Search results for " processing"
showing 10 items of 7549 documents
More restrictive Gray codes for some classes of pattern avoiding permutations
2009
In a recent article [W.M.B. Dukes, M.F. Flanagan, T. Mansour, V. Vajnovszki, Combinatorial Gray codes for classes of pattern avoiding permutations, Theoret. Comput. Sci. 396 (2008) 35-49], Dukes, Flanagan, Mansour and Vajnovszki present Gray codes for several families of pattern avoiding permutations. In their Gray codes two consecutive objects differ in at most four or five positions, which is not optimal. In this paper, we present a unified construction in order to refine their results (or to find other Gray codes). In particular, we obtain more restrictive Gray codes for the two Wilf classes of Catalan permutations of length n; two consecutive objects differ in at most two or three posit…
Multi-frequency orthogonality sampling for inverse obstacle scattering problems
2011
We discuss a simple non-iterative method to reconstruct the support of a collection of obstacles from the measurements of far-field patterns of acoustic or electromagnetic waves corresponding to plane-wave incident fields with one or few incident directions at several frequencies. The method is a variant of the orthogonality sampling algorithm recently studied by Potthast (2010 Inverse Problems 26 074015). Our theoretical analysis of the algorithm relies on an asymptotic expansion of the far-field pattern of the scattered field as the size of the scatterers tends to zero with respect to the wavelength of the incident field that holds not only at a single frequency, but also across appropria…
Crystal field calculations of energy levels of the Ni2+ ions in MgO
2013
Abstract The electronic energy levels of six-fold coordinated Ni 2+ ion in magnesium oxide MgO were calculated using the exchange charge model of crystal field theory. The calculated energetic positions of the Ni 2+ levels match well the experimental spectrum. Inclusion of the spin-orbit (SO) interaction is compulsory to account for the first excited 3 T 2g state fine structure; however, it does not explain why out of four levels arising from the 3 T 2g state, only two are seen in the experimental spectra. One possible explanation to this fact can be advanced by invoking the Jahn–Teller effect.
Valorisation de machines frigorifiques a adsorption sur zeolithes
1991
Abstract The regeneration stage using intermittent thermodynamical cycles based on zeolite adsorption (zeolite 13X-H2O) has been studied. This point is of particular interest for understanding of systems of energy storage and cooling. This paper examines the use of microwave energy sources for analysing the regeneration problem. The method proposed allows a considerable decrease in the regeneration time without an increase of the temperature of the material. The energy yields are high and the adsorption-desorption time cycles are short if the microwave field is well tuned. This last is a function of time and of the filling coefficient. The results obtained using microwave irradiation are co…
Testing the X-IFU calibration requirements: an example for quantum efficiency and energy resolution
2018
With its array of 3840 Transition Edge Sensors (TESs) operated at 90 mK, the X-Ray Integral Field Unit (X-IFU) on board the ESA L2 mission Athena will provide spatially resolved high-resolution spectroscopy (2.5 eV FWHM up to 7 keV) over the 0.2 to 12 keV bandpass. The in-flight performance of the X-IFU will be strongly affected by the calibration of the instrument. Uncertainties in the knowledge of the overall system, from the filter transmission to the energy scale, may introduce systematic errors in the data, which could potentially compromise science objectives - notably those involving line characterisation e.g. turbulence velocity measurements - if not properly accounted for. Defining…
The performance of the ATHENA X-ray Integral Field Unit
2018
The X-ray Integral Field Unit (X-IFU) is a next generation microcalorimeter planned for launch onboard the Athena observatory. Operating a matrix of 3840 superconducting Transition Edge Sensors at 90 mK, it will provide unprecedented spectro-imaging capabilities (2.5 eV resolution, for a field of view of 5') in the soft X-ray band (0.2 up to 12 keV), enabling breakthrough science. The definition of the instrument evolved along the phase A study and we present here an overview of its predicted performances and their modeling, illustrating how the design of the X-IFU meets its top-level scientific requirements. This article notably covers the energy resolution, count-rate capability, quantum …
Ultimate field-free molecular alignment by combined adiabatic-impulsive field design
2008
We show that a laser pulse designed as an adiabatic ramp followed by a kick allows one to reach a perfect postpulse molecular alignment, free of saturation. The mechanism is based on an optimized distribution of the energy between a weakly efficient but non saturating adiabatic ramp and an efficient but saturating impulsive field. Unprecedent degrees of alignment are predicted using state-of-the-art pulse shaping techniques and non-destructive field intensities. The scheme can be extended to reach high degrees of orientation of polar molecules using designed half-cycle pulses.
GekkoFS - A Temporary Distributed File System for HPC Applications
2018
We present GekkoFS, a temporary, highly-scalable burst buffer file system which has been specifically optimized for new access patterns of data-intensive High-Performance Computing (HPC) applications. The file system provides relaxed POSIX semantics, only offering features which are actually required by most (not all) applications. It is able to provide scalable I/O performance and reaches millions of metadata operations already for a small number of nodes, significantly outperforming the capabilities of general-purpose parallel file systems. The work has been funded by the German Research Foundation (DFG) through the ADA-FS project as part of the Priority Programme 1648. It is also support…
Kriterien für die Auswahl von Elektronischen Rechenanlagen für Biomedizinische Forschungsinstitute
1979
Computers are now a recognized tool in biomedical research. They are used for the evaluation of data on one hand and on the other hand for data acquisition and control of experiments. Based on our experience, some suggestions concerning the structure of a mini-computer system suitable for a research laboratory are made. According to the two major classes of application, two sets or requirements arise. We argue that it is effective to use this system for data reduction and evaluation because a large percentage of tasks require program development or at least specific input data handling. Therefore, we call for a multi-user time-sharing system which should be equipped with a set of commands t…
Subband image coding using filter banks with non-uniform passband distribution
2002
Subband filter banks with non-uniform passband distribution in frequency domain are studied. Several design examples are presented and compared with conventional uniform bandwidth filter banks. Image coding results show that filter banks with non-uniform bandwidth outperform filter banks with uniform bandwidth, especially in low bit rate coding.