In this theoretical work, the encapsulation effect of bithiophene (2T) inside single‐walled carbon nanotubes (SWCNTs) is reported. The optimum configurations of 2T inside SWCNTs (2T@SWCNTs) are ...derived from minimum energy calculations using a Lennard‐Jones expression to describe the van der Waals intermolecular interactions. The great number of atoms present the main handicap for the theoretical study of our systems. A hybrid approach is set out to build a dynamic model of 2T@SWCNTs systems. This approach combines density of functional theory and molecular dynamics. We have finally developed the process necessary to build the dynamic matrix of our systems. After calculation of the dynamical model, for the obtained configuration of 2T@SWCNTs, the nonresonant Raman spectra have been calculated using the spectral moment's method. The charges transfer in the hybrid systems has been investigated by analyzing the Raman active modes of 2T molecule and the G‐band modes of free SWCNTs and 2T@SWCNTs hybrid systems.
•Tensile properties of the adhesive joints were obtained at low temperatures.•FE analysis was carried out at low temperatures and various loading modes.•Mixed mode fracture tests were conducted by ...using the special loading device.•Fracture surfaces of samples were analyzed by SEM.
In this work, the fracture parameters of the adhesive joints were investigated at low temperatures. The results of the tensile experiments showed that by decreasing the temperature, the ultimate strength, yield strength and elastic modulus have increasing trends. The effect of temperature and loading mode on the fracture toughness parameters of adhesive joints were examined by using the special test loading device in which by varying the loading angle, pure mode I, II and mixed mode data were obtained experimentally. The results showed that by decreasing the temperature, critical stress intensity factors and critical strain energy release rates increased. However, the increasing trend in mode I was gentle and in mode II was significant. Non-dimensional stress intensity factors were also determined by using finite element method at low temperatures and different loading modes. In order to understand the failure mechanism of adhesive joints, fracture surfaces of samples were analyzed, which showed that, in mode I, the failure mechanism was of a cohesive type and by decreasing the temperature, the joint became brittle and the fracture surface became smooth. The interfacial failure in mode II revealed that the fracture toughness of the adhesive was greater than that of the interface, which leads to deviation of crack growth path from the cohesive to the interfacial fracture.
• For the first time, the comprehensive wave propagation analysis of 2D-FG rotating nanobeams with porosity is considered. • General nonlocal theory is used to establish the governing equation which ...exhibits softening and hardening behaviour. • Reddy's beam theory is applied to model the effects of the higher-order transverse shear strains on the wave propagation. • The effects of material variation, porosity, and the length to thickness ratio on the wave propagation are discussed.
This paper studies the wave propagation of two-dimensional functionally graded (2D-FG) porous rotating nano-beams for the first time. The rotating nano-beams are made of two different materials, and the material properties of the nano-beams alter both in the thickness and length directions. The general nonlocal theory (GNT) in conjunction with Reddy's beam model are employed to formulate the size-dependent model. The GNT efficiently models the dispersions of acoustic waves when two independent nonlocal fields are modelled for the longitudinal and transverse acoustic waves. The governing equations of motion for the 2D-FG porous rotating nano-beams are established using Hamilton's principle as a function of the axial force due to centrifugal stiffening and displacement. The analytic solution is applied to obtain the results and solve the governing equations. The effect of the features of different parameters such as functionally graded power indexes, porosity, angular velocity, and material variation on the wave propagation characteristics of the rotating nano-beams are discussed in detail.
This paper describes the adsorption of heavy metal ions from aqueous solutions by nano structure alumina. Our study tested the removal of three heavy metals: Pb
2+, Ni
2+ and Zn
2+. The optimum ...contact time, adsorbent mass, and pH were determined, and adsorption isotherms were obtained using concentrations of the metal ions ranging from 25 to 150
mg
L
−
1
. The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir and Freundlich adsorption isotherms. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and exothermic under natural conditions. The maximum capacity of adsorbent for Pb
2+, Ni
2+ and Zn
2+ are 125, 83.33 and 58.82
mg
g
−
1
, respectively. This study revealed that nano structure γ-alumina was an effective adsorbent for removal of these ions from aqueous solutions.
•General nonlocal theory with two parameters is used for the porous FG nanobeam.•The nonlocal parameters cause softening and hardening behavior.•Reddy’s beam theory is used to model higher-order ...transverse shear strains.•Material variations in the length and thickness directions are investigated.•The porosity volume fraction and the length to thickness ratio are varied.
A comprehensive vibrational analysis of bi-directional functionally graded (2D-FG) rotating nanobeams with porosities is studied for the first time. The beam is modeled based on general nonlocal theory (GNT) where the beam governing equations are derived depending on two different nonlocal parameters. Unlike Eringen’s conventional form of nonlocal theory, the general nonlocal theory can reveal both hardening and softening behaviors of the material. Here, the attenuation functions are altered in both transverse and longitudinal directions of 2D-FG nanobeam. This feature, which has a significant effect on the vibrational characteristics, has not been considered in previous studies. Moreover, to estimate the effects of the higher-order transverse shear strains on the vibration of the nanobeam, Reddy’s beam theory (RBT), which includes higher-order shear deformation, is employed. The material properties of the 2D-FG rotating nanobeam vary both in the length and thickness directions according to a power law. The generalized differential quadrature method (GDQM) is used to predict the vibration response. Also, the effects of material variation along the length and thickness directions, the rotating velocity of the nanobeam, the porosity volume fraction and the length to thickness ratio of the rotating nanobeam are illustrated and discussed in detail. The investigations performed in this study expose new phenomena for the vibration of nanobeams.
Capacitated facility location problem (CFLP) is a well-known combinatorial optimization problem with applications in distribution and production planning that is classified as an NP-Hard problem. The ...aim is to determine where to locate facilities and how to move commodities such that the customers’ demands are satisfied and the total cost minimized. In this paper, a new hybrid optimization method called Hybrid Evolutionary Firefly-Genetic Algorithm is proposed, which is inspired by social behavior of fireflies and the phenomenon of bioluminescent communication. The method combines the discrete Firefly Algorithm (FA) with the standard Genetic Algorithm (GA). It is devoted to the detailed description of the problem, and an adaption of the algorithm. Computational results on random generated problems consisting of 2000 locations and 2000 customers are reported.
Purpose
Cancer-related fatigue (CRF) is the most reported side effect of cancer and its treatments. Mechanisms of CRF are multidimensional, including neuromuscular alterations leading to decreased ...muscle strength and endurance (i.e., fatigability). Recently, exercise fatigability and CRF have been related, while fatigability mechanisms remain unclear. Traditionally, fatigability is assessed from maximal voluntary contractions (MVC) decrease, but some authors hypothesized that the rate of force development (RFD) determined during a rapid contraction could also be an interesting indicator of functional alterations. However, to our knowledge, no study investigated RFD in cancer patients. The purpose of this study was to determine whether RFD, fatigability amplitude, and etiology are different between fatigued and non-fatigued cancer patients.
Methods
Eighteen participants with cancer, divided in fatigued or non-fatigued groups according their CRF level, completed a 5-min all-out exercise in ankle plantar flexor muscles composed of 62 isometric MVC of 4 s with 1 s rest, to assess fatigability amplitude as the force–time relationship asymptote (
F
A
). Before and after exercise, fatigability etiologies (i.e., voluntary activation (VA) and evoked forces by electrical stimulation (Db
100
)) were assessed as well as RFD in 50 and 100 ms (RFD
50
and RFD
100
, respectively) during rapid contractions.
Results
F
A
is significantly lower in fatigued group. Significant differences were found between pre- and post-exercise VA, Db
100
, RFD
50
, and RFD
100
for both groups, with no statistical difference between groups.
Conclusion
During treatments, fatigability is higher in fatigued patients; however, the mechanisms of fatigability and RFD alterations are similar in both groups.
Trial registration
ClinicalTrials.gov, NCT04391543, May 2020.
In the present paper, an analytical solution based on a molecular mechanics model is developed to evaluate the elastic critical axial buckling strain of chiral multi-walled carbon nanotubes (MWCNTs). ...To this end, the total potential energy of the system is calculated with the consideration of the both bond stretching and bond angular variations. Density functional theory (DFT) in the form of generalized gradient approximation (GGA) is implemented to evaluate force constants used in the molecular mechanics model. After that, based on the principle of molecular mechanics, explicit expressions are proposed to obtain elastic surface Young’s modulus and Poisson’s ratio of the single-walled carbon nanotubes corresponding to different types of chirality. Selected numerical results are presented to indicate the influence of the type of chirality, tube diameter, and number of tube walls in detailed. An excellent agreement is found between the present numerical results and those found in the literature which confirms the validity as well as the accuracy of the present closed-form solution. It is found that the value of critical axial buckling strain exhibit significant dependency on the type of chirality and number of tube walls.
•The infrared active modes in multi-walled boron nitride nanotubes (MWBNNTs) are calculated.•We focus on the inner tube diameter and the size of MWBNNTs effects.•We show that the infrared spectra ...exhibit two main bands located around 800 and 1390 cm−1.•The calculated results are usful to understand the experimental Infrared data of MWBNNT.
In this work, the IX and IZ polarized infrared active modes in multi-walled boron nitride nanotubes (MWBNNTs) are computed using the spectral moment’s method. A Lennard-Jones potential is used to describe the van der Waals coupling interactions between the layers. We discuss the evolution of the low, intermediate and high wave number regions of the infrared spectra as a function of the inner tube diameter and the size of MWBNNTs. Our predictions are useful for understanding the experimental infrared spectra of MWBNNTs.
We investigate instabilities of F(R)-charged AdS4 black holes by a massive charged scalar field in a linear perturbation regime. We study tachyonic instabilities as the near horizon scalar ...condensation in a model of F(R) gravity with planar horizon and investigate properties of possible phase transitions. The results show that such transitions are sensitive to the first derivative of F(R) with respect to R in that the larger its value, the higher the critical temperature, thus resulting in a new generation of high-temperature superconductors. Also, for a certain range of parameters, F(R)-charged AdS4 black holes suffer from superradiant instability. We consider the effects of the scalar mass and charge on such instabilities and conclude that Reissner-Nordstrom (RN) black holes decay into small hairy black holes that have a charged scalar condensate floating near the horizon. It is shown that the existence of phase transition at the critical temperature leading to a hairy black hole solution emerges for T<Tc, while RN black holes exist for T>Tc. The effect of F(R) on the critical temperature is subsequently investigated in the case of superradiant instability, showing that higher critical temperatures would be possible in F(R) gravity. We also check the stability of hairy black holes and show that the resulting hairy solution can be considered as a possible endpoint of superradiant instability of a small charged black hole.
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