Effect of particle content, size and temperature on magneto-thermo-mechanical creep behavior of composite cylinders

The effects of particle content, particle size, operating temperature and magnetic field on steady-state creep behavior of thick-walled rotating cylinders made of Al-SiC composites have been investigated. Loading is composed of a uniform magnetic field in axial direction, steady-state heat conduction in radial direction and an inertia body force due to rotation. The composite creep constitutive equation has been described by Norton’s law in which the creep parameters are functions of particle size, temperature and particle content. The composite properties are radial dependent based on volume fraction of SiC reinforcement. It has been found that the minimum effective creep strain rate belongs to a composite identified by 25% SiC at the inner and 5% at the outer surfaces. Therefore this composite has been selected for the design of the cylinder. It has been concluded that increasing particle size and operating temperature significantly increases the effective creep strain rates. It has also been illustrated that magnetic field decreases the stresses and the effective creep strain rates.     

Magnetothermoelastic creep analysis of functionally graded cylinders

This paper describes time-dependent creep stress redistribution analysis of a thick-walled FGM cylinder placed in uniform magnetic and temperature fields and subjected to an internal pressure. The material creep, magnetic and mechanical properties through the radial graded direction are assumed to obey the simple power law variation. Total strains are assumed to be the sum of elastic, thermal and creep strains. Creep strains are time, temperature and stress dependent. Using equations of equilibrium, stress–strain and strain–displacement a differential equation, containing creep strains, for displacement is obtained. Ignoring creep strains in this differential equation a closed form solution for the displacement and initial magnetothermoelastic stresses at zero time is presented. Initial magnetothermoelastic stresses are illustrated for different material properties. Using Prandtl–Reuss relation in conjunction with the above differential equation and the Norton’s law for the material uniaxial creep constitutive model, the radial displacement rate is obtained and then the radial and circumferential creep stress rates are calculated. Creep stress rates are plotted against dimensionless radius for different material properties. Using creep stress rates, stress redistributions are calculated iteratively using magnetothermoelastic stresses as initial values for stress redistributions. It has been found that radial stress redistributions are not significant for different material properties, however major redistributions occur for circumferential and effective stresses.     

Nonsymmetric thermomechanical analysis of a functionally graded cylinder subjected to mechanical,thermal, and magnetic loads

Thermoelastic analysis of a functionally graded cylinder under nonsymmetric thermal and mechanical loadings subjected to uniform magnetic field is presented in this article. All material properties are assumed to be variable along the thickness direction based on the power law. Due to nonsymmetric thermal and mechanical loadings and boundary conditions, a two-dimensional displacement field along the radial and circumferential directions is assumed for our analysis. The complex form of Fourier series is used as the method of solution. The nonsymmetric analysis of this problem for Lorentz force leads to radial and circumferential force components. The obtained results of this analysis indicate that the different parameters of material and loading have a considerable effect on the nonsymmetric behavior of cylinder.     

Functional finishing of cotton fabrics using graphene oxide nanosheets decorated with titanium dioxide nanoparticles

This study examined an innovative approach for imparting multi-functional properties, i.e. self-cleaning, electrical conductivity, ultraviolet (UV) blocking as well as antimicrobial properties onto cotton fabric. Graphene oxide/TiO₂ nanocomposites were successfully prepared, by a simple method of mixing and sonication, and used for multi-functional treatment of cotton fabrics by dip-drying technique. The physicochemical properties of the prepared samples were characterized with field emission scanning electron microscope, transmission electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy. Self-cleaning performance, electrical resistance, antimicrobial properties, and UV blocking activity of treated fabrics were also assessed. The coated cotton fabrics with graphene oxide/TiO₂ nanocomposite showed excellent photocatalytic self-cleaning activity measured by degradation of methylene blue in aqueous solution under sunlight irradiation. Results showed that the electrical conductivity of the graphene oxide/titanium dioxide nanocomposite-coated fabrics was improved significantly after sunlight irradiation. Moreover, the nanocomposite finished cotton fabric demonstrated proper antimicrobial properties and UV blocking activity.     

The impact of nitrogen low temperature plasma treatment upon the physical–chemical properties of polyester fabric

An approximate theoretical analysis of the cantilever stiffness test is presented. This yields convenient formulae for calculating the bending parameters of fabrics. The formulae show good agreement with Peirce's empirical equation and reasonable agreement with Grosberg and Swani's graphical method.     

Developing a new model for simultaneous scheduling of two grand projects based on game theory and solving the model with Benders decomposition

Grand infrastructure projects, such as dam, power plant, petroleum, and gas industry projects, have several contractors working on them in several independent sub-projects. The concern of reducing the duration of these projects is one of the important issues among various aspects; thus, our aim is to fulfill the requirements by using the game theory approach. In this study, a mixed-integer programming model consisting of game theory and project scheduling is developed to reduce the duration of projects with a minimum increase in costs. In this model, two contractors in successive periods are entered into a step-by-step competition by the employer during dynamic games, considering an exchange in their limited resources. The optimum solution of the game in each stage are selected as the strategy, and the resources during the game are considered to be renewable and limited. The strategy of each contractor can be described as follows: 1) share their resources with the other contractor and 2) not share the resources with the other contractor. This model can act dynamically in all circumstances during project implementation. If a player chooses a non-optimum strategy, then this strategy can immediately update itself at the succeeding time period. The proposed model is solved using the exact Benders decomposition method, which is coded in GAMS software. The results suggest the implementation of four step-by-step games between the contractors. Then, the results of our model are compared with those of the conventional models. The projects’ duration in our model is reduced by 22.2%. The nominal revenue of both contractors has also reached a significant value of 46078 units compared with the relative value of zero units in the original model. Moreover, we observed in both projects the decreases of 19.5%, 20.9%, and 19.7% in the total stagnation of resources of types 1, 2, and 3, respectively.     

The effects of TEOS on the microstructure and phase evolutions of YAG phase by formation of alumina/yttria core‐shell structures

In this work, pure yttrium aluminum garnet was obtained by the partial chemical method at the low temperature. In this approach, alpha‐alumina nanoparticle, yttrium nitrate, urea, and tetraethyl orthosilicate (TEOS) were used as Al³⁺, Y³⁺, precipitation agent, and both dispersant and phase formation assistant agents, respectively. The results showed that TEOS molecules as a dispersant agent caused the less agglomeration of the alumina‐yttria core‐shell structure with a diameter of 200‐300 nm, as compared to particles obtained without using TEOS molecules. Furthermore, by using 0.5 and 1 wt% of TEOS, the YAG formation temperature was decreased from 1400°C to 1200°C through the liquid‐phase diffusion mechanism. Thus, in this case, the TEOS molecules acted as phase formation assistant agent for the constitution of YAG phases.     

Pasternak foundation effect on the axial and torsional waves propagation in embedded DWCNTs using nonlocal elasticity cylindrical shell theory

The axial and torsional wave propagation in a double-walled carbon nanotube (DWCNT) embedded on elastic foundations are investigated using nonlocal continuum shell theory. The effects of the surrounding elastic medium are considered using the spring constant of the Winkler-type and the shear constant of the Pasternak-type. The van der Waals (vdW) forces between the inner and the outer nanotubes are taken into account. The dynamic response of the carbon nanotube is formulated on the basis of nonlocal elasticity shell theory. The cut-off frequencies are obtained and it has been concluded that the cut-off frequencies are independent of small scale coefficient and shear modulus of the elastic medium. It has been found that the phase velocity sharply decreases by increasing the axial half wave number and approaches a constant value. It has also been concluded that the maximum phase velocity predicted by nonlocal theory is located between 5 and 10 nanometers while for local theories the phase velocity sharply decreases in this interval and approaches a constant value. Results show that the effect of Pasternak-type on phase velocity is significant but the effect of Winkler-type is not really considerable.     

Real-Time Refinement of Kinect Depth Maps using Multi-Resolution Anisotropic Diffusion

In this paper, we present a novel real-time algorithm to refine depth maps generated by low-cost commercial depth sensors like the Microsoft Kinect. The Kinect sensor falls under the category of RGB-D sensors that can generate a high resolution depth map and color image of a scene. They are relatively inexpensive and are commercially available off-the-shelf. However, owing to their low complexity, there are several artifacts that one encounters in the depth map like holes, mis-alignment between the depth map and color image and lack of sharp object boundaries in the depth map. This is a potential problem in applications that require the color image to be projected in 3-D using the depth map. Such applications depend heavily on the depth map and thus the quality of the depth map is of vital importance. In this paper, a novel multi-resolution anisotropic diffusion based algorithm is presented that accepts a Kinect generated depth map and color image and computes a dense depth map in which the holes have been filled and the edges of the objects are sharpened and aligned with the objects in the color image. The proposed algorithm also ensures that regions in the depth map where the depth is properly estimated are not filtered and ensures that the depth values in the final depth map are the same values that existed in the original depth map. Experimental results are provided to demonstrate the improvement in the quality of the depth map and also execution time results are provided to prove that the proposed method can be executed in real-time.