Optimal co-adapted coupling for the symmetric random walk on the hypercube

Let X and Y be two simple symmetric continuous-time random walks on the vertices of the n-dimensional hypercube, Z2n. We consider the class of co-adapted couplings of these processes, and describe an intuitive coupling which is shown to be the fastest in this class

MARKET-STRUCTURE DETERMINANTS OF NATIONAL BRAND-PRIVATE LABEL PRICE DIFFERENCES OF MANUFACTURED FOOD PRODUCTS

This paper estimates the relationships between market structure and the Lerner index of monopoly constructed from price data on processed food products sold through grocery stores. A theoretical model of a differentiated oligopoly specifies two determinants of price-cost margins: the Herfindahl-Hirschman index of seller concentration adjusted for the elasticity of demand and the industry advertising-to-sales ratio. The results indicate that the three principal determinants of price-cost margin variation, in order of their impacts, are: advertising intensity, elasticity of demand, and concentration. Previous structure-performance studies that did not incorporate the elasticity of demand were probably misspecified.Agribusiness, Demand and Price Analysis,

NEW ESTIMATES OF WELFARE AND CONSUMER LOSSES IN U.S. FOOD MANUFACTURING

In the past 15 years, industrial-organization economists have significantly expanded the range of algorithms for calculating welfare losses due to imperfect competition. We compare eleven empirical estimates of economic losses due to market power in 47 U.S. food manufacturing industries, almost all of them previously unpublished. Each of the studies incorporate different theoretical assumptions about demand conditions, supply conditions, or industry pricing behavior; or they utilize various data sources, time periods, and assumptions about the proper competitive benchmark. The estimates of average allocative losses due imperfect competition range from 0.2 percent to an impossibly high 289 percent of industry output; consumer losses range from 6.0 percent to 816 percent. However, there is a high degree of congruence in the rankings of economic losses due to market power. Hence, from the perspective of antitrust enforcement, the choice of industry targets has not been greatly altered by advances in estimation techniques.Agribusiness,

Collective Rabi dynamics of electromagnetically-coupled quantum dot ensembles

Rabi oscillations typify the inherent nonlinearity of optical excitations in quantum dots. Using an integral kernel formulation to solve the 3D Maxwell-Bloch equations in ensembles of up to $10^4$ quantum dots, we observe features in Rabi oscillations due to the interplay of nonlinearity, non-equilibrium excitation, and electromagnetic coupling between the dots. This approach allows us to observe the dynamics of each dot in the ensemble without resorting to spatial averages. Our simulations predict synchronized multiplets of dots that exchange energy, dots that dynamically couple to screen the effect of incident external radiation, localization of the polarization due to randomness and interactions, as well as wavelength-scale regions of enhanced and suppressed polarization.Comment: 7 pages, 6 figures, 1 tabl

Perfect Simulation of M/G/cM/G/c Queues

In this paper we describe a perfect simulation algorithm for the stable $M/G/c$ queue. Sigman (2011: Exact Simulation of the Stationary Distribution of the FIFO M/G/c Queue. Journal of Applied Probability, 48A, 209--213) showed how to build a dominated CFTP algorithm for perfect simulation of the super-stable $M/G/c$ queue operating under First Come First Served discipline, with dominating process provided by the corresponding $M/G/1$ queue (using Wolff's sample path monotonicity, which applies when service durations are coupled in order of initiation of service), and exploiting the fact that the workload process for the $M/G/1$ queue remains the same under different queueing disciplines, in particular under the Processor Sharing discipline, for which a dynamic reversibility property holds. We generalize Sigman's construction to the stable case by comparing the $M/G/c$ queue to a copy run under Random Assignment. This allows us to produce a naive perfect simulation algorithm based on running the dominating process back to the time it first empties. We also construct a more efficient algorithm that uses sandwiching by lower and upper processes constructed as coupled $M/G/c$ queues started respectively from the empty state and the state of the $M/G/c$ queue under Random Assignment. A careful analysis shows that appropriate ordering relationships can still be maintained, so long as service durations continue to be coupled in order of initiation of service. We summarize statistical checks of simulation output, and demonstrate that the mean run-time is finite so long as the second moment of the service duration distribution is finite.Comment: 28 pages, 5 figure

ECONOMIC IMPACTS OF BANNING SUBTHERAPEUTIC USE OF ANTIBIOTICS IN SWINE PRODUCTION

Public health officials and physicians are concerned about possible development of bacterial resistance and potential effects on human health that may be related to the use of antimicrobial agents in livestock feed. The focus of this research is aimed at determining the economic effects that subtherapeutic bans of antimicrobials would have on both swine producers and consumers. The results show that a ban on growth promotants for swine would be costly, totaling $242.5 million annually with swine producers sharing the larger portion in the short run and consumers sharing about 75$586 million per year with swine producers sharing about the same as in bans for swine only and consumers sharing significantly more than the swine only case.Crop Production/Industries,

Low altitude temperature and humidity profile data for application to aircraft noise propagation

A data search of the weather statistics from 11 widely dispersed geographical locations within the continental United States was conducted. The sites, located long both sea-coasts and in the interior, span the northern, southern, and middle latitudes. The weather statistics, retrieved from the records of these 11 sites, consist of two daily observations taken over a 10-year period. The data were sorted with respect to precipitation and surface winds and classified into temperature intervals of 5 C and relative humidity intervals of 10 percent for the lower 1400 meters of the atmosphere. These data were assembled in a statistical format and further classified into altitude increments of 200 meters. The data are presented as sets of tables for each site by season of the year and include both daily observations

Noise reduction studies for the Cessna model 337 (0-2) airplane

A study was undertaken to determine the noise reduction potential of the 0-2 airplane in order to reduce its aural detection distance. Static and flyover noise measurements were made to document the noise signature of the unmodified airplane. The results show that significant reductions in aural detection distance can be achieved by the combination of propeller geometry changes and the addition of engine exhaust mufflers. The best results were estimated for the aircraft equipped with a six-blade propeller operating at 3/4 engine speed in combination with a 3.49 cubic foot exhaust muffler installed on each engine. Detection distance for the modified aircraft is estimated to be reduced from about 4-1/4 miles to about 1-1/2 miles when the aircraft is operating at an altitude of 1,000 ft over grassy terrain. Reducing the altitude to 300 ft over a leafy jungle ground cover should reduce the aural detection distance to 0.9 miles. Reduced aural detection distances were also indicated for a modification utilizing a direct-drive six-blade propeller of reduced radius along with smaller exhaust mufflers