Accuracy analysis of a covariance matching approach for identifying errors-in-variables systems

A system identification method for errors-in-variables problems based on covariance matching was recently proposed. In the first step, a small amount of covariances of noisy input–output data are computed, and then a parametric model is fitted to these covariances. In this paper, the method is further analyzed and the asymptotic accuracy of the parameter estimates is derived. An explicit algorithm for computing the asymptotic covariance matrix of the parameter estimates is given, and the identification method is shown to be asymptotically statistically efficient assuming that the given information is the computed covariances. As an important byproduct, an efficient algorithm is presented for computing the covariance matrix of the computed input–output covariances.     

THE STABILITY OF WET SPOUTED BEDS

In granulation, coating or drying of slurries on inert particles a liquid phase is added to a gas-spouted bed. The effect of liquid injection on spouting velocity, fountain height, bed pressure drop and stability of the spouting regime is examined in a 0.15 m diameter bed with four types of inert particles 2 to 5 mm in size, 1140 to 2880 kg/m³ in true density, and 1.3 and 1400 mPa·s in liquid viscosity. Key factors are the liquid content and the presence of cohesive forces due to liquid bonds between particles. In a spoutability chart the maximum spoutable liquid content is related to the ratio of inertial force of a particle to the viscous or cohesive force exerted onto the particle by the liquid film. The spoutability chart serves to define regions of stable spouting.     

Nonlinear buckling analysis of vertical wafer probe technology

Due to the demand of the industry for an increase of the number of I/Os, while decreasing the die size, the bond pads had to shrink and design restrictions for the active structures underneath had to fall. This leads to new challenges for the electrical probing and the mechanical robustness of the under-pad structures. This paper presents analytical and numerical simulation approaches for predicting the force/travel relation of buckling beam-probes that are used for testing the electrical functionality of back-end-of-line (BEOL) interconnect system underneath a chip pad. For this purpose we investigate, first, in a closed-form manner, the elastic stability of the probe needle according to the large deflection theory of buckled bars. Second, we determine, for a specific geometry of the beam, the probe forces as functions of the probe card overdrive by using the closed-form methods as well as finite-element simulations. The results are finally compared to that obtained in (probe card) experiments.     

Elevated temperature X-ray measurement of residual stresses in a fibre reinforced Al alloy

Thermal residual stresses have been measured using X-ray diffraction in an Al-2% Mg matrix with 10, 20 or 26 vol % Al₂O₃ short fibres. Stress measurements were made at room temperature as well asin situ at elevated temperatures up to 250?C. The thermal stresses arise due to the difference in coefficient of thermal expansion (CTE) between the matrix and the reinforcement. The largest CTE is found in the matrix, resulting in tensile residual stresses after a temperature drop, e.g. after processing or annealing. A high fraction of reinforcement implies higher matrix stresses than a low fibre content. The stresses decrease with increasing temperature for all fibre volume fractions. Measurements are compared with calculations using a modified Eshelby model for equivalent inclusions. Parameters taken into account in the model are coefficient of thermal expansion, Young's modulus, and volume fraction and geometric shape of the reinforcing phase. A good correlation between calculations and experimental results has been found, bearing in mind that no plasticity is taken into account in the Eshelby model. The plastic behaviour of the composites has been described using a model based on a rigid spherical cavity in an elastic-plastic matrix.     

Modelling of a fluidized bed bioreactor for immobilized enzymes (Part 2)

In the first part of this contribution, a mathematical model was presented for a liquid fluidized bed using immobilized enzymes, with reversible Michaelis-Menten kinetics. This part is focused on the experimental results. The reaction kinetics of native and immobilized enzymes was determined in continuous stirred tank reactors under comparable conditions. The influence of external mass transfer was investigated in a fixed bed reactor column. The extend of pore diffusional resistance was examined in a continuous stirred tank reactor and with a numerical simulation. Hydrodynamics was measured in different reactor columns (diameter d_t = 0.052 ? 0.225 m; length L: 1.0–2.0m) and with a static mixer. Further, the concentration profile was determined in a fluidized bed reactor with side stream analysis for different biocatalyst samples, fluid velocities and bed heights. The simulation of experimental results indicates that they are well described by the developed model. Furthermore, the model is well suited to predicting the influence of specific parameters on the effective kinetics of the biocatalyst and the expansion of the fluidized bed.     

Modelling of a fluidized bed bioreactor for immobilized enzymes (Part 1)

In the first part of this paper, a mathematical model is presented for a liquid fluidized bed bioreactor using immobilized enzymes with reversible Michaelis-Menten kinetics. The model is based on the axial dispersion model for the bulk liquid phase. Inter- and intraparticle mass transfer as well as enzyme catalyzed reaction inside the porous beads are considered. The overall efficiency of the biocatalysts is calculated by a numerical routine. For the calculation of the concentration profile inside the reactor, a semi-analytical solution is derived which takes into account the height dependence of the effectiveness factor.     

The M1 Energy‐efficiency building Plus – Conclusion of monitoring / Das M1 Energieeffizienzhaus Plus – Abschluss des Monitorings

The M1 energy‐efficiency building Plus was to render practical proof that the advantages of solid construction such as carrying capacity, fire protection and sound protection could be connected to state‐of‐the‐art and future energy efficiency standards in the scope of a pilot project. With simple and thought‐through planning details and a coordinated system technology, energy plus solid houses are no longer merely visions. The M1 project mostly focuses on the claim to economic efficiency and saleability of the product, points out new possibilities for implementation to consumers, planners and executing companies. The house is to document, that the means available now are sufficient to construct a solid building that produces more energy than it consumes. In the technical term of construction physics, the building is targeted at a negative final energy and primary energy consumption. The data presented in this article from the monitoring of the last two years show that a plus energy target can be achieved by “nearly” conventionally built solid buildings. For both years, the M1 pus energy house reached an excess of final and primary energy.