The disc brake squeal is a very annoying sound which affects the customer comfort. The generation of this noise is considered as a structural dynamics and/or tribological problems of the pad-disc ...system. Unlike drum brake design, this system is exposed to external environmental sand particles, wear debris and water spray. Their presence into the disc and pad interface may create dynamic and physics phenomena induced by friction surface changes which lead to brake noise and vibration issues. Thus, this paper aims to investigate the effect of environmental sand particles (silica sand and road sand particles) with a range size of 100–150, 150–200 and 300–400µm on the brake squeal noise occurrences. The sensitivity of the sand particles to produce noise is correlated with the wear scar, friction coefficient and variation of brake operational parameters. It was concluded that the primary reason for the reduced squeal noise generation was contributed to the reduced COF with the particle embedment. The analysis of the particle size influence on the squeal occurrence indicated that a small size of silica sand particle produces less squeal occurrence than that of road sand particles. However, the biggest silica and sand particles seriously damage the pad surface and reduce consequently the real contact surface, inducing a decrease on the friction coefficient.
•COF increases with smaller grit particle size.•Strong effect of external particles on the reduction of brake squeal.•Increasing size of external particle induced a lower squeal sound level.•The natural presence of the sand particles in the pad/disc interface is essential for brake squeal reduction.
In this paper, the
H
∞
reliable control problem is investigated for a class of nonlinear singular systems subject to external disturbance and actuator faults and saturations. By means of the ...Takagi–Sugeno fuzzy model to describe the nonlinear plant, a reliable sliding-mode control scheme is built to compensate for the impact of aforementioned factors on system stability and performance. First, a fuzzy integral sliding function is designed and sufficient conditions are derived such that the sliding-mode dynamics is robustly admissible and satisfies the pre-specified
H
∞
disturbance attenuation requirement. Then, by considering the saturation as nonlinear input, an adaptive sliding-mode control law is synthesized to ensure reachability of the specified sliding surface. Finally, the lower-limb rehabilitation system is exploited to validate the effectiveness of the presented controller design methodology.
In this paper, several different Feed Forward Artificial Neural Networks (FFANNs) were used for forecasting the one-day-ahead Global Horizontal Irradiation (GHI) in Hail region, Saudi Arabia. The ...main motivation behind predicting GHI is that it is a critical parameter in sizing and planning photovoltaic water pumping systems. The novelty of the proposed approach is that it employs only the historical values of the GHI itself as explanatory variables and a fast training algorithm (resilient-propagation). In terms of performance metrics, the rp-trained FFANNs provided better results than Quasi-Newton (bfg) algorithm trained FFANNs for almost all the studied combinations of the FFANN structure. It has been also shown that increasing the number of neurons per layer didn’t improve the performance. Medium structures with fast training algorithms are recommended.
This article is focused on reliable fuzzy H
∞
controller design for a class of Takagi-Sugeno (T-S) fuzzy systems with state delay, actuator failures, disturbance input and norm bounded uncertainties. ...In the design, the H
∞
performance of the closed-loop system is optimised during normal operation (without failures) while the system satisfies a prescribed H
∞
performance level in the case of actuator failures. Two methods are presented in this study. In the first method, delay-dependent conditions are derived based on a single Lyapunov-Krasovskii function. This method improves delay-independent results existing in the literature. Next, to further reduce the conservatism, we use a parameter-dependent Lyapunov-Krasovskii function. The new sufficient conditions for the existence of the suboptimal robust reliable controller are shown in terms of linear matrix inequalities (LMIs), which can be solved by using LMI optimisation techniques. A simulation example shows the effectiveness of the proposed methods.
Femme de 28 ans sans antécédents admise en janvier 2015 pour faiblesse et engourdissement des membres inférieurs d’aggravation progressive sur 4 semaines. L’examen trouve une paraparésie, ...hypoésthésie distale, des ROT abolis. Le diagnostic d’un Guillain Barré (GB)est suspecté, mais devant l’atteinte du VI, VII droit, et VIII bilatéral, une IRM cérébrale est faite. Plusieurs empyèmes extra-axiaux avec épaississement et prise de contraste leptoméningée associées à des hypersignaux mésencéphalique gauche sont observés. VS=70mm. L’analyse du LCR révèle une hyperprotéinorrachie : 3,13g/l, hypoglucorrachie : index IgG/l et hypercellularité (99cellules/μL, 100 % lymphocytes). La culture du LCR est négative. La recherche de BK est négative. Le test d’agglutination sérique de Wright est positif (sang : 1/80) et (LCR 1/40). Il existe une synthèse intrathécale d’immunoglobuline, Index IgG : 1,26 et profil immunoéléctrophorétique type 2. Devant cette leucoencéphalopathie GB-like, le diagnostic d’une Neurobrucellose est posé malgré une titration faible. Sachant que le seuil de positivité est fixé à 1/160. Un traitement associant (Rifampicine-Doxycycline et Cotrimoxazole) est débuté immédiatement. L’amélioration nette aussi bien clinique que radiologique a permis de conforter le diagnostic (Figures). Paradoxalement aux résultats retrouvés dans le model animal témoignant d’une altération de la fonction phagocytaire des macrophages, certaines études montrent une forte réponse inflammatoire type TH1. L’augmentation de Index IgG témoigne de l’activation des LB. Brucella encore endémique dans nos pays et connue avoir un tropisme pour le système reticulo-lymphocytaire, attaque le système nerveux central via plusieurs mécanismes qui seront discutés. L’implication immune via les lymphocytes T et B est actuellement certaine. Des recherches dans le domaine de la neuroimmunologie sont très utiles dans les cas à présentations atypiques ou en cas de négativité des tests hématologiques et du LCR dont la sensibilité reste discutée.
During hot forming process, tools are exposed to severe and complex loads. As result, damages by oxidation and thermal and mechanical fatigue are generated which cause tool failure. The aim of this ...work is a multi-scale analysis of damaged hot forging tools. An expertise of main failures on industrial hot-forging die, made of hot-working die steel X40CrMoV5-1 is presented. Die was previously sectioned and examined after its service life. The measurements of micro-hardness depth profiles, SEM and optical observations of oxidized surfaces were achieved on the most loaded sections of the die. An analysis of residual stresses in damaged die was also performed in order to estimate and then predict the most solicited zones on the die, a simplified numerical approach was investigated. The cracks on the observed areas are caused by local elasto-plastic stress due to mechanical load. A good correlation between expertise and numerical results was established.
•A failure analysis of used hot forming die is presented.•Different damage phenomena characterizations, occurred in failed die are discussed.•As the complexity damage modes, analysis of residual stresses is also performed.•Local stress is determined by numerical approach based on multilinear hardening model.•A thermal superficial softening of failed die is investigated during forging process.
Résumé: La survenue d’un épanchement pleural au cours du myélome multiple est relativement rare. Il est le plus souvent en rapport avec une atteinte non spécifique de la maladie. Nous rapportons une ...observation d’épanchement pleural, dont l’origine myélomateuse est retenue devant le résultat de la biopsie pleurale. L’évolution est marquée par un décès rapide de la patiente. L’apparition d’un épanchement par envahissement pleural plasmocytaire dans le myélome multiple traduit l’agressivité de la maladie et son caractère péjoratif.
Abstract: Pleural effusions are relatively rare during the course of multiple myeloma and most often occur with non-specific disorders of the disease. We report an observation of myelomatous pleural effusion; the diagnostic was ascertained by the pleural biopsy. The patient did not respond to the therapy and died after few days. Occurrence in the course of multiple myeloma of pleural effusions due to infiltration of the pleura by plasma cells reflects aggressive disease and indicates a poor prognosis.
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