353,325 research outputs found
Results of the attitude reconstruction for the UniSat-6 microsatellite using in-orbit data
UniSat-6 is a civilian microsatellite that was launched in orbit on the 19th of June, 2014. Its main mission consisted in the in-orbit release of a number of on-board carried Cubesats and in the transmission to the UniSat-6 ground station of telemetry data and images from an on-board mounted camera. The spacecraft is equipped with a passive magnetic attitude control system. Gyros and magnetometers provide the information about the attitude of the spacecraft. The importance of reconstructing the attitude motion of UniSat-6 lies in the dual possibility, for future missions, of:controlling the direction of ejection of the on-board carried satelliteshaving an accurate pointing for remote sensing operation.The reconstruction of the attitude motion of UniSat-6 is based on the data of the on-board Commercial Off The Shelf (COTS) gyros and magnetometers, downloaded at the passages over the ground station in Roma, Italy. At ground, these data have been processed with the UnScented QUaternion Estimator (USQUE) algorithm. This estimator is an adaptation of the Unscented Filter to the problem of spacecraft attitude estimation. The USQUE is based on a dual attitude representation, which involves both quaternions and Generalized Rodrigues Parameters. In this work, the propagation phase of the algorithm contains only a kinematic model of the motion of the spacecraft. This paper presents the results of the reconstruction of the UniSat-6 attitude using on-board measurements. The results show that the spacecraft effectively stabilized its attitude motion thanks to the on-board magnetic devices
Reconstructed Rough Growing Interfaces; Ridgeline Trapping of Domain Walls
We investigate whether surface reconstruction order exists in stationary
growing states, at all length scales or only below a crossover length, . The later would be similar to surface roughness in growing crystal
surfaces; below the equilibrium roughening temperature they evolve in a
layer-by-layer mode within a crossover length scale , but are always
rough at large length scales. We investigate this issue in the context of KPZ
type dynamics and a checker board type reconstruction, using the restricted
solid-on-solid model with negative mono-atomic step energies. This is a
topology where surface reconstruction order is compatible with surface
roughness and where a so-called reconstructed rough phase exists in
equilibrium. We find that during growth, reconstruction order is absent in the
thermodynamic limit, but exists below a crossover length , and that this local order fluctuates critically. Domain walls become
trapped at the ridge lines of the rough surface, and thus the reconstruction
order fluctuations are slaved to the KPZ dynamics
Positive Operator-Valued Measure reconstruction of a beam-splitter tree based photon-number-resolving detector
Here we present a reconstruction of the Positive Operator-Value Measurement
of a photon-number-resolving detector comprised of three 50:50 beamsplitters in
a tree configuration, terminated with four single-photon avalanche detectors.
The four detectors' outputs are processed by an electronic board that
discriminates detected photon number states from 0 to 4 and implements a "smart
counting" routine to compensate for dead time issues at high count rates
Corporate Misgovernance at the World Bank
We test for evidence of corporate misgovernance at the World Bank. Most major decisions at the World Bank are made by its Board of Executive Directors. However, in any given year the majority of the Bank's member countries do not get a chance to serve on this powerful body. In this paper, we empirically investigate whether board membership leads to higher funding from the World Bank's two main development financing institutions, the International Bank for Reconstruction and Development (IBRD) and the International Development Association (IDA). We find that developing countries serving on the Board of Executive Directors can expect an approximate doubling of funding from the IBRD. In absolute terms, countries serving on the board are rewarded with an average $60 million "bonus" in IBRD loans. This is more likely driven by soft forces like boardroom culture rather than by the power of the vote itself. We find no significant effect in IDA funding.
The reconstruction of Ni and Rh (001) surfaces upon Carbon, Nitrogen, or Oxygen adsorption
Nickel and Rhodium (001) surfaces display a similar - as from STM images -
clock reconstruction when half a monolayer of C/Ni, N/Ni or O/Rh is adsorbed;
no reconstruction is observed instead for O/Ni. Adsorbate atoms sit at the
center of the black squares of a chess-board, , pattern and two
different reconstructions are actually compatible with the observed STM images
- showing a pattern - according to whether a rotation of the
black or white squares occurs. We report on a first - principles study of the
structure of X/Ni(001) and X/Rh(001) surfaces (X=C,N,O) at half a monolayer
coverage, performed using density-functional theory. Our findings are in
agreement with all available experimental information and shed new light on the
mechanisms responsible for the reconstructions. We show that the same substrate
may display different reconstructions - or no reconstruction - upon adsorption
of different atomic species, depending on the relative importance of the
chemical and steric factors which determine the reconstruction.Comment: 18 pages, 5 figure
Corticospinal Tract (CST) reconstruction based on fiber orientation distributions(FODs) tractography
The Corticospinal Tract (CST) is a part of pyramidal tract (PT), and it can
innervate the voluntary movement of skeletal muscle through spinal interneurons
(the 4th layer of the Rexed gray board layers), and anterior horn motorneurons
(which control trunk and proximal limb muscles). Spinal cord injury (SCI) is a
highly disabling disease often caused by traffic accidents. The recovery of CST
and the functional reconstruction of spinal anterior horn motor neurons play an
essential role in the treatment of SCI. However, the localization and
reconstruction of CST are still challenging issues; the accuracy of the
geometric reconstruction can directly affect the results of the surgery. The
main contribution of this paper is the reconstruction of the CST based on the
fiber orientation distributions (FODs) tractography. Differing from
tensor-based tractography in which the primary direction is a determined
orientation, the direction of FODs tractography is determined by the
probability. The spherical harmonics (SPHARM) can be used to approximate the
efficiency of FODs tractography. We manually delineate the three ROIs (the
posterior limb of the internal capsule, the cerebral peduncle, and the anterior
pontine area) by the ITK-SNAP software, and use the pipeline software to
reconstruct both the left and right sides of the CST fibers. Our results
demonstrate that FOD-based tractography can show more and correct anatomical
CST fiber bundles
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