基于水声信道传播时延排序的分层空时信号检测

基于分层空时编码的多输入多输出技术是一种极具潜力的高速水声通信技术, 但要实现这种潜力需要复杂的空时信号处理方法, 以抵消来自水声信道的多径干扰和异步到达干扰, 以及叠加在接收端的各层信号之间的干扰. 对低复杂度的空时信号处理方案进行了研究, 提出了一种基于子信道传播时延排序的有序连续干扰抵消信号检测算法, 利用子信道间的传播时延差, 实现可使差错概率最小的最佳检测排序; 给出了利用信道估计, 以极低的计算量确定排序的方法, 从而可以大幅降低信号检测的计算复杂度. 采用低复杂度的单载波频域均衡来抵消水声信道中的码间干扰和异步到达干扰. 仿真结果表明, 基于时延排序的信号处理算法可以获得检测性能的改善, 而且性能增益在高数据率时更加显著. 研究结果表明, 采用有效的信号处理方法可使水声信道中造成信号检测干扰的传播时延成为改善系统性能的有利因素.     

Activation of Au–Ag Plasmonic Bimetallic Nanocatalysts with Cold Plasma: The Role of Loading Sequence of Plasmonic Metals and Discharge Atmosphere

The activation of Au–Ag plasmonic bimetallic nanocatalyst can make the nanocatalyst exhibit superior visible-light (VL) photocatalytic activity. An efficient activation of Au–Ag nanocatalyst by cold plasma requires the restructuring of Au and Ag species over catalyst surface to form Au–Ag alloy nanoparticles while suppressing agglomeration of the nanoparticles. We here report that the loading sequence of Au and Ag components on titanium dioxide (TiO₂) support during catalyst preparation and discharge atmosphere play important roles in the plasma activation. Preparation of AuAg/TiO₂ nanocatalyst by depositing Ag and Au in sequence could avoid the undesired loss of Ag component, and ensure an effective restructuring of Au and Ag species in O₂ plasma activation. Compared with the reductive (H₂) and inert (Ar and N₂) plasmas, discharge in oxidative O₂ establishes Coulomb field with the negatively charged species over catalyst surface and enable the restructuring and intimate interaction of Au and Ag species. The catalyst characterization and density functional theory calculations suggest that O₂ plasma endows AuAg/TiO₂ nanocatalyst with large numbers of Au–Ag alloy nanoparticles, small size of plasmonic nanoparticles, high density of coordinatively unsaturated sites, and high content of surface oxygen species in the activation, which facilitates the adsorption and activation of O₂, and thus CO oxidation reaction under VL irradiation.

     

Analytical and Numerical Studies for Chaotic Dynamics of a Duffing Oscillator with a Parametric Force

The chaotic dynamics of a Duffing oscillator with a parametric force is investigated. By using the direct perturbation technique, we analytically obtain the general solution of the lst-order equation. Through the boundedness condition of the general solution we get the famous Melnikov function predicting the onset of chaos. When the parametric and external forces are strong, numerical simulations show that increasing the amplitude of the parametric or external force can lead the system into chaos via period doubling.     

Numerical simulation of pedestrian flow past a circular obstruction

In this paper, a revisiting Hughes' dynamic continuum model is used to investigate and predict the essential macroscopic characteristics of pedestrian flow, such as flow, density and average speed, in a two dimensional continuous walking facility scattered with a circular obstruction. It is assumed that pedestrians prefer to walk a path with the lowest instantaneous travel cost from origin to destination, under the consideration of the current traffic conditions and the tendency to avoid a high-density region and an obstruction. An algorithm for the pedestrian flow model is based on a cellcentered finite volume method for a scalar conservation law equation, a fast sweeping method for an Eikonal-type equation and a second-order TVD Runge-Kutta method for the time integration on unstructured meshes. Numerical results demonstrate the effectiveness of the algorithm. It is verified that density distribution of pedestrian flow is influenced by the position of the obstruction and the path-choice behavior of pedestrians.     

Analytical and Numerical Studies for Chaotic Dynamics of a Duffing Oscillator with a Parametric Force

The chaotic dynamics of a Duffing oscillator with a parametric force is investigated. By using the direct perturbation technique, we analytically obtain the general solution of the 1st-order equation. Through the boundedness condition of the general solution we get the famous Melnikov function predicting the onset of chaos. When the parametric and external forces are strong, numerical simulations show that increasing the amplitude of the parametric or external force can lead the system into chaos via period doubling.     

一维链状配位聚合物[Cu(en)2]2[Cu(en)2α-AsⅢ8VⅣ14O42(HPO4)]·8H2O的合成与晶体结构

钒氧化合物由于其有趣的阴离子结构和在催化反应、药物化学以及材料科学等领域中的应用而受到人们的关注[1,2].     

SnCl4对纳米二氧化钛晶相结构的低温转变控制研究

采用二种方法制备了低温下晶相结构可控制转变的纳米二氧化钛。一种方法是采用乙醇作溶剂的溶胶-凝胶法,通过控制SnCl₄的添加量,便可在450℃热处理下实现纳米TiO₂从纯锐钛矿到不同比例的复合相直至纯金红石相的转变。另一种方法是采用钛酸丁酯为原料直接低温水解,通过加入不同量的SnCl₄,制备了具有晶态结构的二氧化钛复合溶胶,在120℃下干燥处理便可实现TiO₂从锐钛矿到不同比例的复合相(金红石型、锐钛矿型和板钛矿型)直至纯金红石相的转变,制备所需晶态结构的纳米TiO₂。所有样品进行了透射电镜与XRD表征,制备的纳米TiO₂及其TiO₂-SnO₂纳米复合材料颗粒小、分布均匀、分散性好,没有检测到SnO₂晶体的X-衍射特征峰。     

去势手术对大鼠肾上腺中孕烯醇酮、17α-羟孕烯醇酮和脱氢表雄酮代谢的影响

雄激素阻断治疗作为临床上治疗前列腺癌的主要方式,已被证明能够引起肾上腺中CYP17α1基因表达的增强.由于该基因所编码的酶为肾上腺中的肾上腺雄激素合成的关键酶,因此去势后由该酶所催化的甾体激素合成途径中的孕烯醇酮、17a-孕烯醇酮以及脱氢表雄酮的含量应会出现相应变化.本文建立了一种适用于生物组织样品中上述3种激素的Gc...     

双重对象同时检测的新型荧光纳米粒子传感器的制备

报道了一种基于荧光共振能量转移理论合成的新型纳米粒子. 新型纳米粒子A中掺杂了由亲和素-生物素桥联并可发生荧光共振能量转移(FRET)的供体染料和受体染料; 新型纳米粒子B中只掺杂了供体染料. 在使用供体染料的特征激发波长同时激发纳米粒子A和B时, 纳米粒子A由于荧光共振能量转移而发射出受体染料的特征波长, 而纳米粒子B则只发射供体染料的特征波长. 这样, 在单一波长激发下, 可很容易地实现双重对象同时检测.