bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Temperature Sintering of Nanoscale Silver Pastes for High-Performance and Highly-Reliable Device Interconnection
Authors: Bai John G. , Zhang Zach Z. , Calata Jesus N. , Lu Guo-Quan
Published: April 2008

In this paper, we report our development on making of nanoscale silver pastes and their low-temperature sintering for semiconductor device interconnections. The nanoscale silver pastes were prepared by dispersing 30-nm silver powder under ultrasonic vibration and mechanical agitation in an organic vehicle. Sintering of the silver paste prints at 280°C for 10 minutes resulted in a density of ~80% in the air ambient. Some important properties of the low-temperature sintered silver include ~2.4 W/K-cm for thermal conductivity, ~3.8 × 10−6 Ω-cm for electrical resistivity, and ~9 GPa for the effective elastic modulus. SiC Schottky rectifiers attached to either silver- or gold-coated direct bond copper (DBC) substrates show low forward voltage drops. The silver joints do not contain large voids but rather uniformly distributed microscale pores. Die-shear tests showed that bonding strengths of the silver joints were around 21 MPa on the gold-coated DBC substrates and 38 MPa on the silver-coated DBC substrates, respectively. The latter is comparable to that of reflowed eutectic lead-tin solder joints. Based on the findings in this work, the low-temperature sintering of nanoscale silver pastes is promising to be a high performance and highly-reliable semiconductor device bonding solution for high power packages.
Optimal Design of Composite Laminate With Uncertainty in Loading and Material Properties Considered
Authors: Kim Tae-Uk , Hwang In Hee , Sin Hyo-Chol
Published: April 2008

Optimal design of composite laminates with uncertain in-plane loadings and material properties is considered. The stacking sequence is designed to have maximum buckling load based on anti-optimization approach. To consider the above-mentioned uncertain properties, the convex modeling and Monte Carlo simulation techniques are used in calculating objective function. For the stacking sequence optimization, it is used the modified genetic algorithm which handles the discrete ply angles and the constraints easily. Numerical results are given for rectangular laminates of various aspect ratios. The optimal solutions from the deterministic and the stochastic cases are obtained and it is demonstrated the importance of considering uncertainty. The buckling load carried by a deterministic design is much less than the one carried by a design uncertainty considered when both are subjected to uncertain loads. Also, it is examined the effects of the method for considering uncertainty on the optimization process in the light of computational efficiency and reliability of solutions obtained.
Experimental Investigations on a Compressed Natural Gas Operated Dual Fuel Engine
Authors: Kapilan N. , Somayaji Chandramohan , Mohanan P. , Reddy R. P.
Published: April 2008

In the present work, an attempt has been made for the effective utilization of Compressed Natural Gas (CNG) in diesel engine. A four stroke, single cylinder diesel engine was modified to work on dual fuel mode. The effect of CNG flow rate and Exhaust Gas Recirclulation (EGR) on the performance and emissions of the dual fuel engine was studied. The variables considered for the tests were different CNG flow rates (0.2, 0.3, 0.4, 0.5, 0.6 and 0.7 kg/hr), EGR (0 %, 4.28 %, 6.63 % and 8.12 %) and loads (25 %, 50 %, 75 % and 100 % of full load). From the test results, it was observed that the EGR rate of 4.28 % results in better brake thermal efficiency and lower CO and NOx emissions than other ERG rates at 25 %, 50% and 75% of full loads. At full load, EGR rate of 8.12 % results in higher brake thermal efficiency and lower NOx emissions.
Evaluation of Solid Particle Erosion Damage on E-Glass/Epoxy Composites Using Acoustic Emission Activity
Authors: Yang N. H. , Nayeb-Hashemi H.
Published: April 2008

The effect of solid particle erosion on the strength properties of E-glass/epoxy composite was investigated. Solid particle erosion with SiC particles 400 μm to 500 μm in diameter was simulated on 12 ply [45°/−45°/0°/45°/−45°/0°]s E-glass/epoxy composites with constant particle velocity of 42.5 m/s at impact angles of 90°, 60°, and 30° for 30, 60, 90 and 120 seconds. Damaged and undamaged specimens were subjected to tensile tests while monitoring their acoustic emission (AE) activity. An erosion damage parameter was defined as a function of the particle impact angle and erosion duration to determine the residual tensile strength of the composite. Scanning electron microscope (SEM) images of the erosion damaged specimens revealed the same damage mechanism occurred at different impact angles. The distribution of AE events by event duration, ring down counts and energy distribution were used to characterize the different damage mechanisms that occurred during tensile loading of damaged and undamaged specimens. The results showed AE activity could be used to distinguish between different damage mechanisms within the composite, such as fiber/matrix debonding, delamination and fiber fracture. The Weibull probability distribution model and the AE stress delay parameter model were developed to relate the AE activity to the erosion damage and residual strength. The results showed both the Weibull probability model and the stress delay model could be used to predict residual strength of the composites.
Friction Stir Riveting: Impact of Process Parameters on Joint Performance
Authors: Stevenson Robin , Wang P.-C.
Published: April 2008

The Friction Stir Riveting (FSR) process consists of rapidly rotating a suitably shaped rivet, bringing it into contact with the workpieces to be joined and slowly driving the rotating rivet into the workpieces. The process, which borrows some features of Friction Stir Welding results in heating the workpieces through friction, thereby locally softening the workpieces and enabling the insertion of the rivet under reduced force. While conceptually simple the details and subtleties of the joining process have not been studied, thus little insight into the influence of processing characteristics has been generated and knowledge of procedures for enhancing joint strength is lacking. The intent of this study is to investigate the influence of rivet composition, rotational speed and penetration rate on joint performance and to compare overall joint performance with that obtained using conventional resistance spot welds.
Development of Lower Frequency Disturbance Detector for Reaction Wheel Analysis
Authors: Taniwaki S. , Hatsutori Y. , Ohkami Y.
Published: April 2008

The reaction wheel (RW) is a key component in the attitude control system of spacecraft, but it is also a major source of disturbances. In this paper, we present a recently developed two types of disturbance detectors. One is the two-dimensional force and torque sensor with an air-table mechanism, the other is one-dimensional force sensor with an air-slide mechanism. Both of them are sensitive to low-frequency disturbances which are difficult to be detected with previous technique. In this paper, their measurement principle, measurement accuracy and measurement examples for RW induced disturbances are shown.
Smart Ionic Polymer Conductor Composite Materials as Multifunctional Distributed Nanosensors, Nanoactuators and Artificial Muscles
Authors: Shahinpoor Mohsen
Published: April 2008

Basic recent results, properties and characteristics of ionic polymer conductor composites (IPCC) and ionic polymer metal composites (IPMC) as biomimetic distributed nanosensors, nanoactuators, nanotransducers and artificial muscles are briefly discussed in this paper. In particular the paper first starts with some fundamental considerations on biomimetic distributed nanosensing and nanoactuation and then expands its coverage to some recent advances in manufacturing techniques, force optimization, 3-D fabrication of IPMC’s, recent modeling and simulations, sensing and transduction and product development. The paper also covers some recent industrial and medical applications including a multi-fingered grippers (macro, micro, nano), biomimetic robotic fish and caudal fin actuators, diaphragm micropump, multi-string musical instruments, linear actuators made with IPMC’s, IPMC-based data glove and attire, IPMC-based heart compression/assist devices and systems, wing flapping flying system made with IPMC’s and a host of others.
Multi-Variable, High Order, Performance Models (2005C)
Authors: Japikse David , Dubitsky Oleg , Oliphant Kerry N. , Pelton Robert J. , Maynes Daniel , Bitter Jamin
Published: April 2008

In the course of developing advanced data processing and advanced performance models, as presented in companion papers, a number of basic scientific and mathematical questions arose. This paper deals with questions such as uniqueness, convergence, statistical accuracy, training, and evaluation methodologies. The process of bringing together large data sets and utilizing them, with outside data supplementation, is considered in detail. After these questions are focused carefully, emphasis is placed on how the new models, based on highly refined data processing, can best be used in the design world. The impact of this work on designs of the future is discussed. It is expected that this methodology will assist designers to move beyond contemporary design practices.
On-Board System Identification of Systems With Unknown Input Nonlinearity and System Parameters
Authors: Liu Song , Yao Bin
Published: April 2008

Input nonlinearities, or actuator nonlinearities, can be seen in a lot of systems and have significant effects on the system performance. From the controller design point of view, accurate yet simple model of input nonlinearities is essential to compensate their effects and to achieve high level control performance. Unfortunately, most input nonlinearities are neither known nor easy to characterize, especially when the input nonlinearities and unknown system parameters are present simultaneously in the system dynamics. Off-board calibration may be possible yet it is very time consuming and requires additional calibration systems. This paper focuses on a class of systems with unknown input nonlinearities and system parameters and proposes an on-board system identification process to model the unknown nonlinearities. The input nonlinearities are decomposed into localized orthogonal basis and then estimated together with the system parameters. The proposed method is applied to model the nonlinear flow mapping of cartridge valves. Simulation and experimental results are obtained to illustrate the effectiveness and practicality of the proposed method.
A Novel Approach for Batch Fabrication of Bifunctional AFM-SECM Probes
Authors: Shin Heungjoo , Hesketh Peter J. , Kranz Christine , Rudolph Douglas A. , Mizaikoff Boris
Published: April 2008

This paper presents a novel batch fabrication process for manufacturing bifunctional Scanning Electrochemical-Atomic Force Microscopy (AFM-SECM) probes with a recessed integrated ring electrode. The presented tip fabrication procedure enables the integration of a micro ring electrode at a precisely defined distance above the apex of the AFM tip. The electroactive area integrated into a scanning probe tip allows obtaining electrochemical data independently and separated from the topographical image. The tip fabrication is based upon batch processing, which provides bifunctional scanning probe tips on a wafer scale at low cost with high processing reproducibility and uniformity. Electrochemical characterization of an AFM tip-integrated ring electrode and combined electrochemical and topographical imaging using the bifunctional probe are demonstrated in this study.
Modeling of a Light-Weight Composite Blast-Containment Vessel
Authors: Trabia Mohamed B. , O’Toole Brendan J. , Thota Jagadeep , Matta Kiran K.
Published: April 2008

This paper presents finite element modeling of a lightweight composite vessel for blast containment purposes. The vessel has a steel liner that is internally reinforced with throttles and gusset plates and wrapped with a basalt fiber/epoxy composite. The vessel design is fairly complex, including many geometric details, and several different materials. The objective of this work is to determine an efficient analysis procedure that can be used in an iterative optimization process. Analysis approaches using various combinations of element type, material models, and geometric detail are explored. Finite element results are compared to experimental data. Accuracy and efficiency are compared for all cases and a suitable analysis method is recommended.
Studies of Temperature and Pressure Dependence in Thermocompression Gold Joints
Authors: Ang X. F. , Zhang G. G. , Wei J. , Chen Z. , Wong C. C.
Published: April 2008

Low temperature interconnection is a critical component of 3D integration and packaging technology. In this study, we investigate the characteristics of thermocompression metal bonding using gold stud bumps formed on Si die in the temperature range of 100-300 °C and the pressure range of 200–600 g/bump. We observed a critical bonding temperature below which bonding did not occur and above which shear strength improves linearly with bonding temperature. This critical temperature can be interpreted to be the onset of the break-up of organic barrier films while the linear rise in shear strength can be attributed to the increase in the true bonded area. Above this critical temperature, the tensile strength of the Au-Au bond exhibits a maximum with increasing bonding pressure. This can be related to the pressure dependence of the interfacial stress distribution and its effect on unbonded radius, r. SEM fractographs of the failed surfaces suggest a combination of cohesive and adhesive failures along the bonded interface.
Development of Advanced Lead-Free Solder Based Interconnect Materials Containing Nanosized Y2O3 Particulates
Authors: Nai S. M. L. , Wei J. , Gupta M.
Published: April 2008

This study addresses the development of lead-free nanocomposite solders. Lead-free composite solders were successfully synthesized, with varying amount of nanosized Y2O3 particulates incorporated into 95.8 Sn - 3.5 Ag - 0.7 Cu solder. These composite materials were fabricated using the powder metallurgy technique involving blending, compaction, sintering and extrusion. The extruded materials were then characterized in terms of their physical properties, microstructural development, thermal and mechanical properties. Results revealed that with the incorporation of increasing amount of reinforcements, the density values of the composite solders decreased while their corresponding porosity levels increased. Thermomechanical analysis of the solder nanocomposites showed that the use of reinforcements lowered the average coefficient of thermal expansion of the solder materials. Moreover, the results of mechanical property characterizations revealed that the addition of reinforcements aids in improving the overall strength of the nanocomposite solder. Particular emphasis is placed in this study to correlate the effect of increasing presence of Y2O3 particulates with the properties of the resultant nanocomposite materials. These advanced interconnect materials will benefit industries like the microelectronics flip chip assembly and packaging, MEMS systems and NEMS systems.
Stress Concentration in Laminated Composites With a Central Circular Hole Under Biaxial Load
Authors: Hu Zhong , Delfanian Fereidoon
Published: April 2008

The anisotropic nature of the laminate composites creates a unique opportunity and also a great challenge for tailoring its properties according to the design requirements. In this work investigating the strength of laminate composite, a nonlinear finite element analysis was used to simulate the stress concentration in a two dimensional element caused by a central circular hole subjected to the biaxial loading. The effects of elastic and plastic deformation of a metallic material, fiber orientation and stacking order of a laminated composite on stress concentration were investigated. This evaluation provides a clear indication and a key step in understanding failures initiated by stress concentration which may lead to the growth of a crack. Comparison between the effects of the hole both on a metallic material and on a fiber-reinforced laminate exposes a totally different situation. In general, the stress concentration depends largely on the material properties, the layer stacking order, and the orientation.
Model-Free Trajectory Control of a Two-Link Flexible-Joint Robot: Theory and Experiment
Authors: Chatlatanagulchai Withit , Meckl Peter H.
Published: April 2008

We present a state-feedback control of a two-link flexible-joint robot. First, we obtain desired control laws from Lyapunov’s second method. Then, we use three-layer neural networks to learn the unknown parts of the desired control laws. In this way, the control algorithm does not require the mathematical model representing the robot. We use a smooth variable structure controller to handle uncertainties from the neural network approximation and external disturbances. To show the effectiveness and practicality of this control algorithm, we performed an experiment on one of the robots in our laboratory.
Development of Bulk-Titanium-Based MEMS RF Switch for Harsh Environment Applications
Authors: Ding C. , Huang X. , Gregori G. , Parker E. R. , Rao M. P. , Clarke D. R. , MacDonald N. C.
Published: April 2008

This paper presents a preliminary investigation into the viability of a new route for the fabrication of titanium-based MEMS RF switches for harsh environment applications. Titanium’s intrinsic toughness and corrosion resistance suggest that it would be highly suitable for such applications and recently developed titanium micromachining technologies now make exploration of this potential possible. Two design generations of electrostatically-actuated Bulk-Titanium MEMS (BT-MEMS) switches were fabricated and tested. First generation devices demonstrated that actuation at moderate voltages could be achieved (~60V), however stiction upon contact was common. This stiction was mitigated in the second generation devices through design modification and development of a new Titanium on Insulator (TOI) based process. These devices displayed stiction-free actuation and relatively low contact resistance (~1Ω). These preliminary results therefore demonstrate the potential of this process technology for fabrication of titanium-based RF switches for harsh environment applications.
An Application and Investigation of Rotating Heat Pipes on Motor Rotor Cooling
Authors: Cai Qingjun , Chen Chung-Lung , Dong Jimmy Q.
Published: April 2008

In some industrial AC motor applications, higher heat dissipation results in faster rotor losses than that can be accommodated with conventional shaft-mounted-fan cooling designs. In this paper, one of the heat pipe technologies - rotating heat pipe - is presented as a means of enhancing motor rotor cooling. Novel rotating heat pipes are designed to improve heat transfer performance at various rotational speeds. Preliminary experimental results indicate that this thermal solution can effectively improve motor rotor cooling. Further, the rotating heat pipes with internal wicks can reduce temperature gradients at low rotational speed.
A MEMS Thermal Biosensor for Metabolite Measurements
Authors: Wang Li , Lin Qiao
Published: April 2008

We present a MEMS differential thermal biosensor integrated with microfluidics for metabolite concentration measurements either in flow-injection or flow-through modes. The biosensor consists of two identical freestanding polymer thin membranes, resistive on-chip heaters, and a metal thermoelectric differential temperature sensor between the two membranes. Integrated with polymer microfluidic channels and chambers, the biosensor allows efficient handling and measurements of small volumes (~1 μl) of liquid samples. Calibrated with on-chip resistive heaters, the biosensor shows a sensitivity of 1.2 V/W and time constant of 0.58 s. Enzyme-functionalized beads are packed in the chambers and interacted with metabolite solutions. The heat released from the enzymatic reactions is detected by the temperature sensor and used to measure the metabolite concentration. The biosensor demonstrated a glucose concentration resolution of 0.12 mM for flow-injection mode, and 0.48 mM for flow-through mode with a flow rate of 0.5 ml/h. It is found that there exists an optimal flow rate that corresponds to the maximum thermopile output voltage when the biosensor works in the flow-through mode.
Isolation Application of Controlled and Uncontrolled Magnetorheological Dampers for Random Base Excitaion
Authors: Narimani A. , Golnaraghi M. F.
Published: April 2008

This paper presents experimental investigation of modeling and control of magnetorhological damper for transient base excitation inputs. Force characteristics of a commercially available MR damper (RD-1005-3) for shock and other transient base excitation are analytically obtained and validated using a scaled suspension model. The proposed model characterizes damper behavior more accurately and efficiently for analytical applications. The time and frequency responses of the developed model are compared with the experimental results and show good agreement. Finally, using the RMS optimization method the performance of the system for different types of controllers is compared with the optimal values of linear isolator system. Experimental results show that the performance of base isolation systems for transient and shock inputs significantly improves by utilizing a controlled semi-active damper over uncontrolled MR damper or an optimally designed passive isolator.
Expert System Modeling, Analysis and Validation of Surface Roughness in Drilling
Authors: Sivarao P. S. , Muhamad Mohd Razail
Published: April 2008

Surface finish is an important parameter in manufacturing engineering. It is a characteristic that could influence the performance of mechanical parts and the production cost. It is also an aspect for designing mechanical elements and frequently presented as a quality and precision indicator of manufacturing processes. Various failures, sometimes catastrophic, leading to high cost have been attributed to the surface finish of the components in question. Therefore, the quality of surface roughness is essential feature of drilling operation since most of hole applications are assembly works, especially focused on the relative movement and tight tolerance work. Hence, high standard quality control needs to be introduced. The aim of this experimental and analytical research is to identify the parameters which enable the prediction of surface roughness in drilling. Two expert systems were used to analyze the best fit model in predicting the output of surface roughness for this specific drill job.
Low Volume Plastics Manufacturing Strategies
Authors: Karania Ruchi , Kazmer David
Published: April 2008

Plastic components are vital components of many engineered products, frequently representing 20–40% of the product value. While injection molding is the most common process for economically producing complex designs in large quantities, a large initial monetary investment is required to develop appropriate tooling. Accordingly, injection molding may not be appropriate for applications that are not guaranteed to recoup the initial costs. This paper extends previous work [1] with component cost and lead-time models developed from extensive industry data. The application is an electrical enclosure consisting of two parts produced by a variety of low to high volume manufacturing processes including CNC machining, fused deposition modeling, selective laser sintering, vacuum casting, direct fabrication, and injection molding with soft prototype and production tooling. The viability of each process is compared for production quantities of one hundred, one thousand, and ten thousand. The results indicate that the average cost per enclosure assembly is highly sensitive to the production quantity, varying in range from US$0.35 per enclosure for ten thousand assemblies produced via injection molding to US$49.30 per enclosure for one hundred assemblies produced via fused deposition modeling. The results indicate the cost and lead time advantages of the alternative processes; a flow chart is provided to assist process selection in engineering design.
Nonlinear Decentralized Position Control of Electrohydraulic Actuators in Road Simulation
Authors: Ayalew Beshahwired , Kulakowski Bohdan T.
Published: April 2008

In this paper, a nonlinear position tracking controller is derived based on feedback linearization to globally linearize the nonlinear dynamics of an electrohydraulic actuator with nonlinear state feedback. A detailed computer model is developed for a four-post road simulation system with a transit bus as the test vehicle. Using this model, comparisons are conducted between the proposed nonlinear decentralized controller and a traditional linear decentralized controller. Previously introduced interaction measures suitable for time domain analysis of nonlinear systems confirm that, for the test vehicle considered, load plate position loop interactions are quickly eliminated by either the linear or nonlinear decentralized position controllers. The performance of the road simulator as gauged by a position tracking error metric for a typical rough road profile is improved by over 60% across all actuators and response matching of sprung mass vertical acceleration PSD is likewise improved by over 50% when using the nonlinear decentralized controller.
Analytical Model of Heat Conduction in a Tubular Geometry With Application to a Nano-Structured Thermal Interface
Authors: Desai Anand , Geer James , Sammakia Bahgat
Published: April 2008

Power dissipation in electronic devices is projected to increase significantly over the next ten years to the range of 50-150 Watts per cm2 for high performance applications [1]. This increase in power represents a major challenge to systems integration since the maximum device temperature needs to be around 100 C. One of the primary obstacles to the thermal management of devices operating at such high powers is the thermal resistance between the device and the heat spreader or heat sink that it is attached to. Typically the in situ thermal conductivity of interface materials is in the range of 1 to 4 W/mK, even though the bulk thermal conductivity of the material may be significantly higher. In order to improve the effective in-situ thermal conductivity of interface materials nanotubes are being considered as a possible addition to such interfaces. The primary approach taken in the current study is to analyze the enhancement of the thermal interface by adding carbon nano tubular cylinders that are oriented in the direction of transport. This paper presents the results of an analytical study of transport in a thermal interface material that is enhanced with carbon nanotubes. A variety of parametric analyses are carried out, such as by varying the inner diameter of the nanotube and the power dissipation, and the effect on spreading resistance is calculated. The results indicate that for high thermal conductivity nanotubes there is a significant increase in the effective thermal conductivity of the thermal interface material.
Towards Autonomous Fixed-Wing MAVs With Hovering Capabilities
Authors: Green William E. , Oh Paul Y.
Published: April 2008

Near-Earth environments, such as forests, caves, tunnels, and urban structures make reconnaissance, surveillance and search-and-rescue missions dificult and dangerous to accomplish. Micro-Air-Vehicles (MAVs), equipped with wireless cameras, can assist in such missions by providing real-time situational awareness. This paper describes an additional flight modality enabling fixed-wing MAVs to supplement existing endurance superiority with hovering capabilities. This secondary flight mode can also be used to avoid imminent collisions by quickly transitioning from cruise to hover ight. A sensor suite which will allow for autonomous hovering by regulating the aircraft’s yaw, pitch and roll angles is also described.
Penetration of Aerated Liquid Fuel Jet in Supersonic Cross Flow
Authors: Ghenai C. , Sapmaz H. , Lin C. X.
Published: April 2008

The success of supersonic air-breathing propulsion systems will be largely dependent on efficient injection, mixing, and combustion inside the supersonic combustion chamber. Fuel/air mixing enhancement inside the combustion chamber will depend on the strategies used to control the fuel jet penetration and liquid fuel droplet size, trajectory, and dispersion. We present in this paper experimental results on the penetration and mixing of aerated liquid fuel jet in supersonic cross flow (M=1.5). The aerated liquid jet or the barbotage technique where a small amount of gas is added to the liquid fuel will accelerate the atomization of the liquid jet and offer a good fuel penetration. High speed imaging system is used in this study for the visualization of pure and aerated liquid jet. For the aerated liquid jet the gas/liquid mass ratio was varied between 0 and 9.9 %. The results presented in this paper shows the effect of jet/cross flow momentum ratio, and gas/liquid mass ratio on the structure and penetration of aerated liquid jet (methanol) in high speed cross flow. The data generated in this study are used for the development of active control strategies to optimize the liquid fuel jet penetration and supersonic fuel/air mixing.
Space Filling Curves: Its Design and Fabrication for Extrusion Based SFF Systems
Authors: Starly Binil , Shor Lauren , Sun Wei , Darling Andrew
Published: April 2008

Scaffolds with designed interior pore architecture, predefined porosity and a well interconnected predetermined network has been the most favored design approach for tissue engineering applications. Solid freeform fabrication technologies have provided the capability of fabricating tissue scaffolds with desired characteristics due to its integration with CAD enabled tools. However, currently the interior macro pore design of scaffolds have been limited to simple regular shapes of either squares or circles due to limited CAD capability. In this paper we seek to enhance the design of the scaffold architecture by using space filling curves within its interior space. The process involves: definition and characterization of space filling curves such as the Hilbert Curve and Sierpinski Curves, applying the principle of layered manufacturing to determine the scaffold individual layered process planes and layered contours; Feasibility studies applying the curve generators to sample models and the generation of fabrication planning instructions for extrusion based SFF systems is presented.
Experimental Study of the Dynamics of Synthetic Jet Actuators With Different Orifice Sizes
Authors: Sekhri Rahul , Schoen Marco P. , Lin Feng , Williams Brian G.
Published: April 2008

Synthetic jet actuators (SJA) are one of the newly developed actuators that have demonstrated its great potentials in active flow applications, particularly in closed-loop flow controls. The SJA contains a piezoelectric membrane in a cavity, which vibrates and generates a periodic jet at the exit of the cavity through an orifice that is mounted flush with the solid wall of the flow field. In order to design the feedback control laws, it is crucial to be able to quantitatively capture the dynamics of SJA. In this paper, the dynamics of SJAs with six different orifice sizes are experimentally investigated. A synthesis using system identification for the purpose of constructing mathematical models of these zero mass-flux actuators is offered. The experimental study includes two output parameters, the acoustic sound pressure generated by the SJA and the mechanical membrane vibration of the SJA. State-space models for these outputs (sound pressure and mechanical vibration) are developed as a function of orifice size. These results form a foundation for future intelligent design of SJA.
Development of a Light-Driven Thin-Film Piezoelectric Microactuator
Authors: Deshpande Mandar , Saggere Laxman
Published: April 2008

This paper presents the design, fabrication and experimental characterization of a self-contained light-driven microactuator that could find a potential application in a novel retinal prosthesis. The conceived actuator system comprises of a miniaturized solid-state solar cell connected in series with a thin-film piezoelectric microactuator, both fabricated and integrated on a single chip through conventional microfabrication processes. When irradiated with light, the solar cell generates voltage across the thin-film microactuator, which bends and produces mechanical actuation. The novelty of the actuator system lies in its unique integrated design to meet its unique application requirements of producing the output mechanical actuation for input light energy at low illumination levels in the range of 0.1–3 W/m2. The work demonstrates the fabrication feasibility of the miniaturized solar cell and the PZT thin-film microactuator, and characterizes their performance separately. The solar cell is fabricated by creating a p-n junction over a small area on a single crystal p-type silicon substrate. The microactuator is fabricated as a 600 nm sol-gel derived 52/48 PZT thin-film on a silicon diaphragm. The voltage output characteristics of the solar cell, experimentally studied as a function of the incident irradiance, shows an open circuit voltage of 250–300 mV under 0.6–1.6 W/m2 irradiance. The PZT thin-film microactuator, actuated under low voltages of 0–700 mV, showed deflections in the range of 0–16 nm. Finally, the light-driven actuation is demonstrated by connecting the miniaturized solar cell with the PZT thin-film microactuator and measuring deflections of 5–7 nm under low illumination levels of 0.6–1.6 W/m2.
Study on Mechanisms and Model of Heat Transfer in Spray Cooling
Authors: Lei Shu-Ye , Lu Qiu-Min
Published: April 2008

The paper presented two heat transfer coefficients: apparent heat transfer coefficient and real heat transfer coefficient. Apparent HTC is overall HTC, which is affected by many factors, such as liquid heat dissipation; on the other hand, real HTC is the HTC between heater and liquid film, which only relates to spray momentum. Local spray cooling experiments and PDA measurement experiments were conducted and the real heat transfer empirical correlation was developed. A half empirical and half analysis model involving the heat dissipation is acquired. At last, experimental apparent HTC was compared with the computed value to check the heat transfer model. It is shown that it is possible to predict HTC with pure water coolant and full cone sprays for non-boiling spray cooling.
Wheel-Rail Thermal Contact on Rail Corrugation During Wheel Braking
Authors: Chen Yung-Chuan , Kuang Jao-Hwa , Chen Li-Wen , Shin Jiang-Che , Lee Sing-You
Published: April 2008

This paper uses the finite element method to investigate the effect of rail corrugation on the wheel-rail thermal contact pressure and temperature distributions during wheel braking. Contact elements are used to simulate the contact between a wheel and a rail. Various friction coefficients, wavelengths and amplitudes of corrugated rails as well as braking times are considered in this study. The results indicate that, in the wheel-rail contact area, the rail corrugation affects the contact pressure and temperature distributions significantly. A modified equation with time-dependent heat partition factor is proposed to predict the rail surface temperature distribution for rails with smooth surfaces. Simulation results show that the proposed equation works very well. The results also indicate that the corrugated rail can lead to a wavy temperature distribution on the rail surface. Also, a smaller corrugated rail amplitude results in a higher maximum temperature near the trough region and a lower one near the crest region.
Using Bezier-Splines for Design Optimization of CAMS Regarding Valve Train Dynamics
Authors: Scheucher R. , Hellinger W.
Published: April 2008

The aim of this work is the improvement of the cam design for automotive valve trains. A constrained optimization problem is defined, using the control points of the cam profile, which is represented by harmonic splines, as design variables. Additionally to the optimization problem the advantages of the calculation of sensitivity information using direct or adjoint methods are determined. The valve train model is defined by a multi body system containing discontinuities due to the loss of contact between two consecutive components of the valve train. The objective function is to maximize the area below the valve lift, which has a great influence on the gas flow. Constraints for dynamic force, the valve opening and closing phase and the valve lift based on the engine’s thermodynamics considerations are taken into account. Furthermore some constraints for the geometric coordinates of the control points of the cam profile must be imposed.
Estimating the Statistical Distribution of Human Damage Produced by a Fire in a Building Using Bayesian Belief Nets
Authors: Hanea Daniela M. , Ale Ben J. M.
Published: April 2008

The complexity of the cities’ layout and other public spaces, together with the large number of people involved leads to increased strain on the resources of emergency responders. An accident, such as a fire, remains a rare event so it is difficult for those in charge of preparing for an emergency and deciding on the acceptability of risk to get a picture of such an event. The interest of all emergency response agencies is to minimize the impact of disaster events on the entities of interest, which include first of all the human population. For this, there is need for a tool that helps the decision makers estimate the distribution of the fire outcome, given different information about the environment in which the fire takes place. This paper discusses the possibility of using continuous Bayesian belief nets for the study of the factors that influence the risk to which the people involved in a building fire are exposed, and how these factors influence the risk. The big advantage of Bayesian belief net approach is that it can model uncertain events. The distribution of the variables of interest can be easily updated given information about some of the other variables. Moreover, the intuitive visual representation of the problem at hand can help people to understand complex systems or processes, like a fire in a building. In this study, the approach is tested for a small example and the results are analyzed. The possibility of extending this method to a more complex model is discussed.
Semi-Active Vibration Control of Adaptive Structures Using Magnetorheological Dampers
Authors: Dominguez Aurelio , Sedaghati Ramin , Stiharu Ion
Published: April 2008

In this study a new nonlinear hysteresis dynamic model is employed to simulate the hysteresis behavior of a commercial MR damper. The model determines the hysteresis force considering the amplitude, frequency and current excitation as independent variables. Subsequently, based on this model, the finite element formulation of the MR damper is developed and is incorporated into the finite element formulation of the whole space truss structures with embedded MR dampers. A direct integration method with inner iterative algorithm is applied to obtain the solution of the resulting nonlinear system. The experimental study has also been conducted to validate the simulation. For the experimental set-up, a 3-Dimensional space truss structure with 4 bays in which one of the members can be replaced by MR damper has been fabricated. The experimental results have shown a good agreement with the mathematical simulation. It has been demonstrated that the vibration can be efficiently suppressed by the controllable MR dampers.
Non-Nominal Path Planning of Assembly Processes
Authors: Carlson Johan S. , So¨derberg Rikard , Bohlin Robert , Lindkvist Lars , Hermansson Tomas
Published: April 2008

One important aspect in the assembly process design is to assure that there exist a collision-free assembly path for each part and subassembly. In order to reduce the need of physical verification the automotive industry use digital mock-up tool with collision checking for this kind of geometrical assembly analysis. To manually verify assembly feasibility in a digital mock-up tool can be hard and time consuming. Therefore, the recent development of efficient and effective automatic path planning algorithm and tools are highly motivated. However, in real production, all equipment, parts and subassemblies are inflicted by geometrical variation, often resulting in conflicts and on-line adjustments of off-line generated assembly paths. To avoid problems with on-line adjustments, state-of-the-art tools for path-planning can handle tolerances by a general clearance for all geometry. This is a worst-case strategy, not taking account for how part and assembly variation propagates through the positioning systems of the assembly resulting in geometry areas of both high and low degree of variation. Since, this latter approach results in unnecessary design changes or in too tight tolerances we have developed a new algorithm and working procedure enabling and supporting a more cost effective non-nominal path planning process for assembly operations. The basic idea of the paper is to combine state of the art technology within variation simulation and automatic path planning. By integrating variation and tolerance simulation results into the path planning algorithm we can allow the assembly path going closer to areas of low variation, while avoiding areas of high variation. The benefits of the proposed approach are illustrated on an industrial case from the automotive industry.
Thermoelastic Damping in Flexural-Mode Ring Gyroscopes
Authors: Hao Zhili , Ayazi Farrokh
Published: April 2008

This paper provides a comprehensive derivation for thermoelastic damping (TED) in flexural-mode ring gyroscopes, in light of recent efforts to design high rate-resolution gyroscopes. Imposing an upper limit on the attainable mechanical noise floor of a vibratory gyroscope, thermoelastic damping in a ring gyroscope is extracted from the equations of linear thermoelasticity. By assuming that it is small and therefore has negligible effect on the flexural-mode vibrations in a ring, thermoelastic damping manifests itself through temporal attenuation, where a complex frequency is used to quantitatively evaluate this damping. The exact solution to thermoelastic damping is derived and verified with experimental data in the literature. This work not only provides significant insight to the geometrical design in high-Q ring gyroscopes, but also defines their performance limit.
Effect of Processing Parameters on the Conductivity of the Solid Oxide Anode for Fuel Cells
Authors: Rajaram Gukan , Xu Zhigang , Pai Devdas M. , Sankar Jag
Published: April 2008

Good electrical conductivity is highly desirable in Ni / YSZ cermet anodes for solid oxide fuel cells (SOFCs), that operate at temperatures typically around 700 – 900 °C. The conductivity of the cell controls the polarization loss of the cell which affects the overall efficiency of the fuel cell. In the current study, the effect of processing parameters on the conductivity of the anode cermet at room temperature is studied. The cermet is prepared with two different NiO vol. % and also sintered at two different temperatures. Different sintering temperatures lead to different microstructure and overall pore volume. The dependency of the conductivity on the microstructure, pore volume, sintering temperature and also the Ni content in the cermet are analyzed. The current analysis shows that the conductivity of the anode cermet strongly depends on the overall pore volume. Increase in sintering temperature reduces the pore volume and also reduces the active electrical conduction path. Increased density also decreases the active diffusion path which eventually means that there is a reduction in electrochemically active sites. These changes directly affect the efficiency of the cell. The Ni content in the cermet also influences the conductivity. The conductivity of the cermet varies with the Ni volume present in the cermet.
Effects of Dwell-Time and Ramp-Rate on The Thermal-Fatigue Life of SnAgCu Joints
Authors: Dauksher Walter , Lau John
Published: April 2008

Finite element analysis examines lead-free part-on-board accelerated thermal environments comprised of ramp and dwell times lasting between 5 and 15 minutes. The accumulated creep strain energy density is determined for each environment and used to evaluate cost-effective accelerated test environments.
Adaptive Vibration Control of Flexible Structure With Sliding Mode Compensator
Authors: Fei J. , Batur C.
Published: April 2008

This paper presents the adaptive control scheme with sliding mode compensator for vibration control problem in the presence of disturbance. The dynamic model of the flexible cantilever beam using finite element modeling is derived. The adaptive control with sliding mode compensator using output feedback for output tracking is developed to reject the disturbance, and to improve the tracking performance. Satisfactory simulation results verify that the effectiveness of adaptive control scheme with sliding mode compensator.
Measurement of Liquid Layer Thickness Using Ultrasound Technique
Authors: Mundla V. , Kadambi J. R. , Sastry S. , Deng C. , Zhou Y.
Published: April 2008

The use of ultrasound technique to obtain the liquid film thickness was investigated. Ultrasound imaging is a technique that uses high frequency sound waves to produce precise images of structures. Ultrasound imaging is based on the same principle as SONAR (Sound Navigation and Ranging) during which a transducer capable of generating and receiving high frequency sound waves, sends pulses of sound waves into the interrogation area and the sound reflected back (echo) form any interface (such as water air interface) within the interrogation plane is obtained by the transducer. The time taken for the sound wave to travel from the transducer surface to the water air interface is obtained from the delay of the echo signal with regard to the transmitted signal; this time is used to compute the distance of the interface knowing the velocity of sound in medium. An experiment was set up to measure the depth of water in a container using ultrasound technique. A-mode (amplitude-mode) scanning was used where a pulsed ultrasound wave is directed into the interrogation region and echoes generated at various interfaces are detected. It is observed that levels as low as 0.55 mm were measured.
Sveltness, Freedom to Morph, and the Constructal Design of Multi-Scale Flow Structures
Authors: Lorente S. , Bejan A.
Published: April 2008

This paper reviews recent progress on constructal theory and design. The emphasis is on the development of multi-scale, nonuniformly distributed flow structures that offer increased compactness (e.g., heat transfer density). Examples are counterflow heat exchangers with tree-shaped hot and cold streams, and tree architectures on a disc. Every flow system has a global property called sveltness (Sv), which is the ratio between its external (global) length scale and its internal length scale (V1/3), where V is the volume occupied by all the ducts. Emphasis is placed on the development of simple strategies for decreasing the computational cost required by the development of such structures. The generation of multi-scale flow configurations is a process that can be projected on a diagram having global performance on the abscissa and degrees of freedom on the ordinate. This process rules the development (evolution) of all flow configurations for systems with global objective, global constraints and freedom to morph.