459 research outputs found
Low Complexity Algorithm for Range-Point Migration-Based Human Body Imaging for Multistatic UWB Radars
High-resolution, short-range sensors that can be applied in optically challenging environments (e.g., in the presence of clouds, fog, and/or dark smog) are in high demand for various applications. Ultrawideband radar is a promising sensor that is suitable for short-range surveillance or watching sensors. Range-point migration (RPM) has been recently established as a promising imaging approach to achieve accurate and real-time 3-D imaging. However, when objects with many scattering points are dealt with, such as a human body, RPM suffers from high computational costs. In this letter, we propose an algorithm with a lower complexity for an RPM-based 3-D imaging method by introducing a sampling-based scattering center extraction with a simplified evaluation function, in which an efficient sample pattern is provided by a golden ratio. The results from a finite-difference time-domain-based numerical test, which introduces a realistic human body object, demonstrate that our proposed method remarkably reduces the computational cost without sacrificing the reconstruction accuracy
Acceleration of Range Points Migration-Based Microwave Imaging for Nondestructive Testing
We report on an experimental investigation of the properties of volume holographic recording in photopolymerizable nanoparticle?polymer composites (NPCs) doped with chain transferring multifunctional di- and tri-thiols as chain transfer agents. It is shown that the incorporation of the multifunctional thiols into NPCs more strongly influences on volume holographic recording than that doped with mono-thiol since more chemical reactions involve in the polymer network formation. It is found that, as similar to the case of mono-thiol doping, there exist optimum concentrations of di- and tri-thiols for maximizing the saturated refractive index modulation. It is also seen that recording sensitivity monotonically decreases with an increase in multifunctional thiol concentration due to the partial inhibition of the photopolymerization event by excessive thiols
Range-Point Migration-Based Image Expansion Method Exploiting Fully Polarimetric Data for UWB Short-Range Radar
Ultrawideband radar with high-range resolution is a promising technology for use in short-range 3-D imaging applications, in which optical cameras are not applicable. One of the most efficient 3-D imaging methods is the range-point migration (RPM) method, which has a definite advantage for the synthetic aperture radar approach in terms of computational burden, high accuracy, and high spatial resolution. However, if an insufficient aperture size or angle is provided, these kinds of methods cannot reconstruct the whole target structure due to the absence of reflection signals from large part of target surface. To expand the 3-D image obtained by RPM, this paper proposes an image expansion method by incorporating the RPM feature and fully polarimetric data-based machine learning approach. Following ellipsoid-based scattering analysis and learning with a neural network, this method expresses the target image as an aggregation of parts of ellipsoids, which significantly expands the original image by the RPM method without sacrificing the reconstruction accuracy. The results of numerical simulation based on 3-D finite-difference time-domain analysis verify the effectiveness of our proposed method, in terms of image-expansion criteria
Super-Resolution Time of Arrival Estimation Using Random Resampling in Compressed Sensing
There is a strong demand for super-resolution time of arrival (TOA) estimation techniques for radar applications that can that can exceed the theoretical limits on range resolution set by frequency bandwidth. One of the most promising solutions is the use of compressed sensing (CS) algorithms, which assume only the sparseness of the target distribution but can achieve super-resolution. To preserve the reconstruction accuracy of CS under highly correlated and noisy conditions, we introduce a random resampling approach to process the received signal and thus reduce the coherent index, where the frequency-domain-based CS algorithm is used as noise reduction preprocessing. Numerical simulations demonstrate that our proposed method can achieve super-resolution TOA estimation performance not possible with conventional CS methods
Onsager-Machlup action-based path sampling and its combination with replica exchange for diffusive and multiple pathways
For sampling multiple pathways in a rugged energy landscape, we propose a
novel action-based path sampling method using the Onsager-Machlup action
functional. Inspired by the Fourier-path integral simulation of a quantum
mechanical system, a path in Cartesian space is transformed into that in
Fourier space, and an overdamped Langevin equation is derived for the Fourier
components to achieve a canonical ensemble of the path at a finite temperature.
To avoid "path trapping" around an initially guessed path, the path sampling
method is further combined with a powerful sampling technique, the replica
exchange method. The principle and algorithm of our method is numerically
demonstrated for a model two-dimensional system with a bifurcated potential
landscape. The results are compared with those of conventional transition path
sampling and the equilibrium theory, and the error due to path discretization
is also discussed.Comment: 20 pages, 5 figures, submitted to J. Chem. Phy
Parametric Wind Velocity Vector Estimation Method for Single Doppler LIDAR Model
Doppler lidar (LIght Detection And Ranging) can provide accurate wind velocity vector estimates by processing the time delay and Doppler spectrum of received signals. This system is essential for real-time wind monitoring to assist aircraft taking off and landing. Considering the difficulty of calibration and cost, a single Doppler lidar model is more attractive and practical than a multiple lidar model. In general, it is impossible to estimate two or three dimensional wind vectors from a single lidar model without any prior information, because lidar directly observes only a 1-dimensional (radial direction) velocity component of wind. Although the conventional VAD (Velocity Azimuth Display) and VVP (Velocity Volume Processing) methods have been developed for single lidar model, both of them are inaccurate in the presence of local air turbulence. This paper proposes an accurate wind velocity estimation method based on a parametric approach using typical turbulence models such as tornado, micro-burst and gust front. The results from numerical simulation demonstrate that the proposed method remarkably enhances the accuracy for wind velocity estimation in the assumed modeled turbulence cases, compared with that obtained by the VAD or other conventional method
Three-Dimensional Imaging Method Incorporating Range Points Migration and Doppler Velocity Estimation for UWB Millimeter-Wave Radar
High-resolution, short-range sensors that can be applied in optically challenging environments (e.g., in the presence of clouds, fog, and/or dark smog) are in high demand. Ultrawideband (UWB) millimeter-wave radars are one of the most promising devices for the above-mentioned applications. For target recognition using sensors, it is necessary to convert observational data into full 3-D images with both time efficiency and high accuracy. For such conversion algorithm, we have already proposed the range points migration (RPM) method. However, in the existence of multiple separated objects, this method suffers from inaccuracy and high computational cost due to dealing with many observed RPs. To address this issue, this letter introduces Doppler-based RPs clustering into the RPM method. The results from numerical simulations, assuming 140-GHz band millimeter radars, show that the addition of Doppler velocity into the RPM method results in more accurate 3-D images with reducing computational costs
Nature of self-diffusion in two-dimensional fluids
Self-diffusion in a two-dimensional simple fluid is investigated by both
analytical and numerical means. We investigate the anomalous aspects of
self-diffusion in two-dimensional fluids with regards to the mean square
displacement, the time-dependent diffusion coefficient, and the velocity
autocorrelation function using a consistency equation relating these
quantities. We numerically confirm the consistency equation by extensive
molecular dynamics simulations for finite systems, corroborate earlier results
indicating that the kinematic viscosity approaches a finite, non-vanishing
value in the thermodynamic limit, and establish the finite size behavior of the
diffusion coefficient. We obtain the exact solution of the consistency equation
in the thermodynamic limit and use this solution to determine the large time
asymptotics of the mean square displacement, the diffusion coefficient, and the
velocity autocorrelation function. An asymptotic decay law of the velocity
autocorrelation function resembles the previously known self-consistent form,
, however with a rescaled time.Comment: 10 pages, to appear in New Journal of Physic
Mainstreaming the Handicapped: A Design Guide
A design guide for mainstreaming handicapped children in educational facilities. Based on a user-oriented programming process and existing research literature, 18 design principles are advanced for helping physically disabled and mildly retarded children cope with school facilities. Design principles suggest the important characteristics of environments hypothesized to promote children\u27s interaction, positive self-image, confidence, accessibility and academic development.https://dc.uwm.edu/caupr_mono/1030/thumbnail.jp
Multidimensional replica-exchange method for free-energy calculations
We have developed a new simulation algorithm for free-energy calculations.
The method is a multidimensional extension of the replica-exchange method.
While pairs of replicas with different temperatures are exchanged during the
simulation in the original replica-exchange method, pairs of replicas with
different temperatures and/or different parameters of the potential energy are
exchanged in the new algorithm. This greatly enhances the sampling of the
conformational space and allows accurate calculations of free energy in a wide
temperature range from a single simulation run, using the weighted histogram
analysis method.Comment: 13 pages, (ReVTeX), 9 figures. J. Chem. Phys. 113 (2000), in pres
- …