1,721,183 research outputs found
Segregation in carbon steels
No full textIn the shipping industry, carbon steel is widely used to build ship decks and oil rigs. Carbon steel is able to withstand heavy load but due to the segregation problem, it causes delamination. Cracks can be easily initiated and propagated along regions with high level of segregation. Segregation is a manufacturing problem that is very difficult to avoid. It is caused by the non-uniformity of chemical composition within metals and alloys during solidification. From a commercial point of view, when segregation centerline (high level of segregation at center region) is detected, it will be costly to replace the whole component. Therefore heat treatment process will be carried out on the carbon steel to eliminate the segregation problem. The author hopes the information will aid the metallurgists and engineers when performing heat treatment on carbon steel.
In this project, the carbon steel, EH36, is worked under various temperatures and holding times. Therefore, this report aims to investigate the optimum conditions that will eliminate the segregation problem. Subsequently, the impact strength, the hardness and ductility of the material heated statically was also examined.
In conducting the literature review, the author gives an overview about heat treatment process, properties of carbon steel, especially medium carbon steel and the causes and effects of segregation in carbon steel. The techniques used to remove the segregation centerline are mentioned in greater detail as well.
The series of tests and observations to determine the tensile strength, hardness and removal of segregation centerline include the Tensile Test, Brinell Hardness test and Charpy Impact test, their principles and results analyzed. For large metal pieces that cannot be cut into smaller pieces for experimental purposes, the Ultrasound test is used to determine the defect in the metal. The occurrence of an optimum temperature at which the segregation centerline is removed and the minimal loss of strength is discussed.
In the concluding segment, a general overview of analysis is given and possible recommendations are proposed as well.Bachelor of Engineering (Mechanical Engineering
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
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
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
Investigation of nano-mechanical properties of TiNiCu shape memory thin films after annealing
No full textShape Memory Alloys (SMAs) are a group of metallic alloys that has the ability to remember and recover to its original shape after heating or loading. This ability is due to a solid state martensitic phase transformation. In recent years, SMA thin films have attracted increasing attention due to their promising applications in Micro-Electro-Mechanical Systems (MEMS) devices, which required efficient actuation and sensing mechanisms. Knowledge of mechanical properties of the SMA thin films at room temperatures, as well as elevated and lowered temperatures, is of great importance when designing for use at different ambient temperatures.
In this study, TiNiCu3 SMA thin films were prepared by the co-sputtering of TiNi and Cu targets using a Magnetron Sputtering system at room temperature. The as-deposited 550nm TiNiCu samples were amorphous. As Shape Memory Effect only occurs after crystallization, the films underwent either Rapid Thermal Annealing (RTA 10 seconds, 60 seconds, 120 seconds, and 180 seconds) or Conventional Thermal Annealing (CTA 1 Hour) at 480˚C.
The surface features of the annealed samples were studied by Atomic Force Microscope (AFM) and Scanning Electron Microscope. All annealed films were crack-less and suitable for Nanoindentation. It was found that surface roughness of TiNiCu3 thin films increased with increasing RTA time. The higher roughness of RTA as compared to CTA samples might be due their differences in heating mechanisms and ramping rates. Thus, CTA process might be a better annealing method, if surface roughness were a critical concern in industrial applications.
Nanoindentation was performed on the annealed samples at room temperature (23˚C) to study their mechanical properties. It was discovered that both the indentation modulus and hardness increased, in a similar trend, with RTA time. The error bars for indentation modulus and hardness were much narrower for fully-crystallized samples (RTA 180 seconds and CTA 1 hour), as compared to amorphous or half-crystallized samples. This is likely due to the more homogenized crystal structure in fully-crystallized samples.
Later, to study the Recovery of the crystallized samples (RTA 180 seconds and CTA 1 Hour) at temperatures 0, 13, 23, 33, 43 and 50˚C, a Thermal Stage was designed, fabricated and implemented into the Nanoindentation testing. It was found that the best Recovery occurred at 23˚C, which means the phase present at 23˚C was most likely fully Austenite, and within the temperature range of optimum Superelasticity. Above or below 23˚C, Recovery % of the crystallized samples decreased increasingly. The load-depth curves of RTA and CTA crystallized samples were consistent for all tested temperatures except at 0˚C; the Thermal Stage might not be suitable for Nanoindentation at subzero temperatures yet, due to humidity issues.Bachelor of Engineering (Mechanical Engineering
Failure analysis of mechanical and electrical components
No full textIn this work, the failure analysis procedure was carried out on various industrial
mechanical and electrical components, namely gear train components of an overhead
travelling crane and polymer coatings from an induction motor stator winding. The
gear components include a large driven gear in which all its teeth have been lost from
apparent frictional wear, a smaller driving gear with partially broken-off teeth and a
shaft which has broken clean in half. Windings extracted from one slot of a large AC
induction motor stator were made up of 8 strands of copper conductors which have
debonded from each other and both their polymeric enamel and glass fibre coatings
appear to be peeled off.
The main objectives were to investigate the failure mechanisms involved in the final
failure and to finally deduce the most probable main root causes of failure for the
respective components. Various analytical procedures were carried out to achieve the
preceding objectives, such as fractography and metallography using scanning
electron microscopy (SEM) and electron dispersive x-ray spectrometry (EDX) for
metallic samples, and thermal analysis using thermogravimetry (TGA) and
differential scanning calorimetry (DSC) for polymeric samples.
Results indicated that large concentrations of defects were found within two of the
three gear train components provided with lack of fatigue failure features, thus
suggesting failure of the travelling overhead crane due to overloading. Visual
observations of the polymer coatings in its as-received condition strongly indicated
signs of thermal degradation. No solid proof of contamination or corrosion was found in both samples. Suggestions for future work were also put forth in order to
improve the findings which were obtained.Bachelor of Engineering (Mechanical Engineering
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