Elastic moduli of nanocrystallites in carbon fibers measured by in-situ X-ray microbeam diffraction

The in-plane Young’s modulus and the shear modulus of carbon nanocrystallites were investigated during in-situ tension tests of single carbon fibers by X-ray diffraction using the shift of the 10 band in the meridional direction and the change in the azimuthal width of the 002 reflection. The limiting value for the Young’s modulus was found to be 1140 GPa, which is higher than the value for graphite obtained from macroscopic specimens, but coincides with recent measurements on nanotubes. Furthermore, the shear modulus was evaluated using a uniform stress approach and was found to increase with increasing misorientation of the crystallites. It turns out that both the in-plane Young’s modulus and the shear modulus are not constant, but dependent on the orientation parameter.     

A new approach for kinetic modeling and optimization of rubber molding

Although extensive research has been carried out on the understanding of the complex vulcanization process, the influence of reversion through exposure time and temperature on the vulcanization degree remains unclear. Therefore, the main aim of this study was a novel optimization approach that can help the industrial practitioners to select the optimal operating parameters, exposure time, and molding temperature, to achieve desired vulcanization degree of selected product. Spheres of four different diameters (2.5, 5, 10, and 20 cm) were selected as test geometry for simulation and optimization of rubber molding. Obtained vulcanization rheometer data for commercially available rubber blend (NR/SBR) were fitted by a new modeling approach, dividing vulcanization curve into two fitting sets: curing and reversion. The heat transfer equations for chosen geometry were coupled with proposed kinetic model. A new temperature-dependent kinetic parameter x, as the maximal reversion degree, was introduced, enabling determination of the lowest operating molding temperature (T_min = 132.36 °C), preventing high reversion and overheating of the rubber product. The final optimization goal was assessment of the optimal temperature and vulcanization time dependence on the rubber products dimensions. Proposed models have precise prediction with R² values greater than 0.8328 and MAPE less than 2.3099%.     

Modeling and validation of a boost pressure actuation system,for a series sequentially turbocharged SI engine

An actuation system for flexible control of an advanced turbocharging system is studied. It incorporates a vacuum pump and tank that are connected to pulse width modulation controlled vacuum valves. A methodology for modeling the entire boost pressure actuation system is developed. Emphasis is placed on developing component models that are easily identified from measured data, without the need for expensive measurements.The models have physical interpretations that enable handling of varying surrounding conditions.The component models and integrated system are evaluated on a two stage series sequential turbo system with three actuators having different characteristics.Several applications of the developed system model are presented, including a nonlinear compensator for voltage disturbance rejection where the performance of the compensator is demonstrated on an engine in a test cell. The applicability of the complete system model for control and diagnosis of the vacuum system is also discussed.     

Analysis of an improved width-flow concept for the production of ribbed strips by cold rolling

In today's increasingly competitive business environment, companies must look for innovative solutions to survive the competition. In the metal forming industry the engineers are turning to new technologies in order to achieve the goals. One new innovative process is the macroscopic structuration of strips by cold rolling for use in light-weight constructions. Components with a macro-structured surface demonstrate - on the condition of equal weight - a higher area moment of inertia and consequently a higher stiffness than non-structured workpieces. The subjects presented in this paper refer to ribbed sheets produced in a cold-rolling process. Particularly the material flow into the rib pocket is studied in a simplified model as a function of different set-up parameters like tool geometry, deformation, and friction. The theoretical investigations are carried out by the upper-bound theory. The results are compared with an FEM-analysis.     

Symmetric Non-rigid Registration: A Geometric Theory and Some Numerical Techniques

This paper proposes ℒ₂- and information-theory-based (IT) non-rigid registration algorithms that are exactly symmetric. Such algorithms pair the same points of two images after the images are swapped. Many commonly-used ℒ₂ and IT non-rigid registration algorithms are only approximately symmetric. The asymmetry is due to the objective function as well as due to the numerical techniques used in discretizing and minimizing the objective function. This paper analyzes and provides techniques to eliminate both sources of asymmetry. This paper has five parts. The first part shows that objective function asymmetry is due to the use of standard differential volume forms on the domain of the images. The second part proposes alternate volume forms that completely eliminate objective function asymmetry. These forms, called graph-based volume forms, are naturally defined on the graph of the registration diffeomorphism f, rather than on the domain of f. When pulled back to the domain of f they involve the Jacobian J _f and therefore appear “non-standard”. In the third part of the paper, graph-based volume forms are analyzed in terms of four key objective-function properties: symmetry, positive-definiteness, invariance, and lack of bias. Graph-based volume forms whose associated ℒ₂ objective functions have the first three properties are completely classified. There is an infinite-dimensional space of such graph-based forms. But within this space, up to scalar multiple, there is a unique volume form whose associated ℒ₂ objective function is unbiased. This volume form, which when pulled back to the domain of f is (1+det(J _f )) times the standard volume form on Euclidean space, is exactly the differential-geometrically natural volume form on the graph of f. The fourth part of the paper shows how the same volume form also makes the IT objective functions symmetric, positive semi-definite, invariant, and unbiased. The fifth part of the paper introduces a method for removing asymmetry in numerical computations and presents results of numerical experiments. The new objective functions and numerical method are tested on a coronal slice of a 3-D MRI brain image. Numerical experiments show that, even in the presence of noise, the new volume form and numerical techniques reduces asymmetry practically down to machine precision without compromising registration accuracy.