Dimensional instability of cement bonded particleboard: Modelling CBPB as a composite of two materials

Copyright @ Springer Verlag. This is a post print version of the article. The official published version can be obtained from the link below.Previous papers have quantitatively indicated that the total movement of cement bonded particleboard (CBPB) is equal to the sum of the movement of its components. This paper examined the efficacy of the law of mixtures when applied to the movement of a wood-cement composite under internal swelling or shrinkage stresses. Abundant data generated in companion papers were first manipulated to develop the universal formulae for predicting the movement of components. In conjunction with previous numerical results from image analysis of the structure of CBPB, and the orientated elasticity and stress algorithms, the models for theoretically predicting mass and dimensional changes of CBPB were derived. Validation studies were conducted and these demonstrated an excellent agreement of the theoretical predictions with experimental data for both mass and dimensional changes of CBPB due to internal swelling or shrinkage stresses during adsorption and desorption. The success also implied that CBPB can be treated as a composite and its properties can be well derived by the law of mixtures even though CBPB is an unusual type of composite having a very high volume fraction of wood chips, but a very high mass fraction of cement paste

Dimensional instability of cement bonded particleboard - Part 2: Behaviour and its prediction under cyclic changes in RH

This is a post print version of the article. The official published version can be obtained from the link below.This paper examines the dimensional instability of cement bonded particleboard (CBPB) and discusses the behaviour of CBPB during cyclic changes in relative humidities (RH). The results indicated that the changes of CBPB in both mass and dimensions reflected the changes in RH; in a cycle 90–65–35–65–90%RH the change of per percentage change in RH was 1.0:1.3:1.3:2.5 for mass, 1:2:2:1 for length and 1.3:1.1:1.0:1.0 for thickness. The changes were closely related to the structure of CBPB and the nature of the cement paste and wood chips. Thickness change was double that of the length change between 65 and 35%RH and triple that between 65 and 90%RH. The rate of change in mass was much higher than that in dimensions. The hysteresis loops were dissimilar to those of other wood and wood-based materials, with the loops of mass change closed between 65 and 90%RH, while the loops for dimensional changes were open. A set of the former loops moved upward and the latter moved downward with increasing number of cycles, corresponding to an accumulated increase in mass, but decrease in dimensions. The models developed for CBPB under constant and a single changing RH were successfully applied to changes under cyclic RH. The sorption behaviour and dimensional movement of CBPB has been shown to be influenced not only by RH, but also by its intermediate history, with the maximum values for change within every phase of sorption, in both mass and dimensions, being higher for the cycling between 35–90%RH than the cycling regime 35–65–90%RH. The ratios of dimensional changes to mass change of CBPB were greater under the latter regime than under the former regime.Partly Financial Support from the British Council

Ion Beam Induced Charge Microscopy of Integrated Circuits

The ion beam induced charge (IBIC) microscopy technique has recently been developed as a means of imaging the depletion regions of working microelectronic devices beneath their thick metallisation and passivation layers. IBIC microscopy is analogous to electron beam induced current microscopy but has the advantages of a larger analytical depth, lower lateral scattering of the incident focused MeV ion beam and negligible charging effects. These characteristics enable IBIC to image small, buried active device regions without the need to remove the surface layers prior to analysis. The basis of this new technique is outlined and the applications for integrated circuit analysis, characterising upset mechanisms, and for imaging dislocation networks in semiconductor wafers are reviewed

A Theoretical Analysis of Two-Stage Recommendation for Cold-Start Collaborative Filtering

In this paper, we present a theoretical framework for tackling the cold-start collaborative filtering problem, where unknown targets (items or users) keep coming to the system, and there is a limited number of resources (users or items) that can be allocated and related to them. The solution requires a trade-off between exploitation and exploration as with the limited recommendation opportunities, we need to, on one hand, allocate the most relevant resources right away, but, on the other hand, it is also necessary to allocate resources that are useful for learning the target's properties in order to recommend more relevant ones in the future. In this paper, we study a simple two-stage recommendation combining a sequential and a batch solution together. We first model the problem with the partially observable Markov decision process (POMDP) and provide an exact solution. Then, through an in-depth analysis over the POMDP value iteration solution, we identify that an exact solution can be abstracted as selecting resources that are not only highly relevant to the target according to the initial-stage information, but also highly correlated, either positively or negatively, with other potential resources for the next stage. With this finding, we propose an approximate solution to ease the intractability of the exact solution. Our initial results on synthetic data and the Movie Lens 100K dataset confirm the performance gains of our theoretical development and analysis

Dimensonial Instability of Cement-Bonded Particleboard: Behavior of Cement Paste And Its Contribution To The Composite

This paper examines the behavior of cement paste under constant and changing relative humidity (RH) conditions to evaluate the contribution of cement paste to the dimensional instability of cement-bonded particleboard (CBPB). It was found that the trend of changes in cement paste was very similar to, but the degree of changes was different from, that of CBPB at various exposures. The comparison of the results of cement paste with those of CBPB indicated that the inclusion of wood chips accelerated the carbonation reaction, and that carbonation of the cement paste exerted additional stresses on the wood chips in CBPB; this resulted in a slightly higher increase in mass but an appreciably greater decrease in the dimension of CBPB under constant 20°C/65% RH. The cement paste had considerably lower changes in mass and dimension with a single change in RH between 35 and 90% RH (except for the increase in mass on adsorption at 90% RH) compared to CBPB. The inflection in the relationship between mass and dimensional changes of cement paste was more distinct than that of CBPB with the change of mass per unit length change after the "inflection point" being about eight times higher than that of CBPB on desorption. Under cyclic RH, the response to the level of RH and the history of sorption was different between cement paste and CBPB, with the difference in dimensional change between adsorption and desorption being more significant, while the adsorption at 90% RH for the cement paste was considerably higher. Fitting of models previously developed to the data permitted the prediction of accumulated change of the cement paste with a good degree of fit and established the suitability of using these formulae for modelling CBPB as a composite to be described in a further paper in this series

Micro-PIXE with 3.5 MeV protons for the study of low copper concentrations in atherosclerotic artery

The onset and progression of many degenerative diseases including atherosclerosis, have been shown to directly link to the presence/absence of certain metal ions. Consequently, the detection of these ions in tissues may improve the understanding of the driving pathophysiology. The Cu content during atherosclerosis development has not been studied due to its low concentration involved. In this work, the Cu level in atherosclerotic rabbit tissue is determined using PIXE with a 3.5 MeV proton beam. The arteries of three animal groups fed with different diets were studied: group 1, rabbits on normal standard diet, group 2, on High Fat Diet (HFD) and group 3, on HFD + Zinc diet. Zinc supplement has been proven to inhibit the beginning of atherosclerotic lesion. The result of this study shows that the Cu levels in all the atherosclerotic lesions were lower than that in the arterial walls of the samples in HFD groupThis work has been partially funded by a UAM-Banco de Santander Interuniversity Cooperation with Asia Grant (2017–2018) and by the Ministerio de Ciencia, Innovacióny Universidades (CTQ2017-84309-C2-2-R