Mechanical response of novel SiOC glasses to high temperature exposition

The presented work describes mechanical properties of materials prepared by the pyrolysis of polysiloxane resins. The polymeric precursors have different chemical composition. Materials under investigation are predetermined for high temperature resistant applications usually in composite form, i.e. accompanied by some reinforcement. Instrumented hardness tests were employed for material characterisation. The Vickers hardness, Martens hardness and indentation elastic modulus were the key parameters, determined either from the standard optical technique or load–indentation depth curves. The influence of mechanical properties on the monomers ratio was established. The exposition to the temperature between 1200 °C and 1500 °C in air was applied to observe damage caused by these severe conditions.     

Formulation of consistent restoring stiffness in ship hydroelastic analysis

In this article, the role of the restoring stiffness, as one of the basic parameters in ship hydroelastic analysis, is brought out. It is formulated using the variational principle and the method of virtual displacements. It is shown that asymmetry of the restoring stiffness is a physical reality. Moreover, it is confirmed that modal variation, still disputed in the relevant literature, has to be taken into account to satisfy the ship’s stability. Consistent stiffness is formulated here by regarding stiffness definition as relation between forces and displacements. Hybrid stiffness known from the literature is wrong since some terms are specified as relation between forces and displacement gradient. Influence of the consistent and symmetrized stiffness matrix, and the hybrid one, on dynamic response is illustrated for a prismatic pontoon and a large container ship. It is found that the latter two matrices do not assure convergence of transfer functions of sectional forces to zero value as the wave frequency approaches zero. The rigid body and elastic responses are compared, and pertinent conclusions are drawn. It is also shown that it is not necessary to use the unified geometric and restoring stiffness for ordinary hydroelastic analysis of ship structures. The consistent formulation of the restoring stiffness matrix will be useful for extending linear potential theory hydrodynamic codes for rigid body analysis to deformable bodies.     

Inverse modelling of an aneurysm’s stiffness using surrogate-based optimization and fluid-structure interaction simulations

Characterization of the mechanical properties of arterial tissues is highly relevant. In this work, we apply an inverse modelling approach to a model accounting for an aneurysm and the distal part of the circulation which can be modified using two independent stiffness parameters. For given values of these parameters, the position of the arterial wall as a function of time is calculated using a forward simulation which takes the fluid-structure interaction (FSI) into account. Using this forward simulation, the correct values of the stiffness parameters are obtained by minimizing a cost function, which is defined as the difference between the forward simulation and a measurement. The minimization is performed by means of surrogate-based optimization using a Kriging model combined with the expected improvement infill criterion. The results show that the stiffness parameters converge to the correct values, both for a zero-dimensional and for a three-dimensional model of the aneurysm.     

Modelling of wind energy‐based microgrid system implementing MMC

Nowadays, renewable energy systems have come up with more potential in power generation so as to meet the power demand. Among all the renewable systems, the wind energy generating system is believed to be at the peak. However, the wind energy‐based microgrid system is associated with many problems such as fluctuations in output voltage due to the fluctuated wind speeds and harmonics generations in the system. To address these issues, this article proposes a new method in order to achieve harmonic mitigation across its output by maintaining constant voltage. Nevertheless, particular attention has been given to the form and function of modular multilevel converter with multi‐winding transformer connected to the grid. Modular multilevel converter has been implemented with an advanced voltage controller tuned to control the voltage at its output. Also, a new system topology has been introduced with two wind turbines that are interconnected to multi‐winding transformer through asynchronous generators. The proposed system has been implemented with constant and variable wind speeds, and their respective results have also been analysed. The proposed scheme shows its effectiveness by theoretical calculations, verified by simulation and experimental results. Copyright © 2016 John Wiley & Sons, Ltd.     

Granulometry,cluster analysis and spatial distribution of manganese contaminated soils,Kgwakgwe, southeastern Botswana

The particle size distribution (PSD) of 400 Mn contaminated soil samples was established, and generated data were statistically analysed and spatially presented. The PSD for the 53 µm – 4 µm size fraction soil samples ranged from 11.05 to 100 wt %, whereas that for < 4 µm was from 0.3 to 30 wt %. Texturally, samples were dominantly silt loam, although silt and sandy loam were also present, as well as loam, loamy sand and clay classes. Six clusters were identified with cluster one being the most dominant occurring in sandy loam, silt loam and loamy sand. The < 53 µm fraction had three dominant areas, and the < 4 µm fraction had several unevenly presented populations as reflected in the maps. Because of its spatial distribution, the < 4 µm fraction may pose hazards to human health. Furthermore, predominance of Mn limits land use to subsistence agriculture with possibly low crop yield.     

The Fifth WS/DGAT Enzyme of the Bacterium Marinobacter aquaeolei VT8

Wax esters (WE) belong to the class of neutral lipids. They are formed by an esterification of a fatty alcohol and an activated fatty acid. Dependent on the chain length and desaturation degree of the fatty acid and the fatty alcohol moiety, WE can have diverse physicochemical properties. WE derived from monounsaturated long-chain acyl moieties are of industrial interest due to their very good lubrication properties. Whereas WE were obtained in the past from spermaceti organs of the sperm whale, industrial WE are nowadays mostly produced chemically from fossil fuels. In order to produce WE more sustainably, attempts to produce industrial WE in transgenic plants are steadily increasing. To achieve this, different combinations of WE producing enzymes are expressed in developing Arabidopsis thaliana or Camelina sativa seeds. Here we report the identification and characterization of a fifth wax synthase from the organism Marinobacter aquaeolei VT8, MaWSD5. It belongs to the class of bifunctional wax synthase/acyl-CoA:diacylglycerol O-acyltransferases (WSD). The protein was purified to homogeneity. In vivo and in vitro substrate analyses revealed that MaWSD5 is able to synthesize WE but no triacylglycerols. The protein produces WE from saturated and monounsaturated mid- and long-chain substrates. Arabidopsis thaliana seeds expressing a fatty acid reductase from Marinobacter aquaeolei VT8 and MaWSD5 produce WE. Main WE synthesized are 20:1/18:1 and 20:1/20:1. This makes MaWSD5 a suitable candidate for industrial WE production in planta.     

Adsorption onto fluidized powdered activated carbon flocs-pACF

This work presents a new adsorption technique where the adsorbent (powdered activated carbon-PAC) is in the form of suspended flocs formed with water-soluble polymer flocculants. Thus, the adsorption of a typical dye, methylene blue (MB), was studied onto polyacrylamide flocs of PAC (PACF) in a fluidized bed reactor. The technique is based on the fact that the adsorption capacity of PAC does not decrease after flocculation because the adsorbed polymer occupies only a few surface sites, in the form of trains, loops, and tails. Moreover, the adsorption was found to proceed through a rapid mass transfer of MB to the adsorbing PAC flocs, in the same extent as onto PAC. Because of the rapid settling characteristics of the aggregates formed, the two phase separations, loaded PAC and solution, become easier. Thus, the technique offers the advantages of conducting simultaneously both adsorption and solid/liquid separation all in one single stage. Results obtained showed that high MB removal values can be attained in a fluidized bed reactor (>90%) and that PACF presents a much higher adsorption capacity (breakthrough points) than granulated activated carbon (GAC) in the same adsorbing bed. It is believed that this technique highly broadens the potential of the use of powdered activated carbon or other similar ultrafine adsorbents.