THE DETERMINATION OF OPTIMUM GATE LENGTHS FOR TIME‐VARYING WIENER FILTERING

Geophysics ◽  
1969 ◽  
Vol 34 (5) ◽  
pp. 683-695 ◽  
Author(s):  
R. J. Wang
Keyword(s):  
Upper Bound ◽  
Time Windows ◽  
Observation Time ◽  
Time Varying ◽  
Wiener Filters ◽  
The Mean ◽  
Ordinary Time ◽  
Time Invariant ◽  
Better Than

The response function of a time‐varying filter changes with the output signal, or observation time. Most existing time‐varying filter techniques involve the empirical division of a seismic trace into a number of gates (or time windows) of given length, and a time‐invariant filter is determined for each such gate. Few treatments have dealt with analytical methods to establish the gate lengths according to some optimum criterion. This paper describes a technique for the determination of optimum gate lengths. It is based on the work of Berndt and Cooper, which is here applied to the calculation of time‐varying Wiener filters. The Berndt and Cooper technique produces an upper bound for the mean‐square error between the true and a given approximated time‐varying correlation function. The minimization of this upper bound leads to a relation which enables one to establish gate lengths directly from the input trace. Thereafter, ordinary time‐invariant Wiener filters can be computed for each gate. The overall filtered trace is obtained in the form of a suitably combined version of the individually filtered gates. Experimentally it is shown that, with the Berndt and Cooper technique to determine optimum gate lengths, time‐varying Wiener filters can be better than a time‐invariant filter.

Dosage du Sr-90 dans l'eau des lacs et des rivières du Québec par précipitation avec l'oxine et comptage β

1988 ◽  
Vol 66 (1) ◽  
pp. 174-177 ◽  
Author(s):  
E. Haddad ◽  
L. Zikovsky
Keyword(s):  
Detection Limit ◽  
Surface Waters ◽  
New Method ◽  
The Mean ◽  
Better Than

A new method for the determination of Sr-90 dissolved in surface waters has been developed. It is based on the precipitation of Sr with 8-hydroxyquinoline at pH 11.3 and counting of β particles with energy above 150 keV. The detection limit obtained is 0.5 mBq/L and the mean yield is 28%. The decontamination factors from other β emitters achieved are better than 10 000. This method has been used to measure the Sr-90 in 5 lakes and 5 rivers in Québec and activities ranging from 3 to 15 mBq/L were obtained. This new method is as efficient and reliable as conventional techniques while being less tedious.

Determination of Ibuprofen in Human Plasma and Urine by Gas Chromatography/Mass Spectrometry

2014 ◽  
Vol 97 (2) ◽  
pp. 415-420 ◽  
Author(s):  
Bilal Yilmaz ◽  
Ali Fuat Erdem
Keyword(s):  
Human Plasma ◽  
Internal Standard ◽  
Gas Chromatography Mass Spectrometry ◽  
Oral Tablet ◽  
Liquid Liquid Extraction ◽  
Human Plasma And Urine ◽  
The Mean ◽  
Interday Precision ◽  
Better Than

Abstract This paper describes a GC/MS method for the determination of ibuprofen in human plasma and urine. Ibuprofen and internal standard naproxen were extractedfrom plasma and urine by using a liquid–liquid extraction method. Derivatization was carried outusing N-methyl-N-(trimethylsilyl) trifluoroacetamide. Calibration curves were linear over the concentration range of 0.05–5.0 and 0.1–10.0 μg/mL for plasma and urine, respectively. Intraday and interday precision (RSD) values for ibuprofen in plasma and urine were less than 6.31%, and accuracy (relative error) was better than 12.00%. The mean recovery of ibuprofen was 89.53% for plasma and 93.73% for urine. TheLOD was 0.015 and 0.03 μg/mL and the LOQ was 0.05 and 0.1 μg/mL for plasma and urine, respectively. The method was successfully applied to blood samples from three healthy male volunteers who had been given an oral tablet of 600 mg ibuprofen.

scholarly journals Euler-type approximation for systems of stochastic differential equations

1989 ◽  
Vol 2 (4) ◽  
pp. 239-249 ◽  
Author(s):  
J. Golec ◽  
G. Ladde
Keyword(s):  
Differential Equations ◽  
Stochastic Differential Equations ◽  
Sufficient Conditions ◽  
Taylor Formula ◽  
Time Varying ◽  
Stochastic Version ◽  
Type Approximation ◽  
Mean Square Convergence ◽  
The Mean ◽  
Time Invariant

By developing a stochastic version of the Taylor formula, the mean-square convergence of the Euler-type approximation for the solution of systems of Itô-type stochastic differential equations is investigated. Sufficient conditions are given to obtain time-varying and time-invariant error estimates.

Frequency resolution of Fourier and maximum entropy spectral estimates

Geophysics ◽  
1982 ◽  
Vol 47 (9) ◽  
pp. 1303-1307 ◽  
Author(s):  
S. L. Marple
Keyword(s):  
Maximum Entropy ◽  
Signal To Noise Ratio ◽  
Frequency Resolution ◽  
Sampled Data ◽  
Signal To Noise ◽  
Analytic Determination ◽  
Spectral Estimates ◽  
The Mean ◽  
Better Than

An analytic determination of the frequency resolution for maximum entropy and conventional Blackman‐Tukey spectral estimates is made for the case of known autocorrelation. As the signal‐to‐noise ratio decreases, the maximum entropy resolution is no better than that achievable by the Blackman‐Tukey spectral estimate. The mean resolution of an ensemble of spectra constructed from sampled data sequences agrees with the analytic result.

scholarly journals An Advanced Method to Estimate Deep Currents from Profiling Floats

2005 ◽  
Vol 22 (8) ◽  
pp. 1294-1304 ◽  
Author(s):  
Jong Jin Park ◽  
Kuh Kim ◽  
Brian A. King ◽  
Stephen C. Riser
Keyword(s):  
Indian Ocean ◽  
Accurate Determination ◽  
New Method ◽  
Advanced Method ◽  
Subsurface Ocean ◽  
Least Squares Fit ◽  
Geostrophic Shear ◽  
The Mean ◽  
Better Than

Abstract Subsurface ocean currents can be estimated from the positions of drifting profiling floats that are being widely deployed for the international Argo program. The calculation of subsurface velocity depends on how the trajectory of the float while on the surface is treated. The following three aspects of the calculation of drift velocities are addressed: the accurate determination of surfacing and dive times, a new method for extrapolating surface and dive positions from the set of discrete Argos position fixes, and a discussion of the errors in the method. In the new method described herein, the mean drift velocity and the phase and amplitude of inertial motions are derived explicitly from a least squares fit to the set of Argos position fixes for each surface cycle separately. The new method differs from previous methods that include prior assumptions about the statistics of inertial motions. It is concluded that the endpoints of the subsurface trajectory can be estimated with accuracy better than 1.7 km (East Sea/Sea of Japan) and 0.8 km (Indian Ocean). All errors, combined with the error that results from geostrophic shear and extrapolation, should result in individual subsurface velocity estimates with uncertainty of the order of 0.2 cm s−1.

scholarly journals The accuracy of the determination of terrestrial refraction from reciprocal zenith angles

1979 ◽  
Vol 89 ◽  
pp. 203-212 ◽  
Author(s):  
K. Ramsayer
Keyword(s):  
Mean Difference ◽  
Mean Deviation ◽  
Refraction Coefficient ◽  
Refraction Angle ◽  
Observation Station ◽  
The Mean ◽  
True Values ◽  
Better Than

To investigate the accuracy of the determination of terrestrial refraction from reciprocal zenith angles and astronomical latitudes and longitudes at both ends of a line a test net with lines from 4 km to 23 km was observed and three dimensionally adjusted. As the measurements of the zenith angles were repeated every hour 40 times in an average the adjusted values were taken as a substitute for the true values. It is shown, that the mean refraction coefficient k, which is changing from k = 0.10 at day up to k = 0.34 at night, and the corresponding refraction angle can be determined very accurately, if both angles are measured simultaneously. Observations with day light are better than observations in the night. For observations with day light the mean difference between the true refraction angle at the observation station and the mean refraction angle of the observed line was smaller than ± 1″ independent of the length of the line. That means that the mean deviation of the true effective refraction coefficient in the observation station and the mean refraction coefficient of the observed line was inverse proportional to the distance.

Automated Fluorometric Determination of Thiamine and Riboflavin in Infant Formulas

1979 ◽  
Vol 62 (3) ◽  
pp. 642-647
Author(s):  
Walter E Dunbar ◽  
Kenneth E Stevenson
Keyword(s):  
Sample Preparation ◽  
Infant Formulas ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Automated Method ◽  
Coefficients Of Variation ◽  
Manual Methods ◽  
The Mean ◽  
Better Than

Abstract Commercial infant formulas were analyzed simultaneously for thiamine and riboflavin by an automated fluorometric method and by the AOAC manual fluorometric methods. For 10 products, the mean thiamine and riboflavin results determined using the automated method ranged from 104 to 113% and 90 to 112%, respectively, of those by the AOAC manual methods. The coefficients of variation for thiamine and riboflavin ranged from 1.05 to 3.90% and 0.60 to 2.48%, respectively, for the automated method, and 1.48 to 3.86% and 0.69 to 10.9%, respectively, for the manual methods. Using the automated method, mean recoveries of thiamine and riboflavin added to samples were 103 and 104%, respectively. The automated method used a common sample preparation to determine both thiamine and riboflavin, and gave results equivalent to, or better than, those obtained by the manual methods.

scholarly journals The Zero-Point of the IAU Standard Velocity System

1985 ◽  
Vol 111 ◽  
pp. 583-586
Author(s):  
C. D. Scarfe
Keyword(s):  
Radial Velocity ◽  
Zero Point ◽  
Radial Velocities ◽  
Orbital Elements ◽  
Camera System ◽  
Individual Stars ◽  
The Past ◽  
The Mean ◽  
Better Than

Radial velocities of bright IAU standards have been obtained photographically over the past decade using the long camera of the DAO 1.2 meter telescope's coudé spectrograph. Most of the stars observed have been found to be constant in velocity to better than 0.15 km/s over that interval. The mean velocities agree with the IAU velocities, on the average, within 0.10 km/s, although mean velocities of some individual stars differ considerably more than this from the IAU value. A preliminary determination of the zero point of the long camera system, and hence of the IAU system, has been made from observations of the asteroid Vesta, whose actual radial velocity has been calculated from its orbital elements.

Determination of Plasminogen in Human Plasma by a Casein Method*

1965 ◽  
Vol 14 (03/04) ◽  
pp. 545-561 ◽  
Author(s):  
Ulla Hedner ◽  
Inga Marie Nilsson
Keyword(s):  
Liver Cirrhosis ◽  
Human Plasma ◽  
Normal Group ◽  
Optimal Conditions ◽  
Reference Curves ◽  
Plasmin Inhibitors ◽  
The Mean ◽  
Sensitive Method ◽  
Better Than

SummaryA modification of the casein method for determination of plasminogen in plasma has been devised.1. Urokinase instead of streptokinase was used for activation of plasminogen in order to eliminate the effect of any antistreptokinase antibodies in the plasma.2. A purified and stable plasmin preparation according to Wallén was used for preparing reference curves.3. The plasminogen activity of plasma was converted into arbitrary casein - olytic units (ACU) defined in such a way that 10 caseinolytic units gave an extinction of 0.300.4. Removal of the plasmin inhibitors by acidification of plasma to pH 2.0 was found to be better than using euglobulin precipitation.5. The plasma should be tested immediately after thawing and not allowed to stand after acidification for obtaining optimal conditions.6. The method can be used for determination of plasminogen in plasma in patients treated with ssss-ACA and AMCA.7. The error of the method was found to be small ssss0.4.The mean plasminogen level in a normal group of 72 was found to be 9.5 ssss 1.7 ACU/ml plasma. No variation with sex and age was found.The method proved clinically useful. During the latter half of pregnancy the plasminogen level was found to be clearly elevated. In patients with liver cirrhosis the plasminogen level was low. It was a sensitive method for following the plasminogen content during streptokinase treatment.

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