异构混合相关熵有源噪声控制算法

近几年兴起的基于最大相关熵准则的FxMCC算法在有源噪声控制系统中取得了良好的降噪性能。然而,已有的FxMCC算法仅使用了单一的高斯核,算法在强脉冲噪声环境下降噪能力严重退化,且算法对核宽参数极敏感,不合适的核宽会降低算法降噪性能。为了弥补FxMCC算法的不足,该文引入异构混合相关熵,使用由高斯核和拉普拉斯核组成的混合核作为代价函数,推导了基于异构混合相关熵的FxMCC-MK算法。该文进一步分析了所提算法的收敛条件和稳定性,并与已有的算法进行了计算复杂度比较。仿真结果表明,在标准对称α稳定分布脉冲噪声和真实噪声录声的有源噪声控制中,相比于已有的相关熵算法,该文提出的FxMCC-MK算法具有更低的核宽参数敏感度,更强的鲁棒性和更快追踪能力。     

Dimming control scheme based on hybrid LACO-SCFDM for visible light communications

This paper proposes a hybrid layered asymmetrically clipped optical(HLACO) single-carrier frequency-division multiplexing(SCFDM) scheme for dimmable visible light communication. It designs a signal structure that combines layered asymmetrically clipped optical(LACO)-SCFDM and negative LACO-SCFDM in proportion for improving the inherent weaknesses of orthogonal frequency-division multiplexing(OFDM)-based dimmable schemes and further enhancing the system performance. Compared to the HLACO-OFDM-based dimming scheme, it obtains a lower bit error ratio and enables efficient communication over broader dimming range. Its spectral efficiency realizes 2.875 bit·s-1·Hz-1 within the dimming range of 30%–70%, and the attainable average spectral efficiency gains exceed at least 19.21% compared to other traditional dimmable schemes.     

Load-redistribution strategy based on time-varying load against cascading failure of complex network

Cascading failure can cause great damage to complex networks, so it is of great significance to improve the network robustness against cascading failure. Many previous existing works on load-redistribution strategies require global information, which is not suitable for large scale networks, and some strategies based on local information assume that the load of a node is always its initial load before the network is attacked, and the load of the failure node is redistributed to its neighbors according to their initial load or initial residual capacity. This paper proposes a new load-redistribution strategy based on local information considering an ever-changing load. It redistributes the loads of the failure node to its nearest neighbors according to their current residual capacity, which makes full use of the residual capacity of the network. Experiments are conducted on two typical networks and two real networks, and the experimental results show that the new load-redistribution strategy can reduce the size of cascading failure efficiently.     

Analysis of cascading failure in electric grid based on power flow entropy

Large-scale blackouts are an intrinsic drawback of electric power transmission grids. Here we propose a concept of power flow entropy to quantify the overall heterogeneity of load distribution and then investigate the relationship between the power flow entropy and cascading failure. Simulation results, from the small-world 300-node test system and the IEEE 300-bus system, show that the power flow entropy has close relations with the cascading failure in terms of both the dynamic propagation course and the static blackout size. Particularly, at the early stage of failure spreading the potential large blackout can be identified according to the power flow entropy. The power flow entropy can serve as an index not only for long-term planning, but also for short-term operational defense to large-scale blackouts.     

基于空间光调制器的光束大角度扫描技术研究

为实现一束激光在90°锥形范围内的扫描,利用液晶空间光调制器在光束偏转控制时精度高、无机械惯性等优点,研究并建立了基于液晶空间光调制器的光束偏转和角放大光路系统。提出了空间光调制器的可编程相位调制算法和角放大光路结构,推导了空间光调制器光束偏转角度与相位灰度驱动图的关系,设计了角度放大倍率高于22倍的角放大光路系统。在此基础上,建立了光束扫描控制实验系统,对该装置角度出射范围进行了测量,将实际的角放大倍率与设计值进行对比。实验结果表明:研制系统的出射视场角可达91.22°,并可通过畸变校正实现出射视场角范围内的规则形状扫描。该研究在光束敏捷控制、无线激光通信、目标搜索与追踪等领域具有重要的研究价值和应用前景。     

基于单星模拟器星等控制光源的研究

为了适应航天技术的发展和更高的技术要求,设计了一种带闭环控制的单星模拟器。介绍了单星模拟器的工作原理、单星模拟器的光能分析、单星模拟器光源及相关组件的选取、闭环控制系统的设计及星模拟器星等的实现。所设计的星模拟器能够实现对-2~+6星等的模拟,稳定性误差不超过相应星等照度的±10%。检测结果表明,该单星模拟器稳定可靠,调节灵活,能满足单星模拟器设计要求。     

Optical control of light propagation in photonic crystal based on electromagnetically induced transparency

A kind of photonic crystal structure with modulation of the refractive index is investigated both experimentally and theoretically for exploiting electromagnetically induced transparency(EIT).The combination of EIT with periodically modulated refractive index medium gives rise to high efficiency reflection as well as forbidden transmission in a threelevel atomic system coupled by standing wave.We show an accurate theoretical simulation via transfer-matrix theory,automatically accounting for multilayer reflections,thus fully demonstrate the existence of photonic crystal structure in atomic vapor.     

Active control of radiated sound power of a smart cylindrical shell based on radiation modes

A new approach is proposed in this paper based on radiation modes to control the radiated sound pressure of a smart cylindrical shell equipped with piezoelectric sensor and actuators. The radiation modes determine the specific distribution of normal velocity of the shell that independently radiates sound to the surrounding space. In this study, the first radiation mode is controlled since it is the most effective mode in terms of the radiated power. The results indicate that most of the sound power is attenuated by controlling only this mode. The extended Hamilton’s principle, the Sanders shell theory and the assumed mode method are used to derive the equations of motion in a state space form that is suitable to design the controller. The radiated sound pressure is calculated using the simplified Kirchhoff-Helmholtz integral along with a Kalman filter to observe the system states, and a modified higher harmonic control (MHHC) is designed to attenuate the sound power. A numerical simulation demonstrated the effectiveness of the proposed approach compared to active vibration control (AVC) in attenuating the radiated sound in the low frequency domain.     

Active Brownian motion tunable by light

Active Brownian particles are capable of taking up energy from their environment and converting it into directed motion; examples range from chemotactic cells and bacteria to artificial micro-swimmers. We have recently demonstrated that Janus particles, i.e.?gold-capped colloidal spheres, suspended in a critical binary liquid mixture perform active Brownian motion when illuminated by light. In this paper, we investigate in more detail their swimming mechanism, leading to active Brownian motion. We show that the illumination-borne heating induces a local asymmetric demixing of the binary mixture, generating a spatial chemical concentration gradient which is responsible for the particle's self-diffusiophoretic motion. We study this effect as a function of the functionalization of the gold cap, the particle size and the illumination intensity: the functionalization determines what component of the binary mixture is preferentially adsorbed at the cap and the swimming direction (towards or away from the cap); the particle size determines the rotational diffusion and, therefore, the random reorientation of the particle; and the intensity tunes the strength of the heating and, therefore, of the motion. Finally, we harness this dependence of the swimming strength on the illumination intensity to investigate the behavior of a micro-swimmer in a spatial light gradient, where its swimming properties are space-dependent.     

基于声辐射模态的有源结构声传入及其辐射控制

从辐射模态的概念和角度研究利用结构误差传感方法对弹性封闭空间结构声辐射进行传感和有源控制。首先分析了辐射模态的数学和物理意义并揭示了辐射模态与声腔模态之间的内在耦合关系。通过声辐射模态建立了弹性封闭空间结构声辐射传感和有源控制模型,并提出了通过传感器阵列测量结构表面有限点的振速分布和设计特定的辐射模态空间滤波器来获得控制所需的误差信号。在此基础上对封闭空间结构声辐射有源控制和误差传感策略进行了深入的理论和数值仿真分析,重点讨论了传感器的数量和布放对辐射模态传感及其有源控制效果的影响。结果表明:辐射模态与声腔模态的耦合具有严格的选择性,各阶辐射模态的形状和与相耦合的主导声模态在耦合面上的形状非常相似;利用结构传感技术传感封闭空间的辐射模态时测点不足或空间采样不足将可能产生较严重的模态泄漏问题,使得不希望的结构模态泄露进所测的辐射模态当中来。在低频范围内,一般只需传感并最小化前三阶有效辐射模态声势能,在更低频和空间声模态频率附近,只需最小化前一阶最有效辐射模态声势能,便能和总声势能最小化策略控制效果基本一样。     

All optical arbitrary waveform generation by optical frequency comb based on cascading intensity modulation

We propose and experimentally demonstrate an all optical arbitrary waveform generation by optical frequency comb (OFC) based on cascading intensity modulation. By selecting spectral lines of interest from OFC through optical filters, 10 GHz, 20 GHz, and 60 GHz sinusoidal signals with low phase noise and more complex waveforms, including ultra-short pulse, half-wave cosine, and single frequency modulated MMW signals, are generated easily.     

Airy光纤:基于阵列波导耦合的光场调控方法

近年来,Airy光束作为一种无衍射光束,其特性引起了研究者的广泛关注,人们对它的理论研究、实验验证、实际应用多个方面都取得了长足的进步.而Airy光纤作为一种可生成Airy光束的波导器件,结合其光纤自身优点可适用于多种应用领域,因此开展新型Airy光纤的探索研究、拓展Airy光束的应用范围具有重要现实意义.本文从Airy光束的原理、光纤结构设计、光纤内部光束生成机理、生成光束波长响应特性以及Airy光纤研究现状和应用五个方面展开了较系统的讨论.     

2 W quasi-white-light based on idler-resonant optical parametric oscillation cascading sum-frequency generation with PPSLT

We present a high power red-green-blue (RGB) laser light source based on cascaded quasi-phasematched wavelength conversions in a single stoichiometric lithium tantalate. The superiority of the experimental setup is: the facula of the incident beam is elliptical to increase interaction volume, and the cavity was an idler resonant configuration for realizing more efficient red and blue light output. An average power of 2 W of quasi-white-light was obtained by proper combination of the RGB three colors. The conversion efficiency for the power of the quasi-white-light over pump power reached 36%. This efficiency and powerful RGB laser light source has potential applications in laser-based projection display et al.     

基于免疫双态微粒群的混沌系统自抗扰控制

利用人工免疫算法及粒子群优化算法融合的优点,提出了一种免疫双态微粒群算法(immune binary-state particle swarm optimization, IBPSO)的自抗扰控制器(IBPSO-ADRC),应用于混沌系统控制,构建一种混沌系统自抗扰控制系统.实验研究表明:该控制方法无需了解动态系统精确模型,具有响应速度快,有效抑制混沌系统参数摄动及较强抗干扰能力的特点. 关键词： 人工免疫系统 微粒群算法 混沌系统 自抗扰控制器     

基于相继故障信息的网络节点重要度演化机理分析

分析了过载机制下节点重要度的演化机理.首先,在可调负载重分配级联失效模型基础上,根据节点失效后其分配范围内节点的负载振荡程度,提出了考虑级联失效局域信息的复杂网络节点重要度指标.该指标具有两个特点:一是值的大小可以清晰地指出节点的失效后果;二是可以依据网络负载分配范围、负载分配均匀性、节点容量系数及网络结构特征分析节点重要度的演化情况.然后,给出该指标的仿真算法,并推导了最近邻择优分配和全局择优分配规则下随机网络和无标度网络节点重要度的解析表达式.最后,实验验证了该指标的有效性和可行性,并深入分析了网络中节点重要度的演化机理,即非关键节点如何演化成影响网络级联失效行为的关键节点.     

Edge-based-attack induced cascading failures on scale-free networks

Most previous existing works on cascading failures only focused on attacks on nodes rather than on edges. In this paper, we discuss the response of scale-free networks subject to two different attacks on edges during cascading propagation, i.e., edge removal by either the descending or ascending order of the loads. Adopting a cascading model with a breakdown probability p of an overload edge and the initial load (k_ik_j)^α of an edge ij, where k_i and k_j are the degrees of the nodes connected by the edge ij and α is a tunable parameter, we investigate the effects of two attacks for the robustness of Barabási-Albert (BA) scale-free networks against cascading failures. In the case of α<1, our investigation by the numerical simulations leads to a counterintuitive finding that BA scale-free networks are more sensitive to attacks on the edges with the lowest loads than the ones with the highest loads, not relating to the breakdown probability. In addition, the same effect of two attacks in the case of α=1 may be useful in furthering studies on the control and defense of cascading failures in many real-life networks. We then confirm by the theoretical analysis these results observed in simulations.     

Active control of double-glazed windowsPart I: Feedforward control

This paper describes an experimental investigation of an actively controlled double-glazed window. It is the first part of two companion papers, and it shows the results with a feedforward controller. In the second part about results obtained with adaptive feedback control will be reported. A laboratory version of the window was equipped with loudspeakers and microphones inside the cavity. Various positions of loudspeakers and microphones were tested with band-limited white noise excitation. Different combinations of distributed loudspeakers were realized driving them in parallel by single channels of the controller. Similarly the signals of microphones were summed to realize simple modal filters. Plane mode control as well as control of higher cavity modes were performed with a feedforward controller and the reference signal taken directly from the primary signal. Additionally tests with different traffic noise examples were performed showing the ability of the actively controlled window to enhance protection against traffic noise.     

Active and switchable thermal control

<正>In the past century, actively controlling electron transport has led to unprecedented advances in the digital world. Controlling phonon(i.e., thermal) transport like electron transport is a current topic of interest. To realize active and switchable thermal control(Figure 1), numerous studies have been conducted recently due to the emerging challenges in the fields of thermal management, heating and refrigeration,