Advantages and drawbacks of applying periodic time-variant modal analysis to spur gear dynamics

A simplified torsional model with a reduced number of degrees-of-freedom is used in order to investigate the potential of the technique. A time-dependent gear mesh stiffness function is introduced and expanded in a Fourier series. The necessary number of Fourier terms is determined in order to ensure sufficient accuracy of the results. The method of time-variant modal analysis is applied, and the changes in the fundamental and the parametric resonance frequencies as a function of the rotational speed of the gears, are found. By obtaining the stationary and parametric parts of the time-dependent modes shapes, the importance of the time-varying component relative to the stationary component is investigated and quantified. The method used for calculation and subsequent sorting of the left and right eigenvectors based on a first order Taylor expansion is explained. The advantages and drawbacks of applying the methodology to wind turbine gearboxes are addressed and elucidated.     

Are News Audiences Increasingly Fragmented? A Cross-National Comparative Analysis of Cross-Platform News Audience Fragmentation and Duplication

The move to high-choice media environments has sparked fears over audience fragmentation. We analyze news audiences across media platforms (print, television, and online) in 6 countries, going beyond platform-specific, single-country studies. We find surprisingly high levels of news audience duplication, but also that cross-platform audiences vary from country to country, with fragmentation higher in Denmark and the United Kingdom than in Spain and the United States. We find no support for the idea that online audiences are more fragmented than offline audiences, countering fears associated with audience segmentation and filter bubbles. Because all communication exists in the context of its audience, our analysis has implications across the field, underlining the importance of research into how trends play out in different contexts.     

Untersuchung des Strahlverschleißmechanismus von Metallen

Problems of Mechanism of Erosion in Abrasive Stream. The results of investigation obtained by different methods (metallographical and electron microscopy, X-ray analysis, microhardness testing, profile measurement) are presented in the paper. Changes in surface layers prior to chip formation and its separation have been investigated. The specimens, mainly of soft and hardened steels were tested for wear in the stream of abrasive particles with a hardness greater than that of the specimens. The data of investigations show that the so-called polydeformation wear mechanism is of prime importance with soft steels subjected to erosion (mean cycle number n = 4 … 10). In the case oif hardened steels separation of the wear particles is experienced at greater and medium impact angles along the ?white layers”?. The cycle number of particle separation with hardened steels constitutes 1 … 2 only. In the case of quite small impact angles microcutting predominates for all metals.     

Novel homogeneous gel fibers and capillaries from blend of titanium tetrabutoxide and siloxane functionalized ionic liquid

The preparation of ionogels by sol–gel processing has attracted much attention, because the final ceramic materials combine properties of both inorganic matrix (thermal and mechanical stability) and the ionic liquid (ionic conductivity). The aim of this study was to combine different imidazolium based ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF₄], 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF₄], 1-decyl-3-methylimidazolium tetrafluoroborate [DMIM][BF₄] and 1-methyl-3-[3′-(triethoxysilyl)propyl]imidazolium chloride MTICl) with titanium(IV) butoxide to prepare homogenous hybrid fibers through aqueous sol–gel reaction. The study showed that ionic liquid miscibility with metal alkoxide plays an important role in the preparation of homogenous fibers. Unlike simple imidazolium salts functionalized ionic liquid was dispersed homogenously in fibers, but the main advantage is derived from its chemical structure. New stable ionic liquid can be involved in sol–gel processes through ethoxy groups and as a result it associates with titanium alkoxide network by covalent bonding providing non-leaking ceramic hybrid material. Indirect and direct characterization studies of the product were carried out by energy-dispersive X-ray spectroscopy (EDX), silicon-29 nuclear magnetic resonance spectroscopy (²⁹Si NMR), scanning electron microscopy (SEM) and optical microscopies; also infrared spectra (IR) were recorded. Thermal analyses were performed by differential scanning calorimetry (DSC).     

Topology optimization of piezoelectric macro-fiber composite patches on laminated plates for vibration suppression

Structural and Multidisciplinary Optimization - This work presents a new methodology for the topology optimization of piezoelectric actuators in laminated composite structures with the objective of...     

Fibroblast growth on micro- and nanopatterned surfaces prepared by a novel sol–gel phase separation method

Physical characteristics of the growth substrate including nano- and microstructure play crucial role in determining the behaviour of the cells in a given biological context. To test the effect of varying the supporting surface structure on cell growth we applied a novel sol–gel phase separation-based method to prepare micro- and nanopatterned surfaces with round surface structure features. Variation in the size of structural elements was achieved by solvent variation and adjustment of sol concentration. Growth characteristics and morphology of primary human dermal fibroblasts were found to be significantly modulated by the microstructure of the substrate. The increase in the size of the structural elements, lead to increased inhibition of cell growth, altered morphology (increased cytoplasmic volume), enlarged cell shape, decrease in the number of filopodia) and enhancement of cell senescence. These effects are likely mediated by the decreased contact between the cell membrane and the growth substrate. However, in the case of large surface structural elements other factors like changes in the 3D topology of the cell’s cytoplasm might also play a role.     

A critical analysis of erosion problems which have been little studied

During the last ten years numerous papers on the erosion of materials have been published. Many contain general conclusions based either on limited research material or without considering all the factors involved.This paper concentrates attention on some of the laws of erosion which, hitherto, have received little study, and which are important in the first instance for the designing and operation of impact mills.It is shown, that variation within the limits of particle concentrations, causes an up to threefold change and the presence of a comparatively small amount of nonabrasive impurities a more than twofold change in erosion. Data are provided to illustrate the complexity of evolving a mathematical model for calculating the effect of the impact velocity of abrasive particles, particularly at higher impact velocities.