1,720,983 research outputs found
Electronic Configuration and Bond Characterization on Ni, Cu and Se Containing Compounds through Charge Density Studies and X-ray Absorption Spectroscopy
No full text一系列以含硫且具自身氧化能力的配位基MNT (maleonitriledithiolate； S2C2(CN)2)所形成的金屬-硫錯合物(PyH)z[M(MNT)2] (M = 鎳、銅；z = 2、1)，展現了位置選擇性的氧化還原性質。金屬的K-edge及L-edge X光吸收光譜分別對鎳與銅金屬氧化態提供了直接的證據。在鎳錯合物的系統中，氧化還原反應發生在具自身氧化還原能力的配位基上(Ligand-Based)。相反地，在銅的錯合物系統中，氧化還原反應發生在金屬銅本身(Metal-Based)。此外，硫的X光吸收光譜配合DFT計算亦提供了金屬-硫鍵結的資訊，結合鎳、銅金屬及硫的X光吸收光譜結果確認了此系列樣品的氧化還原性質。經由高解析的低溫X光單晶繞射數據所得到的電子密度分析，藉由變型電子密度分析及鍵臨界點的拓樸分析也提供了金屬-配位基的鍵結特性。由多極模型導出的金屬d軌域電子分佈及monopole charge皆驗證了XAS所提出的氧化還原性質。
含第四週期元素硒原子之樣品的電子密度研究：第一個樣品為3,4-trimethylene-6a-selenaselenophthene，此分子包含了一接近線型排列且具有三中心四電子鍵結特性的三核硒鏈型部分。第二個樣品為平面四方形的鎳-硒錯合物Ni[Se2P(O-iPr)2]2，其分子間具有微弱的硒-硒作用力(3.294A)，有趣地，透過分子內及分子間的硒-硒作用力形成了平面四方的硒原子網狀結構，結合拓樸分析及Hirshfeld surface證實了微弱的分子間硒-硒作用力。
為了合理解釋以atr (azotriazole)為架橋配位基的三維及二維自旋交叉錯合物Fe(atr)3(ClO4)2‧2H2O與Fe(atr)(pyz)(NCS)2 之兩階段自旋交叉的磁行為與結構的關係，進行了詳細的磁性量測實驗，證實三維系統中兩階段的磁行為是取於晶格中溶劑分子的存在與否，且二維與三維的樣品皆明顯地展現出晶格中的溶劑分子影響磁行為改變的溫度，溶劑影響自旋交叉現象的也成功地利用X光單晶結構解析加以證明。A series of metal-sulfur square planar complexes, (PyH)z[M(MNT)2], where M = Ni and Cu, MNT a non-innocent ligand maleonitriledithiolate, [S2C2(CN)2]z-, z=2, 1, are synthesized in order to characterize the site-selected oxidation-reduction properties. Metal K-edge and L-edge X-ray absorption spectroscopy(XAS) are used to deliver the direct evidence for the oxidation state of metal ion. It is clearly demonstrated that redox reaction takes place in the ligand (Ligand-Based) for Ni complexes but in the metal (Metal-Based) for the Cu complexes. In addition, the sulfur K-edge absorption together with the DFT calculation gives a clear picture on the covalency of M-S bond. With the XAS of metal and S, the oxidation reduction site is firmly established for Cu and Ni complexes. The charge density studies from high resolution single crystal X-ray diffraction measurements at 100K are also investigated to aim at the understanding on the nature of the metal-ligand bond in terms of deformation densities and topological properties associated with the bond critical points (BCP). The d-Orbital populations of metal ion derived from multipole model and the monopole charge thus obtained are agreeable with the redox properties established from XAS.
Charge density studies on Se-containing compounds are undertaken: 3,4-trimethylene-6a-selenaselenophthene contains a linear tri-selenium chain in the molecule, which exhibits a three-centered four-electron bond for Se-Se-Se part. A square planar Ni complex bonded with four selenide ligands, Ni[Se2P(O-iPr)2]2 is studied. Ni-Se bonds are characterized together with the short intermolecular Se-Se contact of 3.294 A. Interestingly, there is a Se square network in the crystal through the intra- and inter- molecular Se×××Se contacts. Such contacts are first characterized by topological analysis and Hirshfeld surface mapping.
The magnetic measurements of three-dimensional and two-dimensional atr-based Fe(II) spin crossover (SCO) framework systems (Fe(atr)3(ClO4)2‧2H2O and Fe(atr)(pyz)(NCS)2‧4H2O) are studied in detail in order to solve the puzzle of the stepwise spin transition phenomena. It is found that the stepwise transition is due to the loss of water molecules in the lattice, where the hydrated/dehydrated forms of 2D and 3D systems apparently exhibit quite different transition temperatures. The solvent-dependent spin crossover phenomena in these structures are systematically demonstrated
Electron Density Study of Sulfur Chain Containing Compound “2,5-Dimethyl-3,4-trimethylene-6a-thiathiophthene” using X-ray diffraction, XAS and DFT calculation
No full textThiathiophthene(TTP)為一具有兩個五圓雜環及硫-硫-硫直鏈的平面分子，由於此種分子擁有非常不尋常的的鍵結特性及芳香性質，因此引起了相當大的興趣與討論。為了嘗試瞭解此種獨特的鍵結情況，我們利用X-ray單晶繞射技術及DFT理論計算來研究其衍生物2,5-dimethyl-3,4-trimethylene-6a -thiathiophthene (C10H12S3)。我們分別在室溫(295K)及低溫(100K)收取了繞射數據，室溫時空間群C 2/m，而當溫度降低到100K時，空間群轉變成P 21/n，其原因是原本室溫時垂直二轉軸的鏡面消失了，此種對稱降低的情形也同樣地顯現在TTP的另一個衍生物2,5-Dimethyl-6a-thiathiophthene上。室溫時，兩硫硫之間的距離皆為2.33419(8)Å，但當溫度降到100K後，兩硫硫之間的鍵長明顯地變不一樣了，距離分別為2.3274(5)及2.3393(5) Å。為了更深入瞭解此鍵結特性，在實驗方面，利用X光單晶繞射的結果獲得分子的總電荷密度分佈後，引入Coppens等人所提出的多極模型精算理論，將球形原子模型擴展到非球形原子模型，使得電荷更符合分子內原子的狀態。在理論方面，我們利用密度泛函理論的方法求得分子的電子密度分佈，所選用的基底函數為B3LYP 6-31G**，硫的部份則多加一個擴散函數。由實驗與理論兩方面的結果配合拓樸學分析，使我們更瞭解分子的鍵結型態，也證實了中央的硫原子為電子密度較低的，兩側的硫為電子密度較高的。此外，利用費米孔洞分析也證明了兩個五圓環的芳香性及兩硫原子之間為稍弱的共價鍵性質。最後，我們再利用X光吸收光譜來進一步對不同的硫做探討。Thiathiophthene(TTP), a planar molecule with two fused heterocyclic five-membered rings and essentially a linear S-S-S bond, is a molecule of great interest due to the unusual bonding characters and the possible aromatic properties of the two five-memberd rings. In order to understand the remarkable bonding properties, the electron density distribution of one of the derivatives, i.e. 2,5-dimethyl-3,4-trimethylene-6a -thiathiophthene (C10H12S3), was investigated both by single crystal X-ray diffraction and by DFT calculations. The X-ray crystal structure of C10H12S3 was studied both at 295 K and at 100 K. The Space group is C2/m at 295 K, which is transformed to P21/n at 100 K. The mirror symmetry perpendicular to 2-fold axis disappears at low temperature. Such reduction of symmetry elements was also found in a previous study on the 2,5-dimethyl-6a-thiathiophthene. The bond lengths of two S-S bonds are crystallographically same [2.3341(8)Å] at 295K, but are significantly different [2.3274(5) and 2.3393(5) Å] at low temperature. The experimental electron density is produced according to multipole model. The theoretical electron density is calculated by DFT calculation, where the basis set of 6-31G** is used for all the atoms but an additional diffuse function is added for S atom. Results on the electron density distribution will be presented in terms of deformation density, Laplacian maps and the topological properties. Sulfur K-edge X-ray absorption spectroscopy (XAS) is also undertaken to further our knowledge on the electronic configuration of S atom.中文摘要................................................Ⅰ
英文摘要................................................Ⅱ
目錄....................................................Ⅲ
表目錄..................................................Ⅵ
圖目錄..................................................Ⅷ
第一章 序 論.............................................1
第二章 原 理.............................................4
2-1. X光單晶繞射.......................................4
2-2.多極模型與淨電荷分析...............................6
2-2-1.單極精算.......................................6
2-2-2.多極精算.......................................7
2-2-3.淨電荷分析.....................................8
2-3.拓樸學分析理論.....................................9
2-3-1. Atoms in Molecules理..........................9
2-3-2. 電荷密度的拓樸分析...........................10
2-3-3.原子圖像......................................17
2-4.費米孔洞分析......................................18
2-5.理論計算..........................................19
2-5-1. HF-SCF簡介...................................19
2-5-2. DFT簡介......................................20
2-5-3. MPA簡介......................................22
2-6. X光吸收光譜......................................23
2-6-1.同步輻射加速器設施..............................23
2-6-2.吸收光譜原理....................................23
第三章 實驗與結構分析...................................26
3-1.實驗方法..........................................26
3-1-1.晶體合成與命名................................26
3-1-2. X光單晶繞射實驗..............................26
3-1-3. X光繞射數據分析..............................29
3-1-4. 吸收校正.....................................30
3-2.結構解析..........................................34
3-2-1.室溫及低溫結構討論............................34
3-2-2.TTP衍生物結構比較.............................42
第四章 電荷密度分析.....................................46
4-1.多極模型精算之軸向設定............................46
4-2.多極精算..........................................47
4-3.拓樸學分析........................................48
4-3-1.剩餘電子密度......................................49
4-3-2.分子內作用力......................................50
4-3-3. TTP衍生物之臨界點性質比較....................59
4-3-4. S-S, S-C, C-C的鍵臨界點性質比較..................62
4-3-5. VSCC (Valence Shell Charge Concentration)........67
4-4.靜電荷分佈........................................69
4-5.費米孔洞分析......................................71
第五章 X光吸收光譜分析..................................73
5-1.吸收光譜實驗方法..................................73
5-2.吸收光譜數據分析與討論............................75
第六章 結 論............................................83
參考文獻................................................84
附錄一. Nobel Prize ( about x-ray ) ....................88
附錄二. Atomic fractional coordinates at 298K...........89
附錄三. LT Bond distances and bond angles...............89
附錄四. RT Bond distance and bond angles................90
附錄五. Internal coordinate setting.....................90
附錄六. Macro...........................................9
Design the upnp player which can play rmvb in Linux by using ip spoofing concept
No full text由於近幾年UPNP和DLNA的堀起，可以輕易的建立一個數位家庭，讓整個家裡只要架一個電腦server，在家裡任何一個地方只要有網路和電腦，就可以立即讀取存放在server的多媒體資料(如：電影、mp3)，也不需要安裝任何驅動程式。而且現在很多電腦都有支援UPNP的功能，所以只要架設一台UPNP Server就可以提供多媒體資料讓Client使用。目前Linux和Windows都有提供Server的架設軟體，所以都可以輕易的建立一台server，至於client的部分，兩個OS也都有提供，但是最大的缺憾就是很少可以支援rmvb檔的部分。簡單的說，mpeg的影片可以透過upnp利用streaming的方式播放，但是大部分的播放軟體都不支援rm檔的播放。為了解決這類的問題，所以要設計一個軟體來達到這個目的，既可以播放rm檔又擁有upnp的功能。此外，為了安全性的問題，希望提供影片的電腦，可以隱藏不讓外部Client知道是從那台電影傳送影片，所以運用IP spoofing的概念，將傳送出去的封包利用程式把Server的IP更改掉，讓Client誤以為是從別台電影傳送影片封包，即使被攻擊，真正的Server端也不會受到侵害。Because the contribution of UPnP and DLNA, we can build a digit home. We can access the server which is set in home by using any device supported UPnP without installing any driver. Any multimedia put on the UPnP server can be used easier by any UPnP client.Both Linux and Windows have UPnP server software, so it is very easy to set up a UPnP environment. Both operating system have UPnP client, but all the player can not play rmvb movies. For example, mpeg movies can be played through UPnP by using streaming. But no player can play rmvb movies by using UPnP. We want to design a program to play rmvb movies through UPnP.We hope the server supported multimedia can hide the server IP when send the packets to client. This uses the IP spoofing concept to change the server IP when send the streaming packets. The client thinks the packets are come from the IP we change. We can avoid the server attacking by hacker.誌謝 I要 IIbstract III目錄 VI一章 序論 1.1 研究動機 1.2 研究問題 1.3 研究目標 2二章 系統背景 3.1 UPNP and DLNA 介紹 3.1.1 UPnP簡介 3.1.2 UPnP運作方式概述 6.1.3 DLNA簡介 8.2 Mplayer and VedioLAN 10.2.1 MPlayer： 10.2.2 Vlc 12.3 UPNP Server和Client的現行例子 13.3.1 UPNP Server： 13.3.2 UPNP Client： 17三章 系統實作 23.1系統概念 23.2系統背景 23.2.1 UPNP Library 23.2.2 整合Mplayer 24.2.3 個人防火牆 24.2.4 WinPcap 25.3 實作困難 25.3.1 播放器 25.3.2 個人防火牆 26.3.3 WinPcap 27.4 系統實作 27.4.1 UPNP Player： 27.4.2 費爾防火牆： 27.4.3 Winpcap： 29四章 系統操作與展示 31.1 UPNP Player播放影片 31.2 封包的轉送與接收 33五章 效能比較 39六章 未來展望 42.1 系統操作心得與改進 42.2 UPNP的連結和搜尋 42.3 整合網頁、UPnP、IP spoofing 42.4 自動填寫IP 43考文獻 4
Structural Phase Transition without Accompanied Spin Transition of Complex t-{Fe(abpt)(2)[N(CN)(2)](2)}
No full textBond Characterization on a Cr-Cr Quintuple Bond: A Combined Experimental and Theoretical Study
No full text
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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