1,720,979 research outputs found
Sub-wavelength gratings in silicon photonic devices for mid-infrared spectroscopy and sensing
No full textMid-infrared spectroscopy enabled by silicon photonics has received great interest in recent years as a pathway for a scalable sensing technology. The development of such devices would realise inexpensive and accessible instrumentation for a wide variety of uses over numerous fields. However, not every sensing application is the same; to produce sensors for real-world scenarios, engineers need flexibility in device design but also need to maintain compatibility with scalable fabrication processes. Sub-wavelength gratings can offer a solution to this problem, as they enable the engineering of optical properties using standard fabrication techniques and without requiring new materials. By using sub-wavelength gratings, specific design approaches can be tailored to different applications, such as increasing the interaction of a sensor with an analyte or broadening the bandwidth of an integrated photonic device. Here, we review the development of sub-wavelength grating-based devices for mid-infrared silicon photonics and discuss how they can be exploited for spectroscopic and sensing devices
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
Novel microwave microfluidic sensor using a microstrip split-ring resonator
No full textIn this paper, a new type of microwave microfluidic sensor is proposed to detect and determine the dielectric properties of common liquids. The technique is based on perturbation theory, in which the resonant frequency and quality factor of the microwave resonator depend on the dielectric properties of the resonator. A microstrip split-ring resonator with two gaps is adopted for the design of the sensors (i.e., a double split-ring resonator). This resonator is both compact and planar, making it suitable for a lab-on-a-chip approach. Several types of solvents are tested with two types of capillaries to verify sensor performance. At 3 GHz, very good agreement is demonstrated between simulated and measured results
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
Novel coupling structure for the resonant coaxial probe
No full textHerein we present a technique for performing complex permittivity measurements with an overmoded, evanescently perturbed coaxial resonator at microwave frequencies. The design of a noninvasive electromagnetic coupling structure, which allows transmission measurements to be taken from one end of a resonant section of coaxial cable, is discussed in detail. Quasi-spectral information was obtained through the exploitation of higher order resonances, and complex permittivity measurements of a number of common industrial solvents were taken at multiple discrete frequencies between 1 and 8 GHz. A combination of experimental and simulated results was used also to characterise the device behavior. The high stability of temporal measurements, coupled with the robustness of the design, make this device ideal for analytical chemistry and industrial process control
Microfluidic device for compositional analysis of solvent systems at microwave frequencies
No full textA device for analysing the chemical composition of single- and multi-phase solvent flows using microfluidic dielectric spectroscopy is demonstrated in this work. An open-circuited, half-wavelength, coaxial resonator operating at microwave frequencies (i.e. harmonics of 600 MHz) was embedded in a compression-sealed polytetrafluoroethylene microfluidic chip for in situ characterization of solvent–solvent and solute–solvent mixtures of varying concentration, and an aqueous–organic segmented flow. Results are shown for a solvent mixture of acetonitrile in toluene as a test system, exhibiting a sensitivity limit of 400 nM. In addition to being highly sensitive, the measurement system is fast, robust and non-invasive, and can be readily miniaturized
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
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