bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer of Two-Phase Impinging Jet: Two-Phase Flow in Capillary Nozzle Tubes
Authors: Horiki Sachiyo , Osakabe Masahiro
Published: April 2008

To enhance the heat transfer coefficient and save the amount of coolant, two-phase jets have been applied to the cooling of heat transfer surface. The slugging in capillary nozzle tubes and the gushing behavior at outlet of tubes would strongly affect the impingement heat transfer. The slug (or churn) to annular flow transition dominated by the slugging mechanism was investigated in the previous experimental data in capillary nozzle tubes. Two-phase experiments were conducted with vertical tubes of 1, 2, 4, 5 and 10mm in inner diameter. The oscillatory behavior of bubble, slug and churn flow was observed. The peculiar phenomena in capillary nozzle tubes were not observed. The differential pressures between 500mm vertical span were measured. The root mean square (RMS) value of differential pressure was well correlated with Lockhart-Martinelli parameter. The RMS value was expected to be a key parameter related to the heat transfer enhancement with the two-phase impinging jet.
Multivariate Knock Detection for Development and Production Applications
Authors: Tousignant Todd E. , Reader Graham T. , Tjong Jimi
Published: April 2008

Combustion knock caused by end gas autoignition continues to be a limiting factor in the performance of automotive internal combustion engines. As such, the availability of efficient knock detection methods is a prime requirement for the optimization of engine mapping and control. Current production knock control systems are based on the measurement of mechanical vibration induced by the acoustic resonance excited in the combustion chamber during autoignition. These vibrations are measured using accelerometers on the engine block. Conversely, knock detection in the laboratory environment during engine development or calibration generally involves either acoustic methods or acquisition of in-cylinder pressure. The purpose of this study is to develop an improved multi-transducer vibration-based knock detection method with applications in engine development and production. The possibility of replacing the pressure-based detection methods in the laboratory environment presents many advantages relating to cost and efficiency. Moreover, the economy of a vibration-based system coupled with improved correlation to laboratory methods represents great potential for performance improvements if applied to production applications.
Study on the Structural Analysis Method of Wheel Loaders Based on Static and Dynamic Measurements
Authors: Choung Joonmo , Kim Gyusung , Jang Youngsik , Choe Ickhung , Heo Minsoo
Published: April 2008

This paper presents several investigations for improved structural analysis method of wheel loaders based on the static and dynamic measurements including strength and motion characteristics. Physical quantities such as stresses, hydraulic cylinder pressures and strokes were obtained from static tests for prepared operating scenarios. The dynamic measurements were also carried out for two types of motions: simple reciprocations of a boom and a bucket and actual working motion including traveling, digging and dumping. It was shown from static measurements that static stress level induced by the bucket cylinder operation was higher than that by the boom cylinder operation. It was confirmed from dynamic measurements that stress histories during actual working seemed to be static rather than dynamic. A fully assembled finite element model was prepared for structural analysis. A practical trial and error scheme was adopted in order to handle non-linearity caused by lift-up of wheels. For both measurements and structural analysis, it was shown that structural behaviors with the brake on were quite different from those with brake off. Sensitivity analysis showed that there was much difference between digging forces from conventional formula and structural analysis.
Flow of Surfactant Solutions Past a Circular Cylinder
Authors: Osano Yoshihisa , Ogata Satoshi , Watanabe Keizo
Published: April 2008

To clarify the effects of surfactant solutions on the drag coefficient of a circular cylinder, the flow past a circular cylinder was investigated in the Reynolds number range of 10 to 7,000 by measuring the drag and by visualizing flow. In addition, the flow pattern was simulated numerically to examine the effect of the viscoelasticity of the surfactant solution. Six cylinders with diameters between 2 and 20 mm were tested, and the ratio of length to diameter (l/d) was 12~48. The test surfactant solutions were aqueous solutions of oleyl-methyldihydroxyethyl ammonium chloride (trade name: Ethoquad O/12) in the concentration range of 50 to 200 ppm and sodium salicylate was added as a counterion. It was clarified that the drag coefficient of surfactant solutions increases comparing with that of tap water in the Reynolds number range of 1,000 < Re 3,000 and drag reduction occurs when Re > 3,000 for a cylinder diameter of 20 mm. The maximum drag reduction ratio was approximately 55% for 200 ppm solution at Re = 7,000. The flow visualization results showed that the drag of surfactant solutions increases because of the existence of the wide stagnant zone around the cylinder. This zone disappeared in the Reynolds number range in which drag reduction occurred. In addition, the width of the wake of surfactant solutions decreases compared with that of tap water, and the Ka´rma´n vortex street is not found. These effects seem to be due to the elasticity caused by the micellar network in surfactant solution.
Growth of Microcellular Foams in Viscoelastic Mediums
Authors: Kim Ki Young , Kang Sung Lin , Kwak Ho-Young
Published: April 2008

The growing of the critical bubble by diffusion process in visco-elastic medium was treated by an integral method for the concentration boundary layer. In this study, we obtained a set of the first order time dependent equations to obtain bubble radius and gas pressure inside the bubble simultaneously. The calculated final cell sizes depending on the initial saturation pressure are in close agreement with the observed ones. The governing equations developed in this study may be used in polymer processing of microcellular foams.
Unstable Vibration of Simply Supported Thin Cylindrical Shells Subjected to Axial Leakage Flows Using Flu¨gge’s Shell Theory
Authors: Fujita Katsuhisa , Kato Makoto
Published: April 2008

The unstable vibration of thin cylindrical shells subjected to axial leakage flows is investigated in this paper. Considering the fluid structure interaction between shells and fluids flowing through a narrow passage, the coupled equation of motion between shells and flowing fluids is derived using the Flu¨gge’s shell theory and the Navier-Stokes equation. Focusing on the vibrational characteristics of a thin cylindrical shell with both simply-supported ends, that are the axisymmetric vibration, the lateral vibration and the circumferential vibration, the unstable phenomenon of thin cylindrical shells are clarified by using the root locus based on the complex eigenvalue analysis. The numerical parameter studies on the shells with both simply-supported ends are performed taking the dimensions of shells, the characteristics of flowing fluids and the clearance of an annular gap as parameters. The influences of these parameters on the threshold of the instability of the coupled vibration between a shell and a flowing fluid are discussed.
Heat Transport and Temperature Distribution in PEFCs
Authors: Burford Daniel J. , Mench Matthew M.
Published: April 2008

For detailed understanding of water and thermal management and degradation mechanisms, knowledge of the internal temperature distribution in a polymer electrolyte fuel cell (PEFC) is critical. Internal electrolyte temperature measurements as a function of current density and cathode inlet humidity were obtained using a specialized, 50cm2 fuel cell with micro-thermocouples embedded in the thin-film electrolyte at various locations. A simplified model of heat transport in the fuel cell materials was used to estimate the thermal conductivity in the gas diffusion layer media and polymer electrolyte membrane. At the same current and location in the fuel cell, steady state electrolyte temperature generally decreased with increasing humidity, a result of decreased internal resistance and/or latent heat effects. The diffusion media used had an estimated thermal conductivity 0.13–0.19 W/mK. The polymer electrolyte used (Nafion®) was estimated to have a thermal conductivity of 0.025–0.25 W/mK. The thermal conductivity and thickness of the diffusion media limits heat transfer, and opportunity exists for tailoring temperature profile in the PEFC through the diffusion layers.
Shape Recovery Characteristics of Pipes With Heavy Wall Thickness Made by Ferrous Shape Memory Alloy
Authors: Joto Yoshinori , Wada Manabu , Naoi Hisashi , Maruyama Tadakatsu
Published: April 2008

Recently, ferrous shape memory alloys have been developed. Shape recovery strains of ferrous shape memory alloys are smaller than those of Ti-Ni shape memory alloys[1,2]. Strength, ductility and workability of the former alloy are higher than those of the latter alloy. Therefore, ferrous shape memory alloys are tried to apply for several kinds of pipe joints, as an example, joints of support pipes in the tunnel[3]. One of the other applications, the alloys is used as the material of simulation model to analyze the deformation behavior of the core tube in the fast breeder reactor. In this study, we investigated the shape recovery characteristics of pipes with heavy wall thickness made by ferrous shape memory alloy. Chemical compositions of this alloy are Fe, 28%Mn, 6%Si and 5%Cr. The alloy is melted, and round bars are manufactured by rolling, and pipes are machined from them. Tensile strength is 1100MPa, and yield strength is 320MPa. Ratios of wall thickness to central diameter of pipes are 10, 15, 20 and 25%. We insert tapered punch in the pipe, and expanded it by test machine. Then the circumferential strain of the center diameter of the pipes is 7%. And finally, the heat treatment is conducted at 350 degrees C in order to induce the shape recovery strain, and the pipe diameter decreases by means of austenitic transformation. The results obtained by the experiment are shown as follows. As the value of ratios of wall thickness to center diameter decreases, shape recovery strain increases and seems to approach the shape recovery strain obtained by uni-axial tension test, which was conducted in the past time.
Analysis of Different Kinds of Measurements on the Estimation of Time Dependent Mass and Heat Transfer Coefficients in Drying
Authors: Saker Leonardo F. , Orlande Helcio R. B. , Huang Cheng-Hung , Kanevce Gligor H. , Kanevce Ljubica P.
Published: April 2008

In this paper we present the solution of the inverse problem of simultaneously estimating the heat and mass transfer coefficients at the surface of a drying one-dimensional body. The physical problem is formulated in terms of the linear Luikov equations and the unknown functions are time dependent. The inverse problem is solved by using the conjugate gradient method of function estimation with adjoint problem. Results are presented for the estimation of discontinuous functions by using simulated measurements of local temperature, local moisture content and/or total moisture weight. The main objective of the paper is to examine the effects of different types of measurements on the inverse problem solution.
Optimization of Shell and Tube Heat Exchanger Networks
Authors: Fakheri Ahmad , Fazel Maryam
Published: April 2008

A methodology is presented for the optimization of a network of shell and tube heat exchangers connected in series. For a given total rate of heat transfer and the known inlet and exit temperatures of the hot and cold fluids, the total area of the heat exchanger network is minimized. In the proposed methodology, the heat exchangers are assumed to be different. This is a generalization compared to the traditional approach where all the heat exchangers are taken to have the same area and the same LMTD (Log Mean Temperature Difference) correction factor. In the traditional approach the minimum number of identical shells, for which a feasible solution exists and meets the design criteria, is used as the optimum solution. The proposed optimization approach shows that using larger number of smaller heat exchangers results in less overall heat exchanger area due to the more efficient operation of the individual heat exchangers.
Wireless Starting System and Emergency Stop for Teleoperated Hydraulic Mobile Machine
Authors: Uusisalo Jarno R. A. , Raneda Albert , Vilenius Jani M. , Huhtala Kalevi J.
Published: April 2008

A small general-purpose teleoperated hydraulic mobile machine is studied at the Institute of Hydraulics and Automation at the Tampere University of Technology. Thanks to teleoperation, the operator of the machine is able to be in safe place during the driving when necessary. However, the actions of the machine can be dangerous for the people or the objects in the environment if problems appear for instance in the control system. On that account, safety issues must be considered carefully. Special attention has to be paid to stop the machine and start the engine again once the machine has recovered from an error situation. The goal of this paper is to describe the design and implementation of different kind of solutions to start and stop the machine wirelessly. The emergency stop can be activated through the wireless connection by the operator or by the automatic diagnostic system of the hydraulic mobile machine. The control system monitors the state of several hydraulic components such as hydraulic valves and motors by means of sensors during the operations of machine. The machine is teleoperated by using WLAN (Wireless Local Area Network) connection. The developed wireless starting system and emergency stop is totally independent of the WLAN link. In the first prototype of the wireless starting system and emergency stop, the wireless connection is carried out by using commercial, cost effective RF (Radio Frequency) modules. The data transfer protocol which is used by the modules is designed for this application. Protocol implementation is carried out with microcontrollers. Another version of the wireless starting system and emergency stop is carried out by using radio modems. The modems have better properties than the cost effective RF modules used in the first prototype due to their higher RF output power. Programmatically carried out automatic emergency stop, which stops the machine, if the WLAN connection between the control station and the machine breaks, is discussed. In that case, the independent wireless emergency stop connection is not needed. Implementations of the system are introduced in this paper. Also, some testing results and user experiences are described. Properties of these different implementations are compared: cost of the system, range, reliability and complexity of the implementation. By means of the studied results the most suitable solution to start the engine and stop the actions of the machine is chosen.
A Bypass Flow Control System to Improve the Transient Response of an Energy Efficient Hydraulic Pump-Motor System
Authors: Shang Tonglin , Schoenau Greg , Burton Richard
Published: April 2008

In this paper a hydraulic circuit that demonstrates both high dynamic performance and high energy efficiency is presented. The system uses a variable displacement pump which represents an energy efficient choice but can display poor transient response characteristics due to slow response of the pump. In this study, a DC motor is used to control the pump swashplate directly to increase the dynamic response of the pump. The problem with this arrangement is that the overshoot of the hydraulic motor is substantially increased. To reduce the effect of the overshoot, a bypass flow control system is utilized to bypass part of the pump flow during the transient. This allows the system to converge to steady state conditions more rapidly while maintaining an energy efficient system.
Development of a Measuring System for Planar Cam Profiles and Their Follower Motions
Authors: Tsay Der-Min , Tseng Kuo-Shu , Chen Hsin-Pao
Published: April 2008

A measuring system that can be used to inspect planar cam contours and to evaluate their follower displacement, velocity, and acceleration curves with a higher degree of accuracy without the aid of approximating follower displacements in traditional methods is constructed. Based on the geometric relationships at the contact point between a planar cam profile and its follower, analytical descriptions that can be utilized to determine the follower displacement curve and its derivatives are first identified. To verify the feasibility and accuracy of the algorithms proposed for the measuring system, analytical results generated from a theoretical design are compared to those obtained by the application of the computing procedure. To demonstrate the effectiveness and usefulness of the developed procedure, a measuring test bed has been constructed for a practical application example. Furthermore, the results obtained by using the built measuring system are also compared to those obtained by using a coordinate measuring machine (CMM) with the proposed algorithms.
Obstacle Avoidance and Minimum Time Control of Cranes Using Flat Outputs and Nonlinear Programming
Authors: Kumar Randhir , Issac K. Kurien
Published: April 2008

The problem addressed here is to determine controls for moving a load along specified trajectories which avoid obstacles. It is possible to use flat outputs to determine inputs when hoist motion is present. However, when hoist is locked, the system does not appear to be differentially flat, and hence the above approach could not be used. We propose an iterative algorithm for the problem of calculating trolley motions in this case. Results for load motions requiring (a) travel and traverse of the trolley and hoist, (b) travel and hoist, and (c) travel alone, are presented. We also use flat outputs to formulate the minimum time control problem as a nonlinear programming problem, with constraints arising from limits on trolley and hoist accelerations and velocities, and positive rope tension. Solutions obtained are also presented.
Modeling and Validation of a Pressure-Wave Supercharger Using a Finite Difference Method
Authors: Spring Peter , Piechna Janusz , Onder Christopher H.
Published: April 2008

Modern pressure-wave supercharging devices offer many degrees of freedom in operation with an internal combustion engine. Both the independent set of wave rotor speed and the offset between air and gas casing can guarantee optimum efficiency even under problematic operating conditions. However, these systems require very accurate models that can reproduce the physical effects occurring in the charger. In this paper, a finite difference tool is presented where a set of Euler-type partial differential equations is numerically solved to simulate the 1-dimensional unsteady gas dynamics in the cell wheel, taking into account such phenomena as leakage, heat transfer, and friction. In order to show its general applicability, the model was validated with measurement results from two different PWS-boosted engines on a test rig.
Modeling and Multivariable Control of a High Precision Multidimensional Positioner
Authors: Hu Tiejun , Kim Won-Jong
Published: April 2008

A precision positioner using a novel concentrated-field permanent-magnet matrix is presented in this paper. This integrated multidimensional positioner is actuated by three novel planar motors, which are attached on the bottom of the positioner. It can generate all 6-DOF motions with only a single moving part. The integrated multi-dimensional positioner offers a unique combination of range and precision: a planar traveling range of 160 mm × 160 mm with a position resolution of 30 nm and position noise of 10 nm rms. The repeatability of the positioner is as good as 30 nm. The maximum velocity achieved so far is 0.5 m/s with 5-m/s2 acceleration. With direct-quadrature (DQ) decomposition theory, the positioner is modelled as a multi-input multi-output (MIMO) electromagnetic system: it has six inputs (currents) and six outputs (displacements). After the state-space model of the system is derived, multivariable controllers are designed for this high-precision positioner. To eliminate the steady-state error, discrete time integrator combined Linear Quadratic Regulation (LQR) and reduced order Linear Quadratic Gaussian (LQG) control methodologies are applied and implemented. Finally, the experimental results are presented in this paper. Several experimental results verified the utility of this positioner in precision applications, such as semiconductor manufacturing.
Modelling and Adaptive Control of Tendon-Driven Micromanipulators in the Presence of Van-der-Waals Forces
Authors: Tsoukalas Athanasios , Tzes Anthony
Published: April 2008

In this article, the design problem of an adaptive controller for a robotic micromanipulator, including the effects of the applied Van der Waals (VdW) forces is considered. The micro-manipulator’s dynamic model is appropriately modified in order to include the interaction of the attractive VdW-forces. Inhere, every link is decomposed into a series of elementary particles (e.g. spheres), each one interacting with the robot’s neighboring objects during its motion. This interaction induces nonlinear additive terms in the model, attributed to the overall effect of the VdW-forces. The actuation is achieved by a tendon-driven system. At each joint, a pair of tendons is attached and act in an almost passive antagonistic manner. The kinematic and dynamic analysis of the tendon-driven actuation mechanism is offered. Consequently, the microrobot’s model is shown to be linearly parameterizable. Subject to this observation, a globally stabilizable adaptive control scheme is derived, estimating the unknown parameters (masses, generalized VdW-forces) and compensating any variations of those. Simulation studies on a 2-DOF micro-manipulator are offered to highlight the effectiveness of the proposed scheme.
Neural Network Based Run-to-Run Process Controller for Copper Chemical Mechanical Polishing
Authors: Wang Gou-Jen , Lin Bor-Shin , Chang Kang J.
Published: April 2008

Process Control is one of the key methods to improve manufacturing quality. This research proposes a neural network based run-to-run process control scheme that is adaptive to the time-varying environment. Two multilayer feedforward neural networks are implemented to conduct the process control and system identification duties. The controller neural network equips the control system with more capability in handling complicate nonlinear processes. With the system information provided by this neural network, batch polishing time (T) an additional control variable, can be implemented along with the commonly used down force (p) and relative speed between the plashing pad and the plashed wafer (v). Computer simulations and experiments on copper chemical mechanical polishing processes illustrate that in drafting suppression and environmental changing adaptation that the proposed neural network based run-to-run controller (NNRTRC) performs better than the double exponentially weighted moving average (d-EWMA) approach. It is also suggested that the proposed approach can be further implemented as both an end-point detector and a pad-conditioning sensor.
Compliant and Low-Cost Humidity Sensors Using Nano-Porous Polymer Membranes
Authors: Yang Bozhi , Aksak Burak , Liu Shan , Lin Qiao , Sitti Metin
Published: April 2008

This paper proposes non-fragile compliant humidity sensors that can be fabricated inexpensively on various types of nano-porous polymer membranes such as polycarbonate, cellulose acetate, and nylon membranes. The sensor contains a pair of interdigitated electrodes deposited on the nano-porous polymer membranes. The resistance and/or capacitance between these electrodes vary at different humidity levels with a very high sensitivity due to the water adsorption (capillary condensation) inside the nano-pores. The proposed sensors are low-cost in both material and fabrication. Due to its compliance, the sensors can be suitable for certain applications such as in-situ water leakage detection on roofs, where people can walk on top of them. Testing results demonstrated that the sensor changes resistance within large range of humidity values. For most sensors, the resistance changes from 0.1 GΩ to 2000 GΩ when the relative humidity changes from 39% to 100% at room temperature. It takes about 4–8 minutes for the resistance to reach steady state when the sensor was taken from 100% to 39% relative humidity at the room temperature.
Heat Transfer in Two-Pass Rotating Rectangular Channels (AR=2:1) With Discrete V-Shaped and Discrete Angled Rib Turbulators
Authors: Fu Wen-Lung , Wright Lesley M. , Han Je-Chin
Published: April 2008

This paper reports the heat transfer coefficients in a two-pass rotating, rectangular channel with ribs, applicable to an internally cooled turbine blade. The channel aspect ratio is 2:1. Five different turbulators are studied: 45° angled ribs, V-shaped ribs, discrete 45° angled ribs, discrete V-shaped ribs, and crossed V-shaped ribs. The ribs are placed on the leading and trailing surfaces. The Reynolds numbers range from 5000 to 40000. The corresponding rotation numbers vary from 0.21 to 0.026 for a fixed rotating speed of 550 rpm. The rib height-to-hydraulic diameter ratio (e/D) is 0.094, the rib pitch-to-height ratio (P/e) is 10, and the inlet coolant-to-wall density ratio (Δρ/ρ) is maintained around 0.115. For each case, two channel orientations are studied, 90° and 135° with respect to the plane of rotation. The results show the V-shaped ribs and discrete V-shaped ribs have higher heat transfer enhancement than the 45° angled ribs and discrete 45° angled ribs for both rotating and non-rotating cases.
Discontinuous Finite Element Phase-Field Modeling of Solidification Microstructure Formation
Authors: Shu Y. , Ai X. , Li B. Q.
Published: April 2008

A discontinuous Galerkin finite element computational methodology is presented for the solution of the coupled phase-field and heat conduction equations for modeling microstructure evolution during solidification. The details of the discontinuous formulation and the solution procedures are given. A major difference between the current method and those used in the literatures is the application of higher-order localized formulation and unstructured mesh, which holds a great promise in both parallel computing and adaptive meshing. The accuracy of the discontinuous model is checked with the analytic solution for a simple 1-D solidification problem. Numerical simulations and selected results are given for more complex 2-D dendrite structures formed during solidification. The calculated results are consistent with those reported in literature.
Simulation and Analysis of a Secondary HVAC System Using MATLAB/SIMULINK Platform
Authors: Novak Paulo Rogerio , Mendes Nathan , Oliveira Gustavo Henrique da Costa
Published: April 2008

In this paper, the mathematical model of a secondary system (fan-coil) of a HVAC equipment is described. This system was inserted into a computer code developed in Matlab/Simulink platform devoted to the analysis of buildings hygrothermal behavior and performance of closed-loop control systems. The model is presented in terms of state-space variables that represent the energy and mass balance for each component of the fan-coil. Results are presented in terms of a comparative analysis of the cooling coil temperature and external air ventilation rate effects on the room air psychrometrics state. Finally, the control system performance is presented for both temperature and relative humidity.
Application of Operational Modal Analysis to a Machine Tool Testing
Authors: Kushnir Emmanuil
Published: April 2008

Modal analysis testing of a mechanical structure is performed usually by artificial excitation of a structure and measuring input forces and output responses of a mechanical system. The excitation is either transient (impact hammer testing), random, burst-random or sinusoidal (shaker testing). The modern signal processing tools enable to determine properties of a mechanical structure such as resonance frequencies, damping ratios, and mode patterns by measuring the response of the structure without using an artificial excitation. The advantage of this technique is that modal parameters of a structure may be evaluated while the structure is under actual operating conditions. That will allow developing a model within true boundary conditions and actual force and vibration levels. The machine tool structure characteristics that effect productivity and quality have to be evaluated by testing. These characteristics include natural frequencies, modes of vibration, and external sources of high level vibration. Not all modes of machine tool structure effect machine quality. As a result only the modes that are excited during cutting have to be taken in the account. This approach narrowed the frequency range, which has to be considered in test. The machine tool during cutting and/or idling is loaded by a set of external and internal exciting forces. Spectrum, frequency range and application points of these forces are unknown in many cases. Under these exciting forces the vibration between the tool and workpiece, and vibration of machine tool components are sums of many independent vibrations and may be considered as stationary random processes. This assumption allows applying the theory of stationary random processes to machine tool dynamic testing during cutting. Several characteristics of random processes are used to separate harmonic vibration from narrow-band random vibration at natural frequencies. The spectral analysis of machined surface profiles and its correlation with observed vibration allows choosing modes that have to be developed. The analysis of these modes provides a basis for machine tool structure improvement. The proposed experimental approach was verified by experiments at different machine tools. Results of these tests are presented in the paper.
Compliant Mechanism Configurations for Vehicle Suspension Systems
Authors: Allred Timothy , Howell Larry L. , Magleby Spencer P. , Guerinot Alexandre E.
Published: April 2008

This paper explores the use of compliant mechanisms or flexible beams in vehicle suspension systems. An example of a compliant suspension mechanism is the leaf spring suspension commonly found on trucks. New concepts are developed through rigid-body replacement synthesis and other methods with the objective of improving wheel control. The compliant A-arm is discussed and shown to be a promising concept for further research based on FEA results and other comparisons. The A-Arm concept performs well in controlling wheel deflections and has low stress values in response to control forces when compared to other compliant concepts considered and leaf spring configurations. The A-Arm uses less space than than the other compliant concepts considered and the potential cost of manufacture and assembly is potentially equal to current leaf spring congifurations.
Design of Testing Apparatus to Evaluate the Strength of Guardrail Systems
Authors: McKenzie E. A. , Bobick T. G. , Cantis D. M.
Published: April 2008

Fall-related occupational injuries and fatalities are serious problems in the U.S. construction industry. An important sub-set of falls-to-lower-level incidents is when workers fall through openings or surfaces, including skylights. OSHA regulations require that holes (openings) in roofs must be protected by a guardrail or cover, or nearby workers must use personal fall-arrest systems. The National Institute for Occupational Safety and Health (NIOSH), Division of Safety Research, Morgantown, WV has initiated a pilot project to evaluate the effectiveness of guardrail systems. Two commercially available edge-protection products were evaluated as guardrails around a roof opening. Installation methods for the two edge-protection products, which have not been designed to be used as guardrails for openings, are compared to job-built guardrails constructed of two-by-four lumber. To evaluate how well the commercial products comply with existing OSHA regulations as a guardrail, an experimental hypothesis and a laboratory-based testing system were developed. OSHA regulations require that a force of at least 200 pounds shall be supported by the top rail of the guardrail system. The governing variable is the 200-pound force. This was generated by using a weighted rescue dummy mounted on a specially designed hinged steel frame. Adjusting the fall distance of the dummy, a dynamic 200-pound force was generated in the middle of the top rail. To evaluate the overall strength of the guardrail systems, a hydraulic testing apparatus was designed. Combining a hydraulic cylinder and pump, with a piezoelectric force transducer, a pull-to-failure (PTF) test apparatus was developed. This system was designed to pull the guardrail systems in the same direction in which the test dummy fell. Maximum PTF forces were recorded for both commercially available products and then compared with the job-built systems.
On the Size-Effect in Micro-Cutting at Low and High Rake Angles
Authors: Subbiah Sathyan , Melkote Shreyes N.
Published: April 2008

A partial explanation of the size-effect in the specific cutting energy in micro-cutting is provided in this paper. For a simple orthogonal cutting condition, with constant width of cut, the specific cutting energy is viewed as a ratio of the cutting force and the uncut chip thickness. Size-effect, i.e., an unbounded increase in the specific cutting energy with decrease in uncut chip thickness, will occur under two conditions: one, if a component of the cutting force remains constant with uncut chip thickness and two, if some component of the cutting force increases with the uncut chip thickness. Experiments have been performed at high rake angles in an attempt to isolate and detect the presence of the constant component of the cutting force. The trend confirming the presence of this component is reported and explained.
Finite Element Analysis of Solidifying Processes in Rapid Freeze Prototyping
Authors: Liu Qingbin , Leu Ming C.
Published: April 2008

Rapid Freeze Prototyping (RFP) can generate three-dimensional ice patterns from CAD models by depositing and solidifying water droplets layer by layer. One important issue of the RFP process is how to fabricate the ice pattern to desired accuracy in an acceptable short time. The waiting time between two successive layers is a critical factor. A waiting time that is too short will lead to unacceptable part accuracy, while a waiting time that is too long will lead to an excessive build time. Finite Element Analysis is employed in the study, as described in the present paper, to predict the solidification time of a newly deposited water layer and to develop a better understanding of heat transfer during the RFP process. ANSYS is utilized to develop software for the prediction of solidification time. Effect of various process parameters on the solidification time of an ice column and a vertical ice wall is investigated. These parameters include environment temperature, heat convection coefficient, initial water droplet temperature, layer thickness, and waiting time between two successive layers.
Design of a Hot Gas Vane Motor
Authors: Li Bo , Barth Eric J. , Fite Kevin B. , Goldfarb Michael
Published: April 2008

This paper describes the design of a hot gas vane motor. The motor is intended as a portable direct drive actuator powered by a hot gaseous working fluid as an alternative to battery-powered electromagnetic motors. The objective is thus to convert a maximum amount of enthalpy at the inlet into mechanical rotational output energy in a compact and lightweight package. The described motor incorporates a non-circular stator shape and a geometry of injection and exhaust ports to maximize conversion efficiency. An analytical model is developed to describe the torque output and efficiency of the motor. Simulations are performed to provide insight into the motor behavior and characterize the expected motor performance.
Finite Element Simulation of Rotary Ultrasonic Machining for Advanced Ceramics
Authors: Li Zhichao , Cai Liang-Wu , Pei Z. J. , Treadwell Clyde
Published: April 2008

Rotary ultrasonic machining (RUM), a hybrid machining process that combines diamond grinding and ultrasonic machining, has been utilized as a cost-effective material removal method for hard-to-machine materials such as advanced ceramics. In this study, the stress and deformation fields in a ceramic workpiece (92% Al2O3) and the formation of edge chipping during RUM process are investigated using finite element method. Based on a simplified model of RUM process, a three-dimensional finite element model is constructed using axisymmetric eight-node quadrilateral element. In the finite element model, the areas of the workpiece bottom surface that are in contact with the fixture are defined as boundaries of zero displacement in normal direction. A static load is applied to the cutting zone, which is the contact area between the tool’s end face and the bottom surface of the machined slot in the workpiece. The value of the load is calculated from experimental measurements using a dynamometer. Using this model, the maximum von Mises stresses are computed. Initiation and location of the crack, which leads to chipping in RUM process, are also analyzed and compared with experimental results observed under a microscope.
Iterative Modeling and Identification of a CO2 Air Conditioning System
Authors: Rasmussen Bryan P. , Alleyne Andrew , Musser Andrew
Published: April 2008

This paper uses an air conditioning system to illustrate the benefits of iteratively combining first principles and system identification techniques to develop control-oriented models of complex systems. A transcritical vapor compression system is initially modeled with first principles and then verified with experimental data. Both SISO and MIMO system identification techniques are then used to construct locally linear models. Motivated by the ability to capture the salient dynamic characteristics with low order identified models, the physical model is evaluated for essentially nonminimal dynamics. A singular perturbation model reduction approach is then applied to obtain a minimal representation of the dynamics more suitable for control design, and yielding insight to the underlying system dynamics previously unavailable in the literature. The results demonstrate that iteratively modeling a complex system with first principles and system identification techniques gives greater confidence in the first principles model, and better understanding of the underlying physical dynamics. Although this iterative process requires more time and effort, significant insight and model improvements can be realized.
Three-Dimensional Occupancy Grids With the Use of Vision and Proximity Sensors in a Robotic Workcell
Authors: Kumar Manish , Garg Devendra P.
Published: April 2008

This paper discusses the use of multiple vision sensors and a proximity sensor to obtain three-dimensional occupancy profile of robotic workspace, identify key features, and obtain a 3-D model of the objects in the work space. The present research makes use of three identical vision sensors. Two of these sensors are mounted on a stereo rig on the sidewall of the robotic workcell. The third vision sensor is located above the workcell. The vision sensors on the stereo rig provide information about three-dimensional position of any point in the robotic workspace. The camera to robot calibration for these vision sensors in stereo configuration has been obtained with the help of a three-layered feedforward neural network. Squared Sum of Difference (SSD) algorithm has been used to obtain the stereo matching. Similarly, camera to robot transformation for the camera located above the work cell has been obtained with the help of a three-layered feedforward neural network. Three-dimensional positional information from vision sensors on stereo rig and two-dimensional positional information from a camera located above the workcell and a proximity sensor mounted on the robot wrist have been fused with the help of Bayesian technique to obtain more accurate positional information about locations in workspace.
Flow Through a Micro-Bioreactor in a Neural Interface System
Authors: Vukasinovic Jelena , Glezer Ari
Published: April 2008

A micro-bioreactor is developed for in vitro, controlled, growth of three-dimensional dissociated neural cultures that enables simultaneous, multipoint, electrical and fluidic interfacing, monitoring and recording of the response signals that are relevant to the studies of traumatic injury. Present experiments focus on the microfluidic system that is used to control the spatial concentration of nutrients and stimuli in the incubated tissue. The three-dimensional cellular environment in a micro-bioreactor is controlled by means of convective and diffusive fluidic processes to improve the neural cell survival rate, direct the cell growth and examine the network formation. To achieve global and local manipulation of the critical cell functions, flow within the reactor is induced from arrays of micro-machined nozzles in planar surfaces and within microscale hydrogel scaffolding. The flow and concentration fields within reactor are analyzed using microscale particle image velocimetry (PIV) and fluorescence. The flow within 25 μm thick layers between microfabricated structures is investigated using image-processing algorithms that are developed to improve spatial resolution by excluding out-of-focus particles. Mixing induced by delivery of stimuli/nutrients and waste extraction is considered by following the time-evolution and spatial propagration of the mixing front between the liquids based on the intensity of reflected light that is previously calibrated with concentration.
An Intelligent Systems Approach for an Ultrasonic Based Neuro-Navigation System
Authors: Akers Jennifer , Chitikeshi Sanjeevi , Mahajan Ajay , Chu Tsuchin , Witte Etienne , Lal Sumeer
Published: April 2008

This paper shows the feasibility of using an intelligent systems approach to increase the accuracy of a 3D ultrasonic position estimation system for real-time image guided neurosurgery. Current image guided systems use camera based technology that is space-intensive, have an accuracy of about 1.0–2.0 mm, and are prone to occasional failures. The 3D system presented in this paper eliminates the space intensive camera, has an accuracy of around 1.0 mm in the operating range of about 200–400 mm, makes the system independent of line-of-sight occlusion problems, and is expected to pave the way for accurate fusion models of MRI and ultrasonography to account for brain shifts during surgery. Hence, the proposed system provides many more advantages over existing systems without compromising on the accuracy. This paper presents the system formulation, a neural network model that uses the raw signals, the electronic hardware for data acquisition and processing as well as simulation and actual results.
Functional Location of Subject-Specific Joint Axes of the Human Ankle Complex
Authors: Lewis Gregory S. , Piazza Stephen J.
Published: April 2008

Two non-invasive methods for locating the functional joint axes of the ankle complex were assessed. There is believed to be considerable variation in joint axis location among individuals, making he accurate subject-specific location of these axes important for improved orthopaedic treatment of musculoskeletal disorders of the foot and ankle. The first method, based on the work of previous investigators, uses optimization. An assessment of the accuracy of this method, not performed to date, was carried out on an anthropomorphic mechanical linkage and three cadaver specimens. This method was substantially more accurate when tested on the linkage than when tested on the cadavers, suggesting that its application is limited in vivo. The second method uses a novel approach to move the foot primarily about the subtalar joint, therefore allowing the subtalar joint axis to be located using helical axis decomposition. The accuracy and repeatability of this method were also assessed on six cadaver specimens, with generally good results. In three specimens, subtalar axis location errors were typically less than 10° and 2 mm.
Predicting Cost of Poor Quality and Reliability for Systems Using Failure Modes and Effects Analysis
Authors: Rhee Seung J. , Ishii Kosuke
Published: April 2008

Failure Modes and Effects Analysis (FMEA) is a design tool that mitigates risks during the design phase before they occur. Although many industries use the traditional FMEA technique, it has many limitations and problems. Traditional FMEA identifies failure modes with high risk but does not consider the consequences in terms of cost, which could lead to unnecessarily expensive solutions. We have used a new methodology, “Life Cost-Based FMEA,” which measures risk of failure in terms of cost to compare two different technologies that might be used for the Next Linear Collider (NLC) magnets: electromagnets or permanent magnets. We derived the availability estimates for the two different types of magnet systems using empirical data from Stanford Linear Accelerator Center’s (SLAC) accelerator failure database as well as expert opinions on permanent magnet failure modes and industry standard failure data. We can predict the labor and material costs to repair magnet failures using a Monte Carlo simulation of all possible magnet failures over a 30-year lifetime. Our goal is to maximize up-time of the NLC through magnet design improvements and the optimal combination of electromagnets and permanent magnets, while reducing magnet system lifecycle costs.
Experimental Repeatability of a Thermal Actuator for Nanopositioning
Authors: Hubbard Neal B. , Howell Larry L.
Published: April 2008

Microactuators are increasingly being applied to nanometer-accurate position control. The purpose of this paper is to investigate the feasibility of using the thermomechanical in-plane microactuator (TIM) in nanopositioning applications. The TIM is a class of thermal actuators in which electric current flows through thin beams which are arranged in a chevron pattern. The beam angle and end constraints amplify the thermal expansion to achieve a larger output displacement. As a fully compliant mechanism, the TIM has potential for superb accuracy because it does not experience friction or backlash. Repeatability tests are conducted with two different TIM configurations. Both are fabricated from polycrystalline silicon by surface micromachining. The first configuration is actuated 33 times with an open loop current of 4 mA. The steady-state displacements are measured from scanning electron micrographs. The average displacement is 222 nm and the standard deviation is 8.4 nm, which results in a 95% precision interval of ±17 nm. The second configuration is cycled 31 times with 10 mA and an average displacement of 697 nm. The standard deviation is 6.8 nm and the 95% precision interval is ±14 nm. The open-loop repeatabilities observed in these tests indicate that the TIM is suitable for nanopositioning, and even better performance is anticipated with the implementation of feedback control.