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Effects of coverage layer on the electrochemical corrosion behaviour of Mg-Al-Mn alloy subjected to massive laser shock peening treatment
摘要： Effects of coverage layer on electrochemical corrosion behaviour and pitting morphologies of Mg-Al-Mn alloy subjected to massive laser shock peening (LSP) treatment were investigated by potentiodynamic polarisation test, electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) observations. Microstructures of Mg-Al-Mn alloy subjected to massive LSP treatment were also characterized. Results showed that LSP induced an obvious improvement in electrochemical corrosion resistance with increasing coverage layer. Even in a higher corrosive solution concentration, LSP could still prevent corrosion to some extent. The improvement in electrochemical corrosion resistance was due to the grain refinement and compressive residual stress induced by massive LSP treatment. Finally, the influence mechanism of the coverage layer on electrochemical corrosion behavior of Mg-Al-Mn alloy was revealed.
关键词： Microstructure.,Electrochemical corrosion,Mg-Al-Mn alloy,Coverage layer,Laser shock peening
更新于2025-09-23 15:23:52
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Antenna Placement and Performance Tradeoffs with Hand Blockage in Millimeter Wave Systems
摘要： The ongoing commercial deployment of millimeter wave systems brings into focus a number of practical issues in form factor user equipment (UE) design. With wavelengths becoming smaller, antenna gain patterns becoming directional, and link budgets critically dependent on beamforming, it becomes imperative to use a number of antenna modules at different locations of the UE for good performance. While more antennas/modules can enhance beamforming array gains, it comes with the tradeoff of higher component cost, power consumption of the associated radio frequency circuitry, and a beam management overhead in learning the appropriate beam weights. Thus, the goal of a good UE design is to provide robust spherical coverage corresponding to good array gains over the entire sphere around the UE with a low beam management overhead, complexity, and cost. The scope of this paper is to study the implications of two popular commercial millimeter wave UE designs (a face and an edge design) on spherical coverage. We show that analog beam codebooks can result in good performance for both the designs, and the edge design provides a better tradeoff in terms of robust performance (with hand blockage), beam management overhead, implementation complexity from an antenna placement standpoint and cost.
关键词： hand blockage,5G-New Radio,Millimeter wave,spherical coverage,commercial deployments,antenna placement,UE design,modular design
更新于2025-09-23 15:23:52
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[IEEE 2018 International Flexible Electronics Technology Conference (IFETC) - Ottawa, ON, Canada (2018.8.7-2018.8.9)] 2018 International Flexible Electronics Technology Conference (IFETC) - Electromagnetic Engineered Surface Gratings at 5G Bands Using Printed Electronics
摘要： Electromagnetic engineered surfaces (EES) are a recently introduced concept with the implementation goal of controlling the electromagnetic scattering in communications environments. This paper will focus on EES design techniques to enable the passive extension of line of sight (LoS) coverage into non-LoS regions.
关键词： coverage,electromagnetic engineered surfaces (EES),mm-wave,5G,gratings,communications environment
更新于2025-09-23 15:23:52
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Monitoring vegetation coverage in Tongren from 2000 to 2016 based on Landsat7 ETM+ and Landsat8
摘要： Vegetation coverage is an important indicator in regional ecological environment monitoring and plays a key role in its quality assessment. We consider Landsat7 ETM+ in 2000 and Landsat8 in 2016 as data sources using a different time phase partial image substitution method to eliminate cloud effects and an NDVI dimidiate pixel model to invert the vegetation coverage of the two time phases. We further classify them into five grades, provide statistics and analyse the areas of different grades at different time periods, while monitoring the spatial evolution of vegetation coverage over the past 16 years in Tongren. Experimental results showed that: (1) the different time phase partial image substitution method could reduce the influence of clouds on vegetation extraction; (2) in Tongren, the vegetation coverage area was decreased from 17,300.1 km2 to 17,224.8 km2 (i.e. decreased by 75.3 km2); (3) the areas of grade I and V increased by 0.42% and 15.08%, respectively, whereas the areas of grade II, III and IV decreased by 3.15%, 6.98% and 5.37%, respectively, which indicates that most of the area containing lower amount of vegetation gradually altered into an area containing a higher coverage of vegetation, whereas a few areas became bare land; and (4) the vegetation areas decreased due to expansion of cities and construction of dams, while vegetation increased due to the cultivation of crops and trees. Research shows that the overall evolution of vegetation coverage in Tongren is considerably good. However, while undertaking future development in the mountainous Karst region, one should be aware of the land’s intensive use and environmental protection.
关键词： Landsat8,change detection,China Tongren,Landsat7 ETM+,vegetation coverage
更新于2025-09-23 15:22:29
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Inorganic cesium-lead mixed halide perovskite p-i-n solar cells deposited using layer-by-layer vacuum deposition technique
摘要： Heterogeneous cellular networks (HetCNets) offer a promising solution to cope with the current cellular coverage crunch. Due to the large transmit power disparity, while following maximum power received (MPR) association scheme, a larger number of users are associated with macro-cell BS (MBS) than small-cell BSs (SBSs). Therefore, an imbalance load arrangement takes place across the HetCNets. Hence, using cell range expansion-based cell association, we can balance the load across the congested MBS. However, using MPR association scheme, users’ of?oading leads to two challenges: 1) macro-cell interference, in which the MBS interferes with the of?oaded users, and 2) coupled downlink-uplink cell association, in which a random user associates with a single tier’s base station (BS) both in uplink (UL) and downlink (DL) directions. This paper aims to address these problems while considering a two-tier scenario consisting of small-cell and macro-cell tiers. For the MBS interference mitigation, we employ a reverse frequency allocation (RFA) scheme. Besides coupled DL–UL association (Co-DUA), this paper also highlights the notion of decoupled DL–UL association (De-DUA). In De-DUA, a random user associates with two different tiers’ BSs, i.e., with one tier’s BS in the DL direction and with the other tier’s BS in the UL direction. Our results illustrate that, in comparison with the Co-DUA, De-DUA with RFA employment achieves a better coverage performance.
关键词： small-cell BSs,decoupled downlink-uplink association,Heterogeneous cellular networks,coverage performance,reverse frequency allocation
更新于2025-09-23 15:21:01
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Controlling dye coverage instead of addition of organic acid to reduce dye aggregation in dye-sensitized solar cells
摘要： The photo-generated electron injection yield of dye-sensitized solar cells (DSSCs) based on donor-acceptor conjugated dyes is lowered by the aggregation of surface adsorbed organic dyes that pose a low-photoenergy conversion efficiency. Coadsorbates used to prevent the aggregation cause to decompose or detach the dye molecules anchored on the TiO2 surface. In this study, the effect of coadsorption of organic acid and organic dyes on photovoltaic performances was systematically scrutinized by means of adsorption isotherms and photovoltaic measurements. Our laboratory synthesized {0 1 0}-faceted TiO2 (PA TiO2) and P25 TiO2 were used as meso-porous nanocrystals, D149 organic dye was used as a sensitizer and cheno-deoxycholic acid, CDA, was used as a coadsorbate. The coadsorption of CDA reduces the adsorption parameters, maximum adsorption density (Qm) and adsorption constant (Kad), and the reduction depended on the type of TiO2. The photovoltaic performance indicates that the D149 dye has the best dye coverage at around 70% for the effective photovoltaic energy conversion. The coadsorption of CDA increased the photovoltaic performances of DSSCs based on P25 TiO2 but, CDA decreased the photovoltaic performances of DSSCs based on PA TiO2 due to the reduction of the dye coverage below 70%. The results suggest that the coadsorption of organic acids is not necessary if the particular TiO2 can maintain its coverage at the best coverage. Thus, the requirement of coadsorbates to reduce the dye aggregation depends on the type of TiO2 used in DSSCs.
关键词： Coverage,Adsorption isotherms,Coadsoptions,Aggregations,Photovoltaic performances,Dye-sensitized solar cells
更新于2025-09-23 15:21:01
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Laser cavitation peening of gray cast iron: Effect of coverage layer on the surface integrity
摘要： Copper coverage layer was employed to the laser cavitation peening (LCP) of HT200 gray cast iron. The process of bubble evolution, velocity field of bubble, impact of water-jet, deformation and stress of material were simulated. The effects of coverage layer on the surface integrity (surface morphology and roughness, residual stress, micro-hardness) of LCP treated HT200 under various laser energies and defocusing amounts were systemically investigated. The results indicate that the maximum velocity of water-jet is 380 m/s and the diameter is 0.1 mm. The surface roughness of HT200 increases after the treatment of LCP. The presence of Copper coverage layer makes the HT200 surface more flat and the surface roughness decreases by half. At the case of no coverage layer, the parameters of 200 mJ laser energy and 1 mm defocusing amount are optimal for roughness, compressive residual stress and micro-hardness. Higher laser energy produces higher magnitude of micro-hardness and compressive residual stress in the case of coverage layer, and the optimal defocusing amount is 0 mm.
关键词： Coverage layer,surface integrity,simulation,Laser cavitation peening,HT200 gray cast iron
更新于2025-09-23 15:21:01
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Tiled Monolayer Films of 2D Molybdenum Disulphide Nanoflakes Assembled at Liquid/Liquid Interfaces
摘要： Thin films of MoS2 bilayer nanoflakes, which are predominantly a single flake thick and in edge-to-edge contact, have been produced via self-assembled tiling at the planar interface between two immiscible liquids. Films of several square centimeters extent can be produced with total covered area approaching 90 % and over 70 % of the film covered by single flakes without overlap. Films produced through liquid/liquid assembly are shown to produce a lower uncovered area fraction and more uniform thickness when compared with films of similar areal coverage produced by the “top-down” techniques of spin coating and spray coating. Statistical analysis of flake coverage data, measured by AFM, shows that liquid/liquid assembly produces a distinctly different variation in film thickness than conventional “top-down” deposition. This supports the hypothesis that the 2D confinement of liquid/liquid assembly produces more uniform films. Demonstrator field-effect transistors (FETs) manufactured from the films exhibit mobility and on/off current ratios of 0.73 cm2 V-1 s-1 and 105 respectively; comparable to FETs of similar layout and CVD-grown or mechanically cleaved single crystal MoS2 channel material. This work demonstrates the use of liquid/liquid interfaces as a useful tool for self-assembly of high performance thin film devices made from dispersions of 2D materials.
关键词： self-assembly,2D materials,coverage,device fabrication,thin films,Poisson distribution
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 5G World Forum (5GWF) - Silicon Valley, CA, USA (2018.7.9-2018.7.11)] 2018 IEEE 5G World Forum (5GWF) - 5G NR Coverage, Performance and Beam Management Demonstrated in an Outdoor Urban Environment at 28 GHz
摘要： This paper investigates the behaviour of a 28 GHz Massive MIMO 5G new radio (NR) test system operating with 400 MHz bandwidth and one transmission/reception point in a semi-open urban environment. Single-user multiple-input multiple-output (MIMO) performance was evaluated in terms of coverage and propagation. For the considered test area reflections improved the channel conditions. The peak throughput was 6.2 Gbps in line-of-sight corresponding to 15.5 bps/Hz. One transmission/reception point was found to be sufficient to provide good coverage. Furthermore, significant multi-user MIMO gains – often more than 60% for the (median) system downlink throughput – were demonstrated with two users and beam forming with beam tracking in a single cell. This further demonstrates the capacity benefits from beam forming.
关键词： coverage,multiuser MIMO,mobility,beam tracking,5G,beamforming
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-TW) - YILAN, Taiwan (2019.5.20-2019.5.22)] 2019 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-TW) - Basic Study on Measurement of Multiple Users' Breathing by Using Far Infrared Imaging
摘要： Heterogeneous cellular networks (HetCNets) offer a promising solution to cope with the current cellular coverage crunch. Due to the large transmit power disparity, while following maximum power received (MPR) association scheme, a larger number of users are associated with macro-cell BS (MBS) than small-cell BSs (SBSs). Therefore, an imbalance load arrangement takes place across the HetCNets. Hence, using cell range expansion-based cell association, we can balance the load across the congested MBS. However, using MPR association scheme, users’ of?oading leads to two challenges: 1) macro-cell interference, in which the MBS interferes with the of?oaded users, and 2) coupled downlink-uplink cell association, in which a random user associates with a single tier’s base station (BS) both in uplink (UL) and downlink (DL) directions. This paper aims to address these problems while considering a two-tier scenario consisting of small-cell and macro-cell tiers. For the MBS interference mitigation, we employ a reverse frequency allocation (RFA) scheme. Besides coupled DL–UL association (Co-DUA), this paper also highlights the notion of decoupled DL–UL association (De-DUA). In De-DUA, a random user associates with two different tiers’ BSs, i.e., with one tier’s BS in the DL direction and with the other tier’s BS in the UL direction. Our results illustrate that, in comparison with the Co-DUA, De-DUA with RFA employment achieves a better coverage performance.
关键词： reverse frequency allocation,small-cell BSs,decoupled downlink-uplink association,Heterogeneous cellular networks,coverage performance
更新于2025-09-23 15:19:57