A finite differences MATLAB code for the numerical solution of second order singular perturbation problems

We show the main features of the MATLAB code HOFiD_UP for solving second order singular perturbation problems. The code is based on high order finite differences, in particular on the generalized upwind method. Within its simplicity, it uses order variation and continuation for solving any difficult nonlinear scalar problem. Several numerical tests on linear and nonlinear problems are considered. The best performances are reported on problems with perturbation parameters near the machine precision, where most of the codes for two-point BVPs fail.     

Determination of wine aroma compounds by dehydration followed by GC/MS

A new extraction method for the analysis of the volatile fraction of white and red wines has been developed and validated. A dehydration step with MgSO4 separated an aroma compounds-rich alcoholic-glycerine layer. Spiked samples showed good recoveries in the range between 75 and 120% with CVmax% of 17, except for 2-phenylethanol and y-butyrolactone for which recoveries in red wines were under 60%, and for monoethylsuccinate, where recoveries averaged 50 and 60% in white and red wines, respectively. Method repeatability and intermediate precision showed good CVmax% with minimum and maximum values between 7.7 and 24, and between 18.7 and 25.0, respectively. The average determination coefficients were greater than 0.99 with CVmax% of 13. The instrumental LOD and LOQ were, in all cases, under 0.05 mg/L, except for 2,3 butanediol (0.20 mg/L). Overall, the presence of wine matrix affected aroma compounds responses in GC/MS analysis. These observations indicate that the use of a matrix-matched calibration curve is mandatory to obtain reliable quantitative data.     

Side-chain liquid crystalline polyesters for optical information storage

Azobenzene side-chain liquid crystalline polyester structures suitable for permanent optical storage are described. The synthesis and characterization of the polyesters together with differential scanning calorimetry and X-ray investigations are discussed. Optical anisotropic investigations and holographic storage in one particular polyester are described in detail and polarized Fourier transform infrared spectroscopic data complementing the optical data are presented. Optical and atomic force microscope investigations point to a laser-induced aggregation as responsible for permanent optical storage.     

Extended Fuzzy C-Means and Genetic Algorithms to Optimize Power Flow Management in Hybrid Electric Vehicles

The need for personal transportation must be harmonized by considering the impact of so huge number of vehicles on the environment. The adoption of hybrid electric vehicles can provide a sensible improvement from an environmental viewpoint, but at the same time makes more difficult the definition and implementation of the overall powertrain control mechanism. In fact, powertrain control problems are known to be very complex due to conflicting requirements, and this difficulty augments in case of hybrid electric vehicles. Most of the features of the future hybrid electric vehicles are enabled by a new energy flow management unit designed to split the instantaneous power demand between the internal combustion engine and the electric motor, ensuring both an efficient power supply and reduced emissions. Classic approaches that rely on static thresholds, optimized on a fixed drive cycle, cannot face the high dynamicity and unpredictability of real-life drive conditions. The need to actually control a real vehicle stimulates the research of innovative methodologies for the real-time identification of the operating points of each energy source. This paper is framed into this context: after a brief discussion about a non-conventional formalization of the energy flows problem based on a multiobjective function, a knowledge-based control system for splitting the vehicle's power demand between the engine and motor is presented. The proposed approach exploits a fuzzy clustering criterion that combined with a genetic algorithm, permits to achieve better results, both in terms of a reduced computational effort and an improved efficiency of the control system over various driving cycles. To validate the proposed approach, simulation tests and comparisons with other energy management strategies are discussed.     

Correlation Inequalities for Spin Glasses

We prove a correlation type inequality for spin systems with quenched symmetric random interactions. This gives monotonicity of the pressure with respect to the strength of the interaction for a class of spin glass models. Consequences include existence of the thermodynamic limit for the pressure and bounds on the surface pressure. We also describe other conjectured inequalities for such systems. Submitted: January 6, 2007. Accepted: May 10, 2007.     

Parallel ODE solvers based on block BVMs

In this paper we deal with Boundary Value Methods (BVMs), which are methods recently introduced for the numerical approximation of initial value problems for ODEs. Such methods, based on linear multistep formulae (LMF), overcome the stability limitations due to the well-known Dahlquist barriers, and have been the subject of much research in the last years. This has led to the definition of a new stability framework, which generalizes the one stated by Dahlquist for LMF. Moreover, several aspects have been investigated, including the efficient stepsize control [17,25,26] and the application of the methods for approximating different kinds of problems such as BVPs, PDEs and DAEs [7,23,41]. Furthermore, a block version of such methods, recently proposed for approximating Hamiltonian problems [24], is able to provide an efficient parallel solver for ODE systems [3].     

Nonlinear evolution inclusions arising from phase change models

The paper is devoted to the analysis of an abstract evolution inclusion with a non-invertible operator, motivated by problems arising in nonlocal phase separation modeling. Existence, uniqueness, and long-time behaviour of the solution to the related Cauchy problem are discussed in detail. The Italian authors would like to point out financial support from theMIUR-COFIN 2002 research program on “Free boundary problems in applied sciences”. The second author was supported by GA ČR under Grant No. 201/02/1058, and by GNAMPA of INDAM during his stay at Pavia in May 2003: in this respect, the kind hospitality of the Department of Mathematics in Pavia is gratefully acknowledged as well. The work also benefited from partial support of the IMATI of CNR in Pavia, Italy.