1,720,978 research outputs found
Preparation, processing and analysis of physical properties of calcium ferrite-CNTs/PET nano-composite
Get PDFThe present work is focused on the preparation of composites based on Poly(ethylene terephthalate) (PET) and novel nano-hybrid filler composed of Calcium Ferrite (CF)-Carbon Nanotubes (CNTs), obtained by direct growth of CNTs on CF based iron catalysts. The carbon content in the hybrid filler was 76 wt%. Composites loaded with 1.0, 1.5, 2.0, 3.0 wt% of filler were obtained by melt compounding and processed by thin-wall injection molding. Unfilled Poly(ethylene terephthalate) was processed using the same techniques. Structural characterization and physical properties (thermal, mechanical and electrical) were analyzed and correlated to the hybrid filler loading, and to the percentage of carbon nanotubes
Hydrogenation of citral and cinnamaldehyde over bimetallic Ru-Me/Al2O3 catalysts
No full textHydrogenations of citral and cinnamaldehyde have been investigated over Ru-Me/Al2O3 (Me = Ge, Sn, Pb). Two series of catalysts have been prepared by using the controlled surface reaction (CSR) technique (RuEC series) and the more conventional co-impregnation method (RuNI series). Addition of Ge increases the catalytic activity on the RuEC series whereas no modifications are found on the samples prepared by co-impregnation. The selectivity to unsaturated alcohols is not influenced by the presence of Ge. Addition of tin increases both the activity and the selectivity regardless of the preparation method. The presence of lead does not modify the selectivity and a slight decrease in the catalytic activity is observed on the sample of the RuNI series. On the basis of the characterization data available on the investigated catalysts, it is suggested that Ru and Ge interacts when the samples are obtained through the CSR technique, Such an interaction increases the catalytic activity likely through a decrease of the strength of adsorption of one of the reaction components. The positive effect of tin on the catalytic activity and selectivity is discussed
Effect of alternating humidity and dryness on the durability of adsorbent sheets used in open cycle adsorption processes
Get PDFSilica gel based composite materials are considered as promising materials in open-cycle adsorption processes for water vapor adsorption/desorption. However, their long-term performance under fluctuating humidity conditions remains unclear. This study investigates the role of alternating humid and dry aging cycles on the mechanical and water vapor adsorption properties of silica gel-polymer matrix composite sheets. Controlled humid/dry cycles mimicking real operating conditions were applied to the sheets, followed by tensile strength and water vapor adsorption tests to assess performance degradation. The aim was to understand how these cycles affect the sheets' ability to capture and release water vapor effectively over time. The findings show the material's good hydrothermal stability, maintaining mechanical strength and water vapor adsorption after aging. The 50–100–0 samples had the lowest performance post-aging (average strength and modulus of 1.13 MPa and 26.8 MPa, respectively). Critical conditions occur in long aging cycles, such as 40–1000 and 50–1000 batches, leading to substantial performance decline post-drying, hinting at slight permanent damage. The 50–1000 batch showed a tensile modulus of 34.8 MPa after 7 days of dry storage, about 18.8 % less than unaged samples. This information serves as a preliminary approach for optimizing the material design of these sheets for open-cycle adsorption applications. By identifying potential weaknesses arising from humidity cycling, the study paves the way for improvements that ensure long-term effectiveness and reliability in these systems
Stability of Adsorbent Sheets Under Accelerated-Aging Tests for Open-Cycle Adsorption Processes
Get PDFThis study aims to assess the stability of silica gel/polymer composites designed for open-cycle air dehumidification, humidification, and heat storage by employing a comprehensive set of characterization methods. To evaluate their resistance to various environmental factors, the materials were subjected to a series of aging treatments: (i) repeated adsorption/desorption cycles under representative operational conditions; (ii) post-drying at 30 °C, 40 °C, and 60 °C; (iii) immersion in water for 30 days; (iv) exposure to a salt–fog environment for 30 days; and (v) accelerated aging by alternation between wet and dry cycles. Prolonged exposure to liquid water significantly reduced the material’s stability, resulting in an 83% reduction in tensile strength after 30 days of immersion. However, discontinuous exposure to liquid water at low drying temperatures did not critically affect the material’s mechanical properties during wet/dry cycles. Furthermore, post-drying (performed at 22 °C and 50% RH) allows the recovery of mechanical performance, with a tensile strength reached comparable to those of the unaged composites. Similarly, adsorption/desorption cycles in water vapor did not trigger degradation in the material, with its water vapor adsorption capacity remaining comparable to the unaged material after 100 cycles. The results confirm the reliability of these composite materials as to their potential uses in open-cycle dehumidification, humidification, and heat-storage applications
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
Novel Nanomaterials for Thermochemical Storage
Get PDFThe book offers recent developments in terms of thermochemical energy storage materials (TCM), covering the full temperature range of application, low, medium and high. Beginning with a review of the recent advancements in the field of adsorption thermal energy storage systems, this book goes on to discuss innovative TC nanomaterials, in terms of synthesis, characterization and validation
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
