The effect of spatial coherence of sound field on subspace-based high-resolution spatial spectrum estimation

When the signals received by any two array elements are not fully correlated, the performance of DOA (Direction Of Arrival) estimation methods might degrade if the plane-wave model assumption is still used. For narrowband uniform linear array, by utilizing the property of Toeplitz matrix, it is proved that the received signals can be expressed as the sum of several plane-wave signals, which can be viewed as the "splitting" parts of the true sources. The "splitting" of sources makes it difficult to estimate the true number of sources. As a result, spurious peaks might occur in the spatial spectrum when subspace-based high-resolution spatial spectrum estimation technique is used.     

A WATER-COMPATIBLE PHENOLIC HYDROXYL MODIFIED POLYSTYRENE AS AN ADSORBENT FOR ADSORBING PHENOLIC COMPOUNDS FROM AQUEOUS SOLUTIONS

1. INTRUDUCTION As most phenolic compounds are extremely toxic at the concentrations discharged into accepting effluents, the removal or destruction of phenolic compounds from such streams has become a significant environmental task [1]. Increasing concern for public health and environmental quality has led to the establishment of limits on the acceptable environmental levels of specific pollutants [2]. Consequently there has been a growing interest in developing and implementing various …     

A smart and portable micropump for stable liquid delivery

Precise and reliable liquid delivery is vital for microfluidic applications. Here, we illustrate the design, fabrication, characterization, and application of a portable, low cost, and robust micropump, which brings solution to stable liquid delivery in microfluidic environment. The pump is designed with three optional speeds of different pumping flow rates, and it can be simply actuated by spring‐driven mechanism. The different flow rates of the pump are realized via passive microvalves in a compact microfluidic chip, which is installed in the pump. Importantly, the membrane structures of the microvalves allow accurate liquid control, and stable flow rates can be achieved via a spring setup. The proposed pump is applied to continuously and stably infuse microbead suspension into an inertial microfluidic chip, and good particle focusing is realized in the spiral channel of the inertial microfluidic chip. The proposed portable, self‐powered, and cost‐efficient pump is crucial for microfluidic lab‐on‐a‐chip system integration, which may facilitate microfluidic application for precise liquid delivery, control, measurement, and analysis.     

理论研究二米基硼B(Mes)2位置异构对Ir(III)配合物Ir(ppy)2(acac)的光物理性质的影响

采用DFT/TDDFT方法研究了二米基硼B（Mes）₂基团修饰的一类Ir（ppy）₂（acac）配合物1～3的光物理性质. 计算了电子结构,吸收和发射光谱以及自旋轨道耦合矩阵< T₁^α|H_SOC|S_n >和辐射跃迁速率（k_r）,探讨了取代基位置不同对磷光辐射和非辐射跃迁性质的影响. 研究结果表明：向ppy配体的吡啶环引入B（Mes）₂基团,能够加强金属铱（Ir）与配体乙酰丙酮（acac）的相互作用,减小单-三重态能级差ΔE（S₁-T₁）,提高系间窜跃速率和磷光辐射跃迁速率. 向ppy配体的苯环引入B（Mes）₂基团则增大了S₀与T₁的结构变形和自旋轨道耦合矩阵< S₀|H_SOC|T₁ >,使非辐射跃迁速率增加. B（Mes）₂基团位置异构,导致金属d轨道分裂方式不同,其在三个方向的自旋轨道耦合作用不同,辐射跃迁和非辐射跃迁都随之改变. 从理论上解释了通过对ppy配体的吡啶环修饰可获得高磷光量子产率的原因.     

FORMULATION AND EVALUATION OF AN ANALYTICAL STUDY FOR CYLINDRICAL HELICAL SPRINGS

The free vibration analysis of cylindrical helical springs is carried out by means of an analytical study.In the governing equations of the motion of the springs,all displacement functions are defined at the centroid axis and also the effects of the rotational inertia,axial and shear deformations are included in the proposed model.Explicit analytical expressions which give the vibrating mode shapes are derived by rigorous application of the symbolic computing package MATHEMATICA and a process of searching is used to determine the exact natural frequencies.Numerical examples are provided for fixed-fixed boundary conditions.The free vibrational parameters are chosen as the number of coils(n=4 ～ 14),the helix pitch angle(α=5 ～ 30?) and as the ratio of the diameters of the cylinder and the wire(D/d=4 ～ 18) in a wide range.Validation of the proposed model has been achieved through comparison with a finite element model using two-node standard beam elements and the results available in published literature,which in these cases indicates a very good correlation.     

以介孔分子筛为金属催化剂载体制备纳米碳管

 以不同的介孔分子筛作为金属催化剂载体,对催化合成纳米碳管进行了系统的研究,讨论了反应条件对纳米碳管纯度和产量的影响. 结果表明,不同的介孔分子筛对金属活性中心的形成、碳组分的扩散、纳米碳管的管径及形态均有明显的影响. 此外,金属的种类、状态和含量也影响纳米碳管的合成. 探索了合成高产量纳米碳管的条件,并对介孔分子筛上生长纳米碳管的特点进行了讨论.     

Kinetic and spectroscopic characterization of ACMSD from Pseudomonas fluorescens reveals a pentacoordinate mononuclear metallocofactor

The enzyme alpha-amino-beta-carboxy-muconic-epsilon-semialdehyde decarboxylase (ACMSD) plays an important role in the biodegradation of 2-nitrobenzoic acid in microorganisms and in tryptophan catabolism in humans. We report that the overexpressed ACMSD enzyme from Pseudomonas fluorescens requires a divalent metal, such as Co(II), Fe(II), Cd(II), or Mn(II), for catalytic activity and that neither a redox reagent nor an organic cofactor is required for the catalytic function. The metal ions can be taken up in either cell or cell-free preparations for generating the active form of ACMSD. The kinetic parameters and enzyme specific activity are shown to depend on the metal ion present in the enzyme, suggesting a catalytic role of the metal center. EPR spectrum of Co(II)-ACMSD provides a high-spin (S = 3/2 mononuclear metal ion in a non-heme, noncorrinoid environment with a mixed nitrogen/oxygen ligand field. We observe hyperfine interactions due to 59Co nucleus at temperatures below 5 K but not at higher temperatures. Ten hyperfine lines are present in the g(perpendicular) region, and three equivalent nitrogen hyperfine couplings are required to simulate the resonances in the EPR spectrum. The results for the metal binding site are also assessed using the copper-substituted enzyme, and the EPR spectral assignments for both cobalt and copper proteins give strong support for a distorted trigonal bipyramidal geometry of the metal center. Ultimately, these results suggest for the first time that ACMSD is a metal-dependent enzyme that catalyzes a novel nonoxidative decarboxylation.     

Oscillation properties of nonlinear impulsive delay differential equations and applications to population models

Comparison theorem and explicit sufficient conditions are obtained for oscillation and nonoscillation of solutions of nonlinear impulsive delay differential equations which can be utilized to population dynamic models. Our results in this paper generalize and improve several known results.     

measurement of Third Order Hyperpolarizability of Some Dyes

A degenerate four-wave mixing experiment with the solutions of some dyes has been performed using 10ns pulses at 530nm. Large resonant and off-resonant third order hyperpolarizabilities were obtained.