7,936 research outputs found
Contingency Model Predictive Control for Automated Vehicles
We present Contingency Model Predictive Control (CMPC), a novel and
implementable control framework which tracks a desired path while
simultaneously maintaining a contingency plan -- an alternate trajectory to
avert an identified potential emergency. In this way, CMPC anticipates events
that might take place, instead of reacting when emergencies occur. We
accomplish this by adding an additional prediction horizon in parallel to the
classical receding MPC horizon. The contingency horizon is constrained to
maintain a feasible avoidance solution; as such, CMPC is selectively robust to
this emergency while tracking the desired path as closely as possible. After
defining the framework mathematically, we demonstrate its effectiveness
experimentally by comparing its performance to a state-of-the-art deterministic
MPC. The controllers drive an automated research platform through a left-hand
turn which may be covered by ice. Contingency MPC prepares for the potential
loss of friction by purposefully and intuitively deviating from the prescribed
path to approach the turn more conservatively; this deviation significantly
mitigates the consequence of encountering ice.Comment: American Control Conference, July 2019; 6 page
Long-Term Dynamics and the Orbital Inclinations of the Classical Kuiper Belt Objects
We numerically integrated the orbits of 1458 particles in the region of the
classical Kuiper Belt (41 AU < a < 47 AU) to explore the role of dynamical
instabilities in sculpting the inclination distribution of the classical Kuiper
Belt Objects (KBOs). We find that the selective removal of low-inclination
objects by overlapping secular resonances (nu_17 and nu_18) acts to raise the
mean inclination of the surviving population of particles over 4 billion years
of interactions with Jupiter, Saturn, Uranus and Neptune, though these
long-term dynamical effects do not themselves appear to explain the discovery
of KBOs with inclinations near 30 degrees. Our integrations also imply that
after 3 billion years of interaction with the massive planets, high inclination
KBOs more efficiently supply Neptune-encountering objects, the likely
progenitors of short-period comets, Centaurs, and scattered KBOs. The secular
resonances at low inclinations may indirectly cause this effect by weeding out
objects unprotected by mean motion resonances during the first 3 billion years.Comment: 23 pages, including 10 figures. Accepted for publication in A
âFinalâ Awards Reconceptualized: A Proposal to Resolve the Hall Street Circuit Split
This article discusses the current circuit split over the continued validity of manifest disregard of the law (âmanifest disregardâ) as a nonstatutory ground for vacatur of arbitration awards under the Federal Arbitration Act (âFAAâ). Today, as commercial parties decide whether to include arbitration agreements in their business contracts, they weigh the risks of proceeding to arbitration versus litigation to resolve their disputes. This topic is especially pertinent in light of the current economic climate. Dicta from the U.S. Supreme Courtâs decision in Hall Street Associates, L.L.C. v. Mattel, Inc. called into question the continued validity of nonstatutory grounds for vacatur. The circuit courts have severely split on the question of one ground in particular: manifest disregard. Although seemingly ripe for review, the Supreme Court has appeared reluctant to resolve the issue, even side-stepping the Second Circuitâs opinion in Stolt-Nielsen S.A. v. AnimalFeeds International Corp. and ruling on other grounds. Rather than opining on which side of the split should prevail, this article posits first that manifest disregard should never have been a valid ground for vacatur under the FAA. Next, the article takes a historical perspective that shows the FAA does not allow courts to look at the merits of an arbitration award. Instead, courts should look only to the award itself, determining its enforceability exclusive of the merits of the arbitratorâs or tribunalâs decision. Inquiry into the merits of the decision violates the FAA and damages arbitrationâs finality and efficiency, two of the most important benefits of the arbitration bargain. Excluding the merits from judicial review conforms to FAA requirements and retains these two critical benefits. In other words, this article proposes a resolution to the circuit split that maintains the integrity of both the FAA and the arbitration process without excluding concerns surrounding a full abandonment of judicial review
Behavioral biases when viewing multiplexed scenes:scene structure and frames of reference for inspection
Where people look when viewing a scene has been a much explored avenue of vision research (e.g., see Tatler, 2009). Current understanding of eye guidance suggests that a combination of high and low-level factors influence fixation selection (e.g., Torralba et al., 2006), but that there are also strong biases toward the center of an image (Tatler, 2007). However, situations where we view multiplexed scenes are becoming increasingly common, and it is unclear how visual inspection might be arranged when content lacks normal semantic or spatial structure. Here we use the central bias to examine how gaze behavior is organized in scenes that are presented in their normal format, or disrupted by scrambling the quadrants and separating them by space. In Experiment 1, scrambling scenes had the strongest influence on gaze allocation. Observers were highly biased by the quadrant center, although physical space did not enhance this bias. However, the center of the display still contributed to fixation selection above chance, and was most influential early in scene viewing. When the top left quadrant was held constant across all conditions in Experiment 2, fixation behavior was significantly influenced by the overall arrangement of the display, with fixations being biased toward the quadrant center when the other three quadrants were scrambled (despite the visual information in this quadrant being identical in all conditions). When scenes are scrambled into four quadrants and semantic contiguity is disrupted, observers no longer appear to view the content as a single scene (despite it consisting of the same visual information overall), but rather anchor visual inspection around the four separate âsub-scenes.â Moreover, the frame of reference that observers use when viewing the multiplex seems to change across viewing time: from an early bias toward the display center to a later bias toward quadrant centers
On the factors causing processing difficulty of multiple-scene displays
Multiplex viewing of static or dynamic scenes is an increasing feature of screen media. Most existing multiplex experiments have examined detection across increasing scene numbers, but currently no systematic evaluation of the factors that might produce difficulty in processing multiplexes exists. Across five experiments we provide such an evaluation. Experiment 1 characterises difficulty in change detection when the number of scenes is increased. Experiment 2 reveals that the increased difficulty across multiple-scene displays is caused by the total amount of visual information accounts for differences in change detection times, regardless of whether this information is presented across multiple scenes, or contained in one scene. Experiment 3 shows that whether quadrants of a display were drawn from the same, or different scenes did not affect change detection performance. Experiment 4 demonstrates that knowing which scene the change will occur in means participants can perform at monoplex level. Finally, Experiment 5 finds that changes of central interest in multiplexed scenes are detected far easier than marginal interest changes to such an extent that a centrally interesting object removal in nine screens is detected more rapidly than a marginally interesting object removal in four screens. Processing multiple-screen displays therefore seems dependent on the amount of information, and the importance of that information to the task, rather than simply the number of scenes in the display. We discuss the theoretical and applied implications of these findings
An Intelligent Fuse-box for use with Renewable Energy Sources integrated within a Domestic Environment
This paper outlines a proposal for an intelligent fuse-box that can replace existing fuse-boxes in a domestic context such that a number of renewable energy sources can easily be integrated into the domestic power supply network, without the necessity for complex islanding and network protection. The approach allows intelligent control of both the generation of power and its supply to single or groups of electrical appliances. Energy storage can be implemented in such a scheme to even out the power supplied and simplify the control scheme required, and environmental monitoring and load analysis can help in automatically controlling the supply and demand profiles for optimum electrical and economic efficiency. Simulations of typical scenarios are carried out to illustrate the concept in operation
Probing the Inner Regions of Protoplanetary Disks with CO Absorption Line Spectroscopy
Carbon monoxide (CO) is the most commonly used tracer of molecular gas in the
inner regions of protoplanetary disks. CO can be used to constrain the
excitation and structure of the circumstellar environment. Absorption line
spectroscopy provides an accurate assessment of a single line-of-sight through
the protoplanetary disk system, giving more straightforward estimates of column
densities and temperatures than CO and molecular hydrogen emission line
studies. We analyze new observations of ultraviolet CO absorption from the
Hubble Space Telescope along the sightlines to six classical T Tauri stars. Gas
velocities consistent with the stellar velocities, combined with the
moderate-to-high disk inclinations, argue against the absorbing CO gas
originating in a fast-moving disk wind. We conclude that the far-ultraviolet
observations provide a direct measure of the disk atmosphere or possibly a slow
disk wind. The CO absorption lines are reproduced by model spectra with column
densities in the range N(^{12}CO) ~ 10^{16} - 10^{18} cm^{-2} and N(^{13}CO) ~
10^{15} - 10^{17} cm^{-2}, rotational temperatures T_{rot}(CO) ~ 300 - 700 K,
and Doppler b-values, b ~ 0.5 - 1.5 km s^{-1}. We use these results to
constrain the line-of-sight density of the warm molecular gas (n_{CO} ~ 70 -
4000 cm^{-3}) and put these observations in context with protoplanetary disk
models.Comment: 12 pages, 14 figures, ApJ - accepte
Increased hazard of myocardial infarction with insulinâprovision therapy in actively smoking patients with diabetes mellitus and stable ischemic heart disease: The BARI 2D (Bypass Angioplasty Revascularization Investigation 2 Diabetes) trial
Background
In the BARI 2D (Bypass Angioplasty Revascularization Investigation 2 Diabetes) trial, randomization of diabetic patients with stable ischemic heart disease to insulin provision (
IP
) therapy, as opposed to insulin sensitization (
IS
) therapy, resulted in biochemical evidence of impaired fibrinolysis but no increase in adverse clinical outcomes. We hypothesized that the prothrombotic effect of
IP
therapy in combination with the hypercoagulable state induced by active smoking would result in an increased risk of myocardial infarction (
MI
).
Methods and Results
We analyzed
BARI
2D patients who were active smokers randomized to
IP
or
IS
therapy. The primary end point was fatal or nonfatal
MI
.
PAI
â1 (plasminogen activator inhibitor 1) activity was analyzed at 1, 3, and 5Â years. Of 295 active smokers,
MI
occurred in 15.4% randomized to
IP
and in 6.8% randomized to
IS
over the 5.3Â years (
P
=0.023).
IP
therapy was associated with a 3.2âfold increase in the hazard of
MI
compared with
IS
therapy (hazard ratio: 3.23; 95% confidence interval, 1.43â7.28;
P
=0.005). Baseline
PAI
â1 activity (19.0 versus 17.5Â Au/mL,
P
=0.70) was similar in actively smoking patients randomized to
IP
or
IS
therapy. However,
IP
therapy resulted in significantly increased
PAI
â1 activity at 1Â year (23.0 versus 16.0Â Au/mL,
P
=0.001), 3Â years (24.0 versus 18.0Â Au/mL,
P
=0.049), and 5Â years (29.0 versus 15.0Â Au/mL,
P
=0.004) compared with
IS
therapy.
Conclusions
Among diabetic patients with stable ischemic heart disease who were actively smoking,
IP
therapy was independently associated with a significantly increased hazard of
MI
. This finding may be explained by higher
PAI
â1 activity in active smokers treated with
IP
therapy.
Clinical Trial Registration
URL
:
http://www.clinicaltrials.gov
. Unique identifier:
NCT
00006305.
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Derby Fisheries, Individual Quotas, and Transition in the Fish Processing Industry
Processors adapt to the pulse of landings in derby fisheries by investing in large-scale facilities capable of preserving and storing fish products. In fisheries where the pulse of landings suppresses the ability of processors to meet consumer demand for fresh product, the imposition of individual quota (IQ) systems transforms the associated fish processing industry. The cost of fresh fish processing is generally lower and more malleable than that for preserved fish, and consumers may pay a price premium for fresh product, which creates an opportunity for entry by fresh-fish processors and results in higher equilibrium ex-vessel prices. Incumbent firms are likely to experience an economic dislocation due to a diminished value of nonmalleable capital used to preserve and store fish products. Our paper generalizes and provides a modeling framework for the observed changes in the British Columbian halibut harvester/processor industry complex following the introduction of an IQ system.Derby fishery, individual quotas, pulse of landings, fish processing, fresh fish, preserved fish, product forms, ex-vessel price, wholesale fish price, processing capital, malleability, Resource /Energy Economics and Policy, Q13, Q22,
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