bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Retention of LOX in an Off-Axis Accelerating Environment
Authors: Simmons B. D. , Hochstein J. I. , Marchetta J. G. , Collicott S. H.
Published: April 2008

Magnetic positive propellant positioning (MP3) of cryogenic propellants in spacecraft tanks may outperform existing technologies and, unlike some of the competing technologies, MP3 can be an adaptive management system that optimizes performance for the entire mission profile. Surface Evolver, (SE), a public domain program that seeks minimum energy configurations for modeled systems, provided a foundation on which to build a computational simulation to begin investigating the promise of MP3. Energies modeled include surface tension, potential energy due to background acceleration, and the change in potential energy due to the presence of a fluid in a magnetic field. A detailed development of these models is presented as well as specific expressions that other researchers can use with SE to study MP3. Verification and validation of the comprehensive model has been performed using several “known” solutions, three of which are reported herein: a constant gradient, a current carrying wire, and a dipole magnetic field. The computational tool is then used to study the ability of a magnet to retain a pool of LO2 about it when subjected to background acceleration. Results from this study, presented herein, indicate the promise of MP3 for adaptive cryogenic propellant management systems for future spacecraft and fuel depot applications.
Modeling and Controller Tuning Techniques for Feed Drive Systems
Authors: Sato Ryuta , Tsutsumi Masaomi
Published: April 2008

In this paper, a new modeling, and controller tuning method for feed drive systems is described. Typical feed drive systems consist of an AC servo motor, a ball screw, linear guides, and a servo controller. In order to design high performance systems, it is effective to make a model and analyze its behavior. In this study, a feed drive system is modeled by a vibration model with two degrees of freedom. Various kinds of motions are measured and simulated. The results of the experiment and simulation show that these motions are well simulated by the model. This means that the proposed model can accurately estimate the transfer function of the actual system. As a result, it is easy to design a controller based on the transfer function. The gains in the velocity control loop are calculated based on the partial model-matching method. Two PI and I-P velocity controllers are applied to the feed drive system. The step responses are then compared to each other. The position loop gain is calculated from the frequency response of the velocity control system. The proposed method is applied to an actual feed drive system, and it is confirmed that the proposed method yields comparable performance to the system designed by the conventional tuning way.
A Thermo-Fluid/Electrochemical Model for Micro-SOFC
Authors: Ji Yan , Chung J. N. , Yuan Kun
Published: April 2008

In this paper, a three dimensional thermo-fluid/electro-chemical model is proposed to simulate the heat and mass transfer phenomena in a micro-geometry co-flow solid oxide fuel cell. Governing equation of mass, momentum and energy conservation are simultaneously solved. A network circuit is applied to simulate the electrical potential, ohmic losses and activation polarization. Cyclic boundary conditions are imposed at the top and bottom of the model domains, while the lateral walls were assumed adiabatic and insulation. A parametric study examines the effect of micro-channel on the temperature field, concentration field, local current density and power density. Results demonstrate that microchannels can reduce temperature or concentration difference between reaction locations and stream. The local current density is much more uniform and output voltage is also improved. Numerical simulation will be expected to help optimize the design of a micro solid oxide fuel cell.
Cryogenic Two-Phase Flow and Heat Transfer Under Terrestrial and Microgravity
Authors: Yuan Kun , Chung J. N. , Ji Yan
Published: April 2008

This paper presents experimental investigations of cryogenic nitrogen two-phase flow in horizontal transparent tubes (diameters of 11.1mm) under terrestrial and micro-gravity (10−4g) conditions during the chilldown process, and the focus is on the film boiling region. Constant mass flow rate is achieved by a motor driven bellows, and three different mass fluxes from 9.2 to 27.6kg/m2 · s are tested in the experiments. A drop tower is applied to simulate the micro-gravity environment. During the chilldown process, we measure the time-dependent temperatures at three circumferential locations at different downstream locations. Video images are recorded for identifying the flow patterns. The experiments show that under normal gravity, the flow pattern change from dispersed flow to inverted annular flow and then to unsteady stratified flow according to different wall temperatures, the temperature differences between the lower and upper part of the test section increase with increasing flow rate. Under microgravity, when the temperature is high, the liquid chunks trend to be lifted up and confined mainly in the central core of the tube; when the temperature is low, the liquid chunks are more evenly dispersed inside the whole tube, and some touch the upper wall. It is also found that the measured wall temperatures drop more quickly under microgravity condition compared with that under normal gravity. Moreover, under microgravity condition, the measured temperatures drop more quickly with lower wall temperature. The gravity effect on the quenching curves is alleviated with increasing mass flow rate. Thus gravity effect is more important in low mass flow rate two-phase flow.
Modeling and Vibration Analysis of Vibrating Beam Microgyroscopes Under Longitudinal Rotation of the Support
Authors: Esmaeili Mehdi , Durali Mohammad , Jalili Nader
Published: April 2008

This paper discusses the effects of substrate motions on the performance of a microgyroscope modeled as a suspended beam with a tip mass. These motions can be either along or around the three axes. Using the Extended Hamilton’s Principle, the equations of motion are derived. In these equations, the effects of beam distributed mass, tip mass, angular accelerations, centripetal and coriolis accelerations are well apparent. The effect of electrostatic forces inducing the excitation vibrations are considered as linear functions of beam displacement. The response of the system to different inputs is studied and the system sensitivity to input parameter changes are examined. Finally, the sources of error in the measurement of input rotational rate are investigated and identified. The study demonstrates the importance of errors caused by cross axes inputs on the gyroscope output measurements.
Characterization of Low-K Dielectrics Sol-Gel Coating by Spectroscopy Ellipsometry
Authors: Xie H. , Wei J.
Published: April 2008

Porous silicate based sol-gel coatings are promising candidate for low-K dielectric materials for ultra large-scale integrated circuits (ULSIs). To optimize the sol-gel coating process to meet the increasingly stringent requirements in performance and reliability, it is critical to explore advanced analytical tools and techniques to characterize and monitor the coating structure and properties. Spectroscopic ellipsometry, a non-invasive optical technique for determining optical properties and coating thickness, can provide insight into coating structure and properties. In this paper, we determined the refractive index, optical dielectric constant and porosity of sol-gel coatings using ellipsometry with the hypothesis of considering the coating as the mixture of matrix material with void. Models including linear calculation and effective medium approximation (EMA) were employed in ellipsometric data analyses. The ambiguity was effectively reduced for the analyses with EMA model by including the intensity of reflectance of coating in the analyses. This can greatly improve the applicability of the analyses of ellipsometry for porous coatings.
Energy Loss and Entropy Generation Analysis in Fundamental Convective Heat Transfer Problems
Authors: Javadinejhad S. R.
Published: April 2008

Energy loss characteristics of heat transfer and fluid flow due to forced convection of steady laminar flow of incompressible fluid inside channel with circular cross section and channel made of two parallel plates is analyzed. Energy loss profiles and heat transfer characteristics for different problems have been discussed. In each case energy loss due to heat transfer effect and fluid friction have been drived analytically. For energy loss calculations a new dimensionless number have been introduced that is the energy loss to total heat transfer rate ratio. The energy loss dimensionless number behavior have been compared with entropy generation dimensionless number behavior for various problems.
Numerical Analysis of Powder Forging Under Various Initial Density Distributions and Friction Conditions
Authors: Asawapishayachote T. , Carmai J. , Manonukul A.
Published: April 2008

Finite element models have been developed to simulate forging of sintered porous powder metal. The deformation behaviour of the porous preform during hot forging has been described by the Duva and Crow porous material constitutive model. It has been implemented into general purpose nonlinear finite element software within a large deformation formulation. Most of the previous finite element analyses of the deformation of this porous preform always assume an initial homogeneous density distribution within the compacted porous preform. However, the compacted parts obtained after compaction and sintering usually possess inhomogeneous density distribution. The present finite element models therefore take into account the initial distribution of relative density within the preform. The simulations have been conducted for various initial density distributions and under various frictional conditions in order to investigate the deformation characteristics and the evolution of voids in the forging process.
A Design Modification of the Delivery Valve and the Constant Pressure Valve in a Medium Speed Diesel Engine Fuel Injection System for the Prevention of Cavitation Damage and Secondary Injection
Authors: Kim Dong-Hun , Kim Hong-Won , Ghal Sang-Hak , Ha Ji-Soo
Published: April 2008

A fuel injection with high pressure in a medium speed diesel engine would increase the possibility of cavitation damage in the fuel injection system or secondary injection to the combustion chamber. The purpose of this study is to prevent cavitation and secondary injection in a medium speed diesel engine by modifying the design of the delivery valve and the constant pressure valve in a fuel injection system. Three-dimensional flow analyses for the fuel injection nozzle, delivery valve, constant pressure valve and spill port were performed using FLUENT S/W to calculate loss coefficients of them. Simulation of fuel injection system with loss coefficients from results of three-dimensional flow analyses were performed using FLOWMASTER2 S/W and the simulation results were compared with the experimental data. The delivery valve and constant pressure valve were modified to prevent cavitation and secondary injection and proved in the field test.
Stress Analysis and the Characteristics of T-Shape Bolted Joints Under Tensile Loadings
Authors: Sawa Toshiyuki , Hamamoto Seiichi
Published: April 2008

In designing a bolted joint, it is important to examine the interface stress distribution (clamping effect) and to estimate the load factor, that is the ratio of an additional axial bolt force to a load. In order to improve the clamping effect raised faces of the interface have been used. But these interfaces in bolted joints have been designed empirically and the theoretical grounds are not made clear. In the present paper, in the case of T-shaped flanges with raised faces the clamping effect is analyzed by a two-dimensional theory of elasticity and the point matching method. Then, the load factor is analyzed. Moreover, with the application of the load a bending moment is occurred in bolts and the stress is added due to this bending moment. The bending moment in the bolt is also analyzed. In order to verify these analyses experiments to measure the load factor and the maximum bolt stress were carried out. The values of the load factor and the load when interface start to separate are compared with those of the joints with flat-faces. The analytical results are in fairly good agreements with the experimental ones.
Casting Defects Analysis Making the Best Use of High-Energy X-Ray CT
Authors: Numata Shouhei , Yashiki Tatsurou , Sadaoka Noriyuki
Published: April 2008

A novel method of analyzing casting defects such as shrinkage cavities by utilizing high-energy x-ray computed tomography (CT) has been developed. The method was realized as the module of three-dimensional (3-D) bitmap CAD software StereoCooker for utilizing x-ray CT images. The cavity measurement method was based on the defocusing feature of an x-ray CT image. The authors assumed the defocusing to Gaussian, and therefore the diameter of the cavity could be calculated from the summation of the voxel value profile of the cavity and the circumference. The Gaussian defocusing hypothesis was confirmed by the CT reconstruction simulation with an accuracy higher than 10% for the conditions of the actual x-ray CT apparatus. The cavity measurement method was verified by applying it to cavity test pieces. The test pieces had cavity diameters of 0.5, 0.6, 0.7, 0.8 and 1.0mm. Using the rotate-only mode of the 6MeV x-ray CT, cavities of 0.6mm or greater in diameter could be detected. The accuracy of the cavity size is higher than 0.1mm for diameters of 0.7mm and greater. The verification of simulation by a comparison of the defects predicted by a simulation and those measured by this method has been proposed.
Modeling and Simulation of Residual Stresses in Mechanical Autofrettage
Authors: Malik M. Afzaal , Rashid Badar , Khan Muddasar , Khushnood Shahab
Published: April 2008

The autofrettage process is used to induce advantageous residual hoop stresses into pressure vessels to enhance their fatigue lifetime. Such pre-stressed pressure vessels are routinely used in power, nuclear, process, armament, and food industries. The autofrettage process can be accomplished by applying hydraulic or mechanical pressure or by the pressure of powder gas to the bore of a thick cylinder to induce residual stresses. The two processes are referred to as hydraulic and mechanical autofrettage respectively. The objective of this research is to analyze mechanical or swage autofrettage, which is achieved by ramming an oversized conical mandrel into the bore, thus driving it into the plastic regime. When the mandrel is removed, the outer elastic portion compresses onto the inner plastic regime, thus causing compressive residual stresses. The percentage of material that undergoes plastic deformation determines the level of autofrettage. A computer code based on finite element method is developed to analyze residual stresses including Bauschinger effect duly incorporating failure criteria such as von Mises and Tresca conditions. The computer code developed is benchmarked using analytical solutions based on Lame’s equations. Using this code, parametric studies are carried out to optimize the depth of penetration of the plastic regime into the material thickness of the bore. The results based on modeling and simulations are validated by using other available computer codes and experimental data.
On-Chip Microdialysis System With In-Line Sensing Capabilities
Authors: Hsieh Yi-Cheng , Zahn Jeffrey D.
Published: April 2008

Microdialysis probes have been used for diabetes treatment as continuous monitoring system coupled to a glucose sensor. An on-chip microdialysis system with in-line sensing electrodes is demonstrated. The response time of the microdialysis system was characterized and the permeability of the polycarbonate membrane (100nm pore size) to glucose was determined to be 2.53 μm/s (std:0.372 μm/s). As a first step towards greater biosensor integration with this miniaturized microdialysis system, a stacked system with in-line sensing electrodes was developed. Impedance electrodes within the microchannels were used to determine fluid resistance from a dialyzed phosphate buffered saline (PBS) solution, which characterizes solution conductivity as a function of PBS concentration. The permeability of the membrane to the salt ions was obtained as 0.74 μm/s (15 nm pores). Subsequently, experiments measuring PBS dialysis in the time-domain at 60% recovery were conducted. The PBS concentration of the reservoir was changed in either a step response or sinusoidally with an 800 second period. The subsequently measured impedance indicates that the system is able to continuously track concentration changes in the reservoir with a 180 second system response delay. Most of this delay is due to the dead volume within the tubing between the syringe pumps and the microsystem In addition the predicted response was modeled using linear systems theory and matches the experimental measurements. This system is expected to have the proper sensitivity to track physiologically relevant concentration changes of biomolecules such as glucose (which has a physiological maximum change rate of ~4mg/dL-min with a periodicity of 1 hour or greater) with minimal lag time and amplitude reduction.
Effects of Pre-Pressurization on Damage of Blast-Loaded Reinforced Plates
Authors: Veldman R. L. , Ari-Gur J. , Clum C.
Published: April 2008

The effects of pre-pressurization on blast-loaded reinforced rectangular aluminum plates were studied experimentally. In this study, small (0.508 × 0.609 × 0.0016 meter) clamped plates with rivet attached reinforcing members were used as a basic model of the fuselage skin of a commercial aircraft. Both non-pressurized and pre-pressurized plates (static pressure of 41.4 kPa (6.0 psi)) were considered to simulate the typical in-flight loads experienced by a commercial aircraft due to cabin pressurization. This work extends previous research on blast loading of pre-pressurized plates to incorporate the effects of reinforcing members [1]. An experimental configuration was designed using a vacuum vessel system to apply a pressure differential to the reinforced test plate. Bare spherical explosive charges of C4 were then detonated at fixed distances from the plate. The permanent plate deformations or the amount of tearing in the plates were measured for seventeen explosive tests that considered two different blast load intensities. Additionally, a high-speed camera was used to determine the mechanism and time scale of failure propagation in the reinforced panels. The high speed camera was used found to be an excellent tool to record the failure progression in the reinforced panels under blast loading. In general, commencing with the onset of panel deformation, the blast-loaded panels exhibited rivet failure in less than 0.5 milliseconds, initiation of plate tearing in less than 1.0 millisecond, and completion of plate tearing by about 10.0 milliseconds. A comparison of plate deformations and damage showed two distinct results. For the least intense blast load case, both the non-pressurized and pressurized panels deformed but did not tear. In this case, very little effect of pre-pressurization on final panel deformation was noted. For the more intense blast load case, a significant increase in panel damage was observed as static pre-pressurization increased from 0.0 kPa to 41.4 kPa.
Mechanistic Modeling of Process Damping in Peripheral Milling
Authors: Huang C. Y. , Wang J.-J. Junz
Published: April 2008

This paper extends analytical modeling of the milling process to include process damping effects. Two cutting mechanisms (shearing and plowing mechanisms) and two process damping effects (directional and magnitude effects) are included. The directional effect is related to vibration energy dissipation due to directional variation of cutter/workpiece relative motion. The magnitude effect is associated with change in force magnitude due to variation of rake angle and clearance angle. Process damping is summarized as containing these separate components; direction-shearing, direction-plowing, magnitude-shearing and magnitude-plowing. The total force model including the process damping effect is obtained through convolution integration of the local forces. The analytical nature of this model makes it possible to determine unknown process damping coefficients from measured vibration signal during milling. The effects of cutting conditions (cutting speed, feed, axial and radial depths of cut) on process damping are systematically examined. It is shown that total process damping increases with increasing feed, axial and radial depths of cut, but decreases with increasing cutting velocity. Predictions based on the analytical model are verified by experiment. Results show that plowing mechanism contributes more to the total damping effect than the shearing mechanism, and magnitude-plowing effect has by far the greatest influence on total damping.
3-E Analysis of a Heat Pump Driven by a Micro-Cogenerator
Authors: Sasso Maurizio , Possidente Raffaello , Roselli Carlo , Sergio Sibilio
Published: April 2008

The cogeneration, or the combined production of electric (and/or mechanical) and thermal energy, is a well established technology, which has important environmental benefits and it has been noted by the European Community as one of the first elements to save primary energy, to avoid network losses and to reduce the greenhouse gas emissions. In particular, the study will be focused on the micro-cogeneration process with micro-combined heat and power system, or MCHP (electric power output ≤ 15 kW), which represents a valid and interesting application of this technology applicable, above all, to residential and light commercial users. This paper presents the Energy, Economic and Environmental (3-E) analysis of a natural gas-fired MCHP in combination with an electric heat pump (EHP). The 3-E analysis of the MCHP/EHP begins with the results of a detailed experimental activity developed in a test facility [1] for a wide range of conditions. Two operating conditions were simulated: a heating mode with co-production of electric and thermal energy, and a cooling mode with co-production of electric, thermal and cooling energy (tri-generation). The annual operating performance, also based on the typical features of the Italian market, is also discussed with a simplified approach.
Fully-Coupled Modeling of Composite Piezoelectric Plates
Authors: Yu Wenbin , Liao Lin
Published: April 2008

A fully coupled model considering both sensing and actuation for composite plates with embedded piezoelectrics is constructed using the variational asymptotic method. Without invoking any ad hoc kinematic assumptions, we take advantage of the geometric small parameter inherent in the structure to mathematically split the original three-dimensional, geometrically nonlinear, piezoelectricity problem into: a coupled, linear, one-dimensional piezoelectric through-the-thickness analysis and a coupled, geometrically nonlinear, two-dimensional piezoelectric plate analysis. Two asymptotically correct models of multi-layer plates are developed for two different types of electrode arrangements. The constructed models are of the form of classical plate theory having a layerwise displacement and electric potential distribution. The present theory is implemented using the finite element method into the computer program VAPAS (variational-asymptotic plate and shell analysis). Simple examples are used to demonstrate the application of the present theory.
A Dual-EDM Reverse Damascene Process for RF Switches and Other Bulk Metal Devices
Authors: Udeshi K. , Richardson M. , Hung J.-J. , Que L. , Rebeiz G. M. , Gianchandani Y. B.
Published: April 2008

This paper reports a manufacturing process suitable for lithography-compatible fabrication of suspended micro-structures from any conductive material (including bulk metal) that is available in sheet form. It uses two aligned steps of batch mode micro-electro-discharge machining followed by a series of filling and lapping steps similar to a damascene process. The process is demonstrated by the fabrication of a bi-stable RF switch from #302 stainless steel foil. The fabricated devices have a footprint of 5 × 5 mm2, with 25 μm thickness, and a minimum feature size of 5 μm.
Stiffness Controlled Piezoelectric Stick-Slip Actuator for Rapid Positioning Applications
Authors: Headings Leon M. , Washington Gregory N.
Published: April 2008

Rotary screw-type stick-slip actuators driven by smart materials offer the attractive characteristics of large stroke, fine resolution, high power-off holding force, and relative simplicity to manufacture. However, the actuation speed of current rotary stick-slip actuators limits their applications. The research presented in this study focuses on rapid positioning applications and involves the development of two mechanism designs. Both designs utilize piezoelectric stacks driven by sawtooth waves to provide stick-slip contact between two partially threaded jaws and a 1/4-80 screw. The first mechanism design utilizes two piezoelectric stacks in a push-pull configuration. The motion of the two stacks is coupled through a lever amplification mechanism. The second design uses a single stack to directly drive the jaws without amplification. However, a second stack is oriented perpendicular to the first stack and driven with a triggered square wave. This stack varies the normal and thus frictional force between the jaws and screw, permitting more efficient slipping and sticking of the actuator. This allows for potential increases in both output speed and force. Existing actuators were modeled using both theoretical and finite element analysis techniques. These results were compared with experimental data to validate the models.
Numerical Modeling of Boiling Heat Transfer in Microchannels
Authors: Sarangi R. K. , Bhattacharya A. , Prasher R. S. , Narasimhan S.
Published: April 2008

In this paper we report the results of our modeling studies on two-phase forced convection in microchannels using water as the fluid medium. The study incorporates the effects of fluid flow rate, power input and channel geometry on the flow resistance and heat transfer from these microchannels. Two separate numerical models have been developed assuming homogeneous and annular flow boiling. Traditional assumptions like negligible single-phase pressure drop or fixed inlet pressure have been relaxed in the models making analysis more complex. The governing equations have been solved from the grass-root level to predict the boiling front, pressure drop and thermal resistance as functions of exit pressure and heat input. The results of both the models are compared to each other and with available experimental data. It is seen that the annular flow model typically predicts higher pressure drop compared to the homogeneous model. Finally, the model has also been extended to study the effects of nonuniform heat input along the flow direction. The results show that the nonuniform power map can have a very strong effect on the overall fluid dynamics and heat transfer.
A Singular Value Decomposition Approach to Servo Systems Diagnosis of CNC Machine Tools
Authors: Xu Zhixiang , Green Tim , Liu Jian
Published: April 2008

Based on the Singular Value Decomposition (SVD) of time series, this contribution addresses an innovative approach to provide essential information about the condition of servo systems for servo fault location or servo parameters tuning during diagnosing and calibrating CNC machine tools. When carrying out circular interpolation, the displacements of two involved axes are sampled as two independent time series. We adopt SVD algorithm to process the sampled data. A special matrix called attractor is constructed. By applying the Singular Value Ratio (SVR) spectrum, we have proposed the similarity ratio and then the similarity of two series is compared. The similarity ratio reflects the degree of mismatch between the coordinated axes.
A Comparison of Finite Element Beam Formulations for Thermoelastic Behavior of Functionally Graded Structures
Authors: Eason Thomas G. , Caraballo Simo´n A.
Published: April 2008

Modeling at the structural scale most often requires the use of beam and shell elements. This paper compares two finite element formulations based on first-order shear deformation theory undergoing thermo-mechanical loading. One formulation is a two node beam element employing static condensation based on the work of Chakraborty et al. The second formulation follows a more traditional route using FSOD theory for a three node beam element. Both formulations are used to investigate the behavior of a functionally graded beam under axial and through-the-thickness temperature gradients. Both formulations work well for a constant uniform mechanical or temperature loading. However, for beam structures containing a thermal gradient in the axial direction, the two node beam element performs poorly as compared to the three node element in terms of transverse shearing stress calculated from the equilibrium equation.
Robot Localization Using Fuzzy Logic
Authors: Dharne Avinash G. , Jayasuriya Suhada
Published: April 2008

Robot Localization is an issue of vital importance for the functioning of autonomous mobile robots. Location information, allows a robot to navigate complex environments and perform local tasks successfully. In mobile sensor networks, this information facilitates important functions like topology control, collision avoidance and development and security of routing protocols. This issue can be divided into the problems of global position estimation, and once that is achieved, of local position tracking. To tackle these, two distinct methods have been used in the past. One is the use of specialized hardware and another is the use of probabilistic Bayesian estimation methods. This paper proposes the use of Fuzzy Logic to tackle this problem. Fuzzy Logic allows us to do away with strict probabilistic rules and to set up heuristic fuzzy rules. It also reduces computation time. A grid-based map is used to describe the environment of the robot and the robot’s confidence in it’s position at each grid-point is determined using sensor measurements. In case the robot is receiving information from multiple sensors, this paper demonstrates the robustness of the scheme to inaccurate sensor information or robot confidence within practical limits. This paper also applies the fuzzy rules to track the robot’s position as it moves. In order to reduce computational cost, this paper proposes limiting the computation of confidences to significant grid-points only.
Modeling Closed Kinematic Chains for Control: A Comparative Study
Authors: Wang Zhiyong , Ghorbel Fathi H.
Published: April 2008

In this paper, we compare our recently developed modeling method for closed kinematic chains (CKC), namely the singular perturbation formulation (SPF), to the singularly perturbed sliding manifold (SPSM) method from the literature. We show the advantages and disadvantages of each method from a theoretical as well as a implementation standpoint. The comparison indicates that for model-based control of CKCs, our SPF approach naturally lends itself to control design, and for simulation, our SPF approach is computationally more efficient. A common drawback of both the SPF approach and the SPSM method is that they cannot handle singularities.
Low Cycle Fatigue of Single Crystal Nickel-Base Superalloy CMSX-4 Coated With a New Coating IC1
Authors: Stekovic Svjetlana
Published: April 2008

High strength nickel base superalloys have often been used in turbine blades because of their superior performances at high temperatures. One of them is CMSX-4, an ultra high strength, single crystal. CMSX-4 is a second generation rhenium-containing, nickel-base superalloy capable of high temperature and stress operations of at least 1150 °C [1]. The superalloy has limited oxidation and corrosion resistance at the high temperatures and to improve the oxidation and corrosion resistance, the base material is protected with coatings [2]. However, coatings exhibit a ductile-to-brittle transition temperature (DBTT) which causes early cracking of the coating and failure due to fatigue. The paper details low cycle fatigue (LCF) properties and degradation mechanisms of uncoated and IC1 coated single crystal CMSX-4. The tests were performed at two temperatures, 500 °C and 900 °C. Cylindrical solid specimens were cyclically deformed with fully reversed tension-compression loading with total strain amplitude control and at a constant strain rate of 10−4s−5 in air atmosphere without any dwell time. At 500 °C the coating has a detrimental effect on the fatigue life of CMSX-4 while at 900 °C IC1 does improve the fatigue life of the superalloy. The reduction of the fatigue life can be related to early cracking of the coating under its ductile to brittle transition temperature while the beneficial effect of the coating at 900 °C may be due to slower propagation of cracks caused by oxidation at the front of the crack tip.
Model-Based Coordination of Autonomous Vehicle Teams
Authors: Czichon Cary , Peterson Robert W. , Mettala Erik , Speer Jerry , Stahl Jeff
Published: April 2008

In order to coordinate autonomous robotic vehicle teams as they perform tactical tasks, a task formalism incorporating graphical (but mathematically rigorous) process models is being used. This extendable formalism, associated modeling methodology, and integrated modeling and execution environment are being developed by a U.S. Army funded SBIR project (RDECOM Contract N61339-04-C-0005). Colored Petri Nets (CPNs) provide the mathematical rigor needed for task and composite (ensemble) behavior modeling, while being conceptually elegant and easily displayed. Higher level task models can contain more fundamental models, allowing hierarchical model composition. Typed places within CPNs can hold tokens representing robotic equipment performing specific roles in a mission comprised of one or more tactical tasks. Army Tactical Tasks (ARTs) are defined within the Army Universal Task List (AUTL), FM 7-15. CPN mechanics support task synchronization and process simulation. CPN-based models can be enhanced to incorporate adaptive reasoning and dynamic/summative evaluation capabilities. In this SBIR project, executable task models are encapsulated by task agents operating within agent clusters. These clusters control virtual robotic vehicles (existing within constructive simulators like OneSAF) while multi-stage tactical missions are being performed.
Progressive Filtration of the Induced Effects in Thermoeconomic Diagnosis of Energy Systems
Authors: Verda V. , Borchiellini R.
Published: April 2008

In this paper, the thermoeconomic diagnosis of an energy system is discussed. Several important contributions that make the diagnosis more reliable and practical are introduced. This is obtained through an initial filtration of the effects caused by the dependence of the efficiencies of components on their operating condition. With respect to some previously proposed approaches, simple models are used to achieve this objective. These models are productive models, relating resources and products through linear functions. The drawbacks associated with the use of these simple models are overcome through the use of a technique called the anamnesis, which is the analysis of the case history of a system. A second contribution introduced in this paper is constituted by the analysis of four significant cases of anomalies that can occur in a heat recovery steam generator. Two of them have been obtained by simulating the presence of a single anomaly, each time in a different component. In the other cases, two anomalies have been produced at the same time in two different components. The operating conditions have been obtained by using a simulator, but the effects caused by errors in measurements are taken into account. An analysis has been also performed in order to present the advantages connected with the use of simple productive models, instead of physical models, when measured data are processed.
Reducing Barriers to Interdisciplinary Design Teams
Authors: Hight Tim , Kitts Chris
Published: April 2008

The proportion of Santa Clara University School of Engineering interdisciplinary senior design teams has been rising over the last five years. While many of those teams have been very successful, there has been a significant overhead price paid by the team members who chose to tackle these projects. Since the spring of 2004, an interdisciplinary team of faculty at SCU has been working to reduce the obstacles that have hindered interdisciplinary design teams in the past. Each department had independently developed its own processes and time schedule over the years, and the variations inherent in these separate programs had created some significant difficulties for the students trying to satisfy incongruent requirements. Recent advances have focused primarily on three departments: Mechanical, Electrical, and Computer Engineering. Curricular changes across departments include a number of innovations ranging from aligning schedules and deliverables to introducing joint team-building activities. A short history of the development of each department’s approach will be presented, followed by the current, more integral, plan and the issues that have arisen in its implementation. Many of the changes that have been made are closely tied to ABET-related continuous improvement efforts. A strong commitment to enhancing interdisciplinary design team experiences has been a core tenet of the involved departments. Lessons learned and successes will be discussed as well.
Active Sound Transmission Control for Windows Using Cabon Nanotube Based Transparent Thin Film Speakers
Authors: Yu X. , Rajamani R. , Stelson K. A. , Cui T.
Published: April 2008

This paper explores the development of active sound transmission control systems for windows using transparent thin film speakers. A unique transparent thin film speaker consisting of a piezoelectric PVDF thin film coated with compliant carbon nanotube (CNT) based transparent conductors is developed. Acid treatment for single-walled carbon nantotubes (SWNTs) and layer-by-layer (LBL) nanoassembly based surface modification of the substrates are used to obtain highly transparent and conductive CNT thin films on both sides of a PVDF film. The developed thin film speaker shows good acoustic response over a broadband frequency range, and has the advantages of being flexible, transparent, and lightweight. Experimental results are presented showing that over 10 dB reduction in sound transmission is achieved globally. The transparent thin film actuators can thus be effectively used as actuators for active sound transmission control systems for windows.
Modeling and Characterization of Dielectrophoretic Assembly Process for Nanobelts
Authors: Hesketh Peter J. , Gallivan Martha A. , Kumar Surajit , Erdy Christine J. , Wang Zhong L.
Published: April 2008

Robust manufacturing methods are needed for nanocomponent assembly, and one must understand the physics to optimize the processing and to develop control schemes to deal with the inherent uncertainty. We are studying field induced assembly of a new class of semiconducting metal oxides — nanobelts — that have been demonstrated for chemical sensing. We have demonstrated the integration of nanobelts with electrodes to make sensors by dielectrophoresis (DEP). The SnO2 nanobelts (width ~ 100–300 nm, thickness ~ 30–40 nm) were suspended in ethanol and introduced into a microchannel, and were assembled across the electrodes. Modeling suggests that attraction should occur at all frequencies over this range. Targeted experiments were performed to quantify surface and material properties for input to the modeling, and FEMLAB simulations were performed to validate the model. The goal of the modeling is to optimize the assembly of nanostructures in a manufacturing process at the wafer-scale.
High Flow Rate Per Power Pumping of Aqueous Solutions and Organic Solvents With Electroosmotic Pumps
Authors: Kim Daejoong , Posner Jonathan D. , Santiago Juan G.
Published: April 2008

We present experimental investigations of porous glass electroosmotic pumping of various low conductivity solutions. We evaluate pump pressure, flow rate, and current for sodium borate buffer, deionized water, deuterium oxide, methanol, and acetone. We present data for several figures of merit associated with steady state pumping, and present selected transient data measurements.
Bouyancy-Induced Convective Heat Transfer in Cylindrical Transformers Filled With Mineral Oil With Nano-Suspensions
Authors: Walker D. G. , Davidson J. L. , Taylor P. G. , Soh K. L. , Rogers Bruce
Published: April 2008

The heat transfer characteristics of a transformer using both standard mineral oil and nanodiamond oil was investigated numerically and compared to experimental measurements. The results of the model agree well with the standard oil measurements and with theoretical convective flows from the literature. However, the simulations could not predict the magnitude of the temperature variation in the nanodiamond oil, although the appropriate trend was observed. Because properties of the nanodiamond transformer oil are not well known, good agreement is not expected. Nevertheless, nanodiamond in transformer oil shows enhanced heat transfer performance over standard transformer oil.
Towards the Development of a Methodology for the Optimization of the Metal Cutting Process in Multiedge Tools From Data Collected With Single Edge Tools
Authors: Acosta V. A. , Miranda J. C.
Published: April 2008

Metal cutting processes constitute one of the more common processes in manufacturing. This is due to its versatility in obtaining different geometries and for the dimensional precision obtained in comparison with other processes. In order to optimize these processes it is necessary to understand the behavior of all involved variables which usually require running a large number of experiments for any specific pair of tool-workpiece that is evaluated. Even when several studies are available to optimize metal cutting processes, many of them are restricted to single edge tooling processes since proper experimentation in processes like milling which involve multi-edge tooling is difficult to carry out. In this sense, it becomes convenient to develop strategies that allow an engineer to optimize milling processes for a specific pair of tool-workpiece using data obtained from turning using a similar pair. In this work, the first steps followed in the development of a methodology capable of establishing optimal cutting parameters for milling from data obtained from turning is presented were relevant variables and relations between both processes are identified and evaluated.
A Numerical Approach of Assessing Fluid Oscillatory Motions in 3D Partially Filled Horizontal Cylindrical Tanks
Authors: Xu Liang , Dai Liming
Published: April 2008

The longitudinal liquid dynamics in partially filled horizontal cylindrical tanks is studied on the basis of a fully 3D mathematical approach. Governing equations based on the potential flow theory for liquid in tanks are solved to obtain natural frequencies and transient liquid motion. The governing equations are transformed by continuous coordinate mappings to perform the discretization in the computational domain for overcoming the difficulties in dealing with the boundary conditions at the curved walls and the free surface. The natural frequencies of liquid sloshing in partially filled tanks are determined by solving the generalized eigenvalue problem of liquid under different fill levels and for different tank configurations. The efficiency of the method is presented by comparing with the frequency results reported in other publications.
A Web-Based Approach to Real-Time Machine Condition Monitoring and Control
Authors: Wang Lihui , Shen Weiming
Published: April 2008

The objective of this research is to develop a web-based approach to remote machine condition monitoring and control enabled by Java technologies and based on publish-subscribe design pattern. On top of a Wise-ShopFloor framework (Web-based integrated sensor-driven e-ShopFloor), this system can serve real-time data from bottom up and can function as a constituent component of e-manufacturing, particularly for web-based collaborative manufacturing. It is designed to use the popular client-server architecture, VCM (view-control-model) design pattern, and publish-subscribe design pattern for secure device control and efficient machine condition monitoring. This paper presents the basis of the developed technology for building a web-based monitoring and control system that can be easily integrated to the e-manufacturing paradigm. A case study of a tripod parallel kinematic machine is carried out to demonstrate the effectiveness and validate our approach to web-based real-time machine condition monitoring and remote control for collaborative manufacturing.
Multi-Objective Optimization of Tip Tracking Control Using LMI
Authors: Xie Bo , Yao Bin
Published: April 2008

This paper presented multi-objective optimization of tip tracking control for non-collocated flexible beam. The desired trajectory is specified at the tip displacement of the flexible structure, which undergoes translation base motion actuated by a linear motor. The system model is first formulated from modal truncation approach for the flexible structure representing a single Cartesian robot manipulator. The linear system model of the flexible structure always has structural uncertainties. Robust stability and robust performance on tip tracking can be expressed as H2/H∞ norm constraints, which are converted into the Linear Matrix Inequality (LMI). The multi-objective controller design is solved by the convex minimization. In order to reduce the conservatism generated when the same Lyapunov matrix is selected, the Lyapunov matrix is scaled for different norm constraints. Simulation results have demonstrated favorable tip tracking of the proposed robust controller.
Planar, Large Excursion Bond Graph Model for Full Suspension Mountain Biking
Authors: Redfield Robin C.
Published: April 2008

A bond graph model of a fully suspended mountain bike and non-seated rider is created to develop predictions for the performance of mountain bikes during large excursion maneuvers such as drops, jumps, crashes, and rough terrain riding. The model assumes planar dynamics, a single pivot full suspension bicycle, and a rigid-body rider suspended from the bicycle. The main frame, front fork, rear triangle, two wheels, and rider are modeled as separate bodies interconnected at the main pivot, telescoping fork, pedals, handlebars, and axles. Suspensions are between the main frame and front fork, main frame and rear triangle, handlebars and rider (arms) and pedals and rider (legs). An algorithm is used to allow tracking of a virtual tire-ground contact point for events that separate the wheels from the ground. Significant excursions of motion are allowed to model major slope changes, separations from the ground, and large rotational events (endos). The bond graph approach allows kinematics to drive the significant dynamic interactions with the effort (force and torque) relationships being derived for “free”. Simulations of a ground profile with a rise followed by a steep drop are performed for various initial conditions to qualitatively validate the predictions of the model. Rider strategies for negotiating the drop are examined in the process. Overarching goals of the research are to examine and understand the dynamics and control of interactions between a cyclist and mountain bike. Specific, longer term, goals are to understand the improvement in performance afforded by an experienced rider, to hypothesize human control algorithms that allow riders to perform maneuvers well and safely, to predict structural bike and body forces from these maneuvers, and to quantify performance differences between hard-tail and various full suspension bicycles.