Activated sludge modelling: development and potential use of a practical applications database

2011 ◽  
Vol 63 (10) ◽  
pp. 2164-2182 ◽  
Author(s):  
H. Hauduc ◽  
L. Rieger ◽  
T. Ohtsuki ◽  
A. Shaw ◽  
I. Takács ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Practical Experience ◽  
Model Parameters ◽  
Practical Applications ◽  
Biokinetic Model ◽  
Starting Point ◽  
Technical Report ◽  
Typical Parameter ◽  
Parameter Values ◽  
Activated Sludge Models

This study aims at synthesizing experiences in the practical application of ASM type models. The information is made easily accessible to model users by creating a database of modelling projects. This database includes answers to a questionnaire that was sent out to model users in 2008 to provide inputs for a Scientific and Technical Report of the IWA Task Group on Good Modelling Practice – Guidelines for use of activated sludge models, and a literature review on published modelling projects. The database is analysed to determine which biokinetic model parameters are usually changed by modellers, in which ranges, and what values are typically used for seven selected activated sludge models. These results should help model users in the calibration step, by providing typical parameter values as a starting point and ranges as a guide. However, the proposed values should be used with great care since they are the result of averaging practical experience and not taking into account specific parameter correlations.

scholarly journals Hodgkin–Huxley revisited: reparametrization and identifiability analysis of the classic action potential model with approximate Bayesian methods

2015 ◽  
Vol 2 (12) ◽  
pp. 150499 ◽  
Author(s):  
Aidan C. Daly ◽  
David J. Gavaghan ◽  
Chris Holmes ◽  
Jonathan Cooper
Keyword(s):  
Action Potential ◽  
Additional Data ◽  
Potential Model ◽  
Model Parameters ◽  
Potassium Ion Channels ◽  
Identifiability Analysis ◽  
Starting Point ◽  
Approximate Bayesian ◽  
Parameter Values ◽  
Sodium And Potassium

As cardiac cell models become increasingly complex, a correspondingly complex ‘genealogy’ of inherited parameter values has also emerged. The result has been the loss of a direct link between model parameters and experimental data, limiting both reproducibility and the ability to re-fit to new data. We examine the ability of approximate Bayesian computation (ABC) to infer parameter distributions in the seminal action potential model of Hodgkin and Huxley, for which an immediate and documented connection to experimental results exists. The ability of ABC to produce tight posteriors around the reported values for the gating rates of sodium and potassium ion channels validates the precision of this early work, while the highly variable posteriors around certain voltage dependency parameters suggests that voltage clamp experiments alone are insufficient to constrain the full model. Despite this, Hodgkin and Huxley's estimates are shown to be competitive with those produced by ABC, and the variable behaviour of posterior parametrized models under complex voltage protocols suggests that with additional data the model could be fully constrained. This work will provide the starting point for a full identifiability analysis of commonly used cardiac models, as well as a template for informative, data-driven parametrization of newly proposed models.

Distribution of content words and phrases in text and language modelling

1996 ◽  
Vol 2 (1) ◽  
pp. 15-59 ◽  
Author(s):  
SLAVA M. KATZ
Keyword(s):  
Information Retrieval ◽  
General Interest ◽  
Model Parameters ◽  
Text Documents ◽  
Practical Applications ◽  
Language Modelling ◽  
Meaningful Text ◽  
Parameter Values ◽  
Text Formation ◽  
Technical Terms

This paper addresses the problem of distribution of words and phrases in text, a problem of great general interest and of importance for many practical applications. The existing models for word distribution present observed sequences of words in text documents as an outcome of some stochastic processes; the corresponding distributions of numbers of word occurrences in the documents are modelled as mixtures of Poisson distributions whose parameter values are fitted to the data. We pursue a linguistically motivated approach to statistical language modelling and use observable text characteristics as model parameters. Multi-word technical terms, intrinsically content entities, are chosen for experimentation. Their occurrence and the occurrence dynamics are investigated using a 100-million word data collection consisting of a variety of about 13,000 technical documents. The derivation of models describing word distribution in text is based on a linguistic interpretation of the process of text formation, with the probabilities of word occurrence being functions of observable and linguistically meaningful text characteristics. The adequacy of the proposed models for the description of actually observed distributions of words and phrases in text is confirmed experimentally. The paper has two focuses: one is modelling of the distributions of content words and phrases among different documents; and another is word occurrence dynamics within documents and estimation of corresponding probabilities. Accordingly, among the application areas for the new modelling paradigm are information retrieval and speech recognition.

Calibration of an Activated Sludge Model Based on Human Expertise and on a Mathematical Optimization Technique – a Comparison

1992 ◽  
Vol 25 (6) ◽  
pp. 141-148 ◽  
Author(s):  
Oskar Wanner ◽  
Jürg Kappeier ◽  
Willi Gujer
Keyword(s):  
Activated Sludge ◽  
Optimization Technique ◽  
Mathematical Optimization ◽  
The Other ◽  
Sequential Procedure ◽  
Alternative Methods ◽  
Model Parameters ◽  
Activated Sludge Model ◽  
Parameter Values ◽  
Mathematical Optimization Technique

Two alternative methods, which both can be used to estimate some of the kinetic parameters of the IAWPRC Activated Sludge Model Nr. 1, are compared. By one method, which is based on professional experience and expertise, the unknown parameter values are determined one after the other by a sequential procedure. By the other method, the parameter values are determined simultaneously by use of a mathematical optimization technique. Both methods allow a good fit of a set of 25 experimental oxygen respiration rate time-series and yield accurate estimates of the model parameters. The sequential procedure can readily be employed for the evaluation of single experiments. The optimization technique is more suitable for the evaluation of larger data sets and allows for additional analysis of the data.

Evaluations of the CREAMS model. III. Simulation of the hydrology of vertisols

Soil Research ◽  
1992 ◽  
Vol 30 (5) ◽  
pp. 547 ◽  
Author(s):  
DM Silburn ◽  
DM Freebairn
Keyword(s):  
Soil Moisture ◽  
Management Strategies ◽  
Field Measurements ◽  
Curve Number ◽  
Model Parameters ◽  
Practical Applications ◽  
Total Soil ◽  
Site Characteristics ◽  
Parameter Values ◽  
Source Of Error

The CREAMS hydrology model was evaluated for two Vertisols, each with three fallow management strategies, by comparing predictions of runoff, soil moisture and drainage with 5-8 years of measured data. Model parameter values were derived by: (i) using a combination of measured site characteristics and published values, and (ii) optimizing selected parameters, particularly the runoff parameter (curve number). With parameter values from published sources, runoff was overpredicted by 1 to 39%; good estimates of total soil moisture were obtained. Using optimized curve numbers, runoff was predicted well (daily, r2 = 0.83; monthly, r2 = 0.92; annual, r2 = 0.94). Total soil moisture values were predicted well, the main source of error being from overprediction of transpiration. Errors in predicted runoff caused little of the error in predicted total soil moisture. The distribution of soil moisture in the soil was poorly predicted. Drainage predictions were similar to estimates from steady-state solute mass balance. Optimized curve numbers derived in this study provide parameter values for modelling the water balance of self-mulching Vertisols. Values of other model parameters, derived from field measurements and published sources were near optimal, and predictions were not improved by adjusting the more sensitive of these parameters. The model is considered adequate for many practical applications. Some enhancements to the model are suggested.

Parameter sensitivity analysis for activated sludge models No. 1 and 3 combined with one-dimensional settling model

2006 ◽  
Vol 53 (1) ◽  
pp. 129-138 ◽  
Author(s):  
J.R. Kim ◽  
J.H. Ko ◽  
J.J. Lee ◽  
S.H. Kim ◽  
T.J. Park ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Activated Sludge ◽  
High Sensitivity ◽  
Model Parameters ◽  
Effluent Quality ◽  
Analysis Technique ◽  
Highly Sensitive ◽  
Reasonable Approach ◽  
Sensitive Parameters ◽  
Activated Sludge Models

The aim of this study was to suggest a sensitivity analysis technique that can reliably predict effluent quality and minimize calibration efforts without being seriously affected by influent composition and parameter uncertainty in the activated sludge models No. 1 (ASM1) and No. 3 (ASM3) with a settling model. The parameter sensitivities for ASM1 and ASM3 were analyzed by three techniques such as SVM-Slope, RVM-SlopeMA, and RVM-AreaCRF. The settling model parameters were also considered. The selected highly sensitive parameters were estimated with a genetic algorithm, and the simulation results were compared as ΔEQ. For ASM1, the SVM-Slope technique proved to be an acceptable approach because it identified consistent sensitive parameter sets and presented smaller ΔEQ under every tested condition. For ASM3, no technique identified consistently sensitive parameters under different conditions. This phenomenon was regarded as the reflection of the high sensitivity of the ASM3 parameters. But it should be noted that the SVM-Slope technique presented reliable ΔEQ under every influent condition. Moreover, it was the simplest and easiest methodology for coding and quantification among those tested. Therefore, it was concluded that the SVM-Slope technique could be a reasonable approach for both ASM1 and ASM3.

Challenges encountered when expanding activated sludge models: a case study based on N2O production

2014 ◽  
Vol 70 (7) ◽  
pp. 1251-1260 ◽  
Author(s):  
L. J. P. Snip ◽  
R. Boiocchi ◽  
X. Flores-Alsina ◽  
U. Jeppsson ◽  
K. V. Gernaey
Keyword(s):  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
N2o Emission ◽  
Full Scale ◽  
Ammonia Oxidizing Bacteria ◽  
N2o Formation ◽  
N2o Production ◽  
Parameter Values ◽  
Activated Sludge Models

It is common practice in wastewater engineering to extend standard activated sludge models (ASMs) with extra process equations derived from batch experiments. However, such experiments have often been performed under conditions different from the ones normally found in wastewater treatment plants (WWTPs). As a consequence, these experiments might not be representative for full-scale performance, and unexpected behaviour may be observed when simulating WWTP models using the derived process equations. In this paper we want to highlight problems encountered using a simplified case study: a modified version of the Activated Sludge Model No. 1 (ASM1) is upgraded with nitrous oxide (N2O) formation by ammonia-oxidizing bacteria. Four different model structures have been implemented in the Benchmark Simulation Model No. 1 (BSM1). The results of the investigations revealed two typical difficulties: problems related to the overall mathematical model structure and problems related to the published set of parameter values. The paper describes the model implementation incompatibilities, the variability in parameter values and the difficulties of reaching similar conditions when simulating a full-scale activated sludge plant. Finally, the simulation results show large differences in oxygen uptake rates, nitritation rates and consequently the quantity of N2O emission (GN2O) using the different models.

scholarly journals Determination of synchronous generator nonlinear model parameters based on power rejection tests using a gradient optimization algorithm

2017 ◽  
Vol 65 (4) ◽  
pp. 479-488 ◽  
Author(s):  
A. Boboń ◽  
A. Nocoń ◽  
S. Paszek ◽  
P. Pruski
Keyword(s):  
Parameter Estimation ◽  
Objective Function ◽  
Optimization Algorithm ◽  
Least Squares Method ◽  
Synchronous Generator ◽  
Operating Conditions ◽  
Model Parameters ◽  
State Variables ◽  
Starting Point ◽  
Gradient Optimization

AbstractThe paper presents a method for determining electromagnetic parameters of different synchronous generator models based on dynamic waveforms measured at power rejection. Such a test can be performed safely under normal operating conditions of a generator working in a power plant. A generator model was investigated, expressed by reactances and time constants of steady, transient, and subtransient state in the d and q axes, as well as the circuit models (type (3,3) and (2,2)) expressed by resistances and inductances of stator, excitation, and equivalent rotor damping circuits windings. All these models approximately take into account the influence of magnetic core saturation. The least squares method was used for parameter estimation. There was minimized the objective function defined as the mean square error between the measured waveforms and the waveforms calculated based on the mathematical models. A method of determining the initial values of those state variables which also depend on the searched parameters is presented. To minimize the objective function, a gradient optimization algorithm finding local minima for a selected starting point was used. To get closer to the global minimum, calculations were repeated many times, taking into account the inequality constraints for the searched parameters. The paper presents the parameter estimation results and a comparison of the waveforms measured and calculated based on the final parameters for 200 MW and 50 MW turbogenerators.

scholarly journals Assimilation of Dynamic Combined Finite Discrete Element Methods Using the Ensemble Kalman Filter

2021 ◽  
Vol 11 (7) ◽  
pp. 2898
Author(s):  
Humberto C. Godinez ◽  
Esteban Rougier
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Peak Stress ◽  
Discrete Element ◽  
Material Behavior ◽  
Model Parameters ◽  
Hopkinson Pressure Bar ◽  
Parameter Values

Simulation of fracture initiation, propagation, and arrest is a problem of interest for many applications in the scientific community. There are a number of numerical methods used for this purpose, and among the most widely accepted is the combined finite-discrete element method (FDEM). To model fracture with FDEM, material behavior is described by specifying a combination of elastic properties, strengths (in the normal and tangential directions), and energy dissipated in failure modes I and II, which are modeled by incorporating a parameterized softening curve defining a post-peak stress-displacement relationship unique to each material. In this work, we implement a data assimilation method to estimate key model parameter values with the objective of improving the calibration processes for FDEM fracture simulations. Specifically, we implement the ensemble Kalman filter assimilation method to the Hybrid Optimization Software Suite (HOSS), a FDEM-based code which was developed for the simulation of fracture and fragmentation behavior. We present a set of assimilation experiments to match the numerical results obtained for a Split Hopkinson Pressure Bar (SHPB) model with experimental observations for granite. We achieved this by calibrating a subset of model parameters. The results show a steady convergence of the assimilated parameter values towards observed time/stress curves from the SHPB observations. In particular, both tensile and shear strengths seem to be converging faster than the other parameters considered.

scholarly journals Influence of Selected Model Parameters on the Electromagnetic Levitation Melting Efficiency

2021 ◽  
Vol 11 (9) ◽  
pp. 3827
Author(s):  
Blazej Nycz ◽  
Lukasz Malinski ◽  
Roman Przylucki
Keyword(s):  
Electromagnetic Levitation ◽  
Optimization Methods ◽  
Calculation Model ◽  
Model Parameters ◽  
Starting Point ◽  
Low Efficiency ◽  
The Relationship ◽  
Reactive Metals ◽  
Electromagnetic Levitation Melting ◽  
Metal Melting

The article presents the results of multivariate calculations for the levitation metal melting system. The research had two main goals. The first goal of the multivariate calculations was to find the relationship between the basic electrical and geometric parameters of the selected calculation model and the maximum electromagnetic buoyancy force and the maximum power dissipated in the charge. The second goal was to find quasi-optimal conditions for levitation. The choice of the model with the highest melting efficiency is very important because electromagnetic levitation is essentially a low-efficiency process. Despite the low efficiency of this method, it is worth dealing with it because is one of the few methods that allow melting and obtaining alloys of refractory reactive metals. The research was limited to the analysis of the electromagnetic field modeled three-dimensionally. From among of 245 variants considered in the article, the most promising one was selected characterized by the highest efficiency. This variant will be a starting point for further work with the use of optimization methods.

On the Description and Definition of Human Factors/Ergonomics

1998 ◽  
Vol 42 (10) ◽  
pp. 671-674 ◽  
Author(s):  
Michael S. Wogalter ◽  
Peter A. Hancock ◽  
Patrick G. Dempsey
Keyword(s):  
Human Factors ◽  
Engineering Science ◽  
Human Factors Engineering ◽  
Lay Persons ◽  
Starting Point ◽  
Technical Report ◽  
Definition Of ◽  
Engineering Psychology

This work examines the terms most frequently used to describe our field, which has variously been named Ergonomics, Human Factors, Human Factors Engineering, and Engineering Psychology. A large number of definitions were collected, including those assembled in an earlier technical report by Licht, Polzella, and Boff (1990). First, the definitions were stripped of connector words. Second, the prefix root terms that had the same meaning were combined and third, the words were tabulated and sorted to reveal the content terms most frequently employed. These data may be used to develop core, concise definitions or longer more expository descriptions of the field. The list of terms could also be used as a starting point for the development of definitions oriented for different target audiences (e.g., lay persons vs. other engineering/science experts) as a method of disseminating information concerning what we do.

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