1,721,083 research outputs found
Hannah Chow oral history interview recording and transcript
No full textThis recording and transcript form part of a collection of oral history interviews conducted by the Chao Center for Asian Studies at Rice University. This collection includes audio recordings and transcripts of interviews with Asian Americans native to Houston.Hannah Chow, interviewed by Yuanzhuo Wang and Pin-Fang Wang, July 14, 2010, in Houston, Texas
Esther Quan oral history interview recording and transcript
No full textThis recording forms part of a collection of oral history interviews conducted by the Chao Center for Asian Studies at Rice University. This collection includes audio recordings and transcripts of interviews with Asian Americans native to Houston.Interview of Esther Quan conducted by Pin-Fang Wang and Clarissa Cox, June 3, 2010 in Houston, Texas
George Gee oral history interview recording and transcript
No full textThis recording forms part of a collection of oral history interviews conducted by the Chao Center for Asian Studies at Rice University. This collection includes audio recordings and transcripts of interviews with Asian Americans native to Houston.George Gee, interviewed by Pin-Fang Wang and Tracey Lam, June 17, 2010, in Houston, Texas
Wea Lee oral history interview recording and transcript
No full textThis recording forms part of a collection of oral history interviews conducted by the Chao Center for Asian Studies at Rice University. This collection includes audio recordings and transcripts of interviews with Asian Americans native to Houston.Wea Lee, interviewed by Pin-Fang Wang and Yuanzhuo Wang, July 2 & 3, 2010, in Houston, Texas
Jane Gee oral history interview recording and transcript
No full textThis recording and transcript form part of a collection of oral history interviews conducted by the Chao Center for Asian Studies at Rice University. This collection includes audio recordings and transcripts of interviews with Asian Americans native to Houston.Jane Gee, interviewed by Pin-Fang Wang and Clarissa Cox, June 16, 2010, in Houston, Texas
Warm Season Afternoon Thunderstorm Characteristics under Weak Synoptic-Scale Forcing over Taiwan Island and Its Objective Prediction
No full text摘 要
台灣地區在弱綜觀環境條件下的暖季，午後對流(afternoon thunderstorm, TSA)為其主要的天氣型態，而其準確的時空預報極具挑戰性。由於雷達資料為本研究主要定義與特徵化午後對流之資料，為避免非氣象回波影響本研究分析結果，尤其在具複雜地形的台灣地區，故其品質控制(quality control, QC)為首要進行目標。本研究利用三年(2005–2007)的氣象局屬四座雷達回波資料建立其氣候統計資訊並結合地形以及其各掃描策略，所架構之各雷達具氣象條件影響之合成仰角(hybrid scan)，經評估可有效去除受地形雜波(ground clutter)及地形遮蔽(beam blockage)效應所影響之回波資料。
利用上述經QC的雷達資料，以及雲對地閃電、衛星、探空和地面氣象站等資料，探討在弱綜觀環境條件下共四年(2005–2008)的暖季(5–10月)午後對流特徵。在此期間，平均時雨量顯示其最大降雨量發生於1500–1600 LST (local standard time)間，而降雨的最大發生頻率則是侷限於平行於山脈走向的低斜坡帶上。進一步利用經QC的雷達資料將弱綜觀環境再區分為有發生午後對流(TSA days)及無發生午後對流(non-TSA days)兩類，其地面平均風向、溫度及露點溫度均呈現明顯差異。在TSA days期間，其對流前環境(preconvective environment)於近地面層具有相對較non-TSA days而言較暖(約0.3–2.4 °C)及較濕(約1.6–2.8 °C)的環境。探空除了顯示整層也有較為濕暖及較小風速的環境條件外，於850–650 hPa層間，露點差異在TSA days與non-TSA days間，可高達3.0–4.5 °C。
這些對流前的環境差異(預報因子)，可做為模糊邏輯算則(fuzzy logic algorithm)之隸屬函數(membership function)，提供TSA的客觀預報。由地面測站與探空資料所得的預報因子之特徵函數，可強調在TSA days與non-TSA days期間的對流前特徵差異。本研究建立的客觀預報TSA之fuzzy logic方法，整合28個隸屬函數，並根據最佳化臨界成功指數(critical success index, CSI)得其權重。這些權重可定量描述對流發生前相對較暖濕的綜觀環境、海風傳送水氣至內陸，以及內陸的弱風速等，皆為提供有利發展午後對流活動的條件。除此之外，持續性預報法(persistence forecast)亦可視為預報TSA的參考預報因子。經兩年(2009–2010)暖季(5–10月)之個案進行驗證並評估，顯示此客觀預報TSA的fuzzy logic方法可整合弱綜觀環境所呈現之各項對流前環境參數特徵，提供TSA的機率性預報，未來可進ㄧ步運用於作業中。
關鍵詞：回波氣候統計，合成仰角，午後對流特徵，對流前環境特徵，模糊邏輯算則，隸屬函數。Over Taiwan island with complex terrain, during the warm season (May–October) under weak synoptic-scale forcing, afternoon thunderstorms are the main weather system, and it is still faced the rigorous challenges to accurately forecast the thunderstorms on small temporal and spatial scales. In this study, quality control of radar reflectivity data is the primary procedure to accomplish since radar is the mainly dataset for identifying and characterizing afternoon thunderstorms (TSA). Three years’ of radar reflectivity data from four radars from 2005 to 2007 are analyzed and the reflectivity climatology is developed. The climatology is applied in the construction of climatology–based hybrid scans to minimize the impact of ground clutter and beam blockages.
The spatial and temporal characteristics and distributions of thunderstorms in Taiwan during the warm season (May–October) from 2005–2008 and under weak synoptic-scale forcing are documented using radar reflectivity, cloud–to–ground lightning, satellite, radiosonde, and surface observations. Average hourly rainfall amounts peaked in mid-afternoon (1500–1600 local standard time, LST). The maximum frequency of rain was located in a narrow strip, along the lower slopes of the mountains and parallel to the orientation of the mountains. Significant diurnal variations are found in surface wind, temperature, and dewpoint temperature between days with and without afternoon thunderstorms (TSA and non-TSA days). Before thunderstorms occurred, on TSA days, the surface temperature was warmer (about 0.3–2.4 °C) and the surface dewpoint temperature was moister (about 1.6–2.8 °C) than non-TSA days. Sounding observations from northern Taiwan also showed warmer, higher moisture, and smaller wind–speed conditions on TSA days relative to non-TSA days. The largest average difference was in the 850–650 hPa layer with values of 3.0–4.5 °C drier on non-TSA days. And, wind speeds on non-TSA days between near surface and 6 km were 2–3 m s–1 stronger than on TSA days.
A fuzzy logic algorithm has been proposed to provide the objective guidance for the prediction of TSA using these membership functions of preconvective factors. Features functions of thunderstorms are derived from surface stations and sounding measurements that highlight the preconvective characteristics of days with TSA that best differentiate them from synoptically undisturbed days. There are total 28 membership functions and associated weights in fuzzy logic approach are derived and determined based on the optimization of the critical success index (CSI). The results quantitatively illustrate that synoptically relatively warmer and moister conditions, sea breezes transport moisture into the inland, and weak winds in the inland provide the proper conditions in inducing afternoon convective activity. In addition, the relatively simple persistence rule is also useful for prediction of afternoon thunderstorms, i.e., there is high probability that afternoon thunderstorms occur consecutively for a few days when the environmental conditions are right. Evaluation with the validation dataset (2009–2010) suggests that the fuzzy logic algorithm has the capability to integrate the preconvective factors and provide the probability guidance for the predictions of TSA, and the highly predictive potential that could be implemented in real-time operations
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
Optical and Material Characteristics of InAs/GaAs Quantum Dots and Ga2O3/GaAs Thin Film
No full text本論文主要研究熱退火處理之砷化銦/砷化鎵量子點與氧化鎵/砷化鎵薄膜的光學與材料特性，依其熱退火條件與環境的不同下做各種研究，內容大致分成三大部份：
(一) 在As4 環境下熱退火處理之砷化銦/砷化鎵量子點的研究：
砷化銦量子點是採用MBE製程生長在半絕緣的砷化鎵基板上，並在上以不同的熱退火溫度成長砷化鎵間隔層，使用原子力顯微鏡(AFM)、 變溫及變功率光激發螢光量測系統來做觀測比較與分析。由AFM實驗可知生長溫度較低者有較大的量子點產生及最小的密度，隨著溫度變高，量子點的尺寸變小密度變大；由光激發螢光(PL)實驗可知生長溫度較低者峰值有最高的能量與較高的強度，隨著溫度上升，峰值能量與強度皆變小。由此可知，量子點中的電子能量跟量子點的大小有極大的關係，越大的量子點會導致樣品有越小的能量。我們也藉由峰值位置、半高寬、峰值強度與溫度變化之間的關係，分別對各退火溫度之樣品做分析，發現到熱退火溫度為五百度C之樣品其光學特性較佳，活化能也最小，代表著此樣品其品質較佳，量子點的大小與密度也最均勻，而後由變功率光激發螢光實驗也證明此一論點。
(二) 在P2 環境下熱退火處理之砷化銦/砷化鎵量子點的研究：
此部份樣品其生長條件與之前量子點雷同，只是在不同的氣體環境下熱退火成長砷化鎵間隔層。由AFM實驗可知，隨著溫度變高，量子點的生長遭到破壞而消失，這跟磷原子與砷原子之間的化學鍵結有關係，當熱退火溫度越高其化學反應越劇烈，砷磷化銦的形成轉而取代砷化銦並造成量子點的減少。由光激發螢光(PL)實驗可知生長溫度較低者峰值有最高的能量，隨著溫度上升，峰值能量逐漸變小。而在熱退火溫度為五百度C的樣品中，我們在其變溫光激發螢光(PL)實驗中觀測到有趣的現象，其內部量子點所造成的大小峰值強度會隨著溫度增加而改變，此現象可以用來解釋量子點內部載子隨溫度變化的移動情形。
(三)熱退火處理之三氧化二鎵薄膜成長的研究：
三氧化二鎵薄膜以濺鍍方式成長在砷化鎵基板上，藉由X射線光電子能譜儀(XPS)分析，知道其不同熱退火條件下的樣品束縛能產生變化，推測熱退火溫度的不同造成樣品結構的改變。之後又經由掃瞄式電子顯微鏡(SEM)與X射線能量散佈分析儀(EDX)實驗，證實其氧原子與鎵原子的比例確實隨著熱退火溫度不同而改變。最後再藉由X射線繞射儀(XRD)分析，由其峰值改變以及半高寬的減少判定樣品的品質與熱退火溫度之間的關係。This thesis concerns with the studies on the optical properties and material characteristics of thermal annealing InAs/GaAs quantum dots and Ga2O3/GaAs. Many optical measurements are carried out to study the physical properties according to the conditions of thermal annealing. Many peculiar phenomena have been observed, which are very useful for understanding as well as application of these materials.
(1) Characterization of the InAs/GaAs quantum dots with spacer annealed under AS4：
InAs quantum dots were deposited onto GaAs layer with different growth temperature spacer layer by molecular beam epitaxy and compared using temperature dependence photoluminescence measurements, power dependence photoluminescence measurements and atomic force microscope (AFM).From the AFM measurement, we can know the sample annealed at lower temperature has lager size quantum dots and smaller density of quantum dots. And the size of quantum dots is getting smaller and the density of quantum dots is getting larger as the annealing temperature increase. The photoluminescence energy was considerably increased for samples grown in lower temperature. So the energy of quantum dots related with the size of quantum dots. We also analyzed samples by the peak positions, FWHMs, and PL integrated intensity as a function of temperature. The sample annealed at 500 has better optical properties and less activation energy and the density of quantum dots is most uniform. Power-dependent photoluminescence measurements also confirm the contention.
(2) Characterization of the InAs/GaAs quantum dots with spacer annealed under P2：
The samples had the same growth conditions just annealed under P2. From the AFM charts, the amount of quantum dots is destroyed and decreased. It rely on the bonding of phosphorus atoms and arsenic atoms. When the annealing temperature is getting higher, the chemical reaction is getting violent, so the alloy of InPxAs1-x was grown instead of InAs. The photoluminescence energy was decreased for samples grown in higher temperature. And we find an interesting phenomenon in the temperature-dependent photoluminescence measurement of the sample annealed at 500 . The two broad peaks are attributed to the combined size distribution of the bimodal quantum dots. The change of peak intensity between them can be explained the movement of the carriers in the quantum dots as the temperature increased.
(3) Characterization of thermal annealing Ga2O3 thin films：
Ga2O3 thin films were deposited onto GaAs substrate with different annealing temperature. We can know the change in binding energy as the different annealing temperature and suppose the composition of samples is changed by X-ray Photoelectron Spectroscopy (XPS) measurement. Subsequently, we confirmed the increase of ratio of oxygen to gallium assuredly as the annealing temperature increased by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) measurement. Finally, from the X-ray diffraction (XRD) measurement analysis, we can identify the relations between the quality of the interface and annealing temperature by the increased peak positions and decreased FWHMs in the spectra.口試委員審定書......................................I
誌謝...............................................II
中文摘要…………………………………………………..…...III
Abstract…………………………………………………..…..…V
Contents….………………………………………………......VIII
Last of Figure and Table..........................................................XII
Chapter 1
Introduction………………………………………………...…...1
1.1 Nature and Applications of InAs Quantum Dots…………....….....1
1.2 Nature and Applications of gallium oxide materials………….…...4
Reference…………...…………………………………………….……6
Chapter 2
Experimental Principle、Set Up and Measuring Method ...10
2.1 Atomic Force Microscopy (AFM)…………………………..……10
2.2 Photoluminescence………..………………………………….…..14
2.2.1 The Principle of Photoluminescence…..........................…..14
2.2.2 Measurement System Set Up of Photoluminescence….......20
2.3 X-ray Photoelectron Spectroscopy (XPS)…..............................…21
2.4 X-ray diffraction (XRD)…………………………………………25
Reference…………………………………………………….………30
Chapter 3
Design, Growth, and Characterization of InAs/GaAs Quantum Dots….........................................................................33
3.1 Introduction of Quantum Dot…………………………..………...33
3.2 Optical Transitions in Self-Assembled Quantum Dots………..…42
3.3 Annealing Experiments…….........................................……… …45
3.4 Characterization of the Samples with Spacer Annealed under AS4.................................................................................................48
3.4.1 Low Temperature Photoluminescence measurements results and analysis…......................................................................50
3.4.2 Temperature-dependent Photoluminescence measurements results and analysis.........................................................….51
3.4.3 Power-dependent Photoluminescence measurements results and analysis….................................................................….64
3.5 Characterization of the Samples with Spacer Annealed Under P2…...............................................................................................66
3.5.1 Low Temperature Photoluminescence measurements results and analysis…..........................................................70
3.5.2 Temperature-dependent Photoluminescence measurements results and analysis…..........................................................71
3.6 Summary……………………………………………………….....79
Reference…………………………………………………..…………83
Chapter 4
Optical Characterization in Ga2O3 Thin Film...................…..87
4.1 Introduction of Ga2O3 ……............................................................87
4.2 Structural and Optical Properties of Ga2O3 Thin Film.............….88
4.2.1 X-ray Photoelectron Spectroscopy (XPS) measurement results and analysis...............................................................89
4.2.2 Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray spectroscopy (EDX) measurement results and analysis..........................................................................92
4.2.3 X-ray diffraction (XRD) measurement results and analysis.97
4.3 Summary…....................................................................................99
Chapter 5
Conclusion…........................................…………………….…103
Appendix A
Optical Studies of YAG Crystals ............................................106
A.1 Introduction¬ of YAG Crystals.............................................................106
A.2 Experimental Methods…………………………..…..............………109
A.3 Results and Discussion…………………….……...…………...……110
A.3.1 Room temperature photoluminescence measurements results and analysis of YAG crystals ………………...……………….110
A.3.2 Room temperature optical transmission measurements results and analysis of YAG crystals…………...………...……………111
A.3.3 Raman scattering measurements results and analysis of YAG crystal……………...………...………………………….……..113
A.4 Conclusion..........................................................................................120
Reference………………………………………...………………………121
Appendix B
X-ray diffraction (XRD) Spectra of Ga2O3 / GaAs Thin Film…………………………………………………………....122
Appendix C
Fourier Transform Infrared Spectroscopy (FTIR) Spectra of Ga2O3 / GaAs Thin Film……………….......12
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