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131.
Marek Kraft Michał Nowicki Adam Schmidt Michał Fularz Piotr Skrzypczyński 《Machine Vision and Applications》2017,28(1-2):61-74
Although the introduction of commercial RGB-D sensors has enabled significant progress in the visual navigation methods for mobile robots, the structured-light-based sensors, like Microsoft Kinect and Asus Xtion Pro Live, have some important limitations with respect to their range, field of view, and depth measurements accuracy. The recent introduction of the second- generation Kinect, which is based on the time-of-flight measurement principle, brought to the robotics and computer vision researchers a sensor that overcomes some of these limitations. However, as the new Kinect is, just like the older one, intended for computer games and human motion capture rather than for navigation, it is unclear how much the navigation methods, such as visual odometry and SLAM, can benefit from the improved parameters. While there are many publicly available RGB-D data sets, only few of them provide ground truth information necessary for evaluating navigation methods, and to the best of our knowledge, none of them contains sequences registered with the new version of Kinect. Therefore, this paper describes a new RGB-D data set, which is a first attempt to systematically evaluate the indoor navigation algorithms on data from two different sensors in the same environment and along the same trajectories. This data set contains synchronized RGB-D frames from both sensors and the appropriate ground truth from an external motion capture system based on distributed cameras. We describe in details the data registration procedure and then evaluate our RGB-D visual odometry algorithm on the obtained sequences, investigating how the specific properties and limitations of both sensors influence the performance of this navigation method. 相似文献
132.
133.
Sebastian Sturm Maria Siglreitmeier Daniel Wolf Karin Vogel Micha Gratz Damien Faivre Axel Lubk Bernd Büchner Elena V. Sturm Helmut Clfen 《Advanced functional materials》2019,29(45)
Inspired by chains of ferrimagnetic nanocrystals (NCs) in magnetotactic bacteria (MTB), the synthesis and detailed characterization of ferrimagnetic magnetite NC chain‐like assemblies is reported. An easy green synthesis route in a thermoreversible gelatin hydrogel matrix is used. The structure of these magnetite chains prepared with and without gelatin is characterized by means of transmission electron microscopy, including electron tomography (ET). These structures indeed bear resemblance to the magnetite assemblies found in MTB, known for their mechanical flexibility and outstanding magnetic properties and known to crystallographically align their magnetite NCs along the strongest <111> magnetization easy axis. Using electron holography (EH) and angular dependent magnetic measurements, the magnetic interaction between the NCs and the generation of a magnetically anisotropic material can be shown. The electro‐ and magnetostatic modeling demonstrates that in order to precisely determine the magnetization (by means of EH) inside chain‐like NCs assemblies, their exact shape, arrangement and stray‐fields have to be considered (ideally obtained using ET). 相似文献
134.
Takaya Arita Michał Joachimczak Takashi Ito Atsushi Asakura Reiji Suzuki 《Artificial Life and Robotics》2016,21(2):141-148
Evolutionary developmental biology, evo-devo, emerged to integrate evolution and development in the 1980s, in which evolution is conceptualized as heritable changes in development. Recently, the field is moving to a new synthesis: ecological evolutionary developmental biology, eco-evo-devo. We believe that artificial life (ALife) approach will provide new insights into the field, and also contribute to the field of robotics through the emergence perspective and the constructive methodology. This paper explores the potential of such an artificial life approach based on the evolution of virtual creatures by presenting our ongoing studies with three models: (1) metamorphosis model, (2) exaptation model and (3) Prey-predator model. 相似文献
135.
Tomasz Zawistowski Michał Kleiber 《Archives of Computational Methods in Engineering》2017,24(3):519-542
High pressure variable displacement axial piston pumps are subject to complex dynamic phenomena. Their analysis is difficult, additionally complicated by leakage of the working fluid. Analytically gap flow is calculated with the Reynolds equation which describes the pressure distribution in a thin lubricating layer. The paper presents various approaches to analyze gap flow both in traditional axial piston pump and novel type of hydraulic pump, designed at the Polish Gdansk Institute of Technology. Because of large aspect ratio between the height of the gap and the size of pump elements, the authors present the numerical simulation approach using a local model to define a lubrication gap, linked to a global model of a pump from which boundary conditions were imported. User defined functions implemented in Fluent and Excel were used to calculate the pressure and velocity fields and assess the fluid flow rate. 相似文献
136.
Modulating the Ferromagnet/Molecule Spin Hybridization Using an Artificial Magnetoelectric 下载免费PDF全文
Michał Studniarek Salia Cherifi‐Hertel Etienne Urbain Ufuk Halisdemir Rémi Arras Beata Taudul Filip Schleicher Marie Hervé Charles‐Henri Lambert Abbass Hamadeh Loïc Joly Fabrice Scheurer Guy Schmerber Victor Da Costa Bénédicte Warot‐Fonrose Cécile Marcelot Olivia Mauguin Ludovic Largeau Florian Leduc Fadi Choueikani Edwige Otero Wulf Wulfhekel Jacek Arabski Philippe Ohresser Wolfgang Weber Eric Beaurepaire Samy Boukari Martin Bowen 《Advanced functional materials》2017,27(27)
Spin‐polarized charge transfer at the interface between a ferromagnetic (FM) metal and a molecule can lead to ferromagnetic coupling and to a high spin polarization at room temperature. The magnetic properties of these interfaces can not only alter those of the ferromagnet but can also stabilize molecular spin chains with interesting opportunities toward quantum computing. With the aim to enhance an organic spintronic device's functionality, external control over this spin polarization may thus be achieved by altering the ferromagnet/molecule interface's magnetic properties. To do so, the magnetoelectric properties of an underlying ferroelectric/ferromagnetic interface are utilized. Switching the ferroelectric polarization state of a PbZr0.2Ti0.8O3 (PZT) bottom layer within a PZT/Co/FePc‐based (Pc ‐ phthalocyanine) device alters the X‐ray magnetic circular dichroism of the Fe site within the phthalocyanine molecular top layer. Thus, how to electrically alter the magnetic properties of an interface with high spin polarization at room temperature is demonstrated. This expands electrical control over spin‐polarized FM/molecule interfaces, which is first demonstrated using ferroelectric molecules, to all molecular classes. 相似文献
137.
Regardless the low production rate, electrospinning remains the attractive technique for the nanofibers production in various fields. Thus, the development of a multi-jet technologies for electrospinning gives an opportunity to scale up and increase throughput of the fibers production. However, the multi-jet electrospinning technologies exhibit one major drawback– electrostatic mutual jet repulsion issue. In present research, we propose air blow-assisted multi-jet electrospinning system allowing production of nanofibers with yield, at least, tenfold higher than single jet electrospinning. The system produces nanofibers in two modes: multi-jet electrospinning and blow-assisted multi-jet electrospinning. In case of the latter, the application of sheath air stream allows the system to overcome the electrostatic mutual repulsion issue. These lead to the reduction of deviation of the polymer solution jets, the reduction of instabilities of the jets and the improvement of the control of the nanofibers deposition. Nanofibers morphology and size were investigated based on the scanning electron microscope micrographs. The comparison of the two modes shows changes in nanofibers morphology from beaded structure to fine nanofibers, and the slight increase in fiber mean size when the blowing assistance was applied to the process. 相似文献
138.
Guido Bertoni Joan Daemen Michaël Peeters Gilles Van Assche 《International Journal of Information Security》2014,13(4):335-353
Hash functions are usually composed of a mode of operation on top of a concrete primitive with fixed input-length and fixed output-length, such as a block cipher or a permutation. In practice, the mode is often sequential, although parallel (or tree) hashing modes are also possible. The former requires less memory, while the latter has several advantages such as its inherent parallelism and a lower cost of hash value recomputation when only a small part of the input changes. In this paper, we consider the general case of (tree or sequential) hashing modes that make use of an underlying hash function, which may in turn be sequential. We formulate a set of three simple conditions for such a (tree or sequential) hashing mode to be sound. By sound, we mean that the advantage in differentiating a hash function obtained by applying a tree hashing mode to an ideal underlying hash function from an ideal monolithic hash function is upper bounded by \(q^2/2^{n+1}\) with \(q\) the number of queries to the underlying hash function and \(n\) the length of the chaining values. We provide a proof of soundness in the indifferentiability framework. The conditions we formulate are easy to implement and to verify and can be used by the practitioner to build a tree hashing mode on top of an existing hash function. We show how to apply tree hashing modes to sequential hash functions in an optimal way, demonstrate the applicability of our conditions with two efficient and simple tree hashing modes and provide a simple method to take the union of tree hashing modes that preserves soundness. It turns out that sequential hashing modes using a compression function (i.e., a hash function with fixed input-length) can be considered as particular cases and, as a by-product, our results also apply to them. We discuss the different techniques for satisfying the three conditions, thereby shedding a new light on several published modes. 相似文献
139.
Raphael Berger Yigal Lilach Yousif Ayoub Micha Asscher 《Israel journal of chemistry》2005,45(1-2):97-109
The photochemistry of molecules constrained within a confining environment on surfaces has been studied. Orientation of methyl bromide could be controlled methyl down or up by varying the pre-adsorbed oxygen coverage due to electrostatic interactions on Ru(001) under UHV conditions. Irradiation of the coadsorption system at 193 nm has shown that the resulting photochemical activity is sensitive to the molecular orientation. Photodesorption and dissociation cross sections were 1.0·10−19 cm−2 for methyl-down and 3.0·10−19 cm−2 for the methyl-up configurations. This observation represents the first report of the steric effect in electron-molecule interaction due to the dissociative electron attachment mechanism of photochemical processes on surfaces. A second system of CO2 molecules caged within ice has also been studied. Here the trapped carbon dioxide molecules cannot leave the surface at their normal desorption temperature near 100 K, but are explosively desorbing at the onset of ice evaporation near 165 K. Upon UV irradiation, enhanced dissociation to adsorbed CO and oxygen is recorded. In addition, a new reactivity channel is observed to form H2CO, tentatively identified as formaldehyde. The relevance of photochemistry of caged molecules within ice to interstellar hydrocarbon formation as a possible route for the origin of life is discussed. 相似文献
140.
In this paper, we present two linear-size external memory data structures for approximate range searching. Our first structure,
the BAR-B-tree, stores a set of N points in ℝ
d
and can report all points inside a query range Q by accessing O(log
B
N+ε
γ
+k
ε
/B) disk blocks, where B is the disk block size, γ=1−d for convex queries and γ=−d otherwise, and k
ε
is the number of points lying within a distance of ε⋅diam (Q) to the query range Q. Our second structure, the object-BAR-B-tree, is able to store objects of arbitrary shapes of constant complexity and provides similar query guarantees. In addition,
both structures can support other types of range searching queries such as range aggregation and nearest-neighbor. Finally,
we present I/O-efficient algorithms to build these structures. 相似文献