130,524 research outputs found
Post-synthetic Isotopic Labeling of an Azamacrocyclic Ligand
No full textA simple post-synthetic method for the preparation of 1,4,7-triazacyclononane-d(12) (90% atom D) is reported. The macrocycle is first converted into 1,4,7-trinitroso-1,4,7-triazacyclononane, whose solid-state and solution properties are herein described. In CD3OD/D2O solution, the trinitroso derivative undergoes fast base-catalyzed H,D exchange on the whole set of methylene hydrogens and can be subsequently denitrosated by reduction with Ni/Al alloy
BEGA Starter/Alternator - Vector Control Implementation and Performance for Wide Speed Range at Unity Power Factor Operation
No full textBiaxial Excitation Generator for Automobile (BEGA) is proposed as a solution for integrated starter/alternator systems used in hybrid electric vehicles (HEVs). This paper demonstrates through experiments and simulations that BEGA has a very large constant power speed range (CPSR), theoretically to infinite. A vector control structure is proposed for BEGA operation during motoring and generating, at unity power factor with zero d-axis current (id) and zero q-axis flux (Ψq) control. In such conditions BEGA behaves like a truly dc. brush machine (with zero reactance in steady state !). A high iq current is required in order to cancel the q-axis flux, during unity power factor operation. This engages higher copper losses in the machine. In order to minimize the copper losses, for lower load levels, a current referencer is proposed. Due to higher dc field excitation time constant, the dc field current response is not very fast, especially for high current excursion. In order to increase the torque response quickness, the daxis current id is controlled with non-zero reference value only during transients, when there is a difference between the reference and measured dc field current. This way high dynamic performance is secured. Implementation and extensive experiments validate the proposed solutions.Biaxial Excitation Generator for Automobile (BEGA) is proposed as a solution for integrated starter/alternator systems used in hybrid electric vehicles (HEVs). This paper demonstrates through experiments and simulations that BEGA has a very large constant power speed range (CPSR), theoretically to infinite. A vector control structure is proposed for BEGA operation during motoring and generating, at unity power factor with zero d-axis current (id) and zero q-axis flux (Ψq) control. In such conditions BEGA behaves like a truly dc. brush machine (with zero reactance in steady state !). A high iq current is required in order to cancel the q-axis flux, during unity power factor operation. This engages higher copper losses in the machine. In order to minimize the copper losses, for lower load levels, a current referencer is proposed. Due to higher dc field excitation time constant, the dc field current response is not very fast, especially for high current excursion. In order to increase the torque response quickness, the daxis current id is controlled with non-zero reference value only during transients, when there is a difference between the reference and measured dc field current. This way high dynamic performance is secured. Implementation and extensive experiments validate the proposed solutions
BEGA Starter/Alternator—Vector Control Implementation and Performance for Wide Speed Range at Unity Power Factor Operation
No full textThe Biaxial Excitation Generator for Automobiles (BEGA) is proposed as a solution for integrated starter/alternator systems used in hybrid electric vehicles. This paper demonstrates through experiments and simulations that BEGA has a very large constant power speed range. A vector control structure is proposed for BEGA operation during motoring and generating, at unity power factor with zero d-axis current (id) and zero q-axis flux (Ψq) control. In such conditions, BEGA behaves like a separately excited dc brush(commutator) machine, in the sense that no stator inductance voltage drop occurs in such constraint control conditions. A high iq current is required in order to cancel the q-axis flux, during unity power factor operation. This engages higher copper losses in the machine under light load. In order to minimize the copper losses, for lower load levels, a current referencer is proposed. Due to higher dc field excitation time constant, the dc field current response is not very fast, particularly for high-current excursion. In order to increase the torque response quickness, the d-axis current id is controlled with a nonzero reference value only during transients, when there is a difference between the reference and measured dc field currents. This way, high dynamic performance is secured. Implementation, digital simulation, and experimental results validate the proposed solutions
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
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
The Tilghman around Australia party on return from the Oodnadatta to Darwin expedition, Bega, New South Wales, 1927 [picture].
No full textPart of: Tilghman collection of photographs.; Title devised by cataloguer based on acquisitions documentation.; Inscription: "Mo85 The return home. Bega 1927"--In ink on negative sleeve.; This is a copy made by the National Library of Australia from an original in private ownership.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-vn4769264
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
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