2015 Informs Annual Meeting

TC12

INFORMS Philadelphia – 2015

TC11 11-Franklin 1, Marriott Advances in Discrete Optimization Sponsor: Optimization/Integer and Discrete Optimization Sponsored Session Chair: Gustavo Angulo, Assistant Professor, Pontificia Universidad Catolica de Chile, Vicuña Mackenna 4860, Macul, Santiago, 7820436, Chile, gangulo@ing.puc.cl 1 - Optimization over Structured Subsets of Positive Semidefinite Matrices via Column Generation

4 - Creativity under Fire: The Effects of Competition on Creative Production Daniel P. Gross, Post-doctoral Fellow, NBER/Harvard Business School, Soldiers Field Road, Boston, MA, 02163, United States of America, dgross@hbs.edu This paper studies the incentive effects of competition on individuals’ creative production. Using a sample of commercial logo design competitions, and a novel, content-based measure of originality, I find that competition has an inverted-U effect on creativity. The results reconcile conflicting evidence from an extensive literature on the effects of competition on innovation, with implications for R&D policy, competition policy, and organizations in creative or research industries.

TC10 10-Room 310, Marriott e-Media and Health Care Practices

Sanjeeb Dash, IBM Research, Yorktown Heights, NY, United States of America, sanjeebd@us.ibm.com, Amir Ali Ahmadi, Georgina Hall

We describe LP and SOCP algorithms that optimize over some structured subsets of the cone of positive semidefinite matrices (PSD cone) in an iterative fashion via column generation, starting with an initial linear approximation of the PSD cone given by Ahmadi and Majumdar (2014). We apply our techniques to sum-of- squares programming for nonconvex polynomial optimization problems, and to a

Sponsor: E-Business Sponsored Session

Chair: Harpreet Singh, University of Texas at Dallas, 800 West Campbell Road, Richardson, United States of America, Harpreet@utdallas.edu 1 - Does the Adoption of EMR Systems Inflate Medicare Reimbursements? Kartik Ganju, Temple University, Fox School of Business, Philadelphia, PA, United States of America, tuc67632@temple.edu, Hilal Atasoy, Paul Pavlou We study if the adoption of the CPOE system is associated with an increase in the complexity of the case mix that hospitals report (upcoding). We use the staggered roll-out of the Recovery Audit Program as a natural experiment to assess the impact of the adoption of the CPOE systems on the case mix that a hospital reports. We find that the adoption of CPOE systems is associated with an increase in the reported case mix of hospitals but the Audit program has had an effect on reducing this. 2 - Profit Complementarities in Adopting Electronic Medical Records by U.S. Hospitals Jianjing Lin, University of Arizona, 1130 E Helen St, Tucson, AZ, 85719, United States of America, jianjingl@email.arizona.edu This paper tries to examine by how much hospitals’ profit can be increased if they choose the locally market-leading vendor. Using a nationwide sample of U.S. hospitals from 2006 to 2010, I construct a dynamic oligopoly model and recover the model primitives with a classic approach in Economics. I find hospitals gain significant benefits from choosing the local leader and if hospitals were incentivized to choose such a technology, it would help improve the market coordination substantially. 3 - Get in Shape with Online Friends: Obesity and Social Networks Behnaz Bojd, University of Washington, Seattle WA, United States of America, behnaz@uw.edu, Yong Tan, Lu Yan Obesity is one of the most prevalent health problems in the world. Individuals suffering from this condition may use online social networks to get medical information or emotional support. In this study, we examine the effects of online social networking on individual weight-loss behavior, using a unique data set from a platform where people can track their weight, seek food and fitness information, share experiences, find buddies, and participate in different challenges. 4 - Digital Word-of-mouth and Consumer Demand for Credence Services: Evidence from a Natural Experiment Aishwarya Deep Shukla, PhD Student, University of Maryland, College Park, 3330C R H Smith School of Business, College Park, 20742, United States of America, adshukla@rhsmith.umd.edu, Ritu Agarwal, Gordon Gao This paper examines the impact of online word-of-mouth on consumer demand for credence services. We utilize a natural experiment setting from one of the largest physician appointment booking platforms in India, when the website made the doctor “recommendations” visible to users. In addition, we explore the long term effect of this visibility of recommendations in the context of matching the severity of the patient to the skill of the doctor.

copositive programming relaxation of the stable set problem. 2 - Cutting Planes from Extended LP Formulations Merve Bodur, UW-Madison, 1513 University Avenue,

Madison, WI, 53706, United States of America, mbodur@wisc.edu, Sanjeeb Dash, Oktay Gunluk

For mixed-integer sets, we study extended formulations of their LP relaxations. We show that applying split cuts to such extended formulations can be more effective than applying split cuts to the original formulation. For any 0-1 mixed- integer set with n integer and k continuous variables, we construct an extended formulation with 2n+k-1 variables whose split closure is integral. We extend this to general mixed-integer sets and construct the best extended formulation with respect to split cuts. 3 - Robust (MONOTONE) Submodular Function Maxmization Rajan Udwani, ORC, MIT, 70 Pacific Street, 324C, Cambridge, MA, 02139, United States of America, rudwani@mit.edu, James Orlin, Andreas Schulz Consider two common instances of monotone submodular function maximization with cardinality constraint, feature selection (machine learning) and sensor placement. In both, it is often the case that out of the chosen set of features (sensors), some may be corrupt (may fail). Thus, we would like our chosen set to be robust to removal of some elements. We consider a previously known formulation of this problem and give the first constant factor approximation algorithms. 4 - On a Semicontinuous Relaxation of Fixed-charge Network Flow Problems Gustavo Angulo, Assistant Professor, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Macul, Santiago, 7820436, Chile, gangulo@ing.puc.cl Usual formulations of fixed-charge network flow problems make use of binary variables to indicate whether an arc is open or not, and to impose lower and upper bounds on the flow whenever an arc is used. We propose a relaxation where both binary and flow variables are treated as unbounded semicontinuous variables. We derive a complete linear description of the convex hull of this relaxation and show the tractability of the associated separation problem.

TC12 12-Franklin 2, Marriott Optimization Integer Programming I Contributed Session

Chair: John Chinneck, Professor, Carleton University, Systems and Computer Engineering, 1125 Colonel By Drive, Ottawa, ON, K1S5B6, Canada, chinneck@sce.carleton.ca 1 - School Districting Problem (SDP) Framed as a Spatial Optimization Model/mixed Integer Program Shawn Helm, Senior Manager, Portland Public Schools, 501 North Dixon Street, Portland, OR, 97227-1807, United States of America, shelm@pps.net, Will Kearney, Sahan Dissanayake SDPs assign neighborhoods to schools given physical, demographic, and policy constraints. We control capacity; compactness; contiguity; amount of demographic change. Users specify class size; grade band; neighborhood capture assumptions; room uses; which current assignments are retained. The integrated framework uses real GIS data from Portland Public Schools and available solvers to identify best school-neighborhood assignments; solves model to display results and inform boundary decisions.

321