Rotor Failure Diagnosis of Induction Motors by Wavelet Transform and Fourier Transform in Function of the Load

This paper presents two diagnostic methods for the online detection of broken bars in induction motors with squirrel-cage type rotors. The wavelet representation of a function is a new technique. Wavelet transform of a function is the improved version of Fourier transform. Fourier transform is a powerful tool for analyzing the components of a stationary signal. But it is failed for analyzing the non-stationary signal whereas wavelet transform allows the components of a non-stationary signal to be analyzed. In this paper, our main goal is to find out the advantages of wavelet transform compared to Fourier transform in rotor failure diagnosis of induction motors.

Synthesis and optical property of MgMoO4 crystals

In this work, we report on the synthesis of MgMoO4 crystals by oxide mixed method. The powder was calcined at 1100 degrees C for 4h and analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Field emission gun scanning electron microscopy (FEG-SEM), Ultraviolet-visible (UV-vis) absorption spectroscopy and Photoluminescence (PL) measurement. XRD analyses revealed that the MgMoO4 powders crystallize in a monoclinic structure and are free secondary phases. UV-vis technique was employed to determine the optical band gap of this material. MgMoO4 crystals exhibit an intense PL emission at room temperature with maximum peak at 579 nm (yellow region) when excited by 350 nm wavelength at room temperature.

Photopatternable di-ureasil-zirconium oxocluster organic-inorganic hybrids as cost effective integrated optical substrates

Organic-inorganic hybrids containing methacrylic acid (McOH, CH(2)= C(CH(3))COOH)) modified zirconium tetrapropoxide, Zr(OPr(n))(4), classed as di-ureasil-zirconium oxo-cluster hybrids, have been prepared and structurally characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), Fourier transform infrared (FT-IR) and Raman (FT-Raman) spectroscopies, Si and C nuclear magnetic resonance (NMR), and atomic force microscopy (AFM). XRD and SAXS results have pointed out the presence of Si- and Zr-based nanobuilding blocks (NBBs) dispersed into the organic phase. Inter-NBBs correlation distances have been estimated for the pure di-ureasil and a model compound obtained. by hydrolysis/condensation of Zr(OPr(n))(4):McOH (molar ratio 1: 1): d(Si) approximate to 26 +/- 1 angstrom and d(Zr) approximate to 16 +/- 1 angstrom, respectively. In the case of the di-ureasil-zirconium oxo-cluster hybrids, these distances depend on the Zr relative molar percentage (rel. mol. Zr %) (d(Si) ranges from 18 to 25 angstrom and d(Zr) from 14 to 23 angstrom, as the rel. mol. Zr % increases from 5 to 75), suggesting that the Si- and Zr-based clusters are interconstrained. Complementary data from FT-IR, FT-Raman, (29)Si and (13)C NMR, and AFM support to a structural model where McOH-modified Zr-based NBBs (Zr-OMc) are present over the whole range of composition. At low Zr-OMc contents (rel. mol. Zr % <30) the clusters are well-dispersed within the di-ureasil host, whereas segregation occurs at the 0.1 mu m scale at high Zr-OMc concentration (rel. mol. Zr % = 50). No Zr-O-Si heterocondensation has been discerned. Monomode waveguides, diffractions gratings, and Fabry-Perot cavities have been written through the exposure of the hybrid monoliths to UV light. FT-Raman has shown that the chemical process that takes place under illumination is the polymerization of the methacrylate groups of the Zr-OMc NBBs. The guidance region in patterned channels is a Gaussian section located below the exposed surface with typical dimensions of 320 mu m wide and 88 mu m deep. The effective refractive index is 1.5162 (maximum index contrast on the order of 1 x 10(-4)) and the reflection coeficient of the Fabry-Perot cavity (formed by a grating patterned into a 0.278 cm channel) is 0.042 with a free spectral range value of 35.6 GHz.

Structural refinement, optical and microwave dielectric properties of BaZrO3

In this work, barium zirconate (BaZrO3) ceramics synthesized by solid state reaction method and sintered at 1670 degrees C for 4 h were characterized by X-ray diffraction (XRD), Rietveld refinement, and Fourier transform infrared (FT-IR) spectroscopy. XRD patterns, Rietveld refinement data and FT-IR spectra which confirmed that BaZrO3 ceramics have a perovskite-type cubic structure. Optical properties were investigated by ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) measurements. UV-vis absorption spectra suggested an indirect allowed transition with the existence of intermediary energy levels within the band gap. Intense visible green PL emission was observed in BaZrO3 ceramics upon excitation with a 350 nm wavelength. This behavior is due to a majority of deep defects within the band gap caused by symmetry breaking in octahedral [ZrO6] clusters in the lattice. The microwave dielectric constant and quality factor were measured using the method proposed by Hakki-Coleman. The dielectric resonator antenna (DRA) was investigated experimentally and numerically using a monopole antenna through an infinite ground plane and Ansoft's high frequency structure simulator software, respectively. The required resonance frequency and bandwidth of DRA were investigated by adjusting the dimension of the same material. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Functional Magnetic Resonance Imaging Data Analysis by Autoregressive Estimator

The autoregressive (AR) estimator, a non-parametric method, is used to analyze functional magnetic resonance imaging (fMRI) data. The same method has been used, with success, in several other time series data analysis. It uses exclusively the available experimental data points to estimate the most plausible power spectra compatible with the experimental data and there is no need to make any assumption about non-measured points. The time series, obtained from fMRI block paradigm data, is analyzed by the AR method to determine the brain active regions involved in the processing of a given stimulus. This method is considerably more reliable than the fast Fourier transform or the parametric methods. The time series corresponding to each image pixel is analyzed using the AR estimator and the corresponding poles are obtained. The pole distribution gives the shape of power spectra, and the pixels with poles at the stimulation frequency are considered as the active regions. The method was applied in simulated and real data, its superiority is shown by the receiver operating characteristic curves which were obtained using the simulated data.

Cluster Coordination and Photoluminescence Properties of alpha-Ag2WO4 Microcrystals

In this paper, we report our initial research to obtain hexagonal rod-like elongated silver tungstate (alpha-Ag2WO4) microcrystals by different methods [sonochemistry (SC), coprecipitation (CP), and conventional hydrothermal (CH)] and to study their cluster coordination and optical properties. These microcrystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinements, Fourier transform infrared (FT-IR), X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopies. The shape and average size of these alpha-Ag2WO4 microcrystals were observed by field-emission scanning electron microscopy (FE-SEM). The optical properties of these microcrystals were investigated by ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) measurements. XRD patterns and Rietveld refinement data confirmed that alpha-Ag2WO4 microcrystals have an orthorhombic structure. FT-IR spectra exhibited four IR-active modes in a range from 250 to 1000 cm(-1). XANES spectra at the W L-3-edge showed distorted octahedral [WO6] clusters in the lattice, while EXAFS analyses confirmed that W atoms are coordinated by six O atoms. FE-SEM images suggest that the alpha-Ag2WO4 microcrystals grow by aggregation and the Ostwald ripening process. PL properties of alpha-Ag2WO4 microcrystals decrease with an increase in the optical band-gap values (3.19-3.23 eV). Finally, we observed that large hexagonal rod-like alpha-Ag2WO4 microcrystals prepared by the SC method exhibited a major PL emission intensity relative to alpha-Ag2WO4 microcrystals prepared by the CP and CH methods.

Structural refinement, growth process, photoluminescence and photocatalytic properties of (Ba1-xPr2x/3)WO4 crystals synthesized by the coprecipitation method

Barium praseodymium tungstate (Ba1-xPr2x/3)WO4 crystals with (x = 0, 0.01, and 0.02) were prepared by the coprecipitation method. These crystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinements, Fourier-transform Raman (FT-Raman) and Fourier-transform infrared (FT-IR) spectroscopies. The shape and size of these crystals were observed by field emission scanning electron microcopy (FE-SEM). Their optical properties were investigated by ultraviolet visible (UV-vis) absorption and photoluminescence (PL) measurements. Moreover, we have studied the photocatalytic (PC) activity of crystals for degradation of rhodamine B (RhB) dye. XRD patterns, Rietveld refinements data, FT-Raman and FT-IR spectroscopies indicate that all crystals exhibit a tetragonal structure without deleterious phases. FT-Raman spectra exhibited 13 Raman-active modes in a range from 50 to 1000 cm(-1), while FT-IR spectra have 8 infrared active modes in a range from 200 to 1050 cm(-1). FE-SEM images showed different shapes (bonbon-, spindle-, rice-and flake-like) as well as a reduction in the crystal size with an increase in Pr3+ ions. A possible growth process was proposed for these crystals. UV-vis absorption measurements revealed a decrease in optical band gap values with an increase of Pr3+ into the matrix. An intense green PL emission was noted for (Ba1-xPr2x/3)WO4 crystals (x = 0), while crystals with (x = 0.01 and 0.02) produced a reduction in the wide band PL emission and the narrow band PL emission which is related to f-f transitions from Pr3+ ions. High photocatalytic efficiency was verified for the bonbon-like BaWO4 crystals as a catalyst in the degradation of the RhB dye after 25 min under UV-light. Finally, we discuss possible mechanisms for PL and PC properties of these crystals.

Influence of microstructure variability on short crack growth behavior

Fatigue life in metals is predicted utilizing regression analysis of large sets of experimental data, thus representing the material’s macroscopic response. Furthermore, a high variability in the short crack growth (SCG) rate has been observed in polycrystalline materials, in which the evolution and distributionof local plasticity is strongly influenced by the microstructure features. The present work serves to (a) identify the relationship between the crack driving force based on the local microstructure in the proximity of the crack-tip and (b) defines the correlation between scatter observed in the SCG rates to variability in the microstructure. A crystal plasticity model based on the fast Fourier transform formulation of the elasto-viscoplastic problem (CP-EVP-FFT) is used, since the ability to account for the both elastic and plastic regime is critical in fatigue. Fatigue is governed by slip irreversibility, resulting in crack growth, which starts to occur during local elasto-plastic transition. To investigate the effects of microstructure variability on the SCG rate, sets of different microstructure realizations are constructed, in which cracks of different length are introduced to mimic quasi-static SCG in engineering alloys. From these results, the behavior of the characteristic variables of different length scale are analyzed: (i) Von Mises stress fields (ii) resolved shear stress/strain in the pertinent slip systems, and (iii) slip accumulation/irreversibilities. Through fatigue indicator parameters (FIP), scatter within the SCG rates is related to variability in the microstructural features; the results demonstrate that this relationship between microstructure variability and uncertainty in fatigue behavior is critical for accurate fatigue life prediction.

Studio di semiconduttori mesoporosi

I semiconduttori porosi in passato erano considerati dannosi per l'industria microelettronica: solo negli ultimi decenni è stato scoperto che essi posseggono particolari proprietà che li differenziano fortemente dai rispettivi semiconduttori integri, pertanto questa categoria di materiali oggi rappresenta un nuovo settore di ricerca. In questo lavoro di tesi si discutono: la classificazione, la geometria e la morfologia delle strutture porose; la tecnica di "etching" elettrochimico impiegata per realizzare i pori nei semiconduttori; i modelli e i meccanismi di formazione dei pori; la tecnica di spettroscopia elettrochimica FFT-IS("Fast Fourier Transform Impedance Spectroscopy") utile nell'analisi in tempo reale della formazione dei pori; le possibili applicazioni di questi materiali.

Parallel vector processing of multidimensional orthogonal transforms for digital signal processing applications

The performance of the parallel vector implementation of the one- and two-dimensional orthogonal transforms is evaluated. The orthogonal transforms are computed using actual or modified fast Fourier transform (FFT) kernels. The factors considered in comparing the speed-up of these vectorized digital signal processing algorithms are discussed and it is shown that the traditional way of comparing th execution speed of digital signal processing algorithms by the ratios of the number of multiplications and additions is no longer effective for vector implementation; the structure of the algorithm must also be considered as a factor when comparing the execution speed of vectorized digital signal processing algorithms. Simulation results on the Cray X/MP with the following orthogonal transforms are presented: discrete Fourier transform (DFT), discrete cosine transform (DCT), discrete sine transform (DST), discrete Hartley transform (DHT), discrete Walsh transform (DWHT), and discrete Hadamard transform (DHDT). A comparison between the DHT and the fast Hartley transform is also included.(34 refs)

Artists' advance: decreased upper alpha power while drawing in artists compared with non-artists

Brain mechanisms associated with artistic talents or skills are still not well understood. This exploratory study investigated differences in brain activity of artists and non-artists while drawing previously presented perspective line-drawings from memory and completing other drawing-related tasks. Electroencephalography (EEG) data were analyzed for power in the frequency domain by means of a Fast Fourier Transform (FFT). Low Resolution Brain Electromagnetic Tomography (LORETA) was applied to localize emerging significances. During drawing and related tasks, decreased power was seen in artists compared to non-artists mainly in upper alpha frequency ranges. Decreased alpha power is often associated with an increase in cognitive functioning and may reflect enhanced semantic memory performance and object recognition processes in artists. These assumptions are supported by the behavioral data assessed in this study and complement previous findings showing increased parietal activations in non-artists compared to artists while drawing. However, due to the exploratory nature of the analysis, additional confirmatory studies will be needed.

PROPERTIES AND STRUCTURES OF Li-N BASED HYDROGEN STORAGE MATERIALS

Traditional transportation fuel, petroleum, is limited and nonrenewable, and it also causes pollutions. Hydrogen is considered one of the best alternative fuels for transportation. The key issue for using hydrogen as fuel for transportation is hydrogen storage. Lithium nitride (Li3N) is an important material which can be used for hydrogen storage. The decompositions of lithium amide (LiNH2) and lithium imide (Li2NH) are important steps for hydrogen storage in Li3N. The effect of anions (e.g. Cl-) on the decomposition of LiNH2 has never been studied. Li3N can react with LiBr to form lithium nitride bromide Li13N4Br which has been proposed as solid electrolyte for batteries. The decompositions of LiNH2 and Li2NH with and without promoter were investigated by using temperature programmed decomposition (TPD) and X-ray diffraction (XRD) techniques. It was found that the decomposition of LiNH2 produced Li2NH and NH3 via two steps: LiNH2 into a stable intermediate species (Li1.5NH1.5) and then into Li2NH. The decomposition of Li2NH produced Li, N2 and H2 via two steps: Li2NH into an intermediate species --- Li4NH and then into Li. The kinetic analysis of Li2NH decomposition showed that the activation energies are 533.6 kJ/mol for the first step and 754.2 kJ/mol for the second step. Furthermore, XRD demonstrated that the Li4NH, which was generated in the decomposition of Li2NH, formed a solid solution with Li2NH. In the solid solution, Li4NH possesses a similar cubic structure as Li2NH. The lattice parameter of the cubic Li4NH is 0.5033nm. The decompositions of LiNH2 and Li2NH can be promoted by chloride ion (Cl-). The introduction of Cl- into LiNH2 resulted in the generation of a new NH3 peak at low temperature of 250 °C besides the original NH3 peak at 330 °C in TPD profiles. Furthermore, Cl- can decrease the decomposition temperature of Li2NH by about 110 °C. The degradation of Li3N was systematically investigated with techniques of XRD, Fourier transform infrared (FT-IR) spectroscopy, and UV-visible spectroscopy. It was found that O2 could not affect Li3N at room temperature. However, H2O in air can cause the degradation of Li3N due to the reaction between H2O and Li3N to LiOH. The produced LiOH can further react with CO2 in air to Li2CO3 at room temperature. Furthermore, it was revealed that Alfa-Li3N is more stable in air than Beta-Li3N. The chemical stability of Li13N4Br in air has been investigated by XRD, TPD-MS, and UV-vis absorption as a function of time. The aging process finally leads to the degradation of the Li13N4Br into Li2CO3, lithium bromite (LiBrO2) and the release of gaseous NH3. The reaction order n = 2.43 is the best fitting for the Li13N4Br degradation in air reaction. Li13N4Br energy gap was calculated to be 2.61 eV.

Universally Applicable Model for the Quantitative Determination of Lake Sediment Composition Using Fourier Transform Infrared Spectroscopy

ABSTRACT: Fourier transform infrared spectroscopy (FTIRS) can provide detailed information on organic and minerogenic constituents of sediment records. Based on a large number of sediment samples of varying age (0�340 000 yrs) and from very diverse lake settings in Antarctica, Argentina, Canada, Macedonia/Albania, Siberia, and Sweden, we have developed universally applicable calibration models for the quantitative determination of biogenic silica (BSi; n = 816), total inorganic carbon (TIC; n = 879), and total organic carbon (TOC; n = 3164) using FTIRS. These models are based on the differential absorbance of infrared radiation at specific wavelengths with varying concentrations of individual parameters, due to molecular vibrations associated with each parameter. The calibration models have low prediction errors and the predicted values are highly correlated with conventionally measured values (R = 0.94�0.99). Robustness tests indicate the accuracy of the newly developed FTIRS calibration models is similar to that of conventional geochemical analyses. Consequently FTIRS offers a useful and rapid alternative to conventional analyses for the quantitative determination of BSi, TIC, and TOC. The rapidity, cost-effectiveness, and small sample size required enables FTIRS determination of geochemical properties to be undertaken at higher resolutions than would otherwise be possible with the same resource allocation, thus providing crucial sedimentological information for climatic and environmental reconstructions.