Comment on ‘Frequency domain identification of Wiener models’, by E.W. Bai, Automatica 39 (2003), 1521–1530

A frequency-domain identification method is proposed by Bai (2003) for Wiener systems. The key component is a phase estimator that gives estimates of the linear subsystem phase for different frequencies. These estimates are then used to identify the whole system. In this note, it is shown that the phase estimator is not generally consistent. Consequently, consistency of the overall identification method is in turn not generally guaranteed.     

Hammerstein Systems Identification in Presence of Hard Nonlinearities of Preload and Dead-Zone Type

Hammerstein system identification is considered in presence of preload and dead zone nonlinearities. The discontinuous feature of these nonlinearities makes it difficult to get a single system parameterization involving linearly all unknown parameters (those of the linear subsystem and those of the nonlinearity). Therefore, system identification has generally been dealt with using multiple stage schemes including different parametrizations and several data acquisition experiences. However, the consistency issue has only been solved under restrictive assumptions regarding the identified system. In this paper, a new identification scheme is designed and shown to be consistent under mild assumptions.     

Influences of copolymers (Copovidone,Eudragit RL PO and Kollicoat MAE 30 DP) on stability and bioactivity of spray-dried and freeze-dried lysozyme

Protein stability is the most crucial factor in protein pharmaceutical preparations. Various techniques were applied for producing stable protein formulations such as spray-drying and freeze-drying. However, heating and freezing stresses are disadvantages for proteins using these methods, respectively. Accordingly, excipients have been used to preserve therapeutic effects of proteins during processing and for long period of time. Therefore, influences of Copovidone, Eudragit^® RL-PO and Kollicoat^® MAE-30 DP (as excipients) on stability and integrity of lysozyme (as a model protein) in spray-dried and freeze-dried forms were investigated. Protein formulations in both dried forms were prepared without and with the addition of mentioned excipients at different concentrations. Protein formulations were characterized for yield determination, morphology using scanning electron microscopic (SEM), thermal analysis by Differential Scanning Calorimetry (DSC), secondary structure stability using Fourier transform infrared (FT-IR) spectroscopy and biological activity. All protein formulations were subjected to a stability study as solid protein formulations for 3 weeks at 24?°C/76% relative humidity and aqueous protein samples were stored at 50?°C for 30?min in a water bath. Results showed that Copovidone successfully preserved integrity and biological activity of lysozyme before and after storage in both spray-dried and freeze-dried forms with more advantage for using higher concentration of the same excipient. Smooth spheres of spray-dried lysozyme formulations with Copovidone were smaller than spray-dried lysozyme without and with Kollicoat^® MAE-30 DP, which affected %yield produced. Copovidone has demonstrated valuable protection ability for lysozyme.     

A special finite element for the analysis of the singularity in a bimaterial containing a crack perpendicular to the interface

It is shown that the singularity of stresses near the tip of crack in an elastic bi-material can be obtained by using degenerate triangular elements, the shape functions of which are derived from those classical isoparametric elements. A four node triangular element is tested on two different samples. The results obtained are compared with those which exist already in bibliography.     

Industrial systems maintenance modelling using Petri nets

This article presents a new algorithm that we have developed to find the minimal cut-sets of a coherent fault tree. The model presented is based on Petri nets. We also show that for a large fault tree, we are faced with the complexity problem. We suggest the use of place fusion as well as a methodology that can allow us to overcome this difficulty.     

The Use of a Eutectic Mixture of Olive Pomace Oil Fatty Amides to Easily Prepare Sulfated Amides Applied as Lime Soap Dispersants

Sulfated diethanolamides of fatty acids are known to be effective lime soap dispersing agents. However, their preparation from fatty acids via fatty amides requires the use of organic solvents due to the high viscosity of both fatty amides and sulfated fatty amides. This study shows that the preparation of sulfated fatty amides is relatively easy when using olive pomace oil as the raw material. The latter, is converted into sulfated fatty amides by performing the following steps: saponification, hydrolysis, esterification, amidation, and sulfation. In the final step, the mixture obtained has sufficient fluidity, due to its high linoleic acid amide content, to obviate the use of organic solvents, as usually suggested in the literature. Characterization of the product was carried out by chemical analyses, FTIR, ¹³C NMR, GC, and HPLC. It was shown that the yield of the amidation reaction is about 80%, and that of the sulfation reaction can exceed 100% against the pure amide (more than one sulfate group could be linked to one amide molecule). On the other hand, the Borghetty test showed that the product is an effective dispersant with a lime soap dispersing power equal to five.     

Corrosion and scale inhibition of low carbon steel in cooling water system by 2-propargyl-5-o-hydroxyphenyltetrazole

The 2-propargyl-5-o-hydroxyphenyltetrazole (PHPT) has been tested as corrosion inhibitor for low carbon steel in simulated cooling water. The polarization curves showed that PHPT acts as mixed-type inhibitor. Its inhibition efficiency was found to enhance with increase of the inhibitor concentration and immersion time due to the formation of the inhibitor film on the metal surface as indicated by electrochemical impedance spectroscopy measurements.To complete the formulation further, a non oxidizing biocide was added. Its presence with PHPT does not affect its inhibitory performance and it can be served as a basic component of the formulation for cooling water system.     

Analogies between Internet network and logistics service networks: challenges involved in the interconnection

Logistics networks that are currently formed by supply chains are intertwined but remain heterogeneous and not very interconnected. In computer networks, this stage was overtaken with the arrival of Internet. In this paper we explore the possible analogies and transpositions between computer networks, in particular Internet, and logistic networks. To this end, a new logistical concept was proposed: Physical Internet that aims at the interconnection of networks of logistic services. In fact, there are strong similarities between these networks in spite of the basic differences in the type of objects that prevent an integral transposition. To illustrate the pertinence of this analogy, the authors illustrate the interconnection potential of logistics networks with a stylised model. In view of the exploratory nature of this work, this impact will be assessed by means of an analytic model based on a method of continuous approximations. This illustration provides an indication of the potential inherent in the interconnection of logistics networks.     

Parameter identification of Hammerstein systems containing backlash operators with arbitrary-shape parametric borders

A two-stage parameter identification method is developed for Hammerstein systems containing backlash nonlinearities bordered by parametric arbitrary-shape lines. In the first stage, a persistently exciting input is designed so that the linear subsystem can be made decoupled from the nonlinear element. Therefore, linear subsystem identification is coped with using a least squares estimator enjoying consistency, due to input persistent excitation. Then, the backlash parameters are estimated using appropriate periodic exciting signals and consistent parameter estimators.