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1
Constantino, Thomas, und Isabelle Baraffe. „Significant uncertainties from calibrating overshooting with eclipsing binary systems“. Astronomy & Astrophysics 618 (Oktober 2018): A177. http://dx.doi.org/10.1051/0004-6361/201833568.
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The precise measurement of the masses and radii of stars in eclipsing binary systems provides a window into uncertain processes in stellar evolution, especially mixing at convective boundaries. Recently, these data have been used to calibrate models of convective overshooting in the cores of main sequence stars. In this study we have used a small representative sample of eclipsing binary stars with 1.25 ≤ M/M⊙ < 4.2 to test how precisely this method can constrain the overshooting and whether the data support a universal stellar mass–overshooting relation. We do not recover the previously reported stellar mass dependence for the extent of overshooting and in each case we find there is a substantial amount of uncertainty, that is, the same binary pair can be matched by models with different amounts of overshooting. Models with a moderate overshooting parameter 0.013 ≤ fos ≤ 0.014 (using the scheme from Herwig et al. 1997, A&A, 324, L81) are consistent with all eight systems studied. Generally, a much larger range of f is suitable for individual systems. In the case of main sequence and early post-main sequence stars, large changes in the amount of overshooting have little effect on the radius and effective temperature, and therefore the method is of extremely limited utility.
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Pfannschmidt, Joachim. „Expanding the knowledge of oligometastatic disease—but uncertainties remain significant“. Journal of Thoracic Disease 11, S15 (September 2019): S2008—S2011. http://dx.doi.org/10.21037/jtd.2019.06.39.
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3
Levine, Marc H., und Adrian P. Fitzsimons. „New AcSEC requirements for disclosure of certain significant risks and uncertainties“. Journal of Corporate Accounting & Finance 6, Nr. 3 (1995): 109–20. http://dx.doi.org/10.1002/jcaf.3970060312.
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Wang, Y.-Y., H.-S. Lau und Z.-S. Hua. „Three revenue-sharing variants: their significant performance differences under system-parameter uncertainties“. Journal of the Operational Research Society 63, Nr. 12 (Dezember 2012): 1752–64. http://dx.doi.org/10.1057/jors.2011.131.
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5
Skillman, Evan D. „Uncertainties in nebular helium abundances“. Proceedings of the International Astronomical Union 5, S268 (November 2009): 113–18. http://dx.doi.org/10.1017/s1743921310003947.
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AbstractEfforts to determine the primordial helium abundance via observations of metal poor HII regions have been limited by significant uncertainties. Because of a degeneracy between the solutions for density and temperature, the precision of the helium abundance determinations is limited. Spectra from the literature are used to show the effects of new atomic data and to demonstrate the challenges of determining precise He abundances. Several suggestions are made for meeting these challenges.
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Gerber, Brian D., und William L. Kendall. „Adaptive management of animal populations with significant unknowns and uncertainties: a case study“. Ecological Applications 28, Nr. 5 (01.06.2018): 1325–41. http://dx.doi.org/10.1002/eap.1734.
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Yu, Z., C. S. Kochanek, B. M. Peterson, Y. Zu, W. N. Brandt, E. M. Cackett, M. M. Fausnaugh und I. M. McHardy. „On reverberation mapping lag uncertainties“. Monthly Notices of the Royal Astronomical Society 491, Nr. 4 (11.12.2019): 6045–64. http://dx.doi.org/10.1093/mnras/stz3464.
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ABSTRACT We broadly explore the effects of systematic errors on reverberation mapping lag uncertainty estimates from javelin and the interpolated cross-correlation function (ICCF) method. We focus on simulated light curves from random realizations of the light curves of five intensively monitored AGNs. Both methods generally work well even in the presence of systematic errors, although javelin generally provides better error estimates. Poorly estimated light-curve uncertainties have less effect on the ICCF method because, unlike javelin , it does not explicitly assume Gaussian statistics. Neither method is sensitive to changes in the stochastic process driving the continuum or the transfer function relating the line light curve to the continuum. The only systematic error we considered that causes significant problems is if the line light curve is not a smoothed and shifted version of the continuum light curve but instead contains some additional sources of variability.
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Kainiemi, Laura, Sanni Eloneva und Mika Järvinen. „An assessment of the uncertainties related to bioenergy applications“. Management of Environmental Quality: An International Journal 25, Nr. 3 (08.04.2014): 301–12. http://dx.doi.org/10.1108/meq-11-2013-0124.
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Purpose – The purpose of this paper is to identify the most significant uncertainties for bioenergy applications, in order to identify factors determining the success of introducing bioenergy into the current energy system. Design/methodology/approach – A framework is built for identifying the most significant uncertainties based on studies exploring the positive potentials as well as possible negative effects of bioenergy. The framework is applied to explore uncertainties of bioenergy-based transport fuels and heat and power generation through two real life case studies. Findings – The results indicate that the most significant uncertainties are environmental and economic. Bioenergy applications have potential to mitigate climate change, but also come with negative environmental effects. Case studies show that operations in developing nations contain higher political/institutional and social uncertainty than those in developed countries, due to weaker regulations and enforcement. Research limitations/implications – The paper is part of an on-going research project. Results will be verified with stakeholder interviews and analysis. Further institutional analysis of the country settings is necessary. Practical implications – The use of a feedstock with high environmental, social and institutional uncertainties will lower public acceptance. Acting in accordance to the law is not sufficient to ensure sustainability and additional, voluntary measures should be undertaken. Originality/value – The paper identifies the most significant uncertainties for bioenergy. Uncertainties from social acceptance and institutional settings are higher in developing countries and acceptability requires more than following regulations.
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Goudar, D. M., M. S. Hossain, Christopher E. Truman, Ed J. Kingston und David John Smith. „Uncertainties in Triaxial Residual Stress Measurements“. Materials Science Forum 681 (März 2011): 498–503. http://dx.doi.org/10.4028/www.scientific.net/msf.681.498.
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Residual stress measurement techniques using mechanical strain relaxation depend on a number of physical quantities and are therefore sensitive to errors associated with the measured data. The resulting stress uncertainties can easily become significant and compromise the usefulness of the results or lead to misinterpretation of the behaviour of the residual stress distributions. It is therefore essential to develop an error analysis procedure for the measurements undertaken. Error analysis procedures for the deep hole drilling (DHD) method are developed to consider triaxial residual stresses. A modified deep hole drilling method, called the incremental deep-hole drilling (iDHD), was applied to measure the near yield residual stress distributions in a cold water quenched aluminium 7010 alloy forged block. The experimental results are used to illustrate the errors.
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Nessim, M. A., H. P. Hong und I. J. Jordaan. „Environmental Load Uncertainties for Offshore Structures“. Journal of Offshore Mechanics and Arctic Engineering 117, Nr. 4 (01.11.1995): 245–51. http://dx.doi.org/10.1115/1.2827230.
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A methodology for assessing the effect of different sources of uncertainty on the calculation of load effect on offshore structures is presented. A consistent classification of uncertainties was adopted and used as a basis to develop models to estimate the effect of different uncertainties on specified design loads. It is shown that distribution parameter uncertainties arising from limitations on the quantity of statistical data are not likely to have a significant effect on design loads. By contrast, model uncertainties can greatly increase the design loads, and the increase is sensitive to the probabilistic models used to describe model error. The methodology and results can be used by design engineers to take model uncertainties into account in estimating specified loads. They also form the basis for developing and calibrating a new information-sensitive code format.
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Bradley, Brendon A. „Epistemic Uncertainties in Component Fragility Functions“. Earthquake Spectra 26, Nr. 1 (Februar 2010): 41–62. http://dx.doi.org/10.1193/1.3281681.
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This paper is concerned with the inclusion of epistemic uncertainties in component fragility functions used in performance-based earthquake engineering. Conventionally fragility functions, defining the probability of incurring at least a specified level of damage for a given level of seismic demand, are defined by a mean and standard deviation and assumed to have a lognormal distribution. However, there exist many uncertainties in the development of such fragility functions. The sources of epistemic uncertainty in fragility functions, their consideration, combination, and propagation are presented and discussed. Two empirical fragility functions presented in literature are used to illustrate the epistemic uncertainty in the fragility function parameters due to the finite size of the datasets. These examples and the associated discussions illustrate that the magnitude of epistemic uncertainties are significant and there are clear benefits of the consideration of epistemic uncertainties pertaining to the documentation, quality assurance, implementation, and updating of fragility functions. Epistemic uncertainties should therefore always be addressed in future fragility functions developed for use in seismic performance assessment.
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Preisler, Haiganoush K., Karin L. Riley, Crystal S. Stonesifer, Dave E. Calkin und W. Matthew Jolly. „Near-term probabilistic forecast of significant wildfire events for the Western United States“. International Journal of Wildland Fire 25, Nr. 11 (2016): 1169. http://dx.doi.org/10.1071/wf16038.
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Fire danger and potential for large fires in the United States (US) is currently indicated via several forecasted qualitative indices. However, landscape-level quantitative forecasts of the probability of a large fire are currently lacking. In this study, we present a framework for forecasting large fire occurrence – an extreme value event – and evaluating measures of uncertainties that do not rely on distributional assumptions. The statistical model presented here incorporates qualitative fire danger indices along with other location and seasonal specific explanatory variables to produce maps of forecasted probability of an ignition becoming a large fire, as well as numbers of large fires with measures of uncertainties. As an example, 6 years of fire occurrence data from the Western US were used to study the utility of two fire danger indices: the 7-Day Significant Fire Potential Outlook issued by Predictive Services in the US and the National Fire Danger Rating’s Energy Release Component. This exercise highlights the potential utility of the quantitative risk index as a real-time decision support tool that can enhance managers’ abilities to discriminate among planning areas in terms of the likelihood and range of expected significant fire events. The approach is applicable wherever there are archived historical data from both observed fires and fire danger indices.
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Murphy, Declan G., und Derya Tilki. „Getting the Balance Right—The Benefits and Uncertainties of Focal Therapy for Significant Prostate Cancer“. European Urology 74, Nr. 4 (Oktober 2018): 430–31. http://dx.doi.org/10.1016/j.eururo.2018.06.035.
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Bayhaqi, Ahmad. „KETIDAKPASTIAN DALAM PEMODELAN PERUBAHAN IKLIM“. OSEANA 44, Nr. 1 (30.04.2019): 38–53. http://dx.doi.org/10.14203/oseana.2019.vol.44no.1.30.
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THE UNCERTAINTIES IN CLIMATE CHANGE MODELING. Climate in the Earth has changed over the periods and will be estimated to give the a significant impact for environment in the future. Climate prediction using a simulation model, as a tool to predict the future climate and it requires the high quantitative skills and technology, has showed the significant improvement. However, the climate model depends on the input variable and the result may be inaccurate because its biases and uncertainties. Information of the uncertainties in the climate model can determine the modification in climate change mitigation and show the way how to adapt with the inevitable changes.
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Le Menn, M. „About uncertainties in practical salinity calculations“. Ocean Science Discussions 6, Nr. 3 (28.10.2009): 2461–85. http://dx.doi.org/10.5194/osd-6-2461-2009.
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Abstract. Salinity is a quantity computed, in the actual state of the art, from conductivity ratio measurements, knowing temperature and pressure at the time of the measurement and using the Practical Salinity Scale algorithm of 1978 (PSS-78) which gives practical salinity values S. The uncertainty expected on PSS-78 values is ±0.002, but nothing has ever been detailed about the method to work out this uncertainty, and the sources of errors to include in this calculation. Following a guide edited by the Bureau International des Poids et Mesures (BIPM), this paper assess, by two independent methods, the uncertainties of salinity values obtained from a laboratory salinometer and Conductivity-Temperature-Depth (CTD) measurements after laboratory calibration of a conductivity cell. The results show that the part due to the PSS-78 relations fits is sometimes as much significant as the instruments one's. This is particularly the case with CTD measurements where correlations between the variables contribute to decrease largely the uncertainty on S, even when the expanded uncertainties on conductivity cells calibrations are largely up of 0.002 mS/cm. The relations given in this publication, and obtained with the normalized GUM method, allow a real analysis of the uncertainties sources and they can be used in a more general way, with instruments having different specifications.
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Ball, M. R., C. McEwan, D. R. Novog und J. C. Luxat. „The Dilution Dependency of Multigroup Uncertainties“. Science and Technology of Nuclear Installations 2014 (2014): 1–14. http://dx.doi.org/10.1155/2014/306406.
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The propagation of nuclear data uncertainties through reactor physics calculation has received attention through the Organization for Economic Cooperation and Development—Nuclear Energy Agency’s Uncertainty Analysis in Modelling (UAM) benchmark. A common strategy for performing lattice physics uncertainty analysis involves starting with nuclear data and covariance matrix which is typically available at infinite dilution. To describe the uncertainty of all multigroup physics parameters—including those at finite dilution—additional calculations must be performed that relate uncertainties in an infinite dilution cross-section to those at the problem dilution. Two potential methods for propagating dilution-related uncertainties were studied in this work. The first assumed a correlation between continuous-energy and multigroup cross-sectional data and uncertainties, which is convenient for direct implementation in lattice physics codes. The second is based on a more rigorous approach involving the Monte Carlo sampling of resonance parameters in evaluated nuclear data using the TALYS software. When applied to a light water fuel cell, the two approaches show significant differences, indicating that the assumption of the first method did not capture the complexity of physics parameter data uncertainties. It was found that the covariance of problem-dilution multigroup parameters for selected neutron cross-sections can vary significantly from their infinite-dilution counterparts.
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Coleman, Hugh W., W. Glenn Steele und Robert P. Taylor. „Implications of Correlated Bias Uncertainties in Single and Comparative Tests“. Journal of Fluids Engineering 117, Nr. 4 (01.12.1995): 552–56. http://dx.doi.org/10.1115/1.2817300.
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The effects of correlated bias uncertainties are considered for both single and comparative tests, and the implications of these effects on experimental results and their uncertainties are investigated. In single tests, correlated bias uncertainties can cause a significant increase or a significant decrease in uncertainty in the result as compared to the uncertainty when there are no correlation effects. In comparative tests, the experimental result is the difference of two test results or the ratio of two test results. If the same test apparatus and instrumentation are used to obtain the two test results, the systematic uncertainty in the difference or the ratio can be significantly less than the systematic uncertainly in the individual test results. However, the effects of systematic uncertainties do not cancel out in comparative tests in which the result is the difference in the results of two tests, contrary to assertions made in some engineering standards.
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Le Menn, M. „About uncertainties in practical salinity calculations“. Ocean Science 7, Nr. 5 (17.10.2011): 651–59. http://dx.doi.org/10.5194/os-7-651-2011.
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Abstract. In the current state of the art, salinity is a quantity computed from conductivity ratio measurements, with temperature and pressure known at the time of the measurement, and using the Practical Salinity Scale algorithm of 1978 (PSS-78). This calculation gives practical salinity values S. The uncertainty expected in PSS-78 values is ±0.002, but no details have ever been given on the method used to work out this uncertainty, and the error sources to include in this calculation. Following a guide published by the Bureau International des Poids et Mesures (BIPM), using two independent methods, this paper assesses the uncertainties of salinity values obtained from a laboratory salinometer and Conductivity-Temperature-Depth (CTD) measurements after laboratory calibration of a conductivity cell. The results show that the part due to the PSS-78 relations fits is sometimes as significant as the instrument's. This is particularly the case with CTD measurements where correlations between variables contribute mainly to decreasing the uncertainty of S, even when expanded uncertainties of conductivity cell calibrations are for the most part in the order of 0.002 mS cm−1. The relations given here, and obtained with the normalized GUM method, allow a real analysis of the uncertainties' sources and they can be used in a more general way, with instruments having different specifications.
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Bei, N., G. Li und L. T. Molina. „Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign“. Atmospheric Chemistry and Physics Discussions 12, Nr. 7 (03.07.2012): 16293–326. http://dx.doi.org/10.5194/acpd-12-16293-2012.
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Abstract. The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 &microg m−3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but has same significance compared to the ensemble mean.
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Bei, N., G. Li und L. T. Molina. „Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign“. Atmospheric Chemistry and Physics 12, Nr. 23 (03.12.2012): 11295–308. http://dx.doi.org/10.5194/acp-12-11295-2012.
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Abstract. The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 μg m−3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but the ratio of the ensemble spread to mean does not change significantly.
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Pan, X. P. „Systematic biases and uncertainties of Hipparcos parallax“. Proceedings of the International Astronomical Union 3, S248 (Oktober 2007): 78–81. http://dx.doi.org/10.1017/s1743921308018668.
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AbstractGround-based optical/IR interferometers have provided strong support to the space-based astrometric mission Hipparcos ever since the Hipparcos instrument was in operation in 1989. Interferometric observations also produced critical corrections of orbital motion to many targets, including radio stars, which link the Hipparcos system to the International Celestial Reference Frame (ICRF). In particular, orbital parallax from interferometers confirmed the 10% bias of the Pleiades distance from Hipparcos, and thus avoids revision of classical astronomy. Significant offsets and errors of Hipparcos parallax introduced by binary jitters are demonstrated in this work. By comparing the Hipparcos results with long baseline interferometry and other techniques including spectroscopy, multi-color photometry, Main-Sequence fitting, light curve measurements, Lunar occultation, Fine Guidance Sensor, etc., systematic biases and uncertainties of Hipparcos parallaxes are investigated and analyzed. We have established good models for major error sources of Hipparcos parallax, such as zonal bias, binary jitters, and luminosity-dependent errors. The lessons learned from the systematic biases of Hipparcos parallax are valuable to future space missions like SIM and Gaia.
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Fu, Cuiwei, Xiaogang Qin und Yu Wang. „Effects of Parameter Uncertainties on Interaction between Submarine Telecommunication Cables and Lateral Seabed Movements“. Advances in Civil Engineering 2020 (20.08.2020): 1–13. http://dx.doi.org/10.1155/2020/8824391.
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Submarine telecommunication cables are the physical backbone of the Internet. They are often buried shallowly beneath seabed and affected by seabed movements. Due to the long distance of cables and the complexity of submarine environment, interaction between cables and seabed movements inevitably involves various parameter uncertainties. However, effects of parameter uncertainties on submarine cable responses to seabed movements have not been fully investigated. This paper aims to address this problem using random finite element method (RFEM) that integrates finite element (FE) analysis with Monte Carlo simulation (MCS). First, deterministic FE analysis is performed to investigate cable responses to lateral seabed movements. Then MCS is implemented to study the effects of parameter uncertainties on cable responses. Statistical analysis of the MCS results is performed to prioritize the effects of parameter uncertainties on cable damage probability. Random field is also used to model spatial variability of soil parameters. Effect of the correlation length on cable damage probability is investigated. The results show that uncertainty of the anchored cable length La has the most significant effect on cable damage probability, while the effects of uncertainties in soil friction angle ϕ and effective unit weight γ′ are minor. Ignoring spatial variability of soil parameters may lead to significant misjudgment of cable damage risk.
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Li, Tuanjie, Hanqing Deng, Yaqiong Tang, Jie Jiang und Xiaofei Ma. „Accuracy analysis and form-finding design of uncertain mesh reflectors based on interval force density method“. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, Nr. 11 (03.08.2016): 2163–73. http://dx.doi.org/10.1177/0954410016662061.
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Mesh reflectors are uncertain structures because of the existing errors of dimension and material in the procedure of design and manufacture. These uncertainties have significant impacts on the mechanical and electrical properties, which must be considered during the design phase. Three directly related factors of cable uncertainties in mesh reflectors are considered in this paper, including the initial length, cross-sectional area, and elastic modulus. The analytical relationship between the cable uncertainties and the surface accuracy of mesh reflectors is deduced by interval analysis, and an interval force density method is thus proposed. First, this method is used to analyze the influence of the cable uncertainties on the surface accuracy. Then it is applied into the form-finding optimization of uncertain mesh reflectors to minimize the influence of cable uncertainties on the surface accuracy. Three kinds of cable nets of mesh reflectors are illustrated to analyze the influence of the cable uncertainties on the surface accuracy, and the mesh reflectors with high surface accuracy are obtained by the proposed method. Finally, the influences of both the design values and deviation amplitudes of cable uncertainties on the surface accuracy are revealed.
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Citeli de Freitas, Miguel, Vitor Dantas Meireles und Viktor V. Dodonov. „Minimal Products of Coordinate and Momentum Uncertainties of High Orders: Significant and Weak High-Order Squeezing“. Entropy 22, Nr. 9 (03.09.2020): 980. http://dx.doi.org/10.3390/e22090980.
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We consider the problem of minimization of products of mean values of the high powers of operators x and p. From this point of view, we study several two-term superpositions of the Fock states, as well as three popular families of infinite superpositions: squeezed states, even/odd coherent states, and orthogonal even coherent states (or compass states). The new element is the analysis of products of the corresponding (co)variances and the related generalized (Robertson–Schrödinger) intelligent states (RSIS). In particular, we show that both Fock and pure Gaussian homogeneous states are RSIS for the fourth powers (but not for the sixth ones). We show that lower bounds of the high-order uncertainty products can be significantly below the vacuum values. In this connection, the concept of significant and weak high-order squeezing is introduced.
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Schwarz, M., M. Innocenzi, I. Giacomelli, F. Fracchiolla, V. Patera und R. Righetto. „EP-1848 Inaccuracies in proton dose calculation may be as significant as setup and range uncertainties“. Radiotherapy and Oncology 133 (April 2019): S1003—S1004. http://dx.doi.org/10.1016/s0167-8140(19)32268-6.
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Caballero, Julio F., und Delphia F. Harris. „There Seems To Be Uncertainty about the Use of Significant Figures in Reporting Uncertainties of Results“. Journal of Chemical Education 75, Nr. 8 (August 1998): 996. http://dx.doi.org/10.1021/ed075p996.
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Peng, Yuehua, Wansuo Duan und Jie Xiang. „Can the uncertainties of Madden-Jullian Oscillation cause a significant “Spring Predictability Barrier” for ENSO events?“ Acta Meteorologica Sinica 26, Nr. 5 (Oktober 2012): 566–78. http://dx.doi.org/10.1007/s13351-012-0503-7.
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Korayem, M. H., M. Taherifar und H. Tourajizadeh. „Compensating the flexibility uncertainties of a cable suspended robot using SMC approach“. Robotica 33, Nr. 3 (05.03.2014): 578–98. http://dx.doi.org/10.1017/s0263574714000472.
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SUMMARYA sliding mode controller is designed to compensate for the flexibility uncertainties of a cable robot and improve its tracking performance. Of the most significant sources of these uncertainties are the elasticity of the cables and the flexibility of the joints. A favorable approach to improve the accuracy of the system is first to model the cable and joint flexibilities and then convert the model uncertainties into parametric uncertainties. Parametric uncertainties are the product of imprecise flexibility coefficients and are finally neutralized by a sliding mode controller. The flexibility in cables is modeled by considering the longitudinal vibration of the time-varying length cables. A simulation study is carried out to confirm the presented model and the positive effect of the designed controller. Then the impact of these uncertainties on the dynamic load carrying capacity (DLCC) of the robot is examined and compared for different cases. Finally, experimental tests are conducted on the IUST (Iran University of Science and Technology) cable-suspended robot to validate the presented theories and simulation results.
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Wang, Yuan, Xiangming Zheng, Hongda Li und Xiaoran Li. „An internal model control-cascade Proportion-Integration-Differentiation method for manipulation of nano-quad-rotors“. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, Nr. 8 (10.02.2019): 2948–55. http://dx.doi.org/10.1177/0954410018824928.
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Nowadays, manipulation of quad-rotors faces complexity in controller parameter tuning process and system instability under uncertainties. Internal model control is featured with less controller parameters, simpler tuning process than conventional methods, good robustness and perfect capability in rejection of uncertainties. All its merits can be applied in the field of nano-quad-rotor control since its internal model is easy to be obtained and the suffered uncertainties, especially persistent ones such as model uncertainties and winds, can be rejected by the algorithm effectively. In this paper, an internal model control cascade Proportion-Integration-Differentiation (PID) method is developed to enhance the robustness and improve the capability of uncertainty rejection of nano-quad-rotors flying under persistent uncertainties. The system can be stabilized in a very easy way with all controller parameters tuned within 0 to 1. Comparison with internal model control method was carried out numerically; the results show that, in dealing with persistent uncertainties, the internal model control cascade PID-based method presents significant superiority in the maintenance of both the accuracy of trajectory tracking and the stability of attitude.
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Walz, Nico-Philipp, und Michael Hanss. „Fuzzy Arithmetical Analysis of Multibody Systems with Uncertainties“. Archive of Mechanical Engineering 60, Nr. 1 (01.03.2013): 109–25. http://dx.doi.org/10.2478/meceng-2013-0007.
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The consideration of uncertainties in numerical simulation is generally reasonable and is often indicated in order to provide reliable results, and thus is gaining attraction in various fields of simulation technology. However, in multibody system analysis uncertainties have only been accounted for quite sporadically compared to other areas. The term uncertainties is frequently associated with those of random nature, i.e. aleatory uncertainties, which are successfully handled by the use of probability theory. Actually, a considerable proportion of uncertainties incorporated into dynamical systems, in general, or multibody systems, in particular, is attributed to so-called epistemic uncertainties, which include, amongst others, uncertainties due to a lack of knowledge, due to subjectivity in numerical implementation, and due to simplification or idealization. Hence, for the modeling of epistemic uncertainties in multibody systems an appropriate theory is required, which still remains a challenging topic. Against this background, a methodology will be presented which allows for the inclusion of epistemic uncertainties in modeling and analysis of multibody systems. This approach is based on fuzzy arithmetic, a special field of fuzzy set theory, where the uncertain values of the model parameters are represented by socalled fuzzy numbers, reflecting in a rather intuitive and plausible way the blurred range of possible parameter values. As a result of this advanced modeling technique, more comprehensive system models can be derived which outperform the conventional, crisp-parameterized models by providing simulation results that reflect both the system dynamics and the effect of the uncertainties. The methodology is illustrated by an exemplary application of multibody dynamics which reveals that advanced modeling and simulation techniques using some well-thought-out inclusion of the presumably limiting uncertainties can provide significant additional benefit.
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Ma, Hai Yi, Shu Ping Yi, Guo Cheng Ren und Xue Ling Hu. „Analysis of Uncertainties Affecting Numerical Transport Models for a Potential Radioactive Waste Disposal Site“. Advanced Materials Research 955-959 (Juni 2014): 1607–14. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.1607.
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Numerical models have been commonly used to study solute transport behaviours both in laboratory-and field-scale cases. However, numerical interpretation and predictions of solute transport are complicated by various uncertainties and therefore can be misleading and lead to incorrect understanding of solute transport behaviours in hydrogeological systems. Such uncertainties have been discussed with a case study of radionuclides transport at a potential site for disposal of Low-and Intermediate-Level radioactive Wastes (LILW) in southern China. Firstly, pre-modelling assumptions cause uncertainties for model performance and have a significant influence on the model output. Therefore, such assumptions and related factors should be thoroughly considered and minimized in laboratory experiments or investigated in the field. Secondly, difference in the calculated plumes caused by uncertainties in the development of conceptual models suggests that the hydrogeological conceptual model should be developed based on intrinsic understanding of the transport problems and relevant data collection. Thirdly, relative sensitivity (RS) has been calculated to analyse the parameter uncertainties. Results indicate that the uncertainties are tracer-, parameter-and time-dependent. Therefore, model uncertainties arising from parameters should be considered for each specific parameter with the specific period. Finally, prediction scenarios are associated with uncertainties in the model prediction stage. Results suggest that the uncertainties in scenarios of future transport conditions should be recognized prior to model prediction. This study illustrates some of the uncertainties that might affect numerical transport models and therefore will be a useful reference for application of solute transport models to assessment of contamination risks from a LILW disposal site.
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Jonathan, Philip, und Kevin Ewans. „Uncertainties in Extreme Wave Height Estimates for Hurricane-Dominated Regions“. Journal of Offshore Mechanics and Arctic Engineering 129, Nr. 4 (30.01.2007): 300–305. http://dx.doi.org/10.1115/1.2746401.
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Inherent uncertainties in estimation of extreme wave heights in hurricane-dominated regions are explored using data from the GOMOS Gulf of Mexico hindcast for 1900–2005. In particular, the effect of combining correlated values from a neighborhood of 72 grid locations on extreme wave height estimation is quantified. We show that, based on small data samples, extreme wave heights are underestimated and site averaging usually improves estimates. We present a bootstrapping approach to evaluate uncertainty in extreme wave height estimates. We also argue in favor of modeling supplementary indicators for extreme wave characteristics, such as a high percentile (95%) of the distribution of 100-year significant wave height, in addition to its most probable value, especially for environments where the distribution of 100-year significant wave height is strongly skewed.
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Kuhn, Emma J., G. Stewart Walker, Harriet Whiley, Jackie Wright und Kirstin E. Ross. „Household Contamination with Methamphetamine: Knowledge and Uncertainties“. International Journal of Environmental Research and Public Health 16, Nr. 23 (23.11.2019): 4676. http://dx.doi.org/10.3390/ijerph16234676.
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Contamination of residential homes with methamphetamine is an emerging issue of significant concern to public health. Cooking or smoking methamphetamine in a residential property contaminates the house, furnishings and personal possessions within it, with subsequent exposure through ingestion, dermal absorption and/or inhalation causing adverse health effects. Current guidelines identifying levels of methamphetamine contamination that require remediation vary between countries. There is also no international standard protocol for measuring levels of contamination and research has shown that different materials give rise to different recovery rates of methamphetamine. There are a number of currently used remediation methods; however, they have varying levels of success with limited studies comparing their long-term efficacies. Most importantly, there are few guidelines available that are based on a transparent, health risk-based approach, and there are many uncertainties on exposures and health effects, making it difficult to ensure the health of people residing in homes that have been used to cook or smoke methamphetamine are sufficiently protected. This manuscript presents the current state of knowledge regarding the contamination of residential homes with methamphetamine and identifies the current gaps in knowledge and priority areas for future research. The current regulatory approach to public health protection associated with exposure to residential premises contaminated with methamphetamine in Australia, New Zealand and the USA is also discussed.
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Whitmyre, Gary K., Jeffrey H. Driver, Michael E. Ginevan, Robert G. Tardiff und Scott R. Baker. „Human Exposure Assessment I: Understanding the Uncertainties“. Toxicology and Industrial Health 8, Nr. 5 (September 1992): 297–320. http://dx.doi.org/10.1177/074823379200800507.
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Exposure estimates produced using predictive exposure assessment methods are associated with a number of uncertainties that relate to the inherent variability of the values for a given input parameter (e.g., body weight, ingestion rate, inhalation rate) and to unknowns concerning the representativeness of the assumptions and methods used. Despite recent or ongoing consensus-building efforts that have made significant strides forward in promoting consistency in methodologies and parameter default values, the potential variability in the output exposure estimates has not been adequately addressed from a quantitative aspect. This is exemplified by remaining tendencies within federal and state agencies to use worst-case approaches for exposure assessment. In this study, range-sensitivity and Monte Carlo analyses were performed on several different exposure scenarios in order to illustrate the impact of the variability in input parameters on the total variability of the exposure output. The results of this study indicate that the variability associated with the example scenarios range up to more than four orders of magnitude when just some of the parameters are allowed to vary. Comparison of exposure estimates obtained using Monte Carlo simulations (in which selected parameters were allowed to vary over their observed ranges) to exposure estimates obtained using standard parameter default assumptions demonstrate that a default value approach can produce an exposure estimate that exceeds the 95th percentile exposure in an exposed population.
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Sorribes, Carles Pont, und Sergi Cortiñas Rovira. „Journalistic practice in risk and crisis situations: Significant examples from Spain“. Journalism 12, Nr. 8 (07.09.2011): 1052–66. http://dx.doi.org/10.1177/1464884910388233.
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In a democratic society, the media are central to the communication of risks and uncertainties to the public. This article presents 10 proposals for improving media coverage in social risk situations. The article focuses on the production logic of the media and its consequences for society. The proposals and the conclusions of this research are supported by an analysis of three Spanish cases: the risk implied by the Tarragona chemical complex (one of the biggest in Europe); the terrorist attacks on 11 March 2004 in Madrid; and the Carmel tunnel disaster in Barcelona on January 2005. The authors are participating in a research project on public perception of risk funded by the Spanish Education Ministry on public perception of risk (2004–2007 and 2007–2010).
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Shafiei, Behrooz, Mohsen Ekramian und Khoshnam Shojaei. „Robust Tension Control of Strip for 5-Stand Tandem Cold Mills“. Journal of Engineering 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/409014.
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Tandem cold rolling process is a nonlinear complex system with external and internal uncertainties and significant disturbances. The improvement in the quality of the final output depends on the control strategy of centerline thickness and interstand tension. This paper focuses on interstand tension control problem in 5-stand tandem cold rolling mills. Tension dynamics can be described by a nominal model perturbed by parametric uncertainties. In order to overcome the model uncertainties and external disturbances, suboptimalH∞andμcontrollers are proposed and the Hankel-norm approximation is used to reduce the order ofμcontroller. The performance of the proposed controllers is demonstrated by some simulations.
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Chagumaira, Christopher, Joseph G. Chimungu, Dawd Gashu, Patson C. Nalivata, Martin R. Broadley, Alice E. Milne und R. Murray Lark. „Communicating uncertainties in spatial predictions of grain micronutrient concentration“. Geoscience Communication 4, Nr. 2 (29.04.2021): 245–65. http://dx.doi.org/10.5194/gc-4-245-2021.
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Abstract. The concentration of micronutrients in staple crops varies spatially. Quantitative information about this can help in designing efficient interventions to address micronutrient deficiency. Concentration of a micronutrient in a staple crop can be mapped from limited samples, but the resulting statistical predictions are uncertain. Decision makers must understand this uncertainty to make robust use of spatial information, but this is a challenge due to the difficulties in communicating quantitative concepts to a general audience. We proposed strategies to communicate uncertain information and present a systematic evaluation and comparison in the form of maps. We proposed testing five methods to communicate the uncertainty about the conditional mean grain concentration of an essential micronutrient, selenium (Se). Evaluation of the communication methods was done through a questionnaire by eliciting stakeholder opinions about the usefulness of the methods of communicating uncertainty. We found significant differences in how participants responded to the different methods. In particular, there was a preference for methods based on the probability that concentrations are below or above a nutritionally significant threshold compared with general measures of uncertainty such as the prediction interval. There was no evidence that methods which used pictographs or calibrated verbal phrases to support the interpretation of probabilities made a different impression than probability alone, as judged from the responses to interpretative questions, although these approaches were ranked most highly when participants were asked to put the methods in order of preference.
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Carter, Joshua A., Jennifer C. Yee, Jason Eastman, B. Scott Gaudi und Joshua N. Winn. „Analytic approximations for transit light curve observables and uncertainties“. Proceedings of the International Astronomical Union 4, S253 (Mai 2008): 392–93. http://dx.doi.org/10.1017/s1743921308026732.
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AbstractThe light curve of an exoplanetary transit can be used to estimate the planetary radius and other parameters of interest. Because accurate parameter estimation is a non-analytic and computationally intensive problem, it is often useful to have analytic approximations for the parameters as well as their uncertainties and covariances. Here we give such formulas, for the case of an exoplanet transiting a star with a uniform brightness distribution. When limb darkening is significant, our parameter sets are still useful, although our analytic formulas underpredict the covariances and uncertainties.
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Stolarski, R. S., und S. Frith. „Search for evidence of trend slow-down in the long-term TOMS/SBUV total ozone data record: the importance of instrument drift uncertainty and fingerprint detection“. Atmospheric Chemistry and Physics Discussions 6, Nr. 3 (16.05.2006): 3883–912. http://dx.doi.org/10.5194/acpd-6-3883-2006.
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Abstract. We have developed a merged ozone data (MOD) data set for the period October 1978 through October 2005 combining total ozone measurements (version 8 retrieval) from the TOMS (Nimbus 7, Meteor 3, and Earth Probe) and SBUV/SBUV2 (Nimbus 7, NOAA 9/11/16) series of satellite instruments. We use MOD to search for evidence of ozone recovery in response to the observed leveling off of chlorine compounds in the stratosphere. A crucial step in any time series analysis is the evaluation of uncertainties. In addition to the standard statistical time-series uncertainties, we evaluate the possible instrumental drift uncertainty for the MOD data set. We combine these two sources of uncertainty and apply them to a cumulative sum of residuals (CUSUM) analysis for trend slow-down. For the quasi-global mean between 60° S and 60° N, the apparent slow-down in trend is found to be clearly significant if instrument uncertainties are ignored. When instrument uncertainties are added, the slow-down becomes marginally significant at the 2σ level. For the mid-latitudes of the northern hemisphere (30° to 60° N) the trend slow-down is significant. For the mid-latitudes of the southern hemisphere (30° to 60° S) it is not significant. The fingerprint of ozone recovery expected from model calculations suggests both northern and southern mid-latitude total ozone levels should recover together. Our result fails this fingerprint test and is therefore not a demonstration of the response of total ozone to the leveling off of chlorine.
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Valentini, R., A. Arneth, A. Bombelli, S. Castaldi, R. Cazzolla Gatti, F. Chevallier, P. Ciais et al. „The full greenhouse gases budget of Africa: synthesis, uncertainties and vulnerabilities“. Biogeosciences Discussions 10, Nr. 5 (17.05.2013): 8343–413. http://dx.doi.org/10.5194/bgd-10-8343-2013.
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Abstract. This paper, developed under the framework of the RECCAP initiative, aims at providing improved estimates of the carbon and GHG (CO2, CH4 and N2O) balance of continental Africa. The various components and processes of the African carbon and GHG budget were considered, and new and available data derived by different methodologies (based on inventories, ecosystem fluxes, models, and atmospheric inversions) were integrated. The related uncertainties were quantified and current gaps and weakness in knowledge and in the monitoring systems were also considered in order to provide indications on the future requirements. The vast majority of the results seem to agree that Africa is probably a small sink of carbon on an annual scale, with an average value of −0.61 ± 0.58 Pg C yr−1. Nevertheless the emissions of CH4 and N2O may turn Africa into a source in terms of CO2 equivalents. At sub-regional level there is a significant spatial variability in both sources and sinks, mainly due to the biome's differences and the different anthropic impacts, with southern Africa as the main source and central Africa, with its evergreen tropical forests, as the main sink. Emissions from land use change in Africa are significant (around 0.32 ± 0.05 Pg C yr−1) and even higher than the fossil fuel ones; this is a unique feature among all the continents. In addition there can be significant carbon losses from land even without changes in the land use (forest), as results from the impact of selective logging. Fires also play a significant role, with 1.03 ± 0.22 Pg C yr−1 of carbon emissions, mainly (90%) originated by savanna and woodland burning. But whether fire carbon emissions are compensated by CO2 uptake during the growing season, or are a non-reversible loss of CO2, remains unclear. Most of these figures are subjected to a significant interannual variability, on the order of ± 0.5 Pg C yr−1 in standard deviation, accounting for around 25% of the year-to-year variation in the global carbon budget. These results, even if still highly uncertain, show the important role that Africa plays in the carbon cycle at global level, both in terms of absolute values and variability.
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Han, Seunghee, Jooyong Jun und Eunjung Yeo. „In Pursuit of Sustainable Mobile Policy: A Study of Consumer Tariff Preferences under Uncertainty“. Sustainability 13, Nr. 2 (08.01.2021): 540. http://dx.doi.org/10.3390/su13020540.
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Literature suggests that consumers expect disutility not only from payment uncertainties but also from reference uncertainties embedded in mobile plans. This paper develops a model of mobile plan choice incorporating both reference and payment uncertainties and uses this model to derive testable implications. The paper argues that consumer choice reflects those uncertainties more than could be justified by rational choice theory. Such patterns, the paper hypothesizes, would be more salient in the choice of data plan than voice plan because consumers tend to perceive data usage to be less controllable than voice usage, thus preferring the plan that reduces uncertainty. The paper tests the predictions with data from a laboratory study analyzing a series of choices between plans with different tariff structures—flat-rate, two-part, and three-part tariffs. As predicted, the results suggest that payment and reference uncertainties create significant disutility for consumers, especially when they perceive high uncertainty about their usage. Such understanding of consumer preference and underlying psychological biases is important in the sense that it provides an essential basis for the development of sustainable mobile policy.
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Bei, N., W. Lei, M. Zavala und L. T. Molina. „Ozone predictabilities due to meteorological uncertainties in Mexico City basin using ensemble forecasts“. Atmospheric Chemistry and Physics Discussions 10, Nr. 2 (05.02.2010): 3229–63. http://dx.doi.org/10.5194/acpd-10-3229-2010.
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Abstract. The purpose of the present study is to investigate the sensitivity of ozone concentration ([O3]) predictions in Mexico City to meteorological initial uncertainties and planetary boundary layer (PBL) parameterization schemes using state-of-the-art meteorological and photochemical prediction models through ensemble forecasts. The simulated periods (3, 9, 15, and 29 March 2006), represent four typical meteorological episodes ("South-Venting", "O3-North", "O3-South" and "Convection-North", respectively) in the Mexico City basin during the MCMA-2006/MILAGRO campaign. Our results demonstrate that uncertainties in meteorological initial conditions have significant impacts on O3 predictions, including the peak time [O3], as well as the horizontal and vertical [O3] distributions, and temporal variations. The ensemble spread of the simulated peak [O3] averaged over the city's ambient monitoring sites can reach up to 10 ppb. The magnitude of the ensemble spreads varies with different PBL schemes and meteorological episodes. The uncertainties in O3 predictions caused by PBL schemes mainly come from their ability to represent the mixing layer height, but overall, these uncertainties are smaller than those from uncertainties in meteorological initial conditions.
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Han, Seunghee, Jooyong Jun und Eunjung Yeo. „In Pursuit of Sustainable Mobile Policy: A Study of Consumer Tariff Preferences under Uncertainty“. Sustainability 13, Nr. 2 (08.01.2021): 540. http://dx.doi.org/10.3390/su13020540.
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Literature suggests that consumers expect disutility not only from payment uncertainties but also from reference uncertainties embedded in mobile plans. This paper develops a model of mobile plan choice incorporating both reference and payment uncertainties and uses this model to derive testable implications. The paper argues that consumer choice reflects those uncertainties more than could be justified by rational choice theory. Such patterns, the paper hypothesizes, would be more salient in the choice of data plan than voice plan because consumers tend to perceive data usage to be less controllable than voice usage, thus preferring the plan that reduces uncertainty. The paper tests the predictions with data from a laboratory study analyzing a series of choices between plans with different tariff structures—flat-rate, two-part, and three-part tariffs. As predicted, the results suggest that payment and reference uncertainties create significant disutility for consumers, especially when they perceive high uncertainty about their usage. Such understanding of consumer preference and underlying psychological biases is important in the sense that it provides an essential basis for the development of sustainable mobile policy.
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WANG, CHUN-CHIEH, und JUHNG-PERNG SU. „COMPOSITE SLIDING MODE CONTROL OF CHAOTIC SYSTEMS WITH UNCERTAINTIES“. International Journal of Bifurcation and Chaos 13, Nr. 04 (April 2003): 863–78. http://dx.doi.org/10.1142/s0218127403006984.
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This paper presents a new approach to the design of a composite sliding mode control for a class of chaotic systems with uncertainties. A significant feature of this control scheme is the incorporation of a new complementary sliding variable to the conventional sliding variable in order that a high-performance controller can be obtained. It has been shown that the guaranteed steady-state error bounds are reduced by half, as compared with the conventional sliding control. Moreover, the dynamic responses during the reaching phase are also significantly improved. We used a controlled uncertain Lorenz system and a controlled uncertain Chua's circuit as illustrative examples to demonstrate the effectiveness of the design.
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Li, Yang, Hefu Liu, Matthew Lee und Qian Huang. „Information privacy concern and deception in online retailing“. Internet Research 30, Nr. 2 (10.07.2019): 511–37. http://dx.doi.org/10.1108/intr-02-2018-0066.
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Purpose Previous studies have attempted to address online uncertainties from the relationship marketing perspective. The purpose of this paper is to argue that the integration of media richness theory (MRT) and cognitive fit theory (CFT) can contribute a new perspective in addressing consumers’ transaction-specific uncertainties in online retailing. Design/methodology/approach On the basis of MRT and CFT, a research model was developed by correlating online channel media richness (OCMR), online–offline information integration (OOII), information privacy concern, perceived deception and online loyalty. The model was empirically examined based on survey data collected from 258 multi-channel consumers in China. Findings An analysis of structural equation model showed that OCMR is negatively associated with information privacy concern and perceived deception but is not significant to online loyalty. Information privacy concern has a negative influence on online loyalty, but the effect of perceived deception is not significant. Moreover, information privacy concern is positively related to perceived deception. The OOII strengthens the influence of OCMR but not the moderating effect of integrated promotion, product and price information on the relationship between OCMR and online loyalty. Originality/value This study contributes to the extant literature on online retailing by examining the effect of OCMR on online transaction uncertainties. Information integrity in the form of OOII was proposed to complement OCMR. Results have shown that OCMR is significant in reducing online uncertainties, and OOII strengthens this effect, thereby enhancing online loyalty.
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Ida, Takashi. „Experimental estimation of uncertainties in powder diffraction intensities with a two-dimensional X-ray detector“. Powder Diffraction 31, Nr. 3 (04.07.2016): 216–22. http://dx.doi.org/10.1017/s0885715616000324.
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A method to obtain both one-dimensional powder diffraction intensities I(2θ) and statistical uncertainties σ(2θ) from the data collected with a flat two-dimensional X-ray detector is proposed. The method has been applied to analysis of the diffraction data of fine quartz powder recorded with synchrotron X-ray. The profile and magnitude of the estimated uncertainties σ(2θ) have shown that the effects of propagation of the errors in 2θ are dominant as the uncertainties about the observed intensity values I(2θ). The powder diffraction intensity data I(2θ), including nine reflection peaks have been analyzed by the Rietveld method incorporating the experimentally estimated uncertainties σ(2θ). The observed I(2θ) data have been reproduced with a symmetric peak profile function (Rwp = 0.84 %), and no significant peak shifts from calculated locations have been detected as compared with the experimental errors. The optimized values of the lattice constants of the quartz sample have nominally been estimated at a = 4.9131(4) Å and c = 5.4043(2) Å, where the uncertainties in parentheses are evaluated by the Rietveld optimization based on the estimated uncertainties σ(2θ) for intensities I(2θ). It is likely that reliability of error estimation about unit-cell dimensions has been improved by this analytical method.
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Chang, Xue Fei, Zhe Yong Piao, Xiang Yu Lv und De Xin Li. „Co-Optimization of Output and Reserve with Significant Penetration of Renewables“. Applied Mechanics and Materials 427-429 (September 2013): 341–45. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.341.
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Co-optimization of output and reserve is necessary in order to provide maximum benefit to both consumers and producers. Once renewable generation sources like wind or solar begin to make up a large proportion of the generation mix, this co-optimization becomes much more difficult since the output of renewable sources is not well-known in advance. In this paper, a uniform reliability level is used as a constraint in the process of output and reserve. The proposed model is tested on the modified 5-bus PJM system. The co-optimization is performed by sequential quadratic programming techniques. The results show that the co-optimization results are strongly related to the uncertainties of wind power, the reliability level of the system, and the reliability of generators when wind makes up a significant portion of the generation mix.
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Friston, K. J., C. D. Frith, P. F. Liddle und R. S. J. Frackowiak. „Comparing Functional (PET) Images: The Assessment of Significant Change“. Journal of Cerebral Blood Flow & Metabolism 11, Nr. 4 (Juli 1991): 690–99. http://dx.doi.org/10.1038/jcbfm.1991.122.
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Statistical parametric maps (SPMs) are potentially powerful ways of localizing differences in regional cerebral activity. This potential is limited by uncertainties in assessing the significance of these maps. In this report, we describe an approach that may partially resolve this issue. A distinction is made between using SPMs as images of change significance and using them to identify foci of significant change. In the first case, the SPM can be reported nonselectively as a single mathematical object with its omnibus significance. Alternatively, the SPM constitutes a large number of repeated measures over the brain. To reject the null hypothesis, that no change has occurred at a specific location, a threshold adjustment must be made that accounts for the large number of comparisons made. This adjustment is shown to depend on the SPM's smoothness. Smoothness can be determined empirically and be used to calculate a threshold required to identify significant foci. The approach models the SPM as a stationary stochastic process. The theory and applications are illustrated using uniform phantom images and data from a verbal fluency activation study of four normal subjects.
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Beven, K. J., W. P. Aspinall, P. D. Bates, E. Borgomeo, K. Goda, J. W. Hall, T. Page et al. „Epistemic uncertainties and natural hazard risk assessment – Part 1: A review of the issues“. Natural Hazards and Earth System Sciences Discussions 3, Nr. 12 (07.12.2015): 7333–77. http://dx.doi.org/10.5194/nhessd-3-7333-2015.
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Abstract. Uncertainties in natural hazard risk assessment are generally dominated by the sources arising from lack of knowledge or understanding of the processes involved. There is a lack of knowledge about frequencies, process representations, parameters, present and future boundary conditions, consequences and impacts, and the meaning of observations in evaluating simulation models. These are the epistemic uncertainties that can be difficult to constrain, especially in terms of event or scenario probabilities, even as elicited probabilities rationalized on the basis of expert judgements. This paper reviews the issues raised by trying to quantify the effects of epistemic uncertainties. Such scientific uncertainties might have significant influence on decisions that are made for risk management, so it is important to communicate the meaning of an uncertainty estimate and to provide an audit trail of the assumptions on which it is based. Some suggestions for good practice in doing so are made.
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Işık, Cem, Ercan Sirakaya-Turk und Serdar Ongan. „Testing the efficacy of the economic policy uncertainty index on tourism demand in USMCA: Theory and evidence“. Tourism Economics 26, Nr. 8 (22.11.2019): 1344–57. http://dx.doi.org/10.1177/1354816619888346.
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The global economic outlook is more uncertain than ever before and sensitive to uncertainties related to a variety of economic policies decisions of all stakeholders and governments. These perceived uncertainties may be the culprit in shrinking the size of overall economic activity. Under increasing uncertainties, travel and vacation plans of consumers can be canceled or postponed. Therefore, policy-related economic uncertainties are expected to affect tourism demand beyond well-established economic and noneconomic factors. In this study, we explore the efficacy and the impact of the economic policy uncertainty (EPU) index in predicting the tourism demand on international tourist arrivals (a measure of tourism demand) to the United States from Mexico and Canada over the period of January 1996–September 2017. The findings of the study reveal that EPU is a significant predictor as increases in the EPU index lead to decreases in tourism demand to the United States. Canadian tourists seem to be more sensitive to EPUs. Increases in the EPU index cause them to reduce Canadians’ vacations to the United States proportionally more than the Mexicans. To enhance the explanatory power of current models, the uncertainty can be a theoretically significant construct thus needs to be included when calibrating demand models.