scholarly journals Simplification of Carbon Bond Mechanism IV (CBM-IV) under Different Initial Conditions by Using Concentration Sensitivity Analysis

Molecules ◽  
2019 ◽  
Vol 24 (13) ◽  
pp. 2463 ◽  
Author(s):  
Le Cao ◽  
Simeng Li ◽  
Ziwei Yi ◽  
Mengmeng Gao
Keyword(s):  
Sensitivity Analysis ◽  
Reaction Mechanism ◽  
Initial Conditions ◽  
Model Simulation ◽  
Computing Time ◽  
Reaction System ◽  
Carbon Bond ◽  
Reduced Mechanism ◽  
Concentration Sensitivity ◽  
Bond Mechanism

Carbon Bond Mechanism IV (CBM-IV) is a widely used reaction mechanism in which VOCs are grouped according to the molecular structure. In the present study, we applied a sensitivity analysis on the CBM-IV mechanism to clarify the importance of each reaction under two different initial conditions (urban and low-NO scenarios). The reactions that exert minor influence on the reaction system are then screened out from the mechanism, so that a reduced version of the CBM-IV mechanism under specific initial conditions can be obtained. We found that in a typical urban condition, 11 reactions can be removed from the original CBM-IV mechanism, and the deviation is less than 5% between the results using the original CBM-IV mechanism and the reduced mechanism. Moreover, in a low-NO initial condition, two more reactions, both of which are nitrogen-associated reactions, can be screened out from the reaction mechanism, while the accuracy of the simulation is still maintained. It is estimated that the reduction of the CBM-IV mechanism can save 11–14% of the computing time in the calculation of the chemistry in a box model simulation.

Study of different Carbon Bond 6 (CB6) mechanisms by using a concentration sensitivity analysis

2021 ◽  
Vol 21 (16) ◽  
pp. 12687-12714
Author(s):  
Le Cao ◽  
Simeng Li ◽  
Luhang Sun
Keyword(s):  
Sensitivity Analysis ◽  
Early Stage ◽  
Reaction System ◽  
The Other ◽  
Peroxy Radicals ◽  
Nox Formation ◽  
Carbon Bond ◽  
Surface Emission ◽  
Concentration Sensitivity ◽  
The Difference

Abstract. Since the year 2010, different versions of the Carbon Bond 6 (CB6) mechanism have been developed to accurately estimate the contribution to air pollution by the chemistry. In order to better understand the differences in simulation results brought about by the modifications between different versions of the CB6 mechanism, in the present study, we investigated the behavior of three different CB6 mechanisms (CB6r1, CB6r2 and CB6r3) in simulating ozone (O3), nitrogen oxides (NOx) and formaldehyde (HCHO) under two different emission conditions by applying a concentration sensitivity analysis in a box model. The results show that when the surface emission is weak, the O3 level predicted by CB6r1 is approximately 7 ppb higher than that predicted by CB6r2 and CB6r3, specifically due to the change in the sink of acyl peroxy radicals with high-order carbons (i.e., species CXO3) in the mechanism and the difference in the ozone dependence on the isoprene emission. In contrast, although CB6r1 estimates higher values of NOx and HCHO than the other two mechanisms at an early stage of the simulation, the levels of NOx and HCHO estimated by these three CB6 mechanisms at the end of the 7 d simulation are mostly similar, when the surface emission is weak. After the increase in the surface emission, the simulated profiles of O3, NOx and HCHO obtained by CB6r2 and CB6r3 were found to be nearly the same during the simulation period, but CB6r1 tends to estimate substantially higher values than CB6r2 and CB6r3. The deviation between the O3 levels provided by CB6r1 and the other two CB6 mechanisms (i.e., CB6r2 and CB6r3) was found to be enlarged compared with the weak-emission scenario because of the weaker dependence of ozone on the emission of isoprene in CB6r1 than those in CB6r2 and CB6r3 in this scenario. Moreover, HCHO predicted by CB6r1 was found to be larger than those predicted by CB6r2 and CB6r3, which is caused by an enhanced dependence of HCHO on the emission of isoprene in CB6r1. Regarding NOx, it was found that CB6r1 gives a higher value than the other two mechanisms, which is caused by the relatively stronger connection between the NOx prediction and the release of NO and NO2 in CB6r1 due to the change in the product of the reaction between isoprene and NO3 in CB6r1. Consequently, more emitted NOx is involved in the reaction system denoted by CB6r1, which enables a following NOx formation and thus a higher NOx prediction of CB6r1.

scholarly journals Derivation of the reduced reaction mechanisms of ozone depletion events in the Arctic spring by using concentration sensitivity analysis and principal component analysis

2016 ◽  
Vol 16 (23) ◽  
pp. 14853-14873 ◽  
Author(s):  
Le Cao ◽  
Chenggang Wang ◽  
Mao Mao ◽  
Holger Grosshans ◽  
Nianwen Cao
Keyword(s):  
Principal Component Analysis ◽  
Sensitivity Analysis ◽  
Reaction Mechanism ◽  
Ozone Depletion ◽  
Principal Component ◽  
Component Analysis ◽  
Reaction Scheme ◽  
The Arctic ◽  
Maximum Deviation ◽  
Concentration Sensitivity

Abstract. The ozone depletion events (ODEs) in the springtime Arctic have been investigated since the 1980s. It is found that the depletion of ozone is highly associated with an auto-catalytic reaction cycle, which involves mostly the bromine-containing compounds. Moreover, bromide stored in various substrates in the Arctic such as the underlying surface covered by ice and snow can be also activated by the absorbed HOBr. Subsequently, this leads to an explosive increase of the bromine amount in the troposphere, which is called the “bromine explosion mechanism”. In the present study, a reaction scheme representing the chemistry of ozone depletion and halogen release is processed with two different mechanism reduction approaches, namely, the concentration sensitivity analysis and the principal component analysis. In the concentration sensitivity analysis, the interdependence of the mixing ratios of ozone and principal bromine species on the rate of each reaction in the ODE mechanism is identified. Furthermore, the most influential reactions in different time periods of ODEs are also revealed. By removing 11 reactions with the maximum absolute values of sensitivities lower than 10 %, a reduced reaction mechanism of ODEs is derived. The onsets of each time period of ODEs in simulations using the original reaction mechanism and the reduced reaction mechanism are identical while the maximum deviation of the mixing ratio of principal bromine species between different mechanisms is found to be less than 1 %. By performing the principal component analysis on an array of the sensitivity matrices, the dependence of a particular species concentration on a combination of the reaction rates in the mechanism is revealed. Redundant reactions are indicated by principal components corresponding to small eigenvalues and insignificant elements in principal components with large eigenvalues. Through this investigation, aside from the 11 reactions identified as unimportant in the concentration sensitivity analysis, additionally nine reactions were indicated to contribute only little to the total response of the system. Thus, they can be eliminated from the original reaction scheme. The results computed by applying the reduced reaction mechanism derived after the principal component analysis agree well with those by using the original reaction scheme. The maximum deviation of the mixing ratio of principal bromine species is found to be less than 10 %, which is guaranteed by the selection criterion adopted in the simplification process. Moreover, it is shown in the principal component analysis that O(1D) in the mechanism of ODEs is in quasi-steady state, which enables a following simplification of the reduced reaction mechanism obtained in the present study.

scholarly journals Study of Different Carbon Bond 6 (CB6) Mechanisms by Using a Concentration Sensitivity Analysis

2021 ◽  
Author(s):  
Le Cao ◽  
Simeng Li ◽  
Luhang Sun
Keyword(s):  
Air Pollution ◽  
Sensitivity Analysis ◽  
Nitrogen Oxides ◽  
The Other ◽  
Box Model ◽  
Carbon Bond ◽  
Surface Emission ◽  
Urban Condition ◽  
Concentration Sensitivity ◽  
Simulation Results

Abstract. Since the year 2010, different versions of the Carbon Bond 6 (CB6) mechanism have been developed, to accurately estimate the contribution to the air pollution by the chemistry. However, the discrepancies in simulation results brought about by the modifications between different versions of the CB6 mechanism are still not fully understood. Therefore, in the present study, we investigated the behavior of three different CB6 mechanisms (CB6r1, CB6r2 and CB6r3) in simulating ozone (O3), nitrogen oxides (NOx) and formaldehyde (HCHO) under an urban condition, by applying a concentration sensitivity analysis in a box model. The results show that when the surface emission is excluded, the O3 level predicted by CB6r1 is approximately 6 % and 8 % higher than that predicted by CB6r2 and CB6r3, specifically due to the change in the sink of CXO3 in the mechanism. In contrast, the levels of NOx and HCHO estimated by these three CB6 mechanisms are mostly similar, when the surface emission is turned off. After adding the surface emission, the simulated profiles of O3, NOx and HCHO obtained by CB6r2 and CB6r3 are similar. However, the deviation between the O3 levels provided by CB6r1 and the other two CB6 mechanisms (i.e. CB6r2 and CB6r3) is enlarged, because of the weakening of the ozone dependence on the emission of isoprene in CB6r1. Moreover, HCHO predicted by CB6r1 is found larger than that predicted by CB6r2 and CB6r3, which is caused by an enhanced dependence of HCHO on the emission of isoprene in CB6r1. Regarding to NOx, it was found that CB6r1 gives a higher value during the daytime and a lower value during the nighttime than the other two mechanisms, which is caused by the relatively stronger connection between the NOx prediction and the local chemistry in CB6r1, so that more NOx is consumed and converted to PANX (peroxyacyl nitrate with three and higher carbons) in the nighttime and more NOx is reformed by the photolysis of PANX in the daytime.

scholarly journals Derivation of the Reduced Reaction Mechanisms of Ozone Depletion Events in Polar Spring by Using Concentration Sensitivity Analysis and Principal Component Analysis

2016 ◽  
Author(s):  
Le Cao ◽  
Chenggang Wang ◽  
Mao Mao ◽  
Holger Grosshans ◽  
Nianwen Cao
Keyword(s):  
Principal Component Analysis ◽  
Sensitivity Analysis ◽  
Reaction Mechanism ◽  
Ozone Depletion ◽  
Principal Component ◽  
Component Analysis ◽  
Reaction Scheme ◽  
Maximum Deviation ◽  
Mixing Ratio ◽  
Concentration Sensitivity

Abstract. The ozone depletion events (ODEs) in the spring of Arctic have been investigated since the 1980s. It is found that the depletion of ozone is highly associated with an auto-catalytic reaction cycle in which the bromine containing compounds are mostly involved. Moreover, bromide stored in various substrates in the Arctic such as the underlying surface covered by ice and snow can be also activated by the absorbed HOBr. Subsequently this leads to an explosive increase of the bromine amount in the troposphere, which is the so-called "bromine explosion mechanism". In the present study, a reaction scheme representing the chemistry of ozone depletion and halogen release is processed with two different mechanism reduction approaches, namely the concentration sensitivity analysis and the principal component analysis. In the concentration sensitivity analysis, the interdependence of the mixing ratios of ozone and principal bromine species on the rate of each reaction in the mechanism of ODEs is identified. Furthermore, the most influential reactions in different time periods of ODEs are also revealed. By removing 11 reactions with the maximum absolute values of sensitivities lower than 10 %, a reduced reaction mechanism of ODEs is derived. The onsets of each time period of ODEs in simulations using the original reaction mechanism and the reduced reaction mechanism are identical while the maximum deviation of the mixing ratio of principal bromine species between different mechanisms is found less than 1 %. By performing the principal component analysis on an array of the sensitivity matrices, the dependence of a particular species concentration on a combination of the reaction rates in the mechanism is revealed. Redundant reactions are indicated by principal components corresponding to small eigenvalues and insignificant elements in principal components with large eigenvalues. Through this investigation, aside from the 11 reactions which have been identified as unimportant in the concentration sensitivity analysis, additionally nine reactions were identified to contribute only little to the total response of the system. Thus, they can be eliminated from the original reaction scheme. The results computed by applying the reduced reaction mechanism derived after the principal component analysis agree well with those by using the original reaction scheme. The maximum deviation of the mixing ratio of principal bromine species is found less than 10 %, which is guaranteed by the selection criterion adopted in the simplification process. Moreover, it is shown in the principal component analysis that O(1D) in the mechanism of ODEs is in quasi-steady state, which enables a following simplification of the reduced reaction mechanism obtained in the present study.

Kinematic characteristics of longitudinal double folding wings

2021 ◽  
pp. 1-25
Author(s):  
L. Tiegang ◽  
C. Guoguang ◽  
L. Shuai
Keyword(s):  
Angular Velocity ◽  
Structural Model ◽  
Initial Conditions ◽  
Aerodynamic Force ◽  
Model Simulation ◽  
Lagrange Equation ◽  
Grid Method ◽  
Weapon Systems ◽  
Folding Wing ◽  
Double Folding

ABSTRACT A folding wing is a tactical missile launching device that needs to be miniaturised to facilitate storage, transportation, and launching; save missile and transportation space; and improve the combat capability of weapon systems. This study investigates the aeroelastic characteristics of the secondary longitudinal folding wing during the unfolding process. First, the Lagrange equation is used to establish the structural dynamics model of the folding wing, the kinematics characteristics during the deformation process are analysed, and the unfolding movement of the folding wing is obtained using the dynamic equations in the process. Then, the generalised unsteady aerodynamic force is calculated using the dipole grid method, and the multi-body dynamics equation of the folding wing is obtained. The initial angular velocity required for the deployment of the folding wing is analysed through structural model simulation, and the influence of the initial angular velocity on the opening process is studied. Finally, aeroelastic flutter analysis is performed on the folding wing, and the physical model of the folding wing verified experimentally. Results show that the type of aeroelastic response is sensitive to the initial conditions and the way the folding wing opens.

CELLULAR NEURAL NETWORKS CAN MIMIC SMALL-WORLD NETWORKS

1999 ◽  
Vol 09 (10) ◽  
pp. 2105-2126 ◽  
Author(s):  
TAO YANG ◽  
LEON O. CHUA
Keyword(s):  
Neural Networks ◽  
Coupling Strength ◽  
Initial Conditions ◽  
Computing Time ◽  
Small World ◽  
Cellular Neural Networks ◽  
Clustering Coefficient ◽  
High Survival ◽  
Game Of Life ◽  
Hole Detection

Small-world phenomenon can occur in coupled dynamical systems which are highly clustered at a local level and yet strongly coupled at the global level. We show that cellular neural networks (CNN's) can exhibit "small-world phenomenon". We generalize the "characteristic path length" from previous works on "small-world phenomenon" into a "characteristic coupling strength" for measuring the average coupling strength of the outputs of CNN's. We also provide a simplified algorithm for calculating the "characteristic coupling strength" with a reasonable amount of computing time. We define a "clustering coefficient" and show how it can be calculated by a horizontal "hole detection" CNN, followed by a vertical "hole detection" CNN. Evolutions of the game-of-life CNN with different initial conditions are used to illustrate the emergence of a "small-world phenomenon". Our results show that the well-known game-of-life CNN is not a small-world network. However, generalized CNN life games whose individuals have strong mobility and high survival rate can exhibit small-world phenomenon in a robust way. Our simulations confirm the conjecture that a population with a strong mobility is more likely to qualify as a small world. CNN games whose individuals have weak mobility can also exhibit a small-world phenomenon under a proper choice of initial conditions. However, the resulting small worlds depend strongly on the initial conditions, and are therefore not robust.

scholarly journals Estimating Changes in Temperature Distributions in a Large Ensemble of Climate Simulations Using Quantile Regression

2018 ◽  
Vol 31 (20) ◽  
pp. 8573-8588 ◽  
Author(s):  
Matz A. Haugen ◽  
Michael L. Stein ◽  
Elisabeth J. Moyer ◽  
Ryan L. Sriver
Keyword(s):  
Quantile Regression ◽  
Radiative Forcing ◽  
Initial Conditions ◽  
Model Simulation ◽  
Extreme Temperature ◽  
Single Model ◽  
New Approach ◽  
Temperature Distributions ◽  
Climate Simulations ◽  
Community Earth System Model

Understanding future changes in extreme temperature events in a transient climate is inherently challenging. A single model simulation is generally insufficient to characterize the statistical properties of the evolving climate, but ensembles of repeated simulations with different initial conditions greatly expand the amount of data available. We present here a new approach for using ensembles to characterize changes in temperature distributions based on quantile regression that more flexibly characterizes seasonal changes. Specifically, our approach uses a continuous representation of seasonality rather than breaking the dataset into seasonal blocks; that is, we assume that temperature distributions evolve smoothly both day to day over an annual cycle and year to year over longer secular trends. To demonstrate our method’s utility, we analyze an ensemble of 50 simulations of the Community Earth System Model (CESM) under a scenario of increasing radiative forcing to 2100, focusing on North America. As previous studies have found, we see that daily temperature bulk variability generally decreases in wintertime in the continental mid- and high latitudes (>40°). A more subtle result that our approach uncovers is that differences in two low quantiles of wintertime temperatures do not shrink as much as the rest of the temperature distribution, producing a more negative skew in the overall distribution. Although the examples above concern temperature only, the technique is sufficiently general that it can be used to generate precise estimates of distributional changes in a broad range of climate variables by exploiting the power of ensembles.

Large eddy simulation of multi-regime burner: a reaction mechanism sensitivity analysis

2022 ◽  
Author(s):  
Lorenzo Angelilli ◽  
Pietro Paolo Ciottoli ◽  
Francisco E. Hernandez Perez ◽  
Mauro Valorani ◽  
Hong G. Im ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Reaction Mechanism ◽  
Large Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy
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