1,720,981 research outputs found
Study of Relationship between Size Distribution and Energy Levels in InAs Self-assembled Quantum Dots
No full text本論文探討三種不同結構的固態分子束磊晶成長的自我組成砷化銦量子點，作為本論文主軸。我們利用光調制反射率光譜實驗來探索各樣品中量子點在50 K下的光學能階特性。同時利用雷射必v變化之光致螢光光譜實驗可以找出基態與激發態的躍遷能階，進一步可以吻合至光調制反射率光譜上。我們也以掃描式電子顯微術(scanning electron microscope；SEM)與原子力式顯微鏡(atomic force microscope ,AFM)來觀測量子點2D與3D的形態，進而推估出量子點尺寸的分布情形，以了解躍遷能階與量子點大小的關係。我們進行溫度低溫至室溫之光致螢光光譜實驗可以發現，能階隨著溫度上升會有紅移現象，特別是當量子點覆誘FInGaAs(9ML)，將使量子點能階比未覆貌漣C、同時半高寬縮減，隨著溫度變化分布的情況可以發現樣品A、B與C的第一群基態之半高全寬值幾乎不隨著溫度改變而產生變化，是因為熱效應所造成的響應。反觀當有第二群量子點時，則溫度超過200K後而有逐漸下降的趨勢。利用熱效應使得載子在高能階的量子點不容易被侷限住而放光，反而會脫離出去後，再重新分布來加以解釋此現象。In this thesis, we use photoreflectance (PR) and the temperature dependent photoluminescence (PL) techniques to study the optical properties of self-assembled InAs quantum dot (QDs). In the PR experiments, the energy values of the QD optical transitions could be obtained. Compared with PL experiments, we defined clearly the effect of the lower energy levels. In order to understand the relation between the size of quantum dos and energy levels, we use scanning electron microscope (SEM) and atomic force microscope (AFM) to measure the size distribution of quantum dots. At last, we performed the temperature dependent PL experiments to measure optical energy and broadening parameter. In these experiments, we observed that the intensity of ground state decreased with increasing temperature. However, the broadening parameter show different trend with varying temperature. The broadening parameter of the QDs of the first group isn’t affected at different temperature. But, for the second group, the broadening parameter decreased with increasing temperature at low temperature. It’s caused the higher-energy carriers of QDs escape from the confine state and induce repopulation effect. Then, due to lattice vibration, broadening parameter increased from 100 K to 250 K. Finally, it decreased again. It reveals that this abnormal behavior of broadening parameter closely relate to the temperature. In summary, the thermal effect and sample structure play an important role in the optical properties of QDs.誌謝 I
摘要 III
Abstract IV
目錄 V
圖目 VI
表目 VII
第 一 章、引 言 1
第 二 章 理論背景 5
2. 1 調制光譜術 5
2. 1. 1 調制反射光譜術和介電函數的關係 9
2. 1. 2 奇異點之討論 11
2. 1. 3 三次微分譜形 12
2. 1. 4 一次微分譜形 14
2. 2 掃描式探針顯微鏡的原理與架構 16
2. 3 自我組成之量子點 21
第 三 章 實驗方法與樣品分析 23
3. 1 樣品描述 23
3. 2 光調制反射率光譜實驗 25
3. 3 光致螢光光譜實驗 26
3. 4 原子力顯微鏡系統架構 27
第 四 章 結果與討論 29
4. 1 光調制反射率光譜實驗結果 29
4. 2 光致螢光光譜與光調制反射率光譜實驗對應 32
4. 2. 1 樣品A實驗結果 32
4. 2. 2 樣品B實驗結果 37
4. 2. 3 樣品C實驗結果 42
4. 3 量子點形態 46
4. 3. 1 以掃描式電子顯微術探測量子點 46
4. 3. 2 以原子力顯微術探測量子點 48
4. 4 光致螢光光譜術溫變量測與分析 52
第 五 章 結論 58
附錄 60
參考文獻 6
Structural Regulation of Television Industry in Taiwan: Contextual Analysis on the Interactions of Power Organs
No full text本文試圖藉由探討政經脈絡的歷史發展，以及規範形塑的過程，了解電視產業結構管制的運作規則，並且對於目前的問題作出初步的政策建議方案。 在歷史脈絡方面，本文將電視產業的發展分為威權時期、民主化時期與全球化時期。在威權時期，我國電視產業則由黨國掌握。在民主化時期，我國國會全面改選，這當中中央與地方的對抗、執政黨與在野黨的對抗，讓我國的電視產業逐漸蓬勃發展。在全球化時代，我國開放外國投資電視產業，系統業者的整合加速。近幾年來，國內更出現內國企業利用國際金融槓桿投資我國電視產業，取代了以外國為主的併購模式。之後出現的媒金結合、跨媒體結合也引發了相當劇烈的反媒體壟斷運動。 在規範形塑方面，面對上述的政經發展脈絡，威權時期的立法相對沈默，行政權的提案。到了國會全面改選後，新一屆的國會反對黨議員提出相當基進的改革方案，然而此時執政黨仍有相當實力。在全球化時期，除了跨國資本投入外，我國也發生了第一次的行政權政黨輪替，出現朝小野大的局勢。此時行政權的提案受到相當大的挑戰，在野黨在通傳會立法取得較大優勢。於此之後，我國的修法呈現停滯狀態。 綜合對於政經局勢以及規範形塑的觀察，本文認為規範形塑對於社會議題的回應由消極趨向積極，但是效能在提升之後卻又在近幾年進入衰退。筆者認為我國電視產業結構管制的變遷趨力來自於民主化與全球化雙重因素。而我國規範形塑的立法動能來源，主要來自於行政機關的管制需求、在野黨與社會運動等等反對者對於電視產業結構管制改革的呼聲，以及法院判決對於管制機關的不利判決。同時本文也發現國會的規範形塑往往遲於政經局勢的變動，社會上的修法呼聲往往需要經過許多年的努力才能反映到通過的立法。 就這些特色，本文提出以權力分散、動態制衡為基調的改革方案。也就是深化電視產業公司治理模式，改革有線電視系統業者的市場結構，以及將通傳會定位為監理機關，並就與其他機關之分工、具體決定之作成、法院審查之判准作出改革。Regarding to the political and economical context, and the framing of the regulation norms, this Thesis aims to propose an initial solution program for the present issues on the regulation of television industry in Taiwan. On the political and economic context, this Thesis divided the period of television industry development into three eras: authoritarian era, democratization era, and globalization era. In the authoritarian era, the television industry is control by the party state led by the Chinese Nationalist Party (Kuomingtang, KMT). In the democratization era, challenges from the opposition parties, and the local governments companied with the vigorous television industry. In the globalization era, foreign investors greatly got involved in the mergers of television industry. Financial leverage, multi-media concentration, and the merger of finance and media brought great concerns of media monopoly in the civil society in Taiwan. On the framing of the regulation norms, this Thesis proposes an analysis considering the mentioned political and economic context. In the authoritarian era, the Parliament is relatively silent on the bills proposed by the executive branch of the government. In the democratization era, the Parliament was more vibrant on proposing comprehensive reform agenda, while the executive began compromising in certain legislations. In the globalization era, the vibrant trend of reform lasted for few years. The KMT-led Parliament strongly controlled the legislation against the executive led by the Democratic Progressive Party (DPP). However, in recent years, the reform on television industry regulation seemed stagnated. This Thesis finds that the driving force of the structural regulation of television industry derives from democratization and globalization. For the framing of the regulation norms, it is pushed by the regulation demand of the executive organs, the opposition parties, and the impacts of judicial judgments. Therefore, the framing of regulations is usually lag to the trends of political and economic changes. In conclusion, this Thesis proposed that the corporation governance and the market structure be reformed by new legislations. The National Communication Commission (NCC) shall also be regarded as a supervisory organ. Therefore, its functions, ways of decision-making, and the standards of court review should be adjusted
Application of Dynamic Voltage Regulator for a Grid-Connected Induction Generator
No full text隨著石化燃料的逐漸減少而且價格日漸高漲，造成發電的成本越來越高；並伴隨著環保意識的抬頭，各國開始控管溫室效應氣體的排放，提倡使用綠色能源，所以替代能源的開發刻不容緩的進行中。替代能源的種類有許多種，例如風力、太陽能、地熱、潮汐、生質能…等。台灣西部沿海及外島地區擁有相當豐富的風能資源，所以非常適合風力發電的發展。 風力發電機組的主流型式之一為使用感應式發電機組來發電，但是感應機本身有電壓調整能力不佳的缺點，加上風力是時變無法預測的，將使得所發出來的電力不穩定，造成所連接的匯流排電壓不穩定。電力品質對科技產業的影響極大，不穩定的供電將會造成產品不良率的升高及敏感設備的損壞，所以如何改善電力系統的電壓穩定，維持良好的電力品質將是未來電力工程師努力的目標及所面對的問題。 動態電壓調整器是利用弦式脈波寬調變技術來將直流側電容所儲存的能量轉換成交流成份送出，並可以藉由改變輸出電壓的角度，來調整所輸出實、虛功，達到系統電壓控制的目的。將藉由MATLAB/Simulink的模擬，來驗證本論文設計的動態電壓調整器適合應用於感應式發電機併聯系統。As a result of the price hike in fossil fuels and the effort to control CO2 emissions, developing green energies received much attention in recent years. There are a great variety of green energies such as wind power, solar power, geothermal energy, tide energy, bio-energy,…,etc. Fortunately, Taiwan appears to be a good place to develop of wind power generation, especially in the west coast and the islands around Taiwan.nduction generators have been widely used for wind power generators due to their low cost. When they are driven by a variable speed wind turbine tend to have poor voltage regulation. As a result, how to improve the voltage profile of a wind power generation system is of major concern in this work.o stabilize the output voltage of a wind power generation system, a dynamic voltage regulator, which comprises a voltage source inverter and a dc capacitor, is proposed in this thesis. Through the modulation of the real and reactive power outputs of the DVR, the dc capacitor voltage and the ac system voltage can be held at the specified values. Through dynamic simulations using MATLAB/Simulink, the effectiveness of the proposed dynamic voltage regulator in regulating the output voltage of a wind power generator is demonstrated.誌謝 i要 iibstract iii錄 iv目錄 vi目錄 ix一章 緒論 1.1 研究背景與動機 1.2 文獻回顧 2.3 風力發電機簡介 6.4 研究方法 7.5 論文內容介紹 8二章 基礎理論分析 9.1 串聯補償器原理 9.1.1 電壓穩定度 13.1.2 暫態穩定度 14.1.3 電力系統振盪阻尼 15.2 串聯型補償器之發展 16.3 同步旋轉座標轉換 18三章 變流器設計 21.1 前言 21.2 脈波寬度調變（PWM）切換技術 21.2.1 弦式脈波寬度調變控制器 21.2.2 變流器切換頻率之分析 23.3 其他元件參數之決定 25.3.1 隔離變壓器之選定 25.3.2 濾波電感器之選定 26.3.3 補償器之容量計算 27四章 動態電壓調整器分析 28.1 前言 28.2 動態電壓調整器之實虛功分析 28.3 動態電壓調整器之控制 31.3.1 數學模型建立 31.3.2 解耦合電流控制 33.3.3 直流電壓及交流電壓之控制 37.4 動態電壓調整器之控制器 38五章 模擬結果與分析 39.1 前言 39.2 強系統（Strong System）下發電機轉速及負載變動 39.2.1 發電機轉速變動 41.2.2 負載變化 45.3 弱系統（Week System）下發電機轉速及負載變動 47.3.1 發電機轉速變動 47.3.2 負載變化 51.4 結果討論 53六章 結論 55.1 結論 55.2 未來研究方向 55考文獻 57者簡介 6
A New Visual Stimulation Program for Improving Visual Acuity in Children with Visual Impairment: A Pilot Study
No full textThe purpose of this study was to investigate the effectiveness of visual rehabilitation of a computer-based visual stimulation (VS) program combining checkerboard pattern reversal (passive stimulation) with oddball stimuli (attentional modulation) for improving the visual acuity (VA) of visually impaired (VI) children and children with amblyopia and additional developmental problems. Six children (three females, three males; mean age = 3.9 +/- 2.3 years) with impaired VA caused by deficits along the anterior and/or posterior visual pathways were recruited. Participants received eight rounds of VS training (two rounds per week) of at least eight sessions per round. Each session consisted of stimulation with 200 or 300 pattern reversals. Assessments of VA (assessed with the Lea symbol VA test or Teller VA cards), visual evoked potential (VEP), and functional vision (assessed with the Chinese-version Functional Vision Questionnaire, FVQ) were carried out before and after the VS program. Significant gains in VA were found after the VS training [VA = 1.05 IogMAR +/- 0.80 to 0.61 IogMAR +/- 0.53, Z = -2.20, asymptotic significance (2-tailed) = 0.028]. No significant changes were observed in the FVQ assessment [92.8 +/- 12.6 to 100.8 +/- SD = 15.4, Z = -1.46, asymptotic significance (2-tailed) = 0.144]. VEP measurement showed improvement in P100 latency and amplitude or integration of the waveform in two participants. Our results indicate that a computer-based VS program with passive checkerboard stimulation, oddball stimulus design, and interesting auditory feedback could be considered as a potential intervention option to improve the VA of a wide age range of VI children and children with impaired VA combined with other neurological disorders
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
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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