Symbolic simulators for the fault diagnosis of nonlinear analog circuits

A new symbolic technique for the realization of simulators for nonlinear analog circuits is presented. The generated simulators work with input/output in numerical form, but they are very efficient due to the use of the symbolic approach. For nonlinear components a PWL (PieceWise Linearization) method is used. The proposed approach permits to obtain libraries of simulators which can be very useful in many application fields. In particular we present a possible application to an expert system devoted to nonlinear circuit fault diagnosis. The program package, realized for this application, is described from both algorithmic and functional points of view. Some simple examples are presented in order to illustrate the main features of the program.1. We are supposing that all the nonlinear elements are represented by a characteristic of the kindI =G(V)     

Physicochemical Characterization of a Heat Treated Calcium Alginate Dry Film Prepared with Chicken Stock

Solid sodium alginate was dissolved into chicken stock in order to give a final alginate concentration of 0.9 percent (w/v). Calcium ions present in chicken stock were enough to induce ionic gelation. After drying, Fourier transform infrared spectroscopy, thickness and mechanical properties of films obtained were determined. Calcium alginate‐chicken stock films were heated at 130 °C for different times between 0 and 15 min. Mechanical and optical studies, differential scanning calorimetry, visual aspect and scanning electron microscopy were carried out to describe physicochemical properties of heat treated films. Heating developed a maroon ochre color and increased the brittleness (crispness) of the films related to the intensity of the treatment. Differential scanning thermometry and study on appearance of the films suggested that Maillard reactions may be responsible for the observed changes. Maillard reactions mainly occurred between reducing sugar monomers and free amino groups of gelatin peptides present in the chicken stock, and between alginate and gelatin peptides to a lesser extent. In addition, the plasticizing effect of fat added with chicken stock was also studied. These studies suggest a potential use of heat treated chicken stock films as a substitute of roasted chicken skin.     

System identification and modelling based on a double modified multi-valued neural network

A novel identification technique for the extraction of lumped circuit models of general distributed or stray devices is presented. The approach is based on two multi-valued neuron neural networks used in a joined architecture able to extract hidden parameters. The convergence allows the validation of the approximated lumped model and the extraction of the correct values. The inputs of the neural network are the geometrical parameters of a given structure, while the outputs represent the estimation of the lumped circuit parameters. The method uses a frequency response analysis approach in order to elaborate the data to present to the net.     

Neuropsychological characteristics of parkinsonian patients with lateralized motor impairment

Parkinsonians with predominantly unilateral signs provide an interesting experimental means to evaluate if asymmetric nigro-striatal degeneration may affect neuropsychological functions. The aim of our study was to establish if the side of onset of idiopathic Parkinson's disease, right (PDR) or left (PDL), determines a selective pattern of cognitive performances. Furthermore, we verified if PDR and PDL groups show a different frequency of dementia. PDR and PDL patients with at least seven years of disease duration, matched for age, schooling, severity of extrapyramidal symptomatology and index of lateralization, were evaluated by using an extensive neuropsychological battery aimed at assessing hemispheric cognitive asymmetries. Current side of greater motor impairment was the same as the one affected at the onset of the disease. Only subtle differences in the profile of neuropsychological dysfunction emerged from the comparison of PDR and PDL subjects. Moreover, the number of parkinsonians showing dementia syndrome was the same in both groups. Our results suggest that the side of onset of motor impairment does not significantly influence the cognitive performances in PD. Subcortical anatomic and/or functional asymmetries seem to play a less important role in the intellectual functions than in motor activities.     

Selectivity control in substituted fatty amines synthesis from esters or nitriles in the presence of bifunctional catalysts

Copper chromite-type catalysts, supported by alumina or graphite and promoted with barium, were used for the onestep synthesis of tertiary fatty amines [R₂NCH₃ or RN(CH₃)₂] from ester, acid or nitrile and ammonia, methanol and hydrogen. The surface composition of the catalysts, studied by X-ray photoelectron spectroscopy and by adsorption experiments, showed that there was a correlation between selectivity and the presence of a well-dispersed CuCrO₂ phase, stabilized with barium. Moreover, the elements influencing the stability of the copper catalysts were also studied, and the promoter or/and the support increased the copper surface area and the stability of the catalyst in the presence of water or ammonia.     

A method for acceptability region representation in analogue linear networks

A new simple approach to acceptability region representation in analogue linear circuit design is presented. The proposed method is also able to characterize non‐convex and disjoint acceptability regions with low computational effort. In fact, the developed procedure is based on the use of symbolic analysis techniques, which permit one to perform only one simulation of the circuit under consideration, thus reducing the computational efforts. The theoretical basis and the algorithm implementing the technique are presented. A circuital example is also included. Copyright © 2008 John Wiley & Sons, Ltd.     

A new biquadratic topology for mosfet-C filters using non-balanced structures

A new topology for the realization of MOSFET-C integrated biquadratic filters is proposed which uses an MOS differentiator with non-balanced structures. an interesting characteristic of the new topology is the possibility of realizing lowpass, bandpass and highpass filters with a one-to-one relationship between the biquadratic parameters and the circuit elements. This characteristic allows the implementation of programmable switchable filters.     

Symbolic Techniques for the Selection of Test Frequencies in Analog Fault Diagnosis

In this work symbolic methods are used for implementing a procedure for the selection of test frequencies in multifrequency parametric fault diagnosis of analog linear circuits. The proposed approach is based on the evaluation of the condition number and the norm of a sensitivity matrix of the circuit under test. This matrix is determined by exploiting the testability and ambiguity group concepts. A Test Error Index (T.E.I.) is obtained which permits to select the set of frequencies which better leads to locate parametric faults in analog linear circuits. A program implementing the proposed procedure has been realized by using symbolic techniques. Examples of application are also included.     

A new multi-valued neural network for the extraction of lumped models of analog circuits

A novel identification technique for lumped models of general distributed circuits (i.e. microwave transmission lines, monolithic integrated circuits and filters) is presented. The approach is based on a hybrid multi-valued neuron neural network with a modified layer and learning process, whose convergence allows the validation of the approximated lumped model. The modified layer is generated by symbolic analysis of the model under exam. The inputs of the neural network are geometrical parameters, while the outputs represent the estimation of the lumped circuit parameters.