Two-dimensional reflective optical encoder based on point source illuminated grating imaging

2019 ◽  
Author(s):  
Hang Chen ◽  
Jian Wang ◽  
Yue Gao ◽  
Cheng-Chih Hsu ◽  
Peng Jin ◽  
...  
Keyword(s):  
Point Source ◽  
Two Dimensional ◽  
Optical Encoder

scholarly journals System matrix computation for iterative reconstruction algorithms in SPECT based on direct measurements

2011 ◽  
Vol 21 (1) ◽  
pp. 193-202 ◽  
Author(s):  
Damian Borys ◽  
Katarzyna Szczucka-Borys ◽  
Kamil Gorczewski
Keyword(s):  
Point Source ◽  
Iterative Reconstruction ◽  
Gaussian Function ◽  
Detector Response ◽  
Two Dimensional ◽  
Reconstruction Algorithms ◽  
System Matrix ◽  
Matrix Computation ◽  
Direct Measurements ◽  
Matrix Calculation

System matrix computation for iterative reconstruction algorithms in SPECT based on direct measurements A method for system matrix calculation in the case of iterative reconstruction algorithms in SPECT was implemented and tested. Due to a complex mathematical description of the geometry of the detector set-up, we developed a method for system matrix computation that is based on direct measurements of the detector response. In this approach, the influence of the acquisition equipment on the image formation is measured directly. The objective was to obtain the best quality of reconstructed images with respect to specified measures. This is indispensable in order to be able to perform reliable quantitative analysis of SPECT images. It is also especially important in non-hybrid gamma cameras, where not all physical processes that disturb image acquisition can be easily corrected. Two experiments with an 131I point source placed at different distances from the detector plane were performed allowing the detector response to be acquired as a function of the point source distance. An analytical Gaussian function was fitted to the acquired data in both the one- and the two-dimensional case. A cylindrical phantom filled with a water solution of 131I containing a region of "cold" spheres as well as a uniform solution (without any spheres) was used to perform algorithm evaluation. The reconstructed images obtained by using four different of methods system matrix computation were compared with those achieved using reconstruction software implemented in the gamma camera. The contrast of the spheres and uniformity were compared for each reconstruction result and also with the ranges of those values formulated by the AAPM (American Association of Physicists in Medicine). The results show that the implementation of the OSEM (Ordered Subsets Expectation Maximization) algorithm with a one-dimensional fit to the Gaussian CDR (Collimator-Detector Response) function provides the best results in terms of adopted measures. However, the fit of the two-dimensional function also gives satisfactory results. Furthermore, the CDR function has the potential to be applied to a fully 3D OSEM implementation. The lack of the CDR in system matrix calculation results in a very noisy image that cannot be used for diagnostic purposes.

Free Surface Green Function Research Based on Cloud Computing for Ship Movement on the Water

2013 ◽  
Vol 344 ◽  
pp. 27-30
Author(s):  
Cong Zhang ◽  
Xin Wang ◽  
Jie Zhao ◽  
She Sheng Zhang
Keyword(s):  
Cloud Computing ◽  
Free Surface ◽  
Green Function ◽  
Point Source ◽  
Calculation Procedure ◽  
Green Functions ◽  
Two Dimensional ◽  
Surface Green Function ◽  
Cloud Computation ◽  
Control Equation

In order to easy use Green function on cloud computation, the author consider control equation of point source with free surface, and discuss the representation of Green function on cloud computation, and then propose the discrete calculation expression as well as the calculation procedure. Finally, the two-dimensional graphics of the Green functions real and imaginary parts are plotted.

Inverse source problem based on two dimensionless dispersion-current functions in 2D evolution transport equations

2016 ◽  
Vol 24 (6) ◽  
Author(s):  
Adel Hamdi ◽  
Imed Mahfoudhi
Keyword(s):  
Velocity Field ◽  
Point Source ◽  
Time Dependent ◽  
Inverse Source Problem ◽  
Two Dimensional ◽  
Reaction Equation ◽  
Advection Dispersion ◽  
Dispersion Tensor ◽  
Spatially Varying ◽  
Dependent Point

AbstractThe paper deals with the nonlinear inverse source problem of identifying an unknown time-dependent point source occurring in a two-dimensional evolution advection-dispersion-reaction equation with spatially varying velocity field and dispersion tensor. The

711 Turbulent Flow and Dispersion from a Point Source over a Two-Dimensional Hill

2009 ◽  
Vol 2009.58 (0) ◽  
pp. 419-420
Author(s):  
Tomoya HOURA ◽  
Masanori KAWAGUCHI ◽  
Masato TAGAWA ◽  
Yasutaka NAGANO
Keyword(s):  
Turbulent Flow ◽  
Point Source ◽  
Two Dimensional

Subwavelength imaging of a point source based on two-dimensional photonic crystals

2016 ◽  
Vol 41 (16) ◽  
pp. 3833 ◽  
Author(s):  
Hongliang Ma ◽  
Binming Liang ◽  
Songlin Zhuang ◽  
Jiabi Chen ◽  
Qiang Jiang ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Point Source ◽  
Two Dimensional ◽  
Subwavelength Imaging

scholarly journals Complex Motions in Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 346-346
Author(s):  
Vincent Icke
Keyword(s):  
Point Source ◽  
Numerical Simulations ◽  
Equatorial Plane ◽  
Planetary Nebulae ◽  
Second Order ◽  
Two Dimensional ◽  
Order Accuracy ◽  
Cylindrically Symmetric

I have made an extensive series of numerical simulations of aspherical PNs. This interacting-winds model consists of a point source of fast tenuous gas embedded in a flattened cloud of dense slow gas which is two-dimensional and cylindrically symmetric. I used a hydrocode specially designed to handle the extremely large gradients between the winds to second order accuracy. The outer shock shapes correspond very well to my analytic predictions. This shock may form cusps which compress the gas to form two rings on opposite sides of the equatorial plane.

Seismic waves from finite faults in layered media

1979 ◽  
Vol 69 (6) ◽  
pp. 1693-1714
Author(s):  
F. Abramovici ◽  
J. Gal-Ezer
Keyword(s):  
Point Source ◽  
Half Space ◽  
Seismic Waves ◽  
Time Dependent ◽  
Homogeneous Layer ◽  
Two Dimensional ◽  
Homogeneous Half Space ◽  
Finite Line ◽  
Finite Line Source ◽  
Time Dependent Solution

abstract The time-dependent solution for a multipolar source in a structure consisting of a homogeneous layer over a homogeneous half-space is obtained as a sum of generalized rays. Numerical seismograms are calculated for a horizontal strikeslip and a horizontal dip-slip for a point-source, a finite line-source, and a finite two-dimensional source in the form of a rectangle. For comparison, the displacements in a homogeneous space and half-space are also calculated. The seismograms for finite sources are similar to those for a point-source but show less conspicuous phases, the arriving pulses being wider and less sharp.

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