Experimental studies have observed synaptic potentiation when a presynaptic neuron fires shortly before a postsynaptic neuron, and synaptic depression when the presynaptic neuron fires shortly after. The dependence of...
Experimental studies have observed synaptic potentiation when a presynaptic neuron fires shortly before a postsynaptic neuron, and synaptic depression when the presynaptic neuron fires shortly after. The dependence of synaptic modulation on the precise timing of the two action potentials is known as spike-timing dependent plasticity or STDP. We derive STDP from a simple computational principle: synapses adapt so as to minimize the postsynaptic neuron's variability to a given presynaptic input, causing the neuron's output to become more reliable in the face of noise. Using an entropy-minimization objective function and the biophysically realistic spike-response model of Gerstner (2001), we simulate neurophysiological experiments and obtain the characteristic STDP curve along with other phenomena including the reduction in synaptic plasticity as synaptic efficacy increases. We compare our account to other efforts to derive STDP from computational principles, and argue that our account provides the most comprehensive coverage of the phenomena. Thus, reliability of neural response in the face of noise may be a key goal of cortical adaptation.
Recently, Web services have become a new technology trend for Enterprise Application Integration (EAI) and more and more applications based on Web services are emerging. One of the problems in using Web services in bu...
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(纸本)0769521673
Recently, Web services have become a new technology trend for Enterprise Application Integration (EAI) and more and more applications based on Web services are emerging. One of the problems in using Web services in business applications such as logistics is services composition automatically and efficiently. In this paper, we present a Dynamic, Demand-Driven Web services Engine called D3D-Serv to implement composite service functionality that is used to dynamically build composite services from existing services according to different business logics and requirements. In this D3D_Serv framework, the most challenging function to implement is dynamic selection of service providers at run time. The highly dynamic and distributed nature of Web services often makes some service providers overloaded at certain times while others idle. To solve this problem, we propose an efficient services selection and execution strategy that is based on the queuing theory and can provide guarantees for the QOS (Quality of Service) under provider's limited resources. Preliminary experimental results have shown that this algorithm is effective.
This paper makes two contributions to the study of configuring real-time aspects into quality of service (QoS)-enabled component middleware for distributed real-time and embedded (DRE) systems. First, it compares and ...
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Artificial immune systems (AISs) are biologically inspired problem solvers that have been used successfully as intrusion detection systems (IDSs). In this paper we compare a genetic hacker with 12 evolutionary hackers...
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Artificial immune systems (AISs) are biologically inspired problem solvers that have been used successfully as intrusion detection systems (IDSs). In this paper we compare a genetic hacker with 12 evolutionary hackers based on particle swarm optimization (PSO) that have been effectively used as vulnerability analyzers (red teams) for AIS-based IDSs. Our results show that the PSO-based red teams that use Clerc's constriction coefficient outperform those that do not. Our results also show that the three types of red teams (genetic, basic PSO, and PSO with the constriction coefficient) have distinct search behaviors that are complimentary. This result suggests that red teams based on genetic swarms may hold the most promise.
Due to not only proven stability and reliability but a significant investment and years of accumulated experience and knowledge, legacy systems have supported the core business applications of a number of organization...
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Objective: Our objective is to describe how softwareengineering might benefit from an evidence-based approach and to identify the potential difficulties associated with the approach. Method: We compared the organisat...
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Objective: Our objective is to describe how softwareengineering might benefit from an evidence-based approach and to identify the potential difficulties associated with the approach. Method: We compared the organisation and technical infrastructure supporting evidence-based medicine (EBM) with the situation in softwareengineering. We considered the impact that factors peculiar to softwareengineering (i.e. the skill factor and the lifecycle factor) would have on our ability to practice evidence-based softwareengineering (EBSE). Results: EBSE promises a number of benefits by encouraging integration of research results with a view to supporting the needs of many different stakeholder groups. However, we do not currently have the infrastructure needed for widespread adoption of EBSE. The skill factor means softwareengineering experiments are vulnerable to subject and experimenter bias. The lifecycle factor means it is difficult to determine how technologies will behave once deployed. Conclusions: softwareengineering would benefit from adopting what it can of the evidence approach provided that it deals with the specific problems that arise from the nature of softwareengineering.
High-assurance development of large-scale, network-centric systems must address challenging engineering realities. Flow-Service-Quality (FSQ) engineering provides foundations and practices that accommodate these reali...
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High-assurance development of large-scale, network-centric systems must address challenging engineering realities. Flow-Service-Quality (FSQ) engineering provides foundations and practices that accommodate these realities to maintain intellectual control in system analysis, development, and evolution.
The focus of this paper is to propose a service-oriented multi-agent framework to better integrate Web services and agents. In the making of this framework, there are four main components: (1) a possibilistic Petri-Ne...
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The focus of this paper is to propose a service-oriented multi-agent framework to better integrate Web services and agents. In the making of this framework, there are four main components: (1) a possibilistic Petri-Nets (PPN) based service matchmaking mechanism for service discovery, (2) a service description language based on PPN for describing agent services and Web services, (3) a set of ontologies to facilitate the semantic matchmaking, and (4) an extension of tModels to bridge the Web services registered in UDDI to the PPN matchmaker.
Computational Grids are emerging as a new infrastructure for Internet-based parallel and distributed computing. They enable the sharing, exchange, discovery, and aggregation of resources distributed across multiple ad...
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A network of heterogeneous workstations is an efficient, cost-effective alternative to parallel supercomputers. We present a non-preemptive heuristic algorithm called Heterogeneous Critical Node First (HCNF) that stat...
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