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  • Open Access

    ARTICLE

    The Influence of Annealing in Nitrogen Atmosphere on the Electrical, Optical and Structural Properties of Spray-Deposited ZnO Thin Films

    Shadia J Ikhmayies1, Naseem M. Abu El-Haija2, Riyad N. Ahmad-Bitar3

    FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.2, pp. 219-232, 2010, DOI:10.3970/fdmp.2010.006.219

    Abstract Large area and highly uniform polycrystalline ZnO thin films have been produced by a spray pyrolysis (SP) technique resorting to a customized system (spraying) on glass substrates at temperature Ts= 450℃. This study deals with the related investigation about the influence of heat treatment (in nitrogen atmosphere) on the resulting properties (electrical, optical and structural) of such films. Properties are analyzed by means of I-V plots, transmittance curves, X-Ray diffractograms (XRD) and scanning electron microscope (SEM) micrographs. Results show that the resistivity of the films decreases from about 200W.cm for the as-deposited films to about 95W.cm for annealed films. XRD… More >

  • Open Access

    ARTICLE

    The Influence of Flow Pressure Gradient on Interfacial Wave Properties in Annular Two-Phase Flow at Microgravity and Normal Gravity Conditions

    Huawei Han1, Kamiel S. Gabriel2

    FDMP-Fluid Dynamics & Materials Processing, Vol.2, No.4, pp. 287-298, 2006, DOI:10.3970/fdmp.2006.002.287

    Abstract Data on air-water co-current two-phase annular flow in a tube with an inner diameter of 9.525 mm (3/8 in) were previously collected at both microgravity u-g and normal gravity (1-g) conditions. The data contained measurements of pressure drop, in addition to previously published data of liquid film thickness. This paper presents the results and analysis of the influence of flow pressure gradient on interfacial wave properties of annular flow at both microgravity and normal gravity. The examined wave properties include wave base thickness, wave height (or roughness height), wave spacing, wave speed and wave frequency. It was found that, the… More >

  • Open Access

    ARTICLE

    Influence of Layer Height on Thermal Buoyancy Convection in A System with Two Superposed Fluids Confined in A Parallelepipedic Cavity

    Sunil Punjabi1, K. Muralidhar2, P. K. Panigrahi2

    FDMP-Fluid Dynamics & Materials Processing, Vol.2, No.2, pp. 95-106, 2006, DOI:10.3970/fdmp.2006.002.095

    Abstract Convection in a differentially heated two-layer system consisting of air and water was studied experimentally, using laser-interferometry. The cavity used for flow visualization was square in cross-section and rectangular in-plan having dimensions of 447 × 32 × 32 mm3. Experiments performed over different layer thicknesses of water filled in a square cross-section cavity, the rest being air, are reported in the present work. The following temperature differences for each layer height were imposed across the hot and the cold walls of the superposed fluid layers: (i) ΔT=10K and (ii)ΔT =18 K. The present study was aimed at understanding the following… More >

  • Open Access

    ARTICLE

    Influence of Thermocapillary Convection on Solid-liquid Interface

    K. Matsunaga1, H. Kawamura1

    FDMP-Fluid Dynamics & Materials Processing, Vol.2, No.1, pp. 59-64, 2006, DOI:10.3970/fdmp.2006.002.059

    Abstract Existing studies on solidification phenomena mainly focused on the solidification processes per se. In real systems, however, one cannot neglect the effects of molten material convective flow, such as natural and thermocapillary convection (they strongly affect the resulting quality of the solidified materials). The present study aims to experimentally investigate on the effect of the thermocapillary flow upon the directional solidification in a liquid layer with a free upper surface. If no free surface exists, the solid--liquid interface (SLI) is vertical and straight, while, with the free surface, the SLI is inclined against the wall-normal direction and is curved in… More >

  • Open Access

    ARTICLE

    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

    ARTICLE

    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

    ARTICLE

    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

    ARTICLE

    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

    ARTICLE

    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

    ARTICLE

    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 >

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