Complementary modelling of fluid separation processes

Optimal functioning of numerous technological processes depends primarily on relevant process design, properly selected column internals and sufficient understanding of the process behaviour. This can be achieved only with the help of accurate and reliable process models capable of considering process rates in a rigorous way, with respect to both transport phenomena and chemistry. In this article, a new modelling concept called complementary modelling is suggested for a large class of fluid separation processes. Since the conditions and criteria for these processes vary considerably, it is impossible to develop a unified modelling approach. Instead, a reasonable and effective combination of different modelling approaches provides solutions to many present and future tasks. The complementary modelling is discussed in detail and illustrated with several case studies.     

A practical approximation algorithm for optimal k-anonymity

k-Anonymity is a privacy preserving method for limiting disclosure of private information in data mining. The process of anonymizing a database table typically involves generalizing table entries and, consequently, it incurs loss of relevant information. This motivates the search for anonymization algorithms that achieve the required level of anonymization while incurring a minimal loss of information. The problem of k-anonymization with minimal loss of information is NP-hard. We present a practical approximation algorithm that enables solving the k-anonymization problem with an approximation guarantee of O(ln k). That algorithm improves an algorithm due to Aggarwal et al. (Proceedings of the international conference on database theory (ICDT), 2005) that offers an approximation guarantee of O(k), and generalizes that of Park and Shim (SIGMOD ’07: proceedings of the 2007 ACM SIGMOD international conference on management of data, 2007) that was limited to the case of generalization by suppression. Our algorithm uses techniques that we introduce herein for mining closed frequent generalized records. Our experiments show that the significance of our algorithm is not limited only to the theory of k-anonymization. The proposed algorithm achieves lower information losses than the leading approximation algorithm, as well as the leading heuristic algorithms. A modified version of our algorithm that issues ℓ-diverse k-anonymizations also achieves lower information losses than the corresponding modified versions of the leading algorithms.     

Preadhesion Laser Treatment of Aluminum Surfaces

An excimer laser may be used for preadhesion treatment of aluminum alloys. This method presents an alternative to the use of ecologically unfriendly chemicals involved in conventional anodizing pretreatments.

Experimental results indicate that preadhesion laser surface treatment significantly improved the shear strength of modified-epoxy bonded aluminum specimens compared with untreated and anodized substrates. The best results were obtained with laser energy of about 0.2 J/Pulse/cm² where single lap shear strength was improved by 600-700% compared with that of untreated Al alloy, and by 40% compared with chromic acid anodizing pretreatment.

The mode of failure changed from adhesive to cohesive as the number of laser pulses increased during treatment. The latter phenomenon has been correlated with morphology changes as revealed by electron microscopy, and chemical modification as indicated by Auger and infrared spectroscopy.

It can be concluded that the excimer laser has potential as a precise, clean and simple preadhesion treatment of Al alloys.     

Dielectric and magnetic properties of random and segregated ferrite polystyrene composites

The dielectric and magnetic properties of polystyrene composites containing barium or nickel-zinc ferrites were studied as function of the ferrite concentration and field frequency. The composites were prepared by methods yielding a random distribution of the ferrite particles or segregated structures. Barium ferrite-poly-styrene composites exhibited a typical insulator behavior, and only above 60% ferrite were high values of the dielectric properties noted at the lower frequencies, decreasing gradually with frequency to the low values typical of the higher frequencies. The mode of barium ferrite particle distribution did not affect the dielectric properties. The nickel-zinc ferrite systems demonstrated a conductor type behavior. An apparent insulator-conductor transition was observed, having lower values for segregated than for random distributions. The magnetic permability of barium ferrite-polystyrene composites above 10% ferrite increases with the ferrite concentration, whereas the magnetic dissipation factor steeply increases with concentration above 40% ferrite.     

The Effect of Moisture Content in Epoxy Film Adhesives on their Performance. III: Bulk Properties

Humidity absorbed by epoxy film adhesives during low temperature storage or exposure to atmosphere may result in reversible changes and irreversible modifications. Vacuum treatment may partially remedy the reversible changes. The consequences of vacuum drying are manifested in enhancement of both the peel and shear properties of bonded joints (Part I and Part II of this series of papers) and the thermal, physical and mechanical properties of the bulk adhesive, characterized in the present study.

Experimental results have shown that the bulk properties of structural epoxy based adhesives are highly correlated with the aging processes caused by water absorption in the prepolymerized adhesive. Applying the vacuum process is harmful to fresh unaged adhesive due to devolatization of low molecular species of the film adhesive.

The characterization of bulk properties for the purpose of following the aging and recovery processes is advantageous, since the bulk is independent of geometrical and interfacial effects which dominate in the case of property evaluation of the adhesive in a bonded joint.     

Analysis of variance in capillary rheometry

The effect of deformation history (hysteresis) on transient capillary rheometric data was studied compared to conventional assumptions regarding steady state data. The factors studied were: the position instrumentation, the pressure instrumentation, entrance and exit effects, polymer melt compressibility, pressure dependence of the viscosity, and polymer melt viscous heating. Statistical analysis of variance was performed to statistically determine the sources of variance to specific degrees of confidence. The polymer melt compressibility, pressure dependence, and viscous heating were found to be statistically significant contributors of the observed variation at the 95% confidence level; the capillary length and instrumentation were not found to be significant. The results indicate that the transient behavior can vary the modeling of the apparent viscosity in a significant manner such that the model fidelity and model coefficients may vary substantially. Hence, polymer melt compressibility, pressure dependence, and viscous heating should be considered during rheological model fitting to increase model fidelity and predictive accuracy in end‐use. POLYM. ENG. SCI., 56:895–904, 2016. © 2016 Society of Plastics Engineers     

Three-phase syntactic foams

Three-phase syntactic foams consisting of a close-packed microballoons bed, binding resin, and air voids are reported. Preparation methods varied from simple dry-blending with a solid powdery resin-to-resin coating of spheres from polymer solutions. By holding the hollow spheres volume fraction constant and at the maximum packing, a property studied was a function of a single variable, namely, resin volume fraction, void content or density. Mechanical properties are reported as function of one of these variables. The temperature effect was investigated on polyimide based foams. The dielectric constant is shown to obey a logarithmic rule of mixtures. Modified modulus-composition equations are shown to be applicable for prediction of moduli values of the three-phase systems.     

Effect of particulate reinforcement on creep behavior of polyurethane foams

The compressive creep behavior of rigid unreinforced and particulate reinforced polyurethane foams at different densities, filler contents, temperatures, and loads was investigated. The creep behavior could be described by a power function of time and its temperature dependence by an Arrhenius type relation. The addition of particulate rigid fillers enhances the creep resistance as well as the foam elastic modulus. Particulate reinforcement of polyurethane foams was found to be efficient for the higher foam densities, especially for higher filler levels.     

Development of parametric material, energy, and emission inventories for wafer fabrication in the semiconductor industry

Currently available data suggest that most of the energy and material consumption related to the production of an integrated circuit is due to the wafer fabrication process. The complexity of wafer manufacturing, requiring hundreds of steps that vary from product to product and from facility to facility and which change every few years, has discouraged the development of material, energy, and emission inventory modules for the purpose of insertion into life cycle assessments. To address this difficulty, a flexible, process-based system for estimating material requirements, energy requirements, and emissions in wafer fabrication has been developed. The method accounts for mass and energy use atthe unit operation level. Parametric unit operation modules have been developed that can be used to predict changes in inventory as the result of changes in product design, equipment selection, or process flow. A case study of the application of the modules is given for energy consumption, but a similar methodology can be used for materials, individually or aggregated.     

Numerical investigation of carbon dioxide absorption in a falling-film micro-contactor

A rigorous mathematical model is developed to describe chemical absorption of carbon dioxide in a falling-film micro-contactor. Contrary to previous models described in literature, hydrodynamics in both phases is accurately captured by the Navier–Stokes equations. By this means, backmixing effects can be accounted for. Furthermore, the interface position is determined directly using the level-set method. The developed model is validated with experimental data obtained from literature and a good agreement is established. With the validated model, detailed studies are performed to investigate the impact of process parameters.