A Comparison of the Dynamic and Physical Apertures of the RHIC90 Lattice

This report addresses a comparison of the dynamic and physical apertures of the RHIC90 lattice

Formulating Linear and Integer Linear Programs: A Rogues' Gallery

INFORMS Transactions on Education, 7, 2007, pp. 153-159.The article of record as published may be located at http://dx.doi.org/10.1287/ited.7.2.153The art of formulating linear and integer linear programs is, well, an art: It is hard to teach, and even harder to learn. To help demystify this art, we present a set of modeling building blocks that we call “formulettes.” Each formulette consists of a short verbal description that must be expressed in terms of variables and constraints in a linear or integer linear program. These formulettes can better be discussed and analyzed in isolation from the much more complicated models they comprise. Not all models can be built from the formulettes we present. Rather, these are chosen because they are the most frequent sources of mistakes. We also present Naval Postgraduate School (NPS) format; a define-before-use formulation guide we have followed for decades to express a complete formulation

Numerical Methods versus Asymptotic Expansion for Torsion of Hollow Elastic Beams

  &nbsp

Noncommutative Computer Algebra in the Control of Singularly Perturbed Dynamical Systems

Most algebraic calculations which one sees in linear systems theory, for example in IEEE TAC, involve block matrices and so are highly noncommutative. Thus conventional commutative computer algebra packages, as in Mathematica and Maple, do not address them. Here we investigate the usefulness of noncommutative computer algebra in a particular area of control theory-singularly perturbed dynamic systems-where working with the noncommutative polynomials involved is especially tedious. Our conclusion is that they have considerable potential for helping practitioners with such computations. For example, the methods introduced here take the most standard textbook singular perturbation calculation, [KK086], one step further than had been done previously. Commutative Groebner basis algorithms are powerful and make up the engines in symbolic algebra packages’ Solve commands. Noncommutative Groebner basis algorithms are more recent, but we shall see that they are useful in manipulating the messy sets of noncommutative polynomial equations which arise in singular perturbation calculations. We use the noncommutative algebra package NCAlgebra and the noncommutative Groebner basis package NCGB which runs under it

Aerosol-based antimicrobial photoinactivation in the lungs: an action spectrum study

AbstractChronic lung infections are among the most diffused human infections, being often associated with multidrug-resistant bacteria. In this framework, the European project "Light4Lungs" aims at synthesizing and testing an inhalable light source to control lung infections by antimicrobial photoinactivation (aPDI), addressing endogenous photosensitizers only (porphyrins) in the representative case of S. aureus and P. aeruginosa. In the search for the best emission characteristics for the aerosolized light source, this work defines and calculates the photo-killing action spectrum for lung aPDI in the exemplary case of cystic fibrosis. This was obtained by applying a semi-theoretical modelling with Monte Carlo simulations, according to previously published methodology related to stomach infections and applied to the infected trachea, bronchi, bronchioles and alveoli. In each of these regions, the two low and high oxygen concentration cases were considered to account for the variability of in vivo conditions, together with the presence of endogenous porphyrins and other relevant absorbers/diffusers inside the illuminated biofilm/mucous layer. Furthermore, an a priori method to obtain the "best illumination wavelengths" was defined, starting from maximizing porphyrin and light absorption at any depth. The obtained action spectrum is peaked at 394 nm and mostly follows porphyrin extinction coefficient behavior. This is confirmed by the results from the best illumination wavelengths, which reinforces the robustness of our approach. These results can offer important indications for the synthesis of the aerosolized light source and definition of its most effective emission spectrum, suggesting a flexible platform to be considered in further applications

Scheduling Coast Guard District Cutters

Interfaces, 26, March - April 1996, pp. 59-72Center for Infrastructure Defense (CID) Paper.United States Coast Guard (USCG) districts schedule cutters 180 feet or less in length to weekly statuses (statuses is USCGjargon for assignments) from which they primarily respond to calls for search and rescue, law enforcement, and pollution control. The First Coast Guard District, based in Boston, has one of the largest scheduling problems: Each of 16 cutters is as- signed weekly to one of six statuses to ensure patrol coverage, enforce equitable distribution of patrols, and honor restrictions on consecutive cutter statuses. When we state this quarterly scheduling problem as an elastic mixed-integer linear program, we obtain face-valid schedules—superior to manually prepared schedules for all measures of effectiveness considered—within a few minutes on a personal computer. Initial acceptance of the model was hampered by disruptive schedule revisions that re- sulted from minor changes in input. Modifications to preserve run-to-run persistence of solutions have brought success

Web User Session Reconstruction Using Integer Programming

An important input for web usage mining is web user sessions that must be reconstructed from web logs (sessionization) when such sessions are not otherwise identified. We present a novel approach for sessionization based on an in- teger program. We compare results of our approach with the timeout heuristic on web logs from an academic web site. We find our integer program provides sessions that better match an expected empirical distribution with about half of the standard error of the heuristic.This work has been partially supported by the National Doctoral Grant from Conicyt Chile and by the Chilean Millennium Scientific Institute of Complex Engineering Systems

What Do We Learn from the Weather? The New Climate-Economy Literature

A rapidly growing body of research applies panel methods to examine how temperature, precipitation, and windstorms influence economic outcomes. These studies focus on changes in weather realizations over time within a given spatial area and demonstrate impacts on agricultural output, industrial output, labor productivity, energy demand, health, conflict, and economic growth, among other outcomes. By harnessing exogenous variation over time within a given spatial unit, these studies help credibly identify (i) the breadth of channels linking weather and the economy, (ii) heterogeneous treatment effects across different types of locations, and (iii) nonlinear effects of weather variables. This paper reviews the new literature with two purposes. First, we summarize recent work, providing a guide to its methodologies, datasets, and findings. Second, we consider applications of the new literature, including insights for the "damage function" within models that seek to assess the potential economic effects of future climate change