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Wool fabric plasma treatment: resulting properties evaluation and applications in field
No full textIndustry is on a continuous way to search new treatments and novel technologies to
reduce costs, increase productivity, decrease waste generation and treatment. The
textile industry is characterized by mature processes and its breakthrough has
necessarily to come from technological transfer from research. Plasma treatment being
based on a gaseous technology does not require to use many chemicals, as well as the
precious resource given by freshwater. In this view, plasma treatment of textile
materials appears very promising in replacing a number of current wet chemical
processes, or at least, intensifying them.
Plasma is commonly known as the fourth state of matter, being constituted by ionized
gas in a neutral state with an equal density of positive and negative charges. It consists
of a fast evolving mix of ions, electrons, free radicals, meta-stable excited species,
molecular and polymeric fragments. Additionally, a high energetic content given by
visible, UV and IR radiations characterizes plasmas.
Decades of development have allowed researchers and scientists to confine
geometrically plasma, control its energy and develop applications in material processing
and waste reduction by designing devices suitable to very many industrial uses.
Although plasma treatments have been used for years to process materials including
semiconductors, microchips, and other electrical and electronic components, only
recently the textile industry has considered the use of plasma for fabric processing with
particular emphasis given to the surface of this material. Plasma treatments are
classified among nanotechnologies since they interact with the fiber surface only and do
not alter the properties of the fiber core.
Plasmas can be classified according two major categories: thermal and non-thermal. A
thermal plasma is characterized by a very high temperature and it is not suitable for
applications to heat-sensitive materials. A non-thermal plasma is generated at moderate temperature and it is suitable for heat-sensitive materials such as textiles. Non-thermal
plasmas are also known as low-temperature plasmas (LTP) and can be classified into
many different categories depending on operating pressure, type of power supply (lowfrequency,
radio-frequency and microwave) and geometrical arrangements.
Plasmas modify the surface of materials by transferring energy from the excited plasma
particles to the substrate. Thanks to this interaction, both chemical and physical
modifications can be obtained. The mechanisms, which give origin to these
modifications, include surface etching, surface activation, cross-linking, chain scission,
de-crystallization, oxidation and surface chemical reactions. The reaction type depends
largely on the type of gas used. For instance, inert gases such as argon and helium
typically generate surface activation. Compounds that contain oxygen are commonly
used as etching gases. Most likely, nitrogen is prone to cause reduction reactions.
Pre-treatment and finishing of textile materials with LTP offers many advantages over
conventional chemical processes, because most part of LTP surface modification
treatments do not require use of water or chemicals and are characterized by an
extremely low energy need. The possible applications of LTP in the textile field are
commonly dyeing and finishing oriented; they include several types of functionalization
such as hydrophilic enhancement to improve wetting, dyeing or adhesive bonding.
Hydrophobic enhancement gives origin to water- and oil-repellent textiles. It is
possible to change physical and/or electrical properties, clean surfaces, remove sizing
agents, and perform surface sterilization of fiber at room temperature. Although most
of the LTP treatments on polymeric materials, including textiles, developed by
researcher have been carried out using low-pressure plasma, the atmospheric pressure
plasma has demonstrated to be a much more interesting technology for large-scale
applications. However, data and results from low-pressure plasma applications can be
used to predict, compare or optimize atmospheric pressure plasma processes.
In the work of this PhD research project all plasma treatments used are conducted at
atmospheric pressure with a variety of gases such as nitrogen, oxygen, helium, argon a
mixture of them and ambient air. Only atmospheric plasma equipment were selected
because of easy applicability in a continuous mode, by considering that according to
economical reasons, the evolution of textile technologies is oriented to continuous
processes.
In this thesis, Chapter I gives a general description of the LTP physics, main plasma
generation systems and processing equipment, including also typical applications.
In Chapter II a brief description of the selected textile characterization methods adopted
in this work is provided. SEM, ATR-FTIR and XPS analyses, wettability tests, air and
water vapor permeability measurement, tensile strength and low-stress mechanical
properties test were selected to characterize and evaluate textile modifications carried
out by plasma. Additionally, also the transformation mechanisms are enlightened. Chapter III comparatively describes the effect of three kinds of atmospheric plasma
treatment. These treatments, finalized to wool fabric hydrophilicity enhancement, were
performed in reducing, oxidizing and neutral conditions.
A novel wool fabric dyeing process is described in Chapter IV. This process, requiring
plasma as a pre-treatment, gives emphasis to water and energy saving, as well as to
process productivity. Then, the fabric produced was characterized according to standard
methods.
The study presented in Chapter V deals with the comparison of a standard pad-dry-cure
coating process for water- and oil-repellent finishing with respect to a plasma
intensified pad-dry-cure coating process and a plasma enhanced chemical vapor
deposition (PECVD) process. These two innovative processes were performed to
improve coating durability, reduce chemical consumption and avoid the least use of
water, as in the PECVD case
Design criteria of continuously operating biological aerated filters
No full textBiological Aerated Filter (BAF) represent a compact wastewater technology aimed at improving treatment effectiveness by contemporarily minimizing the volume of the sludge-to-water contactor. BAFs can be classified as three-phase systems as far as their hydrodynamics is concerned and make use of granulated activated carbon (GAC) as a solid support; the macro-pores of this solid immobilize the growing biomass and assure a high sludge-to wastewater flow rate ratio. Our study stars from the standard design criteria adopted for a batch unit and extends the application of BAFs to continuous systems to attain simpler operations. The new concept unit is implemented with an air-lift regulated GAC recirculation and a section for separating the sludge from GAC. The treated water is segregated from the sludge suspension thanks to a careful regulation of flow rates in the biological reactor, which has some similarities with the so-called "backwash upflow sand filter". The experimental work, ahead of treating wastewater from textile industries, defines all the operating variables suitable to steadily maintain the contact time between the liquid and solid phases, the hold-up and recirculation time of GAC and the flow rate ratio between the cleared stream and purge liquid. The experimentation has brought to define: the geometrical features of the unit, GAC hold-up and recirculation rate, main and air lift flow rates. In this research program a 0.28 m ID, 2 m high Perspex unit is used for the hydrodynamical study and an identical geometry SS biological contactor for real industrial wastewater treatmen
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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