Autocorrelation Ensemble Average of Larger Amplitude Impact Transients for the Fault Diagnosis of Rolling Element Bearings

Rolling element bearings are one of the critical elements in rotating machinery of energy engineering systems. A defective roller of bearing moves in and out of the load zone during each revolution of the cage. Larger amplitude impact transients (LAITs) are produced when the defective roller passes the load zone centre and the defective area strikes the inner or outer races. A series of LAIT segments with higher signal to noise ratio are separated from a continuous vibration signal according to the bearing geometry and kinematics. In order to eliminate the phase errors between different LAIT segments that can arise from rotational speed fluctuations and roller slippages, unbiased autocorrelation is introduced to align the phases of LAIT segments. The unbiased autocorrelation signals make the ensemble averaging more accurate, and hence, archive enhanced diagnostic signatures, which are denoted as LAIT-AEAs for brevity. The diagnostic method based on LAIT separation and autocorrelation ensemble average (AEA) is evaluated with the datasets captured from real bearings of two different experiment benches. The validation results of the LAIT-AEAs are compared with the squared envelope spectrums (SESs) yielded based on two state-of-the-art techniques of Fast Kurtogram and Autogram.

Magnon and Phonon Excitations in Nanosized NiO

Single-crystal, microcrystalline and nanocrystalline nickel oxides (NiO) have been studied by Raman spectroscopy. A new band at ~200 cm−1 and TO-LO splitting of the band at 350–650 cm−1 have been found in the spectra of single-crystals NiO(100), NiO(110) and NiO(111). The Raman spectra of microcrystalline (1500 nm) and nanocrystalline (13–100 nm) NiO resemble those of the single crystals. They all contain the two-magnon band at 1500 cm−1, indicating that the oxides remain at room temperature in the antiferromagnetic phase. Besides, a new sharp Raman band has been observed at 500 cm−1 in nanocrystalline NiO. Its temperature dependence suggests the magnetic origin of the band, possibly associated with the one-phonon–one-magnon excitation at the Brillouin zone centre.

Fundamental aspects of symmetry and order parameter coupling for martensitic transition sequences in Heusler alloys

Martensitic phase transitions in which there is a group–subgroup relationship between the parent and product structures are driven by combinations of soft-mode and electronic instabilities. These have been analysed from the perspective of symmetry, by considering possible order parameters operating with respect to a parent structure which has space group Im{\bar 3} m. Heusler structures with different stoichiometries are derived by operation of order parameters belonging to irreducible representations {\rm H}^{+}_{1}and P1 to describe the atomic ordering configurations. Electronic instabilities are ascribed to an order parameter belonging to the Brillouin zone centre, \Gamma^{+}_{3}, which couples with shear strains to give tetragonal and orthorhombic distortions. An additional zone centre order parameter, with \Gamma^{+}_{5} symmetry, is typically a secondary order parameter but in some cases may drive a transition. Soft-mode instabilities produce commensurate and incommensurate structures for which the order parameters have symmetry properties relating to points along the Σ line of the Brillouin zone for the cubic I lattice. The electronic and soft-mode order parameters have multiple components and are coupled in a linear–quadratic manner as \lambda q_{\Gamma}q_{\Sigma}^{2}. As well as providing comprehensive tables setting out the most important group–subgroup relationships and the order parameters which are responsible for them, examples of NiTi, RuNb, Ti50Ni50−x Fe x , Ni2+x Mn1−x Ga and Ti50Pd50−x Cr x are used to illustrate practical relevance of the overall approach. Variations of the elastic constants of these materials can be used to determine which of the multiple order parameters is primarily responsible for the phase transitions that they undergo.

Efficacité Du Kaolin (Kalaba) Dans La Gestion Intégrée Des Chenilles Endocarpiques Du Cotonnier Dans La Zone Centre Du Bénin

The study on the efficacy of Kaolin in the integrated management of the endocarpiques larvae of cotton was undertaken in the center of Benin. The objective of the work was to evaluate the potentiality of Kaolin in the control of some endocarpiques larvae of the cotton plant. To achieve this goal, a Fisher block device with 4 treatments and 4 repetitions were set up on two sites. The treatments developed consisted of an untreated plot ; a plot treated with Lambdacyalothrine 15 g/l - chlorpyrifos ethyl 300 g/l; a plot treated with kaolin 5% and another one with the mixture kaolin + Lambdacyalothrine 15 g/l - chlorpyrifos ethyl 300 g/l. The treatment with kaolin was achieved with a back, maintained pressure sprayer. Ten applications were conducted with the kaolin used alone and 6 with the other objects. Results showed that there is no significant difference between the average number of larvae recorded in the plots treated with kaolin and plots which served as control of reference (Lambdacyalothrine 15 g/l - chlorpyrifos ethyl 300 g/l at 1 l/ha). It was the same for the percentage of attacked green capsules and cotton seed production. The effect of kaolin in the control of Haritalodes derogata was low (11.6% of plants attacked against 0.1 % for the chemical reference control and 22.9 % for the untreated plot). The results of Kaolin associated with the binary acaricide, showed that the number of endocarpiques larvae has been significantly reduced compared to the reference control. This study indicates that kaolin can be used like other biological pesticides, as alternative to chemical control and then, constituted an important component of the integrated cotton pests management.

Hydrodynamics of submerged vegetated alluvial channel with downward seepage

The flow conditions in a channel covered with fully submerged Oryza sativa has been investigated considering downward seepage. The flow measurements taken at the upstream free vegetation zone, centre of the vegetation zone, and downstream free vegetation zone will provide a better understanding regarding the flow hydrodynamics in a vegetated channel. The flow velocity, Reynolds stress, and turbulent intensities are reduced at the downstream vegetated section. Downward seepage increases the occurrence of streamwise flux along the length of the channel and vertical flux in the vertically downward direction. Integral length and time scales increase as the percentage of downward seepage increases.

Microstructural, modal and geochemical changes as a result of granodiorite mylonitisation – a case study from the Rolovská shear zone (Čierna hora Mts, Western Carpathians, Slovakia)

Strong tectonic remobilisation and shear zone development are typical features of the easternmost part of the Veporicum tectonic unit in the Western Carpathians. The granodiorite mylonites in the area of the Rolovská shear zone (Čierna hora Mts) underwent a complex polystage evolution during the Hercynian and Alpine orogenies. Deformation during the latter reached greenschist facies under metamorphic conditions. Mylonites are macroscopically foliated rocks with a stretching lineation and shear bands. Structurally different mylonite types, ranging from protomylonites to ulramylonites with typical grainsize reduction from the margins towards the shear zone centre, have been assessed. The modal mineralogy of the different mylonite types changes considerably. Typical is a progressive decrease in feldspar content and simultaneously the quartz and white mica content increases from protomylonites towards the most strongly deformed ultramylonites. The deformation had a brittle character in less deformed rocks and a ductile one in more deformed tectonites. Obvious chemical changes occur in mesomylonites and ultramylonites. During mylonitisation, the original biotite granodiorite was depleted of Mg, Fe, Na, Ca and Ba, while K, Rb and mainly Si increased considerably. Other (major and trace) elements reflect erratic behaviour due to lateral mobility. Chemical changes indicate the breakdown and subsequent recrystallisation of biotite and feldspars and, in turn, the crystallisation of albite and sericite. REE decrease in ultramylonites due to the breakup of accessory minerals during deformation and alteration.

Defect structure and optical phonon confinement in ultrananocrystalline BixSn1−xO2 (x = 0, 0.03, 0.05, and 0.08) synthesized by a sonochemical method

Relaxation of the zone-centre optical phonon selection rule due to size effect causes interesting changes in vibrational spectra.