GPU-based implementation of real-time system for spiking neural networks

Real-time simulations of biological neural networks (BNNs) provide a natural platform for applications in a variety of fields: data classification and pattern recognition, prediction and estimation, signal processing, control and robotics, prosthetics, neurological and neuroscientific modeling. BNNs possess inherently parallel architecture and operate in continuous signal domain. Spiking neural networks (SNNs) are type of BNNs with reduced signal dynamic range: communication between neurons occurs by means of time-stamped events (spikes). SNNs allow reduction of algorithmic complexity and communication data size at a price of little loss in accuracy. Simulation of SNNs using traditional sequential computer architectures results in significant time penalty. This penalty prohibits application of SNNs in real-time systems. Graphical processing units (GPUs) are cost effective devices specifically designed to exploit parallel shared memory-based floating point operations applied not only to computer graphics, but also to scientific computations. This makes them an attractive solution for SNN simulation compared to that of FPGA, ASIC and cluster message passing computing systems. Successful implementations of GPU-based SNN simulations have been already reported. The contribution of this thesis is the development of a scalable GPU-based realtime system that provides initial framework for design and application of SNNs in various domains. The system delivers an interface that establishes communication with neurons in the network as well as visualizes the outcome produced by the network. Accuracy of the simulation is emphasized due to its importance in the systems that exploit spike time dependent plasticity, classical conditioning and learning. As a result, a small network of 3840 Izhikevich neurons implemented as a hybrid system with Parker-Sochacki numerical integration method achieves real time operation on GTX260 device. An application case study of the system modeling receptor layer of retina is reviewed

High Sensitivity Magnetic Sensors Based on Off-diagonal Magnetoimpedance in Amorphous FeCoSiB Wires

The magnetoimpedance (MI) effect has a potential for the development of high performance magnetic sensors. For sensor applications, off-diagonal configuration is preferable when the MI element is excited by ac current and the output is detected from the coil. In the present work, the off-diagonal sensor design was advanced by utilising a complex waveform excitation produced by a microcontroller and applied to a multiple wire MI element. For optimised excitation with a waveform close to a positive half sine form and characteristic frequency of 8 MHz the field resolution of about 60 mV/Oe was achieved. The pulse excitation does not require an additional bias since it includes controllable low frequency components. The concept of microcontroller driven sensor element could be attractive for the development of intellectual sensors. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3358

Pd single-atom sites on the surface of PdAu nanoparticles: A DFT-based Topological search for suitable compositions

Structure of model bimetallic PdAu nanoparticles is analyzed aiming to find Pd:Au ratios optimal for existence of Pd1 single-atom surface sites inside outer Au atomic shell. The analysis is performed using density-functional theory (DFT) calculations and topological approach based on DFT-parameterized topological energy expression. The number of the surface Pd1 sites in the absence of adsorbates is calculated as a function of Pd concentration inside the particles. At low Pd contents none of the Pd atoms emerge on the surface in the lowest-energy chemical orderings. However, surface Pd1 sites become stable, when Pd content inside a Pd-Au particle reaches ca. 60%. Further Pd content increase up to almost pure Pd core is accompanied by increased concentration of surface Pd atoms, mostly as Pd1 sites, although larger Pd ensembles as dimers and linear trimers are formed as well. Analysis of the chemical orderings inside PdAu nanoparticles at different Pd contents revealed that enrichment of the subsurface shell by Pd with predominant occupation of its edge positions precedes emergence of Pd surface species

Optical Absorption and Raman Spectroscopy Study of the Fluorinated Double-Wall Carbon Nanotubes

Double-wall carbon nanotube (DWNT) samples have been fluorinated at room temperature with varied concentration of a fluorinating agent BrF3. Content of the products estimated from X-ray photoelectron data was equal to CF0.20 and CF0.29 in the case of deficit and excess of BrF3. Raman spectroscopy showed considerable decrease of carbon nanotube amount in the fluorinated samples. Analysis of optical absorption spectra measured for pristine and fluorinated DWNT samples revealed a selectivity of carbon nanotube fluorination. Nanotubes with large chiral angle are more inert to the fluorinating agent used

Effect of Bias Fields on off-Diagonal Magnetoimpedance (MI) Sensor Performance

This paper investigates the performance of off-diagonal magnetoimpedance in Co-based amorphous wire subjected to dc bias fields: circular and orthogonal (with respect to the wire axis). Typically it is as-sumed that the wire impedance is insensitive to the orthogonal field so the wire element can be used to construct 3D sensors. Our results demonstrated the possibility of large impedance change due to this field, in the range of 10 mV/Oe. The dc current in a wire generating a circular field results in improved sensitivi-ty due to elimination of the domain structure and smoothing the effect of the anisotropy deviations. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3633

Mythologization of Youth Culture in Conditions of Instability of the Social Environme

В статье рассмотрена совокупность причин, формирующих основу популярности скандинавской культуры среди гражданской и военной молодежи. Автором представлены результаты контент-анализа, позволяющего оценить базовые механизмы, направленные на привлечение целевой аудитории.The article discusses a set of reasons that form the basis of the popularity of Scandinavian culture among civilian and military youth. The author presents the results of content analysis, which makes it possible to evaluate the basic mechanisms aimed at attracting the target audience

Thermal Behavior of Fluorinated Double-Walled Carbon Nanotubes

Double-walled carbon nanotubes (DWNTs), produced by a catalytic chemical vapor deposition method, have been fluorinated using a volatile mixture of BrF3 and Br2. Optical absorption spectroscopic study on the product detected nonfluorinated nanotubes, which could correspond to the inner walls of DWNTs. The fluorinated DWNTs have been annealed in vacuum at fixed temperatures, and X-ray photoelectron spectroscopy showed almost no fluorine in the sample heated to 300 °C. Comparison between X-ray fluorescent C KR spectra of the pristine DWNT sample and the annealed fluorinated sample revealed change of the atomic structure of graphitic shells in the process of thermal defluorination

Magneto-Ellipsometry Investigations of Multilayer Nanofilms of Fe and Co

Spectral ellipsometry technique is demonstrated to be a useful tool for the investigation of optical and magneto-optical parameters of magnetic heterostructures. Ellipsometry parameters ψ, Δ were measured in the range of 350-1000 nm. Solving the inverse problem by a regression method the refractive index and thickness of the layers were deduced. Magneto-optical spectra were detected in the configuration of equatorial Kerr effect which is fully compatible with the ellipsometry measurements. Spectroscopic ellipsometry method of magnetic structure characterisation can be used for in situ monitoring of magnetic film growth in various processes such as magnetron sputtering, electron beam evaporation and ion beam sputtering. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3357

Electron-electron interaction in multiwall carbon nanotubes

Magnetic susceptibility $\chi$ of pristine and brominated arc-produced sample of multiwall carbon nanotubes was measured from 4.2 to 400 K. An additional contribution $\Delta \chi(T)$ to diamagnetic susceptibility $\chi(T)$ of carbon nanotubes was found at T $<$ 50 K for both samples. It is shown that $\Delta \chi(T)$ are dominated by quantum correction to $\chi$ for interaction electrons (interaction effects-IE). The IE shows a crossover from two-dimensional to three-dimensional at $B$ = 5.5 T. The effective interaction between electrons for interior layers of nanotubes are repulsion and the electron-electron interaction $\lambda$$_c$ was estimated to be $\lambda_c\sim$ 0.26.Comment: 10 pages, 7 figure