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Hua Z.,Hohai University | Yang B.,Hohai University | Chen W.,Beijing Institutive of Technology | Bai X.,Hohai University | And 2 more authors.
Applied Surface Science | Year: 2014

We proposed a robust method for surface-functionalizing magnetic polyvinyl alcohol microspheres to detect heavy metal ions in aqueous solutions. The prepared chemosensor (PAR-MPVA) was characterized through scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectra (XPS). In neutral solutions, PAR-MPVA selectively recognized diatomic heavy metal ions, as indicated with a color change from earth yellow to red; in strong acidic solutions, the chemosensor only selectively detected Cu2+. PAR-MPVA microspheres had a detection limit as low as 0.5 μM by naked-eye and 0.16 μM by UV-vis spectrometer for Cu2+. Moreover, the sensor possessed magnetism for effective recovery, could easily be regenerated by a solution of EDTA, and also displayed perferable stability. The PAR-MPVA microspheres possessed preeminent properties of detecting copper (II) ions in aqueous solutions. © 2014 Elsevier B.V. All rights reserved.

Peng H.,Beijing Institutive of Technology | Peng H.,CAEP - China Academy of Engineering Physics | Li P.,Beijing Institutive of Technology | Li P.,CAEP - China Academy of Engineering Physics | And 4 more authors.
Wuli Xuebao/Acta Physica Sinica | Year: 2014

In this paper, the rate-dependent characteristics of oxygen-free high-purity copper (OFHC) under plate-impact loading is investigated experimentally. The velocity of flyers is measured by magnetic measurement system, and the free surface velocity of targets is measured by Doppler pins system (DPS). Characteristic parameters of free surface velocity are calculated using the measured data. Results show that the spall strength of OFHC is enhanced with the increase in strain rate. It is indicated that the rate from the minima to the spall peak grows slowly at low stain rate, but steeply at high strain rate. The slope as it appears, from the minima to the spall peak is very different as the strain rate increases, The interaction of shock waves in the copper samples is systematically analysed to access the slope characteristics. ©2014 Chinese Physical Society

Bai X.,Hohai University | Bai X.,Tsinghua University | Gu H.,Hohai University | Chen W.,Beijing Institutive of Technology | And 4 more authors.
Applied Biochemistry and Biotechnology | Year: 2014

Poly(vinyl alcohol) (PVA) microspheres were prepared by inverse suspension crosslinked method, with glutaraldehyde as a crosslinking agent. PVA microspheres activated with aldehyde groups were employed for Trametes versicolor laccase immobilization. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the activated PVA microspheres and PVA microspheres with immobilized laccase (Lac/PVA microspheres), which show that laccase was successfully immobilized on the PVA microspheres. The optimum pH and temperature coupling conditions for the immobilized laccase were determined to be 3.3 and 30°C, respectively. Residual activity was also investigated by soaking the immobilized laccase in organic solvents at different concentrations, proving it chemically stable. Immobilized laccase exhibited good storage stability at 4°C. The enzyme biosensor showed good performance in 2,2-azinobis(3-ethylthiazoline-6-sulfonate) and bisphenol A, with concentration ranges of 2 to 8 mM and 0.05 to 0.25 mM, respectively. Therefore, PVA microspheres may have high potential as support for enzyme thermistor applications. © 2014 Springer Science+Business Media.

Zhang H.,Southwest Jiaotong University | Zhu Z.,Southwest Jiaotong University | Zhu Z.,Chinese Academy of Sciences | Ning J.,Beijing Institutive of Technology | And 2 more authors.
Guti Lixue Xuebao/Acta Mechanica Solida Sinica | Year: 2014

Investigation of dynamic behavior of frozen soil is of great importance to artificial ground freezing method in underground engineering, etc. In this article, split Hopkinson pressure bar (SHPB) was employed to investigate the dynamic behavior of artificial frozen soil under uni-axial stress condition. Tests were conducted at the temperature of -3, -8, -13, - 7, -23 and -28°C and strain rates from 300 to 1200 s-1. The stress-strain curves at different conditions were obtained. Result showed that: (1) the uni-axial stress-strain curves of frozen soil show brittle character; (2) the compressive strength of frozen soil shows positive strain-rate and negative temperature sensitivity, and the final strain of frozen soil shows positive strain-rate sensitivity over the range of strain rates and temperature considered; (3) the thermal effect of frozen soil is greater at higher loading strain rates, and the strain rates sensitivity of frozen soil is higher at lower temperature. The viscoelastic damage model mentioned in this article can describe the stress strain relation of frozen soil under dynamic loading.

Gao F.G.,Luoyang Institute of Science and Technology | Hou A.J.,Luoyang Institute of Science and Technology | Yang X.L.,Luoyang Institute of Science and Technology | Yang J.,Beijing Institutive of Technology
Rock Mechanics: Achievements and Ambitions - Proceedings of the 2nd ISRM International Young Scholars' Symposium on Rock Mechanics | Year: 2012

To study the impact properties oflimestone subjected to shock load, stress-time curvesin different impact velocity were measured by one-stage light-gas gun experimental device. The Lagrange analysis method was used to process the stress-time curves, and the distributions of mechanical parameters against time and space in the flow field were obtained, then the stress-strain experimental curves were obtained also. Based on the experimental research and Lagrange analysis, the dynamic constitutive behavior of limestone under shock load was analyzed. At last, a visco-elastic damage constitutive Equation was established by visco-elastic theory and damage evolution of rate type. Numerical fitting indicates that theoretical prediction is good agreement with experiment. © 2012 Taylor & Francis Group.

Ren H.-L.,Beijing Institutive of Technology | Ning J.-G.,Beijing Institutive of Technology | Ma T.-B.,Beijing Institutive of Technology
Engineering Failure Analysis | Year: 2013

Advanced multi-channels acoustic emission (AE) system is used to study the fracture process of alumina material subjected by three-point-bending loading. Using AE counts and AE hits, the location of damage and damage characteristics are discussed. AE energy, AE counts, AE amplitude changing with loading time are analyzed for the notched alumina specimen. It is indicated that AE characteristic parameters reflect the damage process and fracture of material. © 2013 Elsevier Ltd.

Ren H.,Beijing Institutive of Technology | Long B.,Beijing Institutive of Technology | Ning J.,Beijing Institutive of Technology | Chu L.,Beijing Institutive of Technology
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2015

Mechanical properties and toughening mechanisms of three ceramics, 99.5vol% Al2O3 (AD995) ceramic, ZrO2(15vol%)/Al2O3 ceramic and ZrO2(25vol%)/Al2O3 ceramic prepared by hot pressing sintering were investigated by experimental and theoretical research. Based on the micro-mechanics theory of composites, a micromechanical constitution model was developed to describe mechanical properties of ZrO2/Al2O3 considering phase transformation of ZrO2. The results show that the grain size of Al2O3 matrix decreases and densification is improved with addition of ZrO2. The failure of three ceramic specimens show characteristic of small deformation to brittle failure. The compression stress-strain curves show an approximately linear relationship. The fracture toughness of AD995 ceramic is 5.65 MPa·m1/2, while ZrO2(25vol%)/Al2O3 is 8.42 MPa·m1/2, approximately 50% improvement.With toughening phase ZrO2 content increasing, elastic modulus of ZrO2/Al2O3 decreases and fracture toughness increases, which are consistent with experimental results. ©, 2015, Beijing University of Aeronautics and Astronautics (BUAA). All right reserved.

Zhang Z.,Beijing Institutive of Technology | Zhang Z.,Taiyuan University of Science and Technology | Zhao H.,Beijing Institutive of Technology | Yu H.,Beijing Institutive of Technology
Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics | Year: 2011

A light gas gun was used to conduct the dynamic mechanical properties experiments of plain concrete material under three different impact velocities, getting the time-stress curves. Then, numerical calculations were used to simulate concrete's light gas gun experiments, comparing the simulation results with experimental results. In this paper the propagation of wave in flyer and target was formulated. Further analysis shows that concrete material has obvious rate-related properties, lag effect and stress wave's attenuation features, and all of this is closely related to the evolution of internal damage in material. Concrete material finally forms macro fracture under the interaction of compression wave, side release effect and reflected tensile wave of left and right free surface. The size of target in the experiment is reasonable, avoiding the effect of side releasing on the test signals of manganin piezoresistive transducer.

Ren H.-L.,Beijing Institutive of Technology | Guo T.-T.,Beijing Institutive of Technology | Ning J.-G.,Beijing Institutive of Technology
Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics | Year: 2011

A theory model to calculate the target resistance is established to evaluate the ballistic properties; the parameters used in the numerical simulations were determined by simulating the experiment of long rod penetration into alumina ceramic target; the theoretical model is proved to be reasonable by simulating the penetration of shaped charge jet into alumina ceramic. The impact of the geometric size of the shaped charge on the jet velocity and penetration results was studied. It can be concluded that the bigger the angle and the thickness of the shaped charge are, the lower the jet velocity is, and the impact of the thickness on the velocity gradient is severe; the angle of the shaped charge has a significant influence on the penetration depth.

Zhang Z.,Beijing Institutive of Technology | Zhang Z.,Taiyuan University of Science and Technology | Luan G.-B.,Beijing Institutive of Technology | Ning J.-G.,Beijing Institutive of Technology
Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics | Year: 2011

The split Hopkinson pressure bar and light gas gun as the two common means of dynamic loading are widely used in dynamic mechanical characteristics of many materials, while it can not meet the experimental study requirements of the concrete and reinforced concrete because of the small loading samples dimensions. To solve this problem, a simple large-dimension explosive loading assembly, which directly drive the flyer devised cone shape to achieve a large-dimension loading, was presented. Numerical simulation was first used to complete the design optimization of experiment conception. The dynamic process which an explosion drove the flyer was simulated based on ALE and Lagrange coupling methods. Then target range experiments were performed and the flyer flatness was measured by using self-made concentric pins, pulse networks and two oscilloscopes. The improvement was proposed prepared for the finally dynamic experiments of the large-dimension concrete and reinforced concrete samples.

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