6,714 research outputs found
A Constrained Tectonics Model for Coronal Heating
An analytical and numerical treatment is given of a constrained version of
the tectonics model developed by Priest, Heyvaerts, & Title [2002]. We begin
with an initial uniform magnetic field that is
line-tied at the surfaces and . This initial configuration is
twisted by photospheric footpoint motion that is assumed to depend on only one
coordinate () transverse to the initial magnetic field. The geometric
constraints imposed by our assumption precludes the occurrence of reconnection
and secondary instabilities, but enables us to follow for long times the
dissipation of energy due to the effects of resistivity and viscosity. In this
limit, we demonstrate that when the coherence time of random photospheric
footpoint motion is much smaller by several orders of magnitude compared with
the resistive diffusion time, the heating due to Ohmic and viscous dissipation
becomes independent of the resistivity of the plasma. Furthermore, we obtain
scaling relations that suggest that even if reconnection and/or secondary
instabilities were to limit the build-up of magnetic energy in such a model,
the overall heating rate will still be independent of the resistivity
A Model that Predicts the Material Recognition Performance of Thermal Tactile Sensing
Tactile sensing can enable a robot to infer properties of its surroundings,
such as the material of an object. Heat transfer based sensing can be used for
material recognition due to differences in the thermal properties of materials.
While data-driven methods have shown promise for this recognition problem, many
factors can influence performance, including sensor noise, the initial
temperatures of the sensor and the object, the thermal effusivities of the
materials, and the duration of contact. We present a physics-based mathematical
model that predicts material recognition performance given these factors. Our
model uses semi-infinite solids and a statistical method to calculate an F1
score for the binary material recognition. We evaluated our method using
simulated contact with 69 materials and data collected by a real robot with 12
materials. Our model predicted the material recognition performance of support
vector machine (SVM) with 96% accuracy for the simulated data, with 92%
accuracy for real-world data with constant initial sensor temperatures, and
with 91% accuracy for real-world data with varied initial sensor temperatures.
Using our model, we also provide insight into the roles of various factors on
recognition performance, such as the temperature difference between the sensor
and the object. Overall, our results suggest that our model could be used to
help design better thermal sensors for robots and enable robots to use them
more effectively.Comment: This article is currently under review for possible publicatio
The Child Health Scenario in India: An Application of Bayesian Approach
Background: The child mortality rate of a place is an indication of the basic health facility prevalent there. A place with better medical facility records low child mortality. The child mortality rate reduction is not as expected in many developing countries. In last two decades the child death rate has not been reduced significantly in India. The aim of this work is to explore the child death rate in different Indian states.
Materials and Methods: The Bayesian approach has been applied to control the over dispersion due to presence of zero (i.e. no-death count) in the data set. The Zero Inflated Poisson (ZIP) has been applied to control the presence of over the Zero Inflation Distribution. The data set has been considered from Indian National Health and Family Survey (NFHS-3) conducted during 2005-2006. The women having at least one living child of age less than five years has been selected as study subjects
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