Ein neues Bleistrontiumferrat(III): Die Kristallstruktur der Phase Pb4Sr2Fe6O15

A New Lead Strontium Ferrate(III): The Crystal Structure of the Phase Pb₄Sr₂Fe₆O₁₅ At orthorhombic single crystals of Pb₄Sr₂Fe₆O₁₅ (a = 568.73(8), b = 392.03(4), c = 2107.5(3) pm; Z = 4/3, space group Pnma) a X-ray structure determination has been performed (R₁ = 0,036 for 488 ?observed”? resp. wR₂ = 0,073 for all 643 independent reflexions). It revealed a framework of polyhedra related to perovskite, in which chains of edgesharing pyramids [FeO₅] (average Fe1? O: 197 pm; Fe1? Fe1: 305.5 pm) are linked via apices with corner-sharing [FeO₆] octahedra (Fe2? O: 201 pm). 12–fold, strongly distorted cuboctahedrally coordinated ?perovskite positions”? show mixed occupancy by 2/3 Sr + 1/3 Pb (= Sr2; Sr2? O: 287 pm). More spacy channels, running parallel to the chains of pyramids along [010] of the structure, contain lead atoms only. The double occupancy of the corresponding cages results in short distances Pb1? Pb1 (355.9 pm) and Pb1? Fe2 (314.4 pm), as well as in a very asymmetric [PbO₆] coordination (Pb1? O: 253 pm), in the opposite hemisphere of which the lone electron pair s² is supposed to be located. Details are communicated and structural relations discussed.     

Assembly of molecular squares and helical chain polymers of Mo(W)/Cu/S clusters using thiolato ligands as linkers

Reactions between thiomolybdate or thiotungstate [Et₄N]₂[MS₄] (M = Mo, W) and CuSBu^t led to the formation of two novel Mo(W)/Cu/S clusters [Et₄N]₄[{MS₄Cu₂(μ-SBu^t)}₄] (1, M = Mo; 2, M = W). Single-crystal X-ray diffraction studies reveal that 2 is the first example of a molecular square containing CuS₂WS₂Cu building blocks. The reactions of [Et₄N]₂[MS₄] with CuCl followed by the addition of K₂SSS (SSS = 1,3,4-thiadiazole-2,5-dithiolate) yielded novel polymers {[Et₄N]₂[MS₄Cu₂(SSS)]}_n (3, M = Mo; 4, M = W). Crystal structure determination shows that the CuS₂WS₂Cu building blocks in the anion of 4 are bridged by SSS²⁻ ligands to produce a helical chain running down the crystallographic b axis.     

液铜快速冷却过程微观结构演变的计算机模拟

利用计算机模拟了在周期性边界条件下由500个原子构成的液态Cu模型系统以 4.2 * 10~(13) K/s的速率快速凝固的全过程。模拟在FS相互作用势的基础上，通 过双体分布函数、键对分析技术、键取向序等多种方法，对液Cu快冷凝固过程的微 观结构转变特性作了分析，给出了连续快速冷凝过程中液Cu原子间依靠相互作用力 形成的独特的微观结构图像。模拟结果重现了实验值，且表明在快速冷却过程中液 Cu没有形成body center cubic结构的倾向。     

基于提升小波改进型阈值函数的雷达生命信号去噪技术

通过引入生物电理论,完善了连续波雷达生命信号的理论模型;采用提升小波变换和改进型阈值函数去噪技术对强噪声干扰的雷达生命信号进行去噪处理,将166.67mm波长雷达生命信号的信噪比由2.046 8优化到6.696 9,均方误差由1.763 9优化到0.909 9;8.57mm波长雷达生命信号的信噪比由0.942 6优化到2.541 8,均方误差由1.980 6优化到1.286 0.结果表明:本文建立的连续波雷达生命信号理论模型与实际情况相符,采用的去噪方案适用于雷达生命检测系统不同波长的雷达波.     

Average sampling and reconstruction for reproducing kernel stochastic signals

This paper mainly considers the problem of reconstructing a reproducing kernel stochastic signal from its average samples. First, a uniform convergence result for reconstructing the deterministic reproducing kernel signals by an iterative algorithm is established. Then, we prove that the quadratic sum of the corresponding reconstructed functions is uniformly bounded. Moreover, the reconstructed functions provide a frame expansion in the special case p = 2. Finally, the mean square convergence for recovering a weighted reproducing kernel stochastic signal from its average samples is given under some decay condition for the autocorrelation function, which can be removed for the case p = 2. Copyright © 2015 John Wiley & Sons, Ltd.     

Decomposition of Bicolored Square Arrays into Bichromatic Diagonals

Let M be an array (), where each of its cells is colored in one of two colors. We give a necessary and sufficient condition for the existence of a partition of M into n diagonals, each containing at least one cell of each color. As a consequence, it follows that if each color appears in at least cells, then such a partition exists. The proof uses results on completion of partial Latin squares.     

The commutator of the Kato square root for second order elliptic operators on ℝ<Superscript><Emphasis Type="Italic">n</Emphasis></Superscript>

Let L=-div(A▽) be a second order divergence form elliptic operator, and A be an accretive, n×n matrix with bounded measurable complex coefficients in Rⁿ. We obtain the L^p bounds for the commutator generated by the Kato square root √L and a Lipschitz function, which recovers a previous result of Calderón, by a different method. In this work, we develop a new theory for the commutators associated to elliptic operators with Lipschitz function. The theory of the commutator with Lipschitz function is distinguished from the analogous elliptic operator theory.     

充满多孔介质的方腔内双扩散自然对流格子Boltzmann模拟

采用格子Boltzmann方法,对4个壁面均为低温、低浓度,内置高浓度发热圆的充满均匀多孔介质的方腔内双扩散自然对流现象进行了数值模拟研究.分析了Darcy(达西)数Da(10-4≤D_a≤10~(-2))和浮升力比B(-5.0≤B≤5.0)对内部发热圆表面平均Nusselt(努赛尔)数Nuav和平均Sherwood(舍伍德)数Shav的影响.模拟结果表明:除B=-1.0时,Nu_(av)和Sh_(av)随D_a的增加而增大;当-5.0B5.0,在D_a=10~(-4)时,Nu_(av)和Sh_(av)几乎不受B变化的影响;在Da=10~(-3)和Da=10~(-2)时,Nu_(av)和Sh_(av)随B的增加先减小后增大,在B=-1.0时取得最小值.     

Robust modeling of acoustic paths using a sparse adaptive algorithm

Acoustic impulse response functions are generally sparse in nature and traditionally these are modeled by adaptive finite impulse response (FIR) filters trained using a least mean square (LMS) algorithm. The conventional LMS algorithm is not effective in modeling sparse systems and sparse LMS algorithms have been recently developed to improve the modeling in such scenarios. However, the traditional sparse LMS algorithms are not robust to disturbances at the error sensor and may diverge in some scenarios. With an objective to overcome this limitation of conventional sparse adaptive algorithm, this paper presents a robust sparse adaptive algorithm. The new algorithm has been shown to effectively model sparse systems in a robust manner. In addition, the algorithm has been successfully applied in modeling the acoustic feedback path in a behind the ear digital hearing aid.