Impacts of BeiDou stochastic model on reliability: overall test,w-test and minimal detectable bias

GPS Solutions - Extensive studies have concluded that the GNSS observations are heteroscedastic and physically correlated. Typically, the observation precisions are elevation dependent and...     

Infrared spectroscopic properties of goethite: anharmonic broadening,long-range electrostatic effects and Al substitution

The infrared spectrum and its temperature dependence (20–320 K) were collected on a synthetic goethite sample (α-FeOOH). In addition, the infrared powder absorption spectrum of goethite and aluminum-substituted goethite was computed using ab initio quantum mechanical calculations based on density functional theory. This combined experimental and theoretical approach allows (1) the unequivocal assignment of absorption bands to the corresponding vibrational modes, (2) separate identification of the effects of the particle shape and of the aluminum substitution on the infrared spectrum, and (3) a discussion of the anharmonic properties and the origin of the line broadening in goethite. In particular, the two well-resolved OH bending absorption bands show different temperature evolution. Their detailed analysis suggests that the broadening of the band at ~800 cm^?1 cannot be described solely by a usual three-phonon process. The strong anharmonic behavior of this mode implies the addition of a four-phonon process, such as a pure dephasing process. In our calculations, the effect of the Hubbard U correction is also investigated and found to be most visible on the OH stretching and bending modes, in relation to the associated structural relaxation. The OH stretching frequencies decrease, leading to a better agreement with experimental frequencies, while the OH bending frequencies increase.     

Design of an integrated shallow water wave experiment

The experimental design and instrumentation for an integrated shallow-water surface gravity wave experiment is discussed. The experiment required the measurement of the water surface elevation, meteorological parameters, and directional spectra at a number of locations on a shallow lake. In addition, to acquire data under a wide range of conditions, an experimental period of three years was required. A system of telephone and radio modem links were installed to enable real-time monitoring of instrument performance at eight separate measurement locations on the lake. This system also enabled logging sessions to be optimized to ensure the maximum possible data return from this extended experiment     

The ratio test for future GNSS ambiguity resolution

The performance of the popular ambiguity ratio test is analyzed. Based on experimental and simulated data, it is demonstrated that the current usage of the ratio test with fixed critical value is not sustainable in light of the enhanced variability that future global navigation satellite system (GNSS) ambiguity resolution will bring. As its replacement, the model-driven ratio test with fixed failure rate is proposed. The characteristics of this fixed-failure rate ratio test are described, and a performance analysis is given. The relation between its critical value and various GNSS model parameters is also studied. Finally, a procedure is presented for the creation of fixed failure rate look-up tables for the critical values of the ratio test.     

Hot springs of Rhodesia: Their noble gases,isotopic and chemical composition

Four of Rhodesia's hottest spring complexes (54–100°C) were studied. Tritium contents were very low, compared to adjacent rivers, indicating that the samples studied were indigenous, deep-seated water which had undergone negligible intermixing with surface water.The noble-gas measurements revealed: (1) the waters are meteoric; (2) the noble gases were kept in closed-system conditions in the ground; (3) paleotemperatures are 26–31°C; (4) the boiling Binga springs lost part of their noble gases.Independently, measurements of stable isotopes indicate the meteoric origin of the springs. The chemical composition of the waters clearly reflects their origin from two groups of rocks — one from Karroo sediments and one from crystalline rocks.     

Testing the potential of Sentinel-1A TOPS interferometry for the detection and monitoring of landslides at local scale (Veneto Region,Italy)

The recent Sentinel-1 mission, started by the European Space Agency in April 2014, provides the scientific community with new capabilities for the monitoring of the Earth surface. In particular, the Terrain Observation by Progressive Scans imaging technique used in the Interferometric Wide swath acquisition mode permits to acquire data over very wide areas (250 km of swath extension) at 20-m spatial resolution, with 12-day revisit time, making it suitable for ground displacement monitoring applications. With more than 1 year of synthetic aperture radar images available, it is now possible to carry out monitoring activities of slow moving phenomena such as landslides at both regional and local scales. In this work, the potential of Sentinel-1A for the monitoring of shallow (from 2 to 6 m of depth) landslides occurring in the North-Eastern Italian Pre-Alps was tested. Two stacks of Sentinel-1A scenes acquired in both ascending and descending orbits were processed using the Permanent Scatterer Interferometry (PSI) technique. The results, analysed in terms of PS density and quality, were compared with the ERS-1/2 and ENVISAT PSI database available from the Italian National Cartographic Portal to assess the capabilities of Sentinel-1A in detecting and monitoring landslides in respect to the previous satellite missions. The results of this work show the great potential of Sentinel-1A in the continuous monitoring of landslide-prone territories even at local scale. The achievable results can provide information that is useful to delineate the spatial and temporal evolution of landslides and precisely assess their rates of deformation.     

Slope dynamics of Lake Albano (Rome,Italy): insights from high resolution bathymetry

New detailed data about the morphology of the submerged slopes of Lake Albano (Rome, Italy) have been collected by a sonar multibeam survey financed by the Italian Department of Civil Protection. These data allow for investigation of the subaqueous slope dynamics of the lake, which partially fills a volcanic depression, and the elucidation of the relationships between subaqueous and subaerial slope processes. Subaerial, submerged and combined subaerial/submerged landslide‐related morphologies were detected around the inner slopes of the lake. In the submerged slopes, several gravity‐induced landforms were recognized: landslide scar areas, landslide accumulations, erosional chutes and channels, block fields, isolated blocks, scarps and slope breaks. An attempt to evaluate the state of activity of the submerged slopes was carried out by taking into consideration the relative freshness of some selected landforms. Interpretation of bathymetric data, as well as direct surveys of the subaerial slopes, was used to assess the morphometric features and interpret the type of movement of the landslides. We propose a comprehensive classification based on the landslide's size and type of movement. We recognized rock fall/topples, debris flows, rock slides and slump, complex rock slides/channelled flows and debris slide and slump. The volume of the main landslides ranged between 10¹ and 10³ m³, while a few rock and debris slides have volumes ranging between 10³ and 10⁵ m³. Two large palaeo‐landslides with volumes on the order of 10⁶ m³ were identified in the southern and northern part of the lake, respectively. Velocities of the recognized landslides range from rapid to extremely rapid. Two main landslide hazard scenarios have been depicted from the results of the integrated analysis of both subaerial and submerged gravity‐induced landforms. The most hazardous scenario involves extremely rapid large volume events (>10⁶ m³) that could, if they interacted with water, induce catastrophic tsunamis. Copyright © 2009 John Wiley & Sons, Ltd.     

Temporal evolution of the Roccamonfina volcanic complex (Pleistocene), Central Italy

The Roccamonfina volcanic complex (RVC), in southern Italy, is an Early to Middle Pleistocene stratovolcano sharing temporal and morphological characteristics with the Somma–Vesuvius and the Alban Hills; both being associated with high volcanic hazard for the cities of Naples and Rome, respectively. The RVC is important for the understanding of volcanic evolution in the Roman and Campanian volcanic provinces. We report a comprehensive study of its evolution based on morphological, geochemical and K–Ar geochronological data.     

Inferring catchment flow path responses using a data-driven model: an exploratory study based on a generalized additive model

Identifying physical catchment processes from streamflow data, such as quick- and slow-flow paths, remains challenging. This study is designed to explore whether a flexible nonparametric regression model (generalized additive model, GAM) can be used to infer different flow paths. This assumes that the data relationship in data-driven models is also a reflection of catchment physical processes. The GAM, using time-lagged flow covariates, was fitted to synthetic rainfall–runoff data simulated using simple linear reservoirs. Partial plots of the time-lagged covariates show that the model could differentiate simple and more complex flow paths in simulated synthetic data with short and long memory systems and varying between dry and wet climates. Further analysis of data from real catchments showed that the model could differentiate catchments dominated by slow flow and by quick flow. Therefore, this study indicates that GAM can be used to identify catchment storages and delay processes from streamflow data.