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Comparison between the ring current energy injection and decay under southward and northward IMF Bz conditions during geomagnetic storms

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Science China(Technological Sciences) 2012年第10期55卷 2769-2777页

作者： SHI xiaofei ZONG QiuGang WANG YongFu Institute of Space Physics and Applied Technology Peking UniversityBeijing 100871China

The geomagnetic storm is one of the most important geomagnetic disturbance phenomena in the *** studies assume that input of solar wind energy into the Earth's ring current only occurs when IMF Bz in GSM coordinates is southward;the ring current energy injection and decay under northward IMF Bz are not well understood and still need further *** this paper,by using the large amount of data from the year 1964 to 2010,we use the empirical phase space analysis method to study the ring current energy injection and decay under northward IMF Bz and compare the results with those under southward IMF Bz *** have found that the largest injection Q under northward IMF Bz condition is only 7% of the largest injection under southward IMF Bz,implying that there is a very limit energy injected into the ring current region when IMF Bz is *** decay time decreases as VBz increases and shows a good linear trend for southward IMF Bz;while for the northward IMF Bz,there is not a clear relation between τ varies and *** taken τ as a function of injection Q instead of VBz,we have obtained the empirical relation of τ with Q for northward and southward IMF Bz conditions:the two categories are further combined together and the empirical relation τ= e(2.6 0.039 Q) is ***,the pressure-corrected Dst formula Dst=Dst b P+c is derived for both southward and northward IMF Bz conditions,where the coefficients b and c are 6.9/10.4 and 10.0/15.2 when IMF Bz is southward and northward *** statistical results on between the different geomagnetic indices(Dst,Kp,AE) and IMF Bz are also obtained.

关键词： pressure-corrected Dst index decay time energy injection

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The Role of Initial Cloud Condensation Nuclei Concentration in Hail Using the WRF NSSL 2-moment Microphysics Scheme

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Advances in Atmospheric Sciences 2017年第9期34卷 1106-1120页

作者： xiaofei LI Qinghong ZHANG Huiwen XUE Department of Atmospheric and Oceanic Sciences School of PhysicsPeking University

The effects of the initial cloud condensation nuclei （CCN） concentrations （100-3000 mg-1） on hail properties were investigated in an idealized non-severe hail storm experiment using the Weather Research and Forecasting （WRF） model, with the National Severe Storms Laboratory 2-moment microphysics scheme. The initial CCN concentration （CCNC） had obvious non-monotonic effects on the mixing ratio, number concentrations, and radius of hail, both in clouds and at the surface, with a CCNC threshold between 300 and 500 mg-1. An increasing CCNC is conducive （suppressive） to the amount of surface hail precipitation below （above） the CCNC threshold. The non-monotonic effects were due to both the thermodynamics and microphysics. Below the CCNC threshold, the mixing ratios with the increasing CCNC, resulting in more latent heat released of cloud droplets and ice crystals increased dramatically from condensation and frozen between 4 and 8 km and intensified updraft volume. The extent of the riming process, which is the primary process for hail production, increased dramatically. Above the CCNC threshold, the mixing ratio of cloud droplets and ice crystals increased continuously, but the maximum updraft volume was weakened because of reduced frozen latent heating at low level. The smaller ice crystals reduced the formation of hail and smaller clouds, with decreased rain water reducing riming efficiency so that graupel and hail also decreased with increasing CCNC, which is unfavorable for hail growth.

关键词： CCN hail microphysics thermodynamics threshold

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Deciphering the cellular heterogeneity of the insect brainwith single-cell RNA sequencing

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Insect Science 2024年第2期31卷 314-327页

作者： xiaofei Wang Yifan Zhai Hao Zheng Institute of Plant Protection Shandong Academy of Agricultural SciencesJinanChina College of Food Science and Nutritional En-gineering China Agricultural UniversityBeijingChina Key Laboratory of Natural Enemies Insects Ministry of Agriculture and RuralAffairsJinanChina Shandong Provincial Engineering Technology Research Center on Biocontrol of Crops Diseases and In-sectPests JinanChina

Insects show highly complicated adaptive and sophisticated behaviors, includ-ing spatial orientation skills, learning ability, and social interaction. These behaviors arecontrolled by the insect brain, the central part of the nervous system. The tiny insect brainconsists of millions of highly differentiated and interconnected cells forming a complexnetwork. Decades of research has gone into an understanding of which parts of the insectbrain possess particular behaviors, but exactly how they modulate these functional conse-quences needs to be clarified. Detailed description of the brain and behavior is required todecipher the complexity of cell types, as well as their connectivity and function. Single-cell RNA-sequencing (scRNA-seq) has emerged recently as a breakthrough technologyto understand the transcriptome at cellular resolution. With scRNA-seq, it is possible touncover the cellular heterogeneity of brain cells and elucidate their specific functions andstate. In this review, we first review the basic structure of insect brains and the links toinsect behaviors mainly focusing on learning and memory. Then the scRNA applicationson insect brains are introduced by representative studies. Single-cell RNA-seq has allowedresearchers to classify cell subpopulations within different insect brain regions, pinpointsingle-cell developmental trajectories, and identify gene regulatory networks. These devel-opments empower the advances in neuroscience and shed light on the intricate problemsin understanding insect brain functions and behaviors.

关键词： behavior brain cell type insect single-cell RNA sequencing

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The design and analysis of unequal error protection fountain coding for multiple source networks over binary erasure channels

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Science China(Information Sciences) 2014年第8期57卷 9-17页

作者： SHAO HanQin XU DaZhuan ZHANG xiaofei College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics

A novel network model of multiple source fountain coding is developed and a novel class of generic multiple source fountain codes with unequal error protection(UEP)property is *** And–Or tree analysis technique is generalized to analyze the asymptotic performance of the proposed codes and a joint optimization method employing both linear and nonlinear programs is developed to optimize the degree ***,we propose three basic methods to achieve UEP property and the performance of each method is *** employ these analytical results and optimization method to design and discuss several UEP codes with two and four sources for different application *** results verify that the proposed codes can be applied to the networks with any number of sources and can provide strong UEP property in various ways based on the proposed three basic methods.

关键词： asymptotic analysis fountain codes binary erasure channels network coding linear program nonlinear program unequal error protection multiple source networks

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Structural damage assessment using improved Dempster-Shafer data fusion algorithm

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Earthquake Engineering and Engineering Vibration 2019年第2期18卷 395-408页

作者： Ding Yijie Yao xiaofei Wang Sheliang Zhao Xindong School of Civil Engineering Xi'an Univ.of Arch.& Tech. CCCC First Highway Consultants Co. Ltd.

As an efficient tool in handling uncertain issues, Dempster-Shafer evidence theory has been increasingly used in structural health monitoring and damage detection. In applications, however, Dempster-Shafer evidence theory sometimes leads to counter-intuitive results. In this study, a new fusion algorithm of evidence theory is put forward to address various counter-intuitive problems and manage the reliability difference of the evidence. The proposed algorithm comprises the following aspects:(1) Dempster's combination rule is generalized by introducing the concept of evidence ullage. The new rule allows classical Dempster's rule and can resolve counter-intuitive problems cause by evidence conflict and evidence compatibility;(2) a reliability assessing method based on a priori and posterior knowledge is proposed. Compared with conventional reliability assessment, the proposed method can reflect the actual evidence reliabilities and can efficiently reduce decision risk. Numerical examples confirm the validity and utility of the proposed algorithm. In addition, an experimental investigation on a spatial truss structure is carried out to illustrate the identified ability of the proposed approach. The results indicate that the fusion algorithm has no strict request on the accuracy and consistency of evidence sources and can efficiently enhance diagnostic accuracy.

关键词： Dempster-Shafer evidence theory damage detection evidence confl ict evidence reliability spatial truss structure

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What group 2 innate lymphoid cells tell themselves:autocrine signals play essential roles in mucosal immunity

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Signal Transduction and Targeted Therapy 2021年第8期6卷 2264-2265页

作者： Yang Zhao Wenxian Guan xiaofei Shen State Key Laboratory of Membrane Biology Institute of ZoologyChinese Academy of SciencesBeijingChina Department of General Surgery Nanjing Drum Tower HospitalAffiliated Hospital of Nanjing University Medical SchoolNanjingJiangsu ProvinceChina

Recently,two article papers(Chu et al.1 and Roberts et al.2)were published describing that autocrine regulation mediated by the choline acetyltransferase(ChAT)-acetylcholine(ACh)is critical for optimal Group 2 innate ... 详细信息

关键词： immunity lymphoid

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A Real-Valued 2D DOA Estimation Algorithm of Noncircular Signal via Euler Transformation and Rotational Invariance Property

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第3期35卷 437-448页

作者： Chen Xueqiang Wang Chenghua Zhang xiaofei Key Laboratory of Radar Imaging and Microwave Photonics Nanjing University of Aeronautics and Astronautics College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics

The problem of two-dimensional(2 D)direction of arrival(DOA)estimation for double parallel uniform linear arrays is investigated in this paper.A real-valued DOA estimation algorithm of noncircular(NC)signal is proposed,which combines the Euler transformation and rotational invariance(RI)property between *** this work,the effective array aperture is doubled by exploiting the noncircularity of *** complex arithmetic is converted to real arithmetic via Euler *** main contribution of this work is not only extending the NC-Euler-ESPRIT algorithm from uniform linear array to double parallel uniform linear arrays,but also constructing a new 2 Drotational invariance property between subarrays,which is more complex than that in NCEuler-ESPRIT *** proposed 2 DNC-Euler-RI algorithm has much lower computational complexity than2 DNC-ESPRIT *** proposed algorithm has better angle estimation performance than 2 DESPRIT algorithm and 2 D NC-PM algorithm for double parallel uniform linear arrays,and is very close to that of 2 D NC-ESPRIT *** elevation angles and azimuth angles can be obtained with automatically *** proposed algorithm can estimate up to 2(M-1)sources,which is two times that of 2 D ESPRIT ***-Rao bound(CRB)of noncircular signal is derived for the proposed *** complexity comparison is also ***,simulation results are presented to illustrate the effectiveness and usefulness of the proposed algorithm.

关键词： array signal processing direction of arrival(DOA)estimation noncircular signal Euler transformation

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Nongeneric Bifurcations Near a Nontransversal Heterodimensional Cycle

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Chinese Annals of Mathematics,Series B 2018年第1期39卷 111-128页

作者： Xingbo LIU xiaofei WANG Ting WANG Department of Mathematics East China Normal University School of Mathematics and Physics Handan College

In this paper bifurcations of heterodimensional cycles with highly degenerate conditions are studied in three dimensional vector fields,where a nontransversal intersection between the two-dimensional manifolds of the saddle equilibria *** setting up local moving frame systems in some tubular neighborhood of unperturbed heterodimensional cycles,the authors construct a Poincar′e return map under the nongeneric conditions and further obtain the bifurcation *** means of the bifurcation equations,the authors show that different bifurcation surfaces exhibit variety and complexity of the bifurcation of degenerate heterodimensional ***,an example is given to show the existence of a nontransversal heterodimensional cycle with one orbit flip in three dimensional system.

关键词： Local moving frame Nontransversal heterodimensional cycle Orbit flip Poincare return map

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A TRUST-REGION-BASED ALTERNATING LEAST-SQUARES ALGORITHM FOR TENSOR DECOMPOSITIONS

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Journal of Computational Mathematics 2018年第3期36卷 351-373页

作者： Fan Jiang Deren Han xiaofei Zhang Jiangsu Key Laboratory of NSLSCS School of Mathematical Sciences Nanjing Normal University Nanjing 210023 China Information Technology Department Chinascope Nanjing 210023 China

Tensor canonical decomposition （shorted as CANDECOMP/PARAFAC or CP） decomposes a tensor as a sum of rank-one tensors, which finds numerous applications in signal processing, hypergraph analysis, data analysis, etc. Alternating least-squares （ALS） is one of the most popular numerical algorithms for solving it. While there have been lots of efforts for enhancing its efficiency, in general its convergence can not been guaranteed. In this paper, we cooperate the ALS and the trust-region technique from optimization field to generate a trust-region-based alternating least-squares （TRALS） method for CP. Under mild assumptions, we prove that the whole iterative sequence generated by TRALS converges to a stationary point of CP. This thus provides a reasonable way to alleviate the swamps, the notorious phenomena of ALS that slow down the speed of the algorithm. Moreover, the trust region itself, in contrast to the regularization alternating least-squares （RALS） method, provides a self-adaptive way in choosing the parameter, which is essential for the efficiency of the algorithm. Our theoretical result is thus stronger than that of RALS in [26], which only proved the cluster point of the iterative sequence generated by RALS is a stationary point. In order to accelerate the new algorithm, we adopt an extrapolation scheme. We apply our algorithm to the amino acid fluorescence data decomposition from chemometrics, BCM decomposition and rank-（Lr, Lr, 1） decomposition arising from signal processing, and compare it with ALS and RALS. The numerical results show that TRALS is superior to ALS and RALS, both from the number of iterations and CPU time perspectives.

关键词： Tensor decompositions Trust region method Alternating least-squares Ex-trapolation scheme Global convergence Regularization.

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Speech Enhancement Using Multi-channel Post-Filtering with Modified Signal Presence Probability in Reverberant Environment

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Chinese Journal of Electronics 2016年第3期25卷 512-519页

作者： WANG xiaofei GUO Yanmeng FU Qiang YAN Yonghong Key Laboratory of Speech Acoustics and Content Understanding Institute of AcousticsChinese Academy of Sciences

In this paper, a multi-channel post-filtering approach in reverberant environment based on detection and estimation scheme is presented. A modified Signal presence probability(SPP), which is in consideration of reverberation, is proposed with a novel estimator Direct-toreverberate ratio(DRR) to adapt to distant-talking *** is known a key estimator to instruct the updating of transient noise or residual directional interference and form gain function in the time-frequency domain, consequently a new desired signal detection scheme is proposed to improve its accuracy. Appropriate spectral enhancement technique is applied to the noisy speech signal taking advantage of the modified SPP estimator. The proposed multi-channel post-filtering is tested in different nonstationary noisy and reverberant environments. Experimental results show that it achieves considerable improvement on signal preservation of the desired speech with more noise reduction over the comparative algorithms.

关键词： Speech enhancement Multi-channel post-filtering Reverberation robust Signal detection

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