167,886 research outputs found
Mass Displacement Networks
Despite the large improvements in performance attained by using deep learning
in computer vision, one can often further improve results with some additional
post-processing that exploits the geometric nature of the underlying task. This
commonly involves displacing the posterior distribution of a CNN in a way that
makes it more appropriate for the task at hand, e.g. better aligned with local
image features, or more compact. In this work we integrate this geometric
post-processing within a deep architecture, introducing a differentiable and
probabilistically sound counterpart to the common geometric voting technique
used for evidence accumulation in vision. We refer to the resulting neural
models as Mass Displacement Networks (MDNs), and apply them to human pose
estimation in two distinct setups: (a) landmark localization, where we collapse
a distribution to a point, allowing for precise localization of body keypoints
and (b) communication across body parts, where we transfer evidence from one
part to the other, allowing for a globally consistent pose estimate. We
evaluate on large-scale pose estimation benchmarks, such as MPII Human Pose and
COCO datasets, and report systematic improvements when compared to strong
baselines.Comment: 12 pages, 4 figure
Heterogeneity among Displaced Workers
We combine post-displacement survey data with information from a displacing firm's personnel files in order to reveal sources of worker heterogeneity in search time and wage losses. First, we detail how experience-related characteristics affect workers' labour market careers during a period of three years after the bankruptcy of the firm. We find that wage losses are large. Interestingly, firm, rank, or job tenure do not explain observed wage differences. Idiosyncratic ability, job rotations prior to displacement, and differences in pre- and post-displacement job characteristics contribute most to observed variations in wages. The individual post-displacement labor market histories allow for testing the Blanchard-Diamond (1994) ranking model for which we find no support. We then develop a dynamic reservation wage updating model. The method of updating is based on the simple idea that job seekers are informed about successful matches of their former colleagues (Rees, 1966; Granovetter, 1974). The model fits the data well.idiosyncratic ability, mass lay-off, social networks, unemployment
Distance to Center of Mass Encoding for Instance Segmentation
The instance segmentation can be considered an extension of the object
detection problem where bounding boxes are replaced by object contours.
Strictly speaking the problem requires to identify each pixel instance and
class independently of the artifice used for this mean. The advantage of
instance segmentation over the usual object detection lies in the precise
delineation of objects improving object localization. Additionally, object
contours allow the evaluation of partial occlusion with basic image processing
algorithms. This work approaches the instance segmentation problem as an
annotation problem and presents a novel technique to encode and decode ground
truth annotations. We propose a mathematical representation of instances that
any deep semantic segmentation model can learn and generalize. Each individual
instance is represented by a center of mass and a field of vectors pointing to
it. This encoding technique has been denominated Distance to Center of Mass
Encoding (DCME)
DNA as a universal substrate for chemical kinetics
Molecular programming aims to systematically engineer molecular and chemical systems of autonomous function and ever-increasing complexity. A key goal is to develop embedded control circuitry within a chemical system to direct molecular events. Here we show that systems of DNA molecules can be constructed that closely approximate the dynamic behavior of arbitrary systems of coupled chemical reactions. By using strand displacement reactions as a primitive, we construct reaction cascades with effectively unimolecular and bimolecular kinetics. Our construction allows individual reactions to be coupled in arbitrary ways such that reactants can participate in multiple reactions simultaneously, reproducing the desired dynamical properties. Thus arbitrary systems of chemical equations can be compiled into real chemical systems. We illustrate our method on the Lotka–Volterra oscillator, a limit-cycle oscillator, a chaotic system, and systems implementing feedback digital logic and algorithmic behavior
Time-Response Functions of Mechanical Networks with Inerters and Causality
This paper derives the causal time-response functions of three-parameter
mechanical networks that have been reported in the literature and involve the
inerter-a two-node element in which the force-output is proportional to the
relative acceleration of its end-nodes. This two-terminal device is the
mechanical analogue of the capacitor in a force-current/velocity-voltage
analogy. The paper shows that all frequency-response functions that exhibit
singularities along the real frequency axis need to be enhanced with the
addition of a Dirac delta function or with its derivative depending on the
strength of the singularity. In this way the real and imaginary parts of the
enhanced frequency response functions are Hilbert pairs; therefore, yielding a
causal time-response function in the time domain. The integral representation
of the output signals offers an attractive computational alternative given that
the constitutive equations of the three-parameter networks examined herein
involve the third derivative of the nodal displacement which may challenge the
numerical accuracy of a state-space formulation when the input signal is only
available in digital form as in the case of recorded seismic accelerograms
Three-Dimensional Network Model for Coupling~of~Fracture and Mass Transport in Quasi-Brittle Geomaterials
Dual three-dimensional networks of structural and transport elements were
combined to model the effect of fracture on mass transport in quasi-brittle
geomaterials. Element connectivity of the structural network, representing
elasticity and fracture, was defined by the Delaunay tessellation of a random
set of points. The connectivity of transport elements within the transport
network was defined by the Voronoi tessellation of the same set of points. A
new discretisation strategy for domain boundaries was developed to apply
boundary conditions for the coupled analyses. The properties of transport
elements were chosen to evolve with the crack opening values of neighbouring
structural elements. Through benchmark comparisons involving non-stationary
transport and fracture, the proposed dual network approach was shown to be
objective with respect to element size and orientation
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