共查询到20条相似文献,搜索用时 0 毫秒
1.
Cordea M.D. Petriu D.C. Petriu E.M. Georganas N.D. Whalen T.E. 《IEEE transactions on instrumentation and measurement》2002,51(4):640-644
This paper discusses a tracking method allowing real-time recovery of the three-dimensional (3-D) position and orientation of a moving head. The described method uses a wireframe model of the head, a feature-based matching algorithm, and an extended Kalman filter estimator. The resulting motion tracking system works in a realistic environment without makeup on the face, with uncalibrated camera, and unknown lighting conditions and background. 相似文献
2.
Automated phase-measuring profilometry of 3-D diffuse objects 总被引:9,自引:0,他引:9
3.
4.
5.
We present a novel approach for generating three-dimensional (3-D) integral images from a fringe pattern of 3-D objects. A recorded hologram of 3-D objects is segmented into a number of subholograms. Then, different views of 3-D objects are reconstructed from them because each subhologram has its own perspective of 3-D objects in the recording process. These locally reconstructed images can be rearranged as the same subimage array of the conventional integral-imaging system and transformed into virtually picked-up elemental images of 3-D objects. From this newly generated elemental image array, 3-D images could easily be reconstructed by using a white light. Experiments with a 3-D test object have been performed and the results have been presented. 相似文献
6.
7.
8.
A comparative study of statistical particle model theory of diffuse reflectance has been made. Theories have been applied to six particulate samples having different optical characteristics and average particle sizes that vary from 42 to 106 mum. We made an overall assessment of each theoretical model by determining the CIELAB color difference using experimentally measured and theoretically predicted diffuse reflectance spectra in the visible spectral range. We discuss the performance ratings of the models of other researchers and discovered numerous typographical errors in Fresnel reflection coefficient expressions. We provide the correct versions for these expressions. 相似文献
9.
10.
Pua EC Fronheiser MP Noble JR Light ED Wolf PD von Allmen D Smith SW 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(11):1999-2008
Laparoscopic ultrasound has seen increased use as a surgical aide in general, gynecological, and urological procedures. The application of real-time, three-dimensional (RT3D) ultrasound to these laparoscopic procedures may increase information available to the surgeon and serve as an additional intraoperative guidance tool. The integration of RT3D with recent advances in robotic surgery also can increase automation and ease of use. In this study, a 1-cm diameter probe for RT3D has been used laparoscopically for in vivo imaging of a canine. The probe, which operates at 5 MHz, was used to image the spleen, liver, and gall bladder as well as to guide surgical instruments. Furthermore, the three-dimensional (3-D) measurement system of the volumetric scanner used with this probe was tested as a guidance mechanism for a robotic linear motion system in order to simulate the feasibility of RT3D/robotic surgery integration. Using images acquired with the 3-D laparoscopic ultrasound device, coordinates were acquired by the scanner and used to direct a robotically controlled needle toward desired in vitro targets as well as targets in a post-mortem canine. The rms error for these measurements was 1.34 mm using optical alignment and 0.76 mm using ultrasound alignment. 相似文献
11.
Ivancevich NM Dahl JJ Trahey GE Smith SW 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(8):1432-1439
We tested the feasibility of using adaptive imaging, namely phase-aberration correction, with two-dimensional (2-D) arrays and real-time, 3-D ultrasound. Because of the high spatial frequency content of aberrators, 2-D arrays, which generally have smaller pitch and thus higher spatial sampling frequency, and 3-D imaging show potential to improve the performance of adaptive imaging. Phase-correction algorithms improve image quality by compensating for tissue-induced errors in beamforming. Using the illustrative example of transcranial ultrasound, we have evaluated our ability to perform adaptive imaging with a real-time, 3-D scanner. We have used a polymer casting of a human temporal bone, root-mean-square (RMS) phase variation of 45.0 ns, full-width-half-maximum (FWHM) correlation length of 3.35 mm, and an electronic aberrator, 100 ns RMS, 3.76 mm correlation, with tissue phantoms as illustrative examples of near-field, phase-screen aberrators. Using the multilag, least-squares, cross-correlation method, we have shown the ability of 3-D adaptive imaging to increase anechoic cyst identification, image brightness, contrast-to-speckle ratio (CSR), and, in 3-D color Doppler experiments, the ability to visualize flow. For a physical aberrator skull casting we saw CSR increase by 13% from 1.01 to 1.14, while the number of detectable cysts increased from 4.3 to 7.7. 相似文献
12.
Experimental data on desulphurisation of a simulated coal gas mixture containing 200 ppm H2S, using CuO/ZnO mixed oxide sorbent in a fluidised bed reactor, are used to evaluate four representative structural models
for gas-solid non-catalytic reactions. The four models chosen for evaluation are the spherical changing-grain-size model of
Georgakis and co-workers, the rectangular grains version of the general formulation of Szekely and co-workers, the single-pore
model of Ramachandran and Smith and the random pore model of Bhatia and Perlmutter. All the model parameters except the reaction
rate constant are calculated from experimental measurements or from literature correlations. The rate constant alone is adjusted
so as to obtain good agreement between the model and the experiment. It is shown that at any given temperature all the models
describe the data well. However, the random pore model predicts conversions lower than experiment at large times while the
rectangular grains model predicts conversions higher than experiment for small times. The rate constants decrease as temperature
increases indicating an inadequacy of all the models in this regard. The models also predict much smaller variations in conversion
with change in particle size than those observed experimentally. 相似文献
13.
Various methodologies that aim at an analytic representation of the dielectric response function (DRF) of liquid water with emphasis on the Bethe ridge region are compared. The use of optical data is a common feature to all models presented providing an empirical ground for modelling the valence energy losses where many-body (and phase) effects are expected to be most prevalent. The dispersion models used for describing the momentum dependence of the DRF are evaluated against the recent inelastic X-ray scattering (IXS) spectroscopy data. Recent developments along the lines of Ritchie's extended-Drude scheme for an improved representation of the experimental Bethe ridge are presented. 相似文献
14.
Massicotte D. Legendre S. Barwicz A. 《IEEE transactions on instrumentation and measurement》1998,47(2):362-370
The problem of applying the neural networks for static calibration of measuring systems and for measurand reconstruction is addressed. A multilayered neural network based method for the static calibration of this system is proposed. The functioning of the calibrated measuring system is based on three fiber-optic transducers whose static characteristics are nonmonotonic and significantly influenced by temperature. The applicability of the proposed calibration method is demonstrated in the case under consideration using synthetic and real data. The neural network is designed and implemented in a general purpose microcontroller. In comparison with the spline-based method of calibration, for the same reference data, the proposed method allows obtention of a better quality of calibration and, most important, when calibrated, the multilayered neural network does not require the measurement of temperature for pressure reconstruction 相似文献
15.
This paper discusses techniques for the automatic construction of numerical analysis models for multiple scale analyses which employ interacting models at two, or more, physical scales. Consideration is given to the methods to define the geometric representations and generate the discretizations needed by the numerical analysis procedures. The application of the techniques to multichip modules and composite structures, with interacting macromechanical and micromechanical level analyses, is demonstrated. In the multichip module analyses both heat conduction and thermomechanical analysis are performed using different numerical analysis techniques, and the two interaction of the analyses at the through levels is through a basic global/local methodology. The composite structure analysis considers crack propagation at the micromechanical level interacting with the macromechanical analysis through finite element based adaptive multiscale analysis. In both example applications the focus of the discussion is on the automatic construction of the required geometric models and their automatic discretization. 相似文献
16.
Stereoscopic 3D objects evoke stronger saliency for nonverbal working memory: An fMRI study 下载免费PDF全文
Byoung‐Ju Yun Sung‐Uk Jin Sang‐Hoon Lee Shi‐Hyun Ahn Yusun Min Tae‐Du Jung Hui Joong Lee Yongmin Chang 《International journal of imaging systems and technology》2016,26(1):76-84
Effective working memory (WM) training is often desired to improve WM. Recent studies have suggested that WM training is more successful when participants monitor scenes in three‐dimensional (3D) environments. Although previous neuroimaging studies have examined visuospatial WM in relation to a 3D scene or object, these studies did not investigate WM using stereoscopic 3D object stimuli. We used functional magnetic resonance imaging (fMRI) to identify brain activation during an N‐back task with 3D object stimuli, and determined the difference in activation pattern between stereoscopic versus shaded 3D objects. We found that the anterior insula, ventral striatum, and posterior orbitofrontal cortex showed greater activation during the 2‐back task with stereoscopic 3D objects than with shaded 3D objects. These regions have previously been associated with a salience network. 相似文献
17.
In this paper, the problem of fracture initiation in an aluminum alloy thin plate containing a central crack is examined by employing several phenomenological continuum damage mechanics models. These models differ mainly in the selection of the kind of tensorial property the damage variable assumes, the nature of the equivalence postulate between damaged and pseudo undamaged material states, and the way damage evolution laws are formulated. Two formulations of damage effect tensor based on the engineering notation and the normative notation of stress and strain, respectively, are compared. In addition, the hypothesis of strain equivalence is compared to that of stress working equivalence. The error in the assumption of isotropic damage development in the crack tip process zone is also checked against that of anisotropic damage. In the numerical algorithm, both updated Lagrangian formulation and small displacement formulation of material non-linearity only are adopted and compared. The influence of non-proportionality in stress histories present in the crack tip region is accounted for by introducing a dynamic coordinate system of principal damage such that the principal direction of damage rotates in accordance with that of the loading. The calculated fracture initiation loads are finally compared with those determined experimentally. 相似文献
18.
Three different boundary element methods (BEM) for transient dynamic crack analysis in two-dimensional (2-D), homogeneous,
anisotropic and linear elastic solids are presented. Hypersingular traction boundary integral equations (BIEs) in frequency-
domain, Laplace-domain and time-domain with the corresponding elastodynamic fundamental solutions are applied for this purpose.
In the frequency-domain and the Laplace-domain BEM, numerical solutions are first obtained in the transformed domain for discrete
frequency or Laplace-transform parameters. Time-dependent results are subsequently obtained by means of the inverse Fourier-transform
and the inverse Laplace-transform algorithm of Stehfest. In the time-domain BEM, the quadrature formula of Lubich is adopted
to approximate the arising convolution integrals in the time-domain BIEs. Hypersingular integrals involved in the traction
BIEs are computed through a regularization process that converts the hypersingular integrals to regular integrals, which can
be computed numerically, and singular integrals which can be integrated analytically. Numerical results for the dynamic stress
intensity factors are presented and discussed for a finite crack in an infinite domain subjected to an impact crack-face loading. 相似文献
19.
20.
Steven C. Pack James A. Mandel 《International journal for numerical methods in engineering》1983,19(1):113-124
A finite element technique, for efficient solution of a class of 3-D elasticity problems, is presented. In this method, standard 2-D finite elements are used along with a ‘connector’ element. An element, previously used to model material interfaces, is shown to provide the properties for use as a ‘connector’ element, if input variables are redefined. The accuracy of the technique is illustrated with a sample solution. 相似文献