6,013 research outputs found
Kerf Taper Defect Minimization Based on Abrasive Waterjet Machining of Low Thickness Thermoplastic Carbon Fiber Composites C/TPU
Carbon fiber-reinforced thermoplastics (CFRTPs) are materials of great interest in industry.
Like thermosets composite materials, they have an excellent weight/mechanical properties ratio and a
high degree of automation in their manufacture and recyclability. However, these materials present
di culties in their machining due to their nature. Their anisotropy, together with their low glass
transition temperature, can produce important defects in their machining. A process able to machine
these materials correctly by producing very small thermal defects is abrasive waterjet machining.
However, the dispersion of the waterjet produces a reduction in kinetic energy, which decreases its
cutting capacity. This results in an inherent defect called a kerf taper. Also, machining these materials
with reduced thicknesses can increase this defect due to the formation of a damage zone at the
beginning of cut due to the abrasive particles. This paper studies the influence of cutting parameters
on the kerf taper generated during waterjet machining of a thin-walled thermoplastic composite
material (carbon/polyurethane, C/TPU). This influence was studied by means of an ANOVA statistical
analysis, and a mathematical model was obtained by means of a response surface methodology
(RSM). Kerf taper defect was evaluated using a new image processing methodology, where the initial
and final damage zone was separated from the kerf taper defect. Finally, a combination of a hydraulic
pressure of 3400 bar with a feed rate of 100 mm/min and an abrasive mass flow of 170 g/min produces
the minimum kerf taper angle
Microburst characteristics determined from 1988-1991 TDWR testbed measurements
This paper presents some recent results germane to airborne windshear system design and certification. We first discuss the data analysis procedure and the associated caveats. The relative frequency, severity, and duration of microburst hazards at the various locations is important for determining the tradeoffs between safety and operational impact of false alerts which are encompassed in detection system thresholds. We then consider radar/lidar design issues such as reflective in microbursts and the vertical structure of outflows. Finally, we provide recent surface thermodynamic data associated with microbursts
Inter-filament Attractions Narrow the Length Distribution of Actin Filaments
We show that the exponential length distribution that is typical of actin
filaments under physiological conditions dramatically narrows in the presence
of (i) crosslinker proteins (ii) polyvalent counterions or (iii) depletion
mediated attractions. A simple theoretical model shows that in equilibrium,
short-range attractions enhance the tendency of filaments to align parallel to
each other, eventually leading to an increase in the average filament length
and a decrease in the relative width of the distribution of filament lengths.Comment: 5 pages, 4 figure
Slow Coarsening in a Class of Driven Systems
The coarsening process in a class of driven systems is studied. These systems
have previously been shown to exhibit phase separation and slow coarsening in
one dimension. We consider generalizations of this class of models to higher
dimensions. In particular we study a system of three types of particles that
diffuse under local conserving dynamics in two dimensions. Arguments and
numerical studies are presented indicating that the coarsening process in any
number of dimensions is logarithmically slow in time. A key feature of this
behavior is that the interfaces separating the various growing domains are
smooth (well approximated by a Fermi function). This implies that the
coarsening mechanism in one dimension is readily extendible to higher
dimensions.Comment: submitted to EPJB, 13 page
La compassion comme valeur romanesque : l’exemple de Marie-Claire Blais
Cet article propose une lecture comparée des romans Une saison dans la vie d’Emmanuel (1965) et Soifs (1995) de Marie-Claire Blais. Autant le premier est marqué par l’ironie et le rire du personnage de Jean Le Maigre, autant le second se caractérise par une compassion généralisée à l’égard de personnages qui ont en commun d’être des marginaux. La compassion devient une valeur romanesque non pas seulement comme thème, mais aussi comme principe de composition. Au-delà du seul cas de Marie-Claire Blais, un tel déplacement paraît symptomatique d’un changement plus général qui tient à la fonction réparatrice ou rédemptrice que le romancier contemporain assume de plus en plus ouvertement.This article invites a comparative reading of the novels A Season in the Life of Emmanuel (1965) and Soifs (1995) (These Festive Nights, translation 2004) by Marie-Claire Blais. While Emmanuel takes an ironic and bantering view of its protagonist, Jean Le Maigre, Soifs expresses a general compassion towards its characters who share the fact of being outsiders. Compassion therefore becomes a value quality of the novel, both as theme and principle of composition. Marie-Claire Blais is not alone in manifesting this shift which is symptomatic of an expression of healing and redemption increasingly endorsed by contemporary writers
The Traveling Salesman Problem: Deceptivley Easy to State; Notoriously Hard to Solve
The purpose of this thesis is to give an overview of the history of the Traveling Salesman Problem and to show how it has been an integral part of the development of the fields of Integer Programming, and Combinatorial Optimization. The thesis starts in the 1800s and progresses through current attempts on solutions of the problem. The thesis is not meant to describe in detail every attempt made, nor to describe an original solution, but to provide a high level overview of every solution attempt, and to guide the reader on what has been done, and what still can be done
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