April 22-24, 2005
We present a primal-dual interior-point algorithm for solving linear programming problems using the notion of the quasicentral path as a central region. We introduce a Newton direction associated to the quasicentral path that yields an implementation using only primal and complementarity variables. A semi-iterative solvers for obtaining this Newton direction is presented where only one matrix factorization is done in all the iterative procedure. A promising numerical experimentation using a predictor-corrector algorithm is performed on the set of NETLIB test problems.Read More...
Driever and Nusslein-Volhard showed that the bicoid gene protein determines position in the Drosophila embryo in a concentration-dependent manner. We combine our knowledge of this result with the gene circuit model which is based on 4 steps: formulate a theoretical model, acquire data, optimize using simulated annealing and learn new biology. Published versions of the gene circuit model yielded biologically inaccurate results. First, we modify the model to get biologically robust results. Then, we propose a manner to characterize statistically biological robustness despite changes in the bicoid dosage.Read More...
Managing a portfolio of computer and software resources in a sufficiently large business enterprise is a complicated and daunting task involving an analysis of a myriad of factors to include business capabilities, business value and business risk. A finite horizon discrete time Markov decision process (MDP) is developed to model enterprise portfolio transformation.Read More...
The ability to detect anomalies as clustering in data sets plays an important role in spatial data analysis. Tango (1995) developed a statistic that can be used to detect clusters in data sets. Rogerson (1999) observed that Tango's index may be decomposed into the summation of two distinct statistics, the first part a test of goodness-of-fit (GOF), and the second part an index of spatial autocorrelation (SA) similar to Moran's I. In this poster we investigate the effectiveness of Rogerson's expression of Tango's statistic in separating GOF from SA in data sets containing clusters. We simulate data under the null hypothesis of no clustering as well as two alternative hypotheses. The first alternative hypothesis induces a poor fit from the null hypothesis while maintaining independent observations and the second alternative hypothesis induces spatial autocorrelation while maintaining fit. Using Rogerson's decomposition and leukemia incidence data from New York, we show graphically one is unable to statistically distinguish poor fit from autocorrelation.Read More...
In the course of carrying out your research and proposal writing, it is not difficult to amass dozens or hundreds of research papers relevant to your work. Fortunately, online journals, websites, and colleagues often make their material available in PDF (Adobe Portable Document Format) which can then be stored in a single directory on your computer or on a portable USB thumb drive. What is needed, however, is a special PDF document that conveniently lists all of the titles and bibliographic information for the PDFs that you have collected. Some special features of this index should include the ability to: click on a title name and instantly have that research article appear, and click on a title citation and have its bibliographic information appear. Furthermore, this index should be easy to create, maintain, and archive (for backup purposes). We describe how to build this type of index to your collected PDF files using tools commonly or freely available for your laptop machine (e.g., LaTeX, Emacs, the Adobe acrobat reader).Read More...
For many, the thought of funding your research career is something you never considered. My presentation will be an informal discussion on the art of research funding.Read More...
Joint work with Sergio Cabrera, Alberto Aguirre, Miguel Argaez, Eduardo Vidal Jr.Read More...
This poster present the latest results of an ongoing project to assess the impact of lossy compression applied to three-dimensional meteorological data. The main innovative outcomes presented are based on different bit allocation techniques used to compress Karhunen-Loeve transformed data. The transform is applied in the z-direction (between slices) as suggested in the JPEG2000 Part 2 standard. New results using these bit allocation techniques are presented on two data sets. The performance results are presented in terms of SNR, root-mean squared error (RMSE), and the maximum absolute error (MAE) for the entire cube of data.
We study the existence and uniqueness of pseudo almost
periodic solutions to semilinear abstract differential equations of the form
u'(t)+ Au(t) = f(t,u(t)) (*)
where -A is the infintesimal generator of an analytic semigroup acting
on a (complex) Banach space X, and f: RxX ---> X is a jointly continuous
function. Under some additional assumptions on A and f, the existence
and uniqueness of pseucdo almost periodic (classical) solutions to (*)
is obtained by using both fractional powers of operators and the Banach
This paper examines the steady-state solutions of strongly exothermic reaction of a viscous combustible material in a channel filled with saturated porous medium under Arrhenius kinetics, neglecting the consumption of the material. The Brinkman model is employed and analytical solutions are constructed for the governing nonlinear boundary-value problem using perturbation technique together with a special type of Hermite-Padé approximants and important properties of the temperature field including bifurcations and thermal criticality are discussed.Read More...
Keywords: Porous medium flows, Arrhenius kinetics, Hermite-Padé approximants, Thermal criticality.
Our study uses Clarke's decoupling technique to obtain Euler-Lagrange and Hamiltonian necessary conditions for the problem of Bolza with Lipschitz continuously varying delay in both the state and velocity parameters.Read More...
We discuss the paucity of hearing-impaired people with PhDs in mathematics
given the incidence of hearing loss in the general population to be one in
ten. We list the names and background of 18 such people including
Charlotte Agnas Scott who was a co-founder of the American Mathematical
Society and Kathleen Ollerenshaw who became the President of the UK-based
Institute of Mathematics and its Applications in the late 1970s. We
comment on the possibility that web-based mathematics could be the way to
attract people from all under-represented communities as well as those in
the mainstream.Read More...
In this motivational talk the speaker will describe formative interesting experiences, challenges and successes encountered along his life's journey from a childhood in the barrios of Los Angeles to a University Mathematics Professor, a President Clinton appointee to the National Science Board, and the first domestic born Latino elected to the prestigious National Academy of Engineering. A first-generation Mexican-American and a product of public education, Los Angeles City Schools and UCLA, the speaker's path reinforces the view that many paths lead to the same place. Discussion points will include
- Should race and ethnicity play a role in academic science, engineering , and mathematics? As underrepresented minorities are we round pegs in square holes; how much do we have to change to be academically successful? What are the extra dimensions that we bring to the table; are they embraced, appreciated, rewarded?Read More...
A model to study the strength and effects of axial diffusion on many interacting capillaries in skeletal muscle is presented. The method consists of determining the oxygen concentration in a functional unit,consisting of a single capillary surrounded by a region of tissue, in which a flux is prescribed on the outer boundary of the region. This flux, which is a result of the interaction among all of the capillaries comprising the vascular bed, is found by matching the concentration along the common border between adjacent units.Read More...
Because capillary lengths are large compared to their spacing, diffusion in the tissue in the direction parallel to the capillaries (axial diffusion) is small compared to diffusion in the plane perpendicular to the capillaries. For this reason axial diffusion is often neglected in diffusion analyses. However, axial diffusion does have a significant effect on oxygen and substrate concentration within the tissue, and on how these substances are delivered to the tissue by the capillaries. Axial diffusion is included in the analysis by obtaining the solutions to the differential equation derived from the model with axial diffusion as a perturbation to the solution without axial diffusion. However, in the region near the arterial end axial diffusion is comparable to diffusion in the plane perpendicular to the capillaries. Hence singular perturbation techniques are used to study these regions and appropriately match these regions (inner regions) to the regions where axial diffusion is negligible (outer region) using the method of matched asymptotic expansion.
We present an extension of the Cayley-Hamilton Theorem over a seperable Hilbert space . Applications of our results include expressions on the one-sided inverse and the resolvent of an elliptic operator, and some new insights into finding the inverse of a frame operator.Read More...
Joint work with Brenda Bueno and Miguel Argaez
We study a nonlinear least squares problem that arises in a process of mapping selected atom positions of the beta sheets in proteins onto a hyperboloid. We use the TIM barrel data as a test case since it has a clear barrel structure, and it is expected for the mapped atoms to arrange themselves in a barrel shape around the calculated hyperboloid. Then, we investigate allosteric enzymes and describe the conformational changes of the beta sheets between the active (R) and the inactive (T) states.Read More...
Close to a solution of the nonlinear program, the Jacobian associated with
the Karush-Kuhn-Tucker (KKT) system is nonsingular. However, for points far
from a solution of the nonlinear program, the Jacobian may be singular. In this
paper, we propose a global method that obtains a least-squares solution to the
linearization of the perturbed KKT conditions subject to a limit on the step
size. In addition, we use the 2
norm of the KKT conditions as a merit function to solve the nonlinear program.
We implement trust-region and interior-point methods to solve the nonlinear
We consider the complex Ginzburg-Landau equation form
which describes the femtosecond pulses propagation in
optical system. Using the separation method, we
obtained under some specific constraint conditions the
existence of dark soliton. In the particular case of
degenearcy, a generalized method, which is generally
called the projective Riccati equation method is used
to construct new exact solutions of the above
mentioned equation based on a system of Riccati
equations. These new solutions include bright soliton,
dark soliton, new solitary wave solutions and periodic