A Discrete and Bounded Envy-free Cake Cutting Protocol for Four Agents

We consider the well-studied cake cutting problem in which the goal is to identify a fair allocation based on a minimal number of queries from the agents. The problem has attracted considerable attention within various branches of computer science, mathematics, and economics. Although, the elegant Selfridge-Conway envy-free protocol for three agents has been known since 1960, it has been a major open problem for the last fifty years to obtain a bounded envy-free protocol for more than three agents. We propose a discrete and bounded envy-free protocol for four agents

Phase Space Dissimilarity Measures for Structural Health Monitoring

A novel method for structural health monitoring (SHM), known as the Phase Space Dissimilarity Measures (PSDM) approach, is proposed and developed. The patented PSDM approach has already been developed and demonstrated for a variety of equipment and biomedical applications. Here, we investigate SHM of bridges via analysis of time serial accelerometer measurements. This work has four aspects. The first is algorithm scalability, which was found to scale linearly from one processing core to four cores. Second, the same data are analyzed to determine how the use of the PSDM approach affects sensor placement. We found that a relatively low-density placement sufficiently captures the dynamics of the structure. Third, the same data are analyzed by unique combinations of accelerometer axes (vertical, longitudinal, and lateral with respect to the bridge) to determine how the choice of axes affects the analysis. The vertical axis is found to provide satisfactory SHM data. Fourth, statistical methods were investigated to validate the PSDM approach for this application, yielding statistically significant results

Global status of groundfish stocks

We review the status of groundfish stocks using published scientific assessments for 349 individual stocks constituting 90% of global groundfish catch. Overall, average stock abundance is increasing and is currently above the level that would produce maximum sustainable yield (MSY). Fishing pressure for cod-like fishes (Gadiformes) and flatfishes (Pleuronectiformes) was, for several decades, on average well above levels associated with MSY, but is now at or below the level expected to produce MSY. In contrast, fishing pressure for rockfishes (Scorpaeniformes) decreased from near MSY-related levels in the mid-1990s, and since the mid-2000s has remained on average at only one third of MSY-related levels. Regions with the most depressed groundfish stocks are the Northwest Atlantic and the Pacific coast of South America, while stocks from the Northeast and Eastern Central Pacific, Northeast Atlantic, Southeast Atlantic and Southwest Pacific tend to have greatest average abundance relative to MSY-based reference points. In the most recent year available for each stock, the catch was only 61% of MSY. Equilibrium yield curves indicate that 76% of global potential groundfish yield could be achieved using current estimates of fishing pressure. 15% of this is lost by excess fishing pressure, 67% results from lower than optimal fishing pressure on healthy stocks and 18% is lost from stocks currently overfished but rebuilding. Thus, there is modest opportunity to increase catch of global groundfish fisheries by reducing overfishing on some stocks, but more by increasing harvest on others. However, there may be other reasons not to fully exploit these stocks.Fil: Hilborn, Ray. University of Washington; Estados UnidosFil: Hively, Daniel J.. University of Washington; Estados UnidosFil: Baker Loke, Nicole. University of Washington; Estados UnidosFil: de Moor, Carryn L.. University Of Cape Town; SudáfricaFil: Kurota, Hiroyuki. Japan Fisheries Research and Education Agency; JapónFil: Kathena, Johannes N.. Ministry of Fisheries and Marine Resources; NamibiaFil: Mace, Pamela M.. Ministry for Primary Industries; Nueva ZelandaFil: Minto, Cóilín. Galway-Mayo Institute of Technology; IrlandaFil: Parma, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Quiroz, Juan-Carlos. Instituto de Fomento Pesquero; ChileFil: Melnychuk, Michael C.. University of Washington; Estados Unido

A latent trait look at pretest-posttest validation of criterion-referenced test items

Since Cox and Vargas (1966) introduced their pretest-posttest validity index for criterion-referenced test items, a great number of additions and modifications have followed. All are based on the idea of gain scoring; that is, they are computed from the differences between proportions of pretest and posttest item responses. Although the method is simple and generally considered as the prototype of criterion-referenced item analysis, it has many and serious disadvantages. Some of these go back to the fact that it leads to indices based on a dual test administration- and population-dependent item p values. Others have to do with the global information about the discriminating power that these indices provide, the implicit weighting they suppose, and the meaningless maximization of posttest scores they lead to. Analyzing the pretest-posttest method from a latent trait point of view, it is proposed to replace indices like Cox and Vargas’ Dpp by an evaluation of the item information function for the mastery score. An empirical study was conducted to compare the differences in item selection between both methods

FED-A, an advanced performance FED based on low safety factor and current drive

This document is one of four describing studies performed in FY 1982 within the context of the Fusion Engineering Device (FED) Program for the Office of Fusion Energy, U.S. Department of Energy. The documents are: 1. FED Baseline Engineering Studies (ORNL/FEDC-82/2), 2. FED-A, An Advanced Performance FED Based on Low Safety Factor and Current Drive (this document), 3. FED-R, A Fusion Device Utilizing Resistive Magnets (ORNL/FEDC-82/1), and 4. Technology Demonstration Facility TDF. These studies extend the FED Baseline concept of FY 1981 and develop innovative and alternative concepts for the FED. The FED-A study project was carried out as part of the Innovative and Alternative Tokamak FED studies, under the direction of P. H. Rutherford, which were part of the national FED program during FY 1982. The studies were performed jointly by senior scientists in the magnetic fusion community and the staff of the Fusion Engineering Design Center (FEDC). Y-K. M. Peng of the FEDC, on assignment from Oak Ridge National Laboratory, served as the design manager

Mitigation of phosphorus, sediment and Escherichia coli losses in runoff from a dairy farm roadway

peer reviewedDairy cow deposits on farm roadways are a potential source of contaminants entering streams. Phosphorus (P), suspended sediment (SS) and Escherichia coli (E. coli) loads in 18 runoff events over 12 mo from two-halves of a section of dairy farm roadway that spilt into an adjacent P-impacted stream were measured. The runoff from one half was untreated while the other half was directed through a filter of steel melter slag [termed aluminium chlorohydrate (ACH)-altered slag] sprayed with 1% ACH solution to improve P sorption capacity. An uncertainty analysis was conducted to ascertain potential loads of P lost from roadways considering variation in deposit weight, number and P content. Over the monitoring period, the total load decreased P (92%), SS (98%) and E. coli (76%) from the ACHaltered slag roadway compared to the control. However, uncertainty analysis showed that the amount of dung-P deposited on the roadway could be 10-fold greater

Heating by collisional slowing of fast ions in non-circular tokamaks

Plasma heating by energetic, charged fusion-products is a crucial issue for obtaining fusion reactors conditions. The evolution of alpha particle density, momentum, kinetic energy and heat flux is important in the study of start-up and ignition scenarios as well as in steady-state operation. Since fast ions have large banana-width guiding-center orbits in tokamaks, the usual locally-defined particle distribution function loses its usefulness. Accordingly, the fast ion collisional slowing-down problem has been formulated to describe these orbits in an axisymmetric, non-circular tokamak