The analog data assimilation

In light of growing interest in data-driven methods for oceanic, atmospheric, and climate sciences, this work focuses on the field of data assimilation and presents the analog data assimilation (AnDA). The proposed framework produces a reconstruction of the system dynamics in a fully data-driven manner where no explicit knowledge of the dynamical model is required. Instead, a representative catalog of trajectories of the system is assumed to be available. Based on this catalog, the analog data assimilation combines the nonparametric sampling of the dynamics using analog forecasting methods with ensemble-based assimilation techniques. This study explores different analog forecasting strategies and derives both ensemble Kalman and particle filtering versions of the proposed analog data assimilation approach. Numerical experiments are examined for two chaotic dynamical systems: the Lorenz-63 and Lorenz-96 systems. The performance of the analog data assimilation is discussed with respect to classical model-driven assimilation. A Matlab toolbox and Python library of the AnDA are provided to help further research building upon the present findings.Fil: Lguensat, Redouane. Université Bretagne Loire; FranciaFil: Tandeo, Pierre. Université Bretagne Loire; FranciaFil: Ailliot, Pierre. University of Western Brittany. Laboratoire de Mathématiques de Bretagne Atlantique; FranciaFil: Pulido, Manuel Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; ArgentinaFil: Fablet, Ronan. Université Bretagne Loire; Franci

Computational and Numerical Simulations

Computational and Numerical Simulations is an edited book including 20 chapters. Book handles the recent research devoted to numerical simulations of physical and engineering systems. It presents both new theories and their applications, showing bridge between theoretical investigations and possibility to apply them by engineers of different branches of science. Numerical simulations play a key role in both theoretical and application oriented research

COBE's search for structure in the Big Bang

The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle

FPGAs in Industrial Control Applications

The aim of this paper is to review the state-of-the-art of Field Programmable Gate Array (FPGA) technologies and their contribution to industrial control applications. Authors start by addressing various research fields which can exploit the advantages of FPGAs. The features of these devices are then presented, followed by their corresponding design tools. To illustrate the benefits of using FPGAs in the case of complex control applications, a sensorless motor controller has been treated. This controller is based on the Extended Kalman Filter. Its development has been made according to a dedicated design methodology, which is also discussed. The use of FPGAs to implement artificial intelligence-based industrial controllers is then briefly reviewed. The final section presents two short case studies of Neural Network control systems designs targeting FPGAs

Technique-Based Exploitation Of Low Grazing Angle SAR Imagery Of Ship Wakes

The pursuit of the understanding of the effect a ship has on water is a field of study that is several hundreds of years old, accelerated during the years of the industrial revolution where the efficiency of a ship’s engine and hull determined the utility of the burgeoning globally important sea lines of communication. The dawn of radar sensing and electronic computation have expanding this field of study still further where new ground is still being broken. This thesis looks to address a niche area of synthetic aperture radar imagery of ship wakes, specifically the imaging geometry utilising a low grazing angle, where significant non-linear effects are often dominant in the environment. The nuances of the synthetic aperture radar processing techniques compounded with the low grazing angle geometry to produce unusual artefacts within the imagery. It is the understanding of these artefacts that is central to this thesis. A sub-aperture synthetic aperture radar technique is applied to real data alongside coarse modelling of a ship and its wake before finally developing a full hydrodynamic model for a ship’s wake from first principles. The model is validated through comparison with previously developed work. The analysis shows that the resultant artefacts are a culmination of individual synthetic aperture radar anomalies and the reaction of the radar energy to the ambient sea surface and spike events

NASA Tech Briefs, February 1993

Topics include: Communication Technology; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Research and Technology Objectives and Plans Summary (RTOPS)

This publication represents the NASA research and technology program for FY-93. It is a compilation of the Summary portions of each of the RTOP's (Research and Technology Objectives and Plans) used for management review and control of research currently in progress throughout NASA. The RTOP Summary is designed to facilitate communication and coordination among concerned technical personnel in government, in industry, and in universities. The first section containing citations and abstracts of the RTOP's is followed by four indexes: Subject, Technical Monitor, Responsible NASA Organization, and RTOP Number

Representing local dynamics within water resource systems through a data-driven emulation approach

Growing population and socio-economic activities along with looming effects of climate change have led to enormous pressures on water resource systems. To diagnose and quantify potential vulnerabilities, effective tools are required to represent the interactions between limited water availability and competing water demands across a range of spatial and temporal scales. Despite significant progresses in integrated modeling of water resource systems, the majority of existing models are still unable to fully describe the contemplating dynamics within and between elements of water resource systems across all relevant scales and/or variables. Here, a data-driven approach is suggested to represent local details of a water resource system through emulating an existing water resource system model, in which these details have been missed. This is through advising a set of interconnected functional mappings, i.e. integrated emulators, parameterized using the simulation results of the existing model at a common scale and/or variable but can support process representation with finer resolution and/or details. The proposed approach is applied to a complex water resource system in Southern Alberta, Canada, to provide a detailed understanding of the system’s dynamics at the Oldman Reservoir, which is the key to provision of effective water resource management in this semi-arid and already stressed cold region. By proposing a rigorous setup/falsification procedure, a set of alternative hypotheses for emulators describing the local dynamics of local irrigation demand and withdrawals along with reservoir release and evaporation is developed. Findings show that emulators formed using Artificial Neural Networks mainly outperform simpler emulators developed for the variables considered. The non-falsified emulators are then coupled to represent the local dynamics of the water resource system at the reservoir location, considering the underlying interplays with hydro-climatological conditions and human decision on the irrigation area. It is found that emulators with input variables identified through expert knowledge can outperform fully data-driven emulators in which proxies were selected based on an input variable selection method. The top non-falsified coupled models are able to capture the dynamic of lake evaporation, water withdrawal, irrigation demand, reservoir release and storage with coefficient of determination of 0.80 to 0.82, 0.45 to 0.55, 0.52 to 0.59, 0.98 to 0.99 and 0.72 to 0.88, respectively. The practical utility of the proposed approach is demonstrated through an impact assessment study by analysing four performance criteria, corresponding to reservoir’s storage, local irrigation demand, number of spill events and median reservoir release, in three stress-tests. These stress tests asses the local sensitivity of water resource system at the Oldman reservoir at three different levels, corresponding to (1) changing incoming streamflow to the basin in a bottom-up approach; (2) joint scenario of changing streamflow and warming climate, using a coupled bottom-up/top-down approach; and (3) specific changes in incoming streamflow, climate and irrigation area in a heuristic approach. For the first experimentation, weekly realizations for possible water availability are stochastically reconstructed and fed into the top non-falsified integrated emulator. By defining warm/dry, historical and cold/wet flow conditions, we found through alteration from dry to wet regime condition, the expected number of low storage duration is not changed, and expected annual water deficit is declined. Moreover, the expected number of spill events increases whereas median reservoir release increases. In the next impact assessment study, different scenarios of warming climate obtained from NASA-NEX downscaled global climate projections and the joint impact of changing streamflow and temperature on the system’s behaviour is evaluated. This assessment demonstrated that in warmer climate, the expected number of low storage duration in dry condition increases whereas in historical and wet conditions, the low storage duration does not change. In addition, the expected annual water deficit increases while the expected number of spill events decreases in the three flow regime conditions. Moreover, the expected median reservoir release increases in the dry, historical and wet regime conditions. In the final level of assessment, vulnerability of the system under changing streamflow, climate including temperature and precipitation and changing irrigation area is assessed. Results show that increasing irrigation area combined with declining inflow can considerably increase the duration of low reservoir storage in the Oldman Reservoir. Increasing temperature can lead to decline in both reservoir storage and outflow. In addition, when combined with declining inflow, increasing temperature can severely increase the annual water deficit for irrigation sector. Furthermore, it is noted that although the performance of unfalsified models are identical in representing the dynamics of the Oldman Reservoir under the historical data, but assessment can be slightly to moderately different depending on the defined scenarios of change. This is due to the choice of model configuration and can address the uncertainty regarding the system’s behaviour. Our study shows the promise of data-driven emulation approach as a tool for developing more enhanced water resource system models to face emerging management problems in the era of change

DL­R­magazine 166 – Next stop: the fu­ture

Lightweight, manoeuvrable and safe: the Safe Light Regional Vehicle (SLRV) features on the cover of Issue 166 of the DLRmagazine and is one of the new vehicle concepts developed at DLR with the potential to shape the future of transport. When designing such vehicles, researchers find it important that their drive systems are as resource-efficient as possible. To this end, the SLRV prototype is powered by a combination of a fuel cell and a battery, and runs on hydrogen. This is just one of the ways that DLR is combining cutting-edge fundamental research with the applied development of innovative ideas. In the field of aviation, DLR is researching how aircraft can be made more fuel-efficient. To do so, the balance between stability and flexibility is crucial. Wolf Krüger from the DLR Institute of Aeroelasticity is investigating particularly flexible aircraft wings and explains in an interview why there is still no need to worry when you see them bend while looking out of an aircraft window. Meanwhile, researchers at DLR in Oldenburg are trialling the sustainable energy supply of the future. This issue of the DLRmagazine takes you on a visit to their new NESTEC laboratory. Another highlight in this issue is the story of Blaubeuren, the largest stony meteorite ever found in Germany. The Helmholtz Centre Dresden-Rossendorf has now determined the impressive age of this heavyweight from outer space: it landed on Earth approximately 10,000 years ago. Other topics include an overview of 40 years of applied remote sensing at DLR where researcher process information from Earth observation satellites and forge valuable tools from their data. You can discover a project to secure communication and navigation systems against cyberattacks. And the magazine also takes you to the new DLR Responsive Space Cluster Competence Center in Trauen, where experts pursue the ambitious goal of replacing defective or missing satellites within seven days – a project that could make a James Bond film look like a documentary