bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Event Tree/Fault Tree Modeling Approach to the Evaluation of Proliferation Resistance
Authors: Coles Garill A. , Zentner Michael D.
Published: May 2009

With the increasing popularity of nuclear energy as a means to address dwindling fossil resources and generation of greenhouse gases, comes a concern over the potential for increased proliferation of nuclear materials. Newly proposed processes/facilities will require an efficient, timely, and systematic assessment of the potential for proliferation to support decisions about optimum solutions to these competing concerns. Currently, evaluation of proliferation resistance is largely done by experts in an informal and unstructured fashion. As a result the evaluation may not always be repeatable or supportable. In 2002 an expert group was formed by The Generation IV International Forum to develop an internationally accepted methodology for assessing the proliferation resistance of a nuclear energy system (NES) and its individual elements. A pilot study was performed to test the methodologies being developed. The pilot consisted of assessing the proliferation resistance of a specific NES example with each analysis method. The example chosen was called the Example Sodium Fast Reactor which was designed to accept spent sodium-bonded, metallic fuel from four advanced fast reactors and to convert it into new fuel assemblies. A number of different approaches were taken to evaluate the diversion of material from the facility to assess their applicability and usefulness. This paper describes a Decision/Event Tree and Fault Tree Analysis approach.
Time-Resolved Micro-Raman Thermometry for Microsystems
Authors: Serrano Justin R. , Kearney Sean P.
Published: May 2009

Micro-Raman thermometry has demonstrated to be a feasible technique for obtaining micron-scale spatial resolution of microelectronic and micro-electromechanical system (MEMS) temperatures. However, the low intensities of the Raman signals emerging from the device under study force the need for prolonged data collection times in order to obtain reliable temperature information. This characteristic currently limits Raman thermometry to steady state conditions, and thereby prevents temperature measurements of transient and fast time-scale events. In this paper we discuss the extension of the micro-Raman thermometry diagnostic technique to obtain transient temperature measurements on microelectromechanical devices with 100 μs temporal resolution. Through the use of a phase-locked technique we are able to obtain temperature measurements on electrically-powered MEMS actuators powered with a periodic signal. Furthermore, we demonstrate a way of obtaining reliable micro-scale temperature measurements on devices that undergo mechanical movement during the device operation.
A Two-Phase Model of Bubbly Fluids
Authors: Li Weiming , Paolucci Samuel
Published: May 2009

We use a continuum theory for multiphase immiscible mixtures whose individual components are separated by infinitesimally thin interfaces. The average balance equations for the different phases, as well as for the mixture, result from a systematic spatial averaging procedure. In addition to equations for mass, momentum, and energy, together with the entropy inequality, the balance equations also include equations for microinertia and microspin tensors. These equations, together with appropriate constitutive equations consistent with the entropy inequality, enable the modeling of immiscible multiphase materials where internal parameters are important. Here, we apply the results to a simple microstretch bubbly fluid. We show that the equations for microspin and microinertia, under a number of simplifying assumptions, combine to yield a general form of the Rayleigh-Plesset equation.
Efficient and Robust Synchronization of Twin-Gyro Systems
Authors: Shahruz Shahram M. , Yi Jingang
Published: May 2009

In this paper, design of control laws for V-gimbaled control-moment-gyro (CMG) devices is studied. Such a device has two gyros that are used to control the slewing motion of space truss arms. Control laws are designed to make the gyros of a CMG device track a desired function of time synchronously. Synchronous tracking makes the angular displacement of a truss arm track a desired function of time. Application of the synchronizing control laws to two-gyro systems in the absence and presence of parametric uncertainties and disturbances is studied. In both cases, the designed control laws achieve the desired goals.
Design and Laboratory Experimental Tests of a Turbine Ventilator
Authors: Murcia Juan P. , Pinilla A´lvaro
Published: May 2009

The purpose of this paper is to present the experimental performance tests of a family of turbine ventilators designed, using the momentum-blade element theory. The turbine ventilator is designed such that multiple blade configurations and different geometric angles of attack were varied. A total of 108 turbine configurations were tested. The experimentation process is carried out with an open section Low-Speed wind tunnel at the Universidad de los Andes in Bogota´, Colombia. The power coefficient CP and torque coefficient CT curves were derived from rotational speed data measured using a 100 pulses-per-second optical encoder. The best configuration achieved consists of a 16 blades turbine with a −70° geometric angle of attack which has the following maximum values: CP of 0.18, CT of 0.82. This paper outlines the results obtained during a four month (150 hours - 3 academic credits) length undergraduate research project completed at the Universidad de los Andes.
Analysis of Functionally Graded Cylindrical Panel Under Mechanical Loading
Authors: Ghaderi P. , Fathizadeh A. , Bankehsaz M.
Published: May 2009

In this paper a semi-analytical method is developed to analyze functionally graded cylindrical panels. In this method, the radial domain is divided into some finite sub-domains and the material properties are assumed to be constant in each subdomain. Imposing the continuity conditions at the interface of the adjacent sub-domains, together with the global boundary conditions, a set of linear algebraic equations are derived. Solving the linear algebraic equations, the elastic response for the thick-walled FG cylindrical panel is obtained. The method can be used for all material properties variations but in present study, material properties are assumed vary with Mori-Tanaka estimation. Results are compared with the first order shear deformation theory and third order shear deformation theory of Reddy and accuracy of these theories in assessed for FG cylindrical panels with different aspect ratios.
Preparing Practicing Engineers for Distance ME Graduate Programs
Authors: Kazakia Jacob Y.
Published: May 2009

Practicing Mechanical engineers desire to advance their careers and job satisfaction by pursuing distance graduate degree programs, mainly towards Master’s degrees. The start up stage of such studies is problematic among engineers who stayed away from formal education for a period of years. The structure of the Graduate Program in Mechanical Engineering at Lehigh University and some history of frustrated attempts of distance students is first discussed. Subsequently, the concept of making available a course which will prepare a fraction of distance students by refreshing their memory of some basic skills is presented and the methods of preparing and offering such a course are outlined. Illustrations of the relevant course material and a short discussion of the academic history of distance students who participated in this course are presented.
Enhanced Cross-Axis Rejection Capacitive Strain Gauge
Authors: Jamshidi Babak , Azevedo Robert G. , Jog Anand V. , Pisano Albert P.
Published: May 2009

A novel bending plate capacitive strain gauge is designed, fabricated, and tested to measure strain in the range of 1 to 1000 με. This silicon-based strain sensor uses a unique structural design to increase the on-axis gain through the use of a bending beam structure while attenuating signals due to cross-axis strain. A differential capacitive measurement is used to improve the output, reduce the parasitic capacitance, and eliminate the capacitance measurement error due to temperature. The device is fabricated using silicon-on-insulator (SOI) technology. Experimental results exhibit an on-axis sensitivity of 50 aF/με and attenuation of the cross-axis sensitivity to shear strain to less than 10 percent of the applied shear strain. A detailed mechanical analysis of the suspension and deflection-amplifying bent-beam capacitor will be presented. Furthermore, the capacitive plate analytical model is compared to finite element simulations and verified with experimental results. In addition, a noise assessment of the device shows the electronics noise dominates the Brownian noise.
Numerical Investigation on Cooling of Small Form Factor Computer Cases
Authors: Orhan O¨mer Emre , Tarı I˙lker
Published: May 2009

In this study, cooling of small form factor computers is numerically investigated. The numerical model is analyzed using a commercial finite volume computational fluid dynamics software package. The effects of grid selection, discretization schemes and turbulence model selection on simulation results are discussed. In addition, recirculation and relaminarization are addressed briefly as examples of physical phenomena affecting cooling. For a comparison with the computational fluid dynamics results, an experiment is conducted and some temperature measurements are obtained from critical locations inside the chassis. The computational results were found to be in good agreement with the experimental ones.
Oregon Institute of Technology Robotic Control System
Authors: Bates Charles R. , Oare Joshua , Carey Brady , Gaston Nicholas
Published: May 2009

For our Junior Project course we worked with John Anderson, apart of the Mechanical and Manufacturing Engineering and Technology department at Oregon Institute of Technology, to build a Robotic Control System. This system would allow a more cost effective way for teachers and students to create scripts for running a robot in an industry style assembly line. The basic functionality of such a program is to allow the user to create, manage, debug, run and save scripts that will directly manipulate a connected robot. The long term goal was to have a system that will allow any kind of robot to be implemented and have our front end connect to it and work exactly the same. We accomplished this using careful planning to give it the most agile feel possible. We are also attempting to utilize a combination of Microsoft Robotics Studio and direct serial port communication to interact with a Lynxmotion Lynx6 robot.
Study of Flame Retardancy of Carbon Nanopaper Sheets in Glass Fiber-Reinforced Polyester Composites
Authors: Zhao Z. F. , Gou J.
Published: May 2009

In recent years, more severe requirement of budget and safety from industrial fields, especially space exploration and defense field, demand a new class of materials whose characteristics can satisfy both various engineering requirement and strict safety standard. The latter demands materials to have good thermal properties and significantly improved fire retardant property. In this research, multifunctional materials with layered structures are made from polyester resin, glass fiber mats and carbon nanofibers (CNFs). CNFs are added to the resin component of the composite laminates as additives in pulverised form and carbon nanofiber paper sheets (CNFS), respectively. Their flammability behaviors are investigated with cone calorimeter under well-controlled combustion conditions. And their heat release rate and other test parameters are compared and discussed, such as ignition time, heat release rate (HRR), peak heat release rate (PHRR), and so on. Although its PHRR is sharply increased to higher level for CNFS enforced composite laminates, its HRR curve is lowered greatly in most flaming time. Therefore, the pre-incorporated CNFS may act as an excellent insulator and mass transport barrier, improving the flame retardant property.
Substrate Preparation by Magnetron Sputtering and CVD Growth of Carbon Nanotube Arrays
Authors: Salunke Pravahan , Fischbach Kyle , Yarmolenko Sergei , Li Ge , Yun Yeo-Heung , Neralla Sudhir , Schulz Mark , Sankar Jag , Shanov Vesselin
Published: May 2009

In this study we explored the use of magnetron sputtering as an alternative to e-beam deposition for preparation of the alumina intermediate layer and of the metal catalyst on an oxidized Si wafer. This approach offers large area deposition of the layered substrate including the intermediate alumina layer and the final catalyst film. The effects of the substrate design on the growth of long multi-wall carbon nanotube (MWCNT) arrays by CVD (Chemical Vapor Deposition) were also explored. The CNT synthesis was carried on in a hydrogen/ethylene/water/argon environment at 750 °C for different periods of deposition time. Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA) and Transmission Electron Microscopy (TEM) were employed to characterize the substrates and the CNT arrays. The study showed that for specific processing conditions the length of highly oriented CNTs strongly depends on the thickness of Al2O3 intermediate layer and on the catalyst film. The results obtained confirm that magnetron sputtering can be successfully employed as a tool for substrate preparation to grow 7 mm long CNT arrays with high purity. The aligned nanotubes do not suffer from limitations typical for powdered (spaghetti type) nanotubes which opens up new applications.
Delamination Onset and Growth Prediction of Advanced Composite Materials With a Fabrication Flaw
Authors: Lua Jim , Sankar Jagannathan
Published: May 2009

The delamination failure mode is particularly significant in the damage tolerance design of advanced composite, since manufacturing flaws and in-service damage most often manifest themselves as interlaminar cracks. The primary goal of this paper is to evaluate the validity and accuracy of the developed cohesive interface model in predicting the fracture parameters at coupon and component level. To capture crack initiation and growth under mixed mode loading, a cohesive model based on a bi-linear constitutive material law is implemented in LSDYNA via a user-defined material model. The cohesive model parameters and the associated fracture toughness are determined for both primary and secondary bond coupons subjected to double cantilever beam and end notch flexure loading. An iterative solution procedure is used to determine the cohesive parameters by matching the failure load/displacement prediction with the observed test data. To explore the feasibility of using coupon level fracture parameters for fracture prediction at component level, the determined cohesive models are used to predict the critical failure load associated with delamination onset and growth of doubler specimens under axial and bending loads.
Flexural Testing of Shape Memory Polymers for Morphing Aircraft Applications
Authors: Gross Korey , Weiland Lisa
Published: May 2009

Shape memory polymers (SMPs) have garnered significant attention in recent years for their potential to return to a “memorized” state when warmed above their glass transition temperature Tg. However, they also have potential in morphing aircraft applications because of their significant modulus change above and below Tg. Much less energy is required to deform this material when in its soft state, but when the material returns to the hard state, it is able to support significant loads. In the proposed effort, SMP is experimentally considered as a candidate material for morphing aircraft applications where the material’s ability to support out of plane loads above and below the Tg is of primary importance. The SMP of study in the work is Veriflex®.
Numerical and Experimental Study of Merging Fires in Square Arrays
Authors: Satoh Kohyu , Naian Liu , Qiong Liu , Yang K. T.
Published: May 2009

In large-scale forest fires and city fires, merging fires and fire whirls have often been observed, which cause substantial casualties and property damages. It is important to know particularly where and under what conditions of weather such merging fires and fire whirls appear in cities or forests. However, there have been no adequate answers, since the detailed physical characteristics about them are not fully clarified yet, although previous studies have examined the phenomena of merging flames. Therefore, we have carried out preliminary studies and found that the merged tall fires can enhance the fire spread, and developed a method to analyze burn-out data of fire arrays. If sufficient knowledge can be obtained by relevant experiments and numerical computations, it may be possible to mitigate the damages due to merged fires and fire whirls. The objective of this study is to investigate the merging conditions of fires in square arrays in laboratory experiments and also by CFD numerical simulations, varying the size of square array, inter-fire distance and heat release rate, to judge ‘unmerged’ or ‘merged’ conditions in the fire array. It has been found that the fire merging is dependent on the inter-fire distance in the array and also on the total heat release rate of all fires surrounding the center region of the array. Also found that the experimental and simulated results on the merged and unmerged cases in the fire array, as affected by the total heat release rate and the inter-fire distance, which control the convective gas flow into the array, behave very similarly. Therefore, it can be concluded that the fire merging in array fires are highly based on the convection in the flow field due to fires and can be predicted by simple CFD simulations.
Analysis to Develop Hydrogen Production From Bio-Oils
Authors: Ciocci R. C. , Abu-Mahfouz I. , Elnashaie S. S. E. H.
Published: May 2009

The United States economy’s dependence on fossil fuels has historical significance but lacks vision for a long-lasting fuel consumption policy. Political complications, economic instabilities, supply shortages, and continued pollution contributions pose significant obstacles to continued reliance on oil. Alternative technologies based on renewable resources offer much more promise for a sustainable approach to meeting global energy needs. Recent research and applications have established hydrogen as a viable clean fuel source. Those applications, including fuel cells, have shown promise for the eventual migration from a fossil-fuel economy to one based on renewable energy sources. Air pollution, specifically contributions to greenhouse gases, is a major environmental hazard due to the use of fossil fuel-related hydrocarbons for fuel and industrial applications. An alternative, hydrogen, offers significant advantages as an ultra-clean fuel of the future when it is burned directly or processed through fuel cells. Currently, the main process for hydrogen production is catalytic steam reforming of natural gas. This process is relatively inefficient and does not allow the use of a wide range of feedstock materials including renewable sources. The objective of impending research is to develop this new, ultra-clean and efficient process, which converts a wide range of hydrocarbons, including renewable bio-oils, into pure hydrogen suitable for fuel cells and which also converts CO2 emission into syngas. The main impact is clearly on air pollution and global warming through the minimization of greenhouse gas emission and the economical production of pure hydrogen to foster the hydrogen economy. This new process will achieve considerable increase in hydrogen productivity and considerable decrease in the energy consumed to produce it. The technology will center on a circulating fluidized bed (CFB) that will separate hydrogen from bio-oils in an efficient process that greatly reduces polluting hydrocarbons compared to traditional fossil fuel processing. Early studies will include the mathematical modeling of computational fluid dynamics to identify process parameters. Eventually, a pilot plant will be used to verify/modify the mathematical model, for a wide range of conditions and renewable feedstocks. Testing the pilot plant will lead to the development of reliable design equations suitable for replication, build, and tight control of this novel process.
Using Parameterized Pareto Sets to Model Design Concepts
Authors: Malak Richard J. , Paredis Christiaan J. J.
Published: May 2009

Decisions made during conceptual design can have a major impact on the success of a design project, and designers must take care to select a concept that leads to a desirable design solution. However, the inherently imprecise nature of design concepts complicates decision making. A single concept relates to a large set of specific design implementations, each of which has a different level of desirability based on the tradeoffs designers are willing to make. Thus, designers must consider tradeoffs across the many possible implementations of a design concept in order to decide between concepts rigorously. To accomplish this efficiently, designers require an abstract understanding of the characteristics of a design concept. In this paper, we describe an approach to modeling design concepts that is based on an extension of the notion of a Pareto set, called a parameterized Pareto set. Using this construct, designers can generate a model based on information about prior implementations of a design concept in a way that includes tradeoff information while being independent of implementation details and reusable for different design problems. We demonstrate the approach on the conceptual design of a gearbox. The example involves two different design scenarios that serve to demonstrate the reusability of the model and effectiveness of the overall approach.
Smooth Non-Linear Springs, Particularly Smooth Progressive-Rate Steel Springs
Authors: Oledzki Wieslaw J.
Published: May 2009

In this paper I discuss my invention that solves the problem of designing and manufacturing springs made of elastic materials, particularly steel springs, with prescribed characteristic (dependence of flex on external load) given by a smooth (i.e. differentiable) non-linear function. The method according to the invention consists in forming an elastic body with suitably shaped regions of diversified stiffness and (possibly) diversified initial internal stresses. This suitable shape of the regions lies at the hart of the invention and is briefly discussed in the paper. I also give some formulas for the spring characteristic of the springs according to the invention and describe a method for obtaining these formulas. The paper is a companion to my patent applications “Smooth non-linear springs, particularly smooth progressive rate steel springs, progressive rate vehicle suspensions and method”, US 11/950,935 and PL P380,914.
Analysis on Rapid Cooling and Epitaxial Solidification of a Plasma-Sprayed Yttria Stabilized Zirconia Splat on a High-Temperature Substrate
Authors: Xing Ya-Zhe , Li Chang-Jiu , Qiao Jiang-Hao , Wang Guo-Xiang
Published: May 2009

In many applications, it will be beneficial if the plasma-sprayed Yttria stabilized zirconia (YSZ) coatings exhibit epitaxial growth. Early experiments in plasma spray have shown that a high initial substrate temperature may help develop epitaxial growth from the previous deposited splats. This paper has performed an experiment to demonstrate the possibility of epitaxial growth in plasma-sprayed YSZ coatings at high substrate temperatures. A quantitative analysis of splat cooling and rapid solidification of the YSZ splat is then presented. The analysis is based on a one-dimension heat transfer model of a thin liquid YSZ layer in contact with an YSZ substrate at fairly high initial temperature. The model calculations indicate that equilibrium solidification may take place on the YSZ substrate but with a solidification temperature that is much higher than the YSZ substrate temperature. Such equilibrium solidification requires nucleation of new crystalline YSZ and therefore only leads to non-epitaxial growth. Epitaxial growth, on the other hand, requires a large melt undercooling so the YSZ crystalline can grow directly from the substrate surface, which is at a much lower temperature than the equilibrium melting point. The effect of the substrate initial temperature on the development of melt undercooling within the splat is investigated in detail. Some interesting observations have been made which may explain the physics of epitaxial growth in YSZ coatings.
Inducing Residual Stress in Bone Using Abrasive Air-Jet Surface Treatment
Authors: Hizal Alpay , Sadasivam Balaji , Arola Dwayne
Published: May 2009

Based on past research, the growth and repair of bone is a function of physical activity (i.e. stresses) and bone chemistry. As such, the rate of recovery of an individual that has undergone total joint arthroplasty could be influenced by the introduction of changes in bone chemistry and “apparent” stress state in the bone that results from the surgical procedures and/or treatments. This preliminary study explored the opportunity for introducing residual stresses in hard tissues using an air-jet surface treatment. Cortical bone was obtained from bovine femurs and treated with an abrasive jet process. The radius of curvature of the bone specimens was estimated before and after treatment and used in estimating the magnitude of surface residual stress. An SEM analysis was also performed to examine structural changes in the bone caused by the surface treatment. Results showed that it is possible to impart residual stress within bone using an air-jet surface treatment. The magnitude of surface residual stress was 16 ± 0.8 MPa. Residual stresses appeared to result from a combination of near-surface deformation and embedded particles.
How the Input Impedance Relates to Airway Characteristics
Authors: Cheong S. H. , Ro S. H. , Al-Jumaily A. M.
Published: May 2009

To understand how the input impedance determined at the throat correlates with changes in the dynamic characteristics of the airways, a simplified 5-lobe model is developed and simulated. The model takes into account some realistic conditions such as varying cross-sectional areas, flexible wall properties and branching. The lobe terminal impedances are implemented in the model to predict the input impedance at the throat. The effects of airway constrictions and wall eleatance variations on this impedance are determined for a range of frequencies. It is concluded that the developed model is capable of predicting various physiological changes in the airway passages.
A Review of Available Computer Software Packages for Use in an Undergraduate Heat Transfer Course
Authors: Karimi Amir , De Leon Jeanette , Hannan Mohamed
Published: May 2009

Available computer software packages for use in an undergraduate or introductory graduate heat transfer course are reviewed. Brief introductions for using each of the software are provided. A comparison of these software packages highlighting the strengths and limitations of each software is also discussed. A few examples are included to demonstrate the application of the available software in analysis of heat transfer problems.
Study of the Mechanical Properties of Nanostructured Aluminum Obtained by SMAT
Authors: Chan H. L. , Lu J. , Schoberth A.
Published: May 2009

Enhanced mechanical properties were found on an Aluminum alloy treated by Surface Mechanical Attrition Treatment (SMAT) in this work. The average hardness of the annealed Aluminum alloy at the surface was enhanced up to 43% and reached 170 HV, and that of the bulk part could also be improved up to 20% which is 140 HV. The yield strength obtained under tensile test had significant improvement which may achieve up to 400 MPa. In this study, it is discovered that the surface nanostructured layer obtained by SMAT can be as thick as 100 μm and its effect can be observable along a specimen of 2 mm thickness. In the paper, more detailed experimental results will be presented as well as the experimental setup. The present study demonstrates the potential of the process for obtaining good strength on Aluminum alloy for aerospace applications.
Aerodynamic Performance of Wind Turbine Blades in Dusty Environments
Authors: Khakpour Yasmin , Bardakji Suheila , Nair Sudhakar
Published: May 2009

The performance of wind turbine blades can be affected by conditions such as sand concentration in dry dusty environments. The mathematical formulations for continuum phase (air) and discrete phase (sand particles) along with the imposed assumptions and applied boundary conditions are presented in this paper. The numerical simulation conducted in this paper studied the effect of sand particles on flow structure and essential dimensionless numbers for flow over the primary airfoil of the wind turbine. The effects of controlling parameters such as sand dimensions, sand/air drift velocity and sand/air mass flow rate ratio are studied and the results are compared against the conditions of uniform, far-field air flow. The results are presented in terms of pressure distribution over the airfoil surface, drag and lift coefficients along with variation of erosion and accretion due to the collision of sand particles over the airfoil surface for various attack angles.
Nonlinear Behavior of Micro Bubbles Under Ultrasound Due to Heat Transfer
Authors: Im Chansoo , Kim Jeong Eun , Lee Jae Young , Kwak Ho-Young
Published: May 2009

Nonlinear behavior of a microbubble under ultrasound was investigated with consideration of heat transfer inside bubble and through the bubble wall. The polytropic relation which has been used for the process of volume change of ideal gases cannot properly treat the heat transfer involving the oscillating bubble under ultrasound. In this study, the heat transfer related to the motion of the bubble under ultrasound, which is affected by heat transfer across the bubble wall crucially was investigated by a set of solutions of the Navier-Stokes equations for the gas inside the bubble and an analytical treatment of the Navier-Stokes equations for the liquid adjacent to the bubble wall. The entropy generation due to finite heat transfer, which induces the lost work during bubble evolution, reduces the collapsing process, and affects the nonlinear behavior of bubble considerably.
A Novel Parallel Mechanism With 3-RRUR Legs
Authors: Li Yanwen , Zhang Yueyue , Wang Lumin , Huang Zhen
Published: May 2009

This paper investigates a novel 4-DOF 3-RRUR parallel manipulator, the number and the characteristics of its degrees of freedom are determined firstly, the rational input plan and the invert and forward kinematic solutions are carried out then. The corresponding numeral example of the forward kinematics is given. This type of parallel manipulators has a symmetrical structure, less accumulated error, and can be used to construct virtual-axis machine tools. The analysis in this paper will play an important role in promoting the application of such manipulators.
Numerical Study on Slag Flow in an Entrained-Flow Gasifier
Authors: Liu Sheng , Hao Yingli
Published: May 2009

A 2-D model for the slag flow, heat and mass transfer and solidification was developed to simulate the slag motion in the entrained-flow gasifier. Some assumptions were adopted to make the simulation practical and reduce the calculating time. The slag is treated as Newtonian fluid at the temperature above the temperature of critical viscosity, and solid below the temperature of critical viscosity. VOF model is used to capture the free surface between the syngas and slag layer. Numerical simulation of the slag flow in the gasifier is conducted by solving the equations of motion. The thickness of the slag layer, temperature distribution in the gasifier can be obtained. A series of simulations have been carried out to test the model. The effects of main variables on the flow, heat and mass transfer of slag on the refractory wall in the gasifier are analyzed numerically.
Blade Material Fatigue Assessment Using Elman Neural Networks
Authors: Yan Jihong , Wang Pengxiang
Published: May 2009

Material degradation evaluation and life prediction of major components such as blades, rotors, valves of steam turbines not only guarantees reliable, efficient and continuous operation of electric plants, but also offers the promise of substantially reducing the cost of repair and replacement of defective parts, and may even result in saving lives. In this paper, a recurrent neural network based strategy was developed for material degradation assessment and fatigue damage propagation prediction. Two Elman Neural Networks were developed for fatigue severity assessment and trend prediction correspondingly. The performance of the proposed prognostic methodology was evaluated by using blade material fatigue data collected from a material testing system. The prognostic method is found to be a reliable and robust material fatigue predictor.
Stability Behavior of Model Reference Adaptive Control Methods in Presence of Aircraft Structural Damage
Authors: Nespeca Pascal , Sarigul-Klijn Nesrin
Published: May 2009

Any classical control design starts by first satisfying stability and then looking towards satisfying transient requirements. Similarly, a Model Reference Adaptive Control (MRAC) Method should start with a stability analysis. Lyapunov function analysis is first used to justify the stability of the adaptive scheme. Next, a numerical study is conducted to predict the stability behavior of three different MRAC methods in the presence of large unanticipated changes in the dynamics of an aircraft. The Model reference adaptive control methods studied are: Method:1, an adaptive gain method; Method:2, a Neural Network (NN) approximation technique; and, Method:3, a linear approximation technique. For comparison purposes, the aircraft is assumed to have Linear Time Invariant, LTI dynamics. Each algorithm is given full state feedback, an inaccurate reference model and a poor Linear Quadratic Regulator, LQR design for the true plant. It is seen that when the LQR stabilizes the true plant, the three algorithms all achieve the same steady state error to a step command. Numerical results predict the different types of stability behavior that the algorithms provide. It is seen that the Methods: 2 and 3 can only provide a bounded stability, whereas Method: 1 can provide an asymptotic stability. A robust static controller can satisfy stability, but a robust static controller that accommodates variations in plant dynamics might not always be able to match transient requirements as expected. Although there may be no analytical guarantee from adaptive controllers of transient performance, one might look at anecdotal performances.
The Movement Simulation of 3-RPS Parallel Pyramid Mechanism
Authors: Mu Dejun , Huang Zhen
Published: May 2009

3-RPS parallel pyramid mechanism has three constraining force screw to limit the translations of the pyramid in three directions. Three dimensions rotation is allowed. The axis of rotation does not intersect at one point. In the paper, the motion and input rationality of the 3-RPS pyramid mechanism are analyzed using the screw theory, the inverse solution and forward solution of mechanism are studied. Applying the relative constrains to this mechanism, the CARDAN movement of the pyramid mechanism was simulated by MATLAB.
Design of Biomechanical Testing Methods and Metrics to Evaluate the Performance of Synthetic Spinal Implants Versus Bone Graft for Lumbar Corpectomy
Authors: Huang P. , Sarigul-Klijn N. , Hazelwood S. , Gupta M. , Roberto R.
Published: May 2009

The human spine is a mechanically complex system of joints crucial for stable posture and movement. The ultimate goal of a vertebral body replacement following a spinal injury that necessitates such a procedure is to have the replacement strut fully incorporate into the spine. This incorporation process is known as bony “fusion”, which facilitates the restoration of stability. Bone graft and metallic implants have been used for vertebral body replacement procedures. Both methods have been associated with failure of fusion and recurrence of instability. The development and rationale of the mechanical testing procedures implemented to best differentiate the stability afforded by bone graft versus expandable titanium cage is presented.
Energy Allocation in Piezoelectric Superlattices
Authors: Chou Yuan-Fang , Yang Ming-Yi
Published: May 2009

A piezoelectric superlattice is formed by intervallic polarizing oppositely along one direction in a piezoelectric solid. Due to the strong coupling between acoustic and electromagnetic behavior, Newton’s equations of motion and Maxwell’s equations have to be satisfied simultaneously. The polariton behavior in the superlattice is studied by plane-wave expansion method. Both band structure and field patterns are calculated. In the vicinity of the center of the first Brillouin zone, strong coupling of acoustic and electromagnetic energies are found in both passing and stopping bands. The kinetic, strain, electric, and magnetic energies of polariton are analyzed in detail. Correlation between energy allocation and field patterns is investigated.
Sandwich Core Cracks Approaching the Interface Between the Core and Face Sheets
Authors: Andreasen J. H.
Published: May 2009

Cracks approaching the interfaces in the core of a sandwich construction are investigated. For pure tension, pure bending and shear the cracks are shown to go through a regime where a maximum stress intensity factor is attained before the crack tips enter the interface. The cracks are analyzed within the framework of analytical elasticity. The analysis methods are outlined, and the solution is established in an object oriented programming environment, which allows solutions to be obtained for a wide variety of parameters. Results are given in terms of a case study pertaining to sandwich constructions with aluminum faces and two different foamed PVC core, as well as in more generalized terms.
Relaxation Investigation for Terminals of Electronic Connectors Under Thermal Shock Test
Authors: Liao K.-C. , Lin K.-H.
Published: May 2009

Electronic connectors are in general required to pass specifications of the thermal shock test. The contact force of the terminal could decay gradually due to the stress relaxation effect under thermal loading conditions. A finite element analysis is conducted to examine the contact force variation of the terminal in the present study. Both a plug and a receptacle socket of mini USB are chosen for the investigation here. A mated socket pair is placed in the temperature-controlled chamber, and the associated electrical resistance is then measured on-line in certain periods based on the specifications of the thermal shock test. Experiments indicate that the electrical resistance rises slowly as the thermal cycle number increases. Viscoplasticity is adopted for the terminal material of phosphor bronze alloy in the numerical analysis. Stress-strain relations of the terminal at various temperatures are measured via the uniaxial tensile test. A power-law creep model with the strain-hardening form is selected to account for the relaxation behavior of the terminal. Corresponding parameters of the creep model are evaluated based on the uniaxial tensile relaxation test. Simulation results show that the decreased amount of the contact force is rather limited after ten thermal cycles. Relationships between the contact force and the electrical resistance increasing percentage are then investigated.
A Comparative Analysis of the Economic Viability of STEM and Other Fields of Study
Authors: Wong Kau-Fui V. , Kuhn Thomas
Published: May 2009

Finding a high paying job in an expanding market is a challenging goal that many people face today. The current work addresses the issue, principally to aid parents, college undergraduates and high school seniors. With many different options available, it is important to identify those options that can lead to economic success with expected job growth. One measure that can be used is monthly income. Looking at the past values for monthly income will give a good idea of which fields are high paying. It is also necessary to project future monthly income based on field of baccalaureate degree earned in order to accurately see what direction the fields are headed financially. Applying the data available to various stationary and trend based models will allow predictions to be made for the future monthly earnings for a field. This paper will aim to validate STEM as a viable option to choose for high pay and increased job growth.
Development of a Cost-Effective Hydrogen Production System for Vehicle Fueling Stations
Authors: Aaron Timothy M. , Schwartz Joseph M.
Published: May 2009

The need to transition from oil dependency to an alternative transportation fuel has been well documented over the last 30 years. Many alternative energy sources have been researched and developed, but none, to this point, has been able to compete with the cost and versatility of gasoline. The use of hydrogen fuel cells for transportation is one of the concepts being highly supported as a potential environmentally clean alternative energy technology. Significant research and development has dramatically increased the feasibility of this technology, but many additional breakthroughs, including a cost effective supply of hydrogen at fueling stations, will be required for fuel cell vehicles (FCV) to compete with gasoline fueled internal combustion engines (ICE). This paper describes the development of an on-site hydrogen supply system based on steam methane reforming (SMR) that could easily be added to a typical fueling station. The system is not intended to fuel the equivalent of all the cars on the road today, but to provide enough hydrogen for the transition period from gasoline powered transportation to the hydrogen fuel cell. Opportunities exist for a significant reduction in hydrogen cost by introducing advanced design technologies, such as Design for Manufacturing and Assembly (DFMA), to the development of hydrogen production systems. A reformer-based system designed using the DFMA approach is expected to significantly reduce the capital cost by minimizing the overall part count, simplifying the design, and optimizing the assembly process. Praxair, in cooperation with the U.S. Department of Energy (DOE), is developing a small SMR-based system using this approach. This paper presents an overview of the impact of this approach on the system design as well as the overall cost for small on-site hydrogen production. The paper also provides an analysis of hydrogen fueling station criteria and an overview of issues related to on-board hydrogen vehicle storage.
Prediction of Ship Acoustic Signature Due to Fluid Flow
Authors: Seto Mae L. , Campregher Rubens , Murphy Stefan , Militzer Julio
Published: May 2009

The contribution of flow noise to the radiated acoustic signature of CFAV Quest is of interest. Quest is the research ship used by Defence R&D Canada as a quiet platform. It is difficult to identify the flow noise component in an acoustic ranging so there is interest in predicting the flow noise as a first step towards extracting it from range measurements. Below propulsor cavitation inception speeds, machinery-induced noise dominates. While flow noise does not usually dominate in the presence of machinery-induced noise or propulsor cavitation, it is unclear what fraction of the total noise power flow noise constitutes. A direct numerical simulation for a complex ship geometry was impractical so an alternative approach was sought. An immersed boundary method was used to model the presence of the ship in the flow domain. The unsteady flow field was calculated using a finite volume method over an unstructured Cartesian grid. The flow field around Quest in straight and level flight was calculated at Reynolds numbers between 1.8×108 and 4.3×108, corresponding to a full-scale speed range of 4 to 10 knots. Results from such flow field predictions become the hydrodynamic sources in the integrals of Lighthill’s acoustic analogy to predict the far-field acoustic signature from the flow past the hull. These far-field predictions consist of computing the propagation and radiation of the hydrodynamic sources. This assumes noise generation and its propagation are decoupled. Under certain circumstances, knowledge of the predicted flow component helps to extract it from a standard acoustic ranging.
Improving Students’ Understanding of the Impact of Engineering Solutions in a Global and Societal Context
Authors: Bannerot Richard , Wilson Chad , Kastor Ross
Published: May 2009

ABET 2000 imposes the requirement that engineering programs demonstrate that graduates “have the broad education necessary to understand the impact of engineering solutions in a global and societal context”. (Criterion 3h) The implication is that providing the “exposure” to the impact of engineering should be sufficient. However, demonstrating learning takes the process another step. Over the past few years, we have added material to several existing, traditional mechanical engineering courses and added one entirely new course in response to the requirements of ABET 2000 in general and Criterion 3h in particular. We have also introduced additional surveys, assignments and testing into these courses to assess specific aspects of student learning. This paper describes the changes in the sophomore design class, the second course in thermodynamics, the heat transfer course, and the capstone course as well as the new College course in technical communications related to the impact of engineering solutions. The assessment processes are also described.
Dynamic Rheology and Microstructure of Polypropylene/Clay Nanocomposites Prepared Under Sc-CO2 by Melt Compounding
Authors: Zhao Yang , Huang Han-Xiong
Published: May 2009

The polypropylene (PP)/clay nanocomposites were prepared using a twin screw extruder with the aid of the supercritical carbon dioxide (Sc-CO2). The dynamic rheological properties were measured using a rheometer in the oscillatory mode. X-ray diffraction and transmission electron microscopy were used to characterize the microstructure of extruded nanocomposites. Results showed that an optimized CO2 concentration existed. When the CO2 concentration increased up to the optimized level, the nanocomposites tended to be more viscous, especially at low frequency. Whereas further increasing the CO2 concentration resulted in the decrease in the complex viscosity and dynamic moduli. The presence of Sc-CO2 with the concentration not higher than the optimized level was helpful to promote the degree of dispersion of the nano-clay in PP matrix, and overloaded CO2 would have negative effect on the clay dispersion.