Engineering Commons^™

Toward A Fast And Accurate Modeling Strategy For Thermal Management In Air-Cooled Data Centers, Long Tran Bao Phan

FIU Electronic Theses and Dissertations

Computational fluid dynamics (CFD) has become a popular tool compared to experimental measurement for thermal management in data centers. However, it is very time-consuming and resource-intensive when used to model large-scale data centers, and may not be ready for real-time thermal monitoring. In this thesis, the two main goals are first to develop rapid flow simulation to reduce the computing time while maintaining good accuracy, and second, to develop a whole building energy simulation (BES) strategy for data center modeling. To achieve this end, hybrid modeling and model training methodologies are investigated for rapid flow simulation, and a multi-zone model …

Ultra-Wideband Secure Communications And Direct Rf Sampling Transceivers, Dimitrios Siafarikas

FIU Electronic Theses and Dissertations

Larger wireless device bandwidth results in new capabilities in terms of higher data rates and security. The 5G evolution is focus on exploiting larger bandwidths for higher though-puts. Interference and co-existence issues can also be addressed by the larger bandwidth in the 5G and 6G evolution. This dissertation introduces of a novel Ultra-wideband (UWB) Code Division Multiple Access (CDMA) technique to exploit the largest bandwidth available in the upcoming wireless connectivity scenarios. The dissertation addresses interference immunity, secure communication at the physical layer and longer distance communication due to increased receiver sensitivity. The dissertation presents the design, workflow, simulations, hardware …

Centralized And Distributed Detection Of Compromised Smart Grid Devices Using Machine Learning And Convolution Techniques, Cengiz Kaygusuz

FIU Electronic Theses and Dissertations

The smart grid concept has further transformed the traditional power grid into a massive cyber-physical system that depends on advanced two-way communication infrastructure. While the introduction of cyber components has improved the grid, it has also broadened the attack surface. In particular, the threat stemming from compromised devices pose a significant danger: An attacker can control the devices to change the behavior of the grid and can impact the measurements or damage the grid equipment. In this thesis, to detect such malicious smart grid devices, we propose a novel machine learning and convolution-based framework, named PowerWatch, that is able to …

Mitigating Colluding Attacks In Online Social Networks And Crowdsourcing Platforms, Georges Arsene K. Kamhoua

FIU Electronic Theses and Dissertations

Online Social Networks (OSNs) have created new ways for people to communicate, and for companies to engage their customers -- with these new avenues for communication come new vulnerabilities that can be exploited by attackers. This dissertation aims to investigate two attack models: Identity Clone Attacks (ICA) and Reconnaissance Attacks (RA). During an ICA, attackers impersonate users in a network and attempt to infiltrate social circles and extract confidential information. In an RA, attackers gather information on a target's resources, employees, and relationships with other entities over public venues such as OSNs and company websites. This was made easier for …

Many-Objective Hybrid Optimization Under Uncertainty With Applications, Sohail Reddy

FIU Electronic Theses and Dissertations

A novel method for solving many-objective optimization problems under uncertainty was developed. It is well known that no single optimization algorithm performs best for all problems. Therefore, the developed method, a many-objective hybrid optimizer (MOHO), uses five constitutive algorithms and actively switches between them throughout the optimization process allowing for robust optimization. MOHO monitors the progress made by each of the five algorithms and allows the best performing algorithm more attempts at finding the optimum. This removes the need for user input for selecting algorithm as the best performing algorithm is automatically selected thereby increasing the probability of converging to …

Unmanned Aerial Vehicles (Uavs) For Integrated Access And Backhaul (Iab) Communications In Wireless Cellular Networks, Abdurrahman Fouda

FIU Electronic Theses and Dissertations

An integrated access and backhaul (IAB) network architecture can enable flexible and fast deployment of next-generation cellular networks. However, mutual interference between access and backhaul links, small inter-site distance and spatial dynamics of user distribution pose major challenges in the practical deployment of IAB networks. To tackle these problems, we leverage the flying capabilities of unmanned aerial vehicles (UAVs) as hovering IAB-nodes and propose an interference management algorithm to maximize the overall sum rate of the IAB network. In particular, we jointly optimize the user and base station associations, the downlink power allocations for access and backhaul transmissions, and the …

Reduction Of Pertechnetate From Off-Gas Condensate Using Aged Zero-Valent Iron As A Reducing Agent, Abraham T. Gebru

FIU Electronic Theses and Dissertations

The Hanford site located in Washington State was one of the major nuclear processing facilities in the U.S. where plutonium was produced between the 1940s and the 1980’s. As a result of this forty yearlong production, approximately 53 million gallons of radioactive waste was generated and currently stored in 177 single and double shelled underground tanks. There were around 60 major and minor leaking incidents in the tanks through the years. These leaking incidents were wakeup calls to a search for an effective long term disposal solution. This paper will concentrate on the low activity waste (LAW), specifically the radioactive …

Non-Intrusive Affective Assessment In The Circumplex Model From Pupil Diameter And Facial Expression Monitoring, Sudarat Tangnimitchok

FIU Electronic Theses and Dissertations

Automatic methods for affective assessment seek to enable computer systems to recognize the affective state of their users. This dissertation proposes a system that uses non-intrusive measurements of the user’s pupil diameter and facial expression to characterize his /her affective state in the Circumplex Model of Affect. This affective characterization is achieved by estimating the affective arousal and valence of the user’s affective state.

In the proposed system the pupil diameter signal is obtained from a desktop eye gaze tracker, while the face expression components, called Facial Animation Parameters (FAPs) are obtained from a Microsoft Kinect module, which also captures …

Abc Closure Joints: Detailing, Design And Service Life, Azadeh Jaberi Jahromi

FIU Electronic Theses and Dissertations

Accelerated Bridge Construction (ABC) is a paradigm change in delivering bridges, which significantly minimizes onsite construction, enhances the safety of the public and construction workers, and uses innovative materials and technologies that can increase the service life of bridges. The most widely used ABC technique utilizes prefabricated modular bridge deck elements; however, there are concerns regarding the structural performance and durability of cast-in-place joints between these elements. Because of the limited experimental data on closure joints, there is a lack of information helpful for detailing, design and service life of these joints. To address these concerns, research was conducted to …

Multiscale Model Of Cerebral Blood Flow Control: Application To Small Vessel Disease And Cortical Spreading Depression, Arash Moshkforoush

FIU Electronic Theses and Dissertations

An in-time delivery of oxygen-rich blood into areas of high metabolic demand is pivotal in proper functioning of the brain and neuronal health. This highly precise communication between neuronal activity and cerebral blood flow (CBF) is termed as neurovascular coupling (NVC) or functional hyperemia. NVC is disrupted in major pathological conditions including Alzheimer’s disease, dementia, small vessel pathologies (SVD) and cortical spreading depression. Despite the utmost importance of NVC, its underlying mechanisms are not fully understood. This dissertation presents a multiscale mathematical modeling framework for studying unresolved mechanisms of NVC with major focus on K⁺ ions as a mediator …

Boron Nitride Nanotube Reinforced Titanium Composite With Controlled Interfacial Reactions By Spark Plasma Sintering, Jenniffer Bustillos

FIU Electronic Theses and Dissertations

In this study, Boron Nitride Nanotube (BNNT) reinforced Titanium matrix composites are synthesized by Spark Plasma Sintering. Two main challenges directly affecting the mechanical performance of BNNT-metal matrix composites are addressed:(i) Homogenous dispersion of high surface energy BNNTs, and (ii) Controlling interfacial reactions at the metal/nanotube interface. High-energy ultrasonication induced dispersion resulted in the functionalization of BNNTs by -OH radicals proving its suitability over surfactant assisted dispersion routes. The sintering of Ti (99% relative density) was achieved at 50% less processing temperature than those used in conventional sintering to minimize interfacial reactions when reinforced with BNNTs. The reduction of temperatures …

Spark Plasma Sintering Of 2d Nitride And Carbide Based Ceramics, Archana Loganathan

FIU Electronic Theses and Dissertations

Two-dimensional (2D) nanomaterials have stimulated significant interest among materials community due to a wide variety of application ranging from functional to structural properties. Boron nitride nanosheets (BNNS), boron-carbon-nitride (BCN), and MXene (M_n+1X_n, transition metal carbides, nitrides or carbonitrides) belongs to 2D materials family with van der Waals bonding between the layers. The research on synthesis and properties of BNNS, BCN and MXene have been predominantly explored for single- or multi-layered 2D nanosheets. In this study, the focus is to synthesize bulk layered BNNS and BCN using single or multilayered 2D nanomaterials by spark plasma sintering (SPS). …

Dynamics Of Falling Droplet Under Effects Of Electric Fields, Esmaiil Ghasemisahebi

FIU Electronic Theses and Dissertations

Physical properties and especially the size of drops are important parameters in many industrial and medical applications. High voltage electric field is one of the effective means to control the final size of drops during the fabrication process which could greatly influence the final size of the product. Therefore a detailed study of electric field effect on a liquid drop is very important. In this work deformation and fragmentation of a falling droplet under gravity and electric force have been studied numerically. The electric force is used as an effective external controlling mechanism to influence the deformation of a drop. …

A Computational Approach For Modeling Plasma Sprayed Coatings From Splat To Bulk Deposits, Sadhana Bhusal

FIU Electronic Theses and Dissertations

In this study, a multi-pronged computational approach is developed to predict the effect of spray parameters on aluminum oxide splat formation and mechanical properties of the coatings. The splat morphology is investigated using computational fluid dynamics approach. Simulated splat morphologies show a good agreement with the experimentally obtained splats. Three-dimensional coating structure is constructed using the stochastic approach using simulated splat morphologies. Finite Element Analysis is used to compute the elastic modulus of the coating. An inter-splat correction factor is introduced which considers inter-splat cracks, interface bonding and other effects like curling of splats and splat sliding. After the correction …

Retrofitting Of Bridge Elements Subjected To Predominantly Axial Load Using Uhpc Shell, Mahsa Farzad

FIU Electronic Theses and Dissertations

In the United States, ~30% of the ~600,000 highway bridges are categorized as structurally deficient or functionally obsolete. These bridges should be replaced or upgraded to sustain the transportation needs of the growing public and private sectors of the U.S. economy. It is not uncommon for structures to have advanced levels of corrosion-induced damage where major repair and maintenance works are required. However, the transportation infrastructure may undergo disruption during rehabilitation causing interruption to critical economic public, civil and commercial activities. This mandates the development of new techniques and materials for accelerated rehabilitation and resilience. To address this issue, a …

Construction Workers' Health And Safety During Post Disaster Reconstruction Phase: A Case Study In Nepal, S M Jamil Uddin

FIU Electronic Theses and Dissertations

The understanding of the concept of construction workers’ health and safety during the post-disaster reconstruction (PDR) phase is still unexplored. The objective of this study is to identify a knowledge gap in the literature through systematic literature review and to find out factors that affect the health and safety of the workers during PDR. To achieve the objectives, in-depth semi-structured interviews are conducted with different stakeholders such as Owners, General Contractors, Government Officials, Safety Supervisors, Engineers and Construction Workers in the context of Nepal Earthquake 2015. Interviews are conducted in a way that the respondents represent a wide range of …

Control And Optimization Of Energy Storage In Ac And Dc Power Grids, Samy Mohamed

FIU Electronic Theses and Dissertations

Energy storage attracts attention nowadays due to the critical role it will play in the power generation and transportation sectors. Electric vehicles, as moving energy storage, are going to play a key role in the terrestrial transportation sector and help reduce greenhouse emissions. Bulk hybrid energy storage will play another critical role for feeding the new types of pulsed loads on ship power systems. However, to ensure the successful adoption of energy storage, there is a need to control and optimize the charging/discharging process, taking into consideration the customer preferences and the technical aspects. In this dissertation, novel control and …

A Constructal Approach To The Design Of Inflected Airplane Wings, Shanae Powell

FIU Electronic Theses and Dissertations

Aeroelastic instabilities such as flutter can be accurately captured by state-of-the-art aeroelastic analysis methods and tools. However, these tools and methods fall short in exposing the reasons behind the occurrence of such instabilities. In this research, the constructal law is used to discover the main cause of the variation in the flutter speed and stress distribution for inflected aircraft wings when compared to its uninflected counterpart. This law considers the design as a physics phenomenon and uses an evolutionary flow principle to explain and predict the occurrence of energy flow configurations (i.e. the flow of stresses throughout the structure).

For …

Nanoparticle-Based Spintronic Computer Logic Switch, Kevin Luongo

FIU Electronic Theses and Dissertations

Spintronics is a rapidly growing research field due to scalability, integrablility within existing VLSI architecture, significantly reduced switching energy and latency while maintaining stable bit orientation (Spin-up, Spin-down). For the first time sub-5nm Spin Transfer Torque –Magnetic Tunneling Junctions (STT-MTJ) were investigated utilizing various Integrated Circuit (IC) fabrication techniques to evaluate novel concepts in logic switches.

Tunneling Magnetoresistance (TMR) was measured in STT-MTJ stacks of Ta/CoFeB/MgO/CoFeB/Ta with differing diameter ferrimagnetic CoFe2O4 nanoparticles (10nm, 4nm and 2nm) embedded in the MgO layer. MR was detected in the 2nm and 4nm particle devices and demonstrated evidence of single electron transport.

Tri-layer STT-MTJ …

Cloud Workload Allocation Approaches For Quality Of Service Guarantee And Cybersecurity Risk Management, Soamar Homsi

FIU Electronic Theses and Dissertations

It has become a dominant trend in industry to adopt cloud computing --thanks to its unique advantages in flexibility, scalability, elasticity and cost efficiency -- for providing online cloud services over the Internet using large-scale data centers. In the meantime, the relentless increase in demand for affordable and high-quality cloud-based services, for individuals and businesses, has led to tremendously high power consumption and operating expense and thus has posed pressing challenges on cloud service providers in finding efficient resource allocation policies.

Allowing several services or Virtual Machines (VMs) to commonly share the cloud's infrastructure enables cloud providers to optimize resource …

Study Of Charge Carrier Transport In Graphene And Graphite As Two Dimensional And Quasi-Two Dimensional Materials And Their Interfaces, Nalat Sornkhampan

FIU Electronic Theses and Dissertations

Evidence of superconductivity in phosphorous-doped graphite and graphene has been observed at temperatures in the vicinity of 260 K. This evidence includes transport current, magnetic susceptibility, Hall and Nernst measurements. All of these measurements indicate a transition of a type II superconductor without a phase of type I until below the limits of the measurement capabilities.

Vortex states are inferred from periodically repeated steps in the R vs. T characteristics of Highly Oriented Pyrolytic Graphite and exfoliated doped multilayer graphene. The presence of vortices has been confirmed with thermal gradient driven Nernst measurements. Magnetic susceptibility measurements have shown results qualitatively …

Project Performance Rating Model And Ipd Implementation Guideline Metric For Water And Wastewater Treatment Plant Projects, Elie G. Andary

FIU Electronic Theses and Dissertations

The public nature of water and wastewater construction capital projects has rendered Design-Bid-Build (DBB) as the delivery method of choice for such projects over the past years. Shortcomings inherent to DBB have had a negative effect on the Key Performance Indicators (KPIs) of these projects. Numerous studies have argued that Integrated Project Delivery (IPD) improves the delivery performance of DBB projects. Project delivery performance is, however, a complex concept that is not easily measured. It involves several criteria with many factors that need to be accounted for. Water and wastewater construction projects do not have well-established overall performance rating models, …

Mesoscale Ceramic Cylindrical Ion Trap Mass Analyzers For In Situ Sample Analysis, Patrick Roman

FIU Electronic Theses and Dissertations

As wireless network devices and IOT connectivity develop, the application and demand for small, low power, in situ sensors and instruments will expand. There are continuous efforts in the miniaturization of sensors and scientific instrument systems for conventional to field deployable and rugged hand held units for personal use to extreme harsh environment applications. This work investigates mesoscale cylindrical ion trap (CIT) mass analyzer design and the benefits of CITs realized via additive manufactured metalized ceramic material systems for improved ion signal, low power performance, and extended dynamic range. Rugged monolithic miniature mass spectrometer ceramic CIT chips have been produced …

The Effect Of Proteome And Lipidome On The Behavior Of Membrane Bound Systems In Thermally-Assisted Acoustophoresis, Elnaz Mirtaheri

FIU Electronic Theses and Dissertations

Changes in the biomechanical properties of cells accompanying the development of various pathological conditions have been increasingly reported as biomarkers for various diseases, including cancers. In cancer cells, the membrane properties have been altered compared to their healthy counterparts primarily due to proteomic and lipidomic dysregulations conferred by the underlying pathology. The separation and selective recovery of these cells or extracellular vesicles secreted from such cells is of high diagnostic and prognostic value.

In this dissertation, the research builds on thermally-assisted acoustophoresis technique which was developed in our laboratory for the separation of vesicles of the same size, charge and …

Context-Aware Personalized Point-Of-Interest Recommendation System, Ramesh Raj Baral

FIU Electronic Theses and Dissertations

The increasing volume of information has created overwhelming challenges to extract the relevant items manually. Fortunately, the online systems, such as e-commerce (e.g., Amazon), location-based social networks (LBSNs) (e.g., Facebook) among many others have the ability to track end users' browsing and consumption experiences. Such explicit experiences (e.g., ratings) and many implicit contexts (e.g., social, spatial, temporal, and categorical) are useful in preference elicitation and recommendation. As an emerging branch of information filtering, the recommendation systems are already popular in many domains, such as movies (e.g., YouTube), music (e.g., Pandora), and Point-of-Interest (POI) (e.g., Yelp).

The POI domain has many …

Numerical Simulation Of Flushing Deposits In Pipelines, Joseph S. Coverston

FIU Electronic Theses and Dissertations

The purpose of this research is to reduce the amount of waste generated in Department of Energy nuclear cleanup efforts currently underway. Due to the highly radioactive nature of the waste, any fluid that contacts the waste must then be treated and processed as waste. To minimize the fluids contaminated during flushing, this research aims to provide a basis for the flushing of High Level Waste (HLW) pipelines. Edgar Plastic Kaolin (EPK) with solid particles of a nominal diameter of 1 micron was used as a simulacrum for HLW. An Eulerian-Eulerian simulation built in StarCCM+ software, with a k-ω turbulence …