3,169 research outputs found
An investigation of hot forming quench process for AA6082 aluminium alloys
This thesis is concerned with the mechanical properties and microstructure evolution during the novel solution Heat treatment Forming cold die Quenching (HFQ) process. HFQ is a hot sheet forming technology which incorporates the forming and quenching stages to produce high strength and high precision Al-alloy sheet parts. The work in the thesis divided into three main sections: Firstly, viscoplastic behaviour of AA6082 at different deformation temperatures and strain rates was identified through analysis of a programme of hot tensile tests. Based on the results from the hot tensile tests, a set of unified viscoplastic-damage constitutive equations was developed and determined for AA6082, providing a good agreement with the experimental results. SEM tests were carried out to investigate the damage nucleation and failure features of the AA6082 during hot forming process and the results are discussed.
Secondly, the viscoplastic-damage constitutive equations were implemented into the commercial software ABAQUS via the user defined subroutine VUMAT for the forming process simulation. An experimental programme was designed and testing facilities were established for the validation of the FE process modelling results. A fairly good agreement between the process simulation and the experimental results was achieved. This confirms that the established FE process simulation model can be used for hot stamping of AA6082 panel parts. Further process modelling work was carried out to identify the optimal forming parameters for a simplified representation of a panel part.
Finally, a precipitation hardening model was developed to predict the post-ageing strength of AA6082 panel parts, having varying amounts of forming-induced plastic strain. The model was tested against results of experiments which were carried out to
investigate the effect of pre-deformation on the ageing kinetics of AA6082. The model is shown to fit and can be used to explain changes in the strength of the material. This set of equations was implemented in the VUMAT, in combination with the viscoplastic damage constitutive equation set, to model the whole HFQ process. The FE model was tested with experimental ageing and hardness results providing good agreements, which are discussed in light of the future development of the HFQ process
Insights into dynamic tuning of magnetic-resonant wireless power transfer receivers based on switch-mode gyrators
Magnetic-resonant wireless power transfer (WPT) has become a reliable contactless source of power for a wide range of applications. WPT spans different power levels ranging from low-power implantable devices up to high-power electric vehicles (EV) battery charging. The transmission range and efficiency of WPT have been reasonably enhanced by resonating the transmitter and receiver coils at a common frequency. Nevertheless, matching between resonance in the transmitter and receiver is quite cumbersome, particularly in single-transmitter multi-receiver systems. The resonance frequency in transmitter and receiver tank circuits has to be perfectly matched, otherwise power transfer capability is greatly degraded. This paper discusses the mistuning effect of parallel-compensated receivers, and thereof a novel dynamic frequency tuning method and related circuit topology and control is proposed and characterized in the system application. The proposed method is based on the concept of switch-mode gyrator emulating variable lossless inductors oriented to enable self-tunability in WPT receiversPeer ReviewedPostprint (published version
Estudio analÃtico de la metáfora y su traducción, ejemplificado en Memorial de Isla Negra de Pablo Neruda
The aim of this research is a linguistic study of metaphor and its translation. From the traditional point of view, the definition of the metaphor should concentrate upon: 1. The replacement of one element with the other. 2. The similarity between those two elements. Nevertheless, those two points are not necessarily essential to the formation of the metaphor. When analyzing the «metaphor», it is noticeable that there is a change in the internal order of the overall features representing the meaning of the word. In that way, some features are neutralized, meanwhile others become more relevant. Hence we analyze the metaphor here as a semantic neutralization process. The analysis of metaphor translation reveals the existence of three problematic issues: 1. The difference in connotative meaning in the two languages. 2. The originality of the metaphor in the two languages. 3. The difference in the structure of the metaphor in the two languages
La hipálage: estudio lingüÃstico con especial atención a las obras de Juan Ramón Jiménez y Rafael Alberti
Nuestro interés a lo largo de este trabajo se centra en torno a cuatro aspectos que consideramos esenciales para la hipálage: su definición, su delimitación con respecto a otras figuras —la metáfora y la metonimia—, asà como su función discursiva dentro del texto poético y las distintas categorÃas que de dicha figura podemos distinguir en función de los criterios lingüÃsticos y formales. Discrepamos aquà con la perspectiva tradicional, que analiza la hipálage como el traslado de un adjetivo de las inmediaciones de un lexema a las de otro. Para ello nos basamos, entre otras cosas, en la existencia de una categorÃa de hipálage en la que no se percibe ningún procedimiento de permutación. Dicha categorÃa apunta a la posibilidad de establecer ciertos vÃnculos entre hipálage y metáfora. En el texto poético, la hipálage posee una gran variedad de funciones. No obstante, todas ellas se pueden reducir a una: la creación de un fuerte enlace de carácter psÃquico-lingüÃstico entre los términos implicados. La tipologÃa que de esta figura intentamos establecer aquÃ, se basa en tres criterios esenciales: el número de elementos implicados, el tipo de anomalÃa semántica que comporta la hipálage y el procedimiento lingüÃstico que la origina.The aim of this research is a linguistic study of hypallage. Here, we’ll concentrate upon four essential aspects: definition of hypallage, delimitation of its area with regard to other rhetoric figures (metaphor and metonymy), semantic function of hypallage in the poetic discourse and the linguistic criteria that can be used to classify its different categories. We don’t agree here with the traditional perspective that analyses hypallage as a result of a permutation process. There is a category of hypallage where it is impossible to perceive any kind of permutation process. In this type of hypallage we can establish a certain relation between this figure and metaphor. The basic function of hypallage in poetic discourse is to enact a psycho-linguistic relation between the implied terms. The typology of hypallage we try to establish in this issue is based upon three essential criteria: the number of implied elements, the type of the semantic anomaly created by hypallage and the linguistic process that produce hypallage
Ambiguity and Humour
Contra lo que pudiera creerse en un primer momento, la ambigüedad del lenguaje tiene numerosos efectos positivos para los componentes esenciales de los actos de habla: los interlocutores, el mensaje y el código. En este trabajo nos proponemos estudiar uno de esos aspectos positivos relacionados con la ambigüedad semántica: el humor, que en muchas ocasiones se origina en la dilogÃa de ciertas unidades lingüÃsticas que aparecen en el discurso. En nuestro estudio, distinguimos entre tres tipos básicos de opacidad semántica: ambigüedad, vaguedad e indeterminación. Para crear la comicidad en el texto, cada una de esas tres categorÃas echa mano de un conjunto de mecanismos distinto. El análisis aplicado en esta ocasión es de carácter pragmático.Ambiguity has many positive effects on the three main elements of speech acts: speakers, message and code. In this paper, we will analyse one of the positive aspects related to semantic ambiguity: humour, which is often based on the ambivalence of certain units of speech. We will also establish three basic types of semantic opacity: ambiguity, fuzziness and generality. Our pragmatic approach will show how several mechanisms account for the way each one of these categories creates humour
Approximation to the Study of the Interjection in Egyptian Dialectal Arabic
Nuestro objetivo aquà es analizar el uso de las interjecciones en el árabe dialectal de Egipto, prestando una especial atención a las de carácter emotivo. Para ello, empezamos por estudiar la naturaleza lingüÃstica de las interjecciones, llegando a la conclusión de que su contenido semántico es de carácter puramente procedimental y su significado exacto depende enormemente del contexto y/o la situación del discurso. Analizando las posibilidades combinatorias de las interjecciones, concluimos que son sintagmas que se muestran reacios a la transposición o a cualquier otro mecanismo de enlace que pueda afectar a su categorÃa sintáctica de entrada. Nos centramos también en el análisis de los valores semánticos con los que se emplean estos elementos en el dialecto que nos incumbe, detectando la existencia de dos mecanismos básicos de creación de nuevas unidades: la lexicalización de expresiones de contenido originalmente vocativo o de carácter religioso.Our aim in this issue is to analyze the use of interjections in the dialectal Arabic of Egypt, giving a special attention to those of emotive sense. We begin studying the linguistic nature of interjections and conclude that they are always used to convey a vague sense, because of the procedural nature that they semantically have. Analyzing the combinatorial possibilities of interjections, we can affirm that they are autonomous sequences that do not accept transposition or any other mechanism of link that could change their original syntactic category. Finally we centre upon the semantic values with which these elements are used in Egyptian Arabic and detect the existence of two basic mechanisms of creation of new interjections: the lexicalization of expressions of original vocative content or religious sense
Driver Distraction Identification with an Ensemble of Convolutional Neural Networks
The World Health Organization (WHO) reported 1.25 million deaths yearly due
to road traffic accidents worldwide and the number has been continuously
increasing over the last few years. Nearly fifth of these accidents are caused
by distracted drivers. Existing work of distracted driver detection is
concerned with a small set of distractions (mostly, cell phone usage).
Unreliable ad-hoc methods are often used.In this paper, we present the first
publicly available dataset for driver distraction identification with more
distraction postures than existing alternatives. In addition, we propose a
reliable deep learning-based solution that achieves a 90% accuracy. The system
consists of a genetically-weighted ensemble of convolutional neural networks,
we show that a weighted ensemble of classifiers using a genetic algorithm
yields in a better classification confidence. We also study the effect of
different visual elements in distraction detection by means of face and hand
localizations, and skin segmentation. Finally, we present a thinned version of
our ensemble that could achieve 84.64% classification accuracy and operate in a
real-time environment.Comment: arXiv admin note: substantial text overlap with arXiv:1706.0949
Measuring efficiency, productivity and financial performance of Libyan manufacturing firms pre and post privatization / Mohamed Saad Mohamed Abokaresh
This study examines the effect of privatization on technical efficiency, productivity and financial performance of 21 Libyan manufacturing firms from 2000 to 2008, and captures also the pre and post privatization effects of those measures, by applying the Frontier Data Envelopment Analysis (DEA) technique. Comparisons are also made meaningful by separating the firms into two ownership structures: state owned and fully privatized. As we are also assessing the pre and post privatization effects, the Wilcoxon Matched-Pairs Signed Rank Test is used to test for independence between-subjects designs. Technical efficiency scores of all manufacturing firms before and after privatization are computed using the input-oriented DEA model, proven to be suitable for determining technical efficiency. The findings from the analysis show that 42.9 per cent of the entire firms operate above average and 57.1 per cent operate below the average score. However, no firm has scored full efficiency (TE = 1.00). Even though the findings show an overall improvement in technical efficiency of 12.8 per cent, this is not consistent with the privatization theory. In evaluating the ownership types for pre and post privatization, the findings reveal that fully privatized firms are more efficient after privatization, implying better performance than state control firms. In terms of the Total Factor Productivity analysis, the findings show that the productivity of 16 (76.19 per cent) firms out of 21 firms decline after privatization
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