Studies regarding simulation process to static loading of the structures obtained from polylactic acid, 3D printed

Being a relatively new process, additive manufacturing needs many studies to be able to produce parts with the required properties. The aim of the paper is to establish whether, based on the physical and mechanical properties determined by tensile testing and by applying finite element analysis (FEA), viable results can be obtained regarding the behavior of the 3D printed structures at the different, static loading. The application of FEA for the tensile testing of 3D specimens led to the results close to those obtained by the tests. The values of the results obtained by simulation are higher by up to 7.2% compared with those recorded by tests. The simulation was applied both for the printed specimens from a single material and from two materials (multi-material). Regardless of the materials used in printing and the simulation method, the results of applying FEA are close to those recorded by testing.     

Pseudo Bond Graph modelling and on-line estimation of unknown kinetics for a wastewater biodegradation process

This paper deals with the problem of modelling and on-line estimation of kinetics for a biomethanation process. This bioprocess is in fact a wastewater biodegradation process with production of methane gas, which takes place inside a Continuous Stirred Tank Bioreactor. The reaction scheme and the analysis of biochemical phenomena inside the bioreactor are used in order to obtain a nonlinear dynamic model of the bioprocess, by means of the pseudo Bond Graph method. Two nonlinear estimation strategies are developed for the identification of unknown kinetics of the bioprocess. First, an estimator is developed by using a state observer based technique. Second, an observer based on high-gain approach is designed and implemented. Several numerical simulations are performed in order to analyse and compare the behaviour and the performance of the proposed estimators.     

Visual Tracking by Continuous Density Propagation in Sequential Bayesian Filtering Framework

Particle filtering is frequently used for visual tracking problems since it provides a general framework for estimating and propagating probability density functions for nonlinear and non-Gaussian dynamic systems. However, this algorithm is based on a Monte Carlo approach and the cost of sampling and measurement is a problematic issue, especially for high-dimensional problems. We describe an alternative to the classical particle filter in which the underlying density function has an analytic representation for better approximation and effective propagation. The techniques of density interpolation and density approximation are introduced to represent the likelihood and the posterior densities with Gaussian mixtures, where all relevant parameters are automatically determined. The proposed analytic approach is shown to perform more efficiently in sampling in high-dimensional space. We apply the algorithm to real-time tracking problems and demonstrate its performance on real video sequences as well as synthetic examples.     

Performance analysis of security aspects by weaving scenarios extracted from UML models

Aspect-oriented modeling (AOM) allows software designers to describe features that address pervasive concerns separately as aspects, and to systematically incorporate the features into a design model using model composition techniques. The goal of this paper is to analyze the performance effects of different security features that may be represented as aspect models. This is part of a larger research effort to integrate methodologies and tools for the analysis of security and performance properties early in the software development process. In this paper, we describe an extension to the AOM approach that provides support for performance analysis. We use the performance analysis techniques developed previously in the PUMA project, which take as input UML models annotated with the standard UML Profile for Schedulability, Performance and Time (SPT), and transform them first into Core Scenario Model (CSM), and then into different performance models. The composition of the aspects with the primary (base) model is performed at the CSM level. A new formal definition of CSM properties and operations is described as a foundation for scenario-based weaving. The proposed approach is illustrated with an example that utilizes two standards, TPC-W and SSL.     

Designing block copolymer architectures for targeted membrane performance

Using a combination of block copolymer self-assembly and non-solvent induced phase separation, isoporous ultrafiltration membranes were fabricated from four poly(isoprene-b-styrene-b-4-vinylpyridine) triblock terpolymers with similar block volume fractions but varying in total molar mass from 43 kg/mol to 115 kg/mol to systematically study the effect of polymer size on membrane structure. Small-angle X-ray scattering was used to probe terpolymer solution structure in the dope. All four triblocks displayed solution scattering patterns consistent with a body-centered cubic morphology. After membrane formation, structures were characterized using a combination of scanning electron microscopy and filtration performance tests. Membrane pore densities that ranged from 4.53 × 10¹⁴ to 1.48 × 10¹⁵ pores/m² were observed, which are the highest pore densities yet reported for membranes using self-assembly and non-solvent induced phase separation. Hydraulic permeabilities ranging from 24 to 850 L m⁻² h⁻¹ bar⁻¹ and pore diameters ranging from 7 to 36 nm were determined from permeation and rejection experiments. Both the hydraulic permeability and pore size increased with increasing molar mass of the parent terpolymer. The combination of polymer characterization and membrane transport tests described here demonstrates the ability to rationally design macromolecular structures to target specific performance characteristics in block copolymer derived ultrafiltration membranes.     

Time-resolved GISAXS and cryo-microscopy characterization of block copolymer membrane formation

Time-resolved grazing-incidence small-angle X-ray scattering (GISAXS) and cryo-microscopy were used for the first time to understand the pore evolution by copolymer assembly, leading to the formation of isoporous membranes with exceptional porosity and regularity. The formation of copolymer micelle strings in solution (in DMF/DOX/THF and DMF/DOX) was confirmed by cryo field emission scanning electron microscopy (cryo-FESEM) with a distance of 72 nm between centers of micelles placed in different strings. SAXS measurement of block copolymer solutions in DMF/DOX indicated hexagonal assembly with micelle-to-micelle distance of 84–87 nm for 14–20 wt% copolymer solutions. GISAXS in-plane peaks were detected, revealing order close to hexagonal. The d-spacing corresponding to the first peak in this case was 100–130 nm (lattice constant 115–150 nm) for 17 wt% copolymer solutions evaporating up to 100 s. Time-resolved cryo-FESEM showed the formation of incipient pores on the film surface after 4 s copolymer solution casting with distances between void centers of 125 nm.     

A general statistical model for computer experiments with time series output

Manufacturing processes increasingly rely on computer experimentation as a substitute for costly physical experimentation. However, computer experimentation may not be very efficient because it often relies on computationally intensive simulation (or computer) models. To address this computational problem, this paper proposes a general statistical model as a computationally fast approximation for computer models with time series output. More precisely, the statistical models will be regression models with input-dependent design matrix and input-correlated errors. An example from the automotive industry will be used to illustrate the methodology.     

ON A THEORY OF INTERACTING CONTINUA WITH MEMORY

A linear theory is developed for thermoviscoelastic composites modeled as interpenetrating solid continua with memory. The response functionals are considered to depend on the past history of displacement fields, displacement gradients, temperature field, and temperature gradient. A uniqueness result and a variational characterization of solutions in the context of the dynamical theory are also established.     

Electrochemical waste water treatment: Electrooxidation of acetaminophen

Oxidation of acetaminophen at boron-doped diamond (BDD) and at Ti/SnO₂ anodes in a plug-flow divided electrochemical reactor led to electrochemical combustion, whereas at Ti/IrO₂ benzoquinone was the exclusive product except at very long electrolysis times. The difference is explicable in terms of the different mechanisms of oxidation: direct oxidation at the anode for Ti/IrO₂ vs. indirect oxidation involving electrogenerated hydroxyl radicals at BDD and Ti/SnO₂. At BDD, at which the efficiency of degradation of acetaminophen was greatest, the rate of electrolysis at constant concentration was linearly dependent on the current, and at constant current linearly dependent on the concentration. Current efficiencies for mineralization up to 26% were achieved without optimization of the cell design.     

Electrochemical reduction of hexahydro-1,3,5-trinitro-1,3,5-triazine in aqueous solutions

Electrochemical reduction of RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine, a commercial and military explosive, was examined as a possible remediation technology for treating RDX-contaminated groundwater. A cascade of divided flow-through cells was used, with reticulated vitreous carbon cathodes and IrO2/Ti dimensionally stable anodes, initially using acetonitrile/water solutions to increase the solubility of RDX. The major degradation pathway involved reduction of RDX to the corresponding mononitroso compound, followed by ring cleavage to yield formaldehyde and methylenedinitramine. The reaction intermediates underwent further reduction and/or hydrolysis, the net result being the complete transformation of RDX to small molecules. The rate of degradation increased with current density, but the current efficiency was highest at low current densities. The technique was extended successfully both to 100% aqueous solutions of RDX and to an undivided electrochemical cell.