bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the Geometries of Current Collectors on the Power Density in a Solid Oxide Fuel Cell
Authors: Li Peiwen , Tao Gege
Published: May 2009

An analytical model is proposed, and the analysis is conducted for solid oxide fuel cells in order to achieve higher power densities. The analytical model is designated to help designers to optimize the current collector sizes and spacing, and also the geometrical shapes of the current collectors as well. The analytical model basically has a whole consideration about the ohmic polarization, the species concentration polarization, and the activation polarization; while the load of optimization computations and analysis is greatly alleviated for engineering designers. From the analysis of several cases, it is recommended that 3D pillars be used for the current collectors in SOFCs incorporating with appropriate measures of a uniform flow distribution. It is also clear that unless limited by the fabrication technologies for the bipolar plates, a smaller control area and current collectors are preferable to SOFCs to have higher power densities.
Reliability Design and Case Study of a Refrigerator Compressor Subjected to Repetitive Loads
Authors: Woo Seong-Woo , O’Neal Dennis L. , Kim Yongchan
Published: May 2009

A newly designed crank shaft of a compressor for a side-by-side (SBS) refrigerator was studied. Using standard mass and energy conservation balances, a variety of compressor loads typically found in a refrigeration cycle were analyzed. The laboratory failure modes and mechanisms were compressor locking and crank shaft wear. These were similar to those of the failed samples in the field. Failure analysis, accelerating life testing (ALT), and corrective action were used to identify the key reliability parameters and their level. The design parameters of the crank shaft included the hole locations and the groove of the crank shaft used for oil lubrication, crank shaft hardness, and thrust washer interference. Based on the analysis and design changes, the B1 life of the new design is now over 10 years with a yearly failure rate of 0.01 percent. A procedure was recommended for refrigerator parts design which included five steps.
Investigation of Turbulence Modeling in a High Speed Centrifugal Pump With an Inducer
Authors: Jafarzadeh Behrooz , Mokhtarpoor Reza , Alishahi Mohammad Mehdi , Akbari Mohammad Hadi
Published: May 2009

In this paper, investigation of turbulence modeling for a centrifugal pump is presented in the form of characteristic curves. A commercial CFD code was used to solve the governing equations of the flow field. Turbulent flow is simulated by employing standard k-ε, RNG and RSM models. Existence of an inducer in the flow direction to prevent cavitation makes two-dimensional simulations of the present configuration impossible. Three-dimensional simulations were therefore performed to predict velocity and pressure fields at different flow rates. Considering the only one available experimental data, the optimum turbulence model for the problem was found. Additionally, effect of number of blades on the efficiency of pump was studied. The number of blades was changed from 6 to 5 and 7, then all calculations were performed afresh. Investigations of this kind may help reduce the required experimental work for the development and design of such devices.
Multidiscipline Learning Materials for Hybrid Electric Vehicle Technology
Authors: Liao Gene Y. , Yeh Chih-Ping , Sawyer James O.
Published: May 2009

World competition and stringent United States fuel economy goals and emission regulations for the 21st Century vehicle have pressured the automotive industry to design and evaluate advanced automobiles at an accelerated rate. The industry consensus is that the Hybrid Electric Vehicle (HEV) is the currently available technology for increasing propulsion system efficiency and decreasing pollutant emissions. However, HEVs operate much differently than conventional vehicles. Therefore, existing design techniques and guidelines developed for conventional powertrains do not apply well to hybrid vehicles. There is a need for training automotive technicians and engineers as well as educating students in this new and emergent technology of HEV. This paper describes a funded project whose goal is to fill this need by developing multidiscipline learning materials for HEV technology. This project targets engineering/engineering technology students in 4-year universities, automotive technology students in community colleges, automotive engineers and technicians in industries, and technology teachers in secondary schools.
Coupled Axisymmetric and Plane Stress Finite Element Model for the Stress Analysis of an Aircraft Engine Compressor
Authors: Immaneni Dinesh , Rencis Joseph J.
Published: May 2009

A coupled finite element model is proposed that can be used to carry out a static stress analysis of rotating parts. The rotating part consists of a disk modeled with four-node axisymmetric quadrilateral elements and blades modeled with four-node quadrilateral plane stress elements. The coupled finite element model is used to carry out a stress analysis of a simple rotor and complex aircraft engine compressor. The coupled model is compared to a solid ANSYS® finite element model using the twenty noded tetrahedral element. The major advantage of the coupled model over a three-dimensional model is that an analysis can be carried out quickly in the early design stage.
Service Courses in Computing and Electronics for Mechanical Engineering Technology and Manufacturing Engineering Technology Programs
Authors: Lunt Barry M.
Published: May 2009

There are approximately 85 4-year institutions in the U.S. with programs in mechanical engineering technology accredited by TAC of ABET. There are also approximately 28 TAC of ABET-accredited 4-year programs in manufacturing engineering technology. Most of these mechanical and manufacturing engineering technology programs require their students to take at least one class in computing or electronics. The purpose of this paper is to provide a descriptive comparison of these 4-year programs in mechanical and manufacturing engineering technology, focusing on the computing and electronics requirements for their students. The details include courses, course titles, and topics covered.
A Refined Model of Viscous Coupling Between Filiform Hairs in the Cricket Cercal System
Authors: Cummins Bree , Gedeon Toma´sˇ
Published: May 2009

A model for the viscous interaction between filiform hairs on the cricket cercus was previously introduced by Cummins et al. [1]. This model simulates hair movement for a small group of arbitrarily positioned hairs stimulated by axial air flow along the cercus by calculating the perturbed boundary layer surrounding the hairs. In order to solve the perturbation calculation, Cummins et al. [1] introduce a simplification. However, this approximation introduces non-negligible error into the boundary conditions of the problem. A method of iterative refinement is presented in this paper that results in a more accurate approximation to the perturbed boundary layer. The changes to the predictions given in the previous paper are discussed.
Modeling Insect Filiform Hair Motion Using the Penalty Immersed Boundary Method
Authors: Gedeon Toma´sˇ , Heys Jeff J. , Knott B. C. , Mulder-Rosi Jonas
Published: May 2009

Many insects are able to sense their surrounding fluid environment through induced motion of their filiform hairs. The mechanism by which the insect can sense a wide range of input signals using the canopy of filiform hairs of different length and orientation is of great interest. Most of the previous filiform hair models have focused on a single, rigid hair in an idealized air field. We have developed [1] a model for a canopy of filiform hairs that are mechanically coupled to the surrounding air. The model equations are based on the penalty immersed boundary method. The key difference between the penalty immersed boundary method and the traditional immersed boundary method is the addition of forces to account for density differences between the immersed solid (the filiform hairs) and the surrounding fluid (air). In this work we validate the model by comparing the model predictions to experimental results on cricket Acheta domestica cercal system.
Improving Sound Rating of the Out Door Unit by Modifying Discharge Tube Design
Authors: Mathuria Parag H. , Me´zache Macinissa
Published: May 2009

In today competitive market, Seasonal Energy Efficiency Ratio (SEER) and sound rating of the out door unit of an air conditioning system are strong marketing and selling parameters. Air conditioning systems consist of an indoor unit and an outdoor unit. The sound of the indoor unit is mainly radiated by the blower or fan of the unit. The outdoor unit has three major components, namely, a compressor, a condenser coil and a fan. In general, the sound power levels produced by the outdoor unit are dominated by the fan, and in some cases, the fan and the compressor. In more recent designs, significant improvement has been made in the sound performance of the fan itself, resulting in a challenge to compressor manufacturers to produce quieter compressors. In this case, compressor-system interaction becomes a serious issue with reference to noise generation. The vibration energy of the compressor is transmitted to the system through the suction and discharge tubes, and the mounting feet. Air conditioning manufacturers are faced with the challenge of eliminating these sources of excitation to improve the sound rating and, more importantly, design better quality products. The main object of the paper is to modify the design of the discharge tube using an experimental iterative approach. A reduction of 2 dB has been achieved in the total sound power level of the system. On the dominant one third octave bands, sound power levels are reduced up to 7 dB. The results of this investigation will serve as the basis for the development of an analytical designed tool for air conditioning system design. These results were validated on four systems.
Non-Stationary Oscillations at Slow Transitions Across Instabilities
Authors: Pusˇenjak Rudolf R. , Oblak Maks M. , Avsec Jurij
Published: May 2009

The paper presents the study of non-stationary oscillations, which is based on extension of Lindstedt-Poincare (EL-P) method with multiple time scales for non-linear dynamical systems with cubic non-linearities. The generalization of the method is presented to discover the passage of weakly nonlinear systems through the resonance as a control or excitation parameter varies slowly across points of instabilities corresponding to the appearance of bifurcations. The method is applied to obtain non-stationary resonance curves of transition across points of instabilities during the passage through primary resonance of harmonically excited oscillators of Duffing type.
Dynamic Simulation of a Biomass-Fired Steam Power Plant: A Comparison Between Causal and A-Causal Modular Modeling
Authors: Casella F. , van Putten J. G. , Colonna P.
Published: May 2009

Dynamic simulation can play a significant role in energy conversion system design, in particular for testing the effect on the system response of different equipment choices, for control system design, operator training and safety/environmental assessment. With reference to a small biomass-fired steam power plant, this paper compares two implementations of a dynamic model of the plant: the first, based on a causal approach and implemented using the Matlab/Simulink software, the second, based on an a-causal object-oriented approach, implemented in the Modelica language and simulated with the Dymola program. The results of transient simulations are compared, and the merits of the two modeling approaches are discussed.
Capstan Design and Control for Drawing Optical Fiber: A Case Study in Mechatronics Design
Authors: Jenkins Hodge E. , Nagurka Mark L.
Published: May 2009

This paper presents a case study on the design of a draw capstan drive with feedback control for use in optical fiber manufacturing. Optical fiber is manufactured by the draw process, which involves heating and pulling high purity glass cylinders to diameters of 125 micron. Of critical concern is producing a constant diameter for the glass fiber and its lightguide core. The diameter of the optical fiber must remain constant to create a product capable of transmitting high-bandwidth optical data. The optical fiber draw capstan design has a significant impact on the resulting fiber quality. As the draw speed is used to control the fiber diameter, the ability of the draw capstan to follow velocity commands directly affects the resulting fiber diameter. In this case study a systems approach is used for the design of the mechanical and control aspects through parametric evaluations and modeling, as well as simulation studies of the capstan drive. Disturbances in the draw process arise from sources such as the variation in the diameter of the input glass cylinder and the draw tension control, affecting the glass temperature and viscosity. Simulation studies demonstrate that speed regulation, to manufacture optical fiber within allowable diameter tolerances, is achievable in the presence of representative disturbances. The capstan model and design along with the fiberdrawing process model presented in this case study are suitable for undergraduate and graduate courses in system dynamics, control, and mechatronics. As is typical of many problems in manufacturing processes, the problem discussed is multidisciplinary. The study highlights the use of mechanical and electrical modeling, system identification, and control design as necessary parts of product and process improvement.
An Innovative Approach to Creating, Developing, and Delivering a New Course Entitled Global Engineering
Authors: Zable Jack , Reamon Derek
Published: May 2009

In 2005, the Industry Advisory Council (IAC) of the Mechanical Engineering Department at the University of Colorado-Boulder (CU) began a discussion about the subject of outsourcing engineering offshore and the possibility of teaching a course to prepare mechanical engineering students for this environment. This in turn, led to the formation of a committee and a series of discussions and recommendations for the content for such a course. The ad-hoc committee comprised of a few IAC members, a few M.E. department design faculty members, and some faculty from the business school. The original course covered the following topics: engineering economics, creating product requirements and specifications, identifying the core competencies of a company, project management, developing a business plan, supply chain logistics/management, intellectual property, understanding cultural and language differences, team dynamics, communication, and creativity. This broad array of subject matter dictated that the course be taught in a non-conventional manner. A team of instructors, comprised of two mechanical engineering professors, two business school professors, three engineers and two businessmen from industry, who are intimately involved with outsourcing, and a patent attorney were assembled to teach different portions of the course. The students also participated in a hands-on outsourcing term project. The class was broken up into ten teams, with each team developing a product in conjunction with a company from India. Each team submitted a set of specifications for a unique product to the offshore company. The company designed the product and produced an approved CAD drawing. After student approval, the company manufactured a prototype of the product, and shipped it to the respective team for analysis. Each team then presented a report on their outsourcing experience, their testing results, and a financial analysis for the product. The class was comprised of mechanical engineering senior and graduate students, with a few students from other engineering disciplines and the business school. Based upon course surveys, this course was very well received by the students and provided an important introduction to business. The semester project proved to be a valuable tool for the students to obtain some direct experience with outsourcing.
Dynamic Modeling of Air Cushion Vehicles
Authors: Pollack M. , Connell B. , Wilson J. , Milewski W.
Published: May 2009

The motion of an Air Cushion Vehicle (ACV) is a complex process involving the nonlinear dynamics of the ship, free surface waves, air cushion cavity, skirt, and air flow hydraulics (e.g. orifice behavior of the bag feed holes). The overall system is tightly coupled, with the loading of the ship dependent on the pressure field within the cavity, and the dynamics of the cavity dependent on the motion of the ship, free surface, and skirt. Principle excitation to the system is through the free surface motion and the fan flow. The large dimensions of the system introduce low frequency acoustic and mechanical resonances, which lead to complex and coupled system dynamics. The focus of this paper is on analytical modeling of an ACV and its physics to enable verification of a numerical model which is under development. The initial focus is on the dynamics of the air cushion cavity, with emphasis on its resonant frequencies and mode shapes. The mode shapes are important because they define the nature of the dynamic pressure distribution acting on the ship, and associated heave, pitch, and roll excitation. The strong dependence of the cavity resonant characteristics on the impedance of the skirt, which bounds the cavity, is first demonstrated by assessing limiting cases of a high impedance skirt (e.g. massive or rigid) and of a low impedance skirt (e.g. light or soft). The changes in resonant frequency and dynamic pressure distribution associated with the changes in skirt impedance are illustrated. Because the actual skirt impedance will lie between these two idealized cases, we also develop a lumped parameter model of the skirt dynamics. Initial parametric studies with this model, which investigate variations in the skirt mass, further demonstrate the strong dependence of the resonant frequencies and pressure distributions on the skirt impedance.
Experimental Study on Thermal Performance of a Forced Air Cooled PBGA Package in the Compact Thin Casing: Effect of Obstacles Placed Inside the Casing
Authors: Ishizuka Masaru , Nakagawa Shinji , Koizumi Katsuhiro
Published: May 2009

At the PC design stage, heat flow analysis in a PC is needed. However, due to the complex printed wiring board structure, a large number of grids are required to enable precise calculation, ruling out calculations using a conventional PC. This has led to attempts to predict the temperature of an actual package by calculation based on a simplified package whose result is then modified. In this study, a compact casing and a package model are used to simulate actual notebook PCs. The performance of a diode package is experimentally obtained, and the flow inside the casing and the thermal performance of the package are studied with an obstacle placed inside the casing. This study is also conducted by aiming at acquisition of benchmark test data for CFD simulations.
Evaluation of RANS Approach in Predicting the Physics of Incompressible Turbulent Jets-Into-Crossflows
Authors: Javadi Khodyar , Taeibi-Rahni Mohammad , Darbandi Masoud
Published: May 2009

This work is conducted with evaluation of different turbulence models capabilities in predicting three dimensional jet-into-crossflow (JICF) interactions. For this purpose, first of all, comprehensive discussions on the near wall flow complexities due to discharge of a jet into a crossflow are presented. In this regards, large scale coherent structures such as: counter rotating vortex pairs (CRVP’s), near wall secondary motions, horseshoe vortices, and wall jets like are discussed. Secondly, the abilities of different turbulence models in predicting such flows (JICF) are evaluated. Our evaluation is based on three points of view including: 1) JICF characteristics, 2) computed location, and 3) sensitivity to different flow variables. In this regard, the turbulence models such as k-ε, k-ω, shear stress transport model (SST), and Reynolds stress model (RSM) are employed. Their related results are compared to credential available experimental/numerical data as well themselves. Since the same basic code with the same grid density as well as numerical discretization scheme is used, it is save to conclude that, any differences in the results are due to the abilities of turbulence models. The flow field computation was governed by Reynolds Averaged Navier-Stokes (RANS) equations performing finite volume method with SIMPLE algorithm over a non-uniform structured grid.
A Study on the Sound Quality Evaluation Model of the Air Cleaner
Authors: Ih Jeong-Guon , Jang Su-Won , Jeong Cheol-Ho , Jeung Youn-Young , Jun Kye-Sup
Published: May 2009

In operating the air cleaner for a long time, people in a quiet enclosed space expect calm sound at low operational levels for a routine cleaning of air; in contrast, a powerful, yet not-annoying, sound is expected at high operational levels for an immediate cleaning of pollutants. In this context, it is important to evaluate and design the air cleaner noise to satisfy such contradictory expectation from the customers. In this study, a model for evaluating the air cleaner sound quality was developed based on the objective and subjective analyses. Sound signals from various air cleaners were recorded and they were edited by increasing or decreasing the loudness at three wide specific-loudness bands: 20–400 Hz (0–3.8 Bark), 400–1250 Hz (3.8–10 Bark), 1.25k–12.5k Hz bands (10–22.8 Bark). Subjective tests using the edited sounds were conducted by the semantic differential method (SDM) and the method of successive intervals (MSI). SDM test for 7 adjective pairs was conducted to find the relation between subjective feeling and frequency bands. Two major feelings, performance and annoyance, were factored out from the principal component analysis. We found that the performance feeling was related to both low and high frequency bands; whereas the annoyance feeling was related to high frequency bands. MSI test using the 7 scales was conducted to derive the sound quality index to express the severity of each perceptive descriptor. Annoyance and performance indices of air cleaners were modeled from the subjective responses of the juries and the measured sound quality metrics: loudness, sharpness, roughness, and fluctuation strength. Multiple regression method was employed to generate sound quality evaluation models. Using the developed indices, sound quality of the measured data were evaluated and compared with the subjective data. The difference between predicted and tested scores was less than 0.5 point.
On the Coupling Between Standing-Wave Thermoacoustic Engine and Piezoelectric Transducer
Authors: Matveev Konstantin I. , Wekin Andy , Richards Cecilia D. , Shafrei-Tehrany Najmeddin
Published: May 2009

Small thermoacoustic engines integrated with piezoelectric elements can be effective small-scale power sources to convert heat to electricity. A simplified mathematical model is developed to illustrate the effect of transducer parameters on the frequency and onset temperature difference in a standing-wave engine and to estimate efficiencies of energy conversion. Results of sample calculations show that efficiencies for the acoustic-electric energy conversion on the order of 10% are feasible.
Design and Performance Prediction of a Ultra-Micro Gas Turbine for Portable Power Generation
Authors: Capata R. , Sciubba E.
Published: May 2009

In the last decades, the enormous growth in portable electronics applications has stimulated research in lightweight and reliable power sources. In this technological niche, the idea of developing miniaturized turbomachinery to serve as portable power sources is attractive, especially in view of the much higher power density of a small turbogas generator in comparison with conventional chemical batteries. The potential social impact of an eventual commercialization of such “nano-devices” is enormous, but the technological and phenomenological complexity of the design and manufacturing of ultra-small machines (with a rotor diameter of the order of 1 cm) poses difficult problems, because some of the well-established design procedures for large and medium scale machines do not seem to be applicable as such at these extremely reduced scales. In this work the design and performance of a miniaturized gas turbine with a tip diameter of about 10 mm is examined from a thermo-fluiddynamic point of view. An extensive series of CFD simulations allows for the quantification of the losses at the resulting low Reynolds numbers (∼4600 in the stator and ∼1500 in the rotor) on the single-curvature geometry imposed by manufacturing constraints. The geometry of the blades is “optimized” on the basis of an entropy generation rate analysis, and the capabilities and limitations of conventional design strategies are assessed.
A Thermally Self-Sustaining Miniature Solid Oxide Fuel Cell
Authors: Ahn Jeongmin , Ronney Paul D. , Shao Zongping , Haile Sossina M.
Published: May 2009

A thermally self-sustaining miniature power generation device was developed utilizing a single-chamber solid oxide fuel cell (SOFC) placed in a controlled thermal environment provided by a spiral counterflow “Swiss roll” heat exchanger and combustor. With the single-chamber design, fuel/oxygen crossover due to cracking of seals via thermal cycling is irrelevant and coking on the anode is practically eliminated. Appropriate SOFC operating temperatures were maintained even at low Reynolds numbers (Re) via combustion of the fuel cell effluent at the center of the Swiss roll. Both propane and higher hydrocarbon fuels were examined. Extinction limits and thermal behavior of the integrated system were determined in equivalence ratio - Re parameter space and an optimal regime for SOFC operation was identified. SOFC power densities up to 420 mW/cm2 were observed at low Re. These results suggest that single-chamber SOFC’s integrated with heat-recirculating combustors may be a viable approach for small-scale power generation devices.
Thermal Drift of Convection-Based Micromachined Accelerometer
Authors: Wu Andy Bo , Jones John
Published: May 2009

A novel micromachined accelerometer without proof mass, based on the buoyancy of a heated fluid around a polysilicon heater, has previously been developed and reported. Significant features of this class of accelerometer include low cost and the combination of high sensitivity with high survivability. However, one of its big disadvantages is thermal drift: the sensitivity changes rapidly as the ambient temperature changes. A recent numerical and experimental study has shown that the sensitivity of the convective accelerometer is a function of the Rayleigh number of the working fluid. Using this criterion, a few liquids were selected as potential working fluids to improve the sensitivity of the accelerometer. The CFD program ‘FLOTRAN’ was used to model accelerometer performance using each of these fluids. Based on FLOTRAN modeling, some fluids were selected for experimental investigation. The thermal drift of the accelerometer using different working fluids was documented and the reasons for this thermal drift were discovered. Based on this observation, some possible solutions were proposed to reduce or eliminate the thermal drift.
Tire Sound Quality Evaluation Tool Using Sound Synthesis With Physical Modeling
Authors: Ishihama Masao , Shimizu Akane , Kakumoto Yu , Hayashi Masato
Published: May 2009

A computer aided tool for tire sound quality evaluation was developed. Automotive engineers can evaluate a tire structure by listening to synthesized sound that the tire would radiate when it rolls on a specific type of road surface. Among three kinds of tire sound, this study dealt with only the tire sound that radiates through its structural vibration caused by road surface texture excitation. The tool can be used on personal computers. To make it happen, tire sound radiation process is modeled into two parts. One is excitation. Tire deformation at the contact patch was calculated from road surface texture database by rolling contact analyses using multi-body dynamics simulation software. The model includes rolling tire structure model with contact compliance and simple suspension system for the wheel axle. Observation of the calculation results gives such an insight that excitation waveforms from road surface have prominent peaks that occur only at high peaks isolated from others, and do not have dips. This transformation process from road surface waveform to excitation is more accurate than tire envelope model and also not prohibitive considering today’s low-price computing power. The other process is tire structure vibration response. By limiting the usage of tire structure models just in representing over all vibration modal responses to road surface excitations in relatively low frequency range, a simple structural finite element model (FEM) was created. In this FEM, tire wall composite structures are modeled as assembly of solid elements with uniform material properties. The trick in using this FEM model lies in its boundary condition setting. By measuring vibration transfer functions from many points on a contact patch to tire tread and sidewalls, excitation in the middle of the contact patch was found to be blocked to travel to the sidewalls in higher frequency range due to the contact restriction on the periphery of the patch. This finding is essential in giving suitable boundary conditions to the FEM model and choosing the excitation points. To make the computing time minimum for synthesis, the vibration responses of the tire are represented by infinite impulse response (IIR) digital filter banks. The waveform obtained by applying the measured road texture waveforms to the IIR filter, was transferred to sound waves by the sound command of Matlab. By modifying the IIR filter, automotive engineers can judge the effect of tire structural design changes.
Simulation of Flow and Conjugate Heat Transfer in a Macro-Channel via Lattice Boltzmann Method
Authors: Mohamad A. A.
Published: May 2009

Contributions of Prof. Kakac to the field of heat transfer, especially forced, internal flows for single and multiphase are significant and will leave with us for generations. It is an honor to celebrate Prof. Kakac’s 75th birthday with remembering his works. This paper is an attempt to produce some of Prof. Kakac’s old results on single phase flow in a duct with emerging method, Lattice Boltzmann Method. Also, to show the method’s capability in handling conjugate effect naturally. The fluxes (momentum and heat) are naturally conserved at the interface between solid and fluid. Conjugate effect becomes important in macro-flows, where the effect of axial heat conduction through the fluid conducting devices significantly affect the rate of heat transfer.
A Virtual Test Track for the Mastery of Solid Mechanics Principles
Authors: Condoor Sridhar S. , Banerjee Sauvik , Kroll Ehud
Published: May 2009

The paper presents an innovative instructional methodology to deliver the fundamental principles of mechanics of solids. The methodology enhances students’ conceptual understanding of mechanics of solids principles and their ability to apply the principles to solve real-world problems. These materials are in the form of self-paced virtual activity modules that account for and incorporate the overall scope of the problem and the design issues, support the interactive development and analysis of the design, and qualitatively validate the results. The paper illustrates the methodology using a case study showing the applicability of various principles to the discipline of mechanical engineering. The case study demonstrates the advantages of experiential learning through virtual activity modules. By augmenting the preparation of “Mechanics of Solids” students, who often lack the relevant conceptual-level skills, for their eventual careers, this virtual test track will ultimately reap substantial benefits for industries that depend on the best use of mechanics principles in the manufacture of their products.
Adaptive Sliding Mode Control With Sliding Mode Observer Design for a MEMS Vibratory Gyroscope
Authors: Fei J. , Batur C.
Published: May 2009

This paper presents a novel adaptive sliding mode control with a sliding mode observer for a MEMS gyroscope. The proposed adaptive sliding mode controller with a sliding mode observer which reconstructs the unmeasured states can estimate the angular velocity and the linear damping and stiffness coefficients of the gyroscope despite parameter variations and external disturbance. An adaptive sliding mode controller with a proportional and integral sliding surface is derived and the stability condition of the closed-loop system is established. The numerical simulation for the MEMS gyroscope model is performed to verify the effectiveness of the proposed adaptive sliding mode control with sliding mode observer.
Delayed Fracture of the Piezoelectric Ceramics Under Electric Fields in Three-Point Bending
Authors: Narita Fumio , Shindo Yasuhide , Hirama Mitsuru
Published: May 2009

This paper investigates experimentally and analytically the delayed fracture in lead zirconate titanate (PZT) ceramics under electromechanical loading. Delayed fracture tests were conducted on single-edge precracked-beam specimens, and time-to-failure and fracture load under different DC electric fields were obtained. Possible mechanisms for delayed fracture were also discussed by scanning electron microscope (SEM) examination of the fracture surface of the PZT ceramics. Further, a nonlinear finite element analysis was employed to calculate the energy release rate for the permeable, impermeable and open crack models, and the effects of applied DC electric fields and localized polarization switching on the energy release rate are examined.
Comparative Finite Difference and Finite Element Analysis of the Dynamic Characteristics of a Load-Beam-Lumped-Mass Unit
Authors: Kazemi Mohammad , Haj-Hariri Hossein
Published: May 2009

The dynamics of a load-beam-lumped-mass unit (LBLMU) in a disk drive is modeled using physically motivated simplifications. Models are developed for sway, bending and torsion modes of vibration assuming mode decoupling. A finite-difference scheme (FDS) is employed to discretize the governing equations for the three modes. The models are verified by comparing the modal results of simplified models with the results of full 3D finite element models (FEMs) for beams with rectangular and U-shaped cross sections. Then, the models are used to predict the natural frequencies of a LBLMU. It is revealed that the simplified models capture well the dynamic characteristics of a LBLMU while requiring much smaller computational resources.
Effect of Notch Location on the Stress Concentration and Reliability of Notched Composite Laminates Based on a Probabilistic Approach
Authors: Ganesan R. , Arumugam A. K.
Published: May 2009

Composite materials and laminates are being widely used in aerospace and automotive industries due to their less weight to stiffness ratio. Especially the use of composite laminates, made up of Carbon or Graphite Fiber Reinforced Plastics (CFRP/GFRP), in military and commercial aircraft structures has progressed steadily over the past few decades. Drilling holes and making cutouts in these laminates are unavoidable for practical reasons. These holes (or) cutouts introduces stress concentration near the hole (or) cutout edge and reduces the load-bearing capacity of the structure. Cutouts are made at the edges of composite laminates for practical purposes, which is capable of reducing the delamination effect in notched laminates. The stress distribution in notched composite laminates can vary according to the location of the notch in the laminate, which leads to the variation in strength and reliability values of notched laminates. The objective of the present work is to study the effect of notch location on the stress concentration and reliability of notched composite laminates. Composite laminate displays significant variation in material and strength properties and the stress distribution in the laminate becomes stochastic in nature. Thus the notched laminates were analyzed using a stochastic approach and designed based on a reliability-based design approach.
Modified Fading Memory Model to Describe ASM Dynamics
Authors: Du Y. , Al-Jumaily A. M.
Published: May 2009

A modified fading memory model is introduced in this work to describe the behavior of airway smooth muscle dynamics. The model is used to simulate two biophysical cases: a finite duration for the step change in length and a case for external longitudinal oscillations. For both cases, the model describes the cross-bridge behaviour well and indicates that the muscle length change is the most important factor to determine the degree of cross-bridge detachment. However, the frequency of oscillation represents the velocity of the length change, which affects the cross-bridge cycling rate as reflected in the lower frequency range. The model is intended to interpret certain biophysical processes and not to accurately model the biophysical events underlying muscle contraction.
Robust Vision-Based Monitoring of Indoor Environments by an Autonomous Mobile Robot
Authors: Di Paola Donato , Milella Annalisa , Cicirelli Grazia , Distante Arcangelo
Published: May 2009

This paper presents a novel vision-based approach for indoor environment monitoring by a mobile robot. The proposed system is based on computer vision methods to match the current scene with a stored one, looking for new or removed objects. The matching process uses both keypoint features and colour information. A PCA-SIFT algorithm is employed for feature extraction and matching. Colour-based segmentation is performed separately, using HSV coding. A fuzzy logic inference system is applied to fuse information from both steps and decide whether a significant variation of the scene has occurred. Results from experimental tests demonstrate the feasibility of the proposed method in robot surveillance applications.
Using Fluid Velocity in Lieu of Impeller Speed for Dimensional Analysis and a Method for Estimating Fluidborne Noise Due to Flow Turbulence Within Centrifugal Pumps
Authors: Argarin Joselito D. , Hambric Stephen
Published: May 2009

An empirical method for estimating fluidborne broadband noise associated with flow turbulence within centrifugal pumps is considered in this paper. Given the flow rate, developed head and the operating speed, an estimate of the pump’s fluidborne broadband noise can be made using the method. The method is developed by correlating the noise performance of centrifugal pumps with different specific speeds to the pump parameters (i.e. impeller dimensions and hydraulic performance). The correlation is achieved by using dimensional analysis, where the Buckingham Pi theorem is applied to relate the acoustic signature of the pump to the characteristics of the pump. Similar analysis had previously been performed on centrifugal pumps using air as a medium. The studies evaluated pumps at different flow coefficients of the same pump speed. To some extent, aerodynamic noise was correlated to the impeller tip speed. However, simply using the impeller tip speed may not be accurate. This paper offers an alternate method in relating noise, where instead of the impeller speed, the actual fluid velocity is calculated and used in the analysis.
Identification of Multi-Channel Cardiovascular System Using Dual-Pole Laguerre Basis Functions for Assessment of Aortic Flow and TPR
Authors: Hahn Jin-Oh , Reisner Andrew T. , Asada H. Harry
Published: May 2009

This paper presents a novel method to identify the multichannel cardiovascular system using two distinct peripheral blood pressure signals. The method can characterize the distinct arterial path dynamics that shape each of the blood pressure signals, and recover the common aortic flow signal fed to them. A Laguerre series data compression technique is used to obtain a compact representation of the cardiovascular system, whose coefficients are identified using the multi-channel blind system identification. A Laguerre model de-convolution algorithm is developed to stably recover the aortic flow signal. Persistent excitation, model identifiability, and asymptotic variance are analyzed to quantify the method’s validity and reliability. From the identified Laguerre series coefficients of the cardiovascular dynamics, mean aortic flow and total peripheral resistance are estimated. Experimental results based on 7,000 data segments obtained from 9 swine models show that the waveform of the aortic flow is stably recovered from peripheral blood pressure signals and that the cardiovascular dynamics can be identified very reliably for all the swine models under diverse physiologic conditions. In addition, the use of the identified cardiovascular dynamics results in the improvement in estimating the mean aortic flow and total peripheral resistance by 60% and 45% in terms of the R2 value, compared to their standard counterparts.
Numerical Analysis of Rapid Micromixers Utilizing Magnetic Particles
Authors: Wang Yiou , Zhe Jiang , Chung Benjamin T. F. , Dutta Prashanta
Published: May 2009

Performances of a magnetic particle driven micromixer are predicted numerically. This micromixer takes advantages of mixing enhancements induced by alternating actuation of magnetic particles suspended in the fluid. Effects of the magnetic actuation force, switching frequency and channel’s lateral dimension have been investigated. Numerical results show that the magnetic particle actuation at an appropriate frequency causes effective mixing. The optimum switching frequency depends on the channel’s lateral dimension and the applied magnetic force. The optimum switching frequency obtained from the present numerical prediction is in good agreement with the theoretical analysis. The proposed simple mixing scheme not only provides an excellent mixing, even in simple microchannel, but also can be easily applied to “lab-on-a-chip” applications with a pair of external electromagnets.
Non-Labeled Cell Tracking Velocimetry for Biological Flows
Authors: Kim Chang-Beom , Steager Edward , Kim Min Jun
Published: May 2009

A tracking algorithm was developed to study the velocity field of flagellated bacteria, Serratia marcescens, swarming on a soft agar plate. Average velocities for local regions regularly arranged over the entire flow field were investigated rather than those for individual bacterium. The velocity field of the bacteria typically featured the combination of curvilinear translation and vortex modes. They repeated these patterns for a short time period, forming several groups and dissipating. To further investigate the flow patterns generated by the collective motion of the swarming bacteria, the velocity field on the swarm was spatially correlated.
Noise Due to Flow Over a Rotating Cylinder With Surface Roughness
Authors: Zoccola Paul , Stewart Devin , Goody Michael , Farabee Theodore
Published: May 2009

An experimental investigation was conducted to determine the scaling properties of noise due to flow over rough surfaces under conditions similar to those that would be found on a full scale marine vessel. Noise due to the flow over the surface of a rotating cylinder in a quiescent medium was measured. Vertical profiles of streamwise mean velocity over the cylinder were also measured. Measurements with various roughness element spacings suggest that for L/R > 6, noise from individual roughness elements is independent of other elements. The spectral density of radiated noise was proportional to V7 for large values of the roughness height (450 < R+ < 1700). Measurements made at R+ = 18 seem to scale best at V5. This suggests that the noise generation mechanism for large values of R+, is different than that for small values of R+.
Effect of Strain Induced Charge Redistribution on Young’s Modulus of Zinc Oxide Nanowires
Authors: Desai A. V. , Haque M. A.
Published: May 2009

As the size of material decreases to nanoscale, fundamental material properties such as Young’s modulus are different from bulk values. In this paper, we propose a new mechanism to explain the difference in experimentally observed Young’s modulus values between zinc oxide nanowires and bulk zinc oxide. As a binary compound material (such as zinc oxide) is strained, the effective charge on the ionic constituents of the material changes (in this case zinc and oxygen). The strain induced charge redistribution effect is more significant in nanostructures (such as nanowires) because of their higher fracture strains compared to their bulk counterparts. Since the Young’s modulus of a material is related to the effective charge, we observe differences in modulus values between nanowires and their bulk equivalent. The strain induced charge redistribution phenomenon can also be used to explain variation in modulus values between bulk and nanoscale for other single crystal piezoelectric materials such as silicon carbide.
Split Singularities: Applications and Implications
Authors: Zhang Zhen , Suo Zhigang
Published: May 2009

In the microelectronic system, many materials are integrated together in complex structures, from the level of transistors to the level of motherboard. These materials are of different thermomechanical properties, and usually meet together to form the sharp features, such as trenches, wedges, corners or junctions. These sharp features can concentrate stresses, which in turn fail the devices in the ways of cracking, debonding, or injecting dislocations, etc. The singular stress field is a linear superposition of two modes, usually of unequal exponents, either a pair of complex conjugates, or two unequal real numbers. In the latter case, a stronger and a weaker singularity coexist, known as split singularities. The weaker singularity can readily affect the outcome of failures. A dimensionless parameter, called the mode mixity, is defined to characterize the proportion of the two modes at the length scale where the processes of fracture occur. If the mode mixity is nearly zero, then the singular stress field can be simplified to a single mode, and be characterized by one stress intensity factor, on which the criteria of avoiding the failure initiated from the sharp features can be established. Otherwise, both modes need to be considered. We apply this theory to crack penetration or debond, and dislocation injection into strained silicon.
Adaptive Control of a Smart Projectile Fin With Unknown High-Frequency Gain by Piezoelectric Actuation
Authors: Mudupu Venkat , Singh Sahjendra , Yim Woosoon
Published: May 2009

This paper delves into adaptive control of a smart projectile fin with unknown high frequency gain using a piezoelectric bimorph. The hollow projectile smart fin is actuated using a cantilevered piezoelectric bimorph that is completely enclosed within the fin. The model of the smart fin system includes the aerodynamic moment which is a function of the angle of attack of the projectile. The rotation angle of the fin is controlled by deforming the piezoelectric bimorph which is hinged at the tip of the rigid fin. It is assumed that fin parameters as well as the high frequency gain of the model are unknown. Moreover, the model includes an unknown bounded time varying aerodynamic disturbance. An adaptive control system using the Nussbaum gain is designed. The structure of the control system is independent of the dimension of the flexible fin model. This is important because the fin model has large number of flexible modes. For the design of the control law, a linear combination of the fin angle and fin angular rate is chosen as the controlled output variable. In the closed loop system, all the signals are bounded and the fin angle tracks the reference trajectory. Simulation results are presented along with the experimental validation done using the subsonic wind tunnel at the University of Nevada, Las Vegas (UNLV). Both simulation and experimental results show that in the closed-loop system, the fin angle is precisely controlled in spite of the uncertainties in the fin parameters and the aerodynamic force.