that may occur in the parameters during a project.     

Black Nickel Coating and Color Anodized Layers for Solar Absorber

Solar selective absorbers are considered as an essential part of a thermal solar collector for which the optical properties are dependent upon their structure and surface morphology. In this paper, optical properties of Ni-pigmented anodized are compared with black electroless nickel coatings. The effect of heat treatment on optical properties of the coatings was also investigated. Anodized films were formed in 6 M phosphoric acid followed by a black coloration process. Scanning electron microscope was used to study the morphology, and X-ray diffraction was employed to identify the phases present. Evaluation of optical properties was carried out by spectral reflectance. Evaluation of the optical characteristics showed that Ni-pigmented anodized and black electroless samples, after heat treatment, had the highest absorption coefficient at about 0.98 as well as the lowest emission coefficient. The ξ factor reached about 6 in heat treated Ni-pigmented anodized layer and offered optimal properties in this research.     

Analysis of multi-layered filament-wound composite pipes under combined internal pressure and thermomechanical loading with thermal variations

The composite pipes manufactured by filament winding technology have anisotropic behavior owing to different reinforced ply angles. Composite pipes can be exposed to the thermomechanical loading due to hot fluid that flows into them. In this paper, based on the three-dimensional anisotropic elasticity, an exact elastic solution for thermal stresses and deformations of the pipes under internal pressure and a temperature gradient has been studied. Giving heat convection conditions the variation of temperature field within the pipe is obtained by solving the conduction equation at the wall. The influence of temperature field in the governing equations of thermoelasticity has been considered via a constitutive law. The shear extension coupling is also considered because of lay-up angles. Stress, strain and deformation distributions for different angle-ply pipe designs are investigated using the present theory.