1,720,998 research outputs found
Evaluation of deep drillholes for high level nuclear waste disposal
Full text linkThesis (Nucl. E.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1992.Includes bibliographical references (p. 217-221).by Weng-Sheng Kuo.Nucl.E
The general evaluation of the nodal synthesis method in nuclear reactor transient analysis
Full text linkThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1994.Includes bibliographical references (leaves 174-177).by Weng-Sheng Kuo.Ph.D
Model on 6+1 Dimensional Cosmology
No full text在本篇論文中，我們在SO(4)群6維的均項性(homogenous)空間，建立一個均項性但各向異性(anisotropic)的度規(metric)，使得這個6維空間分開成3個大的空間維度，以及另外3個極小的額外維度。再利用建立的度規計算在 空間中的曲率，並推導在6+1維度下的愛因斯坦方程式，討論額外維度收縮的過程。
接著我們讓此模型做演化，並分別與古典宇宙學中宇宙演化的各個階段：暴漲(Inflation)、輻射主控時期(Radiation dominated era)、物質主控時期(Matter dominated era)分別做對照。並且計算在此模型中一些重要的數值。In this thesis, we use SO(4) group as a 6 dimensional homogenous space, we can build up a homogenous but anisotropic metric such that the 6 dimensional space become 3 large ordinary dimension and 3 compact extra-dimension. We will calculate the space curvature on the metric. Finally, we will obtain an Einstein’s equation for such a space describing the evolution of space compactification and topology.
Then we will evolve this model with every phase of universe: inflation, radiation dominated era and matter dominated era. Fit this model with cosmology. Finally we will give some estimation and evaluate important quantities in this model
在斜坡多音束側擊的資料分析研究
No full text精確的地形圖是海港工程及海底電纜鋪設工程等必備的重要工具。目前在國內的近岸測深作業仍以單音束測深系統為主流，只要原因是因為其價錢低而且安裝及操作都相當簡單，於施測作業時的船體搖晃程度上的要求也較不如多音束測深系統嚴謹，此種特性雖有利於施測作業的順利進行，但其低效率及低密合性等缺失卻一直無法有效解決。在近岸工程業界者對於水下地形解析度越來越高的要求下，單音束測深的使用已漸不符業者之要求。而多音束測深系統的出現可提供高精度及高解析度的測深資料，故對於多音束測深系統的使用已經成了測深界對於測深系統選擇上的必然趨勢。多音束測深系統對於測深系統的精密度要求大增，且多音束測深系統所得到的水深資料相當龐大，大幅度增加了資料處理上的困難度，故掌控其資料品質需更小心嚴謹。
於近岸區域水深小於5公尺之區域測量水深是相當困難且危險的工作，基於施測作業上的安全性及便利性考量，我們以將音鼓旋轉45°之方式來測量近岸水深。但將音鼓斜置45°之後所測得的水深點往往因為系統偏差校正數值難以估算，因其不似庫底測線可由相鄰不同向之測線等深線來判斷其系統誤差，故往往以庫底的測線資料來判斷近岸資料的系統誤差。本文試著模擬於霧社水庫音鼓側擊時因為音鼓架設產生的系統誤差之邊坡地形，試著釐清個個參數對於地形的影響。摘要...................................................................................... 1
目錄...................................................................................... 3
圖目...................................................................................... 5
表目...................................................................................... 7
第一章 緒論........................................................................ 9
1-1 前言................................................................................ 9
1-2 前人研究....................................................................... 10
1-3 研究目的....................................................................... 12
1-4 多音束測深系統單元介紹......................................... 12
第二章 多音束測深系統誤差與校正............................. 19
2-1 現場疊合測試(Patch Test)............................................ 19
2-2 音鼓正打與側打之成效.............................................. 24
2-2-1 音鼓正打..................................................................... 24
2-2-2 音鼓側打..................................................................... 25
2-3 邊坡側打之誤差型態................................................... 26
第三章 音鼓側打之地形偏差........................................... 36
3-1 橫搖角(roll)偏差............................................................ 37
3-2 縱搖角(pitch)偏差.......................................................... 39
3-2-1 航向與邊坡等深線垂直............................................ 39
3-2-2 航向與邊坡等深線平行............................................ 44
3-2-3 航向與邊坡等深線呈任一角度相交....................... 46
3-3 航偏角(yaw)偏差............................................................. 48
第四章 多音束測深資料於邊坡上之模擬展示............... 53
4-1 橫搖角(roll)偏差之模擬................................................. 55
4-2 縱搖角(pitch)偏差之模擬............................................... 58
4-2-1 航向與邊坡等深線垂直模擬..................................... 58
4-2-2 航向與邊坡等深線平行模擬..................................... 60
4-2-3 航向與邊坡等深線呈角度相交模擬........................ 62
4-3 航偏角(yaw)偏差............................................................. 65
第五章 結論........................................................................... 67
參考文獻............................................................................... 6
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
The Simulation of EASY5 for the Fuel Cell System and Design of the Robust Controller
No full text本篇論文目的主要是利用EASY5軟體模擬100W的燃料電池系統，利用系統識別得到燃料電池的轉移函數來設計強韌控制器與PI控制器，並將兩種控制器模擬的結果做比較。
首先，將100W燃料電池相關的參數建立在EASY5，並將EASY5所模擬的暫態特性及穩態特性與實驗結果做比較。接下來在EASY5做系統識別得到100W燃料電池的轉移函數，利用此轉移函數來設計強韌控制器與PI控制器，強韌控制器設計的方法是 迴路成型(loop shaping)。最後，將兩種控制器模擬的結果做比較與討論，結果顯示強韌控制器不但改善燃料電池的暫態響應而且在電流改變時仍追蹤到參考命令。The purpose of this thesis is mainly to simulate the 100W fuel cell system through the software, EASY5. The transfer function of the fuel cell system obtained through system identification is used to design the robust controller and PI controller, and compare the simulation results of the two controllers.
First, the related parameters of the 100W fuel cell system are set in EASY5, and the transient and steady state characteristics simulated through EASY5 are compared with the experimental results. Next, the transfer function of the 100W fuel cell system is obtained through the system identification done in EASY5, and it is used to design the robust controller and PI controller. The method of designing robust controller is loop shaping. Finally, compare and discuss the simulation results of the two controllers. The result is that the robust controller not only improves the transient response of the fuel cell but tracks the reference command even if the current varies.誌謝Ⅰ
中文摘要Ⅱ
英文摘要Ⅲ
目錄Ⅳ
圖目錄Ⅸ
表目錄XVⅡ
符號說明XVⅢ
第一章 緒論1
1-1 研究動機與目的1
1-2 文獻回顧2
1-3 章節摘要7
第二章 燃料電池的簡介9
2-1 燃料電池的歷史與發展概況9
2-2 燃料電池的種類與特性10
2-3 燃料電池的優缺點14
2-4 質子交換膜燃料電池的構造與原理16
2-4-1 質子交換膜燃料電池的構造16
2-4-2 質子交換膜燃料電池的原理19
2-5 燃料電池的開路電壓20
2-5-1 吉布斯自由能20
2-5-2 氣體壓力對燃料電池開路電壓的影響22
2-6 燃料電池的電壓對電流密度的關係24
2-7 質子交換膜燃料電池的數學模型26
2-7-1 數學模型的基本假設26
2-7-2 陰極氣體擴散模型27
2-7-3 陰極電化學動力模型28
2-7-4 電池的內阻30
2-7-5 燃料電池的穩態電壓31
2-8 質子交換模燃料電池的數學模型方塊圖32
第三章 EASY5的簡介與燃料電池模型建立34
3-1 EASY5的簡介34
3-2 EASY5的模擬流程36
3-3 燃料電池模型的建立38
3-4 燃料電池系統元件的模擬41
3-4-1 高壓氫氣瓶42
3-4-2 氫氣調壓閥43
3-4-3 流量控制閥門44
3-4-4 陽極與陰極氣體需求量的計算46
3-4-5 空氣壓縮機47
3-4-6 質子交換膜燃料電池組48
3-4-7 流量感測器55
3-4-8 空氣壓縮機的冷卻系統55
3-5 燃料電池模型的參數設定57
第四章 強韌控制理論63
4-1 強韌控制的簡介63
4-2 H-infinity控制理論的概念64
4-3 範數65
4-3-1 範數的定義65
4-3-2 信號與系統的範數65
4-4 系統的不確定性68
4-4-1 結構化不確定性69
4-4-2 非結構化不確定性69
4-5 迴路系統的穩定性73
4-6 開迴路函數與系統性能目標的關係75
4-7 H-infinity迴路成型法81
4-7-1 一般閉迴路轉移函數目標81
4-7-2 H-infinity迴路成型控制器的設計步驟82
4-7-3 H-infinity迴路成型與傳統迴路成型之差別87
第五章 燃料電池的系統識別89
5-1 系統識別的簡介89
5-1-1 組成數學模型的方法89
5-1-2 系統識別的原理與目的90
5-1-3 系統識別的步驟91
5-2 識別輸入的選定93
5-2-1 識別輸入的頻率特性93
5-2-2 識別輸入的振幅特性94
5-2-3 識別輸入的選定方針94
5-3 參數模型的種類95
5-3-1 ARX模型95
5-3-2 FIR模型97
5-3-3 ARMAX模型97
5-4 參數模型的識別方法98
5-4-1 遞歸最小平方法99
5-4-2 延伸最小平方法101
5-5 燃料電池的系統識別101
5-5-1 燃料電池系統的方塊圖101
5-5-2 G1的系統識別102
5-5-3 G2的系統識別109
5-5-4 G3的系統識別116
5-5-5 G4的系統識別123
5-5-6 G1在不同電流下的系統識別102
第六章 模擬結果與分析133
6-1 EASY5的模擬結果133
6-2 強韌控制器與PI控制器的比較147
6-3 MIMO強韌控制器的設計157
第七章 結論與未來展望168
7-1 結論168
7-2 未來展望168
參考文獻17
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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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