超弹性膜的等轴拉伸试验方法及仿真

提出了一种针对超弹性膜材料的等轴对称拉伸试验装置,介绍了等轴拉伸试验的原理和方法,并对等轴拉伸试验条件及数据处理进行了分析,最后运用有限元软件ABAQUS对等轴理想拉伸、边角拉伸点不固定的自由拉伸、边角点固定的等轴拉伸3种等轴拉伸方法进行仿真.结果表明,边角点固定的等轴拉伸方法在较大拉伸试验范围内的误差较小,可以满足材...     

喷雾干燥-碳热还原法制备介孔球形LiFePO4/C正极材料

以聚乙二醇(PEG)为辅助模板剂和碳源,以廉价的三价铁为铁源,采用喷雾干燥-碳热还原法制备了LiFePO4/C正极材料,并对该材料的微观结构及PEG添加量、焙烧温度等对材料结构和性能的影响进行了表征和研究.结果表明:制得的LiFePO4/C材料呈介孔结构,具有漂亮的差级球状形貌、高的比表面积和容量、优异的循环性;PEG...     

基于GMM和MRF的自适应阴影检测

运动目标阴影在很大程度上会影响运动目标跟踪、行为识别的正确性和有效性.为此,文中提出了一种基于混合高斯模型和马尔科夫随机场的自适应阴影检测方法.该方法首先对混合高斯模型进行改进,使其可以自适应调整参数学习率以消除浅阴影;然后采用马尔科夫随机场综合邻域的空间依赖性信息进行精确的阴影检测.为了提高基于马尔科夫随机场的阴影检...     

斜入射激光脉冲与稠密等离子体相互作用产生的阿秒脉冲

利用一维粒子模拟程序研究和比较了斜入射和垂直入射激光脉冲与稠密等离子体相互作用得到的阿秒脉冲以及激光强度对阿秒脉冲转换比率的影响.同样参数下,斜入射的阿秒脉冲转换比率明显高于垂直入射的情况,滤波后得到的阿秒脉冲振幅比较大,而脉冲串中阿秒脉冲的个数则是垂直入射时的一半.根据振荡镜面模型对两种情况进行了分析,由镜面振荡方程可以对结果给出解释.保持等离子体密度不变,增大入射激光强度时,随着滤波次数的增加,斜入射与垂直入射的阿秒脉冲的转换比率逐渐趋于相同.300次以上高通滤波后我们得到了处于X射线范围的阿秒脉冲.     

Erratum to: <Emphasis Type="Italic">In vitro</Emphasis> induction of mouse meningeal-derived iPS cells into neural-like cells

The authors report that incorrect figures were included as Figures 4 and 5 in the original publication of this paper. This error occurred during the figure editing process of the publishing company. This information should have been presented as follows:     

Serine/threonine protein phosphatases in DNA damage response

DNA damage response (DDR) is among the most important of the mechanisms that maintain genome stability which, when destabilized, predisposes organs to cancer. Reversible phosphorylation mediated by protein kinases and protein phosphatases regulates most, if not all, cellular activities, including DDR. Protein kinase inhibitors have become the main focus of targeted therapy and anticancer drug development. However, our limited knowledge of protein phosphatase function is compromising our capacity to develop therapeutic agents against phosphatases. In this review, we summarize the roles of serine/threonine protein phosphatases involved in DDR and propose that in situ dephosphorylation of phosphoproteins by protein phosphatases, instead of proteasome-mediated degradation of phosphoproteins, is mainly employed by cells.     

Aero-optical wavefront measurement technique based on BOS and its applications

A collimated light beam will be refracted if it propagates through a flow-field with index-of-refraction variations,and its wavefront will be distorted.If we measure the deflection angle of the light beam,the gradient of the wavefront can be obtained using the Malus law,and the wavefront aberration can be computed with a reconstruction algorithm.Two characteristics of background oriented schlieren(BOS) are conducive to wavefront aberration measurement:BOS can be used to measure the deflection angle of a light beam by measuring the displacement field between the reference image and the experiment image.Moreover,in a BOS system of Schlieren mode,only the ray perpendicular to the background image can be captured with a camera.This is helpful to measure wavefront aberrations that occur after a planar wavefront has passed through the flow-field.Based on these characteristics of BOS of Schlieren mode,a new wavefront measurement technique,which is called the BOS-based wavefront technique(BOS-WT),is proposed in this paper.It works by constructing the relationship between the displacement of the background image and the aero-optical wavefront gradient and uses the Southwell wavefront reconstruction algorithm.A BOS-WT system was assembled,and its temporal resolution was found to be 6 ns,and its temporal-correlation resolution reached 0.2 μs.A BOS-WT can measure the time-correlation transient wavefront quantitatively.It is simple and easy to operate.In this paper,we also present a study of the aero-optical performance of supersonic mixing layer based on our BOS-WT transient wavefronts at an interval of 5 μs.The results showed the wavefront was transient and distorted after it had passed through the mixing layer.Through the analysis of the data at the 5 μs interval,the temporal evolution of wavefront can be obtained.     

Parametric effects on the combustion flow field of a typical strut-based scramjet combustor

The flame-holding mechanism in hypersonic propulsion technology is the most important factor in prolonging the duration time of hypersonic vehicles.The two-dimensional coupled implicit Reynolds-averaged Navier-Stokes equations,the shear-stress transport k-ω turbulence model and the finite-rate/eddy-dissipation reaction models were used to simulate the combustion flow field of a typical strut-based scramjet combustor.We investigated the effects of the hydrogen-air reaction mechanism and fuel injection temperature and pressure on the parametric distributions in the combustor.The numerical results show qualitative agreement with the experimental data.The hydrogen-air reaction mechanism makes only a slight difference in parametric distributions along the walls of the combustor,and the expansion waves and shock waves exist in the combustor simultaneously.Furthermore,the expansion wave is formed ahead of the shock wave.A transition occurs from the shock wave to the normal shock wave when the injection pressure or temperature increases,and the reaction zone becomes broader.When the injection pressure and temperature both increase,the waves are pushed out of the combustor with subsonic flows.When the waves are generated ahead of the strut,the separation zone is formed in double near the walls of the combustor because of the interaction of the shock wave and the boundary layer.The separation zone becomes smaller and disappears with the disappearance of the shock wave.Because of the horizontal fuel injection,the vorticity is generated near the base face of the strut,and this region is the main origin for turbulent combustion.     

Entransy dissipation minimization for optimization of heat exchanger design

In this paper,by taking the water-water balanced counterflow heat exchanger as an example,the entransy dissipation theory is applied to optimizing the design of heat exchangers.Under certain conditions,the optimal duct aspect ratio is determined analytically.When the heat transfer area or the duct volume is fixed,analytical expressions of the optimal mass velocity and the minimal entransy dissipation rate are obtained.These results show that to reduce the irreversible dissipation in heat exchangers,the heat exchange area should be enlarged as much as possible,while the mass velocity should be reduced as low as possible.     

Investigation of an energy nonadditivity for nonextensive systems

We investigate the energy nonadditivity relationship E(AαB) = E(A) + E(B) + αE(A)E(B) which is often considered in the development of the statistical physics of nonextensive systems. It was recently found that α in this equation was not constant for a given system in a given situation and could not characterize nonextensivity for that system. In this work, we select several typical nonextensive systems and compute the behavior of α when a system changes its size or is divided into subsystems in different fashions. Three kinds of interactions are considered. It is found by a thought experiment that α depends on the system size and the interaction as expected and on the way we divide the system. However, one of the major results of this work is that, for given system, α has a minimum with respect to division position. Around this position, there is a zone in which α is more or less constant, a situation where the sizes of the subsystems are comparable. The width of this zone depends on the interaction and on the system size. We conclude that if α is considered approximately constant in this zone, the two mathematical difficulties raised in previous studies are solved, meaning that the nonadditive relationship can characterize the nonadditivity of the system as an approximation. In all the cases, α tends to zero in the thermodynamic limit (N→∞) as expected.