检索结果-南通市图书馆

Numerical analysis of the return flow solar air heater(RF-SAH)with assimilation of V-type artificial roughness

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Energy and Built Environment

Energy and Built Environment 2024年第2期5卷 185-193页

作者： Prashant Raturi Hemlata Deolal Sanjeev Kimothi Department of Mechanical engineering Swami Rama Himalayan University Dehradun248140India Department of Mechanical engineering DIT UniversityDehradun248001India Division of Research&Innovation Dept.of PhysicsUttaranchal University248007India

A novel design of Return Flow Solar Air Heater(RFSAH)with different arrangements of baffles especially V-Type Artificial roughness is simulated and numerically analyzed with energy balance equations.To enhance the effectiveness of baffles,numerous studies have been conducted.The performance of the RFSAH is studied in terms of thermal efficiency,thermo-hydraulic efficiency,and optimization of baffle parameters.Maximum Thermal efficiency and thermo-hydraulic efficiency are found in RFSAH with baffle on both sides of the absorber plate and mass flow rate above 0.2kg/s.Sensitivity analysis of the influencing parameters is carried out and reported the best performance of the system on selective geometrical parameters(ψ=0.7,β=20%,e/H=1,p/e=0.8,α=60°).The results obtained from the present model are validated with the published experimental results and have been found in quite reasonable agreement with an average error of 16.45%.Thermal and Thermohydraulic efficiency of RFSAH with a baffle on both sides of the absorber plate is maximum among baffles below,above,and on both sides of the absorber plate.It is observed that the thermal efficiency of RFSAH is greater than SF-SAH.The proposed optimum baffles roughness is suggested to increase the air upholding time period for more efficient output.

关键词： Numerical analysis Energy Balance Equations Thermal Efficiency Return flow solar air heater V-baffles

Quantized autoencoder(QAE)intrusion detection system for anomaly detection in resource-constrained loT devices using RT-loT2022 dataset

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Cybersecurity 2024年第2期7卷 13-27页

作者： B S Sharmila Rohini Nagapadma Depatment of electronics and Communication engineering The National Institute of EngineeringMysoreKarnataka 570008India

In recent years,many researchers focused on unsupervised learning for network anomaly detection in edge devices to identify attacks.The deployment of the unsupervised autoencoder model is computationally expensive in resource-constrained edge devices.This study proposes quantized autoencoder(QAE)model for intrusion detection systems to detect anomalies.QAE is an optimization model derived from autoencoders that incorporate pruning,clustering,and integer quantization techniques.Quantized autoencoder uint8(QAE-u8)and quantized autoencoder float16(QAE-f16)are two variants of QAE built to deploy computationally expensive Al models into Edge devices.First,we have generated a Real-Time Internet of Things 2022 dataset for normal and attack traffic.The autoencoder model operates on normal traffic during the training phase.The same model is then used to reconstruct anomaly traffic under the assumption that the reconstruction error(RE)of the anomaly will be high,which helps to identify the attacks.Furthermore,we study the performance of the autoencoders,QAE-u8,and QAE-f16 using accuracy,precision,recall,and F1 score through an extensive experimental study.We showed that QAE-u8 outperforms all other models with a reduction of 70.01%in average memory utilization,92.23%in memory size compression,and 27.94%in peak CPU utilization.Thus,the proposed QAE-u8 model is more suitable for deployment on resource-constrained IoT edge devices.

关键词： IoT constrained system

An Improved Modulation Strategy for Single-phase Three-level Neutral-point-clamped Converter in Critical Conduction Mode

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2024年第3期12卷 981-990页

作者： Ning Li Yujie Cao Xiaokang Liu Yan Zhang Ruotong Wang Lin Jiang Xiao-Ping Zhang School of Electrical engineering Xi'an University of Technology the Department of electronics Information and Bioengineering Xi'an Jiaotong University the Department of Electrical engineering and electronics University of Liverpool the Department of Electronic Electrical and Systems Engineering University of Birmingham

Two-level totem-pole power factor correction(PFC) converters in critical conduction mode(CRM) suffer from the wide regulation range of switching frequency. Besides, in highfrequency applications, the number of switching times increases, resulting in significant switching losses. To solve these issues, this paper proposes an improved modulation strategy for the single-phase three-level neutral-point-clamped(NPC) converter in CRM with PFC. By optimizing the discharging strategy and switching state sequence, the switching frequency and its variation range have been efficiently reduced. The detailed performance analysis is also presented regarding the switching frequency, the average switching times, and the effect of voltage gain. A 2 k W prototype is built to verify the effectiveness of the proposed modulation strategy and analysis results. Compared with the totem-pole PFC converter, the switching frequency regulation range of the three-level PFC converter is reduced by 36.48% and the average switching times is reduced by 45.10%. The experimental result also shows a 1.2% higher efficiency for the three-level PFC converter in the full load range.

关键词： Switches Switching frequency Control systems Topology Bridge circuits Inductors Customer relationship management

Fractional-order heterogeneous memristive Rulkov neuronal network and its medical image watermarking application

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2024年第5期33卷 306-314页

作者：丁大为牛炎张红伟杨宗立王金王威王谋媛 School of electronics and Information engineering Anhui UniversityHefei 230601China

This article proposes a novel fractional heterogeneous neural network by coupling a Rulkov neuron with a Hopfield neural network(FRHNN),utilizing memristors for emulating neural synapses.The study firstly demonstrates the coexistence of multiple firing patterns through phase diagrams,Lyapunov exponents(LEs),and bifurcation diagrams.Secondly,the parameter related firing behaviors are described through two-parameter bifurcation diagrams.Subsequently,local attraction basins reveal multi-stability phenomena related to initial values.Moreover,the proposed model is implemented on a microcomputer-based ARM platform,and the experimental results correspond to the numerical simulations.Finally,the article explores the application of digital watermarking for medical images,illustrating its features of excellent imperceptibility,extensive key space,and robustness against attacks including noise and cropping.

关键词： fractional order memristors Rulkov neuron medical image watermarking

A novel Bayesian-based INS/GNSS integrated positioning method with both adaptability and robustness in urban environments

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第6期37卷 205-218页

作者： Zhe YANG Hongbo ZHAO School of electronics and Information engineering Beihang UniversityBeijing 100191China

Achieving higher accuracy positioning results in urban environments at a lower cost has been an important pursuit in areas such as autonomous driving and intelligent transportation.Lowcost Inertial Navigation System and Global Navigation Satellite System(INS/GNSS)integrated navigation systems have been an important means of fulfilling the above quest due to the complementary error characteristics between INS and GNSS.The complex urban driving environment requires the system sufficiently adaptive to keep up with the time-varying measurement noise and sufficiently robust to cope with measurement outliers and prior uncertainties.However,many efforts lack a balance between adaptability and robustness.In this paper,a novel positioning method with both adaptability and robustness is proposed by coupling the Mahalanobis distance method,the Variational Bayesian method and the student’s t-distribution in one process(M-VBt method).This method is robust against non-Gaussian noise and priori uncertainties,plus adaptive against measurement noise uncertainty and time-varying noise.The field test results show that the M-VBt method(especially the Mahalanobis distance part)has significantly improved the system performance in the complex urban driving environment.

关键词： Urban environments Mahalanobis distance Adaptability Robustness Integrated navigation

Product quality prediction based on RBF optimized by firefly algorithm

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems engineering and electronics 2024年第1期35卷 105-117页

作者： HAN Huihui WANG Jian CHEN Sen YAN Manting College of electronics and Information engineering Tongji UniversityShanghai 201804China

With the development of information technology,a large number of product quality data in the entire manufacturing process is accumulated,but it is not explored and used effectively.The traditional product quality prediction models have many disadvantages,such as high complexity and low accuracy.To overcome the above problems,we propose an optimized data equalization method to pre-process dataset and design a simple but effective product quality prediction model:radial basis function model optimized by the firefly algorithm with Levy flight mechanism(RBFFALM).First,the new data equalization method is introduced to pre-process the dataset,which reduces the dimension of the data,removes redundant features,and improves the data distribution.Then the RBFFALFM is used to predict product quality.Comprehensive expe riments conducted on real-world product quality datasets validate that the new model RBFFALFM combining with the new data pre-processing method outperforms other previous me thods on predicting product quality.

关键词： product quality prediction data pre-processing radial basis function swarm intelligence optimization algorithm

A whole-net cooperative positioning method based on CDGNSS and inter-vehicle ranging

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第2期37卷 401-416页

作者： Shan HU Hongbo ZHAO Chen ZHUANG School of electronics and Information engineering Beihang UniversityBeijing 100191China

Relative positioning is recognized as an important issue for vehicles in urban environments.Multi-vehicle Cooperative Positioning(CP)techniques which fuse the Global Navigation Satellite System(GNSS)and inter-vehicle ranging have attracted attention in improving the performance of baseline estimation between vehicles.However,current CP methods estimate the baselines separately and ignore the interactions among the positioning information of different baselines.These interactions are called’information coupling’.In this work,we propose a new multivehicle precise CP framework using the coupled information in the network based on the Carrier Differential GNSS(CDGNSS)and inter-vehicle ranging.We demonstrate the benefit of the coupled information by deriving the Cramer-Rao Lower Bound(CRLB)of the float estimation in CP.To fully use this coupled information,we propose a Whole-Net CP(WN-CP)method which consists of the Whole-Net Extended Kalman Filter(WN-EKF)as the float estimation filter,and the Partial Baseline Fixing(PBF)as the ambiguity resolution part.The WN-EKF fuses the measurements of all baselines simultaneously to improve the performance of float estimation,and the PBF strategy fixes the ambiguities of the one baseline to be estimated,instead of full ambiguity resolution,to reduce the computation load of ambiguity resolution.Field tests involving four vehicles were conducted in urban environments.The results show that the proposed WN-CP method can achieve better performance and meanwhile maintain a low computation load compared to the existing methods.

关键词： GNSS Cooperative positioning Baseline Ambiguity resolution Information coupling

Bioinspired 3D flexible devices and functional systems

在线全文

学校读者我要写书评

暂无评论

National Science Review 2024年第3期11卷 271-295页

作者： Xu Cheng Zhangming Shen Yihui Zhang Applied Mechanics Laboratory Department of Engineering Mechanics Tsinghua University Laboratory of Flexible electronics Technology Tsinghua University

Flexible devices and functional systems with elaborated three-dimensional(3D) architectures can endow better mechanical/electrical performances, more design freedom, and unique functionalities, when compared to their two-dimensional(2D) counterparts. Such 3D flexible devices/systems are rapidly evolving in three primary directions, including the miniaturization, the increasingly merged physical/artificial intelligence and the enhanced adaptability and capabilities of heterogeneous integration.Intractable challenges exist in this emerging research area, such as relatively poor controllability in the locomotion of soft robotic systems, mismatch of bioelectronic interfaces, and signal coupling in multi-parameter sensing. By virtue of long-time–optimized materials, structures and processes, natural organisms provide rich sources of inspiration to address these challenges, enabling the design and manufacture of many bioinspired 3D flexible devices/systems. In this Review, we focus on bioinspired 3D flexible devices and functional systems, and summarize their representative design concepts, manufacturing methods, principles of structure-function relationship and broad-ranging applications. Discussions on existing challenges, potential solutions and future opportunities are also provided to usher in further research efforts toward realizing bioinspired 3D flexible devices/systems with precisely programmed shapes,enhanced mechanical/electrical performances, and high-level physical/artificial intelligence.

关键词： bioinspired designs biomimetic 3D structures 3D flexible electronics 3D functional systems direct 3D manufacture 2D-to-3D assembly

Coherence of nonlinear Bloch dynamics of Bose-Einstein condensates in deep optical lattices

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2024年第4期33卷 297-303页

作者：张爱霞张薇王杰胡潇文米来来薛具奎 College of Physics and electronics engineering Northwest Normal UniversityLanzhou 730070China

Atomic interaction leads to dephasing and damping of Bloch oscillations(BOs)in optical lattices,which limits observation and applications of BOs.How to obtain persistent BOs is particularly important.Here,the nonlinear Bloch dynamics of the Bose-Einstein condensate with two-body and three-body interactions in deep optical lattices is studied.The damping rate induced by interactions is obtained.The damping induced by two-body interaction plays a dominant role,while the damping induced by three-body interaction is weak.However,when the two-body and three-body interactions satisfy a threshold,long-lived coherent BOs are observed.Furthermore,the Bloch dynamics with periodical modulation of linear force is studied.The frequencies of linear force corresponding to resonance and pseudoresonance are obtained,and rich dynamical phenomena,i.e.,stable and strong BOs,drifting and dispersion of wave packet,are predicted.The controllable Bloch dynamics is provided with the periodic modulation of the linear force.

关键词： Bose-Einstein condensate atomic interaction Bloch oscillations