Algorithm Development for a Real-Time Military Noise Monitor

DTIC Science & Technology

2006-03-24

Duration ESLM Enhanced Sound Level Meter ERDC-CERL Engineer Research and Development Center/Construction Engineering Research Laboratory FFT...Fast Fourier Transform FTIG Fort Indiantown Gap Kurt Kurtosis LD Larson Davis Leq Equivalent Sound Level L8eq 8-hr Equivalent...Sound Level Lpk Peak Sound Level m Spectral Slope MCBCL Marine Corps Base Camp Lejeune Neg Number of negative samples NI National

Simulation of Ground Winds Time Series for the NASA Crew Launch Vehicle (CLV)

NASA Technical Reports Server (NTRS)

Adelfang, Stanley I.

2008-01-01

Simulation of wind time series based on power spectrum density (PSD) and spectral coherence models for ground wind turbulence is described. The wind models, originally developed for the Shuttle program, are based on wind measurements at the NASA 150-m meteorological tower at Cape Canaveral, FL. The current application is for the design and/or protection of the CLV from wind effects during on-pad exposure during periods from as long as days prior to launch, to seconds or minutes just prior to launch and seconds after launch. The evaluation of vehicle response to wind will influence the design and operation of constraint systems for support of the on-pad vehicle. Longitudinal and lateral wind component time series are simulated at critical vehicle locations. The PSD model for wind turbulence is a function of mean wind speed, elevation and temporal frequency. Integration of the PSD equation over a selected frequency range yields the variance of the time series to be simulated. The square root of the PSD defines a low-pass filter that is applied to adjust the components of the Fast Fourier Transform (FFT) of Gaussian white noise. The first simulated time series near the top of the launch vehicle is the inverse transform of the adjusted FFT. Simulation of the wind component time series at the nearest adjacent location (and all other succeeding next nearest locations) is based on a model for the coherence between winds at two locations as a function of frequency and separation distance, where the adjacent locations are separated vertically and/or horizontally. The coherence function is used to calculate a coherence weighted FFT of the wind at the next nearest location, given the FFT of the simulated time series at the previous location and the essentially incoherent FFT of the wind at the selected location derived a priori from the PSD model. The simulated time series at each adjacent location is the inverse Fourier transform of the coherence weighted FFT. For a selected design case, the equations, the process and the simulated time series at multiple vehicle stations are presented.

Fast Fourier transformation results from gamma-ray burst profiles

NASA Technical Reports Server (NTRS)

Kouveliotou, Chryssa; Norris, Jay P.; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.; Paciesas, W. S.

1992-01-01

Several gamma-ray bursts in the BATSE data have sufficiently long durations and complex temporal structures with pulses that appear to be spaced quasi-periodically. In order to test and quantify these periods we have applied fast Fourier transformations (FFT) to all these events. We have also performed cross spectral analyses of the FFT of the two extreme (high-low) energy bands in each case to determine the lead/lag of the pulses in different energies.

Low-Power Analog Processing for Sensing Applications: Low-Frequency Harmonic Signal Classification

PubMed Central

White, Daniel J.; William, Peter E.; Hoffman, Michael W.; Balkir, Sina

2013-01-01

A low-power analog sensor front-end is described that reduces the energy required to extract environmental sensing spectral features without using Fast Fouriér Transform (FFT) or wavelet transforms. An Analog Harmonic Transform (AHT) allows selection of only the features needed by the back-end, in contrast to the FFT, where all coefficients must be calculated simultaneously. We also show that the FFT coefficients can be easily calculated from the AHT results by a simple back-substitution. The scheme is tailored for low-power, parallel analog implementation in an integrated circuit (IC). Two different applications are tested with an ideal front-end model and compared to existing studies with the same data sets. Results from the military vehicle classification and identification of machine-bearing fault applications shows that the front-end suits a wide range of harmonic signal sources. Analog-related errors are modeled to evaluate the feasibility of and to set design parameters for an IC implementation to maintain good system-level performance. Design of a preliminary transistor-level integrator circuit in a 0.13 μm complementary metal-oxide-silicon (CMOS) integrated circuit process showed the ability to use online self-calibration to reduce fabrication errors to a sufficiently low level. Estimated power dissipation is about three orders of magnitude less than similar vehicle classification systems that use commercially available FFT spectral extraction. PMID:23892765

Wavelet-based spectral finite element dynamic analysis for an axially moving Timoshenko beam

NASA Astrophysics Data System (ADS)

Mokhtari, Ali; Mirdamadi, Hamid Reza; Ghayour, Mostafa

2017-08-01

In this article, wavelet-based spectral finite element (WSFE) model is formulated for time domain and wave domain dynamic analysis of an axially moving Timoshenko beam subjected to axial pretension. The formulation is similar to conventional FFT-based spectral finite element (SFE) model except that Daubechies wavelet basis functions are used for temporal discretization of the governing partial differential equations into a set of ordinary differential equations. The localized nature of Daubechies wavelet basis functions helps to rule out problems of SFE model due to periodicity assumption, especially during inverse Fourier transformation and back to time domain. The high accuracy of WSFE model is then evaluated by comparing its results with those of conventional finite element and SFE results. The effects of moving beam speed and axial tensile force on vibration and wave characteristics, and static and dynamic stabilities of moving beam are investigated.

Wavelet Filter Banks for Super-Resolution SAR Imaging

NASA Technical Reports Server (NTRS)

Sheybani, Ehsan O.; Deshpande, Manohar; Memarsadeghi, Nargess

2011-01-01

This paper discusses Innovative wavelet-based filter banks designed to enhance the analysis of super resolution Synthetic Aperture Radar (SAR) images using parametric spectral methods and signal classification algorithms, SAR finds applications In many of NASA's earth science fields such as deformation, ecosystem structure, and dynamics of Ice, snow and cold land processes, and surface water and ocean topography. Traditionally, standard methods such as Fast-Fourier Transform (FFT) and Inverse Fast-Fourier Transform (IFFT) have been used to extract Images from SAR radar data, Due to non-parametric features of these methods and their resolution limitations and observation time dependence, use of spectral estimation and signal pre- and post-processing techniques based on wavelets to process SAR radar data has been proposed. Multi-resolution wavelet transforms and advanced spectral estimation techniques have proven to offer efficient solutions to this problem.

Frequency characteristics of the heart rate variability produced by Cheyne-Stokes respiration during 24-hr ambulatory electrocardiographic monitoring.

PubMed

Ichimaru, Y; Yanaga, T

1989-06-01

Spectral analysis of heart rates during 24-hr ambulatory electrocardiographic monitoring has been carried out to characterize the heart rate spectral components of Cheyne-Stokes respiration (CSR) by using fast Fourier transformation (FFT). Eight patients with congestive heart failure were selected for the study. FFT analyses have been performed for 614.4 sec. Out of the power spectrum, five parameters were extracted to characterize the CSR. The low peak frequencies in eight subjects were between 0.0179 Hz (56 sec) and 0.0081 Hz (123 sec). The algorithms used to detect CSR are the followings: (i) if the LFPA/ULFA ratios were above the absolute value of 1.0, and (ii) the LFPP/MLFP ratios were above the absolute values of 4.0, then the power spectrum is suggestive of CSR. We conclude that the automatic detection of CSR by heart rate spectral analysis during ambulatory ECG monitoring may afford a tool for the evaluation of the patients with congestive heart failure.

XMDS2: Fast, scalable simulation of coupled stochastic partial differential equations

NASA Astrophysics Data System (ADS)

Dennis, Graham R.; Hope, Joseph J.; Johnsson, Mattias T.

2013-01-01

XMDS2 is a cross-platform, GPL-licensed, open source package for numerically integrating initial value problems that range from a single ordinary differential equation up to systems of coupled stochastic partial differential equations. The equations are described in a high-level XML-based script, and the package generates low-level optionally parallelised C++ code for the efficient solution of those equations. It combines the advantages of high-level simulations, namely fast and low-error development, with the speed, portability and scalability of hand-written code. XMDS2 is a complete redesign of the XMDS package, and features support for a much wider problem space while also producing faster code. Program summaryProgram title: XMDS2 Catalogue identifier: AENK_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENK_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 2 No. of lines in distributed program, including test data, etc.: 872490 No. of bytes in distributed program, including test data, etc.: 45522370 Distribution format: tar.gz Programming language: Python and C++. Computer: Any computer with a Unix-like system, a C++ compiler and Python. Operating system: Any Unix-like system; developed under Mac OS X and GNU/Linux. RAM: Problem dependent (roughly 50 bytes per grid point) Classification: 4.3, 6.5. External routines: The external libraries required are problem-dependent. Uses FFTW3 Fourier transforms (used only for FFT-based spectral methods), dSFMT random number generation (used only for stochastic problems), MPI message-passing interface (used only for distributed problems), HDF5, GNU Scientific Library (used only for Bessel-based spectral methods) and a BLAS implementation (used only for non-FFT-based spectral methods). Nature of problem: General coupled initial-value stochastic partial differential equations. Solution method: Spectral method with method-of-lines integration Running time: Determined by the size of the problem

Microprocessor implementation of an FFT for ionospheric VLF observations

NASA Technical Reports Server (NTRS)

Elvidge, J.; Kintner, P.; Holzworth, R.

1984-01-01

A fast Fourier transform algorithm is implemented on a CMOS microprocessor for application to very low-frequency electric fields (less than 10 kHz) sensed on high-altitude scientific balloons. Two FFT's are calculated simultaneously by associating them with conjugate symmetric and conjugate antisymmetric results. One goal of the system was to detect spectral signatures associated with fast time variations present in natural signals such as whistlers and chorus. Although a full evaluation of the system was not possible for operational reasons, a measure of the system's success has been defined and evaluated.

Further SEASAT SAR coastal ocean wave analysis

NASA Technical Reports Server (NTRS)

Kasischke, E. S.; Shuchman, R. A.; Meadows, G. A.; Jackson, P. L.; Tseng, Y.

1981-01-01

Analysis techniques used to exploit SEASAT synthetic aperture radar (SAR) data of gravity waves are discussed and the SEASAT SAR's ability to monitor large scale variations in gravity wave fields in both deep and shallow water is evaluated. The SAR analysis techniques investigated included motion compensation adjustments and the semicausal model for spectral analysis of SAR wave data. It was determined that spectra generated from fast Fourier transform analysis (FFT) of SAR wave data were not significantly altered when either range telerotation adjustments or azimuth focus shifts were used during processing of the SAR signal histories, indicating that SEASAT imagery of gravity waves is not significantly improved or degraded by motion compensation adjustments. Evaluation of the semicausal (SC) model using SEASAT SAR data from Rev. 974 indicates that the SC spectral estimates were not significantly better than the FFT results.

Pre-Hardware Optimization and Implementation Of Fast Optics Closed Control Loop Algorithms

NASA Technical Reports Server (NTRS)

Kizhner, Semion; Lyon, Richard G.; Herman, Jay R.; Abuhassan, Nader

2004-01-01

One of the main heritage tools used in scientific and engineering data spectrum analysis is the Fourier Integral Transform and its high performance digital equivalent - the Fast Fourier Transform (FFT). The FFT is particularly useful in two-dimensional (2-D) image processing (FFT2) within optical systems control. However, timing constraints of a fast optics closed control loop would require a supercomputer to run the software implementation of the FFT2 and its inverse, as well as other image processing representative algorithm, such as numerical image folding and fringe feature extraction. A laboratory supercomputer is not always available even for ground operations and is not feasible for a night project. However, the computationally intensive algorithms still warrant alternative implementation using reconfigurable computing technologies (RC) such as Digital Signal Processors (DSP) and Field Programmable Gate Arrays (FPGA), which provide low cost compact super-computing capabilities. We present a new RC hardware implementation and utilization architecture that significantly reduces the computational complexity of a few basic image-processing algorithm, such as FFT2, image folding and phase diversity for the NASA Solar Viewing Interferometer Prototype (SVIP) using a cluster of DSPs and FPGAs. The DSP cluster utilization architecture also assures avoidance of a single point of failure, while using commercially available hardware. This, combined with the control algorithms pre-hardware optimization, or the first time allows construction of image-based 800 Hertz (Hz) optics closed control loops on-board a spacecraft, based on the SVIP ground instrument. That spacecraft is the proposed Earth Atmosphere Solar Occultation Imager (EASI) to study greenhouse gases CO2, C2H, H2O, O3, O2, N2O from Lagrange-2 point in space. This paper provides an advanced insight into a new type of science capabilities for future space exploration missions based on on-board image processing for control and for robotics missions using vision sensors. It presents a top-level description of technologies required for the design and construction of SVIP and EASI and to advance the spatial-spectral imaging and large-scale space interferometry science and engineering.

Model-based spectral estimation of Doppler signals using parallel genetic algorithms.

PubMed

Solano González, J; Rodríguez Vázquez, K; García Nocetti, D F

2000-05-01

Conventional spectral analysis methods use a fast Fourier transform (FFT) on consecutive or overlapping windowed data segments. For Doppler ultrasound signals, this approach suffers from an inadequate frequency resolution due to the time segment duration and the non-stationarity characteristics of the signals. Parametric or model-based estimators can give significant improvements in the time-frequency resolution at the expense of a higher computational complexity. This work describes an approach which implements in real-time a parametric spectral estimator method using genetic algorithms (GAs) in order to find the optimum set of parameters for the adaptive filter that minimises the error function. The aim is to reduce the computational complexity of the conventional algorithm by using the simplicity associated to GAs and exploiting its parallel characteristics. This will allow the implementation of higher order filters, increasing the spectrum resolution, and opening a greater scope for using more complex methods.

Improved argument-FFT frequency offset estimation for QPSK coherent optical Systems

NASA Astrophysics Data System (ADS)

Han, Jilong; Li, Wei; Yuan, Zhilin; Li, Haitao; Huang, Liyan; Hu, Qianggao

2016-02-01

A frequency offset estimation (FOE) algorithm based on fast Fourier transform (FFT) of the signal's argument is investigated, which does not require removing the modulated data phase. In this paper, we analyze the flaw of the argument-FFT algorithm and propose a combined FOE algorithm, in which the absolute of frequency offset (FO) is accurately calculated by argument-FFT algorithm with a relatively large number of samples and the sign of FO is determined by FFT-based interpolation discrete Fourier transformation (DFT) algorithm with a relatively small number of samples. Compared with the previous algorithms based on argument-FFT, the proposed one has low complexity and can still effectively work with a relatively less number of samples.

Insulation bonding test system

NASA Technical Reports Server (NTRS)

Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (Inventor)

1984-01-01

A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.

Investigation of Allan variance for determining noise spectral forms with application to microwave radiometry

NASA Technical Reports Server (NTRS)

Stanley, William D.

1994-01-01

An investigation of the Allan variance method as a possible means for characterizing fluctuations in radiometric noise diodes has been performed. The goal is to separate fluctuation components into white noise, flicker noise, and random-walk noise. The primary means is by discrete-time processing, and the study focused primarily on the digital processes involved. Noise satisfying the requirements was generated by direct convolution, fast Fourier transformation (FFT) processing in the time domain, and FFT processing in the frequency domain. Some of the numerous results obtained are presented along with the programs used in the study.

Spectral turning bands for efficient Gaussian random fields generation on GPUs and accelerators

NASA Astrophysics Data System (ADS)

Hunger, L.; Cosenza, B.; Kimeswenger, S.; Fahringer, T.

2015-11-01

A random field (RF) is a set of correlated random variables associated with different spatial locations. RF generation algorithms are of crucial importance for many scientific areas, such as astrophysics, geostatistics, computer graphics, and many others. Current approaches commonly make use of 3D fast Fourier transform (FFT), which does not scale well for RF bigger than the available memory; they are also limited to regular rectilinear meshes. We introduce random field generation with the turning band method (RAFT), an RF generation algorithm based on the turning band method that is optimized for massively parallel hardware such as GPUs and accelerators. Our algorithm replaces the 3D FFT with a lower-order, one-dimensional FFT followed by a projection step and is further optimized with loop unrolling and blocking. RAFT can easily generate RF on non-regular (non-uniform) meshes and efficiently produce fields with mesh sizes bigger than the available device memory by using a streaming, out-of-core approach. Our algorithm generates RF with the correct statistical behavior and is tested on a variety of modern hardware, such as NVIDIA Tesla, AMD FirePro and Intel Phi. RAFT is faster than the traditional methods on regular meshes and has been successfully applied to two real case scenarios: planetary nebulae and cosmological simulations.

Wide-bandwidth high-resolution search for extraterrestrial intelligence

NASA Technical Reports Server (NTRS)

Horowitz, Paul

1995-01-01

Research was accomplished during the third year of the grant on: BETA architecture, an FFT array, a feature extractor, the Pentium array and workstation, and a radio astronomy spectrometer. The BETA (this SETI project) system architecture has been evolving generally in the direction of greater robustness against terrestrial interference. The new design adds a powerful state-memory feature, multiple simultaneous thresholds, and the ability to integrate multiple spectra in a flexible state-machine architecture. The FFT array is reported with regards to its hardware verification, array production, and control. The feature extractor is responsible for maintaining a moving baseline, recognizing large spectral peaks, following the progress of previously identified interesting spectral regions, and blocking signals from regions previously identified as containing interference. The Pentium array consists of 21 Pentium-based PC motherboards, each with 16 MByte of RAM and an Ethernet interface. Each motherboard receives and processes the data from a feature extractor/correlator board set, passing on the results of a first analysis to the central Unix workstation (through which each is also booted). The radio astronomy spectrometer is a technological spinoff from SETI work. It is proposed to be a combined spectrometer and power-accumulator, for use at Arecibo Observatory to search for neutral hydrogen emission from condensations of neutral hydrogen at high redshift (z = 5).

High-speed spectral calibration by complex FIR filter in phase-sensitive optical coherence tomography.

PubMed

Kim, Sangmin; Raphael, Patrick D; Oghalai, John S; Applegate, Brian E

2016-04-01

Swept-laser sources offer a number of advantages for Phase-sensitive Optical Coherence Tomography (PhOCT). However, inter- and intra-sweep variability leads to calibration errors that adversely affect phase sensitivity. While there are several approaches to overcoming this problem, our preferred method is to simply calibrate every sweep of the laser. This approach offers high accuracy and phase stability at the expense of a substantial processing burden. In this approach, the Hilbert phase of the interferogram from a reference interferometer provides the instantaneous wavenumber of the laser, but is computationally expensive. Fortunately, the Hilbert transform may be approximated by a Finite Impulse-Response (FIR) filter. Here we explore the use of several FIR filter based Hilbert transforms for calibration, explicitly considering the impact of filter choice on phase sensitivity and OCT image quality. Our results indicate that the complex FIR filter approach is the most robust and accurate among those considered. It provides similar image quality and slightly better phase sensitivity than the traditional FFT-IFFT based Hilbert transform while consuming fewer resources in an FPGA implementation. We also explored utilizing the Hilbert magnitude of the reference interferogram to calculate an ideal window function for spectral amplitude calibration. The ideal window function is designed to carefully control sidelobes on the axial point spread function. We found that after a simple chromatic correction, calculating the window function using the complex FIR filter and the reference interferometer gave similar results to window functions calculated using a mirror sample and the FFT-IFFT Hilbert transform. Hence, the complex FIR filter can enable accurate and high-speed calibration of the magnitude and phase of spectral interferograms.

High-speed spectral calibration by complex FIR filter in phase-sensitive optical coherence tomography

PubMed Central

Kim, Sangmin; Raphael, Patrick D.; Oghalai, John S.; Applegate, Brian E.

2016-01-01

Swept-laser sources offer a number of advantages for Phase-sensitive Optical Coherence Tomography (PhOCT). However, inter- and intra-sweep variability leads to calibration errors that adversely affect phase sensitivity. While there are several approaches to overcoming this problem, our preferred method is to simply calibrate every sweep of the laser. This approach offers high accuracy and phase stability at the expense of a substantial processing burden. In this approach, the Hilbert phase of the interferogram from a reference interferometer provides the instantaneous wavenumber of the laser, but is computationally expensive. Fortunately, the Hilbert transform may be approximated by a Finite Impulse-Response (FIR) filter. Here we explore the use of several FIR filter based Hilbert transforms for calibration, explicitly considering the impact of filter choice on phase sensitivity and OCT image quality. Our results indicate that the complex FIR filter approach is the most robust and accurate among those considered. It provides similar image quality and slightly better phase sensitivity than the traditional FFT-IFFT based Hilbert transform while consuming fewer resources in an FPGA implementation. We also explored utilizing the Hilbert magnitude of the reference interferogram to calculate an ideal window function for spectral amplitude calibration. The ideal window function is designed to carefully control sidelobes on the axial point spread function. We found that after a simple chromatic correction, calculating the window function using the complex FIR filter and the reference interferometer gave similar results to window functions calculated using a mirror sample and the FFT-IFFT Hilbert transform. Hence, the complex FIR filter can enable accurate and high-speed calibration of the magnitude and phase of spectral interferograms. PMID:27446666

Evaluation of finite difference and FFT-based solutions of the transport of intensity equation.

PubMed

Zhang, Hongbo; Zhou, Wen-Jing; Liu, Ying; Leber, Donald; Banerjee, Partha; Basunia, Mahmudunnabi; Poon, Ting-Chung

2018-01-01

A finite difference method is proposed for solving the transport of intensity equation. Simulation results show that although slower than fast Fourier transform (FFT)-based methods, finite difference methods are able to reconstruct the phase with better accuracy due to relaxed assumptions for solving the transport of intensity equation relative to FFT methods. Finite difference methods are also more flexible than FFT methods in dealing with different boundary conditions.

Protein-ligand docking using FFT based sampling: D3R case study.

PubMed

Padhorny, Dzmitry; Hall, David R; Mirzaei, Hanieh; Mamonov, Artem B; Moghadasi, Mohammad; Alekseenko, Andrey; Beglov, Dmitri; Kozakov, Dima

2018-01-01

Fast Fourier transform (FFT) based approaches have been successful in application to modeling of relatively rigid protein-protein complexes. Recently, we have been able to adapt the FFT methodology to treatment of flexible protein-peptide interactions. Here, we report our latest attempt to expand the capabilities of the FFT approach to treatment of flexible protein-ligand interactions in application to the D3R PL-2016-1 challenge. Based on the D3R assessment, our FFT approach in conjunction with Monte Carlo minimization off-grid refinement was among the top performing methods in the challenge. The potential advantage of our method is its ability to globally sample the protein-ligand interaction landscape, which will be explored in further applications.

The relation between periods’ identification and noises in hydrologic series data

NASA Astrophysics Data System (ADS)

Sang, Yan-Fang; Wang, Dong; Wu, Ji-Chun; Zhu, Qing-Ping; Wang, Ling

2009-04-01

SummaryIdentification of dominant periods is a typical and important issue in hydrologic series data analysis, since it is the basis of building effective stochastic models, understanding complex hydrologic processes, etc. However it is still a difficult task due to the influence of many interrelated factors, such as noises in hydrologic series data. In this paper, firstly the great influence of noises on periods' identification has been analyzed. Then, based on two conventional methods of hydrologic series analysis: wavelet analysis (WA) and maximum entropy spectral analysis (MESA), a new method of periods' identification of hydrologic series data, main series spectral analysis (MSSA), has been put forward, whose main idea is to identify periods of the main series on the basis of reducing hydrologic noises. Various methods (include fast Fourier transform (FFT), MESA and MSSA) have been applied to both synthetic series and observed hydrologic series. Results show that conventional methods (FFT and MESA) are not as good as expected due to the great influence of noises. However, this influence is not so strong while using the new method MSSA. In addition, by using the new de-noising method proposed in this paper, which is suitable for both normal noises and skew noises, the results are more reasonable, since noises separated from hydrologic series data generally follow skew probability distributions. In conclusion, based on comprehensive analyses, it can be stated that the proposed method MSSA could improve periods' identification by effectively reducing the influence of hydrologic noises.

Combining the Hanning windowed interpolated FFT in both directions

NASA Astrophysics Data System (ADS)

Chen, Kui Fu; Li, Yan Feng

2008-06-01

The interpolated fast Fourier transform (IFFT) has been proposed as a way to eliminate the picket fence effect (PFE) of the fast Fourier transform. The modulus based IFFT, cited in most relevant references, makes use of only the 1st and 2nd highest spectral lines. An approach using three principal spectral lines is proposed. This new approach combines both directions of the complex spectrum based IFFT with the Hanning window. The optimal weight to minimize the estimation variance is established on the first order Taylor series expansion of noise interference. A numerical simulation is carried out, and the results are compared with the Cramer-Rao bound. It is demonstrated that the proposed approach has a lower estimation variance than the two-spectral-line approach. The improvement depends on the extent of sampling deviating from the coherent condition, and the best is decreasing variance by 2/7. However, it is also shown that the estimation variance of the windowed IFFT with the Hanning is significantly higher than that of without windowing.

Efficient FFT Algorithm for Psychoacoustic Model of the MPEG-4 AAC

NASA Astrophysics Data System (ADS)

Lee, Jae-Seong; Lee, Chang-Joon; Park, Young-Cheol; Youn, Dae-Hee

This paper proposes an efficient FFT algorithm for the Psycho-Acoustic Model (PAM) of MPEG-4 AAC. The proposed algorithm synthesizes FFT coefficients using MDCT and MDST coefficients through circular convolution. The complexity of the MDCT and MDST coefficients is approximately half of the original FFT. We also design a new PAM based on the proposed FFT algorithm, which has 15% lower computational complexity than the original PAM without degradation of sound quality. Subjective as well as objective test results are presented to confirm the efficiency of the proposed FFT computation algorithm and the PAM.

A FFT-based formulation for efficient mechanical fields computation in isotropic and anisotropic periodic discrete dislocation dynamics

NASA Astrophysics Data System (ADS)

Bertin, N.; Upadhyay, M. V.; Pradalier, C.; Capolungo, L.

2015-09-01

In this paper, we propose a novel full-field approach based on the fast Fourier transform (FFT) technique to compute mechanical fields in periodic discrete dislocation dynamics (DDD) simulations for anisotropic materials: the DDD-FFT approach. By coupling the FFT-based approach to the discrete continuous model, the present approach benefits from the high computational efficiency of the FFT algorithm, while allowing for a discrete representation of dislocation lines. It is demonstrated that the computational time associated with the new DDD-FFT approach is significantly lower than that of current DDD approaches when large number of dislocation segments are involved for isotropic and anisotropic elasticity, respectively. Furthermore, for fine Fourier grids, the treatment of anisotropic elasticity comes at a similar computational cost to that of isotropic simulation. Thus, the proposed approach paves the way towards achieving scale transition from DDD to mesoscale plasticity, especially due to the method’s ability to incorporate inhomogeneous elasticity.

Proof-of-the-Concept Study on Mathematically Optimized Magnetic Resonance Spectroscopy for Breast Cancer Diagnostics.

PubMed

Belkić, Dževad; Belkić, Karen

2015-06-01

Magnetic resonance (MR)-based modalities aid breast cancer detection without exposure to ionizing radiation. Magnetic resonance imaging is very sensitive but costly and insufficiently specific. Molecular imaging through magnetic resonance spectroscopy (MRS) can provide information about key metabolites. Here, the measured/encoded time signals cannot be interpreted directly, necessitating mathematics for mapping to the more manageable frequency domain. Conventional applications of MRS are hampered by data analysis via the fast Fourier transform (FFT) and postprocessing by fitting techniques. Most in vivo MRS studies on breast cancer rely upon estimations of total choline (tCHO). These have yielded only incremental improvements in diagnostic accuracy. In vitro studies reveal richer metabolic information for identifying breast cancer, particularly in closely overlapping components of tCHO. Among these are phosphocholine (PC), a marker of malignant transformation of the breast. The FFT cannot assess these congested spectral components. This can be done by the fast Padé transform (FPT), a high-resolution, quantification-equipped method, which we presently apply to noisy MRS time signals consistent with those encoded in breast cancer. The FPT unequivocally and robustly extracted the concentrations of all physical metabolites, including PC. In sharp contrast, the FFT produced a rough envelope spectrum with a few distorted peaks and key metabolites absent altogether. As such, the FFT has poor resolution for these typical MRS time signals from breast cancer. Hence, based on Fourier-estimated envelope spectra, tCHO estimates are unreliable. Using even truncated time signals, the FPT clearly distinguishes noise from true metabolites whose concentrations are accurately extracted. The high resolution of the FPT translates directly into shortened examination time of the patient. These capabilities strongly suggest that by applying the FPT to time signals encoded in vivo from the breast, MRS will, at last, fulfill its potential to become a clinically reliable, cost-effective method for breast cancer detection, including screening/surveillance. © The Author(s) 2014.

SDAI: a key piece of software to manage the new wideband backend at Robledo

NASA Astrophysics Data System (ADS)

Rizzo, J. R.; Gutiérrez Bustos, M.; Kuiper, T. B. H.; Cernicharo, J.; Sotuela, I.; Pedreira, A.

2012-09-01

A joint collaborative project was recently developed to provide the Madrid Deep Space Communications Complex with a state-of-the-art wideband backend. This new backend provides from 100MHz to 6 GHz of instantaneous bandwidth, and spectral resolutions from 6 to 200 kHz. The backend includes a new intermediate-frequency processor, as well as a FPGA-based FFT spectrometer, which manage thousands of spectroscopic channels in real time. All these equipment need to be controlled and operated by a common software, which has to synchronize activities among affected devices, and also with the observing program. The final output should be a calibrated spectrum, readable by standard radio astronomical tools for further processing. The developed software at this end is named "Spectroscopic Data Acquisition Interface" (SDAI). SDAI is written in python 2.5, using PyQt4 for the User Interface. By an ethernet socket connection, SDAI receives astronomical information (source, frequencies, Doppler correction, etc.) and the antenna status from the observing program. Then it synchronizes the observations at the required frequency by tuning the synthesizers through their USB ports; finally SDAI controls the FFT spectrometers through UDP commands sent by sockets. Data are transmitted from the FFT spectrometers by TCP sockets, and written as standard FITS files. In this paper we describe the modules built, depict a typical observing session, and show some astronomical results using SDAI.

Research on fast Fourier transforms algorithm of huge remote sensing image technology with GPU and partitioning technology.

PubMed

Yang, Xue; Li, Xue-You; Li, Jia-Guo; Ma, Jun; Zhang, Li; Yang, Jan; Du, Quan-Ye

2014-02-01

Fast Fourier transforms (FFT) is a basic approach to remote sensing image processing. With the improvement of capacity of remote sensing image capture with the features of hyperspectrum, high spatial resolution and high temporal resolution, how to use FFT technology to efficiently process huge remote sensing image becomes the critical step and research hot spot of current image processing technology. FFT algorithm, one of the basic algorithms of image processing, can be used for stripe noise removal, image compression, image registration, etc. in processing remote sensing image. CUFFT function library is the FFT algorithm library based on CPU and FFTW. FFTW is a FFT algorithm developed based on CPU in PC platform, and is currently the fastest CPU based FFT algorithm function library. However there is a common problem that once the available memory or memory is less than the capacity of image, there will be out of memory or memory overflow when using the above two methods to realize image FFT arithmetic. To address this problem, a CPU and partitioning technology based Huge Remote Fast Fourier Transform (HRFFT) algorithm is proposed in this paper. By improving the FFT algorithm in CUFFT function library, the problem of out of memory and memory overflow is solved. Moreover, this method is proved rational by experiment combined with the CCD image of HJ-1A satellite. When applied to practical image processing, it improves effect of the image processing, speeds up the processing, which saves the time of computation and achieves sound result.

Numerical simulations of electrohydrodynamic evolution of thin polymer films

NASA Astrophysics Data System (ADS)

Borglum, Joshua Christopher

Recently developed needleless electrospinning and electrolithography are two successful techniques that have been utilized extensively for low-cost, scalable, and continuous nano-fabrication. Rational understanding of the electrohydrodynamic principles underneath these nano-manufacturing methods is crucial to fabrication of continuous nanofibers and patterned thin films. This research project is to formulate robust, high-efficiency finite-difference Fourier spectral methods to simulate the electrohydrodynamic evolution of thin polymer films. Two thin-film models were considered and refined. The first was based on reduced lubrication theory; the second further took into account the effect of solvent drying and dewetting of the substrate. Fast Fourier Transform (FFT) based spectral method was integrated into the finite-difference algorithms for fast, accurately solving the governing nonlinear partial differential equations. The present methods have been used to examine the dependencies of the evolving surface features of the thin films upon the model parameters. The present study can be used for fast, controllable nanofabrication.

Chemical mass transport between fluid fine tailings and the overlying water cover of an oil sands end pit lake

NASA Astrophysics Data System (ADS)

Dompierre, Kathryn A.; Barbour, S. Lee; North, Rebecca L.; Carey, Sean K.; Lindsay, Matthew B. J.

2017-06-01

Fluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML)—the first full-scale demonstration oil sands end pit lake (EPL)—contains approximately 1.9 × 108 m3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m3 m-2 d-1, which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy.

A high performance parallel algorithm for 1-D FFT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarwal, R.C.; Gustavson, F.G.; Zubair, M.

1994-12-31

In this paper the authors propose a parallel high performance FFT algorithm based on a multi-dimensional formulation. They use this to solve a commonly encountered FFT based kernel on a distributed memory parallel machine, the IBM scalable parallel system, SP1. The kernel requires a forward FFT computation of an input sequence, multiplication of the transformed data by a coefficient array, and finally an inverse FFT computation of the resultant data. They show that the multi-dimensional formulation helps in reducing the communication costs and also improves the single node performance by effectively utilizing the memory system of the node. They implementedmore » this kernel on the IBM SP1 and observed a performance of 1.25 GFLOPS on a 64-node machine.« less

Digital signal processing at Bell Labs-Foundations for speech and acoustics research

NASA Astrophysics Data System (ADS)

Rabiner, Lawrence R.

2004-05-01

Digital signal processing (DSP) is a fundamental tool for much of the research that has been carried out of Bell Labs in the areas of speech and acoustics research. The fundamental bases for DSP include the sampling theorem of Nyquist, the method for digitization of analog signals by Shannon et al., methods of spectral analysis by Tukey, the cepstrum by Bogert et al., and the FFT by Tukey (and Cooley of IBM). Essentially all of these early foundations of DSP came out of the Bell Labs Research Lab in the 1930s, 1940s, 1950s, and 1960s. This fundamental research was motivated by fundamental applications (mainly in the areas of speech, sonar, and acoustics) that led to novel design methods for digital filters (Kaiser, Golden, Rabiner, Schafer), spectrum analysis methods (Rabiner, Schafer, Allen, Crochiere), fast convolution methods based on the FFT (Helms, Bergland), and advanced digital systems used to implement telephony channel banks (Jackson, McDonald, Freeny, Tewksbury). This talk summarizes the key contributions to DSP made at Bell Labs, and illustrates how DSP was utilized in the areas of speech and acoustics research. It also shows the vast, worldwide impact of this DSP research on modern consumer electronics.

Global field synchronization in gamma range of the sleep EEG tracks sleep depth: Artifact introduced by a rectangular analysis window.

PubMed

Rusterholz, Thomas; Achermann, Peter; Dürr, Roland; Koenig, Thomas; Tarokh, Leila

2017-06-01

Investigating functional connectivity between brain networks has become an area of interest in neuroscience. Several methods for investigating connectivity have recently been developed, however, these techniques need to be applied with care. We demonstrate that global field synchronization (GFS), a global measure of phase alignment in the EEG as a function of frequency, must be applied considering signal processing principles in order to yield valid results. Multichannel EEG (27 derivations) was analyzed for GFS based on the complex spectrum derived by the fast Fourier transform (FFT). We examined the effect of window functions on GFS, in particular of non-rectangular windows. Applying a rectangular window when calculating the FFT revealed high GFS values for high frequencies (>15Hz) that were highly correlated (r=0.9) with spectral power in the lower frequency range (0.75-4.5Hz) and tracked the depth of sleep. This turned out to be spurious synchronization. With a non-rectangular window (Tukey or Hanning window) these high frequency synchronization vanished. Both, GFS and power density spectra significantly differed for rectangular and non-rectangular windows. Previous papers using GFS typically did not specify the applied window and may have used a rectangular window function. However, the demonstrated impact of the window function raises the question of the validity of some previous findings at higher frequencies. We demonstrated that it is crucial to apply an appropriate window function for determining synchronization measures based on a spectral approach to avoid spurious synchronization in the beta/gamma range. Copyright © 2017 Elsevier B.V. All rights reserved.

Custom instruction set NIOS-based OFDM processor for FPGAs

NASA Astrophysics Data System (ADS)

Meyer-Bäse, Uwe; Sunkara, Divya; Castillo, Encarnacion; Garcia, Antonio

2006-05-01

Orthogonal Frequency division multiplexing (OFDM) spread spectrum technique, sometimes also called multi-carrier or discrete multi-tone modulation, are used in bandwidth-efficient communication systems in the presence of channel distortion. The benefits of OFDM are high spectral efficiency, resiliency to RF interference, and lower multi-path distortion. OFDM is the basis for the European digital audio broadcasting (DAB) standard, the global asymmetric digital subscriber line (ADSL) standard, in the IEEE 802.11 5.8 GHz band standard, and ongoing development in wireless local area networks. The modulator and demodulator in an OFDM system can be implemented by use of a parallel bank of filters based on the discrete Fourier transform (DFT), in case the number of subchannels is large (e.g. K > 25), the OFDM system are efficiently implemented by use of the fast Fourier transform (FFT) to compute the DFT. We have developed a custom FPGA-based Altera NIOS system to increase the performance, programmability, and low power in mobil wireless systems. The overall gain observed for a 1024-point FFT ranges depending on the multiplier used by the NIOS processor between a factor of 3 and 16. A careful optimization described in the appendix yield a performance gain of up to 77% when compared with our preliminary results.

A spectral approach for the quantitative description of cardiac collagen network from nonlinear optical imaging.

PubMed

Masè, Michela; Cristoforetti, Alessandro; Avogaro, Laura; Tessarolo, Francesco; Piccoli, Federico; Caola, Iole; Pederzolli, Carlo; Graffigna, Angelo; Ravelli, Flavia

2015-01-01

The assessment of collagen structure in cardiac pathology, such as atrial fibrillation (AF), is essential for a complete understanding of the disease. This paper introduces a novel methodology for the quantitative description of collagen network properties, based on the combination of nonlinear optical microscopy with a spectral approach of image processing and analysis. Second-harmonic generation (SHG) microscopy was applied to atrial tissue samples from cardiac surgery patients, providing label-free, selective visualization of the collagen structure. The spectral analysis framework, based on 2D-FFT, was applied to the SHG images, yielding a multiparametric description of collagen fiber orientation (angle and anisotropy indexes) and texture scale (dominant wavelength and peak dispersion indexes). The proof-of-concept application of the methodology showed the capability of our approach to detect and quantify differences in the structural properties of the collagen network in AF versus sinus rhythm patients. These results suggest the potential of our approach in the assessment of collagen properties in cardiac pathologies related to a fibrotic structural component.

FPGA design of correlation-based pattern recognition

NASA Astrophysics Data System (ADS)

Jridi, Maher; Alfalou, Ayman

2017-05-01

Optical/Digital pattern recognition and tracking based on optical/digital correlation are a well-known techniques to detect, identify and localize a target object in a scene. Despite the limited number of treatments required by the correlation scheme, computational time and resources are relatively high. The most computational intensive treatment required by the correlation is the transformation from spatial to spectral domain and then from spectral to spatial domain. Furthermore, these transformations are used on optical/digital encryption schemes like the double random phase encryption (DRPE). In this paper, we present a VLSI architecture for the correlation scheme based on the fast Fourier transform (FFT). One interesting feature of the proposed scheme is its ability to stream image processing in order to perform correlation for video sequences. A trade-off between the hardware consumption and the robustness of the correlation can be made in order to understand the limitations of the correlation implementation in reconfigurable and portable platforms. Experimental results obtained from HDL simulations and FPGA prototype have demonstrated the advantages of the proposed scheme.

High-performance compression and double cryptography based on compressive ghost imaging with the fast Fourier transform

NASA Astrophysics Data System (ADS)

Leihong, Zhang; Zilan, Pan; Luying, Wu; Xiuhua, Ma

2016-11-01

To solve the problem that large images can hardly be retrieved for stringent hardware restrictions and the security level is low, a method based on compressive ghost imaging (CGI) with Fast Fourier Transform (FFT) is proposed, named FFT-CGI. Initially, the information is encrypted by the sender with FFT, and the FFT-coded image is encrypted by the system of CGI with a secret key. Then the receiver decrypts the image with the aid of compressive sensing (CS) and FFT. Simulation results are given to verify the feasibility, security, and compression of the proposed encryption scheme. The experiment suggests the method can improve the quality of large images compared with conventional ghost imaging and achieve the imaging for large-sized images, further the amount of data transmitted largely reduced because of the combination of compressive sensing and FFT, and improve the security level of ghost images through ciphertext-only attack (COA), chosen-plaintext attack (CPA), and noise attack. This technique can be immediately applied to encryption and data storage with the advantages of high security, fast transmission, and high quality of reconstructed information.

Real-time processing of radar return on a parallel computer

NASA Technical Reports Server (NTRS)

Aalfs, David D.

1992-01-01

NASA is working with the FAA to demonstrate the feasibility of pulse Doppler radar as a candidate airborne sensor to detect low altitude windshears. The need to provide the pilot with timely information about possible hazards has motivated a demand for real-time processing of a radar return. Investigated here is parallel processing as a means of accommodating the high data rates required. A PC based parallel computer, called the transputer, is used to investigate issues in real time concurrent processing of radar signals. A transputer network is made up of an array of single instruction stream processors that can be networked in a variety of ways. They are easily reconfigured and software development is largely independent of the particular network topology. The performance of the transputer is evaluated in light of the computational requirements. A number of algorithms have been implemented on the transputers in OCCAM, a language specially designed for parallel processing. These include signal processing algorithms such as the Fast Fourier Transform (FFT), pulse-pair, and autoregressive modelling, as well as routing software to support concurrency. The most computationally intensive task is estimating the spectrum. Two approaches have been taken on this problem, the first and most conventional of which is to use the FFT. By using table look-ups for the basis function and other optimizing techniques, an algorithm has been developed that is sufficient for real time. The other approach is to model the signal as an autoregressive process and estimate the spectrum based on the model coefficients. This technique is attractive because it does not suffer from the spectral leakage problem inherent in the FFT. Benchmark tests indicate that autoregressive modeling is feasible in real time.

High performance Python for direct numerical simulations of turbulent flows

NASA Astrophysics Data System (ADS)

Mortensen, Mikael; Langtangen, Hans Petter

2016-06-01

Direct Numerical Simulations (DNS) of the Navier Stokes equations is an invaluable research tool in fluid dynamics. Still, there are few publicly available research codes and, due to the heavy number crunching implied, available codes are usually written in low-level languages such as C/C++ or Fortran. In this paper we describe a pure scientific Python pseudo-spectral DNS code that nearly matches the performance of C++ for thousands of processors and billions of unknowns. We also describe a version optimized through Cython, that is found to match the speed of C++. The solvers are written from scratch in Python, both the mesh, the MPI domain decomposition, and the temporal integrators. The solvers have been verified and benchmarked on the Shaheen supercomputer at the KAUST supercomputing laboratory, and we are able to show very good scaling up to several thousand cores. A very important part of the implementation is the mesh decomposition (we implement both slab and pencil decompositions) and 3D parallel Fast Fourier Transforms (FFT). The mesh decomposition and FFT routines have been implemented in Python using serial FFT routines (either NumPy, pyFFTW or any other serial FFT module), NumPy array manipulations and with MPI communications handled by MPI for Python (mpi4py). We show how we are able to execute a 3D parallel FFT in Python for a slab mesh decomposition using 4 lines of compact Python code, for which the parallel performance on Shaheen is found to be slightly better than similar routines provided through the FFTW library. For a pencil mesh decomposition 7 lines of code is required to execute a transform.

An exploratory analysis of PubMed's free full-text limit on citation retrieval for clinical questions.

PubMed

Krieger, Mary M; Richter, Randy R; Austin, Tricia M

2008-10-01

The research sought to determine (1) how use of the PubMed free full-text (FFT) limit affects citation retrieval and (2) how use of the FFT limit impacts the types of articles and levels of evidence retrieved. Four clinical questions based on a research agenda for physical therapy were searched in PubMed both with and without the use of the FFT limit. Retrieved citations were examined for relevancy to each question. Abstracts of relevant citations were reviewed to determine the types of articles and levels of evidence. Descriptive analysis was used to compare the total number of citations, number of relevant citations, types of articles, and levels of evidence both with and without the use of the FFT limit. Across all 4 questions, the FFT limit reduced the number of citations to 11.1% of the total number of citations retrieved without the FFT limit. Additionally, high-quality evidence such as systematic reviews and randomized controlled trials were missed when the FFT limit was used. Health sciences librarians play a key role in educating users about the potential impact the FFT limit has on the number of citations, types of articles, and levels of evidence retrieved.

Improved FFT-based numerical inversion of Laplace transforms via fast Hartley transform algorithm

NASA Technical Reports Server (NTRS)

Hwang, Chyi; Lu, Ming-Jeng; Shieh, Leang S.

1991-01-01

The disadvantages of numerical inversion of the Laplace transform via the conventional fast Fourier transform (FFT) are identified and an improved method is presented to remedy them. The improved method is based on introducing a new integration step length Delta(omega) = pi/mT for trapezoidal-rule approximation of the Bromwich integral, in which a new parameter, m, is introduced for controlling the accuracy of the numerical integration. Naturally, this method leads to multiple sets of complex FFT computations. A new inversion formula is derived such that N equally spaced samples of the inverse Laplace transform function can be obtained by (m/2) + 1 sets of N-point complex FFT computations or by m sets of real fast Hartley transform (FHT) computations.

A satellite-based radar wind sensor

NASA Technical Reports Server (NTRS)

Xin, Weizhuang

1991-01-01

The objective is to investigate the application of Doppler radar systems for global wind measurement. A model of the satellite-based radar wind sounder (RAWS) is discussed, and many critical problems in the designing process, such as the antenna scan pattern, tracking the Doppler shift caused by satellite motion, and backscattering of radar signals from different types of clouds, are discussed along with their computer simulations. In addition, algorithms for measuring mean frequency of radar echoes, such as the Fast Fourier Transform (FFT) estimator, the covariance estimator, and the estimators based on autoregressive models, are discussed. Monte Carlo computer simulations were used to compare the performance of these algorithms. Anti-alias methods are discussed for the FFT and the autoregressive methods. Several algorithms for reducing radar ambiguity were studied, such as random phase coding methods and staggered pulse repitition frequncy (PRF) methods. Computer simulations showed that these methods are not applicable to the RAWS because of the broad spectral widths of the radar echoes from clouds. A waveform modulation method using the concept of spread spectrum and correlation detection was developed to solve the radar ambiguity. Radar ambiguity functions were used to analyze the effective signal-to-noise ratios for the waveform modulation method. The results showed that, with suitable bandwidth product and modulation of the waveform, this method can achieve the desired maximum range and maximum frequency of the radar system.

Improved grid-noise removal in single-frame digital moiré 3D shape measurement

NASA Astrophysics Data System (ADS)

Mohammadi, Fatemeh; Kofman, Jonathan

2016-11-01

A single-frame grid-noise removal technique was developed for application in single-frame digital-moiré 3D shape measurement. The ability of the stationary wavelet transform (SWT) to prevent oscillation artifacts near discontinuities, and the ability of the Fourier transform (FFT) applied to wavelet coefficients to separate grid-noise from useful image information, were combined in a new technique, SWT-FFT, to remove grid-noise from moiré-pattern images generated by digital moiré. In comparison to previous grid-noise removal techniques in moiré, SWT-FFT avoids the requirement for mechanical translation of optical components and capture of multiple frames, to enable single-frame moiré-based measurement. Experiments using FFT, Discrete Wavelet Transform (DWT), DWT-FFT, and SWT-FFT were performed on moiré-pattern images containing grid noise, generated by digital moiré, for several test objects. SWT-FFT had the best performance in removing high-frequency grid-noise, both straight and curved lines, minimizing artifacts, and preserving the moiré pattern without blurring and degradation. SWT-FFT also had the lowest noise amplitude in the reconstructed height and lowest roughness index for all test objects, indicating best grid-noise removal in comparison to the other techniques.

An exploratory analysis of PubMed's free full-text limit on citation retrieval for clinical questions

PubMed Central

Krieger, Mary M.; Richter, Randy R.; Austin, Tricia M.

2008-01-01

Objective: The research sought to determine (1) how use of the PubMed free full-text (FFT) limit affects citation retrieval and (2) how use of the FFT limit impacts the types of articles and levels of evidence retrieved. Methods: Four clinical questions based on a research agenda for physical therapy were searched in PubMed both with and without the use of the FFT limit. Retrieved citations were examined for relevancy to each question. Abstracts of relevant citations were reviewed to determine the types of articles and levels of evidence. Descriptive analysis was used to compare the total number of citations, number of relevant citations, types of articles, and levels of evidence both with and without the use of the FFT limit. Results: Across all 4 questions, the FFT limit reduced the number of citations to 11.1% of the total number of citations retrieved without the FFT limit. Additionally, high-quality evidence such as systematic reviews and randomized controlled trials were missed when the FFT limit was used. Conclusions: Health sciences librarians play a key role in educating users about the potential impact the FFT limit has on the number of citations, types of articles, and levels of evidence retrieved. PMID:18974812

Multi-core and GPU accelerated simulation of a radial star target imaged with equivalent t-number circular and Gaussian pupils

NASA Astrophysics Data System (ADS)

Greynolds, Alan W.

2013-09-01

Results from the GelOE optical engineering software are presented for the through-focus, monochromatic coherent and polychromatic incoherent imaging of a radial "star" target for equivalent t-number circular and Gaussian pupils. The FFT-based simulations are carried out using OpenMP threading on a multi-core desktop computer, with and without the aid of a many-core NVIDIA GPU accessing its cuFFT library. It is found that a custom FFT optimized for the 12-core host has similar performance to a simply implemented 256-core GPU FFT. A more sophisticated version of the latter but tuned to reduce overhead on a 448-core GPU is 20 to 28 times faster than a basic FFT implementation running on one CPU core.

Long-range correlation properties of coding and noncoding DNA sequences: GenBank analysis.

PubMed

Buldyrev, S V; Goldberger, A L; Havlin, S; Mantegna, R N; Matsa, M E; Peng, C K; Simons, M; Stanley, H E

1995-05-01

An open question in computational molecular biology is whether long-range correlations are present in both coding and noncoding DNA or only in the latter. To answer this question, we consider all 33301 coding and all 29453 noncoding eukaryotic sequences--each of length larger than 512 base pairs (bp)--in the present release of the GenBank to dtermine whether there is any statistically significant distinction in their long-range correlation properties. Standard fast Fourier transform (FFT) analysis indicates that coding sequences have practically no correlations in the range from 10 bp to 100 bp (spectral exponent beta=0.00 +/- 0.04, where the uncertainty is two standard deviations). In contrast, for noncoding sequences, the average value of the spectral exponent beta is positive (0.16 +/- 0.05) which unambiguously shows the presence of long-range correlations. We also separately analyze the 874 coding and the 1157 noncoding sequences that have more than 4096 bp and find a larger region of power-law behavior. We calculate the probability that these two data sets (coding and noncoding) were drawn from the same distribution and we find that it is less than 10(-10). We obtain independent confirmation of these findings using the method of detrended fluctuation analysis (DFA), which is designed to treat sequences with statistical heterogeneity, such as DNA's known mosaic structure ("patchiness") arising from the nonstationarity of nucleotide concentration. The near-perfect agreement between the two independent analysis methods, FFT and DFA, increases the confidence in the reliability of our conclusion.

Long-range correlation properties of coding and noncoding DNA sequences: GenBank analysis

NASA Technical Reports Server (NTRS)

Buldyrev, S. V.; Goldberger, A. L.; Havlin, S.; Mantegna, R. N.; Matsa, M. E.; Peng, C. K.; Simons, M.; Stanley, H. E.

1995-01-01

An open question in computational molecular biology is whether long-range correlations are present in both coding and noncoding DNA or only in the latter. To answer this question, we consider all 33301 coding and all 29453 noncoding eukaryotic sequences--each of length larger than 512 base pairs (bp)--in the present release of the GenBank to dtermine whether there is any statistically significant distinction in their long-range correlation properties. Standard fast Fourier transform (FFT) analysis indicates that coding sequences have practically no correlations in the range from 10 bp to 100 bp (spectral exponent beta=0.00 +/- 0.04, where the uncertainty is two standard deviations). In contrast, for noncoding sequences, the average value of the spectral exponent beta is positive (0.16 +/- 0.05) which unambiguously shows the presence of long-range correlations. We also separately analyze the 874 coding and the 1157 noncoding sequences that have more than 4096 bp and find a larger region of power-law behavior. We calculate the probability that these two data sets (coding and noncoding) were drawn from the same distribution and we find that it is less than 10(-10). We obtain independent confirmation of these findings using the method of detrended fluctuation analysis (DFA), which is designed to treat sequences with statistical heterogeneity, such as DNA's known mosaic structure ("patchiness") arising from the nonstationarity of nucleotide concentration. The near-perfect agreement between the two independent analysis methods, FFT and DFA, increases the confidence in the reliability of our conclusion.

Family-Focused Therapy for Bipolar Disorder: Reflections on 30 Years of Research.

PubMed

Miklowitz, David J; Chung, Bowen

2016-09-01

Family-focused therapy (FFT) is an evidence-based intervention for adults and children with bipolar disorder (BD) and their caregivers, usually given in conjunction with pharmacotherapy after an illness episode. The treatment consists of conjoint sessions of psychoeducation regarding bipolar illness, communication enhancement training, and problem-solving skills training. This paper summarizes over 30 years of research on FFT and family processes in BD. Across eight randomized controlled trials with adults and adolescents with BD, FFT and mood-stabilizing medications have been found to hasten recovery from mood episodes, reduce recurrences, and reduce levels of symptom severity compared to briefer forms of psychoeducation and medications over 1-2 years. Several studies indicate that the effects of FFT on symptom improvement are greater among patients with high-expressed emotion relatives. New research focuses on FFT as an early intervention for youth at risk for BD, neuroimaging as a means of evaluating treatment mechanisms, and progress in implementing FFT in community mental health settings. © 2016 Family Process Institute.

[Research on spatially modulated Fourier transform imaging spectrometer data processing method].

PubMed

Huang, Min; Xiangli, Bin; Lü, Qun-Bo; Zhou, Jin-Song; Jing, Juan-Juan; Cui, Yan

2010-03-01

Fourier transform imaging spectrometer is a new technic, and has been developed very rapidly in nearly ten years. The data catched by Fourier transform imaging spectrometer is indirect data, can not be used by user, and need to be processed by various approaches, including data pretreatment, apodization, phase correction, FFT, and spectral radicalization calibration. No paper so far has been found roundly to introduce this method. In the present paper, the author will give an effective method to process the interfering data to spectral data, and with this method we can obtain good result.

Optical ranging and communication method based on all-phase FFT

NASA Astrophysics Data System (ADS)

Li, Zening; Chen, Gang

2014-10-01

This paper describes an optical ranging and communication method based on all-phase fast fourier transform (FFT). This kind of system is mainly designed for vehicle safety application. Particularly, the phase shift of the reflecting orthogonal frequency division multiplexing (OFDM) symbol is measured to determine the signal time of flight. Then the distance is calculated according to the time of flight. Several key factors affecting the phase measurement accuracy are studied. The all-phase FFT, which can reduce the effects of frequency offset, phase noise and the inter-carrier interference (ICI), is applied to measure the OFDM symbol phase shift.

Imaging the eye fundus with real-time en-face spectral domain optical coherence tomography

PubMed Central

Bradu, Adrian; Podoleanu, Adrian Gh.

2014-01-01

Real-time display of processed en-face spectral domain optical coherence tomography (SD-OCT) images is important for diagnosis. However, due to many steps of data processing requirements, such as Fast Fourier transformation (FFT), data re-sampling, spectral shaping, apodization, zero padding, followed by software cut of the 3D volume acquired to produce an en-face slice, conventional high-speed SD-OCT cannot render an en-face OCT image in real time. Recently we demonstrated a Master/Slave (MS)-OCT method that is highly parallelizable, as it provides reflectivity values of points at depth within an A-scan in parallel. This allows direct production of en-face images. In addition, the MS-OCT method does not require data linearization, which further simplifies the processing. The computation in our previous paper was however time consuming. In this paper we present an optimized algorithm that can be used to provide en-face MS-OCT images much quicker. Using such an algorithm we demonstrate around 10 times faster production of sets of en-face OCT images than previously obtained as well as simultaneous real-time display of up to 4 en-face OCT images of 200 × 200 pixels2 from the fovea and the optic nerve of a volunteer. We also demonstrate 3D and B-scan OCT images obtained from sets of MS-OCT C-scans, i.e. with no FFT and no intermediate step of generation of A-scans. PMID:24761303

Feed-forward frequency offset estimation for 32-QAM optical coherent detection.

PubMed

Xiao, Fei; Lu, Jianing; Fu, Songnian; Xie, Chenhui; Tang, Ming; Tian, Jinwen; Liu, Deming

2017-04-17

Due to the non-rectangular distribution of the constellation points, traditional fast Fourier transform based frequency offset estimation (FFT-FOE) is no longer suitable for 32-QAM signal. Here, we report a modified FFT-FOE technique by selecting and digitally amplifying the inner QPSK ring of 32-QAM after the adaptive equalization, which is defined as QPSK-selection assisted FFT-FOE. Simulation results show that no FOE error occurs with a FFT size of only 512 symbols, when the signal-to-noise ratio (SNR) is above 17.5 dB using our proposed FOE technique. However, the error probability of traditional FFT-FOE scheme for 32-QAM is always intolerant. Finally, our proposed FOE scheme functions well for 10 Gbaud dual polarization (DP)-32-QAM signal to reach 20% forward error correction (FEC) threshold of BER=2×10^-2, under the scenario of back-to-back (B2B) transmission.

Extension of the frequency-domain pFFT method for wave structure interaction in finite depth

NASA Astrophysics Data System (ADS)

Teng, Bin; Song, Zhi-jie

2017-06-01

To analyze wave interaction with a large scale body in the frequency domain, a precorrected Fast Fourier Transform (pFFT) method has been proposed for infinite depth problems with the deep water Green function, as it can form a matrix with Toeplitz and Hankel properties. In this paper, a method is proposed to decompose the finite depth Green function into two terms, which can form matrices with the Toeplitz and a Hankel properties respectively. Then, a pFFT method for finite depth problems is developed. Based on the pFFT method, a numerical code pFFT-HOBEM is developed with the discretization of high order elements. The model is validated, and examinations on the computing efficiency and memory requirement of the new method have also been carried out. It shows that the new method has the same advantages as that for infinite depth.

Evolution of Functional Family Therapy as an Evidence-Based Practice for Adolescents with Disruptive Behavior Problems.

PubMed

Robbins, Michael S; Alexander, James F; Turner, Charles W; Hollimon, Amy

2016-09-01

This article summarizes the evolution of functional family therapy (FFT) based upon four decades of clinical practice and scientific scrutiny through research evidence. FFT research has evolved from an initial focus upon clinical process research, which examined sequential exchanges between therapists and family members. A key element of this research has been an examination of the way in which clinicians acquire, consolidate, and maintain the skills needed to implement FFT effectively with youth and families. Many randomized efficacy and effectiveness studies have evaluated the impact of FFT across diverse clinical populations. Subsequent research investigated factors that influence the effectiveness of implementation across more than 300 clinical settings in which more than 2,500 trained clinicians have provided service to nearly 400,000 families. Another important set of investigations concerned the cost-effectiveness of the interventions. © 2016 Family Process Institute.

High-Throughput, Adaptive FFT Architecture for FPGA-Based Spaceborne Data Processors

NASA Technical Reports Server (NTRS)

NguyenKobayashi, Kayla; Zheng, Jason X.; He, Yutao; Shah, Biren N.

2011-01-01

Exponential growth in microelectronics technology such as field-programmable gate arrays (FPGAs) has enabled high-performance spaceborne instruments with increasing onboard data processing capabilities. As a commonly used digital signal processing (DSP) building block, fast Fourier transform (FFT) has been of great interest in onboard data processing applications, which needs to strike a reasonable balance between high-performance (throughput, block size, etc.) and low resource usage (power, silicon footprint, etc.). It is also desirable to be designed so that a single design can be reused and adapted into instruments with different requirements. The Multi-Pass Wide Kernel FFT (MPWK-FFT) architecture was developed, in which the high-throughput benefits of the parallel FFT structure and the low resource usage of Singleton s single butterfly method is exploited. The result is a wide-kernel, multipass, adaptive FFT architecture. The 32K-point MPWK-FFT architecture includes 32 radix-2 butterflies, 64 FIFOs to store the real inputs, 64 FIFOs to store the imaginary inputs, complex twiddle factor storage, and FIFO logic to route the outputs to the correct FIFO. The inputs are stored in sequential fashion into the FIFOs, and the outputs of each butterfly are sequentially written first into the even FIFO, then the odd FIFO. Because of the order of the outputs written into the FIFOs, the depth of the even FIFOs, which are 768 each, are 1.5 times larger than the odd FIFOs, which are 512 each. The total memory needed for data storage, assuming that each sample is 36 bits, is 2.95 Mbits. The twiddle factors are stored in internal ROM inside the FPGA for fast access time. The total memory size to store the twiddle factors is 589.9Kbits. This FFT structure combines the benefits of high throughput from the parallel FFT kernels and low resource usage from the multi-pass FFT kernels with desired adaptability. Space instrument missions that need onboard FFT capabilities such as the proposed DESDynl, SWOT (Surface Water Ocean Topography), and Europa sounding radar missions would greatly benefit from this technology with significant reductions in non-recurring cost and risk.

The adoption and implementation of an evidence based practice in child and family mental health services organizations: a pilot study of functional family therapy in New York State.

PubMed

Zazzali, James L; Sherbourne, Cathy; Hoagwood, Kimberly Eaton; Greene, Deborah; Bigley, Michael F; Sexton, Thomas L

2008-03-01

Numerous challenges persist in providing evidence-based treatments to children and families in community-based settings. Functional Family Therapy (FFT), one such evidence-based treatment, is a family prevention and intervention program for adolescents with conduct disorder or oppositional defiant disorder. This paper presents pilot data in support of a conceptual framework explaining the adoption and implementation of FFT in a small sample of family and child mental health services organizations in New York State. The conceptual framework is grounded in the diffusion of innovations and the organizational behavior literatures, as well as previously published accounts of the adoption and implementation of evidence-based treatments in mental health. Pilot study data demonstrated that factors associated with the adoption of FFT included: The program fitting with the mission of the organization, as well as the organization having a strong interest in evidence-based treatments. Once a decision to adopt FFT was made, the degree to which it fit with organizational characteristics (e.g., available resource sets, organizational structure, and culture) influenced the ease with which it was implemented. Implications for the adoption and implementation of other evidence-based treatments are discussed.

Fractal dimension to classify the heart sound recordings with KNN and fuzzy c-mean clustering methods

NASA Astrophysics Data System (ADS)

Juniati, D.; Khotimah, C.; Wardani, D. E. K.; Budayasa, K.

2018-01-01

The heart abnormalities can be detected from heart sound. A heart sound can be heard directly with a stethoscope or indirectly by a phonocardiograph, a machine of the heart sound recording. This paper presents the implementation of fractal dimension theory to make a classification of phonocardiograms into a normal heart sound, a murmur, or an extrasystole. The main algorithm used to calculate the fractal dimension was Higuchi’s Algorithm. There were two steps to make a classification of phonocardiograms, feature extraction, and classification. For feature extraction, we used Discrete Wavelet Transform to decompose the signal of heart sound into several sub-bands depending on the selected level. After the decomposition process, the signal was processed using Fast Fourier Transform (FFT) to determine the spectral frequency. The fractal dimension of the FFT output was calculated using Higuchi Algorithm. The classification of fractal dimension of all phonocardiograms was done with KNN and Fuzzy c-mean clustering methods. Based on the research results, the best accuracy obtained was 86.17%, the feature extraction by DWT decomposition level 3 with the value of kmax 50, using 5-fold cross validation and the number of neighbors was 5 at K-NN algorithm. Meanwhile, for fuzzy c-mean clustering, the accuracy was 78.56%.

Joint compensation scheme of polarization crosstalk, intersymbol interference, frequency offset, and phase noise based on cascaded Kalman filter

NASA Astrophysics Data System (ADS)

Zhang, Qun; Yang, Yanfu; Xiang, Qian; Zhou, Zhongqing; Yao, Yong

2018-02-01

A joint compensation scheme based on cascaded Kalman filter is proposed, which can implement polarization tracking, channel equalization, frequency offset, and phase noise compensation simultaneously. The experimental results show that the proposed algorithm can not only compensate multiple channel impairments simultaneously but also improve the polarization tracking capacity and accelerate the convergence speed. The scheme has up to eight times faster convergence speed compared with radius-directed equalizer (RDE) + Max-FFT (maximum fast Fourier transform) + BPS (blind phase search) and can track up polarization rotation 60 times and 15 times faster than that of RDE + Max-FFT + BPS and CMMA (cascaded multimodulus algorithm) + Max-FFT + BPS, respectively.

Proton exchange membrane fuel cell diagnosis by spectral characterization of the electrochemical noise

NASA Astrophysics Data System (ADS)

Maizia, R.; Dib, A.; Thomas, A.; Martemianov, S.

2017-02-01

Electrochemical noise analysis (ENA) has been performed for the diagnosis of proton-exchange membrane fuel cell (PEMFC) under various operating conditions. Its interest is related with the possibility of a non-invasive on-line diagnosis of a commercial fuel cell. A methodology of spectral analysis has been developed and an evaluation of the stationarity of the signal has been proposed. It has been revealed that the spectral signature of fuel cell, is a linear slope with a fractional power dependence 1/fα where α = 2 for different relative humidities and current densities. Experimental results reveal that the electrochemical noise is sensitive to the water management, especially under dry conditions. At RHH2 = 20% and RHair = 20%, spectral analysis shows a three linear slopes signature on the spectrum at low frequency range (f < 100 Hz). This results indicates that power spectral density, calculated thanks to FFT, can be used for the detection of an incorrect fuel cell water balance.

A new method for gravity field recovery based on frequency analysis of spherical harmonics

NASA Astrophysics Data System (ADS)

Cai, Lin; Zhou, Zebing

2017-04-01

All existing methods for gravity field recovery are mostly based on the space-wise and time-wise approach, whose core processes are constructing the observation equations and solving them by the least square method. It's should be pointed that the least square method means the approximation. On the other hand, we can directly and precisely obtain the coefficients of harmonics by computing the Fast Fourier Transform (FFT) when we do 1-D data (time series) analysis. So the question whether we directly and precisely obtain the coefficients of spherical harmonic by computing 2-D FFT of measurements of satellite gravity mission is of great significance, since this may guide us to a new understanding of the signal components of gravity field and make us determine it quickly by taking advantage of FFT. Like the 1-D data analysis, the 2-D FFT of measurements of satellite can be computed rapidly. If we can determine the relationship between spherical harmonics and 2-D Fourier frequencies and the transfer function from measurements to spherical coefficients, the question mentioned above can be solved. So the objective of this research project is to establish a new method based on frequency analysis of spherical harmonic, which directly compute the confidents of spherical harmonic of gravity field, which is differ from recovery by least squares. There is a one to one correspondence between frequency spectrum and the time series in 1-D FFT. The 2-D FFT has a similar relationship to 1-D FFT. Owing to the fact that any degree or order (higher than one) of spherical function has multi frequencies and these frequencies may be aliased. Fortunately, the elements and ratio of these frequencies of spherical function can be determined, and we can compute the coefficients of spherical function from 2-D FFT. This relationship can be written as equations and equivalent to a matrix, which is solid and can be derived in advance. Until now the relationship has be determined. Some preliminary results, which only compute lower degree spherical harmonics, indicates that the difference between the input (EGM2008) and output (coefficients from recovery) is smaller than 5E-17, while the minimal precision of computer software (Matlab) is 2.2204E-16.

Microcomputer-Based Digital Signal Processing Laboratory Experiments.

ERIC Educational Resources Information Center

Tinari, Jr., Rocco; Rao, S. Sathyanarayan

1985-01-01

Describes a system (Apple II microcomputer interfaced to flexible, custom-designed digital hardware) which can provide: (1) Fast Fourier Transform (FFT) computation on real-time data with a video display of spectrum; (2) frequency synthesis experiments using the inverse FFT; and (3) real-time digital filtering experiments. (JN)

Estimation of Cardiopulmonary Parameters From Ultra Wideband Radar Measurements Using the State Space Method.

PubMed

Naishadham, Krishna; Piou, Jean E; Ren, Lingyun; Fathy, Aly E

2016-12-01

Ultra wideband (UWB) Doppler radar has many biomedical applications, including remote diagnosis of cardiovascular disease, triage and real-time personnel tracking in rescue missions. It uses narrow pulses to probe the human body and detect tiny cardiopulmonary movements by spectral analysis of the backscattered electromagnetic (EM) field. With the help of super-resolution spectral algorithms, UWB radar is capable of increased accuracy for estimating vital signs such as heart and respiration rates in adverse signal-to-noise conditions. A major challenge for biomedical radar systems is detecting the heartbeat of a subject with high accuracy, because of minute thorax motion (less than 0.5 mm) caused by the heartbeat. The problem becomes compounded by EM clutter and noise in the environment. In this paper, we introduce a new algorithm based on the state space method (SSM) for the extraction of cardiac and respiration rates from UWB radar measurements. SSM produces range-dependent system poles that can be classified parametrically with spectral peaks at the cardiac and respiratory frequencies. It is shown that SSM produces accurate estimates of the vital signs without producing harmonics and inter-modulation products that plague signal resolution in widely used FFT spectrograms.

1-FFT amino acids involved in high DP inulin accumulation in Viguiera discolor

PubMed Central

De Sadeleer, Emerik; Vergauwen, Rudy; Struyf, Tom; Le Roy, Katrien; Van den Ende, Wim

2015-01-01

Fructans are important vacuolar reserve carbohydrates with drought, cold, ROS and general abiotic stress mediating properties. They occur in 15% of all flowering plants and are believed to display health benefits as a prebiotic and dietary fiber. Fructans are synthesized by specific fructosyltransferases and classified based on the linkage type between fructosyl units. Inulins, one of these fructan types with β(2-1) linkages, are elongated by fructan:fructan 1-fructosyltransferases (1-FFT) using a fructosyl unit from a donor inulin to elongate the acceptor inulin molecule. The sequence identity of the 1-FFT of Viguiera discolor (Vd) and Helianthus tuberosus (Ht) is 91% although these enzymes produce distinct fructans. The Vd 1-FFT produces high degree of polymerization (DP) inulins by preferring the elongation of long chain inulins, in contrast to the Ht 1-FFT which prefers small molecules (DP3 or 4) as acceptor. Since higher DP inulins have interesting properties for industrial, food and medical applications, we report here on the influence of two amino acids on the high DP inulin production capacity of the Vd 1-FFT. Introducing the M19F and H308T mutations in the active site of the Vd 1-FFT greatly reduces its capacity to produce high DP inulin molecules. Both amino acids can be considered important to this capacity, although the double mutation had a much higher impact than the single mutations. PMID:26322058

A novel power harmonic analysis method based on Nuttall-Kaiser combination window double spectrum interpolated FFT algorithm

NASA Astrophysics Data System (ADS)

Jin, Tao; Chen, Yiyang; Flesch, Rodolfo C. C.

2017-11-01

Harmonics pose a great threat to safe and economical operation of power grids. Therefore, it is critical to detect harmonic parameters accurately to design harmonic compensation equipment. The fast Fourier transform (FFT) is widely used for electrical popular power harmonics analysis. However, the barrier effect produced by the algorithm itself and spectrum leakage caused by asynchronous sampling often affects the harmonic analysis accuracy. This paper examines a new approach for harmonic analysis based on deducing the modifier formulas of frequency, phase angle, and amplitude, utilizing the Nuttall-Kaiser window double spectrum line interpolation method, which overcomes the shortcomings in traditional FFT harmonic calculations. The proposed approach is verified numerically and experimentally to be accurate and reliable.

Handling of uncertainty due to interference fringe in FT-NIR transmittance spectroscopy - Performance comparison of interference elimination techniques using glucose-water system

NASA Astrophysics Data System (ADS)

Beganović, Anel; Beć, Krzysztof B.; Henn, Raphael; Huck, Christian W.

2018-05-01

The applicability of two elimination techniques for interferences occurring in measurements with cells of short pathlength using Fourier transform near-infrared (FT-NIR) spectroscopy was evaluated. Due to the growing interest in the field of vibrational spectroscopy in aqueous biological fluids (e.g. glucose in blood), aqueous solutions of D-(+)-glucose were prepared and split into a calibration set and an independent validation set. All samples were measured with two FT-NIR spectrometers at various spectral resolutions. Moving average smoothing (MAS) and fast Fourier transform filter (FFT filter) were applied to the interference affected FT-NIR spectra in order to eliminate the interference pattern. After data pre-treatment, partial least squares regression (PLSR) models using different NIR regions were constructed using untreated (interference affected) spectra and spectra treated with MAS and FFT filter. The prediction of the independent validation set revealed information about the performance of the utilized interference elimination techniques, as well as the different NIR regions. The results showed that the combination band of water at approx. 5200 cm-1 is of great importance since its performance was superior to the one of the so-called first overtone of water at approx. 6800 cm-1. Furthermore, this work demonstrated that MAS and FFT filter are fast and easy-to-use techniques for the elimination of interference fringes in FT-NIR transmittance spectroscopy.

Removal of the Gibbs phenomenon and its application to fast-Fourier-transform-based mode solvers.

PubMed

Wangüemert-Pérez, J G; Godoy-Rubio, R; Ortega-Moñux, A; Molina-Fernández, I

2007-12-01

A simple strategy for accurately recovering discontinuous functions from their Fourier series coefficients is presented. The aim of the proposed approach, named spectrum splitting (SS), is to remove the Gibbs phenomenon by making use of signal-filtering-based concepts and some properties of the Fourier series. While the technique can be used in a vast range of situations, it is particularly suitable for being incorporated into fast-Fourier-transform-based electromagnetic mode solvers (FFT-MSs), which are known to suffer from very poor convergence rates when applied to situations where the field distributions are highly discontinuous (e.g., silicon-on-insulator photonic wires). The resultant method, SS-FFT-MS, is exhaustively tested under the assumption of a simplified one-dimensional model, clearly showing a dramatic improvement of the convergence rates with respect to the original FFT-based methods.

Information Encoding on a Pseudo Random Noise Radar Waveform

DTIC Science & Technology

2013-03-01

quadrature mirror filter bank (QMFB) tree diagram [18] . . . . . . . . . . . 18 2.7 QMFB layer 3 contour plot for 7-bit barker code binary phase shift...test signal . . . . . . . . 20 2.9 Block diagram of the FFT accumulation method (FAM) time smoothing method to estimate the spectral correlation ... Samples A m pl itu de (b) Correlator output for an WGN pulse in a AWGN channel Figure 2.2: Effectiveness of correlation for SNR = -10 dB 10 2.3 Radar

Efficient implementation of parallel three-dimensional FFT on clusters of PCs

NASA Astrophysics Data System (ADS)

Takahashi, Daisuke

2003-05-01

In this paper, we propose a high-performance parallel three-dimensional fast Fourier transform (FFT) algorithm on clusters of PCs. The three-dimensional FFT algorithm can be altered into a block three-dimensional FFT algorithm to reduce the number of cache misses. We show that the block three-dimensional FFT algorithm improves performance by utilizing the cache memory effectively. We use the block three-dimensional FFT algorithm to implement the parallel three-dimensional FFT algorithm. We succeeded in obtaining performance of over 1.3 GFLOPS on an 8-node dual Pentium III 1 GHz PC SMP cluster.

High-accuracy 3D Fourier forward modeling of gravity field based on the Gauss-FFT technique

NASA Astrophysics Data System (ADS)

Zhao, Guangdong; Chen, Bo; Chen, Longwei; Liu, Jianxin; Ren, Zhengyong

2018-03-01

The 3D Fourier forward modeling of 3D density sources is capable of providing 3D gravity anomalies coincided with the meshed density distribution within the whole source region. This paper firstly derives a set of analytical expressions through employing 3D Fourier transforms for calculating the gravity anomalies of a 3D density source approximated by right rectangular prisms. To reduce the errors due to aliasing and imposed periodicity as well as edge effects in the Fourier domain modeling, we develop the 3D Gauss-FFT technique to the 3D gravity anomalies forward modeling. The capability and adaptability of this scheme are tested by simple synthetic models. The results show that the accuracy of the Fourier forward methods using the Gauss-FFT with 4 Gaussian-nodes (or more) is comparable to that of the spatial modeling. In addition, the "ghost" source effects in the 3D Fourier forward gravity field due to imposed periodicity of the standard FFT algorithm are remarkably depressed by the application of the 3D Gauss-FFT algorithm. More importantly, the execution times of the 4 nodes Gauss-FFT modeling are reduced by two orders of magnitude compared with the spatial forward method. It demonstrates that the improved Fourier method is an efficient and accurate forward modeling tool for the gravity field.

Window and Overlap Processing Effects on Power Estimates from Spectra

NASA Astrophysics Data System (ADS)

Trethewey, M. W.

2000-03-01

Fast Fourier transform (FFT) spectral processing is based on the assumption of stationary ergodic data. In engineering practice, the assumption is often violated and non-stationary data processed. Data windows are commonly used to reduce leakage by decreasing the signal amplitudes near the boundaries of the discrete samples. With certain combinations of non-stationary signals and windows, the temporal weighting may attenuate important signal characteristics to adversely affect any subsequent processing. In other words, the window artificially reduces a significant section of the time signal. Consequently, spectra and overall power estimated from the affected samples are unreliable. FFT processing can be particularly problematic when the signal consists of randomly occurring transients superimposed on a more continuous signal. Overlap processing is commonly used in this situation to improve the estimates. However, the results again depend on the temporal character of the signal in relation to the window weighting. A worst-case scenario, a short-duration half sine pulse, is used to illustrate the relationship between overlap percentage and resulting power estimates. The power estimates are shown to depend on the temporal behaviour of the square of overlapped window segments. An analysis shows that power estimates may be obtained to within 0.27 dB for the following windows and overlap combinations: rectangular (0% overlap), Hanning (62.5% overlap), Hamming (60.35% overlap) and flat-top (82.25% overlap).

Computing the Power-Density Spectrum for an Engineering Model

NASA Technical Reports Server (NTRS)

Dunn, H. J.

1982-01-01

Computer program for calculating of power-density spectrum (PDS) from data base generated by Advanced Continuous Simulation Language (ACSL) uses algorithm that employs fast Fourier transform (FFT) to calculate PDS of variable. Accomplished by first estimating autocovariance function of variable and then taking FFT of smoothed autocovariance function to obtain PDS. Fast-Fourier-transform technique conserves computer resources.

Interpretation of aeromagnetic data over Abeokuta and its environs, Southwest Nigeria, using spectral analysis (Fourier transform technique)

NASA Astrophysics Data System (ADS)

Olurin, Oluwaseun T.; Ganiyu, Saheed A.; Hammed, Olaide S.; Aluko, Taiwo J.

2016-10-01

This study presents the results of spectral analysis of magnetic data over Abeokuta area, Southwestern Nigeria, using fast Fourier transform (FFT) in Microsoft Excel. The study deals with the quantitative interpretation of airborne magnetic data (Sheet No. 260), which was conducted by the Nigerian Geological Survey Agency in 2009. In order to minimise aliasing error, the aeromagnetic data was gridded at spacing of 1 km. Spectral analysis technique was used to estimate the magnetic basement depth distributed at two levels. The result of the interpretation shows that the magnetic sources are mainly distributed at two levels. The shallow sources (minimum depth) range in depth from 0.103 to 0.278 km below ground level and are inferred to be due to intrusions within the region. The deeper sources (maximum depth) range in depth from 2.739 to 3.325 km below ground and are attributed to the underlying basement.

Support vector machine based decision for mechanical fault condition monitoring in induction motor using an advanced Hilbert-Park transform.

PubMed

Ben Salem, Samira; Bacha, Khmais; Chaari, Abdelkader

2012-09-01

In this work we suggest an original fault signature based on an improved combination of Hilbert and Park transforms. Starting from this combination we can create two fault signatures: Hilbert modulus current space vector (HMCSV) and Hilbert phase current space vector (HPCSV). These two fault signatures are subsequently analysed using the classical fast Fourier transform (FFT). The effects of mechanical faults on the HMCSV and HPCSV spectrums are described, and the related frequencies are determined. The magnitudes of spectral components, relative to the studied faults (air-gap eccentricity and outer raceway ball bearing defect), are extracted in order to develop the input vector necessary for learning and testing the support vector machine with an aim of classifying automatically the various states of the induction motor. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Effect of frontal facial type and sex on preferred chin projection.

PubMed

Choi, Jin-Young; Kim, Taeyun; Kim, Hyung-Mo; Lee, Sang-Hoon; Cho, Il-Sik; Baek, Seung-Hak

2017-03-01

To investigate the effects of frontal facial type (FFT) and sex on preferred chin projection (CP) in three-dimensional (3D) facial images. Six 3D facial images were acquired using a 3D facial scanner (euryprosopic [Eury-FFT], mesoprosopic [Meso-FFT], and leptoprosopic [Lepto-FFT] for each sex). After normal CP in each 3D facial image was set to 10° of the facial profile angle (glabella-subnasale-pogonion), CPs were morphed by gradations of 2° from normal (moderately protrusive [6°], slightly protrusive [8°], slightly retrusive [12°], and moderately retrusive [14°]). Seventy-five dental students (48 men and 27 women) were asked to rate the CPs (6°, 8°, 10°, 12°, and 14°) from the most to least preferred in each 3D image. Statistical analyses included the Kolmogorov-Smirnov test, Kruskal-Wallis test, and Bonferroni correction. No significant difference was observed in the distribution of preferred CP in the same FFT between male and female evaluators. In Meso-FFT, the normal CP was the most preferred without any sex difference. However, in Eury-FFT, the slightly protrusive CP was favored in male 3D images, but the normal CP was preferred in female 3D images. In Lepto-FFT, the normal CP was favored in male 3D images, whereas the slightly retrusive CP was favored in female 3D images. The mean preferred CP angle differed significantly according to FFT (Eury-FFT: male, 8.7°, female, 9.9°; Meso-FFT: male, 9.8°, female, 10.7°; Lepto-FFT: male, 10.8°, female, 11.4°; p < 0.001). Our findings might serve as guidelines for setting the preferred CP according to FFT and sex.

Detecting the crankshaft torsional vibration of diesel engines for combustion related diagnosis

NASA Astrophysics Data System (ADS)

Charles, P.; Sinha, Jyoti K.; Gu, F.; Lidstone, L.; Ball, A. D.

2009-04-01

Early fault detection and diagnosis for medium-speed diesel engines is important to ensure reliable operation throughout the course of their service. This work presents an investigation of the diesel engine combustion related fault detection capability of crankshaft torsional vibration. The encoder signal, often used for shaft speed measurement, has been used to construct the instantaneous angular speed (IAS) waveform, which actually represents the signature of the torsional vibration. Earlier studies have shown that the IAS signal and its fast Fourier transform (FFT) analysis are effective for monitoring engines with less than eight cylinders. The applicability to medium-speed engines, however, is strongly contested due to the high number of cylinders and large moment of inertia. Therefore the effectiveness of the FFT-based approach has further been enhanced by improving the signal processing to determine the IAS signal and subsequently tested on a 16-cylinder engine. In addition, a novel method of presentation, based on the polar coordinate system of the IAS signal, has also been introduced; to improve the discrimination features of the faults compared to the FFT-based approach of the IAS signal. The paper discusses two typical experimental studies on 16- and 20-cylinder engines, with and without faults, and the diagnosis results by the proposed polar presentation method. The results were also compared with the earlier FFT-based method of the IAS signal.

Isograde mapping and mineral identification on the island of Naxos, Greece, using DAIS 7915 hyperspectral data

NASA Astrophysics Data System (ADS)

Echtler, Helmut; Segl, Karl; Dickerhof, Corinna; Chabrillat, Sabine; Kaufmann, Hermann J.

2003-03-01

The ESF-LSF 1997 flight campaign conducted by the German Aerospace Center (DLR) recorded several transects across the island of Naxos using the airborne hyperspectral scanner DAIS. The geological targets cover all major litho-tectonic units of a metamorphic dome with the transition of metamorphic zonations from the outer meta-sedimentary greenschist envelope to the gneissic amphibolite facies and migmatitic core. Mineral identification of alternating marble-dolomite sequences and interlayered schists bearing muscovite and biotite has been accomplished using the airborne hyperspectral DAIS 7915 sensor. Data have been noise filtered based on maximum noise fraction (MNF) and fast Fourier transform (FFT) and converted from radiance to reflectance. For mineral identification, constrained linear spectral unmixing and spectral angle mapper (SAM) algorithms were tested. Due to their unsatisfying results a new approach was developed which consists of a linear mixture modeling and spectral feature fitting. This approach provides more detailed and accurate information. Results are discussed in comparison with detailed geological mapping and additional information. Calcites are clearly separated from dolomites as well as the mica-schist sequences by a good resolution of the mineral muscovite. Thereon an outstanding result represents the very good resolution of the chlorite/mica (muscovite, biotite)-transition defining a metamorphic isograde.

Compressive-sampling-based positioning in wireless body area networks.

PubMed

Banitalebi-Dehkordi, Mehdi; Abouei, Jamshid; Plataniotis, Konstantinos N

2014-01-01

Recent achievements in wireless technologies have opened up enormous opportunities for the implementation of ubiquitous health care systems in providing rich contextual information and warning mechanisms against abnormal conditions. This helps with the automatic and remote monitoring/tracking of patients in hospitals and facilitates and with the supervision of fragile, elderly people in their own domestic environment through automatic systems to handle the remote drug delivery. This paper presents a new modeling and analysis framework for the multipatient positioning in a wireless body area network (WBAN) which exploits the spatial sparsity of patients and a sparse fast Fourier transform (FFT)-based feature extraction mechanism for monitoring of patients and for reporting the movement tracking to a central database server containing patient vital information. The main goal of this paper is to achieve a high degree of accuracy and resolution in the patient localization with less computational complexity in the implementation using the compressive sensing theory. We represent the patients' positions as a sparse vector obtained by the discrete segmentation of the patient movement space in a circular grid. To estimate this vector, a compressive-sampling-based two-level FFT (CS-2FFT) feature vector is synthesized for each received signal from the biosensors embedded on the patient's body at each grid point. This feature extraction process benefits in the combination of both short-time and long-time properties of the received signals. The robustness of the proposed CS-2FFT-based algorithm in terms of the average positioning error is numerically evaluated using the realistic parameters in the IEEE 802.15.6-WBAN standard in the presence of additive white Gaussian noise. Due to the circular grid pattern and the CS-2FFT feature extraction method, the proposed scheme represents a significant reduction in the computational complexity, while improving the level of the resolution and the localization accuracy when compared to some classical CS-based positioning algorithms.

Numerical evaluation of the radiation from unbaffled, finite plates using the FFT

NASA Technical Reports Server (NTRS)

Williams, E. G.

1983-01-01

An iteration technique is described which numerically evaluates the acoustic pressure and velocity on and near unbaffled, finite, thin plates vibrating in air. The technique is based on Rayleigh's integral formula and its inverse. These formulas are written in their angular spectrum form so that the fast Fourier transform (FFT) algorithm may be used to evaluate them. As an example of the technique the pressure on the surface of a vibrating, unbaffled disk is computed and shown to be in excellent agreement with the exact solution using oblate spheroidal functions. Furthermore, the computed velocity field outside the disk shows the well-known singularity at the rim of the disk. The radiated fields from unbaffled flat sources of any geometry with prescribed surface velocity may be evaluated using this technique. The use of the FFT to perform the integrations in Rayleigh's formulas provides a great savings in computation time compared with standard integration algorithms, especially when an array processor can be used to implement the FFT.

Broadband Time-Frequency Analysis Using a Multicomputer

DTIC Science & Technology

2004-09-30

FFT 512 pt Waterfall WVD display 8© 2004 Mercury Computer Systems, Inc. Smoothed Pseudo Wigner - Ville Distribution One of many interference reduction...The Wigner - Ville distribution , the scalogram, and the discrete Gabor transform are among the most well-known of these methods. Due to specific...based upon FFT Accumulation Method • Continuous Wavelet Transform (Scalogram) • Discrete Wigner - Ville Distribution with a selected set of interference

Optical coherence tomography imaging based on non-harmonic analysis

NASA Astrophysics Data System (ADS)

Cao, Xu; Hirobayashi, Shigeki; Chong, Changho; Morosawa, Atsushi; Totsuka, Koki; Suzuki, Takuya

2009-11-01

A new processing technique called Non-Harmonic Analysis (NHA) is proposed for OCT imaging. Conventional Fourier-Domain OCT relies on the FFT calculation which depends on the window function and length. Axial resolution is counter proportional to the frame length of FFT that is limited by the swept range of the swept source in SS-OCT, or the pixel counts of CCD in SD-OCT degraded in FD-OCT. However, NHA process is intrinsically free from this trade-offs; NHA can resolve high frequency without being influenced by window function or frame length of sampled data. In this study, NHA process is explained and applied to OCT imaging and compared with OCT images based on FFT. In order to validate the benefit of NHA in OCT, we carried out OCT imaging based on NHA with the three different sample of onion-skin,human-skin and pig-eye. The results show that NHA process can realize practical image resolution that is equivalent to 100nm swept range only with less than half-reduced wavelength range.

Adaptive Pre-FFT Equalizer with High-Precision Channel Estimator for ISI Channels

NASA Astrophysics Data System (ADS)

Yoshida, Makoto

We present an attractive approach for OFDM transmission using an adaptive pre-FFT equalizer, which can select ICI reduction mode according to channel condition, and a degenerated-inverse-matrix-based channel estimator (DIME), which uses a cyclic sinc-function matrix uniquely determined by transmitted subcarriers. In addition to simulation results, the proposed system with an adaptive pre-FFT equalizer and DIME has been laboratory tested by using a software defined radio (SDR)-based test bed. The simulation and experimental results demonstrated that the system at a rate of more than 100Mbps can provide a bit error rate of less than 10-3 for a fast multi-path fading channel that has a moving velocity of more than 200km/h with a delay spread of 1.9µs (a maximum delay path of 7.3µs) in the 5-GHz band.

Efficient Modeling of Gravity Fields Caused by Sources with Arbitrary Geometry and Arbitrary Density Distribution

NASA Astrophysics Data System (ADS)

Wu, Leyuan

2018-01-01

We present a brief review of gravity forward algorithms in Cartesian coordinate system, including both space-domain and Fourier-domain approaches, after which we introduce a truly general and efficient algorithm, namely the convolution-type Gauss fast Fourier transform (Conv-Gauss-FFT) algorithm, for 2D and 3D modeling of gravity potential and its derivatives due to sources with arbitrary geometry and arbitrary density distribution which are defined either by discrete or by continuous functions. The Conv-Gauss-FFT algorithm is based on the combined use of a hybrid rectangle-Gaussian grid and the fast Fourier transform (FFT) algorithm. Since the gravity forward problem in Cartesian coordinate system can be expressed as continuous convolution-type integrals, we first approximate the continuous convolution by a weighted sum of a series of shifted discrete convolutions, and then each shifted discrete convolution, which is essentially a Toeplitz system, is calculated efficiently and accurately by combining circulant embedding with the FFT algorithm. Synthetic and real model tests show that the Conv-Gauss-FFT algorithm can obtain high-precision forward results very efficiently for almost any practical model, and it works especially well for complex 3D models when gravity fields on large 3D regular grids are needed.

Ultrahigh-order Maxwell solver with extreme scalability for electromagnetic PIC simulations of plasmas

NASA Astrophysics Data System (ADS)

Vincenti, Henri; Vay, Jean-Luc

2018-07-01

The advent of massively parallel supercomputers, with their distributed-memory technology using many processing units, has favored the development of highly-scalable local low-order solvers at the expense of harder-to-scale global very high-order spectral methods. Indeed, FFT-based methods, which were very popular on shared memory computers, have been largely replaced by finite-difference (FD) methods for the solution of many problems, including plasmas simulations with electromagnetic Particle-In-Cell methods. For some problems, such as the modeling of so-called "plasma mirrors" for the generation of high-energy particles and ultra-short radiations, we have shown that the inaccuracies of standard FD-based PIC methods prevent the modeling on present supercomputers at sufficient accuracy. We demonstrate here that a new method, based on the use of local FFTs, enables ultrahigh-order accuracy with unprecedented scalability, and thus for the first time the accurate modeling of plasma mirrors in 3D.

A CAMAC based real-time noise analysis system for nuclear reactors

NASA Astrophysics Data System (ADS)

Ciftcioglu, Özer

1987-05-01

A CAMAC based real-time noise analysis system was designed for the TRIGA MARK II nuclear reactor at the Institute for Nuclear Energy, Istanbul. The input analog signals obtained from the radiation detectors are introduced to the system through CAMAC interface. The signals converted into digital form are processed by a PDP-11 computer. The fast data processing based on auto/cross power spectral density computations is carried out by means of assembly written FFT algorithms in real-time and the spectra obtained are displayed on a CAMAC driven display system as an additional monitoring device. The system has the advantage of being software programmable and controlled by a CAMAC system so that it is operated under program control for reactor surveillance, anomaly detection and diagnosis. The system can also be used for the identification of nonstationary operational characteristics of the reactor in long term by comparing the noise power spectra with the corresponding reference noise patterns prepared in advance.

Computation of Power Spectral Densities and Correlations Using Digital FFT Techniques

DTIC Science & Technology

1975-12-01

NUMBER increases and DELTAT decreases the region over which the transform is accurate increases. For NUMBER equal to 2048 , the results are very close...to the actual function G for the entire range plotted. At higher frequencies, even the case for NUMBER equal to 2048 will deviate from the actual...J o o o CM — o o O 30 io-’ io-2 G(w) >-3 IO𔃾 1 1 1 I I I I I O N= 2048 , AT = O.OI NO REFLECTION o N= 2048 , AT =0.0 I

Estimation of Ice Surface Scattering and Acoustic Attenuation in Arctic Sediments from Long-Range Propagation Data

DTIC Science & Technology

1984-01-01

frequencies over the calculation at 1 meter. This was corrected by +60 dB to obtain the signature at I meter, and then by -160 dB to obtain the voltage...FFT with appropriate corrections for one-sided energy spectral density re . 1 V2/Hz. The spectrum was then smeared over a 4 Hz band by a running...after correcting the array estimated slownesses for slight bathymetric dip local to the receiving array. A preliminary inversion of this type is given by

Sparsity-based fast CGH generation using layer-based approach for 3D point cloud model

NASA Astrophysics Data System (ADS)

Kim, Hak Gu; Jeong, Hyunwook; Ro, Yong Man

2017-03-01

Computer generated hologram (CGH) is becoming increasingly important for a 3-D display in various applications including virtual reality. In the CGH, holographic fringe patterns are generated by numerically calculating them on computer simulation systems. However, a heavy computational cost is required to calculate the complex amplitude on CGH plane for all points of 3D objects. This paper proposes a new fast CGH generation based on the sparsity of CGH for 3D point cloud model. The aim of the proposed method is to significantly reduce computational complexity while maintaining the quality of the holographic fringe patterns. To that end, we present a new layer-based approach for calculating the complex amplitude distribution on the CGH plane by using sparse FFT (sFFT). We observe the CGH of a layer of 3D objects is sparse so that dominant CGH is rapidly generated from a small set of signals by sFFT. Experimental results have shown that the proposed method is one order of magnitude faster than recently reported fast CGH generation.

FFT multislice method--the silver anniversary.

PubMed

Ishizuka, Kazuo

2004-02-01

The first paper on the FFT multislice method was published in 1977, a quarter of a century ago. The formula was extended in 1982 to include a large tilt of an incident beam relative to the specimen surface. Since then, with advances of computing power, the FFT multislice method has been successfully applied to coherent CBED and HAADF-STEM simulations. However, because the multislice formula is built on some physical approximations and approximations in numerical procedure, there seem to be controversial conclusions in the literature on the multislice method. In this report, the physical implication of the multislice method is reviewed based on the formula for the tilted illumination. Then, some results on the coherent CBED and the HAADF-STEM simulations are presented.

An improved conscan algorithm based on a Kalman filter

NASA Technical Reports Server (NTRS)

Eldred, D. B.

1994-01-01

Conscan is commonly used by DSN antennas to allow adaptive tracking of a target whose position is not precisely known. This article describes an algorithm that is based on a Kalman filter and is proposed to replace the existing fast Fourier transform based (FFT-based) algorithm for conscan. Advantages of this algorithm include better pointing accuracy, continuous update information, and accommodation of missing data. Additionally, a strategy for adaptive selection of the conscan radius is proposed. The performance of the algorithm is illustrated through computer simulations and compared to the FFT algorithm. The results show that the Kalman filter algorithm is consistently superior.

Design of microcontroller-based EMG and the analysis of EMG signals.

PubMed

Güler, Nihal Fatma; Hardalaç, Firat

2002-04-01

In this work, a microcontroller-based EMG designed and tested on 40 patients. When the patients are in rest, the fast Fourier transform (FFT) analysis was applied to EMG signals recorded from right leg peroneal region. The histograms are constructed from the results of the FFT analysis. The analysis results shows that the amplitude of fibrillation potential of the muscle fiber of 30 patients measured from peroneal region is low and the duration is short. This is the reason why the motor nerves degenerated and 10 patients were found to be healthy.

Spatial features of mid-latitude field-line resonances from simultaneous ground-satellite measurements

NASA Astrophysics Data System (ADS)

Prikner, K.

1996-07-01

Three series of simultaneous pulsation measurements ( f<0.06 Hz) on the Freja satellite and at the Budkov Observatory have been spectrally processed (FFT) in 6-min intervals of Freja's transits near the local Budkov field line. Doppler-shifted, weighted spectral-peak frequencies, determined in both transverse magnetic components in the mean field-aligned coordinate system on Freja, allowed the estimation, by comparison with the stable frequency at Budkov, of fundamental frequencies of the local magnetic-field-line resonance ranged from 13 to 17 mHz in two pulsation events analyzed, with Kp=2+ to 0+. The ratio of total amplitudes of the spectral-pulsation components on the ground and on Freja at an altitude of ~1700 km (values <0.7) characterizes the transmissivity of the ionosphere. In the Pc3 frequency range this correlates well with simulation computations using models of the ionosphere under low solar activity. Acknowledgements. The Editor in Chief thanks two referees for their help in evaluating this paper.--> Correspondence to: L. Alperovich-->

A spectral boundary integral equation method for the 2-D Helmholtz equation

NASA Technical Reports Server (NTRS)

Hu, Fang Q.

1994-01-01

In this paper, we present a new numerical formulation of solving the boundary integral equations reformulated from the Helmholtz equation. The boundaries of the problems are assumed to be smooth closed contours. The solution on the boundary is treated as a periodic function, which is in turn approximated by a truncated Fourier series. A Fourier collocation method is followed in which the boundary integral equation is transformed into a system of algebraic equations. It is shown that in order to achieve spectral accuracy for the numerical formulation, the nonsmoothness of the integral kernels, associated with the Helmholtz equation, must be carefully removed. The emphasis of the paper is on investigating the essential elements of removing the nonsmoothness of the integral kernels in the spectral implementation. The present method is robust for a general boundary contour. Aspects of efficient implementation of the method using FFT are also discussed. A numerical example of wave scattering is given in which the exponential accuracy of the present numerical method is demonstrated.

Fault diagnosis method based on FFT-RPCA-SVM for Cascaded-Multilevel Inverter.

PubMed

Wang, Tianzhen; Qi, Jie; Xu, Hao; Wang, Yide; Liu, Lei; Gao, Diju

2016-01-01

Thanks to reduced switch stress, high quality of load wave, easy packaging and good extensibility, the cascaded H-bridge multilevel inverter is widely used in wind power system. To guarantee stable operation of system, a new fault diagnosis method, based on Fast Fourier Transform (FFT), Relative Principle Component Analysis (RPCA) and Support Vector Machine (SVM), is proposed for H-bridge multilevel inverter. To avoid the influence of load variation on fault diagnosis, the output voltages of the inverter is chosen as the fault characteristic signals. To shorten the time of diagnosis and improve the diagnostic accuracy, the main features of the fault characteristic signals are extracted by FFT. To further reduce the training time of SVM, the feature vector is reduced based on RPCA that can get a lower dimensional feature space. The fault classifier is constructed via SVM. An experimental prototype of the inverter is built to test the proposed method. Compared to other fault diagnosis methods, the experimental results demonstrate the high accuracy and efficiency of the proposed method. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar

PubMed Central

Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

2016-01-01

For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method. PMID:26805835

A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar.

PubMed

Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

2016-01-20

For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method.

icoshift: A versatile tool for the rapid alignment of 1D NMR spectra

NASA Astrophysics Data System (ADS)

Savorani, F.; Tomasi, G.; Engelsen, S. B.

2010-02-01

The increasing scientific and industrial interest towards metabonomics takes advantage from the high qualitative and quantitative information level of nuclear magnetic resonance (NMR) spectroscopy. However, several chemical and physical factors can affect the absolute and the relative position of an NMR signal and it is not always possible or desirable to eliminate these effects a priori. To remove misalignment of NMR signals a posteriori, several algorithms have been proposed in the literature. The icoshift program presented here is an open source and highly efficient program designed for solving signal alignment problems in metabonomic NMR data analysis. The icoshift algorithm is based on correlation shifting of spectral intervals and employs an FFT engine that aligns all spectra simultaneously. The algorithm is demonstrated to be faster than similar methods found in the literature making full-resolution alignment of large datasets feasible and thus avoiding down-sampling steps such as binning. The algorithm uses missing values as a filling alternative in order to avoid spectral artifacts at the segment boundaries. The algorithm is made open source and the Matlab code including documentation can be downloaded from www.models.life.ku.dk.

Risk factors for pericardial effusion after chemoradiotherapy for thoracic esophageal cancer—comparison of four-field technique and traditional two opposed fields technique

PubMed Central

Takata, Noriko; Kataoka, Masaaki; Hamamoto, Yasushi; Tsuruoka, Shintaro; Kanzaki, Hiromitsu; Uwatsu, Kotaro; Nagasaki, Kei; Mochizuki, Teruhito

2018-01-01

Abstract Pericardial effusion is an important late toxicity after concurrent chemoradiotherapy (CCRT) for locally advanced esophageal cancer. We investigated the clinical and dosimetric factors that were related to pericardial effusion among patients with thoracic esophageal cancer who were treated with definitive CCRT using the two opposed fields technique (TFT) or the four-field technique (FFT), as well as the effectiveness of FFT. During 2007–2015, 169 patients with middle and/or lower thoracic esophageal cancer received definitive CCRT, and 94 patients were evaluable (51 FFT cases and 43 TFT cases). Pericardial effusion was observed in 74 patients (79%) and appeared at 1–18.5 months (median: 5.25 months) after CCRT. The 1-year incidences of pericardial effusions were 73.2% and 76.7% in the FFT and TFT groups, respectively (P = 0.6395). The mean doses to the pericardium were 28.6 Gy and 31.8 Gy in the FFT and TFT groups, respectively (P = 0.0259), and the V40 Gy proportions were 33.5% and 48.2% in the FFT and TFT groups, respectively (P < 0.0001). Grade 3 pericardial effusion was not observed in patients with a pericardial V40 Gy of <40%, or in patients who were treated using the FFT. Although the mean pericardial dose and V40 Gy in the FFT group were smaller than those in the TFT group, the incidences of pericardial effusion after CCRT were similar in both groups. As symptomatic pericardial effusion was not observed in patients with a pericardial V40 Gy of <40% or in the FFT group, it appears that FFT with a V40 Gy of <40% could help minimize symptomatic pericardial effusion. PMID:29659940

Risk factors for pericardial effusion after chemoradiotherapy for thoracic esophageal cancer-comparison of four-field technique and traditional two opposed fields technique.

PubMed

Takata, Noriko; Kataoka, Masaaki; Hamamoto, Yasushi; Tsuruoka, Shintaro; Kanzaki, Hiromitsu; Uwatsu, Kotaro; Nagasaki, Kei; Mochizuki, Teruhito

2018-05-01

Pericardial effusion is an important late toxicity after concurrent chemoradiotherapy (CCRT) for locally advanced esophageal cancer. We investigated the clinical and dosimetric factors that were related to pericardial effusion among patients with thoracic esophageal cancer who were treated with definitive CCRT using the two opposed fields technique (TFT) or the four-field technique (FFT), as well as the effectiveness of FFT. During 2007-2015, 169 patients with middle and/or lower thoracic esophageal cancer received definitive CCRT, and 94 patients were evaluable (51 FFT cases and 43 TFT cases). Pericardial effusion was observed in 74 patients (79%) and appeared at 1-18.5 months (median: 5.25 months) after CCRT. The 1-year incidences of pericardial effusions were 73.2% and 76.7% in the FFT and TFT groups, respectively (P = 0.6395). The mean doses to the pericardium were 28.6 Gy and 31.8 Gy in the FFT and TFT groups, respectively (P = 0.0259), and the V40 Gy proportions were 33.5% and 48.2% in the FFT and TFT groups, respectively (P < 0.0001). Grade 3 pericardial effusion was not observed in patients with a pericardial V40 Gy of <40%, or in patients who were treated using the FFT. Although the mean pericardial dose and V40 Gy in the FFT group were smaller than those in the TFT group, the incidences of pericardial effusion after CCRT were similar in both groups. As symptomatic pericardial effusion was not observed in patients with a pericardial V40 Gy of <40% or in the FFT group, it appears that FFT with a V40 Gy of <40% could help minimize symptomatic pericardial effusion.

Transforming a Fructan:Fructan 6G-Fructosyltransferase from Perennial Ryegrass into a Sucrose:Sucrose 1-Fructosyltransferase1[C

PubMed Central

Lasseur, Bertrand; Schroeven, Lindsey; Lammens, Willem; Le Roy, Katrien; Spangenberg, German; Manduzio, Hélène; Vergauwen, Rudy; Lothier, Jérémy; Prud'homme, Marie-Pascale; Van den Ende, Wim

2009-01-01

Fructosyltransferases (FTs) synthesize fructans, fructose polymers accumulating in economically important cool-season grasses and cereals. FTs might be crucial for plant survival under stress conditions in species in which fructans represent the major form of reserve carbohydrate, such as perennial ryegrass (Lolium perenne). Two FT types can be distinguished: those using sucrose (S-type enzymes: sucrose:sucrose 1-fructosyltransferase [1-SST], sucrose:fructan 6-fructosyltransferase) and those using fructans (F-type enzymes: fructan:fructan 1-fructosyltransferase [1-FFT], fructan:fructan 6G-fructosyltransferase [6G-FFT]) as preferential donor substrate. Here, we report, to our knowledge for the first time, the transformation of an F-type enzyme (6G-FFT/1-FFT) into an S-type enzyme (1-SST) using perennial ryegrass 6G-FFT/1-FFT (Lp6G-FFT/1-FFT) and 1-SST (Lp1-SST) as model enzymes. This transformation was accomplished by mutating three amino acids (N340D, W343R, and S415N) in the vicinity of the active site of Lp6G-FFT/1-FFT. In addition, effects of each amino acid mutation alone or in combination have been studied. Our results strongly suggest that the amino acid at position 343 (tryptophan or arginine) can greatly determine the donor substrate characteristics by influencing the position of the amino acid at position 340. Moreover, the presence of arginine-343 negatively affects the formation of neofructan-type linkages. The results are compared with recent findings on donor substrate selectivity within the group of plant cell wall invertases and fructan exohydrolases. Taken together, these insights contribute to our knowledge of structure/function relationships within plant family 32 glycosyl hydrolases and open the way to the production of tailor-made fructans on a larger scale. PMID:18952861

Assessment of Power Quality based on Fuzzy Logic and Discrete Wavelet Transform for Nonstationary Disturbances

NASA Astrophysics Data System (ADS)

Sinha, Pampa; Nath, Sudipta

2010-10-01

The main aspects of power system delivery are reliability and quality. If all the customers of a power system get uninterrupted power through the year then the system is considered to be reliable. The term power quality may be referred to as maintaining near sinusoidal voltage at rated frequency at the consumers end. The power component definitions are defined according to the IEEE Standard 1459-2000 both for single phase and three phase unbalanced systems based on Fourier Transform (FFT). In the presence of nonstationary power quality (PQ) disturbances results in accurate values due to its sensitivity to the spectral leakage problem. To overcome these limitations the power quality components are calculated using Discrete Wavelet Transform (DWT). In order to handle the uncertainties associated with electric power systems operations fuzzy logic has been incorporated in this paper. A new power quality index has been introduced here which can assess the power quality under nonstationary disturbances.

Dataset of quantitative spectral EEG of different stages of kindling acquisition in rats.

PubMed

Jalilifar, Mostafa; Yadollahpour, Ali

2018-02-01

The data represented here are in relation with the manuscript "Quantitative assessments of extracellular EEG to classify specific features of main phases of seizure acquisition based on kindling model in Rat" (Jalilifar et al., 2017) [1] which quantitatively classified different main stages of the kindling process based on their electrophysiological characteristics using EEG signal processing. The data in the graphical form reported the contribution of different sub bands of EEG in different stages of kindling- induced epileptogenesis. Only EEG signals related to stages 1-2 (initial seizure stages (ISSs)), 3 (localized seizure stage (LSS)), and 4-5 (generalized seizure stages (GSSs) were transferred into frequency function by Fast Fourier Transform (FFT) and their power spectrum and power of each sub bands including delta (1-4 Hz), Theta (4-8 Hz), alpha (8-12 Hz), beta (12-28 Hz), gamma (28-40 Hz) were calculated with MATLAB 2013b. Accordingly, all results were obtained quantitatively which can contribute to reduce the errors in the behavioral assessments.

Recordings of mucociliary activity in vivo: benefit of fast Fourier transformation of the photoelectric signal.

PubMed

Lindberg, S; Cervin, A; Runer, T; Thomasson, L

1996-09-01

Investigations of mucociliary activity in vivo are based on photoelectric recordings of light reflections from the mucosa. The alterations in light intensity produced by the beating cilia are picked up by a photodetector and converted to photoelectric signals. The optimal processing of these signals is not known, but in vitro recordings have been reported to benefit from fast Fourier transformation (FFT) of the signal. The aim of the investigation was to study the effect of FFT for frequency analysis of photoelectric signals originating from an artificial light source simulating mucociliary activity or from sinus or nasal mucosa in vivo, as compared to a conventional method of calculating mucociliary wave frequency, in which each peak in the signal is interpreted as a beat (old method). In the experiments with the artificial light source, the FFT system was superior to the conventional method by a factor of 50 in detecting weak signals. By using FFT signal processing, frequency could be correctly calculated in experiments with a compound signal. In experiments in the rabbit maxillary sinus, the spontaneous variations were greater when signals were processed by FFT. The correlation between the two methods was excellent: r = .92. The increase in mucociliary activity in response to the ciliary stimulant methacholine at a dosage of 0.5 microgram/kg was greater measured with the FFT than with the old method (55.3% +/- 8.3% versus 43.0% +/- 8.2%, p < .05, N = 8), and only with the FFT system could a significant effect of a threshold dose (0.05 microgram/kg) of methacholine be detected. In the human nose, recordings from aluminum foil placed on the nasal dorsum and from the nasal septa mucosa displayed some similarities in the lower frequency spectrum (< 5 Hz) attributable to artifacts. The predominant cause of these artifacts was the pulse beat, whereas in the frequency spectrum above 5 Hz, results differed for the two sources of reflected light, the mean frequency in seven healthy volunteers being 7.8 +/- 1.6 Hz for the human nasal mucosa. It is concluded that the FFT system has greater sensitivity in detecting photoelectric signals derived from the mucociliary system, and that it is also a useful tool for analyzing the contributions of artifacts to the signal.

Fast algorithm for computing complex number-theoretic transforms

NASA Technical Reports Server (NTRS)

Reed, I. S.; Liu, K. Y.; Truong, T. K.

1977-01-01

A high-radix FFT algorithm for computing transforms over FFT, where q is a Mersenne prime, is developed to implement fast circular convolutions. This new algorithm requires substantially fewer multiplications than the conventional FFT.

Observation of ion acoustic multi-Peregrine solitons in multicomponent plasma with negative ions

NASA Astrophysics Data System (ADS)

Pathak, Pallabi; Sharma, Sumita K.; Nakamura, Y.; Bailung, H.

2017-12-01

The evolution of the multi-Peregrine soliton is investigated in a multicomponent plasma and found to be critically dependent on the initial bound state. Formation and splitting of Peregrine soliton, broadening of the frequency spectra provide clear evidence of nonlinear-dispersive focusing due to modulational instability, a generic mechanism for rogue wave formation in which amplitude and phase modulation grow as a result of interplay between nonlinearity and anomalous dispersion. We have shown that initial perturbation parameters (amplitude & temporal length) critically determine the number of solitons evolution. It is also found that a sufficiently long wavelength perturbation of high amplitude invoke strong nonlinearity to generate a supercontinuum state. Continuous Wavelet Transform (CWT) and Fast Fourier Transform (FFT) analysis of the experimental time series data clearly indicate the spatio-temporal localization and spectral broadening. We consider a model based on the frame work of Nonlinear Schrodinger equation (NLSE) to explain the experimental observations.

Synthesis of Ag and Au nanoparticles embedded in carbon film: Optical, crystalline and topography analysis

NASA Astrophysics Data System (ADS)

Gholamali, Hediyeh; Shafiekhani, Azizollah; Darabi, Elham; Elahi, Seyed Mohammad

2018-03-01

Atomic force microscopy (AFM) images give valuable information about surface roughness of thin films based on the results of power spectral density (PSD) through the fast Fourier transform (FFT) algorithms. In the present work, AFM data are studied for silver and gold nanoparticles (Ag NPs a-C: H and Au NPs a-C: H) embedded in amorphous hydrogenated carbon films and co-deposited on glass substrate via of RF-Sputtering and RF-Plasma Enhanced Chemical Vapor Deposition methods. Here, the working gas is acetylene and the targets are Ag and Au. While time and power are constant, the only variable parameter in this study is initial pressure. In addition, the crystalline structure of Ag NPs a-C: H and Au NPs a-C: H are studied using X-ray diffraction (XRD). UV-visible spectrophotometry will also investigate optical properties and localized surface plasmon resonance (LSPR) of samples.

The Delicate Analysis of Short-Term Load Forecasting

NASA Astrophysics Data System (ADS)

Song, Changwei; Zheng, Yuan

2017-05-01

This paper proposes a new method for short-term load forecasting based on the similar day method, correlation coefficient and Fast Fourier Transform (FFT) to achieve the precision analysis of load variation from three aspects (typical day, correlation coefficient, spectral analysis) and three dimensions (time dimension, industry dimensions, the main factors influencing the load characteristic such as national policies, regional economic, holidays, electricity and so on). First, the branch algorithm one-class-SVM is adopted to selection the typical day. Second, correlation coefficient method is used to obtain the direction and strength of the linear relationship between two random variables, which can reflect the influence caused by the customer macro policy and the scale of production to the electricity price. Third, Fourier transform residual error correction model is proposed to reflect the nature of load extracting from the residual error. Finally, simulation result indicates the validity and engineering practicability of the proposed method.

A GPU accelerated and error-controlled solver for the unbounded Poisson equation in three dimensions

NASA Astrophysics Data System (ADS)

Exl, Lukas

2017-12-01

An efficient solver for the three dimensional free-space Poisson equation is presented. The underlying numerical method is based on finite Fourier series approximation. While the error of all involved approximations can be fully controlled, the overall computation error is driven by the convergence of the finite Fourier series of the density. For smooth and fast-decaying densities the proposed method will be spectrally accurate. The method scales with O(N log N) operations, where N is the total number of discretization points in the Cartesian grid. The majority of the computational costs come from fast Fourier transforms (FFT), which makes it ideal for GPU computation. Several numerical computations on CPU and GPU validate the method and show efficiency and convergence behavior. Tests are performed using the Vienna Scientific Cluster 3 (VSC3). A free MATLAB implementation for CPU and GPU is provided to the interested community.

Propagation characteristics of optical fiber structures with arbitrary shape and index variation

NASA Technical Reports Server (NTRS)

Manshadi, F.

1990-01-01

The application of the scalar wave-fast Fourier transform (SW-FFT) technique to the computation of the propagation characteristics of some complex optical fiber structures is presented. The SW-FFT technique is based on the numerical solution of the scalar wave equation by a forward-marching fast Fourier transform method. This solution yields the spatial configuration of the fields as well as its modal characteristics in and around the guiding structure. The following are treated by the SW-FFT method: analysis of coupled optical fibers and computation of their odd and even modes and coupling length; the solution of tapered optical waveguides (transitions) and the study of the effect of the slope of the taper on mode conversion; and the analysis of branching optical fibers and demonstration of their mode-filtering and/or power-dividing properties.

Graphics processing unit accelerated phase field dislocation dynamics: Application to bi-metallic interfaces

DOE PAGES

Eghtesad, Adnan; Germaschewski, Kai; Beyerlein, Irene J.; ...

2017-10-14

We present the first high-performance computing implementation of the meso-scale phase field dislocation dynamics (PFDD) model on a graphics processing unit (GPU)-based platform. The implementation takes advantage of the portable OpenACC standard directive pragmas along with Nvidia's compute unified device architecture (CUDA) fast Fourier transform (FFT) library called CUFFT to execute the FFT computations within the PFDD formulation on the same GPU platform. The overall implementation is termed ACCPFDD-CUFFT. The package is entirely performance portable due to the use of OPENACC-CUDA inter-operability, in which calls to CUDA functions are replaced with the OPENACC data regions for a host central processingmore » unit (CPU) and device (GPU). A comprehensive benchmark study has been conducted, which compares a number of FFT routines, the Numerical Recipes FFT (FOURN), Fastest Fourier Transform in the West (FFTW), and the CUFFT. The last one exploits the advantages of the GPU hardware for FFT calculations. The novel ACCPFDD-CUFFT implementation is verified using the analytical solutions for the stress field around an infinite edge dislocation and subsequently applied to simulate the interaction and motion of dislocations through a bi-phase copper-nickel (Cu–Ni) interface. It is demonstrated that the ACCPFDD-CUFFT implementation on a single TESLA K80 GPU offers a 27.6X speedup relative to the serial version and a 5X speedup relative to the 22-multicore Intel Xeon CPU E5-2699 v4 @ 2.20 GHz version of the code.« less

Graphics processing unit accelerated phase field dislocation dynamics: Application to bi-metallic interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eghtesad, Adnan; Germaschewski, Kai; Beyerlein, Irene J.

We present the first high-performance computing implementation of the meso-scale phase field dislocation dynamics (PFDD) model on a graphics processing unit (GPU)-based platform. The implementation takes advantage of the portable OpenACC standard directive pragmas along with Nvidia's compute unified device architecture (CUDA) fast Fourier transform (FFT) library called CUFFT to execute the FFT computations within the PFDD formulation on the same GPU platform. The overall implementation is termed ACCPFDD-CUFFT. The package is entirely performance portable due to the use of OPENACC-CUDA inter-operability, in which calls to CUDA functions are replaced with the OPENACC data regions for a host central processingmore » unit (CPU) and device (GPU). A comprehensive benchmark study has been conducted, which compares a number of FFT routines, the Numerical Recipes FFT (FOURN), Fastest Fourier Transform in the West (FFTW), and the CUFFT. The last one exploits the advantages of the GPU hardware for FFT calculations. The novel ACCPFDD-CUFFT implementation is verified using the analytical solutions for the stress field around an infinite edge dislocation and subsequently applied to simulate the interaction and motion of dislocations through a bi-phase copper-nickel (Cu–Ni) interface. It is demonstrated that the ACCPFDD-CUFFT implementation on a single TESLA K80 GPU offers a 27.6X speedup relative to the serial version and a 5X speedup relative to the 22-multicore Intel Xeon CPU E5-2699 v4 @ 2.20 GHz version of the code.« less

Theoretical Studies of a Transient Stimulated Raman Amplifier

DTIC Science & Technology

1988-04-19

follows: I. contour plot of pump intensity . 1. sections of pump intensity 2. sections of pump phase 3. sections of pump amplitude (real/ imag ) I...contour plot of pump FFT intensity 4. sections of pump FFT intensity 5. sections of pump FFT phase 6. sections of pump FFT amplitude (real/ imag ) II...contour plot of Stokes intensity 7. sections of Stokes intensity 8. sections of Stokes phase 9. sections of Stokes amplitude (real/ imag ) IV. contour plot

A fast numerical solution of scattering by a cylinder: Spectral method for the boundary integral equations

NASA Technical Reports Server (NTRS)

Hu, Fang Q.

1994-01-01

It is known that the exact analytic solutions of wave scattering by a circular cylinder, when they exist, are not in a closed form but in infinite series which converges slowly for high frequency waves. In this paper, we present a fast number solution for the scattering problem in which the boundary integral equations, reformulated from the Helmholtz equation, are solved using a Fourier spectral method. It is shown that the special geometry considered here allows the implementation of the spectral method to be simple and very efficient. The present method differs from previous approaches in that the singularities of the integral kernels are removed and dealt with accurately. The proposed method preserves the spectral accuracy and is shown to have an exponential rate of convergence. Aspects of efficient implementation using FFT are discussed. Moreover, the boundary integral equations of combined single and double-layer representation are used in the present paper. This ensures the uniqueness of the numerical solution for the scattering problem at all frequencies. Although a strongly singular kernel is encountered for the Neumann boundary conditions, we show that the hypersingularity can be handled easily in the spectral method. Numerical examples that demonstrate the validity of the method are also presented.

Fast Fourier transform-based solution of 2D and 3D magnetization problems in type-II superconductivity

NASA Astrophysics Data System (ADS)

Prigozhin, Leonid; Sokolovsky, Vladimir

2018-05-01

We consider the fast Fourier transform (FFT) based numerical method for thin film magnetization problems (Vestgården and Johansen 2012 Supercond. Sci. Technol. 25 104001), compare it with the finite element methods, and evaluate its accuracy. Proposed modifications of this method implementation ensure stable convergence of iterations and enhance its efficiency. A new method, also based on the FFT, is developed for 3D bulk magnetization problems. This method is based on a magnetic field formulation, different from the popular h-formulation of eddy current problems typically employed with the edge finite elements. The method is simple, easy to implement, and can be used with a general current–voltage relation; its efficiency is illustrated by numerical simulations.

Characterization of physical mass transport through oil sands fluid fine tailings in an end pit lake: a multi-tracer study.

PubMed

Dompierre, Kathryn A; Barbour, S Lee

2016-06-01

Soft tailings pose substantial challenges for mine reclamation due to their high void ratios and low shear strengths, particularly for conventional terrestrial reclamation practices. Oil sands mine operators have proposed the development of end pit lakes to contain the soft tailings, called fluid fine tailings (FFT), generated when bitumen is removed from oil sands ore. End pit lakes would be constructed within mined-out pits with FFT placed below the lake water. However, the feasibility of isolating the underlying FFT has yet to be fully evaluated. Chemical constituents of interest may move from the FFT into the lake water via two key processes: (1) advective-diffusive mass transport with upward pore water flow caused by settling of the FFT; and (2) mixing created by wind events or unstable density profiles through the lake water and upper portion of the FFT. In 2013 and 2014, temperature and stable isotopes of water profiles were measured through the FFT and lake water in the first end pit lake developed by Syncrude Canada Ltd. Numerical modelling was undertaken to simulate these profiles to identify the key mechanisms controlling conservative mass transport in the FFT. Shallow mixing of the upper 1.1 m of FFT with lake water was required to explain the observed temperature and isotopic profiles. Following mixing, the re-establishment of both the temperature and isotope profiles required an upward advective flux of approximately 1.5 m/year, consistent with average FFT settling rates measured at the study site. These findings provide important insight on the ability to sequester soft tailings in an end pit lake, and offer a foundation for future research on the development of end pit lakes as an oil sands reclamation strategy. Copyright © 2016 Elsevier B.V. All rights reserved.

Efficient implementation of multidimensional fast fourier transform on a distributed-memory parallel multi-node computer

DOEpatents

Bhanot, Gyan V [Princeton, NJ; Chen, Dong [Croton-On-Hudson, NY; Gara, Alan G [Mount Kisco, NY; Giampapa, Mark E [Irvington, NY; Heidelberger, Philip [Cortlandt Manor, NY; Steinmacher-Burow, Burkhard D [Mount Kisco, NY; Vranas, Pavlos M [Bedford Hills, NY

2012-01-10

The present in invention is directed to a method, system and program storage device for efficiently implementing a multidimensional Fast Fourier Transform (FFT) of a multidimensional array comprising a plurality of elements initially distributed in a multi-node computer system comprising a plurality of nodes in communication over a network, comprising: distributing the plurality of elements of the array in a first dimension across the plurality of nodes of the computer system over the network to facilitate a first one-dimensional FFT; performing the first one-dimensional FFT on the elements of the array distributed at each node in the first dimension; re-distributing the one-dimensional FFT-transformed elements at each node in a second dimension via "all-to-all" distribution in random order across other nodes of the computer system over the network; and performing a second one-dimensional FFT on elements of the array re-distributed at each node in the second dimension, wherein the random order facilitates efficient utilization of the network thereby efficiently implementing the multidimensional FFT. The "all-to-all" re-distribution of array elements is further efficiently implemented in applications other than the multidimensional FFT on the distributed-memory parallel supercomputer.

Efficient implementation of a multidimensional fast fourier transform on a distributed-memory parallel multi-node computer

DOEpatents

Bhanot, Gyan V [Princeton, NJ; Chen, Dong [Croton-On-Hudson, NY; Gara, Alan G [Mount Kisco, NY; Giampapa, Mark E [Irvington, NY; Heidelberger, Philip [Cortlandt Manor, NY; Steinmacher-Burow, Burkhard D [Mount Kisco, NY; Vranas, Pavlos M [Bedford Hills, NY

2008-01-01

The present in invention is directed to a method, system and program storage device for efficiently implementing a multidimensional Fast Fourier Transform (FFT) of a multidimensional array comprising a plurality of elements initially distributed in a multi-node computer system comprising a plurality of nodes in communication over a network, comprising: distributing the plurality of elements of the array in a first dimension across the plurality of nodes of the computer system over the network to facilitate a first one-dimensional FFT; performing the first one-dimensional FFT on the elements of the array distributed at each node in the first dimension; re-distributing the one-dimensional FFT-transformed elements at each node in a second dimension via "all-to-all" distribution in random order across other nodes of the computer system over the network; and performing a second one-dimensional FFT on elements of the array re-distributed at each node in the second dimension, wherein the random order facilitates efficient utilization of the network thereby efficiently implementing the multidimensional FFT. The "all-to-all" re-distribution of array elements is further efficiently implemented in applications other than the multidimensional FFT on the distributed-memory parallel supercomputer.

STS-48 Commander Creighton, in LES, stands at JSC FFT side hatch

NASA Technical Reports Server (NTRS)

1991-01-01

STS-48 Discovery, Orbiter Vehicle (OV) 103, Commander John O. Creighton, wearing a launch and entry suit (LES), stands at the side hatch of JSC's full fuselage trainer (FFT). Creighton will enter the FFT shuttle mockup through the side hatch and take his assigned position on the forward flight deck. Creighton, along with the other crewmembers, is participating in a post-landing emergency egress exercise. The FFT is located in the Mockup and Integration Laboratory (MAIL) Bldg 9A.

Fast Fourier Transform algorithm design and tradeoffs

NASA Technical Reports Server (NTRS)

Kamin, Ray A., III; Adams, George B., III

1988-01-01

The Fast Fourier Transform (FFT) is a mainstay of certain numerical techniques for solving fluid dynamics problems. The Connection Machine CM-2 is the target for an investigation into the design of multidimensional Single Instruction Stream/Multiple Data (SIMD) parallel FFT algorithms for high performance. Critical algorithm design issues are discussed, necessary machine performance measurements are identified and made, and the performance of the developed FFT programs are measured. Fast Fourier Transform programs are compared to the currently best Cray-2 FFT program.

Spatial Frequency Multiplexing of Fiber-Optic Interferometric Refractive Index Sensors Based on Graded-Index Multimode Fibers

PubMed Central

Liu, Li; Gong, Yuan; Wu, Yu; Zhao, Tian; Wu, Hui-Juan; Rao, Yun-Jiang

2012-01-01

Fiber-optic interferometric sensors based on graded-index multimode fibers have very high refractive-index sensitivity, as we previously demonstrated. In this paper, spatial-frequency multiplexing of this type of fiber-optic refractive index sensors is investigated. It is estimated that multiplexing of more than 10 such sensors is possible. In the multiplexing scheme, one of the sensors is used to investigate the refractive index and temperature responses. The fast Fourier transform (FFT) of the combined reflective spectra is analyzed. The intensity of the FFT spectra is linearly related with the refractive index and is not sensitive to the temperature.

A general purpose subroutine for fast fourier transform on a distributed memory parallel machine

NASA Technical Reports Server (NTRS)

Dubey, A.; Zubair, M.; Grosch, C. E.

1992-01-01

One issue which is central in developing a general purpose Fast Fourier Transform (FFT) subroutine on a distributed memory parallel machine is the data distribution. It is possible that different users would like to use the FFT routine with different data distributions. Thus, there is a need to design FFT schemes on distributed memory parallel machines which can support a variety of data distributions. An FFT implementation on a distributed memory parallel machine which works for a number of data distributions commonly encountered in scientific applications is presented. The problem of rearranging the data after computing the FFT is also addressed. The performance of the implementation on a distributed memory parallel machine Intel iPSC/860 is evaluated.

FFT applications to plane-polar near-field antenna measurements

NASA Technical Reports Server (NTRS)

Gatti, Mark S.; Rahmat-Samii, Yahya

1988-01-01

The four-point bivariate Lagrange interpolation algorithm was applied to near-field antenna data measured in a plane-polar facility. The results were sufficiently accurate to permit the use of the FFT (fast Fourier transform) algorithm to calculate the far-field patterns of the antenna. Good agreement was obtained between the far-field patterns as calculated by the Jacobi-Bessel and the FFT algorithms. The significant advantage in using the FFT is in the calculation of the principal plane cuts, which may be made very quickly. Also, the application of the FFT algorithm directly to the near-field data was used to perform surface holographic diagnosis of a reflector antenna. The effects due to the focusing of the emergent beam from the reflector, as well as the effects of the information in the wide-angle regions, are shown. The use of the plane-polar near-field antenna test range has therfore been expanded to include these useful FFT applications.

An investigation of pulsar searching techniques with the fast folding algorithm

NASA Astrophysics Data System (ADS)

Cameron, A. D.; Barr, E. D.; Champion, D. J.; Kramer, M.; Zhu, W. W.

2017-06-01

Here, we present an in-depth study of the behaviour of the fast folding algorithm (FFA), an alternative pulsar searching technique to the fast Fourier transform (FFT). Weaknesses in the FFT, including a susceptibility to red noise, leave it insensitive to pulsars with long rotational periods (P > 1 s). This sensitivity gap has the potential to bias our understanding of the period distribution of the pulsar population. The FFA, a time-domain based pulsar searching technique, has the potential to overcome some of these biases. Modern distributed-computing frameworks now allow for the application of this algorithm to all-sky blind pulsar surveys for the first time. However, many aspects of the behaviour of this search technique remain poorly understood, including its responsiveness to variations in pulse shape and the presence of red noise. Using a custom CPU-based implementation of the FFA, ffancy, we have conducted an in-depth study into the behaviour of the FFA in both an ideal, white noise regime as well as a trial on observational data from the High Time Resolution Universe South Low Latitude pulsar survey, including a comparison to the behaviour of the FFT. We are able to both confirm and expand upon earlier studies that demonstrate the ability of the FFA to outperform the FFT under ideal white noise conditions, and demonstrate a significant improvement in sensitivity to long-period pulsars in real observational data through the use of the FFA.

Robust High-Capacity Audio Watermarking Based on FFT Amplitude Modification

NASA Astrophysics Data System (ADS)

Fallahpour, Mehdi; Megías, David

This paper proposes a novel robust audio watermarking algorithm to embed data and extract it in a bit-exact manner based on changing the magnitudes of the FFT spectrum. The key point is selecting a frequency band for embedding based on the comparison between the original and the MP3 compressed/decompressed signal and on a suitable scaling factor. The experimental results show that the method has a very high capacity (about 5kbps), without significant perceptual distortion (ODG about -0.25) and provides robustness against common audio signal processing such as added noise, filtering and MPEG compression (MP3). Furthermore, the proposed method has a larger capacity (number of embedded bits to number of host bits rate) than recent image data hiding methods.

Improvment of short cut numerical method for determination of periods of free oscillations for basins with irregular geometry and bathymetry

NASA Astrophysics Data System (ADS)

Chernov, Anton; Kurkin, Andrey; Pelinovsky, Efim; Yalciner, Ahmet; Zaytsev, Andrey

2010-05-01

A short cut numerical method for evaluation of the modes of free oscillations of the basins which have irregular geometry and bathymetry was presented in the paper (Yalciner A.C., Pelinovsky E., 2007). In the method, a single wave is inputted to the basin as an initial impulse. The respective agitation in the basin is computed by using the numerical method solving the nonlinear form of long wave equations. The time histories of water surface fluctuations at different locations due to propagation of the waves in relation to the initial impulse are stored and analyzed by the fast Fourier transform technique (FFT) and energy spectrum curves for each location are obtained. The frequencies of each mode of free oscillations are determined from the peaks of the spectrum curves. Some main features were added for this method and will be discussed here: 1. Instead of small number of gauges which were manually installed in the studied area the information from numerical simulation now is recorded on the regular net of the «simulation» gauges which was place everywhere on the sea surface in the depth deeper than "coast" level with the fixed presetted distance between gauges. The spectral analysis of wave records was produced by Welch periodorgam method instead of simple FFT so it's possible to get spectral power estimation for wave process and determine confidence interval for spectra peaks. 2. After the power spectral estimation procedure the common peak of studied seiche can be found and mean spectral amplitudes for this peak were calculated numerically by a Simpson integration method for all gauges in the basin and the mean spectral amplitudes spatial distribution map can be ploted. The spatial distribution helps to study structure of seiche and determine effected dangerous areas. 3. Nested grid module in the NAMI-DANCE - nonlinear shallow water equations calculation software package was developed. This is very important feature for complicated different scale (ocean - sea - bay - harbor) phenomenons studying. The new developed software was tested for Mediterranian, Sea of Okhotsk and South China sea regions. This software can be usefull in local tsunami mapping and tsunami propagation in the coastal zone. References: Yalciner A.C., Pelinovsky E. A short cut numerical method for determination of periods of free oscillations for basins with irregular geometry and bathymetry // Ocean engineering. V. 34. 2007. С. 747 - 757

Fast Fourier Transform Co-Processor (FFTC)- Towards Embedded GFLOPs

NASA Astrophysics Data System (ADS)

Kuehl, Christopher; Liebstueckel, Uwe; Tejerina, Isaac; Uemminghaus, Michael; Wite, Felix; Kolb, Michael; Suess, Martin; Weigand, Roland

2012-08-01

Many signal processing applications and algorithms perform their operations on the data in the transform domain to gain efficiency. The Fourier Transform Co- Processor has been developed with the aim to offload General Purpose Processors from performing these transformations and therefore to boast the overall performance of a processing module. The IP of the commercial PowerFFT processor has been selected and adapted to meet the constraints of the space environment.In frame of the ESA activity “Fast Fourier Transform DSP Co-processor (FFTC)” (ESTEC/Contract No. 15314/07/NL/LvH/ma) the objectives were the following:Production of prototypes of a space qualified version of the commercial PowerFFT chip called FFTC based on the PowerFFT IP.The development of a stand-alone FFTC Accelerator Board (FTAB) based on the FFTC including the Controller FPGA and SpaceWire Interfaces to verify the FFTC function and performance.The FFTC chip performs its calculations with floating point precision. Stand alone it is capable computing FFTs of up to 1K complex samples in length in only 10μsec. This corresponds to an equivalent processing performance of 4.7 GFlops. In this mode the maximum sustained data throughput reaches 6.4Gbit/s. When connected to up to 4 EDAC protected SDRAM memory banks the FFTC can perform long FFTs with up to 1M complex samples in length or multidimensional FFT- based processing tasks.A Controller FPGA on the FTAB takes care of the SDRAM addressing. The instructions commanded via the Controller FPGA are used to set up the data flow and generate the memory addresses.The presentation will give and overview on the project, including the results of the validation of the FFTC ASIC prototypes.

Fast Fourier Transform Co-processor (FFTC), towards embedded GFLOPs

NASA Astrophysics Data System (ADS)

Kuehl, Christopher; Liebstueckel, Uwe; Tejerina, Isaac; Uemminghaus, Michael; Witte, Felix; Kolb, Michael; Suess, Martin; Weigand, Roland; Kopp, Nicholas

2012-10-01

Many signal processing applications and algorithms perform their operations on the data in the transform domain to gain efficiency. The Fourier Transform Co-Processor has been developed with the aim to offload General Purpose Processors from performing these transformations and therefore to boast the overall performance of a processing module. The IP of the commercial PowerFFT processor has been selected and adapted to meet the constraints of the space environment. In frame of the ESA activity "Fast Fourier Transform DSP Co-processor (FFTC)" (ESTEC/Contract No. 15314/07/NL/LvH/ma) the objectives were the following: • Production of prototypes of a space qualified version of the commercial PowerFFT chip called FFTC based on the PowerFFT IP. • The development of a stand-alone FFTC Accelerator Board (FTAB) based on the FFTC including the Controller FPGA and SpaceWire Interfaces to verify the FFTC function and performance. The FFTC chip performs its calculations with floating point precision. Stand alone it is capable computing FFTs of up to 1K complex samples in length in only 10μsec. This corresponds to an equivalent processing performance of 4.7 GFlops. In this mode the maximum sustained data throughput reaches 6.4Gbit/s. When connected to up to 4 EDAC protected SDRAM memory banks the FFTC can perform long FFTs with up to 1M complex samples in length or multidimensional FFT-based processing tasks. A Controller FPGA on the FTAB takes care of the SDRAM addressing. The instructions commanded via the Controller FPGA are used to set up the data flow and generate the memory addresses. The paper will give an overview on the project, including the results of the validation of the FFTC ASIC prototypes.

Determination of chlorine concentration using single temperature modulated semiconductor gas sensor

NASA Astrophysics Data System (ADS)

Woźniak, Ł.; Kalinowski, P.; Jasiński, G.; Jasiński, P.

2016-11-01

A periodic temperature modulation using sinusoidal heater voltage was applied to a commercial SnO2 semiconductor gas sensor. Resulting resistance response of the sensor was analyzed using a feature extraction method based on Fast Fourier Transformation (FFT). The amplitudes of the higher harmonics of the FFT from the dynamic nonlinear responses of measured gas were further utilized as an input for Artificial Neuron Network (ANN). Determination of the concentration of chlorine was performed. Moreover, this work evaluates the sensor performance upon sinusoidal temperature modulation.

A fast finite-difference algorithm for topology optimization of permanent magnets

NASA Astrophysics Data System (ADS)

Abert, Claas; Huber, Christian; Bruckner, Florian; Vogler, Christoph; Wautischer, Gregor; Suess, Dieter

2017-09-01

We present a finite-difference method for the topology optimization of permanent magnets that is based on the fast-Fourier-transform (FFT) accelerated computation of the stray-field. The presented method employs the density approach for topology optimization and uses an adjoint method for the gradient computation. Comparison to various state-of-the-art finite-element implementations shows a superior performance and accuracy. Moreover, the presented method is very flexible and easy to implement due to various preexisting FFT stray-field implementations that can be used.

Investigating the Microbial Degradation Potential in Oil Sands Fluid Fine Tailings Using Gamma Irradiation: A Metagenomic Perspective.

PubMed

VanMensel, Danielle; Chaganti, Subba Rao; Boudens, Ryan; Reid, Thomas; Ciborowski, Jan; Weisener, Christopher

2017-08-01

Open-pit mining of the Athabasca oil sands has generated large volumes of waste termed fluid fine tailings (FFT), stored in tailings ponds. Accumulation of toxic organic substances in the tailings ponds is one of the biggest concerns. Gamma irradiation (GI) treatment could accelerate the biodegradation of toxic organic substances. Hence, this research investigates the response of the microbial consortia in GI-treated FFT materials with an emphasis on changes in diversity and organism-related stimuli. FFT materials from aged and fresh ponds were used in the study under aerobic and anaerobic conditions. Variations in the microbial diversity in GI-treated FFT materials were monitored for 52 weeks and significant stimuli (p < 0.05) were observed. Chemoorganotrophic organisms dominated in fresh and aged ponds and showed increased relative abundance resulting from GI treatment. GI-treated anaerobic FFT aged reported stimulus of organisms with biodegradation potential (e.g., Pseudomonas, Enterobacter) and methylotrophic capabilities (e.g., Syntrophus, Smithella). In comparison, GI-treated anaerobic FFT fresh stimulated Desulfuromonas as the principle genus at 52 weeks. Under aerobic conditions, GI-treated FFT aged showed stimulation of organisms capable of sulfur and iron cycling (e.g., Geobacter). However, GI-treated aerobic FFT fresh showed no stimulus at 52 weeks. This research provides an enhanced understanding of oil sands tailings biogeochemistry and the impacts of GI treatment on microorganisms as an effect for targeting toxic organics. The outcomes of this study highlight the potential for this approach to accelerate stabilization and reclamation end points. Graphical Abstract.

Delineation of First-Order Elastic Property Closures for Hexagonal Metals Using Fast Fourier Transforms

PubMed Central

Landry, Nicholas W.; Knezevic, Marko

2015-01-01

Property closures are envelopes representing the complete set of theoretically feasible macroscopic property combinations for a given material system. In this paper, we present a computational procedure based on fast Fourier transforms (FFTs) for delineation of elastic property closures for hexagonal close packed (HCP) metals. The procedure consists of building a database of non-zero Fourier transforms for each component of the elastic stiffness tensor, calculating the Fourier transforms of orientation distribution functions (ODFs), and calculating the ODF-to-elastic property bounds in the Fourier space. In earlier studies, HCP closures were computed using the generalized spherical harmonics (GSH) representation and an assumption of orthotropic sample symmetry; here, the FFT approach allowed us to successfully calculate the closures for a range of HCP metals without invoking any sample symmetry assumption. The methodology presented here facilitates for the first time computation of property closures involving normal-shear coupling stiffness coefficients. We found that the representation of these property linkages using FFTs need more terms compared to GSH representations. However, the use of FFT representations reduces the computational time involved in producing the property closures due to the use of fast FFT algorithms. Moreover, FFT algorithms are readily available as opposed to GSH codes. PMID:28793566

Moho Modeling Using FFT Technique

NASA Astrophysics Data System (ADS)

Chen, Wenjin; Tenzer, Robert

2017-04-01

To improve the numerical efficiency, the Fast Fourier Transform (FFT) technique was facilitated in Parker-Oldenburg's method for a regional gravimetric Moho recovery, which assumes the Earth's planar approximation. In this study, we extend this definition for global applications while assuming a spherical approximation of the Earth. In particular, we utilize the FFT technique for a global Moho recovery, which is practically realized in two numerical steps. The gravimetric forward modeling is first applied, based on methods for a spherical harmonic analysis and synthesis of the global gravity and lithospheric structure models, to compute the refined gravity field, which comprises mainly the gravitational signature of the Moho geometry. The gravimetric inverse problem is then solved iteratively in order to determine the Moho depth. The application of FFT technique to both numerical steps reduces the computation time to a fraction of that required without applying this fast algorithm. The developed numerical producers are used to estimate the Moho depth globally, and the gravimetric result is validated using the global (CRUST1.0) and regional (ESC) seismic Moho models. The comparison reveals a relatively good agreement between the gravimetric and seismic models, with the RMS of differences (of 4-5 km) at the level of expected uncertainties of used input datasets, while without the presence of significant systematic bias.

Sensor Authentication: Embedded Processor Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Svoboda, John

2012-09-25

Described is the c code running on the embedded Microchip 32bit PIC32MX575F256H located on the INL developed noise analysis circuit board. The code performs the following functions: Controls the noise analysis circuit board preamplifier voltage gains of 1, 10, 100, 000 Initializes the analog to digital conversion hardware, input channel selection, Fast Fourier Transform (FFT) function, USB communications interface, and internal memory allocations Initiates high resolution 4096 point 200 kHz data acquisition Computes complex 2048 point FFT and FFT magnitude. Services Host command set Transfers raw data to Host Transfers FFT result to host Communication error checking

STS-48 Pilot Reightler and MS Brown, in LESs, stand at JSC FFT side hatch

NASA Technical Reports Server (NTRS)

1991-01-01

STS-48 Discovery, Orbiter Vehicle (OV) 103, Pilot Kenneth S. Reightler, Jr (left) and Mission Specialist (MS) Mark N. Brown, wearing launch and entry suits (LESs), stand at the side hatch of JSC's full fuselage trainer (FFT). The crewmembers will enter the FFT shuttle mockup through the side hatch and take their assigned descent (landing) positions in the crew cabin. Reightler and Brown, along with the other crewmembers, are participating in a post-landing emergency egress exercise. The FFT is located in the Mockup and Integration Laboratory (MAIL) Bldg 9A.

Polysomnographic and quantitative EEG analysis of subjects with long-term insomnia complaints associated with mild traumatic brain injury.

PubMed

Williams, Benjamin R; Lazic, Stanley E; Ogilvie, Robert D

2008-02-01

The aims of this study were (1) to characterise the extent and nature of disrupted sleep in individuals with long-term sleep complaints subsequent to mild traumatic brain injury (MTBI), and (2) to determine whether sleep disturbances in MTBI subjects were more characteristic of psychophysiological, psychiatric, or idiopathic insomnia. Nine MTBI patients (27.8 months post-injury; SD=15.5 months) and nine control subjects underwent polysomnographic testing and completed self-report questionnaires on sleep quality. Power spectral (FFT) analysis of the sleep onset period was conducted, with both the power and variability in power being quantified. Individuals with MTBI exhibited long-term sleep difficulties, along with various cognitive and affective abnormalities. The MTBI group had 4% less efficient sleep (p=0.019), shorter REM onset latencies (p=0.011), and longer sleep onset latencies, although the latter were highly variable in the MTBI group (F-test: p=0.012). FFT analysis revealed greater intra-subject variability in the MTBI group in sigma, theta, and delta power during the sleep onset period. MTBI patients with persistent sleep complaints differ significantly from controls on a number of electrophysiological outcomes, but could not be easily classified into existing insomnia subtypes. Sleep disturbances can persist well after the injury in a subset of patients with MTBI.

Error and Complexity Analysis for a Collocation-Grid-Projection Plus Precorrected-FFT Algorithm for Solving Potential Integral Equations with LaPlace or Helmholtz Kernels

NASA Technical Reports Server (NTRS)

Phillips, J. R.

1996-01-01

In this paper we derive error bounds for a collocation-grid-projection scheme tuned for use in multilevel methods for solving boundary-element discretizations of potential integral equations. The grid-projection scheme is then combined with a precorrected FFT style multilevel method for solving potential integral equations with 1/r and e(sup ikr)/r kernels. A complexity analysis of this combined method is given to show that for homogeneous problems, the method is order n natural log n nearly independent of the kernel. In addition, it is shown analytically and experimentally that for an inhomogeneity generated by a very finely discretized surface, the combined method slows to order n(sup 4/3). Finally, examples are given to show that the collocation-based grid-projection plus precorrected-FFT scheme is competitive with fast-multipole algorithms when considering realistic problems and 1/r kernels, but can be used over a range of spatial frequencies with only a small performance penalty.

Can an anti-gravity treadmill improve stability of children with cerebral palsy?

PubMed

Birgani, P M; Ashtiyani, M; Rasooli, A; Shahrokhnia, M; Shahrokhi, A; Mirbagheri, M M

2016-08-01

We aimed to study the effects of an anti-gravity treadmill (AlterG) training on balance and postural stability in children with cerebral palsy (CP). AlterG training was performed 3 days/week for 8 weeks, with up to 45 minutes of training per session. The subject was evaluated before and after the 8-week training. The effects of training on the balance and postural stability was evaluated based on the Romberg test that was performed by using a posturography device. The parameters quantifying Center-of-Pressure (CoP) were calculated using different analytical approaches including power spectral density and principal components analyses. All of the key parameters including the Stabilogram, the Fast Fourier Transform (FFT) Energy, the Eigenvectors, and the Eigenvalues of CoP were modified between 14%-84%. The results indicated that the balance features were improved substantially after training. The clinical implication is that the AlterG has the potential to effectively improve postural stability in children with cerebral palsy.

Analysis of digital communication signals and extraction of parameters

NASA Astrophysics Data System (ADS)

Al-Jowder, Anwar

1994-12-01

The signal classification performance of four types of electronics support measure (ESM) communications detection systems is compared from the standpoint of the unintended receiver (interceptor). Typical digital communication signals considered include binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), frequency shift keying (FSK), and on-off keying (OOK). The analysis emphasizes the use of available signal processing software. Detection methods compared include broadband energy detection, FFT-based narrowband energy detection, and two correlation methods which employ the fast Fourier transform (FFT). The correlation methods utilize modified time-frequency distributions, where one of these is based on the Wigner-Ville distribution (WVD). Gaussian white noise is added to the signal to simulate various signal-to-noise ratios (SNR's).

Efficient matrix approach to optical wave propagation and Linear Canonical Transforms.

PubMed

Shakir, Sami A; Fried, David L; Pease, Edwin A; Brennan, Terry J; Dolash, Thomas M

2015-10-05

The Fresnel diffraction integral form of optical wave propagation and the more general Linear Canonical Transforms (LCT) are cast into a matrix transformation form. Taking advantage of recent efficient matrix multiply algorithms, this approach promises an efficient computational and analytical tool that is competitive with FFT based methods but offers better behavior in terms of aliasing, transparent boundary condition, and flexibility in number of sampling points and computational window sizes of the input and output planes being independent. This flexibility makes the method significantly faster than FFT based propagators when only a single point, as in Strehl metrics, or a limited number of points, as in power-in-the-bucket metrics, are needed in the output observation plane.

Accelerating and focusing protein-protein docking correlations using multi-dimensional rotational FFT generating functions.

PubMed

Ritchie, David W; Kozakov, Dima; Vajda, Sandor

2008-09-01

Predicting how proteins interact at the molecular level is a computationally intensive task. Many protein docking algorithms begin by using fast Fourier transform (FFT) correlation techniques to find putative rigid body docking orientations. Most such approaches use 3D Cartesian grids and are therefore limited to computing three dimensional (3D) translational correlations. However, translational FFTs can speed up the calculation in only three of the six rigid body degrees of freedom, and they cannot easily incorporate prior knowledge about a complex to focus and hence further accelerate the calculation. Furthemore, several groups have developed multi-term interaction potentials and others use multi-copy approaches to simulate protein flexibility, which both add to the computational cost of FFT-based docking algorithms. Hence there is a need to develop more powerful and more versatile FFT docking techniques. This article presents a closed-form 6D spherical polar Fourier correlation expression from which arbitrary multi-dimensional multi-property multi-resolution FFT correlations may be generated. The approach is demonstrated by calculating 1D, 3D and 5D rotational correlations of 3D shape and electrostatic expansions up to polynomial order L=30 on a 2 GB personal computer. As expected, 3D correlations are found to be considerably faster than 1D correlations but, surprisingly, 5D correlations are often slower than 3D correlations. Nonetheless, we show that 5D correlations will be advantageous when calculating multi-term knowledge-based interaction potentials. When docking the 84 complexes of the Protein Docking Benchmark, blind 3D shape plus electrostatic correlations take around 30 minutes on a contemporary personal computer and find acceptable solutions within the top 20 in 16 cases. Applying a simple angular constraint to focus the calculation around the receptor binding site produces acceptable solutions within the top 20 in 28 cases. Further constraining the search to the ligand binding site gives up to 48 solutions within the top 20, with calculation times of just a few minutes per complex. Hence the approach described provides a practical and fast tool for rigid body protein-protein docking, especially when prior knowledge about one or both binding sites is available.

Data acquisition instrument for EEG based on embedded system

NASA Astrophysics Data System (ADS)

Toresano, La Ode Husein Z.; Wijaya, Sastra Kusuma; Prawito, Sudarmaji, Arief; Syakura, Abdan; Badri, Cholid

2017-02-01

An electroencephalogram (EEG) is a device for measuring and recording the electrical activity of brain. The EEG data of signal can be used as a source of analysis for human brain function. The purpose of this study was to design a portable multichannel EEG based on embedded system and ADS1299. The ADS1299 is an analog front-end to be used as an Analog to Digital Converter (ADC) to convert analog signal of electrical activity of brain, a filter of electrical signal to reduce the noise on low-frequency band and a data communication to the microcontroller. The system has been tested to capture brain signal within a range of 1-20 Hz using the NETECH EEG simulator 330. The developed system was relatively high accuracy of more than 82.5%. The EEG Instrument has been successfully implemented to acquire the brain signal activity using a PC (Personal Computer) connection for displaying the recorded data. The final result of data acquisition has been processed using OpenBCI GUI (Graphical User Interface) based through real-time process for 8-channel signal acquisition, brain-mapping and power spectral decomposition signal using the standard FFT (Fast Fourier Transform) algorithm.

Simulation of multivariate stationary stochastic processes using dimension-reduction representation methods

NASA Astrophysics Data System (ADS)

Liu, Zhangjun; Liu, Zenghui; Peng, Yongbo

2018-03-01

In view of the Fourier-Stieltjes integral formula of multivariate stationary stochastic processes, a unified formulation accommodating spectral representation method (SRM) and proper orthogonal decomposition (POD) is deduced. By introducing random functions as constraints correlating the orthogonal random variables involved in the unified formulation, the dimension-reduction spectral representation method (DR-SRM) and the dimension-reduction proper orthogonal decomposition (DR-POD) are addressed. The proposed schemes are capable of representing the multivariate stationary stochastic process with a few elementary random variables, bypassing the challenges of high-dimensional random variables inherent in the conventional Monte Carlo methods. In order to accelerate the numerical simulation, the technique of Fast Fourier Transform (FFT) is integrated with the proposed schemes. For illustrative purposes, the simulation of horizontal wind velocity field along the deck of a large-span bridge is proceeded using the proposed methods containing 2 and 3 elementary random variables. Numerical simulation reveals the usefulness of the dimension-reduction representation methods.

Spectral domain optical coherence tomography of multi-MHz A-scan rates at 1310 nm range and real-time 4D-display up to 41 volumes/second

PubMed Central

Choi, Dong-hak; Hiro-Oka, Hideaki; Shimizu, Kimiya; Ohbayashi, Kohji

2012-01-01

An ultrafast frequency domain optical coherence tomography system was developed at A-scan rates between 2.5 and 10 MHz, a B-scan rate of 4 or 8 kHz, and volume-rates between 12 and 41 volumes/second. In the case of the worst duty ratio of 10%, the averaged A-scan rate was 1 MHz. Two optical demultiplexers at a center wavelength of 1310 nm were used for linear-k spectral dispersion and simultaneous differential signal detection at 320 wavelengths. The depth-range, sensitivity, sensitivity roll-off by 6 dB, and axial resolution were 4 mm, 97 dB, 6 mm, and 23 μm, respectively. Using FPGAs for FFT and a GPU for volume rendering, a real-time 4D display was demonstrated at a rate up to 41 volumes/second for an image size of 256 (axial) × 128 × 128 (lateral) voxels. PMID:23243560

Laser induced periodic surface structuring on Si by temporal shaped femtosecond pulses.

PubMed

Almeida, G F B; Martins, R J; Otuka, A J G; Siqueira, J P; Mendonca, C R

2015-10-19

We investigated the effect of temporal shaped femtosecond pulses on silicon laser micromachining. By using sinusoidal spectral phases, pulse trains composed of sub-pulses with distinct temporal separations were generated and applied to the silicon surface to produce Laser Induced Periodic Surface Structures (LIPSS). The LIPSS obtained with different sub-pulse separation were analyzed by comparing the intensity of the two-dimensional fast Fourier Transform (2D-FFT) of the AFM images of the ripples (LIPSS). It was observed that LIPSS amplitude is more emphasized for the pulse train with sub-pulses separation of 128 fs, even when compared with the Fourier transform limited pulse. By estimating the carrier density achieved at the end of each pulse train, we have been able to interpret our results with the Sipe-Drude model, that predicts that LIPSS efficacy is higher for a specific induced carrier density. Hence, our results indicate that temporal shaping of the excitation pulse, performed by spectral phase modulation, can be explored in fs-laser microstructuring.

A Divergence Median-based Geometric Detector with A Weighted Averaging Filter

NASA Astrophysics Data System (ADS)

Hua, Xiaoqiang; Cheng, Yongqiang; Li, Yubo; Wang, Hongqiang; Qin, Yuliang

2018-01-01

To overcome the performance degradation of the classical fast Fourier transform (FFT)-based constant false alarm rate detector with the limited sample data, a divergence median-based geometric detector on the Riemannian manifold of Heimitian positive definite matrices is proposed in this paper. In particular, an autocorrelation matrix is used to model the correlation of sample data. This method of the modeling can avoid the poor Doppler resolution as well as the energy spread of the Doppler filter banks result from the FFT. Moreover, a weighted averaging filter, conceived from the philosophy of the bilateral filtering in image denoising, is proposed and combined within the geometric detection framework. As the weighted averaging filter acts as the clutter suppression, the performance of the geometric detector is improved. Numerical experiments are given to validate the effectiveness of our proposed method.

Performance of FFT methods in local gravity field modelling

NASA Technical Reports Server (NTRS)

Forsberg, Rene; Solheim, Dag

1989-01-01

Fast Fourier transform (FFT) methods provide a fast and efficient means of processing large amounts of gravity or geoid data in local gravity field modelling. The FFT methods, however, has a number of theoretical and practical limitations, especially the use of flat-earth approximation, and the requirements for gridded data. In spite of this the method often yields excellent results in practice when compared to other more rigorous (and computationally expensive) methods, such as least-squares collocation. The good performance of the FFT methods illustrate that the theoretical approximations are offset by the capability of taking into account more data in larger areas, especially important for geoid predictions. For best results good data gridding algorithms are essential. In practice truncated collocation approaches may be used. For large areas at high latitudes the gridding must be done using suitable map projections such as UTM, to avoid trivial errors caused by the meridian convergence. The FFT methods are compared to ground truth data in New Mexico (xi, eta from delta g), Scandinavia (N from delta g, the geoid fits to 15 cm over 2000 km), and areas of the Atlantic (delta g from satellite altimetry using Wiener filtering). In all cases the FFT methods yields results comparable or superior to other methods.

Breaking the polar-nonpolar division in solvation free energy prediction.

PubMed

Wang, Bao; Wang, Chengzhang; Wu, Kedi; Wei, Guo-Wei

2018-02-05

Implicit solvent models divide solvation free energies into polar and nonpolar additive contributions, whereas polar and nonpolar interactions are inseparable and nonadditive. We present a feature functional theory (FFT) framework to break this ad hoc division. The essential ideas of FFT are as follows: (i) representability assumption: there exists a microscopic feature vector that can uniquely characterize and distinguish one molecule from another; (ii) feature-function relationship assumption: the macroscopic features, including solvation free energy, of a molecule is a functional of microscopic feature vectors; and (iii) similarity assumption: molecules with similar microscopic features have similar macroscopic properties, such as solvation free energies. Based on these assumptions, solvation free energy prediction is carried out in the following protocol. First, we construct a molecular microscopic feature vector that is efficient in characterizing the solvation process using quantum mechanics and Poisson-Boltzmann theory. Microscopic feature vectors are combined with macroscopic features, that is, physical observable, to form extended feature vectors. Additionally, we partition a solvation dataset into queries according to molecular compositions. Moreover, for each target molecule, we adopt a machine learning algorithm for its nearest neighbor search, based on the selected microscopic feature vectors. Finally, from the extended feature vectors of obtained nearest neighbors, we construct a functional of solvation free energy, which is employed to predict the solvation free energy of the target molecule. The proposed FFT model has been extensively validated via a large dataset of 668 molecules. The leave-one-out test gives an optimal root-mean-square error (RMSE) of 1.05 kcal/mol. FFT predictions of SAMPL0, SAMPL1, SAMPL2, SAMPL3, and SAMPL4 challenge sets deliver the RMSEs of 0.61, 1.86, 1.64, 0.86, and 1.14 kcal/mol, respectively. Using a test set of 94 molecules and its associated training set, the present approach was carefully compared with a classic solvation model based on weighted solvent accessible surface area. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Radar Measurements of Ocean Surface Waves using Proper Orthogonal Decomposition

DTIC Science & Technology

2017-03-30

rely on use of Fourier transforms (FFT) and filtering spectra on the linear dispersion relationship for ocean surface waves. This report discusses...the measured signal (e.g., Young et al., 1985). In addition, the methods often rely on filtering the FFT of radar backscatter or Doppler velocities...to those obtained with conventional FFT and dispersion curve filtering techniques (iv) Compare both results of(iii) to ground truth sensors (i .e

Effects of Computer Architecture on FFT (Fast Fourier Transform) Algorithm Performance.

DTIC Science & Technology

1983-12-01

Criteria for Efficient Implementation of FFT Algorithms," IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. ASSP-30, pp. 107-109, Feb...1982. Burrus, C. S. and P. W. Eschenbacher. "An In-Place, In-Order Prime Factor FFT Algorithm," IEEE Transactions on Acoustics, Speech, and Signal... Transactions on Acoustics, Speech, and Signal Processing, Vol. ASSP-30, pp. 217-226, Apr. 1982. Control Data Corporation. CDC Cyber 170 Computer Systems

Fluid density and concentration measurement using noninvasive in situ ultrasonic resonance interferometry

DOEpatents

Pope, Noah G.; Veirs, Douglas K.; Claytor, Thomas N.

1994-01-01

The specific gravity or solute concentration of a process fluid solution located in a selected structure is determined by obtaining a resonance response spectrum of the fluid/structure over a range of frequencies that are outside the response of the structure itself. A fast fourier transform (FFT) of the resonance response spectrum is performed to form a set of FFT values. A peak value for the FFT values is determined, e.g., by curve fitting, to output a process parameter that is functionally related to the specific gravity and solute concentration of the process fluid solution. Calibration curves are required to correlate the peak FFT value over the range of expected specific gravities and solute concentrations in the selected structure.

Fluid density and concentration measurement using noninvasive in situ ultrasonic resonance interferometry

DOEpatents

Pope, N.G.; Veirs, D.K.; Claytor, T.N.

1994-10-25

The specific gravity or solute concentration of a process fluid solution located in a selected structure is determined by obtaining a resonance response spectrum of the fluid/structure over a range of frequencies that are outside the response of the structure itself. A fast Fourier transform (FFT) of the resonance response spectrum is performed to form a set of FFT values. A peak value for the FFT values is determined, e.g., by curve fitting, to output a process parameter that is functionally related to the specific gravity and solute concentration of the process fluid solution. Calibration curves are required to correlate the peak FFT value over the range of expected specific gravities and solute concentrations in the selected structure. 7 figs.

A 640-MHz 32-megachannel real-time polyphase-FFT spectrum analyzer

NASA Technical Reports Server (NTRS)

Zimmerman, G. A.; Garyantes, M. F.; Grimm, M. J.; Charny, B.

1991-01-01

A polyphase fast Fourier transform (FFT) spectrum analyzer being designed for NASA's Search for Extraterrestrial Intelligence (SETI) Sky Survey at the Jet Propulsion Laboratory is described. By replacing the time domain multiplicative window preprocessing with polyphase filter processing, much of the processing loss of windowed FFTs can be eliminated. Polyphase coefficient memory costs are minimized by effective use of run length compression. Finite word length effects are analyzed, producing a balanced system with 8 bit inputs, 16 bit fixed point polyphase arithmetic, and 24 bit fixed point FFT arithmetic. Fixed point renormalization midway through the computation is seen to be naturally accommodated by the matrix FFT algorithm proposed. Simulation results validate the finite word length arithmetic analysis and the renormalization technique.

3D shape measurement of moving object with FFT-based spatial matching

NASA Astrophysics Data System (ADS)

Guo, Qinghua; Ruan, Yuxi; Xi, Jiangtao; Song, Limei; Zhu, Xinjun; Yu, Yanguang; Tong, Jun

2018-03-01

This work presents a new technique for 3D shape measurement of moving object in translational motion, which finds applications in online inspection, quality control, etc. A low-complexity 1D fast Fourier transform (FFT)-based spatial matching approach is devised to obtain accurate object displacement estimates, and it is combined with single shot fringe pattern prolometry (FPP) techniques to achieve high measurement performance with multiple captured images through coherent combining. The proposed technique overcomes some limitations of existing ones. Specifically, the placement of marks on object surface and synchronization between projector and camera are not needed, the velocity of the moving object is not required to be constant, and there is no restriction on the movement trajectory. Both simulation and experimental results demonstrate the effectiveness of the proposed technique.

Differential spectral power alteration following acupuncture at different designated places revealed by magnetoencephalography

NASA Astrophysics Data System (ADS)

You, Youbo; Bai, Lijun; Dai, Ruwei; Xue, Ting; Zhong, Chongguang; Liu, Zhenyu; Wang, Hu; Feng, Yuanyuan; Wei, Wenjuan; Tian, Jie

2012-03-01

As an ancient therapeutic technique in Traditional Chinese Medicine, acupuncture has been used increasingly in modern society to treat a range of clinical conditions as an alternative and complementary therapy. However, acupoint specificity, lying at the core of acupuncture, still faces many controversies. Considering previous neuroimaging studies on acupuncture have mainly employed functional magnetic resonance imaging, which only measures the secondary effect of neural activity on cerebral metabolism and hemodynamics, in the current study, we adopted an electrophysiological measurement technique named magnetoencephalography (MEG) to measure the direct neural activity. 28 healthy college students were recruited in this study. We filtered MEG data into 5 consecutive frequency bands (delta, theta, alpha, beta and gamma band) and grouped 140 sensors into 10 main brain regions (left/right frontal, central, temporal, parietal and occipital regions). Fast Fourier Transformation (FFT) based spectral analysis approach was further performed to explore the differential band-limited power change patterns of acupuncture at Stomach Meridian 36 (ST36) using a nearby nonacupoint (NAP) as control condition. Significantly increased delta power and decreased alpha as well as beta power in bilateral frontal ROIs were observed following stimulation at ST36. Compared with ST36, decreased alpha power in left and right central, right parietal as well as right temporal ROIs were detected in NAP group. Our research results may provide additional evidence for acupoint specificity.

Digital simulation of scalar optical diffraction: revisiting chirp function sampling criteria and consequences.

PubMed

Voelz, David G; Roggemann, Michael C

2009-11-10

Accurate simulation of scalar optical diffraction requires consideration of the sampling requirement for the phase chirp function that appears in the Fresnel diffraction expression. We describe three sampling regimes for FFT-based propagation approaches: ideally sampled, oversampled, and undersampled. Ideal sampling, where the chirp and its FFT both have values that match analytic chirp expressions, usually provides the most accurate results but can be difficult to realize in practical simulations. Under- or oversampling leads to a reduction in the available source plane support size, the available source bandwidth, or the available observation support size, depending on the approach and simulation scenario. We discuss three Fresnel propagation approaches: the impulse response/transfer function (angular spectrum) method, the single FFT (direct) method, and the two-step method. With illustrations and simulation examples we show the form of the sampled chirp functions and their discrete transforms, common relationships between the three methods under ideal sampling conditions, and define conditions and consequences to be considered when using nonideal sampling. The analysis is extended to describe the sampling limitations for the more exact Rayleigh-Sommerfeld diffraction solution.

Induction motors airgap-eccentricity detection through the discrete wavelet transform of the apparent power signal under non-stationary operating conditions.

PubMed

Yahia, K; Cardoso, A J M; Ghoggal, A; Zouzou, S E

2014-03-01

Fast Fourier transform (FFT) analysis has been successfully used for fault diagnosis in induction machines. However, this method does not always provide good results for the cases of load torque, speed and voltages variation, leading to a variation of the motor-slip and the consequent FFT problems that appear due to the non-stationary nature of the involved signals. In this paper, the discrete wavelet transform (DWT) of the apparent-power signal for the airgap-eccentricity fault detection in three-phase induction motors is presented in order to overcome the above FFT problems. The proposed method is based on the decomposition of the apparent-power signal from which wavelet approximation and detail coefficients are extracted. The energy evaluation of a known bandwidth permits to define a fault severity factor (FSF). Simulation as well as experimental results are provided to illustrate the effectiveness and accuracy of the proposed method presented even for the case of load torque variations. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

[Continuum based fast Fourier transform processing of infrared spectrum].

PubMed

Liu, Qing-Jie; Lin, Qi-Zhong; Wang, Qin-Jun; Li, Hui; Li, Shuai

2009-12-01

To recognize ground objects with infrared spectrum, high frequency noise removing is one of the most important phases in spectrum feature analysis and extraction. A new method for infrared spectrum preprocessing was given combining spectrum continuum processing and Fast Fourier Transform (CFFT). Continuum was firstly removed from the noise polluted infrared spectrum to standardize hyper-spectra. Then the spectrum was transformed into frequency domain (FD) with fast Fourier transform (FFT), separating noise information from target information After noise eliminating from useful information with a low-pass filter, the filtered FD spectrum was transformed into time domain (TD) with fast Fourier inverse transform. Finally the continuum was recovered to the spectrum, and the filtered infrared spectrum was achieved. Experiment was performed for chlorite spectrum in USGS polluted with two kinds of simulated white noise to validate the filtering ability of CFFT by contrast with cubic function of five point (CFFP) in time domain and traditional FFT in frequency domain. A circle of CFFP has limited filtering effect, so it should work much with more circles and consume more time to achieve better filtering result. As for conventional FFT, Gibbs phenomenon has great effect on preprocessing result at edge bands because of special character of rock or mineral spectra, while works well at middle bands. Mean squared error of CFFT is 0. 000 012 336 with cut-off frequency of 150, while that of FFT and CFFP is 0. 000 061 074 with cut-off frequency of 150 and 0.000 022 963 with 150 working circles respectively. Besides the filtering result of CFFT can be improved by adjusting the filter cut-off frequency, and has little effect on working time. The CFFT method overcomes the Gibbs problem of FFT in spectrum filtering, and can be more convenient, dependable, and effective than traditional TD filter methods.

A simplified focusing and astigmatism correction method for a scanning electron microscope

NASA Astrophysics Data System (ADS)

Lu, Yihua; Zhang, Xianmin; Li, Hai

2018-01-01

Defocus and astigmatism can lead to blurred images and poor resolution. This paper presents a simplified method for focusing and astigmatism correction of a scanning electron microscope (SEM). The method consists of two steps. In the first step, the fast Fourier transform (FFT) of the SEM image is performed and the FFT is subsequently processed with a threshold to achieve a suitable result. In the second step, the threshold FFT is used for ellipse fitting to determine the presence of defocus and astigmatism. The proposed method clearly provides the relationships between the defocus, the astigmatism and the direction of stretching of the FFT, and it can determine the astigmatism in a single image. Experimental studies are conducted to demonstrate the validity of the proposed method.

Methane Fluxes and Consumption in an Oil Sands Tailings End Pit Lake

NASA Astrophysics Data System (ADS)

Slater, G. F.; Goad, C.; Arriaga, D.; Risacher, F.; Morris, P.; Lindsay, M. B.; Mumford, K. G.; Warren, L. A.

2017-12-01

End pit lakes are engineered freshwater lakes designed to reclaim land impacted by surface mining activities via establishment of a functioning ecosystem where biogeochemical cycling mitigates release of hazardous components either by stabilization or biodegradation. End pit lakes provide unique opportunities to gain insight into microbial nutrient cycling under extreme levels of impact that can be applicable to a range of levels of anthropogenic impacts and issues. This study focuses on microbial CH4 cycling in the underlying fluid fine tailings (FFT) and surface waters of Base Mine Lake (BML), the first full demonstration of end pit lake reclamation in the Athabasca Oil Sands Region (AOSR) of northern Alberta, Canada. Over two field seasons (2015 and 2016) BML was thermally stratified, turning over in spring and fall. Oxygen concentrations in the epilimnion (70 to 80 % saturation) decreased steeply through the metalimnion to 3% saturation in the hypolimnion. Conversely, CH4 concentrations were highest in the hypolimnion of BML (25 to 140 µM) with the highest values being observed at the FFT/Water interface. Concentrations decreased to 1-2 µM at the metalimnion and further decreased to < 0.5 µM in the epilimnion. CH4 δ13C in FFT porewater indicated production via fermentative pathways. FFT settlement and dewatering of 0.73 to 1.0 m/yr results in advection of an estimated 1x107 to 2x107 moles/yr CH4 into the surface water, circa an order of magnitude greater than the 3x106 moles/year estimated for molecular diffusion. Calculated fluxes of dissolved CH4 from the FFT into the hypolimnion were 4 orders of magnitude higher than those from the hypolimnion to the metalimnion, indicating a significant sink for CH4 within the hypolimnion limiting upward dissolved CH4 transport. Dissolution of CH4 from bubbles released from the FFT may be contributing to the observed epilimnion concentrations. CH4 δ13C in the hypolimnion showed only minimal enrichment with decreasing concentrations. However, phospholipid fatty acids of bacteria in the hypolimnion were significantly δ13C depleted indicating CH4 consumption was a primary carbon source for the microbial community in the hypolimnion. Ongoing analyses of samples from 2017 will further elucidate the development of methane biogeochemical cycling in BML.

A Comparison of Direction Finding Results From an FFT Peak Identification Technique With Those From the Music Algorithm

DTIC Science & Technology

1991-07-01

MUSIC ALGORITHM (U) by L.E. Montbrland go I July 1991 CRC REPORT NO. 1438 Ottawa I* Government of Canada Gouvsrnweient du Canada I o DParunnt of...FINDING RESULTS FROM AN FFT PEAK IDENTIFICATION TECHNIQUE WITH THOSE FROM THE MUSIC ALGORITHM (U) by L.E. Montbhrand CRC REPORT NO. 1438 July 1991...Ottawa A Comparison of Direction Finding Results From an FFT Peak Identification Technique With Those From the Music Algorithm L.E. Montbriand Abstract A

Forest fuel treatment detection using multi-temporal airborne Lidar data and high resolution aerial imagery ---- A case study at Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Su, Y.; Guo, Q.; Collins, B.; Fry, D.; Kelly, M.

2014-12-01

Forest fuel treatments (FFT) are often employed in Sierra Nevada forest (located in California, US) to enhance forest health, regulate stand density, and reduce wildfire risk. However, there have been concerns that FFTs may have negative impacts on certain protected wildlife species. Due to the constraints and protection of resources (e.g., perennial streams, cultural resources, wildlife habitat, etc.), the actual FFT extents are usually different from planned extents. Identifying the actual extent of treated areas is of primary importance to understand the environmental influence of FFTs. Light detection and ranging (Lidar) is a powerful remote sensing technique that can provide accurate forest structure measurements, which provides great potential to monitor forest changes. This study used canopy height model (CHM) and canopy cover (CC) products derived from multi-temporal airborne Lidar data to detect FFTs by an approach combining a pixel-wise thresholding method and a object-of-interest segmentation method. We also investigated forest change following the implementation of landscape-scale FFT projects through the use of normalized difference vegetation index (NDVI) and standardized principle component analysis (PCA) from multi-temporal high resolution aerial imagery. The same FFT detection routine was applied on the Lidar data and aerial imagery for the purpose of comparing the capability of Lidar data and aerial imagery on FFT detection. Our results demonstrated that the FFT detection using Lidar derived CC products produced both the highest total accuracy and kappa coefficient, and was more robust at identifying areas with light FFTs. The accuracy using Lidar derived CHM products was significantly lower than that of the result using Lidar derived CC, but was still slightly higher than using aerial imagery. FFT detection results using NDVI and standardized PCA using multi-temporal aerial imagery produced almost identical total accuracy and kappa coefficient. Both methods showed relatively limited capacity to detect light FFT areas, and had higher false detection rate (recognized untreated areas as treated areas) compared to the methods using Lidar derived parameters.

Protein-protein docking on hardware accelerators: comparison of GPU and MIC architectures

PubMed Central

2015-01-01

Background The hardware accelerators will provide solutions to computationally complex problems in bioinformatics fields. However, the effect of acceleration depends on the nature of the application, thus selection of an appropriate accelerator requires some consideration. Results In the present study, we compared the effects of acceleration using graphics processing unit (GPU) and many integrated core (MIC) on the speed of fast Fourier transform (FFT)-based protein-protein docking calculation. The GPU implementation performed the protein-protein docking calculations approximately five times faster than the MIC offload mode implementation. The MIC native mode implementation has the advantage in the implementation costs. However, the performance was worse with larger protein pairs because of memory limitations. Conclusion The results suggest that GPU is more suitable than MIC for accelerating FFT-based protein-protein docking applications. PMID:25707855

An improved scheme for Flip-OFDM based on Hartley transform in short-range IM/DD systems.

PubMed

Zhou, Ji; Qiao, Yaojun; Cai, Zhuo; Ji, Yuefeng

2014-08-25

In this paper, an improved Flip-OFDM scheme is proposed for IM/DD optical systems, where the modulation/demodulation processing takes advantage of the fast Hartley transform (FHT) algorithm. We realize the improved scheme in one symbol period while conventional Flip-OFDM scheme based on fast Fourier transform (FFT) in two consecutive symbol periods. So the complexity of many operations in improved scheme is half of that in conventional scheme, such as CP operation, polarity inversion and symbol delay. Compared to FFT with complex input constellation, the complexity of FHT with real input constellation is halved. The transmission experiment over 50-km SSMF has been realized to verify the feasibility of improved scheme. In conclusion, the improved scheme has the same BER performance with conventional scheme, but great superiority on complexity.

Advanced Engine Health Management Applications of the SSME Real-Time Vibration Monitoring System

NASA Technical Reports Server (NTRS)

Fiorucci, Tony R.; Lakin, David R., II; Reynolds, Tracy D.; Turner, James E. (Technical Monitor)

2000-01-01

The Real Time Vibration Monitoring System (RTVMS) is a 32-channel high speed vibration data acquisition and processing system developed at Marshall Space Flight Center (MSFC). It Delivers sample rates as high as 51,200 samples/second per channel and performs Fast Fourier Transform (FFT) processing via on-board digital signal processing (DSP) chips in a real-time format. Advanced engine health assessment is achieved by utilizing the vibration spectra to provide accurate sensor validation and enhanced engine vibration redlines. Discrete spectral signatures (such as synchronous) that are indicators of imminent failure can be assessed and utilized to mitigate catastrophic engine failures- a first in rocket engine health assessment. This paper is presented in viewgraph form.

Phase-shift detection in a Fourier-transform method for temperature sensing using a tapered fiber microknot resonator.

PubMed

Larocque, Hugo; Lu, Ping; Bao, Xiaoyi

2016-04-01

Phase-shift detection in a fast-Fourier-transform (FFT)-based spectrum analysis technique for temperature sensing using a tapered fiber microknot resonator is proposed and demonstrated. Multiple transmission peaks in the FFT spectrum of the device were identified as optical modes having completed different amounts of round trips within the ring structure. Temperature variation induced phase shifts for each set of peaks were characterized, and experimental results show that different peaks have distinct temperature sensitivities reaching values up to -0.542  rad/°C, which is about 10 times greater than that of a regular adiabatic taper Mach-Zehnder interferometer when using similar phase-tracking schemes.

A method to perform a fast fourier transform with primitive image transformations.

PubMed

Sheridan, Phil

2007-05-01

The Fourier transform is one of the most important transformations in image processing. A major component of this influence comes from the ability to implement it efficiently on a digital computer. This paper describes a new methodology to perform a fast Fourier transform (FFT). This methodology emerges from considerations of the natural physical constraints imposed by image capture devices (camera/eye). The novel aspects of the specific FFT method described include: 1) a bit-wise reversal re-grouping operation of the conventional FFT is replaced by the use of lossless image rotation and scaling and 2) the usual arithmetic operations of complex multiplication are replaced with integer addition. The significance of the FFT presented in this paper is introduced by extending a discrete and finite image algebra, named Spiral Honeycomb Image Algebra (SHIA), to a continuous version, named SHIAC.

On the electromagnetic scattering from infinite rectangular grids with finite conductivity

NASA Technical Reports Server (NTRS)

Christodoulou, C. G.; Kauffman, J. F.

1986-01-01

A variety of methods can be used in constructing solutions to the problem of mesh scattering. However, each of these methods has certain drawbacks. The present paper is concerned with a new technique which is valid for all spacings. The new method involved, called the fast Fourier transform-conjugate gradient method (FFT-CGM), represents an iterative technique which employs the conjugate gradient method to improve upon each iterate, utilizing the fast Fourier transform. The FFT-CGM method provides a new accurate model which can be extended and applied to the more difficult problems of woven mesh surfaces. The formulation of the FFT-conjugate gradient method for aperture fields and current densities for a planar periodic structure is considered along with singular operators, the formulation of the FFT-CG method for thin wires with finite conductivity, and reflection coefficients.

Pipelined digital SAR azimuth correlator using hybrid FFT-transversal filter

NASA Technical Reports Server (NTRS)

Wu, C.; Liu, K. Y. (Inventor)

1984-01-01

A synthetic aperture radar system (SAR) having a range correlator is provided with a hybrid azimuth correlator which utilizes a block-pipe-lined fast Fourier transform (FFT). The correlator has a predetermined FFT transform size with delay elements for delaying SAR range correlated data so as to embed in the Fourier transform operation a corner-turning function as the range correlated SAR data is converted from the time domain to a frequency domain. The azimuth correlator is comprised of a transversal filter to receive the SAR data in the frequency domain, a generator for range migration compensation and azimuth reference functions, and an azimuth reference multiplier for correlation of the SAR data. Following the transversal filter is a block-pipelined inverse FFT used to restore azimuth correlated data in the frequency domain to the time domain for imaging.

Fructan:fructan 1-fructosyltransferase and inulin hydrolase activities relating to inulin and soluble sugars in Jerusalem artichoke (Helianthus tuberosus Linn.) tubers during storage.

PubMed

Maicaurkaew, Sukanya; Jogloy, Sanun; Hamaker, Bruce R; Ningsanond, Suwayd

2017-03-01

Influences of harvest time and storage conditions on activities of fructan:fructan1-fructosyltransferase (1-FFT) and inulin hydrolase (InH) in relation to inulin and soluble sugars of Jerusalem artichoke ( Helianthus tuberosus L.) tubers were investigated. Maturity affected 1-FFT-activity, inulin contents, and inulin profiles of the tubers harvested between 30 and 70 days after flowering (DAF). Decreases in 1-FFT activity, high molecular weight inulin, and inulin content were observed in late-harvested tubers. The tubers harvested at 50 DAF had the highest inulin content (734.9 ± 20.5 g kg -1 DW) with a high degree of polymerization (28% of DP >30). During storage of the tubers, increases in InH activity (reached its peak at 15 days of storage) and gradual decreases in 1-FFT activity took placed. These changes were associated with inulin depolymerization, causing decreases in inulin content and increases in soluble sugars. As well, decreasing storage temperatures would retain high inulin content and keep low soluble sugars; and freezing at -18 °C would best retard 1-FFT, InH, and inulin changes.

On Certain Theoretical Developments Underlying the Hilbert-Huang Transform

NASA Technical Reports Server (NTRS)

Kizhner, Semion; Blank, Karin; Flatley, Thomas; Huang, Norden E.; Petrick, David; Hestness, Phyllis

2006-01-01

One of the main traditional tools used in scientific and engineering data spectral analysis is the Fourier Integral Transform and its high performance digital equivalent - the Fast Fourier Transform (FFT). Both carry strong a-priori assumptions about the source data, such as being linear and stationary, and of satisfying the Dirichlet conditions. A recent development at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), known as the Hilbert-Huang Transform (HHT), proposes a novel approach to the solution for the nonlinear class of spectral analysis problems. Using a-posteriori data processing based on the Empirical Mode Decomposition (EMD) sifting process (algorithm), followed by the normalized Hilbert Transform of the decomposed data, the HHT allows spectral analysis of nonlinear and nonstationary data. The EMD sifting process results in a non-constrained decomposition of a source real-value data vector into a finite set of Intrinsic Mode Functions (IMF). These functions form a nearly orthogonal derived from the data (adaptive) basis. The IMFs can be further analyzed for spectrum content by using the classical Hilbert Transform. A new engineering spectral analysis tool using HHT has been developed at NASA GSFC, the HHT Data Processing System (HHT-DPS). As the HHT-DPS has been successfully used and commercialized, new applications pose additional questions about the theoretical basis behind the HHT and EMD algorithms. Why is the fastest changing component of a composite signal being sifted out first in the EMD sifting process? Why does the EMD sifting process seemingly converge and why does it converge rapidly? Does an IMF have a distinctive structure? Why are the IMFs nearly orthogonal? We address these questions and develop the initial theoretical background for the HHT. This will contribute to the development of new HHT processing options, such as real-time and 2-D processing using Field Programmable Gate Array (FPGA) computational resources,

Light microscopic image analysis system to quantify immunoreactive terminal area apposed to nerve cells.

PubMed

Wu, L C; D'Amelio, F; Fox, R A; Polyakov, I; Daunton, N G

1997-06-06

The present report describes a desktop computer-based method for the quantitative assessment of the area occupied by immunoreactive terminals in close apposition to nerve cells in relation to the perimeter of the cell soma. This method is based on Fast Fourier Transform (FFT) routines incorporated in NIH-Image public domain software. Pyramidal cells of layer V of the somatosensory cortex outlined by GABA immunolabeled terminals were chosen for our analysis. A Leitz Diaplan light microscope was employed for the visualization of the sections. A Sierra Scientific Model 4030 CCD camera was used to capture the images into a Macintosh Centris 650 computer. After preprocessing, filtering was performed on the power spectrum in the frequency domain produced by the FFT operation. An inverse FFT with filter procedure was employed to restore the images to the spatial domain. Pasting of the original image to the transformed one using a Boolean logic operation called 'AND'ing produced an image with the terminals enhanced. This procedure allowed the creation of a binary image using a well-defined threshold of 128. Thus, the terminal area appears in black against a white background. This methodology provides an objective means of measurement of area by counting the total number of pixels occupied by immunoreactive terminals in light microscopic sections in which the difficulties of labeling intensity, size, shape and numerical density of terminals are avoided.

Light microscopic image analysis system to quantify immunoreactive terminal area apposed to nerve cells

NASA Technical Reports Server (NTRS)

Wu, L. C.; D'Amelio, F.; Fox, R. A.; Polyakov, I.; Daunton, N. G.

1997-01-01

The present report describes a desktop computer-based method for the quantitative assessment of the area occupied by immunoreactive terminals in close apposition to nerve cells in relation to the perimeter of the cell soma. This method is based on Fast Fourier Transform (FFT) routines incorporated in NIH-Image public domain software. Pyramidal cells of layer V of the somatosensory cortex outlined by GABA immunolabeled terminals were chosen for our analysis. A Leitz Diaplan light microscope was employed for the visualization of the sections. A Sierra Scientific Model 4030 CCD camera was used to capture the images into a Macintosh Centris 650 computer. After preprocessing, filtering was performed on the power spectrum in the frequency domain produced by the FFT operation. An inverse FFT with filter procedure was employed to restore the images to the spatial domain. Pasting of the original image to the transformed one using a Boolean logic operation called 'AND'ing produced an image with the terminals enhanced. This procedure allowed the creation of a binary image using a well-defined threshold of 128. Thus, the terminal area appears in black against a white background. This methodology provides an objective means of measurement of area by counting the total number of pixels occupied by immunoreactive terminals in light microscopic sections in which the difficulties of labeling intensity, size, shape and numerical density of terminals are avoided.

Fructan active enzymes (FAZY) activities and biosynthesis of fructooligosaccharides in the vacuoles of Agave tequilana Weber Blue variety plants of different age.

PubMed

Mellado-Mojica, Erika; González de la Vara, Luis E; López, Mercedes G

2017-02-01

Biosynthesis of agave fructans occurs in mesontle vacuoles which showed fluctuations in FAZY activities and synthesized a diverse spectrum of fructooligosaccharide isomers. Agave tequilana Weber Blue variety is an important agronomic crop in Mexico. Fructan metabolism in A. tequilana exhibits changes in fructan content, type, degree of polymerization (DP), and molecular structure. Specific activities of vacuolar fructan active enzymes (FAZY) in A. tequilana plants of different age and the biosynthesis of fructooligosaccharides (FOSs) were analyzed in this work. Vacuoles from mesontle (stem) protoplasts were isolated and collected from 2- to 7-year-old plants. For the first time, agave fructans were identified in the vacuolar content by HPAEC-PAD. Several FAZY activities (1-SST, 6-SFT, 6G-FFT, 1-FFT, and FEH) with fluctuations according to the plant age were found in protein vacuolar extracts. Among vacuolar FAZY, 1-SST activities appeared in all plant developmental stages, as well as 1-FFT and FEH activities. The enzymes 6G-FFT and 6-SST showed only minimal activities. Lowest and highest FAZY activities were found in 2- and 6-year-old plants, respectively. Synthesized products (FOS) were analyzed by TLC and HPAEC-PAD. Vacuolar FAZYs yielded large FOS isomers diversity, being 7-year-old plants the ones that synthesized a greater variety of fructans with different DP, linkages, and molecular structures. Based on the above, we are proposing a model for the FAZY activities constituting the FOS biosynthetic pathways in Agave tequilana Weber Blue variety.

On the relationship between competitive flow and FFT analysis of the flow waves in the left internal mammary artery graft in the process of CABG.

PubMed

Mao, Boyan; Wang, Wenxin; Zhao, Zhou; Zhao, Xi; Li, Lanlan; Zhang, Huixia; Liu, Youjun

2016-12-28

During coronary artery bypass grafting (CABG), the ratio of powers of the fundamental frequency and its first harmonic (F0/H1) in fast Fourier transformation (FFT) analysis of the graft's flow waves has been used in the field of evaluation of the patency in anastomosis. But there is no report about using the FFT method to evaluate the magnitude of competitive flow. This study is aiming at exploring the relationship between competitive flow and FFT analysis of the flow waves in left internal mammary artery (LIMA) graft, and finding a new method to evaluate the magnitude of competitive flow. At first, establishing the CABG multiscale models of different stenosis in left anterior descending artery (LAD) to get different magnitude of competitive flows. Then, calculating the models by ANSYS-CFX and getting the flow waves in LIMA. Finally, analyzing the flow waves by FFT method and comparing the FFT results with the magnitude of competitive flow. There is no relationship between competitive flow and F0/H1. As for F0/H2 and F0/H3, they both increase with the reduction of the stenosis in LAD. But the increase of F0/H3 is not obviously enough and it can't identify the significant competitive flow clearly, so it can't be used as the evaluation index. It is found that F0/H2 increases obviously with the increase of the competitive flow and can identify the significant competitive flow. The FFT method can be used in the evaluation of competitive flow and the F0/H2 is the ideal index. High F0/H2 refers to the significant competitive flow. This method can be used during CABG to avoid the risk of competitive flow.

The Fourier analysis of biological transients.

PubMed

Harris, C M

1998-08-31

With modern computing technology the digital implementation of the Fourier transform is widely available, mostly in the form of the fast Fourier transform (FFT). Although the FFT has become almost synonymous with the Fourier transform, it is a fast numerical technique for computing the discrete Fourier transform (DFT) of a finite sequence of sampled data. The DFT is not directly equivalent to the continuous Fourier transform of the underlying biological signal, which becomes important when analyzing biological transients. Although this distinction is well known by some, for many it leads to confusion in how to interpret the FFT of biological data, and in how to precondition data so as to yield a more accurate Fourier transform using the FFT. We review here the fundamentals of Fourier analysis with emphasis on the analysis of transient signals. As an example of a transient, we consider the human saccade to illustrate the pitfalls and advantages of various Fourier analyses.

[Personal long-term reproducibility of the TEOAE time-frequency distributions].

PubMed

Konopka, Wiesław; Grzanka, Antoni; Zalewski, Piotr

2002-01-01

The TEOAE signal is relatively short and content changes in time. Due to the fact that signal is very short (20 ms) a special approach must be applied for the analysis of this nonstationarity. Usually the spectral estimation in TEOAE is based on procedures directly employing the fast Fourier transform (FFT). Because TEOAE signal is non stationary the classical Fourier analysis is not adequate for this signal. The aim of our study was the personal comparison of the TEOAE spectograms by using Wigner-Ville distribution (WVD) before and after one year period. Material consisted of 152 men (304 ears) in the age between 18-19 year with good quality OAE. After one year period the comparison of WVD spectrograms showed the highest similarity in the 274 ears (90%), less in the 24 (8%) and in 6 (2%) similarity was not noticed. Personal similarity of the spectrum TEOAE and differences between individual people's ears despite a long time, give a proof about individual architecture of outer hearing cell and maybe useful in the biometrics as a ear-print.

Comparison of Family Therapy Outcome with Alcohol-Abusing, Runaway Adolescents

ERIC Educational Resources Information Center

Slesnick, Natasha; Prestopnik, Jillian L

2009-01-01

Treatment evaluation for alcohol problem, runaway adolescents and their families is rare. This study recruited primary alcohol problem adolescents (N = 119) and their primary caretakers from two runaway shelters and assigned them to (a) home-based ecologically based family therapy (EBFT), (b) office-based functional family therapy (FFT), or (c)…

Flame analysis using image processing techniques

NASA Astrophysics Data System (ADS)

Her Jie, Albert Chang; Zamli, Ahmad Faizal Ahmad; Zulazlan Shah Zulkifli, Ahmad; Yee, Joanne Lim Mun; Lim, Mooktzeng

2018-04-01

This paper presents image processing techniques with the use of fuzzy logic and neural network approach to perform flame analysis. Flame diagnostic is important in the industry to extract relevant information from flame images. Experiment test is carried out in a model industrial burner with different flow rates. Flame features such as luminous and spectral parameters are extracted using image processing and Fast Fourier Transform (FFT). Flame images are acquired using FLIR infrared camera. Non-linearities such as thermal acoustic oscillations and background noise affect the stability of flame. Flame velocity is one of the important characteristics that determines stability of flame. In this paper, an image processing method is proposed to determine flame velocity. Power spectral density (PSD) graph is a good tool for vibration analysis where flame stability can be approximated. However, a more intelligent diagnostic system is needed to automatically determine flame stability. In this paper, flame features of different flow rates are compared and analyzed. The selected flame features are used as inputs to the proposed fuzzy inference system to determine flame stability. Neural network is used to test the performance of the fuzzy inference system.

Feasibility study, software design, layout and simulation of a two-dimensional fast Fourier transform machine for use in optical array interferometry

NASA Technical Reports Server (NTRS)

Boriakoff, Valentin; Chen, Wei

1990-01-01

The NASA-Cornell Univ.-Worcester Polytechnic Institute Fast Fourier Transform (FFT) chip based on the architecture of the systolic FFT computation as presented by Boriakoff is implemented into an operating device design. The kernel of the system, a systolic inner product floating point processor, was designed to be assembled into a systolic network that would take incoming data streams in pipeline fashion and provide an FFT output at the same rate, word by word. It was thoroughly simulated for proper operation, and it has passed a comprehensive set of tests showing no operational errors. The black box specifications of the chip, which conform to the initial requirements of the design as specified by NASA, are given. The five subcells are described and their high level function description, logic diagrams, and simulation results are presented. Some modification of the Read Only Memory (ROM) design were made, since some errors were found in it. Because a four stage pipeline structure was used, simulating such a structure is more difficult than an ordinary structure. Simulation methods are discussed. Chip signal protocols and chip pinout are explained.

Determination of acoustical transfer functions using an impulse method

NASA Astrophysics Data System (ADS)

MacPherson, J.

1985-02-01

The Transfer Function of a system may be defined as the relationship of the output response to the input of a system. Whilst recent advances in digital processing systems have enabled Impulse Transfer Functions to be determined by computation of the Fast Fourier Transform, there has been little work done in applying these techniques to room acoustics. Acoustical Transfer Functions have been determined for auditoria, using an impulse method. The technique is based on the computation of the Fast Fourier Transform (FFT) of a non-ideal impulsive source, both at the source and at the receiver point. The Impulse Transfer Function (ITF) is obtained by dividing the FFT at the receiver position by the FFT of the source. This quantity is presented both as linear frequency scale plots and also as synthesized one-third octave band data. The technique enables a considerable quantity of data to be obtained from a small number of impulsive signals recorded in the field, thereby minimizing the time and effort required on site. As the characteristics of the source are taken into account in the calculation, the choice of impulsive source is non-critical. The digital analysis equipment required for the analysis is readily available commercially.

OSCAR a Matlab based optical FFT code

NASA Astrophysics Data System (ADS)

Degallaix, Jérôme

2010-05-01

Optical simulation softwares are essential tools for designing and commissioning laser interferometers. This article aims to introduce OSCAR, a Matlab based FFT code, to the experimentalist community. OSCAR (Optical Simulation Containing Ansys Results) is used to simulate the steady state electric fields in optical cavities with realistic mirrors. The main advantage of OSCAR over other similar packages is the simplicity of its code requiring only a short time to master. As a result, even for a beginner, it is relatively easy to modify OSCAR to suit other specific purposes. OSCAR includes an extensive manual and numerous detailed examples such as simulating thermal aberration, calculating cavity eigen modes and diffraction loss, simulating flat beam cavities and three mirror ring cavities. An example is also provided about how to run OSCAR on the GPU of modern graphic cards instead of the CPU, making the simulation up to 20 times faster.

Efficient Terahertz Wide-Angle NUFFT-Based Inverse Synthetic Aperture Imaging Considering Spherical Wavefront.

PubMed

Gao, Jingkun; Deng, Bin; Qin, Yuliang; Wang, Hongqiang; Li, Xiang

2016-12-14

An efficient wide-angle inverse synthetic aperture imaging method considering the spherical wavefront effects and suitable for the terahertz band is presented. Firstly, the echo signal model under spherical wave assumption is established, and the detailed wavefront curvature compensation method accelerated by 1D fast Fourier transform (FFT) is discussed. Then, to speed up the reconstruction procedure, the fast Gaussian gridding (FGG)-based nonuniform FFT (NUFFT) is employed to focus the image. Finally, proof-of-principle experiments are carried out and the results are compared with the ones obtained by the convolution back-projection (CBP) algorithm. The results demonstrate the effectiveness and the efficiency of the presented method. This imaging method can be directly used in the field of nondestructive detection and can also be used to provide a solution for the calculation of the far-field RCSs (Radar Cross Section) of targets in the terahertz regime.

A GaAs vector processor based on parallel RISC microprocessors

NASA Astrophysics Data System (ADS)

Misko, Tim A.; Rasset, Terry L.

A vector processor architecture based on the development of a 32-bit microprocessor using gallium arsenide (GaAs) technology has been developed. The McDonnell Douglas vector processor (MVP) will be fabricated completely from GaAs digital integrated circuits. The MVP architecture includes a vector memory of 1 megabyte, a parallel bus architecture with eight processing elements connected in parallel, and a control processor. The processing elements consist of a reduced instruction set CPU (RISC) with four floating-point coprocessor units and necessary memory interface functions. This architecture has been simulated for several benchmark programs including complex fast Fourier transform (FFT), complex inner product, trigonometric functions, and sort-merge routine. The results of this study indicate that the MVP can process a 1024-point complex FFT at a speed of 112 microsec (389 megaflops) while consuming approximately 618 W of power in a volume of approximately 0.1 ft-cubed.

Fair comparison of complexity between a multi-band CAP and DMT for data center interconnects.

PubMed

Wei, J L; Sanchez, C; Giacoumidis, E

2017-10-01

We present, to the best of our knowledge, the first known detailed analysis and fair comparison of complexity of a 56 Gb/s multi-band carrierless amplitude and phase (CAP) and discrete multi-tone (DMT) over 80 km dispersion compensation fiber-free single-mode fiber links based on intensity modulation and direct detection for data center interconnects. We show that the matched finite impulse response filters and inverse fast Fourier transform (IFFT)/FFT take the majority of the complexity of the multi-band CAP and DMT, respectively. The choice of the multi-band CAP sub-band count and the DMT IFFT/FFT size makes significant impact on the system complexity or performance, and trade-off must be considered.

Distributed Two-Dimensional Fourier Transforms on DSPs with an Application for Phase Retrieval

NASA Technical Reports Server (NTRS)

Smith, Jeffrey Scott

2006-01-01

Many applications of two-dimensional Fourier Transforms require fixed timing as defined by system specifications. One example is image-based wavefront sensing. The image-based approach has many benefits, yet it is a computational intensive solution for adaptive optic correction, where optical adjustments are made in real-time to correct for external (atmospheric turbulence) and internal (stability) aberrations, which cause image degradation. For phase retrieval, a type of image-based wavefront sensing, numerous two-dimensional Fast Fourier Transforms (FFTs) are used. To meet the required real-time specifications, a distributed system is needed, and thus, the 2-D FFT necessitates an all-to-all communication among the computational nodes. The 1-D floating point FFT is very efficient on a digital signal processor (DSP). For this study, several architectures and analysis of such are presented which address the all-to-all communication with DSPs. Emphasis of this research is on a 64-node cluster of Analog Devices TigerSharc TS-101 DSPs.

High resolution 4-D spectroscopy with sparse concentric shell sampling and FFT-CLEAN.

PubMed

Coggins, Brian E; Zhou, Pei

2008-12-01

Recent efforts to reduce the measurement time for multidimensional NMR experiments have fostered the development of a variety of new procedures for sampling and data processing. We recently described concentric ring sampling for 3-D NMR experiments, which is superior to radial sampling as input for processing by a multidimensional discrete Fourier transform. Here, we report the extension of this approach to 4-D spectroscopy as Randomized Concentric Shell Sampling (RCSS), where sampling points for the indirect dimensions are positioned on concentric shells, and where random rotations in the angular space are used to avoid coherent artifacts. With simulations, we show that RCSS produces a very low level of artifacts, even with a very limited number of sampling points. The RCSS sampling patterns can be adapted to fine rectangular grids to permit use of the Fast Fourier Transform in data processing, without an apparent increase in the artifact level. These artifacts can be further reduced to the noise level using the iterative CLEAN algorithm developed in radioastronomy. We demonstrate these methods on the high resolution 4-D HCCH-TOCSY spectrum of protein G's B1 domain, using only 1.2% of the sampling that would be needed conventionally for this resolution. The use of a multidimensional FFT instead of the slow DFT for initial data processing and for subsequent CLEAN significantly reduces the calculation time, yielding an artifact level that is on par with the level of the true spectral noise.

High Resolution 4-D Spectroscopy with Sparse Concentric Shell Sampling and FFT-CLEAN

PubMed Central

Coggins, Brian E.; Zhou, Pei

2009-01-01

SUMMARY Recent efforts to reduce the measurement time for multidimensional NMR experiments have fostered the development of a variety of new procedures for sampling and data processing. We recently described concentric ring sampling for 3-D NMR experiments, which is superior to radial sampling as input for processing by a multidimensional discrete Fourier transform. Here, we report the extension of this approach to 4-D spectroscopy as Randomized Concentric Shell Sampling (RCSS), where sampling points for the indirect dimensions are positioned on concentric shells, and where random rotations in the angular space are used to avoid coherent artifacts. With simulations, we show that RCSS produces a very low level of artifacts, even with a very limited number of sampling points. The RCSS sampling patterns can be adapted to fine rectangular grids to permit use of the Fast Fourier Transform in data processing, without an apparent increase in the artifact level. These artifacts can be further reduced to the noise level using the iterative CLEAN algorithm developed in radioastronomy. We demonstrate these methods on the high resolution 4-D HCCH-TOCSY spectrum of protein G's B1 domain, using only 1.2% of the sampling that would be needed conventionally for this resolution. The use of a multidimensional FFT instead of the slow DFT for initial data processing and for subsequent CLEAN significantly reduces the calculation time, yielding an artifact level that is on par with the level of the true spectral noise. PMID:18853260

Effects of data gaps on Fourier Analysis

NASA Astrophysics Data System (ADS)

Negrea, Catalin; Munteanu, Costel; Echim, Marius

2014-05-01

Fourier Analysis is a vital and widely used tool in all branches of science that require advanced data processing. The method is often used via the Fast Fourier Transform (FFT) implementation readily available in most programming languages. This is a valid approach for data sets with equally spaced data points and no gaps. Such conditions are not always met in real situations where corrections and adjustments to the method are needed. We investigate the intrinsic limitations of four such methods when data gaps are present: 1) linear interpolations and FFT, 2) a direct implementation of the Discrete Fourier Transform, 3) a Z-Transform and 4) the Lomb-Scargle algorithm. Theoretical analysis tools can provide an insight as to the likely problems of such methods and we discuss the likely modifications to the computed spectra. Also, a time series with no data gaps and a constant sampling frequency is altered by introducing several gap configurations and the resulting spectra with the four methods are compared to highlight changes with respect to the original spectrum. Effects on the amplitude and phase of the resulting power spectral densities are analyzed for non-uniformly sampled solar wind data provided by the Venus Express spacecraft. Phase effects are also studied in the context of a sliding window approach. Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.

[Cholinergic mechanisms in the pathogenesis of genetically-caused absence epilepsy].

PubMed

Berdiev, R K; Chepurnov, S A; Chepurnova, N E; van Luijtelaar, E L

2003-01-01

Frontoparietal cortex and the thalamocortical circuit comprising reticular thalamic nucleus (RTN) and relay nuclei of the ventrolateral thalamus (VLT) are critical structures in the generation of spike-wave discharges (SWD) during absence seizures. The activity of these nuclei is under the control of the ascending cholinergic projections of nucleus basalis of Meynert. The aim of our study is to make an attempt to change the pattern of SWD in WAG/Rij rats by injecting of cholinotoxine AF64A to the area of RTN. Spontaneous SWD were registered in cortex of WAG/Rij rats with genetically determined absences. The spectral content of SWD was analyzed by means of the Fast Fourier Transformation (FFT) procedure. Unilateral injections of AF64A (1 nmol) to RTN led the decrease in duration and number of SWD comparing to the basal EEG recordings 2 days after the lesion. The FFT analysis showed the disappearance of 17-18 Hz spike on the side of the lesion compared with the intact side. The immunohistochemical study for acetylcholinetransferase (ChaT)-containing neurons showed the loss of ChaT-positive cells in the nucleus basalis area on the side of the lesion. The removal of cholinergic afferentation of RTN and cortex from nucleus basalis inhibits the SWD developing most likely due to the decrease of cortical excitability. Moreover, possibly cholinergic transmission is involved in the transforation of the synchronized phenomena (SWD) to another with close mechanism of generation.

Doppler lidar power, aperture diameter, and FFT size trade-off study

NASA Astrophysics Data System (ADS)

Chester, David B.; Budge, Scott E.

2017-05-01

In the design or selection of a Doppler lidar instrument for a spacecraft landing system, it is important to evaluate the balance between performance requirements and cost, weight, and power consumption. Leveraging the capability of LadarSIM, a trade-off study was performed to evaluate the interaction between the laser transmission power, aperture diameter, and FFT size in a Doppler lidar system. For this study the probabilities of detection and false alarm were calculated using LadarSIM to simulate FMCW lidar systems with varying power, aperture diameter, and FFT size. This paper reports the results of this trade-off study.

A simplified implementation of edge detection in MATLAB is faster and more sensitive than fast fourier transform for actin fiber alignment quantification.

PubMed

Kemeny, Steven Frank; Clyne, Alisa Morss

2011-04-01

Fiber alignment plays a critical role in the structure and function of cells and tissues. While fiber alignment quantification is important to experimental analysis and several different methods for quantifying fiber alignment exist, many studies focus on qualitative rather than quantitative analysis perhaps due to the complexity of current fiber alignment methods. Speed and sensitivity were compared in edge detection and fast Fourier transform (FFT) for measuring actin fiber alignment in cells exposed to shear stress. While edge detection using matrix multiplication was consistently more sensitive than FFT, image processing time was significantly longer. However, when MATLAB functions were used to implement edge detection, MATLAB's efficient element-by-element calculations and fast filtering techniques reduced computation cost 100 times compared to the matrix multiplication edge detection method. The new computation time was comparable to the FFT method, and MATLAB edge detection produced well-distributed fiber angle distributions that statistically distinguished aligned and unaligned fibers in half as many sample images. When the FFT sensitivity was improved by dividing images into smaller subsections, processing time grew larger than the time required for MATLAB edge detection. Implementation of edge detection in MATLAB is simpler, faster, and more sensitive than FFT for fiber alignment quantification.

Extraluminal venous interruption for free-floating thrombus in the deep veins of lower limbs.

PubMed

Casian, D; Gutsu, E; Culiuc, V

2010-01-01

The free-floating thrombus (FFT) represents a particular form of deep vein thrombosis with extremely high potential of fatal pulmonary embolism. The purpose of the study was to evaluate the early results of aggressive surgical approach to FFT. During the period 2005-2008 years FFT was diagnosed in 13 patients. Demographic characteristics of patients: medium age--54.7 years, male--76.9%, significant comorbidity--5 (38.5%) cases. Localization of FFT: superficial femoral vein (SFV)--5 (38.5%), common femoral vein (CFV)--4 (30.7%), external iliac vein (EIV)--2 (15.4%), inferior cava vein (ICV)--2 (15.4%). Manifestations of previous pulmonary embolism were documented preoperatively in 3 (23.1%) cases. The following emergency surgical procedures were performed: ligation--3 (23.1%) or plication--2 (15.4%) of SFV; plication of CFV--5 (38.5%) patients, combined in 4 cases with partial thrombectomy (free-floating part of thrombus); plication of common iliac vein--1 (7.6%); plication of ICV--2 (15.4%) cases. Primary or recurrent cases of clinically significant pulmonary embolism were not detected in the postoperative period. The accumulated experience of surgical management of patients with FFT reveals the important role of deep vein ligation/plication in prevention of fatal pulmonary embolism.

A new fast algorithm for computing a complex number: Theoretic transforms

NASA Technical Reports Server (NTRS)

Reed, I. S.; Liu, K. Y.; Truong, T. K.

1977-01-01

A high-radix fast Fourier transformation (FFT) algorithm for computing transforms over GF(sq q), where q is a Mersenne prime, is developed to implement fast circular convolutions. This new algorithm requires substantially fewer multiplications than the conventional FFT.

Fast computation of the kurtogram for the detection of transient faults

NASA Astrophysics Data System (ADS)

Antoni, Jérôme

2007-01-01

The kurtogram is a fourth-order spectral analysis tool recently introduced for detecting and characterising non-stationarities in a signal. The paradigm relies on the assertion that each type of transient is associated with an optimal (frequency/frequency resolution) dyad { f,Δf} which maximises its kurtosis, and hence its detection. However, the complete exploration of the whole plane ( f,Δf) is a formidable task hardly amenable to on-line industrial applications. In this communication we describe a fast algorithm for computing the kurtogram over a grid that finely samples the ( f,Δf) plane. Its complexity is on the order of N log N, similarly to the FFT. The efficiency of the algorithm is then illustrated on several industrial cases concerned with the detection of incipient transient faults.

Treatment Development and Feasibility Study of Family-Focused Treatment for Adolescents with Bipolar Disorder and Comorbid Substance Use Disorders

PubMed Central

Goldstein, Benjamin I.; Goldstein, Tina R.; Collinger, Katelyn A.; Axelson, David A.; Bukstein, Oscar G.; Birmaher, Boris; Miklowitz, David J.

2014-01-01

Background Comorbid substance use disorders (SUD) are associated with increased illness severity and functional impairment among adolescents with bipolar disorder (BD). Previous psychosocial treatment studies have excluded adolescents with both BD and SUD. Studies suggest that integrated interventions are optimal for adults with BD and SUD. Methods We modified family-focused treatment for adolescents with BD (FFT-A) in order to explicitly target comorbid SUD (FFT-SUD). Ten adolescents with BD who had both SUD and an exacerbation of manic, depressed, or mixed symptoms within the last 3 months were enrolled. FFT-SUD was offered as an adjunct to pharmacotherapy, with a target of 21 sessions over 12 months of treatment. The FFT-SUD manual was iteratively modified to integrate a concurrent focus on SUD. Results Six subjects completed a mid-treatment 6-month assessment (after a mean of 16 sessions was completed). Of the 10 subjects, 3 dropped out early ( after ≤ 1 session); in the case of each of these subjects, the participating parent had active SUD. No other subjects in the study had a parent with active SUD. Preliminary findings suggested significant reductions in manic symptoms and depressive symptoms and improved global functioning. Reduction in cannabis use was modest and did not reach significance. Limitations Limitations included a small sample, open treatment, concurrent medications, and no control group. Conclusions These preliminary findings suggest that FFT-SUD is a feasible intervention, particularly for youth without parental SUD. FFT-SUD may be effective in treating mood symptoms, particularly depression, despite modest reductions in substance use. Integrating motivation enhancing strategies may augment the effect of this intervention on substance use. Additional strategies, such as targeting parental substance use, may prevent early attrition. PMID:24847999

Micro-topography, rock surface modelling and minerology of notches in Mount Carmel

NASA Astrophysics Data System (ADS)

Brook, Anna; Ben-Binyamin, Atzmon; Shtober-Zisu, Nurit

2016-04-01

Notches are defined as horizontal concaved indentations developed on slopes or cliffs in a basic "C" shape regardless of their location or formation process. Many studies have proclaimed that notches are associated with coastal processes where rocky shore faces are back carved, parallel to sea level by a combination of physical and biological abrasion, and by chemical and biological dissolution. The notches morphologies are various and depend on the lithology, climate, and environment history. These changes involve complex volumetric effects such as weathering and surface mineral dissolution. The main impetus for the present paper is to advance the modeling and the 3D complex pattern reconstruction of notch's cavity surface and detailed shapes and to assess the association between the morphological structures observed upon the notch parts and the fine scale mineralogical composition of the rock. The reconstruction of 3D surfaces using point clouds scanned data is a known problem in computer graphics. Several approaches are based on combinatorial structures, such as Delaunay triangulations, alpha shapes, or Voronoi diagrams. These schemes typically create a triangle mesh that interpolates all or most of the points. In the presence of noisy data, resulting surface is often jagged, and is therefore smoothed or refit to the points in subsequent processing. Fast Fourier Transform (FFT) is a common technique for solving dense, periodic Poisson systems. However, the FFT requires longer time and larger space, quickly becoming prohibitive for fine resolutions. The Poisson approach's key element is the observation that inward normal field of the boundary can be inferred as the gradient of a three dimensional solid indicator function. Thus, the generation of a watertight mesh can be obtained by: (1) transforming the oriented point samples into a continuous vector field referred to as the relationship between the gradient of the indicator function and an integral of surface normals. The computation of the indicator function is reduced to (2) finding a scalar function whose gradients best match the vector field. Point cloud input gives enough information for the approximation of the surface integral with discrete summation. A set of points used for the portioning of the whole scene into distinct patches and also for the surface integral scaled by the patch's area. (3) Extracting the appropriate iso-surface. The roughness spatial variation was calculated according to: 1) removal of the regional slope effect is a pre-step for the surface roughness indices calculation (regression surface is reduced from the original iso-surface model to produce residuals features, surface roughness, from which it possible to calculate the variogram of the residuals), 2) Semivariogram is used to determine the optimal window size for image texture analysis. Mineral composition and structure of the different patches and components define its solubility implying thus upon the micro-morphological differences. Spectral measurements taken in the field and in the lab will be constructed to spectral libraries representing the notch's visor, cavity and floor. The VIS-NIR, SWIR and MIR reflectance data measured by the different types of spectrometers will not be mixed for future evaluation of mineral identification. The constructed spectral libraries was analyzed and processed for the characterization of spectral features of samples. The spectral features were compared with various well characterized resampled mineral spectral libraries for identification of the forming minerals. The mineral composition is defined by spectroscopy and used to capture the areas corresponding to different patterns of micro roughness along the notch's surface. The suggested roughness and 3D surface reconstruction employ real data acquired by the Terrestrial Light and Range Detection (t-LiDAR) scanner. The project stresses an interdisciplinary approach to map the mineral variations along the notch's different components corresponding to the roughness surface changes.

Massively parallel implementation of 3D-RISM calculation with volumetric 3D-FFT.

PubMed

Maruyama, Yutaka; Yoshida, Norio; Tadano, Hiroto; Takahashi, Daisuke; Sato, Mitsuhisa; Hirata, Fumio

2014-07-05

A new three-dimensional reference interaction site model (3D-RISM) program for massively parallel machines combined with the volumetric 3D fast Fourier transform (3D-FFT) was developed, and tested on the RIKEN K supercomputer. The ordinary parallel 3D-RISM program has a limitation on the number of parallelizations because of the limitations of the slab-type 3D-FFT. The volumetric 3D-FFT relieves this limitation drastically. We tested the 3D-RISM calculation on the large and fine calculation cell (2048(3) grid points) on 16,384 nodes, each having eight CPU cores. The new 3D-RISM program achieved excellent scalability to the parallelization, running on the RIKEN K supercomputer. As a benchmark application, we employed the program, combined with molecular dynamics simulation, to analyze the oligomerization process of chymotrypsin Inhibitor 2 mutant. The results demonstrate that the massive parallel 3D-RISM program is effective to analyze the hydration properties of the large biomolecular systems. Copyright © 2014 Wiley Periodicals, Inc.

Wide-bandwidth high-resolution search for extraterrestrial intelligence

NASA Technical Reports Server (NTRS)

Horowitz, Paul

1993-01-01

A third antenna was added to the system. It is a terrestrial low-gain feed, to act as a veto for local interference. The 3-chip design for a 4 megapoint complex FFT was reduced to finished working hardware. The 4-Megachannel circuit board contains 36 MByte of DRAM, 5 CPLDs, the three large FFT ASICs, and 74 ICs in all. The Austek FDP-based Spectrometer/Power Accumulator (SPA) has now been implemented as a 4-layer printed circuit. A PC interface board has been designed and together with its associated user interface and control software allows an IBM compatible computer to control the SPA board, and facilitates the transfer of spectra to the PC for display, processing, and storage. The Feature Recognizer Array cards receive the stream of modulus words from the 4M FFT cards, and forward a greatly thinned set of reports to the PC's in whose backplane they reside. In particular, a powerful ROM-based state-machine architecture has been adopted, and DRAM has been added to permit integration modes when tracking or reobserving source candidates. The general purpose (GP) array consists of twenty '486 PC class computers, each of which receives and processes the data from a feature extractor/correlator board set. The array performs a first analysis on the provided 'features' and then passes this information on to the workstation. The core workstation software is now written. That is, the communication channels between the user interface, the backend monitor program and the PC's have working software.

Analysis of Digital Communication Signals and Extraction of Parameters.

DTIC Science & Technology

1994-12-01

Fast Fourier Transform (FFT). The correlation methods utilize modified time-frequency distributions , where one of these is based on the Wigner - Ville ... Distribution ( WVD ). Gaussian white noise is added to the signal to simulate various signal-to-noise ratios (SNRs).

Application of multiple signal classification algorithm to frequency estimation in coherent dual-frequency lidar

NASA Astrophysics Data System (ADS)

Li, Ruixiao; Li, Kun; Zhao, Changming

2018-01-01

Coherent dual-frequency Lidar (CDFL) is a new development of Lidar which dramatically enhances the ability to decrease the influence of atmospheric interference by using dual-frequency laser to measure the range and velocity with high precision. Based on the nature of CDFL signals, we propose to apply the multiple signal classification (MUSIC) algorithm in place of the fast Fourier transform (FFT) to estimate the phase differences in dual-frequency Lidar. In the presence of Gaussian white noise, the simulation results show that the signal peaks are more evident when using MUSIC algorithm instead of FFT in condition of low signal-noise-ratio (SNR), which helps to improve the precision of detection on range and velocity, especially for the long distance measurement systems.

The Politics of Functional Family Therapy: A Feminist Critique.

ERIC Educational Resources Information Center

Avis, Judith Myers

1985-01-01

Discusses whether the Functional Family Therapy (FFT) model takes a covert political stance which reinforces traditional gender roles in both family and therapist. Examines FFT's affirmation of existing political functions in the family as well as suggested therapist use of self. Discusses implications and recommends changes. (BH)

A remote-control datalogger for large-scale resistivity surveys and robust processing of its signals using a software lock-in approach

NASA Astrophysics Data System (ADS)

Oppermann, Frank; Günther, Thomas

2018-02-01

We present a new versatile datalogger that can be used for a wide range of possible applications in geosciences. It is adjustable in signal strength and sampling frequency, battery saving and can remotely be controlled over a Global System for Mobile Communication (GSM) connection so that it saves running costs, particularly in monitoring experiments. The internet connection allows for checking functionality, controlling schedules and optimizing pre-amplification. We mainly use it for large-scale electrical resistivity tomography (ERT), where it independently registers voltage time series on three channels, while a square-wave current is injected. For the analysis of this time series we present a new approach that is based on the lock-in (LI) method, mainly known from electronic circuits. The method searches the working point (phase) using three different functions based on a mask signal, and determines the amplitude using a direct current (DC) correlation function. We use synthetic data with different types of noise to compare the new method with existing approaches, i.e. selective stacking and a modified fast Fourier transformation (FFT)-based approach that assumes a 1/f noise characteristics. All methods give comparable results, but the LI is better than the well-established stacking method. The FFT approach can be even better but only if the noise strictly follows the assumed characteristics. If overshoots are present in the data, which is typical in the field, FFT performs worse even with good data, which is why we conclude that the new LI approach is the most robust solution. This is also proved by a field data set from a long 2-D ERT profile.

Porting ONETEP to graphical processing unit-based coprocessors. 1. FFT box operations.

PubMed

Wilkinson, Karl; Skylaris, Chris-Kriton

2013-10-30

We present the first graphical processing unit (GPU) coprocessor-enabled version of the Order-N Electronic Total Energy Package (ONETEP) code for linear-scaling first principles quantum mechanical calculations on materials. This work focuses on porting to the GPU the parts of the code that involve atom-localized fast Fourier transform (FFT) operations. These are among the most computationally intensive parts of the code and are used in core algorithms such as the calculation of the charge density, the local potential integrals, the kinetic energy integrals, and the nonorthogonal generalized Wannier function gradient. We have found that direct porting of the isolated FFT operations did not provide any benefit. Instead, it was necessary to tailor the port to each of the aforementioned algorithms to optimize data transfer to and from the GPU. A detailed discussion of the methods used and tests of the resulting performance are presented, which show that individual steps in the relevant algorithms are accelerated by a significant amount. However, the transfer of data between the GPU and host machine is a significant bottleneck in the reported version of the code. In addition, an initial investigation into a dynamic precision scheme for the ONETEP energy calculation has been performed to take advantage of the enhanced single precision capabilities of GPUs. The methods used here result in no disruption to the existing code base. Furthermore, as the developments reported here concern the core algorithms, they will benefit the full range of ONETEP functionality. Our use of a directive-based programming model ensures portability to other forms of coprocessors and will allow this work to form the basis of future developments to the code designed to support emerging high-performance computing platforms. Copyright © 2013 Wiley Periodicals, Inc.

GPU-Accelerated Forward and Back-Projections with Spatially Varying Kernels for 3D DIRECT TOF PET Reconstruction.

PubMed

Ha, S; Matej, S; Ispiryan, M; Mueller, K

2013-02-01

We describe a GPU-accelerated framework that efficiently models spatially (shift) variant system response kernels and performs forward- and back-projection operations with these kernels for the DIRECT (Direct Image Reconstruction for TOF) iterative reconstruction approach. Inherent challenges arise from the poor memory cache performance at non-axis aligned TOF directions. Focusing on the GPU memory access patterns, we utilize different kinds of GPU memory according to these patterns in order to maximize the memory cache performance. We also exploit the GPU instruction-level parallelism to efficiently hide long latencies from the memory operations. Our experiments indicate that our GPU implementation of the projection operators has slightly faster or approximately comparable time performance than FFT-based approaches using state-of-the-art FFTW routines. However, most importantly, our GPU framework can also efficiently handle any generic system response kernels, such as spatially symmetric and shift-variant as well as spatially asymmetric and shift-variant, both of which an FFT-based approach cannot cope with.

GPU-Accelerated Forward and Back-Projections With Spatially Varying Kernels for 3D DIRECT TOF PET Reconstruction

NASA Astrophysics Data System (ADS)

Ha, S.; Matej, S.; Ispiryan, M.; Mueller, K.

2013-02-01

We describe a GPU-accelerated framework that efficiently models spatially (shift) variant system response kernels and performs forward- and back-projection operations with these kernels for the DIRECT (Direct Image Reconstruction for TOF) iterative reconstruction approach. Inherent challenges arise from the poor memory cache performance at non-axis aligned TOF directions. Focusing on the GPU memory access patterns, we utilize different kinds of GPU memory according to these patterns in order to maximize the memory cache performance. We also exploit the GPU instruction-level parallelism to efficiently hide long latencies from the memory operations. Our experiments indicate that our GPU implementation of the projection operators has slightly faster or approximately comparable time performance than FFT-based approaches using state-of-the-art FFTW routines. However, most importantly, our GPU framework can also efficiently handle any generic system response kernels, such as spatially symmetric and shift-variant as well as spatially asymmetric and shift-variant, both of which an FFT-based approach cannot cope with.

A low power biomedical signal processor ASIC based on hardware software codesign.

PubMed

Nie, Z D; Wang, L; Chen, W G; Zhang, T; Zhang, Y T

2009-01-01

A low power biomedical digital signal processor ASIC based on hardware and software codesign methodology was presented in this paper. The codesign methodology was used to achieve higher system performance and design flexibility. The hardware implementation included a low power 32bit RISC CPU ARM7TDMI, a low power AHB-compatible bus, and a scalable digital co-processor that was optimized for low power Fast Fourier Transform (FFT) calculations. The co-processor could be scaled for 8-point, 16-point and 32-point FFTs, taking approximate 50, 100 and 150 clock circles, respectively. The complete design was intensively simulated using ARM DSM model and was emulated by ARM Versatile platform, before conducted to silicon. The multi-million-gate ASIC was fabricated using SMIC 0.18 microm mixed-signal CMOS 1P6M technology. The die area measures 5,000 microm x 2,350 microm. The power consumption was approximately 3.6 mW at 1.8 V power supply and 1 MHz clock rate. The power consumption for FFT calculations was less than 1.5 % comparing with the conventional embedded software-based solution.

Aqueous contaminant detection via UiO-66 thin film optical fiber sensor platform with fast Fourier transform based spectrum analysis

NASA Astrophysics Data System (ADS)

Nazari, Marziyeh; Rubio-Martinez, Marta; Babarao, Ravichandar; Ayad Younis, Adel; Collins, Stephen F.; Hill, Matthew R.; Duke, Mikel C.

2018-01-01

Routine water quality monitoring is required in drinking and waste water management. A particular interest is to measure concentrations of a range of diverse contaminants on-site or remotely in real time. Here we present metal organic framework (MOF) integrated optical fiber sensor that allows for rapid optical measurement based on fast Fourier transform (FFT) spectrum analysis. The end-face of these glass optical fibers was modified with UiO-66(Zr) MOF thin film by in situ hydrothermal synthesis for the detection of the model contaminants, Rhodamine-B and 4-Aminopyridine, in water. The sensing mechanism is based on the change in the optical path length of the thin film induced by the adsorption of chemical molecules by UiO-66. Using FFT analysis, various modes of interaction (physical and chemical) became apparent, showing both irreversible changes upon contact with the contaminant, as well as reversible changes according to actual concentration. This was indicated by the second harmonic elevation to a certain level translating to high sensitivity detection.

Time series analysis of ozone data in Isfahan

NASA Astrophysics Data System (ADS)

Omidvari, M.; Hassanzadeh, S.; Hosseinibalam, F.

2008-07-01

Time series analysis used to investigate the stratospheric ozone formation and decomposition processes. Different time series methods are applied to detect the reason for extreme high ozone concentrations for each season. Data was convert into seasonal component and frequency domain, the latter has been evaluated by using the Fast Fourier Transform (FFT), spectral analysis. The power density spectrum estimated from the ozone data showed peaks at cycle duration of 22, 20, 36, 186, 365 and 40 days. According to seasonal component analysis most fluctuation was in 1999 and 2000, but the least fluctuation was in 2003. The best correlation between ozone and sun radiation was found in 2000. Other variables which are not available cause to this fluctuation in the 1999 and 2001. The trend of ozone is increasing in 1999 and is decreasing in other years.

The Block V Receiver fast acquisition algorithm for the Galileo S-band mission

NASA Technical Reports Server (NTRS)

Aung, M.; Hurd, W. J.; Buu, C. M.; Berner, J. B.; Stephens, S. A.; Gevargiz, J. M.

1994-01-01

A fast acquisition algorithm for the Galileo suppressed carrier, subcarrier, and data symbol signals under low data rate, signal-to-noise ratio (SNR) and high carrier phase-noise conditions has been developed. The algorithm employs a two-arm fast Fourier transform (FFT) method utilizing both the in-phase and quadrature-phase channels of the carrier. The use of both channels results in an improved SNR in the FFT acquisition, enabling the use of a shorter FFT period over which the carrier instability is expected to be less significant. The use of a two-arm FFT also enables subcarrier and symbol acquisition before carrier acquisition. With the subcarrier and symbol loops locked first, the carrier can be acquired from an even shorter FFT period. Two-arm tracking loops are employed to lock the subcarrier and symbol loops parameter modification to achieve the final (high) loop SNR in the shortest time possible. The fast acquisition algorithm is implemented in the Block V Receiver (BVR). This article describes the complete algorithm design, the extensive computer simulation work done for verification of the design and the analysis, implementation issues in the BVR, and the acquisition times of the algorithm. In the expected case of the Galileo spacecraft at Jupiter orbit insertion PD/No equals 14.6 dB-Hz, R(sym) equals 16 symbols per sec, and the predicted acquisition time of the algorithm (to attain a 0.2-dB degradation from each loop to the output symbol SNR) is 38 sec.

Functional Fitness Testing Results Following Long-Duration ISS Missions.

PubMed

Laughlin, Mitzi S; Guilliams, Mark E; Nieschwitz, Bruce A; Hoellen, David

2015-12-01

Long-duration spaceflight missions lead to the loss of muscle strength and endurance. Significant reduction in muscle function can be hazardous when returning from spaceflight. To document these losses, NASA developed medical requirements that include measures of functional strength and endurance. Results from this Functional Fitness Test (FFT) battery are also used to evaluate the effectiveness of in-flight exercise countermeasures. The purpose of this paper is to document results from the FFT and correlate this information with performance of in-flight exercise on board the International Space Station. The FFT evaluates muscular strength and endurance, flexibility, and agility and includes the following eight measures: sit and reach, cone agility, push-ups, pull-ups, sliding crunches, bench press, leg press, and hand grip dynamometry. Pre- to postflight functional fitness measurements were analyzed using dependent t-tests and correlation analyses were used to evaluate the relationship between functional fitness measurements and in-flight exercise workouts. Significant differences were noted post space flight with the sit and reach, cone agility, leg press, and hand grip measurements while other test scores were not significantly altered. The relationships between functional fitness and in-flight exercise measurements showed minimal to moderate correlations for most in-flight exercise training variables. The change in FFT results can be partially explained by in-flight exercise performance. Although there are losses documented in the FFT results, it is important to realize that the crewmembers are successfully performing activities of daily living and are considered functional for normal activities upon return to Earth.

Effects of different carbohydrate sources on fructan metabolism in plants of Chrysolaena obovata grown in vitro

PubMed Central

Trevisan, Flavio; Oliveira, Vanessa F.; Carvalho, Maria A. M.; Gaspar, Marília

2015-01-01

Chrysolaena obovata (Less.) Dematt., previously named Vernonia herbacea, is an Asteraceae native to the Cerrado which accumulates about 80% of the rhizophore dry mass as inulin-type fructans. Considering its high inulin production and the wide application of fructans, a protocol for C. obovata in vitro culture was recently established. Carbohydrates are essential for in vitro growth and development of plants and can also act as signaling molecules involved in cellular adjustments and metabolic regulation. This work aimed to evaluate the effect of different sources of carbohydrate on fructan metabolism in plants grown in vitro. For this purpose, C. obovata plants cultivated in vitro were submitted to carbon deprivation and transferred to MS medium supplemented with sucrose, glucose or fructose. Following, their fructan composition and activity and expression of genes encoding enzymes for fructan synthesis (1-SST and 1-FFT) and degradation (1-FEH) were evaluated. For qRT-PCR analysis partial cDNA sequences corresponding to two different C. obovata genes, 1-SST and 1-FFT, were isolated. As expected, C. obovata sequences showed highest sequence identity to other Asteraceae 1-SST and 1-FFT, than to Poaceae related proteins. A carbon deficit treatment stimulated the transcription of the gene 1-FEH and inhibited 1-SST and 1-FFT and carbohydrate supplementation promoted reversal of the expression profile of these genes. With the exception of 1-FFT, a positive correlation between enzyme activity and gene expression was observed. The overall results indicate that sucrose, fructose and glucose act similarly on fructan metabolism and that 1-FEH and 1-SST are transcriptionally regulated by sugar in this species. Cultivation of plants in increasing sucrose concentrations stimulated synthesis and inhibited fructan mobilization, and induced a distinct pattern of enzyme activity for 1-SST and 1-FFT, indicating the existence of a mechanism for differential regulation between them. PMID:26442003

Effects of different carbohydrate sources on fructan metabolism in plants of Chrysolaena obovata grown in vitro.

PubMed

Trevisan, Flavio; Oliveira, Vanessa F; Carvalho, Maria A M; Gaspar, Marília

2015-01-01

Chrysolaena obovata (Less.) Dematt., previously named Vernonia herbacea, is an Asteraceae native to the Cerrado which accumulates about 80% of the rhizophore dry mass as inulin-type fructans. Considering its high inulin production and the wide application of fructans, a protocol for C. obovata in vitro culture was recently established. Carbohydrates are essential for in vitro growth and development of plants and can also act as signaling molecules involved in cellular adjustments and metabolic regulation. This work aimed to evaluate the effect of different sources of carbohydrate on fructan metabolism in plants grown in vitro. For this purpose, C. obovata plants cultivated in vitro were submitted to carbon deprivation and transferred to MS medium supplemented with sucrose, glucose or fructose. Following, their fructan composition and activity and expression of genes encoding enzymes for fructan synthesis (1-SST and 1-FFT) and degradation (1-FEH) were evaluated. For qRT-PCR analysis partial cDNA sequences corresponding to two different C. obovata genes, 1-SST and 1-FFT, were isolated. As expected, C. obovata sequences showed highest sequence identity to other Asteraceae 1-SST and 1-FFT, than to Poaceae related proteins. A carbon deficit treatment stimulated the transcription of the gene 1-FEH and inhibited 1-SST and 1-FFT and carbohydrate supplementation promoted reversal of the expression profile of these genes. With the exception of 1-FFT, a positive correlation between enzyme activity and gene expression was observed. The overall results indicate that sucrose, fructose and glucose act similarly on fructan metabolism and that 1-FEH and 1-SST are transcriptionally regulated by sugar in this species. Cultivation of plants in increasing sucrose concentrations stimulated synthesis and inhibited fructan mobilization, and induced a distinct pattern of enzyme activity for 1-SST and 1-FFT, indicating the existence of a mechanism for differential regulation between them.

Phase-unwrapping algorithm by a rounding-least-squares approach

NASA Astrophysics Data System (ADS)

Juarez-Salazar, Rigoberto; Robledo-Sanchez, Carlos; Guerrero-Sanchez, Fermin

2014-02-01

A simple and efficient phase-unwrapping algorithm based on a rounding procedure and a global least-squares minimization is proposed. Instead of processing the gradient of the wrapped phase, this algorithm operates over the gradient of the phase jumps by a robust and noniterative scheme. Thus, the residue-spreading and over-smoothing effects are reduced. The algorithm's performance is compared with four well-known phase-unwrapping methods: minimum cost network flow (MCNF), fast Fourier transform (FFT), quality-guided, and branch-cut. A computer simulation and experimental results show that the proposed algorithm reaches a high-accuracy level than the MCNF method by a low-computing time similar to the FFT phase-unwrapping method. Moreover, since the proposed algorithm is simple, fast, and user-free, it could be used in metrological interferometric and fringe-projection automatic real-time applications.

A microcomputer based frequency-domain processor for laser Doppler anemometry

NASA Technical Reports Server (NTRS)

Horne, W. Clifton; Adair, Desmond

1988-01-01

A prototype multi-channel laser Doppler anemometry (LDA) processor was assembled using a wideband transient recorder and a microcomputer with an array processor for fast Fourier transform (FFT) computations. The prototype instrument was used to acquire, process, and record signals from a three-component wind tunnel LDA system subject to various conditions of noise and flow turbulence. The recorded data was used to evaluate the effectiveness of burst acceptance criteria, processing algorithms, and selection of processing parameters such as record length. The recorded signals were also used to obtain comparative estimates of signal-to-noise ratio between time-domain and frequency-domain signal detection schemes. These comparisons show that the FFT processing scheme allows accurate processing of signals for which the signal-to-noise ratio is 10 to 15 dB less than is practical using counter processors.

Synthesis and operation of an FFT-decoupled fixed-order reversed-field pinch plasma control system based on identification data

NASA Astrophysics Data System (ADS)

Olofsson, K. Erik J.; Brunsell, Per R.; Witrant, Emmanuel; Drake, James R.

2010-10-01

Recent developments and applications of system identification methods for the reversed-field pinch (RFP) machine EXTRAP T2R have yielded plasma response parameters for decoupled dynamics. These data sets are fundamental for a real-time implementable fast Fourier transform (FFT) decoupled discrete-time fixed-order strongly stabilizing synthesis as described in this work. Robustness is assessed over the data set by bootstrap calculation of the sensitivity transfer function worst-case H_{\\infty} -gain distribution. Output tracking and magnetohydrodynamic mode m = 1 tracking are considered in the same framework simply as two distinct weighted traces of a performance channel output-covariance matrix as derived from the closed-loop discrete-time Lyapunov equation. The behaviour of the resulting multivariable controller is investigated with dedicated T2R experiments.

A first-order k-space model for elastic wave propagation in heterogeneous media.

PubMed

Firouzi, K; Cox, B T; Treeby, B E; Saffari, N

2012-09-01

A pseudospectral model of linear elastic wave propagation is described based on the first order stress-velocity equations of elastodynamics. k-space adjustments to the spectral gradient calculations are derived from the dyadic Green's function solution to the second-order elastic wave equation and used to (a) ensure the solution is exact for homogeneous wave propagation for timesteps of arbitrarily large size, and (b) also allows larger time steps without loss of accuracy in heterogeneous media. The formulation in k-space allows the wavefield to be split easily into compressional and shear parts. A perfectly matched layer (PML) absorbing boundary condition was developed to effectively impose a radiation condition on the wavefield. The staggered grid, which is essential for accurate simulations, is described, along with other practical details of the implementation. The model is verified through comparison with exact solutions for canonical examples and further examples are given to show the efficiency of the method for practical problems. The efficiency of the model is by virtue of the reduced point-per-wavelength requirement, the use of the fast Fourier transform (FFT) to calculate the gradients in k space, and larger time steps made possible by the k-space adjustments.

Fiber optic pH sensor with self-assembled polymer multilayer nanocoatings.

PubMed

Shao, Li-Yang; Yin, Ming-Jie; Tam, Hwa-Yaw; Albert, Jacques

2013-01-24

A fiber-optic pH sensor based on a tilted fiber Bragg grating (TFBG) with electrostatic self-assembly multilayer sensing film is presented. The pH sensitive polymeric film, poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) was deposited on the circumference of the TFBG with the layer-by-layer (LbL) electrostatic self-assembly technique. The PDDA/PAA film exhibits a reduction in refractive index by swelling in different pH solutions. This effect results in wavelength shifts and transmission changes in the spectrum of the TFBG. The peak amplitude of the dominant spectral fringes over a certain window of the transmission spectrum, obtained by FFT analysis, has a near-linear pH sensitivity of 117 arbitrary unit (a.u.)/pH unit and an accuracy of ±1 a.u. (in the range of pH 4.66 to pH 6.02). The thickness and surface morphology of the sensing multilayer film were characterized to investigate their effects on the sensor's performance. The dynamic response of the sensor also has been studied (10 s rise time and 18 s fall time for a sensor with six bilayers of PDDA/PAA).

Nonlinear dynamic modeling of a simple flexible rotor system subjected to time-variable base motions

NASA Astrophysics Data System (ADS)

Chen, Liqiang; Wang, Jianjun; Han, Qinkai; Chu, Fulei

2017-09-01

Rotor systems carried in transportation system or under seismic excitations are considered to have a moving base. To study the dynamic behavior of flexible rotor systems subjected to time-variable base motions, a general model is developed based on finite element method and Lagrange's equation. Two groups of Euler angles are defined to describe the rotation of the rotor with respect to the base and that of the base with respect to the ground. It is found that the base rotations would cause nonlinearities in the model. To verify the proposed model, a novel test rig which could simulate the base angular-movement is designed. Dynamic experiments on a flexible rotor-bearing system with base angular motions are carried out. Based upon these, numerical simulations are conducted to further study the dynamic response of the flexible rotor under harmonic angular base motions. The effects of base angular amplitude, rotating speed and base frequency on response behaviors are discussed by means of FFT, waterfall, frequency response curve and orbits of the rotor. The FFT and waterfall plots of the disk horizontal and vertical vibrations are marked with multiplications of the base frequency and sum and difference tones of the rotating frequency and the base frequency. Their amplitudes will increase remarkably when they meet the whirling frequencies of the rotor system.

An algorithm for extraction of periodic signals from sparse, irregularly sampled data

NASA Technical Reports Server (NTRS)

Wilcox, J. Z.

1994-01-01

Temporal gaps in discrete sampling sequences produce spurious Fourier components at the intermodulation frequencies of an oscillatory signal and the temporal gaps, thus significantly complicating spectral analysis of such sparsely sampled data. A new fast Fourier transform (FFT)-based algorithm has been developed, suitable for spectral analysis of sparsely sampled data with a relatively small number of oscillatory components buried in background noise. The algorithm's principal idea has its origin in the so-called 'clean' algorithm used to sharpen images of scenes corrupted by atmospheric and sensor aperture effects. It identifies as the signal's 'true' frequency that oscillatory component which, when passed through the same sampling sequence as the original data, produces a Fourier image that is the best match to the original Fourier space. The algorithm has generally met with succession trials with simulated data with a low signal-to-noise ratio, including those of a type similar to hourly residuals for Earth orientation parameters extracted from VLBI data. For eight oscillatory components in the diurnal and semidiurnal bands, all components with an amplitude-noise ratio greater than 0.2 were successfully extracted for all sequences and duty cycles (greater than 0.1) tested; the amplitude-noise ratios of the extracted signals were as low as 0.05 for high duty cycles and long sampling sequences. When, in addition to these high frequencies, strong low-frequency components are present in the data, the low-frequency components are generally eliminated first, by employing a version of the algorithm that searches for non-integer multiples of the discrete FET minimum frequency.

Multi-carrier Communications over Time-varying Acoustic Channels

NASA Astrophysics Data System (ADS)

Aval, Yashar M.

Acoustic communication is an enabling technology for many autonomous undersea systems, such as those used for ocean monitoring, offshore oil and gas industry, aquaculture, or port security. There are three main challenges in achieving reliable high-rate underwater communication: the bandwidth of acoustic channels is extremely limited, the propagation delays are long, and the Doppler distortions are more pronounced than those found in wireless radio channels. In this dissertation we focus on assessing the fundamental limitations of acoustic communication, and designing efficient signal processing methods that cam overcome these limitations. We address the fundamental question of acoustic channel capacity (achievable rate) for single-input-multi-output (SIMO) acoustic channels using a per-path Rician fading model, and focusing on two scenarios: narrowband channels where the channel statistics can be approximated as frequency- independent, and wideband channels where the nominal path loss is frequency-dependent. In each scenario, we compare several candidate power allocation techniques, and show that assigning uniform power across all frequencies for the first scenario, and assigning uniform power across a selected frequency-band for the second scenario, are the best practical choices in most cases, because the long propagation delay renders the feedback information outdated for power allocation based on the estimated channel response. We quantify our results using the channel information extracted form the 2010 Mobile Acoustic Communications Experiment (MACE'10). Next, we focus on achieving reliable high-rate communication over underwater acoustic channels. Specifically, we investigate orthogonal frequency division multiplexing (OFDM) as the state-of-the-art technique for dealing with frequency-selective multipath channels, and propose a class of methods that compensate for the time-variation of the underwater acoustic channel. These methods are based on multiple-FFT demodulation, and are implemented as partial (P), shaped (S), fractional (F), and Taylor series expansion (T) FFT demodulation. They replace the conventional FFT demodulation with a few FFTs and a combiner. The input to each FFT is a specific transformation of the input signal (P,S,F,T), while the combiner performs weighted summation of the FFT outputs. We design an adaptive algorithm of stochastic gradient type to learn the combiner weights for coherent and differentially coherent detection. The algorithm is cast into the framework of multiple receiving elements to take advantage of spatial diversity. Synthetic data, as well as experimental data from the MACE'10 experiment are used to demonstrate the performance of the proposed methods, showing significant improvement over conventional detection techniques with or without inter-carrier interference equalization (5 dB--7 dB on average over multiple hours), as well as improved bandwidth efficiency.

A Parameterized Pattern-Error Objective for Large-Scale Phase-Only Array Pattern Design

DTIC Science & Technology

2016-03-21

12 4.4 Example 3: Sector Beam w/ Nonuniform Amplitude...fixed uniform amplitude illumination, phase-only optimization can also find application to arrays with fixed but nonuniform tapers. Such fixed tapers...arbitrary element locations nonuniform FFT algorithms exist [43–45] that have the same asymptotic complexity as the conventional FFT, although the

Analysis of a Digital Technique for Frequency Transposition of Speech.

DTIC Science & Technology

1985-09-01

scaled excitation function drives the vocal tract model. In a phone interview with James Kaiser of Bell Laboratories, he mentioned that current thinking...is processed using the Fast Fourier Transform (FFT) and then low pass filtered if desired. mAbe (Pb) FFT LPF- nih ~a s5ee.. S. 4Nrf#Nr Flow Chart for

It's fun to transcribe with Fun30: A model for nucleosome dynamics during RNA polymerase II-mediated elongation.

PubMed

Lee, Junwoo; Choi, Eun Shik; Lee, Daeyoup

2018-01-01

The ability of elongating RNA polymerase II (RNAPII) to regulate the nucleosome barrier is poorly understood because we do not know enough about the involved factors and we lack a conceptual framework to model this process. Our group recently identified the conserved Fun30/SMARCAD1 family chromatin-remodeling factor, Fun30 Fft3 , as being critical for relieving the nucleosome barrier during RNAPII-mediated elongation, and proposed a model illustrating how Fun30 Fft3 may contribute to nucleosome disassembly during RNAPII-mediated elongation. Here, we present a model that describes nucleosome dynamics during RNAPII-mediated elongation in mathematical terms and addresses the involvement of Fun30 Fft3 in this process.

The Filled Arm Fizeau Telescope (FFT)

NASA Technical Reports Server (NTRS)

Synnott, S. P.

1991-01-01

Attention is given to the design of a Mills Cross imaging interferometer in which the arms are fully filled with mirror segments of a Ritchey-Chretien primary and which has sensitivity to 27th magnitude per pixel and resolution a factor of 10 greater than Hubble. The optical design, structural configuration, thermal disturbances, and vibration, material, control, and metrology issues, as well as scientific capabilities are discussed, and technology needs are identified. The technologies under consideration are similar to those required for the development of the other imaging interferometers that have been proposed over the past decade. A comparison of the imaging capabilities of a 30-m diameter FFT, an 8-m telescope with a collecting area equal to that of the FFT, and the HST is presented.

Combined orbits and clocks from the IGS 2nd reprocessing

NASA Astrophysics Data System (ADS)

Griffiths, J.; Ray, J.

2016-12-01

In early 2015, the Analysis Centers (ACs) of the International GNSS Service (IGS) completed their second reanalysis of the full history of globally distributed GPS and GLONASS data collected since 1994. The suite of reprocessed AC solutions includes daily product files containing station positions, Earth rotation parameters, satellite orbits and clocks. This second reprocessing—or repro2—provided the IGS contribution to ITRF2014; it follows the successful first reprocessing, which provided the IGS input for ITRF2008. For this poster, we will discuss the newly combined repro2 GPS orbits and clocks. We also revisit our previous analysis of orbit day-boundary discontinuities with several significant changes and improvements: 1) Orbit discontinuities for the contributing ACs were studied in addition to those for the IGS repro2 combined orbits. (2) Apart from homogeneous reprocessing with updated analysis models, the main difference compared to the IGS Final operational products is that NOAA/NGS inputs were not submitted for the IGS reprocessing, yet they contribute heavily in the operational orbits in recent years. (3) Also, during spring 2016, the ESA modified their orbit model so that it is no longer consistent with the one used for reprocessing. A much longer span of orbits was available now, up to 11.2 years for some individual satellites, which allows a far better resolution of spectral features. 4) The procedure to compute orbit discontinuities has been further refined to account for extrapolation edge effects, improved geopotential fields, and to allow for spectral analysis of a longer time series of jumps. The satellite position time series used are complete enough that linear interpolation is necessary for only sparse gaps. So the key results are based on standard FFT power spectra (stacked over the available constellation and lightly smoothed). However, we have also computed Lomb-Scargle periodgrams to provide higher frequency resolution of some spectral peaks and to permit tests of the effect of excluding eclipse periods.

Kernel Principal Component Analysis for dimensionality reduction in fMRI-based diagnosis of ADHD.

PubMed

Sidhu, Gagan S; Asgarian, Nasimeh; Greiner, Russell; Brown, Matthew R G

2012-01-01

This study explored various feature extraction methods for use in automated diagnosis of Attention-Deficit Hyperactivity Disorder (ADHD) from functional Magnetic Resonance Image (fMRI) data. Each participant's data consisted of a resting state fMRI scan as well as phenotypic data (age, gender, handedness, IQ, and site of scanning) from the ADHD-200 dataset. We used machine learning techniques to produce support vector machine (SVM) classifiers that attempted to differentiate between (1) all ADHD patients vs. healthy controls and (2) ADHD combined (ADHD-c) type vs. ADHD inattentive (ADHD-i) type vs. controls. In different tests, we used only the phenotypic data, only the imaging data, or else both the phenotypic and imaging data. For feature extraction on fMRI data, we tested the Fast Fourier Transform (FFT), different variants of Principal Component Analysis (PCA), and combinations of FFT and PCA. PCA variants included PCA over time (PCA-t), PCA over space and time (PCA-st), and kernelized PCA (kPCA-st). Baseline chance accuracy was 64.2% produced by guessing healthy control (the majority class) for all participants. Using only phenotypic data produced 72.9% accuracy on two class diagnosis and 66.8% on three class diagnosis. Diagnosis using only imaging data did not perform as well as phenotypic-only approaches. Using both phenotypic and imaging data with combined FFT and kPCA-st feature extraction yielded accuracies of 76.0% on two class diagnosis and 68.6% on three class diagnosis-better than phenotypic-only approaches. Our results demonstrate the potential of using FFT and kPCA-st with resting-state fMRI data as well as phenotypic data for automated diagnosis of ADHD. These results are encouraging given known challenges of learning ADHD diagnostic classifiers using the ADHD-200 dataset (see Brown et al., 2012).

Multisystemic Therapy and Functional Family Therapy Compared on their Effectiveness Using the Propensity Score Method.

PubMed

Eeren, Hester V; Goossens, Lucas M A; Scholte, Ron H J; Busschbach, Jan J V; van der Rijken, Rachel E A

2018-01-09

Multisystemic Therapy (MST) and Functional Family Therapy (FFT) have overlapping target populations and treatment goals. In this study, these interventions were compared on their effectiveness using a quasi-experimental design. Between October, 2009 and June, 2014, outcome data were collected from 697 adolescents (mean age 15.3 (SD 1.48), 61.9% male) assigned to either MST or FFT (422 MST; 275 FFT). Data were gathered during Routine Outcome Monitoring. The primary outcome was externalizing problem behavior (Child Behavior Checklist and Youth Self Report). Secondary outcomes were the proportion of adolescents living at home, engaged in school or work, and who lacked police contact during treatment. Because of the non-random assignment, a propensity score method was used to control for observed pre-treatment differences. Because the risk-need-responsivity (RNR) model guided treatment assignment, effectiveness was also estimated in youth with and without a court order as an indicator of their risk level. Looking at the whole sample, no difference in effect was found with regard to externalizing problems. For adolescents without a court order, effects on externalizing problems were larger after MST. Because many more adolescents with a court order were assigned to MST compared to FFT, the propensity score method could not balance the treatment groups in this subsample. In conclusion, few differences between MST and FFT were found. In line with the RNR model, higher risk adolescents were assigned to the more intensive treatment, namely MST. In the group with lower risk adolescents, this more intensive treatment was more effective in reducing externalizing problems.

Real-Time, Polyphase-FFT, 640-MHz Spectrum Analyzer

NASA Technical Reports Server (NTRS)

Zimmerman, George A.; Garyantes, Michael F.; Grimm, Michael J.; Charny, Bentsian; Brown, Randy D.; Wilck, Helmut C.

1994-01-01

Real-time polyphase-fast-Fourier-transform, polyphase-FFT, spectrum analyzer designed to aid in detection of multigigahertz radio signals in two 320-MHz-wide polarization channels. Spectrum analyzer divides total spectrum of 640 MHz into 33,554,432 frequency channels of about 20 Hz each. Size and cost of polyphase-coefficient memory substantially reduced and much of processing loss of windowed FFTs eliminated.

Family treatment for bipolar disorder and substance abuse in late adolescence.

PubMed

Miklowitz, David J

2012-05-01

The initial onset of bipolar disorder occurs in childhood or adolescence in about 50% of patients. Early-onset forms of the disorder have a poorer prognosis than adult-onset forms and are frequently characterized by comorbid substance abuse. Clinical trials research suggests that family psychoeducational approaches are effective adjuncts to medication in stabilizing the symptoms of bipolar disorder in adults and youth, although their efficacy in patients with comorbid substance use disorders has not been systematically investigated. This article describes the family-focused treatment (FFT) of a late adolescent with bipolar disorder and polysubstance dependence. The treatment of this patient and family required adapting FFT to consider the family's structure, dysfunctional alliance patterns, and unresolved conflicts from early in the family's history. The case illustrates the importance of conducting manual-based behavioral family treatments with a psychotherapeutic attitude, including addressing unstated emotional conflicts and resistances that may impede progress. © 2012 Wiley Periodicals, Inc.

Radiotelemetry recording of electroencephalogram in piglets during rest.

PubMed

Saito, Toshiyuki; Watanabe, Yasuko; Nemoto, Tetsu; Kasuya, Etsuko; Sakumoto, Ryosuke

2005-04-13

A wireless recording system was developed to study the electroencephalogram (EEG) in unrestrained, male Landrace piglets. Under general anesthesia, ball-tipped silver/silver chloride electrodes for EEG recording were implanted onto the dura matter of the parietal and frontal cortex of the piglets. A pair of miniature preamplifiers and transmitters was then mounted on the surface of the skull. To examine whether other bioelectrical activities interfere with the EEG measurements, an electrocardiogram (ECG) or electromyogram (EMG) of the neck was simultaneously recorded with the EEG. Next, wire electrodes for recording movement of the eyelid were implanted with EEG electrodes, and EEG and eyelid movements were simultaneously measured. Power spectral analysis using a Fast Fourier Transformation (FFT) algorithm indicates that EEG was successfully recorded in unrestrained piglets, at rest, during the daytime in the absence of interference from ECG, EMG or eyelid movements. These data indicate the feasibility of using our radiotelemetry system for measurement of EEG under these conditions.

On the Hilbert-Huang Transform Data Processing System Development

NASA Technical Reports Server (NTRS)

Kizhner, Semion; Flatley, Thomas P.; Huang, Norden E.; Cornwell, Evette; Smith, Darell

2003-01-01

One of the main heritage tools used in scientific and engineering data spectrum analysis is the Fourier Integral Transform and its high performance digital equivalent - the Fast Fourier Transform (FFT). The Fourier view of nonlinear mechanics that had existed for a long time, and the associated FFT (fairly recent development), carry strong a-priori assumptions about the source data, such as linearity and of being stationary. Natural phenomena measurements are essentially nonlinear and nonstationary. A very recent development at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), known as the Hilbert-Huang Transform (HHT) proposes a novel approach to the solution for the nonlinear class of spectrum analysis problems. Using the Empirical Mode Decomposition (EMD) followed by the Hilbert Transform of the empirical decomposition data (HT), the HHT allows spectrum analysis of nonlinear and nonstationary data by using an engineering a-posteriori data processing, based on the EMD algorithm. This results in a non-constrained decomposition of a source real value data vector into a finite set of Intrinsic Mode Functions (IMF) that can be further analyzed for spectrum interpretation by the classical Hilbert Transform. This paper describes phase one of the development of a new engineering tool, the HHT Data Processing System (HHTDPS). The HHTDPS allows applying the "T to a data vector in a fashion similar to the heritage FFT. It is a generic, low cost, high performance personal computer (PC) based system that implements the HHT computational algorithms in a user friendly, file driven environment. This paper also presents a quantitative analysis for a complex waveform data sample, a summary of technology commercialization efforts and the lessons learned from this new technology development.

An Automated Measurement of Ciliary Beating Frequency using a Combined Optical Flow and Peak Detection.

PubMed

Kim, Woojae; Han, Tae Hwa; Kim, Hyun Jun; Park, Man Young; Kim, Ku Sang; Park, Rae Woong

2011-06-01

The mucociliary transport system is a major defense mechanism of the respiratory tract. The performance of mucous transportation in the nasal cavity can be represented by a ciliary beating frequency (CBF). This study proposes a novel method to measure CBF by using optical flow. To obtain objective estimates of CBF from video images, an automated computer-based image processing technique is developed. This study proposes a new method based on optical flow for image processing and peak detection for signal processing. We compare the measuring accuracy of the method in various combinations of image processing (optical flow versus difference image) and signal processing (fast Fourier transform [FFT] vs. peak detection [PD]). The digital high-speed video method with a manual count of CBF in slow motion video play, is the gold-standard in CBF measurement. We obtained a total of fifty recorded ciliated sinonasal epithelium images to measure CBF from the Department of Otolaryngology. The ciliated sinonasal epithelium images were recorded at 50-100 frames per second using a charge coupled device camera with an inverted microscope at a magnification of ×1,000. The mean square errors and variance for each method were 1.24, 0.84 Hz; 11.8, 2.63 Hz; 3.22, 1.46 Hz; and 3.82, 1.53 Hz for optical flow (OF) + PD, OF + FFT, difference image [DI] + PD, and DI + FFT, respectively. Of the four methods, PD using optical flow showed the best performance for measuring the CBF of nasal mucosa. The proposed method was able to measure CBF more objectively and efficiently than what is currently possible.

STS-131 crew training during FFT CCTV Lighting 91019 ( Lights Out).

NASA Image and Video Library

2009-11-16

JSC2009-E-240951 (16 Nov. 2009) --- Japan Aerospace Exploration Agency (JAXA) astronaut Naoko Yamazaki (foreground) and NASA astronaut Stephanie Wilson, both STS-131 mission specialists, participate in a Full Fuselage Trainer (FFT) mock-up training session in the Space Vehicle Mock-up Facility at NASA's Johnson Space Center. United Space Alliance (USA) instructor David L. Williams assisted the crew members.

Three Specialized Innovations for FAST Wideband Receiver

NASA Astrophysics Data System (ADS)

Zhang, Xia; Yu, Xinying; Duan, Ran; Hao, Jie; Li, Di

2015-08-01

The National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) will soon finish the largest antenna in the world. Known as FAST, the Five-hundred-meter Aperture Spherical Radio Telescope will be the most sensitive single-dish radio telescope in the low frequency radio bands between 70 MHz and 3 GHz.To take advantage of its giant aperture, all relevant cutting-edge technology should be applied to FAST to ensure that it achieves the best possible overall performance. The wideband receiver that is currently under development can not only be directly applied to FAST, but also used for other Chinese radio telescopes, such as the Shanghai 65-meter telescope and the Xinjiang 110-meter telescope, to ensure that these telescopes are among the best in the world. Recently, rapid development related to this wideband receiver has been underway. In this paper, we will introduce three key aspects of the FAST wideband receiver project. First is the use of a high-performance analog-to-digital converter (ADC). With the cooperation of Hao Jie’s team from the Institute of Automation of the Chinese Academy of Sciences(CASIA), we have developed 3-Gsps,12-bit ADCs, which have not been used previously in astronomy, and we expect to realize the 3-GHz bandwidth in a single step by covering the entire bandwidth via interleaving or a complex fast Fourier transform (FFT).Second is the front-end analog signal integrated circuit board. We wish to achieve a series of amplification, attenuation, and mixing filtering operations on a single small board, thereby achieving digital control of the bandpass behavior both flexibly and highly-efficiently. This design will not only greatly reduce the required cost and power but will also make the best use of the digital-system’s flexibility. Third is optimization of the FFT: the existing FFT is not very efficient; therefore, we will optimize the FFT for large-scale operation. For this purpose, we intend to cascade two FFTs. Another possibility is to combine digital down conversion (DDC) with the FFT to achieve a flexible FFT.

Nonuniform fast Fourier transform method for numerical diffraction simulation on tilted planes.

PubMed

Xiao, Yu; Tang, Xiahui; Qin, Yingxiong; Peng, Hao; Wang, Wei; Zhong, Lijing

2016-10-01

The method, based on the rotation of the angular spectrum in the frequency domain, is generally used for the diffraction simulation between the tilted planes. Due to the rotation of the angular spectrum, the interval between the sampling points in the Fourier domain is not even. For the conventional fast Fourier transform (FFT)-based methods, a spectrum interpolation is needed to get the approximate sampling value on the equidistant sampling points. However, due to the numerical error caused by the spectrum interpolation, the calculation accuracy degrades very quickly as the rotation angle increases. Here, the diffraction propagation between the tilted planes is transformed into a problem about the discrete Fourier transform on the uneven sampling points, which can be evaluated effectively and precisely through the nonuniform fast Fourier transform method (NUFFT). The most important advantage of this method is that the conventional spectrum interpolation is avoided and the high calculation accuracy can be guaranteed for different rotation angles, even when the rotation angle is close to π/2. Also, its calculation efficiency is comparable with that of the conventional FFT-based methods. Numerical examples as well as a discussion about the calculation accuracy and the sampling method are presented.

Efficient and accurate two-scale FE-FFT-based prediction of the effective material behavior of elasto-viscoplastic polycrystals

NASA Astrophysics Data System (ADS)

Kochmann, Julian; Wulfinghoff, Stephan; Ehle, Lisa; Mayer, Joachim; Svendsen, Bob; Reese, Stefanie

2018-06-01

Recently, two-scale FE-FFT-based methods (e.g., Spahn et al. in Comput Methods Appl Mech Eng 268:871-883, 2014; Kochmann et al. in Comput Methods Appl Mech Eng 305:89-110, 2016) have been proposed to predict the microscopic and overall mechanical behavior of heterogeneous materials. The purpose of this work is the extension to elasto-viscoplastic polycrystals, efficient and robust Fourier solvers and the prediction of micromechanical fields during macroscopic deformation processes. Assuming scale separation, the macroscopic problem is solved using the finite element method. The solution of the microscopic problem, which is embedded as a periodic unit cell (UC) in each macroscopic integration point, is found by employing fast Fourier transforms, fixed-point and Newton-Krylov methods. The overall material behavior is defined by the mean UC response. In order to ensure spatially converged micromechanical fields as well as feasible overall CPU times, an efficient but simple solution strategy for two-scale simulations is proposed. As an example, the constitutive behavior of 42CrMo4 steel is predicted during macroscopic three-point bending tests.

Designing Waveform Sets with Good Correlation and Stopband Properties for MIMO Radar via the Gradient-Based Method

PubMed Central

Tang, Liang; Zhu, Yongfeng; Fu, Qiang

2017-01-01

Waveform sets with good correlation and/or stopband properties have received extensive attention and been widely used in multiple-input multiple-output (MIMO) radar. In this paper, we aim at designing unimodular waveform sets with good correlation and stopband properties. To formulate the problem, we construct two criteria to measure the correlation and stopband properties and then establish an unconstrained problem in the frequency domain. After deducing the phase gradient and the step size, an efficient gradient-based algorithm with monotonicity is proposed to minimize the objective function directly. For the design problem without considering the correlation weights, we develop a simplified algorithm, which only requires a few fast Fourier transform (FFT) operations and is more efficient. Because both of the algorithms can be implemented via the FFT operations and the Hadamard product, they are computationally efficient and can be used to design waveform sets with a large waveform number and waveform length. Numerical experiments show that the proposed algorithms can provide better performance than the state-of-the-art algorithms in terms of the computational complexity. PMID:28468308

Designing Waveform Sets with Good Correlation and Stopband Properties for MIMO Radar via the Gradient-Based Method.

PubMed

Tang, Liang; Zhu, Yongfeng; Fu, Qiang

2017-05-01

Waveform sets with good correlation and/or stopband properties have received extensive attention and been widely used in multiple-input multiple-output (MIMO) radar. In this paper, we aim at designing unimodular waveform sets with good correlation and stopband properties. To formulate the problem, we construct two criteria to measure the correlation and stopband properties and then establish an unconstrained problem in the frequency domain. After deducing the phase gradient and the step size, an efficient gradient-based algorithm with monotonicity is proposed to minimize the objective function directly. For the design problem without considering the correlation weights, we develop a simplified algorithm, which only requires a few fast Fourier transform (FFT) operations and is more efficient. Because both of the algorithms can be implemented via the FFT operations and the Hadamard product, they are computationally efficient and can be used to design waveform sets with a large waveform number and waveform length. Numerical experiments show that the proposed algorithms can provide better performance than the state-of-the-art algorithms in terms of the computational complexity.

Efficient and accurate two-scale FE-FFT-based prediction of the effective material behavior of elasto-viscoplastic polycrystals

NASA Astrophysics Data System (ADS)

Kochmann, Julian; Wulfinghoff, Stephan; Ehle, Lisa; Mayer, Joachim; Svendsen, Bob; Reese, Stefanie

2017-09-01

Recently, two-scale FE-FFT-based methods (e.g., Spahn et al. in Comput Methods Appl Mech Eng 268:871-883, 2014; Kochmann et al. in Comput Methods Appl Mech Eng 305:89-110, 2016) have been proposed to predict the microscopic and overall mechanical behavior of heterogeneous materials. The purpose of this work is the extension to elasto-viscoplastic polycrystals, efficient and robust Fourier solvers and the prediction of micromechanical fields during macroscopic deformation processes. Assuming scale separation, the macroscopic problem is solved using the finite element method. The solution of the microscopic problem, which is embedded as a periodic unit cell (UC) in each macroscopic integration point, is found by employing fast Fourier transforms, fixed-point and Newton-Krylov methods. The overall material behavior is defined by the mean UC response. In order to ensure spatially converged micromechanical fields as well as feasible overall CPU times, an efficient but simple solution strategy for two-scale simulations is proposed. As an example, the constitutive behavior of 42CrMo4 steel is predicted during macroscopic three-point bending tests.

Stripe artifact elimination based on nonsubsampled contourlet transform for light sheet fluorescence microscopy

NASA Astrophysics Data System (ADS)

Liang, Xiao; Zang, Yali; Dong, Di; Zhang, Liwen; Fang, Mengjie; Yang, Xin; Arranz, Alicia; Ripoll, Jorge; Hui, Hui; Tian, Jie

2016-10-01

Stripe artifacts, caused by high-absorption or high-scattering structures in the illumination light path, are a common drawback in both unidirectional and multidirectional light sheet fluorescence microscopy (LSFM), significantly deteriorating image quality. To circumvent this problem, we present an effective multidirectional stripe remover (MDSR) method based on nonsubsampled contourlet transform (NSCT), which can be used for both unidirectional and multidirectional LSFM. In MDSR, a fast Fourier transform (FFT) filter is designed in the NSCT domain to shrink the stripe components and eliminate the noise. Benefiting from the properties of being multiscale and multidirectional, MDSR succeeds in eliminating stripe artifacts in both unidirectional and multidirectional LSFM. To validate the method, MDSR has been tested on images from a custom-made unidirectional LSFM system and a commercial multidirectional LSFM system, clearly demonstrating that MDSR effectively removes most of the stripe artifacts. Moreover, we performed a comparative experiment with the variational stationary noise remover and the wavelet-FFT methods and quantitatively analyzed the results with a peak signal-to-noise ratio, showing an improved noise removal when using the MDSR method.

Extremely simple holographic projection of color images

NASA Astrophysics Data System (ADS)

Makowski, Michal; Ducin, Izabela; Kakarenko, Karol; Suszek, Jaroslaw; Kolodziejczyk, Andrzej; Sypek, Maciej

2012-03-01

A very simple scheme of holographic projection is presented with some experimental results showing good quality image projection without any imaging lens. This technique can be regarded as an alternative to classic projection methods. It is based on the reconstruction real images from three phase iterated Fourier holograms. The illumination is performed with three laser beams of primary colors. A divergent wavefront geometry is used to achieve an increased throw angle of the projection, compared to plane wave illumination. Light fibers are used as light guidance in order to keep the setup as simple as possible and to provide point-like sources of high quality divergent wave-fronts at optimized position against the light modulator. Absorbing spectral filters are implemented to multiplex three holograms on a single phase-only spatial light modulator. Hence color mixing occurs without any time-division methods, which cause rainbow effects and color flicker. The zero diffractive order with divergent illumination is practically invisible and speckle field is effectively suppressed with phase optimization and time averaging techniques. The main advantages of the proposed concept are: a very simple and highly miniaturizable configuration; lack of lens; a single LCoS (Liquid Crystal on Silicon) modulator; a strong resistance to imperfections and obstructions of the spatial light modulator like dead pixels, dust, mud, fingerprints etc.; simple calculations based on Fast Fourier Transform (FFT) easily processed in real time mode with GPU (Graphic Programming).

Properties of Fructan:Fructan 1-Fructosyltransferases from Chicory and Globe Thistle, Two Asteracean Plants Storing Greatly Different Types of Inulin1

PubMed Central

Vergauwen, Rudy; Van Laere, André; Van den Ende, Wim

2003-01-01

Remarkably, within the Asteraceae, a species-specific fructan pattern can be observed. Some species such as artichoke (Cynara scolymus) and globe thistle (Echinops ritro) store fructans with a considerably higher degree of polymerization than the one observed in chicory (Cichorium intybus) and Jerusalem artichoke (Helianthus tuberosus). Fructan:fructan 1-fructosyltransferase (1-FFT) is the enzyme responsible for chain elongation of inulin-type fructans. 1-FFTs were purified from chicory and globe thistle. A comparison revealed that chicory 1-FFT has a high affinity for sucrose (Suc), fructose (Fru), and 1-kestose as acceptor substrate. This makes redistribution of Fru moieties from large to small fructans very likely during the period of active fructan synthesis in the root when import and concentration of Suc can be expected to be high. In globe thistle, this problem is avoided by the very low affinity of 1-FFT for Suc, Fru, and 1-kestose and the higher affinity for inulin as acceptor substrate. Therefore, the 1-kestose formed by Suc:Suc 1-fructosyltransferase is preferentially used for elongation of inulin molecules, explaining why inulins with a much higher degree of polymerization accumulate in roots of globe thistle. Inulin patterns obtained in vitro from 1-kestose and the purified 1-FFTs from both species closely resemble the in vivo inulin patterns. Therefore, we conclude that the species-specific fructan pattern within the Asteraceae can be explained by the different characteristics of their respective 1-FFTs. Although 1-FFT and bacterial levansucrases clearly differ in their ability to use Suc as a donor substrate, a kinetic analysis suggests that 1-FFT also works via a ping-pong mechanism. PMID:12970504

Student experimenter stands near middeck lockers in JSC Bldg 9A mockup

NASA Technical Reports Server (NTRS)

1991-01-01

Student experimenter Constantine Costes, STS-42 Commander Ronald J. Grabe, STS-42 Mission Specialist (MS) William F. Readdy, and Integration Engineer Neal Christie discuss Coates' student experiment 83-02 (SE 83-02) entitled 'Zero-G Capillary Rise of Liquid through Granular Porous Media' in JSC Mockup and Integration Laboratory Bldg 9A Full Fuselage Trainer (FFT). On FFT middeck, Costes stands behind Readdy (kneeling) as Christie demonstrates experiment setup and Grabe looks on (47326). The team also examines experiment components at middeck stowage locker (47323) and at FFT open side hatch (47324, 47325). The experiment is designed to investigate the capillary and forced flow characteristics of blue-tinted water in three glass tubes with three sizes of glass beads. SE 83-02 is scheduled to be flown on STS-42 aboard Discovery, Orbiter Vehicle (OV) 103.

Barriers and Facilitators to Implementing Functional Family Therapy in a Community Setting: Client and Practitioner Perspectives.

PubMed

McPherson, Kerri E; Kerr, Susan; Casey, Beth; Marshall, John

2017-10-01

While Functional Family Therapy (FFT) is known to be effective in addressing adolescent behavioral problems, there has been little exploration of issues relevant to its transport from the tightly controlled setting of clinical trials into routine service delivery. This study sought the views of key stakeholders, clients, and practitioners, on barriers and facilitators to the successful implementation of FFT. Undertaken in a community setting in Scotland, interviews were carried out with 12 adolescents, 14 parents/caregivers, and 6 practitioners. Results focus on: Referral process and pre-intervention contact; Engagement of families; Structure and delivery; Organizational factors. Although barriers to engagement were identified, FFT was viewed as an acceptable, appropriate and feasible intervention with the potential to improve adolescent wellbeing in 'real-world' settings. © 2017 American Association for Marriage and Family Therapy.

FFT swept filtering: a bias-free method for processing fringe signals in absolute gravimeters

NASA Astrophysics Data System (ADS)

Křen, Petr; Pálinkáš, Vojtech; Mašika, Pavel; Val'ko, Miloš

2018-05-01

Absolute gravimeters, based on laser interferometry, are widely used for many applications in geoscience and metrology. Although currently the most accurate FG5 and FG5X gravimeters declare standard uncertainties at the level of 2-3 μGal, their inherent systematic errors affect the gravity reference determined by international key comparisons based predominately on the use of FG5-type instruments. The measurement results for FG5-215 and FG5X-251 clearly showed that the measured g-values depend on the size of the fringe signal and that this effect might be approximated by a linear regression with a slope of up to 0.030 μGal/mV . However, these empirical results do not enable one to identify the source of the effect or to determine a reasonable reference fringe level for correcting g-values in an absolute sense. Therefore, both gravimeters were equipped with new measuring systems (according to Křen et al. in Metrologia 53:27-40, 2016. https://doi.org/10.1088/0026-1394/53/1/27 applied for FG5), running in parallel with the original systems. The new systems use an analogue-to-digital converter HS5 to digitize the fringe signal and a new method of fringe signal analysis based on FFT swept bandpass filtering. We demonstrate that the source of the fringe size effect is connected to a distortion of the fringe signal due to the electronic components used in the FG5(X) gravimeters. To obtain a bias-free g-value, the FFT swept method should be applied for the determination of zero-crossings. A comparison of g-values obtained from the new and the original systems clearly shows that the original system might be biased by approximately 3-5 μGal due to improperly distorted fringe signal processing.

Image Processing Software

NASA Technical Reports Server (NTRS)

1990-01-01

The Ames digital image velocimetry technology has been incorporated in a commercially available image processing software package that allows motion measurement of images on a PC alone. The software, manufactured by Werner Frei Associates, is IMAGELAB FFT. IMAGELAB FFT is a general purpose image processing system with a variety of other applications, among them image enhancement of fingerprints and use by banks and law enforcement agencies for analysis of videos run during robberies.

An algorithm for the basis of the finite Fourier transform

NASA Technical Reports Server (NTRS)

Santhanam, Thalanayar S.

1995-01-01

The Finite Fourier Transformation matrix (F.F.T.) plays a central role in the formulation of quantum mechanics in a finite dimensional space studied by the author over the past couple of decades. An outstanding problem which still remains open is to find a complete basis for F.F.T. In this paper we suggest a simple algorithm to find the eigenvectors of F.T.T.

The fast Padé transform in magnetic resonance spectroscopy for potential improvements in early cancer diagnostics

NASA Astrophysics Data System (ADS)

Belkic, Dzevad; Belkic, Karen

2005-09-01

The convergence rates of the fast Padé transform (FPT) and the fast Fourier transform (FFT) are compared. These two estimators are used to process a time-signal encoded at 4 T by means of one-dimensional magnetic resonance spectroscopy (MRS) for healthy human brain. It is found systematically that at any level of truncation of the full signal length, the clinically relevant resonances that determine concentrations of metabolites in the investigated tissue are significantly better resolved in the FPT than in the FFT. In particular, the FPT has a better resolution than the FFT for the same signal length. Moreover, the FPT can achieve the same resolution as the FFT by using twice shorter signals. Implications of these findings for two-dimensional magnetic resonance spectroscopy as well as for two- and three-dimensional magnetic resonance spectroscopic imaging are highlighted. Self-contained cross-validation of all the results from the FPT is secured by using two conceptually different, equivalent algorithms (inside and outside the unit-circle), that are both valid in the entire complex frequency plane. The difference between the results from these two variants of the FPT is indistinguishable from the background noise. This constitutes robust error analysis of proven validity. The FPT shows promise in applications of MRS for early cancer detection.

Ordered fast fourier transforms on a massively parallel hypercube multiprocessor

NASA Technical Reports Server (NTRS)

Tong, Charles; Swarztrauber, Paul N.

1989-01-01

Design alternatives for ordered Fast Fourier Transformation (FFT) algorithms were examined on massively parallel hypercube multiprocessors such as the Connection Machine. Particular emphasis is placed on reducing communication which is known to dominate the overall computing time. To this end, the order and computational phases of the FFT were combined, and the sequence to processor maps that reduce communication were used. The class of ordered transforms is expanded to include any FFT in which the order of the transform is the same as that of the input sequence. Two such orderings are examined, namely, standard-order and A-order which can be implemented with equal ease on the Connection Machine where orderings are determined by geometries and priorities. If the sequence has N = 2 exp r elements and the hypercube has P = 2 exp d processors, then a standard-order FFT can be implemented with d + r/2 + 1 parallel transmissions. An A-order sequence can be transformed with 2d - r/2 parallel transmissions which is r - d + 1 fewer than the standard order. A parallel method for computing the trigonometric coefficients is presented that does not use trigonometric functions or interprocessor communication. A performance of 0.9 GFLOPS was obtained for an A-order transform on the Connection Machine.

Digital processing of RF signals from optical frequency combs

NASA Astrophysics Data System (ADS)

Cizek, Martin; Smid, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Cip, Ondřej

2013-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Secondly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique used for assessing the offset and repetition frequencies of the comb, resulting in digital servo-loop stabilization of the fs comb. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset frequency of the fs comb.

Digital processing of signals from femtosecond combs

NASA Astrophysics Data System (ADS)

Čížek, Martin; Šmíd, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Číp, Ondrej

2012-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique and with fully digital servo-loop stabilization of the fs comb. Secondly, we are using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset and repetition frequencies of the fs comb.

Mesh Dependence on Shear Driven Boundary Layers in Stable Stratification Generated by Large Eddy-Simulation

NASA Astrophysics Data System (ADS)

Berg, Jacob; Patton, Edward G.; Sullivan, Peter S.

2017-11-01

The effect of mesh resolution and size on shear driven atmospheric boundary layers in a stable stratified environment is investigated with the NCAR pseudo-spectral LES model (J. Atmos. Sci. v68, p2395, 2011 and J. Atmos. Sci. v73, p1815, 2016). The model applies FFT in the two horizontal directions and finite differencing in the vertical direction. With vanishing heat flux at the surface and a capping inversion entraining potential temperature into the boundary layer the situation is often called the conditional neutral atmospheric boundary layer (ABL). Due to its relevance in high wind applications such as wind power meteorology, we emphasize on second order statistics important for wind turbines including spectral information. The simulations range from mesh sizes of 643 to 10243 grid points. Due to the non-stationarity of the problem, different simulations are compared at equal eddy-turnover times. Whereas grid convergence is mostly achieved in the middle portion of the ABL, statistics close to the surface of the ABL, where the presence of the ground limits the growth of the energy containing eddies, second order statistics are not converged on the studies meshes. Higher order structure functions also reveal non-Gaussian statistics highly dependent on the resolution.

Key issues in decomposing fMRI during naturalistic and continuous music experience with independent component analysis.

PubMed

Cong, Fengyu; Puoliväli, Tuomas; Alluri, Vinoo; Sipola, Tuomo; Burunat, Iballa; Toiviainen, Petri; Nandi, Asoke K; Brattico, Elvira; Ristaniemi, Tapani

2014-02-15

Independent component analysis (ICA) has been often used to decompose fMRI data mostly for the resting-state, block and event-related designs due to its outstanding advantage. For fMRI data during free-listening experiences, only a few exploratory studies applied ICA. For processing the fMRI data elicited by 512-s modern tango, a FFT based band-pass filter was used to further pre-process the fMRI data to remove sources of no interest and noise. Then, a fast model order selection method was applied to estimate the number of sources. Next, both individual ICA and group ICA were performed. Subsequently, ICA components whose temporal courses were significantly correlated with musical features were selected. Finally, for individual ICA, common components across majority of participants were found by diffusion map and spectral clustering. The extracted spatial maps (by the new ICA approach) common across most participants evidenced slightly right-lateralized activity within and surrounding the auditory cortices. Meanwhile, they were found associated with the musical features. Compared with the conventional ICA approach, more participants were found to have the common spatial maps extracted by the new ICA approach. Conventional model order selection methods underestimated the true number of sources in the conventionally pre-processed fMRI data for the individual ICA. Pre-processing the fMRI data by using a reasonable band-pass digital filter can greatly benefit the following model order selection and ICA with fMRI data by naturalistic paradigms. Diffusion map and spectral clustering are straightforward tools to find common ICA spatial maps. Copyright © 2013 Elsevier B.V. All rights reserved.

Adaptive Controller for Compact Fourier Transform Spectrometer with Space Applications

NASA Astrophysics Data System (ADS)

Keymeulen, D.; Yiu, P.; Berisford, D. F.; Hand, K. P.; Carlson, R. W.; Conroy, M.

2014-12-01

Here we present noise mitigation techniques developed as part of an adaptive controller for a very compact Compositional InfraRed Interferometric Spectrometer (CIRIS) implemented on a stand-alone field programmable gate array (FPGA) architecture with emphasis on space applications in high radiation environments such as Europa. CIRIS is a novel take on traditional Fourier Transform Spectrometers (FTS) and replaces linearly moving mirrors (characteristic of Michelson interferometers) with a constant-velocity rotating refractor to variably phase shift and alter the path length of incoming light. The design eschews a monochromatic reference laser typically used for sampling clock generation and instead utilizes constant time-sampling via internally generated clocks. This allows for a compact and robust device, making it ideal for spaceborne measurements in the near-IR to thermal-IR band (2-12 µm) on planetary exploration missions. The instrument's embedded microcontroller is implemented on a VIRTEX-5 FPGA and a PowerPC with the aim of sampling the instrument's detector and optical rotary encoder in order to construct interferograms. Subsequent onboard signal processing provides spectral immunity from the noise effects introduced by the compact design's removal of a reference laser and by the radiation encountered during space flight to destinations such as Europa. A variety of signal processing techniques including resampling, radiation peak removal, Fast Fourier Transform (FFT), spectral feature alignment, dispersion correction and calibration processes are applied to compose the sample spectrum in real-time with signal-to-noise-ratio (SNR) performance comparable to laser-based FTS designs in radiation-free environments. The instrument's FPGA controller is demonstrated with the FTS to characterize its noise mitigation techniques and highlight its suitability for implementation in space systems.

Interferometric visualization and demodulation method for measuring quasi-static strain in fiber Bragg grating sensors by a simple rotating etalon filter

NASA Astrophysics Data System (ADS)

Rocco, Alessandra S.; Coppola, Giuseppe; Ferraro, Pietro; Foti, Giuseppe; Iodice, Mario

2004-09-01

Optical fiber sensors are the ideal system to monitor "smart structures" and on-site/real time stress measurements: they can be in fact easily embedded or attached to the structures under test and are not affected by electro- magnetic noise. In particular a signal from a Fiber Bragg grating sensor (FBG) may be processed such that its information remains immune to optical power fluctuations. Different interrogation methods can be used for reading out Bragg wavelength shifts. In this paper we propose a very simple interferometric method for interrogating FBG sensors, based on bi-polished silicon sample acting like an etalon tuneable filter (ETF). The Bragg wavelength shift can be evaluated by analyzing the spectral response of signal reflected by the FBG sensor and filtered by the ETF that is continuously and rapidly tuned. Tuning was obtained by rotating the ETF. Variation in the strain at the FBG causes a phase shift in the analyzed signal. The overall spectral signal, collected with time, consists in an interferometric figure which finesse and fringe contrast depending on the geometrical sizes and facets reflectivity of the silicon sample. The fringe pattern, expressed by the Airy's formula, depends on the wavelength l of the incident radiation and on the angle of incidence. The phase of fringe pattern can be retrieved by a standard FFT method giving quantitative measurements of the quasi-static strain variation sensed by the FBG. In this way, the method allows a valuable visualization of the time-evolution of the incremental strain applied to the FBG. Principle of functioning of this method is described and first results obtained employing such configuration, are reported.

Propagation Characteristics Of Weakly Guiding Optical Fibers

NASA Technical Reports Server (NTRS)

Manshadi, Farzin

1992-01-01

Report discusses electromagnetic propagation characteristics of weakly guiding optical-fiber structures having complicated shapes with cross-sectional dimensions of order of wavelength. Coupling, power-dividing, and transition dielectric-waveguide structures analyzed. Basic data computed by scalar-wave, fast-Fourier-transform (SW-FFT) technique, based on numerical solution of scalar version of wave equation by forward-marching fast-Fourier-transform method.

Power Aware Signal Processing Environment (PASPE) for PAC/C

DTIC Science & Technology

2003-02-01

vs. FFT Size For our implementation , the Annapolis FFT core was radix-256, and therefore the smallest PN code length that could be processed was the...PN-64. A C- code version of correlate was compared to the FPGA 61 implementation . The results in Figure 68 show that for a PN-1024, the...12a. DISTRIBUTION / AVAILABILITY STATEMENT APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. 12b. DISTRIBUTION CODE 13. ABSTRACT (Maximum

Development of a High-Throughput Microwave Imaging System for Concealed Weapons Detection

DTIC Science & Technology

2016-07-15

hardware. Index Terms—Microwave imaging, multistatic radar, Fast Fourier Transform (FFT). I. INTRODUCTION Near-field microwave imaging is a non-ionizing...configuration, but its computational demands are extreme. Fast Fourier Transform (FFT) imaging has long been used to efficiently construct images sampled with...Simulated image of 25 point scatterers imaged at range 1.5m, with array layout depicted in Fig. 3. Left: image formed with Equation (5) ( Fourier

How Many Grid Points are Required for Time Accurate Simulations Scheme Selection and Scale-Discriminant Stabilization

DTIC Science & Technology

2015-11-24

spatial concerns: ¤ how well are gradients captured? (resolution requirement) spatial/temporal concerns: ¤ dispersion and dissipation error...distribution is unlimited. Gradient Capture vs. Resolution: Single Mode FFT: Solution/Derivative: Convergence: f x( )= sin(x) with x∈[0,2π ] df dx...distribution is unlimited. Gradient Capture vs. Resolution: 
 Multiple Modes FFT: Solution/Derivative: Convergence: 6 __ CD02 __ CD04 __ CD06

FFT-local gravimetric geoid computation

NASA Technical Reports Server (NTRS)

Nagy, Dezso; Fury, Rudolf J.

1989-01-01

Model computations show that changes of sampling interval introduce only 0.3 cm changes, whereas zero padding provides an improvement of more than 5 cm in the fast Fourier transformation (FFT) generated geoid. For the Global Positioning System (GPS) survey of Franklin County, Ohio, the parameters selected as a result of model computations, allow large reduction in local data requirements while still retaining the cm accuracy when tapering and padding is applied. The results are shown in tables.

Using single buffers and data reorganization to implement a multi-megasample fast Fourier transform

NASA Technical Reports Server (NTRS)

Brown, R. D.

1992-01-01

Data ordering in large fast Fourier transforms (FFT's) is both conceptually and implementationally difficult. Discribed here is a method of visualizing data orderings as vectors of address bits, which enables the engineer to use more efficient data orderings and reduce double-buffer memory designs. Also detailed are the difficulties and algorithmic solutions involved in FFT lengths up to 4 megasamples (Msamples) and sample rates up to 80 MHz.

Waveform Design for Multimedia Airborne Networks: Robust Multimedia Data Transmission in Cognitive Radio Networks

DTIC Science & Technology

2011-03-01

at the sensor. According to Candes, Tao and Romberg [1], a small number of random projections of a signal that is compressible is all the...Projection of Signal Transform i. DWT ii. FFT iii. DCT Solve the Minimization problem Reconstruct Signal Channel (AWGN ) De -noise Signal Original...Signal (Noisy) Random Projection of Signal Transform i. DWT ii. FFT iii. DCT Solve the Minimization problem Reconstruct Signal Channel (Noiseless) De

DFT Performance Prediction in FFTW

NASA Astrophysics Data System (ADS)

Gu, Liang; Li, Xiaoming

Fastest Fourier Transform in the West (FFTW) is an adaptive FFT library that generates highly efficient Discrete Fourier Transform (DFT) implementations. It is one of the fastest FFT libraries available and it outperforms many adaptive or hand-tuned DFT libraries. Its success largely relies on the huge search space spanned by several FFT algorithms and a set of compiler generated C code (called codelets) for small size DFTs. FFTW empirically finds the best algorithm by measuring the performance of different algorithm combinations. Although the empirical search works very well for FFTW, the search process does not explain why the best plan found performs best, and the search overhead grows polynomially as the DFT size increases. The opposite of empirical search is model-driven optimization. However, it is widely believed that model-driven optimization is inferior to empirical search and is particularly powerless to solve problems as complex as the optimization of DFT.

Synthesis of fructans by fructosyltransferase from the tuberous roots of Viguiera discolor (Asteraceae).

PubMed

Itaya, N M; Figueiredo-Ribeiro, R C; Buckeridge, M S

1999-04-01

Sucrose:sucrose fructosyltransferase (SST) and fructan:fructan fructosyl-transferase (FFT) activities from crude extracts of tuberous roots of Viguiera discolor growing in a preserved area of cerrado were analyzed in 1995-1996. SST activity was characterized by the synthesis of 1-kestose from sucrose and FFT activity by the production of nystose from 1-kestose. The highest fructan-synthesizing activity was observed during early dormancy (autumn), when both (SST and FFT) activities were high. The increase in synthetic activity seemed to start during the fruiting phase in the summer, when SST activity was higher than in spring. During winter and at the beginning of sprouting, both activities declined. The in vitro synthesis of high molecular mass fructans from sucrose by enzymatic preparations from tuberous roots collected in summer showed that long incubations of up to 288 h produced consistently longer polymers which resembled those found in vivo with respect to chromatographic profiles.

Precise and fast spatial-frequency analysis using the iterative local Fourier transform.

PubMed

Lee, Sukmock; Choi, Heejoo; Kim, Dae Wook

2016-09-19

The use of the discrete Fourier transform has decreased since the introduction of the fast Fourier transform (fFT), which is a numerically efficient computing process. This paper presents the iterative local Fourier transform (ilFT), a set of new processing algorithms that iteratively apply the discrete Fourier transform within a local and optimal frequency domain. The new technique achieves 2¹⁰ times higher frequency resolution than the fFT within a comparable computation time. The method's superb computing efficiency, high resolution, spectrum zoom-in capability, and overall performance are evaluated and compared to other advanced high-resolution Fourier transform techniques, such as the fFT combined with several fitting methods. The effectiveness of the ilFT is demonstrated through the data analysis of a set of Talbot self-images (1280 × 1024 pixels) obtained with an experimental setup using grating in a diverging beam produced by a coherent point source.

Component analyses of urinary nanocrystallites of uric acid stone formers by combination of high-resolution transmission electron microscopy, fast Fourier transformation, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy.

PubMed

Sun, Xin-Yuan; Xue, Jun-Fa; Xia, Zhi-Yue; Ouyang, Jian-Ming

2015-06-01

This study aimed to analyse the components of nanocrystallites in urines of patients with uric acid (UA) stones. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy (HRTEM), fast Fourier transformation (FFT) of HRTEM, and energy dispersive X-ray spectroscopy (EDS) were performed to analyse the components of these nanocrystallites. XRD and FFT showed that the main component of urinary nanocrystallites was UA, which contains a small amount of calcium oxalate monohydrate and phosphates. EDS showed the characteristic absorption peaks of C, O, Ca and P. The formation of UA stones was closely related to a large number of UA nanocrystallites in urine. A combination of HRTEM, FFT, EDS and XRD analyses could be performed accurately to analyse the components of urinary nanocrystallites.

AN OPTIMIZED 64X64 POINT TWO-DIMENSIONAL FAST FOURIER TRANSFORM

NASA Technical Reports Server (NTRS)

Miko, J.

1994-01-01

Scientists at Goddard have developed an efficient and powerful program-- An Optimized 64x64 Point Two-Dimensional Fast Fourier Transform-- which combines the performance of real and complex valued one-dimensional Fast Fourier Transforms (FFT's) to execute a two-dimensional FFT and its power spectrum coefficients. These coefficients can be used in many applications, including spectrum analysis, convolution, digital filtering, image processing, and data compression. The program's efficiency results from its technique of expanding all arithmetic operations within one 64-point FFT; its high processing rate results from its operation on a high-speed digital signal processor. For non-real-time analysis, the program requires as input an ASCII data file of 64x64 (4096) real valued data points. As output, this analysis produces an ASCII data file of 64x64 power spectrum coefficients. To generate these coefficients, the program employs a row-column decomposition technique. First, it performs a radix-4 one-dimensional FFT on each row of input, producing complex valued results. Then, it performs a one-dimensional FFT on each column of these results to produce complex valued two-dimensional FFT results. Finally, the program sums the squares of the real and imaginary values to generate the power spectrum coefficients. The program requires a Banshee accelerator board with 128K bytes of memory from Atlanta Signal Processors (404/892-7265) installed on an IBM PC/AT compatible computer (DOS ver. 3.0 or higher) with at least one 16-bit expansion slot. For real-time operation, an ASPI daughter board is also needed. The real-time configuration reads 16-bit integer input data directly into the accelerator board, operating on 64x64 point frames of data. The program's memory management also allows accumulation of the coefficient results. The real-time processing rate to calculate and accumulate the 64x64 power spectrum output coefficients is less than 17.0 mSec. Documentation is included in the price of the program. Source code is written in C, 8086 Assembly, and Texas Instruments TMS320C30 Assembly Languages. This program is available on a 5.25 inch 360K MS-DOS format diskette. IBM and IBM PC are registered trademarks of International Business Machines. MS-DOS is a registered trademark of Microsoft Corporation.

Behavioral Context of Call Production by Eastern North Pacific Blue Whales

DTIC Science & Technology

2007-01-25

pairs occurring in a repeated song sequence; B calls from a different blue whale are also evident; spectrogram parameters: fast Fourier transform (FFT...Acoustic data were viewed in spectrogram form ( fast Fourier transform [FFT] length 1 s, 80% overlap, Hanning window) to de- termine the presence of calls...dura- tion to song A and B units (Table 2), but the intermit - tent timing clearly distinguishes them from song. Whales producing singular calls were

Canonic FFT flow graphs for real-valued even/odd symmetric inputs

NASA Astrophysics Data System (ADS)

Lao, Yingjie; Parhi, Keshab K.

2017-12-01

Canonic real-valued fast Fourier transform (RFFT) has been proposed to reduce the arithmetic complexity by eliminating redundancies. In a canonic N-point RFFT, the number of signal values at each stage is canonic with respect to the number of signal values, i.e., N. The major advantage of the canonic RFFTs is that these require the least number of butterfly operations and only real datapaths when mapped to architectures. In this paper, we consider the FFT computation whose inputs are not only real but also even/odd symmetric, which indeed lead to the well-known discrete cosine and sine transforms (DCTs and DSTs). Novel algorithms for generating the flow graphs of canonic RFFTs with even/odd symmetric inputs are proposed. It is shown that the proposed algorithms lead to canonic structures with N/2 +1 signal values at each stage for an N-point real even symmetric FFT (REFFT) or N/2 -1 signal values at each stage for an N-point RFFT real odd symmetric FFT (ROFFT). In order to remove butterfly operations, several twiddle factor transformations are proposed in this paper. We also discuss the design of canonic REFFT for any composite length. Performances of the canonic REFFT/ROFFT are also discussed. It is shown that the flow graph of canonic REFFT/ROFFT has less number of interconnections, less butterfly operations, and less twiddle factor operations, compared to prior works.

A Fast Approach to Automatic Detection of Brain Lesions

PubMed Central

Koley, Subhranil; Chakraborty, Chandan; Mainero, Caterina; Fischl, Bruce; Aganj, Iman

2017-01-01

Template matching is a popular approach to computer-aided detection of brain lesions from magnetic resonance (MR) images. The outcomes are often sufficient for localizing lesions and assisting clinicians in diagnosis. However, processing large MR volumes with three-dimensional (3D) templates is demanding in terms of computational resources, hence the importance of the reduction of computational complexity of template matching, particularly in situations in which time is crucial (e.g. emergent stroke). In view of this, we make use of 3D Gaussian templates with varying radii and propose a new method to compute the normalized cross-correlation coefficient as a similarity metric between the MR volume and the template to detect brain lesions. Contrary to the conventional fast Fourier transform (FFT) based approach, whose runtime grows as O(N logN) with the number of voxels, the proposed method computes the cross-correlation in O(N). We show through our experiments that the proposed method outperforms the FFT approach in terms of computational time, and retains comparable accuracy. PMID:29082383

Using the fast fourier transform in binding free energy calculations.

PubMed

Nguyen, Trung Hai; Zhou, Huan-Xiang; Minh, David D L

2018-04-30

According to implicit ligand theory, the standard binding free energy is an exponential average of the binding potential of mean force (BPMF), an exponential average of the interaction energy between the unbound ligand ensemble and a rigid receptor. Here, we use the fast Fourier transform (FFT) to efficiently evaluate BPMFs by calculating interaction energies when rigid ligand configurations from the unbound ensemble are discretely translated across rigid receptor conformations. Results for standard binding free energies between T4 lysozyme and 141 small organic molecules are in good agreement with previous alchemical calculations based on (1) a flexible complex ( R≈0.9 for 24 systems) and (2) flexible ligand with multiple rigid receptor configurations ( R≈0.8 for 141 systems). While the FFT is routinely used for molecular docking, to our knowledge this is the first time that the algorithm has been used for rigorous binding free energy calculations. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

On the inversion of geodetic integrals defined over the sphere using 1-D FFT

NASA Astrophysics Data System (ADS)

García, R. V.; Alejo, C. A.

2005-08-01

An iterative method is presented which performs inversion of integrals defined over the sphere. The method is based on one-dimensional fast Fourier transform (1-D FFT) inversion and is implemented with the projected Landweber technique, which is used to solve constrained least-squares problems reducing the associated 1-D cyclic-convolution error. The results obtained are as precise as the direct matrix inversion approach, but with better computational efficiency. A case study uses the inversion of Hotine’s integral to obtain gravity disturbances from geoid undulations. Numerical convergence is also analyzed and comparisons with respect to the direct matrix inversion method using conjugate gradient (CG) iteration are presented. Like the CG method, the number of iterations needed to get the optimum (i.e., small) error decreases as the measurement noise increases. Nevertheless, for discrete data given over a whole parallel band, the method can be applied directly without implementing the projected Landweber method, since no cyclic convolution error exists.

Design of an MR image processing module on an FPGA chip

NASA Astrophysics Data System (ADS)

Li, Limin; Wyrwicz, Alice M.

2015-06-01

We describe the design and implementation of an image processing module on a single-chip Field-Programmable Gate Array (FPGA) for real-time image processing. We also demonstrate that through graphical coding the design work can be greatly simplified. The processing module is based on a 2D FFT core. Our design is distinguished from previously reported designs in two respects. No off-chip hardware resources are required, which increases portability of the core. Direct matrix transposition usually required for execution of 2D FFT is completely avoided using our newly-designed address generation unit, which saves considerable on-chip block RAMs and clock cycles. The image processing module was tested by reconstructing multi-slice MR images from both phantom and animal data. The tests on static data show that the processing module is capable of reconstructing 128 × 128 images at speed of 400 frames/second. The tests on simulated real-time streaming data demonstrate that the module works properly under the timing conditions necessary for MRI experiments.

Design of an MR image processing module on an FPGA chip

PubMed Central

Li, Limin; Wyrwicz, Alice M.

2015-01-01

We describe the design and implementation of an image processing module on a single-chip Field-Programmable Gate Array (FPGA) for real-time image processing. We also demonstrate that through graphical coding the design work can be greatly simplified. The processing module is based on a 2D FFT core. Our design is distinguished from previously reported designs in two respects. No off-chip hardware resources are required, which increases portability of the core. Direct matrix transposition usually required for execution of 2D FFT is completely avoided using our newly-designed address generation unit, which saves considerable on-chip block RAMs and clock cycles. The image processing module was tested by reconstructing multi-slice MR images from both phantom and animal data. The tests on static data show that the processing module is capable of reconstructing 128 × 128 images at speed of 400 frames/second. The tests on simulated real-time streaming data demonstrate that the module works properly under the timing conditions necessary for MRI experiments. PMID:25909646

Textural analyses of carbon fiber materials by 2D-FFT of complex images obtained by high frequency eddy current imaging (HF-ECI)

NASA Astrophysics Data System (ADS)

Schulze, Martin H.; Heuer, Henning

2012-04-01

Carbon fiber based materials are used in many lightweight applications in aeronautical, automotive, machine and civil engineering application. By the increasing automation in the production process of CFRP laminates a manual optical inspection of each resin transfer molding (RTM) layer is not practicable. Due to the limitation to surface inspection, the quality parameters of multilayer 3 dimensional materials cannot be observed by optical systems. The Imaging Eddy- Current (EC) NDT is the only suitable inspection method for non-resin materials in the textile state that allows an inspection of surface and hidden layers in parallel. The HF-ECI method has the capability to measure layer displacements (misaligned angle orientations) and gap sizes in a multilayer carbon fiber structure. EC technique uses the variation of the electrical conductivity of carbon based materials to obtain material properties. Beside the determination of textural parameters like layer orientation and gap sizes between rovings, the detection of foreign polymer particles, fuzzy balls or visualization of undulations can be done by the method. For all of these typical parameters an imaging classification process chain based on a high resolving directional ECimaging device named EddyCus® MPECS and a 2D-FFT with adapted preprocessing algorithms are developed.

Frequency domain averaging based experimental evaluation of gear fault without tachometer for fluctuating speed conditions

NASA Astrophysics Data System (ADS)

Sharma, Vikas; Parey, Anand

2017-02-01

In the purview of fluctuating speeds, gear fault diagnosis is challenging due to dynamic behavior of forces. Various industrial applications employing gearbox which operate under fluctuating speed conditions. For diagnostics of a gearbox, various vibrations based signal processing techniques viz FFT, time synchronous averaging and time-frequency based wavelet transform, etc. are majorly employed. Most of the time, theories about data or computational complexity limits the use of these methods. In order to perform fault diagnosis of a gearbox for fluctuating speeds, frequency domain averaging (FDA) of intrinsic mode functions (IMFs) after their dynamic time warping (DTW) has been done in this paper. This will not only attenuate the effect of fluctuating speeds but will also extract the weak fault feature those masked in vibration signal. Experimentally signals were acquired from Drivetrain Diagnostic Simulator for different gear health conditions i.e., healthy pinion, pinion with tooth crack, chipped tooth and missing tooth and were analyzed for the different fluctuating profiles of speed. Kurtosis was calculated for warped IMFs before DTW and after DTW of the acquired vibration signals. Later on, the application of FDA highlights the fault frequencies present in the FFT of faulty gears. The result suggests that proposed approach is more effective towards the fault diagnosing with fluctuating speed.

An Analysis of Principals' Perceptions of the Primary Teaching Evaluation System Used in Eight U.S. States

ERIC Educational Resources Information Center

Dodson, Richard L.

2017-01-01

This research examines how public school principals in eight U.S. states perceive their teacher evaluation systems, which are based on Charlotte Danielson's Framework for Teaching (FfT). States were selected to represent high, middle, and low scorers in the annual "Education Week" "Quality Counts" report (Education Week, 2016).…

Detection of a Low Power Communication Signal in the Presence of a Strong Co-Channel TV Broadcast Interference Using a Kalman Filter

DTIC Science & Technology

2014-12-01

Australia. These two standards have dominated the TV market for almost 60 years. With the advent of the digital age, NTSC and PAL have lost considerable...Sk(ell, Ktps(ell,:)+1)=-2; % TPS carriers with -2 end % FFT (one based) indices for data (Sdata), pilots (Spilots), TPS ( Stps ) , % nulls

Synthesis, Analysis, and Processing of Fractal Signals

DTIC Science & Technology

1991-10-01

coordinator in hockey, squash, volleyball, and softball, but also for reminding me periodically that 1/f noise can exist outside a computer. More...similar signals as Fourier-based representations are for stationary and periodic signals. Furthermore, because wave- let transformations can be...and periodic signals. Furthermore, just as the discovery of fast Fourier transform (FFT) algorithms dramatically increased the viability the Fourier

Microstructural effects on damage evolution in shocked copper polycrystals

DOE PAGES

Lieberman, Evan J.; Lebensohn, Ricardo A.; Menasche, David B.; ...

2016-07-01

Three-dimensional crystal orientation fields of a copper sample, characterized before and after shock loading using High Energy Diffraction Microscopy, are used for input and validation of direct numerical simulations using a Fast Fourier Transform (FFT)-based micromechanical model. The locations of the voids determined by X-ray tomography in the incipiently-spalled sample, predominantly found near grain boundaries, were traced back and registered to the pre-shocked microstructural image. Using FFT-based simulations with direct input from the initial microstructure, micromechanical fields at the shock peak stress were obtained. Statistical distributions of micromechanical fields restricted to grain boundaries that developed voids after the shock aremore » compared with corresponding distributions for all grain boundaries. Distributions of conventional measures of stress and strain (deviatoric and mean components) do not show correlation with the locations of voids in the post-shocked image. Neither does stress triaxiality, surface traction or grain boundary inclination angle, in a significant way. On the other hand, differences in Taylor factor and accumulated plastic work across grain boundaries do correlate with the occurrence of damage. As a result, damage was observed to take place preferentially at grain boundaries adjacent to grains having very different plastic response.« less

Proceedings: Sisal `93

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feo, J.T.

1993-10-01

This report contain papers on: Programmability and performance issues; The case of an iterative partial differential equation solver; Implementing the kernal of the Australian Region Weather Prediction Model in Sisal; Even and quarter-even prime length symmetric FFTs and their Sisal Implementations; Top-down thread generation for Sisal; Overlapping communications and computations on NUMA architechtures; Compiling technique based on dataflow analysis for funtional programming language Valid; Copy elimination for true multidimensional arrays in Sisal 2.0; Increasing parallelism for an optimization that reduces copying in IF2 graphs; Caching in on Sisal; Cache performance of Sisal Vs. FORTRAN; FFT algorithms on a shared-memory multiprocessor;more » A parallel implementation of nonnumeric search problems in Sisal; Computer vision algorithms in Sisal; Compilation of Sisal for a high-performance data driven vector processor; Sisal on distributed memory machines; A virtual shared addressing system for distributed memory Sisal; Developing a high-performance FFT algorithm in Sisal for a vector supercomputer; Implementation issues for IF2 on a static data-flow architechture; and Systematic control of parallelism in array-based data-flow computation. Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database.« less

Method for Pre-Conditioning a Measured Surface Height Map for Model Validation

NASA Technical Reports Server (NTRS)

Sidick, Erkin

2012-01-01

This software allows one to up-sample or down-sample a measured surface map for model validation, not only without introducing any re-sampling errors, but also eliminating the existing measurement noise and measurement errors. Because the re-sampling of a surface map is accomplished based on the analytical expressions of Zernike-polynomials and a power spectral density model, such re-sampling does not introduce any aliasing and interpolation errors as is done by the conventional interpolation and FFT-based (fast-Fourier-transform-based) spatial-filtering method. Also, this new method automatically eliminates the measurement noise and other measurement errors such as artificial discontinuity. The developmental cycle of an optical system, such as a space telescope, includes, but is not limited to, the following two steps: (1) deriving requirements or specs on the optical quality of individual optics before they are fabricated through optical modeling and simulations, and (2) validating the optical model using the measured surface height maps after all optics are fabricated. There are a number of computational issues related to model validation, one of which is the "pre-conditioning" or pre-processing of the measured surface maps before using them in a model validation software tool. This software addresses the following issues: (1) up- or down-sampling a measured surface map to match it with the gridded data format of a model validation tool, and (2) eliminating the surface measurement noise or measurement errors such that the resulted surface height map is continuous or smoothly-varying. So far, the preferred method used for re-sampling a surface map is two-dimensional interpolation. The main problem of this method is that the same pixel can take different values when the method of interpolation is changed among the different methods such as the "nearest," "linear," "cubic," and "spline" fitting in Matlab. The conventional, FFT-based spatial filtering method used to eliminate the surface measurement noise or measurement errors can also suffer from aliasing effects. During re-sampling of a surface map, this software preserves the low spatial-frequency characteristic of a given surface map through the use of Zernike-polynomial fit coefficients, and maintains mid- and high-spatial-frequency characteristics of the given surface map by the use of a PSD model derived from the two-dimensional PSD data of the mid- and high-spatial-frequency components of the original surface map. Because this new method creates the new surface map in the desired sampling format from analytical expressions only, it does not encounter any aliasing effects and does not cause any discontinuity in the resultant surface map.

A Randomized Clinical Trial Comparing Family-Focused Treatment and Individual Supportive Therapy for Depression in Childhood and Early Adolescence.

PubMed

Tompson, Martha C; Sugar, Catherine A; Langer, David A; Asarnow, Joan R

2017-06-01

Despite the morbidity and negative outcomes associated with early-onset depression, few studies have examined the efficacy of psychosocial treatment for depressive disorders during childhood. Integrating family in treatment could have particularly salutary effects during this developmental period. This trial compared immediate posttreatment effects of family-focused treatment for childhood depression (FFT-CD) with those of individual supportive psychotherapy (IP) for children 7 to 14 years old with depressive disorders. Children were randomized to 15 sessions of FFT-CD (n = 67) or IP (n = 67) over 4 months. The primary treatment outcome was adequate clinical depression response, defined as at least a 50% decrease in score on the Children's Depression Rating Scale-Revised (CDRS-R). Additional outcomes included patient-centered outcomes (parent- and child-reported treatment satisfaction), remission (defined as CDRS-R score ≤28), change in continuous CDRS-R score, and change in child and parent reports of depressive and non-depressive symptoms and social adjustment. Significant improvement was evident across groups for depressive and non-depressive symptoms, global response, and functioning and social adjustment. Compared with children randomized to IP, children randomized to FFT-CD showed higher rates of adequate clinical depression response (77.7% versus 59.9%; number needed to treat = 5.72; odds ratio 2.29; 95% CI 1.001-5.247; t = 1.97, p = .0498). Across treatments, families reported high satisfaction; compared with IP families, FFT-CD families reported greater knowledge and skills for managing depression. There were no significant differences between treatment arms on secondary outcomes. Results support the value of psychosocial intervention, emphasize the important role that families play, and highlight the potential for FFT-CD for supporting recovery in children with depression. Clinical trial registration information-Systems of Support Study for Childhood Depression; http://clinicaltrials.gov; NCT01159041. Copyright © 2017 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

Vegetation community composition in wetlands created following oil sand mining in Alberta, Canada.

PubMed

Roy, Marie-Claude; Foote, Lee; Ciborowski, Jan J H

2016-05-01

Reclaiming wetlands following open pit mining for industrial oil sand extraction is challenging due to the physical and chemical conditions of the post-mined landscape. The aim of our study was to examine and compare the influence of oil sands process water (OSPW) and material (fine fluid tails or FFT) on the plant community composition of created wetlands. Compared to created-unamended and natural wetlands, the created wetlands amended with OSPW and/or FFT (created-tailings wetlands) had significantly higher water salinity, conductivity, dissolved oxygen concentration and lower oxidative-reductive potential. Water chemistry parameters of created-unamended did not differ significantly from those of natural wetlands. The sediment of created wetlands had significantly less moisture, total nitrogen, and organic content than the natural wetlands. The application of OSPW/FFT in created wetlands will likely lead to initial vegetation composition atypical of natural regional wetlands. For the objective of reclaiming vegetation composition to the status of natural regional wetlands, unamended wetlands were the best reclamation option, based on the physical and chemical parameters measured. Despite being the favored reclamation option, created-unamended wetlands' physical and chemical characteristics remain atypical of natural wetlands. Most significantly, the basin morphometry of created wetlands was significantly different from that of naturally-formed wetlands in the region, and this appears to partly explain difference in vegetation composition. We also demonstrate that species richness alone is not a useful measure in wetland monitoring. Instead, plant community composition is a better indicator of wetland conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Radio Implementation of a Testbed For Cognitive Radio Source Localization Using USRPS and GNU Radio

DTIC Science & Technology

2014-09-01

average received energy F FFT vector size FS sampling rate g gain h channel attenuation H0 hypothesis 0 H1 hypothesis 1 I in-phase L packet size...Amplitude Modulation (QAM)). The baseband signal is then sent to the USRP in the form of in-phase (I) and quadrature (Q) complex samples to be further... sampling rate defines the bandwidth of the transmitted signal, which must be less than the channel separation to give non- overlapping channels. The FFT

Gabor fusion master slave optical coherence tomography

PubMed Central

Cernat, Ramona; Bradu, Adrian; Israelsen, Niels Møller; Bang, Ole; Rivet, Sylvain; Keane, Pearse A.; Heath, David-Garway; Rajendram, Ranjan; Podoleanu, Adrian

2017-01-01

This paper describes the application of the Gabor filtering protocol to a Master/Slave (MS) swept source optical coherence tomography (SS)-OCT system at 1300 nm. The MS-OCT system delivers information from selected depths, a property that allows operation similar to that of a time domain OCT system, where dynamic focusing is possible. The Gabor filtering processing following collection of multiple data from different focus positions is different from that utilized by a conventional swept source OCT system using a Fast Fourier transform (FFT) to produce an A-scan. Instead of selecting the bright parts of A-scans for each focus position, to be placed in a final B-scan image (or in a final volume), and discarding the rest, the MS principle can be employed to advantageously deliver signal from the depths within each focus range only. The MS procedure is illustrated on creating volumes of data of constant transversal resolution from a cucumber and from an insect by repeating data acquisition for 4 different focus positions. In addition, advantage is taken from the tolerance to dispersion of the MS principle that allows automatic compensation for dispersion created by layers above the object of interest. By combining the two techniques, Gabor filtering and Master/Slave, a powerful imaging instrument is demonstrated. The master/slave technique allows simultaneous display of three categories of images in one frame: multiple depth en-face OCT images, two cross-sectional OCT images and a confocal like image obtained by averaging the en-face ones. We also demonstrate the superiority of MS-OCT over its FFT based counterpart when used with a Gabor filtering OCT instrument in terms of the speed of assembling the fused volume. For our case, we show that when more than 4 focus positions are required to produce the final volume, MS is faster than the conventional FFT based procedure. PMID:28270987

Detection of small-amplitude periodic surface pressure fluctuation by pressure-sensitive paint measurements using frequency-domain methods

NASA Astrophysics Data System (ADS)

Noda, Takahiro; Nakakita, Kazuyki; Wakahara, Masaki; Kameda, Masaharu

2018-06-01

Image measurement using pressure-sensitive paint (PSP) is an effective tool for analyzing the unsteady pressure field on the surface of a body in a low-speed air flow, which is associated with wind noise. In this study, the surface pressure fluctuation due to the tonal trailing edge (TE) noise for a two-dimensional NACA 0012 airfoil was quantitatively detected using a porous anodized aluminum PSP (AA-PSP). The emission from the PSP upon illumination by a blue laser diode was captured using a 12-bit high-speed complementary metal-oxide-semiconductor (CMOS) camera. The intensities of the captured images were converted to pressures using a standard intensity-based method. Three image-processing methods based on the fast Fourier transform (FFT) were tested to determine their efficiency in improving the signal-to-noise ratio (SNR) of the unsteady PSP data. In addition to two fundamental FFT techniques (the full data and ensemble averaging FFTs), a technique using the coherent output power (COP), which involves the cross correlation between the PSP data and the signal measured using a pointwise sound-level meter, was tested. Preliminary tests indicated that random photon shot noise dominates the intensity fluctuations in the captured PSP emissions above 200 Hz. Pressure fluctuations associated with the TE noise, whose dominant frequency is approximately 940 Hz, were successfully measured by analyzing 40,960 sequential PSP images recorded at 10 kfps. Quantitative validation using the power spectrum indicates that the COP technique is the most effective method of identification of the pressure fluctuation directly related to TE noise. It is possible to distinguish power differences with a resolution of 10 Pa^2 (4 Pa in amplitude) when the COP was employed without use of another wind-off data. This resolution cannot be achieved by the ensemble averaging FFT because of an insufficient elimination of the background noise.

Knowledge-based tracking algorithm

NASA Astrophysics Data System (ADS)

Corbeil, Allan F.; Hawkins, Linda J.; Gilgallon, Paul F.

1990-10-01

This paper describes the Knowledge-Based Tracking (KBT) algorithm for which a real-time flight test demonstration was recently conducted at Rome Air Development Center (RADC). In KBT processing, the radar signal in each resolution cell is thresholded at a lower than normal setting to detect low RCS targets. This lower threshold produces a larger than normal false alarm rate. Therefore, additional signal processing including spectral filtering, CFAR and knowledge-based acceptance testing are performed to eliminate some of the false alarms. TSC's knowledge-based Track-Before-Detect (TBD) algorithm is then applied to the data from each azimuth sector to detect target tracks. In this algorithm, tentative track templates are formed for each threshold crossing and knowledge-based association rules are applied to the range, Doppler, and azimuth measurements from successive scans. Lastly, an M-association out of N-scan rule is used to declare a detection. This scan-to-scan integration enhances the probability of target detection while maintaining an acceptably low output false alarm rate. For a real-time demonstration of the KBT algorithm, the L-band radar in the Surveillance Laboratory (SL) at RADC was used to illuminate a small Cessna 310 test aircraft. The received radar signal wa digitized and processed by a ST-100 Array Processor and VAX computer network in the lab. The ST-100 performed all of the radar signal processing functions, including Moving Target Indicator (MTI) pulse cancelling, FFT Doppler filtering, and CFAR detection. The VAX computers performed the remaining range-Doppler clustering, beamsplitting and TBD processing functions. The KBT algorithm provided a 9.5 dB improvement relative to single scan performance with a nominal real time delay of less than one second between illumination and display.

An integrated workflow for robust alignment and simplified quantitative analysis of NMR spectrometry data.

PubMed

Vu, Trung N; Valkenborg, Dirk; Smets, Koen; Verwaest, Kim A; Dommisse, Roger; Lemière, Filip; Verschoren, Alain; Goethals, Bart; Laukens, Kris

2011-10-20

Nuclear magnetic resonance spectroscopy (NMR) is a powerful technique to reveal and compare quantitative metabolic profiles of biological tissues. However, chemical and physical sample variations make the analysis of the data challenging, and typically require the application of a number of preprocessing steps prior to data interpretation. For example, noise reduction, normalization, baseline correction, peak picking, spectrum alignment and statistical analysis are indispensable components in any NMR analysis pipeline. We introduce a novel suite of informatics tools for the quantitative analysis of NMR metabolomic profile data. The core of the processing cascade is a novel peak alignment algorithm, called hierarchical Cluster-based Peak Alignment (CluPA). The algorithm aligns a target spectrum to the reference spectrum in a top-down fashion by building a hierarchical cluster tree from peak lists of reference and target spectra and then dividing the spectra into smaller segments based on the most distant clusters of the tree. To reduce the computational time to estimate the spectral misalignment, the method makes use of Fast Fourier Transformation (FFT) cross-correlation. Since the method returns a high-quality alignment, we can propose a simple methodology to study the variability of the NMR spectra. For each aligned NMR data point the ratio of the between-group and within-group sum of squares (BW-ratio) is calculated to quantify the difference in variability between and within predefined groups of NMR spectra. This differential analysis is related to the calculation of the F-statistic or a one-way ANOVA, but without distributional assumptions. Statistical inference based on the BW-ratio is achieved by bootstrapping the null distribution from the experimental data. The workflow performance was evaluated using a previously published dataset. Correlation maps, spectral and grey scale plots show clear improvements in comparison to other methods, and the down-to-earth quantitative analysis works well for the CluPA-aligned spectra. The whole workflow is embedded into a modular and statistically sound framework that is implemented as an R package called "speaq" ("spectrum alignment and quantitation"), which is freely available from http://code.google.com/p/speaq/.

Feasibility study, software design, layout and simulation of a two-dimensional Fast Fourier Transform machine for use in optical array interferometry

NASA Technical Reports Server (NTRS)

Boriakoff, Valentin

1994-01-01

The goal of this project was the feasibility study of a particular architecture of a digital signal processing machine operating in real time which could do in a pipeline fashion the computation of the fast Fourier transform (FFT) of a time-domain sampled complex digital data stream. The particular architecture makes use of simple identical processors (called inner product processors) in a linear organization called a systolic array. Through computer simulation the new architecture to compute the FFT with systolic arrays was proved to be viable, and computed the FFT correctly and with the predicted particulars of operation. Integrated circuits to compute the operations expected of the vital node of the systolic architecture were proven feasible, and even with a 2 micron VLSI technology can execute the required operations in the required time. Actual construction of the integrated circuits was successful in one variant (fixed point) and unsuccessful in the other (floating point).

Design and implementation in VHDL code of the two-dimensional fast Fourier transform for frequency filtering, convolution and correlation operations

NASA Astrophysics Data System (ADS)

Vilardy, Juan M.; Giacometto, F.; Torres, C. O.; Mattos, L.

2011-01-01

The two-dimensional Fast Fourier Transform (FFT 2D) is an essential tool in the two-dimensional discrete signals analysis and processing, which allows developing a large number of applications. This article shows the description and synthesis in VHDL code of the FFT 2D with fixed point binary representation using the programming tool Simulink HDL Coder of Matlab; showing a quick and easy way to handle overflow, underflow and the creation registers, adders and multipliers of complex data in VHDL and as well as the generation of test bench for verification of the codes generated in the ModelSim tool. The main objective of development of the hardware architecture of the FFT 2D focuses on the subsequent completion of the following operations applied to images: frequency filtering, convolution and correlation. The description and synthesis of the hardware architecture uses the XC3S1200E family Spartan 3E FPGA from Xilinx Manufacturer.

Big Data in Reciprocal Space: Sliding Fast Fourier Transforms for Determining Periodicity

DOE PAGES

Vasudevan, Rama K.; Belianinov, Alex; Gianfrancesco, Anthony G.; ...

2015-03-03

Significant advances in atomically resolved imaging of crystals and surfaces have occurred in the last decade allowing unprecedented insight into local crystal structures and periodicity. Yet, the analysis of the long-range periodicity from the local imaging data, critical to correlation of functional properties and chemistry to the local crystallography, remains a challenge. Here, we introduce a Sliding Fast Fourier Transform (FFT) filter to analyze atomically resolved images of in-situ grown La5/8Ca3/8MnO3 films. We demonstrate the ability of sliding FFT algorithm to differentiate two sub-lattices, resulting from a mixed-terminated surface. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) of themore » Sliding FFT dataset reveal the distinct changes in crystallography, step edges and boundaries between the multiple sub-lattices. The method is universal for images with any periodicity, and is especially amenable to atomically resolved probe and electron-microscopy data for rapid identification of the sub-lattices present.« less

Big Data in Reciprocal Space: Sliding Fast Fourier Transforms for Determining Periodicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasudevan, Rama K.; Belianinov, Alex; Gianfrancesco, Anthony G.

Significant advances in atomically resolved imaging of crystals and surfaces have occurred in the last decade allowing unprecedented insight into local crystal structures and periodicity. Yet, the analysis of the long-range periodicity from the local imaging data, critical to correlation of functional properties and chemistry to the local crystallography, remains a challenge. Here, we introduce a Sliding Fast Fourier Transform (FFT) filter to analyze atomically resolved images of in-situ grown La5/8Ca3/8MnO3 films. We demonstrate the ability of sliding FFT algorithm to differentiate two sub-lattices, resulting from a mixed-terminated surface. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) of themore » Sliding FFT dataset reveal the distinct changes in crystallography, step edges and boundaries between the multiple sub-lattices. The method is universal for images with any periodicity, and is especially amenable to atomically resolved probe and electron-microscopy data for rapid identification of the sub-lattices present.« less

A combined finite element-boundary integral formulation for solution of two-dimensional scattering problems via CGFFT. [Conjugate Gradient Fast Fourier Transformation

NASA Technical Reports Server (NTRS)

Collins, Jeffery D.; Volakis, John L.; Jin, Jian-Ming

1990-01-01

A new technique is presented for computing the scattering by 2-D structures of arbitrary composition. The proposed solution approach combines the usual finite element method with the boundary-integral equation to formulate a discrete system. This is subsequently solved via the conjugate gradient (CG) algorithm. A particular characteristic of the method is the use of rectangular boundaries to enclose the scatterer. Several of the resulting boundary integrals are therefore convolutions and may be evaluated via the fast Fourier transform (FFT) in the implementation of the CG algorithm. The solution approach offers the principal advantage of having O(N) memory demand and employs a 1-D FFT versus a 2-D FFT as required with a traditional implementation of the CGFFT algorithm. The speed of the proposed solution method is compared with that of the traditional CGFFT algorithm, and results for rectangular bodies are given and shown to be in excellent agreement with the moment method.

A combined finite element and boundary integral formulation for solution via CGFFT of 2-dimensional scattering problems

NASA Technical Reports Server (NTRS)

Collins, Jeffery D.; Volakis, John L.

1989-01-01

A new technique is presented for computing the scattering by 2-D structures of arbitrary composition. The proposed solution approach combines the usual finite element method with the boundary integral equation to formulate a discrete system. This is subsequently solved via the conjugate gradient (CG) algorithm. A particular characteristic of the method is the use of rectangular boundaries to enclose the scatterer. Several of the resulting boundary integrals are therefore convolutions and may be evaluated via the fast Fourier transform (FFT) in the implementation of the CG algorithm. The solution approach offers the principle advantage of having O(N) memory demand and employs a 1-D FFT versus a 2-D FFT as required with a traditional implementation of the CGFFT algorithm. The speed of the proposed solution method is compared with that of the traditional CGFFT algorithm, and results for rectangular bodies are given and shown to be in excellent agreement with the moment method.

Fading channel simulator

DOEpatents

Argo, Paul E.; Fitzgerald, T. Joseph

1993-01-01

Fading channel effects on a transmitted communication signal are simulated with both frequency and time variations using a channel scattering function to affect the transmitted signal. A conventional channel scattering function is converted to a series of channel realizations by multiplying the square root of the channel scattering function by a complex number of which the real and imaginary parts are each independent variables. The two-dimensional inverse-FFT of this complex-valued channel realization yields a matrix of channel coefficients that provide a complete frequency-time description of the channel. The transmitted radio signal is segmented to provide a series of transmitted signal and each segment is subject to FFT to generate a series of signal coefficient matrices. The channel coefficient matrices and signal coefficient matrices are then multiplied and subjected to inverse-FFT to output a signal representing the received affected radio signal. A variety of channel scattering functions can be used to characterize the response of a transmitter-receiver system to such atmospheric effects.

Electro-Optical Imaging Fourier-Transform Spectrometer

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin; Zhou, Hanying

2006-01-01

An electro-optical (E-O) imaging Fourier-transform spectrometer (IFTS), now under development, is a prototype of improved imaging spectrometers to be used for hyperspectral imaging, especially in the infrared spectral region. Unlike both imaging and non-imaging traditional Fourier-transform spectrometers, the E-O IFTS does not contain any moving parts. Elimination of the moving parts and the associated actuator mechanisms and supporting structures would increase reliability while enabling reductions in size and mass, relative to traditional Fourier-transform spectrometers that offer equivalent capabilities. Elimination of moving parts would also eliminate the vibrations caused by the motions of those parts. Figure 1 schematically depicts a traditional Fourier-transform spectrometer, wherein a critical time delay is varied by translating one the mirrors of a Michelson interferometer. The time-dependent optical output is a periodic representation of the input spectrum. Data characterizing the input spectrum are generated through fast-Fourier-transform (FFT) post-processing of the output in conjunction with the varying time delay.

Intermittent 20-HZ-photic stimulation leads to a uniform reduction of alpha-global field power in healthy volunteers.

PubMed

Rau, R; Raschka, C; Koch, H J

2001-01-01

19-channel-EEGs were recorded from scalp surface of 30 healthy subjects (16m, 14f, mean age: 34 ys, SD: 11.7 ys) at rest and under IPS (Intermittent Photic Stimulation) at rates of 5, 10 and 20 Hertz (Hz). Digitalized data underwent spectral analysis with fast fourier transfomation (FFT) yielding the basis for the computation of global field power (GFP). For quantification GFP values in the frequency ranges of 5, 10 and 20 Hz at rest were divided by the corresponding data gained under IPS. While ratios from PDE data showed no stable parameter due to high interindividual variability, ratios of alpha-power turned out to be uniform in all subjects: IPS at 20 Hz always led to a suppression of alpha-power. Dividing alpha-GFP at rest by alpha-GFP under 20-Hz IPS thus resulted in a ratio < 1. We conclude that ratios from GFP data are a stable diagnostic paradigma.

Evaluation of Thymus vulgaris plant extract as an eco-friendly corrosion inhibitor for stainless steel 304 in acidic solution by means of electrochemical impedance spectroscopy, electrochemical noise analysis and density functional theory.

PubMed

Ehsani, A; Mahjani, M G; Hosseini, M; Safari, R; Moshrefi, R; Mohammad Shiri, H

2017-03-15

Inhibition performance of Thymus vulgaris plant leaves extract (thyme) as environmentally friendly (green) inhibitor for the corrosion protection of stainless steel (SS) type 304 in 1.0molL -1 HCl solution was studied by potentiodynamic polarization, electrochemical impedance (EIS) and electrochemical noise measurements (EN) techniques. The EN data were analyzed with FFT technique to make the spectral power density plots. The calculations were performed by MATLAB 2014a software. Geometry optimization and calculation of the structural and electronic properties of the molecular system of inhibitor have been carried out using UB3LYP/6-311++G ∗∗ level. Moreover, the results obtained from electrochemical noise analysis were compared with potentiodynamic polarization and electrochemical impedance spectroscopy. All of the used techniques showed positive effect of green inhibitor with increasing inhibitor concentration. Copyright © 2016 Elsevier Inc. All rights reserved.

Distributed optical fiber vibration sensor based on spectrum analysis of Polarization-OTDR system.

PubMed

Zhang, Ziyi; Bao, Xiaoyi

2008-07-07

A fully distributed optical fiber vibration sensor is demonstrated based on spectrum analysis of Polarization-OTDR system. Without performing any data averaging, vibration disturbances up to 5 kHz is successfully demonstrated in a 1km fiber link with 10m spatial resolution. The FFT is performed at each spatial resolution; the relation of the disturbance at each frequency component versus location allows detection of multiple events simultaneously with different and the same frequency components.

112 Gb/s transmission with a directly-modulated laser using FFT-based synthesis of orthogonal PAM and DMT signals.

PubMed

Ling, William A; Matsui, Yasuhiro; Daghighian, Henry M; Lyubomirsky, Ilya

2015-07-27

We report the experimental measurement of 112 Gb/s transmission back-to-back and through 12 km of S-SMF with a single directly-modulated laser (DML) using the novel modulation format Orthogonal PAM-DMT. This work demonstrates a record DML-based 112 Gb/s receiver sensitivity of -7.1 dBm at a BER of 10(-3), outperforming conventional PAM and DMT by approximately 2.5 dB.

A propagation method with adaptive mesh grid based on wave characteristics for wave optics simulation

NASA Astrophysics Data System (ADS)

Tang, Qiuyan; Wang, Jing; Lv, Pin; Sun, Quan

2015-10-01

Propagation simulation method and choosing mesh grid are both very important to get the correct propagation results in wave optics simulation. A new angular spectrum propagation method with alterable mesh grid based on the traditional angular spectrum method and the direct FFT method is introduced. With this method, the sampling space after propagation is not limited to propagation methods no more, but freely alterable. However, choosing mesh grid on target board influences the validity of simulation results directly. So an adaptive mesh choosing method based on wave characteristics is proposed with the introduced propagation method. We can calculate appropriate mesh grids on target board to get satisfying results. And for complex initial wave field or propagation through inhomogeneous media, we can also calculate and set the mesh grid rationally according to above method. Finally, though comparing with theoretical results, it's shown that the simulation result with the proposed method coinciding with theory. And by comparing with the traditional angular spectrum method and the direct FFT method, it's known that the proposed method is able to adapt to a wider range of Fresnel number conditions. That is to say, the method can simulate propagation results efficiently and correctly with propagation distance of almost zero to infinity. So it can provide better support for more wave propagation applications such as atmospheric optics, laser propagation and so on.

A finite element conjugate gradient FFT method for scattering

NASA Technical Reports Server (NTRS)

Collins, Jeffery D.; Zapp, John; Hsa, Chang-Yu; Volakis, John L.

1990-01-01

An extension of a two dimensional formulation is presented for a three dimensional body of revolution. With the introduction of a Fourier expansion of the vector electric and magnetic fields, a coupled two dimensional system is generated and solved via the finite element method. An exact boundary condition is employed to terminate the mesh and the fast fourier transformation (FFT) is used to evaluate the boundary integrals for low O(n) memory demand when an iterative solution algorithm is used. By virtue of the finite element method, the algorithm is applicable to structures of arbitrary material composition. Several improvements to the two dimensional algorithm are also described. These include: (1) modifications for terminating the mesh at circular boundaries without distorting the convolutionality of the boundary integrals; (2) the development of nonproprietary mesh generation routines for two dimensional applications; (3) the development of preprocessors for interfacing SDRC IDEAS with the main algorithm; and (4) the development of post-processing algorithms based on the public domain package GRAFIC to generate two and three dimensional gray level and color field maps.

Design of an MR image processing module on an FPGA chip.

PubMed

Li, Limin; Wyrwicz, Alice M

2015-06-01

We describe the design and implementation of an image processing module on a single-chip Field-Programmable Gate Array (FPGA) for real-time image processing. We also demonstrate that through graphical coding the design work can be greatly simplified. The processing module is based on a 2D FFT core. Our design is distinguished from previously reported designs in two respects. No off-chip hardware resources are required, which increases portability of the core. Direct matrix transposition usually required for execution of 2D FFT is completely avoided using our newly-designed address generation unit, which saves considerable on-chip block RAMs and clock cycles. The image processing module was tested by reconstructing multi-slice MR images from both phantom and animal data. The tests on static data show that the processing module is capable of reconstructing 128×128 images at speed of 400 frames/second. The tests on simulated real-time streaming data demonstrate that the module works properly under the timing conditions necessary for MRI experiments. Copyright © 2015 Elsevier Inc. All rights reserved.

Numerical implementation of non-local polycrystal plasticity using fast Fourier transforms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lebensohn, Ricardo A.; Needleman, Alan

Here, we present the numerical implementation of a non-local polycrystal plasticity theory using the FFT-based formulation of Suquet and co-workers. Gurtin (2002) non-local formulation, with geometry changes neglected, has been incorporated in the EVP-FFT algorithm of Lebensohn et al. (2012). Numerical procedures for the accurate estimation of higher order derivatives of micromechanical fields, required for feedback into single crystal constitutive relations, are identified and applied. A simple case of a periodic laminate made of two fcc crystals with different plastic properties is first used to assess the soundness and numerical stability of the proposed algorithm and to study the influencemore » of different model parameters on the predictions of the non-local model. Different behaviors at grain boundaries are explored, and the one consistent with the micro-clamped condition gives the most pronounced size effect. The formulation is applied next to 3-D fcc polycrystals, illustrating the possibilities offered by the proposed numerical scheme to analyze the mechanical response of polycrystalline aggregates in three dimensions accounting for size dependence arising from plastic strain gradients with reasonable computing times.« less

Numerical implementation of non-local polycrystal plasticity using fast Fourier transforms

DOE PAGES

Lebensohn, Ricardo A.; Needleman, Alan

2016-03-28

Here, we present the numerical implementation of a non-local polycrystal plasticity theory using the FFT-based formulation of Suquet and co-workers. Gurtin (2002) non-local formulation, with geometry changes neglected, has been incorporated in the EVP-FFT algorithm of Lebensohn et al. (2012). Numerical procedures for the accurate estimation of higher order derivatives of micromechanical fields, required for feedback into single crystal constitutive relations, are identified and applied. A simple case of a periodic laminate made of two fcc crystals with different plastic properties is first used to assess the soundness and numerical stability of the proposed algorithm and to study the influencemore » of different model parameters on the predictions of the non-local model. Different behaviors at grain boundaries are explored, and the one consistent with the micro-clamped condition gives the most pronounced size effect. The formulation is applied next to 3-D fcc polycrystals, illustrating the possibilities offered by the proposed numerical scheme to analyze the mechanical response of polycrystalline aggregates in three dimensions accounting for size dependence arising from plastic strain gradients with reasonable computing times.« less

Identifying tumor vascular permeability heterogeneity using reduced encoding techniques

NASA Astrophysics Data System (ADS)

Aref, Michael

We test the hypothesis that the loss of spatial resolution to gain temporal resolution in clinical dynamic contrast enhanced (DCE) magnetic resonance mammography (MRM) causes partial volume effects that yield inaccurate permeability-surface area products (PS = Kp↔t) which results in erroneous diagnostic information and we offer a potential solution using reduced encoding techniques to solve this problem. We compared the PS obtained from DCE MRI at clinical MRI resolutions (2500 x 2500 mum resolution), to that obtained from resolutions analogous to histopathological in plane resolutions (938 x 938 mum and 469 x 469 mum resolution). Secondly, we determined the accuracy of PS obtained from Keyhole, Ṟeduced-encoding I&barbelow;maging by G&barbelow;eneralized-series Ṟeconstruction (RIGR), and Ṯwo-reference RIGR (TRIGR) using high-resolution baseline data (469 x 469 mum resolution) and clinical resolution dynamic data (2500 x 2500 mum resolution). Lastly, we statistically correlated two-compartment model fitting parameters (tumor EES volume fraction, ve, tumor plasma volume fraction, vp, and PS) obtained from DCE MRI at all three resolutions to histopathologically determined tumor diagnosis. In our model, female Sprague Dawley rats with N-ethyl-N-nitrosourea (ENU) induced mammary tumors imaged with fast T1-weighted gradient echo DCE MRI following a Gd-DTPA injection, there is a window of resolutions that detects similar PS "hot spots" compared to those obtained from the clinical imager resolution. The top five PS "hot spots" obtained from 469 mum resolution FFT are statistically different from those at 938 mum resolution FFT, p = 0.0014, and 2500 mum resolution FFT, p < 0.0001. Keyhole when compared with a FFT of similar resolution does not detect PS "hot spots" of similar value, p = 0.0002. PS "hot spots" obtained from RIGR compared to those from FFT are statistically the same value, p = 0.2734, but do not statistically agree on the location of mapped values. The top five Kp↔t/VT "hot spots" and their corresponding ve can statistically differentiate invasive ductal carcinoma from non-invasive papillary carcinoma for the 469 mum and 938 mum resolution, p = 0.0017 and p = 0.0047, respectively, but not for 2500 mum resolution, p = 0.9008.

Practical Sub-Nyquist Sampling via Array-Based Compressed Sensing Receiver Architecture

DTIC Science & Technology

2016-07-10

different array ele- ments at different sub-Nyquist sampling rates. Signal processing inspired by the sparse fast Fourier transform allows for signal...reconstruction algorithms can be computationally demanding (REF). The related sparse Fourier transform algorithms aim to reduce the processing time nec- essary to...compute the DFT of frequency-sparse signals [7]. In particular, the sparse fast Fourier transform (sFFT) achieves processing time better than the

LBA-ECO TG-07 Ground-based Biometry Data at km 83 Site, TapajosNational Forest: 1997

Treesearch

M.M. Keller; M.W. Palace

2009-01-01

A field inventory of trees was conducted in March of 1997 in a logging concession at the Tapajos National Forest, south of Santarem, Para, Brazil. The inventory was conducted by the foresters and technicians of the Tropical Forest Foundation (FFT) and included all trees with diameter at breast height greater than or equal to 35 cm. Four blocks of approximately 100 ha...

Friction and Wear Sciences for a Highly Durable Railgun Weapon

DTIC Science & Technology

2007-10-01

FFT- Based Numerical Methods for Elasto-Plastic Contacts of Nominally Flat Surfaces,” to appear in Journal of Applied Mechanics. 20. Jin, X...is the fusion enthalpy per unit mass, C!"" ~ = and ! ~ is a dimensionless coefficient and 100 ~ !" . Listed in Table I are the material’s...searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments

Strategies and methodologies to develop techniques for computer-assisted analysis of gas phase formation during altitude decompression

NASA Technical Reports Server (NTRS)

Powell, Michael R.; Hall, W. A.

1993-01-01

It would be of operational significance if one possessed a device that would indicate the presence of gas phase formation in the body during hypobaric decompression. Automated analysis of Doppler gas bubble signals has been attempted for 2 decades but with generally unfavorable results, except with surgically implanted transducers. Recently, efforts have intensified with the introduction of low-cost computer programs. Current NASA work is directed towards the development of a computer-assisted method specifically targeted to EVA, and we are most interested in Spencer Grade 4. We note that Spencer Doppler Grades 1 to 3 have increased in the FFT sonogram and spectrogram in the amplitude domain, and the frequency domain is sometimes increased over that created by the normal blood flow envelope. The amplitude perturbations are of very short duration, in both systole and diastole and at random temporal positions. Grade 4 is characteristic in the amplitude domain but with modest increases in the FFT sonogram and spectral frequency power from 2K to 4K over all of the cardiac cycle. Heart valve motion appears to characteristic display signals: (1) the demodulated Doppler signal amplitude is considerably above the Doppler-shifted blow flow signal (even Grade 4); and (2) demodulated Doppler frequency shifts are considerably greater (often several kHz) than the upper edge of the blood flow envelope. Knowledge of these facts will aid in the construction of a real-time, computer-assisted discriminator to eliminate cardiac motion artifacts. There could also exist perturbations in the following: (1) modifications of the pattern of blood flow in accordance with Poiseuille's Law, (2) flow changes with a change in the Reynolds number, (3) an increase in the pulsatility index, and/or (4) diminished diastolic flow or 'runoff.' Doppler ultrasound devices have been constructed with a three-transducer array and a pulsed frequency generator.

Application of DIRI dynamic infrared imaging in reconstructive surgery

NASA Astrophysics Data System (ADS)

Pawlowski, Marek; Wang, Chengpu; Jin, Feng; Salvitti, Matthew; Tenorio, Xavier

2006-04-01

We have developed the BioScanIR System based on QWIP (Quantum Well Infrared Photodetector). Data collected by this sensor are processed using the DIRI (Dynamic Infrared Imaging) algorithms. The combination of DIRI data processing methods with the unique characteristics of the QWIP sensor permit the creation of a new imaging modality capable of detecting minute changes in temperature at the surface of the tissue and organs associated with blood perfusion due to certain diseases such as cancer, vascular disease and diabetes. The BioScanIR System has been successfully applied in reconstructive surgery to localize donor flap feeding vessels (perforators) during the pre-surgical planning stage. The device is also used in post-surgical monitoring of skin flap perfusion. Since the BioScanIR is mobile; it can be moved to the bedside for such monitoring. In comparison to other modalities, the BioScanIR can localize perforators in a single, 20 seconds scan with definitive results available in minutes. The algorithms used include (FFT) Fast Fourier Transformation, motion artifact correction, spectral analysis and thermal image scaling. The BioScanIR is completely non-invasive and non-toxic, requires no exogenous contrast agents and is free of ionizing radiation. In addition to reconstructive surgery applications, the BioScanIR has shown promise as a useful functional imaging modality in neurosurgery, drug discovery in pre-clinical animal models, wound healing and peripheral vascular disease management.

FPGA Based High Speed Data Acquisition System for Electrical Impedance Tomography

PubMed Central

Khan, S; Borsic, A; Manwaring, Preston; Hartov, Alexander; Halter, Ryan

2014-01-01

Electrical Impedance Tomography (EIT) systems are used to image tissue bio-impedance. EIT provides a number of features making it attractive for use as a medical imaging device including the ability to image fast physiological processes (>60 Hz), to meet a range of clinical imaging needs through varying electrode geometries and configurations, to impart only non-ionizing radiation to a patient, and to map the significant electrical property contrasts present between numerous benign and pathological tissues. To leverage these potential advantages for medical imaging, we developed a modular 32 channel data acquisition (DAQ) system using National Instruments’ PXI chassis, along with FPGA, ADC, Signal Generator and Timing and Synchronization modules. To achieve high frame rates, signal demodulation and spectral characteristics of higher order harmonics were computed using dedicated FFT-hardware built into the FPGA module. By offloading the computing onto FPGA, we were able to achieve a reduction in throughput required between the FPGA and PC by a factor of 32:1. A custom designed analog front end (AFE) was used to interface electrodes with our system. Our system is wideband, and capable of acquiring data for input signal frequencies ranging from 100 Hz to 12 MHz. The modular design of both the hardware and software will allow this system to be flexibly configured for the particular clinical application. PMID:24729790

Fast Spatial Resolution Analysis of Quadratic Penalized Least-Squares Image Reconstruction With Separate Real and Imaginary Roughness Penalty: Application to fMRI.

PubMed

Olafsson, Valur T; Noll, Douglas C; Fessler, Jeffrey A

2018-02-01

Penalized least-squares iterative image reconstruction algorithms used for spatial resolution-limited imaging, such as functional magnetic resonance imaging (fMRI), commonly use a quadratic roughness penalty to regularize the reconstructed images. When used for complex-valued images, the conventional roughness penalty regularizes the real and imaginary parts equally. However, these imaging methods sometimes benefit from separate penalties for each part. The spatial smoothness from the roughness penalty on the reconstructed image is dictated by the regularization parameter(s). One method to set the parameter to a desired smoothness level is to evaluate the full width at half maximum of the reconstruction method's local impulse response. Previous work has shown that when using the conventional quadratic roughness penalty, one can approximate the local impulse response using an FFT-based calculation. However, that acceleration method cannot be applied directly for separate real and imaginary regularization. This paper proposes a fast and stable calculation for this case that also uses FFT-based calculations to approximate the local impulse responses of the real and imaginary parts. This approach is demonstrated with a quadratic image reconstruction of fMRI data that uses separate roughness penalties for the real and imaginary parts.

Phase Noise Influence in Long-range Coherent Optical OFDM Systems with Delay Detection, IFFT Multiplexing and FFT Demodulation

NASA Astrophysics Data System (ADS)

Jacobsen, Gunnar; Xu, Tianhua; Popov, Sergei; Sergeyev, Sergey; Zhang, Yimo

2012-12-01

We present a study of the influence of dispersion induced phase noise for CO-OFDM systems using FFT multiplexing/IFFT demultiplexing techniques (software based). The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) including - for the first time to our knowledge - in explicit form the effect of equalization enhanced phase noise (EEPN). This, in turns, leads to an analytic BER specification. Numerical results focus on a CO-OFDM system with 10-25 GS/s QPSK channel modulation. A worst case constellation configuration is identified for the phase noise influence and the resulting BER is compared to the BER of a conventional single channel QPSK system with the same capacity as the CO-OFDM implementation. Results are evaluated as a function of transmission distance. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. For a total capacity of 400 (1000) Gbit/s, the transmission distance to have the BER < 10-2 for the worst case CO-OFDM design is less than 800 and 460 km, respectively, whereas for a single channel QPSK system it is less than 1400 and 560 km.

Hydrolase and fructosyltransferase activities implicated in the accumulation of different chain size fructans in three Asteraceae species.

PubMed

Itaya, Nair M; Asega, Amanda F; Carvalho, Maria Angela M; Figueiredo-Ribeiro, Rita de Cássia L

2007-09-01

Fructans are widely distributed in Asteraceae from floras with seasonal growth and are thought to be involved in drought and freezing tolerance, in addition to storage function. Reserve organs of Vernonia herbacea and Viguiera discolor, from the cerrado, and of the perennial herb Smallanthus sonchifolius, endemic to Andean region, store over 80% inulin, with different DP (35, 150, and 15, respectively). The fructan pattern in Asteraceae species could be explained by characteristics of their respective 1-FFTs. Hydrolases and fructosyltransferases from S. sonchifolius, V. herbacea and V. discolor were analyzed in plants at the same environmental conditions. The higher 1-FEH activities found in the species with lower DP, S. sonchifolius and V. herbacea reinforce the hypothesis of the involvement of 1-FEH in fructan profile and suggest that the high DP fructan of V. discolor is a consequence of the low affinity of its 1-FEH to the native long chain inulin. Long term incubation with sucrose suggested that the affinity of 1-FFT of V. discolor for 1-kestose is low when compared to that of V. herbacea. Indeed 1-FFT from V. discolor was shown to be an hDP 1-FFT, preferring longer inulins as acceptors. Conversely, 1-FFT from V. herbacea seems to have a higher affinity for short fructo-oligosaccharides, including 1-kestose, as acceptor substrates. Differences in fructan enzymes of the three Asteraceae provide new information towards the understanding of fructan metabolism and control of carbon flow between low and high DP fructans.

Modulation of anisotropy in electrospun tissue-engineering scaffolds: Analysis of fiber alignment by the fast Fourier transform

PubMed Central

Ayres, Chantal; Bowlin, Gary L.; Henderson, Scott C.; Taylor, Leander; Shultz, Jackie; Alexander, John; Telemeco, Todd A.; Simpson, David G.

2010-01-01

We describe the use of the fast Fourier transform (FFT) in the measurement of anisotropy in electrospun scaffolds of gelatin as a function of the starting conditions. In electrospinning, fiber alignment and overall scaffold anisotropy can be manipulated by controlling the motion of the collecting mandrel with respect to the source electrospinning solution. By using FFT to assign relative alignment values to an electrospun matrix it is possible to systematically evaluate how different processing variables impact the structure and material properties of a scaffold. Gelatin was suspended at varying concentrations (80, 100, 130, 150 mg/ml) and electrospun from 2,2,2 trifluoroethanol onto rotating mandrels (200–7000 RPM). At each starting concentration, fiber diameter remained constant over a wide range of mandrel RPM. Scaffold anisotropy developed as a function of fiber diameter and mandrel RPM. The induction of varying degrees of anisotropy imparted distinctive material properties to the electrospun scaffolds. The FFT is a rapid method for evaluating fiber alignment in tissue-engineering materials. PMID:16859744

Big data in reciprocal space: Sliding fast Fourier transforms for determining periodicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasudevan, Rama K., E-mail: rvv@ornl.gov; Belianinov, Alex; Baddorf, Arthur P.

Significant advances in atomically resolved imaging of crystals and surfaces have occurred in the last decade allowing unprecedented insight into local crystal structures and periodicity. Yet, the analysis of the long-range periodicity from the local imaging data, critical to correlation of functional properties and chemistry to the local crystallography, remains a challenge. Here, we introduce a Sliding Fast Fourier Transform (FFT) filter to analyze atomically resolved images of in-situ grown La{sub 5/8}Ca{sub 3/8}MnO{sub 3} (LCMO) films. We demonstrate the ability of sliding FFT algorithm to differentiate two sub-lattices, resulting from a mixed-terminated surface. Principal Component Analysis and Independent Component Analysismore » of the Sliding FFT dataset reveal the distinct changes in crystallography, step edges, and boundaries between the multiple sub-lattices. The implications for the LCMO system are discussed. The method is universal for images with any periodicity, and is especially amenable to atomically resolved probe and electron-microscopy data for rapid identification of the sub-lattices present.« less

Precision and Accuracy in PDV and VISAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ambrose, W. P.

2017-08-22

This is a technical report discussing our current level of understanding of a wide and varying distribution of uncertainties in velocity results from Photonic Doppler Velocimetry in its application to gas gun experiments. Using propagation of errors methods with statistical averaging of photon number fluctuation in the detected photocurrent and subsequent addition of electronic recording noise, we learn that the velocity uncertainty in VISAR can be written in closed form. For PDV, the non-linear frequency transform and peak fitting methods employed make propagation of errors estimates notoriously more difficult to write down in closed form expect in the limit ofmore » constant velocity and low time resolution (large analysis-window width). An alternative method of error propagation in PDV is to use Monte Carlo methods with a simulation of the time domain signal based on results from the spectral domain. A key problem for Monte Carlo estimation for an experiment is a correct estimate of that portion of the time-domain noise associated with the peak-fitting region-of-interesting in the spectral domain. Using short-time Fourier transformation spectral analysis and working with the phase dependent real and imaginary parts allows removal of amplitude-noise cross terms that invariably show up when working with correlation-based methods or FFT power spectra. Estimation of the noise associated with a given spectral region of interest is then possible. At this level of progress, we learn that Monte Carlo trials with random recording noise and initial (uncontrolled) phase yields velocity uncertainties that are not as large as those observed. In a search for additional noise sources, a speckleinterference modulation contribution with off axis rays was investigated, and was found to add a velocity variation beyond that from the recording noise (due to random interference between off axis rays), but in our experiments the speckle modulation precision was not as important as the recording noise precision. But from these investigations we do appreciate that the velocity-uncertainty itself has a wide distribution of values that varies with signal-amplitude modulation (is not a single value). To provide a rough rule of thumb for the velocity uncertainty, we computed the average of the relative standard deviation distributions from 60 recorded traces (with distributions of uncertainties roughly between 0.1 % to 1 % in each trace) and found a mean of the distribution of uncertainties for our experiments is not better than 0.4 % at an analysis window width of 5 ns (although for brief intervals it can be as good as 0.1 %). Further imagination and testing may be needed to reveal other possible hydrodynamics-related sources of velocity error in PDV.« less

Paleoclimate Records from New Zealand Maar Lakes, Insights into ENSO Teleconnections and Climatic Events in the South (West) Pacific.

NASA Astrophysics Data System (ADS)

Shulmeister, J.; Nobes, D. C.; Striewski, B.

2008-05-01

The maar craters of the New Zealand Auckland Volcanic Field (36.5°S, 174.5°E) contain some of the highest resolution late-Quaternary paleoclimate records in the Southern Hemisphere. Here we integrate laminae count results from recent drilling in the Hopua Crater with existing records from the nearby Onepoto Crater (Pepper et al., 2004). In total these records cover many thousands of years between the onset of the last glaciation maximum and the early mid-Holocene. The cores are strongly laminated. Individual laminae in both craters are very fine (sub-mm to mm scale) and form couplets which comprise a darker mineralogenic rich layer and a lighter diatomaceous layer. In places these couplets are annual, and may reflect seasonal algal blooms, but in other sections of the record, notably through the late-Glacial and Holocene, the couplets are deposited at inter-annual time scales. Spectral analyses of couplet thickness counts using a fast Fourier transform (FFT) with 64 to 256-year running windows, and a 50 per cent overlap indicate strong spectral power during the LGM and markedly weaker power during both the deglaciation and early Holocene. In fact there is no spectral strength for most of these periods. Three brief (centennial duration) events punctuate this extended period of low spectral power. These occur at c. 16 ka, c. 14.8 ka and during the early Holocene. They display spectral power in the 5-7yr ENSO window and also at longer time intervals that may be consistent with the Pacific Decadal Oscillation. We infer the local switching on (or up) of ENSO and PDO teleconnections and suspect these are embedded in circum-polar circulation changes. In addition to these spectral power episodes, there is a general increase in the number of couplet cycles per century between the deglaciation and the early mid-Holocene. This matches observations from Equador and Peru and suggests that trans-Pacific ENSO responses are in phase between western tropical South America and New Zealand. Pepper, A.C., Shulmeister, J., Nobes. D.C. and P.C. Augustinus. 2004. Possible ENSO signals prior to the last Glacial Maximum, during the deglaciation and the early Holocene from New Zealand. Geophysical Research Letters. 31:L15206. doi 10.1029/ 2004GL020236

Frequency Estimator Performance for a Software-Based Beacon Receiver

NASA Technical Reports Server (NTRS)

Zemba, Michael J.; Morse, Jacquelynne Rose; Nessel, James A.; Miranda, Felix

2014-01-01

As propagation terminals have evolved, their design has trended more toward a software-based approach that facilitates convenient adjustment and customization of the receiver algorithms. One potential improvement is the implementation of a frequency estimation algorithm, through which the primary frequency component of the received signal can be estimated with a much greater resolution than with a simple peak search of the FFT spectrum. To select an estimator for usage in a QV-band beacon receiver, analysis of six frequency estimators was conducted to characterize their effectiveness as they relate to beacon receiver design.

Time/Frequency Relationships for an FFT-Based Acoustic Modem

DTIC Science & Technology

2010-09-01

Jenkins II 5. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000 8. PERFORMING... seawater , and a fluid- like bottom composed of quartz sand. From [11] ............................................18  Table 3.  Transmission loss at the...in St. Andrew’s Bay, Florida [4]. The goal of this sea testing was to observe the effects of natural and man-made noise on network performance in a

Exploitation of Microdoppler and Multiple Scattering Phenomena for Radar Target Recognition

DTIC Science & Technology

2006-08-24

is tested with measurement data. The resulting GPR images demonstrate the effectiveness of the proposed algorithm. INTRODUCTION Subsurface imaging to...utilizes the fast Fourier . transform (FFT) to expedite the imaging GPR. Recently, we re- .... ported a fast and effective SAR-based subsurface ... imaging tech- nique that can provide good resolutions in both the range and cross-range domains I111. Our algorithm differs from Witten’s [91 and Hansen’s

PFS: the Planetary Fourier Spectrometer for Mars Express

NASA Astrophysics Data System (ADS)

Formisano, V.; Grassi, D.; Orfei, R.; Biondi, D.; Mencarelli, E.; Mattana, A.; Nespoli, F.; Maturilli, A.; Giuranna, M.; Rossi, M.; Maggi, M.; Baldetti, P.; Chionchio, G.; Saggin, B.; Angrilli, F.; Bianchini, G.; Piccioni, G.; di Lellis, A.; Cerroni, P.; Capaccioni, F.; Capria, M. T.; Coradini, A.; Fonti, S.; Orofino, V.; Blanco, A.; Colangeli, L.; Palomba, E.; Esposito, F.; Patsaev, D.; Moroz, V.; Zasova, L.; Ignatiev, N.; Khatuntsev, I.; Moshkin, B.; Ekonomov, A.; Grigoriev, A.; Nechaev, V.; Kiselev, A.; Nikolsky, Y.; Gnedykh, V.; Titov, D.; Orleanski, P.; Rataj, M.; Malgoska, M.; Jurewicz, A.; Blecka, M. I.; Hirsh, H.; Arnold, G.; Lellouch, E.; Marten, A.; Encrenaz, T.; Lopez Moreno, J.; Atreya, S., Gobbi, P.

2004-08-01

The Planetary Fourier Spectrometer (PFS) for the Mars Express mission is optimised for atmospheric studies, covering the IR range of 1.2-45 μm in two channels. The apodised spectral resolution is 2 cm-1, while the sampling is 1 cm-1. The FOV is about 2° for the short wavelength (SW) channel and 4° for the long wavelength (LW) channel, corresponding to spatial resolutions of 10 km and 20 km, respectively, from an altitude of 300 km. PFS will also provide unique data on the surface-atmosphere interaction and the mineralogical composition of the surface. It will be the first Fourier spectrometer covering 1-5 μm to orbit the Earth or Mars. The experiment has real-time onboard Fast Fourier Transform (FFT) in order to select the spectral range of interest for data transmission to ground. Measurement of the 15-μm CO2 band is very important. Its profile gives, via a complex temperature-profile retrieval technique, the vertical pressure temperature relation, which is the basis of the global atmospheric study. The SW channel uses a PbSe detector cooled to 200-220K, while the LW channel is based on a pyroelectric (LiTaO3) device working at room temperature. The interferogram is measured at every 150 nm displacement step of the corner cube retroreflectors (corresponding to 600 nm optical path difference) via a laser diode monochromatic interferogram (a sine wave), with the zero crossings controlling the double pendulum motion. PFS will operate for about 1.5 h around the pericentre of the orbit. With a measurement every 10 s, 600 measurements per orbit will be acquired, corresponding to 224 Mbit. Onboard compression will reduce it to 125 Mbit or less, depending on the allocated data volume per day. An important requirement is to observe at all local times in order to include night-side vertical temperature profiles. Total instrument mass is 31.2 kg.

Lightweight multi-carrier modulation for IoT

NASA Astrophysics Data System (ADS)

Hussein, Ahmed F.; Elgala, Hany

2018-01-01

Visible light communications (VLC) based on intensity-modulation with direct-detection (IM/DD) is a promising technology to offer broadband wireless Internet access. A VLC system based on the well-known multi-carrier orthogonal frequency-division multiplexing (OFDM) modulation has the potential to coexist with radio frequency (RF) technologies such as WiFi. Recently, the VLC technology is considered to enable wireless connectivity of resource limited devices, thus enabling the Internet-of-Things (IoT) vision. This paper presents a novel concept for modulating multiple light sources to realize a lightweight version of OFDM communication chain suitable for resource limited IoT devices. In such proposed system, different sinusoidal streams from an array of light sources are carrying the encoded OFDM time-domain samples, thus enabling the realization of the Fourier transformation in the optical domain. Accordingly, the fast Fourier transform (FFT) operation required for the demodulation at the receiver side is eliminated, which is crucial for resource limited IoT devices. In addition, the proposed concept, (1) offers the same spectral efficiency as the well-known asymmetrically clipped optical OFDM (ACO-OFDM), (2) reduces the bandwidth requirement from individual light sources, (3) reduces the peak-to-average power ratio (PAPR) of the signal formed and transmitted over the optical channel, and (4) supports simultaneous sensing applications using the different sinusoidal streams that are acting as unique beaconing signals. The proposed concept is numerically evaluated and compared with ACO-OFDM. The obtained results reveal a clear reduction in the PAPR with ˜ 5dB at a complementary cumulative distribution function (CCDF) of 10-2 and remarkable enhancement in bit-error performance.

Characterization of human oral tissues based on quantitative analysis of optical coherence tomography images

NASA Astrophysics Data System (ADS)

Salehi, Hassan S.; Kosa, Ali; Mahdian, Mina; Moslehpour, Saeid; Alnajjar, Hisham; Tadinada, Aditya

2017-02-01

In this paper, five types of tissues, human enamel, human cortical bone, human trabecular bone, muscular tissue, and fatty tissue were imaged ex vivo using optical coherence tomography (OCT). The specimens were prepared in blocks of 5 x 5 x 3 mm (width x length x height). The OCT imaging system was a swept source OCT system operating at wavelengths ranging between 1250 nm and 1360 nm with an average power of 18 mW and a scan rate of 50 to 100 kHz. The imaging probe was placed on top of a 2 x 2 cm stabilizing device to maintain a standard distance from the samples. Ten image samples from each type of tissue were obtained. To acquire images with minimum inhomogeneity, imaging was performed multiple times at different points. Based on the observed texture differences between OCT images of soft and hard tissues, spatial and spectral features were quantitatively extracted from the OCT images. The Radon transform from angles of 0 deg to 90 deg was computed, averaged over all the angles, normalized to peak at unity, and then fitted with Gaussian function. The mean absolute values of the spatial frequency components of the OCT image were considered as a feature, where 2-D fast Fourier transform (FFT) was done to OCT images. These OCT features can reliably differentiate between a range of hard and soft tissues, and could be extremely valuable in assisting dentists for in vivo evaluation of oral tissues and early detection of pathologic changes in tissues.

Theoretical and numerical investigations towards a new geoid model for the Mediterranean Sea - The GEOMED2 project

NASA Astrophysics Data System (ADS)

Barzaghi, Riccardo; Vergos, Georgios S.; Albertella, Alberta; Carrion, Daniela; Cazzaniga, Noemi; Tziavos, Ilias N.; Grigoriadis, Vassilios N.; Natsiopoulos, Dimitrios A.; Bruinsma, Sean; Bonvalot, Sylvain; Lequentrec-Lalancette, Marie-Françoise; Bonnefond, Pascal; Knudsen, Per; Andersen, Ole; Simav, Mehmet; Yildiz, Hasan; Basic, Tomislav; Gil, Antonio J.

2016-04-01

The unique features of the Mediterranean Sea, with its large gravity variations, complex circulation, and geodynamic peculiarities have always constituted this semi-enclosed sea area as a unique geodetic, geodynamics and ocean laboratory. The main scope of the GEOMED 2 project is the collection of all available gravity, topography/bathymetry and satellite altimetry data in order to improve the representation of the marine geoid and estimate the Mean Dynamic sea surface Topography (MDT) and the circulation with higher accuracy and resolution. Within GEOMED2, the data employed are land and marine gravity data, GOCE/GRACE based Global Geopotential Models and a combination after proper validation of MISTRAL, HOMONIM and SRTM/bathymetry terrain models. In this work we present the results achieved for an inner test region spanning the Adriatic Sea area, bounded between 36o < φ < 48o and 10o < λ < 22o. Within this test region, the available terrain/bathymetry models have been evaluated in terms of their contribution to geoid modeling, the processing methodologies have been tested in terms of the provided geoid accuracy and finally some preliminary results on the MDT determination have been compiled. The aforementioned will server as the guide for the Mediterranean-wide marine geoid estimation. The processing methodology was based on the well-known remove-compute-restore method following both stochastic and spectral methods. Classic least-squares collocation (LSC) with errors has been employed, along with fast Fourier transform (FFT)-based techniques, the Least-Squares Modification of Stokes' Formula (KTH) method and windowed LSC. All methods have been evaluated against in-situ collocated GPS/Levelling geoid heights, using EGM2008 as a reference, in order to conclude on the one(s) to be used for the basin-wide geoid evaluation.

Early Intervention for Symptomatic Youth at Risk for Bipolar Disorder: A Randomized Trial of Family-Focused Therapy

PubMed Central

Miklowitz, David J.; Schneck, Christopher D.; Singh, Manpreet K.; Taylor, Dawn O.; George, Elizabeth L.; Cosgrove, Victoria E.; Howe, Meghan E.; Dickinson, L. Miriam; Garber, Judy; Chang, Kiki D.

2012-01-01

Objective Depression and brief periods of (hypo)mania are linked to an increased risk of progression to bipolar I or II disorder (BD) in children of bipolar parents. This randomized trial examined the effects of a 4-month family-focused therapy (FFT) program on the 1-year course of mood symptoms in youth at high familial risk for BD, and explored its comparative benefits among youth in families with high vs. low expressed emotion (EE). Method Participants were 40 youth (mean 12.3 ± 2.8 years, range 9–17) with BD not otherwise specified, major depressive disorder, or cyclothymic disorder who had a first-degree relative with BD I or II and active mood symptoms (Young Mania Rating Scale [YMRS] > 11 or Child Depression Rating Scale > 29). Participants were randomly allocated to FFT–High Risk version (FFT-HR; 12 sessions of psychoeducation and training in communication and problem-solving skills) or an education control (EC; 1–2 family sessions). Results Youth in FFT-HR had more rapid recovery from their initial mood symptoms (hazard ratio = 2.69, p = .047), more weeks in remission, and a more favorable trajectory of YMRS scores over 1 year than youth in EC. The magnitude of treatment effect was greater among youth in high-EE (vs. low-EE) families. Conclusions FFT-HR may hasten and help sustain recovery from mood symptoms among youth at high risk for BD. Longer follow-up will be necessary to determine if early family intervention has downstream effects that contribute to the delay or prevention of full manic episodes in vulnerable youth. Clinical trial registration information—Early Family-Focused Treatment for Youth at Risk for Bipolar Disorder; http://www.clinicaltrials.gov/; NCT00943085. PMID:23357439

A real-time KLT implementation for radio-SETI applications

NASA Astrophysics Data System (ADS)

Melis, Andrea; Concu, Raimondo; Pari, Pierpaolo; Maccone, Claudio; Montebugnoli, Stelio; Possenti, Andrea; Valente, Giuseppe; Antonietti, Nicoló; Perrodin, Delphine; Migoni, Carlo; Murgia, Matteo; Trois, Alessio; Barbaro, Massimo; Bocchinu, Alessandro; Casu, Silvia; Lunesu, Maria Ilaria; Monari, Jader; Navarrini, Alessandro; Pisanu, Tonino; Schilliró, Francesco; Vacca, Valentina

2016-07-01

SETI, the Search for ExtraTerrestrial Intelligence, is the search for radio signals emitted by alien civilizations living in the Galaxy. Narrow-band FFT-based approaches have been preferred in SETI, since their computation time only grows like N*lnN, where N is the number of time samples. On the contrary, a wide-band approach based on the Kahrunen-Lo`eve Transform (KLT) algorithm would be preferable, but it would scale like N*N. In this paper, we describe a hardware-software infrastructure based on FPGA boards and GPU-based PCs that circumvents this computation-time problem allowing for a real-time KLT.

Visual Estimation of Bacterial Growth Level in Microfluidic Culture Systems.

PubMed

Kim, Kyukwang; Kim, Seunggyu; Jeon, Jessie S

2018-02-03

Microfluidic devices are an emerging platform for a variety of experiments involving bacterial cell culture, and has advantages including cost and convenience. One inevitable step during bacterial cell culture is the measurement of cell concentration in the channel. The optical density measurement technique is generally used for bacterial growth estimation, but it is not applicable to microfluidic devices due to the small sample volumes in microfluidics. Alternately, cell counting or colony-forming unit methods may be applied, but these do not work in situ; nor do these methods show measurement results immediately. To this end, we present a new vision-based method to estimate the growth level of the bacteria in microfluidic channels. We use Fast Fourier transform (FFT) to detect the frequency level change of the microscopic image, focusing on the fact that the microscopic image becomes rough as the number of cells in the field of view increases, adding high frequencies to the spectrum of the image. Two types of microfluidic devices are used to culture bacteria in liquid and agar gel medium, and time-lapsed images are captured. The images obtained are analyzed using FFT, resulting in an increase in high-frequency noise proportional to the time passed. Furthermore, we apply the developed method in the microfluidic antibiotics susceptibility test by recognizing the regional concentration change of the bacteria that are cultured in the antibiotics gradient. Finally, a deep learning-based data regression is performed on the data obtained by the proposed vision-based method for robust reporting of data.

Enhancement of lung sounds based on empirical mode decomposition and Fourier transform algorithm.

PubMed

Mondal, Ashok; Banerjee, Poulami; Somkuwar, Ajay

2017-02-01

There is always heart sound (HS) signal interfering during the recording of lung sound (LS) signals. This obscures the features of LS signals and creates confusion on pathological states, if any, of the lungs. In this work, a new method is proposed for reduction of heart sound interference which is based on empirical mode decomposition (EMD) technique and prediction algorithm. In this approach, first the mixed signal is split into several components in terms of intrinsic mode functions (IMFs). Thereafter, HS-included segments are localized and removed from them. The missing values of the gap thus produced, is predicted by a new Fast Fourier Transform (FFT) based prediction algorithm and the time domain LS signal is reconstructed by taking an inverse FFT of the estimated missing values. The experiments have been conducted on simulated and recorded HS corrupted LS signals at three different flow rates and various SNR levels. The performance of the proposed method is evaluated by qualitative and quantitative analysis of the results. It is found that the proposed method is superior to the baseline method in terms of quantitative and qualitative measurement. The developed method gives better results compared to baseline method for different SNR levels. Our method gives cross correlation index (CCI) of 0.9488, signal to deviation ratio (SDR) of 9.8262, and normalized maximum amplitude error (NMAE) of 26.94 for 0 dB SNR value. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

AUTOMATIC GENERATION OF FFT FOR TRANSLATIONS OF MULTIPOLE EXPANSIONS IN SPHERICAL HARMONICS

PubMed Central

Mirkovic, Dragan; Pettitt, B. Montgomery; Johnsson, S. Lennart

2009-01-01

The fast multipole method (FMM) is an efficient algorithm for calculating electrostatic interactions in molecular simulations and a promising alternative to Ewald summation methods. Translation of multipole expansion in spherical harmonics is the most important operation of the fast multipole method and the fast Fourier transform (FFT) acceleration of this operation is among the fastest methods of improving its performance. The technique relies on highly optimized implementation of fast Fourier transform routines for the desired expansion sizes, which need to incorporate the knowledge of symmetries and zero elements in the input arrays. Here a method is presented for automatic generation of such, highly optimized, routines. PMID:19763233

The fast decoding of Reed-Solomon codes using number theoretic transforms

NASA Technical Reports Server (NTRS)

Reed, I. S.; Welch, L. R.; Truong, T. K.

1976-01-01

It is shown that Reed-Solomon (RS) codes can be encoded and decoded by using a fast Fourier transform (FFT) algorithm over finite fields. The arithmetic utilized to perform these transforms requires only integer additions, circular shifts and a minimum number of integer multiplications. The computing time of this transform encoder-decoder for RS codes is less than the time of the standard method for RS codes. More generally, the field GF(q) is also considered, where q is a prime of the form K x 2 to the nth power + 1 and K and n are integers. GF(q) can be used to decode very long RS codes by an efficient FFT algorithm with an improvement in the number of symbols. It is shown that a radix-8 FFT algorithm over GF(q squared) can be utilized to encode and decode very long RS codes with a large number of symbols. For eight symbols in GF(q squared), this transform over GF(q squared) can be made simpler than any other known number theoretic transform with a similar capability. Of special interest is the decoding of a 16-tuple RS code with four errors.

Unsteady loads due to propulsive lift configurations. Part C: Development of experimental techniques for investigation of unsteady pressures behind a cold model jet

NASA Technical Reports Server (NTRS)

Haviland, J. K.; Schroeder, J. C.

1978-01-01

As part of an overall study of the scaling laws for the fluctuating pressures induced on the wings and flaps of STOL aircraft by jet engine impingement, an experimental investigation was made of the near field fluctuating pressures behind a cold circular jet, both when it was free and when it was impinging on a flat plate. Miniature static pressure probes were developed for measurements in the free jet and on the flat plate which were connected by plastic tubing to 1/8 inch microphones and acted as pressure transducers. Using a digital correlator together with an FFT program on the CDC 6400 computer, spectral densities, relative amplitudes, phase lags, and coherences were also obtained for the signals from pairs of these probes, and were used to calibrate these probes directly against microphones. This system of instrumentation was employed to obtain single point rms and third octave surveys of the static pressures in the free jet and on the surface of the plate.

Qualitative Features Extraction from Sensor Data using Short-time Fourier Transform

NASA Technical Reports Server (NTRS)

Amini, Abolfazl M.; Figueroa, Fernando

2004-01-01

The information gathered from sensors is used to determine the health of a sensor. Once a normal mode of operation is established any deviation from the normal behavior indicates a change. This change may be due to a malfunction of the sensor(s) or the system (or process). The step-up and step-down features, as well as sensor disturbances are assumed to be exponential. An RC network is used to model the main process, which is defined by a step-up (charging), drift, and step-down (discharging). The sensor disturbances and spike are added while the system is in drift. The system runs for a period of at least three time-constants of the main process every time a process feature occurs (e.g. step change). The Short-Time Fourier Transform of the Signal is taken using the Hamming window. Three window widths are used. The DC value is removed from the windowed data prior to taking the FFT. The resulting three dimensional spectral plots provide good time frequency resolution. The results indicate distinct shapes corresponding to each process.

Data-Dependent Fingerprints for Wireless Device Authentication

DTIC Science & Technology

2014-05-20

enhanced when using a modulation based on orthogonal frequency division multiplexing ( OFDM ) that has a large range of signal levels. However, in...at 70 MHz. The radios use OFDM with 64-point FFT block sizes for transmission so that the bandwidth is divided into Nd = 64 data and Nc = 5 cyclic...τℓTs) (1) where Ts is the OFDM symbol period (and therefore discrete-time sampling period) and L is the number of multipaths in the channel with

Reducing acquisition times in multidimensional NMR with a time-optimized Fourier encoding algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zhiyong; Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian 361005; Smith, Pieter E. S.

Speeding up the acquisition of multidimensional nuclear magnetic resonance (NMR) spectra is an important topic in contemporary NMR, with central roles in high-throughput investigations and analyses of marginally stable samples. A variety of fast NMR techniques have been developed, including methods based on non-uniform sampling and Hadamard encoding, that overcome the long sampling times inherent to schemes based on fast-Fourier-transform (FFT) methods. Here, we explore the potential of an alternative fast acquisition method that leverages a priori knowledge, to tailor polychromatic pulses and customized time delays for an efficient Fourier encoding of the indirect domain of an NMR experiment. Bymore » porting the encoding of the indirect-domain to the excitation process, this strategy avoids potential artifacts associated with non-uniform sampling schemes and uses a minimum number of scans equal to the number of resonances present in the indirect dimension. An added convenience is afforded by the fact that a usual 2D FFT can be used to process the generated data. Acquisitions of 2D heteronuclear correlation NMR spectra on quinine and on the anti-inflammatory drug isobutyl propionic phenolic acid illustrate the new method's performance. This method can be readily automated to deal with complex samples such as those occurring in metabolomics, in in-cell as well as in in vivo NMR applications, where speed and temporal stability are often primary concerns.« less

Design of Passive Power Filter for Hybrid Series Active Power Filter using Estimation, Detection and Classification Method

NASA Astrophysics Data System (ADS)

Swain, Sushree Diptimayee; Ray, Pravat Kumar; Mohanty, K. B.

2016-06-01

This research paper discover the design of a shunt Passive Power Filter (PPF) in Hybrid Series Active Power Filter (HSAPF) that employs a novel analytic methodology which is superior than FFT analysis. This novel approach consists of the estimation, detection and classification of the signals. The proposed method is applied to estimate, detect and classify the power quality (PQ) disturbance such as harmonics. This proposed work deals with three methods: the harmonic detection through wavelet transform method, the harmonic estimation by Kalman Filter algorithm and harmonic classification by decision tree method. From different type of mother wavelets in wavelet transform method, the db8 is selected as suitable mother wavelet because of its potency on transient response and crouched oscillation at frequency domain. In harmonic compensation process, the detected harmonic is compensated through Hybrid Series Active Power Filter (HSAPF) based on Instantaneous Reactive Power Theory (IRPT). The efficacy of the proposed method is verified in MATLAB/SIMULINK domain and as well as with an experimental set up. The obtained results confirm the superiority of the proposed methodology than FFT analysis. This newly proposed PPF is used to make the conventional HSAPF more robust and stable.

Effect of intravenous drug administration mode on drug distribution in a tumor slab: a finite Fourier transform analysis.

PubMed

Subramaniam, B; Claudius, J S

1990-03-08

Cancer therapy using chemotherapeutic drugs frequently involves injection of the drug into the body through some intravenous mode of administration, viz, continuous (drip) infusion or single/multiple bolus injection(s). An understanding of the effect of the various modes of administration upon tumor penetration of drug is essential to rational design of drug therapy. This paper investigates drug penetration into a model tumor of slab geometry (between two capillaries) in which the overall transport rate of drug is limited by intra-tumor transport characterized by an effective diffusion coefficient. Employing the method of Finite Fourier Transforms (FFT), analytical solutions have been obtained for transient drug distribution in both the plasma and the tumor following three modes of administration, viz, continuous infusion, single bolus injection and equally-spaced equal-dose multiple bolus injections, of a given amount of drug. The qualitative trends exhibited by the plasma drug distribution profiles are consistent with reported experimental studies. Two concepts, viz, the dimensionless decay constant and the plasma/tumor drug concentration trajectories, are found to be particularly useful in the rational design of drug therapy. The dimensionless decay constant provides a measure of the rate of drug decay in the plasma relative to the rate of drug diffusion into the tumor and is thus characteristic of the tumor/drug system. The magnitude of this parameter dictates the choice of drug administration mode for minimizing drug decay in the plasma while simultaneously maximizing drug transport into the tumor. The concentration trajectories provide a measure of the plasma drug concentration relative to the tumor drug concentration at various times following injection. When the tumor drug concentration exceeds the plasma drug concentration, the drug will begin to diffuse out of the tumor. Knowledge of the time at which this diffusion reversal occurs is especially useful for optimum scheduling of subsequent bolus injections in a multiple bolus dosing regimen. There are no reported applications of the FFT method to solve repeated input functions in either the chemical engineering or pharmaceutical science literature. Thus, the application of FFT method to solve multiple bolus injections is a unique one. Use of this FFT based analysis as a predictor tool can limit the number of costly experiments which are being done now to achieve this purpose. Even though the model in its present form is simplified, the analysis thereof has nevertheless led to a better understanding of the various factors that must be taken into account for rational design of drug therapy.

Applications Performance on NAS Intel Paragon XP/S - 15#

NASA Technical Reports Server (NTRS)

Saini, Subhash; Simon, Horst D.; Copper, D. M. (Technical Monitor)

1994-01-01

The Numerical Aerodynamic Simulation (NAS) Systems Division received an Intel Touchstone Sigma prototype model Paragon XP/S- 15 in February, 1993. The i860 XP microprocessor with an integrated floating point unit and operating in dual -instruction mode gives peak performance of 75 million floating point operations (NIFLOPS) per second for 64 bit floating point arithmetic. It is used in the Paragon XP/S-15 which has been installed at NAS, NASA Ames Research Center. The NAS Paragon has 208 nodes and its peak performance is 15.6 GFLOPS. Here, we will report on early experience using the Paragon XP/S- 15. We have tested its performance using both kernels and applications of interest to NAS. We have measured the performance of BLAS 1, 2 and 3 both assembly-coded and Fortran coded on NAS Paragon XP/S- 15. Furthermore, we have investigated the performance of a single node one-dimensional FFT, a distributed two-dimensional FFT and a distributed three-dimensional FFT Finally, we measured the performance of NAS Parallel Benchmarks (NPB) on the Paragon and compare it with the performance obtained on other highly parallel machines, such as CM-5, CRAY T3D, IBM SP I, etc. In particular, we investigated the following issues, which can strongly affect the performance of the Paragon: a. Impact of the operating system: Intel currently uses as a default an operating system OSF/1 AD from the Open Software Foundation. The paging of Open Software Foundation (OSF) server at 22 MB to make more memory available for the application degrades the performance. We found that when the limit of 26 NIB per node out of 32 MB available is reached, the application is paged out of main memory using virtual memory. When the application starts paging, the performance is considerably reduced. We found that dynamic memory allocation can help applications performance under certain circumstances. b. Impact of data cache on the i860/XP: We measured the performance of the BLAS both assembly coded and Fortran coded. We found that the measured performance of assembly-coded BLAS is much less than what memory bandwidth limitation would predict. The influence of data cache on different sizes of vectors is also investigated using one-dimensional FFTs. c. Impact of processor layout: There are several different ways processors can be laid out within the two-dimensional grid of processors on the Paragon. We have used the FFT example to investigate performance differences based on processors layout.

Detecting fixation on a target using time-frequency distributions of a retinal birefringence scanning signal

PubMed Central

2013-01-01

Background The fovea, which is the most sensitive part of the retina, is known to have birefringent properties, i.e. it changes the polarization state of light upon reflection. Existing devices use this property to obtain information on the orientation of the fovea and the direction of gaze. Such devices employ specific frequency components that appear during moments of fixation on a target. To detect them, previous methods have used solely the power spectrum of the Fast Fourier Transform (FFT), which, unfortunately, is an integral method, and does not give information as to where exactly the events of interest occur. With very young patients who are not cooperative enough, this presents a problem, because central fixation may be present only during very short-lasting episodes, and can easily be missed by the FFT. Method This paper presents a method for detecting short-lasting moments of central fixation in existing devices for retinal birefringence scanning, with the goal of a reliable detection of eye alignment. Signal analysis is based on the Continuous Wavelet Transform (CWT), which reliably localizes such events in the time-frequency plane. Even though the characteristic frequencies are not always strongly expressed due to possible artifacts, simple topological analysis of the time-frequency distribution can detect fixation reliably. Results In all six subjects tested, the CWT allowed precise identification of both frequency components. Moreover, in four of these subjects, episodes of intermittent but definitely present central fixation were detectable, similar to those in Figure 4. A simple FFT is likely to treat them as borderline cases, or entirely miss them, depending on the thresholds used. Conclusion Joint time-frequency analysis is a powerful tool in the detection of eye alignment, even in a noisy environment. The method is applicable to similar situations, where short-lasting diagnostic events need to be detected in time series acquired by means of scanning some substrate along a specific path. PMID:23668264

Optimized OFDM Transmission of Encrypted Image Over Fading Channel

NASA Astrophysics Data System (ADS)

Eldin, Salwa M. Serag

2014-11-01

This paper compares the quality of diffusion-based and permutation-based encrypted image transmission using orthogonal frequency division multiplexing (OFDM) over wireless fading channel. Sensitivity to carrier frequency offsets (CFOs) is one of the limitations in OFDM transmission that was compensated here. Different OFDM diffusions are investigated to study encrypted image transmission optimization. Peak signal-to-noise ratio between the original image and the decrypted image is used to evaluate the received image quality. Chaotic encrypted image modulated with CFOs compensated FFT-OFDM was found to give outstanding performance against other encryption and modulation techniques.

Frequency Estimator Performance for a Software-Based Beacon Receiver

NASA Technical Reports Server (NTRS)

Zemba, Michael J.; Morse, Jacquelynne R.; Nessel, James A.

2014-01-01

As propagation terminals have evolved, their design has trended more toward a software-based approach that facilitates convenient adjustment and customization of the receiver algorithms. One potential improvement is the implementation of a frequency estimation algorithm, through which the primary frequency component of the received signal can be estimated with a much greater resolution than with a simple peak search of the FFT spectrum. To select an estimator for usage in a Q/V-band beacon receiver, analysis of six frequency estimators was conducted to characterize their effectiveness as they relate to beacon receiver design.

Response-only method for damage detection of beam-like structures using high accuracy frequencies with auxiliary mass spatial probing

NASA Astrophysics Data System (ADS)

Zhong, Shuncong; Oyadiji, S. Olutunde; Ding, Kang

2008-04-01

This paper proposes a new approach based on auxiliary mass spatial probing using spectral centre correction method (SCCM), to provide a simple solution for damage detection by just using the response time history of beam-like structures. The natural frequencies of a damaged beam with a traversing auxiliary mass change due to change in the inertia of the beam as the auxiliary mass is traversed along the beam, as well as the point-to-point variations in the flexibility of the beam. Therefore the auxiliary mass can enhance the effects of the crack on the dynamics of the beam and, therefore, facilitate the identification and location of damage in the beam. That is, the auxiliary mass can be used to probe the dynamic characteristic of the beam by traversing the mass from one end of the beam to the other. However, it is impossible to obtain accurate modal frequencies by the direct operation of the fast Fourier transform (FFT) of the response data of the structure because the frequency spectrum can be only calculated from limited sampled time data which results in the well-known leakage effect. SCCM is identical to the energy centrobaric correction method (ECCM) which is a practical and effective method used in rotating mechanical fault diagnosis and which resolves the shortcoming of FFT and can provide high accuracy estimate of frequency, amplitude and phase. In the present work, the modal responses of damaged simply supported beams with auxiliary mass are computed using the finite element method (FEM). The graphical plots of the natural frequencies calculated by SCCM versus axial location of auxiliary mass are obtained. However, it is difficult to locate the crack directly from the curve of natural frequencies. A simple and fast method, the derivatives of natural frequency curve, is proposed in the paper which can provide crack information for damage detection of beam-like structures. The efficiency and practicability of the proposed method is illustrated via numerical simulation. For real cases, experimental noise is expected to corrupt the response data and, ultimately, the natural frequencies of beam-like structures. Therefore, the response data with a normally distributed random noise is also studied. Also, the effects of crack depth, auxiliary mass and damping ratios on the proposed method are investigated. From the simulated results, the efficiency and robustness of the proposed method is demonstrated. The results show that the proposed method has low computational cost and high precision.

A Synchronous Digital Duplexing Technique for OFDMA-Based Indoor Communications

NASA Astrophysics Data System (ADS)

Park, Chang-Hwan; Ko, Yo-Han; Kim, Yeong-Jun; Park, Kyung-Won; Jeon, Won-Gi; Paik, Jong-Ho; Lee, Seok-Pil; Cho, Yong-Soo

In this paper, we propose a new digital duplexing scheme, called synchronous digital duplexing (SDD), which can increase data efficiency and flexibility of resource by transmitting uplink signal and downlink signal simultaneously in wireless communication. In order to transmit uplink and downlink signals simultaneously, the proposed SDD obtains mutual information among subscriber stations (SSs) with a mutual ranging symbol. This information is used for selection of transmission time, decision on cyclic suffix (CS) insertion, determination of CS length, and re-establishment of FFT starting point.

Fourier analysis and signal processing by use of the Moebius inversion formula

NASA Technical Reports Server (NTRS)

Reed, Irving S.; Yu, Xiaoli; Shih, Ming-Tang; Tufts, Donald W.; Truong, T. K.

1990-01-01

A novel Fourier technique for digital signal processing is developed. This approach to Fourier analysis is based on the number-theoretic method of the Moebius inversion of series. The Fourier transform method developed is shown also to yield the convolution of two signals. A computer simulation shows that this method for finding Fourier coefficients is quite suitable for digital signal processing. It competes with the classical FFT (fast Fourier transform) approach in terms of accuracy, complexity, and speed.

Analysis and Simulation of Narrowband GPS Jamming Using Digital Excision Temporal Filtering.

DTIC Science & Technology

1994-12-01

the sequence of stored values from the P- code sampled at a 20 MHz rate. When correlated with a reference vector of the same length to simulate a GPS ...rate required for the GPS signals, (20 MHz sampling rate for the P- code signal), the personal computer (PC) used run the simulation could not perform...This subroutine is used to perform a fast FFT based 168 biased cross correlation . Written by Capt Gerry Falen, USAF, 16 AUG 94 % start of code

Calculation of spherical harmonics and Wigner d functions by FFT. Applications to fast rotational matching in molecular replacement and implementation into AMoRe.

PubMed

Trapani, Stefano; Navaza, Jorge

2006-07-01

The FFT calculation of spherical harmonics, Wigner D matrices and rotation function has been extended to all angular variables in the AMoRe molecular replacement software. The resulting code avoids singularity issues arising from recursive formulas, performs faster and produces results with at least the same accuracy as the original code. The new code aims at permitting accurate and more rapid computations at high angular resolution of the rotation function of large particles. Test calculations on the icosahedral IBDV VP2 subviral particle showed that the new code performs on the average 1.5 times faster than the original code.

Digital Processing Of Young's Fringes In Speckle Photography

NASA Astrophysics Data System (ADS)

Chen, D. J.; Chiang, F. P.

1989-01-01

A new technique for fully automatic diffraction fringe measurement in point-wise speckle photograph analysis is presented in this paper. The fringe orientation and spacing are initially estimated with the help of 1-D FFT. A 2-D convolution filter is then applied to enhance the estimated image . High signal-to-noise rate (SNR) fringe pattern is achieved which makes it feasible for precise determination of the displacement components. The halo-effect is also optimally eliminated in a new way. With the computation time compared favorably with those of 2-D autocorrelation method and the iterative 2-D FFT method. High reliability and accurate determination of displacement components are achieved over a wide range of fringe density.

Ordered fast Fourier transforms on a massively parallel hypercube multiprocessor

NASA Technical Reports Server (NTRS)

Tong, Charles; Swarztrauber, Paul N.

1991-01-01

The present evaluation of alternative, massively parallel hypercube processor-applicable designs for ordered radix-2 decimation-in-frequency FFT algorithms gives attention to the reduction of computation time-dominating communication. A combination of the order and computational phases of the FFT is accordingly employed, in conjunction with sequence-to-processor maps which reduce communication. Two orderings, 'standard' and 'cyclic', in which the order of the transform is the same as that of the input sequence, can be implemented with ease on the Connection Machine (where orderings are determined by geometries and priorities. A parallel method for trigonometric coefficient computation is presented which does not employ trigonometric functions or interprocessor communication.

A fast estimator for the bispectrum and beyond - a practical method for measuring non-Gaussianity in 21-cm maps

NASA Astrophysics Data System (ADS)

Watkinson, Catherine A.; Majumdar, Suman; Pritchard, Jonathan R.; Mondal, Rajesh

2017-12-01

In this paper, we establish the accuracy and robustness of a fast estimator for the bispectrum - the 'FFT-bispectrum estimator'. The implementation of the estimator presented here offers speed and simplicity benefits over a direct-measurement approach. We also generalize the derivation so it may be easily be applied to any order polyspectra, such as the trispectrum, with the cost of only a handful of Fast-Fourier Transforms (FFTs). All lower order statistics can also be calculated simultaneously for little extra cost. To test the estimator, we make use of a non-linear density field, and for a more strongly non-Gaussian test case, we use a toy-model of reionization in which ionized bubbles at a given redshift are all of equal size and are randomly distributed. Our tests find that the FFT-estimator remains accurate over a wide range of k, and so should be extremely useful for analysis of 21-cm observations. The speed of the FFT-bispectrum estimator makes it suitable for sampling applications, such as Bayesian inference. The algorithm we describe should prove valuable in the analysis of simulations and observations, and whilst, we apply it within the field of cosmology, this estimator is useful in any field that deals with non-Gaussian data.

Investigation of hidden periodic structures on SEM images of opal-like materials using FFT and IFFT.

PubMed

Stephant, Nicolas; Rondeau, Benjamin; Gauthier, Jean-Pierre; Cody, Jason A; Fritsch, Emmanuel

2014-01-01

We have developed a method to use fast Fourier transformation (FFT) and inverse fast Fourier transformation (IFFT) to investigate hidden periodic structures on SEM images. We focused on samples of natural, play-of-color opals that diffract visible light and hence are periodically structured. Conventional sample preparation by hydrofluoric acid etch was not used; untreated, freshly broken surfaces were examined at low magnification relative to the expected period of the structural features, and, the SEM was adjusted to get a very high number of pixels in the images. These SEM images were treated by software to calculate autocorrelation, FFT, and IFFT. We present how we adjusted SEM acquisition parameters for best results. We first applied our procedure on an SEM image on which the structure was obvious. Then, we applied the same procedure on a sample that must contain a periodic structure because it diffracts visible light, but on which no structure was visible on the SEM image. In both cases, we obtained clearly periodic patterns that allowed measurements of structural parameters. We also investigated how the irregularly broken surface interfered with the periodic structure to produce additional periodicity. We tested the limits of our methodology with the help of simulated images. © 2014 Wiley Periodicals, Inc.

A spectral power analysis of driving behavior changes during the transition from nondistraction to distraction.

PubMed

Wang, Yuan; Bao, Shan; Du, Wenjun; Ye, Zhirui; Sayer, James R

2017-11-17

This article investigated and compared frequency domain and time domain characteristics of drivers' behaviors before and after the start of distracted driving. Data from an existing naturalistic driving study were used. Fast Fourier transform (FFT) was applied for the frequency domain analysis to explore drivers' behavior pattern changes between nondistracted (prestarting of visual-manual task) and distracted (poststarting of visual-manual task) driving periods. Average relative spectral power in a low frequency range (0-0.5 Hz) and the standard deviation in a 10-s time window of vehicle control variables (i.e., lane offset, yaw rate, and acceleration) were calculated and further compared. Sensitivity analyses were also applied to examine the reliability of the time and frequency domain analyses. Results of the mixed model analyses from the time and frequency domain analyses all showed significant degradation in lateral control performance after engaging in visual-manual tasks while driving. Results of the sensitivity analyses suggested that the frequency domain analysis was less sensitive to the frequency bandwidth, whereas the time domain analysis was more sensitive to the time intervals selected for variation calculations. Different time interval selections can result in significantly different standard deviation values, whereas average spectral power analysis on yaw rate in both low and high frequency bandwidths showed consistent results, that higher variation values were observed during distracted driving when compared to nondistracted driving. This study suggests that driver state detection needs to consider the behavior changes during the prestarting periods, instead of only focusing on periods with physical presence of distraction, such as cell phone use. Lateral control measures can be a better indicator of distraction detection than longitudinal controls. In addition, frequency domain analyses proved to be a more robust and consistent method in assessing driving performance compared to time domain analyses.

Non destructive defect detection by spectral density analysis.

PubMed

Krejcar, Ondrej; Frischer, Robert

2011-01-01

The potential nondestructive diagnostics of solid objects is discussed in this article. The whole process is accomplished by consecutive steps involving software analysis of the vibration power spectrum (eventually acoustic emissions) created during the normal operation of the diagnosed device or under unexpected situations. Another option is to create an artificial pulse, which can help us to determine the actual state of the diagnosed device. The main idea of this method is based on the analysis of the current power spectrum density of the received signal and its postprocessing in the Matlab environment with a following sample comparison in the Statistica software environment. The last step, which is comparison of samples, is the most important, because it is possible to determine the status of the examined object at a given time. Nowadays samples are compared only visually, but this method can't produce good results. Further the presented filter can choose relevant data from a huge group of data, which originate from applying FFT (Fast Fourier Transform). On the other hand, using this approach they can be subjected to analysis with the assistance of a neural network. If correct and high-quality starting data are provided to the initial network, we are able to analyze other samples and state in which condition a certain object is. The success rate of this approximation, based on our testing of the solution, is now 85.7%. With further improvement of the filter, it could be even greater. Finally it is possible to detect defective conditions or upcoming limiting states of examined objects/materials by using only one device which contains HW and SW parts. This kind of detection can provide significant financial savings in certain cases (such as continuous casting of iron where it could save hundreds of thousands of USD).

On geodynamo integrations conserving momentum flux

NASA Astrophysics Data System (ADS)

Wu, C.; Roberts, P. H.

2012-12-01

The equations governing the geodynamo are most often integrated by representing the magnetic field and fluid velocity by toroidal and poloidal scalars (for example, MAG code [1]). This procedure does not automatically conserve the momentum flux. The results can, particularly for flows with large shear, introduce significant errors, unless the viscosity is artificially increased. We describe a method that evades this difficulty, by solving the momentum equation directly while properly conserving momentum. It finds pressure by FFT and cyclic reduction, and integrates the governing equations on overlapping grids so avoiding the pole problem. The number of operations per time step is proportional to N3 where N is proportional to the number of grid points in each direction. This contrasts with the order N4 operations of standard spectral transform methods. The method is easily parallelized. It can also be easily adapted to schemes such as the Weighted Essentially Non-Oscillatory (WENO) method [2], a flux based procedure based on upwinding that is numerically stable even for zero explicit viscosity. The method has been successfully used to investigate the generation of magnetic fields by flows confined to spheroidal containers and driven by precessional and librational forcing [3, 4]. For spherical systems it satisfies dynamo benchmarks [5]. [1] MAG, http://www.geodynamics.org/cig/software/mag [2] Liu, XD, Osher, S and Chan, T, Weighted Essentially Nonoscillatory Schemes, J. Computational Physics, 115, 200-212, 1994. [3] Wu, CC and Roberts, PH, On a dynamo driven by topographic precession, Geophysical & Astrophysical Fluid Dynamics, 103, 467-501, (DOI: 10.1080/03091920903311788), 2009. [4] Wu, CC and Roberts, PH, On a dynamo driven topographically by longitudinal libration, Geophysical & Astrophysical Fluid Dynamics, DOI:10.1080/03091929.2012.682990, 2012. [5] Christensen, U, et al., A numerical dynamo benchmark, Phys. Earth Planet Int., 128, 25-34, 2001.

Towards a better understanding of the generation of fructan structure diversity in plants: molecular and functional characterization of a sucrose:fructan 6-fructosyltransferase (6-SFT) cDNA from perennial ryegrass (Lolium perenne)

PubMed Central

Lasseur, Bertrand; Lothier, Jérémy; Wiemken, Andres; Van Laere, André; Morvan-Bertrand, Annette; den Ende, Wim Van; Prud'homme, Marie-Pascale

2011-01-01

The main storage compounds in Lolium perenne are fructans with prevailing β(2–6) linkages. A cDNA library of L. perenne was screened using Poa secunda sucrose:fructan 6-fructosyltransferase (6-SFT) as a probe. A full-length Lp6-SFT clone was isolated as shown by heterologous expression in Pichia pastoris. High levels of Lp6-SFT transcription were found in the growth zone of elongating leaves and in mature leaf sheaths where fructans are synthesized. Upon fructan synthesis induction, Lp6-SFT transcription was high in mature leaf blades but with no concomitant accumulation of fructans. In vitro studies with the recombinant Lp6-SFT protein showed that both 1-kestotriose and 6G-kestotriose acted as fructosyl acceptors, producing 1- and 6-kestotetraose (bifurcose) and 6G,6-kestotetraose, respectively. Interestingly, bifurcose formation ceased and 6G,6-kestotetraose was formed instead, when recombinant fructan:fructan 6G-fructosyltransferase (6G-FFT) of L. perenne was introduced in the enzyme assay with sucrose and 1-kestotriose as substrates. The remarkable absence of bifurcose in L. perenne tissues might be explained by a higher affinity of 6G-FFT, as compared with 6-SFT, for 1-kestotriose, which is the first fructan formed. Surprisingly, recombinant 6-SFT from Hordeum vulgare, a plant devoid of fructans with internal glucosyl residues, also produced 6G,6-kestotetraose from sucrose and 6G-kestotriose. In the presence of recombinant L. perenne 6G-FFT, it produced 6G,6-kestotetraose from 1-kestotriose and sucrose, like L. perenne 6-SFT. Thus, we demonstrate that the two 6-SFTs have close catalytic properties and that the distinct fructans formed in L. perenne and H. vulgare can be explained by the presence of 6G-FFT activity in L. perenne and its absence in H. vulgare. PMID:21196473

An investigation of thoracic and lumbar cancellous vertebral architecture using power-spectral analysis of plain radiographs*

PubMed Central

Buck, AM; Price, RI; Sweetman, IM; Oxnard, CE

2002-01-01

The internal architecture of the vertebral bodies spanning the levels T1 to L5 in seven male columns was studied using mammographic-resolution radiographs of 2.5-mm-thick planar parasagittal slices. The overlapping radiographic shadows of vertebral trabeculae combined in the image to form a series of ‘elements’, broadly representative of the cancellous structure. The orientations and sizes of these elements were analysed by applying the Fast Fourier transform (FFT) to the digitized radiographic images. Elements aligned in the ‘vertical’ orientation, along the long axis of the column, were the most prominent for all vertebral levels. The relative prominence of horizontal to vertical elements was generally constant along the column below T5. In contrast, the relative prominence of oblique to vertical elements declined in the cranio-caudal direction, particularly in individuals aged ≥ 60 years. The ratio of ‘large’ (x > 0.3 mm) to ‘small’ (0.15 mm ≤ x ≤ 0.3 mm) elements was unchanged cranio-caudally in specimens < 60 years. However, in individuals ≥ 60 years, large elements increased in relative prominence in the caudal direction. These results suggest that a basic orthogonal pattern of trabeculae is found along the male human spine, regardless of differences in vertebral body size. Power-spectral analysis is shown to yield information summarizing the predominant orientations and sizes of radiographically rendered architectural elements of vertebral cancellous bone, to define the effects of ageing on architecture, and to identify broad structural differences between vertebral levels in the adult male spine. PMID:12090391

Temporal Characteristics of the Sleep EEG Power Spectrum in Critically Ill Children.

PubMed

Kudchadkar, Sapna R; Yaster, Myron; Punjabi, Arjun N; Quan, Stuart F; Goodwin, James L; Easley, R Blaine; Punjabi, Naresh M

2015-12-15

Although empirical evidence is limited, critical illness in children is associated with disruption of the normal sleep-wake rhythm. The objective of the current study was to examine the temporal characteristics of the sleep electroencephalogram (EEG) in a sample of children with critical illness. Limited montage EEG recordings were collected for at least 24 hours from 8 critically ill children on mechanical ventilation for respiratory failure in a pediatric intensive care unit (PICU) of a tertiary-care hospital. Each PICU patient was age- and gender-matched to a healthy subject from the community. Power spectral analysis with the fast Fourier transform (FFT) was used to characterize EEG spectral power and categorized into 4 frequency bands: δ (0.8 to 4.0 Hz), θ (4.1 to 8.0 Hz), α (8.1 to 13.0 Hz), and β1/β2 (13.1 to 20.0 Hz). PICU patients did not manifest the ultradian variability in EEG power spectra including the typical increase in δ-power during the first third of the night that was observed in healthy children. Differences noted included significantly lower mean nighttime δ and θ power in the PICU patients compared to healthy children (p < 0.001). Moreover, in the PICU patients, mean δ and θ power were higher during daytime hours than nighttime hours (p < 0.001). The results presented herein challenge the assumption that children experience restorative sleep during critical illness, highlighting the need for interventional studies to determine whether sleep promotion improves outcomes in critically ill children undergoing active neurocognitive development. © 2015 American Academy of Sleep Medicine.

A new compact and low cost Langmuir Probe and associated onboard data handling system for CubeSat

NASA Astrophysics Data System (ADS)

Muralikrishna, Polinaya; Domingos, Sinval; Paredes, Andres; Abrahão Dos Santos, Walter

2016-07-01

A new compact and low cost Langmuir Probe and associated onboard data handling system are being developed at Instituto Nacional de Pesquisas Espaciais for launching on board one of the future 2U CubeSat missions. The system is a simplified and compacted version of the Langmuir Probe payloads launched on board several Brazilian SONDA III rockets and also developed for the Brazilian scientific satellites SACI-1 and SACI-2. The onboard data handling system will have the dual functions of preprocessing the data collected by the Langmuir Probe and acting as the interface between the experiment and the on board computer. The Langmuir Probe sensor in the form of two rectangular stainless steel strips of total surface area of approximately 80cm2 will be deployed soon after the injection of the CubeSat into orbit. A sweep voltage varying linearly from 0V to 3.0V in about 1.5 seconds and then remaining fixed at 3.0V for 1 second will be applied to the LP sensor to obtain both the electron density and electron temperature. A high sensitivity preamplifier will be used to convert the sensor current expected to be in the range of a few nano amperes to a few micro amperes into a varying potential. In order to cover the large dynamic range of the expected sensor current the preamplifier output will be further amplified by a logarithmic amplifier before being sampled and sent to the data handling system. The data handling system is projected to handle 8 analog channels and 4 digital words of 8 bits each. The incoming data will be stored in a RAM and later sent to the on board computer using a serial RS422 communication protocol. The interface unit will process the telecommands received from the on board computer. The interface is also projected to do FFT analysis of the LP sensor data and send the averaged FFT spectral amplitudes in place of the original unprocessed data. The system details are presented here.

Enhancing Image Processing Performance for PCID in a Heterogeneous Network of Multi-code Processors

NASA Astrophysics Data System (ADS)

Linderman, R.; Spetka, S.; Fitzgerald, D.; Emeny, S.

The Physically-Constrained Iterative Deconvolution (PCID) image deblurring code is being ported to heterogeneous networks of multi-core systems, including Intel Xeons and IBM Cell Broadband Engines. This paper reports results from experiments using the JAWS supercomputer at MHPCC (60 TFLOPS of dual-dual Xeon nodes linked with Infiniband) and the Cell Cluster at AFRL in Rome, NY. The Cell Cluster has 52 TFLOPS of Playstation 3 (PS3) nodes with IBM Cell Broadband Engine multi-cores and 15 dual-quad Xeon head nodes. The interconnect fabric includes Infiniband, 10 Gigabit Ethernet and 1 Gigabit Ethernet to each of the 336 PS3s. The results compare approaches to parallelizing FFT executions across the Xeons and the Cell's Synergistic Processing Elements (SPEs) for frame-level image processing. The experiments included Intel's Performance Primitives and Math Kernel Library, FFTW3.2, and Carnegie Mellon's SPIRAL. Optimization of FFTs in the PCID code led to a decrease in relative processing time for FFTs. Profiling PCID version 6.2, about one year ago, showed the 13 functions that accounted for the highest percentage of processing were all FFT processing functions. They accounted for over 88% of processing time in one run on Xeons. FFT optimizations led to improvement in the current PCID version 8.0. A recent profile showed that only two of the 19 functions with the highest processing time were FFT processing functions. Timing measurements showed that FFT processing for PCID version 8.0 has been reduced to less than 19% of overall processing time. We are working toward a goal of scaling to 200-400 cores per job (1-2 imagery frames/core). Running a pair of cores on each set of frames reduces latency by implementing parallel FFT processing. Our current results show scaling well out to 100 pairs of cores. These results support the next higher level of parallelism in PCID, where groups of several hundred frames each producing one resolved image are sent to cliques of several hundred cores in a round robin fashion. Current efforts toward further performance enhancement for PCID are shifting toward using the Playstations in conjunction with the Xeons to take advantage of outstanding price/performance as well as the Flops/Watt cost advantage. We are fine-tuning the PCID parallization strategy to balance processing over Xeons and Cell BEs to find an optimal partitioning of PCID over the heterogeneous processors. A high performance information management system that exploits native Infiniband multicast is used to improve latency among the head nodes. Using a publication/subscription oriented information management system to implement a unified communications platform makes runs on large HPCs with thousands of intercommunicating cores more flexible and more fault tolerant. It features a loose couplingof publishers to subscribers through intervening brokers. We are also working on enhancing performance for both Xeons and Cell BEs, buy moving selected operations to single precision. Techniques for adapting the code to single precision and performance results are reported.

Impact evaluation of conducted UWB transients on loads in power-line networks

NASA Astrophysics Data System (ADS)

Li, Bing; Månsson, Daniel

2017-09-01

Nowadays, faced with the ever-increasing dependence on diverse electronic devices and systems, the proliferation of potential electromagnetic interference (EMI) becomes a critical threat for reliable operation. A typical issue is the electronics working reliably in power-line networks when exposed to electromagnetic environment. In this paper, we consider a conducted ultra-wideband (UWB) disturbance, as an example of intentional electromagnetic interference (IEMI) source, and perform the impact evaluation at the loads in a network. With the aid of fast Fourier transform (FFT), the UWB transient is characterized in the frequency domain. Based on a modified Baum-Liu-Tesche (BLT) method, the EMI received at the loads, with complex impedance, is computed. Through inverse FFT (IFFT), we obtain time-domain responses of the loads. To evaluate the impact on loads, we employ five common, but important quantifiers, i.e., time-domain peak, total signal energy, peak signal power, peak time rate of change and peak time integral of the pulse. Moreover, to perform a comprehensive analysis, we also investigate the effects of the attributes (capacitive, resistive, or inductive) of other loads connected to the network, the rise time and pulse width of the UWB transient, and the lengths of power lines. It is seen that, for the loads distributed in a network, the impact evaluation of IEMI should be based on the characteristics of the IEMI source, and the network features, such as load impedances, layout, and characteristics of cables.

Polarizable atomic multipole X-ray refinement: application to peptide crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schnieders, Michael J.; Fenn, Timothy D.; Howard Hughes Medical Institute

2009-09-01

A method to accelerate the computation of structure factors from an electron density described by anisotropic and aspherical atomic form factors via fast Fourier transformation is described for the first time. Recent advances in computational chemistry have produced force fields based on a polarizable atomic multipole description of biomolecular electrostatics. In this work, the Atomic Multipole Optimized Energetics for Biomolecular Applications (AMOEBA) force field is applied to restrained refinement of molecular models against X-ray diffraction data from peptide crystals. A new formalism is also developed to compute anisotropic and aspherical structure factors using fast Fourier transformation (FFT) of Cartesian Gaussianmore » multipoles. Relative to direct summation, the FFT approach can give a speedup of more than an order of magnitude for aspherical refinement of ultrahigh-resolution data sets. Use of a sublattice formalism makes the method highly parallelizable. Application of the Cartesian Gaussian multipole scattering model to a series of four peptide crystals using multipole coefficients from the AMOEBA force field demonstrates that AMOEBA systematically underestimates electron density at bond centers. For the trigonal and tetrahedral bonding geometries common in organic chemistry, an atomic multipole expansion through hexadecapole order is required to explain bond electron density. Alternatively, the addition of interatomic scattering (IAS) sites to the AMOEBA-based density captured bonding effects with fewer parameters. For a series of four peptide crystals, the AMOEBA–IAS model lowered R{sub free} by 20–40% relative to the original spherically symmetric scattering model.« less

Strategy for reflector pattern calculation - Let the computer do the work

NASA Technical Reports Server (NTRS)

Lam, P. T.; Lee, S.-W.; Hung, C. C.; Acosta, R.

1986-01-01

Using high frequency approximations, the secondary pattern of a reflector antenna can be calculated by numerically evaluating a radiation integral I(u,v). In recent years, tremendous effort has been expended to reducing I(u,v) to Fourier integrals. These reduction schemes are invariably reflector geometry dependent. Hence, different analyses/computer software development must be carried out for different reflector shapes/boundaries. It is pointed out, that, as the computer power improves, these reduction schemes are no longer necessary. Comparable accuracy and computation time can be achieved by evaluating I(u,v) by a brute force FFT described in this note. Furthermore, there is virtually no restriction on the reflector geometry by using the brute force FFT.

Strategy for reflector pattern calculation: Let the computer do the work

NASA Technical Reports Server (NTRS)

Lam, P. T.; Lee, S. W.; Hung, C. C.; Acousta, R.

1985-01-01

Using high frequency approximations, the secondary pattern of a reflector antenna can be calculated by numerically evaluating a radiation integral I(u,v). In recent years, tremendous effort has been expended to reducing I(u,v) to Fourier integrals. These reduction schemes are invariably reflector geometry dependent. Hence, different analyses/computer software development must be carried out for different reflector shapes/boundaries. it is pointed out, that, as the computer power improves, these reduction schemes are no longer necessary. Comparable accuracy and computation time can be achieved by evaluating I(u,v) by a brute force FFT described in this note. Furthermore, there is virtually no restriction on the reflector geometry by using the brute force FFT.

FFT analysis of sensible-heat solar-dynamic receivers

NASA Astrophysics Data System (ADS)

Lund, Kurt O.

The use of solar dynamic receivers with sensible energy storage in single-phase materials is considered. The feasibility of single-phase designs with weight and thermal performance comparable to existing two-phase designs is addressed. Linearized heat transfer equations are formulated for the receiver heat storage, representing the periodic input solar flux as the sum of steady and oscillating distributions. The steady component is solved analytically to produce the desired receiver steady outlet gas temperature, and the FFT algorithm is applied to the oscillating components to obtain the amplitudes and mode shapes of the oscillating solid and gas temperatures. The results indicate that sensible-heat receiver designs with performance comparable to state-of-the-art two-phase receivers are available.

Distortion analysis of subband adaptive filtering methods for FMRI active noise control systems.

PubMed

Milani, Ali A; Panahi, Issa M; Briggs, Richard

2007-01-01

Delayless subband filtering structure, as a high performance frequency domain filtering technique, is used for canceling broadband fMRI noise (8 kHz bandwidth). In this method, adaptive filtering is done in subbands and the coefficients of the main canceling filter are computed by stacking the subband weights together. There are two types of stacking methods called FFT and FFT-2. In this paper, we analyze the distortion introduced by these two stacking methods. The effect of the stacking distortion on the performance of different adaptive filters in FXLMS algorithm with non-minimum phase secondary path is explored. The investigation is done for different adaptive algorithms (nLMS, APA and RLS), different weight stacking methods, and different number of subbands.

Highly Efficient Parallel Multigrid Solver For Large-Scale Simulation of Grain Growth Using the Structural Phase Field Crystal Model

NASA Astrophysics Data System (ADS)

Guan, Zhen; Pekurovsky, Dmitry; Luce, Jason; Thornton, Katsuyo; Lowengrub, John

The structural phase field crystal (XPFC) model can be used to model grain growth in polycrystalline materials at diffusive time-scales while maintaining atomic scale resolution. However, the governing equation of the XPFC model is an integral-partial-differential-equation (IPDE), which poses challenges in implementation onto high performance computing (HPC) platforms. In collaboration with the XSEDE Extended Collaborative Support Service, we developed a distributed memory HPC solver for the XPFC model, which combines parallel multigrid and P3DFFT. The performance benchmarking on the Stampede supercomputer indicates near linear strong and weak scaling for both multigrid and transfer time between multigrid and FFT modules up to 1024 cores. Scalability of the FFT module begins to decline at 128 cores, but it is sufficient for the type of problem we will be examining. We have demonstrated simulations using 1024 cores, and we expect to achieve 4096 cores and beyond. Ongoing work involves optimization of MPI/OpenMP-based codes for the Intel KNL Many-Core Architecture. This optimizes the code for coming pre-exascale systems, in particular many-core systems such as Stampede 2.0 and Cori 2 at NERSC, without sacrificing efficiency on other general HPC systems.

New super-computing facility in RIKEN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohta, Shigemi

1994-12-31

A new superconductor, Fujitsu VPP500/28, was installed in the Institute of Physical and Chemical Research (RIKEN) at the end of March, 1994. It consists of 28 processing elements (PE`s) connected by a high-speed crossbar switch. The switch is a combination of GaAs and ECL circuitry with peak band width of 800 Mbyte per second. Each PE consists of a GaAs/ECL vector processor with 1.6 Gflops peak speed and 256 Mbyte SRAM local memory. In addition, there are 8 GByte DRAM space, two 100 Gbyte RAID disks and a 10 TByte archive based on SONY File Bank system. The author ranmore » three major benchmarks on this machine: modified LINPACK, lattice QCD and FFT. In the modified LINPACK benchmark, a sustained speed of about 28 Gflops is achieved, by removing the restriction on the size of the matrices. In the lattice QCD benchmark, a sustained speed of about 30 Gflops is achieved for inverting staggered fermion propagation matrix on a 32{sup 4} lattice. In the FFT benchmark, real data of 32, 128, 512, and 2048 MByte are Fourier-transformed. The sustained speed for each is respectively 21, 21, 20, and 19 Gflops. The numbers are obtained after only a few weeks of coding efforts and can be improved further.« less

Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties.

PubMed

Gerngross, Mark-Daniel; Carstensen, Jürgen; Föll, Helmut

2014-01-01

The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor (RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires.

Medical image reconstruction algorithm based on the geometric information between sensor detector and ROI

NASA Astrophysics Data System (ADS)

Ham, Woonchul; Song, Chulgyu; Lee, Kangsan; Roh, Seungkuk

2016-05-01

In this paper, we propose a new image reconstruction algorithm considering the geometric information of acoustic sources and senor detector and review the two-step reconstruction algorithm which was previously proposed based on the geometrical information of ROI(region of interest) considering the finite size of acoustic sensor element. In a new image reconstruction algorithm, not only mathematical analysis is very simple but also its software implementation is very easy because we don't need to use the FFT. We verify the effectiveness of the proposed reconstruction algorithm by showing the simulation results by using Matlab k-wave toolkit.

Aeroelastic-Acoustics Simulation of Flight Systems

NASA Technical Reports Server (NTRS)

Gupta, kajal K.; Choi, S.; Ibrahim, A.

2009-01-01

This paper describes the details of a numerical finite element (FE) based analysis procedure and a resulting code for the simulation of the acoustics phenomenon arising from aeroelastic interactions. Both CFD and structural simulations are based on FE discretization employing unstructured grids. The sound pressure level (SPL) on structural surfaces is calculated from the root mean square (RMS) of the unsteady pressure and the acoustic wave frequencies are computed from a fast Fourier transform (FFT) of the unsteady pressure distribution as a function of time. The resulting tool proves to be unique as it is designed to analyze complex practical problems, involving large scale computations, in a routine fashion.

A study on the measurement of radar cross section of flighting model based on the range-Doppler imaging

NASA Astrophysics Data System (ADS)

Hashimoto, Osamu; Mizokami, Osamu

The method for measuring radar cross section (RCS) based on Range-Doppler Imaging is discussed. In this method, the measured targets are rotated and the Doppler frequencies caused by each scattering element along the targets are analyzed by FFT. Using this method, each scattered power peak along the flying model is measured. It is found that each part of the RCS of a flying model can be measured and its RCS of a main wing (about 46 dB/sq cm) is greater than of its body (about 20-30 dB/sq cm).

Evaluation of burst-mode LDA spectra with implications

NASA Astrophysics Data System (ADS)

Velte, Clara; George, William

2009-11-01

Burst-mode LDA spectra, as described in [1], are compared to spectra obtained from corresponding HWA measurements using the FFT in a round jet and cylinder wake experiment. The phrase ``burst-mode LDA'' refers to an LDA which operates with at most one particle present in the measuring volume at a time. Due to the random sampling and velocity bias of the LDA signal, the Direct Fourier Transform with accompanying weighting by the measured residence times was applied to obtain a correct interpretation of the spectral estimate. Further, the self-noise was removed as described in [2]. In addition, resulting spectra from common interpolation and uniform resampling techniques are compared to the above mentioned estimates. The burst-mode LDA spectra are seen to concur well with the HWA spectra up to the emergence of the noise floor, caused mainly by the intermittency of the LDA signal. The interpolated and resampled counterparts yield unphysical spectra, which are buried in frequency dependent noise and step noise, except at very high LDA data rates where they perform well up to a limited frequency.[4pt] [1] Buchhave, P. PhD Thesis, SUNY/Buffalo, 1979.[0pt] [2] Velte, C.M. PhD Thesis, DTU/Copenhagen, 2009.

High-order nonuniformly correlated beams

NASA Astrophysics Data System (ADS)

Wu, Dan; Wang, Fei; Cai, Yangjian

2018-02-01

We have introduced a class of partially coherent beams with spatially varying correlations named high-order nonuniformly correlated (HNUC) beams, as an extension of conventional nonuniformly correlated (NUC) beams. Such beams bring a new parameter (mode order) which is used to tailor the spatial coherence properties. The behavior of the spectral density of the HNUC beams on propagation has been investigated through numerical examples with the help of discrete model decomposition and fast Fourier transform (FFT) algorithm. Our results reveal that by selecting the mode order appropriately, the more sharpened intensity maxima can be achieved at a certain propagation distance compared to that of the NUC beams, and the lateral shift of the intensity maxima on propagation is closed related to the mode order. Furthermore, analytical expressions for the r.m.s width and the propagation factor of the HNUC beams on free-space propagation are derived by means of Wigner distribution function. The influence of initial beam parameters on the evolution of the r.m.s width and the propagation factor, and the relation between the r.m.s width and the occurring of the sharpened intensity maxima on propagation have been studied and discussed in detail.

FFTs in external or hierarchical memory

NASA Technical Reports Server (NTRS)

Bailey, David H.

1989-01-01

A description is given of advanced techniques for computing an ordered FFT on a computer with external or hierarchical memory. These algorithms (1) require as few as two passes through the external data set, (2) use strictly unit stride, long vector transfers between main memory and external storage, (3) require only a modest amount of scratch space in main memory, and (4) are well suited for vector and parallel computation. Performance figures are included for implementations of some of these algorithms on Cray supercomputers. Of interest is the fact that a main memory version outperforms the current Cray library FFT routines on the Cray-2, the Cray X-MP, and the Cray Y-MP systems. Using all eight processors on the Cray Y-MP, this main memory routine runs at nearly 2 Gflops.

FFT Computation with Systolic Arrays, A New Architecture

NASA Technical Reports Server (NTRS)

Boriakoff, Valentin

1994-01-01

The use of the Cooley-Tukey algorithm for computing the l-d FFT lends itself to a particular matrix factorization which suggests direct implementation by linearly-connected systolic arrays. Here we present a new systolic architecture that embodies this algorithm. This implementation requires a smaller number of processors and a smaller number of memory cells than other recent implementations, as well as having all the advantages of systolic arrays. For the implementation of the decimation-in-frequency case, word-serial data input allows continuous real-time operation without the need of a serial-to-parallel conversion device. No control or data stream switching is necessary. Computer simulation of this architecture was done in the context of a 1024 point DFT with a fixed point processor, and CMOS processor implementation has started.

Differential pulse amplitude modulation for multiple-input single-output OWVLC

NASA Astrophysics Data System (ADS)

Yang, S. H.; Kwon, D. H.; Kim, S. J.; Son, Y. H.; Han, S. K.

2015-01-01

White light-emitting diodes (LEDs) are widely used for lighting due to their energy efficiency, eco-friendly, and small size than previously light sources such as incandescent, fluorescent bulbs and so on. Optical wireless visible light communication (OWVLC) based on LED merges lighting and communications in applications such as indoor lighting, traffic signals, vehicles, and underwater communications because LED can be easily modulated. However, physical bandwidth of LED is limited about several MHz by slow time constant of the phosphor and characteristics of device. Therefore, using the simplest modulation format which is non-return-zero on-off-keying (NRZ-OOK), the data rate reaches only to dozens Mbit/s. Thus, to improve the transmission capacity, optical filtering and pre-, post-equalizer are adapted. Also, high-speed wireless connectivity is implemented using spectrally efficient modulation methods: orthogonal frequency division multiplexing (OFDM) or discrete multi-tone (DMT). However, these modulation methods need additional digital signal processing such as FFT and IFFT, thus complexity of transmitter and receiver is increasing. To reduce the complexity of transmitter and receiver, we proposed a novel modulation scheme which is named differential pulse amplitude modulation. The proposed modulation scheme transmits different NRZ-OOK signals with same amplitude and unit time delay using each LED chip, respectively. The `N' parallel signals from LEDs are overlapped and directly detected at optical receiver. Received signal is demodulated by power difference between unit time slots. The proposed scheme can overcome the bandwidth limitation of LEDs and data rate can be improved according to number of LEDs without complex digital signal processing.

Real-Time Data Display

NASA Technical Reports Server (NTRS)

Pedings, Marc

2007-01-01

RT-Display is a MATLAB-based data acquisition environment designed to use a variety of commercial off-the-shelf (COTS) hardware to digitize analog signals to a standard data format usable by other post-acquisition data analysis tools. This software presents the acquired data in real time using a variety of signal-processing algorithms. The acquired data is stored in a standard Operator Interactive Signal Processing Software (OISPS) data-formatted file. RT-Display is primarily configured to use the Agilent VXI (or equivalent) data acquisition boards used in such systems as MIDDAS (Multi-channel Integrated Dynamic Data Acquisition System). The software is generalized and deployable in almost any testing environment, without limitations or proprietary configuration for a specific test program or project. With the Agilent hardware configured and in place, users can start the program and, in one step, immediately begin digitizing multiple channels of data. Once the acquisition is completed, data is converted into a common binary format that also can be translated to specific formats used by external analysis software, such as OISPS and PC-Signal (product of AI Signal Research Inc.). RT-Display at the time of this reporting was certified on Agilent hardware capable of acquisition up to 196,608 samples per second. Data signals are presented to the user on-screen simultaneously for 16 channels. Each channel can be viewed individually, with a maximum capability of 160 signal channels (depending on hardware configuration). Current signal presentations include: time data, fast Fourier transforms (FFT), and power spectral density plots (PSD). Additional processing algorithms can be easily incorporated into this environment.

The assessment of neural injury following open heart surgery by physiological tremor analysis.

PubMed

Németh, Adám; Hejjel, László; Ajtay, Zénó; Kellényi, Lóránd; Solymos, Andor; Bártfai, Imre; Kovács, Norbert; Lenkey, Zsófia; Cziráki, Attila; Szabados, Sándor

2013-02-21

The appearance of post-operative cognitive dysfunction as a result of open heart surgery has been proven by several studies. Focal and/or sporadic neuron damage emerging in the central nervous system may not only appear as cognitive dysfunction, but might strongly influence features of physiological tremor. We investigated 110 patients (age: 34-73 years; 76 male, 34 female; 51 coronary artery bypass grafting (CABG), 25 valve replacement, 25 combined open heart surgery, 9 off-pump CABG) before surgery and after open-heart surgery on the 3(rd) to 5(th) post-operative day. The assessment of the physiological tremor analysis was performed with our newly developed equipment based on the Analog Devices ADXL 320 JPC integrated accelerometer chip. Recordings were stored on a PC and spectral analysis was performed by fast Fourier transformation (FFT). We compared power integrals in the 1-4 Hz, 4-8 Hz and 8-12 Hz frequency ranges and these were statistically assessed by the Wilcoxon rank correlation test. We found significant changes in the power spectrum of physiological tremor. The spectrum in the 8-12 Hz range (neuronal oscillation) decreased and a shift was recognised to the lower spectrum (p < 0.01). The magnitude of the shift was not significantly higher for females than for males (p < 0.157). We found no significant difference between the shift and the cross-clamp or perfusion time (p < 0.6450). The assessment of physiological tremor by means of our novel, feasible method may provide a deeper insight into the mechanism of central nervous system damage associated with open heart surgery.

SU-E-T-91: Accuracy of Dose Calculation Algorithms for Patients Undergoing Stereotactic Ablative Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tajaldeen, A; Ramachandran, P; Geso, M

2015-06-15

Purpose: The purpose of this study was to investigate and quantify the variation in dose distributions in small field lung cancer radiotherapy using seven different dose calculation algorithms. Methods: The study was performed in 21 lung cancer patients who underwent Stereotactic Ablative Body Radiotherapy (SABR). Two different methods (i) Same dose coverage to the target volume (named as same dose method) (ii) Same monitor units in all algorithms (named as same monitor units) were used for studying the performance of seven different dose calculation algorithms in XiO and Eclipse treatment planning systems. The seven dose calculation algorithms include Superposition, Fastmore » superposition, Fast Fourier Transform ( FFT) Convolution, Clarkson, Anisotropic Analytic Algorithm (AAA), Acurous XB and pencil beam (PB) algorithms. Prior to this, a phantom study was performed to assess the accuracy of these algorithms. Superposition algorithm was used as a reference algorithm in this study. The treatment plans were compared using different dosimetric parameters including conformity, heterogeneity and dose fall off index. In addition to this, the dose to critical structures like lungs, heart, oesophagus and spinal cord were also studied. Statistical analysis was performed using Prism software. Results: The mean±stdev with conformity index for Superposition, Fast superposition, Clarkson and FFT convolution algorithms were 1.29±0.13, 1.31±0.16, 2.2±0.7 and 2.17±0.59 respectively whereas for AAA, pencil beam and Acurous XB were 1.4±0.27, 1.66±0.27 and 1.35±0.24 respectively. Conclusion: Our study showed significant variations among the seven different algorithms. Superposition and AcurosXB algorithms showed similar values for most of the dosimetric parameters. Clarkson, FFT convolution and pencil beam algorithms showed large differences as compared to superposition algorithms. Based on our study, we recommend Superposition and AcurosXB algorithms as the first choice of algorithms in lung cancer radiotherapy involving small fields. However, further investigation by Monte Carlo simulation is required to confirm our results.« less

Theoretical study of the influence of a heterogeneous activity distribution on intratumoral absorbed dose distribution.

PubMed

Bao, Ande; Zhao, Xia; Phillips, William T; Woolley, F Ross; Otto, Randal A; Goins, Beth; Hevezi, James M

2005-01-01

Radioimmunotherapy of hematopoeitic cancers and micrometastases has been shown to have significant therapeutic benefit. The treatment of solid tumors with radionuclide therapy has been less successful. Previous investigations of intratumoral activity distribution and studies on intratumoral drug delivery suggest that a probable reason for the disappointing results in solid tumor treatment is nonuniform intratumoral distribution coupled with restricted intratumoral drug penetrance, thus inhibiting antineoplastic agents from reaching the tumor's center. This paper describes a nonuniform intratumoral activity distribution identified by limited radiolabeled tracer diffusion from tumor surface to tumor center. This activity was simulated using techniques that allowed the absorbed dose distributions to be estimated using different intratumoral diffusion capabilities and calculated for tumors of varying diameters. The influences of these absorbed dose distributions on solid tumor radionuclide therapy are also discussed. The absorbed dose distribution was calculated using the dose point kernel method that provided for the application of a three-dimensional (3D) convolution between a dose rate kernel function and an activity distribution function. These functions were incorporated into 3D matrices with voxels measuring 0.10 x 0.10 x 0.10 mm3. At this point fast Fourier transform (FFT) and multiplication in frequency domain followed by inverse FFT (iFFT) were used to effect this phase of the dose calculation process. The absorbed dose distribution for tumors of 1, 3, 5, 10, and 15 mm in diameter were studied. Using the therapeutic radionuclides of 131I, 186Re, 188Re, and 90Y, the total average dose, center dose, and surface dose for each of the different tumor diameters were reported. The absorbed dose in the nearby normal tissue was also evaluated. When the tumor diameters exceed 15 mm, a much lower tumor center dose is delivered compared with tumors between 3 and 5 mm in diameter. Based on these findings, the use of higher beta-energy radionuclides, such as 188Re and 90Y is more effective in delivering a higher absorbed dose to the tumor center at tumor diameters around 10 mm.

PCTDSE: A parallel Cartesian-grid-based TDSE solver for modeling laser-atom interactions

NASA Astrophysics Data System (ADS)

Fu, Yongsheng; Zeng, Jiaolong; Yuan, Jianmin

2017-01-01

We present a parallel Cartesian-grid-based time-dependent Schrödinger equation (TDSE) solver for modeling laser-atom interactions. It can simulate the single-electron dynamics of atoms in arbitrary time-dependent vector potentials. We use a split-operator method combined with fast Fourier transforms (FFT), on a three-dimensional (3D) Cartesian grid. Parallelization is realized using a 2D decomposition strategy based on the Message Passing Interface (MPI) library, which results in a good parallel scaling on modern supercomputers. We give simple applications for the hydrogen atom using the benchmark problems coming from the references and obtain repeatable results. The extensions to other laser-atom systems are straightforward with minimal modifications of the source code.

Continuum-Scale Modeling of Shear Banding in Bulk Metallic Glass-Matrix Composites

NASA Astrophysics Data System (ADS)

Gibbons, Michael

Metallic glasses represent a relatively new class of materials that have demonstrated enormous potential for functional and structural applications due to the unique set of properties attributed to them as a result of the disordered isotropic structure with metallically bonded elements. Amorphous metals benefit from the strong nature of the metallic bonds, but lack the crystallographic structure and polycrystalline nature of traditional metals which unsurprisingly has huge implications on the material properties, as all deformation mechanisms associated with a lattice are suppressed. This results in excellent strength, a high elastic strain limit, exceptional hardness, and improved corrosion and wear resistance. "Bulk" metallic glasses (BMG) represent the amorphous metals which can be produced at the cm length-scale, thus greatly expanding their applicability for structural applications. However, due to the catastrophic nature of the failure produced upon yielding, monolithic metallic glasses are seldomly used for structural applications. Bulk metallic glass-matrix composites (BMGMCs), however, are able to combine the excellent strength, hardness, and elastic strain limit of amorphous metallic glass with a ductile crystalline phase to achieve extraordinary toughness with minimal degradation in strength. In order to explore the mechanical interactions between the amorphous and crystalline phases, a full-field micromechanical model which couples the free-volume based constitutive behavior for the matrix phase with standard rate-dependent crystal plasticity for the dendrites, and its implementation via an elastic-viscoplastic Fast-Fourier Transform (FFT) solver. The model is calibrated to macroscale stress-strain data for Ti-Zr-V-Cu-Be BMGMCs with varying composition and furthermore by comparing the deformation behavior associated with the shear bands predicted by the model, to the artifacts observed from characterization microscopy analysis on the same failed BMGMC tensile specimens in which the macroscopic composite behavior predicted by the model was validated with. The FFT-based deformation modeling is then exercised to study the nature and origin of shear bands in metallic glass composites. Synthetic 3D microstructures were produced using images of real BMGMCs, and then subjected to uniaxial tension deformation simulations. The findings indicate that in BMGMCs, local inhomogeneities in the glass phase are less influential on the mechanical performance than the contrast in individual phase properties and the spatial distribution of the microstructure. Due to the strong contrast in mechanical properties between the phases, highly heterogeneous stress fields develop, contributing to regionally confined free-volume generation, localized flow and softening in the glass. These softened regions can link and plastic flow then rapidly localizes into a thin shear band with planar like geometry. The availability of finely resolved (spatially and temporally) 3D deformation maps allow for the determination of the mechanism corresponding with these macroscopic stick-slip oscillations apparent in the stress-strain curves. In addition to shedding light on the nature of shear banding in bulk metallic glass-matrix composites, this work also demonstrates the feasibility of using a spectral-based continuum-scale model to efficiently predict the microstructure and individual phase properties that lead to new materials, superior to those found using only experimental techniques.

Validation of micro-mechanical FFT-based simulations using High Energy Diffraction Microscopy on Ti-7Al

DOE PAGES

Tari, Vahid; Lebensohn, Ricardo A.; Pokharel, Reeju; ...

2018-08-01

Here, a validation is reported for micromechanical simulation using a reimplementation of an elasto-viscoplastic FFT-based (EVPFFT) formulation, i.e., the Micromechanical Analysis of Stress-strain Inhomogeneities with fast Fourier transform (MASSIF) code, against experimental data obtained from synchrotron x-ray diffraction. The experimental data was collected during in-situ deformation of a titanium alloy specimen by High Energy Diffraction Microscopy (HEDM), which provided the average elastic strain tensor and orientation of each grain in a polycrystalline sample. MASSIF was used to calculate the local micromechanical fields in a Ti-7Al polycrystalline sample at different load levels. The initially attempted simulation showed that, although the effectivemore » response was calibrated to reproduce the experiment, MASSIF was not able to reproduce the micromechanical fields at the scale of individual grains. The differences between calculated and measured averages at the grain scale were related to initial residual strains resulting from the prior processing of the material, which had not been incorporated in the original calculation. Accordingly, a new simulation was instantiated using information on the measured residual strains to define a set of eigenstrains, calculated via an Eshelby approximation. This initialization significantly improved the correlation between calculated and simulated fields for all strain and stress components, for measurements performed within the elastic regime. For the measurements at the highest load, which was past plastic yield, the correlations deteriorated because of plastic deformation at the grain level and the lack of an accurate enough constitutive description in this deformation regime.« less

Validation of micro-mechanical FFT-based simulations using High Energy Diffraction Microscopy on Ti-7Al

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tari, Vahid; Lebensohn, Ricardo A.; Pokharel, Reeju

Here, a validation is reported for micromechanical simulation using a reimplementation of an elasto-viscoplastic FFT-based (EVPFFT) formulation, i.e., the Micromechanical Analysis of Stress-strain Inhomogeneities with fast Fourier transform (MASSIF) code, against experimental data obtained from synchrotron x-ray diffraction. The experimental data was collected during in-situ deformation of a titanium alloy specimen by High Energy Diffraction Microscopy (HEDM), which provided the average elastic strain tensor and orientation of each grain in a polycrystalline sample. MASSIF was used to calculate the local micromechanical fields in a Ti-7Al polycrystalline sample at different load levels. The initially attempted simulation showed that, although the effectivemore » response was calibrated to reproduce the experiment, MASSIF was not able to reproduce the micromechanical fields at the scale of individual grains. The differences between calculated and measured averages at the grain scale were related to initial residual strains resulting from the prior processing of the material, which had not been incorporated in the original calculation. Accordingly, a new simulation was instantiated using information on the measured residual strains to define a set of eigenstrains, calculated via an Eshelby approximation. This initialization significantly improved the correlation between calculated and simulated fields for all strain and stress components, for measurements performed within the elastic regime. For the measurements at the highest load, which was past plastic yield, the correlations deteriorated because of plastic deformation at the grain level and the lack of an accurate enough constitutive description in this deformation regime.« less

Noniterative MAP reconstruction using sparse matrix representations.

PubMed

Cao, Guangzhi; Bouman, Charles A; Webb, Kevin J

2009-09-01

We present a method for noniterative maximum a posteriori (MAP) tomographic reconstruction which is based on the use of sparse matrix representations. Our approach is to precompute and store the inverse matrix required for MAP reconstruction. This approach has generally not been used in the past because the inverse matrix is typically large and fully populated (i.e., not sparse). In order to overcome this problem, we introduce two new ideas. The first idea is a novel theory for the lossy source coding of matrix transformations which we refer to as matrix source coding. This theory is based on a distortion metric that reflects the distortions produced in the final matrix-vector product, rather than the distortions in the coded matrix itself. The resulting algorithms are shown to require orthonormal transformations of both the measurement data and the matrix rows and columns before quantization and coding. The second idea is a method for efficiently storing and computing the required orthonormal transformations, which we call a sparse-matrix transform (SMT). The SMT is a generalization of the classical FFT in that it uses butterflies to compute an orthonormal transform; but unlike an FFT, the SMT uses the butterflies in an irregular pattern, and is numerically designed to best approximate the desired transforms. We demonstrate the potential of the noniterative MAP reconstruction with examples from optical tomography. The method requires offline computation to encode the inverse transform. However, once these offline computations are completed, the noniterative MAP algorithm is shown to reduce both storage and computation by well over two orders of magnitude, as compared to a linear iterative reconstruction methods.

A Hardware-in-the-Loop Testbed for Spacecraft Formation Flying Applications

NASA Technical Reports Server (NTRS)

Leitner, Jesse; Bauer, Frank H. (Technical Monitor)

2001-01-01

The Formation Flying Test Bed (FFTB) at NASA Goddard Space Flight Center (GSFC) is being developed as a modular, hybrid dynamic simulation facility employed for end-to-end guidance, navigation, and control (GN&C) analysis and design for formation flying clusters and constellations of satellites. The FFTB will support critical hardware and software technology development to enable current and future missions for NASA, other government agencies, and external customers for a wide range of missions, particularly those involving distributed spacecraft operations. The initial capabilities of the FFTB are based upon an integration of high fidelity hardware and software simulation, emulation, and test platforms developed at GSFC in recent years; including a high-fidelity GPS simulator which has been a fundamental component of the Guidance, Navigation, and Control Center's GPS Test Facility. The FFTB will be continuously evolving over the next several years from a too[ with initial capabilities in GPS navigation hardware/software- in-the- loop analysis and closed loop GPS-based orbit control algorithm assessment to one with cross-link communications and relative navigation analysis and simulation capability. Eventually the FFT13 will provide full capability to support all aspects of multi-sensor, absolute and relative position determination and control, in all (attitude and orbit) degrees of freedom, as well as information management for satellite clusters and constellations. In this paper we focus on the architecture for the FFT13 as a general GN&C analysis environment for the spacecraft formation flying community inside and outside of NASA GSFC and we briefly reference some current and future activities which will drive the requirements and development.

Rapid simulation of spatial epidemics: a spectral method.

PubMed

Brand, Samuel P C; Tildesley, Michael J; Keeling, Matthew J

2015-04-07

Spatial structure and hence the spatial position of host populations plays a vital role in the spread of infection. In the majority of situations, it is only possible to predict the spatial spread of infection using simulation models, which can be computationally demanding especially for large population sizes. Here we develop an approximation method that vastly reduces this computational burden. We assume that the transmission rates between individuals or sub-populations are determined by a spatial transmission kernel. This kernel is assumed to be isotropic, such that the transmission rate is simply a function of the distance between susceptible and infectious individuals; as such this provides the ideal mechanism for modelling localised transmission in a spatial environment. We show that the spatial force of infection acting on all susceptibles can be represented as a spatial convolution between the transmission kernel and a spatially extended 'image' of the infection state. This representation allows the rapid calculation of stochastic rates of infection using fast-Fourier transform (FFT) routines, which greatly improves the computational efficiency of spatial simulations. We demonstrate the efficiency and accuracy of this fast spectral rate recalculation (FSR) method with two examples: an idealised scenario simulating an SIR-type epidemic outbreak amongst N habitats distributed across a two-dimensional plane; the spread of infection between US cattle farms, illustrating that the FSR method makes continental-scale outbreak forecasting feasible with desktop processing power. The latter model demonstrates which areas of the US are at consistently high risk for cattle-infections, although predictions of epidemic size are highly dependent on assumptions about the tail of the transmission kernel. Copyright © 2015 Elsevier Ltd. All rights reserved.

A digitally implemented preambleless demodulator for maritime and mobile data communications

NASA Astrophysics Data System (ADS)

Chalmers, Harvey; Shenoy, Ajit; Verahrami, Farhad B.

The hardware design and software algorithms for a low-bit-rate, low-cost, all-digital preambleless demodulator are described. The demodulator operates under severe high-noise conditions, fast Doppler frequency shifts, large frequency offsets, and multipath fading. Sophisticated algorithms, including a fast Fourier transform (FFT)-based burst acquisition algorithm, a cycle-slip resistant carrier phase tracker, an innovative Doppler tracker, and a fast acquisition symbol synchronizer, were developed and extensively simulated for reliable burst reception. The compact digital signal processor (DSP)-based demodulator hardware uses a unique personal computer test interface for downloading test data files. The demodulator test results demonstrate a near-ideal performance within 0.2 dB of theory.

FFT-SOLUTION®

EPA Pesticide Factsheets

Technical product bulletin: this dispersant for oil spill cleanups should be applied as droplets. Manufacturer recommends that spray tips on booms be changed into solid tubing for injection of product 3 to 5 feet below water surface.

Performance analysis of a finite radon transform in OFDM system under different channel models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawood, Sameer A.; Anuar, M. S.; Fayadh, Rashid A.

In this paper, a class of discrete Radon transforms namely Finite Radon Transform (FRAT) was proposed as a modulation technique in the realization of Orthogonal Frequency Division Multiplexing (OFDM). The proposed FRAT operates as a data mapper in the OFDM transceiver instead of the conventional phase shift mapping and quadrature amplitude mapping that are usually used with the standard OFDM based on Fast Fourier Transform (FFT), by the way that ensure increasing the orthogonality of the system. The Fourier domain approach was found here to be the more suitable way for obtaining the forward and inverse FRAT. This structure resultedmore » in a more suitable realization of conventional FFT- OFDM. It was shown that this application increases the orthogonality significantly in this case due to the use of Inverse Fast Fourier Transform (IFFT) twice, namely, in the data mapping and in the sub-carrier modulation also due to the use of an efficient algorithm in determining the FRAT coefficients called the optimal ordering method. The proposed approach was tested and compared with conventional OFDM, for additive white Gaussian noise (AWGN) channel, flat fading channel, and multi-path frequency selective fading channel. The obtained results showed that the proposed system has improved the bit error rate (BER) performance by reducing inter-symbol interference (ISI) and inter-carrier interference (ICI), comparing with conventional OFDM system.« less

Performance analysis of a finite radon transform in OFDM system under different channel models

NASA Astrophysics Data System (ADS)

Dawood, Sameer A.; Malek, F.; Anuar, M. S.; Fayadh, Rashid A.; Abdullah, Farrah Salwani

2015-05-01

In this paper, a class of discrete Radon transforms namely Finite Radon Transform (FRAT) was proposed as a modulation technique in the realization of Orthogonal Frequency Division Multiplexing (OFDM). The proposed FRAT operates as a data mapper in the OFDM transceiver instead of the conventional phase shift mapping and quadrature amplitude mapping that are usually used with the standard OFDM based on Fast Fourier Transform (FFT), by the way that ensure increasing the orthogonality of the system. The Fourier domain approach was found here to be the more suitable way for obtaining the forward and inverse FRAT. This structure resulted in a more suitable realization of conventional FFT- OFDM. It was shown that this application increases the orthogonality significantly in this case due to the use of Inverse Fast Fourier Transform (IFFT) twice, namely, in the data mapping and in the sub-carrier modulation also due to the use of an efficient algorithm in determining the FRAT coefficients called the optimal ordering method. The proposed approach was tested and compared with conventional OFDM, for additive white Gaussian noise (AWGN) channel, flat fading channel, and multi-path frequency selective fading channel. The obtained results showed that the proposed system has improved the bit error rate (BER) performance by reducing inter-symbol interference (ISI) and inter-carrier interference (ICI), comparing with conventional OFDM system.

An FMM-FFT Accelerated SIE Simulator for Analyzing EM Wave Propagation in Mine Environments Loaded With Conductors

PubMed Central

Sheng, Weitian; Zhou, Chenming; Liu, Yang; Bagci, Hakan; Michielssen, Eric

2018-01-01

A fast and memory efficient three-dimensional full-wave simulator for analyzing electromagnetic (EM) wave propagation in electrically large and realistic mine tunnels/galleries loaded with conductors is proposed. The simulator relies on Muller and combined field surface integral equations (SIEs) to account for scattering from mine walls and conductors, respectively. During the iterative solution of the system of SIEs, the simulator uses a fast multipole method-fast Fourier transform (FMM-FFT) scheme to reduce CPU and memory requirements. The memory requirement is further reduced by compressing large data structures via singular value and Tucker decompositions. The efficiency, accuracy, and real-world applicability of the simulator are demonstrated through characterization of EM wave propagation in electrically large mine tunnels/galleries loaded with conducting cables and mine carts. PMID:29726545

FFT Deconvultion of Be Star Hα Line Profiles

NASA Astrophysics Data System (ADS)

Austin, S. J.

2005-12-01

We have been monitoring the spectroscopic variability of Be stars using the UCA Fiber Fed Spectrograph. The spectra are 0.8 Angstrom/pixel resolution of the Hα line. The observed line profiles are a convolution of the actual profile and the instrumental profile. A Fast Fourier Transform (FFT) method has been used to deconvolve the observed profiles, given the instrument profile obtained by observing the narrow lines from the HgNe wavelength calibration lamp. The long-term monitoring of the spectroscopic variability of Be stars is crucial for testing the various Be star models. Deconvolved H-α line profiles, velocities, and variability are shown for gamma Cas, delta Sco, chi Oph, eta PsA, 48 Lib, and upsilon Sgr (HD181615). Funding has been provided by the UCA University Research Council and the Arkansas Space Grant Consortium.

OLT-centralized sampling frequency offset compensation scheme for OFDM-PON.

PubMed

Chen, Ming; Zhou, Hui; Zheng, Zhiwei; Deng, Rui; Chen, Qinghui; Peng, Miao; Liu, Cuiwei; He, Jing; Chen, Lin; Tang, Xionggui

2017-08-07

We propose an optical line terminal (OLT)-centralized sampling frequency offset (SFO) compensation scheme for adaptively-modulated OFDM-PON systems. By using the proposed SFO scheme, the phase rotation and inter-symbol interference (ISI) caused by SFOs between OLT and multiple optical network units (ONUs) can be centrally compensated in the OLT, which reduces the complexity of ONUs. Firstly, the optimal fast Fourier transform (FFT) size is identified in the intensity-modulated and direct-detection (IMDD) OFDM system in the presence of SFO. Then, the proposed SFO compensation scheme including phase rotation modulation (PRM) and length-adaptive OFDM frame has been experimentally demonstrated in the downlink transmission of an adaptively modulated optical OFDM with the optimal FFT size. The experimental results show that up to ± 300 ppm SFO can be successfully compensated without introducing any receiver performance penalties.

Properly used ''aliasing'' can give better resolution from fewer points in Fourier transform spectroscopy

NASA Astrophysics Data System (ADS)

D'Astous, Y.; Blanchard, M.

1982-05-01

In the past years, the Journal has published a number of articles1-5 devoted to the introduction of Fourier transform spectroscopy in the undergraduate labs. In most papers, the proposed experimental setup consists of a Michelson interferometer, a light source, a light detector, and a chart recorder. The student uses this setup to record an interferogram which is then Fourier transformed to obtain the spectrogram of the light source. Although attempts have been made to ease the task of performing the required Fourier transform,6 the use of computers and Cooley-Tukey's fast Fourier transform (FFT) algorithm7 is by far the simplest method to use. However, to be able to use FFT, one has to get a number of samples of the interferogram, a tedious job which should be kept to a minimum. (AIP)

Freezing and frostbite on mount everest: new insights into wind chill and freezing times at extreme altitude.

PubMed

Moore, G W K; Semple, J L

2011-01-01

Cold injury is an acknowledged risk factor for those who venture into high altitude regions. There is, however, little quantitative information on this risk that can be used to implement mitigation strategies. Here we provide the first characterization of the risk of cold injury near the summit of Mount Everest. This is accomplished through the application of a meteorological dataset that has been demonstrated to characterize conditions in the region as inputs to new parameterizations of wind chill equivalent temperature (WCT) and facial frostbite time (FFT). Throughout the year, the typical WCT near the summit of Everest is always <-30°C, and the typical FFT is always less than 20 min. During the spring climbing season, WCTs of -50°C and FFTs of 5 min are typical; during severe storms, they approach -60°C and 1 min, respectively; values typically found during the winter. Further, we show that the summit barometric pressure is an excellent predictor of summit WCT and FFT. Our results provide the first quantitative characterization of the risk of cold injury on Mount Everest and also allow for the possibility of using barometric pressure, an easily observed parameter, in real time to characterize this risk and to implement mitigation strategies. The results also provide additional confirmation as to the extreme environment experienced by those attempting to summit Mount Everest and other high mountains.

Tunable biasing magnetic field design of ferrite tuner for ICRF heating system in EAST

NASA Astrophysics Data System (ADS)

Manman, XU; Yuntao, SONG; Gen, CHEN; Yanping, ZHAO; Yuzhou, MAO; Guang, LIU; Zhen, PENG

2017-11-01

Ion cyclotron range of frequency (ICRF) heating has been used in tokamaks as one of the most successful auxiliary heating tools and has been adopted in the EAST. However, the antenna load will fluctuate with the change of plasma parameters in the ICRF heating process. To ensure the steady operation of the ICRF heating system in the EAST, fast ferrite tuner (FFT) has been carried out to achieve real-time impedance matching. For the requirements of the FFT impedance matching system, the magnet system of the ferrite tuner (FT) was designed by numerical simulations and experimental analysis, where the biasing magnetic circuit and alternating magnetic circuit were the key researched parts of the ferrite magnet. The integral design goal of the FT magnetic circuit is that DC bias magnetic field is 2000 Gs and alternating magnetic field is ±400 Gs. In the FTT, E-type magnetic circuit was adopted. Ferrite material is NdFeB with a thickness of 30 mm by setting the working point of NdFeB, and the ampere turn of excitation coil is 25 through the theoretical calculation and simulation analysis. The coil inductance to generate alternating magnetic field is about 7 mH. Eddy-current effect has been analyzed, while the magnetic field distribution has been measured by a Hall probe in the medium plane of the biasing magnet. Finally, the test results show the good performance of the biasing magnet satisfying the design and operating requirements of the FFT.

A new anisotropy index on trabecular bone radiographic images using the fast Fourier transform

PubMed Central

Brunet-Imbault, Barbara; Lemineur, Gerald; Chappard, Christine; Harba, Rachid; Benhamou, Claude-Laurent

2005-01-01

Background The degree of anisotropy (DA) on radiographs is related to bone structure, we present a new index to assess DA. Methods In a region of interest from calcaneus radiographs, we applied a Fast Fourier Transform (FFT). All the FFT spectra involve the horizontal and vertical components corresponding respectively to longitudinal and transversal trabeculae. By visual inspection, we measured the spreading angles: Dispersion Longitudinal Index (DLI) and Dispersion Transverse Index (DTI) and calculated DA = 180/(DLI+DTI). To test the reliability of DA assessment, we synthesized images simulating radiological projections of periodic structures with elements more or less disoriented. Results Firstly, we tested synthetic images which comprised a large variety of structures from highly anisotropic structure to the almost isotropic, DA was ranging from 1.3 to 3.8 respectively. The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively. In 22 post-menopausal women with osteoporotic fracture cases and 44 age-matched controls, DA values were respectively 1.87 ± 0.15 versus 1.72 ± 0.18 (p = 0.001). From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA. Conclusion The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions. PMID:15927072

A fast pulse design for parallel excitation with gridding conjugate gradient.

PubMed

Feng, Shuo; Ji, Jim

2013-01-01

Parallel excitation (pTx) is recognized as a crucial technique in high field MRI to address the transmit field inhomogeneity problem. However, it can be time consuming to design pTx pulses which is not desirable. In this work, we propose a pulse design with gridding conjugate gradient (CG) based on the small-tip-angle approximation. The two major time consuming matrix-vector multiplications are substituted by two operators which involves with FFT and gridding only. Simulation results have shown that the proposed method is 3 times faster than conventional method and the memory cost is reduced by 1000 times.

A reconfigurable multicarrier demodulator architecture

NASA Technical Reports Server (NTRS)

Kwatra, S. C.; Jamali, M. M.

1991-01-01

An architecture based on parallel and pipline design approaches has been developed for the Frequency Division Multiple Access/Time Domain Multiplexed (FDMA/TDM) conversion system. The architecture has two main modules namely the transmultiplexer and the demodulator. The transmultiplexer has two pipelined modules. These are the shared multiplexed polyphase filter and the Fast Fourier Transform (FFT). The demodulator consists of carrier, clock, and data recovery modules which are interactive. Progress on the design of the MultiCarrier Demodulator (MCD) using commercially available chips and Application Specific Integrated Circuits (ASIC) and simulation studies using Viewlogic software will be presented at the conference.

3D near-to-surface conductivity reconstruction by inversion of VETEM data using the distorted Born iterative method

USGS Publications Warehouse

Wang, G.L.; Chew, W.C.; Cui, T.J.; Aydiner, A.A.; Wright, D.L.; Smith, D.V.

2004-01-01

Three-dimensional (3D) subsurface imaging by using inversion of data obtained from the very early time electromagnetic system (VETEM) was discussed. The study was carried out by using the distorted Born iterative method to match the internal nonlinear property of the 3D inversion problem. The forward solver was based on the total-current formulation bi-conjugate gradient-fast Fourier transform (BCCG-FFT). It was found that the selection of regularization parameter follow a heuristic rule as used in the Levenberg-Marquardt algorithm so that the iteration is stable.

Free-Standing and Transparent Graphene Membrane of Polyhedron Box-Shaped Basic Building Units Directly Grown Using a NaCl Template for Flexible Transparent and Stretchable Solid-State Supercapacitors.

PubMed

Li, Na; Yang, Gongzheng; Sun, Yong; Song, Huawei; Cui, Hao; Yang, Guowei; Wang, Chengxin

2015-05-13

Transparency has never been integrated into freestanding flexible graphene paper (FF-GP), although FF-GP has been discussed extensively, because a thin transparent graphene sheet will fracture easily when the template or substrate is removed using traditional methods. Here, transparent FF-GP (FFT-GP) was developed using NaCl as the template and was applied in transparent and stretchable supercapacitors. The capacitance was improved by nearly 1000-fold compared with that of the laminated or wrinkled chemical vapor deposition graphene-film-based supercapacitors.

Artificial neural network does better spatiotemporal compressive sampling

NASA Astrophysics Data System (ADS)

Lee, Soo-Young; Hsu, Charles; Szu, Harold

2012-06-01

Spatiotemporal sparseness is generated naturally by human visual system based on artificial neural network modeling of associative memory. Sparseness means nothing more and nothing less than the compressive sensing achieves merely the information concentration. To concentrate the information, one uses the spatial correlation or spatial FFT or DWT or the best of all adaptive wavelet transform (cf. NUS, Shen Shawei). However, higher dimensional spatiotemporal information concentration, the mathematics can not do as flexible as a living human sensory system. The reason is obviously for survival reasons. The rest of the story is given in the paper.

An iterative solver for the 3D Helmholtz equation

NASA Astrophysics Data System (ADS)

Belonosov, Mikhail; Dmitriev, Maxim; Kostin, Victor; Neklyudov, Dmitry; Tcheverda, Vladimir

2017-09-01

We develop a frequency-domain iterative solver for numerical simulation of acoustic waves in 3D heterogeneous media. It is based on the application of a unique preconditioner to the Helmholtz equation that ensures convergence for Krylov subspace iteration methods. Effective inversion of the preconditioner involves the Fast Fourier Transform (FFT) and numerical solution of a series of boundary value problems for ordinary differential equations. Matrix-by-vector multiplication for iterative inversion of the preconditioned matrix involves inversion of the preconditioner and pointwise multiplication of grid functions. Our solver has been verified by benchmarking against exact solutions and a time-domain solver.

Composition and structure of porcine digital flexor tendon-bone insertion tissues.

PubMed

Chandrasekaran, Sandhya; Pankow, Mark; Peters, Kara; Huang, Hsiao-Ying Shadow

2017-11-01

Tendon-bone insertion is a functionally graded tissue, transitioning from 200 MPa tensile modulus at the tendon end to 20 GPa tensile modulus at the bone, across just a few hundred micrometers. In this study, we examine the porcine digital flexor tendon insertion tissue to provide a quantitative description of its collagen orientation and mineral concentration by using Fast Fourier Transform (FFT) based image analysis and mass spectrometry, respectively. Histological results revealed uniformity in global collagen orientation at all depths, indicative of mechanical anisotropy, although at mid-depth, the highest fiber density, least amount of dispersion, and least cellular circularity were evident. Collagen orientation distribution obtained through 2D FFT of histological imaging data from fluorescent microscopy agreed with past measurements based on polarized light microscopy. Results revealed global fiber orientation across the tendon-bone insertion to be preserved along direction of physiologic tension. Gradation in the fiber distribution orientation index across the insertion was reflective of a decrease in anisotropy from the tendon to the bone. We provided elemental maps across the fibrocartilage for its organic and inorganic constituents through time-of-flight secondary ion mass spectrometry (TOF-SIMS). The apatite intensity distribution from the tendon to bone was shown to follow a linear trend, supporting past results based on Raman microprobe analysis. The merit of this study lies in the image-based simplified approach to fiber distribution quantification and in the high spatial resolution of the compositional analysis. In conjunction with the mechanical properties of the insertion tissue, fiber, and mineral distribution results for the insertion from this may potentially be incorporated into the development of a structural constitutive approach toward computational modeling. Characterizing the properties of the native insertion tissue would provide the microstructural basis for developing biomimetic scaffolds to recreate the graded morphology of a fibrocartilaginous insertion. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3050-3058, 2017. © 2017 Wiley Periodicals, Inc.

Wide-bandwidth high-resolution search for extraterrestrial intelligence

NASA Technical Reports Server (NTRS)

Horowitz, Paul

1993-01-01

Research accomplished during the third 6-month period is summarized. Research covered the following: dual-horn antenna performance; high electron mobility transistors (HEMT) low-noise amplifiers; downconverters; fast Fourier transform (FFT) array; and backend 'feature recognizer' array.

Transition of cavitating flow to supercavitation within Venturi nozzle - hysteresis investigation

NASA Astrophysics Data System (ADS)

Jiří, Kozák; Pavel, Rudolf; Rostislav, Huzlík; Martin, Hudec; Radomír, Chovanec; Ondřej, Urban; Blahoslav, Maršálek; Eliška, Maršálková; František, Pochylý; David, Štefan

Cavitation is usually considered as undesirable phenomena. On the other hand, it can be utilized in many applications. One of the technical applications is using cavitation in water treatment, where hydrodynamic cavitation seems to be effective way how to reduce cyanobacteria within large bulks of water. The main scope of this paper is investigation of the cavitation within Venturi nozzle during the transition from fully developed cavitation to supercavitation regime and vice versa. Dynamics of cavitation was investigated using experimental data of pressure pulsations and analysis of high speed videos, where FFT of the pixel intensity and Proper Orthogonal Decomposition (POD) of the records were done to identify dominant frequencies connected with the presence of cavitation. The methodology of the high speed (HS) records semiautomated analysis using the FFT was described. Obtained results were correlated and above that the possible presence of hysteresis was discussed.

A study of GPS measurement errors due to noise and multipath interference for CGADS

NASA Technical Reports Server (NTRS)

Axelrad, Penina; MacDoran, Peter F.; Comp, Christopher J.

1996-01-01

This report describes a study performed by the Colorado Center for Astrodynamics Research (CCAR) on GPS measurement errors in the Codeless GPS Attitude Determination System (CGADS) due to noise and multipath interference. Preliminary simulation models fo the CGADS receiver and orbital multipath are described. The standard FFT algorithms for processing the codeless data is described and two alternative algorithms - an auto-regressive/least squares (AR-LS) method, and a combined adaptive notch filter/least squares (ANF-ALS) method, are also presented. Effects of system noise, quantization, baseband frequency selection, and Doppler rates on the accuracy of phase estimates with each of the processing methods are shown. Typical electrical phase errors for the AR-LS method are 0.2 degrees, compared to 0.3 and 0.5 degrees for the FFT and ANF-ALS algorithms, respectively. Doppler rate was found to have the largest effect on the performance.

Cost-effective broad-band electrical impedance spectroscopy measurement circuit and signal analysis for piezo-materials and ultrasound transducers

PubMed Central

Lewis, George K; Lewis, George K; Olbricht, William

2008-01-01

This paper explains the circuitry and signal processing to perform electrical impedance spectroscopy on piezoelectric materials and ultrasound transducers. Here, we measure and compare the impedance spectra of 2−5 MHz piezoelectrics, but the methodology applies for 700 kHz–20 MHz ultrasonic devices as well. Using a 12 ns wide 5 volt pulsing circuit as an impulse, we determine the electrical impedance curves experimentally using Ohm's law and fast Fourier transform (FFT), and compare results with mathematical models. The method allows for rapid impedance measurement for a range of frequencies using a narrow input pulse, digital oscilloscope and FFT techniques. The technique compares well to current methodologies such as network and impedance analyzers while providing additional versatility in the electrical impedance measurement. The technique is theoretically simple, easy to implement and completed with ordinary laboratory instrumentation for minimal cost. PMID:19081773

Real-time digital holographic microscopy using the graphic processing unit.

PubMed

Shimobaba, Tomoyoshi; Sato, Yoshikuni; Miura, Junya; Takenouchi, Mai; Ito, Tomoyoshi

2008-08-04

Digital holographic microscopy (DHM) is a well-known powerful method allowing both the amplitude and phase of a specimen to be simultaneously observed. In order to obtain a reconstructed image from a hologram, numerous calculations for the Fresnel diffraction are required. The Fresnel diffraction can be accelerated by the FFT (Fast Fourier Transform) algorithm. However, real-time reconstruction from a hologram is difficult even if we use a recent central processing unit (CPU) to calculate the Fresnel diffraction by the FFT algorithm. In this paper, we describe a real-time DHM system using a graphic processing unit (GPU) with many stream processors, which allows use as a highly parallel processor. The computational speed of the Fresnel diffraction using the GPU is faster than that of recent CPUs. The real-time DHM system can obtain reconstructed images from holograms whose size is 512 x 512 grids in 24 frames per second.

A combined finite element-boundary element formulation for solution of two-dimensional problems via CGFFT

NASA Technical Reports Server (NTRS)

Collins, Jeffery D.; Jin, Jian-Ming; Volakis, John L.

1990-01-01

A method for the computation of electromagnetic scattering from arbitrary two-dimensional bodies is presented. The method combines the finite element and boundary element methods leading to a system for solution via the conjugate gradient Fast Fourier Transform (FFT) algorithm. Two forms of boundaries aimed at reducing the storage requirement of the boundary integral are investigated. It is shown that the boundary integral becomes convolutional when a circular enclosure is chosen, resulting in reduced storage requirement when the system is solved via the conjugate gradient FFT method. The same holds for the ogival enclosure, except that some of the boundary integrals are not convolutional and must be carefully treated to maintain O(N) memory requirement. Results for several circular and ogival structures are presented and shown to be in excellent agreement with those obtained by traditional methods.

Determination of layer ordering using sliding-window Fourier transform of x-ray reflectivity data

NASA Astrophysics Data System (ADS)

Smigiel, E.; Knoll, A.; Broll, N.; Cornet, A.

1998-01-01

X-ray reflectometry allows the determination of the thickness, density and roughness of thin layers on a substrate from several Angstroms to some hundred nanometres. The thickness is determined by simulation with trial-and-error methods after extracting initial values of the layer thicknesses from the result of a classical Fast Fourier Transform (FFT) of the reflectivity data. However, the order information of the layers is lost during classical FFT. The order of the layers has then to be known a priori. In this paper, it will be shown that the order of the layers can be obtained by a sliding-window Fourier transform, the so-called Gabor representation. This joint time-frequency analysis allows the direct determination of the order of the layers and, therefore, the use of a more appropriate starting model for refining simulations. A simulated and a measured example show the interest of this method.

GPUs benchmarking in subpixel image registration algorithm

NASA Astrophysics Data System (ADS)

Sanz-Sabater, Martin; Picazo-Bueno, Jose Angel; Micó, Vicente; Ferrerira, Carlos; Granero, Luis; Garcia, Javier

2015-05-01

Image registration techniques are used among different scientific fields, like medical imaging or optical metrology. The straightest way to calculate shifting between two images is using the cross correlation, taking the highest value of this correlation image. Shifting resolution is given in whole pixels which cannot be enough for certain applications. Better results can be achieved interpolating both images, as much as the desired resolution we want to get, and applying the same technique described before, but the memory needed by the system is significantly higher. To avoid memory consuming we are implementing a subpixel shifting method based on FFT. With the original images, subpixel shifting can be achieved multiplying its discrete Fourier transform by a linear phase with different slopes. This method is high time consuming method because checking a concrete shifting means new calculations. The algorithm, highly parallelizable, is very suitable for high performance computing systems. GPU (Graphics Processing Unit) accelerated computing became very popular more than ten years ago because they have hundreds of computational cores in a reasonable cheap card. In our case, we are going to register the shifting between two images, doing the first approach by FFT based correlation, and later doing the subpixel approach using the technique described before. We consider it as `brute force' method. So we will present a benchmark of the algorithm consisting on a first approach (pixel resolution) and then do subpixel resolution approaching, decreasing the shifting step in every loop achieving a high resolution in few steps. This program will be executed in three different computers. At the end, we will present the results of the computation, with different kind of CPUs and GPUs, checking the accuracy of the method, and the time consumed in each computer, discussing the advantages, disadvantages of the use of GPUs.

Characterization of coronary plaque regions in intravascular ultrasound images using a hybrid ensemble classifier.

PubMed

Hwang, Yoo Na; Lee, Ju Hwan; Kim, Ga Young; Shin, Eun Seok; Kim, Sung Min

2018-01-01

The purpose of this study was to propose a hybrid ensemble classifier to characterize coronary plaque regions in intravascular ultrasound (IVUS) images. Pixels were allocated to one of four tissues (fibrous tissue (FT), fibro-fatty tissue (FFT), necrotic core (NC), and dense calcium (DC)) through processes of border segmentation, feature extraction, feature selection, and classification. Grayscale IVUS images and their corresponding virtual histology images were acquired from 11 patients with known or suspected coronary artery disease using 20 MHz catheter. A total of 102 hybrid textural features including first order statistics (FOS), gray level co-occurrence matrix (GLCM), extended gray level run-length matrix (GLRLM), Laws, local binary pattern (LBP), intensity, and discrete wavelet features (DWF) were extracted from IVUS images. To select optimal feature sets, genetic algorithm was implemented. A hybrid ensemble classifier based on histogram and texture information was then used for plaque characterization in this study. The optimal feature set was used as input of this ensemble classifier. After tissue characterization, parameters including sensitivity, specificity, and accuracy were calculated to validate the proposed approach. A ten-fold cross validation approach was used to determine the statistical significance of the proposed method. Our experimental results showed that the proposed method had reliable performance for tissue characterization in IVUS images. The hybrid ensemble classification method outperformed other existing methods by achieving characterization accuracy of 81% for FFT and 75% for NC. In addition, this study showed that Laws features (SSV and SAV) were key indicators for coronary tissue characterization. The proposed method had high clinical applicability for image-based tissue characterization. Copyright © 2017 Elsevier B.V. All rights reserved.

Intermediate frequency band digitized high dynamic range radiometer system for plasma diagnostics and real-time Tokamak control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bongers, W. A.; Beveren, V. van; Westerhof, E.

2011-06-15

An intermediate frequency (IF) band digitizing radiometer system in the 100-200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the full wave information of the mm-wave signals under investigation. The system is based on directly digitizing the IF band after down conversion. The enabling technology consists of a fast multi-giga sample analog to digital converter that has recently become available. Field programmable gate arrays (FPGA) are implemented to accomplish versatile real-time data analysis. A prototypemore » system has been developed and tested and its performance has been compared with conventional electron cyclotron emission (ECE) spectrometer systems. On the TEXTOR Tokamak a proof of principle shows that ECE, together with high power injected and scattered radiation, becomes amenable to measurement by this device. In particular, its capability to measure the phase of coherent signals in the spectrum offers important advantages in diagnostics and control. One case developed in detail employs the FPGA in real-time fast Fourier transform (FFT) and additional signal processing. The major benefit of such a FFT-based system is the real-time trade-off that can be made between frequency and time resolution. For ECE diagnostics this corresponds to a flexible spatial resolution in the plasma, with potential application in smart sensing of plasma instabilities such as the neoclassical tearing mode (NTM) and sawtooth instabilities. The flexible resolution would allow for the measurement of the full mode content of plasma instabilities contained within the system bandwidth.« less

Use of Modal Acoustic Emission to Monitor Damage Progression in Carbon Fiber/Epoxy Tows and Implications for Composite Structures

NASA Technical Reports Server (NTRS)

Waller, Jess M.; Saulsberry, Regor L.; Lucero, Ralph; Nichols, Charles T.; Wentzel, Daniel J.

2010-01-01

ASTM-based ILH methods were found to give a reproducible, quantitative estimate of the stress threshold at which significant accumulated damage began to occur. a) FR events are low energy (<2 V(exp 20 microsec) b) FR events occur close to the observed failure locus. c) FR events consist of more than 30% fiber breakage (>300 kHz) d) FR events show a consistent hierarchy of cooperative damage for composite tow, and for the COPV tested, regardless of applied load. Application of ILH or related stress profiles could lead to robust pass/fail acceptance criteria based on the FR. Initial application of FR and FFT analysis of AE data acquired on COPVs is promising.

A simple computer-based measurement and analysis system of pulmonary auscultation sounds.

PubMed

Polat, Hüseyin; Güler, Inan

2004-12-01

Listening to various lung sounds has proven to be an important diagnostic tool for detecting and monitoring certain types of lung diseases. In this study a computer-based system has been designed for easy measurement and analysis of lung sound using the software package DasyLAB. The designed system presents the following features: it is able to digitally record the lung sounds which are captured with an electronic stethoscope plugged to a sound card on a portable computer, display the lung sound waveform for auscultation sites, record the lung sound into the ASCII format, acoustically reproduce the lung sound, edit and print the sound waveforms, display its time-expanded waveform, compute the Fast Fourier Transform (FFT), and display the power spectrum and spectrogram.

Whole-machine calibration approach for phased array radar with self-test

NASA Astrophysics Data System (ADS)

Shen, Kai; Yao, Zhi-Cheng; Zhang, Jin-Chang; Yang, Jian

2017-06-01

The performance of the missile-borne phased array radar is greatly influenced by the inter-channel amplitude and phase inconsistencies. In order to ensure its performance, the amplitude and the phase characteristics of radar should be calibrated. Commonly used methods mainly focus on antenna calibration, such as FFT, REV, etc. However, the radar channel also contains T / R components, channels, ADC and messenger. In order to achieve on-based phased array radar amplitude information for rapid machine calibration and compensation, we adopt a high-precision plane scanning test platform for phase amplitude test. A calibration approach for the whole channel system based on the radar frequency source test is proposed. Finally, the advantages and the application prospect of this approach are analysed.

Mucosal wave characteristics in three voice modes (fry, hiss & overpressure) produced by a female speaker: a preliminary study using stroboscopy, HSDI and analyzed by kymography, P-FFT & Nyquist plots

NASA Astrophysics Data System (ADS)

Izdebski, Krzysztof; Ward, Ronald R.; Yan, Yuling

2012-02-01

HSDI provides a whole new way to investigate visually intra-laryngeal behavior and posturing during phonation by providing detailed real-time information about laryngeal biomechanics that include observations about mucosal wave, wave motion directionality, glottic area wave form, asymmetry of vibrations within and across vocal folds and contact area of the glottis including posterior commissure closure. These observations are fundamental to our understanding and modeling of both normal and disordered phonation. In this preliminary report we focus on direct HSDI in vivo observations of not only the glottic region, but also on the entire supraglottic laryngeal posturing during fry, breathy/hiss and over-pressured phonation modes produced in a non-pathological settings. Analysis included spatio-temporal vibration patterns of vocal folds, multi-line kymograms, spectral PFFT analysis, and Nyquist spatio-temporal plots. The presented examples reveal that supraglottic contraction assists in prolonged closed phase of the vibratory cycle, and that prolonged closed phase is longest in fry and overpressure and shortest albeit complex in hiss. Hiss also allows for vocal fold vibration despite glottis separation. These findings need to be compared to pathologic phonation representing the three voice modes to derive at better differential diagnosis.

An Efficient Adaptive Window Size Selection Method for Improving Spectrogram Visualization.

PubMed

Nisar, Shibli; Khan, Omar Usman; Tariq, Muhammad

2016-01-01

Short Time Fourier Transform (STFT) is an important technique for the time-frequency analysis of a time varying signal. The basic approach behind it involves the application of a Fast Fourier Transform (FFT) to a signal multiplied with an appropriate window function with fixed resolution. The selection of an appropriate window size is difficult when no background information about the input signal is known. In this paper, a novel empirical model is proposed that adaptively adjusts the window size for a narrow band-signal using spectrum sensing technique. For wide-band signals, where a fixed time-frequency resolution is undesirable, the approach adapts the constant Q transform (CQT). Unlike the STFT, the CQT provides a varying time-frequency resolution. This results in a high spectral resolution at low frequencies and high temporal resolution at high frequencies. In this paper, a simple but effective switching framework is provided between both STFT and CQT. The proposed method also allows for the dynamic construction of a filter bank according to user-defined parameters. This helps in reducing redundant entries in the filter bank. Results obtained from the proposed method not only improve the spectrogram visualization but also reduce the computation cost and achieves 87.71% of the appropriate window length selection.

A multi-frequency impedance analysing instrument for eddy current testing

NASA Astrophysics Data System (ADS)

Yin, W.; Dickinson, S. J.; Peyton, A. J.

2006-02-01

This paper presents the design of a high-performance multi-frequency impedance analysing instrument (MFIA) for eddy current testing which has been developed primarily for monitoring a steel production process using an inductive sensor. The system consists of a flexible multi-frequency waveform generator and a voltage/current measurement unit. The impedance of the sensor is obtained by cross-spectral analysis of the current and voltage signals. The system contains high-speed digital-to-analogue, analogue-to-digital converters and dual DSPs with one for control and interface and one dedicated to frequency-spectra analysis using fast Fourier transformation (FFT). The frequency span of the signal that can be analysed ranges from 1 kHz to 8 MHz. The system also employs a high-speed serial port interface (USB) to communicate with a personal computer (PC) and to allow for fast transmission of data and control commands. Overall, the system is capable of delivering over 250 impedance spectra per second. Although the instrument has been developed mainly for use with an inductive sensor, the system is not restricted to inductive measurement. The flexibility of the design architecture is demonstrated with capacitive and resistive measurements by using appropriate input circuitry. Issues relating to optimizing the phase of the spectra components in the excitation waveform are also discussed.

Abundance of complex organic molecules in comets

NASA Astrophysics Data System (ADS)

Biver, N.; Bockelée-Morvan, D.; Debout, V.; Crovisier, J.; Moreno, R.; Boissier, J.; Lis, D.; Colom, P.; Paubert, G.; Dello Russo, N.; Vervack, R.; Weaver, H.

2014-07-01

The IRAM-30m submillimetre radio telescope has now an improved sensitivity and versality thanks to its wide-band EMIR receivers and high-resolution FFT spectrometer. Since 2012, we have undertaken ~70 GHz wide spectral surveys in the 1-mm band in several comets: C/2009 P1 (Garradd), C/2011 L4 (PanSTARRS), C/2012 F6 (Lemmon), C/2012 S1 (ISON), and C/2013 R1 (Lovejoy). Since their discovery in comet C/1995 O1 (Hale-Bopp) in 1997 (Bockelée-Morvan et al. 2000, Crovisier et al. 2004a, 2004b), we have detected complex CHO(N)-molecules such as formic acid (HCOOH), formamide (NH_2CHO), acetaldehyde (CH_3CHO), and ethylene glycol ((CH_2OH)_2) in several other comets. HCOOH has now been detected in 6 other comets since 2004, and formamide, ethylene glycol, and acetaldehyde were re-detected for the first time in comets Lemmon or Lovejoy in 2013 (Biver et al. 2014). We will present the abundances relative to water we derive for these species, and the sensitive upper limits we obtain for other complex CHO-bearing molecules. We will discuss the implication of these findings on the origin of cometary material in comparison with observations of such molecules in the interstellar medium.

Application of an improved Nelson-Nguyen analysis to eccentric, arbitrary profile liquid annular seals

NASA Technical Reports Server (NTRS)

Padavala, Satyasrinivas; Palazzolo, Alan B.; Vallely, Pat; Ryan, Steve

1994-01-01

An improved dynamic analysis for liquid annular seals with arbitrary profile based on a method, first proposed by Nelson and Nguyen, is presented. An improved first order solution that incorporates a continuous interpolation of perturbed quantities in the circumferential direction, is presented. The original method uses an approximation scheme for circumferential gradients, based on Fast Fourier Transforms (FFT). A simpler scheme based on cubic splines is found to be computationally more efficient with better convergence at higher eccentricities. A new approach of computing dynamic coefficients based on external specified load is introduced. This improved analysis is extended to account for arbitrarily varying seal profile in both axial and circumferential directions. An example case of an elliptical seal with varying degrees of axial curvature is analyzed. A case study based on actual operating clearances of an interstage seal of the Space Shuttle Main Engine High Pressure Oxygen Turbopump is presented.

New set of design rules for resonant refractive index sensors enabled by FFT based processing of the measurement data.

PubMed

Gounaridis, Lefteris; Groumas, Panos; Schreuder, Erik; Heideman, Rene; Avramopoulos, Hercules; Kouloumentas, Christos

2016-04-04

It is still a common belief that ultra-high quality-factors (Q-factors) are a prerequisite in optical resonant cavities for high refractive index resolution and low detection limit in biosensing applications. In combination with the ultra-short steps that are necessary when the measurement of the resonance shift relies on the wavelength scanning of a laser source and conventional methods for data processing, the high Q-factor requirement makes these biosensors extremely impractical. In this work we analyze an alternative processing method based on the fast-Fourier transform, and show through Monte-Carlo simulations that improvement by 2-3 orders of magnitude can be achieved in the resolution and the detection limit of the system in the presence of amplitude and spectral noise. More significantly, this improvement is maximum for low Q-factors around 10⁴ and is present also for high intra-cavity losses and large scanning steps making the designs compatible with the low-cost aspect of lab-on-a-chip technology. Using a micro-ring resonator as model cavity and a system design with low Q-factor (10⁴), low amplitude transmission (0.85) and relatively large scanning step (0.25 pm), we show that resolution close to 0.01 pm and detection limit close to 10^-7 RIU can be achieved improving the sensing performance by more than 2 orders of magnitude compared to the performance of systems relying on a simple peak search processing method. The improvement in the limit of detection is present even when the simple method is combined with ultra-high Q-factors and ultra-short scanning steps due to the trade-off between the system resolution and sensitivity. Early experimental results are in agreement with the trends of the numerical studies.

How do we know if a clinical practice guideline is good? A response to Djulbegovic and colleagues' use of fast-and-frugal decision trees to improve clinical care strategies.

PubMed

Mercuri, Mathew

2018-04-17

Clinical practice guidelines (CPGs) and clinical pathways have become important tools for improving the uptake of evidence-based care. Where CPGs are good, adherence to the recommendations within is thought to result in improved patient outcomes. However, the usefulness of such tools for improving patient important outcomes depends both on adherence to the guideline and whether or not the CPG in question is good. This begs the question of what it is that makes a CPG good? In this issue of the Journal, Djulbegovic and colleagues offer a theory to help guide the development of CPGs. The "fast-and-frugal tree" (FFT) heuristic theory is purported to provide the theoretical structure needed to quantitatively assess clinical guidelines in practice, something that the lack of theory to guide CPG development has precluded. In this paper, I examine the role of FFTs in providing an adequate theoretical framework for developing CPGs. In my view, positioning guideline development within the FFT framework may help with problems related to adherence. However, I believe that FTTs fall short in providing panel members with the theoretical basis needed to justify which factors should be considered when developing a CPG, how information on those factors derived from research studies should be interpreted, and how those factors should be integrated into the recommendation. © 2018 John Wiley & Sons, Ltd.

FFT transformed quantitative EEG analysis of short term memory load.

PubMed

Singh, Yogesh; Singh, Jayvardhan; Sharma, Ratna; Talwar, Anjana

2015-07-01

The EEG is considered as building block of functional signaling in the brain. The role of EEG oscillations in human information processing has been intensively investigated. To study the quantitative EEG correlates of short term memory load as assessed through Sternberg memory test. The study was conducted on 34 healthy male student volunteers. The intervention consisted of Sternberg memory test, which runs on a version of the Sternberg memory scanning paradigm software on a computer. Electroencephalography (EEG) was recorded from 19 scalp locations according to 10-20 international system of electrode placement. EEG signals were analyzed offline. To overcome the problems of fixed band system, individual alpha frequency (IAF) based frequency band selection method was adopted. The outcome measures were FFT transformed absolute powers in the six bands at 19 electrode positions. Sternberg memory test served as model of short term memory load. Correlation analysis of EEG during memory task was reflected as decreased absolute power in Upper alpha band in nearly all the electrode positions; increased power in Theta band at Fronto-Temporal region and Lower 1 alpha band at Fronto-Central region. Lower 2 alpha, Beta and Gamma band power remained unchanged. Short term memory load has distinct electroencephalographic correlates resembling the mentally stressed state. This is evident from decreased power in Upper alpha band (corresponding to Alpha band of traditional EEG system) which is representative band of relaxed mental state. Fronto-temporal Theta power changes may reflect the encoding and execution of memory task.

Design for testability and diagnosis at the system-level

NASA Technical Reports Server (NTRS)

Simpson, William R.; Sheppard, John W.

1993-01-01

The growing complexity of full-scale systems has surpassed the capabilities of most simulation software to provide detailed models or gate-level failure analyses. The process of system-level diagnosis approaches the fault-isolation problem in a manner that differs significantly from the traditional and exhaustive failure mode search. System-level diagnosis is based on a functional representation of the system. For example, one can exercise one portion of a radar algorithm (the Fast Fourier Transform (FFT) function) by injecting several standard input patterns and comparing the results to standardized output results. An anomalous output would point to one of several items (including the FFT circuit) without specifying the gate or failure mode. For system-level repair, identifying an anomalous chip is sufficient. We describe here an information theoretic and dependency modeling approach that discards much of the detailed physical knowledge about the system and analyzes its information flow and functional interrelationships. The approach relies on group and flow associations and, as such, is hierarchical. Its hierarchical nature allows the approach to be applicable to any level of complexity and to any repair level. This approach has been incorporated in a product called STAMP (System Testability and Maintenance Program) which was developed and refined through more than 10 years of field-level applications to complex system diagnosis. The results have been outstanding, even spectacular in some cases. In this paper we describe system-level testability, system-level diagnoses, and the STAMP analysis approach, as well as a few STAMP applications.

Spatial filtering velocimeter for vehicle navigation with extended measurement range

NASA Astrophysics Data System (ADS)

He, Xin; Zhou, Jian; Nie, Xiaoming; Long, Xingwu

2015-05-01

The idea of using spatial filtering velocimeter is proposed to provide accurate velocity information for vehicle autonomous navigation system. The presented spatial filtering velocimeter is based on a CMOS linear image sensor. The limited frame rate restricts high speed measurement of the vehicle. To extend measurement range of the velocimeter, a method of frequency shifting is put forward. Theoretical analysis shows that the frequency of output signal can be reduced and the measurement range can be doubled by this method when the shifting direction is set the same with that of image velocity. The approach of fast Fourier transform (FFT) is employed to obtain the power spectra of the spatially filtered signals. Because of limited frequency resolution of FFT, a frequency spectrum correction algorithm, called energy centrobaric correction, is used to improve the frequency resolution. The correction accuracy energy centrobaric correction is analyzed. Experiments are carried out to measure the moving surface of a conveyor belt. The experimental results show that the maximum measurable velocity is about 800deg/s without frequency shifting, 1600deg/s with frequency shifting, when the frame rate of the image is about 8117 Hz. Therefore, the measurement range is doubled by the method of frequency shifting. Furthermore, experiments were carried out to measure the vehicle velocity simultaneously using both the designed SFV and a laser Doppler velocimeter (LDV). The measurement results of the presented SFV are coincident with that of the LDV, but with bigger fluctuation. Therefore, it has the potential of application to vehicular autonomous navigation.

Dynamic area telethermometry and its clinical applications

NASA Astrophysics Data System (ADS)

Anbar, Michael

1995-03-01

Dynamic area telethermometry (DAT) is a recent development in thermology, the science of biological heat generation and dissipation. DAT is based on monitoring changes in infrared emission, deriving from them information on the kinetics and mechanisms of biological thermoregulation. Remotely monitoring infrared emission is the most reliable technique to study bioenergetics, because it minimally perturbs the investigated system. Area monitoring of heat dissipating surfaces is needed because temporal changes in the spatial distribution of temperature conveys information on mechanisms of thermoregulation. DAT can be applied to biological systems ranging from single cells (microtelecalorimetry) to large areas of human skin (clinical thermology). DAT requires the accumulation of many (hundreds to thousands) thermal images followed by analysis of the thermokinetics of each pixel or group of pixels. In clinical thermology this analysis uses FFT to extract systemic, regional and local thermoregulatory frequencies (TRFs). DAT also extracts information on local thermoregulation from the temporal behavior of homogeneity of skin temperature (HST). Analysis of the relative contributions (FFT amplitudes) of the different frequencies allows distinction between vascular, neurological, and immunological thermoregulatory dysfunctions. This analysis, which can reveal the mechanism of the dysfunction, can be very useful in the diagnosis and staging of various disorders, ranging from diabetes mellitus and liver cirrhosis to breast cancer and malignant melanoma. From the engineering standpoint DAT requires highly stable imaging systems and effective display of the spatial distribution of TRFs to allow identification of thermoregulatory pathways and their dysfunction.

Radar cross-section reduction based on an iterative fast Fourier transform optimized metasurface

NASA Astrophysics Data System (ADS)

Song, Yi-Chuan; Ding, Jun; Guo, Chen-Jiang; Ren, Yu-Hui; Zhang, Jia-Kai

2016-07-01

A novel polarization insensitive metasurface with over 25 dB monostatic radar cross-section (RCS) reduction is introduced. The proposed metasurface is comprised of carefully arranged unit cells with spatially varied dimension, which enables approximate uniform diffusion of incoming electromagnetic (EM) energy and reduces the threat from bistatic radar system. An iterative fast Fourier transform (FFT) method for conventional antenna array pattern synthesis is innovatively applied to find the best unit cell geometry parameter arrangement. Finally, a metasurface sample is fabricated and tested to validate RCS reduction behavior predicted by full wave simulation software Ansys HFSSTM and marvelous agreement is observed.

Identification of the numerical model of FEM in reference to measurements in situ

NASA Astrophysics Data System (ADS)

Jukowski, Michał; Bec, Jarosław; Błazik-Borowa, Ewa

2018-01-01

The paper deals with the verification of various numerical models in relation to the pilot-phase measurements of a rail bridge subjected to dynamic loading. Three types of FEM models were elaborated for this purpose. Static, modal and dynamic analyses were performed. The study consisted of measuring the acceleration values of the structural components of the object at the moment of the train passing. Based on this, FFT analysis was performed, the main natural frequencies of the bridge were determined, the structural damping ratio and the dynamic amplification factor (DAF) were calculated and compared with the standard values. Calculations were made using Autodesk Simulation Multiphysics (Algor).

Experimental investigation of shock wave diffraction over a single- or double-sphere model

NASA Astrophysics Data System (ADS)

Zhang, L. T.; Wang, T. H.; Hao, L. N.; Huang, B. Q.; Chen, W. J.; Shi, H. H.

2017-01-01

In this study, the unsteady drag produced by the interaction of a shock wave with a single- and a double-sphere model is measured using imbedded accelerometers. The shock wave is generated in a horizontal circular shock tube with an inner diameter of 200 mm. The effect of the shock Mach number and the dimensionless distance between spheres is investigated. The time-history of the drag coefficient is obtained based on Fast Fourier Transformation (FFT) band-block filtering and polynomial fitting of the measured acceleration. The measured peak values of the drag coefficient, with the associated uncertainty, are reported.

A low-cost vector processor boosting compute-intensive image processing operations

NASA Technical Reports Server (NTRS)

Adorf, Hans-Martin

1992-01-01

Low-cost vector processing (VP) is within reach of everyone seriously engaged in scientific computing. The advent of affordable add-on VP-boards for standard workstations complemented by mathematical/statistical libraries is beginning to impact compute-intensive tasks such as image processing. A case in point in the restoration of distorted images from the Hubble Space Telescope. A low-cost implementation is presented of the standard Tarasko-Richardson-Lucy restoration algorithm on an Intel i860-based VP-board which is seamlessly interfaced to a commercial, interactive image processing system. First experience is reported (including some benchmarks for standalone FFT's) and some conclusions are drawn.

An Accurate and Stable FFT-based Method for Pricing Options under Exp-Lévy Processes

NASA Astrophysics Data System (ADS)

Ding, Deng; Chong U, Sio

2010-05-01

An accurate and stable method for pricing European options in exp-Lévy models is presented. The main idea of this new method is combining the quadrature technique and the Carr-Madan Fast Fourier Transform methods. The theoretical analysis shows that the overall complexity of this new method is still O(N log N) with N grid points as the fast Fourier transform methods. Numerical experiments for different exp-Lévy processes also show that the numerical algorithm proposed by this new method has an accuracy and stability for the small strike prices K. That develops and improves the Carr-Madan method.

FFT-based computation of the bioheat transfer equation for the HCC ultrasound surgery therapy modeling.

PubMed

Dillenseger, Jean-Louis; Esneault, Simon; Garnier, Carole

2008-01-01

This paper describes a modeling method of the tissue temperature evolution over time in hyperthermia. More precisely, this approach is used to simulate the hepatocellular carcinoma curative treatment by a percutaneous high intensity ultrasound surgery. The tissue temperature evolution over time is classically described by Pennes' bioheat transfer equation which is generally solved by a finite difference method. In this paper we will present a method where the bioheat transfer equation can be algebraically solved after a Fourier transformation over the space coordinates. The implementation and boundary conditions of this method will be shown and compared with the finite difference method.

Design of a Ka-Band Propagation Terminal for Atmospheric Measurements in Polar Regions

NASA Technical Reports Server (NTRS)

Houts, Jacquelynne R.; Nessel, James A.; Zemba, Michael J.

2016-01-01

This paper describes the design and performance of a Ka-Band beacon receiver developed at NASA Glenn Research Center (GRC) that will be installed alongside an existing Ka-Band Radiometer [2] located at the east end of the Svalbard Near Earth Network (NEN) complex. The goal of this experiment is to characterize rain fade attenuation to improve the performance of existing statistical rain attenuation models. The ground terminal developed by NASA GRC utilizes an FFT-based frequency estimation [3] receiver capable of characterizing total path attenuation effects due to gaseous absorption, clouds, rain, and scintillation by directly measuring the propagated signal from the satellite Thor 7.

Design of a Ka-band Propagation Terminal for Atmospheric Measurements in Polar Regions

NASA Technical Reports Server (NTRS)

Houts, Jacquelynne R.; Nessel, James A.; Zemba, Michael J.

2016-01-01

This paper describes the design and performance of a Ka-Band beacon receiver developed at NASA Glenn Research Center (GRC) that will be installed alongside an existing Ka-Band Radiometer located at the east end of the Svalbard Near Earth Network (NEN) complex. The goal of this experiment is to characterize rain fade attenuation to improve the performance of existing statistical rain attenuation models. The ground terminal developed by NASA GRC utilizes an FFT-based frequency estimation receiver capable of characterizing total path attenuation effects due to gaseous absorption, clouds, rain, and scintillation by directly measuring the propagated signal from the satellite Thor 7.

Evidence for four- and three-wave interactions in solar type III radio emissions

NASA Astrophysics Data System (ADS)

Thejappa, G.; MacDowall, R. J.; Bergamo, M.

2013-08-01

The high time resolution observations obtained by the STEREO/WAVES experiment show that in the source regions of solar type III radio bursts, Langmuir waves often occur as intense localized wave packets with short durations of only few ms. One of these wave packets shows that it is a three-dimensional field structure with WLneTe ~ 10-3, where WL is the peak energy density, and ne and Te are the electron density and temperature, respectively. For this wave packet, the conditions of the oscillating two-stream instability (OTSI) and supersonic collapse are satisfied within the error range of determination of main parameters. The density cavity, observed during this wave packet indicates that its depth, width and temporal coincidence are consistent with those of a caviton, generated by the ponderomotive force of the collapsing wave packet. The spectrum of each of the parallel and perpendicular components of the wave packet contains a primary peak at fpe, two secondary peaks at fpe ± fS and a low-frequency enhancement below fS, which, as indicated by the frequency and wave number resonance conditions, and the fast Fourier transform (FFT)-based tricoherence spectral peak at (fpe, fpe, fpe + fS, fpe - fS), are coupled to each other by the OTSI type of four-wave interaction (fpe is the local electron plasma frequency and fS is the frequency of ion sound waves). In addition to the primary peak at fpe, each of these spectra also contains a peak at 2fpe, which as indicated by the frequency and wave number resonance conditions, and the wavelet-based bicoherence spectral peak at (fpe, fpe), appears to correspond to the second harmonic electromagnetic waves generated as a result of coalescence of oppositely propagating sidebands excited by the OTSI. Thus, these observations for the first time provide combined evidence that (1) the OTSI and related strong turbulence processes play a significant role in the stabilization of the electron beam, (2) the coalescence of the oppositely propagating up- and down-shifted daughter Langmuir waves excited by the OTSI probably is the emission mechanism of the second harmonic radiation, and (3) the Langmuir collapse follows the route of OTSI in some of the type III radio bursts.

Hardware architecture design of image restoration based on time-frequency domain computation

NASA Astrophysics Data System (ADS)

Wen, Bo; Zhang, Jing; Jiao, Zipeng

2013-10-01

The image restoration algorithms based on time-frequency domain computation is high maturity and applied widely in engineering. To solve the high-speed implementation of these algorithms, the TFDC hardware architecture is proposed. Firstly, the main module is designed, by analyzing the common processing and numerical calculation. Then, to improve the commonality, the iteration control module is planed for iterative algorithms. In addition, to reduce the computational cost and memory requirements, the necessary optimizations are suggested for the time-consuming module, which include two-dimensional FFT/IFFT and the plural calculation. Eventually, the TFDC hardware architecture is adopted for hardware design of real-time image restoration system. The result proves that, the TFDC hardware architecture and its optimizations can be applied to image restoration algorithms based on TFDC, with good algorithm commonality, hardware realizability and high efficiency.

High speed FPGA-based Phasemeter for the far-infrared laser interferometers on EAST

NASA Astrophysics Data System (ADS)

Yao, Y.; Liu, H.; Zou, Z.; Li, W.; Lian, H.; Jie, Y.

2017-12-01

The far-infrared laser-based HCN interferometer and POlarimeter/INTerferometer\\break (POINT) system are important diagnostics for plasma density measurement on EAST tokamak. Both HCN and POINT provide high spatial and temporal resolution of electron density measurement and used for plasma density feedback control. The density is calculated by measuring the real-time phase difference between the reference beams and the probe beams. For long-pulse operations on EAST, the calculation of density has to meet the requirements of Real-Time and high precision. In this paper, a Phasemeter for far-infrared laser-based interferometers will be introduced. The FPGA-based Phasemeter leverages fast ADCs to obtain the three-frequency signals from VDI planar-diode Mixers, and realizes digital filters and an FFT algorithm in FPGA to provide real-time, high precision electron density output. Implementation of the Phasemeter will be helpful for the future plasma real-time feedback control in long-pulse discharge.

Laplace Transform Based Radiative Transfer Studies

NASA Astrophysics Data System (ADS)

Hu, Y.; Lin, B.; Ng, T.; Yang, P.; Wiscombe, W.; Herath, J.; Duffy, D.

2006-12-01

Multiple scattering is the major uncertainty for data analysis of space-based lidar measurements. Until now, accurate quantitative lidar data analysis has been limited to very thin objects that are dominated by single scattering, where photons from the laser beam only scatter a single time with particles in the atmosphere before reaching the receiver, and simple linear relationship between physical property and lidar signal exists. In reality, multiple scattering is always a factor in space-based lidar measurement and it dominates space- based lidar returns from clouds, dust aerosols, vegetation canopy and phytoplankton. While multiple scattering are clear signals, the lack of a fast-enough lidar multiple scattering computation tool forces us to treat the signal as unwanted "noise" and use simple multiple scattering correction scheme to remove them. Such multiple scattering treatments waste the multiple scattering signals and may cause orders of magnitude errors in retrieved physical properties. Thus the lack of fast and accurate time-dependent radiative transfer tools significantly limits lidar remote sensing capabilities. Analyzing lidar multiple scattering signals requires fast and accurate time-dependent radiative transfer computations. Currently, multiple scattering is done with Monte Carlo simulations. Monte Carlo simulations take minutes to hours and are too slow for interactive satellite data analysis processes and can only be used to help system / algorithm design and error assessment. We present an innovative physics approach to solve the time-dependent radiative transfer problem. The technique utilizes FPGA based reconfigurable computing hardware. The approach is as following, 1. Physics solution: Perform Laplace transform on the time and spatial dimensions and Fourier transform on the viewing azimuth dimension, and convert the radiative transfer differential equation solving into a fast matrix inversion problem. The majority of the radiative transfer computation goes to matrix inversion processes, FFT and inverse Laplace transforms. 2. Hardware solutions: Perform the well-defined matrix inversion, FFT and Laplace transforms on highly parallel, reconfigurable computing hardware. This physics-based computational tool leads to accurate quantitative analysis of space-based lidar signals and improves data quality of current lidar mission such as CALIPSO. This presentation will introduce the basic idea of this approach, preliminary results based on SRC's FPGA-based Mapstation, and how we may apply it to CALIPSO data analysis.

DEMONSTRATION BULLETIN: COLLOID POLISHING FILTER METHOD - FILTER FLOW TECHNOLOGY, INC.

EPA Science Inventory

The Filter Flow Technology, Inc. (FFT) Colloid Polishing Filter Method (CPFM) was tested as a transportable, trailer mounted, system that uses sorption and chemical complexing phenomena to remove heavy metals and nontritium radionuclides from water. Contaminated waters can be pro...

Use of recurrence plots in the analysis of pupil diameter dynamics in narcoleptics

NASA Astrophysics Data System (ADS)

Keegan, Andrew P.; Zbilut, J. P.; Merritt, S. L.; Mercer, P. J.

1993-11-01

Recurrence plots were used to evaluate pupil dynamics of subjects with narcolepsy. Preliminary data indicate that this nonlinear method of analyses may be more useful in revealing underlying deterministic differences than traditional methods like FFT and counting statistics.

Hydrogen Epoch of Reinozation Array (HERA) Calibrated FFT Correlator Simulation

NASA Astrophysics Data System (ADS)

Salazar, Jeffrey David; Parsons, Aaron

2018-01-01

The Hydrogen Epoch of Reionization Array (HERA) project is an astronomical radio interferometer array with a redundant baseline configuration. Interferometer arrays are being used widely in radio astronomy because they have a variety of advantages over single antenna systems. For example, they produce images (visibilities) closely matching that of a large antenna (such as the Arecibo observatory), while both the hardware and maintenance costs are significantly lower. However, this method has some complications; one being the computational cost of correlating data from all of the antennas. A correlator is an electronic device that cross-correlates the data between the individual antennas; these are what radio astronomers call visibilities. HERA, being in its early stages, utilizes a traditional correlator system. The correlator cost scales as N2, where N is the number of antennas in the array. The purpose of a redundant baseline configuration array setup is for the use of a more efficient Fast Fourier Transform (FFT) correlator. FFT correlators scale as Nlog2N. The data acquired from this sort of setup, however, inherits geometric delay and uncalibrated antenna gains. This particular project simulates the process of calibrating signals from astronomical sources. Each signal “received” by an antenna in the simulation is given random antenna gain and geometric delay. The “linsolve” Python module was used to solve for the unknown variables in the simulation (complex gains and delays), which then gave a value for the true visibilities. This first version of the simulation only mimics a one dimensional redundant telescope array detecting a small amount of sources located in the volume above the antenna plane. Future versions, using GPUs, will handle a two dimensional redundant array of telescopes detecting a large amount of sources in the volume above the array.

Compact Microscope Imaging System with Intelligent Controls

NASA Technical Reports Server (NTRS)

McDowell, Mark

2004-01-01

The figure presents selected views of a compact microscope imaging system (CMIS) that includes a miniature video microscope, a Cartesian robot (a computer- controlled three-dimensional translation stage), and machine-vision and control subsystems. The CMIS was built from commercial off-the-shelf instrumentation, computer hardware and software, and custom machine-vision software. The machine-vision and control subsystems include adaptive neural networks that afford a measure of artificial intelligence. The CMIS can perform several automated tasks with accuracy and repeatability . tasks that, heretofore, have required the full attention of human technicians using relatively bulky conventional microscopes. In addition, the automation and control capabilities of the system inherently include a capability for remote control. Unlike human technicians, the CMIS is not at risk of becoming fatigued or distracted: theoretically, it can perform continuously at the level of the best human technicians. In its capabilities for remote control and for relieving human technicians of tedious routine tasks, the CMIS is expected to be especially useful in biomedical research, materials science, inspection of parts on industrial production lines, and space science. The CMIS can automatically focus on and scan a microscope sample, find areas of interest, record the resulting images, and analyze images from multiple samples simultaneously. Automatic focusing is an iterative process: The translation stage is used to move the microscope along its optical axis in a succession of coarse, medium, and fine steps. A fast Fourier transform (FFT) of the image is computed at each step, and the FFT is analyzed for its spatial-frequency content. The microscope position that results in the greatest dispersal of FFT content toward high spatial frequencies (indicating that the image shows the greatest amount of detail) is deemed to be the focal position.

Characterizing of tissue microstructure with single-detector polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Liu, Bin; Harman, Michelle; Giattina, Susanne; Stamper, Debra L.; Demakis, Charles; Chilek, Mark; Raby, Stephanie; Brezinski, Mark E.

2006-06-01

Assessing tissue birefringence with imaging modality polarization-sensitive optical coherence tomography (PS-OCT) could improve the characterization of in vivo tissue pathology. Among the birefringent components, collagen may provide invaluable clinical information because of its alteration in disorders ranging from myocardial infarction to arthritis. But the features required of clinical imaging modality in these areas usually include the ability to assess the parameter of interest rapidly and without extensive data analysis, the characteristics that single-detector PS-OCT demonstrates. But beyond detecting organized collagen, which has been previously demonstrated and confirmed with the appropriate histological techniques, additional information can potentially be gained with PS-OCT, including collagen type, form versus intrinsic birefringence, the collagen angle, and the presence of multiple birefringence materials. In part I, we apply the simple but powerful fast-Fourier transform (FFT) to both PS-OCT mathematical modeling and in vitro bovine meniscus for improved PS-OCT data analysis. The FFT analysis yields, in a rapid, straightforward, and easily interpreted manner, information on the presence of multiple birefringent materials, distinguishing the true anatomical structure from patterns in image resulting from alterations in the polarization state and identifying the tissue/phantom optical axes. Therefore the use of the FFT analysis of PS-OCT data provides information on tissue composition beyond identifying the presence of organized collagen in real time and directly from the image without extensive mathematical manipulation or data analysis. In part II, Helistat phantoms (collagen type I) are analyzed with the ultimate goal of improved tissue characterization. This study, along with the data in part I, advance the insights gained from PS-OCT images beyond simply determining the presence or absence of birefringence.

SITE TECHNOLOGY CAPSULE: FILTER FLOW TECHNOLOGY, INC. - COLLOID POLISHING FILTER METHOD

EPA Science Inventory

The Filter Flow Technology, Inc. (FFT) Coloid Polishing Filter Method (CPFM) was demonstrated at the U.S Department of Energy's (DOE) Rock Flats Plant (RFP) as part of the U.S. Environmental Protection Agency's (EPA) Superfund and Innovative Technology Evaluation (SITE) program. ...

Multiple Frequency Contrast Source Inversion Method for Vertical Electromagnetic Profiling: 2D Simulation Results and Analyses

NASA Astrophysics Data System (ADS)

Li, Jinghe; Song, Linping; Liu, Qing Huo

2016-02-01

A simultaneous multiple frequency contrast source inversion (CSI) method is applied to reconstructing hydrocarbon reservoir targets in a complex multilayered medium in two dimensions. It simulates the effects of a salt dome sedimentary formation in the context of reservoir monitoring. In this method, the stabilized biconjugate-gradient fast Fourier transform (BCGS-FFT) algorithm is applied as a fast solver for the 2D volume integral equation for the forward computation. The inversion technique with CSI combines the efficient FFT algorithm to speed up the matrix-vector multiplication and the stable convergence of the simultaneous multiple frequency CSI in the iteration process. As a result, this method is capable of making quantitative conductivity image reconstruction effectively for large-scale electromagnetic oil exploration problems, including the vertical electromagnetic profiling (VEP) survey investigated here. A number of numerical examples have been demonstrated to validate the effectiveness and capacity of the simultaneous multiple frequency CSI method for a limited array view in VEP.

Parallel computing of a digital hologram and particle searching for microdigital-holographic particle-tracking velocimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Satake, Shin-ichi; Kanamori, Hiroyuki; Kunugi, Tomoaki

2007-02-01

We have developed a parallel algorithm for microdigital-holographic particle-tracking velocimetry. The algorithm is used in (1) numerical reconstruction of a particle image computer using a digital hologram, and (2) searching for particles. The numerical reconstruction from the digital hologram makes use of the Fresnel diffraction equation and the FFT (fast Fourier transform),whereas the particle search algorithm looks for local maximum graduation in a reconstruction field represented by a 3D matrix. To achieve high performance computing for both calculations (reconstruction and particle search), two memory partitions are allocated to the 3D matrix. In this matrix, the reconstruction part consists of horizontallymore » placed 2D memory partitions on the x-y plane for the FFT, whereas, the particle search part consists of vertically placed 2D memory partitions set along the z axes.Consequently, the scalability can be obtained for the proportion of processor elements,where the benchmarks are carried out for parallel computation by a SGI Altix machine.« less

Simulation of the modulation transfer function dependent on the partial Fourier fraction in dynamic contrast enhancement magnetic resonance imaging.

PubMed

Takatsu, Yasuo; Ueyama, Tsuyoshi; Miyati, Tosiaki; Yamamura, Kenichirou

2016-12-01

The image characteristics in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) depend on the partial Fourier fraction and contrast medium concentration. These characteristics were assessed and the modulation transfer function (MTF) was calculated by computer simulation. A digital phantom was created from signal intensity data acquired at different contrast medium concentrations on a breast model. The frequency images [created by fast Fourier transform (FFT)] were divided into 512 parts and rearranged to form a new image. The inverse FFT of this image yielded the MTF. From the reference data, three linear models (low, medium, and high) and three exponential models (slow, medium, and rapid) of the signal intensity were created. Smaller partial Fourier fractions, and higher gradients in the linear models, corresponded to faster MTF decline. The MTF more gradually decreased in the exponential models than in the linear models. The MTF, which reflects the image characteristics in DCE-MRI, was more degraded as the partial Fourier fraction decreased.

GPU Optimizations for a Production Molecular Docking Code*

PubMed Central

Landaverde, Raphael; Herbordt, Martin C.

2015-01-01

Modeling molecular docking is critical to both understanding life processes and designing new drugs. In previous work we created the first published GPU-accelerated docking code (PIPER) which achieved a roughly 5× speed-up over a contemporaneous 4 core CPU. Advances in GPU architecture and in the CPU code, however, have since reduced this relalative performance by a factor of 10. In this paper we describe the upgrade of GPU PIPER. This required an entire rewrite, including algorithm changes and moving most remaining non-accelerated CPU code onto the GPU. The result is a 7× improvement in GPU performance and a 3.3× speedup over the CPU-only code. We find that this difference in time is almost entirely due to the difference in run times of the 3D FFT library functions on CPU (MKL) and GPU (cuFFT), respectively. The GPU code has been integrated into the ClusPro docking server which has over 4000 active users. PMID:26594667

GPU Optimizations for a Production Molecular Docking Code.

PubMed

Landaverde, Raphael; Herbordt, Martin C

2014-09-01

Modeling molecular docking is critical to both understanding life processes and designing new drugs. In previous work we created the first published GPU-accelerated docking code (PIPER) which achieved a roughly 5× speed-up over a contemporaneous 4 core CPU. Advances in GPU architecture and in the CPU code, however, have since reduced this relalative performance by a factor of 10. In this paper we describe the upgrade of GPU PIPER. This required an entire rewrite, including algorithm changes and moving most remaining non-accelerated CPU code onto the GPU. The result is a 7× improvement in GPU performance and a 3.3× speedup over the CPU-only code. We find that this difference in time is almost entirely due to the difference in run times of the 3D FFT library functions on CPU (MKL) and GPU (cuFFT), respectively. The GPU code has been integrated into the ClusPro docking server which has over 4000 active users.

Implementation of a High-Speed FPGA and DSP Based FFT Processor for Improving Strain Demodulation Performance in a Fiber-Optic-Based Sensing System

NASA Technical Reports Server (NTRS)

Farley, Douglas L.

2005-01-01

NASA's Aviation Safety and Security Program is pursuing research in on-board Structural Health Management (SHM) technologies for purposes of reducing or eliminating aircraft accidents due to system and component failures. Under this program, NASA Langley Research Center (LaRC) is developing a strain-based structural health-monitoring concept that incorporates a fiber optic-based measuring system for acquiring strain values. This fiber optic-based measuring system provides for the distribution of thousands of strain sensors embedded in a network of fiber optic cables. The resolution of strain value at each discrete sensor point requires a computationally demanding data reduction software process that, when hosted on a conventional processor, is not suitable for near real-time measurement. This report describes the development and integration of an alternative computing environment using dedicated computing hardware for performing the data reduction. Performance comparison between the existing and the hardware-based system is presented.

Investigation of Quasi-periodic Solar Oscillations in Sunspots Based on SOHO/MDI Magnetograms

NASA Astrophysics Data System (ADS)

Kallunki, J.; Riehokainen, A.

2012-10-01

In this work we study quasi-periodic solar oscillations in sunspots, based on the variation of the amplitude of the magnetic field strength and the variation of the sunspot area. We investigate long-period oscillations between three minutes and ten hours. The magnetic field synoptic maps were obtained from the SOHO/MDI. Wavelet (Morlet), global wavelet spectrum (GWS) and fast Fourier transform (FFT) methods are used in the periodicity analysis at the 95 % significance level. Additionally, the quiet Sun area (QSA) signal and an instrumental effect are discussed. We find several oscillation periods in the sunspots above the 95 % significance level: 3 - 5, 10 - 23, 220 - 240, 340 and 470 minutes, and we also find common oscillation periods (10 - 23 minutes) between the sunspot area variation and that of the magnetic field strength. We discuss possible mechanisms for the obtained results, based on the existing models for sunspot oscillations.

Developments on a SEM-based X-ray tomography system: Stabilization scheme and performance evaluation

NASA Astrophysics Data System (ADS)

Gomes Perini, L. A.; Bleuet, P.; Filevich, J.; Parker, W.; Buijsse, B.; Kwakman, L. F. Tz.

2017-06-01

Recent improvements in a SEM-based X-ray tomography system are described. In this type of equipment, X-rays are generated through the interaction between a highly focused electron-beam and a geometrically confined anode target. Unwanted long-term drifts of the e-beam can lead to loss of X-ray flux or decrease of spatial resolution in images. To circumvent this issue, a closed-loop control using FFT-based image correlation is integrated to the acquisition routine, in order to provide an in-line drift correction. The X-ray detection system consists of a state-of-the-art scientific CMOS camera (indirect detection), featuring high quantum efficiency (˜60%) and low read-out noise (˜1.2 electrons). The system performance is evaluated in terms of resolution, detectability, and scanning times for applications covering three different scientific fields: microelectronics, technical textile, and material science.

Research on ground-based LWIR hyperspectral imaging remote gas detection

NASA Astrophysics Data System (ADS)

Yang, Zhixiong; Yu, Chunchao; Zheng, Weijian; Lei, Zhenggang; Yan, Min; Yuan, Xiaochun; Zhang, Peizhong

2015-10-01

The new progress of ground-based long-wave infrared remote sensing is presented, which describes the windowing spatial and temporal modulation Fourier spectroscopy imaging in details. The prototype forms the interference fringes based on the corner-cube of spatial modulation of Michelson interferometer, using cooled long-wave infrared photovoltaic staring FPA (focal plane array) detector. The LWIR hyperspectral imaging is achieved by the process of collection, reorganization, correction, apodization, FFT etc. from data cube. Noise equivalent sensor response (NESR), which is the sensitivity index of CHIPED-1 LWIR hyperspectral imaging prototype, can reach 5.6×10-8W/(cm-1.sr.cm2) at single sampling. Hyperspectral imaging is used in the field of organic gas VOC infrared detection. Relative to wide band infrared imaging, it has some advantages. Such as, it has high sensitivity, the strong anti-interference ability, identify the variety, and so on.

THE PSTD ALGORITHM: A TIME-DOMAIN METHOD REQUIRING ONLY TWO CELLS PER WAVELENGTH. (R825225)

EPA Science Inventory

A pseudospectral time-domain (PSTD) method is developed for solutions of Maxwell's equations. It uses the fast Fourier transform (FFT), instead of finite differences on conventional finite-difference-time-domain (FDTD) methods, to represent spatial derivatives. Because the Fourie...

Temporal Characteristics of the Sleep EEG Power Spectrum in Critically Ill Children

PubMed Central

Kudchadkar, Sapna R.; Yaster, Myron; Punjabi, Arjun N.; Quan, Stuart F.; Goodwin, James L.; Easley, R. Blaine; Punjabi, Naresh M.

2015-01-01

Study Objectives: Although empirical evidence is limited, critical illness in children is associated with disruption of the normal sleep-wake rhythm. The objective of the current study was to examine the temporal characteristics of the sleep electroencephalogram (EEG) in a sample of children with critical illness. Methods: Limited montage EEG recordings were collected for at least 24 hours from 8 critically ill children on mechanical ventilation for respiratory failure in a pediatric intensive care unit (PICU) of a tertiary-care hospital. Each PICU patient was age- and gender-matched to a healthy subject from the community. Power spectral analysis with the fast Fourier transform (FFT) was used to characterize EEG spectral power and categorized into 4 frequency bands: δ (0.8 to 4.0 Hz), θ (4.1 to 8.0 Hz), α (8.1 to 13.0 Hz), and β1/β2 (13.1 to 20.0 Hz). Results: PICU patients did not manifest the ultradian variability in EEG power spectra including the typical increase in δ-power during the first third of the night that was observed in healthy children. Differences noted included significantly lower mean nighttime δ and θ power in the PICU patients compared to healthy children (p < 0.001). Moreover, in the PICU patients, mean δ and θ power were higher during daytime hours than nighttime hours (p < 0.001). Conclusions: The results presented herein challenge the assumption that children experience restorative sleep during critical illness, highlighting the need for interventional studies to determine whether sleep promotion improves outcomes in critically ill children undergoing active neurocognitive development. Citation: Kudchadkar SR, Yaster M, Punjabi AN, Quan SF, Goodwin JL, Easley RB, Punjabi NM. Temporal characteristics of the sleep EEG power spectrum in critically ill children. J Clin Sleep Med 2015;11(12):1449–1454. PMID:26194730

Protein–protein docking by fast generalized Fourier transforms on 5D rotational manifolds

PubMed Central

Padhorny, Dzmitry; Kazennov, Andrey; Zerbe, Brandon S.; Porter, Kathryn A.; Xia, Bing; Mottarella, Scott E.; Kholodov, Yaroslav; Ritchie, David W.; Vajda, Sandor; Kozakov, Dima

2016-01-01

Energy evaluation using fast Fourier transforms (FFTs) enables sampling billions of putative complex structures and hence revolutionized rigid protein–protein docking. However, in current methods, efficient acceleration is achieved only in either the translational or the rotational subspace. Developing an efficient and accurate docking method that expands FFT-based sampling to five rotational coordinates is an extensively studied but still unsolved problem. The algorithm presented here retains the accuracy of earlier methods but yields at least 10-fold speedup. The improvement is due to two innovations. First, the search space is treated as the product manifold SO(3)×(SO(3)∖S1), where SO(3) is the rotation group representing the space of the rotating ligand, and (SO(3)∖S1) is the space spanned by the two Euler angles that define the orientation of the vector from the center of the fixed receptor toward the center of the ligand. This representation enables the use of efficient FFT methods developed for SO(3). Second, we select the centers of highly populated clusters of docked structures, rather than the lowest energy conformations, as predictions of the complex, and hence there is no need for very high accuracy in energy evaluation. Therefore, it is sufficient to use a limited number of spherical basis functions in the Fourier space, which increases the efficiency of sampling while retaining the accuracy of docking results. A major advantage of the method is that, in contrast to classical approaches, increasing the number of correlation function terms is computationally inexpensive, which enables using complex energy functions for scoring. PMID:27412858

A review of empirically supported psychological therapies for mood disorders in adults

PubMed Central

Hollon, Steven D.; Ponniah, Kathryn

2010-01-01

Background The mood disorders are prevalent and problematic. We review randomized controlled psychotherapy trials to find those that are empirically supported with respect to acute symptom reduction and the prevention of subsequent relapse and recurrence. Methods We searched the PsycINFO and PubMed databases and the reference sections of chapters and journal articles to identify appropriate articles. Results One hundred twenty-five studies were found evaluating treatment efficacy for the various mood disorders. With respect to the treatment of major depressive disorder (MDD), interpersonal psychotherapy (IPT), cognitive behavior therapy (CBT), and behavior therapy (BT) are efficacious and specific and brief dynamic therapy (BDT) and emotion-focused therapy (EFT) are possibly efficacious. CBT is efficacious and specific, mindfulness-based cognitive therapy (MBCT) efficacious, and BDT and EFT possibly efficacious in the prevention of relapse/recurrence following treatment termination and IPT and CBT are each possibly efficacious in the prevention of relapse/recurrence if continued or maintained. IPT is possibly efficacious in the treatment of dysthymic disorder. With respect to bipolar disorder, CBT and family-focused therapy (FFT) are efficacious and interpersonal social rhythm therapy (IPSRT) possibly efficacious as adjuncts to medication in the treatment of depression. Psycho-education (PE) is efficacious in the prevention of mania/hypomania (and possibly depression) and FFT is efficacious and IPSRT and CBT possibly efficacious in preventing bipolar episodes. Conclusions The newer psychological interventions are as efficacious as and more enduring than medications in the treatment of MDD and may enhance the efficacy of medications in the treatment of bipolar disorder. PMID:20830696

Parallel Signal Processing and System Simulation using aCe

NASA Technical Reports Server (NTRS)

Dorband, John E.; Aburdene, Maurice F.

2003-01-01

Recently, networked and cluster computation have become very popular for both signal processing and system simulation. A new language is ideally suited for parallel signal processing applications and system simulation since it allows the programmer to explicitly express the computations that can be performed concurrently. In addition, the new C based parallel language (ace C) for architecture-adaptive programming allows programmers to implement algorithms and system simulation applications on parallel architectures by providing them with the assurance that future parallel architectures will be able to run their applications with a minimum of modification. In this paper, we will focus on some fundamental features of ace C and present a signal processing application (FFT).

MEGADOCK 4.0: an ultra-high-performance protein-protein docking software for heterogeneous supercomputers.

PubMed

Ohue, Masahito; Shimoda, Takehiro; Suzuki, Shuji; Matsuzaki, Yuri; Ishida, Takashi; Akiyama, Yutaka

2014-11-15

The application of protein-protein docking in large-scale interactome analysis is a major challenge in structural bioinformatics and requires huge computing resources. In this work, we present MEGADOCK 4.0, an FFT-based docking software that makes extensive use of recent heterogeneous supercomputers and shows powerful, scalable performance of >97% strong scaling. MEGADOCK 4.0 is written in C++ with OpenMPI and NVIDIA CUDA 5.0 (or later) and is freely available to all academic and non-profit users at: http://www.bi.cs.titech.ac.jp/megadock. akiyama@cs.titech.ac.jp Supplementary data are available at Bioinformatics online. © The Author 2014. Published by Oxford University Press.

Multitasking domain decomposition fast Poisson solvers on the Cray Y-MP

NASA Technical Reports Server (NTRS)

Chan, Tony F.; Fatoohi, Rod A.

1990-01-01

The results of multitasking implementation of a domain decomposition fast Poisson solver on eight processors of the Cray Y-MP are presented. The object of this research is to study the performance of domain decomposition methods on a Cray supercomputer and to analyze the performance of different multitasking techniques using highly parallel algorithms. Two implementations of multitasking are considered: macrotasking (parallelism at the subroutine level) and microtasking (parallelism at the do-loop level). A conventional FFT-based fast Poisson solver is also multitasked. The results of different implementations are compared and analyzed. A speedup of over 7.4 on the Cray Y-MP running in a dedicated environment is achieved for all cases.

A spectral analysis of team dynamics and tactics in Brazilian football.

PubMed

Moura, Felipe Arruda; Martins, Luiz Eduardo Barreto; Anido, Ricardo O; Ruffino, Paulo Régis C; Barros, Ricardo M L; Cunha, Sergio Augusto

2013-01-01

The purposes of this study were to characterise the total space covered and the distances between players within teams over ten Brazilian First Division Championship matches. Filmed recordings, combined with a tracking system, were used to obtain the trajectories of the players (n = 277), before and after half-time. The team surface area (the area of the convex hull formed by the positions of the players) and spread (the Frobenius norm of the distance-between-player matrix) were calculated as functions of time. A Fast Fourier Transform (FFT) was applied to each time series. The median frequency was then calculated. The results of the surface area time series median frequencies for the first half (0.63 ± 0.10 cycles · min⁻¹) were significantly greater (P < 0.01) than the second-half values (0.47 ± 0.14 cycles · min⁻¹). Similarly, the spread variable median frequencies for the first half (0.60 ± 0.14 cycles · min⁻¹) were significantly greater (P < 0.01) than the second-half values (0.46 ± 0.16 cycles · min⁻¹). The median frequencies allowed the characterisation of the time series oscillations that represent the speed at which players distribute and then compact their team formation during a match. This analysis can provide insights that allow coaches to better control the team organisation on the pitch.

Extremely low frequency (ELF) stray magnetic fields of laboratory equipment: a possible co-exposure conducting experiments on cell cultures.

PubMed

Gresits, Iván; Necz, Péter Pál; Jánossy, Gábor; Thuróczy, György

2015-09-01

Measurements of extremely low frequency (ELF) magnetic fields were conducted in the environment of commercial laboratory equipment in order to evaluate the possible co-exposure during the experimental processes on cell cultures. Three types of device were evaluated: a cell culture CO2 incubator, a thermostatic water bath and a laboratory shaker table. These devices usually have electric motors, heating wires and electronic control systems, therefore may expose the cell cultures to undesirable ELF stray magnetic fields. Spatial distributions of magnetic field time domain signal waveform and frequency spectral analysis (FFT) were processed. Long- and short-term variation of stray magnetic field was also evaluated under normal use of investigated laboratory devices. The results show that the equipment under test may add a considerable ELF magnetic field to the ambient environmental magnetic field or to the intentional exposure to ELF, RF or other physical/chemical agents. The maximum stray magnetic fields were higher than 3 µT, 20 µT and 75 µT in the CO2 incubator, in water bath and on the laboratory shaker table, respectively, with high variation of spatial distribution and time domain. Our investigation emphasizes possible confounding factors conducting cell culture studies related to low-level ELF-EMF exposure due to the existing stray magnetic fields in the ambient environment of laboratory equipment.

U.S. EPA, Pesticide Product Label, , 07/17/1984

EPA Pesticide Factsheets

2011-04-14

... ff~(;t bcgirullng \\I;hen qta!":~ reSU:',C'5 gro'wo't.h ill t.ile G!'ring (t"~~rcb-;\\} rll}. Rcpelit. at 7 to 10 day ... 1 : .I 1 L t "rll~lt l Iy l! ~ I '" I ' , • , ,t '.; r • ',.r ...

Optimal Simulations by Butterfly Networks: Extended Abstract,

DTIC Science & Technology

1987-11-01

Typescript , Univ. of Massachusetts; submitted for nublication. 1_2.2 Ll, - W 12. ifliU 1.8 UI1.25 . l i I 61 MICROCOPY RESOLUTION TEST CHART NATIONAL...1987): An optimal mapping of the FFT algorithm onto the tlypercube architecture. Typescript , Univ. of Massachusetts; submitted for publication. (HR I

Narrowband Interference Suppression in Spread Spectrum Communication Systems

DTIC Science & Technology

1995-12-01

receiver input. As stated earlier, these waveforms must be sampled to obtain the discrete time sequences. The sampling theorem states: A bandlimited...From the FFT chips, the data is passed to a Plessey PDSP16330 Pythagoras Processor. The 16330 is a high-speed digital CMOS IC that converts real and

Comparison of Orthogonal Transforms for Teleseismic Data

DTIC Science & Technology

1974-10-31

inverse transform Because the computations are done in-plaee( Y is both input and output arrays; X is a complex buffer array. The program generates...the forward transform the FFT is done first, then the array is phase-shifted; for the inverse transform the reverse procedure is followed. Each

Dimensionality of Upper Elementary Mathematics Instruction: Exploring Factors across Two Observational Instruments

ERIC Educational Resources Information Center

Blazar, David; Braslow, David; Charalambous, Charalambos Y.

2015-01-01

Over the past several years, research teams have developed observational instruments to measure the quality of teachers' instructional practices. Instruments such as Framework for Teaching (FFT) and the Classroom Assessment Scoring System (CLASS) assess general teaching practices, including student-teacher interactions, behavior management, and…

Effects of Amplitude Compression on Relative Auditory Distance Perception

DTIC Science & Technology

2013-10-01

FFT analyses are shown in Figure 4. The use of convolution of the stimuli with the binaural impulse responses recorded from KEMAR resulted in the...human sound localization (pp. 36-200). Cambridge, MA: The MIT Press. Carmichel, E. L., Harris, F. P., & Story, B. H. (2007). Effects of binaural

Bottle-Neck Feature Extraction Structures for Multilingual Training and Porting (Pub Version, Open Access)

DTIC Science & Technology

2016-05-03

24 Mel-scaled filters applied on squared FFT magnitudes (critical band energies, CRBE) and 10 F0-related coefficients. The filter- bank spans...Acknowledgements This work was supported by the Intelligence Advanced Research Projects Activity (IARPA) via Department of Defense US Army Research Laboratory

Machine Learning-Aided, Robust Wideband Spectrum Sensing for Cognitive Radios

DTIC Science & Technology

2015-06-12

to even Approved for public release; distribution is unlimited. 2 on the order of a giga -Hertz (GHz). Due to wide bandwidth and noncontiguous...Frequency Band CS Compressive Sampling DFT Discrete Fourier Transform EMI Electro Magnetic Interference FFT Fast Fourier Transform GHz Giga Hertz Hz Hertz

Nested Conjugate Gradient Algorithm with Nested Preconditioning for Non-linear Image Restoration.

PubMed

Skariah, Deepak G; Arigovindan, Muthuvel

2017-06-19

We develop a novel optimization algorithm, which we call Nested Non-Linear Conjugate Gradient algorithm (NNCG), for image restoration based on quadratic data fitting and smooth non-quadratic regularization. The algorithm is constructed as a nesting of two conjugate gradient (CG) iterations. The outer iteration is constructed as a preconditioned non-linear CG algorithm; the preconditioning is performed by the inner CG iteration that is linear. The inner CG iteration, which performs preconditioning for outer CG iteration, itself is accelerated by an another FFT based non-iterative preconditioner. We prove that the method converges to a stationary point for both convex and non-convex regularization functionals. We demonstrate experimentally that proposed method outperforms the well-known majorization-minimization method used for convex regularization, and a non-convex inertial-proximal method for non-convex regularization functional.

Tensorial Basis Spline Collocation Method for Poisson's Equation

NASA Astrophysics Data System (ADS)

Plagne, Laurent; Berthou, Jean-Yves

2000-01-01

This paper aims to describe the tensorial basis spline collocation method applied to Poisson's equation. In the case of a localized 3D charge distribution in vacuum, this direct method based on a tensorial decomposition of the differential operator is shown to be competitive with both iterative BSCM and FFT-based methods. We emphasize the O(h4) and O(h6) convergence of TBSCM for cubic and quintic splines, respectively. We describe the implementation of this method on a distributed memory parallel machine. Performance measurements on a Cray T3E are reported. Our code exhibits high performance and good scalability: As an example, a 27 Gflops performance is obtained when solving Poisson's equation on a 2563 non-uniform 3D Cartesian mesh by using 128 T3E-750 processors. This represents 215 Mflops per processors.

[Quantitative relationships between hyper-spectral vegetation indices and leaf area index of rice].

PubMed

Tian, Yong-Chao; Yang, Jie; Yao, Xia; Zhu, Yan; Cao, Wei-Xing

2009-07-01

Based on field experiments with different rice varieties under different nitrogen application levels, the quantitative relationships of rice leaf area index (LAI) with canopy hyper-spectral parameters at different growth stages were analyzed. Rice LAI had good relationships with several hyper-spectral vegetation indices, the correlation coefficient being the highest with DI (difference index), followed by with RI (ratio index), and NI (normalized index), based on the spectral reflectance or the first derivative spectra. The two best spectral indices for estimating LAI were the difference index DI (854, 760) (based on two spectral bands of 850 nm and 760 nm) and the difference index DI (D676, D778) (based on two first derivative bands of 676 nm and 778 nm). In general, the hyper-spectral vegetation indices based on spectral reflectance performed better than the spectral indices based on the first derivative spectra. The tests with independent dataset suggested that the rice LAI monitoring models with difference index DI (854,760) as the variable could give an accurate LAI estimation, being available for estimation of rice LAI.

A fatigue monitoring system based on time-domain and frequency-domain analysis of pulse data

NASA Astrophysics Data System (ADS)

Shen, Jiaai

2018-04-01

Fatigue is almost a problem that everyone would face, and a psychosis that everyone hates. If we can test people's fatigue condition and remind them of the tiredness, dangers in life, for instance, traffic accidents and sudden death will be effectively reduced, people's fatigued operations will be avoided. And people can be assisted to have access to their own and others' physical condition in time to alternate work with rest. The article develops a wearable bracelet based on FFT Pulse Frequency Spectrum Analysis and IBI's standard deviation and range calculation, according to people's heart rate (BPM) and inter-beat interval (IBI) while being tired and conscious. The hardware part is based on Arduino, pulse rate sensor, and Bluetooth module, and the software part is relied on network micro database and APP. By doing sample experiment to get more accurate standard value to judge tiredness, we prove that we can judge people's fatigue condition based on heart rate (BPM) and inter-beat interval (IBI).

Logarithmic Laplacian Prior Based Bayesian Inverse Synthetic Aperture Radar Imaging.

PubMed

Zhang, Shuanghui; Liu, Yongxiang; Li, Xiang; Bi, Guoan

2016-04-28

This paper presents a novel Inverse Synthetic Aperture Radar Imaging (ISAR) algorithm based on a new sparse prior, known as the logarithmic Laplacian prior. The newly proposed logarithmic Laplacian prior has a narrower main lobe with higher tail values than the Laplacian prior, which helps to achieve performance improvement on sparse representation. The logarithmic Laplacian prior is used for ISAR imaging within the Bayesian framework to achieve better focused radar image. In the proposed method of ISAR imaging, the phase errors are jointly estimated based on the minimum entropy criterion to accomplish autofocusing. The maximum a posterior (MAP) estimation and the maximum likelihood estimation (MLE) are utilized to estimate the model parameters to avoid manually tuning process. Additionally, the fast Fourier Transform (FFT) and Hadamard product are used to minimize the required computational efficiency. Experimental results based on both simulated and measured data validate that the proposed algorithm outperforms the traditional sparse ISAR imaging algorithms in terms of resolution improvement and noise suppression.

Family Focused Therapy for Bipolar Adolescents: Lessons from a Difficult Treatment Case

ERIC Educational Resources Information Center

George, Elizabeth L.; Taylor, Dawn O.; Goldstein, Benjamin I.; Miklowitz, David J.

2011-01-01

This paper examines obstacles and challenges encountered in the manualized Family Focused Therapy-A of an adolescent with bipolar disorder. We begin by describing adolescent bipolar disorder and some of the many complications that frequently accompany it. We summarize Family Focused Therapy (FFT-A), an empirically validated treatment approach for…

Wireless Intrusion Detection

DTIC Science & Technology

2007-03-01

32 4.4 Algorithm Pseudo - Code ...................................................................................34 4.5 WIND Interface With a...difference estimates of xc temporal derivatives, or by using a polynomial fit to the previous values of xc. 34 4.4 ALGORITHM PSEUDO - CODE Pseudo ...Phase Shift Keying DQPSK Differential Quadrature Phase Shift Keying EVM Error Vector Magnitude FFT Fast Fourier Transform FPGA Field Programmable