bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy Efficiency of Low Form Factor Cooling Devices
Authors: Arik Mehmet , Petroski James , Bar-Cohen Avram , Demiroglu Mehmet
Published: May 2009

With increasing attention to the energy efficiency of consumer and commercial products, thermal engineering and science community is devoting greater effort and attention to the design and implementation of energy-efficient cooling solutions. This study focuses on the cooling potential and Coefficient of Performance, (COP), achievable with three distinct meso-scale cooling technologies, applicable to a wide range of electronics cooling challenges. The thermo-fluid and thermodynamic characteristics of synthetic jets, piezo-driven vibrating blades, and compact muffin fans will be addressed. We are dedicating this paper to Prof. Kakac for his contributions to heat transfer science and technology, developing young scientists, writing highly valuable heat transfer textbooks, and most importantly for his kindness and friendship.
Internal Condensing Flows Inside a Vertical Pipe: Experimental/Computational Investigations of the Effects of Specified and Unspecified (Free) Conditions at Exit
Authors: Kurita J. H. , Narain A. , Kivisalu M. , Siemionko A. , Kulkarni S.
Published: May 2009

Reported experimental and computational results confirm that both the flow features and heat transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. The results show that the commonly occuring condensing flows’ special sensitivity to changes in exit conditions (i.e. changes in exit pressure) arise from the ease with which these changes alter the vapor flow field in the interior. When exit pressure is changed from one steady value to another, the changes required of the interior vapor flow towards achieving a new steady duct flow are such that they do not demand removal of the new exit pressure imposition back to the original steady value — as is the case for incompressible single phase duct flows with an original and “required” exit pressure. Instead, new steady flows may be achieved through appropriate changes in the vapor/liquid interfacial configurations and associated changes in interfacial mass, heat transfer rates (both local and overall), and other flow variables. This special feature of these flows is for the commonly occurring large heat sink situations for which the condensing surface temperature (not heat flux) remains approximately the same for any given set of inlet conditions while exit condition changes. In this paper’s context of flows of a pure vapor that experience film condensation on the inside walls of a vertical tube, the reported results provide important quantitative and qualitative understanding as well as allow us to propose important exit-condition based categorization (viz. Categories I – III) of these flows.
Intracellular Ice Formation in Cell Suspensions Measured Using a Cryomicroscope and a Calorimeter
Authors: Acharya Tathagata , Devireddy Ram V.
Published: May 2009

Injury to biological cells during the freezing-thawing process of a cryopreservation protocol is related to the thermodynamic state of the intracellular water. The two primary biophysical phenomena are water transport and intracellular ice formation (IIF). Unfortunately, there is no technique currently available to measure IIF in the cells of opaque tissue sections. In this proceeding we report the use of a calorimeter to assess IIF in two different cell suspensions, adult stem cells and pacific oyster embryos. The close agreement between the IIF data obtained using the calorimetric data with corresponding data obtained using a well-established cryomicroscopy technique validated the calorimetric method. Since, the calorimetric measurements are independent of shape and size, it is ideally suited to measure IIF in opaque tissue sections; the focus of future studies.
Aeroacoustic Analysis of an Unmanned Aerial Vehicle
Authors: Lysak Peter D. , Dreyer James J. , Fahnline John B. , Capone Dean E. , Poremba John E.
Published: May 2009

An acoustic analysis of a ducted fan unmanned aerial vehicle (UAV) was conducted to identify the primary aeroacoustic sources and to determine the potential for reducing the radiated noise levels. Computational fluid dynamics was used to determine the three-dimensional flow field through the ducted fan in hover and maneuvering configurations. The flow solutions provided information about the blade relative velocities, spatially non-uniform inflow, inflow turbulence, boundary layer turbulence, and blade wake velocity deficits for use in acoustical models of broadband and blade passing frequency noise. The computational results were in good agreement with experimentally measured noise levels, and showed that the tonal noise was produced primarily by unsteady forces resulting from the non-uniform inflow, while the broadband noise resulted from the inflow turbulence. Based on these findings, design modifications were recommended which offer the potential to reduce the noise by more than 10 dB.
An Acoustic Superposition Method for Computing Structural Radiation in Spatially Digitized Domains
Authors: Zellers Brian C. , Koopmann Gary H. , Jonson Michael L.
Published: May 2009

This paper presents a new method for computing acoustic fields of structural radiators based on acoustic superposition methods using meshless, spatially digitized domains (ASMDD). Here the system matrices are assembled knowing only coordinate points in 3D space that describe the geometry of the radiating structure. In contrast to conventional methods, ASMDD does not require numerical, high orders of integration over elemental surfaces to populate system matrices. The system’s Green functions are computed simply between source and receiver locations at their respective points. A new derivation provides an analytical solution for coincident source and receiver points where the Green function is singular. The digital domain of ASMDD is a uniform distribution of points equidistant in the x, y, and z directions. The centroid of each activated voxel (used only as a means for visualizing the 3D surface) represents a point on the structural surface being modeled. Work in this paper exploits the inherent uniformity of neighboring points to formulate a locally determined outward-pointing, surface normal needed for acoustic radiation problems. The ability of the calculated surface normals to model the curvature of the continuous radiating surface depends on the density of the meshless grid, i.e., higher curvature requires higher grid densities. The attractiveness of the digital domain approach is its simplicity for morphing of structural shapes in optimization. Shape iterations in the digitized space reduce to a simple process of activating or deactivating selected points in a contiguous manner depending on the desired shape during an optimization. As an example, the ASMDD formulation is used to compute the modal radiation from a square plate in an infinite and cubic baffle. The ASMDD surface points are shown to blend seamlessly with the surface vibration results of the plate generated via meshless structural dynamics (Meshless Local Petrov Galerkin method - MLPG). This is achieved by solving the modal radiated acoustic power from the plate where the surface velocity is specified by the modal results determined by the MLPG method. The sound power calculations are in good agreement with those generated via conventional BEM codes.
Modeling and Simulation of Isotachophoresis for Chemical Separation of Charged Species
Authors: Shim Jaesool , Dutta Prashanta , Ivory Cornelius F.
Published: May 2009

Numerical simulation results are obtained for isotachophoresis (ITP) in two-dimensional straight michrochannel. This 2D ITP model is formulated based on finite volume schemes using 5 ionic components: one leader (LE), one terminator (TE), two samples (Sample A and B), and a counter ion electrolyte (C). Distinct net mobilities and diffusion coefficients are assigned to all ionic components, and an electric field is maintained along the channel to carry out the electrophoretic separation in microchannel. The computer model is developed to solve mass and charge conservation equations and to satisfy electro-neutrality condition in the system. Three different finite volume schemes, e.g. power-law, hybrid and upwind, are tested to obtain the best numerical solution of this electrophoretic problem. Numerical results show that power law scheme performs better; grid Peclet number up to 20 is acceptable for this nonlinear isotachophoresis. The effects of applied electric potential, ionic mobilities and initial distribution of samples on the separation behavior are also presented.
Aerodynamic Factors Affecting Performance of Straight-Bladed Vertical Axis Wind Turbines
Authors: Islam Mazharul , Amin M. Ruhul , Ting David S.-K. , Fartaj Amir
Published: May 2009

Unlike the conventional aerodynamic applications, the straight-bladed vertical axis wind turbines (VAWTs) operate in a circular motion and encounter a wide range of angle of attacks, especially at low tip speed ratios. When the blade angle of attack remains constant or varies slowly with time, it encounters the static stall. However, when the angle of attack changes rapidly with time, it experiences the dynamic stall which is far more difficult to analyze and predict than the static stall. Furthermore, the blade/blade wake interaction in straight-bladed VAWTs also presents modeling problem. In this paper, all of these aforesaid aerodynamic factors are discussed. It was found that these factors need special attention for designing a self-starting straight-bladed VAWT with optimum performance. A numerical method based on Cascade model, proposed by Hirsch and Mandal [1], that gives reasonable correlation with the experimental data available has been used. The effects of dynamic stall and flow curvature on the performance of a straight-bladed VAWT have been analyzed. It is observed from the analysis that aerodynamic forces due to dynamic stall are higher than those due to static stall. As a result, for the performance prediction of straight-bladed VAWTs, especially for the local forces, there can be substantial differences between the experimental data and the calculated values unless the dynamic stall effect is added.
Performance of Transition Metal Ions Exchanged Zeolite 13X in Greenhouse Gas Reduction
Authors: Hui K. S. , Chao Christopher Y. H. , Kwong C. W. , Wan M. P.
Published: May 2009

This study investigated the performance of multi-transition metal (Cu, Cr, Ni and Co) ions exchanged zeolite 13X catalysts on methane emission abatement, especially at methane level of the exhaust from natural gas fueled vehicles. Catalytic activity of methane combustion using multi-ions exchanged catalyst was studied under different parameters: mole % of metal loading, inlet velocity and inlet methane concentration at atmospheric pressure and 500 °C. Performance of the catalysts was investigated and explained in terms of the apparent activation energy, number of active sites and BET surface area of the catalyst. This study showed that the multi-ions exchanged catalyst outperformed the single-ions exchanged and the acidified 13X catalysts. Lengthening the residence time could also lead to higher methane conversion %. Catalytic activity of the catalysts was influenced by the mole % of metal loading which played important roles in affecting the apparent activation energy of methane combustion, active sites and also the BET surface area of the catalyst. Increasing mole % of metal loading in the catalyst decreased the apparent activation energy for methane combustion and also the BET surface area of the catalyst. In view of these, there existed an optimized mole % of metal loading where the highest catalytic activity was observed.
Conversion of Coal Fly Ash Into Zeolite 4A and Its Applications in Waste Water Treatment and Greenhouse Gas Reduction
Authors: Hui K. S. , Chao Christopher Y. H.
Published: May 2009

This study applied a novel conversion method to convert coal fly ash (CFA) into pure form (without mixture of CFA residue), single phase and high crystalline zeolite 4A. This novel conversion method allows a reduction by half of the total conversion time while maintaining a high degree of crystallinity of zeolite 4A which exists in a narrower particle size distribution. Applications of the CFA converted zeolite 4A (C4A) in waste water treatment of multi-heavy-metal-ions and in catalytic methane combustion were evaluated. In waste water treatment, for C4A and commercial zeolite 4A, the equilibrium sorption data were well fitted by the Langmuir model and showed the affinity order: Cu2+ > Cr3+ > Zn2+ > Co2+ > Ni2+. Compared to commercial zeolite 4A, the C4A and the treated CFA residue (TCFAR) were effective in removing multi-heavy-ions in water and could be an alternative material for treatment of wastewater. In catalytic methane combustion, post-treatment of C4A was performed to enhance catalytic activity of the catalyst. Catalytic methane combustion was conducted at atmospheric pressure and gas hourly space velocity (GHSV) between 3230 and 16150 h−1 under different lean fuel concentrations (equivalence ratio of 0.1–0.4) at 500 °C. Thermogravimetry analysis (TGA) results showed the catalyst (M(250)-C4A) could be operated at a temperature of 700 °C without damage to the zeolite structure. At 500 °C, higher combustion efficiency was achieved by either reducing the GHSV under the same fuel concentration or reducing the fuel concentration under the same GHSV. Comparing to a commercial catalyst 2%Pd/Al2O3, the catalyst (M(250)-C4A) achieved a higher methane conversion % in the GHSV range of 3230–9690 h−1. Finally, economic and environmental aspects of converting CFA to zeolite 4A were discussed.
Thermal-Mechanical Coupling Analysis of Board-Level Chip-Scale Packages Subjected to Power Cycling of Different Powering Durations
Authors: Wang Tong Hong , Lee Chang-Chi , Lai Yi-Shao , Lee Kuo-Yuan
Published: May 2009

The sequential thermal-mechanical coupling analysis which solves in turn the transient temperature field and subsequent thermomechanical deformations was performed in this work to investigate thermal characteristics along with fatigue reliability of a thin-profile fine-pitch ball grid array chip-scale package under power cycling. The numerical model was calibrated using steady-state and power cycling experiments. Following the calibrated numerical model, different power cycling durations on the thermal characteristics and fatigue reliability of the solder joints were examined.
Utilization of Process Monitoring in Ti Alloy Welding
Authors: Sun Z. , Pan D.
Published: May 2009

Titanium alloys have found increased applications in various industrial sectors. One of the critical issues in quality control is the weld penetration during welding. In the present paper, tungsten inert gas (TIG) welding was used to weld 8.0-mm thick Ti-6Al-4V alloy plates with and without an activating flux. The effect of the activating flux on Ti alloy welding was investigated. A data acquisition system was used to monitor the welding current and voltage signals during welding. These signals were then correlated to the weld penetration information. Results show that by applying the activating flux on the Ti-6Al-4V alloy surface, weld penetration depth increases, while the corresponding weld bead width is reduced. It was also found that various welding conditions, particularly flux thickness, influence the effectiveness of the activating flux. Results from monitoring of the welding current and voltage signals reveal that there is a clear correlation between the signals and the weld penetration. By analyzing the acquired signals, inconsistency in weld penetration can be identified. This demonstrates that process monitoring can provide an effective way to assess the consistency of the weld penetration and thus the quality of the welds.
Performance Evaluation of a 4.5 kW (1.3 Refrigeration Tons) Air-Cooled Lithium Bromide/Water Hot-Water-Fired Absorption Unit
Authors: Zaltash Abdolreza , Petrov Andrei , Linkous Randall , Vineyard Edward , Goodnack David , Egilegor Bakarne
Published: May 2009

During the summer months, air-conditioning (cooling) is the single largest use of electricity in both residential and commercial buildings with the major impact on peak electric demand. Improved air-conditioning technology has by far the greatest potential impact on the electric industry compared to any other technology that uses electricity. Thermally activated absorption air-conditioning (absorption chillers) can provide overall peak load reduction and electric grid relief for summer peak demand. This paper describes an innovative absorption technology based on integrated rotating heat exchangers to enhance heat and mass transfer resulting in a potential reduction of size, cost, and weight of the “next generation” absorption units. This absorption chiller (RAC) is a 4.5 kW (1.3 refrigeration tons or RT) air-cooled lithium bromide (LiBr)/water unit powered by hot water generated using the solar energy and/or waste heat. Typically LiBr/water absorption chillers are water-cooled units which use a cooling tower to reject heat. Cooling towers require a large amount of space and increase start-up and maintenance costs. However, RAC is an air-cooled absorption chiller which requires no cooling tower. The purpose of this evaluation is to verify RAC performance by comparing the Coefficient of Performance (COP or ratio of cooling capacity to thermal energy input) and the cooling capacity results with those of the manufacturer. The performance of the RAC was tested at Oak Ridge National Laboratory (ORNL) in a controlled environment at various hot and chilled water flow rates, air handler flow rates, and ambient temperatures. Temperature probes, mass flow meters, rotational speed measuring device, pressure transducers, and a web camera mounted inside the unit were used to monitor the RAC via a web control-based data acquisition system using Automated Logic Controller (ALC). Results showed a COP and cooling capacity of approximately 0.58 and 3.7 kW respectively at 35°C (95°F) design condition for ambient temperature with 40°C (104°F) cooling water temperature. This is in close agreement with the manufacturer data of 0.60 for COP and 3.9 kW for cooling capacity. Future work will use these performance results to evaluate the potential benefits of rotating heat exchangers in making the “next-generation” absorption chillers more compact and cost effective without any significant degradation in the performance. Future studies will also evaluate the feasibility of using rotating heat exchangers in other applications.
Application of Nonlinear Time Series Principles to Assess Power Generation Gas Turbine Health
Authors: Bassily Hany , Wagner John
Published: May 2009

Nonlinear time series concepts may be applied to assess the health condition of dynamic systems for which their operating data is neither Gaussian nor periodic. The principles of phase space geometry suit the dynamic behavior exhibited during transient and non-stationary operating modes. In this paper, two strategies are presented to evaluate the dynamic behavior of power generating natural gas turbines based on the phase space properties. Recurrence analysis allows methods to be developed that are suitable for many dynamic systems. The evaluation of extensive operating data for a simple cycle power generating gas turbine was performed to assess the health condition, and to evaluate the performance of equipment clusters in a power generation plant. The analytical results obtained from this implementation, along with the main conclusions drawn regarding the health condition of the machines, demonstrates the opportunity for system diagnostics.
Turbulent Flow in a Microchannel With Surface Patterned Microribs Oriented Parallel to the Flow Direction
Authors: Jeffs K. , Maynes D. , Webb B. W.
Published: May 2009

Due to the increase of application in a number of emerging technologies, a growing amount of research has focused on the reduction of drag in microfluidic transport. A novel approach reported in the recent literature is to fabricate micro-ribs and cavities in the channel wall that are then treated with a hydrophobic coating. Such surfaces have been termed super- or ultrahydrophobic and the contact area between the flowing liquid and the solid wall is greatly reduced. Previous numerical studies have focused primarily on the laminar flow through such channels with reductions in the flow resistance as large as 87% being predicted and observed. There has been little work however, that has explored the physics and the potential drag reduction associated with turbulent flow through microchannels with ultrahydrophobic walls. This paper reports the results of a numerical investigation of the turbulent flow in a parallel plate microchannel with ultrahydrophobic walls. In this study microribs and cavities are oriented parallel to the flow direction. The channel walls are modeled in an idealized fashion, with the shape of the liquid-vapor meniscus approximated as flat. A k-ω turbulence modeling scheme is implemented for closure to the turbulent RANS equations. Results are presented for the friction factor Reynolds number product as a function of relevant governing dimensionless parameters. The Reynolds number was varied from 2,000 to 10,000. Results show, as with the laminar flow case, that as the shear-free region increases the friction factor-Reynolds number product decreases. The observed reduction, however, was found to be significantly greater under turbulent flow conditions than for the laminar flow scenarios.
A Family of Runge-Kutta Based Explicit Methods for Rotational Dynamics
Authors: Ghosh S. , Roy D.
Published: May 2009

The present paper develops a family of explicit algorithms for rotational dynamics and presents their comparison with several existing methods. For rotational motion the configuration space is a non-linear manifold, not a Euclidean vector space. As a consequence the rotation vector and its time derivatives correspond to different tangent spaces of rotation manifold at different time instants. This renders the usual integration algorithms for Euclidean space inapplicable for rotation. In the present algorithms this problem is circumvented by relating the equation of motion to a particular tangent space. It has been accomplished with the help of already existing relation between rotation increments which belongs to two different tangent spaces. The suggested method could in principle make any integration algorithm on Euclidean space, applicable to rotation. However, the present paper is restricted only within explicit Runge-Kutta enabled to handle rotation. The algorithms developed here are explicit and hence computationally cheaper than implicit methods. Moreover, they appear to have much higher local accuracy and hence accurate in predicting any constants of motion for reasonably longer time. The numerical results for solutions as well as constants of motion, indicate superior performance by most of our algorithms, when compared to some of the currently known algorithms, namely ALGO-C1, STW, LIEMID[EA], MCG, SUBCYC-M.
Weld Pool Dynamics and the Formation of Ripples in 3D Gas Metal Arc Welding
Authors: Hu J. , Guo H. , Tsai H. L.
Published: May 2009

This article studies the transient weld pool dynamics under the periodical impingement of filler droplets that carry mass, momentum, thermal energy, and species in a moving 3D gas metal arc welding. The complicated transport phenomena in the weld pool are caused by the combined effect of droplet impingement, gravity, electromagnetic force, plasma arc force, and surface tension force (Marangoni effect). The weld pool shape and the distributions of temperature, velocity, and species in the weld pool are calculated as a function of time. The phenomena of “open and close-up” for a crater in the weld pool and the corresponding weld pool dynamics are analyzed. The commonly observed ripples at the surface of a solidified weld bead are, for the first time, predicted by the present model. Detailed mechanisms leading to the formation of ripples are discussed.
Unified Hybrid Theoretical Analysis of Nonlinear Convective Heat Transfer
Authors: Cotta Renato M. , Cabral dos Santos Carlos Antonio , Kakac¸ Sadik
Published: May 2009

The Generalized Integral Transform Technique (GITT) is extended and unified to handle a wide class of nonlinear convective heat and mass transfer formulations that involve nonlinearities in every each equation and boundary condition coefficients and source terms. The proposed hybrid numerical-analytical approach is applicable to both steady and transient situations, and the integral transformation process is promoted so as to yield an explicit transformed system, which can be more efficiently handled by the well-known numerical algorithms for initial value problems. An application of laminar forced convection in duct flow with temperature dependent thermophysical properties is considered more closely to illustrate the formal solution.
A Finite Element Study of Geometric Modifications to Reduce Thermal Mismatch Curvature in Wafer Bonding
Authors: Duraipandi Devasena , Heck John M. , Yee Raymond K. , Lee Sang-Joon J.
Published: May 2009

Wafer-level packaging of RF MEMS devices offers an attractive option to reduce packaging cost significantly and ensures hermetic encapsulation of devices. Low-temperature cofired ceramic (LTCC) cap wafers are particularly favorable because they can be pre-patterned with through-wafer vias for integrated electrical contacts and high-density packaging, at a much lower cost than silicon wafers with similar features. However, thermal expansion mismatch between ceramic and silicon wafers at high bonding temperatures induces thermal stresses at the interface, resulting in wafer curvature. For example, a 150 mm silicon wafer 675 μm thick with a ceramic cap wafer 500 μm thick has been measured to exhibit out-of-flatness displacement as severe as of 1.7 mm at the center. While the curvature can be reduced significantly using low-thermal-expansion ceramic, such materials are non-standard and require custom formulation. Furthermore, as the wafer diameter is increased, thermal expansion mismatch becomes more problematic. Therefore, it is desirable to address the problem using a geometrical approach in addition to optimizing the ceramic for wafer bonding applications. The present study applies finite element analysis (FEA) to examine the potential for reducing such curvature by introducing slots in the ceramic cap wafer. Two-level factorial design simulations involving five parameters were conducted to investigate the effect of slot parameters on wafer curvature, using 2-D plane strain simulation of wafer cooling from 300 °C to 25 °C. The five parameters investigated were cap wafer thickness, slot width, slot depth, slot separation, and slot orientation. The nonlinear temperature dependence of thermal expansion was also examined based on test data for the ceramic wafers. Furthermore, a 3-D finite element simulation was conducted to compare the 2-D results to overall impact on wafer distortion. FEA results were compared with experimental curvature measurements on sample wafers measured by coordinate measuring machining (CMM). Simulated results suggest that introduction of slots shows reduction in wafer curvature, and the displacement can be reduced by as much as 25% based on the geometric parameter values for slots in the cap wafer.
Design and Test of a Thermoelectric Ground-Source Heat Engine
Authors: Stevens James W.
Published: May 2009

The daily variation in air temperature is large compared with the temperature changes a short distance below the surface of the ground. In theory, a heat engine can be arranged to produce electricity from this temperature difference. In practice, the thermal efficiency of such a device will be low because of the small temperature differences involved. One example of such an energy harvesting device that can produce a small amount of electrical power uses a thermoelectric generator operating between the air and ground temperatures. The low thermal efficiency means that accurately predicting thermal resistances throughout the device and at the air-side and ground-side heat exchangers is critical to the creation of a useful device. Advantages of this device include high reliability, no acoustic emissions, low visibility, significant night-time power production, ruggedness, and long life. With appropriate external power conditioning components, the device could be used to power remote sensors and communications systems. The design of a pair of milliwatt-scale ground source heat engines is described. The devices were fabricated using custom heat exchangers and off-the-shelf thermoelectric modules and other supplies. Both systems were tested over an extended period in order to quantitatively assess effects of sunlight and precipitation on system performance and life. Exhaustive analysis of air-side average heat transfer coefficients, system thermal resistances, and ground-side thermal resistances provide quantitative design information for future applications. Finned and unfinned versions of the device permit assessment of fin performance on both ground-side and air-side heat transfer.
Computational Analysis of Responses of Micro Electro-Thermal Actuators
Authors: Wong C. Channy , Phinney Leslie M.
Published: May 2009

The electrical, thermal, and mechanical responses of surface micromachined (SMM) 2-beam actuators have been simulated using the Calagio code, a coupled physics analysis tool. The present analysis, unlike previous analyses, includes the surrounding air in the computational domain so that heat losses from the beams onto the silicon substrate will be accurately modeled. This setup is essential because the existing ‘shape factor’ correlations have difficulty capturing the three-dimensional geometric effect of the heat loss in the shuttle at the center that connects the bent beams. In addition, results from the present analysis reveal that because the local heat flux can be extremely high, a significant temperature jump can occur across the air-structure interfaces.
The Design of a Dexterous Gripper to be Used for Activities of Daily Living by People With Upper-Extremity Disabilities
Authors: Alqasemi Redwan , Mahler Sebastian , Dubey Rajiv
Published: May 2009

A new robotic gripper was designed and constructed for Activities of Daily Living (ADL) to be used with the new Wheelchair-Mounted Robotic Arm developed at USF. Two aspects of the new gripper made it unique; one is the design of the paddles, and the other is the design of the actuation mechanism that produces parallel motion for effective gripping. The paddles of the gripper were designed to grasp a wide variety objects with different shapes and sizes that are used in every day life. The driving mechanism was designed to be simple, light, effective, safe, self content, and independent of the robotic arm attached to it.
Nonlinear Phenomena in Induced Charge Electroosmosis
Authors: Soni Gaurav , Squires Todd M. , Meinhart Carl D.
Published: May 2009

We present an experimental and numerical investigation of induced charge electroosmosis (ICEO) on a planar electrode surface directly in contact with a high conductivity electrolytic solution. Symmetric rolls of ICEO flow were produced on the electrode by placing it in an AC electric field. The slip velocity was measured for a range of AC voltages and frequencies using micro particle image velocimetry (μPIV). The slip velocity was also calculated by finite element simulations based on a linear and a nonlinear model of electrical double layer, respectively. The μPIV measurements were found to be much lower (two and half orders of magnitude) than the velocities predicted by the linear model. The linear model is valid only under Debye Huckel approximation (φ ≪ kBT/e = 25 mVolt at room temperature) which does not hold true for practical situations. The nonlinear model, on the other hand, predicts velocities which are lower than the linear model and closer to the experimental values. The nonlinearity reduces discrepancy between experimental and numerical results by approximately an order of magnitude. The nonlinear model accounts for nonlinear capacitance of the double layer and lateral conduction of charge in the double layer.
Effects of Material Properties Estimations on the Thermo-Elastic Analysis for Functionally Graded Thick Spheres and Cylinders
Authors: Ghaderi P. , Bankehsaz M.
Published: May 2009

In this paper effects of material properties estimations, used for particulate reinforced composites, on the thermo-mechanical response of functionally graded sphere and cylinder are presented. A numerical solution for an arbitrary material gradation is obtained for each geometry independently. With this assumption, the governing partial differential equations are reduced to an ordinary differential equation in each geometry. The thermo-elastic solution for hollow sphere is derived using spherical symmetry. However, plane strain and axial symmetry are assumed for solving hollow cylinder. In the numerical method, radial domain is divided into some finite sub-domains and material properties are assumed to be constant in each sub-domain. With this assumption, the governing thermal and mechanical equations in each sub-domain are an ODE with constant coefficients. 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 thermo-elastic responses for the thick-walled FG sphere and cylinder are obtained. Three methods of gradation are used for comparing the effects of different material properties estimations on the results; Rule of Mixtures as a conventional method, Mori-Tanaka estimation and self-consistent scheme. The results show that estimations for material properties could be influential to the thermo-elastic response for some profiles of volume fractions of constituents. However, the effect on elastic response is negligible.
Structural Dynamics and Response of Roof Tiles Under Wind Loading: Effect of Vibration on Scattering
Authors: Okamoto S.
Published: May 2009

This study has investigated the nature and source of the vibrating and scattering behavior of roof tiles with the aim of providing a better insight to the mechanism. The 100 roof tiles were set up on 10 lines and 10 lows on the pitched roof in the downstream of the flow from the wind tunnel. These experiments were followed by series of tests where the slope angle of the roof tiles was changed. The vibrations of the roof tiles were simultaneously measured by the two accelerometers, and the motions of the vibration and scattering were observed by the high-speed video camera. The frequency response function and coherence function of roof tile were measured by impact hammer test under no flow condition. Just before scattering of the roof tiles, both vibrations of higher frequency mode and vibrations of lower frequency mode appeared simultaneously in roof tiles. The values of the higher frequencies were corresponding to the values of resonant frequencies of the roof tiles. It was thought that the scattering of roof tiles was influenced by the vibration of the lower frequency mode. The frequencies of the vibration were measured by the high-speed video camera system. The values of the lower frequencies were 10 Hz ∼ 20 Hz. The mechanism of scattering of roof tiles could be understood by means of the information from the accelerations and the images of roof tiles.
Dynamic Manipulation of Objects Using Multiple Manipulators
Authors: Beigzadeh Borhan , Meghdari Ali , Beigzadeh Yasan
Published: May 2009

In this study, we explore the possibility of dynamic object manipulation of objects using a series of manipulators. Here, two three-active-link manipulators have been considered and the generality of the idea to a series of manipulator is developed easily. So without any gripper, and in an unstable grasp manner, we try to throw an object by a manipulator and catch it with another. Also we can consider the impacts generated in the moment of throwing and catching objects, as some disturbance and therefore we damp it. Finally we deal with the whole manipulation process as a system with some noise and disturbance and try to demonstrate its stability. All results have been validated with the aid of simulations.
Design of Fluid Drive Spindle and Its Rotational Speed Control
Authors: Nakao Yohichi , Ishikawa Masanori
Published: May 2009

Water drive spindle has been developed as a spindle for ultra-precision machine tool. Performances of the water drive spindle were evaluated by experiments and simulations. In addition, the spindle was applied to diamond cutting experiments, then, successfully the fine mirrored surfaces were finished. However, rotational direction of the water drive spindle is limited, which is due to the structure of the spindle. Thus, development of water drive spindle that is capable of rotating spindle rotor for both rotational directions is current our objective. In advance of developing the water drive spindle, fluid drive spindle that is similar structure with the water drive spindle, is designed and tested in the present paper. Furthermore, control performances of the fluid drive spindle are studied through simulations. Linearized mathematical models of the fluid drive spindle and servo valve are introduced, then, they are used for the simulations. It is verified that the developed fluid drive spindle is able to rotate for both rotational directions and the spindle speed can be controlled by designed feedback controller.
Using Parallel Joint Compliance to Reduce the Cost of Walking in a Planar Bipedal Robot
Authors: Yang T. , Westervelt E. R. , Schmiedeler J. P.
Published: May 2009

This paper presents numerical and experimental studies of the influence of parallel knee joint compliance on the average power cost of walking in an underactuated planar bipedal robot, ERNIE. The use of parallel compliance does not increase the control design complexity, as would the addition of series compliance. Four scenarios were studied: one without springs, and three with springs of different stiffnesses and preloads. Optimal gaits in terms of average power cost for various speeds were designed for each scenario. It was found that for low-speed walking, soft springs are helpful to reduce power cost, while stiffer springs increase power cost. For high-speed walking, it was found that both soft and stiff springs reduce the average power cost of walking, but stiffer springs reduce the cost more than do softer springs.
Knowledge-Based Automatic Fault Detection in Flight Control System
Authors: Lo C. H. , Fung Eric H. K. , Wong Y. K.
Published: May 2009

There are various possible failures, like, actuator, sensor, or structural, which can occur on a sophisticated modern aircraft. In certain situations the need for an automatic fault detection system provides additional information about the status of the aircraft to assist pilots to compensate for failures. In this paper, we develop an intelligent technique based on fuzzy-genetic algorithm for automatically detecting failures in flight control system. The fuzzy-genetic algorithm is proposed to construct the automatic fault detection system for monitoring aircraft behaviors. Fuzzy system is employed to estimates the times and types of actuator failure. Genetic algorithms are used to generate an optimal fuzzy rule set based on the training data. The optimization capability of genetic algorithms provides and efficient and effective way to generate optimal fuzzy rules. Different types of actuator failure can be detected by the fuzzy-genetic algorithm based automatic fault detection system after tuning its rule table. Simulations with different actuator failures of the non-linear F-16 aircraft model are conducted to appraise the performance of the proposed automatic fault detection system.
A Psychophysical Model of Motorcycle Handlebar Vibrations
Authors: Israr Ali , Tan Hong Z. , Mynderse James , Chiu George T.-C.
Published: May 2009

In this study, we developed a perception-based quantitative model to relate broadband vibrations transmitted through a motorcycle handlebar to a rider’s hands. The test apparatus consisted of the handlebar of a motorcycle rig assembly driven by a computer-controlled actuator. Participants were instructed to hold the handlebar and maintain a sitting posture as they would while riding a motorcycle. In Exp. 1, psychophysical detection thresholds for 10 participants were estimated at ten test frequencies between 20–300 Hz using a two-interval one-up two-down adaptive procedure. The interpolated threshold vs. frequency function specified the minimum acceleration required before a user could perceive the vibration at a particular frequency. In Exp. 2, participants were asked to rate 15 representative handlebar vibrations using a magnitude estimation procedure. The vibration patterns were measured on an actual motorcycle handlebar while the motorcycle traveled at speeds ranging from 25 to 75 mph. Several weighting functions, including the ISO-5349 standards, were applied to the broadband vibration signal in the frequency domain to estimate the total vibration energy by summing up all weighted components. The best weighting function, in the sense that the estimated total energy correlated linearly with the subjective magnitude ratings obtained in Exp. 2, were based on the detection threshold data obtained in Exp. 1. Specifically, the strength of each vibration component was calculated relative to the human detection threshold at the same frequency, thereby taking into account human sensitivity to vibration signals at different frequencies. The resulting weighting function can be applied to other recorded vibration signals to predict user rating of perceived vibration intensities.
Optical Performance of a Hybrid Nano-Polymer Solar Cell
Authors: Kulkarni Sudhir , Mitra Kunal , Ramesh Swaminathan
Published: May 2009

Solar energy harvesting is one of the most fundamental solutions to the energy crisis; photovoltaics are the best way to achieve it. Organic based photovoltaics have potential for application as a renewable source of energy. It is cost-effective, light weight, simple and economical to fabricate. Introduction of nanomaterials into polymers is very promising for enhancing photovoltaic conversion efficiency and can potentially improve photochemical and environmental stability. The objective of this paper is to investigate the influence of the nanocomposite film morphology on the optical performance of the hybrid nano-polymer solar cell. The efficiency of such hybrid solar cell depends mainly on the exciton dissociation efficiency and charge mobility. The exciton dissociation efficiency can be improved by increasing the interfacial area between the nanoparticles and polymer. Charge mobility can be improved by proper distribution of nanoparticles in polymer to form better percolation path of each material. Both these parameters are strongly dependant on better distribution of nanoparticles in the polymer. The approach used here is the application of star dispersant, specifically designed for conducting polymers. This dispersant will modify the arms of the conducting polymer to have a high affinity towards nanoparticles and provide better distribution. In this paper the influence on the morphology of the solar cell by the use of star dispersant and corresponding improvement in optical properties and performance is analyzed. Subsequent papers will describe the photovoltaic enhancements of such a solar cell. The solar cell structure chosen here is ITO / PEDOT:PSS / P3HT:TiO2 / Al. A number of specimens are prepared with and without introduction of the star-dispersant. For structural characterization, Scanning Electron Microscopy (SEM) is used. Absorption spectrum analysis and Photoluminescence (PL) analysis are performed to characterize the optical properties of the active layer. Structural characterization revealed that with the application of the dispersant, better mixing of the nanoparticles and the polymer can be achieved. This will in turn increase the interface area and improve exciton dissociation. Better PL quenching is observed in the dispersant modified active layer confirming an improved degree of exciton dissociation.
Experiments in Local Force Feedback for High-Inertia, High-Friction Telerobotic Systems
Authors: Shull Pete , Niemeyer Gu¨nter
Published: May 2009

Many telerobotic systems include a slave robot with much larger inertial and frictional properties than the master robot and/or a non-backdrivable slave acting as an admittance device. Passive controllers, which are known for their stability and robustness, display the large dynamic forces to the user and/or become insensitive to contact forces. In effect, the user feels the large inertia and friction of the slave robot but does not feel the force of the environment. Force sensors can isolate the environment forces. In this paper, we experiment with local force feedback for an admittance type slave robot. We use the local controller to convert the slave to an apparent impedance device, restoring its sensitivity to environment forces. This will allow the application of stable passive teleoperation controllers. The control structure is validated on a single axis of a large, non-backdrivable, industrial Adept robot operating as a slave in contact and in free space.
Modeling of Ionic Polymer Metal Composite (IPMC) Actuator Dynamics Using Large Deflection Beam Model
Authors: Gutta Shivakanth , Lee Joon S. , Trabia Mohamed B. , Yim Woosoon
Published: May 2009

In this paper, we introduce a novel approach to model the dynamics of segmented Ionic Polymer Metallic Composite (IPMC) actuator. The IPMC actuator is activated using input voltage to its various segments. The proposed finite element approach combines the RC electrical model and a model that describes large deformations of mechanical beams. In the proposed modeling scheme, a local coordinate frame is attached to each beam element that undergoes rigid body motion in addition to elastic deformation. The elastic deformation of the element is modeled using the assumptions of the large deformation beam model. The proposed method has the advantage of accurately modeling large deflection of the IPMC beam actuator using relatively small number of elements. Experiments are conducted to validate the proposed method.
Nanoscale Molding of a Zirconium Based Bulk Metallic Glass
Authors: Rason Kavic , Kinsey Brad
Published: May 2009

Geometrically complex, high aspect ratio microstructures and limited aspect ratio nanostructures have been successfully fabricated in supercooled Bulk Metallic Glass (BMG) substrates by molding against patterned Silicon and Silicon dioxide substrates. However, demand exists for similar metallic substrates with high aspect ratio, nanoscale features. Van Der Waals based interfacial energies between the supercooled liquid BMG and the Silicon cavity represent a substantial obstacle to the direct scaling of the molding process to the nanoscale. In an effort to investigate these effects, experiments were conducted using molds of various compositions: Silicon, SiO2 and SiO2 coated with Gold. The Gold coating failed to impact molding performance due to the thin layer deposited. However, drastically superior results were obtained by using a Silicon mold because of the variation in interfacial interaction between the BMG and the mold material. In addition, a theoretical model to predict achievable aspect ratio is presented and was found to be in qualitative agreement with experimental results. Finally, a value for the surface tension of Viterloy-1b within it’s supercooled liquid state was deduced from experimental data.