Cause of scale inconsistencies in DORIS time series     

Petr Štěpánek  Vratislav Filler 《Studia Geophysica et Geodaetica》2018,62(4):562-585

In this paper we analyze the scale of the DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) solutions with respect to DORIS extension of the International Terrestrial Reference Frame (ITRF) for Precise Orbit Determination DPOD2014. The main goal is to explain the scale inconsistencies and to find the optimal solution reaching low-biased and consistent scale time series. Our analysis profits from 4 different strategies based only on the Geodetic Observatory Pecný analysis center solution, using DORIS exchange format data 2.2. A difference in the sequence of the solutions directly corresponds to one of the changes in the solution settings: data elevation dependent weighting, application of data validity indicators and application of phase center - reference point correction. We process multi-satellite and single-satellite solutions for the time period 2011.0–2017.0. Our analysis examines scale inconsistency issues in 2011/2012 and in 2015. The scale increment in 2011/2012 is explained as a result of the concurrence of changes in satellite constellation and change in the provider data validity standards for Cryosat-2 and Jason-2 satellites. The scale increment in 2015 is explained as the effect of change in the standards for phase center - reference center corrections for Saral, Jason-2 and Cryosat-2 satellites. Moreover, comparing the solutions with and without elevation dependent data downweighting using the same elevation cutoff (10°), we found a significant reduction of scale bias and scale variation applying the data downweighting. The data downweighting improved also the station positioning repeatability. We demonstrate that the solution, which is completely free from the additional data associated with observations in DORIS exchange format 2.2 and includes the data downweighting law, eventuates in a consistent scale time series with the lowest offset with respect to DPOD2014 (version 1.0) (12.7 ± 2.3 mm for 2011.0–2017.0). The only remaining scale issue is the part of 2011/2012 increment of around 5 mm, explained by a change in the DORIS satellite constellation.  相似文献   

SlugIn 1.0: A Free Tool for Automated Slug Test Analysis          下载免费PDF全文

Sergio Martos‐Rosillo  Carolina Guardiola‐Albert  Alberto Padilla Benítez  Joaquín Delgado Pastor  Antonio Azcón González  Juan José Durán Valsero 《Ground water》2018,56(3):362-365

The correct characterization of aquifer parameters is essential for water‐supply and water‐quality investigations. Slug tests are widely used for these purposes. While free software is available to interpret slug tests, some codes are not user‐friendly, or do not include a wide range of methods to interpret the results, or do not include automatic, inverse solutions to the test data. The private sector has also generated several good programs to interpret slug test data, but they are not free of charge. The computer program SlugIn 1.0 is available online for free download, and is demonstrated to aid in the analysis of slug tests to estimate hydraulic parameters. The program provides an easy‐to‐use Graphical User Interface. SlugIn 1.0 incorporates automated parameter estimation and facilitates the visualization of several interpretations of the same test. It incorporates solutions for confined and unconfined aquifers, partially penetrating wells, skin effects, shape factor, anisotropy, high hydraulic conductivity formations and the Mace test for large‐diameter wells. It is available in English and Spanish and can be downloaded from the web site of the Geological Survey of Spain. Two field examples are presented to illustrate how the software operates.  相似文献   

Model for multiblock columns subjected to base excitation          下载免费PDF全文

Tamás Ther  László P. Kollár 《地震工程与结构动力学》2018,47(2):418-437

A new model is presented for multiblock columns subjected to earthquakes, which contains an impact and an opening model. Both in the impact and in the opening model, all the possible opening configurations are investigated because it was found that in many practical cases, unexpected patterns may occur. The model is purely mechanical: assuming rigid blocks and classical (inelastic) impact. The effect of energy dissipation during impact was investigated. Using our model in accordance with the literature, it was found that monolithic blocks are more vulnerable to overturning than multiblock systems.  相似文献   

Identifying slope processes over time and their imprint in soils of medium‐high mountains of Central Europe (the Karkonosze Mountains,Poland)          下载免费PDF全文

Jaroslaw Waroszewski  Markus Egli  Dagmar Brandová  Marcus Christl  Cezary Kabala  Malgorzata Malkiewicz  Jakub Kierczak  Bartłomiej Glina  Paweł Jezierski 《地球表面变化过程与地形》2018,43(6):1195-1212

Soils in mountainous areas are often polygenetic, developed in slope covers that relate to glacial and periglacial activities of the Pleistocene and Holocene and reflect climatic variations. Landscape development during the Holocene may have been influenced by erosion/solifluction that often started after the Holocene climatic optimum. To trace back soil evolution and its timing, we applied a multi‐methodological approach. This approach helped us to outline scenario of soil transformation. According to our results, some aeolian input must have occurred in the late Pleistocene. During that time and the early Holocene, the soils most likely had features of Cryosols or Leptosols. Physico‐chemical and mineralogical analyses have indicated that the material was denudated (between late Boreal to the Atlantic) from the ridge and upper‐slope positions forming a colluvium at mid‐slope positions. Later, during the Sub‐Boreal, mass wasting of the remains of silt material deposited at the end of the Pleistocene age on the ridge top seems to have occurred. In addition, the cool and moist conditions caused the deposition of a colluvium at the lower‐slope positions. The next phase was characterized by the transformation of Leptosols/Cambisols into Podzols at upper‐slope or shoulder positions and to Albic Cambisols at mid‐slope positions. During the Sub‐Boreal period, Stagnosols started to form at the lower part of the slope catena. Overall, the highest erosion rates were calculated at the upper‐slope position and the lowest rates at mid‐slope sites. Berylium‐10 (¹⁰Be) data showed that the Bs, BC/C were covered during the Holocene by a colluvium with a different geological composition which complicated the calculation of erosion or accumulation rates. The interpretation of erosion and accumulation rates in such multi‐layered materials may, therefore, be hampered. However, the multi‐methodological reconstruction we applied shed light on the soil and landscape evolution of the eastern Karkonosze Mountains. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Extracting water-related features using reflectance data and principal component analysis of Landsat images     

Boglárka Balázs  Tibor Bíró  Gareth Dyke  Sudhir Kumar Singh 《水文科学杂志》2018,63(2):269-284

This study aimed to map water features using a Landsat image rather than traditional land cover. We involved the original bands, spectral indices and principal components (PCs) of a principal component analysis (PCA) as input data, and performed random forest (RF) and support vector machine (SVM) classification with water, saturated soil and non-water categories. The aim was to compare the efficiency of the results based on various input data. Original bands provided 93% overall accuracy (OA) and bands 4–5–7 were the most informative in this analysis. Except for MNDWI (modified normalized differenced water index, with 98% OA), the performance of all water indices was between 60 and 70% (OA). The PCA-based approach conducted on the original bands resulted in the most accurate identification of all classes (with only 1% error in the case of water bodies). We therefore show that both water bodies and saturated soils can be identified successfully using this approach.  相似文献   

Depth of closure: New calculation method based on sediment data     

Luis Aragonés  Jose Ignacio Pagán  Isabel López  José C.Serra 《国际泥沙研究》2018,33(2):198-207

Obtaining depth of closure (DoC) in an accurate manner is a fundamental issue for coastal engineering, since good results for coastal structures and beach nourishment depend mainly on DoC. Currently, there are two methods for obtaining the DoC, mathematical formulations and profile surveys. However, these methods can incur important errors if one does not take into account the characteristics and morphology of the area, or if one does not have a sufficiently long time series. In this work the DoC is obtained from the break in the trend of the sediment with the depth, that is, in general with the increase of the depth a decrease in the size of the sediment takes place. However, at one point this tendency changes and the size increases, and then decreases again. When comparing the point where the minimum sediment size occurs before the increase, it is observed that the error incurred is small compared to other methods. If the Standard Deviation of Depth Change (SDDC) method is considered as the most accurate method, the error incurred by the proposed method is less than 7%. In addition, it can be seen that the dispersion of the sediment method always occurs outside the zone of bar movement. Whereas in the methods of profiles survey (using 2 cm precision profiles), sometimes the DoC is obtained within the active zone of bar movement. In addition, where the relative minimum of the median sediment size is found, and the sizes of 0.063 and 0.125 mm predominate in the composition of the sample. Therefore, this new method allows the precise location of the DoC to be obtained in a fast and simple way. Furthermore, this method has the advantage that it is not affected by the modifications that may be experienced by both the study area and the cross-shore beach profile.  相似文献   

Sampling uncertainties and source <Emphasis Type="Italic">b</Emphasis> likelihood for the Gutenberg-Richter <Emphasis Type="Italic">b</Emphasis> value from the Aki-Utsu method     

F. A. Nava  L. Ávila-Barrientos  V. H. Márquez-Ramírez  I. Torres  F. R. Zúñiga 《Journal of Seismology》2018,22(1):315-324

The Aki-Utsu method of Gutenberg-Richter (G-R) b value estimation is often misapplied so that estimations not using the G-R histogram are often meaningless because they are not based on adequate samples. We propose a method to estimate the likelihood Pr(b?b _m , N, M ₁, M ₂) that an observed b _m estimate, based on a sample of N magnitudes within an [M ₁????≤?ΔM/2,?M ₂?+?ΔM/2) range, where ΔM?=?0.1 is the usual rounding applied to magnitudes, is due to a “true” source b value, b, and use these likelihoods to estimate source b ranges corresponding to various confidence levels. As an example of application of the method, we estimate the b values before and after the occurrence of a 7.4-magnitude earthquake in the Mexican subduction zone, and find a difference of 0.82 between them with 100% confidence that the b values are different.  相似文献   

PAR(<Emphasis Type="Bold">p</Emphasis>)-vine copula based model for stochastic streamflow scenario generation     

Guilherme?PereiraEmail author  álvaro?Veiga 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(3):833-842

Synthetic streamflow data is vital for the energy sector, as it feeds stochastic optimisation models that determine operational policies. Considered scenarios should differ from each other, but be the same from a statistical point of view, i.e., the scenarios must preserve features of the original time series such as the mean, variance, and temporal dependence structures. Traditionally, linear models are applied for this task. Recently, the advent of copulas has led to the emergence of an alternative that overcomes the drawbacks of linear models. In this context, we propose a methodology based on vine copulas for the stochastic simulation of periodic streamflow scenarios. Copula-based models that focus on single-site inflow simulation only consider lag-one time dependence. Therefore, we suggest an approach that incorporates lags that are greater than one. Furthermore, the proposed model deals with the strong periodicity that is commonly present in monthly streamflow time series. The resulting model is a non-linear periodic autoregressive model. Our results indicate that this model successfully simulates scenarios, preserving features that are observed in historical data.  相似文献   

Probabilistic leak detectability assessment via state estimation in water transport networks     

Sarai?DíazEmail authorView author&#;s OrcID profile  Roberto?Mínguez  Javier?González 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(7):2111-2128

Leak detectability or leakage awareness refers to the capability of sensing losses from a water supply system. Several methods exist in the technical literature to tackle this problem, but only few address it with a state estimation approach. The aim of this paper is to present a new methodology that enables probabilistic assessment of the extent to which water loss could be detected using state estimation by only analysing a single hydraulic state, i.e. one time period. Significant leaks are sensed by identifying unusually high normalised state estimation residuals, which can be identified based on the largest normalised residual test. More specifically, the probability of detecting leaks is computed here by working with the multivariate distribution among measurements and estimates to take into account the noisy nature of measurements with an analytical approach rather than with sampling experiments, which are time-consuming. The methodology set out herein also provides a procedure to systematically assess the minimum leak that could be detected in different parts of the network for a specific measurement setting and operating condition. The method has been applied to a water transport network case study to show its potential and to highlight the usefulness of such a tool for practitioners. The limitations of such a methodology are also discussed, including its possible use for on-line leak detection strategies.  相似文献   

On the significance of the climate-dataset time resolution in characterising wind-driven rain and simultaneous wind pressure. Part I: scalar approach     

Pérez-Bella  José M.  Domínguez-Hernández  Javier  Cano-Suñén  Enrique  del Coz-Díaz  Juan J.  Alonso-Martínez  Mar 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(6):1783-1797

Stochastic Environmental Research and Risk Assessment - The joint action of wind-driven rain and wind pressure is the main cause of water penetration in building facades, which causes various...  相似文献