Advanced Diagnostics of Position Sensors for the Actuation Systems of High-Speed Tilting Trains

Trains tilting permits a train to travel at a high speed while maintaining an acceptable passenger ride quality with respect to the lateral acceleration, and the consequent lateral force, received by the passengers when the train travels on a curved track at a speed in excess of the balance speed built into the curve geometry. The tilting of a train carbody is performed by a control and actuation system which operates as a closed servoloop accepting the commands from the train control system, generating the torque necessary to tilt the carbody with respect to the bogie and measuring the tilt angle to close the control loop. Measurement of the tilt angle of each train vehicle is performed by two sensors located in the front and rear part of the vehicle. Since a correct tilt angle measurement is vital for the system operation and for ensuring a safe ride, in case of discrepancy between the signals of the two tilt angle sensors of any vehicle, the tilting operation is disabled and the train speed is reduced. An innovative tilt angle sensors health management system is herein presented that makes intelligent use of all available information to allow detection of malfunctioning of an individual tilt angle sensor, thereby enabling a continued operation of the tilting system and a high speed travel after a sensor failure occurs

Multi-domain service orchestration over networks and clouds: a unified approach

End-to-end service delivery often includes transparently inserted Network Functions (NFs) in the path. Flexible service chaining will require dynamic instantiation of both NFs and traffic forwarding overlays. Virtualization techniques in compute and networking, like cloud and Software Defined Networking (SDN), promise such flexibility for service providers. However, patching together existing cloud and network control mechanisms necessarily puts one over the above, e.g., OpenDaylight under an OpenStack controller. We designed and implemented a joint cloud and network resource virtualization and programming API. In this demonstration, we show that our abstraction is capable for flexible service chaining control over any technology domain

Shear viscosity of a model for confined granular media

The shear viscosity in the dilute regime of a model for confined granular matter is studied by simulations and kinetic theory. The model consists on projecting into two dimensions the motion of vibrofluidized granular matter in shallow boxes by modifying the collision rule: besides the restitution coefficient that accounts for the energy dissipation, there is a separation velocity that is added in each collision in the normal direction. The two mechanisms balance on average, producing stationary homogeneous states. Molecular dynamics simulations show that in the steady state the distribution function departs from a Maxwellian, with cumulants that remain small in the whole range of inelasticities. The shear viscosity normalized with stationary temperature presents a clear dependence with the inelasticity, taking smaller values compared to the elastic case. A Boltzmann-like equation is built and analyzed using linear response theory. It is found that the predictions show an excellent agreement with the simulations when the correct stationary distribution is used but a Maxwellian approximation fails in predicting the inelasticity dependence of the viscosity. These results confirm that transport coefficients depend strongly on the mechanisms that drive them to stationary states

Network Virtual Machine (NetVM): A New Architecture for Efficient and Portable Packet Processing Applications

A challenge facing network device designers, besides increasing the speed of network gear, is improving its programmability in order to simplify the implementation of new applications (see for example, active networks, content networking, etc). This paper presents our work on designing and implementing a virtual network processor, called NetVM, which has an instruction set optimized for packet processing applications, i.e., for handling network traffic. Similarly to a Java Virtual Machine that virtualizes a CPU, a NetVM virtualizes a network processor. The NetVM is expected to provide a compatibility layer for networking tasks (e.g., packet filtering, packet counting, string matching) performed by various packet processing applications (firewalls, network monitors, intrusion detectors) so that they can be executed on any network device, ranging from expensive routers to small appliances (e.g. smart phones). Moreover, the NetVM will provide efficient mapping of the elementary functionalities used to realize the above mentioned networking tasks upon specific hardware functional units (e.g., ASICs, FPGAs, and network processing elements) included in special purpose hardware systems possibly deployed to implement network devices

Free Thermal Convection Driven by Nonlocal Effects

We report and explain a convective phenomenon observed in molecular dynamics simulations that cannot be classified either as a hydrodynamics instability nor as a macroscopically forced convection. Two complementary arguments show that the velocity field by a thermalizing wall is proportional to the ratio between the heat flux and the pressure. This prediction is quantitatively corroborated by our simulations.Comment: RevTex, figures is eps, submited for publicatio

On the Efficiency of Packet Telephony

This paper presents a study on the efficiency of packet switching in providing toll quality telephone services. Packet switching is appealing for the implementation of a commercial telephone network because it features lower cost and higher manageability than circuit switching, and enables integration of real-time and non real-time services. This work compares the real-time efficiency of packet switching and circuit switching, i.e., the volume of voice traffic being guaranteed deterministic quality related to the amount of network resources used. For this purpose, we developed a call level simulator which allows a general topology network to be studied. The simulator performs call admission control according to the availability of the resources required to provide a deterministic delay bound for each call. Statistical data on accepted and rejected calls are the simulation output. Results show that packet size - possibly constrained by the protocol in use - is a key factor in determining the real-time efficiency. The packet size which maximizes real-time efficiency is devised analyticall

Hydrodynamic theory for granular gases

A granular gas subjected to a permanent injection of energy is described by means of hydrodynamic equations derived from a moment expansion method. The method uses as reference function not a Maxwellian distribution $f_{\sf M}$ but a distribution $f_0 = \Phi f_{\sf M}$, such that $\Phi$ adds a fourth cumulant $\kappa$ to the velocity distribution. The formalism is applied to a stationary conductive case showing that the theory fits extraordinarily well the results coming from our molecular dynamic simulations once we determine $\kappa$ as a function of the inelasticity of the particle-particle collisions. The shape of $\kappa$ is independent of the size $N$ of the system.Comment: 10 pages, 9 figures, more about our research in http://www.cec.uchile.cl/cinetica

Network Virtual Machine (NetVM): Portabilità ed efficienza nell'elaborazione di pacchetti di rete

Un progettista di dispositivi di rete deve affrontare, oltre alle problematiche di prestazioni legate all'aumento della velocità di rete, anche la necessità di aumentare la programmabilità di tali dispositivi al fine di semplificare l'implementazione di applicazioni come, ad esempio, firewall e sistemi per l'individuazione di intrusioni (intrusion detection system, IDS). Questo articolo presenta la nostra attività di progettazione e realizzazione di un network processor virtuale, chiamato NetVM, che dispone di un insieme di istruzioni ottimizzate per l'elaborazione dei pacchetti. La NetVM si prefigge di fornire uno strato di compatibilità per l'elaborazione di pacchetti (come ad esempio il filtraggio, il conteggio, lo string matching) eseguiti da varie applicazioni (firewall, network monitor, IDS) così che possano essere eseguiti da un qualunque apparato di rete, dal costoso router al piccolo dispositivo (come ad esempio uno smart phone). Inoltre, la NetVM permetterà di ottenere in modo efficiente corrispondenza tra le sopracitate funzinoalità di elaborazione di pacchetti e unità hardware specifiche (come ad esempio, ASIC, FPGA, ed elementi per l'elaborazione di rete) presenti in specifici sistemi hardware, come apparati di rete o loro component