针对滚动轴承故障诊断中故障特征提取困难及诊断准确率低的问题,提出了一种改进的灰狼优化算法(grey wolf optimizer,GWO)-变分模态分解(variational mode decomposition,VMD)的新诊断方法。首先将GWO改进为混沌增强灰狼优化算法(improv...针对滚动轴承故障诊断中故障特征提取困难及诊断准确率低的问题,提出了一种改进的灰狼优化算法(grey wolf optimizer,GWO)-变分模态分解(variational mode decomposition,VMD)的新诊断方法。首先将GWO改进为混沌增强灰狼优化算法(improved enhancement grey wolf optimizer,IEGWO),随后基于改进后的算法优化VMD的关键参数后,对故障信号进行分解。最后将分解后的信号构造故障特征向量并输入到双向长短时神经网络(bi-directional long short-term memory,Bi-LSTM)中进行轴承故障诊断分类。将所提方法与其他故障提取模型进行对比分析实验,结果表明,该模型将故障诊断准确率提高到了99%。实验结果证明,所提方法能够更好地提取故障特征,提高故障诊断的准确率。展开更多
Ferritic steel with a nominal composition of Fe-14Cr-3W-0.42Ti-0.32Y was prepared by mixing gas-atomized prealloyed powder and mechanically alloyed powder. The microstructure is much different fxom other ferritic stee...Ferritic steel with a nominal composition of Fe-14Cr-3W-0.42Ti-0.32Y was prepared by mixing gas-atomized prealloyed powder and mechanically alloyed powder. The microstructure is much different fxom other ferritic steels with the same composition and prepared via only mechanically alloyed powder. A bi-modal structure, which consists of pure ferritic grains and martensitic grains, was obtained after hot forging and air cooling. A phase transformation of αbcc→γfcc→α＇bcc was also discovered in microstructural observation. The bi-modal microstructure shows a good combination of high strength and high ductility.展开更多
β titanium alloys with bi-modal structure which exhibit improved strength-ductility combination and fatigue property are widely used in aviation and aerospace industry.However,owing to the small size of primary α(α...β titanium alloys with bi-modal structure which exhibit improved strength-ductility combination and fatigue property are widely used in aviation and aerospace industry.However,owing to the small size of primary α(αp) and nano-scaled multi variant distribution of secondary α platelets(αs),investigating the deformation behavior is really a challenging work.In this work,by applying transmission electron microscopy(TEM),the slip behavior in αp and transformed β matrix with different tensile strain was studied.After α/β solution treatment,the initial dislocation slips on {110} plane with <1 1 1> direction in β matrix.During furtherdeformation,(110),(101) and(1 1 2) multi slip is generated which shows a long straight cro s sing configuration.Dislocation cell is exhibited in β matrix at tensile strain above 20 %.Diffe rent from the solid solution treated sample,high density wavy dislocations are generated in transformedβ matrix.High fraction fine as hinders dislocation motion in β matrix effectively which in turn dominates the strength of the alloy.In primary α phase(αp),a core-shell structure is formed during deformation.Both pyramidal a+c slip and prismatic/basal a slip are generated in the shell layer.In core region,plastic deformation is governed by prismatic/basal a slip.Formation of the core-shell structure is the physical origin of the improved ductility.On one hand,the work hardening layer(shell) improves the strength of αp,which could deform compatibly with the hard transformed β matrix.Meanwhile,the center area(core) deforms homogeneously which will sustain plastic strain effectively and increase the ductility.This paper studies the slip behavior and reveals the origin of the improved strength-ductility combination in Bi-modal structure on a microscopic way,which will give theoretical advises for developing the next generation high strength β titanium alloys.展开更多
Olfactory receptors(ORs)play a key role in the prime sensorial perception,being highly relevant for intra/interspecific interactions.ORs are a subgroup of G-protein coupled receptors that exhibit highly complex subgen...Olfactory receptors(ORs)play a key role in the prime sensorial perception,being highly relevant for intra/interspecific interactions.ORs are a subgroup of G-protein coupled receptors that exhibit highly complex subgenomes in vertebrates.However,OR repertoires remain poorly studied in fish lineages,precluding finely retracing their origin,evolution,and diversification,especially in the most basal groups.Here,we conduct an exhaustive gene screening upon 43 high-quality fish genomes exhibiting varied gene repertoires(2e583 genes).While the early vertebrates performed gas exchange through gills,we hypothesize that the emergence of new breathing structures(swim bladder and paired lungs)in early osteichthyans may be associated with expansions in the ORs gene families sensitive to airborne molecules.Additionally,we verify that the OR repertoire of moderns actinopterygians has not increased as expected following a whole genome duplication,likely due to regulatory mechanisms compensating the gene load excess.Finally,we identify 25 distinct OR families,allowing us to propose an updated universal nomenclature for the fish ORs.展开更多
随着相控阵技术的快速发展与广泛应用,多功能雷达的工作模式趋于多样化、复杂化。实施快速且准确的雷达工作模式识别,对于后续威胁度分析、行为意图推理、行动决策信息生成具有重要支撑作用。以雷达信号时频图为切入点,结合基于双级路...随着相控阵技术的快速发展与广泛应用,多功能雷达的工作模式趋于多样化、复杂化。实施快速且准确的雷达工作模式识别,对于后续威胁度分析、行为意图推理、行动决策信息生成具有重要支撑作用。以雷达信号时频图为切入点,结合基于双级路由注意力机制的多尺度特征提取方法,对雷达脉冲信号时频演化特征进行精细化、层次化的提取,进而实现识别。实验结果表明,在低信噪比(Signal to Noise Ratio,SNR)环境下(SNR=-20 dB),识别准确率保持在92%左右。在脉冲丢失率和虚假脉冲率分别为10%、20%、30%的情况下,识别准确率分别达到99.36%、96.81%、90.45%。该方法在复杂环境下具有较强的鲁棒性和抗干扰能力,为雷达工作模式识别提供了一种新颖且有效的解决方案。展开更多
文摘针对滚动轴承故障诊断中故障特征提取困难及诊断准确率低的问题,提出了一种改进的灰狼优化算法(grey wolf optimizer,GWO)-变分模态分解(variational mode decomposition,VMD)的新诊断方法。首先将GWO改进为混沌增强灰狼优化算法(improved enhancement grey wolf optimizer,IEGWO),随后基于改进后的算法优化VMD的关键参数后,对故障信号进行分解。最后将分解后的信号构造故障特征向量并输入到双向长短时神经网络(bi-directional long short-term memory,Bi-LSTM)中进行轴承故障诊断分类。将所提方法与其他故障提取模型进行对比分析实验,结果表明,该模型将故障诊断准确率提高到了99%。实验结果证明,所提方法能够更好地提取故障特征,提高故障诊断的准确率。
基金Projects (50634060,50721003) supported by the National Natural Science Foundation of ChinaProject (2009AA03Z526) supported by the High-tech Research and Development Program of ChinaProject supported by the Open-End Fund for Valuable and Precision Instruments of Central South University
文摘Ferritic steel with a nominal composition of Fe-14Cr-3W-0.42Ti-0.32Y was prepared by mixing gas-atomized prealloyed powder and mechanically alloyed powder. The microstructure is much different fxom other ferritic steels with the same composition and prepared via only mechanically alloyed powder. A bi-modal structure, which consists of pure ferritic grains and martensitic grains, was obtained after hot forging and air cooling. A phase transformation of αbcc→γfcc→α＇bcc was also discovered in microstructural observation. The bi-modal microstructure shows a good combination of high strength and high ductility.
基金supported financially by the National Natural Science Foundation of China (Nos. 51671158 and 51621063)the National Program on Key Basic Research Project (No. 2014CB644003)the Programme of Introducing Talents of Discipline to Universities (No. PB2018008)。
文摘β titanium alloys with bi-modal structure which exhibit improved strength-ductility combination and fatigue property are widely used in aviation and aerospace industry.However,owing to the small size of primary α(αp) and nano-scaled multi variant distribution of secondary α platelets(αs),investigating the deformation behavior is really a challenging work.In this work,by applying transmission electron microscopy(TEM),the slip behavior in αp and transformed β matrix with different tensile strain was studied.After α/β solution treatment,the initial dislocation slips on {110} plane with <1 1 1> direction in β matrix.During furtherdeformation,(110),(101) and(1 1 2) multi slip is generated which shows a long straight cro s sing configuration.Dislocation cell is exhibited in β matrix at tensile strain above 20 %.Diffe rent from the solid solution treated sample,high density wavy dislocations are generated in transformedβ matrix.High fraction fine as hinders dislocation motion in β matrix effectively which in turn dominates the strength of the alloy.In primary α phase(αp),a core-shell structure is formed during deformation.Both pyramidal a+c slip and prismatic/basal a slip are generated in the shell layer.In core region,plastic deformation is governed by prismatic/basal a slip.Formation of the core-shell structure is the physical origin of the improved ductility.On one hand,the work hardening layer(shell) improves the strength of αp,which could deform compatibly with the hard transformed β matrix.Meanwhile,the center area(core) deforms homogeneously which will sustain plastic strain effectively and increase the ductility.This paper studies the slip behavior and reveals the origin of the improved strength-ductility combination in Bi-modal structure on a microscopic way,which will give theoretical advises for developing the next generation high strength β titanium alloys.
基金was supported by a PhD grant from "Fundagao para a Ciencia e a Tecnologia"(FCT)(L.S.:SFRH/BD/134565/2017,COVID/BD/151995/2021,T.M.:SFRH/BD/112458/2015supported by a PhD grant from“Fundação para a CiêL.R.:SFRH/BD/142322/2018)+3 种基金A.A.was partially supported by the Strategic Funding UIDB/04423/2020 and UIDP/04423/2020 through national funds provided by FCT and the European Regional Development Fund(ERDF)in the framework of the program PT 2020the European Structural and Investment Funds(ESIF)through the Competitiveness and Internationalization Operational Program e COMPETE 2020 through the FCT project PTDC/CTA-AMB/31774/2017(POCI-01-0145-FEDER/031774/2017)the projects Ocean3R(NORTE-01-0145-FEDER-000064)Atlantida(NORTE-01-0145-FEDER-000040).
文摘Olfactory receptors(ORs)play a key role in the prime sensorial perception,being highly relevant for intra/interspecific interactions.ORs are a subgroup of G-protein coupled receptors that exhibit highly complex subgenomes in vertebrates.However,OR repertoires remain poorly studied in fish lineages,precluding finely retracing their origin,evolution,and diversification,especially in the most basal groups.Here,we conduct an exhaustive gene screening upon 43 high-quality fish genomes exhibiting varied gene repertoires(2e583 genes).While the early vertebrates performed gas exchange through gills,we hypothesize that the emergence of new breathing structures(swim bladder and paired lungs)in early osteichthyans may be associated with expansions in the ORs gene families sensitive to airborne molecules.Additionally,we verify that the OR repertoire of moderns actinopterygians has not increased as expected following a whole genome duplication,likely due to regulatory mechanisms compensating the gene load excess.Finally,we identify 25 distinct OR families,allowing us to propose an updated universal nomenclature for the fish ORs.
文摘随着相控阵技术的快速发展与广泛应用,多功能雷达的工作模式趋于多样化、复杂化。实施快速且准确的雷达工作模式识别,对于后续威胁度分析、行为意图推理、行动决策信息生成具有重要支撑作用。以雷达信号时频图为切入点,结合基于双级路由注意力机制的多尺度特征提取方法,对雷达脉冲信号时频演化特征进行精细化、层次化的提取,进而实现识别。实验结果表明,在低信噪比(Signal to Noise Ratio,SNR)环境下(SNR=-20 dB),识别准确率保持在92%左右。在脉冲丢失率和虚假脉冲率分别为10%、20%、30%的情况下,识别准确率分别达到99.36%、96.81%、90.45%。该方法在复杂环境下具有较强的鲁棒性和抗干扰能力,为雷达工作模式识别提供了一种新颖且有效的解决方案。
