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log-normal脆弱模型下集群失效时间数据的非参数估计方法与应用
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作者 赵雅梅 黄希芬 潘东东 《中国卫生统计》 北大核心 2025年第4期566-569,579,共5页
目的 构建适用于集群失效时间数据的log-normal脆弱模型的非参数极大似然估计方法。方法 采用基于MM(minorization-maximization)算法原理的非参数极大似然估计方法,建立适用于集群失效时间数据的log-normal脆弱模型的非参数估计算法框... 目的 构建适用于集群失效时间数据的log-normal脆弱模型的非参数极大似然估计方法。方法 采用基于MM(minorization-maximization)算法原理的非参数极大似然估计方法,建立适用于集群失效时间数据的log-normal脆弱模型的非参数估计算法框架。结果 log-normal脆弱模型既考虑了集群内失效时间的相依性,又考虑了不同个体间的异质性。模拟结果显示,该方法可以用来分析具有高维协变量的集群失效时间数据,且具有良好的效果。将log-normal脆弱模型应用到慢性肉芽肿患者反复感染的数据集,客观评价了慢性肉芽肿患者反复感染的影响因素。结论 log-normal脆弱模型的MM非参数估计算法对集群失效时间数据具有良好的估计效果。本研究对医学领域处理高维集群失效时间数据具有重要意义。 展开更多
关键词 log-normal脆弱模型 MM算法 集群失效时间数据
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Performance Analysis of a DS-CDMA Cellular System with Effects of Soft Handoff in Log-Normal Shadowing Channels
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作者 YANGFeng-rui LUOHong +1 位作者 ZHOUJie HISAKAZUKikuchi 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 2004年第4期80-85,共6页
Next generation wireless communication is based on a global system of fixed and wireless mobile services thatare transportable across different network back-bones,network service providers and network geographical bou... Next generation wireless communication is based on a global system of fixed and wireless mobile services thatare transportable across different network back-bones,network service providers and network geographical boundaries.This paper presents an approach to investigate the effects of soft handover and perfect power control on the forward link ina DS-CDMA cellular system.Especially,the relationships between the size ofhandover zone and the capacity gain are e-valuated under the log-normal shadow channel.Then the optimization of maximum forward capacity is very necessary tobe done with the maximum size of soft handover zone to the various system characteristics. 展开更多
关键词 DS-CDMA soft handover log-normal shadow perfect power control and near-far problem
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Energy efficiency aware dynamic rate and power adaptation in carrier sensing based WLANs under Rayleigh fading and shadowing
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作者 Forkan Uddin 《Digital Communications and Networks》 SCIE CSCD 2024年第4期918-933,共16页
We consider the problem of energy efficiency aware dynamic adaptation of data transmission rate and transmission power of the users in carrier sensing based Wireless Local Area Networks(WLANs)in the presence of path l... We consider the problem of energy efficiency aware dynamic adaptation of data transmission rate and transmission power of the users in carrier sensing based Wireless Local Area Networks(WLANs)in the presence of path loss,Rayleigh fading and log-normal shadowing.For a data packet transmission,we formulate an optimization problem,solve the problem,and propose a rate and transmission power adaptation scheme with a restriction methodology of data packet transmission for achieving the optimal energy efficiency.In the restriction methodology of data packet transmission,a user does not transmit a data packet if the instantaneous channel gain of the user is lower than a threshold.To evaluate the performance of the proposed scheme,we develop analytical models for computing the throughput and energy efficiency of WLANs under the proposed scheme considering a saturation traffic condition.We then validate the analytical models via simulation.We find that the proposed scheme provides better throughput and energy efficiency with acceptable throughput fairness if the restriction methodology of data packet transmission is included.By means of the analytical models and simulations,we demonstrate that the proposed scheme provides significantly higher throughput,energy efficiency and fairness index than a traditional non-adaptive scheme and an existing most relevant adaptive scheme.Throughput and energy efficiency gains obtained by the proposed scheme with respect to the existing adapting scheme are about 75%and 103%,respectively,for a fairness index of 0.8.We also study the effect of various system parameters on throughput and energy efficiency and provide various engineering insights. 展开更多
关键词 Carrier sense multiple access Energy efficiency Fading and shadowing Rate and power adaptation THROUGHPUT Wireless local area networks
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Vision-Based Digital Shadowing to Reveal Hidden Structural Dynamics of a Real Supertall Building
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作者 Donglian Gu Qingrui Yue +2 位作者 Li Li Chujin Sun Xinzheng Lu 《Engineering》 CSCD 2024年第12期146-158,共13页
Vision-based digital shadowing is a highly efficient way to monitor the health of buildings in use.However,previous studies on digital shadowing have been limited to laboratory experiments.This paper proposes a novel ... Vision-based digital shadowing is a highly efficient way to monitor the health of buildings in use.However,previous studies on digital shadowing have been limited to laboratory experiments.This paper proposes a novel computer-vision-based digital shadow workflow and presents its successful application in a real engineering case.In this case,a 345.8-m supertall building experienced unexpected shaking under normal meteorological conditions.This study established a digital shadow of the building using three-dimensional displacement measurements based on super-resolution monocular vision,revealing the hidden structural dynamics and inherent mechanical reasons for the abnormal shaking.The proposed digital shadowing workflow is a feasible roadmap for developing vision-based digital shadows of realworld structures using low-cost cameras.The abnormal vibration event in the supertall building considered in this study is the first of its type worldwide.The results of this study offer practical strategies and invaluable insights into the prevention and mitigation of this type of global risk,thereby contributing to the lifespan extension of buildings in use worldwide.Furthermore,with the increasing number of general sensing devices,such as surveillance cameras in cities,the proposed method may unleash the immense potential of general sensing devices in achieving the leap from structural health monitoring to city health monitoring. 展开更多
关键词 Digital shadow Digital twin Super-resolution Monocular vision Displacement measurement Finite element simulation Deep learning Structural health monitoring
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Digital shadow of an electric vehicle-permanent magnet synchronous motor drive for real-time performance monitoring
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作者 Mahmoud Ibrahim Viktor Rjabtšikov Anton Rassõlkin 《Digital Twins and Applications》 2025年第1期1-12,共12页
Digital twin(DT)technology has been utilised in many applications including electric vehicles(EVs).A DT is a virtual representation of a physical object,enabled through real-time data integration,simulation,and optimi... Digital twin(DT)technology has been utilised in many applications including electric vehicles(EVs).A DT is a virtual representation of a physical object,enabled through real-time data integration,simulation,and optimisation tools.Unlike conventional simulations,which are typically offline and lack real-time interaction,a DT continuously synchronises with the physical system,enabling dynamic performance monitoring and predictive an-alytics.Achieving a full DT involves progressive stages,with the digital shadow(DS)being the final step before realising a bidirectional DT.Building a DS provides a scalable real-time performance monitoring and fault detection framework,enabling proactive decision-making in EV operations.This study introduces a DS system specifically designed to monitor the performance of a permanent magnet synchronous motor(PMSM)drive system in EVs,marking a critical phase towards a complete DT.The methodology for creating the DS is detailed,including the establishment of a compre-hensive test bench for the EV powertrain as the physical reference model.The mathe-matical model of the EV-PMSM was formulated,and an advanced estimation model utilising the extended Kalman filter(EKF)was implemented.MATLAB/Simulink was employed to develop the motor’s digital model.Real-time data acquisition from the physical model was facilitated through a data acquisition system(DAS)equipped with a controller area network(CAN)communication interface.The digital model underwent thorough validation against sensory data collected from the test bench.The motor digital model was deployed to a DS framework enabled through real-time data flow from the actual EV during real-world driving conditions.The results demonstrated a high accuracy of 97%between the DS predictions and the corresponding EV data,confirming the DS’s reliability.These findings pave the way for future advancements,including bidirectional interaction and the realisation of a full DT. 展开更多
关键词 digital shadow electrical engineering MODELLING MONITORING
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Quasinormal modes and shadow of Schwarzschild black holes embedded in a Dehnen-type dark matter halo exhibiting a cloud of strings
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作者 Ahmad Al-Badawi Sanjar Shaymatov 《Communications in Theoretical Physics》 2025年第3期101-111,共11页
In this paper we consider a static spherically symmetric black hole(BH)embedded in a Dehnen-(1,4,0)-type dark matter(DM)halo in the presence of a cloud string.We examine and present data on how the core density of the... In this paper we consider a static spherically symmetric black hole(BH)embedded in a Dehnen-(1,4,0)-type dark matter(DM)halo in the presence of a cloud string.We examine and present data on how the core density of the DM halo parameter and the cloud string parameter affect BH attributes such as quasinormal modes(QNMs)and shadow cast.To do this,we first look into the effective potential of perturbation equations for three types of perturbation fields with different spins:massless scalar field,electromagnetic field and gravitational field.Then,using the sixth-order Wentzel-Kramers-Brillouin approximation,we examine QNMs of the BH disturbed by the three fields and derive quasinormal frequencies.The changes in QNM versus the core density parameter and the cloud string parameter for three disturbances are explored.We also investigate how the core density and the cloud string parameter affect the photon sphere and shadow radius.Interestingly,the study shows that the influence of Dehnen-type DM and cloud strings increases both the photon sphere and the shadow radius.Finally,we employ observational data from Sgr A^(*) and M87^(*) to set limitations on the BH parameters. 展开更多
关键词 SCHWARZSCHILD Dehnen type dark matter halo string cloud quasinormal modes shadow
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Plasma impact on black hole shadows and gravitational weak lensing in the Einstein-Maxwell-scalar theory
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作者 Mirzabek Alloqulov Sanjar Shaymatov +1 位作者 Abdul Jawad Oripjon Zaripov 《Communications in Theoretical Physics》 2025年第1期130-142,共13页
In this paper,we investigate the optical properties of a non-rotating charged black hole(BH)in the Einstein-Maxwell-scalar(EMS)theory,together with a plasma medium.We first consider the photon sphere and shadow radius... In this paper,we investigate the optical properties of a non-rotating charged black hole(BH)in the Einstein-Maxwell-scalar(EMS)theory,together with a plasma medium.We first consider the photon sphere and shadow radius under the impact of the plasma medium existing in the environment surrounding the BH in the EMS theory.We show that the radius of the photon sphere and the BH shadow decrease under the influence of the parameterβ.We further study gravitational weak lensing in detail by adapting general methods and derive the light ray's deflection angle around the BH together with the plasma environment.It is found that for uniform plasma,the deflection angle increases with the rise of the plasma parameter,whereas it decreases with the increase of the plasma parameter for non-uniform plasma.Besides,we also study the magnification of image brightness. 展开更多
关键词 general relativity black hole shadow gravitational weak lensing
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Space weathering characteristics of lunar permanently shadowed regions soils:Evidence from experimental simulation
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作者 Zixuan Han Yang Li +7 位作者 Chen Li Ronghua Pang Sizhe Zhao Zhuang Guo Kairui Tai Rui Li Zhenhao Hu Li Liu 《Acta Geochimica》 2025年第1期1-10,共10页
Permanently shadowed regions(PSRs)on the Moon are potential reservoirs for water ice,making them hot spots for future lunar exploration.The water ice in PSRs would cause distinctive changes in space weathering there,i... Permanently shadowed regions(PSRs)on the Moon are potential reservoirs for water ice,making them hot spots for future lunar exploration.The water ice in PSRs would cause distinctive changes in space weathering there,in particular reduction-oxidation processes that diff er from those in illuminated regions.To determine the characteristics of products formed during space weathering in PSRs,the lunar meteorite NWA 10203 with artifi cially added water was irradiated with a nanosecond laser to simulate a micro-meteorite bombardment of lunar soil containing water ice.The TEM results of the water-incorporated sample showed distinct amorphous rims that exhibited irregular thickness,poor stratifi cation,the appearance of bubbles,and a reduced number of npFe^(0).Additionally,EELS analysis showed the presence of ferric iron at the rim of the nanophase metallic iron particles(npFe^(0))in the amorphous rim with the involvement of water.The results suggest that water ice is another possible factor contributing to oxidation during micrometeorite bombardment on the lunar surface.In addition,it off ers a reference for a new space weathering model that incorporates water in PSRs,which could be widespread on asteroids with volatiles. 展开更多
关键词 Space weathering Permanently shadowed regions The Moon laser irradiation Water ice
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Rotating regular black holes in AdS spacetime and its shadow for an arbitrary observer
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作者 Balendra Pratap Singh Md Sabir Ali Sushant G Ghosh 《Communications in Theoretical Physics》 2025年第7期174-186,共13页
The photon region surrounding a black hole is crucial for distant observers to receive the emitted spectrum from its vicinity.This paper investigates the optical features of a regular spinning antide Sitter(AdS)black ... The photon region surrounding a black hole is crucial for distant observers to receive the emitted spectrum from its vicinity.This paper investigates the optical features of a regular spinning antide Sitter(AdS)black hole.These kinds of black holes hold deviation parameter k,and the cosmological constant A including their mass M and spin a.The cosmological parameter depends on the curvature radius by A=-3/l~2.We investigate the structure of geodesics for unstable circular orbits of photons as observed by an observer at specific Boyer-Lindquist coordinates(r_(O),v_(O))in the region between the outer and cosmological horizon,so-called the domain of outer communication.Our investigations include the analysis of three observables from its shadow plot:the black hole shadow radius(R_(s)),the distortion of the black hole(δ_(s)),and shadow area A.With the help of these observables,we calculate the angular diameter of the apparent size of the shadow.The shadows cast by spinning regular spacetimes are smaller compared to those produced by rotating black holes in both general relativity and regular spacetimes.We also calculate the rate at which energy is emitted from the black hole. 展开更多
关键词 regular black hole black hole shadow null geodesics and photon orbits
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基于Shadowing模型的无线入侵主机物理定位研究 被引量:4
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作者 付雄 彭冰 《微电子学与计算机》 CSCD 北大核心 2010年第12期4-9,共6页
为了在室内无线局域网环境中及时准确地定位非法入侵主机物理位置,以无线信号强度衰减过程的Shadowing传播模型为基础,研究了在一定的范围内如何合理地布置探测器,如何根据接收到的入侵主机的信号强度进行物理定位的问题.提出的定位方... 为了在室内无线局域网环境中及时准确地定位非法入侵主机物理位置,以无线信号强度衰减过程的Shadowing传播模型为基础,研究了在一定的范围内如何合理地布置探测器,如何根据接收到的入侵主机的信号强度进行物理定位的问题.提出的定位方法可以有效地对抗入侵主机随机更改信号发射功率对定位精度的影响.实际测试结果表明,该方法定位误差平均约为2.3 m,可以满足室内环境下定位非法入侵主机的需求. 展开更多
关键词 无线局域网 室内定位算法 信号强度 shadowing模型
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Log-normal湍流信道中超奈奎斯特传输系统的误码性能 被引量:13
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作者 曹明华 武鑫 +1 位作者 杨顺信 贾科军 《光学精密工程》 EI CAS CSCD 北大核心 2020年第2期465-473,共9页
超奈奎斯特传输理论与调制技术相结合,可有效提高系统的频谱效率。本文将超奈奎斯特理论引入大气激光通信系统,构建了一种适合于log-normal湍流信道的超奈奎斯特光传输系统,推导了QPSK调制方式下超奈奎斯特大气光传输系统平均误码率的... 超奈奎斯特传输理论与调制技术相结合,可有效提高系统的频谱效率。本文将超奈奎斯特理论引入大气激光通信系统,构建了一种适合于log-normal湍流信道的超奈奎斯特光传输系统,推导了QPSK调制方式下超奈奎斯特大气光传输系统平均误码率的表达式,利用蒙特卡洛仿真进一步分析了该系统的误码性能及频谱效率。结果表明:采用超奈奎斯特技术方案可以较大幅度提升大气光传输系统的频谱效率,当SNR为18 dB,S.I.为0.4时其频谱效率可以达到1.7 Baud/Hz,而未采用超奈奎斯特技术时只有1.56 Baud/Hz。另一方面,大气湍流对超奈奎斯特系统误码性能的影响较明显,当S.I.为0.4,BER为3.8×10^-3时,信噪比恶化了约1 dB。相对于频谱效率的提升,误码性能的恶化是能够接受的。因此,可以将FTN技术引入大气光传输系统来提高系统的频谱效率。 展开更多
关键词 超奈奎斯特 log-normal湍流信道 大气激光通信 误码率性能 频谱效率
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圆环上的逆shadowing映射(英文)
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作者 韩英豪 葛琦 南华 《延边大学学报(自然科学版)》 CAS 2005年第3期161-164,187,共5页
本文证明了圆环上shadowing性质和(Tc,Th-)逆shadowing性质的等价性.
关键词 shadowing性质 (Jc Jh^-)逆shadowing性质 shadowing性质
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Poisson Log-normal回归模型的影响评价(英文)
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作者 李泽慧 赵为华 谢晓方 《昆明理工大学学报(自然科学版)》 CAS 北大核心 2013年第4期102-108,共7页
本文利用EM算法研究了来自于Lognormal分布权重的混合Poisson模型,即Poisson Lognormal回归模型,从而利用基于完全数据似然函数的条件期望进行影响评价.基于数据删除模型和局部影响分析方法,分别得到了广义Cook距离、Q距离和三种不同扰... 本文利用EM算法研究了来自于Lognormal分布权重的混合Poisson模型,即Poisson Lognormal回归模型,从而利用基于完全数据似然函数的条件期望进行影响评价.基于数据删除模型和局部影响分析方法,分别得到了广义Cook距离、Q距离和三种不同扰动模型下的正则曲率度量等诊断统计量. 展开更多
关键词 POISSON log-normal回归 EM算法 局部影响分析 数据删除 Gauss—Hermite积分
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变环境不同阶段下Log-normal分布缺失数据的可靠性估计
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作者 李丽 胡尧 邓春霞 《中外企业家》 2015年第5期69-70,73,共3页
本文研究了变环境不同阶段Log-normal分布下,观测数据中包含缺失数据的情形下的可靠性估计问题。通过EM算法估计参数以及可靠性,最后通过模拟研究验证了本文方法的可行性。
关键词 变环境 不同阶段 log-normal分布 缺失数据
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一种估算三参数log-normal分布参数的近似方法 被引量:1
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作者 王立君 《数理统计与管理》 CSSCI 北大核心 1999年第2期40-43,共4页
三参数(log-normal)分布在可靠性工程中有广泛应用,但其分布参数的估计较为困难。为解决这一问题,本文将极大似然法引入其概率图。
关键词 log-normal分布 参数估计 近似法 估算 可靠性
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On the Relation of Shadowing and Expansivity in Nonautonomous Discrete Systems 被引量:9
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作者 Hossein Rasuli Reza Memarbashi 《Analysis in Theory and Applications》 CSCD 2017年第1期11-19,共9页
In this paper we study shadowing property for sequences of mappings on compact metric spaces, i.e., nonautonomous discrete dynamical systems. We investi- gate the relations of various expansivity properties with shado... In this paper we study shadowing property for sequences of mappings on compact metric spaces, i.e., nonautonomous discrete dynamical systems. We investi- gate the relations of various expansivity properties with shadowing and h-shadowing property. 展开更多
关键词 Key Words: shadowing h-shadowing locally expanding uniformly weak expanding locallyweak expanding.
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Review of Shadow Detection and De-shadowing Methods in Remote Sensing 被引量:11
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作者 AmirReza SHAHTAHMASSEBI YANG Ning +2 位作者 WANG Ke Nathan MOORE SHEN Zhangquan 《Chinese Geographical Science》 SCIE CSCD 2013年第4期403-420,共18页
Shadow is one of the major problems in remotely sensed imagery which hampers the accuracy of information extraction and change detection.In these images,shadow is generally produced by different objects,namely,cloud,m... Shadow is one of the major problems in remotely sensed imagery which hampers the accuracy of information extraction and change detection.In these images,shadow is generally produced by different objects,namely,cloud,mountain and urban materials.The shadow correction process consists of two steps:detection and de-shadowing.This paper reviews a range of techniques for both steps,focusing on urban regions(urban shadows),mountainous areas(topographic shadow),cloud shadows and composite shadows.Several issues including the problems and the advantages of those algorithms are discussed.In recent years,thresholding and recovery techniques have become important for shadow detection and de-shadowing,respectively.Research on shadow correction is still an important topic,particularly for urban regions(in high spatial resolution data) and mountainous forest(in high and medium spatial resolution data).Moreover,new algorithms are needed for shadow correction,especially given the advent of new satellite images. 展开更多
关键词 shadow detection de-shadowing URBAN FOREST
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SHADOWING,EXPANSIVENESS AND SPECIFICATION FOR C^1-CONSERVATIVE SYSTEMS 被引量:1
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作者 Mario BESSA Manseob LEE 文晓 《Acta Mathematica Scientia》 SCIE CSCD 2015年第3期583-600,共18页
We prove that a Cl-generic volume-preserving dynamical system (diffeomor- phism or flow) has the shadowing property or is expansive or has the weak specification property if and only if it is Anosov. Finally, as in ... We prove that a Cl-generic volume-preserving dynamical system (diffeomor- phism or flow) has the shadowing property or is expansive or has the weak specification property if and only if it is Anosov. Finally, as in [10, 27], we prove that the Cl-robustness, within the volume-preserving context, of the expansiveness property and the weak specifica- tion property, imply that the dynamical system (diffeomorphism or flow) is Anosov. 展开更多
关键词 shadowing EXPANSIVENESS SPECIFICATION GENERIC Anosov volume-preserving star systems
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Lipschitz Shadowing Property for 1-Dimensional Subsystems of Z^(k)-Actions 被引量:5
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作者 Lin WANG Jinlian ZHANG 《Journal of Mathematical Research with Applications》 CSCD 2021年第6期615-628,共14页
In this paper,the shadowing property for 1-dimensional subsystems of Z^(k)-actions is investigated.The concepts of pseudo orbit and shadowing property for 1-dimensional subsystems of Z^(k)-actions are introduced in tw... In this paper,the shadowing property for 1-dimensional subsystems of Z^(k)-actions is investigated.The concepts of pseudo orbit and shadowing property for 1-dimensional subsystems of Z^(k)-actions are introduced in two equivalent ways.For a smooth Z^(k)-action T on a closed Riemannian manifold,we propose a notion of Anosov direction via the induced nonautonomous dynamical system.Adapting Bowen’s geometric method to our case,we show that T has the Lipschitz shadowing property along any Anosov direction. 展开更多
关键词 Z^(k)-actions Lipschitz shadowing 1-dimensional subsystem
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A new car-following model yielding log-normal type headways distributions 被引量:1
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作者 李力 王法 +2 位作者 姜锐 胡坚明 吉岩 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第2期180-185,共6页
Modeling time headways between vehicles has attracted increasing interest in the traffic flow research field recently, because the corresponding statistics help to reveal the intrinsic interactions governing the vehic... Modeling time headways between vehicles has attracted increasing interest in the traffic flow research field recently, because the corresponding statistics help to reveal the intrinsic interactions governing the vehicle dynamics. However, most previous micro-simulation models cannot yield the observed log-normal distributed headways. This paper designs a new car-following model inspired by the Galton board to reproduce the observed time-headway distributions as well as the complex traffic phenomena. The consistency between the empirical data and the simulation results indicates that this new car-following model provides a reasonable description of the car-following behaviours. 展开更多
关键词 traffic flow CAR-FOLLOWING log-normal distribution
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