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Variability of leaf functional traits of invasive tree Rhus typhina L. in North China 被引量:5
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作者 WEI Mei WANG Shu +3 位作者 WU Bing-de JIANG Kun ZHOU Jia-wei WANG Cong-yan 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第1期155-163,共9页
Functional traits, specifically leaf functional traits, are core-topics to explore importance to the invasion success of invasive plant species. This study aims to address the differences in leaf functional traits and... Functional traits, specifically leaf functional traits, are core-topics to explore importance to the invasion success of invasive plant species. This study aims to address the differences in leaf functional traits and their corresponding variability of the invasive tree staghorn sumac Rhus typhina L. with different invasion success, including lower and higher invasion success, in two climatic regions in North China, including a warm temperate region and a cold temperate region. No significant differences were found for leaf functional traits of staghorn sumac across different invasion success. However, the variability of leaf chlorophyll and nitrogen concentrations of staghorn sumac under higher invasion success were approximately 66.023% and 68.615% higher than those under lower invasion success, respectively. The leaf chlorophyll and nitrogen concentrations of staghorn sumac in the warm temperate region were approximately 18.432% and 16.337% higher than those in cold temperate region, respectively. The variability of specific leaf area of staghorn sumac in warm temperate region was approximately 59.802% higher than that in cold temperate region. Accordingly, leaf chlorophyll and N concentrations as well as specific leaf area of staghorn sumac and their corresponding variability may play an essential role in shaping ecological success of studied invader along a climatic gradient. 展开更多
关键词 climatic region invasive tree coefficient of variation variability specific leaf area Rhus typhina L.
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Switching variability index based multiple strategy CFAR detector 被引量:5
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作者 Yang Li Zhenyuan Ji +1 位作者 Bingfei Li Gil Alterovitz 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2014年第4期580-587,共8页
A switching variability index (SVl) constant false alarm rate (CFAR) detector is proposed for improving the detection performance of VI-CFAR detectors in multiple targets backgrounds. When the presence of non-homo... A switching variability index (SVl) constant false alarm rate (CFAR) detector is proposed for improving the detection performance of VI-CFAR detectors in multiple targets backgrounds. When the presence of non-homogeneity in CFAR reference windows is indicated by a VI-CFAR detector, a switching- CFAR detector is introduced to optimize the performance of the VI-CFAR detector in homogeneous, multiple targets and clutter edge backgrounds. The structure and parameters selection method of the SVI-CFAR detector is presented. Comparisons with classic CFAR detectors and recently proposed detectors are also given. Theoretical analysis and simulation results show that SVICFAR detector maintains the good performance of the VI-CFAR detector in homogeneous and clutter edge backgrounds, while greatly improving the capacity of anti-multi targets. 展开更多
关键词 switching variability index constant false alarm rate(SVI-CFAR) adaptive detection complex environment multiple-strategy detection radar target detection.
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Genetic variability for yield and fiber related traits in genetically modified cotton 被引量:3
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作者 SAHAR Adeela ZAFAR Muhammad Mubashar +9 位作者 RAZZAQ Abdul MANAN Abdul HAROON Muhammad SAJID Sunaina REHMAN Abdul MO Huijuan ASHRAF Muhammad REN Maozhi SHAKEEL Amir YUAN Youlu 《Journal of Cotton Research》 2021年第3期219-228,共10页
Background:Cotton(Gossypium hirsutum L.)is grown for fiber and oil purposes in tropical and sub-tropical areas of the world.Pakistan is the 4th largest producer of cotton.It has a significant contribution in the GDP o... Background:Cotton(Gossypium hirsutum L.)is grown for fiber and oil purposes in tropical and sub-tropical areas of the world.Pakistan is the 4th largest producer of cotton.It has a significant contribution in the GDP of Pakistan.Therefore,the present study was performed to assess the genetic variations and genetic diversity of yield and fiber quality traits in cotton and to analyze the associations present among them.Results:Analysis of variance exhibited significant variation for all studied traits except total number of nodes and the height to node ratio.The phenotypic coefficient of variation was higher than the genotypic coefficient of variation for all studied traits.Plant height,monopodial branches,total number of bolls,lint index,seed index,and seed cotton yield displayed high heritabilities in a broad sense with maximum genetic advanee.Correlation analysis revealed that seed cotton yield had a significant positive association with plant height,the nu mber of monopodial branches,the nu mber of sympodia I branches,ginning outturn(GOT),the number of bolls,seed per boll,seed index,uniformity index,the number of sympodial branches,reflectance,and seed index at the genotypic level while a significant positive relationship was observed with plant height,the number of sympodial branches,boll number,and GOT.Plant height,monopodial branches,GOT,boll weight,seeds per boll,and short fiber index exerted direct positive effects on seed cotton yield.The first 6 principal component analysis(PCs)out of the total fourteen PCs displayed eigenvalues(>1)and had maximum share to total variability(82.79%).The attributes that had maximum share to total divergence in eluded plant height,uniformity index,the nu mber of sympodial branches,seed per boll,GOT,seed cotton yield,and short fiber index.Conclusion:The genotype AA-802,IUB-13,FH-159,FH-458,and CIM-595 were genetically diverse for most of the yield and fiber quality traits and could be utilized for the selection of better performing genotypes for further improvement. 展开更多
关键词 Upland cotton Fiber trait Cotton yield Genetic variability Yield components
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Crops Responses to Inter-Annual Climate Variability in Agroclimatic Zone of Sub-Saharan Africa
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作者 Ayanlade Ayansina N.O.Adeoye +1 位作者 T.O.Odekunle I.O.Orinmogunje 《地学前缘》 EI CAS CSCD 北大核心 2009年第S1期119-119,共1页
Climate variability has become a decisive factor for the crop yields in Sub-Saharan African countries. Inter-annual variability in rainfall has been the key climatic element that determines the success of agriculture ... Climate variability has become a decisive factor for the crop yields in Sub-Saharan African countries. Inter-annual variability in rainfall has been the key climatic element that determines the success of agriculture in this region.From an analysis of recent rainfall conditions in West Africa,FAO(2001) concluded that a long-term change in rainfall has occurred in the semi-arid and sub-humid zones of West Africa.Thus,this study aims at assessing the vulnerability of crop yields to inter-annual variability in rainfall in sub-Saharan African countries taking Nigeria as a case study.A time series of the averaged value of the 12-Month Weighted Anomaly Standardized Precipita- 展开更多
关键词 INTER-ANNUAL climate variability crop yield VULNERABILITY RESPONSES WASP
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Analysis of in-bore balloting and control of jump variability
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作者 Satoru Shoji 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2019年第5期721-734,共14页
The variability of projectile jump is the long-term issue to improve weapon accuracy.Nowadays we have many simulation codes to predict Jump.However,these codes cannot explain explicitly how the variability of jump ari... The variability of projectile jump is the long-term issue to improve weapon accuracy.Nowadays we have many simulation codes to predict Jump.However,these codes cannot explain explicitly how the variability of jump arises.The aims of this paper are,(1)to give fundamental explanations for the variability of Jump,and (2)to offer design factors to make the variability of Jump less.The model presented here was formulated in accordance with the transition of the system in reverse way commencing from the target impact stage to the chambering stage.Objects of the simulation are generic 120mm smooth bore and long rod system which are extremely simplified to the vibration of tube,the spring effect by sabot,and the free-ends beam of penetrator.Parametric calculations clarified that high Jump-variability is generated only when the last rebound is on the muzzle line.This particular state of rebound is achieved by many combinations of input-variable.Guide map named JV-Chart is proposed to show the high Jumpvariability zone. 展开更多
关键词 JUMP variability Coupled vibration In-bore balloting CANTILEVER TUBE
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Incorporating nonuniform arrivals in delay variability modeling at signalized intersections
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作者 陈鹏 刘欢 +1 位作者 祁宏生 王福建 《Journal of Central South University》 SCIE EI CAS 2014年第10期4021-4032,共12页
The delay vehicles experience at signalized intersections is one of the most important indicators for measuring intersection performance. The interpretation of delay variability evolvement at intersections gives a com... The delay vehicles experience at signalized intersections is one of the most important indicators for measuring intersection performance. The interpretation of delay variability evolvement at intersections gives a comprehensive insight into arterial traffic operation. Thus, an analytical model is proposed to investigate delay variability at coordinated intersections. Two different flow rates are assumed for both effective red and green periods in cumulative curves, through which the effect of signal coordination is incorporated in delay estimation. Then, an analogy of Markov chain process is used to explore the mechanism of stochastic overflow queue at signalized intersections. Numerical case studies show that with the decrease of arrival proportions during green, the shape of delay distribution in both undersaturation and oversaturation cases shifts faster towards higher values, implying that the coordination effect between paired intersections has a great effect on the delay distribution. As for delay fluctuation range, favorable coordination is demonstrated to be able to weaken the variability of delay estimates especially for undersaturation conditions. 展开更多
关键词 nonuniform arrival signalized intersection coordination effect delay variability
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Risk quantification in grade variability of gold deposits using sequential Gaussian simulation
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作者 Tayfun Y.Yunsel 《Journal of Central South University》 SCIE EI CAS 2012年第11期3244-3255,共12页
Risk quantification in grade is critical for mine design and planning.Grade uncertainty is assessed using multiple grade realizations,from geostatistical conditional simulations,which are effective to evaluate local o... Risk quantification in grade is critical for mine design and planning.Grade uncertainty is assessed using multiple grade realizations,from geostatistical conditional simulations,which are effective to evaluate local or global uncertainty by honouring spatial correlation structures.The sequential Gaussian conditional simulation was used to assess uncertainty of grade estimates and illustrate simulated models in Sivas gold deposit,Turkey.In situ variability and risk quantification of the gold grade were assessed by probabilistic approach based on the sequential Gaussian simulations to yield a series of conditional maps characterized by equally probable spatial distribution of the gold grade for the study area.The simulation results were validated by a number of tests such as descriptive statistics,histogram,variogram and contour map reproductions.The case study demonstrates the efficiency of the method in assessing risk associated with geological and engineering variable such as the gold grade variability and distribution.The simulated models can be incorporated into exploration,exploitation and scheduling of the gold deposit. 展开更多
关键词 sequential Gaussian simulation risk quantification probability distribution gold grade variability Sivas gold deposit
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Fast speech style adaptation with adjustable prosody and variable duration
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作者 Zhiqiang Hua Lingyun Yu +2 位作者 Chuanbin Liu Dengdi Sun Hongtao Xie 《Journal of University of Science and Technology of China》 北大核心 2026年第1期57-68,I0002,共13页
For achieving personalized speech synthesis,it is indispensable to synthesize speech with diverse prosody for any given text.This task presents two key challenges:first,existing methods struggle to simultaneously extr... For achieving personalized speech synthesis,it is indispensable to synthesize speech with diverse prosody for any given text.This task presents two key challenges:first,existing methods struggle to simultaneously extract local prosody information and control phoneme duration,while overlooking the impact of duration on prosody;second,current speaker adaptation approaches suffer from slow learning speed or poor generalization to unseen speakers outside the training set.To address the aforementioned issues,this paper introduces a novel framework.Our method innovatively introduces the text-to-speech alignment mechanism into prosody modeling,using the aligned text-to-duration to segment speech and obtain local prosodic information,and simultaneously training the two components simplifies the workflow.After obtaining the prosodic information,we use it as a condition to guide the model to learn the corresponding phoneme durations under different types of prosody.We combine this style control work with adapter fine-tuning to quickly synthesize speech with the speaker’s style using small amounts of data from unseen speakers in the training set.Experimental results show that our approach is effective in adjusting prosody and variable duration as well as fast style adapter,and the subjective evaluations of the prosodic modulation model considering duration exhibits a significant improvement. 展开更多
关键词 personalized speech synthesis adjustable prosody variable duration speech style adaption
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Precise calibration of liquid crystal variable retarder for various incident angles
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作者 KONG Quan-hui-zi ZHANG Rui +2 位作者 XUE Peng WANG Zhi-bin JING Ning 《中国光学(中英文)》 北大核心 2026年第2期434-444,共11页
This study investigates the reduction in polarization measurement accuracy caused by varying in-cident angles in a liquid crystal variable retarder(LCVR).The phase delay characteristics of the LCVR were examined,with ... This study investigates the reduction in polarization measurement accuracy caused by varying in-cident angles in a liquid crystal variable retarder(LCVR).The phase delay characteristics of the LCVR were examined,with particular emphasis on the influence of different two-dimensional incident angles on phase delay behavior.Building upon the calibration of phase delay under normal incidence,a phase delay calibra-tion model was developed to account for variations in incident angle and driving voltage.A mathematical re-lationship was established between phase delay and the azimuth angle(α)and pitch angle(β).Experimental validation was conducted under three conditions:α=20°,β=0°;α=0°,β=20°;and an arbitrary angle whereα=5°,β=15°.The results demonstrated that the maximum average deviation between theoretical pre-dictions and experimental measurements did not exceed 0.059 rad.The proposed calibration method proved to be both accurate and practical.This approach offers robust support for LCVR parameter calibration and performance optimization in optical systems,particularly in polarization imaging applications. 展开更多
关键词 liquid crystal variable retarder(LCVR) two-dimensional incident angles drive voltage phase delay calibration
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Optimized fiber allocation for enhanced impact resistance in composites through damage mode suppression
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作者 Noha M.Hassan Zied Bahroun +2 位作者 Mahmoud I.Awad Rami As'ad El-Cheikh Amer Kaiss 《Defence Technology(防务技术)》 2026年第1期316-329,共14页
Variable stiffness composites present a promising solution for mitigating impact loads via varying the fiber volume fraction layer-wise,thereby adjusting the panel's stiffness.Since each layer of the composite may... Variable stiffness composites present a promising solution for mitigating impact loads via varying the fiber volume fraction layer-wise,thereby adjusting the panel's stiffness.Since each layer of the composite may be affected by a different failure mode,the optimal fiber volume fraction to suppress damage initiation and evolution is different across the layers.This research examines how re-allocating the fibers layer-wise enhances the composites'impact resistance.In this study,constant stiffness panels with the same fiber volume fraction throughout the layers are compared to variable stiffness ones by varying volume fraction layer-wise.A method is established that utilizes numerical analysis coupled with optimization techniques to determine the optimal fiber volume fraction in both scenarios.Three different reinforcement fibers(Kevlar,carbon,and glass)embedded in epoxy resin were studied.Panels were manufactured and tested under various loading conditions to validate results.Kevlar reinforcement revealed the highest tensile toughness,followed by carbon and then glass fibers.Varying reinforcement volume fraction significantly influences failure modes.Higher fractions lead to matrix cracking and debonding,while lower fractions result in more fiber breakage.The optimal volume fraction for maximizing fiber breakage energy is around 45%,whereas it is about 90%for matrix cracking and debonding.A drop tower test was used to examine the composite structure's behavior under lowvelocity impact,confirming the superiority of Kevlar-reinforced composites with variable stiffness.Conversely,glass-reinforced composites with constant stiffness revealed the lowest performance with the highest deflection.Across all reinforcement materials,the variable stiffness structure consistently outperformed its constant stiffness counterpart. 展开更多
关键词 Sandwich panel Fiber reinforced plastic composites Finite element analysis Variable stiffness Impact resistance Regression analysis Process optimization
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Longitudinal structural vulnerability analysis of shield tunnels under adjacent excavation disturbances
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作者 PENG Zhu SHI Cheng-hua +2 位作者 WANG Zu-xian LEI Ming-feng PENG Li-min 《Journal of Central South University》 2025年第6期2256-2272,共17页
This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled a... This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled as an Euler Bernoulli beam resting on the Pasternak foundation incorporating variability in subgrade parameters along the tunnel’s length.A random analysis method using random field theory is introduced to evaluate the tunnel’s longitudinal responses to excavation.Next,a risk assessment index system is established.The normalized relative depth between the excavation and the shield tunnel is used as a risk index,while the maximum longitudinal deformation,the maximum circumferential opening,and the maximum longitudinal bending moment serve as performance indicators.Based on these,a method for analyzing the longitudinal fragility of shield tunnels under excavation-induced disturbances is proposed.Finally,the technique is applied to a case study involving a foundation pit excavation above a shield tunnel,which is the primary application scenario of this method.Vulnerability curves for different performance indicators are derived,and the effects of tunnel stiffness and subgrade stiffness on the tunnel vulnerability are explored.The results reveal significant differences in vulnerability curves depending on the performance index used.Compared to the maximum circumferential opening and the maximum longitudinal bending moment,selecting the maximum longitudinal deformation as the control index better ensures the tunnel’s usability and safety under excavation disturbances.The longitudinal vulnerability of the shield tunnel nonlinearly decreases with the increase of the tunnel stiffness and subgrade stiffness,and the subgrade stiffness has a more pronounced effect.Parametric analyses suggest that actively reinforcing the substratum is more effective on reducing the risk of tunnel failure due to adjacent excavations than passive reinforcement of the tunnel structure. 展开更多
关键词 shield tunnel foundation pit excavation foundation variability random field VULNERABILITY
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Comparative analysis of machine learning and statistical models for cotton yield prediction in major growing districts of Karnataka,India 被引量:1
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作者 THIMMEGOWDA M.N. MANJUNATHA M.H. +4 位作者 LINGARAJ H. SOUMYA D.V. JAYARAMAIAH R. SATHISHA G.S. NAGESHA L. 《Journal of Cotton Research》 2025年第1期40-60,共21页
Background Cotton is one of the most important commercial crops after food crops,especially in countries like India,where it’s grown extensively under rainfed conditions.Because of its usage in multiple industries,su... Background Cotton is one of the most important commercial crops after food crops,especially in countries like India,where it’s grown extensively under rainfed conditions.Because of its usage in multiple industries,such as textile,medicine,and automobile industries,it has greater commercial importance.The crop’s performance is greatly influenced by prevailing weather dynamics.As climate changes,assessing how weather changes affect crop performance is essential.Among various techniques that are available,crop models are the most effective and widely used tools for predicting yields.Results This study compares statistical and machine learning models to assess their ability to predict cotton yield across major producing districts of Karnataka,India,utilizing a long-term dataset spanning from 1990 to 2023 that includes yield and weather factors.The artificial neural networks(ANNs)performed superiorly with acceptable yield deviations ranging within±10%during both vegetative stage(F1)and mid stage(F2)for cotton.The model evaluation metrics such as root mean square error(RMSE),normalized root mean square error(nRMSE),and modelling efficiency(EF)were also within the acceptance limits in most districts.Furthermore,the tested ANN model was used to assess the importance of the dominant weather factors influencing crop yield in each district.Specifically,the use of morning relative humidity as an individual parameter and its interaction with maximum and minimum tempera-ture had a major influence on cotton yield in most of the yield predicted districts.These differences highlighted the differential interactions of weather factors in each district for cotton yield formation,highlighting individual response of each weather factor under different soils and management conditions over the major cotton growing districts of Karnataka.Conclusions Compared with statistical models,machine learning models such as ANNs proved higher efficiency in forecasting the cotton yield due to their ability to consider the interactive effects of weather factors on yield forma-tion at different growth stages.This highlights the best suitability of ANNs for yield forecasting in rainfed conditions and for the study on relative impacts of weather factors on yield.Thus,the study aims to provide valuable insights to support stakeholders in planning effective crop management strategies and formulating relevant policies. 展开更多
关键词 COTTON Machine learning models Statistical models Yield forecast Artificial neural network Weather variables
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Undrained mechanical behavior of unsaturated completely weathered granite:Experimental investigation and constitutive modeling 被引量:1
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作者 DU Shao-hua MA Jin-yin +2 位作者 RUAN Bo WU Gen-shui ZHANG Rui-chao 《Journal of Central South University》 2025年第6期2307-2327,共21页
The undrained mechanical behavior of unsaturated completely weathered granite(CWG)is highly susceptible to alterations in the hydraulic environment,particularly under uniaxial loading conditions,due to the unique natu... The undrained mechanical behavior of unsaturated completely weathered granite(CWG)is highly susceptible to alterations in the hydraulic environment,particularly under uniaxial loading conditions,due to the unique nature of this soil type.In this study,a series of unconfined compression tests were carried out on unsaturated CWG soil in an underground engineering site,and the effects of varying the environmental variables on the main undrained mechanical properties were analyzed.Based on the experimental results,a novel constitutive model was then established using the damage mechanics theory and the undetermined coefficient method.The results demonstrate that the curves of remolded CWG specimens with different moisture contents and dry densities exhibited diverse characteristics,including brittleness,significant softening,and ductility.As a typical indicator,the unconfined compression strength of soil specimens initially increased with an increase in moisture content and then decreased.Meanwhile,an optimal moisture content of approximately 10.5%could be observed,while a critical moisture content value of 13.0%was identified,beyond which the strength of the specimen decreases sharply.Moreover,the deformation and fracture of CWG specimens were predominantly caused by shear failure,and the ultimate failure modes were primarily influenced by moisture content rather than dry density.Furthermore,by comparing several similar models and the experimental data,the proposed model could accurately replicate the undrained mechanical characteristics of unsaturated CWG soil,and quantitatively describe the key mechanical indexes.These findings offer a valuable reference point for understanding the underlying mechanisms,anticipating potential risks,and implementing effective control measures in similar underground engineering projects. 展开更多
关键词 completely weathered granite undrained mechanical behavior environmental variable unconfined compression test constitutive model
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Two Second-Order Ecient Numerical Schemes for the Boussinesq Equations
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作者 LIU Fang WANG Danxia ZHANG Jianwen 《应用数学》 北大核心 2025年第1期114-129,共16页
In this paper,we construct two fully decoupled,second-order semi-discrete numerical schemes for the Boussinesq equations based on the scalar auxiliary variable(SAV)approach.By introducing a scalar auxiliary variable,t... In this paper,we construct two fully decoupled,second-order semi-discrete numerical schemes for the Boussinesq equations based on the scalar auxiliary variable(SAV)approach.By introducing a scalar auxiliary variable,the original Boussinesq system is transformed into an equivalent one.Then we discretize it using the second-order backward di erentiation formula(BDF2)and Crank-Nicolson(CN)to obtain two second-order time-advanced schemes.In both numerical schemes,a pressure-correction method is employed to decouple the velocity and pressure.These two schemes possess the desired property that they can be fully decoupled with satisfying unconditional stability.We rigorously prove both the unconditional stability and unique solvability of the discrete schemes.Furthermore,we provide detailed implementations of the decoupling procedures.Finally,various 2D numerical simulations are performed to verify the accuracy and energy stability of the proposed schemes. 展开更多
关键词 Scalar auxiliary variable approach Pressure-correction method Fully decoupled Unconditional stability Boussinesq equations
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Phragmen-Lindelof Alternative Results for the Linear Viscoelastic Damped Wave Equation
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作者 SHI Jincheng LIU Yan LIN Yiwu 《应用数学》 北大核心 2025年第2期508-516,共9页
In this article,the viscoelastic damped was equation in three-dimensional cylindrical domain were studied by using a second-order differential inequality.We proved a Phragm´en-Lindelof alternative results,i.e.,th... In this article,the viscoelastic damped was equation in three-dimensional cylindrical domain were studied by using a second-order differential inequality.We proved a Phragm´en-Lindelof alternative results,i.e.,the smooth solutions either grow or decay exponentially as the distance from the entry section tends to infinity.Our results can be seen as a version of the Saint-Venant principle. 展开更多
关键词 Fractional integral commutators Variable exponent Herz-Hardy space Variable exponent weak Herz space Variable kernel
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Equilibrium Strategies in M/M/1 Retrial Queues with Variable Service Rate
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作者 LIU Yuanyuan YAN Zhaozeng YANG Qin 《应用概率统计》 北大核心 2025年第3期448-466,共19页
We consider a single server constant retrial queue,in which a state-dependent service policy is used to control the service rate.Customer arrival follows Poisson process,while service time and retrial time are exponen... We consider a single server constant retrial queue,in which a state-dependent service policy is used to control the service rate.Customer arrival follows Poisson process,while service time and retrial time are exponential distributions.Whenever the server is available,it admits the retrial customers into service based on a first-come first-served rule.The service rate adjusts in real-time based on the retrial queue length.An iterative algorithm is proposed to numerically solve the personal optimal problem in the fully observable scenario.Furthermore,we investigate the impact of parameters on the social optimal threshold.The effectiveness of the results is illustrated by two examples. 展开更多
关键词 variable service rate retrial queues real-time adaptability equilibrium strategies ALGORITHM
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Two Efficient Numerical Algorithms for the Thermally Coupled Incompressible MHD Equations
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作者 LIAO Mingliang WANG Danxia 《应用数学》 北大核心 2025年第4期932-951,共20页
In this work,we construct two efficient fully decoupled,linear,unconditionally stable numerical algorithms for the thermally coupled incompressible magnetohydrodynamic equations.Firstly,in order to obtain the desired ... In this work,we construct two efficient fully decoupled,linear,unconditionally stable numerical algorithms for the thermally coupled incompressible magnetohydrodynamic equations.Firstly,in order to obtain the desired algorithm,we introduce a scalar auxiliary variable(SAV)to get a new equivalent system.Secondly,by combining the pressure-correction method and the explicit-implicit method,we perform semi-discrete numerical algorithms of first and second order,respectively.Then,we prove that the obtained algorithms follow an unconditionally stable law in energy,and we provide a detailed implementation process,which we only need to solve a series of linear differential equations with constant coefficients at each time step.More importantly,with some powerful analysis,we give the order of convergence of the errors.Finally,to illustrate theoretical results,some numerical experiments are given. 展开更多
关键词 Magnetohydrodynamic equation Fully decoupled Unconditionally stability Scalar auxiliary variable Error analysis
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A New Class of Efficient Schemes for the Cahn-Hilliard-Navier-Stokes Equations
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作者 WANG Lijing WANG Danxia ZHANG Jianwen 《应用数学》 北大核心 2025年第3期607-624,共18页
In this paper,we construct a new class of efficient and high-order schemes for the Cahn-Hilliard-Navier-Stokes equations with periodic boundary conditions.These schemes are based on two types of scalar auxiliary varia... In this paper,we construct a new class of efficient and high-order schemes for the Cahn-Hilliard-Navier-Stokes equations with periodic boundary conditions.These schemes are based on two types of scalar auxiliary variable approaches.By using a new pressure correction method,the accuracy of the pressure has been greatly improved.Furthermore,one only needs to solve a series of fully decoupled linear equations with constant coefficients at each time step.In addition,we prove the unconditional energy stability of the schemes,rigorously.Finally,plenty of numerical simulations are carried out to verify the convergence rates,stability,and effectiveness of the proposed schemes numerically. 展开更多
关键词 Cahn-Hilliard-Navier-Stokes equation Scalar auxiliary variable Pressurecorrection Unconditional energy stability
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Nonnegative Group Lasso and Application in Index Tracking
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作者 GAO Ruiyao QI Kai TU Jingwen 《应用概率统计》 北大核心 2025年第6期890-909,共20页
Index tracking is known to be a passive portfolio management strategy by replicating the performance of a real or virtual index.However,the full replication,which considers all the asserts consisted of the index,often... Index tracking is known to be a passive portfolio management strategy by replicating the performance of a real or virtual index.However,the full replication,which considers all the asserts consisted of the index,often suffers from small and illiquid positions and large transaction costs.Thus,it is preferred to purchase sparse portfolios.Besides,existing literature pointed out the phenomenon of the co-movement in assert returns,indicating that the index tracking problems possibly contain group structures together with sparsity.Based on the consideration of the grouping effects and sparsity in index tracking problems,this paper proposes a grouping sparse index tracking model with nonnegative restrictions.We derive a modified version of coordinate decent algorithm for solving the model.The asymptotic properties are also discussed in detail.To show the efficiency of the model,we apply it into the constrained index tracking problem in Shanghai stock market,i.e.tracking SSE 50 Index.By selecting about 10 stocks,the result shows that nonnegative group lasso outperforms nonnegative lasso in assert allocation. 展开更多
关键词 nonnegative group lasso index tracking asymptotic unbiasedness variable selection consistency block-wise coordinate decent algorithm
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Equivalent Conditions of Complete Convergence for Weighted Sums of Sequences of i.i.d.Random Variables under Sublinear Expectations
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作者 XU Mingzhou CHENG Kun 《应用概率统计》 北大核心 2025年第3期339-352,共14页
The complete convergence for weighted sums of sequences of independent,identically distributed random variables under sublinear expectation space is studied.By moment inequality and truncation methods,we establish the... The complete convergence for weighted sums of sequences of independent,identically distributed random variables under sublinear expectation space is studied.By moment inequality and truncation methods,we establish the equivalent conditions of complete convergence for weighted sums of sequences of independent,identically distributed random variables under sublinear expectation space.The results complement the corresponding results in probability space to those for sequences of independent,identically distributed random variables under sublinear expectation space. 展开更多
关键词 complete convergence weighted sums i.i.d.random variables sublinear expectation
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