scholarly journals Data-Driven Corrections of Partial Lotka–Volterra Models

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1313
Author(s):  
Rebecca E. Morrison
Keyword(s):  
Chemical Species ◽  
Active Species ◽  
Data Driven ◽  
Volterra Models ◽  
Discrepancy Model ◽  
Partial Models ◽  
Sparse Operators ◽  
Partial Interaction ◽  
Interacting Systems ◽  
Physical Information

In many applications of interacting systems, we are only interested in the dynamic behavior of a subset of all possible active species. For example, this is true in combustion models (many transient chemical species are not of interest in a given reaction) and in epidemiological models (only certain subpopulations are consequential). Thus, it is common to use greatly reduced or partial models in which only the interactions among the species of interest are known. In this work, we explore the use of an embedded, sparse, and data-driven discrepancy operator to augment these partial interaction models. Preliminary results show that the model error caused by severe reductions—e.g., elimination of hundreds of terms—can be captured with sparse operators, built with only a small fraction of that number. The operator is embedded within the differential equations of the model, which allows the action of the operator to be interpretable. Moreover, it is constrained by available physical information and calibrated over many scenarios. These qualities of the discrepancy model—interpretability, physical consistency, and robustness to different scenarios—are intended to support reliable predictions under extrapolative conditions.

scholarly journals Chemical Space Mapping for Multicomponent Gas Mixtures

2021 ◽  
Author(s):  
Airat Kotliar-Shapirov ◽  
Fedor S. Fedorov ◽  
Henni Ouerdane ◽  
Stanislav Evlashin ◽  
Albert G. Nasibulin ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Data Processing ◽  
Electrochemical Sensors ◽  
Chemical Space ◽  
Chemical Species ◽  
Single Species ◽  
Data Driven ◽  
Multicomponent Gas ◽  
Data Driven Approach ◽  
Cyclic Voltammetry Data

In our manuscript, we present our protocol for data processing to mitigate the effects of interfering analytes on the identification of the chemical species detected by sensors. Considering NO2 and CO2, we designed electrochemical sensors whose response yielded the cyclic voltammetry data that we analyzed to classify single-species components and their mixtures using a data-driven approach to generate a chemical space where their mixtures can be deconvoluted.<br>

Design Architecture of a Data Driven Environment for Multiphysics Applications

2003 ◽  
Author(s):  
J. Michopoulos ◽  
P. Tsompanopoulou ◽  
E. Houstis ◽  
J. Rice ◽  
C. Farhat ◽  
...  
Keyword(s):  
Information Technologies ◽  
Structure Design ◽  
Data Driven ◽  
Material Structure ◽  
Environment Interaction ◽  
Material Environment ◽  
Problem Solving Environment ◽  
Interacting Systems ◽  
Efficient Prediction ◽  
Prediction Capability

The design architecture of a multidisciplinary problem-solving environment (MPSE) for supporting an efficient prediction capability for the response of continuous interacting systems under multiphysics conditions is presented. The system will be referred to as a Data Driven Environment for Multiphysics Applications (DDEMA) and will be primarily differentiated from previous MPSE efforts on its usage of data for improved confidence of simulation prediction. Its architecture takes into consideration information technologies, coupled multiphysics sciences, and data-driven practices to achieve steering of adaptive modeling and simulation of the underlying systemic behavior. Special emphasis is given on middleware implementation issues based on actor-agent abstractions. A description of the design objectives and architectural variations of DDEMA are also given in the context of two multidisciplinary applications related to material/structure design of supersonic platforms and fire/material/environment interaction monitoring, assessment and management. Validation of the architecture will also be attempted in terms of the same two applications.

scholarly journals On dithiothreitol (DTT) as a measure of oxidative potential for ambient particles: evidence for the importance of soluble transition metals

2012 ◽  
Vol 12 (5) ◽  
pp. 11317-11350 ◽  
Author(s):  
J. G. Charrier ◽  
C. Anastasio
Keyword(s):  
Particulate Matter ◽  
Transition Metals ◽  
Fine Particulate Matter ◽  
Chemical Species ◽  
Past Research ◽  
Active Species ◽  
Oxidative Potential ◽  
Adverse Health Effects ◽  
Redox Active ◽  
Small Set

Abstract. The rate of consumption of dithiothreitol (DTT) is increasingly used to measure the oxidative potential of particulate matter (PM), which has been linked to the adverse health effects of PM. While several quinones are known to be very reactive in the DTT assay, it is unclear what other chemical species might contribute to the loss of DTT in PM extracts. To address this question, we quantify the rate of DTT loss from individual redox-active species that are common in ambient particulate matter. While most past research has indicated that the DTT assay is not sensitive to metals, our results show that seven out of the ten transition metals tested do oxidize DTT, as do three out of the five quinones tested. While metals are less efficient at oxidizing DTT compared to the most reactive quinones, concentrations of soluble transition metals in fine particulate matter are generally much higher than those of quinones. The net result is that metals appear to dominate the DTT response for typical ambient PM2.5 samples. Based on particulate concentrations of quinones and soluble metals from the literature, and our measured DTT responses for these species, we estimate that for typical fine particle samples approximately 80% of DTT loss is from transition metals (especially copper and manganese), while quinones account for approximately 20%. We find a similar result for DTT loss measured in a small set of PM2.5 samples from the San Joaquin Valley of California. Because of the important contribution from metals, we also tested how the DTT assay is affected by EDTA, a chelator that is sometimes used in the assay. EDTA significantly suppresses the response from both metals and quinones; we therefore recommend that EDTA should not be included in the DTT assay.

scholarly journals Recent progress in the application of glow-discharge electrolysis plasma

2014 ◽  
Vol 12 (12) ◽  
pp. 1213-1221 ◽  
Author(s):  
Jie Ren ◽  
Mengqi Yao ◽  
Wu Yang ◽  
Yan Li ◽  
Jinzhang Gao
Keyword(s):  
Glow Discharge ◽  
Environmental Science ◽  
Chemical Species ◽  
Active Species ◽  
Polymer Materials ◽  
Highly Active ◽  
Liquid Phases ◽  
Modify Surface ◽  
Glow Discharge Electrolysis ◽  
Glow Discharge Electrolysis Plasma

AbstractNon-equilibrium plasma makes it is possible to modify surface chemistry, synthetize polymer materials, and oxidize some organic compounds completely by generation of energetic and chemically active species in gas or liquid phases. Glow-discharge electrolysis plasma (GDEP) has been intensely studied for applications in chemistry and in material, environmental, and biomedical engineering during the last few years because of the very highly active chemical species produced during the glow-discharge electrolysis (GDE) process. A brief review is already available regarding applications of glow-discharge electrolysis plasma technique in chemistry and environmental science during the past decade. For convenience of discussion, some papers from prior years are also cited. The contents of this review are focused on the degradation of persistent pollutants, surface modification of materials, and preparation of functional polymers.

Environmentally Enhanced Fracture of Ceramics

1988 ◽  
Vol 125 ◽  
Author(s):  
Stephen W. Freiman
Keyword(s):  
Crack Growth ◽  
Growth Mechanism ◽  
Crack Extension ◽  
Molecular Model ◽  
Chemical Species ◽  
Vitreous Silica ◽  
Active Species ◽  
Chemical Activity ◽  
Polycrystalline Ceramics ◽  
Crack Growth Mechanism

ABSTRACTThis paper presents a review of our current understanding of environmentally induced crack growth in glasses, single crystal ceramics, and polycrystalline ceramics. It is shown that the rate of crack growth is controlled by the chemical activity of the active species in the environment as well as by the crack tip stress. A molecular model of a stress-induced chemical reaction between vitreous silica and water is described, and the implications of this model for predicting the effects of other chemical species on crack growth are discussed. Effects of chemical bonding in the solid as well as in the reacting solutions, on the crack growth mechanism are elucidated. Finally, the complicating effects of multigrain arrays on crack extension in polycrystalline ceramics are pointed out.

Unravelling the nature, evolution and spatial gradients of active species and active sites in the catalyst bed of unpromoted and K/Ba-promoted Cu/Al2O3 during CO2 capture-reduction

2016 ◽  
Vol 4 (18) ◽  
pp. 6878-6885 ◽  
Author(s):  
Tsuyoshi Hyakutake ◽  
Wouter van Beek ◽  
Atsushi Urakawa
Keyword(s):  
Co2 Capture ◽  
Active Sites ◽  
Chemical Species ◽  
Reduction Process ◽  
Active Species ◽  
Surface Chemical ◽  
Time Resolved ◽  
Spatial Gradients ◽  
Space And Time

Space- and time-resolved operando DRIFTS, XAFS, and XRD uncovered the involved surface chemical species and active sites, especially the unique functions of K and Cu, during the CO2 capture-reduction process.

A CHANNEL NETWORK MODEL FOR CHEMICAL MIGRATION IN SUBSURFACE MEDIA

1995 ◽  
Vol 05 (05) ◽  
pp. 641-657
Author(s):  
MARK S. EDWARDS ◽  
PETER GRINDROD
Keyword(s):  
Heterogeneous Media ◽  
Channel Model ◽  
Spatial Scales ◽  
Chemical Species ◽  
Network Models ◽  
Direct Consequence ◽  
Breakthrough Curves ◽  
Active Species ◽  
Channel Network ◽  
Chemical Migration

We consider the migration of chemical species through saturated heterogeneous media, where the scale of the flow path geometry is large enough to invalidate a Fickian based, representative elementary volumes, approach to dispersal. Channel network models combine the effects of channeling over small spatial scales with network mixing which gives rise to an equivalent dispersion effect over large spatial scales. We extend equations and solutions given previously for ideal nonabsorbing tracers, to include the retardation of chemically active species. The primary aim is to derive explicit solutions for future calibration purposes, and illustrate scale dependent dispersive behavior with and without chemical absorption processes. In this paper we develop a twin channel model allowing for various specification of the retardation process. This allows the retardation to be either positively or negatively correlated with pathway apertures (which are in turn related directly to flow rates of the respective channels). We show that if absorption is controlled by specific surface area, then a scaling argument infers that highly transmissive paths are also less retarding. We illustrate the model’s applicability to such cases. We shall discuss the scale dependence of calculated (observed) equivalent dispersivities obtained by analyzing the moments of breakthrough curves at various distances. For a range of parameter values we exhibit scaling behavior similar to that observed in the field and laboratory. This does not necessarily imply any validity to the approach: it is a direct consequence of deferring the network — mixing effect to large length scales. An important point of consideration is that wherever conceptual model choices must be made, in modeling natural processes such as chemical migration, there is a possibility of biasing calculations by sole reliance on a particular approach. Channel network models marry channeling models and classical Fickian models. Thus in calibrating a model such as the Twin Channel model from given experimental behavior, we can immediately estimate over which scales channeling or Fickian dispersive effects are likely to be dominant.

scholarly journals Case study of the diurnal variability of chemically active species with respect to boundary layer dynamics during DOMINO

2012 ◽  
Vol 12 (12) ◽  
pp. 5329-5341 ◽  
Author(s):  
B. J. H. van Stratum ◽  
J. Vilà-Guerau de Arellano ◽  
H. G. Ouwersloot ◽  
K. van den Dries ◽  
T. W. van Laar ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mixed Layer ◽  
Atmospheric Chemistry ◽  
Chemical Species ◽  
Active Species ◽  
Chemical System ◽  
Chemical Production ◽  
Layer Model ◽  
Diurnal Variability ◽  
Mixed Layer Model

Abstract. We study the interactions between atmospheric boundary layer (ABL) dynamics and atmospheric chemistry using a mixed-layer model coupled to chemical reaction schemes. Guided by both atmospheric and chemical measurements obtained during the DOMINO (Diel Oxidant Mechanisms in relation to Nitrogen Oxides) campaign (2008), numerical experiments are performed to study the role of ABL dynamics and the accuracy of chemical schemes with different complexity: the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) and a reduced mechanism of this chemical system. Both schemes produce satisfactory results, indicating that the reduced scheme is capable of reproducing the O3-NOx-VOC-HOx diurnal cycle during conditions characterized by a low NOx regime and small O3 tendencies (less than 1 ppb per hour). By focusing on the budget equations of chemical species in the mixed-layer model, we show that for species like O3, NO and NO2, the influence of entrainment and boundary layer growth is of the same order as chemical production/loss. This indicates that an accurate representation of ABL processes is crucial in understanding the diel cycle of chemical species. By comparing the time scales of chemical reactive species with the mixing time scale of turbulence, we propose a classification based on the Damköhler number to further determine the importance of dynamics on chemistry during field campaigns. Our findings advocate an integrated approach, simultaneously solving the ABL dynamics and chemical reactions, in order to obtain a better understanding of chemical pathways and processes and the interpretation of the results obtained during measurement campaigns.

scholarly journals On dithiothreitol (DTT) as a measure of oxidative potential for ambient particles: evidence for the importance of soluble transition metals

2012 ◽  
Vol 12 (19) ◽  
pp. 9321-9333 ◽  
Author(s):  
J. G. Charrier ◽  
C. Anastasio
Keyword(s):  
Particulate Matter ◽  
Transition Metals ◽  
Fine Particulate Matter ◽  
Chemical Species ◽  
Past Research ◽  
Active Species ◽  
Oxidative Potential ◽  
Adverse Health Effects ◽  
Redox Active ◽  
Small Set

Abstract. The rate of consumption of dithiothreitol (DTT) is increasingly used to measure the oxidative potential of particulate matter (PM), which has been linked to the adverse health effects of PM. While several quinones are known to be very reactive in the DTT assay, it is unclear what other chemical species might contribute to the loss of DTT in PM extracts. To address this question, we quantify the rate of DTT loss from individual redox-active species that are common in ambient particulate matter. While most past research has indicated that the DTT assay is not sensitive to metals, our results show that seven out of the ten transition metals tested do oxidize DTT, as do three out of the five quinones tested. While metals are less efficient at oxidizing DTT compared to the most reactive quinones, concentrations of soluble transition metals in fine particulate matter are generally much higher than those of quinones. The net result is that metals appear to dominate the DTT response for typical ambient PM2.5 samples. Based on particulate concentrations of quinones and soluble metals from the literature, and our measured DTT responses for these species, we estimate that for typical PM2.5 samples approximately 80% of DTT loss is from transition metals (especially copper and manganese), while quinones account for approximately 20%. We find a similar result for DTT loss measured in a small set of PM2.5 samples from the San Joaquin Valley of California. Because of the important contribution from metals, we also tested how the DTT assay is affected by EDTA, a chelator that is sometimes used in the assay. EDTA significantly suppresses the response from both metals and quinones; we therefore recommend that EDTA should not be included in the DTT assay.

scholarly journals Chemical Space Mapping for Multicomponent Gas Mixtures

2021 ◽  
Author(s):  
Airat Kotliar-Shapirov ◽  
Fedor S. Fedorov ◽  
Henni Ouerdane ◽  
Stanislav Evlashin ◽  
Albert G. Nasibulin ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Data Processing ◽  
Electrochemical Sensors ◽  
Chemical Space ◽  
Chemical Species ◽  
Single Species ◽  
Data Driven ◽  
Multicomponent Gas ◽  
Data Driven Approach ◽  
Cyclic Voltammetry Data

In our manuscript, we present our protocol for data processing to mitigate the effects of interfering analytes on the identification of the chemical species detected by sensors. Considering NO2 and CO2, we designed electrochemical sensors whose response yielded the cyclic voltammetry data that we analyzed to classify single-species components and their mixtures using a data-driven approach to generate a chemical space where their mixtures can be deconvoluted.<br>

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