检索结果-南通市图书馆

Chinese Chemical Letters 2010年第8期21卷 931-934页

作者： Hong Sheng li Yi qun li Department of Chemistry Jinan UniversityGuangzhou 510632China

In the presence of diethyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate（DHP） and a catalytic amount of potassium iodide,severalα-halo ketones were easily reduced to the corresponding ketones in acetone *** procedure presented here showed several merits such as short reaction time,practical experimental and isolated procedure,and excellent yields of products.

关键词： Dehalogenation α-Halo ketones Hantzsch ester 1 4-Dihydro-2 6-dimethylpyridine-3 5-dicarboxylate Potassium iodide

Structures of sodium vanadate solution under different conditions

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2018年第1期37卷 59-65页

作者： Ya-li Zhang li-qun Yang Xian-Jin Yu School of Chemical Engineering Shandong University of Technology

Combined with Fourier transform infrared spectroscopy（FTIR） analysis of sodium vanadate solution,the relationship between conductivity and structure was investigated by measuring the electric conductivity of the solution under different alkali concentrations and molar ratios of NaOH to V2O5. Results suggest that the polymerization vanadium acid radical ions gradually transform into monomer with the solution diluting. When the solution is diluted to a certain extent,only the vanadium acid radical ion with V-OH chemical bond exists in the solution. At NaOH concentration of below 105.21 g·L^（-1）,the vanadate anions mainly exist in the form of vanadium acid radical ion with V-OH chemical bond and the ion transference number is approximately from 0.58 to 0.82. In the medium NaOH concentration range of 105.21-117.03 g·L^（-1）, the vanadate anions mostly exist in the form of vanadium acid radical ion with V-OH and V-O-V chemical bonds and the ion transference number is approximately 3.29. At NaOH concentration of above 117.03 g·L^（-1）, vanadate anions exist in the form of vanadium acid radical ion with V-OH and V-O-V chemical bonds.

关键词： Sodium vanadate solution Electric conductivity Migration number Infrared spectroscopy

CHAOS IN PERTURBED PLANAR NON-HAMILTONIAN INTEGRABLE SYSTEMS WITH SLOWLY-VARYINGANGLE PARAMETERS

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2001年第11期22卷 1301-1305页

作者： CHEN li-qun(陈立群) Shanghai Institute of Applied Mathematics and Mechanics Shanghai 200072 P R China

The Melnikov method was extended to perturbed planar non-Hamiltonian integrable systems with slowly-varying angle parameters. Based on the analysis of the geometric structure of unperturbed systems, the condition of transversely homoclinic intersection was established. The generalized Melnikov function of the perturbed system was presented by applying the theorem on the differentiability of ordinary differential equation solutions with respect to parameters. Chaos may occur in the system if the generalized Melnikov function has simple zeros.

关键词： Melnikov method perturbed integrable system transversely homoclinic chaos

Electrochemical Behavior of Oxide Films of Stainless Steel in 40 kHz Sonicated Sulphate Electrolytes

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2007年第2期20卷 148-152页

作者： ZHU li-qun li Min-wei WANG Hui School of Materials Science and Engineering Beij＇ing University of Aeronautics and Astronautics Beijing 100083 China Shenyang liming Aero-Engine Group Corporation Shenyang 110043 China

This paper describes effects of 40 kHz ultrasound on the oxide films of stainless steel in sulphate electrolytes so as to determine the transmitted power and to characterize mass transfer and peak current density on the electrode surface. Emphasis was mainly laid on electrochemical oxidations and peeling mechanism of oxide films in sonicated sulphate solutions （0.5 and 1.0 mol/L）. Polarization voltammetry, current response traces and SEM analysis were carded out in order to provide full information as to oxide films surface. Results shows that the rate of electrochemical oxidation, the shape of polarization curves and the surface micrographs in sonicated sulphate electrolytes are different from those obtained without introduction of ultrasound. It is concluded that ultrasound can change the electro-chemical behavior of oxide films by its cavitaion effects, which would produce transient mechanical impulsive force and enhance electrochemical reactions.

关键词： stainless steel oxide films electrolysis ultrasound cavitation

Icosahedral quasicrystal structure of the Mg_(40)Zn_(55)Nd_(5) phase and its thermodynamic stability

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2022年第8期29卷 1543-1550页

作者： Shuai Zhang Qianqian li Hongcan Chen qun Luo Qian li State Key Laboratory of Advanced Special Steels Shanghai Key Laboratory of Advanced FerrometallurgySchool of Materials Science and EngineeringShanghai UniversityShanghai 200444China Materials Genome Institute Shanghai UniversityShanghai 200444China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China

The quasicrystal phase is beneficial to increasing the strength of magnesium ***,its complicated structure and unclear phase relations impede the design of alloys with good mechanical *** this paper,the Mg_(40)Zn_(55)Nd_(5) icosahedral quasicrystal(I-phase)structure is discovered in an as-cast Mg-58Zn-4Nd alloy by atomic resolution high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).A cloud-like morphology is observed with Mg_(41.6)Zn_(55.0)Nd_(3.4) *** selected area electronic diffrac-tion(SAED)analysis shows that the icosahedral quasicrystal structure has 5-fold,4-fold,3-fold,and 2-fold symmetry zone *** thermo-dynamic stability of the icosahedral quasicrystal is investigated by differential scanning calorimetry(DSC)in the annealed *** an-nealed above 300℃,the Mg_(40)Zn_(55)Nd_(5) quasicrystal is found to decompose into a stable ternary phase Mg_(35)Zn_(60)Nd_(5),a binary phase MgZn,andα-Mg,suggesting that the quasicrystal is a metastable phase in the Mg-Zn-Nd system.

关键词： icosahedral quasicrystal crystal structure thermodynamic stability Mg-Zn-Nd alloys

Dynamic response to a moving load of a Timoshenko beam resting on a nonlinear viscoelastic foundation

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2013年第5期29卷 718-727页

作者： Yan Yang Hu Ding li-qun Chen Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringShanghai University Department of Mechanics Shanghai University

The present paper investigates the dynamic response of finite Timoshenko beams resting on a sixparameter foundation subjected to a moving load. It is for the first time that the Galerkin method and its convergence are studied for the response of a Timoshenko beam supported by a nonlinear foundation. The nonlinear Pasternak foundation is assumed to be cubic. Therefore, the effects of the shear deformable beams and the shear deformation of foundations are considered at the same time. The Galerkin method is utilized for discretizing the nonlinear partial dif- ferential governing equations of the forced vibration. The dynamic responses of Timoshenko beams are determined via the fourth-order Runge-Kutta method. Moreover, the effects of different truncation terms on the dynamic responses of a Timoshenko beam resting on a complex foundation are discussed. The numerical investigations shows that the dynamic response of Timoshenko beams supported by elastic foundations needs super high-order modes. Furthermore, the system parameters are compared to determine the dependence of the convergences of the Galerkin method.

关键词： Nonlinear Timoshenko beam Pasternak foun- dation Galerkin method Convergence

The Effect of Internal Delamination Damage on the Tensile Strength of Aeronautical Composites

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2022年第6期35卷 979-986页

作者： Qiang Wang Qiuyu Chen Yujie Chen Jiandong li qun li School of Equipment Management and Unmanned Aerial Vehicle Engineering Air Force Engineering UniversityXi’an710051China State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an710049China School of Air and Missile Defence Air Force Engineering UniversityXi’an710051China

For aeronautical composite materials,the appearance of internal delamination has a fatal impact on their mechanical properties and may even seriously threaten aircraft flight *** this study,the effect of internal delamination damage with different sizes and depths on the tensile strength of aeronautical composites was ***,based on carbon-fiber-reinforced composites commonly used in aircraft,laminate specimens with internal delamination damages of different depths and diameters were fabricated,and tensile tests of composite materials were carried ***,the finite element model for the carbon-fiber-reinforced laminate specimens was established,and the validity of the model was verified by comparing its simulation results with the experimental ***,by changing the geometric parameters of the internal delamination damage model,the influence of delamination damage on the tensile strength of carbon-fiber-reinforced composites was analyzed and *** results show that,on the one hand,for the internal delamination damages of the same area,the closer is the delamination damage to the surface layer,the lower is the tensile *** particular,the closer is the delamination damage to the surface layer,the greater is the decrease in tensile strength,which exhibits an obvious nonlinear *** the other hand,for the internal delamination defects of the same depth,the difference in delamination area has little effect on the tensile *** law provides a reference for the damage detection and maintenance focus of aeronautical composite structures,which is of great significance to ensure the safe use of aeronautical composites.

关键词： Aeronautical composites Carbon fiber laminate Delamination damage Tensile strength Finite element simulation

Multifunctional Clay/PNIPAM Hydrogel Incorporating HxMoO3 Plasmonic Quantum Dot

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Energy & Environmental Materials 2020年第2期3卷 192-201页

作者： Hao li Youzeng li qun Xu Ali Zhang College of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450052China School of Materials Science and Engineering Dalian University of TechnologyDalian 116000China

Functional hydrogel is becoming a frequently used material in various fields,especially in biological and medical *** order to overcome the barriers of low uniformity of structure and lack of energy dissipation effect in common hydrogel,in this work a strategy of doping plasmonic HxMoO3 quantum dots into PNIPAM(poly(N-isopropylacrylamide)) hydrogel to proceed its multifunctionalization is *** quantum dots-induced tactic could effectuate the enhancement of photothermal conversion,mechanical property,adhesion,and self-healing performance *** particular,for adhesion performance,the toughness value could be elevated to over 2500 J m-2 ***,the enhancement mechanism behind the extraordinary adhesion performance is studied,and it can be contributed to the synergistic effect of pore structure regulation and abundant hydrogen bond,which are both beneficial to the interaction between composite hydrogel and solid ***,based on its extraordinary adhesion and self-healing performance,the applicability of HxMoO3/PNIPAM hydrogel as a M? growth substrate is investigated on wound dressing,and the experimental result demonstrates its excellent M? growth-promoting activity.

关键词： biological application multifunctionalization plasmonic quantum dots ultraadhesive hydrogel

Data-driven active vibration control for helicopter with trailing-edge flaps using adaptive dynamic programming

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第6期37卷 151-166页

作者： Yu CHEN qun ZONG Xiuyun ZHANG Jinna li School of Electrical and Information Engineering Tianjin UniversityTianjin 300072China School of Information and Control Engineering Liaoning Petrochemical UniversityFushun 113001China

The helicopter Trailing-Edge Flaps(TEFs)technology is one of the recent hot topics in morphing wing *** employing controlled deflection,TEFs can effectively reduce the vibration level of ***,designing specific vibration reduction control methods for the helicopters equipped with trailing-edge flaps is of significant practical *** paper studies the optimal control problem for helicopter-vibration systems with TEFs under the framework of adaptive dynamic programming combined with Reinforcement Learning(RL).Time-delay and disturbances,caused by complexity of helicopter dynamics,inevitably deteriorate the control performance of vibration *** solve this problem,a zero-sum game formulation with a linear quadratic form for reducing vibration of helicopter systems is presented with a virtual *** this context,an off-policy reinforcement learning algorithm is developed to determine the optimal control *** algorithm utilizes only vertical vibration load data to achieve a policy that reduces vibration,attains Nash equilibrium,and addresses disturbances while compensating for time-delay without knowledge of the dynamics of the helicopter *** effectiveness of the proposed method is demonstrated in a virtual platform.

关键词： Active control Adaptive dynamic program-ming Helicopter rotor Vibration control Zero-sum game

Regression Analysis of Doubly Censored Data with a Cured Subgroup under a Class of Promotion Time Cure Models

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2021年第6期37卷 835-853页

作者： Min CAI li qun XIAO Shu Wei li School of Economics and Statistics Guangzhou UniversityGuangzhou 510006P.R.China

In some situations,the failure time of interest is defined as the gap time between two related events and the observations on both event times can suffer either right or interval *** data are usually referred to as doubly censored data and frequently encountered in many clinical and observational ***,there may also exist a cured subgroup in the whole population,which means that not every individual under study will experience the failure time of interest *** this paper,we consider regression analysis of doubly censored data with a cured subgroup under a wide class of flexible transformation cure ***,we consider marginal likelihood estimation and develop a two-step approach by combining the multiple imputation and a new expectation-maximization(EM)algorithm for its *** resulting estimators are shown to be consistent and asymptotically *** finite sample performance of the proposed method is investigated through simulation *** proposed method is also applied to a real dataset arising from an AIDS cohort study for illustration.

关键词： Doubly censored data marginal likelihood EM algorithm multiple imputation transformation cure models