315 research outputs found
Design of Cooperative Networks
In this paper we analyse several approaches to the design of Cooperative Algorithms for solving a general problem: That of computing the values of some property over a spatial domain, when these values are constrained (but not uniquely determined) by some observations, and by some a priori knowledge about the nature of the solution (smoothness, for example).
Specifically, we discuss the use of: Variational techniques; stochastic approximation methods for global optimization, and linear threshold networks. Finally, we present a new approach, based on the interconnection of Winner-take-all networks, for which it is possible to establish precise convergence results, including bounds on the rate of convergence.MIT Artificial Intelligence Laborator
A Replica Inference Approach to Unsupervised Multi-Scale Image Segmentation
We apply a replica inference based Potts model method to unsupervised image
segmentation on multiple scales. This approach was inspired by the statistical
mechanics problem of "community detection" and its phase diagram. Specifically,
the problem is cast as identifying tightly bound clusters ("communities" or
"solutes") against a background or "solvent". Within our multiresolution
approach, we compute information theory based correlations among multiple
solutions ("replicas") of the same graph over a range of resolutions.
Significant multiresolution structures are identified by replica correlations
as manifest in information theory overlaps. With the aid of these correlations
as well as thermodynamic measures, the phase diagram of the corresponding Potts
model is analyzed both at zero and finite temperatures. Optimal parameters
corresponding to a sensible unsupervised segmentation correspond to the "easy
phase" of the Potts model. Our algorithm is fast and shown to be at least as
accurate as the best algorithms to date and to be especially suited to the
detection of camouflaged images.Comment: 26 pages, 22 figure
Smallholder Dairy Farmers in the Peruvian Andes Fulfilling the Role of Extension Agents
Dairy farming in the Peruvian Andes is mostly undertaken by smallholder farmers (4-6 cows/family) and of relatively recent development. In fact, over the last 2 decades dairy farming at high altitudes (3,500â4200 masl) has grown rapidly, replacing the camelids and sheep farming that once predominated. Dairying growth has been catalysed by subsides from state and private organizations. It promotes high input systems based on feedlot technology. Compared to sheep and camelids farming, dairying at the Andes does not have yet an inherent local/indigenous knowledge associated to it. High altitude Andean ecosystems pose many constraints for dairy farming (hypoxia and high UV radiation, high variation between day and night temperatures, short rainy season, and hence shortage of feed and water; and not less importantly, accelerated climate change (CC)). Under these conditions, not only are productivity and profitability low, but there are high negative environmental impacts and poor animal welfare. In Peru, institutionalised research and extension (R&E) services are precarious. Research tackling current issues of high-altitude livestock farming is almost inexistent, whereas extension in support of farmers is dispersed, poorly funded, of short duration (a few months), focused on transfer of technology suitable to intensive farming systems, and has a high turnover of staff. A systems approach to address the complexity of Andean livestock farming development is lacking. The initiatives from the institutions promoting farming are directed to remediate recurrent problems (e.g., cold stress) or prioritise high cost, low impact activities (e.g., genetic improvement). Here, we present the successful experience of the New Zealand Peru Dairy Support Project (NZPDSP) to promote the adoption of improved low input pastoral dairying husbandry principles, where trained smallholder farmers play a key role as agents of change
Dairy Cattle Genetics by Environment Interaction Mismatch Contributes to Poor Mitigation and Adaptation of Grazing Systems to Climate Change Actions in the Peruvian High Andes: A Review
The high Andes of Peru includes fragile ecosystems. Nevertheless, it plays important ecosystem functions (e.g., biodiversity, water supply for the lowlands, CO2 sinks in soil, etc). More than 80% of the livestock population of Peru is farmed in this area, supporting the livelihood of approximately 1â400,000 poor families, who are vulnerable to climate change (CC). Climate change in the high Andes is occurring at accelerated rates, compared to lowlands regions. Prevalent factors in the high Andes, such as hypoxia, high UV radiation, climatic extremes, large variation between maximum and minimum temperatures, seasonality in rainfall (determining highly seasonal forage growth) and CC, not only increase the feed and water needs of animals, but also affect animal production, reproduction, rumen function and welfare, making them more vulnerable to CC. During the last three decades, livestock farming in the high Andes has undergone transformation. The farming of camelids and creole species has been almost replaced by smallholder dairying, which have a higher environmental footprint. Institutions promoting dairying neglect the fitness requirement for the animal genetics to perform in such environments. Recent work of the New Zealand Peru Dairy Support Project (NZPDSP; 2016â2020) demonstrated that rapid and significant improvements in animal productivity and profitability of dairying can be achieved by promoting adoption of simple and low-cost husbandry practices. Nevertheless, further improvements are constrained by the unfitness of the current animal genetics. Here, based on a literature review and experience from the NZPDSP, we propose a search for dairy cattle genetics that contributes to mitigation and adaptation to CC, while enhancing the livelihoods of the poor
Image restoration using the chiral Potts spin-glass
We report on the image reconstruction (IR) problem by making use of the
random chiral q-state Potts model, whose Hamiltonian possesses the same gauge
invariance as the usual Ising spin glass model. We show that the pixel
representation by means of the Potts variables is suitable for the gray-scale
level image which can not be represented by the Ising model. We find that the
IR quality is highly improved by the presence of a glassy term, besides the
usual ferromagnetic term under random external fields, as very recently pointed
out by Nishimori and Wong. We give the exact solution of the infinite range
model with q=3, the three gray-scale level case. In order to check our
analytical result and the efficiency of our model, 2D Monte Carlo simulations
have been carried out on real-world pictures with three and eight gray-scale
levels.Comment: RevTex 13 pages, 10 figure
Training University Tutors to Work with Bilingual Students
The purpose of this project was to train university tutors to improve their support of bilingual students (ESL/ELL students). We developed an evidence-based training session that emphasizes university connectedness and cultural inclusion. This one-hour training included background information, tutoring tips, and time for discussion. The majority of tutors (44 out of 47) reported learning something helpful they could use when tutoring. While this intervention was specifically designed to target bilingual students, most evidence-based tips discussed here are applicable to all students. It is crucial to provide tutors with the skills and resources necessary to better connect with their students
Statistical mechanics of image restoration and error-correcting codes
We develop a statistical-mechanical formulation for image restoration and
error-correcting codes. These problems are shown to be equivalent to the Ising
spin glass with ferromagnetic bias under random external fields. We prove that
the quality of restoration/decoding is maximized at a specific set of parameter
values determined by the source and channel properties. For image restoration
in mean-field system a line of optimal performance is shown to exist in the
parameter space. These results are illustrated by solving exactly the
infinite-range model. The solutions enable us to determine how precisely one
should estimate unknown parameters. Monte Carlo simulations are carried out to
see how far the conclusions from the infinite-range model are applicable to the
more realistic two-dimensional case in image restoration.Comment: 20 pages, 9 figures, ReVTe
Bottlenecks in granular flow: When does an obstacle increase the flowrate in an hourglass?
Bottlenecks occur in a wide range of applications from pedestrian and traffic
flow to mineral and food processing. We examine granular flow across a
bottleneck using particle-based simulations. Contrary to expectations we find
that the flowrate across a bottleneck actually increases if an opti- mized
obstacle is placed before it. The dependency of flowrate on obstacle diameter
is derived using a phenomenological velocity-density relationship that peaks at
a critical density. This relationship is in stark contrast to models of traffic
flow, as the mean velocity does not depend only on density but attains
hysteresis due to interaction of particles with the obstacle.Comment: Submitted to Phys. Rev. Let
Commentary on key aspects of fecal microbiota transplantation in small animal practice
The gastrointestinal tract of dogs, cats, and other mammals including humans harbors millions of beneficial microorganisms that regulate and maintain health. Fecal microbiota transplantation (FMT) is a procedure involving the administration of a fecal infusion from a healthy individual (donor) to a patient with disease to help improve health. Despite the effectiveness of FMT to treat intestinal disorders in humans, in particular recurrent Clostridium difficile infection, there is a paucity of scientific data regarding the application of FMT in veterinary patients. Here, we outline key aspects of FMT in small animal practice
Plastic Response of a 2D Lennard-Jones amorphous solid: Detailed analysis of the local rearrangements at very slow strain-rate
We analyze in details the atomistic response of a model amorphous material
submitted to plastic shear in the athermal, quasistatic limit. After a linear
stress-strain behavior, the system undergoes a noisy plastic flow. We show that
the plastic flow is spatially heterogeneous. Two kinds of plastic events occur
in the system: quadrupolar localized rearrangements, and shear bands. The
analysis of the individual motion of a particle shows also two regimes: a
hyper-diffusive regime followed by a diffusive regime, even at zero
temperature
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