Modelling the air cleaning performance of negative air ionisers in ventilated rooms

Negative air ionisers have seen increasing use as devices for improving indoor air quality, including some success in clinical environments for reducing the transmission of infection. This study uses a ventilation model and a CFD model to examine the physical effects of negative ionisers in indoor environments. The results demonstrate how the negative ion distribution and electric field due to an ioniser are influenced by both the room airflow and the ion generation rate. It is shown that ion concentrations greater than 1010 ions/m3 are necessary for the electrical effects to be significant. The effect on particles is also considered, with the results demonstrating that the ioniser will only increase the deposition of particles when the particle concentration is high enough to contribute to the space charge in the room

Modelling the air cleaning performance of negative air ionisers in ventilated rooms

Negative air ionisers have seen increasing use as devices for improving indoor air quality, including some success in clinical environments for reducing the transmission of infection. This study uses a ventilation model and a CFD model to examine the physical effects of negative ionisers in indoor environments. The results demonstrate how the negative ion distribution and electric field due to an ioniser are influenced by both the room airflow and the ion generation rate. It is shown that ion concentrations greater than 1010 ions/m3 are necessary for the electrical effects to be significant. The effect on particles is also considered, with the results demonstrating that the ioniser will only increase the deposition of particles when the particle concentration is high enough to contribute to the space charge in the room

Browsing images using broad classification categories

Browsing can serve an important role as a strategy for retrieving image information and can allow users to recognize what they are looking for more easily than describing it. This article describes a project which developed and tested an art history image data base which used broad classification units to group image sets into meaningful categories that support browsing. Categories from the Art and Architecture Thesaurus were used to provide broad classification units to guide users in browsing and searching. The system provided both browse and search capabilities and was tested with art history specialists and generalist users. The type of user and the use to which the image is put will influence the type of search strategy employed. Preferences for, and perfonnance in, the browse and search modes varied according to the user's familiarity with the subject domain. Both sets of users felt that the ability to use both browse and search in a multimodal system would best meet their search needs

Probing the interfacial and sub-surface structure of Si/Si1 – xGex multilayers

The ability to determine structural and compositional information from the sub-surface region of a semiconductor material has been demonstrated using a new time-of-flight medium energy ion scattering spectroscopy (ToF-MEISS) system. A series of silicon–silicon/germanium (Si/Si1 – xGex) heterostructure and multilayer samples, grown using both solid source molecular beam epitaxy (MBE) and gas source chemical vapor deposition (CVD) on Si(100) substrates, have been investigated. These data indicate that each individual layer of Si1 – xGex (x ~ 0.22) in both two- and three-period samples, can be uniquely identified with a resolution of approximately 3 nm. A comparison of MBE and CVD grown samples has also been made using layers with similar structures and composition. The total Ge content of each sample was confirmed using conventional Rutherford backscattering spectrometry

A prospective study of the incidence and nature of injuries to adult rugby players.

The incidence and nature of injuries occurring in 8 adult club rugby teams was followed prospectively during the 1988 rugby season. The findings were compared with those from two similar studies in schoolboy rugby players. A total of 114 injuries were sustained by 78 players; 85% of injuries occurred during matches. Injury was most prevalent during the first 8 weeks of the season and again after the mid-season break. Hookers (19%), wings (15%), fullbacks (11%) and centres (10%) were the players most often injured. Injury occurred most commonly when the player was tackled (26%), during open play (21%) and during the loose scrum 17%). Muscles (33%) and ligaments (32%) were the anatomical strutures most often injured. Injury caused 35% of injured players to miss more than 35 days of rugby. Thirteen percent of injured players did not play again for the rest of the season and only 14% of injured players returned to rugby after 7 days or less. Prolonged disability was associated with ligament injuries (57%), dislocations (17%) and fractures (10%)

Modelling the air cleaning performance of negative air ionisers in ventilated rooms

Negative air ionisers have seen increasing use as devices for improving indoor air quality, including some success in clinical environments for reducing the transmission of infection. This study uses a ventilation model and a CFD model to examine the physical effects of negative ionisers in indoor environments. The results demonstrate how the negative ion distribution and electric field due to an ioniser are influenced by both the room airflow and the ion generation rate. It is shown that ion concentrations greater than 1010 ions/m3 are necessary for the electrical effects to be significant. The effect on particles is also considered, with the results demonstrating that the ioniser will only increase the deposition of particles when the particle concentration is high enough to contribute to the space charge in the room

Multi-objective variational curves

Riemannian cubics in tension are critical points of the linear combination of two objective functionals, namely the squared norms of the velocity and acceleration of a curve on a Riemannian manifold. We view this variational problem of finding a curve as a multi-objective optimization problem and construct the Pareto fronts for some given instances where the manifold is a sphere and where the manifold is a torus. The Pareto front for the curves on the torus turns out to be particularly interesting: the front is disconnected and it reveals two distinct Riemannian cubics with the same boundary data, which is the first known nontrivial instance of this kind. We also discuss some convexity conditions involving the Pareto fronts for curves on general Riemannian manifolds

The mixing of airborne contaminants by the repeated passage of people along a corridor

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