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Fourier Transform (fourier + transform)
Kinds of Fourier Transform Terms modified by Fourier Transform Selected AbstractsEfficacy of laser Doppler flowmetry for the diagnosis of revascularization of reimplanted immature dog teethDENTAL TRAUMATOLOGY, Issue 2 2001Kallaya Yanpiset Abstract , This study was performed to assess if laser Doppler flowmetry (LDF) is an improved method for the detection of revascularization of replanted teeth. Teeth were extracted and reimplanted under different experimental conditions. LDF readings were taken before extraction and weekly for 3 months. In control teeth, LDF baseline readings were taken and then repeated after the apical blood vessels were cut surgically. At the end of 3 months it was determined radiographically and histologically whether revascularization had occurred, i.e. vitality had returned. Results: LDF readings correctly predicted the pulp status (vital vs. non-vital) in 83.7% of the readings. 73.9% (17 of 23) were correct for the vital teeth and 95% (19 of 20) were correct for the non-vital teeth. Fisher's exact test (2-tail) indicated that there was no significant association between the efficacy of LDF and tooth type (P=0.166), although P2 was the least accurate tooth tested. Wilcoxon's matched-pair signed rank test demonstrated that in the revascularized (vital) teeth, the flux value between the baseline and week 2 dropped significantly (P=0.0001), increased significantly from week 2 to week 4 (P=0.0001) and then decreased steadily until week 12. However, at week 12 the flux was still significantly higher than at week 2 (P=0.010). In the teeth that failed to revascularize, the flux value dropped significantly by weeks 1 and 2 (P=0.004 and P=0.0001, respectively). Flux values did not increase from week 2. A Fast Fourier Transform (FFT) analysis confirmed a pulse of dominant frequency of 2 Hz in the teeth that returned to vitality and the lack thereof in those that stayed non-vital. One tooth in which the flux value evaluation indicated a non-vital tooth but the radiographic/histologic findings showed vital (false negative) possessed a pulse of dominant frequency and proved by this method to have successfully revascularized. [source] The application of modified lapped transform domain median filter to narrow,band interference excision in DSSS systemsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 4 2001Chongni Li Guangruihu A novel communication receiver which uses lapped transform (LT) incorporating modified median filter (MMF) algorithm is designed for narrow,band interference (NB1) excision. Comparing to traditional Fourier Transform, LT has longer basis vectors, less spectral leakage, thus better frequency resolution. The LT domain MMF algorithm takes full advantages of the direct sequence spread spectrum signal, as well as the characteristics of LT, performs the transform domain filtering twice. The first filtering locates the position of interference and mitigates most of them. The second filtering was performed in a small neighborhood of the located interference. So LT domain MMF algorithm can completely mitigate the interference without distorting the desired signal. Simulation results demonstrated the improved BER performance and increased robustness of our approach. [source] Analytical solution for the electric potential in arbitrary anisotropic layered media applying the set of Hankel transforms of integer orderGEOPHYSICAL PROSPECTING, Issue 5 2006E. Pervago ABSTRACT The analytical solution and algorithm for simulating the electric potential in an arbitrarily anisotropic multilayered medium produced by a point DC source is here proposed. The solution is presented as a combination of Hankel transforms of integer order and Fourier transforms based on the analytical recurrent equations obtained for the potential spectrum. For the conversion of the potential spectrum into the space domain, we have applied the algorithm of the Fast Fourier Transform for logarithmically spaced points. A comparison of the modelling results with the power-series solution for two-layered anisotropic structures demonstrated the high accuracy and computing-time efficiency of the method proposed. The results of the apparent-resistivity calculation for both traditional pole-pole and tensor arrays above three-layered sequence with an azimuthally anisotropic second layer are presented. The numerical simulations show that both arrays have the same sensitivity to the anisotropy parameters. This sensitivity depends significantly on the resistivity ratio between anisotropic and adjacent layers and increases for the models with a conductive second layer. [source] A funerary rite study of the Phoenician,Punic necropolis of Mount Sirai (Sardinia, Italy)INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 2 2010G. Piga Abstract A recent excavation in the Phoenician,Punic necropolis of Mount Sirai, located in the southwestern part of Sardinia, Italy, has brought to light a number of tombs contextually attributed to a period from the early 6th to early 5th century BC, which is simultaneous with the beginning of the Carthago influence in Sardinia. Among the interred burials recently brought to light, the skeletal remains, sometimes of two superposed bodies, are found in a primary position and with fine anatomic connection. Some of the bones were visually stained, suggesting they were possibly subjected to fire treatment. In order to ascertain more objectively whether the bodies were subjected to burning, the bones from all the tombs were investigated by powder X-ray diffraction (XRD) and Fourier Transform infra-red (FT-IR) spectroscopy techniques. After excluding the role of important diagenetic effects, from line broadening/sharpening analysis of hydroxylapatite in the bones according to the Rietveld method, it was evaluated that the bodies were probably subjected to a temperature regime from 300 to 700°C. These data were supplemented and confirmed by an analysis of the splitting factor (SF) of apatite phosphate peaks in the infra-red spectrum of the bones. Our results indicate the existence of a rite intermediate between incineration and inhumation. This sort of ,semi-combustion', perhaps limited to the period of the early 5th century BC, appears to be peculiar just to this site. Copyright © 2008 John Wiley & Sons, Ltd. [source] Research Article: Fingerprinting Analysis of Saposhnikovia divaricata using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid ChromatographyJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2010Yue-Yang Xin The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar and polar extracts (control substance for plant drug [CSPD] A and B) from the roots of 12 specimens of Saposhnikovia divaricata (Turcz.) Schischk were achieved with Fourier Transform (FT)-NMR spectrometer and assigned by comparison to each other and to the 1H NMR spectra of the isolated individual compounds. These fingerprints were found to be uniform in terms of the specificity for the implication of all 12 specimens being systematically of the same origin. The uniformity was further affirmed by high performance liquid chromatography (HPLC), which also revealed exactly identical specificity for the identified S. divaricata species with the 1H NMR appearances of corresponding CSPD on the part of the composition of characteristic constituents when comparing to corresponding individual compounds. This investigation unambiguously shows that the specific signals from the chemotaxonomically significant compounds of chromones and coumarins in S. divaricata are exhibited distinctively in the composite features of both 1H NMR fingerprints and HPLC profiles. The 1H NMR and HPLC profiles established can successfully be used as reference for the authentication of the origin of S. divaricata species as well as for chemotaxonomic studies. [source] Fingerprinting Analysis of Rhizoma Chuanxiong of Commercial Types using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography MethodJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2009Hai-Lin Qin Abstract The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar extracts (control substance for a plant drug (CSPD) A) from Rhizoma chuanxiong, the rhizomes of Ligusticum chuanxiong Hort., of seven specimens from different sources were measured on Fourier Transform (FT)-NMR spectrometer and assigned by comparing them with the 1H NMR spectra of the isolated pure compounds. The 1H NMR fingerprints showed exclusively characteristic resonance signals of the major special constituents of the plant. Although the differences in the relative intensity of the 1H NMR signals due to a discrepancy in the ratio of the major constituents among these samples could be confirmed by high performance liquid chromatography analysis, the general features of the 1H NMR fingerprint established for an authentic sample of the rhizomes of L. chuanxiong exhibited exclusive data from those special compounds and can be used for authenticating L. Chuanxiong species. [source] Novel experiments and a mechanistic model for macroinstabilities in stirred tanksAICHE JOURNAL, Issue 2 2006A. Paglianti Abstract In this work a new experimental technique and a simple model for the identification and the analysis of macro-instabilities (MIs) in stirred tanks are presented. A pressure transducer is proposed for detecting the MIs that can take place inside a stirred vessel; its main advantages are the non-intrusivity, cheapness, and simplicity of installation and operation. Moreover, it can be used for both laboratory and industrial scale stirred tanks. The experimental technique and the time series analysis method, based on Fast Fourier Transform (FFT), are shown to provide reliable information on the frequency of MIs, through the comparison of the present data with those, from literature, obtained in similar systems. Its applicability to solid-liquid systems is also assessed. Afterwards, the data collected in several conditions differing by geometric characteristics of the stirred tanks and by the physical properties of the systems are presented. Finally, a new simplified model, based on the theory of impinging jets,1 is suggested for predicting the MI frequency. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Analysis of low content drug tablets by transmission near infrared spectroscopy: Selection of calibration ranges according to multivariate detection and quantitation limits of PLS modelsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2008Manel Alcalà Abstract The content uniformity of low dose products is a major concern in the development of pharmaceutical formulations. Near infrared spectroscopy may be used to support the design and optimization of potent drug manufacturing processes through the analysis of blends and tablets in a relatively short time. A strategy for the selection of concentration ranges in the development of multivariate calibration is presented, evaluating the detection and quantitation limits of the obtained multivariate models. The strategy has been applied to the determination of an active principle in pharmaceutical tablets of low concentration (0,5%, w/w), using Fourier Transform Near Infrared (FT-NIR) transmission spectroscopy. The quantitation and detection limits decreased as the upper concentration level of the calibration models was reduced. The results obtained show that the selection of concentration ranges is a critical aspect during model design. The selection of wide concentration ranges with high levels is not recommended for the determination of analytes at minor levels (<1%, w/w), even when the concentration of interest is within the range of the model. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:5318,5327, 2008 [source] A neural network-based approach to determine FDTD eigenfunctions in quantum devicesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009Antonio Soriano Abstract This article combines a Neural Network (NN) algorithm with the Finite Difference Time Domain (FDTD) technique to estimate the eigenfunctions in quantum devices. A NN based on the Least Mean Squares (LMS) algorithm is combined with the FDTD technique to provide a first approach to the confined states in quantum wires. The proposed technique is in good agreement with analytical results and is more efficient than FDTD combined with the Fourier Transform. This technique is used to calculate a numerical approximation to the eigenfunctions associated to quantum wire potentials. The performance and convergence of the proposed technique are also presented in this article. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2017,2022, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24562 [source] Numerical analysis of interferograms for evaluation of tear film build-up timeOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2009Dorota H. Szczesna Abstract The lateral shearing interferometer was applied to the in vivo dynamic investigation of the external surface of the pre-corneal tear film after an eye blink. Sequences of interferograms were recorded at a sampling frequency of 25 Hz. Immediately after every eye blink, a bright pattern was observed under the interference fringes. This disappeared after a short time interval (around 0.5,2 s): smooth interference fringes were then observed, corresponding to the creation of a smooth anterior optical surface over the cornea. The purpose of this study is to describe in detail the kinetics of pre-corneal tear film stability and to propose quantitative measures of the stabilisation process in healthy eyes during the 3 s period after a blink. Two methods of quantitative assessment of the tear film build-up time are presented. The first is based upon the evaluation of the inhomogeneity of the background of the interferogram; the second evaluates the orientation of the structure of the background by the analysis of the zero order of the Fast Fourier Transform (FFT) spectrum. The quasi-vertically oriented bright line patterns observed in interferograms immediately after a blink and the mirror-symmetry of their tilts for right and left eyes indicate that the pattern is related to the wiping movements of the upper eyelids during the eye blink. [source] Carbon nanotube probe resolution: a quantitative analysis using Fourier TransformPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2004H. R. Gutiérrez Abstract A method to quantify the resolution of atomic force microscopy (AFM) probes using Fourier analysis of the AFM images is proposed. The maximum detectable spatial frequency obtained from the power spectrum was used to estimate the lateral resolution. Carbon nanotube tips were successfully used to study very dense arrays of semiconductor nanostructures. In particular, accurate measurements of shallow facet angles were obtained, which are in perfect agreement with results obtained by two complementary techniques , High Resolution Transmission Electron Microscopy and Reflection High-Energy Electron Diffraction. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Semi-classical calculation of resonant states of a charged particle interacting with a metallic surfacePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2005John Jairo Zuluaga Abstract We assess the applicability of the semi-classical approach of Herman,Kluk with filter diagonalization to determine resonant states of either the electron-surface system or the ion-surface system. An effective potential model of the interaction of an electron with a ruthenium metallic surface is used. The evolution of the wave-function and the resonant states of this system are calculated. Analogous results for the interaction of the system formed by the H, and the ruthenium surface are presented. For the calculation of the resonances, the semi-classical wave-function is found, and the autocorrelation function between the initial and final wave-functions is calculated, from which the position and width of the resonances are extracted by using the harmonic inversion by filter diagonalization. The results are compared with results available in the literature for similar models obtained by quantum calculations using fast Fourier Transform. The positions of the lower-lying resonances found with the semi-classical and quantum approaches match closely, while the values of the widths of the resonances show larger discrepancies. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of coupling agents on the oxidation and darkening of cellulosic materials used as reinforcements for thermoplastic matrices in compositesPOLYMER ENGINEERING & SCIENCE, Issue 2 2000J. Martínez Urreaga Oxidation and darkening occur during the processing of composites made from thermoplastic matrices and cellulosic reinforcements. We have studied the effects of several coupling agents on both the oxidation and darkening of cellulosic materials at temperatures close to those used in the processing of cellulose-reinforced thermoplastics. A maleated polypropylene wax (Epolene E-43TM) and two silanes (N-2-aminoethyl-3-aminopropyltrimethoxy silane and methyltrimethoxysilane) were used as coupling agents. Oxidation was measured by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. Standard colorimetry was used to measure darkening. Coupling agent effects depend on the nature and extent of cellulose modification achieved by treatments and the nature of the coupling agent. Epolene wax E-43 produced scarce effects on both the oxidation and darkening of cellulosic materials at 200°C. Only for longer oxidation times was an increase in oxidation and darkening observed in E-43-treated samples. Silane coupling agents inhibited the formation of carbonyl and carboxyl groups for shorter oxidation times. The diaminosilane produced a stronger darkening, probably due to a chemical reaction that generated new chromophores containing CN bonds. [source] A simple method for computer quantification of stage REM eye movement potentialsPSYCHOPHYSIOLOGY, Issue 3 2001Xin Tan We describe a simple method for computer quantification of eye movement (EM) potentials during REM sleep. This method can be applied by investigators using either period-amplitude (PA) or Fast Fourier Transform (FFT) spectral EEG analysis without special hardware or computer programming. It provides good correlations with visual ratings of EM in baseline sleep and after administration of GABAergic hypnotics. We present baseline data for both PA and FFT measures for 16 normal subjects, studied for 5 consecutive nights. Both visually rated and computer-measured EM density (EMD) showed high night-to-night correlations across baseline and drug nights and the computer measures detected the EMD suppression that is produced by GABAergic drugs. Measurement of EM in addition to stage REM provides biologically significant information and application of this simple computer method, which does not require pattern recognition algorithms or special hardware, could provide reliable data that can be compared across laboratories. [source] Intermediate-term variations in solar radius during solar cycle 23ASTRONOMISCHE NACHRICHTEN, Issue 4 2009H. Kiliç Abstract In this study, we look for the mid-term variations in the daily average data of solar radius measurements made at the Solar Astrolabe Station of TUBITAK National Observatory (TUG) during solar cycle 23 for a time interval from 2000 February 26 to 2006 November 15. Due to the weather conditions and seasonal effect dependent on the latitude, the data series has the temporal gaps. For spectral analysis of the data series, thus, we use the Date Compensated Discrete Fourier Transform (DCDFT) and the CLEANest algorithm, which are powerful methods for irregularly spaced data. The CLEANest spectra of the solar radius data exhibit several significant mid-term periodicities at 393.2, 338.9, 206.5, 195.2, 172.3 and 125.4 days which are consistent with periods detected in several solar time series by several authors during different solar cycles. The knowledge relating to the origin of solar radius variations is not yet present. To see whether these variations will repeat in next cycles and to understand how the amplitudes of such variations change with different phases of the solar cycles, we need more systematic efforts and the long-term homogeneous data. Since most of the periodicities detected in the present study are frequently seen in solar activity indicators, it is thought that the physical mechanisms driving the periodicities of solar activity may also be effective in solar radius variations (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Vibrational spectroscopic studies to acquire a quality control method of Eucalyptus essential oils,BIOPOLYMERS, Issue 5 2005M. Baranska Abstract This article presents a novel and original approach to analyze in situ the main components of Eucalyptus oil by means of Raman spectroscopy. The obtained two-dimensional Raman maps demonstrate a unique possibility to study the essential oil distribution in the intact plant tissue. Additionally, Fourier Transform (FT)-Raman and attenuated total reflection (ATR)-IR spectra of essential oils isolated from several Eucalyptus species by hydrodistillation are presented. Density Functional Theory (DFT) calculations were performed in order to interpret the spectra of the essential oils of the Eucalyptus species. It is shown that the main components of the essential oils can be recognized by both vibrational spectroscopic techniques using the spectral information of the pure terpenoids. Spectroscopic analysis is based on the key bands of the individual volatile substances and therefore allows one to discriminate different essential oil profiles of several Eucalyptus species. It has been found that the presented spectroscopic data correlate very well with those obtained by gas chromatography (GC) analysis. All these investigations are helpful tools to generate a fast and easy method to control the quality of the essential oils with vibrational spectroscopic techniques in combination with DFT calculations. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 237,248, 2005 [source] 4334: Fully automated corneal endothelial morphometry of a large set of images captured by clinical specular microscopyACTA OPHTHALMOLOGICA, Issue 2010C BUCHT Purpose The endothelial cell density is the most important morphological factor of the corneal endothelium. Morphometry of the corneal endothelium is an important part of several clinical applications. Morphometry of the endothelium is presently carried out by semi automated analysis of pictures captured by Clinical Specular Microscopy (CSM). The need of operator involvement makes this process time consuming. This study presents a method for fully automated analysis of a large range of in vivo images of the corneal endothelium, captured by CSM, using Fourier analysis. Methods Software was developed in the mathematical programming language MATLAB. Pictures of the corneal endothelium, captured by CSM, were read into the analysis software. The software performed automated digital enhancement of the images. The enhanced images were Fourier transformed, using the Fast Fourier Transform. Relevant characteristics of the Fourier transformed images were identified and sampled. The data obtained from each transformed image was used to calculate the mean cell density of the original image, which in turn was compared to a semi automated method cell density estimate. The calculation was based on well known diffraction theory. Results Estimated cell densities of the corneal endothelium were obtained, using fully automated analysis software on 292 images captured by CSM. Using linear regression, a relatively large correlation between the estimates of the fully automated method and the semi automated method was found. Conclusion The results using the considerably faster fully automated method are highly encouraging for further development and implementation of the method. [source] Monitoring of Anti Cancer Drug Letrozole by Fast Fourier Transform Continuous Cyclic Voltammetry at Gold MicroelectrodeCHINESE JOURNAL OF CHEMISTRY, Issue 7 2010Parviz Norouzi Abstract A continuous cyclic voltammetric study of letrozole at gold microelectrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorbed at ,200 mV, giving rise to change in the current of well-defined oxidation peak of gold in the flow injection system. The proposed detection method has some of advantages, the greatest of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal-to-noise ratio has significantly increased by application of discrete Fast Fourier Transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as sweep rate, eluent pH, and accumulation time and potential were optimized. The linear concentration range was of 1.0×10,7,1.0×10,10 mol/L (r=0.9975) with a limit of detection and quantitation 0.08 nmol/L and 0.15 nmol/L, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay letrozol in tablets. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the letrozol were considered. [source] Equilibrium and kinetic studies of the cationic dye removal capability of a novel biosorbent Tamarindus indica from textile wastewaterCOLORATION TECHNOLOGY, Issue 5 2010Shooka Khorramfar In this paper, the use of tamarind hull biosorbent (Tamarindus indica) has been investigated to remove cationic dyes from textile eflluent. Basic Violet 6 and Basic Red 18 were used as cationic dye models. The surface characteristics of tamarind hull were investigated using Fourier Transform,infrared and scanning electron microscopy. The influence of process variables such as adsorbent dosage, initial dye concentration and pH were studied. The presence of fuctional groups such as hydroxy and amine groups onto the tamarind hull surface were proved by Fourier Transform,infrared analysis. Data were evaluated for compliance with the Langmuir and Freundlich isotherm models. The results indicated that the data for adsorption of Basic Violet 6 and Basic Red 18 onto tamarind hull fitted well with the Freundlich isotherm model. Also, the adsorption kinetics of Basic Violet 6 and Basic Red 18 on biosorbent was studied. The rates of sorption were found to conform to pseudo-second-order kinetics with good correlation. Results indicated that tamarind hull could be used as a biosorbent to remove cationic organics from contaminated watercourses. [source] Novel anti-bacterial acid dyes derived from naphthalimide: synthesis, characterisation and evaluation of their technical properties on nylon 6COLORATION TECHNOLOGY, Issue 2 2010Zinat Mohammadkhodaei As an attempt to combine the dyeing and functional finishing steps into one process, two novel anti-bacterial monoazo acid dyes based on N -ester-1,8-naphthalimide were synthesised. To do this, 4-amino- N -ethyl glycinate-1,8-naphthalimide was prepared, diazotised and then coupled to thiosalicylic acid or salicylic acid to produce anti-bacterial dyes. The synthesised dyes were purified and then fully characterised using Fourier Transform,infrared spectrometry, proton nuclear magnetic resonance spectroscopy and melting point analysis. Dispersion of the dyes was prepared in water and applied to nylon 6 fabrics. The novel dyes offered good build-up properties on the substrate. The anti-bacterial efficacy of the synthesised dyes was assessed, with the dyes showing activity against both Gram-positive and Gram-negative bacteria. [source] Synthesis, spectral properties and application of novel disazo disperse dyes derived from polyester wasteCOLORATION TECHNOLOGY, Issue 2 2010V S Palekar Terephthalic dihydrazide was obtained through aminolytic depolymerisation of polyester bottle waste by using hydrazine hydrate. It was further reacted with 4-aminobenzoic acid in the presence of polyphosphoric acid to obtain a cyclic compound, 4,4,-[5,5,-(1,4)-phenylene)bis(1,3,4-oxadiazole-5,2-diyl)dianiline, having a heterocyclic moiety. Diazotisation of this compound followed by coupling with various N,N -disubstituted anilines afford a series of novel disazo disperse dyes. The structures of these synthesised dyes were confirmed by elemental analysis and Fourier Transform,infrared, proton nuclear magnetic resonance and mass spectroscopy. Ultraviolet,visible spectra of these azo dyes in different polar solvents showed considerable variation in the wavelength of maximum absorbance (,max). Application of these dyes on polyester and nylon fabrics using high-temperature dyeing methods gave brilliant yellowish red hues with fair to moderate light fastness and very good to excellent wash fastness and sublimation fastness. [source] Three-Dimensional Surface Texture Characterization of Portland Cement Concrete PavementsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2007Ala Abbas Ten PCC field cores of varying surface textures were included in the analysis. X-ray Computed Tomography (CT) was used to scan the upper portion of these cores, resulting in a stack of two-dimensional grayscale images. Image processing techniques were utilized to isolate the void pixels from the solid pixels and reconstruct the three-dimensional surface topography. The resulting three-dimensional surfaces were reduced to two-dimensional "map of heights" images, whereby the grayscale intensity of each pixel within the image represented the vertical location of the surface at that point with respect to the lowest point on the surface. The "map of heights" images were analyzed using four mathematical methods, namely the Hessian model, the Fast Fourier transform (FFT), the wavelet analysis, and the power spectral density (PSD). Results obtained using these methods were compared to the mean profile depth (MPD) computed in accordance with ASTM E1845. [source] Optimizing process allocation of parallel programs for heterogeneous clustersCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 4 2009Shuichi Ichikawa Abstract The performance of a conventional parallel application is often degraded by load-imbalance on heterogeneous clusters. Although it is simple to invoke multiple processes on fast processing elements to alleviate load-imbalance, the optimal process allocation is not obvious. Kishimoto and Ichikawa presented performance models for high-performance Linpack (HPL), with which the sub-optimal configurations of heterogeneous clusters were actually estimated. Their results on HPL are encouraging, whereas their approach is not yet verified with other applications. This study presents some enhancements of Kishimoto's scheme, which are evaluated with four typical scientific applications: computational fluid dynamics (CFD), finite-element method (FEM), HPL (linear algebraic system), and fast Fourier transform (FFT). According to our experiments, our new models (NP-T models) are superior to Kishimoto's models, particularly when the non-negative least squares method is used for parameter extraction. The average errors of the derived models were 0.2% for the CFD benchmark, 2% for the FEM benchmark, 1% for HPL, and 28% for the FFT benchmark. This study also emphasizes the importance of predictability in clusters, listing practical examples derived from our study. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the effectiveness of runtime techniques to reduce memory sharing overheads in distributed Java implementationsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2008Marcelo Lobosco Abstract Distributed Java virtual machine (dJVM) systems enable concurrent Java applications to transparently run on clusters of commodity computers. This is achieved by supporting Java's shared-memory model over multiple JVMs distributed across the cluster's computer nodes. In this work, we describe and evaluate selective dynamic diffing and lazy home allocation, two new runtime techniques that enable dJVMs to efficiently support memory sharing across the cluster. Specifically, the two proposed techniques can contribute to reduce the overheads due to message traffic, extra memory space, and high latency of remote memory accesses that such dJVM systems require for implementing their memory-coherence protocol either in isolation or in combination. In order to evaluate the performance-related benefits of dynamic diffing and lazy home allocation, we implemented both techniques in Cooperative JVM (CoJVM), a basic dJVM system we developed in previous work. In subsequent work, we carried out performance comparisons between the basic CoJVM and modified CoJVM versions for five representative concurrent Java applications (matrix multiply, LU, Radix, fast Fourier transform, and SOR) using our proposed techniques. Our experimental results showed that dynamic diffing and lazy home allocation significantly reduced memory sharing overheads. The reduction resulted in considerable gains in CoJVM system's performance, ranging from 9% up to 20%, in four out of the five applications, with resulting speedups varying from 6.5 up to 8.1 for an 8-node cluster of computers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Semi-empirical model for site effects on acceleration time histories at soft-soil sites.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2004Part 1: formulation, development Abstract A criterion is developed for the simulation of realistic artificial ground motion histories at soft-soil sites, corresponding to a detailed ground motion record at a reference firm-ground site. A complex transfer function is defined as the Fourier transform of the ground acceleration time history at the soft-soil site divided by the Fourier transform of the acceleration record at the firm-ground site. Working with both the real and the imaginary components of the transfer function, and not only with its modulus, serves to keep the statistical information about the wave phases (and, therefore, about the time variation of amplitudes and frequencies) in the algorithm used to generate the artificial records. Samples of these transfer functions, associated with a given pair of soft-soil and firm-ground sites, are empirically determined from the corresponding pairs of simultaneous records. Each function included in a sample is represented as the superposition of the transfer functions of the responses of a number of oscillators. This formulation is intended to account for the contributions of trains of waves following different patterns in the vicinity of both sites. The properties of the oscillators play the role of parameters of the transfer functions. They vary from one seismic event to another. Part of the variation is systematic, and can be explained in terms of the influence of ground motion intensity on the effective values of stiffness and damping of the artificial oscillators. Another part has random nature; it reflects the random characteristics of the wave propagation patterns associated with the different events. The semi-empirical model proposed recognizes both types of variation. The influence of intensity is estimated by means of a conventional one-dimensional shear wave propagation model. This model is used to derive an intensity-dependent modification of the values of the empirically determined model parameters in those cases when the firm-ground earthquake intensity used to determine these parameters differs from that corresponding to the seismic event for which the simulated records are to be obtained. Copyright © 2004 John Wiley & Sons, Ltd. [source] Three-dimensional models of reservoir sediment and effects on the seismic response of arch damsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2004O. Maeso Abstract The important effects of bottom sediments on the seismic response of arch dams are studied in this paper. To do so, a three-dimensional boundary element model is used. It includes the water reservoir as a compressible fluid, the dam and unbounded foundation rock as viscoelastic solids, and the bottom sediment as a two-phase poroelastic domain with dynamic behaviour described by Biot's equations. Dynamic interaction among all those regions, local topography and travelling wave effects are taken into account. The results obtained show the important influence of sediment compressibility and permeability on the seismic response. The former is associated with a general change of the system response whereas the permeability has a significant influence on damping at resonance peaks. The analysis is carried out in the frequency domain considering time harmonic excitation due to P and S plane waves. The time-domain results obtained by using the Fourier transform for a given earthquake accelerogram are also shown. The possibility of using simplified models to represent the bottom sediment effects is discussed in the paper. Two alternative models for porous sediment are tested. Simplified models are shown to be able to reproduce the effects of porous sediments except for very high permeability values. Copyright © 2004 John Wiley & Sons, Ltd. [source] Estimation of Nonlinear Models with Measurement ErrorECONOMETRICA, Issue 1 2004Susanne M. Schennach This paper presents a solution to an important econometric problem, namely the root n consistent estimation of nonlinear models with measurement errors in the explanatory variables, when one repeated observation of each mismeasured regressor is available. While a root n consistent estimator has been derived for polynomial specifications (see Hausman, Ichimura, Newey, and Powell (1991)), such an estimator for general nonlinear specifications has so far not been available. Using the additional information provided by the repeated observation, the suggested estimator separates the measurement error from the "true" value of the regressors thanks to a useful property of the Fourier transform: The Fourier transform converts the integral equations that relate the distribution of the unobserved "true" variables to the observed variables measured with error into algebraic equations. The solution to these equations yields enough information to identify arbitrary moments of the "true," unobserved variables. The value of these moments can then be used to construct any estimator that can be written in terms of moments, including traditional linear and nonlinear least squares estimators, or general extremum estimators. The proposed estimator is shown to admit a representation in terms of an influence function, thus establishing its root n consistency and asymptotic normality. Monte Carlo evidence and an application to Engel curve estimation illustrate the usefulness of this new approach. [source] Estimation of backward impedance on low-voltage distribution system using measured resonant currentELECTRICAL ENGINEERING IN JAPAN, Issue 3 2010Toru Miki Abstract Two estimation methods for a backward impedance of a power distribution system are proposed in this paper. According to the first method, the backward impedance is estimated based on information obtained from the frequency response of a transient current flowing into a capacitor connected to a distribution line. The backward impedance is determined from the attenuation constant and the resonant frequency calculated using the capacitance and the impedance of the power distribution system. These parameters can be reliably obtained from a frequency response of the transient current using the least square method. The accuracy of the method strongly depends on the origin on the time axis for Fourier transform. An additional estimate of the time-origin is required for an accurate estimation of the backward impedance. The second method estimates the backward impedance using two transient current waveforms obtained by alternately connecting different capacitors to a distribution line. The backward impedance can be represented as a function of the frequency responses of these currents. Since this method is independent from the time-origin, it is suitable for automatic measurements of the backward impedance. Proposed methods are applicable to the estimation of harmonic currents in distribution systems. In this paper, harmonic currents flowing through a distribution line are calculated based on the estimated backward impedance and on the measured values of voltage harmonics obtained by the instrument developed by the authors. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 28,40, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20900 [source] Application of DA-preconditioned FINN for electric power system fault detectionELECTRICAL ENGINEERING IN JAPAN, Issue 2 2009Tadahiro Itagaki Abstract This paper proposes a hybrid method of deterministic annealing (DA) and fuzzy inference neural network (FINN) for electric power system fault detection. It extracts features of input data with two-staged precondition of fast Fourier transform (FFT) and DA. FFT is useful for extracting the features of fault currents while DA plays a key role in classifying input data into clusters in a sense of global classification. FINN is a more accurate estimation model than the conventional artificial neural networks (ANNs). The proposed method is successfully applied to data obtained by the Tokyo Electric Power Company (TEPCO) power simulator. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 39, 46, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20497 [source] Signal denoising and baseline correction by discrete wavelet transform for microchip capillary electrophoresisELECTROPHORESIS, Issue 18 2003Bi-Feng Liu Abstract Signal denoising and baseline correction using discrete wavelet transform (DWT) are described for microchip capillary electrophoresis (MCE). DWT was performed on an electropherogram describing a separation of nine tetramethylrohodamine-5-isothiocyanate labeled amino acids, following MCE with laser-induced fluorescence detection, using Daubechies 5 wavelet at a decomposition level of 6. The denoising efficiency was compared with, and proved to be superior to, other commonly used denoising techniques such as Fourier transform, Savitzky-Golay smoothing and moving average, in terms of noise removal and peak preservation by directly visual inspection. Novel strategies for baseline correction were proposed, with a special interest in baseline drift that frequently occurred in chromatographic and electrophoretic separations. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||