Sharif Digital Repository

Long-time interaction of dewetting nanodroplets is investigated using a long-wave approximation method. Although three-dimensional (3D) droplets evolution dynamics exhibits qualitative behavior analogous to two-dimensional (2D) dynamics, there is an extensive quantitative difference between them. 3D dynamics is substantially faster than 2D dynamics. This can be related to the larger curvature and, as a consequence, the larger Laplace pressure difference between the droplets in 3D systems. The influence of various chemical heterogeneities on the behavior of droplets has also been studied. In the case of gradient surfaces, it is shown how the gradient direction could change the dynamics. For a... 

Mesoscopic hydrodynamic equations are solved to investigate late-stage evolution of thin liquid films over step topographies. Different geometrical parameters including step height and initial position and configuration of resultant masses of dewetting (droplets) are probed to find their effects on the mass evolution of the system. Our results indicate that increasing the step height and locating the droplets close to the step enhance the dynamics and accelerate smaller droplet collapse  

Employing a biharmonic boundary integral method with linear elements, coarsening dynamics of nanodroplets on topographical step heterogeneity is investigated. It is shown that the step height and droplet configuration have an influential effect on the dynamics. Increasing the step height slows down the process while locating the droplets close to the step boosts the coarsening rate. Considering a slip boundary condition enhances the dynamics and reveals a transition in the droplet migration direction. Our results reveal that increasing the surface wettability weakens the dynamics. Various types of the disjoining pressure over the step are also considered and their effects on the coarsening... 

In this paper, a new criterion for passivity of haptic devices is obtained. This criterion creates a relationship between Coulomb friction coefficient, viscous friction coefficient, sampling rate, and the maximum simulated stiffness. The process of derivation of the passivity criterion is described in detail. This criterion is improved compared with other existing criteria and predicts passivity in haptic rendering more accurately. In particular, for speeds of less than 5 cm/s, the new passivity criterion should replace the previous criteria to avoid unwanted vibrations of stiff virtual walls. Analytical and numerical investigations are presented to validate the new criterion. A specific... 

Supersonic aeroelastic instability of a three-layered sandwich beam of rectangular cross section with an adaptive magneto-rheological fluid (MRF) core layer is investigated. The panel is excited by an airflow along it's longitudinal direction. The problem formulation is based on classical beam theory for the face layers, magnetic field dependent complex modulus approach for viscoelastic material model and the linear first-order piston theory for aerodynamic pressure. The classical Hamilton's principle and the assumed mode method are used to set up the equations of motion. The validity of the derived formulation is confirmed through comparison with the available results in the literature. The... 

Simple formulas for calculating equivalent von Mises stress and von Mises effective plastic strain in an elastic–plastic ordinary peridynamic analysis are proposed. The equivalent von Mises stress is calculated by equating the deviatoric part of strain energy obtained from classical continuum mechanics and peridynamics. The effective plastic strain is proposed so that it reduced to uniaxial plastic strain in uniaxial tension test. Two example problems of the plate with a hole and a central crack under tension are considered to verify the validity of the proposed formulas. The plots of von Mises stress, equivalent plastic strain, plastic zone area and horizontal and vertical displacements are... 

In this study, new method for NAA purposes at 30 kW Isfahan MNSR is suggested. An algorithm based on ANN is proposed to quantitatively predict the unknown elements with no need standard sample. A three-layer feed-forward ANN with back-propagation algorithm has been used to determine concentration of selenium and fluorine in Multiple Sclerosis patients and healthy people blood samples. Predicted concentration of elements show good agreement between new method and experiment results. The correlation coefficient between the experimentally determined and predicted values are 0.99104 and 0.99364, respectively. This method is a rapid and precise approach for elemental analysis. © 2022, Akadémiai... 

A two-dimensional ordinary state-based peridynamic formulation is proposed for the analysis of elastic–plastic plane structures. Selecting appropriate relation for isotropic extension state, the deviatoric strain energy formulation is derived for plane strain/plane stress cases. Simple formulas to calculate peridynamic equivalent von Mises stress and its equivalent plastic strain are proposed. New yield function and flow rule are introduced. Implicit backward Euler time integration is used to obtain the increment of deviatoric plastic extension. Two example problems of grooved plate specimen and perforated plate under uniform tensile loading are considered to verify the accuracy of the... 

In this paper, a new procedure is developed to monitor a two-stage process with a second stage Poisson quality characteristic. In the proposed method, log and square root link functions are first combined to introduce a new link function that establishes a relationship between the Poisson variable of the second stage and the quality characteristic of the first stage. Then, the standardized residual statistic, which is independent of the quality characteristic in the previous stage and follows approximately standardized normal distribution, is computed based on the proposed link function. Then, Shewhart and exponentially weighted moving average (EWMA) cause-selecting charts are utilized to... 

This paper is an extension of an earlier work on electron correlations in semiconducting GaAs-based quasi-one-dimensional quantum wires. The extension was twofold. First, we developed the Singwi, Tosi, Land, and Sölander (STLS) scheme for multisubband structures. Secondly, we developed the multisubband ladder approximation diagrammatic technique. By using the results obtained for the spin symmetric and spin antisymmetric interpolarization and intrapolarization potentials, we calculate the corresponding electron-electron effective potentials. Our results for a two-subband model show that these effective potentials have an attractive part implying the occurrence of s-wave and p-wave pairings,... 

Constant volume transparent test combustion chambers are extensively used for investigating injection and fuel burning properties of various combustion engines. Their configuration depends on the engine type and the research purpose. Material of components, shape and dimensions of the chamber and its parts, ease of use, accessibility, sealing and safety of the assembly are the parameters needed to be considered in designing the test cell. This paper explains, structural design of a test combustion chamber and its optical windows using finite element analysis of ANSYS 12.0 software for bearing high pressure variations and thermal shocks of combustion. It was designed for conducting CNG direct... 

Tungsten Inert Gas (TIG) process and titanium cored wires filled with micro size TiC particles were employed to produce surface composite coatings on commercial pure Ti substrate for wear resistance improvement. Wire drawing process was utilized to produce several cored wires from titanium strips and titanium carbide powders. Subsequently, these cored wires were melted and coated on commercial pure Ti using TIG process. This procedure was repeated at different current intensities and welding travel speeds. Composite coating tracks were found to be affected by TIG heat input. The microstructural studies using optical and scanning electron microscopy supported by X-ray diffraction showed that... 

Sol composition and ripening conditions are two important parameters in silica fiber production through the conventional sol-gel process. In the current study, silica nanofibers were successfully obtained via the electrospinning technique, and sol-gel formation occurred during this process. Based on previous reports, with the aim of increasing the selectivity, we used the molecular imprinted methodology to produce a selective medium via sol-gel electrospinning. In this process, sol-gel was formed during electrospinning and then, the backbone polymer was removed by heating. To obtain a thin layer of silica nanofibers, the influencing parameters such as backbone polymer types, imprinting time... 

A cryogel–based semi–interpenetrating polymer network (Cryo–SIPN) was prepared in which conductive polymers such as polyaniline (PANI) and polypyrrole (PPy) were formed within the super porous network of acrylic acid cryogel. For completion of cryo-polymerization, all the constituent solutions were severely mixed and placed into the plastic straws and kept at -20°C and then the synthesized cyrogels were cut into the 1-cm length and freeze dried after washing with water. The Cryo–SIPN polymeric composite was applied in micro solid phase extraction (µSPE) of some selected antibiotic residues from various samples. The µSPE method combined with a high performance liquid... 

Horizontal ground heat exchangers (GHEs) have a lower initial installation cost in comparison to vertical ones; however, they require more land area. In order to reduce the required land area of horizontal GHEs, their heat exchange rate per unit land area needs to be enhanced. A remedy to this problem is installing horizontal GHEs in an arrangement with maximum heat exchange rate per unit land area. However, such arrangements have not been introduced for different types of horizontal GHEs thus far. To this end, in this study, the thermal performance of various GHE pipe arrangements for three different types (linear, spiral, and slinky) of horizontal GHEs is evaluated. Comparing the obtained... 

In this work, we implement a relatively new analytical technique, the exp-function method, for solving nonlinear special form of generalized nonlinear (2 + 1) dimensional Broer-Kaup-Kupershmidt equation, which may contain high nonlinear terms. This method can be used as an alternative to obtain analytic and approximate solutions of different types of fractional differential equations which applied in engineering mathematics. Some numerical examples are presented to illustrate the efficiency and reliability of exp method. It is predicted that exp-function method can be found widely applicable in engineering  

A series of samples with different compositions and parameters were welded together. The alloys were based on Ni-8Al-8Cr-l.5Mo-0.01B %wt composition with Zr additions of 1 and 3 %wt. Crack-free full-penetration welds of castable nickel aluminide alloy were performed using autogenous GTAW technique. It was found that Ni-Ni5Zr eutectic was associated with solidification cracks. Alloys were fully dendritic and also, weld metal consisted of columnar and axial dendrites beside the fusion line and in the middle, respectively. Optical and scanning electron microscopy (SEM) techniques were employed to characterize the composition as well as the weld structure. X-Ray diffraction was utilized to... 

With the high rate of mortality associated with breast cancer among women, breast cancer treatment has attracted great deal of attention globally. To reduce the exposure of body organs to high cytotoxicity of the common chemotherapeutic drugs, local co-delivery of selected chemotherapeutics has emerged as a solution. In this work, an electrospun composite including a co-drug-loaded graphene oxide-based nanocarrier is fabricated for local anticancer applications. To increase dispersion and cellular uptake of graphene oxide (GO), first, the hydroxyl groups at the edges of GO are grafted by poly (epichlorohydrin) (PCH) to form GO-PCH. Then, the hydroxyl end groups of PCH are grafted (g) with... 

The humidification-dehumidification (HDH) desalination system with a Horizontal Solar Film Evaporator (HSFE) is a sustainable and economical approach to providing freshwater in remote areas where conventional energy is limited or condensation irrigation in off-grid greenhouses. The present study investigates the baffle turbulators on heat and mass transfer of the HSFE of the HDH desalination system. To this aim, a comprehensive three-dimensional transient computational fluid dynamics model of the HSFE has been developed. The model is then used to evaluate the effect of various design parameters on the performance of the HSFE. The Design of Experiments methodology is adopted to determine... 

Molecular dynamics simulation is an important tool for studying nanomedicines at the atomic scale. Because measuring parameters at the atomic scale is very costly, the use of molecular dynamics simulations can speed up research and reduce costs. Although molecular dynamics simulations are very old, with the development of hardware as well as software and the development of force fields based on experimental data, the use of these simulations has become very useful and common today. In the simulation of molecular dynamics, various mathematical models such as Monte Carlo simulation and molecular bond density theory are used. The definition of nanomedicine includes the design, synthesis,...