Location Embedding and Deep Convolutional Neural Networks for Next Location Prediction

International audienc

Investigation of the Effect of the Force-Frequency on the Behaviour of a New Viscous Damper for Railway Applications

The primary purpose of this work is to experimentally investigate the damping coefficient of a viscous damper, intended to be used in railway applications to reduce noise emission. The viscous shock absorber used in this study is a commercial vehicle damper to which minor modifications were added. This investigation was focused on detecting the variation in the damping coefficient value over a wide range of frequencies. The experimental setup tends to simulate the railway vibration represented by a strong steel metal sheet structure attached to a shaker from its lower side. The shaker itself is connected to the damper rod through a dual acceleration-force sensor. A sinusoidal load with wide range of frequencies was applied by the shaker to the top of the damper's rod. Both acceleration and force time-responses were collected, stored and analyzed to extract the Force-Displacement and the Force-Velocity graphs. Based on the damping coefficients obtained for the different values of excitation frequencies, the results show that the damping coefficient is not constant and depends on the excitation frequency

Les "Diary methods" : présentation et cas d'application d'une méthode de collecte de données basée sur la tenue d'un journal personnel

La vie est ponctuée d'événements quotidiens, prenant la forme de décisions, d'engagements, et d'actes, et suscitant des réactions émotionnelles, attitudinales et comportementales. Une analyse de la vie des salariés dans les organisations, basée sur l'étude des événements semble dés lors cruciale pour la compréhension des expériences quotidiennes vécues dans un contexte de travail. Puisque des événements plus ou moins importants se produisent à toute heure dans une journée de travail, la vie des salariés est régulièrement soumise aux aléas que ces expériences engendrent, même si elle donne l'impression d'une certaine stabilité. Ces événements et ces expériences en évolution quotidienne font que notre humeur peut changer d'un jour à l'autre. Les attitudes et les traits de personnalité sont certes importants, cependant leur impact sur nos vies passe inéluctablement par les événements et les expériences quotidiens. Pour exprimer cela plus formellement, nous pouvons dire que la vie est un processus dynamique, changeant et continue, impliquant événements, expériences, réflexions, sentiments et motivations qui varient considérablement dans le temps.gestion des ressources humaines;méthode du journal personnel

Crystal structure of a new homochiral one-dimensional zincophosphate containing L-methionine

catena-Poly[[(L-me­thio­nine-[kappa]O)zinc]-[mu]3-(hydrogen phosphato)-[kappa]3O:O':O''], [Zn{PO3(OH)}(C5H11NO2S)]n, a new one-dimensional homochiral zincophos­phate, was hydro­thermally synthesized using L-me­thio­nine as a structure-directing agent. The compound consists of a network of ZnO4 and (HO)PO3 tetra­hedra that form ladder-like chains of edge-fused Zn2P2O4 rings propagating parallel to [100]. The chains are decorated on each side by zwitterionic L-me­thio­nine ligands, which inter­act with the inorganic framework via Zn-O coordination bonds. The structure displays inter­chain N-H...O and O-H...S hydrogen bonds

Location Embedding and Deep Convolutional Neural Networks for Next Location Prediction

International audienc

Enhancing the damping effect of MRF damper using an external magnetic excitation system

The magnetic field generated by the damper’s magnetic circuit governs the yield stress value of the Magnetroholgical Fluid (MRF) damper and hence its damping effect. This paper contributes to the literature on the development of MRF dampers by introducing a new design feature to improve the damper’s performance. The presented novel feature tends to amplify the magnetic field value and concentrate its flux within the MR fluid region. The excitation sources consist of 12 coils placed in radial directions surrounding the MRF to focus the energizing magnetic effects. However, the search for efficient solutions is not only focused on generating more energy but also on minimizing its loss. Therefore, a metallic ring was placed around the coils to close the magnetic circuit, guide the flux lines, and avoid any energy dispersion to the surrounding air. As a proof of concept, two materials were tested for the surrounding ring: plastic acrylonitrile butadiene styrene (ABS) and mild steel. The performance of both solutions was assessed experimentally with a Gaussmeter and numerically by using a model developed via COMSOL Multiphysics. Both techniques confirmed the efficiency of the solution based on a steel ring in preventing the flux dispersion into the surrounding air. In addition, an increase of the excitation current from 0 to 5A was found to elevate the magnetic field by 35%, compared with the ABS ring. In the second step, a test rig was designed and built to investigate the damping efficiency of the MRF experimentally. The testing apparatus consisted of a sliding-bearing mechanism connected to a variable speed motor. The damping effect was assessed based on the force and displacement data provided by a linear variable displacement transducer (LVDT) and a force cell. Damping forces were observed at a constant frequency of 0.36 Hz (22 rpm) when the testing system and the attached damper were functioning smoothly away from its resonant frequency. Moreover, the magnetic field excitation current was elevated from 0 A to 5 A with a 1 A step. Again, the metallic ring was found to produce a 112% greater damping coefficient than the case of the plastic ring when the excitation current reached 5A.Financial support for this research was graciously provided by Qatar National Research Fund (a member of Qatar Foundation) via the National Priorities Research Project under Grant No. NPRP-11S-1220-170112

Numerical study on the damping characteristics of a shock absorber valve utilizing different velocities through CFD analysis

Shock absorbers or hydraulic dampers are power dissipating devices. The fluid flow inside the damper is governed by predefined passages. The damping effect is accomplished by the resistance of oil to flow through the restrictions. The impact of the viscosity and the velocity of the oil determines the fluid flow behaviour and hence, the resulting damping effect. The piston inside the damper has various orifices or piston valves that cause different flow losses. These losses are observed during the extension and compression strokes of the damper. In the compression and extension strokes, rebound and compression pressures are developed at the damper orifice. In this work, Computational Fluid Dynamics (CFD) analysis is carried out on a rear side two-wheeler automobile mono tube damper to investigate the variation of the damping properties using viscous oils. Averaged Navier-Stokes equations are solved by the SIMPLE method and the RNG k-ε is used to model turbulence. The piston contains eight orifices which separate the rebound and compression chambers of the damper. The numerical analysis used four values of velocity; 0.8, 1, 1.2, and 1.5 m/s. The viscous fluid model was SVI2.5, having viscosity value of 0.009 Pa.s. The damping coefficient values for rebound and compression sides were obtained based on their pressure values showed in the CFD contour plots. It was noticed that the increasing trend of damping coefficient is linearly for two velocity's intervals; (0.8-1) m/s and (1.2-1.5) m/s, and nonlinearly for velocity interval of (1-1.2) m/s. © 2021 COMPDYN Proceedings

Investigating the characteristics of a magnetorheological fluid damper through CFD modeling

Computational Fluid Dynamics (CFD) analysis is conducted on mono-tube vehicle MRF damper investigated experimentally in a previous study. In this study, the fluid of the type MRF-132DG was inserted inside a damper of a car rear suspension system. The CFD analysis describes the fluid flow through the internal orifices between the compression and the rebound chambers. Averaged Navier-Stokes equations were solved by the SIMPLE method, and the RNG k-ϵ was used to model the turbulence at the fluid crossing through the orifices. All the CFD model boundary conditions' values were set to the same values reported in the previous experimental study, except for the viscosity values. When varying the applied magnetic field density, the changes of MRF's viscosity values were assessed by using a viscosity meter. Results showed a viscosity increase of 70% when the magnetic field excitation current was elevated from 0 A to 5 A. The damping forced and damping values were calculated using the rebound and compression static pressures obtained from the contour plots. It was also observed that the damping values exponentially increase with the increase in viscosity. The results of the CFD simulation were compared against those from the experiments, and good matching was observed

Towards a simplified technique for crack recognition in gearing systems

This paper presents a simple and effective method to identify and quantify the existence of cracks in the teeth roots of spur gears. The problem was numerically analyzed through finite element-based simulation with SolidWorks in the first part of this work. The computed tooth in-plane bending stiffness and natural frequency decreased considerably with an increase in the crack length, while the deformation followed an opposite trend. The numerical results were experimentally validated through a convenient and straightforward test rig developed for this purpose. The experimental results obtained from the modal analysis tests confirmed the previously obtained numerical results. A graphical representation of these parameters on a polar plot shows concentric circles with no particular sign from one tooth to another. However, in the presence of cracks in the vicinity of teeth roots, these circular patterns became deformed in the neighborhood of the teeth with defect, which provides a quick and easy visual check to detect a crack and quantify its extent