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Structured recovery of defective graphene by chemical vapor deposition
No full text石墨烯(graphene)是由碳原子所組成，僅有單原子厚度的材料。石墨烯具有獨特的物理性質，比如高速的電子遷移率，良好的機械強度，高度的化學穩定性。有鑒於常見的力學剝落法(mechanical exfoliation)無法得到可以進行工業以及工程應用的大面積石墨烯，近年來已發展出利用化學液相剝落法，將石墨分離成近似單原子厚度的氧化石墨烯(graphene oxide)。氧化石墨烯具有諸多優點，例如面積比傳統力學剝落法廣大，可達到毫米等級的面積;生產過程簡單，利用修飾過的Hummers method，可以大量地被製備。然而，化學方法製備得到的氧化石墨烯之物理性質，以及電性上的表現卻無法和石墨烯的電性比擬。由於製備過程是在酸性溶液中進行，所以不可避免的氧化石墨烯附著了大量的酸根。因此，如何對氧化石墨烯進行有效率的還原，使其物理性質與化學結構可達到石墨烯的水準，成了一個有趣的研究方向。
本論文的第一部分，著重於如何將電化學方式製備的石墨烯(electrochemically exfoliated graphene)晶格上，於製備過程中所帶來的缺陷，比如銜接了功能基(functional group)後轉變成了不完整晶格結構，利用高溫爐以及氫氣，氬氣，甲烷，在攝氏1000度到1500度之間對電化學方式製備的石墨烯進行退火還原以其結構上的修復以及還原。為了釐清還原機制，以及樣本的物理以及化學性質，利用拉曼散射光譜儀(Raman spectroscopy)，X射線光電子能譜(XPS)量測分析，原子力顯微鏡，對樣本進行最直接的量測與分析以對石墨烯的結構之還原機制作驗證。
本論文的第二部分將討論將氧化石墨烯(graphene oxide)在金屬元素，銅，作為催化劑下，進行高溫退火以及化學氣相沉積法，移除鍵結於氧化石墨烯之晶格上的功能基，並且在銅的催化之下，幫助氧化石墨烯之晶格上的碳原子重新排列形成六角苯環。初步的研究成果觀測到，氧化石墨烯顏色變深，代表其已經被強力還原;還原的樣本之拉曼光譜數據則顯示出，氧化石墨烯原本的非定相結構(amorphous structure)，在銅的催化下，轉變為 sp2鍵結結構。銅在化學氣相沉積法方式製備石墨烯中扮演了石墨烯結晶的平台，但是能否扮演有效修補氧化石墨烯結構的角色仍然未知，此為本論文第二部分待為討論的方向。Graphene, a single layer of carbon atoms in a honeycomb network lattice, has attracted many interests due to its unique physical properties and high optical transparency. In order to achieve large scale production, the electrochemical exfoliation of graphene was demonstrated. However, the honeycomb lattice of as-exfoliated graphene was damaged due to the slight oxidation in the synthesis process.
The main goal of this thesis focuses on the recovery efficiency of the sp2 domain in the graphene-like composites by different heat treatments, utilizing a combination of argon (Ar) and hydrogen (H2) at a temperature between 1000oC and 1500oC and methane (CH4) alone at around 900oC, respectively. In the first part of this thesis, the chemical vapor deposition process, flowing an Ar-H2 mixture at a temperature above 1000oC, utilized to recover the broken honeycomb structure in the defective graphene will be demonstrated. The evolution of the crystallite-domain size in the defective graphene has been monitored and studied by the Raman spectra and the X-ray photoelectron spectroscopy (XPS).The recovery of the sp2 structure in the honeycomb network was revealed from the Raman spectroscopy by the decreasing ratio of D band to G band integrated intensity and the increase of the 2D-to-G integrated intensity ratio. The Tuinstra-Koenig (TK) relation is also used for the characterization of the crystallite-domain size in the annealed samples. XPS measurement was also conducted to characterize the different binding energies of oxygen-containing functional groups in the annealed samples to discover the changes, which may be referred to the loss of oxygen atoms occupying the sp3 carbon sites during the heat treatment, of the atomic structures.
The second part of this thesis investigated the efficiency of recovering the sp2 domain in the carbon honeycomb structure by annealing the graphene oxide (GO) in a chemical vapor deposition (CVD) process using methane (CH4), in which the carbon atom can repair the interrupted sp2 network, as a precursor at a lower processing temperature. Prior to the CVD process, a thin film of copper was deposited onto the GO film by thermal sputtering because copper has been known as an effective catalyst to assist the carbon adatoms to access the broken carbon bonds for the recovery of the graphene structure. The Raman spectra of the reduced graphene oxide (rGO) processed by this method demonstrate a narrowing of G band and an increasing intensity ratio of 2D to G band reaching a value of 0.76, which is a significant improvement compare with a value of ~0 from an amorphous GO
Thermal Flow Field Design for Package of EV`s Range Extender
No full text本研究以華擎開發的車用發電機組（增程發電系統）為研究對象，利用模組化的包覆性結構將增程發電系統放置於結構內，此結構內部含有引擎支撐架及引擎腳作為增程發電系統與結構間的隔振，隔音擋板進行降噪，藉此達到較佳的NVH效果。其中隔音擋板使噪音降低的同時，伴隨著問題是散熱的效果下降導致內部流場溫度升高，使得各元件無法作在適當的操作溫度下運作，造成元件效率下降甚至損毀。為了解決彼此參數互相衝突的情況，本論文與降噪之論文一併進行全面性參數探討影響彼此程度的關係，並利用影響散熱程度較大的參數進行散熱流場的優化設計。本論文研究的工具以商用軟體Fluent進行散熱流場的分析，利用田口式直交表找出針對擋板的安排方式及外殼結構形狀對散熱流場影響較大的參數因子，進而利用此參數因子提出一組最佳的設計，最後加入影響降噪的參數因子如擋板的安排來探討彼此的消長關係，提出一版兼具散熱及降噪效果的包覆性結構。In this study, a vehicle manufacturer’s Genset is used as our object. Using a modular package that covering the Genset , and the modular will has benefit with good performance of vibration isolation by the mounting systems and low nosing by the baffle , in order to get high NVH performance , on the other hand the baffle will let the cooling performance getting lower , led to the objects are working in the high temperature environment , and the objects will getting lower efficiency or even destroying . In order to solve the conflicting relationship with each other , this study in conjunction with the noise of the paper conducted a comprehensive parameter exploring the impaction of the extent of their relationship , and then use the large extent parameters to optimizing the thermal flow design . In this study the commercial software Fluent is the tool for thermal analyzing , which analyzing the influence of the flow field with the arrangement of baffle and the shape of package , the optimum solution will be found out in the section. Arrangements will be concerned both with the acoustic impact factor and thermal management , the acoustic and cooling performances of the developed low noise engine generator set will be found out in the end.1. 第一章：緒論 1
1.1 研究動機與目的 1
1.2 研究架構 3
1.3 研究流程與方法 4
1.4 使用軟體簡介 5
1.4.1 ANSYS Workbench 5
1.4.2 計算流體力學軟體-Fluent 6
1.4.3 流場視覺化軟體-CFD-post 6
1.5 論文架構 7
2. 第二章：文獻回顧 9
2.1 熱傳遞方式 9
2.1.1 熱對流 10
2.2 文獻回顧 11
2.3 田口式直交表實驗法 19
2.3.1 信號雜訊比 20
3. 第三章：包覆性結構雛形設計 24
3.1 結構參數設計 24
3.2 實驗周邊元件製作 25
4. 第四章：散熱流場模擬與驗證 30
4.1 實驗設計 30
4.2 實驗結果 32
4.3 軟體模型建立 36
4.3.1 模擬分析流程圖 36
4.3.2 統御方程式 37
4.3.3 散熱模型建立 38
4.4 軟體模型計算結果 40
4.5 實驗與軟體之比對驗證 41
5. 第五章：包覆性結構優化設計 44
5.1 優化設計流程圖 44
5.2 初始設計及計算結果 47
5.3 散熱流場之優化 49
5.4 散熱流場暨降噪聲場之優化 63
5.5 本章小結 76
6. 第六章：結論與未來方向 78
6.1 研究結論 78
6.2 未來研究方向 79
參考文獻 8
Supplemental Material - Clinical metagenomics-assisted diagnosis of relapsed HIV-associated cryptococcal meningitis
No full textClinical metagenomics-assisted diagnosis of relapsed HIV-associated cryptococcal meningitis by Ting-Kuang Yeh, Kuan-Pei Lin, Yu-Chuan Chuang, Li-An Wang, Chih-Jun Chen, Ding-Yu Lee, Yao-Ting Huang, Po-Yu Liu in International Journal of STD & AIDS</p
Association among Serum Perfluoroalkyl Chemicals, Glucose Homeostasis and Metabolic Syndrome in Adolescents and Adults
No full textOBJECTIVE - Perfluoroalkyl chemicals (PFCs) have been used worldwide in a variety of consumer products. The effect of PFCs on glucose homeostasis is not known. RESEARCH DESIGN AND METHODS - We examined 474 adolescents and 969 adults with reliable serum measures of metabolic syndrome profile from the National Health and Nutrition Examination Survey 1999-2000 and 2003-2004. RESULTS - In adolescents, increased serum perfluorononanoic acid (PFNA) concentrations were associated with hyperglycemia (odds ratio [OR] 3.16 [95% Cl 1.39-7.16], P < 0.05). Increased serum PFNA concentrations also have favorable associations with serum HDL cholesterol (0.67 [0.45-0.99], P < 0.05). Overall, increased serum PFNA concentrations were inversely correlated with the prevalence of the metabolic syndrome (0.37 [0.21-0.64], P < 0.005). In adults, increased serum perfluorooctanoic acid concentrations were significantly associated with increased beta-cell function (beta coefficient 0.07 +/- 0.03, P < 0. 05 ). Increased serum perfluorooctane sulfate (PFOS) concentrations were associated with increased blood insulin (0.14 +/- 0.05, P < 0.01), homeostasis model assessment of insulin resistance (0.14 0.05, P < 0.01), and beta-cell function (0.15 +/- 0.05, P < 0.01). Serum PFOS concentrations were also unfavorably correlated with serum HDL cholesterol (OR 1.61 [95% Cl 1.15-2.26], P < 0.05). CONCLUSIONS - Serum PFCs were associated with glucose homeostasis and indicators of metabolic syndrome. Further clinical and animal studies are warranted to clarify putative causal relationships
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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