1,720,979 research outputs found
Fabrication and Emission Properties of Stable Dual Ion/Electron Point Sources
No full text我們利用銦鉍合金可製造出一種穩定的雙重點狀離子／電子發射源。把銦鉍合金作為液態金屬離子源時，低熔點的特性使他跟商業化的產品-鎵離子源一樣擁有非常好的離子發射性質。在離子源冷卻凝固之後，我們用場發射電子顯微術去研究其電子發射特性。我們也證明利用電化學蝕刻鎢針，可以改進銦鉍合金的電子發射性質，使它能跟目前所發現到具有最好電子發射特性的金銦合金離子／電子發射源之性質相接近。而在研究強電子發射與發射源表面形貌之間的關係時，我們也觀察到一個有趣的現象﹕鎢針鍍上銦之後，在長時間強電子發射下，原本堅固的鎢金屬會產生原子遷移。而這個遷移傾向於形成一個穩定的特殊幾何結構。我們發現鍍上銦的鎢針在經過這樣的過程之後，可以被用作一個擁有非常好電子發射特性的雙重點狀離子／電子發射源。對於未來更進一步發展單軸聚焦離子／電子束系統來說，銦鉍合金離子／電子發射源的發展以及適當地調控發射源，都是重要的突破。We fabricate a stable dual ion/electron point source based on In-Bi alloy. As a liquid metal ion source (LMIS), its emission performance at about 70 – 100℃ is comparable to that of commercial Ga-LMIS. After the In-Bi source is solidified, field electron microscopy is employed to study the pattern of electron emission. In-Bi alloy is inherently soft so that its electron emission is easy to be unstable. To remedy this disadvantage, the In-Bi alloy is loaded onto a sharp tungsten tip fabricated by electrochemical etching. The resulting source exhibits electron emission characteristics comparable to that of Au-In alloy.
We also investigate the correlation between surface morphology of an In/W emitter and its electron emission behavior and observe that, after long-term electron emission, some underlying W migrates to the surface. We attribute the tungsten migration to high electron emission current density. Interestingly, the migration leads to a protrusion with specific geometry on the apex of tip and such an In/W emitter constitutes a dual ion/electron emitter with good electron emission properties. Furthermore, stable ion and electron emission can be interchangeably extracted from the source. Both the successful fabrication of the In-Bi/W and In/W stable dual ion/electron point sources are important steps towards the further development of single-column focused ion/electron beam systems.Chapter 1
Introduction and motivation 2
Chapter 2
Emission properties of a dual ion/electron 5
point emitter based on In-Bi alloy
Chapter 3
Fabrication of a stable dual ion/electron source 16
with very bright single-point electron emission
Chapter 4
Summary 25
Appendix 2
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
Testing theories for thermal transport using high pressure
No full textThis dissertation focuses on experimental studies of thermal transport in various materials, such as heat transfer in crystals and amorphous polymers, and across interfaces, using an ultrafast pump-probe method, time-domain thermoreflectance (TDTR), combined with gem anvil cell techniques. I demonstrated that pressure tuning of physical properties of materials is an elegant approach to test the validity of theories for thermal transport.
Pressure dependence of the cross-plane thermal conductivity Λ(P) of a layered muscovite mica crystal was measured by TDTR combined with diamond anvil cell techniques. Under a simple relaxation time approximation, most of the Λ(P) of muscovite mica can be described by the pressure dependence of the cross-plane sound velocity, indicating that the cross-plane sound velocity plays an important role in the thermal transport in a layered crystal.
The validity of the minimum thermal conductivity model for amorphous polymers was verified by the good agreement between my measurements of the pressure dependent thermal conductivity of poly(methyl methacrylate) (PMMA) and the model prediction. The thermal energy exchange between non-propagating vibrational modes is the dominant mechanism of thermal transport in amorphous polymers.
I also used high pressure to demonstrate the importance of interface stiffness on the interfacial thermal transport. By measuring the pressure dependence of thermal conductance G(P) of clean and modified Al/SiC interfaces, I found that G(P) of a clean interface with high interface stiffness is weakly dependent on pressure and can be well accounted for by the diffuse mismatch model (DMM). By contrast, G(P) of modified interfaces with low interface stiffness initially increase rapidly with pressure; as the interface stiffness is increased to be comparable to the stiffness of chemical bonds, G(P) saturate at the value for the clean interface and value predicted by the DMM.
In order to extend the TDTR measurements to high pressures and high temperatures, I studied the pressure dependent thermoreflectance and piezo-optical coefficient of metal film transducers—Al, Ta, and Au(Pd) alloy (≈5 at. % Pd) at a laser wavelength of 785 nm. The thermoreflectance of Ta and Au(Pd) are comparable to that of Al at ambient conditions and independent of pressure in the range 0<P<10 GPa. Ta and Au(Pd) also present strong acoustic echo strengths in this pressure range. I conclude that Ta and Au(Pd) films can replace Al as metal transducers and extend TDTR to higher pressures and temperatures.Item withdrawn by Mark Zulauf ([email protected]) on 2011-07-20T15:07:43Z
Item was in collections:
University of Illinois Theses & Dissertations (ID: 1)
No. of bitstreams: 2
Hsieh_Wen-Pin.pdf.pdf: 1377619 bytes, checksum: dee6edd7172e7f322969239744ab8611 (MD5)
Hsieh_Wen-Pin.pdf: 1377619 bytes, checksum: dee6edd7172e7f322969239744ab8611 (MD5)Made available in DSpace on 2012-02-06T20:08:25Z (GMT). No. of bitstreams: 2
Hsieh_Wen-Pin.pdf: 1377471 bytes, checksum: 0460a217d3507c748a2e41295eebe465 (MD5)
license.txt: 4058 bytes, checksum: b2c7a4217becd586814cc6d5745fb598 (MD5
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
