Source Of Physical Information Research Articles

A Markov chains prognostics framework for complex degradation processes

This paper presents a prognostics methodology to deal with complex degradation processes for which condition monitoring data constitute the only available source of physical information. The proposed methodology is general, but here it is illustrated and tested using a case study about fatigue crack propagation in metallic structures. The prognostics method relies on a stochastic damage model based on Markov chains, which is embedded within a sequential state estimation framework for remaining useful life prediction and time-dependent reliability estimation. As key contribution, the resulting prediction and updating equations are shown to be obtained as closed-form expressions, whereby analytical equations for the remaining useful life and time-dependent reliability are obtained as by-product. Original contributions to the model parameter inference and the minimum required amount of data for prognostics are also provided.

Entropy generation due to jet impingement on a surface: effect of annular nozzle outer angle

PurposeThe purpose of this paper is to examine entropy generation rate in the flow field due jet emanating from an annular nozzle and impinging on to a flat plate. Since the flow field changes with the geometric configuration of the annular nozzle, the influence of nozzle outer cone angle on the entropy generation rate is considered.Design/methodology/approachThe steady flow field pertinent to jet impingement on to a flat plate is modeled with appropriate boundary conditions. A control volume approach is introduced to discretize the governing equations of flow and to simulate the physical situation numerically. Entropy generation rate due to heat transfer and fluid friction is formulated. The resulting entropy equations are solved numerically.FindingsThermodynamic irreversibility, which is quantified through entropy generation rate, gives insight into the thermodynamics losses in the flow system. Entropy generation rate is highly affected by the nozzle outer cone angle. In this case, increasing nozzle outer cone angle enhances the entropy generation rate, particularly due to fluid friction.Research limitations/implicationsThe predictions may be extended to include the nozzle area ratio and mass flow rate variation.Practical implicationsThe paper is a very useful source of physical information for improving nozzle design, particularly that which is used in a laser thick material cutting operation. It disseminates information for those working on both laser machining applications and entropy generation in flow systems.Originality/valueThis paper discusses the physical issues related to the entropy generation rate and offers practical help to an individual starting out on an academic career.

Simple quantum systems as a source of coherent information

A set of very important simple quantum systems is analyzed from the standpoint of the amount of coherent information that is accessible when information channels corresponding to the systems are used. It is shown that for simple quantum models the coherent information can be calculated and used for estimating the potential possibilities of the corresponding quantum channel as a source of physical information in experiments associated with the effects of the coherence of quantum states. The following physical models are studied: a two-level atom in a laser radiation field, an aggregate of two two-level subsystems in a multilevel atom (hydrogen), a system of two two-level atoms in the process of joint quantum-deterministic evolution and under the action of transformations of quantum measurement and quantum duplication, as well as one and two two-level atoms in the process of emission.

First Frequency-Domain Interferometry Observations of Large-Scale Vertical Motion in the Atmosphere

The spatiotemporal distribution of the vertical velocity at synoptic and subsynoptic scales is key to the patterns of weather and climate on earth. On these scales, the vertical velocity is on the order of one to a few centimeters per second, typically about three orders of magnitude smaller than typical horizontal wind velocities. Because of the smallness of large-scale vertical velocities relative to typical horizontal velocities, a direct observation of the large-scale vertical air velocity is extremely difficult. In a case study on observational material obtained during a 68-h experiment using the SOUSY very high frequency (VHF) radar in the Harz Mountains in Germany, the authors present the first intercomparison between three different sources of physical information that can provide large-scale vertical wind velocities: (i) the Doppler shifts observed with a vertically pointing VHF radar ; (ii) the rates of change of the altitudes of refractiveindex discontinuities as identified with frequency-domain interferometry (FDI), which is still a relatively unexplored technique in meteorology; and (iii) the output of a regional numerical weather prediction model (NWPM), which has been set up to model the meteorological situation during the observational period. There are several phenomena that have been known to possibly cause significant biases in mean vertical velocities retrieved from the Doppler shifts measured with vertically pointing clear-air VHF radars: (i) stationary or nonstationary gravity waves with vertical-velocity amplitudes up to the order o f1ms 21; (ii) stationary or horizontally advected tilted refractive-index discontinuities that are aspect sensitive in the VHF regime; and (iii) a correlation between the radar-reflectivity fluctuations and the vertical-velocity fluctuations within a vertically propagating gravity wave. On the basis of an intercomparison between the vertical velocities retrieved from (i) ‘‘standard Doppler’’ VHF radar observations, (ii) VHF FDI observations, and (iii) the NWPM output, the authors present first evidence that, under ideal conditions, VHF FDI can be used to directly monitor large-scale vertical motion.