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Austin Chapter of SIAM


SIAM: Society for Industrial and Applied Mathematics

The Austin Chapter of SIAM is a society for all those interested in mathematics and its applications. We sponsor guest speakers, career discussions on industry and academia, student-faculty social events, and visits to annual SIAM meetings. We welcome new members from all majors and all University of Texas at Austin members, whether undergraduate, graduate, faculty, or other.

coffee percolator

Spring 2013 SIAM Coffee Breaks

The chapter will be hosting a coffee break on the first and third Monday of each month this spring semester. They will all take place in the ACES 6th floor faculty lounge from 2:30 to 3:00 PM. Chapter members and CSEM students, faculty, and staff are cordially invited to attend.

Related campus organizations

Saturday Morning Math Group
"The Saturday Morning Math Group is a UT sponsored outreach program aimed at junior high and high school students, their teachers, and their parents."
Undergraduate Mathematics Research Group
"[The group] is open to all students interested in mathematics, and especially caters to the UT-Austin pure and applied mathematics communities. Our goal is to enhance the undergraduate math experience by exposing students to beautiful mathematics, interesting research, and helpful information every week."

Related campus departments

Other SIAM chapters in Texas

Related societies

LaTeX Help

TeX lion Latex is a typesetting language widely used in the sciences for writing articles, textbooks, and just about anything with equations in it.


You'll need an installed LaTeX distribution to typeset your work. Several popular distributions are:

If you're using a Linux system (especially on campus), the odds are good that the software you need is already installed.


If you're completely new to LaTeX, here are some good places to get started: Kokpa and Daly LaTeX book Gratzer LaTeX book

Finally, with Beamer, LaTeX can be used to make great presentations. A Beamer Quickstart shows how it's done.


Here are some great places to look when you can't quite figure out how to do what you need:

Useful Packages

Lastly, here are some LaTeX packages that can make your life easier:

This package is the principal package in the AMS-LaTeX distribution. It adapts for use in LaTeX most of the mathematical features found in AMS-TeX; it is a near-indispensable adjunct to serious mathematical typesetting in LaTeX.
A package to draw diagonal lines (“cancelling” a term) and arrows with limits (cancelling a term “to a value”) through parts of maths formulas.
The enumerate package adds an optional argument to the enumerate environment which determines the style in which the counter is printed.
The package provides extensive facilities, both for constructing headers and footers, and for controlling their use (for example, at times when LaTeX would automatically change the heading style in use).
This package sets all 4 margins to be either 1 inch or 1.5 cm, and specifies the page style.
Mathtools provides many useful tools for mathematical typesetting.
An extensive collection of PostScript macros that is compatible with most TeX macro formats, including Plain TeX, LaTeX, AMS-TeX, and AMS-LaTeX. Included are macros for colour, graphics, pie charts, rotation, trees and overlays.
Provides support for setting the spacing between lines in a document. Package options include singlespacing, onehalfspacing, and doublespacing.

CTAN is also a good place to look for specific functionality.

Mathematics help

Here's a collection of classic and not-so-classic references to help you look up an unfamiliar term, find an analytic solution, or refresh you on a high school trig identity:

Programming help

Everyone comes at programming from a different background. Hopefully one of these sites speaks to yours:

Texas Advanced Computing Center Training Classes
"TACC offers various training classes in high performance computing (HPC), scientific visualization (SciVis), distributed and grid computing (DGC), and computational cluster management. TACC training classes teach the programming principles and techniques in HPC and SciVis as well as how to use TACC's high-end systems most effectively."
Software Carpentry
"Many scientists and engineers spend much of their lives programming, but only a handful have ever been taught how to do this well. ... This course is an intensive introduction to basic software development practices for scientists and engineers that can reduce the time they spend programming by 20-25%."
Blaise Barney's Introduction to Parallel Computing
"This tutorial covers the very basics of parallel computing, and is intended for someone who is just becoming acquainted with the subject. It begins with a brief overview, including concepts and terminology associated with parallel computing. The topics of parallel memory architectures and programming models are then explored. These topics are followed by a discussion on a number of issues related to designing parallel programs. The tutorial concludes with several examples of how to parallelize simple serial programs."
Texas Advanced Computing Center Academic Courses
"TACC scientists are teaching ... undergraduate and graduate level courses at The University of Texas at Austin, in the Division of Statistics and Scientific Computation. The courses are designed to enable students to apply scientific computing in research and development for both academic and industry careers."

Software help

This is a small collection of symbolic manipulation, number crunching, and plotting software that will make your life easier:

Presentation tips

Giving a good presentation requires careful preparation. Here's a quick, handy list of presentation tips compiled by Pearl Flath:

  1. Have an outline of the talk on the title page or the first slide so the audience knows where you're going.
  2. Have a short topic header at the top of each slide.
  3. Don't use complete sentences on the slide.
  4. Don't put too much on a slide.
  5. If you have animations, make sure the talk can proceed even if they don't work.
  6. Make sure the font size is large enough to read. Make sure it has enough contrast to read it - light text on dark background or dark text on light background. Don't use strange fonts.
  7. Use graphics and pictures in your slides.
  8. For a graph, have a title and labels for the axes with units.
  9. Don't try to cover too much - a one term course cannot be covered in an hour.
  10. Don't introduce too much jargon.
  11. Don't do a long derivation.
  12. If you do a derivation or a proof, make sure you first write what you are trying to derive or prove. That way, when people get lost, they can look at the top of the board and see where they are trying to go to and where from.
  13. When you have an important equation, try to have a physical or conceptual explanation of it too.
  14. Don't introduce too many new variables.
  15. Practice the talk by yourself and in front of others. Have them give you suggestions for improvement.
  16. During the presentation, look at the audience and make eye contact with a number of people.
  17. Speak loud enough for people to hear you.
  18. Avoid saying fluff words, such as "uh" and "basically."
  19. If you stumble verbally, do not apologize but continue.
  20. Do not rush the presentation.
  21. Look at the computer screen or a print-out of your slides, not the screen behind you.
  22. Do not read your slides or have your presentation memorized word-for-word, but speak about your work from the bullets on the slide or from notes.
  23. Smile.
  24. Stop talking periodically and ask questions to make sure everyone is keeping up with you. In your practice, time the presentation to allow for a few minutes of questions at the end. At the last, ask the question "Are there any questions?"
  25. You should spend at least 75% of your time looking at your audience and at most 25% of your time looking at the blackboard. First-time speakers often spend 100% of their time looking at the blackboard
  26. Plan a closing line. Even if you give a great talk, ending it with "Um, I guess that's all I've got" or "I think that's the last slide" will do nothing for your cause. Say something like "That concludes my presentation--thank you for your attention" or "I'll be happy to take questions now--thanks for coming " or simply "Thank you."


Rules of procedure

This Rules of Procedure (hereinafter called "Rules") apply to the SIAM student chapter called “UT Austin Chapter of SIAM".

The Chapter to which these Rules apply is formed by the Society for Industrial and Applied Mathematics and shall operate within the Bylaws of the parent organization. The SIAM bylaws specify how Chapters are formed; see the SIAM bylaws for details. The Chapter shall not affiliate with any other organization without first obtaining the written approval of SIAM. Provisions for SIAM Student (University) Chapters are contained in the SIAM Bylaws and are included in these Rules. No provisions of these rules shall be construed so as to contradict the Bylaws of SIAM.

Article I: Purpose

The objectives of SIAM, as established in the Certificate of Incorporation, are:

  • To further the application of mathematics to industry and science.
  • To promote basic research in mathematics leading to new methods and techniques useful to industry and science.
  • To provide media for the exchange of information and ideas between mathematicians and other technical and scientific personnel.

The objectives of the UT Austin Student Chapter of SIAM are:

  • To promote interactions between members of the applied mathematics community at UT Austin, across departments, institutes, and professional ranks;
  • To provide a forum for the discussion of applied and computational mathematics research and pedagogy;
  • To help members prepare for future careers in applied and computational mathematics;
  • To promote publications, conferences, prizes, and other opportunities offered by SIAM;

Article II: Activities

Activities anticipated for the chapter include:

  • Regular informal brown bag lunch discussions with local and visiting speakers;
  • Career discussions on applied mathematics in academia and industry;
  • Student chapter representation at SIAM annual meetings;
  • Development and maintenance of a UT Austin Chapter of SIAM website;
  • Annual elections for Chapter officers, beginning in November 2005, for calendar-year terms of service;

Article III: Institution Served

Members shall be recruited from The University of Texas at Austin.

Article IV: Membership

Section 1
Any person engaged or interested in mathematics or computing and their applications shall be eligible for membership in this Chapter. Chapter membership may be interdisciplinary, with members from multiple departments.
Section 2
There are no dues.
Section 3
Chapter members shall have the privileges of SIAM membership only if they are regular or student members of SIAM.
Section 4
All members of the chapter who are students enrolled in the sponsoring institution(s) are eligible for free student memberships in SIAM. The chapter is responsible for providing a list of its student members to SIAM so that complimentary student membership in SIAM can be processed.
Section 5
Termination of student membership will take place upon graduation or withdrawal from the university.

Article V: Sponsorship

Section 1
The Sponsor is UT Austin.
Section 2
The Sponsor of the Chapter shall appoint two Faculty Advisors for the Chapter. One of these must be affiliated with the UT Austin Mathematics Department. One of these must be affiliated with the Institute for Computational Engineering and Sciences (ICES). In the event either Advisor relinquishes his/her position, the Sponsor shall appoint a new Advisor. The responsibilities, rights and duties of the Faculty Advisor shall be those normally assigned to the Faculty Advisor of student organizations of the Sponsor, but in addition, the Faculty Advisor is expected to take leading role in the development of the Chapter activities consistent with the objectives of SIAM.

Article VI: Officers

Section 1
The Chapter shall have a President, a Vice-President, and a Secretary-Treasurer. Officers shall be Student Members in good standing with SIAM, and shall be chosen from Student Members of the Chapter.
Section 2
The President shall preside at the meetings of the Chapter (and the Chapter Executive Committee, see Article VII below). The president must be a graduate student at UT Austin. In the absence of the President, the Vice-President shall assume the duties of the President. In the absence of the latter, the Secretary-Treasurer shall assume said duties.
Section 3
The Secretary-Treasurer shall keep a record of the affairs of the Chapter, handle correspondence, and submit an annual report of Chapter activities to the Secretary of SIAM, which report shall be suitable for publication in SIAM News or its equivalent. The Secretary-Treasurer shall receive and take custody of Chapter funds, and shall submit an annual Treasurer's Report and other financial reports, as requested, to the Treasurer of SIAM. The annual Treasurer's Report shall be prepared as of the end of the academic year and shall be transmitted to the Treasurer of SIAM by no later than 30 days following the end of the academic year.
Section 5
Elections will be held yearly near the end of the Fall semester. Elections may be held earlier in the Fall of 2005 in order to fill the positions of Vice-President and Secretary-Treasurer.

Article VII: Executive Committee

Section 1
The Executive Committee will consist of the President, Vice President, and Secretary-Treasurer. The President is the Committee chair. The Executive Committee is responsible for planning meetings, organizing elections, and maintaining a website. It should have at least quarterly meetings to discuss plans for the chapter.
Section 2
In the event of a vacancy, members shall be notified (by email) and elections held two weeks later.

Article VIII: Other Committees

Section 1
Nominations for officers should be sent to the member of the Executive Committee specified in the announcement of the election.

Article X: Meetings

Section 1
There shall be at least three chapter meetings per year. Meetings will be scheduled and planned by the Executive Committee.
Section 2
The Chapter shall conduct a business meeting once per year during the month of September. Other business meetings may be called by the President or the Treasurer on two weeks notice.

Article XI: Chapter Funds

Section 1
The Chapter shall deposit all unused funds to which it has legal title in excess of $200 in an insured savings account, unless current operating commitments are in excess of that amount or unless the Chapter Treasurer obtains a written authorization from the SIAM Treasurer.
Section 2
The Treasurer shall maintain books of account that show income and expense items for all activities and balances for all accounts of the Chapter.
Section 3
The Chapter may request a grant or loan from the Treasurer of SIAM under the provision of Article XII, Chapter 8 of the Bylaws of SIAM. Such requests shall be made by submission of “Request for Funding” form to SIAM and include a current financial statement for the Chapter and a proposed budget for the requested funds.
Section 4
Other than seeking funds from the sponsoring institutions of the chapter, no officers or member of the Chapter may apply for a grant to support the Chapter activities or enter into any contract to support such activities or provide services, without approval of the President and the Treasurer of SIAM or the Executive Director acting on behalf of the Treasurer.

Article XII: Amendments

Section 1
These Rules may be altered or amended with the approval of the SIAM Board of Trustees. Submission to the board of proposal alterations or amendments shall be made only after approval by majority vote of members of the Chapter present (or represented by proxy) at a scheduled meeting. Before the scheduled meeting, a notice of the upcoming vote shall be sent (by email) to all members at least 1 week in advance.

Article XIII: Termination of the Chapter

Section 1
A Chapter may terminate itself by the unanimous vote of the members of the Chapter present (or represented by proxy) at a scheduled meeting, provided that notice of the proposed termination and the meeting at which it is to be considered has been given to all Chapter members at least 30 days in advance.
Section 2
A Chapter may be terminated by the board if there has been no Chapter activity for one year.
Section 3
In the event a Chapter terminates, the funds to which it has legal title shall revert to the account of SIAM.


  • Approved, SIAM Board of Trustees, December 3, 1977
  • Revised, SIAM Board of Trustees, June 21, 2003
  • Adopted with minor customization, UT Austin Chapter of SIAM, September 29, 2005

SIAM prizes for students

Among many other awards, SIAM sponsors the following prizes for students:

SIAM Student Paper Prize
"The SIAM Student Paper Prizes are awarded every year to the student author(s) of the most outstanding paper(s) submitted to the SIAM Student Paper Competition. This award is based solely on the merit and content of the student's contribution to the submitted paper. The purpose of the Student Paper Prizes is to recognize outstanding scholarship by students in applied mathematics or computing."
SIAM Award in the Mathematical Contest in Modeling
"The SIAM Award in the Mathematical Contest in Modeling (MCM), established in 1988, is awarded to two of the teams judged 'Outstanding' in the Mathematical Contest in Modeling (MCM), administered annually by the Consortium for Mathematics and Its Applications (COMAP). One winning team is chosen for each of the two problems (continuous and discrete) posed in the MCM."
Frank and Brennie Morgan Prize for Outstanding Research in Mathematics by an Undergraduate Student
"The Morgan Prize was established in 1995 and is awarded annually to an undergraduate student (or students having submitted joint work) for outstanding research in mathematics. It is entirely endowed by a gift from Mrs. Frank (Brennie) Morgan. Any student who is an undergraduate in a college or university in Canada, Mexico, the United States or its possessions is eligible to be considered for the prize. The award is made jointly by the American Mathematical Society, the Mathematical Association of America, and the Society for Industrial and Applied Mathematics."
SIAM Student Travel Awards
"SIAM offers travel support for students through SIAM Student Travel Awards. The awards are made from the SIAM Student Travel Fund, created in 1991 and maintained through book royalties donated by generous SIAM authors and by donations from SIAM members. The awards for selected conferences are also supported by donations from industry. Any full-time student in good standing is eligible to receive an award plus gratis meeting registration."

SIAM Resources

The following is a condensed list of SIAM resources. Please see www.siam.org for a complete list of member resources.

Activity Groups
"SIAM Activity Groups (SIAGs) provide a more focused forum for SIAM members interested in exploring one of the areas of applied mathematics, computational science, or applications."
"The mission of SIAM's book program is to make relevant research results accessible to industry and science and to promote the interaction between mathematics and other disciplines such as engineering, science, and computing."
Careers & Jobs
"Whether you are a student considering a career in mathematics, or an established mathematician, you will find the job-search and career information resources in this section invaluable."
"SIAM conferences focus on timely topics in applied and computational mathematics and applications and provide a place for members to exchange ideas and to expand their network of colleagues in both academia and industry."
Search SIAM journals "SIAM publishes 14 peer-reviewed research journals. . . . The full text of SIAM journals is now available electronically on a subscription basis."
Membership List
"Search directory information for members of AMS, MAA, SIAM, AMATYC, AWM, & CMS/SMC."
"SIAM conducts an extensive prize program to recognize outstanding applied mathematicians and computational scientists."
"SIAM publishes selected proceedings from its yearly meetings and conferences."
"Students are the future of applied mathematics and computational science. SIAM welcomes students with opportunities to participate in SIAM, as well as online resources on education and careers."

SIAM student travel awards

SIAM offers travel support for students through SIAM Student Travel Awards.

Commercial jet Any full-time student in good standing is eligible to receive an award plus gratis meeting registration. Top priority will be given to students presenting papers at the meeting, with second priority to students who are co-authors of papers to be presented at the meetings. Only students traveling more than 100 miles to the meetings are eligible for the awards.

An application for a travel award must include:

  1. A letter from the student describing his/her academic standing and interests, his/her expected graduation date and degree, advisor's name, and, if available, a URL for a working Web page.
  2. A one-page vita that includes the student's research interests, projects, and papers published.
  3. A detailed letter from the student's faculty advisor indicating why the student is deserving of receiving a travel award and any special circumstances.
  4. If applicable, the title(s) of the paper(s) to be presented (co-authored) by the student at the meeting.

In most cases, the deadline for complete applications is approximately seven months before the first day of the conference for which support is requested, and awardees will be notified by e-mail five months before the first day of the meeting.

More information, including the online application submission system, is available at SIAM's Student Travel Awards page.

UT graduate student professional development awards

"Professional Development Awards provide support for students to attend major professional meetings at which they present an original paper based on their research. The Graduate School allocates travel funds to each department or program. The graduate adviser and graduate coordinator can nominate students for these awards which are approved and administered by the Graduate School."


For any questions regarding the 2009 TAMMS conference, please contact:

Rhys Ulerich
Rhys Ulerich
201 E. 24th St
ACE 4.102
1 University Station C0200
Austin, Texas 78712

TAMMS 2009 Group Photo

The individuals in the photo are, from left to right and front to back: Yan Li, Yulia Hristova, Pearl Flath, Dr. Raegan Higgins, Rhys Ulerich, Linh Nguyen, Christopher Mirabito, Robert Rosenbaum, Toby Isaac, Ryan Nong, Kaleb McKale, Moritz Allmaras, Dimitar Trenev, Sean Hardesty, Anthony Kellems, and Omar Al Hinai.

The photo was taken by Khoa Tran of U.T. Austin.


There are a variety of hotels within a fifteen minute drive from the University of Texas. Prices vary widely. Downtown hotels are generally the most expensive. Two relatively reasonable options are:

La Quinta Inn Austin Capitol
300 E. 11th St.
Austin, TX 78701
(512) 476-1166
Days Inn Austin/University/Downtown
3105 N I-35
I-35 & 32nd Street
Austin, TX 78722

Keynote speaker: Dr. Raegan Higgins

TAMMS was proud to have Dr. Raegan Higgins give the keynote at our conference. She presented on Friday, March 27th in CPE 2.212 at 4:45 PM.

"An Introduction to the Time Scale Calculus"

A time scale T is just a closed nonempty subset of the real numbers. Time scales include the real numbers, the integers, and the Cantor set. Given a smooth function p(t) defined on a time scale and a point s in the time scale we will define a generalized exponential function ep(t,s) which generalizes the exponential function ept studied in calculus.

Brief Biography

Raegan Higgins received a B.S. degree in mathematics from Xavier University of Louisiana in 2002 , and the degrees of M.S. (2004) and Ph.D. (2008) from the University of Nebraska-Lincoln. Her dissertation work was in the area of oscillation criteria for dynamic equations on time scales.

Dr. Higgins' current research is in time scales; her interests focus on oscillation criteria for certain linear and nonlinear second order dynamic equations. She is also interested in issues that affect pre-service teachers ability to teach mathematics.


RLM and CPE building locations On Friday, March 27th the conference was in the Chemical and Petroleum Engineering Building (CPE) room 2.212. On Saturday, March 28th the conference was in in Robert Lee Moore Hall (RLM) room 4.102. Both buildings are at the corner of Speedway & E Dean Keeton St in the Engineering Area of the University of Texas at Austin campus.

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TAMMS 2009 logo

Texas Applied Mathematics Meeting for Students

The Austin Chapter of SIAM was proud to host the 2009 Texas Applied Mathematics Meeting for Students (TAMMS) on March 27–28th. Attendees had an opportunity both to present their own research and to meet fellow SIAM student members from other Texas institutions.

Date & time:
Friday, March 27th from 2 PM—6 PM
Saturday, March 28th from 8 AM—12:30 PM
CPE 2.212 on Friday
RLM 4.102 on Saturday
Student presentations
Keynote: Dr. Raegan Higgins
Group dinner on Friday night at Sao Paulo's
Participating schools:
U.T. Austin Chapter of SIAM
Rice University
Texas Tech University
Texas A&M University
University of Houston


We recommend that visitors to our campus park at either the Speedway Garage (SWG) or the 27th Street Garage (TSG). From the Speedway garage, it will take you seven minutes to walk to either CPE on Friday or RLM on Saturday. From the 27th street garage, it will take you ten minutes to walk to these two buildings.

Garage parking rates as well as a printable campus visitor map are available from Parking and Transportation Services.


To register for the 2009 Texas Applied Mathematics Meeting for Students, please email siam@ices.utexas.edu and include your

  1. Full name
  2. Email
  3. Position (undergraduate, graduate, faculty)
  4. Department
  5. Institution

At this time, all of our student speaking slots are full. Please indicate in your registration note if you would like to be waitlisted for a speaking opportunity.

The registration fee is $10 if you register in advance or at the door. Registration does not cover the cost of Friday night dinner.

Meeting Schedule

The following talks took place at the conference.

Friday, March 27th 2009 in CPE 2.212

2:00–2:30 PM
Arrival & registration
2:30–2:45 PM
Welcoming remarks
2:45–3:15 PM
James Martin
Computational and Applied Mathematics
UT Austin
A Stochastic Newton's Method for Bayesian Inverse Problems

We present a new MCMC method for sampling high-dimensional, expensive-to-evaluate probability density functions. We improve upon Langevin sampling by using local Hessian information to guide sampling, drastically improving acceptance probabilities and MCMC convergence rates. The resulting method resembles a stochastic variant of Newton's method. We demonstrate by solving a statistical inverse problem governed by 1D seismic wave propagation with up to 65 parameter dimensions, for which the new method is two orders of magnitude faster than conventional MCMC.

3:15–3:45 PM
Yulia Hristova
Texas A&M University
Time reversal in thermoacoustic tomography - an error estimate

In thermoacoustic tomography an object is irradiated by a short electromagnetic pulse and the absorbed energy causes a thermoelastic expansion. This expansion leads to a pressure wave propagating through the object. The goal of thermoacoustic tomography is the recovery of the initial pressure inside the object from measurements of the pressure wave made on a surface surrounding the object. The time reversal method can be used for approximating the initial pressure when the sound speed inside the object is variable (non-trapping as well as trapping).

In this talk I will present error estimates for the time reversal method in the cases of variable, non-trapping sound speeds.

3:45–4:15 PM
Jay Raol
Computational and Applied Mathematics
Rice University
Using Fast Activating Voltage Sensitive Calcium Channels as Voltage Sensors

Calcium plays an important role in neuroscience. Not only is it involved in the pathways that govern learning events in neurons, but it is increasingly being used as the primary means of accessing information about the neuron's state. Unfortunately, for most physiologists, calcium information is an incomplete picture of the neuron.

We developed an algorithm to convert fluorescent calcium data into voltage and conductance information. We simulate our algorithm on synthetic data to illustrate its usefulness.

4:15–4:45 PM
Coffee Break
4:45–5:30 PM
Dr. Raegan Higgins
Mathematics and Statistics
Texas Tech University
An Introduction to the Time Scale Calculus

A time scale T is just a closed nonempty subset of the real numbers. Time scales include the real numbers, the integers, and the Cantor set. Given a smooth function p(t) defined on a time scale and a point s in the time scale we will define a generalized exponential function ep(t,s) which generalizes the exponential function ept studied in calculus.

5:30–6:00 PM
Moritz Allmaras
Texas A&M University
Ultrasound Modulated Optical Tomography: Reconstructions for a Differential Model

Ultrasound Modulated Optical Tomography attempts to improve the severe ill-posedness of the reconstruction problem arising in classical Optical Tomography by combining the advantages of Optical Tomography with those of ultrasound imaging. In this talk, a model is introduced that describes the effect of ultrasound modulation on the light intensity by two coupled diffusion equations, one for the original, unaffected photon intensity and one for a second, virtual intensity field modulated at ultrasound frequency.

In contrast to previous statistics-based approaches, this model allows reconstruction of the absorption coefficient by using efficient, PDE-based solutions for the forward problem. A simple reconstruction algorithm is introduced to demonstrate the feasibility of this reconstruction for 2D problems and well-focused ultrasound signals. For the more realistic case of non-focused ultrasound signals, reconstruction techniques based on inversion of certain integral transforms are suggested. For both of these cases, numerical reconstruction results for artificial absorption phantoms are presented.


Dinner at Sao Paulo's Brazilian Restaurante, 2809 San Jacinto Blvd.

Saturday, March 28th 2009 in RLM 4.102

8:00–8:30 AM
Sean Hardesty
Computational and Applied Mathematics
Rice University
Optimization of Shell Structure Acoustics

Modeling of elastic shell structures coupled with acoustics in a way that is suitable for optimization poses a multitude of challenges. For the exterior problem, it is convenient to use shell elements in conjunction with boundary elements so that shape updates can be performed without modifying the mesh. In order to do so, the shell code must be free of the so-called locking phenomenon, and the boundary element code must be robust and reasonably fast. With the aim of making the implementation of the coupling and adjoint equations as simple as possible, we describe a scheme satisfying these criteria, and present some numerical results.

8:30–9:00 AM
Anthony R. Kellems
Computational and Applied Mathematics
Rice University
Dimension Reduction Techniques that Capture Nonlinear Behavior of Morphologically Accurate Neuronal Models

Simulating active neurons with realistic morphologies and synaptic inputs requires the solution of large systems of nonlinear ordinary differential equations. Using model reduction techniques of proper orthogonal decomposition and an empirical interpolation method, we recover the complete neuronal voltage dynamics using a system of dimension nearly two orders of magnitude smaller than the original and that simulates one order of magnitude faster, without sacrificing the spatially-distributed input structure.

9:00–9:30 AM
Yan Li
Texas A&M University
Local-Global Upscaling of Flow and Transport in heterogeneous porous media

Flow and transport in subsurface formations are affected by geological variability over multiple length scales. We develop a local-global two-phase upscaling approach to generate upscaled transport functions. The upscaling of multiphase flow parameters is challenging due to their strong dependency on global flow effects. The local-global two-phase upscaling directly incorporates global coarse-scale two-phase solutions into local two-phase upscaling calculations. It effectively captures the impact of global flow, while avoiding global two-phase fine-scale simulations. The local boundary conditions are updated with time-dependent coarse-scale solutions. It therefore captures the global flow effects both spatially and temporally. The method is applied to permeability distributions with various correlation lengths. Numerical results show that it consistently improves existing two-phase upscaling methods (e.g., upscaling with effective flux boundary conditions), and provides accurate coarse-scale solutions for both flow and transport.

9:30–10:00 AM
Ryan Nong
Computational and Applied Mathematics
Rice University
Numerical Solutions of Matrix Equations Arising in Model Order Reduction for Linear-Time-Invariant Systems in the Large-Scale Setting

Balanced truncation and positive real balancing techniques in dimension reduction for linear-time-invariant dynamical systems require the solution of multiple large-scale matrix equations. Current iterative solvers include the approximate power method (APM) and the alternating direction implicit (ADI) method. The former is parameter free and tends to be efficient in practice but there is little theoretical understanding of its convergence properties. The latter has a well understood convergence theory but relies heavily upon heuristic parameter selection for rapid convergence. In this talk, I will first introduce a novel algorithm that is based on a synthesis of the two aforementioned techniques. This parameter free ADI-like (PFADI) technique uses an APM iteration as a means to bypass the trouble in parameter selection of the ADI method but still preserves its convergence properties. I will then present new results in optimizing the performance of the PFADI method.

10:00–10:30 PM
Coffee Break
10:30–11:00 AM
Dimitar Trenev
Texas A&M University
Approximating solutions of infinite domain Laplace and Helmholtz problems

In this talk I will discuss the main difficulties that arise when employing the finite element method to approximately solve PDEs posed on infinite domains. I will then present a simple way of overcoming them for the cases of exterior Laplace and Helmholtz problems. Additionally this talk will serve as an introduction to the Perfectly Matched Layer technique - the leading artificial boundary condition for acoustic and electromagnetic scattering problems.

11:00–11:30 AM
Robert Rosenbaum
University of Houston
Correlation Propagation in Networks of Integrate-and-Fire Neurons

Experimental results show that correlations between the spiking activity of neurons are used to encode information about some stimuli. However, experimental and theoretical results show that excess correlation can accumulate in feedforward networks and lead to pathological spiking behaviors. I will discuss some work on correlation transfer properties of analytically tractable neuron models and implications on the activity of feedforward networks.

11:30–12:00 AM
Linh Nguyen
Texas A&M University
On inversion formula in Thermoacoustic Tomography

We present a family of inversion formulas in Thermoacoustic Tomography that contains as special cases most of previously known closed form reconstructions for acoustically homogeneous media.

12:00–12:30 AM
Pearl Flath
Computational and Applied Mathematics
UT Austin
Fast algorithms for uncertainty estimation in large scale linear dynamical systems

We consider the problem of estimating and propagating the uncertainty in the initial condition field of a convection-diffusion problem describing the transport of atmospheric contaminants. Estimation of the uncertainty is treated within a Bayesian framework. Standard Markov chain Monte Carlo approaches are intractable for such high-dimensional problems. Even when the data and prior uncertainty are Gaussian, and as a result the posterior estimate is Gaussian with covariance given by the inverse of the Hessian matrix of the regularized least squares objective, the computation of the exact covariance matrix is intractable due to the large size and extreme cost of forming the inverse of the Hessian. In the case of linear ill-posed inverse problems, we show that fast algorithms can be constructed that provide accurate low rank Hessian approximations of the least squares data misfit, and as a result permit estimation and propagation of the uncertainty for large-scale problems at a small multiple of the cost of solving the forward problem. Large-scale examples demonstrate the main ideas.

12:30–12:45 PM
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