44 research outputs found
Reservoir Computing Approach to Robust Computation using Unreliable Nanoscale Networks
As we approach the physical limits of CMOS technology, advances in materials
science and nanotechnology are making available a variety of unconventional
computing substrates that can potentially replace top-down-designed
silicon-based computing devices. Inherent stochasticity in the fabrication
process and nanometer scale of these substrates inevitably lead to design
variations, defects, faults, and noise in the resulting devices. A key
challenge is how to harness such devices to perform robust computation. We
propose reservoir computing as a solution. In reservoir computing, computation
takes place by translating the dynamics of an excited medium, called a
reservoir, into a desired output. This approach eliminates the need for
external control and redundancy, and the programming is done using a
closed-form regression problem on the output, which also allows concurrent
programming using a single device. Using a theoretical model, we show that both
regular and irregular reservoirs are intrinsically robust to structural noise
as they perform computation
Time of flight measurements based on FPGA using a breast dedicated PET
In this work the implementation of a Time-to-Digital Converter (TDC) using a Nutt
delay line FPGA-based and applied on a Positron Emission Tomography (PET) device is going
to be presented in order to check the system’s suitability for Time of Flight (TOF) measurements.
In recent years, FPGAs have shown great advantages for precise time measurements in PET. The
architecture employed for these measurements is described in detail. The system developed was
tested on a dedicated breast PET prototype, composed of LYSO crystals and Positive Sensitive
Photomultipliers (PSPMTs). Two distinct experiments were carried out for this purpose. In the
first test, system linearity was evaluated in order to calibrate the time measurements, providing a
linearity error of less than 2% and an average time resolution of 1.4 ns FWHM. The second set
of measurements tested system resolution, resulting in a FWHM as good as 1.35 ns. The results
suggest that the coincidence window for the current PET can be reduced in order to minimize the
random events and thus, achieve better image qualityAguilar, A.; GarcĂa Olcina, R.; Martos, J.; Soret, J.; Torres-Pais, J.; Benlloch Baviera, JM.; González MartĂnez, AJ.... (2014). Time of flight measurements based on FPGA using a breast dedicated PET. Journal of Instrumentation. 9:0-8. doi:10.1088/1748-0221/9/05/C05012S08
A Reconfigurable Fabric for Accelerating Large-Scale Datacenter Services
Datacenter workloads demand high computational capabilities, flexibility, power efficiency, and low cost. It is challenging to improve all of these factors simultaneously. To advance datacenter capabilities beyond what commodity server designs can provide, we designed and built a composable, reconfigurable hardware fabric based on field programmable gate arrays (FPGA). Each server in the fabric contains one FPGA, and all FPGAs within a 48-server rack are interconnected over a low-latency, high-bandwidth network. We describe a medium-scale deployment of this fabric on a bed of 1632 servers, and measure its effectiveness in accelerating the ranking component of the Bing web search engine. We describe the requirements and architecture of the system, detail the critical engineering challenges and solutions needed to make the system robust in the presence of failures, and measure the performance, power, and resilience of the system. Under high load, the large-scale reconfigurable fabric improves the ranking throughput of each server by 95% at a desirable latency distribution or reduces tail latency by 29% at a fixed throughput. In other words, the reconfigurable fabric enables the same throughput using only half the number of servers
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Accurate determination of pair potentials for a C{sub w}H{sub x}N{sub y}O{sub z} system of molecules: A semiempirical method
Statistical mechanical chemical equilibrium calculations of the properties of high-pressure high-temperature reactive C,H,N,O mixtures are made to derive an accurate self-consistent set of inter-molecular potentials for the product molecules. Previous theoretical efforts to predict such properties relied in part on Corresponding States theory and shock wave data of argon. More recent high-pressure Hugoniot measurements on a number of elements and molecules allow more accurate determination of the potentials of these materials, and explicit inclusion of additional dissociation products. The present discussion briefly reviews the previous analysis and the method used to produce a self-consistent set of potentials from shock data on N{sub 2}, O{sub 2}, H{sub 2}, NO, an N{sub 2} + O{sub 2} mixture, carbon, CO{sub 2}, and CO, as well as some simple explosive product mixtures from detonation of hexanitrobenzene, PETN, and a mixture of hydrazine nitrate, hydrazine and water. The results are tested using the data from an HMX explosive formulations. The effect of the non-equilibrium nature of carbon clusters is estimated using data for TNT as a standard to determine a nonequilibrium equation of state for carbon. The resulting parameter set is used in a survey of 27 explosives. For the subset that contains no fluorine or two-phase carbon effects the rms deviation from experimental detonation velocity is 1.2%