1,720,959 research outputs found
Microwave intermodulation in high-T-c superconducting microstrip resonators
No full textWillemsen BA, King BH, Dahm T, Scalapino DJ. Microwave intermodulation in high-T-c superconducting microstrip resonators. IEEE Transactions on Applied Superconductivity. 1999;9(2):4181-4184.We present experimental results on microwave intermodulation measurements on a High T-c Superconducting band-reject microstrip resonator which exhibits unconventional 2:1 intermodulation products. We discuss unusual features of this 2:1 behavior that are uncovered by detailed frequency swept and unbalanced power measurements. We also introduce a phenomenological theory which arises from a nonlinear inductance of the form L = L-0 + alpha\I\ which quantitatively describes the observed response
Microwave loss and intermodulation in Tl(2)Ba(2)CaCu(2)O(y) thin films
No full textWillemsen BA, Kihlstrom KE, Dahm T, et al. Microwave loss and intermodulation in Tl(2)Ba(2)CaCu(2)O(y) thin films. Physical Review B. 1998;58(10):6650-6654.A superconducting microstrip hairpin resonator is used as a tool to study the linear and nonlinear microwave response of TBCCO thin films. We extract the surface resistance R(S)(T), penetration depth lambda(T), and intermodulation critical current J(IMD)(T) for such a resonator at 4.2 GHz. The surface impedance results compare well with cavity perturbation measurements on portions of the same wafer. J(IMD)(T) is compared against theoretical models for the intrinsic nonlinear response of s- and d-wave superconductors. We demonstrate that the de critical current J(c) and J(IMD) are distinct material parameters, describing different physical regimes
Phenomenological theory of intermodulation in HTS resonators and filters
No full textDahm T, Scalapino DJ, Willemsen BA. Phenomenological theory of intermodulation in HTS resonators and filters. Journal of Superconductivity. 1999;12(2):339-351.Recent work on nonlinear effects in microwave resonators and filters from high temperature superconductors, focusing on intermodulations, is reviewed. We calculate the intrinsic nonlinear response of s-wave and d-wave superconductors. A phenomenological description of the lowest order nonlinear behavior in high-T-c films in terms of a single parameter, j(IMD), is proposed. We show how this description can be used to calculate the intermodulation power arising in realistic microstrip resonators. These calculations show good agreement with measurements on hairpin resonators. This description can also be used for the modeling of nonlinear behavior of complex microwave filters
Microwave intermodulation in thin film high-T-c superconducting microstrip hairpin resonators: Experiment and theory
No full textWillemsen BA, Dahm T, Scalapino DJ. Microwave intermodulation in thin film high-T-c superconducting microstrip hairpin resonators: Experiment and theory. Applied Physics Letters. 1997;71(26):3898-3900.We present experimental results for microwave intermodulation in a series of superconducting hairpin resonators. We find that geometry-plays a dominant role in determining both the losses and intermodulation in these resonators. The experimental data can be reproduced using recent theoretical calculations with a single parameter, J(IMD) (77 K). We compare the response of the fundamental and the first harmonic modes of these resonators to find that the use of the first harmonic mode gives less intermodulation, but we also find higher losses due to the more extended fields of this mode. (C) 1997 American Institute of Physics
Unusual power dependence of two-tone intermodulation in high-T-c superconducting microwave resonators
No full textWillemsen BA, Kihlstrom KE, Dahm T. Unusual power dependence of two-tone intermodulation in high-T-c superconducting microwave resonators. Applied Physics Letters. 1999;74(5):753-755.We study the power dependence of two-tone intermodulation arising in high-T-c superconducting microwave resonators as a function of each tone separately. In the regime where the intermodulation power varies as the square of the input power for equally strong tones, we observe unexpected behavior of the power dependence on the individual tones. We show that this behavior can be understood in terms of a nonlinear inductance which varies linearly with the magnitude of the input current. These findings provide a consistent phenomenological picture of the unusual power dependence and should place constraints on a microscopic description of nonlinear behavior in high-T-c films where the intermodulation products vary like the square of the input power. (C) 1999 American Institute of Physics. [S0003-6951(99)02205-6]
Microwave intermodulation of a superconducting disk resonator
No full textDahm T, Scalapino DJ, Willemsen BA. Microwave intermodulation of a superconducting disk resonator. Journal of Applied Physics. 1999;86(7):4055-4057.We calculate the third order intermodulation products for the TM(010) mode of a thin film disk resonator and discuss the particular case of a 1 GHz resonator in order to obtain a quantitative idea of the performance that can be obtained. The linear and nonlinear microwave responses of a TM(010) disk resonator are then compared to that of an equivalent half wavelength microstrip resonator. This analysis allows one to independently quantify the contributions to the nonlinear device performance from the material properties, device size and field configuration. (C) 1999 American Institute of Physics. [S0021-8979(99)04819-7]
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
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