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Air pollution is known as one of the most important causes of death in the whole world. Therefore, pollution reduction to achieve clean air was noticed by everyone. This way, using nanotechnology to control air and monitor is a novel approach. This paper investigates the effect of the number of graphene nano-pores on the SiO 2 separation from the H 2 O vapour in the presence of an external electric field with the magnitude of 0.01 V/Å using the molecular dynamics (MD) method. The electric field affects the charged particles and causes disturbance in the structure. It also prevents SiO 2 nanoparticles from passing through the graphene nanosheet. Also, the presence of carbon nanosheets acts as a membrane and affects the diffusion of water in the nanostructure. So, the results show that in the presence of a nano-pore, the number of H 2 O molecules reaches to 496 and 568 in reservoirs 2 and 3. Also, the number of SiO 2 nanoparticles reaches 10 and 4 in reservoirs 2 and 3. This shows that in reservoirs 2 and 3, about 80% and 60% of the SiO 2 nanoparticles are separated. As mentioned before, the electric field prevents the passage of SiO 2 nanoparticles through the graphene nanosheet. As the number of graphene nano-pores increases by 2, 3, 4, and 5, the number of passing water molecules increases. Considering that the number of graphene nano-pores has increased and the movement path of particles has increased, the number of passing particles almost increases. However, the electric field prevents the passage of SiO 2 nanoparticles. According to the results, the suggested setup can be employed for designing highly efficient nanostructured membranes for air purification and monitoring. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Molecular dynamics method was implemented. • The present research investigates the influence of palladium percentage and oxygen ratio on air-methane catalytic combustion. • Combustion performance in the presence of excess oxygen and oxygen deficiency is reported. • Increasing palladium percentage improves the combustion performance. • Oxygen and palladium ratios can benefit the combustion process. Combustion is an exothermic chemical process between an explosive substance and an oxidizing agent that is accompanied by heat generation and chemical change of raw materials. Catalysts are used in a combustion process for various reasons, including the speed at which the material reaches equilibrium. Catalysts are chemicals that increase the rate of reaction in chemical processes. The present research investigates the influence of palladium percentage and oxygen ratio on air-methane catalytic combustion in a helical microchannel. For this purpose, the atomic behavior and combustion performance of the simulated sample in the presence of excess oxygen and oxygen deficiency is reported by the molecular dynamics (MD) method. The potential functions used in this paper were Lennard-Jones, the embedded atom model (EAM), and Coulomb. It is concluded that increasing palladium percentage in limited ratios improves the atomic and combustion performance of the simulated structure, and this enhancement is greater in the presence of excess oxygen. In the presence of excess oxygen, the numerical value of maximum density, velocity and temperature converged from 0.138 atom/Å3, 0.33 Å/ps and 523 K to 0.144 atom/Å3, 0.36 Å/ps and 539 K, respectively with increasing palladium percentage from 1 % to 4 %. And by increasing the palladium ratio to 10 %, these numerical values decrease to 0.137 atom/Å3, 0.31 Å/ps and 530 K. Moreover, in the presence of oxygen deficiency, heat flux, thermal conductivity, and combustion efficiency of atomic samples reached 2049 W/m2, 1.23 W/m.K and 90 % after rising palladium to 4 %, and it decreased to 2035 W/m2, 1.19 W/m.K and 86 % by adding 10 % palladium. Therefore, the results indicate that the oxygen and the catalyst (palladium) ratios can benefit the combustion process. These results can optimize the atomic performance and combustion performance of structures essential for use in various industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study investigates the effect of different nanoparticles on methyl ester-biodiesel fuel's combustion performance. • The following investigated the effects of different volume fractions of CuO nanoparticles. • This research used the MD simulation and the LAMMPS software package. • Heat flux reaches to 4448.89 W/m2 in the presence of 10% CuO nanoparticles. • It is expected that by optimizing this process, the combustion performance of fuels will be improved. Today, the problems, such as the environmental pollution caused by the consumption of fossil fuels, which have disrupted the ecological conditions and created environmental risks, as well as the limited reserves of fossil fuels, have caused countries worldwide to pay more attention to this type of energy. Biofuels are a type of fuel obtained from biomass sources. Biodiesel is one of the fuels produced from natural and renewable sources, which does not harm the environment. On the other hand, the presence of nanoparticles in alternative fuels is particularly important because adding nanoparticles reduces the ignition delay. This study investigated the effect of different nanoparticles, such as copper oxide (CuO) and aluminium oxide (Al 2 O 3), on methyl ester-biodiesel (as base fluid) fuel's combustion performance. The following investigated the effects of different volume fractions of CuO nanoparticles. This research used the molecular dynamics (MD) simulation, and the LAMMPS software package. The results show that CuO nanoparticles had better thermal performance than Al 2 O 3 nanoparticles. By adding Al 2 O 3 and CuO nanoparticles to the base fluid, the heat flux of the simulated nanofluid converged to a numerical value of 2410.31 W/m2 and 2410.31 W/m2, respectively. Because CuO nanoparticles show better thermal performance than Al 2 O 3 nanoparticles, the effect of the volume fractions of CuO nanoparticles on the thermal performance of the studied nanofluid was investigated. For this purpose, CuO nanoparticles with atomic ratios of 1%, 2%, 3%, 5% and 10% were added to the base fluid. The results reveal that the heat flux in atomic samples reached 4448.89 W/m2 in the presence of 10% CuO nanoparticles. It is expected that by optimizing this process, the combustion performance of fuels will be improved, fuel consumption will be optimized, and the emission of pollutants will be reduced. [ABSTRACT FROM AUTHOR]

• Investigation the thermal performance of the PCMs microcapsules with gold nanoparticles. • Using of C 2 H 5 NO, BrC 16 and PCM as microcapsules. • Importance of dimensions of structures in microcapsules to perform the heat transfer process. • Dimensions of designed structures in microcapsules to perform the heat transfer were important. • Increasing the shell thickness in these structures will reduce the heat transfer in the structures under study. This research studied the thermal performance of phase change material (PCM) microcapsules containing gold (Au) nanoparticles (NPs) in a nanochannel (NC) using molecular dynamics (MD) simulations. The MD simulation method is a reliable method for studying at micro and nano scales. In this simulation, the physical equilibrium was studied in the first stage by examining the simulated structure's kinetic and total energies. In the second stage, the thermal performance of simulated structure was surveyed. The thermal performance of structures was studied at different initial temperatures and initial pressure and the number of metal layers in NC shells. The results show that by increasing the initial temperature, the charging and discharging time, the viscosity and phase transition time decrease, and heat flux (HF) and thermal conductivity (TC) increase. Moreover, by changing the initial pressure (from 0 to 5 bar), the simulated samples' charging and discharging time, HF, and TC did not change much. This atomic behavior in the simulated samples shows that the simulated samples could operate without a drop in different initial conditions. The results indicate that by increasing the number of metal layers in the NC shells from 1 to 12, the force on fluid–structure increased, and consequently, the charging and discharging times increase to 2.54 ns and 3.40 ns. On the other hand, increasing the number of metal layers led to decreasing HF and TC of structures to 287.37 W/m2 and 1.18 W/m.K. Therefore, the dimensions of designed structures in atomic microcapsules to perform the heat transfer process were important. Increasing the shell thickness in these structures will reduce the heat transfer in the structures under study. [ABSTRACT FROM AUTHOR]

This study describes the mechanical behavior of a brick structure by inserting graphene nano-sheet (GNS) into this construction material using the Molecular Dynamics (MD) approach. Technically, we utilized Universal Force Field (UFF) and Tersoff Force Field (TFF), respectively, to simulate ideal brick (pristine brick) and graphene structures. The consequence of the equilibrium procedure of atomic structures indicates their suitable physical stability, which emerges from the proper MD simulation settings. Technically, to characterize the mechanical properties (MP) of pristine brick matrix (PBM) and reinforced brick-graphene (RBG) nanocomposite, some parameters like Stress-Strain (S–S) Curve, Young's modulus (YM), and Ultimate Strength (US) of a pristine compound, and reinforced structure are mentioned. Numerically, by inserting the GNS into the PBM with a 5% atomic ratio, Young's modulus of simulated nanostructure reaches 3379 MPa, and the US of brick increases to 19.14 MPa. These simulation results show the important effect of GNS on the MP of the PBM, which is suitable for construction applications such as cologne arches. • We investigated the mechanical behavior of brick structure by inserting Graphene nanosheets. • Stress-strain curve, Young's modulus, and ultimate strength of pristine compound and reinforced structure were reported. • Young's module reaches to 3379 MPa and the ultimate strength of brick increases to 19.14 MPa. • TResults show the effect of graphene nanosheets on mechanical properties. [ABSTRACT FROM AUTHOR]

Graphene is one of the most important two-dimensional carbon allotropes with a plate structure similar to honeycomb nets. Due to its high thermal conductivity (TC), it is an excellent material for the thermal management of electronic nano-components. Investigating and obtaining thermal attributes of graphene for use and replacement in electronic components to study the cooling of parts is one of the important topics discussed by researchers. This research investigates monolayer graphene (MG) and helical graphene (HG). First, the TC of MG is calculated and compared using the equilibrium method (Green-Kubo) and the non-equilibrium method. The produced graphene sheets are usually not perfect and have various defects affecting graphene's thermal and mechanical attributes. Then, the impact of nitrogen doping defect on the TC of MG is investigated. In addition, three samples of HG in different dimensions are simulated using the non-equilibrium method. The TC for each of these samples is obtained and compared. Finally, as an innovation of this research, simulated graphene coated with hydrogen atoms and TC are calculated for this model. The results show that nitrogen doping in the graphene structure reduces the amount of TC. The TC of HG depends on the effective length of the structure and the cross-sectional area of the structure. Also, the TC was reduced by hydrogenating the HG structure. [Display omitted] [ABSTRACT FROM AUTHOR]

• The properties of nanofluid in nanochannel in the presence of surfactant molecules are investigated in rectangular atomic channel. • Water molecules are considered as the base fluid, copper atoms as nanoparticles and CTAB molecules were considered as surfactant. • The Atomic stability of simulated nanofluid don't disrupted by surfactant molecules adding to MD simulation box. • Cu nanoparticles and CTAB molecules adding to base fluid molecules improve their thermal behavior. • MD simulation results which calculated by using the Drieding UFF force, and Charm force fields have similar form. The poor heat transfer properties of the base fluid are the first effective obstacle to improving heat exchangers' efficiency. The key point of using very high conductivity of solid particles (in nanometer dimension) is hundreds of times more than common fluids in heat transfer in the composition of these fluids. Therefore, adding nanoparticles (NPs) to base fluids has been a solution to increase the heat transfer (HT) properties of common energy-carrying fluids. On the other hand, adding surfactants prevents the sedimentation and instability of NPs and improves the thermal performance of nanofluids (NF). So, this study surveyed the thermal properties of water-copper NF with/without surfactant molecules in a rectangular nanochannel using molecular dynamics (MD) simulation. Cetryltrimethylammoniu Bromide (CTAB) molecules were used as surfactants, copper structure as NPs, and water molecules as a base fluid in this simulation. In the present study, the effect of nanochannel wall temperature, copper nanoparticle (NP) size, and force field type (DREIDING, Universal Force-Field (UFF), and CHARM) on thermal conductivity (K nf) of water-copper NF were studied. The results show that as the wall temperature decreased from 80 to 30 K, K nf decreased from 0.783 to 0.753 Wm-1K−1. On the other hand, by increasing the radius of NPs from 0.5 to 2 nm, K nf and heat flux (HF) increase from 0.77 to 0.798 Wm-1K−1 and 5734 to 6352 W.m−2, respectively. One of the important purposes of researchers and engineers in various industries is to increase efficiency and reduce the systems' size. Therefore, it is expected that the results of this study will be effective in many different thermal industries. [ABSTRACT FROM AUTHOR]

• The Molecular Dynamics simulation method is implemented. • This study simulates ammonia refrigerant's atomic behavior with Cu nanoparticles in a nanochannel. • With increasing the external electric field amplitude to 5 Å, the heat flux values converge to 1395 W/m2. • The sample has a higher heat flux in the presence of a rectangular cubic atomic cavity. • Heat flux and aggregation time values for samples with rectangular cubic cavities are 1650 W/m2, 4.59 ns, respectively. With the ever-increasing energy costs, the need to improve the efficiency of cooling systems, reduce costs, and optimize the design is usually the first goal for system designers. One way to improve these systems is to use nano-refrigerants (NRs). This study simulates the thermal manner of ammonia refrigerant with Cu nanoparticles (NPs) in a nanochannel (NC) by calculating parameters such as velocity (V) and temperature (T) profiles, aggregation time (AT), and heat flux (HF). The result shows that by increasing the electric field amplitude (EFA) from 1 to 5 V/m, the maximum V and maximum T increase from 0.00086 Å/ps and 240 K to 0.00089 Å/ps and 245 K, respectively. With increasing the external EFA to 5 V/m, the HF value converges to 1395 W/m2, and the AT decreases to 3.90 ns. On the other hand, the change in maximum V in the samples with the pyramid, half-spherical (HS), and rectangular cubic (RC) cavities reached 0.74000 Å/ps, 0.00072 Å/ps, and 0.6565 Å/ps, respectively, and the maximum T changes to 232 K, 238 K, and 235 K in the RC, HS, and pyramid cavities samples. The results show that the structure has a higher HF in the presence of the RC cavity. So, the HF and AT values for samples with RC cavities are 1650 W/m2 and 4.59 ns, respectively. [ABSTRACT FROM AUTHOR]