75 research outputs found

    Traffic modeling and simulation: A devs library

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    The Cell-DEVS methodology is formal modeling technique that permits defining each cell in a cell space as individual independent entity. We used Cell-DEVS to build a library that allows defining different models of traffic. We show how to model cell spaces with emerging behavior using this methodology. We present basic models and visualization tools based on 3D models in Maya

    An Introduction to Cellular Automata Models with Cell-DEVS

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    In recent years, grid-shaped cellular models have gained popularity in this sense. Cellular Automata (CA) have been widely used with these purposes. The Cell-DEVS formalism is an extension to CA that can be used to build discrete-event cell spaces, improving their definition by making the timing specification more expressive. Different delay functions to specify the timing behavior of each cell, allowing the modeler to represent the timing complex behavior in a simple fashion. CD++ is a modeling and simulation tool that implements DEVS and Cell-DEVS formalisms. Here, we show the use of these techniques through a formal specification, and a variety of application examples, including basic models using CA, and varied extensions including triangular and hexagonal topologies

    Modeling of neural decoder based on binary spiking neurons in DEVS

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    Presented here is the simulation of specific application of reported earlier Binary Spiking Neurons for implementation of the Binary Neural Spiking Decoder, thus attaining next level in hierarchy of the Brain Machine devices based on the binary spiking neurons. This further extends the simulation of selected elements of Brain Machine in DEVS environment employing CD++ toolkit. Targeted applications include development of high throughput communication channels, employing spike encoding - decoding technique at high frequencies. Neural decoder based on binary spiking neurons is chosen for modeling in DEVS formal definitions as top model, which in turn is using previously reported atomic and coupled model associated with binary spiking neurons. In this application the signal of the encoded in ternary alphabet test messages of spike sequences is employed to verify functionality of the resulting spiking neural decoder. Spike sequences are split between two channels - one for initiating spikes and another one for terminating ones. Binary spiking neurons, which by definition have a rectangular response function, are considered in the presented model. Firing condition for the binary spiking neuron is reached when two rectangular responses, one for the initiating spike and another one for terminating spike, overlap in time domain, as a result producing "1" at the neuron's output (firing signal) or alternatively "0" (non-firing output signal)

    CD++ Repository: An internet based searchable database of DEVS models and their experimental frames

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    The development of simulation models for complex systems can be difficult and time consuming. This makes the ability to re-use modelling components of high value. To be able to re-use modeling components it is important to know the context within which a given component was developed. Experimental Frames are useful for capturing this context. We present the CD++ Repository - an internet based searchable database of re-usable CD++ DEVS models and their Experimental Frames. CD++ Repository facilitates the re-use of models and allows users in different geographical locations to collaborate in building complex models. The database is built as a hierarchy of the stored atomic and coupled models, thus eliminating repetition. One of the key features is that along with the storage of the atomic and coupled models, it stores Experimental Frames for each model, which allows users to easily determine the context for which a given model applies

    Aircraft evacuation DEVS implementation & visualization

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    Emergency evacuation from new, higher than normal, aircraft is believed to be affected by a new variable: passenger's hesitation at the exit door. This paper discusses how a previous simulation studying this effect was replicated in Cell-DEVS using the CD++ toolkit and how the results were visualized using the Blender Python interface. We will show how one can relatively easily apply advanced visualization techniques to any DEVS simulator results. As well, we noticed that the initial design of the model and simulation can limit the level of visualization which can be achieved if that design is not intended for visualization in the first place

    Studying the impact of web-services implementation of distributed simulation of DEVS and Cell-DEVS models

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    DEVS is a Modeling and Simulation formalism that has been used to study the dynamics of discrete event systems. Cell-DEVS is a DEVS-based formalism that defines the cell space as a group of DEVS models connected together. This work presents the design and implementation of a distributed simulation engine based on CD++; a modeling and simulation toolkit capable of executing DEVS and Cell-DEVS models. The proposed simulation engine follows the conservative approach for synchronization among the nodes, and takes advantage of web service technologies in order to execute complex models using the resources available in a grid environment. In addition, it allows for the integration with other systems using standard web service tools. The performance of the engine depends on the network connectivity among the nodes; which can be commodity Internet connections, or dedicated pointto-point links created using User Controlled Light Path (UCLP). UCLP is a web service-based network management tool used by grid applications to allocate bandwidth on demand

    Strategic airlift operationalizing constructive simulations

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    Large organizations now use Modeling and Simulation (M&S) for complex systems. This evolution has also resulted in a lack of simple tools and processes to define models and experiments which hinders wide scale user adoption of M&S to solve many real-world problems. By exploring the Arctic logistical support base problem, we will illustrate how a simple M&S process and system can be used by operators with limited knowledge of M&S. This will be demonstrated by determining a temporary logistical support base for re-supplying military operations in the Canadian Arctic

    A System-On-Chip FPGA implementation of embedded CD++

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    The development of embedded systems with real-time constraints has been rapidly advancing in the last 20 years. Most existing methods are still hard to scale up for large systems, or they require expensive testing efforts. Embedded CD++ is a software toolkit that uses model-driven method to develop this kind of applications based on DEVS, a formal technique originally created for modeling and simulation of discrete event systems. Embedded CD++ is a framework to incrementally develop embedded applications, and to seamlessly integrate simulation models with hardware components. We have deployed this tool on a Virtex2 pro FPGA board and made use of different components of an FPGA device to upgrade the hardware control and simulation capabilities of this toolkit. The process of deployment and also execution of a case study control model will be explained in detail

    Context-sensitive personal space for dense crowd simulation

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    Real-time simulation of dense crowds is finding increased use in event planning, congestion prediction, and threat assessment. Existing particle-based methods assume and aim for collision-free trajectories. That is an ideal-yet not overly realistic-expectation, as near-collisions increase in dense and rushed settings compared to typically sparse pedestrian scenarios. This paper presents a method that evaluates the immediate personal space area surrounding each entity to inform its pathing decisions. While personal spaces have traditionally been modeled as having fixed radii, they actually often change in response to the surrounding context. For instance, in cases of congestion, entities tend to share more of their personal space than they normally would, simply out of necessity (e.g. leaving a concert or boarding a train). Likewise, entities travelling at higher speeds (e.g. strolling, running) tend to expect a larger area ahead of them to be their personal space. We illustrate how our agent-based method for local dynamics can reproduce several key emergent dense crowd phenomena; and how it can be efficiently computed on consumer-grade graphics (GPU) hardware, achieving interactive frame rates for simulating thousands of crowd entities in the scene

    MAMS: Mashup architecture with modeling and simulation as a service

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    The Modeling and Simulation (M&S) community has used Web service (WS) technologies to help with the increasing complexity of the applications. Although there are many Web APIs that could be useful for M&S applications, they are rarely used. One of the main reasons is that using M&S related WSs and open APIs makes it difficult to consider their integration for building complex M&S applications. Here we show how to simplify the development and integration process of such M&S applications by using a new architecture for web services Mashups, namely the Mashup Architecture for Modeling and Simulation (MAMS). MAMS is the first environment and architecture to integrate mashups and distributed simulation. MAMS provides means for a lightweight life cycle to develop, deploy, identify, select, integrate and execute varied M&S resources as services in the Cloud. We present different case studies showing the utility of the proposed architecture
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