A typical polymer electrolyte fuel cell (PEFC) flow field consists of micro/minichannels. The continues removal of liquid water from the cathode channels is a critical topic, as water droplets forming in the channels may block the transport of gaseous oxygen to the active sites, which not only gives an uneven current distribution and substantial loss of performance, but also, increases degradation

In this paper, two distinct polymer electrolyte fuel cell stack models are constructed: a detailed numerical model (DNM) employing a fine-scale computational mesh and a coarse-mesh approach based on a distributed resistance analogy (DRA) where diffusion terms in the transport equations are replaced by rate terms. Both methods are applied to a 5-cell, high-temperature polymer electrolyte fuel cell

We develop a simulation method for Markov Jump processes with finite time steps based in a quasilinear approximation of the process and in multinomial random deviates. The second order approximation to the generating function, Error$=O(dt^{2})$, is developed in detailand an algorithm is presented. The algorithm is implemented for a Susceptible-Infected-Recovered-Susceptible (SIRS) epidemic model a

Restaurangen är en yngling, historiskt sett - den kommer från franskt 1700-tal. Men att äta och dricka på lokal, mot betalning, har svenskar gjort långt innan restaurangen blev populär: så snart det område som skulle bli Sverige började enas och kristnas blev behovet av sådana platser en viktig angelägenhet, både från kungligt och kyrkligt håll. Från medeltidens ölbodar och tavernor, via stormakts

Detta kapitel handlar om marknadskrafter och hur dessa kan användas av offentliga myndigheter, medvetet och effektivt, till gagn för medborgarna och skattebetalarna. Ämnet har i många avseenden blivit politiskt. Marknaden har för en del blivit en frälsning, för andra en förbannelse. Det saknas entydiga empiriska belägg för att en fri marknad genererar ökat välstånd, en avsaknad som effektivt hålle

A dermal sling (DS) is used to cover the implant with two layers of tissue when immediate breast reconstruction is performed in women with large and ptotic breasts. It works as an autologous acellular dermal matrix/mesh that can be used to control the implant pocket and inframammary fold, without inferring an extra foreign material and higher costs. There is relatively little published about the D

There is considered a mean square convergence of a stochastic approximation algorithm, are derived, formelas of the asimptotical variances of the solution estimations, which are right for dependent observations as well, is defined optimal consequence of coefficients.

Some representative results from modeling and identification experiments on the Halden boiling water reactor (HBWR) in Norway are presented in this chapter. Linear input–output models, as well as time invariant and time variable linear state models, have been used as model structures. The chapter describes the different phases of identification and modeling of a complex dynamical system. Different

Control of activated sludge process based on measurement of the dissolved oxygen profile has the distinct advantage of using sensors of proven reliability. These measurements, when coupled with the power of an on-line computer, permit the calculation of important variables which cannot be measured directly. The features of the profile which are of major significance are the position of the maximum

Process dynamics and control in biological waste water treatment operations are considered. Particular emphasis has been put on the control of dissolved oxygen and its spatial distribution in activated sludge aerators. It is demonstrated how dissolved oxygen profiles can be used for the estimation of the biodegradable load. Aspects of the control of chemical precipitation are discussed as well.

Research was conducted to examine the transient performance of a final settler. Dynamical models of minimal order were derived based on effluent data collected from a pilot scale settler. Parameter values for the models were adjusted until satisfactory fits to the observed data were obtained. Results were compared to select those models with the simplest structures and the ability to predict the m