Forward dynamical analysis of flexible multibody systems using system-level model reduction

Fast simulation (e.g., real-time) of flexible multibody systems is typically restricted by the presence of both differential and algebraic equations in the model equations, and the number of degrees of freedom required to accurately model flexibility. Model reduction techniques can alleviate the problem, although the classically used body-level model reduction and general-purpose system-level techniques do not eliminate the algebraic equations and do not necessarily result in optimal dimension reduction. In this research, Global Modal Parametrization, a model reduction technique for flexible multibody systems is further developed to speed up simulation of flexible multibody systems. The reduction of the model is achieved by projection on a curvilinear subspace instead of the classically used fixed vector space, requiring significantly less degrees of freedom to represent the system dynamics with the same level of accuracy. The numerical experiment in this paper illustrates previously unexposed sources of approximation error: (1) the rigid body motion is computed in a forward dynamical analysis resulting in a small divergence of the rigid body motion, and (2) the errors resulting from the transformation from the modal degrees of freedom of the reduced model back to the original degrees of freedom. The effect of the configuration space discretization coarseness on the different approximation error sources is investigated. The trade-offs to be defined by the user to control these approximation errors are explained.     

Variations in essential oil and fatty acid composition during Myrtus communis var. italica fruit maturation

The essential oil and fatty acid composition of Myrtus communis var. italica fruit during its ripening was determined. The effect of the harvesting time on some physical properties of Myrtus fruits, fruit weight and moisture content, were significant. The increase of fruit weight (from 2.54 to 8.79 g% fruits) during ripeness was correlated positively with that of moisture content (from 28% to 72%). Fruit essential oil yields varied from 0.003% to 0.01% and showed a remarkable increase at 60 days after flowering to reach a maximum of 0.11%. Forty-seven volatile compounds were identified in fruit essential oils; 1,8-cineole (7.31–40.99%), geranyl acetate (1.83–20.54%), linalool (0.74–18.92%) and α-pinene (1.24–12.64%) were the main monoterpene compounds. Total fatty acid contents varied from 0.81% to 3.10% during fruit maturation and the predominant fatty acids were linoleic (12.21–71.34%), palmitic (13.58–37.07%) and oleic (6.49–21.89%) acids. The linoleic acid proportions correlated inversely with palmitic and oleic acids during all the stages of ripening.     

Effect of mineral filler type on autogenous shrinkage of self-compacting concrete

Based on an experimental programme, including autogenous shrinkage tests on concrete, ultrasonic monitoring of fresh concrete, and mercury intrusion porosimetry, the influence of the filler type on the autogenous shrinkage of self-compacting concrete has been investigated. The onset of percolating structure formation (time zero) is influenced by the filler type due to a possible accelerating effect of the filler on the cement hydration. Limestone filler accelerates the hydration process, and reduces time zero, while this is not the case when using quartzite filler. Using fly ash, showing only a slight acceleration, a slight reduction of time zero is obtained. A very significant swelling peak is noticed during the first day. This swelling peak is not a measuring artefact, but is caused mainly by water absorption on the filler surface and resulting disjoining pressure. Some part of the swelling peak might also be caused by Ca(OH)₂ crystallisation. The fineness of the filler is an important factor for this swelling behaviour, although also the nature of the filler seems to have an influence. The superplasticiser also interacts with the fillers, influencing the swelling behaviour. The different filler types used in this study did not lead to significant differences in critical pore diameter of the microstructure. This might explain why no significant differences have been found in final autogenous shrinkage values using the different filler types.     

Retrovirally transduced bone marrow-derived dendritic cells require CD4+ T cell help to elicit protective and therapeutic antitumor immunity

It has been extensively documented that murine dendritic cells loaded with tumor-associated Ag (TAA)-derived peptides or protein can prime Ag-specific CD8+ cytotoxic T cells in vivo and can elicit Ag-specific immunity. Optimal presentation of TAA might be achieved by retroviral transduction of DCs allowing long term and stable expression of the TAA-peptides as well as the presentation of multiple epitopes in the context of MHC class I and/or class II molecules. Here we show that retroviral transduction of bone marrow-derived dendritic cells (DCs) with chicken OVA cDNA or the reporter gene green fluorescent protein retained their potent stimulatory capacity and that the transduced DCs could process and present the endogenously expressed OVA protein. The DCs transduced with cDNA encoding native OVA protein presented OVA-derived peptides in the context of MHC class I as well as MHC class II and induced a strong Ag-specific CTL response. DCs expressing a cytosolic form of OVA presented OVA peptides only in the context of MHC class I and failed to induce an OVA-specific CTL response in vivo when they had been cultured in the absence of exogenous protein. Immunization with retrovirally transduced DCs resulted in an Ag-specific immunity and rejection of a tumor cell challenge and a significant survival advantage in tumor-bearing mice. These results obtained in this rapidly lethal tumor model suggest that DCs transduced with TAA may be useful for tumor immunotherapy and underscore the importance of the simultaneous delivery of T cell help in the development of Ag-specific cytotoxic T-cells.     

An open book on Facebook? Examining the interdependence of adolescents’ privacy regulation strategies

Users of social network sites (SNSs) use three main strategies that help to manage the privacy of their profile information: (1) limiting the level of data revealed, (2) using privacy settings to exert control over data and (3) audience/friendship management by being restrictive about whom to accept as a ‘friend’. Extant research does not show whether these strategies operate as independent mechanisms or whether they are interdependent and work as a system. Given what offline privacy theorist Irwin Altman (1977 Altman, Irwin. 1977. “Privacy Regulation: Culturally Universal or Culturally Specific?” Journal of Social Issues 33 (3): 66–84. doi: 10.1111/j.1540-4560.1977.tb01883.x[Crossref], [Web of Science ®] , [Google Scholar]) designates as the multi-mechanic nature of privacy protection, we test a model in which we expect to find that the three discerned strategies are related to one another. Structural equation modelling analysis performed on the subsample (n?=?1564) of our study’s data – collected among 1743 adolescents by means of a paper-and-pencil survey – demonstrates that, in line with Altman’s vision of privacy protection, the three discerned strategies effectively operate as an interdependent system. In congruence with the hypotheses derived from extant research, we found that adolescents’ level of disclosure influences adolescents’ involvement in the two other discerned strategies: Adolescents with high levels of personal information disclosure share an increased tendency to have many friends on SNSs and a lower level of using privacy settings.     

Under pressure to sext? Applying the theory of planned behaviour to adolescent sexting

Adolescent sexting – the electronic swapping of sexually intimate texts or images – has attracted significant media and policy attention. However, questions remain about the predictors of this phenomenon, in which mobile phones play a central role in adolescents’ exploration of sexuality. Therefore, a survey involving 498 adolescents aged between 15 and 18 years was conducted. The first aim of this study is to determine the predictive value of personal attitudes, subjective norm (SN) and perceived behavioural control by applying the theory of planned behaviour (TPB). As the second aim, we wish to assess the relative importance of the most salient beliefs underpinning the TPB components, since this will allow us to gain a more nuanced insight into the characteristics of adolescent sexting. Analyses reveal that SN is the most important predictor, followed by adolescents’ attitudes towards sexting. Perceived behavioural control is significantly but weakly associated with teenagers’ sexting intentions. Within SN, friends and romantic partners represent the most important sources of social pressure, while only positive behavioural outcomes are found to affect adolescents’ sexting intentions. The most important control belief affecting adolescents’ intention to sext is the belief that it occurs relatively more often among those whom adolescents feel they can trust entirely.     

Integration approach of the Couette inverse problem of powder type self-compacting concrete in a wide-gap concentric cylinder rheometer: Part II. Influence of mineral additions and chemical admixtures on the shear thickening flow behaviour

The influence of mineral additions and chemical admixtures on the shear thickening flow behaviour of powder type self-compacting concrete (SCC) is studied by means of a wide-gap concentric cylinder rheometer. The Couette inverse problem is treated by means of the integration method in order to derive the flow curve τ(γ?) from the torque measurements.According to the experimental results, the shear thickening effect is found to be strongly influenced by the addition of the chemical admixture (a polycarboxylate ether based superplasticizer), whereas mineral additions were found to modify the intensity of shear thickening. The limestone, quartzite and fly ash addition used in this research project, respectively increase, unalter and decrease the shear thickening intensity. The powder volume and the available amount of free water proved to have a major impact on the viscosity of the powder type SCC mixes. Increasing the powder volume or decreasing the amount of free water results in an increased viscosity of the SCC mix.