超音速来流中爆轰波衍射和二次起爆过程研究

预爆管技术被广泛地应用在爆轰波发动机的起爆过程中,但是在超音速来流中基于预爆管技术起始爆轰波的研究并未被广泛地开展。基于此,本文中数值研究了横向超音速来流对半自由空间内爆轰波的衍射和自发二次起爆、及管道内的衍射和壁面反射二次起爆两种现象的影响。数值模拟的控制方程为二维欧拉方程,空间上使用五阶WENO格式进行数值离散,采用带有诱导步的两步链分支化学反应模型。所模拟的爆轰波具有规则的胞格结构,对应于用惰性气体高度稀释过的可爆混合物中形成的爆轰波。结果表明:在半自由空间内,在本文所模拟的几何尺寸下,爆轰波并未成功发生二次起爆现象,但是爆轰波的自持传播距离随着横向超音速来流强度的增强而增加。在核心的三角形流动区域外,波面诱导产生了更多的横波结构;在管道内,横向的超音速来流在逆流侧对出口气流产生了压缩作用,能有效提高波面压力,因此反射后的激波压力也比较高。在同样的几何尺寸下,爆轰波在静止和超音速(Ma=2.0)气流中分别出现了二次起爆失败和成功两种现象,这是由于在超音速来流中化学反应面的褶皱诱导产生了横波结构,横波与管壁以及其他横波之间的碰撞提高了前导激波的强度,并最终促进了爆轰波在超声速流主管道内的成功起始。     

电子顺磁共振现场研究多孔电极表面自由基的电化学行为

本文建立了一套ESR-EC联合现场测试多孔电极表面顺磁粒子的方法, 并对多孔碳电极上吸附的醌化合物在电极上还原时的自由基中间产物的ESR进行了研究。首次获得了固体电极表面自由基有hfs的高分辨ESR信号。研究结果表明,醌在RB碳电极表面有多种行为各异的吸附态。在测量电位范围内, 观察到了四种吸附醌化合物是通过自由基过程还原的。其中两种通过可旋转单键吸附到碳电极表面, 给出有hfs的ESR谱; 另两种表现为各向异性ESR信号,可能是通过多个位置吸附在碳表面。     

Une généralisation du problème des itérés

For given systems of differential operators of constant coefficients we give algebraic conditions to compare their spaces of Gevrey vectors.     

Design and performance simulation of a molecular Doppler wind lidar

A mobile molecular Doppler wind lidar at an eye-safe wavelength of 355 nm based on double-edge technique is being built in Hefei （China） for wind measurement from 10-to 40-km altitude. The structure of this lidar system is described. A triple Fabry-Perot etalon is employed as a frequency discriminator whose parameters are optimized. The receiver system is designed to achieve compactness and stability by putting in a standard 19-inch socket bench. Simulation results show that within the wind speed dynamic range of ±100 m/s, the horizontal wind errors due to noise are less than 1 m/s bdow 20-km altitude for 100-m vertical resolution, and less than 5.5 m/s from 20 km up to 40 km for 500-m vertical resolution with 400-mJ laser energy, 30-min temporal resolution, and a 45-cm aperture telescooe.     

A novel compact wavelength-division multiplexer using highly dispersive waveguide-to-waveguide coupling

A novel compact wavelength-division multiplexer using highly dispersive waveguide-to-waveguide coupling is designed, simulated and analyzed. The device consists of two very close single-moded waveguides that are periodically connected to form a mode-dependent dispersive grating. It is demonstrated that the wavelengths over the edges of the photonic band gap contributed by the grating can be separated in a very short propagation distance. Using the finite-difference time-domain method, the result shows that the wavelengths of 1570 and 1530 nm are separated by the grating in a coupler length of 57 μm which is much shorter than the required length of about 340 μm without grating assistance. The channel contrast of 20 dB and the insertion loss about 2 dB are achieved.     

Static properties of asymmetric vortex-like domain walls in magnetically uniaxial thick films

The structure and energy of asymmetric vortex-like Bloch and Néel walls in a magnetically uniaxial film with an easy magnetization axis lying in the film plane are investigated by numerically minimizing the total energy within the rigorous micromagnetic approach and the two-dimensional model of the magnetization distribution. The calculations are performed over wide ranges of film thicknesses b (up to b = 1 μm) and magnetic parameters of the films. It is established that the asymmetric vortex-like domain walls are the most universal wall structures in the films under consideration. In magnetically uniaxial films, unlike in magnetically multiaxial films, the asymmetric Bloch walls are always stable.     

Computational tomographic reconstruction for limited Ill-posed interferometric data

The test results of continuous local basis functions, that is, the polynomial, cubic B-spline, and convoluted Hanning functions, are presented for tomographic reconstruction of continuous phase objects from multidirectional projection interfrograms with limited data points. The concept of the approach is based on the use of identical but regularly displaced and overlapping continuous functions that have support only in a local region. They thus produce higher-order approximating power. Their performances are fairly similar; however, the convoluted Hanning function appears to be an excellent candidate. For the conducted tests, in general, the function outperforms the conventional methods including the grid method and convolution back-projection, especially as the noise level or degree of data limitation increases.     

Microporous chiral metal coordination polymers: hydrothermal synthesis, channel engineering and stability of lanthanide tartrates

L-Tartrate ions can endure hydrothermal conditions up to 160 degrees C to form the robust, enantiopure open-framework coordination polymers [Ln2(L-TAR)3(H2O)2]3H2O, 1; the addition of succinate results in formation of the related [Ln2(L-TAR)2(SUC)(H2O)2]5.5H2O, with larger channels than , whereas racemic D/L-tartrate gives the more condensed [Ln2(D/L-TAR)3(H2O)2], . TAR = [C4H4O6]2-.