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Full-Text Articles in Engineering
Effect Of Build Geometry And Build Parameters On Microstructure, Fatigue Life, And Tensile Properties Of Additively Manufactured Alloy 718, Anna Dunn
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Additive Manufacturing (AM), particularly laser powder bed fusion, is being studied for use in critical component applications. Tensile and fatigue testing shows differences when built using different laser powers. However, when fabricated in an as-printed geometry, the gauge sections of the two specimens are different and experience different thermal behavior. This work explores microhardness, microstructure size, Niobium segregation, and porosity from samples made with varying laser power and different build geometry sizes representative of the gauge sections in the tensile and fatigue bars. Results show that microhardness varies spatially across the sample. Smaller diameter metallographic coupons (fatigue diameter) have a …
Influence Of Fill Percentage And Baking Parameters On The Feedability Of Metal-Cored Arc Welding Wires, Angelica Marie Black
Influence Of Fill Percentage And Baking Parameters On The Feedability Of Metal-Cored Arc Welding Wires, Angelica Marie Black
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Adequate feedability is essential for GMAW processes to ensure efficiency. The feedability of a wire refers to the wire’s ability to feed continuously through the contact tip. While there are several known causes of feedability difficulties when using cored welding wires, there are many variables that have yet to be explored thoroughly. Three factors are investigated in this research to determine their effects on feedability of cored wires: fill percentage, baking time, and baking temperature. A set of metal-cored arc welding wires were created with various fill percentages, baking times, and baking temperatures. Tension testing, microhardness testing, microstructural characterization, and …
A Design Thinking Framework For Human-Centric Explainable Artificial Intelligence In Time-Critical Systems, Paul Benjamin Stone
A Design Thinking Framework For Human-Centric Explainable Artificial Intelligence In Time-Critical Systems, Paul Benjamin Stone
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Artificial Intelligence (AI) has seen a surge in popularity as increased computing power has made it more viable and useful. The increasing complexity of AI, however, leads to can lead to difficulty in understanding or interpreting the results of AI procedures, which can then lead to incorrect predictions, classifications, or analysis of outcomes. The result of these problems can be over-reliance on AI, under-reliance on AI, or simply confusion as to what the results mean. Additionally, the complexity of AI models can obscure the algorithmic, data and design biases to which all models are subject, which may exacerbate negative outcomes, …
The Theory And Design Of Class E Power Amplifiers For Impulse Excitation In Nuclear Magnetic Resonance, Owen D. Riemer
The Theory And Design Of Class E Power Amplifiers For Impulse Excitation In Nuclear Magnetic Resonance, Owen D. Riemer
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A new method for analyzing the effectiveness of NMR impulse power amplifiers was developed using a classical linear systems approach to NMR. The method demonstrates a way to compare NMR power amplifiers and outputs. Thermodynamic calculations and the harmonic content of NMR amplifiers is presented to provide a complete description of the NMR power amplifier design problem. A design procedure for class E NMR power amplifiers with a pi-impedance matching network is outlined for matching the amplifier to the transmitter coil. The thesis concludes with the presentation of a 53 MHz power amplifier developed with the procedure. The complete amplifier …
Silk Hydrogels Incorporated With Melanin, Anne Lutz
Silk Hydrogels Incorporated With Melanin, Anne Lutz
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Melanin is a naturally produced pigment found within the human body. Melanin is known for its ability to protect against Ultra Violet light, but also its ability to allow for mechanical protection. Making melanin a good addition to biomedical devices such as hydrogels. Silk hydrogels are weak in their load bearing capabilities but are known for their biocompatibility, biodegradability, and porosity. This makes the silk hydrogel a good material to incorporate melanin into in order to improve the mechanical properties. For the silk solution to form a solid, there must be a presence of both a catalyst and an oxidizer …
Texture Evolution In Materials With Layered Crystal Structures, Vamsi Krishna Vempati
Texture Evolution In Materials With Layered Crystal Structures, Vamsi Krishna Vempati
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Materials with a layered structure consist of crystalline layers that are bonded to each other with secondary bonds (van der Waals interactions). The bonding between crystalline layers is relatively weak compared to the interatomic bonding within the crystalline layers. This research hypothesizes that under appropriate conditions, such as elevated temperature, the deformation of layered materials occurs like the classic “deck of cards” with no preferred direction of slip on the slip planes. The motivation for this study is from the experimental texture evolution of one such material, Bismuth Telluride ,(Bi2Te3), commonly used materials for thermoelectric applications in the range of …
Unraveling The Etiologies Of Discrete Subaortic Stenosis: A Focus On Left Ventricular Outflow Tract Hemodynamics, Jason A. Shar
Unraveling The Etiologies Of Discrete Subaortic Stenosis: A Focus On Left Ventricular Outflow Tract Hemodynamics, Jason A. Shar
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Discrete subaortic stenosis (DSS) is an obstructive cardiac disease characterized by the formation of a thin fibromuscular ring of tissue in the left ventricular (LV) outflow tract (LVOT). Although its etiology is unknown, the association between DSS, pediatric age, and morphological LVOT abnormalities points to a potential hemodynamic etiology. Here, altered subaortic flow dynamics, stemming from deviated LVOT anatomy, may promote lesion formation through local fluid shear stress abnormalities triggering membrane formation. The assessment of this hypothetical pathway requires elucidation of the complex LV wall shear stress (WSS) environment. The central hypothesis of this dissertation is that altered LV hemodynamics, …
Bayesian Inspired Multi-Fidelity Optimization With Aerodynamic Design, Christopher Corey Fischer
Bayesian Inspired Multi-Fidelity Optimization With Aerodynamic Design, Christopher Corey Fischer
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In most engineering design problems, there exist multiple models of varying fidelities for use in predicting a single system response such as Computational Fluid Dynamics (CFD) models constructed using Potential Flow, Euler equations, or full physics Navier Stokes implementation. Engineering design is constantly pushing the forefront of the field through imposing stricter and more complex constraints on system performance, thus elevating the need for use of high-fidelity models in the design process. Increasing fidelity level often correlates to an increase in cost (financial, computational time, and computational resources). Traditional design processes rely upon low-fidelity models for expedience and resource savings. …
Effect Of Cloud Cover On Optimum Orientations Of Fixed Solar Panels For Maximum Yearly Energy Collection, Prethew Prasad
Effect Of Cloud Cover On Optimum Orientations Of Fixed Solar Panels For Maximum Yearly Energy Collection, Prethew Prasad
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The amount of cloud cover present in the sky is a significant factor when determining the solar radiation impinging on a solar panel. The optimum tilt required to achieve maximum energy impingement on a surface is also influenced by the amount of cloud cover. This work presents a method for determining the optimum tilt angle for a fixed solar panel when a set amount of cloud cover is present in the sky. Fixed tilt angles that have the most incident solar energy over the course of a year as a function of cloud cover, latitude, and azimuthal angle orientation are …
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
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In the pursuit of optimum performance, materials engineering seeks to design the microstructure and thus the properties of a material through the control of the material composition and processing. Functionally graded materials (FGM) are designed to incorporate location-specific material properties through compositional changes within the part. Moving toward location-specific design of material properties requires the ability to produce material gradients in three dimensions which can be accomplished through the use of additive manufacturing (AM). This research examines the composition-process-structure-property relationship of early iteration titanium (Ti) and tantalum (Ta) graded alloys built in a novel laser powder bed fusion (LPBF) process …
Application Of Analogical Reasoning For Use In Visual Knowledge Extraction, Kara Lian Combs
Application Of Analogical Reasoning For Use In Visual Knowledge Extraction, Kara Lian Combs
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There is a continual push to make Artificial Intelligence (AI) as human-like as possible; however, this is a difficult task because of its inability to learn beyond its current comprehension. Analogical reasoning (AR) has been proposed as one method to achieve this goal. Current literature lacks a technical comparison on psychologically-inspired and natural-language-processing-produced AR algorithms with consistent metrics on multiple-choice word-based analogy problems. Assessment is based on “correctness” and “goodness” metrics. There is not a one-size-fits-all algorithm for all textual problems. As contribution in visual AR, a convolutional neural network (CNN) is integrated with the AR vector space model, Global …
Application Of Analogical Reasoning For Use In Visual Knowledge Extraction, Kara Lian Combs
Application Of Analogical Reasoning For Use In Visual Knowledge Extraction, Kara Lian Combs
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There is a continual push to make Artificial Intelligence (AI) as human-like as possible; however, this is a difficult task because of its inability to learn beyond its current comprehension. Analogical reasoning (AR) has been proposed as one method to achieve this goal. Current literature lacks a technical comparison on psychologically-inspired and natural-language-processing-produced AR algorithms with consistent metrics on multiple-choice word-based analogy problems. Assessment is based on “correctness” and “goodness” metrics. There is not a one-size-fits-all algorithm for all textual problems. As contribution in visual AR, a convolutional neural network (CNN) is integrated with the AR vector space model, Global …
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
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In the pursuit of optimum performance, materials engineering seeks to design the microstructure and thus the properties of a material through the control of the material composition and processing. Functionally graded materials (FGM) are designed to incorporate location-specific material properties through compositional changes within the part. Moving toward location-specific design of material properties requires the ability to produce material gradients in three dimensions which can be accomplished through the use of additive manufacturing (AM). This research examines the composition-process-structure-property relationship of early iteration titanium (Ti) and tantalum (Ta) graded alloys built in a novel laser powder bed fusion (LPBF) process …
Development And Application Of A Computational Modeling Scheme For Periodic Lattice Structures, Abdalsalam Fadeel
Development And Application Of A Computational Modeling Scheme For Periodic Lattice Structures, Abdalsalam Fadeel
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Sandwich structures are widely used for aerospace, marines and other applications due to their light-weight, strength, and strain energy absorption capability. The cores of the sandwich structure are typically fabricated by using high strength cellular materials such as aluminum and titanium alloys, or polymer foams, and honeycombs. Lattice cell structures (LCS) of different configurations such as body centered cubic (BCC), tetrahedron and pyramidal are being investigated as core material due to their design freedom and periodic nature. Due to the recent advent of additive manufacturing (AM), new research is being sought in the areas of designing and developing application-specific LCS …
Eye-Tracking To Evaluate Trust In Human-Atr Interaction, Samuel Francis Adelman
Eye-Tracking To Evaluate Trust In Human-Atr Interaction, Samuel Francis Adelman
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Human collaboration with targeting aids have allowed analysts to achieve a greater level of coordination and productivity in a variety of fields. This project investigates the impact that an Assisted Target Recognition (ATR) algorithm’s false alarm rate and the task Target of Interest (TOI) level has on user-system trust and use in a targeting decision task. Previous studies suggest that an increased number of false alarms in an ATR task negatively impacts analyst trust in the system. This study will further contribute to this research, aiming to provide a better framework for appropriate tolerance levels within ATR algorithms, utilizing pre-truthed …
Optimization Study Of A Combined Wind-Solar Farm For A Specified Demand, Venkat Siddhartha Rama
Optimization Study Of A Combined Wind-Solar Farm For A Specified Demand, Venkat Siddhartha Rama
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At the present time, using wind and solar energy for producing electricity in the United States is becoming cost competitive. According to Lazard’s 2019 [36] levelized cost of energy (LCOE) analysis of a number of energy sources used for producing electricity in the United States, wind and solar are cheaper than natural gas and coal. While capital, maintenance, operation, and fuel costs are included in LCOE numbers, energy source intermittency is not. Intermittency is an important issue with wind and solar energy sources, but not with natural gas or coal energy sources. Combining wind and solar energy sources into one …
Joint Shelf Design And Shelf Space Allocation Problem For Retailers, Hakan Gecili
Joint Shelf Design And Shelf Space Allocation Problem For Retailers, Hakan Gecili
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Although the retail business has been exploring innovative ways to engage shoppers, the COVID-19 pandemic has sped up their effort. Because of its unique benefits, physical stores will continue to remain an integral part of the overall retail business. However, to stay competitive, retailers will be forced to effectively utilize their available space in physical store (and even reduce it if need be), while offering a reasonably large assortment of products on their shelves. For many such retailers, the design of planograms – visual representation of products on shelves – is still driven by prior experience and intuition. Further, existing …
Adaptive Multi-Fidelity Modeling For Efficient Design Exploration Under Uncertainty, Atticus J. Beachy
Adaptive Multi-Fidelity Modeling For Efficient Design Exploration Under Uncertainty, Atticus J. Beachy
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This thesis work introduces a novel multi-fidelity modeling framework, which is designed to address the practical challenges encountered in Aerospace vehicle design when 1) multiple low-fidelity models exist, 2) each low-fidelity model may only be correlated with the high-fidelity model in part of the design domain, and 3) models may contain noise or uncertainty. The proposed approach approximates a high-fidelity model by consolidating multiple low-fidelity models using the localized Galerkin formulation. Also, two adaptive sampling methods are developed to efficiently construct an accurate model. The first acquisition formulation, expected effectiveness, searches for the global optimum and is useful for modeling …
Hierarchical Structure, Properties And Bone Mechanics At Macro, Micro, And Nano Levels, Farah Mohammed Ridha Abdulateef Hamandi
Hierarchical Structure, Properties And Bone Mechanics At Macro, Micro, And Nano Levels, Farah Mohammed Ridha Abdulateef Hamandi
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This research focuses on the hierarchical structure of bone and associated mechanical properties at different scales to assess damage accumulation leading to premature failure, with or without instrumentation. In this work, an attempt was made to develop a framework of macro, micro, and nano damage accumulation models and implementing them to derive mechanical behavior of the bone. At macrolevel, retrospective evaluation of 313 subjects was conducted, and the damage of bone tissue was investigated with respect to subject demography including age, gender, race, body mass index (BMI), height and weight, and their role in initiating fracture. Experimental data utilized 28 …
Quadrotor Uav Flight Control With Integrated Mapping And Path Planning Capabilities, Jason A. Gauthier
Quadrotor Uav Flight Control With Integrated Mapping And Path Planning Capabilities, Jason A. Gauthier
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Quadrotor UAVs have become a common and easily acquirable hardware platform for research and development with control laws, mapping systems, and path planning. In this research, a non-linear model of a quadrotor UAV is linearized with model parameters being identified using collected flight data. The PID, LQR, and backstepping control laws are implemented. An adaptive control law is also implemented to handle the loss of effectiveness in motor actuation. Additionally, this research also implements a laser-based SLAM algorithm for mapping and localization in an unknown two-dimensional environment. Path planning and obstacle avoidance algorithms are implemented onboard using the Robot Operating …
Stabilization Of Β-Cristobalite In The Sio2-Alpo4-Bpo4 System, Kathryn Doyle
Stabilization Of Β-Cristobalite In The Sio2-Alpo4-Bpo4 System, Kathryn Doyle
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Fused silica (silica glass) is transparent in the optical and near-infrared and has a low dielectric constant, making it suitable as a window material for radio frequency radiation. However, at high temperatures (>1100C), fused silica will easily creep and lose dimensional stability. Crystallized silica is much more creep resistant than fused silica. Silica crystallizes to many different structures including quartz, tridymite, and α- and β cristobalite. The only cubic polymorph, which is suitable for both optical and radio frequency transmission in polycrystalline form, is β -cristobalite. Unfortunately, this polymorph transforms to α-cristobalite at ~300C, and the volume change during …
A First Principles Study Of Pipe Diffusion In Nickel, Luke J. Wirth
A First Principles Study Of Pipe Diffusion In Nickel, Luke J. Wirth
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Vacancy-mediated diffusion along dislocations, often referred to as pipe diffusion, can contribute to creep deformation of metals in many engineering applications. This process is studied along an a/2⟨1 -1 0⟩ screw dislocation in fcc Ni using a density functional theory approach. An accurate geometrical configuration of the screw dislocation core, dissociated into Shockley partial dislocations and separated by a stacking fault, was previously derived using a lattice Green's function technique. Activation energies and frequencies are calculated for atom-vacancy exchanges that contribute to diffusion around and along one of the partial cores. This analysis reveals the significant role of the sites …
Understanding Visual Representation Of Imputed Data For Aiding Human Decision-Making, Ryan M. Thompson
Understanding Visual Representation Of Imputed Data For Aiding Human Decision-Making, Ryan M. Thompson
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The effectiveness of representing higher dimensional data on a two-dimensional visualization was required to be studied in the development of a novel data imputation method, Continuous Imputation With Association Rules (CIWAR). When the CIWAR method is used to impute missing data, the method generates additional metadata that increases each imputed data point's dimensionality. Potential use cases for CIWAR include situations where imputed data would be analyzed by individuals with little or no data analytic experience or situations where imputed data would be used to aid high-stress time-critical human decision processes. A study was conducted to assess the effect of the …
Design And Implementation Of Simplified Sliding-Mode Control Of Pwm Dc-Dc Converters For Ccm, Humam A. Al-Baidhani
Design And Implementation Of Simplified Sliding-Mode Control Of Pwm Dc-Dc Converters For Ccm, Humam A. Al-Baidhani
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The pulse-width modulated (PWM) dc-dc converters play a vital role in several industrial applications that include motor drives, electric vehicles, dc distribution systems, and consumer electronics. The switched-mode power converters step the input voltage up or down based on their typology and provide a regulated output voltage. The stability and regulation performance of a power converter can tremendously be improved via a suitable control design. However, due to the nonlinearity of the power converters and the presence of the line and load disturbances, the design of a robust and low-cost control circuit becomes a challenging task. The sliding-mode control of …
Hierarchical Hybrid Materials From Flexible Fabric Substrates, Wenhu Wang
Hierarchical Hybrid Materials From Flexible Fabric Substrates, Wenhu Wang
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The goal of this project is to investigate fabrication approaches and structure-property relationships of porous and flexible hierarchical hybrid solids suitable for advanced surface-active devices. Multi-scale hierarchical carbon materials are being fabricated by strong covalent attachment of multiwall carbon nanotube(MWCNTs) arrays on flexible carbon fabric substrates in order to enhance the surface area per unit volume. This was done using chemical vapor deposition (CVD) after functionalizing the surface with a plasma-derived nano-oxide coating. Structural and chemical characterization is performed using scanning electron microscope(SEM), energy dispersive spectroscopy(EDS) and x-ray photoelectron spectroscopy(XPS). Surface area estimates have been made by building structural models …
Processing And Properties Of Multifunctional Two Dimensional Nanocomposites Based On Graphene Nano-Flakes, Mohammed K. Mohammed
Processing And Properties Of Multifunctional Two Dimensional Nanocomposites Based On Graphene Nano-Flakes, Mohammed K. Mohammed
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The unique properties of graphene have directed researchers to study and characterize this new material. Graphene production and graphene based materials have been widely explored and developed in the past decade. Most research has aimed at developing scalable, environmentally friendly, and cheap procedures to produce defect-free graphene that can be used in various applications such as mechanical properties enhancement and multifunctional material. The challenge is processing such material on a scale suitable for engineering applications such as advanced photonics and advanced electronics. In this study, we investigate a new processing technique based on Langmuir-Blodgett (LB) Technique. We managed to produce …
Design And Manipulation Of A Power-Generating System With High-Temperature Fuel Cells For Hypersonic Applications, Jack Randolph Chalker
Design And Manipulation Of A Power-Generating System With High-Temperature Fuel Cells For Hypersonic Applications, Jack Randolph Chalker
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Current hypersonic vehicles tend to be incapable of producing onboard power with traditional generators due to their use of supersonic combusting ramjets (scramjets). Because of this, they seek additional energy sources for supporting advanced electronics or other auxiliary power-dependent devices while requiring elaborate thermal management systems to combat temperatures exceeding 700ºC. The incorporation of Solid Oxide Fuel Cell (SOFCs) stacks is an efficient solution, capable of generating large quantities of power through the use of natural fuel sources at high temperatures. Developments in this thesis include the design, construction, and support of a system operating at hypersonic-environment conditions with a …
Design And Implementation Of Periodic Unsteadiness Generator For Turbine Secondary Flow Studies, Nathan James Fletcher
Design And Implementation Of Periodic Unsteadiness Generator For Turbine Secondary Flow Studies, Nathan James Fletcher
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A primary source of periodic unsteadiness in low-pressure turbines is the wakes shed from upstream blade rows due to the relative motion between adjacent stators and rotors. These periodic perturbations can affect boundary layer transition, secondary flow, and loss generation. In particular, for high-lift front-loaded blades, the secondary flowfield is characterized by strong three-dimensional vortical structures. It is important to understand how these flow features respond to periodic disturbances. A novel approach was taken to generate periodic unsteadiness which captures some of the physics of turbomachinery wakes. Using stationary pneumatic devices, pulsed jets were used to generate disturbances characterized by …
Agent-Based Simulation Of Artificial-Intelligence-Assisted Transfer Of Care, Paul B. Stone
Agent-Based Simulation Of Artificial-Intelligence-Assisted Transfer Of Care, Paul B. Stone
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This study demonstrates the application of Agent-Based Simulation as a potential training aid for Transfer of Care (ToC) between EMS and a hospital triage department. The specific aim was to develop a simulation to increase the efficiency and accountability of information communication during ToC to test the suitability of Agent-Based Simulation to address training requirements in complex, health provision settings. This paper focuses on the design of the training simulation, including the development of individual agents within the simulation through the user interface elements and the evaluation and verification of the prototype simulator. The primary objective is for the simulation …
Characterization Of In-Vivo Damage In Implantable Cardiac Devices And The Lead Residual Properties, Anmar Mahdi Salih
Characterization Of In-Vivo Damage In Implantable Cardiac Devices And The Lead Residual Properties, Anmar Mahdi Salih
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Approximately, 92.1 million patients in the US suffer from cardiovascular diseases with an estimated healthcare cost of over $300 billion; out of which at least one million patients have Cardiac Implantable Electronics Devices (CIED). CIED represented by pacemakers, Implantable Cardioversion Defibrillator (ICD), and Cardiac Resynchronization Therapy (CRT) are exposed to in-vivo damage. These damages are complex and composed on multiple levels and present challenges while assessing their combined extent. Since 2004, more than one hundred recalls were reported for cardiac devices. ICD devices had the majority with 40.8% recalls, pacemaker recall percentage was 14.5%, CRT recall percentage was12.7%, leads recalls …