Characterizing dust storms and modeling diffusion in viscous atmospheric aerosol particles
Bibliographic record
Abstract
This thesis includes separate research studies on atmospheric dust particles and viscous aerosol particles. In Chapters 2 and 3, the major source points of atmospheric dust particles in the Middle East are studied. We analyze daily images from a moderate resolution imaging spectroradiometer (MODIS) sensor as well as deep blue aerosol products to select dust events occurred between 2000-2012. Then, source point identification is performed on the images of dust events using an improved version of Middle East dust index (MEDI). Later, we classify the identified sources based on their intensity and frequency to better understand the contribution of each dust source point in generating dust storms. The findings show that Iraq and Syria have the highest active dust sites among all studied countries in the region. Furthermore, we investigate whether the observed intense and frequent dust activities are linked to desertification occurred over the past three decades. Analyzing Landsat TM images (1984 and 2012), it is found that 39% of identified sources in Iraq and its surrounding areas are located in newly desertified regions. Finally, these results are compared with other studies and the implication of the findings are discussed. In Chapter 4, we describe a mathematical formulation of the water exchange diffusion problem and present analytical solutions for this problem for a spherical particle. Two different boundary conditions, constant and equilibrium concentration on the particle surface, are used to obtain solutions to the water exchange diffusion problem. Then, the effect of these boundary conditions is investigated in the context of isotope tracer experiments. Using dimensionless analysis, it is shown that the predicted sorption with fixed concentration on boundary is always greater than or equal to the model with the equilibrium boundary condition. These findings also suggest there are many physically relevant cases where the difference between these two solutions is inconsequential. We further explore these results using three physical examples of binary solution droplets: aqueous sucrose, aqueous citric acid, and aqueous shikimic acid droplets. Using the two derived analytical models, we study the water exchange lifetime. It is observed that the type of boundary condition becomes very significant when RH is very high in all cases. We conclude by discussing the observed discrepancy in the reported diffusion coefficient between isotopic water exchange and water sorption experiments. In Chapter 5, the nonlinear diffusion of water in highly viscous and glassy aerosol particles is modeled and we discuss tracking the associated diffusion front. This tracking is accomplished by analyzing the optical behavior of spherical particle exposed to electromagnetic radiation during the diffusion process. Currently, the numerical multilayer Mie models require a concentration profile as an input. Obtaining this profile requires solving the nonlinear diffusion problem, which is very time consuming. We present an analytical model to simulate the position of morphology dependent resonances (MDRs) of a core-shell aerosol particle. Then, we compare the core-shell model with the previously developed multilayer Mie model. Results demonstrate that the derived characteristic equation can accurately calculate the positions of MDRs in a much faster way compared to the existing multilayer model. From simulation data, the most sensitive region to the gradient of refractive index is found to be very close to the particle surface. This sensitivity becomes insignificant at low relative humidities and limits the application of this work. Our model eliminates the complexity associated with using traditional numerical calculations based on water transport models to analyze single particle measurements.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".