期刊文献+
共找到6,774篇文章
< 1 2 250 >
每页显示 20 50 100
Variations in leaf functional traits among plant species grouped by growth and leaf types in Zhenjiang,China 被引量:12
1
作者 Congyan Wang Jiawei Zhou +2 位作者 Hongguang Xiao Jun Liu Lei Wang 《Journal of Forestry Research》 SCIE CAS CSCD 2017年第2期241-248,共8页
Leaf functional traits are adaptations that enable plants to live under various environmental conditions. This study aims to determine the differences in leaf functional traits among plants grouped by growth habit, le... Leaf functional traits are adaptations that enable plants to live under various environmental conditions. This study aims to determine the differences in leaf functional traits among plants grouped by growth habit, leaf life span,leaf lifestyle, leaf form, and origin. Specific leaf area(SLA) of perennial or evergreen species was lower than that of annual or deciduous species because longer-lived leaves of perennial or evergreen species require more investment in structural integrity and/or defense against disturbances, especially with any resource constraint. SLA of large individuals was lower than that of small individuals. The low SLA in large individuals can improve their response to changing light and water conditions because increasing plant height is advantageous for light competition, but it can also impose a cost in terms of structural support and water transport. Petioles of plants with compound leaves were significantly longer than those of simple leaves because branching is expensive in terms of gaining height. SLA of plants increased with increasing invasiveness accordingly, and SLA of invasive plants was higher than that of their native congeners because invasive plants should invest more biomass on leaf growth rather than leaf structures per unit area to achieve a higher growth rate.Overall, variation in leaf functional traits among different groups may play an adaptive role in the successful survival of plants under diverse environments because leaf functional traits can lead to pronounced effects on leaf function,especially the acquisition and use of light. Plant species with different growth and leaf traits balance resource acquisition and leaf construction to minimize trade-offs and achieve fitness advantages in their natural habitat. 展开更多
关键词 expensive enable constraint perennial advantageous fitness grouped environments minimize habitat
在线阅读 下载PDF
Anomalies of Precursory Group and Grouped Strong Earthquakes in the Sichuan-Yunnan Region 被引量:2
2
作者 ShiShaoxian ChengWanzheng 《Earthquake Research in China》 2004年第4期348-356,共9页
Three methods of extracting the information of anomalies of a precursory group are put forward, i.e., the mathematical analyses of the synthetic information of earthquake precursors (S), the inhomogeneous degree of pr... Three methods of extracting the information of anomalies of a precursory group are put forward, i.e., the mathematical analyses of the synthetic information of earthquake precursors (S), the inhomogeneous degree of precursory groups (ID) and the values of short-term and impending anomaly in near-source area (NS). Using these methods, we calculate the observational data of deformation, underground fluid and hydrochemical constituents obtained from different seismic stations in the Sichuan-Yunnan region and conclude that the synthetic precursory anomalies of a single strong earthquake with M S6.0 differ greatly from those of the grouped strong earthquakes, for the anomalous information of precursory groups are more abundant. The three methods of extracting the synthetic precursory anomaly and the related numerical results can be applied into the practice of prediction to the grouped strong earthquakes in the Sichuan-Yunnan region. Inhomogeneous degree (ID) of synthetic precursory anomaly can be identified automatically because it takes the threshold of distributive characteristics of the anomalies of precursory group as its criterion for anomaly. 展开更多
关键词 Anomalies of precursory group Synthetic information Short-term and impending characteristic anomaly in the near-source area Prediction of the grouped strong earthquakes
在线阅读 下载PDF
STATISTICAL INFERENCE FOR A BIVARIATE EXPONENTIAL DISTRIBUTION BASED ON GROUPED DATA
3
作者 YE CINAN(Department of Applied Mathematics, Naming University of Science & Tech.nology, Naming210014.) 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 1996年第3期285-294,共10页
Consider the bivariate exponential distribution due to Marshall and Olkin[2], whose survival function is F(x, g) = exp[-λ1x-λ2y-λ12 max(x, y)] (x 0,y 0)with unknown Parameters λ1 > 0, λ2 > 0 and λ12 0.Base... Consider the bivariate exponential distribution due to Marshall and Olkin[2], whose survival function is F(x, g) = exp[-λ1x-λ2y-λ12 max(x, y)] (x 0,y 0)with unknown Parameters λ1 > 0, λ2 > 0 and λ12 0.Based on grouped data, a newestimator for λ1, λ2 and λ12 is derived and its asymptotic properties are discussed.Besides, some test procedures of equal marginals and independence are given. Asimulation result is given, too. 展开更多
关键词 Bivariate exponential distribution parameter estimation grouped data asymptoticproperty.
在线阅读 下载PDF
On the Power Performance of Test Statistics for the Generalized Rayleigh Interval Grouped Data
4
作者 Hatim Solayman Migdadi 《Open Journal of Statistics》 2015年第5期474-482,共9页
In this paper, the weighted Kolmogrov-Smirnov, Cramer von-Miss and the Anderson Darling test statistics are considered as goodness of fit tests for the generalized Rayleigh interval grouped data. An extensive simulati... In this paper, the weighted Kolmogrov-Smirnov, Cramer von-Miss and the Anderson Darling test statistics are considered as goodness of fit tests for the generalized Rayleigh interval grouped data. An extensive simulation process is conducted to evaluate their controlling of type 1 error and their power functions. Generally, the weighted Kolmogrov-Smirnov test statistics show a relatively better performance than both, the Cramer von-Miss and the Anderson Darling test statistics. For large sample values, the Anderson Darling test statistics cannot control type 1 error but for relatively small sample values it indicates a better performance than the Cramer von-Miss test statistics. Best selection of the test statistics and highlights for future studies are also explored. 展开更多
关键词 GENERALIZED RAYLEIGH Distribution INTERVAL grouped Data GOODNESS of FIT Tests Empirical Type 1 ERROR Power Function
在线阅读 下载PDF
Study of Paleoearthquakes by Excavation of Grouped Trenches on the Zemuhe Fault in Daqingliangzi,Xichang,Sichuan
5
作者 Tian Qinjian Ren Zhikun Zhang Junlong 《Earthquake Research in China》 2009年第1期56-67,共12页
Uncertainties are common in the dating of paleoearthquakes.To improve the credibility of the dating of paleoearthquakes,analysis was done on fault activity,sedimentary environment and seismo-geomorphology to investiga... Uncertainties are common in the dating of paleoearthquakes.To improve the credibility of the dating of paleoearthquakes,analysis was done on fault activity,sedimentary environment and seismo-geomorphology to investigate paleoearthquakes along the Zemuhe active fault zone.Grouped trenches were excavated near Daqingliangzi,which revealed three palaeoearthquake events aged 160a,3100a and 5500a~8900a,respectively,including recurrence intervals of about 3000a.Sedimentary processes related to strike-slip fault type earthquakes were discussed,and a sedimentary model was put forward for strike-slip faults at hillsides where drumlin and reverse scarp developed. 展开更多
关键词 Palaeoearthquake grouped trenches Micro-geomorphology Zemuhe River sedimentary model
在线阅读 下载PDF
Network autoregression model with grouped factor structures
6
作者 ZHANG Zhiyuan ZHU Xuening 《中山大学学报(自然科学版)(中英文)》 CAS CSCD 北大核心 2023年第5期24-37,共14页
Network autoregression and factor model are effective methods for modeling network time series data.In this study,we propose a network autoregression model with a factor structure that incorporates a latent group stru... Network autoregression and factor model are effective methods for modeling network time series data.In this study,we propose a network autoregression model with a factor structure that incorporates a latent group structure to address nodal heterogeneity within the network.An iterative algorithm is employed to minimize a least-squares objective function,allowing for simultaneous estimation of both the parameters and the group structure.To determine the unknown number of groups and factors,a PIC criterion is introduced.Additionally,statistical inference of the estimated parameters is presented.To assess the validity of the proposed estimation and inference procedures,we conduct extensive numerical studies.We also demonstrate the utility of our model using a stock dataset obtained from the Chinese A-Share stock market. 展开更多
关键词 network autoregression factor structure HETEROGENEITY latent group structure network time series
在线阅读 下载PDF
Novel Grouped Probability Data Association Algorithm for MIMO Detection
7
作者 车文 赵慧 王文博 《Journal of Beijing Institute of Technology》 EI CAS 2008年第1期67-70,共4页
To bridge the performance gap between original probability data association (PDA) algorithm and the optimum maximum a posterior (MAP) algorithm for multi-input multi-output (MIMO) detection, a grouped PDA (GP-... To bridge the performance gap between original probability data association (PDA) algorithm and the optimum maximum a posterior (MAP) algorithm for multi-input multi-output (MIMO) detection, a grouped PDA (GP-PDA) detection algorithm is proposed. The proposed GP-PDA method divides all the transmit antennas into groups, and then updates the symbol probabilities group by group using PDA computations. In each group, joint a posterior probability (APP) is computed to obtain the APP of a single symbol in this group, like the MAP algorithm. Such new algorithm combines the characters of MAP and PDA. MAP and original PDA algorithm can be regarded as a special case of the proposed GP-PDA. Simulations show that the proposed GP-PDA provides a performance and complexity trade, off between original PDA and MAP algorithm. 展开更多
关键词 multi-input multi-output (MIMO) V-BLAST GROUP probability data association (PDA)
在线阅读 下载PDF
Calculating the upper bound of the Gini coefficient using grouped data and a case study of China
8
作者 Pixu Shi Anru R.Zhang 《Science China Mathematics》 2025年第10期2501-2518,共18页
Determining an upper bound,particularly the optimal upper bound of the Gini coefficient when dealing with grouped data without specified income brackets remains an important and open question.In this paper,we introduc... Determining an upper bound,particularly the optimal upper bound of the Gini coefficient when dealing with grouped data without specified income brackets remains an important and open question.In this paper,we introduce an efficient algorithm to calculate the exact optimal upper bound of the Gini coefficient with provable guarantees.To exemplify these methods,we also offer computed results for the Gini coefficients of urban and rural China spanning the years 2003 to 2008. 展开更多
关键词 Gini coefficient grouped data of income upper bound China
原文传递
AN APPROXIMATE ALGORITHM OF OPTIMAL DIGIT-GROUPED PARTITION OF SEQUENCES
9
作者 许国志 陈庆华 刘继勇 《Chinese Science Bulletin》 SCIE EI CAS 1987年第14期942-946,共5页
In this note we give a rather good approximate algorithm of optimal digit-grouped partition of sequences, showing that the optimal complete digit-grouped partition number of a dumbbell type sequence S is equal to its ... In this note we give a rather good approximate algorithm of optimal digit-grouped partition of sequences, showing that the optimal complete digit-grouped partition number of a dumbbell type sequence S is equal to its optimal digit-grouped partition number N(S), hence an estimation of N(S) is obtained. The thickness of a sequence introduced in this note is a key. 展开更多
关键词 PARTITION DIGIT hence APPROXIMATE grouped visualization satisfy POLYNOMIAL SALESMAN showing
在线阅读 下载PDF
ASYMPTOTIC PROPERTIES OF MLE FOR WEIBULL DISTRIBUTION WITH GROUPED DATA
10
作者 XUEHongqi SONGLixin 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2002年第2期176-186,共11页
Abstract. A grouped data model for Weibull distribution is considered. Under mild con-ditions, the maximum likelihood estimators(MLE) are shown to be identifiable, stronglyconsistent, asymptotically normal, and satisf... Abstract. A grouped data model for Weibull distribution is considered. Under mild con-ditions, the maximum likelihood estimators(MLE) are shown to be identifiable, stronglyconsistent, asymptotically normal, and satisfy the law of iterated logarithm. Newton iter-ation algorithm is also considered, which converges to the unique solution of the likelihoodequation. Moreover, we extend these results to a random case. 展开更多
关键词 grouped data MLE Weibull distribution identifiable strongly consistent asymptotically normal the law of iterated logarithm Newton iteration arithmetic.
原文传递
Local Characterizations of Results on the Normal Index of Subgroups in Finite Groups
11
作者 Yubo LV Yangming LI Xiaoxia DONG 《Journal of Mathematical Research with Applications》 2026年第1期33-39,共7页
Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divide... Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divides the order of a group G.In this paper,some characterizations of G being p-solvable or p-supersolvable were obtained by analyzing the normal index of certain subgroups of G.These results can be viewed as local version of recent results in the literature. 展开更多
关键词 p-solvable group p-supersolvable group normal index maximal subgroup 2-maximal subgroup
原文传递
Parameters estimation and application of generalized exponential distribution under grouped and right-censored data
12
作者 Yuzhu TIAN Maozai TIAN Ping CHEN 《Frontiers of Mathematics in China》 CSCD 2023年第3期165-174,共10页
Generalized exponential distribution is a class of important distribution in lifedata analysis,especially in some skewed lifedata.The Parameter estimation problem for generalized exponential distribution model with gr... Generalized exponential distribution is a class of important distribution in lifedata analysis,especially in some skewed lifedata.The Parameter estimation problem for generalized exponential distribution model with grouped and right-censored data is considered.The maximum likelihood estimators are obtained using the EM algorithm.Some simulations are carried out to illustrate that the proposed algorithm is effective for the model.Finally,a set of medicine data is analyzed by generalized exponential distribution. 展开更多
关键词 Generalized exponential distribution grouped and right-censored data EM algorithm
原文传递
Tuna classification using super learner ensemble of region-based CNN-grouped 2D-LBP models
13
作者 Jisha Anu Jose C.Sathish Kumar S.Sureshkumar 《Information Processing in Agriculture》 EI 2022年第1期68-79,共12页
Tuna is superior among the marine fishes that are exported in the forms of raw fish and processed food.Separation of Tuna into their species is done in industries manually,and the process is tiresome.This work propose... Tuna is superior among the marine fishes that are exported in the forms of raw fish and processed food.Separation of Tuna into their species is done in industries manually,and the process is tiresome.This work proposes an automated system for classifying Tuna spe-cies based on their images.An ensemble of region-based deep neural networks is used.A sub region contrast stretching operation is applied to enhance the images.Each fish image is then divided into three regions and is augmented before giving as input to pre-trained convolutional neural networks(CNN).After fine-tuning the models,the output from the last convolutional layer is given to a grouped 2D-local binary pattern descriptor(G2DLBP).Statistical features from the descriptor are applied to different classifiers,and the best clas-sifier for each image region model is identified.Different ensemble methods are subse-quently used to combine the three CNN-G2DLBP models.Among the ensemble techniques,super learner ensemble method with random forest(RF)classifier using 5-fold cross-validation shows the highest classification accuracy of 97.32%.The perfor-mance of different ensemble methods is analyzed in terms of accuracy,precision,recall,and f-score.The proposed system shows an accuracy of 93.91% when evaluated with an independent test dataset.An ensemble of region-based CNN with textural features from G2DLBP is applied for the first time for fish classification. 展开更多
关键词 Tuna classification Convolutional neural network grouped 2D-local binary pattern Super learner ensemble
原文传递
Effect of grouped ST36 or RN12 on gastric motility and sensation
14
作者 Guang Sun Hao Liu +4 位作者 Kun Liu Hong-Feng Wang Mu-Jun Zhi Xin-Yan Gao Bing Zhu 《World Journal of Traditional Chinese Medicine》 2017年第1期31-37,共7页
Objective: To investigate the effects of paired ST36 and RN12 acupuncture stimulation on gastric motility and the firing rate of responsible neurons in anesthetized rats.Methods: Using electrophysiological methods, we... Objective: To investigate the effects of paired ST36 and RN12 acupuncture stimulation on gastric motility and the firing rate of responsible neurons in anesthetized rats.Methods: Using electrophysiological methods, we measured the effects of acupuncture at RN12, ST36, or RN12+ST36 on gastric motility as well as nerve discharges from the gastric sympathetic, vagal nerve, and wide dynamic range(WDR) neurons in the spinal dorsal horn T7-9 in anesthetized rats.Results: 1) Acupuncture at RN12 inhibited gastric motility(83.84±4.49)% and vagal nerve discharge(65.64±5.67)%, but promoted sympathetic nerve activity(243.70±40.67)%; acupuncture at ST36 induced opposing effects on gastric motility(111.31±2.01)% and vagal nerve discharge(166.98±15.92)%. Interestingly, acupuncture at RN12+ST36 together yielded effects similar to that of acupuncture at RN12 alone(93.59±2.05)%,(54.52±7.12)%. 2) WDR neuron discharges induced by gastric distension were inhibited by acupuncture at RN12(194.56 ±18.79)%. However, acupuncture at ST36 induced a more significant inhibitory effect.Conclusion: Acupuncture at RN12 inhibits gastric motility by activation of the sympathetic reflex at the spinal level; acupuncture at ST36 promotes gastric motility by activation of the parasympathetic reflex at the supraspinal level, and acupuncture at RN12+ST36 produces a similar decrease in gastric motility as RN12 stimulation alone. Both acupoints decrease the effect of noxious gastric distention on WDR neuron activity, but paired RN12+ST36 stimulation does not significantly affect WDR neuron discharge. 展开更多
关键词 ST36 RN12 grouped acupoints Gastric motility Gastric sensation
原文传递
FLIGHT:Federated Learning with IRS for Grouped Heterogeneous Training
15
作者 Tong Yin Lixin Li +3 位作者 Donghui Ma Wensheng Lin Junli Liang Zhu Han 《Journal of Communications and Information Networks》 EI CSCD 2022年第2期135-144,共10页
In recent years,federated learning(FL)has played an important role in private data-sensitive scenarios to perform learning tasks collectively without data exchange.However,due to the centralized model aggregation for ... In recent years,federated learning(FL)has played an important role in private data-sensitive scenarios to perform learning tasks collectively without data exchange.However,due to the centralized model aggregation for heterogeneous devices in FL,the last updated model after local training delays the convergence,which increases the economic cost and dampens clients’motivations for participating in FL.In addition,with the rapid development and application of intelligent reflecting surface(IRS)in the next-generation wireless communication,IRS has proven to be one effective way to enhance the communication quality.In this paper,we propose a framework of federated learning with IRS for grouped heterogeneous training(FLIGHT)to reduce the latency caused by the heterogeneous communication and computation of the clients.Specifically,we formulate a cost function and a greedy-based grouping strategy,which divides the clients into several groups to accelerate the convergence of the FL model.The simulation results verify the effectiveness of FLIGHT for accelerating the convergence of FL with heterogeneous clients.Besides the exemplified linear regression(LR)model and convolutional neural network(CNN),FLIGHT is also applicable to other learning models. 展开更多
关键词 federated learning decentralized aggrega-tion intelligent reflecting surfaces grouped learning
原文传递
Vertical Structure and Energy Transfer of Stationary Planetary Waves in Different Prescribed Atmospheric Stratifications
16
作者 Wenqi ZHANG Lin WANG 《Advances in Atmospheric Sciences》 2026年第1期233-246,共14页
This study investigates the relationship between atmospheric stratification (i.e., static stability given by N^(2)) and the vertical energy transfer of stationary planetary waves, and further illustrates the underlyin... This study investigates the relationship between atmospheric stratification (i.e., static stability given by N^(2)) and the vertical energy transfer of stationary planetary waves, and further illustrates the underlying physical mechanism. Specifically, for the simplified case of constant stratospheric N^(2), the refractive index square of planetary waves has a theoretical tendency to increase first and then decrease with an increased N^(2), whereas the group velocity weakens. Mechanistically, this behavior can be understood as an intensified suppression of vertical isentropic surface displacement caused by meridional heat transport of planetary waves under strong N^(2) conditions. Observational analysis corroborates this finding, demonstrating a reduction in the vertical-propagation velocity of waves with increased N^(2). A linear, quasi- geostrophic, mid-latitude beta-plane model with a constant background westerly wind and a prescribed N^(2) applicable to the stratosphere is used to obtain analytic solutions. In this model, the planetary waves are initiated by steady energy influx from the lower boundary. The analysis indicates that under strong N^(2) conditions, the amplitude of planetary waves can be sufficiently increased by the effective energy convergence due to the slowing vertical energy transfer, resulting in a streamfunction response in this model that contains more energy. For N^(2) with a quasi-linear vertical variation, the results bear a resemblance to the constant case, except that the wave amplitude and oscillating frequency show some vertical variations. 展开更多
关键词 planetary waves vertical propagation atmospheric stratification stratospheric circulation group velocity
在线阅读 下载PDF
Anionically-Reinforced Nanocellulose Separator Enables Dual Suppression of Zinc Dendrites and Polyiodide Shuttle for Long-Cycle Zn-I_(2) Batteries
17
作者 Wenhui Liu Hong Ma +4 位作者 Lingli Zhao Weiwei Qian Bo Liu Jizhang Chen Yagang Yao 《Nano-Micro Letters》 2026年第2期569-583,共15页
Zn-I_(2) batteries have emerged as promising next-generation energy storage systems owing to their inherent safety,environmental compatibility,rapid reaction kinetics,and small voltage hysteresis.Nevertheless,two crit... Zn-I_(2) batteries have emerged as promising next-generation energy storage systems owing to their inherent safety,environmental compatibility,rapid reaction kinetics,and small voltage hysteresis.Nevertheless,two critical challenges,i.e.,zinc dendrite growth and polyiodide shuttle effect,severely impede their commercial viability.To conquer these limitations,this study develops a multifunctional separator fabricated from straw-derived carboxylated nanocellulose,with its negative charge density further reinforced by anionic polyacrylamide incorporation.This modification simultaneously improves the separator’s mechanical properties,ionic conductivity,and Zn^(2+)ion transfer number.Remarkably,despite its ultrathin 20μm profile,the engineered separator demonstrates exceptional dendrite suppression and parasitic reaction inhibition,enabling Zn//Zn symmetric cells to achieve impressive cycle life(>1800 h at 2 m A cm^(-2)/2 m Ah cm^(-2))while maintaining robust performance even at ultrahigh areal capacities(25 m Ah cm^(-2)).Additionally,the separator’s anionic characteristic effectively blocks polyiodide migration through electrostatic repulsion,yielding Zn-I_(2) batteries with outstanding rate capability(120.7 m Ah g^(-1)at 5 A g^(-1))and excellent cyclability(94.2%capacity retention after 10,000 cycles).And superior cycling stability can still be achieved under zinc-deficient condition and pouch cell configuration.This work establishes a new paradigm for designing high-performance zinc-based energy storage systems through rational separator engineering. 展开更多
关键词 Zinc-iodine batteries Nanocellulose separators Carboxyl functional groups Polyiodide shuttle effect Dendrite suppression
在线阅读 下载PDF
商业银行基于Group Training技术的小样本学习应用研究
18
作者 吴永飞 寿弘宇 +3 位作者 王彦博 魏文术 徐奇 张月 《金融科技时代》 2025年第3期16-22,共7页
人工智能是推动社会进步和经济发展的关键力量。商业银行已经在诸多业务领域广泛使用人工智能技术,如精准营销、智能风控、智慧运营等业务领域。然而,有些业务场景在“冷启动”阶段面临样本量不足,并且坏样本量极少的小样本学习问题,这... 人工智能是推动社会进步和经济发展的关键力量。商业银行已经在诸多业务领域广泛使用人工智能技术,如精准营销、智能风控、智慧运营等业务领域。然而,有些业务场景在“冷启动”阶段面临样本量不足,并且坏样本量极少的小样本学习问题,这导致现有的人工智能技术可能失效。基于此,文章创新提出了一种Group Training(群组训练)建模思路,可以有效解决小样本学习问题。实证结果表明,Group Training建模方案在多个金融数据集上效果均明显优于传统的建模方案,这为商业银行小样本学习提供了新的研究思路和解决方案。 展开更多
关键词 人工智能 小样本学习 Group Learning Group Training
在线阅读 下载PDF
改进infoGAN和QPSO-VGG16的小样本条件下电机轴承故障诊断方法
19
作者 刘航 张德春 +3 位作者 刘志坚 何蔚 陶韵旭 孟欣雨 《电机与控制学报》 北大核心 2025年第5期167-178,共12页
针对电机轴承故障数据相对于正常数据稀缺的现状,本文提出改进infoGAN和QPSO-VGG16的故障诊断方法。首先采用连续小波变换(CWT)方法将高维故障振动信号转换为对应二维时频图,构建原始图像数据集。建立基于条件信息最大化生成对抗网络(ci... 针对电机轴承故障数据相对于正常数据稀缺的现状,本文提出改进infoGAN和QPSO-VGG16的故障诊断方法。首先采用连续小波变换(CWT)方法将高维故障振动信号转换为对应二维时频图,构建原始图像数据集。建立基于条件信息最大化生成对抗网络(cinfoGAN)的数据增强模型,在统一的框架下完成所有类别故障数据的生成,提升数据增强工作的质量和效率。进一步,构建基于VGG16网络的故障诊断模型,在交替使用原始和增强图像数据集对VGG16网络进行训练的过程中,通过改进的粒子群优化(QPSO)算法对2类数据集的学习率进行联合寻优,确保VGG16网络达到最佳的性能。在真实的电机轴承振动信号上开展数值实验结果表明,将振动信号转换为图像能够充分发挥VGG16模型对图像数据的特征提取能力,且数据增强和交替训练方法能够使故障诊断的准确率依次提升2.6%和4.5%。 展开更多
关键词 电机轴承 故障诊断 连续小波变换 生成对抗网络 Visual Geometry Group 16
在线阅读 下载PDF
Regulating the“core-shell”microstructure of hard carbon through sodium hydroxide activation for achieving high-capacity SIBs anode 被引量:5
20
作者 Haihua Wang Huizhu Niu +6 位作者 Kewei Shu Liyu Sun Yu Wang Yifan Du Yun Han Cunguo Yang Yong-Mook Kang 《Journal of Materials Science & Technology》 2025年第6期161-170,共10页
Pore structure engineering has been acknowledged as suitable approach to creating active sites and en-hancing ion transport capabilities of hard carbon anodes.However,conventional porous carbon materials exhibit high ... Pore structure engineering has been acknowledged as suitable approach to creating active sites and en-hancing ion transport capabilities of hard carbon anodes.However,conventional porous carbon materials exhibit high BET and surface defects.Additionally,the sodium storage mechanism predominantly occurs in the slope region.This contradicts practical application requirements because the capacity of the plateau region is crucial for determining the actual capacity of batteries.In our work,we prepared a novel“core-shell”carbon framework(CNA1200).Introducingclosedporesand carboxylgroupsinto coal-basedcarbon materials to enhance its sodium storage performance.The closed pore structure dominates in the“core”structure,which is attributed to the timely removal of sodium hydroxide(NaOH)to prevent further for-mation of active carbon structure.The presence of closed pores is beneficial for increasing sodium ion storage in the low-voltage plateau region.And the“shell”structure originates from coal tar pitch,it not only uniformly connects hard carbon particles together to improve cycling stability,but is also rich in carboxyl groups to enhance the reversible sodium storage performance in slope region.CNA1200 has ex-cellent electrochemical performance,it exhibits a specific capacity of 335.2 mAh g^(−1)at a current density of 20 mA g^(−1)with ICE=51.53%.In addition,CNA1200 has outstanding cycling stability with a capac-ity retention of 91.8%even when cycling over 200 times.When CNA1200 is used as anode paired with Na_(3)V_(2)(PO_(4))_(3)cathode,it demonstrates a capacity of 109.54 mAh g^(−1)at 0.1 C and capacity retention of 94.64%at 0.5 C.This work provides valuable methods for regulating the structure of sodium-ion battery(SIBs)anode and enhances the potential for commercialization. 展开更多
关键词 Hard carbon plateau region NaOH controlled etching-thermal annealing Closed pore structure Carboxyl groups Coal-based carbon materials
原文传递
上一页 1 2 250 下一页 到第
使用帮助 返回顶部