The value function of an asymptotic exit-time optimal control problem

We consider a class of exit--time control problems for nonlinear systems with a nonnegative vanishing Lagrangian. In general, the associated PDE may have multiple solutions, and known regularity and stability properties do not hold. In this paper we obtain such properties and a uniqueness result under some explicit sufficient conditions. We briefly investigate also the infinite horizon problem

Tools in the orbit space approach to the study of invariant functions: rational parametrization of strata

Functions which are equivariant or invariant under the transformations of a compact linear group $G$ acting in an euclidean space $\real^n$, can profitably be studied as functions defined in the orbit space of the group. The orbit space is the union of a finite set of strata, which are semialgebraic manifolds formed by the $G$-orbits with the same orbit-type. In this paper we provide a simple recipe to obtain rational parametrizations of the strata. Our results can be easily exploited, in many physical contexts where the study of equivariant or invariant functions is important, for instance in the determination of patterns of spontaneous symmetry breaking, in the analysis of phase spaces and structural phase transitions (Landau theory), in equivariant bifurcation theory, in crystal field theory and in most areas where use is made of symmetry adapted functions. A physically significant example of utilization of the recipe is given, related to spontaneous polarization in chiral biaxial liquid crystals, where the advantages with respect to previous heuristic approaches are shown.Comment: Figures generated through texdraw package; revised version appearing in J. Phys. A: Math. Ge

Avaliação de parâmetros ergonômicos : ruído e temperatura no posto operacional de tratores agrícolas

O surgimento de máquinas e implementos utilizados na agricultura mudaram definitivamente as técnicas de produção em todo o mundo, de forma que o aumento da produtividade deste setor levou o homem a ser substituído pelas máquinas a fim de possibilitar o acesso a novas prácas na agricultura. A realização de uma operação segura com trator agrícola é essencial, sendo necessário que o operador tenha o conhecimento de algumas medidas gerais de segurança. Este trabalho foi realizado com o objevo de analisar o ruído e a temperatura como risco fisico no interior da cabine de um trator, considerando os limites de tolerância permitidos pela Norma Regulamentadora 15 (Atividades e Operações Insalubres) e 17 (Ergonomia).ABSTRACT : The emergence of machines and agricultural implements used in agriculture had definitively changed the techniques of production in the whole world, so that the increase of the productivity of this sector took the man to be substituted for the machines in order to make possible the access the new practices in agriculture. The accomplishment of a safe operation with agricultural tractor is essential, being the necessary that the operator has the knowledge of some general measures of security. This work was accomplished with the aim to analyse noise and temperature as physical risk in the interior of the cabin of a tractor, Unhealthy considerando the limits of tolerance allowed by Regulator Norm 15 (Activities and Operations) and 17 (Ergonomics).info:eu-repo/semantics/publishedVersio

Design issues of a standard cell BiCMOS carrier transceiver on low voltage power lines

In this paper are described some of the issues of the mixed signal standard cell VLSI design with emphasis on the practical experience resulted from designing a carrier transceiver in SGS-THOMSON 2 μm BiCMOS technology. Presented are the circuit block structure, some advantages and disadvantages of the standard cell design approach, the testing strategy we implemented, and finally some practical conclusions resulting from our experience

Sol-gel synthesis of spherical monodispersed bioactive glass nanoparticles co-doped with boron and copper

In this work, an optimized sol-gel process for the synthesis of spherical and monodispersed bioactive glass nanoparticles doped with boron and copper was developed, by investigating different synthesis parameters. The obtained glasses were characterized in terms of morphology, composition, dispersibility, structure and in vitro reactivity. The performed characterizations demonstrated that shape, dimension and dispersion can be tailored by acting on the timing of the addition of the catalyst and on the synthesis process, in particular the centrifugation step. The optimized glass particles showed a spherical shape, good ions incorporation and good dispersion. In vitro bioactivity test demonstrated that the boron and copper addition did not interfere with the glass ability to induce the precipitation of hydroxyapatite. The shape, dispersion, bioactive behavior and content of boron and copper of these novel bioactive glass particles make them very promising for both hard and soft tissue engineering applications

Sol-gel synthesis of spherical monodispersed bioactive glass nanoparticles co-doped with boron and copper

In this work, an optimized sol-gel process for the synthesis of spherical and monodispersed bioactive glass nanoparticles doped with boron and copper was developed, by investigating different synthesis parameters. The obtained glasses were characterized in terms of morphology, composition, dispersibility, structure and in vitro reactivity. The performed characterizations demonstrated that shape, dimension and dispersion can be tailored by acting on the timing of the addition of the catalyst and on the synthesis process, in particular the centrifugation step. The optimized glass particles showed a spherical shape, good ions incorporation and good dispersion. In vitro bioactivity test demonstrated that the boron and copper addition did not interfere with the glass ability to induce the precipitation of hydroxyapatite. The shape, dispersion, bioactive behavior and content of boron and copper of these novel bioactive glass particles make them very promising for both hard and soft tissue engineering applications

Linear-logarithmic CMOS pixel with tunable dynamic range

Abstract—A CMOS pixel with linear–logarithmic response and programmable dynamic range (DR), based on a tunable transition point, has purposely been designed for endoscopic applications. A theoretical model of the pixel was developed and validated. A chip with a 100 × 100 pixel array and a 12-b digital output was fabricated in a 0.35-μm technology and was fully tested, thus demonstrating state-of-the-art performance in terms of DR and noise. Intraframe DR proved to be extendable to more than 110 dB through a logarithmic compression of the signal in the light ir-radiation power density (LIPD) range. The measured temporal noise (pixel noise) was less than 0.22 % over the full range. The architecture presented limited fixed pattern noise (FPN) due to the scheme adopted, which allowed its correction over the full signal range: FPN was 0.83 % (1.37%) in the linear (logarithmic) region. Although the test chip was designed mainly for endoscopic applications, the technology may also be applied to other fields, e.g., robotics, security and industrial automation, whenever high DR is a crucial feature. Index Terms—CMOS imager, endoscopy, logarithmic response, pixel. I