检索结果-南通市图书馆

Research on the readout noise suppression method for digital correlated double sampling

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第1期21卷 127-135页

作者： Wei duan Qian Song Ming-zhi Wei Zhao-Wang Zhao Wei Wang Yu-heng Zhang zhi-Wei Feng National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China CAS Key Laboratory of Optical Astronomy National Astronomical ObservatoriesBeijing 100101China

As the areas of CCD detectors and CCD mosaics have become larger and larger,the number of readout channels in astronomical cameras has increased accordingly to keep the image readout time within an acceptable *** the large area cameras or the mosaic cameras,the analog Correlated Double Sampling(aCDS)circuit used in traditional astronomical cameras for suppressing readout noise is difficult to integrate into the camera controllers within the constraints of the space and energy ***,digital CDS(dCDS)technology has been developed to solve this problem,which also offers novel analysis and noise suppression *** this study,a mathematical model is presented to conveniently analyze the frequency characteristic of a dCDS circuit,which is then simulated by a numerical method for investigating the noise suppression capability with different sampling ***,using this model,the extreme point with lowest readout noise can be predicted for a certain dCDS model;and for a specific CCD readout frequency,readout noise can be suppressed by selecting the proper dCDS model.A testing system is then constructed for validating the efficiency of the proposed method.

关键词： instrumentation:detectors methods:analytical methods:numerical

S-wave velocity of the crust around Tianshan Mountains inverted from seismic ambient noise tomography

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2010年第31期55卷 3590-3598页

作者： GUO zhi GAO Xing WANG WeiMin LI GuiLin duan ZongQi SHI heng Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

We process ambient noise data from seismic stations deployed in central Asia to determine the crustal shear wave velocity structure beneath the Tianshan Mountians and surrounding *** 748 inter-station Rayleigh wave empirical Green's functions have been recovered to estimate the phase velocity dispersions over periods from 6 to 50 s using the image transformation *** show that for short periods(6-20 s),the distribution of Rayleigh wave phase velocities is generally consistent with surface geology,with high velocities corresponding to mountain ranges and low velocities to sedimentary *** two profiles,which trend from NE-SW and NW-SE,the shear wave velocity shows a pair of high velocity anomalies dipping in opposite directions beneath the Tianshan *** shallow depths,those high velocity anomalies roughly correlate with areas where the mountain front and the surrounding basin are *** profiles also show a narrow zone beneath the Tianshan Mountains,which may represent a route for the upwelling from upper *** observations suggest that the underthrusting of the Tarim Basin and Kazakh Shield combine with the weakness of the crust,which is heated by the upwelling from upper mantle,may play an important role on the reactivation of the Tianshan Mountains associated with the India-Eurasia collision.

关键词：天山山地 S波速度环境噪声地震断层地壳周边地区沉积盆地速度异常

P-symmetric Subharmonic Solutions for Nonlinear Hamiltonian Systems

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2024年第6期40卷 1388-1408页

作者： duan zhi ZHANG zhi Hao ZHAO School of Mathematical Sciences Nankai UniversityTianjin 300071P.R.China

In this paper,we prove that for each positive k≡1 mod m there exists a P-symmetric kmτ-periodic solution xk for asymptotically linear mτ-periodic Hamiltonian systems,which are nonautonomous and endowed with a *** the P-symmetric Hamiltonian function is semi-positive,one can prove,under a new iteration inequality of the Maslov-type P-index,that xk_(1) and xk_(2) are geometrically distinct for k_(1)/k_(2)≥(2n+1)m+1;and xk_(1),xk_(2) are geometrically distinct for k_(1)/k_(2)≥m+1 provided xk_(1) is non-degenerate.

关键词： P-symmetric subharmonic Hamiltonian systems Maslov-type index theory iteration inequality asymptotically linear

A fusion of least squares and empirical likelihood for regression models with a missing binary covariate

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2016年第10期59卷 2027-2036页

作者： duan XiaoGang WANG zhi Department of Statistics Beijing Normal UniversityBeijing 100875China

Multiply robust inference has attracted much attention recently in the context of missing response data. An estimation procedure is multiply robust, if it can incorporate information from multiple candidate models, and meanwhile the resulting estimator is consistent as long as one of the candidate models is correctly specified. This property is appealing, since it provides the user a flexible modeling strategy with better protection against model misspecification. We explore this attractive property for the regression models with a binary covariate that is missing at random. We start from a reformulation of the celebrated augmented inverse probability weighted estimating equation, and based on this reformulation, we propose a novel combination of the least squares and empirical likelihood to separately handle each of the two types of multiple candidate models,one for the missing variable regression and the other for the missingness mechanism. Due to the separation, all the working models are fused concisely and effectively. The asymptotic normality of our estimator is established through the theory of estimating function with plugged-in nuisance parameter estimates. The finite-sample performance of our procedure is illustrated both through the simulation studies and the analysis of a dementia data collected by the national Alzheimer's coordinating center.

关键词： calibration covariate adjustment effect modification missing at random multiple robustness refitting

Using CMIP5 model outputs to investigate the initial errors that cause the “spring predictability barrier” for El Nio events

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2015年第5期58卷 685-696页

作者： ZHANG Jing duan WanSuo zhi XieFei Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science & Technology State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences

Most ocean-atmosphere coupled models have difficulty in predicting the E1 Nifio-Southern Oscillation （ENSO） when starting from the boreal spring season. However, the cause of this spring predictability barrier （SPB） phenomenon remains elusive. We investigated the spatial characteristics of optimal initial errors that cause a significant SPB for E1 Nifio events by using the monthly mean data of the pre-industrial （PI） control runs from several models in CMIP5 experiments. The results indicated that the SPB-related optimal initial errors often present an SST pattern with positive errors in the central-eastern equatorial Pa- cific, and a subsurface temperature pattern with positive errors in the upper layers of the eastern equatorial Pacific, and nega- tive errors in the lower layers of the western equatorial Pacific. The SPB-related optimal initial errors exhibit a typical La Ni- fia-like evolving mode, ultimately causing a large but negative prediction error of the Nifio-3.4 SST anomalies for El Nifio events. The negative prediction errors were found to originate from the lower layers of the western equatorial Pacific and then grow to be large in the eastern equatorial Pacific. It is therefore reasonable to suggest that the E1 Nifio predictions may be most sensitive to the initial errors of temperature in the subsurface layers of the western equatorial Pacific and the Nifio-3.4 region, thus possibly representing sensitive areas for adaptive observation. That is, if additional observations were to be preferentially deployed in these two regions, it might be possible to avoid large prediction errors for E1 Nifio and generate a better forecast than one based on additional observations targeted elsewhere. Moreover, we also confirmed that the SPB-related optimal initial errors bear a strong resemblance to the optimal precursory disturbance for E1 Nifio and La Nifia events. This indicated that im- provement of the observation network by additional observations in the ident

关键词： El Nino-Southern Oscillation spring predictability barrier optimal initial errors optimal precursory disturbance

Direct numerical simulation of hypersonic transition induced by an isolated cylindrical roughness element

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2014年第12期57卷 2330-2345页

作者： duan zhi Wei XIAO zhi Xiang FU Song School of Aerospace Tsinghua University

Hypersonic boundary layer transition induced by an isolated cylindrical roughness element is investigated using direct numerical simulation method based on a finite volume *** simulate the transition procedure by resolving the generation and evolvement of small-scale coherent structures,and capture the shock wave at the same time,high-order minimum dispersion and controllable dissipation scheme is validated and then *** results are compared with the available measurements in the quiet wind tunnel,such as the dominated frequency and root mean square of *** computational dominated frequency of 19.23 k Hz is very close to the experimental one,21 k ***,the disturbances of the roughness are mostly generated by the"jet"just before the roughness,and then they travel and develop downstream with the shear layer and vortex *** transition is mainly dominated by the instabilities of both the horseshoe vortex and the shear layer.

关键词： hypersonic boundarry layer transtion roughness

Development of a test strip based on DNA-functionalized gold nanoparticles for rapid detection of mercury(II) ions

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2012年第2期23卷 225-228页

作者： Jing duan zhi Yong Guo Faculty of Materials Science and Chemical Engineering Ningbo UniversityNingbo 315211China

A rapid,sensitive,selective and reliable strip assay based on DNA-functionalized gold nanoparticles for Hg^（2＋） detection has been developed,with a detection limit 5 nmol/*** measurement principle was based on thymine-Hg^（2＋）-thymine（T-Hg^（2＋）-T） coordination chemistry and streptavidin-biotin *** major advantages of this assay are that results can be read visually without any instrument in less than 10 min and that it does not require any sample pretreatment.

关键词： Mercury(Ⅱ) ion Test strip Gold nanoparticles DNA

Spatial Density Distributions and Correlations in a Quasi-one-Dimensional Polydisperse Granular Gas

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2009年第2期51卷 259-264页

作者： CHEN zhi-Yuan ZHANG duan-Ming School of Electronic and Information Engineering Xianning College Xianning 437100 China Department of Physics Huazhong University of Science and Technology Wuhan 430074 China

By Monte Carlo simulations, the effect of the dispersion of particle size distribution on the spatial density distributions and correlations of a quasi one-dimensional polydisperse granular gas with fractal size distribution is investigated in the same inelasticity. The dispersive degree of the particle size distribution can be measured by a fractal dimension dr, and the smooth particles are constrained to move along a circle of length L, colliding inelastically with each other and thermalized by a viscosity heat bath. When the typical relaxation time τ of the driving Brownian process is longer than the mean collision time To, the system can reach a nonequilibrium steady state. The average energy of the system decays exponentially with time towards a stable asymptotic value, and the energy relaxation time τB to the steady state becomes shorter with increasing values of df. In the steady state, the spatial density distribution becomes more clusterized as df increases, which can be quantitatively characterized by statistical entropy of the system. Furthermore, the spatial correlation functions of density and velocities are found to be a power-law form for small separation distance of particles, and both of the correlations become stronger with the increase of df. Also, tile density clusterization is explained from the correlations.

关键词： granular gas inelasticity fractal dimension df spatial density distributions spatial correlationsof density and velocities

Profile of Blow-up Solution to Hyperbolic System with Nonlocal Term

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2007年第6期23卷 1083-1094页

作者： zhi Wen duan Kwang Ik KIM Department of Mathematics Huazhong University of Science and Technology Wuhan 430074 P. R. China Department of Mathematics Pohang University of Science and Technology Pohang 790-784 Republic of Korea

This paper is concerned with a nonlocal hyperbolic system as follows utt = △u ＋（∫Ωvdx ）^p for x∈R^N,t〉0 ,utt = △u ＋（∫Ωvdx ）^q for x∈R^N,t〉0 ,u（x,0）=u0（x）,ut（x,0）=u01（x） for x∈R^N,u（x,0）=u0（x）,ut（x,0）=u01（x） for x∈R^N, where 1≤ N ≤3, p ≥1, q ≥ 1 and pq 〉 1. Here the initial values are compactly supported and Ω belong to R^N is a bounded open region. The blow-up curve, blow-up rate and profile of the solution are discussed.

关键词： hyperbolic system nonlocal term blow-up profile