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Capillary-gravity ship wave patterns

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Journal of Hydrodynamics 2017年第5期29卷 825-830页

作者： Hui Liang Xiaobo Chen Deepwater Technology Research Centre(DTRC) Bureau VeritasSingapore College of Shipbuilding Engineering Harbin Engineering UniversityHarbin 150001China

Ship wave pattern is a fascinating research topic in the fields of marine hydrodynamics and water waves. Within the pure-gravity wave theory, the ship wave pattern composed of transverse waves and divergent waves appearing on the downstream is confined within a sector symmetrical about the ship track with a half-angle 19°28＇. However, when the surface tension is accounted for, the wave pattern is greatly modified especially at a low translating speed. Besides the minimum speed of capillary waves c_（min）= 0.23 m/s below which waves cannot be generated, there is another critical speed c_（div）= 0.45 m/s associated with the disappearance of divergent waves. In the present paper, the wave patterns created by a steadily translating source are studied, and they are examined with the crestlines obtained from the asymptotic analysis.

关键词： Ship waves wave pattern gravity-dominant waves capillarity-dominant waves

Wavy properties and analytical modeling of free-surface flows in the development of the multi-domain method

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Journal of Hydrodynamics 2016年第6期28卷 971-976页

作者： Xiaobo Chen Hui LIANG Deepwater Technology Research Centre Bureau Veritas

The wavy （oscillatory both in space and in time） properties of free-surface flows due to presence of floating bodies are analyzed within the framework of the potential-flow theory by assuming that the fluid is perfect and flow irrotational. A so-called new multi-domain method has been developed based on the fluid domain division by an analytical control surface surrounding bodies and the application of different methods adapted in the external and internal domains. In the analytical domain external to the control surface, the fundamental solution satisfying the linear boundary condition on the free surface associated with a point singularity （often called Green fimction and referred here as point solution） is applied to capture all wavy features of free-surface flows extending horizontally to infinity. Unlike classical studies in which the control surface is discretized, the unknown velocity potential and its normal derivatives are expressed by expansions of orthogonal elementary functions. The velocity potential associa- ted with each elementary distribution （elementary solutions） on the control surface can be obtained by performing multi-fold inte- grals in an analytical way. In the domain internal to the control surface containing the bodies, we could apply different methods like the Rankine source method based on the boundary integral equations for which the elementary solutions obtained in the external domain playing the role of Dirichlet-to-Neumarm operator close the problem.

关键词： analytical modeling multi-domain method point solution （PS） elementary solution （ES） body solution （BS）

Recent progress of nanomaterials for microwave absorption

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Journal of Materiomics 2019年第4期5卷 503-541页

作者： Michael Green Xiaobo Chen Department of Chemistry University of Missourie Kansas CityKansas CityMO64110USA

Microwave absorbing materials have received considerable interest over the years for their applications in stealth,communications,and information processing technologies.These materials often require functionalization at the nanoscale so to achieve desirable dielectric and magnetic properties which induce interaction with incident electromagnetic radiation.This article presents a comprehensive review on the recent research progress of nanomaterials for microwave absorption,including the basic mechanism of microwave absorption(e.g.,dielectric loss,magnetic loss,dielectric/magnetic loss coupling),measurement principle(e.g.,fundamentals of analysis,performance evaluation,common interaction pathways:Debye relaxation,Eddy current loss,natural resonance,size and shape factors),and the advances and performance review in microwave absorption(e.g.,absorption bandwidth,reflection loss values,absorption peak position)using various nanomaterials,such as carbon nanotubes,carbon fibers,graphenes,oxides,sulfides,phosphides,carbides,polymers and metal organic frameworks.Overall,this article not only provides an introduction on the fundamentals of microwave absorption research,but also presents a timely update on the research progress of the microwave absorption performance of various nanomaterials.

关键词： Nanomaterials Microwave absorption Carbon nanotubes Metal-organic framework Permeability

Photocatalytic hydrogen production from seawater under full solar spectrum without sacrificial reagents using TiO_(2) nanoparticles

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Nano Research 2022年第3期15卷 2013-2022页

作者： Jining Zhang Yifan Lei Shuang Cao Wenping Hu Lingyu Piao Xiaobo Chen CAS Center for Excellence in Nanoscience National Center for Nanoscience and TechnologyCAS Key Laboratory of Standardization and Measurement for NanotechnologyBeijing 100190China School of Science Tianjin UniversityTianjin 300072China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Department of Chemistry University of Missouri–Kansas CityMO 64110USA

Photocatalytic water splitting(PWS)has attracted widespread attention as a sustainable method for converting solar to green hydrogen energy.So far PWS research has mainly focused on the development of artificial photocatalytic hydrogen production systems for pure water.It is more practically attractive to create systems for seawater,i.e.,to reduce the cost of hydrogen production and make better use of naturally occurring water resources.Herein,brookite,anatase,and rutile TiO_(2)nanoparticles are investigated as photocatalysts to explore the feasibility of such thought and have shown attractive hydrogen production performance under full solar spectrum without any sacrificial agent.It is worth noting that,brookite TiO_(2),has more suitable band gap position and excellent photoelectric properties compared with anatase and rutile TiO_(2),and has higher efficiency and stability in the process of hydrogen production.The photocatalytic hydrogen production rate of brookite TiO_(2)can reach up to 1,476μmol/g/h,the highest value reported for TiO_(2)-based systems and most other photocatalysts in seawater splitting under full spectrum.As the Cl−ions in seawater go through a cycle of oxidation and reduction,no Cl_(2) is detected in the solar hydrogen production from seawater.

关键词： photocatalytic seawater splitting hydrogen production titanium dioxide(TiO_(2))photocatalyst

From plant immunity to crop disease resistance

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Journal of Genetics and Genomics 2022年第8期49卷 693-703页

作者： Yan Zhao xiaobo Zhu Xuewei chen Jian-Min Zhou State Key Laboratory of Plant Genomics Institute of Genetics and Developmental BiologyChinese Academy of SciencesBeijing 100101China State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China Sichuan Agricultural University at WenjiangChengduSichuan 611130China CAS Center for Excellence in Biotic Interactions University of Chinese Academy of SciencesBeijing 100049China Hainan Yazhou Bay Seed Laboratory SanyaHainan 572025China

Plant diseases caused by diverse pathogens lead to a serious reduction in crop yield and threaten food security worldwide.Genetic improvement of plant immunity is considered as the most effective and sustainable approach to control crop diseases.In the last decade,our understanding of plant immunity at both molecular and genomic levels has improved greatly.Combined with advances in biotechnologies,particularly clustered regularly interspaced short palindromic repeat(CRISPR)/Cas9-based genome editing,we can now rapidly identify new resistance genes and engineer disease-resistance crop plants like never before.In this review,we summarize the current knowledge of plant immunity and outline existing and new strategies for disease resistance improvement in crop plants.We also discuss existing challenges in this field and suggest directions for future studies.

关键词： Plant immunity Disease resistance Resistance genes Molecular breeding Genetic engineering Crops

Heterostructuring noble-metal-free 1T'phase MoS_(2) with g-C_(3)N_(4) hollow nanocages to improve the photocatalytic H2 evolution activity

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Green Energy & Environment 2023年第3期8卷 864-873页

作者： Yanjun Xue Yinghong Ji Xinyu Wang Huanli Wang Xiaobo Chen Xiaoli Zhang Jian Tian School of Materials Science and Engineering Shandong University of Science and TechnologyQingdao 266590China School of Environmental and Municipal Engineering Qingdao University of TechnologyQingdao 266033China Department of Chemistry University of MissouriKansas CityMO 64110USA School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China

In this work,we report the preparation of 1T'-MoS_(2)/g-C_(3)N_(4) nanocage(NC)heterostructure by loading 2D semi-metal noble-metal-free 1T'-MoS_(2) on the g-C_(3)N_(4) nanocages(NCs).DFT calculation and experimental data have shown that the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure has a stronger light absorption capacity and larger specific surface area than pure g-C_(3)N_(4) NCs and g-C_(3)N_(4) nanosheets(NSs),and the presence of the co-catalysts 1T'-MoS_(2) can effectively inhibit the photoinduced carrier recombination.As a result,the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure with an optimum 1T'-MoS_(2) loading of 9 wt%displays a hydrogen evolution rate of 1949 mmol h^(-1) g^(-1),162.4,1.2,1.5,1.6 and 1.2 times than pure g-C_(3)N_(4) NCs(12 mmol h^(-1) g^(-1)),Pt/g-C_(3)N_(4) NCs(1615 mmol h^(-1) g^(-1))and Pt/g-C_(3)N_(4) nanosheets(NSs,1297 mmol h^(-1) g^(-1)),1T'-MoS_(2)/g-C_(3)N_(4) nanosheets(1216 mmol h^(-1) g^(-1))and 2H-MoS_(2)/g-C_(3)N_(4) nanocages(1573 mmol h^(-1) g^(-1)),respectively,and exhibits excellent cycle stability.Therefore,1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure is a suitable photocatalyst for green H_(2) production.

关键词： g-C_(3)N_(4) 1T'phase MoS_(2) Nanocage structure Photocatalytic hydrogen production Co-catalysts

Laser directed energy deposited, ultrafine-grained functional titanium-copper alloys tailored for marine environments: Antibacterial and anti-microbial corrosion studies

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Journal of Materials Science & Technology 2023年第35期166卷 21-33页

作者： Jiaqi Li Duyao Zhang Xiaobo Chen Dake Xu Dong Qiu Fuhui Wang Mark Easton Shenyang National Laboratory for Materials Science Northeastern UniversityShenyang 110819China Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China School of Engineering Centre for Additive ManufacturingRMIT UniversityMelbourneVIC 3000Australia

The microorganism-rich nature of the ocean imposes great challenges to the structural integrity of met-als over their service lifespan,including titanium(Ti)alloys,which are usually prone to microbiologically influenced corrosion(MIC).So,multifunctional anti-MIC Ti alloys need to be developed and studied.This paper investigates the effect of copper(Cu)concentration on the MIC resistance of a series of additively manufactured,ultrafine-grained Ti-x Cu(x=3.5,6.5 and 8.5 in wt.%)alloys.The dependence of the cor-rosion resistance and MIC resistance on the Cu concentration of Ti-Cu alloy is interpreted considering all conceivable mechanisms.The mechanisms for excellent corrosion resistance of Ti-Cu alloy in seawater are attributed to the strong passive film and small surface potential difference between phases.Microstruc-tural characterization reveals that uniformly distributed,nanosized Ti_(2) Cu phase led to increased reactive oxygen species in the bacterial membrane,which is the root reason for the superb anti-bacterial property(99.2%)for Ti-8.5Cu.Compared to pure Ti and Ti-6Al-4V,Ti-8.5Cu alloy features both high strength(yield stress>1000 MPa)and the best MIC resistance(97.5%).The combination of such balanced properties enables this functional 3D printed Ti-Cu alloy to become an ideal material for load-bearing applications in the marine environment.

关键词： Multifunctional titanium alloys Additive manufacturing Ultrafine grains Microbiologically influenced corrosion resistance Mechanical property Antibacterial property

Enhanced pitting corrosion resistance of CoCrFeMnNi high entropy alloy in the presence of Desulfovibrio vulgaris via nitrogen doping

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Journal of Materials Science & Technology 2023年第8期139卷 92-102页

作者： Chuntian Yang Hao Feng Xiaobo Chen Yu Han Huabing Li Dake Xu Fuhui Wang Shenyang National Laboratory for Materials Science Northeastern UniversityShenyang110819China Electrobiomaterials Institute Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education)Northeastern UniversityShenyang110819China School of Engineering RMIT UniversityCarltonVIC 3053Australia School of Metallurgy Northeastern UniversityShenyang110819China

Corrosion-resistant high nitrogen high entropy alloys(HEAs)were manufactured by pressurized metal-lurgy.This work revealed the inhibitory effect of nitrogen on pitting corrosion of HEAs caused by sul-fate reducing bacterium Desulfovibrio vulgaris.Results indicated that HEA-0 N was susceptible to pitting corrosion and sulfidation under attack of D.vulgaris,whereas the addition of nitrogen significantly de-creased the pitting sensitivity.Pitting potentials of HEA-0.52 N and HEA-1.23 N increased by 133%and 171%,respectively compared to HEA-0 N in the presence of SRB.X-ray photoelectron spectroscopy results unveiled that nitrogen enriched in passive film and strengthened it by increasing fraction of Cr_(2)O_(3)and Fe^(3+)_(ox).Surface of the nitrogen-alloyed HEAs exhibited less defective passive films as revealed by Mott-Schottky results.Nitrogen doping provides a novel insight into the design of microbial corrosion resistant HEA.

关键词： High entropy alloy Microbiologically influenced corrosion Sulfate reducing bacteria Nitrogen doping Pitting corrosion

High flashover strength and superhydrophobic coatings by constructing porous surface structure

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High Voltage 2023年第4期8卷 728-738页

作者： Mengtao Li Tingxin chen xiaobo Guo Lei Dong Jiming chen Mingxiao Zhu College of New Energy China University of Petroleum(East China)QingdaoChina

Flashover is prone to occur in composite insulation structures such as vacuum-solid and gas-solid,which are universally employed in high-voltage power equipment.In this study,a high flashover strength and superhydrophobic coating were proposed by constructing porous surface morphology.Octadecyl trichlorosilane(OTS)particles were prepared by hydrolysis condensation reaction,and thereafter sprayed onto the substrate surface to form a porous and rough surface structure with hundreds of nanometres of dispersed pores and pits.The coating endowed epoxy resin with maximum 44%flashover voltage increase and the superhydrophobic surface with water contact angle of 158.4°.Since the pore size in OTS coating is close to electron mean free path in atmospheric condition,the collisional ionisation can be effectively hindered,which suppresses the micro-discharge around the triple junction and improves the flashover strength.The present approach provides a new insight for simultaneously improving flashover strength and superhydrophobic properties of dielectric insulation.

关键词： coating strength flash