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Single-Sided Crash Cushion System, John D. Reid, John R. Rohde, Dean L. Sicking
Single-Sided Crash Cushion System, John D. Reid, John R. Rohde, Dean L. Sicking
Department of Mechanical and Materials Engineering: Faculty Publications
A single-sided crash attenuation cushion system having an impact head and three stage energy absorption mechanism. The energy absorbing mechanism has a mandrel for deforming thin-walled tubes in a controlled collapse to absorb impact forces from a colliding vehicle. The third stage of the absorption mechanism includes an additional deformable compressible tube between the fixed-object hazard and the thin walled tubes.
Effects Of Middle Plane Curvature On Vibrations Of A Thickness-Shear Mode Crystal Resonator, J. S. Yang, Xiaomeng Yang, Joseph A. Turner, John A. Kosinski, Robert A. Pastore, Weiping Zhang
Effects Of Middle Plane Curvature On Vibrations Of A Thickness-Shear Mode Crystal Resonator, J. S. Yang, Xiaomeng Yang, Joseph A. Turner, John A. Kosinski, Robert A. Pastore, Weiping Zhang
Department of Engineering Mechanics: Faculty Publications
We study the effects of a small curvature of the middle plane of a thickness-shear mode crystal plate resonator on its vibration frequencies, modes and acceleration sensitivity. Two-dimensional equations for coupled thickness-shear, flexural and extensional vibrations of a shallow shell are used. The equations are simplified to a single equation for thickness-shear, and two equations for coupled thickness-shear and extension. Equations with different levels of coupling are used to study vibrations of rotated Y-cut quartz and langasite resonators. The influence of the middle plane curvature and coupling to extension is examined. The effect of middle plane curvature on normal acceleration …
Role Of Atomic Scale Interfaces In The Compressive Behavior Of Carbon Nanotubes In Composites, S. Namilae, Namas Chandra
Role Of Atomic Scale Interfaces In The Compressive Behavior Of Carbon Nanotubes In Composites, S. Namilae, Namas Chandra
Department of Engineering Mechanics: Faculty Publications
Carbon nanotubes (CNT) are potentially promising fibers for ultra high strength composites. In order to fully har-ness the outstanding mechanical properties of carbon nanotubes as fiber reinforcements, it is essential to understand the nature of load transfer between fiber and matrix under various types of loading conditions that include tension, compression, torsion and a combination thereof. In this paper, we study the compressive behavior (buckling and post-buckling) of carbon nanotubes in the neat form, when they are embedded in polyethylene matrix and with in¬terface chemical modifications using molecular dynamics simulations based on Tersoff–Brenner potential. It is ob¬served that the critical …
Modeling And Simulation Of The Interaction Between Lubricant Droplets On The Slider Surface And Air Flow Within The Head/Disk Interface Of Disk Drives, Lin Wu
Department of Mechanical and Materials Engineering: Faculty Publications
The dynamic interaction phenomenon between three-dimensional (3-D) lubricant droplets located on the air bearing surface and air flow within the head-disk interface is modeled and numerically simulated. A strong interaction is observed for ultra low flying slider design. The droplet motion and deformation are able to induce non-negligible air bearing force and moment change, which in turn may impose a non-negligible disturbance on the slider’s flying attitude.
Load Transfer Issues In The Tensile And Compressive Behavior Of Multiwall Carbon Nanotubes, G. A. Shen, S. Namilae, Namas Chandra
Load Transfer Issues In The Tensile And Compressive Behavior Of Multiwall Carbon Nanotubes, G. A. Shen, S. Namilae, Namas Chandra
Department of Mechanical and Materials Engineering: Faculty Publications
Carbon nanotubes (CNT) are considered to be ultra strong and stiff reinforcements for structural composite applications. The load transfer between the inner and outer nanotubes in multiwall carbon nanotubes (MWCNT) has to be clearly understood to realize their potential in not only composites, but also other applications such as nano-springs and nano-bearings. In this paper, we study the load transfer between the walls of multiwall nanotubes both in tension and compression using molecular dynamics simulations. It is found that very minimal load is transferred to the inner nanotube during tension. The load transfer in compression of capped nanotubes is much …
End Splice Assembly For Box-Beam Guardrail And Terminal Systemis, John D. Reid, John R. Rohde, Dean L. Sicking, King K. Mak
End Splice Assembly For Box-Beam Guardrail And Terminal Systemis, John D. Reid, John R. Rohde, Dean L. Sicking, King K. Mak
Department of Mechanical and Materials Engineering: Faculty Publications
An end splice assembly for a box-beam guardrail and terminal system having a first stage rail element and a second stage rail element. The assembly has two major connecting components. Upper and lower bent plate channels and upper and lower channel splice plates. The channels and plates have side walls which extend laterally to one another when the two rail elements are mated. The channels and plates are fastened together to provide moment strength to the splice within the system.
Preparation Of High-Strength Nanometer Scale Twinned Coating And Foil, Xinghang Zhang, Amit Misra, Michael Nastasi, Richard G. Hoagland
Preparation Of High-Strength Nanometer Scale Twinned Coating And Foil, Xinghang Zhang, Amit Misra, Michael Nastasi, Richard G. Hoagland
Department of Mechanical and Materials Engineering: Faculty Publications
Very high strength single phase stainless steel coating has been prepared by magnetron sputtering onto a substrate. The coating has a unique microstructure of nanometer spaced twins that are parallel to each other and to the substrate surface. For cases where the coating and substrate do not bind strongly, the coating can be peeled off to provide foil.
Droplet On A Fiber: Geometrical Shape And Contact Angle, Xiangfa Wu, Yuris A. Dzenis
Droplet On A Fiber: Geometrical Shape And Contact Angle, Xiangfa Wu, Yuris A. Dzenis
Department of Engineering Mechanics: Faculty Publications
This paper is concerned with the geometrical shape, wetting length, and contact angle of a microdroplet on a fiber by using the method free energy variation. The governing equation and relevant boundary conditions of the microdroplet were re-derived based on the free energy variation of the droplet/ fiber system. The geometrical shape of the droplet was determined as the combination of Legendre’s elliptical functions of the first and second kinds, corresponding to the previous results in literature [6]. For contact angle h >15 degree, a novel efficient semi-analytic approach was proposed to extract the contact angle from experimental data. The …
Steady-Periodic Green’S Functions And Thermal- Measurement Applications In Rectangular Coordinates, Kevin . D. Cole
Steady-Periodic Green’S Functions And Thermal- Measurement Applications In Rectangular Coordinates, Kevin . D. Cole
Department of Mechanical and Materials Engineering: Faculty Publications
Methods of thermal property measurements based on steady-periodic heating are indirect techniques, in which the thermal properties are deduced from a systematic comparison between experimental data and heat-transfer theory. In this paper heat-transfer theory is presented for a variety of two-dimensional geometries applicable to steady-periodic thermal-property techniques. The method of Green’s functions is used to systematically treat rectangles, slabs (two dimensional), and semi-infinite bodies. Several boundary conditions are treated, including convection and boundaries containing a thin, highconductivity film. The family of solutions presented here provides an opportunity for verification of numerical results by the use of distinct, but similar, geometries. …
Microrobot For Surgical Applications: United States Patent No. Us 7,042,184 B2, Dmitry Oleynikov, Shane Farritor, Adnan Hadzialic, Stephen R. Platt
Microrobot For Surgical Applications: United States Patent No. Us 7,042,184 B2, Dmitry Oleynikov, Shane Farritor, Adnan Hadzialic, Stephen R. Platt
Department of Mechanical and Materials Engineering: Faculty Publications
The present invention provides a micro-robot for use inside the body during minimally-invasive surgery. The microrobot may include various sensors, imaging devices or manipulators.
Non-Isothermal Reaction-Diffusion Systems With Thermodynamically Coupled Heat And Mass Transfer, Yaşar Demirel
Non-Isothermal Reaction-Diffusion Systems With Thermodynamically Coupled Heat And Mass Transfer, Yaşar Demirel
Papers in Analytical Chemistry
Non-isothermal reaction-diffusion (RD) systems control the behavior of many transport and rate processes in physical, chemical, and biological systems. A considerable work has been published on mathematically coupled nonlinear differential equations of RD systems by neglecting the possible thermodynamic couplings among heat and mass fluxes, and reaction velocities. Here, the thermodynamic coupling refers that a flux occurs without its primary thermodynamic driving force, which may be gradient of temperature, or chemical potential, or reaction affinity. This study presents the modeling equations of non-isothermal RD systems with coupled heat and mass fluxes excluding the coupling of chemical reactions using the linear …
Modeling And Representation Of Geometric Tolerances Information In Integrated Measurement Processes, Xiaoping Zhao, T. M. Kethara Pasupathy, Robert G. Wilhelm
Modeling And Representation Of Geometric Tolerances Information In Integrated Measurement Processes, Xiaoping Zhao, T. M. Kethara Pasupathy, Robert G. Wilhelm
Department of Mechanical and Materials Engineering: Faculty Publications
Modeling and representation of geometric tolerances information across an enterprise is viable due to the advances in Internet technologies and increasing integration requirements from industry. In Integrated Measurement Processes (IMP), geometric tolerances data model must support different models from several well-defined standards: including ASME Y14.5M-1994, STEP, DMIS, and others. In this paper, we propose a layered conformance level geometric tolerances representation model. This model uses the widely applied ASME Y14.5M-1994 as its foundation layer by abstracting most information from this standard. The additional geometric tolerances information defined by DMIS and STEP is incorporated into this model to form corresponding conformance …
Retrofit Of Distillation Columns Using Thermodynamic Analysis, Yaşar Demirel
Retrofit Of Distillation Columns Using Thermodynamic Analysis, Yaşar Demirel
Papers in Physical Properties
Thermodynamic analysis provides the column grand composite curves and exergy loss profiles, which are becoming readily available for a converged distillation column simulation. For example, the Aspen Plus simulator performs the thermodynamic analysis through its Column–Targeting tool for rigorous column calculations. This study uses the column grand composite curves and the exergy loss profiles obtained from Aspen Plus to assess the performance of the existing distillation columns, and reduce the costs of operation by appropriate retrofits in a methanol plant. Effectiveness of the retrofits is also assessed by means of thermodynamics and economics. The methanol plant utilizes two distillation columns …
Flexible Tools For Specifying Design Variation, Trichy Pasupathy, Xiaoping Zhao, Robert Wilhelm
Flexible Tools For Specifying Design Variation, Trichy Pasupathy, Xiaoping Zhao, Robert Wilhelm
Department of Mechanical and Materials Engineering: Faculty Publications
This paper describes flexible tools for specifying design variations that are based on nonuniform profile tolerance definitions. These tools specify bounds of design performance that can be used for negotiation among engineers in a collaborative design process. These specification methods allow for the capture of many different design functions that are not easily described with current tool designs. In addition, these specification methods lend themselves to efficient verification methods. Profile tolerance definitions provide the most general variation controls for complex mechanical surfaces. Common design practices and engineering standards for profile tolerances exhibit many weaknesses and limitations. We present a rationale …
Raghavan, V., Gogos, G., Babu, V. And Sundararajan, T., “Effect Of Gravity On Methanol Diffusion Flames Burning Within A Forced Convective Environment”, Accepted For Publication In International Communications In Heat And Mass Transfer (2006)
Combustion Research at University of Nebraska-Lincoln
No abstract provided.
Pope, D. And Gogos, G. "Numerical Simulation Of Fuel Droplet Extinction Due To Forced Convection," Combustion And Flame, 142:89-106 (2005)
Combustion Research at University of Nebraska-Lincoln
No abstract provided.
Pope, D.N. And Gogos G. “A New Multicomponent Diffusion Formulation For The Finite-Volume Method: Application To Convective Droplet Combustion,” Numerical Heat Transfer, Part B Fundamentals, Part B, 48, 3:213-234, (2005)
Combustion Research at University of Nebraska-Lincoln
No abstract provided.
Raghavan, V., Pope, D.N., Howard, D. And Gogos, G. “Surface Tension Effects During Low Reynolds Number Methanol Droplet Combustion,” Combustion And Flame, Accepted (2006)
Combustion Research at University of Nebraska-Lincoln
No abstract provided.
Raghavan, V., Pope, D.N. And Gogos, G. “Effects Of Forced Convection And Surface Tension During Methanol Droplet Convection,” Aiaa Journal Of Thermophysics And Heat Transfer, Accepted (2006)
Combustion Research at University of Nebraska-Lincoln
No abstract provided.
Pope, D.N., Howard, D., Lu, K. And Gogos, G. “Combustion Of Moving Droplets And Suspended Droplets: Transient Numerical Results,” Aiaa Journal Of Thermophysics And Heat Transfer, 19:273-281 (2005)
Combustion Research at University of Nebraska-Lincoln
No abstract provided.
Optimization Of Multilayer Wear-Resistant Thin Films Using Finite Element Analysis On Stiff And Compliant Substrates, R. K. Lakkaraju, Florin Bobaru, S. L. Rohde
Optimization Of Multilayer Wear-Resistant Thin Films Using Finite Element Analysis On Stiff And Compliant Substrates, R. K. Lakkaraju, Florin Bobaru, S. L. Rohde
Department of Engineering Mechanics: Faculty Publications
Extensive research has been carried out by researchers on the growth and characterization of multilayer protective coatings, but the design of these coatings still remains largely empirical. In this regard, recent progress has been made in developing a design approach for optimizing a multilayer coating structure before deposition, which would help save time and material. In pursuit of an optimal design, finite element analysis using a plane strain Hertzian contact model was developed to investigate the stress/ strain behavior within the layers of the system. The present study looks to find the optimal thicknesses of individual layers in a multilayer …
A Model For Predicting The Evolution Of Multiple Cracks On Multiple Length Scales In Viscoelastic Composites, David H. Allen, C. R. Searcy
A Model For Predicting The Evolution Of Multiple Cracks On Multiple Length Scales In Viscoelastic Composites, David H. Allen, C. R. Searcy
Department of Engineering Mechanics: Faculty Publications
A model is presented herein for predicting the evolution of numerous cracks on multiple length scales, the objective of such a model being to develop the capability to predict failure of structural components to perform their intended tasks. Such a capability would then be useful as a predictive tool for designing structural components so as not to fail, but rather to succeed in performing their intended tasks. The model developed herein is somewhat involved, being based in continuum mechanics and thermodynamics, but is nevertheless expected to be cost effective (wherever sufficient accuracy permits) when compared to more costly experimental means …
E(Fg)2: A New Fixed-Grid Shape Optimization Method, Florin Bobaru Ph.D., Srinivas Rachakonda
E(Fg)2: A New Fixed-Grid Shape Optimization Method, Florin Bobaru Ph.D., Srinivas Rachakonda
Department of Engineering Mechanics: Faculty Publications
We propose a shape optimization method over a fixed grid. Nodes at the intersection with the fixed grid lines track the domain’s boundary. These “floating” boundary nodes are the only ones that can move/appear/disappear in the optimization process. The element-free Galerkin (EFG) method, used for the analysis problem, provides a simple way to create these nodes. The fixed grid (FG) defines integration cells for EFG method. We project the physical domain onto the FG and numerical integration is performed over partially cut cells. The integration procedure converges quadratically. The performance of the method is shown with examples from shape optimization …
Comparative Modeling Of Performance Limits Of Solid State Neutron Detectors Based On Planar B-Rich Capture Layers, A. D. Harken, Brian W. Robertson
Comparative Modeling Of Performance Limits Of Solid State Neutron Detectors Based On Planar B-Rich Capture Layers, A. D. Harken, Brian W. Robertson
Department of Mechanical and Materials Engineering: Faculty Publications
Solid-state neutron detectors based only on boron-rich semiconductors are of interest for their potential to provide the highest thermal neutron detection efficiencies of any solid-state neutron detectors. A simple physical model, recently shown to generate thermal neutron capture product spectra that agree quantitatively with full-physics GEANT4 simulation, is used to compare the capture product energy spectra and the upper limits to neutron detection efficiency of planar conversion layer, sandwich and all-boron-carbide detectors for the case of normally incident, mono-energetic, thermal neutrons. All-boron-carbide semiconductor detectors are deduced to be greatly superior to all other boron-rich solid-state detector types in their maximal …
Modeling, Analysis, And Experimental Study Of In Vivo Wheeled Robotic Mobility, Mark E. Rentschler, Jason Dumpert, Stephen R. Platt, Karl Iagnemma, Dmitry Oleynikov, Shane M. Farritor
Modeling, Analysis, And Experimental Study Of In Vivo Wheeled Robotic Mobility, Mark E. Rentschler, Jason Dumpert, Stephen R. Platt, Karl Iagnemma, Dmitry Oleynikov, Shane M. Farritor
Department of Mechanical and Materials Engineering: Faculty Publications
Laparoscopy is abdominal surgery performed with long tools inserted through small incisions. The use of small incisions reduces patient trauma, but also eliminates the surgeon’s ability to view and touch the surgical environment directly. These limitations generally restrict the application of laparoscopy to procedures less complex than those performed during open surgery. This paper presents a theoretical and experimental analysis of miniature, wheeled, in vivo robots to support laparoscopy. The objective is to develop a wireless mobile imaging robot that can be placed inside the abdominal cavity during surgery. Such robots will allow the surgeon to view the surgical environment …
Nanoparticle-Induced Negative Differential Resistance And Memory Effect In Polymer Bistable Light-Emitting Device, Ricky J. Tseng, Jianyong Ouyang, Chih-Wei Chu, Jinsong Huang, Yang Yang
Nanoparticle-Induced Negative Differential Resistance And Memory Effect In Polymer Bistable Light-Emitting Device, Ricky J. Tseng, Jianyong Ouyang, Chih-Wei Chu, Jinsong Huang, Yang Yang
Department of Mechanical and Materials Engineering: Faculty Publications
Recently, electrical bistability was demonstrated in polymer thin films incorporated with metal nanoparticles [J. Ouyang, C. W. Chu, C. R. Szmanda, L. P. Ma, and Y. Yang, Nat. Mater. 3, 918 (2004)]. In this letter, we show the evidence that electrons are the dominant charge carriers in these bistable devices. Direct integration of bistable polymer layer with a light-emitting polymer layer shows a unique light-emitting property modulated by the electrical bistability. A unique negative differential resistance induced by the charged gold nanoparticles is observed due to the charge trapping effect from the nanoparticles when interfaced with the light-emitting layer.
The Role Of Electrospinning In The Emerging Field Of Nanomedicine, S. Y. Chew, Y. Wen, Yuris A. Dzenis, K. W. Leong
The Role Of Electrospinning In The Emerging Field Of Nanomedicine, S. Y. Chew, Y. Wen, Yuris A. Dzenis, K. W. Leong
Department of Mechanical and Materials Engineering: Faculty Publications
The fact that in vivo the extracellular matrix or substratum with which cells interact often includes topography at the nanoscale underscores the importance of investigating cell-substrate interactions and performing cell culture at the submicron scale. An important and exciting direction of research in nanomedicine would be to gain an understanding and exploit the cellular response to nanostructures. Electrospinning is a simple and versatile technique that can produce a macroporous scaffold comprising randomly oriented or aligned nanofibers. It can also accommodate the incorporation of drug delivery function into the fibrous scaffold. Endowed with both topographical and biochemical signals such electrospun nanofibrous …
Piezoelectromagnetic Waves In A Ceramic Plate Between Two Ceramic Half-Spaces, S. N. Jiang, Q. Jiang, X. F. Li, S. H. Guo, H. G. Zhou, J. S. Chang
Piezoelectromagnetic Waves In A Ceramic Plate Between Two Ceramic Half-Spaces, S. N. Jiang, Q. Jiang, X. F. Li, S. H. Guo, H. G. Zhou, J. S. Chang
Department of Mechanical and Materials Engineering: Faculty Publications
We analyze the propagation of piezoelectromagnetic waves guided by a plate of polarized ceramics between two ceramic half-spaces. An exact dispersion relation is obtained, which reduces to a few known elastic, electromagnetic, and quasistatic piezoelectric wave solutions in the literature as special cases. Numerical solutions to the equation that determines the dispersion relation show the existence of guided waves. The results are useful for acoustic wave and microwave devices.
Non-Operative Management Of Posterior Tibialis Tendon Dysfunction: Design Of A Randomized Clinical Trial [Nct00279630], Kornelia Kulig, Amy B. Pomrantz, Judith M. Burnfield, Stephen F. Reischl, Susan Mais-Requejo, David B. Thordarson, Ronald W. Smith
Non-Operative Management Of Posterior Tibialis Tendon Dysfunction: Design Of A Randomized Clinical Trial [Nct00279630], Kornelia Kulig, Amy B. Pomrantz, Judith M. Burnfield, Stephen F. Reischl, Susan Mais-Requejo, David B. Thordarson, Ronald W. Smith
Department of Mechanical and Materials Engineering: Faculty Publications
Background: Posterior tibialis tendon dysfunction (PTTD) is a common cause of foot pain and dysfunction in adults. Clinical observations strongly suggest that the condition is progressive. There are currently no controlled studies evaluating the effectiveness of exercise, orthoses, or orthoses and exercise on Stage I or IIA PTTD. Our study will explore the effectiveness of an eccentric versus concentric strengthening intervention to results obtained with the use of orthoses alone. Findings from this study will guide the development of more efficacious PTTD intervention programs and contribute to enhanced function and quality of life in persons with posterior tibialis tendon dysfunction. …
Efficient Inverted Polymer Solar Cells, G. Li, C.-W. Chu, V. Shrotriya, Jinsong Huang, Y. Yang
Efficient Inverted Polymer Solar Cells, G. Li, C.-W. Chu, V. Shrotriya, Jinsong Huang, Y. Yang
Department of Mechanical and Materials Engineering: Faculty Publications
We investigate the effect of interfacial buffer layers—vanadium oxide (V2O5) and cesium carbonate (Cs2CO3)—on the performance of polymer solar cells based on regioregular poly-(3-hexylthiophene) and [6,6]-phenyl C60 butyric acid methyl ester blend. The polarity of solar cells can be controlled by the relative positions of these two interfacial layers. Efficient inverted polymer solar cells were fabricated with the structure of indium tin oxide (ITO)/Cs2CO3/polymer blend/vanadium oxide (V2O5)/aluminum (Al). Short-circuit current of 8.42 mA/cm2, open-circuit voltage of 0.56 V, and power conversion efficiency of …