Treatment Of Systematic Errors Research Articles

Application of the differential decay-curve method to γ–γ fast-timing lifetime measurements

A new procedure for the analysis of delayed-coincidence lifetime experiments focused on the Fast-timing case is proposed following the approach of the Differential decay-curve method. Examples of application of the procedure on experimental data reveal its reliability for lifetimes even in the sub-nanosecond range. The procedure is expected to improve both precision/reliability and treatment of systematic errors and scarce data as well as to provide an option for cross-check with the results obtained by means of other analyzing methods.

Modelling the number density of Hαemitters for future spectroscopic near-IR space missions

The future space missions Euclid and WFIRST-AFTA will use the Halpha emission line to measure the redshifts of tens of millions of galaxies. The Halpha luminosity function at z>0.7 is one of the major sources of uncertainty in forecasting cosmological constraints from these missions. We construct unified empirical models of the Halpha luminosity function spanning the range of redshifts and line luminosities relevant to the redshift surveys proposed with Euclid and WFIRST-AFTA. By fitting to observed luminosity functions from Halpha surveys, we build three models for its evolution. Different fitting methodologies, functional forms for the luminosity function, subsets of the empirical input data, and treatment of systematic errors are considered to explore the robustness of the results. Functional forms and model parameters are provided for all three models, along with the counts and redshift distributions up to z~2.5 for a range of limiting fluxes (F_Halpha>0.5 - 3 x 10^-16 erg cm^-2 s^-1) that are relevant for future space missions. For instance, in the redshift range 0.90<z<1.8, our models predict an available galaxy density in the range 7700--13300 and 2000--4800 deg^-2 respectively at fluxes above F_Halpha>1 and 2 x 10^-16 erg cm^-2 s^-1, and 32000--48000 for F_Halpha>0.5 x 10^-16 erg cm^-2 s^-1 in the extended redshift range 0.40<z<1.8. We also consider the implications of our empirical models for the total Halpha luminosity density of the Universe, and the closely related cosmic star formation history.

Trends of solar ultraviolet irradiance at Barrow, Alaska, and the effect of measurement uncertainties on trend detection

Abstract. Spectral ultraviolet (UV) irradiance has been observed near Barrow, Alaska (71° N, 157° W) between 1991 and 2011 with an SUV-100 spectroradiometer. The instrument was historically part of the US National Science Foundation's UV Monitoring Network and is now a component of NSF's Arctic Observing Network. From these measurements, trends in monthly average irradiance and their uncertainties were calculated. The analysis focuses on two quantities, the UV Index (which is affected by atmospheric ozone concentrations) and irradiance at 345 nm (which is virtually insensitive to ozone). Uncertainties of trend estimates depend on variations in the data due to (1) natural variability, (2) systematic and random errors of the measurements, and (3) uncertainties caused by gaps in the time series. Using radiative transfer model calculations, systematic errors of the measurements were detected and corrected. Different correction schemes were tested to quantify the sensitivity of the trend estimates on the treatment of systematic errors. Depending on the correction method, estimates of decadal trends changed between 1.5% and 2.9%. Uncertainties in the trend estimates caused by error sources (2) and (3) were set into relation with the overall uncertainty of the trend determinations. Results show that these error sources are only relevant for February, March, and April when natural variability is low due to high surface albedo. This method of addressing measurement uncertainties in time series analysis is also applicable to other geophysical parameters. Trend estimates varied between −14% and +5% per decade and were significant (95.45% confidence level) only for the month of October. Depending on the correction method, October trends varied between −11.4% and −13.7% for irradiance at 345 nm and between −11.7% and −14.1% for the UV Index. These large trends are consistent with trends in short-wave (0.3–3.0 μm) solar irradiance measured with pyranometers at NOAA's Barrow Observatory and can be explained by a change in snow cover over the observation period: analysis of pyranometer data indicates that the first day of fall when albedo becomes larger than 0.6 after snow fall, and remains above 0.6 for the rest of the winter, has advanced with a statistically significant trend of 13.6 ± 9.7 days per decade.

A ubiquitous ∼62-Myr periodic fluctuation superimposed on general trends in fossil biodiversity. I. Documentation

We use Fourier analysis and related techniques to investigate the question of periodicities in fossil biodiversity. These techniques are able to identify cycles superimposed on the long-term trends of the Phanerozoic. We review prior results and analyze data previously reduced and published. Joint time-series analysis of various reductions of the Sepkoski Data, Paleobiology Database, and Fossil Record 2 indicate the same periodicity in biodiversity of marine animals at 62 Myr. We have not found this periodicity in the terrestrial fossil record. We have found that the signal strength decreases with time because of the accumulation of apparently “resistant” long-lived genera. The existence of a 62-Myr periodicity despite very different treatment of systematic error, particularly sampling-strength biases, in all three major databases strongly argues for its reality in the fossil record.

QUBIC, a bolometric interferometer to measure the B-modes of the CMB

3rd ARENA Conference: An Astronomical Observatory at CONCORDIA (Dome C, Antarctica)L. Spinoglio and N. Epchtein (eds)EAS Publications Series, 40 (2010) 399-404QUBIC, a bolometric interferometer to measure the B-modes of the CMBJ.-C. Hamilton and R. CharlassierLaboratoire APC, Universite Paris Diderot, Paris 7, CNRS, IN2P3, 10 rue Alice Domon et Leonie Duquet, 75205 Paris, France The quest for the B-modes in the CMB polarization is one of the main challenges of modern cosmology as it would allow to give sharp constraints on the inflationary period.One of the main challenges of B modes detection is the treatment of systematic errors. Comparison of observations subject to different systematics is crucial. Interferometers offer such an alternative to imagers. However, to obtain the required sensitivity, a very large number of baselines is needed, which is extremely difficult to achieve with heterodyne interferometry. Bolometric interferometry copes with this problem using a new technique: the interference pattern produced by a few hundred horns is imaged on a bolometer array, and a time modulation of phase shifts insures the separation of visibilities while coherently adding redundant ones. The QUBIC collaboration proposes to build such an instrument.

Dependence of the treatment of systematic error in interlaboratory comparisons on different classes of standards

A few years ago the question arose whether different types of measurands can be the consequence of the different intrinsic nature of different types of standards, which prompted an analysis resulting in the proposal of two distinct ‘classes’ of standards be considered. They correspond to different situations depending upon whether the aim is to compare laboratory artefact standards (Class 1), or, instead, to compare standards whose values are a measure of the value of the same unequivocally defined physical or chemical condition (Class 2). This distinction is relevant to the statistical treatment of the comparison data, in particular, with respect to the issue of the correct modelling of the data and of the correct choice of the summary statistics for populations of non-repeated data. This paper, after a summary of the rational of making a distinction of standard in “classes”, and discussing the general issue of bias, is discussing some implications of the above distinction, concentrating on cases where the effect of the systematic error is dominating the experimental results, as it commonly happens in several metrology fields. A preferred way to tackle the problem for standards of Class 2 is presented.

Long-Term Cycles in the History of Life: Periodic Biodiversity in the Paleobiology Database

Time series analysis of fossil biodiversity of marine invertebrates in the Paleobiology Database (PBDB) shows a significant periodicity at approximately 63 My, in agreement with previous analyses based on the Sepkoski database. I discuss how this result did not appear in a previous analysis of the PBDB. The existence of the 63 My periodicity, despite very different treatment of systematic error in both PBDB and Sepkoski databases strongly argues for consideration of its reality in the fossil record. Cross-spectral analysis of the two datasets finds that a 62 My periodicity coincides in phase by 1.6 My, equivalent to better than the errors in either measurement. Consequently, the two data sets not only contain the same strong periodicity, but its peaks and valleys closely correspond in time. Two other spectral peaks appear in the PBDB analysis, but appear to be artifacts associated with detrending and with the increased interval length. Sampling-standardization procedures implemented by the PBDB collaboration suggest that the signal is not an artifact of sampling bias. Further work should focus on finding the cause of the 62 My periodicity.

Gravity Probe B data analysis status and potential for improved accuracy of scientific results

Gravity Probe B (GP-B) is a landmark physics experiment in space designed to yield precise tests of two fundamental predictions of Einstein's theory of general relativity, the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Launched on 20 April 2004, data collection began on 28 August 2004 and science operations were completed on 29 September 2005 upon liquid helium depletion. During the course of the experiment, two unexpected and mutually-reinforcing complications were discovered: (1) larger than expected ‘misalignment’ torques on the gyroscopes producing classical drifts larger than the relativity effects under study and (2) a damped polhode oscillation that complicated the calibration of the instrument's scale factor against the aberration of starlight. Steady progress through 2006 and 2007 established the methods for treating both problems; in particular, an extended effort from January 2007 on ‘trapped flux mapping’ led in August 2007 to a dramatic breakthrough, resulting in a factor of ∼20 reduction in data scatter. This paper reports results up to November 2007. Detailed investigation of a central 85-day segment of the data has yielded robust measurements of both relativity effects. Expansion to the complete science data set, along with anticipated improvements in modeling and in the treatment of systematic errors may be expected to yield a 3–6% determination of the frame-dragging effect.

Rectifying system-specific errors in NMR relaxation measurements

15N spin relaxation parameters provide a powerful tool for probing the internal dynamics and thermodynamics of proteins. The biological insight provided by these experiments often involves interpretation of small changes in relaxation parameters. This, in turn, requires careful data analysis, especially in the identification and treatment of systematic error. While progress continues on reduction of experiment-specific errors associated with pulse sequences, system-specific sources of error have received far less attention. The impact of these errors varies between facilities, spectrometers, and biological samples. We demonstrate that performing a series of control experiments along with relaxation measurements can help identify, quantify, and isolate sources of system-specific error, and, in some cases, correct for systematic changes. We further demonstrate that control experiments can be performed without significant loss of spectrometer time, and lead to more accurate relaxation parameter values.

Super-Kamiokande atmospheric neutrinos

Results on atmospheric neutrino analysis at Super-Kamiokande I is presented. The whole data set of atmospheric neutrino sample in Super-Kamiokande I is consistently explained with an assumption of pure ν μ - ν τ oscillations. The allowed range of parameters is 1.5 × 10 −3 Δ m 2 3.4 × 10 −3 eV 2 and sin 2 2 θ > 0.92 at 90% C.L. In the oscillation analysis, we improved the treatment of systematic errors so that they can be considered as independent. This makes possible to find which systematic errors have larger effect on the analysis results. Some sensitivity studies under several assumptions of improvements in systematic errors are presented.

A STUDY OF THE LEP AND SLD MEASUREMENTS OF Ab

A systematic study is made of the data dependence of the parameter A b , that, since 1995, has shown a deviation from the Standard Model prediction of between 2.4 and 3.1 standard deviations. Issues addressed include: The effect of particular measurements, values found by individual experiments, LEP/SLD comparison, and the treatment of systematic errors. The effect, currently at the 2.4σ level, is found to vary in the range from 1.7σ to 2.9σ by excluding marginal or particularly sensitive data. Since essentially the full LEP and SLD Z-decay data sets are now analyzed the meaning of the deviation, (new physics or marginal statistical fluctuation) is unlikely to be given by the present generation of colliders.

Treatment of systematic errors in intrusive concentration and temperature measurements

Typical systematic errors that are made during intrusive concentration and temperature measurements in combustion chambers are illustrated. To decrease the errors, it is necessary to ensure rapid quenching of combustion gases and freezing of the composition of combustion products. Analysis is performed using a simple analytic model for heat transfer in a sampling probe. Results are given in the form of temperature-time dependences, temperature profiles, and quench rates inside the probe. The measurement results are validated on the basis of formulation of a material balance (conservation of number of atoms). The main errors of high-temperature thermocouple measurements are discussed in detail, with emphasis on the radiation correction.

Extraction of parton distributions and $\alpha_{\mathrm{s}}$ from DIS data within a Bayesian treatment of systematic errors

We have performed a NLO QCD global fit of BCDMS, NMC, H1 and ZEUS data with full account of point-to-point correlations using the Bayesian approach to the treatment of systematic errors. Parton distributions in the proton with their experimental uncertainties, including both statistical and systematic, are obtained. The gluon distribution in a wide region of x is found to be softer than the gluon distribution extracted in standard global analyses which include prompt photon data. We obtain a robust estimate of \(\alpha_{\mathrm{s}}(M_Z)=0.1146\pm0.0036 (\ge75\%\) C.L.) based on Chebyshev's inequality, which is compatible with an earlier determination of \(\alpha_{\mathrm{s}}\) from the DIS data, but is less dependent on high-twist effects.

Analyzing power in neutron-deuteron elastic scattering at Elabn=3 MeV.

A measurement of the analyzing power ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}) in neutron-deuteron (n-d) elastic scattering below the deuteron breakup threshold is described, including a detailed discussion of the experimental apparatus and the treatment of systematic errors. The data provide a precise test of Faddeev calculations of the three-nucleon system and of the nucleon-nucleon interaction models used as inputs to these calculations. ${\mathit{A}}_{\mathit{y}}$ was measured at six angles from 44.5 \ifmmode^\circ\else\textdegree\fi{} c.m. to 145.7 \ifmmode^\circ\else\textdegree\fi{} c.m. to a precision of (7--13)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$. Polarized neutrons, produced by the $^{3}\mathrm{H}$(p\ensuremath{\rightarrow},n\ensuremath{\rightarrow}${)}^{3}$He reaction, were incident upon the target, a deuterated organic scintillator. Scattered neutrons were detected in fast coincidence with the recoil deuterons in the target. A computer simulation of the experiment was used to compensate for a number of systematic errors. Particularly important were corrections for neutron multiple scattering, accidental coincidences, and finite geometry effects. The ${\mathit{A}}_{\mathit{y}}$ data have a 2.2% scale factor uncertainty associated with uncertainty in the polarization of the incident neutron beam. The incident neutron polarization was measured in a separate experiment using n${\mathrm{\ensuremath{-}}}^{4}$He scattering from a liquid helium scintillator. The neutron polarization measurement also yielded an improved value for the polarization transfer coefficient [${\mathit{K}}_{\mathit{y}}^{\mathit{y}}$(${0}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$)=0.650\ifmmode\pm\else\textpm\fi{}0.019] in the $^{3}\mathrm{H}$(p\ensuremath{\rightarrow},n\ensuremath{\rightarrow}${)}^{3}$He reaction at ${\mathit{E}}_{\mathrm{lab}}^{\mathit{p}}$=3.80 MeV. A comparison of the ${\mathit{A}}_{\mathit{y}}$ data to Faddeev calculations shows that the discrepancy in ${\mathit{A}}_{\mathit{y}}$ observed previously at higher energies continues below the breakup threshold. A comparsion of the ${\mathit{A}}_{\mathit{y}}$ data to a recent phase shift analysis of proton-deuteron (p-d) scattering indicates that observed differences between n-d and p-d analyzing powers are only partially explained by Coulomb effects.

Systematic errors in ground referenced geometric height monitoring

This paper investigates the existence and treatment of systematic errors in geometric height measurement systems. A minimal system of one SSR aided by a low power omni radar equipped with an independent interrogator is taken for reference. Biases are identified to be created by the aircraft transponder and by the nonlinear processing of the available noisy radar range and bearing measurements. The first source is treated by augmenting the estimation process to include the transponder bias. The latter source creates an ‘inherent bias’ which cannot be estimated by augmenting the estimation process. The inherent bias is further analysed by determining the main factors affecting its magnitude. It is shown that the inherent bias limits the useful area in which the geometric height can be reliably estimated. Although the inherent bias investigation method is primarily derived for the SSR-omni measurement system, it can be applied in a straightforward manner to other geometric height monitoring systems employing nonlinear processing of the original measurements.

Treatment of systematic errors in the processing of wide-angle sonar sensor data for robotic navigation

A methodology has been developed for the treatment of systematic errors that arise in the processing of sparse sensor data. A detailed application of this methodology to the construction, from wide-angle sonar sensor data, of navigation maps for use in autonomous robotic navigation is presented. In the methodology, a four-valued labeling scheme and a simple logic for label combination are introduced. The four labels Conflict, Occupied, Empty, and Unknown are used to mark the cells of the navigation maps. The logic allows for the rapid updating of these maps as new information is acquired. Systematic errors are treated by relabeling conflicting pixel assignments. Most of the new labels are obtained from analyses of the characteristic patterns of conflict that arise during the information processing. The remaining labels are determined by imposing an elementary consistent-labeling condition. >

On-line accuracy assessment for the dual six-port ANA: Treatment of systematic errors

Expressions are derived for calculating estimates of the systematic errors in dual six-port or four-port measurements of reflection coefficient and scattering parameters due to imperfections in the transmission-line standard used to calibrate the system. A new mathematical model for a four-port reflectometer makes it easier to visualize and analyze these errors. In this new model, two of the three parameters needed to characterize a four-port can be determined without standards. All imperfections in the standard perturb only the third parameter which acts as an impedance transformer.

Systematic Measurement Errors

Nature, origin, and treatment of systematic errors in measurements and calibrations are discussed. It is shown how systematic errors can vary, how random errors under one set of conditions will become systematic errors under another set of conditions an..