An enhanced thermal imaging concept made possible through the development of a gradient-indexed metamaterial infrared detector that offers broadband transmission and reflection in THz waves. This thesis proposes a proof of feasibility for a metamaterial infrared detector containing an anti-reflective coating with various geometrically varying periodic metasurfaces, a gradient-indexed dielectric multilayer for near-perfect longpass filtering, and a gradient index of refraction (GRIN) metalens for enhanced focal plane thermal imaging. 2D Rigorous Coupled-Wave Analysis (RCWA) is used for understanding the photonic gratings performance based on material selection and varying geometric structure. Finite Difference Time Domain (FDTD) is used to characterize performance for a diffractive metalens by optimizing the radius and arrangement of cylindrical nanorods to create a desired phase profile that can achieve a desired focal distance for projections on a detector for near- to far-infrared thermal imaging. Through combining a micromachined anti-reflective coating, a near-perfect longpass filter, and metamaterial GRIN metalens, infrared/THz focal plane thermal imaging can obtain faster photo-response and image quality at targeted wavelengths, which allows for scientific advancements in electro-optical devices for the Department of Defense, aerospace, and biochemical detection applications.

Pillared-graphene structure (PGS) is a novel three-dimensional structure consists of parallel graphene sheets that are separated by carbon nanotube (CNT) pillars that is proposed for efficient thermal management of electronics. For microscale simulations, finite element analyses were carried out by imposing a heat flux on several PGS configurations using a Gaussian pulse. The temperature gradient and distribution in the structures was evaluated to determine the optimum design for heat transfer. The microscale simulations also included conducting a mesh-independent study to determine the optimal mesh element size and shape. For nanoscale simulations, Scienomics MAPS software (Materials And Processes Simulator) along with LAMMPS (Large-scale Atomic/ Molecular Massively Parallel Simulator) were used to calculate the thermal conductivity of different configurations and sizes of PGS. The first part of this research included investigating PGS when purely made of carbon atoms using non-equilibrium molecular dynamics (NEMD). The second part included investigating the structure when supported by a copper foil (or substrate); mimicking production of PGS on copper. The micro- and nano-scale simulations show that PGS has a great potential to manage heat in micro and nanoelectronics. The fact that PGS is highly tunable makes it a great candidate for thermal management applications. The simulations were …

This dissertation focuses on studying membrane air dehumidification for a membrane moisture exchanger in a membrane heat pump system. The study has two parts: an optimization of membrane moisture exchanger for air dehumidification in the macroscale, and diffusion of water vapor in polymer nanocomposites membrane for humid air dehumidification in the nanoscale. In the first part of the research, the mass transport of water vapor molecules through hydrophilic silica nanochannel chains in hydrophobic polyurethane matrix was studied by simulations and experiments for different membrane moisture exchanger design configurations. The mass transport across the polymer nanocomposite membrane occurs with the diffusion of moist air water vapor molecules in the membrane moisture exchanger in a membrane heat pump air conditioning system for air dehumidification purposes. The hydrophobic polyurethane matrix containing the hydrophilic silica nanochannel chains membrane is responsible for transporting water vapor molecules from the feed side to the permeate side of the membrane without allowing air molecules to pass through.In the second part of the research, diffusion analysis of the polymer nanocomposite membrane were performed in the nanoscale for the polymer nanocomposite membrane. The diffusion phenomena through the polymer, the polymer nanocomposite without modifying the silica surfaces, and the polymer nanocomposite …

This thesis project investigates, analyzes, designs, simulates, constructs and tests a dual-axis solar tracker system to track the sun and concentrates the heat of the sunlight, using a Fresnel lens, into a small area, which is above of an evaporator, to increase the temperature of the seawater to convert it into freshwater. The dual-axis solar tracker was designed with the main objectives that the structure was portable, dismountable, lightweight, low cost, corrosion resistant, wires inside pipes, accurate, small size, follow the sun automatically, off-grid (electrical), use green energy (solar powered), and has an empty area right below of the lens. First, a 500 mm diameter flat Fresnel lens was selected and simulated based on an algorithmic method achieved by a previous PhD student at UNT using MATLAB®, to give the optimization lens dimensions. The lens profile was drawn with AutoCAD®, then output profile lens was simulated in COMSOL Multiphysics®. The objective was to provide the high efficiency, optimum and high precision of the focal rays and heat to the receiver of the evaporator. A novel dual-axis solar tracker system was then designed that is portable, dismountable, lightweight and corrosion resistant. The solar tracker tracks the sun in two axis of …

Recently, 3D printing has received increasing attention for the fabrication and assembly of electrodes for batteries due to the freedom of creating structures in any shape or size, porosity, flexibility, stretchability, and chemistry. Particularly, zinc ion batteries (ZIBs) are favored due to high safety, cheap materials cost, and high volumetric capacity (5,849 mAh/cm3), however, rapid evaporation of Zn due to low melting temperature has limited its 3D printability via conventional laser-based additive manufacturing technique. Here, we develop a printable ink for the fabrication of flexible and 3D printed Zn anode with varied surface areas using the direct ink writing (DIW) method. Our 3D printed porous and high surface area Zn anode structures effectively suppressed the dendrite growth while providing high Zn ion diffusion towards the cathode to significantly enhance the performance of ZIB. By varying filament distancing and path, we 3D printed zinc anode structures with different active surface areas, surface area to volume ratio, porosity, flexible and multiple layer structures that can be incorporated on any device. Carbon in the composite improved conductivity, and mechanical stability of 3D printed zinc anode. Our 3D printed composite anodes allowed flexible designing of batteries surpassing conventional battery designs such as coin cells …

This thesis is focused on understanding the correct method to simulate atomistic models to calculate coefficient of diffusion of water through the membrane. It also aims to fix the method previously used in molecular modelling in which the simulation results did not match the experimental results. These membranes will be used in air dehumidification systems. The four types of membranes namely, polyurethane, polyurethane with silica nano particles, polyurethane with silica nano particles and amine surface modifier, and polyurethane with silica nano particles and aniline surface modifier. These membranes were also simulated to understand the effects of temperatures and pressure using molecular dynamics. The software packages used are MAPS 4.3, Avogadro, EMC, OVITO, and LAMMPS. MAPS, Avogadro and EMC were used to model the membrane at an atomistic level while LAMMPS is used to simulate the model generated. OVITO is used to analyze the simulation visually. The movement of water vapor molecules were tracked through the membrane in the simulation and diffusion coefficient was calculated using Mean square displacement equation. To create a realistic model, silica was dispersed in the Polyurethane matrix, simulated under standard atmospheric conditions. These results will help in further optimizing the membrane for air dehumidification. This will …

The recipes of optical radiative properties manipulation are their materials chemistry, nano/microscale geometry, and transport properties of quasiparticle carriers such as photons, phonons, and electrons. The important technical element in optical properties is the dielectric function of materials, which is different for metals, dielectrics, 2D materials, and phase transition materials. Graphene has a unique electrical conductivity profile which have metallic nature depending on the frequency, but also has a negative thermal expansion coefficient that makes graphene unique. Hence, graphene creates wrinkles when deposited on the substrate as temperature decreases to room temperature from high substrate temperature. We also study phase transition material, particularly vanadium dioxide that transitions from insulating to metallic phase based on temperature change; we investigate its role in far-field thermal radiation. Other transition metal oxides are studied as a thermally and electrically tunable plasmonic gratings: Transition metal oxides include vanadium dioxide, tungsten trioxide, and molybdenum trioxide. The work demonstrates plasmonic phenomena and absorptance/emittance tunability. First, surface plasmon polariton along the graphene (SPPG) when wrinkles are formed above the plasmonic grating is studied. The resonance peak shift is modeled for both magnetic polariton (MP) with inductor-capacitor (LC) circuit and SPPG with Fabry-Perot phase change model. Second, the self-adaptive …

In this research thermal properties enhancement of phase change material (PCM) using boron nitride nanomaterials such as nanoparticles and nanotubes is studied through experimental measurements, finite element method (FEM) through COMSOL 5.3 package and molecular dynamics simulations via equilibrium molecular dynamics simulation (EMD) with the Materials and Process Simulations (MAPS 4.3). This study includes two sections: thermal properties enhancement of inorganic salt hydrate (CaCl2∙6H2O) as the phase change material by mixing boron nitride nanoparticles (BNNPs), and thermal properties enhancement of organic phase change material (paraffin wax) as the phase change material via encapsulation into boron nitride nanotubes (BNNTs). The results of the proposed research will contribute to enhance the thermal transport properties of inorganic and organic phase change material applying nanotechnology for increasing energy efficiency of systems including electronic devices, vehicles in cold areas to overcome the cold start problem, thermal interface materials for efficient heat conduction and spacecraft in planetary missions for efficient thermal managements.

Novel tissue mimicking materials have been developed for cancer treatment research. In the present research work, the tissue mimicking material is printed using 3D bioprinting technology. The nanoparticles are homogeneously mixed with tissue mimicking materials to enhance the heating capacity. The thermal conductivity of tissue mimicking materials is measured using a micropipette thermal sensor (MTS). Further, the optimal value is identified based on optimization technique and incorporated into a theoretical model to predict the surface temperature of microsphere. The heat conduction governing equation with Lambert law is numerically solved using COMSOL Multiphysics software. To validate the present simulation results, the experiments are conducted using a continuous laser system.

Sequential single-axis vibration testing strategies often produce over-testing when qualifying system hardware. Multi-axis excitation techniques can simulate realistic service environments, but the hardware and testing strategies needed to do so tend to be costly and complex. Test engineers instead must execute sequential tests on single-axis shaker tables to excite each degree of freedom, which the previous two decades of vibration testing literature have shown to cause extensive over-testing when considering cross-axis responses in assessing the severity of the applied test environments. Traditional assessments assume that the test article responds only in the axis of excitation, but often significant response occurs in the off-axes as well. This paper proposes a method to address the over-testing problem by approximating a simultaneous multi-axis test using readily-available, single-axis shaker tables. By optimizing the angle of excitation and the boundary condition through dynamic test fixture design, the test article can be tested using a Single-Input, Multiple-Output (SIMO) test in a way that approximates a Multiple-Input, Multiple-Output (MIMO) test. This paper shows the proposed method in simulation with a 2D finite element box assembly with removable component (BARC) model attached to springs with variable stiffness. The results include quantified test quality assessment metrics with comparison to …

This study investigated a new approach to achieving high energy density supercapacitors (SCs) by using high surface area self-activated carbon from waste coffee grounds (WCGs) and modifying 3D printed electrodes' porous structure by varying infill density. The derived activated carbons' surface area, pore size, and pore volume were controlled by thermally treating the WCGs at different temperatures (1000˚C, 1100˚C, and 1200˚C) and post-treating with HCL to remove water-soluble ashes and contaminants that block activated carbon pores. Surface area characterization revealed that the carbon activated at 1000˚C had the highest surface of 1173.48 m2 g-1, and with the addition of HCL, the surface area increased to 1209.35 m2 g-1. This activated carbon was used for fabricating the electrodes based on the surface area and having both micropores and macropores, which are beneficial for charge storage. Direct ink writing (DIW) method was utilized for 3D printing SC electrodes and changing the electrode structure by increasing the infill densities at 30%, 50%, and 100%. Upon increasing the infill densities, the electrodes' mass increased linearly, porosity decreased, and the total surface area increased for the 30% and 50% infill electrodes but decreased for the 100% infill electrode. Cyclic voltammetry (CV) test on the assembled …

Interfacial mechanical properties of adhesive joints are very crucial in board applications, including composites, multilayer structures, and biomedical devices. Establishing traction-separation (T-S) relations for interfacial adhesion can evaluate mechanical and structural reliability, robustness, and failure criteria. Due to the short range of interfacial adhesion such as micro to nanoscale, accurate measurements of T-S relations remain challenging. The advent of machine learning (ML) became a promising tool to predict materials behaviors and establish data-driven mechanical models. In this study, we integrated a state-of-the-art ML method, finite element analysis (FEA), and standard experiments to develop data-driven models for characterizing the interfacial mechanical properties precisely. Macroscale force-displacement curves are derived from FEA with incorporation of double cantilever beam tests to generate the dataset for ML model. The eXtreme Gradient Boosting (XGBoost) multi-output regressions and classifier models are used to determine T-S relations with R2 score of 98.8% and locate imperfections at the interface with accuracy of around 80.8%. The outcome of the XGBoost models demonstrated accurate predictions and fast calculation speed, outperforming several other ML methods. Using 3D printed double cantilever beam specimens, the performance of the ML models is validated experimentally for different materials. Furthermore, a XGBoost model-based package is designed to …

Lignocellulose is the most abundant biopolymer on earth and offers excellent potential for sustainable manufacturing. Because lignocellulose is structurally complex and resistant to decomposition, innovative degradation strategies are necessary to unlock its value. In this dissertation, a green manufacturing process through enzyme-triggered self-cultured bacteria retting for lignocellulosic fiber was developed and investigated. The mechanism of the lignocellulosic fiber retting at a controlled degradation strategy was studied. This enzymatic degradation strategy utilizes a small amount of enzyme to trigger a large aggregation of specific bacteria to obtain clean fibers. Industrial hemp (Cannabis sativa L.) fiber was successfully retted with this strategy. The degradation of pectin was proved through an environmental scanning electron microscope and reducing sugar analysis. The bacterial successions were identified by 16S rRNA gene metagenomic sequencing. The results showed that Bacillaceae dominated the hemp retting conditions containing 1% pectinase, suggesting that pectinase can manipulate bacterial community succession by changing the nutrients available to bacteria through the degradation of pectin. This degradation strategy has 20-25% less environmental impact than the thermochemical degradation strategy, resulting in better fiber consistency and much shorter processing time (3-5 days) than the traditional water degradation strategy. The study on the degradation of lignin-rich lignocellulose also …

Waste-heat-to-power (WHP) recovers electrical power from exhaust heat emitted by industrial and commercial facilities. Waste heat is available in enormous quantities. The U.S. Department of Energy estimates 5-13 quadrillion BTUs/yr with a technical potential of 14.6 GW are available and could be utilized to generate power by converting the heat into electricity. The research proposed here will define a system that can economically recover energy from waste heat through a thermal regenerative electrochemical system. The primary motivation came from a patent and the research sponsored by the National Renewable Energy Laboratory (NREL). The proposed system improves on this patent in four major ways: by using air/oxygen, rather than hydrogen; by eliminating the cross diffusion of counter ions and using a dual membrane cell design; and by using high concentrations of electrolytes that have boiling points below water. Therefore, this system also works at difficult-to-recover low temperatures. Electrochemical power is estimated at 0.2W/cm2, and for a 4.2 M solution at 1 L/s, the power of a 100 kW system is 425 kW. Distillation energy costs are simulated and found to be 504 kJ/s for a 1 kg/s feed stream. The conversion efficiency is then calculated at 84%. The Carnot efficiency for …

Recent advances in manufacturing and growing concerns on the sustainability of aviation environment have led to a remarkable interest in electrical unmanned aerial systems (UASs) in the past decade. Among various UAS types, the newly designed quadrotor biplane tailsitter class is capable of delivering a wide range of civilian and military tasks, relying on its Vertical Take-Off and Landing (VTOL) capability as well as great maneuverability. Nevertheless, as such UASs employ rotors to generate thrust, and wings to generate lift, and operate at less-understood low to mid-Reynolds flow regime, they experience complicated flight aerodynamics with a noise generation mechanism which is different from common aircrafts. The present work aims at addressing this knowledge gap by studying the aerodynamics and aeroacoustics of a UAS of this type designed by the Army Research Lab. High-fidelity computational fluid dynamics (CFD) simulations are carried out for a wide range of operating conditions to understand the physics involved in the UAS aerodynamics and characterize its performance. Relying on the CFD results, a physics-informed reduced order model (ROM) is developed based on machine learning algorithms, to predict the propellers effects on the wings and calculate the dominant loads. The results of this study indicate that the …

This thesis details the creation and application of a generalized process plan for the hybrid manufacturing of AISI 316L stainless steel, using direct energy deposition (DED) and ball-nose end-mill machining, that includes the inspection and measurement of objects created by that hybrid manufacturing process plan. The proposed process plan progresses through the selection of substrate thickness, single-track, multi-track, and multi-layer depositions, then on to machining processing. A manufacturers' recommended set and range of DED parameters were used to create a designed experiment that aided in the analysis of objects created in each of the DED process planning steps; those objects were then machined in the same enclosure using a set of machining parameters screened from industry recommendations for ball-nose milling of stainless steel, after which measurements were taken for surface roughness, some material characteristics, and for tool deterioration. The results, analyses, and discussions collected herein show that the proposed process plan can provide models for geometrical outputs for each step in the plan, some improvements in substrate stability, surface roughness, tool deterioration, and material porosity due to voids. Current research in hybrid manufacturing does not show generalized process planning influences. The process plan as demonstrated by the work in this …

Machine learning is fast growing field as it can be applied to solve a large amount of problems. One large subsection of machine learning are artificial neural networks (ANN), these work on pattern recognition and can be trained with data sets of known solutions. The objective of this thesis is to discuss the creation of an ANN capable of classifying differences in propylene glycol concentrations, up to 10%. Utilizing a micro pipette thermal sensor (MTS) it is possible to measure the heat propagation of a liquid from a laser pulse. The ANN can then be trained beforehand with simulated data and be tested in real time with temperature data from the MTS. This method could be applied to find the thermal conductivity of unknown fluids and biological samples, such as cells and tissues.

Motivated by previous relevant research on phononics including both active and passive phononics, the interest of faster turnability and more functions of the active phononics of further study led to this proposing research topic: magnetic field tunable active functional phononics. The first design of magnetic field tunable reciprocal--non-reciprocal transmission acoustic device was established, material was characterized, and numerical simulation has been performed. The simulation results show clear T-symmetric breaking non-reciprocity due to energy level splitting effect with Doppler effect – an acoustic Zeeman effect. Inspired by this preliminary work, further experiments were planned to demonstrate this effective Zeeman effect in phononics and effectively charged phonons in water based ferro-fluid. The objectives of this work as the next series of tasks were to illustrate acoustic Zeeman effect and acoustic Landau levels in various strength of magnetic field to investigate a design non-reciprocal sound device with magnetic field switching, which could be controlled on the amount of non-reciprocity with the strength of magnetic field. Once this new field first discovered by the proposed study tasks, more active tunable magnetic field phononics devices could be designed and exemplified in terms of both simulations and experiments. Faster and more controllable active phononic devices could …

Immersed boundary (IB) methods are attractive due to their ability to simulate flow over complex geometries on a simple Cartesian mesh. Unlike conformal grid formulation, the mesh does not need to conform to the shape and orientation of the boundary. This eliminates the need for complex mesh and/or re-meshing in simulations with moving/morphing boundaries, which can be cumbersome and computationally expensive. However, the imposition of boundary conditions in IB methods is not straightforward and numerous modifications and refinements have been proposed and a number of variants of this approach now exist. In a nutshell, IB methods in the literature often suffer from numerical oscillations, implementation complexity, time-step restriction, burred interface, and lack of generality. This limits their ability to mimic conformal grid results and enforce Neumann boundary conditions. In addition, there is no generic IB capable of solving flow with multiple potentials, closely/loosely packed structures as well as IBs of infinitesimal thickness. This dissertation describes a novel 2$ ^{\text{nd}} $ order direct forcing immersed boundary method designed for simulation of two- and three-dimensional incompressible flow problems with complex immersed boundaries. In this formulation, each cell cut by the IB is reshaped to conform to the shape of the IB. IBs …

Nondestructive testing (NDT) using ultrasound band 1-5 MHz, has been widely used for the early-stage detection of structural failure; however, it fails to detectf material degradation, fatigue, and microcracks. NDT with nonlinear ultrasound (NLU) can detect a microscopic discontinuity or imperfection that may be a source of the second harmonic in the reflected signal. In this research, we focus on creating a metamaterial band filter that filters out nonlinearities induced by the instrument itself. A 1D elastic superlattice (SL) acoustic filter is designed with a bandgap in its frequency spectrum that covers the frequency range of second harmonic. The SL is made of periodically alternating Cu and Sn-Pb solder layers. We conducted analytical and numerical calculations to obtain the appropriate thickness of each layer. The metamaterial in this study has the pass band for the fundamental frequency of 5 MHz and the first stop band centered near the frequency of 10 MHz; 5 MHz was chosen because the second harmonic at 10 MHz can detect 200μm micro-scale damage. Experiments with aluminum as the reference specimen and with SL filter were conducted. A function-generator generates 3 pulses sine signal, within the frequency range from 2.5 MHz to 20MHz. Spectral analysis of …

Several active methods, which requires external control systems and moving parts, have been developed to control the fiber orientation during 3D printing. Active mechanisms like rotating nozzle, impeller, and magnetic field have been integrated to realize complex internal fiber structures. In this study, instead of using active methods, I investigate a passive method for controlling the fiber orientation without any moving parts or additional mechatronics added in the printing process. Composites of polydimethylsiloxane (PDMS) and glass fibers (GF) are 3D printed. Channels, such as helicoid, are designed and integrated to guide the ink flow and passively result in different pre-alignment of fibers before the ink flow into narrow nozzle space. While passing through the designed channels, the fibers orient due to the shear between channel walls and the ink. The effect of helicoids with different pitch sizes are investigated via mechanical experiments, microstructural analysis, and numerical simulations. The results show that both surface to volume ratio and helix angle of the channel affect pre-alignment of fiber orientation at the entry of nozzle. The internal fiber structures lead to enhanced and tunable mechanical properties of printed composites. Pitch size 7-9 mm (helix angle of 7.92- 10.15o) is found to be optimal …

In this thesis, friction stir channeling (FSC) and its process parameters influence on geometry, surface quality and productivity are explored. The probe of the friction stir processing (FSP) tool used to perform these tests was a modified submerged bobbin tool made of MP 159 Co-Ni alloy. The body was made from H13 tool steel. To find the optimal channel conditions for a targeted range of process parameters, multiple 6061 aluminum samples were prepared with a U shape guide to test the effects of different spindle speeds and feed rates. Using a gantry-type computer numerical control (CNC) friction stir welding (FSW) machine, the aluminum coupons were subjected to calibration experiments, force control tests, and an increased production rate to test these effects. It was found through experimentation that the programmed feed rates, spindle speeds and forces produced by the machine had an impact on the channel geometry. It was determined from the force-controlled setup that 8.46 mm/s at 750 RPM was the best combination of results for the four conditions tested on a CNC friction stir processing-machine. It was then tested at 10.58 mm/s at 800 RPM, which had comparable results with the best combination of input parameters from the force-controlled …

While ozone design values have decreased since 2000, the values measured in Denton Airport South (DEN), an exurban region in the northwest tip of the Dallas-Fort Worth (DFW) metroplex, remains above those measured in Dallas Hinton (DAL) and Fort Worth Northwest (FWNW), two extremely urbanized regions; in addition, all three sites remained in nonattainment of National Ambient Air Quality Standards (NAAQS) ozone despite reductions in measured NOx and CO concentrations. The region's inability to achieve ozone attainment is tied to its concentration of total non-methane organic compounds (TNMOC). The mean concentration of TNMOC measured at DAL, FWNW, and DEN between 2000 and 2018 were 67.4 ± 1.51 ppb-C, 89.31 ± 2.12 ppb-C, and 220.69 ± 10.36 ppb-C, respectively. Despite being the least urbanized site of the three, the TNMOC concentration measured at DEN was over twice as large as those measured at the other two sites. A factor-based source apportionment analysis using positive matrix factorization technique showed that natural gas was a major contributing source factor to the measured TNMOC concentrations at all three sites and the dominant source factor at DEN. Natural gas accounted for 32%, 40%, and 69% of the measured TNMOC concentration at DAL, FWNW, and DEN, …

The research focuses on the synthesis and application of multifunctional lignocellulosic biomass bioadsorbent and nanobiocomposites for water purification. A bioadsorbent was prepared from kenaf fiber by self-activation without the use of any toxic chemicals in an innovative method. Silver nanoparticles were synthesized by the green route and then impregnated on the surface of kenaf-based activated carbon (KAC), and hemp fibers by heating and photoirradiation. The formation of hemp-based and kenaf-based silver nanocomposites was confirmed using an environmental scanning electron microscope and energy-dispersive x-ray spectroscopy. Low-cost benign nanoadsorbents demonstrated excellent capabilities for the anionic dye Congo red (CR) and cationic dye brilliant green (BG) degradation, inorganic heavy metals [Cu (II), Pb (II), and Cd (II)] adsorption and antibacterial activities. Antibacterial test via a modified disc diffusion method and minimum inhibitory concentrations was assessed towards the pathogenic strains of bacteria, E. coli and S. aureus. A working portable point-of-use filter was designed and developed, with the filter column encapsulated with nanobiocomposites for the removal of multi-metals and dye. Water samples collected from a wastewater treatment plant in Texas and a mining site in Mexico were used to determine the efficacy of the nanobiocomposites columned in the filter. A comparative analysis was also …