bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of Viscoelastic Channel Flow
Authors: Ashrafi Nariman
Published: May 2009

The nonlinear stability and bifurcation of the one-dimensional channel (Poiseuille) flow is examined for a Johnson-Segalman fluid. The velocity and stress are represented by orthonormal functions in the transverse direction to the flow. The flow field is obtained from the conservation and constitutive equations using the Galerkin projection method. Both inertia and normal stress effects are included. The stability picture is dramatically influenced by the viscosity ratio. The range of shear rate or Weissenberg number for which the base flow is unstable increases from zero as the fluid deviates from the Newtonian limit as decreases. Typically, two turning points are observed near the critical Weissenberg numbers. The transient response is heavily influenced by the level of inertia. It is found that the flow responds oscillatorily. When the Reynolds number is small, and monotonically at large Reynolds number when elastic effects are dominated by inertia.
Wheel Wear Mechanisms in Rotary Ultrasonic Machining of Titanium
Authors: Churi N. J. , Pei Z. J. , Treadwell C.
Published: May 2009

Many experiments have been conducted to study various types of outputs (such as material removal rate, material removal mechanisms, cutting force, surface roughness, wheel wear, and edge chipping) while rotary ultrasonic machining (RUM) of different workpiece materials. However, literature review has revealed that there is no reported study on wheel wear while RUM of titanium alloys. This paper reports experimental investigations on the wheel wear mechanisms in RUM of a titanium alloy. The types of wheel wear mechanisms observed include: attritious wear, grain pullout, diamond grain cracking and fracture, metal bond cracking and fracture.
Discrete-Time Closed-Loop Model Identification of Fixed-Structure Unstable Multivariable Systems
Authors: Shakir Huzefa , Kim Won-Jong
Published: May 2009

This paper presents improved empirical representations of a general class of open-loop unstable systems using closed-loop system identification. A multi-axis magnetic-levitation (maglev) nanopositioning system with an extended translational travel range is used as a test bed to verify the closed-loop system-identification method proposed in this paper. A closed-loop identification technique employing the Box-Jenkins (BJ) method and a known controller structure is developed for model identification and validation. Direct and coupling transfer functions (TFs) are then derived from the experimental input-output time sequences and the knowledge of controller dynamics. A persistently excited signal with a frequency range of [0, 2500] Hz is used as a reference input. An order-reduction algorithm is applied to obtain TFs with predefined orders, which give a close match in the frequency range of interest without missing any significant plant dynamics. The entire analysis is performed in the discrete-time domain in order to avoid any errors due to continuous-to-discrete-time conversion and vice versa. Continuous-time TFs are used only for order-reduction and performance analysis of the identified plant TFs. Experimental results in the time as well as frequency domains verified the accuracy of the plant TFs and demonstrated the effectiveness of the closed-loop identification and order-reduction methods.
Computational Noise Prediction of a Centrifugal Fan
Authors: Sorguven Esra , Dogan Yilmaz , Bayraktar Faruk , Arslan Ergin
Published: May 2009

In this study, computational aeroacoustics methods are employed to analyze the flow and the noise emission in a centrifugal fan. Unsteady flow inside the centrifugal fan is predicted with large eddy simulation. Acoustic sources are computed based on the results of the time-dependent flow simulation. The turbulent pressure fluctuations on the blades and on the volute of the fan are used as the source terms in the acoustic analogy of Ffowcs Williams and Hawkings. Propagation, diffraction and scattering of the acoustic sources inside the volute are computed with the boundary element method. Numerically obtained sound pressure level distribution in narrow band frequency spectrum is compared with experimental measurements at certain microphone points. The numerical and experimental sound intensity maps are also compared to validate the numerical prediction of directivity. Computational results agree well with the experimental data and provide an insight of the noise emission mechanisms.
Agent Based Soft Computing Approach for Component Fault Detection and Isolation of CNC X-Axis Drive System
Authors: Sotudeh Chafi M. , Akbarzadeh-T. M.-R. , Moavenian M. , Ziejewski M.
Published: May 2009

A novel agent based soft computing approach is proposed for fault detection and isolation (FDI) systems for industrial plants, in particular a highly nonlinear CNC X-axis drive system’s component fault detection. The fuzzy-neuro architecture utilizes fuzzy clustering to build a nominal model, several fuzzy agents with local expertise, a fuzzy moderator for estimation of fault location, and finally several neuro-based (RBF) agents to estimate fault size. To illustrate the merits of the proposed method, it is applied to diagnosis of component faults of a CNC X-axis drive system amid significant noise levels. Simulation results demonstrate that the resulting FDI system is able to properly locate the fault types under all test conditions, and is sensitive to faults sizes as small as 0.5%.
Dependent Scattering of Acoustic Phonons From Particles Embedded in an Anisotropic Medium
Authors: Zuckerman Neil , Lukes Jennifer R.
Published: May 2009

Dependent scattering of acoustic phonons by multiple nanometer-scale inclusions in anisotropic media is investigated using a new molecular dynamics simulation technique. The spectral-directional characteristics of the scattering are found by calculation of three-dimensional scattering phase functions and cross sections for inclusions of varying sizes in various spatial arrangements. The technique enables computation of the effects of reflected wave interference and sequential scattering, mode conversion, lattice strain, elastic anisotropy, and atomic-scale granularity on acoustic phonon scattering from structured inclusions. The results will improve understanding and prediction of heat transfer in quantum-dot superlattices and other engineered thermal materials with nanometer-scale structures.
Acoustic Bloch Oscillations and Zener Effect in One-Dimensional Sonic Crystals
Authors: Sa´nchez-Dehesa Jose´ , Sanchis-Alepuz He`lios
Published: May 2009

We report the acoustic analogue of electronic Bloch oscillations and Zener tunneling in sonic crystals. First, an analytic theory of acoustic Bloch oscillations is presented for the simple case of a sound waves propagating along the normal of a multilayer made of any two different solid or fluids materials. The formulation is applied to the case of water cavities surrounded by Plexiglas layers. Transfer matrix calculations confirm the validity of the model by assuming that the longitudinal impinging vibration is perpendicular to the surfaces of the layers. An experimental demonstration of the predictions is performed by using a very simple experimental setup consisting of two transducers and a signal analyzer. While the Bloch oscillations can be used as signal modulator, the Zener effect can be applied as a resonant filter.
Integrating Wind Turbine Generators (WTG’s) With GT-CAES (Compressed Air Energy Storage) Stabilizes Power Delivery With the Inherent Benefits of Bulk Energy Storage
Authors: van der Linden Septimus
Published: May 2009

The installed capacity of WTG’s in the US and worldwide, while impressive, suffers from a low capacity factor of 30% or less due to the variability of wind as the motive force. Installing larger wind farms to cover the deficiency of capacity results in high costs per delivered kW/hr. This begs for continued tax incentives to deliver “green” energy to the consumers. The full capability of the WTG is never realized as, at high wind speeds, some of the wind energy has to be “spilled” to maintain a smooth delivery profile. Technology improvements have not overcome the “wasted” capacity of these modern marvels except where Hydro or Pumped Hydro Storage (PHS) facilities are utilized. The Hydro power station can compensate for wind variability while PHS provides energy storage and delivers power during high demand periods. Wind Energy Storage results in a much higher capacity factor, in effect reducing the cost of delivered kW/hrs. The problem with this excellent solution is that the USA or the worldwide installation of WTG’s do not have such facilities readily available, are expensive to construct and difficult to permit in the USA. A readily available, cost effective alternative bulk-energy storage technology is ready for deployment throughout most of the continental USA. The GT-CAES concept incorporates a standard production GT with CAES technology and so covers a wide range of power production that can be matched to specific storage sites. During excess wind power production or nighttime wind, this power is used to drive air compressors to pump up or pressurize storage facilities such as salt caverns, deep aquifers (depleted natural gas wells). The stored compressed air is released to an air expander to recover the stored energy. The air to the expansion turbine is pre-heated to 950 to 1050 oF using the Gas Turbine exhaust energy recovered in a Recuperator (HRU). The low exhaust emissions are reduced further with SCR in the HRU. This paper will examine the early operating CAES concepts vs. the GT-CAES approach and will consider the economics of wind integration for lower costs of electric generation. Wind as a renewable resource would be able to deliver a larger percentage of “green” capacity with the ancillary power benefits of CAES such as Voltage Regulation, load following, spinning reserve, etc., not a feature of WTG’s. The patented GT-CAES system is described with examples of small and large installations using proposed projects with integration of Wind Energy.
A Comparison of Chiral Nematic and Cholesteric Thermochromic Liquid Crystals for Use in a Light Transmission Based Temperature Sensing System
Authors: Pasquerella Dean A. , Anderson Ann M.
Published: May 2009

This paper presents the results of a study performed to examine the effectiveness of several different formulations of thermochromic liquid crystal (TLC) material for use in a light transmission based temperature measurement system. We report on experiments performed on six different types of TLC material. We used a spectrophotometer to measure the percent of light transmitted through a layer of each TLC material for wavelengths from 400 to 700 nm as a function of temperature. We also applied TLC material directly onto electroluminescent lights and used a CCD camera to look at the intensity of red, green, and blue light transmitted through each layer as a function of temperature. We found that pure unsealed materials, both cholesteric and chiral nematic (non-sterol), are not suited for use in a temperature measurement system. They show little response to temperature and are difficult to work with due to their low melting point. On the other hand, the micro-encapsulated TLC slurry materials showed a large responsive range and were easier to work with than the pure materials. The chiral nematic material showed the largest sensitivity to temperature and was found to be more responsive than the cholesteric material.
Probing Student Understanding of Basic Concepts and Principles in Introductory Engineering Thermodynamics
Authors: Kautz Christian H. , Schmitz Gerhard
Published: May 2009

We report on an ongoing research study on student understanding of thermodynamic concepts and principles in the context of an introductory engineering thermodynamics course at Hamburg University of Technology (TUHH). Through analysis of student responses to mostly qualitative questions, we have identified prevalent and persistent difficulties. In this paper, we describe the research methods, present some preliminary results, and discuss the implications of our work for instruction and the development of curricular materials. We also illustrate the use of interactive lecture questions as an instructional tool. In recent decades, research on student understanding in science and engineering has revealed that traditional quantitative problems often are not a suitable tool for the assessment of conceptual understanding. On the basis of results from prior investigations in the context of thermal physics we have therefore begun to administer “conceptual” questions to students of engineering thermodynamics. These questions are delivered through ungraded quizzes, course examinations, and as interactive lecture questions (ILQs or “clicker questions”) via a classroom communication system. While only the two written formats require students to explain the reasoning supporting their answers, we have found that there is good agreement between the results obtained through different methods. Our work so far has concentrated on probing student understanding of (1) work and the application of the first law to closed systems and flow processes, (2) the distinction between state and process quantities, in particular student understanding of entropy as a state function, and (3) the application of the second law, especially to refrigeration cycles. Conceptual difficulties that we have observed include, for example, the students’ tendency to associate an increase in entropy of the system with any irreversible process even if the state function property of the entropy leads to a different result. Similar difficulties have been documented in the context of introductory and upper-level physics courses. While ILQs serve as a research instrument, we also recognize their potential as an effective instructional tool. Data from post-tests suggest that the use of such questions can enhance student learning in traditional lectures. In addition, we discuss how results from this study contributed to the writing of a textbook on engineering thermodynamics.
On-Line Monitoring of Fluid Effective Bulk Modulus Using Piezoelectric Transducer Impedance
Authors: Kim Gi-Woo , Wang K. W.
Published: May 2009

The fluid effective bulk modulus plays a significant role in hydraulic control systems due to its effect on the system response time and performance. In general, the fluid effective bulk modulus is a function of the amount of entrapped air, pressure, and temperature variations. Therefore, it has been recognized that monitoring of the effective bulk modulus is essential for the control of hydraulic actuation system. Measuring of the effective bulk modulus is a very challenging task. Current methods normally require precision testing equipments. Furthermore, the required equipment usually consists of many complex components that will affect the bulk modulus. Their size is in general large and thus makes on-line measurement impractical. In this research, we develop a new on-line effective bulk modulus measuring technique based upon the impedance of piezoelectric transducers. Using the piezoelectric impedance equation, numerical simulation for predicting the peak resonance frequency is performed to identify its dependency on the variation of the fluid bulk modulus. In order to verify the results, the effective bulk modulus of an ATF (automatic transmission fluid) is examined experimentally. The proposed method and the conventional method are also compared. The experimental results show the validity of the proposed method.
MIMO H∞ Control of a Parallel Kinematic XYZ Nano-Positioner
Authors: Dong Jingyan , Salapaka Srinivasa M. , Ferreira Placid M.
Published: May 2009

This paper presents the design, model identification and control of a parallel-kinematics XYZ nano positioning stage for general nano-manipulation and nano-manufacturing applications. The stage features a low degree of freedom monolithic parallel kinematic mechanism with flexure joints. The stage is driven by piezoelectric actuators and its displacement is detected by capacitance gauges. The control loop is closed at the end-effector instead of the each joint, so as to avoid calibration difficulties and guarantee high positioning accuracy. Instead of a single input and single output (SISO) system with joint space control configuration, this design has strongly coupled dynamics with each actuator input producing along multiple axes. The nano-positioner is modeled as a multiple input and multiple output (MIMO) system, where the control design forms an important constituent that accounts for the strongly coupled dynamics. The dynamics that model the MIMO plant is identified by time-domain identification method. A pseudo-random binary signal is used to excite the system while avoiding violent vibrations at resonant frequencies, which comes from the low damping feature of flexure based structure. The order of the model is reduced to make controller efficient and implementable. The control design based on modern robust control theory that gives a high bandwidth closed loop nanopositioning system which is robust to physical model uncertainties arising from flexure-based mechanisms is presented. The nonlinear effects from piezoelectric actuators, such as hysteresis and creep, are compensated effectively by closed loop robust controller. The bandwidth, resolution and repeatability are characterized experimentally, which demonstrate the effectiveness of the robust control approach.
Femtosecond Laser One-Step Microfabrication of Optical Fiber Inline Square Resonators for Chemical Sensing
Authors: Han Yukun , Wu Songping , Chitturi Bala P. B. , Tsai Hai-Lung , Wei Tao , Montoya John , Xiao Hai
Published: May 2009

We report, for the first time, the effort to one-step micromachine an optical fiber inline square resonator by femtosecond (fs) laser ablations. Such an inline square resonator is intended for infield chemical and biological sensing applications. Our preliminary data shows the feasibility of directly machining three dimensional microstructures on a silica optical fiber with a diameter of 125μm. The observed low quality (Q) factor can be further improved by post annealing and chemical etching processes that smooth the surface roughness.
Parametric Instability of a Traveling Plate Partially Supported by a Laterally-Moving Foundation
Authors: Kartik V. , Wickert J. A.
Published: May 2009

The parametric excitation of an axially-moving plate is examined in an application where a partial foundation moves in the plane of the plate and in a direction orthogonal to the plate’s transport. The stability of the plate’s out-of-plane vibration is of interest in a magnetic tape data storage application where the read/write head is substantially narrower than the tape’s width, and is repositioned during track following maneuvers. In this case, the model’s equation of motion has time-dependent coefficients, and vibration is excited both parametrically and by direct forcing. The parametric instability of out-of-plane vibration is analyzed by using the Floquet theory for finite values of the foundation’s range of motion. For a relatively soft foundation, vibration is excited preferentially at the primary resonance of the plate’s fundamental torsional mode. As the foundation’s stiffness increases, multiple primary and combination resonances occur, and they dominate the plate’s stability; small islands, however, do exist within unstable zones of the frequency-amplitude parameter space for which vibration is marginally stable. The plate’s and foundation’s geometry, the foundation’s stiffness, and the excitation’s amplitude and frequency can be selected in order to reduce undesirable vibration that occurs along the plate’s free edge.
Integrated Direct/Indirect Adaptive Robust Control of Multi-DOF Hydraulic Robotic Arms
Authors: Mohanty Amit , Yao Bin
Published: May 2009

In a general DIARC framework [13], the emphasis is always on the guaranteed transient performance and accurate trajectory tracking in the presence of uncertain nonlinearity and parametric uncertainties along with accurate parameter estimation for secondary purpose such as system health monitoring and prognosis. Need for accurate parameter estimation calls for the use of Least Square Estimation (LSE) type of algorithms for such a seamless integration of good tracking performance and accurate parameter estimation. This paper presents a physical model based integrated direct/indirect adaptive robust control (DIARC) strategy for a hydraulically actuated 3-DOF robotic arm. To avoid the need of acceleration feedback for DIARC back-stepping design, the property, that the adjoint matrix and the determinant of the inertial matrix could be linearly parameterized by certain suitably selected parameters is utilized. Unlike gradient-type parameter estimation law, which used overparamterization, there is no multiple estimation of the single parameter. Theoretically, the resulting controller is able to take into account not only the effect of parametric uncertainties coming from the payload and various hydraulic parameters but also the effect of uncertain nonlinearities. Furthermore, the proposed DIARC controller guarantees a prescribed output tracking transient performance and final tracking accuracy while achieving asymptotic output tracking in the presence of parametric uncertainties only. Simulation results based on a three degree-of-freedom (DOF) hydraulic robot arm (a scaled down version of an industrial back-hoe/excavator arm) are presented to illustrate the proposed control algorithm.
Separate Measurement of Current Density Under the Channel and the Shoulder in PEM Fuel Cells
Authors: Wang Lin , Liu Hongtan
Published: May 2009

In a proton exchange membrane (PEM) fuel cell current density under the shoulder can be very different from that under the gas channel and the knowledge of where the current density is higher is critical in flow field designs in order to optimize cell performance. Yet, up to date this issue has not been resolved. In this study, a novel yet simple approach was adopted to directly measure the current densities under the channel and the shoulder in PEM fuel cells separately. In this approach, the cathode catalyst layer was so designed that either the area under the shoulder or the area under the channel was loaded with catalyst. Such a design guaranteed the currents generated under the shoulder and the channel could be measured separately. Experimental results showed that the current density produced under the channel was lower than that under the shoulder except in the high current density region. To determine whether the lateral electrical resistance of the gas diffusion layer (GDL) was the causes for lower current density under the channel, an additional set of experiments were conducted. In this set of experiments, a silver mesh was added on the top of the gas diffusion layer (GDL) and the experimental results showed that GDL lateral electrical resistance was not the cause and it had a negligible effect on lateral current density distribution.
Fostering Undergraduate Research Through Collaboration With Local Engineering Companies
Authors: Schonning Alexandra , Cox Daniel
Published: May 2009

This paper discusses the importance of introducing the undergraduate engineering student to research; it provides examples on how research has been integrated with the curriculum, and how the local engineering industry provides engineering research projects for the students. One research project includes the development of a test fixture to be used in determining the pull-out strength of screws in a biomaterials substrate. Another example presented is the development of a test configuration for determining the under water impact resistance of acoustic windows. Furthermore, a research project will be presented on the creation, testing and analysis of bone cement specimens. Through these projects students learn valuable skills such as performing literature review of a technical topic, developing a statement of work, establishing a research plan, learning appropriate software and hardware tools, carefully documenting their work, analyzing results, writing papers, and presenting their work at conferences. This paper provides details on how these skills are developed through the students’ research experiences and how they will benefit the students upon graduation. In order to expose a large number of undergraduate students to research it is helpful to develop some form of a mentoring program where students learn from each other. The paper describes how this mentoring program is organized and provides details of how the students interact with their peers, the faculty members and representatives from the local industry.
Aerodynamic Flutter and Flight Surface Actuation
Authors: Gadsden S. A. , Habibi S.
Published: May 2009

This paper proposes a novel form of impedance control in order to reduce the effects of aerodynamic flutter on a flight surface actuator. The forces generated by small amplitude flutter were studied on an electrohydrostatic actuator (EHA). The effects of flutter were modeled and analyzed. Through analysis, it was found that in EHA systems, two parameters would impact the response of flutter: damping (B) of the mechanical load, and the effective bulk modulus of the hydraulic oil (βe). These can be actively controlled as proposed here in order to provide variable impedance. The results of changing these variables are discussed and presented here.
Trajectory Following of a Micro Motion Stage Based on Closed-Loop FEM Simulation
Authors: Shahidi A. , Mahboobi S. H. , Pirouzpanah S. , Esteki H. , Sarkar S.
Published: May 2009

Micro motion stages are one of the essential components in field of micro robotics and ultra fine positioning systems. This research presents the optimum design of a 3-DOF micro motion stage and its position control using FEM simulation. This stage to be studied uses a 3 RRR flexure hinge base compliant mechanism driven by three piezoelectric stack actuators to provide micro scale planar motion. First of all parametric modeling of the stage will be fulfilled in ANSYS environment utilizing a commercial piezostack and different types of flexure hinges. Hence the Jacobian matrix will be achieved for each case. The optimum selection of the hinge form will be achieved upon results of the previous phase. Finally embedded closed-loop FEM approach in ANSYS programming will be used to follow a specified trajectory. Hereby, flexibilities of mechanism and piezoelectric actuator behavior will be modeled with more reliability than any other analytical approach.
Experimental Chatter Modeling of Milling Operations
Authors: Catania Giuseppe , Mancinelli Nicolo`
Published: May 2009

This study refers to the investigation on the critical operating condition occurring on high productivity milling machines, known as chatter. This phenomenon is generated by a self-excited vibration, associated with a loss of stability of the system, causing reduced productivity, poor surface finish and noise. This study consists of the theoretical and experimental modeling of machining chatter conditions, in order to develop a real-time monitoring system able to diagnose the occurrence of chatter in advance and to dynamically modify the cutting parameters for process optimization. A prototype NC 3-axis milling machine was ad hoc realized to accomplish this task. The machine was instrumented by a dynamometer table, and a series of accelerometer sensors were mounted in the proximity of the tool spindle and the workpiece. An analytical model was developed, taking into account the periodic cutting force arising during interrupted cutting operation in milling. The system dynamical behavior was described by means of a set of delay differential equations with periodic coefficients. The stability of this system was analyzed by the semi discretization approach based on the Floquet theory. Lobe stability charts were evaluated and associated with frequency diagrams. Two chatter types were analytically and experimentally detected: period-doubling bifurcations and secondary Hopf bifurcations. Measurement data were acquired and analyzed in the time and frequency domain. Several tests were conducted in a wide range of operating conditions, such as radial immersion, depth of cut and spindle speeds and using different tools. Results are reported showing agreement between the numerical analysis and the related experimental tests.
A Hybrid LP/FE Model for the Dynamic Analysis of External Gear Pumps
Authors: Mucchi Emiliano , Venturi Valerio , Dalpiaz Giorgio
Published: May 2009

In this work a hybrid lumped-parameter finite-element model of an external gear pump for automotive applications is presented and experimentally assessed; the finite element (FE) model regards the external parts of the pump (case and end plates) while the lumped-parameter (LP) model regards the interior parts (bushes and gears). The LP model is a non linear kineto-elastodynamic model and includes the most important phenomena involved in the pump operation as time-varying oil pressure distribution on gears, time-varying meshing stiffness and hydrodynamic journal bearing reactions. A forced vibration analysis has been carried out by means of the FE model for the evaluation of the acceleration levels on the external surfaces of the pump; for this analysis, the damping has been estimated using data coming from an experimental modal analysis (EMA) whereas the excitation forces, acting on the internal surface of the case due to bearing reactions and pressure forces, have been obtained from the LP model. In this sense the model is globally a hybrid LP/FE model. The model has been assessed using experiments: the experimental accelerations measured during run-up tests have been compared with the simulated accelerations coming from the FE/LP model. Finally the assessed model has been used in order to identify the effects of design parameters in terms of case vibrations.
On the Vector-Valued Cauchy Stress 2-Form and Its Stress Rate
Authors: Murakami H.
Published: May 2009

Using exterior differential forms, basic equations of continuum mechanics are presented in direct notation. To this end, Elie Cartan’s vector-valued Cauchy stress 2-form is introduced. Its Lie derivative along the world line becomes the Truesdell stress rate. In the presentation, the notation adopted by Theodore Frankel (The Geometry of Physics, Cambridge, New York, 1997) is utilized. With the use of exterior differential forms, complicated computations in tensor analyses in curvilinear coordinates are dramatically simplified. As specific examples, the following subjects are presented: (i) Piola transformations of the Cauchy stress 2-form and (ii) simple shear deformation using the Lie derivative of the Cauchy stress 2-form, i.e., the Truesdell stress rate. It is known that under monotonic shear loading, if inappropriate stress-rates are used, shear stress oscillates. With the use of geometrically correct stress-rate, the shear stress monotonically increases. Thereby, the search for an appropriate stress rate reduces to the correct definition of the stress 2-form and the computation of its Lie derivative with respect to velocity.
An Experimental Investigation of the Auto-Ignition Properties of Two C5 Esters: Methyl Butanoate and Butyl Methanoate
Authors: Walton Stephen M. , Perez Carlos , Wooldridge Margaret S.
Published: May 2009

Ignition studies of two small esters were performed using a rapid compression facility (RCF). The esters (methyl butanoate and butyl methanoate) were chosen to have matching molecular weights, and C:H:O ratios, while varying the lengths of the constituent alkyl chains. The effect of functional group size on ignition delay time was investigated using pressure time-histories and high speed digital imaging. The mixtures studied covered a range of conditions relevant to oxygenated fuels and fuel additives, including bio-derived fuels. Low temperature and moderate pressure conditions were selected for study due to their relevance to advanced low temperature combustion strategies, and internal combustion engine conditions. The results are discussed in terms of the reaction pathways affecting the ignition properties.
Characterization of Thermal Properties and Heat Transfer Behavior of Microencapsulated Phase Change Material Slurry and Multiwall Carbon Nanotubes in Aqueous Suspension
Authors: Alvarado Jorge L. , Marsh Charles , Thies Curt , Soriano Guillermo , Garg Paritosh
Published: May 2009

In the last decade, microencapsulated phase change material (MPCM) slurries have been proposed and studied as novel coolants for heat transfer applications. Such applications include electronics cooling, and secondary coolants in air conditioning systems among others. Experiments have shown that MPCM’s increase the overall thermal capacity of thermal systems by taking advantage of the phase change material’s latent heat of fusion. However, research has also shown that the overall heat transfer coefficient is diminished due to a reduction in the effective thermal conductivity and increased viscosity of the slurry. For this reason, there is an urgent need to modify the content of microcapsules containing phase change material to increase their effective thermal conductivity and the overall heat transport process. Our solution consists of increasing the thermal conductivity of MPCM by adding carbon nanotubes to the shell and core of the microcapsules. Carbon nanotubes have shown to increase the thermal conductivity of liquids by 40% or more in recent experiments. In this paper, MPCM slurry containing octadecane as phase change material and multi-wall carbon nanotubes (MWCNTs) embedded in the capsule material and core are compared with pure water as heat transfer fluid. Thermal and physical properties of MPCM slurry containing carbon nanotubes were determined using a differential scanning calorimeter and concentric viscometer, respectively. Experimental convective heat transfer coefficient data for MWCNT aqueous suspensions under laminar flow and constant heat flux were determined using a bench-top heat transfer loop. Experimental heat transfer results are presented.
A Study of the Nusselt-Rayleigh and Sherwood-Rayleigh Number Relations for Water Undergoing Free-Surface Natural Convection
Authors: Bower S. M. , Saylor J. R.
Published: May 2009

An experimental study is presented of the Nusselt-Rayleigh and Sherwood-Rayleigh number relations for water undergoing free-surface natural convection, which is natural convection beneath an air/water interface. The focus of this work is on the Nu-Ra relationship. This relationship is typically studied using the traditional Rayleigh-Be´nard convection experiment where a fluid layer is bounded above and below by solid plates of different, but constant, temperatures. Hence, the boundary conditions are of the no-slip, constant-temperature type. Power laws are typically used in these studies to correlate the Nu-Ra data, and existing studies have given power law exponents that are usually close to 1/3. The experimental data obtained in this study yields a power law relation of the form: Nu=(0.0016)Ra0.328(1) for 107 < Ra < 1011. This result is surprising in that the effect of the free-surface boundary condition on the power law exponent is quite small when compared to the solid plate case. However, the prefactor in Eq. (1) is significantly smaller than for the solid plate case. The Sh-Ra data obtained in this study are also fit to a power law, giving: Sh=(0.0019)Ra0.329(2) where Sh is the dimensionless mass transfer coefficient for evaporation. The exponent of this power law differs from that which has been observed by prior researchers. However, the prior research on evaporation that utilizes this form for scaling the data is considerably smaller than for the heat transfer case. Possible explanations for the observed behavior are presented.
Warpage Prediction of Ball Grid Array Packaging
Authors: Kim Yeong K. , Peak Russell , Zwemer Dirk
Published: May 2009

The effect of material property modeling on the warpage calculation is studied in this paper. A chip level packaging of ball grid array was considered for the simulation model. The mechanical properties of thin FR-4 and molding compound were modeled as elastic and viscoelastic based on the experimental data, and warpage developments during cooldown were calculated using different types of the mechanical property modeling. It was found that the viscoelastic characters of the FR-4 and the molding compound had significant influence on the warpage development. The results were compared with those of elastic cases, and discussions were given to analyze the deformation mechanism.
Vibroacoustic Analysis of the Switch Reluctance Motor
Authors: Tadayon M. A. , Ziaee Tabatabaie S. S. , Eftekharian A. A.
Published: May 2009

One of the most important types of electromechanical systems is the Switch Reluctance Motors/Machines (SRM) which is attracting considerable interest in industry. In SRM generally there are a lot of disorders and noises due to big vibratory radial loads, such as acoustic noises. In order to prevent these disturbances and decrease environmental noise pollutions, it is very necessary to study them carefully. To reach this purpose in this work first, radial loads of the SRM are investigated and then modal analysis is performed to obtain natural frequencies and mode shapes of the whole system. After that, harmonic analysis of the system is carried out and with the use of these analyses acoustic disorders of the SRM system is obtained. At the end, we investigate the effects of the variation of the end shield in these systems. The results of this work can serve as a guide to the industrial application of SRM, particularly in design of end shields (for all kind of motor with high radial force).
Linking Computer Game Engines With Remote Experiments
Authors: Aziz El-Sayed , Chang Chenghung , Arango Felipe , Esche Sven K. , Chassapis Constantin
Published: May 2009

Recently, the potential of using commercially available computer game engines to implement virtual engineering experiments (which represent pure computer simulations) has been explored by various educational institutions. Using a game engine in conjunction with a corresponding software development kit, it is possible for educators to replace the content of an existing computer game with educational content, thus creating virtual laboratory environments. The utilization of game engines for educational purposes is expected to increase the degree of immersive presence of the students engaging in such game-based laboratory exercises as well as the level of interactivity between the students. This paper will discuss the integration of a game-based virtual laboratory environment with remote experiments conducted using actual physical devices. In particular, the paper will focus on possible ways in which the data transfer between a computer game engine and an existing remote laboratory experiment can be accomplished. Strategies for the extraction of laboratory experiment data and for the conversion of data formats are discussed. Possible methods by which the laboratory experiment output data is accessed and displayed are also addressed. Some of the key questions affecting the possible process flows are if and at what point the laboratory experiment mode of interaction should switch from the game engine to the remote laboratory experiment and then switch back to the game engine, and whether or not the user should know that and when it occurred. Finally, the paper will present a sample implementation of a virtual laboratory, into which a specific remote experiment was integrated.
Modeling of Size Effects on the Flow Stress of Type 304 Stainless Steel and Application in Coining Process
Authors: Kim Gap-Yong , Koc Muammer , Ni Jun
Published: May 2009

Application of microforming in various research areas has received much attention due to the increased demand for miniature metallic parts that require mass production. For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/meso-scale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the “feature/specimen size” effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with experiments obtained from previous research and showed a very good agreement. The model was also applied to forming of micro-features by coining. A flow stress model for Type 304 stainless steel taking into consideration the effect of the grain and feature size was developed and implemented into a finite element simulation tool for an accurate numerical analysis. The scaling model offered a simple way to model the size effect down to length scales of a couple of grains and extended the use of continuum plasticity theories to micro/meso-length scales.
An Industry-Centered Capstone Experience for an Engineering Technology Program
Authors: Cote´ Mark A.
Published: May 2009

Industry-centered education has been an integral part of the educational program at Maine Maritime Academy (MMA) since the founding of the college in 1941. This has included extensive use of cooperative education as part of all MMA academic programs. Employers, graduates, and potential students describe MMA’s “hands-on” focus, reflected in these cooperative education experiences, to be one of the main advantages of an MMA education. The MMA Engineering Department decided to build on this strength as a core component of a new Power Engineering Technology (PET) Capstone experience. The Capstone experience was developed in 2003 as a two-course, nine credit hour sequence that included both individual and team projects. The courses build on previous course material, the student’s cooperative education experience, and include specific new material on project management and teamwork skills. The courses conclude with a major project where teams of students are paired with a local industrial facility. At this facility, the students work with an inhouse mentor and, using project management techniques, with faculty oversight, complete a study of a topic of interest for that facility. The teams then prepare formal written reports and presentations documenting their results. The Capstone experience has become a key feature of the PET program and continues to evolve and improve, receiving positive feedback from graduates and industry participants. This feedback, combined with other improvement efforts, is used to strengthen and improve the Capstone experience and the PET program.
Direct Assessment of Course Outcomes: Strategies and Implementations for Mechanical Engineering Courses
Authors: Zhou J. , Corder P. , Aung K.
Published: May 2009

The process of outcome assessment has become a major tool for evaluation of mechanical engineering programs as required by ABET. There are many ways to conduct assessment of course and program outcomes, but the direct assessment method is preferable to all other methods such as course grades and student surveys. Outcome assessment process of courses involves many steps: identifying the performance criteria, collecting the appropriate data, processing the data based on performance criteria, interpreting the results, and deciding the remediation or corrective actions to take. In this paper, strategies and implementations of direct assessment of course outcomes in the Department of Mechanical Engineering are described and discussed. Application and results of these direct assessments relevant to the Senior Capstone Design course in the Mechanical Engineering curricula are presented as an example. The methodology and implementation discussed in this paper may be beneficial to similar curricula at other institutions.
Adaptive Regulation in Switched Linear Systems
Authors: Wu Zhizheng , Ben Amara Foued
Published: May 2009

This paper considers an adaptive regulation problem for switched linear systems where it is desired to achieve regulation against unknown disturbance or reference signals. Switching among plant models as well as among disturbance and reference signals is defined according to a switching surface. The design of the proposed adaptive regulators involves three main steps. First, a set of observer-based Q-parameterized stabilizing controllers for the switched system is constructed. The stability properties for the resulting closed loop switched system are analyzed. Second, for each subsystem in the switched system, a set of Q-parameters needed to achieve regulation is derived by solving a set of interpolation conditions, and a sufficient regulation condition for the switched system is presented. Third, an adaptive algorithm is developed to tune the Q parameter in the expression of the parameterized controller to converge to the desired Q parameter that guarantees regulation for the switched system. Finally, a numerical example is presented to illustrate the effectiveness of the proposed method.
Supercavitating Vehicle Dynamics With Non-Cylindrical, Non-Symmetric Cavities
Authors: Nguyen Vincent , Balachandran Balakumar , Varghese Abraham N.
Published: May 2009

Dive-plane dynamics of supercavitating vehicles show highly nonlinear behavior. This is attributed to the vehicle/cavity wall interaction, and the cavity shape has been recognized to play an important role in the system dynamics. To date, supercavitating models make use of constant cylindrical cavities. In this work, a dive-plane model with non-cylindrical and nonsymmetric cavity shapes is considered. A numeric cavity model is used, the cavitator angle of attack effects are considered, and a non-steady non-cylindrical planing force model is incorporated. The resulting effects on the system dynamics and control are addressed and discussed.
Bio-Generated Greenhouse Heating Project
Authors: Schmaltz Kevin
Published: May 2009

A 30′ × 60′ greenhouse is being installed on the Western Kentucky University Agriculture Department campus farm that will be heated during winter by energy captured during the decomposition of leaves into compost. The bio-generated heat collection and distribution system was designed, and is currently being built and tested by undergraduate mechanical engineering students at WKU. Currently, the WKU Agriculture Department takes all leaves collected by the city of Bowling Green, processing and selling the resulting compost. While the leaves are composting, a temperature of over 150 °F is reached in the center of the leave piles. Student teams have designed and are installing a water piping system below the leaves to capture the waste heat and deliver the water to a root-zone heating system in the greenhouse. The design also includes a subsurface storage tank and auxiliary heating system to extend the capacity of the heating system. It is intended that WKU Agriculture will be able to operate the greenhouse for educational purposes throughout the year, and also provide the design to regional farmers who currently have greenhouses but cannot afford to heat them during Kentucky winters. This paper will detail the design of the heat collection system below the composting leaves, including sizing calculations and experimental verification, to permit uninterrupted composting activities. The root-zone heating system design will also be covered, including sizing calculations of the piping installation within sand beds in the greenhouse. The overall system control, energy storage and supplemental heating will also be discussed. The goal of the project has been to evaluate the feasibility of a cost-effective agricultural heating system for use in moderate climates throughout the United States.