Search results for "uncertainty."
showing 10 items of 972 documents
A new integrated MBR model for wastewater treatment: sensitivity and uncertainty analysis
2017
In this study a new integrated membrane bioreactor (MBR) model is proposed. The model is able to describe the main biological processes aimed at the carbon and the nutrients (nitrogen, N and phosphorus, P) removal coupled with the soluble microbial products (SMP) formation/degradation. Furthermore, the model describes the key physical processes and the interconnection between SMP and membrane fouling. The model was calibrated by adopting data measured during the monitoring of a University Cape Town (UCT) MBR pilot plant. A sensitivity analysis allowed the reduction of the number of model FACTORs to be calibrated from 122 to 45. A good correlation between measured and simulated data was obta…
Uncertainty of a biological nitrogen and phosphorus removal model
2010
In the last few years, the use of mathematical models in wastewater treatment plant (WWTP) processes has become a common way to predict WWTP behaviour. However, mathematical models generally demand advanced input for their implementation that must be evaluated by an extensive data gathering campaign, which cannot always be carried out. This fact, together with the intrinsic complexity of the model structure, leads to model results that may be very uncertain. Quantification of the uncertainty is imperative. However, despite the importance of uncertainty quantification, only a few studies have been carried out in the wastewater treatment field, and those studies only included a few of the sou…
ERROR AND UNCERTAINTY ANALYSIS OF RESIDUAL STRESS EVALUATION BY USINGTHE RING-CORE METHOD
2014
The Ring-Core Method is a technique used for the experimental analysis of the residual stresses in mechanical components. For uniform and non-uniform residual stresses estimation, the use of the method leads in general to accurate results but, unfortunately at present the user does not have appropriate procedures to correct the obtained results from systematic errors as well as to estimate the uncertainty due to random errors. In order to overcome such drawbacks, in the present work, the procedures for the correction of the effects of the main error sources and for the stress uncertainty estimation, are proposed. The practical application of such procedures allow the user to highlight the r…
ERROR AND UNCERTAINTY ANALYSIS OF THE RESIDUAL STRESSES COMPUTED BY USING THE HOLE DRILLING METHOD
2011
The hole-drilling method is one of the most used techniques for the experimental analysis of the residual stresses in mechanical components. For both through-thickness uniform and non-uniform residual stresses, its practical application is standardised by the ASTM E837-08. For uniform residual stresses, to which the present work deals with, the use of the method in accordance with the ASTM limitations, leads to results with a bias of about 10%. Unfortunately, although some experimental parameters can be frequently out of the corresponding standard limitation, the user does not have appropriate procedures to correct the obtained results which, in accordance with the ASTM standard, have to be…
Adaptive type-2 fuzzy control of non-linear systems
2009
The paper describes the development of two different type-2 adaptive fuzzy logic controllers and their use for the control of a non linear system that is characterized by the presence of bifurcations and parameter uncertainty. Although a type-2 fuzzy logic controller is able to handle the non linearities and the uncertainties present in a system, its robustness and effectiveness can be increased by the use of an opportune adaptive algorithm. A simulation study was conducted to compare the behavior of adaptive controllers with that of simple type-1 and type-2 fuzzy logic controllers. The system to be controlled, used for the simulation, is a continuous bioreactor for the treatment of mixed w…
Nonlinear fuzzy control of a fed-batch reactor for penicillin production
2012
Abstract The process of penicillin production is characterized by nonlinearities and parameter uncertainties that make it difficult to control. In the paper the development and testing of a multivariable fuzzy control system that makes use of type-2 fuzzy sets for the control of pH and temperature are described. The performance of the type-2 fuzzy logic control system (T2FLCS) is compared by simulation with that of a type-1 fuzzy logic control system (T1FLCS) and that of a control system with traditional proportional-integral-derivative (PID) controllers proposed in the literature. The fuzzy controllers are optimized using an ANFIS algorithm. The best results are obtained with the T2FLCS pa…
Robust Discrete-Time Lateral Control of Racecars by Unknown Input Observers
2023
This brief addresses the robust lateral control problem for self-driving racecars. It proposes a discrete-time estimation and control solution consisting of a delayed unknown input-state observer (UIO) and a robust tracking controller. Based on a nominal vehicle model, describing its motion with respect to a generic desired trajectory and requiring no information about the surrounding environment, the observer reconstructs the total force disturbance signal, resulting from imperfect knowledge of the time-varying tire-road interface characteristics, presence of other vehicles nearby, wind gusts, and other model uncertainty. Then, the controller actively compensates the estimated force and as…
A meta-cognitive architecture for planning in uncertain environments
2013
Abstract The behavior of an artificial agent performing in a natural environment is influenced by many different pressures and needs coming from both external world and internal factors, which sometimes drive the agent to reach conflicting goals. At the same time, the interaction between an artificial agent and the environment is deeply affected by uncertainty due to the imprecision in the description of the world, and the unpredictability of the effects of the agent’s actions. Such an agent needs meta-cognition in terms of both self-awareness and control. Self-awareness is related to the internal conditions that may possibly influence the completion of the task, while control is oriented t…
Electron structure, ultra-dense hydrogen and low energy nuclear reactions
2019
In this paper, a simple Zitterbewegung electron model, proposed in a previous work, is presented from a different perspective based on the principle of mass- frequency equivalence. A geometric- electromagnetic interpretation of mass, relativistic mass, De Broglie wavelength, Proca, Klein- Gordon, Dirac and Aharonov- Bohm equations in agreement with the model is proposed. A non-relativistic, Zitterbewegung interpretation of the 3.7 keV deep hydrogen level found by J. Naudts is presented. According to this perspective, ultra-dense hydrogen can be conceived as a coherent chain of bosonic electrons with protons or deuterons located in the center of their Zitterbewegung orbits. This approach sug…
Medical image registration: Interpolations, similarities and optimizations strategies
2010
This paper presents a study conducted for evaluating different interpolation schemes, similarity metrics and optimization algorithms for the purpose of volumetric medical image registration. Each technique has been implemented to be plugged in a modular system. Rotation, translation and scale error has been measured to obtain a performance evaluation for all of the combinations of the considered techniques. Several experimental tests were conducted for validation both on synthetic and real datasets providing an exhaustive overview of the various strategies used.