186,183 research outputs found
Sublinear-Time Probabilistic Cellular Automata
No full textWe propose and investigate a probabilistic model of sublinear-time
one-dimensional cellular automata. In particular, we modify the model of ACA
(which are cellular automata that accept if and only if all cells
simultaneously accept) so that every cell changes its state not only dependent
on the states it sees in its neighborhood but also on an unbiased coin toss of
its own. The resulting model is dubbed probabilistic ACA (PACA). We consider
one- and two-sided error versions of the model (in the same spirit as the
classes and ) and establish a separation between
the classes of languages they can recognize all the way up to
time. As a consequence, we have a lower bound for
derandomizing constant-time two-sided error PACAs (using deterministic ACAs).
We also prove that derandomization of -time PACAs (to polynomial-time
deterministic cellular automata) for various regimes of
implies non-trivial derandomization results for the class (e.g.,
). The main contribution is an almost full
characterization of the constant-time PACA classes: For one-sided error, the
class equals that of the deterministic model; that is, constant-time one-sided
error PACAs can be fully derandomized with only a constant multiplicative
overhead in time complexity. As for two-sided error, we identify a natural
class we call the linearly testable languages () and prove that
the languages decidable by constant-time two-sided error PACAs are "sandwiched"
in-between the closure of under union and intersection and the
class of locally threshold testable languages ().Comment: 27 pages, 4 figures. Appeared in STACS 2023 (corrected typo in
abstract
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
No full textWe 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
Dr. Edward P. Wimberly, ITC, July 2011
No full textThis video is a conversation with Dr. Edward P. Wimberly. Dr. Wimberly talks about his book, "No Shame in Wesley's Gospel: A Twenty-First Century Pastoral Gospel". Brad Ost, AUC Woodruff Library, is the interviewer
Impact of compensation on solar grade silicon for photovoltaics
No full textThe steep increase in the market price for silicon feedstock for solar cells experienced at the beginning of the last decade, coupled with a developing industry, opened the possibility for materials produced from different sources and delivered at lower production cost. Compensated solar grade silicon for solar cell provided these opportunities. The motivation behind the present work was, therefore, to study the effect of such a material on the bulk and cell properties, in respect to the commonly used feedstock produced via the Siemens process. The materials presented in this work were produced at Elkem Solar AS, who has provided materials with decreasing dopant concentration over the project time.
The main focus was to investigate the manner in which materials cast from compensated solar grade feedstock behave compared to materials cast from reference electronic grade feedstock. Different properties were measured, both in the bulk and on solar cells. Resistivity was observed to increase along the growth direction due to the different segregation profiles of the main doping species, i.e. boron and phosphorus. Dissolved oxygen concentration was observed not to depend on feedstock, whereas higher dissolved carbon concentration was measured in the compensated materials. Minority carrier lifetime is reduced, although the performance of the materials after solar cell processing is comparable to the electronic grade reference materials. Majority carrier mobility is strongly reduced at temperatures below 150K, whereas the reduction at high temperatures (above 250 K) is much lower.
The possibility to use international standards to convert the measured resistivity in net doping density for compensated materials was investigated. The aim was to provide an easy and direct method to assess these materials. Through the comparison of the net doping density calculated from the measured resistivity and the net doping density measured by glow discharge mass spectrometry, the accuracy of the standard was evaluated for the compensated materials.
Silicon nitride crucibles are an alternative to the widely used silica crucibles for directional solidification of mc-Si ingots. Their main advantages are reusability for repeated castings and the opportunity to eliminate the crucible as a source of oxygen contamination of the ingot. In this work, several ingots cast in such crucibles were studied and compared to ingots cast in silica crucibles. Advantages and limitations related to the use of such crucibles are discussed, with focus on the required changes to the solidification process.
Chromium is an impurity known to be detrimental for the material quality of silicon for solar cells. Its effect is of particular interest for less pure materials such as those studied in this work, where the concentration of Cr can be expected to be greater than in electronic grade materials. The impact of Cr on the properties of the compensated solar grade silicon materials was studied through the comparison of ingots with and without deliberate chromium doping. It was found that, although minority carrier lifetime is significantly impaired by the addition, a strong improvement occurred through adequate solar cell processing, which included a phosphorus diffusion step.PhD i materialteknologiPhD in Materials Science and Engineerin
Author Rights and Scholarly Publishing
No full textOriginally posted at
http://blog.library.gsu.edu/2014/10/24/author-rights-and-scholarly-publishing/</p
Mapping the Discipline of the Olympic Games An Author-Cocitation Analysis
No full textThe authors conducted an author cocitation analysis on prominent authors writing about the Olympics during the 1990s. Author cocitation is an established bibliometric technique that can be used to measure the relative similarities of topics written about by the cited authors. This enables a visual representation of the “intellectual space” of the discipline, in this case the Olympics, to be created for the period under review. So core and peripheral research areas are identified, along with their major contributors. The representation appears as a two-dimensional cluster-enhanced map. Subject expertise was then applied to the results to place labels on the generated clusters of authors and their topics
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