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Unicyclic graphs with extremal Lanzhou index

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Applied Mathematics(A Journal of Chinese Universities) 2022年第3期37卷 350-365页

作者： LIU Qian-qian LI Qiu-li zhang He-ping School of Mathematics and Statistics Lanzhou UniversityLanzhou 730000China

Very recently *** et al.[8]introduced a new topological index for a molecular graph G named Lanzhou index as∑_(u∈V(G))d_(u)d^(2)_(u),where d_(u)and d_(u)denote the degree of vertex u in G and in its complement *** index Lz(G)can be expressed as(n-1)M_(1)(G)-f(G),where M_(1)(G)and f(G)denote the first Zagreb index and the forgotten index of G respectively,and n is the number of vertices in *** turns out that Lanzhou index outperforms M_(1)(G)and f(G)in predicting the logarithm of the octanol-water partition coefficient for octane and nonane *** was shown that stars and balanced double stars are the minimal and maximal trees for Lanzhou index *** this paper,we determine the unicyclic graphs and the unicyclic chemical graphs with the minimum and maximum Lanzhou indices separately.

关键词： Lanzhou index unicyclic graph extremal graph Zagreb index forgotten index

Constitutive Modeling of Slip, Twinning and Detwinning for Mg Alloy and Inhomogeneous Evolution of Microstructure

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Acta Mechanica Solida Sinica 2018年第4期31卷 493-511页

作者： Yuan Chen Guijuan Hu Yongting Lan Keshi zhang Ganwei Cai Key Laboratory of Disaster Prevention and Structural Safety Guangxi University Nanning 530004 China School of Vocational and Technical Education Guangxi University of Science and Technology Liuzhou 545006 China School of Mechanical Engineering Guangxi University Nanning 530004 China School of Landscape Architecture Zhejiang A & F University Hangzhou 311300 China

To investigate the relationship between macro-plastic behavior and meso-deformation mechanism of Mg alloy AZ31, the mathematical models for various deformation mechanisms of slip, twinning and detwinning are established, respectively. furthermore, in order to capture the Bauschinger effect under cyclic loading, the back stress is introduced into the three independent deformation mechanisms, respectively. finally, using the above-mentioned model, a new cyclic plastic constitutive model based on the constitutive theory of crystal deformation for magnesium alloy is established. On this basis, the numerical simulation for AZ31 under cyclic loading with the axial strain amplitude of 1.2% is carried out in accordance with the aforementioned crystal plas- ticity theory associated with the representative volume element model. The comparison between the stress-strain curves obtained from the simulation and the experiments shows that the macro- scopic mechanical responses predicted using the proposed model are in good agreement with the experimental results. In particular, the unique characteristics of cyclic macro-plastic behavior observed in the experiments can be satisfactorily captured by the presented crystal plasticity model. At the mesoscale, these features are caused by the alternate occurrence of twinning and detwinning mechanisms. The further analysis of meso-plastic behavior shows that there are het- erogeneous distributions of twinning, stress-strain and stress triaxiality in polycrystal under cyclic loading.

关键词： Cyclic plastic constitutive model Mg alloy AZ31 Detwinning deformation Rep-resentative volume element Back stress

Application of novel force control strategies to enhance robotic abrasive belt grinding quality of aero-engine blades

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Chinese Journal of Aeronautics 2019年第10期32卷 2368-2382页

作者： xiaohu xU Dahu ZHU Haiyang zhang Sijie YAN Han DING State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China Hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of TechnologyWuhan 430070China Hubei Collaborative Innovation Center for Automotive Components Technology Wuhan University of TechnologyWuhan 430074China Wuxi CRRC Times Intelligent Equipment Co. Ltd.Wuxi 214174China

Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and *** surface machining consistency,however,is difficult to be guaranteed in such a *** overcome this problem,a method of hybrid force-position control combined with PI/PD control is proposed to be applied in robotic abrasive belt grinding of complex *** signals are firstly obtained and transformed to force information with signal conditioning ***,zero drift and gravity compensation algorithms are presented to calibrate the f/T transducer which is installed on the robot ***,a force control strategy combining hybrid force-position control with PI/PD control is introduced to be employed in robotic abrasive belt grinding operations where the force control law is applied to the Z direction of the tool frame and the positon control law is used in the x direction of the tool ***,the accuracy of the f/T transducer and the robotic force control system is analyzed to ensure the stability and reliability of force control in the robotic grinding ***,two typical cases on robotic belt grinding of a test workpiece and an aero-engine blade are conducted to validate the practicality and effectiveness of the force control technology proposed.

关键词： Gravity compensation Hybrid force-position control PI/PD control Robotic belt grinding Zero drift compensation

Green synthesis of MnO_x nanostructures and studies of their supercapacitor performance

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Science China Chemistry 2015年第4期58卷 627-633页

作者： Wei Du xiaoqian xu Di zhang Qingyi Lu feng Gao State Key Laboratory of Coordination Chemistry Nanjing National Laboratory of Microstructures Coordination Chemistry Institute School of Chemistry and Chemical Engineering Nanjing University Department of Materials Science and Engineering Nanjing University

Manganese oxides with different crystalline phases and morphologies were prepared by calcining Mn CO3 precursors. The Mn CO3 precursors with different morphologies were obtained through a green route under hydrothermal conditions with orange pericarp extracting solution as the reducing agent. By calcining the precursor under different temperatures and atmospheres, Mn Ox with different stoichiometric ratios(i.e., Mn O, Mn O2, Mn2O3, and Mn3O4) can be obtained. Electrochemical studies reveal that among these manganese oxides, Mn O or Mn O2 are more suitable as supercapacitor working electrodes than Mn2O3 or Mn3O4. They exhibit high specific capacitance up to 296.6 f/g and also possess good cycling stability, which make them potential electrode materials for supercapacitors.

关键词： MnOx nanostructures green synthesis supercapacitor

Numerical Simulation of Interaction Between Tributary Debris flow and Main River

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四川大学学报（工程科学版） 2005年第S1期37卷 75-80页

作者： zhang, Wanshun Cui, Peng Wang, Ying Qiao, fei Wang, xiekang School of Resource and Environmental Sci. Wuhan Univ. Wuhan 430072 China Inst. of Mountain Hazards and Environmental Disaster Chinese Academy of Sciences Chengdu 610041 China State Key Lab. of Hydraulics and Mountain River Eng. Sichuan Univ. Chengdu 610065 China

Based on two-phase flow theory and shallow water flow assumption,a mathematical model is applied to simulate debris *** model considers a two-phase mixture of sediments and water *** that the sediments and the water fluid move downstream with the same velocity,the flow of the mixture is described using a two dimensional depth averaged model with a unique 2-D momentum equation and two mass balance e- quations for the mixture and the sediments,*** finite volume method is used f...

关键词： Debris flow water flow confluence theory numerical simulation

Leading-edge flow separation control over an airfoil using a symmetrical dielectric barrier discharge plasma actuator

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Chinese Journal of Aeronautics 2019年第5期32卷 1190-1203页

作者： xin zhang Huaxing LI Yong HUANG Kun TANG Wanbo WANG School of Aeronautics Northwestern Polytechnical University Low Speed Aerodynamics Institute China Aerodynamics Research and Development Center

In order to promote an in-depth understanding of the mechanism of leading-edge flow separation control over an airfoil using a symmetrical Dielectric Barrier Discharge(DBD) plasma actuator excited by a steady-mode excitation, an experimental investigation of an SC(2)-0714 supercritical airfoil with a symmetrical DBD plasma actuator was performed in a closed chamber and a low-speed wind tunnel. The plasma actuator was mounted at the leading edge of the ***-resolved Particle Image Velocimetry(PIV) results of the near-wall region in quiescent air suggested that the symmetrical DBD plasma actuator could induce some coherent structures in the separated shear layer, and these structures were linked to a dominant frequency of f0= 39 Hz when the peak-to-peak voltage of the plasma actuator was 9.8 kV. In addition, an analysis of flow structures without and with plasma actuation around the upper side of the airfoil at an angle of attack of18° for a wind speed of 3 m/s(Reynolds number Re = 20000) indicated that the dynamic process of leading-edge flow separation control over an airfoil could be divided into three stages. Initially, this plasma actuator could reinforce the shedding vortices in the separated shear layer. Then, these vortical structures could deflect the separated flow towards the wall by promoting the mixing between the outside flow with a high kinetic energy and the flow near the surface. After that, the plasma actuator induced a series of rolling vortices in the vicinity of the suction side of the airfoil, and these vortical structures could transfer momentum from the leading edge of the airfoil to the separated region, resulting in a reattachment of the separated flow around the airfoil.

关键词： Airfoil Dielectric Barrier Discharge(DBD) flow control Particle Image Velocimetry(PIV) Plasma actuator

Crystal structure,chemical bond characteristics,infrared reflection spectrum,and microwave dielectric properties of Nd_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9) ceramics

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Journal of Advanced Ceramics 2023年第1期12卷 82-92页

作者： Jian BAO Yuping zhang Hideo KIMURA Haitao WU Zhenxing YUE School of Environmental and Material Engineering Yantai UniversityYantai 264005China State Key Laboratory of New Ceramics and fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Microwave dielectric ceramics(MWDCs)with low dielectric constant and low dielectric loss are desired in contemporary society,where the communication frequency is developing to high frequency(sub-6G).Herein,Nd_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)(NZ_(1−x)T_(x)M,x=0.02-0.10)ceramics were prepared through a solid-phase *** to x-ray diffraction(xRD)patterns,the ceramics could form a pure crystal structure with the R3c(167)space *** internal parameters affecting the properties of the ceramics were calculated and analyzed by employing Clausius-Mossotti relationship,Shannon’s rule,and Phillips-van Vechten-Levine(P-V-L)***,theoretical dielectric loss of the ceramics was measured and analyzed by a fourier transform infrared(IR)radiation ***,when x=0.08 and sintered at 700℃,optimal microwave dielectric properties of the ceramics were obtained,including a dielectric constant(ε_(r))=10.94,Q·f=82,525 GHz(at 9.62 GHz),and near-zero resonant frequency temperature coefficient(τ_(f))=−12.99 ppm/℃.This study not only obtained an MWDC with excellent properties but also deeply analyzed the effects of Ti^(4+)on the microwave dielectric properties and chemical bond characteristics of Nd_(2)Zr_(3)(MoO_(4))_(9)(NZM),which laid a solid foundation for the development of rare-earth molybdate MWDC system.

关键词： microwave dielectric ceramics(MWDCs) Nd_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)(NZ_(1−x)T_(x)M) Phillips-van Vechten-Levine(P-V-L)theory theoretical dielectric loss

Decomposition process of bastnaesite concentrate in NaOH-CaO-H2O system

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Journal of Rare Earths 2019年第7期37卷 760-766页

作者： Jiang Liu Ting’an zhang Zhihe Dou Yan Liu Guozhi Lv Key Laboratory of Ecological Metallurgy of Multi-Metal Intergrown Ores of Ministry of Education School of Metallurgy Northeastern University

A novel process of calcification-leaching for bastnaesite concentrate(REfCO3) was proposed. The prior calcification was carried out in the system of NaOH-CaO-H2O and the lgC-pH pattern for Ce-f-Ca-C-H2O system was drawn. The thermodynamics result indicates that decomposition for bastnaesite requires certain alkaline condition, but excessive alkalinity also causes decomposition of Caf2. xRD and SEM-EDS analyses on the calcification-leaching process reveal that bastnaesite first decomposes into RE(OH)3 and Caf2. Then, by HCl leaching rare earths were extracted,while Caf2 was left in the leaching residue. In addition, effects of temperature, time, NaOH and CaO on the calcification were investigated. The results show that the leaching rate of rare earths(REs)reaches 72.5 wt%, at the same time 99.2 wt% of f is left in leaching residue with 20 wt% NaOH and 38 wt% CaO at 493 K for 180 min.

关键词： Bastnaesite concentrate Calcification process Thermodynamics fluorine Rare earths

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大语言模型及其在政务领域的应用

清华大学学报（自然科学版） 2024年第4期64卷 649-658页

作者：王昀胡珉塔娜孙海涛郭毅峰周武爱郭昱张皖哲冯建华清华大学计算机科学与技术系北京100084 中移信息系统集成有限公司北京100032 中国人民大学新闻学院北京100872

大语言模型是自然语言处理的核心研究内容之一,已广泛应用于包括政务在内的诸多领域。首先,介绍了统计语言模型、神经网络语言模型等早期语言模型的研究进展;其次,重点综述了大语言模型研究进展;最后,介绍了大语言模型在政务领域的应用... 详细信息

大语言模型是自然语言处理的核心研究内容之一,已广泛应用于包括政务在内的诸多领域。首先,介绍了统计语言模型、神经网络语言模型等早期语言模型的研究进展;其次,重点综述了大语言模型研究进展;最后,介绍了大语言模型在政务领域的应用情况,包括政务文本分类、政务问答、政务命名实体识别、舆情风险识别和政务关系抽取,并提出政务大语言模型研究需要解决的问题,即数据多模态化、正确面对“模型即服务”趋势、注重数据高安全性、明确责任边界。此外,还提出了政务大语言模型研究的技术路径。大语言模型正处于蓬勃发展的阶段,随着中国推动人工智能技术研究及其在政务领域的应用,大语言模型将在政务领域发挥更大作用。

关键词：语言模型自然语言处理人工智能迁移学习数字政府