A generalized Adadorov theory for anisotropic thin-walled beams

This paper presents a generalized Adadorov theory for anisotropic thin—walled beams. The theory takes account of the shear strain of the middle surface, which exerts a significant influence on the anisotropic thin-walled beams. A new approach is established to solve the governing equations, which have the same form for both open and closed section beams. The numerical examples show that the effects of the shear strain cannot be neglected for this class of beams.This work was part of research project supported by the National Natural Science Foundation of China     

A simple four-node quadrilateral finite element for plates

A simple and accurate four-node quadrilateral finite element based on the Mindlin plate theory and Kirchhoff constraints is presented for general thin plate bending applications. The derivation of the element stiffness properties is straightforward, starting with a specified eight-node interpolation; usual discrete Kirchhoff (DK) constraints are employed to constrain out the four midside nodes of the element. The present resulting DK element passes patch tests with elements of arbitrary and even highly distorted mesh types. Numerical studies of the element convergence behaviours are undertaken for various plate bending problems so far investigated. It is indicated from comparative examples that fairly good convergence characteristics have been achieved.     

Determination of 17 kinds of banned organochlorine pesticides in water by activated carbon fiber-solid phase microextraction coupled with GC-MS.

Activated carbon fiber (ACF) as extraction fiber for solid-phase microextraction (SPME) and its application for the analysis of banned organochlorine pesticides (OCPs) were investigated. Firstly, ACF was activated by different concentration of zinc chloride, which indicated that ACF activated by 60% zinc chloride had a reasonable specific surface area, pore volume and pore distribution. Secondly, the parameters for the ACF-SPME procedure, the adsorption and desorption conditions, were also optimized when coupled with gas chromatography-mass spectrometry (GC-MS). Thirdly, the ACF-SPME was used to analyze 17 kinds of OCPs in water. The linearity of most pesticides was found to be between 0.2 and 50 microg/l with GC-MS under the selected ion monitoring (SIM) acquisition mode. The limits of detection (LOD) at the sub microg/l were obtained. The work demonstrated here shows that ACF is a promising alternative for the SPME procedure.     

Multiple quasi-phase-matching in two-dimensional domain-inverted aperiodic optical superlattice

Quasi-phase-matching (QPM) is an alterative approach for nonlinear optical frequency conversion compared to conventional birefringent method in the bulk crystal. In this Letter, two-dimensional aperiodic optical superlattice (2DAOS) for achieving multi-QPM is proposed. A special optical superlattice structure containing pre-designed values of the reciprocal lattice vector G that can accomplish multi-QPM process is given by using stimulated annealing (SA) algorithm.     

Real-time membrane fusion of giant polymer vesicles

Membrane fusion is very important for the formation of many complex organs in metazoans throughout evolution, such as muscles, bones, and placentae. Lipid vesicles (liposomes) are frequently used as model membranes to study the fusion process. This work demonstrates for the first time the real-time membrane fusion of giant polymer vesicles by directly displaying a series of high-resolution and real-time transformation images of individual vesicles. The fusion process includes the sequential steps of membrane contact, forming the center wall, symmetric expansion of fusion pore and complete fusion, undergoing the intermediates of "8" shape with a protruding rim at the contact site, peanut (pear) shape, and oblate sphere. The vesicle swells during fusion, and the fusing vesicle only deforms in the neck domain around the fusion pore in the lateral direction, which verifies the importance of the lateral tension on the fusion pore at the vesicle deformation level. The successful fusion of the synthetic and protein-free polymer vesicles reported here also supports that vesicle proximity combined with membrane perturbation suffices to induce membrane fusion, and that the protein is not necessary for the fusion process.     

Effect of long-period stacking ordered phase on thermal stability of refined grains in Mg-RE-based alloys

The refined grains in both as-cast Mg-10Y-1Zn-2Zr (WZ101?K, wt.%) and Mg-10Y-1Al (WA101, wt.%) alloys have been found to have superior thermal stability after solution treatment. Plate-shaped, but different polytypes of long-period stacking ordered (LPSO) phases distributed along grain boundaries are considered as the predominant inhibitors of grain growth. Based on the plate-shaped features of the LPSO phases, a modified Zener’s model is established and the predicted limiting grain sizes are in a good agreement with the experimental results. Therefore, this model has strong potential for designing advanced Mg-RE-based alloys with high strength and high creep resistance at high temperatures.     

Realization of optical limiting with a magnetic fluid film

In this paper, optical limiting property in a magnetic fluid film is studied. The relationship between the emergent power and the incident power is investigated experimentally and theoretically. It is found that the limiting threshold is linear with the diaphragm aperture which accord with the theoretical prediction. The external magnetic field will affect the limiting property, and increase the limiting threshold.     

具有特大磁电阻效应钙钛矿材料的制备及性能分析

通过固相烧结法制备了具有特大磁电阻效应的钙钛矿材料Pr0.64Ag0.044MnAl0.2O3.利用结构和成分分析,发现此材料只有在1 100℃高温烧结下才能生成完整的钙钛矿结构,且属于立方晶系,晶格常量a≈0.386 nm.在0.4 T的外磁场下,磁电阻值在122 K处达到最大,约为19.2%,为巨磁电阻实验提供了较好的样品.     

Ablation induced by single-and multiple-femtosecond laser pulses in lithium niobate

We present results on the surface-damage threshold of lithium niobate after single-and multiple-femtosecond laser pulse irradiation at the pulse duration of 80 fs, with a 800-nm wavelength, and a repetition rate of 1 kHz. The surface-ablation threshold was found to decrease significantly with an increase in the pulse number applied to the surface until reaching an almost constant level due to an incubation effect, which is attributed to the laser-induced defect formation. The threshold of lithium niobate under a single shot is found to be 2.82 J/cm², and the threshold fluence for an infinite number of pulses F _th(∞) converges to a common value of 0.52 ± 0.06 J/cm² for N > 80. The results have the potential for application in laser micromachining and the fabrication of related optical devices and applications in frequency conversion by a femtosecond laser in lithium niobate.