Topology error identification using a two-stage DC state estimator

One of the fundamental tenets in deregulation of the power system is to provide fair and open access to transmission facilities. This requires that market participants, both power brokers and generation companies, have complete and timely information as to the transmission availability. The present system of posting available transmission capacities (ATC) is useful but limited because there is no information to predict how these ATCs will change with changing power transfers. It has been proposed that all traders have access to the real-time data of the full transmission model, i.e., state estimator results from the control centers, but this may be too complex and voluminous to be useful to the traders. Instead, making DC power flow data for real-time conditions may provide enough transmission data for traders to make knowledgeable decisions. In this paper, we show how the results of a DC state estimator can be accurately made available to all concerned.     

Optimising industrial hemp fibre for composites

The optimisation of New Zealand grown hemp fibre for inclusion in composites has been investigated. The optimum growing period was found to be 114 days, producing fibres with an average tensile strength of 857 MPa and a Young’s modulus of 58 GPa. An alkali treatment with 10 wt% NaOH solution at a maximum processing temperature of 160 °C with a hold time of 45 min was found to produce strong fibres with a low lignin content and good fibre separation. Although a good fit with the Weibull distribution function was obtained for single fibre strength, this did not allow for accurate scaling to strengths at different lengths. Alkali treated fibres, polypropylene and a maleated polypropylene (MAPP) coupling agent were compounded in a twin-screw extruder, and injection moulded into composite tensile test specimens. The strongest composite consisted of polypropylene with 40 wt% fibre and 3 wt% MAPP, and had a tensile strength of 47.2 MPa, and a Young’s modulus of 4.88 GPa.     

Photogrammetric measurement process capability for metrology assisted robotic machining

This paper documents the findings of experiments done to assess the capability of a photogrammetric measurement process for use in a metrology assisted robotic machining application. Capability is judged from the perspective of uncertainty and error across various part geometries over several days. The influence of operator technique on error and point acquisition ability for challenging geometry is also assessed. The process is found to be resistant to short-term error drift when operating in a controlled environment but systematic and random errors are demonstrated to be highly dependent on geometry. Operator influence on capability is found to be minimal when scanning freeform geometry, although this is unlikely for more complex parts. Acquisition of inspection points on cylindrical pockets is found to be a limitation. Technological development opportunities are highlighted in the context of the metrology assistance application considered. Overall, a thorough assessment of the measurement process capability is made and findings provide a quantification of current state, setting a base case for comparing research progress against.     

Robust Passivity and Stability Analysis of Uncertain Complex-Valued Impulsive Neural Networks with Time-Varying Delays

Neural Processing Letters - In this article, we investigate the robust passivity and stability analysis of uncertain complex-valued impulsive neural network (UCVINN) models with time-varying...     

Microstructure characterization and properties of carbon steel to stainless steel dissimilar metal joint made by friction welding

Dissimilar metals of 1045 carbon steel and 304 stainless steel are joined successfully by friction welding. The microstructure variation and mechanical properties are studied in detail. The weld interface can be clearly identified in central zone, while the two metals interlock with each other by the mechanical mixing in peripheral zone. On carbon steel side, a thin proeutectoid ferrite layer forms along weld interface. On stainless steel side, austenite grains are refined to submicron scale. The δ-ferrite existing in stainless steel decreases from base metal to weld interface and disappears near the weld interface. Severe plastic deformation plays a predominant role in rapid dissolution of δ-ferrite compared with the high temperature. Carbide layer consisting of CrC and Cr₂₃C₆ forms at weld interface because of element diffusion. Metastable phase CrC is retained at room temperature due to the highly non-equilibrium process and high cooling rate in friction welding. The fracture appearance shows dimple fracture mode in central zone and quasi-cleavage fracture mode in peripheral zone. Further analysis indicates that welding parameters govern tensile properties of the joint through influencing the thickness of carbide layer at weld interface and heterogeneous microstructure in thermo-mechanically affected zone on carbon steel side.     

Effect of Process Parameters on Microstructure and Mechanical Properties of Al-11.5%Si-1%Mg/bimodal SiC(m–n)composites

Silicon - Bimodal size SiC particles reinforced Al-Si alloy composites were fabricated by powder metallurgy route. Three different bimodal reinforcements with various volume fractions of micro and...     

Optimization of friction welding parameters using evolutionary computational techniques

The purpose of this study is to propose a method to decide near optimal settings of the welding process parameters in friction welding of stainless steel (AISI 304) by using non conventional techniques and artificial neural network (ANN). The methods suggested in this study were used to determine the welding process parameters by which the desired tensile strength and minimized metal loss were obtained in friction welding. This study describes how to obtain near optimal welding conditions over a wide search space by conducting relatively a smaller number of experiments. The optimized values obtained through these evolutionary computational techniques were compared with experimental results. The strength and microstructural aspects of the processed joints were also analyzed to validate the optimization.     

Materials in RE: Key to renewables exploitation

Those who see renewable energies as naturalistic and representing a return to ‘earth values’ might be surprised at the nature of some of the materials that are key to achieving sustainable energy usage on a commercial scale. Some, indeed, are exotic: products of science and technology at the highest levels. George Marsh reports.     

Polymer and salt selection for lithium polymer batteries

Several network-based polymer electrolytes provide both thermal, mechanical and redox stabilities, while insuring a high conductivity level. Linear unsaturated polyether precursors may be obtained either by step-growth polymerization from oligomeric polyethers or by ring-opening polymerization from oxirane mixtures. In addition, theoretical investigations on several lithium salts are presented, which allowed optimized geometries as well as charge densities to be established in the gas phase.