bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Haptic Fidelity via Reduced Sampling Period With an FPGA-Based Real-Time Hardware Platform
Authors: Sevcik Kevin S. , Kopp Emilie , O’Malley Marcia K.
Published: May 2009

Impedance based haptic interfaces face inherent challenges in displaying stiff virtual environments. Fidelity of a virtual environment is enhanced by stiff virtual walls combined with low damping and passive behavior of the interface. However, the stiffness of virtual walls displayed on an impedance based interface is limited by the damping inherent in the controller, the sampling rate of the control loop, and the quantization of the controller’s position. Attempting to display a stiffness larger than this limiting value destroys the passivity of the interface, leading to active controller behavior and eventually closed loop instability. We propose a method of increasing the fidelity of a PHANToM Premium 1.0 commercial haptic interface by controlling it via a Field Programmable Gate Array (FPGA) both alone and with a Real Time Operating System (RTOS) control system. This custom controller enjoys several benefits over the standard control achieved via a proprietary control card in a Multitasking OS, including reduced system overhead and deterministic loop rate timing. The performance of the proposed FPGA/RTOS controller compares favorably with the performance of an FPGA/Multitasking OS controller. The FPGA/RTOS controller achieves control loop rates an order of magnitude greater than that of the proprietary controller, allowing virtual walls to be displayed with greatly increased stiffnesses, while retaining the passivity and low damping of the PHANToM interface.
Constrained Distributed RHC Based on Vector Lyapunov Functions and Comparison Model
Authors: Cai Xuejing , Wu Fen
Published: May 2009

In this paper, we propose a distributed receding horizon control (RHC) algorithm for a class of constrained and dynamically interconnected systems with stability and performance guarantees. For weak coupling between subsystems, a vector Lyapunov function off-line is derived and will be used as terminal cost for distributed RHC. Moreover, comparison models will be used to predict subsystem states over future horizon. An example is provided to demonstrate the control design procedure.
Assessment of Uncertainty in Equivalent Sand-Grain Roughness Methods
Authors: Bhatt Chinmay P. , McClain Stephen T.
Published: May 2009

The equivalent sand-grain roughness model is an empirical model initiated by Schlichting for predicting skin friction and heat transfer for turbulent flows over rough surfaces. For the equivalent sand-grain roughness model, rough surfaces with various features are compared to data from Nikuradse concerning flow in pipes with varying sizes of sieved sand glued to the wetted surface. Rough surfaces are assigned a value of equivalent sand-grain roughness height based on comparisons with Nikuradse’s fully rough data. Recent literature on the equivalent sand-grain roughness method has involved seeking correlations for equivalent sand-grain roughness height based on roughness metrics such as height, shape, and density. The Sigal-Danberg parameter has demonstrated the most promise for correlating the available equivalent roughness height data to geometric surface information. The Sigal-Danberg parameter was recently modified to include the mean surface elevation as an important parameter. While the modified Sigal-Danberg parameter provides a unified correlation for the equivalent sand-grain roughness height, the new formulation does not improve the scatter of the experimental data around the correlation. An uncertainty analysis is presented to evaluate the uncertainty of equivalent sand-grain roughness height predictions using the unified correlation. The analysis begins by estimating the uncertainties in the experimental measurements of Schlichting, and the uncertainty propagation is evaluated through each step of the equivalent sand-grain method development. The uncertainty associated with using empirical equations and conceptual uncertainties not associated with experimental measurements are also discussed. The result is an improved understanding of and uncertainty quantification for skin friction and heat transfer predictions made using equivalent sand-grain roughness methods.
Influence of Acoustic Noise on the Dynamic Performance of MEMS Gyroscopes
Authors: Castro Simon , Dean Robert , Roth Grant , Flowers George T. , Grantham Brian
Published: May 2009

Advances in MEMS technology have resulted in relatively low cost gyroscopes and accelerometers and, correspondingly, inexpensive inertial measurement systems. This has opened up the field of applications for inertial measurement units (IMUs) and they are currently being proposed for use in a wide variety of possible applications, with environmental conditions ranging from mild to harsh. Of particular interest in this study are MEMS gyroscopes, which are based upon vibratory, rather than rotational, designs and are especially susceptible to the effects of acoustic noise, as compared to conventional gyroscopes. This is particularly true for certain applications. For example, in some aerospace environments, noise levels can be greater than 120 dB and extend over a frequency range greater than 20 kHz. Output signals can be overwhelmed by such effects, becoming extremely contaminated and noisy and, can even be completely saturated. So, it is important to develop an understanding of the influence of high levels of noise on MEMS gyroscope performance and to develop methodologies to mitigate such effects. In the present investigation, a series of experimental studies were conducted for a variety of MEMS gyroscope designs. Each unit was exposed to a range of acoustic noise amplitudes and frequencies. The output signals were recorded and analyzed. The results are presented and discussed in detail. Strategies for mitigating such effects were identified and tested. Those results are also discussed in detailed.
Computational Simulation for Predicting Flow Through a Belleville Washer Damper Unit
Authors: Patel Anil , Tilley Derek , Darling Jos
Published: May 2009

A Belleville washer can be best described as a non flat washer with a conical shape and a uniform cross section. They are also known as disk springs and as the name suggests they are often utilised for their load bearing capabilities. Due to their compactness along the axis of loading and a wide range of attainable load-deflection characteristics they are an attractive alternative to conventional springs. Though Belleville washers are primarily used for their load bearing capabilities, they can also be used to build a damping device; which in turn can be used as part of a suspension system. The non linear deflection of the spring makes it difficult to predict the resulting pressure-flow characteristic and as a result the damper pack is built either by an experienced operative or by a trial and improvement method. Without an analytical tool to predict the behaviour a designer cannot exploit the full functionality of this type of spring. The intension of this paper is to present research undertaken to develop a correlation which describes the pressure drop required for various flow rates when using Belleville washers as damping elements. Using existing load-deflection theory an initial model was developed to relate load with pressure and deflection with flow area which could be used to estimate flow rate. The solutions from a computer simulation showed similar trends to those found in the experimental study, but they estimated smaller pressure drops for a given flow rate. It was postulated that the exit velocity of the fluid created a region of low pressure which tended to close the opening and thus increase the pressure drop. This hypothesis was examined and confirmed with a computational fluid dynamic simulation and the results were used to modify the existing model. Analysis of the new model showed good agreement with the experimental study.
Visualization and Tracking of Electrospray Droplet Emissions Using Fluorescence and Holographic Techniques
Authors: Zorzos Anthony N. , Guasto Jeffrey S. , Breuer Kenneth S.
Published: May 2009

We report results from optical characterization of the stream of droplets emitted from the tip of a Taylor cone. We demonstrate the ability to image and track individual droplets emitted from a Taylor cone using fluorescence microscopy with pulsed laser illumination and statistical particle tracking velocimetry (SPTV). Additionally, we demonstrate the use of holographic imaging to examine the three dimensional electrospray droplet structure. Single-exposed images were used to measure droplet diameters between 1.5 to 2.5 μm for flow rates ranging from 15 to 25 nL/s. Velocity distributions with mean velocities over 40 m/s were obtained from analysis of double-exposure images using SPTV. In addition to droplet size and velocity distributions, we present data on the instability of the tip stream and on the formation and subsequent evolution of the spray cone for emission frequencies over 3.5 MHz.
Deformation Analysis of Aero Thin-Walled Workpiece Under Multi-Stress Coupled Effect
Authors: Lu Dong , Li Jianfeng , Rong Yiming , Sun Jie , Zhang Song , Zhou Jun , Jiang Feng
Published: May 2009

Cutting stress coupled with clamping stress and initial stress affects the workpiece deformation. To predicate the workpiece deformation during machining, the multi-stress coupled model was developed. The finite element model of milling process is established and the milling forces were predicted. The predicated milling force, clamping force and initial stress were taken as initial conditions and were inputted into the multi-stress coupled model. Workpiece deformation during machining and reaction forces of locators were predicated. To maintain workpiece in a stable condition during machining, reaction forces of the locators when the cutting tool moving along the clamp side must be monitored.
Cooling of the Coil Heads for a Totally Enclosed Motor
Authors: Bamford Robert , Heyward Robert , Hill Timothy , Lamar Carl , Matlock Amir
Published: May 2009

In an effort to obtain additional power from an AC motor, a reduction in coil head temperature was needed. Furthermore, there are additional considerations, such as safety and reliability that need to be taken into account when developing a coil head reduction plan. Three possible solutions were prototyped and tested: a highly emissive paint, a thermally conductive polymer, and the utilization of heat pipes. Each idea was tested to determine the reduction in coil head temperature. Of these designs, the use of a highly emissive paint on the internal surface of the motor’s end cap, allowed the most heat to be dissipated. For $4, this solution yielded a 1.8°C decrease in coil head temperature.
State Feedback and Output Feedback Control of Polynomial Nonlinear Systems Using Fractional Lyapunov Functions
Authors: Zheng Qian , Wu Fen
Published: May 2009

In this paper, we will study the state feedback control problem of polynomial nonlinear systems using fractional Lyapunov functions. By adding constraints to bound the variation rate of each state, the general difficulty of calculating derivative of nonquadratic Lyapunov function is effectively overcome. As a result, the state feedback conditions are simplified as a set of Linear Matrix Inequalities (LMIs) with polynomial entries. Computationally tractable solution is obtained by Sum-of-Squares (SOS) decomposition. And it turns out that both of the Lyapunov matrix and the state feedback gain are state dependent fractional matrix functions, where the numerator as well as the denominator can be polynomials with flexible forms and higher nonlinearities involved in. Same idea is extended to a class of output dependent nonlinear systems and the stabilizing output feedback controller is specified as polynomial of output. Synthesis conditions are similarly derived as using constant Lyapunov function except that all entries in LMIs are polynomials of output with derivative of output involved in. By bounding the variation rate of output and gridding on the bounded interval, the LMIs are solvable by SOS decomposition. Finally, two examples are used to materialize the design scheme and clarify the various choices on state boundaries.
Added-Mass Effect in Modeling of Cilia-Based (Vibrating Cantilever-Type) Devices for Microfluidic Systems
Authors: McKay B. , Iamratanakul D. , Oh K. , Chung J.-H. , Riley J. , Devasia S.
Published: May 2009

This article shows that the added mass due to fluid structure interaction significantly affects the vibrational dynamics of cilia-based (vibrating cantilever-type) devices for handling micro/nano-scale fluid flows. Commonly, the hydrodynamic interaction between the cilia-based actuator and fluid is modeled as a Stokes drag force that is proportional to the velocity. Our main contribution is to show that such a drag effect cannot explain the substantial reduction in the resonant frequency of the cilia actuator operating in liquid when compared to the natural frequency of the cilia in air. It is shown that an added-mass approach can explain this reduction in the resonant frequency when operating cantilever-type devices in fluid. Thus, this article shows the need to model the added-mass effect, both, theoretically and by using experimental results.
Development of Simulation Software for a Planar Mechanisms Laboratory Equipment
Authors: Rami´rez Juan A. , Va´squez Rafael E. , Va´squez Juan M.
Published: May 2009

This work addresses the development of a simulation software for the analysis of four-bar planar mechanisms, ADM4BSoftware V1.0, used for teaching in the Department of Mechanical Engineering at the Universidad Pontificia Bolivariana. The software is developed in order to optimize the students’ analysis tasks in the mechanisms’ Lab. The software solves the set of equations that represents the direct kinematics, and the direct dynamics. The software is an interactive application performed in Matlab™. The simulation environment allows the students to change the analysis option, the visualization mode, animate the mechanism, show different graphics and export theoretical data as a plain text file (.prn) or as a Excel™ spreadsheet (.xls). Therefore, students can compare and contrast experimental and theoretical data faster. Consequently, they can dedicate their time to analyze physical phenomena present in mechanisms. The ADM4BSoftware V1.0 has become a useful tool for instructors in teaching subjects related to the mechanics of machines.
Optimal Design of Asymmetric Passive and Semi-Active Dampers
Authors: Eslaminasab N. , Arzanpour S. , Golnaraghi M. F.
Published: May 2009

Vibration isolators are essentially used to reduce the magnitude of motion or force transmitted from a vibrating source to vibration recipient bodies. Such recipients might be a foundation, a structure, or even a human’s body. Despite all the advancement in vibration control using active and semi-active systems, passive vibration isolators are still widely used in different industrial applications because of their simplicity and low cost. In this paper we investigate an asymmetric one-degree of freedom vibration isolator. This is very important in practice, because all hydraulic dampers are asymmetric in nature. Due to the non-linearity of this system as a result of asymmetric damping, analytical methods of averaging and numerical simulation are used to analyze its frequency and time response characteristics. Optimal damping and stiffness values for the isolator are obtained by minimizing the cost functions, which are the Root Mean Square (RMS) of the acceleration transmissibility and the relative displacement transmissibility. The effect of the asymmetric damping on the optimal values in passive systems are then analyzed and used to create a design chart for the isolator parameters. In addition, the effect of asymmetry on the conventional semi-active systems is studied and the method to the optimal design of asymmetric semi-active systems is discussed.
Modeling and Analysis of Fiber Optic Bragg Grating Shape Sensors
Authors: Alemohammad Hamidreza , Toyserkani Ehsan
Published: May 2009

The present work aims at modeling of fiber Bragg gratings (FBG) used as shape sensors. FBGs, which are commonly used for sensing physical parameters (e.g., strain, temperature, pressure), can be effectively used for shape detection in flexible bodies. They can be embedded in flexible structures for in-situ measurement of curvature. In order to design the embedded sensors and identify the spectral response of FBG, the effects of different geometrical and structural parameters on the optical response of the fiber should be investigated. In this paper, an opto-mechanical model is developed to assess the shape detection with FBGs. In the proposed model, non-symmetric coating of optical fibers with metallic materials is investigated. The model is a combination of structural and optical analyses; the structural analysis is used to find the change in optical properties of the sensor due to photo-elastic effect and the optical analysis is conducted to find the spectral response of FBG. It is shown that the non-symmetric coating can increase the sensitivity of the sensor. While the bare sensor shows little sensitivity to the curvature, the sensitivity increases with non-symmetric coating.
Magnetorheological Elastomers With Increased Structural Integrity for Multifunction Applications
Authors: Aga Zelalem , Feimster Dan , Faidley LeAnn
Published: May 2009

Magnetorheological Elastomers (MREs) are composite materials formed of a soft elastomer matrix and a magnetic-powder filler. The interaction of the matrix and filler in a magnetic field causes the effective elastic modulus of the MRE to be controllable by an external field. In previous studies the applications of MREs have been severely limited by their lack of structural integrity, forcing them to be applied only as soft pads or as the filler in sandwich beams. This study represents initial steps towards improving the structural integrity of MREs while retaining some level of modulus variability. Specimens are made from Sylgard 184 Silicone with a variety of cure temperatures and filler volume percentages. Longitudinal swept-sine vibration tests are performed to measure the dependence of elastic modulus on applied fields of up to 40 kA/m. It is found that the softer specimen (ie: the lowest cure temperature) with 27% percent filler exhibits the largest percent change in effective modulus of almost 40%. The zero-field modulus for this specimen is 5.7 MPa giving it the structural integrity needed for multifunction applications in which the material is both active and load bearing. Many novel applications exist including active modulus control of sound radiating plates, novel design of vibration isolation tables, and more.
Comparison of Analytical, Numerical, and Experimental Results for a Simplified CPU/Heatsink Model
Authors: Robinson Russell , Genova Mike , Cook Daniel P.
Published: May 2009

The behavior of a plate finned heatsink and simulated CPU were assessed using analytical and computational models, and these results were compared to data taken from an experimental model. The analytical model considered fin effects and after considering several options used a Nusselt number correlation for laminar flow over a flat plate to find the convection heat transfer coefficient and consequent maximum temperature at the base of the simulated CPU. Icepak thermal modeling software was utilized to create and solve the computational model. All three models considered only steady-state conditions. Maximum temperatures from the analytical, computational, and experimental models varied from one another by no more than 2% with respect to the mean temperature in Kelvin. Though these results are promising, they were achieved only through multiple refinements to the various models.
An Embedded Pressure Sensing Approach for Stamping Process Monitoring
Authors: Sah Sripati , Gao Robert X.
Published: May 2009

This paper investigates the interactions between sheet metal stamping tool and workpiece through finite element simulation and experiments using an array of force sensors embedded into a customized stamping test fixture. The study is aimed at developing a more effective means for stamping process monitoring as compared to the conventionally used tonnage sensing technique. An analytical framework for processing data acquired from the sensor array is established, and the spatial significance of the sensor positions has been incorporated into the analysis. The utility of two numeric surface generation schemes has been investigated to interpolate the pressure distribution at any point across the tooling surface, based on measurements from limited, spatially distributed sensing points. The suitability of the surface schemes has been evaluated using finite element models established for the customized test fixture. The feasibility of embedded pressure sensing for defect detection in stamping operations has been demonstrated.
A Subharmonic Resonance-Based MEMS Filter
Authors: Hammad Bashar K. , Nayfeh Ali H. , Abdel-Rahman Eihab
Published: May 2009

We present a novel micromechanical filter exploiting the subharmonic resonance of order one-half to obtain a center frequency twice the fundamental frequency of the primary resonators, an ideal stopband, and a sharp roll-off. The filter is made up of two clamped-clamped microbeam resonators connected by a coupling beam. We discretize the distributed-parameter system using the Galerkin procedure to obtain a reduced-order model composed of two nonlinear coupled ODEs. It accounts for geometrical and electrical nonlinearities as well as the coupling between these two fields. Using the method of multiple scales, we determine four first-order nonlinear ODEs describing the amplitudes and phases of the modes. We use these equations to determine closed-form expressions for the static and dynamic deflections of the filter. The basis functions in the discretization are the linear undamped global mode shapes of the unactuated filter. The filtering mechanism is based on the exploitation of the interval where the trivial response to subharmonic excitations is unstable. We found criteria to tune the effective nonlinearities of the filter to realize a bandpass filter of an ideal stopband rejection and a sharp roll-off. When these criteria are not met, multivalued responses appear and distort the filter performance.
Formation of Environmental Impacts in Energy Conversion Processes Revealed by a Novel Exergoenvironmental Analysis
Authors: Meyer Lutz , Buchgeister Jens , Tsatsaronis George , Schebek Liselotte
Published: May 2009

An exergoenvironmental analysis has been developed that reveals to what extent each component of an energy conversion system is responsible for the overall environmental impact, and identifies the sources of the impact. The approach of the exergoeconomic analysis is modified to deal, instead with an economic problem, with an evaluation of the ecological impact. The basic idea is that exergy represents a proper basis for assigning both costs and environmental impact in energy conversion processes. As a case study, an energy conversion system consisting of a high-temperature solid oxide fuel cell integrated with an allothermal biomass gasification process has been analyzed. The exergoenvironmental analysis allows to identify the environmentally most relevant system components and provides information about possibilities for design improvements. A special focus is laid on the role of exergy destruction. It is shown that the location of the exergy destruction in the process has influence on the resulting environmental impacts. A certain amount of exergy destruction leads to a different extent to environmental impacts depending on the position of the component where the exergy destruction occurs. The exergoenvironmental analysis reveals the thermodynamic inefficiencies that have the greatest environmental impacts.
Whole Chip Temperature Measurements Using Thin-Film PDMS/Rhodamine B for Microfluidic Chip Design
Authors: Samy Razim , Glawdel Tomasz , Ren Carolyn
Published: May 2009

A novel method for in-situ temperature measurements of microfluidic devices using thin-film poly(dimethylsiloxane) (PDMS) saturated with Rhodamine B dye is reported. Rhodamine B is commonly injected into the working fluid for on-chip temperature field visualization of glass and silicon based microfluidic devices since its fluorescent intensity is temperature dependent. However, such a visualization method results in unreliable temperature measurements for polymeric devices such as PDMS due to high absorption and adsorption. Thus, an inexpensive temperature measurement technique was developed in which a thin PDMS layer (∼30 μm) is fabricated and submersed for several days into a Rhodamine B solution. To prevent backward diffusion of the dye into the working fluid during operation, a glass barrier (∼150 μm) is bonded between the thin film and the PDMS mold containing the microchannel design. Temperature measurements are made by utilizing standard method of measuring changes in the normalized fluorescent intensity. For verification purposes, a new calibration curve is developed and the thin film is tested with a tapered microchannel subjected to joule heating. The resulting temperature field along the axial direction of the channel for different input power compares well with numerical simulations. Errors in temperature measurement due to the current design are discussed.
Analysis of the Performance of Ionic Liquids in Cooling Loops
Authors: Sen Mihir , Paolucci Samuel , Liu Wenjun
Published: May 2009

Liquids are often pumped in closed loops to transfer heat from a high temperature source to a low temperature sink. They operate at low Reynolds number when the diameter of the pipe is small, the fluid velocity is low, or when the working liquid is very viscous. Ionic liquids, though environmentally friendly, typically have viscosities much larger than water. An analytical study is made of the process for the purpose of determining what the important physical parameters of the system are that will enable the largest quantity of heat to be transferred for unit work expended. For this purpose, a loop is considered that has a pump that generates a certain pressure rise and two heat exchangers, one for heating the fluid and the other for cooling it. Laminar flow that is fully-developed hy-drodynamically and thermally is assumed. The analysis is based on constant fluid properties, and analytical expressions are obtained for the heat rate and the work input.
Bicycle Infrastructure Development Strategy for Suburban Commuting
Authors: Layton Bradley , Jablonowski Lauren , Kirby Ryan , Lampe Nicholas
Published: May 2009

We present a “Bicycle Highway” transportation alternative to automobile commuting by exploring avenues for reducing perceived impediments to bicycle commuting. The three primary goals of the project are: 1) Address the American diabetes and obesity epidemics by making exercising on a daily basis a more desirable and viable alternative. 2) Address the problem of greenhouse gas emissions and pollutants by partially replacing combustion engines with human-powered transportation. 3) Address the problem of the United States’ dependence on foreign oil by diminishing energy demand for short-range transportation. The primary variables we will consider are N, the number of people being transported, d, the distance being traveled, C, the energy cost required to travel the distance, and t, the time required to travel the distance. The Bicycle Highway was found to have a poorer throughput rating when only construction costs were considered, but a better throughput rating when vehicle and fuel costs are introduced. The Bicycle Highway offers a timely and economical solution to the numerous side-effects of the century-long success of the gasoline-powered automobile. A transportation corridor that is designated solely for bicyclists, human-electric hybrid and zero-emission vehicles, would allow for a greater volume of commuter traffic with minimal energetic and entropic impact. This proposed roadway promises to make bicycle travel much safer and will alleviate frustration felt by motorists sharing the road with bicycles. We expect cost-effectiveness of our design to be enhanced further if reductions in obesity, asthma, and lung-disease related costs are considered in future case studies.
New Approach of Tracking Control for a Class of Non-Minimum Phase Linear Systems
Authors: Xie Bo , Yao Bin
Published: May 2009

The paper presents a new tracking control approach for a class of non-minimum phase linear systems. The proposed approach consists of two parts: trajectory planning and tracking controller design. The trajectory planning is solved as an optimization problem to improve the achievable transient performance under the fundamental constraints associated with perfect tracking of non-minimum phase systems. The recently proposed adaptive robust tracking controller for a class of non-minimum phase systems is then applied to guarantee that the tracking error dynamics can be stabilized with bounded internal states. The effectiveness of the proposed approach is illustrated through simulation on tracking control of a second order non-minimum phase linear system. Further works are underway to extend the proposed control strategy and trajectory design to a class of non-minimum phase nonlinear systems.
A Novel Y-Channel Design for Measuring the Zeta Potential Using the Current Monitoring Technique
Authors: Almutairi Zeyad A. , Glawdel Tomasz , Ren Carolyn L. , Johnson David A.
Published: May 2009

A Y-channel design is proposed to find the zeta potential for PDMS and PDMS/glass microchannels with the current monitoring technique. The major advantages of this design are four fold: i) the displacement process can be quickly repeated many times increasing the amount of measurements for a single fluid; ii) start and end times are well defined since there is minimal diffusion at the liquid/liquid interface; iii) overall preparation and operation are simplified; and iv) errors caused by undesirable pressure driven flow (Laplace and head differences) and changes in pH due to electrolysis are suppressed. The zeta potential found from current monitoring experiments with the new Y-channel design gave similar results when compared to results found in literature using a conventional straight channel design. Modifications on the slope calculation method were proposed and results agreed with the total length calculation method within 6.8% variation of the zeta potential values averaged for all experiments compared to the total length method. Using the new design, the zeta potential of a number of commonly used buffer solutions for protein and DNA application were tested in PDMS and PDMS/glass hybrid channels.
Effect of a Circumferential Arc Crack on the Vibration Characteristics of a Flexible Spinning Disk
Authors: Nair Nikhit N. , Hashemi Hamid N. , Warner Grant M.
Published: May 2009

The vibration characteristics of a circumferentially cracked rotating disk are investigated. The disk is assumed to be axisymmetric, flexible and clamped at the center. The crack increases the local flexibility of the disk at the crack location and is modeled as linear and torsional springs, connecting the two segments of the disk. The spring constants are evaluated by considering crack opening displacements due to bending moment and shear force at the crack location. The equations of motion of two segments of the disk, for disk operating in vacuum as well as subjected to shear fluid flow are developed. Using the Finite Difference Technique, the coupled systems of equations are solved and the natural frequencies and mode shapes are obtained. The mode shapes are seen to be comparatively flattened in the inner region of the disk separated by the crack and heightened towards the periphery of the disk. Shear fluid loading reduces the critical speeds and results in a quicker onset of instability. The degree of instability caused by the crack is a function of crack depth and location. Critical speeds increase with increasing crack distance from the central clamp and decrease with increasing crack depth.
CARS Probing of Meter-Scale Turbulent Pool Fires
Authors: Kearney Sean P. , Grasser Thomas W.
Published: May 2009

We report an application of coherent anti-Stokes Raman scattering (CARS) to full-scale fire testing. A CARS instrument has been constructed at the newly commissioned FLAME (Fire Laboratory for Accreditation of Models and Experiments) facility at Sandia, where the CARS system has been used for thermometry in 2-m-diameter, turbulent pool fires. The details of a CARS instrument for probing the challenging pool-fire environment are presented, along with the construction of the unique new FLAME facility itself, which has been designed to accommodate optical and laser-based diagnostics to full-scale fire experimentation. Single-shot CARS spectra and best-fit temperatures from turbulent pool fires are presented, and an estimate of the pdf of the temperature fluctuations from the pool-fire environment is obtained.
Vibrations of Functionally Graded Shells
Authors: Abrate Serge
Published: May 2009

The behavior of functionally graded structures has received a great deal of attention in recent years. Usually, these structures are made out of a composite material with a modulus of elasticity, a Poisson’s ratio, and a density that vary through the thickness. The non-uniformity through the thickness introduces coupling between the transverse deformations and the deformations of the mid-surface. Previous publications have shown how to account for these added complexities and have presented extensive results in tabular form. In this article, available results are used to show that the behavior of functionally graded shells is similar to that of homogeneous isotropic shells. It is well known that for isotropic shells, results can be presented in non-dimensional form so that, once results are obtained for one material, they can be simply scaled to obtain the corresponding results for shells made out of another material. The same can then be done for functionally graded shells. In addition, if functionally graded shells behave like homogeneous shells, no new method of analysis is required. The second part of the paper examines why this is true.
Numerical Investigation of Microscale Slot Jet Impingement Using DSMC-IP and CFD
Authors: Kursun U. , Sleiti A. K. , Kapat J. S.
Published: May 2009

The standard Direct Simulation Monte Carlo (DSMC) simulation is not capable of producing statistically meaningful results for low Re flows which are often encountered in microflows. Therefore, the non-isothermal Information Preservation (IP) algorithm is utilized in this study to predict the flow structure and the heat transfer characteristics of a microscale, slot, and confined jet impinging on a flat surface with uniform temperature boundary condition. The flow Knudsen number based on the slot width is in the slip flow and the lower transition regime. The jet is impinging at jet-to-target surface gaps normalized by slot width (H/W) of 0.25, 1 and 2 at a pressure ratio of 2.0. The effects of impingement gap (H/W) on flow structure and heat transfer are investigated. The velocity, pressure and Nusselt number distributions on the impingement target surface are presented. The results are compared to corresponding conventional large-scale values.
Winning the ASEE 2006 Robotics Design Competition: Guiding Students to Success
Authors: Yilmaz Emin , Nagchaudhuri Abhijit
Published: May 2009

Robotics Model Design Competition sponsored by the Two Year College Division (TYCD) of American Society for Engineering Education (ASEE) provides an avenue for freshman and sophomore student teams in two year as well as four year colleges and universities to participate in a creative engineering design project. Historically Black Colleges and University - Undergraduate Program (HBCU-UP) at National Science Foundation (NSF) have provided support for development of ACTION (Advanced Curriculum and Technology-based Instructional Opportunities Network) at UMES. The ACTION program promotes inquiry based active learning and research projects among undergraduate STEM (Science, Technology, Engineering and Mathematics) majors. Engineering, Technology, and Mathematics students responded enthusiastically when the authors proposed the idea of participating in the (ASEE) 2006 Robotic Model Design Competition at one of the American Society for Mechanical Engineers (ASME) student section meetings at UMES in the fall of 2005. (The authors serve as the advisors for ASME student section chapter at UMES). The student leader of the section quickly put together a team of five freshman and sophomore engineering, engineering technology and mathematics students to develop a proposal to UMES ACTION program. The authors supported the proposal development efforts. The proposal got funded and provided the resources for project execution and travel. A team of eleven freshmen and sophomore students from Engineering, Engineering Technology and Mathematics departments of University of Maryland Eastern Shore (UMES) participated in the American Society for Engineering Education’s (ASEE) 2006 Robotics Model Design Competition project. The event was sponsored by the Two-year College Division (TYCD) of ASEE and was open to freshman and sophomore student teams from two year as well as four year colleges and universities. The competition required teams to design and build an autonomous robot capable of delivering ping pong balls to each of four corner pockets located on an 8ft×8ft plywood track in a sequence. Each team was evaluated on the basis of a written report, an oral presentation, and scores obtained from the best two runs out of four runs on the racing track. Sixteen student teams across the nation participated in the event. UMES entered two teams in the competition who called themselves “Hawks 1” and “Hawks 4”. The student team “Hawks 1” won the competition. Video clips of both design projects as they executed the specified task at the 2006 ASEE Robotics Model Design Competition can be viewed at: http://www.umes.edu/asme/robots.htm. This paper describes the design projects “Hawks 1” and “Hawks 4” and its relevance to ABET learning outcomes.
On-Chip Indirect Detection of Non-Fluorescent Analytes Using Fluorescent Spacers
Authors: Khurana Tarun K. , Santiago Juan G.
Published: May 2009

We present a technique that accomplishes on-chip preconcentration, separation and indirect detection of nonfluorescent analytes by leveraging isotachophoresis (ITP) and a set of fluorescent species termed spacers. The non-fluorescent analyte zones are detected as dark zones/gaps between fluorescent spacer zones. The length of this gap quantifies the initial concentration of the non-fluorescent analyte and mobilities of the fluorescent spacers on either side provide the upper and lower bound for the analyte mobility. We have successfully demonstrated separation and detection of amino acids, serine and phenylalanine, as well as other organic acids, acetic acid and phenylpropionic acid with this technique. Using three fluorescent spacers, we were able to detect ∼10 μM concentration of non-fluorescent analytes.
Data Driven Simplified Three-Way Catalyst Health Diagnostic Models: Experimental Results
Authors: Dawson Brandon M. , Franchek Matthew A. , Grigoriadis Karolos
Published: May 2009

Presented is the identification of simplified three-way catalyst (TWC) models from vehicle data. The simplified models are developed for multiple TWCs from two different classes: full useful life and threshold. The full useful life (FUL) TWCs represent catalysts from vehicles with 100,000 miles whereas threshold TWCs represent catalysts from vehicles with over 150,000 miles. The results showed that these simplified models have consistent parameter estimates when identified in a passive monitoring mode as the vehicle experiences a driving cycle from the Federal Test Procedure (FTP). Moreover the parameters of the simplified TWC models contain TWC health/age information. The model input is the air mass flow rate (AM) into the engine and the model output is a proposed TWC health measure developed in this paper. The impact of TWC temperature will also be detailed.
A Micromechanical Approach to Model Residual Stress Relaxation and Fatigue Crack Nucleation in High Strength Gear Steels
Authors: Prasanna Rajesh , McDowell David L.
Published: May 2009

It is well known that mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly-stressed metallic components. Of particular interest here are the residual stresses induced through shot peening process. Compressive residual stresses of high magnitudes are induced at and near the surface during shot peening process by virtue of constrained plastic deformation. These stresses enhance the service life of component by resisting fatigue crack nucleation and growth on surface of the specimen. Unfortunately, these residual stresses can relax significantly due to subsequent mechanical and/or thermal loading even under normal operating conditions.
The Real World: A Factor That Engineering Faculty Consider in Making Decisions About Teaching
Authors: Yellin Jessica M. H. , Huang Yi-Min , Turns Jennifer , Sattler Brook , Birge Colin , Larson Jerrod A.
Published: May 2009

This paper describes a critical decision method (CDM) study for investigating the phenomenon of teaching-related decision-making in engineering education. We interviewed 33 engineering faculty using this method and asked them to identify two memorable, recent teaching-related decisions: one pre-active (planning) decision and one interactive (in-class) decision. Faculty described the situation, the process of making the decision, the factors that they took into account, and their level of satisfaction with the outcomes of their teaching-related decision. In this paper, we focus on one specific factor that emerged across the majority of the interviews: the real world. We present ways in which faculty referred to the real world, and more specifically preparing students for professional practice, when making decisions about their teaching. Three themes provided insight regarding the participants’ beliefs about this concept; that the real world is hands-on, defineable in terms of professional standards, and that addressing it explicitly in teaching involves trade-offs.
Microfluidic Assembly of Quantum Dot Micelles
Authors: Schabas Greg , Moffitt Matthew G. , Sinton David
Published: May 2009

The controlled self-assembly of polymer-stabilized CdS quantum dot nanoparticles into quantum dot compound micelles (QDCMs) using microfluidics is demonstrated. In a flow-focusing configuration, water is introduced to a blend solution of block copolymer-stabilized quantum dots with amphiphilic block copolymer stabilizing chains. QDCM assembly via initial phase separation and subsequent agglomeration continue until a downstream quench step. Control over mean particle size and size distribution characteristics is demonstrated via both inlet concentrations and flow rate. The QDCMs assembled through this method are stable in aqueous solutions, and show internal and external structure in keeping with previous assembly methods. The on-chip evolution of QDCM formation and growth is resolved through fluorescence scattering. Particle size distributions and associated statistics are determined through off-chip analysis.
Components for the Design of Lamina Emergent Mechanisms
Authors: Jacobsen Joseph O. , Howell Larry L. , Magleby Spencer P.
Published: May 2009

This paper presents components for lamina emergent mechanism (LEM) that can be used as building blocks to create mechanisms capable of more complex motion. As the name suggests, lamina emergent mechanisms are fabricated out of planar materials (the lamina) but their motion is out of that plane (emergent). Lamina emergent mechanisms can provide benefits that include reduced manufacturing costs and minimal volume when in the planar state. The compact initial state of LEMs is beneficial in reducing shipping costs, especially in volume critical applications. LEMs also exhibit the potential benefits of compliant mechanisms, namely increased precision, reduced weight, reduced wear, and part count reduction. Due to the deflection of their members, compliant mechanisms have the ability to store energy, and the resulting effect can be used to perform the function of springs. The LEM components presented in this paper include flexible segments, and mechanisms with behaviors similar to planar change-point four-bar and six-bar mechanisms, and spherical change-point mechanisms.
Modeling of a Diffusion Controlling Oxidation Process With Scale Removal in Oxygen-Containing Liquid Flow
Authors: Tan Taide , Chen Yitung , Chen Huajun , Hsieh Hsuan-Tsung
Published: May 2009

A diffusion controlling oxidation model, considering scale removal, is developed in an oxygen-containing liquid flow environment. Scale removal is implemented and the effect of the scale removal rate on the formation mechanism of the duplex oxide layer structure is analyzed in the model. The volume expansion effect caused by density difference is coupled with the weight gain during oxidation. A coordinate transform technique is employed to obtain the diffusion equations with advection term. The governing equations are non-dimensionalized and analogized with the Stefan problem and solved numerically by the finite difference method. The non-dimensional parameters are studied and the model is extended to an oxide growth model with duplex layer structure and noble elements. The model is benchmarked with previous results, and good agreement is obtained.
Fault Diagnosis of an Industrial Machine Through Neuro-Fuzzy Sensor Fusion
Authors: Lang Haoxiang , Wang Ying , de Silva Clarence W.
Published: May 2009

In this paper a neuro-fuzzy approach of multi-sensor fusion is developed for a fault diagnosis system. The approach is validated by applying it to a machine called the Iron Butcher, which is used in industry for the removal of heads in fish prior to further processing for canning. An important goal of this approach developed in this paper is to make an accurate decision of the machine condition by fusing information from different sensors. Specifically, sound, vibration and vision measurements are acquired from the machine using a microphone, an accelerometer and a digital CCD camera, respectively. Next, the sound and vibration signals are transformed into the frequency domain using Fast Fourier Transform (FFT). A feature vector from the FFT frequency spectra is defined and extracted from the acquired information. Also, a feature based vision tracking approach—the Scale Invariant Feature Transform (SIFT)—is applied to the vision data to track the object of interest (fish) in a robust manner. In the diagnosis process, a candidate fish is detected and tracked. Sound, vibration and vision features are extracted as inputs for the neuro-fuzzy fault diagnosis system. A four-layer neural network including a fuzzy hidden layer is developed to analyze and diagnose any existing faults. By training the neural network with sample data for typical faults, six crucial faults in the fish cutting machine are detected precisely. In this manner, alarms to warn about impending faults may be generated as well during the machine operation. Developed approaches are validated using computer simulations and physical experimentation using the industrial machine.