Kernel Generalization of Multi-Rate Probabilistic Principal Component Analysis for Fault Detection in Nonlinear Process

In practical process industries,a variety of online and offline sensors and measuring instruments have been used for process control and monitoring purposes,which indicates that the measurements coming from different sources are collected at different sampling rates.To build a complete process monitoring strategy,all these multi-rate measurements should be considered for data-based modeling and monitoring.In this paper,a novel kernel multi-rate probabilistic principal component analysis(K-MPPCA)model is proposed to extract the nonlinear correlations among different sampling rates.In the proposed model,the model parameters are calibrated using the kernel trick and the expectation-maximum(EM)algorithm.Also,the corresponding fault detection methods based on the nonlinear features are developed.Finally,a simulated nonlinear case and an actual pre-decarburization unit in the ammonia synthesis process are tested to demonstrate the efficiency of the proposed method.

Performance Improvement of DCF Supporting Multi-Rate in IEEE 802.11b Wireless LAN

This paper proposes a new channel access algorithm based on channel occupancy time （COT） fairness to guarantee fairness and improve the aggregate throughput of 802.11b multi-rate WLANs. In the algorithm, the COT is used as fairness index to analyze the fairness of WLANs instead of the channel access probability （CAP） used in the distributed coordination function （DCF）. The standard COT is given by access point （AP） and broadcasted to all wireless stations. The AP and wireless stations in the WLAN can achieve COT-based fairness by adjusting their packet length, sending the multiple back-to-back packets at one time, or giving up an opportunity to access the channel. Analysis and simulations show that our algorithm can provide COT-fairness. Compared with the CAP-based algorithm, the proposed algorithm leads to improvements in aggregate throughput of IEEE 802. lib multi-rate WLANs.

Research of Multi-Rate LDPC Decoding in Optical Communication System

Low-density parity-check code (LDPC) not only has good performance approaching the Shannon limit, but also has low decoding complexity and flexible structure. It is a research hot-spot in the field of channel coding in recent years and has a wide range of application prospects in optical communication systems. In this paper, the decoding aspects and performance of LDPC codes are analyzed and compared according to the bit error rate (BER) of LDPC codes. The computer simulation was carried out under additive white Gaussian noise (AWGN) channel and binary phase shift keying (BPSK) modulation. Through theoretical analysis and simulation results, this paper explores the way of multi-rate LDPC decoding.

A NEW DESIGN METHOD OF CDMA SPREADING CODES BASED ON MULTI-RATE UNITARY FILTER BANK

It is well-known that the multi-valued CDMA spreading codes can be designed by means of a pair of mirror multi-rate filter banks based on some optimizing criterion. This paper indicates that there exists a theoretical bound in the performance of its circulating correlation property, which is given by an explicit expression. Based on this analysis, a criterion of maximizing entropy is proposed to design such codes. Computer simulation result suggests that the resulted codes outperform the conventional binary balanced Gold codes for an asynchronous CDMA system.

Study of multi-rate multi-user detection based on supervision decision

Multi-user detection (MUD) based on multirate transmission in code division multiple access (CDMA) system is discussed. Under the requirement of signal interference ratio (SIR) detection at base station and framework with parallel interference cancellation, a supervision decision algorithm based on pre-decision of probabilistic data association (PDA) and hard decision is proposed. The detection performance is analyzed and simulation is implemented to show that the supervision decision algorithm improves the detection performance effectively.

Multi-rate sensor fusion-based adaptive discrete finite-time synergetic control for flexible-joint mechanical systems

This paper proposes an adaptive discrete finite-time synergetic control （ADFTSC） scheme based on a multi-rate sensor fusion estimator for flexible-joint mechanical systems in the presence of unmeasured states and dynamic uncertainties. Multi-rate sensors are employed to observe the system states which cannot be directly obtained by encoders due to the existence of joint flexibilities. By using an extended Kalman filter （EKF）, the finite-time synergetic controller is designed based on a sensor fusion estimator which estimates states and parameters of the mechanical system with multi-rate measurements. The proposed controller can guarantee the finite-time convergence of tracking errors by the theoretical derivation. Simulation and experimental studies are included to validate the effectiveness of the proposed approach.

A SINGLE PROCESSOR MULTI-RATE VOCODER

This paper presents the design of a full-duplex multi-rate vocoder which implements an LPC-10, CELPC and VSELPC algorithms in real time. A single commercially available digital signal processor IC, the TMS320C25, is used to perform the digital processing. The channel interfaces are configured with the design of ASIC, and including timing and control logic circuits.

Multi-rate tracking controller analysis and design for target tracking systems

As the sampling rates of the inner loop and the outer loop of the target tracking control system are different,a typical digital multi-rate control system was formed.If the traditional single-rate design method was applied,the low sampling rate loop will seriously impact the dynamical characteristic of the system.After analyzing and calculating the impact law of the low sampling rate loop to the bandwidth and the stability of the tracking system,a kind of multi-rate control system design method was introduced.Corresponding to the different sampling rates of the inner loop and the outer loop,the multi-rate control strategy was constituted by a high sampling rate sub-controller and a low sampling rate sub-controller.The two sub-controllers were designed separately and connected by means of the sampling rate converter.The low sampling rate controller determined the response rapidity of the system,while the high sampling rate controller applied additionally effective control outputs to the system during a sampling interval of the low sampling rate controller.With the introduced high and low sampling rates sub-controllers,the tracking control system can achieve the same performance as a single-rate controller with high sampling rate,yet it works under a much lower sampling rate.The simulation and experimental results show the effectiveness of the introduced multi-rate control design method.It reduces the settling time by 5 times and the over shoot by 4 times compared with the PID control.

CHANNEL ESTIMATION OF MULTI-RATE DS-CDMA SIGNALS IN SLOW FADING MULTIPATH CHANNELS

In Direct-Sequence Code Division Multiple Access(DS-CDMA) mobile communi-cation systems, it is very important to obtain accurate estimation of the channel parameters,especially that of the propagation delay. But the near-far problem may make the estimationcomplicated and can degrade the estimation performance significantly. In this paper, an efficientMaximum Likelihood (ML) method is presented for channel parameter estimation of multi-rateDS-CDMA systems in slow fading multipath channels in a near-far scenario. The algorithmextended the ML approach to multi-rate DS-CDMA systems, and proposes decomposing a multi-dimensional optimization problem into a series of one-dimensional optimization and has improvedcomputational efficiency. Theoretical analysis and numerical examples show that the estimatorproposed is effective and near-far resistant.

A NOVEL CROSS-LAYER STRATEGY OF VIDEO TRANSMISSION TO SOLVE PERFORMANCE ANOMALY IN MULTI-RATE IEEE 802.11 NETWORKS

When wireless hosts use different rates to transmit data in IEEE 802.11 networks, it will take on the state of performance anomaly which will severely decrease the throughputs of all the higher rate hosts. Hence, it is bad for video service transmission. Considering that video is very sensitive to packet delivery delay but can tolerate some packet losses, we propose a novel cross-layer scheme which takes these two characteristics into consideration. Firstly, the maximum number of retransmissions for a video Medium Access Control (MAC) frame is computed in MAC layer according to video frame rate requirement of application layer and current access delay of MAC layer. Secondly, within the margin of the tolerant Packet Loss Rate (PLR) of application layer, several video MAC frames are allowed to drop so that we can adaptively select the transmission rate as high as possible for the rest of video MAC frames in terms of current channel quality and the maximum number of retransmissions. Experiment results show that the proposed method can reduce the delay and jitter of video service and improve the throughputs of fast hosts. Therefore, it increases the quality of reconstructed video to a certain extent and relieves the performance anomaly of network effectively.

BLIND DETECTION FOR MULTI-RATE DS-CDMA SYSTEM WITH ANTENNA ARRAY AT THE BASE STATION

In this paper, we propose the blind space-time high rate multi-user detector for synchronous uplink multi-rate Direct Sequence Code Division Multiple Access （DS-CDMA） systems with antenna array at the base station. By employing antenna array at the base stations, the spatial dimension is used efficiently to suppress co-channel interference and increase the capacity for multi-rate CDMA system. After low rate physical users in the system are modeled as corresponding high rate virtual users, we construct the space-time signature vectors of virtual users. And subspace projection algorithm is employed to estimate space-time signature vectors blindly. Then a soft-decision high rate lnultiuser detector is proposed based on the estimated signature vectors, which avoids estimating the ambiguous complex factors which are necessary in traditional blind detector. Numerical simulation results evaluate the performance in terms of Bit Error Rate （BER） for the proposed scheme. Simultaneously, it demonstrates that the system capability increases two times when using twoelement antenna array.

On the Performance of Blind Chip Rate Estimation in Multi-Rate CDMA Transmissions Using Multi-Rate Sampling in Slow Flat Fading Channels

This paper considers blind chip rate estimation of DS-SS signals in multi-rate and multi-user DS-CDMA systems over channels having slow flat Rayleigh fading plus additive white Gaussian noise. Channel impulse response is estimated by a subspace method, and then the chip rate of each signal is estimated using zero crossing of estimated differential channel impulse response. For chip rate estimation of each user, an algorithm which uses weighted zero-crossing ratio is proposed. Maximum value of the weighted zero crossing ratio takes place in the Nyquist rate sampling frequency, which equals to the twice of the chip rate. Furthermore, bit time of each user is estimated using fluctuations of autocorrelation estimators. Since code length of each user can be obtained using bit time and chip time ratio. Fading channels reduce reliability factor of the proposed algo-rithm. To overcome this problem, a receiver with multiple antennas is proposed, and the reliability factor of the proposed algorithm is analyzed over both spatially correlated and independent fading channels.

智能钻井多目标协同优化系统研究与应用

在深井超深井钻探过程中,井眼中高强度、高研磨性地层导致的钻头早期磨损、井下钻具振动剧烈、井眼清洁不足等,严重制约了深井超深井的安全快速钻进。针对上述问题,文章提出了一种智能钻井多目标协同优化系统,可以实时跟踪、优化钻井参数,提高钻井性能。同时基于机械钻速和机械比能,定义了钻井性能综合评价指标;结合地应力、钻具振动、摩阻扭矩、井眼清洁和破岩能效等地质、物理模型,提出了包含探索、学习和应用三种模式的钻井参数实时优化流程,训练了融合支持向量回归模型和随机森林回归模型的钻井参数实时优化算法。该系统在深地川科1井进行了现场应用,提速比达到了41.5%,为深井超深井钻井优化提速提供了一种新的技术手段。

基于灵敏度协同的多馈入新能源集群最大容量优化分配方法

随着新能源接入比例的不断提高,并网系统逐渐演变为多馈入系统且电网强度逐渐变弱,谐振问题将成为限制新能源渗透率提升的关键因素之一。为此,提出一种谐振约束下用于提升多馈入新能源集群最大接入容量的优化分配方法。首先,建立含工作点的并网逆变器阻抗模型,基于电网络理论获得了广义多馈入系统的聚合模型。然后,构建相角裕度关于集群容量的极值函数,并应用拉格朗日乘数法获得了一定容量下稳定裕度最大时集群阻抗灵敏度需保持一致的极值条件。在此基础上,面向谐振约束下区域电网新能源最大支撑需求,提出基于灵敏度协同的集群容量阈值求解及分配优化方法,并对所提方法复杂度进行分析。所提方法简单高效,在容量规划时算力需求量小。最后,通过IEEE 9节点和IEEE 33节点区域微网实时数字仿真系统(RTDS)硬件在环算例,验证了上述理论分析和所提方法的可行性。

多率采样机制下多智能体动态事件触发二分一致性研究

针对满足细节平衡结构的对抗交互多智能体系统,研究多率采样机制下其动态事件触发二分一致性问题。在多率采样机制下,通过构造一个多率缓存器解决多率采样时序不匹配的问题,设计一类多率观测器便于获得系统的估计状态以实现目标控制。通过引入动态事件触发机制,多率观测器在事件触发时刻广播其状态数据至通信网络中的邻居智能体。每个智能体基于触发时刻的观测器状态信息,利用一组开环估计器以获得连续的智能体状态估计值。在此基础上,设计一个分布式控制协议,利用代数黎卡提方程和李雅普诺夫稳定性理论证明系统可以在细节平衡的多智能体系统通信网络中实现二分一致性,并且排除动态事件触发可能导致的芝诺行为。通过一个包含3种不同采样机制和控制方案的对比仿真,证明了所提控制方案的有效性,表明多率采样机制相较于传统的单率采样机制具有更快和更稳定的收敛性能,并且动态事件触发相较于静态事件触发可以进一步降低触发次数。

Recursive filtering of multi-rate cyber-physical systems with unknown inputs under adaptive event-triggered mechanisms

Cyber-physical systems(CPSs)take on the characteristics of both multiple rates of information collection and processing and the dependency on information exchanges.The purpose of this paper is to develop a joint recursive filtering scheme that estimates both unknown inputs and system states for multi-rate CPSs with unknown inputs.In cyberspace,the information transmission between the local joint filter and the sensors is governed by an adaptive event-triggered strategy.Furthermore,the desired parameters of joint filters are determined by a set of algebraic matrix equations in a recursive way,and a sufficient condition verifying the boundedness of filtering error covariance is found by resorting to some algebraic operation.A state fusion estimation scheme that uses local state estimation is proposed based on the covariance intersection(CI)based fusion conception.Lastly,an illustrative example demonstrates the effectiveness of the proposed adaptive event-triggered recursive filtering algorithm.

多模态信息增强的短视频推荐模型

提出用于短视频点击率预估任务的多模态增强模型(MMa4CTR).模型综合利用用户与短视频交互中的多模态数据,以构建用户的嵌入表示,并学习用户的多模态兴趣.通过组合和交叉不同模态特征,探索各模态间的共同语义.通过引入自动学习率调整和验证中断这2种训练策略,提升模型整体的推荐性能.为了解决多模态数据量增加带来的计算挑战,采用计算效率较高的多层感知机.在微信视频号和抖音短视频数据集上进行性能比较实验和超参数敏感性实验,结果显示MMa4CTR在保持较低计算开销的同时,实现了超越基线模型的卓越推荐效果.通过在2个数据集上进行的消融实验,进一步证实了短视频模态交叉模块、用户多模态嵌入层以及自动学习率调整策略和验证中断策略在提升推荐性能方面的重要性和有效性.

一种GNSS/加速度计数据融合方法探讨

针对目前桥梁施工合拢过程中的关键技术挂篮安全监测的方法主要利用全站仪和水准仪等传统设备,人员成本高,效率低,且难以满足实时监测等问题,提出一种GNSS/加速度计数据融合方法:分析全球卫星导航系统(GNSS)由于其具有无须通视、全天候以及能够直接测量点的三维坐标等优点,已广泛应用于变形监测领域,但受多路径、采样率等因素影响,对高频振动不敏感,而加速度计具有高采样率、性能稳定等优点,但其对低频信息不敏感;结合2种传感器的优势,利用基于Rauch-Tung-Striebel(RTS)平滑的多速率抗差卡尔曼滤波方法对GNSS和加速度数据进行融合处理。实验结果表明,该方法可有效提高GNSS挂篮振动监测的采样率和精度。

“一枝独秀”还是“并驾齐驱”?——基于北京养老金三支柱体系的研究

我国人口老龄化问题日益加剧,基本养老金即将面临给付危机,为此我国提出要发展多层次、多支柱的养老保障体系。为了检验我国多支柱养老金体系是否能够保障职工退休后的生活水平,本文以延迟退休为研究背景,以北京城镇职工为研究对象,结合2022年11月出台的个人养老金账户,构建多支柱养老金财富和替代率的精算模型。研究发现,适度延迟退休年龄能够提高职工的养老金财富和替代率。敏感性分析发现,养老金财富和替代率对名义工资增长率的变动最为敏感。其中,第一支柱对养老金财富和替代率的贡献最大,第二、第三支柱起到补充作用。建议在采取灵活的延迟退休政策的基础上,稳定推进第一、第二支柱,加强完善个人养老金制度。

新型电力系统电磁暂态并行仿真关键技术及展望

在“碳达峰、碳中和”战略目标驱动下,电力系统逐渐发展成为高比例新能源并网和高比例电力电子设备接入的新型电力系统,其电源结构、电网形态和运行特征发生了显著变化。电磁暂态仿真由于能够全面、精确刻画电力系统的高频动态特性,已成为掌握新型电力系统运行特性的关键手段。然而,传统串行计算模式下的电磁暂态仿真技术在仿真效率上无法应对新能源大规模并网、交直流复杂耦合的仿真场景,亟需从高效并行算法和硬件加速角度出发,开展并行计算模式下的电磁暂态仿真相关研究。为此,首先概括了新型电力系统对电磁暂态仿真的新需求;其次,介绍了电磁暂态仿真的分网并行算法;再次,介绍了能够进一步提升电磁暂态仿真效率的多速率仿真方法;接着,介绍了基于并行计算设备的并行仿真实现方案;最后,梳理了国内外电磁暂态仿真平台的并行策略,总结指出算法硬件深度融合的仿真平台是未来的发展方向,并对其中的关键技术进行分析和展望。