1,720,956 research outputs found
STSAT-2C mission achievements with on orbit verifications
No full textThe STSAT-2C is a small satellite with 100kg mass and was launched on 30 January 2013, on the third fight of the KSLV-1, Korean rocket. Lift of occurred from the Naro Space Centre in Korea, and the launch vehicle successfully deployed the satellite into at 297km by 1,512km Low Earth Orbit inclined at 80.3 degrees. The objectives of STSAT-2C consist of three missions. The first is to demonstrate the capability of the KSLV-I as a launch vehicle for LEO missions. The Second is observation of space environment. And the third is to perform new space technology demonstration in orbit. The STSAT-2C was developed very shortly in a year for the KSLV-1, which had previously failed to launch STSAT-2A in 2009 and STSAT-2B in 2010. The STSAT-2C is operated by Satellite Technology Research Center of KAIST and was achieved mission requirement successfully in orbit. It has new developed space technology include IR Sensor, Femto-Second Laser, Reaction Wheel and Li-Ion battery system using COTS devices and etc
비접촉 내구 진단 장치 및 방법
No full textA non-contact durability diagnosis apparatus includes: (a) applying non-contactly and sequentially at least two excitation ultrasonic waves to an object and storing frequency signals generated from the object; (b) applying non-contactly and simultaneously the at least two excitation ultrasonic waves to the object and storing frequency signals generated from the object; (c) storing derived frequency signals remaining after removing an overlapping portion of the frequency signals of step (a) and the frequency signals of step (b); and (d) determining that the object is damaged when at least one of the generated frequency signals of step (c) is larger than a predetermined value
Detection of fatigue crack on a rotating steel shaft using air-coupled nonlinear ultrasonic modulation
No full textRotating shafts in drop lifts of manufacturing facilities are susceptible to fatigue cracks as they are under repetitive heavy loading and high speed spins. However, it is challenging to use conventional contact transducers to monitor these shafts as they are continuously spinning with a high speed. In this study, a noncontact crack detection technique for a rotating shaft is proposed using air-coupled transducers (ACTs). (1) Low frequency (LF) and high frequency (HF) sinusoidal inputs are simultaneously applied to a shaft using two ACTs, respectively. A fatigue crack can provide a mechanism for nonlinear ultrasonic modulation and create spectral sidebands at the modulation frequencies, which are the sum and difference of the two input frequencies Then LF and HF inputs are independently applied to the shaft using each ACT. These three ultrasonic responses are measured using another ACT. (2) The damage index (DI) is defined as the energy of the first sideband components, which corresponding to the frequency sum and difference between HF and LF inputs. (3) Steps 1 and 2 are repeated with various combinations of HF and LF inputs. Crack existence is detected through an outlier analysis of the DIs. The effectiveness of the proposed technique is investigated using a steel shaft with a real fatigue crack
High Efficiency and High Power Density Weinberg Converter Reducing Conduction Loss and Output Current Ripple for Space Applications
No full textWeinberg converter is widely used to battery discharge regulator of satellite system because it guarantees soft-switching of all devices and has low output current ripple. However, due to leakage inductance of the coupled inductor and transformer, the voltage stress of powering diode and the output current spike are increased. To overcome these problems, weinberg converter with auxiliary switch and capacitor is presented in this paper. The proposed converter significantly reduces the voltage stress of powering diode. In additions, the output current spike is decreased by adopting auxiliary circuit. Thus, the conduction loss of the powering diode and output current ripple are reduced. As a results the proposed converter achieves high efficiency and high power density with the reduced output filter. The verification is performed with 400 W/50 V prototype
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
- …
