Low resistive silicon substrate as an etch-stop layer for drilling thick SiO2 by spark assisted chemical engraving (SACE)

Controlling precisely the depth in glass micro-drilling by spark assisted chemical engraving (SACE) remains challenging, particularly for low depths. The possibility of using an electrically conductive material as an etch-stop layer for SACE gravity-feed drilling is investigated in this paper. Micromachining with constant DC and pulsed DC of 30–35 μm thick SiO₂ deposited on low resistive silicon substrate demonstrated the etch-stop function of the conductive silicon. Measurements of etch rates and hole profiles along with scanning electron microscope imaging revealed the mechanism underlying the etch-stop process. Low resistive silicon is demonstrated to be a good etch-stop layer for SACE gravity-feed drilling. Demonstration of machining of SiO₂ layer on silicon as a substrate and an etch-stop layer opens up new possibilities to adapt SACE for developing devices on silicon platform.     

The potential for large-scale savings from insulating residential buildings in the EU

Energy used in buildings is responsible for more than 40% of energy consumption and greenhouse gas (GHG) emissions of the EU and their share in cost-efficient GHG mitigation potentials is estimated to be even higher. In spite of its huge savings potential of up to 80%, achievements are very slow in the building sector and much stronger political action seems to be needed. One important step in this direction has been the recast of the Energy Performance of Buildings Directive (EPBD) in autumn 2009. However, strong national implementation including powerful packages of flanking measures seems to be crucial to really make significant progress in this important field. In order to directly improve political action, we provide a differentiated country-by-country bottom up simulation of residential buildings for the whole EU, Norway, Iceland, Croatia and Liechtenstein. The analysis provides a database of the building stock by construction periods, building types, as well as typical building sizes. It includes a simulation of the thermal quality and costs of the components of the building shell for new buildings as well as the refurbishment of the existing building stock. Based on this differentiated analysis, we show in detail what would be needed to accelerate energy savings in the building sector and provide a more precise estimate of the potentials to be targeted by particular policies. We demonstrate, e.g. that the potential of building codes set via the EPBD would be located mainly in those countries that already have quite stringent codes in place. We show as well the high relevance of accelerating refurbishments and re-investment cycles of buildings. By providing a clear estimate of the full costs related to such a strategy, we highlight a major obstacle to accelerated energy-efficient building renovation and construction.     

Parameter identification and shape optimization

Simulation of metal forming processes using the Finite Element Method (FEM) is a well established procedure, being nowadays possible to develop alternative approaches, such as inverse methodologies, in solving complex problems. In the present paper, two types of inverse approaches will be discussed, namely the parameter identification and the shape optimization problems. The aim of the former is to evaluate the input parameters for material constitutive models that would lead to the most accurate set of results respecting physical experiments. The second category involves determining the initial geometry of a given specimen leading to a desired final geometry after the forming process. The purpose of the present work is then to formulate these inverse problems as optimization problems, introducing a straightforward methodology of process optimization in engineering applications such as metal forming and structural analysis. To reach this goal, an integrated optimization approach, using a finite element code together with a numerical optimization program, was employed. A gradient-based optimization method, as a combination of the steepest-descent method and the Levenberg-Marquardt techniques, was used. Numerical applications in the parameter optimization category include, namely, the characterization of a non-linear elasto-plastic hardening model and the determination of the parameters for a nonlinear hyperelastic model. It is also discussed the simultaneous identification of both constitutive material model parameters and the friction coefficient parameters. From the point of view of shape optimization problems, the determination of the initial geometry of a specimen in a upsetting billing problem as well as a methodology for defining the most suited blank shape to be formed in a square cup, are discussed. The final results for both categories show that this kind of algorithms have great potential for future developments in more demanding and realistic benchmarks. It is also worth noting that the presented integrated methodology can be easily applied to a first introduction of optimization techniques and numerical simulation to undergraduate courses in engineering.     

Comparison of Drying Kinetics for Small Fruits with and without Particle Shrinkage Considerations

Experimental values of volume and area changes for sweet (Prunus avium) and sour (Prunus cerasus) cherry and rose hips (Rosa rubiginosa) measured in previous works were analyzed to propose generalized correlations for the three fruits which predicted with low errors. The correlation developed is lineal and the highest errors were observed for fruit water contents corresponding to storage stability values. The shape factors were measured for the fruits, which were close to spherical values as the fruits dried. This would enable the assumption of spherical shape to calculate characteristic dimensions used in modeling. Moreover, the predictions of kinetic models were compared with experimental data for three radii: the initial, assumed constant; variable, estimating the radius with the correlations published for each fruit; and variable, calculating the radius with the generalized correlation developed in this work. The RMSE between the experimental data and the predictions by the kinetic model were between 0.321 and 0.562; 0.021 and 0.111; and 0.020 and 0.093, respectively.     

Large Time Step Finite Volume Evolution Galerkin Methods

We present two new large time step methods within the framework of the well-balanced finite volume evolution Galerkin (FVEG) schemes. The methodology will be illustrated for low Froude number shallow water flows with source terms modeling the bottom topography and Coriolis forces, but results can be generalized to more complex systems of balance laws. The FVEG methods couple a finite volume formulation with approximate evolution operators. The latter are constructed using the bicharacteristics of multidimensional hyperbolic systems, such that all of the infinitely many directions of wave propagation are taken into account explicitly. We present two variants of large time step FVEG method: a semi-implicit time approximation and an explicit time approximation using several evolution steps along bicharacteristic cones.     

Pick-by-vision: there is something to pick at the end of the augmented tunnel

We report on the long process of exploring, evaluating and refining augmented reality-based methods to support the order picking process of logistics applications. Order picking means that workers have to pick items out of numbered boxes in a warehouse, according to a work order. To support those workers, we have evaluated different HMD-based visualizations in six user studies, starting in a laboratory setup and continuing later in an industrial environment. This was a challenging task, as we had to conquer different kinds of navigation problems from very coarse to very fine granularity and accuracy. The resulting setup consists of a combined and adaptive visualization to precisely and efficiently guide the user even if the actual picking target is not always in the field of view of the HMD.