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Application of Impact-Echo Phase to Detect Reinforcing Steel Bar and Crack
No full text敲擊回音法已廣泛應用於混凝土內部缺陷檢測，該方法在試體表面敲擊激發應力波，並量取試體表面之位移響應以進行傅立葉轉換，再由頻譜中回音尖峰之頻率判讀缺陷位置。然而回音尖峰並無法顯示內部反應界面究竟是鋼筋或裂縫所造成。
本研究之目的即在提出一個可分辨混凝土內部裂縫與鋼筋回音訊號的方法。首先對待測試體進行敲擊回音試驗，將訊號之時間原點延後以移除表面波，接著進行傅立葉轉換，並找出頻譜之回音尖峰之相位，再以回音相位之數值與斜率研判回音係由裂縫或鋼筋造成。
本研究先以動態有限元素法模擬試體內含鋼筋與裂縫之波傳行為，並分析此兩類訊號之相位特徵與差異，接著再以模型實驗進行驗證。從數值與實驗結果可看出裂縫回音之相位較趨近於0且相位斜率較大，而鋼筋回音之相位則較趨近於 且相位斜率較小。
相較於一般敲擊回音分析，本研究提出之方法除了可以計算內部反射面之位置，亦可辨識該反射面為鋼筋或裂縫。The impact-echo test is a nondestructive testing technique for civil structures. In the test, the surface response of the target structure due to an impact is measured. Then, the Fourier transform is adopted to transform the signal from the time domain to the frequency domain. The frequencies of the peaks can be used to determine the size of the structure or the location of the defect. In practice, the inclusion of target structure is unknown. Therefore, it cannot infer the interfaces is crack or reinforcing steel bar only by observing the frequencies of peaks.
The purpose of this study is to analyze the phase characteristic of stress wave that comes from crack and reinforcing steel bar. Frist, progress the impact-echo test to obtain the impact-echo signal and remove surface wave of impact-echo signal by delaying the time origin. Then, use the Fourier transform to transform the impact-echo signal to frequency domain and find the phase of echo peak. Finally, identify the echo caused by crack or reinforcing steel bar by the phase and phase slope.
The explicit finite element methods was firstly adopt to simulate the stress wave propagation when stress wave encounter crack and reinforcing steel bar. Then, the model tests were used to verify the numerical results. From the numerical and experimental results, one can conclude that the phase of crack echo approximate to zero and the phase slope is high. The phase of reinforcing steel bar echo approximate to and the phase slope is small.
Compared to the conventional impact-echo data analysis, the proposed methods can not only determine the defect depth but also identify the defect that is crack or reinforcing steel bar.口試委員審查同意書 I
致謝 II
摘要 III
英文摘要 IV
目錄 VI
圖目錄 VIII
表目錄 XII
第一章 前言 1
1-1研究動機 1
1-2文獻回顧 2
1-3內容大綱 4
第二章 敲擊回音法之原理 5
2-1 應力波傳行為 5
2-2 敲擊回音法 7
2-3 敲擊回音試驗參數 10
2-3-1 敲擊源 10
2-3-2 總取樣時間 12
2-3-3 取樣時距 13
2-4 敲擊回音法於異質材質偵測之應用 14
第三章 敲擊回音相位之應用 25
3-1 相位理論 25
3-2 敲擊回音相位分析 28
3-2-1 應力波於不同邊界條件時的相位差異 28
3-2-2敲擊回音法對相位的影響 30
3-2-3 誤差分析於敲擊回音相位 32
第四章 數值模擬 46
4-1 有限元素法 47
4-1-1 有限元素法之軟體介紹 47
4-1-2 有限元素法分析之步驟 48
4-2 數值模擬算例 51
4-2-1 數值算例 51
4-3 小結 52
第五章 模型試驗 61
5-1 模型試體 61
5-2 實驗設備及參數設定 62
5-2-1 實驗設備 62
5-2-2 參數設定 63
5-3 實驗結果 64
5-3-1 模型試驗一 64
5-3-2 模型試驗二 65
5-4 小結 66
第六章 結論與未來展望 84
參考資料 8
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
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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
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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
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koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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