Search for: dynamic-adaptations
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    Context-aware provisional access control

    , Article 2nd International Conference on Information Systems Security, ICISS 2006, 19 December 2006 through 21 December 2006 ; Volume 4332 LNCS , 2006 , Pages 132-146 ; 03029743 (ISSN); 9783540689621 (ISBN) Masoumzadeh, A. R ; Amini, M ; Jalili, R ; Sharif University of Technology
    Springer Verlag  2006
    High heterogeneity and dynamicity of pervasive computing environments introduces requirement of more flexible and functional access control policies. The notion of provisional actions has been defined previously to overcome the insufficient grant/denial response to an access request and has been incorporated in the provision-based access controlmodel(PBAC).BasedonPBAC,weproposeacontext-aware provision-based access control model, capable of dynamic adaptation of access control policy according to the changing context. In particular, the model facilitates the definition of context-aware policies and enriches the access control by enforcing provisional actions in addition to common permissions.... 

    Introducing an adaptive robust controller for artificial heart

    , Article Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics, 24 June 2012 through 27 June 2012 ; June , 2012 , Pages 413-418 ; 21551774 (ISSN) ; 9781457711992 (ISBN) Ravanshadi, S ; Jahed, M ; Sharif University of Technology
    Prolonged and uncontrolled high shear stresses and turbulence can cause hemolysis, while alternating and low-level stresses may contribute to platelet activation and thrombus formation. Such deficiencies are reported for Total Artificial Heart (TAH) systems which are generally not fully capable of dynamic adaptation to sudden pressure and volume changes. This study introduces an adaptive robust controller for a linear motor based TAH (LMTAH) which overcomes such shortcomings. Proposed controller performance is compared with simulated natural heart in normal and stressed physiological conditions. Application of adaptive robust control results in flows with less stress variation and... 

    Adaptive prescribed performance control of switched MIMO uncertain nonlinear systems subject to unmodeled dynamics and input nonlinearities

    , Article International Journal of Robust and Nonlinear Control ; Volume 28, Issue 18 , 2018 , Pages 5981-5996 ; 10498923 (ISSN) Malek, S. A ; Shahrokhi, M ; Vafa, E ; Moradvandi, A ; Sharif University of Technology
    In this paper, the design of an adaptive tracking control for a class of switched uncertain multiple-input–multiple-output nonlinear systems in the strict-feedback form with unmodeled dynamics in the presence of three types of input nonlinearity under arbitrary switching has been addressed. By means of an intelligent approximator like a fuzzy logic system or a neural network, the unknown dynamics are estimated. The unmodeled dynamics have been tackled with a dynamic signal. A universal framework for describing different types of input nonlinearity including saturation, backlash, and dead zone has been utilized. By applying the backstepping approach and the common Lyapunov function method,... 

    Adaptive control of robot manipulators including actuator dynamics and without joint torque measurement

    , Article 2010 IEEE International Conference on Robotics and Automation, ICRA 2010, Anchorage, AK, 3 May 2010 through 7 May 2010 ; 2010 , Pages 4639-4644 ; 10504729 (ISSN) ; 9781424450381 (ISBN) Salimi Khaligh, Y ; Namvar, M ; Sharif University of Technology
    Ignoring actuator dynamics in control of rigid manipulators can in practice result in performance degradation or loss of system stability. However, consideration of actuator dynamics usually requires measurement of robot joint torques. This paper addresses motion tracking control of an n-DOF rigid robot by taking into account its actuator dynamics. Joint torque measurement is avoided by using an adaptive observer. The backstepping technique is adopted to develop a dynamically smooth adaptive nonlinear controller dealing with uncertainties in manipulator and actuator dynamics. Semi-global convergence of motion tracking errors as well as torque estimation error are proven without any... 

    A context-aware mandatory access control model for multilevel security environments

    , Article 27th International Conference on Computer Safety, Reliability, and Security, SAFECOMP 2008, Newcastle upon Tyne, 22 September 2008 through 25 September 2008 ; Volume 5219 LNCS , 2008 , Pages 401-414 ; 03029743 (ISSN); 3540876979 (ISBN); 9783540876977 (ISBN) Jafarian, J. H ; Amini, M ; Jalili, R ; Sharif University of Technology
    Mandatory access control models have traditionally been employed as a robust security mechanism in multilevel security environments like military domains. In traditional mandatory models, the security classes associated with entities are context-insensitive. However, context-sensitivity of security classes may be required in some environments. Moreover, as computing technology becomes more pervasive, flexible access control mechanisms are needed. Unlike traditional approaches for access control, such access decisions depend on the combination of the required credentials of users and the context of the system. Incorporating context-awareness into mandatory access control models results in a...