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  • 1
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    Practical input optimization for aircraft parameter estimation experiments (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The object of this research was to develop an algorithm for the design of practical, optimal flight test inputs for aircraft parameter estimation experiments. A general, single pass technique was developed which allows global optimization of the flight test input design for parameter estimation using the principles of dynamic programming with the input forms limited to square waves only. Provision was made for practical constraints on the input, including amplitude constraints, control system dynamics, and selected input frequency range exclusions. In addition, the input design was accomplished while imposing output amplitude constraints required by model validity and considerations of safety during the flight test. The algorithm has multiple input design capability, with optional inclusion of a constraint that only one control move at a time, so that a human pilot can implement the inputs. It is shown that the technique can be used to design experiments for estimation of open loop model parameters from closed loop flight test data. The report includes a new formulation of the optimal input design problem, a description of a new approach to the solution, and a summary of the characteristics of the algorithm, followed by three example applications of the new technique which demonstrate the quality and expanded capabilities of the input designs produced by the new technique. In all cases, the new input design approach showed significant improvement over previous input design methods in terms of achievable parameter accuracies.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-CR-191462 , NAS 1.26:191462
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Determining the accuracy of maximum likelihood parameter estimates with colored residuals (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An important part of building high fidelity mathematical models based on measured data is calculating the accuracy associated with statistical estimates of the model parameters. Indeed, without some idea of the accuracy of parameter estimates, the estimates themselves have limited value. In this work, an expression based on theoretical analysis was developed to properly compute parameter accuracy measures for maximum likelihood estimates with colored residuals. This result is important because experience from the analysis of measured data reveals that the residuals from maximum likelihood estimation are almost always colored. The calculations involved can be appended to conventional maximum likelihood estimation algorithms. Simulated data runs were used to show that the parameter accuracy measures computed with this technique accurately reflect the quality of the parameter estimates from maximum likelihood estimation without the need for analysis of the output residuals in the frequency domain or heuristically determined multiplication factors. The result is general, although the application studied here is maximum likelihood estimation of aerodynamic model parameters from flight test data.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-CR-194893 , NAS 1.26:194893
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Optimal input design for aircraft instrumentation systematic error estimation (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new technique for designing optimal flight test inputs for accurate estimation of instrumentation systematic errors was developed and demonstrated. A simulation model of the F-18 High Angle of Attack Research Vehicle (HARV) aircraft was used to evaluate the effectiveness of the optimal input compared to input recorded during flight test. Instrumentation systematic error parameter estimates and their standard errors were compared. It was found that the optimal input design improved error parameter estimates and their accuracies for a fixed time input design. Pilot acceptability of the optimal input design was demonstrated using a six degree-of-freedom fixed base piloted simulation of the F-18 HARV. The technique described in this work provides a practical, optimal procedure for designing inputs for data compatibility experiments.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 91-2850 , AIAA Atmospheric Flight Mechanics Conference; Aug 12, 1991 - Aug 14, 1991; New Orleans, LA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Optimal input design for aircraft parameter estimation using dynamic programming principles (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new technique was developed for designing optimal flight test inputs for aircraft parameter estimation experiments. The principles of dynamic programming were used for the design in the time domain. This approach made it possible to include realistic practical constraints on the input and output variables. A description of the new approach is presented, followed by an example for a multiple input linear model describing the lateral dynamics of a fighter aircraft. The optimal input designs produced by the new technique demonstrated improved quality and expanded capability relative to the conventional multiple input design method.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 90-2801 , AIAA Atmospheric Flight Mechanics Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
    Format: text
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  • 5
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    Comparison between different methodologies for detecting Radon in soil along an active fault: the case of the Pernicana fault system, Mt. Etna (Italy) (2008)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Three different methodologies were used to measure Radon (222Rn) in soil, based on both passive and active detection system. The first technique consisted of Solid State Nuclear Track Detectors (SSNTD), CR-39 type, and allowed integrated measurements. The second one consisted of a portable device for short time measurements. The last consisted of a continuous measurement device for extended monitoring, placed in selected sites. Soil 222Rn activity was measured together with soil Thoron (220Rn) and soil carbon dioxide (CO2) efflux, and it was compared with the content of radionuclides in the rocks. Two different soil gas horizontal transects were investigated across the Pernicana fault system (NE flank of Mount Etna), from November 2006 to April 2007. The results obtained with the three methodologies are in a general agreement with each other and reflect the tectonic settings of the investigated study area. The lowest 222Rn values were recorded just on the fault plane, and relatively higher values were recorded a few tens of meters from the fault axis on both of its sides. This pattern could be explained as a dilution effect resulting from high rates of soil CO2 efflux. Time variations of 222Rn activity were mostly linked to atmospheric influences, whereas no significant correlation with the volcanic activity was observed. In order to further investigate regional radon distributions, spot measurements were made to identify sites having high Rn emissions that could subsequently be monitored for temporal radon variations.. SSNTD measurements allow for extended-duration monitoring of a relatively large number of sites, although with some loss of temporal resolution due to their long integration time. Continuous monitoring probes are optimal for detailed time monitoring, but because of their expense, they can best be used to complement the information acquired with SSNTD in a network of monitored sites.
    Description: In press
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 4.4. Scenari e mitigazione del rischio ambientale
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Soil Radon and Thoron activity ; soil CO2 efflux ; Pernicana fault system ; Mount Etna ; volcano-tectonic monitoring ; 03. Hydrosphere::03.04. Chemical and biological::03.04.07. Radioactivity and isotopes ; 03. Hydrosphere::03.04. Chemical and biological::03.04.08. Instruments and techniques ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.02. Exploration geophysics::04.02.05. Downhole, radioactivity, remote sensing, and other methods ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    Imaging lateral heterogeneity in the northern Apennines from time reversal of reflected surface waves (2008)
    Details
    Publication Date: 2017-04-04
    Description: Prominent arrivals in the coda of seismograms from the wider Alpine area can be associated with lateral reflections of Love waves at the northern Apennines mountain chain (Italy), where structural heterogeneity causes an abrupt contrast in phase velocity. We discuss an approach to image lateral heterogeneity from reflected surface waves using intermediate-period, three-component coda waveforms as sources for an adjoint wavefield that propagates the reflections backward in time. We numerically compute three-dimensional sensitivity kernels for the dependence of coda waveforms on P-velocity, S-velocity and density, based upon correlations between the adjoint and the regular forward wavefields. We consider synthetic coda waveforms for a simplified model of the northern Apennines, as well as real coda observations from five moderate magnitude earthquakes (MW 4.6-5.6) in the southern Alps. Wave propagation is simulated based upon the spectral-element method, for which a three-dimensional regional earth model is used in the case of real data. Single event sensitivity kernels and their stacks provide clear images of the reflectivity associated with the northern Apennines in kernels for density and S- wave speed. The kernels show that surface-wave reflections occur near the axial zone of the mountain chain. Apart from the Apennines, the approach is able to unravel other smaller reflectivity patches from the coda waveforms, located for example at the Ivrea zone in the southern Alps. Our coda misfit kernels can be integrated in a gradient- based waveform tomography, where they could enhance the sharpness of the model at lateral heterogeneities.
    Description: In press
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Prominent arrivals in the coda of seismograms from the wider Alpine ; time-reversal imaging ; sensitivity kernel ; surface waves ; lithospheric heterogeneity ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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    The Moho depth map of the Antarctica region (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2020-02-24
    Description: Different tectonic units cover the Antarctic territory: platform, orogens and depression structures. This structural variability is reflected both in thickness and physical properties of the crust.We present a new Moho map for the Antarctica, derived from geophysical data selected from the literature. Themodel covers thewhole Antarctic region, from the South Pole out to the continental margin, including the Antarctic Peninsula. TheMoho depth is represented with a resolution of 1°×1° on a Cartesian grid obtained by an equidistant azimuthal geographical projection. A large volume of new data has been analyzed: mostly seismic experiments, as well as receiver functions and geological studies. In general,we can identify three large domainswithin the Antarctic continental crust. The oldest Archean and Proterozoic crust of East Antarctica has a thickness of 36–56 km (with an average of about 41 km). The continental crust of the Transantarctic Mountains, the Antarctic Peninsula and Wilkes Basin has a thickness of 30–40 km (with an average Moho of about 30 km). The youngest rifted continental crust of the West Antarctic Rift System has a thickness of 16–28 km (with an average Moho of about 26 km). The mean Moho depth of the whole model is 33.8 km. The new Moho model exhibits some remarkable disagreements at places with respect to global model CRUST 2.0. Difference between these two models may range up to −10/+24 km. The new model is available for download in digital format. We plan to update the model in the near future by including new data, particularly in the most poorly covered regions.
    Description: Published
    Description: 299-313
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Crustal structure ; Moho ; Antarctica ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Seismic Anisotropy of the Victoria Land region, Antactica (2010)
    Details
    Publication Date: 2017-04-04
    Description: We present shear-wave splitting results obtained from the analysis of core refracted teleseismic phases recorded by permanent and temporary seismographic stations located in the Victoria Land region (Antarctica). We use an eigenvalue technique to isolate the rotated and shifted shear-wave particle motion, in order to determine the best splitting parameters. Average values show clearly that dominant fast axis direction is NE-SW oriented, in accordance with previous measurements obtained around this zone. Only two stations, OHG and STAR show different orientations, with N-S and NNW-SSE main directions. On the basis of the periodicity of single shear-wave splitting measurements with respect to back-azimuths of events under study, we infer the presence of lateral and vertical changes in the deep anisotropy direction. To test this hypothesis we model waveforms using a cross-convolution technique for the cases of one and two anisotropic layers. We obtain a significant improvement on the misfit in the double layer case for the two stations. For stations where a multi-layer structure does not fit, we investigate lateral anisotropy changes at depth through Fresnel zone computation. We find that anisotropy beneath the Transantarctic Mountains (TAM) is considerably different from that beneath the Ross Sea. This feature influences the measurement distribution for the two permanent stations TNV and VNDA. Our results show a dominant NE-SW direction over the entire region, but other anisotropy directions are present and maybe interpreted in the context of regional tectonics.
    Description: Published
    Description: 421-432
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: Mantle Processes ; Seismic anisotorpy ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    EPcrust : A reference crustal model for the European plate (2011)
    Blackwell Publishing Ltd
    Details
    Publication Date: 2017-04-04
    Description: We present a new crustal model for the European plate, derived from collection and critical integration of information selected from the literature. The model covers the whole European plate from North Africa to the North Pole (20N - 90N) and from the Mid-Atlantic Ridge to the Urals (40W - 70E). The chosen parameterization represents the crust in three layers (sediments, upper crust and lower crust), and describes the 3D geometry of the interfaces and seismologically-relevant parameters — isotropic P- and S-wave velocity, plus density — with a resolution of 0.5 × 0.5 degrees on a geographical latitude-longitude grid. We selected global and local models, derived from geological assumptions, active seismic experiments, surface-wave studies, noise correlation, receiver functions. Model EPcrust presents significant advantages with respect to previous models: it covers the whole European plate; it is a complete and internally-consistent model (with all the parameters provided, also for the sedimentary layer); it is reproducible; it is easy to update in the future by adding new contributions; and it is available in a convenient digital format. EPcrust could be used to account for crustal structure in seismic wave propagation modeling at continental scale or to compute linearized crustal corrections in continental-scale seismic tomography, gravity studies, dynamic topography and other applications that require a reliable crustal structure. Because of its resolution, our model is not suited for local-scale studies, such as the computation of earthquake scenarios, where more detailed knowledge of the structure is required. We plan to update the model as new data will become available, and possibly improve its resolution for selected areas in the future.
    Description: Published
    Description: 352-364
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Europe ; crust ; crustal properties ; Moho ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.01. Earth Interior::04.01.01. Composition and state
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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