Exact Solution for Thermal Buckling of Functionally Graded Plates Resting on Elastic Foundations with Various Boundary Conditions

In this article, we investigate the buckling analysis of plates that are made of functionally graded materials (FGMs) resting on two-parameter Pasternak's foundations under thermal loads. Three different thermal loads were considered, i.e., uniform temperature rise (UTR), linear and non-linear temperature distributions (LTD and NTD) through the thickness. The mechanical and thermal properties of functionally graded material (FGM) vary continuously along the plate thickness according to a simple power law distribution. Employing an analytical approach, the five coupled governing stability equations, which are derived based on first-order shear deformation plate theory, are converted into two uncoupled partial differential equations (PDEs). Considering the Levy-type solution, these two PDEs are reduced to two ordinary differential equations (ODEs) with variable coefficients. Then, the ODEs are solved using an exact analytical solution, which is called the power series Frobenius method. The appropriate convergence study and comparison with previously published related articles was employed to verify the accuracy of the proposed method. After such verifications, the effects of parameters such as the plate aspect ratio, side-to-thickness ratio, gradient index, and elastic foundation stiffnesses on the critical buckling temperature difference are illustrated and explained. The critical buckling temperatures of functionally graded rectangular plates with six various boundary conditions are reported for the first time and can serve as benchmark results for researchers to validate their numerical and analytical methods in the future.     

Combining continuous catalytic regenerative naphtha reformer with thermally coupled concept for improving the process yield

Advancements in the catalytic naphtha reforming process, as one of the main processes in petrochemical industry, contributed to development of continuous catalytic regenerative naphtha reformer units. Increasing the yield of aromatic and hydrogen as well as saving the energy in this process through the application of thermal coupling technique is a potentially interesting idea. This novel idea has been assessed in this paper. In the proposed configuration, continuous catalyst regeneration naphtha reforming process is coupled with hydrogenation of nitrobenzene in a two co-axial reactor separated by a solid wall, where the generated heat in nitrobenzene hydrogenation reaction transfers to naphtha reforming reaction medium through the surface of the tube. A steady-state, homogeneous, two-dimensional model is used to describe the performance of this configuration and a kinetic model including 32 pseudo-components with 84 reactions is considered for naphtha reforming reaction. After validating the model with the commercial data of a domestic plant, the obtained results of coupled reactor are compared by the conventional one. The obtained results show the superiority of CCR coupled reactor against the conventional one.     

Leaching of a zinc ore and concentrate using the Geocoat™ technology

In this study, the Geocoat™ technology was used for the extraction of zinc from a mineral concentrate obtained from the Kooshk mine (Yazd, Iran) by a culture dominated by the mesophilic bacterium Acidithiobacillusferrooxidans in a packed column bioreactor. A low grade sphalerite ore was used as support for the concentrate coating. During the 100 days of leaching pH, Fe³⁺, Fe^total, microbial population density and zinc extraction were measured. The final zinc extraction from concentrate and low grade support was 97% and 78%, respectively, and it was found that leaching from the support does not proceed significantly before leaching from the coating is completed.     

Numerical evaluation and the effects of geometrical and operational parameters on thermal performance of the shell and double coil tube heat exchanger

Heat exchangers are extensively used in various industries. In this study, the impact of geometric and flow parameters on the performance of a shell and double helical coil heat exchanger is studied numerically. The investigated geometric parameters include external coil pitch, internal coil pitch, internal coil diameter, and coil diameter. The influences of considered geometrical parameters are analyzed on the output temperature of the hot and cold fluid, convective heat transfer coefficient, pressure drop, and average Nusselt number. Water is considered as working fluid in both shell and tube. As an innovation, double helical coils are used instead of one in the heat exchanger. To compare the obtained results accurately, in each section, the heat transfer area (coil outer surface) is kept constant in all models. The results show that the geometrical parameters of double helical coils significantly affect the heat transfer rate.     

Environmental sustainability assessment of buildings in hot climates: the case of the UAE

Sustainability has acquired great importance due to the negative impact of various developments on the environment. The rapid growth during the last decade has been accompanied by active construction which, in some instances, neglected the impact on the environment and human activities. The impact of developments on the traditional heritage has not been taken into consideration although the latter represents a rich resource for sustainable building practices. The study aims at examining these developments in the UAE using an assessment tool that measures the performance of buildings in terms of their sustainability. This study attempts to: (a) develop a comprehensive definition of sustainability to suit UAE needs; (b) classify sustainable building practices at international and regional levels; (c) assess building performance in the UAE; and (d) establish guidelines for future sustainable architecture. T-Sol software was used to predict the CO₂ emission level in selected buildings in the UAE. Results illustrate that average energy use/area in domestic buildings is high (213 kWh/m²) and public buildings showed less sustainable measures in terms of energy features, energy performance and environmental features. Issues considered in the assessment of buildings such as energy use per square metre and CO₂ emission are alarming. Traditional buildings in the UAE were more sustainable than contemporary buildings, however.     

A waste heat recovery system development and analysis using ORC for the energy efficiency improvement in aluminium electrolysis cells

The present work investigates an active waste heat recovery system for the side walls of the aluminium electrolysis cells, enabling utilization of the extracted heat in power generation. This will potentially lead to energy efficiency improvement in the primary aluminium production industry and an enhanced aluminium production rate. An experimentally validated loop thermosyphon heat pipe model was used for heat extraction from the cell side wall. Boosting system thermal efficiency through waste heat recovery, by means of a heat utilization system, and increasing the level of control, as well as thermal equilibrium, stand as the main addressed objectives of the current study, which consequently result in an increased aluminium production rate. An organic Rankine cycle is incorporated into the system, and its performance is evaluated, taking into consideration the operating situations in terms of available temperature and thermal power range.     

A multi-criteria context-sensitive approach for social image collection summarization

Recent increase in the number of digital photos in the content sharing and social networking websites has created an endless demand for techniques to analyze, navigate, and summarize these images. In this paper, we focus on image collection summarization. Earlier methods in image collection summarization consider representativeness and diversity criteria while recent ones also consider other criteria such as image quality, aesthetic or appeal. In this paper, we propose a multi-criteria context-sensitive approach for social image collection summarization. In the proposed method, two different sets of features are combined while each one looks at different criteria for image collection summarization: social attractiveness features and semantic features. The first feature set considers different aspects that make an image appealing such as image quality, aesthetic, and emotion to create attractiveness score for input images while the second one covers semantic content of images and assigns semantic score to them. We use social network infrastructure to identify attractiveness features and domain ontology for extracting ontology features. The final summarization is provided by integrating the attractiveness and semantic features of input images. The experimental results on a collection of human generated summaries on a set of Flickr images demonstrate the effectiveness of the proposed image collection summarization approach.     

Electro-magneto temperature-dependent vibration analysis of functionally graded-carbon nanotube-reinforced piezoelectric Mindlin cylindrical shells resting on a temperature-dependent,orthotropic elastic medium

Vibration smart control analysis of a temperature-dependent functionally graded-carbon nanotube-reinforced piezoelectric cylindrical shell embedded in an orthotropic elastic medium is investigated. The mixture law is used for obtaining the material properties of the structure. The structure is subjected to a 2D magnetic field. Considering the first-order shear deformation theory, the motion equations are obtained. Based on an analytical method and differential quadrature method, the frequency is calculated. The effects of applied voltage, magnetic field, volume percent, and distribution type of carbon nanotubes, temperature, orthotropic elastic medium, and length to radius ratio of the shell are shown on system frequency.     

Generalized Gabor filters for palmprint recognition

Orientation-based coding approaches have recently been widely employed for face and palmprint recognition where generally, one starts with a set of Gabor filters to extract orientation information and then proceeds to code dominant orientations as features for each point of the palmprint. However, as the Gabor filter is developed to model two-dimensional receptive fields of simple cells in straits cortex, it might not be our best choice when dealing with curved and complex structures inherent in the palmprint texture. Motivated by this intuition, this paper shows that Gabor filters are a subset of a bigger family of filters which we refer to as generalized Gabor filter (GGF). Depending on the values of its parameters, a GGF takes a rather diverse shapes and orientations, which results in a potentially finer feature extraction capability. We show this improved capability by employing GGFs in the palmprint verification process. In applying our method, two different sub-banks of GGFs are defined for the orientation-based feature extraction of palmprints, and when compared with Gabor filters, it will be shown that GGFs have the upper hand in capturing orientation features. Furthermore, compared with the competitive code—one of the well-known orientation-based coding methods—the number of employed orientations is reduced to half. This would automatically compensate for a double usage of the filter banks, which otherwise could increase the time complexity of using GGFs. These ideas are further elaborated using a set of experiments on PolyU II and PolyU 2D/3D palmprint databases. The results show the preeminence of using GGFs both in terms of accuracy and efficiency.