نشریه علوم کاربردی و محاسباتی در مکانیک
سال سی و پنجم شماره 3 (پاییز 1402)

Atomic force microscopy is a powerful and precise tool for identifying particle properties and studying intermolecular forces, surface topography, and particle manipulation in the micro-nano dimension. Nanomanipulation is one process that makes good use of this tool. Today, with advances in science and technology, manipulation is used to modify and manufacture the properties of materials, produce more valuable medical components and fewer raw materials, alter the structure of living cells and much more. We are working at the nanoscale. Therefore, in this study, we used atomic force microscopy to investigate the mechanical properties of breast cancer tissue during the nanomanipulation process. By considering the changes induced by the displacement force, force curves and penetration depths are plotted over time. Given the importance of nanoparticle-particle contact and the tatara contact model and breast cancer tissue geometry, simulations were performed to extract the Young's modulus. Experimental experiments and experimental charts were also performed to verify the agreement between the results of the simulation process based on atomic force microscopy. Finally, using the comparisons made in this study and considering the tatara contact model, a range of 2–2.5 kPa was calculated for breast cancer tissue volume.

Numerical study of hyperthermia was performed using a microwave slot antenna in the treatment of liver cancer. The modeling of the problem in Comsol software is done symmetrically and two-dimensionally and the electromagnetic equation is coupled with the biothermal transfer equation. Temperature distribution, cancer tissue destruction, microwave absorption in liver tissue and specific absorption rate (SAR) are presented as results. The results showed that the two-hole antenna has a wider distribution of the amount of microwave absorbed than the single-slot antenna. The SAR distribution along the longitudinal axis of the antennas gradually increases and reaches its maximum point where the slot is located, and then the SAR distribution decreases rapidly and reaches its minimum at the end of the antenna. According to the results, changes in temperature in liver tissue also depend on the type of antenna and penetration depth, and temperature distribution and SAR distribution have a similar trend. Also, single-slot antenna is suitable for elliptical tumors and double-slot antenna is suitable for spherical tumors.

In this paper, for the first time, to investigate the potential and feasibility of using PVT-ST in relatively hot and moderate weather conditions, it has been studied in four different cities and compared with two common solar systems, PVT and ST. Therefore, the performance of the system is evaluated in terms of the first and second laws of thermodynamics based on the FORTRAN code, and then using the obtained results to analyze the energy consumption of a residential unit in 4 different cities using Carrier software. In addition, the effects of the mass flow rate of the working fluid, in both laminar and turbulent regimes, on the module performance are investigated. Considering the mass flow rate of 0.0304 kg/s (turbulent regime) in July, the thermal efficiency of ST, PVT-ST, and PVT systems are 85.7%, 78%, and 72.9%, respectively. Finally, the investigation of system performance in different cities shows that this system can produce the highest thermal power in Basra. However, the maximum power generation with an average of 77 watts per square meter belongs to Baghdad. Finally, the energy supply of a residential house by combined systems has been investigated. By considering 8 integrated systems, most of the electricity consumption of a residential house can be supplied, but it should be kept in mind that during the peak hours of consumption if this amount of electricity production does not meet the capacity of the house, a fraction of the electricity shortage can be supplied from the stored electricity.

In this study, investigated heat transfer of Nanofluid laminar flow in a channel with obstacles along different geometry such as triangular, rectangular and half-cylinder and the effect of adding Nano particles on based flow. The result showed that the average Nusselt number increased with an increasing volumetric fraction of nano particles. However, the increasing average Nusselt number is dependent on the type of obstacles geometry that rectangular shape is more than others, because area of heat transfer is more than other obstacles. The Nusselt number with rectangular geometry is 30% more than the Nusselt number with half-cylinder geometry. Also, using obstacles with different geometry and the adding of the nanoparticles, the hydraulic-thermal performance has been increased up to 44%. The local Nusselt number for nanofluid of volume fraction with 1% is 2.38% higher than volume fraction of nanofluid with 2%. The local Nusselt number of volume fraction of nano particle with 1% is 10% less than based fluid.

Today, wooden products are widely spread in the industry of furniture, art boards, wooden dishes, etc. The traditional and manual manufacturing methods of producing these artefacts cannot compete with mechanized production methods, especially computer numerical control (CNC) machines. Therefore, using of these devices is always increasing. Nevertheless, one of the parameters that affect the production speed is the surface roughness, and the workshops have to spend a lot of time on polishing the products. For this reason, in the present research, the effect of machine parameters (feed speed, rotational speed and transverse step) and tool characteristics (diameter, number of cutting edge and type of cutting edge) on surface roughness of beech wood has been investigated. The outcomes demonstrated that cutting tools with two spiral cutting edges have a more favorable surface roughness than cutting tools with a straight cutting edge and one spiral cutting edge, and tools with a straight edge are not suitable for beech wood. It was also observed that by reducing the transverse step from 0.7D to 0.3D, a lower surface roughness is created. By reducing the tool diameter from 6 to 4 and 3 (mm), reducing the feed speed from 60 to 20 (mm/min) and increasing the rotational speed from 15000 to 25000 (rpm), the surface roughness of final product was improved, significantly.

The design and development of high-performance airfoils is essential for the development of the aviation industry. At larger angles of attack, higher lift and shorter flight bands are achieved. But at high angle of attack, the phenomenon of flow separation occurs so that after the stall angle, the flow is completely separated from the upper surface of the wing, resulting in a sharp drop in lift and drag increase. In this study, an attempt has been made to prevent the separation of flow by using the moving surface in the ratio of high velocities on NACA 0012 airfoil and to improve the aerodynamic performance of NACA 0012 airfoil by increasing the lift force and reducing the drag force. The velocity ratio means the ratio of the moving surface velocity to the free flow velocity. This research was performed by numerically in two dimensions using Ansys Fluent and k-ω-SST turbulence model with SIMPLE algorithm. The use of a moving surface in the form of a rotating cylinder at the leading edge of the NACA 0012 airfoil at a high speed ratio, in addition to preventing current separation and increasing the lift, has negatively affected the drag, which indicates its propulsive force contribution. Of all the simulated states, the velocity ratio of 20 at attack angle of 24 with a lift coefficient of 3.564 and a drag coefficient of -0.185 had the most favorable aerodynamic performance.

In this study, the magnetic field effect on the hydrodynamics and heat transfer of the laminar flow of a nanofluid in a microchannel with one-sided sudden expansion at a low Reynolds number is investigated. The governing equations including mass, momentum, and energy conservation equations are discretized and solved on a staggered grid using the finite difference method by developing a Fortran code. The simulation results show that at a low Reynolds number, no vortex is formed after the step. In the presence of a magnetic field, the friction coefficient decreases with volume fraction. At a volume fraction of 0.04, this reduction in comparison with water at Hartmann numbers of 20 and 40 is 25 and 18 percent, respectively. By applying the magnetic field, the friction factor increases. For nanofluid with a volume fraction of 0.04, the enhancement of average friction factor in comparison with water at Hartmann numbers of 20 and 40 is 176 and 337 percent, respectively. At a low Reynolds number, the magnetic field effect on the Nusselt number is negligible. The Nusselt number decreases with volume fraction. At a volume fraction of 0.04, a reduction of about 12 percent is observed in the Nusselt number in comparison with water. Examining the performance evaluation criteria shows that applying a magnetic field improves the system's performance. At a Hartmann number of 20 and volume fraction of 0.04, an enhancement of about 11 percent in performance coefficient is observed in comparison with the case that the magnetic field is absent.

Heart failure is one of the cardiovascular diseases that causes changes in the structure of the heart and reduces the output of the heart. This disease can be divided into two categories: diastolic and systolic heart failure. In diastolic heart failure, the thickness of the ventricular walls increased and is associated with concentric hypertrophy. In this study, concentric hypertrophy is considered to be caused by pressure overload, as a result of which, the number of sarcomeres increases in parallel, and as a result, causes a relative increase in the transverse area of the cardiomyocytes. Continuum equations of concentric hypertrophy by using an idealized biventricular geometry have been implemented in COMSOL Multiphysics software, the approach presented for implementing the equations is completely new and has fundamental advantages over the implementation of the previous approach, and does not require coding and can be easily implemented in a finite element software. The results of the simulation showed that the thickness of the ventricular walls increases and the volume of the ventricular chambers decreases. The mentioned results are consistent with the clinical observations of the disease and shows that computational modeling can be used as a powerful tool to increase specialist’s knowledge of diseases that have a high mortality rate.