Sharif Digital Repository

In this paper, the fully coupled rolling contact problem of a graded coating/substrate system under the action of a rigid cylinder is investigated. Using the singular integral equation approach, the governing equations of the rolling contact problem are constructed for all possible stick/slip regimes. Applying the Gauss-Chebyshev numerical integration method, the governing equations are converted to systems of algebraic equations. A new numerical algorithm is proposed to solve these systems of equations. Both the coupled and the uncoupled solutions to the problem are found through an implemented iterative procedure. In Part I of this paper, the analytical formulation of the rolling contact... 

This paper investigates the subsurface stress field induced by a rigid cylinder rolling over a functionally graded coating-substrate system. The Fourier transform is employed to extract the stress components within the graded coating and the homogeneous substrate. The distributions of the stresses are given through the depth and along the coating-substrate interface. The contour plots of normalized Von Mises stresses are provided as well. The results indicate that continuous variation of the shear modulus substantially reduces the difference between the in-plane stresses along the interface. Also, the softening coating leads to the minimum value of the stress concentration near the contact... 

In this letter, both the number of participating nodes and spatial dispersion are incorporated to establish a bi-objective optimization problem for maximizing the quality of aggregation under interference and delay constraints in tree-based wireless sensor networks (WSNs). The formulated problem is proved to be NP-hard with respect to Weighted-sum scalarization and a distributed heuristic aggregation scheduling algorithm, named SDMAX, is proposed. Simulation results show that SDMAX not only gives a close approximation of the Pareto-optimal solution, but also outperforms the best, to our knowledge, existing alternative proposed so far in the literature  

In this paper, the two-dimensional tractive rolling contact problem between a rigid cylinder and an orthotropic half plane is considered. A pair of singular integral equations is derived for the contact tractions using the Fourier transform technique. The governing integral equations are decoupled using the Goodman approximation and then solved numerically. Finally, the distribution of surface tractions is achieved in the contact region. This study emphasizes the significant effect of the orthotropic material parameters and the coefficient of friction on the contact tractions as well as the rolling contact characteristics for an orthotropic medium. © 2016, Springer-Verlag Wien  

In the study, the daily and monthly performance of a photovoltaic thermal system integrated with phase change material is investigated in Shanghai, China. A three-dimensional model of photovoltaic thermal system integrated with phase change material system is developed and numerically simulated. Water is considered as working fluid, and the fluid flow regime is laminar and incompressible. Both quasi-steady and transient models are compared together, and the transient model is selected because of its higher accuracy. Validation analysis is performed on the numerical model to show the reasonable agreement of current research compared to some other research. After obtaining the suitable... 

The solar collectors absorb solar irradiation and then produce thermal energy; however, they cannot generate electrical power. Electricity and thermal energy can be produced by the photovoltaic thermal module, simultaneously, while the outlet temperature of the photovoltaic thermal module is not usually high enough to provide thermal requirements of a building such as hot water or space heating. This work proposes a novel compound system created by the connection of a solar collector in series with a photovoltaic thermal module to resolve the issue of low outlet temperature in the photovoltaic thermal module and lack of electrical power in solar collectors. To examine the feasibility of this... 

In this paper, a comprehensive three-dimensional model of photovoltaic thermal system integrated with phase change material (PVT/PCM) is developed and simulated. The effect of some key parameters using parametric analysis on performance of PVT/PCM system with water as working fluid is investigated. Parameters considered in this study include the properties of PCM (i.e. melting temperature, enthalpy of fusion and thermal conductivity), solar radiation and mass flow rate. The parametric analysis ranges are selected according to the properties of the most of available PCMs on the market, which shows the practical application of the numerical research. Furthermore, a three-dimensional model of... 

Because of the low outflow temperature of the conventional photovoltaic thermal systems and lack of electrical production of the solar thermal collectors, a novel combined system is proposed to solve the two mentioned drawbacks. This novel system is achieved by connecting a photovoltaic thermal unit to a solar thermal collector in series. To increase the overall performance of this novel combined system, different hybrid nanofluids include (1) multiwall carbon nanotube-aluminum oxide (2) multiwall carbon nanotube-silicon carbide (3) graphene-aluminum oxide, and (4) graphene-silicon carbide are compared. The investigation is performed based on the three-dimensional simulation, and the... 

The bifacial photovoltaic/thermal module is an emerging concept that can provide electricity and heat simultaneously, taking advantage of both front and rear sides of the panel; therefore, exhibiting a better performance compared to a conventional photovoltaic module or photovoltaic thermal module. In this study, four configurations of the bifacial photovoltaic/thermal module with different cooling methods have been proposed, i.e., cooling performed at either the upper or the lower surface, in parallel (applied to both upper and lower surfaces having similar start/endpoints), and swinging air back and forth (by guiding the air over the upper and lower surfaces, respectively). The... 

In the current research, a three-dimensional photovoltaic thermal system integrated with phase change material system with nanofluids is investigated. The working fluids involved in this study include nano-magnesium oxide, multiwall carbon nano tube and hybrid (mixture of nano-magnesium oxide and nano-multiwall carbon nano tube) nanofluids dispersed in pure water. After comparing single-phase model and mixture model, the mixture model is used in the study and fluid flow regime in the collector is assumed to be laminar, fully develop, uniform and incompressible, to model the nanofluid in the system. A parametric analysis is conducted to examine the effect of various parameters such as working... 

In this study, the tractive rolling contact problem between a rigid cylinder and a graded coating is investigated. The main objective of this study is to investigate the effect of the stiffness ratio, the coefficient of friction and the coating thickness on the surface contact tractions, the surface in-plane stress, the stick zone length and the creep ratio parameter that may have a bearing on the fatigue life of the component. Assuming that the shear modulus varies exponentially through the thickness of the coating, the governing integral equations associated with the rolling contact problem are constructed. Furthermore, it is supposed that the contact patch is controlled by a central stick... 

Application of organic−inorganic nanocomposite membranes for water treatment is exceptionally growing owing to their tunable functionalities in addition to their enhanced permeation and antifouling propensity. In the present work, novel nanocomposite polyethersulfone (PES) membrane was synthesized using antimony-doped tin oxide (ATO) nanoparticles (NPs) via phase separation technique. It was found that the modified PES-ATO nanocomposite membranes exhibited significantly higher fouling resistance and larger permeate flux recovery ratio when tested with oil sands produced water than unmodified PES membranes. Furthermore, the PES-ATO membranes provided 40% more organic matter removal compared... 

In this paper, three metal-organic frameworks (Materials of Institut Lavoisier: MILs-100 (Fe)) as porous nanomaterials were synthesized using FeCl3, Fe(NO3)3 and Fe2(SO4)3 and denoted as MIL-100-1, MIL-100-2 and MIL-100-3, respectively. The synthesized MILs-100 (Fe) were characterized by FTIR, SEM, TEM, XRD, UV–vis DRS and zeta potential. Basic Blue 41 (BB41) was used as a model dye to study the photocatalytic dye degradation ability of the synthesized metal organic frameworks. The results showed that the synthesized nanomaterials decolorized BB41. The decolorization kinetics followed first-order kinetic model. The rate constant was 0.0034, 0.0041, 0.0091 and 0.0289 (1/min) for 0.01, 0.02,... 

Applications of starch nanostructured-based packaging for food items have been discussed in this chapter. These films can perform a wide range of functions, create the appropriate stimulus response packaging following the needs of the food and have a supervised liberation impact on the functional ingredients in the film by combining with thermally-sensitive, gas-sensitive, moisture-sensitive or other multi-purpose packaging materials to create unique intelligent packaging. Even though starch-based active and intelligent packaging has issues with material selection, preparation and function, starch has undeniably emerged as the most feasible material to substitute petroleum-based conventional... 

The development of RFID systems in sensitive applications like e-passport, e-health, credit cards, and personal devices, makes it necessary to consider the related security and privacy issues in great detail. Among other security characteristic of an RFID authentication protocol, untraceability and synchronization are the most important attributes. The former is strongly related to the privacy of tags and their holders, while the latter has a significant role in the security and availability parameters. In this paper, we investigate three RFID authentication protocols proposed by Duc and Kim, Song and Mitchell, and Cho, Yeo and Kim in terms of privacy and security. We analyze the protocol... 

In this work, bending and dynamic analyses of a three-layered functionally graded micro annular plate whit piezomagnetic layers are investigated based on FSD circular plate theory. The micro plate is subjected to magnetic field. It is assumed that the micro annular plate is resting on an orthotropic elastic medium. The stress relations which cooperate both mechanical and magnetic interactions are calculated based on MSGT and the governing equations are extracted through Hamilton’s principles. In order to solve the governing equations of micro annular plate, the numerical Ritz method is applied. After convergence of Ritz solving domain the obtained results are compared and adapted with the... 

Delivery of the Smart Grid is a topic of considerable interest within the power industry in general, and the IEEE specifically. This paper presents the smart grid landscape as seen by the IEEE Dielectrics and Electrical Insulation Society (DEIS) Technical Committee on Smart Grids. We define the various facets of smart grid technology, and present an examination of the impacts on dielectrics within power assets. Based on the trajectory of current research in the field, we identify the implications for asset owners and operators at both the device level and the systems level. The paper concludes by identifying areas of dielectrics and insulation research required to fully realize the smart...