1,721,056 research outputs found
A thermodynamic study of phase equilibria in the Sn-Bi-Pb solder system
No full textAs a basis for the design and development of low-temperature solder alloys, the thermodynamic calculation of phase equilibria has been carried out on the binary Bi-Pb and ternary Sn-Bi-Pb systems over the entire composition range. The Gibbs free energy of individual phases has been approximated using the sub-regular solution model and thermodynamic parameters for each phase have been evaluated using available experimental information on phase boundaries and other related thermodynamic properties. The calculated phase diagrams and thermodynamic quantities of the Bi-Pb binary system show good agreement with the experimental data, and the liquidus projection and vertical sections in the Sn-Bi-Pb ternary system are well reproduced using assessed thermodynamic parameters derived in this work
Calculation of surface tension and wetting properties of Sn-based solder alloys
No full textThis study has been supported by the Minstry of Science and Technology (MOST) through the Center for Interface Science and Engineering of Materials (CISEM
Novel synthetic strategy for developing an isospeciric unbridged metallocene system for propylene polymerization
No full textNew unbridged zirconocenes functionalized with a Lewis base, [{1(E-C6H4)-3,4-Me(2)C(5)H2}(2)ZrCl2] (E = pNMe(2) (3); p-OMe (4); p-SMe (5)) were prepared and their propylene polymerization behavior was examined. Under methylaluminoxane (MAO) activation at atmospheric monomer pressure, these complexes afford mixtures of polymers exhibiting multimelting transition temperatures and broad molecular weight distribution, whereas they produce completely atactic polypropylenes under [Ph3C][B(C6F5)(4)] activation. Stepwise solvent extraction of the polymer mixtures reveals that the polymers consist of amorphous, moderately isotactic, as well as, highly isotactic portions and the weight ratio of each portion is dependent upon reaction temperature. The generation of rigid rac-like cationic active species in situ by the interaction between basic sites of catalysts and acidic sites of the [Me-MAO](-) counter anion is considered to be the origin of the observed isospecificity. Further investigation of bulk polymerization in liquid propylene shows not only a considerable increase of the isotactic portion of the obtained polypropylenes but also apparent isospecificity of 4 and 5/MAO systems even at high temperature. Variation of the Lewis basic center leads to a dramatic change in stereoselectivity of the catalyst in the decreasing order of 3 > 4 >> 5, in spite of their structural similarity.CMDSACHTUNGTRENUNG(KOSEF), POMRC, and the BK-21 projec
Endowing aspecific, unbridged-metallocene propylene-polymerization catalysts with isospecificity: The unprecedented role of MAO
No full textCMDS
POMRC
BK-21 project
Honam Petrochemical C
Effect of under bump metallurgy and reflows on shear strength and microstructure of joint between Cu substrate and Sn-36Pb-2Ag solder alloy
No full textThe interfacial reaction between Sn-36Pb-2Ag (numbers are all in mass% unless specified otherwise) solder balls and Ni, Ag and Ni/Ag electroplated on a Cu substrate was investigated and the joint bonding strength was measured using a ball shear tester. The intermetallic Ag(3)Sn was observed at the interface of the Cu/Ag/solder joint and Ni(3)Sn(4) was found at the Cu/Ni/solder joint. In the case of Cu/Ni/Ag substrate, the layer sequence was observed to be Cu/Ni/Ni(3)Sn(4)/Ag(3)Sn/solder. The Ag layer was completely consumed by formation of Ag(3)Sn but the Ni layer remained. Environmental tests showed that the Cu/Ni/Ag substrate retained better solder joint reliability than either Ni or Ag single plated Cu substrate. Two types of reflow profiles were tested and the specimen reflowed by a higher temperature profile showed a higher solder joint strength. Solder joint strength and microstructural change were observed with several reflow cycles in considering the real board mounting conditions. There was significant evolution of solder and joint microstructures with reflow cycles and it explained well the change of solder joint strength.This study has been supported by the CEPM (Center for Electronic Packaging Materials) of the KOSEF (Korea Science and Engineering Foundation)
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
5 similar to 6 GHz-band GaAs MESFET-based cross-coupled differential oscillator MMICs with low phase-noise performance
No full textLC-tank oscillators in the 5similar to6 GHz frequency range have been designed and implemented in a commercial 0.6 mum GaAs MESFET technology. One is a voltage-controlled oscillator (VCO), and the other is an oscillator without a controlling element. The output frequency range of the VCO is from 5.44 to 6.14 GHz, and the measured phase-noise is -101.67 dBc/Hz at an offset frequency of 600 KHz from the 5.44 GHz carrier. The phase-noise of the 6.44 GHz oscillator is -108 dBc/Hz at an offset frequency of 600 KHz, and the phase-noise curve, in the offset frequency range between 100 KHz and 1 MHz, shows a -20 dB/decade slope. These phase-noise characteristics are comparable to, or better than, those of the reported 5similar to6 GHz-band CMOS oscillators. To our knowledge, this is the first GaAs MESFET-based oscillator which has a cross-coupled differential topology and a capacitive coupling feedback to suppress the up-conversion of 1/f noise. Also, it is first reported that the GaAs MESFET-based oscillator shows 1/f(2) phase-noise behavior across the offset frequency range from 100 KHz to 1 MHz
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