RM-RT^(2)NI:融合评论时效与可信近邻影响力的推荐模型

基于矩阵分解的推荐模型虽然能够处理高维评分数据,但容易遭受评分数据稀疏性的困扰。基于评分和评论的推荐模型通过外加隐藏在评论中的用户偏好与物品属性信息,缓解了评分数据的稀疏性,但在特征提取时大多没有关注评论时效性和可信近邻影响力,无法获得更丰富的用户和物品特征。为进一步提高推荐精度,提出了融合评论时效与可信近邻影响力的推荐模型RM-RT^(2)NI。基于评分矩阵,该模型使用矩阵分解提取了用户偏好和物品属性的浅层特征,利用云模型和修正的用户相似度评估模型和新构建的信度评估模型提取出可信近邻影响力;基于评论文本,该模型利用BERT模型获得每条评论的隐表达,利用双向GRU提取评论间的联系,利用新构建的融合时间因子的注意力机制识别各评论的时效贡献度,以获取用户和物品的深层特征。在此基础上,将用户浅层特征、深层特征以及可信近邻影响力特征融合成用户特征,将物品浅层特征和深层特征融合成物品特征,并将它们输入全连接神经网络以预测用户-物品评分。在5组公开数据集上对RM-RM-RT^(2)NI的推荐性能进行了实验评估,结果显示,与7个基线模型相比,RM-RT^(2)NI具有更高的评分预测精度,且RMSE平均降低了3.0657%。

计及电-碳交易与综合贡献率的多微网合作运行优化策略

多微网协同互联能够提高系统运行的稳定性与可靠性。针对多微网(multi-microgrids,MMG)系统合作运行过程中由于各微网分属于不同的利益主体而产生的微电网之间的电能交易问题、碳交易问题与利益分配问题,提出一种计及电-碳交易与综合贡献率的多微网合作运行优化策略。首先,分析了含点对点(peer-to-peer,P2P)电-碳交易的多微网合作运行架构,并引入碳捕集系统(carbon capture system,CCS)与电转气(power to gas,P2G)装置,建立了微电网系统及设备模型。其次,在单微网模型构建之后,基于纳什议价理论,构建了含P2P电-碳交易的多微网系统合作运行模型,并将非凸非线性的纳什议价问题转化为易于求解的MMG合作成本最小化与支付收益最大化两个子问题。然后,在合作后的利益分配过程中,量化各微电网对MMG的综合贡献程度并计算出各自的综合贡献率,通过综合贡献率来分配各微网的收益。最后,采用交替方向乘子法(alternating direction multiplier method,ADMM)求解,有效保护了各微网隐私。算例分析与方案对比结果表明,所提策略能够实现微网间的P2P电-碳交易,有效降低MMG总运行成本,减少系统的碳排放量,并且采用的利益分配策略公平合理,能够有效提升各微网参与合作运行的积极性。

改进的MVO-GRNN神经网络岩爆预测模型研究

准确预测岩爆烈度等级能有效指导岩爆灾害的防控。根据影响岩爆发生及烈度等级的3个因素构建岩爆评价指标体系,提出一种基于改进多元宇宙算法(Improved Multi-Verse Optimizer,IMVO)优化广义回归神经网络(General Regression Neural Network,GRNN)的岩爆预测模型。在普通多元宇宙算法(MVO)的基础上,运用自适应平衡机制调节MVO算法中的虫洞存在概率(V_(WEP))和旅行距离率(V_(TDR))两个重要参数来改进该算法;再运用改进的多元宇宙算法优化广义回归神经网络的光滑度,通过训练数据优选出最佳光滑因子σ,得到IMVO-GRNN神经网络岩爆烈度预测模型;最后结合工程实例验证模型的性能。研究表明,该模型相比传统模型寻优能力更强,精度更高,为岩爆预测提供了一种新的思路。

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 802.11b multi-rate WLANs.

Joint Link Allocation and Rate Assignment Algorithm for Multi-Channel Wireless Networks

This paper presents a link allocation and rate assignment algorithm for multi-channel wireless networks.The objective is to reduce network conflicts and guarantee the fairness among links.We first design a new network model.With this network model,the multi-channel wireless network is divided into several subnets according to the number of channels.Based on this,we present a link allocation algorithm with time complexity O(l2) to allocate all links to subnets.This link allocation algorithm adopts conflict matrix to minimize the network contention factor.After all links are allocated to subnets,the rate assignment algorithm to maximize a fairness utility in each subnet is presented.The rate assignment algorithm adopts a near-optimal algorithm based on dual decomposition and realizes in a distributed way.Simulation results demonstrate that,compared with IEEE 802.11b and slotted seeded channel hopping algorithm,our algorithm decreases network conflicts and improves the network throughput significantly.

Advancing COVID-19 Diagnosis with CNNs: An Empirical Study of Learning Rates and Optimization Strategies

The rapid spread of the novel Coronavirus (COVID-19) has emphasized the necessity for advanced diagnostic tools to enhance the detection and management of the virus. This study investigates the effectiveness of Convolutional Neural Networks (CNNs) in the diagnosis of COVID-19 from chest X-ray and CT images, focusing on the impact of varying learning rates and optimization strategies. Despite the abundance of chest X-ray datasets from various institutions, the lack of a dedicated COVID-19 dataset for computational analysis presents a significant challenge. Our work introduces an empirical analysis across four distinct learning rate policies—Cyclic, Step Based, Time-Based, and Epoch Based—each tested with four different optimizers: Adam, Adagrad, RMSprop, and Stochastic Gradient Descent (SGD). The performance of these configurations was evaluated in terms of training and validation accuracy over 100 epochs. Our results demonstrate significant differences in model performance, with the Cyclic learning rate policy combined with SGD optimizer achieving the highest validation accuracy of 83.33%. This study contributes to the existing body of knowledge by outlining effective CNN configurations for COVID-19 image dataset analysis, offering insights into the optimization of machine learning models for the diagnosis of infectious diseases. Our findings underscore the potential of CNNs in supplementing traditional PCR tests, providing a computational approach to identify patterns in chest X-rays and CT scans indicative of COVID-19, thereby aiding in the swift and accurate diagnosis of the virus.

Image Tamper Detection and Multi-Scale Self-Recovery Using Reference Embedding with Multi-Rate Data Protection

This paper proposes a multi-scale self-recovery(MSSR)approach to protect images against content forgery.The main idea is to provide more resistance against image tampering while enabling the recovery process in a multi-scale quality manner.In the proposed approach,the reference data composed of several parts and each part is protected by a channel coding rate according to its importance.The first part,which is used to reconstruct a rough approximation of the original image,is highly protected in order to resist against higher tampering rates.Other parts are protected with lower rates according to their importance leading to lower tolerable tampering rate(TTR),but the higher quality of the recovered images.The proposed MSSR approach is an efficient solution for the main disadvantage of the current methods,which either recover a tampered image in low tampering rates or fails when tampering rate is above the TTR value.The simulation results on 10000 test images represent the efficiency of the multi-scale self-recovery feature of the proposed approach in comparison with the existing methods.

OPTIMAL FEED RATE CONTROL FOR MULTI-AXIS CNC MACHINING OF FREE FORM SURFACES

Considering machining efficiency, surface quality and wear of cutter and machine, it is necessary to maintain high, stable and constant surface feed rate as far as possible.The feed late control strategy for multi-axis CNC machining of free-form surfaces is presented. It comprises: ①the determination of effective feed rate; ②the adoption of suitable approaches to smooth feed rate. This strategy considers path geometry, actuator limitation and machine dynamics. The result shows that machining efficiency is improved effectively.

基于改善率统计的MAPF-LNS2+算法

MAPF-LNS2是一种基于大邻域搜索的算法,用于解决多智能体路径规划问题。优势在于其速度更快,在大多数情况下提供接近最优解的解决方案。但该算法在分配权重时仅考虑当前邻域搜索策略的近期表现并有可能分配了较高的权重,使其他邻域搜索策略出现短暂的“饥饿”现象,导致增加算法的总运行时间。针对该问题基于MAPF-LNS2算法,通过引入改善率统计和时间窗口提出了一种新的多智能体路径规划算法。结果表明,无论是在运行时长还是成功率方面,MAPF-LNS2+算法均优于MAPF-LNS2算法,运行时间最高降低了65.1%,成功率最大提升了16%。

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.

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.

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.

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.

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.

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.

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 sup-press 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 vec-tors blindly. Then a soft-decision high rate multiuser detector is proposed based on the estimated signature vectors, which avoids estimating the ambiguous complex factors which are necessary in traditional blind de-tector. Numerical simulation results evaluate the performance in terms of Bit Error Rate (BER) for the pro-posed scheme. Simultaneously, it demonstrates that the system capability increases two times when using two- element antenna array.

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.

基于CP重构的高时间传输效率CP-UFMC接收方法

针对循环前缀(cyclic prefix,CP)不足的情况对循环前缀通用滤波多载波(cyclic prefix-universal filtered multi-carrier,CP-UFMC)系统的影响进行了数学推导,提出了一种基于CP重构的高时间传输效率CP-UFMC接收方法来改善系统性能,并进一步研究了选择性重构方法的性能。之后仿真研究了不同CP长度,不同载波频率偏移和不同正交振幅调制阶数时的系统误符号率(symbol error rate,SER)表现。仿真结果表明,基于CP重构的CP-UFMC接收方法可以改善CP不足导致的系统SER恶化问题,使其接近CP充足时的SER,并优于对比的其他通用滤波多载波系统接收方法。

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.

Adaptive Rate Control for Multi-Antenna Multicast in OFDM Systems

We propose two rate control schemes for multi-antenna multicast in OFDM systems, which aim to maximize the minimum average rate over all users in a multicast group. In our system, we do not require all multicast users to successfully recover the signals received on each subcarrier. In contrast, we allow certain loss for multicast users, such that the multicast transmission rate can be increased. We assume that the loss-repairing can be completed at upper protocol layers via advanced fountain codes. Following this principle, we formulate the rate control problem via beamforming in multi-antenna multicast to optimize the minimum achievable rate for all multicast users. While the computation complexity to solve for the optimal beamformer is prohibitively high, we propose a suboptimal iterative rate control scheme. Moreover, we modify the above optimization problem by selecting a ?xed proportion of users on each subcarrier. The beamformer searching process will then be performed only based on the selected users on each subcarrier, such that the complexity can be further reduced. We also solve this new problem with a low complexity approach. Theoretical analyses and simulation results show that our proposed two rate control schemes can have higher minimum average rate than the baseline scheme without rate control, while achieving low complexity.