Optimizing Concentration of Drag Reducing Polymer in Case of One- and Two-Phase Flow in 90° Copper Elbow

Journal of Failure Analysis and Prevention - The rate of diffusion-controlled corrosion of 90° Copper Elbow by acidified dichromate has been investigated in relation to the following...     

Impact of morphological analysis and a large training corpus on the performances of Arabic diacritization

The absence of short vowels in Arabic texts is the source of some difficulties in several automatic processing systems of Arabic language. Several developed hybrid systems of automatic diacritization of the Arabic texts are presented and evaluated in this paper. All these approaches are based on three phases: a morphological step followed by statistical phases based on Hidden Markov Model at the word level and at the character level. The two versions of the morpho-syntactic analyzer Alkhalil were used and tested and the outputs of this stage are the different possible diacritizations of words. A lexical database containing the most frequent words in the Arabic language has been incorporated into some systems in order to make the system faster. The learning step was performed on a large Arabic corpus and the impact of the size of this learning corpus on the performance of the system was studied. The systems use smoothing techniques to circumvent the problem of missing transitions words and the Viterbi algorithm to select the optimal solution. Our proposed system that benefits from the wealth of morphological analysis and a large diacritized corpus presents interesting experimental results in comparison to other automatic diacritization systems known until now.     

Kinetic model of solute aqueous extraction from Fennel (Foeniculum vulgare) treated by pulsed electric field, electrical discharges and ultrasonic irradiations

This work investigates the aqueous extraction from Fennel (Foeniculum vulgare) assisted by pulsed electric field (PEF), electrical discharges (ED) and ultrasound irradiations (UI). It aims the improvement of the solutes yield and the extraction kinetics at room temperature.Fennel gratings of size (1.5 × 0.75 × 30-50 mm³; width × height × length), were treated by PEF (intensity: 50-1200 V/cm and number of pulses: 50-1000), ED (voltage: 40 kV and number of discharges: 10-60) and ultrasound (intensity: 400 W/cm² and treatment duration: 10-350 min). The liquid-to-solid (weight/weight) ratio equal to 2. All tests were carried out at room temperature (20 °C), under stirring at 250 rpm. The extraction kinetics was modelled using a simplified two-exponential kinetic model, which corresponds to mass transfer in two stages (rapid washing and slow diffusion).The optimal parameters of PEF, ED and UI, giving the maximal juice yield, were determined and the effect of these three treatments on the mass transfer rate was studied.     

Dodecylhydroxydiphosphonic Acid for Solvent Extraction

Abstract

The extraction behavior of Zn(II) and Cu(II) in acetate media has been investigated using dodecylhydroxydiphosphonic acid, DHDPA, which was previously synthesized and characterized. The extraction of both cations was carried out in different media with the addition of CH₃COOH, HCl or H₂SO₄ at different pH. The maximum extraction yield of 80% for zinc, was obtained in one step after the addition of sulfuric acid at pH_i=5.5 and for copper after the addition of 10 mg of sodium acetate. The authors plan additional tests using polar solvents.     

Four‐parameter beta distribution estimation and skewness test

Sequential tolerance control (STC) is a tolerance control methodology used in discrete parts manufacturing. Recently, an adaptive sphere‐fitting method for STC (ASF–STC) was developed to account for potential skewness in manufacturing operations' distributions, a factor not considered in conventional STC. ASF–STC offers significant improvements over conventional STC when such skewness exists. The direction of skewness of an operations' distribution is a necessary input to ASF–STC. Thus, a novel approach to determining the skewness of a distribution for small sample sizes is presented here. ASF–STC has an additional requirement of distribution information for each operation. The beta distribution is an ideal candidate here, as it is very flexible in shape. The literature on four‐parameter beta estimation is very limited, and their performance for small sample sizes is poor. STC was designed for low‐volume production, thus the estimation for small sample sizes is necessary here. This study presents a heuristic, based on the method of moments estimates for a beta distribution, that estimates the four parameters for a beta distribution with small sample size. Several computational results are provided to compare this heuristic to the best‐known procedure, with the heuristic found to perform better for the test problems considered. Copyright © 2002 John Wiley & Sons, Ltd.     

Distributed energy efficiency in future home environments

In this paper, a new architecture for sharing resources among home environments is proposed. Our approach goes far beyond traditional systems for distributed virtualization, like PlanetLab or grid computing, as it relies on complete decentralization in a peer-to-peer (P2P) like manner and, above all, aims at energy efficiency. Energy metrics are defined, which have to be optimized by the system. The system itself uses virtualization to transparently move tasks from one home to another to optimally utilize the existing computing power. We present an overview of our proposed architecture, consisting of a middleware interconnecting computers and routers in possibly millions of homes using P2P techniques. For demonstrating the potential energy saving of distributed applications, we present an analytical model for sharing downloads, which is verified by discrete event simulation. The model represents an optimistic case without P2P overhead and fairness. The model allows to assess the upper limit of the saving potential. An enhanced version of the simulation model also shows the effect of fairness. The fairer the system gets, the less efficient it is.     

Comparison of thermoreflectance and scanning thermal microscopy for microelectronic device temperature variation imaging: Calibration and resolution issues

We have studied temperature variations on two submicrometric dissipative structures with two different techniques. On one hand, we have used a thermoreflectance imaging technique which is a well-known non contact optical method to evaluate temperature variations but whose spatial resolution is limited by diffraction. On the other hand, we have used a scanning thermal microscope (SThM) to study the thermal behaviour of these small dissipative structures. We present qualitative results obtained by both methods and we compare their advantages and drawbacks in terms of calibration and spatial resolution for thermal measurements on microelectronic devices. In particular, we show how the thermoreflectance coefficient can become an advantage to enhance the image contrast and favour the spatial resolution.     

Distributed address auto configuration protocol for Manet networks

In heterogeneous network environments, the network connections of a multi-homed device may have significant bandwidth differential. For a multi-homed transmission protocol designed for network failure tolerance, such as SCTP, path selection algorithms for data transmission drastically affect performance. This article studies the effect of path bandwidth differential on the performance of retransmission strategies in multi-homing environments. It identifies that fast retransmission on an alternate path may cause receive buffer blocking when path bandwidth differential is significant and the receive buffer is limited. A theoretical model is proposed for selecting retransmission path during the fast retransmission phase, based on receive buffer and path conditions. From these observations and analysis results, this article proposes that path selection strategies for transmitting new data and retransmitted data should be decoupled. A new path selection scheme is proposed and evaluated through SCTP simulations.     

Preparation, characterisation of thermally treated Algerian dolomite powders and application to azo-dye adsorption

Dolomite powder from Ouled Mimoun, Tlemcen (western region of Algeria) was thermally treated within the temperature range 450-1000 °C. The modifications undergone by dolomite, inherent to thermal treatment, were investigated from X-ray diffraction patterns. The results were also discussed using scanning electronic microscopy and nitrogen adsorption. The XRD data, analysed from X Pert Plus program, showed that the dolomite phase ceases at 700 °C and is relayed by the formation of in situ calcite and periclase. The crystallographic parameters of these two phases tend towards that of pure periclase and calcite at 1000 and 900 °C, respectively. SEM analysis indicated that the morphological properties were profoundly affected. SEM images of D-1000 (sample treated at 1000 °C) indicated that the original particle shape of dolomite (presence of discrete grains having sharp edges with presence of cleavages) was totally destroyed, leading to small spherical particles with a diameter of 0.1 μm. The specific surface area value of D-1000 increased more than 6 times against that of the raw dolomite. Adsorption of azo-dye Orange I from aqueous solutions onto untreated and treated dolomites was also reported. The isotherms were of L-type. The interaction was explained by electrostatic considerations between sulfonate groups of the dye (D-SO₃Na), which are dissociated in the aqueous system, and positively charged adsorption sites. The affinity of orange I for the dolomitic solids follows the sequence D-900 > D-1000 > D-800 > > D-600 > raw dolomite. The maximum retention capacity shown by D-900 was explained and correlated with its crystallographic properties.