176 research outputs found
Instance Flow Based Online Multiple Object Tracking
We present a method to perform online Multiple Object Tracking (MOT) of known
object categories in monocular video data. Current Tracking-by-Detection MOT
approaches build on top of 2D bounding box detections. In contrast, we exploit
state-of-the-art instance aware semantic segmentation techniques to compute 2D
shape representations of target objects in each frame. We predict position and
shape of segmented instances in subsequent frames by exploiting optical flow
cues. We define an affinity matrix between instances of subsequent frames which
reflects locality and visual similarity. The instance association is solved by
applying the Hungarian method. We evaluate different configurations of our
algorithm using the MOT 2D 2015 train dataset. The evaluation shows that our
tracking approach is able to track objects with high relative motions. In
addition, we provide results of our approach on the MOT 2D 2015 test set for
comparison with previous works. We achieve a MOTA score of 32.1
Refinement of Xâray and electron diffraction crystal structures using analytical Fourier transforms of Slaterâtype atomic wavefunctions in Olex2
An implementation of Slaterâtype spherical scattering factors for Xâray and electron diffraction for elements in the range Z = 1â103 is presented within the software Olex2. Both highâ and lowâangle Fourier behaviour of atomic electron density and electrostatic potential can thus be addressed, in contrast to the limited flexibility of the four Gaussian plus constant descriptions which are currently the most widely used method for calculating atomic scattering factors during refinement. The implementation presented here accommodates the increasing complexity of the electronic structure of heavier elements by using complete atomic wavefunctions without any interpolation between precalculated tables or intermediate fitting functions. Atomic wavefunctions for singly charged ions are implemented and made accessible, and these show drastic changes in electron diffraction scattering factors compared with the neutral atom. A comparison between the two different spherical models of neutral atoms is presented as an example for four different kinds of Xâray and two electron diffraction structures, and comparisons of refinement results using the existing diffraction data are discussed. A systematic but slight improvement in R values and residual densities can be observed when using the new scattering factors, and this is discussed relative to effects on the atomic displacement parameters and atomic positions, which are prominent near the heavier elements in a structure
Diâtertâbutyldiphosphatetrahedrane: Catalytic Synthesis of the Elusive Phosphaalkyne Dimer
While tetrahedranes as a family are scarce, neutral heteroatomic species are all but unknown, with the only reported example being AsP3. Herein, we describe the isolation of a neutral heteroatomic X2Y2 molecular tetrahedron (X, Y=p-block elements), which also is the long-sought-after free phosphaalkyne dimer. Di-tert-butyldiphosphatetrahedrane, (tBuCP)(2), is formed from the monomer tBuCP in a nickel-catalyzed dimerization reaction using [(NHC)Ni(CO)(3)] (NHC=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (IPr)). Single-crystal X-ray structure determination of a silver(I) complex confirms the structure of (tBuCP)(2). The influence of the N-heterocyclic carbene ligand on the catalytic reaction was investigated, and a mechanism was elucidated using a combination of synthetic and kinetic studies and quantum chemical calculations
The Parent Diarsene HAs=AsH as side-on bound ligand in an Iron Carbonyl Complex
The terminal diarsene HAs=AsH ligand attracts special interest concerning its bonding relation in comparison to its isolable relative, ethene. Herein, by the methanolysis of [{Fe(CO)4}As(SiMe3)3] (1) the synthesis of [{Fe(CO)4}(η2âAs2H2)] (2) is reported, containing a parent diarsene as unprecedented sideâon coordinated ligand. Following this synthetic route, also the Dâlabeled complex [{Fe(CO)4}(η2âAs2D2)] (2D) could be isolated. The electronic structure and bonding situation of 2 was elucidated by DFT calculations revealing that 2 is best described as an olefinâlike complex. Moreover, the reactivity of 2 towards the Lewis acids [{M(CO)5}(thf)] (M=Cr, W) was investigated, leading to the complexes [Fe(CO)4AsHW(CO)5]2 (3) and [{Fe(CO)4}2AsH{Cr(CO)5}] (4), respectively
Uncertainty-aware Vision-based Metric Cross-view Geolocalization
This paper proposes a novel method for vision-based metric cross-view
geolocalization (CVGL) that matches the camera images captured from a
ground-based vehicle with an aerial image to determine the vehicle's geo-pose.
Since aerial images are globally available at low cost, they represent a
potential compromise between two established paradigms of autonomous driving,
i.e. using expensive high-definition prior maps or relying entirely on the
sensor data captured at runtime.
We present an end-to-end differentiable model that uses the ground and aerial
images to predict a probability distribution over possible vehicle poses. We
combine multiple vehicle datasets with aerial images from orthophoto providers
on which we demonstrate the feasibility of our method. Since the ground truth
poses are often inaccurate w.r.t. the aerial images, we implement a
pseudo-label approach to produce more accurate ground truth poses and make them
publicly available.
While previous works require training data from the target region to achieve
reasonable localization accuracy (i.e. same-area evaluation), our approach
overcomes this limitation and outperforms previous results even in the strictly
more challenging cross-area case. We improve the previous state-of-the-art by a
large margin even without ground or aerial data from the test region, which
highlights the model's potential for global-scale application. We further
integrate the uncertainty-aware predictions in a tracking framework to
determine the vehicle's trajectory over time resulting in a mean position error
on KITTI-360 of 0.78m
Stabilization of Pentaphospholes as η5 -coordinating Ligands. Stabilisierung von Pentaphospholen als η5-koordinierende Liganden
Electrophilic functionalisation of [Cp*Fe(eta(5)-P-5)] (1) yields the first transition-metal complexes of pentaphospholes (cyclo-P5R). Silylation of1with [(Et3Si)(2)(mu-H)][B(C6F5)(4)] leads to the ionic species [Cp*Fe(eta(5)-P5SiEt3)][B(C6F5)(4)] (2), whose subsequent reaction with H2O yields the parent compound [Cp*Fe(eta(5)-P5H)][B(C6F5)(4)] (3). The synthesis of a carbon-substituted derivative [Cp*Fe(eta(5)-P5Me)][X] ([X](-)=[FB(C6F5)(3)](-)(4 a), [B(C6F5)(4)](-)(4 b)) is achieved by methylation of1employing [Me3O][BF4] and B(C6F5)(3)or a combination of MeOTf and [Li(OEt2)(2)][B(C6F5)(4)]. The structural characterisation of these compounds reveals a slight envelope structure for the cyclo-P5R ligand. Detailed NMR-spectroscopic studies suggest a highly dynamic behaviour and thus a distinct lability for2and3in solution. DFT calculations shed light on the electronic structure and bonding situation of this unprecedented class of compounds
Diâ tert âbutyldiphosphatetrahedran: Katalytische Synthese des freien PhosphaalkinâDimers. Diâtertâbutyldiphosphatetrahedrane: Catalytic Synthesis of the Elusive Phosphaalkyne Dimer
While tetrahedranes as a family are scarce, neutral heteroatomic species are all but unknown, with the only reported example being AsP3. Herein, we describe the isolation of a neutral heteroatomic X2Y2 molecular tetrahedron (X, Y=p-block elements), which also is the long-sought-after free phosphaalkyne dimer. Di-tert-butyldiphosphatetrahedrane, (tBuCP)(2), is formed from the monomer tBuCP in a nickel-catalyzed dimerization reaction using [(NHC)Ni(CO)(3)] (NHC=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (IPr)). Single-crystal X-ray structure determination of a silver(I) complex confirms the structure of (tBuCP)(2). The influence of the N-heterocyclic carbene ligand on the catalytic reaction was investigated, and a mechanism was elucidated using a combination of synthetic and kinetic studies and quantum chemical calculations
Germanium/phosphorus cage compounds with germanium in three different oxidation states
Novel germanium/phosphorus cage compounds with new structural motifs have been synthesized containing germanium in three different oxidation states. The key to obtain this new class of compounds is the use of monolithiated primary phosphine LiHPtBu in the reaction with GeX2
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