2,510 research outputs found
A Polynomial-time Bicriteria Approximation Scheme for Planar Bisection
Given an undirected graph with edge costs and node weights, the minimum
bisection problem asks for a partition of the nodes into two parts of equal
weight such that the sum of edge costs between the parts is minimized. We give
a polynomial time bicriteria approximation scheme for bisection on planar
graphs.
Specifically, let be the total weight of all nodes in a planar graph .
For any constant , our algorithm outputs a bipartition of the
nodes such that each part weighs at most and the total cost
of edges crossing the partition is at most times the total
cost of the optimal bisection. The previously best known approximation for
planar minimum bisection, even with unit node weights, was . Our
algorithm actually solves a more general problem where the input may include a
target weight for the smaller side of the bipartition.Comment: To appear in STOC 201
Fractional diffusion emulates a human mobility network during a simulated disease outbreak
From footpaths to flight routes, human mobility networks facilitate the
spread of communicable diseases. Control and elimination efforts depend on
characterizing these networks in terms of connections and flux rates of
individuals between contact nodes. In some cases, transport can be
parameterized with gravity-type models or approximated by a diffusive random
walk. As a alternative, we have isolated intranational commercial air traffic
as a case study for the utility of non-diffusive, heavy-tailed transport
models. We implemented new stochastic simulations of a prototypical
influenza-like infection, focusing on the dense, highly-connected United States
air travel network. We show that mobility on this network can be described
mainly by a power law, in agreement with previous studies. Remarkably, we find
that the global evolution of an outbreak on this network is accurately
reproduced by a two-parameter space-fractional diffusion equation, such that
those parameters are determined by the air travel network.Comment: 26 pages, 4 figure
Vehicle lead-acid battery state-of-charge meter
We describe a state-of-charge, or âresidual-capacityâ meter for lead-acid batteries that intelligently synthesizes coulometric and terminal-voltage methods in a new algorithm to provide reliable, continuous readout of remaining capacity. Novel electronic circuit design eliminates the need to install a shunt in the vehicle. The meter learns the characteristics of a battery to which it is attached, removing the need for setup, customisation, programming or calibration at time of installation or battery replacement. The meter can thus be installed by unqualified personnel. Initial measurements suggest the design to be robust and accurate
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Integrating research, surveillance, and practice in environmental public health tracking.
The Centers for Disease Control and Prevention in the U.S. Department of Health and Human Services is working with selected state and local health departments, academic centers, and others to develop an environmental public health tracking initiative to improve geographic and temporal surveillance of environmental hazards, exposures, and related health outcomes. The objective is to support policy strategies and interventions for disease prevention by communities and environmental health agencies at the federal, state, and local levels. The first 3 years of the initiative focused on supporting states and cities in developing capacity, information technology infrastructure, and pilot projects to demonstrate electronic linkage of environmental hazard or exposure data and disease data. The next phase requires implementation across states. This transition could provide opportunities to further integrate research, surveillance, and practice through attention to four areas. The first is to develop a shared and transparent knowledge base that draws on environmental health research and substantiates decisions about what to track and the interpretation of results. The second is to identify and address information needs of policy and stakeholder audiences in environmental health. The third is to adopt mechanisms for coordination, decision making, and governance that can incorporate and support the major entities involved. The fourth is to promote disease prevention by systematically identifying and addressing population-level environmental determinants of health and disease
A Feasibility Template for Small, Multi-Species Meat Processing Plants
This article describes a spreadsheet-based template designed to help livestock producers and others examine the feasibility of operating a small, multi-species meat processing plant. The template allows users to define plant size and capacity, including the breakdown of processing activities by species and additional revenue opportunities. The spreadsheet utilizes user-defined information on capital and operating costs to develop depreciation schedules, loan amortization schedules, 10-year profit/loss projections, cash flow projections, and various measure of return on investment. An imbedded user\u27s guide and a companion how to use video helps template users examine the financial feasibility of a meat plant venture
Integration of a contaminant source land use regression model in the Bayesian Maximum Entropy spatiotemporal geostatistical estimation of groundwater tetrachloroethylene across North Carolina
The assessment of groundwater tetrachloroethylene (PCE or PERC) exposure across North Carolina is currently hindered due to limited statewide spatiotemporal contaminant maps. In this study we incorporate data from multiple sources to create estimation maps of groundwater PCE. A land use regression (LUR) mean trend model was developed as a function of exponentially decaying contribution from contaminant sources in North Carolina. This mean trend model was integrated in a Bayesian Maximum Entropy (BME) framework to produce informative space/time (S/T) maps. We compare our method with standard geostatistical methods (i.e. kriging and BME with constant mean trends) and find a 25 % reduction in cross-validation mean square error. Our results suggest that dry cleaning and hazardous waste generator sites influence groundwater at distances of 1 km and 800 m respectively. This work introduces a novel integrated LUR and BME approach which produces accurate visual representations of PCE exposure across North Carolina
Experimental Phase-equilibrium Constraints on the Phonolite Magmatic System of Erebus Volcano, Antarctica
International audienceField observations and petrological studies have recently advanced understanding of the magmatic system of Erebus volcano, renowned for its sustained CO2-rich degassing, and long-lived phonolitic lava lake. However, this body of work has highlighted uncertainty in several key parameters, including the magma temperature, redox state and the depth of the reservoir presumed to maintain the lava lake. Here, we use experimentally determined phase equilibria to constrain these unknowns. The experiments ranged in temperature from 900 to 1025°C, in pressure from atmospheric to 300 MPa, in water content from 0 to 8 wt %, and in oxygen fugacity from NNO + 4 (where NNO is nickel-nickel oxide) to QFM - 2 (where QFM is quartz-fayalite-magnetite). The natural system was experimentally reproduced at 950 ± 25°C, a pressure below 200 MPa, redox conditions between QFM and QFM - 1, and remarkably low water contents of less than 0*5 wt %. These findings help in understanding petrological observations, including melt inclusion data, as well as the measured composition of gas emissions from the lava lake. Biotite and amphibole appear in the crystallization sequence at around 925°C, even under very dry conditions (biotite). Both biotite and amphibole are absent in the phonolites erupted over the last 20 kyr at Erebus. The constant abundance of anorthoclase observed in the erupted lavas and bombs indicates that the shallow magmatic system feeding the Erebus lava lake (below pressures of 200 MPa) has been thermally buffered at 950 ± 25°C over this time period, possibly reflecting steady-state connection with the deep feeding system rooted in the mantle. Combined with recent seismological data, our results suggest that if a large phonolitic reservoir exists, then it should lie in the depth range 4-7*5 km. The tight constraints on temperature and redox conditions will be valuable for future thermodynamical and rheological modelling
Leaders Like Me
The Workshop Program at the University of Rochester infuses collaborative learning into a variety of introductory STEM and non-STEM courses through small, weekly, peer-led problem solving sessions called Workshops. Decades of data from these Workshops indicate that 1) African American, Black, Hispanic, and Latinx students are less likely to attend them than White and Asian students and 2) that every additional Workshop students attend improves their final course grades, even if they only miss a single Workshop out of the 13 or 14 that are offered each semester. To address this situation, the UR Workshop Program has partnered with the People Like Me project at Bucknell University. Before the start of the Fall 2018 semester, Workshop leaders were asked to respond to the People Like Me survey questions, and we crafted their responses into profiles. We then posted these profiles for students in the courses to view on a platform on which we could track those views at the individual student level. In this work-in-progress, we hope to answer the question: to what extent does viewing personal information about Workshop leaders affect students\u27 likelihood to attend Workshops
Textual comparison of role model and mentor profiles developed to increase participation of underrepresented minorities in STEM
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