Encapsulation of air vessel design in a neural network

The trial and error process of calculating the characteristics of an air vessel suitable to protect a rising main against the effects of hydraulic transients has proved to be cumbersome for the design engineer. The own experience and sets of charts, which can be found in the literature, can provide some help. The aim of this paper is to present a neural network allowing instantaneous and direct calculation of air and vessel volumes from the system parameters. This neural network has been implemented in the hydraulic transient simulation package DYAGATS.     

Testing for serial correlation of unknown form in cointegrated time series models

Portmanteau test statistics are useful for checking the adequacy of many time series models. Here we generalized the omnibus procedure proposed by Duchesne and Roy (2004,Journal of Multivariate Analysis,89, 148–180) for multivariate stationary autoregressive models with exogenous variables (VARX) to the case of cointegrated (or partially nonstationary) VARX models. We show that for cointegrated VARX time series, the test statistic obtained by comparing the spectral density of the errors under the null hypothesis of non-correlation with a kernel-based spectral density estimator, is asymptotically standard normal. The parameters of the model can be estimated by conditional maximum likelihood or by asymptotically equivalent estimation procedures. The procedure relies on a truncation point or a smoothing parameter. We state conditions under which the asymptotic distribution of the test statistic is unaffected by a data-dependent method. The finite sample properties of the test statistics are studied via a small simulation study.     

Errors in crack closure measurements caused by flexure test fixture support effects

Flexural tests are sometimes used for the evaluation of fatigue and fracture properties, especially for thin cross sections such as plate material where compact tension speciments cannot be used, or where material thicness is limited in the direction required for data generation. The method is also useful for evaluation of crack closure provided the force transfer occurs correctly. This paper shows how the influence of incorrect test fixture supports, which are outside the standard testing arrangement for such test specimens, can affect the force-displacement curves as evidenced using the backface strain method. The results show that incorrect test fixture supports may cause deviations in the force-displacement trace as an artifact of the testing conditions. This effect can severely influence crack closure measurements. The effect was also modeled with finite element analysis.     

From Effective Hamiltonians to Fluctuation and Dissipation

Irreversible quantum dynamics is reviewed by means of projected resolvents and effective Hamiltonians. It is shown that for a particular partition the dynamical equations are formally identical to the generalized Langevin equation of non-equilibrium statistical mechanics. Three model applications underline the fundamental role played by fluctuations to study line profiles in spectroscopy and to discuss the relationship between fluctuation and dissipation. A new expression of the parameter q characterizing Fano profiles is presented.Dedicated to Jean-Paul Malrieu who advocated the analyses of molecular wave functions in terms of atomic observables and of their fluctuations.     

Thermoplastic blend demixing by a high‐pressure,high‐temperature process

The analysis of a thermoplastic polymer blend requires a precise separation of the blend components, which is usually performed by selective solvent extraction. However, when the components are high‐molecular‐weight polymers, a complete separation is very difficult. The use of fluids in near critical and supercritical conditions becomes a promising alternative to reach a much more precise separation. In this work, a method to separate reactive and physical blends from high‐molecular‐weight commercial polymers is proposed. Polyethylene (PE)/polystyrene (PS) blends were separated into their components with n‐propane, n‐pentane, and n‐heptane at near critical and supercritical conditions. The selectivity of each solvent was experimentally studied over a wide range of temperatures for assessing the processing windows for the separation of pure components. The entire PE phase was solubilized by n‐pentane and n‐heptane at similar temperatures, whereas propane at supercritical conditions could not dissolve the fraction of high‐molecular‐weight PE. The influence of the blend morphology and composition on the efficiency of the polymer separation was studied. In reactive blends, the in situ copolymer formed was solubilized with the PE phase by chemical affinity. The method proposed for blend separation is easy, rapid, and selective and seems to be a promising tool for blend separation, particularly for reactive blends, for which the isolation of the copolymer is essential for characterization © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2361–2369, 2005     

Evidence for non-yrast states in 254No

Evidence for the decay of non-yrast states in ²⁵⁴No has been observed for the first time in an experiment performed at the University of Jyv?skyl?. The experiment employed the JUROGAM array of germanium detectors coupled to the gas-filled recoil separator RITU and the focal-plane spectrometer GREAT. The ground-state rotational band has been tentatively extended up to a spin of 24ℏ and has a smoothly behaving dynamical moment of inertia. It is speculated that the observation of high-energy γ-rays is due to the decay of a K = 3 band-head state.     

Measurement and analysis of complex modulated motions in a weakly nonlinear system

The two-timing dynamics of a forced, weakly nonlinear system are considered. Experimental results on a roll-forced spherical pendulum verify the occurrence of slow-time, subharmonically and chaotically modulated oscillations in a frequency band near resonance; the modulatory behavior follows the occurrence of a Hopf bifurcation in the slow-time coordinates. A phase-sensitive detection method for experimentally isolating the slow-time behavior is described. A Lagrangian model for the pendulum is developed, and slow-time equations are presented. A two-thirds power scalling law relating roll angle to the appearance of the modulations is derived from the slow-time equations and tested with experimental results.     

关于有界性的勒茹米辛型定理

本文对于泛函微分方程建立了关于有界性的新的勒茹米辛型定理，其中不仅可避免采用不易寻找的函数Ｐ，而且还可以采用若干个含有状态变量ｘ的部分变元的李雅普诺夫函数，这样，本文中所得的结果大大改进了已知结果。一方面，它更易于应用；另一方面，保证有界性的条件较少限制，并且，还给出了一些例子来说明所得结果的优越性。     

A Truncated Nonmonotone Gauss-Newton Method for Large-Scale Nonlinear Least-Squares Problems

In this paper, a Gauss-Newton method is proposed for the solution of large-scale nonlinear least-squares problems, by introducing a truncation strategy in the method presented in [9]. First, sufficient conditions are established for ensuring the convergence of an iterative method employing a truncation scheme for computing the search direction, as approximate solution of a Gauss-Newton type equation. Then, a specific truncated Gauss-Newton algorithm is described, whose global convergence is ensured under standard assumptions, together with the superlinear convergence rate in the zero-residual case. The results of a computational experimentation on a set of standard test problems are reported.     

时变脉冲时滞微分方程的稳定性

本文讨论脉冲时滞微分方程零解的稳定性 .应用Lyapunov函数法结合Razu mikhin技巧得到这类方程零解一致稳定和渐近稳定的充分性条件 ,并给出例子以说明所得结论