The authors consider an integrated switching element with a shared buffer memory and a constant hardware delay. This hardware delay is caused by the hardware operations required to process the routing information of i...
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The authors consider an integrated switching element with a shared buffer memory and a constant hardware delay. This hardware delay is caused by the hardware operations required to process the routing information of incoming cells. A general uncorrelated cell arrival process in the switch, an independent and uniform routing process of cells from the inlets to the outlets of the switch and a first-come-first-served queueing discipline are assumed. The performance of the switching element is evaluated by means of an analytical technique based on an extensive use of probability generating functions. Explicit expressions for the probability generating functions, the mean values, the variances and the tail probabilities of the occupancy and the cell delay of the switch are obtained. Numerical examples show that the hardware delay has an important impact on the switch performance.
This article classifies a group of complicated relational calculus queries whose search algorithms run in time O(I Log(d) I + U) and space 0(1), where I and U are the sizes of the input and output, and d is a constant...
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This article classifies a group of complicated relational calculus queries whose search algorithms run in time O(I Log(d) I + U) and space 0(1), where I and U are the sizes of the input and output, and d is a constant depending on the query (which is usually, but not always, equal to zero or one). Our algorithm will not entail any preprocessing of the data. (C) 2002 Elsevier Science (USA).
During the drug development, nonlinear mixed effects models are routinely used to study the drug's pharmacokinetics and pharmacodynamics. The distribution of random effects is of special interest because it allows...
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During the drug development, nonlinear mixed effects models are routinely used to study the drug's pharmacokinetics and pharmacodynamics. The distribution of random effects is of special interest because it allows to describe the heterogeneity of the drug's kinetics or dynamics in the population of individuals studied. Parametric models are widely used, but they rely on a normality assumption which may be too restrictive. In practice, this assumption is often checked using the empirical distribution of random effects' empirical Bayes estimates. Unfortunately, when data are sparse ( like in patients phase III clinical trials), this method is unreliable. In this context, nonparametric estimators of the random effects distribution are attractive. Several nonparametric methods ( estimators and their associated computation algorithms) have been proposed but their use is limited. Indeed, their practical and theoretical properties are unclear and they have a reputation for being computationally expensive. Four nonparametric methods in comparison with the usual parametric method are evaluated. Statistical and computational features are reviewed and practical performances are compared in simulation studies mimicking real pharmacokinetic analyses. The nonparametric methods seemed very useful when data are sparse. On a simple pharmacokinetic model, all the nonparametric methods performed roughly equivalently. On a more challenging pharmacokinetic model, differences between the methods were clearer. (C) 2008 Elsevier B. V. All rights reserved.
Searching and retrieving the demanded correct information is one important problem in networks;especially, designing an efficient search algorithm is a key challenge in unstructured peer-to-peer (P2P) networks. Breadt...
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Searching and retrieving the demanded correct information is one important problem in networks;especially, designing an efficient search algorithm is a key challenge in unstructured peer-to-peer (P2P) networks. Breadth-first search (BFS) and depth-first search (DFS) are the current two typical search methods. BFS-based algorithms show the perfect performance in the aspect of search success rate of network resources, while bringing the huge search messages. On the contrary, DFS-based algorithms reduce the search message quantity and also cause the dropping of search success ratio. To address the problem that only one of performances is excellent, we propose two memory function degree search algorithms: memory function maximum degree algorithm (MD) and memory function preference degree algorithm (PD). We study their performance including the search success rate and the search message quantity in different networks, which are scale-free networks, random graph networks, and small-world networks. Simulations show that the two performances are both excellent at the same time, and the performances are improved at least 10 times.
In this study, the authors study the relays assignment problem in cooperative wireless networks with self-interested nodes. The authors propose a cooperation mechanism which includes the cooperative relationship forma...
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In this study, the authors study the relays assignment problem in cooperative wireless networks with self-interested nodes. The authors propose a cooperation mechanism which includes the cooperative relationship formation stage and cooperation maintenance stage. The cooperative relationship among the nodes can be modelled as an exchange market game where nodes trade transmission power between each other to obtain diversity gain. The exchange games have a basic assumption that each node conforms to trade agreement so that each agent has the option to trade its good to obtain a better one. In such a game, strict core is considered as individual rational, Pareto optimal and relationship-stable solution. A cooperation cycle formation (CCF) algorithm is proposed to obtain the strict core solution. However, in networks, some deviated nodes may break the cooperation agreement to obtain more utility gain. Such deviated behaviours in the cooperation cycles can totally destroy the cooperation relationship. However, the data transmissions in networks have the repeated element. Hence, based on the cooperative cycle formed by CCF, the authors introduce a repeated game model for cooperation maintenance in the second stage. A dynamic punishment and recover mechanism is proposed to punish the deviated behaviours and recover cooperation.
With the constantly increasing pressure of the competitive environment, supply chain (SC) decision makers are forced to consider several aspects of business climate. More specifically, they should take into account th...
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With the constantly increasing pressure of the competitive environment, supply chain (SC) decision makers are forced to consider several aspects of business climate. More specifically, they should take into account the endogenous features (e.g., available means of transportation, and the variety of products) and exogenous criteria (e.g., the environmental uncertainty, and transportation system conditions). In this paper, a mixed integer nonlinear programming (MINLP) model for dynamic design of a supply chain network is proposed. In this model, multiple products and multiple transportation modes, the time value of money, traffic congestion, and both supply-side and demand-side uncertainties are considered. Due to the complexity of such models, conventional solution methods are not applicable;therefore, two hybrid Electromagnetism-Like algorithms (EMA) are designed and discussed for tackling the problem. The numerical results show the applicability of the proposed model and the capabilities of the solution approaches to the MINLP problem.
Dense deployment of femtocells can cause serious intra-tier interference in femtocell networks. In this paper, a new cooperative interference management approach which allows the femtocell user equipment (FUE) to merg...
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Dense deployment of femtocells can cause serious intra-tier interference in femtocell networks. In this paper, a new cooperative interference management approach which allows the femtocell user equipment (FUE) to merge into cooperative groups, that is, coalitions, for the uplink transmissions in a femtocell network is proposed, so as to reduce the intra-tier interference and improve the system performance. Taking into account the power cost for cooperation, we claim that all the FUEs are impossible to merge together, and we formulate the proposed cooperative problem as a coalitional game in partition form with an externality due to the interference between the formed coalitions. To get the solution, a novel distributed coalition formation algorithm that takes advantage of the characteristics of femtocell network and allows the FUEs to interact and individually decide on which coalitions to participate in is proposed. Furthermore, we analyze the convergence and stability of the proposed algorithm. Simulations are conducted to illustrate the behavior and the performance of the proposed coalition formation algorithm among FUEs. Results show that the proposed algorithm can improve the system performance with much lower complexity than some previously proposed coalition formation algorithms.
The numerical algorithm for tracing exact frequency-dependent rays, which makes it possible to trace these rays in arbitrary media is proposed. In addition, a numerical investigation of the properties of rays under co...
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The numerical algorithm for tracing exact frequency-dependent rays, which makes it possible to trace these rays in arbitrary media is proposed. In addition, a numerical investigation of the properties of rays under consideration and comparison of them with the standard ray theory and finite-difference simulation was performed. The results of numerical experiments for a number of models, including the Sigsbee model, containing a salt body of complex shape are presented.
This paper presents a unifying approach for a reliable calculation of all azeotropes and pinch points for homogeneous and heterogeneous non-reactive mixtures. The approach builds on a reformulation of the pinch-equati...
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This paper presents a unifying approach for a reliable calculation of all azeotropes and pinch points for homogeneous and heterogeneous non-reactive mixtures. The approach builds on a reformulation of the pinch-equation system and an efficient continuation algorithm including bifurcation analysis. The calculation of azeotropes is based on an analogy of univolatility curves and the pinch branches for pure component products. The resulting method can efficiently and reliably calculate all homogeneous and heterogeneous non-reactive azeotropes. The only exception would be the existence of isolated univolatility curves inside the composition space, which to the best knowledge of the authors has never been reported. Since the method can further determine the pinch branches and pinch points based on the knowledge of the azeotropes, it presents a self-contained method for calculation of the most important information on nonideal multicomponent mixtures to support process synthesis. The application of the method is illustrated by means of several complex mixtures.
The article describes an approach to explore music collections by navigating through different views. The technique used is called aligned self-organizing maps (SOM). The SOM is an unsupervised neural network with app...
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The article describes an approach to explore music collections by navigating through different views. The technique used is called aligned self-organizing maps (SOM). The SOM is an unsupervised neural network with applications in various domains including audio analysis. As a clustering algorithm, the SOM is very similar to other partitioning algorithms such as K-means. In terms of topology preservation for visualization of high-dimensional data, alternatives include multi-dimensional scaling, Sammon's mapping and generative topographic mapping. The objective of the SOM is to map high-dimensional data into two-dimensional map in such a way that similar items are located near each other. The SOM consists of an ordered set of units that are arranged in two-dimensional visualization called the map. Common choices to arrange the map units are rectangular or hexagonal grids. There are two main parameters for the SOM algorithm. One is the map size the other is the final neighborhood radius. A larger map gives a higher resolution of the mapping but is computationally more expensive. The final neighborhood radius defines the smoothness of the mapping and should be adjusted depending on the noise level in the data. The SOM is a useful tool for exploring a data set according to a given similarity measure. An aligned SOM is an extension to the basic SOM that allows for interactively shifting the focus between different aspects and exploring the resulting gradual changes in the organization of the data.
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