101 research outputs found
A method for three-dimensional reconstruction of a train accident scene using photographs
Railway accidents that usually cause numerous property and life losses occurred in recent years all around the world. In general, resources such as financial supports and incident rescue programs are required to minimize the losses after an accident. Due to lack of comprehensive information collected from accident sites, most railway emergency management departments face a predicament in setting up rescue schemes. To tackle the issue, realistic three-dimensional virtual accident scene reconstruction technology is developed, which provides and visualises supplementary materials and information about a train accident and can offer assistance to emergency crews when making decisions. We propose a photo-based three-dimensional reconstruction framework of vehicles for measuring the positions and poses of carriages involved in an accident. We implement and examine two case studies to validate this reconstruction method, which performs well in the assigned tasks
3D reconstruction of train accident scene based on monocular image
To help with making an emergency rescue plan for train accidents, a rapid 3D reconstruction
method of train accident scene based on a monocular image was proposed. Taking two
camera projection models for different application scenarios into consideration, the SIFT algorithm
was introduced to extract and match image feature with the CAD model of an accident train.
Geometric constraints between carriages were provided to transform the 3D reconstruction to
solving a nonlinear least square problem with constraints, by which the position and pose of accident
subjects were reduced at last. To quantitatively and qualitatively verify the calculation performance
of this method, the mimicked train accident scene and real train accident scene were
respectively used to carry out 3D reconstruction. The precise finite camera projection model was
applied in the mimicked train accident scene to carry out offline calibration, and the stable
pin-hole model was adopted in the real train accident scene to carry out auto calibration. Analysis
result shows that through quantitative analysis of mimicked scene the maximal and average relative
error of 8 nodes for measurement in reconstructing two carriages are 4.54% and 1.85% respectively.
Through qualitative analysis of the real scene, the 3D reduction of position and pose
for carriages can also be realized with combining the topographic information correction. The
whole accident environmental panorama can be reduced visually with the help of 3D visualization
engine. This method can also be used in developing emergency rescue electronic sand table for
train accident analysis and safety education
Image-based 3D Scene Reconstruction and Rescue Simulation Framework for Railway Accidents
Although the railway transport is regarded as a relatively safe transportation tool, many railway accidents have still happened worldwide. In this research, an image-based 3D scene reconstruction framework was proposed to help railway accident emergency rescues. Based on the improved constrained non-linear least square optimization, the framework can automatically model the accident scene with only one panorama in a short time. We embedded the self-developed global terrain module into the commercial visualization and physics engine, which makes the commercial engine can be used to render the static scene at anywhere and simulate the dynamic rescue process respectively. In addition, a Head Mounted Device (HMD) was integrated into this framework to allow users to verify their rescue plan and review previous railway accidents in an immersive environment
Measurement and calculation of neutron leakage spectra from slab samples of beryllium, gallium and tungsten irradiated with 14.8 MeV neutrons
Hydrogen bond activated glycosylation under mild conditions
Herein, we report a new glycosylation system for the highly efficient and stereoselective formation of glycosidic bonds using glycosyl N-phenyl trifluoroacetimidate (PTFAI) donors and a charged thiourea hydrogen-bond-donor catalyst. The glycosylation protocol features broad substrate scope, controllable stereoselectivity, good to excellent yields and exceptionally mild catalysis conditions. Benefitting from the mild reaction conditions, this new hydrogen bond-mediated glycosylation system in combination with a hydrogen bond-mediated aglycon delivery system provides a reliable method for the synthesis of challenging phenolic glycosides. In addition, a chemoselective glycosylation procedure was developed using different imidate donors (trichloroacetimidates, N-phenyl trifluoroacetimidates, N-4-nitrophenyl trifluoroacetimidates, benzoxazolyl imidates and 6-nitro-benzothiazolyl imidates) and it was applied for a trisaccharide synthesis through a novel one-pot single catalyst strategy.Bio-organic Synthesi
Partial Wave Analysis of
BES data on are presented. The
contribution peaks strongly near threshold. It is fitted with a
broad resonance with mass MeV, width MeV. A broad resonance peaking at 2020 MeV is also required
with width MeV. There is further evidence for a component
peaking at 2.55 GeV. The non- contribution is close to phase
space; it peaks at 2.6 GeV and is very different from .Comment: 15 pages, 6 figures, 1 table, Submitted to PL
A Measurement of Psi(2S) Resonance Parameters
Cross sections for e+e- to hadons, pi+pi- J/Psi, and mu+mu- have been
measured in the vicinity of the Psi(2S) resonance using the BESII detector
operated at the BEPC. The Psi(2S) total width; partial widths to hadrons,
pi+pi- J/Psi, muons; and corresponding branching fractions have been determined
to be Gamma(total)= (264+-27) keV; Gamma(hadron)= (258+-26) keV, Gamma(mu)=
(2.44+-0.21) keV, and Gamma(pi+pi- J/Psi)= (85+-8.7) keV; and Br(hadron)=
(97.79+-0.15)%, Br(pi+pi- J/Psi)= (32+-1.4)%, Br(mu)= (0.93+-0.08)%,
respectively.Comment: 8 pages, 6 figure
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
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