1,720,962 research outputs found
Nanocrystal Memories: An Evolutionary Approach to Flash Memory Scaling and a Class of Radiation-Tolerant Devices
No full textThe Flash memory was conceived as an improvement of the EPROM (Erasable Programmable Read Only Memory) concept invented in 1980s from an initial idea of Frohman-Bentchkowsky [1]. The EPROM memory electrically programmed and erased by ultraviolet (UV) - irradiation became the most important non-volatile memory (NVM) application in the 1980s. The Flash, which owes its name to the fact that the whole memory array can be erased quickly in the same time, introduced the advantages of the electrical erase and the possibility to reprogram the read only memory in situ, with no need of removing it from the system [2,3].
Over the years Flash memory has widely been accepted as the NVM of choice for many applications and today the large majority of NVMs is based on Flash technology. The Flash market has grown in a very fast way due to the large diffusion of portable and low power consumption multi-media applications, which requires an extensive use of NVMs. The continuous scaling of nonvolatile memories has pushed the Flash technology toward its limits [4]. Now, several constraints, mainly due to electrical and reliability reasons, are threatening the future scaling of the Flash technology and new concepts of non-volatile memories have been proposed.
NVMs based on natural traps in dielectrics (such as SONOS) or on floating nanocrystals (NCs), artificially embedded in dielectrics, offer an interesting scaling alternative to the Flash with the conventional floating gate, because of several potential advantages associated with the discrete nature of the storage [5-7]. These memories are an evolution of the Flash concept where the monolithic floating gate is supplanted by a number of discrete charge trapping nodes. Because in these discrete storage nodes devices charges are immune to the leakage caused by localized oxide defects, they can allow for a very aggressive scaling of the tunnel oxide and hence of the cell area, by keeping good performance and reliability characteristics.
Today, nanocrystal and SONOS memories have found an important field of application in embedded systems where the non-volatile memory is hosted into a logic system. The high interest toward embedded applications is mainly driven by the easiness of process, due to the fact that a very thin storage layer can be implemented in place of the thick poly-silicon floating gate as well as to the possibility of using lower voltages. Some semiconductor companies have announced that they have started production of embedded memories based on nanocrystals. Nanocrystals memory has also shown a higher endurance to high temperature than its counterpart SONOS. Recently the NC memories have shown a promising route toward radiation tolerant application. Actually, as information is stored in discrete centers, they are expected to exhibit a higher tolerance to radiation effects such as total ionizing dose effects (TID) and single event effects (SEE).
In the first part of this chapter we will present an overview of the nanocrystal memory technology as candidate to be an alternative to conventional Flash NVMs, by showing a comparison with the mainstream technology. The discussion will be focused on the scalability of the device and on its performances and reliability. In the second part of the chapter we will address the application of NC memories as radiation tolerant devices, such as in military applications, nuclear power stations, nuclear waste disposal sites, high-altitude avionics, medical and space applications. In particular, we will compare NC memories characteristics with the ones of Flash memories
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Investigation of Proton and X-Ray Irradiation Effects on Nanocrystal and Floating Gate Memory Cell Arrays
No full textWe compared the radiation tolerance of nanocrystal and floating gate memories, fabricated with the same technology. We investigated the effects of 5-MeV proton and 10-keV X-Ray irradiations, focusing on the charge loss, the permanent degradation of the electrical characteristics, and the data retention. We also presented a first order model of the charge loss and the permanent threshold voltage shift. The model and the experimental results show that nanocrystal memories feature improved radiation robustness against total ionizing dose. Nanocrystal memories can withstand a radiation dose 3 and 10 times larger than floating gate memories, in terms of charge loss and data retention, respectivel
Readout drain current dependence of programming window in nanocrystal memory cells
No full textThe different behaviour of nanocrystal memory cells in linear and subthreshold region was studied. It was found that the programming window reduces with increasing readout drain current. This peculiar behaviour derives from the presence of the discrete nanodots and it has not been observed in conventional floating gate memories
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