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1.
Capacity-achieving sequences for the erasure channel 总被引:6,自引:0,他引:6
Oswald P. Shokrollahi A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(12):3017-3028
This paper starts a systematic study of capacity-achieving (c.a.) sequences of low-density parity-check codes for the erasure channel. We introduce a class A of analytic functions and develop a procedure to obtain degree distributions for the codes. We show various properties of this class which help us to construct new distributions from old ones. We then study certain types of capacity-achieving sequences and introduce new measures for their optimality. For instance, it turns out that the right-regular sequence is c.a. in a much stronger sense than, e.g., the Tornado sequence. This also explains why numerical optimization techniques tend to favor graphs with only one degree of check nodes. 相似文献
2.
A new and simple method of finite-element grid improvement is presented. The objective is to improve the accuracy of the analysis. The procedure is based on a minimization of the trace of the stiffness matrix. For a broad class of problems this minimization is seen to be equivalent to minimizing the potential energy. The method is illustrated with the classical tapered bar problem examined earlier by Prager and Masur. Identical results are obtained. 相似文献
3.
4.
The Mössbauer effect measurements of as-ball-milled mechanically alloyed Fe?Zn intermediate phases of Γ (Fe3Zn10) and Γ1 (Fe5Zn21) compositions exhibit characteristic spectra consisting of triplets. Each is characterized with an Fe site with unusually large quadrupole splittings measuring 0.940 mm/s in the cubic Fe?Zn phases and, in addition, three other doublets. In the aged state, both compositions show spectra free of the Fe site with quadrupole splitting of 0.940 mm/s, designated as MSΓFe1 and MSΓ 1Fe1, respectively. This suggests that the metastable states are similar, while their separate transformation paths to stable equilibrium lead to distinct crystal structures. The parameters for the aged states are compared with those reported in the literature for both phases. 相似文献
5.
Dieter Oswald 《真空研究与实践》1996,8(2):88-91
All vacuumpummps which use a liquid as a sealing-agent have to take care of their specific demands. In this paper liquid-ring-vacuum-pumps will be short mentioned, because the user is familiar with this pumps and alternative fluids. Using other fluids in other mecanical vacuumpumps are not in operation in the field of the various applications frequently. You will find some ideas for using other fluids which are possibly used in rotary-vane vacuum-pumps to find more consideration in the future. 相似文献
6.
This article focuses on power analysis attacks because they have received by far the most attention in recent years. They are powerful and can be executed relatively easily. This article provides an introduction to these attacks and discusses countermeasures against them. In particular, we focus on countermeasures that can be implemented at the cell level. This article presents an overview of power analysis attacks, which are based on the measurement of the power consumed by cryptographic ICs, and countermeasures against them. 相似文献
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8.
There exist many ideas and assumptions about the development and meaning of modularity in biological and technical neural systems. We empirically study the evolution of connectionist models in the context of modular problems. For this purpose, we define quantitative measures for the degree of modularity and monitor them during evolutionary processes under different constraints. It turns out that the modularity of the problem is reflected by the architecture of adapted systems, although learning can counterbalance some imperfection of the architecture. The demand for fast learning systems increases the selective pressure towards modularity. 相似文献
9.
Marion Oswald 《Artificial Life and Robotics》2009,13(2):390-393
We briefly discuss variants of (extended) spiking neural P systems that combine features from the areas of membrane computing
and spiking neurons.
This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January
31–February 2, 2008 相似文献
10.
S. Kúdela V. Gergely A. Schweighofer S. Baunack S. Oswald K. Wetzig 《Journal of Materials Science》1994,29(19):5071-5077
The chemical and phase transformations of -Al2O3 (Saffil) fibres during their infiltration with Mg-8 wt% Li were studied by scanning and transmission electron microscopy, Auger electron spectroscopy, secondary ion mass spectrometry and X-ray diffraction methods. The infiltration experiments were carried out in autoclave under argon pressure at temperatures of 883–908 K and contact times of 4–30 s as well as at 918 K/420 s. During the course of infiltration, lithium penetrates the Saffil fibres and this process is accompanied by the gradual transformation of the tetragonal -Al2O3 lattice towards the cubic spinel LiAl5O8 compound, where part of the Li+ ions is probably substituted by Mg2+ No remarkable interfacial zone at the fibre/matrix interface was observed; however, the Saffil fibres became brittle which had been manifested by the occurrence of fragmentation on the metallographically treated fibre cross-sections. The tensile strength (maximum 220 MPa) of the corresponding metal matrix composite clearly decreased with increased infiltration time. 相似文献