Sharif Digital Repository

In this paper, we present a novel structure of a snake-like robot. This structure enables passive locomotion in snake-like robots. Dynamic equations are obtained for motion in a horizontal plane, using Gibbs-Appell method. Kinematic model of the robot include numerous nonholonomic constraints, which can be omitted at the beginning by choosing proper coordinates to describe the model in Gibbs-Appell framework. In such a case, dynamic equations will be significantly simplified, resulting in considerable reduction of simulation time. Simulation results show that, by proper selection of initial conditions, joint angles operate in a limit cycle and robot can locomote steadily on a passive... 

In this paper we present a novel planar structure of a snake-like robot. This structure enables passive locomotion in snake-like robots through an auxiliary link in joint and a torsional spring. Dynamic equations are derived, using Gibbs-Appell method. Kinematic model of the robot include numerous non-holonomic constraints, which can be omitted at the beginning by choosing proper coordinates to describe the model in Gibbs-Appell framework. In such a case, dynamic equations will be significantly simplified, resulting in significant reduction of simulation time. Simulation results show that, by proper selecting initial conditions, joint angles operate in a limit cycle and robot can locomote... 

Inclusion of carbon nanotubes (CNTs) into the titanium dioxide coating on 1050 aluminium alloy was studied with the aim at enhancing the corrosion resistance of the surface. Composite coatings with various contents of CNTs were prepared via the sol-gel method and dip coating. XRD and FTIR phase and structural evaluations showed the presence of anatase phase in all thin films. Concomitant enhanced corrosion behaviour in the presence of CNTs was resulted from polarization potentiodynamic test. Band-gap evaluation was performed using absorbance spectra of coatings and showed considerable decrease of band-gap energy in the presence of CNTs. Photocatalytic properties and hydrophilicity of... 

Nowadays, as technology grows, human life formation changes every second. These changes sometimes create harmful habits and affect our lifestyle, which unfortunately bring various diseases and disorders. ADHD (Attention Deficit Hyperactivity Disorder) & SPD (Sensory Processing Disorder) are common disorders in children. By giving children the right treatment at the younger ages, we can help them overcome their disabilities and not face any symptoms in their adulthood. The multi-sensory balance board is designed and developed to help medics diagnose the disorders in patients at early stages and monitor the treatment progress. The balance board uses multiple sensors to detect common human... 

In this research, titanium dioxide (TiO2) ultra-thin films have been successfully obtained on lamina-glass substrates by thermal oxidation of DC magnetron sputtered titanium. The as-deposited and the annealed films have been characterized by different techniques. The X-ray diffraction (XRD) results revealed the amorphous structure of as-deposited titanium and anatase crystal structure for the annealed films. The atomic force microscopy (AFM) results showed that increasing the annealing temperature could lead to rougher and larger grain size in the films. Finally, the optical data and band-gap calculations of the films were obtained using the transmittance spectrum, indicating that... 

Introduction: Diabetic neuropathy is a common complication of diabetes mellitus. It is associated with nerve damage due to oxidative stress and high levels of pro-inflammatory mediators. In the present study, we examined the anti-nociceptive effects of Fullerene nanoparticle, as a potent anti-oxidant, during diabetic neuropathy. Methods: Diabetes mellitus induced through injection of streptozotocin (STZ) (40 mg/kg). Four groups were used in the study as follows: the control, control+fullerene, diabetes, and diabetes +fullerene groups. All four groups received sesame oil. Treatment rats received fullerene C60 (1mg/kg/day) for 9 weeks by intra-gastric gavage. Then, cold allodynia, histology,... 

Background & Objective: The potent antioxidant property of fullerene C60 nanoparticles and their derivatives has been demonstrated in a wide range of in vitro and in vivo studies. Hence, we examined the effects of fullerene C60 on the oxidative stress parameters in brain and liver of the rats in normal situation. Materials & Methods: The study was performed in two groups of Wistar rats (each group, n = 6); normal and fullerene-treated normal animals. Treated rats received fullerene via oral gavage at dose of 1 mg/kg/day for 60 days. At termination of the study, the oxidative stress parameters were determined in brain and liver tissues, including the contents of glutathione (GSH) and... 

A series of experiments were carried out to investigate unsteady behavior of the flow field as well as the boundary layer of an airfoil oscillating in plunging-type motion in a subsonic wind tunnel. The measurements involved surface-mounted hot films complimented with surface pressure. In addition, wind tunnel wall pressure distribution was acquired to furnish a baseline for the wall interference corrections. The airfoil is the section of a 660-kW wind turbine blade. The experiments were conducted at a Reynolds number of 0.42 million, and over two reduced frequencies of k = 0.06 and 0.085, at prestall, nearstall, and poststall regions. The unsteady aerodynamic loads were calculated from the... 

In recent years, subsidy payment has been made a main challenge for governments due to growth of population and energy price in global markets. Targeted subsidy plan has been implemented in Iran since last year, and this article discusses its effects on costs and revenues of Tehran Electricity Company as one of the major subdivisions of Iran's electricity industry. In the new system, structural changes have been made in electricity tariffs, so it is not possible to predict the future trends in electricity consumption only based on the past consumptions. In order to model the decision making structure in the recent conditions, a system dynamics method is applied. In addition to modeling the... 

Accurate and early detection of anomalies in peripheral white blood cells plays a crucial role in the evaluation of well-being in individuals and the diagnosis and prognosis of hematologic diseases. For example, some blood disorders and immune system-related diseases are diagnosed by the differential count of white blood cells, which is one of the common laboratory tests. Data is one of the most important ingredients in the development and testing of many commercial and successful automatic or semi-automatic systems. To this end, this study introduces a free access dataset of normal peripheral white blood cells called Raabin-WBC containing about 40,000 images of white blood cells and color... 

In this paper fabrication of a 0-3 ceramic/ceramic composite lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 thin film has been presented and then a pressure sensor based on multilayer thin-film PZT diaphragm contain of Lead Zirconate Titanate nanocrystalline powders was designed, modeled and optimized. This multilayer diaphragm in general acts as sensor or actuator. ANSYS was used for simulation of diaphragm. Dynamics characteristics of this multilayer diaphragm have been investigated. By this simulation the effective parameters of the multilayer PZT diaphragm for improving the performance of a pressure sensor in different ranges of pressure are optimized. The optimized thickness ratio of PZT... 

The main concern in Molecular Dynamics (MD) simulations is the computational cost, and coarse-graining methods accelerate simulations by reducing the degrees of freedom in the system. Yet, the utilization of these methods should be carefully followed. In this paper, we presented an energy-based coarse-graining method for Tersoff and Stillinger-Weber potential functions. The presented coarse-graining method is based on the domain mapping and modification of potential function. The focus of this paper is on Carbon and Silicon materials; however, this method can be applied to model other materials for which Tersoff and Stillinger-Weber potentials are defined. This method has been validated by... 

In this paper we follow two approaches in optimal nonlinear control of a snake-like robot. After deriving the dynamic equations of motion using Gibbs-Appell method, reducing these equations, and some assumptions, feedback-linearization method was used to linearize the nonlinear system. The obtained controller is used in simulations to control robot to track a desired line, with minimum required torques. Two goals are desired. First the robot's head is expected to track a distinct line with a given speed. And next, tracking the serpenoid curve is desired. The simulation results prove the controller efficiency. The robustness of the designed controller is shown by comparing the torques with... 

Flow through the pores of granular materials has many instances in practice. Therefore, it is interesting to realize how some parameters, such as the shape of the particles affect the passing flow. Following the recent mathematical theory proposed by the authors, this paper deals with the issue of how tortuosity and permeability are influenced by the particle shape. Comparison of the results with the experimental data reveals the competency of the theory in predicting the impact of particle geometry  

A facile hydrothermal method and subsequent electroactivation have been developed to fabricate three-dimensional (3D) CuO nanosheet arrays on the copper foil substrate, which can be used directly as a binder-free electrode for supercapacitor applications. Under optimum conditions, by using this facile method, a high capacitance of 125 mF/cm2 at a current density of 0.3 mA/cm2 is obtained. The prepared supercapacitor showed a good rate capability (46.4% capacitance retention, when the current density is increased to more than 30 times) and an excellent cyclability (more than 88% capacitance retention after 3000 cycles). © 2017 Elsevier B.V  

Nature, as a rich source of solutions, can be an inspirational guide to answer scientific expectations. Seed dispersal mechanism as one of the most common reproduction method among the plants is a unique technique with millions of years of evolutionary history. In this paper, inspired by plants survival, a novel method of optimization is presented, which is called Fertile Field Algorithm. One of the main challenges of stochastic optimization methods is related to the efficiency of the searching process for finding the global optimal solution. Seeding procedure is the most common reproduction method among all the plants. In the proposed method, the searching process is carried out through a... 

Simulation of x-ray generation from bombardment of various solid targets by quasimonoenergetic electrons is considered. The electron bunches are accelerated in a plasma produced by interaction of 500 mJ, 30 femtosecond laser pulses with a helium gas jet. These relativistic electrons propagate in the ion channel generated in the wake of the laser pulse. A beam of MeV electrons can interact with targets to generate x-ray radiation with keV energy. The MCNP-4C code based on Monte Carlo simulation is employed to compare the production of bremsstrahlung and characteristic x rays between 10 and 100 keV by using two quasi-Maxwellian and quasimonoenergetic energy distributions of electrons. For a... 

This article investigates the influence of porosity on free and forced vibration characteristics of a nanoshell reinforced by graphene platelets (GPL). The material properties of piece-wise graphene-reinforced composites (GPLRCs) are assumed to be graded in the thickness direction of a cylindrical nanoshell and estimated using a nanomechanical model. In addition, because of imperfection of the current structure, three kinds of porosity distributions are considered. The nanostructure is modeled using modified strain gradient theory (MSGT) which is a size-dependent theory with three length scale parameters. The novelty of the current study is to consider the effects of porosity, GPLRC and MSGT... 

Nanostructured and mesoporous TiO2-Ta2O5 films and powders with various TiO2:Ta2O5 molar ratios and high specific surface area (SSA) have been prepared by a straightforward particulate sol-gel route. Titanium isopropoxide and tantalum ethoxide were used as precursors and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the SSA. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that powders contained both hexagonal δ-Ta2O5 and monoclinic β-Ta2O5 phases, as well as anatase and rutile. It was observed that Ta2O5 retarded anatase-to-rutile transformation. Furthermore, δ → β phase transformation temperature increased... 

The original article contained a mistake in Equation 1. The corrected Equation 1 is shown below: MX+Cx+Kx=f.The original article has been updated © Springer Nature B.V. 2022