177,177 research outputs found
Alternatives to the World Bank’s strategies for education and development
No full textOver the past several decades, policy has become increasingly global. In economics, for example, policy has followed the so-called Washington Consensus of privatization, liberalization, and deregulation. In education, global policy has included the proliferation of strategies including standardized testing, paraprofessional teachers, user fees, and privatization. There are many problems with these neoliberal policies. Foremost among them, is the havoc they wreak on the lives of so many children and adults. Poverty, inequality, and myriad associated problems have reached new heights in this neoliberal era. Moreover, these policies have been adopted uncritically and alternative policies have been ignored, which leads to our focus here
Occupational health issues in the pharmaceutical research and development process.
No full textThe research and development process for bringing a new drug to market can span 8-12 years and many testing stages, during which the number of people with the potential for occupational exposure to dangerous compounds and their targets (infectious organisms) increases. Drs. Klees and Joines carefully guide the reader through the R & D process, indicating potential hazards along the way
Separating geophysical signals using GRACE and high-resolution data: a case study in Antarctica
No full textDataset contains the original data underlying the paper: Engels, O., Gunter, B. C., Riva, R. E. M., & Klees, R. (2018). Separating geophysical signals using GRACE and high-resolution data: A case study in Antarctica, Geophysical Research Letters, 45. <https://doi.org/10.1029/2018GL079670
Roadmap to a mutually consistent set of offshore vertical reference frames
No full textThis thesis presents a combined approach for the realization of the (quasi-)geoid as a height reference surface and the vertical reference surface at sea (chart datum). This approach, specifically designed for shallow seas and coastal waters, provides the relation between the two vertical reference surfaces without gaps down to the coast. It uses a shallow water hydrodynamic model which provides water levels relative to a given (quasi-)geoid. The latter requires that the hydrodynamic model is vertically referenced to the same (quasi-)geoid. Vice versa, the hydrodynamic model is also used to realize a (quasi-)geoid by providing corrections to the dynamic sea surface topography, which are used to reduce radar altimeter-derived sea surface heights to the (quasi-)geoid. The coupled problem of vertically referencing the hydrodynamic model and computing the (quasi-)geoid is solved iteratively. After convergence of the iteration process, the vertically referenced hydrodynamic model is used to realize the chart datum. In this way, consistency between the chart datum and (quasi-)geoid is ensured. The feasibility and performance of this approach is demonstrated for the Dutch North Sea and mainland. It is shown that the differences between modeled and observed instantaneous and mean dynamic sea surface topography is 8-10 cm and 5.8 cm, respectively, for the Dutch North Sea. On land, it is shown that the methodology provides a (quasi-)geoid which has a lower standard deviation than the European Gravimetric Geoid 2008 (EGG08) and the official Netherlands (quasi-)geoid NLGEO2004-grav when compared to GPS-levelling data. The standard deviation at 81 GPS-levelling points is below 1 cm; no correction surface is needed. Finally, it is shown that the chart datum (lowest astronomical tide, LAT) agrees with the observed chart datum at 92 onshore tide gauges to within 21.5 cm standard deviation. This study also examines the impact of instantaneous dynamic sea surface topography (DT) corrections to be applied to altimeter-derived sea surface slopes on the quasi-geoid in the shallow and coastal waters of the North Sea. It is found that the steric and surge parts of the DT mainly contribute to improvements in the signal-to-noise ration at longer wavelengths down to 100-200 km and that the improvements increase towards the southern North Sea. It is also found that the shallow water hydrodynamic model provides better tidal corrections compared to a global ocean tide model, which are most pronounced in the southern North Sea and affect almost the entire spectrum. In terms of quasi-geoid heights, the differences are very small differences (mostly below ±2 cm). This is explained by the fact that altimeter-derived (quasi-)geoid slopes hardly contribute to the estimated quasi-geoid if shipboard gravity data are included. The last question treated in this thesis is whether a spherical Slepian basis representation enables to obtain spectral consistency between a high- and low-resolution data set (following recent studies, this question is treated in the context of mean dynamic topography (MDT) estimation by computing the difference between a high-resolution mean sea level (MSL) model obtained from satellite altimetry and a low-resolution gravimetric geoid). The answer is no; a Slepian representation of the low-resolution MSL signal suffers from broadband leakage. Furthermore, it is shown that a meaningful definition of a low-resolution MSL over incomplete spherical domains involves orthogonal basis functions with additional properties that Slepian functions do not possess. One of these sets of orthogonal basis functions are computed using the Gram-Schmidt orthogonalization for spherical harmonics. For the oceans, an orthogonal basis could be constructed only for resolutions equivalent to a spherical harmonic degree 36. The computation of a basis with a higher resolution failed due to inherent instabilities. More research is needed to solve the instability problem.Geoscience and Remote SensingCivil Engineering and Geoscience
Global Earth Structure Recovery from State-of-the-art Models of the Earth's Gravity Field and Additional Geophysical Information
No full textCurrently, a tremendous improvement is observed in the accuracy and spatial resolution of global Earth’s gravity field models. This improvement is achieved due to using various new data, including those from satellite gravimetry missions (CHAMP, GRACE, and GOCE); terrestrial and airborne gravity data, as well as altimetry data. The new gravity field models can be applied, in particular, to improve our knowledge of the Earth’s interior structure. The aim of this study is to compile a global map of the Moho interface using a global gravity model and additional available information about the crust density structure. In our study, we use the gravity field model EIGEN-6C2 and the global crustal model CRUST1.0 derived from seismic data. In addition, we utilize seismic-based models of Moho as prior information: CRUST1.0 model, as well as the Crust07 model, which was derived by a fully non-linear inversion of fundamental mode surface waves. The observed gravity field contains nuisance signals from the topography and density heterogeneities related to bathymetry, ice, sediments, and other crustal components. Therefore, we model and sequentially subtract these signals by applying so-called stripping corrections. This results in crust-stripped gravity field quantities (gravity anomalies and gravity disturbances). In the course of research, we review different analytical, semi-analytical, and numerical forward modeling techniques to compute the gravitational attraction of a body. We also derive an analytical formula for the computation of gravitational potential generated by a polyhedral body having linearly varying density. We compute the correction to observed gravity field using the analytical methods in the vicinity of the body and using semi-analytical methods in the far zone. We demonstrate that the sequential correction of gravity disturbances and gravity anomalies for nuisance signals increases the correlation with the Moho depths. We use the corrected gravity field to find the global (mean) value for the crust-mantle density contrast using the Pearson's correlation method. We use an empirical technique in which the absolute correlation between the Moho depth from CRUST 1.0 model and the updated crust stripped gravity disturbances/anomalies is minimized. The updated stripped gravity disturbances/anomalies are obtained by adding a contribution (attraction) related to the density contrast between the reference crust and the upper most mantle to stripped gravity disturbances/anomalies. The recovery of the Moho geometry is based on solving a system of linear equations which relates the crust-stripped gravity field (represented in terms of spherical harmonic coefficients) and the geometry of the Moho interface (represented in terms of Moho depths at the nodes of an equiangular geographical grid). In this way, corrections to the prior Moho configuration are estimated. It is known that a stand-alone inversion of gravimetric data may lead to inaccurate results because it is impossible to separate the signal from the interface under consideration and gravimetric signals from other sources (particularly, those located deeper inside the Earth). To suppress the latter signals (e.g, related to inhomogeneities of the mantle density and deep Earth structure), we propose to eliminate the contribution of low-degree spherical harmonics from input gravity data. Furthermore, we apply degree-dependent weights to the remaining spherical harmonics coefficients. The weight matrix is designed in such a way that low degrees are weighted less and high degree more. We have developed an advanced inversion procedure in which gravity data and information from other (seismic) sources are exploited simultaneously, using zero-order and first-order Tikhonov regularization concepts. The variance components estimation (VCE) procedure is used for the estimation of relative weights of different data sets. We consider a number of inversion strategies based on different combinations of data sets, regularization types, degree-dependent weights applied to input gravity data, as well as input gravity data minimum and maximum truncation degrees. For the selection of optimal inversion parameters, we compare the developed Moho models with the two regional Moho models for the European crust. The two models includes the EuCrust07 and EuM09 developed by Magdala Tesauro et al. and Marek Grad et al., respectively. We find that the best model is obtain when using a joint inversion (gravity data plus CRUST 1.0 and CRUST07 seismic models), first-order Tikhonov regularization, degree-dependent weights proportional to the fourth power of the degree and setting the minimum and maximum truncation degree equal to 90 and 180, respectively. The final Moho model (DMM-1) is compared with two regional models: (1) for the South America and (2) for Africa. From the comparison and statistical analysis we found that our developed model DMM-1 have the best RMS fit with the two regional models as well as with observed point values.Geoscience and Remote SensingCivil Engineering and Geoscience
Optimal mascon geometry in estimating mass anomalies within Greenland from GRACE
No full textThe mascon approach is a well-known technique to estimate mass anomalies in Greenland using GRACE satellite gravity data. It partitions the area of interest into laterally-homogeneous patches (mascons). An important aspect of the mascon approach is the chosen geometry of mascons. So far, its impact has not been fully understood. In this study, we use a full-scale numerical study and real data analysis to identify the optimal strategy (primarily, the size of the mascons) for the extrac- tion of mass anomalies over the Greenland drainage systems from GRACE monthly solutions. We use ordinary and weighted least-squares techniques to estimate the mascon parameters. The weighted least-squares estimator uses the full noise covari- ance matrices of monthly GRACE models, i.e. is designed to suppress random noise in the estimates. In addition, the zero-order Tikhonov regularization is applied. Four types of quantities of interest, which are associated with dierent temporal scales, are investigated in this study: monthly mass anomalies, mean mass anomalies per calendar month, inter-annual mass variations, and long-term linear trends. We show that the dominant error sources are random errors and parameterization (model) errors, as well as the bias introduced by the regularization. Errors in long-term lin- ear trend estimates are dominated by parameterization errors, whereas the role of random errors increases with the decreasing temporal scale. The best solutions are Downloaded from https://academic.oup.com/gji/advance-article-abstract/doi/10.1093/gji/ggy242/5040767 by guest on 05 July 2018 2 J. Ran, P. Ditmar and R. Klees obtained when the territory of Greenland is split into at least 23 mascons (the area of each one being 90; 000 km2). The usage of smaller mascons does not worsen the solutions in most cases, which is explained by the application of the regularization. Usage of larger mascons leads in most cases to inferior results due to the impact of parameterization errors. The application of the weighted least-squares estimator noticeably improves the quality of the solutions, with the exception of long-term linear trends estimated at the drainage system scale. In addition, we considered the long-term linear trend estimates integrated over entire Greenland. It is shown that the best results are obtained in that case when no regularization is applied. The results of real GRACE data processing are consistent with those obtained in the numerical study. Physical and Space Geodes
Global gravity field recovery from satellite-to-satellite tracking data with the acceleration approach
No full textAerospace Engineerin
[Introduction to : Education for Societal Transformation : Alternatives for a Just Future, a cura di F. Adamson [et al.], Ginevra, NORRAG, 2024]
No full textThe influence of data quality on the detectability of sea-level height variations
No full textCivil Engineering and Geoscience
Quality assessment of satellite-based global gravity field models
No full textCivil Engineering and Geoscience
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