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2014

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Articles 1831 - 1860 of 7239

Full-Text Articles in Engineering

Integrating Visual Mnemonics And Input Feedback With Passphrases To Improve The Usability And Security Of Digital Authentication, Kevin Juang Aug 2014

Integrating Visual Mnemonics And Input Feedback With Passphrases To Improve The Usability And Security Of Digital Authentication, Kevin Juang

All Dissertations

The need for both usable and secure authentication is more pronounced than ever before. Security researchers and professionals will need to have a deep understanding of human factors to address these issues. Due to their ubiquity, recoverability, and low barrier of entry, passwords remain the most common means of digital authentication. However, fundamental human nature dictates that it is exceedingly difficult for people to generate secure passwords on their own. System-generated random passwords can be secure but are often unusable, which is why most passwords are still created by humans. We developed a simple system for automatically generating mnemonic phrases …

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Optical Forces In Nanophotonic Structures, Chenguang Huang Aug 2014

Optical Forces In Nanophotonic Structures, Chenguang Huang

All Dissertations

Nowadays, optical forces are widely used to control or measure the position of micrometer- to nanometer-sized particles, such as living cells, DNA and bacteria. Two major categories of optical forces are discussed here: gradient or dipole force and scattering force. The gradient force is originated from the fact that a polarizable micro-particle placed in a laterally varying optical field will experience different forces in the positively and negatively charged sides. In this thesis, we investigate the optical gradient force in 2D hybrid and plasmonic waveguides. Compared to the conventional dielectric waveguides, we show that the optical force can be enhanced …

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Predictive Model Development For Adsorption Of Organic Contaminants By Carbon Nanotubes, Onur Apul Aug 2014

Predictive Model Development For Adsorption Of Organic Contaminants By Carbon Nanotubes, Onur Apul

All Dissertations

The main objective of the study was to investigate mechanisms and statistical modeling of synthetic organic contaminant (SOC) adsorption by carbon nanotubes (CNTs). First, predictive models were developed for adsorption of low molecular weight aromatic compounds by multi-walled carbon nanotubes (MWCNTs) using experimental data for 59 compounds. Quantitative structure-activity relationship (QSAR) and linear solvation energy relationship (LSER) approaches were employed and developed models were externally validated using an independent dataset obtained from the literature. Up to date, no QSAR model has been reported for predicting adsorption of organics by CNTs. No LSER model is available which comprehensively investigates the adsorption …

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Synthesis And Characterization Of Nanoscale Polymer Films Grafted To Metal Surfaces, Yuriy Galabura Aug 2014

Synthesis And Characterization Of Nanoscale Polymer Films Grafted To Metal Surfaces, Yuriy Galabura

All Dissertations

Anchoring thin polymer films to metal surfaces allows us to alter, tune, and control their biocompatibility, lubrication, friction, wettability, and adhesion, while the unique properties of the underlying metallic substrates, such as magnetism and electrical conductivity, remain unaltered. This polymer/metal synergy creates significant opportunities to develop new hybrid platforms for a number of devices, actuators, and sensors. This present work focused on the synthesis and characterization of polymer layers grafted to the surface of metal objects. We report the development of a novel method for surface functionalization of arrays of high aspect ratio nickel nanowires/micronails. The polymer 'grafting to' technique …

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Projections Of Future Us Design Wind Speeds Due To Climate Change For Estimating Hurricane Losses, Fangqian Liu Aug 2014

Projections Of Future Us Design Wind Speeds Due To Climate Change For Estimating Hurricane Losses, Fangqian Liu

All Dissertations

Hurricane is among the most dangerous and costliest natural hazards that affect the coastal environment of the United States (U.S.) every year. Hurricane activities have been observed to change in many aspects since the last century including the changes in both intensity and annual storm frequency. The extent to which aspect of climate change contributes to the variation in hurricane activities from long-term historical statistics is still not clearly understood at this point. This study examines the impacts of two climate change effects (change in annual storm frequency and sea surface temperature) on future U.S. design wind speeds for the …

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Investigation Of Concurrent Energy Harvesting From Ambient Vibrations And Wind, Amin Bibo Aug 2014

Investigation Of Concurrent Energy Harvesting From Ambient Vibrations And Wind, Amin Bibo

All Dissertations

In recent years, many new concepts for micro-power generation have been introduced to harness wasted energy from the environment and maintain low-power electronics including wireless sensors, data transmitters, controllers, and medical implants. Generally, such systems aim to provide a cheap and compact alternative energy source for applications where battery charging or replacement is expensive, time consuming, and/or cumbersome. Within the vast field of micro-power generation, utilizing the piezoelectric effect to generate an electric potential in response to mechanical stimuli has recently flourished as a major thrust area. Based on the nature of the ambient excitation, piezoelectric energy harvesters are divided …

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Towards Efficient File Sharing And Packet Routing In Mobile Opportunistic Networks, Kang Chen Aug 2014

Towards Efficient File Sharing And Packet Routing In Mobile Opportunistic Networks, Kang Chen

All Dissertations

With the increasing popularity of portable digital devices (e.g., smartphones, laptops, and tablets), mobile opportunistic networks (MONs) [40, 90] consisting of portable devices have attracted much attention recently. MONs are also known as pocket switched networks (PSNs) [52]. MONs can be regarded as a special form of mobile ad hoc networks (MANETs) [7] or delay tolerant networks (DTNs) [35, 56]. In such networks, mobile nodes (devices) move continuously and meet opportunistically. Two mobile nodes can communicate with each other only when they are within the communication range of each other in a peer-to-peer (P2P) manner (i.e., without the need of …

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The Effects Of Amine Structure, Chloramine Species And Oxidation Strategies On The Formation Of N-Nitrosodimethylamine, Meric Selbes Aug 2014

The Effects Of Amine Structure, Chloramine Species And Oxidation Strategies On The Formation Of N-Nitrosodimethylamine, Meric Selbes

All Dissertations

To comply with the increasingly stringent disinfection by-product (DBP) regulations in the United States, many water treatment plants have been switching from chlorination to chloramination in the last decade. Although chloramination reduces the formation of regulated DBPs such as trihalomethanes and haloacetic acids, it causes the formation of nitrosamines. Nitrosamines are a class of compounds that are probable human carcinogens, mutagens and teratogens at concentrations as low as 0.2 ng/L. In particular, N-nitrosodimethylamine (NDMA) is the most frequently detected nitrosamine in distribution systems in the United States. Although, nitrosamines are currently not regulated by the USEPA, they have been recently …

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Advanced Bulk Processing Of Lightweight Materials For Utilization In The Transportation Sector, Justin Milner Aug 2014

Advanced Bulk Processing Of Lightweight Materials For Utilization In The Transportation Sector, Justin Milner

All Dissertations

The overall objective of this research is to develop the microstructure of metallic lightweight materials via multiple advanced processing techniques with potentials for industrial utilization on a large scale to meet the demands of the aerospace and automotive sectors. This work focused on (i) refining the grain structure to increase the strength, (ii) controlling the texture to increase formability and (iii) directly reducing processing/production cost of lightweight material components. Advanced processing is conducted on a bulk scale by several severe plastic deformation techniques including: accumulative roll bonding, isolated shear rolling and friction stir processing to achieve the multiple targets of …

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Unified Dynamics And Control Of A Robot Manipulator Mounted On A Vtol Aircraft Platform, Peng Xu Aug 2014

Unified Dynamics And Control Of A Robot Manipulator Mounted On A Vtol Aircraft Platform, Peng Xu

All Dissertations

An innovative type of mobile manipulator, designated Manipulator on VTOL (Vertical Take-Off and Landing) Aircraft (MOVA), is proposed as a potential candidate for autonomous execution of field work in less-structured indoor and outdoor environments. Practical use of the MOVA system requires a unified controller that addresses the coupled and complex dynamics of the composite system; especially the interaction of the robotic manipulator with the aircraft airframe. Model-based controller design methods require explicit dynamics models of the MOVA system. Preliminary investigation of a two-dimensional MOVA system toward a dynamics model and controller design is presented in preparation for developing the controller …

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Microfluidic Particle And Cell Manipulation Using Reservoir-Based Dielectrophoresis, Saurin Patel Aug 2014

Microfluidic Particle And Cell Manipulation Using Reservoir-Based Dielectrophoresis, Saurin Patel

All Dissertations

Controlled manipulation of synthetic particles and biological cells from a complex mixture is important to a wide range of applications in biology, environmental monitoring, and pharmaceutical industry. In the past two decades microfluidics has evolved to be a very useful tool for particle and cell manipulations in miniaturized devices. A variety of force fields have been demonstrated to control particle and cell motions in microfluidic devices, among which electrokinetic techniques are most often used. However, to date, studies of electrokinetic transport phenomena have been primarily confined within the area of microchannels. Very few works have addressed the electrokinetic particle motion …

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Electrostatic And Electrical Transport Analysis Of Nanomaterials And Numerical Methods Development, Hua Li Aug 2014

Electrostatic And Electrical Transport Analysis Of Nanomaterials And Numerical Methods Development, Hua Li

All Dissertations

The nanotechnology today is continuously boosting the application of nanostructured materials in the development and innovation of electronic devices, such as Nano &ndash Electromechanical Systems (NEMS), electrical transistors, thermoelectric devices, and solar cells. Due to the size miniaturization, quantum mechanical effects play important roles in the performance of such devices. To correctly capture the quantum mechanical effects and understand how these effects influence the electrostatic and electrical transport properties of nanomaterials, efficient and accurate computational models are highly desirable. Currently, the commonly used model for electrostatic analysis of nanoscale devices is based on self &ndash consistent solution of the effective …

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Fluid Mud Gravity Currents Through Emergent Aquatic Vegetation, Nazli Yilmaz Aug 2014

Fluid Mud Gravity Currents Through Emergent Aquatic Vegetation, Nazli Yilmaz

All Dissertations

In this theoretical and experimental investigation, the propagation dynamics of the fluid-mud underflows form in pipeline dredge disposal operations in the designated areas are studied. These areas such as wetlands, nearshore waters are typically covered with stiff, cylindrical, emergent aquatic vegetation. The main goals of this study are to propose mathematical formulations for the bottom shear force and drag force of emergent stiff aquatic vegetation acting on the gravity current, and to present novel propagation modeling approaches. To be able to predict these forces, a friction coefficient (for the bottom shear force), and a drag coefficient (for vegetation skin friction …

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A Biophysical Understanding Of The Applications And Implications Of Nanomaterials, Nicholas Geitner Aug 2014

A Biophysical Understanding Of The Applications And Implications Of Nanomaterials, Nicholas Geitner

All Dissertations

The last few decades have seen an explosion in the study and application of nanomaterials that continues to grow at a dizzying pace. Despite exciting applications in nano-enabled electronics, materials, medicine, and environmental remediation, an understanding of the interactions of these materials with natural materials and systems and the resulting implications lags severely behind. The purpose of this Dissertation is to illuminate these interactions as well as develop novel environmental applications from a biophysical perspective. Following an introduction and literature review in Chapter 1, Chapters 2-4 will explore the application of dendritic polymers as novel and biocompatible oil dispersants for …

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Two-Stage Methodology For Managing And Controlling Material Flow Between Multiple Construction Projects, Fatmah Almazkoor Aug 2014

Two-Stage Methodology For Managing And Controlling Material Flow Between Multiple Construction Projects, Fatmah Almazkoor

All Dissertations

There is a strong connection between managing and controlling material flow in a supply chain and its performance. While this is true in all supply chains, it is particularly true in the construction supply chain (CSC) where the total demand for parts is finite, the storage space available can be small, and the variability in consumption is high. On the other hand, effectively controlling the CSC can have a significant impact on controlling risk and buffering their impact so that projects stay on schedule and within budget. Currently, a common control of the CSC is with a push-based material ordering …

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Effect Of Silicone Finishes On The Burning Behavior Of Polyester, Julien Boyon Aug 2014

Effect Of Silicone Finishes On The Burning Behavior Of Polyester, Julien Boyon

All Dissertations

Polyester fibers are widely used as filling in home applications such as pillows or comforters. Silicone finishes can be used to reduce friction between fibers during processing or as softeners to impart a pleasant down like hand on the fibers. However, it has been reported that these added silicone-based finishes may have a negative effect on the burning behavior of polyester. This research examined the possible mechanisms that can modify the response of polyester fibers when subjected to a flame source. In this study, a spunbond needled polyester nonwoven substrate was treated with different commercial silicone-based finishes. A vertical flame …

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A Decision Support Model For Process Planning In Remanufacturing Using Fuzzy Set Theory And Genetic Algorithm, Juan C. Martinez Aug 2014

A Decision Support Model For Process Planning In Remanufacturing Using Fuzzy Set Theory And Genetic Algorithm, Juan C. Martinez

Theses and Dissertations - UTB/UTPA

The environmental awareness and resources preservation has boosted the use of remanufacturing processes. Many important studies have been made in this area, but there are still pitfalls and opportunities that have not been explored yet. Specifically, the cleaning processes play a critical role in remanufacturing. It is among the top of most costly processes and it plays a key step in remanufacturing because delivers a free of contaminant product ready for reprocessing. Understanding and selecting the best processes to meet the need and goals of remanufacturers are important for effective and efficient remanufacturing. Due to variables and high uncertainty associated …

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A Study Comparing The Pedagogical Effectiveness Of Virtual Worlds And Of Traditional Training Methods, Benjamin Peters Aug 2014

A Study Comparing The Pedagogical Effectiveness Of Virtual Worlds And Of Traditional Training Methods, Benjamin Peters

Theses and Dissertations - UTB/UTPA

This experiment tests whether a virtual world is a more suitable alternative to classical paper and pen case studies for teaching people how to disarm improvised explosive devices (IED). Following preliminary training, the subjects are separated into a group of 32 and one of 33. The odd-numbered subjects receive case studies while the even-numbered subjects receive training in the virtual world, Second Life. After their training, each subject is put into a simulated test where they attempt to properly disarm a mock IED attached to a victim played by an actor/actress. The results of the experiment show no significant difference …

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Evaluation And Flight Assessment Of A Scale Glider, Alvydas Anthony Civinskas Aug 2014

Evaluation And Flight Assessment Of A Scale Glider, Alvydas Anthony Civinskas

Doctoral Dissertations and Master's Theses

The objective of this project is to do a flight assessment of a Phoenix K8B radio controlled glider to see what process is needed to verify its glide slope and stability characteristics. The flight test analysis, plus a computational fluid dynamics analysis, and an industry-like component build-up aerodynamic analysis were done to provide comparable estimates for the aircraft glide slope. A stability and control derivative analysis was also completed and compared using SURFACES, USAF Datcom, and MIT AVL software. The glide slope estimate and stability and control derivatives obtained from flight test data showed considerable range and uncertainty. Potential sources …

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Execution Of A Hybrid Vehicle Controls Development Effort Utilizing Model-Based Design, Hardware-In-The-Loop Testing, Agile Scrum Methods And Requirements Engineering, Derek Simon Bonderczuk Aug 2014

Execution Of A Hybrid Vehicle Controls Development Effort Utilizing Model-Based Design, Hardware-In-The-Loop Testing, Agile Scrum Methods And Requirements Engineering, Derek Simon Bonderczuk

Doctoral Dissertations and Master's Theses

Modern hybrid vehicles require sophisticated supervisory control systems in order to realize competitive efficiency gains. Processes such as model-based design, HIL simulation and Agile Scrum methods can allow for quicker and less costly development of a complex product. The design of a supervisory control system for a prototype PHEV vehicle was executed with the intent of developing a mule vehicle into a 99% production ready vehicle. The control system design process was carried through from requirements definition to operating parameter optimization of utilizing model-based design, HIL simulation and the Scrum model. A prototype vehicle that has a fully functioning hybrid …

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Investigation Of Traditional And Alternate Living Hinge Designs For Fused Deposition Modeling Additive Manufacturing Process, Cassandra Sue Gribbins Aug 2014

Investigation Of Traditional And Alternate Living Hinge Designs For Fused Deposition Modeling Additive Manufacturing Process, Cassandra Sue Gribbins

Doctoral Dissertations and Master's Theses

A manuscript-style thesis composed of three studies covered the application of living hinge designs in the additive manufacturing process of fused deposition modeling. Initial research included comparing numerical and analytical linear analyses on a traditional living hinge design. The second research consisted of tensile testing for the material properties of the Acrylonitrile Butadiene Styrene (ABS) used in fused deposition modeling (FDM) process by the MakerBot 2X as well as adjusting the traditional design to be printed. The third study explored alternate living hinge designs that utilize the geometric freedom provided by additive manufacturing to more evenly distribute stress across the …

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Unsteady Viscous Cavity Flow Using Computational Fluid Dynamics, Chandramouli Vadlamudi Aug 2014

Unsteady Viscous Cavity Flow Using Computational Fluid Dynamics, Chandramouli Vadlamudi

Doctoral Dissertations and Master's Theses

The problem of unsteady viscous incompressible flow in a two-dimensional cavity is treated using the unsteady incompressible Navier-Stokes equations with various initial and boundary conditions. First the case of a square cavity with one inlet and one outlet is treated in steady and unsteady flows. The software package ANSYS FLUENT was used in the CFD simulations. This approach captures the appearance of separation bubbles and vortex formation inside the cavity. Steady state flows are also obtained from the unsteady simulations after convergence of the time dependent solutions. Then the case of a cavity with a synthetic jet and two outlets …

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Software Porting Of A 3d Reconstruction Algorithm To Razorcam Embedded System On Chip, Kevin Curtis Gunn Aug 2014

Software Porting Of A 3d Reconstruction Algorithm To Razorcam Embedded System On Chip, Kevin Curtis Gunn

Graduate Theses and Dissertations

A method is presented to calculate depth information for a UAV navigation system from Keypoints in two consecutive image frames using a monocular camera sensor as input and the OpenCV library. This method was first implemented in software and run on a general-purpose Intel CPU, then ported to the RazorCam Embedded Smart-Camera System and run on an ARM CPU onboard the Xilinx Zynq-7000. The results of performance and accuracy testing of the software implementation are then shown and analyzed, demonstrating a successful port of the software to the RazorCam embedded system on chip that could potentially be used onboard a …

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Application Of Membrane Processes For Concentration And Separation Of Sugar Streams In Biofuel Production, Mohammadmahdi Malmali Aug 2014

Application Of Membrane Processes For Concentration And Separation Of Sugar Streams In Biofuel Production, Mohammadmahdi Malmali

Graduate Theses and Dissertations

The overall objective of this study was identification and development of a sugar concentration/separation membrane filtration unit to improve the bioconversion of lignocellulosic biomass into chemicals and fuels. This thesis is divided into three main parts. The first part is about our studies on the use of nanofiltration membranes for concentration of sugars in a lignocellulosic biomass hydrolysate. In addition, the feasibility of simultaneous removal of acetic acid, 5-(hydroxymethyl)furfural and furfural from the hydrolysate has also been investigated. The results obtained indicate that both concentration of sugars and removal of hydrolysis degradation products is feasible. However, careful selection of the …

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Characterizing Nanoparticle Size By Dynamic Light Scattering Technique (Dls), Marzia Zaman Aug 2014

Characterizing Nanoparticle Size By Dynamic Light Scattering Technique (Dls), Marzia Zaman

Graduate Theses and Dissertations

The Dynamic Light Scattering Technique was used to determine the size, shape and diffusion coefficient of nanoparticle. The intensity auto correlation functions of light scattered by particles in a solution were measured by using a photomultiplier tube and analyzed to get the relaxation rates for decay of intensity correlations, which correspond to the diffusion constants pertaining to the motion of the particle. In the case of nanorods there are two types of motion - translational and rotational. By dis-entangling the relaxation rates, corresponding to these two types of motion, the shape and size of nanoparticle could be characterized. These experiments, …

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An Empirical Study Of Off-Line Configuration And On-Line Adaptation In Operator Selection, Zhi Yuan, Stephanus Daniel Handoko, Duc Thien Nguyen, Hoong Chuin Lau Aug 2014

An Empirical Study Of Off-Line Configuration And On-Line Adaptation In Operator Selection, Zhi Yuan, Stephanus Daniel Handoko, Duc Thien Nguyen, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

Automating the process of finding good parameter settings is important in the design of high-performing algorithms. These automatic processes can generally be categorized into off-line and on-line methods. Off-line configuration consists in learning and selecting the best setting in a training phase, and usually fixes it while solving an instance. On-line adaptation methods on the contrary vary the parameter setting adaptively during each algorithm run. In this work, we provide an empirical study of both approaches on the operator selection problem, explore the possibility of varying parameter value by a non-adaptive distribution tuned off-line, and incorporate the off-line with on-line …

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Diversity-Oriented Bi-Objective Hyper-Heuristics For Patrol Scheduling, Mustafa Misir, Hoong Chuin Lau Aug 2014

Diversity-Oriented Bi-Objective Hyper-Heuristics For Patrol Scheduling, Mustafa Misir, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

The patrol scheduling problem is concerned with assigning security teams to different stations for distinct time intervals while respecting a limited number of contractual constraints. The objective is to minimise the total distance travelled while maximising the coverage of the stations with respect to their security requirement levels. This paper introduces a hyper-heuristic strategy focusing on generating diverse solutions for a bi-objective patrol scheduling problem. While a variety of hyper-heuristics have been applied to a large suite of problem domains usually in the form of single-objective optimisation, we suggest an alternative approach for solving the patrol scheduling problem with two …

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Hybrid Metaheuristics For Solving The Quadratic Assignment Problem And The Generalized Quadratic Assignment Problem, Aldy Gunawan, Kien Ming Ng, Kim Leng Poh, Hoong Chuin Lau Aug 2014

Hybrid Metaheuristics For Solving The Quadratic Assignment Problem And The Generalized Quadratic Assignment Problem, Aldy Gunawan, Kien Ming Ng, Kim Leng Poh, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

This paper presents a hybrid metaheuristic for solving the Quadratic Assignment Problem (QAP). The proposed algorithm involves using the Greedy Randomized Adaptive Search Procedure (GRASP) to construct an initial solution, and then using a hybrid Simulated Annealing and Tabu Search (SA-TS) algorithm to further improve the solution. Experimental results show that the hybrid metaheuristic is able to obtain good quality solutions for QAPLIB test problems within reasonable computation time. The proposed algorithm is extended to solve the Generalized Quadratic Assignment Problem (GQAP), with an emphasis on modelling and solving a practical problem, namely an examination timetabling problem. We found that …

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A Mathematical Model And Metaheuristics For Time Dependent Orienteering Problem, Aldy Gunawan, Zhi Yuan, Hoong Chuin Lau Aug 2014

A Mathematical Model And Metaheuristics For Time Dependent Orienteering Problem, Aldy Gunawan, Zhi Yuan, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

This paper presents a generalization of the Orienteering Problem, the Time-Dependent Orienteering Problem (TDOP) which is based on the real-life application of providing automatic tour guidance to a large leisure facility such as a theme park. In this problem, the travel time between two nodes depends on the time when the trip starts. We formulate the problem as an integer linear programming (ILP) model. We then develop various heuristics in a step by step fashion: greedy construction, local search and variable neighborhood descent, and two versions of iterated local search. The proposed metaheuristics were tested on modified benchmark instances, randomly …

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Hydraulic Fracturing Water Recycle Through Optimal Ultrafiltration And Nanofiltration Membranes System Design, Long Tran Aug 2014

Hydraulic Fracturing Water Recycle Through Optimal Ultrafiltration And Nanofiltration Membranes System Design, Long Tran

Graduate Theses and Dissertations

Innovations in hydraulic fracturing technology have created opportunities for petroleum and natural gas production. This technology injects water, sand, and additives to create fissures in rock formations and discharge oil and gas to the surface. The average amount of water used per well is approximately 4.4 million gallons. The large water demand and the complexities involved in wastewater treatment make this process very expensive and not sustainable as far as water use is concerned. Flexible membrane technology has not been developed to process fracking water for re-use across the U.S. The objective of this project is to compare and analyze …

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