期刊文献+
共找到1,047篇文章
< 1 2 53 >
每页显示 20 50 100
State vector evolution localized over the edges of a square tight-binding lattice
1
作者 何良明 石端文 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第3期1214-1220,共7页
We study thc time evolution of a state vector in a square tight-binding lattice, focusing on its evolution localized over the system surfaces. In this tight-binding lattice, the energy of atomic orbital centred at sur... We study thc time evolution of a state vector in a square tight-binding lattice, focusing on its evolution localized over the system surfaces. In this tight-binding lattice, the energy of atomic orbital centred at surface site is different from that at the interior (bulky) site by an energy shift U. It is shown that for the state vector initially localized on a surface, there exists an exponential law (y = ae^x/b + Y0) determined by the absolute value of the energy shift, |U|, which describes the transition of the state evolving on the square tight-binding lattice, from delocalized over the whole lattice to localized over the surfaces. 展开更多
关键词 Anderson localization surface states state vector evolution
原文传递
State Vectors—A New Method for Seismicity Analysis
2
作者 YinXiangchu YuHuaizhong ZhangYongxian 《Earthquake Research in China》 2004年第3期263-270,共8页
The concept of state vector stems from statistical physics, where it is usually used to describe the evolution of a continuum field in its way of coarse-graining. In this paper, the state vector is employed to depict ... The concept of state vector stems from statistical physics, where it is usually used to describe the evolution of a continuum field in its way of coarse-graining. In this paper, the state vector is employed to depict the evolution of seismicity quantitatively, and some interesting results are presented. The authors investigated some famous earthquake cases (e.g., the Haicheng earthquake, the Tangshan earthquake, the west Kunlun Mountains earthquake, etc.) and found that the state vectors evidently change prior to the occurrence of large earthquakes. Thus it is believed that the state vector can be used as a kind of precursor to predict large earthquakes. 展开更多
关键词 state vector SEISMICITY Earthquake prediction
在线阅读 下载PDF
Einstein Dilemma and Two-State Vector Formalism
3
作者 Kunihisa Morita 《Journal of Quantum Information Science》 2015年第2期41-46,共6页
In the famous EPR paper published in 1935, Einstein, Podolsky, and Rosen suggested a thought experiment, which later became known as the “EPR experiment”. Using the EPR experiment, they posited that quantum mechanic... In the famous EPR paper published in 1935, Einstein, Podolsky, and Rosen suggested a thought experiment, which later became known as the “EPR experiment”. Using the EPR experiment, they posited that quantum mechanics was incomplete. Einstein, however, was dissatisfied with the EPR paper and published a second work on the EPR experiment, in which he discussed the dilemma of choosing whether quantum mechanics was incomplete or nonlocal. Currently, most physicists choose the nonlocality of quantum mechanics over Einstein’s choice of the incompleteness of quantum mechanics. However, with an appropriate alternate hypothesis, both of these choices can be rejected. Herein, I demonstrate an approach to overcome the Einstein Dilemma by proposing a new interpretation invoked by a new formalism of quantum mechanics known as two-state vector formalism. 展开更多
关键词 Two-state vector FORMALISM EINSTEIN DILEMMA COMPLETENESS LOCALITY
在线阅读 下载PDF
Measurement Problem and Two-State Vector Formalism
4
作者 Kunihisa Morita 《Journal of Modern Physics》 2015年第13期1864-1867,共4页
In this paper, I show that an interpretation of quantum mechanics using two-state vector formalism proposed by Aharonov, Bergmann, and Lebowitz, can solve one of the measurement problems formulated by Maudlin. Accordi... In this paper, I show that an interpretation of quantum mechanics using two-state vector formalism proposed by Aharonov, Bergmann, and Lebowitz, can solve one of the measurement problems formulated by Maudlin. According to this interpretation, we can simultaneously insist that the wave function of a system is complete, that the wave function is determined by the Schr?dinger equation, and that the measurement of a physical quantity always has determinate outcomes, although Maudlin in his formulation of the measurement problem states that these three claims are mutually inconsistent. Further, I show that my interpretation does not contradict the uncertainty relation and the no-go theorem. 展开更多
关键词 Two-state vector FORMALISM Measurement Problem No-Go THEOREM
在线阅读 下载PDF
MODIFIED H-R MIXED VARIATIONAL PRINCIPLE FOR MAGNETOELECTROELASTIC BODIES AND STATE-VECTOR EQUATION 被引量:8
5
作者 卿光辉 邱家俊 刘艳红 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2005年第6期722-728,共7页
Based upon the Hellinger-Reissner (H-R) mixed variational principle for three-dimensional elastic bodies, the modified H-R mixed variational theorem for magnetoelectroelastic bodies was established. The state-vector e... Based upon the Hellinger-Reissner (H-R) mixed variational principle for three-dimensional elastic bodies, the modified H-R mixed variational theorem for magnetoelectroelastic bodies was established. The state-vector equation of magnetoelectroelastic plates was derived from the proposed theorem by performing the variational operations. To lay a theoretical basis of the semi-analytical solution applied with the magnetoelectroelastic plates, the state-vector equation for the discrete element in plane was proposed through the use of the proposed principle. Finally, it is pointed out that the modified H-R mixed variational principle for pure elastic, single piezoelectric or single piezomagnetic bodies are the special cases of the present variational theorem. 展开更多
关键词 magnetoelectroelastic body variational principle laminated plates state-vector equation semi-analytical solution
在线阅读 下载PDF
State vector solutions for nonaxisymmetric problem of multilayered half space piezoelectric medium 被引量:1
6
作者 王建国 《Science China Mathematics》 SCIE 1999年第12期1323-1331,共9页
A state space formulation is established for the nonaxisymmetric space problem of transversely isotropic piezoelectric media in a system of cylindrical coordinate by introducing the state vector. Using the Hankel tran... A state space formulation is established for the nonaxisymmetric space problem of transversely isotropic piezoelectric media in a system of cylindrical coordinate by introducing the state vector. Using the Hankel transform and the Fourier series, the state vector equations are transformed into ordinary differential equations. By the use of the matrix methods, the analytical solutions of a single piezoelectric layer are presented in the form of the product of initial state variables and transfer matrix. The applications of state vector solutions are discussed. An analytical solution for a semiinfinite piezoelectric medium subjected to the vertical point force P_z, horizontal point force P_x along x-direction and point electric charge Q at the origin of the surface is presented. According to the continuity conditions at the interfaces, the general solution formulation for N-layered transversely isotropic piezoelectric media is given. 展开更多
关键词 MULTILAYERED PIEZOELECTRIC media TRANSVERSE ISOTROPY nonaxisymmetric problems state vector EQUATIONS transfer matrix analytical solutions.
原文传递
Dynamics of Quantum State and Effective Hamiltonian with Vector Differential Form of Motion Method
7
作者 Long Xiong Wei-Feng Zhuang Ming Gong 《Chinese Physics Letters》 SCIE EI CAS CSCD 2022年第7期36-40,共5页
Effective Hamiltonians in periodically driven systems have received widespread attention for realization of novel quantum phases, non-equilibrium phase transition, and Majorana mode. Recently, the study of effective H... Effective Hamiltonians in periodically driven systems have received widespread attention for realization of novel quantum phases, non-equilibrium phase transition, and Majorana mode. Recently, the study of effective Hamiltonian using various methods has gained great interest. We consider a vector differential equation of motion to derive the effective Hamiltonian for any periodically driven two-level system, and the dynamics of the spin vector are an evolution under the Bloch sphere. Here, we investigate the properties of this equation and show that a sudden change of the effective Hamiltonian is expected. Furthermore, we present several exact relations, whose expressions are independent of the different starting points. Moreover, we deduce the effective Hamiltonian from the high-frequency limit, which approximately equals the results in previous studies. Our results show that the vector differential equation of motion is not affected by a convergence problem, and thus, can be used to numerically investigate the effective models in any periodic modulating system. Finally, we anticipate that the proposed method can be applied to experimental platforms that require time-periodic modulation, such as ultracold atoms and optical lattices. 展开更多
关键词 Dynamics of Quantum state and Effective Hamiltonian with vector Differential Form of Motion Method HAMILTONIAN vector QUANTUM
原文传递
Generation of Quantum Vector States Using the Exchange Interaction
8
作者 Mrittunjoy Guha Majumdar 《Journal of Applied Mathematics and Physics》 2019年第12期3116-3131,共16页
In this paper, I study the invariant subspaces of quantum states under SWAPα gates arising from the exchange interaction and their use in quantum computation. I investigate the generation and characterization of inva... In this paper, I study the invariant subspaces of quantum states under SWAPα gates arising from the exchange interaction and their use in quantum computation. I investigate the generation and characterization of invariant-subspace vector-states that arise from such gates. I also state a condition for the locus of states that are accessible using the SWAPα gates, given an initial input state. 展开更多
关键词 QUANTUM ENTANGLEMENT vector stateS EXCHANGE INTERACTION
在线阅读 下载PDF
量子力学角动量理论之缺陷与修正 被引量:1
9
作者 汪克林 曹则贤 《物理》 北大核心 2025年第5期344-351,共8页
角动量理论是量子力学的重要内容。基于角动量分量同三维转动生成元具有同样的基本对易关系的考量,则由基本对易关系就得到了分立的本征值谱(J^(2),J_(z))~(j(j+1),m)。又由于球坐标系下角动量平方J^(2)与动能算符的角部分相同,角动量... 角动量理论是量子力学的重要内容。基于角动量分量同三维转动生成元具有同样的基本对易关系的考量,则由基本对易关系就得到了分立的本征值谱(J^(2),J_(z))~(j(j+1),m)。又由于球坐标系下角动量平方J^(2)与动能算符的角部分相同,角动量就这样被纳入了波力学方程,由此解得的定态波函数是(H,J^(2),J_(z))的共同本征函数。然而,不同于波函数理论体系,在后来发展的算符—态矢理论体系中,态矢携带关于系统的全部信息。将角动量用必要的三组独立产生—湮灭算符表示,并在算符—态矢理论体系中考察角动量算符,会发现定态不必然还是(H,J^(2),J_(z))的共同本征态。以在球坐标系和直角坐标系下皆可分离变量的严格可解三维各向同性谐振子为依据,作者详细研究了定态对应的态矢子空间中的(H,J^(2),J_(z))本征值谱问题。在给定总粒子数n的情形下,即限制在特定的n所决定的子空间中,算符—态矢表示给出的角动量分量J_(z)具有分立的本征值而角动量的本征值却可以是连续变化的,而这正反映出角动量算符J=x×p的根本性质。当角动量分量本征值(以ℏ为单位)接近总粒子数n时,基于态矢的计算与基于波函数的计算其结果是一致的,原因是n一定的定态被限制在态矢空间中的一个由等能面所定义的子空间中了。认识到既有的量子力学角动量理论的一些缺陷,则此前涉及轨道角动量之物理效应的相关表述都有修正的必要。 展开更多
关键词 角动量 轨道角动量 转动生成元 基本对易关系 拉普拉斯算符 本征值谱 共同本征态 波函数 态矢量 态矢空间 三维谐振子
原文传递
2022年青海门源6.9级地震前态矢量异常研究
10
作者 张小涛 余怀忠 《地震研究》 北大核心 2025年第2期247-252,共6页
2022年1月8日青海门源6.9级地震前存在多项地震活动性和地球物理异常,利用态矢量方法回溯性研究其震前异常,通过遍历3°×3°至12°×12°的研究区域发现,选取8°×8°的研究范围能更好地反映震前... 2022年1月8日青海门源6.9级地震前存在多项地震活动性和地球物理异常,利用态矢量方法回溯性研究其震前异常,通过遍历3°×3°至12°×12°的研究区域发现,选取8°×8°的研究范围能更好地反映震前异常;震前门源地震存在态矢量的模(M)、态矢量增量的模(ΔM)、态矢量之间的夹角变化(φ)和态矢量与单位矢量的转角变化(φ_(c))4个参量的异常;4个参量中的M和ΔM映震效果要优于φ和φ_(c)。总体来看,门源地震前态矢量异常变化平稳,震前异常突出,属于中短期异常。 展开更多
关键词 态矢量 门源地震 回溯性研究 地震异常
在线阅读 下载PDF
Predicting of Power Quality Steady State Index Based on Chaotic Theory Using Least Squares Support Vector Machine 被引量:2
11
作者 Aiqiang Pan Jian Zhou +2 位作者 Peng Zhang Shunfu Lin Jikai Tang 《Energy and Power Engineering》 2017年第4期713-724,共12页
An effective power quality prediction for regional power grid can provide valuable references and contribute to the discovering and solving of power quality problems. So a predicting model for power quality steady sta... An effective power quality prediction for regional power grid can provide valuable references and contribute to the discovering and solving of power quality problems. So a predicting model for power quality steady state index based on chaotic theory and least squares support vector machine (LSSVM) is proposed in this paper. At first, the phase space reconstruction of original power quality data is performed to form a new data space containing the attractor. The new data space is used as training samples for the LSSVM. Then in order to predict power quality steady state index accurately, the particle swarm algorithm is adopted to optimize parameters of the LSSVM model. According to the simulation results based on power quality data measured in a certain distribution network, the model applies to several indexes with higher forecasting accuracy and strong practicability. 展开更多
关键词 CHAOTIC THEORY Least SQUARES Support vector Machine (LSSVM) Power Quality STEADY state Index Phase Space Reconstruction Particle SWARM Optimization
在线阅读 下载PDF
网格激光高反抑制与中心提取误差修正
12
作者 王标 吴南南 +3 位作者 马宇晗 姚彦峰 王永红 李骏睿 《光学精密工程》 北大核心 2025年第1期57-74,共18页
线激光在扫描金属工件时,部分金属表面存在高反光区域导致扫描效果不好,网格激光相较于单线与多线而言扫描效率更快,但存在中心提取以及光平面定位困难等问题。为了满足金属工件高效实时检测的需求,设计了一种网格激光的偏振态获取方法... 线激光在扫描金属工件时,部分金属表面存在高反光区域导致扫描效果不好,网格激光相较于单线与多线而言扫描效率更快,但存在中心提取以及光平面定位困难等问题。为了满足金属工件高效实时检测的需求,设计了一种网格激光的偏振态获取方法,对偏振片旋转角度进行标定,达到对高反光表面的最佳程度抑制。基于法向量的激光中心与光平面对应方法,利用像素Hessian矩阵特征值最大时的特征向量,将激光中心与所属的光平面对应。采用基于仿射变换的中心提取方法,将非正交网格通过仿射变换转为正交后提取中心点,提高三维重建的准确性。最后建立了测量误差与高度的误差修正模型,减少了测量系统误差。实验结果表明,网格激光传统算法扫描金属表面高反光区域,扫描结果会有边缘缺失,测量误差为0.8 mm;而本文所提方法能够有效抑制金属表面高反光带来的影响,实现激光中心提取与光平面的准确对应,测量误差达到0.39 mm,最后经过误差修正,金属表面高光区域测量精度有较大提升,测量误差可达0.1 mm。本文所提方法与网格激光传统算法测量结果相比,测量误差减少了87.5%。该方法实现了金属表面高反光抑制下的网格激光扫描三维重建,扫描效率与测量精度得到提升,为未来的工业测量提供方法和参考。 展开更多
关键词 三维测量 网格激光 偏振态 中心提取 法向量
在线阅读 下载PDF
电力变压器内部故障的递进分层诊断方法 被引量:1
13
作者 咸日常 李云淏 +4 位作者 刘焕国 王昭璇 张海强 胡玉耀 王玮 《电网技术》 北大核心 2025年第4期1726-1734,I0079,I0080,共11页
电力变压器内部故障成因复杂、种类繁多,精确诊断难度大,现有诊断技术大多滞留于故障定性阶段。为实现多类型故障的精准定位,该文通过建立多状态量与故障特征之间的递进映射关系,提出一种改进灰狼算法与最小二乘支持向量机耦合的电力变... 电力变压器内部故障成因复杂、种类繁多,精确诊断难度大,现有诊断技术大多滞留于故障定性阶段。为实现多类型故障的精准定位,该文通过建立多状态量与故障特征之间的递进映射关系,提出一种改进灰狼算法与最小二乘支持向量机耦合的电力变压器故障递进分层诊断方法。首先介绍改进灰狼算法与最小二乘支持向量机的原理,建立电力变压器故障递进分层、自动诊断及定位模型;其次基于300组电力变压器的状态量,利用核主成分分析法进行降维处理,选取线性无关的特征状态量,依据DL/T 1685—2017《油浸式变压器状态评价导则》进行离散化处理,借助算法模型递进分层、自动诊断:第一层诊断故障回路、第二层确定故障部位、第三层明确故障原因,得到各分类器的诊断准确率及惩罚系数和核函数参数的最优组合解,并与其他算法模型的故障诊断结果进行分析对比;最后以实际故障案例验证方法的有效性。结果表明:该文所提诊断模型比其他方法拥有更高准确率和更快的运算速度。 展开更多
关键词 电力变压器 改进灰狼算法 最小二乘支持向量机 多状态量 内部故障 递进分层诊断
原文传递
Determination of Total Vector Error of the Phasor Measurement Unit (PMU) Using the Phase Angle Error of a Constant Amplitude Voltage Signal
14
作者 Gabriel Musonda Ackim Zulu Charles S. Lubobya 《Journal of Power and Energy Engineering》 2024年第11期34-47,共14页
This paper investigates the effect of the Phase Angle Error of a Constant Amplitude Voltage signal in determining the Total Vector Error (TVE) of the Phasor Measurement Unit (PMU) using MATLAB/Simulink. The phase angl... This paper investigates the effect of the Phase Angle Error of a Constant Amplitude Voltage signal in determining the Total Vector Error (TVE) of the Phasor Measurement Unit (PMU) using MATLAB/Simulink. The phase angle error is measured as a function of time in microseconds at four points on the IEEE 14-bus system. When the 1 pps Global Positioning System (GPS) signal to the PMU is lost, sampling of voltage signals on the power grid is done at different rates as it is a function of time. The relationship between the PMU measured signal phase angle and the sampling rate is established by injecting a constant amplitude signal at two different points on the grid. In the simulation, 64 cycles per second is used as the reference while 24 cycles per second is used to represent the fault condition. Results show that a change in the sampling rate from 64 bps to 24 bps in the PMUs resulted in phase angle error in the voltage signals measured by the PMU at four VI Measurement points. The phase angle error measurement that was determined as a time function was used to determine the TVE. Results show that (TVE) was more than 1% in all the cases. 展开更多
关键词 Phasor Measurement Unit (PMU) Phase Angle Error Total vector Error (TVE) state estimation Time Source Error Constant Amplitude Signal
在线阅读 下载PDF
State of Health Estimation of Lithium-Ion Batteries Using Support Vector Regression and Long Short-Term Memory
15
作者 Inioluwa Obisakin Chikodinaka Vanessa Ekeanyanwu 《Open Journal of Applied Sciences》 CAS 2022年第8期1366-1382,共17页
Lithium-ion batteries are the most widely accepted type of battery in the electric vehicle industry because of some of their positive inherent characteristics. However, the safety problems associated with inaccurate e... Lithium-ion batteries are the most widely accepted type of battery in the electric vehicle industry because of some of their positive inherent characteristics. However, the safety problems associated with inaccurate estimation and prediction of the state of health of these batteries have attracted wide attention due to the adverse negative effect on vehicle safety. In this paper, both machine and deep learning models were used to estimate the state of health of lithium-ion batteries. The paper introduces the definition of battery health status and its importance in the electric vehicle industry. Based on the data preprocessing and visualization analysis, three features related to actual battery capacity degradation are extracted from the data. Two learning models, SVR and LSTM were employed for the state of health estimation and their respective results are compared in this paper. The mean square error and coefficient of determination were the two metrics for the performance evaluation of the models. The experimental results indicate that both models have high estimation results. However, the metrics indicated that the SVR was the overall best model. 展开更多
关键词 Support vector Regression (SVR) Long Short-Term Memory (LSTM) Network state of Health (SOH) Estimation
在线阅读 下载PDF
基于卡尔曼前馈拟合状态观测器的储纬器用永磁同步电动机霍尔位置检测方法
16
作者 孟子钰 鲁文其 +3 位作者 张颂 苗盛鸿 黄富华 彭来湖 《纺织学报》 北大核心 2025年第9期232-241,共10页
基于开关型霍尔位置传感器的永磁同步电动机控制系统虽具有高功率密度、高效率等优势,但该类型传感器的信号跳变离散,使电动机的位置和速度估算出现较大误差,进而影响了储纬器纱线输送的运行性能。为提高电动机转子估算的精度,以增强储... 基于开关型霍尔位置传感器的永磁同步电动机控制系统虽具有高功率密度、高效率等优势,但该类型传感器的信号跳变离散,使电动机的位置和速度估算出现较大误差,进而影响了储纬器纱线输送的运行性能。为提高电动机转子估算的精度,以增强储纬器纱线输送的稳定性,提出了基于卡尔曼前馈拟合状态观测器的电动机转子位置和速度估计方法。首先采用卡尔曼迭代算法对离散的霍尔信号进行滤波及拟合,以消除霍尔安装偏差造成的噪声扰动;其次,采用全维状态观测器对电动机的转子位置信息进行估算,最终获得连续的电动机转子位置和速度信息。为验证提出算法的有效性,搭建实验平台进行了测试。结果表明:相较于传统的线性外插算法,采用改进卡尔曼前馈拟合状态观测器算法的系统,在启动阶段,电动机转子位置及速度的估算精度更高;在整个运行过程,纱线输送的动态性能和稳态性能更好。 展开更多
关键词 霍尔传感器 永磁同步电动机 储纬器 卡尔曼滤波 全维状态观测器 矢量控制
在线阅读 下载PDF
An Improved, Downscaled, Fine Model for Simulation of Daily Weather States 被引量:1
17
作者 江志红 丁裕国 +1 位作者 郑春雨 陈威霖 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2011年第6期1357-1366,共10页
In this study,changes in daily weather states were treated as a complex Markov chain process,based on a continuous-time watershed model(soil water assessment tool,SWAT) developed by the Agricultural Research Service... In this study,changes in daily weather states were treated as a complex Markov chain process,based on a continuous-time watershed model(soil water assessment tool,SWAT) developed by the Agricultural Research Service at the U.S.Department of Agriculture(USDA-ARS).A finer classification using total cloud amount for dry states was adopted,and dry days were classified into three states:clear,cloudy,and overcast(rain free).Multistate transition models for dry-and wet-day series were constructed to comprehensively downscale the simulation of regional daily climatic states.The results show that the finer,improved,downscaled model overcame the oversimplified treatment of a two-weather state model and is free of the shortcomings of a multistate model that neglects finer classification of dry days(i.e.,finer classification was applied only to wet days).As a result,overall simulation of weather states based on the SWAT greatly improved,and the improvement in simulating daily temperature and radiation was especially significant. 展开更多
关键词 stochastic simulation daily weather state series Markov chain state vector.
在线阅读 下载PDF
大数据驱动下舰船无线通信网异常状态辨别研究
18
作者 仇丹丹 段新华 《舰船科学技术》 北大核心 2025年第16期185-189,共5页
为解决舰船无线通信网的“小样本-高噪声”问题,避免过拟合,研究大数据驱动下舰船无线通信网异常状态辨别方法。采集舰船无线通信网大数据,提取舰船无线通信网状态特征,通过大数据驱动的半监督学习算法为未知标签的无线通信网状态特征... 为解决舰船无线通信网的“小样本-高噪声”问题,避免过拟合,研究大数据驱动下舰船无线通信网异常状态辨别方法。采集舰船无线通信网大数据,提取舰船无线通信网状态特征,通过大数据驱动的半监督学习算法为未知标签的无线通信网状态特征样本生成高可信度的伪标签,以已知标签样本和带伪标签的未知样本为大数据驱动的最小二乘半监督支持向量机模型的输入,输出舰船无线通信网异常状态辨别结果。实验证明,该方法可有效采集舰船无线通信网大数据,并提取网络状态特征;该方法异常状态辨别残差的最高自相关系数约为0.2,即辨别结果与实际结果的差距小,异常状态辨别精度高。 展开更多
关键词 大数据驱动 舰船通信网 异常状态辨别 支持向量机
在线阅读 下载PDF
基于向量机多分类模型的城市交通状态演化特性
19
作者 张开文 冯阳 +2 位作者 王岚 朱云波 王龙健 《公路交通科技》 北大核心 2025年第4期8-16,共9页
【目标】为实时准确识别城市路网交通流状态,以期为缓解城市区域交通拥堵问题提供理论依据。【方法】采用支持向量机多分类算法(SVM)识别交通流状态,基于马尔可夫链构建交通流状态迁移概率模型,以西安市雁塔区的部分区域路网出租车GPS... 【目标】为实时准确识别城市路网交通流状态,以期为缓解城市区域交通拥堵问题提供理论依据。【方法】采用支持向量机多分类算法(SVM)识别交通流状态,基于马尔可夫链构建交通流状态迁移概率模型,以西安市雁塔区的部分区域路网出租车GPS数据为基础,通过工作日和节假日对比分析,深入剖析交通流运行状态的定性定量特征及其时空变化规律。【结果】标定后的主干路SVM模型识别精确度为96.875%,次干路SVM模型识别精确度为93.519%,满足识别精度要求。工作日雁塔区部分区域主干路和次干路的拥挤流状态均更易向外迁移,其内部迁移概率分别为51.19%和43.95%,小于其他交通流状态的内部迁移概率。而节假日主干路稳定流状态更易向外迁移,其内部迁移概率为50.87%,小于其他交通流状态的内部迁移概率。工作日主干路主要处于稳定流状态,占比30.89%,次干路主要处于畅通流状态,占比54.49%。节假日主干路和次干路主要处于畅通流状态,占比分别为30.43%和54.68%。【结论】在没有外界干扰的前提下,研究区域的交通流状态较为稳定,呈现逐步迁移,较少发生跳跃迁移。当发生突发事件后研究区域的交通流状态发生明显的变化,会产生跳跃迁移。该研究可用于判别常发性和偶发性交通拥堵,为城市交通的控制、诱导、管理和决策提供有力支持。 展开更多
关键词 智能交通 交通流状态 支持向量机 城市交通状态 出租车GPS
原文传递
基于稳态特征提取和CWLS-SVM的W火焰锅炉NOx排放量预估 被引量:1
20
作者 于闻歌 赵文杰 《华北电力大学学报(自然科学版)》 北大核心 2025年第4期116-124,共9页
燃煤电厂排放的氮氧化物是环境污染的主要来源之一,燃烧优化可以有效降低锅炉NOx排放量,NOx排放量预测模型作为燃烧优化的基础,受到了人们广泛的关注。针对火电厂W火焰锅炉,提出了一种基于稳态特征提取的模型样本集构造方法,在此基础上... 燃煤电厂排放的氮氧化物是环境污染的主要来源之一,燃烧优化可以有效降低锅炉NOx排放量,NOx排放量预测模型作为燃烧优化的基础,受到了人们广泛的关注。针对火电厂W火焰锅炉,提出了一种基于稳态特征提取的模型样本集构造方法,在此基础上,提出一种组合加权最小二乘支持向量机(CWLS-SVM)建立NOx排放量预测模型。首先通过机理分析确定模型输入变量,基于滑动窗口对海量历史运行数据进行稳态特征搜索,以组合相似度判断法进一步筛选特征,构造模型样本集;然后,针对实际生产中LS-SVM对异常值和噪声干扰敏感、不同输入变量对结果的差异性影响等问题,采用基于局部异常因子的经验风险项加权和基于最大信息系数的特征变量加权的方法对LS-SVM进行了改进;最后进行了多种仿真对比实验。结果表明,CWLS-SVM相比于LS-SVM与其他神经网络模型,具有更强的鲁棒性和泛化能力,对实现锅炉燃烧优化具有重要意义。 展开更多
关键词 NOx排放量预测 稳态特征提取 最小二乘支持向量机 样本集构造 特征加权
在线阅读 下载PDF
上一页 1 2 53 下一页 到第
使用帮助 返回顶部