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Primož Kocutar^{1, *}, Jure Ravnik¹, Leopold Škerget¹
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 1-22, 2020, DOI:10.32604/cmes.2020.08728 - 01 April 2020
Abstract In this paper, we develop and test a unified hybrid LES/URANS turbulence model with two different Large Eddy Simulation (LES) turbulence models. The numerical algorithm is based on the Boundary Element Method. In the existing hybrid LES/URANS turbulence model we implemented a new Smagorinsky LES turbulence model. The hybrid LES/URANS turbulence model is unified, which means that the LES/URANS interface is changed dynamically during simulation using a physical quantity. In order to define the interface between LES and unsteady Reynolds Averaged Navier Stokes (URANS) zones during the simulation, we use the Reynolds number based on… More >

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2185

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Davide Piovesan^{1, *}, Roberto Bortoletto²
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 23-47, 2020, DOI:10.32604/cmes.2020.09231 - 01 April 2020
（This article belongs to the Special Issue: Computer Methods in Bio-mechanics and Biomedical Engineering)
Abstract Exoskeletons are designed to control the forces exerted during the physical coupling between the human and the machine. Since the human is an active system, the control of an exoskeleton requires coordinated action between the machine and the load so to obtain a reciprocal adaptation. Humans in the control loop can be modeled as active mechanical loads whose stiffness is continuously changing. The direct measurement of human stiffness is difficult to obtain in real-time, thus posing a significant limitation to the design of wearable robotics controllers. Electromyographic (EMG) recordings can provide an indirect estimation of… More >

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2704

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Jianhua Dong¹, Lifeng Wu², Xiaogang Liu^{1, *}, Cheng Fan¹, Menghui Leng³, Qiliang Yang¹
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 49-73, 2020, DOI:10.32604/cmes.2020.09014 - 01 April 2020
Abstract Solar radiation is an important parameter in the fields of computer modeling, engineering technology and energy development. This paper evaluated the ability of three machine learning models, i.e., Extreme Gradient Boosting (XGBoost), Support Vector Machine (SVM) and Multivariate Adaptive Regression Splines (MARS), to estimate the daily diffuse solar radiation (R_d). The regular meteorological data of 1966-2015 at five stations in China were taken as the input parameters (including mean average temperature (T_a), theoretical sunshine duration (N), actual sunshine duration (n), daily average air relative humidity (RH), and extra-terrestrial solar radiation (R_a)). And their estimation accuracies were subjected to… More >

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3396

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2145

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Min Luo¹, Tingting Xu^{1, *}, Jiajun Jiang², Xu Chi³, Jing Wang⁴, Shihua Xue¹
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 75-100, 2020, DOI:10.32604/cmes.2020.09236 - 01 April 2020
Abstract The lack of research on flexible drilling tool leads to limited application of ultra-short radius horizontal wells. The flexible drilling tool is different from the conventional drilling tool. The flexible drilling pipe involves a mutual transition between the structure and the mechanism during the deformation process. At the same time, the flexible drilling pipe and the eccentric guide tube, the guide tube and the wellbore generate random contact. In this paper, 3-D beam elements, universal joint elements, rigid beam elements and the beam-beam contact elements are combined to establish a two-layer contact nonlinear finite element… More >

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3453

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2160

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Meijuan Shan^{1, 2}, Libin Zhao^{2, *}, Wei Huang³, Fengrui Liu², Jianyu Zhang^{4, *}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 101-127, 2020, DOI:10.32604/cmes.2020.09099 - 01 April 2020
Abstract The high demands for load-carrying capability and structural efficiency of composite-metal bolted joints trigger in-depth investigations on failure mechanisms of the joints in hygrothermal environments. However, few studies have been presented to exhaustively reveal hygrothermal effects on the failure of CFRP-metal bolted joints, which differ from CFRP-CFRP or metal-metal bolted joints because of the remarkably different material properties of CFRPs and metals. In this paper, hygrothermal effects on tensile failures of single-lap and double-lap CFRP-aluminum bolted joints were experimentally and numerically investigated. A novel numerical model, in which a hygrothermal-included progressive damage model of composites… More >

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2417

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Xu Liu¹, Xiaoyang Chen^{1, *}, Rongyu Kang¹, Xuejin Shen¹, Ben Ni²
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 129-152, 2020, DOI:10.32604/cmes.2020.07836 - 01 April 2020
Abstract In this paper, the oscillatory oil squeeze film is taken as a research object, and a coupled cavitation model based on the theory of bubble dynamics and hydrodynamic lubrication is used and a specific method of numerical calculation is given. Then the parallel-plate squeeze film test apparatus is used to validate the coupled cavitation model. The pictures of the cavitation were captured by a high-speed camera and then processed to obtain the variation of the cavitation area in experiments. Compared with the experimental results, the model can successfully predict the process of generation and development… More >

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1901

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Xiang Liu¹, Liangbo Sun², Mingzhen Wang^{3, 4}, Bin Li², Lisheng Liu^{1, 5, *}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 153-183, 2020, DOI:10.32604/cmes.2020.08716 - 01 April 2020
Abstract A vein model was established to simulate the periodic characteristics of blood flow and valve deformation in blood-induced valve cycles. Using an immersed finite element method which was modified by a ghost fluid technique, the interaction between the vein and blood was simulated. With an independent solid solver, the contact force between vein tissues was calculated using an adhesive contact method. A benchmark simulation of the normal valve cycle validated the proposed model for a healthy vein. Both the opening orifice and blood flow rate agreed with those in the physiology. Low blood shear stress… More >

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2042

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Yongping Yu¹, Lihui Chen¹, Shaopeng Zheng¹, Baihui Zeng¹, Weipeng Sun^{2, ∗}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 185-200, 2020, DOI:10.32604/cmes.2020.07997 - 01 April 2020
Abstract This paper is focused on the post-buckling behavior of the fixed laminated composite beams with effects of axial compression force and the shear deformation. The analytical solutions are established for the original control equations (that is not simplified) by applying the Maclaurin series expansion, Chebyshev polynomials, the harmonic balance method and the Newton’s method. The validity of the present method is verified via comparing the analytical approximate solutions with the numerical ones which are obtained by the shooting method. The present third analytical approximate solutions can give excellent agreement with the numerical solutions for a More >

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1929

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Yao Ma¹, Xibiao Cai^{1, *}, Fuming Sun²
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 201-216, 2020, DOI:10.32604/cmes.2020.07867 - 01 April 2020
（This article belongs to the Special Issue: Security Enhancement of Image Recognition System in IoT based Smart Cities)
Abstract Image quality assessment has become increasingly important in image quality monitoring and reliability assuring of image processing systems. Most of the existing no-reference image quality assessment methods mainly exploit the global information of image while ignoring vital local information. Actually, the introduced distortion depends on a slight difference in details between the distorted image and the non-distorted reference image. In light of this, we propose a no-reference image quality assessment method based on a multi-scale convolutional neural network, which integrates both global information and local information of an image. We first adopt the image pyramid More >

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2383

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2

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Shuifen Zhan^{1, 2, 3}, Mingchao Wang^{2, *}, Min Wang^{5, *}, Qianqian Shao⁴, Zefang Zhang³, Wenxin Jiang², Xuemin Chen¹
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 217-235, 2020, DOI:10.32604/cmes.2020.08289 - 01 April 2020
（This article belongs to the Special Issue: Advances in Modeling and Simulation of Complex Heat Transfer and Fluid Flow)
Abstract Considering the accidents of ships for dangerous chemicals transportation in inland rivers, a numerical method for the simulation of the leakage and diffusion processes of dangerous chemicals in inland rivers is proposed in this paper. Geographic information, such as rivers and buildings in the model, is obtained through Google Earth and structures of rivers and buildings are described by Auto CAD. In addition, the Fluent is adopted to simulate the leakage and diffusion processes of the dangerous chemicals where the standard k-ε model is used to calculate the turbulent flow. Considering the interaction between chemicals and… More >

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2020

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ARTICLE

Yong Guan¹, Wanling Hu^{1, 2, *}, Yun Zhang¹, Kewei Song^{2, 3}, Liangbi Wang^{2, 3}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 237-256, 2020, DOI:10.32604/cmes.2020.09141 - 01 April 2020
（This article belongs to the Special Issue: Advances in Modeling and Simulation of Complex Heat Transfer and Fluid Flow)
Abstract The application of vortex generators in tube-finned heat exchangers is very universal. The vortex generators can generate secondary flow, and as we all know secondary flow can obviously strengthen heat transfer. To use vortex generators much more efficiently in the circle tube-finned heat exchangers, the intensity correlation study between secondary flow and heat transfer is needed. 22 different structures of circle tubefinned heat exchangers were numerically studied, including the plain fin cases and the cases with vortex generators. In addition, the influence of fin spacing, transverse and longitudinal tube pitch, heights and attack angle of More >

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2212

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ARTICLE

Wei Liu^{1, 2, *}, Zhaoyang Song², Yunchang Wang²
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 257-282, 2020, DOI:10.32604/cmes.2020.07220 - 01 April 2020
（This article belongs to the Special Issue: Numerical Modeling and Simulation for Structural Safety and Disaster Mitigation)
Abstract Seismic analysis of buried pipes has been one study focus during the last decades, but the systematic seismic research of pipe connections, especially its relationship with the connected straight pipe, is nearly blank. On the basis, the influence of pipe connections on the joint deformations (JDs) of buried segmented pipes is analyzed in detail by considering different parameters, namely, connection shapes, ground conditions, pipe diameters, branch angles, seismic incident angles, and input ground motions. Moreover, an influence coefficient, which measures the influence of pipe connections on pipe JDs, is calculated. Results show that pipe connections More >

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2498

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ARTICLE

Chengbao Hu^{1, 2, 3}, Liang Wang⁴, Daosheng Ling^{1, 2, 3, *}, Wujun Cai⁵, Zhijie Huang^{1, 2}, Shilin Gong^{1, 2, 3}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 283-307, 2020, DOI:10.32604/cmes.2020.07842 - 01 April 2020
（This article belongs to the Special Issue: Numerical Modeling and Simulation for Structural Safety and Disaster Mitigation)
Abstract This paper performed flexural test and numerical simulation of clay-beams with different water contents to study the tensile fracture of clay soil and the relevant mechanisms. The crack initiation and propagation process and the accompanied strain localization behaviors were all clearly observed and analyzed. The exponential cohesive zone model was proposed to simulate the crack interface behavior of the cohesivefrictional materials. The experimental results show that the bending capacity of claybeams decrease with the water content, while those of the crack mouth opening displacement, crack-tip strain and the strain localization range increase. The numerical predictions More >

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Wencai Sun^{1, ∗}, Zichun Yang¹
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 309-332, 2020, DOI:10.32604/cmes.2020.08386 - 01 April 2020
（This article belongs to the Special Issue: Numerical Modeling and Simulation for Structural Safety and Disaster Mitigation)
Abstract It is very difficult to know the exact boundaries of the variable domain for problems with small sample size, and the traditional convex set model is no longer applicable. In view of this, a novel reliability model was proposed on the basis of the fuzzy convex set (FCS) model. This new reliability model can account for different relations between the structural failure region and variable domain. Key computational algorithms were studied in detail. First, the optimization strategy for robust reliability is improved. Second, Monte Carlo algorithms (i.e., uniform sampling method) for hyper-ellipsoidal convex sets were More >

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2591

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T. Binesh^{1, *}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 333-351, 2020, DOI:10.32604/cmes.2020.08097 - 01 April 2020
（This article belongs to the Special Issue: Numerical Methods for Differential and Integral Equations)
Abstract Wavelength-dependent mathematical modelling of the differential energy change of a photon has been performed inside a proposed hypothetical optical medium. The existence of this medium demands certain mathematical constraints, which have been derived in detail. Using reverse modelling, a medium satisfying the derived conditions is proven to store energy as the photon propagates from the entry to exit point. A single photon with a given intensity is considered in the analysis and hypothesized to possess a definite non-zero probability of maintaining its energy and velocity functions analytic inside the proposed optical medium, despite scattering, absorption, More >

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2160

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Zhen Wang^{1, *}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 353-376, 2020, DOI:10.32604/cmes.2020.08776 - 01 April 2020
（This article belongs to the Special Issue: Numerical Methods for Differential and Integral Equations)
Abstract In this paper, a special case of nonlinear time fractional cable equation is studied. For the equation defined on a bounded domain, the existence, uniqueness, and regularity of the solution are firstly studied. Furthermore, it is numerically studied via the weighted and shifted Grünwald difference (WSGD) methods/the local discontinuous Galerkin (LDG) finite element methods. The derived numerical scheme has been proved to be stable and convergent with order O(∆t² + h^k+1), where ∆t, h, k are the time stepsize, the spatial stepsize, and the degree of piecewise polynomials, respectively. Finally, a numerical experiment is presented to verify the More >

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2096

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Muhammad Shuaib¹, Muhammad Bilal¹, Muhammad Altaf Khan^{2, *}, Sharaf J. Malebary³
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 377-400, 2020, DOI:10.32604/cmes.2020.08076 - 01 April 2020
（This article belongs to the Special Issue: Numerical Methods for Differential and Integral Equations)
Abstract An unsteady viscous fluid flow with Dufour and Soret effect, which results in heat and mass transfer due to upward and downward motion of flexible rotating disk, has been studied. The upward or downward motion of non rotating disk results in two dimensional flow, while the vertical action and rotation of the disk results in three dimensional flow. By using an appropriate transformation the governing equations are transformed into the system of ordinary differential equations. The system of ordinary differential equations is further converted into first order differential equation by selecting suitable variables. Then, we More >

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2615

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Junbiao Liu^{1, 6}, Duanpo Wu^{2, 3}, Zimeng Wang², Xinyu Jin^{1, *}, Fang Dong⁴, Lurong Jiang⁵, Chenyi Cai⁶
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 401-426, 2020, DOI:10.32604/cmes.2020.08731 - 01 April 2020
（This article belongs to the Special Issue: Computer Methods in Bio-mechanics and Biomedical Engineering)
Abstract In the field of medical informatics, sleep staging is a challenging and timeconsuming task undertaken by sleep experts. According to the new standard of the American Academy of Sleep Medicine (AASM), the stages of sleep are divided into wakefulness (W), rapid eye movement (REM) and non-rapid eye movement (NREM) which includes three sleep stages (N1, N2 and N3) that describe the depth of sleep. This study aims to establish an automatic sleep staging algorithm based on the improved weighted random forest (WRF) and Hidden Markov Model (HMM) using only the features extracted from double-channel EEG… More >

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3050

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ARTICLE

Wei Zhao^{1, 2}, Shuai Feng¹, Yadan Wang¹, Yuanguo Wang¹, Zhihui Han¹, Hu Peng^{1, *}
CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 427-440, 2020, DOI:10.32604/cmes.2020.09387 - 01 April 2020
（This article belongs to the Special Issue: Computer Methods in Bio-mechanics and Biomedical Engineering)
Abstract Frame rate is an important metric for ultrasound imaging systems, and high frame rates (HFR) benefit moving-target imaging. One common way to obtain HFR imaging is to transmit a plane wave. Delay-and-sum (DAS) beamformer is a conventional beamforming algorithm, which is simple and has been widely implemented in clinical application. Fourier beamforming is an alternative method for HFR imaging and has high levels of imaging efficiency, imaging speed, and good temporal dynamic characteristics. Nevertheless, the resolution and contrast performance of HFR imaging based on DAS or Fourier beamforming are insufficient due to the single plane… More >

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