No description available.

Membrane separation is known as an economic and environmental friendly mode of separation and is used in various types of separation processes. The major challenges regarding membrane separation are the internal and external fouling of the membrane which reduces the permeate flux of the membranes by inducing extra resistance to flow. Synthetic membranes are designed and implemented to separate solutes or particles in a feed stream by rejecting them and permitting the liquid to pass through the membrane pores; however, most of the feed streams, such as wastewaters, contain more than one type of solute. This yields a distribution of particle sizes in the feed. Many wastewaters contain supracolloidal particles (1-100µm). Most membrane separations aim to remove these particles from the feed solution. Wastewaters also contain colloidal particles (0.001-1µm). These particles are less concentrated than supracolloidal particles in the feed but they are more problematic since they are able to penetrate into the membrane pores and cause internal fouling which is the main source of irreversible flux decline. Fouling mechanisms are traditionally classified into four types. Among these mechanisms, standard pore blocking (pore constriction) refers to internal fouling while the other types model external fouling. On the effect of pore geometry, as a morphological factor, studies to date have been limited to external membrane fouling. However, it is believed that up to 80% of the permeate flux can be affected by pore constriction which is caused by particle penetration and deposition into membrane pores (internal fouling). The effect of pore geometry, as a factor, in flux decline due pore constriction of membranes was investigated in this work. Pore constriction by particles was approximated by maximum particle deposition onto the interior wall of the pores and simulated using MATLAB image processing toolbox (MIPT). Sixteen different basic geometries were considered for the simulation of pore constriction by particles. These include circular pores, 3 groups of rectangular, triangular and oval geometries at four different aspect ratios (3, 7, 15 and 30) and three combined geometries of star, cross and a rectangle with rounded ends. The simulation of maximum particle deposition onto pore walls was carried out for a range of particle diameters to pore hydraulic diameters (λ) of 0.1 to the complete rejection of the particle by the pore. As the result of the simulation, the ratio of the available pore cross-sectional area after pore constriction to initial pore cross-sectional area (α) and the ratio of pore channel hydraulic diameter after pore constriction to initial pore hydraulic diameter (β) were measured and recorded. It was observed that for λ<0.2 (small particles compared to pore size) some geometries showed the same values of α and β. However, for λ>0.2, other geometries showed different values of α and β. It was also observed that several geometries reject the particle at different λ ratios. Using the values of α and β, the fluxes of membranes having different pore geometries, after pore constriction by particles, were calculated and compared. These results show that for a very small particle size, compared to pore size, there is no preference for a specific geometry over another; however, for intermediate particle sizes, membranes having triangular and star pore shapes provide higher fluxes compared to other membranes. The effect of pore aspect ratio (PAR) on the flux of membranes after pore constriction was also examined. In order to compare the combined effect of pore geometry on particle rejection and pore constriction, fluxes of membranes having different pore shapes were compared in light of several pore size distributions (PSDs). For this part of the study, the pore geometries of circular, rectangular, triangular and oval were considered at four PARs. Different values for the hydraulic diameter of the largest rejecting pore (D_(H,LRP)) were observed for different geometries. Rectangular pores showed the largest values of D_(H,LRP), at a constant PAR, which affirms their superior rejection behavior. The overall flux of the membranes after pore constriction was determined by a combination of three effects: the position of D_(H,LRP) in the PSD, the pore constriction behavior of the pore geometry and the shape of the PSD. Generally, for the PSDs for which most of the pores in the membrane physically reject the particles, membranes having rectangular pores showed higher fluxes, due to the greater rejection of particles. However, for PSDs for which a major number of pores are constricted by the particles, membranes with triangular pores offered higher flux after membrane pore constriction. The results of this work indicate a new direction for the design of membranes having defined pore geometries.

Membrane separation is known as an economic and environmental friendly mode of separation and is used in various types of separation processes. The major challenges regarding membrane separation are the internal and external fouling of the membrane which reduces the permeate flux of the membranes by inducing extra resistance to flow. Synthetic membranes are designed and implemented to separate solutes or particles in a feed stream by rejecting them and permitting the liquid to pass through the membrane pores; however, most of the feed streams, such as wastewaters, contain more than one type of solute. This yields a distribution of particle sizes in the feed. Many wastewaters contain supracolloidal particles (1-100µm). Most membrane separations aim to remove these particles from the feed solution. Wastewaters also contain colloidal particles (0.001-1µm). These particles are less concentrated than supracolloidal particles in the feed but they are more problematic since they are able to penetrate into the membrane pores and cause internal fouling which is the main source of irreversible flux decline. Fouling mechanisms are traditionally classified into four types. Among these mechanisms, standard pore blocking (pore constriction) refers to internal fouling while the other types model external fouling. On the effect of pore geometry, as a morphological factor, studies to date have been limited to external membrane fouling. However, it is believed that up to 80% of the permeate flux can be affected by pore constriction which is caused by particle penetration and deposition into membrane pores (internal fouling). The effect of pore geometry, as a factor, in flux decline due pore constriction of membranes was investigated in this work. Pore constriction by particles was approximated by maximum particle deposition onto the interior wall of the pores and simulated using MATLAB image processing toolbox (MIPT). Sixteen different basic geometries were considered for the simulation of pore constriction by particles. These include circular pores, 3 groups of rectangular, triangular and oval geometries at four different aspect ratios (3, 7, 15 and 30) and three combined geometries of star, cross and a rectangle with rounded ends. The simulation of maximum particle deposition onto pore walls was carried out for a range of particle diameters to pore hydraulic diameters (λ) of 0.1 to the complete rejection of the particle by the pore. As the result of the simulation, the ratio of the available pore cross-sectional area after pore constriction to initial pore cross-sectional area (α) and the ratio of pore channel hydraulic diameter after pore constriction to initial pore hydraulic diameter (β) were measured and recorded. It was observed that for λ<0.2 (small particles compared to pore size) some geometries showed the same values of α and β. However, for λ>0.2, other geometries showed different values of α and β. It was also observed that several geometries reject the particle at different λ ratios. Using the values of α and β, the fluxes of membranes having different pore geometries, after pore constriction by particles, were calculated and compared. These results show that for a very small particle size, compared to pore size, there is no preference for a specific geometry over another; however, for intermediate particle sizes, membranes having triangular and star pore shapes provide higher fluxes compared to other membranes. The effect of pore aspect ratio (PAR) on the flux of membranes after pore constriction was also examined. In order to compare the combined effect of pore geometry on particle rejection and pore constriction, fluxes of membranes having different pore shapes were compared in light of several pore size distributions (PSDs). For this part of the study, the pore geometries of circular, rectangular, triangular and oval were considered at four PARs. Different values for the hydraulic diameter of the largest rejecting pore (D_(H,LRP)) were observed for different geometries. Rectangular pores showed the largest values of D_(H,LRP), at a constant PAR, which affirms their superior rejection behavior. The overall flux of the membranes after pore constriction was determined by a combination of three effects: the position of D_(H,LRP) in the PSD, the pore constriction behavior of the pore geometry and the shape of the PSD. Generally, for the PSDs for which most of the pores in the membrane physically reject the particles, membranes having rectangular pores showed higher fluxes, due to the greater rejection of particles. However, for PSDs for which a major number of pores are constricted by the particles, membranes with triangular pores offered higher flux after membrane pore constriction. The results of this work indicate a new direction for the design of membranes having defined pore geometries.

This work focuses on the development of efficient methods for wing shape optimization for morphing wing technologies. Existing wing shape optimization processes typically rely on computational fluid dynamics tools for aerodynamic analysis, but the computational cost of these tools makes optimization of all but the most basic problems intractable. In this work, we present a set of tools that can be used to efficiently explore the design spaces of morphing wings without reducing the fidelity of the results significantly. Specifically, this work discusses automatic differentiation of an aerodynamic analysis tool based on lifting line theory, a light-weight gradient-based optimization framework that provides a parallel function evaluation capability not found in similar frameworks, and a modification to the lifting line equations that makes the analysis method and optimization process suitable to wings of arbitrary aspect ratio. The toolset discussed is applied to several wing shape optimization problems. Additionally, a method for visualizing the design space of a morphing wing using this toolset is presented. As a result of this work, a light-weight wing shape optimization method is available for analysis of morphing wing designs that reduces the computational cost by several orders of magnitude over traditional methods without significantly reducing the accuracy of the results.

Particle technology affects the entire human population. It is involved in the manufacture of agriculture chemicals, asphalt, paint, and pharmaceuticals, just to name a few. The size and shape of the particles play an important role in the manufacturing processes. A change in size or shape can change the product produced. Experiments were run to test the effects of agitation rate, magma density, and residence time on adipic acid and sodium chloride crystals. Experiments were executed in a one-liter, double-jacketed, stirred vessel. Digital images of the broken crystals were taken with a microscope/digital camera combo. ImagePro Plus was used to analyze the size of the broken crystals. The greatest change was seen between the two magma densities. It can be determined that change in size and shape based on the variables does exist. A specific set of variables should be introduced for each process in industry to achieve the desired results.

Concrete is among the most common materials utilized to construct protective elements in hardened structures. Subsequently, understanding how a concrete member will respond to explosively driven fragment or projectile impact is critical to the protective design process. Explosively driven fragments can have many different shapes and sizes depending on the event that resulted in their creation. These geometric variations can include a high-aspect, or width to thickness, ratio; however, impact from fragments with elevated aspect ratios on hardened concrete has not been extensively studied. Therefore, reinforced concrete specimens were subjected to impact from fragments with different aspect ratios to illustrate and quantify the effect of fragment characteristics, protective element features, and experimental target size on local impact performance. A novel experimental technique was developed to allow for high-aspect ratio fragment impact on concrete slabs to be evaluated. The same concrete materials were also impacted with lower aspect ratio fragments for comparative purposes. Data collected from these two experimental series were utilized to analyze the effects of compressive strength, thickness, and fiber reinforcement on impact performance. The accuracy of existing penetration and spall prediction methodologies were evaluated for both fragment types. The kinetic energy required to cause reinforced concrete to present a breached condition due to the high-aspect ratio fragment was also analyzed. Modifications were made to existing contact charge equations to account for differences between the contact charge energy required to cause a breach condition and that required from fragment impact to produce a breach condition. The breach envelope defined by these relationships was further evaluated using a computational model calibrated specifically for this impact scenario. Finally, the effect of impact specimen geometry and confinement type on target performance was numerically evaluated. Artificial and inertial confinement were examined through varying target diameter to projectile diameter ratio with and without artificial circumferential confinement. Given the minimal data associated with local effects of high-aspect ratio fragment impact and the many factors that can influence concrete impact resistance, the information and relationships learned along with the analysis techniques developed herein can be utilized to improve the state of the art of protective design.

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This thesis investigates the effect of aspect ratio on visual perception in scatterplots. Four tasks explored how the aspect ratio affects participants' perception of distance, amount, and correlation in scatterplots. The results showed that square aspect ratio scatterplots are more suitable for detecting length and number, while rectangular aspect ratio scatterplots are better for detecting correlation. In addition, the JND (Just Noticeable Difference) was used in evaluating the visual perception of scatterplots in this experiment. The findings of this study have important implications for the design of scatterplots in data visualization, as well as for future research on visual perception in data visualization. / Master of Science / This thesis focuses on understanding how the aspect ratio of scatterplots affects how people perceive data. Scatterplots are graphs that display data points on two variables, allowing researchers to identify relationships between variables visually. The aspect ratio of a scatterplot refers to the percentage of its width to height. This study found that people are better at detecting distances and amounts in scatterplots with a square aspect ratio. In contrast, they better see scatterplot correlations with a rectangular aspect ratio. The results suggest that the aspect ratio of a scatterplot plays a critical role in how people perceive and interpret data. These findings are essential for researchers, analysts, and designers who want to create compelling and accurate data visualizations.

High aspect-ratio flying wing configurations designed for high altitude, long endurance missions are characterized by high flexibility, leading to significant static aeroelastic deformation in flight, and coupling between aeroelasticity and flight dynamics. As a result of this coupling, an integrated model of the aeroelasticity and flight dynamics has to be used to accurately model the dynamics of the flexible flying wing. Such an integrated model of the flight dynamics and the aeroelasticity developed by Patil and Hodges is reviewed in this dissertation and is used for studying the unique flight dynamics of high aspect-ratio flexible flying wings. It was found that a rigid body configuration that accounted for the static aeroelastic deformation at trim captured the predominant flight dynamic characteristics shown by the flexible flying wing. Moreover, this rigid body configuration was found to predict the onset of dynamic instability in the flight dynamics seen in the integrated model. Using the concept of the mean axis, a six degree-of-freedom reduced order model of the flight dynamics is constructed that minimizes the coupling between rigid body modes and structural dynamics while accounting for the nonlinear static aeroelastic deformation of the flying wing. Multi-step nonlinear dynamic inversion applied to this reduced order model is coupled with a nonlinear guidance law to design a flight controller for path following. The controls computed by this flight controller are used as inputs to a time-marching simulation of the integrated model of aeroelasticity and flight dynamics. Simulation results presented in this dissertation show that the controller is able to successfully follow both straight line and curved ground paths while maintaining the desired altitude. The controller is also shown to be able to handle an abrupt change in payload mass while path-following. Finally, the equations of motion of the integrated model were non-dimensionalized to identify aeroelastic parameters for optimization and design of high aspect-ratio flying wings. / Ph. D.

During the production of paper in paper mills, detrimental wood resin is released into the water circuit of the mill during the pulping process of the wood into fibres. This wood resin, termed pitch, can detrimentally deposit on the paper and on the paper machine equipment. The deposits mark the paper or can lead to a tear of the paper web involving a loss of output and a reduction in paper quality. Furthermore, the wood resinous compounds in paper mill effluents need to be reduced in order to minimise their toxic effects on water organisms. Talc has been the benchmark for many years as a mineral additive in pitch control. Since the papermaking process has changed over the years, the concept of mineral addition needs to be redefined and adopted towards the new circumstances. By understanding the fundamentals behind the adsorption of wood resin compounds from aqueous systems on to talc new mineral additives can be developed. A model for the determination of the aspect ratio of platy and rod-like particles has been developed, based on commonly available characterisations such as particle size, specific surface area and shape. It was found that the adsorption capacity of a mineral is directly proportional to its specific surface area, but only within its mineral family. Including the effect of surface hydrophilicity and hydrophobicity allowed fine tuning of the adsorption capacity of newly developed calcium carbonate grades. Furthermore, size exclusion effects, in porous, high surface area modified calcium carbonate, were seen to hinder complete coverage of the surface area by wood resin. With increasing pH, the adsorption efficiency of talc for colloidal wood resin was found to decrease. Under these alkaline conditions, which are common in modern paper making processes, talc preferentially adsorbed dissolved species. The use of the newly developed surface treated and modified calcium carbonates allowed more efficient adsorption of the colloidal fraction and, therefore, represent an efficient alternative to talc in pitch control. An increase in temperature led to an increased adsorption capacity of talc. This observation indicates the type of interaction tat controls the adsorption of hydrophobic pitch particles onto talc, i.e. the entropically favoured release of water from the hydrophobic talc surface as well as the hydrophobic methylene backbone of the hemicellulose.