Monte Carlo simulation on tensile failure process of unidirectional carbon fiber reinforced nano-phased epoxy

This paper presents an analytical approach which combines the modified shear-lag model and Monte Carlo simulation technique to simulate the tensile failure process of unidirectional T700 carbon reinforced composite. Two kinds of matrix were investigated in the present paper, one is neat epoxy and the other one is SiC nano-particle filled epoxy. In the model, the strength of the fiber elements is randomly allocated by the Monte Carlo method, the elastic properties of the matrix elements and the friction after the interfaces breakage are definitely allocated. Using this model, the deformation, damage and failure process of the composite are simulated on the microscopic level, the tensile stress–strain relationship is well predicted. The relationship between mechanical properties of the fiber, matrix and composites was discussed. The analysis also shows that, compared with the neat system, nano-phased composite exhibits 10% improvement in tensile strength, which agrees with the experimental data.     

A transaction model and multiversion concurrency control for mobile database systems

Transaction management on Mobile Database Systems (MDS) has to cope with a number of constraints such as limited bandwidth, low processing power, unreliable communication, and mobility etc. As a result of these constraints, traditional concurrency control mechanisms are unable to manage transactional activities to maintain availability. Innovative transaction execution schemes and concurrency control mechanisms are therefore required to exploit the full potential of MDS. In this paper, we report our investigation on a multi-versions transaction processing approach and a deadlock-free concurrency control mechanism based on multiversion two-phase locking scheme integrated with a timestamp approach. We study the behavior of the proposed model with a simulation study in a MDS environment. We have compared our schemes using a reference model to argue that such a performance comparison helps to show the superiority of our model over others. Experimental results demonstrate that our model provide significantly higher throughput by improving degree of concurrency, by reducing transaction wait time, and by minimizing restarts and aborts.     

Novel reagents for iron and sulphur control in medium temperature leaching of sulphide concentrates

Hydrometallurgical leaching of sulphide concentrates of copper and nickel at medium temperature (150°C) produces residues that contain sulphur and iron-bearing minerals and phases. During leaching, and depending on various process parameters, iron may be precipitated as hematite, goethite, jarosite or other oxyhydroxides, which may be more or less crystalline. Hematite is the favoured iron precipitate, because it is the most environmentally stable and does not ad/absorb as much copper, nickel or other solution constituents during precipitation. However, the low solubility of iron during the medium temperature processing of sulphide ores can favour the formation of poorly crystalline, nano-scale iron oxide/oxyhydroxide phases. In some cases, these phases have been positively identified as the metastable ferrihydrite, which transforms into iron oxides such as goethite, hematite and magnetite over time. A better understanding of what may help drive this transformation during leaching would ultimately result in lower valuable metal losses and more stable leach residues. Higher acid concentrations result in increased copper extractions and favour the formation of hematite during concentrate leaching, rather than other metastable phases. Furthermore, commercially available water displacement formula ‘WD40®’ and other novel reagent(s) affect Fe precipitation and sulphur chemistry, leading to very different process outcomes such as improved extractions and larger, more easily separated, sulphur particles.     

Development of a wind turbine gearbox virtual load sensor using multibody simulation and artificial neural networks

A current development trend in wind energy is characterized by the installation of wind turbines (WT) with increasing rated power output. Higher towers and larger rotor diameters increase rated power leading to an intensification of the load situation on the drive train and the main gearbox. However, current main gearbox condition monitoring systems (CMS) do not record the 6‑degree of freedom (6-DOF) input loads to the transmission as it is too expensive. Therefore, this investigation aims to present an approach to develop and validate a low-cost virtual sensor for measuring the input loads of a WT main gearbox. A prototype of the virtual sensor system was developed in a virtual environment using a multi-body simulation (MBS) model of a WT drivetrain and artificial neural network (ANN) models. Simulated wind fields according to IEC 61400‑1 covering a variety of wind speeds were generated and applied to a MBS model of a Vestas V52 wind turbine. The turbine contains a high-speed drivetrain with 4‑points bearing suspension, a common drivetrain configuration. The simulation was used to generate time-series data of the target and input parameters for the virtual sensor algorithm, an ANN model. After the ANN was trained using the time-series data collected from the MBS, the developed virtual sensor algorithm was tested by comparing the estimated 6‑DOF transmission input loads from the ANN to the simulated 6‑DOF transmission input loads from the MBS. The results show high potential for virtual sensing 6‑DOF wind turbine transmission input loads using the presented method.

     

Surface Characteristics of Kaolinite and Other Selected Two Layer Silicate Minerals

The electrokinetic features and interfacial water structure, as revealed from molecular dynamics simulations (MDS) are considered with respect to the anisotropic features of selected two layer silicate minerals. Planar structures of kaolinite and antigorite are compared to the, compositionally equivalent, tubular structures of halloysite and chrysotile with respect to the pH dependency of zeta potential as determined from the electrophoretic mobility measurements. The importance of the atomic mismatch between the tetrahedral and octahedral sheets in a particular bilayer is discussed in order to explain the electrokinetic behaviour of these two layer silicate minerals. Interfacial water structure from MDS suggests that the silica tetrahedral surface is not wetted by water. In the case of planar silicates structural imperfections are considered to explain wetting characteristics. The possibility of polarity reversal (domain inversion) within a tetrahedral/octahedral layer and an out‐of‐order layer (inserted layer) within the tetrahedral/octahedral stack are considered in order to explain electrokinetic behaviour and wetting characteristics.     

Effect of Annealing on the Optical Properties of GaN Films Grown by Pulsed Laser Deposition

In the present study,gallium nitride thin films were grown by using pulsed laser deposition.After the growth samples were annealed at 400 and 600℃in the nitrogen atmosphere.Surface morphology of the as-grown and annealed samples was observed by atomic force microscopy.Post-growth annealing results in an improved surface roughness of the films.Chemical analysis of the samples was performed by X-ray photoelectron spectroscopy.Stoichiometric gallium nitride thin films were obtained for the samples annealed at 600℃.Optical measurements of the samples were performed to measure the band gap and optical constants of the films.Effect of annealing on the band gap and optical constants of the films was studied.     

Three-Dimensional Nonlinear Finite-Element Analysis of Gasketed Flange Joint under Combined Internal Pressure and Variable Temperatures

Performance of a flange joint is characterized mainly due to its “strength” and “sealing capabilit.” A number of analytical and experimental studies have been conducted to study these characteristics only under internal pressure loading. The effect of steady state thermal loading is a well recognized problem and makes the problem more complex under combined application of internal pressure and temperature. To investigate fundamental joint characteristics, joint strength and sealing capability under combined internal pressure, and variable steady state thermal loading, a three-dimensional nonlinear finite-element analysis of gasketed flange joint is carried out using ANSYS commercial software. Reduced joint strength is concluded due to the flange rotation resulting in flange yielding under bolt up and applied operating conditions. Reduced joint sealing is concluded due to the variation in gasket seating or contact pressure due to bolt load variation. Flange rotation, bolt bending, and joint relaxation concluded fatigue and dynamic behavior in the gasketed joint. These effects are observed to be more pronounced at higher temperatures. Verification of finite-element model with available classical theories is also performed and discussed.     

Damage-Associated Molecular Patterns (DAMPs) in Retinal Disorders

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of damaged tissue or dead cells. Recent evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, high glucose, oxidative stress, ischemia, mechanical trauma, stress, or environmental conditions, in retinal diseases. DAMPs activate the innate immune system, suggesting their role to be protective, but may promote pathological inflammation and angiogenesis in response to the chronic insult or injury. DAMPs are recognized by specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs) and the NOD-like receptor family (NLRs), and purine receptor 7 (P2X7), in systemic diseases. However, studies describing the role of DAMPs in retinal disorders are meager. Here, we extensively reviewed the role of DAMPs in retinal disorders, including endophthalmitis, uveitis, glaucoma, ocular cancer, ischemic retinopathies, diabetic retinopathy, age-related macular degeneration, rhegmatogenous retinal detachment, proliferative vitreoretinopathy, and inherited retinal disorders. Finally, we discussed DAMPs as biomarkers, therapeutic targets, and therapeutic agents for retinal disorders.