Davide Colombo

Combination of Conventional and Advanced DInSAR to Monitor Very Fast Mining Subsidence with TerraSAR-X Data: Bytom City (Poland)

In this work, the analysis of TerraSAR-X satellite images combining both conventional and advanced Differential Synthetic Aperture Radar Interferometry (DInSAR) approaches has proven to be effective to detect and monitor fast evolving mining subsidence on urban areas in the Upper Silesian Coal Basin (Poland). This region accounts for almost three million inhabitants where mining subsidence has produced severe damage to urban structures and infrastructures in recent years. Conventional DInSAR approach was used to generate 28 differential interferograms between 5 July 2011 and 21 June 2012 identifying 31 subsidence troughs that account up to 245 mm of displacement in 54 days (equivalent to 1660 mm/year). SqueeSARTM processing yielded a very dense measurement point distribution, failing to detect faster displacements than 330 mm/year, which occur within the subsidence troughs detected with conventional DInSAR. Despite this limitation, this approach was useful to delimit stable areas where mining activities are not conducted and areas affected by residual subsidence surrounding the detected subsidence troughs. These residual subsidence mining areas are located approximately 1 km away from the 31 detected subsidence troughs and account for a subsidence rate greater than 17 mm/year on average. The validation of this methodology has been performed over Bytom City were underground mining activity produced severe damages in August 2011. Conventional DInSAR permitted to successfully map subsidence troughs between July and August 2011 that coincide spatially and temporally with the evolution of underground mining excavations, as well as with the demolition of 28 buildings of Karb district. Additionally, SqueeSARTM displacement estimates were useful to delimit an area of 8.3 km2 of Bytom city that is affected by a residual mining subsidence greater than 5 mm/year and could potentially suffer damages in the midterm. The comparison between geodetic data and SqueeSARTM for the common monitoring period yields and average absolute difference of 7 mm/year, which represents 14% of the average displacement rate measured by the geodetic benchmarks. These results demonstrate that the combined exploitation of high-resolution satellite SAR data through both conventional and advanced DInSAR techniques could be crucial to monitor fast evolving mining subsidence, which may severely impact highly populated mining areas such as the Upper Silesia Coal Basin (USCB).

Vertical arrays of nanofluidic channels fabricated without nanolithography

Vertical arrays of sealed nanofluidic channels, in which both cross-sectional dimensions are controllable down to 10 nm, were fabricated by selective side etching of a SiGe heterostructure comprised of layers of alternating Ge fractions. Capillary filling of these nanochannel arrays with fluorescent dye solutions was investigated using a confocal microscope. The feasibility of using nanochannels for size-based separation of biomolecules was demonstrated by imaging aggregates of tagged amyloid-beta peptide. The ability to integrate a large number of nanochannels shows promise for high throughput applications involving lab-on-a-chip systems.

Advanced InSAR Techniques to Support Landslide Monitoring

Interferometric Synthetic Aperture Radar (InSAR) uses satellite radar imagery to precisely measure ground deformation. TRE developed advanced techniques, \(\text {PSInSAR}^\mathrm{{TM}}\) and subsequently \(\text {SqueeSAR}^\mathrm{{TM}}\), as a standard monitoring tools in several applications: natural hazards, geothermal, oil and gas, mining, urban and infrastructures monitoring. Thanks to its capability in detecting millimetre level displacements over long periods and large areas, \(\text {SqueeSAR}^\mathrm{{TM}}\) analysis can be considered complementary to conventional geological and geomorphological studies in landslide detection and monitoring. Several Italian Regions were studied with \(\text {SqueeSAR}^\mathrm{{TM}}\) in order to detect and monitor slope instability phenomena. One of the most successfully application was carried out on the whole Valle d’Aosta Region (NW Italy) area. The increasing interest of Italian authorities in the application of \(\text {SqueeSAR}^\mathrm{{TM}}\) resulted in a national project, Piano Straordinario di Telerilevamento (PST), founded by the Ministry of the Environment. The aim of the project was to create the first national-scale database of interferometric information to map unstable areas. \(\text {SqueeSAR}^\mathrm{{TM}}\) analysis is particularly suitable for the study of Deep-seated Gravitational Slope Deformations (DGSD), characterized by large areal extent and surface displacement rate is very low, ranging from few millimeters to tens of millimeters per year.

Land subsidence in the Firenze-Prato-Pistoia basin measured by means of spaceborne SAR interferometry

This work concerns the application of space-borne SAR interferometry (InSAR) to the study of the land subsidence problem affecting the urban areas of the Firenze-Prato-Pistoia basin (Central Italy). Such a phenomenon is mainly related to the large amount of ground-water pumped for the industrial activities of this area. The interferometric analysis has been carried out by means of both traditional Differential Interferometry (DInSAR) and Permanent Scatterers technique (PS) by using SAR data acquired by the ESA ERS1/2 satellites. Different patterns of terrain subsidence have been detected in the industrial areas of the monitored basin.

Size Evolution of Ordered SiGe Islands Grown by Surface Thermal Diffusion on Pit-Patterned Si(100) Surface

The ordered growth of self-assembled SiGe islands by surface thermal diffusion in ultra high vacuum from a lithographically etched Ge stripe on pit-patterned Si(100) surface has been experimentally investigated. The total surface coverage of Ge strongly depends on the distance from the source stripe, as quantitatively verified by Scanning Auger Microscopy. The size distribution of the islands as a function of the Ge coverage has been studied by coupling atomic force microscopy scans with Auger spectro-microscopy data. Our observations are consistent with a physical scenario where island positioning is essentially driven by energetic factors, which predominate with respect to the local kinetics of diffusion, and the growth evolution mainly depends on the local density of Ge atoms.

Utilizzo di dati telerilevati nella mappatura e nel monitoraggio dei fenomeni franosi e nell'analisi della suscettibilità da frana

Remote sensing as a tool for landslide mapping, monitoring and hazard assessment ABSTRACT: The recent advances in the optical satellites capabilities (e.g. high spatial resolution, stereoscopy), the development of new robust techniques based on the interferometric analysis of radar images, such as the Permanent Scatterers (PS) and the possibility of integrating these data within a Geographical Information System (GIS) have dramatically increased the potential of remote sensing for landslide investigations. The Arno river basin (Italy), with a spatial extension of about 9131 km 2 , has been chosen a as test area for the presence of a relevant number of mass movements (27270 landslides have been mapped by the institutional authorities by the end of 2004) and for its significance concerning the Italian Apennine territory. The aim of the research was to integrate the inventory maps produced through traditional methods with the information derived from the Permanent Scatterers standard interferometric analysis. The spatial significance of the PS point measures (about 600000 PS for the whole Arno river basin), also in terms of geological and geomorphological interpretation, was inferred with the help of optical satellite images and aerial-photos. This approach allowed the mapping of new unstable areas or the modification of boundaries and state of activity of existing landslides. The standard PS analysis was also employed for the validation of a statistically-based susceptibility map of the Arno river basin, through the analysis of predicted susceptibility over the areas identified as new landslides by the PS analysis. An advanced PS analysis, capable of detecting the time evolution of single important mass movements, was also applied over 4 test sites. The results for the Chianciano landslide are in particular presented. The integration of the advanced analysis with on site geotechnical monitoring confirmed the inactivity of the principal landslide body but it revealed the presence of two possible minor movements. Key terms: Landslides, Permanent Scatterers, landslide inventory map, Arno river Termini chiave: Frane, Permanent Scatterers, carta inventario, fiume Arno

The European DORIS downstream service as a multi-scale system for landslides and subsidence risk management

We focused on the joint exploitation of satellite and ground-based technologies in order to understand the kinematic behavior of landslides and subsidence phenomena relevant to different test sites in Europe. In this context, we efficiently exploited C-band and X-band satellite and ground-based SAR data for the investigation of the temporal and spatial pattern of ground deformations caused by natural and human-induced hazards. The present work has been conducted within the FP7-EU DORIS project.

Use of Satellite Radar Data for Surface Deformation Monitoring: A Wrap-Up After 10 Years of Experimentation

Surface deformation monitoring can provide valuable information in assessing the environmental impact of activities, evaluating volume/pressure changes in a reservoir, as well as estimating other geophysical parameters. ENI and Stogit have been studying the use of Interferometric Synthetic Aperture Radar (InSAR) data for surface deformation monitoring since 2001. Based on almost 10 years of R&D and operational projects, this paper aims to summarise the strengths and weaknesses of this space geodetic tool, as well as providing an outlook on future developments in the up and down-stream activities. During the last decade, satellite InSAR data have been gaining increasing attention for their unique technical features and costeffectiveness. In particular, second-generation InSAR techniques (e.g. PSInSARTM) are capable of providing thousands of displacement measurements per sqkm at millimeter precision. Since 2001, ENI has financed projects based on InSAR data, first for environmental assessment and then for reservoir monitoring. In parallel, Stogit has used these techniques for the standard monitoring of gas storage fields. Projects and results have followed as a result of the development of InSAR technology. Radar data were first validated, compared with optical leveling surveys, integrated with GPS data, and then used for geophysical inversion, in both local and regional analyses. For some areas, data have been gathered by two different satellite platforms, providing unique datasets for a thorough analysis of different data sources. Long-time records of injected/extracted gas volumes, together with a multi-year displacement data set, have allow the calibration of fluid-dynamic and geo-mechanical models, that can be used to investigate the effects of increased working gas volumes, especially in overpressure conditions, in natural gas storage fields. In the authors‟ opinion, InSAR data will become a standard tool for reservoir monitoring in the next few years. The experience summarised in this paper can provide a useful contribution for petroleum engineers and the oil&gas community in general. Introduction Apart from the environmental impact of subsidence and uplift phenomena induced by fluid injection and/or extraction, recent reservoir optimisation techniques ask for timely information about many geophysical parameters, both downhole and on the surface. In particular, surface deformation measurements are lately gaining increasing attention within the reservoir engineer community, which is searching for new monitoring tools to complement seismic surveys. These monitoring technologies are relatively low in cost and their information adds significant value, if properly interpreted and integrated with more conventional data. One such technology – synthetic aperture radar interferometry (InSAR) can provide high-quality, remotely acquired data about surface deformation affecting large areas. Since 2001, ENI has financed projects based on InSAR data, first for environmental assessment and then for reservoir monitoring. Environmental monitoring is legally obliged in Italy according to the Italian mining legislation. Oil, gas and mining companies must develop monitoring plans that should be approved by the Ministry of Environment and local administrations before the start of operations. Initially, the request for InSAR analyses was simply a way to evaluate a new technology to complement conventional geodetic data from leveling networks and GPS stations. Indeed, in the late nineties, InSAR was a new space geodetic tool that had been used primarily by seismologists and volcanologists for research purposes, whose impact on reservoir engineering had still to be determined. The main question, at that time, was whether or not this technology could really provide precise and reliable estimates of surface deformation over large areas and allow the operator to obtain a data stream of geodetic measurements, correlated to other geophysical parameters of the reservoir, and be regularly updated. It‟s important to point out that, rather than assessing the advantages and drawbacks of conventional InSAR analysis, ENI decided to test an advanced InSAR technology patented in 1999 by Politecnico di Milano (POLIMI) technical university,

Gate-controlled rectifying barrier in a two-dimensional hole gas

The current flowing in a homogeneous low-dimensional conductor is shown to be rectified by a gate-controlled asymmetric barrier resembling a Schottky barrier. The barrier shape is set by varying the potential along a nanofabricated nonequipotential gate which allows simple external control over the device function independent of material properties. A forward-to-reverse current ratio of more than 10(4) is obtained. The merits of diodes fabricated in this way with respect to conventional diodes are discussed.

X-ray investigation of thick epitaxial GaAs/InGaAs layers on Ge pseudosubstrates

We present an investigation ofa series ofsamples with GaAs/InGaAs layers grown on Ge/Si pseudo-substrates. The strain in the GaAs and InGaAs layers were calculated after measuring the lattice constants of the layers using the x-ray diffraction technique. Both layers were found to be under low tensile stress restulting from the lattice mismatch and the difference in thermal expansion coefficients between the adjacent layers. We explore a new concept based on cotnterbalancing this thermal