Fourier transform Research Papers - Academia.edu (original) (raw)

We present new multiband CCD photometric observations of three chromospherically active stars with long periods (V2075 Cyg, FG UMa and BM CVn). The observations were made at the Çanakkale Onsekiz Mart University Observatory in 2006 and 2007. We analyzed BVRI (Bessell) CCD observations of these three RS CVn-type SB1 binaries with the following three steps: (i) Photometric rotation periods were obtained by analyzing their light variations with a differential corrections method and a Fourier transform technique. (ii) Light variations, observed over three or more consecutive orbital cycles, were investigated by using dark (cool) spot models with the program SPOT. (iii) Surface differential rotation coefficients for the primary components of these binaries were derived using our own photometric periods together with orbital periods taken from the literature.

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- Fourier transform

In Earth observation programs there is a need of passive low frequency (L-band) measurements to monitor soil moisture and ocean salinity with high spatial resolution 10-20 Km, a radiometric resolution of 1K and a revisit time of 1-3 days [1]. Compared to total power radiometers aperture synthesis interferometric radiometers are technologically attractive because of their reduced mass and hardware requirements. In this field it should be mentioned the one-dimensional (1-D) linear interferometer ESTAR developed by NASA [2] and MIRAS a two-dimensional (2-D) Y-shaped interferometer currently under study by European Space Agency (ESA) [3]. Interferometer radiometers measure the correlation between pairs of nondirective antennas. Each complex correlation is a sample of the "visibility" function which, in the ideal case, is the spatial Fourier transform of the brightness temperature distribution. Since most receiver phase and amplitude errors can be hardware calibrated, Fourier based iterative inversion methods will be useful when antenna errors are small, their radiation voltage patterns are not too different, and mutual coupling is small. In order to minimize on-board hardware requirements-antennas, receivers and correlators-the choice of the interferometer array shape is of great importance since it determines the (u; v) sampling strategy and the minimum number of visibility samples required for a determined aliasing level. In this sense, Y-shaped and triangularshaped arrays with equally spaced antennas are optimal. The main contribution of this paper is a technique that allows us to process the visibility samples over the hexagonal sampling grids given by Y-shaped and triangular-shaped arrays with standard rectangular FFT routines. Since no interpolation processes are involved, the risk of induced artifacts in the recovered brightness temperature over the wide field of view required in Earth observation missions is minimized and signal to noise ratio (SNR) is preserved.

- by Francesc Torres
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- Geophysics, Low Frequency, Geoscience and remote sensing, Earth Observation

AbstractIn Earth observation programs there is a need of passive low frequency (L-band) measurements to monitor soil moisture and ocean salinity with high spatial resolution 1020 Km, a radiometric resolution of 1K and a revisit time of... more

- by Francesc Torres
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- Geophysics, Low Frequency, Geoscience and remote sensing, Earth Observation

Tsallis statistics (or q-statistics) in nonextensive statistical mechanics is a one-parameter description of correlated states. In this paper we use a translated entropic index: 1−qtoq1 - q \to q1−qtoq . The essence of this translation is to improve the mathematical symmetry of the q-algebra and make q directly proportional to the nonlinear coupling. A conjugate transformation is defined $\hat q

- by Sabir Umarov
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- Stochastic Process, Power Law, Gaussian distribution, Fourier transform

Invariant optical correlation method for 3D target detection is addressed. Tridimensionality is expressed in terms of range images. The recognition model is based on a vector space representation using an orthonormal image basis. The recognition method proposed is based on the calculation of the angle between the vector associated with a certain 3D object and a vector subspace. Scale and rotation invariant 3D target detection are obtained using the phase Fourier transform (PhFT) of the range images. In fact, when the 3D object is scaled, the PhFT becomes a distribution multiplied by a constant factor. On the other hand a rotation of the 3D object around the z axis, implies a shift in the PhFT. So, changes of scale and rotation of 3D objects are replaced by changes of intensity and position of PhFT distributions. We applied intensity invariant correlation methods for recognition. In addition to tolerance to scale and rotation, high discrimination against false targets is also achieved.

- by JOSE VALLES
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- Engineering, Physics, Fourier transform, Vector Space

Visual Servoing is generally contained of control and feature tracking. Study of previous methods shows that no attempt has been made to optimize these two parts together. In kernel based visual servoing method, the main objective is to combine and optimize these two parts together and to make an entire control loop. This main target is accomplished by using Lyapanov theory. A Lyapanov candidate function is formed based on kernel definition such that the Lyapanov stability can be verified. The implementation is done in four degrees of freedom and Fourier transform is used for decomposition of the rotation and scale directions from 2D translation. In the present study, a new method in scale and rotation correction is presented. Log-Polar Transform is used instead of Fourier transform for these two degrees of freedom. Tracking in four degrees of freedom is synthesized to show the visual tracking of an unmarked object. Comparison between Log-Polar transform and Fourier transform shows the advantages of the presented method. KBVS based on Log-Polar transform proposed in this paper, because of its robustness, speed and featureless properties.

The microwave spectra of the three singly substituted 13 C isotopomers and 18 O isotopomer of equatorialtrans cyclobutanol, c-C 4 H 7 OH, have been observed in natural abundance by a pulsed-jet Fourier transform microwave spectrometer. The fit for the normal species was improved from the previous study. The rotational constants for the a-13 C, b-13 C, c-13 C and 18 O isotopic species were determined. The five quartic centrifugal distortion constants were determined for the first time. These experimental values are compared to those obtained from ab initio and density functional theory calculations. By utilizing the previously reported microwave rotational constants for the O-D species along with the 15 constants determined from this study combined with the structural parameters predicted from the MP2(full)/6-311+G(d,p) calculations, adjusted r 0 parameters have been obtained. The determined heavy atom distances in Å are: r 0 (C 1 -C 4,5 ) = 1.547(3), r 0 (C 6 -C 4,5 ) = 1.556(3), r 0 (C-O) = 1.412(3) Å and angles O 2 C 1 C 4;5 ¼ 120:2ð5Þ, C 4 C 1 C 5 ¼ 88:9ð5Þ and puckering angle sC 6 C 5 C 4 C 1 = 31.3(10)°. The parameters are compared to the similar ones for some other monosubstituted cyclobutanes as well as to those for cyclobutane.

- by Glen Lindeke
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- Chemistry, Ab initio calculations, Molecular, Fourier transform

It has been developed a general strategy for the determination of pesticides in agrochemicals by Fourier transform near infrared (FT-NIR) spectroscopy. The methodology is based on previous extraction of the active principles through sonication with acetonitrile and direct determination by transmission measurements, using glass vials as measurement cells and univariate calibration at selected wavenumbers as a function of the pesticide to be analyzed. Chlorsulfuron, metamitron, iprodione, pirimicarb, procymidone and tricyclazole were used as test molecules and data obtained by FT-NIR for 20 samples containing one of these active principles compare well with those found by reference liquid chromatography (HPLC) procedures. In short, FT-NIR provides relative standard deviations between 0.04 and 0.7% and limit of detection values ranging from 0.004 to 0.17 mg g −1 with recovery values between 96.4 and 100.5%. On the other hand, FT-NIR offers a 10 times faster methodology than chromatography ones and an environmentally friendly alternative which reduces the reagent consumption to 1 mL acetonitrile per sample.

- by Miguel De La Guardia
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- Analytical Chemistry, Near Infrared, Sample Preparation, Pesticide

We define a notion of Radon Transform for data in an n by n grid. It is based on summation along lines of absolute slope less than 1 (as a function either of x or of y), with values at non-Cartesian locations defined using trigonometric interpolation on a zero-padded grid. The definition is geometrically faithful: the lines exhibit no 'wraparound effects'. For a special set of lines equispaced in slope (rather than angle), we describe an exact algorithm which uses O(N log N) flops, where N = n 2 is the number of pixels. This relies on a discrete projection-slice theorem relating this Radon transform and what we call the Pseudopolar Fourier transform. The Pseudopolar FT evaluates the 2-D Fourier transform on a non-Cartesian pointset, which we call the pseudopolar grid. Fast Pseudopolar FT-the process of rapid exact evaluation of the 2-D Fourier transform at these non-Cartesian grid points-is possible using chirp-Z transforms. This Radon transform is one-to-one and hence invertible on its range; it is rapidly invertible to any degree of desired accuracy using a preconditioned conjugate gradient solver. Empirically, the numerical conditioning is superb; the singular value spread of the preconditioned Radon transform turns out numerically to be less than 10%, and three iterations of the conjugate gradient solver typically suffice for 6 digit accuracy. We also describe a 3-D version of the transform. We review closely related algorithmic work of Mersereau and Oppenheim (1974), Pasciak (1980), Edholm and Herman (1988), Lawton (1988) and Bailey and Swartztrauber (1991) which are precursors of these ideas, but miss the mathematical framework, the geometric faithfulness, and the invertibility.

The direct l-type resonance spectrum of CF 3 CCH has been measured in the v 10 Z3 vibrational state by means of waveguide microwave Fourier transform spectroscopy in the range 8-26 GHz. Three types of direct l-type resonance transitions induced by the (DkZDlZG2) interaction could be observed: 140 transitions following the DJZ0, DkZDlZG2, DjljZ0, selection rule covering values of JZ17-61 and GZjkKlj from 1 to 7, 94 transitions following the DJZ0, DkZDlZG2, DjljZG2, selection rule covering values of JZ26-57 and G from 15 to 24, 90 transitions following the DJZ0, DkZDlZG4 selection rule covering values of JZ34-80 and G from 3 to 12 and 13 transitions following the DJZ0, DkZDlZG6, kZH1, lZH15kZG5, lZG3 selection rule for JZ71-83. 14 A 1-A 2 splitting transitions with klZC1 were measured from JZ33 to 49. Strong perturbations due to D(kKl)ZG3 interactions made possible the observation of perturbation-allowed transitions with selection rule kZG4, lZG35kZG3, lZH1. Furthermore, the rotational transitions JZ2-1, 3-2 and 4-3 have been measured. To make use of the multiple fitting concept, the theory of reduction developed for the v t Z2 vibrational state by Sarka and Harder [K. Sarka, H. Harder, J. Mol. Spectrosc. 197 (1999) 254] has been extended to the v t Z3 vibrational state including terms up to H 62. Owing to problems in the reproduction of data with low K and A 1-A 2 symmetry, two types of fits have been performed using five reduced forms of the effective Hamiltonian. The first type of fit used a reduced data set for which part of the transitions has been omitted. The unitary equivalence of the determined parameter sets has been demonstrated including newly derived relations for parameters in v 10 Z3. In the second type of fit, the complete data set has been included, yielding satisfactory results only in one reduction. In both type of fits, parameters up to sixth order have been determined including the axial rotational constant A and the Coriolis constant Az for both values of l. General features of the direct l-type resonance spectrum in a v t Z3 level are discussed.

- by P. Pracna
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- Engineering, Chemical Physics, Physical sciences, CHEMICAL SCIENCES

There is a vast demand for in vivo methods for the detection of skin cancer, one of the most dangerous skin lesions. Use of near infrared Fourier transform (NIR-FT)-Raman spectroscopy virtually eliminates the fluorescence of the normal cell constituents and provides a signal to noise ratio, r SN , large enough to successfully evaluate the spectra using chemometric methods. A novel fiber optic probe for NIR-FT-Raman spectroscopy was used, which allows sterilization and the prevention of hazards due to laser radiation and makes in vivo measurements possible. The Raman spectra of normal skin are dominated by the connective tissue, mainly collagen type I. The Raman spectra of skin with inflammatory diseases show an increased lipid and water content. Kaposi sarcomas show typical features of tumors mainly in the amide III and the protein backbone range. A clear separation of Raman spectra of normal skin from those of benign and malignant neoplasms can be achieved by cluster analysis. However, the unequivocal diagnosis of skin cancer needs investigation of a larger number of more defined skin samples, taking into consideration the concurrent appearance of different skin symptoms like coloring and inflammation. cal fibers are used in Raman endoscopes [14] for measurement.

- by Sonja Wessel
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- Raman Spectroscopy, Near Infrared, Skin Cancer, Connective tissue

Laser measurement applications Tunable laser measurement Thin film Laser tuning Thin film measurement applications Fourier-transform based analysis a b s t r a c t Film thickness is not only a crucial parameter in producing processes, such as semiconductor and optics production, but also a monitored variable in chemistry and biology, for example for tissue microscopy. Many working principles have been demonstrated and are in use in different fields due to their different limitations (observation film thickness, accuracy, measurement speed, etc.). One of these working principles is thin film reflectometry (TFR). One method is based on a laser source and monitors the reflected intensity over growing film time. Another one employs a spectrally broad light source and measures the reflected intensity using a spectrometer. We introduce and demonstrate a measurement system based on a tunable laser stage. There are several different setups for laser wavelength tuning. One of the most promising solutions is based on monolithic laser diodes. Rapid tuning of the lasers wavelength is crucial for achieving high measurement rates. Monolithic laser diodes offer highest tuning rates and hence high performance. On the other hand, mechanically tunable lasers show broadband spectra that result in higher thickness accuracy in this particular application. Hence, we show a comparison of thin film measurements with a monolithic and a mechanically tunable laser source. This comparison shows that the measurement accuracy of the monolithic laser diode can compete with mechanical tuning. Furthermore, it is a promising approach when measurement tuning speed is an issue.

- by Alexander K Koch
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- Thin Film, Long-range planning, Optical physics, High performance

ing neutral salt and a medium chain alcohol . There-The effect of medium chain alcohol molecules on the size and fore, these elements make the basic components in most shape of sodium dodecylsulfate micelles, and on the self-diffusion microemulsions. However, the intricate behavior of these coefficient of the surfactant and alcohol, has been investigated by mixed micellar aggregates makes it difficult to predict any means of small angle neutron scattering (SANS), and Fourier variation in the system upon variation in the composition of transform pulsed field gradient spin echo (FT-PGSE) nuclear the solution. This problem is caused by a delicate balance magnetic resonance measurements. All measurements were done of attractive and repulsive forces among the amphiphilic in D 2 O containing a sodium chloride concentration of 0.4 mol/kg, molecules in the micelles. and a surfactant concentration of 0.04 mol/kg. The alcohols used

- by Kell Mortensen
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- Engineering, Nuclear Magnetic Resonance, Physical sciences, Structural Change

We study the addditon problem for strongly matricially free random variables which generalize free random variables. Using operators of Toeplitz type, we derive a linearization formula for the matricial R-transform related to the associated convolution. It is a linear combination of Voiculescu's R-transforms in free probability with coefficients given by internal units of the considered array of subalgebras. This allows us to view this formula as the matricial linearization property of the Rtransform. Since strong matricial freeness unifies the main types of noncommutative independence, the matricial R-transform plays the role of a unified noncommutative analog of the logarithm of the Fourier transform for free, boolean, monotone, orthogonal, s-free and c-free independence.

- by Romuald Lenczewski
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- Functional Analysis, Pure Mathematics, Fourier transform, Free Probability

Filter banks with fixed time-frequency resolution, such as the Short-Time Fourier Transform (STFT), are a common tool for many audio analysis and processing applications allowing effective implementation via the Fast Fourier Transform (FFT). The fixed time-frequency resolution of the STFT can lead to the undesirable smearing of events in both time and frequency. In this paper, we suggest adaptively varying STFT time-frequency resolution in order to reduce filter bank-specific artifacts while retaining adequate frequency resolution. Several strategies for systematic adaptation of time-frequency resolution are proposed. The introduced approach is demonstrated as applied to spectrogram displays, noise reduction, and spectral effects processing.

- by Alexey Lukin
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- Computer Science, Audio Signal Processing, Time-Frequency Analysis, Noise reduction

Dedicated to Harry Kurreck on the occasion of his 65th birthday Abstraet. The mechanism of 4-chlorophenol (4CP) photolysis was investigated with the aid of Fou-¡ Transform Electron Paramagnetic Resonance (FT-EPR) and pulsed-laser photolysis combined with High Performance Liquid Chromatography (HPLC) deteetion of stable (diamagnetic) products. With FT-EPR transient free radicals produced by pulsed-laser excitation of solutions of 4CP in alcohols could be identified. Time profiles of the FT-EPR spectra provided information on reaction kinetics and Chemically Indueed Dynamic Electron Polarization (CIDEP) effects. Ir was found that 4CP photolysis in alcohols leads to the simultaneous formation of the phenoxyl radical and radieals produced by hydrogen abstraction from the solvent. CIDEP pattems establish that these radicals are formed in a reaction sequence involving a triplet state precursor and radical pair intermediate. Results of earlier transient optical absorption measurements indicate that the t¡ precursor must be the carbene 4-oxocyclohexa-2,5-dienylidene. This assignment is supported by the finding that photolysis of quinone diazide in a hydrogen-donating solvent gives the same free radical products as those obtained from 4CP. The formation of the phenoxyl radical intermediate accounts for the finding that photolysis of deoxygenated solutions of 4CP in alcohols gives phenol as stable diamagnetic product. By contrast, photolysis of aerated and deoxygenated aqueous solutions of 4CP produces benzoquinone and hydroquinone as primary produets, respectively.

The present work looks into the property changes of polytetra uoro ethylene as a reaction to 23 kGy dose of 2 MeV electron irradiation. A systematic investigation of modiÿcation in physico-chemical properties of the polymer by electron irradiation has been carried out by di erent characterisation techniques viz. fourier transform IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, di erential scanning calorimetry and X-ray di raction analysis. The electron irradiation induced chain scission in the polymer, which resulted in the appearance of some new absorbance bands in the IR region, the formation of relatively stable free radical, decrease in melting point, reduction in thermal stability and decrease in crystallinity of the polymer.

- by D. Khathing
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- Geology, Electron Spin Resonance, Free Radical, Differential scanning calorimetry

Two anamorphic and achromatic Fourier processors were designed and constructed using diffractive and refractive cylindrical lenses. The diffractive lenses are holographic lenses recorded on silver halide material. In both processors the achromatic one-dimensional Fourier transform plane was obtained with two holographic lenses and one refractive cylindrical lens. The image with the same magnification in both directions at the output plane was formed with two different combinations of lenses. The differences between the two processors are analyzed, and in both cases the chromatic aberration in the Fourier plane and in the output plane is evaluated. Even though single cylindrical refractive lenses were used to image in one direction, good results were obtained.

- by Jesús Atencia
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- Mechanical Engineering, Optical Signal Processing, Applied Optics, Optical physics

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- by claude amiot
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- Molecular Spectroscopy, Nitric oxide, High Resolution, Spectrum

Chitosan films obtained by dry phase inversion were prepared from an aqueous solution of chitosan in acetic acid. The films, of thickness less than 20 μm, were transparent, very flexible and had smooth surfaces. Increasing the film thickness induced an increase of the internal tensions and the consequent formation of a rough surface. Structural investigations by X-ray diffraction and Fourier transform IR analysis, showed that the chitosan films, as prepared, are amorphous. Further annealing to evaporate acetic acid and water traces, changed the amorphous phase into a more ordered phase, characterized by diffraction peaks at 2θ values of 9, 17, 20 and 23 degrees. Thermal investigations by TG, DTG, and DTA revealed that the decomposition of the chitosan films as prepared proceeds in two stages, starting from 180°C and 540°C.

- by Vasile Tura
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- Central European history, CHEMICAL SCIENCES, X ray diffraction, Fourier transform

A three-sensor element multipoint optical fibre sensor system capable of detecting varying ethanol concentrations in water for use in industrial process water systems is reported. The sensor system utilizes a U-bend configuration for each sensor element in order to maximize the sensitivity of each of the sensing regions along the optical fibre cable. The sensor system is interrogated using a technique known as optical time domain reflectometry, as this method is capable of detecting attenuation over distance. Analysis of the data arising from the sensor system is performed using artificial neural network pattern recognition techniques, coupled with Fourier-transform-based signal processing. The signal processing techniques are applied to the obtained sensor system data, prior to the artificial neural network analysis, with the aim of reducing the computational resources required by the implemented artificial neural network.

A new digital-signal-processing method for performing modulation tests on Bluetooth transmitters is presented and validated. No preliminary demodulation of the radio frequency transmitted signal is needed to gain the instantaneous frequency trace, on which standard measurement procedures have to be applied. The aforementioned task is, in fact, fulfilled through the application of the short-time Fourier transform (STFT), a typical time-frequency representation, to the acquired samples of the aforementioned signal. Moreover, no specific information concerning the operating conditions of the transmitter under test, such as carrier frequency and hopping sequence, is needed, thus facilitating measurement automation. The optimal tuning of STFT parameters, which are capable of providing the best reconstruction of the instantaneous frequency trajectory as well as the most accurate measurement outcomes, is established as the result of an exhaustive experimental activity.

- by Mauro D'Arco
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- Digital Signal Processing, Radio Frequency, Quality assessment, Fourier transform

A new optical method capable of measuring out-of-plane deformations of rotating objects based on the Fourier transform phase decoding technique is presented. Digital holography is used to test the method, which digitally derotates one of the holograms at its phase reconstruction stage to accurately remove object rotation fringes, uniquely rendering phase maps that quantitatively show the out-of-plane deformation. Commonly, object

- by Carlos Lopez
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- Digital Holography, Optical physics, Fourier transform, Fourier Optics

Wireline transceivers for high-speed data transmission through backplane and ethernet cables are important applications for microelectronic and nanoelectronic CMOS technologies. Although many circuit simulators provide correct system-level and transistor-level simulations, they usually fail to give correct results for many highly lossy or/and highly dispersive channels. This paper discusses the advanced simulator that we developed. It can give correct simulation results

- by dianyong Chen
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- Local Area Networks, Fourier transform, Least Mean Square, Signal to Noise Ratio

This paper describes a novel structure for a hardwired fast Fourier transform (FFT) signal processor that promises to permit digital spectrum analysis to achieve throughput rates consistent with extremely wide-band radars. The technique is based on the use of serial storage for data and intermediate results and multiple arithmetic units each of which carries out a sparse Fourier transform. Details of the system are described for data sample sizes that are binary multiples, but the technique is applicable to any composite number. Index Terms-Cascade Fourier transform, digital signal processor, Doppler radar, fast Fourier transform, radar-sonar signal processor, radix-two fast Fourier transform, real-time signal processor.

- by George Works
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- Distributed Computing, Computer Hardware, Computer Software, Sample Size

We determine all signals giving equality for the discrete Hirschman uncertainty principle. We single out the case where the entropies of the time signal and its Fourier transform are equal. These signals (up to scalar multiples) form an orthonormal basis giving an orthogonal transform that optimally packs a finite-duration discrete-time signal. The transform may be computed via a fast algorithm due to its relationship to the discrete Fourier transform.

- by Murad Ozaydin
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- Mathematics, Information Theory, Entropy, Uncertainty

Novel, two-dimensional MEMS-controllable microlens array has been integrated with a vertical cavity surface emitting laser (VCSEL) array using¯ip-chip assembly. The MEMS/VCSEL hybrid system is built as an ef®cient and reliable smart pixel array for board-to-board or chip-to-chip optical interconnects in digital systems. Theory including geometrical and Fourier transform analysis and beam steering experimental results are presented. By translating polymer microlens, fabricated on a MEMS X±Y movable plate, using electro-thermal actuators, a beam steering angle of 70 mrad is achieved. VCSEL beam steering was successfully demonstrated in our MEMS/VCSEL hybrid system to collimate and steer laser beam for a precision alignment in a two-dimensional free-space optical interconnect. #

Fourier transform infrared (ITIR) spectroscopic measurements, performed in the far-IR region (200400 cm-') on binary coprecipitated Ni(II)-Fe(II1) hydroxides (20-60 at.% Fe/(Ni + Fe)), are presented and discussed. Heating the sample containing 60 at.% Fe to 6OO"C, monitored by differential scanning calorimetry (DSC) measurements, results in the formation of a nickel ferrite structure from its precursor present in binary hydroxides. The role of Fe-to-Ni ratio non-uniformities within the surface and bulk of the binary hydroxide crystallites, as revealed by Miissbauer measurements, Auger electron spectroscopy and depth profiling performed previously, is also discussed with regard to the formation of a-Fe20j and NiO impurities on thermal treatment. 0 1997 Elsevier Science B.V.

- by Mira Ristić
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- Physical Chemistry, FTIR spectroscopy, Differential scanning calorimetry, Nickel

We used high-resolution neutron powder diffraction to accurately measure the atomic positions and bond lengths in biogenic and geological calcite. A special procedure for data analysis was developed in order to take into account the considerable amounts of magnesium present in all the investigated samples. As a result, in biogenic calcite we found some atomic bonds to have significantly different lengths as compared to those in geological calcite, after the contribution of magnesium is accounted for. The maximum effect (elongation up to 0.7%) was found for the C-O bonds. We also analyzed changes in frequencies and spectral widths of normal vibrations of carbonate groups in biogenic calcite (as compared to geological calcite) measured by Raman and Fourier transform IR techniques. Surprisingly, the frequency shifts after subtracting the magnesium contribution are close to zero. At the same time, substantial spectral broadening (up to 1.2%) in biogenic calcite as compared to geological samples was detected. Possible explanations for the experimental findings are discussed.

- by Yael Politi
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- Materials Engineering, Inorganic Chemistry, Data Analysis, Powder Diffraction

We address theoretically the linear stability of a variable aspect ratio, rectangular plate in an uniform and incompressible axial flow. The flutter modes are assumed to be two-dimensional but the potential flow is calculated in three dimensions. For different values of aspect ratio, two boundary conditions are studied: a clampedfree plate and a pinned-free plate. We assume that the fluid viscosity and the plate viscoelastic damping are negligible. In this limit, the flutter instability arises from a competition between the destabilising fluid pressure and the stabilising flexural rigidity of the plate. Using a Galerkin method and Fourier transforms, we are able to predict the flutter modes, their frequencies and growth rates. The critical flow velocity is calculated as a function of the mass ratio and the aspect ratio of the plate. A new result is demonstrated: a plate of finite span is more stable than a plate of infinite span.

- by Christophe Eloy
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- Engineering, Viscoelasticity, Vibration, Aeroelasticity

In this paper, the problem of spectral search-free direction-of-arrival (DOA) estimation in arbitrary nonuniform sensor arrays is addressed. In the first part of the paper, we present a finite-sample performance analysis of the well-known manifold separation (MS) based root-MUSIC technique. Then, we propose a new class of search-free DOA estimation methods applicable to arrays of arbitrary geometry and establish their relationship to the MS approach. Our first technique is referred to as Fourier-domain (FD) root-MUSIC and is based on the fact that the spectral MUSIC function is periodic in angle. It uses the Fourier series to expand this function and reformulate the underlying DOA estimation problem as an equivalent polynomial rooting problem. Our second approach applies the zero-padded inverse Fourier transform to the FD root-MUSIC polynomial to avoid the polynomial rooting step and replace it with a simple line search. Our third technique refines the FD root-MUSIC approach by using weighted least-squares approximation to compute the polynomial coefficients. The proposed techniques are shown to offer substantially improved performance-to-complexity tradeoffs as compared to the MS technique.

We present error bounds for the interpolation with anisotropically transformed radial basis functions for both function and its partial derivatives. The bounds rely on a growth function and do not contain unknown constants. For polyharmonic basic functions in R 2 we show that the anisotropic estimates predict a significant improvement of the approximation error if both the target function and the placement of the centres are anisotropic, and this improvement is confirmed numerically.

- by Rick Beatson
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- Applied Mathematics, Approximation Theory, Radial Basis Function, Pure Mathematics

Silver sulfide nanoparticles dispersed in sol-gel derived hydroxypropyl cellulose (HPC)-silica films have been successfully synthesized using H 2 S gas diffusion method. This is the first attempt to produce silver sulfide nanoparticles using this technique. Ag 2 S nanoparticles are generated through reaction of H 2 S gas with AgNO 3 precursor dissolved in the HPC-silica matrix. Transmission electron microscope (TEM) and atomic force microscope (AFM) analysis reveal nanoparticles size distribution from 2.5 nm to 56 nm for H 2 S gas exposed sample. The surface chemistry of Ag 2 S nanoparticles and sol-gel derived HPC-silica matrix is confirmed by X-ray photoelectron spectroscopy (XPS). The negative shifts in the core-level XPS Ag (3d) binding energy of Ag 2 S nanoparticles are attributed to Ag : S surface atomic ratio exhibited by these nanoparticles with varying processing conditions. Following processing and characterization, suitability of the present method to produce silver sulfide ion-selective electrode is demonstrated by depositing Ag 2 S nanoparticles on a graphite rod. The high reponse function of the electrode is due to the presence of nanoparticles. Work is under progress in our laboratory to synthesize and characterize sol-gel derived Hydroxypropyl Cellulose (HPC)-silica films containing sulfide and metallic nanoparticles of group IB elements. In our earlier communications, the synthesis and characterization of sol-gel derived HPC-silica films containing Au [6] and CuS [7] nonoparticles have been reported. The present technique is a three-step process by which sulfide/metallic nanoparticles embedded in a sol-gel derived HPC-silica film can be synthesized. In the first step, the selected precursor is dissolved in alcoholic solution containing both silica sol and organic

- by Pooja Kumari
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- Materials Engineering, Catalysis, Nanoparticle, Morphology

The Fraunhofer diffraction pattern of an aperture function, which can be described in terms of the superposition of a known aperture function with a half plane, has an amplitude distribution which is real along one direction and complex along the orthogonal direction. The real and imaginary parts of the amplitude distribution are related by Hubert transforms (dispersion relations). These disper sion relations can be used to arrive at the diffraction patterns of a variety of apertures having symmetry properties. Theoretical results are presented to illustrate the diffraction pattern of various apertures.

- by Rajpal S Sirohi
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- Optics, Medical Imaging, Fiber Optics, Telecommunications

an emotion is a mental and physiological state associated with a wide variety of feelings, thoughts, and behavior. Emotions are subjective experiences, or experienced from an individual point of view. Emotion is often associated with mood, temperament, personality, and disposition. Hence, in this paper method for detection of human emotions is discussed based on the acoustic features like pitch, energy etc. The proposed system is using the traditional MFCC approach [2] and then using nearest neighbor algorithm for the classification. Emotions has been classified separately for male and female based on the fact male and female voice has altogether different range [1][4] so MFCC varies considerably for the two. Keywords— Emotion Recognition from Speech, Fourier Transform, MelFilterBank, MFCC, Modern MFCC Approach, Nearest Neighbor Algorithm

- by sohan panwar
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- MFCC, Fourier transform, K-Nearest Neighbor Algorithm

Linear and nonlinear stoehastie wave equations given by a spaee-time Gaussian white noise are eonsidered in a spaee of dimension d 2: 2. In the linear ease the solution is a random Sehwartz distribution. In the nonlinear ease existence and uniqueness of solutions is proven in the framework of Colombeau random generalized funetions. In the ease where the nonlinear drift is given by the Fourier transform f of a eomplex measure (for instanee when f is a trigonometrie funetion) the solution is proven to be IJ1 associated with the solution of the free equation, for any p 2: I.

- by Francesco Russo
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- Mathematical Sciences, Space Time, Wave Equation, Fourier transform

In this report we show that the amplitude of specularly diffracted light from a plane rough surface as a function of incident angle cosine is Fourier transform of the height distribution on the surface. Therefore, an even height distribution function, which is the case for many rough surfaces, can be obtained by measuring the specularly diffracted light intensities. Also, it is observed that for polychromatic illumination the spectrum of the specularly diffracted light is modified and the modification depends on roughness, incident angle, and wavelength. It is also shown that, for a fixed incident angle, the height distribution on the rough plane is Fourier transform of the spectral modifying function. Experimental studies on some surfaces of different roughnesses, prepared by grinding sheet-glasses by powders of different grain sizes, show that the corresponding height distributions are Gaussian and the rms heights obtained by the two approaches are quite consistent.

- by Masoomeh M Dashtdar
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- Light Scattering, Glass, Coherence, Grain size
- by Money Editor
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- Differential Equations, Laplace Transform, Fourier transform

Phase sensitive measurement techniques, such as THz time-domain spectroscopy or dispersive Fourier transform spectroscopy, are very useful tools to obtain a complete set of optical material parameters. When recording the electric field as a function of time delay between THz and optical pulse, the absorption coefficient and the index of refraction can be extracted. However, the analysis shows ambiguity. Here, we describe an analysis which yields a complete set of mathematical solutions and show how the physically relevant can be deduced. We present a comprehensive mathematical survey for parameter extraction. We have recorded the THz spectra of anthracene and the fatty acid capric acid as examples for weakly absorbing solid samples, and an ionic liquid as an example for a strongly absorbing liquid sample. Finally, we discuss the uncertainty of the obtained optical parameters using error propagation of the Fourier transformation with a simple model and a rigorous mathematical procedure.

This paper deals with an application of the Wigner-Ville distribution (WVD) and with usual digitalprocessing techniques, such as the short-time Fourier transform (STET), used in dedicated instrumentation for measuring nonstationary signals. The processed real signals are made analytic by means of Hilbert transformations; then suitable implementations of the windowed STFT and of the pseudo Wigner-Ville distribution (PWVD) in the time domain have been performed. Particularly, the fast Hartley transform (FHT) is used to evaluate the PWVD in the real domain. Furthermore, the use of an efficient interpolation algorithm and of a suitable flat-top windowing function is proposed in order to give accurate real-time frequency and amplitude measurements, respectively.

- by Gregorio Andria
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- Hilbert transform, Digital Systems, Real Time, Fourier transform

A new dynamic harmonic estimator is presented as an extension of the fast Fourier transform (FFT), which assumes a fluctuating complex envelope at each harmonic. This estimator is able to estimate harmonics that are time varying inside the obser- vation window. The extension receives the name &amp;amp;amp;amp;amp;amp;amp;quot;Taylor-Fourier transform (TFT)&amp;amp;amp;amp;amp;amp;amp;quot; since it is based on the McLaurin series expan- sion of

- by Miguel Platas
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- Harmonic Analysis, Thin Film Transistor, Frequency Estimation, Fourier transform

Abstract—The diffraction of E-polarized plane waves by a tandem impedance,slit waveguide is investigated rigorously by using the Fourier transform technique in conjunction with the Mode Matching method. This mixed method,of formulation gives rise to a scalar Wiener-Hopf equation of the second kind,the solution of which contains infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution

- by alinur buyukaksoy
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- Linear Algebra, Fourier transform, Boolean Satisfiability, Numerical Solution

This work aims at exploring the potentiality of the Fourier transform IR spectroscopy (FTIR) to study the effects that can be generated on plastic materials based on poly(vinyl chloride) (PVC) used for extra-corporal medical disposables, after industrial processes such as extrusion, sterilization and conservation. In particular, FTIR equipped with a single attenuated total reflection accessory (ATR) mounted on an infrared microscope (Mic-IR) has been used. At the same time, this paper proposes a quality-control method for semi-finished blood circuits' components, based on the chemometric evaluation of surface-selective spectroscopic signals, i.e. Mic-IR/ATR spectra. Results suggest that IR spectroscopic technique coupled with a multivariate approach might represent a simple and powerful method for quality control of industrial processes.

- by Marina Cocchi
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- Analytical Chemistry, Manufacturing, Chemometrics, Principal Component Analysis

In this work we present final solving Millennium Prize Problems formulated Clay Math. Inst., Cambridge. A new uniform time estimation of the Cauchy problem solution for the Navier-Stokes equations is provided.Describes the loss of... more

- by Aset Durmagambetov
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- Mathematics, Natural Science, Navier-Stokes Equations, Cauchy Problem

A fast and environmentally friendly procedure has been developed for Fourier transform Raman (FT-Raman) determination of a quaternary ammonium compound, Mepiquat chloride, in pesticide emulsifiable concentrate formulations. The method is based on the measurement of peak area values between 711 and 701 cm À1 corrected using a baseline defined at 620 cm À1 and interpolated in an external calibration of Mepiquat chloride standards dissolved in water. FT-Raman spectra were collected over 1.5 min from samples confined in screw cap standard chromatographic glass vials, at a nominal resolution of 4 cm À1 accumulating 25 scans per spectra and using a laser power of 1000 mW. Five commercial samples containing around 4.5% (w/v) Mepiquat chloride (3.8% (w/v) Mepiquat) were analysed by the proposed FT-Raman procedure and results obtained were statistically comparable with those obtained by a chromatographic reference procedure. The developed FT-Raman procedure does not use toxic or harmful solvents and also minimises the contact of the operator with toxic products, being a fast alternative to the chromatographic procedure. #

- by Matti Räsänen
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- Earth Sciences, Geology, Brackish Water, Peru

The standing debate over whether hydrological systems are deterministic or stochastic has been taken to a new level by controversial applications of chaos mathematics. This paper reviews the procedure, constraints, and past usage of a popular chaos time series analysis method, correlation integral analysis, in hydrology and adds a new analysis of daily stream¯ow from a pristine watershed. Signi®cant problems with the use of correlation integral analysis (CIA) were found to include a continued reliance on the original algorithm even though it was corrected subsequently and failure to consider the physics underlying mathematical results. The new analysis of daily stream¯ow reported here found no attractor with D T 5. Phase randomization of the Fourier Transform of stream¯ow was used to provide a better stochastic surrogate than an Autoregressive Moving Average (ARMA) model or gaussian noise for distinguishing between chaotic and stochastic dynamics. Ó : S 0 3 0 9 -1 7 0 8 ( 9 9 ) 0 0 0 0 8 -1

The rheology of crude and purified barley (BBG) and oat (OBG) β-glucan samples were characterized. Sample content and major impurities was characterized by Fourier-transform near infrared Raman and infrared (FT-IR) spectroscopy revealing substantial differences between the β-glucan samples. The purification procedure increased the β-glucan content from 66.7 to 82.4% and from 30.1 to 68.4% for BBG and OBG, respectively. Proton nuclear magnetic resonance ( 1 H NMR) analysis was applied to estimate the β-(1 → 3) to β-(1 → 4) linkage ratio of the β-glucans. The molar mass of BBG and OBG was determined by high performance size-exclusion chromatography (HPSEC) using β-glucan standards and was found to be 126 and 355 kDa, respectively. The viscosity of crude and purified β-glucans was studied at various concentrations (2.5, 5% w/v), temperatures (10-80°C) and shear rates (1-100 s − 1 ). BBG was characterized as a low-viscosity β-glucan with Newtonian flow behavior while OBG was characterized as a high-viscosity β-glucan with shear thinning flow behavior. At equivalent β-glucan concentration in solutions the viscosity for OBG was found to be~100 fold higher than for BBG. A direct viscosity dependence on exact β-glucan content regardless of amount and composition of αglucan impurities was found for both OBG and BBG. This study suggests that the structural characteristics of the β-glucan polymers such as molar mass are of greater functional importance than the presence of lager amounts of starch/α-dextrins as long as the β-glucan samples are compared at equivalent β-glucan doses.

- by Søren B Engelsen and +2
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- Chemical Engineering, Nuclear Magnetic Resonance, Food, Near Infrared