Mechanical Engineering Commons^™

The Effect Of A Powered Ankle Foot Orthosis On Walking In A Stroke Subject: A Case Study, Ali Pourghasem, Ismail Ebrahimi Takamjani, Mohammad Taghi Karimi, Mohammad Kamali, Mohammad Jannesari, Iman Salafian

Department of Mechanical and Materials Engineering: Faculty Publications

[Purpose] Standing and walking are impaired in stroke patients. Therefore, assisted devices are required to restore their walking abilities. The ankle foot orthosis with an external powered source is a new type of orthosis. The aim of this study was to evaluate the performance of a powered ankle foot orthosis compared with unpowered orthoses in a stroke patient.

[Subjects and Methods] A single stroke subject participated in this study. The subject was fitted with three types of ankle foot orthosis (powered, posterior leg spring, and carbon ankle foot orthoses). He was asked to walk with and without the three types …

Self-Patterning Gd Nano-Fibers In Mg-Gd Alloys, Yangxin Li, Jian Wang, Kaiguo Chen, Meiyue Shao, Yao Shen, Li Jin, Guo-Zhen Zhu

Department of Mechanical and Materials Engineering: Faculty Publications

Manipulating the shape and distribution of strengthening units, e.g. particles, fibers, and precipitates, in a bulk metal, has been a widely applied strategy of tailoring their mechanical properties. Here, we report self-assembled patterns of Gd nano-fibers in Mg-Gd alloys for the purpose of improving their strength and deformability. 1-nm Gd nano-fibers, with a 〈c〉-rod shape, are formed and hexagonally patterned in association with Gd segregations along dislocations that nucleated during hot extrusion. Such Gd-fiber patterns are able to regulate the relative activities of slips and twinning, as a result, overcome the inherent limitations in strength and ductility of Mg alloys. …

Microstructure And Properties Of Spark Plasma Sintered Moalb Ceramics, Ting Lou

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Molybdenum aluminum boride (MoAlB) is a ternary transition metal boride which has promising aeronautic and nuclear applications. It inheres excellent properties of the binary transitional metal borides (e.g., MoB, ZrB₂) such as high melting temperature, high hardness, and thermal conductivity. Besides, MoAlB is superior to MoB because: (1) the Al element provides an oxidation resistance at high temperatures; (2) its nanolaminated structure consisting of M-B layers with alternating Al layers results in a unique damage tolerance property. In this research, polycrystalline MoAlB have been successfully synthesized and simultaneously sintered using spark plasma sintering (SPS) from molybdenum boride (MoB) …

Design Of A Flexible Control Platform And Miniature In Vivo Robots For Laparo-Endoscopic Single-Site Surgeries, Lou P. Cubrich

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Minimally-invasive laparoscopic procedures have proven efficacy for a wide range of surgical procedures as well as benefits such as reducing scarring, infection, recovery time, and post-operative pain. While the procedures have many advantages, there are significant shortcomings such as limited instrument motion and reduced dexterity. In recent years, robotic surgical technology has overcome some of these limitations and has become an effective tool for many types of surgeries. These robotic platforms typically have an increased workspace, greater dexterity, improved ergonomics, and finer control than traditional laparoscopic methods. This thesis presents the designs of both a four degree-of-freedom (DOF) and 5-DOF …

Models For Decanting Gaseous Fuel Tanks: Simulations With Gfssp Thermal Model, Kailash Kumar Jain Munoth

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Transport of fuel from distillation/storage plant to different parts of the world has always been challenging task for Engineers. Different methods have been proposed over the time for transporting fuel efficiently and at low cost which include Marine vessels, Pipelines, Rail Cars and Trucks. In order to transport useful amount of fuel in a reasonably sized tank, we have to liquefy it. While few fuels are easy to liquefy there are great number of fuels which liquefy only under extreme pressure/temperature conditions. Methane has a boiling point of -161.7°C at atmospheric pressure which means it has to be cooled to …

Design And Evaluation Of Pediatric Gait Rehabilitation Robots, Cale J. Stolle

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Gait therapy methodologies were studied and analyzed for their potential for pediatric patients. Using data from heel, metatarsal, and toe trajectories, a nominal gait trajectory was determined using Fourier transforms for each foot point. These average trajectories were used as a basis of evaluating each gait therapy mechanism. An existing gait therapy device (called ICARE) previously designed by researchers, including engineers at the University of Nebraska-Lincoln, was redesigned to accommodate pediatric patients. Unlike many existing designs, the pediatric ICARE did not over- or under-constrain the patient’s leg, allowing for repeated, comfortable, easily-adjusted gait motions. This design was assessed under clinical …

Dynamic Responses Of Wheel-Rail Systems With Block Dampers, Tzuyu Tseng

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The wheel-rail interaction problem has been widely studied in the past few decades. In this problem, dynamic responses at the contact areas remain the central issue since they induce damage to the rail over time. In particular, the dynamic responses at the contact areas between the wheels and rails present difficulties in understanding and mathematical modeling. Even with the computer power one has today, its mathematical modeling employs the versatile numerical analysis method, the finite element method (FEM) remains a formidable challenge due to its extremely small contact areas and in turn the extremely high stress levels. In addition, friction …

Single Site Robotc Device And Related Systems And Methods, Jack Mondry, Shane M. Farritor, Eric Markvicka, Thomas Frederick, Joseph Bartels

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical device components, including components that can be incor porated into robotic and/or in vivo medical devices. Certain embodiments include various medical devices for in vivo medical procedures.

Video Capture And Post-Processing Technique For Approximating 3d Projectile Trajectory, Chase M. Pfeifer, Judith M. Burnfield, Guilherme M. Cesar, Max H. Twedt, Jeff A. Hawks

Department of Mechanical and Materials Engineering: Faculty Publications

In this paper we introduce a low-cost procedure and methodology for markerless projectile tracking in three-dimensional (3D) space. Understanding the 3D trajectory of an object in flight can often be essential in examining variables relating to launch and landing conditions. Many systems exist to track the 3D motion of projectiles but are often constrained by space or the type of object the system can recognize (Qualisys, Göteborg, Sweden; Vicon, Oxford, United Kingdom; Opti-Track, Corvallis, Oregon USA; Motion Analysis, Santa Rosa, California USA; Flight Scope, Orlando, Florida USA). These technologies can also be quite expensive, often costing hundreds of thousand dollars. …

Flex-Ro: Design, Implementation, And Control Of Subassemblies For An Agricultural Robotic Platform, Jared Patrick Werner

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Automation technology in agriculture is growing, making agricultural robotics viable. Innovative field usable multi-purpose robotic platforms are needed for the successful progression of agricultural robotics. Furthermore, the field of agricultural robotics would benefit from a robotic platform design allowing for variable height, thus accommodating navigation throughout various crop growth stages. A variable height machine, Flex-Ro was developed to accommodate this feature. Multiple sub-assemblies were designed and implemented for Flex-Ro. An electronic control unit (ECU) enabled engine was used to power Flex-Ro. An embedded application program was developed to control engine speed using proprietary Controller Area Network (CAN) messages in conjunction …

Material Evaluation: Self Damping Wire Sd/Acsr Conductor Failures, Daniel F. Weyer

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Following numerous 954 ACSR SD Wire failures from 2010 to 2012, Nebraska Public Power District (NPPD) implemented an inspection program to determine the extent of condition for this type of widely used conductor. NPPD transmission system includes over 2000 miles of this particular conductor.

Transmission line splices are installed every 15-20 spans, with failures being located in a span containing a splice. NPPD worked with Kinectrics to complete electromagnetic field inspections for three days in 2013, with retesting performed in 2015. Throughout this inspection of 54 spans of conductor, 36 were found to have deterioration and corrosion.

Over 80% of …

Thermal Analysis Of Continuous And Patterned Multilayer Films In The Presence Of A Nanoscale Hot Spot, Jia-Yang Juang, Jinglin Zheng

Department of Mechanical and Materials Engineering: Faculty Publications

Thermal responses of multilayer films play essential roles in state-of-the-art electronic systems, such as photo/micro-electronic devices, data storage systems, and silicon-on-insulator transistors. In this paper, we focus on the thermal aspects of multilayer films in the presence of a nanoscale hot spot induced by near field laser heating. The problem is set up in the scenario of heat assisted magnetic recording (HAMR), the next-generation technology to overcome the data storage density limit imposed by superparamagnetism. We characterized thermal responses of both continuous and patterned multilayer media films using transient thermal modeling. We observed that material configurations, in particular, the thermal …

Fluid Dynamic Factors As A Cause And Effect Of Biofilm Formation Of Staphylococcus Aureus Biofilms, Erica Sherman

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Staphylococcus aureus bacteria are able to form biofilms and distinctive tower structures that facilitate their ability to tolerate treatment and to spread within the human body. The formation of towers, which break off, get carried downstream and serve to initiate biofilms in other parts of the body are of particular interest here. It is known that flow conditions play a role in the development, dispersion and propagation of biofilms. The influence of flow on tower formation and what factors lead to tower formation is not at all understood The hypothesis being examined is that tower structures form within a specific …

Case Study Of Quantifying Energy Loss Through Ceiling-Attic Recessed Lighting Fixtures Through 3d Numerical Simulation, Ri Na, Shengmao Lin, Zhigang Shen, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Abstract Air leakage through recessed lighting fixtures has been identified as a common issue that causes extra energy consumption in residential buildings. However, few quantitative studies in this area were found. As such, a preliminary assessment of the magnitude of this type of energy loss was conducted by using three-dimensional (3D) transient computational fluid dynamics (CFD) models. A hypothetical layout of recessed lighting fixtures was designed with boundary conditions of four different seasons, which were obtained from recorded roof/attic temperature data sets. The results of the study indicate that leakage of recessed lighting fixtures could be a significant channel of …

Compositionally Graded Bulk Heterojunction Devices And Methods Of Manufacturing The Same, Jinsong Huang, Zhengguo Xiao

Department of Mechanical and Materials Engineering: Faculty Publications

Systems and methods are described to form compositionally graded BHJ structures utilizing solvent-fluxing techniques. In implementations, the systems and methods described herein involve a high boiling point additive, a solution of a polymer donor and an acceptor, a substrate material, a working solvent, and a flux solvent for formation of compositionally graded BHJ structures.

Bioink Properties Before, During And After 3d Bioprinting, Katja Hölzl, Shengmao Lin, Liesbeth Tytgat, Sandra Van Vlierberghe, Linxia Gu, Aleksandr Ovsianikov

Department of Mechanical and Materials Engineering: Faculty Publications

Bioprinting is a process based on additive manufacturing from materials containing living cells. These materials, often referred to as bioink, are based on cytocompatible hydrogel precursor formulations, which gel in a manner compatible with different bioprinting approaches. The bioink properties before, during and after gelation are essential for its printability, comprising such features as achievable structural resolution, shape fidelity and cell survival. However, it is the final properties of the matured bioprinted tissue construct that are crucial for the end application. During tissue formation these properties are influenced by the amount of cells present in the construct, their proliferation, migration …

Optical Patterning Of Trapped Charge In Nitrogen-Doped Diamond, Harishankar Jayakumar, Jacob Henshaw, Siddharth Dhomkar, Daniela Pagliero, Abdelghani Laraoui, Neil B. Manson, Remus Albu, Marcus W. Doherty, Carlos A. Meriles

Department of Mechanical and Materials Engineering: Faculty Publications

The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here, we use two-colour optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce …

Height And Pressure Test For Improving Spray Application, Anna Siebe, Joe D. Luck

UCARE Research Products

Pesticide application in agricultural fields affects a little over a million acres each year (USDA 2012). Current spray application equipment can automatically adjust nozzle flow rates in reaction to speed changes to maintain consistent application rates across the field. Uniform distribution of pesticides from the spray boom is critical to ensure proper crop care while minimizing negative environmental effects. Boom pressure and height are two primary factors that affect proper spray uniformity; however information on the combined effects of these factors are limited. The goal of this study was to provide end users with quantified data regarding the effects of …

Design, Testing And Evaluation Of Robotic Mechanisms And Systems For Environmental Monitoring And Interaction, James K. Higgins

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Unmanned Aerial Vehicles (UAVs) have significantly lowered the cost of remote aerial data collection. The next generation of UAVs, however, will transform the way that scientists and practitioners interact with the environment. In this thesis, we address the challenges of flying low over water to collect water samples and temperature data. We also develop a system that allows UAVs to ignite prescribed fires. Specifically, this thesis contributes a new peristaltic pump designed for use on a UAV for collecting water samples from up to 3m depth and capable of pumping over 6m above the water. Next, temperature sensors and their …

Contribution Of Fiber Undulation To Mechanics Of Three-Dimensional Collagen-I Gel, Shengmao Lin, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The collagen-I gel is extensively used as a scaffold material in tissue engineering due to its ability to mimic the extracellular matrix (ECM). In this study, the mechanics of collagen-I gel is investigated using a numerical model of three-dimensional collagen network. The resulted mechanical behavior was validated against the published experimental data. Results illustrated that fiber alignment was dominated in the low strain region, and its transition to stretching dominated phenomena at higher strain led to the strain stiffening of collagen gel. The collagen undulation at the microscopic level was found to delay the initiation of strain stiffening

Effects Of Electrode Off Centre On Trapped Thickness-Shear Modes In Contoured At-Cut Quartz Resonators, Junjie Shi, Cuiying Fan, Minghao Zhao, Jiashi S. Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We investigated thickness-shear vibrations of a contoured, AT-cut quartz resonator with a pair of electrodes displaced from the resonator centre. The scalar differential equations by Stevens and Tiersten for thickness-shear vibrations of electroded and unelectroded quartz plates were employed. Based on the variational formulation of the scalar differential equations established in a previous paper and the variation-based Ritz method with trigonometric functions as basis functions, free vibration resonance frequencies and trapped thickness-shear modes were obtained. The effects of the electrode off centre on resonance frequencies and mode shapes were examined. When the electrode off centre is about one hundredth of …

Focal Adhesion Kinase Regulation In Stem Cell Alignment And Spreading On Nanofibers, Mohammad Nahid Andalib, Jeong Soon Lee, Ligyeom Ha, Yuris A. Dzenis, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

While electrospun nanofibers have demonstrated the potential for novel tissue engineering scaffolds, very little is known about the molecular mechanism of how cells sense and adapt to nanofibers. Here, we revealed the role of focal adhesion kinase (FAK), one of the key molecular sensors in the focal adhesion complex, in regulating mesenchymal stem cell (MSC) shaping on nanofibers. We produced uniaxially aligned and randomly distributed nanofibers from poly(L-lactic acid) to have the same diameters (about 130 nm) and evaluated MSC behavior on these nanofibers comparing with that on flat PLLA control. C3H10T1/2 murine MSCs exhibited upregulations in FAK expression and …

Agricultural Field Robotics For Plant Data Acquisition, Jeremy S. Blackford, Jared Werner, Tyler A. Troyer, Ethan Nutter

UCARE Research Products

As the demand for food increases, we are presented with the challenge of producing food more efficiently. With the help of agricultural robots it will be possible to achieve greater yields by the application of seeds, fertilizers and chemicals in the most efficient way possible. With more advanced robotic systems accurate crop data can be obtained to improve farming products and techniques.

Flex-Row is a medium sized agricultural robotic platform built for autonomously traversing through rough fields during multiple crop growing stages. This platform consisting of a flexible frame with the ability to vary both width and height will initially …

Effects Of Noise, Reverberation And Foreign Accent On Native And Non-Native Listeners’ Performance Of English Speech Comprehension, Zhao Ellen Peng, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

A large number of non-native English speakers may be found in American classrooms, both as listeners and talkers. Little is known about how this population comprehends speech in realistic adverse acoustical conditions. A study was conducted to investigate the effects of background noise level (BNL), reverberation time (RT), and talker foreign accent on native and non-native listeners' speech comprehension, while controlling for English language abilities. A total of 115 adult listeners completed comprehension tasks under 15 acoustic conditions: three BNLs (RC-30, RC-40, and RC-50) and five RTs (from 0.4 to 1.2 s). Fifty-six listeners were tested with speech from native …

Tractor Measurement And Data Acquisition System For Hydraulic Power, Draft Force, And Power Take-Off Torque, James Roeber

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Numerous advancements in machinery performance of agricultural tractors have been made in recent years. The Organisation for Economic Co-operation and Development (OECD) tests predetermined points (e.g., maximum power and torque) for drawbar, Power Take-Off (PTO), and hydraulic power as separate tests for tractor performance. Testing methods with the tractor operating at a steady state have been done for years, which were uncharacteristic of agricultural tractor operations in field conditions. As part of this thesis work, field usable data acquisition systems (DAQs) were developed to record implement energy consumption (e.g., drawbar loading, PTO torque, and hydraulic power). The system used LabVIEW …

An Evaluation Of Agricultural Tractors Hydraulic Lift Performance, Grant Melotz

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

The current OECD Code 2 detailing the procedures for the hydraulic lift test of agricultural tractors, section 4.3, published lift values that were sometimes unattainable. The static weight of 2WD, two wheel drive, and MFWD, mechanical front wheel drive, tractors and the amount of lifting force have increased at a greater rate than the amount of static weight on the front axle. This increase in lifting force has led to a decrease in the percent of weight as the upward support force on the front axle of a tractor. Many of the 2WD and MFWD unballasted tractors tested at the …

Design And Optimization Of Membrane-Type Acoustic Metamaterials, Matthew G. Blevins

Durham School of Architectural Engineering and Construction: Dissertations, Thesis, and Student Research

One of the most common problems in noise control is the attenuation of low frequency noise. Typical solutions require barriers with high density and/or thickness. Membrane-type acoustic metamaterials are a novel type of engineered material capable of high low-frequency transmission loss despite their small thickness and light weight. These materials are ideally suited to applications with strict size and weight limitations such as aircraft, automobiles, and buildings. The transmission loss profile can be manipulated by changing the micro-level substructure, stacking multiple unit cells, or by creating multi-celled arrays. To date, analysis has focused primarily on experimental studies in plane-wave tubes …

Temporally And Spatially Resolved Quantification Of Hemodynamic Forces And Endothelial Mechanics, Lori M. Lambert

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The endothelium is a thin layer of endothelial cells that line the interior surface of an artery. Due to their direct contact with blood flow, endothelial cells experience varying hemodynamic forces and respond to these forces by altering their morphology. When plaque and other substances accumulate in the walls of arteries, i.e., atherosclerosis, endothelial cells have abnormal responses to blood flow. Studying atherosclerosis progression is, therefore, a two-fold investigation into 1) the hemodynamic forces that cause endothelial responses, and 2) the biological and mechanical responses of endothelial cells. The ultimate goal of this study was to develop an experimental …

Mild Traumatic Brain Injury: Combined In Silico And In Vitro Studies, Yi Hua

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Mild traumatic brain injury (TBI) is a significant public health concern worldwide and has attracted significant attention due to high-impact sport as well as improvised explosive devices used in military conflicts. The earliest sign of mild TBI is associated with cognitive, behavioral and physical/somatic changes, which are commonly invisible to existing medical techniques. Thus it is essential to target mechanisms of mild TBI and its associated damage measures for earlier diagnosis/treatment and enhanced protection strategies.

In this work, the mechanism of blast-induced mild TBI was inspected through integrated in silico and in vitro models. A three-dimensional (3D) human head model …

Improving Radiation And Stress Corrosion Cracking Resistance Of Austenitic Stainless Steels By Laser Shock Peening, Qiaofeng Lu

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Structural alloys for Generation-IV nuclear reactors need to endure a high neutron dose, high temperature, and corrosive coolant. Austenitic stainless steels, particularly the oxide-dispersion-strengthened (ODS) austenitic steels, are promising candidate materials, but they suffer several limits such as irradiation damage and stress corrosion cracking (SCC). This research applies a laser shock peening (LSP) process to improve the radiation and SCC resistance of austenitic stainless steels in simulated nuclear reactor environments. A high density dislocation networks, stacking faults and twin boundaries were generated in the surface region of 304 steels by the shock wave-material interactions in the LSP process. In-situ TEM …