1,720,965 research outputs found
A Low-cost, Continuously Adjustable, High-voltage, Regulated Dc Power-supply
No full textWe have designed a simple, low-cost HV (0-400 V) DC power supply
whose output can be varied continuously down to zero volts, with very high ripple
rejection and with low noise (AV/ V< 25 x IO^-6)
Inexpensive but accurate driving circuits for the quartz microbalance
No full textThe quartz crystal microbalance (QCM) is a common technique which finds a wide variety of applications in many different areas like adsorption, catalysis, analytical chemistry, biochemistry, etc., and more generally as a sensor in the investigation of viscoelastic films. In this article we describe some driving circuits of the quartz which we have realized and tested in our laboratory. These can be assembled with standard components which can be easily found. Their performance, in some cases, is as good as that of the much more expensive frequency modulation technique employed in very precise QCM measurements and which requires high-quality commercial radiofrequency generators and amplifiers. (C) 1999 American Institute of Physics
Level meter for dielectric liquids
No full textWe describe a novel device which can measure, with low dissipation and high resolution, the level of a dielectric liquid. This device can also be used with cryogenic liquids, in particular with liquid helium. The high degrees of stability and of reproducibility make this apparatus an instrument of performances largely competitive with respect to others commonly used
A low-cost GPIB programmable precision voltage source
No full textWe have developed a simple, low-cost, GPIB programmable precision voltage source for laboratory use with two outputs in the range [0,-5]V and [0,+5]V. The original goal was to allow the interfacing to personal computer of older high-voltage sources that can be remotely driven by an analog signal. This voltage source can be more generally used whenever a GPIB programmable low-power precision voltage source is needed. (C) 1997 American Institute of Physics
Novel needle microbalance for adsorption studies
No full textMicrobalances an quite often used in the investigation of adsorption phenomena. In this article we describe a novel "needle" microbalance characterized by a magnetic restoring torque particularly fit to study the growth of thick films on solid surfaces. In particular, it does not present any particular problem in the study of thick solid films which generally affect the stiffness of the restoring springs, present in nearly all mechanical devices, in a difficult to predict way. Another important feature of this microbalance is that its use is not Limited to one specific adsorbing solid surface. (C) 1997 American Institute of Physics
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
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
- …
