The effectiveness of conceptual airport terminal designs

It is forecast that there will be a large growth in air traffic over the next decade or so and to accommodate this will require investment in airport infrastructure including terminals. These buildings represent large, lumpy investments so it is important to provide the capacity to accommodate the forecast traffic. However, this depends on at least two factors; the accuracy of the forecast of future demand and the process of translating these forecasts into designs. Errors in either of these can be financially catastrophic. The latter of these two factors depend on “rules of thumb” formulae that convert design hour flows into area requirements for each terminal facility. This paper will look in detail at the process of translating demand forecasts into conceptual terminal designs. The basic methods that are used will be outlined and how they affect the conceptual terminal design process will be revealed. It will be shown that even if demand forecasts can be taken to be completely accurate, there can still be errors in terminal design and size resulting from the use of these “rules of thumb.

Nutrient transport in bioreactors for bone tissue growth : why do hollow fiber membrane bioreactors work

One of the main aims of bone tissue engineering is to produce three-dimensional soft bone tissue constructs of acceptable clinical size and shape in bioreactors. The tissue constructs have been proposed as possible replacements for diseased or dysfunctional bones in the human body through surgical transplantations. However, because of certain restrictions to the design and operation of the bioreactors, the size of the tissue constructs attained are currently below clinical standards. We believe that understanding the fluid flow and nutrient transport behaviour in the bioreactors is critical in achieving clinically viable constructs. Nevertheless, characterization of transport behaviour in these bioreactors is not trivial. As they are very small in size and operate under stringent conditions, in-situ measurements of nutrients are almost impossible. This issue has been somewhat resolved using computational modelling in previous studies. However, there is still a lack of certainty on the suitability of bioreactors. To address this issue we systematically compare the suitability of three bioreactors for growing bone tissues using mathematical modelling tools. We show how nutrient transport may be improved in these bioreactors by varying the operating conditions and suggest which bioreactor may be best suited for operating at high cell densities in order to achieve soft bone tissues of clinical size. The governing equations defined in our mathematical frameworks are solved through finite element method. The results show that the hollow fiber membrane bioreactor (HFMB) is able to maintain higher nutrient concentration during operation at high cell densities compared to the other two bioreactors, namely suspended tube and confined profusion type bioreactor. Our results show that by varying the operating conditions nutrient transport may be enhanced and the nutrient gradient can be substantially reduced. These are consistent with previous claims suggesting that the HFMB is suited for bone tissue growth at high cell densities