2,702 research outputs found
The Whole World in Your Hand: Active and Interactive Segmentation
Object segmentation is a fundamental problem
in computer vision and a powerful resource for
development. This paper presents three embodied approaches to the visual segmentation of objects. Each approach to segmentation is aided
by the presence of a hand or arm in the proximity of the object to be segmented. The first
approach is suitable for a robotic system, where
the robot can use its arm to evoke object motion. The second method operates on a wearable system, viewing the world from a human's
perspective, with instrumentation to help detect
and segment objects that are held in the wearer's
hand. The third method operates when observing
a human teacher, locating periodic motion (finger/arm/object waving or tapping) and using it
as a seed for segmentation. We show that object segmentation can serve as a key resource for
development by demonstrating methods that exploit high-quality object segmentations to develop
both low-level vision capabilities (specialized feature detectors) and high-level vision capabilities
(object recognition and localization)
Prethermal Strong Zero Modes and Topological Qubits
We prove that quantum information encoded in some topological excitations,
including certain Majorana zero modes, is protected in closed systems for a
time scale exponentially long in system parameters. This protection holds even
at infinite temperature. At lower temperatures the decay time becomes even
longer, with a temperature dependence controlled by an effective gap that is
parametrically larger than the actual energy gap of the system. This
non-equilibrium dynamical phenomenon is a form of prethermalization, and occurs
because of obstructions to the equilibriation of edge or defect degrees of
freedom with the bulk. We analyze the ramifications for ordered and topological
phases in one, two, and three dimensions, with examples including Majorana and
parafermionic zero modes in interacting spin chains. Our results are based on a
non-perturbative analysis valid in any dimension, and they are illustrated by
numerical simulations in one dimension. We discuss the implications for
experiments on quantum-dot chains tuned into a regime supporting end Majorana
zero modes, and on trapped ion chains.Comment: 20 pages. v2: reorganized and added overview sectio
Long coherence times for edge spins
We show that in certain one-dimensional spin chains with open boundary
conditions, the edge spins retain memory of their initial state for very long
times. The long coherence times do not require disorder, only an ordered phase.
In the integrable Ising and XYZ chains, the presence of a strong zero mode
means the coherence time is infinite, even at infinite temperature. When Ising
is perturbed by interactions breaking the integrability, the coherence time
remains exponentially long in the perturbing couplings. We show that this is a
consequence of an edge "almost" strong zero mode that almost commutes with the
Hamiltonian. We compute this operator explicitly, allowing us to estimate
accurately the plateau value of edge spin autocorrelator.Comment: 13 pages, 13 figures; references adde
Disciplinary Proceedings by the S. E. C. Against Attorneys
The securities and exchange commission, created by Section 4 (a) of the Securities Exchange Act of 1934, has from its earliest days proclaimed its right to determine who may appear before or transact business with it in a representative capacity and in Rule 2 (e) of its present Rules of Practice has reserved to itself the right, in its discretion, to deny, temporarily or permanently, the privilege of appearing or practicing before it in any way to any person who is found by the Commission after notice of and opportunity for hearing in the matter (1) not to possess the requisite qualifications to represent others, or (2) to be lacking in character or integrity or to have engaged in unethical or improper professional conduct
Electrostatic charging of non-polar colloids by reverse micelles
Colloids dispersed in a non-polar solvent become charged when reverse
micelles are added. We study the charge of individual sterically-stabilized
poly(methyl methacrylate) spheres dispersed in micellar solutions of the
surfactants sodium bis(2-ethyl 1-hexyl) sulfosuccinate [AOT], zirconyl 2-ethyl
hexanoate [Zr(Oct)], and a copolymer of poly(12-hydroxystearic
acid)--poly(methyl methacrylate) [PHSA-PMMA]. Although the sign of the particle
charge is positive for Zr(Oct), negative for AOT, and essentially neutral
for PHSA-PMMA the different micellar systems display a number of common
features. In particular, we demonstrate that, over a wide range of
concentrations, the colloid charge is independent of the number of micelles
added and scales linearly with the colloid size. A simple thermodynamic model,
in which the particle charge is generated by the competitive adsorption of both
positive and negative micelles, is in good agreement with the experimental
data
Operational criteria used by professional social workers to assess relationship
Thesis (M.S.)--Boston Universit
Can Chromatography Occur in Nature?
Adsorption of calcium and magnesium on a sandstone from a bicarbonate solution has been demonstrated. On elution with water saturated with carbon dioxide, the magnesium passes off first. The chromatographic separation of magnesium from calcium can thus occur under conditions which can prevail in nature
Recommended from our members
Fish Passage Studies IV: Horizontal and Vertical Screens: Efficacy in Guiding Fish Schools
Recommended from our members
The influence of plant type on green roof rainfall retention
Green roofs can mitigate the flood risk by reducing the volume of runoff through direct interception and subsequent evapotranspiration (ET), but the planting choices can influence the extent of this service. Glasshouse experiments were carried out in spring/summer using simulated rainfall to compare the rainfall retention capacity of three physiologically active broadleaf species (Heuchera micrantha, Salvia officinalis and Stachys byzantina), which have previously shown to provide improved rooftop cooling, to an industry standard green roof species, Sedum spurium. Furthermore, the impact of varying ambient temperature and humidity conditions on the ability of these species to restore the substrate retention capacity through ET was also tested in a series of controlled-environment experiments simulating a range of potential UK summertime scenarios.
Canopies alone retained up to 17% (Sedum) of the total rainfall in this study, with Salvia and Stachys also retaining in excess of 10%, and can make a substantial contribution to rainfall retention on a green roof. Rainfall retention was also strongly correlated with total ET in the preceding 72 hours (R2 = 0.94; P < 0.001). Species with high ET rates (Salvia and Stachys) were able to provide the greatest stormwater management service (up to 72% retention due to ET component). Furthermore, species ‘rankings’, in terms of ET and thus restoration of substrate retention capacity, were the same in all simulated potential UK summertime temperature and relative humidity scenarios, indicating that ‘superior’ species will be able to provide the greatest stormwater management provision in all climatic conditions
- …