bluuebunny/crossref_metadata_2025 huggingface dataset:
Breakup Model for Annular Liquid Sheets
Authors: Ibrahim Ashraf A. , Jog Milind A.
Published: April 2008

The instability and breakup of annular liquid sheet is encountered in liquid atomization process used in numerous applications including liquid fuel injection in combustion engines and spray drying of foods. A nonlinear breakup model for annular liquid sheet exposed to both inner and outer air streams by a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter has been developed. The liquid sheet moves at a uniform axial velocity and subjects to axially moving inner and outer gas streams. The temporal evolution of the dimensionless surface deformation at the inner and outer liquid-gas interface has been evaluated until the point of breakup. The breakup length predictions show good agreement with the available experimental data.
Optimization of Organic Rankine Cycles Using Dry Fluids
Authors: Mago P. J. , Chamra L. M. , Somayaji C.
Published: April 2008

This paper presents an optimization of Organic Rankine Cycles "ORC" using dry organic fluids, to convert waste energy to power from low grade heat sources. The dry organic working fluids under investigation are R113, R245ca, R123, and Isobutene. Different configurations such as reheat ORC and regenerative ORC will be analyzed and compared with the basic ORC in order to determine the configuration that presents the best performance. The optimization for the different configurations will be performed using a combined first and second law analysis by varying some system operating parameters at various reference temperatures and pressures. Some of the results show that regenerative ORC produces higher efficiency compared with the basic ORC while also reducing the amount of waste heat needed to produce the same power with a less irreversibility.
Engine Mount Optimization for Vibration Isolation in Motorcycles
Authors: Kaul Sudhir , Dhingra Anoop K. , Hunter Timothy G.
Published: April 2008

This paper presents a comprehensive model to capture the dynamics of a motorcycle system in order to evaluate the quality of vibration isolation. The two main structural components in the motorcycle assembly - the frame and the swing-arm - are modeled using reduced order finite element models; the power-train assembly is modeled as a six degree-of-freedom (DOF) rigid body connected to the frame through the engine mounts and to the swing-arm through a shaft assembly. The engine mounts are modeled as tri-axial spring-damper systems. Models of the front-end assembly as well as front and rear tires are also included in the overall model. The complete vehicle model is used to solve the engine mount optimization problem so as to minimize the total force transmitted to the frame while meeting packaging and other side constraints. The mount system parameters - stiffness, position and orientation vectors - are used as design variables for the optimization problem. The imposed loads include forces and moments due to engine imbalance as well as loads transmitted due to irregularities in the road surface through the tire patch.
Microdrop Manipulation and Mixing Using Dynamic Ferrofluid Cage Array
Authors: Song Woo-Bin , Ding Zhenwen , Son Chulwoo , Ziaie Babak
Published: April 2008

In this paper, we present a simple method to manipulate free microdroplets using ferrofluid dynamics. First, we use two strip magnets (20 Gauss) to generate a ferrofluid cage-array pattern. Then, a magnetic stirrer (200 Gauss) is placed and rotated underneath them to induce a dynamic change in the pattern. The generated ferrofluid pattern and its dynamics are compared with the simulation results of the magnetic field distribution under various static/dynamic configurations using finite element method (FEM). The mixing effect in individual cells is investigated using silica beads (0.2 μm in size) and a water droplet (40 microliter in volume) first. In order to demonstrate free droplet mixing, two colored water microdroplets (10 microliter in volume) are placed in two separate wells and are driven to move and mix without sample evaporation.
Virtually Variable Displacement Hydraulic Pump Including Compressability and Switching Losses
Authors: Batdorff Mark A. , Lumkes John H.
Published: April 2008

Hydraulic pumps can be fixed or variable displacement. Fixed displacement pumps are typically smaller, lighter, less expensive, and can be of any design (gear, vane, axial piston, radial piston, ect.)[1]. Variable displacement pumps are often axial piston with an adjustable swash plate. A virtually variable displacement pump (VVDP) is a fixed displacement pump combined with a fast switching control valve that performs the same function as a variable displacement pump. This is done by always pumping full flow, but using the control valve to divert only a certain percentage of flow to the system, and the rest back to tank. A VVDP has several advantages over a traditional variable swash axial piston pump. First, the pump can be of any design, not just axial piston. Second, the flow control bandwidth can be much faster because it is only limited by the bandwidth of the fast switching control valve and system accumulator, not the bandwidth of a swash plate. Third, a VVDP pump can be more efficient because it can operate at its optimum pressure and flow setting. On the downside a VVDP will require a high speed valve. There are also added switching power losses due to constant metering over valves, compressing and decompressing hydraulic oil, and metering during transition between pumping to system and tank. This paper concentrates on modeling these three switching losses.
Power Harvesting for Rotating Structure Using Piezoelectric Generators
Authors: Gupta Saurav , Warner Grant M.
Published: April 2008

Conventional method of measuring the mechanical properties of rotating machinery is to couple sensors on the machine through a slip ring, which is a non-trivial, expensive, lengthy and manpower intensive process. An alternative to this is to use a contactless RF slip ring which has no physical wear and hence no maintenance. But application of contactless RF slip ring is possible only if these services are low powered and sensor signals can be multiplexed. With the advance in low powered MEMS sensors, contactless slip ring system can be used. But providing power to these sensors is an issue. One approach would be to harness power from the untapped surrounding energy which could be used to recharge and/or replace battery powered connections. One method to accomplish this is to use piezoelectric materials (PZT) to capture energy lost due to vibration and rotation of the test equipment. This captured energy can then be used to provide uninterrupted power to the appropriate sensors. Focusing our attention on blades, rotating structures will be modeled as cantilever beam. Piezoelectric bimorph attached to the rotating cantilever beam will provide an estimate for the available power that can be used for harvesting.
Mechanical Characterization of Polymer Nanowires Using MEMS
Authors: Samuel B. A. , Yi Bo , Rajagopalan R. , Foley H. C. , Haque M. A.
Published: April 2008

We present results on the mechanical properties of single freestanding poly-furfuryl alcohol (PFA) nanowires (aspect ratio > 50, diameters 100–300 nm) from experiments conducted using a MEMS-based uniaxial tensile testing device in-situ inside the SEM. The specimens tested were pyrolyzed PFA nanowires (pyrolyzed at 800° C).
Teaching Human Termal Comfort Through a Software Graphic Interface
Authors: Arezes P. , Lea˜o C. P. , Ferreira M. L. , Teixeira S. F.
Published: April 2008

Human comfort has become a key issue in developing new technologies and products. Thermal comfort perception is mainly affected by heat and mass transfer processes between the human body and its environment. In teaching this subject to Mechanical Engineering undergraduate students at University of Minho, the thermal comfort index PMV (Predicted Mean Vote) has often been used. It gives a statistical mean value of comfort sensation and it is very simple to use. On the other hand, a full computer simulation software of the human bodyclothing-environment system is a more effective way to study thermal comfort. However, computer models can be quite complicated to follow and to use in classes. A thermal human comfort model has been incorporated into a graphical interface in order to facilitate its current use. The graphical interface appears to be a very useful tool to interact with the thermal human comfort model developed. During its development stage, the interface has been tested using questionnaires in order to optimize its usability as a learning tool. Three different groups have been targeted by the questionnaires: first group of students from the Industrial Engineering degree, who have already some general knowledge about ergonomics, the second group included Post-Graduate students in Human Engineering, and the third group included students from Mechanical Engineering degree. Comparing results and also motivating students to this interesting and demanding subject has been the main objective of the present work.
A Temperature-Based Analysis Technique and Distributed Model Lean NOx Trap Catalyst
Authors: Midlam-Mohler Shawn , Guezennec Yann
Published: April 2008

The management of an automotive Lean NOx Trap (LNT) catalyst requires periodic, brief periods of net rich exhaust to regenerate the catalyst by reducing the stored NOx. During the regeneration event, the fuel rich gas first affects the front of the catalyst then, as reductants are available, reach the downstream sections of the catalyst. In a typical engine test cell, it is not feasible to witness these distributed effects by simultaneously measuring multiple points in a catalyst bed due for a number of practical reasons. This is inconvenient because it is often desired to have a continuous or distributed lump model of the catalyst, which is difficult to calibrate without spatially and temporally resolved measurements. A novel measurement technique is presented which uses internal catalyst temperature measurements to detect the gross chemical reactions occurring in the catalyst during the rich reduction phase. The magnitude of the temperature change is shown to correlate with the mass of NOx and O2 reduced from the catalyst substrate. This information is available at each temperature measurement location, allowing spatial information to be collected non-intrusively. Furthermore, the technique contains temporal information regarding the key reactions. The type of information made available, as well as the convenience of the measurement system, makes the technique useful for a number of applications. The basis of the measurement technique is first presented from a theoretical basis, relating the temperature rise of the substrate to the various gross chemical reactions. Experimental validation of the method is then provided, illustrating the good correlation between the mass of stored NOx and O2 estimated by the method and the mass of stored NOx calculated from traditional gas analyzer measurements during the NOx storage phase. After demonstrating the applicability of the method, several applications are suggested including use of the technique for LNT modeling, LNT regeneration control, and sulfur poisoning detection.
Teaching Partial Differential Equations With Computer-Based Problem Solving
Authors: Carneiro A. F. , Teixeira S. F. C. F.
Published: April 2008

A new approach for solving partial differential equations in the field of heat transfer and fluid mechanics, accompanied by specific software has been developed. Its purpose was to enhance learning effectiveness of Numerical Methods in the post graduate course of Mechanical Engineering and is based upon the use of purpose built software. The packages learned in this course include some commercial codes as, EXCEL, MATLAB and FLUENT. Two other tools, developed at the University of Minho to support the classes of numerical methods, were also used: CoNum and a graphics application PDE v.1. The teaching method presented in this paper has been applied at post graduate classes and the feedback received from the students was very positive. The softwares and graphics interface were used as learning tools and proved to be very versatile and effective in explaining the resolution of partial differential equations.
Two-Dimensional Meshless Numerical Modeling of the Blood Flow Within Arterial End-to-Side Distal Anastomoses
Authors: Zahab Zaher El , Divo Eduardo A. , Kassab Alain J. , Mitteff Eric A.
Published: April 2008

In the current paper we introduce the localized meshless method to resolve the two-dimensional blood flow in the vicinity of a peripheral bypass graft end-to-side distal anastomosis. The goal is to incorporate this new numerical technique in extracting the values of the fluid mechanics wall parameters, such as the wall shear stress and the wall shear stress gradients, which are suggested as contributory factors to the growth of post-operative intimal hyperplasia at the anastomosis. The localized meshless method depends on the Hardy Multiquadrics radial basis function to locally expand the flow variables over a set of nodes distributed in the computational domain. An explicit scheme is adapted for the meshless formulation of the laminar incompressible Navier Stokes equations. Our special interest in the localized meshless method arises from its automated point distribution feature that significantly facilitates the pre-processing of the solution. The blood flow is simulated in three different anastomosis model geometries; the conventional or direct model, the Miller Cuff model, and the Taylor Patch model. The results of the current localized meshless numerical method show a great agreement with the results provided by a well-established finite volume method commercial software.
Slurry Viscosity Study and Its Influence on Heat Transfer Enhancement Effect of PCM Slurry Flow in Micro/Mini Channels
Authors: Xing K. Q. , Tao Y.-X. , Hao Y. L.
Published: April 2008

A recent numerical study [1] involving micro-size Phase- Change-Materials (PCM) particles in micro-channels revealed significant heat transfer enhancement, provided that an optimal balance among the Reynolds number, particle size, tube length and heat flux is achieved. The numerical simulation is based on a model developed in [1] for non-thermal equilibrium, twophase (solid-fluid) flow using the continuum theory, in which each phase is treated separately in thermal, mass and momentum transports, yet they are related through interaction terms. A particle viscosity μP is introduced in this model and it's not available for the system of liquid-solid two phase flow. Therefore, this paper focuses on the study of the particle viscosity and its relation to the bulk viscosity to clarify its influence to the heat transfer enhancement effect of the PCM slurry flow. A review and comparative analysis of the available literature concerning particulate flow viscosity are presented. Different correlations to calculate the bulk viscosities are analyzed and their application range and limitations are discussed. Then, by using these different viscosity correlations to the numerical simulations, their influence to the heat transfer enhancement effect of the PCM slurry flow is discussed and a more realistic particle viscosity correlation for the PCM slurry flow is suggested through comparison with our experimental results.
Corrosion/Precipitation in Non-Isothermal Lead Alloy Coolant Systems
Authors: Tan Taide , Chen Yitung , Chen Huajun , Hsieh Hsuan-Tsung
Published: April 2008

A kinetic model was developed to investigate the corrosion and precipitation in non-isothermal lead alloy coolant systems. By considering a turbulent core region and a laminar sub-layer, analytical solutions of the mass transfer equations in both regions were obtained. The analytical expressions of both the local corrosion/ precipitation rate and the bulk concentration were obtained from the present kinetic model. Numerical models were also developed for simulating the corrosion and precipitation in non-isothermal Lead alloy pipe/loop systems and the results were compared with the analytical solutions. By applying this model to a test loop named "DELTA" set up at the Los Alamos National Laboratory the present study illustrates systematically dependence of the corrosion/precipitation rate and bulk concentration on the axial temperature profile and other hydraulic factors. The results were compared with the available experimental data.
Review of the Development of Compact, High Performance Heat Exchangers for Gas Turbine Applications
Authors: Herring Neal R. , Heister Stephen D.
Published: April 2008

This study provides a review of the current state-of-the-art in compact heat exchangers and their application to gas turbine thermal management. Specifically, the challenges and potential solutions for a cooled cooling air system using the aircraft fuel as a heat sink were analyzed. As the sensible heat absorbed by the fuel in future engines is increased, the fuel will be exposed to increasingly hotter temperatures. This poses a number of design challenges for fuel-air heat exchangers. The most well known challenge is fuel deposition or coking. Another problem encountered at high fuel temperatures is thermo-acoustic oscillations. Thermo-acoustic oscillations have been shown to occur in many fluids when heated near the critical point, yet the mechanism of these oscillations is poorly understood. In some cases these instabilities have been strong enough cause failure in the thin walled tubes used in heat exchangers. For the specific application of a fuel-air heat exchanger, the advantages of a laminar flow device are discussed. These devices make use of the thermal entry region to achieve high heat transfer coefficients. To increase performance further, heat transfer enhancement techniques were reviewed and the feasibility for aerospace heat exchangers was analyzed. Two of the most basic techniques for laminar flow enhancement include tube inserts and swirl flow devices. Additionally, the effects of these devices on both coking and instabilities have been assessed.
Cross-Sectional Nanoindentation of Alumina Thin Films Deposited by Pulsed Laser Deposition Process
Authors: Neralla Sudheer , Yarmolenko Sergey , Kumar Dhananjay , Pai Devdas , Sankar Jag
Published: April 2008

Alumina is a widely used ceramic material due to its high hardness, wear resistance and dielectric properties. The study of phase transformation and its correlation to the mechanical properties of alumina is essential. In this study, interfacial adhesion properties of alumina thin films are studied using cross-sectional nanoindentation (CSN) technique. Alumina thin films are deposited at 200 and 700 °C, on Si (100) substrates with a weak Silica interface, using pulsed laser deposition (PLD) process. Effect of annealing on the surface morphology of the thin films is studied using atomic force microscopy. Xray diffraction studies revealed that alumina thin films are amorphous in nature at 200 °C and polycrystalline with predominant gamma alumina phase at 700 °C.
Modified Weibull Failure Theory for Size Effect Prediction of Brittle Thin Film
Authors: Khandaker M. , Dhorje M. , Ekwaro-Osire S.
Published: April 2008

A brittle thin film bonded to a substrate is common in MEMS components. At the edge of the interface, high stress gradients exist. It has been observed that mechanical strengthening of the thin film with decreasing film size occurs due to two constraints, namely, the microstructural constraint and the geometrical constraint. Consideration of both these constraints is required to properly predict the size effect impact on the strength of a brittle thin film. In this paper, a statistical approach is developed to predict the size effect of a brittle thin film on a substrate.
Developing of an Active Hydraulic Bushing for Multi-Displacement Engines
Authors: Arzanpour S. , Golnaraghi M. F.
Published: April 2008

This paper outlines the development of an active hydraulic bushing system for the Multi Displacement System (MDS) Engine isolation problems. The prior art research effort on engine mounts and bushings has so far focused on the improvement of the mount dynamic stiffness properties. The optimum dynamic stiffness and damping of the engine bushings is both frequency and amplitude dependent. While these systems are available commercially, they have many limitations, particularly for new vehicle models and new engine generations such as MDS engines. A suitable isolator for an MDS engine should be half as stiff in the operating frequency range of the engine (5-70 Hz) in MDS mode, while showing the same performance as conventional hydraulic bushings in normal engine operations. Passive hydraulic bushings are not capable of meeting the isolation requirements discussed for the MDS engines because they are not adjustable. There are different parameters which contribute to the dynamic stiffness response of a hydraulic bushing. Some of those parameters are defined by passive components such as rubber stiffness and damping. However, other parameters such as the pressure inside the bushing can be altered actively. The mathematical model of a conventional hydraulic bushing is given in this paper. The model suggests that the pressure inside the bushing has a significant role in the dynamic stiffness response of the bushing. As a result, an additional pumping chamber is introduced as a solution. The pump is utilized to adjust the pressure inside the bushing based on the engine excitation frequency. This pump can be driven by proper actuators which can produce pressure differences in the frequency range of interest. The mechanical and mathematical model of such a system is derived using a simplified linear model. This technique enables the engine mount to adjust to the dynamic stiffness characteristics by applying a feedback signal to the actuator. The feedback signal to the actuator is also obtained using the mathematical model for many required cases yet adjustable for others. The response of the system is discussed in frequency domains. The simulation results prove that the additional pumping chamber can effectively be used to control the stiffness of the conventional hydraulic bushings.
Modal Interactions in Contact-Mode Atomic Force Microscopes
Authors: Arafat Haider N. , Nayfeh Ali H. , Abdel-Rahman Elihab M.
Published: April 2008

Atomic force microscopes (AFM) are used to estimate material and surface properties. When using contact-mode AFM, the specimen or the probe is excited near a natural frequency of the system to estimate the linear coefficient of the contact stiffness. Because higher modes offer lower thermal noise, higher quality factors, and higher sensitivity to stiff samples, their use in this procedure is more desirable. However, these modes are candidates for internal resonances, where the energy being fed into one mode may be channeled to another mode. If such interactions are ignored, the results obtained from the probe may be distorted. The method of multiple scales is used to derive an approximate analytical expression to the probe response in the presence of two-to-one autoparametric resonance between the second and third modes. We examine characteristics of this solution in relation to a single-mode response and consider its implications in AFM measurements.
An Online Estimator for Heavy Vehicle's Mass and Road Grade
Authors: McIntyre M. , Vahidi A. , Dawson D.
Published: April 2008

This work proposes a two stage estimation strategy to determine a heavy duty vehicles's mass and road grade. The estimation strategy uses standard signals available through the vehicle control area network. The first stage of this approach utilizes an adaptive least-squares estimation strategy to determine the vehicle's mass. Due to the time varying nature of the road grade, a nonlinear estimator is then developed that provides a more accurate estimate of the road grade. An estimation analysis is provided for both stages that proves, under a set of qualifying conditions, both the mass and road grade can be estimated. The validity of this two stage approach is verified using experimental data.
Phase-Dield Simulation of Rhombohedral and Tetragonal Phases in Ferroelectric Single Crystals
Authors: Liu T. , Lynch C. S.
Published: April 2008

Ferroelectric materials exhibit spontaneous polarization and domain structures below the Curie temperature. In this work the phase field approach has been used to simulate phase transformations and the formation of ferroelectric domain structures. The evolution of phases and domain structures was simulated in ferroelectric single crystals by solving the time dependent Ginzburg-Landau (TDGL) equation with polarization as the order parameter. In the TDGL equation the free energy of a ferroelectric crystal is written as a function of polarization and applied fields. Change of temperature as well as application of stress and electric fields leads to change of the free energy and evolution of phase states and domain structures. In this work the finite difference method was implemented for the spatial description of the polarization and the temporal evolution of polarization field was computed by solving the TDGL equation with an explicit time integration scheme. Cubic to tetragonal, cubic to rhombohedral and rhombohedral to tetragonal phase transformations were modeled, and the formation of domain structures was simulated. Field induced polarization switching and rhombohedral to tetragonal phase transition were simulated.
Optical Testing of Polycrystalline Silicon Flexure-Type Optical Actuators
Authors: Serrano Justin R. , Phinney Leslie M.
Published: April 2008

Optical actuation is a necessity for the development of alloptical MEMS devices. Optically-powered actuators relying on a photothermal process are limited by overheating and structural damage resulting from the absorption of laser power. Surface micromachined polycrystalline silicon (polysilicon) optical actuators, powered using an 808 nm continuous wave laser, were evaluated for displacement performance and susceptibility to damage. The tested actuators were of a flexure-type design fabricated from either a single 2.25 μm polysilicon layer or a 4.5 μm polysilicon laminate layer, and in three different designs. Displacement of the actuators was linear with power for all tested designs for powers below those that cause damage to the irradiated surface. Maximum displacement observed was in the 7-9 μm range regardless of actuator design. After surface damage is initiated, displacement of the actuator during irradiation recedes in all actuators, with actuators with a 50 μm-wide target surface exhibiting complete recession in their displacement. The return position of the actuators after the irradiated surface has damaged also exhibits recession on the order of 4-5 μm for surfaces damaged with up to 650 mW. Exposing the actuator surfaces to longer irradiation times had no effect on the displacement if the surface had no damage, but resulted in regression of the displacement as the irradiation time increased if the surface had preexisting damage.
Modeling and Control of Ferromagnetic Shape Memory Alloys (FSMA) Actuators
Authors: Tan Honghao , Elahinia Mohammad H.
Published: April 2008

FSMAs like Ni-Mn-Ga have attracted significant attention over the last few years. As actuators, these materials offer high energy density, large stroke, and high bandwidth. These properties make FSMAs potential candidates for the new generation of actuators. The preliminary dynamic characterization of Ni-Mn-Ga illustrates evident nonlinear behaviors including hysteresis, saturation, first cycle effects, and dead zone. In order to control precisely the position output, a dynamic model is presented for a Ni-Mn-Ga actuator. The actuator model consists of the dynamics of the actuator, kinematics of the actuator, constitutive model of the material, and reorientation kinetics. Simulations results are presented to demonstrate the dynamic behavior of the actuator. Then, a Proportional-Integral-Derivative (PID) control algorithm is developed based on the simulation model. The simulation results of step response reveal that the controllable position is between the residual displacement and the maximum stroke. This range is determined by the properties of materials and the stiffness of the spring. The tracking are achieved with the PID controller when the reference are with the valid range.
Modeling Vortex Shedding Over a Stationary Circular Cylinder
Authors: Marzouk Osama , Nayfeh Ali H. , Akhtar Imran , Arafat Haider N.
Published: April 2008

Numerical simulations of flow past a stationary circular cylinder at different Reynolds numbers have been performed using a computational fluid dynamics (CFD) solver that is based on the Reynolds-averaged Navier-Stokes equations (RANS). The results obtained are used to develop reduced-order models for the lift and drag coefficients. The models do not only match the numerical simulation results in the time domain, but also in the spectral domain. They capture the steady-state region with excellent accuracy. Further, the models are verified by comparing their results in the transient region with their counterparts from the CFD simulations and a very good agreement is found. The work performed here is a step towards building models for vortex-induced vibrations (VIV) encountered in offshore structures, such as risers and spars.
A Low Cost Signal Conditioning Module for Mechanical Measurements
Authors: Myszka David H. , Patterson Mark A. , Globig James E.
Published: April 2008

Mechanical and electronic engineering technology faculty members at the University of Dayton have collaborated on the design of a signal conditioning circuit board for a mechanical measurements laboratory. This board includes amplification and filters necessary to interface a low voltage output from analog sensors with a computer data acquisition system. Printed circuit boards were produced, with easy to understand connections. Multiple units were assembled at a cost of under $20 per board. The price of other commercially available signal conditioning modules is 10 to 20 times that amount. This paper will present the details of the design and performance assessment of the signal conditioning module.
Development of Analysis Algorithm and Computational Methodology for the Evaluation of Non-Uniform Energy Conversion System Performance: Part I — Component Analysis Modules
Authors: Loughrin Casey , Park Hyunjae , Weber Robert
Published: April 2008

This paper examines the development of the individual component analysis modules applied to two selected energy conversion systems; a vapor-compression refrigeration system and a boiler heating system. The energy conversion components used in this work are the evaporator, condenser, expansion valve, mixing chamber, open feedwater heater, pipe, boiler, pump, and compressor. The developed component analysis modules are able to apply input data and specifications to estimate the corresponding thermal performance of the component. Upon investigation of the two case studies presented, it was found that the two-phase heat exchanging components such as the evaporator, condenser and boiler were the primary sources of the non-uniform system performance characteristics. As a consequence, a system connectivity matrix has been developed to evaluate the mass and energy flow characteristics of working fluids between components. The developed component analysis modules, in conjunction with the system connectivity matrix, were exclusively used to calculate the local and overall system thermal performance.
Development of Analysis Algorithm and Computational Methodology for the Evaluation of Non-Uniform Energy Conversion System Performance: Part II — System Connectivity
Authors: Loughrin Casey , Park Hyunjae , Weber Robert
Published: April 2008

It has been proposed to develop a component analysis module for each energy and heat exchanging component in a system. A system connectivity matrix has been developed to evaluate the mass and energy flow characteristics between components and the system performance. The developed component analysis modules, in conjunction with the system connectivity matrix, are exclusively used to calculate the overall and local system thermal performance. In this work, two sample energy conversion systems were selected; a vaporcompression refrigeration system and a boiler heating system. This paper examines the development of the system connectivity matrices and the corresponding iterative and/or non-iterative analysis algorithm and computational methodology. Proper mass and energy balances are formed based on the structure of the system connectivity matrix along with appropriate thermodynamic property models. The balance equations are then solved iteratively by using the developed component analysis modules until the residuals meet the convergence criteria. It was found that for the selected two systems the variations in thermal effectiveness of the two-phase heat and energy exchanging components, such as the evaporator, condenser and boiler in this work, were the main contributor of non-uniform system thermal performance.
Validation of a Composite Strength Prediction Methodology Based on Critical Failure Volume
Authors: Iarve Endel V. , Mollenhauer David H. , Whitney Thomas J.
Published: April 2008

The strength prediction of composites with stress concentrations is concerned with material response in small highly stressed volumes. Direct evaluation of material strength in such areas is difficult to achieve in practice. On the other hand, the ability of such small regions to sustain loads exceeding the average strength measured on uniformly loaded coupons, e.g. ASTM standard for axial strength testing in unidirectional composites, is the foundation of the long standing Whitney-Nuismer point and average stress failure criteria. These criteria postulate that the failure of a composite with stress concentrations occurs when a finite size volume near the stress concentration is loaded at or above the average strength measured on standard test coupons without stress concentrators. The size of this volume constitutes an additional material property. While proving accurate and efficient for capturing the notch size effect on strength within a given laminate family, these dimensions have not found clear physical interpretation and appear not to represent a fundamental material property. The present paper reports results for a Weibull-based integral approach for composite laminates with open holes. The emphasis is on evaluation of the limits of the applicability of the traditional Weibull integral based fiber-direction strength scaling.
Sensitivity of General Compound Planetary Gear Natural Frequencies and Vibration Modes to Model Parameters
Authors: Guo Yichao , Parker Robert G.
Published: April 2008

This paper studies sensitivity of compound planetary gear natural frequencies and vibration modes to system parameters. Based on a lumped parameter model of general compound planetary gears and their distinctive modal properties [1], the eigensensitivities to inertias and stiffnesses are calculated and expressed in compact formulae. Analysis reveals that eigenvalue sensitivities to stiffness parameters are directly proportional to modal strain energies, and eigenvalue sensitivities to inertia parameters are proportional to modal kinetic energies. Furthermore, the eigenvalue sensitivities to model parameters are determined by inspection of the modal strain and kinetic energy distributions. This provides an effective way to identify those parameters with the greatest impact on tuning certain natural frequencies. The present results, combined with the modal properties of general compound planetary gears, show that rotational modes are independent of translational bearing/shaft stiffnesses and masses of carriers/central gears, translational modes are independent of torsional bearing/shaft stiffnesses and moment of inertias of carriers/central gears, and planet modes are independent of all system parameters of other planet sets, the shaft/bearing stiffness parameters of carriers/rings, and the mass/moment of inertia parameters of carriers/central gears.
Laser Induced Fluorometry and Velocimetry
Authors: Kandlakunta Sahithi , Panchagnula Mahesh
Published: April 2008

The characteristics of fuel atomizers have been studied by using a fluorescence optical patternator via establishing a laser sheet illumination of the spray and an image capturing system. Line laser Mie-scattering and fluorescence imaging technique is used to study the fuel mass distribution, geometrical properties, angle and symmetry in sprays. The proposed experimental setup employs Rhodamine 6G as the fluorophore. A set of filters have been used to reduce the signature from the combustion fire while being able to image the nanoparticles. Experimental results are obtained under the conditions of the fuel with and without being seeded with quantum dots and under both non-combusting and combusting spray conditions. The results from the study are validated against existing volume flux distribution measurements by conventional techniques. Owing to the high luminescence properties of quantum dots, the liquid volume distribution can accurately be determined in an evaporating as well as a non-evaporating spray using this technique. Quantum dots are semiconductor nanoparticles whose emission wavelength can be tuned by the choice of their size. Also their, high luminescence properties are advantageous in a spectrally "noisy" combustion environment.
Nonlinear Dynamics of a Clamped, Buckled Plate: Some Results
Authors: Shukla Amit , Koo Jeong Hoi
Published: April 2008

Accurate prediction of nonlinear response of a homogenous, buckled plate with clamped boundary conditions is essential in designing aircraft structures for long life and extreme combined loading. It is well known that the dynamic response becomes highly nonlinear for large response amplitudes of a buckled plate with clamped boundary condition. In this paper, a rectangular plate is experimentally studied for its nonlinear dynamic response. The results obtained are compared for the two buckling modes. Further, the numerical observations are conducted to differentiate the effect of amplitude of excitation on the nonlinear response, specifically characterizing the parametric regimes (amplitude and frequency) to differentiate between the small amplitude linear response and large amplitude snap-through response. It is desired to understand the parametric boundary separating these two qualitatively different response characteristics for its obvious impact on the fatigue life of the structure.
Rigid Formation of a Group of Vehicles Using Constraint Forces
Authors: Zou Yunfei , Pagilla Prabhakar
Published: April 2008

We consider the problem of controlling a group of vehicles to a rigid formation. Our approach mimics the development of dynamics of a system of particles subject to constraints. In particular, we use the notion of constraint forces to achieve, and maintain, a given formation. As opposed to the potential function approach used in the literature, the proposed constraint force approach directly compensates for only those parts of the applied forces which act against the constraints. We develop a stable control algorithm that will achieve the formation while ensuring navigation of the group based on the desired trajectories that are consistent with the constraints. Simulation results on an example are shown to verify the proposed method.
New Finite Element Formulation for Micro Electro-Thermo-Mechanical Domains
Authors: Motiee Mehrnaz , Khajepour Amir , Mansour Raafat R.
Published: April 2008

In the analysis and modeling of MEMS devices, a general finite element formulation is necessary to solve a multidisciplinary domain of the device with large number of nodes and elements. In this paper, we present a step by step finite element formulation for automated modeling of multi-disciplinary domains. The electro-thermo-mechanical domain is explained and an algorithmic approach for sequential analysis of an arbitrary ground structure with multi-disciplinary boundaries is developed and implemented in Matlab with a graphical user interface. The results of the finite element approach is compared and verified with exact solutions and test results from literature. The agreement of results verifies the application of proposed finite element formulation to the analysis of elector-thermo-mechanical domains. This formulation provides a fast and reliable tool to analyze electro-thermo-elastic devices which allows large flexibility in the selection of mechanical and electrical boundary conditions.
Probabilistic Analysis of MEMS Asymmetric Gear Tooth
Authors: Karpat F. , Ekwaro-Osire S. , Khandaker M. P. H.
Published: April 2008

Asymmetric gear teeth are used to improve the performance of gears by increasing the load capacity or by reducing vibrations. Recently these types of gears have found application in MEMS devices where the use of gears is on the rise. In this research a probabilistic computer program, in conjunction with a commercially available finite element program, is developed and the reliability of the asymmetric gear tooth is studied. Specifically, the probability of failure of the asymmetric gear is extracted for various parameters. The parameters considered included pressure angle, tooth height, and contact ratio. The efficacy of using asymmetric gear tooth is shown in this study.
Integration of Mechatronics, Geospatial Information Technology, and Remote Sensing in Agriculture and Environmental Stewardship
Authors: Nagchaudhuri Abhijit , Mitra Madhumi , Brooks Carolyn , Earle Tracie J. , Ladd Gabriel , Bland Geoffrey L.
Published: April 2008

University of Maryland Eastern Shore (UMES) is located in the eastern shore region of Delmarva Peninsula. Rural environment of the region and the proximity to Chesapeake Bay makes agricultural needs and environmental concerns some of the key issues in the area. Precision Agriculture integrates advanced mechatronics, geoinformatics, and remote sensing to address these issues in an effective manner. This paper will highlight ongoing efforts to develop the infrastructure for this advanced technology driven agricultural practice at UMES that has significant intersection with broad umbrella of the field of "Mechatronics". Particular emphasis will be on integration of yield monitor and a GPS unit with the existing UMES combine/mechanical harvester; remote sensing from UAV (Unmanned Aerial Vehicle), RAV (Remote Controlled Aerial Vehicle), and manned airplane equipped with camera systems; advanced technologies for sensing and monitoring, datalogging, and wireless transmission of environmental data; geospatial information technology; future plans involving variable rate application of nutrients and fertilizers. The paper will also describe aspects of three ongoing multidisciplinary projects titled (i) Environmentally Conscious Precision Agriculture (ECPA); (ii) Airborne Science and Technology Institute (ASTI) and (iii) Aerial Imaging and Remote Sensing for Precision Agriculture and Environmental Stewardship (AIRSPACES) that have contributed significantly in advancing the broad project goals that are not only consistent with the economic necessities of the region but also the land grant mission of UMES.
Cross-Coupled Iterative Learning Control for Manufacturing Applications: Design and Implementation
Authors: Barton Kira L. , Alleyne Andrew G.
Published: April 2008

This paper presents an improved method for precision motion control by combining Iterative Learning Control (ILC) and Cross-Coupled Control (CCC) in a novel way that improves overall tracking performance. Previous developments in precision motion control have introduced a CCC feedback method which results in improved contour error. Contour error is a nonlinear combination of the individual axis tracking errors [1]. In this paper, ILC and CCC are combined to overcome limitations present in each technique. In this new method, multi-axis CCC is reformatted into a single-input single-output (SISO) ILC approach, in which learning of the cross-coupled error leads to a modified control signal and subsequent improvements in the trajectory tracking performance. This approach is different from multi-input multi-output (MIMO) ILC [2] approaches in that two non-coupled systems are combined into one nonlinear system in which the coupling is introduced through only the error dynamics. In this paper, sufficient stability and convergence properties are given for the proposed algorithm. A design for a Cross-Coupled ILC (CCILC) system is presented, and the performance of this system is compared to the performance of existing control systems. Computer simulation and experimental testing of this design are implemented on a microscale robotic deposition (μ - RD) system [3] to assess the overall performance benefits. It is shown through simulation and experimental testing that combining CCILC with individual axis ILC produces the greatest overall performance improvement by capitalizing on the gains acquired from each technique.
Speciation of Chlorine and Alkali Metals in Biomass Combustion and Gasification
Authors: Sonwane Pavankumar , Ban Heng , Gale Thomas K.
Published: April 2008

Alkali metals, mainly sodium and potassium, together with other ash forming inorganic components in biomass increases fouling, slagging, and high temperature corrosion during biomass combustion or gasification. To reduce the amount of alkali vapor to an acceptable level, which may be affected by Si, Al, Ca, S, Mg, and P, the information on the speciation of alkali metals is essential. In this study, thermodynamic equilibrium calculations were performed to determine the distribution and mode of occurrence of gaseous chlorine and alkali metals of three types of biomass (corn stover, switch grass, and wheat straw) in combustion and gasification processes. The influence of temperature, pressure, and air-fuel ratio was also evaluated. Results show that the excess air has limited influence on the speciation of chlorine and potassium during combustion. However, the influence of the excess air is significant during gasification. Increasing excess air enhances the formation of vapor HCl and KOH as well as reduction in vapor KCl and K2Cl2. In biomass combustion and gasification, increasing pressure increases vapor HCl and K2Cl2 and reduces the amount of vapor KCl and KOH. At higher temperatures (>1100K), the gaseous alkali species increased greatly. The results will be useful in the better development of hot gas clean-up technologies.
Air Stable High Resolution OFET (Organic Field Effect Transistor) Fabrication Using Inkjet Printing and Low Temperature Selective Laser Sintering Process
Authors: Ko Seung Hwan , Pan Heng , Grigoropoulos Costas P. , Poulikakos Dimos
Published: April 2008

A novel high resolution OFET (organic field effect transistor) fabrication process has been developed to realize low cost, large area electronics at low processing temperature without use of expensive, high temperature lithography process in vacuum. A drop-on-demand (DOD) ink-jetting system was used to print gold nano-particles suspended in Alpha-Terpineol solvent. Continuous Argon ion laser was irradiated locally to evaporate carrier solvent as well as sinter gold nano-particles in order to fabricate metal source and drain electrodes with high resolution and minimal thermal damage to the substrate. PVP (poly-4-vinylphenol) in Hexanol solvent and air-stable semiconductor polymer (Carboxulate - functionalized Polythiophenes) in 1,2-dichlorobenzene (o-DCB) solvent were spin-coated to form thin film of dielectric layer and semiconducting active layer. All of the processes were carried out in plastic-compatible low temperature, ambient air and atmospheric pressure environment. The OFETs showed good accumulation mode p-channel transistor behavior with carrier mobility of 0.01cm2/V·s and Ion/Ioff ratio of ranging from 103 to 104.