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Icing Mitigation Via High-Pressure Membrane Dehumidification In An Aircraft Thermal Management, Danielle D. Hollon
Icing Mitigation Via High-Pressure Membrane Dehumidification In An Aircraft Thermal Management, Danielle D. Hollon
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Icing, or the formation of ice from water via freezing or water vapor via desublimation, is a phenomenon that commonly occurs within air cycle-based refrigeration systems and requires thermal control that limits system performance. In aircraft applications icing frequently occurs in the heat exchangers and turbine(s) that are part of the air cycle machine, the refrigeration unit of the environmental control system. Traditionally, water vapor is removed from an air cycle machine via condensing in a heat exchanger and subsequent high-pressure water separation. This approach is not capable of removing all of the vapor present at low altitude conditions, corresponding …
Investigation Of Surface Roughness Effects On Additively Manufactured Metals Under Dynamic Loading, Rachel Elizabeth Tullis
Investigation Of Surface Roughness Effects On Additively Manufactured Metals Under Dynamic Loading, Rachel Elizabeth Tullis
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The as-printed surfaces of parts produced through laser powder bed fusion are significantly rougher than surfaces produced through traditional manufacturing processes. This increased roughness can have a significant impact on mechanical properties, with perhaps the most notable detriment in the fatigue life of the part. Therefore, the as-printed surface roughness in additively manufactured materials must be studied more extensively to determine its impact on fatigue performance. This work investigates the surface roughness of additively manufactured specimens through the investigation of processing parameters and their effects on surface roughness in metal additive manufacturing. Furthermore, the relationships between as-printed surface roughness and …
Monitoring Blood Flow In Animal Models Using A Camera-Based Technique, Dharminder Singh Langri
Monitoring Blood Flow In Animal Models Using A Camera-Based Technique, Dharminder Singh Langri
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Blood flow dynamics plays a critical role in maintaining tissue health, as it delivers nutrients and oxygen while removing waste products. It is especially important when there is a disruption in cerebral autoregulation due to trauma, which can induce ischemia or hyperemia and can lead to secondary brain injury. Thus, there is a need for noninvasive techniques that can allow continuous monitoring of blood flow during intervention. Optical techniques have become increasingly practical for measuring blood flow due to their non-invasive, continuous, and relatively lower-cost nature. This research focused on developing a low-cost, scalable optical technique for measuring blood flow …
Experimental And Numerical Studies On The Projective Dye Visualization Velocimetry In A Squared Vertical Tube, Mark Bradley Johnson
Experimental And Numerical Studies On The Projective Dye Visualization Velocimetry In A Squared Vertical Tube, Mark Bradley Johnson
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In fluid flow experiments, there have been numerous techniques developed over the years to measure velocity. Most popular techniques are non-intrusive such as particle image velocimetry (PIV), but these techniques are not suitable for all applications. For instance, PIV cannot be used in examining in-vivo measurements since the laser is not able to penetrate through the patient, which is why medical applications typically use X-rays. However, the images obtained from X-rays, in particular digital subtraction angiography, are projective images which compress 3D flow features onto a 2D image. Therefore, when intensity techniques, such as optical flow method (OFM), are applied …
A Machine Learning Framework For Hypersonic Vehicle Design Exploration, Atticus Beachy
A Machine Learning Framework For Hypersonic Vehicle Design Exploration, Atticus Beachy
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The design of Hypersonic Vehicles (HVs) requires meeting multiple unconventional and often conflicting design requirements in a hostile, high-energy environment. The most fundamental difference between ordinary aerospace design and hypersonic flight is that the extreme conditions of hypersonic flight require parts to perform multiple functions and be tightly integrated, resulting in significant coupled effects. Critical couplings among the disciplines of aerodynamics, structures, propulsion, and thermodynamics must be investigated in the early stages of design exploration to reduce the risk of requiring major design changes and cost overruns later. In addition, due to a lack of validated test data within the …
Icing Mitigation Via High-Pressure Membrane Dehumidification In An Aircraft Thermal Management System, Danielle D. Hollon
Icing Mitigation Via High-Pressure Membrane Dehumidification In An Aircraft Thermal Management System, Danielle D. Hollon
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Icing, or the formation of ice from water via freezing or water vapor via desublimation, is a phenomenon that commonly occurs within air cycle-based refrigeration systems and requires thermal control that limits system performance. In aircraft applications icing frequently occurs in the heat exchangers and turbine(s) that are part of the air cycle machine, the refrigeration unit of the environmental control system. Traditionally, water vapor is removed from an air cycle machine via condensing in a heat exchanger and subsequent high-pressure water separation. This approach is not capable of removing all of the vapor present at low altitude conditions, corresponding …
Modeling The Tribo-Dynamic Behavior Of Roller Contact, Ali Kolivand
Modeling The Tribo-Dynamic Behavior Of Roller Contact, Ali Kolivand
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This study proposes dynamic modeling of lubricated rolling contact and a numerical sub-model for fatigue life prediction of rollers under starved lubrication conditions. Excitation caused by surface defects in rolling disks is numerically calculated and used as a metric in predicting surface pitting failure occurrence. Surface topography of mating surfaces is used as input to the model for determining maximum acceleration, approach velocity, and approach distance of rollers in presence of pits (defects). Resultant bearing force, contacting force versus approach distance are generated and compared for different pit sizes, developing an accurate tool for design purposes. Maximum acceleration and displacement …
Cmos Wide Tuning Gilbert Mixer With Controllable If Bandwidth In Upcoming Rf Front End For Multi-Band Multi-Standard Applications, Jianfeng Ren
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The current global system for mobile communications, wireless local area, Bluetooth, and ultra-wideband demands a multi-band/multi-standard RF front end that can access all the available bandwidth specifications. Trade-offs occur between power consumption, noise figure, and linearity in CMOS Gilbert mixer wide tuning designs. Besides, it is preferable to have a constant IF bandwidth for different gain settings as the bandwidth varies with the load impedance when an RF receiver is tuned to a higher frequency. My dissertation consists of three parts. First, a tunable constant IF bandwidth Gilbert mixer is introduced for multi-band standard wireless applications such as 802.11 a/b/g …
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, …
Quadrature Phase-Domain Adpll With Integrated On-Line Amplitude Locked Loop Calibration For 5g Multi-Band Applications, Xiaomeng Zhang
Quadrature Phase-Domain Adpll With Integrated On-Line Amplitude Locked Loop Calibration For 5g Multi-Band Applications, Xiaomeng Zhang
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5th generation wireless systems (5G) have expanded frequency band coverage with the low-band 5G and mid-band 5G frequencies spanning 600 MHz to 4 GHz spectrum. This dissertation focuses on a microelectronic implementation of CMOS 65 nm design of an All-Digital Phase Lock Loop (ADPLL), which is a critical component for advanced 5G wireless transceivers. The ADPLL is designed to operate in the frequency bands of 600MHz-930MHz, 2.4GHz-2.8GHz and 3.4GHz-4.2GHz. Unique ADPLL sub-components include: 1) Digital Phase Frequency Detector, 2) Digital Loop Filter, 3) Channel Bank Select Circuit, and 4) Digital Control Oscillator. Integrated with the ADPLL is a 90-degree active …
Further Exploration Of Optical/Thermal Interaction Effects On High-Power Laser System Performance And Optimization Through Multiphysics System-Level Modeling, Nathaniel J. Butt
Further Exploration Of Optical/Thermal Interaction Effects On High-Power Laser System Performance And Optimization Through Multiphysics System-Level Modeling, Nathaniel J. Butt
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High-power laser systems (HPLS) have wide-ranging applications in many prominent areas. HPLS use laser diodes to pump fiber gain media. Understanding the functionality of both components is critical for achieving effective HPLS operation. System optical efficiency is a function of diode junction temperature. As junction temperature changes, the wavelength spectrum of the diode output shifts causing optical power losses in the fiber gain media. Optical/thermal interactions of the dynamically coupled laser diodes and fiber gain media are not fully understood. A system level modeling approach considering the interactions between optical performance and component temperature is necessary. Four distinct models were …
Low-Power, Low-Cost, & High-Performance Digital Designs : Multi-Bit Signed Multiplier Design Using 32nm Cmos Technology, N V Vijaya Krishna Boppana
Low-Power, Low-Cost, & High-Performance Digital Designs : Multi-Bit Signed Multiplier Design Using 32nm Cmos Technology, N V Vijaya Krishna Boppana
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Binary multipliers are ubiquitous in digital hardware. Digital multipliers along with the adders play a major role in computing, communicating, and controlling devices. Multipliers are used majorly in the areas of digital signal and image processing, central processing unit (CPU) of the computers, high-performance and parallel scientific computing, machine learning, physical layer design of the communication equipment, etc. The predominant presence and increasing demand for low-power, low-cost, and high-performance digital hardware led to this work of developing optimized multiplier designs. Two optimized designs are proposed in this work. One is an optimized 8 x 8 Booth multiplier architecture which is …
Reverse Engineering Spinal Motoneuron Properties In Slice And Whole-Cord Preparations Using Computational Modeling, Mohamed H. Mousa
Reverse Engineering Spinal Motoneuron Properties In Slice And Whole-Cord Preparations Using Computational Modeling, Mohamed H. Mousa
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Since Hodgkin and Huxley’s discoveries in the 1950s, mathematical modeling became an indispensable tool in neuroscience. The evolution of computer systems paved the way for computational models to improve our understanding of the nervous system. The long-term goals of this research are to develop tools for examining, understanding, and analyzing experimental data from spinal motoneurons (MNs), which are implicated in many motor disorders. Specifically, I developed high-fidelity, anatomically-detailed computational models that could be used to 1) study the cellular mechanisms underlying the non-linear MNs firing behaviors, 2) analyze the multifactorial process of MNs excitability regulation, and how it is affected …
Unit Circle Roots Based Sensor Array Signal Processing, Jared P. Smith
Unit Circle Roots Based Sensor Array Signal Processing, Jared P. Smith
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As technology continues to rapidly evolve, the presence of sensor arrays and the algorithms processing the data they generate take an ever-increasing role in modern human life. From remote sensing to wireless communications, the importance of sensor signal processing cannot be understated. Capon's pioneering work on minimum variance distortionless response (MVDR) beamforming forms the basis of many modern sensor array signal processing (SASP) algorithms. In 2004, Steinhardt and Guerci proved that the roots of the polynomial corresponding to the optimal MVDR beamformer must lie on the unit circle, but this result was limited to only the MVDR. This dissertation contains …
Design And Implementation Of Fully Integrated Cmos On-Chip Bandpass Filter With Wideband High-Gain Low Noise Amplifier, Yu Wang
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Current trends of fully integrated CMOS on-chip bandpass filter are classified into 1) the component level (i.e., active inductor, Q-enhanced passive inductor, negative resistance cancellation), and 2) the circuit level (i.e., adding transmission zeros on stopband, applying the zigzag technique for fewer inductors, superposition of different resonators). The demand for monolithic designs for portable devices attracts market interest in a fully integrated CMOS on-chip bandpass filter. Optimized minimal inductors (OMI) bandpass filter is a good platform for use in both active and passive bandpass filters, mainly because 1) it provides good stopband rejection for high interface attenuation, and 2) the …
Phase Transformation In The Aluminum/Tungsten System, Ammar Azeez Mahdi Al Yasari
Phase Transformation In The Aluminum/Tungsten System, Ammar Azeez Mahdi Al Yasari
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Formation and growth mechanisms of intermetallic compounds in the aluminum/tungsten system were studied during consolidation and subsequent heat treatment. Three different processes, spark plasma sintering (SPS), laser powder bed fusion (LPBF), and metal inert gas welding (MIG) were used, and each of these processes were followed up with heat treatment at different conditions. Al12W, Al5W and Al4W are the three intermetallics that are stable in the system in room temperature, and they were expected to form at the interface between tungsten and aluminum at different temperature ranges. Contrary to expectations, the Al5W phase was not observed during this study and …
Noninvasive Blood Flow And Oxygenation Measurements In Diseased Tissue, Benjamin S. Rinehart
Noninvasive Blood Flow And Oxygenation Measurements In Diseased Tissue, Benjamin S. Rinehart
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The research presented in this dissertation focused on the application of optical imaging techniques to establish blood flow and oxygen saturation as effective biomarkers for two disease cases, Autism Spectrum Disorder (ASD) and Huntington’s Disease (HD). The BTBR mouse model of ASD was utilized to validate measurements of cerebral blood flow and oxygenation as biomarkers for autism. The R6/2 mouse model of juvenile HD was utilized to validate measurements of skeletal muscle blood flow following tetanic muscle contractions induced by electrical nerve stimulation. Next, a noncontact, camera-based system to measure blood flow and oxygen saturation maps was implemented to improve …
The Course Scheduling Problem With Room Considerations, Lijian Xiao
The Course Scheduling Problem With Room Considerations, Lijian Xiao
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The course scheduling problem (CSP), more commonly referred to as the university timetabling problem, belongs to the larger family of general scheduling problems, where the aim is to assign students, faculties, exams, or lectures to a limited number of rooms over time in accordance under real-world constraints. Such problems are known to be NP-complete and have been the subject of study for the optimization society for many decades. This research extends the classical CSP to the CSP with Room Considerations (CSP-R) by incorporating two room-related considerations; cohort-to-room preference and topic-to-room preference. While the former refers to students in each cohort …
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 …
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. …
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, …
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 …
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 …
The Effect Of Winding Curvature And Core Permeability On The Power Losses And Leakage Inductance Of High-Frequency Transformers, Daniel J. Whitman
The Effect Of Winding Curvature And Core Permeability On The Power Losses And Leakage Inductance Of High-Frequency Transformers, Daniel J. Whitman
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At the frequencies used in switching dc-dc converters, the skin and proximity effects have a significant effect on both the losses and leakage inductance of the transformers used in these circuits. Analytical expressions that have been derived to calculate ac resistance and leakage inductance have primarily used a 1-D approximation. They also have used Cartesian coordinates or approximations that are equivalent to Cartesian coordinates, as well as usually assuming an ideal core of infinite permeability. The classical result in the case of the resistance/losses is Dowell’s equation, and there are analogous results for leakage inductance. This dissertation derives new equations …
Gated Hall And Field-Effect Transport Characterization Of E-Mode Zno Tfts, Jason C. Anders
Gated Hall And Field-Effect Transport Characterization Of E-Mode Zno Tfts, Jason C. Anders
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Amorphous and nano-crystalline metal oxide semiconductors are an important class of materials under continuing investigation for emerging technologies. Accurate measurements of electron mobility in these materials is critical for furthering overall device development. This is complicated due to the fact that device measurements such as current response, transistor input and output characteristics, as well as mobility are affected by transport-limiting factors, such as charge trapping effects at the dielectric / active layer interface, and restriction of electronic transport across grain boundaries. In this work, we focus on the binary metal oxide thin film transistor (ZnO TFT), a normally-off (e-mode) transistor …
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 …
Small-Signal Analysis Of Non-Isolated Ćuk Dc-Dc Converter, Lokesh Kathi
Small-Signal Analysis Of Non-Isolated Ćuk Dc-Dc Converter, Lokesh Kathi
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In the future, renewable energy sources will be the primary energy sources due to non-renewable energy resources depletion. Having a sustainable energy source as an input voltage source for the electrical system is essential. Its applications can be widely used in hybrid solar-wind energy systems, electric vehicles, etc. This converter is invented and named after by Slobodan Cuk. An analysis describing a detailed steady-state operation of the non-isolated Cuk converter operating in continuous-conduction mode (CCM) is provided. The expected steady-state current and voltage waveforms across different components of the converter are analytically derived. Design equations for the converter are provided. …
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 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 …
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 …