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Considering that the exact solution for thermal buckling and post-buckling of the graphene platelets (GPLs)-reinforced composite beam in exposure to temperature changes has not been so far addressed, this problem is investigated in this research. The governing equations of the beam under thermal buckling load were acquired using the principle of virtual work, first-order shear deformation theory, and von Kármán strain field. The effective properties of the materials were then determined using the Halpin–Tsai model and rule of mixtures. Three coupled nonlinear equations are established and solved directly. Results are obtained for beams with clamped and simply supported edges. After validating the results, the effects of changing the GPLs distribution pattern and weight fraction changes on the critical thermal buckling load were evaluated. It is highlighted that for beams with simply supported edges and asymmetric distribution of material properties, the response is not of the bifurcation type.

In this research, the extrusion of copper and aluminum in cylindrical forms was investigated by finite element simulation. In addition, the effect of angle and internal profile of the mold on the extrusion force and dimensional uniformity of the produced part was investigated using two types of molds with conical and curved geometry, and its effect on extrusion force was examined by changing the friction coefficient. Based on the results, increasing the conical mold's profile angle leads to an increase in dimensional non-uniformity in the piece and increases the extrusion force. Conversely, the use of curved molds lead to reduction of extrusion force and dimensional uniformity. Interchanging the material of the core and shell can also affect the extrusion force and diameter. Furthermore, curved molds use leads to close the copper core/aluminum shell extrusion product and affect the extrusion force and dimensional changes. Based on investigating the effect of friction coefficient, extrusion forces were increased by increasing the coefficient and shear stress of material flow. The results were compared and validated with similar experimental research.

In the view of the latest status and the potential of developing wind energy in South Africa, the present study aims to perform technical–economic–environmental​ analysis on a wind turbine system with HOMER software using the 20-years average data of the wind speed obtained from NASA’s database, for providing the electricity to residential buildings. The results showed that the Port Elizabeth station, had the lowest levelized cost of electricity (LCOE) with the value of -0.363 $/kWh when using the EOLO wind turbine, and the Bloemfontein station had the highest LCOE with the value of 1.601 $/kWh when using the Turby wind turbine. The results from the step-wise assessment ratio analysis (SWARA) weighting method demonstrated the wind penetration, total production, and capital cost as the most important sub-indices with the weights of 0.106, 0.095, and 0.091, respectively. Using the additive ratio assessment (ARAS), weighted sum method (WSM), and weighted aggregated sum product assessment (WASPAS) techniques, the cities under study were ranked, and the cities of East London and Bloemfontein were identified as the most suitable and the most unsuitable stations for the use of household-scale wind turbines, respectively.

PurposeRural areas are one of the effective regions in economy and self-sufficiency field especially in agricultural and livestock section. Planning in the rural section and the effort in solving the problems of farmers lead to increase their interest in farming and manufacturing in the villages and decrease their migration to the cities and metropolitans. Therefore, the present study aimed at feasibility of electricity to a rural household in Iran using off-grid solar-based hybrid system.Design/methodology/approachIn renewable energy projects, a successful evaluation requires suitable criteria so that one can properly analyze the operational behavior of all feasible scenarios. In the present paper, HOMER software has been used for this purpose for a village with no access to electricity grid (Bar Aftab-e Jalaleh, Iran). Due to drastic fluctuation of fossil fuel prices and varied solar radiations in various years because of climate change, sensitivity analysis has been performed using HOMER.FindingsIn the optimum status economically, 70% of needed energy is provided by solar cells at the price 0.792 $/kWh. The comparison between the optimum condition economically and the condition that only use fossil fuels revealed that the return on investment will occur after less than 2 years and have remained profitable over 23 years.Social implicationsThe authors hope that the results of this study can be used in planning of the authorities to realize the interests of people in this village.Originality/valueAccording to the surveys, despite Iran being the first country in terms of providing solar power to the villages, so far no socio-economic-environmental assessment has been done for a solar cell-based micro-grid in an off-grid mode for a remote village that is deprived of electricity from a national electricity grid. In addition, for the first time in Iran, the effect of the fuel price and solar radiation parameters variability on the performance of system have been investigated.

Given the available capacities in Iran in terms of wind and solar renewable energies and regarding the fact that, to achieve a high economic growth, Iran needs to rise its power generation ...

As properties of nonlinear systems can introduce particular responses not present in linear systems, results from linear models can be inaccurate or misleading. Therefore, studying nonlinear vibrations is of extreme importance in structural vibration analysis. Nonlinear vibrations of a Timoshenko nanobeam were analyzed for the first time using the stress driven nonlocal theory (SDM) and the strain gradient theory (SGT). Nonlinear equations of motion were solved for simply supported- simply supported, clamped-clamped and clamped- simply supported beams using the homotopy analysis method. The results indicated that as the dimensionless characteristic parameter increased, the nonlinear natural frequency increased accordingly. High agreement was observed between the results from a linear frequency of Timoshenko beam model based on the SGT and those from previous research.

Fluid-solid interaction phenomenon study is necessary for the analysis of several engineering systems such as structures and vessels that interact with wind and blood flow, respectively. In this study, the interactions between buoyancy-driven airflow and elastic baffle(s) inside a square enclosure were modeled numerically. While the two sidewalls of the enclosure were insulated, the lower and upper walls were kept at hot and cold temperatures, respectively. The heat transfer rate through the hot wall by calculating the Nusselt number and von Mises stress at the baffles’ root for various configurations of baffle(s) was considered. The domain was modeled in ANSYS Workbench, and the k-ε model was employed to solve the turbulent convective flow (Ra > 107). A two-way algorithm along with the finite element method was employed to simultaneously solve the equations governing the fluid flow and the solid phase. The dynamic mesh method was employed to account for the change in the location of the fluid domain at a new time step. The results show the elastic baffle, in comparison to solid baffle, intensifies the heat transfer rate by 15%. The results also indicate that the Nusselt number in the single-baffle case is higher than in double-baffle cases. The fact that the amount of von Mises is a function of the baffles’ configuration is another point obtained from the results. It was found that the von Mises stress at the baffles’ root represents more unsteady fluctuations in the asymmetric case, while it approaches a constant value in the symmetric case.

The integration of renewable energy sources like wind and solar is very important to combat climate change, also to reduce carbon dioxide in many countries. Afghanistan with low energy consumption has a great potential for using renewable energies., also therefore, this study attempts to find suitable locations for constructing solar-wind power-plants using solar and wind data from 46 stations by HOMER and GIS softwares. Based on the available data, results indicate that Uruzgan and Balk stations, each with $12006 and $13941 respectively, have the lowest and highest net present cost. Also, in terms of using renewable energies (%) and producing CO2 emissions, Qandahar with 99% and 7 kg/yr and Balkh with 87% and 235 kg/yr are respectively the best and the worst stations from an environmental perspective. According to the results, average price per kWh of energy generated in Afghanistan is $0.638, average percentage of using renewables is about 96.46%, and the average rate of producing CO2 emissions is 70.39 kg/yr. The analysis results of turbulence intensity parameter shows that 23 stations in Afghanistan have a low turbulence intensity which means the mechanical components of wind turbines are under low fatigue loads and the rest of stations have a medium turbulence intensity which means the mechanical components of wind turbines are under medium fatigue loads. The highest and lowest values of turbulence intensity parameter are associated with Sindand and Qunduz stations respectively. Given the apparent and urgent need to develop renewable energy sources in Afghanistan, results of the present study, in addition to improving people's lives, could accompany economic development.

Delamination is a well-known defect mode that can arise in the manufacturing process of laminated composite plates. Due to the importance of analyzing the destructive effects of delamination on the mechanical behavior of composite plates, the flexural analysis of circular laminated composite plates with circular delamination is presented here. The governing equilibrium equations of laminated plates are first determined using third-order shear deformation theory. Both the linear and geometrically nonlinear strain states are considered, and the variational approach with a moving boundary is employed to derive the equilibrium equations. The governing equations in terms of the displacement field are then solved using the Galerkin method and the spectral homotopy analysis method to obtain the linear and nonlinear strain states, respectively. The effect of the variations of the elastic material properties on the strain energy release rate is also comprehensively studied. The results of the present study are consistent with the results of other methods found in the literature.

Nowadays, renewable energies are more preferable to fossil fuels because of being free, widely available and producing minimal pollution. One of the disadvantages of renewable energy systems is that using only one type of renewable energy cannot guarantee a continuous power generation. To overcome this problem, two or more renewable energy systems should be used simultaneously to compensate for times when one of them is not available or the renewable system should be used aligned with the generator. In addition, another weakness is that they are not accessible in every geographical position and location. It is clear that renewable energy systems can be exploited to their fullest capacity when used in the proper place. Therefore, given the importance of finding suitable places for co-utilization of several renewable energies, present paper attempted to find the ideal locations for construction of hybrid solar-wind power stations in Middle-East using Boolean model in GIS software. The Boolean method is, in a way, a more stringent method compared to the other positioning methods. Therefore, the selected locations will definitely have greater energy potential by using the Boolean method. Data obtained by RETScreen4 software from 400 stations in Middle-East were used for collecting monthly weather information. Results of the current paper may be helpful in creating prospects for sustainable energy development for systems based on natural resources and facilitating the national power transmission and sustainable environmental policies.

Commonly facing some irregular situations such as natural disasters and experiencing power interruptions as a consequence, the power grid in Manjil located in the north of Iran needs to be capable of power delivery to its local load points in an isolated manner. This paper aims to study the feasibility of this situation once local wind turbines are used as the power generation facilities. The imbalances of power supply and demand due to the high variation of wind power is overcome in this paper via employing and comparing two hydro-wind and diesel-wind power systems which are comprised of energy storage systems. This paper also investigates the balance feasibility of power supply and demand once the system is isolated from the whole power grid and offers an approach to identify the size and type of energy storages in this respect. The proposed method is proved to be an economic approach and results in an acceptable level of system reliability.