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Design of multiband electromagnetic wave absorber based on a periodic surface for electromagnetic wave measurement facility applications
No full textIn this paper, the periodic structure-based absorber operating at dual-band or more for applying to new electromagnetic wave measurement facility that does not contain a conventional pyramidal absorber is presented. To achieve the objective, the absorber structure takes the format of two-layer periodic surfaces. Based on the logical design principles, the parametric study results to obtain the desired performance and the final experimental result are addressed. The measured result shows a broadband reflectivity characteristic from 0.60 to 3.27 GHz on the basis of below 210 dB. As a result, the absorber shows the performance supporting CDMA, WCDMA, and WLAN bands in the electromagnetic wave measurement facility. (C) 2016 Wiley Periodicals, Inc.
An ultracompact CRLH‐TL bandpass filter for VHF applications
No full textThis article proposes a new design approach to an ultracompact composite right-/left-handed transmission line (CRLH-TL) bandpass filter with good passband and very broad stopband performances. In order to reduce the size, a series connection of the interdigital capacitor and shorted spiral inductor for realizing CRLH-TL is adopted and optimized to create the target Terrestrial-Digital Multimedia Broadcasting (T-DMB, 174-216 MHz) bandpass filtering. T-DMB was developed in South Korea. The results of a Bloch impedance analysis suggest that the proposed approach generates good impedance matching. The proposed filter has overall dimensions of (g)/19 by (g)/34 in terms of a center frequency of 180 MHz, a 3 dB fractional bandwidth of over 28%, an insertion loss of much lower than 2 dB, and a good return loss performance in the predicted and measured results
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
이동통신 단말기용 mobile antenna의 설계와 안테나 성능상의 handset case, battery, 그리고 인체 두부의 영향
No full text학위논문(석사) - 한국정보통신대학원대학교 : 공학부, 2004, [ ix, 56 p. ]Aesthetical design and marketing aspects have a large impact on the development of mobile phone. Therefore there is a remarkable trend to fully integrate the antenna in the mobile phone. Compared to traditional antennas it is more complicated to master the typical parameters like bandwidth, radiation pattern, and radiation gain of the antenna within the limited antenna volume. Besides, the influence of the user and handset parameters like the housing, LCD, keypad, and battery on the antenna performance causes the design procedure of antenna to be more complicated. This becomes even more critical with respect to multiband functionality which is an essential feature of modem mobile phone. To enable a rapid and efficient design some general relations concerning the physical behavior of an antenna in a small mobile have to be considered.
This thesis focuses on the two most important issues in internal and external antennas for multiband operation of mobile handsets: the design technique of small broadband antenna and investigation of the housing, battery, and human head effect on the antenna performance. A broadband external antenna with tuning patch which facilitates the adjustment of the resonant frequencies and leads to a large bandwidth design is proposed, and for internal type the idea which enables the proposed antenna to operate at multiple bands is presented. Each of these antennas with compact size is built in mobile phone with battery, and by applying to head phantom the variation of the antenna characteristic due to those parameters is investigated.
First of all, a triple-band stubby antenna fed by coaxial probe and the tuning technique are proposed for operating at PCS, IMT-2000, and Bluetooth bands. The proposed antenna shielded by the antenna cover consists of the two radiating elements. The impedance matching and bandwidth for the proposed antenna are mainly affected by the length of the ground patch at the bottom of small substrate. By properly ...한국정보통신대학원대학교 : 공학부
무선기기의 OTA 성능 평가를 위한 전자파 측정실 개발에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 정보통신공학과, 2019.2,[vi, 102 p. :]In the present communication network, anechoic chambers are continuously used for evaluating OTA (Over-The-Air) performance of wireless devices such as smart phones, and they are considered as a powerful method in the 5G wireless communications in the future. In recent years, interest in reverberation chambers has been increasing to overcome drawbacks of anechoic chamber. Reverberation chamber technology provides a variety of methodologies in testing the key performance indicators for wireless devices. In this case, the design of reverberation chamber that has a more stringent field uniformity performance than the standard, which is for electromagnetic compatibility (EMC), is required. To this end, new reasonable design approach is required. In the case of anechoic chamber, it is necessary to solve the disadvantages for specific purposes in the development stage, such as improving the internal electromagnetic environment and reducing costs while supporting approximate measurement of performance of wireless devices. Therefore, a thin planar absorber structure capable of replacing the pyramidal absorber of anechoic chamber is required.
A study on development of new electromagnetic wave measurement facilities for performance assessment of wireless devices is presented in this thesis. First, in the case of reverberation chamber, a reverberation chamber structure consisting of new mode stirrer and reflector for EMC and wireless device performance evaluation is proposed. The key design considerations for them are determined through a reasonable approach to analyze the eigenmode for a reverberation chamber and the standard deviation of its working volume. The fabricated reverberation chamber satisfies the requirements exceeding the specifications of commercial product, shows the same level of results as the anechoic chamber in the evaluation of OTA performance of commercial long-term evolution (LTE) mobile phone, and has excellent reproducibility characteristics. In the case of anechoic chamber, a planar resonance type electromagnetic wave absorber based on a periodic structure is proposed as a substitute for a pyramidal absorber to support performance measurements of small antennas for a specific mobile communication frequency band and to make an eco-friendly testing space that can reduce manufacturing and maintenance costs. Analytical methods based on impedance matching are proposed for effective design and a novel technique for widening the absorption bandwidth is introduced. In order to verify the feasibility of the proposed objective, an anechoic chamber composed of a simple structure absorber is fabricated and the measurement results of internal electromagnetic wave environment and antenna performance are presented.
The developed electromagnetic wave measurement facilities can be competitive with the products of overseas monopoly company, and it can be said that it is significant in that they were transferred to domestic companies and localized.한국과학기술원 :정보통신공학과
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
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