Mechanical Engineering Commons^™

Floating-Gate Transistor Photodetector With Light Absorbing Layer, Jinsong Huang, Yongbo Yuan

Department of Mechanical and Materials Engineering: Faculty Publications

A field effect transistor photodetector that can operate in room temperature includes a source electrode, a drain electrode, a channel to allow an electric current to flow between the drain and source electrodes, and a gate electrode to receive a bias voltage for controlling the current in the channel. The photodetector includes a light-absorbing material that absorbs light and traps electric charges. The light-absorbing material is configured to generate one or more charges upon absorbing light having a wavelength within a specified range and to hold the one or more charges. The one or more charges held in the light-absorbing …

Secondary Pool Boiling Effects, C. Kruse, A. Tsubaki, C. A. Zuhlke, T. P. Anderson, Dennis R. Alexander, George Gogos, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

A pool boiling phenomenon referred to as secondary boiling effects is discussed. Based on the experimental trends, a mechanism is proposed that identifies the parameters that lead to this phenomenon. Secondary boiling effects refer to a distinct decrease in the wall superheat temperature near the critical heat flux due to a significant increase in the heat transfer coefficient. Recent pool boiling heat transfer experiments using femtosecond laser processed Inconel, stainless steel, and copper multiscale surfaces consistently displayed secondary boiling effects, which were found to be a result of both temperature drop along the microstructures and nucleation characteristic length scales. The …

Experimental Explanation Of The Formation Mechanism Of Surface Mound-Structures By Femtosecond Laser On Polycrystalline Ni60Nb40, Edwin Peng, A. Tsubaki, Craig A. Zuhlke, Meiyu Wang, Ryan Bell, Michael J. Lucis, Troy P. Anderson, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Femtosecond laser surface processing (FLSP) is an emerging technique for creating functionalized surfaces with specialized properties, such as broadband optical absorption or superhydrophobicity/ superhydrophilicity. It has been demonstrated in the past that FLSP can be used to form two distinct classes of mound-like, self-organized micro/nanostructures on the surfaces of various metals. Here, the formation mechanisms of below surface growth (BSG) and above surface growth (ASG) mounds on polycrystalline Ni₆₀Nb₄₀ are studied. Cross-sectional imaging of these mounds by focused ion beam milling and subsequent scanning electron microscopy revealed evidence of the unique formation processes for each class of …

Biomimetic Substrate Control Of Cellular Mechanotransduction, Mohammad Nahid Andalib, Yuris A. Dzenis, Henry J. Donahue, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

Extracellular mechanophysical signals from both static substrate cue and dynamic mechanical loading have strong potential to regulate cell functions. Most of the studies have adopted either static or dynamic cue and shown that each cue can regulate cell adhesion, spreading, migration, proliferation, lineage commitment, and differentiation. However, there is limited information on the integrative control of cell functions by the static and dynamic mechanophysical signals. For example, a majority of dynamic loading studies have tested mechanical stimulation of cells utilizing cultures on flat surfaces without any surface modification. While these approaches have provided significant information on cell mechanotransduction, obtained outcomes …

Characterizing The Boundary Lateral To The Shear Direction Of Deformation Twins In Magnesium, Y. Liu, N. Li, S. Shao, M. Gong, J Wang, R.J. Mccabe, Y. Jiang, C.N. Tome

Department of Mechanical and Materials Engineering: Faculty Publications

The three-dimensional nature of twins, especially the atomic structures and motion mechanisms of the boundary lateral to the shear direction of the twin, has never been characterized at the atomic level, because such boundary is, in principle, crystallographically unobservable.We thus refer to it here as the dark side of the twin. Here, using high-resolution transmission electron microscopy and atomistic simulations, we characterize the dark side of {1012} deformation twins in magnesium. It is found that the dark side is serrated and comprised of {1012} coherent twin boundaries and semi-coherent twist prismatic–prismatic {2110} boundaries that control twin growth. The conclusions of …

Graphene Platform For Neural Regenerative Medicine, Tasneem Bouzid, Alexander Sinitskii, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

Graphene is a material composed of a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. The unique electrical, optical, thermal, and mechanical properties of graphene are extensively exploited for various applications in electronics, energy, and sensors. Studies also proposed the potential of graphene for biomedical applications. The intrinsic characteristics of graphene and its availability for chemical and physical modifications make graphene a promising vehicle for various biomedical applications including drug delivery, bioimaging, disease diagnostics, etc. The chemical structure of graphene and, in turn, its functionality, can be altered by attaching functional groups, which not only modify the …

Mode-Converted Ultrasonic Scattering In Polycrystals With Elongated Grains, Andrea P. Arguelles, Christopher M. Kube, Ping Hu, Joseph A. Turner

Department of Mechanical and Materials Engineering: Faculty Publications

Elastic wave scattering is used to study polycrystalline media for a wide range of applications. Received signals, which include scattering from the randomly oriented grains comprising the polycrystal, contain information from which useful microstructural parameters may often be inferred. Recently, a mode-converted diffuse ultrasonic scattering model was developed for evaluating the scattered response of a transverse wave from an incident longitudinal wave in a polycrystalline medium containing equiaxed single-phase grains with cubic elastic symmetry. In this article, that theoretical mode-converted scattering model is modified to account for grain elongation within the sample. The model shows the dependence on scattering angle …

Expanded 3d Nanofiber Scaffolds: Cell Penetration, Neovascularization, And Host Response, Jiang Jiang, Zhuoran Li, Hongjun Wang, Yue Wang, Mark A. Carlson, Matthew J. Teusink, Matthew R. Macewan, Linxia Gu, Jingwei Xie

Department of Mechanical and Materials Engineering: Faculty Publications

Herein, a robust method to fabricate expanded nanofiber scaffolds with controlled size and thickness using a customized mold during the modified gas-foaming process is reported. The expansion of nanofiber membranes is also simulated using a computational fluid model. Expanded nanofiber scaffolds implanted subcutaneously in rats show cellular infiltration, whereas non-expanded scaffolds only have surface cellular attachment. Compared to unexpanded nanofiber scaffolds, more CD68+ and CD163+ cells are observed within expanded scaffolds at all tested time points post-implantation. More CCR7+ cells appear within expanded scaffolds at week 8 post-implantation. In addition, new blood vessels are present within the expanded scaffolds at …

Enhancing Stability And Efficiency Of Perovskite Solar Cells With Crosslinkable Silane-Functionalized And Doped Fullerene, Yang Bai, Qingfeng Dong, Yuchuan Shao, Yehao Deng, Qi Wang, Liang Shen, Dong Wang, Wei Wei, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite solar cells. Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p–i–n planar heterojunction-structure perovskite devices. Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant. Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold. With crosslinkable silane-functionalized and doped fullerene electron transport layer, the …

Stabilized Wide Bandgap MapbbrXI3– X Perovskite By Enhanced Grain Size And Improved Crystallinity, Miao Hu, Cheng Bi, Yongbo Yuan, Yang Bai, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Methylammonium lead trihalide perovskite (MAPbX₃, where MA is methylammonium, and X is a halide)-based solar cells have been intensively investigated recently, with the demonstrated certified solar power conversion efficiency (PCE) exceeding 20%. To further boost the PCE to beyond the Schockley–Queisser limit, tandem structured solar cells have been investigated based on integrating MAPbX₃ and low bandgap solar cells. However, the efficiency of the two-terminal integrated perovskite-silicon tandem cells is still low. The best reported efficiency of 13.7% for this type of tandem cells is far smaller than the individual cells yet, partially due to the limited performance …

Ultrahigh Sensitivity Of Methylammonium Lead Tribromide Perovskite Single Crystals To Environmental Gases, Hong-Hua Fang, Sampson Adjokatse, Haotong Wei, Jie Yang, Graeme R. Blake, Jinsong Huang, Jacky Even, Maria Antonietta Loi

Department of Mechanical and Materials Engineering: Faculty Publications

One of the limiting factors to high device performance in photovoltaics is the presence of surface traps. Hence, the understanding and control of carrier recombination at the surface of organic-inorganic hybrid perovskite is critical for the design and optimization of devices with this material as the active layer. We demonstrate that the surface recombination rate (or surface trap state density) inmethylammonium lead tribromide (MAPbBr3) single crystals can be fully and reversibly controlled by the physisorption of oxygen and water molecules, leading to a modulation of the photoluminescence intensity by over two orders of magnitude.We report an unusually low surface recombination …

Cfd Prediction And Simulation Of A Pumpjet Propulsor, Lin Lu, Guang Pan, Prasanta K. Sahoo

Ocean Engineering and Marine Sciences Faculty Publications

In this study an attempt has been made to study the hydrodynamic performance of pumpjet propulsor. Numerical investigation based on the Reynolds Averaged NaviereStokes (RANS) computational fluid dynamics (CFD) method has been carried out. The structured grid and SST keu turbulence model have been applied. The numerical simulations of open water performance of marine propeller E779A are carried out with different advance ratios to verify the numerical simulation method. Results show that the thrust and the torque are in good agreements with experimental data. The grid independent inspection is applied to verify accuracy of numerical simulation grid. The numerical predictions …

A Biomimetic, Energy-Harvesting, Obstacle-Avoiding, Path-Planning Algorithm For Uavs, Snorri Gudmundsson

Doctoral Dissertations and Master's Theses

This dissertation presents two new approaches to energy harvesting for Unmanned Aerial Vehicles (UAV). One method is based on the Potential Flow Method (PFM); the other method seeds a wind-field map based on updraft peak analysis and then applies a variant of the Bellman-Ford algorithm to find the minimum-cost path. Both methods are enhanced by taking into account the performance characteristics of the aircraft using advanced performance theory. The combined approach yields five possible trajectories from which the one with the minimum energy cost is selected. The dissertation concludes by using the developed theory and modeling tools to simulate the …

Linear Burn Rates Of Monopropellants For Multi-Mode Micropropulsion, Alex J. Mundahl, Steven P. Berg, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Multi-mode micro propulsion is a potential game-changing technology enabling rapidly composable small satellites with unprecedented mission flexibility. Maximum mission flexibility requires propellant that is shared between the chemical and electric propulsion systems. Previous research has identified a promising monopropellant that is both readily catalytically exothermically decomposed (chemical mode) and electro sprayable (electric mode). In this work the linear burn rate of this monopropellant is determined to aid design of the microtube catalytic chemical thruster. A pressurized fixed volume reactor is used to determine the linear burn rate. Benchmark experiments use a 13-molar mixture of hydroxylammonium nitrate and water and show …

Optimal Configuration And Tuning Of Wave Energy Converter Arrays, Emma Edwards

Link Foundation Ocean Engineering and Instrumentation Fellowship Reports

Power from ocean waves is becoming an increasingly attractive option as a source of renewable energy. Ocean waves are more reliable and predictable than sun and wind, and have a higher energy density [1]. There are locations where solar and wind energy would not be viable, due to the large amount of space they take up, either on land (solar) or above ground (wind). In addition, wave energy devices are less of a visual deterrent than wind turbines, and wave energy is particularly attractive for areas with a lot of coast line. Wave energy is still in its infancy, though, …

Characterization Of Tensile Deformation In Az91 Mg Alloy Castings, Ogun Unal

UNF Graduate Theses and Dissertations

Tensile deformation characteristics of cast aluminum alloys have been investigated extensively. Cast Mg alloys have remained mostly neglected by researchers, despite their potential for weight savings. This present study is motivated by this gap in the literature and consists of two stages; in Stage 1, analysis of tensile data gathered from literature were reanalyzed, and in Stage 2, data generated from tensile testing of 60 specimens of AZ91 Mg alloy castings in both T4 and T6 conditions were analyzed to characterize work hardening behavior.

In Stage 1, more than 1600 data were collected from the literature for various Mg alloy …

The Relationship Between High-Cycle Fatigue And Tensile Properties In Cast Aluminum Alloys, Huseyin Ozdes

UNF Graduate Theses and Dissertations

Cast aluminum alloys are common in automotive and aerospace applications due to their high strength-to-density ratio. Fracture data for cast aluminum alloys, such as fatigue life, tensile strength and elongation, are heavily affected by the structural defects, such as pores and bifilms. There have been numerous studies in which either fatigue performance or tensile deformation were characterized and linked to casting defects. However, a comprehensive study that correlates tensile and fatigue properties has not been reported. The present study is motivated to fill this gap. The main objective of the investigation is to analyze the link between tensile and fatigue …

Design Of A Mobile Underwater Charging System, Brian R. Page

Dissertations, Master's Theses and Master's Reports

Autonomous Underwater Vehicles (AUVs) are extremely capable vehicles for numerous ocean related missions. AUVs are energy limited, resulting in short mission endurance on the scale of hours to days. Underwater Gliders (UGs) are able to operate on the order of months to years by using nontraditional propulsion methods. UGs, however, are unable to perform missions requiring high speed or direct forward motion due to the nature of their buoyancy driven motion. This work reviews the current state of the art in recharging AUVs and offers an underwater recharging network concept at a significantly reduced cost to traditional methods. The solution …

Comparative Analysis Of Locally Available Materials For Treadle Pump Seals In Senegal, West Africa, Brennan Tymrak

Dissertations, Master's Theses and Master's Reports

For rural farmers in Senegal, West Africa, pulling water for irrigation can be a laborious but necessary task during the dry season to earn income from vegetable gardening. Traditional water pulling methods are inexpensive but require great physical effort, while modern machines decrease the labor burden but at a high financial cost. This study looked at an intermediate water pulling technology, the treadle pump, and how it could be improved to become more desirable for use in agricultural irrigation. A treadle pump was built and tested during field work in a rural Senegalese village. Observations from field testing prompted a …

Design, Fabrication And Analysis Of An Auxiliary Power Unit On A Heavy-Duty Truck To Power The Hvac Systems Of The Truck During Driver Off-Duty Conditions, Rohan Milind Kalurkar

Dissertations, Master's Theses and Master's Reports

Currently, one of the biggest challenges the world is facing is energy insufficiency. One of the contributors to energy consumption in United States are the idling semi-trailer trucks. In May 2001, President Bush issued The National Energy Policy in which he directed The Environmental Protection Agency (EPA) and Department of Transportation (DOT) to reduce the idling of trucks. This was done in order to reduce energy consumption by lowering fuel consumption and emissions coming out of semi-trailer trucks in the United States of America.

This project deals with the efforts of installing an Auxiliary Power Unit (APU) as a device …

Novel Design And Manufacturing Strategies For Portable Air-Breathing Proton Exchange Membrane Fuel Cells, Sriram Praneeth Isanaka

Doctoral Dissertations

"The purpose of this dissertation is to study the importance of design novelty and advanced manufacturing and assembly practices towards portable air-breathing proton exchange membrane fuel cells. Traditional proton exchange membrane fuel cell designs have always been based on prismatic shapes and expensive materials like graphite and steel. The novel design strategies theorized as part of this research though have led to the creation of working prototypes with unconventional form factors, materials and manufacturing methods. The benefits include improved reactant flow characteristics, superior power densities, reduced cost, and simplified manufacturing and assembly complexity as compared to conventional proton exchange membrane …

Modeling, Analysis, And Simulation For Aqueous-Based Ceramic Pastes In Freeze-Form Extrusion Fabrication Process, Mingyang Li

Doctoral Dissertations

"During the freeze-form extrusion fabrication process, both the extrusion and freezing processes are complex due to the aqueous-based ceramic pastes' non-Newtonian behavior, large latent heat of the water contained in the paste, and the small temperature difference between the ambient and the paste. In this study, the steady-state relationship between plunger velocity and extrusion force is developed based on a modified Herschel-Bulkley viscosity model and the Navier-Stokes equations, and the dynamic response of the extrusion force is described by a first-order nonlinear equation when plunger velocity is taken as an input. It is shown that the extrusion response time depends …

Efficient Time-Dependent System Reliability Analysis, Zhifu Zhu

Doctoral Dissertations

"Engineering systems are usually subjected to time-variant loads and operate under time-dependent uncertainty; system performances are therefore time-dependent. Accurate and efficient estimate of system reliability is crucial for decision makings on system design, lifetime cost estimate, maintenance strategy, etc. Although significant progresses have been made in time-independent reliability analysis for components and systems, time-dependent system reliability methodologies are still limited. This dissertation is motivated by the need of accurate and effective reliability prediction for engineering systems under time-dependent uncertainty. Based on the classic First and Second Order Reliability Method (FORM and SORM), a system reliability method is developed for multidisciplinary …

Real-Time Monitoring Of Personal Exposures To Carbon Dioxide, Elliott T. Gall, Toby Cheung, Irvan Luhung, Stefano Schiavon, William W. Nazaroff

Mechanical and Materials Engineering Faculty Publications and Presentations

Elevated indoor CO₂ levels are indicative of insufficient ventilation in occupied spaces and correlate with elevated concentrations of pollutants of indoor origin. Adverse health and well-being outcomes associated with elevated indoor CO₂ levels are based on CO₂ as a proxy, although some emerging evidence suggests CO₂ itself may impact human cognition. Using portable monitors, we conducted an exposure study with 16 subjects in Singapore to understand the levels, dynamics and influencing factors of personal exposure to CO₂. Participants carried a CO₂ monitor continuously for 7-day periods recording their exposure levels at 1-min intervals. …

Physical Modeling Of The Atmospheric Boundary Layer In The University Of New Hampshire’S Flow Physics Facility, Stephanie Gilooly, Gregory Taylor-Power

Honors Theses and Capstones

The atmospheric boundary layer is the lowest part of the atmosphere, and is defined by a region from the surface of the earth to approximately 500-1000m altitude in which air velocity changes from zero at the surface to the velocity of the wind at a certain altitude. The type of atmospheric boundary layer is characterized by the terrain it encounters, varying from open sea and mud flats to suburban areas and city centers with high- and low-rise buildings. The goal of this project is to generate different types of atmospheric boundary layers for scale model testing in the UNH Flow …

Creating Multi-Functional G-Code For Multi-Process Additive Manufacturing, Efrain Aguilera Jr

Open Access Theses & Dissertations

Additive manufacturing (AM) started over thirty years ago and with it a manufacturing revolution that moves industrial production into the personal home. With recent interest shifting into multi-functional parts fabricated through AM technologies, unified systems are being developed. Merging different manufacturing technologies into one single machine is a challenge but undergoing research has shown promise in the development of multi-functional systems. Concurrent work is being done in the software, automation, and hardware aspect of multi-functional systems. An effort to use industry compatible Computer Aided Design (CAD) software to design multi-functional parts including circuits, micro-machining, and foil embedding then exporting and …

Modeling And Characterization Of Piezoelectric Based Multifunctional Structures, Ricardo Martinez Hernandez

Open Access Theses & Dissertations

Continuous monitoring of high pressure and high temperature in energy system applications has been a developing research area in today’s energy sector. Multifunctional materials have the potential to provide real-time monitoring of structures where temperature and pressure sensing is critical to its performance and efficiency. In this study, multifunctional materials are studied by embedding piezoelectric materials with two ongoing technologies, woven fabric composites and additive manufacturing (AM). The AM technology allows the flexibility of embedding a sensor within the structure, all while not compromising the mechanical performance requirements. The “smart parts” are fabricated modifying the standard additive manufacturing process, using …

Microstructural Characterization Of High Velocity Oxy Fuel Coatings Of Inconel 718 And Iron Aluminides, Ana Cecilia Rios Ibanez

Open Access Theses & Dissertations

Thermal spray guns are used today to deposit metallic powders as homogeneous and durable coatings with low porosity onto metals. The objective is to improve their wear resistance and their corrosion resistance in order to withstand conditions such as abrasion and erosion. This can improve the life of turbines, generators and such devices in environments found in ultra-supercritical coal-fired (AUSC) boilers, steam turbines and gas turbines (Mohammed & Cabrera, 2014). Industries like manufacturing, automobile and especially in the sustainable energy area, have used this technique to improve component characteristics, extend product life, increase performance as well as reduce production and …

Design Of A 500 Lbf Liquid Oxygen And Liquid Methane Rocket Engine For Suborbital Flight, Jesus Eduardo Trillo

Open Access Theses & Dissertations

Liquid methane (LCH4)is the most promising rocket fuel for our journey to Mars and other space entities. Compared to liquid hydrogen, the most common cryogenic fuel used today, methane is denser and can be stored at a more manageable temperature; leading to more affordable tanks and a lighter system. The most important advantage is it can be produced from local sources using in-situ resource utilization (ISRU) technology. This will allow the production of the fuel needed to come back to earth on the surface of Mars, or the space entity being explored,making the overall mission more cost effective by enabling …

Through-Thickness Reinforcement For Woven Laminates, Alejandra G. Castellanos

Open Access Theses & Dissertations

Fiber reinforced polymer composites have gained popularity in aerospace and naval applications due to their tailorable mechanical properties and high strength-to-weight. Despite these advantages, between the layers of fabric (laminas), there is a resin-rich region known as interlaminar region, with no reinforcement which is very susceptible to damage. Different types of reinforcements have been tested for the interlaminar region. However, all of these methods have proved to decrease the in-plane properties due to damage to the fibers. In this Thesis, a new reinforcement technique with ZnO nanowires is proposed to increase the damage resistance. This Thesis describes the design, manufacturing …