1,720,996 research outputs found
Experimental Investigation of the Laser Micro Drilling of Different Alloys by means of Nd:YAG Green Laser
No full textAbstract
Micro-machining have been subjected to an important develop in fabrication of components for informatics,
electronic, and mobile telephone systems. Now a day they have been having a significant development in many
strategic sectors like the mechanical, the chemical and the medical one. A lot of structures with dimension of few
microns like micro pumps, micro motors, micro systems for the DNA analysis have been realized during the last
ten years. The micromachining sector is potentially a strategic field in industry as actually occurs a big demand of
micro components. For such a reason the following work has been carried on. The behaviour of different metals
undergone to laser micro drilling varying the machining parameters has been studied in this work. The source used
for the experiments is a Nd:YAG Q-Switched green laser. Materials machined are AISI 304, WC, Titanium,
Inconel 718 and Brass. Machining parameters varied are: frequency and power of laser beam, focal lens length
and thickness of materials. After the drilling the micro-holes obtained has been observed with a scanning electron
microscope (SEM) with the aim of analyze their quality attributes. Quality attributes of the realized machining are:
radial and vertical spatter, tapering and dimensions of the holes. Experimentation has been carried out using the
method of design of experiment (DOE FACTORIAL). It is advantageous to realize micro-holes using a laser
because this alternative technology allows to realize machining without contact between piece and tool. Such a
machining permits also to reduce working time and to process materials very difficult to machine with other
technologies
Ultraviolet laser micromachining of kapton: experimental and theoretical analysis
No full textAbstract
Micromachining technologies offer new opportunities for a wide range of applications in many technical
fields, where very small components requiring dimensional accuracy on the order of microns are needed.
Electronics, medical devices, jewellery, equipments for digital press, and many others are examples of such
fields. Among available laser systems, Nd:YAG lasers are particular suited for micromachining technologies,
due to the quality of the beam, the emission wavelength that makes the beam absorbable by the most part of
materials, and the flexibility in beam manipulation, being for such reasons the most employed systems for
micromachining technologies. In the present work, a new application of Nd:YAG laser in micromachining is
investigated, i.e. the cutting of polyimide films. Polyimide materials are having considerable development in
several industrial sectors due to their unique combination of properties, which keep constant over a wide
temperature range. In particular, polyimide films find employment in devices where high resistance to heat
and ability to prevent the propagation of fire are needed. In this work, an experimental investigation has been
performed employing a Q-switched ultraviolet (λ = 355 nm) Nd:YAG laser system
Investigation on High Speed Laser Cutting of Monocrystalline Silicon
No full textABSTRACT. Micromachining of silicon plays an important role in the development of devices for
optoelectronics and micro electromechanical systems (MEMS) applications. Micromachining of silicon
can be realized by several modes, such as electron beam lithography (EBL), reactive ion dry etching
(RIE), diamond tools (silicon cutting), and now by laser. The principal problem related with silicon
cutting is crack formation near the cutting zone and the low speed of the cutting process. In this paper a
new application is presented, i.e. high speed silicon laser cutting. A 355 nm third harmonic Nd:YAG laser
was employed to cut silicon in a process conducted in air. In this paper an investigation on the dimension
of cuts, laser induced thermal damage, re-deposition of material and micro-cracking arising near the
cutting region as a function of laser cutting parameters is reported
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
La cardiomiopatia aritmogena del ventricolo destro nel Bulldog Inglese: Una patologia emergente
No full textArrhythmogenic right ventricular cardiomyopathy is a familial heart disease characterized by a progressive replacement of myocardium with fibro-fatty tissue. These structural changes are accompanied by functional changes with the onset of ventricular arrhythmias and myocardial dysfunction. In veterinary medicine, this disease has been reported sporadically in several canine and feline breeds, while in the Boxer breed the ultra-structural alterations, genetic transmission, and clinical and instrumental findings of the disease have been extensively described. Recently arrhythmogenic right ventricular cardiomyopathy has also been recognized in the English Bulldog, with distinctive features such as the presence of monomorphic ventricular tachycardia with left bundle branch block morphology and an incessant behaviour and the presence, in two thirds of affected dogs, of a segmental form with aneurysms of the right ventricular outflow tract. The purpose of the present manuscript is to describe clinical and instrumental findings of this disease in English Bulldog comparing them with those reported in Boxer breed dogs
Echo-assisted percutaneous renal biopsy in dogs. A retrospective study of 229 cases
No full textRenal biopsies were carried out on 229 dogs using an echo-assisted, semi-automatic method. Complications arising after the biopsy were also evaluated. The biopsies were examined for the accuracy of diagnosis and the presence of histologically demonstrable primary renal pathologies. A retrospective study of the observed lesions and parenchymal echogenicity showed a correlation between these factors involving the tubulo-interstitial compartment. Histopathological renal lesions and their correlation with laboratory methods are the only parameters that allow a correct diagnostic, prognostic, and therapeutic work-up in cases of clinical kidney disease in canines. © 2003 Elsevier Ltd. All rights reserved
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