The Experts below are selected from a list of 150 Experts worldwide ranked by ideXlab platform

V. Andreassian - One of the best experts on this subject based on the ideXlab platform.

  • Hydrological modelling at multiple sub-daily time steps: model improvement via flux-matching.
    Journal of Hydrology, 2019
    Co-Authors: A. Ficchì, C. Perrin, V. Andreassian
    Abstract:

    Consistent hydrological models for multiple time steps are needed to respond to the Operational Requirement of using a model for different objectives and with varied data sets. In this paper, we propose a rationale for multitime step model development based on the temporal consistency of the fluxes modelled. The new methodology is applied for the temporal downscaling of a lumped rainfall-runoff model (GR4J) from daily to sub-hourly time steps, within a coherent modelling framework. The modelling tests are performed at eight time steps from daily to 6-min, for a set of 240 French catchments, for which 2400 flood events were selected. To identify an improved multi-time step model structure, a two-step approach is followed. First, we propose a model diagnosis to evaluate the internal behaviour of the baseline model across time steps, whereby a significant inconsistency was found in the simulated water fluxes, especially interception. Second, we recommend a prognosis to improve the scale invariance of the modelled water balance by matching the model fluxes across time scales. The new model structure retained for sub-daily time steps is derived from the daily baseline model by refining the representation of the interception process, so that the flux-matching condition is satisfied. A complementary modification of the groundwater exchange function is also resumed following a previous study. The structural changes are motivated by the improvement of model flux consistency across time steps, while also improving model performance. This new dual paradigm for model identification, based on both flux coherence and output accuracy, also results in more robust model parameters across time steps.

A. Ficchì - One of the best experts on this subject based on the ideXlab platform.

  • Hydrological modelling at multiple sub-daily time steps: model improvement via flux-matching.
    Journal of Hydrology, 2019
    Co-Authors: A. Ficchì, C. Perrin, V. Andreassian
    Abstract:

    Consistent hydrological models for multiple time steps are needed to respond to the Operational Requirement of using a model for different objectives and with varied data sets. In this paper, we propose a rationale for multitime step model development based on the temporal consistency of the fluxes modelled. The new methodology is applied for the temporal downscaling of a lumped rainfall-runoff model (GR4J) from daily to sub-hourly time steps, within a coherent modelling framework. The modelling tests are performed at eight time steps from daily to 6-min, for a set of 240 French catchments, for which 2400 flood events were selected. To identify an improved multi-time step model structure, a two-step approach is followed. First, we propose a model diagnosis to evaluate the internal behaviour of the baseline model across time steps, whereby a significant inconsistency was found in the simulated water fluxes, especially interception. Second, we recommend a prognosis to improve the scale invariance of the modelled water balance by matching the model fluxes across time scales. The new model structure retained for sub-daily time steps is derived from the daily baseline model by refining the representation of the interception process, so that the flux-matching condition is satisfied. A complementary modification of the groundwater exchange function is also resumed following a previous study. The structural changes are motivated by the improvement of model flux consistency across time steps, while also improving model performance. This new dual paradigm for model identification, based on both flux coherence and output accuracy, also results in more robust model parameters across time steps.

Ma Ya-ping - One of the best experts on this subject based on the ideXlab platform.

  • Study of Operational Requirement Analysis Framework about Weapons SoS
    Computer Simulation, 2009
    Co-Authors: Ma Ya-ping
    Abstract:

    As a new concept in the domain of Operational Requirement analysis(ORA) in information age,ORA of weapons SoS is significant to the development of joint combat capability.Through lucubrating Joint Capability Integration and Development System(JCIDS) of the US army,a new ORA framework about weapons SoS was proposed.The framework based on two pivotal technology: formal description of Operational mission and quantification of combat capability.The main processes of the framework included Requirement analysis of essential task,Requirement analysis of combat capability,production of solution and post independent analysis.The experiments show that the framework can transform joint operation concepts and joint mission into relevant Operational Requirement effectively,and has wider application perspective.

Moti Yung - One of the best experts on this subject based on the ideXlab platform.

  • Scalable Group Signatures with Revocation
    Advances in Cryptology – EUROCRYPT 2012, 2012
    Co-Authors: Benoît Libert, Thomas Peters, Moti Yung
    Abstract:

    Group signatures are a central cryptographic primitive, simultaneously supporting accountability and anonymity. They allow users to anonymously sign messages on behalf of a group they are members of. The recent years saw the appearance of several constructions with security proofs in the standard model (i.e., without appealing to the random oracle heuristic). For a digital signature scheme to be adopted, an efficient revocation scheme (as in regular PKI) is absolutely necessary. Despite over a decade of extensive research, membership revocation remains a non-trivial problem in group signatures: all existing solutions are not truly scalable due to either high overhead (e.g., large group public key size), or limiting Operational Requirement (the need for all users to follow the system’s entire history). In the standard model, the situation is even worse as many existing solutions are not readily adaptable. To fill this gap and tackle this challenge, we describe a new revocation approach based, perhaps somewhat unexpectedly, on the Naor-Naor-Lotspiech framework which was introduced for a different problem (namely, that of broadcast encryption). Our mechanism yields efficient and scalable revocable group signatures in the standard model. In particular, the size of signatures and the verification cost are independent of the number of revocations and the maximal cardinality N of the group while other complexities are at most polylogarithmic in N. Moreover, the schemes are history-independent: unrevoked group members do not have to update their keys when a revocation occurs.

Courtney P Cote - One of the best experts on this subject based on the ideXlab platform.

  • MQ-1C Gray Eagle Unmanned Aircraft System (MQ-1C Gray Eagle)
    2015
    Co-Authors: Courtney P Cote
    Abstract:

    Abstract : The MQ-1C Gray Eagle Unmanned Aircraft System (MQ-1C Gray Eagle) provides the Division Commander a dedicated, assured, multi-mission unmanned aircraft system for the tactical fight assigned to the Combat Aviation Brigade (CAB) in each Division and supports the Division Fires, Battlefield Surveillance Brigades, and Brigade Combat Teams based upon the Division Commanders priorities. Additionally, MQ-1C Gray Eagle provides reconnaissance, surveillance, and target acquisition; command and control; communications relay; signals intelligence; electronic warfare; attack; detection of weapons of mass destruction; battle damage assessment; and manned-unmanned teaming capabilities. Fifteen Gray Eagle Warfighting companies are assigned as follows: ten companies assigned to Army divisions, one company to the National Training Center (NTC), one company to the U.S. Army Special Operations Command (USASOC), and three companies to the Intelligence and Security Command (INSCOM). Version 8.7, Revision 3 of the CPD for MQ-1C Gray Eagle defines an Operational Requirement for Improved Gray Eagle (IGE). IGE provides for increased range, endurance, and payload carrying capability for Echelons Above Division. IGE provides the Army with an extended range, multi-purpose unmanned aircraft system capable of executing reconnaissance, security, attack, and intelligence collection missions in the range of military operations. Sensors/payloads include an Electro-Optical/Infrared/Laser Designator, Synthetic Aperture Radar/Moving Target Indicator, Signals Intelligence, and Hellfire missiles; providing a near all-weather mission capability. When integrated with manned systems, manned-unmanned teaming, IGE enhances the capability to provide more accurate and timely information and intelligence, and significantly reduces the time to conduct tactical engagements. A total of 36 of the 167 MQ-1C UAS aircraft will be delivered in the IGE configuration.