Simulation of viscoelastic materials by ABAQUS

The goal of present article is to simulate the behavior of viscoelastic materials. By using ABAQUS software, we can simulate the behavior of viscoelastic materials, conditional to calculate storing shear module and wasting module of viscoelastic materials by the test. First, we give descriptions required parameters such as shear module and loss factor in order to anticipate the behavior of viscoelastic materials. Then, the measurement of each above variable will be illustrated by test. To make use of the result from test, related theories should be explained in brief. Finally, resultant variables are used to simulate in ABAQUS software. The results of test are compared with software results. This comparison indicates that the results are well consistent

Modal parameter identification of a three-storey structure using frequency domain techniques FDD and EFDD and time domain technique SSI: experimental studies and simulations

The aim of this study is to modal parameter identification of a three-storey structure using operational modal analysis. In this research, available techniques in both time domain and frequency domain have been utilized. In time domain, the Stochastic Subspace Identification (SSI) technique, and in the frequency domain, Frequency Domain Decomposition (FDD) and Extended Frequency Domain Decomposition (EFDD) have been used. The modal parameters of a three-storey structure have been calculated using both experimental and finite element method. For this purpose, first, the three-storey structure was modeled in the ANSYS software and then, using the vibration analysis, structural responses are determined. The structure responses are used as inputs of the operational modal analysis algorithms and the modal parameters are obtained. Then, by constructing and exciting the structure by a variety of external excitation, the responses are measured and then, they are used as inputs to the operational modal analysis algorithm to obtain the modal parameters. Since the input signal in OMA method should be random, random, periodic random, pseudo-random, and burst random signals are used for exciting the structure. Finally, the calculated modal parameters from the finite element method and empirical method are compared with each other

Forced transverse vibration analysis of a Rayleigh double-beam system with a Pasternak middle layer subjected to compressive axial load

Based on the Rayleigh beam theory, the forced transverse vibrations of an elastically connected simply supported double-beam system with a Pasternak middle layer subjected to compressive axial load are investigated. It is assumed that the two beams of the system are continuously joined by a Pasternak layer. The dynamic responses of the system caused by arbitrarily distributed continuous loads are obtained. The effect of Pasternak layer on the forced vibrations of the Rayleigh double-beam system are discussed for one particular case of excitation loading. The properties of the forced transverse vibrations of the system are found to be significantly dependent on the compressive axial load and shear foundation modulus of Pasternak layer. Vibrations caused by the harmonic exciting forces are discussed, and conditions of resonance and dynamic vibration absorption are formulated. The important result on which this paper puts emphasis is that the magnitudes of the steady-state vibration amplitudes become smaller when the shear Pasternak modulus increases and Pasternak layer can reduce the magnitudes of the steady-state vibration amplitudes more than a Winkler elastic layer. Thus the Rayleigh beam-type dynamic absorber with a Pasternak layer can be used to suppress the excessive vibrations of corresponding beam systems instead of those with a Winkler elastic laye

Forced time-harmonic vertical vibration of a rigid disk embedded in a transversely isotropic full-space medium

This research is concerned with the investigation of forced time-harmonic vertical vibration of a rigid disk enclosed in a transversely isotropic full space medium. By properties of integral transform methods, the generalized mixed boundary-value problem is formulated as a set of dual integral equations, which in turn, are reduced to a Fredholm equation of the second kind. The obtained Fredholm integral equation is solved by well-known numerical methods. Selected results for the load distribution on the disk and complex compliance are presented for various ranges of frequency periments

Tunable Metasurface-based Waveplates- A Proposal Using Inverse Design

An approach to achieve tunable free-space waveplate operation based on a two-layer cascaded metastructure is proposed. Phase retardation is varied through changing the axial distance between the two layers. Full control on the ellipticity of the output wave is attained with wavelength-scale variations in the axial distance. The theoretically desired characteristics of the metastructures are presented and multiple physical implementations are suggested based on inverse design topology optimization

Prevalence of Color Blindness in Iranian Students: A Meta-analysis

Color blindness (color vision deficiency) is a disorder that impairs the true perception of colors. Using the information in this study, appropriate policy can be made to identify high-risk groups, as well as educational policies for families to perform more effective genetic diagnosis methods. This study aims to examine the prevalence of color blindness in Iranian students through a meta-analysis. Articles related to color blindness published between January 1990 and December 2020 were searched in Scopus, Cochrane Library, Web of Science (WoS), Science Direct, Embase, SID, MagIran, IranDoc, Medline, and Google Scholar databases. The keywords used were based on medical subject topics (MeSH Terms) and, after careful review, articles were selected according to varied sections of Participants, Exposure, Comparison, and Outcomes (PECO). Participants: students; Exposure: students with color blindness were examined; Comparison: Students from multiple provinces and regions of Iran were surveyed for color blindness; Outcomes: the pooled prevalence of color blindness in Iranian students reported from different provinces. The prevalence of color blindness in Iranian students was 3.8% (95% CI: 2.7–5.4%). The pooled prevalence of color blindness in Iranian male and female students was 4.7% (95% CI: 3.5–6.4%) and 0.7% (95% CI: 0.3–1.3%), respectively. The pooled prevalence of red–green color blindness (Tritan) was 41.7% (95% CI: 18.9–68.8%). The pooled prevalence of red color blindness (Protan) was 13.9% (95% CI: 7.8–23.8%), and the pooled prevalence of green color blindness (Deutan) based on meta-analysis was 45.3% (95% CI: 29–62.7%). Due to the high prevalence of color blindness in students, especially male students, it is necessary to be screened for through genetic tests in couples before having children