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The morphological scheme devised by Hubble and followers to
classify galaxies has proven over many decades to be quite
effective in directing our quest for the fundamental pa rameters
describing the extragalactic manifold. This statement is however
far more true for spirals than for ellipticals. Echoing the
concluding remarks in Scott Tremaine's sum mary talk at the
Princeton meeting on Structure and Dynamics of Elliptical Galaxies,
"the Hubble classification of spirals is useful because many
properties of spirals (gas con tent, spiral arm morphology, bulge
prominence, etc. ) all correlate with Hubble time. By contrast,
almost nothing correlates with the elliptical Hubble sequence El to
E7. " During the last few years much effort has been put into the
search for a more meaningful classification of ellipticals than
Hubble's. Concomitantly, forwarded by some provocative conjectures
by R. Michard, the classical question of whether E galaxies form a
physically homogeneous family has been brushed up once more.
Results of these and other parallel studies look rather promising
and point to suture part of the dichotomy between ellipticals and
disk galaxies which had become popular in the early eighties, owing
to dynamical arguments. At the same time it appears more and more
clear that, besides the usual genetic varieties of galaxies,
products of environmental evolution must also be contemplated in
building our modern picture of the "reign of galaxies" . The above
considerations prompted us to solicit Prof."
The morphological scheme devised by Hubble and followers to
classify galaxies has proven over many decades to be quite
effective in directing our quest for the fundamental pa rameters
describing the extragalactic manifold. This statement is however
far more true for spirals than for ellipticals. Echoing the
concluding remarks in Scott Tremaine's sum mary talk at the
Princeton meeting on Structure and Dynamics of Elliptical Galaxies,
"the Hubble classification of spirals is useful because many
properties of spirals (gas con tent, spiral arm morphology, bulge
prominence, etc. ) all correlate with Hubble time. By contrast,
almost nothing correlates with the elliptical Hubble sequence El to
E7. " During the last few years much effort has been put into the
search for a more meaningful classification of ellipticals than
Hubble's. Concomitantly, forwarded by some provocative conjectures
by R. Michard, the classical question of whether E galaxies form a
physically homogeneous family has been brushed up once more.
Results of these and other parallel studies look rather promising
and point to suture part of the dichotomy between ellipticals and
disk galaxies which had become popular in the early eighties, owing
to dynamical arguments. At the same time it appears more and more
clear that, besides the usual genetic varieties of galaxies,
products of environmental evolution must also be contemplated in
building our modern picture of the "reign of galaxies" . The above
considerations prompted us to solicit Prof."
Astrophysical analysis relating to solid matter requires data on
properties and processes. Such data, however, expecially
appropriate to space conditions are mostly lacking. It appeared
then very tempting to gather together experimentalists, ob servers
and theoreticians working in the field of cosmic dust and in
related areas. The Workshop held in Capri (Italy) from September
8th till 12th 1987 gave the participants a unique opportunity for
exchange of ideas and discussions of problems and experimental
procedures. Introductory reports were prepared with the aim of
giving the state of the art about single subjects; contributed
poster papers presented, on the contrary, very recent results in
the various fields. According to his specific interest each
attendant has also contributed to three Working Groups respectively
on a) carbon, b) silicates, c) ice and related topics. Scientifical
and technical problems about these items were discussed in great
detail. Though no definite answers were given, useful indications
come out which will be of some help for future works. In addition
to the scientific efforts, the Capodimonte Observatory and the
Istituto Universitario Navale sought to give a warm welcome to the
participants. Thanks to several sponsors, the LOC could organize
some excursions and shows to entertain people during their spare
time."
The four chapters of this volume, written by prominent workers in
the field of adaptive processing and linear prediction, address a
variety of problems, ranging from adaptive source coding to
autoregressive spectral estimation. The first chapter, by T.C.
Butash and L.D. Davisson, formulates the performance of an adaptive
linear predictor in a series of theorems, with and without the
Gaussian assumption, under the hypothesis that its coefficients are
derived from either the (single) observation sequence to be
predicted (dependent case) or a second, statistically independent
realisation (independent case). The contribution by H.V. Poor
reviews three recently developed general methodologies for
designing signal predictors under nonclassical operating
conditions, namely the robust predictor, the high-speed Levinson
modeling, and the approximate conditional mean nonlinear predictor.
W. Wax presents the key concepts and techniques for detecting,
localizing and beamforming multiple narrowband sources by passive
sensor arrays. Special coding algorithms and techniques based on
the use of linear prediction now permit high-quality voice
reproduction at remorably low bit rates. The paper by A. Gersho
reviews some of the main ideas underlying the algorithms of major
interest today.
The general problem studied by information theory is the reliable
transmission of information through unreliable channels. Channels
can be unreliable either because they are disturbed by noise or
because unauthorized receivers intercept the information
transmitted. In the first case, the theory of error-control codes
provides techniques for correcting at least part of the errors
caused by noise. In the second case cryptography offers the most
suitable methods for coping with the many problems linked with
secrecy and authentication. Now, both error-control and
cryptography schemes can be studied, to a large extent, by suitable
geometric models, belonging to the important field of finite
geometries. This book provides an update survey of the state of the
art of finite geometries and their applications to channel coding
against noise and deliberate tampering. The book is divided into
two sections, "Geometries and Codes" and "Geometries and
Cryptography." The first part covers such topics as Galois
geometries, Steiner systems, Circle geometry and applications to
algebraic coding theory. The second part deals with unconditional
secrecy and authentication, geometric threshold schemes and
applications of finite geometry to cryptography. This volume
recommends itself to engineers dealing with communication problems,
to mathematicians and to research workers in the fields of
algebraic coding theory, cryptography and information theory.
The concept of time and frequency representation of signals
dates back to the first notation for music. From a mathematical
viewpoint we can associate the time function to its Fourier
transform. This book introduces a useful representation of signals
simultaneously in time and frequency.
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