Calibration procedure for 3D measurement systems using two cameras and a laser line

In order to ensure the precision of the measurement of complex 3D object surfaces using non-contact laser scanning systems, a novel stereo vision calibration procedure based on a laser line projection plane is presented. This calibration procedure can also be used in measurement systems based on a single camera and a laser line projection. This procedure, while using only laser-coplanar points, is oriented towards laser line detection and allows the matching of two images on the laser projection plane without the use of a rigid motion equation. These features make this procedure very precise, simple and, consequently, easier to implement.     

On necessary conditions for state constrained problems

Necessary conditions of optimality in the form of Unmaximized Inclusions (UI) were derived for optimal control problems with pathwise state inequality constraints. An approach similar to that used to derive such type of necessary conditions can be followed to obtain relaxation of hypotheses previously imposed on the regularity of the state constraint function. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Model based optimization of a statistical simulation model for single diamond grinding

We present a model for simulating normal forces arising during a grinding process in cement for single diamond grinding. Assuming the diamond to have the shape of a pyramid, a very fast calculation of force and removed volume can be achieved. The basic approach is the simulation of the scratch track. Its triangle profile is determined by the shape of the diamond. The approximation of the scratch track is realized by stringing together polyhedra. Their sizes depend on both the actual cutting depth and an error implicitly describing the material brittleness. Each scratch track part can be subdivided into three three-dimensional simplices for a straightforward calculation of the removed volume. Since the scratched mineral subsoil is generally inhomogeneous, the forces at different positions of the workpiece are expected to vary. This heterogeneous nature is considered by sampling from a Gaussian random field. To achieve a realistic outcome the model parameters are adjusted applying model based optimization methods. A noisy Kriging model is chosen as surrogate to approximate the deviation between modelled and observed forces. This deviation is minimized and the results of the modelled forces and the actual forces from conducted experiments are rather similar.     

The pyrolysis of isoxazole revisited: a new primary product and the pivotal role of the vinylnitrene. A low-temperature matrix isolation and computational study

This paper describes the pyrolysis of parent isoxazole and of its 5-methyl and 3,5-dimethyl derivatives by the high-pressure pulsed pyrolysis method, where activation of the precursor molecules occurs predominantly by collisions with the host gas (Ar in our case), rather than with the walls of the pyrolysis tube, where catalyzed processes may occur. The products were trapped at 15 K in Ar matrices and were characterized by vibrational spectroscopy. Thereby, hitherto unobserved primary products of pyrolysis of isoxazole and of its 5-methyl derivative, 3-hydroxypropenenitrile or 3-hydroxybutenenitrile, respectively, were observed. E-Z photoisomerization could be induced in the above hydroxynitriles. On pyrolysis of isoxazole, ketenimine and CO were observed as decomposition products, but this process did not occur when the 5-methyl derivative was pyrolyzed. Instead, the corresponding ketonitrile was formed. In the case of 3,5-dimethylisoxazole, 2-acetyl-3-methyl-2H-azirine was detected at moderate pyrolysis temperatures, whereas at higher temperatures, 2,5-dimethyloxazole was the only observed rearrangement product (next to products of dissociation). These findings are rationalized on the basis of quantum chemical calculations. Thereby it becomes evident that carbonyl-vinylnitrenes play a pivotal role in the observed rearrangements, a role that had not been recognized in previous theoretical studies because it had been assumed that vinylnitrenes are closed-shell singlet species, whereas they are in fact open-shell singlet biradicaloids. Thus, the primary processes had to be modeled by the multiconfigurational CASSCF method, followed by single-point MR-CISD calculations. The picture that emerges from these calculations is in excellent accord with the experimental findings; that is, they explain why some possible products are observed while others are not.     

Amperometric sensor based on carbon nanotubes and electropolymerized vanillic acid for simultaneous determination of ascorbic acid,dopamine, and uric acid

This paper describes the development of a simple and efficient nanostructured platform based on multi-walled carbon nanotubes (MWCNT) functionalized with an in situ generated vanillic acid (VA) polymer. It was used as an analytical sensor for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electropolymerization process of VA, performed on MWCNT-modified glassy carbon electrode, produces three redox systems based on quinone/hydroquinone functionality, as observed by cyclic voltammetry. The amperometric sensor has as figures of merit for the simultaneous determination of AA, DA, and UA the following values: for AA, a linear range of 5–120 μM and detection limit of 3.5 μM; for DA, a linear range of 5–120 μM and detection limit of 4.5 μM; and for UA, a linear range of 5–120 μM and a detection limit of 1.5 μM. From the obtained performance, the development of the platform based on MWCNT/poly-VA is justified for the simultaneous determination of AA, DA, and UA.     

Evaluation of mitochondrial respiratory chain activity in wound healing by low-level laser therapy

Laser therapy is used in many biomedical sciences to promote tissue regeneration. Many studies involving low-level laser therapy have shown that the healing process is enhanced by such therapy. In this work, we evaluated mitochondrial respiratory chain complexes II and IV and succinate dehydrogenase activities in wounds after irradiation with low-level laser. The animals were divided into two groups: group 1, the animals had no local nor systemic treatment and were considered as control wounds; group 2, the wounds were treated immediately after they were made and every day after with a low-level laser (AsGa, wavelength of 904 nm) for 10 days. The results showed that low-level laser therapy improved wound healing. Besides, our results showed that low-level laser therapy significantly increased the activities of complexes II and IV but did not affect succinate dehydrogenase activity. These findings are in accordance to other works, where cytochrome c oxidase (complex IV) seems to be activated by low-level laser therapy. Besides, we showed, for the first time, that complex II activity was also activated. More studies are being carried out in order to evaluate other mitochondrial enzymes activities after different doses and irradiation time of low-level laser.     

Mixed constraints in optimal control: an implicit function theorem approach

^** Email: mrpinho{at}fe.up.pt^*** Corresponding author. Email: jfrl{at}servidor.unam.mx This paper concerns a derivation of second-order necessary conditionsfor a fixed-endpoint control problem of Lagrange involving mixedequality and/or inequality constraints, posed over piecewisecontinuous controls. These conditions are obtained in a clearand transparent way by reducing the original problem, throughan implicit function theorem approach, to an unconstrained controlproblem.     

Combustion of slugs of propane and air moving up through an incipiently fluidized bed

A mathematical model is proposed to show the evolution of temperature, chemical composition and energy release or transfer in slugs, clouds and particulate phase, in a fluidized bed where there are slugs, of a mixture of air and propane, moving up through the particulate phase previously set in the state of incipient fluidization with air. The analysis begins as the slugs are formed at the orifices of the distributor, until they explode inside the bed or emerge at the free surface. The model also makes the analysis of what happens in the gaseous mixture that leaves the free surface of the fluidized bed until the propane is thoroughly burnt. It is essentially built upon a simple quasi-global mechanism for the combustion reaction and the mass and heat transfer equations from the two-phase model of fluidization. The aim was not to propose a new modelling approach, but to combine classical models, one concerning the reaction kinetics and the other the bed hydrodynamic aspects, to obtain a better insight on the events occurring inside a fluidized bed reactor, enhancing the understanding of this type of reactor. Experimental data to balance with the numerical model were obtained through tests on the combustion of commercial propane, in a laboratory scale fluidized bed, using four sand particle sizes: 400–500, 315–400, 250–315 and 200–250 μ m. The mole fractions of CO₂, CO and O₂ in the flue gases and the temperature of the fluidized bed were measured and compared with the numerical results.     

A Reynolds stress model for turbulent flows of viscoelastic fluids

A second-order closure is developed for predicting turbulent flows of viscoelastic fluids described by a modified generalised Newtonian fluid model incorporating a nonlinear viscosity that depends on a strain-hardening Trouton ratio as a means to handle some of the effects of viscoelasticity upon turbulent flows. Its performance is assessed by comparing its predictions for fully developed turbulent pipe flow with experimental data for four different dilute polymeric solutions and also with two sets of direct numerical simulation data for fluids theoretically described by the finitely extensible nonlinear elastic – Peterlin model. The model is based on a Newtonian Reynolds stress closure to predict Newtonian fluid flows, which incorporates low Reynolds number damping functions to properly deal with wall effects and to provide the capability to handle fluid viscoelasticity more effectively. This new turbulence model was able to capture well the drag reduction of various viscoelastic fluids over a wide range of Reynolds numbers and performed better than previously developed models for the same type of constitutive equation, even if the streamwise and wall-normal turbulence intensities were underpredicted.