bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Ship Tilt and Pitch on a Capillary Assisted Thermosyphon (CAT) for Shipboard Electronics Cooling
Authors: Larsen E. H. , Smith A. N. , Cerza M. , Conroy C. Thomas
Published: May 2008

As microprocessors shrink in size and increase in power dissipation levels, the current need for advanced electronics cooling techniques is paramount. Power dissipation levels are rapidly exceeding the capabilities of forced air convection cooling. This paper reports an investigation of using a capillary assisted thermosyphon (CAT) for the shipboard cooling of electronics components. The CAT differs from the capillary pumped loop (CPL) or loop heat pipe (LHP) system in that the basic cooling loop is based on a thermosyphon. The capillary assist comes from the fact that there is a wicking structure in the flat evaporator plate. The wicking structure is there to spread the working fluid across the vertical flat plate evaporator to the areas under the heat sources. This differs from a capillary pumped loop in that the capillary pumping action of the wick structure does not produce the sole pumping head from the liquid return to the vapor outlet side of the evaporator. In fact, the liquid return and vapor outlet are almost at the same pressure. The forced circulation in the thermosyphon is caused by a gravity head between the condenser cold plate and the flat plate evaporator. An experimental facility for conducting research on a CAT was developed. In order to simulate the shipboard cooling water encountered at various locations of the ocean, the heat sink temperature of the facility was varied. A vertical flat plate, CAT evaporator was designed and tested with a thermal sink temperature of 21° C. The condenser cold plate cooling water flowrate was set at 3.8 lpm. The heat input was held constant at 1500 W for the independent tilt and pitch cases. For the extreme tilt and pitch combined case, the heat input varied from 400 to 2000 W. The flat evaporator plate was tilted from side to side over a range +/− 45 degrees from vertical and the plate was pitched fore and aft over a range of +/− 45 degrees. This tilt and pitch orientation was to simulate that orientation which a ship might undergo in various sea states. In addition an extreme case which consisted of a 45 degree tilt and a 45 degree pitch was tested and compared to the normal vertical geometry. Results indicate that the CAT loop was very robust and handled all geometric orientations with minimal degradation in operating temperature performance.
Higher Order Computations of the Convection-Diffusion Equation With Curved Boundaries
Authors: Lee Heejin , Chen Michael M.
Published: May 2008

In computational heat transfer and fluid mechanics, high order accuracy methods are desirable in order to reduce computational effort or to obtain more accurate solutions for a given mesh coarseness. On structured grids, the finite difference method is especially easy for deriving and implementing higher order schemes. In spite of this advantage, for complex geometries high order schemes have not been attractive due to the restriction of the structured grid in dealing with curved boundaries. Therefore, for complex geometries most computational methods are based on finite element or finite volume methods with unstructured or boundary-fitted mesh at the expense of difficult and complicated implementation. For this reason, few computations for complex geometries have attempted more than near-second-order accuracy. In our paper, we demonstrate a high order scheme to deal with curved boundaries of complex geometries in Cartesian coordinate system using the finite difference method, taking advantages of the ease and simplicity of structured grid. The method is based on an extension of the full second order methods presented previously by Jung et al. [2000] and Lee and Chen [2002]. The temperature distributions and maximum errors in a cylindrical solid and an annulus where the velocity distribution is given were calculated with a third order accurate scheme, and compared with exact solutions. Theoretical derivations and numerical experiments show that true third order accuracy have been attained in advection-diffusion problems with curved boundaries. The results reinforce the assertion that the same concepts can be extended to any order accuracy so far as such accuracy is deemed desirable for the problem of interest.
Hourly Distribution of Diffuse Illuminance
Authors: Satyamurty V. V. , Ravikumar P.
Published: May 2008

It has been found that the values of ratio of hourly diffuse illuminance to daily diffuse illuminance, rvd, are very close to the corresponding values for diffuse solar radiation, rd, examined from the measured data of two locations. This has been further confirmed by examining the values for rvd and rd as calculated from TMY2 [1] data base for primary locations. Based on this, it has been proposed that the correlations available in literature to predict rd can be employed to predict rvd Adequacy of the correlation due to Satyamurty and Lahiri [2] available for rd has been examined to predict rvd as obtained from TMY2 data base for the 56 primary locations. It has been found that the values of rvd obtained from measured illuminance data of two locations have been predicted within a rms difference of 7.1% and within a rms difference of 4.3% for the 56 primary locations of TMY2 data when the correlation due to Satyamurty and Lahiri for rd has been employed after suitable modification.
Stability Boundaries of High-Speed Milling Corresponding to Period Doubling Are Essentially Closed Curves
Authors: Szalai Ro´bert , Ste´pa´n Ga´bor
Published: May 2008

In this paper a new method for the stability analysis of high-speed milling processes is introduced. The approach is based on the construction of a characteristic function whose complex roots determine the stability of the system. By using the argument principle, the number of roots causing instability can be counted, and thus, an exact stability chart can be drawn. In the special case of period doubling bifurcation, the corresponding multiplier −1 is substituted into the characteristic function leading to an implicit formula of the stability boundaries. Further investigations show that all the period doubling boundaries are closed curves, except the first lobe at the highest cutting speeds. Together with the stability boundaries of Neimark-Sacker (or secondary Hopf) bifurcations, the unstable parameter domains are formed from the union of lobes and lenses.
Scaling of Turbine Blade Roughness for Model Studies
Authors: McIlroy Hugh M. , Budwig Ralph S. , McEligot Donald M.
Published: May 2008

The purpose of this note is to provide an approach to scaling turbine blade roughness so a large-scale experiment will yield useful results despite lack of detailed knowledge about the application. In the process, an apparently new approach for scaling of actual turbine blade roughness on an experimental model of a rough turbine blade is presented. Rough surface data from a first-stage high-pressure turbine rotor, estimates of engine operating conditions representative of high-performance aircraft, and assumed matches of the Reynolds number and acceleration parameter ranges are used. A scaling factor is determined by estimating and matching the nondimensional roughness (in wall coordinates) of a typical airfoil for a model.
Challenges in Energy Efficient Thermal Management
Authors: Yazawa Kazuaki
Published: May 2008

For a surveillance of energy efficient thermal management, an extended review of literatures has been done. Covered cooling technologies are intended for or supposed to relate to energy efficient design. Individual technologies are categorized with the discussion of advantage/disadvantages. In addition, the impact such as volume and mass of total system design is discussed. A universal criterion of metric to measure the effectiveness of optimization for minimum energy input is proposed. Extensive review of the supposed relevant technologies gives the idea that each model could be used for energy efficient thermal design. On the other hand, it has been found that the lack of system level modeling as well as the considerations of transient phenomena is not enough. Since these are essential, it should be the challenge toward the future of environmental friendly thermal designs.
Flow and Heat Transfer in an Upper Half Cooled Lower Half Heated Enclosure With Horizontal Temperature Deviations
Authors: Li H. , Paudel G. , Braun M. J. , Evans E. A. , Wang G.-X.
Published: May 2008

The nature and patterns of solution flow in hydrothermal autoclaves are critical to the quality, growth uniformity, and growth rates of synthetic single crystals. Small horizontal temperature deviations, which exist in industrial practice, were found to be critical in establishing flow patterns. However, the mechanism that determines how temperature deviations affect flow pattern is not well understood. In this study, an experimental system is set-up to study the flow in a model reactor (an enclosure). Temperature in the enclosure is visualized using liquid crystals. With the experimental results, a numerical model is validated and then used to simulate flows in enclosures that are subjected to similar thermal condition as industrial autoclaves. Flow patterns are obtained with various temperature deviations, for various aspect ratios and various Rayleigh (Ra) number between 4.05E8 to 3.24E9. Flows studied are unsteady in nature. Without temperature deviations, the overall flow pattern is anti-symmetric. With a temperature deviation, the wall layers are un-balanced. The impingement of streams on the wall layers does not affect the wall layer flow at low Ra numbers. At high Ra number, wall layers are broken by the impinging streams. The dominant heat transfer mechanism in the enclosure changes significantly as the aspect ratio of the enclosure changes. In enclosures of high aspect ratios that heat transfer resistance is mainly at the fluid exchange between the two halves, temperature deviations significantly affect heat transfer by stabilizing the direction of the streams.
Component Assemblies in a Flexible Work-Cell via Intelligent Control
Authors: Gulati Navneet , Garg Devendra P.
Published: May 2008

The requirement to quickly change a product, the need to deliver high quality component, and a desire to reduce manufacturing related costs has led to the development of flexible work-cells. Integration of different sensors along with the careful selection/design of fixtures can add to the flexibility of a work-cell. Furthermore, an effective control of hardware in a flexible work-cell can increase the efficiency of a work-cell. This can be achieved by using available software (such as MATLAB, C++) to integrate the hardware for programming. This technique also leads to the control of a work-cell that is both real time and user-friendly. The strategy is demonstrated with the help of an example where two different types of assemblies were carried out in the same setup of a flexible work-cell.
Effect of Hygroscopic Swelling of Mold Compound on PEM Reliability
Authors: Han B. , Stellrecht E. , Pecht M.
Published: May 2008

Polymeric mold compounds absorb moisture, and thus swell, when exposed to a humid environment [1]. Hygroscopic stresses arise in plastic encapsulated microcircuits (PEMs) when the mold compound swells upon absorbing moisture and the lead frame, die paddle, and semiconductor chip, do not experience swelling.
Numerical Simulation of Two-Phase Flow and Heat Transfer in a Composite Duct
Authors: Yuan Jinliang , Sunde´n Bengt
Published: May 2008

In this work, a three-dimensional computational method has been further developed for a composite duct, to analyze water phase change and liquid water saturation level, two-phase flow and heat transfer in a multi-component mixture. The duct under consideration consists of a flow duct, porous layer and solid structure. Advanced boundary conditions are applied in the analysis, concerning the thermal boundary conditions, mass consumption and generation appearing on the active surface, interfacial conditions between the flow duct and the porous layer etc. The coupled effects of species composition, mass transfer, phase change/balance have been taken into account. It has been found that the two-phase flow is sensitive to the operating parameters, and liquid water transport is dominated by diffusion in the porous layer, based on its mass composition gradient.
Use of High Intensity Milling and Equal Channel Angular Extrusion to Produce and Consolidate Nanostructured Titanium Silicide
Authors: Kaculi Xhemal , Srinivasan Malur N. , Hartwig K. Ted
Published: May 2008

The focus of this research is on (a) the use of mechanical alloying (MA) to produce nanostructured titanium silicide (Ti5Si3) powder and (b) use of equal channel angular extrusion (ECAE) for powder consolidation to preserve the fine scale structure achieved via mechanical alloying. MA is a high-intensity ball milling process that can be used to produce nanocrystalline and amorphous powders. A 23 factorial design is applied to optimize the process and study the effect of MA parameters (milling time, milling speed, ball-to-powder ratio) on the grain size of powder. ECAE is a process that produces intense and uniform plastic deformation caused by simple shear of the material. A 4 × 2 factorial design was used to study the effect of ECAE parameters (number of extrusions, billet orientation, temperature) on the properties of the final product. The final product possesses a grain size of less than 20 nanometers.
Preventing Ceramic Chip Capacitor Cracking During Printing Wiring Board Bending
Authors: Blattau Nathan J. , Barker Donald B. , Hillman Craig D.
Published: May 2008

The purpose of this study is to investigate the possibility of using finite element models of varying complexities to better understand and predict the durability of multi-layer ceramic chip capacitors subjected to printed wiring board flexure. This study covers low voltage capacitors (0805, 1206, 1812, 2220 sizes) constructed from X7R ceramic mounted on FR-4 printed wiring boards. Existing failure data obtained from Kemet’s experiments on 0805 and 1206 capacitors is used to establish and verify the failure criterion, which is based upon the tensile stresses in the capacitor. This failure limit is determined by performing a finite element analysis that adequately represents the experiments performed by Kemet. The failure limit (overstress) is then extended to a family of capacitors to predict their durability with regard to printed wiring board flexure. Guidelines can then be established to aid designers in preventing failures of capacitors due to printed wiring board flexure.
Intelligent Techniques for Star-Pattern Recognition
Authors: Paladugu Lalitha , Schoen Marco P. , Williams Brian G.
Published: May 2008

This work presents the study of two different approaches for the attitude determination of space vehicles. The Neural Network approach is based on a simple Kohonen network, where the characteristics of a star distribution within the Field Of View (FOV) are matched against an on-board stored star map. The second approach utilizes a Genetic Algorithm (GA). The GA minimizes the discrepancy between the characteristics of the stars inside the FOV and a candidate FOV selected from the star map. Preliminary simulations indicate that both approaches work well and deliver good accuracy in determining the bore sight direction of the space vehicle with respect to the star map.
Development of Analytical Endmill Deflection and Dynamics Models
Authors: Kivanc Evren Burcu , Budak Erhan
Published: May 2008

Accurate knowledge of machine dynamics is required for predicting stability and precision in a machining process. Frequency response function (FRF) measurements need to be performed to identify the dynamics of the systems experimentally. This can be very time consuming considering the number of tool-tool holder combinations in a production facility. In this paper, methods for modelling dynamics of milling tool is presented. Static and dynamic analysis of tools with different geometry and material are carried out by Finite Element Analysis (FEA). Some practical equations are developed to predict the static and dynamic properties of tools. Receptance coupling and substructuring analyses are used to combine the dynamics of individual component dynamics. In this analysis, experimental or analytic FRFs for the individual components are used to predict the final assembly’s dynamic response. The critical point in this analysis is to identify the interface stiffness and damping between the tool and tool holder. The effects of changes in tool parameters and clamping conditions are evaluated. The predictions are verified by measurements.
Fabrication and Testing of a Novel Microelectromechnical Device for the Study of Boiling Bubble Dynamics
Authors: Moghaddam Saeed , Kiger Kenneth T. , Henriette Jean-Marc , Ohadi Michael
Published: May 2008

An array of 44 resistance temperature sensors with a radial resolution of 35 μm was fabricated around a re-entrant cavity (3 μm mouth diameter) on a thin silicon diaphragm with the intended purpose of obtaining highly resolved spatial and temporal measurements of the wall surface temperature during the boiling process. An Argon ion laser beam was used to provide a constant net flux of thermal energy to the backside of the diaphragm underneath the cavity and sensor area. This microsystem initiates and grows a single bubble at the center of the radial sensor array; all while the temperature variation underneath the bubble region during growth, departure, and rewetting is being measured with a frequency of 10 kHz. A high-speed CCD camera capable of taking over 3700 pictures per second is used to monitor the growth rate and departure process of the bubble from the surface, and correlated with the surface temperature measurement. The resulting temperature data can then be used to calculate the variation of the heat transfer coefficient under the bubble during the process of growth, departure, and rewetting. This experimental study provided unique experimental data to evaluate varieties of theories and speculations about the dynamics of bubbling at a microscale level. The focus of the current paper is on the details of the apparatus development and fabrication.
Modeling of Regenerative Furnace Ports
Authors: Golchert B. , Chang S. L. , Zhou C. Q. , Wang J.
Published: May 2008

In order to increase overall efficiency, many industrial glass furnaces are regenerative; that is, the heat from the exhaust gases is used to preheat in the in-coming combustion air. The ports on these furnaces inject stream(s) of fuel into the preheated air stream and then combustion occurs inside the combustion chamber. Modeling of the exact detail of these furnace ports in addition to modeling the combustion space proper becomes computationally burdensome since many of these furnaces are extremely large. This paper presents an engineering approach using computational fluid dynamics to model both the major effects of the furnace ports in addition to calculating the detailed flow field in the combustion space. This approximation has been incorporated into a complete (combustion space/glass melt) furnace simulation. This engineering approach significantly reduces run time while still maintaining results that represent the conditions seen in the furnace. This paper will present this approach as well as some preliminary comparisons with actual furnace data/observations.
Convertibility and Productivity of Manufacturing System Configurations
Authors: Maier-Speredelozzi Valerie , Freiheit Theodor , Hu S. Jack
Published: May 2008

Conversions between different products manufactured on the same system often require time-consuming shut-downs and thus, incur productivity losses. Producing multiple products on the same line complicates system productivity analysis because production rates, failure rates, and repair rates vary between different part types. Certain manufacturing system configurations have advantages when convertibility is considered. Ideally, manufacturing lines that produce a mix of products or undergo a product rollover would not see any loss in production relative to lines that continuously produce a single product throughout the system lifetime. This paper investigates the interactions between convertibility and productivity for different manufacturing system configurations, using analytical methods. The methods presented in this paper can be applied to assembly or machining stations in dedicated, flexible, or reconfigurable manufacturing systems. When designing such systems, it is important to recognize that more convertible systems are more productive over the long-term, as product designs change.
Interactive Design and Visualization of a Chemical Plant
Authors: Bhandwale Amit , Kesavadas Thenkurussi , English Ken , Bloebaum Christina , Lewis Kemper , Chugh Kevin
Published: May 2008

This paper describes a Virtual Reality (VR) based environment for conceptual design that allows the generation of an entire plant design along with an accurate cost estimate. The use of visualization coupled with advanced design and optimization methodologies help to rapidly investigate competing plant designs. The software is composed of two modules; the Optimization Engine or Optimizer and the Graphical User Interface (GUI) or Visualizer. The Optimizer comes up with various layouts (designs) along with a cost estimate, which the Visualizer uses to give a 3-D model of the plant. The Visualizer operate in three different modes; (1) Virtual Reality mode with advanced interface to visualize on a CAVE type large display systems, (2) Web viewer designed to be used in conjunction with a distributed design environment and (3) a PC desktop mode for quick design review with additional functionalities over a Web based system. To allow a seamless integration between the Optimizer and the Visualizer an efficient XML based data transfer has been developed. XML provides a robust, non-proprietary, persistent and verifiable file format for the storage and transmission of text and data. As XML data is to be manipulated from within a programming language, the Xerces XML parser, written in a portable subset of C++, has been used.
Development of Compact Models for Electronics Cooling: Using the Multigrid Operator to Generate Reduced Order Description of Devices
Authors: Sathyamurthy Prabhu , Nagulapally Manoj , Nair Rajesh
Published: May 2008

The need for compact models for ICs is a well-recognized problem in electronics cooling simulations of systems containing multiple PCBs and many devices per board. The disparate length scales inherent in the problem and the necessity of resolving these size scales renders the computational problem intractable. Many resistance-capacitance (RC) network compact models have been proposed in the literature. We present a methodology to automatically construct both the topology and characteristics of the reduced-order or compact models of devices (primarily Integrated Circuit (IC) packages) for use in system-level simulations using the multigrid operator. The multigrid technique has been extensively used over the past 20 years to accelerate the solution of liner systems. In addition to automatically generating both the RC network topology and its values, the procedure is general enough to be applicable for complex IC device types like Multi-Chip Modules (MCMs), stack up dies, distributed sources on the die, DC-DC converters and devices such as hard disk drives.
A DOS-Enhanced Numerical Simulation of Heat Transfer and Fluid Flow Through an Array of Offset Fins With Conjugate Heating in the Bounding Solid
Authors: Sparrow Ephraim M. , Abraham John P. , Chevalier Paul W.
Published: May 2008

The method of Design of Simulation (DOS) was used to guide and enhance a numerical simulation of fluid flow and heat transfer through offset-fin arrays which from the interior geometry of a cold plate. The basic problem involved 12 independent parameters. This prohibitive parametric burden was lessened by the creative use of nondimensionalization that was brought to fruition by a special transformation of the boundary conditions. Subsequent to the reduction of the number of parameters, the DOS method was employed to limit the number of simulation runs while maintaining an accurate representation of the parameter space. The DOS method also provided excellent correlations of both the dimensionless heat transfer and pressure drop results. The results were evaluated with respect to the Colburn Analogy for heat and momentum transfer. It was found that the offseting of the fins created a larger increase in the friction factor than that which was realized for the dimensionless heat transfer coefficient.
On the Nature of Critical Heat Flux in Microchannels
Authors: Bergles A. E. , Kandlikar S. G.
Published: May 2008

The critical heat flux (CHF) limit is an important consideration in the design of any flow boiling unit. Before the use of microchannels under flow boiling conditions becomes widely accepted in critical applications, such as electronics cooling and laser lenses, it is essential to develop CHF data for microchannels. The experiments required to obtain this information pose unique challenges as the channel dimensions become smaller. The issues of parallel channel instability, experimental control, experimental uncertainty, and conjugate effects need to be carefully addressed. These issues are addressed in the present paper, and guidelines helpful in the design of CHF experiments are outlined.
Assembly Quality Methodology: A New Method for Evaluating Assembly Complexity in Globally Distributed Manufacturing
Authors: Shibata Hirokazu , Cheldelin Brent , Ishii Kosuke
Published: May 2008

As suggested by several past studies (Barkan and Hinckley, 1993; Eking, 1988; Gebala, 1992; Beiter et al., 2000; Shibata et al., 2001), complexity in the assembly process has a strong correlation with the occurrence of defects. The authors propose a new method that uses a product’s complexity to predict defect rate (Shibata et al., 2001 and 2003). This method provides metrics for assembly complexity using two engineering measures: 1) assembly time estimates and 2) ease-of-assembly ratings. Extensive field data for consumer audio equipment assembled at various manufacturing sites around the world provide the means to validate the proposed metrics. A new process-based complexity factor uses a “time standard” defined for a set of assembly tasks. Predicted defect rates, based on this process complexity, exhibit a significant correlation with actual defect data. Another factor, the design-based complexity factor, uses the “Design for Assembly” method for evaluating an assembly and allows the user to predict defect sources not captured by the process-based complexity factor. Combining these complexity factors not only improves prediction accuracy but also provides guidelines for improving the original design concept as well as each process step. The authors conclude with an example of implementing the Assembly Quality Methodology using the new complexity factors for globally distributed manufacturing.
Quintic Spline Interpolation With Minimal Feed Fluctuation
Authors: Erkorkmaz Kaan , Altintas Yusuf
Published: May 2008

This paper presents a parameterization and an interpolation method for quintic splines, which result in a smooth and consistent feedrate profile. The discrepancy between the spline parameter and the actual arc length leads to undesirable feed fluctuations and discontinuity, which elicit themselves as high frequency acceleration and jerk harmonics, causing unwanted structural vibrations and excessive tracking error. Two different approaches are presented that alleviate this problem: The first approach is based on modifying the spline toolpath so that it is optimally parameterized with respect to its arc length. The second approach is based on scheduling the spline parameter to accurately yield the desired arc displacement (i.e. feedrate), either by approximation of the relationship between the arc length and the spline parameter with a feed correction polynomial, or by solving the spline parameter iteratively in real-time at each interpolation step. The two approaches are compared to nearly arc length parameterized C3 quintic spline interpolation in terms of feedrate consistency and experimental tracking accuracy.
Analytical Modal Analysis of Thin-Film Flat Lenses
Authors: Moxey L. , Hamidzadeh H.
Published: May 2008

Dynamics of circular and elliptical thin-film lens are investigated. In particular, linear closed-form solutions for free vibrations of these structures were achieved and modal analysis was performed. The vibration response of the thin film membranes were mathematically modeled using Mathieu equation. Numerical results for various nodal diameters were computed. For the limited case when an elliptical lens becomes circular, an excellent comparison was established with the available analytical solution. Experimental analyses were conducted to determine the effects of various parameters such as material properties, membrane pre strain and the geometry on the dynamic response of these structures. The comparison verified the adequacy of linear solutions to predict the dynamic response of thin film lenses.
Shape and Displacement Control of Beams With Various Boundary Conditions Via Photostrictive Optical Actuators
Authors: Shih Hui-Ru , Watkin Jonathan , Tzou H. S.
Published: May 2008

Photostrictive material is emerging as a new actuation medium. In contrast to traditional transducers, photostrictive material can produce actuation strains as a result of irradiation from high-intensity light, having neither electric lead wires nor electric circuits. In this paper, a static analytical model is derived for a flexural beam with surface bonded photostrictive optical actuators. Analysis of the proposed model is carried out by considering the induced force and bending moment produced on the beam by the patched actuator. Analytical solutions of the transverse deflection, induced by the photostrictive actuators, are derived for different boundary conditions. Those solutions are explicity expressed in terms of the geometry and position of the actuators patched on the beam. Finite element verification of the proposed model is presented. This paper presents the analytical predictions on optimal placement of photostrictive actuators for displacement control of beam structures. The objective is to determine the optimum photostrictive actuator locations to minimize the maximum beam deflection.
Numerical Modeling of LES Based Turbulent Flow Induced Vibration
Authors: Pittard Matthew T. , Blotter Jonathan D.
Published: May 2008

Flow-induced vibration caused by fully developed pipe flow has been recognized, but not fully investigated under turbulent conditions. This paper focuses on the development of a numerical, fluid-structure interaction (FSI) model that will help define the relationship between pipe wall vibration and the physical characteristics of turbulent flow. Commercial FSI software packages are based on Reynolds Averaged Navier-Stokes (RANS) fluid models which do not compute the instantaneous fluctuations in turbulent flow. This paper presents an FSI approach based on Large Eddy Simulation (LES) flow models that compute the instantaneous fluctuations in turbulent flow. The results based on the LES models indicate that these fluctuations contribute to the pipe vibration. It is shown that there is a near quadratic relationship between the standard deviation of the pressure field on the pipe wall and the flow rate. It is also shown that a strong relatonship between pipe vibration and flow rate exists. This research has a direct impact on the geothermal, nuclear, and other fluid transport industries.
Dynamic Modeling of a Hybrid Electric Drivetrain for Fuel Economy, Performance and Driveability Evaluations
Authors: Wei Xi , Pisu Pierluigi , Rizzoni Giorgio , Yurkovich Stephen
Published: May 2008

Both automakers and customers keep on pursuing better fuel economy, performance and driveability. A “mild” hybrid drivetrain is of great interest due to its potential capability on improving these targets. This drivetrain contains a spark ignition (SI) engine, an integrated starter/alternator (ISA), a torque converter (TC), a continuously variable transmission (CVT), a final drive (FD), a driveshaft, a brake-by-wire (BBW) system and wheels. While the challenge is to model and to develop an optimal control algorithm for this hybrid electric vehicle (HEV), this paper will focus only on the modeling aspect. Model-based control design and the nature of human perceptible driveability issues require low-frequency dynamic models. Therefore, a nonlinear control-oriented model which is sufficiently accurate but not excessively complicated is proposed here. Simulation results demonstrate that this model is effective to capture the main behaviors of vehicle dynamics and to evaluate fuel economy, performance and driveability objectively.
Some Techniques for Order Reduction of Nonlinear Time Periodic Systems
Authors: Redkar Sangram , Sinha S. C. , Butcher Eric A.
Published: May 2008

In this paper, some techniques for order reduction of nonlinear systems with time periodic coefficients are introduced. The equations of motion are first trasformed using the Lyapunov-Floquet transformation such that the linear parts of the new set of equations are time-invariant. To reduce the order of this transformed system three model reduction techniques are suggested. The first approach is simply an application of the well-known linear method to nonlinear systems. In the second technique, the idea of singular perturbation and noninear projection are employed, whereas the concept of invariant manifold for time-periodic system forms the basis for the third method. A discussion of nonlinear projection method and time periodic invariant manifold technique is included. The invariant manifold based technique yields a ‘reducibility condition’. This is an important result due to the fact that various types of resonance are present in such systems. If the ‘reducibility condition’ is satisfied only then a nonlinear order reduction is possible. In order to compare the results obtained from various reduced order modeling techniques, an example consisting of two parametrically excited coupled pendulums is included. Reduced order results and full-scale dynamics are used to construct approximate and exact Poincare´ maps, respectively, because it portrays the long-term behavior of system dynamics. This measure is more convincing than just comparing the time traces over a short period of time. It is found that the invariant manifold yields the most accurate results followed by the nonlinear projection and the linear techniques.
The Acceleration of Micro- and Nano-Particles in Supersonic De-Laval-Type Nozzle
Authors: Jen Tien-Chien , Li Longjian , Chen Qinghua , Cui Wenzhi , Zhang Xinming
Published: May 2008

The particle velocity in cold gas dynamic spraying (CGDS) is one of the most important factors that can determine the properties of the bonding to the substrate. The acceleration of gas to particles is strongly dependent on the densities of particles and the particle size. In this paper, the acceleration process of micro-scale and nano-scale copper (Cu) and platinum (Pt) particles in De-Laval-Type nozzle is investigated. A numerical simulation is performed for the gas-particle two phase flow with particle diameter ranging from 100nm to 50μm, which are accelerated by carrier gas Nitrogen in a supersonic De-Laval-type nozzle. The results show that cone-shape weak shocks (compression waves) occur at the exit of divergent section and the particle density has significant effect on the accele ration of micro-scale particles. At same inlet condition, the velocity of the smaller particles is larger than the larger particles at the exit of the divergent section of the nozzle.
Local Discontinuous Galerkin and Classical Finite Element Methods: Differences and Similarities
Authors: Castillo Paul
Published: May 2008

In this work a quantitative and qualitative comparison of the Local Discontinuous Galerkin method and classical finite element methods applied to elliptic problems is performed. High order discretizations are considered. The methods are compared with respect to accuracy of the approximation, rates of convergence, asymptotic behavior of the spectral condition number of the stiffness matrix.
Optimal Robust Fixture Configuration Design Using Computer Experiment
Authors: Xie L. Shelley , Sudjianto Agus
Published: May 2008

A new FEA based design approach of optimal robust fixture configuration is proposed in this paper, which employs a surrogate model through computer experiment to significantly reduce the intensive computing effort involving numerous FEA system response evaluations. The effects of the fixture variability to the workpiece performance variability are assessed through an efficient robustness evaluation method, First Order Reliability Method (FORM), based on the surrogate computer model. Not restricted to primary datum surface, this new approach enables simultaneous determination of robust locator/clamp locations and clamping forces for a deformable workpiece and thus captures interaction between locating and clamping. The effectiveness of this approach is illustrated though an application example. The results of robustness analysis reveal new information and suggest that the optimal solution resulted from deterministic optimization may not be the best solution when the design is subjected to variability.
On the Safety of Consumer Deep Fryers
Authors: Brickman Dennis B.
Published: May 2008

A 27 month old boy sustained burn injuries from a consumer electric cooker which was pulled off a kitchen countertop. Approaches utilized in the safety analysis include accident reconstruction, critical accident statistics analysis, UL 1083 standard research, and an evaluation of design alternatives. This paper investigates the safety implications of the new UL required break-away power cord for electric cookers/deep fryers.
A Multi-Objective Sliding Mode Approach for the Energy Saving Control of Pneumatic Servo Systems
Authors: Al-Dakkan Khalid A. , Barth Eric J. , Goldfarb Michael
Published: May 2008

This paper proposes a variation on a sliding mode control approach that provides significant energy savings for the control of pneumatic servo systems. The control methodology is formulated by first decoupling the standard four-way spool valve used for pneumatic servo control into two three-way valves, then using the resulting two control degrees of freedom to simultaneously satisfy both the sliding mode sliding condition and a dynamic constraint that minimizes airflow. The control formulation is presented, followed by experimental results that indicate significant energetic savings with essentially no compromise in tracking performance relative to a standard four-way spool valve approach. Specifically, relative to standard four-way spool valve pneumatic servo actuator control, the experimental results indicate energy saving of 27 to 45%, depending on the desired tracking frequency.
Experiences of Teaching “Life Cycle Design” Course at Tokyo Metropolitan University
Authors: Umeda Yasushi
Published: May 2008

This paper describes the outline of “life cycle design” course the author teaches and illustrates some experiences and findings with results of questionnaires to attendees of the lecture. “Life cycle design” is a half-year course to third-year students at Tokyo Metropolitan University, Japan. The main subject is environmentally conscious design focusing on life cycle thinking. This course intends to establish general and correct viewpoints toward relationship between manufacturing industry and the environmental issues, which are indispensable knowledge as mechanical engineers, rather than to educate environmental specialists. Results of questionnaires indicate that this course succeeded in increasing students’ interest in this area and awareness of importance of the environmental issues. However, some students feel bewildered because of wide variety of topics and, therefore, lack of a central theory.
High Aspect Ratio Polymer Micro/Nano-Structure Manufacturing Using Nanoembossing, Nanomolding and Directed Self-Assembly
Authors: Sitti Metin
Published: May 2008

This paper proposes three methods to fabricate synthetic gecko foot-hair high aspect ratio polymer micro/nanostructures. In the first method, nano-robotically indented templates are molded with liquid polymers, and the cured polymer is peeled off or etched away. Atomic force microscope and scanning tunneling microscope probe tips are used to emboss/indent flat wax surfaces, and silicone rubber micro/nano-bump structures are demonstrated. The second one uses a self-organized polycarbonate nano-pore membrane as the molding template. PDMS is molded into these micro/nano-pores under vacuum, and 1:2 and 1:9 aspect ratio pillar structures with 5 micron and 0.6 micron diameters are manufactured successfully. Finally, a directed self-assembly technique is proposed to grow regularly spaced and oriented micro/nano-pillars. Here, instability of a liquid polymer thinfilm under a DC electric field is used to grow nano-pillars, and stretching and shearing of the grown hairs enable high aspect ratio and oriented hair structures. These hair structures will be utilized as novel biomimetic dry adhesives in future miniature space and surgical robot feet.
A Comparative Study of the Variable Structure Filter
Authors: Habibi Saeid
Published: May 2008

A new strategy for state estimation has recently been proposed referred to as the Variable Structure Filter. This filter is model-based and can be applied to discrete-time systems that are subject to random disturbances and measurement noise. The advantage of the Variable Structure Filter is that it can be formulated to accommodate and explicitly account for modeling uncertainties. A proof of stability for the filter is provided. In this paper, the Variable Structure Filter is applied to a third order system with an uncertain mathematical model. A performance comparison is presented by comparing the state estimation errors of the Variable Structure Filter to those obtained from an equivalent Kalman Filter and a digital Infinite Impulse Response filter.
Assessing the Use of Tensor Closure Methods With Orientation Distribution Reconstruction Functions
Authors: Jack David A. , Smith Douglas E.
Published: May 2008

Orientation tensors are widely used to describe fiber distri-butions in short fiber reinforced composite systems. Although these tensors capture the stochastic nature of concentrated fiber suspensions in a compact form, the evolution equation for each lower order tensor is a function of the next higher order tensor. Flow calculations typically employ a closure that approximates the fourth-order orientation tensor as a function of the second order orientation tensor. Recent work has been done with eigen-value based and invariant based closure approximations of the fourth-order tensor. The effect of using lower order tensors tensors in process simulations by reconstructing the distribution function from successively higher order orientation tensors in a Fourier series representation is considered. This analysis uses the property that orientation tensors are related to the series expansion coefficients of the distribution function. Errors for several closures are investigated and compared with errors developed when using a reconstruction from the exact 2nd, 4th, and 6th order orientation tensors over a range of interaction coefficients from 10−4 to 10−1 for several flow fields.
Energy-Saving System Applying Pressure Accumulators for VVVF Controlled Hydraulic Elevators
Authors: Xu Bing , Ouyang Xiaoping , Yang Huayong
Published: May 2008

In order to improve the energy utilization efficiency of hydraulic elevators, an innovative energy-saving controlled system applying pressure accumulators in hydraulic elevators was brought forward in this paper. Firstly the working principle of the system was discussed and analyzed under different working status. Then the mathematical models of the system were established. Numerical simulations for the static and dynamic of the system were studied on the Simulink environment of MATLAB kits. Experiments on the upward and downward movement of elevator were done under different typical working conditions. Numerical simulations coincided with experimental results in general. Compared with other type hydraulic elevator systems, such as conventional valve controlled system, inverter controlled system, the system with pressure accumulators has the highest energy-saving efficiency. In summary, the innovative energy-saving system which runs steadily and comfortably, saves energy remarkably, has good potential for application in not only hydraulic elevators but also in other vertically reciprocating mechanical systems.
Active and Passive Evaluation of Proprioception for the Shoulder and Knee
Authors: Nowak Michael , Asaki Takafumi , Nissen Carl , Joseph Michael
Published: May 2008

This paper utilizes a 2nd generation proprioception device to evaluate active and passive proprioception in the shoulder and knee. The device is developed for this study is designed to be portable, inexpensive and easy to use.
An Integrated Rapid Prototyping Environment for Reconfigurable Manufacturing Systems
Authors: Yuan Chengyin , Ferreira Placid
Published: May 2008

At the enterprise level, manufacturing organizations are faced with accelerating technological cycles, global competition and an increasingly mobile work force. The flexibility of an enterprise and its ability to respond to new customer demands governs the competitiveness of the enterprise to changes in its market and in the society in which it operates. The flexibility in production processes must be able to accommodate differing product mixes with the changing availability of a skilled work force. It has been recognized for many years that flexibility on the enterprise shop floor can always be achieved if the resulting cost of product, process and system changeovers are not considered. However, with the increasing competitive pressures on today’s manufacturing enterprise; a highly flexible and reconfigurable manufacturing environment must be achieved at relatively low cost and high work-force productivity while maintaining a competitive advantage. To accomplish this goal the manufacturing enterprise must be able to be reconfigured with an increased level of automation that is scalable and flexible to meet diverse product demands. In this paper, we will introduce EMBench as the design and simulation environment for reconfigurable manufacturing systems. This environment provides a universal GUI (Graphical User Interface) that allows user to design, configure and simulate various resources on the shop floor level. In this paper, we present the resource model, workstation model and cell model and explore their characteristics and behaviors. We also propose the general interface for different models using IEC-61499 function blocks that allow scalable expansion and modular design. We use IEC-61499 function blocks and a service layer architecture to integrate various resources on the enterprise shop floor and achieve flexibility at a low cost. This environment facilitates a modular, component-based design of services for enterprise shop floor control.