bluuebunny/crossref_metadata_2025 huggingface dataset:
Manufacturing and Flexure Properties Characterization of Hybrid Nano-/Micro-Fiber Reinforced Epoxy Composites
Authors: Barua Bipul , Saha Mrinal C.
Published: August 2012

We report an approach for the deposition of carbon nanotubes (CNTs) on carbon fabrics (CFs) en route for the development of hybrid nano-/micro-fiber composite structures. Ultrasonic atomization process was utilized for the direct deposition of CNTs on the surface of carbon fiber fabric. A dilute solution of CNTs was prepared by dispersing very small amount of multi walled CNTs (MWNT) in N,N-Dimethylformamide (DMF) using a low frequency ultrasonic water bath. The dispersed solution was then fed into the ultrasonic atomizer probe using a syringe pump and sprayed directly on the carbon fiber fabric rested on a hot plate. The dispersion of MWNTs in DMF solvent was characterized using UV spectroscopy and the distribution of CNTs on CF was characterized using scanning electron microscopy (SEM). Vacuum assisted resin transfer molding (VRTM) was used to manufacture composite laminates using several layers of CNTs hybrid CF fabrics. We prepared hybrid composite laminates containing 0.03-wt% of CNTs. Dispersion of CNTs in DMF and distribution of CNTs on CFs was found to be very good which we believed to be resulted in about 15% improvement in flexure strength and about 12% improvement in strain to failure compared to neat composites. Such improvements in composite properties with only 0.03% CNTs are very promising in hybrid composite structures.
CFD Computation, Analysis and Design of a Two-Bladed Wastewater Pump
Authors: Litfin Oliver , Mohr Christian , Haddad Kais , Epple Philipp , Semel Matthias , Becker Klaus , Klein Horst , Delgado Antonio
Published: August 2012

In this work a wastewater pump with a two-bladed prototype impeller and a specific speed of 0.68, referring to a well-established industrial design, was simulated in a commercial CFD solver, ANSYS CFX. Simulations of the impeller only and of the complete pump with spiral casing including a detailed analysis of the flow patterns were performed. A parameter study with around 25 new designs containing variations of the inlet angle and the wrap angle was carried out, leading to significant improvements of the flow pattern as well as of the hydraulic efficiency. Based on the optimum leading edge and wrap angle, the total head was improved by variation of the exit blade angle. Having set the better main dimensions, the effect of the blade shape, i.e. blade angle distribution, was investigated. Here it is shown that changing the blade angle distribution in such a way that the point of maximum blade angle is shifted to a bigger radius can lead to substantial improvements. One special focus in this whole study was also to describe and control the behavior of the relative eddy, which is directly related also to the slip factor. In the scope of this work it is shown how it is possible to influence and move the relative eddy to the best position, since due to the small relative velocities in the blade passage it is impossible to fully avoid it. A detailed analysis of these CFD results is presented as well as the recommendations for an efficient design of this special type of wastewater pump impellers.
Development of an Ultrasound Hyperthermia Simulator for Therapeutic Applications
Authors: Echeverria Esteban , Thamire Chandrasekhar
Published: August 2012

In recent times, Ultrasound for therapeutic applications is becoming increasingly popular due to its high practicality and efficiency. However, determination of adequate dosages presents a great challenge due to the difficulty of measuring tissue temperatures during the process. Further, accurate calculation of temperature field induced by ultrasound within the tissue is difficult to develop because of the time-scale differences between pressure and temperature analyses. In order to overcome this issue, practical and accurate methods to couple both analyses are needed. In the present study, Westervelt’s nonlinear wave equation is used to simulate ultrasonic propagation driven by an unfocused piston source in an axisymmetric biological tissue phantom. Using the Finite Difference Time Domain (FDTD) method, a pressure field was calculated for different sinusoidal bursts, frequencies, and source pressures. Average heat generation fields were calculated from the pressure field within an adequate time range for practical purposes. The Pennes bioheat transfer equation with the calculated heat generation fields were used to acquire transient temperature distributions. Effect of source pressure, frequency, source radius, and trial duration on the temperature profiles was examined. It can be observed from the simulations that continuous wave signals increase temperature at a focus in shorter times, while discrete pulses with adequate duty factors can be useful in maintaining required temperatures constant while diffusing heat along the tissue. The methodology presented here can be of use in many applications such as increasing necrotic volume for tissue ablation purposes.
Combat Helmet-Headform Coupling Characterized From Blunt Impact Events
Authors: Vasquez Kimberly B. , Logsdon Katie P. , Dorman Daniel B. , Chancey Valeta Carol
Published: August 2012

Observed head injury has historically been mechanically related to headform center of gravity (CG) acceleration. Helmets (motorcycle, sports, military, etc.) are evaluated based on the headform CG peak acceleration for blunt impacts. However, recent interest has shifted to collecting data from the helmet shell itself, as it is an optimal location for mounting sensors due to ease of access, sufficient surface area availability, and limited interference to the wearer. In order to accurately predict head injury from data collected on the helmet shell, the helmet and headform must be rigidly coupled. Headform-helmet fit typically is dependent on the pad fitting system and the person mounting the helmet to the headform because a standard states which headform to use. The objective of this study is to compare the Department of Transportation (DOT) headform (currently used in military blunt impact testing) to the more anthropomorphic International Standard Organization (ISO) half headform. Testing was completed on a monorail drop tower to analyze the effect of helmet/headform coupling on the blunt impact behavior of ACH helmets using FMVSS test methodology. Three headform configurations were used: the DOT headform (standard for military helmet blunt impact testing) with required surrogate chin, the ISO half headform (standard for ASTM helmet testing), and the ISO half headform with a surrogate chin. The two currently field-approved pad types were also used to determine best headform-helmet fit. Results from these series of tests will be presented, including headform peak acceleration and relative motion between the helmet and headform.
A Semi-Staggered Numerical Procedure for the Incompressible Navier-Stokes Equations on Curvilinear Grids
Authors: Babaee Hessam , Acharya Sumanta
Published: August 2012

An accurate and efficient finite difference method for solving the three dimensional incompressible Navier-Stokes equations on curvilinear grids is developed. The semi-staggered grid layout has been used in which all three components of velocity are stored on the corner vertices of the cell facilitating a consistent discretization of the momentum equations as the boundaries are approached. Pressure is stored at the cell-center, resulting in the exact satisfaction the discrete continuity. The diffusive terms are discretized using a second-order central finite difference. A third-order biased upwind scheme is used to discretize the convective terms. The momentum equations are integrated in time using a semi-implicit fractional step methodology. The convective and diffusive terms are advanced in time using the second-order Adams-Bashforth method and Crank-Nicolson method respectively. The Pressure-Poisson is discretized in a similar approach to the staggered gird layout and thus leading to the elimination of the spurious pressure eigen-modes. The validity of the method is demonstrated by two standard benchmark problems. The flow in driven cavity is used to show the second-order spatial convergence on an intentionally distorted grid. Finally, the results for flow past a cylinder for several Reynolds numbers in the range of 50–150 are compared with the existing experimental data in the literature.
Thermal Transport Measurements of Bilayer and Few-Layer Graphene Supported on Silicon Dioxide
Authors: Sadeghi Mir Mohammad , Shi Li
Published: August 2012

The thermal conductivity of bilayer graphene (BLG) and few-layer graphene (FLG) samples supported on a silicon dioxide (SiO2) bridge has been measured in the temperature range between 80 K and 375 K. In the experiments, resistance heater and thermometer lines at the two ends of the bridge were used to implement steady-state thermal conductance measurements of the sample before and after the graphene on the bridge was etched away. The obtained thermal conductivity of the supported graphene increases and the temperature for the peak thermal conductivity decreases with increasing layer thickness. Compared to the reported thermal conductivity of suspended FLG samples, the opposite behavior observed here for the supported FLG reveals that interaction with the SiO2 support and also possibly polymer residue on top of the FLG sample suppresses the thermal conductivity of the supported FLG more than interlayer interaction within the FLG. The linear rise of thermal conductivity with layer number up to 8 layers suggests that the scattering effects due to substrate and polymer residue penetrates much more than 4 layers into a multilayer flake.
Numerical Modeling of the Distributed Electrochemistry and Performance of Solid Oxide Fuels Cells
Authors: Recknagle Kurtis P. , Ryan Emily M. , Khaleel Moe A.
Published: August 2012

A cell-level distributed electrochemistry (DEC) modeling tool has been developed to enable predicting trends in solid oxide fuel cell performance by considering the coupled and spatially varying multi-physics that occur within the tri-layer. The approach calculates the distributed electrochemistry within the electrodes, which includes the charge transfer and electric potential fields, ion transport throughout the tri-layer, and gas distributions within the composite and porous electrodes. The thickness of the electrochemically active regions within the electrodes is calculated along with the distributions of charge transfer. The DEC modeling tool can examine the overall SOFC performance based on electrode microstructural parameters, such as particle size, pore size, porosity, electrolyte- and electrode-phase volume fractions, and triple-phase-boundary length. Recent developments in electrode fabrication methods have lead to increased interest in using graded and nano-structured electrodes to improve the electrochemical performance of SOFCs. This paper demonstrates how the DEC modeling tool can be used to help design novel electrode microstructures by optimizing a graded anode for high electrochemical performance.
Analysis of Solid Oxide Fuel Cell LSM-YSZ Composite Cathodes With Varying Starting Powder Sizes
Authors: Harris William M. , Nelson George J. , Lombardo Jeffrey J. , Cocco Alex P. , Izzo John R. , Chiu Wilson K. S. , Tanasini Pietro , Van herle Jan , Comninellis Christos , Andrews Joy C. , Liu Yijin , Pianetta Piero , Chu Yong S.
Published: August 2012

Solid oxide fuel cell cathodes have been examined using non-destructive x-ray nanotomography. The cathodes examined were a composite of strontium-doped lanthanum manganite (LSM) and yttria-stabilized zirconia (YSZ), with three different starting powder sizes of 0.3 μm, 0.5 μm, and 1 μm. Differential absorption contrast imaging was performed over the manganese K-edge (6539 eV) for the identification of the LSM, YSZ, and pore phases. The three phases were each segmented from reconstruction of the tomography data. Three dimensional volumes of the segmented phases were used to calculate structural characterization parameters of the sample including porosity, pore size distributions, and mean phase sizes. These parameters are reported and some correlations are drawn to the starting powder size.
Three-Dimensional Numerical Evaluation of Thermal Performance of Uninsulated Wall Assemblies
Authors: Ridouane El Hassan , Bianchi Marcus V. A.
Published: August 2012

Uninsulated wall assemblies are typical in older homes, as many were built before building codes required insulation. Building engineers need to understand the thermal performance of these assemblies as they consider home energy upgrades if they are to properly predict pre-upgrade performance and, consequently, prospective energy savings from the upgrade. Most whole-building energy simulation tools currently use simplified, 1D characterizations of building envelopes and assume a fixed thermal resistance that does not vary over a building’s temperature range. This study describes a detailed 3D computational fluid dynamics model that evaluates the thermal performance of uninsulated wall assemblies. It accounts for conduction through framing, convection, and radiation and allows for material property variations with temperature. Parameters that were varied include ambient outdoor temperature and cavity surface emissivity. The results may serve as input for building energy simulation tools that model the temperature-dependent energy performance of homes with uninsulated walls.
Wetting Behavior and Drainage of Water Droplets on Microgrooved Brass Surface
Authors: Rahman M. A. , Jacobi A. M.
Published: August 2012

In the present study, we report the contact angle hysteresis and drainage behavior of water drops on a number of brass surfaces with parallel microgrooves and compare them to the flat baseline surfaces. Parallel micro-grooves with different groove dimensions are fabricated by micro end-milling process without any modification of the surface chemistry. Advancing and receding contact angles in both parallel and perpendicular direction of the grooves and also the drainage behavior of water droplets on the microgrooved surfaces is found to be considerably affected by change in groove geometry parameters. Very high hysteresis is observed for both low (< 0.2) and high aspect ratio (> 0.7) of grooves and also for surfaces with lower groove spacing due to the droplets being in a Wenzel state. For intermediate aspect ratio (0.25–0.70) and larger spacing of the grooves, droplets remain in a Cassie state and the hysteresis is lower in both directions than that on the flat surfaces. Variation of critical sliding angle (angle at the point of incipient sliding of water droplets due to gravity) with groove geometry is investigated for a range of water droplet volume of 15 to 75 μl. Droplets of all volumes are found to slide much more readily on grooved surfaces than when placed on the flat baseline surfaces. Height and spacing of the grooves are also found to have significant influence on the sliding of the water droplets, as critical inclination angle decreased with groove height and increased with groove spacing. The results from this study may be useful in a broad range of applications where water retention plays an important role.
A Silicon Thermomechanical In-Plane Microactuation System for Large Displacements in Aqueous Environments
Authors: Holst Gregory L. , Jensen Brian D.
Published: August 2012

This paper presents an underwater, silicon, thermal microactuation system capable of moving a 200 μN load to a displacement of 110 μm. Its function relies on a thermal actuator capable of 9 μm of displacement in an aqueous environment. This actuator is combined with a ratcheting device to achieve the 110 μm of displacement. The system is a microelectromechanical system (MEMS) fabricated with a two layer surface-micromachining process, PolyMUMPS. The actuation system is designed to provide motion to biological microelectromechanical systems (BioMEMS) in aqueous environments. This paper presents the design and experimental demonstration of the actuation system. The in-depth analysis of the thermal, mechanical, and fabrication aspects of the actuation system are outlined, and the experimental procedure and test parameters are discussed.
A Mechanistic Model of Two-Phase Pressure Drop in Microchannels
Authors: Field Brandon S. , Hrnjak Pega
Published: August 2012

A mechanistic model of two-phase pressure drop has been developed for microchannel flow. The primary flow regimes observed in microchannel two-phase flow regime maps were the inertial dominated regime (annular flow) and the surface tension dominated regime (slug or bubbly flow). Mechanistic models of pressure drop for each of these regimes are developed and compared to pressure drop in microchannel flows of four different refrigerants with widely varying fluid properties: R134, R410A, R290 (propane) and R717 (ammonia) of varying hydraulic diameters between 70 microns to 305 microns. The mechanistic model compares favourably to the experimental pressure drop data from microchannel flow measurements with an overall mean deviation of 18.1%. The model is also compared with refrigerant-oil flow of R134a and two different weights of POE oil, using fluid property correlations developed for those mixtures, with a mean deviation of 18.9%. While this accuracy is not stellar, the significance is that no empirical coefficients were needed to close the model.
A Study on Dimension Synthesis for the Peaucellier Mechanism
Authors: Buckley Jessica , Huang Ming Z.
Published: August 2012

Straight-line motion, albeit simple, manifest itself in numerous applications, from running steam engines and oil wells to manufacturing parts with straight edges and sides. The drive to maximize production creates a need for continuously running assembly-line manufacturing comprised of precise, individually optimized components. While there are many so-called straight-line generating mechanisms, few actually produce a true straight-line, most generate only approximate straight-line. Featured an eight-link rhomboidal system with length constraints, the Peaucellier mechanism is one that actually produces a true straight line intrinsically. This paper presents a study on the dimension synthesis of the Peaucellier mechanism, namely by identifying the correct ratio of linkage lengths to produce the longest straight line stroke. In addition to designing for stroke, another objective of interest is to attain a desired velocity profile along the path. Kinematic analysis of the velocity profile on the mechanism will render the creation of input angular velocity standards based on desired stroke speed. Given the stroke and velocity specifications, specific steps to size the dimensions of the mechanism developed as result of this study will be presented.
A Mature Engineering Response Toward Climate Change
Authors: Catlow Fred
Published: August 2012

Engineers respond to the needs of society by providing effective technical solutions, based on scientific truths, to problems. Not all problems have clear cut answers and some have ‘fuzzy’ areas that can be the subject of interpretation and debate. Sometimes the solutions may create new problems which may not always be obvious to their proponents. Different solutions to the energy problem and their perceived effect on climate change are examined from various perspectives such as effectiveness, controllability, availability, demand, safety, environmental and social factors, economics and sustainability. This is achieved using existing and projected data. Also the situation in different countries is discussed, specific installations and their acceptance by their communities. The paper concludes by discussing some of the political, scientific and social implications and the implications for the future.
A Numerical Study of Coupling of Thermal and Hydrodynamic Oscillations in a Hybrid Rocket Motor
Authors: Akyuzlu K. M. , Albayrak K.
Published: August 2012

A one-dimensional, mathematical model is adopted to investigate, numerically, the instabilities experienced inside a hybrid rocket propulsion system. The presumption is that such oscillations feed into combustion instabilities and result in poor performance of the propulsion system and/or result in mechanical vibrations that lead to failure of the rocket motor. The model adopted for the numerical study is a one-dimensional, multi-node representation of a subscale hybrid rocket propulsion system. A one dimensional channel with circular cross-section is configured to simulate a combustion chamber of a rocket hybrid rocket motor and is connected to a converging–diverging nozzle in the downstream and to a plenum with a flow straightener in the upstream side. The working fluid is supplied from a pressurized storage tank to the upstream plenum through a throttle valve. A multi-component approach is used to model, mathematically, the propulsion system. In this integrated-component model, the unsteady flow through the throttle valve and the nozzle is assumed to be one-dimensional and isentropic whereas the flow in the forward plenum and in the combustion chamber is assumed to be a one-dimensional, unsteady, compressible, turbulent, and subsonic. The physics based mathematical model of the flow in the channel consists of conservation of mass, momentum and energy equations subject to appropriate boundary conditions as defined by the physical problem stated above. The working fluid is assumed to be compressible through a simple ideal gas relation. The governing equations of the compressible flow in the combustion chamber are discretized using the second order accurate MacCormack finite difference scheme. Convergence and grid independence studies were done to determine the optimum mesh size and computational time increment needed for the present simulations. Furthermore, steady state results of the proposed model are compared to the results of the isentropic, Fanno (viscous 1-D flow), and Rayleigh (1-D flow with heat input) case studies to verify the accuracy of the numerical predictions. Numerical experiments were then carried out to simulate the flow oscillations in the combustion chamber of a sample subscale hybrid rocket motor. Experiments were repeated for various operating conditions (Re numbers between 104 and 106) to determine the flow regions where these oscillations are sustained. The numerical simulation results indicate that the proposed mathematical model predicts the expected unsteady axial distributions of temperature, velocity, and pressure in the combustion chamber and the general characteristics of the experimentally observed instabilities associated with hybrid rocket propulsion systems.
Unsteady Flow Characteristics and Viscous Flow Losses Behind Multiple Rows of Circular Pin Fins in Coolant Channels
Authors: Gokce Zeki Ozgur , Camci Cengiz
Published: August 2012

This article deals with a computational assessment of 3D viscous flow behind multiple rows of circular pin fins in coolant channels used in gas turbine systems. Unsteady oscillations and turbulent flow characteristics especially near the endwall surfaces generate the much needed heat transfer enhancement that is usually from the walls to the coolant fluid. The current study is about a comprehensive assessment of present day computational fluid dynamics solvers for the enhancement of wall to coolant heat transfer rates. The paper presents details regarding many flow characteristics, including particle streamlines, as well as total pressure, turbulent kinetic energy and hub heat transfer coefficient contours. The endwall fence placed upstream of the cylinder generates a measurable increase in heat transfer rates downstream of the cylinder. The paper also includes a number of suggested ways to enhance endwall heat transfer rates for use in gas turbine cooling configurations and total pressure improvements near the turbine hub endwall.
Two-Phase Flow Simulations of Protective Gas Layer for Spallation Neutron Source Target
Authors: Abdou Ashraf , Wendel Mark , Riemer Bernard , Volpenhein Eric , Brewster Robert
Published: August 2012

The Spallation Neutron Source (SNS) is an accelerator-based neutron source at Oak Ridge National Laboratory (ORNL). The nuclear spallation reaction occurs when a proton beam hits liquid mercury. This interaction causes thermal expansion of the liquid mercury which produces high pressure waves. When these pressure waves hit the target vessel wall, cavitation can occur and erode the wall. Research and development efforts at SNS include creation of a vertical protective gas layer between the flowing liquid mercury and target vessel wall to mitigate the cavitation damage erosion and extend the life time of the target. Since mercury is opaque, computational fluid dynamics (CFD) has been used to visualize the general behavior of a protective gas layer arising from various delivery and retention concepts as a guide for design of experimental efforts. Recent advancements in capacity for large scale CFD modeling via the high performance compute systems of ORNL now enable high-fidelity simulation approaching full geometric scale. Accordingly, in this study, CFD simulations of three dimensional, unsteady, turbulent, two-phase flow of helium gas injection in flowing liquid mercury over textured walls are carried out for target design purposes with the commercially available CFD code STARCCM+. The Volume of Fluid (VOF) model is used to track the helium-mercury interface. Different combinations of conical pits and V-shaped straight grooves at different orientations with respect to the gravity vector are simulated at the SNS proton beam window to increase the helium gas holdup. Time integration of predicted helium gas volume fraction over time is done for the design alternatives considered to compare the gas coverage and average thickness of the helium gas layer.
Analysis of Nonlinear Forced Vibrations of Shallow Shells With Cut-Outs by Using the R-Function Method
Authors: Pilgun Galyna , Amabili Marco
Published: August 2012

Geometrically nonlinear forced vibrations of shells based on the domains with cut-outs are investigated. Classical nonlinear shallow-shell theories retaining in-plane inertia is used to calculate the strain energy; the shear deformation is neglected. A mesh-free technique based on classic approximate functions and the R-function theory is used to build the discrete model of the nonlinear vibrations. This allowed for constructing the sequences of admissible functions that satisfy given boundary conditions in domains with complex geometries. Shell displacements are expanded by using Chebyshev orthogonal polynomials. A two-step approach is implemented to solve the problem: first a linear analysis is conducted to identify natural frequencies and corresponding natural modes to be used in the second step as a basis for nonlinear displacements. The system of ordinary differential equations is obtained by using Lagrange approach on both steps. The convergence of the solution is studied by using different multimodal expansions. The pseudo-arclength continuation method and bifurcation analysis are used to study the nonlinear equations of motion. Numerical responses are obtained in the spectral neighbourhood of the lowest natural frequency. When possible, obtained results are compared to those available in the literature.
Passive Morphing Airfoil With Honeycombs
Authors: Heo Hyeonu , Ju Jaehyung , Kim Doo-Man , Jeon Chang-Soo
Published: August 2012

A passive morphing may improve the aerodynamic characteristics through structural shape change by aerodynamic loads during the flight, resulting in improving fuel efficiency. The passive morphing structure should have a capability to be highly deformed while maintaining a sufficient stiffness in bending. Honeycombs may be good for controlling both stiffness and flexibility. This paper investigates a honeycomb airfoil’s static deformations through the fluid-structure interaction using computational fluid dynamics and structural finite element analysis. The structural performance will be investigated with varying honeycomb geometries including regular, auxetic and chiral meso-structures.
Life-Cycle Assessment of Electric Rice Cooker: A Case Study
Authors: Sha Zhenghui , Ameta Gaurav
Published: August 2012

Nowadays, almost every family has one electric rice cooker, thus making electric rice cooker one of the most popular household appliance in our society. If the product is not designed ecologically and is used heavily, then the product may lead to large ecological impact to our environment. To assess a product’s environmental impacts, Life Cycle Assessment (LCA) methodology is utilized. However, to the best of the authors’ knowledge, for one such technology (electric rice cooker), no complete LCA studies have existed by far. Therefore, the question about the electric rice cooker’s environmental performance is still open. This paper presents an LCA study for the complete life cycle of an electric rice cooker with the power 500Watts as the functional unit. In order to conduct LCA study, the whole life cycle of electric rice cooker was divided into four primary phases: raw materials acquisition, product manufacturing, product utilization and final disposal. To facilitate the data collection and LCA implementation, the whole life cycle system was classified as two subsystems — background system and foreground system. Based on the proposed method, primary data and environmental impact calculation was aided by Simapro 7.2 software. In the light of the Ecoindicator-99 methodology, eleven impact categories (Carcinogens, Resp. organics, Resp. inorganics, Climate change, Radiation, Ozone layer, Ecotoxicity, Acidification, Land use, Minerals, Fossil fuels) were used for the classification and characterization of the life cycle impact assessment. In this paper, the LCA study was found as a very helpful tool to define ecodesign measures for this product. Several measures are suggested to the manufacturers to implement the ecodesign in the future: 1) Use recyclable plastics in the minor parts and hidden components, such as switcher, handle etc.; 2) Reduce the number of different materials in packaging; 3) Avoid incompatible plastics during recycling; 4) Minimize the volume of the heat plate on the premise of meeting the rated heating power.
Modeling of Impact Response of Composite Graded Structure
Authors: Ali M. , Hoffman J. , Clark J. , Takak S.
Published: August 2012

The work presented in this paper is a continuation of a study on exploring energy absorbing characteristics of a composite functionally graded structure found in a banana peel [1]. The impact behavior of peel structure under strain rates ranging from 4000 s−1 to 15000s−1 are studied. A modified mathematical model is presented, which calculates the initial dynamic crushing stresses of the structure at different impact velocities. The model outputs are compared with finite element simulations for the initial crushing stress, densification strain, global and local deformation modes, reactive force pulse, and total energy absorbed. A reasonable agreement is found between the proposed model and finite element simulations in determining the initial dynamic crushing stress and total energy absorbed by the structure.
Creating an Interactive Light Studio for the American Sign Language and English Lower School
Authors: Baglione Melody , Wong Nicholas , Clevenson Hannah , O’Meara Bridget , Baker James
Published: August 2012

The Cooper Union for the Advancement of Science and Art created an Interactive Light Studio for pre-kindergarten students at The American Sign Language and English Lower School (P.S. 347) in New York City. Specific goals included designing a space for science exploration and creating ways for both deaf and hearing students to explore light and sound. Deaf and hearing impaired students, in particular, benefit from the design of a sound-to-light installation that uses microphones to provide visual feedback. Another installation includes a network of circuits, which imitate the interaction of fireflies when placed in various configurations by the children. The Interactive Light Studio promotes science to young children and engages a diverse student population in science and engineering. The project offers undergraduate engineering students an opportunity to improve their technical and professional skills and develop a broader appreciation of the role of engineers in bettering society.
Amplification-Free DNA Detection Using a Microtip-Sensor Decorated With LNA Probes for Rapid TB Screening
Authors: Inoue Shinnosuke , Yeo Woon-Hong , Kim Jong-Hoon , Chung Jae-Hyun , Lee Kyong-Hoon , Gao Dayong , Oh Kieseok , Cangelosi Gerard
Published: August 2012

Tuberculosis (TB) is an epidemic affecting one-third of the world’s population, mostly in developing and low-resource settings. People having active pulmonary TB are considered highly infectious; therefore, it is critical to identify and treat these patients rapidly before spreading to others. However, the most reliable TB diagnostic methods of bacterial culture or nucleic acid amplification are time-consuming and expensive. The challenge of TB diagnosis lies in highly sensitive and specific screening with low cost. Here, we present an LNA-modified microtip-sensor, which is capable of selectively detecting low-abundance DNA from bacteria. When genomic DNA of Bacillus Calmette-Gue´rin (BCG, a surrogate marker of Mycobacterium bovis), and genomic DNA of Staphylococcus epidermidis (S. epi) are used, the microtip-sensor yields the detection limit of 1,000 copies/mL within 20 minutes. The high sensitivity and specificity approaching nucleic acid amplification methods can potentially overcome the current challenges for rapid TB screening.
Nonlinear Dynamic Viscoelastic Model for Osteoarthritic Cartilage Indentation Force
Authors: Vidal-Lesso A. , Ledesma-Orozco E. , Lesso-Arroyo R. , Daza-Benitez L.
Published: August 2012

Biomechanical properties and dynamic response of soft tissues as articular cartilage remains issues for attention. Currently, linear isotropic models are still used for cartilage analysis in spite of its viscoelastic nature. Therefore, the aim of this study was to propose a nonlinear viscoelastic model for cartilage indentation that combines the geometrical parameters and velocity of the indentation test with the thickness of the sample as well as the mechanical properties of the tissue changing over time due to its viscoelastic behavior. Parameters of the indentation test and mechanical properties as a function of time were performed in Laplace space where the constitutive equation for viscoelasticity and the convolution theorem was applied in addition with the Maxwell model and Hayes et al. model for instantaneous elastic modulus. Results of the models were compared with experimental data of indentation tests on osteoarthritic cartilage of a unicompartmental osteoarthritis cases. The models showed a strong fit for the axial indentation nonlinear force in the loading curve (R2 = 0.992) and a good fit for unloading (R2 = 0.987), while an acceptable fit was observed in the relaxation curve (R2 = 0.967). These models may be used to study the mechanical response of osteoarthritic cartilage to several dynamical and geometrical test conditions.
Development of a Methodology for Adaptation of Refractive Index Under Controlling Kinematic Viscosity for PIV
Authors: Shida Shuya , Kosukegawa Hiroyuki , Ohta Makoto
Published: August 2012

Blood vessel diseases such as ischemic cardiac disease or cerebral aneurysm are life-threatening disorders and as large a cause of death as cancer in many countries. The rupture of a cerebral aneurysm usually causes subarachnoidal hemorrhage the mortality of which is very high. Previous studies have proved that the genesis and growth of aneurysm are related to hemodynamics. Especially, in endovascular therapy for cerebral aneurysms using medical devices such as coils or stents, hemodynamics in an aneurysm are related to thrombosis formation in the aneurysm and to its repair. In vascular research using a biomodel (blood vessel phantom with mechanical properties similar to a human artery) for treating cerebral aneurysm, the working fluid, termed Blood-Mimicking Fluid (BMF), should mimic human blood with respect to viscosity so as to obtain realistic blood flow modeling in in vitro measurements. Moreover, refractive indices of BMF must be adjusted to fit biomodel materials because the materials used for Particle Image Velocimetry, one of the best tools for measurement of flow, have various refractive indices. For simultaneous adjustment of the two parameters, i.e. kinematic viscosity and refractive index, an aqueous mixture of glycerol and sodium iodide has been used in previous research. In this paper, we develop a systematic way to precisely find the two targeted parameters of BMF by showing the measurement values of the refractive index and the viscosity of the two aqueous solutions. The refractive index to light of fluorescent was measured with a critical angle refractometer while temperature of sample was also measured. And a vibration-type viscometer was used to obtain the dynamic viscosity under the same condition as refractive index measurement. These measurements were carried out at room temperature and pressure, respectively. As a result of detailed measurements at various proportions, refractive indices of the aqueous solution of glycerol (Gly. aq.) increase monotonically. On the one hand, the kinematic viscosity of Gly. aq. increases very slightly with its proportion and that of the aqueous solution of sodium iodide (NaI aq.) exhibits unique behavior. The results of combining Gly. aq. and NaI aq. indicate that the mixture has a wide range of kinematic viscosity, including the value of blood (around 3.8 mm2/s), at the targeted refractive index. In conclusion, this mixing method is useful for BMF preparation with the adjustment of refractive index and kinematic viscosity.
Ultrasonic Excitation Induced Wenzel to Cassie Transition
Authors: Ni Qi , Crane Nathan B. , Guldiken Rasim O.
Published: August 2012

Wetting on textured solids has gained much attention in the past decade due to increasing interest in artificial superhydrophobic surfaces. (Bahadur & Garimella, 2007; Boreyko & Chen, 2009; Forsberg, Nikolajeff, & Karlsson, 2011; Heikenfeld & Dhindsa, 2008) On textured surfaces, the wetting liquid can be in either the Cassie–Baxter state, which the liquid does not fill the surface texture; or the Wenzel state, which the liquid completely wets the surface and fills the recesses. For a hydrophobic micro-scale rough surface, the Cassie state is usually a more favorable state since it requires less energy. However, due to contact angle hysteresis, the Wenzel state can also be meta-stable. By controlling the roughness of the texture and initial droplet position, both Cassie and Wenzel states can be stable simultaneously. (Koishi, Yasuoka, Fujikawa, Ebisuzaki, & Xiao, 2009) However, with the proper energy input, the droplets can be induced to transition between states. While multiple methods have been developed to switch from Cassie to Wenzel states (Bormashenko, Pogreb, Whyman, & Erlich, 2007; Krupenkin et al., 2007; Kumari & Garimella, 2011; Ran, Ding, Liu, Deng, & Hou, 2008), it is much more difficult to switch from the Wenzel state to the Cassie state. Wenzel-Cassie transitions have been achieved by changing the surface structure to destabilize the Wenzel state (Krupenkin et al., 2007)(Ran et al., 2008) or by changing the ambient fluid. (Dhindsa et al., 2006)
A Polymeric Piezoelectric Synthetic Jet for Electronic Cooling
Authors: Zhang Min , Simon Terrence W. , Huang Longzhong , Selvi Vinnee Bharathi A. , North Mark T. , Cui Tianhong
Published: August 2012

Polymer synthetic jets driven by cantilever PZT bimorphs were fabricated and their cooling performance on a heat sink fin tip surface was investigated. Geometrical parameters of the synthetic jets, including cavity size, cavity depth, orifice size, orifice length, and diaphragm thickness, were optimized for increased jet velocity and high cooling performance using the Taguchi test method. Based on the test results, a synthetic jet with an optimized structure was fabricated. Measurements showed that the optimized jet can produce a peak air velocity of 50 m/s at 900 Hz from a round orifice 1.0 mm in diameter. The power consumption of the jet in this condition is 0.69 W and the total mass is 6 g. Using the optimized synthetic jet, a heat transfer coefficient of 576 W/m2K was achieved on the fin tip, indicating an increase of 630% over natural convection values.
Comparative Study of the Dynamic Response of Different Materials Subjected to Compressed Gas Blast Loading
Authors: Hinz Brandon J. , Grimm Matthew V. , Muci-Ku¨chler Karim H. , Walsh Shawn M.
Published: August 2012

Understanding the dynamic response of materials under blast and impact loading is of interest for both military and civilian applications. In the case of blast loading, the mitigation characteristics of materials employed in personal protective equipment (PPE) is of particular importance. Without adequate protection, exposure of the head to blast waves may result in or contribute to brain tissue damage leading to traumatic brain injury (TBI). The development of simple but representative laboratory experiments that can be used to study the mechanical response of different materials and/or material combinations to blast loading could be very useful for the design of PPE such as helmets. This paper presents a basic experimental setup that can be conveniently used to perform such studies using small scale compressed gas blasts. An open end shock tube is employed to generate the blasts used to load flat plate samples placed in a special rigid holder. Acceleration time histories at selected locations in the sample are used to generate data to compare the dynamic response and blast mitigation effectiveness of different specimens. High speed schlieren video is used to correlate the arrival of the shock wave and air flow that follows with the motion of the test sample.
Blast Resistant Elastomeric Polymer-by-Design
Authors: Schaaf Kristin L. , Nemat-Nasser Sia
Published: August 2012

The essence of this research is to mitigate shock through material design. Here we seek to develop a thorough understanding of the material through experimental characterization methods that lend themselves to creating verifiable constitutive relations, all while working towards the development of a new blast resistant elastomeric composite material. The host elastomer, polyurea, is created by reacting Versalink P-1000 with Isonate 143L. This study evaluates the impact of both chemistry modifications and the integration of micro-scale additives on the polyurea material system properties and performance. The properties of the resultant elastomers and elastomeric composite materials are mechanically and thermally characterized using durometer testing, dynamic mechanical analysis (DMA) testing, and differential scanning calorimetry (DSC) testing in order to determine the hardness, storage and loss moduli, and glass transition temperature of the composites, respectively. Preliminary results indicate that the durometer and dynamic mechanical properties of the material can be significantly altered through such modifications. The work described here is part of an ongoing effort to develop and verify rules and tools for creating elastomer-based composite materials with optimally designed compositions and characteristics.
A Numerical Approach of Estimating Dental Implant Healing Process Using Resonance Frequency Analysis (RFA)
Authors: Harirforoush Reza , Arzanpour Siamak
Published: August 2012

This paper investigates primary stability of dental implant that indicates the process of bone-implant integration. This integration is known to happen at the boundary of the bone and dental implant contact surface. The resonance frequency of dental implant is used as the parameter for this investigation due to its high sensitivity to boundary condition variations. In this study, resonance frequency analysis (RFA) of the jaw-implant structure is carried out using finite element modeling. The FEM analyses are conducted in ANSYS modal analysis simulation environment. The FEM model of the structure includes titanium implant, Cancellous and cortical bone. Different implant-bone interface conditions are studied for this investigation. Various boundary conditions were studied to identify natural frequencies of jaw-implant structure. Our analysis shows that the resonance frequency of the implant increases during the healing period and reaches a plateau when the implant-bone interface was fully integrated. The results show that RFA could be suggested as a non-invasive, reliable and accurate diagnostic method for early assessment of the healing stages.
An Algorithm of Separating Rigid-Body Linear Displacement From FEA Data of Optical Imaging System
Authors: Guo Xinmin , Kang Weimin , Zhao Jie
Published: August 2012

Optical imaging system always appears an asymmetric displacement under finite element analysis (FEA) for the asymmetry of the loads and the optomechanical structure, although the system is designed by an axisymmetric way. The asymmetric displacement can generate a misalignment, between “the (0,0) field” of the aberration analysis and “the central field” through the optical axis, and decline the accuracy of objective function of an optimization design. An algorithm is presented to separate the rigid-body linear displacement, which has no influence on the imaging quality, from the FEA data. Actually the linear displacement of system is a special region around the (0,0) field on the image surface rather than a displacement such as any single optical element. In the algorithm, the region with the same value of optical modulation transfer function (MTF) calculated by the optical ray tracing tools is defined as a domain D(x,y), where the (x,y) is a set or subset of (x0,y0) and MTF(x0,y0) is equal to MTF(0,0). The nodal displacements can add or subtract a certain value while the modified central point on or in the region in an optimal design of optical system under any static, dynamic and vibratory loads. And an example is demonstrated that the nodal displacement processed by the algorithm is more suitable to optimize the imaging system suffered from the static and vibration conditions than the original FEA data.
Demonstration of a Modeling Error Extrapolation Method in Verification, Validation and Uncertainty Quantification of a Stress Concentration in a Cantilever Beam
Authors: Kargar Soudabeh , Bardot D. M.
Published: August 2012

In order to assert that a complex simulation is an adequate representation of the real world the computational model must be validated against experimental results. Typically this validation is conducted at a small number of specified conditions, and set points. The simulation will differ from the experimental result due to experimental, numerical and simulation input uncertainties as well as un-modeled physics. The latter contributor is the modeling error. At these validation set points the modeling error can be estimated to fall within an interval. This range is the simulation minus experiment, plus/minus the combined experimental, numerical and simulation input uncertainties [1]. However, the purpose of creating a simulation is to predict results at set points where experimental results are unavailable. The uncertainty in this prediction is a combination of numerical and simulation input uncertainties along with the modeling error. In order to specify a prediction uncertainty it is necessary to extrapolate the modeling error interval to these prediction set points.