JITL-based concentration control for semi-batch pH-shift reactive crystallization of l-glutamic acid

Although concentration control (C-control) strategy has been shown to give effective and robust control performance for batch cooling and semi-batch antisolvent crystallizations in recent years, no research work was reported concerning the potential application of conventional C-control for the more challenging semi-batch pH-shift reactive crystallization that is common in the process industries. To this end, this paper presents detailed analysis to find out that it is not feasible to apply the C-control to semi-batch pH-shift reactive crystallization. To circumvent this problem, a variant of C-control strategy by incorporating the Just-in-Time Learning (JITL) method to cope with strong process nonlinearity inherent in the pH-shift reactive crystallization is developed in this paper. Simulation results are presented to illustrate the proposed design and a comparison with conventional optimal control is made.     

Computing point estimates from a non-Gaussian posterior distribution using a probabilistic k-means clustering approach

The Kalman filter algorithm gives an analytical expression for the point estimates of the state estimates, which is the mean of their posterior distribution. Conventional Bayesian state estimators have been developed under the assumption that the mean of the posterior of the states is the ‘best estimate’. While this may hold true in cases where the posterior can be adequately approximated as a Gaussian distribution, in general it may not hold true when the posterior is non-Gaussian. The posterior distribution, however, contains far more information about the states, regardless of its Gaussian or non-Gaussian nature. In this study, the information contained in the posterior distribution is explored and extracted to come up with meaningful estimates of the states. The need for combining Bayesian state estimation with extracting information from the distribution is demonstrated in this work.     

Antiviral properties of milk proteins and peptides

A substantial body of evidence, primarily from in vitro studies, suggests that some milk proteins interfere with viral infections. Lactoferrin (LF) has been the protein most comprehensively studied for its antiviral effects. Interference with viral infections is primarily based on adsorption of LF to receptors on the host cell's surface or on binding to viral particles, both enveloped and non-enveloped. In either mechanism, viral particles are prevented from attaching to host cells. Electrostatic attraction seems to play an important role in both mechanisms. In general, bovine LF is more effective against viral infections than human LF. Apo-LF is less effective than the iron-saturated LF. Antiviral effects of lactoferricin and other peptides liberated from LF are weaker than those of intact LF. Proteins other than LF, such as lactadherin, and peptides such as glycomacropeptide, also interfere with infection by some viruses. Chemical modifications of milk proteins that lead to changes in charges on proteins, and in charge distribution, enhance their effects against certain viruses.     

AgMgAl metallic glassy and intermetallic thin films for electric contact applications

The AgMgAl thin films, in an attempt in replacing the expensive pure Au contact films, are prepared by co-sputtering. The surface morphology, roughness, amorphous or crystalline atomic structure, grain size, and electric resistivity are systematically examined. Depending on the film compositions, the films can be fully amorphous or fully nanocrystalline, or a composite with the mixture of nanocrystalline phases dispersed in the amorphous matrix. Under the as-sputtered condition, the crystalline group has the lowest resistivity, ranging from 27 to 37 μΩ·cm, the composite group lies in the middle, 31–70 μΩ·cm, and the fully amorphous group possesses the highest resistivity, 87–122 μΩ·cm. Appropriate short thermal annealing for the amorphous films can drastically lower the resistivity down to as low as 9 μΩ·cm, already compatible to pure Au (3–7 μΩ·cm). This study demonstrates the feasibility of the AgMgAl films in replacing the pure Au.     

A multi-agent architecture for diagnosing simultaneous faults along water canals

Water is intensively used in mankind activities, in particular in agriculture. Water is commonly conveyed for agriculture purposes through water canal networks which are large-scale spatially distributed systems crossing extensive regions. In the presence of leaks, unauthorized water withdrawals, water depth sensor faults or gate faults, the quality of service can be severely compromised. A system able to diagnose which type of fault is present at a given time is of vital importance to access the current state of the water canal and proceed to restore its nominal condition. This paper proposes a multi-agent architecture to simultaneously detect, isolate and estimate lateral outflows (e.g., leaks or water withdrawals) and hardware faults (e.g., a gate obstruction or a downstream water depth sensor fault) in water canal networks. First, the main canal network is broken down into several subsystems composed of a single canal pool with the corresponding gate. Then, an agent is assigned to each subsystem aiming at its fault diagnosis. The approach is based on the generation and evaluation of residuals obtained from the comparison of model-based output signals with real data. Application to an experimental water canal bears out the proposed architecture as a valuable tool for monitoring and supervising general water canals.     

A semi-analytical model for predicting the flow into a wellbore completed by inflow control devices

A method to predict the detailed flow into horizontal wellbores completed by inflow control devices is presented. In this work, the inflow control device (ICD) is a sequence of pipes lining the wellbore and perforated by many holes to enable the inflow of hydrocarbons. The reservoir is assumed to be infinite in the radial and axial directions and its permeability is assumed to be uniform. The pore pressure at infinity and inside the wellbore, is constant. To solve the problem of the flow into a single hole, we first treat it as if the pressure field is singular at the hole acting like an unknown point source. In this way we produce an outer approximation of the problem. We then examine the region where the singularity occurs and find a regular solution for this region only. Finally we match the two asymptotic solutions in the overlap zone, where they are both valid. Beginning with the problem of a single hole on the ICD, we use the superposition principle to add the pressure produced by the flow from the other holes at position i. We are left with a linear system of N equations relating the N unknown point sources of the N holes, with the given pressure drawdown. This system is inverted to give the strength of the point sources. This method is potentially very CPU demanding and an approximate method is also developed to deal with a lot of holes. The two methods are compared and the performance of a realistic ICD is compared against an open-hole.     

Low-velocity impact damage on dispersed stacking sequence laminates. Part II: Numerical simulations

This paper is the follow-up on the previous work by the authors on the experimental evaluation of the impact damage resistance of laminates with dispersed stacking sequences. The current work focuses on the evaluation of the impact performance of the tested laminates by innovative numerical methods.Constitutive models which take into account the physical progressive failure behaviour of fibres, matrix, and interfaces between plies were implemented in an explicit finite element method and used in the simulation of low-velocity impact events on composite laminates. The computational effort resulted in reliable predictions of the impact dynamics, impact footprint, locus and size of delaminations, matrix cracks and fibre damage, as well as the amount of energy dissipated through delaminations, intraply damage and friction. The accuracy achieved with this method increases the reliability of numerical methods in the simulation of impact loads enabling the reduction of the time and costs associated with mechanical testing.     

Multiple modes of a natural circulation evaporator

The system behaviour of an open single tube, steam heated natural circulation evaporator has been investigated at heating steam pressures up to 0.44 MPa and different subcoolings of the process medium water. In the studied range of parameters, diverse operational states occurred which have been recognized for the first time as geysering coupled with manometer oscillation as well as first, second and third orders of density wave oscillation of type I. Due to the strong nonlinear behaviour of the system, up to three states appear in certain ranges of parameter constellations. By defined setting of initial conditions and distinct perturbations of the system, the individual states can be set.     

Experimental analysis of damage creation and permanent indentation on highly oriented plates

This paper presents an experimental investigation concerning low-velocity impact and quasi-static indentation tests on highly oriented laminates used in aeronautical and aerospace applications. The damage observed in such laminates is very particular. Post mortem analysis were carried out which helped to define an impact damage scenario. Microscopic observations led to explain the mechanism of permanent indentation formation which is a fundamental point of damage tolerance justification. Equivalence between static and dynamic is also discussed.     

Modelling discrete failures in composites with interface elements

The application of cohesive zone interface elements to modelling discrete matrix dominated failures in polymer composites is reviewed. It is shown that because they can accurately represent the physical mechanisms controlling damage development and failure, they are able to give excellent simulations of a wide variety of phenomena including delamination, laminate in-plane failure, behaviour at notches, impact damage and structural failure due to debonding.