排序方式: 共有19条查询结果,搜索用时 62 毫秒
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Lianghao Song Tiantian Xu Daowei Gao Prof. Xun Hu Prof. Cuncheng Li Prof. Shun Li Prof. Guozhu Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6621-6627
CeO2-based catalysts are widely studied in catalysis fields. Developing one novel synthetic approach to increase the intimate contact between CeO2 and secondary species is of particular importance for enhancing catalytic activities. Herein, an interfacial reaction between metal–organic framework (MOF)-derived carbon and KMnO4 to synthesize CeO2−MnO2, in which carbon is derived from the pyrolysis of Ce-MOFs under an inert atmosphere, is described. The MOF-derived carbon is found to restrain the growth of CeO2 crystallites under a high calcination temperature and, more importantly, intimate contact within CeO2/C is conveyed to CeO2/MnO2 after the interfacial reaction; this is responsible for the high catalytic activity of CeO2−MnO2 towards CO oxidation. 相似文献
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Nonlinear Dynamics - This paper discusses the finite time consensus (FTC) issue of nonlinear heterogeneous multi-agent systems (HMASs) by combining integral sliding-mode control (SMC),... 相似文献
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一种鲁棒性的最小方差无失真响应波束形成算法及其应用 总被引:1,自引:0,他引:1
理论上,自适应波束形成方法要比不依赖于输入数据的常规波束形成方法有更好的目标参数估计能力和干扰抑制能力.但在实际水声环境中,声传播模型、接收阵阵列流形以及信号统计特征等因素往往与实际情况存在一定的差异,导致传统的自适应波束形成方法性能下降.因此,提高自适应波束形成方法对上述因素的鲁棒性变得越来越重要.本文基于最差条件最优化的思想,改进MVDR(最小方差无失真响应)方法的约束条件提出了一种鲁棒性最小方差无失真响应自适应波束形成算法(R-MVDR),并对输入数据协方差矩阵和方向向量存在不确定性的情况进行了性能分析,推导给出了波束形成的加权向量和空间谱估计表达式,最后通过海上实验数据进行了验证.结果证明本文提出的算法在实际环境中有更好的方位分辨能力和干扰抑制能力. 相似文献
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I.IntroductionPassiverangeanddepthlocalizationofanacousticsourceinshallowwaterisadifficult,yetinterestingproblemthathasreceivedagreatdealofattentioninthelastfewyears['5].Thesimu1taneousestimationofrangeanddepthrequirestheuseofnumericalpropagationmodels.Theclassicalapproachtothisproblemisto"match"thereceivedacousticdatawiththesoundfieldpredictedbythepropagationmodelforanumberofhypotheticalrange/depthsourcelocatiolls.Thistechniqueiscalledmatchedfieldprocessing.Itiscommonlyacceptedthatthewavepro… 相似文献
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针对近水面声源和水下声源的深度判别问题,根据近水面声源难以激发低阶模态的物理现象,研究利用声源波数谱结构和波数位置的不同来分辨近水面声源和水下声源。通过采用MVDR的谱估计方法进行模态域波束形成,补偿水平阵各阵元之间各号简正波的相位差,获得主瓣窄、旁瓣低的声源信号波数谱。波数谱的波数位置与频率呈近似线性关系,水中声速剖面、海底参数、海深都会影响波数谱的具体结构和位置。此外,声源信号的到达角估计误差同样也会影响波数谱主瓣的位置估计。数值仿真结果表明,在浅海负跃层声速剖面条件下,可利用水平阵模态域波束形成判别声源深度,区分近水面声源和水下声源。 相似文献
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自适应波束形成在弱目标检测和空域滤波中应用广泛。然而在实际海洋环境中,失配情况比较普遍,往往会导致传统自适应波束形成方法性能明显下降。针对此问题,本文基于特征分析重构观测信号协方差矩阵来抑制干扰对弱目标检测的影响,在此基础上进一步利用凸优化算法来提高波束形成方法的鲁棒性。数值仿真和海试数据处理结果表明,本文所提方法在抑制干扰对弱目标影响的基础上,在阵元位置平均误差不超过入射信号中心频率对应波长的40%的情况下,仍可以鲁棒地检测目标信号。同时,该方法显著提高了自适应波束形成方法的输出信干噪比,且受对角加载量取值的影响较小。 相似文献
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对于单一静止的观测平台,针对直航运动的目标,提出了一种利用频域β-warping变换的浅海目标航向估计方法。该方法利用频域β-warping变换从简正波互相关项中提取与目标距离呈线性关系的脉冲时延,进而估计距离特征量,并根据几何关系建立了目标航向、目标方位和距离特征量的数学模型,利用渐近无偏最小二乘方法对目标航向进行估计。数值仿真和实验数据处理结果表明:在浅海水平不变波导远场条件下,该方法可以对直航运动的目标进行可靠地航向估计,航向估计性能与观测时间内的平均方位变化率密切相关。 相似文献
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Xinyu Li Lianghao Song Daowei Gao Baotao Kang Prof. Huaiqing Zhao Prof. Cuncheng Li Prof. Xun Hu Prof. Guozhu Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4419-4424
Heterogeneously catalyzed, selective hydrogenation in the liquid phase is widely used in industry for the synthesis of chemicals. However, it can be a challenge to prevent active nanoparticles (e.g., palladium) from aggregation/leaching and meanwhile achieve high conversion as well as selectivity, especially under mild conditions. To address these issues, a CeO2 nanotube/Pd@MIL-53(Al) sandwich-structured catalyst has been prepared in which the MIL-53(Al) porous shell can efficiently stabilize the palladium nanoparticles. When this catalyst was used in a tandem catalytic reaction involving the dehydrogenation of ammonia borane and the hydrogenation of phenylacetylene, remarkably, the hydrogen released from the dehydrogenation of ammonia borane boosted the catalytic process, with 100 % conversion of phenylacetylene and a selectivity of 96.2 % for styrene, even at room temperature and atmospheric pressure, within 1 min. This work therefore provides an alternative strategy for balancing the conversion and selectivity of liquid-phase hydrogenation reactions. 相似文献
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传统的水下被动测向方法通过波束形成估计目标角度,水平线列阵波束形成中的参考声速应使用声传播的相速度,在被动测向中,由于声源距离未知,因此在对目标角度估计时选取的参考声速与接收阵处的相速度往往存在偏差,从而影响测向精度。本文提出了一种水平线列阵方位-相速度联合的纯方位扩展卡尔曼滤波方法,该方法引入相速度作为估计状态量以此校准参考声速,提高测向精度,进而改善了由于测向误差较大引起的纯方位扩展卡尔曼滤波算法跟踪结果发散的问题。浅海传播条件下的数值仿真结果表明,改进方法较常规纯方位扩展卡尔曼滤波算法具有更高的跟踪精度及稳健的跟踪性能。 相似文献