Engineering Commons^™

A Modified Surface On Titanium Deposited By A Blasting Process, Caroline O' Sullivan, Peter O'Hare, Greg Byrne, Liam O'Neill, Katie B. Ryan, Abina M. Crean

Publications

Abstract

: Hydroxyapatite (HA) coating of hard tissue implants is widely employed for its biocompatible and osteoconductive properties as well as its improved mechanical properties. Plasma technology is the principal deposition process for coating HA on bioactive metals for this application. However, thermal decomposition of HA can occur during the plasma deposition process, resulting in coating variability in terms of purity, uniformity and crystallinity, which can lead to implant failure caused by aseptic loosening. In this study, CoBlast™, a novel blasting process has been used to successfully modify a titanium (V) substrate with a HA treatment using a dopant/abrasive regime. …

The Pulled-Macro-Dataflow Model: An Execution Model For Multicore Shared-Memory Computers, Daniel Joseph Richins

Theses and Dissertations

The macro-dataflow model of execution has been used in scheduling heuristics for directed acyclic graphs. Since this model was developed for the scheduling of parallel applications on distributed computing systems, it is inadequate when applied to the multicore shared-memory computers prevalent in the market today. The pulled-macro-dataflow model is put forth as an alternative to the macro-dataflow model, having been designed specifically to accurately describe the memory bandwidth limitations and request-driven nature of communications characteristic of today's machines. The performance of the common scheduling heuristics DSC and CASS-II are evaluated under the pulled-macro-dataflow model and it is shown that their …

Stochastic Modeling Of Salt Accumulation In The Root Zone Due To Capillary Flux From Brackish Groundwater, S. H.H. Shah, R. W. Vervoort, S. Suweis, Andrew J. Guswa, A. Rinaldo, S. E.A.T.M. Van Der Zee

Engineering: Faculty Publications

Groundwater can be a source of both water and salts in semiarid areas, and therefore, capillary pressure-induced upward water flow may cause root zone salinization. To identify which conditions result in hazardous salt concentrations in the root zone, we combined the mass balance equations for salt and water, further assuming a Poisson-distributed daily rainfall and brackish groundwater quality. For the water fluxes (leaching, capillary upflow, and evapotranspiration), we account for osmotic effects of the dissolved salt mass using Vant Hoff's law. Root zone salinity depends on salt transport via capillary flux and on evapotranspiration, which concentrates salt in the root …

Reducing Selection Bias In Case-Control Studies From Rare Disease Registries, J. Alexander Cole, John S. Taylor, Thomas N. Hangartner, Neal J. Weinreb, Pramod K. Mistry, Aneal Khan

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Background: In clinical research of rare diseases, where small patient numbers and disease heterogeneity limit study design options, registries are a valuable resource for demographic and outcome information. However, in contrast to prospective, randomized clinical trials, the observational design of registries is prone to introduce selection bias and negatively impact the validity of data analyses. The objective of the study was to demonstrate the utility of case-control matching and the risk-set method in order to control bias in data from a rare disease registry. Data from the International Collaborative Gaucher Group (ICGG) Gaucher Registry were used as an example.

Methods: …

Understanding Formation And Transport Of Amorphous Iron Oxyhydroxides In Porous Media Using Microfluidic Flow Cells- A Novel Method To Study Freshwater Iron Cycling, Neha A. Ghaisas

Master's Theses

The ground water and surface water interface (GSI or Hyporheic zone) is a spatially- and temporally-fluctuating biogeochemical transition zone connecting these two distinct hydrological components. The mixing zone is characterized by a near neutral pH, ambient temperature and a sharp oxygen concentration which in turn has deep impact on the iron cycling and thus the fate of contaminants in the water column. We constructed an experimental micromodel that to observe key processes that affect biogeochemical iron cycling in the fresh water interface zones where the oxic surface water mixes with Fe (II) rich underlying ground water. The flow cell was …

Nonlinear Thermal Transport And Negative Differential Thermal Conductance In Graphene Nanoribbons, Jiuning Hu, Yan Wang, Ajit Vallabhaneni, Xiulin Ruan, Yong P. Chen

Birck and NCN Publications

We employ classical molecular dynamics to study the nonlinear thermal transport in graphene nanoribbons (GNRs). For GNRs under large temperature biases beyond linear response regime, we have observed the onset of negative differential thermal conductance (NDTC). NDTC is tunable by varying the manner of applying the temperature biases. NDTC is reduced and eventually disappears when the length of the GNR increases. We have also observed NDTC in triangular GNRs, where NDTC exists only when the heat current is from the narrower to the wider end. These effects may be useful in nanoscale thermal managements and thermal signal processing utilizing GNRs. …

Electric Vehicle Battery - Wind Energy Storage System, Steven K. Srivastava, Gary Nola

Green Manufacturing Research Journal

The proposed concept utilizes the EV battery waste stream as a means to store wind energy in order to increase wind energy capacity factor, improve utilization, and make more efficient use of EV batteries prior to recycling. Michigan is an ideal location for such a facility because many of the battery and automotive manufacturers are located here. A 200 MW wind farm can charge a battery farm which consists of all reject and post-consumer batteries and all EVs located in Michigan by 2015. Michigan is on track to meet a 10% renewable portfolio by 2015 with over 1100 MW of …

Synthesis Of Crosslinked Polyurethane And Network Constrained Surface Phase Separation, Chenyu Wang Jr.

Theses and Dissertations

To create functional surfaces for soft materials, such as polyurethanes, our approach is to use a semifluorinated surface modifier as minor component to the matrix material. The surface modifier, driving by reduction in surface energy, surface-concentrates to form a functionalized surface layer at the air-polymer interface. In our previous studies, linear PTMO-based polyurethanes were used as the matrix material. These systems undergo slow surface phase separation at room temperature due to the thermodynamically immiscibility of the soft blocks. In this study, chemically crosslinked matrix was developed to provides a steric hindrance to constrain the mobility of surface modifier and to …

Ceas E-News 09.08.2011, College Of Engineering And Applied Sciences

College of Engineering and Applied Sciences News

Welcome Week for First Year Students, Mod Designer of the

Vision-Based Path Planning, Collision Avoidance, And Target Tracking For Unmanned Air And Ground Vehicles In Urban Environments, Huili Yu

Theses and Dissertations

Unmanned vehicle systems, specifically Unmanned Air Vehicles (UAVs) and Unmanned Ground Vehicles (UGVs) have found potential use in both military and civilian applications. For many applications, unmanned vehicle systems are required to navigate in urban environments where obstacles with various types and sizes exist. The main contribution of this research is to offer vision-based path planning, collision avoidance, and target tracking strategies for Unmanned Air and Ground vehicles operating in urban environments. Two vision-based local-level frame mapping and planning techniques are first developed for Miniature Air Vehicles (MAVs). The techniques build maps and plan paths in the local-level frame of …

Using Borehole Logging And Electron Backscatter Diffraction To Orient An Ice Core From Upper Fremont Glacier, Wyoming, Usa, R. W. Obbard, T. Cassano, K. Aho, G. Troderman, I. Baker

Dartmouth Scholarship

While glacier fabric reflects the accumulated strain, detailed azimuthal information is required to link the microstructure to the flow, and this is not easily gathered at depth. Borehole logging provides a way to obtain a log of azimuthal orientation of tilted stratigraphic features that can be used to orient the core with respect to glacier flow. We demonstrate this using acoustic borehole logs and the ice core from a 162 m borehole in Upper Fremont Glacier, Wind River Range, Wyoming, USA. We measured the dip of tilted dust and bubble layers in the actual ice core, identified them on the …

Semiconducting Nanowire Solar Cells For Enhanced Energy Harvesting, Dong Rip Kim

Link Foundation Energy Fellowship Reports

Solar cells are attractive candidates for generating clean and renewable energy. Nanowires (NWs) due to their unique electrical and optical properties offer new opportunities to solar cells for reduced cost and improved efficiency. Although SiNWs have been already demonstrated as promising solar cell elements1 , to harness the full potential of SiNWs, SiNW solar cells require further characterizations and optimizations, including device integrations of SiNWs and surface treatments of SiNWs. Herein we report three main research results to characterize and optimize the performance of SiNW solar cells: 1) single and tandem axial p-i-n SiNW solar cells, 2) direct growth of …

Reduced Order Modeling Of Delayed Peec Circuits, Francesco Ferranti, Michel Nakhla, Giulio Antonini, Tom Dhaene, Luc Knockaert, Albert E. Ruehli

Electrical and Computer Engineering Faculty Research & Creative Works

We propose a novel model order reduction technique that is able to accurately reduce electrically large systems with delay elements, which can be described by means of neutral delayed differential equations. It is based on an adaptive multipoint expansion and model order reduction of equivalent first order systems. the neutral delayed differential formulation is preserved in the reduced model. Pertinent numerical results validate the proposed model order reduction approach. © 2011 IEEE.

2011 Fall Engr333 Project Assignment, Matthew K. Heun

ENGR 333

The Fall 2011 ENGR333 project focused on the Bunker Interpretive Center (BIC) at Calvin University.

I asked the students “What would it take for Calvin College to obtain an Energy Star rating for the BIC? Or, if the BIC already qualifies for an Energy Star rating, what would it take to improve the energy efficiency of the BIC (as measured by Energy Star metrics) by 15%, thereby ensuring Energy Star performance of the building into the future?”

Customer

As I recall, the customer for this project was Biology faculty member Randy Van Dragt.

Effect Of The Thickness Of Undoped Gan Interlayers Between Multiple Quantum Wells And The P-Doped Layer On The Performance Of Gan Light-Emitting Diodes, T. Lu, S. Li, K. Zhang, C. Liu, Y. Yin, L. Wu, H. Wang, Xiaodong Yang, G. Xiao, Y. Zhou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

InGaN based light-emitting diodes (LEDs) with undoped GaN interlayer of variant thicknesses grown by metal-organic chemical vapor deposition technique have been investigated. It was found that the thickness of undoped GaN interlayers affected LEDs' performance greatly. The LED with 50 nm undoped GaN interlayer showed higher light output power and lower reverse-leakage current compared with the others at 20 mA. Based on electrical and optical characteristics analysis and numerical simulation, these improvements are mainly attributed to the improvement of the quality of depletion region by inserting an undoped GaN layer, as well as reduction of the Shockley-Read-Hall recombination in InGaN/GaN …

Evaluation Of Cathode Materials For Low Temperature (500-700c) Solid Oxide Fuel Cells, Alexander M. Lassman

Master's Theses

Solid oxide fuel cells (SOFC) have gained a great deal of interest, due to their potential for high efficiency power generation and ability to utilize hydrogen fuel, as well as various hydrocarbon-based fuels. A recent trend in SOFC development has been towards lower operating temperatures (500-700°C), which can substantially reduce the cost and complexity of the system. This thesis presents an investigation into state of the art Ba- and La- based cathode materials for use in low temperature (500-700°C) solid oxide fuel cells.

Synthesis of A-site deficient [A=0.97] Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃ (BSCF) was …

Strain Engineering Via Amorphization And Recrystallization In Si/Ge Heterostructures, Yumi Park, Winnie Tan, Alejandro Strachan

Birck and NCN Publications

We use molecular dynamics with the reactive potential ReaxFF to study strain relaxation during the amorphization and recrystallization of silicon-germanium epitaxial nanolaminates. Starting with a coherent heterostructure with (010) Si/Ge interfaces and 3D periodic boundary conditions, we use local heating and quenching to amorphize half of the simulation cell with crystal-amorphous interfaces normal to [001]. We find strain relaxation along [001] as the crystalline Ge section expands into the amorphous material and crystalline Si contracts from it. The amount of strain relaxation correlates with the atomic transport from the amorphized Ge to Si section and increases as the periodic width …

Soft Tissue Cutting With Ultrasonic Mechanical Waveguides, Mark Wylie, Garrett Mcguinness, Graham Gavin

Conference Papers

The use of ultrasonic vibrations transmitted via small diameter wire waveguides represents a technology that has potential for minimally invasive procedures in surgery. This form of energy delivery results in distal tip mechanical vibrations with amplitudes of vibration of up to 50 μm and at frequencies between 20-50 kHz commonly reported. This energy can then be used by micro-cutting surgical tools and end effectors for a range of applications such as bone cutting, cement removal in joint revision surgery and soft tissue cutting. One particular application which has gained regulatory approval in recent years is in the area of cardiovascular …

Amorphous Interface Layer In Thin Graphite Films Grown On The Carbon Face Of Sic, R. Colby, M. L. Bolen, Michael A. Capano, E. A. Stach

Birck and NCN Publications

Cross-sectional transmission electron microscopy (TEM) is used to characterize an amorphous layer observed at the interface in graphite and graphene films grown via thermal decomposition of C-face 4H-SiC. The amorphous layer does not cover the entire interface, but uniform contiguous regions span microns of cross-sectional interface. Scanning transmission electron microscopy (STEM) images and electron energy loss spectroscopy (EELS) demonstrate that the amorphous layer is a carbon-rich composition of Si/C. The amorphous layer is clearly observed in samples grown at 1600 degrees C for a range of growth pressures in argon, but not at 1500 degrees C, suggesting a temperature-dependent formation …

Analysis Of Converter Connected Synchronous Wind Turbines To Grid Disturbances., Joseph Kearney, Michael Conlon, Eugene Coyle

Conference papers

This paper investigates the performance of synchronous generators to grid voltage unbalance and grid faults. A Model of a synchronous generator with a full converter is implemented in the SimPowerSystems toolbox in Matlab/Simulink. Methods to modify the converter control schemes to improve the synchronous generator systems response to grid voltage unbalance and grid faults are investigated. Grid faults including grid voltage unbalance, and line-to-ground faults are introduced into the model at specific times to analyse the performance of the wind generation system. Improvements in the performance of the synchronous generator WECS to the grid disturbances are illustrated.

Near Optimal Control Of Mobile Robot Formations, Travis Dierks, Bryan Brenner, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, the infinite horizon optimal tracking control problem is solved online and forward-in-time for leader-follower based formation control of nonholonomic mobile robots. using the backstepping design approach, the dynamical controller inputs for the robots are approximated from nonlinear optimal control techniques in order to track the control velocities designed to keep the formation. the proposed nonlinear optimal control technique, referred to as adaptive dynamic programming, uses neural networks (NN's) to solve the optimal formation control problem in discrete-time in the presence of unknown internal dynamics and a known control coefficient matrix. All NN's are tuned online using novel …

Design Of A Gainp/Gaas Tandem Solar Cell For Maximum Daily, Monthly, And Yearly Energy Output, Alexander W. Haas, John R. Wilcox, Jeffery L. Gray, Richard J. Schwartz

Birck and NCN Publications

Solar concentrator cells are typically designed for maximum efficiency under the AM1.5d standard spectrum. While this methodology does allow for a direct comparison of cells produced by various laboratories, it does not guarantee maximum daily, monthly, or yearly energy production, as the relative distribution of spectral energy changes throughout the day and year. It has been suggested that achieving this goal requires designing under a nonstandard spectrum. In this work, a GaInP/GaAs tandem solar cell is designed for maximum energy production by optimizing for a set of geographically-dependent solar spectra using detailed numerical models. The optimization procedure focuses on finding …

Role Of Surface Orientation On Atomic Layer Deposited Al2o3/Gaas Interface Structure And Fermi Level Pinning: A Density Functional Theory Study, Ganesh Hegde, Gerhard Klimeck, Alejandro Strachan

Birck and NCN Publications

We investigate the initial surface reaction pathways in the atomic layer deposition (ALD) of Al2O3 on GaAs (111)A and (111)B substrates using precursors trimethylaluminum (TMA) and water to ascertain the effect of surface orientation on device performance. We find that the condition of the respective substrates prior to deposition of TMA and water has a major impact on the surface reactions that follow and on the resulting interface structure. The simulations explain the atomistic mechanism of the interfacial self-cleaning effect in ALD that preferentially removes As oxides. The electronic structure of the resulting atomic configurations indicates states throughout the bandgap …

Achievable Rate Region Characterization Of The Mimo Broadcast Channel With Channel Distribution Information, Yongpeng Wu, Shi Jin, Xiqi Gao, Chengshan Xiao, Matthew R. Mckay

Electrical and Computer Engineering Faculty Research & Creative Works

We investigate the multiple-input multiple-output broadcast channel with channel distribution information available at the transmitter. the so-called fading-paper model is considered with Nt transmit antennas, and each user having Nr receive antennas. Near-optimal designs are proposed for the inflation factor matrix under general fading conditions, based on maximizing the approximation of linear assignment capacity. It is proved that for Nt ≤ Nr, this matrix has a similar structure and achieves a similar interference elimination effect as dirty-paper coding. Also, low complexity iterative algorithms are proposed for Nt > N r case, which yield a good choice for the inflation factor matrix …

Linear Precoding For Relay Networks With Finite-Alphabet Constraints, Weiliang Zeng, Chengshan Xiao, Mingxi Wang, Jianhua Lu

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, we investigate the optimal precoding scheme for relay networks with finite-alphabet constraints. We show that the previous work utilizing various design criteria to maximize either the diversity or the transmission rate with the Gaussian inputs assumption may lead to significant loss for a practical system with finite constellation set constraint. a linear precoding scheme is proposed to maximize the transmission rate, i.e., the mutual information, for relay networks. We exploit the structure of the optimal precoding matrix and develop a unified two-step iterative algorithm utilizing the theory of convex optimization and optimization on the complex Stiefel manifold. …

Low Complexity Turbo Detection Of Coded Under-Determined Mimo Systems, Michael L. Walker, Jun Tao, Jingxian Wu, Yahong Rosa Zheng

Electrical and Computer Engineering Faculty Research & Creative Works

The turbo detection of a coded under-determined multiple-input multiple-output (UD-MIMO) system is studied in this paper. a UD-MIMO system with N transmit antennas and M < N receive antennas has more unknowns than the observations. However, most existing low complexity detectors, such as the vertical Bell Laboratories Layered Space-Time (V-BLAST) or the block decision feedback equalizer (BDFE), work only when M ≥ N. We propose a new turbo detector structure that combines the existing generalized parallel interference cancellation (GPIC) technique and a new generalized serial interference cancellation (GSIC) technique, with a soft-input soft-output (SISO) BDFE. in the first iteration, the GPIC-BDFE equalization is adopted. from the second iteration and beyond, due to the availability of the a priori soft information, the UD-MIMO system can be partitioned into multiple sub-systems by using a reliability-Based partition scheme. Then, the GSIC-BDFE equalization, which has a much lower complexity than the GPIC-BDFE equalization, can be used. Simulation results show that the new detection scheme achieves significant performance gain as the iteration progresses with a reasonable complexity. © 2011 IEEE.

Space Environment-Iii Lecture - Powerpoint Presentation, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

Professor Bob Twiggs' lecture on Space Environment-III PowerPoint presentation delivered on September 2, 2011.

Space Environment - A Review, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs on "Space Environment" on September 2, 2011.

Stochastically Resilient Observer Design For A Class Of Continuous-Time Nonlinear Systems, Chung Seop Jeong, Edwin E. Yaz, Yvonne I. Yaz

Electrical and Computer Engineering Faculty Research and Publications

This work addresses the design of stochastically resilient or non-fragile continuous-time Luenberger observers for systems with incrementally conic nonlinearities. Such designs maintain the convergence and/or performance when the observer gain is erroneously implemented due possibly to computational errors i.e. round off errors in computing the observer gain or changes in the observer parameters during operation. The error in the observer gain is modeled as a random process and a common linear matrix inequality formulation is presented to address the stochastically resilient observer design problem for a variety of performance criteria. Numerical examples are given to illustrate the theoretical results.

Assessing Near-Field Black Carbon Variability Due To Wood Burning And Evaluating Regression Models And Isc Dispersion Modeling, Stella Tan

Master's Theses

PM_2.5 variability within the neighborhood scale has not been thoroughly studied for wood burning communities. High variability in near-field PM_2.5 concentration may lead to harmful public exposure since monitoring does not occur on that scale. This study measures near-field PM_2.5 variability by measuring black carbon (BC), a component of PM_2.5, in a 1 km² area located in Cambria, California. BC and meteorological data (when meteorological instruments were available) were measured over thirteen 12-hour intensive operation periods (IOPs) occurring over the winters of 2009 and 2010. Near-field BC variability was measured to understand the type …