Maintenance of light-standards—a case-study

This paper discusses several strategies for the maintenance of light-standards, where each light-standard consists of n independent and identical lamps screwed on a lamp assembly. The lamps are subject to stochastic failures, and must be correctly replaced if the number of failed lamps reaches a prespecified number m, a norm that is set by the local management to guarantee a minimum luminance. As lamps have an increasing hazard rate and there is a fixed cost of hoisting the assembly, we propose various variants of the m-failure group replacement rule which have in particular an age-criterion to indicate which of the non-failed lamps must be preventively replaced at the time that the assembly is lowered for a corrective lamp replacement. We show how the optimal threshold age can be determined. It appears that this modification reduces the long run average maintenance cost of the Europe Combined Terminals by approximately 8.3%.     

The distribution |f|λ, oscillating integrals and principal value integrals

We study the coefficients of asymptotic expansions of oscillating integrals. We also consider the connection with the coefficients of Laurent expansions at candidate poles of the distribution |f|^λ and show that some of these coefficients vanish. Next, we express some of the most important of these coefficients as the so-called principal value integrals, first introduced by Langlands. Together with our results on principal value integrals, this leads to new results on the vanishing of these coefficients.     

Sonolysis of metal beta-diketonates in alkanes

The kinetics of metal beta-diketonates sonolysis was studied in hexadecane solutions using a UV/VIS spectrophotometric technique. The following complexes were prepared and studied: Cu(HFAA)(2), Cu(DPM)(2), Fe(ACAC)(3), Ni(DPM)(2), Er(DPM)(3), Nd(DPM)(3), Th(DPM)(4), UO(2)(BTFA)(2).TOPO, and Np(HFAA)(4), where HHFAA is hexafluoroacetylacetone, HDPM is dipivaloylmethane, HACAC is acetylacetone, HBTFA is benzoyltrifluoroacetone, and TOPO is trioctylphosphine oxide. Sonolysis was performed under the following conditions: ultrasonic frequency 22 kHz, intensity of ultrasound 3-5 Wcm(-2), temperature 70-92 degrees C, Ar atmosphere. The kinetic behavior of the studied complexes are interpreted using a two-site model of the sonochemical processes. In the case of metal beta-diketonates with high vapor pressure the sonochemical reactions tend to occur in the gaseous phase of the cavitating bubbles. The sonolysis of less volatile complexes first occur in the liquid reaction zone surrounding the bubbles. Sonication of the studied complexes results in the formation of X-ray amorphous products consisted of a mixture of metal beta-diketonates partial degradation products. Heating of as-prepared sonication products in air yields nanocrystalline oxides of corresponding metals.     

Statistical moments of travel times at second order in isotropic and anisotropic random media

We study the high-frequency propagation of acoustic plane and spherical waves in random media. With the geometrical optics and the perturbation approach, we obtain the travel-time mean and travel-time variance at the second order. The main hypotheses are the Gaussian distribution of the acoustic speed perturbation and a factorized form for its correlation function. The second-order travel-time variance explains the nonlinear behaviour at large propagation distance observed with numerical experiments based on ray tracing. Usually, homogeneity and isotropy of the refractive index are considered. Using the geometrical anisotropy hypothesis we extend the theory to a general class of statistically anisotropic random media.     

Application of mathematical programming in planning of human diets

Mathematical programming models have been developed to find utility maximized nutritious diets. The utility maximized diets have been shown to be more practical, more realistic, and less costly than the non-utility maximized diets. In this study we further increase the desirability of diets by gradually softening those nutrients which have been supplied by the foods in the diet at a cost which is above the market price of the respective nutrient. Marginal analysis is used to find marginal costs of the nutrients. The parametric quadratic programming is used to find the optimum diet where the cost of nutrient is equal to the market price of the nutrient supplement. The resulting diet is more desireable and less costly than the previous diets.     

First Spectra from a New, Wide Band, Hybrid Digital Correlator Spectrometer for the First-HIFI Instrument

We have designed and built a new, wide band, modulable resolution spectrometer, in view of full astronomical qualifying tests, and to prepare future models for the FIRST satellite's heterodyne instrument. Our spectrometer, a hybrid digital Autocorrelator, offers flexibility in terms of bandwidth (from 170MHz to 680MHz) and resolution (from 700kHz to 3MHz). This spectrometer required the development of a dedicated analog filter bank, homemade samplers, and the design of full custom GaAs integrated circuits.Laboratory tests have shown excellent agreement with expected performances and observations performed with the IRAM 30-m radiotelescope have qualified its capabilities. Despite the relatively limited number of channels of our current prototype compared to others spectrometers, the main advantages are its stability (inherent to digital technique), and its spectral versatility.Recent microelectronics advances and rad-tolerance of our spectrometer components are used to prepare a new, compact, and low power consumption autocorrelator in view of a flight model for HIFI, the heterodyne instrument on the ESA cornerstone mission FIRST.     

Identification of Zonal Flows and Their Spatial Distribution in the TJ-II Stellarator Plasmas

JETP Letters - The magnetic and electronic properties of quasi-one-dimensional iron chalcogenide compound KFeS2 have been calculated within two DFT + U approaches based on the simplified LSDA + U...     

Strangelet search and particle production studies in Pb+Pb collisions at 158 AGeV/c at CERN SPS

We searched for long-lived strange quark matter particles, so-calledstrangelets, and studied particle and antiparticle production in Pb+Pb collisions at 158 GeV/c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/c ² and lifetimest _lab>1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.     

Attenuation of Cross-Flow Instability in a Three-Dimensional Boundary Layer by Means of a Multidischarge Actuator System

Doklady Physics - The results of experiments in a low-turbulence subsonic wind tunnel confirming the possibility of a significant attenuation of the cross-flow velocity and the intensity of...     

Feynman path integrals and the trace formula for the Schrödinger operators

We study Schrödinger operators of the form on ^d , whereA ² is a strictly positive symmetricd×d matrix andV(x) is a continuous real function which is the Fourier transform of a bounded measure. If _n are the eigenvalues ofH we show that the theta function is explicitly expressible in terms of infinite dimensional oscillatory integrals (Feynman path integrals) over the Hilbert space of closed trajectories. We use these explicit expressions to give the asymptotic behaviour of (t) for smallh in terms of classical periodic orbits, thus obtaining a trace formula for the Schrödinger operators. This then yields an asymptotic expansion of the spectrum ofH in terms of the periodic orbits of the corresponding classical mechanical system. These results extend to the physical case the recent work on Poisson and trace formulae for compact manifolds.Partially supported by the USP-Mathematisierung, University of Bielefeld (Forschungsprojekt Unendlich dimensionale Analysis)