305,381 research outputs found
Investigation of electroless nickel undercoat for duplex nickel chromium electrodeposition onto aluminium and its alloys
No full textA thesis submitted in partial fulfillment of the requirement of the University of Wolverhampton for the
Degree of Master of Philosophy.The study investigates the deposition of a multilayer coating onto two aluminium alloys: Al 1050 and Al 6061. Of particular interest has been the treatment of the surface of both these samples for deposition of metallic coatings through a zincate based immersion process. The zinc immersion layer chemically displaces the oxide film on Al 1050 and Al 6061 and then zinc is deposited followed by nickel and chromium electrodeposition. Superior adhesion was associated with uniform, thin and fine grained deposits from Bondal solution which exhibited rapid and complete coverage of both aluminium samples. The metallurgical characteristics of the aluminium alloys and the processing sequence developed had a significant influence on the growth and morphology of the deposits from the Bondal solution and affected subsequent adhesion of electroplated nickel and chromium. This engendered the treated surface with sufficient catalytic nature to be able to receive a subsequent electroless nickel layer together with finishing layers of electrolytic nickel and chromium respectively. Due to the favourable physical properties of aluminium and its alloys (density, strength to weight ratio), there is a growing demand for nickel/chromium coated aluminium components for automotive and other applications. The most common method currently is to directly electroplate nickel onto the aluminium substrate. However, this can lead to problems with components having complex geometry in that chemical attack on the pretreated aluminium can occur in low current density areas before the substrate can be completely covered with nickel due to the acidic nature and high temperature of the nickel electroplating process. One way of preventing this current density related problem is to use an electroless nickel undercoat before the nickel/chromium deposit is applied. The mechanism by which this occurs is not fully understood and it is an objective of the current research to investigate the mechanism of nucleation of the electroless nickel layer on zincated aluminium. Results of X-ray photoelectron spectroscopy showed that the zincated layer was dissolved in the electroless nickel bath but zinc was detected below 10 nm from the top surface of the homogenous nickel phosphorus film, while aluminium and alloying elements from both alloys have diffused into the film. Hexavalent chromium electroplating from chromic acid is under pressure due to its health hazard and environmental problems and is subjected to increasingly stringent control and legislation. Health and safety considerations have prompted the electroplating industry to consider alternatives to coating processes that involve hexavalent chromium. It is a further objective of the research to compare the properties of nickel/chromium coated aluminium with top coats of chromium deposited from hexavalent and trivalent (chloride based) electrolytes. Duplex nickel and chromium electrodeposition were modified with an electroless nickel undercoat, thus four coatings were studied for the aluminium samples. Results obtained from the hardness measurements of Al 1050 and Al 6061 were compared for four coatings. Hardness tests profiles obtained for Al 1050 and Al 6061 show that deposits from trivalent chromium electrolytes were not as hard as hexavalent chromium deposits. However, the hardness of duplex nickel/chromium coatings was improved by use of an electroless nickel undercoat. Scratch adhesion tests were focused on the failure mode of coatings evaluated on the basis of scratch channels, frictional force and acoustic emission signals. The adhesion test showed buckling and chipping of the coatings with no sign of spallation or delamination. Four coatings exhibited a higher critical load for both aluminium alloy samples. This confirmed that failure occurred within the coatings, rather than adhesive failure at the coating/substrate interface. Results obtained from copper acetic acid salt spray and electrochemical corrosion tests for Al 1050 and Al 6061 exhibited excellent corrosion resistance. Scanning electron microscope images showed initiation and propagation of small pits which did not coalesce to form large and deep craters that could result in the eventual failure of the coatings. Micro discontinuous chromium deposits spread the corrosion current, thus improving corrosion performance. Icorr values obtained from linear polarization corrosion tests show higher values for duplex nickel/chromium coatings on Al 1050 than Al 6061. Icorr values show similar trends for duplex nickel/chromium coating on Al 1050 and Al 6061 modified with an electroless nickel undercoat. In conclusion results showed a significant improvement in the chromium electroplating characteristics of Al 1050 and Al 6061 with an electroless nickel undercoat
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Assessing the Processes of Family-To-work Spillover: A Comparison of National Guard At-Home Partners Experiencing Military Deployment and a Non-Deploying Group
No full textScholars have characterized as “extreme” the intersection of work and family in military service (MacDermid Wadsworth & Southwell, 2011) and periods of deployment involve further stress for partners of military members (e.g. Not having enough personal time, having too many responsibilities at home, changing marital roles, and parenting hassles) that may make managing both work and family life more difficult (Chandra et al., 2011). Research with partners of deployed service members has focused primarily on mental health (Donoho et al., 2018; Mansfield et al., 2010) as well as parenting and household responsibilities (Chandra et al., 2011), but less is known about partners’ employment related outcomes. In the current study, both role strain and role enhancement processes were tested over time in a sample of employed partners of deployed Army National Guard Members (GMs) and a comparison group composed of partners of non-deploying GMs. In accordance with theories of work-family conflict (Greenhaus & Beutell, 1985) and resource drain theory (Rothbard, 2001), a model utilizing two waves of data was tested; household challenges experienced by at-home partners were hypothesized to be related to more negative family-to-work spillover, and ultimately associated with less job engagement and more depressive symptoms. In addition theories of work-family facilitation (Grzywacz & Butler, 2005) and workfamily enrichment (Greenhaus & Powell, 2006) were utilized to test whether family strengths (e.g. effective family functioning and military spouse role satisfaction) in the face of deployment were associated with positive FTW spillover, and ultimately with more job engagement and fewer depressive symptoms. Results revealed that household challenges were related to more negative family-to-work spillover, more depressive symptoms, and less job engagement. Effective family functioning was related to more positive FTW spillover, which was related to more job engagement. Results were consistent across the deploying and non-deploying group with the following exception: in the deploying group only, negative FTW spillover was associated with more depressive symptoms. The current study has implications for the field of work and family research, employers, and military family service providers. First, the current study provided evidence of cross-domain work-family conflict and work-family enrichment in a sample of partners of National Guard members. Second, the study highlighted numerous consequences for employees facing significant household challenges. The role of household challenges in employees’ lives may have implications for how employers should structure workplace culture and the employee supports they offer. Finally, only partners of deployed GMs experienced more depressive symptoms associated with negative FTW conflict. Military family service providers may use that information to better serve partners of deploying service members who are at risk of mental health concerns during deployment
Mining e-mail content for author identification forensics
No full textWe describe an investigation into e-mail content mining for author identification, or authorship attribution, for the purpose of forensic investigation. We focus our discussion on the ability to discriminate between authors for the case of both aggregated e-mail topics as well as across different email topics. An extended set of e-mail document features including structural characteristics and linguistic patterns were derived and, together with a Support Vector Machine learning algorithm, were used for mining the e-mail content. Experiments using a number of e-mail documents generated by different authors on a set of topics gave promising results for both aggregated and multi-topic author categorisation
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