Engineering Commons^™

Material Characterization And Computational Simulation Of Steel Foam For Use In Structural Applications, Brooks H. Smith

Masters Theses 1911 - February 2014

Cellular metals made from aluminum, titanium, or other metals are becoming increasingly popular for use in structural components of automobiles, aircraft, and orthopaedic implants. Civil engineering applications remain largely absent, primarily due to poor understanding of the material and its structural properties. However, the material features a high stiffness to weight ratio, excellent energy dissipation, and low thermal conductivity, suggesting that it could become a highly valuable new material in structural engineering. Previous attempts to characterize the mechanical properties of steel foam have focused almost exclusively upon uniaxial compression tests, both in experimental research and in computational simulations. Further, computational …

Critical Area Driven Dummy Fill Insertion To Improve Manufacturing Yield, Nishant Dhumane

Masters Theses 1911 - February 2014

Non-planar surface may cause incorrect transfer of patterns during lithography. In today’s IC manufacturing, chemical mechanical polishing (CMP) is used for topographical planarization. Since polish rates for metals and oxides are different, dummy metal fills in layout is used to minimize post-CMP thickness variability. Traditional metal fill solutions focus on satisfying density target determined by layout density analysis techniques. These solutions may potentially reduce yield by increasing probability of failure (POF) due to particulate defects and also impact design performance. Layout design solutions that minimize POF and also improve surface planarity via dummy fill insertions have competing requirements for line …

Scheduling Heuristics For Maximizing The Output Quality Of Iris Task Graphs In Multiprocessor Environment With Time And Energy Bounds, Rajeswaran Chockalingapuram Ravindran

Masters Theses 1911 - February 2014

Embedded real time applications are often subject to time and energy constraints. Real time applications are usually characterized by logically separable set of tasks with precedence constraints. The computational effort behind each of the task in the system is responsible for a physical functionality of the embedded system. In this work we mainly define theoretical models for relating the quality of the physical func- tionality to the computational load of the tasks and develop optimization problems to maximize the quality of the system subject to various constraints like time and energy. Specifically, the novelties in this work are three fold. …

Optimizing The Safety Stock Inventory Cost Under Target Service Level Constraints, Chetan T. Shivsharan

Masters Theses 1911 - February 2014

The level of customer satisfaction largely depends on manufacturer’s ability to respond to customer orders with promptness. The swiftness with which the manufacturers are able to meet customer demand is measured by the service level. There are two service level measures typically used. The first one is type 1 service level which denotes the probability of not stocking out over a planning period. The other is fill rate which denotes the proportion of demand satisfied with the existing inventory. We review the rich and diverse literature available on inventory cost optimization under these service level constraints. Subsequently two optimization models …

User Equilibrium In A Disrupted Network With Real-Time Information And Heterogeneous Risk Attitude, Ryan J. Pothering

Masters Theses 1911 - February 2014

The traffic network is subject to random disruptions, such as incidents, bad weather, or other drivers’ random behavior. A traveler’s route choice behavior in such a network is thus affected by the probabilities of such disruptions, his/her attitude towards risk, and real-time information on revealed traffic conditions that could potentially reduce the level of uncertainty due to the disruptions. As the road network’s performance is de-termined collectively by all travelers’ choices, it is also affected by these factors. This thesis features the development of a multi-class user equilibrium model based on hetero-geneous risk attitude distributions and a user equilibrium model …

Towards Logic Functions As The Device Using Spin Wave Functions Nanofabric, Prasad Shabadi

Masters Theses 1911 - February 2014

As CMOS technology scaling is fast approaching its fundamental limits, several new nano-electronic devices have been proposed as possible alternatives to MOSFETs. Research on emerging devices mainly focusses on improving the intrinsic characteristics of these single devices keeping the overall integration approach fairly conventional. However, due to high logic complexity and wiring requirements, the overall system-level power, performance and area do not scale proportional to that of individual devices.

Thereby, we propose a fundamental shift in mindset, to make the devices themselves more functional than simple switches. Our goal in this thesis is to develop a new nanoscale fabric paradigm …

A Combined Quadtree/Delaunay Method For 2d Mesh Generation, Simon Tang

Masters Theses 1911 - February 2014

Unstructured simplicial mesh is an integral and critical part of many computational electromagnetics methods (CEM) such as the finite element method (FEM) and the boundary element method (BEM). Mesh quality and robustness have direct impact on the success of these CEM methods.

A combined quadtree/Delunay 2D mesh generator, based on the early work of Schroeder (1991, PhD), is presented. The method produces a triangulation that approximates the original geometric model but is also topologically consistent. The key advantages of the method are: (a) its robustness, (b) ability to create a-priori graded meshes, and (c) its guaranteed mesh quality.

The method …

The Measurement Of Internal Temperature Anomalies In The Body Using Microwave Radiometry And Anatomical Information: Inference Methods And Error Models, Tamara V. Sobers

Masters Theses 1911 - February 2014

The ability to observe temperature variations inside the human body may help in detecting the presence of medical anomalies. Abnormal changes in physiological parameters (such as metabolic and blood perfusion rates) cause localized tissue temperature change. If the anatomical information of an observed tissue region is known, then a nominal temperature profile can be created using the nominal physiological parameters. Temperature-varying radiation emitted from the human body can be captured using microwave radiometry and compared to the expected radiation from nominal temperature profiles to detect anomalies. Microwave radiometry is a passive system with the ability to capture radiation from tissue …

Probabilistic Analysis Of Offshore Wind Turbine Soil-Structure Interaction, Wystan Carswell

Masters Theses 1911 - February 2014

A literature review of current design and analysis methods for offshore wind turbine (OWT) foundations is presented, focusing primarily on the monopile foundation. Laterally loaded monopile foundations are typically designed using the American Petroleum Institute (API) p-y method for offshore oil platforms, which presents several issues when extended to OWTs, mostly with respect to the large pile diameters required and the effect of cyclic loading from wind and waves. Although remedies have been proposed, none have been incorporated into current design standards. Foundations must be uniquely designed for each wind farm due to extreme dependence on site characteristics. The uncertainty …

Effect Of Slip On Flow Past Superhydrophobic Cylinders, Pranesh Muralidhar

Masters Theses 1911 - February 2014

Superhydrophobic surfaces are a class of surfaces that have a microscale roughness imposed on an already hydrophobic surface, akin to a lotus leaf. These surfaces have been shown to produce significant drag reduction for both laminar and turbulent flows of water through large and small-scale channels. The goal of this thesis was to explore how these surfaces alter the vortex shedding dynamics of a cylindrical body when coated on its surface, thus leading to an alteration in drag and lift on these surfaces. A cylindrical body was chosen as it is a very nice representative bluff body and sets the …

Torsional Shear Strength And Size Effect In Structural Composite Lumber, Zhuo Yang

Masters Theses 1911 - February 2014

The natural variation of strength properties within brittle materials leads to size effect, a well-known phenomenon whereby the mean strength of a material is observed to decrease as the stressed volume increases. An important implication of size effect is that size adjustment parameters must be incorporated into multi-axial constitutive and failure models used in numerical simulations to predict material response to loading. This experimental study seeks to verify and quantify the presence of depth effect under shear failure in the orthotropic principal material directions of parallel strand lumber (PSL) and laminated veneer lumber (LVL). Torsion tests have been performed on …

Evaluating And Modeling Traveler Response To Real-Time Information In The Pioneer Valley, Tyler De Ruiter

Masters Theses 1911 - February 2014

This study used focus groups and surveys to provide a comprehensive evaluation of the Regional Traveler Information Center (RTIC) at UMass Amherst. The evaluation was completed by obtaining the awareness, usage, and perceived effectiveness of RTIC’s information by residents in the Pioneer Valley. It was found that awareness of RTIC is limited due to its lack of advertisement. Usage is focused primarily on its webcams and advisory information. Surveys showed that participants perceive RTIC to be useful, even though they may never have seen the information before (the survey provided a chance for them to become familiar with the service). …

Reformulation Of The Muffin-Tin Problem In Electronic Structure Calculations Within The Feast Framework, Alan R. Levin

Masters Theses 1911 - February 2014

This thesis describes an accurate and scalable computational method designed to perform nanoelectronic structure calculations. Built around the FEAST framework, this method directly addresses the nonlinear eigenvalue problem. The new approach allows us to bypass traditional approximation techniques typically used for first-principle calculations. As a result, this method is able to take advantage of standard muffin-tin type domain decomposition techniques without being hindered by their perceived limitations. In addition to increased accuracy, this method also has the potential to take advantage of parallel processing for increased scalability.

The Introduction presents the motivation behind the proposed method and gives an overview …

Vibration Reduction Of Offshore Wind Turbines Using Tuned Liquid Column Dampers, Colin Roderick

Masters Theses 1911 - February 2014

Offshore wind turbines (OWTs) are becoming an accepted method for generating electricity. The environmental conditions of offshore locations often impose high wind and wave forces on OWTs making them susceptible to intense loading and undesirable vibrations. One method to reduce system vibrations is through the use of structural control devices typically utilized in civil structures. Tuned liquid column dampers (TLCDs) show great promise in the application to OWTs due to their high performance and low cost. This thesis examines the use of TLCDs in OWTs.

Equations of motion for limited degree-of-freedom TLCD-turbine models are presented. A baseline analysis of each …

Spatial And Temporal Correlations Of Freeway Link Speeds: An Empirical Study, Piotr J. Rachtan

Masters Theses 1911 - February 2014

Congestion on roadways and high level of uncertainty of traffic conditions are major considerations for trip planning. The purpose of this research is to investigate the characteristics and patterns of spatial and temporal correlations and also to detect other variables that affect correlation in a freeway setting. 5-minute speed aggregates from the Performance Measurement System (PeMS) database are obtained for two directions of an urban freeway – I-10 between Santa Monica and Los Angeles, California. Observations are for all non-holiday weekdays between January 1st and June 30th, 2010. Other variables include traffic flow, ramp locations, number of lanes and the …

Techniques For Detection Of Malicious Packet Drops In Networks, Vikram R. Desai

Masters Theses 1911 - February 2014

The introduction of programmability and dynamic protocol deployment in routers, there would be an increase in the potential vulnerabilities and attacks . The next- generation Internet promises to provide a fundamental shift in the underlying architecture to support dynamic deployment of network protocols. In this thesis, we consider the problem of detecting malicious packet drops in routers. Specifically, we focus on an attack scenario, where a router selectively drops packets destined for another node. Detecting such an attack is challenging since it requires differentiating malicious packet drops from congestion-based packet losses. We propose a controller- based malicious packet detection technique …

A Theoretical Approach To Fault Analysis And Mitigation In Nanoscale Fabrics, Md Muwyid Uzzaman Khan

Masters Theses 1911 - February 2014

High defect rates are associated with novel nanodevice-based systems owing to unconventional and self-assembly based manufacturing processes. Furthermore, in emerging nanosystems, fault mechanisms and distributions may be very different from CMOS due to unique physical layer aspects, and emerging circuit and logic styles. Thus, theoretical fault models for nanosystems are necessary to extract detailed characteristics of fault generation and propagation. Using the intuition garnered from the theoretical analysis, modular and structural redundancy schemes can be specifically tailored to the intricacies of the fabric in order to achieve higher reliability of output signals.

In this thesis, we develop a detailed analytical …

Vortex-Induced Vibrations Of An Inclined Cylinder In Flow, Anil B. Jain

Masters Theses 1911 - February 2014

When a bluff body is placed in flow, vortices are shed downstream of the body. For the case of a bluff body with a circular cross-section (a cylinder) attached to a spring and a damper, when the frequency of vortex shedding is close to the natural frequency of the structure, the cylinder oscillates in a direction perpendicular to the flow. This is called Vortex Induced Vibration (VIV) and is a canonical problem in fluid-structure interactions. The majority of studies on VIV of a flexibly mounted rigid cylinder are for the cases where the flow direction is perpendicular to the long …

Benchmarking Virtual Network Mapping Algorithms, Jin Zhu

Masters Theses 1911 - February 2014

The network architecture of the current Internet cannot accommodate the deployment of novel network-layer protocols. To address this fundamental problem, network virtualization has been proposed, where a single physical infrastructure is shared among different virtual network slices. A key operational problem in network virtualization is the need to allocate physical node and link resources to virtual network requests. While several different virtual network mapping algorithms have been proposed in literature, it is difficult to compare their performance due to differences in the evaluation methods used. In this thesis work, we proposed VNMBench, a virtual network mapping benchmark that provides a …

The Process By Which Physicians Extract Information From Electronic Progress Notes During Handoffs, Brian D. Amster

Masters Theses 1911 - February 2014

A handoff requires that the responsibility for patient patient’s care is transferred from one healthcare professional to another. The goals of this research were to identify, evaluate, and use analytical methods to describe how physicians (n=10) extracted information from electronic progress notes, one important source of information used during handoffs. Participants also verbally summarized the notes as they would during handoffs. Six methods were used to analyze how participants read progress notes, each uniquely contributing to our understanding of physicians’ visual attention patterns during this process. The participants focused their visual attention on the Impression and Plan section of the …

Finite Element Analysis Of A Femur To Deconstruct The Design Paradox Of Bone Curvature, Sameer Jade

Masters Theses 1911 - February 2014

The femur is the longest limb bone found in humans. Almost all the long limb bones found in terrestrial mammals, including the femur studied herein, have been observed to be loaded in bending and are curved longitudinally. The curvature in these long bones increases the bending stress developed in the bone, potentially reducing the bone’s load carrying capacity, i.e. its mechanical strength. Therefore, bone curvature poses a paradox in terms of the mechanical function of long limb bones. The aim of this study is to investigate and explain the role of longitudinal bone curvature in the design of long bones. …

Investigating The Relationship Between Material Property Axes And Strain Orientations In Cebus Apella Crania, Christine M. Dzialo

Masters Theses 1911 - February 2014

Probabilistic finite element analysis was used to determine whether there is a statistically significant relationship between maximum principal strain orientations and orthotropic material stiffness orientations in a primate cranium during mastication. We first sought to validate our cranium finite element model by sampling in-vivo strain and in-vivo muscle activation data during specimen mastication. A comparison of in vivo and finite element predicted (i.e. in silico) strains was performed to establish the realism of the FEM model. To the best of our knowledge, this thesis presents the world’s only complete in-vivo coupled with in-vitro validation data set of a primate cranium …

Heterogeneous Graphene Nanoribbon-Cmos Multi-State Volatile Random Access Memory Fabric, Santosh Khasanvis

Masters Theses 1911 - February 2014

CMOS SRAM area scaling is slowing down due to several challenges faced by transistors at nanoscale such as increased leakage. This calls for new concepts and technologies to overcome CMOS scaling limitations. In this thesis, we propose a multi-state memory to store multiple bits in a single cell, enabled by graphene and graphene nanoribbon crossbar devices (xGNR). This could provide a new dimension for scaling. We present a new multi-state volatile memory fabric called Graphene Nanoribbon Tunneling Random Access Memory (GNTRAM) featuring a heterogeneous integration between graphene and CMOS. A latch based on the xGNR devices is used as the …

The Radiation Quality Factor Of Vertically Polarized Spherical Antennas Above A Conducting Ground Plane, Hsieh-Chi Chang

Masters Theses 1911 - February 2014

The radiation quality factor of small vertically polarized antennas above a ground plane is investigated. Although the quality factor of small antennas in free space has been investigated extensively in the past, the exact effect of a conducting ground plane on the antenna bandwidth is not clearly understood. In this thesis, quality factors of vertically polarized antennas above a ground plane are computed and compared with their free-space counterparts. The theoretical results on quality factors are validated with simulations of electrically small spherical helix antennas.

A Nonlinear Model For Wind-Induced Oscillations Of Trees, Lakshmi Narayanan Ramanujam

Masters Theses 1911 - February 2014

Ambient wind causes trees to oscillate. Wind-induced oscillations of trees constitute a fluid-structure interaction problem, which has been studied by many researchers from various points of view. However, there is yet a lot to be done. From an engineering point of view, the complex structure of trees, which are very different from man-made structures, as well as the highly nonlinear interaction between wind and tree, makes it a challenging task to predict the amplitude and frequency of the resulting oscillations. From a biological point of view, the influence of wind on photosynthesis as well as the growth and death of …

Physical Model Of The Feeding Strike Of The Mantis Shrimp, Suzanne M. Cox

Masters Theses 1911 - February 2014

A physical model was built to study the properties of the feeding strike of the mantis shrimp that are responsible for drag reduction and cavitation control. The model had three goals: 1) The model was to be outfitted with a method to collect kinematic, force and cavitation data. 2) The velocity and acceleration profile of the model were to be predicted with a mathematical model of the mechanism. 3) The model was to match as many drag and cavitation sensitive properties of the mantis shrimp strike as feasible and have a means to control the rest. The first iteration of …

Catalytic Fast Pyrolysis Of Biomass In A Bubbling Fluidized Bed Reactor With Gallium Promoted Zsm-5 Catalyst, Jian Shi

Masters Theses 1911 - February 2014

The huge energy demand of our society is causing fossil fuel resources to diminish rapidly. Therefore, it is critical to search for alternative energy resources. Biomass is currently both abundant and inexpensive. Biofuels (fuels produced from biomass) have the potential to replace fossil fuels if a cost effective process can be develop to convert biomass into fuels.

Catalytic fast pyrolysis is a technology that can convert biomass into gasoline ranged aromatics in a single step. By heating biomass quickly to an intermediate temperature, biomass will thermally decompose into small molecules which can fit into zeolite catalyst pores. Inside the catalyst …

Terahertz Imaging For Cancer Detection, Benjamin A. St. Peter

Masters Theses 1911 - February 2014

This project evaluates the ability of terahertz (THz) radiation to differentiate cancerous from non-cancerous human breast lumpectomy and mastectomy tissue. This is done by aiming a narrow-band THz beam at medical samples and measuring reflected power. THz images of specimens from Breast Conservation Surgery (BCS) were created using a gas laser source and mechanical scanning. The design and characterization of this system is discussed in detail. The images were correlated with optical histological micrographs of the same specimens and discrimination values of more than 70% were found for five of the six samples using Receiver Operating Characteristic (ROC) analysis.

High Speed Flow Simulation In Fuel Injector Nozzles, Sukanta Rakshit

Masters Theses 1911 - February 2014

Atomization of fuel is essential in controlling combustion inside a direct injection engine. Controlling combustion helps in reducing emissions and boosting efficiency. Cavitation is one of the factors that significantly affect the nature of spray in a combustion chamber. Typical fuel injector nozzles are small and operate at a very high pressure, which limit the study of internal nozzle behavior. The time and length scales further limit the experimental study of a fuel injector nozzle. Simulating cavitation in a fuel injector will help in understanding the phenomenon and will assist in further development.

The construction of any simulation of cavitating …

Bioretention: Evaluating Their Effectiveness For Improving Water Quality In New England Urban Environments, Mary Dehais

Masters Theses 1911 - February 2014

Nonpoint source (NPS) pollution is one of the leading causes of water quality problems in the United States. Bioretention has become one of the more frequently used stormwater management practices for addressing NPS pollution in urbanized watersheds in New England. Yet despite increased acceptance, bioretention is not widely practiced. This study explores and evaluates the efficacy of bioretention for protecting urban water quality.

This research found that numerous monitoring methods are used by researchers and industry experts to assess the effectiveness of stormwater best management practices (BMPs) and low impact development (LID) practices that include bioretention. The two most common …