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A block zero-padding method based on DCFT for L1 parameter estimations in weak signal and high dynamic environments

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Frontiers of Information Technology & Electronic Engineering 2015年第9期16卷 796-804页

作者： Chao WU lu-ping xu Hua ZHANG Wen-bo ZHAO School of Aerospace Science and Technology Xidian University

Weak L1 signal acquisition in a high dynamic environment primarily faces a challenge： the integration peak is neg- atively influenced by the possible bit sign reversal every 20 ms and the frequency error. The block accumulating semi-coherent integration of correlations （BASIC） is a state-of-the-art method, but calculating the inter-block conjugate products restricts BASIC in a low signal-to-noise ratio （SNR） acquisition. We propose a block zero-padding method based on a discrete chirp-Fourier transform （DCFT） for parameter estimations in weak signal and high dynamic environments. Compared with the conventional receiver architecture that uses closed-loop acquisition and tracking, it is more suitable for open-loop acquisition. The proposed method combines DCFT and block zero-padding. In this way, the post-correlation signal is coherently post-integrated with the bit sequence stripped off, and the high dynamic parameters are precisely estimated using the threshold set based on a false alarm probability. In addition, the detection performance of the proposed method is analyzed. Simulation results show that compared with the BASIC method, the proposed method can precisely detect the high dynamic parameters in lower SNR when the length of the received signal is fixed.

关键词： Threshold detection Discrete chirp-Fourier transform Block zero-padding High dynamic Weak L1 signal acquisition

Multi-stage dual replica bit-line delay technique for process-variation-robust timing of low voltage SRAM sense amplifier

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Frontiers of Information Technology & Electronic Engineering 2015年第8期16卷 700-706页

作者： Chao WU lu-ping xu Hua ZHANG Wen-bo ZHAO School of Aerospace Science and Technology Xidian University

A multi-stage dual replica bit-line delay （MDRBD） technique is proposed for reducing access time by suppressing the sense-amplifier enable （SAE） timing variation of low voltage static randomaccess memory （SRAM） applications. Compared with the traditional technique, this strategy, using statistical theory, reduces the timing variation by using multi-stage ideas, meanwhile doubling the replica bit-fine （RBL） capacitance and discharge path simultaneously in each stage. At a supply voltage of 0.6 V, the simulation results show that the standard deviations of the SAE timing and cycle time with the proposed technique are 69.2% and 47.2%, respectively, smaller than that with a conventional RBL delay technique in TSMC 65 nm CMOS technology （Taiwan Semiconductor Manufacturing Company, Taiwan）.

关键词： Process-variation-robust Sense amplifier (SA) Replica bit-line (RBL) delay Timing variation

Feasibility analysis for attitude estimation based on pulsar polarization measurement

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Journal of Zhejiang University-Science C(Computers and Electronics) 2013年第6期14卷 425-432页

作者： Nan luO lu-ping xu Hua ZHANG Qiang XIE School of Electronic Engineering Xidian University

One of the important characteristics of pulsar radiation is *** is considered not only as a probe for recognizing the structure of a magnetic field,but also as a lighthouse for estimating spacecraft attitude via orientation information between the pulsar and the *** polarization of a pulsar has been studied for decades,until recently applications to determination of spacecraft attitude have been seldom *** paper deals with analysis of the feasibility of applying polarization information to attitude *** stability factor(SFR) and observation fluctuation factor(OFR) are introduced to analyze the stability of a pulsar's polarized position *** on European Pulsar Network(EPN) data,several simulated instances are used to demonstrate that the accuracy requirement of attitude determination can be met via polarization *** SFR of a pulsar is evaluated using simulated polarization data,and the OFR is used to analyze the relationship between fluctuation extent and observation *** results show that the polarized measurement of candidate pulsars PSR B0470-28 and PSR B2319+60 reaches the specification for attitude determination.

关键词： Pulsar Polarization Attitude determination Stable factor

Determination of inter-satellite relative position using X-ray pulsars

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Journal of Zhejiang University-Science C(Computers and Electronics) 2013年第2期14卷 133-142页

作者： Da-jun FENG lu-ping xu Hua ZHANG Shi-bin SONG School of Electronic Engineering Xidian University Institute of Astronautics and Aeronautics Xidian University

Pulsars are rapidly rotating neutron stars that generate pulsed electromagnetic radiation.A new method for intersatellite relative position determination between a global navigation satellite system(GNSS) and spacecraft using X-ray pulsars is proposed in this *** geometric model of this method is formulated,and two different resolution algorithms are introduced and *** phase cycle ambiguity resolution is investigated,and a new strategy is proposed and *** the direct vector parameters of the pulsar,geometric dilution of precision(GDOP) is *** is shown that this method has advantages of simplicity and efficiency,and is able to eliminate the clock *** analytical results are verified numerically via computer simulations.

关键词： Pulsar navigation Position determination Phase cycle ambiguity Geometric dilution of precision(GDOP)

A New Feature Vector Using Selected Line Spectra for Pulsar Signal Bispectrum Characteristic Analysis and Recognition

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Chinese Journal of Astronomy and Astrophysics 2007年第4期7卷 565-571页

作者： Zhen-Hua Xie lu-ping xu Guang-Ren Ni Yan Wang School of Electronic Engineering Xidian University Xi＇an 710071 National Time Service Center Chinese Academy of Sciences Xi＇ an 710600

Average pulse profiles of pulsar signals are analyzed using the bispectrum technique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and propagation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for extracting pulsar signal characteristic is proposed. Compared with selected bispectra, the proposed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance.

关键词： pulsars: general-stars: magnetic fields-stars: fundamental parameters (classification)

A new maximum-likelihood phase estimation method for X-ray pulsar signals

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Journal of Zhejiang University-Science C(Computers and Electronics) 2014年第6期15卷 458-469页

作者： Hua ZHANG lu-ping xu Yang-he SHEN Rong JIAO Jing-rong SUN School of Aerospace Science and Technology Xidian University

X-ray pulsar navigation(XPNAV) is an attractive method for autonomous navigation of deep space in the future. Currently, techniques for estimating the phase of X-ray pulsar radiation involve the maximization of the general non-convex object functions based on the average profile from the epoch folding method. This results in the suppression of useful information and highly complex computation. In this paper, a new maximum likelihood(ML) phase estimation method that directly utilizes the measured time of arrivals(TOAs) is presented. The X-ray pulsar radiation will be treated as a cyclo-stationary process and the TOAs of the photons in a period will be redefined as a new process, whose probability distribution function is the normalized standard profile of the pulsar. We demonstrate that the new process is equivalent to the generally used Poisson model. Then, the phase estimation problem is recast as a cyclic shift parameter estimation under the ML estimation, and we also put forward a parallel ML estimation method to improve the ML solution. Numerical simulation results show that the estimator described here presents a higher precision and reduces the computational complexity compared with currently used estimators.

关键词： X-ray pulsar Poisson model Phase estimation Maximum likelihood

Application of a microscopic optical potential of chiral effective field theory in (p, d) transfer reactions

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Nuclear Science and Techniques 2024年第1期35卷 134-144页

作者： Yi-ping xu Si-lu Chen Dan-Yang Pang School of Nuclear Science and Engineering North China Electric Power UniversityBeijing 102206China School of Physics Beihang UniversityBeijing 100191China

The microscopic global nucleon–nucleus optical model potential(OMP)proposed by Whitehead,Lim,and Holt,the WLH potential(Whitehead et al.,Phys Rev Lett 127:182502,2021),which was constructed in the framework of many-body per-turbation theory with state-of-the-art nuclear interactions from chiral effective field theory(EFT),was tested with(p,d)transfer reactions calculated using adiabatic wave *** target nuclei included both stable and unstable nuclei,and the incident energies reached 200 *** results were compared with experimental data and predictions using the phenomenological global optical potential of Koning and Delaroche,the KD02 ***,we found that the micro-scopic WLH potential described the(p,d)reaction angular distributions similarly to the phenomenological KD02 potential;however,the former was slightly better than the latter for radioactive *** average,the obtained spectroscopic factors(SFs)using both microscopic and phenomenological potentials were similar when the incident energies were below approxi-mately 120 ***,their difference tended to increase at higher incident energies,which was particularly apparent for the doubly magic target nucleus 40Ca.

关键词： Microscopic optical model potential (p,d)transfer Spectroscopic factors

Development and application of the new BPM system data processing program at Hefei light source

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Nuclear Science and Techniques 2012年第5期23卷 261-266页

作者： MA Tianji YANG Yongliang SUN Baogen ZOU Junying lu ping ZHOU Zeran xu Hongliang NSRL School of Nuclear Science and Technology University of Science and Technology of China Hefei 230029 China

A data processing program has been applied for the new beam position monitor (BPM) system of the storage ring at Hefei Light Source (HLS). The new BPM system in the upgrade project will be equipped with Libera Brilliance BPM processors to replace the old Bergoz MX-BPM processors. The embedded Linux system on Libera has completed some important work, including instrument status check,data acquisition, position calculation, EPICS IOC data release,and so on. A new EPICS record type has been developed to recalculate the beam position with log-ratio method. The property of the new position data was analyzed in the time and frequency domain. The results show that the rms value of beam position measurement resolution can be up to submicron. Preliminary studies have been carried out on the measurement of the tune and the beam lifetime with this new BPM system.

关键词：数据处理程序 PM系统合肥光源嵌入式Linux系统 EPICS 应用开发位置数据

Doping engineering of iron oxide nanoparticles towards high performance and biocompatible T_(1)-weighted MRI contrast agents

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Rare Metals 2024年第1期43卷 298-308页

作者： xue xu ping-Li Dong Yu-Yun Chai Run Yang Zhen-Hui Ma Chi-Chong lu Department of Chemistry College of Chemistry and Materials EngineeringBeijing Technology and Business UniversityBeijing 100048China Department of Physics Beijing Technology and Business UniversityBeijing 100048China

Extremely small-sized iron oxide nanoparticles(IONPs) are of great interest in magnetic resonance imaging(MRI) due to their biosafety as an alternative to clinical gadolinium(Ⅲ) complexes-based contrast *** when the particle size is less than 10 nm,it has strong diffusion ability and deep penetration distance in tumor *** doping can significantly enhance the T_(1)contrast effect of nanoparticles by regulating the surface exposed ***,the nucleation and growth processes of multi-component synthesis systems are complex and difficult to be accurately controlled,leading to great challenges in the synthesis of ultra-small-sized nanoparticles with different components and ***,extremely smallsized superparamagnetic gadolinium-doped iron oxide nanoparticles(GdIONPs,Gd_(x)Fe_(3-x)O_(4) NPs) with adjustable doping amount and controllable size in the range of 3.5-7.5 nm were synthesized by thermal ***,as-synthesized GdIONPs were surface modified with a highly water-soluble and biocompatible carboxyl-polyethylene glycol-phosphoric acid ligand with high binding ***_(0.65)Fe_(2.35)O_(4) NPs exhibited very high r_(1) relaxivity of 10.6 mmol^(-1)·L·s^(-1) in terms of all metal concentrations and 49.0 mmol^(-1)·L·s^(-1) in terms of gadolinium alone,respectively,3 and 14 times higher than clinical T_(1) contrast agents(Gd-DTPA).GdIONPs can continuously obtain high resolution images of blood vessels,and can be used as an efficient and multifunctional contrast agent for MR T_(1)*** stable and efficient doping strategy provides an easy and effective method to individually optimize the magnetic properties of complex oxides and their relaxation effects for a variety of biomedical applications.

关键词： Iron oxide nanoparticles Small size Magnetic resonance imaging Substitutional doping Gd dopant