310 research outputs found
Single point positioning using GPS, GLONASS and BeiDou satellites
This paper introduces the Chinese BeiDou satellite system and its comparison with the actual
completed American GPS and the Russian GLONASS systems. The actual
BeiDou system consists
of
14 satellites covering totally the Asia
-Pacific area. A Single Point Positioning (SPP) test has been
realised in Changsha, Hunan province, China, to show the advantage of using combined pseud
o-
range solutions from these 3 satellite navigation systems especially in obstructed sites.
The test
shows that, with an elevation mask angle of 10
°
, the accuracy is improved by about 20% in hor
i-
zontal coordinates and nearly
50% in the vertical component using the simultaneous observa
tions
of the 3 systems compared
to the GPS/GLONASS solution. For the processing with an elev
ation
mask angle of 30
°
, most of the time less than 4 GPS satellites were available for the GPS-
only case
and no solution was possible. However, in this difficult situation, the combined GPS/GLON
ASS/
BeiDou solutions provided an
accuracy (rms values) of about 5 m
Kinematic Absolute Positioning with Quad-Constellation GNSS
The absolute positioning technique is based on a point positioning mode with a single Global Navigation Satellite System (GNSS) receiver, which has been widely used in many fields such as vehicle navigation and kinematic surveying. For a long period, this positioning technique mainly relies on a single GPS system. With the revitalization of Global Navigation Satellite System (GLONASS) constellation and two newly emerging constellations of BeiDou Navigation Satellite System (BDS) and Galileo, it is now feasible to carry out the absolute positioning with quad-constellation of GPS, GLONASS, BDS, and Galileo. A combination of multi-constellation observations can offer improved reliability, availability, and accuracy for position solutions. In this chapter, combined GPS/GLONASS/BDS/Galileo point positioning models for both traditional single point positioning (SPP) and precise point positioning (PPP) are presented, including their functional and stochastic components. The traditional SPP technique has a positioning accuracy at a meter level, whereas the PPP technique can reach an accuracy of a centimeter level. However, the later relies on the availability of precise ephemeris and needs a long convergence time. Experiments were carried out to assess the kinematic positioning performance in the two different modes. The positioning results are compared among different constellation combinations to demonstrate the advantages of quad-constellation GNSS
Matching-CNN Meets KNN: Quasi-Parametric Human Parsing
Both parametric and non-parametric approaches have demonstrated encouraging
performances in the human parsing task, namely segmenting a human image into
several semantic regions (e.g., hat, bag, left arm, face). In this work, we aim
to develop a new solution with the advantages of both methodologies, namely
supervision from annotated data and the flexibility to use newly annotated
(possibly uncommon) images, and present a quasi-parametric human parsing model.
Under the classic K Nearest Neighbor (KNN)-based nonparametric framework, the
parametric Matching Convolutional Neural Network (M-CNN) is proposed to predict
the matching confidence and displacements of the best matched region in the
testing image for a particular semantic region in one KNN image. Given a
testing image, we first retrieve its KNN images from the
annotated/manually-parsed human image corpus. Then each semantic region in each
KNN image is matched with confidence to the testing image using M-CNN, and the
matched regions from all KNN images are further fused, followed by a superpixel
smoothing procedure to obtain the ultimate human parsing result. The M-CNN
differs from the classic CNN in that the tailored cross image matching filters
are introduced to characterize the matching between the testing image and the
semantic region of a KNN image. The cross image matching filters are defined at
different convolutional layers, each aiming to capture a particular range of
displacements. Comprehensive evaluations over a large dataset with 7,700
annotated human images well demonstrate the significant performance gain from
the quasi-parametric model over the state-of-the-arts, for the human parsing
task.Comment: This manuscript is the accepted version for CVPR 201
Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin.
A long-standing issue in the field of signal transduction is to understand the cross-talk between receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major and distinct signaling hubs that control eukaryotic cell behavior. Although stimulation of many RTKs leads to activation of trimeric G proteins, the molecular mechanisms behind this phenomenon remain elusive. We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins. Using a combination of homology modeling, protein-protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands. Using protein-protein interaction assays, we demonstrated that both SH2 and GEF domains of GIV are required for the formation of a ligand-activated ternary complex between GIV, Gαi, and growth factor receptors and for activation of Gαi after growth factor stimulation. Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV-Akt enhancement, actin remodeling, and cell migration. The mechanistic and structural insights gained here shed light on the long-standing questions surrounding RTK/G protein cross-talk, set a novel paradigm, and characterize a unique pharmacological target for uncoupling GIV-dependent signaling downstream of multiple oncogenic RTKs
Initial spread of 137Cs from the Fukushima Dai-ichi Nuclear Power Plant over the Japan continental shelf : a study using a high-resolution, global-coastal nested ocean model
© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 10 (2013): 5439-5449, doi:10.5194/bg-10-5439-2013.The 11 March 2011 tsunami triggered by the M9 and M7.9 earthquakes off the Tōhoku coast destroyed facilities at the Fukushima Dai-ichi Nuclear Power Plant (FNPP) leading to a significant long-term flow of the radionuclide 137Cs into coastal waters. A high-resolution, global-coastal nested ocean model was first constructed to simulate the 11 March tsunami and coastal inundation. Based on the model's success in reproducing the observed tsunami and coastal inundation, model experiments were then conducted with differing grid resolution to assess the initial spread of 137Cs over the eastern shelf of Japan. The 137Cs was tracked as a conservative tracer (without radioactive decay) in the three-dimensional model flow field over the period of 26 March–31 August 2011. The results clearly show that for the same 137Cs discharge, the model-predicted spreading of 137Cs was sensitive not only to model resolution but also the FNPP seawall structure. A coarse-resolution (∼2 km) model simulation led to an overestimation of lateral diffusion and thus faster dispersion of 137Cs from the coast to the deep ocean, while advective processes played a more significant role when the model resolution at and around the FNPP was refined to ∼5 m. By resolving the pathways from the leaking source to the southern and northern discharge canals, the high-resolution model better predicted the 137Cs spreading in the inner shelf where in situ measurements were made at 30 km off the coast. The overestimation of 137Cs concentration near the coast is thought to be due to the omission of sedimentation and biogeochemical processes as well as uncertainties in the amount of 137Cs leaking from the source in the model. As a result, a biogeochemical module should be included in the model for more realistic simulations of the fate and spreading of 137Cs in the ocean.This project
was supported by the US National Science Foundation RAPID
grants No. 1141697 and No. 1141785 and the Japan Science
and Technology Agency J-RAPID program. The development
of Global-FVCOM was supported by NSF grants ARC0712903,
ARC0732084, and ARC0804029. Z. Lai’s contribution was
supported by the Natural Science Foundation of China project
41206005, China MOST project 2012CB956004, and Sun Yat-Sen
University 985 grant 42000-3281301. C. Chen serves as chief
scientist for the International Center for Marine Studies, Shanghai
Ocean University, and his contribution was supported by the
Program of Science and Technology Commission of Shanghai
Municipality (09320503700)
3D Trajectory Design for UAV-Assisted Oblique Image Acquisition
In this correspondence, we consider a new unmanned aerial vehicle
(UAV)-assisted oblique image acquisition system where a UAV is dispatched to
take images of multiple ground targets (GTs). To study the three-dimensional
(3D) UAV trajectory design for image acquisition, we first propose a novel
UAV-assisted oblique photography model, which characterizes the image
resolution with respect to the UAV's 3D image-taking location. Then, we
formulate a 3D UAV trajectory optimization problem to minimize the UAV's
traveling distance subject to the image resolution constraints. The formulated
problem is shown to be equivalent to a modified 3D traveling salesman problem
with neighbourhoods, which is NP-hard in general. To tackle this difficult
problem, we propose an iterative algorithm to obtain a high-quality suboptimal
solution efficiently, by alternately optimizing the UAV's 3D image-taking
waypoints and its visiting order for the GTs. Numerical results show that the
proposed algorithm significantly reduces the UAV's traveling distance as
compared to various benchmark schemes, while meeting the image resolution
requirement
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