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On the Stability of Tangent Bundle on Double Coverings

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Acta Mathematica Sinica,English Series 2017年第8期33卷 1039-1047页

作者： yongming zhang School of Mathematical Sciences Fudan UniversityShanghai 200433P.R.China

Let Y be a smooth projective surface defined over an algebraically closed field k with char k ≠ 2, and let π ： X → Y be a double covering branched along a smooth divisor. We show that Jx is stable with respect to... 详细信息

关键词： Stability tangent bundle double covering Frobenius morphism

Self-consistent parabolized stability equation(PSE) method for compressible boundary layer

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Applied Mathematics and Mechanics(English Edition) 2015年第7期36卷 835-846页

作者： yongming zhang Caihong SU Department of Mechanics Tianjin University Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin University

The parabolized stability equation （PSE） method has been proven to be a useful and convenient tool for the investigation of the stability and transition problems of boundary layers. However, in its original formulation, for nonlinear problems, the complex wave number of each Fourier mode is determined by the so-called phase-locked rule, which results in non-self-consistency in the wave numbers. In this paper, a modification is proposed to make it self-consistent. The main idea is that, instead of allowing wave numbers to be complex, all wave numbers are kept real, and the growth or decay of each mode is simply manifested in the growth or decay of the modulus of its shape function. The validity of the new formulation is illustrated by comparing the results with those from the corresponding direct numerical simulation （DNS） as applied to a problem of compressible boundary layer with Mach number 6.

关键词： parabolized stability equation (PSE) boundary layer direct numericalsimulation (DNS) self-consistent

Determination of water flushing characteristics and their influencing factors on the Dahuofang Reservoir in China using an improved ECOMSED model

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Frontiers of Earth Science 2015年第3期9卷 394-411页

作者： Ming zhang yongming SHEN State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116023 China

A three-dimensional hydrodynamic model with the capability to deal with changing land water boundaries was developed based on ECOMSED in this study. The model was configured to numerically study the water flushing characteristics of Dahuofang Reservoir in China through the determination of spatially distributed residence times. The model successfully reproduced the intra-annual water level variations, as well as the temporal evolution and spatial distribution of water temperature. Through a series of numerical experiments, it can be concluded that （1） the water flushing of the reservoir is both temporally and spatially variable; and （2） inflows and withdrawals are the decisive factors influencing the water flushing characteristics. Heat fluxes are the controlling factors of the water flushing of a strong stratified reservoir. Wind has the weakest effect, but it still should be considered in determination of reservoir water flushing characteristics.

关键词： numerical modeling residence time flushing,influence factor Dahuofang Reservoir

Study on crystallization and microstructure of Li_2O-Al_2O_3-SiO_2 glass ceramics

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Journal of University of Science and Technology Beijing 2006年第6期13卷 564-569页

作者： Zhaoxia Hou yongming zhang Huashan zhang Hongbo zhang Jing Shao Chunhui Su School of Materials and Chemical Engineering Changchun University of Science and Technology Changchun 130022 China Department of Chemical Engineering Jilin Institute of Chemical Technology Jilin 132022 China Department of Material Science and Engineering Shenyang Institute of Chemical Technology Shenyang 110142 China

Lithium aluminosilicate （LAS） glasses are generally difficult to prepare because of their high melting temperature. In this study, the preparation of LAS glasses was achieved at a relatively low melting temperature. The batch containing MgO-ZnO-LiEO- Al2O3-SiO2 was melted in a platinum crucible at 1550℃ for 2 h and was then followed by two- or three-step heat treatment processes for nucleation and crystal growth. The characterizations were carried out by differential thermal analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and UV-Vis-NIR scanning spectrophotometry. The hexagonal stuffed β-eucryptite solid solution crystallized at 840-960℃. Most of the hexagonal β-eucryptite solid solution transformed into the tetragonal β-spodumene solid solution at 1100℃. Almost all the aluminum atoms entered into the tetrahedral sites in the aluminosilicate network of the 6- eucryptite/β-quartz solid solution. All of the Al atoms did not belong to the aluminosilicate network of the β-spodumene solid solution. The glass ceramic with a mean grain size of 10-20 nm is transparent, the transmittance reaches -85% in the visible light wavelength.

关键词： inorganic compounds glass ceramics crystallization behavior microstructure characterization

A gelable pure organic luminogen with fluorescence-phosphorescence dual emission

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Science China Chemistry 2017年第6期60卷 806-812页

作者： Kaixuan Li Lifang Zhao Yongyang Gong Wang-zhang Yuan yongming zhang School of Chemistry and Chemical Engineering Shanghai Key Lab of Electrical Insulation and Thermal AgingShanghai Electrochemical Energy Devices Research Center Shanghai Jiao Tong University Shanghai 200240 China

Pure organic luminogens with room temperature phosphorescence(RTP) have drawn much attention due to their fundamental importance and promising applications in optoelectronic devices, bioimaging, sensing, etc. Fluorescence-phosphorescence dual emission at room temperature, however, is rarely observed in pure organic materials. Herein, we reported a metal-and heavy-atom free pure organic luminogen with tert-butyl groups, DtBuCZBP, which is ready to form organogels in dimethylsulfoxide(DMSO).It emits prompt and delayed fluorescence, as well as RTP, namely dual emission in as-prepared solid, gels and polymeric *** the best of our knowledge, it is the first example of metal-and heavy-atom free pure organic gelator with RTP emission. Such unique RTP and moreover dual emission properties in different states make DtBuCZBP a potential material for diverse applications.

关键词： pure organic luminogens dual emission room temperature phosphorescence organogel

Effect of Yb^(3+) concentration on the structures and upconversion luminescence properties of Y_2O_3:Er^(3+) ultrafine phosphors

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Rare Metals 2008年第6期27卷 603-607页

作者： zhang yongming LI Yanhong zhang Yang HONG Guangyan YU Yingning School of Materiasls Science and Engineering Shenyang Institute of Chemical Technology Shenyang 110142 China Key Laboratory of Rare Earth Chemistry and Physics Chinese Academy of Sciences Changchun 130022 China

Y2O3：Er^3＋ ultrafine phosphors with a varying Yb^3＋ ion concentration were prepared by a urea homogeneous precipitation method. The results of XRD show that all the samples are of a pure cubic structure and the average crystallite sizes can be calculated as 45, 34, and 28 nm for Y2O3：Er^3＋ ultrafine phosphors with Yb^3＋ ion concentrations of 0, 10%, and 20%, respectively. The lattice constant and cell volume of the ultrafine phosphors decrease with enhancing Yb^3＋ ion concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green and red upconversion emission were observed, and attributed to the ^2H11/2→^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 →^4I15/2 transitions of Er^3＋, respectively. The intensity of red emission increases with increasing Yb^3＋ ion concentration. The effect of Yb^3＋ ion concentration on the structures and upconversion luminescence mechanism were discussed.

关键词： ultrafine phosphor ion concentration urea homogeneous precipitation method upconversion luminescence

Synergistic effect of ozonation and ionizing radiation for PVA decomposition

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Journal of Environmental Sciences 2015年第8期27卷 63-67页

作者： Weihua Sun Lujun Chen yongming zhang Jianlong Wang College of Life and Environmental Sciences Shanghai Normal University School of Environment Tsinghua University Zhejiang Provincial Key Laboratory of Water Science and Technology Laboratory of Environmental Technology INET Tsinghua University

Ozonation and ionizing radiation are both advanced oxidation processes（AOPs） without chemical addition and secondary pollution. Also, the two processes＇ efficiency is determined by different p H conditions, which creates more possibilities for their combination. Importantly,the combined process of ozonation and ionizing radiation could be suitable for treating wastewaters with extreme p H values, i.e., textile wastewater. To find synergistic effects, the combined process of ozonation and ionizing radiation mineralization was investigated for degradation of polyvinyl alcohol（PVA） at different p H levels. A synergistic effect was found at initial p H in the range 3.0–9.4. When the initial p H was 3.0, the combined process of ozonation and ionizing radiation gave a PVA mineralization degree of 17%. This was 2.7 times the sum achieved by the two individual processes, and factors of 2.1 and 1.7 were achieved at initial p H of7.0 and 9.4, respectively. The combined process of ozonation and ionizing radiation was demonstrated to be a feasible strategy for treatment of PVA-containing wastewater.

关键词： PVA Ozonation Ionizing radiation Synergistic effect Mineralization

Critical Transition Reynolds Number for the Incompressible Flat-plate Boundary Layer as Searched by Numerical Simulation

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Advances in Applied Mathematics and Mechanics 2023年第4期15卷 1056-1075页

作者： yongming zhang Di Liu Ning Li Laboratory for High-Speed Aerodynamics Tianjin UniversityTianjin 300072China Department of Mechanics Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin 300072China Research Institute of Petroleum Exploration&Development PetroChinaBeijing 100083China

The critical transition Reynolds number is the lowest value at which the turbulent flow can hold in real *** determination of the critical transition Reynolds number not only is a scientific problem,but also is important for some engineering ***,there is no available theoretical method to search the critical *** the hypersonic boundary layer with significant importance for engineering problems,there is no available experimental method to search the critical value so ***,it is imperative to take numerical method to search *** this paper,direct numerical simulations(DNS)method is employed to determine the critical transition Reynolds number for the incompressible flat-plate boundary ***,under the assumption of parallel flow,the temporal mode DNS is performed to determine the critical value as Re_(xpcr)=43767,which is quite close to the numerical results of other ***,under the condition of nonparallel flow,the spatial mode DNS is performed to determine the critical transition Reynolds number as Re_(xcr)=3×10^(5),which is well consistent with the experimental *** principle,the proposed method in this paper can be extended to the supersonic/hypersonic boundary layer,and that problem will be discussed in the subsequent papers.

关键词： Critical transition Reynolds number flat-plate boundary layer DNS temporal mode spatial mode

Clustering-triggered Emission of Nonaromatic Polymers with Multitype Heteroatoms and Effective Hydrogen Bonding

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Chemical Research in Chinese Universities 2021年第1期37卷 177-182页

作者： KAUSAR Fahmeeda YANG Tianjia ZHAO Zihao zhang yongming YUAN Wang zhang School of Chemistry and Chemical Engineering Frontiers Science Center for Transformative MoleculesShanghai Key Lab of Electrical Insulation and Thermal AgingShanghai Jiao Tong UniversityShanghai200240P.R.China

Nonconventional luminophores without large conjugated structures are attracting increasing attention for their unique aggregation-induced emission(AIE)properties and promising applications in optoelectronic and biomedical *** emission mechanism,however,remains elusive,which makes rational molecular design ***,we proposed the clustering-triggered emission(CTE)mechanism to illustrate the *** clustering of electron-rich nonconventional chromophores withπand/or n electrons and consequent electron cloud overlap is crucial to the ***,based on the CTE mechanism,nonaromatic polymers containing multitype heteroatoms(i.e.,O,N,and S)and involving amide(CONH)and sulfide(-S-)groups were designed and synthesized through facile thiol-ene click *** resulting polymers demonstrated typical concentration-enhanced emission,AIE phenomenon,and excitation-dependent ***,compared with polysulfides,these polymers exhibited much higher solid-state emission efficiencies,because of the incorporation of amide units,which contributed to the formation of emissive clusters with highly rigidified conformations through effective hydrogen ***,distinct persistent cryogenic phosphorescence or even room temperature phosphorescence(RTP)was *** photophysical behaviors can well be rationalized in terms of the CTE mechanism,indicating the feasibility of rational molecular design and luminescence regulation.

关键词： Clustering-triggered emission Aggregation-induced emission Nonaromatic polymer Heteroatom Phosphorescence