期刊文献+
共找到6,841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
Trajectory prediction based on grouped spatial-temporal encoder
8
作者 Di ZHOU Ying GAO +2 位作者 Hui LI Xiaoya LIU Qinghua LIN 《Frontiers of Computer Science》 2025年第11期173-175,共3页
1 Introduction Due to the complexity of traffic scenarios,the motion of agents is influenced not only by road geometry and traffic rules but also by surrounding agents,making trajectory prediction for autonomous vehic... 1 Introduction Due to the complexity of traffic scenarios,the motion of agents is influenced not only by road geometry and traffic rules but also by surrounding agents,making trajectory prediction for autonomous vehicles exceptionally challenging.The movement pattern of a single vehicle is typically influenced by nearby vehicles and its surrounding environmental information.Social psychologists have pointed out that individuals often imitate or follow other members of a group[1],using them as a reference for their behavior,which leads to the frequent occurrence of the herd effect in vehicle movement patterns[2]. 展开更多
关键词 trajectory prediction autonomous vehicles traffic scenarios movement pattern imitate follow other members group using motion agents grouped spatial temporal encoder
原文传递
Calculating the upper bound of the Gini coefficient using grouped data and a case study of China
9
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
Research Status and Prospects of Platinum Group Metal Coatings with High-Temperature Oxidation Resistance
10
作者 Ding Chenxi Liu Zhongyu +3 位作者 Fang Zhen Wang Haoxu Lv Biao Hu Zhenfeng 《稀有金属材料与工程》 北大核心 2026年第2期333-344,共12页
Platinum group metals have high melting points,strong corrosion resistance,stable chemical properties,and low oxygen permeability in high-temperature oxygen-containing environments.As thermal protective coating materi... Platinum group metals have high melting points,strong corrosion resistance,stable chemical properties,and low oxygen permeability in high-temperature oxygen-containing environments.As thermal protective coating materials,they have gained essential applications in the aerospace field and have excellent prospects for application in frontier military fields,such as protecting hot-end components of hypersonic aircraft.This research reviewed the latest research progress of platinum group metal coatings with hightemperature oxidation resistance,including coating preparation techniques,oxidation failure,and alloying modification.The leading preparation techniques of current platinum group metal coatings were discussed,as well as the advantages and disadvantages of various existing preparation techniques.Besides,the intrinsic properties,failure forms,and failure mechanisms of coatings of single platinum group metal in high-temperature oxygen-containing environments were analyzed.On this basis,the necessity,main methods,and main achievements of alloying modification of platinum group metals were summarized.Finally,the future development of platinum group coatings with high-temperature oxidation resistance was discussed and prospected. 展开更多
关键词 platinum group metal coatings preparation technique high temperature oxidation resistance alloying modification
原文传递
Development Status and Existing Problems of Ion-Solvation Membranes for Electrolysis of Water
11
作者 Zheng-Yuan Zhou Yu-Tao Sun +5 位作者 Zheng-Bang Liu Chuan-Zheng Wang Yong-Nan Zhou Xi Luo Tian-Chi Zhou Jin-Li Qiao 《电化学(中英文)》 北大核心 2026年第1期1-26,共26页
Ion-solvaing membranes(ISMs)have received extensive attention in recent years as a key component in electrochemical energy conversion and storage devices.This article provides an overview of structural composition,per... Ion-solvaing membranes(ISMs)have received extensive attention in recent years as a key component in electrochemical energy conversion and storage devices.This article provides an overview of structural composition,performance advan-tages,research progress,ion conduction mechanism and existing issues of ISMs,primarily classifying them according to the matrix structure.A detailed analysis of performance enhancement methods,key performance indicators of ISMs and performance influencing factors is also presented.The article contributes to further optimizing the design and application of ion-solvation membranes,providing theoretical support for the development of fields such as hydrogen production through electrolysis of water and electrochemical energy in the future. 展开更多
关键词 Ion-solvation membrane Alkaline water electrolysis Deprotonated group Ionic conduction mechanism Hydrogen energy
在线阅读 下载PDF
AN APPROXIMATE ALGORITHM OF OPTIMAL DIGIT-GROUPED PARTITION OF SEQUENCES
12
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
13
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
SPG contributes wisdom and strength to cultivating international standardization talent
14
作者 Xu Guowang 《China Standardization》 2026年第1期46-46,共1页
Established in 2019,the Shandong Port Group(SPG)comprises four port groups(Qingdao Port,Rizhao Port,Yantai Port,and Bohaiwan Port)and 12 business segments.SPG connects 3,345 kilometers of coastline within Shandong Pro... Established in 2019,the Shandong Port Group(SPG)comprises four port groups(Qingdao Port,Rizhao Port,Yantai Port,and Bohaiwan Port)and 12 business segments.SPG connects 3,345 kilometers of coastline within Shandong Province.Its cargo throughput has consistently ranked first globally for many years,and its container volume growth ranks second globally,forming a port cluster covering the entire industrial chain. 展开更多
关键词 port cluster port groups talent cultivation industrial chain international standardization Shandong Port Group cargo throughput container volume
原文传递
Local Characterizations of Results on the Normal Index of Subgroups in Finite Groups
15
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
16
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
Advances and challenges in the synthesis of N-fluoroalkyl compounds
17
作者 Lvqi Jiang Wenbin Yi 《Science China Chemistry》 2026年第2期535-538,共4页
The incorporation of small fluorinated functional groups,including CF_(3),CF_(2)H,and CFH_(2),into small molecules represents a crucial strategy for modulating their physical,chemical,and biological characteristics[1,... The incorporation of small fluorinated functional groups,including CF_(3),CF_(2)H,and CFH_(2),into small molecules represents a crucial strategy for modulating their physical,chemical,and biological characteristics[1,2].Consequently,organofluorine compounds are frequently encountered in pharmaceuticals and agrochemicals.Significant advances have been made in the introduction of fluoroalkyl groups into small molecules since the beginning of the 21st century. 展开更多
关键词 introduction fluoroalkyl groups incorporation small fluorinated functional groupsincluding synthesis N fluoroalkyl compounds fluoroalkyl compounds fluorinated functional groups CF H small molecules
原文传递
Tuna classification using super learner ensemble of region-based CNN-grouped 2D-LBP models
18
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
19
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
Asymmetric construction of non-activated C-SCF_(3) stereocenter via copper-catalyzed hydroallylation of SCF_(3)-alkenes
20
作者 Wei-Cheng Zhao Yan He +4 位作者 Chen-Hui Jiang Peng Liu Qian Gao Duo-Duo Hu Xi-Sheng Wang 《Chinese Chemical Letters》 2026年第2期424-429,共6页
Fluorinated motifs are prevalent in both pharmaceuticals and agrochemicals.The incorporation of fluorine-containing moieties to drug candidates has emerged as a potent strategy for lead optimization in pharmaceutical ... Fluorinated motifs are prevalent in both pharmaceuticals and agrochemicals.The incorporation of fluorine-containing moieties to drug candidates has emerged as a potent strategy for lead optimization in pharmaceutical research and development.While extensive research has been devoted to constructing molecules that incorporate a trifluoromethylthio(SCF_(3)−)group on a stereogenic carbon,the synthesis of trifluoromethylthiolated alkanes featuring a SCF_(3)-substituted stereogenic carbon at non-activated site remains understudied.Herein,we report a Cu-catalyzed regio-and enantioselective hydroallylation of 1-trifluoromethylthiolated alkenes.Important to the process is the regio-and enantioselective Cu-H insertion to SCF_(3)-substituted alkene to form chiralα-SCF_(3) alkyl copper intermediates,outcompeting unproductive insertion to the coupling partner,and eventually proceed to afford optically active homoallylic trifluoromethylthiolated products. 展开更多
关键词 Asymmetric construction Non-activated Hydroallylation Trifluoromethylthio group COPPER-CATALYZED
原文传递
上一页 1 2 250 下一页 到第
使用帮助 返回顶部