Miguel Casquilho

Kinetics of water absorbency in AA/AMPS copolymers: applications of a diffusion–relaxation model

Abstract Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a divinyl crosslinker, N , N ′-methylenebisacrylamide, have been synthesized by free radical solution and inverse emulsion polymerization. The copolymerization has been carried at different pH values of the monomer mix reaction medium. The copolymers were characterized by their dynamic swelling behavior in deionized water, i.e. the mass of water absorbed by a sample of copolymer was measured vs time. The results were analyzed in terms of the Berens–Hopfenberg non-Fickian equation, leading to a one-only-term relaxation. These kinetics were interpreted by the diffusion–relaxation model and offer quantitative information by diffusivity at 20°C of water in the copolymers. In this investigation, the results have been confirmed within experimental error as the sample of the copolymer is swollen.

A statistical analysis of the impact of nematode attack symptomatology on the mechanical behaviour of Pinus pinaster Ait. wood

An appraisal was made about the impact of pinewood nematode (Bursaphelenchus xylophilus, Nickle) attack symptomatology on the mechanical behaviour of wood from Pinus Pinaster Ait. Two sets of 200 wood specimens were obtained for the study of both mechanical and other physical properties. The specimens, about half of which presented symptoms of nematode, were obtained from a set of 66 wood planks, cut from an equal number of trees, originating from the Setúbal Peninsula (Portugal). Logistic analysis using symptomatology as a binary dependent variable showed adequacy of models containing compression tension to rupture and number of wood rings per unit radial length for the prediction of nematode attack. Analysis of variance revealed that the presence of the disease symptoms was correlated to static bending rupture, modulus of elasticity, work to maximum bending load, and axial compression rupture, causing their decrease at a significance level of 5%.

A minimum distance: arithmetic and harmonic means in a geometric dispute

Given two points, the source and the destination, on one side of an angle, the simple problem of finding a point on the other side at minimum total travelling distance has a solution that, when the angle tends to zero, is somewhat counterintuitive, leading to a geometric dispute between the arithmetic and the harmonic means.

Remote Scientific Computing over the Internet: An Example in Geometry

Scientific computing over the Internet can suit many activities that have not, in the authors’ opinion, been explored enough in general. Resources such as executables, languages, packages, can be used from a remote computing system. In this study, largely based on academic practice, a simple illustrative example in Geometry is implemented on a distributed system that outsources the computing-intensive tasks to remote servers that may be located in other universities or companies, linked to grids and clusters and so on. The software stack and software developed to support the communication is explained in detail. The architecture developed stresses the interoperability of the software, and a high degree of decoupling between components hosted in various locations. The results of this study motivate further work and serve a practical purpose that may be useful to everyone doing scientific computing.

Applied scientific computing over the Web with remote servers: Sampling with and without replacement

Scientific computing over the Web can be applied to solve problems of many types, namely as appear in the activity of companies. In this study, the computation is done with two remote servers, without the users perception, thus disclosing no clues on the computation. As an illustration, we make use of random sampling, which is needed in many activities, such as manufacture and research. Sampling is presented in its two basic versions, with and without replacement, the latter the typical choice in practice. Our objectives are: to emphasize the pertinence of the Web for scientific computing; to illustrate this computing with one of its countless applications; to show the possibilities of using remote, distributed servers; and to imply that this can provide the desired link between industry and the university. In our opinion, the full benefits of scientific computing over the Web have not been reaped, despite the availability of this communication medium.

Web-based scientific computing, a little explored field an engineering problem: Pneumatic transport

Web-based computing makes calculations available to any user just by means of a browser, i. e., without installing any software in the users computer, which thus does not need any especially high computing power or specific operating system. As a mere illustration, an Engineering problem in pneumatic transport is addressed, to determine the minimum transport velocity, as needed in some industries. This determination is made available to any user through a web-based executable program made by the authors that computes the velocity, following common theory. This study is an instance of computing over the Web, a way of computing that employs exactly the same executable programs as classical computing, these being typically the hard task in most Engineering and other problems. This type of computing, with the corresponding tailored executables, can be used to solve innumerable other problems. This web-based technique also facilitates cooperative work, given the current ease of worldwide communication. We find it to be a comparatively little explored field of the Web.

Optimization Concepts: II—A More Advanced Level

Optimization subjects are addressed from both an introductory and an advanced standpoint. Theoretical subjects and practical issues are focused, conjugating Optimization basics with the implementation of useful tools and supply chain (SC) models. In the prior Introductory chapter on Optimization concepts, Linear Programming, Integer Programming, related models, and other basic notions were treated. Here, the More Advanced chapter is directed to Robust Optimization, complex scheduling and planning applications, thus the reading of the prior Introductory chapter is recommended. Through a generalization approach, scheduling and planning models are enlarged from deterministic to stochastic frameworks and robustness is promoted: model robustness, by reducing the statistical measures of solutions variability; and solutions robustness, by reducing the capacity slackness, the non-used capacity of chemical processes that would imply larger investment costs.

Optimization Concepts—I: Introductory Level

Optimization subjects are addressed from both an introductory and an advanced standpoint. Theoretical subjects and practical issues are focused, conjugating Optimization basics with the implementation of useful tools and SC (supply chain) models. By now, in the Introductory section, Linear Programming, Integer Programming, related models, and others of interest are treated. In another chapter about these subjects in this handbook, more advanced related topics are addressed.