فهرست مقالات برحسب موضوع Mechanical Engineering
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دسترسی آزاد مقاله
1 - Ab-initio Investigation of Mechanical Properties of MX2(M=Zr, Hf; X=S, Se, Te) Transition Metal Dichalcogenides Nano Tubes (TMDNTs)
Abdollah Haji Malekkheili Mojtaba Yaghoubi Alireza AmaniMiniaturization of bulk crystals in any direction down to nanometer dimensions leads to the emergence of quantum confinement phenomenon, which is technologically favorable. Transition Metal Dichalcogenides (TMDs) are important mechanical materials that have a layered st چکیده کاملMiniaturization of bulk crystals in any direction down to nanometer dimensions leads to the emergence of quantum confinement phenomenon, which is technologically favorable. Transition Metal Dichalcogenides (TMDs) are important mechanical materials that have a layered structure. In addition, ach layer consists of three atomic layers. TMD Nano Tubes (TMDNTs) can be created by rolling such a layer. This study investigates structural, mechanical, and bonding properties of TMDNTs. In particular, two important quantities, Young’s modulus and Poisson’s ratio, are calculated for 6 zigzag MX2 (M=Zr, Hf; X=S, Se, Te) nanotubes and the results are compared with those of other known nanotubes. The computed value of Young’s modulus is greater than that of blue Phosphorus and, in some cases, higher than those of WS2 nanotubes (which are experimentally synthesized). Given the increase in the bond length between M and X atoms, the ratio of Young’s modulus to Poisson’s increases as the atomic number X is reduced. However, there is no significant difference in the aforementioned quantity for ZrX2 and HfX2 nanotubes due to the close bond lengths of Zr-X and Hf-X. The band gap confirms this finding. A Mulliken charge analysis was conducted to investigate the amount of charge transfer between M and X atoms to observe the strength of bond lengths. پرونده مقاله -
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2 - Reduce Energy Consumption by Optimizing Temperature and Enforcing Smart Rules in Residential Buildings
Yazdan Daneshvar Majid Sabzehparvar Seyed Amir Hossein HashemiIn this article, to reduce energy consumption and manage its consumption in smart residential buildings, considering the convenience of people, a set of rules for determining intelligent temperature has been selected. For this purpose, expert rules and questionnaires ha چکیده کاملIn this article, to reduce energy consumption and manage its consumption in smart residential buildings, considering the convenience of people, a set of rules for determining intelligent temperature has been selected. For this purpose, expert rules and questionnaires have been prepared and used to make the indoor temperature intelligent based on individuals' emotional components, including clothing, outdoor temperature, age, body mass index, humidity, and the number of inhabitants. For this purpose, the ideal temperature under normal conditions of 22 degrees Celsius is considered by existing standards. The standard for determining the thermal indexes of PMV4 and PPD5 is used to validate the rules, and the result is acceptable compliance of these rules with the existing standard. According to the intervals set for the characteristics used, 1215 rules are defined for this system. A dashboard has been prepared in Excel software to adjust the temperature according to the existing rules, which is displayed as output by entering each available data based on qualitative and quantitative amounts of appropriate temperature. To evaluate the energy consumption, the two modes of temperature regulation with intelligent systems and manual temperature regulation have been compared. Results. For example, manually adjusting the temperature in 12 to 18 hours is a constant consumption pattern. By adjusting the temperature of the expert system per second, the consumption pattern changes based on residents’ satisfy. پرونده مقاله -
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3 - Flexural and Compressive Behaviour of M-shaped Core Sandwich Panel with Hybrid Carbon-Glass Fiber
Himan khalediIn the present research, the flexural and compressive behavior of foam-filled sandwich panels M-shaped core with hybrid carbon-glass fiber composite have been experimentally investigated. In order to fabricate the sandwich panels, the vacuum assisted resin transfer mold چکیده کاملIn the present research, the flexural and compressive behavior of foam-filled sandwich panels M-shaped core with hybrid carbon-glass fiber composite have been experimentally investigated. In order to fabricate the sandwich panels, the vacuum assisted resin transfer molding (VARTM) has been used to achieve a laminate without any fault. Afterward, polyurethane foam with density of 80 Kg/m3 has been injected into the core of the sandwich panel. The flexural and compressive properties of sandwich panel with hybrid carbon-glass fiber [CGCG]s have been compared to those of eight-layered carbon fiber [C]8 and the eight-layered glass fiber [G]8. The study of force-displacement curves obtained from the compressive and three-point bending tests showed that the [CGCG]s has larger elastic region than [C]8 and larger plastic region than [G]8. Also, it was found that polyurethane foam enhanced the ultimate compressive and bending loads and absorber features of sandwich panels Finally, the extra foam coming out of the sides of the sandwich panel is cut after rigidization. پرونده مقاله -
دسترسی آزاد مقاله
4 - Intelligent and Optimal Control of Air Conditioning Systems by Achieving Comfort and Minimize Energy
Yazdan Daneshvar Majid Sabzehparvar Seyed Amir Hossein HashemiIn this study, artificial neural networks, artificial neural network combination with genetic algorithm and neural network combination with Kalman filter were used to optimally model and control a real air conditioning system. Using the above methods, the system is firs چکیده کاملIn this study, artificial neural networks, artificial neural network combination with genetic algorithm and neural network combination with Kalman filter were used to optimally model and control a real air conditioning system. Using the above methods, the system is first trained and after verifying the modeling accuracy, the capability of this modeling to predict the future conditions of the system is investigated. In addition to the subsystems investigated in both heating and cooling phases by mass and energy equations in Simulink simulated by Matlab software, the results of this section are finally compared with the optimal modeling results. The most important advantage of artificial neural network modeling over mass and energy equation modeling approaches is that it captures all the uncertainties and nonlinear properties of the air conditioning system due to the use of real data for modeling. It takes. Therefore, this method can optimize energy consumption in air conditioners by predicting the future conditions of the system and by precisely adjusting the time of turning on and off the main energy consuming equipment. The most important achievement of this research is more accurate and realistic modeling of the nonlinear air conditioning system.Comparing the methods used in the research for simulation methods using mass and energy equations, modeling using Bayesian trained neural network, artificial neural network modeling using MLP, modeling using neural network and genetic algorithm, modeling Using neural network and Kalman filter, the square error is equal to 0.006, 0.18, 0.056, 0.1456 and more than 0.5, respectively. پرونده مقاله -
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5 - The Effect of Alkaline Media and Temperature on the Structure and Magnetic Properties of Magnetic Nanoparticles Modified with PEG
Abolfazl Khodadadi Yaghoob Mohammadmoradi Mohammad Rahim TalebtashMagnetic nanoparticles were synthesized and coated by the situ-coprecipitation method with FeCl3.6H2O and FeCl2.4H2O precursors in the presence of NH4OH (or NaOH) reduction and PEG coated agent. Preparation of modified magnetic nanoparticles were performed at two differ چکیده کاملMagnetic nanoparticles were synthesized and coated by the situ-coprecipitation method with FeCl3.6H2O and FeCl2.4H2O precursors in the presence of NH4OH (or NaOH) reduction and PEG coated agent. Preparation of modified magnetic nanoparticles were performed at two different temperatures under the influence of different alkaline media. The effect of strength of alkaline media and reaction temperature of the magnetic properties (Magnetic saturation, Magnetic remanent, coercive force (of modified MNPs were investigated. To study structure, morphology, optic and magnetic properties MNPs were characterized by XRD, FTIR, TEM and VSM analyzes.The results showed that modified magnetic nanoparticles have superparamagnetic properties and have high magnetic saturation and small coercive force, so the magnetic properties of the modified MNPs are depended to the strength of the alkaline remanent directly. The saturation magnetization of the synthesized sample in NH4OH and NaOH at 80° C was determined as 60.94 and 49.39 emu/g, respectively. Also increasing temperature, improves magnetic properties coated MNPs) at temperatures below the blocking temperature. (The results of the XRD analysis showed that the structure of the modified magnetic nanoparticles is inverted spinel and the size of the nanoparticles synthesized in the ammonia media is smaller than the other media. The results of FTIR optical analysis revealed that the peaks at ~570 and ~440 cm^(-1) indicates the bond Fe-O. TEM analysis indicated that the shape of the MNPs is pseudo-spherical. VSM analysis indicated that the magnetic nanoparticles synthesized in stronger alkaline media (ammonia) and high temperature showed better magnetic behavior by higher magnetic properties. پرونده مقاله -
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6 - Non-resonant Four-body Decay of B→D^- π^+ π^+ π^-
Yaghoob Mohammadmoradi Mohammad Rahim Talebtash Abolfazl KhodadadiWe have calculated the branching ratio of the non-resonant B→D^- π^+ π^+ π^- four body decay using a simple model based on the framework of the naïve factorization approach where one can ommit the nonfactorization effects. In naive factorization appro چکیده کاملWe have calculated the branching ratio of the non-resonant B→D^- π^+ π^+ π^- four body decay using a simple model based on the framework of the naïve factorization approach where one can ommit the nonfactorization effects. In naive factorization approach, according to the Feynman diagram, there are only two tree diagrams for this decay mode. In the first diagram, the matrix element of decay mode is factorized into a B→D form factor multiplied by a 3π decay constant and in the second diagram, the matrix element is factorized into a B→Dπ form factor multiplied by a 2π decay constant, According to the rest mass of the particles, we assume that in the rest frame of B meson, the D meson remains stationary, so we obtain the value (3.47±0.14)×10^(-3) for the branching ratio of the B→D^- π^+ π^+ π^- decay mode in naive factorization approach, while the experimental results is (3.9±1.9)×10^(-3). پرونده مقاله -
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7 - Increasing the Heat Transfer Performance of a Turbulator Equipped Concentric Gas-liquid Heat Exchanger Using Al2O3 – Water Nanofluid
seyyed rahim hosseini Seyyed Masoud Seyyedi Mehdi Hashemi TilenoeeIn this study, the turbulent fluid flow and heat transfer performance of a concentric two-tube (air-nanofluid) heat exchanger with a helical turbulator is studied using STAR-CCM+. First, the computational code is validated according to the related experimental data and چکیده کاملIn this study, the turbulent fluid flow and heat transfer performance of a concentric two-tube (air-nanofluid) heat exchanger with a helical turbulator is studied using STAR-CCM+. First, the computational code is validated according to the related experimental data and its simulation results for air and water. Then, the heat transfer performance and the effect of the different pitches of the helical turbulators are analyzed by replacing nanofluid instead of water for heat removal. The results show that the turbulator and nanoparticle has a high impact on heat transfer capability of the heat exchanger. The result shows that, the heat transfer is increased using turbulators in comparison with smooth tube for pitches of 15, 30 and 45 mm, respectively. In addition, the STAR-CCM+ is a proper tool for simulation of a complex geometries in three-dimensional. It is not only the CFD solver, STAR- CCM+ is an entire engineering process for solving problems involving flow (of fluids or solids), heat transfer and stress. It provides a suite of integrated components that combine to produce a powerful package that can address a wide variety of modeling needs. These components include: • 3D-CAD Modeler • CAD Embedding • Surface Preparation Tools • Automatic Meshing Technology • Physics Models • Post-processing پرونده مقاله -
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8 - A Review on the Photovoltaic Panels: Applications, Modeling and Economic Evaluation with Focusing on the Phase Change Material Cooling Method
Seyyed Masoud SeyyediA photovoltaic (PV) panel consists of several photovoltaic cells designed to convert solar radiation into electrical energy. Cooling of PV cells is an important task to increase PV panel efficiency, improve output power and optimize performance parameters. There are var چکیده کاملA photovoltaic (PV) panel consists of several photovoltaic cells designed to convert solar radiation into electrical energy. Cooling of PV cells is an important task to increase PV panel efficiency, improve output power and optimize performance parameters. There are various methods for PV cooling. Phase change materials (PCMs) can be used to cool PV panels. The integrated system is called PV-PCM system. This paper provides an overview of the history, applications, mathematical modeling and economic evaluation for PV-PCM systems. The focus of this study is on the cooling of the PV cells using PCMs. Furthermore, the other types of PV systems (hybrid systems) are investigated. The effects of main parameters on the performance of PV or PV-PCM systems are investigated, too. Mathematical modeling including thermal and electrical models are presented. Finally, the advantages and disadvantages of PV-PCM system and its future overview are discussed. The results discover that the PV panel temperature up to 20 °C and electrical efficiency up to 5% can be reduced by PCM.. The results discover that the PV panel temperature up to 20 °C and electrical efficiency up to 5% can be reduced by PCM. پرونده مقاله