Informs 2015

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INFORMS Philadelphia – 2015
460
WD19
19-Franklin 9, Marriott
Core Algorithms and Techniques for Computational
Optimization
Sponsor: Computing Society
Sponsored Session
Chair: Atharv Bhosekar, Carnegie Mellon University, 5000 Forbes
Avenue, Pittsburgh, Pe, 15213, United States of America,
1 - Update Algorithms for the Roundoff-error-free LU and Cholesky
Factorizations
Adolfo Escobedo, PhD Candidate, Texas A&M, 3131, TAMU,
College Station, TX, 77843, United States of America,
, Erick Moreno-centeno
We introduce efficient update algorithms for the Roundoff-error-free (REF) LU
and Cholesky factorizations. The updates are addition, deletion, and replacement
of rows and columns of a basis. Combined with REF substitution, the featured
algorithms provide a complete framework for solving LPs exactly and efficiently.
A significant advantage of the REF LP framework is that the length of any
coefficient calculated via its algorithms is bounded polynomially without having
to use gcd operations.
2 - Status Update on GCG, a Generic Branch-price-and-cut Solver
Marco Luebbecke, Aachen University, Germany,
Jonas Witt,
Michael Bastubbe, Christian Puchert
GCG is a source-open extension to SCIP to solve mixed-integer programs (MIPs)
via branch-price-and-cut without any user interaction. It is meant as a research
vehicle and “another trick in the bag” to solve MIPs. For specially structured
MIPs, GCG (not surprisingly) outperforms standard MIP solvers by far while it
(also not surprisingly) colossally fails on other instances. We report on the
project’s status, recent novelties, future plans, and potential benefits for a general
audience.
3 - Integer Programming as Projection
John Hooker, Carnegie Mellon University, 5000 Forbes Avenue,
Pittsburgh, PA, 15213, United States of America,
, H. P. Williams
We develop an alternative theory of integer programming (IP) based on
projection. We define valid inequalities that are analogous to Chvatal-Gomory
cuts but based on congruences rather than rounding and have bounded rank. We
show how to solve a general IP by branching solely on finite-domain auxiliary
variables. We define an IP dual as a value function that is obtained by nested
rounding of bounded depth and becomes shift periodic for large perturbations.
4 - Computational Experience with the Bam Global Optimization
Algorithm for Derivative-Free Optimization
Atharv Bhosekar, Carnegie Mellon University, 5000 Forbes
Avenue, Pittsburgh, PA, 15213, United States of America,
Luis Miguel Rios, Nikolaos Sahinidis
Branch-and-model (BAM) is a derivative-free optimization (DFO) algorithm that
builds a model around each evaluated point using the surrounding evaluated
points. The algorithm performs a dense search and employs a local search
algorithm to identify local optima. We present extensive computational
experience with the algorithm and comparisons with other DFO algorithms.
WD21
21-Franklin 11, Marriott
Operations Research Methodologies to Improve
Healthcare Operations
Sponsor: Health Applications
Sponsored Session
Chair: Nazanin Esmaili, PhD Candidate, University of Pittsburgh,
1048 Benedum Hall, Pittsburgh, PA, United States of America,
1 - Impact of Care Discontinuity on Patients’ Length of Stay
Kimia Ghobadi, Massachusetts Institute of Technology,
77 Massachusetts Ave, Cambridge, MA, United States of America,
Retsef Levi, Ana Cecilia Zenteno Langle,
Andrew Johnston
The Department of Medicine in Massachusetts General Hospital serves a wide
variety of patients with various care levels. This functional heterogeneity has led
to distributed care models which combined with consistent growth in demand has
resulted in a congested system. In this talk, we explore contributors to clinically
unnecessary delays in patient progression through the hospital, and more
specifically, the impact of care discontinuity during team handovers on patients’
total length of stay.
2 - Appointment Scheduling Based Upon Continuously and
Periodically Reported Data
Zlatana Nenova, University of Pittsburgh, 241 Mervis Hall,
Roberto Clemente Drive, Pittsburgh, PA, 15260,
United States of America, , Jerrold H. May
We discuss an approach to determining the optimal timing of appointments for
diabetic patients, based upon their blood glucose, blood pressure, and cholesterol
readings. Blood pressure and cholesterol are reported periodically; blood glucose
is reported multiple times per day. The approach is illustrated using examples
from the VA Health System.
3 - Simulation of a Phlebotomy Station in an Outpatient
Chemotherapy Infusion Clinic
Matthew Rouhana, University of Michigan, 1205 Beal Avenue,
Ann Arbor, MI, United States of America,
Amy Cohn, Pamela Martinez Villarreal, Marian Grace Boxer,
Carolina Typaldos
We study the organization and operation of a phlebotomy station at the
University of Michigan Comprehensive Cancer Center. By developing a
simulation of the patient and work flow through the station, we evaluate
alternative methods to reduce patient wait time and improve full-day patient
experiences. For educational purposes, we create a simplified table-top version to
demonstrate the underlying probability theory for hospital leadership.
4 - Hospital Nurse Staffing Improvements through Better Prediction
of Surgical Case Volume
Nazanin Zinouri, Clemson University, 130 Freeman Hall,
Clemson, SC, United States of America, ,
Kevin Taaffe
Accurate approximations of final surgical case volume are difficult due to the high
surgical demand variations. Staffing adjustments a few days prior to the day of
surgery are difficult and inefficient. Having accurate demand prediction weeks in
advance would help improve staff scheduling and decrease nurse workload
pressure by allowing more flexibility in the schedule. We have studied current
staff scheduling and workload prediction methods at a hospital to identify areas
for improvement.
5 - Hybrid Inventory Policies for Hospitals with Shelf
Space Restriction
Nazanin Esmaili, PhD Candidate, University of Pittsburgh,
1048 Benedum Hall, Pittsburgh, PA, United States of America,
Bryan Norman, Jayant Rajgopal
We address the management of inventory for multiple non-perishable routine use
items in a healthcare setting. We present a mixed-integer programming model for
selecting the best inventory control system for each item and the best shelf
configuration considering space, shelf, and inventory control policy constraints.
The objective is to minimize the total average effort to monitor, manage and
replenish items. We illustrate the model with data from a hospital.
WD22
22-Franklin 12, Marriott
Stochastic Processes I
Contributed Session
Chair: Toshikazu Aiyama, Professor, Tokyo Metropolitan University,
1-1 MinamiOhsawa, HachiOhji, Japan,
1 - A Multi-Resolution Stochastic Graphene Growth Kinetics Model
Sobambo Sosina, Harvard University, 1 Oxford Street, 7th Floor
Science Center, Cambridge, MA, 02138, United States of America,
Tirthankar Dasgupta, Qiang Huang
Graphene has many important properties and has been identified as key
component in many industrial applications. It is thus crucial that its growth
process and the kinetics behind that process be thoroughly understood. Extending
work done by collaborators, we derive a stochastic model for multi-resolution
observations, which correctly quantifies uncertainty in the kinetics.
2 - Queueing Network Approximations with MAP(3)s
Sunkyo Kim, Professor, Ajou University, 206 World Cup Road,
Youngtong Gu, Suwon, 16499, Korea, Republic of,
We propose a minimal representation of MAP(3)s and present an exact moment
matching method. The marginal and joint LST of stationary intervals of the
MAP(3) is given in terms of nine parameters. As for queueing network
applications, arrival and departure processes are approximated as a MAP(3) based
on nine moments. We show that the MAP(3) approximation performs better than
MAP(2) especially under moderate traffic intensities.
WD19