1,721,419 research outputs found
Stability Analysis and Feedback Stabilization of Discrete-Time Delay Systems
No full text本論文主要使用線性矩陣不等式的方法研究離散時間延遲系統。研究主題包括具有時變之狀態時間延遲的離散系統、具有時變之狀態時間延遲與非線性擾動的離散系統，及具有時變之狀態間隔時間延遲的離散系統，探討其穩定性分析與輸出迴授穩定化設計。在穩定性分析方面，本論文提出一些以線性矩陣不等式表示的穩定性準則，且在推導穩定性準則的過程中引入新的自由權重矩陣，及使用最少的不等式，儘可能不使用會產生保守性的條件。在輸出迴授控制器的設計上，本論文提出一套以線性矩陣不等式作為條件的穩定化方法，不僅可容許較大的延遲範圍使得閉迴路延遲系統穩定，對於控制器增益尚可直接求得，以對控制器增益作適當的限制，這在實際工業應用上提供設計者相當大的便利性。最後，在數值範例的測試上，本論文所提的方法不僅可以得到較為不保守的條件，甚至對於一般文獻無法討論的穩定度系統也能夠適用。This dissertation studies discrete-time systems with a time-varying state delay via the linear matrix inequality approach. The research includes the developments of delay- dependent stability analysis and output feedback stabilization for discrete-time systems with a time-varying state delay, discrete-time systems with a time-varying state delay and nonlinear perturbations, and discrete-time systems with an interval time-varying state delay. The derivations are based on the Lyapunov method and formulated by the linear matrix inequalities, which are convenient to solve. In the development of stability condi- tions, new free-weighting matrices are introduced, and the least number of inequalities are utilized, with the attempt to reduce as much conservatism as possible. In the proposed novel stabilizing output feedback controller design method, the gain matrix is a direct design variable, which offers great flexibility for the design purpose. To test the derived results, many numerical examples are adopted. Comparisons with results by existing methods indeed show that the proposed method is less conservative for the examples
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
The higher osteoprotective activity of psoralidin in vivo than coumestrol is attributed by its presence of an isopentenyl group and through activated PI3K/Akt axis
No full textData source: Supplementary data, https://doi.org/10.1016/j.biopha.2018.03.166Abstract not availableYuankun Zhai, Qingfeng Wang, Yingying Li, Jiawei Cui, Kun Feng, Xijian Kong, Cory J. Xia
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