bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Risk Analysis to Identify Cost Effective Improvements to a Semiconductor Fabrication Chemical Distribution Facility
Authors: Leverenz Fred L.
Published: May 2008

In today’s semiconductor industry, the business loss associated with one full day of lost production can have a significant impact on revenues. Key factors affecting overall profitability are unplanned fabrication downtimes and contamination resulting in defective products. It is critical, therefore, to implement effective risk management strategies for the fabrication process to eliminate yield-limiting defects and to improve the overall production. This paper will discuss a study completed for a semiconductor chemical supplier. Battelle applied a methodology based on the Process Event Tree/Hazard and Operability Study (PET-HAZOP) methodology, identifying numerous ways to avoid unnecessary outages and lost production at a specific client’s semiconductor fabrication facility. This methodology uses a systematic approach to identifying risks in a process, and risks are quantified in terms of expected dollars per year. Within the analysis, the importance of individual equipment items in the process is measured with respect to risk. Two risk measures are used in the analysis: Risk Reduction Worth (RRW) and Risk Achievement Worth (RAW). The RRW identifies opportunities for areas of risk reduction and the RAW identifies critical equipment that must be maintained to prevent the overall risk of the system from increasing significantly. Results were provided in a cost-benefit form for the top items on the RRW and RAW lists. For example, replacing existing chemical distribution pumps with completely non-metallic pumps (cost of about $60,000) would result in savings, due to avoidance of possible chemical contamination, of $430,000 per year. This, and other findings, proved that a systematic approach to evaluating risks for the semiconductor front-end process can identify valuable risk reduction alternatives resulting in significant cost savings.
Influence of Entrance Geometry on Heat Transfer in Narrow Rectangular Cooling Channels (AR = 4:1) With Angled Ribs
Authors: Wright Lesley M. , Lee Eungsuk , Han Je-Chin
Published: May 2008

The effect of entrance geometry on the heat transfer in rotating, narrow rectangular cooling channels is investigated in this study. Both smooth channels and channels with angled ribs are considered with three different entrance conditions: fully developed, sudden contraction, partial sudden contraction. The rectangular channel has as aspect ratio of 4:1, and it is oriented at 135° with respect to the plane of rotation. In the test section with angled ribs, the ribs are angled at 45° to the mainstream flow. The rib height-to-hydraulic diameter ratio (e/Dh) is 0.078, and the rib pitch-to-height ratio (P/e) is 10. The range of flow parameters includes Reynolds number (Re = 5000–40000), rotation number (Ro = 0.0–0.302), and inlet coolant-to-wall density ratio (Δρ/ρ = 0.12). The heat transfer at the entrance of the heated portion of the smooth channel is significantly enhanced with the sudden contraction and partial sudden contraction entrances. In the smooth rotating channels, the effect of the entrance geometry is also present; however, as the rotation number increases, the effect of the entrance geometry decreases. It was also found in this study that the sudden and partial sudden contraction entrances provide higher heat transfer enhancement than the fully developed entrance through the first 3 to 4 hydraulic diameters of the channels with angled ribs. Again, the effect of the entrance geometry is greater in the stationary channels with angled ribs than the rotating channels with ribs. In both stationary and rotating channels, the influence of the entrance geometry on the heat transfer is more apparent in the smooth channels than in the ribbed channels.
The Setting and Management of Design Targets in Complex Systems Using System Norms: Extension to Multiple Attributes
Authors: Mehmoud Haitham A. , Kabamba Pierre T. , Ulsoy A. Galip , Brusher Gerald A.
Published: May 2008

This paper describes a novel approach to the design of complex systems with performance specifications from multiple disciplines. Rather than apply hierarchical optimization methods to the decomposed system, we cast the problem in the framework of robust control design. This reformulation allows us to apply existing resulsts from the field of robust control to traditional robust design. Key elements of this reformulation include using linear fractional transformations to pull out design variables and system parameters. The concepts of small gain and small μ are then used to determine limits on the magnitudes of the uncertain parameters that would enable the design of the subsystems to proceed in parallel, as called for by the Systems Engineering methodology. The uncertain parameters for one subsystem will include design variables and outputs from other subsystems that are needed in that subsystem analysis. The results are illustrated using a simple example representing a corner-car model.
Theoretical Analysis and Experimental Verification of a Monopropellant Driven Free Piston Hydraulic Pump
Authors: McGee Timothy G. , Raade Justin W. , Kazerooni H.
Published: May 2008

The authors present a novel power supply for mobile robotic systems. A monopropellant (e.g. hydrogen peroxide) decomposes into high temperature gases, which drive a free piston hydraulic pump (FPHP). The elimination of fuel/oxidizer mixing allows the design of simple, lightweight systems capable of operation in oxygen free environments. A thermodynamic analysis has been performed, and an experimental FPHP has been built and tested. The prototype successfully pumped hydraulic fluid, although the flow rate was limited by the off-the-shelf components used.
Simulations of Metal Foam Cooling of High-Power Electronics Using the Equivalent Thermal Conductivity
Authors: Dukhan Nihad , Quinones Pable D.
Published: May 2008

A one-dimensional heat transfer model for open-cell metal foam is presented. The model includes both the conduction and the convection in the ligaments and in the pores of the foam. It uses the typical foam parameters provided by the manufacturers. Three aluminum foams having different relative surface areas, relative densities, ligament diameters, and number of pores per inch are analyzed and an effective thermal conductivity is determined. The heat transfer increases with the number of pores per inch. The resulting improvement in heat transfer can be as high as 57 percent over solid aluminum. The model is general enough such that it can handle other types of foam and geometries. For simulations using packages for thermal management, the foam can be modeled as a solid having an equivalent conductivity with an effective convection heat transfer on its outer surfaces. This eliminates the need to model the microscopic flow and heat transfer in and around the pores. It also allows quick feasibility studies and comparisons of different arrangements using aluminum foams for thermal management systems of high-power electronics. A few such simulations are presented in this work. The simulations show a big promise for using the foam in place of the traditional heat sinks for cooling high-power electronics: they reduce the cooling system’s weight substantially and reduce the maximum temperature significantly.
Peclet Number Behaviour on the 1-D Heat Conduction-Convection Problem With a Control Volume Capacitance Method
Authors: Rodri´guez N. J. , Davey K. , Castillo P. M. V.
Published: May 2008

Modelling of solidification with transport of mass is of paramount importance for the heat transfer community. Phase change problems have received considerable research attention over the last two decades. Numerical methods for fixed and moving grids have been developed with increasing accuracy and performance, although fundamental aspects still elude modeling such as numerical oscillations. The discovery of Control Volume Capacitance Methods (CVCM) is an attempt to eliminate the need to use classical Petrov-Galerkin and Bubnov-Galerkin formulations. The theory underpinning CVCM methods is presented. A novel modified CVCM is presented which is transformable into a FEM that is similar to that used to model heat-conduction. The method is applied to the 1-D semi-infinite problem, where mesh is spatially fixed whilst mass is transported, in order to investigate the Peclet number behavior. Numerical tests are compared against analytical solutions; the approach is shown to be accurate, stable and computationally competitive.
Testing and Evaluation of Control Strategies for a Prototype Hydraulic Press
Authors: Cruz J. M. , Ferreira J. A.
Published: May 2008

The work that this paper describes is the attempt to safely optimize, test and evaluate the performance of advanced strategies for the control of hydraulic systems. The method proposed is to use a computer model of a prototype hydraulic press to develop, optimize and test various controllers. The same tests are then repeated on the actual prototype of the press. The results of the experiments are compared to evaluate the accuracy of the model, the performance of the controllers, and the validity of the method.
A Real-Time Digital Control Environment Based on MATLAB, xPC-Target Along With a Magnetic Levitation Device for Neural Network Control Law Implementation and Verification
Authors: Shiakolas P. S. , Van Schenck S. R. , Frangeskou I.
Published: May 2008

The objective of this article is to present the development and hardware implementation of a robust control system for a custom made magnetic levitation device. This hardware in the loop (HIL) device was developed for the purpose of real time control experimentation and education. The digital controller requires a C++ complier and MATLAB, Simulink, Real Time Workshop, and xPC Target by MathWorks. The controller itself consists of a classical lead/lag compensator augmented by static (apriori trained) and dynamically trained neural network (NN) controllers. The need for a dynamically trained NN is supported by the effects of nonlinearities and time changing unmodeled dynamics as compared to an apriori trained static NN. The digital controller may be quickly reconfigured to use either NN allowing for quick comparison. The steady state error of each NN control technique will be compared and the effects of unmodeled changes to the HIL will be discussed in support of the superior performance of the dynamic NN.
Static and Dynamic Analysis of HIL Simulator for Fluid Power Driven Machines
Authors: Eskola Tero , Handroos Heikki
Published: May 2008

A Hardware-in-the-loop (HIL) simulation based method for designing and testing of fluid power driven machines has recently been studied in [1], [2] and [3]. In those papers the method has successfully been tested for driving physical prototypes with simulation models of various hydraulic circuits. Although the results of the tested method have appeared to be reasonable the critical boundary conditions of the system has not yet been studied. In this paper a simple hydraulic system is modeled and used for driving the simulator. The simulated system is then built from real components and measured. The measured and simulated results are compared. One of the main goals of this paper is to find answer to the following question: What is the maximum bandwidth that can be put out from the simulator with sufficient accuracy. The answer demonstrates the applicability of the developed HIL-simulator. Also different sizes of time steps are studied.
Modeling and Control of a Morphing Airfoil
Authors: Whitmer Christopher E. , Kelkar Atul G. , Vu Phuc , Chavez Frank R.
Published: May 2008

This paper presents aeroelastic modelling and robust control design for a morphing airfoil concept. A finite dimensional linear time invariant aeroelastic model is developed for a multi-input multi-output morphing airfoil structure. The shape of the airfoil (NACA airfoil series 2415) is controlled by actuators distributed along the top airfoil surface that produce vertical deflections of the top surface at several locations. This results in an airfoil shape change (i.e., “morphing” of the wing), which causes changes in the aerodynamic loading on the wing. The objective is to control the deformation of the airfoil in realtime so as to achieve the desirable aerodynamic forces on the wing. The structural model is developed using the finite element approach. A finite element toolbox in Matlab, namely FEMLAB, is used to obtain eigenfrequencies and mode shapes. A finite dimensional dynamic model of the structure is obtained by the assumed modes method. A static aerodynamic model is developed with a vortex lattice method and coupled with the structural dynamic model to yield a linear aeroelastic model of the morphing wing. A robust LQG design is presented for tracking the commanded lift and roll moment. Some parametric studies are also presented for the choice of different materials. Simulation results are given to demonstrate the viability of the proposed modelling and control methodology for morphing wing concept.
A Critical Review of the Thermoeconomic Diagnosis Methodologies for the Location of Causes of Malfunctions in Energy Systems
Authors: Lazzaretto Andrea , Toffolo Andrea
Published: May 2008

Thermoeconomic diagnosis procedures in the literature rely on the assumption that specific consumption of resources in the components are the key to interpret the effects of malfunctions and then to trace a path towards the sources of anomalies. The main obstacle to a successful application of these approaches is represented by the actual interactions existing among components which cause a propagation of the alteration of component specific consumptions and therefore mask those effects that would allow a direct identification of the origin of malfunction. This paper presents an extensive discussion of potentialities and limits of diagnosis procedures proposed in the literature in distinguishing the effects induced by component interactions from those that are intrinsically generated by the anomaly, which is considered here as the main task to locate effectively causes of malfunctions in energy systems.
A Cyber Security Self-Assessment Method for Critical Infrastructure Protection
Authors: Glantz Clifford S. , Bass Robert B. , Cash James R. , Coles Garill A. , Currie Andrea J. , Gower David J. , Heilman Jeffrey J. , Lammers Matthew D. , Thomas Jeffrey L.
Published: May 2008

Pacific Northwest National Laboratory is working with federal-and private-sector representatives to develop a cyber security self-assessment method (the Method) for use in the electric power industry. The Method will assist facility owners in identifying and characterizing cyber vulnerabilities, potential adverse consequences, cyber security risk levels, and cost-effective protection and mitigation measures. The Method supports a comprehensive, expeditious assessment that can be integrated efficiently into normal business practices. Personnel in information systems, plant operations, and security all would contribute to the assessment. The risk assessment stage of the Method evaluates both external and internal threats. In the risk management stage, potential protection and mitigation measures are evaluated based on risk reduction; the costs of purchasing, installing, operating, and maintaining new protection and mitigation measures; and changes in the cost of doing business that may be associated with the implementation of new measures.
Numerical Solution of Melting in Side-Heated Rectangular Enclosure Under Electromagnetically Simulated Low Gravity
Authors: Gonc¸alves Eduardo , Faghri M. , Asako Y. , Charmchi M.
Published: May 2008

Electromagnetic simulation of low-gravity environment has been numerically investigated to study the transport phenomena associated with melting of an electrically conducting phase change material, (Gallium), inside a rectangular enclosure. Electromagnetic fields are configured such that the resulting Lorentz force can be used to damp and/or counteract the natural convection and thereby simulating the low gravity environment of outer space. The governing equations are discretized using a control-volume-based finite difference scheme. The solutions are obtained for true lowgravity environment as well as for the simulated-low-gravity. The results show that when the Lorentz force is due to the presence of magnetic field alone, the low-gravity condition is simulated by the damping effect, which is shown to have a profound effect on the flow field. On the other hand, it was shown that under electromagnetic field simulation, where the Lorentz force is caused by the transverse electric and magnetic fields, it is possible to minimize the flow field distortion caused by the high magnetic field and therefore achieve a much better simulation of low-gravity. Furthermore, it was found that under electromagnetic simulation of low gravity the flow field can be reduced or even reversed but never completely halted.
Molecular Dynamics Simulation of Friction for MEMS Application
Authors: Lutade Amlesh , Krishnamurthy K.
Published: May 2008

Adhesion and dry sliding friction are modeled and simulated using molecular dynamics principles in this study. The interaction between two aluminum surfaces is simulated since the focus of this study is on the atomic-scale frictional characterization of metallic microcomponents. The Morse potential function is used to calculate the intra-and inter-atomic forces between the atoms of the sliding surfaces. Results are presented that simulate the adhesion process when the surfaces come in contact. Also, the calculated coefficient of friction for various values of contact pressure, sliding speed and asperity level are presented. The general trends observed here agree with the results obtained by other researchers for different materials.
Optimal Feedback Design of Delayed Linear Systems With Experimental Validation
Authors: Sheng Jie , Sun J. Q.
Published: May 2008

This paper presents an application of semi-discretization method to stability analysis of feedback controls of linear systems with time delay. The method develops a mapping of the system response in a finite dimensional state space. Minimization of the largest absolute value of the eigenvalues of the mapping leads to optimal control gains. Experimental validation is presented to demonstrate the method. We have found that the semi-discretization method provides accurate stability boundaries and performance contours in the parametric space of control gains, and offers an alternative to the classic design approaches of feedback controls.
Molecular Tagging in Microchannels With Microbubble Lensing-Induced Photobleaching (µ-BLIP)
Authors: Sinton D. , Erickson D. , Li D.
Published: May 2008

The curvature of gas-liquid interfaces and the step change in properties across these interfaces in microchannels are shown here to create a powerful lens/mirror effect. In a hydrophilic system, light incident on the bubble is focused into the surrounding liquid resulting in a locally increased total light exposure. The optical phenomena leading to this are discussed and the effect is demonstrated experimentally by imaging the increased photobleaching rate of fluorophores in the near-bubble region. Numerical simulations of the system are performed to investigate the electrical potential and flow fields resulting from the application of an axial electric field. Microbubble Lensing-Induced Photobleaching (μ-BLIP) is then applied as a method of molecular tagging for flow visualization in microchannels. Once formed, the electrokinetic transport of the marker is analyzed to determine the cross-channel velocity profile of the liquid phase, and the liquid velocity in the film. Experimental data is verified by comparison with numerical predictions and previous experimental studies. This contribution represents both a new application of microscale gas-liquid interfacial phenomena, and a new technique for microfluidic flow visualization, particularly applicable (though not limited) to the study of multiphase microchannel flows.
Computational Analysis of Fluid-Wall Interactions in Micro- and Nano-Domains
Authors: Wong C. Channy , Noble David R.
Published: May 2008

In many micro-scale fluid dynamics problems, molecular-level processes can control the interfacial energy and viscoelastic properties at a liquid-solid interface. This leads to a flow behavior that is very different from those similar fluid dynamics problems at the macro-scale. Presently, continuum modeling fails to capture this flow behavior. Molecular dynamics simulations have been applied to investigate these complex fluid-wall interactions at the nano-scale. Results show that the influence of the wall crystal lattice orientation on the fluid-wall interactions can be very important. To address those problems involving interactions of multiple length scales, a coupled atomistic-continuum model has been developed and applied to analyze flow in channels with atomically smooth walls. The present coupling strategy uses the molecular dynamics technique to probe the non-equilibrium flow near the channel walls and applies constraints to the fluid particle motion, which is coupled to the continuum flow modeling in the interior region. We have applied this new methodology to investigate Couette flow in micro-channels.
Efficiency and Accuracy of Semi-Discretization Schemes for Time Delayed Feedback Control Systems
Authors: Elbeyli Ozer , Sun J. Q.
Published: May 2008

Semi-discretization is an effective method for analysis and control design of time-invariant as well as periodic linear systems with time delay. This paper briefly describes various approximation schemes in conjunction to the semi-discretization method. Comparison measures making use of the stability bounds of control gains and the controlled response of the system are presented. The accuracy and efficiency of the method with the zeroth order, improved zeroth order and first order approximations are compared through numerical simulations. Another first order approximation of the system with multiple time delays under a non-delayed feedback leads to integro-differential equations where a simple approximation is utilized to generate discrete maps. It is found that the first order approximation provides substantial improvements in accuracy and efficiency for feedback control design of LTI and periodic systems.
Anatomically Accurate Haemodynamic Simulations of Abdominal Aortic Aneurysms
Authors: Boutsianis Evangelos , Frauenfelder Thomas , Wildermuth Simon , Poulikakos Dimos , Ventikos Yiannis
Published: May 2008

The pulsatile blood flow field in a patient-specific pathology of a large Abdominal Aortic Aneurysm (AAA) is being simulated, both pre and post interventionally. The anatomies of the aortic wall and blood lumen have been derived by digitized Computerized Tomography (CT) scans. Three dimensional unsteady computational fluid dynamics simulations have provided a comprehensive collection of quantitative information on the haemodynamics and the flow features that present themselves in both the temporal and spatial spaces. The focus lies on alterations in the haemodynamics triggered by the interventional procedure itself, which consists of the endoluminal introduction of a stent-graft. Significant information may also be deduced concerning the hydrodynamic loading of such implants. Computational tools of this nature, along with the non-invasive CT or Magnetic Resonance (MR) aortic imaging techniques, could enable an objective assessment of the possible effects of any interventional scenario in a virtual noninvasive environment both proximally and distally to the diseased region.
Studies on Esters of Coconut Oil as Fuel for LPG-Biodiesel Dual Fuel Engine
Authors: Kapilan N. , Reddy R. P. , Mohanan P.
Published: May 2008

The rapid depletion in world petroleum reserves and uncertainty in petroleum supply due to political and economical reasons, as well as, the sharp escalation in the petroleum prices, have stimulated the search for alternatives to petroleum based fuels specially diesel and gasoline. Biodiesel is one of the renewable fuels, which will be the good replacement to diesel. But as a sole fuel, it gives poor performance and higher emissions. From the literature survey, it is observed that not much work has been done to use Methyl Ester (ME) of coconut oil as liquid fuel in sole and dual fuel mode of operation. Hence, in the present work, ME of coconut oil is chosen as a sole fuel to run the diesel engine and an alternative pilot fuel to run LPG-Biodiesel dual fuel engine. In dual fuel mode operation, LPG is used as the inducted gaseous fuel. LPG has been chosen as the inducted fuel on account of its easy availability in abundance in the present time. The existing compression ignition diesel engine was modified to work on dual fuel mode. Tests were carried out on a single cylinder, four strokes, water-cooled, direct injection, compression ignition engine using ME of coconut oil as fuel. To study the effect of injection timing, its is advanced and retarded from the standard injection timing recommended for diesel operation. From the results, it is observed that the advanced injection timing results in better performance and lower emissions of the diesel engine. In dual fuel mode operation, first the engine was started with ME of coconut oil as fuel and then the LPG flow rate was increased. With appropriate proportions of the injected (0.45, 0.65 and 0.75 kg/hr) and inducted fuels it is possible to improve the engine performance and reduce its emissions. From the experimental results, it is found that the pilot fuel rate of 0.65 kg/hr is preferred from the point view of brake thermal efficiency, fuel consumption and smooth running. ME of coconut oil were successfully used as sole fuel and pilot fuel. The performance and emission of the engine in sole fuel mode with better injection timing and dual fuel mode with better pilot quantity were compared. From the comparison, it is observed that the ME of coconut oil can be used as pilot fuel in dual fuel engine compared to sole fuel with regard to performance and emissions.
Effects of Flexibility on the Stability of Flying Aircraft
Authors: Tuzcu Ilhan , Meirovitch Leonard
Published: May 2008

Traditionally, flying aircraft have been treated within the confines of flight dynamics, which is concerned for the most part with rigid aircraft. On the other hand, flexible aircraft fall in the domain of aeroelasticity. Although some attempts have been made to include aircraft rigid body degrees of freedom, aeroelasticity is concerned mostly with the vibration and flutter instability of wings fixed at the root. In reality all aircraft possess some measure of flexibility and carry out rigid body maneuvers, so that the question arises as to whether flexibility can have adverse effects on the stability of flying aircraft. This paper addresses the question of flexibility effects on the stability of flying aircraft by solving the eigenvalue problem associated with the following three cases: 1) the flight dynamics of a flexible aircraft regarded as rigid and whose perturbations about the flight path are controlled by feedback control, 2) the aeroelasticity of a corresponding flexible aircraft prevented from undergoing rigid body translations and rotations and 3) the control of the actual flexible aircraft using the same control gains as in the first case. This investigation demonstrates that it is not always safe to treat separately rigid body effects and flexibility effects in a flying flexible aircraft. Indeed, it is shown that on the one hand the flight of a flexible aircraft treated as rigid can be stabilized by means of feedback controls and on the other hand that the motion of the same flexible aircraft prevented from undergoing rigid body motions tends to consist of damped oscillation. But, when the flying flexible aircraft is treated as it actually is, namely, a single system, the elastic vibration and the perturbations from the flight path can be rendered unstable by feedback controls designed by ignoring the elastic variables.
Effective Feedforward/Feedback Controller Design With Command Shaping to Reduce Residual Vibration
Authors: Meckl Peter H. , Shin Young Joo
Published: May 2008

Many manufacturing devices must execute motions as quickly as possible to achieve profitable high-volume production. This paper develops a control strategy that combines feedforward and feedback control with command shaping. First, the feedback controller is designed to increase damping and eliminate steady-state error. Next, the feedforward controller is designed to speed up the transient response. Finally, an appropriate reference profile is generated using command-shaping techniques to ensure fast point-to-point motions with minimum residual vibration. The particular focus of the paper is to understand the interactions between these individual control components. The resulting control strategy is demonstrated on a model of a high-speed semiconductor manufacturing machine.
Construction of a 3D MEMS Microcoil Using Sequential Robotic Microassembly Operations
Authors: Dechev Nikolai , Cleghorn William L. , Mills James K.
Published: May 2008

This paper describes the contruction of an out-of-plane MEMS (Micro-Electro Mechanical System) microcoil, by assembling together multiple surface micromachined microparts. A microgripper, which is bonded to the end-effector of a robotic workstation, is able to remove a micro-part from a MEMS chip, reorient the micro-part in space, move it to a secondary location, and join it to another micro-part. In this way, complex 3D microstructures can be assembled from a set of initially planar and parallel micro-parts. The microcoil is built from four loop elements, each 200 μm tall by 140 μm wide. The loop is closed by a base structure on the substrate, and the loops are spaced 50 μm apart. This four-loop microcoil is 200 × 140 × 200 μm in size. Using the described microassembly method, it is possible to fabricate microcoils with many loop elements of various sizes, spaced as closely as 25 μm apart.
A MEMS Active Cooling Substrate for Microelectronics Thermal Management
Authors: Wang Yong , Yuan Guang , Yoon Yong-Kyu , Allen Mark G. , Bidstrup Sue Ann
Published: May 2008

Thermal management of electronic systems is of increasing concern as densities and power consumption increase. Typical thermal management solutions are modular in nature; e.g., a heat sink and/or fan area added to a heat-producing part. In this work, an integrated solution, the active cooling substrate (ACS) is proposed, in which the cooling functionality is included in the printed wiring board alongside the electrical wiring. The mechanism for cooling is the use of synthetic jets embedded in the substrate. The utility of the active cooling substrate is demonstrated through quantitative measurements of thermal performance of instrumented platinum heater testbeds. Thermal management is enhanced through the additional heat convection mode introduced by the embedded synthetic jets in the active cooling substrate.
The Dynamics of the Large-Scale Turbulent Structures in the Impinging Round Jet
Authors: Hall Joseph W. , Ewing Dan , Xu Zhuyun , Hangan Horia
Published: May 2008

Experiments were performed to characterize the development of the large-scale structures in the stagnation and wall-jet regions of a turbulent impinging jet with a nozzle-to-plate spacing of 2 diameters and a Reynolds number of 20000. In particular, the instantaneous pressure was measured at 137 points on the wall using 6 concentric rings of pressure taps located 0.25, 0.5, 1.0, 1.5, 2.0 and 2.5 pipe diameters from the jet centreline. The 6 rings respectively contained 8, 16, 16, 32, 32 and 32 equally spaced taps as well as a single pressure tap placed at the jet centerline. The fluctuating pressure was decomposed into azimuthal modes and it was found that a significant portion of the field was contained in azimuthal mode 0 associated with the axisymmetric ring structures and azimuthal mode 1, often associated with jet precessing. The instantaneous pressure was filtered so that only azimuthal modes 0, 1 and −1 remained, and the dynamics of the large-scale structures associated with these modes was examined. These structures were found to be convected radially outward, were highly intermittent, and found to not rotate in a preferred direction.
A Stochastic Model for the Random Impact Series Method in Modal Testing
Authors: Wong C. N. , Zhu W. D. , Zheng N. A.
Published: May 2008

A novel stochastic model is developed to describe a random series of impacts in modal testing. The number of the force pulses in a finite time interval is modeled as a Poisson process. The force pulses in the series are assumed to have an arbitrary, deterministic shape function and random amplitudes and arrival times. A detailed stochastic analysis is undertaken and is validated by numerical simulation. The main advantages of the random impact series method are increased energy input to the test structure and improved signal-to-noise ratio. The method can also average out the slight nonlinearities that can exist in the structure and extract the linearized modal parameters. The model developed in this work can be used to describe a random series of pulses in other applications.
Numerical Prediction of Flow and Heat Transfer Past a Circular Tube With Annular Fins
Authors: Chakraborty D. , Biswas G. , Panigrahi P. K.
Published: May 2008

A numerical investigation was carried out to study the flow and heat transfer behavior of a vertical circular tube, which is situated between two annular fins in cross-flow. The flow structure of the limiting streamlines on the surface of the circular tube and the annular fins was analysed. A finite volume method was employed to solve the Navier-Stokes and energy equations. The numerical results pertaining to heat transfer and flow characteristics were compared with the available experimental results. The following salient features were observed in this configuration. A horseshoe vortex system was formed at the junction of the stagnation line of the circular tube and the annular fin. The separation took place at the rear of the tube. The influence of the horseshoe vortices on local heat transfer was substantial. The ratio of the axial gap between two annular fins (L) to the radial protrusion length of the annular fin (LR) was identified as an important parameter. The flow and heat transfer results were presented for different L/LR ratios for a Reynolds number of 1000.
Dynamic Modeling on the Hybrid MCFC-Gas Turbine Bottoming Cycle
Authors: Zhang Huisheng , Weng Shilie , Su Ming
Published: May 2008

The intention of this paper is to present the dynamic models for the MCFC-gas turbine hybrid cycle. This paper analyzes the performance of various components in the hybrid power plant, such as compressor, turbine, recuperator, generator, fuel cell stack etc. The modular simulation models of these components are presented. Based on the dynamic simulation modeling principle, one bottoming hybrid MCFC-Micro turbine cycle was studied to carry out the simulation, the simulation result is reasonable.
Visualization of Multi-Digit Manipulation Mechanics
Authors: Dun Shouchen , Li Zong-Ming
Published: May 2008

The purpose of this study was to develop a 3D visulaization tool to investigate the contact mechanics at the object-digit interfaces and the force coordination among multiple digits during manipulation tasks. Five miniature 6-component force/torque transducers were used to record force and torque data at the tips of individual digits during 5-digit grasping, rotating, and lifting tasks. A digitizing device was used to obtain 3D coordinates of anatomical landmarks of the hand for the construction of a hand geometric model. Three dimensional force vectors and the centers of pressure were obtained using the force and torque data collected during the manipulation tasks and were displayed at the tips of the 5 digits. The visualization methods developed in this study could potentially provide an effective tool for the study of object-digit interaction mechanics and inter-digit force coordination during various manipulation tasks.
Behavior of Magneto-Rheological Fluids Subject to Impact and Shock Loading
Authors: Norris James A. , Ahmadian Mehdi
Published: May 2008

Investigations on the design of controllable magneto-rheological (MR) fluid devices have focused heavily on low velocity and frequency applications. The extensive work in this area has led to a good understanding of MR fluid properties at low velocities and frequencies. However, the issues concerning MR fluid behavior in impact and shock applications are relatively unknown. To investigate MR fluid properties in this regime, a drop-tower was developed to subject MR fluid dampers to impulsive loads. The drop-tower design uses a guided drop-mass, which is released from variable heights to achieve different impact energies. The nominal drop-mass is 55 lb and additional weight may be added to reach a maximum of 500 lb. The nominal drop-mass of 55 lb was used throughout this study. Five drop-heights were investigated, 12, 24, 48, 72 and 96 inches, corresponding to impact velocities of 86, 127, 182, 224 and 260 in/s. Two fundamental MR damper configurations were tested, a single-stage, double-ended piston and a two-stage, mono-tube with nitrogen accumulator. Both dampers operate in the valve flow mode and contain MRF-128 TD fluid from Lord Corporation. The results indicate that the two damper configurations exhibit different force-displacement characteristics during impulsive loading. For the single-stage, double-ended damper, the peak force occurs close to the beginning of the impact. Conversely, the two-stage, mono-tube damper does not reach the peak force until after the nitrogen accumulator bottoms out. To verify this behavior, a theoretical model of the accumulator is derived and compared to the experimental data. The results also show that for a given impact velocity, the peak force does not depend on the current supplied to the damper. Since increasing the supply current causes an increase in the apparent yield stress, it was anticipated that the peak force would depend on the supply current as well. This disagreement is hypothesized to be the result of the fluid inertia preventing the fluid from accelerating fast enough to accommodate the rapid piston displacement. Thus, the peak force is primarily attributed to fluid compression, rather than the resistance to flow associated with the fluid passing through the magnetic field. It is important to note that this study is in its early stages and only preliminary conclusions are presented. Follow up publications will include additional results and modeling, and attempt to relate device design and MR fluid properties to dynamic behavior.
A Bistable Electromagnetic Actuated Microvalve With Integrated Switching Mechanism
Authors: Bintoro Jemmy Sutano , Hesketh Peter J.
Published: May 2008

This paper presents a new design and fabrication method for a bistable electromagnetic actuated microvalve. The complete magnetically close structure has been designed by ANSYS 5.7 [1] and was fabricated in 7 masks steps. The fabrication processes were entirely done by surface micromachining and electroplating on a single wafer with the maximum fabrication temperature of 300 °C, providing potentially a CMOS compatible process. The microvalve has additional feature called integrated switching mechanism used to detect the position of the membrane under fully open or closed position. The fabrication steps for the microvalve are different from previous work; the hole is etched through the back of wafer after the whole valve structure been built on the top of wafer. This provides the flexibility to fabricate an actuator first before finally producing a microvalve.
An Agar and Saline Phantom for Perfused Tissue
Authors: Madden Marie C. , Scott Elaine P.
Published: May 2008

A simple and accurate perfused tissue phantom would be a useful tool for biomedical research. The phantom described here is an agar-saline model that can be easily constructed. Space between finely diced pieces of agar is perfused with saline. A rotator Boekel-Orbitron® is used to perfuse the agarsaline mixture, mimicking the non-directional movement of blood. Dye injected into the phantom records the volumetric movement of saline for a set time period on the Orbitron. These data are used to determine perfusion estimates in units of g/s/mL. Experimental results can be appropriately scaled and additional modifications can be better mimic specific in-vivo conditions.
Measurement of Circumferential Fuel Distribution With Laser Transmission Beam for Fuel Nozzle
Authors: Gan Xiaohua , Liu Jizhou , Li Xifa , Wang Hongming
Published: May 2008

This paper presents a new technique for measuring the non-uniformity of circumferential distribution of fuel by means of laser transmission beam for fuel nozzle. Using this technique, the physical and mathematical relationships have been developed and validated by experimental data. The development of the new technique is based on the fact that, when the fuel flow rate increases, the spray concentration at a given measurement point will be higher, the light intensity intercepted by the spray will be increased, and the portion received by the terminal detector will be decreased.
Numerical Analysis of the Convective Heat Transfer in a Combustor Cooling Jacket
Authors: Gutierrez Gustavo , Jen Tien-Chien , Yan Tuan-Zhou
Published: May 2008

In any combustors and chemical reactos, to achieve high efficiency it is very important to maintain the high gas temperature inside the combustion chamber without significant deterioration of the materials of the walls. Thus, a critical aspect of the design of a combustor or reactor is the development of a method to cool the inner walls of a combustor such that the temperatures on the inner wall are well below the temperature a material can sustain. A typical method to cool a combustor chamber is to use a cooling jacket adjacent to the inner wall of the combustor. In general, the efficiency of this cooling jacket depends on the heat removal capability of the cooling water and the flow channel geometry. It is critically important to control these parameters to enhance the performance of the combustion chamber by decreasing the inner wall temperature below its material limit. This study considers a cylindrical combustor, rotating around its axis. A detailed investigation of the fluid flow and heat transfer processes throughout the cooling jacket is performed. A two-dimensional axial symmetric Navier-Stokes equations and energy equation as a conjugate problem are solved. The flow patterns and temperature distributions of the cooling jacket under the effect of rotation are presented. Also, local friction factor and Nusselt number are calculated along the axial direction.
Pressure Induced Stresses and Strains in a Simulated Femoral Artery Bypass Graft Junction
Authors: Cole Reena , Campbell Triona M. , Davies Mark R. D.
Published: May 2008

It has been clinically proven that vascular reconstructions tend to restenose within a relatively short period of time. Intimal hyperplasia and smooth muscle proliferation appear to be promoted by the altered intramural stress distributions at the distal anastomosis of the artery-graft junction. This paper examines the pressure induced stresses and strains in a simulated artery and bypass graft junction. Numerical and experimental methods were used to determine both the magnitude and location of the stresses and strains. A Finite Element package and silicon models were used for the in vitro analysis. Initial numerical analysis involved the modeling of a cylinder with homogenous material properties, followed by the modeling of a homogenous graft artery junction under static pressures. These experimental results were then used to validate the numerical model.
Workspace Analysis of Reconfigurable Robotic Arms Using Parallel Platforms as Modules
Authors: Badescu Mircea , Mavroidis Constantinos
Published: May 2008

In this paper the workspace analysis of reconfigurable hyper-redundant robotic arms using as modules lower mobility parallel platforms is presented. The modules of the reconfigurable robotic arm are the 3-legged translational UPU and orientational UPS parallel platforms. Each arm is composed of a large number of these modules having a very large number of degrees of freedom. New performance indices to characterize the workspace of such arms are defined and used to analyze their different configurations. Results of this analysis are presented in table and graphic forms and the corresponding best designs are identified. All possible arm assembly configurations with two, three, and four parallel platform modules and one configurations with five parallel platform modules have been taken into consideration, analyzed and compared.
The Development of Non-Radiative Probes for In Vivo Applications
Authors: Tsourkas Andrew , Josephson Lee , Weissleder Ralph
Published: May 2008

Recently, the field of activatable probes has been extended from fluorescence to magnetic resonance (MR). Magnetic relaxation switches take advantage of the change in T2 relaxation time that occurs upon binding of multiple bioconjugated superparamagnetic iron-oxide nanoparticles to a target. Here, we use a model system to detect biotinilated BSA using switchable magnetic particles. The presence of the biotinilated BSA results in the aggregation of nanoparticles and leas to a substantial decrease in the T2 relaxation time. Magnetic relaxation switches show great promise for clinical in vitro diagnostics and in vivo imaging since changes in T2 are independent of the sample medium. Tests can be performed in turbid solutions without loss of sensitivity, unlike with fluorescence measurements.
Transport Delay Compensation for the Image Generator Used in the National Advanced Driving Simulator
Authors: Salaani M. Kamel , Heydinger Gary J. , Grygier Paul A. , Garrott W. Riley
Published: May 2008

Despite the advances in computer graphics speed and quality, Image Generator (IG) delys are unavoidable due to the demanding details and complex scenarios run at the National Advanced Driving Simulator (NADS), in particular for urban traffic scenes. This paper introduces a new dynamic compensation algorithm for automotive driving simulator visual displays. The compensation method is based on an original approach used by NASA Ames Research Center for flight simulator applications. The compensator designed has nearly zero phase with well-maintained magnitued within the bandwidth. The algorithm has magnitude attenuation outside the bandwidth without altering the desired frequency response of the compensator. This paper discusses the compensation method, and presents results from the NADS showing drivers’ ability to steer the vehicle through corners without excessive overshoot resulting from human reactions to visual delays. The results demonstrate that compensating for visual delays for high-end driving simulators is vital for real-time fidelity.