The Islay wave power project: an engineering prospective

The design, construction and subsequent operation of the 75 kW oscillating water column wave power plant on the Isle of Islay has provided a significant insight into the practicality of wave power conversion. The development of wave power plant poses a significant design and construction challenge for not only civil but also mechanical and electrical engineers. The plant must withstand the immense forces imposed during storms, yet efficiently convert the slow cyclic motion of waves into a useful energy source such as electricity and do so at a price competitive with other forms of generation. In addition, the hostile marine environment hampers the construction process and the variability of the wave resource poses problems for electrical control and grid integration. Many sceptics consider wave power conversion to be too difficult, too expensive and too variable to justify the effort and expense necessary to develop this technology. However, the authors contend that with modular wave power systems developed from the practical experience gained with the Islay plant, wave power is a viable technology with a considerable world market potential. However, this technology is still at the early stages of development and will require the construction of a number of different prototypes before there is extensive commercial exploitation.

Structure of Ionic Liquid-Benzene Mixtures

Neutron diffraction has been used to investigate the structure of liquid mixtures of 1,3-dimethylimidazolium hexafluorophosphate with benzene. Two concentrations of benzene were investigated, namely, 33 mol % and 67 mol %, and show similar structures in each case. The presence of benzene significantly alters the ionic liquid structure, in particular, in the cation-cation interactions, in agreement with the single-crystal structure described recently (Holbrey, J. D.; Reichert, W. M.; Nieuwenhuyzen, M.; Sheppard, O.; Hardacre, C.; Rogers, R. D. Chem. Commun. 2003, 476). In each case, the data was analyzed using an empirical potential structure refinement process.

Un episodio en la recepción cultural dieciochesca de lo exótico: la llegada del elefante a Madrid en 1773

At the end of 1773 an Indian elephant, brought for the royal ménagerie at Aranjuez, was shown in the streets of Madrid. The resulting public fascination provoked by the intrusion of this exotic animal can be traced through poems (Tomás de Iriarte), short plays (Ramón de la Cruz), articles in the periodical press, popular and scientific prints representing the animal, and even in the costumbrista pastels of Lorenzo Tiepolo. The mythic and premodern knowledge of animal nature collides in a debate with the new scientific observation. In the final decades of the 18th century, the image of the captive elephant acquired in Europe a new symbolic meaning linked with the political fight against slavery. All these very different elements converge in Goya's Disparate de bestia.

Compressive membrane action in composite floor slabs in the Cardington LBTF

This paper presents the results of an experimental study (the ultimate load capacity of composite metal decking/concrete floor slabs. Full-scale in situ testing of composite floor slabs was carried out in the Building Research Establishment's Large Building Test Facility (LBTF) at Cardington. A parallel laboratory test programme, which compared the behaviour of composite floor slabs strips, also carried out at Queen's University Belfast (QUB). Articular attention was paid to the contribution of compressive membrane action to the load carrying capacity. The results of both test programmes were compared with predictions by yield line theory and a theoretical prediction method in which the amount of horizontal restraint mid be assessed. The full-scale tests clearly demon-wed the significant contribution of compressive membrane effects to the load capacity of interior floor panels with a lesser contribution to edge/corner panels.

Modelling of saline intrusion in marine outfalls

Since their introduction in the 1950s, marine outfalls with diffusers have been prone to saline intrusion, a process in which seawater ingresses into the outfall. This can greatly reduce the dilution and subsequent dispersion of wastewater discharged, sometimes resulting in serious deterioration of coastal water quality. Although long aware of the difficulties posed by saline intrusion, engineers still lack satisfactory methods for its prediction and robust design methods for its alleviation. However, with recent developments in numerical methods and computer power, it has been suggested that commercially available computational fluid dynamics (CFD) software may be a useful aid in combating this phenomenon by improving understanding through synthesising likely behaviour. This document reviews current knowledge on saline intrusion and its implications and then outlines a model-scale investigation of the process undertaken at Queen's University Belfast, using both physical and CFD methods. Results are presented for a simple outfall configuration, incorporating several outlets. The features observed agree with general observations from full-scale marine outfalls, and quantify the intricate internal flow mechanisms associated with saline intrusion. The two-dimensional numerical model was found to represent saline intrusion, but in a qualitative manner, not yet adequate for design purposes. Specific areas requiring further development were identified. The ultimate aim is to provide a reliable, practical and cost effective means by which engineers can minimise saline intrusion through optimised outfall design.

Reuse of construction waste: performance under repeated loading

The use of recycled aggregates has increased greatly over the last decade owing to enhanced environmental sensitivities. The level of performance required by such materials is dependent upon the applications for which they are used. Many recycled construction wastes have adequate shear strength in relation to various geotechnical applications. However, a possible drawback of these materials is the risk of crushing during repeated loading. The work reported in this paper examined two waste materials: crushed concrete and building debris, both regarded as construction wastes. Tests were also performed on traditionally used crushed rock, in this case basalt. The materials were subjected to repeated loading in a large direct shear apparatus. The amount of crushing was quantified by performing particle size analysis of the tested material. The results have shown that both recycled construction wastes were susceptible to particle crushing. The amount of crushing was influenced by both the vertical pressure and the number of loading cycles. This leads to a marked decrease in peak friction angle

Arching action in high strength concrete slabs

The corrosion of reinforcement in bridge deck slabs has been the cause of major deterioration and high costs in repair and maintenance.This problem could be overcome by reducing the amount of reinforcement and/or altering the location.This is possible because, in addition to the strength provided by the reinforcement, bridge deck slabs have an inherent strength due to the in-plane arching forces set up as a result of restraint provided by the slab boundary conditions. This is known as arching action or Compressive Membrane Action (CMA). It has been recognised for some time that laterally restrained slabs exhibit strengths far in excess of those predicted by most design codes but the phenomenon has not been recognised by the majority of bridge design engineers. This paper presents the results of laboratory tests on fifteen reinforced concrete slab strips typical of a bridge deck slab and compares them to predicted strengths using the current codes and CMA theory. The tests showed that the strength of laterally restrained slabs is sensitive to both the degree of external lateral restraint and the concrete compressive strength.The tests particularly highlighted the benefits in strength obtained from very high strength concrete slabs. The theory extends the existing knowledge of CMA in slabs with concrete compressive strengths up to 100 N/mm[2] and promotes more economical and durable bridge deck construction by utilising the benefits of high strength concrete.