bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Adaptive Control for Tracking Wing Trajectories
Authors: Murphy Ian P. , Dadashi Shirin , Gregory Jessica , Lei Yu , Bayandor Javid , Kurdila Andrew
Published: April 2014

Studies of Micro Air Vehicles (MAVs) have gained increased attention over the past decade, while a significant range of open problems in this emerging field remain unaddressed. This paper highlights the investigations entailing flapping wing vehicles, designed based on inspiration from observations of avian flight. The nonlinear equations of motion of a ground fixed flapping wing robot are derived that incorporates a quasi-steady model of aerodynamics. The equations of motion are developed using Lagrange’s equations and the aerodynamic contributions are formulated using virtual work principles. The aerodynamics are constructed with a quasi-steady state formulation where the functions representing lift and drag coefficients as a function of angle of attack are treated as unknowns. An adaptive controller is introduced that seeks to learn the aerodynamic effects. A Lyapunov analysis of the controller guarantees boundedness of all error terms and asymptotic stability in both the joint position and derivative error. The controllers are simulated using two dynamic models based on flapping wing prototypes designed at Virginia Tech. The numerical experiments validate the Lyapunov analysis and verify that unknown parameters are learned if persistently excited.
Study on the Effects of Femoral Muscle Forces on Performance of Internal Fixation Devices Utilizing a Simulation Based Approach
Authors: Eap Laurent , El-Gizawy A. Sherif
Published: April 2014

Fractures of the distal femur are severe traumatic injuries that are treated with the utilization of internal fixation devices. Current preclinical device designs have primarily been investigated without observance of femoral muscle group effects — in addition to joint hip reaction forces — and irregular geometry of the human femora. This has led to a need to optimize the performance and fit of internal fixation devices to produce maximal reliability and structural integrity. The present study utilizes a systematic design approach that employs computer-aided modeling, robust design methodology, finite element methods, and optimization processes for a femoral locking plate system. In doing so, a computer-aided model was constructed to illustrate a distal femoral fracture fixation system. Femoral muscle force directions and magnitudes associated with a normal walking gait cycle were inputted into the system to simulate realistic loading conditions. In conjunction with finite element methods, the model was used to assess stress and strain distributions along the femur, femoral plate, and screws. Subsequently, optimization processes were then employed to assess the effects of varying device geometric parameters and bone topology on the bone-implant stress distributions and overall device design. The proposed simulation-based optimization process was able to yield a more accurate representation of the biomechanics within the bone-implant interaction by taking into consideration the substantial effects of femoral muscle groups. In doing so, a robust device design is developed which improves overall performance via minimizing weight and maximizing overall factor of safety.
An Algorithm to Determine the Optimized Data Range in Transient Hotwire Thermal Property Measurement
Authors: Bran-Anleu Gabriela , Lavine Adrienne S. , Wirz Richard E. , Baghaei Lakeh Reza , Kavehpour H. Pirouz
Published: April 2014

There exists a limited amount of data for thermal properties of supercritical fluids. Accurate measurement of these properties is needed to supply benchmark data to the scientific community and to establish promising candidates for supercritical fluids applications such as energy storage systems [1]. The transient hotwire method has been widely used to measure the thermal conductivity of fluids. The ideal working equation is based on the transient solution of Fourier’s law for an infinite linear heat source assuming no natural convection or thermal end effects. In practice, the assumptions inherent in the model are only valid for a portion of the measurement time. In this study, an algorithm was developed to automatically select the proper data range from a transient hotwire experiment. Numerical simulations of the experiment were used in order to validate the algorithm. The experimental results show that the developed algorithm can be used to improve the accuracy of thermal conductivity measurements.
Analysis of the Microstructure of Polymers With Regard to Their Thermomechanical History: STHM and DSC Measurements
Authors: Boutaous M’hamed , Gomes Séverine , Zakariaa Refaa , Zinet Matthieu , Bourgin Patrick
Published: April 2014

The variation of the microstructure within the thickness of moulding plates of two semicrystalline polymers, an isotactic Poly-Propylene and a Poly-Butylene Terephtalate, was observed by optical microscopy technique. These observations allowed specifying the different zones of iso-microstructure within the plate thickness, commonly called “skin zone”, “shear zone”, “post filling zone ”and“ core zone”in terms of crystallite size and zone thickness. The variation of the melting temperature was then analysed by using a local thermal analysis method based on the scanning thermal microscopy technique in each of these zones. Our results show the expected link between the local microstructure and the polymer melting temperature. They also highlight a strong coupling between the microstructure, the material and its processing conditions.
Comparing the Behavior of Homogeneous vs. Fluid Filled Solid Headforms Under Blunt Impact Loading Conditions
Authors: Selvan Veera , Halls Virginia , Zheng James , Chandra Namas
Published: April 2014

A single point acceleration measurement at the center of gravity (C.G) of the rigid headform has been typically used to assess the head injuries under the blunt loading conditions. The head protective equipment (e.g. Helmets) used in sports, vehicles and defense fields are developed and tested based on this single point acceleration. This raises two critical questions; 1) can a homogeneous rigid headform represent the heterogeneous skull-brain complex; 2) If not, which is the critical point of measurement in the compliant headform. To answer these questions, compliant (acrylic gel complex) and rigid (aluminum body) head surrogates with an identical mass are subjected to similar blunt loading conditions. Target surfaces of different stiffness and an impact velocity of 1 m/s are employed to evaluate the critical difference in the head surrogates. Acceleration (C.G) and shell strain (impact location) in the compliant surrogate and acceleration (C.G) and the impact force in the rigid surrogate are experimentally measured. Experimental and computational studies illustrate that the acceleration field in the gel-filled case varies from coup to counter-coup region; however, the acceleration field in the rigid headform is uniform. The variation in the acceleration field is influenced by the shell deformation that in turn depends on the stiffness of the target surface. In deformable target surfaces, the acceleration and head injury criterion (HIC) values are higher in the compliant surrogate than the rigid surrogate; the effect is reversed for rigid target surfaces.
Characterization of Micromachined Seesaw Type Microphone
Authors: Kim Byungki , Phamduy Paul
Published: April 2014

A seesaw type microphone is characterized to study its feasibility for sound source localization. The microphone is composed of a flexible rectangular diaphragm sustained by two torsion-bars. With this structure, the microphone has two main dynamic modes: rocking mode from the twisting of the torsion bars and bending mode from the bending of the flexible diaphragm. Thus, the microphone’s motion is a combination of the two modes. Depending on the frequency of the incident sound and its arrival time difference at each side of the seesaw type microphone, relative motion of both sides of the seesaw type microphone is changed. By measuring relative amplitude and phase of the motion at each side of the microphone, arrival time difference of the sound source at each side can be estimated, and then, localization of the sound source is feasible. In this paper, we present that the microphone shows a significant vibration difference from each side when AC with 45° phase difference is applied to each side of the microphone to mimic the microphone receiving angled incoming sound.
Experimental Study of Deicing Process in an Airfoil Application
Authors: Perez Pereira Pablo , Vilar-Carrasquillo Luis D. , Carbajal Gerardo
Published: April 2014

A customized airfoil for deicing process was designed, built and tested in order to investigate the effect of icing on the airfoil and the process of removing it by heating processed. A numerical simulation was performed to provide more details of the fluid flow characteristics of the presence of the ice and the temperature distribution on the airfoil when it reached the steady state conditions. An experimental setup was developed to measure and record the transient temperature response on the trailing and leading edge respectively. The experimental results suggest that from a minimum temperature of −10°C on the trailing edge, and 0°C in the leading edge with ice on the surface, the time to reach the steady state temperature of 46°C in the leading edge and 38°C in the trailing edge was close to 8 minutes approximately.
Experimental Measurements of the Thermal Conductivity of Nanoparticle Packed Beds
Authors: Clarke Kevin , Elsahati Muftah , Richards Robert F.
Published: April 2014

Experimental measurements of heat transfer across packed beds of ceramic and metallic nanoparticles are presented. Round disk-shaped cakes of nanoparticles approximately one millimeter thick and 6.75 millimeters diameter are produced by packing either copper or silica nanoparticles into a mold. The thermal conductivity of these packed beds are then determined using a Guard-Heated Calorimeter under steady state conditions. SEM imaging of the packed beds indicates that the copper nanoparticles are neither monosized nor entirely spherical while the silica nanoparticles, are both highly spherical and monosized. However, both packed beds were found to have very similar effective thermal conductivities. The thermal conductivity of the copper nanoparticle packed bed is found to be 0.054 ± 0.006 W/m°C, while the thermal conductivity of silica nanoparticle packed bed is found to be 0.018 ± 0.007 W/m°C. As a result, it is seen that, at least in this limited comparison, particle material and thermal conductivity (metal with high conductivity, or ceramic with low conductivity), as well as the regularity of the nanoparticle itself (size distribution and sphericity) appear to have a small effect on overall packed bed thermal conductivity.
Study of the Combined Effect of Isoproterenol and Mechanical Oscillation on the Contractile Response of Mice Airways From Healthy and Asthmatic Subjects (In Vivo)
Authors: Jo-Avila M. , Al-Jumaily A. , Lu J. , Sobrevia L.
Published: April 2014

The main driving mechanism during an asthma attack is the hyperconstriction of airway smooth muscle (ASM), which reduces the airway lumen and makes normal breathing difficult. The contraction can be relieved by using bronchodilator drugs such as Isoproterenol (ISO). This paper hypothesizes that superimposed length oscillations (SILO) may improve drug therapy when combined with ISO or used alone in asthmatic subjects. The aim of this study is to assess SILO patterns directly onto the airways of healthy and asthmatic subjects (mice), while they are under anaesthesia breathing spontaneously and pre-constricted (mimicking and asthmatic attack), and compared the response with the relaxation observed just with ISO.
Modeling the Circular Shear in Light Activated Shape Memory Polymers With Three Networks
Authors: Cui Fangda , Rao I. J.
Published: April 2014

Shape memory polymers (SMP’s) are polymers that have the ability to retain a temporary shape, which can revert back to the original shape on exposure to specific triggers such as increase in temperature or exposure to light at specific wavelengths. A new type of shape memory polymer, light activated shape memory polymers (LASMP’s) have been developed in the past few years. In these polymers the temporary shapes are fixed by exposure to light at a specific wavelength. Exposure to light at this wavelength causes the photosensitive molecules, which are grafted on to the polymer chains, to form covalent bonds. These covalent bonds are responsible for the temporary shape and act as crosslinks. On exposure to light at a different wavelength these bonds are cleaved and the material can revert back to its original shape. A constitutive model of LASMP’s which based on the notion of multiple natural configurations has been developed (see Sodhi and Rao [1]). It has been applied to model the circular shear of light activated shape memory polymer with two networks. In this work we use this model to analyze the mechanical behavior of LASMP’s with three different networks undergoing a circular shear deformation cycle. This involves study of the behavior of the LASMP’s when two temporary configurations are formed by exposing the polymer to light at different time during the deformation process. In addition, we show that these materials are able to undergo complex cycles of deformation due to the flexibility with which these temporary configurations can be formed and removed by exposure to light.
Analytical Modeling of Mechanical Properties and Behavior of Nanotube-Based Nanocomposites
Authors: Askari Davood , Ghasemi-Nejhad Mehrdad N. , Kalamkarov Alexander L.
Published: April 2014

The objective of this paper is to introduce analytical closed form solutions for the prediction of effective axial and transverse Young’s modulus and Poisson ratios of a matrix-filled nanotube (i.e., a representative element of nanotube reinforced nanocomposites) as well as its mechanical behavior (i.e., displacements, strains and stress distributions) when it is subjected to externally applied uniform axial and radial loads. In this work, both the nanotube and its filler material are considered to be generally cylindrical orthotopic. For the derivation of exact solutions for radial loading case, no plain strain condition is assumed and effects of axial strain is taken into consideration to obtain a more precise set of solutions. Analytical formulae are developed based on the principles of linear elasticity and continuum mechanics and then exact solutions are obtained for displacements, strains and stress distributions within the domain of each individual constituent. To validate and verify the accuracy of the closed form solutions obtained from the analytical approach, a 3-D model of a matrix-filled nanotube is generated and solved for displacements, strains and stresses, numerically, using a finite element method. Excellent agreements were achieved between the results obtained from the analytical and numerical methods.
Development of a Dual-Axis Phase-Locked Excitation (PhLEX) Resonant Fatigue Test Method for Wind Turbine Blades
Authors: Beckwith Jenna A. , White Darris , Barsotti Domenic L.
Published: April 2014

Collaborative efforts between Embry-Riddle Aeronautical University (ERAU) and the National Renewable Energy Laboratory (NREL) have resulted in an innovative dual-axis Phase-Locked EXcitation (PhLEX) resonant test method for structural fatigue testing of wind turbine blades. Laboratory fatigue test results give blade manufacturers important information regarding the structural integrity of their designs and can offer insight on how to further increase the strength and efficiency of these blades. The PhLEX test method applies loads in a manner that is more representative of wind loading experienced through field operation conditions as compared to current dual-axis quantum resonant methods. The method developed involves exciting the blade at resonance in the edge direction, while simultaneously applying a direct actuation force in the flap direction at the first edge frequency. As a proof of concept, this method was employed on a 9-meter (m) blade test article at NREL’s National Wind Technology Center (NWTC) located near Boulder, Colorado. Preliminary results show that the PhLEX method is able to control the phase angle between application of flap and edge loads while decreasing testing time due to faster test frequencies and the ability to maintain constant amplitude loading.
Feasibility Analysis for a Tidal Energy Pilot Site in the Gulf of California
Authors: Tapia Olivas Juan Carlos , Ramírez Campbell Hector Enrique , Gil Samaniego Ramos Margarita
Published: April 2014

Baja California is located in the northwestern region of Mexico and is a peninsula that borders the west by the Pacific coast and on the east by the Gulf of California, with 1,280 km of coastal area of which 560 km belong to the Gulf California and the rest to the Pacific Ocean. It is privileged with renewable energy resources and already has 720 MW of geothermal, 10 MW of Wind and 5 MW of Solar that presently are under construction. With the growing demand for electricity especially in the summer period, the use of tidal power is an opportunity to use a resource of this type in the coastal towns.

This paper presents an analysis which assesses the bays of Santa Maria, San Luis Gonzaga, Los Angeles, El Pescador, El Soldado, Las Animas and San Rafael, as sites with ideal features for the implementation of tidal power generation technology. The analysis, weighed the constructive feasibility, site bathymetry, environmental impact to the area, roads, generation capacity and population of nearby sites. The Port of San Felipe with a population of 16,945 inhabitants, is located in the Gulf of California, having a population growth rate of 2.3 % year, and has 4,579 users in the residential sector who demand 27,483 MWh annually, being the months of July to August when they consume 60% of the year’s energy.

It was calculated that the maximum estimated power potential was in the Bay of San Rafael with 14 MW, and the minimum power value was obtained for Bay of Soldado with 1.3 MW. However the Bay of Santa Maria with a maximum power of 2.5 MW is considered the most viable site for the development of a tidal project according to the weighing used primarily, due to its proximity to the Port of San Felipe.

One of the main restrictions for the development of tidal energy on these sites is the high environmental impact that could occur in these areas. Due to the that as biophysical characteristics and coastal geomorphology of these bays, these sites are very fragile in terms of negative impacts that could be generated by changes in ocean currents due to the construction of infrastructure for tidal generation.
Numerical Study of Transient Multiphase Slug Flow Through a Tube at High Velocity
Authors: Adam Carlton , Hadim Hamid
Published: April 2014

A transient, two-dimensional computational fluid dynamics model is used to simulate the flow of a liquid slug through a pipe at high velocities. The slug is driven by a gas which enters the system at a constant pressure of 10 MPa. The gas accelerates the slug from rest through a distance of about 45 cm, after which the slug discharges into the open atmosphere. The interface between the two phases is initially uniform and flat, however as the flow develops, significant interphase mixing and deformation of the interface occurs.

The simulation is ultimately used to predict the velocity and dispersion pattern of the liquid slug upon discharge into the atmosphere. The gas pressure and dispersion pattern over time are compared to experimental data collected via high-speed cinematography and piezoelectric pressure gauges. The numerical model predicts a slug exit velocity of 108 m/s which agrees reasonably well with empirical measurements. However, the numerical model fails to accurately predict the structure of the dispersion pattern of the exiting liquid, specifically in terms of the amount of mixing between the liquid and gas phases. To address these discrepancies between the model and the empirical data, a follow-on effort will be performed in an attempt to better capture the formation of the large expansion plume seen in the high-speed video. Specifically, phase changes in the liquid and gas will be addressed in the follow-on effort, as will turbulence effects on mixing at small scales.
The Effects of Surfactant on Simplex Nozzle Spray Behavior and its Comparison to Liquid Fuels
Authors: Davanlou Ashkan , Lee Joshua , Basu Saptarshi , Kumar Ranganathan
Published: April 2014

Pressure-swirl nozzles (simplex nozzles) are used in various field applications such as aero-engines, power generation, spray painting and agricultural irrigation. For this particular nozzle, research in the past decade has dealt with the development of numerical models for predicting droplet distribution profiles. Although these results have been valuable, the experimental results have been contradictory, therefore fundamental understanding of the influence of properties in nozzle is important. This paper experimentally investigates the effect of surfactants on breakup and coalescence. Since most of the fuels and biofuels have low surface tension compared to water, a comparative analysis between a surfactant solution and a liquid fuel is imperative. For this experimental study, a simplex nozzle characterized as flow number 0.4 will be utilized. The injection pressures will range from 0.3–4Mpa while altering the surface tension from 72 to 28mN/m. By applying Phase Doppler Particle Anemometry (PDPA) which is a non-intrusive laser diagnostic technique, the differences in spray characteristics due to spray surface tension can be highlighted. The average droplet diameter decreases for a low surface tension fluid in the axial direction in comparison to pure water. The average velocity of droplets is surprisingly lower in the same spray zone. Measurements made in the radial direction show no significant changes, but at the locations close to the nozzle, water droplets have larger diameter and velocity. The results indicate the breakup and coalescence regimes have been altered when surface tension is lowered. A decrease in surface tension alters the breakup length while increasing the spray angle. Moreover, higher injection pressure shortens the breakup length and decrease in overall diameter of the droplets.

By performing this experimental study the fundamentals of spray dynamics, such as spray formation, liquid breakup length, and droplet breakup regimes can be observed as a function of surface tension and how a surrogate fuel compares with a real fuel for experimental purposes. This knowledge potentially will lead to designing a better atomizer or new biofuels.
E-Training Development Approach for Enterprise Knowledge Evolution
Authors: Sarraipa Joao , Gomes-de-Oliveira Pedro , Marques-Lucena Catarina , Jardim-Goncalves Ricardo , Mendonça da Silva João
Published: April 2014

A practical e-training development approach can facilitate and promote the development of competencies and knowledge in industry. This paper presents a training strategy and a common methodology for building training courses with the purpose to provide an efficient inter-organizational approach to industrial training development. The methodology for building e-training courses proposes to create training materials in an easier way, enabling various organizations to actively participate on its production. The result is an approach able to facilitate intra and inter enterprises knowledge creation and transfer.
Thermal-Economic Modeling of a Micro-CHP Unit Based on a Stirling Engine
Authors: Ferreira Ana C. , Teixeira Senhorinha , Ferreira Christophe , Teixeira José , Nunes Manuel L. , Martins Luís B.
Published: April 2014

The last decade has witnessed a growing interest in the use of Stirling engine cogeneration systems for residential applications, due to their prospect for high efficiency, good performance at partial load, fuel flexibility, including the possible use of renewables, low emissions, vibration and noise levels. Stirling engines have sealed operating chambers, low wear and, as a consequence, low operating costs. In the European building sector, micro-cogeneration power plants are being designed to fulfill the heating requirements of the building and, additionally, generate electricity for internal consumption or for feeding into the local grid.

Thermal-economic evaluation represents an effective tool to optimize a power plant with this type of technology. The mathematical formulation includes a set of equations able to describe and simulate the physical system, as well as a set of equations that define the cost of each plant component.

This paper presents a numerical study faithfully simulating the real conditions of a micro-CHP unit based on an alpha type Stirling Engine. The simulations were performed through a MatLab® code that assesses the thermodynamic efficiency, including heat transfer limitations and pumping losses throughout the system.

Results showed that heat-transfer limitations strongly affect cycle efficiency, particularly in the regenerator case. The pumping losses are less important when hydrogen or helium are used.
Active Aerodynamic Systems
Authors: Curtis Craig , Fuller Thomas , Hashem Christopher , Joiner Megan , Nadeau Benjamin
Published: April 2014

Active Aerodynamic Systems (AAS) are aerodynamic control surfaces that use the shape memory mechanism of Nitinol wires which have been embedded into an elastic medium. Nitinol is an alloy of Nickel and Titanium which possesses pseudo-elastic properties, causing it to shrink a considerable amount when it reaches an activation temperature. By achieving accurate control of the Nitinol and integrating it into an airplane wing, a method for inducing rolling rate can be developed which contains fewer moving parts. With a well-developed implementation of this technology, controlled flight would be made more accurate, more responsive, and have lower turbulence. The shape of the system is manipulated using a microprocessor based digital control system. The control circuit will utilize pulse width modulation to precisely control the temperature of the Nitinol wire in order to change the curvature of the control surface with more accuracy. AAS aims to revolutionize the use of shape memory alloys in the design of more organic aerodynamic applications.
Combustion Characteristics of Biomass Ash and Lignite Blend Under Oxy-Fuel Conditions
Authors: Atibeh Ehsan Abbasi , Yozgatligil Ahmet
Published: April 2014

In this study an attempt was done to profoundly explore the pyrolysis and combustion behaviors and emission characteristics of lignite samples in O2/N2 and O2/CO2 (oxy-fuel conditions) ambients. A special focus was allocated to the effects of three inorganic materials, potassium (K), calcium (Ca) and iron (Fe) on combustion characteristics of Turkish lignite using non-isothermal Thermo-gravimetric Analysis (TGA) technique combined with Fourier Transform Infrared (FTIR) spectroscopy and the effects of ambient gases and various oxygen mole fractions were considered. Eventually the co-processing combustion tests of lignite and the ash contents of different biomass fuels were investigated and the possible way of using biomass as a potential source of inexpensive catalysts in combustion processes were discussed. Co-processing combustion tests of lignite and biomass ash contents indicated that the hazelnut shell and walnut shell ash contents were significantly effective in increasing the char reactivity of lignite due to high concentration of potassium based oxides during combustion tests carried out in both air and 30% O2 in CO2 ambients. Furthermore the catalytic reactivity of wheat straw and cattle manure ash contents were observed in the second region of combustion regarding volatile matter release and combustion in both air and 30% O2 in CO2 ambients. These results are thought to be due to high concentrations of Alkali and Alkaline earth metals existed in the impregnated lignite samples with wheat straw and cattle manure ash contents and especially Na-based oxides in the cattle manure form. Finally in the case of lignite sample impregnated with saw dust ash content, it was observed that the impregnated lignite was significantly more reactive in devolatalization process in 30% O2 in CO2 ambients. These results revealed that the ash contents of walnut and hazelnut shell biomass fuels can be used as a potential source of inexpensive K-based catalysts in the co-processing of coal and biomass ash. Furthermore high concentrations of Alkali and Alkaline earth metals existed in the ash contents of biomass fuels like wheat straw, cattle manure and saw dust can make them suitable sources of inexpensive catalysts and develop a step forward in economic aspects of catalytic coal combustion.
Thermophysical Properties of AS4/3501-6 Carbon-Epoxy Composite
Authors: Vital Amber , Doleman Bradley , Saad Messiha
Published: April 2014

As today’s technology continues to develop at a rate that was once unimaginable, the demand for new materials that will outperform traditional materials also increases dramatically. To meet these challenges, monolithic materials are being combined to develop new unique materials called composites. Thermophysical properties of composite materials such as thermal conductivity, diffusivity, specific heat, and thermal expansion are very important in engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells. Thermal conductivity is the property that determines the working temperature levels of a material and plays a critical role in the performance of materials in high temperature applications. This parameter is important in problems involving heat transfer and thermal structures.

The objective of this paper is to develop a thermal properties database for the carbon-epoxy AS4/3501-6 composite. The AS4 carbon fiber used is a unidirectional continuous PAN based fiber, and the 3501-6 epoxy resin is amine cured and provides low shrinkage during the curing process while maintain resistance to chemicals and solvents. The thermophysical properties of the AS4 composite have been investigated using experimental methods. The flash method was used to measure the thermal diffusivity of the composite based on the American Society for Testing and Materials standard, ASTM E1461. In addition, the Differential Scanning Calorimeter was used in accordance with the ASTM E1269 standard to measure the specific heat. The measured thermal diffusivity, specific heat, and density were used to compute the thermal conductivity, thus adding to the currently insufficient database for composite materials and foams.
Rotary Multimodal Energy Harvesting Device
Authors: Larkin Miles , Tadesse Yonas
Published: April 2014

In this paper, a new multimodal energy harvesting device consisting of two transduction mechanisms and having unique properties at various operating modes is presented. The hybrid system includes electromagnetic and piezoelectric energy harvesting technologies, and uses linear motion and impact forces from human motion for energy harvesting. The device is based on an unbalanced electromagnetic rotor made of three beams of piezoelectric material that have magnets attached to the ends. The device is to be worn on the legs or arms of a person. Linear motion, from the arms or legs swinging, causes the rotor to spin and the magnets to pass over the coils. Impact forces, from stepping, induce stress on the piezoelectrics which generates voltage across the electrode. The results of several numerical simulations are presented. For the piezoelectric beams, numerical simulations were done to find the deflection, stress, optimum operating frequency, and mode shapes taking into account environmental conditions. For the electromagnetic generation, numerical simulations were done to find the optimal load resistance and power generation for several different orientations. Other design related issues will also be investigated to fully realize the device in real world applications.
Euler-Lagrange Simulations of Bubble Cloud Dynamics Near a Wall
Authors: Ma Jingsen , Hsiao Chao-Tsung , Chahine Georges L.
Published: April 2014

We present in this paper a two-way coupled Eulerian-Lagrangian model to study the dynamics of microbubble clouds exposed to incoming pressure waves and the resulting pressure loads on a nearby rigid wall. The model simulates the two-phase medium as a continuum and solves the N-S equations using Eulerian grids with a time and space varying density. The microbubbles are modeled as interacting spherical bubbles, which follow a modified Rayleigh-Plesset-Keller-Herring equation and are tracked in a Lagrangian fashion. A two-way coupling between the Euler and Lagrange components is realized through the local mixture density associated with the bubbles volume change and motion.

Using this numerical framework, simulations involving a large number of bubbles were conducted under driving pressures of different frequencies. The results show that the frequency of the driving pressure is critical in determining the overall dynamics: either a collective strongly coupled cluster behavior or non-synchronized weaker multiple bubble oscillations. The former creates extremely high pressures with peak values orders of magnitudes higher than that of the excitation pressures. This occurs when the driving frequency matches the natural frequency of the bubble cloud. The initial distance between the bubble cloud and the wall is also critical on the resulting pressure loads. A bubble cloud collapsing very close to the wall exhibits a cascading collapse with the bubbles farthest from the wall collapsing first and the nearest ones collapsing last, thus the energy accumulates and then results in very violent pressure peaks at the wall. Farther from the wall, the bubble cloud collapses quasi spherically with the cloud center collapsing last.
Requirements Analyses to Support a Material Information Model for Sustainability
Authors: Harinder Arvind , Witherell Paul , Morris K. C.
Published: April 2014

Materials, and therefore material selections, influence the sustainable impact of a product from beginning to end-of-life. With improved access to material information, product designers can attain newfound insight into the sustainability implications of their design decisions. Insight to lifecycle tradeoffs requires access to both upstream and downstream information at design time. This access can be facilitated by information transparency between the different information representations assumed by a product throughout its lifecycle. A well-constructed Material Information Model (MIM) can provide the necessary access, and therefore the desired insight.

In this paper we present an initial set of requirements that a MIM for sustainability must support to provide the desired design-time information access. Using these requirements as guidelines, we then analyze several information representations currently available for information management at various stages of the lifecycle. We compare and contrast the extent to which these representations meet the information needs of the MIM, using example implementations as guidelines. We discuss the level to which information synthesis may be achieved given the varying degrees to which the MIM requirements are met. Finally, we introduce where synthesis challenges lie and the steps required to overcome them.
A Simple 2D Wheelchair Positioning: Correcting IMU’s Data Using One Encoder and Applying Kalman Filtering
Authors: Salimi Zohreh , Ferguson-Pell Martin W.
Published: April 2014

Inertial Measurement Units (IMU) are widely used for spatial positioning. They are well known, however, for signal drift. A common way of overcoming the drift is to use Kalman Filtering. In this study, we have undertaken some experiments during wheelchair propulsion, recording data with an IMU, an Encoder (tachometer) and an Optotrak (motion analysis system). We then applied Kalman filtering (with two approaches) to IMU’s data. Eventually, in order to verify Kalman’s results, they were compared to Optotrak’s data.

As result of this study, 2D wheelchair tracking can be done with acceptable precision, using one IMU and one Encoder and applying Kalman filtering. Kalman filtering with approach B was a better predictor of subject’s spatial position than approach A. Kalman and even IMU’s results for rotation were of good accuracy; therefore IMU’s data can be used to find all angular characteristics of subject’s position, even without applying Kalman filtering, if the offsets are precisely found through a stationary test.
A Probabilistic Strength Distribution Model in Predicting Damage Evolution due to Thermo-Oxidation of Polymeric Matrix Composites
Authors: Liang Jianyong , Pochiraju Kishore
Published: April 2014

Thermal oxidation growth and damage evolution are highly coupled as oxidative reactions produce thermal stress and weaker materials leading to crack growth, which in turn accelerates the penetration of oxide layers deeper into the structure. Oxygen diffusion-reaction model can predict the time-dependent oxidation state and evolution of oxide layers in unidirectional composites. With given oxidation state and presumed initial cracks, extend finite element method (XFEM) can be used to calculate the damage evolution due to oxidation-induced stress in the composites. These two models run iteratively to predict the oxidation degradation of polymer composites serving at high temperature.

A probabilistic strength distribution model is formulated in this research to represent the scatter of mechanical properties of composite materials and initiate discrete cracks with Hashin failure criteria. With initiated discrete cracks, damage evolution due to high-temperature thermal oxidation can be calculated. The oxidation growth and damage evolution predicted correlate well with experimental observations. The probabilistic strength distribution model enables crack initiation and damage evolution prediction of use-life and durability of composites structures operating at high temperatures.
Virtual Design Technologies for 21rst Century Engineers: In What Ways Do Gestures Impact Interactions?
Authors: Hayes Caroline C. , Nguyen Mai Anh , Cornelius Caroline J. , Clayson Ashley , Drew Daniel , Cheng Xuan
Published: April 2014

The goal of this work is to measure the degree to which communication through gestures in virtual environments helps or hinders collaborative work on spatial tasks. People often gesture when they talk to each other about spatial concepts; in response to this behavior, many virtual collaboration tools have been created over the years to augment distance collaborations with gestures (see “Related Work”). However, relatively little work has been done do assess whether the addition of gestures actually improves collaboration, and in if so how does it help them? This work begins the exploration of these questions so as to better inform the design of future virtual collaboration tools. We explored these questions by performing controlled laboratory experiments. To do so, we developed an experimental test bed, Collabora-table, in which we could control the communication modes available to pairs of participants while they interacted in a 2D virtual space to complete shared tasks. Participants were asked to use three different interfaces, face-to-face, virtual sketching, and virtual sketching with hand images. The latter was found to reduce workload to levels indistinguishable from face-to-face interactions for conceptual product design tasks. However the effect appears to be sensitive to the task, and the implementation of the interfaces. Gestures may be an important communication channel to support in future tools to support virtual product design.
An Electrospun Polyaniline Nanofiber as a Novel Platform for Real-Time COX-2 Biomarker Detection
Authors: Veisi Zeinab , Ceylan Muhammet , Mahapatro Anil , Asmatulu Ramazan
Published: April 2014

The presence of Cyclooxygenase-2 (COX-2) biomarker has been associated with the development of certain types of cancer such as breast cancer. Moreover, reliable quantification of COX-2 as an enzyme responsible for pain and inflammation is vital. Here we demonstrate the feasibility of sensitive COX-2 detection via integration of nanoporous polyaniline fibers on the microfabricated platform to develop a label-free biosensor. Highly porous polyaniline nanofibers were fabricated in different diameters and integrated on the interdigitated microelectrodes to develop electrochemical platforms. Characterization results revealed that the smaller diameter improved the sensitivity of the biosensor due to enhancement in the specific surface area. The developed biosensor was able to detect analyte as low as 0.1pg/mL with a large dynamic linear range of 10fg/mL to 1μg/mL. The fabricated sensor showed remarkable sensitivity towards COX-2 antigen suggesting the significant contribution of this nanofiber based platform to the enhanced sensitivity in COX-2 analyte detection.
High-Speed Aerosol Flow Through Micro-Nozzles for Direct-Write Processes
Authors: Hoey Justin M. , Bhattacharya Sourin , Lutfurakhmanov Artur , Robinson Michael , Swenson Orven F. , Akhatov Iskander S.
Published: April 2014

Aerosol direct-write printing for mesoscale features has been commercially available since around 2002 from Optomec®. We have developed variances to this process first in Collimated Aerosol Beam-Direct Write (CAB-DW) for printing sub-10 μm features and in Micro Cold Spray for printing with solid metallic aerosols. These deposition tools offer extensive uses, but are still limited in certain applications by either line widths or the amount of overspray. Modeling of aerosol flow through micro-nozzles used in these applications yields a greater understanding of the focusing of these aerosol particles, and may provide a vehicle for new nozzle designs which will further enhance these tools. Recent modeling applied both Stokes and Saffman force to the aerosol particles. Under certain conditions particle rotation and Magnus force may also be necessary to accurately predict the aerosol particles. In this paper we will present our recent results of high-speed flow of 1–10 μm diameter aerosol particles through micro-nozzles in which the model includes all three forces (Stokes, Saffman, Magnus) of fluid-particle interaction, and a comparison of these results to experiments.
Prognostic Health Monitoring Method for Fatigue Failure of Solder Joints on Printed Circuit Boards Based on a Canary Circuit
Authors: Hirohata Kenji , Hisakuni Yousuke , Omori Takahiro , Monda Tomoko , Mukai Minoru
Published: April 2014

Continuing improvements in both capacity and miniaturization of electronic equipment such as solid state drives (SSDs) are spurring demand for high-density packaging of NAND-type flash memory mounted on SSD printed circuit boards. High-density packaging leads to increased fatigue failure risk of solder joints due to the decreased reliability margin for stress. We have developed a failure precursor detection technology based on fatigue failure probability estimation during use. This method estimates the cycles to fatigue failure of an actual circuit by detecting broken connections in a canary circuit (a dummy circuit of daisy-chained solder joints). The canary circuit is designed to fail earlier than the actual circuit under the same failure mode by using accelerated reliability testing and inelastic stress simulation. The statistical distribution of the strain range of solder joints can be provided by Monte Carlo simulations based on the finite element method and random load modeling. A feasibility study of the failure probability estimation method is conducted by applying the method to a printed circuit board on which a ball grid array (BGA) package is mounted using BGA solder joints. The proposed method is found to be useful for prognostic health monitoring of solder joint’s fatigue failure.
Experimental Study of Dispersion of Particles at a Two-Fluid Interface
Authors: Linevich Vadim , Pillapakkam Shriram , Singh Pushpendra
Published: April 2014

When small particles like, flour, pollen, etc., contact an air-liquid interface, they disperse rapidly in the lateral direction. Using direct numerical simulation (DNS) we showed that the rapid dispersion is due to the fact that the capillary force pulls particles into the interface causing them to accelerate to a large velocity. The vertical motion of a particle during its adsorption causes a radially-outward lateral flow on the interface that causes nearby particles to move away. The goal of this study is to experimentally analyze the reasons for the rapid dispersion of particles when they are simultaneously adsorbed at a two-fluid interface. Specifically, we will analyze the effect of particle size on the oscillatory behavior of a single particle, as it is being trapped at an air-water interface. The diameter of a particle will be varied between 300–850 μm. Our experimental setup consists of a high speed camera with a resolution of 512×512 pixel and the recording speed up to 3000 frames per second which is connected to a 12X microscope. The camera outputs are analyzed to determine the frequency and amplitude of oscillation during adsorption. The measured amplitudes and frequencies for the micro glass spheres used in the experiment were found to be in qualitative match with the DNS results.
Response Surface Based Optimization of an Electro-Thermal Microactuator for High Track Density Optical Disk Drives
Authors: Xie Qikai , Chen Xiaolin
Published: April 2014

Optical disk drives (ODD) have become one of the most popular solutions for large storage capacity applications and are widely used in consumer electronics. For precise positioning in optical disk drives (ODD), the actuating system using MEMS technology has been considered as a very promising solution. This paper aims to optimize a recently proposed microactuator design as a fine-tracking device for high-density ODD. The microactuator device is electrothermally driven and consists of suspended bimorph beams that are connected to electric heater through linkage hinges on a micromirror platform. Static and dynamic characteristics of the microactuator device are analyzed using coupled electrothermal-mechanical finite element models. Our modeling results reveal that the performance of the original design is undesirable as the central mirror platform is undergoing a lateral shift and is bent concave down when the microactuator is activated. In order to maintain the relative flatness of the mirror surface, a new design with a folded-arm structure is proposed. The design is further optimized using experimental design and response surface method to achieve large actuation displacement and improved resonant frequency response. Overall, the results show that the optimized design outperforms the original design in achieving large displacement, fairly small lateral shift and mirror flatness under the same actuating voltage, while maintaining a compact size and supporting the high bandwidth servo control.