Interacting Hybrid Systems Research Articles

Electronic Structure of Low‐Dimensional Inorganic/Organic Interfaces: Hybrid Density Functional Theory, G0W0, and Electrostatic Models

First‐principles simulations of electronic properties of hybrid inorganic/organic interfaces are challenging, as common density functional theory (DFT) approximations target specific material classes like bulk semiconductors or gas‐phase molecules. Taking as a prototypical example anthracene (ANT) physisorbed on monolayer MoS2, the ability of different ab initio schemes to describe the electronic structure using semilocal and hybrid DFT is assessed. For the latter, an unconstrained three‐parameter range‐separation scheme is used. Comparisons against results from the many‐body perturbation theory indicate that properly parametrized hybrid functionals can approximate with reasonable accuracy the quasiparticle properties of both ANT and MoS2 taken by themselves. However, this is not the case for the hybrid interface, where neither functional can predict the correct‐level alignment nor provide a particularly good starting point for G 0 W 0 calculations. It is shown that nonempirically parametrized electrostatic models can accomplish the same task at negligible computational costs. Such schemes can include substrates of hybrid interfaces in good agreement with experimental data. The results indicate that currently, fully atomistic, many‐body simulations of weakly interacting hybrid systems are not worth the required computational resources. In contrast, ab initio‐parametrized effective models mimicking the environment offer a scalable alternative without compromising accuracy and predictivity.

Effect of 3D paradigm synchronous motion for SSVEP-based hybrid BCI-VR system.

A brain-computer interface (BCI) system and virtual reality (VR) are integrated as a more interactive hybrid system (BCI-VR) that allows the user to manipulate the car. A virtual scene in the VR system that is the same as the physical environment is built, and the object's movement can be observed in the VR scene. The four-class three-dimensional (3D) paradigm is designed and moves synchronously in virtual reality. The dynamic paradigm may affect their attention according to the experimenters' feedback. Fifteen subjects in our experiment steered the car according to a specified motion trajectory. According to our online experimental result, different motion trajectories of the paradigm have various effects on the system's performance, and training can mitigate this adverse effect. Moreover, the hybrid system using frequencies between 5 and 10Hz indicates better performance than those using lower or higher stimulation frequencies. The experiment results show a maximum average accuracy of 0.956 and a maximum information transfer rate (ITR) of 41.033 bits/min. It suggests that a hybrid system provides a high-performance way of brain-computer interaction. This research could encourage more interesting applications involving BCI and VR technologies.

Formal modeling and analysis of interacting hybrid systems in HI-Maude: What happened at the 2010 Sauna World Championships?

In this paper we use HI-Maude to model and analyze the human thermoregulatory system and the effect of extreme heat exposure to the human body. The case study is motivated by the 2010 Sauna World Championships, which ended in a tragedy when the last two finalists were severely burnt in surprisingly short time (one of them died the next day). HI-Maude is a rewriting-logic-based formal modeling language and analysis tool for complex hybrid systems whose components influence each others' continuous dynamics. One distinguishing feature of HI-Maude is that the user only needs to describe the continuous dynamics of single components and interactions, instead of having to explicitly define the continuous dynamics of the entire system. HI-Maude analyses are based on numerical approximations of the system's continuous behaviors. We use HI-Maude to analyze how long the human body can survive when experiencing extreme conditions such as those encountered in the Sauna World Championships.

Predicting the electronic structure of weakly interacting hybrid systems: The example of nanosized peapod structures

We provide a simple scheme for predicting the electronic structure of van der Waals bound systems, based on the mere knowledge of the electronic structure of the subunits. We demonstrate this with the example of nanopeapods, consisting of polythiophene encapsulated in single-wall carbon nanotubes. Using density functional theory we disentangle the contributions to the level alignment. The main contribution is shown to be given by the ionization potential of the polymer inside the host, which in turn is determined by the curvature of the tube. Only a small correction arises from charge redistributions within the domains of the constituents. Polarization effects turn out to be minor due to the cylindrical geometry of the peapods and their dielectric characteristics. Our findings open the possibility of designing optoelectronic properties of such complex materials.

Adaptive-Step-Size Numerical Methods in Rewriting-Logic-Based Formal Analysis of Interacting Hybrid Systems

This paper focuses on the formal modeling, simulation, and analysis of interacting hybrid systems that influence each otherʼs continuous behaviors. We define in the rewriting-logic-based Real-Time Maude tool a method for the numerical approximation of the continuous dynamics specified by ordinary differential equations. We adapt the Runge-Kutta-Fehlberg 4/5 method to define an adaptive-step-size technique that allows a more accurate approximation with less computational effort than fixed-step-size techniques. We also present experimental results for two thermal systems using different error tolerances.

NEW MODEL BASED ON CELLULAR AUTOMATA AND MULTIAGENT TECHNIQUES

The need for intelligent systems has grown in the past decade because of the increasing demand on humans and machines to perform better. The researchers of artificial intelligence (AI) have responded to these needs with the development of intelligent hybrid systems. This paper describes the modeling language for interacting hybrid systems in which we will build a new hybrid model of cellular automata and multiagent technology. Simulations with complex behavior will be model social dynamics where the focus is on the emergence of properties of local interactions. Therefore, in our approach, cellular automata form a useful framework for the multiagent simulation model and the model will be used for traffic system which lies in coordinating the local behavior of individual agent to provide an appropriate system-level behavior in grid of interacting organisms.

Compositional modeling and refinement for hierarchical hybrid systems

In this paper, we develop a theory of modular design and refinement of hierarchical hybrid systems. In particular, we present compositional trace-based semantics for the language C haron that allows modular specification of interacting hybrid systems. For hierarchical description of the system architecture, C haron supports building complex agents via the operations of instantiation, hiding, and parallel composition. For hierarchical description of the behavior of atomic components, C haron supports building complex modes via the operations of instantiation, scoping, and encapsulation. We develop an observational trace semantics for agents as well as for modes, and define a notion of refinement for both, based on trace inclusion. We show this semantics to be compositional with respect to the constructs in the language.

Generating embedded software from hierarchical hybrid models

Benefits of high-level modeling and analysis are significantly enhanced if code can be generated automatically from a model such that the correspondence between the model and the code is precisely understood. For embedded control software, hybrid systems is an appropriate modeling paradigm because it can be used to specify continuous dynamics as well as discrete switching between modes. Establishing a formal relationship between the mathematical semantics of a hybrid model and the actual executions of the corresponding code is particularly challenging due to sampling and switching errors. In this paper, we describe an approach to compile the modeling language Charon that allows hierarchical specifications of interacting hybrid systems. We show how to exploit the semantics of Charon to generate code from a model in a modular fashion, and identify sufficient conditions on the model that guarantee the absence of switching errors in the compiled code. The approach is illustrated by compiling a model for coordinated motion of legs for walking onto Sony's AIBO robot.

Hierarchical modeling and analysis of embedded systems

This paper describes the modeling language CHARON for modular design of interacting hybrid systems. The language allows specification of architectural as well as behavioral hierarchy and discrete as well as continuous activities. The modular structure of the language is not merely syntactic, but is exploited by analysis tools and is supported by a formal semantics with an accompanying compositional theory of refinement. We illustrate the benefits of CHARON in the design of embedded control software using examples from automated highways concerning vehicle coordination.

Interactive hybrid (symbolic-numeric) system approach to near optimal design of mechanical components

A hybrid symbolic-numeric system, referred to as OPTDEX, (Optimal Design Expert) for the optimal design of mechanical components and systems has been developed. The system is written in Golden Common LISP and IBM Professional (Ryan-McFarland) FORTRAN for execution on the IBM PC/AT microcomputer. Graphical output has been implemented using the Graphical Kernal System (GKS) standard. This microcomputer-based implementation makes the system particularly attractive as an easily accessible, low-cost engineering analysis and design tool.