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1 |
The physical and mechanical properties for flexible biomass particles using computer vision
خواص فیزیکی و مکانیکی ذرات زیست توده انعطاف پذیر با استفاده از بینایی کامپیوتری-2022 The combustion and fluidization behavior of biomass depend on the physical properties (size, morphology, and
density) and mechanical performances (elastic modulus, Poisson’s ratio, tensile strength and failure strain), but
their quantitative models have rarely been focused in previous researchers. Hence, a static image measurement
for particle physical properties is studied. Combining the uniaxial tension and digital image correlation tech-
nology, the dynamic image measurement method for the mechanical properties is proposed. The results indicate
that the average roundness, rectangularity, and sphericity of present biomass particles are 0.2, 0.4, and 0.16,
respectively. The equivalent diameter and density obey the skewed normal distribution. The tensile strength and
failure stress are sensitive to stretching rate, fiber size and orientation. The distribution intervals of elastic
modulus and Poisson’s ratio are 30–600 MPa and 0.25–0.307, respectively. The stress–strain curves obtained
from imaging experiments agree well with the result of finite element method. This study provides the operating
parameters for the numerical simulation of particles in the fluidized bed and combustor. Furthermore, the
computer vision measurement method can be extended to the investigations of fossil fuels. keywords: ذرات زیست توده | مشخصات فیزیکی | اجرای مکانیکی | تست کشش | آزمایش تصویربرداری | بینایی کامپیوتر | Biomass particle | Physical properties | Mechanical performances | Tensile testing | Imaging experiment | Computer vision |
مقاله انگلیسی |
2 |
A computer vision-based method for bridge model updating using displacement influence lines
یک روش مبتنی بر بینایی کامپیوتری برای بهروزرسانی مدل پل با استفاده از خطوط موثر جابجایی-2022 This paper presents a new computer vision-based method that simultaneously provides the moving vehicle’s
tire loads, the location of the loads on a bridge, and the bridge’s response displacements, based on which the
bridge’s influence lines can be constructed. The method employs computer vision techniques to measure the
displacement influence lines of the bridge at different target positions, which is then later used to perform
model updating of the finite element models of the monitored structural system.
The method is enabled by a novel computer vision-based vehicle weigh-in-motion method which the coauthors recently introduced. A correlation discriminating filter tracker is used to estimate the displacements at target points and the location of single or multiple moving loads, while a low-cost, non-contact weigh-in-motion technique evaluates the magnitude of the moving vehicle loads. The method described in this paper is tested and validated using a laboratory bridge model. The system was loaded with a vehicle with pressurized tires and equipped with a monitoring system consisting of laser displacement sensors, accelerometers, and cameras. Both artificial and natural targets were considered in the experimental tests to track the displacements with the cameras and yielded robust results consistent with the laser displacement measurements. The extracted normalized displacement influence lines were then successfully used to perform model updating of the structure. The laser displacement sensors were used to validate the accuracy of the proposed computer vision-based approach in deriving the displacement measurements, while the accelerometers were used to derive the system’s modal properties employed to validate the updated finite element model. As a result, the updated finite element model correctly predicted the bridge’s displacements measured during the tests. Furthermore, the modal parameters estimated by the updated finite element model agreed well with those extracted from the experimental modal analysis carried out on the bridge model. The method described in this paper offers a low-cost non-contact monitoring tool that can be efficiently used without disrupting traffic for bridges in model updating analysis or long-term structural health monitoring. keywords: Computer vision | Displacement influence line | Vehicle weigh-in-motion | Structural identification | Finite element method model | Model updating | Modal analysis | Bridge systems |
مقاله انگلیسی |
3 |
Effect of CNT additives on the electrical properties of derived nanocomposites (experimentally and numerical investigation)
تأثیر افزودنیهای CNT بر خواص الکتریکی نانوکامپوزیتهای مشتقشده (بررسی تجربی و عددی)-2021 In this work, two simulations models have been developed to study the electrical percolation and the
electrical conductivity of epoxy-based nanocomposite containing Multi-walled Carbon Nanotubes. The
models are based on resistor-model and finite element analysis. The former was evaluated using
MATLAB code and the finite element analysis using DIGIMAT software. The maximum tunneling distance
and its influence on the percolation probability and final electrical conductivity were studied. Electrical
measurements on the samples were conducted for numerical validation. The experimental data showed a
percolation achievement around 2 wt%, which was confirmed in the numerical simulations. This study
provides evidence of the effectiveness of the resistor model and finite element method approach to predict the electrical conductivity of nanocomposites.
Keywords: Polymer-matrix composites (PMCs) | Nanocomposites | Carbon nanotube | Electrical properties | Computational modelling |
مقاله انگلیسی |
4 |
Natural vibrations and stability of loaded cylindrical shells partially filled with fluid, taking into account gravitational effects
ارتعاشات طبیعی و پایداری پوستههای استوانهای بارگذاری شده تا حدی پر از مایع، با در نظر گرفتن اثرات گرانشی-2021 The paper presents the results of studying circular cylindrical shells partially filled with an ideal liquid and
subjected to uniform external and internal hydrostatic pressure. The behavior of an elastic structure and a
compressible fluid is described in the framework of the classical nonlinear theory of shells, based on the
Kirchhoff – Love hypotheses, and the Euler equations. The problem is solved using a semi-analytical version
of the finite element method. The influence of the level of fluid in the shell on the critical values of external
pressure is analyzed with and without consideration of gravitational effects on the free and lateral surfaces
of the fluid. Shells with different boundary conditions and linear dimensions are considered. It has been
shown that for certain geometrical parameters the gravitational field can significantly affect the dynamic
characteristics of the structure.
Keywords: Classical shell theory | Ideal compressible fluid | Finite element method | Gravitational field | Natural vibrations | Stability |
مقاله انگلیسی |
5 |
Methods for field measurement of electrical parameters of soil as functions of frequency
روشهای اندازهگیری میدانی پارامترهای الکتریکی خاک به عنوان توابع فرکانس-2021 In this article, the application of four-electrode and two-electrode arrays to measure electrical parameters of soil
as functions of frequency is investigated and its feasibility is evaluated by simulations and measurements. First,
the experimental arrays are simulated using finite element method to solve a rigorous electromagnetic problem.
New geometric factors are presented, which yield correct estimates of resistivity and permittivity even for
reduced spacing. Formulas are proposed for calculating the geometric factors. Then, a series of case studies is
carried out considering different soil representations, geometric parameters and excitation frequencies. It was
found that increasing excitation frequency and distance between electrodes decreases accuracy. However, resistivity and permittivity of soil can be determined for frequencies up to 2 MHz when using reduced spacing. For
the four-electrode array, a discrepancy of less than 3% between estimate and reference is obtained when using
distance between electrodes less than 0.5 m. Next, measurements using four and two electrode methods were
performed, and it was found that the four-electrode method is the most suitable for measuring soil parameters,
given that it was the one that provided consistent results. An analytical equation was also proposed to represent
the electrical parameters measured for this case.
Keywords: Grounding | Permittivity | Resistivity measurement | Soil electrical parameters |
مقاله انگلیسی |
6 |
Analysis of power law fluid-structure interaction in an open trapezoidal cavity
تجزیه و تحلیل تعامل قدرت ساختار سیال در قانون در حفره ذوزنقه باز-2020 The present paper investigates the mixed convection heat transfer of non-Newtonian fluid-structure interaction (FSI) inside an open trapezoidal cavity. The base of the cavity is fixed at constant temperature while the other walls are adiabatic. The flow passes over the open side of the cavity through a parallel-plate channel. An elastic fin is dangled from the top wall of the channel and stand facing the open cavity. The current model presents a two- dimensional incompressible laminar flow and unsteady-state conditions using the non-Newtonian power- law fluids. Numerical simulation is achieved using finite element method with arbitrary Lagrangian–Eulerian (ALE) scheme. The effects of Cauchy number, Reynolds number, Richardson number and the index of power law fluid are examined with ranges of (Ca = 10 − 20 –10 − 3 , Re = 100–300, Ri = 0.01–10 and n = 0.5–1.5). The results show that at Re = 300, Nusselt number of a stifffin is 2.6% and 7% higher than that of softer flexible fin for n = 0.5 and 1.5, respectively. For low Ri number, shear-thickening fluid manifests higher Nusselt number while for high Ri number, the shear-thinning fluid has the higher values. It is found also that the fluttering phenomenon of the fin takes place at the highest Ri and Re numbers with shear-thinning fluid and Newtonian fluid as well. Keywords: Non-Newtonian fluid | Power law | FSI | Mixed convection | Trapezoidal cavity | Channel |
مقاله انگلیسی |
7 |
A comparative analysis of flow features of Newtonian and power law material: A New configuration
تجزیه و تحلیل مقایسه ای از ویژگی های جریان مواد نیوتن و قانون قدرت: پیکربندی جدید-2020 In recent years, material analysis of fluids has generated prodigious interest of researchersdue to their effective role in interdisciplinary sciences. In view of its importance, the presentcommunication is devoted to analyze the flow of power law fluid representing the fea-tures of shear thinning, shear thickening and Newtonian materials. Constitutive equationsexpressed in the form of tensorial representations depicting power law relation betweenviscosity and shear rate. The whole mathematical model is solved computationally via offinite element method by using stable P2− P1finite element pair. A highly refined hybridmesh is obliged for the accurate computation of results. Material properties of power lawfluid are disclosed in physical configuration renowned as channel driven cavity combiningvarious benchmark problems like cavity flow, forward and backward facing steps and chan-nel flow. Impact of material parameters on pertinent profiles is disclosed through graphs.Verification of computed results is done by comparing the velocity, viscosity, pressure fieldsfor power law fluid with the Newtonian case. Keywords: Finite element method | Power-law fluid | Channel driven cavity | Shear thinning and shear thickening |
مقاله انگلیسی |
8 |
CFD analysis for characterization of non-linear power law material in a channel driven cavity with a square cylinder by measuring variation in drag and lift forces
تجزیه و تحلیل CFD برای توصیف مواد قانون قدرت غیر خطی در حفره کانال هدایت شده با یک سیلندر مربع با اندازه گیری تغییر در نیروهای درگ و بالابر-2020 Current communication is manifested to investigate flowing features of power law mate-rial in a newly proposed physical configuration namely the channel driven cavity. Sincepower law fluid discloses the dynamical features of shear thinning, shear thickening andNewtonian materials so in present communication it is considered for depiction of flowattributes. To achieve the desired outcomes from the work, a unit length cavity is placedbelow the channel. The flow is induced with parabolic inlet velocity and a Neumann condi-tion is applied at the outlet, while no slip condition is set at all other boundaries. A squarecylinder is placed in the channel with varying positions giving rise to three computationalgrids named as G1, G2and G3.Mathematical modelling is constructed by obliging funda-mental conservation and rheological laws for power law fluid. Since the representativeequations are complex in nature so an efficient computational procedure based on finiteelement method (FEM) is executed. A hybrid computational grid is generated at coarse leveland then further refinement is done to improve the accuracy of the solution. The solution isapproximated by adopting P2− P1element based on second and first order polynomial shapefunctions. Graphical trends against involved parametric variables are adorned. In additionfor more physical insight of problem velocity and pressure plots and line graphs are added.Furthermore, the hydrodynamical benchmark quantities like pressure drop, drag and liftcoefficients are evaluated in tabular form around the outer surface of obstacle. Keywords:Finite element method | Power law materia | lDrag and lift coefficients| Channel-driven cavity |
مقاله انگلیسی |
9 |
Two dimensional joint inversion of direct current resistivity and radiomagnetotelluric data based on unstructured mesh
وارونگی مشترک دو بعدی مقاومت جریان مستقیم و داده های رادیوماگنتوتلوژنی بر اساس مش بدون ساختار-2020 Using the unstructured mesh, a new two-dimensional joint inversion algorithm has been developed for
Radiomagnetotelluric and Direct current resistivity data. The unstructured mesh is generated with triangular
cells, whose vertical and lateral lengths increase towards the depths. The Finite Element Method (FEM) has
been used in the forward modelling part of the developed joint inversion algorithm. In the previous studies,
structured grid-based joint inversion algorithms have been developed using the Finite Difference Method
(FDM). In the structured grid-based algorithms, when the mesh is being generated with rectangular cells, the
vertical lengths of the cells get bigger towards the depths while the lateral lengths remain constant. With the
structured mesh, the undulated surface topography cannot be represented well enough. Also, because of the incompatible
aspect ratio ofmodel cell sizes in deepermodel sections, the resolution of themodel parameters will
get smaller and cannot be resolved well with the structured grids. Imaging of surface topography and underground
resistivity structures by the new algorithm requires fewer elements than those using structured grids.
Therefore, the developed algorithm is faster than traditional 2D inversion algorithms. Furthermore, the resolution
of the deeper model parameters has been increased by using the definition of the unstructured grid. A regularized
inversion scheme with a smoothness-constrained stabilizer has been employed to invert the data. First,
we have tested the developed joint inversion algorithm using synthetic data simplified from archaeological and
mine site scenario and the results have been compared with the conventional algorithms using structured grids.
We have also tested our algorithmwith the real data which were collected frommineral investigation site at approximately
10 kmeast of the Elbistan district of Kahramanmaraş province, in thewest of the TaurusMountains,
Turkey. The results show that the developed joint inversion algorithm is a powerful tool to detect both resistive
and conductive targets. Keywords: Direct current resistivity | Radiomagnetotelluric | Joint Inversion | Mineral Exploration | Unstructured mesh | Modelling |
مقاله انگلیسی |
10 |
Explicit dynamic approach for unbounded domains in frictional contact with Rate and State laws
رویکرد پویای صریح برای دامنه های بدون مرز در تماس اصطکاک با میزان قوانین ایالتی-2020 The paper explores the ability of an explicit time integration procedure to simulate the dynamics of shear rupture
between unbounded elastic blocks on frictional interface, modeled with the finite element method. The behaviour
of the interface is governed by Rate and State (RS) friction laws, proposed to describe the rate dependent phenomena
observed in experiments on rocks and many other materials in sliding contact. The method for the
frictional contact between bodies is integrated in the framework of heterogeneous asynchronous time integrator
(HATI). Dual formulation, requiring the introduction of Lagrange multipliers, is adopted by dealing in a weak way
with the normal contact conditions as well as the tangential frictional conditions expressed in velocity. Taking
advantage of the flexibility of the HATI framework, precise formulations of Perfectly Matched Layers (PML) are
also incorporated, enabling us to treat semi-infinite media in frictional contact. Simulations concerning an unbounded
elastic block on a rigid flat plane, initially compressed and sheared with remote loadings, are carried out.
Advantages of the PML are underlined during the preliminary stages of loading as well as during the nucleation
and propagation of the shear rupture along the interface. Numerical oscillations inherent from the high nonlinearity
of the RS friction law, characterized by significant variations of the friction coefficient with small
changes in tangential velocity, are drastically reduced thanks to the HATI method. Keywords: Finite element method | Hybrid asynchronous time integrator | Frictional contact | Rate and State friction law | Unbounded domains | Perfectly matched layers |
مقاله انگلیسی |