177,538 research outputs found
Curved Track Analysis of FSO Link for Ground-to-Train Communications
No full textIn this work, a free space optical (FSO) link for the ground-to-train (G2T-FSO) communications is proposed. Analytical analysis is carried out for the curved rail tracks. We show that the transmitter divergence angle, the transmit power and the size of the concentration lens need to increase for the curved section of the rail track compared to the straight track. We derive the analytical expression for the received power level based on the link geometry for the case of the curved track In the worst case scenario when the curvature radius is 120 m, the transmit power at the optical base station (BS) needs to increase by over 2 dB when the concentration lens radius is increased by 5 times. Analyses also show that the received power along the track increases with the curvature radius for the same transmit power and receiver optics illustrating the effect due to link geometry. Additionally, the signal-to-noise ratio (SNR) and the bit error rate (BER) performance of the system for the curved track with different curvature radii is analysed at data rates of 10 Mbps and 100 Mbps for an additive white Gaussian noise (AWGN) channel showing a good agreement between the theoretical and the simulated BER. Finally, effect of scintillations on the G2T-FSO link performance is discussed
High-energy diode-pumped picosecond multi-pass Nd:GdVO<sub>4</sub> laser source for nonlinear optical spectroscopy
No full textIn this report, we demonstrate a simple laser source which is compact
and has a broad tunability necessary for CARS spectroscopy/microscopy
applications. The source is based on the Nd:GdVO4
high energy (up to 0.5 µJ per pulse) picosecond laser, from which a
bright spectral continuum can be generated in a specially selected
highly-doped GeO2
fiber. The pump power is from 30-W fiber-coupled laser diode array (LIMO) with the emission wavelength at 808.5 nm
Βιβλιοκρισία του: EIRINI AFENTOULIDOU-LEITGEB, Die Hymnen des Theoktistos Studites auf Athanasios I. von Konstantinopel. Einleitung, Edition, Kommentar [Öst. Akad. d. Wissenschaften]. WBS XXVII, Wien 2008
No full textΒιβλιοκρισία: Eirini Afentoulidou-Leitgeb, Die Hymnen des Theoktistos Studites auf Athanasios I. von Konstantinopel. Einleitung, Edition, Kommentar [Österreichische Akademie der Wissenschaften. Institut für Byzanzforschung. Institut für Byzantinistik und Neogräzistik der Universität Wien, WBS XXVII], Wien 2008, σσ. 246+7 πίν. ISBN 978-3-7001-6043-4.Βιβλιοκρισία: Eirini Afentoulidou-Leitgeb, Die Hymnen des Theoktistos Studites auf Athanasios I. von Konstantinopel. Einleitung, Edition, Kommentar [Österreichische Akademie der Wissenschaften. Institut für Byzanzforschung. Institut für Byzantinistik und Neogräzistik der Universität Wien, WBS XXVII], Wien 2008, σσ. 246+7 πίν. ISBN 978-3-7001-6043-4
Analysis and evaluation of optimum wavelengths for free-space optical transceivers
No full textThe objective of this paper is to analyse and present the latest results obtained for free-space optics (FSO) within the EU COST Action IC-0802 and within the European Space Agency (ESA) contract. First, the FSO technology is briefly discussed and some performance evaluation criteria for FSO are provided. Some optical signal propagation experiments through the atmosphere (including the recent investigations in airborne and satellite application for FSO) are also shown. In the main part, considerations on suitability of different optical wavelengths are brought into question. The wavelength selection is dependent on the atmospheric effects and on the availability of receiver and transmitter components. Discussion on the available receiver(s) and transmitter(s) includes the focus on advantages and mainly the costs of the different systems. In the final part, we examine the latest practical results (carried out within the COST Action IC-0802) on modelling of the FSO channel under fog conditions and other atmospheric effects. Additionally, recent results, showing major performance improvement, based on the hybrid system and specific modulation and coding schemes are presented
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
BER and outage probability of DPSK subcarrier intensity modulated free space optics in fully developed speckle.
No full textIn this paper a differential phase shift keying (DPSK) subcarrier intensity modulated (SIM) free space optical (FSO) link is considered in negative exponential atmospheric turbulence environment. To mitigate the scintillation effect, the selection combining spatial diversity scheme (SelC) is employed at the receiver. Bit error rate (BER) and outage probability (Pout) analysis are presented with and without the SelC spatial diversity. It is shown that at a BER of 10-6, a maximum diversity gain 25 dB is predicted. And about 60 dBm signal power is required to achieve an outage probability of 10-6, based on a threshold BER of 10-4
"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.
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
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
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
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