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Transition prediction for supersonic and hypersonic boundary layers on a cone with angle of attack

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Science china(Physics,mechanics & Astronomy) 2009年第8期52卷 1223-1232页

作者： su caihong1 & {2. heng1,2.1 Department of mechanics,tianjin university,tianjin 300072.china 2.Liu-Hui Center of Applied Mathematics,Nankai university and tianjin university,tianjin 300072.china Department of mechanics Tianjin University Tianjin 300072 China Liu-Hui Center of Applied Mathematics Nankai University and Tianjin University Tianjin 300072 China

Transition prediction for boundary layers has always been one of the urgent problems waiting for a solution for the development of aero-space technology,yet there is no reliable and effective method due to the complexity of the *** eN method has been regarded as an effective method for the transition prediction of boundary ***,it heavily relies on experiment or *** in cases with three-dimensional base flow,for instance,the boundary layer on a cone with angle of attack,the result of its application is not *** authors have found its cause and proposed the method for its improvement,which did yield the fairly satisfactory result for a given test case,and also did not rely so much on experiment or ***,before people can really apply this method to practical problems,more test cases have to be *** this paper,more test cases for the application of the improved eN method to problems of transition prediction of supersonic and hypersonic boundary layers on cones with angle of attack will be *** results are compared with those obtained by experiments and/or direct numerical simulations,confirming that the improved eN method is effective and *** also find that there may be more than one ZARF for each meridian plane,and which one should be chosen for the eN method has been clarified.

关键词： angle of attack cone boundary layer transition eN method

Transition prediction of a hypersonic boundary layer over a cone at small angle of attack——with the improvement of e^N method

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Science china(Physics,mechanics & Astronomy) 2009年第1期52卷 115-123页

作者： su caihong1 & {2. heng1,2.1 Department of mechanics, tianjin university, tianjin 300072, china 2.Liu-Hui Center of Applied Mathematics, Nankai university and tianjin university, tianjin 300072, china 1. Department of mechanics Tianjin University Tianjin 300072 China 2. Liu-Hui Center of Applied Mathematics Nankai University and Tianjin University Tianjin 300072 China

The problem of transition prediction for hypersonic boundary layers over a sharp cone has been studied in this work. The Mach number of the oncoming flow is 6, the cone half-angle is 5°, and the angle of attack is 1°. The conventional e N method is used, but the transition location so obtained is obviously incorrect. The reason is that in the conventional method, only the amplifying waves are taken into account, while in fact, for different meridians the decay processes of the disturbances before they begin to grow are different. Based on our own previous work, new interpretation and essential improvement for the e N method are proposed. Not only the amplification process but also the decay process is considered. The location, where by linear stability theory, the amplitude of disturbance wave is amplified from its initial small value to 1%, is considered to be the transition location. The new result for transition prediction thus obtained is found to be fairly satisfactory. It is also indicated that for the calculation of base flow, boundary layer equations can be used for a small angle of attack. Its computational cost is much smaller than those for DNS.

关键词： angle of attack cone transition eN method

The variation of transition location in response to the variation of the amplitudes of initial disturbances

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Science china(Physics,mechanics & Astronomy) 2010年第6期53卷 1109-1115页

作者： su caihong & {2. heng Department of mechanics,tianjin university,tianjin 300072.china 1. Department of mechanics Tianjin University Tianjin 300072 China

The transition location of a boundary layer depends on the amplitude and characteristic of initial disturbances. The larger the amplitude and the amplification rate of the initial disturbances are,the more upstream the transition location is. However,the environment surrounding the flying vehicle is variable,so the amplitude and characteristic of the disturbances triggered in the boundary layer through receptivity are also variable. In this paper,how the transition location varies in response to the variation of the initial disturbance amplitudes is studied by using direct numerical simulation. The results show that if the initial disturbance amplitudes become smaller,the transition location moves downstream correspondingly,but there is a time delay compared to the time of arrival of the disturbances with reduced amplitudes. Moreover,the speed of moving downstream is appreciably lower than the propagation speed of the disturbances. On the other hand,if the amplitudes of the initial disturbances recover their original value,the transition would immediately take place whenever the disturbances reach the former transition location,but the laminar flow between the new and old transition locations would not become turbulent immediately. Theoretical explanations are provided based on the transition mechanism found by our group.

关键词： transition boundary layer stability modification of mean flow direct numerical simulation

Generating non-jumps from a known one

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Science china Mathematics 2024年

作者： Jianfeng Hou heng Li caihong Yang Yixiao Zhang Center for Discrete Mathematics Fuzhou University

Let r≥2.be an integer. The real number α∈[0, 1) is a jump for r if there exists a constant c> 0 such that for any ε> 0 and any integer m≥r, there exists an integer n0（ε, m） satisfying any r-uniform graph with n≥n0（ε, m） vertices and density at least α+εcontains a subgraph with m vertices and density at least α+c. A result of Erd?s and Simonovits （1966） and Erd?s and Stone （1946） implies that every α∈[0, 1) is a jump for r=2. Erd?s （1964） asked whether the same is true for r≥3. Frankl and R?dl （1984） gave a negative answer by showing that 1-1/（lr-1） is not a jump for r if r≥3 and l> 2.. After that, more non-jumps are foundlr-1is not a juby using a method of Frankl and R?dl （1984）. Motivated by an idea of Liu and Pikhurko （2.2.）, in this paper,we show a method to construct maps f:[0, 1)→[0, 1) that preserve non-jumps, i.e., if α is a non-jump for r given by the method of Frankl and R?dl （1984）, then f （α） is also a non-jump for r. We use these maps to study hypergraph Tura′n densities and answer a question posed by Grosu （2.16）.

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Amorphous Sb/C composite with isotropic expansion property as an ultra-stable and high-rate anode for lithium-ion batteries

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Rare Metals 2024年第5期43卷 2039-2052页

作者： Ze-zhou Yang Cheng-Yi Zhang Yu-Qing Ou Zhi-Kang {2. Yan Zhao heng-Jiang Cong Xin-Ping Ai Jiang-Feng Qian Hubei Key Laboratory of Electrochemical Power Sources College of Chemistry and Molecular SciencesWuhan UniversityWuhan430072China Institute of Technological Sciences Wuhan UniversityWuhan 430072China

Antimony(Sb)is an intriguing anode material for Li-ion batteries(LIBs)owing to its high theoretical capacity of 660 m Ah·g^(-1)and appropriate working potential of~0.8 V(***^(+)/Li).However,just like all alloying materials,the Sb anode suffers from huge volume expansion(2.0%)during repeated insertion/extraction of Li+ions,resulting in structural deterioration and rapid capacity *** this work,a novel amorphous Sb/C composite with atomically dispersed Sb particles in carbon matrix is prepared via a straightforward high-energy ball milling *** intimate intermixing of amorphous Sb with C provides homogeneous element distribution and isotropic volume expansion during cycling,resulting in persistent structural ***,the disordered structure of amorphous material shortens the diffusion distance of lithium ions/electrons,promoting fast reaction kinetics and rate *** from the aforementioned effects,the amorphous Sb/C exhibits a high reversible capacity of537.4 m Ah·g^(-1)at 0.1 A·g^(-1)and retains 2.1.0 m Ah·g^(-1)at an ultrahigh current rate of 10.0 A·g^(-1).Even after 1500deep cycles at 2.0 A·g^(-1),the amorphous Sb/C electrode still maintains 86.3%of its initial capacity,which outperforms all existing Sb-based anodes reported so *** analysis further reveals a greatly reduced volume variation of merely 34.6%for the amorphous Sb/C electrode,much lower than that of 2.3.1%for crystalline Sb *** study presents a new approach to stabilizing Sb-based alloy anodes and contributes to the construction of high-performance amorphous anode materials for LIBs,enabling advanced energy storage.

关键词： Amorphous Sb/C anode Homogeneous element distribution Isotropic volume expansion Ultra-long cycle stability High-rate capability Lithium-ion battery

Synergistic Effect of Nitrogen/Phosphorus Co-Doping and Molybdenum Carbide Induced Electron Redistribution of Carbon Layer to Boost Hydrogen Evolution Reaction

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Chinese Journal of Chemistry 2024年第1期42卷 55-60页

作者： Jiamin Xiao Peng Li Yanyan sun heng Liu Javid Khan Handong Zhang Han {2. Yaqiong su Shuangyin Wang Lei Han College of Materials Science and Engineering Hunan Joint International Laboratory of Advanced Materials and Technology for Clean EnergyHunan UniversityChangshaHunan 410082China School of Chemistry Engineering Research Center of Energy Storage Materials and Devices Ministry of EducationXi'an Key Laboratory of Sustainable Energy Materials ChemistryState Key Laboratory of Electrical Insulation and Power EquipmentXi'an Jiaotong UniversityXi'anShaanxi 710049China School of Materials Science and Engineering Central South UniversityChangshaHunan 410083China state Key Laboratory of Chem/Bio-Sensingand Chemometrics College of Chemistry and Chemical EngineeringHunan University ChangshaHunan 410082China Laboratory of Inorganic Materials and Catalysis Department of Chemical Engineering and ChemistryEindhoven University of Technology P.O.Box5135600 MB EindhovenThe Netherlands

The development of highly efficient non-precious-metal-based electrocatalysts for the hydrogen evolution reaction is imperative for promoting the large-scale application of electrochemical water ***,nitrogen/phosphorus co-doped carbon nanorods encapsulated Mo_(2.C nanoparticles(Mo_(2.C@PNc)have been prepared by pre-phosphating treatment in combination of the coordination with polydopamine and the subsequent *** phosphating temperature has a significant effect on the content of phosphorus within the resultant Mo_(2.C@PNC,and the optimal catalyst delivers superior HER activity with the low overpotential of 104 mV at a current density of 10 mAcm^(-2. and good stability for 8 h,which has been theoretically demonstrated to originate from the synergistic effect between P doping and Mo_(2.C induced electron redistribution of nitrogen-doped carbon layer.

关键词： Molybdenum carbide N/P co-doped carbon Hydrogen evolution Synergistic effect Electron redistribution Comprehensive

Extraction,chemical components,bioactive functions and adulteration identification of walnut oils:A review

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Grain & Oil Science and Technology 2024年第1期7卷 30-41页

作者： Yuan Gao Jia Hu Xia su Qi Li caihong su Yongling Li Gaiqin Ma Siyu Zhang Xiuzhu Yu Engineering Research Center of Grain and Oil Functionalized Processing College of Food Science and EngineeringNorthwest A&F UniversityShaanxi 712100China Animal Products and Animal Medicine Feed Quality Inspection Center Hebei 050041China

Walnut oil is a functional wood oil known to researchers that may potentially be a large source of Chinese edible *** are various extraction methods for walnut oil,including traditional(pressing,solvent-and enzymeassisted extraction)and novel methods(microwave,ultrasound,supercritical CO_(2.,subcritical and other extraction technologies).Walnut oil is rich in nutrients,including phytosterols,tocopherols,polyphenols,squalene and *** provides many health benefits,such as antioxidant,antitumor,anti-inflammatory,antidiabetic and lipid metabolism-related *** addition,the authentication of walnut oil has received much research *** present review provides detailed research on walnut oil extraction,composition,health benefits and adulteration identification *** path toward further walnut oil improvement in the context of the market value of walnut oil is also discussed.

关键词： Extraction technology Chemical composition Bioactive Authentication

Calculation of Mass Concrete Temperature and Creep Stress under the Influence of Local Air Heat Transfer

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Computer Modeling in Engineering & Sciences 2024年第9期140卷 2977-3000页

作者： heng Zhang Chao su Xiaohu Chen Zhizhong Song Weijie Zhan Academy of Science and Technology Changjiang Institute of Survey Planning Design and ResearchWuhan430010China College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210098China Chief Engineer Office Wujiang Company of Goupitan Power Construction CooperationYuqing564408China

Temperature-induced cracking during the construction of mass concrete is a significant *** simulations of concrete temperature have primarily assumed that the concrete is placed in an open *** problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation ***,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it *** accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through ***,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep *** results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete *** with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/*** results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/***,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.

关键词： Conjugate heat transfer temperature field mass concrete creep stress

Preparation of maximally-entangled states with multiple cat-state qutrits in circuit QED

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Frontiers of physics 2024年第3期19卷 239-251页

作者： Chui-Ping Yang Jia-heng Ni Liang Bin Yu Zhang Yang Yu Qi-Ping su Department of Physics Hangzhou Normal UniversityHangzhou 311121China School of Physics Nanjing UniversityNanjing 210093China Institute for Quantum Science and Technology University of CalgaryAlberta T2N 1N4Canada

In recent years,cat-state encoding and high-dimensional entanglement have attracted much ***,previous works are limited to generation of entangled states of cat-state qubits(two-dimensional entanglement with cat-state encoding),while how to prepare entangled states of cat-state qutrits or qudits(high-dimensional entanglement with cat-state encoding)has not been *** here propose to generate a maximally-entangled state of multiple cat-state qutrits(three-dimensional entanglement by cat-state encoding)in circuit *** entangled state is prepared with multiple microwave cavities coupled to a superconducting flux ququart(a four-level quantum system).This proposal operates essentially by the cavity-qutrit dispersive *** circuit hardware resource is minimized because only a coupler ququart is *** higher intermediate level of the ququart is occupied only for a short time,thereby decoherence from this level is greatly suppressed during the state ***,the state preparation time does not depend on the number of the qutrits,thus it does not increase with the number of the *** an example,our numerical simulations demonstrate that,with the present circuit QED technology,the high-fidelity preparation is feasible for a maximally-entangled state of two cat-state ***,we numerically analyze the effect of the inter-cavity crosstalk on the scalability of this *** proposal is universal and can be extended to accomplish the same task with multiple microwave or optical cavities coupled to a natural or artificial four-level atom.

关键词： maximally-entangled states cat state qutrit circuit QED