RILEM Draft Recommendation ‘Determination of the modulus of elasticity of prestressing steel strands’

RILEM Draft Recommendations

RILEM Draft Recommendation ‘Determination of the modulus of elasticity of prestressing steel strands’     

How to evaluate the degree of interdisciplinarity of an institution?

The Stirling index of the set of references of the corpus documents is widely used in the literature on interdisciplinary research and is defined as the integration score of the corpus under study. Such an indicator is relevant at the scale of a research institution, however, there is a gap between the integration scores of individual documents, and a global score computed on the whole set of references. The difference between the global index and the average of individual document indexes carries another relevant information about the corpus: it measures the diversity between the reference profiles of the corpus documents. It is, therefore, named between article index whereas the average of the individual article indexes is called within article index. The statistical properties of these two indexes as well as of the global index are derived from a general approximation method for distributions and lead to statistical tests which can be used to make meaningful comparisons between an institution indexes and benchmark values. The two dimensions of the global index provide a more acute information on the interdisciplinary practices of an institution researchers in a given research domain and is, therefore, likely to contribute to strategic and management issues.     

Risk as social process: the end of 'the age of appealing to the facts'?

This paper utilises the notion of the risk society to argue that the ways in which technical practices, knowledge and rationality have become structured into governance are counter-productive and now instrumental to the proliferation of risk and destabilisation of governance. This problem is epitomised by how decisions have evolved to become a matter determined by 'facts' rather than by a determination of the community impact of outcomes and further compounded by the institutionally embedded blindness to wider social concerns that this entails. It is argued that what are required are processes integrating 'factual' technical and 'value-laden' societal concerns and avenues for this and their ramifications are elaborated and explored. Central to such developments will be a democratisation of technical practices and the institutions in which they are embedded. The broader political implications of these developments are examined and found to involve a radical extension of democracy involving an extensive reshaping of the topography of governance.     

How do recycled concrete aggregates modify the shrinkage and self-healing properties?

This paper presents the main results of a research carried out to analyze the mechanical properties, intrinsic permeability, drying shrinkage, carbonation, and the self-healing potential of concrete incorporating recycled concrete aggregates. The recycled concrete mixtures were designed by replacing natural aggregates with 0%, 30%, and 100% of recycled concrete gravel (RG) and 30% of recycled concrete sand (RS). The water to equivalent binder ratio was kept constant and recycled concrete aggregates were initially at saturated surface dried (SSD) state. The contribution of the porosity of natural and recycled aggregates to the porosity of concrete was estimated to understand the evolution of the intrinsic permeability and the open porosity. At long term, the maximum variation of drying shrinkage magnitude due to recycled concrete gravels did not exceed 15%. The correlation between drying shrinkage and mass-loss through “drying depth” concept showed that recycled concrete aggregates are affected by drying as soon as concrete is exposed to desiccation. A good correlation between 1-day compressive strength and 18-month carbonation depth was observed. The recycled concrete aggregates presented a good potential for self-healing as the relative recovery of cracks reached up to 60%.     

How to forecast the electrical behaviour of ionic conductor composites?

The theoretical models that might be used to forecast the electrical behaviour of ionic conductor composites for application in SOFCs are reviewed. A comparison of the different models is performed and comparative analysis of their power is presented on the basis of a case simulation (YSZ (7,54 mol%Y₂O₃)-Al₂O₃ (5 wt%) composite). The lack of systematic experimental works makes a wide comparison with the theoretical results very difficult, so the real power of the models can not yet be fully assessed and only introductory considerations are tentatively given. Nevertheless from the preliminary results, it seems possible to affirm that Electrical Network Models are able to better sustain the simulation of the electrical properties of YSZ-Al₂O₃ composites. Certainly many other improvements have to be done before ENMs became confident tools for tailoring ab initio the electrical properties of two phase mixtures.     

The determination of the permeability of concrete to oxygen by the Cembureau method—a recommendation

A committee was set up in 1981 by the Cembureau Working Party on the Quality of Concrete with the following aims and objectives:

How to reduce the number of rating scale items without predictability loss?

Rating scales are used to elicit data about qualitative entities (e.g., research collaboration). This study presents an innovative method for reducing the number of rating scale items without the predictability loss. The “area under the receiver operator curve method” (AUC ROC) is used. The presented method has reduced the number of rating scale items (variables) to 28.57% (from 21 to 6) making over 70% of collected data unnecessary. Results have been verified by two methods of analysis: Graded Response Model (GRM) and Confirmatory Factor Analysis (CFA). GRM revealed that the new method differentiates observations of high and middle scores. CFA proved that the reliability of the rating scale has not deteriorated by the scale item reduction. Both statistical analysis evidenced usefulness of the AUC ROC reduction method.     

How do concrete rheology,tribology, flow rate and pipe radius influence pumping pressure?

Finding the critical factors that influence the pressure during pumping of concrete has been investigated for years. From fluid mechanics, the relationship between pressure and flow rate, radius or viscosity is known. In the practical guidelines for pumping of conventional vibrated concrete (CVC) the viscosity term is replaced by the concrete yield stress. However, recently, the influence of viscosity on pumping pressure has been reevaluated for self-consolidating concrete (SCC).In this paper, the influence of concrete rheology, tribology, flow rate and pipe radius on pumping pressure are discussed, based on full-scale pumping tests. The concrete mixtures varied from pumpable CVC to segregating SCC. The influence of flow rate and viscosity on pumping of concrete has been confirmed. It is also shown that with a 20% decrease in pipe radius (from 125 to 100 mm), the pumping pressure can be roughly doubled. An increase in yield stress also increases the pumping pressure, but its influence is only visible when the viscosity is approximately constant. The total flow resistance in the tribometer also appears to correlate well with the pumping pressure, proving that the developed tribometer mimics quite well the flow of concrete in a pipe.     

Effect of confinement level,aspect ratio and concrete strength on the cyclic stress–strain behavior of FRP-confined concrete prisms

Behavior of rectangular concrete columns confined with FRP composites depends on several parameters, including unconfined concrete strength, confinement level, aspect ratio of cross-section (defined as the depth/width of the cross-section), and the sharpness of the section corners. For modeling the cyclic stress–strain behavior of FRP-confined rectangular concrete columns, effect of column parameters on the cyclic behavior of these columns should be examined properly. In this paper, effects of unconfined concrete strength, confinement level and the aspect ratio of cross-section are studied. The test database includes 10 prisms from recent study of authors and 18 prisms from a new experiment. Results of tests show that some aspects of cyclic behavior of FRP-confined concrete prisms such as envelope curve and stress deterioration are unaffected by the considered parameters. Results also indicate that the plastic strain decreases as the unconfined concrete strength increases, but it is independent of the aspect ratio and the confinement level. While the reloading path in all specimens was almost linear, the unloading path was highly nonlinear and was affected by unconfined concrete strength.     

Stability of Bingham flows: from the earliest works of A.A. Il’yushin to the present

A review of the works devoted to stability of Bingham flows with respect to perturbations of various kinds is presented. Both hydrodynamic aspects and bifurcation approaches to stability are affected. Much attention is given to Il’yushin’ articles in the late 1930s and the early 1940s of the twentieth century which had been pioneer in these subjects.     

Measurement of Young’s modulus of oxides at high temperature related to the oxidation study

Abstract

α-Al₂O₃, Cr₂O₃, and α-Fe₂O₃ specimens were prepared by a sintering process. A 400 – 1000-Hz sine wave was applied to the specimen at 290 – 1273 K. The applied and respond waves were monitored by using force and acceleration sensors. The intensity ratio and phase shift between the applied and respond waves were analysed, and the anti-resonance frequency was obtained. Young’s moduli of α-Al₂O₃, Cr₂O₃, and α-Fe₂O₃ are estimated to be 386, 286, and 220 GPa at 298 K, respectively. The temperature dependence values of these oxides are estimated to be 54.3, 46.9, and 42.0 MPa K^-1, respectively. The temperature dependence of Young’s modulus can be classified on the basis of the crystal structure of solids. The estimation of Young’s modulus at 1273K is possible with an error range of 10 – 30 GPa for a crystalline solid if the crystal structure of the solid is known. It is found that the temperature dependence of Young’s modulus depends on the density of the oxides, and an experiment in which well-characterized crystalline solids are used must be conducted to minimize the error range.     

Maximisation of the ratio of microhardness to the Young's modulus of Ti–12Mo–13Nb alloy through microstructure changes

Alloys for orthopaedic and dentistry applications require high mechanical strength and a low Young's modulus to avoid stress shielding. Metastable β titanium alloys appear to fulfil these requirements. This study investigated the correlation of phases precipitated in a Ti–12Mo–13Nb alloy with changes in hardness and the Young's modulus. The alloy was produced by arc melting under an argon atmosphere, after which, it was heat treated and cold forged. Two different routes of heat treatment were employed. Phase transformations were studied by employing X-ray diffraction and transmission electron microscopy. Property characterisation was based on Vickers microhardness tests and Young's modulus measurements. The highest ratio of microhardness to the Young's modulus was obtained using thermomechanical treatment, which consists of heating at 1000 °C for 24 h, water quenching, cold forging to reduce 80% of the area, and ageing at 500 °C for 24 h, where the final microstructure consisted of an α phase dispersed in a β matrix. The α phase appeared in two different forms: as fine lamellas (with 240 ± 100 nm length) and massive particles of 200–500 nm size.     

How different are the indicatrixes of the leaves of various woody plant species?

Some researchers assume that the light reflection from leaves is Lambertian, but I verify that some leaves exist showing no Lambertian reflection. One can measure the indicatrixes of leaves of various woody plant species by the use of a goniophotometer. Minnaert constants can be calculated from these indicatrixes for quantitative evaluation. I discuss why light scattering from leaves does not always obey Lambertian law.     

Simulating the behaviour of fresh concrete with the Distinct Element Method – Deriving model parameters related to the yield stress

This article describes a numerical approach based on the Distinct Element Method (DEM) as a means of simulating fresh concrete during its different working processes. First, a rheological model for fresh concrete and its implementation into a DEM code are presented. Then the main focus is directed at establishing an algorithm to derive the model parameters related to yield stress according to the Bingham model. For this an analytical prediction of stress distribution at the beginning of the slump-flow test is used as reference for the corresponding numerical analysis. For the sake of validation, the analytical and numerical predictions of the final shape of the concrete cake in the slump-flow test are compared. The validation was performed for three different reference values of yield stress. Additionally, the numerical and analytical results of the so-called LCPC-box test were evaluated for the same sets of parameters. The results of the numerical analysis agreed well with the results predicted by analytical solutions for all parameter combinations. Therefore, the proposed algorithm was shown to be a sound procedure in linking yield stress of the simulated concrete to the bond strength, which is the main parameter of the model suggested.     

How would setting policy priorities according to cost-benefit analyses affect the provision of road safety?

This paper analyses how setting priorities for road safety strictly according to cost-benefit analysis would affect the provision of road safety in Norway and Sweden. The paper is based on recent analyses of the efficiency of road safety policies in these two countries. The argument sometimes made by critics of cost-benefit analysis, that only a few road safety measures are cost-effective (have benefits greater than costs), is not supported. Cost-effective road safety policies could prevent between 50 and 60% of the current number of road accident fatalities in both Norway and Sweden, if pursued consistently during a period of 10 years (2002-2011). If current policies are continued, only about 10-15% of the current number of road accident fatalities are likely to be prevented during the next 10 years. A number of sources of inefficiency in road safety policy are identified. A source of inefficiency is anything that prevents policy priorities from being set according to cost-benefit analysis. These include: (a) lack of power, which means that national governments do not have the formal authority to introduce a certain road safety measure, in Europe, this applies to new vehicle safety standards, which are passed almost exclusively by the European Union; (b) the existence of social dilemmas, which means that measures that are cost-effective from a societal point of view are not so from the point of view of individual road users; (c) priority given to other policy objectives, in particular regional development. Scarcity of resources, which obtains when public budgets have to be increased to make room for all cost-effective measures, was not found to be a constraint. All cost-effective measures can be funded within current budgets, provided the use of inefficient measures ceases.     

How can graphene reduce the flammability of polymer nanocomposites?

Nanocomposites based on poly(vinyl alcohol) (PVA) and graphene nanosheets have been prepared by polymer solution blending and their flame retardant properties have been evaluated by a cone calorimetry test. It has been shown that there is a strong influence of graphene nanosheets on the fire behaviour of the composites with a significant reduction in peak heat release rate (PHRR) and a much longer time to ignition. Compared to pure PVA, the PHRR of PVA filled with 3 wt.% graphene is reduced by 49%. The flame retardancy of graphene for PVA matrix surpasses that of both Na-MMT and MWNTs with the same addition content. Such a remarkable behaviour might be explained by the forming of a compact, dense and uniform char during combustion.     

How big is the linear region of irreversible thermodynamics?

The driving forces of diffusion reach their largest values in thin films. Temperature and voltage gradients may be steep simply because the film is thin.The matter and energy fluxes of diffusion contain, in principle, a whole series of cross terms. Commonly, we take only first order terms and ignore those of second and higher order; we restrict ourselves to “small” temperature and voltage gradients, to “the linear region of irreversible thermodynamics”.But how big is “small”? The present paper proposes that the linear region of irreversible thermodynamics extends from complete equilibrium to limits in which the energy change in the carrier system (e.g. phonons or plasmons), over a distance of one mean free path along the energy gradient, is comparable with the total energy in the carrier system. If the energy is E and the mean free path is λ, the limit occurs when

$\text{λ▽E}\text{E→1}$

Within this limit, experiments in thermomigration and electromigration measure equilibrium properties. The “reduced heat of transport” of a crystal defect is rigorously identified as the thermal energy of the defect structure.     

Laser-induced liquid bead ion desorption mass spectrometry: an approach to precisely monitor the oligomerization of the β-amyloid peptide

In the present work, the recently developed laser-induced liquid bead ion desorption mass spectrometry (LILBID MS) is applied as a novel technique to study Aβ oligomerization, thought to be crucial in Alzheimer's disease (AD). The characterization of the earliest nucleation events of this peptide necessitates the application of several techniques to bridge the gap between small oligomers and large fibrils. We precisely monitored in time the transformation of monomeric Aβ (1-42) into oligomeric Aβ(n) (n < 20) and its dependence on concentration and agitation. The distribution shows signs of the hexamer being crucial in the assembly process. The intensity of the monomer decreases in time with a time constant of about 9 h. After a lag time of around 10 h, a phase transition occurred in which the total ion current of the oligomers goes to nearly zero. In this late stage of aggregation, protofibrils are formed and mass spectrometry is no longer sensitive. Here fluorescence correlation spectroscopy (FCS) and transmission electron microscopy (TEM) are complementary tools for detection and size characterization of these large species. We also utilized the oligomers of Aβ (1-42) as a model of the corresponding in vivo process to screen the efficacy and specificity of small molecule inhibitors of oligomerization. The LILBID results are in excellent agreement with condensed phase behavior determined in other studies. Our data identified LILBID MS as a powerful technique that will advance the understanding of peptide oligomerization in neurodegenerative diseases and represents a powerful tool for the identification of small oligomerization inhibitors.