1,721,564 research outputs found
Synthesis and characterization of thermoelectric materials : bulk and nanostructure approach
No full textThe potential of a material for thermoelectric applications is determined by it's dimensionless thermoelectric figure of merit. A promising route to enhance ZT is the use of guest atoms in oversized cages as in intermetallic clathrates or filled skutterudites. The new cage compound Ce4[Ce tief 4]Pt12[Pt tief 12]Sn25[Sn tief 25] is investigated in this aspect. Nevertheless, our experimental result shows that the thermoelectric figure of merit of Ce4[Ce tief 4]Pt12[Pt tief 12]Sn25[Sn tief 25] is small compared to the traditional thermoelectric materials. This is primarily due to its metallicity. However, Ce4[Ce tief 4]Pt12[Pt tief 12]Sn25[Sn tief 25] turned out to be interesting in a different context. It is a strongly correlated material with a low- lying antiferromagnetic transition that can be continuously suppressed by a magnetic field of 1 T and thus exhibits a quantum critical point.The zero-field resistivity reveals Landau Fermi liquid behavior and a gapped spin wave contribution with [Delta] = 0.54 K. Above TN [T tief N] a sublinear temperature dependence is observed up to 1.9 K that might be explained by short-range order fluctuations and/or the opening of the spin gap [Delta]. The low-temperature electrical resistivity measurements of Ce4[Ce tief 4]Pt12[Pt tief 12]Sn25[Sn tief 25] in various magnetic fields show the evolution of its antiferromagnetic state with magnetic field. Another cage compound, Ce3[Ce tief 3]Ru4[Ru tief 4]Sn13[Sn tief 13], is an interesting compound in view of both its peculiar crystal structure and its rich low-temperature properties. At room temperature, Ce3[Ce tief 3]Ru4[Ru tief 4]Sn13[Sn tief 13], behaves like an ordinary paramagnetic metal. The susceptibility shows deviations from Curie-Weiss behavior only below 50 K. These deviations are due to the formation of a gap, due to crystalline electric field (CEF) splitting of the ground state multiplet of Ce3+[Ce hoch 3+] or due to antiferromagnetic correlations. The existence of crystal fields, as well as the high-temperature effective moment for Ce3[Ce tief 3]Ru4[Ru tief 4]Sn13[Sn tief 13], suggests a localized Ce3+[Ce hoch 3+] state. There is a well-defined specific heat anomaly confirming the transition observed in the electrical resistivity measurement below 2 K. The resistivity and specific heat measurements confirm that this anomaly is due to antiferromagnetic (AFM) ordering. By optimizing nanowire diameters, the power factor can be increased by quantum confinement and the lattice component of the thermal conductivity can be reduced by scattering. FeSb2[FeSb tief 2] has been considered as a novel thermoelectric material due to a giant Seebeck coefficient at low temperatures. However, due to the large lattice thermal conductivity, the dimensionless thermoelectric figure of merit is small. Various techniques were attempted to synthesize FeSb2[FeSb tief 2] nanowires; the solvothermal technique in an autoclave, a membrane filling technique using alumina nanochannel matrices, and a vapor-liquid-solid mechanism.The former route yielded so far the best results. FeSb2[FeSb tief 2] nanowires were also fabricated by focussed ion beam (FIB) cutting.PtSn4[PtSn tief 4] single crystals were obtained as a by-product in the process of synthesizing Ce4[Ce tief 4]Pt12[Pt tief 12]Sn25[Sn tief 25].The high quality of the samples made it possible to observe quantum oscillations in both the magnetization M(H) and the resistivity with fields along the three principal crystallographic directions. Due to their proximity with the theoretical value we could assign most of the experimentally observed dHvA frequencies with different sheets of the Fermi surface of PtSn4[PtSn tief 4]. Another approach to reduce phonon thermal conductivity is site substitution with iso-electronic elements to preserve a crystalline electronic structure while creating large mass contrast to disrupt the phonon path. The thermoelectric figure of merit of FeSi is low, mostly due to the high lattice thermal conductivity.This can be reduced for instance by a partial substitution of Fe by an iso-electronic element
Nano-lasers and nano-LEDs
No full textOne-dimensional nanostructures have been of great interest for photonic devices. In this talk I will give a review of the one-dimensional ZnO nanostructures for ultraviolet and visible regions. I will discuss earlier and last results regarding room temperature and low temperature spontaneous and stimulated emission. For lasers we will discuss both optically and electrically pumped lasers. For the LEDs particularly I will discuss the white light emission from LEDs. Substrates like graphene, paper, textile and semiconductors will be discussed. Finally, also results from other devices based on hybrid materials will be analyzed
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
Sensing Technologies for Real Time Monitoring of Water Quality
No full textWiley_Sensing Technologies for Real Time Monitoring of Water Quality_978-1-119-77581-2.pd
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
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
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