328 research outputs found
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
Attention-Guided Version of 2D UNet for Automatic Brain Tumor Segmentation
Gliomas are the most common and aggressive among brain tumors, which cause a
short life expectancy in their highest grade. Therefore, treatment assessment
is a key stage to enhance the quality of the patients' lives. Recently, deep
convolutional neural networks (DCNNs) have achieved a remarkable performance in
brain tumor segmentation, but this task is still difficult owing to high
varying intensity and appearance of gliomas. Most of the existing methods,
especially UNet-based networks, integrate low-level and high-level features in
a naive way, which may result in confusion for the model. Moreover, most
approaches employ 3D architectures to benefit from 3D contextual information of
input images. These architectures contain more parameters and computational
complexity than 2D architectures. On the other hand, using 2D models causes not
to benefit from 3D contextual information of input images. In order to address
the mentioned issues, we design a low-parameter network based on 2D UNet in
which we employ two techniques. The first technique is an attention mechanism,
which is adopted after concatenation of low-level and high-level features. This
technique prevents confusion for the model by weighting each of the channels
adaptively. The second technique is the Multi-View Fusion. By adopting this
technique, we can benefit from 3D contextual information of input images
despite using a 2D model. Experimental results demonstrate that our method
performs favorably against 2017 and 2018 state-of-the-art methods.Comment: 7 pages, 5 figures, 4 tables, Accepted by ICCKE 201
Patterns and Pathways: Applying Social Network Analysis to Understand User Behavior in the Tourism Industry Websites
The contemporary tourism landscape is undergoing rapid digitization,
necessitating a nuanced comprehension of online user behavior to guide
data-driven decision-making. This research bridges an existing gap by
investigating the tourism website ecosystem through social network analysis. It
focuses specifically on inter-website communication patterns based on user
navigation. Data mining facilitates the identification of 162 core Iranian
tourism websites, which are visualized as an interconnected network with
websites as nodes and user transitions as weighted directed edges. By
implementing community detection, eight key clusters are discerned,
encompassing domains like ticket/tour bookings, accommodations, location
services, and cuisine. Further analysis of inter-community relationships
reveals website groupings frequently accessed together by users, highlighting
complementary services sought during travel planning. The research derives
invaluable insights into user preferences and information propagation within
the tourism ecosystem. The methodology and findings contribute original
perspectives to academia while offering pragmatic strategic recommendations to
industry stakeholders like service providers, investors, and policymakers. This
pioneering exploration of latent user behavior patterns advances comprehension
of the evolving digital tourism landscape in Iran. It contributes pathways
toward a sustainable future vision of the ecosystem, guiding stakeholders in
targeted decision-making based on empirical evidence derived from social
network analysis of websites and consumption patterns. The innovative
methodology expands the toolkit for data-driven tourism research within
academia
An improved droop-based control strategy for MT-HVDC systems
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This paper presents an improved droop-based control strategy for the active and reactive power-sharing on the large-scale Multi-Terminal High Voltage Direct Current (MT-HVDC) systems. As droop parameters enforce the stability of the DC grid, and allow the MT-HVDC systems to participate in the AC voltage and frequency regulation of the different AC systems interconnected by the DC grids, a communication-free control method to optimally select the droop parameters, consisting of AC voltage-droop, DC voltage-droop, and frequency-droop parameters, is investigated to balance the power in MT-HVDC systems and minimize AC voltage, DC voltage, and frequency deviations. A five-terminal Voltage-Sourced Converter (VSC)-HVDC system is modeled and analyzed in EMTDC/PSCAD and MATLAB software. Different scenarios are investigated to check the performance of the proposed droop-based control strategy. The simulation results show that the proposed droop-based control strategy is capable of sharing the active and reactive power, as well as regulating the AC voltage, DC voltage, and frequency of AC/DC grids in case of sudden changes, without the need for communication infrastructure. The simulation results confirm the robustness and effectiveness of the proposed droop-based control strategy
A bidirectional power charging control strategy for Plug-in Hybrid Electric Vehicles
© 2019 by the authors. Plug-in Hybrid Electric Vehicles (PHEVs) have the potential of providing frequency regulation due to the adjustment of power charging. Based on the stochastic nature of the daily mileage and the arrival and departure time of Electric Vehicles (EVs), a precise bidirectional charging control strategy of plug-in hybrid electric vehicles by considering the State of Charge (SoC) of the batteries and simultaneous voltage and frequency regulation is presented in this paper. The proposed strategy can control the batteries charge which are connected to the grid, and simultaneously regulate the voltage and frequency of the power grid during the charging time based on the available power when different events occur over a 24-h period. The simulation results prove the validity of the proposed control strategy in coordinating plug-in hybrid electric vehicles aggregations and its significant contribution to the peak reduction, as well as power quality improvement. The case study in this paper consists of detailed models of Distributed Energy Resources (DERs), diesel generator and wind farm, a generic aggregation of EVs with various charging profiles, and different loads. The test system is simulated and analyzed in MATLAB/SIMULINK software
An improved mixed AC/DC power flow algorithm in hybrid AC/DC grids with MT-HVDC systems
© 2019 by the authors. One of the major challenges on large-scale Multi-Terminal High Voltage Direct Current (MT-HVDC) systems is the steady-state interaction of the hybrid AC/DC grids to achieve an accurate Power Flow (PF) solution. In PF control of MT-HVDC systems, different operational constraints, such as the voltage range, voltage operating region, Total Transfer Capability (TTC), transmission reliability margin, converter station power rating, etc. should be considered. Moreover, due to the nonlinear behavior of MT-HVDC systems, any changes (contingencies and/or faults) in the operating conditions lead to a significant change in the stability margin of the entire or several areas of the hybrid AC/DC grids. As a result, the system should continue operating within the acceptable limits and deliver power to the non-faulted sections. In order to analyze the steady-state interaction of the large-scale MT-HVDC systems, an improved mixed AC/DC PF algorithm for hybrid AC/DC grids with MT-HVDC systems considering the operational constraints is developed in this paper. To demonstrate the performance of the mixed AC/DC PF algorithm, a five-bus AC grid with a three-bus MT-HVDC system and the modified IEEE 39-bus test system with two four-bus MT-HVDC systems (in two different areas) are simulated in MATLAB software and different cases are investigated. The obtained results show the accuracy, robustness, and effectiveness of the improved mixed AC/DC PF algorithm for operation and planning studies of the hybrid A/DC grids
- …