A two-stage heuristic method for balancing mixed-model assembly lines with parallel workstations

This work presents a new mathematical programming model for the mixed-model assembly line balancing problem with parallel workstations and zoning constraints. It allows the user to control the process to create parallel workstations. The model's primary goal is to minimize the number of workstations along the line, for a given cycle time, and its secondary goal is to balance the workloads between and within workstations. A two-stage procedure, using a simulated annealing approach, was developed to tackle this complex problem. The first stage of the procedure looks for a sub-optimal solution to the problem's primary goal, whilst the second stage deals with the secondary goal. The procedure is illustrated with a numerical example and the results from computational experiments show that even for large-scale problems the proposed procedure performs very well.     

Unsteady aspects of sodium–water–air reaction

One important issue for the Sodium Fast Reactor (SFR) concept is the reactivity of metallic sodium and its exothermal reaction with water. In particular during equipments washing operations, sodium needs to be firstly converted (‘destroyed’) into non reactive species via a chemical reaction with water. Today, such operations are performed in tanks that confine the system and mitigate the consequences of any possible abnormal condition.     

Transient dynamic analysis of a fluid-saturated porous gradient elastic column

The dynamic response of a fluid-saturated porous gradient elastic column to a transient disturbance is determined analytically and numerically. The basic dynamic theory of a fluid-saturated poroelastic medium due to Biot is modified by replacing the classical linear elastic model of the solid skeleton by the simple gradient elastic model of Mindlin with just one elastic constant (internal length scale) in addition to the classical ones. Thus, the new theory, which is presently restricted to the one-dimensional case, can take into account the microstructural effects of the solid skeleton. After the establishment of appropriate boundary and initial conditions, the one-dimensional dynamic column problem is solved analytically with the aid of the Laplace transform with respect to time. The time domain response is finally obtained by a numerical inversion of the transformed solution. The effect of the solid microstructure on the response is assessed and discussed.     

A case study of product engineering: Performance of microencapsulated perfumes on textile applications

The evaluation of the performance of new products to be released on the market is essential to measure its acceptability by consumers. In this work, the performance of an added‐value product, microencapsulated perfumes applied on textiles for man suits, was predicted and evaluated. The odor intensity and character of the perfume ingredients was measured by headspace gas chromatography after dry cleaning and abrasion tests on textiles impregnated with microcapsules. The evaporation and diffusion of the fragrances in the encapsulated perfume was assessed. For this type of application, limonene has shown a better performance in the perfume mixture, being the dominant note over time and distance. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1939–1950, 2012     

A third sector in the core-periphery model: non-tradable goods

We extend an analytically solvable core-periphery model by introducing a monopolistically competitive sector of non-tradable goods that is mobile across regions. We find that when the elasticity of substitution among non-tradable goods is very low, there is agglomeration of all the production (of both tradable and non-tradable goods). When the elasticity of substitution among non-tradable goods is sufficiently high (“no black-hole” condition), then there is symmetric dispersion of all the production, if trade costs are high; or full agglomeration of the production of tradable goods with partial agglomeration of the production of non-tradable goods, if trade costs are low.     

Emerging mitigation needs and sustainable options for solving the arsenic problems of rural and isolated urban areas in Latin America - A critical analysis

In this work, current information about the contamination of ground- and surface-water resources by arsenic from geogenic sources in Latin America is presented together with possible emerging mitigation solutions. The problem is of the same order of magnitude as other world regions, such as SE Asia, but it is often not described in English. Despite the studies undertaken by numerous local researchers, and the identification of proven treatment methods for the specific water conditions encountered, no technologies have been commercialized due to a current lack of funding and technical assistance.Emerging, low-cost technologies to mitigate the problem of arsenic in drinking water resources that are suitable for rural and urban areas lacking centralized water supplies have been evaluated. The technologies generally use simple and low-cost equipment that can easily be handled and maintained by the local population. Experiences comprise (i) coagulation/filtration with iron and aluminum salts, scaled-down for small community- and household-scale-applications, (ii) adsorption techniques using low-cost arsenic sorbents, such as geological materials (clays, laterites, soils, limestones), natural organic-based sorbents (natural biomass), and synthetic materials. TiO₂-heterogeneous photocatalysis and zerovalent iron, especially using nanoscale particles, appear to be promising emergent technologies. Another promising innovative method for rural communities is the use of constructed wetlands using native perennial plants for arsenic rhizofiltration. Small-scale simple reverse osmosis equipment (which can be powered by wind or solar energy) that is suitable for small communities can also be utilized.The individual benefits of the different methods have been evaluated in terms of (i) size of the treatment device, (ii) arsenic concentration and distribution of species, chemical composition and grade of mineralization in the raw water, (iii) guidelines for the remaining As concentration, (iv) economical constrains, (v) complexity of installation and maintenance, and infrastructure constraints (e.g. electricity needs).     

Effect of glycation of bovine β-lactoglobulin with galactooligosaccharides on the growth of human faecal bacteria

The in vitro fermentation selectivity of purified galactooligosaccharides (GOS) after their conjugation with bovine β-lactoglobulin (β-LG) via the Maillard reaction and a subsequent simulated gastrointestinal digestion was evaluated. Changes in human faecal bacterial populations, lactic acid and short-chain fatty acids after 10 h and 24 h of fermentation of the digested β-LG:GOS conjugates revealed that this mixture of glycated peptides had a similar bifidogenic activity to the unconjugated GOS. These findings could open up new applications for Maillard reaction products in the functional foods field.     

The governance of knowledge in project-based organizations

This research investigates patterns of knowledge governance practices in project-based organizations (PBOs). Five propositions about knowledge governance in PBOs were deductively and empirically tested using qualitative data from 82 interviews. The results were triangulated with those of prior studies. Results indicate that knowledge governance practices in PBOs are impacted by structural and situational factors, such as being a subsidiary or standalone PBO, a PBO striving for excellence or not, as well as some preconditions, such as the executives' competence in project governance. The results show that informal governance mechanisms are more useful than formal when it comes to knowledge creating processes. Governance of informal knowledge creating mechanisms appears to be complex for executives and their preconceptions showed either to be enablers or barriers to productive knowledge governance practices. Executive's competence and preconditions, concerning aspects like human capabilities and attitudes to professional ethos, seems to impact knowledge governance strategies. In subsidiary PBOs knowledge governance provides practitioners with proper assistance to avoid unbeneficial situations of having knowledge silos among loosely coupled islands.