171 research outputs found

    Instance Flow Based Online Multiple Object Tracking

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    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 X‐ray and electron diffraction crystal structures using analytical Fourier transforms of Slater‐type atomic wavefunctions in Olex2

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    An implementation of Slater‐type spherical scattering factors for X‐ray and electron diffraction for elements in the range Z = 1–103 is presented within the software Olex2. Both high‐ and low‐angle 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 X‐ray 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

    Di‐tert‐butyldiphosphatetrahedrane: Catalytic Synthesis of the Elusive Phosphaalkyne Dimer

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    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

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    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}(η2‐As2H2)] (2) is reported, containing a parent diarsene as unprecedented side‐on coordinated ligand. Following this synthetic route, also the D‐labeled complex [{Fe(CO)4}(η2‐As2D2)] (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 olefin‐like 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

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    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

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    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

    Di‐ tert ‐butyldiphosphatetrahedran: Katalytische Synthese des freien Phosphaalkin‐Dimers. Di‐tert‐butyldiphosphatetrahedrane: Catalytic Synthesis of the Elusive Phosphaalkyne Dimer

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    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

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    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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