The J-Box Problem

The study group was presented with the problem of determining the behaviour of a web of wet cellulose fibres - called a tow - as it passes through part of the manufacturing process. The name of the problem derives from the fact that on its passage down the production line the tow passes through a J-shaped box, whose purpose is to provide a buffer where the tow is stored long enough and hot enough for certain chemical reactions to take place, mainly concerned with giving the right quality to the fibre surface. (The production line in fact involves two J-boxes, one containing wet tow, the other dry, and we are here entirely concerned with the first of these, the wet J-box.) Three aspects of the tow behaviour were proposed for investigation: 1. What is the mechanical behaviour of the tow within the J-box ? Specifically, how do the time spent within the J-box and the shape of the tow outlet column depend on the J- box geometry, tow density and compressibility, flow rate, friction coefficients etc. 2. What is the temperature history, and hence the chemical history, of the tow within the J-box? 3. Why do dislocations and loops occur within the tow? We first give typical parameters and other details of the process, and then further details of these three questions

Circulation in inviscid gas flows with shocks

In this note, we show that the circulation $\Gamma=\int_C\mathbf{u}\cdot\mathbf{dx}$ around a closed material curve $C(t)$ in an inviscid gas flow develops according to the equation $\frac{d\Gamma}{dt}=\int_CT\,dS$, even when the curve may cross shocks, with the entropy jumps at the shocks excluded from the right-hand side

Agrifood Campaign Planning

The challenge was to find ways for the players in an agricultural food supply chain to interact in ways that enable the chain to operate more efficiently. What information do they need to exchange, and what incentives need to be in place between them? What software would help the information exchange and responsive actions to take place? The problem was thought about with the UK sugar beet industry as the working example, but similar considerations, with many differences of detail, are expected to apply in other contexts