1,720,956 research outputs found
Application of Subspace Identification in System Identification and Structural Damage Detection
No full text本研究的目的在於探討子空間識別法(Subspace Identification)於系統識別及結構損壞診斷上的應用範疇，並根據實際的分析結果來決定適合發展於土木結構物長期健康監測系統的相關技術。首先，根據使用資料的類型將子空間識別法分為兩種並介紹各自的理論推導：(1)單獨以輸出資料為基礎進行系統識別的隨機子空間識別法(Stochastic Subspace Identification, SSI)，其實際分析時所使用的資料為結構微振動下所量測得的反應；(2)以輸入及輸出資料為基礎的子空間識別法(Subspace Identification, SI)，其使用資料為地震時所記錄到的地表加速度歷時與結構反應。在應用上，子空間識別法會面臨如何決定系統參數及挑選真實模態的問題，本研究將以實際案例的分析經驗來說明相關問題的解決之道。在結構損壞診斷的技術發展上，本研究將介紹三種不同的方法：(1)以零子空間為基礎的損壞診斷法(Null Subspace-Based Damage Detection)；(2)正規化勁度與阻尼矩陣的逆算法(Inverse Methods)；(3)二階段有限元素更新法(Two-State Finite Element Model Updating)，利用子空間識別法的分析結果，上述三種方法皆可準確地識別出結構的實際損壞狀況。為達成建立長期監測系統的目的，本研究提出一套適用於更新LQ分解(LQ Decomposition)的演算方法，有助於加速傳統遞歸式子空間識別法的計算時間，由數值模擬與真實實驗之分析結果顯示，該方法理論推導無誤並可有效地追蹤識別結構特性的改變，最後，此方法已經被使用在台大土木研究大樓的監測系統開發上，經由分析結果可知，該結構隔震層在地震時的非線性行為確實會導致結構自然頻率與阻尼比的改變，並與隔震層的層間位移量有直接關係。This study applies the subspace identification to system identification and damage detection. Many of the damage detection methods are surveyed in order to establish a continuous monitoring system of the civil engineering structures. First, according to the use of the collection data two theoretical derivations are introduced: (1) the stochastic subspace identification (SSI) using output-only data, or the ambient vibration data for continuous monitoring; and (2) the subspace identification (SI) using input/output data, or the seismic responses. The user-defined parameters in the subspace identification are studied through the laboratory and field tests and also three noise-rid methods are employed to distinguish the noise modes from the results of analysis. For damage detection three methods are introduced: (1) null subspace-based damage detection; (2) inverse methods for the identification of the normalized stiffness and damping matrices; and (3) two-stage finite element model updating. These methods can accurately detect the location or quantification of the structural damage from the results of identification. For the purpose of continuous monitoring, in this study a new technique for updating LQ decomposition is proposed to achieve the recursive computation of the subspace identification. From the results of the numerical simulation and the laboratory experiment it is proven that the proposed method of the recursive subspace identification can accurately detect the abrupt damage of the structure. Finally, the proposed methods are applied to the long-term monitoring of the new Civil Engineering Department Research Building in the campus of National Taiwan University, which is a mid-story isolation building. The relationship between the natural frequencies and the drift of the isolation system is established to provide a reference for future research
Feature extraction and system identification of reinforced concrete structures considering degrading hysteresis
No full textStructural damage diagnosis based on on-line recursive stochastic subspace identification
No full textOutput-only modal identification of a cable-stayed bridge using wireless monitoring systems
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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
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