1,023 research outputs found
NORTH AMERICAN INTEGRATION IN AGRICULTURE: A SURVEY PAPER
This paper surveys the economic literature about North American integration in the agri-food sector. The purpose of this survey is two-fold: it summarizes the lessons learned, and it identifies areas where further research could provide valuable input into policy discussions. As the integration of North American agriculture progresses, the range of agri-food policies with strictly domestic effects becomes increasingly narrow. Thus, policymakers in North America need to consider the effects that their decisions will have on other NAFTA countries, as well as the impact that decisions by other NAFTA governments will have at home. The paper is organized as follows. Section 2 identifies the major factors contributing to integration and comments on their relative importance. Section 3 summarizes research into the indicators of integration. These studies focus on price co-movements and trade flow data. Section 4 outlines the state of current knowledge regarding foreign direct investment in the agri-food sector, while Section 5 assesses the impact of integration on the structure and performance of the sector. Section 6 discusses opportunities for further integration in the sector, and Section 7 concludes the paper. Throughout the paper, gaps in the knowledge base are highlighted, along with suggested areas for further research.Industrial Organization,
IR Motion Tracking Robotic Arm
The Motion Tracking Robot Arm is a senior Electrical Engineering Capstone project designed by Andrew Doan, Avery Guillermo, Gavin Low, and Dayna Yoshimura. The project serves as an exploration of alternative control methods for robotic arms. While standard robotic arms are often controlled with physical controllers or computer programs, this robotic arm will be controlled with a LEAP motion controller. The user will be able to control the robotic arm using his or her own arm; no extra control inputs will be necessary.https://pilotscholars.up.edu/egr_project/1005/thumbnail.jp
Domain Adaptation for Satellite-Borne Hyperspectral Cloud Detection
The advent of satellite-borne machine learning hardware accelerators has
enabled the on-board processing of payload data using machine learning
techniques such as convolutional neural networks (CNN). A notable example is
using a CNN to detect the presence of clouds in hyperspectral data captured on
Earth observation (EO) missions, whereby only clear sky data is downlinked to
conserve bandwidth. However, prior to deployment, new missions that employ new
sensors will not have enough representative datasets to train a CNN model,
while a model trained solely on data from previous missions will underperform
when deployed to process the data on the new missions. This underperformance
stems from the domain gap, i.e., differences in the underlying distributions of
the data generated by the different sensors in previous and future missions. In
this paper, we address the domain gap problem in the context of on-board
hyperspectral cloud detection. Our main contributions lie in formulating new
domain adaptation tasks that are motivated by a concrete EO mission, developing
a novel algorithm for bandwidth-efficient supervised domain adaptation, and
demonstrating test-time adaptation algorithms on space deployable neural
network accelerators. Our contributions enable minimal data transmission to be
invoked (e.g., only 1% of the weights in ResNet50) to achieve domain
adaptation, thereby allowing more sophisticated CNN models to be deployed and
updated on satellites without being hampered by domain gap and bandwidth
limitations
Electrochemical Characterization of Self-Assembled Monolayers on Gold Substrates Derived from Thermal Decomposition of Monolayer-Protected Cluster Films
Networked films of monolayer-protected clusters (MPCs), alkanethiolate-stabilized gold nanoparticles, can be thermally decomposed to form stable gold on glass substrates that are subsequently modified with self-assembled monolayers (SAMs) for use as modified electrodes. Electrochemical assessment of these SAM-modified gold substrates, including double-layer capacitance measurements, linear sweep desorption of the alkanethiolates, and diffusional redox probing, all show that SAMs formed on gold supports formed from thermolysis of MPC films possess substantially higher defect density compared to SAMs formed on traditional evaporated gold. The density of defects in the SAMs on thermolyzed gold is directly related to the strategies used to assemble the MPC film prior to thermolysis. Specifically, gold substrates formed from thermally decomposing MPC films formed with electrostatic bridges between carboxylic acid-modified MPCs and metal ion linkers are particularly sensitive to the degree of metal exposure during the assembly process. While specific metal dependence was observed, metal concentration within the MPC precursor film was determined to be a more significant factor. Specific MPC film linking strategies and pretreatment methods that emphasized lower metal exposure resulted in gold films that supported SAMs of lower defect density. The defect density of a SAM-modified electrode is shown to be critical in certain electrochemical experiments such as protein monolayer electrochemistry of adsorbed cytochrome c. While the thermal decomposition of nanoparticle film assemblies remains a viable and interesting technique for coating both flat and irregular shaped substrates, this study provides electrochemical assessment tools and tactics for determining and controlling SAM defect density on this type of gold structure, a property critical to their effective use in subsequent electrochemical applications
Stress Induced Structural Transformations in Au Nanocrystals
Nanocrystals can exist in multiply twinned structures like the icosahedron,
or single crystalline structures like the cuboctahedron or Wulff-polyhedron.
Structural transformation between these polymorphic structures can proceed
through diffusion or displacive motion. Experimental studies on nanocrystal
structural transformations have focused on high temperature diffusion mediated
processes. Thus, there is limited experimental evidence of displacive motion
mediated structural transformations. Here, we report the high-pressure
structural transformation of 6 nm Au nanocrystals under nonhydrostatic pressure
in a diamond anvil cell that is driven by displacive motion. In-situ X-ray
diffraction and transmission electron microscopy were used to detect the
transformation of multiply twinned nanocrystals into single crystalline
nanocrystals. High-pressure single crystalline nanocrystals were recovered
after unloading, however, the nanocrystals quickly reverted back to multiply
twinned state after redispersion in toluene solvent. The dynamics of recovery
was captured using transmission electron microscopy which showed that the
recovery was governed by surface recrystallization and rapid twin boundary
motion. We show that this transformation is energetically favorable by
calculating the pressure-induced change in strain energy. Molecular dynamics
simulations showed that defects nucleated from a region of high stress region
in the interior of the nanocrystal, which make twin boundaries unstable.
Deviatoric stress driven Mackay transformation and dislocation/disclination
mediated detwinning are hypothesized as possible mechanisms of high-pressure
structural transformation.Comment: 32 pages, 14 figures, and 1 movie (please open pdf with Adobe Acrobat
Reader to see the embedded movie
On Bayesian Modelling of the Uncertainties in Palaeoclimate Reconstruction
We outline a model and algorithm to perform inference on the palaeoclimate
and palaeoclimate volatility from pollen proxy data. We use a novel
multivariate non-linear non-Gaussian state space model consisting of an
observation equation linking climate to proxy data and an evolution equation
driving climate change over time. The link from climate to proxy data is
defined by a pre-calibrated forward model, as developed in Salter-Townshend and
Haslett (2012) and Sweeney (2012). Climatic change is represented by a
temporally-uncertain Normal-Inverse Gaussian Levy process, being able to
capture large jumps in multivariate climate whilst remaining temporally
consistent. The pre-calibrated nature of the forward model allows us to cut
feedback between the observation and evolution equations and thus integrate out
the state variable entirely whilst making minimal simplifying assumptions. A
key part of this approach is the creation of mixtures of marginal data
posteriors representing the information obtained about climate from each
individual time point. Our approach allows for an extremely efficient MCMC
algorithm, which we demonstrate with a pollen core from Sluggan Bog, County
Antrim, Northern Ireland.Comment: 25 pages, 7 figure
Displacement experiments provide evidence for path integration in Drosophila
Like many other animals, insects are capable of returning to previously visited locations using path integration, which is a memory of travelled direction and distance. Recent studies suggest that Drosophila can also use path integration to return to a food reward. However, the existing experimental evidence for path integration in Drosophila has a potential confound: pheromones deposited at the site of reward might enable flies to find previously rewarding locations even without memory. Here, we show that pheromones can indeed cause naĂŻve flies to accumulate where previous flies had been rewarded in a navigation task. Therefore, we designed an experiment to determine if flies can use path integration memory despite potential pheromonal cues by displacing the flies shortly after an optogenetic reward. We found that rewarded flies returned to the location predicted by a memory-based model. Several analyses are consistent with path integration as the mechanism by which flies returned to the reward. We conclude that although pheromones are often important in fly navigation and must be carefully controlled for in future experiments, Drosophila may indeed be capable of performing path integration
Nucleation of Dislocations in 3.9 nm Nanocrystals at High Pressure
As circuitry approaches single nanometer length scales, it is important to
predict the stability of metals at these scales. The behavior of metals at
larger scales can be predicted based on the behavior of dislocations, but it is
unclear if dislocations can form and be sustained at single nanometer
dimensions. Here, we report the formation of dislocations within individual 3.9
nm Au nanocrystals under nonhydrostatic pressure in a diamond anvil cell. We
used a combination of x-ray diffraction, optical absorbance spectroscopy, and
molecular dynamics simulation to characterize the defects that are formed,
which were found to be surface-nucleated partial dislocations. These results
indicate that dislocations are still active at single nanometer length scales
and can lead to permanent plasticity.Comment: 33 pages, 12 figure
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