BACKGROUND: The operation of a high-rate anaerobic process usually suffers from problems of high sensitivity to disturbances arising from environmental and operational factors. Application of advanced process controls...
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BACKGROUND: The operation of a high-rate anaerobic process usually suffers from problems of high sensitivity to disturbances arising from environmental and operational factors. Application of advanced process controls is an efficient approach to enhancing process robustness and stability. RESULTS: A multivariable linear quadratic tracking (LQT) approach to the output tracking of an anaerobic reactor was proposed, using external recirculation-to-feed ratio (R-s) and external bypass-to-feed ratio (R-r). The anaerobic digestion process is described by a distributed parameter model with a two-step (acidogenesis-methanization) kinetics. A state space model was developed using linear approximations of the nonlinear terms, and an output tracking method was developed combining linear quadratic tracking (LQT) and an integral action. CONCLUSION: Simulations show that, compared with the normal LQT method and proportional-integral (PI) controller, using both R-r and R-s and a conventional dilution rate (D,) based single variable PI controller, the proposed control approach achieved better results in both output set-point tracking and stabilization of effluent quality under influent disturbances and model-process mismatch. The new control strategy also had the advantage of using less storage capacity. (c) 2008 Society of Chemical Industry.
Transient contaminant dispersion is of high importance to human comfort, health and safety. Lumped parametermodel is usually applied to predict the evolution of contaminant dispersion, which, however, will not be eff...
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Transient contaminant dispersion is of high importance to human comfort, health and safety. Lumped parametermodel is usually applied to predict the evolution of contaminant dispersion, which, however, will not be effective when the contaminant distribution is not uniform. When airflow field is steady, the contaminant concentration distribution versus time will be determined by the concentration of supply air, contaminant source and initial concentration distribution in the ventilated space. An analytic expression of distributed contaminant concentration was developed using the accessibility of supply air (ASA), accessibility of contaminant source (ACS) and accessibility of initial condition (AIC). The ASA, ACS and AIC describe the contribution of supply air, contaminant source and initial condition to any point in ventilated space, and are determined by the airflow field if the contaminant sources and initial distribution are given. The analytic expression was validated by the tracer gas measurement in a test chamber. Based on the application of the expression in typical cases, the differences as well as connections between the analytic expression and lumped model were discussed. It is shown that the analytic expression is helpful for the understanding of the contaminant evolution process and may be used to obtain effective ventilation strategy for comfort and emergency. (C) 2008 Elsevier Ltd. All rights reserved.
When faults occur in transmission lines, the high frequency signals are caused by fault generated traveling waves and the spectrum is a series of harmonic in frequency domain. This paper utilizes lumped and distribute...
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ISBN:
(纸本)9781424419050
When faults occur in transmission lines, the high frequency signals are caused by fault generated traveling waves and the spectrum is a series of harmonic in frequency domain. This paper utilizes lumped and distributed parameter models to express transmission tines respectively, analyzes the character of nature frequencies. Different influencing factors including different fault conditions, source impedance, bus capacitance, series compensated capacitance and shunt reactor are discussed in this paper. The results have been proven by ATP procedure in a typical 500-kv power transmission line.
This paper addresses the problem of suppressing torsional vibration induced by a disturbance torque in a high performance two-disk system. The plant consists of two inertia disks connected by a weakly damped link and ...
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ISBN:
(纸本)0780389980
This paper addresses the problem of suppressing torsional vibration induced by a disturbance torque in a high performance two-disk system. The plant consists of two inertia disks connected by a weakly damped link and is driven by a brushless DC motor connected to one of the disks. A distributed parameter model of the system is developed and a lumped parametermodel including the dominant torsional modes is then extracted. A multi-loop controller is designed on the basis of the lumped parametermodel and is shown to be capable of suppressing the vibration to a reasonable level and over a wide frequency range.
In this paper, a novel fault location algorithm is presented, which uses synchronized samples of two ends of the transmission line to obtain the voltages along the line based on precise integration method. The locatio...
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In this paper, a novel fault location algorithm is presented, which uses synchronized samples of two ends of the transmission line to obtain the voltages along the line based on precise integration method. The location of the fault point is yielded by voltage comparison. An example shows that This algorithm is simple, accurate and stable.
A general framework for a partial differential equation (PDE) model predictive control (MPC) problem is formulated. A first principle model of the system. described by a semi-linear PDE system with boundary control, i...
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A general framework for a partial differential equation (PDE) model predictive control (MPC) problem is formulated. A first principle model of the system. described by a semi-linear PDE system with boundary control, is employed in a model predictive control (MPC) framework. Here, the aim is to determine, off-line (i.e. without process measurement), the theoretical optimal behavior of the process that will be used during on-line MPC. Input and output constraints are handled in the optimization task using a nonlinear programming method. This strategy is evaluated for the optimization of processing temperatures during the manufacture of thick-sectioned polymer composite laminates. The off-line optimization task consists of determining the optimal temperature profile, otherwise known as the cure cycle. Moreover, for this particular process, the existence of a feasible constrained optimization problem is discussed through the design of a constraint bound. (C) 2003 Elsevier Ltd. All rights reserved.
Various approaches can be used to simulate groundwater flow in karst systems, including equivalent porous media distributedparameter, lumped parameter, and dual porosity approaches, as well as discrete fracture or co...
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Various approaches can be used to simulate groundwater flow in karst systems, including equivalent porous media distributedparameter, lumped parameter, and dual porosity approaches, as well as discrete fracture or conduit approaches. The purpose of this study was to evaluate two different equivalent porous media approaches: lumped and distributedparameter, for simulating regional groundwater flow in a karst aquifer and to evaluate the adequacy of these approaches. The models were applied to the Barton Springs Edwards aquifer, Texas. Unique aspects of this study include availability of detailed information on recharge from stream-loss studies and on synoptic water levels, long-term continuous water level monitoring in wells throughout the aquifer, and spring discharge data to compare with simulation results. The MODFLOW code was used for the distributed parameter model. Estimation of hydraulic conductivity distribution was optimized by using a combination of trial and error and automated inverse methods. The lumped parametermodel consists of five cells representing each of the watersheds contributing recharge to the aquifer. Transient simulations were conducted using both distributed and lumped parametermodels for a 10-yr period (1989-1998). Both distributed and lumped parametermodels fairly accurately simulated the temporal variability in spring discharge;therefore, if the objective of the model is to simulate spring discharge, either distributed or lumped parameter approaches can be used. The distributed parameter model generally reproduced the potentiometric surface at different times. The impact of the amount of pumping on a regional scale on spring discharge can be evaluated using a lumped parametermodel;however, more detailed evaluation of the effect of pumping on groundwater levels and spring discharge requires a distributed parameter modeling approach. Sensitivity analyses indicated that spring discharge was much more sensitive to variations in recharge
In this work we consider an infinite dimensional model of a large space structure with flexible elements. The control purpose consists of ensuring stability while performing large slew maneuvers. To this aim, a suitab...
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In this work we consider an infinite dimensional model of a large space structure with flexible elements. The control purpose consists of ensuring stability while performing large slew maneuvers. To this aim, a suitably accurate description of the nonlinear coupling between the rigid and the flexible motions of a spacecraft with flexible appendages is necessary. A control law from the state, ensuring global stabilization of the closed-loop solutions for any initial condition, is designed. Furthermore, considering the practical problems arising from the implementation of such a feedback, a control law from the output guaranteeing semiglobal stabilization, i.e., for any initial condition in a chosen region, is proposed. As opposite to the finite dimensional approach, which suffers the spillover effect, the proposed controllers ensure the asymptotic stabilization of all the modes.
Predicting the reversible interactions between aromatic amines and soil is essential for assessing the mobility, bioavailability and exposure from contaminated sites. Reversible sorption mechanisms of aniline and alph...
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Predicting the reversible interactions between aromatic amines and soil is essential for assessing the mobility, bioavailability and exposure from contaminated sites. Reversible sorption mechanisms of aniline and alpha -naphthylamine were investigated by using single and binary solute sorption to five soils at several pH values, and by applying a distributedparameter (DP) model. The DP model assumes linear partitioning of the neutral species into soil organic matter domains and organic cation binding on negative-charged sites with the exchange coefficients represented by a Gaussian probability distribution. Sorption nonlinearity was attributed to cation exchange with varying site affinities, which was adequately simulated using the DP model. Greater uptake by hydrophobic partitioning and selectivity for cation exchange sites was observed for alpha -naphthylamine compared to aniline. Sorption of alpha -naphthylamine was not impacted quantitatively by aniline under those conditions examined;however, aniline sorption was reduced by alpha -naphthylamine with the largest reduction occurring in the soil with the lowest pH. DP model simulations showed that although hydrophobic partitioning increases with soil-solution pH, cation exchange still contributes significantly to the total sorption even at soil-solution pH values greater than pK(a) + 2. (C) 2001 Elsevier Science Ltd. All rights reserved.
distributed parameter model is used for computation of the performances of single pixel of PZT ferroelectric thin Mm infrared uncooled focal plane array(IR-UFPA) with two kinds of thermal isolation structures. The det...
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ISBN:
(纸本)0819437298
distributed parameter model is used for computation of the performances of single pixel of PZT ferroelectric thin Mm infrared uncooled focal plane array(IR-UFPA) with two kinds of thermal isolation structures. The detector performances are found to be related closely to the thermal isolation structure. The preferred thickness of pyroelectric thin film is in the region of 0.3-2 mum for pixel dimensions 50x50 and 100x100 mum(2). And the preamplifier current noise is the dominant noise when it more than 10(-16)A . Hz(-1/2) in PZT-UFPA device.
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