1,026,596 research outputs found

    EPICS: A Framework for Enforcing Security Policies in Composite Web Services

    Get PDF
    With advances in cloud computing and the emergence of service marketplaces, the popularity of composite services marks a paradigm shift from single-domain monolithic systems to cross-domain distributed services, which raises important privacy and security concerns. Access control becomes a challenge in such systems because authentication, authorization and data disclosure may take place across endpoints that are not known to clients. The clients lack options for specifying policies to control the sharing of their data and have to rely on service providers which offer limited selection of security and privacy preferences. This lack of awareness and loss of control over data sharing increases threats to a client's data and diminishes trust in these systems. We propose EPICS, an efficient and effective solution for enforcing security policies in composite Web services that protects data privacy throughout the service interaction lifecycle. The solution ensures that the data are distributed along with the client policies that dictate data access and an execution monitor that controls data disclosure. It empowers data owners with control of data disclosure decisions during interactions with remote services and reduces the risk of unauthorized access. The paper presents the design, implementation, and evaluation of the EPICS framework

    Autonomous Agents and Intelligent Assistants for Exploration Operations

    Get PDF
    Human exploration of space will involve remote autonomous crew and systems in long missions. Data to earth will be delayed and limited. Earth control centers will not receive continuous real-time telemetry data, and there will be communication round trips of up to one hour. There will be reduced human monitoring on the planet and earth. When crews are present on the planet, they will be occupied with other activities, and system management will be a low priority task. Earth control centers will use multi-tasking "night shift" and on-call specialists. A new project at Johnson Space Center is developing software to support teamwork between distributed human and software agents in future interplanetary work environments. The Engineering and Mission Operations Directorates at Johnson Space Center (JSC) are combining laboratories and expertise to carry out this project, by establishing a testbed for hWl1an centered design, development and evaluation of intelligent autonomous and assistant systems. Intelligent autonomous systems for managing systems on planetary bases will commuicate their knowledge to support distributed multi-agent mixed-initiative operations. Intelligent assistant agents will respond to events by developing briefings and responses according to instructions from human agents on earth and in space

    Control Architecture Modeling for Future Power Systems

    Get PDF
    Uncontrollable power generation, distributed energy resources, controllable demand, etc. are fundamental aspects of energy systems largely based on renewable energy supply. These technologies have in common that they contradict the conventional categories of electric power system operation. As their introduction has proceeded incrementally in the past, operation strategies of the power system could be adapted. For example much more wind power could be integrated than originally anticipated, largely due to the flexibility reserves already present in the power system, and the possibility of interregional electricity exchange. However, at the same time, it seems that the overall system design cannot keep up by simply adapting in response to changes, but that also new strategies have to be designed in anticipation. Changes to the electricity markets have been suggested to adapt to the limited predictability of wind power, and several new control strategies have been proposed, in particular to enable the control of distributed energy resources, including for example, distributed generation or electric vehicles. Market designs addressing the procurement of balancing resources are highly dependent on the operation strategies specifying the resource requirements. How should one decide which control strategy and market configuration is best for a future power system? Most research up to this point has addressed single isolated aspects of this design problem. Those of the ideas that fit with current markets and operation concepts are lucky; they can be evaluated on the present design. But how could they be evaluated on a potential future power system? Approaches are required that support the design and evaluation of power system operation and control in context of future energy scenarios. This work addresses this challenge, not by providing a universal solution, but by providing basic modeling methodology that enables better problem formulation and by suggesting an approach to addressing the general chicken/egg problem of planning and re-design of system operation and control. The dissertation first focuses on the development of models, diagrams, that support the conceptual design of control and operation strategies, where a central theme is the focus on modeling system goals and functions rather than system structure. The perspective is then shifted toward long-term energy scenarios and adaptation of power system operation, considering the integration of energy scenario models with the re-design of operation strategies. The main contributions in the first part are, firstly, by adaptation of an existing functional modeling approach called Multilevel Flow Modeling (MFM) to the power systems domain, identifying the means-ends composition of control levels and development of principles for the consistent modeling of control structures, a formalization of control-as-a-service; secondly, the formal mapping of fluctuating and controllable resources to a multi-scale and multi-stage representation of control and operation structures; and finally the application to some concrete study cases, including a present system balancing, and proposed control structures such as Microgrids and Cells. In the second part, the main contributions are the outline of a formation strategy, integrating the design and model-based evaluation of future power system operation concepts with iterative energy scenario development. Finally, a new modeling framework for development and evaluation of power system operation in context of energy-storage based power system balancing is introduced.<br/

    A Web-based Operation Management System for Distributed Divisional Organizations

    Get PDF
    Operation Management is an important and complex task for a divisional structured organization, especially when the divisions are distributed geographically. In most cases, such organizations didn’t not urge all of it’s divisions to use an integrated information system at the very beginning. But with the development and the expanding of the organization, they sometimes found themselves in the trouble of information exchange and almost lost control of their divisions. At such time, however, on one hand the head quarter inquires more detailed information and more business control on the divisions. On the other hand, some divisions are well built and have its own business processes and information systems. It’s impossible for them to rebuild the information system to integrate with the other divisions and the head quarter as well. Operation Management System (OPMGT) enables real-time inspection of the divisions’ operational data and flexible operation evaluation of each division via the Internet and without much change on the other information systems. The OPMGT presented in this paper was originally developed for the head quarter of a distributed divisional based organization to govern the distributed divisions. System analysis, design and implementation of OPMGT are discussed in detail. Having been developed on the basis of eFramework, a J2EE framework, OPMGT is proved to be highly sufficient in operation management of a distributed divisional structured organization, and it may also do some help to integrate information systems in some degree

    Spatial effects and strategic behavior in a multiregional transboundary pollution dynamic game

    Get PDF
    We analyze a transboundary pollution differential game where pollution control is spatially distributed among a number of agents with predetermined spatial relationships. The analysis emphasizes, first, the effects of the different geographical relationships among decision makers; and second, the strategic behaviour of the agents. The dynamic game considers a pollution stock (the state variable) distributed among one large region divided in subregions which control their own emissions of pollutants. The emissions are also represented as distributed variables. The dynamics of the pollution stock is defined by a parabolic partial differential equation. We numerically characterize the feedback Nash equilibrium of a discrete-space model that still captures the spatial interactions among agents. We evaluate the impact of the strategic and spatially dynamic behaviour of the agents on the design of equilibrium environmental policiesThis research is partially supported by MINECO under projects MTM2013-42538-P, MTM2016-78995-P (AEI) (first author) and ECO2014-52343-P (second author), co-financed by FEDER funds. The authors thank the support of European Cooperation in Science and Technology through COST Action IS1104, ``The EU in the new complex geography of economic systems: models, tools and policy evaluation"

    User Interface Design for Supervisory Control of Multiple Manned and Unmanned Air Vehicles

    Get PDF
    This dissertation research will cover lessons learned from the three-year, iterative design and evaluation of TECUMSA (Tasking and Execution of Collaborative Unmanned and Manned Systems with Autonomy). TECUMSA is a graphical user interface and autonomous tool suite that enables a single operator (e.g., an Air Mission Commander) to team with autonomous capabilities (e.g., route planning, aircraft task allocation) to effectively command and control multiple manned and unmanned aircraft in a contested battlespace. The user/AMC was responsible for accomplishing a series of reconnaissance, surveillance, and threat neutralization tasks in a hostile and dynamic simulated battlespace. The main challenges in this problem space are cognitive bandwidth of operators (e.g., maintaining situation awareness, allocating attention flexibly across multiple aircraft), and their ability to coordinate and collaborate with subordinate autonomous agents. The main objective of this research was therefore determining what control mechanisms offered the TECUMSA operator stability and reliability of control. Two formal system evaluations will be discussed, where a total of 15 Army aviators used TECUMSA to complete multiple hours of simulated air assault operations in a synthetic task environment. This research explored distributed supervisory control, where the operator distributed authority to automation for continuous manual control tasks using Play Calling (i.e., directability). The following research will also cover observations from the system evaluations highlighting interface features that afforded the user the ability to observe, perceive, and understand the state of the world relative to their goals and intentions (i.e., observability). One of the major themes in this dissertation is the importance of observability and directability as design principles, and the implications they have for both user interface design and human-autonomy teaming

    Automatic visualization and control of arbitrary numerical simulations

    Get PDF
    Authors’ preprint version as submitted to ECCOMAS Congress 2016, Minisymposium 505 - Interactive Simulations in Computational Engineering. Abstract: Visualization of numerical simulation data has become a cornerstone for many industries and research areas today. There exists a large amount of software support, which is usually tied to specific problem domains or simulation platforms. However, numerical simulations have commonalities in the building blocks of their descriptions (e. g., dimensionality, range constraints, sample frequency). Instead of encoding these descriptions and their meaning into software architecures we propose to base their interpretation and evaluation on a data-centric model. This approach draws much inspiration from work of the IEEE Simulation Interoperability Standards Group as currently applied in distributed (military) training and simulation scenarios and seeks to extend those ideas. By using an extensible self-describing protocol format, simulation users as well as simulation-code providers would be able to express the meaning of their data even if no access to the underlying source code was available or if new and unforseen use cases emerge. A protocol definition will allow simulation-domain experts to describe constraints that can be used for automatically creating appropriate visualizations of simulation data and control interfaces. Potentially, this will enable leveraging innovations on both the simulation and visualization side of the problem continuum. We envision the design and development of algorithms and software tools for the automatic visualization of complex data from numerical simulations executed on a wide variety of platforms (e. g., remote HPC systems, local many-core or GPU-based systems). We also envisage using this automatically gathered information to control (or steer) the simulation while it is running, as well as providing the ability for fine-tuning representational aspects of the visualizations produced

    Automatic visualization and control of arbitrary numerical simulations

    Get PDF
    Authors’ preprint version as submitted to ECCOMAS Congress 2016, Minisymposium 505 - Interactive Simulations in Computational Engineering. Abstract: Visualization of numerical simulation data has become a cornerstone for many industries and research areas today. There exists a large amount of software support, which is usually tied to specific problem domains or simulation platforms. However, numerical simulations have commonalities in the building blocks of their descriptions (e. g., dimensionality, range constraints, sample frequency). Instead of encoding these descriptions and their meaning into software architecures we propose to base their interpretation and evaluation on a data-centric model. This approach draws much inspiration from work of the IEEE Simulation Interoperability Standards Group as currently applied in distributed (military) training and simulation scenarios and seeks to extend those ideas. By using an extensible self-describing protocol format, simulation users as well as simulation-code providers would be able to express the meaning of their data even if no access to the underlying source code was available or if new and unforseen use cases emerge. A protocol definition will allow simulation-domain experts to describe constraints that can be used for automatically creating appropriate visualizations of simulation data and control interfaces. Potentially, this will enable leveraging innovations on both the simulation and visualization side of the problem continuum. We envision the design and development of algorithms and software tools for the automatic visualization of complex data from numerical simulations executed on a wide variety of platforms (e. g., remote HPC systems, local many-core or GPU-based systems). We also envisage using this automatically gathered information to control (or steer) the simulation while it is running, as well as providing the ability for fine-tuning representational aspects of the visualizations produced

    Modelling and Control of Grid-connected Solar Photovoltaic Systems

    Get PDF
    At present, photovoltaic (PV) systems are taking a leading role as a solar-based renewable energy source (RES) because of their unique advantages. This trend is being increased especially in grid-connected applications because of the many benefits of using RESs in distributed generation (DG) systems. This new scenario imposes the requirement for an effective evaluation tool of grid-connected PV systems so as to predict accurately their dynamic performance under different operating conditions in order to make a comprehensive decision on the feasibility of incorporating this technology into the electric utility grid. This implies not only to identify the characteristics curves of PV modules or arrays, but also the dynamic behaviour of the electronic power conditioning system (PCS) for connecting to the utility grid. To this aim, this chapter discusses the full detailed modelling and the control design of a three-phase grid-connected photovoltaic generator (PVG). The PV array model allows predicting with high precision the I-V and P-V curves of the PV panels/arrays. Moreover, the control scheme is presented with capabilities of simultaneously and independently regulating both active and reactive power exchange with the electric grid. The modelling and control of the three-phase grid-connected PVG are implemented in the MATLAB/Simulink environment and validated by experimental tests

    SDN-Based Network Intrusion Detection as DDoS defense system for Virtualization Environment

    Get PDF
    Nowadays, DDoS attacks are often aimed at cloud computing environments, as more people use virtualization servers. With so many Nodes and distributed services, it will be challenging to rely solely on conventional networks to control and monitor intrusions. We design and deploy DDoS attack defense systems in virtualization environments based on Software-defined Networking (SDN) by combining signature-based Network Intrusion Detection Systems (NIDS) and sampled flow (sFlow). These techniques are practically tested and evaluated on the Proxmox production Virtualization Environment testbed, adding High Availability capabilities to the Controller. The evaluation results show that it promptly detects several types of DDoS attacks and mitigates their negative impact on network performance. Moreover, it also shows good results on Quality of Service (QoS) parameters such as average packet loss about 0 %, average latency about 0.8 ms, and average bitrate about 860 Mbit/s
    • …
    corecore