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On a Spanning K-tree Containing Specified Vertices in a Graph

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Acta Mathematicae Applicatae Sinica 2019年第4期35卷 919-923页

作者： Fei-fei SONG zhi-quan hu Department of Information & Computational Science He’nan Agricultural University Zhengzhou 450002 China Faculty ofMath & Statistics Central China Normal UniversityWuhan 430079 China

A k-tree is a tree with maximum degree at most k. In this paper, we give a sharp degree sum condition for a graph to have a spanning k-tree in which specified vertices have degree less than t, where 1≤t≤*** denote by σ_k(G) the minimum value of the degree sum of k independent vertices in a graph G. Let k≥2,s≥0 and 1≤t≤k be integers, and suppose G is an(s + 1)-connected graph with σ_k(G)≥|G|+(k-t)*** for any s specified vertices, G contains a spanning k-tree in which every specified vertex has degree at most t. This improves a result obtained by Matsuda and Matsumura.

关键词： spanning tree k-tree (s + 1)-connected graphs degree sum condition specified vertices

The Surface Modification of Tourmaline Powder with Triethoxyvinylsilane and Characterization

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武汉理工大学学报 2015年第2期37卷 40-43,49页

作者： hu zhi-ying School of Materials Science and Engineering Wuhan University of Technology

The surface modification of the tourmaline powder with triethoxyvinylsilane was studied to prepare the polymerizable organic *** experimental results showed that the surface of modified tourmaline had the better hydrophobicity compared with unmodified tourmaline,when the mass ratio of triethoxyvinylsilane to tourmaline powder was 1∶5,and reacted at 60 ℃for 1.5hin the mixed-solvent of ethanol and distilled water(1∶5in volume ratio).The structure characterization results indicated that the vinylsiloxane was introduced into the surface of tourmaline powder to generate the polymerizable organic tourmaline,and the crystal structure of tourmaline had no change.

关键词： tourmaline triethoxyvinylsilane surface modification functional polymer

Dynamic Performance Investigation of A Spar-Type Floating Wind Turbine Under Different Sea Conditions

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China Ocean Engineering 2018年第3期32卷 256-265页

作者： WANG Han hu zhi-qiang MENG Xiang-yin State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai 200240China School of Engineering Newcastle UniversityNewcastle upon TyneNE1 7RU UK

Both numerical calculation and model test are important techniques to study and forecast the dynamic responses of the floating offshore wind turbine(FOWT). However, both the methods have their own limitations at present. In this study, the dynamic responses of a 5 MW OC3 spar-type floating wind turbine designed for a water depth of 200 m are numerically investigated and validated by a 1:50 scaled model test. Moreover, the discrepancies between the numerical calculations and model tests are obtained and discussed. According to the discussions, it is found that the surge and pitch are coupled with the mooring tensions, but the heave is independent of them. Surge and pitch are mainly induced by wave under wind wave conditions. Wind and current will induce the low-frequency average responses, while wave will induce the fluctuation ranges of the responses. In addition, wave will induce the wavefrequency responses but wind and current will restrain the ranges of the responses.

关键词： spar-type floating wind turbine dynamic response numerical calculation model test time domain analysis frequency domain analysis

Microstructure and mechanical properties of friction stir welding joint during post weld heat treatment with different zigzag lines

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Rare Metals 2019年第11期38卷 1070-1077页

作者： zhi-Li hu Qiu Pang Ming-Liang Dai hubei Key Laboratory of Advanced Technology of Automobile Components Wuhan University of TechnologyWuhan 430070China hubei Collaborative Innovation Center for Automotive Components Technology Wuhan University of TechnologyWuhan 430070China School of Mechanical and Electrical Engineering Wuhan Donghu UniversityWuhan 430212China

Zigzag line is a common defect in friction stir welding(FSW) *** formation mechanism of the zigzag line in Al-Cu alloy FSW joint and its influence on the microstructure and mechanical properties during post weld heat treatment(PWHT) were studied by scanning electron microscopy(SEM),microhardness and tensile *** is found that the occurrence of zigzag line for PWHT joint is determined by PWHT process which in nature depends on residual stress and thermal stress of FSW *** optimization of PWHT process to reduce the residual and thermal stress can trigger for the deterioration of mechanical properties of PWHT joints with zigzag *** obvious decrease of tensile properties is observed for T6-450 and T6-495 joints although zigzag line appears in the *** determines the sizes of zigzag line cracks and consequently determines the fracture location and characteristics of FSW joint.

关键词： Friction stir welding Post weld heat treatment Zigzag line Mechanical properties

Platinum Atoms Dispersed in Single-chain Polymer Nanoparticles

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Chinese Journal of Polymer Science 2021年第4期39卷 441-446,I0005页

作者： zhi-Yu hu Hong-Ting Pu Jian-Guo Wu Department of Polymeric Materials School of Materials Science&EngineeringTongji UniversityShanghai 201804China Key Laboratory of Advanced Civil Engineering Materials School of Materials Science&EngineeringTongji UniversityShanghai 201804China

The intramolecular cross-linking of single polymer chains can form single-chain nanoparticles(SCNPs),which have many *** this study,styrenic copolymers with pendent triphenylphosphine as the coordination site for platinum ions(Pt(Ⅱ))and benzocyclobutene as the latent reactive groups are *** groups in the chains can coordinate Pt(Ⅱ)and aid slight single-chain folding in dilute *** intramolecular cross-linking caused by the ring-open reaction of benzocyclobutene completes the single-chain collapse and forms stable SCNPs in dilute ***(Ⅱ)embedded in SCNPs can be further reduced to platinum atoms(Pt(0)).Pt(0)steadily and atomically dispersed in SCNPs exhibits better catalytic properties than normal polymer carried platinum particles do for the reduction of p-nitrophenol to p-aminophenol.

关键词： Single-chain Polymer nanoparticles Intramolecular cross-linking Platinum Coordination

HYDRODYNAMIC INTERACTION BETWEEN FLNG VESSEL AND LNG CARRIER IN SIDE BY SIDE CONFIGURATION

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Journal of Hydrodynamics 2012年第5期24卷 648-657页

作者： ZHAO Wen-hua YANG Jian-min hu zhi-qiang State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China

The Floating Liquefied Natural Gas （FLNG） is a new type of floating platform for the exploitation of stranded offshore oil/gas fields. The side by side configuration for the FLNG vessel and the LNG carrier arranged in parallel is one of the possible choices for the LNG offloading. During the offloading operations, the multiple floating bodies would have very complex responses due to their hydrodynamic interactions. In this study, numerical simulations of multiple floating bodies in close proximity in the side by side offloading configuration are carried out with the time domain coupled analysis code SIMO. Hydrodynamic interactions between the floating bodies and the mechanical coupling effects between the floating bodies and their connection systems are included in the coupled analysis model. To clarify the hydrodynamic effects of the two vessels, numerical simulations under the same environmental condition are also conducted without considering the hydrodynamic interactions, for comparison. It is shown that the hydrodynamic interactions play an important role in the low frequency motion responses of the two vessels, but have little effect on the wave frequency motion responses. In addition, the comparison results also show that the hydrodynamic interactions can affect the loads on the connection systems.

关键词： Floating Liquefied Natural Gas (FLNG) hydrodynamic interactions side by side operation relative motions

Numerical and experimental study on the hydraulic characteristics of a vertical axial pump under various clearances of flare tube

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Journal of Hydrodynamics 2023年第1期35卷 125-144页

作者： Jia-qi Chen zhi-kui He zhi-yang hu Hong-bo Shi Xikun Wang Research Center of Fluid Machinery Engineering and Technology Jiangsu UniversityZhenjiang212013China Chongqing Pump Industry Co.Ltd. Chongqing400033China

In order to investigate the characteristics of a vertical axial flow pump under various clearances of flare tube, the bell-shaped inlet and box culvert outlet channels with flare tube are studied numerically and experimentally. Then, the cases of inlet and outlet channels with the least hydraulic loss are selected to form an integral pump system, for which both numerical simulation and experimental investigation are carried out. The numerical results agree well with the experimental data. It is shown that the clearances of the interfaces between different components of the pump system have a significant impact on the internal flow structure, turbulent entropy and hydraulic performance of the inlet and outlet channels. For the cases of normalized bottom clearance less than 0.5 and normalized top clearance larger than 0.4, the internal flow and hydraulic performance indexes of inlet and outlet channels are relatively poor. There also exists a critical clearance in either inlet or outlet channel at which the hydraulic loss reaches the maximum. The results serve as an important reference for the design as well as safe and efficient operation of the vertical axial flow pump system.

关键词： Axial flow pump clearance of flare tube numerical simulation experiment hydrodynamic characteristics

High efficient multipacket decoding approach for network coding in wireless networks

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The Journal of China Universities of Posts and Telecommunications 2013年第1期20卷 95-100页

作者： YAO Yu-kun WEN Ya-di REN zhi LIU zhi-hu Chongqing Key Laboratory of Mobile Communication Technology Chongqing University of Posts and Telecommunications

To improve the performance of transmission by reducing the number of transmission and network overhead of wireless single-hop networks, this paper presents a high efficient multipacket decoding approach for network coding （EMDNC） in wireless networks according to the idea of encoding packets which cannot be decoded and are stored in buffer by receiving nodes, the lost packets can be recovered from these encoded packets. Compared with the network coding wireless broadcasting retransmission （NCWBR）, EMDNC can improve the efficiency of decoding and reduce the number of retransmission and transmission delay. Simulation results reveal that EMDNC can effectively reduce the number of retransmission and network overhead.

关键词： wireless single-hop networks network coding number ofretransmission transmission delay network overhead

Strong invariance principle for a counterbalanced random walk

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Applied Mathematics(A Journal of Chinese Universities) 2024年第2期39卷 370-380页

作者： TAN hui-qun hu zhi-shui DONG Liang International Institute of Finance School of ManagementUniversity of Science and Technology of ChinaHefei 230026China Center for Basic Teaching and Experiment Nanjing University of Science and TechnologyJiangyin 214443China

We study a counterbalanced random walkS_(n)=X_(1)+…+X_(n),which is a discrete time non-Markovian process andX_(n) are given recursively as *** n≥2,X_(n) is a new independent sample from some fixed law̸=0 with a fixed probability p,andX_(n)=−X_(v(n))with probability 1−p,where v(n)is a uniform random variable on{1;…;n−1}.We apply martingale method to obtain a strong invariance principle forS_(n).

关键词： random walk martingale invariance principle