Properties Of Hybrid Systems Research Articles

Multitask Synthesis of Hybrid Systems via Temporal Logic

In this note, we propose a unified framework for the study of hybrid systems, where the tasks of the systems are encoded as signal temporal logic (STL) specifications. First, we establish the mathematical expression of a class of hybrid systems consisting of continuous and logical parts. Then, we introduce the concept of locally finite time interval dwell (LFTID), which matches the conditions to satisfy such the STL specifications. After that, combining the semi-tensor product (STP) and Lyapunov-like methods, we obtain the sufficient conditions to satisfy the given STL specifications. This approach can be used to study temporal tasks and properties of hybrid systems, such as practical stability, finite-time stability, etc. Furthermore, we consider a special class of hybrid systems with control. Based on the theoretical analysis, a controller design algorithm that enables the system to fulfill the most tasks is provided. Finally, the effectiveness of the method is illustrated by an example.

Evolution of Statistical Properties of Hybrid System Starting from Binary Field States Constructed in Experiments

In quantum optics, researchers usually study evolution of states starting from traditional ones: coherent, squeezed, Fock, and their superpositions. In a recent work (Ferreira et al. Int. J. Mod. Phys. B, 1850222, 2018), we discussed an example of ex- periment involving “atom”-field interaction allowing us to construct a list of field states inside a high-Q microwave cavity. The procedure employed a dispersive Hamiltonian ensuring both sub-systems to remain with only two Fock state components for all times of their evolution. The aim was to use this sequence of states having pre-selected properties as initial states in other investigations. Here, we use an updated platform and a variety of states at our disposal in the mentioned list to study the evolution of a hybrid system under the action of the Jaynes-Cummings Hamiltonian. Interesting results are obtai- ned, e.g., when we examine how the “atomic” population inversion and field statistics evolve in time from initial field states with different degrees of super- and sub-Poissonian effects. The experimental feasibility of the proposal was also discussed.

Bounded Model Checking of Hybrid Systems for Control

A bounded LTL model checking algorithm to check the properties of hybrid systems is presented. The proposed algorithm can also be applied to control systems as counterexamples of a negated goal contain information to achieve the original goal. This approach is different than existing abstraction-based techniques. While many of the latter approaches build a control strategy after partitioning a state space, the proposed approach constructs a necessary set of constraints and computes a possibly optimal control input on the fly. The bounded LTL semantics of this paper is more expressive than those of bounded reachability: in addition to the finite computation paths that the reachability checkers can handle, the proposed algorithm can check infinite paths ending with a loop. Furthermore, the LTL operators provide a convenient and expressive way of writing complicated specifications.

Nonlinear Optical Studies of SWCNT+Coproporphyrin III Hybrid Systems

We report nonlinear optical properties of hybrid systems that contain single-walled carbon nanotubes and Coproporphyrin dye suspensions. The studies were performed in Vis-NIR spectral range. Our results depict both bleaching and limiting properties. A phenomenon of optical power limiting synergism is demonstrated.

Improved binding and stability in Si/CNT hybrid nanostructures via interfacial functionalization: a first-principles study

We use first-principles calculations to investigate the geometric structure, energetics and electronic properties of silicon cluster/carbon nanotube (Si/CNT) hybrid nanostructures with potential application as Li-ion battery anodes. The effects of the main components (i.e. Si cluster, CNT support and linker) on the properties of hybrid system, such as morphology, interfacial bonding and electronic structure have been systematically evaluated. After comparing several functional groups, it has been shown that the functionalization of CNT not only increases the binding strength between Si clusters and CNT by 3 times under normal conditions, but also greatly contributes to the stability of hybrid material during lithiation. Importantly, we have shown that Li insertion leads to the weakening of Si/CNT interface, which could be one of the key reasons for the experimentally observed capacity fade in hybrid Si/CNT anodes. The structural integrity of Si/CNT nanostructure could be improved after the functionalization of CNT surface, potentially leading to the longer cycle life of the hybrid anode. Our results support recent experimental findings and reveal the importance of interface engineering in the design of hybrid nanostructures for various applications.

Falsification of LTL safety properties in hybrid systems

This paper develops a novel approach for the falsification of safety properties given by a syntactically safe linear temporal logic (LTL) formula $${\phi}$$ for hybrid systems with nonlinear dynamics and input controls. When the hybrid system is unsafe, the approach computes a trajectory that indicates violation of $${\phi}$$ . The approach is based on an effective combination of model checking and motion planning. Model checking searches on-the-fly the automaton of $${\neg\phi}$$ and an abstraction of the hybrid system for a sequence σ of propositional assignments that violates $${\phi}$$ . Motion planning incrementally extends trajectories that satisfy more and more of the propositional assignments in σ. Model checking and motion planning regularly exchange information to find increasingly useful sequences σ for extending the current trajectories. Experiments that test LTL safety properties on a robot navigation benchmark modeled as a hybrid system with nonlinear dynamics and input controls demonstrate the computational efficiency of the approach. Experiments also indicate significant speedup when using minimized DFA instead of non-minimized NFA for representing $${\neg\phi}$$ .

Abstraction and Counterexample-Guided Refinement in Model Checking of Hybrid Systems

Hybrid dynamic systems include both continuous and discrete state variables. Properties of hybrid systems, which have an infinite state space, can often be verified using ordinary model checking together with a finite-state abstraction. Model checking can be inconclusive, however, in which case the abstraction must be refined. This paper presents a new procedure to perform this refinement operation for abstractions of hybrid systems. Following an approach originally developed for finite-state systems [11, 25], the refinement procedure constructs a new abstraction that eliminates a counterexample generated by the model checker. For hybrid systems, analysis of the counterexample requires the computation of sets of reachable states in the continuous state space. We show how such reachability computations with varying degrees of complexity can be used to refine hybrid system abstractions efficiently. Examples illustrate our counterexample-guided refinement procedure. Experimental results for a prototype implementation indicate significant advantages over existing methods.

Ordered Magnetic Nanostructures. Fabrication and Properties

AbstractFor Abstract see ChemInform Abstract in Full Text.

Differential Predicate Transition Petri Nets and Objects, an Aid for Proving Properties in Hybrid Systems

This paper introduces a new approach for the verification of behaviour properties in hybrid systems. By using Petri nets and object oriented concepts the proof of a system property is reduced from a complex proof involving the overall model to a set of simpler proofs involving the model of one or a few objects. Each local proof is made considering a set of hypotheses that should then be proven. Particularly, this paper considers the case of proving safety properties

Ordered magnetic nanostructures: fabrication and properties

The fabrication methods and physical properties of ordered magnetic nanostructures with dimensions on the submicron to nanometer scale are reviewed. First, various types of nanofabrication techniques are described, and their capabilities and limitations in achieving magnetic nanostructures are discussed. Specifically, we address electron beam lithography, X-ray lithography, laser interference lithography, scanning probe lithography, step growth methods, nanoimprint, shadow masks, radiation damage, self-assembled structures, and the use of nanotemplates. Then the magnetic properties of these nanostructures are reviewed, including properties of single dots, magnetic interactions in arrays, dynamic effects, magnetic behavior of nanostructured lines and wires, giant magnetoresistance effect, and properties of films with arrays of holes. Finally, the physical properties in hybrid systems, where the magnetic arrays interact with superconducting and semiconducting layers, are summarized.

AN APPROACH TO REASONING ABOUT HYBRID SYSTEMS

A formal approach is presented for proving temporal properties of dynamic systems. Its main advantage is that it can be used to prove properties of hybrid systems, i.e. those whose state contains both discrete and continuous parameters. In contrast, most current temporal reasoning techniques are restricted either to purely discrete systems or to purely continuous systems. Our approach is based upon a new modeling technique called DMOD. A DMOD model of a system defines the causality relation between events in the system, using definite clauses, i.e. logic programs. Thereby, the problem of reasoning about hybrid systems is reduced to one of reasoning about the behavior of definite clauses. As these possess a simple proof theory, reasoning is substantially simplified.

Hybrid approximation technique for multivariable control systems

Some inherent properties of hybrid systems are investigated with respect to various control applications. For the systems which include both digital and analogue components a unified operator representation is established. The upper and lower bounds are obtained for the hybrid operator representation in the normed (Banach) space. The problem of optimal hybrid approximation for a nominal continuous time system is formulated and considered. The solution to this problem is found under rather general assumptions, its physical meaning is interpreted and practical applicability discussed, as well as sampling and hold device implementation. The obtained general results ore illustrated by widely used practical examples