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Articles 1 - 10 of 10
Full-Text Articles in Engineering
Nitrogen Doped Carbon Nanofibers Derived From Water-Soluble Precursors, Lee Cremar, Ben Jones, Nicole Martinez, Gustavo Mejia, Hilario Cortez, Edgar Muñoz, Rocío Nava, Karen Lozano
Nitrogen Doped Carbon Nanofibers Derived From Water-Soluble Precursors, Lee Cremar, Ben Jones, Nicole Martinez, Gustavo Mejia, Hilario Cortez, Edgar Muñoz, Rocío Nava, Karen Lozano
Mechanical Engineering Faculty Publications and Presentations
Nitrogen doped carbon fibers were synthesized from polyvinyl alcohol (PVA), a water soluble precursor. The PVA fine fibers were first developed by centrifugally spinning an aqueous based solution using Forcespinning® technology. The precursor fibers were then exposed to sulfuric acid vapors to partially carbonize and stabilize the fibers for further heat treatment. For nitrogen doping, the fibers were exposed to two different heat treatment routes. One was under a nitrogen atmosphere at 850°C followed by exposure to ammonia gas at 500°C. The second route consisted of heating the treated fibers in pure ammonia gas only, up to 850°C. Both heating …
Suspension-Driven Gravity Surges On Horizontal Surfaces: Effect Of The Initial Shape, Nadim Zgheib, T. Bonometti, S. Balachandar
Suspension-Driven Gravity Surges On Horizontal Surfaces: Effect Of The Initial Shape, Nadim Zgheib, T. Bonometti, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results from highly resolved direct numerical simulations of canonical (axisymmetric and planar) and non-canonical (rectangular) configurations of horizontal suspension-driven gravity surges. We show that the dynamics along the initial minor and major axis of a rectangular release are roughly similar to that of a planar and axisymmetric current, respectively. However, contrary to expectation, we observe under certain conditions the final extent of the deposit from finite releases to surpass that from an equivalent planar current. This is attributed to a converging flow of the particle-laden mixture toward the initial minor axis, a behaviour that was previously reported for …
Polyethylene Oxide—Fullerene Nanocomposites, Nasar Ali, Dorina M. Chipara, Karen Lozano, James R. Hinthorne, Mircea Chipara
Polyethylene Oxide—Fullerene Nanocomposites, Nasar Ali, Dorina M. Chipara, Karen Lozano, James R. Hinthorne, Mircea Chipara
Mechanical Engineering Faculty Publications and Presentations
Polyethylene oxide – fullerene nanocomposites have been prepared by using the solution path with water as solvent (only for the polymer). The dispersion of C60 within the polymer solution was achieved by high power sonication. The study aims to a better understanding on the effect of C60 nanoparticles on the macromolecular chains. Raman Wide Angle X Ray spectroscopy, Differential Scanning Calorimetry, and Thermogravimetric Analysis were used to inspect the interactions between the nanofiller and macromolecular chains. The experimental results revealed a completely different behavior of fullerene dispersed within polymeric matrices than using carbon nanotubes or nanofibers as nanofiller. …
A Vertical Axis Rotor For Wave Energy Conversion, Yingchen Yang, Joab Soto, Francisco Salazar
A Vertical Axis Rotor For Wave Energy Conversion, Yingchen Yang, Joab Soto, Francisco Salazar
Mechanical Engineering Faculty Publications and Presentations
The present work augments vertical-axis unidirectional wave energy converter (WEC) designs with a new approach. The enabling technique is the hydrodynamic design of a special rotor, which consists of a series of uniquely shaped blades in a certain formation. Specifically, individual blades are realized by revolving a two-dimensional symmetric hydrofoil about its chord line. Then the blades are arranged around a vertical shaft in a desired formation to form the rotor. When driven by an approaching flow through interaction, the rotor naturally rotates about the vertical shaft in a predefined direction. The approaching flow could be from any spatial direction, …
Radiative Heat Transfer Analysis Of Railroad Bearings For Wayside Hot-Box Detector Optimization, Arthur Mealer, Constantine Tarawneh, Stephen Crown
Radiative Heat Transfer Analysis Of Railroad Bearings For Wayside Hot-Box Detector Optimization, Arthur Mealer, Constantine Tarawneh, Stephen Crown
Mechanical Engineering Faculty Publications and Presentations
The railroad industry utilizes wayside detection systems to monitor the temperature of freight railcar bearings in service. The wayside hot-box detector (HBD) is a device that sits on the side of the tracks and uses a non-contact infrared sensor to determine the temperature of the train bearings as they roll over the detector. Various factors can affect the temperature measurements of these wayside detection systems. The class of the railroad bearing and its position on the axle relative to the position of the wayside detector can affect the temperature measurement. That is, the location on the bearing cup where the …
Hysteresis Heating Of Railroad Bearing Thermoplastic Elastomer Suspension Element, Oscar O. Rodriguez, Arturo A. Fuentes, Constantine Tarawneh, Robert E. Jones
Hysteresis Heating Of Railroad Bearing Thermoplastic Elastomer Suspension Element, Oscar O. Rodriguez, Arturo A. Fuentes, Constantine Tarawneh, Robert E. Jones
Mechanical Engineering Faculty Publications and Presentations
Thermoplastic elastomers (TPE’s) are increasingly being used in rail service in load damping applications. They are superior to traditional elastomers primarily in their ease of fabrication. Like traditional elastomers they offer benefits including reduction in noise emissions and improved wear resistance in metal components that are in contact with such parts in the railcar suspension system. However, viscoelastic materials, such as the railroad bearing thermoplastic elastomer suspension element (or elastomeric pad), are known to develop self-heating (hysteresis) under cyclic loading, which can lead to undesirable consequences. Quantifying the hysteresis heating of the pad during operation is therefore essential to predict …
Front Dynamics Of Elliptical Gravity Currents On A Uniform Slope, S. J. Zhu, Nadim Zgheib, S. Balachandar, A. Ooi
Front Dynamics Of Elliptical Gravity Currents On A Uniform Slope, S. J. Zhu, Nadim Zgheib, S. Balachandar, A. Ooi
Mechanical Engineering Faculty Publications and Presentations
In the present investigation, we report data from direct numerical simulations of elliptical, finite release, Boussinesq gravity currents propagating down a uniform slope. The study comprises a series of simulations of elliptical gravity currents on a range of slope angles. The shape parameters are varied to study the effects of the initial cross-sectional aspect ratio (Λ0) and mean height to lock radius ratio (Γ) on the dynamics of the gravity current. It is found that the long-time development of the current spatial mass distribution is influenced by its initial shape at smaller slope angles (θ=5∘ and 10∘) whereas the long-time …
Development Of Prognostic Techniques For Surface Defect Growth In Railroad Bearing Rolling Elements, Nancy De Los Santos, Robert Jones, Constantine Tarawneh, Arturo A. Fuentes, Anthony Villarreal
Development Of Prognostic Techniques For Surface Defect Growth In Railroad Bearing Rolling Elements, Nancy De Los Santos, Robert Jones, Constantine Tarawneh, Arturo A. Fuentes, Anthony Villarreal
Mechanical Engineering Faculty Publications and Presentations
Prevention of bearing failures which may lead to catastrophic derailment is a major safety concern for the railroad industry. Advances in bearing condition monitoring hold the promise of early detection of bearing defects, which will improve system reliability by permitting early replacement of failing components. However, to minimize disruption to operations while providing the maximum level of accident prevention that early detection affords, it will be necessary to understand the defect growth process and try to quantify the growth speed to permit economical, non-disruptive replacement of failing components rather than relying on immediate removal upon detection. The study presented here …
A Vertical Axis Wave Turbine With Hydrofoil Blades, Yingchen Yang, Isaiah Diaz, Sergio Soto Quintero
A Vertical Axis Wave Turbine With Hydrofoil Blades, Yingchen Yang, Isaiah Diaz, Sergio Soto Quintero
Mechanical Engineering Faculty Publications and Presentations
This work discusses a new wave energy converter (WEC) design that, when deployed in waves, performs unidirectional rotation about a vertical shaft. The uniqueness of this new WEC design is on utilizing omnidirectional water flow generated by waves to drive a rotor to perform unidirectional rotation about a vertical axis. This unique feature circumvents the frequency-dependent issue of common WECs, and eliminate realignment needs to cope with dynamically changing wave propagation directions. The key component of the WEC is a rotor, which has a vertical shaft with a number of blades mounted to it. Each blade has a hydrofoil-shaped cross …
Frequency Response Reduced Order Model Of Primary Resonance Of Electrostatically Actuated Mems Circular Plate Resonators, Dumitru I. Caruntu, Reynaldo Oyervides
Frequency Response Reduced Order Model Of Primary Resonance Of Electrostatically Actuated Mems Circular Plate Resonators, Dumitru I. Caruntu, Reynaldo Oyervides
Mechanical Engineering Faculty Publications and Presentations
This paper deals with the amplitude-frequency response of soft AC electrostatically actuated MEMS clamped circular plates. Alternating Current (AC) frequency is near half natural frequency of the plate. This results in primary resonance of the system. Two methods are used and compared, namely the Method of Multiple Scales (MMS), and Reduced Order Model (ROM). Both methods are in excellent agreement for amplitudes less than 0.4 of the gap. For amplitudes between 0.4 and 1 of the gap only seven terms ROM accurately predicts the behavior of the system. The effects of the voltage and damping parameters on the frequency response …