Graphene is one of the youngest member of the nano-carbon material with two-dimensional structure which has extraordinary mechanical and electrical properties. Graphene sheets can also be used as mass sensors. In this paper, the special applications of this substance as a mass sensor are considered. The VIBRATIONAL behavior of a graphene mass sensor is studied by molecular DYNAMICS simulation method. Also, the effects of increase the dimensions of the rectangular sheet in two zigzag and armchair directions has been studied on natural frequencies. For this purpose, a square graphene sheet has been created in the molecular dynamic environment and the particle displacement is obtained from the molecular DYNAMICS method. The displacements are analyzed using the frequency domain decomposition method and the first natural frequency of the sheet is calculated. Then, the dimensions of graphene sheet have been changed in the zigzag and armchair directions, and the natural frequency of the sheet is also estimated. In order to validate the method, the estimated natural frequency is compared with the results of one of the improved theories of continuous mechanics. In the following, the ability of graphene sheet for detection of attached mass has been examined using the presence of concentrated gold particles. Finally, the sensitivity of graphene sheet to the attached masses is presented.

The classical methods utilized for modeling the nano-scale systems are not practical because of the enlarged surface effects that appear at small dimensions. Contrarily, implementing more accurate methods results in prolonged computations as these methods are highly dependent on quantum and atomistic models and they can be employed for very small sizes in brief time periods. In order to speed up the molecular DYNAMICS (MD) simulations of the silicon structures, coarse-graining (CG) models are put forward in this research. The procedure consists of establishing a map between the main structure’ s atoms and the beads comprising the CG model and modifying the systems parameters such that the original and the CG models reach identical physical parameters. The accuracy and speed of this model is investigated by carrying out various static and dynamic simulations and assessing the effect of size. The simulations show that for a nanowire with thickness over 10a, where parameter a is the lattice constant of diamond structure, the Young modulus obtained by CG and MD models differs less than 5 percent. The results also show that the corresponding CG model behaves 190 time faster compared to the AA model.

Using molecular DYNAMICS simulations, the structural properties and VIBRATIONAL behavior of single- and double-walled carbon nanotubes (CNTs) under physical adsorption (functionalization) of Flavin Mononucleotide (FMN) biomolecule are analyzed and the effects of different boundary conditions, the weight percentage of FMN, radius and number of walls on the natural frequency are investigated. As the functionalized nanotubes mainly operate in aqueous environment, two different simulation environments, i.e. vacuum and aqueous environments, are considered. Considering the structural properties, increasing the weight percentage of FMN biomolecules results in linearly increasing the gyration radius. Also, it is observed that presence of water molecules expands the distribution of FMN molecules wrapped around CNTs compared to that of FMN molecules in vacuum. It is demonstrated that functionalization reduces the frequency of CNTs, depending on their boundary conditions in vacuum which is more considerable for fully clamped (CC) boundary conditions. Performing the simulations in aqueous environments demonstrates that, in the case of clamped-free (CF) boundary conditions, the frequency increases unlike that of CNTs with fully clamped and fully simply supported boundary conditions. The value of frequency shift increases by raising the weight percentage of FMN biomolecule. Moreover, it is observed that the frequency shifts of SWCNTs with bigger radius are more considerable, whereas the sensitivity of frequency shift to the weight percentage of FMN biomolecule reduces and this is more pronounced as the simulation environment is aqueous.

In this paper, the VIBRATIONAL properties of fullerene hydrides with the chemical formula C60H2n are investigated using a method based on the potential energy of the molecule. The potential used in this methodology is AIREBO (Adaptive Intermolecular Reactive Empirical Bond Order). Using this interatomic potential, some of the most important frequencies of the fullerene hydrides, such as the breathing mode frequency, were calculated and then analyzed. It was observed that in addition to the number of hydrogen atoms in the structure, their position on the C60 cage has a significant effect on the natural frequency corresponding to a particular mode shape. The results obtained by this method have been compared and validated with quantum mechanics and experimental observations. The simulations results demonstrate that the proposed method is capable of calculating the VIBRATIONAL properties of fullerene hydrides with high precision and low computational cost.

Due to the stochastic nature of wind energy, allocating an appropriate investment incentive for wind generation technology (WGT) is a complicated issue. We propose an improvement on the traditional incentive, known as capacity payment mechanism (CPM), to reward the wind generators based on their performance exogenously affected by the wind energy potential of the location where the turbines are installed, and therefore, lead the investments towards locations with more generation potential. In CPM, a part of investment cost of each generator is recovered through fixed payments. However, in our proposal, wind generators are rewarded according to dynamic forecasts of the wind energy potential of the wind farm where they are located. We use an auto-regressive moving average (ARMA) model to forecast the wind speed fluctuations in long-term while capturing the auto-correlation of wind velocity variation in consecutive time intervals. Using the system DYNAMICS (SD) modelling approach a competitive electricity market is designed to examine the efficiency of the proposed incentive. Performing a simulation analysis, we conclude that while a fixed CPM for wind generation can decrease the loss of load durations and average prices in long-term, the proposed improvement can provide quite similar results more efficiently.

Poly (vinylidene chloride) (PVDC) is a barrier polymer which has a wide scope in food packaging industries. A comprehensive study of the normal modes and their dispersion in PVDC using Wilson’s GF matrix method as modified by Higgs is reported. It provides a detailed interpretation of IR and Raman spectra. Characteristic feature of dispersion curves, such as regions of high density-of-states, repulsion, and character mixing of dispersion modes, are discussed. Heat capacity has been calculated in the range 50–500 K via density-of-states using Debye relation. It is in fairly good agreement with the experimental data. Heat capacity behavior of PVDC with temperature was observed nearly linear in nature. Heat capacity provides a relationship between microscopic behavior and a macroscopic property. The thermal stability of a polymeric system and its interactive nature with other properties, such as phonon-phonon coupling is also related to thermodynamic behavior. The present study provides a theoretical framework to understand experimental measurements.