Research and application of coupled two-dimensional asymmetric bistable stochastic resonance system

Considering that the vibration signal of rolling bearing is very weak and difficult to be extracted under the working environment noise, a two-dimensional asymmetric bistable system (TDAB) is proposed. The system is coupled by two systems, and the weak signal is enhanced by adjusting the control system (monostable system) to adjust the controlled system (asymmetric bistable system). First, under the condition of adiabatic approximation system, the signal-to-noise ratio (SNR) is deduced, and analyzes the influence of different system parameters on the shape of potential function. Then the effects of each parameter on the SNR of the system are analyzed theoretically. Finally, combined with the adaptive intelligent algorithm, the parameters of the controlled system are optimized, and then the coupling coefficient and control system parameters are adjusted to obtain better system performance. The TDAB system obtained is applied to different bearing fault diagnosis and compared with different coupling systems. The experimental results show that the method can extract the characteristic frequency effectively and has good spectrum amplification performance and anti-noise capability. It is proved that the TDAB system can also have good detection effect in practical application.     

Inverse full state hybrid projective synchronization for chaotic maps with different dimensions

A new synchronization scheme for chaotic(hyperchaotic) maps with different dimensions is presented.Specifically,given a drive system map with dimension n and a response system with dimension m,the proposed approach enables each drive system state to be synchronized with a linear response combination of the response system states.The method,based on the Lyapunov stability theory and the pole placement technique,presents some useful features:(i) it enables synchronization to be achieved for both cases of n m and n m;(ii) it is rigorous,being based on theorems;(iii) it can be readily applied to any chaotic(hyperchaotic) maps defined to date.Finally,the capability of the approach is illustrated by synchronization examples between the two-dimensional H′enon map(as the drive system) and the three-dimensional hyperchaotic Wang map(as the response system),and the three-dimensional H′enon-like map(as the drive system) and the two-dimensional Lorenz discrete-time system(as the response system).     

Quantization of a nonholonomic system

In this Letter, we consider the problem of quantizing a nonholonomic system. This is highly nontrivial since such a system, which is subject to nonholonomic constraints, is not variational (or Hamiltonian). Our approach is to couple the system to a field which enforces the constraint in a suitable limit. We consider a simple but representative nonholonomic system, the Chaplygin sleigh. We then quantize the full (Hamiltonian) system. This system exhibits a key complicating feature of some nonholonomic systems-internal dissipative dynamics.     

La_(1．6-x)Nd_(0．4)Sr_xCuO_4超导电性的反常特性

分析并讨论了La_(1．6-x)Nd_(0．4)Sr_x CuO_4系列单相性样品(x=0．08～0．25)的晶体结构和超导电性。结果表明,晶体结构随着Sr掺杂量的变化规律与La_(2-x)Sr_x CuO_4系列相似。超导电性方面,La_(1．6-x)Nd_(0．4)Sr_x CuO_4系列超导转变温度均远小于相应的La_(2-x)Sr_xCuO_4系列组分。同La_(1．875)Ba_(0．125)CuO_4相似,La_(1．48)Nd_(0．4)Sr_(0．12)CuO_4处出现显著的极小值8K但高于La_(1．875)Ba_(0．125)CuO_4。La_(1．6-x)Nd_(0．4)Sr_x CuO_4系列的超导电性明显与La_(2-x)Sr_x CuO_4系列有着不同的特性,虽然同La_(2-x) Ba_xCuO_4系列相似但仍有区别。我们从其晶体结构的反常变化的角度对La_(1．6-x)Nd_(0．4)Sr_x CuO_4系列反常的超导电性做了初步的解释。     

Time-wavelength assignment algorithms: Hardware/performance tradeoffs

In this paper we present time-wavelength assignment algorithms that consider the following system parameters: (1) the system hardware in terms of the transmitters' and receivers' tuning capabilities (slow or fast tuning) and (2) the traffic matrix. The ulgorithms' objective is to maximize the bandwidth efficiency, i.e., to minimize the frame duration. Each algorithm will be suitable for a different set of system parameters. We present trade-offs between the system hardware and the algorithm' performance for various traffic patterns. These trade-offs can be used as guidelines for the system designer that needs to decide the system hardware for a given traffic pattern and required system performance. Moreouer, for a given system hardware and traffic patterns, each node can distributively decide which algorithm should be used, i.e., the algorithm that will maximize the system performance.     

大型ICF实验物理诊断系统的集中控制设计

 大型惯性约束聚变(ICF)实验中需要配备精密的物理诊断集中控制系统，以保证实验能够安全、高效地进行。针对国内正在建设的ICF大型激光装置，提出了一个完整的物理诊断集中控制系统构建框架。该ICF的物理诊断集中控制系统分两个层次。上层是管理控制层，由大型计算机组建的工作站和服务器构成，提供集中式操作控制、状态报告、数据采集、管理、处理和集中显示。下层是由大量嵌入式处理器构成的实时控制层，它直接面对装置各部分的控制点，由上层管理系统来协调下层每个处理器工作。采用现场可编程门阵列(FPGA)技术为该系统设计了两个子控制系统：在FPGA上为指令同步系统实现了一个高性能的嵌入式片上系统平台；利用FPGA将同步触发信号系统整合到PXI系统中实现集中控制。     

Impulsive generalized synchronization of chaotic system

In this paper, with a given manifold y= H(x) , we have constructed a response system for a continuous-time chaotic system as a drive system, and used impulsive control theory to demonstrate theoretically that this response system can achieve impulsive generalized synchronization (GS) with the drive system. Our theoretical result is supported by numerical examples.     

Chemorheological studies on a thermoset PU/clay nanocomposite system

Chemorheology of neat polyurethane (PU) system, composed of a diisocyanate and a polyol, and a PU/clay nanocomposite system with an organoclay 5 phr was investigated. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were used to study the polymerization behavior of both systems. The PU/clay nanocomposite system showed a faster polymerization rate than neat PU system. The rheological property change during isothermal and dynamic polymerization of both systems was measured using a rheometer to analyze chemorheology of them. A viscosity function that can describe viscosity change of a thermoset resin system during polymerization was adopted to analyze the viscosity data obtained from the rheometer. The PU/clay nanocomposite system had shorter gelation time than neat PU system. Structural analyses of the PU/clay nanocomposite were performed by X-ray diffractometer (XRD) and transmission electronic microscope (TEM).     

基于深度学习的无波前探测自适应光学系统研究进展

近年来自适应光学（AO）系统向着小型化和低成本化趋势发展,无波前探测自适应光学（WFSless AO）系统由于结构简单、应用范围广,成为目前相关领域的研究热点。硬件环境确定后,系统控制算法决定了WFSless AO系统的校正效果和系统收敛速度。新兴的深度学习及人工神经网络为WFSless AO系统控制算法注入了新的活力,进一步推动了WFSless AO系统的理论发展与应用发展。在回顾前期WFSless AO系统控制算法的基础上,全面介绍了近年来卷积神经网络（CNN）、长短期记忆神经网络（LSTM）、深度强化学习在WFSless AO系统控制中的应用,并对WFSless AO系统中各种深度学习模型的特点进行了总结。概述了WFSless AO技术在天文观测、显微成像、眼底成像、激光通信等领域的应用。     

CFETR水冷包层一回路系统初步设计和配套设备的模拟

通过设计两套独立的聚变堆一回路系统(PHTS),分别为増殖区(BZ)和第一壁(FW)提供冷却,采用在FW PHTS和电力转换系统(PCS)之间设计一套中间传热系统(IHTS)的方案,解决了托卡马克装置脉冲操作对PCS的影响。同时利用Ebsilon软件建立一套核电厂配套设备(BOP)的系统模型,模拟该系统在1.5GW聚变功率下的运行状况。初步的设计包括管道、蒸汽发生器(SG)、中间换热器(IHX)、给水泵在内的PHTS设计和布局,并确定了系统各部件的主要参数。从Ebsilon软件模拟的结果可以看出,该系统可以在脉冲/间隙时间为2h/0.5h的模式下以80%的功率下平稳的运行,保证了PCS有持续稳定的电力输出。     

Notes on Multi-linear Variable Separation Approach

The multi-linear variable separation approach method is very useful to solve (2+1)-dimensional integrable systems. In this letter, we extend this method to solve (1+1)-dimensional Boiti system, (2+1)-dimensional Burgers system, (2+1)-dimensional breaking soliton system, and (2+1)-dimensional Maccari system. Some new exact solutions are obtained and the universal formula obtained from many (2+1)-dimensional systems is extended or modified.     

基于新型安全架构的HEPS插入件安全控制系统

高能同步辐射光源（HEPS）插入件控制系统的主要功能是实现插入件磁间隙的开合运动控制。插入件控制系统的安全运动对插入件、储存环和光束线站的设备和人员安全至关重要。针对HEPS插入件控制系统的安全需求,研究了工业安全设计的标准和规范,在国内外同类型插入件控制系统中首次设计和实现了基于新型安全架构的安全系统。安全系统的设计和实施符合国际安全标准,并达到了安全完整性三级的高安全等级。该系统已成功应用在HEPS测试束线低温波荡器中,并完成了系统性的测试。测试结果表明,HEPS插入件安全系统实现了所有预期的安全指标,达到了高安全等级工业控制系统的标准。     

Generalized Projective Synchronization Between Rössler System and New Unified Chaotic System

Based on symbolic computation system Maple and Lyapunov stability theory, an active control method is used to projectively synchronize two different chaotic systems — Lorenz-Chen-Lü system (LCL) and Rössler system, which belong to different dynamic systems. In this paper, we achieve generalized projective synchronization between the two different chaotic systems by directing the scaling factor onto the desired value arbitrarily. To illustrate our result, numerical simulations are used to perform the process of the synchronization and successfully put the orbits of drive system (LCL) and orbits of the response system (Rössler system) in the same plot for understanding intuitively.     

Auction-based spectrum allocation for CoMP systems utilizing hybrid division duplex

The coordinated multi-point (CoMP) transmission is a well-recognized promising technique for achieving high spectral efficiency. In this paper, we study the performance of the spectrum allocation and the system utility of the CoMP systems. First, we combine the hybrid division duplex (HDD) with a CoMP system to form a CoMP–HDD system, for the purpose of guaranteeing the quality demand of the channel state information (CSI) feedback. Second, in order to improve the system utility and the spectrum allocation efficiency of the CoMP–HDD system, we utilize the auction theory for the spectrum allocation. A system utility maximization problem is formulated as an NP-hard problem. Finally, we propose a multi-band multi-winner (MBMW) greedy algorithm to optimize the system utility and the spectrum allocation efficiency. Our simulation results demonstrate the effectiveness of the proposed algorithm.     

波前编码成像系统景深延拓扩展率的研究

研究三次相位板的波前编码光学系统,发现在一定的条件下系统调制传递函数(MTF)对波前编码系统的离焦不敏感,才能得到波前编码系统的景深.对比传统光学系统的景深,得到波前编码系统的景深延拓扩展率的表达式.分析空间频率取值范围和三次相位板系数α,发现当a=20π时,波前编码系统可以将传统光学系统的景深扩大60倍以上.     

精密工作台的设计与实验研究

微器件装配技术是实现组合结构的微机械电子学系统(MEMS)的关键技术之一,精密工作台系统则是微装配系统的一个重要组成部分。精密工作台系统包括粗动工作台和微动工作台:粗动工作台包括精密机械及其传动系统、光栅定位系统、直流力矩电机驱动系统及计算机控制系统;微动工作台包括微动台、压电陶瓷驱动电源和电感测微移。实验结果表明,粗动台系统的最高速度为5mm/s,最低速度为3.4μm/s,系统的重复定位精度为±1μm;微动台系统的定位精度可达到±1μm。     

An improved channel estimation method for a WDM transmission system derived from the CO-OFDM with PDM 64-QAM

In this study, firstly we presented a wavelength division multiplexed (WDM) transmission system derived from the coherent optical orthogonal frequency division multiplexing (CO-OFDM) with polarization division multiplexing (PDM) and 64 order quadrature amplitude modulation (QAM). We then proposed an improved channel estimation method based on discrete Fourier transform for the system to further improve the performance of the WDM transmission system. Under the experimental conditions employed, the principle and the spectral efficiency of the system, including a proposed algorithm to improve its performance (e.g. the robustness of the transmission impairments of the system) were studied. The simulations results demonstrated that our method improved the system efficient significantly. The system signal at 24 Tb/s can achieve a spectral efficiency of 12.5 bit/s/Hz up to a distance of 2000 km.     

基于线性相位反演技术的自适应光学闭环实验研究

利用成像光学系统、变形镜、装有图像采集卡和D/A卡的PC机等建立了一套基于线性相位反演技术的自适应光学闭环实验系统.在Windows操作系统下用VC完成图像处理和控制算法.利用一台高测量精度的哈特曼传感器测量波前信息并评价自适应光学系统的校正效果.在不同像差大小状态下研究了这种基于线性相位反演技术的自适应光学系统的像差校正能力.收敛速度,稳定性等.实验结果表明,基于线性相位反演技术的自适应光学系统对静态小像差有较好的校正效果.     

Optical design and analysis of illumination system based on augmented reality北大核心CSCD

照明系统是增强现实光学系统的重要组成部分,其体积、照度均匀性、能量利用率直接影响增强现实照明系统的质量,因此在照明系统中对光源二次配光非常重要。针对增强现实系统的自由曲面透镜形式和照明系统开展研究,重点分析准直系统集光角度与体积的对应关系,在对光源准直系统的面型构建详细分析基础上,对中心透射边缘反射的折反射式准直系统的面型进行求解,结合偏微分方程法和划分网格法,设计了自由曲面透镜,该系统与偏振分光棱镜共同组成硅基液晶（liquid crystal on silicon,LCoS）照明系统。仿真分析结果表明:系统照度均匀性达到91.96%,若不计偏振影响,照明系统光学效率达到66.6%。该系统具有结构简单紧凑、体积小、质量轻、照度均匀性高等特点,满足增强现实眼镜的需求。