bluuebunny/crossref_metadata_2025 huggingface dataset:
Near-Grazing Based Intermittent Contact Mode Atomic Force Microscopy
Authors: Dick Andrew J.
Published: August 2009

The dynamic behavior of an atomic force microscope cantilever probe is studied for dual frequency excitation. By using the Euler-Bernoulli beam equation with a multi-mode approximation, the system is modeled with base excitation and tip-sample interaction forces obtain from molecular dynamics simulations. The dynamic response of the cantilever probe is simulated for a range of separation distance values and analyzed using Poincare´ sections, bifurcation diagrams, and spectral analysis. The response of the cantilever probe is found to display a qualitative change when influenced by surface forces. The frequency component at half of the fundamental frequency provides an effective way to monitor the amount of force that the probe is applying to the surface of the sample. With this frequency component, an amplitude modulation operation mode is proposed in order to maintain near-grazing behavior during imaging.
Adaptive Nonlinear Control of SMA-Based Bending Micro Actuator
Authors: Chen Shuo , Craft William J. , Song David Y. , Whitsett Charmisa
Published: August 2009

Shape Memory Alloys (SMAs) have several attractive features that make them potentially useful concepts as bending micro actuators. SMA linear actuators are among those producing the highest strains and highest forces available, and when employed in a bending mode, their deflection capability is enhanced even more leading to potential new applications. This paper addresses the basic design concept for a bi-material actuator modeled as an initially curved composite beam with one active layer, the SMA material, and one conventional elastic layer. This device must be accurately controlled to achieve an optimal range of motion and to serve in many new applications so we have designed a nonlinear and adaptive control scheme based on Lypaunove stability theory to prevent erratic motion and even component separation and partial buckling. In addition, this control scheme is able to achieve high precision tracking without the need for detailed system parameters. Simulation is conducted which confirm the effectiveness of the proposed method.
Analysis of Nanowire Heat Pumps for Local Hot Spot Cooling
Authors: Castillo Eduardo , Ramanath Ganapathiraman , Borca-Tasciuc Theodorian
Published: August 2009

Conventional cooling techniques cannot be effectively employed in thermal management of high flux microscale to nanoscale hot spots that will occur in new generations of nanoelectronics and interconnects. Solid-state nanoscale heat pumps based on the Peltier effect have been proposed to alleviate the hot spot by producing a localized cooling effect in the vicinity of the hot spot. The proximity to the hot spot is expected to lead to efficient hot spot removal. In addition, such nanowire heat pumps may have higher coefficients of performance than their bulk materials counterparts due to enhanced thermoelectric figure of merit in optimized nanostructures. In this work nanoscale heat pumps are assumed to be assembled either parallel or perpendicular to the substrate around the hot spot with the cold junctions in contact with the hot spot and the hot junctions distributed at a constant distance from the hot spot. The objective of this work is to quantify and optimize the heat transfer rate of the nanoscale heat pump devices. An analytical model is employed to predict the heat transfer rate attainable with nanowire devices and their dependence on nanowire and hot spot dimensions, the junction temperature, and heat flux from the heat spot. Experimental efforts are on the way to demonstrate such devices.
Dynamic Joining of Polymer Composites to Metals
Authors: Whitney Thomas J. , Bettinger David
Published: August 2009

Joining polymer matrix composites to metal, such as stainless steel for structural loading, requires the resolution of inherent differences in joining characteristics of each material. The missing element is a material that would be an intermediary between the metal and the composite. The ideal intermediate material would be weldable, as hard as steel, but able to pick up the fiber stress of the composite. Energy absorption through plastic behavior of the joint would also be desired.
A Technique for Interface Thermal Resistance Measurements Between a Nanoelectrode and a Substrate Using the 3ω Method
Authors: Son Youngsuk , Mazumder Monalisa , Borca-Tasciuc Theodorian
Published: August 2009

Developing a fundamental understanding regarding energy flow across nanoscale interfaces is critical in realizing viable nanoelectronics device systems and efficient low-dimensional thermoelectric devices. This work presents investigations of the interface thermal resistance (ITR) in a nanoelectrode-on-substrate system using the DC heating as well as the 3ω method.
Normal Mode Analysis of a Single Polyethylene Chain
Authors: Henry Asegun , Chen Gang
Published: August 2009

In certain cases, atomistic simulations of systems with one-dimensional symmetry have shown divergent (infinite) heat conduction properties, even when the interactions are anharmonic. One limitation of many previous works, however, is that toy models were used and thus the resulting conclusions could not be easily extended to more real materials found in nature. In this paper, we examine a more realistic model of a single polyethylene chain, using the AIREBO potential to describe the atomic interactions. We computed normal mode correlation functions and noticed that when the domain is longer than 40 unit cells, the lowest frequency modes in the system remain strongly correlated after five nanoseconds of simulation time. This retention of energy correlation over such a long period identifies these modes as possible sources of anomalous energy transport in a real system. This finding suggests that new and cheap polymeric materials can be engineered to exhibit high thermal conductivity.
Design of Experiments as Effective Design Tools
Authors: Nasser Mohamed , Jawad Badih
Published: August 2009

Design of Experiment (DOE) provides a highly structured way to study the effects of multiple variables on product performance as well as efficient and effective methods for determining the most significant factors and interactions in a given design problem. Design of Experiments (DOE) is an off line quality improvement methodology that dramatically improves industrial products and processes. Input factors are varied in a planned manner to optimize output responses with minimal variability. Design of Experiments is a standard statistical technique used in quality engineering, pharmaceuticals, manufacturing, and other industries to identify key factors and levels that influence system performance and variability. This technique is especially useful when there is the need to understand the interactions and effects of several system variables and an absence of concrete information. In industry, designed experiments can be used to systematically investigate the process or product variables that influence product quality.
Friction Heat Due to Sliding of Rough Surfaces: Micro-Scale Interactions and Their Macro-Scale Effect
Authors: Farhang K. , Elhomani A.
Published: August 2009

When two rough surfaces are in sliding contact an asperity on a surface would experience intermittent temperature flashes as it comes in momentary contact with asperities on a second surface. The frequency of the flash temperatures, their strength and duration depend, in addition to the sliding speed, on the topology of the two surfaces. In this paper a model is developed for the work-heat relation with a consideration of the above-mentioned intermittent nature of contact. The work of friction on one asperity is derived in integral form and closed-form equations. The rate of generation of heat is found due to a single asperity. Using the statistical account of asperity friction heat generation, rate of heat generation between two rough surfaces is obtained both in statistical integral form and in the approximate closed form.
A Methodology for Identifying Hardware States and Requirements to Ensure System Reliability and Success in Software-Hardware Systems
Authors: Mueller Jonathan D. , Tumer Irem Y.
Published: August 2009

Software and hardware elements in software-driven complex systems are often designed independent from one another, and merged later. The problem with this design approach is that the requirements that involve hardware and software dependencies are not taken into consideration effectively, potentially causing the system to fail or be in an undesirable state. This research argues that, by considering software and hardware requirements together from the earliest design stages, a more reliable system will be designed by knowing the possible failure situations that may occur. In order to increase the reliability of the final system, this paper introduces a methodology to follow the software-hardware system as it completes a command and identifies the failure situations that may occur and the requirements needed to ensure successful completion of the command. The overall goal is to provide designers with an integrated design methodology to capture safety, reliability, and mission success related requirements in software-driven complex hardware systems. The benefits of the methodology are illustrated and the steps demonstrated using NASA’s K10 Rover as an example. The methodology is applied to the command of Move Rover, with the software and hardware interactions that may cause failures clearly identified in the model. Specifically, the hardware and software states that would allow for correct operation of the command are identified and clearly displayed on the model. The visual model and requirements that are developed can be used by the designers of the software to ensure mission success.
Imperative Expectations and Impediments for a Mechanical Engineering Program
Authors: Hamidzadeh Hamid R. , Clark Yvonne Y.
Published: August 2009

This paper addresses indispensable values essential for students who pursue bachelor degrees in mechanical engineering. It presents topics such as the required curriculum for rigorous education of students and full implementation of the code of professional conduct and ethics by faculty and staff. In addition, this article introduces the vital steps and processes needed to assure that the students entering a program, graduate as individuals of character, sensitive to the needs of the community, competent to contribute to society, and civil in their habits of thought and action. Furthermore, significance of having ethical, knowledgeable, up-to-date, and motivated faculty members, as well as, a sound technical and well rounded program for achievement of high standards by students are discussed.
Effect of Fiber Orientation and Stacking Sequence on Bending Properties of Fiber/Metal Laminates
Authors: Sadighi M. , Dariushi S.
Published: August 2009

Fiber metal laminates (FMLs) are hybrid composites consisting of alternating thin layers of metal sheets and fiber reinforced epoxy. In this work, the bending behavior of this attractive material is investigated. 9 sets of specimens were made with different fiber orientation. Also, the effect of stacking sequence is studied. Test results show that suitable layering and using aluminum layers in the back and front of specimens improve the bending strength. Statistical analysis of data shows that the most important parameter is glass fibers orientation in the lower glass/epoxy layer.
Regeneration of Ligaments and Tendons With ECM Bioscaffolds
Authors: Woo Savio L.-Y. , Fisher Matthew B. , Almarza Alejandro J.
Published: August 2009

Ligaments and tendons of the knee are subjected to large loads during sports and work related activities, and thus, are frequently injured. For the anterior cruciate ligament (ACL) and medial collateral ligament (MCL), there are over 100,000 and 50,000 annual tears, respectively, in the United States alone. As a torn ACL has limited healing potential, surgical reconstruction using autograft replacements, such as the bone-patellar tendon-bone (BPTB) as well as the quadrupled semitendinosus and gracilis tendons, are performed in a large number of patients to restore knee stability. In spite of the over 25 years of experience, knee extension deficits and many long term complications associated with the BPTB autograft, including the progression of osteoarthritis, are serious post-surgical problems. Additionally, there are complications associated with donor site morbidity, anterior knee pain, arthrofibrosis, and inferior biomechanical properties of the patellar tendon (PT). In the case of MCL injuries, functional treatment is sufficient for rapid tissue healing; however, the neo-MCL is known to have significantly inferior tissue quality compared to the intact MCL, and the remodeling process can take years. Thus, it presents an increased chance for reinjury.
Measurement and Comparison of Airflow in Condenser Axial-Flow Fans With Aluminum and Fiberglass Blades
Authors: Hosseini N. , Raad M. H. , Moghiman M.
Published: August 2009

This paper presents an experimental investigation of effects of physical characteristics of blades on the airflow rate of an axial-flow fan. Two types of fiberglass and aluminum blades have been compared. The comparison includes air velocity, air flow and physical characteristics; like airfoil design, twist, tip clearance and chord variation. Pitot tube has been used as the most compatible device for airflow measurement. Results show that aluminum blades have performed better than fiberglass blades and the comparison of experimental measurements against calculated results, regarding fan laws, shows good agreement.
Teaching Sustainable Engineering Throughout the Mechanical Engineering Curriculum
Authors: Hallinan Kevin , Kissock Kelly , Pinnell Margaret
Published: August 2009

The natural world has long been impacted by technological society; however, in recent years environmental impacts and constraints are increasingly on the global, rather than local or regional, scale. Moreover, the interconnectivity of biological systems with energy and material flows is increasingly evident. Today, it is well understood that climate change, energy constraints and biological degradation are largely a consequence of technological production and energy use. In this context, one would expect engineering education to have evolved to prepare engineers to be capable of addressing these issues. Rather, excluding the resurgence in design education, we see a curriculum that remains largely unchanged. In this context, we propose an integrated mechanical engineering curriculum that emphasizes sustainable engineering and whole-system design. The curriculum provides mechanical engineering students with a deeper understanding of the broader impact of the products and processes they design, the tools to assess that impact, and the system level thinking to design technologies for a sustainable future.
Numerical Simulation of Transfer Process in Imperial Smelting Furnace
Authors: Zhou Ping , Liu Chaodong , Jiang Aihua , Chen Wen , Mei Chi
Published: August 2009

The mathematical models, which describe the transfer process in Imperial Smelting Furnace (ISF) of Pb-Zn, were established by means of the rules of metallurgical reaction engineering, mass and energy conservation. These models took into account 4 important chemical reactions, heat and mass transfer between gas and solid. The solid particles were treated as porous media when the diffusion of the gas was calculated. The main parameters, such as temperature, the mass of every species, etc, were measured for an operating ISF, and were used as boundary conditions. Based on the Fortran program language, the code to solve the corresponding govern equations was developed, and thermal processes in the furnace were numerically simulated. The results show that the maximum temperature is about 1870K, which is around 1m from the inlet of primary air. The temperature of gas from the top of burden is about 1300K, which is lower than that in the similar furnace. So, it is necessary to take some means to decrease the heat loss from the wall of ISF. A lot of CO exists in the flue gas, which can be used as fuel of boiler or combustion equipment. Based on the mass flow rate and temperature distribution of gas and burden in ISF, the height of five zones, i.e. preheating zone, PbO reduction zone, ZnO reduction zone, coke gasification zone and coke combustion zone, are respectively 2.0m, 0.6m, 3.8m, 4.0m and 2.5m The predicted results by the model are accordant with the measured values in an operating ISF.
A Comprehensive Multiphysics, Multiscale Study of Reactor Chamber and Substrate Orientation Effects on Carbon Nanotube Synthesis During Chemical Vapor Deposition Process
Authors: Hosseini Mahmoud Reza , Jalili Nader , Bruce David A.
Published: August 2009

A comprehensive multiphysics, multiphase model of carbon nanotube (CNT) fabrication process by chemical vapor deposition (CVD) is utilized to study the effects of several physical phenomena inside the quartz tube. The investigations include fluid flow properties, temperature profile and heat transfer as well as diffusion and concentration of carbon species along the substrate. These properties are examined in a great detail for a horizontally placed substrate. For each physical property, the effects of substrate dislocation as well as the angle between substrate and reactor chamber longitudinal axis are investigated. It is shown that the temperature in the gas phase reactions region is significantly lower compared to the temperature profile around the substrate. Based on the obtained results, two new CVD system designs are proposed to enhance the temperature in the reactor chamber section where gas phase reactions take place. Moreover, it is shown that substrate dislocation and angle change result in physical property change such as species concentration on upper and lower substrate surfaces. This study is also applicable to other CVD-based fabrication process such as deposition of any layer, since the methodology of the fabrication process remains the same.
Atomic Scale Investigation of Nanoparticle and Fabrication Temperature Effects on Carbon Nanotube Diameter and Chirality
Authors: Hosseini Mahmoud Reza , Jalili Nader , Alway-Cooper Rebecca M.
Published: August 2009

Carbon nanotubes (CNTs) are one of the best candidates for utilizing in the future nanoelectronic devices. However, the semiconductivity property of CNTs varies as diameter and chirality number change. Several nanoelectronic applications require semiconductivity to be of a certain value with little variability. Therefore, it is necessary to reliably produce uniform CNTs with unique diameter and chirality. However, this still remains one of the challenging problems in the large scale production and application of CNTs. In this paper, the effect of fabrication temperature change on CNTs diameter and chirality are experimentally and theoretically studied. Utilizing chemical vapor deposition (CVD) fabrication process and by conducting experimental investigation, it is observed that a CNT possesses a larger diameter at its base compared to the section far away from deposited nanoparticles. Moreover, using MD simulation technique, it is observed that the energy of the CNTs molecular structure will increase by applying higher fabrication temperature. Usually this energy increase is greater in the thicker CNTs. However, the energy increase percentage is found to be affected by the chirality of the CNT. Among CNTs of the same diameter, the armchair conformation has the highest percent increase, followed by the chiral CNTs, and the zigzag nanotube has the lower percent increase. The obtained results can be utilized in a controllable CNTs diameter and chirality design process.
Simulation of Dynamic Fracture Along Solder-Pad Interfaces Using a Cohesive Zone Model
Authors: Jing Jianping , Gao Feng , Johnson Janine , Liang Frank Z. , Williams Richard L. , Qu Jianmin
Published: August 2009

In this paper, dynamic fracture of a single solder joint specimen is numerically simulated using the finite element method. The solder-IMC and IMC-Cu pad interfaces are modeled as cohesive zones. The simulated results show that under pure tensile loading, damage typically starts at the edge of the solder-IMC interface, then moves to IMC-Cu pad interface. Eventual failure is typically a brittle interfacial failure of the IMC-Cu interface.
Real-Time Detection of Estrogen by Microcantilever Sensor in Microfluidic Channel
Authors: Islam Nazmul
Published: August 2009

As the world becomes increasingly concerned with endocrine disruptor from estrogenic activity, and since the threat of estrogen can be substantially mitigated if detected early, the demand for real-time/on-site detection of estrogen is expanding quickly. However, current technology is expensive, technically complicated and not available for estrogen level determination at the contamination sites. The primary objective of this research is to develop and validate a robust, rapid lab-on-chip for detecting estrogen in environmental water samples. Anti-estrogen antibodies can be layered to the microcantilever (MC) surface through passive adsorption using a dilute solution of antibody. The estrogen in the water will bind/react with antibody, which will result in a strain in the cantilever. The strain of the cantilever can ultimately be measured as a resistance change in the microsystem. MC will be integrated with AC electokinetic to produce a lab-on-a-chip that can concentrate measure and differentiate viable estrogen.
Biased AC Electroosmosis Micropump for Water Management in PEM Fuel Cells
Authors: Islam Nazmul
Published: August 2009

Proton exchange membrane (PEM) fuel cells are among the most promising fuel cell technologies. Recent experimental and numerical investigations [1–3] on PEM fuel cells (PEMFC) identified water management as one of the most critical issues for designing robust, high-performance PEM fuel cells. Proper water management within the cell is therefore essential, as dehydration of the membrane or flooding of the cathode result in increasing resistive losses. Flooding reduction in the fuel cell is commonly done by removing water with excessive reactant (H2 or O2) flow rates and elevated gas pressures. This mixture makes air delivery the largest parasitic load on fuel cells. Typically, this type of air delivery consumes more than 20% of the fuel cell power. As an alternative, we have developed a novel biased AC electroosmtic micropump for PEM fuel cell applications that can be fabricated with micro-electro-mechanical-systems (MEMS) compatible semiconductor micro-fabrication. This research paper will experimentally demonstrate the bi-directional pumping action that can prevent flooding, increase power density, and ensure stable performance of fuel cell by removing water from flooded regions and redistributing it to under-saturated regions.
Design and Performance of a Folding Flow Network Micromixer
Authors: Chen Z. , MacInnes J. M. , O’Sullivan B. , Zhou P.
Published: August 2009

Effective and rapid mixing of liquid solutions is a fundamental requirement in the design of many types of micro-flow systems. Constraints of both rapid and complete mixing place considerable demands on mixer performance. Especially for those liquids with high viscosities and low diffusivities, mixing is particularly important, however, difficult, for processes associated with chemical reaction. A design of a mixer using a network of microchannels to split and recombine the flow repeatedly is introduced in the paper. Such a mixer has been incorporated by the authors into a device for carrying out measurements of chemical reaction kinetics in ionic liquid solutions. Rapid mixing of reagent solutions is required to produce a uniform reaction mixture in a time that is short compared to the kinetic time scales of interest. Since the ionic liquids have low molecular diffusivities and high viscosities, and for practical conditions, flow is necessarily in the Stokes regime (Re<1), this liquid system provides an extremely challenge for mixer design. The performance of the mixer is then investigated by experiments.
Numerical Investigation of Air Forced Convection in Channels With Transverse Ribs
Authors: Fedele G. , Manca O. , Nardini S. , Ricci D. , Masullo G.
Published: August 2009

Heat transfer in fluids is very important in many industrial heating and cooling equipments. Convective heat transfer can be enhanced passively by changing flow geometry, boundary conditions or by increasing thermal conductivity of the fluid. Another possibility for increase heat transfer with fluid is to employ extended surfaces. When fluid flows in a channel, transversal ribs works as fins and break the laminar sub-layer the laminar sub-layer creating local wall turbulence. As a consequence the presence of the ribs can significantly augment pressure drop. In this paper a numerical investigation is carried out on forced convection in a channel with constant flux applied on the external walls. The fluid is air and an incompressible model is employed. Ribs of the same material of the channel walls are introduced and several shape and arrangement are analyzed. The investigation is accomplished by means of the commercial code Fluent. A turbulence model is used. Results are presented in terms of temperature and velocity fields, average heat transfer coefficients and pressure drops. The aim of this study is to find the shape and arrangement of ribs such to give high heat transfer coefficients and low pressure drops.
Finite Element Model of a Heated Wire Catalyst in Cross Flow
Authors: Leichliter Katie , Lounsbury Bob , Steciak Judi , Budwig Ralph , Beyerlein Steve
Published: August 2009

Experimentally obtained temperatures of a heated coiled platinum wire in low Reynolds Number cross-flow were compared with a three-dimensional finite element (finite volume) model. The calculated average wire temperature was in good agreement with experimentally obtained values with deviations close to experimental uncertainty bounds at temperatures between 530K and 815K. The model predicted a temperature variation along each coil, with the lowest temperatures along the leading edges of the coil and the higher temperatures at the trailing edges. The rate of heat generated at the wire surface from catalytic reactions was found for the ignition of lean propane/oxygen/nitrogen mixtures. We studied the coiled catalytic wire as part of our efforts to ignite very lean homogeneous air-fuel mixtures in transportation engines under conditions approaching Homogeneous Charge Compression Ignition (HCCI).
Numerical Simulation on Fluid Flow and Combustion in a Subcritical Pressure Boiler With Various Hybrid Coal
Authors: Zhu Zaixing , Zhou Jiemin , Wang Ying , Zhou Ping , Ma Aichun
Published: August 2009

With a 300t/h Hg1025/18.2-YM13 sub-critical natural circulation tangentially corner-fired boiler serving as a prototype, a realizable k–ε turbulent mathematical model was established. This model used computational fluid dynamics software FLUENT6.2 and unstructured mesh generating technique of Gambit to reduce numerical false diffusion of the computational results. The fluid flow, heat transfer and combustion processes in the boiler were investigated numerically with different types of coal. The simulation data was compared and analyzed. The influences of primary air ratio, excess air ratio, pulverized fuel feeder on the combustion processes have been studied. These results could be of great help in the operation of tangentially fired furnace of pulverized coal boilers.
Development of a Product Development Lab Course: Application of Theoretical, FEA and Experimental Techniques
Authors: Khandaker M. , Ekwaro-Osire S.
Published: August 2009

Finite Element Analysis (FEA) and experimental techniques based laboratory courses are used in the mechanical engineering curriculum to equip students with numerical and experimental abilities to solve design problems. Review of mechanical engineering curricula in US universities found no definite structure for the numerical and experimental based laboratory courses to support the core courses. Also, the authors found that due to lack of knowledge about the application of finite element analysis and lack of collaboration of experimental laboratories in the universities and colleges, students are unable to apply theory, numerical tool and experiment, when it comes to complete product design. To be effective product development engineers, students have to know how to use these engineering tools effectively for various mechanical systems to design a product with perfection. This motivated the authors to develop, teach, and evaluate a laboratory course before the senior design project, where students will have hands on experience with product design. The application of theoretical, numerical and experimental techniques, and their interconnectedness, will also be addressed in this new course. The main three learning objectives of this course were: (1) the ability to apply physical and mathematical models to analyze or design the mechanical systems; (2) the ability to use numerical tools (e.g., FEA) and a fundamental understanding of the limitations of such tools; and (3) the ability to correlate the theoretical knowledge with FEA and experimental findings. Some of the issues observed from the previously taught FEA laboratory related course are: (1) students do not understand how to use FEA tools in practical design problems; (2) students are unable to relate the theory with numerical and experimental result; (3) students do not understand the importance of verification of numerical results; and (4) students with knowledge of a particular analysis background have problems setting up the product design requirements dealing with different analysis systems. To overcome these difficulties, the proposed course will select design problems related to heat, fluid, vibration, and fracture and examine the overall design process including preliminary design, material selection, manufacturing, analysis, and testing. Simulating the complexity of “real world” engineering will prepare students for their senior design projects. The main benefits of this course are: (1) application of theoretical, numerical, and experimental techniques to solve a design problem, and (2) hands on experience with design problems.
Effects of Rotor Recess Geometries on Combustion Process in Diesel Rotary Engine
Authors: Zhou Nai-Jun , Pei Hai-Ling , Gao Hong-Liang , Zhou Ping
Published: August 2009

A two-dimensional model for diesel rotary engine combustion has been developed using the dynamic mesh technology on the platform of CFD software FLUENT6.2 by compiling with user defined program. A numerical study aiming to investigate the effects of four different geometries of rotor recess on combustion process has been carried out in a diesel rotary engine model. The results have been used to predict the effects of rotor recess geometry on combustion process, performance and emission. The results show that slow mixing of fuel and air has been identified as the major cause leading to incomplete combustion. Better combustion efficiency and lower NO emission can be obtained when rotor recess is located in the middle and shallower.
Residual Stress in Bone: A Parametric Study
Authors: Hizal A. , Sadasivam B. , Arola D.
Published: August 2009

A preliminary study was conducted to evaluate the parametric dependence of the residual stress distributions in bone that result from an abrasive air-jet surface treatment. Specifically, the influence of particle size and shape used in the treatment on the residual stress, propensity of embedding particles and material removal were studied. Rectangular beams of cortical bone were prepared from bovine femurs and treated with aluminum oxide and glass particles with different treatment angles. Residual stresses within the bone were quantified in terms of the radius of curvature of the bone specimens measured before and after the treatments, as well as a function of time to quantify decay in the stress. The sub-surface distribution was also examined using the layer removal technique. Results showed that the particle size and shape could be used to control the amount of material removal and the magnitude of residual stress within the treated surfaces. An increase in size of the glass particles resulted in an increase in the residual stress and a decrease in material removed during the treatment. The magnitude of residual stress ranged from 22 MPa to nearly 44 MPa through modulation of the particle qualities (size and shape). A microscopic examination of the treated surfaces suggests that the residual stresses resulted primarily from near-surface deformation.
Yaw Rate and Velocity Tracking Control of a Hands-Free Bicycle
Authors: Peterson Dale L. , Hubbard Mont
Published: August 2009

The control of a bicycle has been well studied when a steer torque is used as the control input. Less has been done to investigate the control of a hands free bicycle through the rider’s lean relative to the bicycle frame. In this work, we extend a verified benchmark bicycle model to include a rider with the ability to lean in and out of the plane of the bicycle frame. A multi-input multi-output LQR state feedback controller is designed with the control objective being the tracking of a reference yaw rate and rear wheel angular velocity through the use of rider lean torque and rear wheel (pedaling) torque. The LQR controller is tested on the nonlinear model and numerical simulation results are presented. Conclusions regarding the required lean angle of the rider relative to the bicycle frame necessary to execute a steady turn are made, as well as observations of the effects of right half plane zeros in the transfer function from rider lean torque to yaw rate.
A Titanium Based Flat Heat Pipe
Authors: Ding Changsong , Soni Gaurav , Bozorgi Payam , Piorek Brian , Meinhart Carl D. , MacDonald Noel C.
Published: August 2009

We are developing innovative heat pipes based on Nano-Structured Titania (NST) with a potential for high heat carrying capacity and high thermal conductivity. These heat pipes have a flat geometry as opposed to a cylindrical geometry found in conventional heat pipes. The flatness will enable a good contact with microprocessor chips and thus reduce the thermal contact resistance. We refer to it as a Thermal Ground Plane (TGP) because of its flat and thin geometry. It will provide the ability to cool the future generations of power intensive microprocessor chips and circuit boards in an efficient way. It also brings the potential to function in high temperature (>150°C) fields because of its high yield strength and compatibility [1]. The TGP is fabricated with Titanium. It adopts the recently developed high aspect ratio Ti processing techniques [2] and laser packaging techniques. The three main components of the TGP are 1) a fine wick structure based on arrays of high aspect ratio Ti pillars and hair like structures of Nano-Structured Titania (NST), 2) A shallow Ti cavity welded onto the wick structure and 3) the working fluid, water, sealed between the cavity and the wick. The heat carrying capacity and the thermal conductivity of a heat pipe are generally determined by the speed of capillary flow of the working fluid through its wick. The TGP wick has the potential to generate high flow rates and to meet the growing challenges faced by electronics cooling community. The TGP wick structure, developed by etching high aspect ratio pillars in a titanium substrate and growing nano scale hairs on the surface of the pillars, is super hydrophilic and capable of wicking water at velocities ∼ 10−2 m/s over distances of several centimeters. The thermal conductivity of the current TGP device was measured to be k = 350 W/m·K. The completed TGP device has the potential of attaining a higher conductivity by improving the wicking material and of carrying higher power density. Washburn equation [3] for dynamics of capillary flow has been employed to explain the results of our experiments. The experiment shows a good agreement with Washburn equation.
Nonlinear Dynamics of Electrically-Actuated Carbon Nanotube Resonator
Authors: Ouakad Hassen M. , Younis Mohammad I.
Published: August 2009

This paper presents an investigation into the nonlinear dynamics of a carbon nanotube (CNT) actuated electrically by a DC force and an AC harmonic load. The CNT is described by an Euler Bernoulli beam model that accounts for the system nonlinearities due to mid-plane stretching and electrostatic forcing. A reduced-order model based on the Galerkin method is developed and utilized to simulate the static and dynamic response of the CNT. The static deflection of the CNT and its pull-in voltage are calculated and validated by comparing them to published results. It was found that mid-plane stretching has a major impact on the pull-in prediction of CNT. Dynamic analysis is conducted to explore the nonlinear oscillation of the CNT near its fundamental natural frequency (primary resonance) and near one half, twice, and three times its natural frequency (secondary resonances). The nonlinear analysis is carried out using a shooting technique combined with the Floquet theory to capture periodic orbits and analyze their stability. The results show that these resonances can lead to complex nonlinear dynamics phenomena such as hysteresis, dynamic pull-in, hardening and softening behaviors, and frequencies bands with an inevitable escape from a potential well.
A Thermal System for a High Throughput Continuous Flow Polymerase Chain Reaction Device (CFPCR)
Authors: Chen P.-C. , Park D. S. , You B. H. , Kim N. , Park T. , Desta Y. , Park S. , Nikitopoulos D. E. , Soper S. A. , Murphy M. C.
Published: August 2009

A thermal system used to evaluate a high throughput 96 continuous flow polymerase chain reactor (CFPCR) array was designed, fabricated, and tested. Each polymerase chain reactor (PCR) in the array required three different temperature zones to realize denaturaiton at 90°C–94°C, renaturation at 50°C–70°C, and extension at 72°C; a total of 288 temperature zones were required for the 96 CFPCR array. In an initial configuration, 18 copper strips were used to define the 288 temperature zones. Each copper strip was controlled by a PID feedback control loop. Numerical simulations were used to understand the thermal crosstalk phenomena between the micromilled copper strips, which were tightly packed since the high throughput micro-titer plate format restricted each CFPCR to a square 8 mm on a side. The lowest achievable temperature in each renaturation zone in this complicated thermal environment was also identified. Thermal crosstalk limited the minimum renaturation temperature to 61.1°C. An infrared camera was used to investigate the temperature uniformity over a 0.25 mm thick polycarbonate sheet mounted on the thermal system. The temperature distribution was not uniform due to poor contact between the copper strips and device, warm air accumulated between the packed copper strips, and greater heat transfer around the boundaries of the device. More work is required to overcome these limitations and achieve a more uniform temperature distribution for a multi well CFPCR.
Characterization of AC Electrokinetic Forces Using Pressure-Driven Flow in a Microchannel
Authors: Capurro Jorge J. , Noh Hongseok Moses
Published: August 2009

Ac electrokinetics is a versatile technique for particle and fluid manipulation in microfluidic environment. However, analyzing and predicting particle motions due to the ac electrokinetic effects is a difficult task because it requires the quantitative understanding of multiple phenomena such as dielectrophoresis (DEP), ac electroosmosis (ACEO), and electrothermal effects (ETE). In this paper we present a force balance approach to analyze ac electrokinetic effects, particularly ACEO. Pressure-driven flows were used to quantify the ACEO and DEP forces acting on a particle. Polystyrene microbeads suspended in KCl solution were introduced in polydimethylsiloxane (PDMS) microchannels attached to a glass plate with gold microelectrodes. The microbeads were initially collected and aligned along the center of the electrodes at 1 kHz and 1 Vp-p, and then a well-controlled pressure-driven flow was introduced resulting in the translation of the particles. Particles moved to a new location where a new force balance is reached. This particle translation on the surface of the electrode was carefully monitored as varying the applied flow rate. The net force due to ac electrokinetic effects at different locations over the electrode was calculated using the experimental data and the force balance relationship.
Modeling and Experiments of Underfill Flow in Large Dies With Non-Uniform Bump Patterns
Authors: Zheng Leo , Sun Ying , Singler Timothy , Libres Jeremias , Gurrum Siva , Thompson Patrick
Published: August 2009

This paper presents numerical modeling and experimental results for the problem of underfill flow in a large die with a non-uniform bump pattern in a flip-chip packaging configuration. Two different 2-D flow models coupled with the volume-of-fluid (VOF) method are applied to track the underfill flow front during the simulation of flip-chip encapsulation. The first model employs the modified Washburn model and uses a time-dependent inlet velocity to account for the flow resistance across the gap direction in the presence of bump interconnects. The second model introduces a momentum source term in the Stokes equation to represent the gapwise resistance. Rheological properties, surface tension, and dynamic contact angles for an underfill material are experimentally determined. Simulation results based on the two models are compared with in-situ flow visualization conducted using bumped quartz dies. The comparison demonstrates the applicability of each model for simulating the underfill encapsulation process.
Multi-Scale Account of Friction Heat and Heat Transfer in an Automotive Brake
Authors: Elhomani A. , Farhang K.
Published: August 2009

In applications involving substantial friction, surface failure is an inevitable phenomenon. Friction induced failure typically involves the generation of considerable heat. Existence of significant frictional force leads to relatively high interface temperature as a result of dynamic nature of flash temperatures at the contact areas. A first step in predicting friction induced failure is to develop an accurate thermo-mechanical model of the friction system. A 3D thermo-mechanical model is developed in this paper based on a lumped parameter representation of a two-disk brake. A disk is viewed as consisting of three main regions, (1) the surface contact, (2) the friction interface, and (3) the bulk. The 3D lumped parameter model is obtained by dividing a disk into a number of sub-sectors, adjacent sectors, and stacked layers. The friction layer contains both the interface and contact elements, each include the equivalent thermal capacitance and conductive resistance. The contact capacitance and resistance are described in terms of the elastic contact interaction between the surfaces of the two disks. Therefore they are obtained using the Greenwood and Williamson model for contact of rough surfaces. Each is described as a statistical summation of the micron-scale interaction of the surfaces.
Approximate Closed-Form Equations for Elastic Beam Experiencing Large Deflection
Authors: Farhang K.
Published: August 2009

The problem associated with beams subject to large elastic deflection finds application in micro switches and other MEMS. Perhaps the most challenging task in finding approximate closed form equations is the choice of the function form. While systematic least squares fit of polynomial or power functions are means of finding such approximations, usually the error in the approximations rises with increase in the range of deflection. An interactive/optimization based scheme is employed in this paper to derive the closed form approximate equations for elastic beams experiencing large angular and transverse deflections as a result of application of relatively large loads. It is shown that the approximate equations provide prediction of beam tip angular deflection in the range 0–82 degrees, with error less than 0.2 degrees. The approximate equations are employed to define a pseudo-rigid body link of a compliant MEMS.
Computer-Aided Analysis of Muscular Movement of Lower Limbs and Gait Change When Walking With Unstable Shoes
Authors: Pyo Changmin , Park Sungwoo , Kim Namhoon , Kwon Junghoon , Lee Kunwoo
Published: August 2009

Several healthcare products have been developed and marketed in recent times as a result of people’s growing interest in personal health. Unstable shoes have been introduced to revitalize the muscles of the lower limbs and to modify the gait posture while walking. However, healthcare products for people should first be proved functional and safe, as some of those can sometimes result in severe injuries and side effects. Certification is, therefore, necessary in the case of unstable shoes. In this study, the functionality of unstable shoes was analyzed; it was proved that difference in pressure distribution resulting from the shape of the unstable shoes helps strengthen the muscles of the lower limbs. These analyses focused on the activation of the muscles by employing EMG (Electromyography). However, the approach involving EMG cannot carry out measurements on hidden muscles, and the noise involved is a source of potential error; therefore, this study utilizes the simulation software SIMM (Software for Interactive Musculoskeletal Modeling) for this purpose. We performed a biomechanical study using a full-body musculoskeletal model. Using the captured 3D motion data and ground reaction forces data, kinetic data was calculated in order to determine its influence on the adjacent segments. We captured the movements of six volunteers, all males in their twenties. The volunteers wore both unstable and normal shoes during each trial. This study focuses on the activation of muscles of the lower limbs when wearing unstable shoes. We inspected the muscles and analyzed the disparities between unstable and normal shoes. We observed from experimental results that most muscles of the lower limbs were revitalized. Further, we observed an improvement in the gait posture after unstable shoes were used for a period of 12 weeks. This analysis of inner muscles that cannot be examined by direct methods can help consumers make informed choices regarding healthcare products. Such analysis is made possible by simulation programs such as SIMM.