Characterization of a High-Temperature Thermal Conductivity Reference Material

The development of thermal conductivity reference materials for high-temperature insulation consists of three stages: provisional assessment of candidate reference materials, detailed assessment of candidate reference material(s) and corresponding inter-laboratory comparisons. This paper describes the detailed characterization of a candidate high-temperature thermal conductivity reference material, a high-density calcium silicate (HDCaSi-N). The selection criteria, assessments of uniformity and stability, the thermal expansion behavior and their effects on the thermal conductivity reference specimens are presented in the paper. The uniformity assessments include the thermal expansion variation in orthogonal orientations and different locations and from different boards, as well as thermal conductivity variation within the batch of the specimens. The dimensional stability assessment in terms of thermal expansion and the short-term stability in terms of thermal conductivity are also presented.     

Robust production planning and control for multi-stage systems with flexible final assembly lines

Production planning of final assembly systems is a challenging task, as the often fluctuating order volumes require flexible solutions. Besides, the calculated plans need to be robust against the process-level disturbances and stochastic nature of some parameters like manual processing times or machine availability. In the paper, a simulation-based optimisation method is proposed that utilises lower level shop floor data to calculate robust production plans for final assembly lines of a flexible, multi-stage production system. In order to minimise the idle times when executing the plans, the capacity control that specifies the proper operator–task assignments is also determined. The analysed multi-stage system is operated with a pull strategy, which means that the production at the final assembly lines generates demands for the preceding stages providing the assembled components. In order to guarantee the feasibility of the plans calculated for the final assembly lines, a decomposition approach is proposed to optimise the production plan of preceding stages. By this way, the robust production can be ensured resulting in reduced losses and overall production costs even though the system is exposed to changes and disturbances.     

Effect of Combined Natural Antimicrobials on Spoilage Microorganisms and Listeria Innocua in a Whey Cheese “Ricotta”

The effect of nisin alone and in combination with Microgard? on the natural microbial flora of ricotta cheese and in post-process contamination with Listeria innocua was studied. Microbial groups studied were mesophilic, psychrotrophic, proteolytic, lactic acid and coliform bacteria, and total molds and yeasts. Considering the evolution of all microbial groups and failure criteria adopted for mesophilic and coliform bacteria, this product reached the end of its shelf life before 5 days, which is insufficient time for product commercialization. The combined use of nisin and Microgard? proved to be more effective than the individual application on these microbial groups, resulting in a 13 days shelf life extension. Additionally, the combined treatment reduced the growth of L. innocua as a post-process contamination.     

A bill of materials-based approach for end-of-life decision making in design for the environment

Re-use, recycling or remanufacturing of products and components are good alternatives for reducing the environmental problems resulting from the huge amounts of waste currently arriving at landfills. A new approach is proposed in this paper for enhancing these alternatives from the earliest stages of product design. Given the product structure (obtained from its bill of materials (BOM)) and the joining and geometrical relationships among the components (obtained from the three-dimensional, computer-aided design representation), a model is proposed that will determine the EOL (EOL) strategy, i.e. the depth of disassembly inside the structure and the final end (re-use, recycle, remanufacture or disposal) for each disassembled part leading to the highest profit. A scatter search (SS) metaheuristic is used to determine the disassembly cost at each level of the BOM. The model presents a number of major improvements with respect to previous research. It addresses the problems of simultaneously determining both the best EOL strategy and the disassembly sequence, as well as allowing removal of components not only over the two or three Cartesian axes and affording the possibility of modifying the encountered strategy in a further step so as to fulfil other business criteria (such as disassembly time, resources availability or maximum waste generation rate).     

Parallelization of the FMM on distributed-memory GPGPU systems for acoustic-scattering prediction

In this work, we carry out the parallelization of the single level Fast Multipole Method (FMM) for solving acoustic-scattering problems (using the Helmholtz equation) on distributed-memory GPGPU systems. With the aim of enlarging the scope of feasible simulations, the presented solution combines the techniques developed for our distributed-memory CPU solver with our shared-memory GPGPU solver. The performance of the developed solution is proved using two different GPGPU clusters: the first one consists of two workstations with NVIDIA GTX 480 GPUs linked by a Gigabit Ethernet network, and the second one comprises four nodes with NVIDIA Tesla M2090 GPUs linked by an Infiniband network.     

Regional differences in price levels across the European Union and their implications for its regional policy

Although regional price levels should be accounted for in any analysis of well-being in regions, the European Union fails to reflect them because they are not currently available for most EU member states. To fill this gap, we estimate regional price levels for all EU regions on the basis of available regional price level data from six EU countries. Once socio-economic indicators are recalculated using our estimates, substantially higher differences in living standards emerge. These results also have important implications for the European cohesion policy, with 9% of regions currently misclassified as a consequence of regional price levels not being used.     

Application of digital image correlation at the microscale in fiber-reinforced composites

Digital image correlation (DIC) is applied to analyzing the deformation mechanisms under transverse compression in a fiber-reinforced composite. To this end, compression tests in a direction perpendicular to the fibers were carried out inside a scanning electron microscope and secondary electron images obtained at different magnifications during the test. Optimum DIC parameters to resolve the displacement and strain field were computed from numerical simulations of a model composite and they were applied to micrographs obtained at different magnifications (250×, 2000×, and 6000×). It is shown that DIC of low-magnification micrographs was able to capture the long range fluctuations in strain due to the presence of matrix-rich and fiber-rich zones, responsible for the onset of damage. At higher magnification, the strain fields obtained with DIC qualitatively reproduce the non-homogeneous deformation pattern due to the presence of stiff fibers dispersed in a compliant matrix and provide accurate results of the average composite strain. However, comparison with finite element simulations revealed that DIC was not able to accurately capture the average strain in each phase.     

Comparative behavior of glucose oxidase and oxalate oxidase immobilized in mucin/chitosan hydrogels for biosensors applications

The analytical response of amperometric glucose electrodes was explained in the framework of the properties of hydrogels with different muc/chit ratio at pH = 7.00 used as immobilization matrix for glucose oxidase. The continuous increase in the sensitivity of the electrodes with the amount of chitosan was attributed to a more efficient crosslinking without affecting the enzyme activity. The results were compared with those obtained using the same matrices to immobilize Oxalate Oxidase at pH = 2.85 where it has the highest activity. A maximum sensitivity at muc/chit 70/30 ratio for these oxalate electrodes was observed. Decrease in permeability of negatively charged oxalate with the chitosan content in the matrices, in spite of the high partition coefficient, explains the analytical differences with glucose electrodes. Swelling and viscoelasticity of the hydrogels allowed to asses the importance of a hydrophilic environment for the enzyme in both cases.