Comments on ‘Parity vector approach for detecting failures in dynamic systems’

It is shown that the parity vector method defined by Chen and Zhang (1990) is equivalent to the innovation approach for a simple choice of the parity matrix.     

Airborne microwave Doppler measurements of ocean wave directional spectra

Abstract

A technique is presented for measuring ocean wave directional spectra from aircraft using microwave Dopper radar. The technique involves backscattering coherent microwave radiation from a patch of sea surface which is small compared to dominant ocean wavelengths in the antenna look direction, and large compared to these lengths in the perpendicular (azimuthal) direction. The mean Doppler shift of the return signal measured over short time intervals is proportional to the mean sea surface velocity of the illuminated patch. Variable sea surface velocities induced by wave motion therefore produce time-varying Doppler shifts in the received signal. The large azimuthal dimension of the patch implies that these variations must be produced by surface waves travelling near the horizontal antenna look direction thus allowing determination of the direction of wave travel. Linear wave theory is used to convert the measured velocities into ocean wave spectral densities. Spectra measured simultaneously with this technique and two laser profilometers, and nearly simultaneously with a surface buoy, are presented. Applications and limitations of this airborne Doppler technique are discussed.     

DETERMINATION OF ORTHO-NASAL AROMA THRESHOLD FOR MULTICOLORED ASIAN LADY BEETLE IN A CONCORD GRAPE JUICE

ABSTRACT

Sensory evaluation was used to determine the aroma threshold of Harmonia axyridis (multicolored Asian lady beetle [MALB]) in Concord grape juice. Prior to Concord grape juice preparation, MALB was added to the Concord grapes at concentrations of 0 and 8.4 MALB/kg fresh grapes. To determine the odor threshold, the three alternative forced‐choice method of sample presentation was used, with an ascending concentration series of 0.5, 1.5 and 4.5 MALB/kg fresh grapes. The panel aroma threshold concentration, calculated using the best estimate threshold over two panel sessions, was 1.8 MALB/kg fresh grapes. Individual detection thresholds ranged from 0.29 to 7.79 MALB/kg fresh grapes, with 75% of the panelists having a detection threshold at or below 0.87 MALB/kg fresh grapes. These results indicate the influence of low numbers of MALB on Concord grape juice aroma, and suggest the importance of quality control programs, including the implementation of established tolerance limits, to monitor grape quality.

PRACTICAL APPLICATIONS

Harmonia axyridis, the multicolored Asian Ladybeetle (MALB), was originally introduced as a method of biocontrol. However, its presence is now becoming problematic with respect to crop quality. In order to minimize economic losses to the Concord grape industry, determination of the number of MALB required to produce a detectable change in Concord grape juice is critical for juice producers in the establishment of their quality control programs. Therefore, the objective of this study was to determine the aroma threshold level of MALB in Concord grape juice. The panel aroma threshold concentration, calculated using the best estimate threshold was 1.8 MALB/kg fresh grapes, with 75% of the panelists having a detection threshold at or below 0.87 MALB/kg fresh grapes. These results indicate the influence of low numbers of MALB on Concord grape juice aroma, and suggest the importance of quality control programs, including the implementation of established tolerance limits, to monitor grape quality.

     

Transient charging and discharging current study in pure PVF and PVF/PVDF fluoro polyblends for application in microelectronics

The transient current were analysed by considering the effect of variation of forming time, temperature, field and composition of blend specimens. Measurements indicated that transient charging and discharging currents exhibited thermally activated character but did not show mirror image behaviour at different temperatures and field values. The log I\emph{I}–log t\emph{t} plots were found to follow the Curie–Von Schweidler law with the value of decay constant ‘n\emph{n}’ lying in the range of 0·029–2·9456. These observed characteristics also indicated that the transient charging in PVF:PVDF fluoro polyblends occur partly due to orientation of dipoles but predominantly due to trapped space charges and hopping of charge carriers amongst localized states. The modification in transient behaviour on blending PVDF with PVF have been explained on the basis of plasticization effect which increases free volume and molecular mobility and T _g modification in the trap structure.     

THE IMPACT FATIGUE PROPERTIES OF PEARLITIC PLAIN CARBON STEELS

A literature search has revealed that the most extensive study of impact fatigue reported is still that of Stanton and Bairstow (1908) who were the first to work on this topic. Their results, which were on pearlitic plain carbon steels, have been reanalyzed in an attempt to deduce from them the effects of chemical composition on impact fatigue in this class of materials. The results show that when the number of impacts to failure, N_f, is greater than about 10³, N_f and the energy absorbed per impact, E_i, are related by the equation: E_i, =E_o+E_kN_f^?p, where E_o appears to be the impact endurance limit. It is suggested that E_k and p be named respectively the “impact fatigue parameter” and “impact fatigue exponent”. E_k is independent of composition except that it is lower by a factor of about four for two materials which probably failed by an intercrystalline rather than transcrystalline fracture; p has a value of 0.6; and E_o increases monotonically with silicon content but does not vary systematically with the carbon, manganese, sulphur or phorphorus contents. The significance of these results is discussed.     

Creep Parameters of Alumina Containing a Glass Phase Determined in Bending Creep Tests

An alumina ceramic containing a glass phase is investigated in bending creep tests. It is shown how the constitutive equation describing the material behavior can be derived from outer fiber strain measurements.     

Announcing new books in material science

Announcing new books in material science