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Generation of unsteady waves by concentrated disturbances in an inviscid fluid with an inertial surface

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Acta Mechanica Sinica 2008年第3期24卷 267-275页

作者： d.q.Lu S.q.dai Shanghai Institute of Applied Mathematics and Mechanics Shanghai University200072 ShanghaiChina Shanghai Key Laboratory of Mechanics in Energy and Environment Engineering 200072 ShanghaiChina

The surface waves generated by unsteady concentrated disturbances in an initially quiescent fluid of infinite depth with an inertial surface are analytically investigated for two- and three-dimensional cases. The fluid is assumed to be inviscid, incompressible and homogenous. The inertial surface represents the effect of a thin uniform distribution of non-interacting floating matter. Four types of unsteady concentrated disturbances and two kinds of initial values are considered, namely an instantaneous/oscillating mass source immersed in the fluid, an instantaneous/oscillating impulse on the surface, an initial impulse on the surface of the fluid, and an initial displacement of the surface. The linearized initial-boundary-value problem is formulated within the framework of potential flow. The solutions in integral form for the surface elevation are obtained by means of a joint Laplace-Fourier transform. The asymptotic representations of the wave motion for large time with a fixed distance- to-time ratio are derived by using the method of stationary phase. The effect of the presence of an inertial surface on the wave motion is analyzed. It is found that the wavelengths of the transient dispersive waves increase while those of the steady-state progressive waves decrease. All the wave amplitudes decrease in comparison with those of conventional free-surface waves. The explicit expressions for the freesurface gravity waves can readily be recovered by the present results as the inertial surface disappears.

关键词： Waves Inertial surface Concentrated disturbances Asymptotic representation

An RGB-d Camera Based Visual Positioning System for Assistive Navigation by a Robotic Navigation Aid

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IEEE/CAA Journal of Automatica Sinica 2021年第8期8卷 1389-1400页

作者： He Zhang Lingqiu Jin cang Ye The authors are with the department of Computer Science Virginia Commonwealth UniversityRichmondVA 23284 USA

There are about 253 million people with visual impairment *** of them use a white cane and/or a guide dog as the mobility tool for daily *** decades of efforts,electronic navigation aid that can replace white cane is still research in *** this paper,we propose an RGB-d camera based visual positioning system(VPS)for real-time localization of a robotic navigation aid(RNA)in an architectural floor plan for assistive *** core of the system is the combination of a new 6-dOF depth-enhanced visual-inertial odometry(dVIO)method and a particle filter localization(PFL)*** estimates RNA’s pose by using the data from an RGB-d camera and an inertial measurement unit(IMU).It extracts the floor plane from the camera’s depth data and tightly couples the floor plane,the visual features(with and without depth data),and the IMU’s inertial data in a graph optimization framework to estimate the device’s 6-dOF *** to the use of the floor plane and depth data from the RGB-d camera,dVIO has a better pose estimation accuracy than the conventional VIO *** reduce the accumulated pose error of dVIO for navigation in a large indoor space,we developed the PFL method to locate RNA in the floor *** leverages geometric information of the architectural CAd drawing of an indoor space to further reduce the error of the dVIO-estimated *** on VPS,an assistive navigation system is developed for the RNA prototype to assist a visually impaired person in navigating a large indoor *** results demonstrate that:1)dVIO method achieves better pose estimation accuracy than the state-of-the-art VIO method and performs real-time pose estimation(18 Hz pose update rate)on a UP Board computer;2)PFL reduces the dVIO-accrued pose error by 82.5%on average and allows for accurate wayfinding(endpoint position error≤45 cm)in large indoor spaces.

关键词： Assistive navigation pose estimation robotic navigation aid(RNA) simultaneous localization and mapping visual-inertial odometry visual positioning system(VPS)

Analytical Arbitrary-Wave Solutions of the deformed Hyperbolic Eckart Potential by the Nikiforov–Uvarov Method

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Chinese Physics Letters 2013年第11期30卷 10-13页

作者： ZHANG Min-cang Zhi-Zhi Literature Information Resources Center Shaanxi Normal UniversityXi'an 710062

The arbitrary l-wave solutions to the Schrödinger equation for the deformed hyperbolic Eckart potential is investigated analytically by using the Nikiforov–Uvarov *** centrifugal term is treated with the improved Greene and Aldrich approximation *** wave functions are expressed in terms of the Jacobi polynomial or the hypergeometric *** discrete spectrum is obtained and it is shown that the deformed hyperbolic Eckart potential is a shape-invariant potential and the bound state energy is independent of the deformation parameter q.

关键词： function method hyperbolic

Strongly One-Sided (b,c)-Inversesin Rings

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ALGEBRA COLLOqUIUM 2024年第4期31卷 549-558页

作者： Wu, cang Chen, Jianlong Southeast Univ Sch Math Nanjing 210096 Peoples R China

We give some new characterizations of strongly one-sided ( b,c ) -invertibility of elements in rings, and establish the relations between one-sided ( b,c ) -inverses and strongly one-sided ( b,c ) -inverses. When b=c , Kaplansky's theorem on the number of one-sided inverses is generalized to the case of strongly one-sided ( b,c ) -inverses. Moreover, we give some new characterizations of dedekind-finite rings from the viewpoint of ( b,c ) -finiteness, and thus answer a question in [L. Wang, d. Mosic, The one-sided inverse along two elements in rings, Linear Multilinear Algebra 69 (13) (2021) 2410-2422].

关键词： (b, c)-inverse strongly left (b, c)-inverse regularity (b, c)-finiteness dedekind-finite ring

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

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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

Elastoplastic homogenization of particulate composites complying with the Mohr–Coulomb criterion and undergoing isotropic loading

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Acta Mechanica Sinica 2015年第3期31卷 392-405页

作者： d.Yang q.C.He School of Mechanical Engineering Southwest Jiaotong University Université Paris-Est Laboratoire Modélisation et Simulation Multi Echelle UMR 8208 CNRS

This work aims at determining the overall response of a two-phase elastoplastic composite to isotropic loading. The composite under investigation consists of elastic particles embedded in an elastic perfectly plastic matrix governed by the Mohr-Coulomb yield criterion and a non-associated plastic flow rule. The composite sphere assemblage model is adopted, and closed-form estimates are derived for the effective elastoplastic properties of the composite either under tensile or compressive isotropic loading. In the case when elastic particles reduce to voids, the composite in question degenerates into a porous elastoplastic material. The results obtained in the present work are of interest, in particular, for soil mechanics.

关键词： Composite Porous medium. Elastoplasticity Mohr-Coulomb yield criterion Non-associated flow rule Homogenization

Effects of simulated on-fire processing conditions on the microstructure and mechanical performance of q345R steel

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International Journal of Minerals,Metallurgy and Materials 2016年第1期23卷 49-56页

作者： Yi-chao Peng Hao-hao Xu Mai-cang Zhang department of Materials Technology Zhejiang Energy Technology & Research Co.Ltd. department of Materials Science and Engineering University of Science and Technology Beijing

A series of simulated on-fire processing experiments on q345R steel plates was conducted, and the plates＇ Brinell hardness, ten- sile strength, and impact energy were tested. Microstructure morphologies were systematically analyzed using a scanning electron micro- scope with the aim of investigating the effect of the steel＇s microstructure on its performance. All examined performance parameters exhib- ited a substantial decrease in the cases of samples heat-treated at temperatures near 700℃. However, although the banded structure decreased with increasing treatment temperature and holding time, it had little effect on the performance decline in fact. Further analysis revealed that pearlite degeneration near 700℃, which was induced by the interaction of both subcritical annealing and conventional spherical annealing, was the primary reason for the degradation behavior. Consequently, some nonlinear mathematical models of different mechanical perform- ances were established to facilitate processing adjustments.

关键词： low alloy steels heat treatment mechanical properties microstructure nonlinear mathematical models

Acute and chronic excitotoxicity in ischemic stroke and late-onset Alzheimer's disease

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Neural Regeneration Research 2025年第7期20卷 1981-1988页

作者： Shan Ping Yu Emily Choi Michael qJiang Ling Wei department of Anesthesiology Emory University School of MedicineAtlantaGAUSA Center for Visual and Neurocognitive Rehabilitation Atlanta Veterans Affairs Medical CenterDecaturGAUSA

Stroke and Alzheimer's disease are common neurological disorders and often occur in the same *** comorbidity of the two neurological disorders represents a grave health threat to older *** review presents a brief background of the development of novel concepts and their clinical *** activity of glutamatergic N-methyl-d-aspartate receptors and N-methyl-d-aspartate receptor-mediated Ca^(2+)influx is critical for neuronal *** ischemic insult induces prompt and excessive glutamate release and drastic increases of intracellular Ca^(2+)mainly via N-methyl-d-aspartate receptors,particularly of those at the extrasynaptic *** Ca^(2+)-evoked neuronal cell death in the ischemic core is dominated by necrosis within a few hours and days known as acute ***,mild but sustained Ca^(2+)increases under neurodegenerative conditions such as in the distant penumbra of the ischemic brain and early stages of Alzheimer's disease are not immediately toxic,but gradually set off deteriorating Ca^(2+)-dependent signals and neuronal cell loss mostly because of activation of programmed cell death *** on the Ca^(2+)hypothesis of Alzheimer's disease and recent advances,this Ca^(2+)-activated“silent”degenerative excitotoxicity evolves from years to decades and is recognized as a unique slow and chronic *** N-methyl-d-aspartate receptor subunit GluN3A,primarily at the extrasynaptic site,serves as a gatekeeper for the N-methyl-d-aspartate receptor activity and is neuroprotective against both acute and chronic *** stroke and Alzheimer's disease,therefore,share an N-methyl-d-aspartate receptor-and Ca^(2+)-mediated mechanism,although with much different time *** is thus proposed that early interventions to control Ca^(2+)homeostasis at the preclinical stage are pivotal for individuals who are susceptible to sporadic late-onset Alzheimer's disease and Alzheimer's disease-related

关键词： Ca^(2+)hypothesis cognitive deficits hyperactivity late-onset Alzheimer's disease neurodegeneration N-methyl-d-aspartate receptors N-methyl-d-aspartate receptor subunits pathogenesis preventive treatment

EXPERIMENTS OF HYdROdYNAMICS ANd STABILITY OF IMMERSEd TUBE TUNNEL ON TRANSPORTATION ANd IMMERSING

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Journal of Hydrodynamics 2001年第2期13卷 121-126页

作者： Zhan, d.X. Wang, X.q. dept. of Naval Arch. and Ocean Eng. Wuhan Univ. of Technol. Wuhan 430063 China

Effects of environment conditions, such as current, wave etc., are more important for immersed tube tunnel's transportation and immersing. The hydrodynamics and stability of immersed tube tunnel during its towing and immersing are interested for departments of design and construction. A serial model tests are made in towing tank and water channel for Nanjing immersed tube tunnel, and the first immersed tunnel has been designed in Yangtzi River in China. The hydrodynamic forces and rope tensions of the tunnel are measured with strain balances when it is towed by ship and immersed by winches for a different current velocity and wave height. In addition, the stability of tunnel for a different ballast water is tested and discussed.

关键词： Hydrodynamics Stability Tensile testing Test facilities