Fast parallel factor decomposition technique for coherently distributed source localization

This paper links parallel factor（PARAFAC） analysis to the problem of nominal direction-of-arrival（DOA） estimation for coherently distributed（CD） sources and proposes a fast PARAFACbased algorithm by establishing the trilinear PARAFAC model.Relying on the uniqueness of the low-rank three-way array decomposition and the trilinear alternating least squares regression, the proposed algorithm achieves nominal DOA estimation and outperforms the conventional estimation of signal parameter via rotational technique CD（ESPRIT-CD） and propagator method CD（PM-CD）methods in terms of estimation accuracy. Furthermore, by means of the initialization via the propagator method, this paper accelerates the convergence procedure of the proposed algorithm with no estimation performance degradation. In addition, the proposed algorithm can be directly applied to the multiple-source scenario,where sources have different angular distribution shapes. Numerical simulation results corroborate the effectiveness and superiority of the proposed fast PARAFAC-based algorithm.

Continuously tunable sub-half-wavelength localization via coherent control of spontaneous emission

We propose a continuously tunable method of sub-half-wavelength localization via the coherent control of the spontaneous emission of a four-level Y-type atomic system, which is coupled to three strong coupling fields including a standing-wave field together with a weak probe field. It is shown that the sub-half-wavelength atomic localization is realized for both resonance and off-resonance cases. Furthermore, by varying the probe detuning in succession, the positions of the two localization peaks are tuned continuously within a wide range of probe field frequencies, which provides convenience for the realization of sub-half-wavelength atomic localization experimentally.

Sensing Matrix Optimization for Multi-Target Localization Using Compressed Sensing in Wireless Sensor Network

In the multi-target localization based on Compressed Sensing(CS),the sensing matrix's characteristic is significant to the localization accuracy.To improve the CS-based localization approach's performance,we propose a sensing matrix optimization method in this paper,which considers the optimization under the guidance of the t%-averaged mutual coherence.First,we study sensing matrix optimization and model it as a constrained combinatorial optimization problem.Second,the t%-averaged mutual coherence is adopted as the optimality index to evaluate the quality of different sensing matrixes,where the threshold t is derived through the K-means clustering.With the settled optimality index,a hybrid metaheuristic algorithm named Genetic Algorithm-Tabu Local Search(GA-TLS)is proposed to address the combinatorial optimization problem to obtain the final optimized sensing matrix.Extensive simulation results reveal that the CS localization approaches using different recovery algorithms benefit from the proposed sensing matrix optimization method,with much less localization error compared to the traditional sensing matrix optimization methods.

MULTI-SCALE COHERENT STRUCTURES IN TURBULENT BOUNDARY LAYER DETECTED BY LOCALLY AVERAGED VELOCITY STRUCTURE FUNCTIONS

The time sequence of longitudinal velocity component at different vertical locations in turbulent boundary layer was finely measured in a wind tunnel. The concept of coarse_grained velocity structure functions, which describes the relative motions of straining and compressing for multi_scale eddy structures in turbulent flows, was put forward based on the theory of locally multi_scale average. Based on the consistency between coarse_grained velocity structure function and Harr wavelet transformation,detecting method was presented, by which the coherent structures and their intermittency was identified by multi_scale flatness factor calculated by locally average structure function. Phase_averaged evolution course for multi_scale coherent eddy structures in wall turbulence were extracted by this conditional sampling to educe scheme. The dynamics course of multi_scale coherent eddy structures and their effects on statistics of turbulent flows were studied.

Electron localization in ultrathin films of three-dimensional topological insulators

The recent discovery of three-dimensional（3D） topological insulators（TIs） has provided a fertile ground for obtaining further insights into electron localization in condensed matter systems.In the past few years,a tremendous amount of research effort has been devoted to investigate electron transport properties of 3D TIs and their low dimensional structures in a wide range of disorder strength,covering transport regimes from weak antilocalization to strong localization.The knowledge gained from these studies not only offers sensitive means to probe the surface states of 3D TIs but also forms a basis for exploring novel topological phases.In this article,we briefly review the main experimental progress in the study of the localization in 3D TIs,with a focus on the latest results on ultrathin TI films.Some new transport data will also be presented in order to complement those reported previously in the literature.

基于功能影像学探讨百会治疗失眠的中枢机制

百会为治疗失眠的效穴,临床使用频率高。功能影像学,广义上包括多种成像技术,狭义主要指功能性磁共振成像(fMRI),数据分析方法分为功能分离和功能整合两类,试验设计方案包括任务态(Tb-fMRI)与静息态(Rs-fMRI),静息态因操作简便且能直观反映针刺持续和累积效应而被广泛应用。多项fMRI研究表明,失眠患者在视觉区、感觉运动区、情绪相关脑区等存在局部功能异常,针刺百会单穴或组穴可引起特定脑区如顶叶、额叶、颞叶等的改变,从而改善睡眠。针刺单穴百会主要集中在Rs-fMRI局部一致性(ReHo)、比率低频振幅(fALFF)研究,而针刺百会组穴研究从Rs-fMRI局部一致性(ReHo)、度中心度(DC)、种子连接(FC),以及Tb-fMRI比率低频振幅(fALFF)等方面展开,研究发现不同研究方法和穴位组合下的脑区激活改变存在差异,且针刺百会组穴所调控脑区多于单穴针刺,体现了百会对失眠、认知和情绪的调节作用以及腧穴间的协同作用。然而,针刺百会引起的中枢信号改变复杂,功能影像作为评估失眠的中枢指标虽有潜力,但仍需更规范、深入的研究。

Bright and dark small amplitude nonlinear localized modes in a quantum one-dimensional Klein-Gordon chain

By means of the Glauber＇s coherent state method combined with multiple-scale method, this paper investigates the localized modes in a quantum one-dimensional Klein-Gordon chain and finds that the equation of motion of annihilation operator is reduced to the nonlinear Schroedinger equation. Interestingly, the model can support both bright and dark small amplitude travelling and non-travelling nonlinear localized modes in different parameter spaces.

Investigation on Surface Plasmon Polaritons and Localized Surface Plasmon Production Mechanism in Micro-Nano Structures

The simulation mechanism of surface plasmon polaritons(SPPs)and localized surface plasmon(LSP)in different structures was studied,including the Au reflection grating(Au grating),Au substrate with dielectric ribbons grating(Au substrate grating),and pure electric conductor(PEC)substrate with Au ribbons grating(Au ribbons grating).And the characteristics of the Smith-Purcell radiation in these structures were presented.Simulation results show that SPPs are excited on the bottom surface of Au substrate grating grooves and LSP is stimulated on the upper surface both of Au ribbons grating grooves and Au grating grooves.Owing to the irreconcilable contradiction between optimizing the grating diffraction radiation efficiency and optimizing the SPPs excitation efficiency in the Au substrate grating,only 40-times enhancement of the radiation intensity was obtained by excited SPPs.However,the LSP enhanced structure overcomes the above problem and gains much better radiation enhancement ability,with about 200-times enhancement obtained in the Au ribbons grating and more than 500-times enhancement obtained in the Au grating.The results presented here provide a way of developing miniature,integratable,tunable,high-power-density radiation sources from visible light to ultraviolet rays at room temperature.

Tunable multiple plasmon resonances and local field enhancement of nanocrescent/nanoring structure

According to the plasmon hybridization theory, the plasmon resonance characteristics of the gold nanocrescent/nanoring(NCNR) structure are systematically investigated by the finite element method. It is found that the extinction spectra of NCNR structure exhibit multiple plasmon resonance peaks, which could be attributed to the result of the plasmon couplings between the multipolar plasmon modes of nanocrescent and the dipolar, quadrupolar, hexapolar, octupolar,decapolar plasmon modes of nanoring. By changing the geometric parameters, the intense and separate multiple plasmon resonance peaks are obtained and can be tuned in a wide wavelength range. It is further found that the plasmon coupling induces giant multipole electric field enhancements around the tips of the nanocrescent. The tunable and intense multiple plasmon resonances of NCNR structure may provide effective applications in multiplex biological sensing.

USING WAVELET TRANSFORM TO STUDY THELIPSCHITZ LOCAL SINGULAR EXPONENTIN WALL TURBULENCE

In this paper, wavelet,transform is introduced to study the Lipschitz local singular exponent for characterising the local singularity behavior of fluctuating velocity in wall turbulence. I, is found that the local singular exponent is negative when the ejections and sweeps of coherent structures occur in a turbulent boundary layer.

New Exact Solutions and Localized Structures for (3+1)-Dimensional Burgers System

With an extended mapping approach and a linear variable separation method, new families of variable separation solutions （including solitary wave solutions, periodic wave solutions, and rational function solutions） with arbitrary functions for （3＋1）-dimensionai Burgers system is derived. Based on the derived excitations, we obtain some novel localized coherent structures and study the interactions between solitons.

Three-Level Λ-Type Atomic System Localized by the Parameters of the Two Orthogonal Standing-Wave Fields

Localization of the three-level Λ-type atomic system interacting with two orthogonal standing-wave fields is proposed. Two equal and tunable peaks in the 2D plane are obtained by the detunings corresponding to the two orthogonal standing-wave fields when the decreasing intensities of spontaneously generated coherence (SGC) arise in the three-level Λ-type atomic system, while one circular ring with shrinking radii in the 2D plane is obtained by the adjusted phases and wave vectors of the standing-wave fields when the increasing intensities of SGC occur in the three-level Λ-type atomic system. 2D atom localization with the single ring with shrinking radii realized by the multiple parametric manipulations demonstrated the flexibility for our scheme.

Robustness of coherence between two quantum dots mediated by Majorana fermions

We study three important measurements used to identify the quantum correlations between two quantum dots （QDs） mediated by a pair of Majorana fermions （MFs） in a superconducting quantum wire. We find that, in addition to the quantum discord, the robustness of coherence （ROC） can also be considered as a quantity to measure the quantum correlation for the special case where the quantum entanglement is vanishing. For comparison, we study the quantum correlation between two QDs mediated by other fermions, i.e., regular fermions and superconducting fermions. We find that, when the quantum entanglement is not vanishing, i.e., the concurrence is finite, the detailed difference between the concurrence and ROC can be considered as an important implication for the existence of MFs.

A Physical Basis for Entanglement in a Non-Local Hidden Variable Theory

Problem: Superposition and entanglement are coherent effects, which can be quantified by quantum mechanics (QM), but lack descriptive explanations. They are typically analysed with inequality methods, and the results favour QM and reject physical realism and hidden-variable solutions. In particular, Colbeck & Renner (2011) showed that no extension of quantum theory can exist with better predictive power than quantum mechanics itself. Purpose: The purpose here is to critically evaluate from a conceptual and philosophical perspective the ontological underpinnings of the inequality approach. The current work is speculative in nature as it is based on a conjectured non-local hidden-variable (NLHV) design for particles, and does not yet have a mathematical formalism. Nonetheless this is worth attempting for the philosophical questions it poses about the nature of reality, and the pointers it gives to possible future directions in fundamental physics. Findings: The premises of the C & R proof (that particles are points, that locality exists, that quantum theory is correct) are inconsistent, hence invalidate its conclusion. We also show that superposition and entanglement may be qualitatively explained if particles were to have the internal structure proposed by the Cordus NLHV theory. Originality: The ability to explain superposition and entanglement conceptually in terms of physical realism is relevant because it rebuts the claim that it is impossible that such a hidden-variable theory could exist. This is significant because previously it has been believed that these phenomena are explainable by QM only.

Discourse Coherence in College English Reading and Writing

The development of reading and writing ability in English are the major goals in College English Curriculum Requirements(2020).The paper discusses the importance of discourse coherence in teaching reading and writing.Some parts from textbook Going Global(Elementary)are used as examples to discuss the issue.Coherence is very crucial in reading and writing process and some processing strategies are suggested to better learners’discourse understanding.The paper addresses the issue of local and global coherence and then proceed to analyze the teaching material form Going Global.It is emphasized that learners’consciousness about local and global coherence should be raised in both their reading and writing process.And some teaching implications and learning strategies are suggested based on the discussion.

局限性硬皮病诊断技术研究进展

局限性硬皮病(LS)是一种主要影响皮肤、皮下脂肪和深层组织的自身免疫性疾病,可能导致严重的功能障碍和外观受损。及时准确的诊断对于患者的治疗和管理至关重要,但目前LS在诊断方面尚存在困难。本文综述了LS诊断领域的最新进展,包括高频超声、磁共振成像、光学相干断层扫描及分子和基因检测等。这些技术提高了诊断的精确性和即时性。高频超声能够精确评估皮肤病变;磁共振成像有助于深层组织受累的评估;光学相干断层扫描和皮肤镜揭示皮肤微小结构变化;分子和基因检测为理解疾病机制及个体化治疗提供新视角。尽管新技术的应用受到成本和设备普及度的限制,但其在改善诊断流程、提供个性化治疗方面有着显著的潜力。未来研究需要进一步探讨这些技术与传统方法的整合及其在LS不同亚型和疾病阶段中的应用。

面向深层干热岩体的全波形速度反演建模方法

随着勘探深度增加,地震信号衰减严重,常规速度建模方法精度较低,无法满足深层干热岩体高精度勘探的需求。为提高速度建模的精度,采用全波形反演方法,但受局部优化算法的限制,其应用存在收敛速度慢、反演深度浅以及容易陷入局部极值等问题。为此,对梯度应用预条件处理和平滑处理,并使用共轭梯度优化算法,以解决地下照明不均匀问题,提高反演深度、精度和收敛速度。同时,为缓解局部极小值问题,引入局部相似性全波形反演方法来更新初始模型,并对构建的干热岩模型进行数值测试。结果表明:即使在初始模型极不准确的情况下,该方法仍能避免周波跳跃的不利影响,实现稳健的迭代更新;该方法能够显著增加反演深度和精度,并且对高速岩体有较好的刻画,最终能获得浅、中、深全层系高精度速度模型;提出的全波形反演方法为深层高温花岗岩体的勘探提供了一个切实可行的建模流程。

考虑地震动空间效应的斜拉桥模型振动台台阵试验

针对大跨斜拉桥空间跨度范围广、局部场地条件差异性大,服役期内可能遭受空间地震动影响的问题,开展了空间地震动作用下大跨斜拉桥振动台台阵试验。研究了地震动空间效应对斜拉桥关键截面动力响应(加速度、位移和应变)的影响规律。研究结果表明:地震动空间效应对斜拉桥的地震动力响应有明显影响,其中行波效应影响较小,考虑行波效应和相干效应时影响次之,同时考虑行波效应、相干效应和局部场地效应时影响最为显著。以主塔为例,与一致激励相比,同时考虑空间地震动的行波效应、相干效应和局部场地效应时,主塔加速度、位移和应变最大增加幅值分别为55.69%、62.37%和67.37%。因此,开展大跨斜拉桥结构抗震设计时,采用一致激励或仅考虑行波效应时可能会低估斜拉桥的实际地震响应,应综合考虑行波效应、相干效应和局部场地效应等地震动空间效应。

Quantitative determination of the critical points of Mott metal–insulator transition in strongly correlated systems

Mottness is at the heart of the essential physics in a strongly correlated system as many novel quantum phenomena occur in the metallic phase near the Mott metal–insulator transition. We investigate the Mott transition in a Hubbard model by using the dynamical mean-field theory and introduce the local quantum state fidelity to depict the Mott metal–insulator transition. The local quantum state fidelity provides a convenient approach to determining the critical point of the Mott transition. Additionally, it presents a consistent description of the two distinct forms of the Mott transition points.

Synthetic Aperture Positioning: A Review

Obtaining precise position of interested emitters passively has wide applications in both civilian and military fields.Different from traditional parameter measurement and direct position determination(DPD)method,recently a new passive localization method based on synthetic aper-ture technique,named synthetic aperture positioning(SAP),has been proposed.The method com-pensates for the nonlinear phase produced by relative motion between the moving platform and the emitter,achieving coherent summation of intercepted signals.The SAP can obtain high-resolution and high-precision localization results at a low signal-to-noise ratio.This paper summarizes the research progress of SAP,including localization principles,spaceborne applications,and application scope analysis.Besides,the possible future outlook of SAP is considered.