The accuracy and the dependence on parameters of a general scheme for the analysis of time-varying image sequences are discussed. The approach is able to produce vector fields from which it is possible to recover 3-D motion parameters such as time-to-collision and angular velocity. The numerical stability of the computed optical flow and the dependence of the recovery of 3-D motion parameters on spatial and temporal filtering is investigated. By considering optical flows computed on subsampled images or along single scanlines, it is also possible to recover 3-D motion parameters from reduced optical flows. An adequate estimate of time-to-collision can be obtained from sequences of images with spatial resolution reduced to 128×128 pixels or from sequences of single scanlines passing near the focus of expansion. The use of Kalman filtering increases the accuracy and the robustness of the estimation of motion parameters. The proposed approach seems to be able to provide not only a theoretical background but also practical tools that are adequate for the analysis of time-varying image sequences 相似文献
Summary Multiple-scale Kernel Particle methods are proposed as an alternative and/or enhancement to commonly used numerical methods
such as finite element methods. The elimination of a mesh, combined with the properties of window functions, makes a particle
method suitable for problems with large deformations, high gradients, and high modal density. The Reproducing Kernel Particle
Method (RKPM) utilizes the fundamental notions of the convolution theorem, multiresolution analysis and window functions.
The construction of a correction function to scaling functions, wavelets and Smooth Particle Hydrodynamics (SPH) is proposed.
Completeness conditions, reproducing conditions and interpolant estimates are also derived. The current application areas
of RKPM include structural acoustics, elastic-plastic deformation, computational fluid dynamics and hyperelasticity. The effectiveness
of RKPM is extended through a new particle integration method. The Kronecker delta properties of finite element shape functions
are incorporated into RKPM to develop a Cm kernel particle finite element method. Multiresolution and hp-like adaptivity are illustrated via examples. 相似文献
Changes in plasma membrane curvature and intracellular ionic strength are two key features of cell volume perturbations. In this hypothesis we present a model of the responsible molecular apparatus which is assembled of two molecular motors [non-muscle myosin II (NMMII) and protrusive actin polymerization], a spring [a complex between the plasma membrane (PM) and the submembrane actin-based cytoskeleton (smACSK) which behaves like a viscoelastic solid] and the associated signaling proteins. We hypothesize that this apparatus senses changes in both the plasma membrane curvature and the ionic strength and in turn activates signaling pathways responsible for regulatory volume increase (RVI) and regulatory volume decrease (RVD). During cell volume changes hydrostatic pressure (HP) changes drive alterations in the cell membrane curvature. HP difference has opposite directions in swelling versus shrinkage, thus allowing distinction between them. By analogy with actomyosin contractility that appears to sense stiffness of the extracellular matrix we propose that NMMII and actin polymerization can actively probe the transmembrane gradient in HP. Furthermore, NMMII and protein-protein interactions in the actin cortex are sensitive to ionic strength. Emerging data on direct binding to and regulating activities of transmembrane mechanosensors by NMMII and actin cortex provide routes for signal transduction from transmembrane mechanosensors to cell volume regulatory mechanisms. 相似文献
The membrane forces induced by horizontal ground motion are derived to be used in the coupled Hill's equations for a complete dynamic stability analysis. Excellent agreement between theoretical and available experimental results is obtained. A majority of buckling modes can be correctly identified by considering a geometrical imperfection. The influence of the imperfection on the dynamic buckling characteristics is also discussed. 相似文献
The relationship between the degree of ionization and the environment of a strong acid is of basic scientific interest. Often this relationship reduces to the interdependence of ion/acid hydration and proton transfer. Despite the presence of pure water, the surface of crystalline ice, particularly at cryogenic temperatures, is one of limited (controlled?) availability of water of hydration. Here, the detailed nature of the ice surface and the states of strong acids adsorbed to ice at cryogenic temperatures are examined. These subjects are of special current interest since the ability to model the complex chemistry that occurs on the surfaces of water-rich particles in the atmosphere, particularly in the stratosphere over the polar regions, requires a valid concept of the acid-ice interface. Our combined spectroscopic and simulation studies have identified the surface of free-standing ice particles as badly disordered, with a range of water-ring sizes and an increased level of H-bond saturation relative to an ordered ice surface. FT-IR results are reported for the interaction of the surface of such ice particles with submonolayer amounts of adsorbed DCl, DBr, and HNO3 and for multilayer exposure to DCl. The DCl and DBr adsorbed states demonstrate behavior familiar from observations on strongly bound molecular adsorbates. Two methods have been devised for exposure of the nanocrystals to HNO3 One gives an ionic state initially, while the initial state of the other approach is molecular. In both instances, the system is observed to evolve, with time/warming, towards a common mixed molecular–ionic adsorbed state. 相似文献
p-NiO/n-Si heterodiode was deposited with an easy and cheap sol–gel route using a spin coater. The XRD results revealed that NiO film had polycrystalline cubic bunsenite structure with (200) preferential direction. The AFM and SEM micrographs indicated that the film was composed of homogenously distributed nanoparticles on n-Si surface. The uniform scattering of Ni and O elements was also seen from EDX mapping pictures. The band gap value for NiO sample was found to be 3.74 eV. The current–voltage (I–V) properties of Ag/p-NiO/n-Si heterojunction were inquired in the temperature range of 80 K to 300 K (−193 °C to 27 °C). The temperature coefficient of barrier height of the Ag/p-NiO/n-Si heterojunction was determined to be 2.6 meV/K. The I-V measurements showed that the barrier height of the heterojunction increased with an increment in the temperature.
In this study, a convenient method for the synthesis of thirteen novel disazo dyes containing 25,26,27‐tribenzoyloxy‐28‐hydroxycalix[4]arene have been described. 5,11,17,23‐Tetra‐tert‐butyl‐25,26,27,28‐tetrahydroxycalix[4]arene, 25,26,27,28‐tetrahydroxycalix[4]arene and 25,26,27‐tribenzoyloxy‐28‐hydroxycalix[4]arene were synthesised based on previously published literature. 2‐Arylhdrazone‐3‐ketiminobutyronitriles were synthesised and reacted with hydrazine hydrate to afford the corresponding 5‐amino‐4‐arylazo‐3‐methyl‐1H‐pyrazoles. Thirteen novel hetaryldisazocalix[4]arene derivatives were achieved by diazotisation of 5‐amino‐4‐arylazo‐3‐methyl‐1H‐pyrazoles using nitrosylsulphuric acid, coupled with 25,26,27‐tribenzoyloxy‐28‐hydroxycalix[4]arene. The obtained hetaryldisazocalix[4]arene dyes were characterised based on Fourier Transform–infrared, proton nuclear magnetic resonance and mass spectroscopic techniques, as well as elemental analysis. The solvatochromic behaviour of these dyes in various solvents was examined. Acid‐base effects on the visible absorption maxima of the dyes were also reported. 相似文献
In this paper, the governing equations which consider dynamic fluid-structure interaction, modal coupling in both axial and circumferential directions, and dynamic buckling are derived. The various pressure components acting on the shell wall due to a seismic event are also analyzed. The matrix equation of motion for liquid-filled shells is obtained through a Galerkin/Finite Element discretization procedure. The modal coupling among the various combinations of axial and circumferential modes are identified with a particular reference to the fluid-structure system under seismic excitation. Finally, the equations for the dynamic stability analysis of liquid-filled shells are presented. 相似文献