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.

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 Concentration modeling of hydrocarbons, carbon monoxide, carbon dioxide and nitrogen oxides emitted from cigarette consumption in atmosphere of Isfahan, Iran

2019 ◽  
Author(s):  
Amirreza Talaiekhozani ◽  
Ali Mohammad Amani ◽  
Zeinab Eskandari ◽  
Reza Sanaye
Keyword(s):  
Carbon Dioxide ◽  
Air Pollution ◽  
Carbon Monoxide ◽  
Nitrogen Oxides ◽  
Emission Factors ◽  
The Other ◽  
Cigarette Consumption ◽  
Pollutant Emissions ◽  
Pollutant Sources ◽  
Pollutants Dispersion

Introduction: Although many studies on Isfahan’s air pollution have been done, there is no report about the effects of cigarette consumption in Isfahan. The aims of this study were (a) to find the amount of nitrogen oxides, hydrocarbons, carbon monoxide and carbon dioxide emitted by cigarette consumption in Isfahan; and (b) to model the distribution of such pollutants in Isfahan’s atmosphere. Materials and methods: Based on the literature, it is assumed that 15% of Isfahan’s people consume cigarettes and each smoker on average smokes 1,147 cigarettes per year. Based on these assumptions, the 249,000 smokers living in Isfahan consume 285,000,000 cigarettes per year. The amount of pollutant emissions was calculated by existing emission factors for cigarette consumption. Finally, the distribution of the emitted pollutants from cigarette consumption in Isfahan’s atmosphere was modeled using AERMOD. Results: The results illustrated that each year, 2.85 kg nitrogen oxides, 2.85 kg hydrocarbons, 37.05 kg carbon monoxide and 142.5 kg carbon dioxide are emitted into Isfahan’s atmosphere from residents’ smoking. The modeling of pollutants’ dispersion in Isfahan’s atmosphere showed that only some of these pollutants result from cigarette consumption. Conclusion: This study demonstrated that the amount of pollutants emitted by cigarette consumption was negligible compared to the other pollutant sources in Isfahan.

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.

scholarly journals Influence of the Background Nitrogen Oxides on the Tropospheric Ozone Depletion Events in the Arctic during Springtime

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 344
Author(s):  
Jiashu Zhou ◽  
Le Cao ◽  
Simeng Li
Keyword(s):  
Sensitivity Analysis ◽  
Nitrogen Oxides ◽  
Ozone Depletion ◽  
Chemical Species ◽  
Background Level ◽  
Critical Value ◽  
The Arctic ◽  
Mixing Ratio ◽  
Depletion Rate ◽  
Concentration Sensitivity

Ozone depletion events (ODEs) in the springtime of the Arctic have been frequently observed since the early 1980s, and the correlation between the ozone mixing ratio during the ODEs and the nitrogen oxides (NOx) concentration is still unclear. In the present study, the role of the background level of NOx in ODEs was investigated by using a box model implementing a chemical reaction mechanism containing 49 chemical species and 141 related reactions. A concentration sensitivity analysis was also applied to discover the dependence of the ozone mixing ratio during the ODEs on each constituent of the initial air composition. The simulation results showed that a critical value of the NOx background level exists, with which the ozone depletion rate is independent of the initial concentration of NOx, and the critical value was found to be approximately 55 ppt (ppt = part per trillion, 10−12 mol/mol) in the present study. The concentration sensitivity analysis also showed that the existence of NOx has a two-sided impact on the depletion of ozone, depending on the initial amount of NOx. With a low background level of NOx (less than 55 ppt), the increase of the initial NOx can advance the ozone depletion. On the contrary, with a high initial NOx level (more than 55 ppt), NOx would delay the consumption of ozone during the ODEs.

An Intuitionistic Fuzzy Based Novel Approach to CPU Scheduler

2020 ◽  
Vol 16 (4) ◽  
pp. 316-328
Author(s):  
Supriya Raheja
Keyword(s):  
Fuzzy Inference ◽  
The Other ◽  
Simulation Environment ◽  
Inference System ◽  
Intuitionistic Fuzzy ◽  
Novel Approach ◽  
Continuous Feedback ◽  
Simulation Results ◽  
Effectiveness And Efficiency ◽  
Unique Capability

Background: The extension of CPU schedulers with fuzzy has been ascertained better because of its unique capability of handling imprecise information. Though, other generalized forms of fuzzy can be used which can further extend the performance of the scheduler. Objectives: This paper introduces a novel approach to design an intuitionistic fuzzy inference system for CPU scheduler. Methods: The proposed inference system is implemented with a priority scheduler. The proposed scheduler has the ability to dynamically handle the impreciseness of both priority and estimated execution time. It also makes the system adaptive based on the continuous feedback. The proposed scheduler is also capable enough to schedule the tasks according to dynamically generated priority. To demonstrate the performance of proposed scheduler, a simulation environment has been implemented and the performance of proposed scheduler is compared with the other three baseline schedulers (conventional priority scheduler, fuzzy based priority scheduler and vague based priority scheduler). Results: Proposed scheduler is also compared with the shortest job first CPU scheduler as it is known to be an optimized solution for the schedulers. Conclusion: Simulation results prove the effectiveness and efficiency of intuitionistic fuzzy based priority scheduler. Moreover, it provides optimised results as its results are comparable to the results of shortest job first.

A Multiregion Model with Capital Accumulation and Endogenous Amenities

2007 ◽  
Vol 39 (9) ◽  
pp. 2248-2270 ◽  
Author(s):  
Wei-Bin Zhang
Keyword(s):  
Capital Accumulation ◽  
Comparative Statics ◽  
The Other ◽  
High Rate ◽  
Unique Equilibrium ◽  
Economic Activities ◽  
Technological Differences ◽  
National Output ◽  
Simulation Results ◽  
Wage Disparities

The author develops a multiregional growth model with endogenous amenity and capital accumulation for any number of regions. The simulation results demonstrate that the national dynamics have a unique equilibrium. Comparative statics analysis shows that, if environmental improvement occurs in the technologically advanced (less advanced) region, the national output rises (falls). As a region improves its technology, the other two regions' aggregated output levels fall—not only in relative, but also in absolute, terms. This implies that if any region has a high rate of technological change and the other regions remain technologically stationary, then economic activities will tend to be concentrated in the technologically advancing region. It is also shown that technological differences appear to play only a small role in accounting for spatial wage disparities and endowments.

Simulation on Effect of Five Kinds of Belt Structures on Tire Performance

2012 ◽  
Vol 501 ◽  
pp. 151-155
Author(s):  
Yong Liu ◽  
Ge Zhang ◽  
Hua Yan ◽  
Yu Mei Ding ◽  
Wei Min Yang
Keyword(s):  
The Other ◽  
Molding Process ◽  
Simulation Results ◽  
Better Than

In this article, three kinds of belt named B, C and D type are invented, then their main performance are compared with the other two kinds of belt structures introduced in previous papers. Simulation results showed that B and D-type belts are better than the other three. Comparatively the latter needs less material, its molding process is easier, and the tire body is lighter than B type tire, so in general it can be considered that D-type belt is the best among the five kinds of belt structures.

Sign in / Sign up

Export Citation Format

Share Document