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| 2. |
- Bruederle, Daniel, et al.
(författare)
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A comprehensive workflow for general-purpose neural modeling with highly configurable neuromorphic hardware systems
- 2011
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Ingår i: Biological Cybernetics. - : Springer Science and Business Media LLC. - 0340-1200 .- 1432-0770. ; 104:4-5, s. 263-296
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we present a methodological framework that meets novel requirements emerging from upcoming types of accelerated and highly configurable neuromorphic hardware systems. We describe in detail a device with 45 million programmable and dynamic synapses that is currently under development, and we sketch the conceptual challenges that arise from taking this platform into operation. More specifically, we aim at the establishment of this neuromorphic system as a flexible and neuroscientifically valuable modeling tool that can be used by non-hardware experts. We consider various functional aspects to be crucial for this purpose, and we introduce a consistent workflow with detailed descriptions of all involved modules that implement the suggested steps: The integration of the hardware interface into the simulator-independent model description language PyNN; a fully automated translation between the PyNN domain and appropriate hardware configurations; an executable specification of the future neuromorphic system that can be seamlessly integrated into this biology-to-hardware mapping process as a test bench for all software layers and possible hardware design modifications; an evaluation scheme that deploys models from a dedicated benchmark library, compares the results generated by virtual or prototype hardware devices with reference software simulations and analyzes the differences. The integration of these components into one hardware-software workflow provides an ecosystem for ongoing preparative studies that support the hardware design process and represents the basis for the maturity of the model-to-hardware mapping software. The functionality and flexibility of the latter is proven with a variety of experimental results.
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| 3. |
- Wendt, M., et al.
(författare)
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Localization of the High Frequency Field in a Beam-Plasma Diode Due to Density Gradients
- 2001
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Ingår i: Physica Scripta. - 0281-1847. ; 63, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study of the high frequency (hf) interaction of a strong, warm electron beam with an inhomogeneous, bounded plasma is presented and compared with particle-in-cell simulations. The density is highest in the center of the diode and decreases towards the boundaries. The electric field in the center is dominated by the unstable slow-space-charge wave, but experimental evidence is found, that reflected waves are present near the beam injection grid, where the oscillation frequency f is higher than the local plasma frequency f(pe)(x). The strong field at the resonance point (f = f(pe)(x)) is proposed to excite the unstable beam mode. Simulations confirm this picture by showing a concentration of the spectral power of the beam waves to the frequencies of the trapped Langmuir waves. Linear growth and Landau damping concentrate the beam wave to a 1.5-2 wavelengths wide region. Trapped Langmuir waves can accordingly determine the frequencies and position of the hf-field even for moderate density gradients and field strengths below the threshold for Langmuir collapse.
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