A backoff strategy for model‐based experiment design under parametric uncertainty

Model‐based experiment design techniques are an effective tool for the rapid development and assessment of dynamic deterministic models, yielding the most informative process data to be used for the estimation of the process model parameters. A particular advantage of the model‐based approach is that it permits the definition of a set of constraints on the experiment design variables and on the predicted responses. However, uncertainty in the model parameters can lead the constrained design procedure to predict experiments that turn out to be, in practice, suboptimal, thus decreasing the effectiveness of the experiment design session. Additionally, in the presence of parametric mismatch, the feasibility constraints may well turn out to be violated when that optimally designed experiment is performed, leading in the best case to less informative data sets or, in the worst case, to an infeasible or unsafe experiment. In this article, a general methodology is proposed to formulate and solve the experiment design problem by explicitly taking into account the presence of parametric uncertainty, so as to ensure both feasibility and optimality of the planned experiment. A prediction of the system responses for the given parameter distribution is used to evaluate and update suitable backoffs from the nominal constraints, which are used in the design session to keep the system within a feasible region with specified probability. This approach is particularly useful when designing optimal experiments starting from limited preliminary knowledge of the parameter set, with great improvement in terms of design efficiency and flexibility of the overall iterative model development scheme. The effectiveness of the proposed methodology is demonstrated and discussed by simulation through two illustrative case studies concerning the parameter identification of physiological models related to diabetes and cancer care. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Radioactive Marker Measurements in Heterogeneous Reservoirs: Numerical Study

A numerical study is performed to simulate the vertical deformation of a depth interval representing a marker spacing (10.5 m) located in a deep heterogeneous sedimentary reservoir. Realistic lithostratigraphic sequences typical of the Northern Adriatic basin are used. A number of scenarios are addressed consistent with the available data. In particular two basic geologic scenarios at the marker scale are simulated, one where sands prevail within the marker spacing (SD), and another where thin sandy and clayey layers alternate (CL). The sensitivity of the marker response is investigated in relation to clay and sand permeability and compressibility contrast, Biot’s coefficient, and respective position of monitoring and fluid pumping wells. The modeling results show that rock may indeed expand above and below depleted layers. Depending on the marker position the expansion may partially offset the compaction, especially in the CL scenario with a very low permeable clay. To obtain a representative field compaction the markers should span a depth interval made mostly by sand and entirely depleted, and should be installed in a test hole far from producing wells. Compressibility contrast and the Biot coefficient play a secondary role. Very critical measurements are provided by two markers which incorporate a thin (≈1 m) depleted level overlain and underlain by almost impermeable clay layers.     

Development of smooth finishes in electrostatic fluidized bed (EFB) coating process of high-performance thermoplastic powders (PPA 571 H)

This paper deals with the analysis of the evolution of the surface morphology of metal substrates coated with high-performance thermoplastic powders, namely PPA 571 H, by using electrostatic fluidized bed (EFB) process. Attention has been particularly focused on the relationship between baking time and temperature of EFB coated substrates and the morphological characteristics of the resulting polymeric films.

First, thermal behaviour of PPA 571 H polymeric powders was characterized by using standard calorimetric techniques. Accordingly, PPA 571 H melting kinetic was experimentally deduced. Based upon experimental findings, predictive analytical model was also developed and employed to trace ‘iso-conversion’ curves out.

Second, metal substrates, made from low carbon steel (AISI 1040), were EFB coated and baked at several baking time and temperatures. Combined analyses of scanning electron and confocal microscopes were led to measure the evolution of the films surface morphology under different baking conditions. Accordingly, a relationship between film morphologies and melting degree was sought. Consistent trends of roughness parameters versus baking parameters were found, with smoother finishes of the polymeric films being achieved for higher degrees of melting, that is, for higher baking temperature and time. Full maps and related analytical models of the finishing levels according to baking parameters were also built up, hence providing first useful indications to powder coaters on how to best deal with their settings.     

Transceiver Front-End Technology for Software Radio Implementation of Wideband Satellite Communication Systems

The evolution of satellite communication systems for the design of both the satellite’s communication payload and the ground-station are towards the implementation of such systems using the Software Radio (SR) technology. This paper focuses on a key element of the SR, that is, the wideband front-end which still poses the greatest technological challenge for design and proliferation of SR. In particular, we look at the front-end architecture of wideband receivers, outline the key aspects of the design of such front-end systems, specify the performance metrics associated with their design, present an architecture of a promising wideband analog to digital converter, and finally present the results of our design, implementation, and test campaign of a prototype PC-based SR system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Risk analysis of underground infrastructures in urban areas

The paper presents an integrated approach for vulnerability and resilience analysis for underground infrastructures, i.e. a societal risk analysis of the failures of underground services for an urban area. The approach is based on the detailed study of (1) domino-effects for the components of a single infrastructure and for a given set of infrastructures interoperated and/or belonging to the same area; (2) risk and vulnerability analysis of a given area; (3) identification of a set of intervention guidelines, in order to improve the overall system resilience. The use of an integrated (interoperability and area) approach, breaking down the analysis area extent into sub-areas and assessing the dependencies among sub-areas both in terms of interoperability and damage propagation of critical infrastructures, demonstrates a useful advantage in terms of resilience analysis, more consistent with the “zoned” nature of failures of the underground infrastructures. An applied case, describing the interoperability and damage propagation analysis with the evaluation of time-dependency for the infrastructures and targets and of different kinds of interventions of the underground infrastructures of a town, is presented for this purpose.     

Characterization of Pt/AlN/Pt-based structures for high temperature, microwave electroacoustic devices applications

Highly c-axis oriented AlN films, 3.15 μm thick, were grown by rf reactive sputtering technique at 200 °C on bare and Pt-covered Si(100) substrates previously oxidized to a thickness of about 2 μm in wet oxygen atmosphere. A Pt film, 2200 Å thick, was then sputtered on the free surface of the AlN/Pt/SiO₂/Si multilayer at 200 °C without breaking the vacuum in order to avoid any oxidation effects of the layers. The multilayers were then annealed in air at 900 °C for different time lengths up to 32 h in order to test the materials' resistivity to harsh environment. The influence of this high temperature annealing (HTA) on the thin films' crystallinity, as well as on the c-AlN piezoelectricity and Pt sheet resistivity was investigated at room temperature before and after each annealing. X ray diffraction investigations revealed that the films' crystallinity was improved by the HTA: the full width of half maximum of the AlN(002) and Pt(111) peaks decreases from 0.39° to 0.24°, and from 0.42° to 0.28° after 32-hours-HTA. Scanning electron microscopy, four points probe and piezoelectricity tests revealed that the morphology and the sheet resistivity (in the range from 0.6 to 0.5 Ω/sq) of the outer Pt film, as well as the AlN piezoelectric constants d₃₃ (in the range from 6.2 to 7.4⋅10⁻¹² C/N) was quite unaffected by the HTA even after 32 h of annealing.     

Using MPC to control middle-vessel continuous distillation columns

The use of model predictive control (MPC) in middle-vessel continuous distillation column (MVCC) is discussed. It is shown that using a 5 × 5 MPC implementation (where all levels are included in MPC as integral process variables) allows using a smaller middle-vessel, particularly when disturbances can be measured: a good performance is ensured without having the middle vessel drained or overfilled. Also, it is shown that MPC practically circumvents the issue of tuning the middle-vessel level controller. Furthermore, the MVCC design makes conventional decentralised control perform comparably to MPC.     

Selective CO-oxidation over Ru-based catalysts in H2-rich gas for fuel cell applications

Topics in Catalysis - Ru-based catalysts supported on A zeolites and alumina were synthesised, characterised (XRD, SEM-EDS, TPR) and tested under realistic conditions for the preferential oxidation...