bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials Science and Fabrication Techniques in the Entertainment Industry: A Collaboration Between Fine Arts and Engineering
Authors: Cook Daniel P. , Wysocki Robert
Published: April 2008

The College of Engineering and the College of Fine Arts at UNLV are collaborating in the creation of an interdisciplinary program in Entertainment Engineering and Design. In one of the first classes that has been offered in the program, the students learn materials science fundamentals through applications in basic fabrication techniques. Combining traditional lecture sessions from engineering and studio sessions from fine arts, the students work in teams on projects derived from the entertainment industry. This paper describes the format of the course, the projects that the students are assigned and how the course will fit into the overall curriculum of the new program.
Analysis of Solder Wetting in Sn-Ag-Cu.05 Lead Free Alloy
Authors: Anson Scott J. , Slezak Jacob G. , Srihari Krishnaswami
Published: April 2008

Lead free electronics soldering is driven by a combination of health and environmental concerns, international legislation and marketing pressure by lead free electronics manufacturing competitors. Since July 1, 2006 companies that do not comply with the European Union legislation are not able to sell circuit assemblies with lead solder in the European Union. China has developed its own regulations, based on the European Union documents with a compliance date of March 1, 2007. Lead free soldering requires an increase in reflow peak temperatures which will further aggravate component moisture sensitivity risks and thereby decrease assembly yield. Prior research has revealed a counterintuitive enhanced solder spreading phenomena at lower peak temperature and shorter time above liquidus with 63Sn/37Pb solder. This present study investigated solder wetting reactions in 96.5Sn/3.0Ag/.5Cu (WT%) (SAC305) using materials and manufacturing systems that are relevant to the electronics manufacturing industry. The objective was to advance the knowledge base of metal wetting such that solder joints can be effectively produced while avoiding heating the assembly any hotter then necessary for effective soldering, which would increase the risk of component damage due to rapid moisture outgassing and associated popcorn delamination. A classical design of experiments (DOE) approach was used with wetted area as the response variable. Additional sample characterization will be conducted outside of the DOE. The samples will be analyzed for correlation of reflow peak temperature, reflow time above liquidus, and wetted area. The expected results are 1) improved understanding of SAC lead free solder wetting reactions, 2) reduced SAC reflow peak temperatures, and thereby reduced risk of moisture sensitivity damage to components.
MIMO-FEA for Design and Active Vibration Suppression of an Adaptive Circular Composite Plate
Authors: Ghasemi-Nejhad Mehrdad N. , Sakagawa Randy
Published: April 2008

Adaptive structures combine sensors, actuators, and control systems for intelligent responses to their environment and promise a novel approach to satisfying the stringent performance requirements of future aerospace and space applications. This study focuses on a multi-input-multi-output finite element analysis for the design and active vibration suppression of an adaptive circular composite plate used here as the top device-plate for an intelligent composite platform that is designed for thrust vector control of a satellite thruster. The adaptive circular composite plate has three pairs of back-to-back embedded piezoelectric active fiber composite actuator patches. A finite element harmonic analysis is employed to develop a vibration suppression scheme, which is then used to study the vibration suppression of the circular composite plate using the piezoelectric patches embedded in the plate. In this approach, the responses of the structure to an arbitrary external force as well as an arbitrary internal piezoelectric control voltage are first determined, individually. Using the linearity of the system, the responses are then assembled in a system of equation as a coupled system and then solved simultaneously to determine the control voltages and their respective phases for the system actuators for a given external disturbance. This approach is an effective technique for the design of smart structures with complex geometry and multi-input-multi-output sensor and actuator systems to study their active vibration suppression capabilities and effectiveness. The design and active vibration suppression of the adaptive circular composite plate are explained and discussed.
Chirality Effects on Axial Thermomechanical Properties of Carbon Nanotubes
Authors: Askari Davood , Ghasemi-Nejhad Mehrdad N.
Published: April 2008

The nearly one dimensional carbon nanotubes with their novel physical and mechanical properties have received ever increasing attention in recent years for the use in a wide range of applications in which semiconductor nano-structures, nano-devices/sensors, and nano-electro-mechanical systems are to be integrated. However, carbon nanotubes exist in various chirality configurations each of which may perform differently when they are subjected to external mechanical and thermal loads, temperatures changes, and magnetic fields. Therefore, a detailed and fundamental investigation of the effects of chirality angles on thermomechanical performance of carbon nanotubes is needed to explain the behavior of such structures. Here in this work, finite element method (FEM) is employed to numerically investigate the responses of carbon nanotubes to external mechanical loads and temperatures changes. Single-walled carbon nanotubes (SWCNTs) with different chirality configurations, i.e., zigzag, armchair, and chiral are modeled and their effective thermomechanical properties are investigated. Finally, results are discussed and compared with the existing results from literature.
3-D Simulation of Conservative and Non-Conservative Density Current
Authors: Hormozi S. , Firoozabadi B. , Jahromi H. Ghasvari , Hekmati S. M. H. Moosavi
Published: April 2008

Flows generated by density differences are called gravity or density currents which are generic features of many environmental flows. These currents are classified as the conservative and non-conservative flows whether the buoyancy flux is conserved or changed respectively. In this paper, a low Reynolds k-ε turbulence model is used to simulate three dimensional density and turbidity currents. Also, a series of experiments were conducted in a straight channel to study the characteristics of the non-conservative density current. In experiments, Kaolin was used as the suspended material. Comparisons are made between conservative and non-conservative's height, concentration and velocity profiles of the current and their variations along the transverse intersections. Outcomes indicate that the presence of the particles influences the flow structure sensibly. The results are compared with the experiments and showed a good agreement.
Active Command-Steering Control of Tractor and Three Full Trailers for Tractor-Track Following
Authors: Rangavajhula Krishna , Tsao H.-S. Jacob
Published: April 2008

A key source of safety and infrastructure issues for operations of longer combination vehicles (LCVs) is off-tracking, which has been used to refer to the general phenomenon that the rear wheels of a truck do not follow the track of the front wheels and wander off the travel lane. In this paper, we examine the effectiveness of command-steering in reducing off-tracking during a 90-degree turn at low and high speeds in an articulated system with a tractor and three full trailers. In command steering, rear front axles of the trailers are steered proportionately to the articulation angle between the tractor and trailing units. We then consider several control strategies to minimize off-tracking and rearward amplification of this system. A minimum rearward amplification ratio (RWA), as a surrogate for minimum off tracking, has been used as the control criterion for medium to high speeds to arrive at an optimal Linear Quadratic Regulator (LQR) controller. As for low speeds, the maximum radial offset between the tractor and trailer 3 is minimized in the design of the controller. Robustness of the optimal controller with respect to tyre-parameter perturbations is then examined. Based on the simulation results, we find that, active command steering is very effective in reducing off tracking at low- as well as high-speed 90-degree turns. To achieve acceptable levels of RWA and off tracking, at least two of the three trailers must be actively command-steered. Among the three two-trailer-steering possibilities, actively steering trailers 1 and 2 is most cost-effective and results in the lowest RWA for medium- to high- speeds (at which RWA is important), and off-tracking is practically eliminated for all speed regimes considered.
Using Assessment as a Teaching Tool
Authors: Marques Joa˜o E. M.
Published: April 2008

Based upon two personal beliefs, with regard to teaching that firstly "teaching is helping others to discover" and secondly that "assessment is a necessary inconvenience", a method has been developed in teaching Fluid Dynamics to undergraduate students, in a Mechanical Engineering Course. The main goal of this method is changing from a traditional theoretical approach of teaching "what is in the book" to a much more practical confrontation between theory and what can be found in laboratory experiment. The program contents are covered by four laboratory apparatuses: • Reynolds experiment, • Head losses in tubes, • Hydraulic turbines, • Centrifugal pumps, which are presented to all the students during a particular class so they can prepare for their next return to the laboratory, now organized into small groups. Meanwhile, each group must define their specific objectives and work planning, so the students can accomplish the experiments off-line, with the laboratory supervisor's eventual help and subsequent report must be written within a determined period. The main results achieved a success rate which has risen from about 50%, of the evaluated students before setting up the method to 70%, but keeping the same lecturer, i.e. the same quality demand.
Smooth Muscle Stiffness Variation Due to External Oscillation
Authors: Du Y. , Al-Jumaily A. M.
Published: April 2008

The static and dynamic stiffnesses of contracted trachea smooth muscles are determined before, during and after length oscillations in isometric contraction. An appropriate Neural Network model is developed to normalize the data. The results indicate that the dynamic stiffness has the tendency of decreasing as the frequency and/or amplitude of external excitation increases. However, the static stiffness decreases with an increase in the frequency and amplitude of excitation until it reaches a critical value of frequency where no variation in stiffness is observed. It is postulated that the tissue elasticity and inertia are the main contributors to the dynamic stiffness while the myosin-actin cross bridge cycling is the main contributor to the static stiffness.
Three-Dimensional FEM Simulation of a Microfluidic Diode Considering Coupled Fluid-Structure Interaction
Authors: Yang Bozhi , Lin Qiao
Published: April 2008

This paper presents fluid-structure interaction (FSI) simulation of a microfluidic diode, which features a thin flexible flap and a rigid stopper embedded closely inside a microchannel. The thin flap deforms under different applied pressure, leading to a small flow resistance for forward flow and a large flow resistance for reverse flow. Three-dimensional simulations of structure deflection and CFD were interactively carried out to calculate the flap deformation and flow filed using ANSYS® Multi-field™ solver. In the simulations nonlinear hyperelastic material property was used for the thin flap, and the pressure drop across device inlet and outlet was applied in small increments to solve the nonlinear continuum mechanics problems. The simulated flap deflections under both forward and reverse flow show nonlinear relation between deflection and pressure, consistent with experimental data. The simulated flow rates under various pressures also agree well with the measurement results, within 15% error for forward flow and 17% for reverse flow. The simulations can be used as guidelines for optimal design of the microfluidic diode.
Effect of Flow Field on Online Shear Viscosity of PP/nano-CaCO3 Composites
Authors: Jiang Guo , Huang Hanxiong
Published: April 2008

Polymer nanocomposites have been regarded as a new category of engineering materials and attracted technical and scientific interest. Recently rheological analysis became an effective tool for investigating the microstructures of nanocomposites. However, the online rheological property of nanocomposites during compounding was seldom studied. In this work, two types of screw configurations in twin-screw extruder were selected, one provides high shearing intensity and the other provides high shearing/mixing intensity. In addition, chaotic mixing was induced by installing a single screw extruder with a convective screw at the end of the twin-screw extruder to compound the nanocomposites. The online melt shear viscosity of nanocomposite was measured using Haake ProFlow online rheometer. Effects of high shearing, high shearing/mixing, and chaotic mixing on the online shear viscosity for polypropylene (PP)/nano-calcium carbonate (nano-CaCO3) composites were investigated. The study showed that the chaotic mixing facilitates the processing of the nanocomposite.
Zero Dimensional Model for the Growth of Heterogeneous Gas Bubbles
Authors: Wasfy Hatem M. , Wasfy Tamer M.
Published: April 2008

A zero dimensional energy based model for heterogeneous gas bubble growth from conical surface pits is presented. The spherical cap bubble growth is divided into 3 stages. In the first stage, the bubble is within the surface pit. In the second stage, the bubble is anchored to the circular opening of the surface cavity and the apparent bubble contact angle decreases while the bubble's contact radius remains the same. The third growth stage starts when the apparent contact angle becomes the same as the contact angle under the ambient conditions. In the third growth stage, the contact radius increases while the contact angle remains constant. The predicted bubble radius versus time since the detachment of the previous bubble was found to be in good agreement with published experimental data for CO2 bubbles growing in water. The long wait time observed in the experiments before a measurable bubble appears after the detachment of the previous bubble was also calculated.
Heat Transfer Characteristics in Flue Gas Fired Regenerators of Water/Lithium Bromide Absorption Chillers
Authors: Kren Christoph , Schweigler Christian , Ziegler Felix
Published: April 2008

It has already been shown that efficiency of direct-fired absorption chillers or tri-generation systems (CCHP) can be increased if the hot flue gas - from internal gas burner or from motor engines or gas turbines - is successively utilized in the absorption cycle at several temperature levels. For successful realization of such concepts, however, efficient heat exchanger designs are required. An increase in complexity on the flue gas side of the chiller must not introduce a proportional increase in size, cost, and pressure drop. Thus, the development of a compact and efficient flue gas fired regenerator design with low flue gas pressure drop is a major step towards COP increase in direct-fired and exhaust-fired absorption chillers. The potential of different regenerator concepts including common smoke tube design and alternative boiling tube designs with natural circulation of the lithium bromide solution and flue gas flow across bundles of plain or finned tubes is discussed. Promising designs are identified on basis of numerical calculations. A semi-industrial sized prototype of a direct-fired regenerator with consecutive sections of plain and finned vertical boiling tubes has been tested in laboratory over a range of thermal inputs up to 256 kW (net. CV). Experimental results of heat transfer and combustion side pressure drop investigations at the novel regenerator are presented. Accordance of experimental results with theoretical predictions is shown.
Use of Nanoindentation to Characterise the Plasma Damage Region in Low-k Dielectric Films
Authors: Molina-Aldareguia Jon M. , Elizalde Maria R. , Ocan˜a Ibon , Gil-Sevillano Javier , Marti´nez-Esnaola Jose´ M. , Iacopi Francesca , Travaly Youssef , Van Hove Marleen
Published: April 2008

The thermo-mechanical robustness of interconnect structures is a key reliability concern for integrated circuits. The introduction of new low dielectric constant (low-k) materials with deteriorated mechanical strength (i.e., Young Modulus decreases exponentially with film porosity, which is needed to lower the k value of the dielectric materials) to meet the RC delay goals increase the risk of mechanical adhesive and/or cohesive failure of the device during packaging or even in service. Therefore, the mechanical properties of low-k dielectrics must be studied in detail. This is made very challenging by the fact that they have submicron thickness and that they often display a graded structure due to the damage introduced by exposure to different plasmas during processing. In this context, we demonstrate that nanoindentation is very well suited to study this type of materials. We will show how conventional depth sensing nanoindentation is of limited value to characterise the extent of the plasma induced damage because this extents just a few tens of nanometres and the graded structure can not be sampled with enough depth resolution. However, nanoindentation in modulus mapping mode can achieve enough depth resolution to characterise such nanoscale graded structures. In this technique, the electrostatic force acting on the indenter tip is sinusoidally modulated, while contact mode imaging at a very small force is performed. The dynamical response is then analyzed to extract the local indentation modulus of the sample at each pixel. By using this technique, we have depth profiled the mechanical properties of the plasma induced damage region of OSG films exposed to different plasmas, by acquiring modulus maps as a function of thickness removed in wear experiments. The results correlate well with the density depth profiles derived from X-Ray Reflectivity measurements.
Automatic Gearshift Algorithm and Its Dynamic Performance Simulation of Tracked Vehicle With Integrated Power Train System
Authors: Yin Huabing , Fan Jingling , Hu Lichen , Ma Xiaofneg
Published: April 2008

The automatic gearshift algorithm and its dynamic control is an important research area in tracked vehicle design. In the paper the models of power train system such as engine, transfer gearbox, hydraulic torque converter, planetary gearbox, running gear propulsion system and virtual terrain are built. The program for gearshift algorithm design is developed. The model of designed gearshift algorithm is developed with MATLAB/simulink and finite state machine theory. The hydraulic control system is modeled with MATLAB/simulink and the oil pressures can be applied on the clutches and brakes of power train system. The planetary gearbox and other transmission parts are modeled through EASY5 power train library models and the gear contact stiffness, torsional stiffness of links between planetary gear sets and shafts are taken into consideration. The running gear system model are built with ADAMS, and the terrain loads from the interaction between terrain and tracks are applied on the sprocket extended to the power train, which considers the dynamic contacts among road wheel, track and terrain. Many terrain models including the slope, obstacle and road model with A, B, C, D etc. levels at different vehicle speeds can be built and integrated with the virtual prototyping models These different disciplinary models are integrated with MATLAB, ADAMS and EASY5 development environment and the virtual test can be done in various operation conditions. The integrated method is through the interfaces provided by these simulation software. It realizes the time synchronization between two different models of EASY5 and MATLAB/simulink with the digital electric circuit theory. The virtual test is been made in the integrated MATLAB/simulink development environment. The tracked vehicle's acceleration performance is simulated. The acceleration time from second gear to 32 km/h is about 14.5 seconds. Many other performances such as the virtual dynamic torque loads of rotating parts, the clutch torque capacity and the jerks of any parts in the power train can be obtained from simulation and can be verified with the physical tests later. There are some innovations in modeling method in this paper. Firstly, it builds many subsystem models with the virtual prototyping technology. Secondly, it builds the integration environment and interfaces. Many models of different areas are integrated to simulate transmission gearshift process. Thirdly, it provides a modeling method and environment for power train modeling and simulation. Fourthly, the acceleration performance of a tracked vehicle is simulated and the two results of virtual and physical tests are close.
Coupled Durability and Functionality of Piezoelectric Polymers
Authors: Vinogradov Aleksandra M.
Published: April 2008

The main characteristic of piezoelectric polymers is coupling of their mechanical and physical properties. In this view, progressive material degradation of the polymers under cyclic loading conditions is an important factor in terms of both their long-term integrity and functional performance. The study reported herein demonstrates that the piezoelectric polymer polyvinylidene fluoride (PVDF) tends to exhibit accelerated creep rates under superimposed static and cyclic loads. Creep acceleration under such conditions has been observed even in the range of stresses well below the viscoelastic linearity limit. In the paper, the effects of material degradation caused by creep-fatigue interaction in PVDF are discussed. The study includes efforts to develop a constitutive viscoelastic material model taking into account damage evolution due to synergistic creep-fatigue interaction effects. The model is based on the principles of continuum damage mechanics and linear viscoelasticity.
Efficient and Flexible Tri-Generation With Two-Stage Absorption Chiller
Authors: Plura S. , Kren C. , Schweigler C.
Published: April 2008

Aiming for the European and North American tri-generation market, highly-efficient systems are being developed. At the moment, single-stage absorption chillers are typically coupled to co-generation engines through a single hot water loop at temperatures below 100°C (210°F). In this configuration, the heat from the exhaust gas at temperatures of about 400-500°C (750-930°F) is transferred to the water loop, which is accompanied by a significant loss of exergy. A substantial increase in system performance can be achieved by a stepwise utilisation of the exhaust gas enthalpy in a Double-Effect and a Single-Effect cycle. In this combination of one-and two-stage chillers the coefficient of performance (COP) increases from about 0.7 to almost 1.0 whereby the cooling capacity rises by about 25%. In order to facilitate optimum adaptation of the aggregates - i.e. motor engine and absorption chiller - and to give maximum flexibility an innovative system concept has been developed. The new coupling scheme is based on a standard direct-fired Double-Effect chiller and introduces only minor design changes, like adaptation of the thermal layout of the exhaust gas driven regenerator heat exchanger of the chiller. No additional low temperature regenerators are required. In case of simultaneous heating and cooling the system supports a continuous switchover between maximum cooling and maximum heating capacity. In this mode up to 80% of the driving heat for cold production can be recovered as useful heat at temperatures up to 100°C (210°F). A description of the coupling scheme together with a discussion of energetic and operational characteristics of the concept is presented. Full-scale demonstration projects are under preparation.
Use of Numerical Modeling in Air System Design and Analysis
Authors: Jorgensen Kris L. , Dudek Scott A. , Hopkins Mitchell W.
Published: April 2008

Combustion air systems are an important aspect of any combustion system. With the complexity of modern combustion systems, numerical modeling has become a valuable tool for design and analysis. Two examples of the use of numerical modeling for combustion air systems on pulverized coal utility boilers are presented: first, a combustion analysis to evaluate air system design on combustion performance, and second, the design of a secondary air system windbox. These examples demonstrate the usefulness and value of modeling as a design and analysis tool.
Effects of Fuzzy-Tuning the Boundary Conditions on the Active Control of a Single-Link Flexible Robotic Manipulator
Authors: Abdelgalil Y. A. , Chalhoub N. G.
Published: April 2008

A new approach has been proposed in this study to effectively control the rigid and flexible motions of a single-link robotic manipulator. This is done by developing a two-layered control strategy. The upper layer is solely concerned with the process of fuzzy-tuning the boundary conditions of the flexible link. The rationale is to exploit the advantages, attributed to varying the boundary conditions of the compliant beam, in rendering the joint controller more effective in suppressing the unwanted vibrations of the arm. The lower or second layer of the control strategy is considered herein to be either a conventional or a fuzzy-tuned control scheme. Its main task is to determine the appropriate joint control torque needed to perform good set-point tracking while suppressing the undesired vibrations of the robot. The digital simulation results confirm that the process of fuzzy-tuning the boundary conditions of the flexible link has a tendency to significantly enhance the capability of the joint controller in suppressing the unwanted vibrations of the manipulator.
Isothermal Microtube Heat Transfer With Second-Order Slip Flow and Temperature Jump Boundary Conditions
Authors: Xiao Nian , Elsnab John , Thomas Susan , Ameel Tim
Published: April 2008

Two analytical models are presented in which the continuum momentum and energy equations, coupled with second-order slip flow and temperature jump boundary conditions, are solved. An isothermal boundary condition is applied to a microchannel with a circular cross section. The flow is assumed to be hydrodynamically fully developed and thermal field is either fully developed or thermally developing from the tube entrance. A traditional first-order slip boundary condition is found to over predict the slip velocity compared to the second-order model. Heat transfer increases at the upper limit of the slip regime for the second-order model. The maximum second-order correction to the first-order Nusselt number is on the order of 18% for air. The second-order effect is also more significant in the entrance region of the tube. The Nusselt number decreases relative to the no-slip value when slip and temperature jump effects are of the same order or when temperature jump effects dominate. When temperature jump effects are small, the Nusselt number increases relative to the no-slip value. Comparisons to a previously reported model for an isoflux boundary condition indicate that the Nusselt number for the isoflux boundary condition exceeds that for the isothermal case at all axial locations.
What Will It Take to Deliver a Zero-to-Landfill Product?
Authors: Boyer Jeffrey R.
Published: April 2008

Driven by legal mandates and consumer demand, sustainable businesses will be those that recognize the need for extended responsibility for their products beyond the point of sale. One strategy gaining increasing attention throughout the world is the production and sale of Zero-to-Landfill products - products that contain nothing that is disposed of at the end of their useful life. A product take-back process is required to ensure products that reach the end of their useful lives are reclaimed for reuse, remanufacturing, or recycling. But can companies develop products that are truly zero-to-landfill? What must manufacturers do to deliver products offering this environmental beneficence? The stakeholders in a sustainable enterprise are considered, and the desire for zero-to-landfill products from their perspectives will be examined. Implications for government regulations, reverse logistics, product design and manufacturing, and for corporate profits are examined. The emphasis will be on how such a strategy will impact today's design and manufacturing engineers. Through the use of representative examples, it will be shown that many of the requisite behaviors and processes are being implemented, but that it is still early to quantify the impacts and to understand the emergence of unforeseen consequences.
Numerical and Experimental Analysis of the Static and Dynamic Morphing Characteristics of a Chiral Core Airfoil
Authors: Sapdoni Alessandro , Ruzzene Massimo
Published: April 2008

Aeroelastic tailoring requires structural compliance and thus often conflicts with stiffness requirements to carry prescribed aerodynamic loads. Recently, however, the application of cellular structural concepts has suggested the potential to achieve compliance while conserving required load-carrying capacity. Among the proposed concepts, a chiral geometry in particular is a novel configuration which features an in-plane negative Poisson's ratio which leads to a very high shear modulus, while maintaining some degree of compliance. In particular, the chiral geometry allows large continuous deformations of the airfoil assembly, with the constitutive material remaining in the linear region of its stress-strain curve. The ability to sustain large deformations without exceeding yield conditions is required to recover the original shape and to provide smooth deformations as required by aerodynamic considerations. In previous work, a coupled-physics model, comprising of simultaneous CFD and elastic analyses, is developed to investigate the influence of the chiral core geometry on the behavior of a given airfoil. The modification of geometric parameters defining the considered layout leads to significant variations in mechanical properties, which can be exploited to achieve various levels of compliance. The morphing capabilities of the proposed airfoil, quantified as camber changes, are evaluated for various design configurations of the internal core structure. Specifically, three such airfoils have been constructed to study the influence of core geometric parameters on the elastic behavior observed in numerical simulations. Experiments on the aforementioned airfoil samples are characterized by imposing large camber-wise deflections, via static loading, and measuring the resulting strain, both in the honeycomb core and in the airfoil profile. The experimental results confirm the ability of the airfoils to sustain large deflections while not exceeding yield strain limits, in addition to producing continuous deformations, which are critical for the implementation of aeroelastic tailoring.
Thermal Analysis for Cryosurgery of Nodular Basal Cell Carcinoma
Authors: Sun Feng , Aguilar G. , Kelly K. M. , Wang G.-X.
Published: April 2008

Basel cell carcinoma (BCC) is the most common human skin malignancy. Its incidence has increased significantly in Australia, Europe and North America over the past decade. A number of modalities are currently used for treatment of BCC, including cryosurgery which offers a potential for high cure rate, low cost, minimal bleeding and good cosmetic effect. However, cryosurgery is not used frequently for BCC because no current method exists to design adequate treatment parameters. We present a numerical analysis on the thermal history of the target tissue during cryosurgery of a nodular BCC using liquid nitrogen (LN2) spray. The model uses Pennes equation to describe the heat transfer within the target tissue. A convective thermal boundary is used to describe the heat interaction between the tissue and LN2, and the apparent heat capacity method is applied to address the tissue phase change process. A parametric study is conducted on the convective heat transfer coefficient (hs: 104~106 W/m2·K), cooling site area (rs/R0: 0.5~1.0) and spray time (t: 0~30 sec.), with the objective to understand the thermal history during tissue freezing, including lethal temperature (-50 °C) and cooling rate (CR). Results demonstrate that propagation of the lethal isotherm is sensitive to the convective heat transfer coefficient, hs, with a range of 104~5×104 W/m2·K. Increasing the cooling site area can significantly enhance cooling efficiency, producing dramatic increase in the amount of tissue encompassed by the lethal isotherm. The cooling rate (CR) shows a highly dynamic distribution during the cooling process: the highest CR drops quickly from 140 °C/sec. (t=0.5 sec.) to 20 °C/sec. (t=5 sec.). The highest CR is initially located close to the cooling site but moves toward the inside of the tissue as treatment proceeds. The model presented herein provides a simulation tool for treatment planning of cryosurgery using LN2 spray, in which the protocol parameters, e.g. cooling site area and spray time, can be determined for an optimal outcome. The quantitative predictions on the propagation of lethal isotherm and the distribution of CR should help to optimize cryosurgery efficacy.
Fabrication of Bi Nanowires Using a Vacuum Melting and Mechanical Injection Technique
Authors: Bisrat Y. , Chen C. C. , Luo Z. P. , Chao C. G. , Davis D. , Lagoudas D.
Published: April 2008

A mechanical pressure injection technique has been developed to fabricate uniform metallic nanowires in the pores of anodic aluminum oxide (AAO) template. The AAO template was prepared from general purity aluminum by a two-step anodization followed by heat treatment to achieve highly ordered nanochannels. The nanowires were fabricated by an injection process using a hydraulic pressure method. A mold containing the AAO template and a metal foil was placed inside a vacuum chamber and heated up to the melting temperature of the given metal using a hot plate. The hot chamber was then removed from the hot plate and pressure was applied on the melt through the sliding column of the chamber, using a hydraulic jack to impregnate the molten metal into the nanochannels of the AAO. The nanowires were found to be dense and continuous with uniform diameter throughout their length. Diffraction experiment in the transmission electron microscope revealed that individual nanowires are single crystalline. This paper will present the fabrication process of the AAO template, and the fabrication of Bi nanowires as well as their characterization conducted using SEM, TEM, XRD and DSC.
Teaching Design Methodology to Undergraduates Through Multi-Year Projects
Authors: Azemi Asad , Esparragoza Ivan
Published: April 2008

This paper presents a new approach for teaching engineering design methodology that consists of covering different steps of the design process in four semesters focusing on a specific problem. During the first semester students are introduced to the overall design methodology and are asked to identify the needs, tasks and outputs, based on a given problem statement. During the second semester students are asked to come up with a conceptual design and modify the inputs, tasks and outputs. During the third semester students are asked to come up with a working preliminary design solution and obtain some output data. And during the fourth semester students are asked to modify their design, based on their results from the previous semesters and the problem requirements, and come up with the final detailed design. Each part requires a separate report, with the results from the first three being referenced in the final report. At this time due to several considerations, including limited resources, we are only targeting engineering honors students and using robotics related problems for the multi-year design projects. The four-semester long project will be the "honors option" for the courses that engineering honor students must take during the first two years at our campus. A detailed description of this approach, including advantages and disadvantages, future directions and recommendations, are included.
Laminar Pressure Loss Coefficient in Close Coupled Fittings
Authors: Lakshmiraju Murthy , Cui Jie
Published: April 2008

Close-coupled fittings are widely used in piping system to change the direction of the fluid and to connect pipes. These fittings cause losses and these losses play a significant role in the total pressure loss in a duct system. Numerical simulations were performed using Fluent on laminar flows in a circular pipe to obtain pressure loss coefficients associated with different fittings of two elbows and three elbows. Each configuration was studied with different intermediate distances between fittings of 0, 1, 3, 5, and 10 pipe diameters. It was observed that for a Reynolds number of 100 and for an intermediate distance less than 5 pipe diameters, the pressure loss coefficient for the coupled fittings was less than that of the uncoupled fittings. While the fittings become uncoupled when the intermediate distance was greater than 5 pipe diameters. Variation of velocity along the axis of the pipe was analyzed to understand the mechanism of the pressure loss for various fitting configurations with different intermediate distances.
A Combined Stress Model for the Elasto-Plastic Analysis of Clamp Loads in Bolted Joints Under a Cyclic Separating Force
Authors: Nassar Sayed A. , Yang Xianjie
Published: April 2008

In this paper, a nonlinear combined stress model is established for a typical bolted joint for the purpose of studying its behavior under a separating service load. The combined effect of axial and torsional stresses in the tightened threaded fastener is considered. A new approach for the analysis of the clamping force loss is proposed under different pre-tightening with different thread friction coefficient and different separating loading. The_nonlinear model is established based on the elasto-perfectly plasticity in order to describe the fastener behavior over the yielding of its material, and to determine the relationship between the axial bolt force and elongation under tightening and the separating loading with specific twist angle, and to predict the clamp force loss due to the permanent set in the fastener after the separating force has been removed. The nonlinear relationship between the bolt axial force and the bolt elongation depends on the initial twist angle and the tightening preload. Finally, the effects_of the fastener pre-tightening, the initial twist angle and the bolt and joint members' elastic properties on the amount of clamp load loss are investigated.
Optimizing the Efficiency of Electro-Hydraulic Powertrains
Authors: Montgomery Alexander J. , Alleyne Andrew G.
Published: April 2008

The evolution of the hydrostatic transmission system from mechanical systems to electronically controlled systems creates opportunity for improvements in efficiency through the use of intelligent control algorithms. In systems for which the prime mover is an internal combustion (IC) engine, overall system efficiency depends greatly on the prime mover's operating conditions. The use of variable displacement pumps can add a degree of freedom and allow engine operation to be optimized. However, this strategy requires a desired engine power value based on operating states and load references. This paper proposes a novel solution to this problem by using a dynamic engine power demand estimate to meet steady-state load demands using minimal engine power.
Femtosecond Laser Fabrication of a Lab-on-a-Chip in Glass for Enhancing Detection Sensitivity
Authors: Cheng Y. , Hockenhull Tracy E. , Tsai H. L.
Published: April 2008

Lab-on-a-chip devices offer faster, cheaper, and better ways of doing chemical and biological analyses. In this paper, we will show that both 3D micro-fluidic and 3D micro-optical structures can be directly formed in photosensitive glass using a femtosecond laser and an annealing and etching process. Particularly, we will demonstrate the fabrication and examine the function of lab-on-a-chip biosensors integrated with micro-optical loops for enhancing detection sensitivity. The fabricated lab-on-a-chip biosensors are composed of a micro-fluidic channel into which sample under test will be injected. Five micro-optical mirrors are distributed on both sides of the micro-channel to form a zigzag optical path, which forces a micro-optical beam to cross the micro-fluidic channel three times before entering into a photodetector. This design can effectively extend the absorption path length and result in enhanced detection sensitivity of photoabsorption spectroscopic analysis. To examine the function of the micro-device, we filled the microfluidic channel with a dye solution (Rhodamine 640 dissolved in methanol) and shone a green laser beam (532nm) from a laser pointer into the microstructure. The fluorescence emission from the dye solution indicated that the light beam passed through the microchannel; however, due to the strong absorption, the output beam was not obvious. Quantitative characterization is under way for evaluating the detection limit of the lab-on-a-chip micro-device.
Characteristics of Nucleate Boiling With Gold Nanoparticles in Water
Authors: Jackson Jenny E. , Borgmeyer Brian V. , Wilson Corey A. , Chen Peng , Bryan James E.
Published: April 2008

An experiment was designed to test the pool boiling performance of 3 nm gold nanofluid on a flat circular copper coupon. Compared to pure water, an increase of up to 175% in the critical heat flux was seen with gold nanofluids. However, a 25-30% deterioration in the heat transfer coefficient was also observed. The heating surface was observed before and after boiling with a scanning electron microscope. A thin, dark film was observed on the surface, which was due to the deposition of gold particles.
Mechanical Behavior of a Shape Memory Polymer
Authors: Wu Xin , Dauerman Leonard , Zhang Song , Qiao Xiao , Mabesa Jose
Published: April 2008

In recent years shape memory effect in polymer systems has drawn great attention for its potential applications for MEMS and medical devices. In this paper, the visco-elastic and plastic behavior and strain recovery characteristics of a thermoplastic have been studied extensively. Creep deformation by compression was performed under load or displacement control mode, and under monotonic or cyclic loading. The strain recovery ratio of the shape memory polymer is found to be strongly affected by the deformation temperature, isothermal holding temperature and time, amount of forward strain and relaxation time, and the number of cycles of strain/recovery. The creep behavior of the material is modeled.
Techniques for the Implementation, Administration, and Evaluation of Industrially Sponsored Capstone Design Projects in the ME Curriculum
Authors: Brackin Patricia D. , Gibson J. Darrell
Published: April 2008

The benefits of company sponsored capstone design projects, both to academia and to industry, have been well established. At Rose-Hulman the benefits to students include the broadening of their engineering skills, the required interaction with practicing engineers, the strengthening of teaming skills by working in design groups, the development of communication skills with required oral and written reports, and the experiences of project management. These projects are "owned and managed" by the student teams with company contacts providing appropriate data and information and with faculty serving as advisors only. The authors have developed and improved these student/industry interactions over the last few years with over 120 students working with about 30 different companies each year. ABET 2000 requires that graduates demonstrate the ability to design a system, component or process to meet a given need. The capstone design course is the natural place to assess whether or not the outcome is met. It is the purpose of this paper to identify the necessary steps for soliciting, screening, and selecting the types of company projects that will enhance educational objectives and further industrial partnerships. A further purpose is to demonstrate how the course is used to assess the ABET design outcome. Finally the paper discusses how the authors have recently improved this client based design experience and the quality of the final design by utilizing project managers from Rose-Hulman Ventures (the innovation and incubation technology arm of Rose-Hulman) as "design review teams" to meet with and to serve as additional resources to the student teams.
Combined Robust Design and Robust Control of an Electric DC Motor
Authors: Alyaqout Sulaiman F. , Papalambros Panos Y. , Ulsoy A. Galip
Published: April 2008

System performance can significantly benefit from optimally integrating the design and control of engineering systems. To improve the robustness properties of systems, the present article introduces an approach that combines robust design with robust control and investigates the coupling between them. However, the computational cost of improving this robustness can often be high due to the need to solve a resulting minimax design and control optimization problem. To reduce this cost, sequential and iterative strategies are proposed and compared to an all-in-one strategy for solving the minimax problem. These strategies are then illustrated for a case-study: Robust design and robust control of a DC motor. Results show that the resulting strategies can improve the robustness properties of the DC motor. In addition, the coupling strength between robust design and robust control tends to increase as the applied level of uncertainty increases.
Numerical Simulation of a Chemical Vapor Deposition/Infiltration Reactor
Authors: Kamel John K. , Paolucci Samuel
Published: April 2008

A chemical vapor deposition/infiltration reactor used to manufacture carbon aircraft brakes has been simulated numerically. This simulation accounts for a homogeneous gas reaction mechanism as well as a heterogeneous surface reaction mechanism. Non-Boussinesq equations are used to predict fluid flow, heat transfer, and species concentrations inside the reactor and porous brakes. A time-splitting algorithm is used to overcome stiffness associated with the reactions. A commercial code is used to solve for the convection/diffusion step while an implicit time-integration algorithm is used to solve for the reaction step. Results showing the flow, temperature and concentration fields, as well as the deposition rate of carbon, are presented.