13,801 research outputs found
Human-in-the-Loop SLAM
Building large-scale, globally consistent maps is a challenging problem, made
more difficult in environments with limited access, sparse features, or when
using data collected by novice users. For such scenarios, where
state-of-the-art mapping algorithms produce globally inconsistent maps, we
introduce a systematic approach to incorporating sparse human corrections,
which we term Human-in-the-Loop Simultaneous Localization and Mapping
(HitL-SLAM). Given an initial factor graph for pose graph SLAM, HitL-SLAM
accepts approximate, potentially erroneous, and rank-deficient human input,
infers the intended correction via expectation maximization (EM),
back-propagates the extracted corrections over the pose graph, and finally
jointly optimizes the factor graph including the human inputs as human
correction factor terms, to yield globally consistent large-scale maps. We thus
contribute an EM formulation for inferring potentially rank-deficient human
corrections to mapping, and human correction factor extensions to the factor
graphs for pose graph SLAM that result in a principled approach to joint
optimization of the pose graph while simultaneously accounting for multiple
forms of human correction. We present empirical results showing the
effectiveness of HitL-SLAM at generating globally accurate and consistent maps
even when given poor initial estimates of the map.Comment: AAAI 201
Effect of realistic interatomic interactions and two-body correlation on the heat capacity of a trapped BEC
An approximate many-body theory has been used to calculate the heat capacity
and the condensate fraction of a BEC with effective repulsive interaction. The
effect of interactions has been analyzed and compared with the non-interacting
case. It has been found that the repulsive interaction lowers the critical
temperature from the value found in the non-interacting case. The difference
between the critical temperatures increases with the increase in the total
number of atoms in the trap.Comment: 15 pages, 5 figure
The Complex Time WKB Approximation And Particle Production
The complex time WKB (CWKB) approximation has been an effective technique to
understand particle production in curved as well as in flat spacetime. Earlier
we obtained the standard results on particle production in time dependent gauge
in various curved spacetime. In the present work we generalize the technique of
CWKB to the equivalent problems in space dependent gauge. Using CWKB, we first
obtain the gauge invariant result for particle production in Minkowski
spacetime in strong electric field. We then carry out particle production in
de-Sitter spacetime in space dependent gauge and obtain the same result that we
obtained earlier in time dependent gauge. The results obtained for de-Sitter
spacetime has a obvious extension to particle production in black hole
spacetime. It is found that the origin of Planckian spectrum is due to repeated
reflections between the turning points. As mentioned earlier, it is now
explicitly shown that particle production is accompanied by rotation of
currents.Comment: 12 pages, Revte
On Modified Gravity
We consider some aspects of nonlocal modified gravity, where nonlocality is
of the type . In particular, using ansatz of the form
we find a few solutions for the spatially flat
FLRW metric. There are singular and nonsingular bounce solutions. For late
cosmic time, scalar curvature R(t) is in low regime and scale factor a(t) is
decelerated. R (t) = 0 satisfies all equations when k = -1.Comment: added references; made some clarifications; 8 page
Study of QCD generalized ghost dark energy in FRW universe
A phenomenological generalized ghost dark energy model has been studied under
the framework of FRW universe. In ghost dark energy model the energy density
depends linearly on Hubble parameter (H) but in this dark energy model, the
energy density contains a the sub-leading term which is depends on , so the energy density takes the form ,
where and are the constants. The solutions of the Friedman
equation of our model leads to a stable universe. We have fitted our model with
the present observational data including Stern data set. With the help of best
fit results we find the adiabatic sound speed remains positive throughout the
cosmic evolution, that claims the stability of the model. The flipping of the
signature of deceleration parameter at the value of scale factor
indicates that the universe is at the stage of acceleration i.e. de Sitter
phase of the universe at late time. Our model shows that the acceleration of
the universe begin at redshift and the model is also
consistent with the current observational data.Comment: 9 pages, 9 figure
On-farm impact analysis of resource conservation technology on wheat at Tarai-Teesta Flood plain of Eastern Indo-Gangetic Plain (IGP)
Adoption of resource conservation technologies (RCT) may improve the productivity, reduce cost and sustainability of wheat production in the irrigated areas of eastern Indo-Gangetic plains (IGP) of South Asia. Critical on –farm study on factors favouring adoption and non-adoption is required. Findings from an on-farm trial conducted during 2005-2009 are used to evaluate the on-farm impacts of zero tillage (ZT) in wheat from three sites at Tarai-Teesta flood plain of eastern IGP. On an average, there was 11.54% increase in productivity in ZT wheat over conventional tilled (CT) wheat. Water productivity increased from 1.99 kg m-3 in CT to 2.73 kg m-3 in ZT due to lower estimated water use (1147 m3 ha-1 in ZT than 1435 m3 ha-1 in CT) and higher productivity (3.38 t ha-1 in ZT than 3.03 t ha-1 in CT). Saving in tractor operation and diesel use in farmers’ ZT wheat fields were 3.23 and 19.09 hours ha-1. Sowing can be done earlier by one week through adoption of ZT machine for better utilization of limited winter. Savings in ZT on farmers’ fields were in the components of land preparation (1938 Rs ha-1), seed (462 Rs ha-1), nitrogen (269 Rs ha-1), phosphate fertilizer (104 Rs ha-1) and irrigation (380 Rs ha-1) over conventional wheat cultivation. Availability of zero-till seeder and its servicing, skilled operator and sometimes reluctance of local tiller operator for apprehension of lower earnings from single tillage pass are also revealed as the factors of non-adoption. More such in-depth studies should be conducted on site-specific basis so that it can be replicated more widely in areas for the benefit of the farming community
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