bluuebunny/crossref_metadata_2025 huggingface dataset:
MEMS Demodulator
Authors: Chung So-Ra , Park Sangtak , Abdel-Rahman Eihab M. , Yeow John , Khater Mahmoud
Published: October 2013

This paper presents research focusing on developing and simulating a new way of digital demodulation for the front end Radio frequency (RF) mechanically using MEMS electrostatic actuator by sensing the displacement of a parallel-plates. The operating principle based on the coupling multi-physics of the proposed demodulation device is explained. The analytical modeling and simulation results with experimental data are presented. Recent developments in the Micro Electro Mechanical Systems (MEMS) technology have shown the benefits of reliable mechanical strength that merges with electrical properties. Interest has increased and thus on to improve their performance by applying MEMS technology as to replace existing industrial parts and tools. A typical RF receiver consists of a front end, a band-pass filter, low noise amplifier (LNA), a local oscillator, and a mixer that recovers a baseband signal from a modulated RF signal. In a heterodyne receiver there is more than one intermediate stage. ASK and FSK digital demodulation using electrostatic actuator indicates better feasibility at lower frequency lower than 100 Hz for digital demodulation while indicating wide range of potential baseband range up to 1 kHz.
Towards Electrostatic Force-Feedback for Reducing Thermally-Induced Vibrations of MEMS
Authors: Sayed Shehrin , Andrews Nathanael D. , Clark Jason V.
Published: October 2013

We propose using electrostatic force-feedback to counter thermally-induced structural vibrations in micro electro mechanical systems (MEMS). Noise, coming from many different sources, often negatively affects the performance of N/MEMS by decreasing the precision for sensors and position controllers. As dimensions become small, mechanical stiffness decreases and the amplitude due to temperature increases, thereby making thermal vibrations become more significant. Thermal noise is most often regarded as the ultimate limit of sensor precision. This limit in precision impedes progress in discovery, the development of standards, and the development of novel NEMS devices. Hence, practical methods to reduce thermal noise are greatly needed. Prior methods to reduce thermal vibration include cooling and increasing flexure stiffness. However, the cooling increases the overall size of the system as well as operating power. And increasing the flexure stiffness can come at the cost of reduced performance. Electrostatic position feedback has been used in accelerometers and gyroscopes to protect against shock and improve performance, but we appear to be the first to propose that the method be applied to reduce vibration from noise by using velocity controlled force-feedback. Our study includes analytical models with parasitics that we verify through simulation. Using transient analysis, we show the vibrational effects of white thermal noise upon a MEMS, and we show greatly reduced vibration due to the inclusion of a simple electrostatic feedback system.
Analysis and Design of a Two-Wheeled Robot With Multiple User Interface Inputs and Vision Feedback Control
Authors: Olson Eric , Rizwan Mohsin , Shiakolas Panos S. , Thanekar Amit
Published: October 2013

Environments for robotics research and education are usually based on open source code or use proprietary software tools. Open source usually requires a user to know a low level programming language and proprietary software does not provide the environment needed for research and educational activities. In addition to the software, the hardware must be inexpensively and easily fabricated and assembled for teaching and experimentation purposes. In this manuscript, we will present the design and fabrication of a small size two-wheel mobile robotic platform developed for research and education purposes. Subsequently, the software environment for controlling the robot which is based on LabVIEW will be presented. LabVIEW was chosen because it provides many built-in toolboxes, and it is characterized by expandability and ease of interface with external devices. The software allows experienced as well as novice users to develop control code with ease. The robot communicates with control software in LabVIEW through a Bluetooth device. The developed environment is used to control the robot through multiple interfaces, to implement obstacle avoidance algorithms with ease, to implement open and closed loop control algorithms, to easily incorporate and use an inexpensive web camera for vision calibration, and is currently used to implement image processing and voice processing algorithms for robot localization and control both for research and education in both undergraduate and graduate courses.
On Demand Thermal Protection (ODTP): A New Approach for Designing Garments Exposed to Flash Flame Incidents
Authors: Mendoza Eduardo , Cooper Jean-pierre , Evangelista John W. , Auerbach Margaret , Arnas Özer
Published: October 2013

Soldiers, first responders and other high risk occupations such as power line technicians are routinely exposed to dangerous situations where severe burn injuries are possible. Standard flame resistant (FR) fabrics provide minimal burn protection when exposed to a flash flame incident. As a result, improvement in thermal protection is desperately needed and remains an ongoing subject of research and development. A simplified one dimensional physical model composed of a muscle layer, skin/fat layer, air gap(s) and fabric layer(s) is used to model heat transfer entering the body covered by a garment that is exposed to a flash flame. Heat transfer within the skin and muscle layers is modeled by combined conduction, metabolic heat generation and blood perfusion by a recently developed modification to the heat equation termed the bio-heat equation. Boundary conditions include a fixed temperature (core body temperature) at the inside of the muscle layer and combined convection and radiation from the flame on the outside of the fabric. The heat equation is solved by discretizing the domain in one dimension and using a finite volume approach to derive the finite difference equations. This model is an initial step to be used to provide an assessment of common FR garments with respect to both comfort in ambient conditions and protection during a flash flame. It also provides for parametric analysis to determine ideal thermo-physical properties, fabric thicknesses and layering for better protection during flash flame incidents. Estimates for time to burn injury from the numerical model is presented with experimental results using live mannequin flame tests (ASTMF-1930), standard vertical flame tests (ISO-17492) and a non-standard flame test with combined convection and radiation heat fluxes up to 85 kW/m2.

The main effort of this study revolves around an initial working design for a dynamic garment termed On Demand Thermal Protection (ODTP). The primary focus of the design is the development of a thermistor circuit embedded in a protective garment to act as an electric sensor for rapidly deploying the necessary thermal protection that is needed as predicted by the numerical model instantaneously in the event of a flash flame incident. An initial prototype is being developed with a focus on designing the thermistor circuit to mechanically actuate protective components in a flash-flame environment. Concepts include rapidly releasing a pressurized flame retardant fluid through vinyl tubing sewn into a garment and deploying a protective barrier around the face and neck when the thermistor circuit detects a sudden change in heat transfer. A summary of the prototype along with experimental testing to date compared to the theoretical predictions from the model described above is presented.
Nucleate Boiling on Biotemplated Nanostructured Surfaces
Authors: Rahman Md. Mahamudur , King Stephen M. , Olceroglu Emre , McCarthy Matthew
Published: October 2013

The fabrication and characterization of biotemplated nanostructured surfaces for enhanced pool boiling heat transfer is reported. By introducing micro/nano-porosity and surface roughness at the liquid-vapor interface, significant enhancement in surface heat transfer capability can be achieved during nucleate boiling. This work uses the self-assembly and mineralization of the Tobacco mosaic virus (TMV) to create superhydrophilic (∼9°), superhydrophobic (∼163°), and mixed hydrophilic-hydrophobic (∼70°) surfaces to investigate the effects of surface wettability and heterogeneity on boiling heat transfer performance. Pool boiling results showing CHF and HTC values for nickel-coated TMV, Teflon-coated TMV, mixed nickel + Teflon coated TMV, flat silicon, and flat Teflon are reported. The mixed surfaces demonstrate a CHF enhancement of ∼ 70% compared to flat silicon and ∼140% compared to flat Teflon. The results are in good agreement with the literature and will guide the design of optimized surfaces for further enhancement. This work demonstrates the feasibility of enhancing pool boiling heat transfer using TMV based nanostructured coatings.
Finite Element Analysis of Weld Area in Spot Bonding Process to Predict Bond Strength in Transparent Materials Using Ultrafast Lasers
Authors: Khan Salman N. , Shiakolas Panos S. , Rizwan Mohsin
Published: October 2013

Laser spot bonding is an approach to weld transparent materials at micro level or bonding in/for MEMs devices. This manuscript intends to investigate the dynamics of welding procedure in transparent materials with ultrafast lasers acting as the heat source. Spot bonding takes place when a laser beam creates a molten pool of the two materials to be bonded and subsequently the molten materials interact, gel with each other and solidify to create a bond. Thus, predicting the correct amount of molten matter is highly important for a reliable bond. Proper understanding of ultrafast laser matter interaction will provide the means to define ultrafast laser parameters for controlled molten volume leading to controlled bonding strength. This study will utilize the non linear breakdown caused by ultrafast lasers in borosilicate glass to determine the temperature profile and estimate the radial weld area. A finite element (FE) model of the system is presented and solved in ANSYS to estimate the weld area in borosilicate glass strips under action of a single ultrafast laser pulse. The effects of the focusing location of the laser beam, laser process parameters (energy level, focusing lens, pulse width) and material properties (optical and thermal absorptivity) will be discussed.
Fire Assessment of Steel Beam Members With Partial Passive Fire Protection Coverage
Authors: Smith Hunter , Ayhan Yavuz , Sari Ali
Published: October 2013

In offshore structures there are instances where the application of passive fire protection (PFP) is not possible or desired on certain portions of a structural member’s surface area. The most common cases are those where the top surface is left unprotected due to the presence of deck grating or plating. Current code and standard provisions on heat transfer and strength assessment of restrained flexural members are not directly applicable to these cases. Thus, a case study is presented for performing a fire assessment of a restrained plate girder subjected to jet fire impingement with the top flange surface left unprotected. To assess residual strength and perform non-linear analyses under combined thermal and static loading, a heat transfer analysis was first performed to obtain the time histories of the two dimensional heat distributions throughout the studied cross-section. The results showed that the top flange heats up rapidly and the heat conducts very slowly down the web to the rest of the cross-section, with a very large thermal gradient occurring over the height of the section. Approximate screening calculations for the cross-section, based on AISC capacity equations, indicated that the member will quickly exceed its elastic capacity and that local buckling may occur prior to yielding. Advanced non-linear finite element analysis of the mechanical response confirmed large amounts of plasticity and local buckling occur, but showed that global integrity of the member is maintained for the duration of the fire due to redundancy and catenary action. Recommendations and conclusions on analysis methods for partially protected deck members are made based on the results of this study.
Towards a Self-Calibratable IMU
Authors: Jin Xing , Clark Jason V.
Published: October 2013

In this paper, we propose a method that might enable an inertial measurement unit (IMU) to self-calibrate. Self-calibration of IMU is important for: sensing accuracy, reducing manufacturing costs, recalibration upon harsh environmental changes, recalibration after long-term dormancy, and reduced dependence on global positioning systems. What is unique about our technology is that it is the first to offer post-packaged calibration of displacement, force, system stiffness, and system mass. The IMU considered in our study consists of three pairs of accelerometer-gyroscope systems located within the xy-, xz-, and yz-planes of the system. Each pair of sensors oscillates 90 degrees out of phase for continuous sensing during turning points of the oscillation where velocity goes to zero. We demonstrate self-calibration using preliminary data, and we model IMU accuracy and uncertainty through sensitivity analysis.
The Impact of Electricity Market Conditions on the Value of Flexible CO2 Capture
Authors: Cohen Stuart M. , Webber Michael E. , Rochelle Gary T.
Published: October 2013

Carbon dioxide (CO2) capture with amine scrubbing at coal-fired power plants can remove 90% of the CO2 from flue gas, but operational energy requirements reduce net electrical output by 20–30%. Temporarily reducing the load on energy intensive components of the amine scrubbing process could temporarily increase power output and allow additional electricity sales when prices are high. Doing so could entail additional CO2 emissions, or amine solvent storage can be utilized to allow increased power output without additional CO2 emissions. Price-responsive flexible capture is studied for $0–200/tCO2 and $2–11/MMBTU natural gas using a nominal 500 MW coal-fired facility in the 2010 Electric Reliability Council of Texas (ERCOT) grid. CO2 capture systems use a 7 molal monoethanolamine (MEA) solvent. Venting additional CO2 while increasing electrical output provides significant benefit only at $30–60/tCO2 and when natural gas prices exceed $4/MMBTU. Solvent storage can improve profitability with CO2 capture at higher CO2 emissions penalties, but primarily at low-to-moderate natural gas prices when power plant capacity factor is less than 90%.
Combined Effect of Isoproterenol and Mechanical Oscillation on the Contractile Response of Mice Airway Smooth Muscle From Healthy and Asthmatic Subjects
Authors: Jo-Avila M. J. , Al-Jumaily A. M. , Lu J. , Sobrevia L.
Published: October 2013

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 mechanical oscillations may improve drug therapy when combined with ISO or used alone in asthmatic subjects. Preliminary results indicate that combining ISO with breathing equivalent mechanical oscillations tends to increase the relaxation response, as compared to ISO alone in airways from healthy subjects, but not in the same manner in asthmatic airways. The effect of superposed oscillations of 1% and 1.5% amplitude in the range 5–20 Hz applied over breathing equivalent mechanical oscillations was also assessed in the study.
Modeling Heat Transfer During Furnace Fire Exposures
Authors: Nahid Mohammad N. , Lattimer Brian Y.
Published: October 2013

Thermal modeling is an important aspect in evaluating the fire resistance of a structure subjected to a furnace exposure. A common approach for predicting temperatures in thermo-structural modeling is with an effective emissivity meant to account for radiation exchange between surfaces of different temperature (“shadow effect”), radiation from gas participating media, and surface emissivity. Several methods have been proposed using gas radiation only models to provide a basis for the choice of effective emissivity, but no evaluations have considered the gas interaction and surface-to-surface interactions in understanding the controlling behavior. In this paper an analytical model was developed for net-radiation in a three surface enclosure filled with an isothermal medium to investigate the role of surface radiation exchange versus gas radiation effects. As expected, surface-to-surface radiation dominates at lower gas emissivity since radiation is not attenuated by the gases, while gas radiation dominates at higher emissivities. With furnace environments produced using clean burning processes, a methodology for predicting thermal response of complex structures in furnace tests based on radiation exchange was used to predict experimental data for steel-concrete floor systems. The furnace exposure was modeled using the Abaqus Version 6.10EF-1 built-in radiation exchange model and convection interaction. All predicted temperatures of the structural element were within 5% of the measured temperatures. This indicates the model without gas participating media effects reasonably predicts the radiation exchange between surfaces of the test article and furnace, and it accounts for the shadow effect.
Out-of-Plane MEMS Actuation Using a Scanning Electron Microscope
Authors: Hogan Alexander L. , Ford Kurtis R. , Harvey Ian R.
Published: October 2013

In the world of micro-electromechanical systems (MEMS) R&D efforts are expended creating new means of actuation, usually trading either force or displacement. In our scheme we pump charge into an electrically isolated conductive system with a Scanning Electron Microscope (SEM) to achieve a net force away from the substrate. Though we observe a highly dynamic response, we have approximated the force of the system with a quasi-static mechanical force sensor. The study of this actuation has focused on a spiral spring fabricated in Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT-V™). Experiments show the effect of SEM beam conditions on this device, most notably finding the operation to begin at 5 keV accelerating voltage, where our Monte Carlo simulation predicts the beam will begin penetrating the 0.3 μm thick polySi. The out-of-plane motion has been measured as high as 220 μm which is approximately 2/3 of the diameter of the 2D spiral. A linear elastic model of the force sensor shows that in mechanical equilibrium the deflection is associated with an equivalent uniform pressure up to 90 Pa.
Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data
Authors: Azizi Yousof , Davies Patricia , Bajaj Anil K.
Published: October 2013

Flexible polyethylene foam, which is used in many engineering applications, exhibits nonlinear and viscoelastic behavior. To date, several models have been proposed to characterize the complex behavior of foams from the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. A nonlinear viscoelastic model, which is an extension of previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is assumed in the model that total stress is decomposed into the sum of a nonlinear elastic component, which is modeled by a higher order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures are developed to estimate the model parameters using uniaxial compression data from experiments conducted at different rates. The performance of this model is compared to that of other nonlinear viscoelastic models.
Damage Detection in Composite Laminates Based on Adaptive Phase Estimation of Lamb Waves
Authors: Azizi Yousof , Jha Ratneshwar
Published: October 2013

This research presents the development of a novel structural health monitoring method for identifying damage location within a composite structure. The proposed method for damage detection is based on sinusoid-tracking algorithm (STA), which is an adaptive nonstationary signal processing tool. Sinusoid-tracking algorithm is a method of extraction of nonstationary sinusoidal signals and estimation of their parameters, namely amplitude, phase and frequency which vary over time. This helps to analyze the nonstationary signals, due to nonlinearity caused by damage, in identification procedure. The proposed method makes use of the estimated phase recorded at different spots on the structure under study. Estimated phase is used to define the damage indices. By comparing the value of indices from a baseline (or healthy) case to a damaged case, at different locations on the structure, variations in the value of indices are observed especially adjacent to the location of damage. The proposed methodology is applied to experimental plate. The results of proposed method is promising in detecting location of damage.
A Uniform Standard for the Teaching of Energy Perspectives in Statistics and Dynamics
Authors: Kobus C. J. , Chang Y. P.
Published: October 2013

It has become increasingly apparent in our combined years of teaching engineering subjects that there is a discontinuity between how related subjects are taught. By that, we mean that fundamental principles of mass, energy and momentum are indifferent to the application, yet they are introduced and utilized very differently in various engineering courses, specifically those in the general area of solid mechanics versus those in the fluid and thermal sciences. One example of this disparity is the conservation of energy principle, one of the two most fundamental of principles for which all things appear subject to without limitation. Also known as the 1st Law of Thermodynamics, the statement simply says “energy cannot be created nor destroyed.” This implies that, within these broad but absolute limits, energy can be converted from one form to another or transported from one place to another, or both, but that the total energy remains a constant.

This 1st Law of Thermodynamics is taught earlier in the curriculum from its namesake, thermodynamics. In fact, most introductory statics and dynamics courses do teach some form of the conservation of energy, but usually call it “energy methods.” The plural form “energy methods” indicates that there is more than one, which can be readily observed in most statics and dynamics textbooks. Unfortunately, these methods are only special-cases of the conservation of energy principle. At no time, however, in any statics and dynamics textbook that we have seen, is the full conservation of energy principle utilized, which is unfortunate for reasons of consistency and continuity in the curriculum.

It is the intent of this paper to show, through an example, that the same basic form of the conservation of energy can and should be utilized throughout the curriculum, starting with basic statics and dynamics and progressing into thermodynamics and the rest of the curriculum. This would indeed help student comprehension and retention of this very important principle in implication and application.
Investigation of Riding Position Effects on Time-Trial Bicycle Drag Coefficient at Different Yaw Angles
Authors: Doval Peter N. , Avdeev Ilya V.
Published: October 2013

Time-trial bicycle racing is highly influenced by aerodynamics, perhaps more so than any other form of bicycle racing. Companies competing in this class of racing spend millions of dollars trying to optimize the geometry of the bicycles and the gear each rider wears in order to reduce aerodynamic drag. The idea behind this project was to investigate other ways to optimize the aerodynamic efficiency of the rider, considering that the rider contributes the majority of the drag force of the bicycle-rider system. A large contributor to drag is the frontal area of the object of interest (a silhouette of the object in the fluid flow direction). This illustrates how much the rider’s body contributes to overall drag. If small riding adjustments could be made to the rider’s body during riding, drag may be significantly reduced. This idea and the fact that the direction of wind impacting the rider can vary influenced the concept of this project.

It was hypothesized that adjusting the time-trial handlebars on the bicycle to place one of the rider’s hands further aft than the other would influence the upper body to rotate slightly. This could then reduce the frontal area of the rider in the wind direction, therefore reducing the aerodynamic drag. To simulate this situation, a non-contact 3-D digitizer was used to scan a rider aboard a bicycle in a normal riding position and in the above-mentioned, asymmetric position. This 3-D scan was then imported into the computational fluid dynamics (CFD) program Star-CCM+ and several simulations were run. Each of the two riding positions was simulated at differing yaw angles, ranging from −45° to 45°. The initial simulations seem to prove the theory as the asymmetrical riding position experiences decreased drag at significant yaw angles while the normal riding position does not. These results are encouraging and it is desired to continue refinement of the scanning and simulation methods as well as to validate these findings in a wind tunnel.
Comparison of Computer Algebra Systems for Closed Form Stiffness Matrix Generation
Authors: Shiakolas Panos S. , Wilhite David C. , McCaslin Sara E.
Published: October 2013

Computer algebra systems (CAS) have been advantageously employed to generate closed form expressions for finite elements. The advantages relate to the time improvements or savings realized by employing closed form generated expressions as compared to numerical integration. However as the element order increases, the size of the closed form generated expressions become unmanageable causing the source code files to possibly become unusable due to their size. One approach to reducing the size of the source files is to take advantage of the utilities found in CAS to identify common expressions or sub-expressions. In this manuscript we present on-going research by comparing two widely used CAS, Mathematica and Maple, as they relate to identifying common expressions in low order tetrahedral finite element stiffness matrices generated in symbolic form, associated time savings and possible issues. The results indicate that the use of CAS could be advantageously employed to identify common subexpressions through pattern matching to further reduce the size of the generated source files and realize time improvements during execution of the source codes. In addition, the developed procedures could be easily applied to higher order elements with much larger number of entries of closed form expressions where even more savings could be realized.
Beta Testing a Web-Based Writing Coach
Authors: Todd Beth A. , Niiler Luke , Brown Marcus , Bahri Prateek , Tamondong Virginia , Beams David M. , Barth Joan , Warren Garry , Swinney Kenneth R. , Cordes David W.
Published: October 2013

“The Coach” is a web-based tool developed to guide students through the technical writing process. It provides instruction about form as well as critique of different aspects of the students’ writing. It goes beyond the Microsoft word spell check and grammar check. It gives feedback about writing complexity and appropriateness for different word choices in a technical document. It also gives background about the appropriate contents for technical writing in addition to example documents. The latter is extremely important for the novice writer who may not have much experience in working with technical reports.

The initial document type in “The Coach” is a lab report. If the lab report can be developed into the web-based tool, other forms will be more easily implemented. In addition to developing the website, the development team is preparing a document and a video for a professor to use to instruct students on the use of “The Coach.”

The instructional materials and “The Coach” were beta tested with a freshman engineering class. A baseline writing sample was collected before the introduction of “The Coach.” Students in some sections were instructed in use of “The Coach,” and other sections were controls. Additional beta testing is ongoing.
Natural Convection in Rectangular Cavity With Nanoparticle Enhanced Ionic Liquids (NEILs)
Authors: Paul Titan C. , Morshed A. K. M. M. , Fox Elise B. , Visser Ann E. , Bridges Nicholas J. , Khan Jamil A.
Published: October 2013

A systematic natural convection heat transfer experiment has been carried out of nanoparticle enhanced ionic liquids (NEILs) in rectangular enclosures (lengthxwidthxheight, 50×50×50mm and 50×50×75mm) heated from below condition. In the present experiment NEIL was made of N-butyl-N-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl} imide, ([C4mpyrr][NTf2]) ionic liquid with 0.5% (weight%) Al2O3 nanoparticles. In addition to characterize the natural convection behavior of NEIL, thermophysical properties such as thermal conductivity, heat capacity, and viscosity were also measured. The result shows that the thermal conductivity of NEIL enhanced ∼3% from the base ionic liquid (IL), heat capacity enhanced ∼12% over the measured temperature range. The natural convection experimental result shows consistent for two different enclosures based on the degrading natural convection heat transfer rate over the measured Rayleigh number range. Possible reasons of the degradation of natural convection heat transfer may be the relative change of the thermophysical properties of NEIL compare to the base ionic liquid.
Structural Optimization of Laminated Composite Blade Using Particle Swarm Optimization
Authors: Li H. , Chandrashekhara K.
Published: October 2013

Composite blades working underwater experience complicated loading conditions. Robust design of a composite blade for hydrokinetic applications should satisfy varying loading conditions and conservative failure evaluations. Blade manufacturing using composites requires extensive optimization studies in terms of composite materials, number of layers, stacking sequences, ply thickness and orientation. In the current study, particle swarm optimization (PSO) technique is adopted to conduct composite lay-up optimization for the turbine blade. Layer numbers, ply thickness and ply orientations are optimized using standard PSO (SPSO) to minimize weight. Composite failure criteria are applied using finite element method to generate the most conservative blade design. Based on the blade lay-up design with minimized weight, stacking sequence of the blade lay-up was optimized to maximum safety factor of the designed blade using permutation discrete PSO (PDPSO). To improve the efficiency of the algorithm, the concepts of valid/invalid exchange, and memory checking were introduced into PDPSO. Meanwhile, another discrete PSO using partially mapped crossover (PMX) technique was used to validate the simulation results optimized by PDPSO. A final composite blade design with minimized weight and maximized load-carrying capacity was presented.
Investigation of Size Effect on the Emissivity of Thin Films
Authors: Edalatpour Sheila , Francoeur Mathieu
Published: October 2013

The size effect on the emissivity of thin films is analyzed via a direct method based on Maxwell’s equations combined with fluctuational electrodynamics. Traditional indirect approaches involve computation of absorption, and the emissivity is then predicted by invoking Kirchhoff’s law. The direct method employed in this work does not require Kirchhoff’s law. Instead, Kirchhoff’s law emerges naturally from the mathematical model. Simulation results reveal that the emissivity of metal films increase above bulk values as the film thickness decreases. This counterintuitive behavior is due to the extraneous contributions of waves experiencing multiple reflections within the thin layer, which are usually internally absorbed for metallic bulks. Conversely, for dielectrics, the emissivity of films decreases as the film thickness decreases due to a loss of source volume. The critical thickness above which no size effect is observed for metals is about a hundred of nanometers, while it is as large as a few centimeters for dielectrics. Finally, a simple approximate expression is suggested for evaluating the critical thickness; this expression can be used as a quick reference to determine if the size effect on the emissivity of thin films should be considered.
Droplet Spray Behavior of an Atomization-Based Cutting Fluid (ACF) System for Machining of Titanium Alloys
Authors: Nath Chandra , Kapoor Shiv G. , Srivastava Anil K. , Iverson Jon
Published: October 2013

The aim of this research is to study droplet spray characteristics of an atomization-based cutting fluid (ACF) spray system including droplet entrainment angle and flow development regions with respect to three ACF spray parameters, viz., droplet and gas velocities, and spray distance. ACF spray experiments are performed by varying droplet and gas velocities. The flow development behavior is studied by modeling the droplets entrainment mechanism, and the density and distribution of the droplets across the jet flare. Machining experiments are also performed in order to understand the effect of the droplet spray behavior on the machining performances, viz., tool life/wear, and surface roughness during turning of a titanium alloy, Ti-6Al-4V. Experiments and the modeling of flow development behavior reveal that a higher droplet velocity and a smaller gas velocity result in smaller droplet entrainment angle leading to a gradual and early development of the co-flow with a smaller density and a better distribution of the droplet across the jet flare. Machining experiments also show that a higher droplet velocity, a lower gas velocity and a longer spray distance significantly improve the machining performances such as tool life and wear, and surface finish.
Development and Optimization of a Small Scale Pellet Burner
Authors: Teixeira José Carlos , Ferreira Rui , Seabra Eurico A. , Ferreira Manuel Eduardo
Published: October 2013

Environmental concerns and the drive to reduce the dependence on petroleum brought the use of renewable energies to the forefront. Biomass appears as a very interesting alternative for direct conversion into heat. In this context, densified forms of biomass such as pellets are of great relevance because of their easy of use, high efficiency and low emissions.

The practical interest in pellet combustion has been driven by the domestic heating sector, which favors the characteristics that are intrinsic of this fuel, despite its relatively higher price. However, the growing costs of fossil fuels have extended the interest of pellet fuels into industrial applications, including co-firing in power stations.

A fast growing market includes the retrofitting of existing fuel boilers and furnaces with alternative burners that can be fitted into existing combustion systems. Such an approach has proved very attractive due to the low installation cost and the growing existence of fuels produced in the vicinity of the end user. This involves in most cases a custom built application which requires a high level of flexibility to variable operating conditions.

This work reports on the development of a 120 kW pellet burner. A prototype of the burner was built that enables the independent control of the air supply into various regions of the combustion chamber and an accurate supply of fuel. The burner was fitted into a testing furnace of cylindrical shape oriented horizontally. Its diameter is 0.5 m and is constructed in a modular fashion with a total length of 2.2 m. All the facility is fully instrumented and includes: temperature data in various locations inside the chamber, flue gases emissions (CO, CO2, NOx) measurements and flow rates.

The objective of the test and development is to optimize the combustion over the thermal load range of the facility. The excess air, fuel supply (primary and secondary) and the shape of the furnace grate enable the optimization of the burner with CO emissions of approximately 50 ppm, well below the acceptable limits.
Identification and Quantification of Residual Strains During Curing of Carbon Fiber Epoxy Laminates
Authors: Mailen Russell , Jack David A. , Wright Lesley M.
Published: October 2013

Residual strains develop from matrix shrinkage and non-isotropic coefficients of thermal expansion in composite laminates throughout the cure cycle. These strains influence the final shape and strength of the laminate. It is hypothesized that cure strains depend on lamina orientation, lamina stacking sequence, spatial location, and cure kinetics. In the present study, embedded strain gages are used to monitor residual strain development. Changes in strain due to elevated temperature post cure are quantified and a study of the curing epoxy characteristics is performed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). These later studies provide insight to the measured internal laminate stresses and provide guidance in the interpretation of the strain measurements.
A Thermodynamic Analysis of a Solar Organic Rankine Cycle
Authors: McClintic John , Kistenmacher David A. , Anderson Josh , Demirer Onur , Berberoglu Halil
Published: October 2013

A systems level analysis is presented for a solar organic Rankine cycle (S-ORC) for assessing the feasibility of the cycle to be used in small scale rural/residential power generation. A thermodynamic model was generated for a system composed of the collector, the heat transfer fluid, the pump, the expander, and the heat exchangers, using five different working fluids. Based on the collector efficiency and incident radiation, the thermodynamic efficiency of the system was evaluated. For flat panel solar collectors, the highest system efficiency was found to be 6.2% when using R-134a as a working fluid. R-134a also required the least boiler heat transfer area, although its operation required relatively higher pressures. The performance of the solar-ORC system is compared with that of photovoltaic systems and the practicality of these solar thermal systems are discussed in terms of system size and end use.
Design and Development of a Vector Thrusting Quadrotor for Minimally Induced Pitch and Roll Motions
Authors: Brech Dale E. , St. Amand Joseph D. , Hoover Randy C. , McGough Jeff S. , Bedillion Mark
Published: October 2013

Due to its hovering capabilites and maneuverability, the quadrotor provides an excellent platform for unmanned systems and robotics research. Localization of the vehicle is typically done via laser ranging or photometric and depth cameras. The design of the quadrotor introduces a problem, however, when it is to travel parallel to the ground plane. Due to the rigid body of the quadrotor and the fixed orientation of the thrusters it is impossible for the quadrotor to undergo this motion without inducing a change in the pitch and/or roll orientation. This introduces a problem in finding the true orientation at which sensor measurements are taken, requiring advanced computer vision algorithms, mechanical gimbal systems or other means to compensate for the motion. This paper focuses on the design of a quadrotor that has the capability to travel parallel to the ground plane while minimizing the induced pitch and roll motion. The unique contribution to the quadrotor design is to allow each of the quadrotor arms to rotate about their respective horizontal axis in order to accomplish thrust vectoring of the individual motors. By controlling both the magnitude and direction of each of the motor thrusts, pure translational maneuvers are possible without inducing pitch and/or roll motions. Simulation results are presented as well as the controller used to govern the behavior of the craft.
DSMC Simulations of Squeeze Film Under a Harmonically Oscillating Micro RF Switch With Large Tip Displacements
Authors: Diab Nadim A. , Lakkis Issam A.
Published: October 2013

The two-dimensional unsteady behavior of a rarefied gas film under an oscillating micro-cantilever RF switch is presented. The microbeam, undergoing a parabolic deflection profile, is allowed to oscillate harmonically between its equilibrium position and the fixed substrate underneath for large beam-tip displacements. The gas film dynamics in terms of the flow field velocity and fluid forces exerted on the oscillating microbeam are discussed. The numerical technique used to model the rarefied gas flow is the Direct Simulation Monte Carlo (DSMC) method where the Knudsen (Kn) number is greater than 0.01 (ie. non-continuum regime). Unlike previous work in literature, the beam undergoes large deflections, which requires implementation, in DSMC, of a more realistic molecule-beam reflection behavior based on the instantaneous beam’s position and velocity. The effects of inertia, both local acceleration (St) and convection term (Re), and compressibility (Ma) on the gas film dynamics are examined over ranges of oscillating frequencies, velocity amplitudes, and microbeam’s lengths.
Experimental and Computational Investigation of Debonding at the Interface of Two L-Shaped Polycarbonate Plates
Authors: Yavas Denizhan , Uyar Imren , Gozluklu Burak , Coker Demirkan
Published: October 2013

L-shaped composite structures are increasingly replacing metal ribs and box structures especially in recent civil aerospace structures and wind turbine blades. Delamination of these L-shaped composite laminates occur by interlaminar opening stresses at the curved region under perpendicular loading to one arm. In this study, delamination at the curved region is studied experimentally and computationally by using a simplified model material consisting of two L-shaped polycarbonate plates bonded together. The effect of precrack size at the curved region on the initiation and propagation of delamination under loading perpendicular to one of the arms is studied. Experimental observations are carried out using photoelasticity to visualize the isochromatic stress patterns in the model. Finite element analysis (ABAQUS) is carried out using static (implicit) analysis during elastic loading followed by dynamic (explicit) analysis during crack growth in conjunction with a bilinear cohesive zone model. For precracks smaller than 40mm, a sudden drop in load-displacement plot is observed corresponding to dynamic crack growth at 80 m/s crack tip speed from the corner to the arms. Afterwards, a generally monotonic increase in load-displacement behavior is observed albeit with a lower stiffness corresponding to continued stable crack growth. For larger pre-cracks, load-displacement increases monotonically even after crack initiates with stable stick-slip type crack growth. These two regimes of crack growth are consistent with the observations of Wimmer et al (2009) on cross-ply composite L-beams.
Performance and Economic Analysis of Biomass/Coal Co-Gasification IGCC Systems With Supercritical Steam Bottom Cycle: Part 1 — Post-Combustion Carbon Capture
Authors: Wang Ting , Long Henry A.
Published: October 2013

In recent years, Integrated Gasification Combined Cycle (IGCC) technology has been gaining steady popularity for use in clean coal power operations with Carbon Capture and Sequestration (CCS). This study focuses on investigating two approaches to improve efficiency and further reduce the greenhouse gas (GHG) emissions. First, replace the traditional subcritical Rankine steam cycle portion of the overall plant with a supercritical steam cycle. Second, add different amounts of biomass as feedstock to reduce emissions. Part 1 focuses on investigating post-combustion CCS and Part 2 on analyzing pre-combustion CCS, using both sour-shift and sweet-shift processes. Employing biomass as a feedstock has the advantage of being carbon neutral or even carbon negative if CCS is implemented. However, due to limited feedstock supply, such plants are usually small (2–50MW), which results in lower efficiency and higher capital and production costs. Considering these challenges, it is more economically attractive and less technically challenging to co-combust or co-gasify biomass wastes with coal.

Using the commercial software, Thermoflow®, this study analyzes the baseline plants around 235MW and 267 MW for the subcritical and supercritical designs, respectively. The results clearly show that utilizing a certain type of biomass with low-grade coals up to 50% (wt.) can, in most cases, not only improve the efficiency and reduce overall emissions, but may be economically advantageous, as well. The CO2 emissions decrease by about 7,000 tons/MW-year, making both plants carbon-negative with only 10% biomass in the feedstock. In addition, implementing a supercritical steam cycle raises the efficiency (1.6 percentage points) and lowers the capital costs ($300/kW), regardless of plant layout. Implementing post-combustion CCS consistently causes a drop in efficiency (at least 7–8 points) from the baseline, and increases the costs by $3,000-$4,000/kW and $0.06-$0.07/kW-hr. The SOx emissions also decrease by about 190 tons/year (7.6 × 10−6 tons/MW-year), while the NOx emissions are all but eliminated through post-combustion CCS. Finally, the CCS cost is around $65-$72 per ton of CO2.
Cavity Filling Analysis for the Fabrication of an Alignment Structure in Micro Hot Embossing
Authors: Gomez J. A. , Conner T. G. , Song I.-H. , Chun D.-H. , Kim Y.-J. , You B.-H.
Published: October 2013

The flow behavior of polymers was analyzed using a commercial finite element software, DEFORM-2D, for the replication of microstructures. An alignment structure for microassembly, a hemisphere-tipped post, was modeled to demonstrate the polymer flow in hot embossing. The mold filling with polymer was evaluated by the heights of molded posts. The results of simulation showed better replication fidelity of the post with the increase of the molding temperature and displacement of the mold insert. The complete filling of a mold cavity was achieved at the molding temperatures of 112.5, 125, 137.5, and 150°C when the displacements were 1.5, 2.0 and 2.5 mm. The model can be used to design the process parameters for the reliable replication of microstructures.
Symmetrical Heating and Cooling of a Moving Microfluidic Sample
Authors: Harandi Amir , Hooks Joshua , Farquhar Tony
Published: October 2013

Research on microanalytical systems is shifting away from academia and into the corporate arena. For business reasons, the nature of today’s research is increasingly applied and focused on cost and reliability in particular applications. In general, the advantages of the lab-on-a-chip test (as compared to a full scale benchtop test) typically include lower power consumption, lower reagent consumption and lower operational costs. In most cases, the lab-on-a-chip test is also faster and, potentially, more accurate, in part because smaller sample volume implies a much larger surface to volume ratio.
Reinventing MEMS Through Genetic Programming
Authors: Ghoshal Samik , Clark Jason
Published: October 2013

As the functional requirements of MEMS devices become more complex, advanced optimization techniques become more necessary in determining acceptable parameters, or even creating new components to satisfy a desired output. These challenges are being met through the use of genetic programming (GP), a brand of optimization that determines parameters through its “artificial intelligence” selecting and choosing the best output.

The applications of genetic programming to MEMS have been mostly limited to the task of optimizing parameters and components for existing devices. In addition to these applications, GP can also be utilized to create original MEMS devices. Existing MEMS devices can also be reinvented to match the shape and structure of existing devices based solely on the device’s performance characteristics. This paper will discuss how the electro-thermal actuator and the chevron actuator were successfully reinvented through this process.