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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
An approach for developing a preliminary cost estimating methodology for USCG vessels
Get PDFThesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1987.Bibliography: v. 2, leaves 287-291.by Mark James Gray.M.S
The effect of molecular anisotropy on the properties of liquid crystals
No full textIn this Thesis we present the results of investigations into the effect of structural changes on the liquid crystalline properties of poly-aromatic molecules . Following a brief introduction to various aspects of liquid crystalline phases, we describe the synthesis and characterisation of two homologous series of halo substituted 4"-n-alkyloxy-p-perphenyls, namely the 4-alkyloxy-4"-fluoro-p-terphenyls and 4-alkyloxy-4"-choloro-p-terphenyls. The physical properties of these novel compounds are compared with those of the analogous cyano substituted compounds. In Chapter 3 we describe the synthesis of a number of specifically deuteriated 4-alkyloxy-4"-cyano-p-terphenyls and 4-alkyl-4"-cyano-p-terphenyls. The effect of the linking oxygen atom on the liquid crystalline phases formed by these materials is investigated using deuterium NMR spectroscopy.The remainder of this work is concerned with dimeric liquid crystals, where two mesogenic moieties are connected via a flexible alipahtic chain. Chapter 4 describes the synthesis and characterisation of a number of novel homologous series in which the 4-cyanophenyl group is linked to the 4-cyanobiphenyl and 4-cyano-p-terphenyl moieties, namely the α-(4-cyanophenyloxy)-ω-(4'cyanobiphenyl-4-yloxy) alkanes, the α-(4-cyanophenyloxy)-ω-(4"-cyano-p-terphenyl-4-yloxy) alkanes and the α-(4-cyanophenyloxy)-ω-(4"cyano-p-terphenyl-4-yl) alkanes. In Chapter 5 we describe the synthesis and characterisation of the biphenyl analogues to the compounds described in Chapter 4, the α-(4'-cyanobiphenyl-4-yloxy)-ω-(4"cyano-p-terphenyl-4-yloxy) alkanes and the α-(4'-cyanophenyl-4-yloxy)-ω-(4"cyano-p-terphenyl-4-yl) alkanes. The unusual smectic phase that is observed for two of these materials is then investigated using ESR and NMR. These results are compared with those obtained for model compounds known to form a smectic A antiphase.</p
Carbon-based negative electrodes for rechargeable lithium batteries
No full textChapter Four presents an extensive study of single cycle experiments carried out on a variety of electrode composites containing various quantities of coke, carbon fibre and carbon black conductivity additives. It has been shown that the first cycle is very important in determining the usefulness of electrode materials for multiple cycle experiments. It has also been shown that particle size and the quantity of conductivity additive within the electrode composite has a significant effect on the performance of the electrode. A new, high surface area, carbon fibre, SA86, has been studied and it has been shown that the surface area has a detrimental effect on the cycling behaviour of this material. The affect that interparticle contact has on the capacities of fibrous electrodes has been demonstrated. Scanning electron microscopy has been used to probe the degradation that these electrodes suffer during the course of the insertion-extraction cycle and a method of presenting the insertion data has been used to show regions of lithium plating.. A preliminary study of the diffusion coefficient of lithium within these electrode composites, calculated from the insertion data, has been undertaken.Chapter Five uses the results from Chapter Four to aid in the choice of electrode composites that will be cycled a number of times. It has been shown that by raising the lower potential limit to values above the lithium plating region, cycling efficiencies of 99% can be obtained over multiple cycles. It is also evident that the better fabricated, preprepared electrodes have higher capacities and cycling efficiencies than those that have not been ball-milled.</p
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