1,720,982 research outputs found
The influence of surface finishing on the electrocatalityc properties of nickel for the oxygen evolution reaction (OER) in alkaline solution
No full textAbstract-The oxygen evolution reaction (OER) was investigated at 60‘C in 15wt% NaOH solution on nickel electrodes. Different surface treatments such as sandblasting and/or chemical pickling were employed. Fresh and aged electrodes were subjected to electrochemical measurements. The galvanostatic electrochemical ageing was performed for 21 days, applying an anodic current equal to 150mAcm-“. From the Tafel plots for the OER, two well-defined Tafel slopes were observed for all the electrodes, before and after the electrochemical ageing. This behaviour is due to the transformation of Ni(OH), to p-NiOOH, which is the “right type of oxide” for the oxygen evolution reaction. The kinetic parameters obtained on the electrodes with different surface finishing show that the sandblasted/pickled nickel substrate loses its electrocatalytic properties for the OER early on in the experiment. 80 1997 International Association for Hydrogen Energ
Coatings for concrete and reinforced concrete protection
No full textThe rapid change in the environment in recent decades, caused by several human activities, has produced conditions causing
f requent and unexpect ed si t uat i ons of seri ous decay i n t he gene - r a l p r o p e r t i e s o f r e i n f o rc e d c o n c r e t e s t r u c t u r e s ( c i v i l c o n s t r u c - t i ons , gi r de r s , br i dge s , pi l i ngs , pi pe s , e t c . ) . Ac t ual l y t he s t r e n g h t o f c o n c r e t e a n d o f r e i n f o r c e d c o n c r e t e d e c r e a s e s o v e r t i me d u e to the deterioration of their costituents which are exposed to the o u t s i d e e n v i r o n me n t .
Besides the nature of aggressive atmospheric agents, other fac - tors depending on the intrinsic quality of concrete are to be con - s i d e re d f o r a c o m p l e t e a n a l y s i s o f t h e m a t t e r o f r e i n f o r c e d c o n - c re t e d u r a b i l i t y :
- t h e c h a r a c t e r i s t i c s o f c o n c r e t e c o n s t i t u e n t s ( c e me n t , a g g r e g a t e , w a t e r, a d d i t i v e s ) ,
- t h e p r o p e r t i e s o f t h e mi x ( w/ c r a t i o , g r a n u l o me t r i c c u r v e o f t h e aggregate),
- the construction techniques used,
- the curing conditions
When speaking about the possible alterations that can affect re i n f o rc e d c o n c r e t e i t i s i mp o r t a n t t o p o i n t o u t t h a t t h e s e a r e
a l wa y s a s s o c i a t e d wi t h wa t e r p e n e t r a t i o n o f t h e s t r u c t u re wa t e r plays a leading role in the degradation phenomena since it is the main vehicle for the penetration of aggressive agents such as
c hl or i de and s ul phat e i nt o t he c onc r e t e .
The penetration of the concrete by atmospheric carbon dioxide
i s t h e o t h e r ma i n f a c t o r l e a d i n g t o r e i n f o r c e d c o n c r e t e d e c a y . Some fundamental parameters that have to be considered to
a v o i d t h e p r e m a t u r e c o r r o s i o n o f t h e r e i n f o r c e me n t s a r e t h e q u a - l i t y o f t h e c o n c r e t e c o v e r , a n e c e s s a r y c o n d i t i o n f o r t h e p r oduc - tion of durable concrete, a minimum acceptable thickness of the c o n c r e t e c o v e r ( b e t w e e n 2 5 a n d 4 0 mm d e p e n d i n g o n t h e e n v i - ronmental conditions), a necessary condition to assure a dura - ble passivation of the steel embedded in the concrete [1]; an adequate w/c ratio (0,4) to minimise the permeability of the con - crete cover.
The most durable concrete is that with the highest impermeabi - lity, able to resist external aggression and protect the r einforce - ments from corrosion, but it is difficult to produce this on site, because of the high number of process variables, a possible
s o l u t i o n t o t h e d e g r a d a t i o n o f r e i n f o rc e d c o n c r e t e s t r u c t u re s i s the application of protective coatings to the concrete surface. T h i s c o a t i n g s , i f a p p l i e d o n n e w s t r u c t u re s a s s o o n a s t h e h a r d e - n i n g i s f i n i s h e d , h a v e t h e ma i n f u n c t i o n o f p r e s e r v i n g t h e p r o t e c - tive alkaline environment of the concrete so corrosion of the embedded steel cannot occur
Determination of the electrochemical characteristics of traditional and innovative antifouling paint systems by impedance measurements
No full textOxygen evolution on Co3O4 and Li-doped Co3O4 coated electrodes in an alkaline solution
No full textThe oxygen evolution reaction "OER# was investigated at 59>C in 04 wt) NaOH solution on Co2O3\ Li!doped Co2O3 and perovskite!type oxide "LaNiO2# electrodes[ Cobalt and Li!doped cobalt oxides were obtained by di}erent preparation techniques and were applied to chemically!pickled nickel plates[ The obtained phases were structurally characterized by X!ray powder di}raction[ The electrodes were subjected to electrochemical measurements\ before and after elec! trochemical ageing "10 days\ 049 mA cm−1#[ The correlation between the coating preparations and their electrocatalytic activity was investigated[ The e.ciency of the studied electrodes seems to depend on the preparation method[ Two Tafel slopes for the OER were observed in most cases[ This behaviour was interpreted on the basis of a change in the valence state of the surface oxide[ Þ 0888 International Association for Hydrogen Energy[ Published by Elsevier Science Ltd[ All rights reserved
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
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