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  • Open Access

    ARTICLE

    IRS Assisted UAV Communications against Proactive Eavesdropping in Mobile Edge Computing Networks

    Ying Zhang1,*, Weiming Niu2, Leibing Yan1

    CMES-Computer Modeling in Engineering & Sciences, Vol.138, No.1, pp. 885-902, 2024, DOI:10.32604/cmes.2023.029234

    Abstract In this paper, we consider mobile edge computing (MEC) networks against proactive eavesdropping. To maximize the transmission rate, IRS assisted UAV communications are applied. We take the joint design of the trajectory of UAV, the transmitting beamforming of users, and the phase shift matrix of IRS. The original problem is strong non-convex and difficult to solve. We first propose two basic modes of the proactive eavesdropper, and obtain the closed-form solution for the boundary conditions of the two modes. Then we transform the original problem into an equivalent one and propose an alternating optimization (AO) based method to obtain a… More >

  • Open Access

    ARTICLE

    Design and Experimental Testing of an Electric Field-Driven Droplet Injection Device

    Fulai Cao1,*, Yanpu Chao1,*, Hao Yi2,3, Shuai Lu1, Chengshui Guo4

    FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.11, pp. 2891-2905, 2023, DOI:10.32604/fdmp.2023.029243

    Abstract The properties of droplets produced by existing on-demand injection systems are typically determined by the nozzle diameter, i.e., only droplets with size larger than this diameter can be obtained. To solve this problem, a system for electric field-driven droplet injection and deposition was developed, and the related performances were compared with those of a standard pneumatic system. The results show that the diameter of droplets generated accordingly can be significantly smaller than the nozzle diameter. In particular, the effects of frequency and duty ratio on the number of droplets were studied by assuming microcrystalline wax as work material. A deposition… More > Graphic Abstract

    Design and Experimental Testing of an Electric Field-Driven Droplet Injection Device

  • Open Access

    ARTICLE

    On the Effect of Mist Flow on the Heat Transfer Performances of a Three-CopperSphere Configuration

    Karema A. Hamad*, Yasser A. Mahmood

    FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.11, pp. 2863-2875, 2023, DOI:10.32604/fdmp.2023.029049

    Abstract The cooling of a (pebble bed) spent fuel in a high-temperature gas-cooled reactor (HTGR) is adversely affected by an increase in the temperature of the used gas (air). To investigate this problem, a configuration consisting of three copper spheres arranged in tandem subjected to a forced mist flow inside a cylindrical channel is considered. The heat transfer coefficients and related variations as a function of Reynolds number are investigated accordingly. The experimental results show that when compared to those with only airflow, the heat transfer coefficient of the spherical elements with mist flow (j = 112 kg/m2 hr, Re =… More >

  • Open Access

    PROCEEDINGS

    Self-Driven Droplet on the Bilayer Two-Dimensional Materials and Nanoscale Channel with Controllable Gradient Wettability

    Hongfei Ye1,*, Chenguang Yin1, Jian Wang1, Yonggang Zheng1, Hongwu Zhang1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.27, No.1, pp. 1-1, 2023, DOI:10.32604/icces.2023.09741

    Abstract The wetting behavior is ubiquitous in natural phenomenon as well as engineering application. As an intrinsic property of solid surface, the wettability with a controllable gradient has been an attractive issue with a wide application in various fields, including microfluidic devices, self-driven transport, biotechnologies, etc. Generally, it often requires elaborate design of microstructure or its response under the electrical, thermal, optical, pH stimuli, etc. However, the relevant complex underlying mechanism makes it difficult to construct quantitative relations between the wettability and the external field for the fine design. In this work, based on the bilayer two-dimensional materials, a simple controlling… More >

  • Open Access

    PROCEEDINGS

    Self-Driving Behavior and Pinning Effect of Droplets on GrapheneCovered Functional Textured Surfaces

    Fujian Zhang1, Xiang Gao1, Zhongqiang Zhang1,2,*

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.26, No.4, pp. 1-1, 2023, DOI:10.32604/icces.2023.09169

    Abstract Biological features such as the bumps on the back of desert beetles and the spikes of cacti enable the directional transport of water droplets, creating conditions for their survival in nature. Inspired by the interesting natural phenomenon, a novel design of nanopillared surface with a gradient density of structural pillar matrix covered by a monolayer graphene is proposed to realize ultrafast self-driving of water droplets. The droplet can move spontaneously at ultrahigh speed of 75.7 m/s (272.52 km/h) from sparsest to densest regions of pillars while a wettability gradient is created by the gradient distribution density of pillar matrix relying… More >

  • Open Access

    PROCEEDINGS

    Nanoarray-Embedded Hierarchical Hydrophobic Surfaces for Enhancing Durable Dropwise Condensation

    Yue Hu1, Lu-Wen Zhang1,*

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.26, No.1, pp. 1-1, 2023, DOI:10.32604/icces.2023.010595

    Abstract Liquid accretion control plays a key role across a wide range of industrial applications, such as anti-icing, power generation, sewage treatment, water desalination, and energy harvesting. In condensation system, durable dropwise condensation of saturated vapor for heat transfer and energy saving in extensive industrial applications. While numerous superhydrophobic surfaces can promote steam condensation, maintaining discrete microdroplets on surfaces without the formation of a flooded filmwise condensation at high subcooling remains challenging. Here, we report the development of carbon nanotube arrayembedded hierarchical composite surfaces that enable ultra-durable dropwise condensation under a wide range of subcooling temperatures (∆Tsub = 8 K–38 K),… More >

  • Open Access

    PROCEEDINGS

    Ultrafast Adsorption of Tiny Oil Droplets Within Water by Superhydrophobic-Superoleophilic Conical Micro-arrays

    Yunyun Song1, Xu Zhang1, Jialei Yang1, Zhongqiang Zhang1,*, Guanggui Cheng1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.25, No.2, pp. 1-1, 2023, DOI:10.32604/icces.2023.09916

    Abstract Although floating oil with large particle sizes can easily be separated from water by membrane separation methods, tiny oil droplets with tremendously small volume force and density gradient at oil-water interfaces within water lead to barriers of oil-water separation. Consequently, tiny oil droplets remain in the water, resulting in energy waste, environmental pollution and biological health hazard. Traditional super-wetting membranes with extremely small pore sizes were easily blocked during the oil-water separation process. Inspired by the cactus and rice leaf, we developed a superhydrophobic-superoleophilic surface with conical micro-arrays to realize ultrafast adsorption of tiny oil droplets within the water. The… More >

  • Open Access

    PROCEEDINGS

    Self-swimming of a Droplet Induced by Combined Diffusiophoresis and Marangoni Effects

    Yuhang Wang1,2, Gaojin Li1,2,*

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.25, No.2, pp. 1-2, 2023, DOI:10.32604/icces.2023.09895

    Abstract The chemically active droplets, which converts the chemical energy into a localized fluid flow at the interfaces by generating a concentration gradients of surfactant, can realize self-propulsion with complex trajectories and have been widely studied to mimic the swimming behavior of micro-organisms. In reality, the motion of chemically active droplets is influenced by a combination of diffusiophoresis and Marangoni effect under concentration gradients of surfactant. However, the interaction between these two effects has been only studied for a drop under the constraint of the axial-symmetric motion. To understand the hydrodynamics of the unconstraint motion, we consider a two-dimensional drop model… More >

  • Open Access

    ARTICLE

    CFD INVESTIGATIONS OF THERMAL AND DYNAMIC BEHAVIORS IN A TUBULAR HEAT EXCHANGER WITH BUTTERFLY BAFFLES

    AlemKarimaa,*, Sahel Djamelb , Nemdili Alic, Ameur Houarid

    Frontiers in Heat and Mass Transfer, Vol.10, pp. 1-7, 2018, DOI:10.5098/hmt.10.27

    Abstract In the present paper, the effects of a new baffle design on the efficiency of a tubular heat exchanger are numerically investigated. It concerns butterfly baffles inserted in a cylindrical tube heat exchanger. We focus on the influence of the shape of baffles, the space between baffles (pitch ratio, PR) and the baffle size (i.e. the blockage ratio, BR) on the heat transfer and flow characteristics. Three geometrical configurations with different PRs are realized (PR = 1, 2 and 4) and five others with different blockage ratios (BR = 0.1, 0.2, 0.3, 0.4 and 0.5). The investigations are achieved for… More >

  • Open Access

    ARTICLE

    Surfactant-Modified Hydrophobic Biochar Derived from Laver (Porphyra haitanensis) with Superior Removal Performance for Kitchen Oil

    Jiaxing Sun1, Lili Ji1,*, Qianrui He1, Ran Li1, Xiaoyue Xia2, Yaning Wang1, Yi Yang2, Lu Cai3, Jian Guo2

    Journal of Renewable Materials, Vol.11, No.8, pp. 3227-3243, 2023, DOI:10.32604/jrm.2023.027160

    Abstract

    In this study, a novel absorpent (MSAR600°C) with a hydrophobic surface and hierarchical porous structure for the removal of kitchen oil was facilely fabricated from the macroalgae, laver (Porphyra haitanensis) by incorporating high-temperature carbonization and alkyl polyglucosides (APG) and rhamnolipid (RL) surfactants modification. The characterization results showed MSAR600°C possessed a louts-leaf-like papillae microstructure with high contact angle (137.5°), abundant porous structure with high specific surface area (23.4 m2/g), and various oxygen-containing functional groups (-OH, C=O, C-O). Batch adsorption experiments were conducted to investigate the effect of adsorption time, temperature, pH, and absorbent dose on kitchen oil adsorption performance. Then the… More > Graphic Abstract

    Surfactant-Modified Hydrophobic Biochar Derived from Laver (<i>Porphyra haitanensis</i>) with Superior Removal Performance for Kitchen Oil

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