Non-steady Phenomena in the Vibration of Viscous Cylindrical Long Liquid Bridges

This paper deals with the dynamic response of long cylindrical viscous liquid bridges subjected to an oscillatory microgravity field whose frequency varies linearly with time. The problem has been solved by using a one-dimensional model for the dynamics, derived from Cosserat theory for continuum, in which the axial velocity is considered to be constant over each cross-section of the liquid column. The dynamic response of the liquid bridge has been obtained by applying the Laplace transform to the problem formulation. The results obtained show that a variable -frequency excitation could give rise to erroneous measurements of the resonance frequencies of viscous liquid bridges

Specification and Verification of Distributed Embedded Systems: A Traffic Intersection Product Family

Distributed embedded systems (DESs) are no longer the exception; they are the rule in many application areas such as avionics, the automotive industry, traffic systems, sensor networks, and medical devices. Formal DES specification and verification is challenging due to state space explosion and the need to support real-time features. This paper reports on an extensive industry-based case study involving a DES product family for a pedestrian and car 4-way traffic intersection in which autonomous devices communicate by asynchronous message passing without a centralized controller. All the safety requirements and a liveness requirement informally specified in the requirements document have been formally verified using Real-Time Maude and its model checking features.Comment: In Proceedings RTRTS 2010, arXiv:1009.398

A Theoretical Approach to Impulsive Motion of Viscous Liquid Bridges

This paper deals with the dynamics of isothermal, axisymmetric, viscous liquid columns held by capillary forces between two circular, concentric, solid disks. The transient response of the bridge to an excitation consisting of a small change in the value of the acceleration acting along its axis has been solved by using a linearised one-dimensional Cosserat model, which includes viscosity effects. The main hypothesis of this model is that the axial velocity is considered constant in each section of the liquid bridge. The analysis has been performed by using the Laplace transform

Distributed Real-Time Emulation of Formally-Defined Patterns for Safe Medical Device Control

Safety of medical devices and of their interoperation is an unresolved issue causing severe and sometimes deadly accidents for patients with shocking frequency. Formal methods, particularly in support of highly reusable and provably safe patterns which can be instantiated to many device instances can help in this regard. However, this still leaves open the issue of how to pass from their formal specifications in logical time to executable emulations that can interoperate in physical time with other devices and with simulations of patient and/or doctor behaviors. This work presents a specification-based methodology in which virtual emulation environments can be easily developed from formal specifications in Real-Time Maude, and can support interactions with other real devices and with simulation models. This general methodology is explained in detail and is illustrated with two concrete scenarios which are both instances of a common safe formal pattern: one scenario involves the interaction of a provably safe pacemaker with a simulated heart; the other involves the interaction of a safe controller for patient-induced analgesia with a real syringe pump.Comment: In Proceedings RTRTS 2010, arXiv:1009.398

Response of a liquid bridge to an acceleration varying sinusoidally with time

The response of a long cylindrical liquid column subjected to an axial microgravity field has been experimentally studied on a TEXUS sounding rocket flight to check with theoretical predictions. The expected response of the liquid bridge was a quasi-static amphora-type deformation of the cylindrical shape. However, the experimental results showed a more complex behaviour. Nevertheless it has been possible to find out the reasons of this discrepancy except for a mysterious 0.5% uncertainty in the stimuli

Axisymmetric long liquid bridges in a time-dependent microgravity field

This paper deals with the dynamics of liquid bridges when subjected to an oscillatory microgravity field. The analysis has been performed by using a one-dimensional slice model, already used in liquid bridge problems, which allows to calculate not only the resonance frequencies of a wide range of such fluid configurations but also the dependence of the dynamic response of the liquid bridge on the frequency on the imposed perturbations. Theoretical results are compared with experimental ones obtained aboard Spacelab-Dl, the agreement between theoretical and experimental results being satisfactor

Stability of slender, axisymmetric liquid bridges between unequal disks

The stability of slender, axisymmetric liquid bridges held by surface tension forces between two coaxial, parallel solid disks having different radii is studied by using standard perturbation techniques. The results obtained show that the behaviour of such configurations becomes similar to that of liquid bridges between equal disks when subject to small axial gravity forces

The influence of axial microgravity on the breakage of axisymmetric slender liquid bridges

The dynamics of inviscid, axisymmetric liquid bridges permits a simplified treatment if the bridge is long enough. Under such condition the evolution of the liquid zone is satisfactorily explained through a non-linear one-dimensional model. In the case of breaking, the one-dimensional model fails when the neck radius of the liquid column is close to zero; however, the model allows the calculation of the time variation of the liquid-bridge interface as well as of the fluid velocity field and, because the last part of the evolution is not needed, the overall results such as the breaking time and the volume of each of the two drops resulting after breakage can be calculated. In this paper numerical results concerning the behavior of clinical liquid bridges subjected to a small axial gravitational field are presented