3,688 research outputs found
UrbanScene3D: A Large Scale Urban Scene Dataset and Simulator
The ability to perceive the environments in different ways is essential to
robotic research. This involves the analysis of both 2D and 3D data sources. We
present a large scale urban scene dataset associated with a handy simulator
based on Unreal Engine 4 and AirSim, which consists of both man-made and
real-world reconstruction scenes in different scales, referred to as
UrbanScene3D. Unlike previous works that purely based on 2D information or
man-made 3D CAD models, UrbanScene3D contains both compact man-made models and
detailed real-world models reconstructed by aerial images. Each building has
been manually extracted from the entire scene model and then has been assigned
with a unique label, forming an instance segmentation map. The provided 3D
ground-truth textured models with instance segmentation labels in UrbanScene3D
allow users to obtain all kinds of data they would like to have: instance
segmentation map, depth map in arbitrary resolution, 3D point cloud/mesh in
both visible and invisible places, etc. In addition, with the help of AirSim,
users can also simulate the robots (cars/drones)to test a variety of autonomous
tasks in the proposed city environment. Please refer to our paper and
website(https://vcc.tech/UrbanScene3D/) for further details and applications.Comment: Project page: https://vcc.tech/UrbanScene3D
High-responsivity vertical-illumination Si/Ge uni-traveling-carrier photodiodes based on silicon-on-insulator substrate
Si/Ge uni-traveling carrier photodiodes exhibit higher output current when
space-charge effects are overcome and thermal effects are suppressed, which is
highly beneficial for increasing the dynamic range of various microwave
photonic systems and simplifying high-bit-rate digital receivers in different
applications. From the point of view of packaging, detectors with
vertical-illumination configuration can be easily handled by pick-and-place
tools and are a popular choice for making photo-receiver modules. However,
vertical-illumination Si/Ge uni-traveling carrier (UTC) devices suffer from
inter-constraint between high speed and high responsivity. Here, we report a
high responsivity vertical-illumination Si/Ge UTC photodiode based on a
silicon-on-insulator substrate. The maximum absorption efficiency of the
devices was 2.4 times greater than the silicon substrate owing to constructive
interference. The Si/Ge UTC photodiode was successfully fabricated and had a
dominant responsivity at 1550 nm of 0.18 A/W, a 50% improvement even with a 25%
thinner Ge absorption layer.Comment: 5pages,2figure
Ballistic Missile Warhead Recognition based on Micro-Doppler Frequency
To elucidate the spinning-precession signatures of ballistic warhead, the model of spinning precessionfor ballistic missile warhead is established and the mathematics of micro-Doppler signatures caused by spinning-precession is derived. Then the micro-Doppler features are analysed using high-resolution time-frequencytransform, and the model predictions match the experimental data well. Based on different mass of warheadsand decoys, the feature, which can reflect the mass of the targets, is extracted from the time-frequency plane,proving a new method for recognising warheads and discriminating these from decoys. Finally the validityof the feature extracted in this study is verified by computer simulations even with low signal-to-noise ratio.Defence Science Journal, 2008, 58(6), pp.705-709, DOI:http://dx.doi.org/10.14429/dsj.58.169
Reaction Behaviors of Bagasse Modified with Phthalic Anhydride in 1âAllylâ3âMethylimidazolium Chloride with Catalyst 4âDimethylaminopyridine
The modification of lignocellulose with cyclic anhydrides could confer stronger hydrophilic properties to lignocellulose, which could be used in many industrial fields. To elucidate the modification mechanism of lignocellulose, bagasse was phthalated comparatively with its three main components in 1âallylâ3âmethylimidazolium chloride (AmimCl) using 4âdimethylaminopyridine as catalyst and phthalic anhydride as acylation reagent in the present study. From FTâIR and 2D HSQC analyses, the skeleton of bagasse and the fractions were not significantly changed during phthalation in AmimCl. 2D HSQC results suggested that the reactive hydroxyls in bagasse were partially phthalated, and the reactivity of the hydroxyls in anhydroglucose units followed the order Câ6 > Câ2 > Câ3. Similarly, the reactivity order of hydroxyls in anhydroxylose units was Câ2 > Câ3. For lignin, the predominant diesterification occurred during the homogeneous modification, and both aliphatic and aromatic hydroxyls were phthalated. The reactivity order of phenolic hydroxyls was SâOH > GâOH > HâOH, which was distinct from that without catalyst. In addition, it was found that the thermal stability of phthalated bagasse was affected by the disruption of cellulose crystallinity and the degradation of components. The thermal stability of the phthalated bagasse decreased upon chemical modification and regeneration
40-Gbps vestigial sideband half-cycle Nyquist subcarrier modulation transmission experiment and its comparison with orthogonal frequency division multiplexing
This is the published version. Copyright 2014 Society of Photo-optical Instrumentation EngineersWe experimentally demonstrate the superior performance of a 40-Gbps 16-QAM half-cycle Nyquist subcarrier modulation (SCM) transmission over a 100-km uncompensated standard single-mode fiber using dual-drive Mach-Zehnder modulator-based vestigial sideband intensity modulation and direct detection. The impact of modulator chirp on the system performance is experimentally evaluated. This Nyquist-SCM technique is compared with optical orthogonal frequency division multiplexing in both back-to-back and 100-km transmission experiments, and the results show that the Nyquist system has a better performance
Iterative intersymbol interference cancellation in vestigial sideband Nyquistâsubcarrier modulation system
This is the published version. © 2014 Society of Photo-Optical Instrumentation Engineers
(SPIE)The intersymbol interference caused by dispersion, chirp, and a vestigial sideband filter in intensity
modulation and a direct detection single carrier system is analyzed theoretically and numerically. An iterative
nonlinear intersymbol interference cancellation technique is proposed and experimentally demonstrated in a 40-
Gbps 16-QAM Mach-Zehnder modulator-based vestigial sideband intensity modulation and direct detection halfcycle
Nyquistâsubcarrier modulation system over a 100-km uncompensated standard single-mode fiber transmission
for the first time. The experimental results show that 2.2-dB receiver sensitivity improvement is obtained
at the forward error correction limit by using the iterative technique
{6-[2,5-Bis(chloroÂmethÂyl)-3,4-dihydroxyÂtetraÂhydroÂfuran-2-ylÂoxy]-3-chloro-4,5-dihydrÂoxy-3,4,5,6-tetraÂhydro-2H-pyran-2-yl}methyl acetate dihydrate
The title compound, C14H21Cl3O9·2H2O, is a disaccharide constructed from a galactose and a fructose. In the molÂecular structure, the tetraÂhydroÂfuran five-membered ring and tetraÂhydroÂpyran six-membered ring assume envelope and chair conformations, respectively. An extensive OâHâŻO hydrogen-bonding network occurs in the crystal structure
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