The modelling of the nitrification process of high-strength ammonium wastewater must be designed to consider it as a two-step reaction with substrate inhibition. Consequently, kinetic and stoichiometric parameters of both steps are required. In this work, the second step in the nitrification process was studied: a biological nitrite oxidation model was formulated, calibrated and validated using only oxygen uptake rate (OUR) measurements. The model included biomass growth and substrate inhibition. First, the biomass yield coefficient for nitrite-oxidising biomass was determined. Then, a respirometric experiment with one nitrite pulse of 500 mg N-NO2− L−1 was performed to estimate the rest of the model parameters. The practical identifiability study showed that the parameters were strongly correlated. Hence, a new experimental design consisting of two consecutive pulses and a delayed third one was designed to improve the parameter identifiability. Both experimental designs were compared using contour plots of the objective function and optimal experimental design criteria for parameter estimation. It was concluded that the parameter identifiability was improved with the new experimental design. Finally, the estimated parameters were validated and the pH effect on the inhibition coefficient was evaluated. 相似文献
We investigate the problem of placing monitors to localize node failures in a communication network from binary states (normal/failed) of end-to-end paths, under the assumption that a path is in normal state if and only if it contains no failed nodes. To uniquely localize failed nodes, the measurement paths must show different symptoms (path states) under different failure events. Our goal is to deploy the minimum set of monitors to satisfy this condition for a given probing mechanism. We consider three families of probing mechanisms, according to whether measurement paths are (i) arbitrarily controllable, (ii) controllable but cycle-free, or (iii) uncontrollable (i.e., determined by the default routing protocol). We first establish theoretical conditions that characterize network-wide failure identifiability through a per-node identifiability measure that can be efficiently evaluated for the above three probing mechanisms. Leveraging these results, we develop a generic monitor placement algorithm, applicable under any probing mechanism, that incrementally selects monitors to optimize the per-node measure. The proposed algorithm is shown to be optimal for probing mechanism (i), and provides upper and lower bounds on the minimum number of monitors required by the other probing mechanisms. In the special case of single-node failures, we develop an improved monitor placement algorithm that is optimal for probing mechanism (ii) and has linear time complexity. Using these algorithms, we study the impact of the probing mechanism on the number of monitors required for uniquely localizing node failures. Our results based on real network topologies show that although more complicated to implement, probing mechanisms that allow monitors to control measurement paths substantially reduce the required number of monitors. 相似文献
A four compartment mechanistic mathematical model is developed for the pharmacokinetics of the commonly used anti-malarial drug artesunate and its principle metabolite dihydroartemisinin following oral administration of artesunate. The model is structurally unidentifiable unless additional constraints are imposed. Combinations of mechanistically derived constraints are considered to assess their effects on structural identifiability and on model fits. Certain combinations of the constraints give rise to locally or globally identifiable model structures. 相似文献
Many performance indices for parallel mechanism are put forward in the phase of dimensional synthesis,except for identifiability index,which determines the difficulty of kinematical calibration.If the ... 相似文献
Mathematical models, in particular, physics-based models, are essential tools to food product and process design, optimization and control.
The success of mathematical models relies on their predictive capabilities. However, describing physical, chemical and biological changes in food processing requires the values of some, typically unknown, parameters. Therefore, parameter estimation from experimental data is critical to achieving desired model predictive properties.
This work takes a new look into the parameter estimation (or identification) problem in food process modeling. First, we examine common pitfalls such as lack of identifiability and multimodality. Second, we present the theoretical background of a parameter identification protocol intended to deal with those challenges. And, to finish, we illustrate the performance of the proposed protocol with an example related to the thermal processing of packaged foods. 相似文献