323 research outputs found
Self-Field Effects in Magneto-Thermal Instabilities for Nb-Sn Strands
Recent advancements in the critical current density (Jc) of NbSn conductors, coupled with a large effective filament size, have drawn attention to the problem of magnetothermal instabilities. At low magnetic fields, the quench current of such high Jc NbSn strands is significantly lower than their critical current because of the above-mentioned instabilities. An adiabatic model to calculate the minimum current at which a strand can quench due to magneto-thermal instabilities is developed. The model is based on an 'integral' approach already used elsewhere [1]. The main difference with respect to the previous model is the addition of the self-field effect that allows to describe premature quenches of non-magnetized NbSn strands and to better calculate the quench current of strongly magnetized strands. The model is in good agreement with experimental results at 4.2 K obtained at Fermilab using virgin Modified Jelly Roll (MJR) strands with a low Residual Resistivity Ratio (RRR) of the stabilizing copper. The prediction of the model at 1.9 K and the results of the tests carried out at CERN, at 4.2 K and 1.9 K, on a 0.8 mm Rod Re-Stack Process (RRP) strand with a low RRR value are discussed. At 1.9 K the test revealed an unexpected strand performance at low fields that might be a sign of a new stability regime
SAJaS: enabling JADE-based simulations
Multi-agent systems (MAS) are widely acknowledged as an appropriate modelling paradigm for distributed and decentralized systems, where a (potentially large) number of agents interact in non-trivial ways. Such interactions are often modelled defining high-level interaction protocols. Open MAS typically benefit from a number of infrastructural components that enable agents to discover their peers at run-time. On the other hand, multi-agent-based simulations (MABS) focus on applying MAS to model complex social systems, typically involving a large agent population. Several MAS development frameworks exist, but they are often not appropriate for MABS; and several MABS frameworks exist, albeit sharing little with the former. While open agent-based applications benefit from adopting development and interaction standards, such as those proposed by FIPA, MABS frameworks typically do not support them. In this paper, a proposal to bridge the gap between MAS simulation and development is presented, including two components. The Simple API for JADE-based Simulations (SAJaS) enhances MABS frameworks with JADE-based features. While empowering MABS modellers with modelling concepts offered by JADE, SAJaS also promotes a quicker development of simulation models for JADE programmers. In fact, the same implementation can, with minor changes, be used as a large scale simulation or as a distributed JADE system. In its current version, SAJaS is used in tandem with the Repast simulation framework. The second component of our proposal consists of a MAS Simulation to Development (MASSim2Dev) tool, which allows the automatic conversion of a SAJaS-based simulation into a JADE MAS, and vice-versa. SAJaS provides, for certain kinds of applications, increased simulation performance. Validation tests demonstrate significant performance gains in using SAJaS with Repast when compared with JADE, and show that the usage of MASSim2Dev preserves the original functionality of the system. Ă© Springer-Verlag Berlin Heidelberg 2015
Explaining Semantic Reasoning Using Argumentation
Multi-Agent Systems (MAS) are popular because they provide a paradigm that naturally meets the current demand to design and implement distributed intelligent systems. When developing a multi-agent application, it is common to use ontologies to provide the domain-specific knowledge and vocabulary necessary for agents to achieve the system goals. In this paper, we propose an approach in which agents can query semantic reasoners and use the received inferences to build explanations for such reasoning. Also, thanks to an internal representation of inference rules used to build explanations, in the form of argumentation schemes, agents are able to reason and make decisions based on the answers from the semantic reasoner. Furthermore, agents can communicate the built explanation to other agents and humans, using computational or natural language representations of arguments. Our approach paves the way towards multi-agent systems able to provide explanations from the reasoning carried out by semantic reasoners
Procedures for acute headache treatment in an emergency room
ImportĂąncia do problema: cefalĂ©ia Ă© dos sintomas mais comuns na prĂĄtica clĂnica, responsĂĄvel por cerca de 9% dos atendimentos em unidades primĂĄrias de saĂșde e por 1% a 3% dos atendimentos em unidades de emergĂȘncia, acarretando, portanto, considerĂĄvel impacto econĂŽmico sobre o serviço pĂșblico de saĂșde.ComentĂĄrios: a maioria das unidades de emergĂȘncia, em nosso meio, nĂŁo dispĂ”em de drogas utilizadas em outros paĂses para tratamento agudo da cefalĂ©ia, como os compostos ergotamĂnicosou triptanos. Os autores revisam aspectos diagnĂłsticos e terapĂȘuticos das cefalĂ©ias primĂĄrias agudas, propondo protocolos para seu tratamento em uma unidade de emergĂȘncia.Headache is one of the most common symptoms in the clinical practice and it is responsible for about 9% of the appointments in primary care units and for 1% to 3% in the emergency rooms, leading to a considerable economic impact in the public health care system. Most of the emergency rooms in Brazil does not have drugs, like ergotics compounds and tryptans, used in other countries for the acute treatment of headache. The authors make a review of the diagnostic and therapeutic aspects of the acute primary headaches, suggesting protocols for its treatment in an emergency unit
Phase Transformations during the Reaction Heat Treatment
The evolution of Nb containing phases during the diffusion heat treatment of three different high critical current NbSn strand types is compared, based on synchrotron X-ray diffraction results that have been obtained at the ID15 beam line of the European Synchrotron Radiation Facility (ESRF). In all strands studied, NbSn formation is preceded by the formation of a Cu-Nb-Sn ternary phase, NbSn2 and Nb6Sn5. As compared to the PIT and Tube Type strand, the amount of these phases formed in the RRP strand is relatively small. In the RRP strand subelements with a fine filament structure NbSn grows more quickly, thereby preventing to a large extent the formation of the other higher tin phases
Incorporating social practices in BDI agent systems
When agents interact with humans, either through embodied agents or because
they are embedded in a robot, it would be easy if they could use fixed
interaction protocols as they do with other agents. However, people do not keep
fixed protocols in their day-to-day interactions and the environments are often
dynamic, making it impossible to use fixed protocols. Deliberating about
interactions from fundamentals is not very scalable either, because in that
case all possible reactions of a user have to be considered in the plans. In
this paper we argue that social practices can be used as an inspiration for
designing flexible and scalable interaction mechanisms that are also robust.
However, using social practices requires extending the traditional BDI
deliberation cycle to monitor landmark states and perform expected actions by
leveraging existing plans. We define and implement this mechanism in Jason
using a periodically run meta-deliberation plan, supported by a
metainterpreter, and illustrate its use in a realistic scenario.Comment: An extended abstract of this paper has been accepted for the
Eighteenth International Conference on Autonomous Agents and Multiagent
Systems (AAMAS), 201
A survey on parallel and distributed Multi-Agent Systems
International audienceSimulation has become an indispensable tool for researchers to explore systems without having recourse to real experiments. Depending on the characteristics of the modeled system, methods used to represent the system may vary. Multi-agent systems are, thus, often used to model and simulate complex systems. Whatever modeling type used, increasing the size and the precision of the model increases the amount of computation, requiring the use of parallel systems when it becomes too large. In this paper, we focus on parallel platforms that support multi-agent simulations. Our contribution is a survey on existing platforms and their evaluation in the context of high performance computing. We present a qualitative analysis, mainly based on platform properties, then a performance comparison using the same agent model implemented on each platform
Multiagent cooperation for solving global optimization problems: an extendible framework with example cooperation strategies
This paper proposes the use of multiagent cooperation for solving global optimization problems through the introduction of a new multiagent environment, MANGO. The strength of the environment lays in itsflexible structure based on communicating software agents that attempt to solve a problem cooperatively. This structure allows the execution of a wide range of global optimization algorithms described as a set of interacting operations. At one extreme, MANGO welcomes an individual non-cooperating agent, which is basically the traditional way of solving a global optimization problem. At the other extreme, autonomous agents existing in the environment cooperate as they see fit during run time. We explain the development and communication tools provided in the environment as well as examples of agent realizations and cooperation scenarios. We also show how the multiagent structure is more effective than having a single nonlinear optimization algorithm with randomly selected initial points
Separating Agent-Functioning and Inter-Agent Coordination by Activated Modules: The DECOMAS Architecture
The embedding of self-organizing inter-agent processes in distributed
software applications enables the decentralized coordination system elements,
solely based on concerted, localized interactions. The separation and
encapsulation of the activities that are conceptually related to the
coordination, is a crucial concern for systematic development practices in
order to prepare the reuse and systematic integration of coordination processes
in software systems. Here, we discuss a programming model that is based on the
externalization of processes prescriptions and their embedding in Multi-Agent
Systems (MAS). One fundamental design concern for a corresponding execution
middleware is the minimal-invasive augmentation of the activities that affect
coordination. This design challenge is approached by the activation of agent
modules. Modules are converted to software elements that reason about and
modify their host agent. We discuss and formalize this extension within the
context of a generic coordination architecture and exemplify the proposed
programming model with the decentralized management of (web) service
infrastructures
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