Toward nonlinear wave digital filters

The wave digital filter (WDF) theory provides us with a systematic methodology for building digital models of analog filters through the discretization of their individual circuit components. In some situations, WDF principles can also be successfully used for modeling circuits in which a nonlinear circuit element is present under mild conditions on its characteristic. We propose an extension of the classic WDF principles, which allows us to considerably extend the class of nonlinear elements that can be modeled in the wave digital domain. The method we propose is based on a new class of waves that can be chosen in such a may that incorporates the intrinsic dynamics of a nonlinear element into a new class of dynamic multiport adaptors. This family of junctions represents a generalization of the concept of “mutator” in the analog nonlinear circuit theory because it allows us to treat a nonlinear dynamic element as if it were instantaneous (resistive)     

Exact Schema Theory for Genetic Programming and Variable-Length Genetic Algorithms with One-Point Crossover

A few schema theorems for genetic programming (GP) have been proposed in the literature in the last few years. Since they consider schema survival and disruption only, they can only provide a lower bound for the expected value of the number of instances of a given schema at the next generation rather than an exact value. This paper presents theoretical results for GP with one-point crossover which overcome this problem. First, we give an exact formulation for the expected number of instances of a schema at the next generation in terms of microscopic quantities. Due to this formulation we are then able to provide an improved version of an earlier GP schema theorem in which some (but not all) schema creation events are accounted for. Then, we extend this result to obtain an exact formulation in terms of macroscopic quantities which makes all the mechanisms of schema creation explicit. This theorem allows the exact formulation of the notion of effective fitness in GP and opens the way to future work on GP convergence, population sizing, operator biases, and bloat, to mention only some of the possibilities.     

Tests on joints between steel and graphite

Abstract

Under a research programme devoted to the study of metalceramic joints, which are of considerable importance in the field of advanced technology, various tests were performed on joining carbon steel to graphite by brazing with different filler metals.

The results of each test are reported, with particular emphasis on the quality of the welded joint. The structural stability of the joints was also verified by long term annealing treatments at high temperature (850°C).     

Analogue evolutionary brain computer interfaces [Application Notes]

The keyboard is a device that, with its many switches, provides us with an interface that is reliable but also very unnatural. The mouse is only slightly less primitive, being an electro-mechanical transducer of musculoskeletal movement. Both have been with us for decades, yet they are unusable for people with severe musculoskeletal disorders and are themselves known causes of work-related upperlimb and back disorders, both hugely widespread problems [1], [2]. It will be a major contribution to computer interface technology one day to be able to replace mouse and keyboard with Brain-Computer Interfaces (BCIs) capable of directly interpreting the desires and intentions of computer users.     

Design knowledge acquisition for DFM methodologies

Design for Manufacturability (DFM) is a philosophy that encourages the communication of manufacturing information at the earliest stages of design in order to design parts and products that can be produced with greater ease and economy. This paper discusses the extensive experience gathered during the development of several DFM models in order to draw some conclusions and express some concerns that should be of interest to all those who develop or use manufacturing models that rely on design knowledge acquisition of knowledge from domain experts and/or industrial sites.     

Tomato purèe quality from transgenic processing tomatoes

Summary  The quality of tomato purèe prepared from transgenic fruits ( Lycopersicon esculentum ) which had reduced amounts of polygalacturonase (PG) activity, were evaluated. The application of genetic modification yields products which have lower Bostwick consistency values (from 35 to 55%), reduced serum separation ( c . 40%) and better sensory appearance and acceptability in comparison with their conventional counterparts. A new way of producing high quality tomato products using genetically modified fruits together with mild heat treatments is described.     

Modeling of photonic crystal fiber Raman amplifiers

An accurate model has been developed to study photonic crystal fiber Raman amplifiers. The proposed approach calculates the Raman gain efficiency starting from the knowledge of the fiber cross-sectional characteristics, i.e., the geometric parameters and the germania concentration in the doped area. The model allows the study of the Raman amplification process in a photonic crystal fiber with any air-hole dimension and disposition, with or without a central doped area, as well as in standard single-mode fibers with an arbitrary refractive-index profile. This flexibility allows identification of the optimum values of the physical and geometrical photonic crystal fiber parameters, and thus it guarantees an efficient design for Raman amplifiers. For example, a Raman gain of 13.7 dB at 1554.8 nm has been obtained with a 6-km-long low-loss germania-doped triangular photonic crystal fiber with d//spl Lambda/=0.44 and /spl Lambda/=4.2 /spl mu/m.     

Modeling and control of expressiveness in music performance

Expression is an important aspect of music performance. It is the added value of a performance and is part of the reason that music is interesting to listen to and sounds alive. Understanding and modeling expressive content communication is important for many engineering applications in information technology. For example, in multimedia products, textual information is enriched by means of graphical and audio objects. In this paper, we present an original approach to modify the expressive content of a performance in a gradual way, both at the symbolic and signal levels. To this purpose, we discuss a model that applies a smooth morphing among performances with different expressive content, adapting the audio expressive character to the user's desires. Morphing can be realized with a wide range of graduality (from abrupt to very smooth), allowing adaptation of the system to different situations. The sound rendering is obtained by interfacing the expressiveness model with a dedicated postprocessing environment, which allows for the transformation of the event cues. The processing is based on the organized control of basic audio effects. Among the basic effects used, an original method for the spectral processing of audio is introduced.     

Characterization of α-carrageenan solution behavior by field-flow fractionation and multiangle light scattering

The salt mediated molecular conformation change of alpha (α)-carrageenan was studied in 0.1 M solutions of NaCl, NaI, and KCl. Asymmetric Field-Flow Fractionation with multiangle laser light scattering (AFFF/MALLS) detection was used to determine the average molecular weight, radius of gyration, and hydrodynamic radius which were in turn used to calculate the molecular density. In the presence of 0.1 M NaCl, an inert salt that does not promote gelation, α-carrageenan has a denser structure compared to κ-carrageenan of a similar molecular weight. A distinct and dramatic increase in the molecular weight (factor of 2) was observed for α-carrageenan in 0.1 M NaI compared to 0.1 M NaCl. This combined with only a slight change in the radius of gyration, suggests intermolecular interaction to a more compact structure (e.g., coaxial helices). A similar increase in molecular weight is observed in 0.1 M KCl, accompanied with an approximate 50% increase in the radius of gyration as well as an increase in polydispersity. This may also be attributed to intermolecular interaction with helix formation (coaxial or lateral) or may be due to K⁺ cations interacting with naturally occurring residual ι-carrageenan in the sample. As previously reported for other carrageenans the random coil to helix transition of α-carrageenan appears to be stabilized by K⁺ cation or I⁻ anion in an aqueous environment.