不确定线性组合系统的鲁棒H_∞性能的判定

针对一类线性组合不确定系统的结构特征提出了分散鲁棒 H∞ 性能的概念。它充分利用组合系统的互联结构 ,为研究大系统 H∞ 性能提供了新途径。给出了大系统具有分散鲁棒 H∞ 性能的条件 ,以及利用分散鲁棒 H∞ 性能判断大系统的整个鲁棒 H∞ 性能的方法。结果表明 ,大系统的 H∞ 性能与子系统H∞ 性能密切相关。只要每个子系统具有鲁棒 H∞ 性能 ,则在同样的控制条件下 ,大系统也具有鲁棒 H∞性能 ,只是性能指标弱一些。     

一类相似广义互联系统的导数-输出反馈鲁棒控制器设计

以广义系统中受限系统等价概念和导数反馈- 输出反馈为基础,定义了一类广义互联系统的相似结构,提出了相似性研究的新方向.这类系 统具有不满足匹配条件的非线性不确定互联项.设计了导数-输出反馈鲁棒分散控制器,使互 联系统在平衡点处渐近稳定.由于控制器本身也具有相似结构,因此易于工程实现.     

动态背景体育运动视频合成对比*

针对在同一场景下获取的体育运动视频,提出了一种基于全局运动补偿及运动前景区域信息的体育运动视频合成方法。首先,对待合成视频,通过全局运动估计与补偿,将相邻帧在空间上对齐到当前帧。通过计算帧差,得到当前帧中的运动前景区域信息。然后根据两段待合成视频之间背景的相似性,计算并修正全局运动参数,确定待合成对应帧之间的位置关系。最后,依据已经获得的运动前景区域信息,生成合成帧。实验结果表明,该方法可自动合成在同一场景中获得的有相似动态背景的体育视频,保持了前景与背景的清晰度,能清晰地显示运动员动作的差异。     

Correlation between acidic properties of nickel sulfate supported on TiO2-ZrO2 and catalytic activity for ethylene dimerization

A series of catalysts, NiSO₄/TiO₂-ZrO₂, for ethylene dimerization was prepared by the impregnation method using an aqueous solution of nickel sulfate. For NiSO₄/TiO₂ -ZrO₂ sample, no diffraction line of nickel sulfate was observed up to 30 wt%, indicating good dispersion of nickel sulfate on the surface of TiO₂-ZrO₂. The addition of nickel sulfate to TiO₂-ZrO₂ shifted the phase transition of TiZrO₄ from amorphous to orthorhombic to a higher temperature because of the interaction between nickel sulfate and TiO₂-ZrO₂. The number of acid sites of NiSO₄/TiO₂-ZrO₂ increased in proportion to the nickel sulfate content up to 20 wt% of NiSO₄. Nickel sulfate supported on TiO₂-ZrO₂ was found to be very active even at room temperature, giving a maximum in both activity and acidity when the catalyst containing 20% NiSO₄ was calcined and evacuated at 500°C The asymmetric stretching frequency of the S=O bonds for NiSO₄/TiO₂-ZrO₂ samples was related to the acidic properties and catalytic activity. That is, the higher the frequency, the higher both the number of acid sites and the catalytic activity for ethylene dimerization.     

Effect of nanopore size on poly(dT)30 translocation through silicon nitride membrane

The nanopore size effect on translocation of poly(dT)30through Si3N4 membrane is investigated.In this paper,we report that the speed of the poly(dT)30 transport through Si3N4 nanopores can be slowed down by half through increasing the nanopore diameter from 4.8 nm to 10.8 nm.The results are consistent with our simulation results.Besides,the current blockage induced by DNA passing through the nanopore is less obvious as pore diameter is larger,which is in good agreement with the theoretical prediction.The conclusion about DNA transport through nanopores is beneficial for the design of DNA sequencing devices.     

Preparation and mechanical behavior of Mg-based bulk metallic glasses and their matrix composite

Mg87-xCuxDy13(x=22,27,32) bulk metallic glasses (BGMs) with a diameter of 6-8 mm and in-situ Mg phase reinforced Mg70Cu17Dy13 BMG matrix composite with a diameter of 3 mm have been prepared by copper mould casting. The glass forming ability (GFA) of Mg-Cu-Dy alloys have been investigated by differential scanning calorimetry (DSC) and X-Ray diffraction (XRD) and tne mechanical properties have been measured. Results show that Mg87-xCuxDy13(x=22,27,32) alloys in the Mg-Cu-Dy alloy system exhibit excellent GFA, and Mg60Cu27Dy13 alloy has the largest GFA among these alloys. And In-situ Mg phase reinforced Mg70Cu17Dy13 BMG matrix composite exhibits some work hardening and a high fracture compressive strength of 702.38 MPa and some plastic strain of 0.81%. The improvement of the mechanical properties is attributed to the fact that the Mg phase distributed in the amorphous matrix of the alloy has some effective load bearing and plastic deformation ability to restrict the expanding of shear bands and cracks and produce its own plastic deformation.     

一种改进的FSVM语音情感识别算法

针对语音特征参数对某类情感具有不确定性的问题,提出一种基于典型相关性分析的改进模糊支持向量机算法,应用于语音情感识别.采用典型相关性分析方法对特征向量进行降维,得到样本的约简向量集,在此约简向量集上建立模糊支持向量机模型判定情感类型.仿真实验结果表明,该方法相比于传统支持向量机法和模糊支持向量‘机法具有较高的识别准确率.     

黄河流域实施水功能区限制纳污红线管理的整体构想与初步实践

水功能区限制纳污红线管理是实行最严格水资源管理制度的核心内涵之一。黄河流域水安全问题是中国水安全问题的缩影,探索构建行之有效且具有黄河流域特色的纳污红线管理制度体系和工作格局,对于提高黄河流域水安全保障能力意义重大。针对黄河流域的水资源质量状况,探索建立流域与区域相结合、水利与环保相联合的黄河水资源保护管理体系,构建流域水功能区划及水资源保护规划体系,依法强化以入河排污口为重点的水功能区管理,积极探索水生态系统保护与修复,加强水质监测网络体系建设等一系列措施,为黄河流域实施纳污红线管理提供了良好的工作基础和能力支撑,并在此基础上阐述了黄河流域实施纳污红线管理的整体构想与初步实践。     

Dynamical synapses enhance neural information processing: gracefulness, accuracy, and mobility

Experimental data have revealed that neuronal connection efficacy exhibits two forms of short-term plasticity: short-term depression (STD) and short-term facilitation (STF). They have time constants residing between fast neural signaling and rapid learning and may serve as substrates for neural systems manipulating temporal information on relevant timescales. This study investigates the impact of STD and STF on the dynamics of continuous attractor neural networks and their potential roles in neural information processing. We find that STD endows the network with slow-decaying plateau behaviors: the network that is initially being stimulated to an active state decays to a silent state very slowly on the timescale of STD rather than on that of neuralsignaling. This provides a mechanism for neural systems to hold sensory memory easily and shut off persistent activities gracefully. With STF, we find that the network can hold a memory trace of external inputs in the facilitated neuronal interactions, which provides a way to stabilize the network response to noisy inputs, leading to improved accuracy in population decoding. Furthermore, we find that STD increases the mobility of the network states. The increased mobility enhances the tracking performance of the network in response to time-varying stimuli, leading to anticipative neural responses. In general, we find that STD and STP tend to have opposite effects on network dynamics and complementary computational advantages, suggesting that the brain may employ a strategy of weighting them differentially depending on the computational purpose.     

Joint segmentation of collectively moving objects using a bag-of-words model and level set evolution

In scenes with collectively moving objects, to disregard the individual objects and take the entire group into consideration for motion characterization is a promising approach with wide application prospects. In contrast to studies on the segmentation of independently moving objects, our purpose is to construct a segmentation of these objects to characterize their motions at a macroscopic level. In general, the collectively moving objects in a group have very similar motion behavior with their neighbors and appear as a kind of global collective motion. This paper presents a joint segmentation approach for these collectively moving objects. In our model, we extract these macroscopic movement patterns based on optical flow field sequences. Specifically, a group of collectively moving objects correspond to a region where the optical flow field has high magnitude and high local direction coherence. As a result, our problem can be addressed by identifying these coherent optical flow field regions. The segmentation is performed through the minimization of a variational energy functional derived from the Bayes classification rule. Specifically, we use a bag-of-words model to generate a codebook as a collection of prototypical optical flow patterns, and the class-conditional probability density functions for different regions are determined based on these patterns. Finally, the minimization of our proposed energy functional results in the gradient descent evolution of segmentation boundaries which are implicitly represented through level sets. The application of our proposed approach is to segment and track multiple groups of collectively moving objects in a large variety of real-world scenes.