ITU-T有关下一代网络的研究

作为一个全新的概念,下一代网络(NGN)常常被人们用来描绘未来电信网的概貌。但是,不同的运营商、制造商或业务提供商对NGN有着不同的理解而且差别甚大,故希望在NGN的定义上能够统一,并能最终实现标准化。这就是国际电信联盟标准委员会(ITU-T)决定启动NGN项目的原因。该项工作由其下属的第13研究组(SG-13)负责。该项目的研究目标将与原有     

Coupled effect of time and temperature on variations of yield value of highly flowable mortar

In order to enhance the performance of self-consolidating concrete, it is important to have a better understanding of the rheological behavior of the material. The initial rheological parameters and their variations with time are closely affected by material temperature, type and dosage of high range water-reducing admixture (HRWRA), and elapsed time. This paper presents the results of an investigation aimed at evaluating the coupled influence of time and temperature on the variations of yield value with time of mortars made with two types of HRWRA: polynaphtalene sulfonate and polycarboxylate polymer. Four mortars extracted from self-consolidating concrete mixtures proportioned with various binder types and with water-to-binder ratios of 0.42 and 0.53 were prepared at 10 to 30 °C.Test results show that the yield value varies linearly with the coupled effect of time and temperature during the dormant period for mixtures made with polynaphtalene sulfonate-based HRWRA. However, such changes are found to depend on the mixture temperature for mixtures made with polycarboxylate-based HRWRA, which can influence the dispersion efficiency of the polycarboxylate polymer. The threshold temperature of mixtures made with PCP-HRWRA is shown to vary with mixture composition. Below a given threshold temperature, the mortar exhibits a considerable degree of retention or even reduction in yield value over 30% of the dormant period. A sharp increase in yield value is observed beyond 30% of the dormant period. Above this threshold temperature, the yield value is shown to increase linearly with time.     

Prediction and optimization of electroplated Ni-based coating composition and thickness using central composite design and artificial neural network

Journal of Applied Electrochemistry - The choice of the electroplating conditions of Ni-based alloys has always been a serious research question. In this study, an artificial neural network based...     

WHAD: Wikipedia historical attributes data

This paper describes the generation of temporally anchored infobox attribute data from the Wikipedia history of revisions. By mining (attribute, value) pairs from the revision history of the English Wikipedia we are able to collect a comprehensive knowledge base that contains data on how attributes change over time. When dealing with the Wikipedia edit history, vandalic and erroneous edits are a concern for data quality. We present a study of vandalism identification in Wikipedia edits that uses only features from the infoboxes, and show that we can obtain, on this dataset, an accuracy comparable to a state-of-the-art vandalism identification method that is based on the whole article. Finally, we discuss different characteristics of the extracted dataset, which we make available for further study.     

Modeling soft granular materials

Soft-grain materials such as clays and other colloidal pastes share the common feature of being composed of grains that can undergo large deformations without rupture. For the simulation of such materials, we present two alternative methods: (1) an implicit formulation of the material point method (MPM), in which each grain is discretized as a collection of material points, and (2) the bonded particle model (BPM), in which each soft grain is modeled as an aggregate of rigid particles using the contact dynamics method. In the MPM, a linear elastic behavior is used for the grains. In order to allow the aggregates in the BPM to deform without breaking, we use long-range center-to-center attraction forces between the primary particles belonging to each grain together with steric repulsion at their contact points. We show that these interactions lead to a plastic behavior of the grains. Using both methods, we analyze the uniaxial compaction of 2D soft granular packings. This process is nonlinear and involves both grain rearrangements and large deformations. High packing fractions beyond the jamming state are reached as a result of grain shape change for both methods. We discuss the stress-strain and volume change behavior as well as the evolution of the connectivity of the grains. Similar textures are observed at large deformations although the BPM requires higher stress than the MPM to reach the same level of packing fraction.     

Geometry of Interaction V: Logic in the hyperfinite factor

Geometry of Interaction is a transcendental syntax developed in the framework of operator algebras. This fifth installment of the program takes place inside a von Neumann algebra, the hyperfinite factor. It provides a built-in interpretation of cut-elimination as well as an explanation for light, i.e., complexity sensitive, logics.     

Negative results for software effort estimation

More than half the literature on software effort estimation (SEE) focuses on comparisons of new estimation methods. Surprisingly, there are no studies comparing state of the art latest methods with decades-old approaches. Accordingly, this paper takes five steps to check if new SEE methods generated better estimates than older methods. Firstly, collect effort estimation methods ranging from “classical” COCOMO (parametric estimation over a pre-determined set of attributes) to “modern” (reasoning via analogy using spectral-based clustering plus instance and feature selection, and a recent “baseline method” proposed in ACM Transactions on Software Engineering). Secondly, catalog the list of objections that lead to the development of post-COCOMO estimation methods. Thirdly, characterize each of those objections as a comparison between newer and older estimation methods. Fourthly, using four COCOMO-style data sets (from 1991, 2000, 2005, 2010) and run those comparisons experiments. Fifthly, compare the performance of the different estimators using a Scott-Knott procedure using (i) the A12 effect size to rule out “small” differences and (ii) a 99 % confident bootstrap procedure to check for statistically different groupings of treatments. The major negative result of this paper is that for the COCOMO data sets, nothing we studied did any better than Boehms original procedure. Hence, we conclude that when COCOMO-style attributes are available, we strongly recommend (i) using that data and (ii) use COCOMO to generate predictions. We say this since the experiments of this paper show that, at least for effort estimation, how data is collected is more important than what learner is applied to that data.     

A new DFM approach to combine machining and additive manufacturing

Design for manufacturing (DFM) approaches aim to integrate manufacturability aspects during the design stage. Most of DFM approaches usually consider only one manufacturing process, but product competitiveness may be improved by designing hybrid modular products, in which products are seen as 3-D puzzles with modules realized individually by the best manufacturing process and further gathered. A new DFM system is created in order to give quantitative information during the product design stage of which modules will benefit in being machined and which ones will advantageously be realized by an additive process (such as Selective Laser Sintering or laser deposition). A methodology for a manufacturability evaluation in case of a subtractive or an additive manufacturing process is developed and implemented in a CAD software. Tests are carried out on industrial products from automotive industry.     

Synthèse optimale d’un réseau de télécommunication avec contraintes de sécurité

A commonly used method for achieving a prescribed security level in a telecommunication network is to manage extra capacities all over the network. This paper describes a number of computational methods, both exact and approximate, for determining a minimum cost network of extra capacities needed to achieve security under any given trunk dimensioning, routing and grouping policy. From a mathematical point of view, it is shown that the problem reduces to the determination of a minimum cost network subject to a number of non simultaneous multicommodity flow requirements. Since real life instances of such problems commonly result in very large linear programs of many thousands of variables and constraints, the techniques of linear programming would be unacceptably time and space-consuming. Instead, it is shown how the use of Lagrangean relaxation in conjunction with sub-gradient optimization schemes can lead to efficient and easy-to-implement solution methods. The various procedures described in this paper form the heart of a general software product for long and medium term planning applications (Supersec program) which has already been used to investigate the economical implications of security requirements in telecommunication networks.