138 research outputs found
Fingerprint Identification Using Noise in the Horizontal-to-Vertical Spectral Ratio: Retrieving the Impedance Contrast Structure for the Almaty Basin (Kazakhstan)
Detailed knowledge of the 3D basin structure underlying urban areas is of major importance for improving the assessment of seismic hazard and risk. However, mapping the major features of the shallow geological layers becomes expensive where large areas need to be covered. In this study, we propose an innovative tool, based mainly on single station noise recordings and the horizontal-to-vertical spectral ratio (H/V), to identify and locate the depth of major impedance contrasts. The method is based on an identification of so-called fingerprints of the major impedance discontinuities and their migration to depth by means of an analytical procedure. The method is applied to seismic noise recordings collected in the city of Almaty (Kazakhstan). The estimated impedance contrasts vs. depth profiles are interpolated in order to derive a three-dimensional (3D) model, which after calibration with some available boreholes data allows the major tectonic features in the subsurface to be identified
On-site early-warning system for bishkek (Kyrgyzstan)
<p>In this work, the development of an on-site early warning system for Bishkek (Kyrgyzstan) is outlined. Several low cost sensors equipped with MEMS accelerometers are installed in eight buildings distributed within the urban area. The different sensing units communicate each other via wireless links and the seismic data are streamed in real-time to the data center using internet. Since each single sensing unit has computing capabilities, software for data processing can be installed to perform decentralized actions. In particular, each sensing unit can perform event detection task and run software for on-site early warning. If a description for the vulnerability of the building is uploaded in the sensing unit, this piece of information can be exploited to introduce the expected probability of damage in the early-warning protocol customized for a specific structure.</p
Effects of tillage systems and mechanization on work time, fuel and energy consumption for cereal cropping in Austria
The machinery stock, fuel consumption and work time are crucial economic factors for the profit potential in the arable farming sector. The influence of five soil tillage systems (two conventional tillage systems and three conservation tillage systems) and two tractor sizes (92 kW-tractor and 59 kW-tractor) on work time, fuel and energy consumption was measured in the semi-arid region in Austria. The tractors were equipped with a high-performance flow meter and a radar sensor to measure the fuel consumption (L h-1) and working speed (km h-1). The conventional tillage with mouldboard plough has the highest working time and fuel consumption rate. The replacement of plough with a cultivator, reduces the work time and fuel consumption for soil tillage as well as the energy consumption per moved soil matter to more than 50% roughly. The highest saving effects (more than 85%) were achieved with the direct drilling without soil tillage system. A well loaded engine in a small tractor with small implements is more fuel efficient than a worse loaded engine in a “big tractor”. An adjusted tractor-implement combination, which is well implemented in the 59-kW mechanization, decreases the fuel consumption to up to 30% and 46%. Due to lower field capacity in the 59-kW mechanization, the work time is higher between 2.4% and 11.7%. Keywords: fuel consumption, mechanization, tillage system, work tim
Malignant neuroendocrine tumour of the appendix in childhood with loco-regional lymph node invasion
The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1006600359152743 ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13000-015-0287-z) contains supplementary material, which is available to authorized users
NERA project - Deliverable D11.4: Array measurements
The aim of this Task is to present the seismological data and some preliminary empirical
results related to two deployed specific arrays; (a) the Argostoli seismological array and
(b) the Fucino seismological array. Both experiment arrays provided high quality data
that along with corresponding geological and geophysical measurements may serve to
critical evaluation of site effects and basin effects. In addition, work on modelling of
basin effects may be significantly benefited by the observed acquired in both sites. Given
that the analyses of the data obtained during the aforementioned experimental arrays
will be performed in close link with activity of NERA-JRA3, the following goals are set:
To investigate the link between ground motion spatial variability, strains, seismic
wavefield and subsurface properties
To compare numerical estimates of ground strain with actual measurements
To investigate the capability of estimating ground strains from noise correlation
studies.
In order to organize and accomplish the work according to the initial schedule, several
meetings (actual or/and Skype) among the participants took place during the 2nd year of
the NERA-JRA1 project. Minutes of these meetings are given in Appendices 1, 2, 3 and 4.Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation Project, Seventh Framework Programme EC project number: 262330Published4T. Sismologia, geofisica e geologia per l'ingegneria sismic
Concepts and Applications of Aerodynamic Attitude and Orbital Control for Spacecraft in Very Low Earth Orbit
Spacecraft operations below 450km, namely Very Low Earth Orbit (VLEO), can offer significant advantages over traditional low Earth orbits, for example enhanced ground resolution for Earth observation, improved communications latency and link budget, or improved signal-to-noise ratio. Recently, these lower orbits have begun to be exploited as a result of technology development, particularly component miniaturisation and cost-reduction, and concerns over the increasing debris population in commercially exploited orbits. However, the high cost of orbital launch and challenges associated with atmospheric drag, causing orbital decay and eventually re-entry are still a key barrier to their wider use for large commercial and civil spacecraft. Efforts to address the impact of aerodynamic drag are being sought through the development of novel drag-compensation propulsion systems and identification of materials which can reduce aerodynamic drag by specularly reflecting the incident gas. However, the presence of aerodynamic forces can also be utilised to augment or improve spacecraft operations at these very low altitudes by providing the capability to perform coarse pointing control and trim or internal momentum management for example. This paper presents concepts for the advantageous use of spacecraft aerodynamics developed as part of DISCOVERER, a Horizon 2020 funded project with the aim to revolutionise Earth observation satellite operations in VLEO. The combination of novel spacecraft geometries and use of aerodynamic control methods are explored, demonstrating the potential for a new generation of Earth observation satellites operating at lower altitudes
Attitude control for satellites flying in VLEO using aerodynamic surfaces
This paper analyses the use of aerodynamic control surfaces, whether passive or active, in order to carry out very low Earth orbit (VLEO) attitude maneuver operations. Flying a satellite in a very low Earth orbit with an altitude of less than 450 km, namely VLEO, is a technological challenge. It leads to several advantages, such as increasing the resolution of optical payloads or increase signal to noise ratio, among others. The atmospheric density in VLEO is much higher than in typical low earth orbit altitudes, but still free molecular flow. This has serious consequences for the maneuverability of a satellite because significant aerodynamic torques and forces are produced. In order to guarantee the controllability of the spacecraft they have to be analyzed in depth. Moreover, at VLEO the density of atomic oxygen increases, which enables the use of air-breathing electric propulsion (ABEP). Scientists are researching in this field to use ABEP as a drag compensation system, and consequently an attitude control based on aerodynamic control could make sense. This combination of technologies may represent an opportunity to open new markets. In this work, several satellite geometric configurations were considered to analyze aerodynamic control: 3-axis control with feather configuration and 2-axis control with shuttlecock configuration. The analysis was performed by simulating the attitude of the satellite as well as the disturbances affecting the spacecraft. The models implemented to simulate the disturbances were the following: Gravitational gradient torque disturbance, magnetic dipole torque disturbance (magnetic field model IGRF12), and aerodynamic torque disturbances (aerodynamic model DTM2013 and wind model HWM14).The maneuvers analyzed were the following: detumbling or attitude stabilization, pointing and demisability. Different VLEO parameters were analyzed for every geometric configuration and spacecraft maneuver. The results determined which of the analyzed geometric configurations suits better for every maneuver
Discoverer - Making commercial satellite operations in very low earth orbit a reality
DISCOVERER is a €5.7M European Commission funded Horizon 2020 project developing technologies to enable commercially-viable sustained-operation of satellites in very low Earth orbits. Why operate closer to the Earth? For communications applications latency is significantly reduced and link budgets improved, and for remote sensing improved link budgets allow higher resolution or smaller instruments, all providing cost benefits. In addition, all applications benefit from increased launch mass to lower altitudes, whilst end-of-life removal is ensured due to the increased atmospheric drag. However, this drag must also be minimised and compensated for. One of the key technologies being developed by DISCOVERER are materials that encourage specular reflection of the residual atmosphere at these altitudes. Combined with appropriate geometric designs these can significantly reduce drag, provide usable lift for aerodynamic attitude and orbit control, and improve the collection efficiency of aerodynamic intakes for atmosphere breathing electric propulsion systems, all of which are being developed as part of DISCOVERER. The paper provides highlights from the developments to date, and the potential for a new class of aerodynamic commercial satellites operating at altitudes below the International Space Station
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