Effect Of Such Errors Research Articles

Navigation message demodulation for GPS receiver on-board spinning rockets

We describe a demodulation scheme for the navigation message of GPS receivers on spin-stabilized rockets. Doppler frequencies due to fast and complex dynamics, in particular high-rate spin, cause errors in carrier frequency tracking. The effects of such errors on navigation message demodulation are described through theoretical analysis and numerical simulation. A demodulation scheme that includes a frequency estimator is proposed to account for frequency tracking errors. It is demonstrated that demodulation performance is degraded 5 dB due to frequency uncertainty. Simulation results showed that a demodulator which includes maximum likelihood (ML) frequency estimator achieves near-optimal symbol error rate under these conditions. Demodulation with ML estimator achieves a bit error rate below 10?5 for a C/N 0 = 35 dB---Hz, for spin rates below 2.7 Hz, and a rocket radius smaller than 1 m. For the cases in which computational capabilities of the on-board GPS receiver is insufficient to implement the demodulator with ML estimator, frequency estimation methods with low complexity were also tested through numerical simulation. The proposed Kay and Quinn-Fernandes combination achieves a bit error rate below 10?5 for a C/N 0 = 37 dB---Hz while requiring 1/10 of processing time.

Rotational motions for teleseismic surface waves

We report the findings for the first teleseismic six degree‐of‐freedom (6‐DOF) measurements including three components of rotational motions recorded by a sensitive rotation‐rate sensor (model R‐1, made by eentec) and three components of translational motions recorded by a traditional seismometer (STS‐2) at the NACB station in Taiwan. The consistent observations in waveforms of rotational motions and translational motions in sections of Rayleigh and Love waves are presented in reference to the analytical solution for these waves in a half space of Poisson solid. We show that additional information (e.g., Rayleigh wave phase velocity, shear wave velocity of the surface layer) might be exploited from six degree‐of‐freedom recordings of teleseismic events at only one station. We also find significant errors in the translational records of these teleseismic surface waves due to the sensitivity of inertial translation sensors (seismometers) to rotational motions. The result suggests that the effects of such errors need to be counted in surface wave inversions commonly used to derive earthquake source parameters and Earth structure.

Modeling and Mitigating Transient Errors in Logic Circuits

Transient or soft errors caused by various environmental effects are a growing concern in micro and nanoelectronics. We present a general framework for modeling and mitigating the logical effects of such errors in digital circuits. We observe that some errors have time-bounded effects; the system's output is corrupted for a few clock cycles, after which it recovers automatically. Since such erroneous behavior can be tolerated by some applications, i.e., it is noncritical at the system level, we define the critical soft error rate (CSER) as a more realistic alternative to the conventional SER measure. A simplified technology-independent fault model, the single transient fault (STF), is proposed for efficiently estimating the error probabilities associated with individual nodes in both combinational and sequential logic. STFs can be used to compute various other useful metrics for the faults and errors of interest, and the required computations can leverage the large body of existing methods and tools designed for (permanent) stuck-at faults. As an application of the proposed methodology, we introduce a systematic strategy for hardening logic circuits against transient faults. The goal is to achieve a desired level of CSER at minimum cost by selecting a subset of nodes for hardening against STFs. Exact and approximate algorithms to solve the node selection problem are presented. The effectiveness of this approach is demonstrated by experiments with the ISCAS-85 and -89 benchmark suites, as well as some large (multimillion-gate) industrial circuits.

Exploring the effects of aggregation error in the estimation of consumer demand elasticities

Errors introduced by using aggregate data in estimating a consumer demand model have long been a concern. We study the effects of such errors on elasticity estimates derived from AIDS and QUAIDS models. Based on a survey of published articles, a generic parameterization of the income distribution, and the range of Gini coefficients reported for 28 OECD countries, we generate and analyze a large number of “observations” on the differences between elasticities calculated at the aggregate level and those calculated at the micro level. We suggest a procedure for evaluating the likely range of aggregation error when a model is estimated with aggregate data.

Influence of Global Navigation Satellite System errors in positioning inventory plots for tree-height distribution studiesThis article is one of a selection of papers from Extending Forest Inventory and Monitoring over Space and Time.

Validation of predictive models in remote sensing requires a good coregistration of field and sensor data sets. However, previous research has demonstrated that Global Navigation Satellite System survey techniques often produce large positioning errors when applied to areas under forest canopies. In this article, we present a repeatable methodology for analyzing the effect of such errors when validating models that predict tree-height distributions from LiDAR data sets. The method is based on conditional probability theory applied to error positioning and includes an error assessment of the surveying technique. A technical criterion for selecting the plot radius that avoids significant effects of positioning errors was proposed. We demonstrated that for a plot radius greater than 10 m, the effects of positioning errors introduced by a phase-differential device were insignificant when studying forest tree-height distributions.

Irreversible treatment decisions under consideration of the research and development pipeline for new therapies

This article addresses a topic not considered in previous models of patient treatment: the possible downstream availability of improved treatment options coming out of the medical research and development (R&D) pipeline. We provide clinical examples in which a patient may prefer to wait and take the chance that an improved therapy comes to market rather than choose an irreversible treatment option that has serious quality of life ramifications and would render future treatment discoveries meaningless for that patient. We then develop a Markov decision process model of the optimal time to initiate treatment, which incorporates uncertainty around the development of new therapies and their effects. After deriving structural properties for the model, we provide a numerical example that demonstrates how models that do not have any foresight of the R&D pipeline may result in optimal policies that differ from models that have such foresight, implying erroneous decisions in the former models. Our example quantifies the effects of such errors.

The robustness of keystone indices in food webs

Species that have outstanding importance in the functioning of a community are called keystone species. Network indices are increasingly used to identify them, e.g. for conservation biological purposes. The problem is that the calculation of these indices is based on the particular network model of the studied food web, which can include network construction errors. For example, additional, unnecessary trophic links can be built in, or, to the contrary, functional links can be left out. What is the effect of such errors on the result of network analysis, e.g. the centrality values of species? Can you rely on the importance rank of species that you calculated? We developed a robustness measure ( R) for network indices to answer these questions. R is proportional to the likeliness that the importance rank of nodes in the given network according to a given index would not change due to possible errors in network construction. For calculating R, first the maximum expected error ( P) has to be computed which represents the potential range of error in estimating the keystone index in question. Basically, R is calculated by comparing P to the keystone indices of species to assess the reliability of the importance rank of species based on the network model. We calculated the robustness of 13 different structural indices in 26 food webs of different size to test the P and R values. We found that fragmentation indices and the number of dominated nodes can be characterized by quite low R values, while betweenness, topological importance, keystoneness and mixed trophic impact have high R values, which means that they are relatively more reliable for assessing the importance rank of species in an uncertain network model. However, as R was found to be very variable, depending on the topology of a given network, a detailed description is provided for performing the actual calculations case-by-case.

A NON-ITERATIVE APPROACH TO SOLVING HORIZONTAL CURVES

The five elements of any horizontal circular curve, which are tangent distance, T, external distance, E, middle ordinate, M, chord length C, and length of curve, L, can be directly determined if the radius R and deflection angle Δ are given. Practically, there are some cases where the deflection angle Δ and the radius R cannot be measured due to the inaccessibility of the intersection point PI. Thus, two other curve elements have to be known in order to layout the horizontal circler curve.This paper presents a direct method to extract the unknown elements exploiting a cubic polynomial equation which characterizes the curve deflection angle. The least squares technique is considered in order to facilitate the solution with fair accuracy.Particularly, the cubic polynomial is selected as it generates an adequate desired accuracy. If higher accuracy is aspired, higher order polynomials, i.e. quartics, quintics,..., may be adopted.On contrast to other methods, which adopt iteration process, the presented method is direct, non-iterative, accurate, and easy to handle values of deflection angle, Δ, ranging from 0 to π without imposing any derivatives.The major benefits of the proposed method are illustrated as: firstly it is direct method which may easily be executed using the pocket calculator with high accuracy, and secondly, it avoids the uncertainty of the convergence due to the lack of pre-estimation of the initial value of deflection angle and number of iteration trials required when iteration solution is considered.The applicability and accuracy of the presented method is justified through a numerical application. Using the same values of L and T, it has been found that the percent of error for the previous methods in five digits values vary from 0 to 0.00133% for Δ and 0.00084 % to 0.00252 % for R. The proposed method gives an error of 0.00533 % for Δ and 0.00644 % for R. The effect of such errors in roadway geometry design is negligible.

Ensuring Sound Numerical Simulation of Hybrid Automata

A hybrid system is a dynamical system in which states can be changed continuously and discretely. Simulation based on numerical methods is the widely used technique for analyzing complicated hybrid systems. Numerical simulation of hybrid systems, however, is subject to two types of numerical errors: truncation error and round-off error. The effect of such errors can make an impossible transition step to become possible during simulation, and thus, to generate a simulation behavior that is not allowed by the model. The possibility of an incorrect simulation behavior reduces con.dence in simulation-based analysis since it is impossible to know whether a particular simulation trace is allowed by the model or not. To address this problem, we define the notion of Instrumented Hybrid Automata (IHA), which considers the effect of accumulated numerical errors on discrete transition steps. We then show how to convert Hybrid Automata (HA) to IHA and prove that every simulation behavior of IHA preserves the discrete transition steps of some behavior in HA; that is, simulation of IHA is sound with respect to HA.

Looking forwards or looking backwards in avian phylogeography? A comment on Zink and Barrowclough 2008

Looking forwards or looking backwards in avian phylogeography? A comment on Zink and Barrowclough 2008

Hypothesis Testing

Hypothesis Testing

High-frequency corrections to the detector response and their effect on searches for gravitational waves

Searches for gravitational waves with km-scale laser interferometers often involve the long-wavelength approximation to describe the detector response. The prevailing assumption is that the corrections to the detector response due to its finite size are small and the errors due to the long-wavelength approximation are negligible. Recently, however, Baskaran and Grishchuk (2004 Class. Quantum Grav. 21 4041) found that in a simple Michelson interferometer such errors can be as large as 10%. For more accurate analysis, these authors proposed to use a linear-frequency correction to the long-wavelength approximation. In this paper we revisit these calculations. We show that the linear-frequency correction is inadequate for certain locations in the sky and therefore accurate analysis requires taking into account the exact formula, commonly derived from the photon round-trip propagation time. Also, we extend the calculations to include the effect of Fabry–Perot resonators in the interferometer arms. Here we show that a simple approximation which combines the long-wavelength Michelson response with the single-pole approximation to the Fabry–Perot transfer function produces rather accurate results. In particular, the difference between the exact and the approximate formulae is at most 2–3% for those locations in the sky where the detector response is greater than half of its maximum value. We analyse the impact of such errors on detection sensitivity and parameter estimation in searches for periodic gravitational waves emitted by a known pulsar, and in searches for an isotropic stochastic gravitational-wave background. At frequencies up to 1 kHz, the effect of such errors is at most 1–2%. For higher frequencies, or if more accuracy is required, one should use the exact formula for the detector response.

Potential Vorticity Diagnosis of the Severe Convective Regime. Part I: Methodology

Abstract Observational and modeling studies have shown that shear and instability are powerful predictors of the likelihood of severe weather and tornadoes. To the extent that upper-tropospheric forecast errors can be described as potential vorticity (PV) anomalies on the forecasted PV field, knowing (and being able to quantify) the effects of such errors on shear and instability would allow forecasters to anticipate the effects of those errors on the likely mode of severe weather. To test the sensitivity of the severe convective environment to PV fluctuations, a PV inversion framework is adopted that utilizes nonlinear balance. The observed PV field is modified in a way that mimics realistic perturbations of trough intensity, location, or shape. Soundings, including moisture profiles, are reconstructed from the balanced geopotential height field assuming that air parcels conserve mixing ratio while their isentropic surfaces are displaced upward or downward by the addition of anomalous PV. Unperturbed balanced soundings agree reasonably well with full, unbalanced soundings, and differences are attributable to departures from nonlinear balance in areas of strong vorticity or acceleration. Balanced vertical wind profiles do not include the effects of friction, so the vertical shear of the balanced wind departs unacceptably from total shear within the lowest 1 km of the troposphere. The balanced wind perturbations are added to the total analyzed shear profile to estimate the effect of PV perturbations on shear and storm-relative helicity. By this process, the importance of typical or hypothesized upper-tropospheric forecast errors may be addressed in an idealized, case-study, or operational context.

Errors and weaknesses detected by the European Court of Auditors in the reports on the European Structural Funds 2000–2004

The present paper shows the weaknesses and the errors detected by the European Court of Auditors (ECA) in the reports regarding the Structural Funds (the European Social Fund (ESF); the European Agricultural Guidance and Guarantee Fund, ‘Guidance’ section (EAGGF-Guidance), the European Regional Development Fund (ERDF) and the Financial Instrument for Fisheries Guidance (FIFG)), presented by 15 countries of the European Union from the year 2000 to 2004. We have classified the said countries in four groups, regarding the date of their EU incorporation. The main aim of our work is to highlight the errors made by the Member States on the management and control of the structural funds received from the EU, analysing the likely causes and consequences of such errors.

Modelling of errors in databases

A lot of time and energy are expended assembling national databases containing information about health care processes and outcomes. Unfortunately, given the complexity of the data gathering procedures involved, errors occur. This inevitably leads to problems when it comes to the analysis of data from such sources. Indeed, sometimes it is very much a matter of faith that summary statistics represent a true reflection of the facts. On the assumption that one knows the rates at which different forms of errors occur, mathematical modelling methods can be used to obtain estimates of the effects of such errors on the estimates that would be derived for summary statistics associated with an erroneous data base.

Computing traveltime and amplitude sensitivity kernels in finite-frequency tomography

The efficient computation of finite-frequency traveltime and amplitude sensitivity kernels for velocity and attenuation perturbations in global seismic tomography poses problems both of numerical precision and of validity of the paraxial approximation used. We investigate these aspects, using a local model parameterization in the form of a tetrahedral grid with linear interpolation in between grid nodes. The matrix coefficients of the linear inverse problem involve a volume integral of the product of the finite-frequency kernel with the basis functions that represent the linear interpolation. We use local and global tests as well as analytical expressions to test the numerical precision of the frequency and spatial quadrature. There is a trade-off between narrowing the bandpass filter and quadrature accuracy and efficiency. Using a minimum step size of 10km for S waves and 30km for SS waves, relative errors in the quadrature are of the order of 1% for direct waves such as S, and a few percent for SS waves, which are below data uncertainties in delay time or amplitude anomaly observations in global seismology. Larger errors may occur wherever the sensitivity extends over a large volume and the paraxial approximation breaks down at large distance from the ray. This is especially noticeable for minimax phases such as SS waves with periods >20s, when kernels become hyperbolic near the reflection point and appreciable sensitivity extends over thousands of km. Errors becomes intolerable at epicentral distance near the antipode when sensitivity extends over all azimuths in the mantle. Effects of such errors may become noticeable at epicentral distances>140°. We conclude that the paraxial approximation offers an efficient method for computing the matrix system for finite-frequency inversions in global tomography, though care should be taken near reflection points, and alternative methods are needed to compute sensitivity near the antipode.

Environmental Realism: From Apologetics to Substance

This article assesses the cornucopian theory of the mastery of plastic nature. Serious deficiencies are found, especially the theory's complacent faith in economic rationality and its underestimation of nature's capacity for unexpected emergent disturbances. Conclusions about the real state of the world and realistic expectations for the future must take into account not only present trends, but also the findings of research into disasters and societies that have collapsed. Learning from the analysis of such discontinuities and breaking points will help to avoid simplistic presumptions of safety based on extrapolating time-series trends of present well-being in wealthy societies into the distant future. It is precisely disaster research and studies of collapsed societies that can teach us about failures of foresight concerning nature's dynamics, about the material consequences of such errors, about the uncertainties involved in foreseeing nature's emergent dynamics, and about social barriers to learning from the prompts of nature. Although apologetics for business-as-usual, full-steam-ahead practices that masquerade as realism should be rejected, a deeper realism that has learned to expect the unexpected from nature is necessary. Such a critical realist perspective for investigating prompts from nature has been elaborated in this article.

Error Propagation in the Elicitation of Utility and Probability Weighting Functions

Elicitation methods in decision-making under risk allow us to infer the utilities of outcomes as well as the probability weights from the observed preferences of an individual. An optimally efficient elicitation method is proposed, which takes the inevitable distortion of preferences by random errors into account and minimizes the effect of such errors on the inferred utility and probability weighting functions. Under mild assumptions, the optimally efficient method for eliciting utilities and probability weights is the following three-stage procedure. First, a probability is elicited whose subjective weight is one half. Second, the utility function is elicited through the midpoint chaining certainty equivalent method using the probability elicited at the first stage. Finally, the probability weighting function is elicited through the probability equivalent method.

Mathematical analysis of the impact of timing synchronization errors on the performance of an OFDM system

This letter addresses the effect of synchronization errors that are introduced by an erroneous detection of the start of an orthogonal frequency-division multiplexing (OFDM) symbol. Throughout this letter, the term timing error would refer to this type of error. Such errors degrade the performance of an OFDM receiver by introducing intercarrier interference (ICI) and intersymbol interference (ISI). They can occur due to either an erroneous initial frame synchronization or a change in the power delay profile of the channel. In this letter, we provide a mathematical analysis of the effect of errors on the performance of an OFDM receiver in a frequency-selective fading environment. The analysis presented in this letter is for the case that no equalization technique has been used to mitigate the introduced ICI and ISI. We find exact formulas for the power of interference terms and the resulting average signal-to-interference ratio. We further extend the analysis to the subsample level. Our results show the nonsymmetric effect of errors on the performance of an OFDM system. Finally, simulation results confirm the analysis. The results of this letter can be easily extended to address the effect of such errors on DMT modems.

Assessment of ancestry probabilities in the presence of genotyping errors

This paper extends an approach for estimating the ancestry probability, the probability that an inbred line is an ancestor of a given hybrid, to account for genotyping errors. The effect of such errors on ancestry probability estimates is evaluated through simulation. The simulation study shows that if misclassification is ignored, then ancestry probabilities may be slightly overestimated. The sensitivity of ancestry probability calculations to the assumed genotyping error rate is also assessed.