1,720,995 research outputs found
Interference effect between sonic nozzles
No full textCalibration of a large capacity gas flow meter may be accomplished with a sonic nozzle bank as a reference system. For the design of a compact movable prover which is made with many nozzles, the nozzles should be installed as close as possible. The interference effect between neighbouring nozzles can be an additional error source for prediction of the mass flow of the assembly from the calibration of individual nozzles. A nozzle bank was assembled from seven toroidal throat nozzles with a nominal throat diameter (d) of 4.3 mm in a hexagonal pattern, it was calibrated by a primary gas flow system at stagnation pressures from 0.5 to 2 MPa and throat Reynolds number from 0.4 to 1.2 x 10(6). Three installation plates of sonic nozzles were fabricated with distances between nozzles of 16-81 mm (L/d of 3.7 to 9.5). The average discharge coefficient of the seven nozzles in a nozzle bank was calculated from the discharge coefficients of the individually measured sonic nozzles. The differences from the directly measured results were within +/-0.05% for all test cases. Also, the proximity of the wall for the six outer nozzles located at 2.3 d from the pipe wall had no influence on the experimental results. The discharge coefficients as a function of throat Reynolds number were in agreement with the recommended equation of ISO 9300. (C) 1998 Elsevier Science Ltd. All rights reserved
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
Interference effects of three sonic nozzles of different throat diameters in the same meter tube
No full textFor calibration of a large capacity gas flow meter, a sonic nozzle bank may be used as a reference system. International standards (ISO9300:1990) allow installation of a single nozzle in a meter tube as a flow transfer standard. For multiple nozzles in a single tube, the effect of interference between sonic nozzles and the chamber wall must be measured to predict the discharge coefficient of a nozzle array from those of single nozzles. The interference effect between neighboring nozzles can be additional error sources in mass flow measurement. Sonic nozzles with three different throat diameters (d = 4.3, 8.1, and 13.4 mm) were tested in a single meter tube in three geometrical arrangements. The mass flow rate was measured against a primary gas flow standard system. Three installation plates for sonic nozzles were made to vary the distance between nozzles and distance from the chamber wall. Discharge coefficients of the three individual nozzles were in agreement with the ISO recommended equation within +/- 0.2%. Discharge coefficients of the nozzle bank calculated from those of the individual sonic nozzle were the same as the direct measurements within +/- 0.098% at the 95% confidence level for all cases. For these experiments, the results were not influenced by the proximity of the tube wall or the interaction of the nozzles. (C) 1999 Elsevier Science Ltd. All rights reserved
Electronic structure simulation of chromium aluminum oxynitride by discrete variational-X alpha method and X-ray photoelectron spectroscopy
No full textWe use a first-principles discrete variational (DV)-Xalpha method to investigate the electronic structure of chromium aluminum oxynitride. When nitrogen is substituted for oxygen in the Cr-Al-O system, the N2p level appears in the energy range between O2p and Cr3d levels. Consequently, the valence band of chromium aluminum oxynitride becomes broader and the band gap becomes smaller than that of chromium aluminum oxide, which is consistent with the photoelectron spectra for the valence band using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). We expect that this valence band structure of chromium aluminum oxynitride will modify the transmittance slope which is a requirement for photomask application.Ministry of Science and
Technology of Kore
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
Force Ripple Compensation and High Speed Tracking Control of a High Precision Linear Motor System using Multi-Segment Magnet Array
No full textDesign of high precision linear stage with double-sided multi-segmented trapezoidal magnet array and its compensations for force ripples
No full textGenerally, linear motor is used as actuators for high precision stage which requires long stroke, high speed and high precision capability. In order to meet the needs of high speed and high precision, it is important that the motor generates large force and has small size. In this paper we propose a linear motor with multi-segmented (MST) magnet array to maximize actuating force per unit volume. The MST magnet array is a modified version of standard Halbach magnet array. Each magnet in the MST magnet array has various shapes and dimensions while standard Halbach magnet array has identical magnets. In order to optimize the shapes and dimensions, design optimization of the motor is carried out and its performance is investigated. We conclude that the linear motor with the MST array can generate more actuating force per unit volume than the one with conventional magnet array and standard Halbach magnet array. A high precision stage is constructed using the optimized MST magnet array. Even though we obtain maximized actuating force, the flux density by the MST array is seriously distorted from ideal sinusoidal flux density with respect to mover position. This distorted flux density results in force ripples when we use three phase commutation. And no matter how small force ripples would be, serious tracking errors occur in high precision linear stages. Thus, force ripple must be compensated. In this paper, we proposed a simple method to reduce the ripple by current shaping. (C) 2006 Elsevier Ltd. All rights reserved
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
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