The incidence of needle stick injuries among medical students at Tabriz Imam Reza hospital in 2014

Background and aims: Needle stick injuries are a common and serious occupational hazard in the medical settings. So, this study was aimed to assess the incidence of needle stick injury among medical students at Tabriz Imam Reza Hospital in 2014. Methods: This is a cross-sectional study which its data was collected from 211 medical students in Tabriz Imam Reza Hospital. The study was done using valid and reliable researcher's made questionnaire in December 2014 with getting inform consent from participants. The mentioned tool has two main parts; the first part studies the demographic and background variables and the second part focuses on the phenomenon of needle stick injuries and its relevant parameters. The data were firstly analyzed descriptively and the obtained results reported the qualitative variables in form of frequency (percentage) and for the quantitative variables the mean (standard deviation) was reported. Further on, the statistical relationship between demographic and background with Needle stick injuries parameters were assessed using Chi-square test. All these analyses were conducted using SPSS software and in all cases the significance of P was considered as less than 0.05. Results: Obtained findings showed that 36 of the medical students have experienced needle stick injuries in the last year (with Confidence Interval of 95) and the mean annual frequency is equal to 3.11 times per person. Moreover, the study findings indicated that there is a statistical relationship between needle stick exposure and age (P=0.019), educational level (P=0.001) and the hospital ward (P=0.004) which students older than 30, medical research fellows and students working in the surgery and pathology wards experience needle stick injuries more than others significantly. Conclusion: This study showed the high incidence of needle stick injuries in medical students and highlighted the need for implementing precise interventions

Water cluster motifs in structurally similar N-(2-Aminoethyl)-1-Methylimidazole-2-Carboxamide metal complexes: synthesis, characterization, thermal and electrical properties.

Water is a remarkable molecule and in all of its forms exhibits an amazing collection of properties and functions. Besides its crucial role in life and many technological processes, water displays some unusual and anomalous properties at various interfaces and under different conditions. Although the role of hydrogen-bonding interactions and their fluctuations are well known to determine the properties of water, the main obstacle exists in the complexity of correctly describing the interactions between water molecules. The key to understanding the behavior of water is to collect precise structural data of various H-bonded water networks in diverse environments. In this dissertation, the formation of various water cluster motifs is investigated in a series of structurally similar complexes. Their thermal and electrical properties are studied using characterization techniques including, X-ray crystallography, UV-visible spectroscopy, IR, thermal analyses, electrochemical impedance spectroscopy (EIS) and two-probe resistance measurement studies. Chapter III focuses on a group of structurally related Ni(II) complexes containing N3X (X = S or O) donors. The complexes crystallize with water of hydration forming extended H-bonding networks. The morphology of the network is dependent on small changes in the ligand framework leading to different orientations of the carboxamido oxygens, which influences the solid state packing, H-bonding patterns and accordingly thermal and electrical properties. Chapter IV builds on chapter III through modification of the steric bulk around the carboxamido-O which result in isostructural complexes confining 1D coiled water wires in their crystal lattice and show quite similar packing pattern and thermal properties. Chapter V continues to study on electrical properties of one of synthesized complexes in Chapter IV. It explains the reversible surface conductivity changes upon variation of water vapor pressure for a single crystal

Development of automotive industry in developing countries during the last two decades

In recent century, globalization has appeared as one of the fundamental and powerful drivers forming the world economies. The automobile industry is one of the key industries which determines the economic power of different countries. During the last two decades the Global Value Chains (GVCs) in automotive industry have faced with considerable transformations. The economic crisis 2008-2009 has shifted the automotive industry to developing countries and increased the significance of some large growing economies such as China and India. This master thesis was conducted in order to investigate the circumstances of automotive industry from the past to present especially during the last two decades. The literature review highlights the globalization and its substantial effects to the car industry in developing countries. Literature review has proven that the Foreign Direct Investment (FDI) plays a significant role in the development of the automotive industry in developing countries. Also, the literature review highlights the significance of developing countries in mitigation of greenhouse emissions by presentation of electric vehicles (EVs) to their people and creation of consumption patterns for this production. To answer the research question author used secondary data from different secondary data re-sources. These data analysis helped the author to determine the trend of automobile industry development in developing countries. Results from this study showed the positive effects of globalization to the automotive industry in developing countries. The transformation of global value chains and globalization resulted in considerable development to the automotive industry in developing countries

The Effects of Exhaust Vent Location on Thermal Comfort Inside the Residential Buildings Equipped With an Evaporative Cooling System

Inlet and outlet conditions, Including size and location, have significant effects on the air distribution, temperature, humidity and thermal comfort in the buildings. In the current study, various strategies are presented for exhaust air vents and the effects of inlet and outlet vents locations are evaluated on providing thermal comfort in the residential and industrial buildings. To provide thermal comfort, three key factors need to be investigated based on ASHRAE standard 55- 2013 as follows: Comfort Zone, Thermal Sensation and Draft Rate. Flow distribution is studied as well in order to investigate the strategies, which make more vorticity in the ventilated air in living spaces as a factor of increasing discomfort in the building. The case study is located in Las Vegas where the weather is hot and dry in the summer time and the relative humidity is less than 8 %. In this regard, an evaporative cooling system is considered to increase humidity in the building since not only lack of humidity cause discomfort but also has many effects on breathing and skin dryness. A Computational Fluid Dynamic (CFD) study is developed as a numerical solution for obtaining temperature profile, relative humidity profile in different sections of the building regarding the evaluation of Thermal comfort in most critical spaces. In this study, relative humidity definition is formulated and imported as a field function in STAR-CCM+ to track relative humidity in each points of the building. As the temperature of ventilated air increases by absorbing heat, the percentage of relative humidity will be decreased consequently inside the building. By evaluating various strategies of exhaust vents in different hours of the day, it can be concluded that the thermal comfort will be provided most appropriate if the exhaust vents in each room are on the intersection of ceiling with the middle of farthest walls from the room’s entrance in a building with a single evaporative cooler. The results presented in this study can be used in the design of air conditioning systems in residential and industrial buildings, which leads to improvement in performance of air conditioning systems without any extra expenses

The sound simulation of ancient musical instruments: state of the art and challenges

openThe discourse of state-of-the-art digital technologies delves into the skillful deployment, primarily anchored in the domain of 3D modeling, for the meticulous documentation and painstaking reconstruction of archaeological artifacts, with a particular emphasis on the realm of ancient musical instruments.The discourse of state-of-the-art digital technologies delves into the skillful deployment, primarily anchored in the domain of 3D modeling, for the meticulous documentation and painstaking reconstruction of archaeological artifacts, with a particular emphasis on the realm of ancient musical instruments

Advanced Microfabrication Techniques for the Development of Microfluidic-Based Artificial Placenta-Type Lung Assist Device

Preterm infants are at risk for respiratory distress syndrome (RDS) due to immature lungs, leading to notable neonatal mortality. About 10% of US births are premature. While mechanical ventilation is a common RDS treatment, it can cause complications. If it fails, extracorporeal membrane oxygenation (ECMO) is employed, but standard ECMO devices are not suited for preterm babies. The limitations of hollow fiber membrane oxygenators used in ECMO have spurred interest in an artificial placenta that connects to the umbilical cord and supports lung growth. Microfluidic blood oxygenators, with their biomimetic designs, have being explored for this purpose. This thesis advances microfabrication techniques for Lung Assist Devices (LADs), focusing on two main objectives: I. Improving Throughput for Elevated Blood Flow Rates: This section delves into refining Microfluidic Blood Oxygenators (MBOs) to accommodate greater blood flow rates. By combining parallel units, we increased throughput and optimized LAD designs. Newly designed MBOs, with an expanded gas exchange surface area, can manage blood flow rates up to 60 mL/min. Using these enhanced MBOs, we constructed a novel LAD achieving superior oxygenation compared to predecessors. Our in vitro tests confirmed that this LAD can sustain blood flow rates of up to 150 ml/min, elevating oxygen saturation by approximately 20%—equivalent to an oxygen transfer of 7.48 mL/min, a leading figure for AP-type devices. II. Hierarchically Designed Microchannels: The second objective revolves around developing microchannels with a hierarchical layout to mitigate stagnation and high shear stress regions. Traditional photolithography poses challenges at channel intersections, inducing clotting risks. We pioneered alternative microfabrication methods, yielding diverse microchannels and intricate hierarchical designs that emulate natural vascular networks devoid of dead zones. These advancements have propelled the microfabrication domain for artificial placenta-like LADs. Utilizing our method, we produced channels varying from hundreds to a few microns in height with a single exposure and an opal diffuser. Thin membranes (~60 µm top and ~45 µm bottom) were amalgamated, culminating in a total depth of about 200 µm. Such oxygenators excel in oxygenating blood even at intense flow rates of up to 15 mL/min per unit. Leveraging these hierarchically designed MBOs, we crafted a LAD supporting a flow rate of 100 mL/min, offering an oxygen transfer of 5.21 mL/min. Both LADs developed in this research proficiently support premature neonates weighing up to 2 kg. Notably, the priming volume of the LAD using the enhanced MBOs has been substantially minimized, underscoring its advancements over earlier models. Realizing these objectives can transform neonatal care, addressing respiratory challenges in premature neonates and bolstering their chances for a healthier life.ThesisMaster of Science (MSc

A Different Traditional Approach for Automatic Comparative Machine Learning in Multimodality Covid-19 Severity Recognition

In March 2020, the world health organization introduced a new infectious pandemic called “novel coronavirus disease” or “Covid-19”, origin dates back to World War II (1939) and spread from the city of Wuhan in China (2019). The severity of the outbreak affected the health of abundant folk worldwide. This bred the emergence of unimodal artificial intelligence approaches in the diagnosis of coronavirus disease but solely led to a significant percentage of false-negative results. In this paper, we combined 2500 Covid-19 multimodal data based on Early Fusion Type-I (EFT1) architecture as a severity recognition model for the classification task. We designed and implemented one-step systems of automatic comparative machine learning (AutoCML) and automatic comparative machine learning based on important feature selection (AutoIFSCML). We utilized our posed assessment method called “Descended Composite Scores Average (DCSA)”. In AutoCML, Extreme Gradient Boost (DCSA=0.998) and in AutoIFSCML, Random Forest (DCSA=0.960) demonstrated the best performance for multimodality Covid-19 severity recognition while 70% of the characteristics with high DCSA were chosen by the internal important features selection system (AutoIFS) to enter the AutoCML system. The DCSA-based designed systems can be useful in implementing fine-tuned machine learning models in medical processes by leveraging the capacities and performances of the model in all methods. As well as, ensemble learning made sounds good among evaluated traditional models in systems

Identification and Evaluation of Livability Components in Urban Areas (A Case Study: Esfarayen City)

Urban livability deals with all aspects and dimensions of urban settlements that seek to create a healthier and more livable urban environment for current and future generations. In line with the importance of livability for cities, in the present study, we have analyzed and evaluated the livability of urban areas within the municipality of Esfarayen. The present study is descriptive-analytical in purpose and applied in research results. First, using the Delphi technique, the dimensions and components affecting urban livability were identified according to the metropolitan area of ​​Esfarayen. Then, after ranking these dimensions, the situation of Esfarayen urban neighborhoods in terms of livability was examined using the ANP method. Finally, the livability of this city in terms of physical, economic, social, and environmental dimensions with a favorable situation was studied and compared. Findings showed that among the most critical factors affecting urban livability in Esfarayen city include components of adequate housing dimensions and identity and sense of place, income level, education and quality, quality of sidewalks and public spaces, access to centers Commercial and service, access to medical centers, parks, and green spaces. The research findings also indicate that the most livable urban areas of Esfarayen include neighborhoods 20, 16, and 14, with the highest livability. The results of the study showed that although the city of Esfarayen is in a favorable condition in terms of environmental viability, which is due to the excellent climate, open and green urban spaces, and beautiful landscapes of the city, In terms of physical and economic dimensions, it is in a moderately downward position. Extended Abstract 1-Introduction Sustainability refers to a healthy, safe, and well-accessible urban system that provides a high quality of life and an attractive environment for citizens. The basic principles of this concept include accessibility, equality, and participation. They gather and integrate physical and social well-being parameters and characteristics to strengthen and maintain a perspective of human existence in a fruitful and meaningful way. Sustainability is a broad and collective term that embraces similar concepts such as sustainability, quality of life, quality of place, and a healthy city. In its primary and general meaning, it means achieving livability. To the extent of access, residents' quality of life depends on infrastructure, transportation, communications, water and sanitation, food, clean air, adequate housing, satisfying jobs, and green spaces and parks. In line with the importance of livability for cities, this study aims to analyze and evaluate the livability of urban areas in Esfarayen. 2-Materials and Methods The present study is considered applied research. For analuzing the information, the primary components affecting urban livability in Esfarayen were identified by examining the theoretical foundations and theory of research. Then, these dimensions, which include 23 features, were prepared and compiled in the form of a Delphi questionnaire. Delphi panel members then examined these indicators. These members have 35 urban planning specialists in universities and research centers. The selection criteria of these experts are theoretical mastery, scientific experience, willingness, ability to participate in research, and access. Then, the research indicators were determined by removing the indicators that did not score the necessary points. After examining the significance coefficient of each of these indicators by ANP network sequence analysis, these indicators were examined in Esfarayen city. At first, according to the determined dimensions, the viability of each urban area of Esfarayen was determined using the Mabak method. Then, the general situation of Esfarayen city was examined through the indicators selected in the form of 4 physical, economic, social, and environmental dimensions, as well as the total livability with the desired condition. The basis of the desired situation is determined from the average of the lowest and highest points based on the Likert spectrum, and the number 3 is placed. Indicators that crossed the green line (number 3) are in the desired position. Indicators below the green line and above the red line are not in the desired position. In other words, they are in the central place. 3- Results and Discussion Findings revealed that among the most critical factors affecting urban livability in the city of Esfarayen including components of adequate housing dimensions and identity and sense of place, income level, education and quality, quality of sidewalks And public spaces, access to commercial and service centers, access to medical centers, parks, and green spaces. Also, the results of the Mabak ranking showed that the most livable urban areas of Esfarayen include neighborhoods 20, 16, and 14, with the highest livability. Also, neighborhoods 11, 4, and 13 have the lowest viability rate. Finally, the t-test results showed that Esfarayen city is in a favorable situation regarding environmental viability and economic and social viability indicators. Also, the viability of all indicators is in a low to average condition. 4- Conclusion According to the results of the study, it can be said that although Esfarayen is in a favorable situation in terms of environmental viability, due to the mild climate, open and green urban spaces, beautiful scenery, but in terms of physical, economic, and social dimensions, it is in a moderately low condition. This situation is more evident in the central neighborhoods of the city. Accordingly, results include specific suggestions on the renovation and increase of quality of significant tissues of the town along with decentralization of activities and fair distribution of services, the need to increase livability and move towards social and biological sustainability of Esfarayen. Finally, widespread attention to the key factors is identified. Considering the quantity, shortcomings, and weaknesses of Esfarayen urban neighborhoods, the local study of livability can effectively present strategies and move towards a livable city

Hydrodynamics of Bubble Column Reactors Operating with Non-Newtonian Liquids

Dans l'industrie, de nombreux procédés nécessitent le contact entre une phase gazeuse et une phase liquide, avec ou sans solide en suspension, et ce afin de donner lieu à une grande variété de réactions chimiques. Bien que de nombreux types de réacteurs peuvent être utilisés à cet effet, au cours de la dernière décennie les réacteurs à colonne à bulles ont reçu une attention particulière car ils offrent certains avantages uniques tels que la facilité d'utilisation, des taux élevés de transfert de masse et de chaleur, et des frais d'entretien réduits en raison de l'absence de pièces mécaniques en mouvement. La conception et la mise à l'échelle d'une colonne à bulles nécessitent une compréhension complète de son hydrodynamique complexe. Ce dernier dépend des propriétés physiques des phases liquides et gazeuses, des conditions d'opération, et des paramètres de conception. A l'heure actuelle, du au manque de connaissance de ces systèmes, la conception des colonnes à bulles nécessite généralement des études expérimentales à différentes échelles (laboratoire, pilote, etc.), ce qui est coûteux en capital et en temps. Au cours des dernières années, les liquides et les solutions aqueuses en suspension utilisées dans les colonnes à bulles sont visqueuses et présentent habituellement, aux conditions opératoires utilisées, des comportements non newtoniens complexes. De plus, dans les colonnes à bulles utilisant des liquides non-newtoniens, non seulement la viscosité du liquide est habituellement variable selon les conditions d'écoulement, mais également leurs éventuelles propriétés élastiques. Pour cette variété de liquides non-newtoniens possédant des propriétés élastiques, ces dernières sont susceptibles d’affecter et de modifier fortement les comportements des bulles. En dépit de la demande croissante d'utilisation de fluides non newtoniens dans les réacteurs à colonnes à bulles, notre compréhension actuelle des effets des propriétés non-newtoniennes sur différents aspects hydrodynamiques des colonnes à bulles est loin d'être complète. Parmi les quelques études réalisées sur l'effet des propriétés rhéologiques de la phase liquide dans les colonnes de bulles, l'influence de l'élasticité du liquide sur les paramètres hydrodynamiques n'a jamais été étudiée distinctement et les modèles et concepts disponibles à l'heure actuelle sur ce sujet sont insuffisants pour une application industrielle. Afin d'obtenir un aperçu global de la performance des colonnes à bulles utilisant des liquides non-newtoniens, les effets de toutes les propriétés rhéologiques de la phase liquide, et non pas l'effet d'un seul paramètre qu'est la viscosité, doivent être étudiés. Cette thèse vii est donc dédiée à l'étude de l’hydrodynamique des colonnes à bulles fonctionnant avec des liquides non-newtoniens possédant des propriétés rhéologiques variées. Le principe de fonctionnement, les aspects hydrodynamiques de base du réacteur à colonne à bulles, ainsi que les liquides non-newtoniens et leurs propriétés rhéologiques sont brièvement discutés dans les deux premiers chapitres de cette thèse. Le premier objectif de ce travail est de comprendre l'effet des propriétés rhéologiques du liquide sur les différents paramètres hydrodynamiques d'une colonne à bulles. À cet égard, l'effet de la rhéologie de la phase liquide sur l'hydrodynamique d'un réacteur à colonne à bulles à l'échelle pilote est largement étudiée en sélectionnant stratégiquement divers types de liquides. La rétention de gaz et ses variations radiales et axiales, le point de transition du régime opératoire et la taille des bulles sont évalués au moyen de deux sondes à fibre optiques fabriquées dans nos laboratoires, ainsi que plusieurs capteurs de pression. Afin de mieux comprendre l'effet de la rhéologie sur les paramètres hydrodynamiques de la phase gazeuse, plusieurs analyses en fonction du temps et des fréquences sont réalisées sur les signaux de fluctuations de pression. Les effets visqueux et élastiques simultanés des liquides non-newtoniens sont étudiés à l'aide d'une nouvelle approche basée sur les modules dynamiques des solutions viscoélastiques. Il a été trouvé que la viscosité du liquide favorise la coalescence des bulles, alors que son élasticité l'entrave, se comportant comme un solide à l'interface de deux bulles. La présence d'élasticité dans le liquide mène à la réduction de la longueur de corde moyenne des bulles et à l’augmentation de la rétention globale de gaz. Les résultats obtenus dans cette partie du travail sont primordiaux afin d'atteindre le second objectif, qui vise principalement à étudier localement les paramètres hydrodynamiques et à développer de nouvelles corrélations pour estimer la taille des bulles et la rétention de gaz dans les réacteurs à colonne à bulles utilisant des liquides non-newtoniens. Par conséquent, dans la deuxième partie de ce travail, les propriétés locales des bulles telles que leur fréquence, leur longueur de corde et leur vitesse d'ascension ainsi que leurs distributions radiales et axiales, sont évaluées à l'aide de deux sondes à fibres optiques placées à des endroits différents dans le réacteur à colonne à bulles opéré avec différents liquides non-newtoniens. Il a été observé que le profil radial de la fréquence des bulles, de leur longueur de corde et de leur vitesse d'ascension sont relativement plats à basse vitesse superficielle de gaz, mais deviennent paraboliques lorsque la vitesse superficielle du gaz augmente. En outre, à l'aide d'une analyse adimensionnelle, deux corrélations ont été développées afin de prédire la taille des bulles et la rétention de gaz dans les colonnes à bulles opérées avec des liquides non-newtoniens. Ces viii deux nouvelles corrélations sont capables de prédire correctement la taille des bulles et la rétention de gaz au sein des colonnes à bulle, à l'aide du rapport entre modules dynamiques des solutions viscoélastiques. Une variété de procédés industriels tels que la synthèse de Fischer-Tropsch, la synthèse du méthanol, l'oxydation partielle de l'éthylène, l’hydrocraquage des résidus lourds, et l'hydroformylation utilise des colonnes à bulles, mais à haute pression. Par le passé, il a été découvert que la pression d'opération a un effet significatif sur les caractéristiques hydrodynamiques des colonnes à bulles. Par exemple, une augmentation de la pression opératoire conduit normalement à la formation de plus petites bulles au niveau du distributeur de gaz. Bien que l'étude des effets de la pression dans les colonnes à bulles ait fait l'objet de certains travaux de recherche, de nombreuses zones restent à éclairer et il existe encore un grand intérêt des chercheurs et des concepteurs de réacteurs à conduire des études approfondies afin d'élucider l'influence de la pression d'opération sur les différents aspects de l'hydrodynamique et, en conséquence, sur la performance de réacteurs à colonne à bulles. Afin d'optimiser les procédés industriels cités ci-dessus, il est indispensable d'avoir une compréhension complète de l'effet de la pression d'opération sur la cinétique chimique, les propriétés du liquide (viscosité et tension superficielle), le régime d'écoulement de liquide, la dynamique des bulles (taille des bulles, forme de la bulle, éclatement et taux de coalescence, vitesse d'ascension) et le taux de transfert de chaleur et de masse. Par conséquent, le dernier objectif de ce travail est consacré à étudier l'effet de la pression d'opération sur l'hydrodynamique de la colonne à bulles et en présence de liquides non-newtoniens. A cet effet, un ensemble de réacteurs à haute pression/ haute température, dont une colonne à bulles et un réacteur à lit fluidisé ont été conçus et construits. En plus des réacteurs en tant que tels, cette installation inclus différents équipements tels que des compresseurs, des cylindres de stockage de gaz à haute pression, des éléments chauffants, un réservoir d'alimentation de liquide, une pompe centrifuge pour liquide, des séparateurs gaz-liquide, une unité de contrôle, un système d'acquisition de données, etc. Cette installation expérimentale sera introduite plus en détails au Chapitre 5. Au sein de cette installation et à l'aide de mesures de signaux de pression différentiels et dynamiques, divers caractéristiques hydrodynamiques des colonnes à bulles, comme la rétention totale du gaz et sa distribution axiale, le point de transition de régime d'écoulement, les fluctuations de pression et son écart-type, ont été étudiées. La vitesse superficielle du gaz a été variée de 1 à 35 (cm s-1) couvrant les deux régimes ix d'écoulement, homogène et hétérogène. La pression de fonctionnement a également été variée de 0.1 à 1 (MPa) pendant les expériences. Il a été étudié que la rétention totale de gaz augmente à la fois avec la pression opératoire et avec l'élasticité de la phase liquide ; l'impact de la pression est d’autant plus prononcé à de basses pressions d'opération. Il a également été identifié que l'augmentation de la pression d’opération conduit à un décalage du point de transition entre régimes hydrodynamiques à de plus haute vitesses de gaz superficielles. En conclusion, il a été prouvé que non seulement la rhéologie de la phase liquide, mais également la pression d'opération, ont un effet important sur l'hydrodynamique des réacteurs à colonnes à bulles. Les connaissances scientifiques développées dans ce travail peuvent ainsi aider les industriels à mieux décrire les phénomènes présents dans les colonnes bulles utilisant des liquides non-newtoniens très visqueux et des pressions élevées, ce qui leur permettrait une conception, exploitation et mise à l’échelle plus avisée et performante des réacteurs à colonne à bulles commerciaux. ---------- Processes based on the contact between gas and liquid/slurry phases are commercially used for performing a variety of chemical reactions. Although different types of reactors are used for this purpose, bubble column reactors have received more attention during the past decade since they offer some unique advantages, such as ease of operation, high rates of heat and mass transfer, and lower maintenance costs due to the absence of moving parts. The design and scale-up of a bubble column reactor require a complete understanding of its complex hydrodynamics, which is influenced by the physical properties of the phases, the operating variables, and the design parameters. Current design procedures for bubble columns involve several steps of pilot-plant experimentation using equipment of different scales, which is expensive and time consuming. In recent years, the liquid and/or slurry phases which are processed in bubble columns in many applications are viscous and normally demonstrate non-Newtonian behaviors during the process operation. Hydroconversion of heavy oil and petroleum residues, wastewater treatment, processing of fermentation broths, polymer composite processing, and slurry-phase synthesis are some of those processes in which viscous and non-Newtonian liquids are often encountered in bubble column reactors. On the other hand, in bubble columns operating with non-Newtonian liquids, the viscosity changes upon the flow conditions, and also a variety of non-Newtonian liquids possess elastic properties that can affect and alter bubble behavior to a great extent. Although there has been an increasing application of non-Newtonian fluids in bubble column reactors, our present understanding of the effects of non-Newtonian properties on different hydrodynamic aspects of bubble columns is far from complete. Only few studies are reported on the effect of liquid phase rheological properties in bubble columns so that the influence of liquid elasticity on the hydrodynamic parameters such as gas holdup and bubble properties has never been studied distinctly, and the models and concepts currently available on this subject are insufficient for chemical practice. To gain adequate insight into the performance of bubble columns operating with non-Newtonian liquids, the effects of all rheological properties of the liquid phase need to be investigated rather that the effect of a single parameter like viscosity. This thesis is, therefore, dedicated to investigating the hydrodynamics of bubble columns operating with non-Newtonian liquids having different rheological properties. xi The operation principle and basic hydrodynamic aspects of the bubble column reactors, as well as non-Newtonian liquids and their rheological properties, are briefly discussed in the first two chapters. The first objective of this work is to understand the effect of the rheological properties of liquid on different hydrodynamic aspects of a bubble column reactor including gas holdup and its radial and axial distributions, bubble size and its axial distribution, standard deviation, power spectral density and average frequency of pressure signals. In this regard, the effect of liquid phase rheology on the hydrodynamics of a pilot-scale bubble column reactor is extensively investigated by strategically selecting various types of liquids. The selected liquids include water as a reference and low-viscosity liquid, an aqueous glucose solution as a highly viscous Newtonian and inelastic liquid, a Boger fluid which has a constant viscosity identical to the glucose solution but it is slightly elastic, and finally two non-Newtonian (shear-thinning) and elastic Carboxymethyl cellulose (CMC) and Xanthan gum solutions. Gas holdup and its radial and axial variations, the operating flow regime transition and bubble size are evaluated by means of two in-house made optical fiber probes and several pressure transducers. Different time-domain and frequency-domain analyses are applied to the pressure fluctuation signals in order to better understand the effect of liquid phase rheology on the gas holdup and bubble size. The simultaneous viscous and elastic effects of non-Newtonian liquids are studied by proposing a new approach based on the dynamic moduli of viscoelastic solutions. It was found that the viscosity of liquid is more favorable for bubble coalescence; however, the elasticity can hinder bubble coalescence as it can demonstrate a solid-like behavior at the interface of two bubbles. The presence of elasticity in the liquid was shown to reduce the average bubble chord length and increase the overall gas holdup. The results obtained in this part of the work are essential for achieving the second objective, which is aimed at studying the local hydrodynamic parameters such as local bubble frequency and bubble rise velocity and developing new correlations to estimate bubble size and gas holdup in bubble column reactors operating with non-Newtonian liquids. Therefore, in the second part of this work, local bubble properties such as bubble frequency, bubble chord length, and bubble rise velocity, as well as their radial and axial distributions, are evaluated by installing two optical fiber probes at various locations within a bubble column reactor operating with different non-Newtonian liquids. It was observed that the radial profiles of bubble frequency, bubble chord length and bubble rise velocity are relatively flat at low superficial gas velocities, while they become parabolic as the superficial gas velocity increases. Moreover, by applying the dimensional analysis, two new correlations are xii developed to predict the bubble size and gas holdup in bubble columns operating with non-Newtonian liquids. The two correlations are developed by taking into consideration the ratio between the dynamic moduli of viscoelastic solutions and are capable of accurately predicting both bubble size and gas holdup. Moreover, a variety of commercial processes such as Fischer-Tropsch synthesis, Methanol synthesis, Partial oxidation of ethylene, Residuum hydrotreating, and Hydroformylation are carried out in bubble columns at elevated pressures. The operating pressure is found to have a significant effect on the hydrodynamic characteristics of bubble columns such as bubble properties and gas holdup. For instance, an increase in the operating pressure normally results in the formation of smaller bubbles at the gas distributor and this is mainly due to the higher gas density at elevated pressure. Although investigating the pressure effects in the bubble columns has been the subject of some research, there is still a strong need toward more studies on the influence of operating pressure on different hydrodynamic aspects, and, accordingly, on the performance of bubble column reactors. Therefore, the last objective of this work is devoted to investigating the effect of operating pressure on the hydrodynamics of bubble column reactors in presence of non-Newtonian liquids. For this purpose, a high-pressure/high-temperature multiphase reactors unit including a bubble column reactor with an inner diameter of 0.152 m and a total height of 4.8 m has been designed and constructed to perform experiments at elevated pressures. The multiphase reactors unit was equipped with different equipment, including air compressors, high-pressure gas storage cylinders, gas heating elements, liquid supply tank, liquid centrifugal pump, gas-liquid separators, PLC control unit, etc. This experimental unit is introduced in more detail in Chapter 5. Various hydrodynamic characteristics of bubble column reactors, such as the total gas holdup and its axial distribution, operating flow regime transition point, pressure fluctuation and its standard deviation have been studied by means of pressure signal measurements with several differential and dynamic pressure traducers. The superficial gas velocity varied from 1 to 35 (cm s-1), covering both homogeneous and heterogeneous flow regimes. Operating pressure also changed from 0.1 to 1 (MPa) during the experiments. The total gas holdup was found to increase with both operating pressure and the elasticity of liquid phase, and the effect of pressure was shown to be more pronounced at lower operating pressures. The operating pressure was shown to shift the flow regime transition point to higher superficial gas velocities. A new correlation was also derived for predicting the gas holdup in bubble column reactors operating at elevated pressure. As a xiii conclusion, both the rheology of the liquid phase and operating pressure are shown to have important effects on the hydrodynamics of bubble column reactors. Moreover, the scientific findings of the present work may have significant implications for the more accurate design, operation and scale-up of commercial bubble column reactors, where highly viscous and non-Newtonian liquids and high pressures are often applied