A solar receiver-reactor with specularly reflecting walls for high-temperature thermoelectrochemical and thermochemical processes

A new kind of receiver-reactor for high temperature solar furnaces is proposed. The main body of the receiver component is an ellipsoid of revolution with specularly reflecting inner walls. The reactor component, a crucible, is placed at one focal point and the aperture at the other. With this arrangement, substantially all of the incident radiation from the concentrator should reach the reactor directly or after one reflection from the cavity walls. An analysis of the radiative exchange among the surfaces is presented. The analysis provides a tool for a parametric study and optimization of the design. It is found that, in contrast to that of conventional well-insulated cavity receivers, its collection efficiency is not very sensitive to the size of its aperture.     

Large-scale polyaniline batteries

The electrochemical performance of polyaniline film (PAnF) and polyaniline powder (synthesized chemically, (PAnC), or electrochemically (PAnE)) as the positive electrode material in zinc rechargeable batteries has been examined. The energy density of the different forms of polyaniline is in the order: PAnF > PAnE > PAnC. Diffusion of reacting species has been identified as the principal factor determining the characteristics of the polyaniline powder electrode. The 1A form of polyaniline provides a slightly greater energy density than the 1S form.     

Fast and exact method for line outage studies in power systems

This paper presents an exact and fast method to evaluate the effect of line contingencies upon the system bus voltages. The base-case load flow, utilizing the second-order terms to reach a steady-state solution, has been extended to study the effect of different line outages. The Jacobian matrix of the base-case load flow is kept constant during the line outage studies, and a few additional terms are added in the iterative process to simulate a line contingency.The validity of the new method was tested by its application to the 220 kV 31-bus system representing the unified power network of Lower Egypt.     

Electrochemical and structural aspects of lithium insertion into the new layered compound CdIn2S2Se2

Electrochemical lithium insertion in pure and (PTFE-and/or C-) mixed CdIn₂S₂Se₂ has been investigated by galvanostatic discharge experiments in the (−) Li/organic electrolyte/CdIn₂S₂Se₂ (+) cell, also considering the behaviour in quasi-equilibrium open-circuit conditions, and by cyclic voltammetry. Structural changes induced by lithium insertion have been observed by powder X-ray diffraction measurements. The reversibility of the process is poor in the whole range explored, but differences in behaviour are noticed. During a galvanostatic discharge of the cell up to about 0.7 F.mol⁻¹ no structural change takes place and the lithium diffusion process is slow, as shown by the very low value of the chemical diffusion coefficient (around 10⁻¹² cm².s⁻¹, at 30 °C) determined according to a current-pulse relaxation technique. During a deeper discharge up to 5.35 F.mol⁻¹ two plateaux — a short and an extended one — are noted in the experimental curve, while pseudocrystalline phases are formed. As a consequence of these structural rearrangements, the time needed to reach open-circuit quasi-equilibrium conditions after a galvanostatic discharge is high, particularly in the region of the first plateau. Analyses of the results evidence that CdIn₂S₂Se₂ is a very interesting new compound, more significant for its fundamental properties than in view of its application as cathode material in aprotic solvent lithium cells.     

Synergism in novel silver-copper/hydroxyapatite composites for increased antibacterial activity and biocompatibility

This study develops a novel silver-copper/hydroxyapatite composite (Ag–Cu/HA) with high biocompatibility and antibacterial activity. Two different materials were synthesized, namely silver-hydroxyapatite (Ag-HA) and copper-hydroxyapatite (Cu-HA) composites, with 0.1%, 0.5%, and 1.0% (mol) of each metal. These materials were mixed in a planetary mill to obtain the Ag–Cu/HA composites. The results of our characterization demonstrated the low cytotoxicity and hemolytic response. The composite showed higher percent-inhibition for bacterial growth compared to those in separated composites of silver or copper with hydroxyapatite. Hence, these new materials promise higher efficacy as antibacterial hydroxyapatites.     

Localising discontinuities using weak continuity constraints

Many processes in computer vision can be formulated concisely as optimisation problems. In particular the localisation of discontinuities can be regarded as optimisation under weak continuity constraints. A weak constraint is a constraint which can be broken — but at a cost.In this paper we illustrate the use of weak constraints by considering a simple example — edge detection in 1D. Finite elements are used to discretise the problem. The cost function is minimised using a ‘graduated non-convexity’ algorithm. This gives a local relaxation scheme which could be implemented in parallel.Results are given for a serial computer implementation of the method. They show that the algorithm does perform as theoretically predicted, and that it is robust in the presence of noise. Results are also given for a 2D version of the method, applied to real images.     

Bangladesh energy resources and renewable energy prospects

Bangladesh is a low-economy country with annual commercial energy consumption of only 35 kgOE/capita. Fossil fuel reserves are meagre; about 80% of the total energy supply comes from biomass. The fuel import bill is ~ 70% of total export earnings. Solar and wind energy have bright prospects for parts of the country where natural gas is not available and the cost of electricity, generated from oil-fired units, is high. Solar energy is abundant while wind speeds are high in some coastal areas. For rural electrification, the high cost of distribution lines makes solar electricity viable for remote locations, while wind machines may be set up in coastal areas.     

Microstructural evolution and micromechanical properties of thermally sprayed hydroxyapatite coating

ABSTRACT

The effects of preheating and annealing processes on the micromechanical features of thermally sprayed hydroxyapatite (HA) coatings were investigated. The results indicated that subsequent heat treatment at 700°C for 60?min promotes the development of a crystalline HA coating. The EDS line scan showed that the oxygen content was homogeneous along the thickness direction from the coating surface to the titanium–HA interface, whereas the calcium and phosphorus concentration gradually decreased at 7?μm from the interface. From the roughness profiles, the coatings on preheated substrates gave lower roughness compared to the coatings at room temperature. According to the nanoindentation results, the sample preheated at 300°C after annealing at 700°C exhibited an elastic modulus of 108.1?±?6?GPa and hardness of 5.97?±?0.3?GPa, which were almost 3% lower and 171% higher than the bare substrate, respectively.