Analysis of complex integral photoelectron spectra

Thesis (M.Sc.) -- University of Adelaide, Dept. of Physics, 1985

Assessing geomorphosites used for rock climbing : the example of Monteleone Rocca Doria (Sardinia, Italy)

Abstract. Within the framework of geomorphosite assessment with reference to tourism potential, a new field of research has opened up focusing on sites used for outdoor activities, like free climbing. This line of research in particular focuses on the suitability of geological and geomorphological characteristics of a specific site for a particular sport. Concentrating on geomorphological hazard, rock quality, tourism capacity and site vulnerability, a method of assessment was designed and tested on a number of important Itahan climbing sites. Using the results of the Monteleone Rocca Dona (Sardinia, Italy), the article presents the proposed approach of assessment. Although the site in question is recognised for its «scientific», «aesthetic» and «cultural value», it has drawn attention for its attractiveness for rock climbers in particular. Thus, the aim of the assessment was to support management of the site by proposing options for utüisation that are sensitive to both the needs of the climbers and the environment in which the site is embedded. In particular, attention was given to potential geomorphologically-related risks for climbers, the impacts linked to human presence and the specific characteristics of the geomorphosite

Monolithic Bidirectional Switch Based on GaN Gate Injection Transistors

The paper deals with a bi-directional switch based on N-channel enhancement-mode GaN FET. The proposed device is a Gate Injection Transistor monolithic solution to reduce the volume of the switch with high current density and blocking voltage of 600V. It features a dual-gate control pin and two power terminal. In the paper, the main characteristics of the bi-directional switch and the performance in the four-quadrant of operation are examined and discussed. The device characteristics are compared with the traditional MOSFET and IGBT solutions. The gate driver design issues are considered to optimize the switching transient of the GaN-based switch. Finally, an experimental evaluation of the GaN FET as the bidirectional circuit breaker is carried out in an AC power supply system to validate the effectiveness of the proposed monolithic new device

A Critical Analysis on the Current Design Criteria for Cathodic Protection of Ships and Superyachts

Classification Society and ISO standard regulate the design of cathodic protection (CP) plans of ships and superyachts. However, due to shipyards’ long experience, the hull vessel protection plans often rely on an adaptation of previous CP designs for similar ships. This simple practice could expose ships to low protection or overprotection. Here, the protection plan of an existing 42 m superyacht is considered to highlight critical CP design issues. The numerical analysis gives evidence of discrepancies between the CP design proposed in accordance with ISO standard and the protection plan that was actually implemented. Indeed, for a proper protection plan, the anode weight according to the ISO standard is 2.7 kg, whereas the real protection plan uses a 7 kg anode. The numerical optimization highlights an optimal anode mass of 5 kg (−28.5% in weight). It provides sufficient protection for the expected lifetime, and will preserve the system in cases of damage to the hull and a consequent increase in the breakdown factor. This new solution underlines the importance and necessity of improving cathodic protection plan design

Fibre Reinforced Geopolymers as Inorganic Strengthening Composites for Masonry Structures

The study presents an assessment of externally bonded Fibre-Reinforced GeoPolymers (FRGPs) as strengthening material for masonry structures. Thanks to their tailored chemical and mechanical characteristics, geopolymer matrices can fulfil the restoration criteria for Built Heritage (BH) with the benefit of heat-resistant performances better than those of organic and inorganic matrices used in Externally Bonded Fibre Reinforced Polymers (EB-FRP) and Fabric-Reinforced Cementitious Matrix (FRCM) materials, respectively. This work is built on the outcomes of a previous investigation that proved the suitability of the developed geopolymer matrix for applications on clay bricks, revealing a good adhesion to masonry substrates and to embedded reinforcements. The behaviour of three FRGPs, including either a bi-directional basalt mesh, a bi-directional carbon mesh or a unidirectional Ultra High Strength Steel (UHSS) fabric, was explored by means of local tests on masonry sub-assemblages made of soft-mud clay bricks and hydraulic lime mortar. In overall, 9 single-lap shear tests on single bricks with a bonded length of 200 mm and 9 three-point bending tests on 2-brick slices, connected by a mortar joint and reinforced at the bottom face, were carried out. Lastly, the behaviour in alkaline environments of each reinforcement was investigated through tensile tests on coupons immersed for 28 days in alkaline solutions simulating the conditions of the geopolimeric matrices. Results confirmed the interesting potential of FRGPs for strengthening masonry elements, highlighting a good performance of steel and carbon reinforcements. On the other hand, precautions should be taken with basalt meshes that, as expected, were more sensitive to alkaline environment

A comparison of electrochemical degradation of phenol on boron doped diamond and lead dioxide anodes

This work compares two electrode materials used to mineralize phenol contained in waste waters. Two disks covered with either boron doped diamond (BDD) or PbO2 were used as anodes in a one compartment flow cell under the same hydrodynamic conditions. Efficiencies of galvanostatic electrolyses are compared on the basis of measurements of Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD). Galvanostatic electrolyses were monitored by analysis of phenol and of its oxidation derivatives to evaluate the operating time needed for complete elimination of toxic aromatics. The experimental current efficiency is close to the theoretical value for the BDD electrode. Other parameters being equal, phenol species disappeared at the same rate using the two electrode materials but the BDD anode showed better efficiency to eliminate TOC and COD. Moreover, during the electrolysis less intermediates are formed with BDD compared to PbO2 whatever the current density. A comparison of energy consumption is given based on the criterion of 99% removal of aromatic compounds

Electrochemical polymerisation of phenol in aqueous solution on a Ta/PbO2 anode

This paper deals with the treatment of aqueous phenol solutions using an electrochemical technique. Phenol can be partly eliminated from aqueous solution by electrochemically initiated polymerisation. Galvanostatic electrolyses of phenol solutions at concentration up to 0.1 mol dm−3 were carried out on a Ta/PbO2 anode. The polymers formed are insoluble in acidic medium but soluble in alkaline. These polymers were filtered and then dissolved in aqueous solution of sodium hydroxide (1 mol dm−3). The polymers formed were quantified by total organic carbon (TOC) measurement. It was found that the conversion of phenol into polymers increases as a function of initial concentration, anodic current density, temperature, and solution pH. The percentage of phenol polymerised can reach 15%

Electrochemical synthesis of peroxomonophosphate using boron-doped diamond anodes

A new method for the synthesis of peroxomonophosphate, based on the use of boron-doped diamond electrodes, is described. The amount of oxidant electrogenerated depends on the characteristics of the supporting media (pH and solute concentration) and on the operating conditions (temperature and current density). Results show that the pH, between values of 1 and 5, does not influence either the electrosynthesis of peroxomonophosphate or the chemical stability of the oxidant generated. Conversely, low temperatures are required during the electrosynthesis process to minimize the thermal decomposition of peroxomonophosphate and to guarantee significant oxidant concentration. In addition, a marked influence of both the current density and the initial substrate is observed. This observation can be explained in terms of the contribution of hydroxyl radicals in the oxidation mechanisms that occur on diamond surfaces. In the assays carried out below the water oxidation potential, the generation of hydroxyl radicals did not take place. In these cases, peroxomonophosphate generation occurs through a direct electron transfer and, therefore, at these low current densities lower concentrations are obtained. On the other hand, at higher potentials both direct and hydroxyl radical-mediated mechanisms contribute to the oxidant generation and the process is more efficient. In the same way, the contribution of hydroxyl radicals may also help to explain the significant influence of the substrate concentration. Thus, the coexistence of both phosphate and hydroxyl radicals is required to ensure the generation of significant amounts of peroxomonophosphoric acid

Characterisation of La0.6Sr0.4Co0.2Fe0.8O3-\u3b4- Ba0.5Sr0.5Co0.8Fe0.2O3-\u3b4composite as cathode for solid oxide fuel cells

Mixture of La0.6Sr0.4Co0.2Fe0.8O3-\u3b4 and Ba0.5Sr0.5Co0.8Fe0.2O3-\u3b4, was investigated as promising cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The two perovskites possess high catalytic activity for the oxygen reduction (ORR), although some problems related to their chemical and structural stability have still to be overcome in view of improving durability of the cell performance. The achievement of a stable and high-performing composite material is the aim of this study. In principle, chemical equilibrium at the LSCF-BSCF interface may be reached through ions interdiffusion during the sintering process, resulting in the chemical stabilization of the material. The composite-cathode deposited on Ce0.8Sm0.2O2-\u3b4 electrolyte was then investigated by Electrochemical Impedance Spectroscopy (EIS) as a function of temperature, overpotential and time. The results exhibited an interesting electrochemical behavior of the electrode toward oxygen reduction reaction. XRD analysis was performed to detect structural modification during thermal or operation stages and it was found that after the sintering the two starting perovskites were no longer present; a new phase with a rhombohedral La0,4Sr0,6FeO3-type structure (LSF) is formed. An improvement in composite cathode durability has been detected under the considered operating conditions (200 mAcm-2, 700 \ub0C) in comparison with the pure BSCF electrode. The results confirmed this new electrode as promising system for further investigation as IT-SOFC cathode