1,721,050 research outputs found
Development of aluminium-copper die-attach alloy for high operational temperature application / Siah Meng Zhe
Full text linkDie attach material plays an important role in electronic packaging as it serves as an interconnection between SiC device and substrate, provides physical and mechanical support and serves as a heat dissipating path. An aluminum-copper (Al-Cu) nanopaste formulated by mixing Al and Cu nanoparticles with organic additives (i.e., resin binder, terpineol and ethylene glycol) which is meant for high-temperature die-attach applications has been developed. Various weight percent of V006A (4%,5%,6% and 7%) and the Al loading (10%, 20%, 30% and 40%) have been loaded into the Al-Cu nanopaste, followed by sintering in open air at temperature of 380°C for 30 min without the need of applied external pressure. The physical and electrical properties were investigated. X-ray diffraction results showed that Al2Cu and CuO phases were formed in sintered Al-Cu nanopaste. Overall, Al-Cu nanopaste with 5% V006A has exhibited the best electrical conductivity [21??.cm], lowest oxygen element [15.36%] and smallest crystallite size [8.15nm], which is suitable for high temperature electronic applications. Also, Al0.5-Cu4.5 demonstrated the lowest electrical resistivity at 21.70 ??.cm, which is acceptable for a high temperature die-attach material
Summary of the Doctoral Thesis By MENG Zhe-nan and the Examiner's Comments
Full text link4KJ00006708919論文Articledepartmental bulletin pape
Poly(ethylene oxide)- lithium zirconium phosphate sulfophenylphosphonate nanocomposites for solid polymer electrolyte and their application in lithium polymer batteries
No full text由於良好的化學穩定性及低成本，Poly(ethylene oxide) (PEO)系統固態高分子電解質受到廣泛研究，然而其室溫傳導度及離子遷移係數較差，必須升溫才可以應用。引入奈米陶瓷粒子於高分子主體PEO中，可以抑制PEO的結晶度，進而提升離子傳導性質。 本研究首將磷酸鋯衍生物lithium zirconium phosphate sulfophenylphosphonate (ZrSPPLi)導入PEO系統。ZrSPPLi為表面及內部皆飾有磺酸鋰之非晶質奈米粒子，其平均直徑大小為30nm。PEO-ZrSPPLi複合高分子電解質經由混合PEO(Mn~600K)、LiClO4、ZrSPPLi溶液於乙腈，並採用溶劑揮發法製備。我們系統化的研究ZrSPPLi添加量對PEO-ZrSPPLi複合電解質的熱性質，機械性質，傳導性質，電化學穩定性和鋰金屬電池充放電行為的影響。 在含有1wt%的ZrSPPLi之12系列電解質表現出最佳的傳導性質和電池充放電效率。由於ZrSPPLi抑制PEO的結晶度，其室溫的離子傳導度相較於無添加ZrSPPLi之電解質提升二倍。於60oC，鋰離子遷移係數自0.25提升到0.37，電化學穩定性可達4.8V，使用磷酸鋰鐵為陰極，鋰金屬為陽極，所組裝得鋰金屬電池，展性出優良的穩定性及庫倫效率。於0.8C的放電電容量可達138 mAh g-1。Poly(ethylene oxide)-based solid polymer electrolytes (SPE) have been the most studied solid state electrolyte system for lithium batteries because of good chemical stability and low cost. Nevertheless, low ion conductivity, low lithium transference number (tLi+) and the need of operating at elevated temperatures severely challenged the success of this system. Introducing ceramic nanofillers into PEO matrix to form nanocomposites has been the most adopted approach to enhance the transport properties of PEO-based SPEs by suppressing the crystallinity of PEO. In this research, lithium zirconium phosphate sulfophenylphosphonate (ZrSPPLi) is synthesized and incorporated into PEO for the first time . ZrSPPLi is an amorphous nanoparticle containing lithium sulfonate groups both within and at the surface of the globular particles with an average diameter of 30nm. The PEO-ZrSPPLi nanocomposites with different ZrSPPLi loading and EO/Li ratio are prepared by solvent-casting from the solution mixture of as-synthesized ZrSPPLi, PEO (Mn ~ 600k) and lithium perchlorate (LiClO4). Systematic studies regarding the loading amount of ZrSPPLi on ion conductivity, lithium transfer number( tLi+), mechanical property, thermal property as well as the performance of lithium metal battery and electrochemical stability are performed. The composite with 1 wt% ZrSPPLi loading in EO/Li = 12/1 matrix exhibits the best transport property and cell performance among all composites. Comparing to the reference SPE without ZrSPPLi, the ion conductivity at room temperature is 2 times higher due to significantly suppressed crystallinity of PEO. With the addition of 1 wt% ZrSPPLi, tLi+ at 60oC would increase to 0.37 from 0.25 of the pristine PEO SPE and the composite exhibits a stable electrochemical window of 4.8V. The LiFePO4 /(PEO)12LiClO4-1wt%ZrSPPLi /Li battery operating at 60oC demonstrates good capacity retention and columbic efficiency at various discharge rate. The discharge capacity could reach 138 mAh g-1 at 0.8C
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
- …
