检索结果-南通市图书馆

Stability analysis of linear/nonlinear switching active disturbance rejection control based MIMO continuous systems

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2021年第4期32卷 956-970页

作者： WAN Hui QI Xiaohui LI Jie Department of Unmanned Aerial Vehicle Engineering Army Engineering University of PLAShijiazhuang 050003China The 32nd Research Institute China Electronics Technology Group CorporationShanghai 201800China

In this paper,a linear/nonlinear switching active disturbance rejection control(SADRC)based decoupling control approach is proposed to deal with some difficult control problems in a class of multi-input multi-output(MIMO)systems such as multi-variables,disturbances,and coupling,etc.Firstly,the structure and parameter tuning method of SADRC is introduced into this paper.Followed on this,virtual control variables are adopted into the MIMO systems,making the systems decoupled.Then the SADRC controller is designed for every subsystem.After this,a stability analyzed method via the Lyapunov function is proposed for the whole system.Finally,some simulations are presented to demonstrate the anti-disturbance and robustness of SADRC,and results show SADRC has a potential applications in engineering practice.

关键词： linear/nonlinear switching active disturbance rejection control(SADRC) multi-input multi-output(MIMO)continuous system decoupling control stability analysis

维普期刊数据库

Time-varying reliability indexes for multi-AUV cooperative system

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2017年第2期28卷 401-406页

作者： Qingwei Liang Tianyuan Sun Dongdong Wang College of Marine Science and Technology Northwestern Polytechnical University Xi’an 710072 China The 32nd Research Institute of China Electronic Technology Group Corporation Shanghai 200233 China

With the development of multi-autonomous underwater vehicle (AUV) cooperative systems, the evaluation of their reliability is becoming more and more important. Since AUVs are always in motion, the reliability of the system is not stationary, but it varies with time. This paper studies the time-varying reliability evaluation indexes for multi-AUV cooperative systems. Aimed at elucidating the characteristics of the system, by considering the motion of the AUVs, two time dependent reliability evaluation indexes, natural connectivity and all-terminal reliability of the basic reliability indexes, are determined with the graph theory. Then the time-varying reliability of multi-AUV cooperative systems is evaluated combining with an actual example. This paper provides a method to evaluate the time-varying reliability of multi-AUV cooperative systems. ? 2017 Beijing institute of Aerospace Information.

关键词： Graph theory Offshore pipelines Reliability Reliability theory

维普期刊数据库

Survivability Mechanisms of Complex Computer Systems Based on Common Information Space

在线全文

学校读者我要写书评

暂无评论

计算机工程 2019年第7期45卷 41-45页

作者： DODONOV Oleksandr JIANG Bo DODONOV Vadym institute for Information Recording of National Academy of Sciences of Ukraine Kyiv 03113Ukraine The 32nd Research Institute of China Electronics Technology Group Corporation Shanghai 201808China institute for System research and Information Technologies of the Ukrainian Academy of Sciences Kyiv 03179Ukraine

The survivability of computer systems should be guaranteed in order to improve its operation efficiency,especially for the efficiency of its critical functions.This paper proposes a decentralized mechanism based on Software-Defined Architecture(SDA).The concepts of critical functions and critical states are defined,and then,the critical functional parameters of the target system are collected and analyzed.Experiments based on the analysis results are performed for reconfiguring the implementations of the whole system.A formal model is presented for analyzing and improving the survivability of the system,and the problem investigated in this paper is reduced to an optimization problem for increasing the system survival time.

关键词： survivability evaluation common information space Software-Defined Architecture(SDA) complex computer systems

维普期刊数据库

Early smoke and flame detection based on transformer

在线全文

学校读者我要写书评

暂无评论

Journal of Safety Science and Resilience 2023年第3期4卷 294-304页

作者： Xinzhi Wang Mengyue Li Mingke Gao Quanyi Liu Zhennan Li Luyao Kou School of Computer Engineering and Science Shanghai UniversityShanghai 200444China The 32nd Research Institute of China Electronics Technology Group Corporation Shanghai 201808China College of Civil Aviation Safety Engineering Civil Aviation Flight University of ChinaGuanghan 618307China Department of Engineering Physics Tsinghua UniversityBeijing 100084China

Fire-detection technology plays a critical role in ensuring public safety and facilitating the development of smart cities.Early fire detection is imperative to mitigate potential hazards and minimize associated losses.However,existing vision-based fire-detection methods exhibit limited generalizability and fail to adequately consider the effect of fire object size on detection accuracy.To address this issue,in this study a decoder-free fully transformer-based(DFFT)detector is used to achieve early smoke and flame detection,improving the detection performance for fires of different sizes.This method effectively captures multi-level and multi-scale fire features with rich semantic information while using two powerful encoders to maintain the accuracy of the single-feature map prediction.First,data augmentation is performed to enhance the generalizability of the model.Second,the detection-oriented transformer(DOT)backbone network is treated as a single-layer fire-feature extractor to obtain fire-related features on four scales,which are then fed into an encoder-only single-layer dense prediction module.Finally,the prediction module aggregates the multi-scale fire features into a single feature map using a scale-aggregated encoder(SAE).The prediction module then aligns the classification and regression features using a task-aligned encoder(TAE)to ensure the semantic interaction of the classification and regression predictions.Experimental results on one private dataset and one public dataset demonstrate that the adopted DFFT possesses high detection accuracy and a strong generalizability for fires of different sizes,particularly early small fires.The DFFT achieved mean average precision(mAP)values of 87.40%and 81.12%for the two datasets,outperforming other baseline models.It exhibits a better detection performance on flame objects than on smoke objects because of the prominence of flame features.

关键词： Early fire Smoke and flame detection Fire detection Vision transformer Public safety

A survey of time consistency of dynamic risk measures and dynamic performance measures in discrete time: LM-measure perspective

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

Probability, Uncertainty and Quantitative Risk 2017年第1期2卷 35-86页

作者： Tomasz R.Bielecki Igor Cialenco M.Pitera Department of Applied Mathematics Illinois Institute of Technology10 W 32nd StrBuilding E1Room 208ChicagoIL 60616USA institute of Mathematics Jagiellonian UniversityCracowPoland

In this work we give a comprehensive overview of the time consistency property of dynamic risk and performance measures,focusing on a the discrete time setup.The two key operational concepts used throughout are the notion of the LMmeasure and the notion of the update rule that,we believe,are the key tools for studying time consistency in a unified framework.

关键词： Time consistency Update rule Dynamic LM-measure Dynamic risk measure Dynamic acceptability index Measure of performance

Scintillation Identification Based on Spectral Features

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

Scintillation Identification Based on Spectral Features

An ionospheric disturbance index for SBAS based on gradient variation

第十四届中国卫星导航年会

作者： Dun Liu Li Chen Shan Guo Qinglin Zhu The 22nd research institute CETC

Performance of machine learning(ML) methods to identify scintillation events is analyzed for a variety of scenarios.It shows that spectrum embodies various features on scintillation variation.Different methods can be developed with ML to find out potential scintillation impacts,and satisfied results generally could be arrived with accuracy of 95%.It also point out that the descending trend existed over Fresnel frequency is essential to distinguish a potential scintillation.So selecting a proper frequency band to make spectral features more distinguishable plays an important role in ML realization.It further shows that precise GNSS routine observations with the sampling rate of 1Hz can be served to recognize scintillation event if a sound spectrum range has been chosen.When a set of parameters on spectrum characteristics could be derived and used for ML training,better performance can even be expected.

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

An ionospheric disturbance index for SBAS based on gradient ...

Validation of relationship between ROTI and S4 with array of GNSS measurements

第十三届中国卫星导航年会

作者： Dun Liu Yan Wang Na Xu Li Chen Huafeng Wang No.22nd research institute CETC

A simply constructed index is generally wanted to give direct indication of ionospheric status for Space-based augmentation system（SBAS） users. To this end, we make extensive analysis of ionospheric grid model performance under typical ionospheric storms. It was found that ionospheric delay gradients, instead of delays itself, are the main contributors for larger model errors. This feature makes indexes, which are defined on delay temporal variations, not preferred candidates for ionospheric condition indicating. A new index based on mean ionospheric delay gradients is then proposed and its applicability is analyzed. Results shows its consistence with grid model error variations, and the readily found threshold. Further analysis points out indexes based on delay spatial gradients, instead of temporal variations, is the key to construct sensible indicator for ionosphere status for SBAS.

关键词： Ionosphere Disturbance Grid model Spatial gradients SBAS

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Validation of relationship between ROTI and S4 with array of...

Variant selection in laser powder bed fusion of non-spherical Ti-6Al-4V powder

第十三届中国卫星导航年会

作者： Dun Liu Xiao Yu Yan Wang Li Chen Weimin Zhen No.22nd research institute CETC

With phase structure function, a theory model could be constructed to describe the rate of total electron content index(ROTI) and its relationship with amplitude scintillation index S . The model is validated with measurements from GNSS array on short baseline. It is also found the effective scan azimuth angle α with value of 25° could serve as threshold for effective S prediction from ROTI. Further analysis point out the effective scan speed effV and its ways passing through ionosphere determine the temporal and spatial sampling rate on irregularity, and when the different time separation for ROTI and S locates in the same range of phase structure function, the model could be extrapolated to predict S with ROTI measurements. The results suggest the possibility of using regular GNSS observations for scintillation monitoring.

关键词： Ionospheric scintillation Irregularity Scintillation index S4 ROTI Drift speed

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第16期147卷 56-67页

作者： Mohammadreza Asherloo Ziheng Wu Julian E.C.Sabisch Iman Ghamarian Anthony D.Rollett Amir Mostafaei Department of Mechanical Materials and Aerospace EngineeringIllinois Institute of Technology10 W 32nd StreetChicagoIL 60616United States Materials Engineering Division Lawrence Livermore National Laboratory7000 East AveLivermoreCA 94550United States Samuel Roberts Noble Microscopy Laboratory University of OklahomaNormanOK 73019United States School of Aerospace and Mechanical Engineering University of OklahomaNormanOK 73019United States Department of Materials Science and Engineering Carnegie Mellon UniversityPittsburghPA 15213United States

The presence ofα/αon priorβ/βgrain boundaries directly impacts the final mechanical properties of the titanium alloys.Theβ/βgrain boundary variant selection of titanium alloys has been assumed to be unlikely owing to the high cooling rates in laser powder bed fusion(L-PBF).However,we hypothesize that powder characteristics such as morphology(non-spherical)and particle size(50–120μm)could affect the initial variant selection in L-PBF processed Ti-6Al-4V alloy by locally altering the cooling rates.Despite the high cooling rate found in L-PBF,results showed the presence ofβ/βgrain boundaryαlath growth inside two adjacent priorβgrains.Electron backscatter diffraction micrographs confirmed the presence ofβ/βgrain boundary variant selection,and synchrotron X-ray high-speed imaging observation revealed the role of the“shadowing effect”on the locally decreased cooling rate because of keyhole depth reduction and the consequentβ/βgrain boundaryαlath growth.The self-accommodation mechanism was the main variant selection driving force,and the most abundantα/αboundary variant was type 4(63.26°//[10553¯]).The dominance of Category IIαlath clusters associated with the type 4α/αboundary variant was validated using the phenomenological theory of martensite transformations and analytical calculations,from which the stress needed for theβ→αtransformation was calculated.

关键词： Variant selection Phase formation Additive Manufacturing Hydride-dehydride powder Texture analysis Electron backscattered diffraction