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Global Regularity of Solutions for a One-dimensional Nuclear Fluid with Non-monotone Pressure

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Acta Mathematicae Applicatae Sinica 2019年第4期35卷 798-811页

作者： bao-wei FENG Department of Economic Mathematics Southwestern University of Finance and Economics

We consider a one-dimensional continuous thermal model of nuclear matter, which is described by a compressible Navier-Stokes-Poission system with a non-monotone equation of state owing to the effective Skyrme nuclear interaction between particles. We prove the global existence of solutions in H^4 space for a free boundary value problem with a possible destabilizing influence of the pressure which is not always positive,provided a sufficient thermal dissipation is present and first obtain the existence of classical solutions.

关键词： global existence compressible fluid non-monotone fluid

Entrance Effect on Load Capacity of Orifice Compensated Aerostatic Bearing with Feeding Pocket

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Chinese Journal of Mechanical Engineering 2010年第4期23卷 451-459页

作者： LONG wei bao Gang School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China

The current research of the aerostatic thrust bearing mainly focuses on the porous material bearing and inherent compensated air bearing, which aims at obtaining small physical dimension and large load capacity. Although porous material bearing appears larger load capacity, materials anisotropy itself and void content distortion caused in heat-treating, and machining processes add greater complexity to internal flow transfer process. Inherent compensated air bearing has the advantages of simple structure and good stability, but its load capacity and static stiffness is not worth somewhat. In this paper, based on hydrostatic lubrication theory, finite volume method is presented for taking entrance effects into account in computing pressure distribution, load capacity and mass flow rates of circular aerostatic thrust bearings. Technical analysis, numerical simulations and laboratory demonstration tests of influence of pocket diameter and pocket depth on loading capacity of aerostatic thrust bearing are carried out on simple orifice compensated air bearings with feeding pockets. The static parameters, such as air consumption and pressure distributions, are measured as a function of supply pressure and air gap height for several different orifices and pockets size. Entrance effects are described in term of typical throttling types, and the effect of pocket diameter and pocket depth on load capacity is systematically described respectively. The proposed research results uncover the causation of throttling action of the orifice compensated air bearing with feed pocket and further develop and improve the design theory of air bearing.

关键词： aerostatic thrust bearing feeding pocket entrance effects

A power conversion system for PMSG-based WECS operating with fully-controlled current-source converters

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Journal of Zhejiang University-Science C(Computers and Electronics) 2014年第3期15卷 232-240页

作者： Jian-yu bao wei-bing bao Yu-ling LI Ningbo Institute of Technology Zhejiang University Zhijiang College Zhejiang University of Technology College of Electrical Engineering Zhejiang University

We propose a new power conversion system for a permanent magnet synchronous generator(PMSG) based grid-connected wind energy conversion system(WECS) operating with fully-controlled back-to-back current-source converters. On the generator side, two independent current-source rectifiers(CSRs) with space-vector pulse width modulation(SVPWM) are employed to regulate and stabilize DC-link currents. Between DC-link and the electrical grid, a direct-type three-phase five-level current-source inverter(CSI) is inserted as a buffer to regulate real and reactive power fed to the grid and thus adjusts the grid side power-factor. We also present a current-based maximum power point tracking(MPPT) scheme, which helps the generator extract the maximum power through closed-loop regulation of the generator speed. By applying the multilevel modulation and control strategies to the grid-side five-level CSI, a multilevel output current waveform with less distortion is produced, and the bulk requirement of the output capacitor filter to eliminate the harmonic current is reduced. All the proposed concepts are verified by simulation models built in a PSIM environment.

关键词： Grid-connected Wind energy conversion Current-source rectifier Multilevel current-source inverter

Generalized multilevel current source inverter topology with self-balancing current

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第7期11卷 555-561页

作者： Jian-yu bao wei-bing bao Zhong-chao ZHANG Ningbo Institute of Technology Zhejiang University Ningbo 315100 China Zhijiang College Zhejiang University of Technology Hangzhou 310024 China Electrical Engineering College Zhejiang University Hangzhou 310027 China

A generalized single-phase multilevel current source inverter (MCSI) topology with self-balancing current is proposed, which uses the duality transformation from the generalized multilevel voltage source inverter (MVSI) topology. The existing single-phase 8-and 6-switch 5-level current source inverters (CSIs) can be derived from this generalized MCSI topology. In the proposed topology, each intermediate DC-link current level can be balanced automatically without adding any external circuits; thus, a true multilevel structure is provided. Moreover, owing to the dual relationship, many research results relating to the op- eration, modulation, and control strategies of MVSIs can be applied directly to the MCSIs. Some simulation results are presented to verify the proposed MCSI topology.

关键词： Multilevel current source inverter (MCSI) Topology Self current balancing Duality

Microstructural evolution,tensile property and dynamic compressive property of FSWed Ti-6Al-4V alloy

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Rare Metals 2020年第2期39卷 169-175页

作者： Jia-wei bao Su-Yuan Yang Ting Yang School of Materials Science and Engineering Beijing Institute of TechnologyBeijing100081China

Friction stir welding was applied to Ti-6 A1-4 V plates with 5 mm in *** microstructure and mechanical properties were investigated.A full lamellar microstructure was developed near the top surface,and the size of priorβgrain gradually decreases as the distance from the top surface *** microstructure of the bottom is fine equiaxed a grains,and the mean size is2μm.A mixture microstructure consisting of primary a,lamellarα+βand fine equiaxedαis discovered in thermomechanically affected zone(TMAZ).Results of transverse tensile test show that the tensile strength of the joint reaches 98%that of the base material(BM).Quasi-static compression test shows that the joint exhibits larger compressive strength and failure strain than the *** compressive strength of the joint is close to that of the BM;furthermore,the strain at the peak stress and energy absorption of the joint are larger than those of the BM.

关键词： Friction stir welding Ti-6Al-4V Microstructure Tensile property Dynamic compressive property

Investigation on the Orientation Transition of Oriented Magnetostrictive TbDyFe Crystals

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Chinese Journal of Aeronautics 2006年第B12期19卷 183-186页

作者： LIU wei JIANG Cheng-bao School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

〈110〉 and 〈112〉 TbDyFe magnetostrictive oriented crystals were prepared by the zone-melting unidirectional solidification method at 240 mmfh and 720 mm/h respectively. 〈112〉 oriented crystals were also obtained with 〈110〉 oriented seeds with the same technique as for growing the 〈112〉 oriented crystals. It is confirmed that this technique is stable for growing the oriented crystals in the TbDyFe alloys. Meanwhile, the variation of orientation, the solidification morphology and the magnetostriction were studied during the transition from 〈110〉 oriented seeds to the 〈112〉 oriented crystal growth. As the growth speeds up, the preferred orientation changed from 〈110〉 to 〈112〉, and its morphology develops from of initial cellular to dendritic gradually. When an axial compressive pre-stress of 10 MPa is applied, the magnetostriction at the bottom, the middle and the top are 972× 10^6, 918 × 10^-6 and 900× 10^-6 at 100 mT respectively. The middle sections with mixed orientations have the same high magnetostriction performance as those with a single preferred orientation, which may be due to its celluar-dendritic morphology.

关键词： TbDyFe magnetostriction directional solidification oriented crystal

Efficient dechlorination of 2,4-dichlorophenol in an aqueous media with a mild pH using a Pd/TiO2NTs/Ti cathode

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Frontiers of Environmental Science & Engineering 2015年第5期9卷 919-928页

作者： Jiangkun DU Jianguo bao wei HU School of Environmental Studies China University of Geosciences Wuhan 430074 China

In this study, palladium-loaded titania nano- tubes was fabricated on a titanium plate （Pd/TiO2NTs/Ti） for efficient electrodechlorination of 2,4-chlorophenol with a mild pH condition. The nature of PdYTiO2NTs/Ti electrodes was characterized by field-emission scanning electron microscope （FESEM）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, and cyclic voltammetry （CV） techniques. The characterization results indicated the generation of Pd~ nanoparticles which were evenly dispersed on titania nanotubes arrays on the Pd/ TiO2NTs/Ti surface. An effective degradation efficiency of up to 91% was achieved within 60 min at cathode potential of -0.7 V （vs. SCE） and initial pH of 5.5. The effects of the applied cathode potential and initial pH on the degradation efficiency were studied. A near neutral condition was more favorable since very low and very high pHs were not conducive to the dechlorination process. Furthermore, the intermediates analysis showed that the Pd/TiO2NTs/Ti electrode could completely remove chlor- ine from 2, 4-dichlorophenol since only phenol was detected as the byproduct and the concentration of released chlorine ions indicated near-complete dechlorination. This work presents a good alternative technique for eliminating persistent chlorophenols in polluted wastewater without maintaining strong acidic environment.

关键词： Pd/TiO2NTs/Ti cathode chlorophenols electrocatalytic dechlorination wastewater treatment

InStereo2K: a large real dataset for stereo matching in indoor scenes

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Science China(Information Sciences) 2020年第11期63卷 136-146页

作者： wei bao wei WANG Yuhua XU Yulan GUO Siyu HONG Xiaohu ZHANG School of Electrical Engineering and Automation Hefei University of Technology School of Electronics and Communication Engineering Sun Yat-sen University College of Electronic Science and Technology National University of Defense Technology School of Aeronautics and Astronautics Sun Yat-sen University

Deep neural networks have shown great success in stereo matching in recent years. On the KITTI datasets, most top performing methods are based on neural networks. However, on the Middlebury datasets,these methods usually do not perform well. The KITTI datasets are collected in outdoor scenes while the Middlebury datasets are collected in indoor scenes. It is commonly believed that the community still lacks a large labelled dataset for stereo matching in indoor scenes. In this paper, we introduce a new stereo dataset called InS tereo2K. It contains 2050 pairs of stereo images with highly accurate groundtruth disparity maps, including 2000 pairs for training and 50 pairs for test. Experimental results show that our dataset can significantly improve the performance of several latest networks(including StereoNet and PSMNet) on the Middlebury 2014 dataset. The large scale, high accuracy and rich diversity of the proposed InS tereo2K dataset provide new opportunities to researchers in the area of stereo matching and beyond. It also takes end-to-end stereo matching methods a step towards practical applications.

关键词： stereo matching depth estimation convolutional neural network dataset

Mechanical and magnetic hysteresis as indicators of the origin and inception of fatigue damage in steel

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第8期11卷 580-586页

作者： Sheng bao wei-liang JIN Ming-feng HUANG Institute of Structural Engineering Zhejiang University Hangzhou 310058 China

N2 and N3 are known as the transition points of the three principal stages of fatigue: initial accommodation, accretion of damage and terminal fatigue. Many experiments show that the ratios of N2/Nf and N3/Nf tend to be stable even though the specific N2 and N3 values may fluctuate widely. The primary goal of this research is to study the piezomagnetic field surrounding AISI 1018 steel specimen under repeated loads and to find the ratio values of N2/Nf and N3/Nf by analyzing 11 sets of low-cycle fatigue data. An MTS-810 testing system with a peak capacity of 222 kN was used to obtain the data which consisted of stress, strain, and piezomagnetic field. A computer program was constructed to track the evolution of the piezomagnetic field and re- gression analysis was carried out to determine N2 and N3 values. It was observed that there exists a consistent relationship between N2 and Nf. The apparent invariance of the ratio N2/Nf implies that N2 may be identified as an index of performance in the early loading response of a specimen that forecasts its fatigue life, Nf. It has been demonstrated that measurements of the magnetic and mechanical hysteresis can yield significant insights into the various stages of the development of a fatigue critical microstructure which culminates in complete rupture of the material.

关键词： Piezomagnetic effects. Fatigue damage. Mechanical hvsteresis. Magnetic hysteresis