Experimental and Computational Investigation of binary drop collisions under elevated pressure

[EN] Spray systems often operate under extreme ambient conditions like high pressure, which can have a significant influence on important spray phenomena. One of these phenomena is binary drop collisions. Such collisions, depending on the relative velocity and the impact parameter (eccentricity of the collision), can lead to drop bouncing, coalescence or breakup. This experimental and computational study is focused on the description of the phenomenon of drop bouncing, which is caused by a thin gas layer preventing the drops coalescence. To identify the main influencing parameters of this phenomenon, experiments on binary drop collisions are performed in a pressure chamber. This experimental system allows us to investigate the effect of an ambient pressure (namely the density and viscosity of the surrounding gas) on the bouncing/coalescence threshold.This research was supported by the the German Scientific Foundation (Deutsche Forschungsgemeinschaft) in the framework of the SFB TRR 75 Collaborative Research Center, subprojects C04 and A07. The author Louis Reitter has contributed to the present manuscript in the framework of the course "Sprays and Atomization".Reitter, L.; Liu, M.; Breitenbach, J.; Huang, K.; Bothe, D.; Brenn, G.; Pan, K.... (2017). Experimental and Computational Investigation of binary drop collisions under elevated pressure. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 815-821. https://doi.org/10.4995/ILASS2017.2017.4758OCS81582

Имитация распределенной обработки информации в вычислительных системах и локальных вычислительных сетях

Предложено использовать для анализа вариантов организации распределенной обработки информации в вычислительных системах и локальных вычислительных сетях вероятностный граф реализации вычислительного процесса с явными связями типа вероятностных сетевых графиков.Запропоновано використовувати для аналізу варіантів організації розподіленої обробки інформації в обчислювальних системах і в локальних обчислювальних мережах імовірнісний граф реалізації обчислювального процесу з явними зв’язками типу імовірнісних сіткових графіків.It іs оffered to use for analyzing variants of organization of distributed information processing in computing systems and local computing networks a probabilistic graph for realizing a computing process with evident relationships of the type probabilistic network diagrams

Drop and spray impact onto a hot substrate: Dynamics and heat transfer

Non-isothermal spray/wall interaction is an important process encountered in a large number of existing and emerging technologies, such as fuel injection in aircraft gas engines and internal combustion engines, and is the underlying phenomenon associated with spray cooling technology. Spray cooling is a very promising technique for the cooling of devices with very high heat flux densities (as encountered in the fields of metalworking, cooling of electronic components or light-water nuclear reactors), surpassing all other conventional cooling methods. The effectiveness of spray cooling is influenced by a large number of parameters, including spray characteristics like drop size, velocity and number density, the surface morphology, but also on the temperature range and thermal properties of the materials involved. Indeed, the temperature of the substrate can have significant influence on the hydrodynamics of drop and spray impact, an aspect which is seldom considered in model formulation. This process is extremely complex and current approaches are highly empirical in nature. In the present thesis the single drop impact as a central element of spray impact is experimentally investigated for various thermodynamic and hydrodynamic conditions. Understanding single drop impact is an important and necessary preliminary work in the description and modeling of non-isothermal spray impact. The observed outcomes of single drop impact are classified for various impact conditions according to the well-known heat transfer regimes: single phase cooling, nucleate boiling, transition boiling and film boiling. Observations from the present work also introduce the thermal atomization regime. The phenomenon is characterized by the dewetting of the substrate, caused not by rim dynamics but induced by thermal effects, and an intensive evaporation leading to a fine secondary spray. Various theoretical considerations for the heat transfer regimes single phase cooling, nucleate boiling, thermal atomization and film boiling are obtained to describe the quantities involved in the non-isothermal drop impact. The theories allow predictions of the heat transferred from the hot substrate to the impinging drop, the typical time of drop contact, and the secondary spray. These quantities are of paramount importance for spray cooling application, since they can be used to determine the optimum spray. The theoretical predictions account for the underlying physical phenomena and are validated with existing data. Finally, the consideration for the single drop impact is used for the development of a theoretical model for an average heat transfer coefficient for spray cooling in the film boiling regime. The model captures the influence of spray characteristics and accounts for the probability of drop interactions on the wall, when the droplet number density in the spray is high. The theory agrees well with existing experimental data

Drop and spray impact onto a hot substrate: Dynamics and heat transfer

Non-isothermal spray/wall interaction is an important process encountered in a large number of existing and emerging technologies, such as fuel injection in aircraft gas engines and internal combustion engines, and is the underlying phenomenon associated with spray cooling technology. Spray cooling is a very promising technique for the cooling of devices with very high heat flux densities (as encountered in the fields of metalworking, cooling of electronic components or light-water nuclear reactors), surpassing all other conventional cooling methods. The effectiveness of spray cooling is influenced by a large number of parameters, including spray characteristics like drop size, velocity and number density, the surface morphology, but also on the temperature range and thermal properties of the materials involved. Indeed, the temperature of the substrate can have significant influence on the hydrodynamics of drop and spray impact, an aspect which is seldom considered in model formulation. This process is extremely complex and current approaches are highly empirical in nature. In the present thesis the single drop impact as a central element of spray impact is experimentally investigated for various thermodynamic and hydrodynamic conditions. Understanding single drop impact is an important and necessary preliminary work in the description and modeling of non-isothermal spray impact. The observed outcomes of single drop impact are classified for various impact conditions according to the well-known heat transfer regimes: single phase cooling, nucleate boiling, transition boiling and film boiling. Observations from the present work also introduce the thermal atomization regime. The phenomenon is characterized by the dewetting of the substrate, caused not by rim dynamics but induced by thermal effects, and an intensive evaporation leading to a fine secondary spray. Various theoretical considerations for the heat transfer regimes single phase cooling, nucleate boiling, thermal atomization and film boiling are obtained to describe the quantities involved in the non-isothermal drop impact. The theories allow predictions of the heat transferred from the hot substrate to the impinging drop, the typical time of drop contact, and the secondary spray. These quantities are of paramount importance for spray cooling application, since they can be used to determine the optimum spray. The theoretical predictions account for the underlying physical phenomena and are validated with existing data. Finally, the consideration for the single drop impact is used for the development of a theoretical model for an average heat transfer coefficient for spray cooling in the film boiling regime. The model captures the influence of spray characteristics and accounts for the probability of drop interactions on the wall, when the droplet number density in the spray is high. The theory agrees well with existing experimental data

High-Performance Detection of Corneal Ulceration Using Image Classification with Convolutional Neural Networks

Corneal Ulcer, also known as keratitis, represents the most frequently appearing symptom among corneal diseases, the second leading cause of ocular morbidity worldwide. Consequences such as irreversible eyesight damage or blindness require an innovative approach that enables a distinction to be made between patterns of different ulcer stages to lower the global burden of visual disability. This paper describes a Convolutional Neural Network-based image classification approach that allows the identification of different types of Corneal Ulcers based on fluorescein staining images. With a balanced accuracy of 92.73 percent, our results set a benchmark in distinguishing between general ulcer patterns. Our proposed method is robust against light reflections and allows automated extraction of meaningful features, manifesting a strong practical and theoretical relevance. By identifying Corneal Ulcers at an early stage, we aid reduction of aggravation by preventively applying and consequently tracking the efficacy of adapted medical treatment, which contributes to IT-based healthcare