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Revisiting the Thermosensitivity of Poly(acrylamide-co-diacetone acrylamide)

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Chinese Journal of Polymer Science 2014年第5期32卷 531-539页

作者： Xin-ming Xing Guang-ming Liu Yan-wei Ding 张广照 Hefei National Laboratory for Physical Sciences at the Microscale Department of Chemical Physics University of Science and Technology of China Faculty of Materials Science and Engineering South China University of Technology

The lower critical solution temperature （LCST） behavior of poly（acrylamide-co-diacetone acrylamide）（poly（AM-co-DAM）） copolymer in aqueous solutions was studied. The results demonstrate the LCST linearly decreases as the molar fraction of DAM （fDAM） increases. In the range of fDAM 〈 0.36, the transmittance increases as fDAM decreases because the more hydrophilic copolymer chains can form looser aggregates with a lower refractive index. The transmittance exhibits a minimum when fDAM is less than 0.28 as the chains form micelle-like structure with a size smaller than the wavelength. The LCST decreases with the initial polymer concentration, but it levels off when the polymer concentration is high enough. Moreover, no hysteresis can be observed in the change of transmittance during the heating-cooling process because no additional hydrogen bonds are formed in the collapsed state due to the steric hindrance of the large side groups in DAM units.

关键词： Thermosensitive Aggregation Hydrogen bonds Steric hindrance Hysteresis.

Experimental study of a controlled variable double-baffle distortion generator engine test rig

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Chinese Journal of Aeronautics 2018年第9期31卷 1880-1893页

作者： Aiguo XIA Xudong HUANG wei TUO ming ZHOU School of Aerospace Engineering Tsinghua University Beijing Aeronautical Technology Research Center

In order to explore the total-pressure distortion test assessment method for a turbofan engine, a Controlled Variable Double-Baffle Distortion Generator(CVDBDG) with a horizontal symmetry moving form was developed, which can adjust the steady-state and time–variant distortion separately in real time. The inlet total-pressure distortion test was conducted on an afterburner turbofan engine. The distortion parameters of CVDBDG and the instability characteristics of the engine were measured. The experimental data were modeled and analyzed by using back propagation artificial neural networks, and the work envelope of CVDBDG was obtained. Based on the analysis of the data on the engine’s instability, the properties of CVDBDG used for the stability assessment were preliminarily evaluated. The results show that CVDBDG can simulate both steady-state and time–variant distortions simultaneously in a range determined by three *** the condition of symmetric double baffles, a critical depth of insertion exists, beyond which the symmetric baffles will generate an asymmetric flow field. In the case of double baffles, compared to a single baffle, the engine exhibited different instability characteristics. Based on CVDBDG, it is expected that more efficient engine stability and durability assessment methods can be developed.

关键词： Distortion generator Engine stability Inlet flow Inlet total-pressure distortion Turbofan engines

Velocity profile of debris flow based on quadratic rheology model

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Journal of Mountain Science 2021年第8期18卷 2120-2129页

作者： DU Cui WU wei-ming MA Chao School of Civil Engineering Henan University of Science and TechnologyLuoyang471000China Department of Civil and Environmental Engineering Clarkson UniversityNew York13699USA School of Soil and Water Conservation Beijing Forestry UniversityBeijing100083China

The quadratic rheology model considers the yield stress,viscous stress,turbulent stress and disperse stress,so it is used in this study to derive the velocity profile of debris *** quadratic model with the parabolic eddy viscosity was numerically solved,and an analytical solution was derived for the quadratic model with a constant eddy *** two solutions were compared with the Arai-Takahashi model that excluded the viscous stress and the yield *** three models were tested by using 17 experiment cases of debris flows over rigid *** results prove that the quadratic model with parabolic and constant eddy viscosities is applicable to muddy and granular flows,whereas the Arai-Takahashi model tends to overestimate the flow velocity near the water surface if a plug-like layer *** addition,the von Karman constant and the zero-velocity elevation in the three models are related to sediment *** von Karman constant decreases first and then increases as the sediment concentration *** zero-velocity elevation is below the bed surface,likely due to the invalidity of the non-slip boundary condition for the debris flows over fixed beds.

关键词： Debris flow Velocity profile Parabolic model von Karman constant

Investigation Into Vibration Characteristic in Vibrothermography

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Photonic Sensors 2019年第2期9卷 108-114页

作者： Yin LI Anbo ming Ruimin ZHANG wei ZHANG Rocket Force University of Engineering Xi'an 710025China High-tech Institute Fan Gong-ting South Street on the 12thQingzhou 262550China

Vibration characteristic plays an important role in vibrothermography, which directly affects the heating during the test. In this work, involving all the contacts in the vibrothermography, the "double-mass-thiree-spring" model is established to explore the vibration characteristic. The obtained results show that ultrasonic gun vibrates at fundamental frequency (FF), while the specimen vibrates at multi-frequencies including FF, 2FF, 3FF, and 4FF, which is validated through experimental investigation results. Additionally, the model proposed in this work reveals a high order harmonics in the vibrothermography test and makes the specimen conduct the steady vibration, which indicates that the model is closer to the practical equipment and can ensure the heating efficiency induced by vibration of specimen to improve the detection capability.

关键词： Vibrothermography vibration characteristic “double-mass-three-spring” model

Carbon aerogels for electric double-layer capacitors

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Rare Metals 2006年第Z1期25卷 51-57页

作者： ZHANG Lin LIU Hongbo WANG ming LIU wei College of Materials Science and Engineering Hunan University Changsha 410082 China College of Materials Science and Engineering Hunan University Changsha 410082 China College of Materials Science and Engineering Hunan University Changsha 410082 China College of Materials Science and Engineering Hunan University Changsha 410082 China

In this study, carbon aerogels were derived via the pyrolysis of resorcinol-formaldehyde (RF) aerogels, which were cost-effectively manufactured from RF wet gels by an ambient drying technique instead of conventional supercritical drying. By varying the R/C ratio (molar ratio of resorcinol to catalyst), mesoporous carbon aerogels with high specific surface area were prepared successfully and further investigated as electrode materials for electric double-layer capacitors (EDLCs). The textural properties of carbon aerogels obtained were characterized by nitrogen adsorption/desorption analysis and SEM. The electrochemical performances of carbon aerogels were investigated by impedance spectroscopy, galvanostatic charge/discharge and cyclic voltammetry methods. The results show that BET surface area and specific capacitance increase with R/C ratio, the maximum values of 727 m2·g-1 and 132 F·g-1 are achieved at R/C ratio will of 300. Increasing R/C ratio increase the average pore size of carbon aerogel electrode, which has improved the rate capability. Furthermore, EDLC with carbon aerogel electrodes has an excellent stability at large discharge current and long cycle life.

关键词： carbon aerogel electric double-layer capacitors texture electrochemical performance

Nickel release rate of 18KW gold alloy for ornaments

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Rare Metals 2013年第1期32卷 33-39页

作者： Jun-Ping Yuan wei Li Wen-ming Liu Department of Materials Science and Engineering Jinan University Jewelry Institute of Guangzhou Panyu Polytechnic

Nickel is widely used as a bleaching element in white gold alloys, but it is a potential allergen. In this paper, a popular 18 KW gold alloy, often called ＂safe nickel,＂ was chosen as the experimental material; its nickel release rates under six different processing conditions were evaluated according to the EN1811 standard. The results reveal that both the surface processing method and heat treatment technology significantly affect the nickel release rate. A coarse surface releases more nickel ions than a smooth surface. The sample normalized at 700 ~C in the single region has a lower nickel release rate than the one treated at 550 ~C in the two-phase phase region, while high temperature normalizing at 800 ~C will accelerate it. All the measured nickel release rates of the experimental material under various processing conditions exceed the permitted threshold value in the Nickel Directive, which indicates that there exists the potential risk of nickel- induced allergy when it is used to make jewelries, espe- cially for piercing types.

关键词： 18 KW Gold alloy Jewelry Nickel releaserate Nickel Directive Processing conditions

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

A novel robust design method for improving stability of optimized structures

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Acta Mechanica Sinica 2015年第1期31卷 104-111页

作者： ming-Jie Cao Hai-Tao Ma Peng wei State Key Laboratory of Subtropical Building Science Department of Civil Engineering South China University of Technology State Key Laboratory of Structural Analysis of Industrial Equipment Dalian University of Technology

It is known that structural optimization may lead to designs of structures having low stability and sometimes even kinematically unstable designs. This paper presents a robust design method for improving the stability of opti mized structures. A new approach is proposed, in which cer tain perturbation loads are introduced and the corresponding compliance is added to the objective function as a penaliza tion. The stability of the optimized structures can thus be improved substantially by considering structural responses to the original and the introduced loads. Numerical exam ples show the simplicity and effectiveness of the proposed method.

关键词： Structural optimization Robust design Penal-ization Perturbation loads

Effect of rare earth samarium addition on the kinetics of precipitation in Al-Cu-Mn casting alloy

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International Journal of Minerals,Metallurgy and Materials 2014年第2期21卷 155-161页

作者： Zhong-wei Chen ming-jun Tang Kai Zhao State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The mechanical properties of Al-Cu-Mn casting alloy mainly depend on the morphology, distribution, size, and number ofθ′（Al2Cu） precipitates. In this study, we have analyzed the effect of rare earth samarium （Sm） addition on the kinetics of precipitation in the Al-Cu-Mn casting alloy by using differential scanning calorimetry （DSC） and high-resolution transmission electron microscopy. Thermal ef-fect peaks that are attributed to the formation and the dissolution of Guinier-Preston （GP） zone andθ′phase were identified from the DSC curves. The activation energy ofθ′formation was calculated by using both the Kissinger method and the analytical model, and the corre-sponding results were compared. Results suggest that the activation energy ofθ′formation in Al-Cu-Mn alloy is dramatically higher than that in Al-Cu-Mn-Sm alloy. Accordingly, it is concluded that the addition of rare earth Sm decreases the activation energy ofθ′formation and promotes the formation ofθ′precipitates.

关键词： aluminum copper alloys rare earth additions samarium precipitation kinetics