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This two-volume set constitutes the refereed post-conference proceedings of the 8th International Conference on Advancement of Science and Technology, ICAST 2020, which took place in Bahir Dar, Ethiopia, in October 2020.The 74 revised full papers were carefully reviewed and selected from more than 200 submissions of which 157 were sent out for peer review. The papers present economic and technologic developments in modern societies in 6 tracks: Chemical, food and bio-process engineering; Electrical and computer engineering; IT, computer science and software engineering; Civil, water resources, and environmental engineering; Mechanical and industrial engineering; Material science and engineering.

Technological innovations --- Application software. --- Data structures (Computer science). --- Information theory. --- Artificial intelligence. --- Computer networks. --- Computer and Information Systems Applications. --- Data Structures and Information Theory. --- Artificial Intelligence. --- Computer Communication Networks. --- AI (Artificial intelligence) --- Artificial thinking --- Electronic brains --- Intellectronics --- Intelligence, Artificial --- Intelligent machines --- Machine intelligence --- Thinking, Artificial --- Bionics --- Cognitive science --- Digital computer simulation --- Electronic data processing --- Logic machines --- Machine theory --- Self-organizing systems --- Simulation methods --- Fifth generation computers --- Neural computers --- Communication theory --- Communication --- Cybernetics --- Information structures (Computer science) --- Structures, Data (Computer science) --- Structures, Information (Computer science) --- File organization (Computer science) --- Abstract data types (Computer science) --- Application computer programs --- Application computer software --- Applications software --- Apps (Computer software) --- Computer software --- Communication systems, Computer --- Computer communication systems --- Data networks, Computer --- ECNs (Electronic communication networks) --- Electronic communication networks --- Networks, Computer --- Teleprocessing networks --- Data transmission systems --- Digital communications --- Electronic systems --- Information networks --- Telecommunication --- Cyberinfrastructure --- Network computers --- Distributed processing --- Innovacions tecnològiques --- Ciència --- Data structures (Computer science)

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This two-volume set constitutes the refereed post-conference proceedings of the 8th International Conference on Advancement of Science and Technology, ICAST 2020, which took place in Bahir Dar, Ethiopia, in October 2020.The 74 revised full papers were carefully reviewed and selected from more than 200 submissions of which 157 were sent out for peer review. The papers present economic and technologic developments in modern societies in 6 tracks: Chemical, food and bio-process engineering; Electrical and computer engineering; IT, computer science and software engineering; Civil, water resources, and environmental engineering; Mechanical and industrial engineering; Material science and engineering.

Mathematical control systems --- Programming --- Computer architecture. Operating systems --- Information systems --- Artificial intelligence. Robotics. Simulation. Graphics --- Computer. Automation --- applicatiebeheer --- apps --- informatica --- informatietechnologie --- KI (kunstmatige intelligentie) --- computernetwerken --- architectuur (informatica) --- informatietheorie --- AI (artificiële intelligentie)

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Mathematical control systems --- Programming --- Computer architecture. Operating systems --- Information systems --- Artificial intelligence. Robotics. Simulation. Graphics --- Computer. Automation --- applicatiebeheer --- apps --- informatica --- informatietechnologie --- KI (kunstmatige intelligentie) --- computernetwerken --- architectuur (informatica) --- informatietheorie

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Bij zowel voor- als naoogstbehandelingen van tuinbouwproducten wordt spuittechnologie gebruikt met het oog op een verbeterde productkwaliteit. Het onderzoek richtte zich op twee verschillende spuitsystemen in de productieketen van tuinbouwproducten: dwarsstroom boomgaardspuittoestellen met luchtondersteuning en bevochtingssystemen op basis van microverneveling. In de eerste toepassing leidt onoordeelkundig gebruik van de toepassingtechniek tot drift en milieuschade en fytotoxische effecten ten gevolge van overdosissen. De tweede toepassing beoogt het voorkomen van te sterke uitdroging van product, terwijl verkeerd gebruik leidt tot een afname van de koelefficiëntie en de uitgroei van microörganismen. In dit onderzoek beogen we een beter ontwerp en engineering van spuitsystemen. De hoofddoelstelling is het ontwikkelen van een modelgebaseerde methodologie voor ontwerp en engineering van spuitsystemen. De kern van deze methodologie is een 3-dimensioneel Computational Fluid Dynamics (CFD) model dat de relevante variabelen van het spuitproces in de verschillende toepassingen berekent als functie van de instelparameters en omgevingscondities. Het pad van de vernevelde druppels wordt voorspeld door middel van een Euleriaans-Lagrangiaans deeltjestransportmodel. Dit model brengt de effecten van turbulente dispersie, druppelverdamping, en de volledige koppeling van momentum, warmte- en massaoverdracht tussen de continue luchtfase en de discrete druppelfase in rekening. De berekeningen maken het voor het eerst mogelijk om voor elke specifieke configuratie een gedetailleerde en kwantitatieve evaluatie te maken van de spuitnevelverdeling, de luchtstroming, de depositie van de druppels, de temperatuur en de relatieve vochtigheid, zowel ruimtelijk als in functie van de tijd. Voor boomgaardspuiten werd een gevalideerd CFD model ontwikkeld dat rekening houdt met het profiel van de luchtondersteuning, de tractorsnelheid en de dopkarakteristieken. Zo werd het mogelijk ontwerp en instelling van spuittoestellen te verbeteren en te implementeren in de praktijk, met een verlaagd risico op drift en een uniformere spuitnevel. Dwarsstroom boomgaardspuittoestellen produceren een complex drie-dimensioneel profiel van de luchtondersteuning, dat niet kan beschreven worden met de bestaande theorie van luchtstralen. Het volledige 3-D profiel van de luchtstroming beïnvloedt in grote mate de beweging van de druppels, en is sterk afhankelijk van ventilatorsnelheid en tractorsnelheid. Het verticaal profiel van de spuitnevel wordt tevens sterk beïnvloed door de druppelgrootteverdeling van de spuitdoppen. Voor een reductie van drift, moeten het aandeel van fijnere druppels zo laag mogelijk worden gehouden, en de instellingen van de luchtondersteuning aangepast. Het gebruik van veldspuitdoppen werd aangereikt als een middel om dit te verwezenlijken. Voor bevochtingssystemen in koude bewaarruimten werd een gevalideerd multischaal CFD model ontwikkeld dat rekening houdt met het ontwerp van de bewaarruimte en koelinstallatie, de thermofysische producteigenschappen, de stapelwijze en de dopkarakteristieken. De plaatsing en instelling van bevochtigers en het ontwerp van de bewaarruimte werd aanzienlijk verbeterd om te komen tot een reductie van de condensatie en een verhoogde waarde en uniformere verdeling van de relatieve vochtigheid in de ruimte bij lage temperatuur. Het multischaalmodel bestaat enerzijds, op de kleinste schaal van de individuele box met producten, uit een gecombineerd discrete-elementen (DE) en CFD model en anderzijds, op de schaal van de complete bewaarruimte, uit een CFD model met een poreus-medium model van de productstapel. De anisotrope parameters van het poreus-medium model werden bepaald door het DE-CFD model. Er werd aangetoond dat deze multischaal aanpak resulteerde in nauwkeurigere voorspellingen van luchtsnelheid, temperatuur en relatieve vochtigheid in toepassingen met gestapelde producten. Intervalbevochtiging met hoge-druk doppen werd voorgesteld als oplossing voor het verhogen van de relatieve vochtigheid, reductie van de inkoeltijd en het verkleinen van vochtverlies van de producten in de bewaarruimte. Om te komen tot en reductie van excessieve condensatie, moet deze methode evenwel gecombineerd worden met een geoptimaliseerde plaatsing, druk en debiet van de doppen, een voldoende lang verdampingspad voor de vernevelde druppels en het juiste bevochtingsinterval en –duur. De geoptimaliseerde waarden zijn specifiek voor een bepaalde bewaarruimte en toepassing. De resultaten toonden aan dat verbeteringen in de praktijk mogelijk zijn aan de hand van de generieke ontwerpmethodologie die in dit doctoraat werd ontwikkeld. Spraying systems are used extensively in horticulture both during the preharvest as well as the postharvest stage. This study considers air-assisted orchard sprayers and cold storage humidification systems. During the application of pesticides using air-assisted orchard sprayers, environmental contamination and an increase in production cost due to off target deposition of pesticide chemicals, low level and non uniform deposition on the target canopy, and in some cases phytotoxicity due to higher level of target deposition, are common problems. Humidification during long-term cooled storage of fruits is being introduced into practice to prevent excessive moisture loss and quality degradation. However, maintaining the required high relative humidity (RH) (>95 %) with minimum deposition of the sprayed water droplets on the product and room surfaces is very challenging. The water droplets that are deposited on the product surface may favour the growth of micro-organisms, and at sub-zero storage temperatures this water may freeze and decrease the cooling efficiency of the room by obstructing the circulation of the cooling air. The overall aim of this work is to study the optimal design and operation of the sprayers. To this end, a three dimensional (3D) computational fluid dynamics (CFD) model that is capable of predicting the relevant parameters is developed. The path of sprayed droplets is tracked using an Eulerian-Lagrangian particle tracking multiphase flow model. The model considers the dispersion of the droplets due to turbulence, droplet evaporation and two-way coupling for the exchange of momentum, heat and mass between the continuous air phase and the discrete droplet phase. The specific objectives of this research were: (i) for air-assisted orchard sprayers, to develop and validate a CFD model that can predict the air and spray flow, taking into account the velocity variation at the fan outlet, sprayer ground speed, the nozzle characteristics and liquid atomization and to apply the model for evaluating design and operation of the sprayer; (ii) for cold storage humidification, to develop and validate a multiscale model that predicts the storage room air velocity, temperature and humidity distributions and fate of the water droplets that are sprayed from humidifying nozzles and to apply the model for engineering design of cold storage humidification systems. For air-assisted orchard sprayer, a good agreement was found between measurements and simulations of transient velocity profiles as well as the vertical jet velocity and spray distributions at different distances from the jet outlet. Due to a large variation in magnitude and direction of the jet outlet velocity, the power-law maximum air jet velocity decay was not the same at every vertical position. Instead, a complex 3D jet profile was established. The decay of the moving sprayer was best described with an inverse-proportional relationship with normal distance from the jet outlet. The decay coefficient was linearly proportional to the ground speed to jet outlet velocity ratio. Clearly, such systems are difficult to describe by other means than a complete CFD model as the one presented here. Air jet velocity and spray distribution were highly affected by sprayer fan speed and ground speed. Generally, there was a strong relation among droplet distribution, air jet velocity and direction. Most of the droplets were following the direction of the air jet. The vertical spray distribution profile was also affected by the characteristics of the nozzles. Smaller nozzles produced finer droplets that increased the amount of droplets to the top section of the spray; these fine droplets are prone to air drift. Larger nozzles produced coarser droplets that can increase spray ground deposition. The uniformity and symmetry of the air jet velocity and spray liquid distributions and the drift risk of hazardous pesticide droplets were highly affected by the design of spraying machine. The study also confirmed the prospect of drift reduction using a boom sprayer setup to orchard spraying applications which was verified by experiments. For a cold storage humidification system, a CFD based multiscale model was used. For system design and optimization, at the smallest scale of individual boxes, the flow through stacked products in boxes was predicted using a direct model that combined discrete element (DE) and CFD modelling. At a larger scale, a loaded cool room model that predicts the storage room air velocity, temperature and humidity distributions and fate of the water droplets was developed. The loaded product was considered as a porous medium, where the anisotropic loss coefficients were determined from the combined DE-CFD simulation. An interval humidification during the cooling and storage period of horticultural products raised the RH of the room, reduced the cooling time and minimized the amount of product moisture loss. Good agreement was found between measured and predicted results. The efficiency of a cold storage humidification system was affected by nozzle pressure, vertical nozzle position and angle, nozzle number, cold store design, stacking height and duration of spraying at every spraying interval. The validated model was applied to evaluate and propose some actions that are helpful for increasing the efficiency of the humidification system that is installed in a large Belgian chicory root cold storage room. The results demonstrated clearly the applicability of CFD models to identify the optimum operating and design parameters of spraying systems for a wide range of horticultural applications. Spraying systems are used extensively in horticulture both during the preharvest as well as the postharvest stage. This study considers air-assisted orchard sprayers and cold storage humidification systems. During the application of pesticides using air-assisted orchard sprayers, environmental contamination and an increase in production cost due to off target deposition of pesticide chemicals and low biological efficacy are common problems. Humidification during long-term cooled storage of fruits is being introduced into practice to prevent excessive moisture loss and quality degradation. However, maintaining the required high relative humidity (RH) with minimum deposition of the sprayed water droplets on the product and room surfaces is very challenging. The droplets that are deposited on the product surface may favour the growth of micro-organisms, and at sub-zero storage temperatures this water may freeze and decrease the cooling efficiency of the room by obstructing the circulation of the cooling air. The overall aim of this work was to study the optimal design and operation of the sprayers. To this end, a three dimensional (3D) computational fluid dynamics (CFD) model that is capable of predicting the relevant parameters has been developed. The path of sprayed droplets was tracked using an Eulerian-Lagrangian particle tracking multiphase flow model. The model considers the dispersion of the droplets due to turbulence, droplet evaporation and two-way coupling for the exchange of momentum, heat and mass between the continuous air phase and the discrete droplet phase. As inputs for the model, appropriate properties of the continuous air phase and nozzle characteristics were applied. The model required velocity, direction, temperature and RH of the continuous air phase at appropriate boundaries of the system. The characteristics of spray nozzles that were required include nozzle type and size, droplet size distribution, droplet velocity, liquid pressure and flow rate, and spray angle. For modelling cold storage humidification systems, the stored product was taken as a porous media. The pressure loss coefficients were calculated using a novel approach of explicit combined discrete element (DE)-CFD simulation. In general, a good agreement between measured and predicted results was found. In air-assisted orchard sprayers, air and spray flow distributions are affected by sprayer design, fan speed, sprayer driving speed and nozzle characteristics. The efficiency of cold storage humidification system is affected by nozzle pressure, vertical nozzle position and angle, number of nozzles, cold store design, stacking height and duration of humidification. This research showed the applicability of CFD to study different design and operational parameters of air-assisted orchard sprayer and cold storage humidification systems. For the two applications at hand, we have demonstrated that a CFD approach is required to solve design and engineering questions, which could not be answered by other means in an equally efficient way.