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Tensile and torsional loads stress distribution along the drill string for deep wells
Get PDFCommon knowledge and rule of thumb tell us that tensile failures will
mostly occur in the pipe body, while torsion failures will occur in the tool joints.
The total stresses on the drill string should be considered which are induced by
combined bending, torsion and tensile stresses. The latter can usually be operating
up until 80 % of the pipe body yield stress, a level which is considered as a safe
working limit. Moreover, torque and drag are caused by the lateral forces and the
friction between the borehole wall and the drill pipe. The lateral forces depend on
the weight of the drill string. Torque and drag are sometimes overlooked when
drilling simple wells. In deep well this is not acceptable. Proper decision made
using correct torque and drag can make all the difference between TD drilling and
suspended drilling. Therefore the over pull load plus the torque are the most
important points to be considered in deep well drilling, since the resistance of the
drill string body to the combined efforts will probably limit its tensional limit. By
this I mean, exerting both a tension and torsion load on the drill string of this later
will weaken its yield stress consequently applying a high tension effort combined
with a significant torque lead to plastifying of the drill pipe body thus reducing its
fatigue life. This problem is well observed in back-reaming operation. The results
show that fatigue damage from rotation in dogleg during backreaming operation is a
significant problem if the severity is greater than the critical value. So the position
of drill pipe in the string will influence the amount of fatigue damage it sustains.
Furthermore, back reaming can reduce the fatigue life of the drill pipe significantly
because of the stress reversal of the drill string under tension in a dogle
Extraction de motif de mouvement de la foule par le flot optique
No full textDans ce travail, nous nous intéressons à l’analyse d'extraction de motifs de mouvement par la technique de flot optique, dans le but d’analysé le comportement de la foule. Ces scènes se caractérisent par la présence d’un grand nombre de personnes dans le champ de vision des caméras. Le problème majeur est l’élaboration et d’utilisation d’une technique sans modélisation de l’arrière-plan pour détecter les mouvements de la foule. Par la suite une étape de détection d’anomalies par la technique des réseaux de neurones artificiels (RNA). Nous présentons dans cet article une comparaison de l’approche proposée pour la détection des mouvements dans des scènes très denses et celle d'utilisation de modèle social de force. Pour plus de robustesse et d’efficacité, nous avons introduit la routine permettant d’élimination des ombres
Analyse visuelle d’événements anormaux de foules
Get PDFL’analyse du comportement humain depuis la vidéo est un domaine vaste de la vision par ordinateur. Dans ce travail, nous nous intéressons à l’analyse du comportement de la foule et de ses entités dans une scène dense. Ces scènes se caractérisent par la présence d’un grand nombre de personnes dans le champ
de vision des caméras. Le problème majeur est l’élaboration d’une approche de gestion autonome d’un grand nombre d’anomalies qui est quasiment impossible à effectuer par des opérateurs. Nous présentons dans cet article une nouvelle
approche pour la détection d’anomalies dans des scènes très
denses en se basant sur la vitesse des individus et celle du groupe.
Les différentes anomalies sont détectées d’une manier
automatique sans apprentissage en utilisant la densité à base du partitionnement spatial avec application du bruit (Density Based
Spatial Clustering of Application with Noise « DBSCAN »). Pour plus de robustesse et ’efficacité, nous avons introduit deux
routines permettant l’élimination des ombres et la gestion des d’occlusion
A Tutorial on Speech Synthesis Models
No full textFor Speech Synthesis, the understanding of the physical and mathematical models of speech is essential. Hence, Speech Modeling is a large field, and is well documented in literature. The aim in this paper is to provide a background review of several speech models used in speech synthesis, specifically the Source Filter Model, Linear Prediction Model, Sinusoidal Model, and Harmonic/Noise Model. The most important models of speech signals will be described starting from the earlier ones up until the last ones, in order to highlight major improvements over these models. It would be desirable a parametric model of speech, that is relatively simple, flexible, high quality, and robust in re-synthesis. Emphasis will be given in Harmonic / Noise Model, since it seems to be more promising and robust model of speech. (C) 2015 The Authors. Published by Elsevier B.V
EXPERIMENTAL INVESTIGATION OF THE FREE SURFACE EFFECT ON THE CONICAL TAYLOR-COUETTE FLOW SYSTEM
No full textThe aim of this work is to highlight the critical thresholds corresponding to the onset of different instabilities considered in the flow between two vertical coaxial cones with and without free surface. The inner cone is rotating and the outer one is maintained at rest. Both cones have the same apex angle Phi = 12 giving a constant annular gap delta = d/R-1max. The height of the fluid column is H = 155mm and can be progressively decreased for each studied case of the flow system. Two kinds of configuration are studied, small and large gap configurations The working fluid is assumed as Newtonian and having constant properties as density and viscosity within the range of the required experimental conditions. By means of visualization technique of the flow we were able to show the different transition modes occurring in the conical flow system according to the aspect ratio and then the induced action of the free surface which introduces a delay in the onset of different instability modes. The obtained results in term of features and stability of the flow are compared to those of M. Wimmer [3-8] and N Noui-Mehidi [9]
المسؤولية السياسية للحكومة : دراسة مقارنة بين الدستور الجزائري لسنة 6991 المعدل و الدستور المغربي لسنة 1166
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