Showing 5 results for Type of Study: Applicable
F. Shirmohammadi, M. M. Saadatpour,
Volume 37, Issue 1 (9-2018)
Abstract
In this article spectral modal method is developed for studying wave propagation in thin plates with constant or variable thickness. Theses plates are subjected to the impact forces and different boundary conditions. Spectral modal method can be considered as the combination of Dynamic Stiffness Method (DSM), Fourier Analysis Method (FAM) and Finite Stripe Method (FSM). Using modeling of continuous distribution of mass and an exact stiffness causes solutions in frequency domain. Unlike the most numerical methods, in this method refining meshes is no longer necessary in which the cost and computational time is decreased. In this paper the important parameters of the method and their effects on results are studied through different examples.
I. Ahmadi, D. Kouhbor, R. Taghiloo,
Volume 38, Issue 1 (8-2019)
Abstract
In this paper, a finite element model is presented for the transient analysis of low velocity impact, and the impact induced damage in the composite plate subjected to low velocity impact is studied. The failure criteria suggested by Choi and Chang and the Tsai-Hill failure criteria are used for the prediction of the damage in the composite plate; then the effect of various parameters on the impact induced damage is investigated. The first order shear deformation plate theory and the Ritz finite element method are employed for modeling the behavior of plate, and the modified Hertz contact low is used for the prediction of the contact force through the impact. In the numerical results, the time history of indentation, contact force and stress during the impact and the impact induced damage is investigated. The matrix cracking and delamination in the plies of the laminated composite plate subjected to low velocity impact are studied and the effects of various parameters are investigated.
Z. Arefinia,
Volume 38, Issue 2 (2-2020)
Abstract
As thermalisation loss is the dominant loss process in the quantum dot intermediate band solar cells (QD-IBSCs), it has been investigated and calculated for a QD-IBSC, where IB is created by embedding a stack of InAs(1-x) Nx QDs with a square pyramid shape in the intrinsic layer of the AlPySb(1-y) p-i-n structure. IB, which is an optically coupled but electrically isolated mini-band, divides the total band gap of AlPySb(1-y) into two sub-band gaps. To obtain the thermalisation loss of AlPySb(1-y)/InAs(1-x)Nx QD-IBSCs, the position and width of IB in the band gap of AlPySb(1-y) should be calculated. The position of IB, which is equal to the first eigen-energy of a unit cell of QD, is obtained by solving the 3D Schrödinger equation with a finite-element method and the width of IB is obtained by the absorption characteristics. Then, with the investigation of the effect of nitrogen and phosphorous molar fraction, QDs size and the distance between the QDs on the thermalisation loss, the minimized loss for the optimized structure of AlPySb(1-y)/InAs(1-x)Nx QD-IBSCs is obtained
R. Ghiasi , M. R. Ghasemi ,
Volume 39, Issue 1 (8-2020)
Abstract
This paper focuses on the processing of structural health monitoring (SHM) big data. Extracted features of a structure are reduced using an optimization algorithm to find a minimal subset of salient features by removing noisy, irrelevant and redundant data. The PSO-Harmony algorithm is introduced for feature selection to enhance the capability of the proposed method for processing the measured big data, which have been collected from sensors of the structure and uncertainties associated with this process. Structural response signals under ambient vibration are preprocessed according to wavelet packet decomposition (WPD) and statistical characteristics for feature extraction. It optimizes feature vectors to be used as inputs to surrogate models based on the wavelet weighted support vector machine (WWLS-SVM) and radial basis function neural network (RBFNN). Two illustrative test examples are considered, the benchmark dataset from IASC-ASCE SHM group and a 120-bar dome truss. The results indicate that the features acquired by WPT from vibrational signal have higher sensitivity to the damage of the structure. Furthermore, the proposed PSO-Harmony is compared with four well-known metaheuristic optimization algorithms. The obtaind results show that the proposed method has a better performance and convergence rate. Finally, the proposed feature subset selection method has the capability of 90% data reduction
R. Salamat Mamakani , A. Azhari,
Volume 40, Issue 2 (1-2022)
Abstract
Dynamic stability and liquefaction of tailings dams are great concerns for geotechnical engineers. In this study, the seismic response of the Esphordi mine tailing dam located in Bafgh seismic region of Yazd province is investigated. A finite-difference code (FLAC2D) is used to model the seismic liquefaction applying two constitutive criteria, namely Mohr-Coulomb and Finn-Byrne. For this purpose, a fish function is implemented into the code to simulate the non-linear elasto-plastic Finn-Byrne constitutive model. Horizontal and vertical displacements (subsidence) in the dam body, additional pore pressure, failure zones, and liquefaction due to seismic load were determined using the two selected criteria under the seismic load of the 6.4 magnitude earthquake occurred in 2005. Considering the type of behavioral model, Mohr-Coulomb and Finn-Byrne, the maximum horizontal displacement of 5 and 35 cm in the dam body and downstream, and subsidence of 4 and 23 cm at the dam crest and upstream are observed, respectively. Also, the calculated ratio of excess pore pressure (Ru), for both criteria, was less than the liquefaction limit (0.9), the maximum value of which was 0.7 for the Finn-Byrne criterion and 0.2 for the Mohr-Coulomb criterion. In general, the results show that considering the cumulative effect of the seismic load cycles in the Finn- Byrne model, this criterion provides a better understanding of the liquefaction phenomenon.
