1,721,116 research outputs found
Single Event Upset Characterisation of NOEL-V soft processor: Draft version
No full textThis thesis evaluates the susceptibility to high energy proton irradiation of the NOEL-V soft processor (SP), a promising and highly modular soft processor by Cobham Gaisler. In order to characterise the performance of the NOEL-V SP in the harsh space radiation environment, the KCU105 development board is used as Device Under Test (DUT).User logic upsets and configuration SRAM upsets are extracted and compared for multiple configurations of the processor. Although the higher performance configurations utilise more resources of the FPGA, this has not necessarily proven to also cause a higher susceptibility. The biggest influence on user logic upsets is observed to be the use of an operating system. Marginal decrease in susceptibility is found when employing the floating point unit of the processor, also an influence of the L2Cache is shown.Findings indicate that the NOEL-V processor, with the implementation of targeted fault tolerant measures, can be a viable choice for space missions. Due to its modularity, the processor can be used for a multitude of mission types ranging from high performance general purpose to low end microcontroller applications.Aerospace Engineerin
Extending the NOEL-V Platform with a RISC-V Vector Processor for Space Applications
No full textThis paper describes the work carried out to extend the NOEL-V platform to include data-level parallelism (DLP) by implementing an integer subset of the RISC-V Vector Extension. The performance and resource utilization efficiency of the resulting vector processor for different levels of DLP (i.e., number of lanes) have been compared to the baseline scalar processor on a Xilinx Kintex Ultrascale field-programmable gate array, employing typical kernels for compute-intensive applications. The role of the memory subsystem has also been investigated, comparing the results obtained with a low-latency and a high-latency main memory. The results show that the speed-up due to the use of the vector pipeline increases with the number of lanes in the vector processor, achieving up to 23.0× the performance of the scalar processor with only 4.3× the resources of the baseline scalar processor. Using an implementation with 32 lanes increases performance even for problem sizes larger than the number of lanes, achieving up to more than 11.7× the performance of the scalar processor with just 1.9× its resource utilization for 128 × 128 matrix multiplications. This work proves that implementations of the selected subset are easily scalable and fit for small-processor implementations in highly constrained space embedded systems.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Space Systems Egineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Global representation and multiscale expansion for the Dirichlet problem in a domain with a small hole close to the boundary
Full text linkFor each pair (Formula presented.) of positive parameters, we define a perforated domain (Formula presented.) by making a small hole of size (Formula presented.) in an open regular subset (Formula presented.) of (Formula presented.) ((Formula presented.)). The hole is situated at distance (Formula presented.) from the outer boundary (Formula presented.) of the domain. Thus, when (Formula presented.) both the size of the hole and its distance from (Formula presented.) tend to zero, but the size shrinks faster than the distance. Next, we consider a Dirichlet problem for the Laplace equation in the perforated domain (Formula presented.) and we denote its solution by (Formula presented.) Our aim is to represent the map that takes (Formula presented.) to (Formula presented.) in terms of real analytic functions of (Formula presented.) defined in a neighborhood of (0, 0). In contrast with previous results valid only for restrictions of (Formula presented.) to suitable subsets of (Formula presented.) we prove a global representation formula that holds on the whole of (Formula presented.) Such a formula allows us to rigorously justify multiscale expansions, which we subsequently construct
SafeLS: Toward Building a Lockstep NOEL-V Core
Full text linkSafety-critical systems such as those in automotive, avionics and space,
require appropriate safety measures to avoid silent data corruption upon random
hardware errors such as those caused by radiation and other types of
electromagnetic interference. Those safety measures must be able to prevent
faults from causing the so-called common cause failures (CCFs), which occur
when a fault produces identical errors in redundant elements so that comparison
fails to detect the errors and a failure arises. The usual solution to avoid
CCFs in CPU cores is using lockstep cores, so that two cores execute the same
flow of instructions, but with some time staggering so that their state is
never identical and faults can only lead to different errors, which are then
detectable by means of comparison. This paper extends Gaisler's RISC-V NOEL-V
core with lockstep; and presents future prospects for its use and distribution.Comment: Abstract presented at the RISC-V Summit, June 2023, Barcelona (Spain
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