Analysis of Temporal Compression Characteristics using Active Phase conjugation in systems with multiple antenna elements

In this paper we give first account of a simple analysis tool for modeling temporal compression for automatic mitigation of multipath induced intersymbol interference through the use of active phase conjugation (APC) technique. The temporal compression characteristics of an APC system is analyzed using a simple discrete channel model, and numerical results are provided to justify the theoretical findings.

Tri-axial accelerometers tease apart discrete behaviours in the common cuttlefish Sepia officinalis

Acceleration data loggers can be used to construct time-energy budgets or identify specific behaviours in free living animals. Within a marine context such devices have been largely deployed on vertebrates with comparatively little attention paid to commercially important invertebrates such as cephalopod molluscs. Here we tested the utility of tri-axial accelerometers to tease apart six discrete behaviours in the common cuttlefish Sepia officinalis. By considering depth profiles in conjunction with body pitch and roll and overall dynamic body acceleration we were able to make distinctions between resting at the seabed, active swimming, mating, post-coital panting and active manoeuvring along the seabed. © 2012 Marine Biological Association of the United Kingdom.

A framework for challenging deficits in compression bandaging techniques

Northern Irish (and all UK-based) health care is facing major challenges. This article uses a specific theory to recommend and construct a framework to address challenges faced by the author, such as deficits in compression bandaging techniques in healing venous leg ulcers and resistance found when using evidence-based research within this practice. The article investigates the challenges faced by a newly formed community nursing team. It explores how specialist knowledge and skills are employed in tissue viability and how they enhance the management of venous leg ulceration by the community nursing team. To address these challenges and following a process of reflection, Lewin's forcefield analysis model of change management can be used as a framework for some recommendations made.

Morphology and compression behaviour of biodegradable scaffolds produced by the sintering process

Porous poly(L-lactic acid) (PLA) scaffolds of 85 per cent and 90 per cent porosity are prepared using polymer sintering and porogen leaching method. Different weight fractions of 10 per cent, 30 per cent, and 50 per cent of hydroxyapatite (HA) are added to the PLA to control the acidity and degradation rate. The three-dimensional (3D) morphology and surface porosity are tested using micro-computer tomography (micro-CT), optical microscopy, and scanning electron microscopy (SEM). Results indicate that the surface porosity does not change on the addition of HA. The micro-CT examinations show a slight decrease in the pore size and increase in the wall thickness accompanied by reduced anisotropy for the scaffolds containing HA. Scanning electron micrographs show detectable interconnected pores for the scaffold with pure PLA. Addition of the HA results in agglomeration of the HA particles and reduced leaching of the porogen. Compression tests of the scaffold identify three stages in the stress-strain curve. The addition of HA results in a reduction in the modulus of the scaffold at the first stage of elastic bending of the wall, but this is reversed for the second and third stages of collapse of the wall and densification in the compression tests. In the scaffolds with 85 per cent porosity, the addition of a high percentage of HA could result in 70 per cent decrease in stiffness in the first stage, 200 per cent increase in stiffness in the second stage, and 20 per cent increase in stiffness in the third stage. The results of these tests are compared with the Gibson cellular material model that is proposed for prediction of the behaviour of cellular material under compression. The pH and molecular weight changes are tracked for the scaffolds within a period of 35 days. The addition of HA keeps the pH in the alkaline region, which results in higher rate of degradation at an early period of observation, followed by a reduced rate of degradation later in the process. The final molecular weight is higher for the scaffolds with HA than for scaffolds of pure PLA. The manufactured scaffolds offer acceptable properties in terms of the pore size range and interconnectivity of the pores and porosity for non-load-bearing bone graft substitute; however, improvement to the mixing of the phases of PLA and HA is required to achieve better integrity of the composite scaffolds. © 2008 IMechE.

Influence of fill factor variation in high shear granulation on the post granulation processes: Compression and tablet properties

This paper describes an investigation of the effect of fill factor; on the compaction behaviour of the granules during tableting and hence mechanical properties of tablets formed. The fill factor; which is the ratio of volume of wet powder material to vessel volume of the granulator, was used as an indicator of batch size. It has been established previously that in high shear granulation the batch size influences the size distribution and granule mechanical properties [1]. The work reported in this paper is an extension to the work presented in [1], hence granules from the same batches were used in production of tablets. The same tabletting conditions were employed during tabletting to allow a comparison of their properties. The compaction properties of the granules are inferred from the data generated during the tabletting process. The tablet strength and dissolution properties of the tablets were also measured. The results obtained show that the granule batch size affects the strength and dissolution of the tablets formed. The tablets produced from large batches were found to be weaker and had a faster dissolution rate. The fill factor was also found to affect the tablet to tablet variation of a non-functional active pharmaceutical ingredient included in the feed powder. Tablets produced from larger batches show greater variation compared to those from smaller batches.

A device to investigate the axial strain dependence of the critical current density in superconductors

We have developed an instrument to study the behavior of the critical current density (J(c)) in superconducting wires and tapes as a function of field (mu(0)H), temperature (T), and axial applied strain (epsilon(a)). The apparatus is an improvement of similar devices that have been successfully used in our institute for over a decade. It encompasses specific advantages such as a simple sample layout, a well defined and homogeneous strain application, the possibility of investigating large compressive strains and the option of simple temperature variation, while improving the main drawback in our previous systems by increasing the investigated sample length by approximately a factor of 10. The increase in length is achieved via a design change from a straight beam section to an initially curved beam, placed perpendicular to the applied field axis in the limited diameter of a high field magnet bore. This article describes in detail the mechanical design of the device and its calibrations. Additionally initial J(c)(epsilon(a)) data, measured at liquid helium temperature, are presented for a bronze processed and for a powder-in-tube Nb3Sn superconducting wire. Comparisons are made with earlier characterizations, indicating consistent behavior of the instrument. The improved voltage resolution, resulting from the increased sample length, enables J(c) determinations at an electric field criterion E-c=10 muV/m, which is substantially lower than a criterion of E-c=100 muV/m which was possible in our previous systems. (C) 2004 American Institute of Physics.

Direction-contingent duration compression is primarily retinotopic

Previous research has shown that prior adaptation to a spatially circumscribed, oscillating grating results in the duration of a subsequent stimulus briefly presented within the adapted region being underestimated. There is an on-going debate about where in the motion processing pathway the adaptation underlying this distortion of sub-second duration perception occurs. One position is that the LGN and, perhaps, early cortical processing areas are likely sites for the adaptation; an alternative suggestion is that visual area MT+ contains the neural mechanisms for sub-second timing; and a third position proposes that the effect is driven by adaptation at multiple levels of the motion processing pathway. A related issue is in what frame of reference – retinotopic or spatiotopic – does adaptation induced duration distortion occur. We addressed these questions by having participants adapt to a unidirectional random dot kinematogram (RDK), and then measuring perceived duration of a 600 ms test RDK positioned in either the same retinotopic or the same spatiotopic location as the adaptor. We found that, when it did occur, duration distortion of the test stimulus was direction contingent; that is it occurred when the adaptor and test stimuli drifted in the same direction, but not when they drifted in opposite directions. Furthermore the duration compression was evident primarily under retinotopic viewing conditions, with little evidence of duration distortion under spatiotopic viewing conditions. Our results support previous research implicating cortical mechanisms in the duration encoding of sub-second visual events, and reveal that these mechanisms encode duration within a retinotopic frame of reference.

Influence of embedded length on strength of BFRP rods bonded parallel to the grain in low grade timber by pullout-bending tests

Bonded-in rod connections in timber possess many desirable attributes in terms of efficiency, manufacture, performance, aesthetics and cost. In recent years research has been conducted on such connections using fibre reinforced polymers (FRPs) as an alternative to steel. This research programme investigates the pull-out capacity of Basalt FRP rods bonded-in in low grade Irish Sitka Spruce. Embedded length is thought to be the most influential variable contributing to pull- out capacity of bonded-in rods after rod diameter. Previous work has established an optimum embedded length of 15 times the hole diameter. However, this work only considered the effects of axial stress on the bond using a pull-compression testing system which may have given an artificially high pull out capacity as bending effects were neglected. A hinge system was utilised that allows the effects of bending force to be taken in to consideration along with axial forces in a pull-out test. This paper describes an experimental programme where such pull-bending tests were carried out on samples constructed of 12mm diameter BFRP bars with a 2mm glueline thickness and embedded lengths between 80mm and 280mm bonded-in to low-grade timber with an epoxy resin. Nine repetitions of each were tested. A clear increase in pull-out strength was found with increasing embedded length.