From: calendar@ALMADEN.IBM.COM (IBM Almaden Research Center Calendar)
Newsgroups: ba.seminars
Subject: IBM ARC seminars 27 - 31 JUL 92
Date: 22 Jul 92 22:50:56 GMT


                     IBM Almaden Research Center
                           650 Harry Road
                       San Jose, CA 95120-6099

                              CALENDAR

                          July 27-31, 1992


07/27 - ELECTRO-OPTIC EFFECT AND SECOND HARMONIC GENERATION IN THIN
POLYMER FILMS
Dr. K. Clays, Eastman Kodak Company

Poly. Sci. & Tech. Sem.    Mon., July 27    10:00 a.m.    Room:  J2-601

The importance of electrochromic effects in the ellipsometric
determination of the electro-optic coefficient is discussed for poled
polymer systems.  An imaginary part is introduced in the definition of
the complex electro-optic coefficient.  The dispersion of the real part
of the electro-optic coefficient is shown to follow the simple two-level
model description.  A relation between the imaginary part and
electrochromism is proposed.  The dispersion of the imaginary part shows
the derivative-like features of the electrochromism spectra.  Second
harmonic radiation in waveguide format is discussed for
Langmuir-Blodgett structures.  Blue (430 nm) and green (532 nm)
Cerenkov-type second-harmonic radiation has been generated in an
all-polymeric Langmuir-Blodgett waveguide.  A non-zero second-order
nonlinear optical susceptibility was obtained by alternate deposition of
nonlinear optical active and a passive polymer.  The Cerenkov condition
was fulfilled through thickness control of the film and the model
dispersion relations for waveguides.  The second-harmonic light,
generated in the waveguide, leaks into the substrate at the Cerenkov
angle.  The Cerenkov-type guided mode-to-substrate-radiation-mode-
phase-matching scheme reduces the waveguides attenuation for the
second harmonic and provides a convenient way of separating the
second harmonic from the fundamental.
Host:  C. Moylan


07/27 - COHERENT PHONON DETECTION FROM ULTRAFAST SURFACE VIBRATIONS
Dr. O. B. Wright, Electronics Research Labs, Nippon Steel Corp., Japan

Phys. Sci. Sem.    Mon., July 27    1:30 p.m.    Room:  D2-450

We have observed longitudinal acoustic phonon pulses in the 0.1 THz
range in thin films by direct time-resolved detection of picosecond
vibrations of the film surface using a laser picosecond pump-probe
technique.  The phonon strain pulse shape can be obtained from the
surface displacement variation, and the phonon spectrum derived.  We
apply this technique to various metallic and semiconductor thin films,
and demonstrate, in contrast to the conventional laser picosecond
acoustic method, phonon detection independent of the photoelastic
constants of the film.  Application to ultrathin film detection is also
described.
Host:  H. Coufal


07/27 - OPTICAL PROPERTIES OF WAVEGUIDING STRUCTURES IN POLYMERS
W. F. X. Frank, German Telekom Research Ctr., D-6100 DARMSTADT, FRG

Poly. Sci. & Tech. Sem.    Mon., July 27    1:30 p.m.    Room:  J2-601

Waveguides of different types such as strip, rip and buried ones have
been realized in poly-(methyl-methacrylate) as well as in several types
of poly-(imide) by application of different methods.  Ion implantation,
ultraviolet irradiation and excimer laser ablation have been
successfully applied in order to form channel waveguides of straight,
curved and branched structures of 2-10 mu m in width and more than
20 mm of length.  The optical properties like mode spectrum loss and beam
profile were measured.  The chemical processes in the material have been
studied by infrared spectroscopy (Attenuated Total Reflectance
Technology) and residual gas analysis.  Surface profilometry and
Scanning Electron Microscopy reveal the geometrical properties of the
waveguides.  Special preparation of the end faces enable a good coupling
of light from an optical fiber into the waveguide.
Host:  J. Swalen


07/27 - FROM STATISTICS TO BELIEFS
J. Halpern, Mathematics and Related Computer Science

Comp. Sci. Sem.    Mon., July 27    3:00 p.m.    Room:  Aud. A

Consider an agent who has a knowledge base KB consisting of first-order
and statistical information.  (The agent could be, say, a doctor, with a
database of information regarding diseases and symptoms.)  To make
decisions, it is often useful for the agent to assign a numerical
"degree of belief" to measure the strength of his belief in a given
statement.  We investigate three principled techniques for doing so.
All three are applications of the principle of indifference, because
they assign equal degree of belief to all basic "situations" consistent
with the knowledge base.  They differ because there are competing
intuitions about what the basic situations are.  Various natural
patterns of reasoning, such as the preference for the most specific
statistical data available, turn out to follow from some or all of the
techniques.  This is an improvement over earlier approaches, which
arbitrarily postulate these patterns without offering any deeper
explanation.

We show relationships connections between these methods and the
principle of maximum entropy, a principle of maximal independence, and a
"center of mass" principle.  There are also unexpected connections
between the three that help us understand why the specific language
chosen (for the knowledge base) is much more critical in inductive
reasoning of the sort we consider than it is in traditional deductive
reasoning.

This work is joint with Fahiem Bacchus, Adam Grove, and Daphne Koller.
Host:  R. Fagin


07/31 - 07/27 - FROM STATISTICS TO BELIEFS SYMBOLIC COMPUTATION, AND WHY
IT IS WE NEED TO
S. Landau, University of Massachusetts

Comp. Sci. Sem.    Fri., July 31    10:30 a.m.    Room:  B2-307

This talk will center on two problems in symbolic computation:
factoring polynomials, and simplifying nested radicals.  Both are
fundamentals in symbolic computation.  Both are important, both have
elegant algorithms, and both are way too slow.  I will briefly discuss
the algorithms and their bottlenecks, and how the two problems tie
together.
Host:  B. Simons


07/31 - THREE-VIEWGRAPH FORUM
B. Jones, J. Pacansky and, R. Wilson, Almaden Research Center

Phys. Sci. Colloq.    Fri., July 31    10:30 a.m.    Room:  Aud. A

These talks are presented as part of our summer series of
Three-Viewgraph Forums.  Each presentation will be a brief talk with the
main points emphasized by a maximum of three viewgraphs.  The
presentations will be followed by informal discussion.

1.  Barbara Jones--Quantum Wall States and Exchange Coupling in Magnetic
    Multilayers

2.  Jake Pacansky--The Center for Computational Chemistry

3.  Bob Wilson--STM of Solution Deposited Bio-polymers on Pt(111)

Host:  J. Kaufman

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For further information on individual talks, please contact the host
listed above.

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