Correlation estimators based on simple nonlinear transformations

The computational cost of estimating correlations may be reduced by employing sums of simple nonlinear functions of the data. A quadruplex transformation is presented and the performance of the associated estimator is analyzed for real and complex Gaussian processes. With independent observations, the variance of the estimator is approximately 14% higher than that obtained by averaging lag products     

Novel active-R synthesis of a driving-point impedance

A novel active-R synthesis baaed on the single-pole rolloff characteristics of operational amplifiers is described. Various types of driving-point impedance, such as an inductance, frequency-dependent negative-resistance and frequency-dependent negative-inductance are systematically derived by the suitable choice of the amplifier transfer function. It is shown by experiments that the inductance simulator presents reliable high frequency performance.     

AFDX端系统协议软件设计与实现

网络作为航电系统的核心部分,其性能直接影响航电系统。AFDX网络是新一代航空电子系统的传输网络技术,具有高速、确定性和稳定性的特点。在深入研究AFDX网络协议的基础上,结合航电网络的实际应用,根据AFDX端系统关于冗余管理、完整性检测和VL隔离的特点,提出了一种AFDX端系统协议软件的设计方法。该方法通过采样、队列和SAP三类端口实现了AFDX标准数据的发送和接收功能,支持10(Mb.s-1)/100(Mb.s-1)的数据传输,并采用了VL管理、冗余管理和完整性检测方法,有效提高了数据传输的确定性和稳定性。多次的功能和性能测试表明,该软件设计方法实现了ARINC664 P7协议规定的AFDX端系统协议栈功能,具有良好的正确性和可靠性。     

基于PXA255的彩色LCD驱动的设计与实现

LCD(液晶显示屏)功能实现的好坏直接关系到掌上电脑的整体性能表现。然而LCD种类繁多,工程师需要针对各种显示屏的时序匹配以及控制器的不同特点进行设计。基于嵌入式Linux和PXA255处理器的背景下,介绍了彩色LCD显示功能的实现方法。其中,首先描述了显示驱动程序的架构;接着介绍了实现LCD的显示功能的硬件平台;和说明了PXA255的显示控制器的使用;最后给出了实现LCD显示功能的可行的软件方案。     

Blocking probability of heterogeneous traffic in a multiratemulticast switch

A multirate multicast switch, which can provide a single uniform switching function for vastly different classes of traffic, is crucial for the successful deployment of integrated broadband networks. We analyze the call blocking probability of heterogeneous circuit switched traffic in a multirate multicast switch using the arrival modulation technique. For the analysis, we introduce two simple traffic models: fan-out heterogeneous traffic and bandwidth heterogeneous traffic. The analysis of two simplified traffic models shows that calls of different characteristics interact in complex yet subtle ways. Our results on fan-out heterogeneous traffic show that the performance gap between large fan-out traffic and small fan-out traffic increases when two types of traffic are mixed. On the other hand, in bandwidth heterogeneous traffic, the performance gap between traffic of different bandwidth decreases. A further investigation indicates that the two types of interactions coexist in general heterogeneous traffic. We conclude the paper introducing several methods to improve the performance of multirate multicast traffic     

A Simulation Study of Clock Recovery in QPSK and 9QPRS Systems

Computer simulation is employed to assess jitter performance of a clock recovery circuit as a function of the characteristics of the rectifier being used. Several types of rectifiers are compared, some operating at baseband, others at intermediate frequency (IF). It is shown that the best choice between them depends both on the modulation format and on the excess bandwidth factor of the pulse spectrum. In QPSK systems, fourth-law rectifiers outperform the others for rolloff factors up to 0.2 while, for higher values, baseband absolutevalue rectifiers are preferable. In the case of 9QPRS, baseband absolutevalue rectifiers provide jitter reductions of one order of magnitude at high signal-to-noise ratios.     

BDS在轨卫星钟性能评估与对比

从卫星钟基本特性、频率稳定度、钟差预报精度等方面对 BDS 三种类型卫星钟 (RAFS-1、RAFS-2、PHM)进行综合对比分析，结果表明：PHM 卫星钟性能指标显著优于 RAFS； RAFS-2 卫星钟性能指标显著优于 RAFS-1，频率稳定度指标和钟差预报精度提升了 1 倍左右，且 RAFS-2 卫星钟增加了相位连接功能，保证了在轨卫星钟在调整过程中不会影响时间频率服务。     

WPAN应用电磁环境中干扰模型的分析及仿真

文中首先介绍了无线个域网所要面对的各种干扰及它们各自的特点，给出了干扰的拓扑结构和传播模型；针对干扰的特点，由阻塞率的模型，经过数学变换推导出以干扰总电平为变量的统计模型，以此为基础分析干扰的统计特性；利用统计模型分析跳频技术在WPAN应用环境下性能的同时，也利用有关软件对跳频技术在这些干扰环境中的性能作了仿真，从两者比较结果中可以看出，干扰的统计模型是比较准确的，它对今后的实际研究工作具有一定的指导意义。     

A Bio‐inspired Potassium and pH Responsive Double‐gated Nanochannel

Bio‐inspired nanochannels have emerged as an interface to mimic the functionalities of biological nanochannels. One remaining challenge is to develop double‐gated nanochannels with dual response, which can regulate the ion transport direction by alternately opening and closing the two gates. In this work, a bio‐inspired potassium and pH responsive double‐gated nanosystem is presented, constructed through immobilizing C‐quadruplex and G‐quadruplex DNA molecules onto the top and bottom tip side of a cigar‐shaped nanochannel, respectively. It is demonstrated that the two gates of the nanochannel can be opened and closed alternately/simultaneously. This phenomenon results from the attached DNA conformational transition caused by adjusting the concentrations of potassium ion and proton. This design is believed to be the first example of dual‐responsive double‐gated nanosystem, and paves a new way to investigate more intelligent bio‐inspired nanofluidic system.     

RO PUF硬件物理指纹性能评估

入网设备的身份认证是工业互联网、物联网安全运行的基础.通过分析物理不可克隆函数(Physical Unclonable Function,PUF)作为入网设备的身份凭据应具有的特性,建立了其性能的多层指标体系.按照性能指标的重要性分为必要指标、重要指标和应用指标,对每项指标及其评估方法进行了说明,并给出了可用于PUF选型的综合评估方案.实验结果表明,该PUF性能指标体系和评估方案在工程上是可行的.     

相关跳频序列的Viterbi译码算法及其纠错性能分析

该文分析了相关跳频通信系统中频率转移函数的纠错性能,将Viterbi算法应用于接收端跳变频点序列的译码,并结合相关跳频转移函数的特点对译码过程作出了改进.针对满足最大相关纠错性能的频率转移函数,详细分析了Viterbi算法的译码性能.仿真结果表明,通过相关纠错,对随机错误在低信噪比条件下可以获得5-8dB的增益.     

Design of Two-Dimensional Pseudorotated Digital Filters Using Concept of Generalized Immittance Converter

A new realization procedure based on the concept of the generalized immittance converter (GIC) is proposed for two-dimensional (2D) pseudorotated digital filters that have circularly symmetric magnitude response characteristics. By applying a suitable transformation to a one-dimensional stable discrete transfer function, the 2D discrete transfer function of the corresponding pseudorotated filter is obtained. This transfer function is then realized by using a direct computer-based method. It is shown that four types of GIC pseudorotated filter structures can be obtained by interconnecting a few specific types of digital modules. The modularity and regularity nature of these filters make them attractive for very large-scale integration implementation.     

Spectral Correlation of Modulated Signals: Part I--Analog Modulation

The importance of the concept of cyclostationarity in design and analysis of signal detectors, synchronizers, and extractors in communication systems is briefly discussed, and the central role of spectral correlation, in the characterization of random processes that are cyclostationary in the wide sense, is explained. A spectral correlation function that is a generalization of the power spectral density function is described, and a corresponding generalization of the Wiener-Khinchine relation and several other fundamental spectral correlation relations also are described. Explicit formulas for the spectral correlation function for various types of analog-modulated signals are derived. This includes pulse and carrier amplitude modulation, quadrature amplitude carrier modulation, and phase and frequency carrier modulation. To illustrate the differing spectral correlation characteristics of different modulation types, the magnitudes of the spectral correlation functions are graphed or described in graphical terms as the heights of surfaces above a bifrequency plane.     

DNA‐Au Nanomachine Equipped with i‐Motif and G‐Quadruplex for Triple Combinatorial Anti‐Tumor Therapy

In the present study, the design, construction, and operation of a functional DNA‐decorated dynamic gold (Au) nanomachine as a therapeutic agent for triple combinatorial anti‐cancer therapy are revealed. Taking advantage of the intrinsic optical properties of Au nanoparticles, which depend on their size, a cytosine rich i‐motif sequence is employed for intracellular pH‐sensitive duplex dissociation and subsequent aggregation of the DNA‐Au nanomachine, enabling anticancer drug release and photothermal ablation upon irradiation with infrared light. Moreover, another functional DNA sequence, a G‐quadruplex, is exploited for the stable loading and intracellular delivery of a photosensitizer to achieve effective photodynamic therapy under red light illumination. The G‐quadruplex‐assisted enhanced reactive oxygen species generation, pH‐responsive dynamic aggregation behavior, consequent drug release, and the photothermal effect are investigated. Furthermore, the combinatorial chemo, photodynamic, and photothermal therapeutic effects of the functional DNA‐decorated Au nanomachines are evaluated in vitro and in vivo using a triple negative breast cancer model.     

迷彩涂层1064 nm激光散射特性测量及建模

迷彩涂层1064 nm激光散射特性对激光探测装备的极限作用距离和军事装备激光隐身性能有显著影响,而目前对涂层材料的激光散射特性的研究大都是针对单一种类涂层。本文根据不同类型迷彩涂层由不同颜色组成的特点,通过分别测量不同颜色迷彩涂层的双向反射分布函数(BRDF),再根据国军标中不同迷彩涂层颜色的面积比例规定进行加权计算,得到不同种类迷彩涂层的BRDF。以草原夏季型迷彩涂层为例,利用上述方法对其BRDF进行测量和计算,并利用五参数经验模型进行参数建模,得到草原夏季型迷彩涂层的参数模型。通过拼接实验,验证了计算方法的正确性。对于进一步研究军事装备的涂层材料激光散射特性提供数据依据,为研究类似情况下多种材料复合涂层的激光散射特性研究提供了借鉴思路。     

基于冲激谱线检测的调制识别

现代卫星通信系统为满足传输速率和加密等要求,采用了多种复杂或高阶复合调制信号。为实现各类调制信号的检测与识别,信号之间不同类型谱的谱线分布是重要特征之一。在介绍常见通信卫星调制信号在不同类型谱下的冲激谱线特征基础上,提出了一种基于线性调频Z变换的冲激谱线检测方法,消除了离散频谱“栅栏效应”对检测值的影响。通过高次方谱和分数低阶循环自相关谱的区域谱线检测方法,构建特征向量进行分类设计,实现对常见通信卫星调制信号的分类识别。该算法在低信噪比、未知码元速率等先验信息的情况下具有较好的识别效果。     

Use of periodic and monotonic activation functions in multilayerfeedforward neural networks trained by extended Kalman filter algorithm

The authors investigate the convergence and pruning performance of multilayer feedforward neural networks with different types of neuronal activation functions in solving various problems. Three types of activation functions are adopted in the network, namely, the traditional sigmoid function, the sinusoidal function and a periodic function that can be considered as a combination of the first two functions. To speed up the learning, as well as to reduce the network size, the extended Kalman filter (EKF) algorithm conjunct with a pruning method is used to train the network. The corresponding networks are applied to solve five typical problems, namely, 4-point XOR logic function, parity generation, handwritten digit recognition, piecewise linear function approximation and sunspot series prediction. Simulation results show that periodic activation functions perform better than monotonic ones in solving multicluster classification problems. Moreover, the combined periodic activation function is found to possess the fast convergence and multicluster classification capabilities of the sinusoidal activation function while keeping the robustness property of the sigmoid function required in the modelling of unknown systems     

压电执行器及其在液压阀中的应用

以压电执行器为核心的高速开关阀及伺服阀等压电式液压阀具有频响高,微动性能好,结构紧凑等优点,是新型阀控类型之一,受到国内外研究者的持续关注。首先,该文介绍了阀用压电执行器的分类和特点,根据工作原理分为直推式和步进式2类4种形式;其次,对先导型、直动型、喷嘴挡板型和开关型4种典型压电阀的研究进展进行了梳理,分析了各自的代表性结构、性能特点。结果表明,随着未来对液压阀精密化、智能化需求的提升,压电液压阀的应用前景更广。因此,除高性能介电材料开发外,如微位移放大、迟滞补偿控制等关键压电驱动与控制技术仍有待深入研究。     

Performance Comparison of Graphene Nanoribbon FETs With Schottky Contacts and Doped Reservoirs

We present an atomistic 3-D simulation study of the performance of graphene-nanoribbon (GNR) Schottky-barrier field-effect transistors (SBFETs) and transistors with doped reservoirs (MOSFETs) by means of the self-consistent solution of the Poisson and SchrÖdinger equations within the nonequilibrium Green's function (NEGF) formalism. Ideal MOSFETs show slightly better electrical performance for both digital and terahertz applications. The impact of nonidealities on device performance has been investigated, taking into account the presence of single vacancy, edge roughness, and ionized impurities along the channel. In general, MOSFETs show more robust characteristics than SBFETs. Edge roughness and single-vacancy defect largely affect the performance of both device types.      

Study on Two‐Coil and Four‐Coil Wireless Power Transfer Systems Using Z‐Parameter Approach

A wireless power transfer (WPT) system is usually classified as being of either a two‐coil or four‐coil type. It is known that two‐coil WPT systems are suitable for short‐range transmissions, whereas four‐coil WPT systems are suitable for mid‐range transmissions. However, this paper reveals that the two aforementioned types of WPT system are alike in terms of their performance and characteristics, differing only when it comes to their matching‐network configurations. In this paper, we first find the optimum load and source conditions using Z‐parameters. Then, we estimate the maximum power transfer efficiency under the optimum load and source conditions, and we describe how to configure the matching networks pertaining to both types of WPT system for the given optimum load and source conditions. The two types of WPT system show the same performance with respect to the coupling coefficient and load impedance. Further, they also demonstrate an identical performance in the two cases considered in this paper, that is, a strong‐coupled case and a weak‐coupled case.