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Journal of Bionic Engineering 2017年第3期14卷 486-496页

作者： Wei Gong Yuying Yan sheng chen Donald Giddings Fluids & Thermal Engineering Research Group Faculty of Engineering University of Nottingham University Park Nottingham NG7 2RD UK Center for Fluids & Thermal Engineering University of Nottingham Ningbo China

The hydrophobicity of natural surfaces has drawn much attention of scientific communities in recent years. By mimicking natural surfaces, the manufactured biomimetic hydrophobic surfaces have been widely applied to green technologies such as self-cleaning surfaces. Although the theories for wetting and hydrophobicity have been developed, the mechanism of wetting transitions between heterogeneous wetting state and homogeneous wetting state is still not fully clarified. As understanding of wetting transitions is crucial for manufacturing a biomimetic superhydrophobic surface, more fundamental discussions in this area should be carried out. In the present work, the wetting transitions are numerically studied using a phase field lattice Boltzmann approach with large density ratio, which should be helpful in understanding the mechanism of wetting transitions. The dynamic wetting transition processes between Cassie-Baxter state and Wenzel state are presented, and the energy barrier and the gravity effect on transition are discussed. It is found that the two wetting transition processes are irreversible for specific inherent contact angles and have different transition routes, the energy barrier exists on an ideally patterned surface and the gravity can be crucial to overcome the energy barrier and trigger the transition.

关键词： wetting transitions biomimetic surfaces energy barrier gravity effect numerical study lattice Boltzmann method

Wetting transition energy curves for a droplet on a square-post patterned surface

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Science Bulletin 2017年第2期62卷 136-142页

作者： Wei Gong Yingqing Zu sheng chen Yuying Yan Fluids & Thermal Engineering Research Group Faculty of Engineering University of Nottingham Department of Aeronautics and Astronautics Fudan University

Due to the property of water repellence, biomimetic superhydrophobic surfaces have been widely applied to green technologies, in turn inducing wider and deeper investigations on superhydrophobic surfaces. Theoretical, experimental and numerical studies on wetting transitions have been carried out by researchers, but the mechanism of wetting transitions between Cassie-Baxter state and Wenzel state, which is crucial to develop a stable superhydrophobic surface, is still not fully understood. In this paper, the flee energy curves based on the transition processes are presented and discussed in detail. The exis- tence of energy barriers with or without consideration of the gravity effect, and the irreversibility of wet- ting transition are discussed based on the presented energy curves. The energy curves show that different routes of the Cassie-to-Wenzel transition and the reverse transition are the main reason for the irre- versibility. Numerical simulations are implemented via a phase field lattice Boltzmann method of large density ratio, and the simulation results show good consistency with the theoretical analysis.

关键词： Wetting transition Energy curves Lattice Boltzmann method

Density enhancement mechanism of upwind schemes for low Mach number flows

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Acta Mechanica Sinica 2018年第3期34卷 431-445页

作者： Bo-Xi Lin Chao Yan Shu-sheng chen School of Aeronautic Science and Engineering Beihang University

Many all-speed Roe schemes have been proposed to improve performance in terms of low speeds. Among them, the F-Roe and T-D-Roe schemes have been found to get incorrect density fluctuation in low Mach flows, which is expected to be with the square of Mach number. Asymptotic analysis presents the mechanism of how the density fluctuation problem relates to the incorrect order of terms in the energy equation paU△U. It is known that changing the upwind scheme coefficients of the pressure-difference dissipation term DP and the velocity-difference dissipation term in the momentum equation DPU to the order of O （c- 1） and O（c0） can improve the level of pressure and velocity accuracy at low speeds. This paper shows that corresponding changes in energy equation can also improve the density accuracy in low speeds. We apply this modification to a recently proposed scheme, TV-MAS, to get a new scheme, TV-MAS2. Unsteady Gresho vortex flow, double shear-layer flow, low Mach number flows over the inviscid cylinder, and NACA0012 airfoil show that energy equation modification in these schemes can obtain the expected square Ma scaling of density fluctuations, which is in good agreement with corresponding asymptotic analysis. Therefore, this density correction is expected to be widely implemented into allspeed compressible flow solvers.

关键词： Energy equation Density fluctuation Roe TV-MAS Low speeds All speeds Computational fluid dynamics

Insight into the covalent grafting of organic films onto carbon steel surfaces for protection

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Chinese Science Bulletin 2014年第10期59卷 971-980页

作者： sheng-Juan Huo Li-Hong chen chen-sheng Chu Jian-Hui Fang Department of Chemistry Science College Shanghai University

The novel use of p-nitrophenyldiazonium tetrafluoroborate salt(GG salt)as a protectant that is electrochemically grafted onto carbon steel has been investigated in0.05 mol L-1H2SO4and 5 wt%NaCl solutions using various corrosion monitoring techniques,such as electrochemical impedance spectroscopy,potentiodynamic polarisation,infrared spectra and scanning electron microscopy *** electrochemical study reveals that this compound is a mixed inhibitor that predominantly controls the cathodic *** surface-grafted film decreases the double-layer capacitance and obviously increases the charge transfer resistance relative to a bare carbon *** values of inhibition effect remain nearly unchanged with an increase in temperature range of 298–318 *** aryl diazonium is covalently bonded on the steel surface,causing a slight decrease in the apparent activation ***,the surface-grafted films exhibit excellent inhibition performance in acid and saline solutions within the studied temperature range.

关键词： Surface grafting- Carbon steel electrode Aryl diazonium salt Corrosion inhibition Temperature effect

Autoencoder with Fitting Network for Terahertz Wireless Communications:A Deep Learning Approach

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China Communications 2022年第3期19卷 172-180页

作者： Zhaohui Huang Dongxuan He Jiaxuan chen Zhaocheng Wang sheng chen Beijing National Research Center for Information Science and Technology Department of Electronic EngineeringTsinghua UniversityBeijing 100084China Shenzhen International Graduate School Tsinghua UniveristyShenzhen 518055China School of Electronics and Computer Science University of SouthamptonSouthampton SO171BJU.K.

Terahertz wireless communication has been regarded as an emerging technology to satisfy the ever-increasing demand of ultra-high-speed wireless ***,affected by the imperfections of cheap and energy-efficient Terahertz devices,Terahertz signals suffer from serve hybrid distortions,including in-phase/quadrature imbalance,phase noise and nonlinearity,which degrade the demodulation performance *** improve the robustness against these hybrid distortions,an improved autoencoder is proposed,which includes coding the transmitted symbols at the transmitter and decoding the corresponding signals at the ***,due to the lack of information of Terahertz channel during the training of the autoencoder,a fitting network is proposed to approximate the characteristics of Terahertz channel,which provides an approximation of the gradients of *** results show that our proposed autoencoder with fitting network can recover the transmitted symbols under serious hybrid distortions,and improves the demodulation performance significantly.

关键词： Terahertz wireless communication hybrid distortion signal demodulation autoencoder

Ultra-fine-Grained Ferrite Prepared from Dynamic Reversal Austenite During Warm Deformation

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Acta Metallurgica Sinica(English Letters) 2020年第2期33卷 290-298页

作者： Hong-Bin Li Ming-Song chen Ya-Qiang Tian Lian-sheng chen Li-Qing chen College of Metallurgy and Energy North China University of Science and TechnologyTangshan 063210China School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China Key Laboratory of the Ministry of Education for Modern Metallurgy Technology Tangshan 063210China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

The ultra-fine-grained ferrite(UFGF) with the size of less than 1 μm is often difficult to be obtained for low-alloyed steel in practical production *** this study,considering the rod and wire production process,a new method for preparing the UFGF with submicron scale is proposed by warm deformation of six passes with total strain of 2.6,followed by the cooling process in Gleeble-3500 thermo-mechanical *** results show that the UFGF with an average size of 0.64 μm could be obtained via the phase transformation from austenite grains with an average size of 3.4 μm,which are achieved by the deformation-induced reversal austenization during the high strain rate warm *** main driving force for the reversal transformation is the *** the interval between the passes also plays an important role in the reversal austenization.

关键词： Ultra-fine-grained ferrite Dynamic reversal transformation(DRT) Warm deformation Deformation-induced reversal transformation Cooling process

Efficient design of rotary traveling wave oscillator array via geometric programming

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第12期10卷 1815-1823页

作者： Li-jia chen Hua-feng ZHANG Jin-fang ZHOU Kang-sheng chen Department o fin formation Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

This paper presents an efficient method for globally optimizing and automating component sizing for rotary traveling wave oscillator arrays. The lumped equivalent model of transmission lines loaded by inverter pairs is evaluated and posynomial functions for oscillation frequency, power dissipation, phase noise, etc. are formulated using transmission line theory. The re- sulting design problem can be posed as a geometric programJning problem, which can be efficiently solved with a convex opti- mization solver. The proposed method can compute the global optima more efficiently than the traditional iterative scheme and various design problems can be solved with the same circuit model. The globally optimal trade-off curves between competing objectives are also computed to carry out robust designs and quickly explore the design space.

关键词： Rotary traveling wave oscillator array (RTWOA) Clock distribution Transmission line resonator Global optimi-zation Geometric programming (GP)

Analysis of Key Technologies and Equipments Development of Largescale Melted Extrusion Manufacturing Systems

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Journal of Materials Science & Technology 2003年第z1期19卷 215-217页

作者： Lei ZHANG sheng chen Yongnian YAN Renji ZHANG Center for Laser Rapid Forming Dept. of Mechanical Engineer Tsinghua University Beijing 100084 China Center for Laser Rapid Forming Dept. of Mechanical Engineer Tsinghua University Beijing 100084 China Center for Laser Rapid Forming Dept. of Mechanical Engineer Tsinghua University Beijing 100084 China Center for Laser Rapid Forming Dept. of Mechanical Engineer Tsinghua University Beijing 100084 China

To develop large-scale RP systems used to producing functional parts and large-sized models has become an urgentcall now. In this paper, a large-scale RP system, MEM600-l, based on the melted extrusion manufacturing (MEM)process has been developed successfully. And the key issues to develop such a system are discussed. Based on theactual forming experiment, it is concluded that the MEM600-l works reliably and the forming efficiency is muchhigher than its parallel equipments.

关键词： Melted extrusion manufacturing, Large-scale RP systems, Forming efficiency

Is the East Asian flora ancient or not?

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National Science Review 2018年第6期5卷 920-932页

作者： Yong-sheng chen Tao Deng Zhuo Zhou Hang Sun Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of BotanyChinese Academy of Sciences College of Life Science Northeast Agricultural University University of Chinese Academy of Sciences

The East Asian flora(EAF) is a key biodiversity hotspot for understanding the origin and evolution of Northern Hemisphere floras, but there is an ongoing debate on whether it is a museum or a cradle for seed plants. Within the EAF, two main floras, the Sino-Himalayan Flora(mainly the Rhododendron Flora) and the Sino-Japanese Flora(mainly the Metasequoia Flora), have been recognized. Previous studies suggested that the EAF is ancient and the Metasequoia Flora is older than the Rhododendron Flora. To test this hypothesis, we synthesized molecular as well as fossil data on seed plants, focusing on the biogeographical origins and historical evolution of the EAF. We compared the ages of its two constituent floras, and examined the impact of the Asian monsoon and other environmental changes on the development of EAF through meta-analysis. Our results suggest that the EAF might be relatively young, with most of its clades originating since the Miocene. The Rhododendron Flora and the Metasequoia Flora are probably of a similar age. The formation and development of the Asian monsoon might have been the main factors that have driven the evolution of EAF. In the Rhododendron Flora, the north-south mountain chains increased the concentration of species and reduced extinction, and the barriers between the east and west have resulted in species differentiation, which triggered it to become a diversity center. The EAF appears to have multiple biogeographical origins, having closely affiliated not only with other floras in the Northern Hemisphere, but also with Gondwanan floras.

关键词： Asian monsoon East Asian Flora Metasequoia Flora Rhododendron Flora temporal and spatial evolution

Two New Glucosides from Radix Polygoni multiflori Preparata

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Chinese Chemical Letters 2001年第6期12卷 503-506页

作者： Wan sheng chen Wei Dong ZHANG Gen Jing YANG Hai sheng chen Chuan Zhuo QIAO Department of Pharmacognosy School of PharmacySecond Military Medical UniversityShanghai 200433

2,3,5,4'-tetrahydroxystilbene-2-O-(2'-O-feruloyl)-beta -D-glucopyranoside, 2,3,5,4'-tetra hydroxystilbene-2-O-(2'-O-p-coumaroyl)-beta -D-glucopyranoside were isolated from Radix Polygoni multiflori Preparata. Structur... 详细信息

关键词： Radix Polygoni multiflori Preparata 2,3,5,4 '-tetrahydroxystilbene-2-O-(2 ''-O-feruloyl)-beta-D-glucopyranoside 2,3,5,4 '-tetrahydroxystilbene-2-O-(2 ''-O-p-coumaroyl)-beta-D-gluco pyranoside