共查询到20条相似文献，搜索用时 15 毫秒
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The characterization of an unknown quantum system requires the Hamiltonian identification. The full access to the system, however, is usually restricted, hindering the direct retrieval of the relevant parameters, and a reliable indirect estimation is usually required. In this work, based on the reformulated form of the original algorithm of Burgarth et al.[Phys. Rev. A 79 020305(2009)], the robustness of the estimation scheme against numerous sources of errors during the actual measurement is analyzed. The scheme is numerically studied for sites with a chain structure, exploring its applicability against observational errors including the limited signal-noise ratio and the finite spectral width. The spectral distribution of the end site is shown to determine the applicability of the method, and reducing the influence from truncated spectral components is critical to realize the robust reconstruction of the coupling strengths. 相似文献
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Yong-Long Wang Chuan-Cong Wang Xue-Feng Ning Shu-Tao Ai Hong-Zhe Pan Tong-Song Jiang 《International Journal of Theoretical Physics》2008,47(9):2319-2325
For constrained Hamiltonian systems, the motion equations are deduced from total Hamiltonian and extended Hamiltonian with
Lagrangian multipliers depending on time t and canonical variables q
i
and p
i
. When the multipliers reduced to only depend on time t, the motion equations exactly agree with the old results. Under the same conditions (Lagrangian multipliers depend on time
t and canonical variables q
i
and p
i
), the relation equations of coefficients in the generator of gauge transformation are deduced, but the equations have an
additive term besides the well-known results. This additive term is from Lagrangian multipliers depending on canonical variables,
and it might perform the gauge symmetries that needs to be discussed further.
This project is supported by the fund of National Natural Science (10671086) and by National Laboratory for Superlattices
and Microstructures (CHJG200605). 相似文献
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基于改进粒子群优化算法的混沌系统参数估计方法 总被引：22，自引：0，他引：22
估计混沌系统的未知参数是混沌控制与同步中必须解决的关键问题.利用群集智能的新进展粒子群优化算法(PSO)的全局搜索能力,从初始粒子群的产生、目标函数的处理的角度改进PSO,将改进的PSO引入混沌系统参数估计和在线估计.仿真试验表明,改进算法具有良好的适应性、较高的收敛可靠性及精度,对信号叠加噪声的情形也具有较高的鲁棒性,是混沌系统参数估计的一种成功算法.关键词：混沌系统参数估计在线估计粒子群优化算法 相似文献
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Reliability of linear coupling synchronization of hyperchaotic systems with unknown parameters 
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下载免费PDF全文 Complete synchronization could be reached between some chaotic and/or hyperchaotic systems under linear coupling. More generally, the conditional Lyapunov exponents are often calculated to confirm the stability of synchronization and reliability of linear controllers. In this paper, detailed proof and measurement of the reliability of linear controllers are given by constructing a Lyapunov function in the exponential form. It is confirmed that two hyperchaotic systems can reach complete synchronization when two linear controllers are imposed on the driven system unidirectionally and the unknown parameters in the driving systems are estimated completely. Finally, it gives the general guidance to reach complete synchronization under linear coupling for other chaotic and hyperchaotic systems with unknown parameters. 相似文献
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Kadir Aktas Madis Kiisk Andrea Giammanco Gholamreza Anbarjafari Mrt Mgi 《Entropy (Basel, Switzerland)》2022,24(11)
The performance of cosmic-ray tomography systems is largely determined by their tracking accuracy. With conventional scintillation detector technology, good precision can be achieved with a small pitch between the elements of the detector array. Improving the resolution implies increasing the number of read-out channels, which in turn increases the complexity and cost of the tracking detectors. As an alternative to that, a scintillation plate detector coupled with multiple silicon photomultipliers could be used as a technically simple solution. In this paper, we present a comparison between two deep-learning-based methods and a conventional Center of Gravity (CoG) algorithm, used to calculate cosmic-ray muon hit positions on the plate detector using the signals from the photomultipliers. In this study, we generated a dataset of muon hits on a detector plate using the Monte Carlo simulation toolkit GEANT4. We demonstrate that two deep-learning-based methods outperform the conventional CoG algorithm by a significant margin. Our proposed algorithm, Fully Connected Network, produces a 0.72 mm average error measured in Euclidean distance between the actual and predicted hit coordinates, showing great improvement in comparison with CoG, which yields 1.41 mm on the same dataset. Additionally, we investigated the effects of different sensor configurations on performance. 相似文献
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夫兰克-赫兹实验教学的发展与完善 总被引：1，自引：1，他引：1
根据不同时期对夫兰克-赫兹实验仪的改进及对实验内容的改革扩充,阐述了该实验教学的不断发展与完善.重点介绍了对第一代夫兰克-赫兹实验的改造,增加了数据采集、电脑显示及数据处理等功能,实现集模拟与数字化为一体的实验装置. 相似文献
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水声通信中传统帧同步方法仅仅依赖于匹配滤波输出的相关系数,在复杂信道条件下,容易出现误触发和漏同步。针对这一问题,分析了水声信道中噪声、多普勒和多径对帧同步的影响,提出了一种基于参数估计的帧同步方法.在同步过程中引入参数估计,将信号参数作为检测判决依据,以降低误触发率和漏检率;同时对最大似然估计算法进行适当简化,以降低实现复杂度。计算机仿真实验验证了新的帧同步方法相对于传统方法在定时精度和相关系数方面的优势。实际水声通信实验结果表明,无论是静止平台还是移动平台之间的通信,新的帧同步方法均能有效提高匹配滤波器输出的相关系数,提升接收机检测能力,从而避免出现误触发和漏同步。 相似文献
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混沌系统中参数估计的演化建模方法 总被引：1，自引：0，他引：1
借助于演化算法的自组织、自适应和自学习特征,本文提出了基于演化算法的参数辨识方案,并利用经典的Lorenz方程进行了数值仿真试验,研究了参数辨识方案对于单参数、双参数以及Lorenz系统三个参数完全未知时的性能.数值试验结果表明,新方法能够很好的对未知参数进行较为快速、准确的辨识,但存在对多个参数同时搜索时速度较慢的缺陷.鉴于此,将演化算法变异操作中的参数变异范围附加一种约束机理,试验结果表明,这一约束机理有效地提高了多参数估计中算法的收敛速度. 相似文献
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W. W. Cheng 《Annalen der Physik》2023,535(11):2300180
The impact of nonequilibrium environment effects on the accuracy of quantum parameter estimation is investigated, and it is found that these effects can significantly affect estimation accuracy. Using an individual estimation strategy reveals that the nonequilibrium effects consistently enhance accuracy, regardless of the coupling strength between the probe and its environment. In contrast, weak memory effects undermine estimation accuracy. When employing a multi-parameter simultaneous estimation strategy, it is observed that the nonequilibrium effects consistently improve the advantages of simultaneous estimation, as analyzed by the ratio of total variances between the two estimation scenarios. However, the memory effects on these advantages depend on the coupling strength between the qubit and the environment. These findings suggest that appropriate parameters of a nonequilibrium environment can increase the quantum Fisher information (QFI), thereby enhancing the accuracy of quantum parameter estimation. These significant results are essential for improving parameter estimation accuracy in quantum systems interacting with nonequilibrium environments. 相似文献
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荧光分子断层成像支持在体无创研究长时间跨度的分子事件,满足21世纪系统化地观测生命过程的要求。在其复杂且耗时的重建中,先验信息有助于加快重建速度,提高重建图像的质量。文章将求解荧光物的深度作为待优化问题,由单幅荧光图像直接快速地估计深度信息。首先根据生物组织内的扩散模型和外推边界条件,推导出生物体边界上两点处荧光强度的比值Rf。然后用粒子群优化算法,在吸收系数和散射系数的估计区间内,由最小化生物体边界上两点处模型值RMf与测量值RTf之间的差,估计出荧光物的深度。不同尺寸荧光物的两个仿体实验的结果表明,所提出的方法不需要网格剖分和重建,能快速简单地估计出单个类似于球体的荧光物的深度。 相似文献
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Hindmarsh-Rose混沌神经元自适应同步和参数识别的优化研究 总被引：1，自引：0，他引：1
以Hindmarsh-Rose混沌神经元模型为例,讨论了基于自适应同步识别混沌系统多个参数方法的优化问题.在构造的李亚普诺夫函数中引入可调节的增益系数来控制系统同步和参数观测器的暂态过程长短.在应用单个控制器和5个参数观测器来同步和识别Hindmarsh-Rose混沌神经元中5个未知参数时发现最小参数的识别结果出现了振荡而其他参数都能准确识别现象,分析其原因可能在于要识别的目标参数的巨大差异性.通过增加控制器的个数(选择两个控制器)可以克服这个困难.研究发现增益系数太小不能实现完全同步和参数的准确识别,当增益系数太大则延长了识别参数的暂态过程.在恰当的增益系数下可以在比较短的暂态过程下准确识别系统参数.进一步讨论了系统参数发生阶跃变化时系统参数的识别问题,数值计算结果验证了该方法的可靠性和有效性. 相似文献
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测量材料热物性的准稳态方法与参数估计张欣欣，殷晓静（北京科技大学热能工程系北京１０００８３）关键词热物性，参数估计，准稳态测量方法１前言材料的导热系数人建立了热流密度与温度梯度的关系，表征物质的导热能力；体积热容量ｐＣ则表征单位体积物质的蓄热能力；对... 相似文献
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M. S. DE GROOT I. A. M. HESSELMANN J. SCHMIDT J. H. VAN DER WAALS 《Molecular physics》2013,111(1):31-43
Experiments have been performed to determine the path of entry into and exit from the phosphorescent triplet state T0 of quinoxaline in a durene host. First of all the decay of phosphorescence after flash excitation was followed at 4.2 and 1.34 °K. It was found that for both perdeutero- and perhydroquinoxaline the lifetime is shortened by a factor of about three when the temperature is lowered from 4.2 to 1.34 °K. At 1.34 °K relaxation between the spin components (i.e. re-orientation of the triplet spin angular momentum) is slow relative to the decay, and the observed reduction in lifetime indicates that entry into and exit from T0, are through the same spin component. Similar decay experiments were then carried out at 1.34 °K in a 10 kG magnetic field or in a somewhat weaker field so chosen that the effect of microwave saturation of one of the E.S.R. transitions between the components could be observed. From the results it follows that on intersystem crossing the molecules enter the manifold T0 through the top zero-field component and thus initially have their spins aligned. Decay departs almost exclusively from the same component, even in the case of perhydroquinoxaline, where at least 45 per cent of it must be radiationless. The decay route agrees with out-of-plane polarization of phosphorescence for the free molecule. Finally, spin alignment on intersystem crossing is discussed from the theoretical point of view. It appears that the phenomenon is clear-cut only in molecules such as those of the aza-aromatics, where strong spin-orbit coupling of the atomic type occurs betwen ππ? and nπ? states. 相似文献
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This paper considers the periodic self-exciting threshold integer-valued autoregressive processes under a weaker condition in which the second moment is finite instead of the innovation distribution being given. The basic statistical properties of the model are discussed, the quasi-likelihood inference of the parameters is investigated, and the asymptotic behaviors of the estimators are obtained. Threshold estimates based on quasi-likelihood and least squares methods are given. Simulation studies evidence that the quasi-likelihood methods perform well with realistic sample sizes and may be superior to least squares and maximum likelihood methods. The practical application of the processes is illustrated by a time series dataset concerning the monthly counts of claimants collecting short-term disability benefits from the Workers’ Compensation Board (WCB). In addition, the forecasting problem of this dataset is addressed. 相似文献