bluuebunny/crossref_metadata_2025 huggingface dataset:
A Flow Study of Pulsed Jet Cross-Flow Interaction by Micro Particle Image Velocimetry
Authors: Watanabe Kenichi , Nakatsuka Tomonori , Suzuki Daichi , Nagumo Takashi , Motosuke Masahiro , Honami Shinji
Published: April 2008

Recent development of micro devices is remarkable as in the examples of Micro-TAS, Lab-on-a-chip or ultra micro gas turbine. In order to make the micro devices smaller and more effective, an appropriate use of a micro scale jet as an actuator can be a key technology. Aiming at the development of a measurement system of the micro flow control devices in the future micro aerodynamics, we have established a system to measure a continuous jet, a pulsed jet and a synthetic jet for the flow control in the low Reynolds number air flow with a micro length scale. The two-dimensional flow field around the micro jet using micro particle image velocimetry (PIV) was measured. The jet was injected through the device using an acoustic speaker. It was observed that a saddle point existed at the certain phase where the velocity is 0 at the boundary of the jet blowing and suction phase for the synthetic jet into a still air. It was found that the pulsed jet and the synthetic jet are more effective in the fluid mixing in the low Reynolds number flow than the continuous jet. The dead water region was observed downstream of the jet in case of the jet injection into cross flow. It was recognized that the synthetic jet at the certain oscillation frequency generated a vortex pair near the jet hole.
Transport Coefficients and Orientational Distributions of a Dilute Colloidal Dispersion Composed of Hematite Particles: Analysis for an Applied Magnetic Field Parallel to the Angular Velocity Vector of Simple Shear Flow
Authors: Hayasaka Ryo , Satoh Akira , Majima Tamotsu
Published: April 2008

We have studied the influences of the magnetic field, shear rate, and random forces on transport coefficients such as viscosity and diffusion coefficient, and also on the orientational distributions of hematite particles composed of a dilute colloidal dispersion. Hematite particles are modeled as spheroids with a magnetic moment normal to the particle axis. In the present analysis, these particles are assumed to conduct the rotational Brownian motion in a simple shear flow as well as an external magnetic field. The basic equation of the orientational distribution function has been derived from the balance of the torques and solved by the numerical analysis method. The results obtained here are summarized as follows. With increasing the magnetic field, since the magnetic moment is strongly restricted to the magnetic field direction, the motion of the particle is forced to rotate in directions normal to the shear flow direction. In the case of a strong magnetic field and a smaller shear rate, the rodlike particles can freely rotate in the xy-plane with the magnetic moment remaining pointing to the magnetic field direction. On the other hand, for a strong shear flow, the particle has a tendency to incline in the flow direction with the magnetic moment pointing to the magnetic field direction. Additionaly, the diffusion coefficient gives rise to smaller values than expected, since the rodlike particle sediments with the particle inclining toward directions normal to the moment direction.
Objective Evaluation of Diesel Combustion Noise in Vehicle Passenger Compartment
Authors: Kang Koo Tae , Byun Uhn Seob
Published: April 2008

The combustion noise of diesel engine during run up and idle condition makes unpleasant interior noise in passenger car whose market share is increasing nowadays. There were few studies to quantify the unpleasantness of combustion noise. We tried to introduce an objective metrics which matches well with subjective ratings of combustion noise. To get the objective metrics, the combustion noise signal was analyzed by many different methods based on the human hearing sense. In the end, we found out that the modulation amplitudes of each frequency band match well with the unpleasant characteristics of combustion noise. Then, an objective index was developed from the combination of modulation amplitudes on the basis of the human hearing sense. The index was shown to be in good correlations with subjective ratings in general.
Energy and Exergy Analysis of an IGCC With In-Situ CO2 Capture
Authors: Klimantos P. , Koukouzas N. , Kakaras E.
Published: April 2008

Within this study energetic and exergetic theoretical analyses of a novel IGCC power plant concept with CO2 capture are carried out. The core process of the concept examined is based on the high pressure steam gasification of high moisture low grade coals where CO2 is captured reacting exothermically with CaO-based sorbents and high hydrogen-content carbon-free fuel gas is produced without using additional shift reactors and CO2 separation stages. The carbonated sorbents are continuously fed to an oxygen blown calcination reactor where pure CO2 is released and active CaO is reproduced. This concept can be realised in a dual fluidised bed reactor system where coal gasification and CaCO3 calcination are taking place simultaneously. In this paper possible plant configurations are presented and detailed simulation of 400 MWe IGCC power plant based on a state of the art gas turbine cycle with a three pressure stage heat recovery steam generator is performed using the ASPEN Plus simulator. The calculated results demonstrate the capability of the power plant to deliver almost decarbonised electricity while achieving net plant efficiencies at about 38.4% of coal lower heating value (LHV). Based on the energy analysis and the data generated from the simulation an exergy analysis was performed in order to quantify and localize the thermodynamic irreversibility in each process component as well as to asses the overall thermodynamic imperfection of the proposed process.
Nonlinear Analysis and Optimization of Diamond Cell Morphing Wings
Authors: Johnson Terrence , Frecker Mary , Joo James , Abdalla Mostafa , Sanders Brian , Gurdal Zafer , Lindner Doug
Published: April 2008

In this work, a design optimization procedure is developed to maximize the energy efficiency of a scissor mechanism for the NextGen's Batwing application. The unit cells are modeled using a finite element approach. The model considers elastic skin, modeled as linear springs, as well as actuator and aerodynamic loads. A nonlinear large displacement analysis is conducted, and the position of the actuator is optimized using Matlab's gradient based optimization algorithm FMINCON. This optimization procedure is used to investigate the effect of different constraints and load cases. The model is expanded to include multiple unit cells and actuators. A two stage optimization process using a Genetic Algorithm and traditional gradient based optimization (FMINCON) is also developed. The two stage optimization is used to optimize actuator position and placement for different constraints and load cases. Results show that placement and position optimization produce small gains in maximizing energy efficiency; morphing using a soft isotropic skin is more efficient than stiff isotropic and anisotropic skin. In addition, the GA did not use the all of the available actuators to maximize energy efficiency.
Modeling of a Novel Multi-Jet Emitter for ESI-MS Applications
Authors: Sen A. K. , Darabi J. , Knapp D. R
Published: April 2008

This paper presents the concept and simulation of a novel multiple electrospray emitters for electrospray ionization mass spectrometric (ESI-MS) applications. The proposed emitter is based on an array of carbon nanofibers (CNF) vertically grown around the orifice of a microscale thermoplastic capillary. The electrospray ionization process is simulated using a CFD code that utilizes Taylor-Melcher leaky-dielectric formulations for the electrohydrodynamics and volume-of-fluid (VOF) method for tracking the interface. The modeling results predict that under steady state conditions, individual cone-jets are established around each of the CNFs resulting in an array of electrosprays. Effects of several design and operational parameters on the electrospray performance are thoroughly investigated. The results of the present study will facilitate design, fabrication and experiments using the CNF emitter. Higher spray current and lower jet diameter indicate that the proposed emitter can perform equivalent to nanospray emitters exhibiting improved MS sensitivity while using a microscale orifice. Use of microscale orifice benefits in terms of higher sample throughput and eliminates potential clogging problem inherent in nanoscale capillaries. Overall, the proposed emitter is believed to be a suitable candidate for ESI-MS applications.
Application of Long-Distance Forward-Scattering Particle Image Velocimetry in Micro-Scale Turbulent Jet Flow Tests
Authors: Gui Lichuan , Jansen Bernard J. , Seiner John M.
Published: April 2008

A new particle image velocimetry system is applied to measure turbulent air jet flows from a micro-scale nozzle. The applied MPIV system includes a long-distance microscope that enables not only a long working distance, but also a forward-scattering optical setup. By using a high repeating rate Nd:YAG laser and an advanced digital camera, particle image recordings can be captured at 60 fps, i.e. 30 PIV recording pairs per second, with an interframing time of 180 ns, so that a high-speed flow measurement is enabled in micro scale. Measurements were conducted in the central plane of an air jet from a nozzle of 500 μm in diameter at flow velocity up to 110 m/s. Mean velocity and Reynolds stress distributions were determined with statistical analyses of thousands of instantaneous velocity maps.
Study of Hot Embossing Behavior and Comparison at Normalized Temperatures of PolyCarbonate , PolyMethylMethAcrylate and Poly L-Lactic Acid
Authors: Belligundu Sunil , Shiakolas Panos S. , Aswath Pranesh , Uppal Nitin
Published: April 2008

Hot embossing microreplication microfabrication (HEMM) process is one of the methods used for the fabrication of polymer based microdevices. The molds used for hot embossing have been fabricated using a Femtosecond Laser Microfabrication (FLM) system. Embossing experiments are performed on three polymers; Poly Carbonate (PC), PolyMethylMethAcrylate (PMMA), and Poly L-Lactic Acid (PLLA). These polymers have different glass transition and melting temperatures leading to different embossing process parameters. Normalization of embossing temperatures is performed to assess the HEMM process performance as a function of a normalized quantity that considers the glass transition, melting and embossing temperatures of a polymer. The performance comparison is based on evaluating the flow rate or measuring the height of an embossed feature for a given applied embossing pressure and holding time.
Design and Testing of a Prototype Atmospheric Gas Collection Apparatus for a Mission to Mars
Authors: Bernardin John D. , Konecni Snezana , Wiens Roger
Published: April 2008

A novel spacecraft, the Sample Collection for Investigation of Mars (SCIM), was proposed for the collection and return of atmospheric gas and dust samples from the martian atmosphere. The SCIM mission, part of NASA's Mars Exploration Strategy, would allow scientists to greatly enhance our understanding of Mars' water, climate, and geological evolution by studying the element and isotopic composition of the gas and dust. The SCIM spacecraft was proposed to collect its samples during a single high-speed pass through the martian atmosphere at an altitude of 37 km and return the samples back to earth. For the atmospheric gas sampling aspect the SCIM employs the Atmospheric Collection Experiment (ACE), a dual-component apparatus consisting of a passive and a cryogenic sorption gas collection system. Each of these systems possesses a collection vessel that is initially under high vacuum. At the time of entry into the martian atmosphere, valves on SCIM open and gas flows into the parallel-plumbed passive and cryogenic sorption gas collection systems. The passive system simply allows the incoming gas to fill an initially evacuated 1 Liter vessel. The cryogenic sorption system employs a Joule-Thompson cryocooler and sorption medium that initially condenses and captures the incoming gas. As the SCIM begins to exit the atmosphere isolation valves close and trap the gas samples in their collection systems for the return journey back to earth. The minimum SCIM mission goal was to collect 100 cm3 @STP(≈ 0.2 g) of martian atmospheric gas and the ACE was being designed to gather 1000 cm3 @STP (≈ 2.0 g) using both the passive and cryogenic systems. The volumes referred to above correspond to standard temperature and pressure on Earth (e.g., STP). The goals of this study were to prove the gas collection concepts mentioned above and develop the numerical and experimental tools to allow for the optimization of a flight worthy ACE. This paper discusses the design, analysis, and testing of a prototype ACE. First, more specific details on the design and testing methodology for the prototype are presented. Next, the development of a computational fluid dynamics (CFD) model is discussed. Finally, empirical pressure data from the prototype tests are used to assess the performances of the passive and cryogenic sorption gas collection systems and are compared to numerical pressure predictions to provide a benchmark for the CFD model. Results indicate that the prototype ACE is capable of meeting the design goal of 1000 cm3 @STP (2.0 g) of total gas collection.
Electrohydrodynamic Conduction Pumping of Liquid Film in Horizontal Annular Configuration
Authors: Yazdani Miad , Seyed-Yagoobi Jamal
Published: April 2008

Electrohydrodynamic (EHD) conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes, which are based on the process of dissociation of the neutral electrolytic species and recombination of the generated ions. This work numerically studies the electrically driven liquid film flow in horizontal annular configuration based on electric conduction phenomenon. The numerical domain considered is represented by a two dimensional developing axisymmetric channel flow of a liquid separated from vapor by a horizontal interface. Two electrode designs are selected for this study: zero drag and non-zero drag electrode configurations. Laminar formulation is utilized for annular flow in the absence of gravity. The electric field and electric body force distributions in axial and radial directions along with flow field and velocity profiles for two electrode designs are presented and fundamentally analyzed. IN addition to the above, similar but limited results are provided for EHD conduction pumping of liquid film in horizontal annular configuration in the presence of gravity. In this case, a k — ε model with near wall treatment is incorporated for turbulence distribution. The electric body force distribution in axial and radial directions and flow pattern are fundamentally illustrated.
Investigating the Accuracy of Subjective Clustering and Bootstrap Application to Subjective Clustering Using an Empirical Population
Authors: Bhardwaj Nishant , Takai Shun
Published: April 2008

For a new product to be successful in today's market, engineers need to identify representative customer needs. One approach to identify representative needs from a large number of needs is Subjective Clustering (SC). A set of clusters obtained from SC is a point estimate of clusters generated by a population of customers. Another approach is to apply Bootstrap (BS) to SC. By applying BS to SC, engineers can draw an inference about population primary clusters. This paper compares the accuracy of estimating population primary clusters using SC and Bootstrap applied to SC (BS-SC). The authors recruited participants to perform the clustering experiments and assumed that these participants consist a population. The authors randomly sampled subsets of participants and evaluated how accurately SC and BS-SC identify population primary clusters. When the sample size is small relative to the population, BS-SC estimated population primary clusters more accurately than SC.
Residual Stresses in Passenger Car Wheels
Authors: Liu Shuangqin , Perlman Benjamin , Gordon Jeffrey
Published: April 2008

Knowledge of the residual stress state in wheels resulting from manufacturing and subsequent service loading is useful for several practical reasons. The ability to estimate residual stress levels permits the tuning of manufacturing processes to control the magnitude and distribution of these stresses in new wheels in order to achieve safe performance in service. Similarly, understanding the redistribution of residual stresses following application of service loads (wheel/rail contact and thermal stresses) is crucial to avoid operating conditions which may lead to premature wheel failure. Axisymmetric (2-dimensional) analyses are typically performed in order to conduct manufacturing process simulations since these processes affect the entire wheel in a circumferentially uniform sense. Generally, analyses involving service loading have sought to identify the "shakedown state" at which the residual stress distribution stabilizes after some number of loading cycles. In order to properly account for service loads, 3-dimensional models are required since contact and brake shoe thermal loading are not axisymmetric. Since the as-manufactured residual stress distribution must be considered in a service loading simulation, 3-dimensional modeling of this process is required. This paper presents a preliminary comparison of 2- and 3-dimensional modeling of the wheel heat treatment process. Except for the increased computational time required for the 3-dimensional analysis, the results agree favorably. The 3-dimensional model is used to simulate service loads involving wheel-rail contact loading representative of a typical passenger car. The model is exercised with a variety of material models for comparison with previous work. Results are presented for multiple loading scenarios and shakedown stress states are established for a range of applied loads.
A Silicon Gyroscope With Electronic Frequency Tuning
Authors: Wang Frank , Hobbs Larry , Smith Marc
Published: April 2008

In micromachined gyroscopes, the vibrating masses are generally coupled by one of two means. The most common means is mechanical, meaning a spring or equivalent structure links the two masses. Alternatively, the coupling is produced electrostatically, where the displacement of the masses causes the gap of a capacitive structure to vary. In this paper, a new approach called electronic coupling is employed. The tuning structure and circuit are presented. Simulation results are discussed.
D’Alembert’s Principle and the Equations of Motion for Nonholonomic Systems
Authors: Feeny B. F.
Published: April 2008

D'Alembert's principle is manipulated in the presence of nonholonomic constraints to derive the principle of virtual power in nonholonomic form, and Lagrange's equations for nonholonomic systems. The Lagrangian equations had been expressed previously for conservative systems, derived by variational methods. The D'Alembert derivation confirms the roles of constrained and unconstrained Lagrangians directly by the presence of constrained and unconstrained velocities in D'Alembert's principle. The constrained form of nonconservative generalized forces is also determined for both particles and rigid bodies. An example is a rolling disk.
Development of Active Laminates and Composites
Authors: Asanuma Hiroshi
Published: April 2008

The present paper describes development of active laminates and composites proposed by Asanuma. The active laminates were successfully made by hot-pressing of an aluminum plate as a high CTE (Coefficient of Thermal Expansion) material, a unidirectional CFRP (Carbon Fiber Reinforced Plastics) prepreg as a low CTE material and an electric resistance heater, and a KFRP (Kevlar Fiber Reinforced Plastics) prepreg as a low CTE material and an insulator between them. Curvature of the active laminate linearly changes only in the fiber direction as a function of temperature, and it was made into complicated forms and their actuation performances were successfully demonstrated. As a high temperature type active laminate, three types of SiC/Al composites, that is, a laminate of continuous-fiber layer and unreinforced one, that of discontinuous-fiber layer and unreinforced one, and that of continuous-fiber layer and discontinuous-fiber one were fabricated, and it became clear that all of the composites curve unidirectionally in the fiber direction, and the curvatures reproducibly change during thermal cycles between room temperature and 813 K. Tensile strength of the combination type is higher than that of the continuous-fiber type, and its curvature exists between the continuous-fiber type and the discontinuous-fiber type.
A Dynamic Model for a Closed-Loop Continuous Energy System Using Solar Power
Authors: Culwell Bradford M. , Revankar Shripad T. , Kotha Radhika
Published: April 2008

One key advantage of solar power over more traditional power sources is its modular nature, allowing it to be used in remote locations or as a supplementary source of power. Recent studies show fuel cell technology as a good means of providing a continuous supply of electricity from a solar array, eliminating drawbacks caused by solar energy's cyclical nature. The high power density of such a system makes it ideal for use in areas such as unmanned aerial vehicles and space exploration. Due to the complexity and relatively high initial cost of current fuel cells, however, optimization of such a system is critical. This paper examines a dynamic model of a solar regenerative fuel cell system built in MATLAB Simulink. The system uses a polymer electrolyte membrane (PEM) fuel cell, running on stored hydrogen and oxygen, to produce power when solar energy is insufficient. It uses a PEM based electrolyzer to produce hydrogen and oxygen from water when solar energy exceeds demand. The mathematical model includes modules for each component, including solar cells, fuel cell, electrolyzer, and auxiliary systems. Models were built based on fundamental physics to the extent practical. The individual modules were first tested for their performances and then were integrated to form an integrated solar powered regenerative fuel cell system. The simulations were carried out for a day and night cycle and the results show that the closed loop system can be operated providing continuous supply of electric power.
Simulation of Heat Exchanger Transients in Sulfuric-Acid and Hydrogen-Iodide Decomposition
Authors: Brown N. R. , Oh S. , Revankar S. T.
Published: April 2008

In the Sulfur-Iodine (SI) water splitting cycle hydrogen is produced via the decomposition of Hydrogen-Iodide (HI) and sulfuric acid (H2SO4). These reactions proceed at around 400 °C and 850 °C respectively. A high temperature heat source, such as nuclear reactor heat, is required for the SI cycle. Since both the nuclear plant and the SI cycle plant are coupled through heat exchangers, any transients for either plant will affect the entire system. For a nuclear reactor system, it is especially important to understand the transient behavior of the SI cycle during a reactor startup or an emergency shutdown. A simplified transient model of the SI cycle, which can be coupled to heat from a nuclear plant, has been developed. Preliminary results from both steady state and transient calculations are presented in this paper.
Orienting Body Coordinate Frames Using Karhunen-Loe`ve Expansion for More Effective Structural Simplification
Authors: Ersal Tulga , Fathy Hosam K. , Stein Jeffrey L.
Published: April 2008

Previous work by the authors developed a junction-inactivity-based structural simplification technique for bondgraph models. The technique is highly sensitive to the orientation of the body coordinate frames in multibody systems: improper alignment of body coordinate frames may prohibit a significant simplification. This paper demonstrates how the Karhunen-Loe`ve expansion can be used to automatically detect the existence of and to find the transformation into body coordinate frames that render the bond-graph of a multibody system more conducive to simplification. The conclusion is that the Karhunen-Loe`ve expansion complements well the junction-inactivity-based structural simplification technique when multibody dynamics are involved in the system.
Validation of a New Aluminum Honeycomb Constitutive Model for Impact Analyses
Authors: Hinnerichs Terry , Pulling Eric , Neilsen Mike , Lu Wei-Yang
Published: April 2008

A new constitutive model for large deformation of aluminum honeycomb has been developed. This model has 6 yield surfaces that are coupled to account for the orthotropic behavior of the cellular honeycomb being crushed on-axis and off-axis. Model parameters have been identified to fit uniaxial and biaxial crush test data for high density (38 lb/ft3) aluminum honeycomb. The honeycomb crush model has been implemented in the transient dynamic Presto finite element code for impact simulations. Simulations of calibration and validation experiments will be shown with model predictions compared with test data. Also, the honeycomb model's predictions will be compared with the older Orthotropic Rate Model predictions.
Shear Piezoresistive Response of a Graphite/Silicone Suspension
Authors: Edmiston John , Shkel Yuri M.
Published: April 2008

A shear piezoresistive effect has been observed for micrographite particles suspended in uncured silicone elastomer. A phenomenological formulation of piezoresistivity is presented and an experimental approach is discussed within this paper. The experimental objective is to extract two material parameters, fully describing the piezoresistance effect in deformed isotropic materials. A rheometer in the cone-and-plate configuration provides well-defined oscillatory shear flow of the suspension; it also measures rheological characteristics of the suspension. The piezoresistive response is probed using interdigitated electrodes, which are attached to the rheometer plate. The electrodes are arranged in parallel-to-flow and perpendicular-to-flow orientations. The signal acquired from two such orthogonal electrode pairs can be combined in a way to exclude any contribution of volumetric deformations to the piezoresistance signal. The experimental results indicate a second harmonic relationship between the mechanical oscillation and the resistive response. These two-probe measurement results represent the first observations of a non-volumetric deformation contribution to the piezoresistivity of viscoelastic liquid suspensions.
Comparison of Galerkin, POD and Nonlinear-Normal-Modes Models for Nonlinear Vibrations of Circular Cylindrical Shells
Authors: Amabili M. , Touze´ C. , Thomas O.
Published: April 2008

The aim of the present paper is to compare two different methods available to reduce the complicated dynamics exhibited by large amplitude, geometrically nonlinear vibrations of a thin shell. The two methods are: the proper orthogonal decomposition (POD) and an asymptotic approximation of the Nonlinear Normal Modes (NNMs) of the system. The structure used to perform comparisons is a water-filled, simply supported circular cylindrical shell subjected to harmonic excitation in the spectral neighbourhood of the fundamental natural frequency. A reference solution is obtained by discretizing the Partial Differential Equations (PDEs) of motion with a Galerkin expansion containing 16 eigenmodes. The POD model is built by using responses computed with the Galerkin model; the NNM model is built by using the discretized equations of motion obtained with the Galerkin method, and taking into account also the transformation of damping terms. Both the POD and NNMs allow to reduce significantly the dimension of the original Galerkin model. The computed nonlinear responses are compared in order to verify the accuracy and the limits of these two methods. For vibration amplitudes equal to 1.5 times the shell thickness, the two methods give very close results to the original Galerkin model. By increasing the excitation and vibration amplitude, significant differences are observed and discussed.
Characterization of Spectral Response of a FBG Sensor Embedded in a Metallic Structure Using Laser Solid Freeform Fabrication
Authors: Alemohammad Hamidreza , Toyserkani Ehsan
Published: April 2008

This paper focuses on spectral response characterization of fiber Bragg grating (FBG) sensors embedded in metallic structures using laser solid freeform fabrication (LSFF). Fiber Bragg grating sensors are capable of measuring temperature, strain and pressure and can be embedded in metallic structures to monitor thermal and structural loads. Due to the sensitivity of the FBG sensors to high temperatures and stresses, the embedding process using LSFF is a challenging task. In the present work, a finite element model is developed to predict the stress and temperature fields adjacent to the fiber optic sensor embedded the metallic structure. The FE results are transferred to opto-mechanical model of the FBG sensor to predict the change in the spectral response of the sensor. Finally, the finite element model is verified using an existing analytical model which predicts the temperature field and melt pool geometry in LSFF process.
An Actuation Mechanism for a Dual-Arm Robotic Manipulator
Authors: Hosek Martin
Published: April 2008

An actuation mechanism for a dual-arm scara-type robot for automated pick-place operations in semiconductor and flatpanel-display manufacturing applications is described. The mechanism consists of a pivoting platform and two linkages coupled to the platform through a pair of revolute joints. The opposite ends of the linkages are connected to the upper arms of the robot by another pair of revolute joints, forming a pair of three-bar mechanisms coupled through the pivoting platform. When the platform is in its neutral position, both of the arms are retracted. The geometry of the components of the mechanism is selected so that rotation of the platform from the neutral position in one direction produces desirable radial motion of one arm while the other arm is kept almost stationary in the retracted position. The arms exchange their roles when the platform rotates from the neutral position in the opposite direction. Alternatively, to achieve absolutely no motion of the retracted arm while the other one extends, the pivoting motion of the platform can be replaced by a rocking arrangement with two pivot points. In this configuration, the locations of the two pivot points coincide with the locations of the revolute joints between the linkages and the upper arms when the platform is in the neutral position. As a result, rotation of the platform with respect to one of the pivot points produces no motion of the corresponding arm while the other one extends. Compared to a conventional design, which utilizes a pair of motors coupled to the robot arms through a pair of belt arrangements, the present mechanism eliminates one of the two motors, including its electronic circuitry, and replaces the belt drives with rigid linkages, thus reducing the complexity and cost, and improving the reliability and cleanliness of the robotic system.
Performance Predictions of a Moisture Management Device for Fuel Cell Applications
Authors: Killion J. D. , Garimella S.
Published: April 2008

Moisture management in proton-exchange-membrane fuel cells is crucial to durability and performance. This frequently requires external humidification of the reactant gas streams to maintain sufficient humidity levels at the membranes, especially at higher operating temperatures. Direct-contact humidifiers using louvered fins brazed to rectangular tubes, similar to those frequently employed in automotive condensers and radiators, can be used to humidify a gas stream. A gas stream in which liquid water is sprayed flows through the passages formed by the louvered fins counter-current to a heating fluid flowing in the rectangular tubes sandwiching the fins. A mathematical model of this type of direct-contact humidifier is presented. The equations of energy and mass conservation are simultaneously solved for a number of segments along the humidifier. An equivalent resistance network is used to capture the temperature profile of the fins and liquid film surrounding them. The thickness of the liquid film is calculated from a shear balance at the film interface. The heat and mass transfer analogy is used with empirically derived transfer coefficients to solve the coupled heat and mass transfer problem in the gas phase. Predicted results are presented for typical operating conditions corresponding to a wide range of fuel cell operating conditions. The results show how the humidification process varies along the length of the humidifier. It is also shown that, although evaporation of the liquid film takes place throughout the entire humidifier, the direction of sensible heat transfer between the gas and liquid film can switch at some distance along the humidifier. This confirms the need for the equivalent resistance network model of the fin and film since simple fin efficiency models would fail in this situation. The model provides a basis for design optimization and performance predictions for this type of direct-contact moisture management device.
Energy Transfer and Molecule-Radiation Interaction in Optical Microcavities
Authors: Quan Haiyong , Guo Zhixiong (James)
Published: April 2008

Laser energy transfer and molecule-radiation interaction in optical microcavity devices are characterized. The device is operated at whispering-gallery modes, and consists of a microcavity and a micro-waveguide coupled by a sub-micrometer air-gap. Emphases are placed on the influences of microcavity size and waveguide compatibility on the energy transfer and storage capability, on the interactions of foreign molecules with the evanescent radiation field surrounding a resonant microcavity. An optimal gap is found for the considered device configuration where maximum energy storage is achieved. This optimal gap is dependent on the resonance mode as well as the morphology. The Q factor increases exponentially with increasing gap and saturates as the gap approaches the optical wavelength. The influence of molecules attachment is demonstrated and the potential in molecular detection is discussed.
Optimal Synthesis, Verification and Identification of a High-Performance Inertial Isolation System
Authors: Bortoluzzi Daniele , Bertolazzi Enrico , Biral Francesco , Bosetti Paolo
Published: April 2008

Measuring small forces or impulses needs a mechanical system in an isolated inertial frame. The isolated system has to be set in a "free-fall" condition along one or more so-called "soft" degrees of freedom (DOF). Such a condition is achieved by means of dedicated mechanisms acting as inertial isolation systems. In the LISA Pathfinder space mission, a critical phase has been identified when a mechanism must release an object in free-fall conditions inside the spacecraft. A ground-based experiment reproducing this free-fall condition has been planned to verify the feasibility of such a phase. For this experiment, the Roberts linkage has been proposed as a suitable mechanism to realize an inertial isolation stage with two soft DOFs on the horizontal plane. The key feature of the linkage dynamic response is the virtual surface generated by a reference point belonging to its suspended part. The geometry of the linkage has been optimized in order to conform the virtual surface to the required free-fall level of the suspended system. A prototype has been realized and the virtual surface has been measured. Through a reverse engineering approach the characteristics of the surface geometry affecting the mechanism performance have been extracted. By comparison between nominal and actual surfaces, information is drawn on the mechanism quality and about the adjustment procedure to improve its response.
Flow of Viscoplastic Liquids Through a Planar Expansion Followed by a Contraction
Authors: Naccache Moˆnica F. , Barbosa Rafael S.
Published: April 2008

In this work, the creeping flow of a viscoplastic fluid through a planar channel with an expansion followed by a contraction is analyzed numerically. The solution of the conservation equations of mass and momentum is obtained via the finite volume method. In order to model the non-Newtonian behavior of the fluid, it was used the Generalized Newtonian Fluid constitutive equation. The viscosity function was the one proposed by Souza Mendes and Dutra [1]. The yielded and unyielded regions are obtained for several combinations of rheological parameters. The influence of these parameters on pressure drop through the cavity is also obtained and analyzed.
Decoupled Task- and Null-Space Dynamic Control of a Redundant Nonholonomic Mobile Manipulator
Authors: White Glenn D. , Krovi Venkat N.
Published: April 2008

Our overall goal is to develop semi-autonomous and decentralized task performance capabilities during cooperative payload transport by a fleet of wheeled mobile manipulators (WMM). Each nonholonomic WMM consists of a planar two-link manipulator mounted on top of a differentially-driven wheeled mobile base. The nonholonomic base and the significant inherent redundancy create challenges for control of end-effector motion/force outputs. Nevertheless, realizing this capability is a critical precursor to decentralized payload manipulation operations. To this end, a dynamic redundancy resolution strategy is critical in order to control the dynamic interactions. The system dynamics are decomposed into a task space component (consisting of end-effector motions/forces) and a decoupled dynamically-consistent null-space part (of internal-motions/forces). A task-space controller is developed that allows each WMM module to be able to control its end-effector (motions/forces) interactions with respect to the payload. The surplus of actuation is then used to independently control internal-motions (of the mobile base) as long as they do not conflict with the primary goal. A variety of numerical simulations are then performed to test this capability of the end-effector and mobile base to independently track complex motion/force trajectories.
Eulerian Multi-Fluid Model of Air Blast Atomization
Authors: Bhamidipati Srimani , Panchagnula Mahesh , Peddieson John
Published: April 2008

The application of fully Eulerian "multi-fluid" models to air blast atomization is discussed. Such models envision the system as consisting one carrier fluid phase and multiple drop phases, each having a discrete size. A model problem is formulated which allows a general closed form solution in terms of recurrence relations. This closed form solution is employed to produce representative results. A selection of these is used to illustrate interesting aspects of the predictions.
Improving Student Design Skills Through Successive Design and Build Projects
Authors: Choate Rober , Schmaltz Kevin
Published: April 2008

Mechanical Engineering students at Western Kentucky University (WKU) are given instruction and must demonstrate their abilities to execute design projects during each of their four years of study. The features and goals of these projects are governed by a Professional Plan, which assures that graduates of the program have experienced key areas of the engineering profession and shown the ability to perform in an acceptable professional manner. The Engineering Design component of the Professional Plan is the focal point of the professional experiences. For students to be able to execute a structured approach to solving problems with an appreciation for the art of engineering, they must experience meaningful projects that expand and challenge their capabilities. WKU ME freshmen individually create physical devices with little engineering science, developing a sense of the manufacturing skills required for realistic designs. Sophomore students execute a team design project with more technical expectations, and also individually complete a design and build project that continues from their freshman project. As juniors, the team design experience is extended to an external audience with greater technical rigor, and additionally student teams implement the ASME Student Design Competition (ASME SDC) as their design and build project. The goal is for seniors to be prepared to implement an industry-based design and build project subject to realistic constraints and customer needs. The implementation of the Engineering Design Component has evolved over the past four years guided by ongoing assessment of both course outcomes and program outcomes, internal and external evaluations of the design project outcomes, and the maturing status of the program facilities and curriculum. One strength of the Professional Plan framework is the ability to build upon previous coursework, assess student progress, and adjust course activities based on prior assessment results to assure that graduates are capable of practicing as engineers. This paper will detail a sustainable model for implementing the design process across the curriculum, with the basis for selecting projects, managing the efforts of student teams, and providing effective feedback. In addition to the engineering design component, the use of professional communications and professional tools are also structured within the design projects.
Tuning Criterion of Variable Piezoelectric Circuitry for Frequency-Shift-Based Damage Identification Enhancement
Authors: Jiang L. J. , Tang J. , Wang K. W.
Published: April 2008

A new concept of using piezoelectric transducer circuitry with tunable inductance to enhance the performance of frequency-shift-based damage identification method has been recently proposed. While previous work has shown that the frequency-shift information used for damage identification can be significantly enriched by tuning the inductance in the piezoelectric circuitry, a fundamental issue of this approach, namely, how to tune the inductance to best enhance the damage identification performance, has not been addressed. Therefore, this research aims at advancing the state-of-the-art of such a technology by proposing guidelines to form favorable inductance tuning such that the enriched frequency measurement data can effectively capture the damage effect. Our analysis shows that when the inductance is tuned to accomplish eigenvalue curve veering, the change of system eigenvalues induced by structural damage will vary significantly with respect to the change of inductance. Under such curve veering, one may obtain a series of frequency-shift data with different sensitivity relations to the damage, and thus the damage characteristics can be captured more effectively and completely. When multiple tunable piezoelectric transducer circuitries are integrated with the mechanical structure, multiple eigenvalue curve veering can be simultaneously accomplished between desired pairs of system eigenvalues. An optimization scheme aiming at achieving desired set of eigenvalue curve veering is formulated to find the critical inductance values that can be used to form the favorable inductance tuning for multiple piezoelectric circuitries. In the numerical analyses of damage identification, an iterative second-order perturbation-based algorithm is used to identify damages in beam and plate structures. Numerical results show that the performance of damage identification is significantly affected by the selection of inductance tuning, and only when the favorable inductance tuning is used, the locations and severities of structural damages can be accurately identified.
Aircraft Flight Control Using Nonlinear Adaptive Backstepping
Authors: Zou Yunfei , Pagilla Prabhakar
Published: April 2008

The aircraft flight control problem is addressed via a nonlinear adaptive backstepping control. A reconfigurable flight controller is designed that achieves robust, high accuracy command angle tracking in spite of uncertain aerodynamic coefficients. The backstepping controller makes use of a recursive procedure that breaks down the control problem for the full system into a sequence of designs for lower order systems. The angular rates of the aircraft are considered as virtual inputs for slow dynamics, which includes velocity roll angle, angle of attack and sideslip angle, to track the given commands. It is assumed that the aerodynamic coefficients include uncertainties, and a gradient projection algorithm is used in an adaptive controller to estimate the uncertain aerodynamic coefficients. Stability of the proposed adaptive backstepping controller is shown and discussed. Finally, these results are applied to a nonlinear six-degree-of-freedom aircraft model. Simulation results are presented to demonstrate that the stability and high accuracy tracking performance is accomplishedin spite of uncertainties in the model.
Adhesive Strength Characterization of CYTOP™: Low Temperature Wafer-Level Packaging
Authors: Patil Vikram , O'Neal Chad B.
Published: April 2008

This study describes a wafer bonding technique using CYTOP™ inking method for the high volume packaging of micro-electro mechanical system (MEMS) devices. CYTOP™ is a class of perfluoro (alkenyl vinyl ether) polymer which is obtained by cyclopolymerization of perfluoro. The CYTOP™ adhesive bonding requires much lower temperature (150 to 200° C) compared to other bonding techniques such as soldering (> 250° C) or anodic (~350° C) bonding. The lower temperatures involved in the process reduce the risk of thermal damage to temperature sensitive devices during packaging. The described bonding process consists of a wet inking technique in which wet CYTOP™ ink is applied on soft cured CYTOP™ before bonding. In this study, CYTOP™ is characterized for its bonding strength and quality. The experiments are performed on silicon and glass wafer substrates. The bonded samples are pull-tested and tensile stress values are recorded at the instance of bond failure. About 90% of the samples failed at the bonding interface which indicates that the recorded stress values are the bond strength of CYTOP™. The bond strength of CYTOP™ depends upon the curing temperature and the curing time. The highest bond strength of 16. 46 MPa is recorded at 200° C and 45 min. of curing. The CYTOP™ bond strength at 200° C is comparable with bond strength of BCB at 250° C.
Incorporated Flow Patterns Into a Model of Two-Phase Heterogeneous Mixture Flow in Microchannels
Authors: Keska Jerry K.
Published: April 2008

In the two-phase or multiphase flow of such heterogeneous mixture like gas-liquid many more independent parameters are involved, thereby making this process more complicated and less transparent for understanding, mathematical modeling and simulating or calculating of such parameter like the length pressure gradient. In two-phase flow, there is a very complicated and random phenomenon of flow patterns, which needs to be quantitatively and accurately incorporated. Unfortunately, nowadays, a method of how to measure flow patterns is not available. And, also there is a need for mathematical models with quantitatively incorporated flow patterns in full range of flow. It is understandable that in all such cases any reasonable attempt to define and incorporate quantitatively this phenomenon in mathematical model will be beneficial. Recognizing these challenges this paper will present an approach to incorporate flow pattern phenomenon into the two-phase flow model by (1) developing a mathematical model for pressure losses in two-phase flow based on in-situ parameters, (2) developing and defining a flow pattern coefficient, which incorporates the flow pattern phenomena, and (3) present the developed mathematical model with the incorporation of flow patterns, which demonstrated significant increase of accuracy of calculations based on conducted experimental research on air-water twophase mixture flow in a horizontal square microchannel.