Robustness analysis and distributed control of a networked system with time-varying delays

This paper is concerned with the robustness analysis and distributed output feedback control of a networked system with uncertain time-varying communication delays. This system consists of a collection of linear time-invariant subsystems that are spatially interconnected via an arbitrary directed network. Using a dissipation inequality that incorporates dynamic hard IQCs (integral quadratic constraints) for the delay uncertainties, we derive some sufficient robustness conditions in the form of coupled linear matrix inequalities, in which the coupled parts reflect the interconnection structure of the system. We then provide a procedure to construct a distributed controller to ensure the robust stability of the closed-loop system and to achieve a prescribed $\ell_2$-gain performance. The effectiveness of the proposed approach is demonstrated by some numerical examples.     

Y2O3-MgO纳米复相红外透明陶瓷制备及其性能研究

以商用Y2O3、MgO纳米粉体为原料,通过球磨混合方法制备了不同Y2O3/MgO配比的Y2O3-MgO纳米复合粉体,使用X射线衍射、扫描电镜、能量色散谱等表征手段对制备粉体的晶体结构、形貌、成分以及均匀性进行了表征。然后采用热压烧结方法制备Y2O3-MgO复相红外透明陶瓷,使用红外光谱仪、维氏硬度计等测试设备对复相透明陶瓷的光学和力学性能进行了分析。重点研究了粉体配比、热压温度、保温和保压时间等关键制备参数对Y2O3-MgO复相红外透明陶瓷晶粒尺度、致密化程度、光学及力学性能的影响。并通过调控粉体制备工艺和热压烧结工艺,制备出了红外透过率达到~80%的Y2O3-MgO复相红外透明陶瓷。同时在Y2O3:Mg0=1:1时,该复相陶瓷的硬度达到了12.3 GPa。     

热稳定处理时间对TNM合金糊状区组织的影响

利用真空非自耗电弧炉制备了TNM(Ti-44Al-4Nb-1Mo-0.1B at.%)合金锭,研究其铸态组织形貌,并利用Bridgeman定向凝固装置对TNM合金进行热稳定处理实验,分析热稳定处理时间对合金定向凝固糊状区的影响。实验结果显示,其铸态组织是以(α₂+γ)片层团为主体,网络状B2相、细小的γ相及硼化物分布于片层团间的近片层组织。热稳定处理时,热稳定时间越长、TNM合金固/液界面越平整,界面前沿温度场和溶质场趋向均匀,但从减少坩埚对熔体的污染的角度考虑,热稳定处理时间不宜过长,30~60 min的热稳定时间即可提供平整的定向凝固启动界面。 热稳定处理影响着TNM合金固/液界面附近固液两相中Al元素的分布,进而影响硼化物的分布。     

Nitrogen-doped graphene-supported zinc sulfide nanorods as efficient Pt-free for visible-light photocatalytic hydrogen production

Nitrogen-doped graphene-ZnS composite (NG-ZnS) was synthesized by thermal treatment of graphene-ZnS composite (G-ZnS) in NH₃ medium. In the second step, the as-synthesized samples were deposited on indium tin oxide glass (ITO) by electrophoretic deposition for photocatalytic hydrogen evolution reaction. The as-prepared NG-ZnS-modified ITO electrode displayed excellent photocatalytic activity, rapid transient photocurrent response, superior stability and high recyclability compared to the pure ZnS and G-ZnS-modified ITO electrode due to the synergy between the photocatalytic activity of ZnS nanorods and the large surface area and high conductivity of N-graphene.     

A three-stage real-time detector for traffic signs in large panoramas

Computational Visual Media - Traffic sign detection is one of the key components in autonomous driving. Advanced autonomous vehicles armed with high quality sensors capture high definition images...     

用于矿山等极端环境中的高精度定位算法

高精度室内定位技术在矿山、建筑、施工等多种极端环境下都有需求。基于超宽带通信(Ultra Wideband,UWB)的室内定位技术能够提供较高的定位精度,但超宽带信号易受到障碍物的干扰,并且在类似矿山等极端环境中,障碍物不可避免。因此,超宽带非视线传输(Non-Line-of-Sight,NLoS)测距成为当前的一个研究热点。当前研究大多集中在识别和消除非视线传输对超宽带测距的影响上,实际应用中,大多数情形下超宽带信号根本无法穿透障碍物,会导致定位标签只能够与2个或1个信标节点通信,但完成三边定位至少需要3个信标节点。为此,提出了一种基于目标行为分析的定位算法,该算法能够在短时间内仅剩余一个信标节点与标签通信时,也可实现高精度定位。该算法以超宽带通信为基础,使用信号飞行时间(Time of Flight,TOF)算法测距并定位。通过分析信号正常时的目标运动轨迹来判断其速度和方向,当信号不正常时(可通信的信标节点减少),可利用预测的速度和方向参数来实现辅助定位。将该算法部署在一个基于超宽带定位的系统中进行了测试,结果表明:当能够与标签通信并完成TOF算法的信标节点数量少于3个时,基于NLoS传输识别和消除的算法无法完成定位,而基于目标行为分析的定位算法依然能够实现定位,在单信标节点区域的平均定位误差为0.93 m,最大误差为1.41 m,在2个信标节点测距的区域,平均定位误差为0.64 m,最大误差为1.2 m。     

钽表面铜掺杂Ta2O5纳米棒的制备及抗菌性能研究

本实验采用两步水热法在钽基体表面制备出掺杂Cu_²⁺的Ta₂O₅纳米棒薄膜。采用XRD、SEM、XPS等方法分析了材料的物相和表面微观结构。用ICP检测了样品在生理盐水中离子析出浓度,最后通过平板计数法检验了不同含量铜掺杂Ta₂O₅薄膜的抗菌能力。结果表明,通过两步水热处理,在钽表面生成了简单斜方晶体结构的Ta₂O₅纳米棒阵列,Cu_²⁺的掺杂不会对纳米棒薄膜的微观形貌和物相造成显著影响。随时间的增加,掺铜薄膜的铜离子析出速率逐渐趋于平缓。平板计数法表明,Cu_²⁺ 的掺杂量达到2.68At%时,铜掺杂Ta₂O₅纳米棒薄膜的抗菌性能最好,抗菌率达99.2%。