Abstract-The effect of the companding process on QAM signals
has been under investigation for the past several years. The
compander, included in the PCM telephone network to improve
voice performance, has an unusual affect on digital QAM data
signals which are transmitted over the same channel. The quantization
noise, generated by the companding process which is multiplicative
(and asymmetric), degrades the detectability performance
of the outermost points of the QAM constellation more
than that of the inner points.
The combined effect of the companding noise and the inherent
white gaussian noise of the system, leads us to a re-examination of
signal constellation design.
In this paper we investigate the detectability performance of a
number of candidates for signal constellations including, a typical
rectangular QAM constellation, the same constellation with the
addition of a smear-desmear operation, and two new improved
QAM constellation designs with two-Dimensional warpi
The OpenGL graphics system is a software interface to graphics hardware. (The GL stands for Graphics Library.) It allows you to create interactive programs that produce color images of moving three-Dimensional objects.
外國人開發的電磁時域有限差分方法工具包
Electromagnetic Finite-Difference Time-Domain (EmFDTD)
is a basic two-Dimensional FDTD code developed at the
School of Electrical Engineering, Sharif University of
Technology.
This code has been written based on the standard
Yee s FDTD algorithm. Applications include propagation,
scattering, and diffraction of electromagnetic waves
in homogeneous and non-homogeneous isotropic media
for in-plane propagating waves. Negative permittivites
or permeabilities as well as dispersion is not included.
Zero, Periodic, and Perfectly Matched Layer boundary
conditions may be selectively applied to the solution
domain.
The program is best suited for study of propagation and
diffraction of electromagnetic waves in Photonic Crystal
structures.
EmFDTD is written in MATLAB language and has been
tested under MATLAB 5.0 and higher versions.
We describe and demonstrate an algorithm that takes as input an
unorganized set of points fx1 xng IR3 on or near an unknown
manifold M, and produces as output a simplicial surface that
approximates M. Neither the topology, the presence of boundaries,
nor the geometry of M are assumed to be known in advance — all
are inferred automatically from the data. This problem naturally
arises in a variety of practical situations such as range scanning
an object from multiple view points, recovery of biological shapes
from two-Dimensional slices, and interactive surface sketching.
Range imaging offers an inexpensive and accurate means for
digitizing the shape of three-Dimensional objects. Because most
objects self occlude, no single range image suffices to describe the
entire object. We present a method for combining a collection of
range images into a single polygonal mesh that completely describes
an object to the extent that it is visible from the outside.
This MATLAB M-file implements the finite-difference time-domain solution of Maxwell s curl equations over a one-Dimensional space lattice comprised of uniform grid cells.
A cylindrical wave expansion method is developed to obtain the scattering field for an ideal
two-Dimensional cylindrical invisibility cloak. A near-ideal model of the invisibility cloak is set up
to solve the boundary problem at the inner boundary of the cloak shell. We confirm that a cloak
with the ideal material parameters is a perfect invisibility cloak by systematically studying the
change of the scattering coefficients from the near-ideal case to the ideal one. However, due to the
slow convergence of the zeroth order scattering coefficients, a tiny perturbation on the cloak would
induce a noticeable field scattering and penetration.
The frequency domain plays an important role in image
processing to smooth, enhance, and detect edges of images. Although
image data typically does not include imaginary values, the fast Fourier
transform (FFT) has been used for obtaining spectra. In this paper,
the fast Hartley transform (FHT) is used to transform two-Dimensional
image data. Because the Hartley transform is real valued, it does
not require complex operations. Both spectra and autocorrelations of
two-Dimensional ultrasound images of normal and abnormal livers were
computed.
Face Transfer is a method for mapping videorecorded perfor-mances of one individual to facial animations of another. It extracts visemes (speech-related mouth articulations), expressions, and three-Dimensional (3D) pose from monocular video or 鏗乴m footage.
C Algorithms for Real-Time DSP
Chapter 4 covers the basic real-time filtering techniques which are the cornerstone of one-Dimensional real-time digital signal processing.
