Repetitive model refactoring strategy for the design space exploration of intensive signal processing applications

The efficient design of computation intensive multidimensional signal processing applications requires dealing with three kinds of constraints: those implied by the data dependencies, the non-functional requirements (real-time, power consumption) and resources availability of the execution platform. Modeling and Analysis of Real-time and Embedded systems (MARTE) UML profile through its repetitive structure modeling (RSM) package is well suited to model the inherent parallelism within these applications, a compact representation of parallel execution platforms and the distributive mapping of one on another. The execution of such a specification respects the whole set of constraints defined upon, while the quality of the scheduling is directly linked to the quality of the mapping of the multidimensional structures (data arrays or parallel loop nests) into time and space. We propose here a strategy to use a refactoring tool dedicated to this kind of application that allows to find good trade-offs in the usage of storage and computation resources and in parallelism (both task and data parallelism) exploitation. This strategy is illustrated on an industrial radar application.     

Dialogue in context, towards a referential approach in collective learning

In this article, we present research in the making of a collective work environment within the framework of a distance education course. We base our theoretical and methodological standpoints on examples of dialogical discourses recorded within the framework of this CSCL system called Symba. In fact, the results of previous research lead us to rethink our vision of the study of collaborative moments between participants in a computer-supported human learning environment that proposes several communication tools. Redefining the methodological process aiming at finding and understanding these rich learning moments is also necessary. We intend to describe “socio-technical” instances during which these collaboration phases appear. More generally speaking, our aim is to draw up both new theoretical and methodological perspectives that would be reusable in CSCL environments; in view of the nature of these two perspectives, and the diversity of the domain knowledge (sociology, cognitivism, linguistics, philosophy, statistics, etc.) brought to bear in the study of the environment in question, our approach constitutes a trans-disciplinary reassessment of the uses of the communication tools—and the study thereof—proposed.

Evaluating location management schemes for third generation mobile networks

Several strategies have been proposed recently to improve the performance of the IS-41 location management scheme. A forwarding pointers' strategy and a built-in memory strategy are proposed to reduce the signaling cost for location update and improve the IS-41 location update procedure. In this paper, we present a performance analysis of each strategy in an arbitrary time interval. In this analysis, users are classified by their call to mobility ratio which is defined as the call arrival rate divided by the mobility rate. We evaluate each of these strategies using this call to mobility ratio in order to come up with a set of recommendations that determine when each strategy is beneficial and for which class of users. We provide also a simplified analysis of the database loads generated by each strategy.     

A model of the temperature distribution in an alumina coating during plasma spraying

An attempt to develop a theory for the calculation of the temperature distribution in a plasma-sprayed coating is presented. This theory takes into account both the physical properties of sprayed (not the bulk) material and the effect of thermal resistance between the coating and the substrate. The calculation procedure employed (finite differences) permits the theoretical prediction of the temperature distribution in samples of limited dimensions. The theory was used to determine the temperature distribution in alumina coatings plasma sprayed onto copper or mild steel substrates. A comparison between the theoretical predictions and experimentally determined surface coating temperatures is also presented. The experiments were carried out using IR thermography. For these measurements it was necessary to determine the emissivity of the sprayed alumina at the IR wavelength of interest. The influence of the spraying distance, the substrate material and cooling of the sprayed samples on the coating surface temperature was investigated. The predicted temperatures are within 20% of the experimental values.     

Performance of lactating dairy cows fed silage from corn of varying maturities

The deleterious effect of frost on corn harvested for silage was investigated with 30 lactating Holstein cows fed silages from corn harvested at the milk or dough stage, or after one, two, or five frosts. The fibrous components of the corn plant increased as maturity and dry matter content increased, whereas the mineral content tended to decrease. Dry matter intake and 4% fat-corrected milk increased as maturity of the silage increased up to the silage harvested after two frosts and then declined for the silage harvested after five frosts. Gross energy apparent digestibility decreased from 64.9% for milk stage silage to 60.6% for silage from corn harvested after five frosts. Partitioning of gross energy, nitrogen, calcium, phosphorus, potassium, and magnesium provided similar increasing trends in feed intake, utilization, and milk production from milk stage silage to that harvested after two frosts, then a decline of all measurements occurred with silage harvested after five frosts. Net energy for lactation was calculated for each silage from the observed digestible energy, from a regression equation used by the provincial feed evaluation laboratories, and from a recently published summative equation; the latter method appeared best.     

Estimation of combined ice and wind load on overhead transmission lines

In recent years, the design of high-voltage transmission lines has been increasingly optimized. In areas where ice accretion on conductors is possible, the load resulting from added weight or increased aerodynamic forces becomes an important design parameter. At present, calculations for combined ice-wind loads do not take the effect of accretion shape into account. In this study, ice accretions are formed on a conductor in a wind tunnel for three types of ice: soft rime, hard rime and glaze. Aerodynamic vertical and horizontal forces are then measured for different wind velocities. It is shown that when the wind remains in the direction of ice build-up, the aerodynamic force due to the asymmetric shape is responsible for a significant increase in the total force and that the present combined ice-wind load calculations can dangerously underestimate the risk of an overload.     

Robust eigenstructure clustering by non-smooth optimisation

We extend classical eigenstructure assignment to more realistic problems, where additional performance and robustness specifications arise. Our aim is to combine time-domain constraints, as reflected by pole location and eigenvector structure, with frequency-domain objectives such as the H₂, H_∞ or Hankel norms. Using pole clustering, we allow poles to move in polydisks of prescribed size around their nominal values, driven by optimisation. Eigenelements, that is poles and eigenvectors, are allowed to move simultaneously and serve as decision variables in a specialised non-smooth optimisation technique. Two aerospace applications illustrate the power of the new method.     

Adsorption des acides humiques sur charbon active en poudre. Influence du triphosphate de sodiumAdsorption of humic acids onto powdered activated carbon. The influence of sodium triphosphate

The use of activated carbon beds for the removal of natural humic and fulvic substances found in water supplies, has recently received considerable attention in water treatment operation (Lee et al., 1980; Le Cloirec et al., 1983). Moreover, the use of carbon adsorption for the reduction of haloform precursors (Anderson et al., 1981) and trihalomethanes produced by chlorination process, has contributed to a comprehensive investigation of adsorption characteristics of natural organic compounds (McCreary and Snoeyink, 1981). Many recent works showed the influence of adsorption system characteristics, such as pH, salt type, salt concentration and ionic heterogeneity in multicomponent adsorption systems, on the removal efficiency of humic and fulvic substances by activated carbon (McCreary and Snoeyink, 1980; Randtke and Jepsen, 1982; Weber et al., 1983). The purpose of this study is to examine the effect of a main component of domestic detergents, sodium triphosphate (STP), on the adsorptive capacities of powdered activated carbon (PAC) for commercially supplied humic acids, at different pH values in distilled water. Also, the effect of STP concentration and pH on the adsorption affinity of the PAC for humic acids, is discussed in relation with electrokinetic properties of carbon particles (zeta potential measurements).A first batch equilibrium study (Figs 1 and 2), showed an effective enhancement of adsorption capacity for humic acids as a function of STP concentration, in a non buffered media (pH of distilled water, close to 5.0). For example, visible absorption analysis of humic acids indicates an increase of 93% (500 mg l^?1 PAC) and 133% (1000 mg l^?1 PAC) in the carbon adsorption efficiency for a STP concentration from 0.2 to 1.0mM. A second batch equilibrium study (Figs 3 and 4) led to adsorption isotherms for humic acids in distilled water, as a function of STP concentration and initial pH value of the non buffered multicomponent system. Freundlich isotherms showed an increase in the adsorption capacity of the PAC for humic acids, with a decrease in pH and an increase in STP concentration. However, the adsorption capacity for humic acids is quite reduced at high pH values in presence of STP, in comparison with results obtained with distilled water.Electrokinetic measurements on PAC suspensions (Fig. 5) indicates that both humic acids and STP induce a negative variation of the zeta potential of carbon particles. In such a binary system, the zeta potential is a linear function of the pH; the negative surface charge of the carbon increasing with an elevation of pH (Fig. 6). Therefore, it appears that some adsorption of triphosphate polyanion from solution could occur, contributing then to the apparent negative surface charge of PAC particles.It has been previously showed that the type of anion in sodium salts, had little effect on the enhancement of adsorptive capacities of activated carbon for humic substances (Lafrance and Mazet, 1985), due to Na⁺ ions. However, adsorption of TP anions on the carbon surface may produce a source of repulsive charges, unfavourable to the co-adsorption of humic acids as the pH of the binary system reach more basic conditions. The influence of possible electrostatic interactions between adsorbates at the carbon surface, on the adsorption efficiency for humic acids, could then be studied by zeta potential measurements of PAC particles during the adsorption process.     

Predictors of outpatient mental health service use by American youth.

Among American children and adolescents aged 1 to 17 years, the 12- to 17-year-olds represent the largest users of outpatient mental health services. This study utilizes a nationally representative sample of this age group from the 2005 National Survey on Drug Use and Health to illuminate predictors of services use from three treatment settings: day treatment programs, mental health clinics/centers, and private/in-home settings. Univariate analyses were used to calculate the percentages of the study sample that used mental health services in these settings. In bivariate analyses, the authors estimated the strength of the associations between available predisposing, need, and enabling factors and the outcomes. Multiple logistic regressions estimated the independent effects of each covariate on the outcomes. Lifetime depression, lifetime general anxiety, delinquent behaviors, drug dependence, and Medicaid were consistent predictors of services use in the three treatment settings. Several other factors were associated with services use in bivariate analyses but lost most of their statistical significance when the authors adjusted for other confounders. Interpreted in light of its potential limitations, this study has important research and policy significance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)