检索结果-南通市图书馆

Structured backward error for palindromic polynomial eigenvalue problems~ II:Approximate eigentriplets

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Mathematics in China 2018年第6期13卷 1397-1426页

作者： Changli liU ren-cang li School of Mathematics Sichuan UniversityChengdu 610065China Department of Mathematics University of Texas at ArlingtonArlingtonTX 76019USA

A detailed structured backward error analysis for four kinds of palindromic polynomial eigenvalue problems (PPEPs) $$P(\lambda ) \equiv (\sum\limits_{\ell = 0}^d {{A_\ell }{\lambda ^\ell }} )x = 0,{A_{d - \ell }} = \varepsilon A_\ell ^*,\ell = 0,1...,\left\lfloor {\frac{d}{2}} \right\rfloor,$$ for an approximate eigentriplet is performed, where * is one of the two actions: transpose and conjugate transpose, and ε ∈ {±1} The analysis is concerned with estimating the smallest perturbation to P(λ); while preserving the respective palindromic structure, such that the given approximate eigentriplet is an exact eigentriplet of the perturbed PPEP. Previously, R. li, W. lin, and C. Wang [Numer. Math., 2010, 116(1): 95[122] had only considered the case of an approximate eigenpair for PPEP but commented that attempt for an approximate eigentriplet was unsuccessful. Indeed, the latter case is much more complicated. We provide computable upper bounds for the structured backward errors. Our main results in this paper are several informative and very sharp upper bounds that are capable of revealing distinctive features of PPEP from general polynomial eigenvalue problems (PEPs). In particular, they reveal the critical cases in which there is no structured backward perturbation such that the given approximate eigentriplet becomes an exact one of any perturbed PPEP, unless further additional conditions are imposed. These critical cases turn out to the same as those from the earlier studies on an approximate eigenpair.

关键词： Palindromic polynomial eigenvalue problem (PPEP) eigentriplet structured backward error error bound

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Mathematics and Statistics 2014年第2期2卷 139-153页

作者： ren-cang li Qiang Ye Department of Mathematics University of Texas at ArlingtonP.O.Box 19408ArlingtonTX 76019-0408USA Department of Mathematics University of KentuckyLexingtonKY 40506USA

We present simultaneous reduction algorithms for two(nonsymmetric)matrices A and B to upper Hessenberg and lower Hessenberg forms,*** is through the simultaneous similarity reduction and the other is through a Lanczos–Arnoldi-type *** algorithm that uses the Lanczos–Arnoldi-type iteration can be considered as a generalization of both the nonsymmetric Lanczos algorithm and the standard Arnoldi *** shall also apply our reduction to construct a model reduction for certain kind second-order single-input single-output *** is proved that the model reduction has the desirable moment matching property.

关键词： Simultaneous reductions Lanczos–Arnoldi iteration Krylov subspace method Model reduction

Nearly optimal stochastic approximation for online principal subspace estimation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Mathematics 2023年第5期66卷 1087-1122页

作者： Xin liang Zhen-Chen Guo li Wang ren-cang li Wen-Wei lin Yau Mathematical Sciences Center Tsinghua UniversityBeijing 100084China Yanqi Lake Beijing Institute of Mathematical Sciences and Applications Beijing 101408China Department of Mathematics Nanjing UniversityNanjing 210093China Department of Mathematics University of Texas at ArlingtonArlingtonTX 76019USA Department of Mathematics Hong Kong Baptist UniversityHong KongChina Nanjing Center for Applied Mathematics Nanjing 211135China Department of Applied Mathematics Yang Ming Chiao Tung UniversityHsinchu 300China

Principal component analysis(PCA) has been widely used in analyzing high-dimensional data. It converts a set of observed data points of possibly correlated variables into a set of linearly uncorrelated variables via an orthogonal transformation. To handle streaming data and reduce the complexities of PCA,(subspace)online PCA iterations were proposed to iteratively update the orthogonal transformation by taking one observed data point at a time. Existing works on the convergence of(subspace) online PCA iterations mostly focus on the case where the samples are almost surely uniformly bounded. In this paper, we analyze the convergence of a subspace online PCA iteration under more practical assumptions and obtain a nearly optimal finite-sample error bound. Our convergence rate almost matches the minimax information lower bound. We prove that the convergence is nearly global in the sense that the subspace online PCA iteration is convergent with high probability for random initial guesses. This work also leads to a simpler proof of the recent work on analyzing online PCA for the first principal component only.

关键词： principal component analysis principal component subspace stochastic approximation high-dimensional data online algorithm nite-sample analysis

同方期刊数据库

Iron-handling solute carrier SLC22A17 as a blood-brain barrier target after stroke

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第11期20卷 3207-3208页

作者： Xueqi ren Wenlu li Key Laboratory of Neuropharmacology and Translational Medicine of Zhejiang Province School of Pharmaceutical SciencesZhejiang Chinese Medical UniversityHangzhouZhejiang ProvinceChina Neuroprotection Research Laboratories Departments of Radiology and NeurologyMassachusetts General HospitalHarvard Medical SchoolBostonMAUSA

The pathophysiology of ischemic stroke is complex and multifactorial,involving various forms of cell death such as apoptosis,autophagy,and necrosis.A recent study suggests that oxidative and inflammatory stress can induce ferroptosis,a specialized form of cell death characterized by the accumulation of lipid peroxides dependent on intracellular iron overload(li and Jia,2023).

关键词： death specialized barrier

Tailoring light–Matter Interactions in Overcoupled Resonator for Biomolecule Recognition and Detection

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2025年第1期17卷 262-280页

作者： Dongxiao li Hong Zhou Zhihao ren Cheng Xu Chengkuo Lee Department of Electrical and Computer Engineering National University of SingaporeSingapore 117583Singapore Center for Intelligent Sensors and MEMS(CISM) National University of SingaporeSingapore 117608Singapore

Plasmonic nanoantennas provide unique opportunities for precise control of light–matter coupling in surface-enhanced infrared absorption(SEIRA)spectroscopy,but most of the resonant systems realized so far suffer from the obstacles of low sensitivity,narrow bandwidth,and asymmetric Fano resonance ***,we demonstrated an overcoupled resonator with a high plasmon-molecule coupling coefficient(μ)(OC-Hμresonator)by precisely controlling the radiation loss channel,the resonator-oscillator coupling channel,and the frequency detuning *** observed a strong dependence of the sensing performance on the coupling state,and demonstrated that OC-Hμresonator has excellent sensing properties of ultra-sensitive(7.25%nm^(−1)),ultra-broadband(3–10μm),and immune asymmetric Fano *** characteristics represent a breakthrough in SEIRA technology and lay the foundation for specific recognition of biomolecules,trace detection,and protein secondary structure analysis using a single array(array size is 100×100μm^(2)).In addition,with the assistance of machine learning,mixture classification,concentration prediction and spectral reconstruction were achieved with the highest accuracy of 100%.Finally,we demonstrated the potential of OC-Hμresonator for SARS-CoV-2 *** findings will promote the wider application of SEIRA technology,while providing new ideas for other enhanced spectroscopy technologies,quantum photonics and studying light–matter interactions.

关键词： Plasmonic nanoantennas light-matter interaction Surface-enhanced infrared absorption Overcoupled Biosensing

Transforming growth factor-beta 1 enhances discharge activity of cortical neurons

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第2期20卷 548-556页

作者： Zhihui ren Tian li Xueer liu Zelin Zhang Xiaoxuan Chen Weiqiang Chen Kangsheng li Jiangtao Sheng Department of Microbiology and Immunology Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular ImmunopathologyShantou University Medical CollegeShantouGuangdong ProvinceChina Department of Neurosurgery First Affiliated Hospital of Shantou University Medical CollegeShantouGuangdong ProvinceChina

Transforming growth factor-beta 1(TGF-β1)has been extensively studied for its pleiotropic effects on central nervous system *** neuroprotective or neurotoxic effects of TGF-β1 in specific brain areas may depend on the pathological process and cell types ***-gated sodium channels(VGSCs)are essential ion channels for the generation of action potentials in neurons,and are involved in various neuroexcitation-related ***,the effects of TGF-β1 on the functional properties of VGSCs and firing properties in cortical neurons remain *** this study,we investigated the effects of TGF-β1 on VGSC function and firing properties in primary cortical neurons from *** found that TGF-β1 increased VGSC current density in a dose-and time-dependent manner,which was attributable to the upregulation of Nav1.3 *** VGSC current density and Nav1.3 expression were significantly abolished by preincubation with inhibitors of mitogen-activated protein kinase kinase(PD98059),p38 mitogen-activated protein kinase(SB203580),and Jun NH2-terminal kinase 1/2 inhibitor(SP600125).Interestingly,TGF-β1 significantly increased the firing threshold of action potentials but did not change their firing rate in cortical *** findings suggest that TGF-β1 can increase Nav1.3 expression through activation of the ERK1/2-JNK-MAPK pathway,which leads to a decrease in the firing threshold of action potentials in cortical neurons under pathological ***,this contributes to the occurrence and progression of neuroexcitatory-related diseases of the central nervous system.

关键词： central nervous system cortical neurons ERK firing properties JNK Nav1.3 p38 transforming growth factor-beta 1 traumatic brain injury voltage-gated sodium currents

Induced pluripotent stem cell-related approaches to generate dopaminergic neurons for Parkinson's disease

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第11期20卷 3193-3206页

作者： ling-Xiao Yi Hui ren Woon Genevieve Saw li Zeng Eng King Tan Zhi Dong Zhou National Neuroscience Institute Singapore Nanyang Technology University Singapore Department of Neurology Singapore General HospitalSingapore Signature Research Program in Neuroscience and Behavioral Disorders Duke-NUS Medical SchoolSingapore

The progressive loss of dopaminergic neurons in affected patient brains is one of the pathological features of Parkinson's disease,the second most common human neurodegenerative *** the detailed pathogenesis accounting for dopaminergic neuron degeneration in Parkinson's disease is still unclear,the advancement of stem cell approaches has shown promise for Parkinson's disease research and *** induced pluripotent stem cells have been commonly used to generate dopaminergic neurons,which has provided valuable insights to improve our understanding of Parkinson's disease pathogenesis and contributed to anti-Parkinson's disease *** current review discusses the practical approaches and potential applications of induced pluripotent stem cell techniques for generating and differentiating dopaminergic neurons from induced pluripotent stem *** benefits of induced pluripotent stem cell-based research are *** dopaminergic neuron differentiation protocols from induced pluripotent stem cells are *** emerging three-dimension-based brain organoid models compared with conventional two-dimensional cell culture are ***,limitations,challenges,and future directions of induced pluripotent stem cell–based approaches are analyzed and proposed,which will be significant to the future application of induced pluripotent stem cell-related techniques for Parkinson's disease.

关键词： dopaminergic neurons induced pluripotent stem cells Parkinson's disease stem cell approaches

Early identification of stroke through deep learning with multi-modal human speech and movement data

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第1期20卷 234-241页

作者： Zijun Ou Haitao Wang Bin Zhang Haobang liang Bei Hu Longlong ren Yanjuan liu Yuhu Zhang Chengbo Dai Hejun Wu Weifeng li Xin li School of Computer Science and Engineering Sun Yat-sen UniversityGuangzhouGuangdong ProvinceChina Department of Neurology Guangdong Neuroscience InstituteGuangdong Provincial People’s Hospital(Guangdong Academy of Medical Sciences)Southern Medical UniversityGuangzhouGuangdong ProvinceChina Department of Emergency Medicine Guangdong Provincial People’s Hospital(Guangdong Academy of Medical Sciences)Southern Medical UniversityGuangzhouGuangdong ProvinceChina

Early identification and treatment of stroke can greatly improve patient outcomes and quality of *** clinical tests such as the Cincinnati Pre-hospital Stroke Scale(CPSS)and the Face Arm Speech Test(FAST)are commonly used for stroke screening,accurate administration is dependent on specialized *** this study,we proposed a novel multimodal deep learning approach,based on the FAST,for assessing suspected stroke patients exhibiting symptoms such as limb weakness,facial paresis,and speech disorders in acute *** collected a dataset comprising videos and audio recordings of emergency room patients performing designated limb movements,facial expressions,and speech tests based on the *** compared the constructed deep learning model,which was designed to process multi-modal datasets,with six prior models that achieved good action classification performance,including the I3D,SlowFast,X3D,TPN,TimeSformer,and *** found that the findings of our deep learning model had a higher clinical value compared with the other ***,the multi-modal model outperformed its single-module variants,highlighting the benefit of utilizing multiple types of patient data,such as action videos and speech *** results indicate that a multi-modal deep learning model combined with the FAST could greatly improve the accuracy and sensitivity of early stroke identification of stroke,thus providing a practical and powerful tool for assessing stroke patients in an emergency clinical setting.

关键词： artificial intelligence deep learning diagnosis early detection FAST screening stroke

Synthesis and characterization of li_4Ti_5O_(12) via a hydrolysis process from TiCl_4 aqueous solution

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2014年第4期33卷 459-465页

作者： Xuan-Yu Wang Yun-Jiao li cang Xu Long Kong lin li School of Metallurgical Science and Engineering Central South University

Spinel-type lithium and titanium composite oxide li4TisO12 was successfully synthesized via a novel hydrolysis method followed by calcination using titanium tetrachloride （TIC14） and lithium hydroxide （liOH.H2O） as raw materials. Three major factors, including liOH con- centration, liOH dosage, and hydrolysis temperature were studied for optimizing the synthetic conditions to obtain a phase-pure li4Ti5012. The physical and electrochemical properties of samples were characterized by X-ray dif- fraction （XRD）, thermogravimetric analysis （TGA）, fourier transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, and constant current discharge-charge test. The FT-IR results indicate the presence of [TiO6] octahedra. The SEM images show that the li4Ti5O12 pre- cursor obtained is an amorphous solid with an irregular and rough morphology. It is revealed that the phase-pure spinel li4Ti5O12 powders with well crystallization and regular morphology can be obtained by calcining the precursor at 800 ℃ for 6 h. The constant current discharge-charge tests indicate that the li4TisO12 material delivers an excellent cycling ability, maintaining 93.8 % of its initial specific capacity after 60 cycles at a current density of 0.5C.

关键词： lithium ion battery Titanium tetrachloride li4Ti5O12 Synthesis Hydrolysis method