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Bright Heralded Single-Photon Source Saturating Theoretical Single-photon Purity

LASER & PHOTONICS REVIEWS 2025年第9期19卷

作者： Wang, Haoyang Yuan, Huihong Zeng, Qiang Zhou, Lai Ma, Haiqiang Yuan, Zhiliang Beijing Acad Quantum Informat Sci Beijing 100193 Peoples R China Beijing Univ Posts & Telecommun Sch Sci Beijing 100876 Peoples R China Beijing Univ Posts & Telecommun State Key Lab Informat Photon & Opt Commun Beijing 100876 Peoples R China

Single-photon source is the cornerstone for modern quantum information processing. The present work derives the theoretical limit of single-photon purity for general parametric heralded single-photon sources, and subsequently demonstrates a bright, gigahertz-pulsed heralded source with the purity saturating the limit. By stimulating spontaneous four-wave mixing effect in the silicon spiral waveguide, this on-chip source is measured to have a coincidence rate exceeding 1.5 MHz at a coincidence-to-accidental ratio (CAR) of 16.77 in the photon pair correlation experiment. The single-photon purity of this source, quantified by the heralded auto-correlation function gh(2)(0)$g<^>{(2)}_{\text{h}}(0)$, is measured by a heralded Hanbury Brown-Twiss setup to reach the theoretical limit with the lowest value of 0.00094 +/- 0.00002$0.00094 \pm 0.00002$ obtained at a coincidence rate of 0.8 kHz and a CAR of 2220. The performance improvements are attributed to effective spectral filtering suppressing the noise as well as the coherent pump condition helped by optical injection locking. The reported results provide a reliable standard for benchmarking heralded single-photon sources and present a state-of-the-art heralded source for quantum information processing.

关键词： auto-correlation function heralded single-photon source silicon waveguide

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Time-correlation function and average energy of molecules in presence of Deng-Fan potential in a moving boundary

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NONLINEAR DYNAMICS 2022年第2期110卷 1597-1612页

作者： Nath, Debraj Roy, Amlan K. Vivekananda Coll Dept Math Kolkata 700063 WB India Indian Inst Sci Educ & Res IISER Kolkata Dept Chem Sci Nadia 741246 WB India

For the Deng-Fan potential within a moving boundary condition, the time-dependent Schrodinger equation is considered analytically. The eigenvalue equation is solved by using a combination of Pekeris and Greene-Aldrich approximations. Various time-dependent quantities including density distribution function, auto-correlation function, disequilibrium, average energy, quantum similarity, and quantum similarity index are obtained for selected eight diatomic molecules. The motion of the peak of the density function, with moving boundary condition is investigated for ground states of some diatomic molecules along with the corresponding peak values.

关键词： Deng-Fan potential Ro-vibrational energy Average energy Time-correlation function auto-correlation function Quantum similarity index Moving boundary

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An Unambiguous Acquisition Algorithm Based on Unit correlation for BOC(n,n) Signal

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IEICE TRANSACTIONS ON COMMUNICATIONS 2017年第8期E100B卷 1507-1513页

作者： Ji, Yuan-fa Liu, Yuan Zhen, Wei-min Sun, Xi-yan Yu, Bao-guo State Key Lab Satellite Nav Syst & Equipment Tech Shijiazhuang 050000 Hebei Peoples R China Guilin Univ Elect Technol Guangxi Key Lab Precis Nav Technol & Applicat Guilin 541004 Peoples R China Key Lab Radio Wave Environm & Modeling Technol Qingdao 266000 Peoples R China Guangxi Expt Ctr Informat Sci Guilin 541004 Peoples R China

To overcome the false lock or detection missing problems caused by the multiple peaks of the auto-correlation function (ACF) of Binary Offset Carrier (BOC) modulated signal, an acquisition algorithm based on unit correlation for BOC(n,n) signal is proposed in this paper. The local BOC signal is separated into two unit signals, an odd one and an even one. Then a reconstruction of the unit correlation functions between the unit signals and the received BOC signal is performed and M sections of reconstructed correlation function are accumulated according to the non coherent method, so that this novel acquisition algorithm can not only eliminate the multiple secondary peaks, but also retain the advantage of the narrow correlation main peak. Simulation results show that the acquisition sensitivity of the proposed algorithm is increased 3 dBHz compared with the ASPeCT method, and the computation cost is only 41.46% of the ASPeCT method when M=2.

关键词： multiple peaks auto-correlation function unit correlation separation and reconstruction non-coherent

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Evaluation of decay ratio of BWRs using singular value decomposition method

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JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2005年第2期42卷 169-182页

作者： Tsuji, M Shimazu, Y Hokkaido Univ Grad Sch Engn Dept Nucl Engn Kita Ku Sapporo Hokkaido 0608628 Japan

A new rnethod for evaluating the decay ratio of boiling water reactors (BWR) using the singular value decomposition (SVD) method was proposed. In the SVD method, time-series data are decomposed into uncorrelated signal components and the auto-correlation functions (ACF) of these decomposed components are calculated. The ACF having a form of damping oscillation is related to the complex conjugate dominant poles of the frequency transfer function of BWR dynamics. The decay ratio and the natural frequency can be determined by applying a least square fitting to the ACE The proposed method was applied to LPRM and APRM signals measured during stability experiments performed in Ringhals-1 at BOC-14. It was found that LPRM signals that were measured under 9 operating conditions were consistently decomposed into three type components whose ACFs had the forms of slow attenuation, fast attenuation and damping oscillation. Under the respective operating conditions, LPRM signals measured at various positions were decomposed into the ACFs with almost the same values of the decay ratio and the natural frequency. In virtue of this high decomposition performance, the decay ratios can be estimated with small standard deviations compared with conventional methods. Some guidelines for an accurate determination of decay ratios are also presented.

关键词： decay ratio BWR type reactors stability monitoring space embedding singular value decomposition auto-correlation function covariance matrix autoregressive model identification local power range monitor Ringhals-1

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Method of shaft crack detection based on squared gain of vibration amplitude

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NONLINEAR DYNAMICS 2019年第1期98卷 671-690页

作者： Gradzki, Rafal Kulesza, Zbigniew Bartoszewicz, Blazej Bialystok Tech Univ Fac Mech Engn Ul Wiejska 45C PL-15351 Bialystok Poland

Rotating machines are exposed to different faults such as shaft cracks, bearing failures, rotor misalignment, stator to rotor rub, etc. Therefore, turbo-generators, aircraft engines, compressors, pumps, and many other rotating machines should be constantly diagnosed to warn about the probable appearance of a possible rotor failure. Unfortunately, despite the ongoing work on various rotor fault detection methods, there are still very few techniques that can be considered as reliable and applicable in practical problems. The difficulty lies in the fact that usually the fault introduces very subtle local changes in the overall structure of the rotor. The symptoms of these changes must be isolated and extracted from a wide spectrum of vibration data obtained from sensors measuring the vibrations of the machine. The measured data are usually disturbed with some noise or other disturbances, and that is why the detection of a possible rotor fault is even more difficult. The paper presents a new rotor fault detection method. The method is based on a new diagnostic model of rotor signals and external disturbances. The model utilizes auto-correlation functions of measured rotor's vibrations. By proper processing of the measured vibration data, the influence of environmental disturbances is completely compensated and reliable indications of the possible rotor fault are obtained. The method has been tested numerically using the finite element model of the rotor and then verified experimentally at the shaft crack detection test rig. The results are presented in a readable graphical form and confirm high sensitivity and reliability of the method.

关键词： auto-correlation function Power spectral density function Signal processing Fault detection Damage map

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Investigations on Line-Edge Roughness (LER) and Line-Width Roughness (LWR) in Nanoscale CMOS Technology: Part I-Modeling and Simulation Method

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IEEE TRANSACTIONS ON ELECTRON DEVICES 2013年第11期60卷 3669-3675页

作者： Jiang, Xiaobo Wang, Runsheng Yu, Tao Chen, Jiang Huang, Ru Peking Univ Inst Microelect Beijing 100871 Peoples R China Peking Univ Dept Elect Beijing 100871 Peoples R China

In this paper, the correlation between line-edge roughness (LER) and line-width roughness (LWR) is investigated. Based on the characterization methodology of auto-correlation functions (ACF), a new theoretical model of LWR is proposed, which indicates that the LWR ACF is composed of two parts: one involves LER information;the other involves the cross-correlation of the two edges. Additional characteristic parameters for LER/LWR are proposed to represent the missing cross-correlation information in conventional approaches of LER/LWR description, other than LER/LWR amplitude and auto-correlation length. An improved simulation method for correlated LERs is also proposed, which can provide helpful guidelines for the characterization, modeling, and the optimization of LER/LWR in nanoscale CMOS technology. The experimental results and device simulation results are discussed in detail in the part II of this paper.

关键词： auto-correlation function cross-correlation line-edge-roughness (LER) line-width-roughness (LWR) modeling variability

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Variations in seismic velocity and attenuation associated with seismogenesis: A numerical verification using ambient noise

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TECTONOPHYSICS 2013年 584卷 54-63页

作者： Rohrbach, Eric Liu, Lanbo Wang, Linying Univ Connecticut Dept Civil & Environm Engn Storrs CT 06269 USA United Technol Res Ctr E Hartford CT 06108 USA China Earthquake Adm Inst Geophys Beijing Peoples R China

Seismic velocity variations associated with the seismogenic process have been studied worldwide for almost half a century since the dilatancy hypothesis proposed in early 1970s. However, the reports in seismogenesis-associated variations in attenuation are rare. Reports on simultaneous variation of velocity and attenuation are even rarer. The conventional way to obtain the seismogenic temporal variation in velocity and attenuation is through the observation of travel time and amplitude variations of microseismicity in a seismogenic zone. Anyhow, for some major earthquakes there may not always be microseismicity prior to the mainshock. Thus, obtaining a complete record of seismic velocity and attenuation variation from microseismicity is severely limited if pre-mainshock microseismicity exists. In contrast, seismic ambient noise is an ideal source for crustal stimulation for monitoring temporal variations in velocity and attenuation in a seismogenic zone. In this paper the seismogenesis-associated seismic velocity and attenuation variations shown as some observable parameters in ambient noise measurements are verified using a numerical simulation approach. First, based on the temporal variation in seismic velocity observed along the Longmenshan fault associated with the 2008 Wenchuan earthquake, we divided the seismogenic process into six phases upon velocity drop stages in an elliptic area in the crust. Second, using finite difference time domain method we generated 30-minute low frequency ambient noise over a vertical profile of 200x45 km and recorded it with a 90-station array on the surface. Next, we processed the synthetic ambient noise records to get the auto-correlation function (ACF), cross-correlation function (CCF), Rayleigh wave dispersion curve, and horizontal-to-vertical spectral ratio (H/V). Finally, we examined the temporal variation of these parameters versus the phases of the seismogenic process and found the most pronounced changes occur in the phas

关键词： Seismogenesis Ambient noise auto-correlation function Cross-correlation function Phase velocity dispersion Horizontal-to-vertical spectral ratio

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Time-varying system identification using a newly improved HHT algorithm

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COMPUTERS & STRUCTURES 2009年第23-24期87卷 1611-1623页

作者： Bao, Chunxiao Hao, Hong Li, Zhong-Xian Zhu, Xinqun Tianjin Univ Sch Civil Engn Tianjin 300072 Peoples R China Univ Western Australia Sch Civil & Resource Engn Nedlands WA 6009 Australia

A newly improved Hilbert-Huang transform (HHT) algorithm is presented for identification of time-varying systems and analysis of nonlinear structural response with closely spaced modes. In this improved HHT, the auto-correlation function of the structural response is taken as a substitute of input to reduce noise effect. A band-pass filter scheme and an effective intrinsic mode function (IMF) selection principle are combined to overcome the modal perturbation problem. Based on these, a time-varying system identification procedure is developed. Its robustness and effectiveness are verified by both numerically simulated and laboratory measured vibration data on a scaled concrete-steel composite beam model. (c) 2009 Elsevier Ltd. All rights reserved.

关键词： Time-varying system identification Improved HHT auto-correlation function Close mode separation Scaled concrete-steel composite beam model Dynamic test

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Formulae of roughness peak distribution parameters with standard deviation and correlation length

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY 2015年第12期229卷 1395-1408页

作者： Zhou, Wei Tang, Jinyuan He, Yanfei Cent S Univ State Key Lab High Performance Complex Mfg Changsha 410083 Hunan Peoples R China

Principle error exists when peak distribution parameters are calculated based on the random process theory, and the microtopography simulation with desired peak distributions still cannot be realized. To solve these problems, the relationship between peak distribution parameters and surface statistical distribution parameters is studied through lots of rough surface reconstructions. The effects of high-pass filtering with different cut-off lengths are analyzed. In addition, formulae of peak distribution parameters with standard deviation and correlation length are constructed by mathematical fitting. The formulae are verified with experimental data and compared with classical literature. Finally, an example of application of the formulae to microtopography simulation is provided.

关键词： Surface topography roughness peak distribution auto-correlation function simulation

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Enumeration of Both-Ends-Fixed k-Ary Necklaces and Its Applications

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2023年第3期E106A卷 431-439页

作者： Fujisaki, Hiroshi Kanazawa Univ Grad Sch Nat Sci & Technol Kanazawa 9201192 Japan

We consider both-ends-fixed k-ary necklaces and enumer-ate all such necklaces of length n from the viewpoints of symbolic dynamics and/3-expansions, where n and k(>= 2) are natural numbers and/3(> 1) is a real number. Recently, Sawada et al. proposed an efficient construction of k-ary de Bruijn sequence of length kn, which for each n >= 1, requires O(n) space but generates a single k-ary de Bruijn sequence of length kn in O(1)-amortized time per bit. Based on the enumeration of both-ends-fixed k-ary necklaces of length n, we evaluate auto-correlation values of the k-ary de Bruijn sequences of length kn constructed by Sawada et al. We also estimate the asymptotic behaviour of the obtained auto-correlation values as n tends to infinity.

关键词： k-ary necklaces symbolic dynamics 3-expansions k-ary de Bruijn sequences auto-correlation function

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