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  • Open Access


    Influence of the Air Gap Layer Thickness on Heat Transfer Between the Glass Cover and the Absorber of a Solar Collector

    F.Z. Ferahta1,2, S. Bougoul1, M. Médale2, C. Abid2

    FDMP-Fluid Dynamics & Materials Processing, Vol.8, No.3, pp. 339-352, 2012, DOI:10.3970/fdmp.2012.008.339

    Abstract A numerical study is carried out to evaluate the thermal performances of a solar collector. As it is well known, that the thermal losses of such systems are mainly of a convective nature, the study is concentrated in particular on the features of natural convection that is activated in the air domain delimited by the upper glass and the lower absorber of the solar collector. The efficiency of such a system depends essentially on both the temperature difference and the distance between the absorber and the glass. Since the temperature difference remains an uncontrolled variable (because it depends on the… More >

  • Open Access


    Fluid Flow Behavior of a Binary Mixture Under the Influence of External Disturbances Using Different Density Models

    A. Parsa1, M.Z. Saghir1

    FDMP-Fluid Dynamics & Materials Processing, Vol.8, No.1, pp. 27-50, 2012, DOI:10.3970/fdmp.2011.008.027

    Abstract Experiments onboard the International Space Station typically display undesired convective flow as a results of unwanted oscillatory g-jitters. A cubic rigid cell filled with water (90%) and isopropanol (10%) with a thermal gradient and forced vibrations is considered. The cell is under the influence of three different levels of periodic oscillation (Ravib ≈ 1.6, 650 and 4000) applied perpendicular to the temperature gradient. In this paper, we examine the transport process (fluid flow, heat transfer and mass transfer) due to oscillatory g-jitters in the presence of Soret effect. The full transient Navier Stokes equations coupled with the mass and heat… More >

  • Open Access


    Numerical Study of Liquid Metal Flow in a Rectangular Duct under the Influence of a Heterogeneous Magnetic Field

    Evgeny V. Votyakov1, Egbert A. Zienicke1

    FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.2, pp. 97-114, 2007, DOI:10.3970/fdmp.2007.003.097

    Abstract We simulated numerically the laminar flow in the geometry and the magnetic field of the experimental channel used in [Andreev, Kolesnikov, and Thess (2006)]. This provides detailed information about the electric potential distribution for the laminar regime (numerical simulation) and in the turbulent regime as well (experiment). As follows from comparison of simulated and experimental results, the flow under the magnet is determined by the interaction parameter N = Ha2 / Re representing the ratio between magnetic force, determined by the Hartmann number Ha, and inertial force, determined by the Reynolds number Re. We compared two variants: (i)(Re,N)=(2000,18.6) (experiment), (400,20.25)… More >

  • Open Access


    Examining the Impacts of Key Influencers on Community Development

    Di Shang1,*, Mohammed Ghriga1

    CMC-Computers, Materials & Continua, Vol.61, No.1, pp. 1-10, 2019, DOI:10.32604/cmc.2019.08217

    Abstract In this research, we aim to identify and investigate the impacts of key influencers on community formations and developments. We assess the impacts of key influencers by analyzing the activities and structure of the social media presence of a local community. Results of our analysis show that key influencers play important roles in connecting the community, transferring information, and improving overall sentiment of the community members. Our findings suggest that community practitioners can apply social network analysis to identify value-added influencers and discover strategies for improving the community and keeping leadership roles. More >

  • Open Access


    A DDoS Attack Situation Assessment Method via Optimized Cloud Model Based on Influence Function

    Xiangyan Tang1, Qidong Zheng1,*, Jieren Cheng1,2, Victor S. Sheng3, Rui Cao1, Meizhu Chen1

    CMC-Computers, Materials & Continua, Vol.60, No.3, pp. 1263-1281, 2019, DOI:10.32604/cmc.2019.06173

    Abstract The existing network security situation assessment methods cannot effectively assess the Distributed denial-of-service (DDoS) attack situation. In order to solve these problems, we propose a DDoS attack situation assessment method via optimized cloud model based on influence function. Firstly, according to the state change characteristics of the IP addresses which are accessed by new and old user respectively, this paper defines a fusion feature value. Then, based on this value, we establish a V-Support Vector Machines (V-SVM) classification model to analyze network flow for identifying DDoS attacks. Secondly, according to the change of new and old IP addresses, we propose… More >

  • Open Access


    The Influence of the Imperfectness of Contact Conditions on the Critical Velocity of the Moving Load Acting in the Interior of the Cylinder Surrounded with Elastic Medium

    M. Ozisik1,*, M. A. Mehdiyev2, S. D. Akbarov2,3

    CMC-Computers, Materials & Continua, Vol.54, No.2, pp. 103-136, 2018, DOI:10.3970/cmc.2018.054.103

    Abstract The dynamics of the moving-with-constant-velocity internal pressure acting on the inner surface of the hollow circular cylinder surrounded by an infinite elastic medium is studied within the scope of the piecewise homogeneous body model by employing the exact field equations of the linear theory of elastodynamics. It is assumed that the internal pressure is point-located with respect to the cylinder axis and is axisymmetric in the circumferential direction. Moreover, it is assumed that shear-spring type imperfect contact conditions on the interface between the cylinder and surrounding elastic medium are satisfied. The focus is on the influence of the mentioned imperfectness… More >

  • Open Access


    Seepage-Stress-Damage Coupled Model of Coal Under Geo-Stress Influence

    Yi Xue1,2,3, Faning Dang2, Rongjian Li2, Liuming Fan2, Qin Hao4, Lin Mu2, Yuanyuan Xia2

    CMC-Computers, Materials & Continua, Vol.54, No.1, pp. 43-59, 2018, DOI:10.3970/cmc.2018.054.043

    Abstract In the seepage-stress-damage coupled process, the mechanical properties and seepage characteristics of coal are distinctly different between pre-peak stage and post-peak stage. This difference is mainly caused by damage of coal. Therefore, in the process of seepage and stress analysis of coal under the influence of excavation or mining, we need to consider the weakening of mechanical properties and the development of fractures of damaged coal. Based on this understanding, this paper analyzes the influence of damage on mechanics and seepage behavior of coal. A coupled model is established to analyze the seepage-stress-damage coupled process of coal. This model implemented… More >

  • Open Access


    Mathematical Modelling and 3D FEM Analysis of the Influence of Initial Stresses on the ERR in a Band Crack’s Front in the Rectangular Orthotropic Thick Plate

    Arzu Turan Dincel1, Surkay D. Akbarov2,3

    CMC-Computers, Materials & Continua, Vol.53, No.3, pp. 249-270, 2017, DOI:10.32604/cmc.2017.053.265

    Abstract This paper deals with the mathematical modelling and 3D FEM study of the energy release rate (ERR) in the band crack’s front contained in the orthotropic thick rectangular plate which is stretched or compressed initially before the loading of the crack's edge planes. The initial stretching or compressing of the plate causes uniformly distributed normal stress to appear acting in the direction which is parallel to the plane on which the band crack is located. After the appearance of the initial stress in the plate it is assumed that the crack's edge planes are loaded with additional uniformly distributed normal… More >

  • Open Access


    Influence of functionalization on the structural and mechanical properties of graphene

    L.S. Melro1,2, L.R. Jensen1

    CMC-Computers, Materials & Continua, Vol.53, No.2, pp. 109-127, 2017, DOI:10.3970/cmc.2017.053.111

    Abstract Molecular dynamics simulations were applied in order to calculate the Young’s modulus of graphene functionalized with carboxyl, hydroxyl, carbonyl, hydrogen, methyl, and ethyl groups. The influence of the grafting density with percentages of 3, 5, 7, and 10% and the type of distribution as a single cluster or several small clusters were also studied. The results show that the elastic modulus is dependent on the type of functional groups. The increasing coverage density also evidenced a decrease of the Young’s modulus, and the organization of functional groups as single cluster showed a lesser impact than for several small clusters. Furthermore,… More >

  • Open Access


    The Influence of Gravitational Field on Generalized Thermoelasticity with Two-Temperature under Three-Phase-Lag Model

    Mohamed I. A. Othman1,2,3, W. M. Hasona2,4, Nehal T. Mansour2,5

    CMC-Computers, Materials & Continua, Vol.45, No.3, pp. 203-220, 2015, DOI:10.3970/cmc.2015.045.203

    Abstract The problem of the generalized thermoelastic medium for three different theories under the effect of a gravitational field is investigated. The Lord- Shulman, Green-Naghdi III, three-phase-lag theories are discussed with twotemperature. The normal mode analysis is used to obtain the analytical expressions of the displacement components, force stress, thermodynamic temperature and conductive temperature. The numerical results are given and presented graphically, when the thermal force is applied. Comparisons are made with the results predicted by three-phase-lag model, Green-Naghdi III and Lord-Shulman theories in the presence and absence of gravity as well as two temperature. More >

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