Chemical Aspects of the Synergistic Hypergolic Ignition in Hybrid Systems with N2O4 as Oxidizer

Synergistic hypergolic ignition with nitrogen tetroxide ( N2O4) as oxidizer has been observed in hybrid systems comprising of a mixture of magnesium and Schiff bases as fuels. The ignition delays (IDs) measured using a modified device, have been compared with those of magnesium-Schiff base-WFNA systems under identical conditions. The ID has been found to vary with the nature of the substitution in both the benzene rings. A linear relationship emerges when the ignition delays are plotted against the Hammett substitution constants (σ). The preignition products of the reaction of N2O4 with magnesium and benzylidineaniline have been analysed to be Mg(NO3)2, benzenediazonium salt and benzaldehyde. Based on the preignition products isolated, a probable reaction mechanism has been proposed. The previously proposed preignition mechanism for the Schiff base-magnesium-WFNA system has been further supported from the present ignition delay data.

Hybrid systems through natural product leads: An approach towards new molecular entities

Hybrid systems are constructs of different molecular entities, natural or unnatural, to generate functional molecules in which the characteristics of various components are modulated, amplified or give rise to entirely new properties. These hybrids can be designed from carefully selected components either through domain intergration of key structural/functional features or via straightforward covalent linkages. Some of the recently reported hybrid systems based on steroid, carbohydrate, C-60-fullerene platforms, amongst others, mainly crafted with the object of enhancement of the therapeutical spectrum, will be discussed.

Optical and Electronic Properties of Conjugated Polymer -Nanocluster Semiconductor Hybrid Systems

Conjugated polymers are intensively pursued as candidate materials for emission and detection devices with the optical range of interest determined by the chemical structure. On the other hand the optical range for emission and detection can also be tuned by size selection in semiconductor nanoclusters. The mechanisms for charge generation and separation upon optical excitation, and light emission are different for these systems. Hybrid systems based on these different class of materials reveal interesting electronic and optical properties and add further insight into the individual characteristics of the different components. Multilayer structures and blends of these materials on different substrates were prepared for absorption, photocurrent (Iph), photoluminescence (PL) and electroluminscence (EL) studies. Polymers chosen were derivatives of polythiophene (PT) and polyparaphenylenevinylene (PPV) along with nanoclusters of cadmium sulphide of average size 4.4 nm (CdS-44). The photocurrent spectral response in these systems followed the absorption response around the band edges for each of the components and revealed additional features, which depended on bias voltage, thickness of the layers and interfacial effects. The current-voltage curves showed multi-component features with emission varying for different regimes of voltage. The emission spectral response revealed additive features and is discussed in terms of excitonic mechanisms.

Modeling stochastic hybrid systems

Stochastic hybrid systems arise in numerous applications of systems with multiple models; e.g., air traffc management, flexible manufacturing systems, fault tolerant control systems etc. In a typical hybrid system, the state space is hybrid in the sense that some components take values in a Euclidean space, while some other components are discrete. In this paper we propose two stochastic hybrid models, both of which permit diffusion and hybrid jump. Such models are essential for studying air traffic management in a stochastic framework.

Conflict-tolerant specifications for hybrid systems

We propose a framework for developing and reasoning about hybrid systems that are comprised of a plant with multiple controllers, each of which controls the plant intermittently. The framework is based on the notion of a ``conflict tolerant'' specification for a controller, and provides a modular way of developing and reasoning about such systems. We propose a novel mechanism of defining conflict-tolerant specifications for general hybrid systems, using ``acceptor'' and ``advisor'' components. We also give a decision procedure for verifying whether a controller satisfies its conflict-tolerant specification, in the special case when the components are modeled using initialized rectangular hybrid automata.

Optimization of Organic-Inorganic Inter-phase in Hybrid Systems Based on Waterborne Polyurethanes and Silica Nanostructures

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Min-Max Moving Horizon Estimation for a Class of Hybrid Systems

In this paper, a strategy for min-max Moving Horizon Estimation (MHE) of a class of uncertain hybrid systems is proposed. The class of hybrid systems being considered are Piecewise Affine systems (PWA) with both continuous valued and logic components. Furthermore, we consider the case when there is a (possibly structured) norm bounded uncertainty in each subsystem. Sufficient conditions on the time horizon and the penalties on the state at the beginning of the estimation horizon to guarantee convergence of the MHE scheme will be provided. The MHE scheme will be implemented as a mixed integer semidefinite optimisation for which an efficient algorithm was recently introduced.

Verification of periodically controlled hybrid systems: Application to an autonomous vehicle

This article introduces Periodically Controlled Hybrid Automata (PCHA) for modular specification of embedded control systems. In a PCHA, control actions that change the control input to the plant occur roughly periodically, while other actions that update the state of the controller may occur in the interim. Such actions could model, for example, sensor updates and information received from higher-level planning modules that change the set point of the controller. Based on periodicity and subtangential conditions, a new sufficient condition for verifying invariant properties of PCHAs is presented. For PCHAs with polynomial continuous vector fields, it is possible to check these conditions automatically using, for example, quantifier elimination or sum of squares decomposition. We examine the feasibility of this automatic approach on a small example. The proposed technique is also used to manually verify safety and progress properties of a fairly complex planner-controller subsystem of an autonomous ground vehicle. Geometric properties of planner-generated paths are derived which guarantee that such paths can be safely followed by the controller. © 2012 ACM.

Periodically controlled hybrid systems verifying a controller for an autonomous vehicle

This paper introduces Periodically Controlled Hybrid Automata (PCHA) for describing a class of hybrid control systems. In a PCHA, control actions occur roughly periodically while internal and input actions may occur in the interim changing the discrete-state or the setpoint. Based on periodicity and subtangential conditions, a new sufficient condition for verifying invariance of PCHAs is presented. This technique is used in verifying safety of the planner-controller subsystem of an autonomous ground vehicle, and in deriving geometric properties of planner generated paths that can be followed safely by the controller under environmental uncertainties.

Sufficient conditions for zeno behavior in lagrangian hybrid systems

This paper presents easily verifiable sufficient conditions for the existence of Zenobehavior in Lagrangian hybrid systems, i.e., hybrid systems modeling mechanical systemsundergoing impacts. © 2008 Springer-Verlag Berlin Heidelberg.