148 Matching Results

Search Results

Advanced search parameters have been applied.

Sensitivity Enhancement by Exchange Mediated MagnetizationTransfer of the Xenon Biosensor Signal

Description: Hyperpolarized xenon associated with ligand derivitized cryptophane-A cages has been developed as a NMR based biosensor. To optimize the detection sensitivity we describe use of xenon exchange between the caged and bulk dissolved xenon as an effective signal amplifier. This approach, somewhat analogous to 'remote detection' described recently, uses the chemical exchange to repeatedly transfer spectroscopic information from caged to bulk xenon, effectively integrating the caged signal. After an optimized integration period, the signal is read out by observation of the bulk magnetization. The spectrum of the caged xenon is reconstructed through use of a variable evolution period before transfer and Fourier analysis of the bulk signal as a function of the evolution time.
Date: August 31, 2006
Creator: Garcia, Sandra; Chavez, Lana; Lowery, Thomas J.; Han, Song-I.; Wemmer, David E. & Pines, Alexander
Partner: UNT Libraries Government Documents Department

Investigation of Aperiodic Time Processes With Autocorrelation and Fourier Analysis

Description: "Autocorrelation and frequency analyses of a series of aperiodic time events, in particular, filtered noises and sibilant sounds, were made. The position and band width of the frequency ranges are best obtained from the frequency analysis, but the energies contained in the several bands are most easily obtained from the autocorrelation function. The mean number of zero crossings of the time function was determined from the curvature of the latter function in the vicinity of the zero crossing, and also with the aid of a decimal counter. The second method was found to be more exact" (p. 1).
Date: March 1958
Creator: Exner, Marie Luise
Partner: UNT Libraries Government Documents Department

Material-dependent high-frequency current fluctuations of cathodicvacuum arcs: Evidence for the ecton cutoff of the fractal model

Description: Current fluctuations of cathodic arcs were recorded withhigh analog bandwidth (up to 1 GHz) and fast digital sampling (up to 5Gsamples/sec). The power spectral density of the arc current wasdetermined by fast Fourier transform clearly showing material dependent,non-linear features in the frequency domain. These features can beassociated with the non-linear impedance of the conducting channelbetween cathode and anode, driven by the explosive nature of electronemission and plasma formation. The characteristic times of less than 100ns can be associated with individual explosive processes, "ectons," andtherefore represent the short-time physical cutoff for the fractal modelof cathodic arcs.
Date: December 22, 2005
Creator: Anders, Andre & Oks, Efim
Partner: UNT Libraries Government Documents Department

Program for the Location of Fourier Peak Centers. Final Report of Program 4.10.27

Description: The computer program MET-146, in FORTRAN, locates maxima on Fourier (or Patterson) maps from 27 surrounding points in the 3-dimensional Fourier case and from 9 points for a 2-dimensional case. Input, output, and operations are described. Results obtained with this program are compared with those from other programs and from analytical extrapolation. A test problem is also included. (D.C.W.)
Date: July 1, 1963
Creator: Mueller, M. H.; Clark, F. & Simonsen, S. H.
Partner: UNT Libraries Government Documents Department

Fourier analysis

Description: What follows is a description of my analysis. First, the FFT that I use is described on the attached pages. Note that the scaling factor for the forward transform is 1/N. I compute the following rms values: rms(original data) = 64.9463 nm; rms(data*hanning) = 55.7723 nm (before renormalization). The use of the hanning filter is accompanied by a renormalization to insure that the rms value is maintained. I also fit to the curvature of the scan. The data corrected for focus gives the following rms values: rms(corrected data) = 56.8835 nm; rms(corrected data*hanning) = 53.2179 nm (before renormalization). The PSD is shown for various data. The PSD is calculated as: PSD = | FFT(y) | {sup 2} * xl where xl is the length of the x axis, 45.9952. I did find an error in the plot that you were sent. If kx is the frequency axis, i.e., values from (0,Nyquist), then kx(l,Nyquist) is plotted versus PSD(0,Nyquist). This error is corrected in the attached plots. The plot you have appears to be the PSD of the original data with no hanning applied. The removal of the quadratic term appear to have a negligible effect on the PSD. It changes only the first couple of terms (which lie outside of the data valid range). The removal of the center feature has a much stronger effect.
Date: March 3, 1997
Creator: Lawson, J.
Partner: UNT Libraries Government Documents Department

FOURIER ANALYSIS OF EXTENDED FINE STRUCTURE WITH AUTOREGRESSIVE PREDICTION

Description: Autoregressive prediction is adapted to double the resolution of Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) Fourier transforms. Even with the optimal taper (weighting function), the commonly used taper-and-transform Fourier method has limited resolution: it assumes the signal is zero beyond the limits of the measurement. By seeking the Fourier spectrum of an infinite extent oscillation consistent with the measurements but otherwise having maximum entropy, the errors caused by finite data range can be reduced. Our procedure developed to implement this concept applies autoregressive prediction to extrapolate the signal to an extent controlled by a taper width. Difficulties encountered when processing actual ARPEFS data are discussed. A key feature of this approach is the ability to convert improved measurements (signal-to-noise or point density) into improved Fourier resolution.
Date: January 1, 1985
Creator: Barton, J. & Shirley, D.A.
Partner: UNT Libraries Government Documents Department

HIGH RESOLUTION FOURIER ANALYSIS WITH AUTO-REGRESSIVE LINEAR PREDICTION

Description: Auto-regressive linear prediction is adapted to double the resolution of Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) Fourier transforms. Even with the optimal taper (weighting function), the commonly used taper-and-transform Fourier method has limited resolution: it assumes the signal is zero beyond the limits of the measurement. By seeking the Fourier spectrum of an infinite extent oscillation consistent with the measurements but otherwise having maximum entropy, the errors caused by finite data range can be reduced. Our procedure developed to implement this concept adapts auto-regressive linear prediction to extrapolate the signal in an effective and controllable manner. Difficulties encountered when processing actual ARPEFS data are discussed. A key feature of this approach is the ability to convert improved measurements (signal-to-noise or point density) into improved Fourier resolution.
Date: April 1, 1984
Creator: Barton, J. & Shirley, D.A.
Partner: UNT Libraries Government Documents Department

Characterizing the Nanoscale Layers of Tomorrow___s Electronics An Application of Fourier Analysis

Description: Thin film applications are of great interest to the semiconductor industry due to the important role they play in cutting edge technology such as thin film solar cells. X-Ray Reflectivity (XRR) characterizes thin films in a non-destructive and efficient manner yet complications exist in extracting these characteristics from raw XRR data. This study developed and tested two different algorithms to extract quantity of layers and thickness information on the nanometer scale from XRR data. It was concluded that an algorithm involving a local averaging technique revealed this information clearly in Fourier space.
Date: August 24, 2012
Creator: Payne, Christopher Bishop & /SLAC, /Princeton U.
Partner: UNT Libraries Government Documents Department

A Software System for Modeling and Controlling Accelerator Physics Parameters at the Advanced Light Source

Description: We describe a software system used at the Advanced Light Source for accelerator physics studies and accelerator control. The system consists of a number of Unix processes that can be connected together in modular ways. Processes communicate using messages with a common data, format, but processes do not know where their messages come from or go to, making each process easily replaceable by others using different algorithms, measurement techniques, or models. Some of the controls and correction functions we have implemented using the system are closed-orbit correction, continuous tune display, and Fourier analysis of turn-by-turn beam position monitor data.
Date: May 1, 1993
Creator: Schachinger, L.C. & Paxson, V.
Partner: UNT Libraries Government Documents Department

Fourier analysis of cell-wise Block-Jacobi splitting in two-dimensional geometry

Description: A Fourier analysis is conducted in two-dimensional (2D) geometry for the discrete-ordinates (SN) approximation of the neutron transport problem solved with Richardson iteration (Source Iteration) using the cell-wise Block-Jacobi (B1) algorithm. The results of the Fourier analysis show that convergence of cell-wise BJ can degrade, leading to a spectral radius equal to 1, in problems containing optically thin cells. For problems containing cells that are optically thick, instead, the spectral radius tends to O. Hence, in the optically thick-cell regime, cell-wise BJ is rapidly convergent even for problems that are scattering dominated, with a scattering ratio c close to I.
Date: January 1, 2009
Creator: Rosa, Massimiliano; Warsa, James S & Kelley, Timothy M
Partner: UNT Libraries Government Documents Department

Spectral analysis of reltivistic bunched beams

Description: Particles in a storage ring are oscillating in the longitudinal and transverse dimensions, and therefore, the frequency domain is natural for analyzing many beam generated signals. Information ranging from oscillation frequencies to beam phase space distributions can be extracted from the spectral content of these signals. The spectrum of a single particle is like a Green`s function, and it is the key to understanding the spectrum produced by a beam. Three separate cases are consider in an order of increasing complexity: (1) constant revolution frequency, (2) Frequency Modulation introduced by synchrotron oscillations, and (3) Amplitude Modulation introduced by betatron oscillations.
Date: May 1, 1996
Creator: Siemann, R.H.
Partner: UNT Libraries Government Documents Department

GAS CURTAIN EXPERIMENTAL TECHNIQUE AND ANALYSIS METHODOLOGIES

Description: The qualitative and quantitative relationship of numerical simulation to the physical phenomena being modeled is of paramount importance in computational physics. If the phenomena are dominated by irregular (i. e., nonsmooth or disordered) behavior, then pointwise comparisons cannot be made and statistical measures are required. The problem we consider is the gas curtain Richtmyer-Meshkov (RM) instability experiments of Rightley et al. (13), which exhibit complicated, disordered motion. We examine four spectral analysis methods for quantifying the experimental data and computed results: Fourier analysis, structure functions, fractal analysis, and continuous wavelet transforms. We investigate the applicability of these methods for quantifying the details of fluid mixing.
Date: January 1, 2001
Creator: KAMM, J. R. & AL, ET
Partner: UNT Libraries Government Documents Department

Summary, Analysis, and Comparison of Data from Experiments with the EBR-II Mark IIB Oscillator Rod

Description: The Mark IIB oscillator rod was used in EBR-II runs 48-55. Data were collected, digitized, and processed by on-line computer analysis, and Fourier analysis was used to obtain frequency-response functions. Feedback frequency-response functions are compared with those obtained by rod-drop experiments and are qualitatively identical. Experimental results are also compared with the EBR-II dynamic simulation computer program, EROS. Through the use of basic neutronic and heat-transfer principles, this program is shown to adequately represent the reactor feedback frequency-response function. The experimental data from EBR-II runs 48-55 are presented in both tabular and graphic form.
Date: 1977?
Creator: Larson, H. A. & Dean, E. M.
Partner: UNT Libraries Government Documents Department

Fourier mode analysis of slab-geometry transport iterations in spatially periodic media

Description: We describe a Fourier analysis of the diffusion-synthetic acceleration (DSA) and transport-synthetic acceleration (TSA) iteration schemes for a spatially periodic, but otherwise arbitrarily heterogeneous, medium. Both DSA and TSA converge more slowly in a heterogeneous medium than in a homogeneous medium composed of the volume-averaged scattering ratio. In the limit of a homogeneous medium, our heterogeneous analysis contains eigenvalues of multiplicity two at ''resonant'' wave numbers. In the presence of material heterogeneities, error modes corresponding to these resonant wave numbers are ''excited'' more than other error modes. For DSA and TSA, the iteration spectral radius may occur at these resonant wave numbers, in which case the material heterogeneities most strongly affect iterative performance.
Date: April 1, 1999
Creator: Larsen, E & Zika, M
Partner: UNT Libraries Government Documents Department

Fourier mode analysis of slab-geometry transport iterations in spatially periodic media

Description: We describe a Fourier analysis of the diffusion-synthetic acceleration (DSA) and transport-synthetic acceleration (TSA) iteration schemes for a spatially periodic, but otherwise arbitrarily heterogeneous, medium. Both DSA and TSA converge more slowly in a heterogeneous medium than in a homogeneous medium composed of the volume-averaged scattering ratio. In the limit of a homogeneous medium, our heterogeneous analysis contains eigenvalues of multiplicity two at ''resonant'' wave numbers. In the presence of material heterogeneities, error modes corresponding to these resonant wave numbers are ''excited'' more than other error modes. For DSA and TSA, the iteration spectral radius may occur at these resonant wave numbers, in which case the material heterogeneities most strongly affect iterative performance.
Date: May 7, 1999
Creator: Larsen, E W & Zika, M R
Partner: UNT Libraries Government Documents Department

FT-ICR mass spectrometry of very highly charged atomic ions

Description: The authors report FT-ICR measurements of samples trapped in the electron beam ion trap (EBIT) at Livermore. They made use of the access provided by the radial x-ray slots. They constructed two probes that could be inserted into the 2-mm wide slots. The probes each subtend only 25{degree} and face each other 180{degree} apart. They show a typical transformed spectrum of highly charged {sup 84}Kr ions obtained with this system. The spectrum was obtained by exciting with a 300-{mu}s sweep from 17.5 to 19.5 MHz. The resonance peaks of {sup 84}Kr{sup 34+}, {sup 84}Kr{sup 35+}, and {sup 84}Kr{sup 36+} are clearly visible.
Date: May 15, 1995
Creator: Schweikhard, L.; Beck, B. & Beiersdorfer, P.
Partner: UNT Libraries Government Documents Department

External Second Gate-Fourier Transform Ion Mobility Spectrometry.

Description: Ion mobility spectrometry (IMS) is recognized as one of the most sensitive and versatile techniques for the detection of trace levels of organic vapors. IMS is widely used for detecting contraband narcotics, explosives, toxic industrial compounds and chemical warfare agents. Increasing threat of terrorist attacks, the proliferation of narcotics, Chemical Weapons Convention treaty verification as well as humanitarian de-mining efforts has mandated that equal importance be placed on the analysis time as well as the quality of the analytical data. (1) IMS is unrivaled when both speed of response and sensitivity has to be considered. (2) With conventional (signal averaging) IMS systems the number of available ions contributing to the measured signal to less than 1%. Furthermore, the signal averaging process incorporates scan-to-scan variations decreasing resolution. With external second gate Fourier Transform ion mobility spectrometry (FT-IMS), the entrance gate frequency is variable and can be altered in conjunction with other data acquisition parameters to increase the spectral resolution. The FT-IMS entrance gate operates with a 50% duty cycle and so affords a 7 to 10-fold increase in sensitivity. Recent data on high explosives are presented to demonstrate the parametric optimization in sensitivity and resolution of our system.
Date: January 1, 2005
Creator: Tarver, Edward E., III
Partner: UNT Libraries Government Documents Department

ANALYSIS OF SIMPLY SUPPORTED GRIDS OF PERPENDICULAR BEAMS

Description: An analysis of a rectangular grid of perpendicular beams simply supported at the ends is presented. Bending, shearing, and torsionnl effects of beams with arbitrary cross sections are taken into account, and the beams may be subjected to uniform or concentrated loads. An energy method is used in the analysis, and a matrix formulation for determining the unknown coefficients appearing in the Fourier series expression for the lateral deflection is given. This formulation is especially suited for computer application, and a computer program for performing the analysis is described. Data are presented for use in the design and evaluation of certain grid configurations. Applications to nonrectangular grids are also considered. (auth)
Date: March 1, 1964
Creator: Witt, F.J.
Partner: UNT Libraries Government Documents Department

STM Studies of TbTe3: Evidence for a Fully Incommensurate Charge Density Wave

Description: We observe unidirectional charge density wave ordering on the cleaved surface of TbTe{sub 3} with a Scanning Tunneling Microscope at {approx}6 K. The modulation wave-vector q{sub CDW} as determined by Fourier analysis is 0.71 {+-} 0.02 x2{pi}/c. (Where c is one edge of the in-plane 3D unit cell.) Images at different tip-sample voltages show the unit cell doubling effects of dimerization and the layer below. Our results agree with bulk X-ray measurements, with the addition of (1/3) x2{pi}/a ordering perpendicular to the CDW. Our analysis indicates that the CDW is incommensurate.
Date: September 28, 2007
Creator: Fang, A.; Ru, N.; Fisher, I.R.; /Stanford U., Appl. Phys. Dept.; Kapitulnik, A. & /Stanford U., Appl. Phys. Dept. /Stanford U., Phys. Dept.
Partner: UNT Libraries Government Documents Department

TBT optics and impedance measurements at the Fermilab Main Injector

Description: The Fourier analysis of Turn by Turn (TBT) data provides valuable information about the machine linear and non-linear optics. This technique introduced first at Fermilab in 2006 for correcting the Tevatron linear coupling, has been now extended to the Main Injector with the aim of a better understanding of the beam dynamics, in particular in view of a substantial beam intensity increase in the frame of the laboratory neutrino program.
Date: June 1, 2007
Creator: Alexahin, Y. & Gianfelice-Wendt, G.
Partner: UNT Libraries Government Documents Department