bluuebunny/crossref_metadata_2025 huggingface dataset:
A One-Dimensional Model Capturing Selective Ion Transport Effects in Nanofluidic Devices
Authors: Hughes Brice T. , Berg Jordan M. , James Darryl L. , Ibraguimov Akif , Liu Shaorong , Temkin Henryk
Published: May 2009

This paper presents a numerical model of one-dimensional, steady-state, multi-species, ion transport along a channel of variable width and depth. It is intended for computationally efficient simulation of devices with large variations in characteristic length scale—for example those incorporating both micro- and nanochannels. The model represents both volume charge in the fluid and surface charge on the channel walls as equivalent linear charge densities. The relative importance of the surface terms is captured by a so-called “overlap parameter” that accounts for electric double-layer effects, such as selective ion transport. Scale transitions are implemented using position-dependent area and perimeter functions. The model is validated against experimental results previously reported in the literature. In particular, model predictions are compared to measurements of fluorescent tracer species in nanochannels, of nanochannel conductivity, and of the relative enhancement and depletion of negatively and positively charged tracer species in a device combining micro- and nanochannels. Surface charge density is a critical model parameter, but in practice it is often poorly known. Therefore it is also shown how the model may be used to estimate surface charge density based on measurements. In two of the three experiments studied the externally applied voltage is low, and excellent results are achieved with electroosmotic terms neglected. In the remaining case a large external potential (∼ 1 kV) is applied, necessitating an additional adjustable parameter to capture convective transport. With this addition, model performance is excellent.
Overview of the Safety Analyses and Risk Assessments of Nuclear Space Missions
Authors: Prassinos Peter G. , Lyver John W.
Published: May 2009

Space missions are conducted to gain an understanding of the universe and our solar system; to study the surface of planets other than earth; and to explore our extraterrestrial environment. Many of these missions travel to the far reaches of the solar system or explore regions that require a continuous source of electrical power that is more than what is available from the conversion of solar energy. For these space missions, electrical power is supplied by a radioisotope thermoelectric generator (RTG) that uses the heat generated by the decay radioactive material. The approval to launch and fly space vehicles using nuclear material is governed by Presidential Directive and requires authorization by the Executive Office of the President. As part of the launch approval process for these missions, a comprehensive safety analysis is conducted. This safety analysis employs a full-scope probabilistic risk assessment (PRA) to help identify improvement in launch and flight systems and quantify the risk associated with potential accidents and abort conditions during the mission. In general, the PRA follows a typical scenario-based assessment similar to PRAs that have been conducted for terrestrial hazardous facilities and operations. However, there are some significant differences when conducting a PRA of a space mission. This paper will provide a general overview of the PRA process as applied to nuclear space missions including; defining the analysis objective, system familiarization, accident sequence analysis, accident analysis, atmospheric transport, consequence analysis, and risk integration and uncertainty analysis.
Non Linear Finite Element Stress Analysis of a Restored Tooth in the Oral Cavity
Authors: Uddanwadiker Rashmi , Padole Pramod , Arya Harshwardhan
Published: May 2009

The aim of the present study is to obtain the stress distribution pattern on the different domains of the tooth in the oral cavity, taking into account non linear properties of the periodontal ligaments (PDL)surrounding the tooth. The stresses and deformation under the action of chewing forces are studied to estimate the risk of tooth fractures. Initially, linear stress and deformation analysis is carried out with three posts different in constitution. However, considering the role of periodontal ligaments, which ensures uniform stress distribution in tooth structure, due to its elastic and non-linear properties, it is felt necessary to simulate the model for non linear analysis. The study reveals that non-linear analysis gives more realistic results as compared to linear analysis. It is observed that under similar loading conditions, the stresses are approximately 25% less in case of non linear analysis and the deformation is 50% more as compared to linear static analysis for an endodontically treated maxillary central incisor. The Dentist can do selection of optimum post core system with better accuracy.
Flow Similarity Applied in Convection-Based Tilt Sensor
Authors: Peng Shiliu , Zheng Yonghong
Published: May 2009

The environment temperature has inevitable effects on property of the convection-based tilt sensors. It not only redefines the application, but also prevents the improvement of the sensor performance. Numerical simulation of the fluid flow in the chamber of a sensor was performed and the influence of the environment temperature was studied in this paper. At zero tilt angle, the temperature distribution along the perpendicular line cross the heat source at various environment temperatures was presented. It was found that the flow varied dramatically at different environment temperatures, which would cause the output signal vary accordingly, even when the tilt angle was kept at a constant, because this device works by sensing the change of flow. At the same condition, we present the numerical results when the temperature difference across the heat source and the environment was kept at the same, in those results, it was found that the temperature difference at every point along the perpendicular line cross the heat source keep the same, this result confirms the similarity principle of nature convection. Second, A method of eliminating environment temperature infect on property of convection-based tilt sensor, which is based on the theory of flow similarity, is proposed. It was found that a thermal transistance can be piped on the circuit of heat source to compensate the temperature of the heat source. A compensative circuit was specially designed which can keep flow similarity by changing heat source temperature in order to eliminate the influence of environment temperature. The experiment results show that above 70% temperature drift can be eliminated by this compensative circuit.
Nonlinear Analysis of a Simple Pendulum With Large Displacement
Authors: Ma Rujian , Li Guixi , Zhao Dong
Published: May 2009

The vibration of simple pendulum with large displacement is a kind of nonlinear system. The relationship between spectra of response and excitation is established by nonlinear analysis method under the assumption of the displacement response being a zero-mean Gaussian process, which is proved to be true by numerical simulation. The numerical computation is used to investigate the amplitude-frequency characteristics of the system. The results show that the value of amplitude-frequency characteristics decreases significantly with the increase of natural frequency and damping ratio near the point of frequency ratio being one, and the changes become less notable when the frequency ratio is greater than two.
Structural Performance of Slab Track to High-Speed Train
Authors: Chen Yung-Hsiang , Shiu Z.-Ming
Published: May 2009

The dynamic characteristic and response of the Japanese A51-type slab track subjected to the Japanese S.K.S. high-speed train are under investigation. The high-speed train running on the slab track is modeled as a sequence of individual loads moving on a layered beam on viscoelastic foundation. The dynamic stiffness matrix of a layered beam on viscoelastic foundation is established for the structural analysis. Finally the structural performance of the dynamic stability and vibrational control of the slab track to the high speed train are intensively studied and discussed.
Dynamic Analysis of the Vibration System With Nonlinear Springs
Authors: Li Guixi , Ma Rujian , Wang Jungang
Published: May 2009

The dynamic characteristics of vibration systems with nonlinear springs is analyzed in the paper. The relationship between spectra of response and excitation intensity is established by nonlinear analysis method under the assumption of the displacement response being a zero-mean Gaussian process, which is proved to be true by numerical simulation. The numerical computation is used to obtain the spectral densities of responses and, furthermore, to investigate the amplitude-frequency characteristics of the system. The results show that the peak of the amplitude-frequency curve goes higher with increase of the gap, yet lowers with the increase of natural frequency and drops significantly with the increase of damping ratio.
Advance in Research on Air Cushion Surge Chamber in Hydropower Plant
Authors: Hu Jianyong , Zhang Jian , Suo Lisheng , Fang Jie
Published: May 2009

Air cushion surge chamber is an important measure of water hammer protection in hydropower plant. Compared with conventional surge tank, air cushion surge chamber is more efficient to decrease the water hammer pressure and improve operating condition of turbine and is more economic. At the same time, because it is often constructed in the ground, it destroyed the natural environment slightly less than conventional surge tank. Condition of engineering geology is a key factor if air cushion surge chamber will be applied. Quantity of air leakage is directly relative to the normal operation of air surge chamber. Appropriate design of operation control mode is also important to the safety of hydropower plant. In this paper, principle and application of air cushion surge chamber in hydropower plant are introduced briefly; the main engineering problems are presented; achievements of research are summarized and analyzed including engineering geology, air characteristics, prediction and control of air leakage, hydraulic performance and operation control. Finally, problems that need to be research in the future and prospective applications are provided.
Natural Frequencies of Stiffenened and Unstiffened Laminated Composite Plates
Authors: Ahmadian M. T. , Pirbodaghi T. , Pak M.
Published: May 2009

In this study, the free vibration of laminated composite plates with and without stiffeners subjected to axial loads is carried out using finite element method. The plates are stiffened by laminated composite strip and Timoshenko beam. The plates and the strips are modeled with rectangular 9 noded isoparametric quadratic elements with three degrees of freedom per node and the Timoshenko beam is modeled with linear 2 noded isoparametric quadratic elements with 2 degrees of freedom per node. The effects of both shear deformation and rotary inertia are implemented in the modeling of plate and stiffener. The governing differential equations are obtained in terms of the mid-plane displacement components and shear rotations using Hamilton’s principle. The effects of axial tension and compression loads and stiffeners on the natural frequencies of the plate are investigated. Results indicate the tension loads and stiffeners will increase the natural frequencies while the compression loads reduce the natural frequencies. The buckling force of plate is computed by increasing the absolute value of compressive force until the first natural frequency tends to zero. Results of simple cases are compared with finding in the literature and a good agreement was achieved.
Control System for an Elbow Joint Motion Simulator
Authors: Schimoler Patrick J. , Vipperman Jeffrey S. , Kuxhaus Laurel , Flamm Angela M. , Budny Daniel D. , Baratz Mark E. , Miller Mark Carl
Published: May 2009

The many muscles crossing the elbow joint allow for its motions to be created from different combinations of muscular activations. Muscles are strictly contractile elements and the joints they surround rely on varying loads from opposing antagonists for stability and movement. In designing a control system to actuate an elbow in a realistic manner, unidirectional, tendon-like actuation and muscle co-activation must be considered in order to successfully control the elbow’s two degrees of freedom. Also important is the multifunctionality of certain muscles, such as the biceps brachii, which create moments impacting both degrees of freedom: flexion / extension and pronation / supination. This paper seeks to develop and implement control algorithms on an elbow joint motion simulator that actuates cadaveric elbow specimens via four major muscles that cross the elbow joint. The algorithms were validated using an anatomically-realistic mechanical elbow. Clinically-meaningful results, such as the evaluation of radial head implants, can only be obtained under repeatable, realistic conditions; therefore, physiologic motions must be created by the application of appropriate loads. This is achieved by including load control on the muscles’ actuators as well as displacement control on both flexion / extension and supination / pronation.
Effects of Inelastic Scattering on Thermal Boundary Conductance at Metal-Dielectric Interfaces
Authors: Hopkins Patrick E. , Norris Pamela M. , Stevens Robert J.
Published: May 2009

The accuracy of predictions of thermal boundary conductance using traditional models such as the diffuse mismatch model (DMM) varies depending on the types of material comprising the interface. These traditional models assume that phonons are elastically scattered which drives the energy conductance across the interface. It has been shown that at relatively high temperatures (i.e., above the Debye temperature) inelastic scattering events can drive interfacial transport. In this case, the predictions from traditional models become highly inaccurate. In this paper, the effects of inelastic scattering on thermal boundary conductance at metal/dielectric interfaces are studied. Experimental transient thermoreflectance data showing inelastic trends are reviewed and compared to traditional models. Using the physical assumptions in the traditional models and the experimental data, the relative contributions of inelastic and elastic scattering on thermal boundary conductance is inferred.
Educating the Citizen Engineer: Making a Case for Community Service in Engineering
Authors: Fleischmann Shirley T.
Published: May 2009

The first two fundamental principles in the ASME Code of Ethics are that” engineers uphold and advance the integrity, honor and dignity of the engineering profession by: I. Using their knowledge and skill for the advancement of human welfare; II. Being honest and impartial, and serving with fidelity the public, their employers and clients…” These principles involve the concept of “the public good” and are properly part of engineering ethics — yet it is difficult to find a good place in the curriculum to address these principles. This paper will present the idea of using community service in engineering as a context for teaching this aspect of engineering ethics. The author has considerable experience in community service projects — related to engineering courses in which project work is required and graded, and also related to projects that involve purely voluntary efforts. Specific examples of projects that have been used will be given. The projects have also been presented as part of the larger Honor Concept that the author has been instrumental in developing for the School of Engineering at Grand Valley State University. “The habit of apprehending a technology in its completeness: this is the essence of technological humanism, and this is what we should expect education in higher technology to achieve. I believe it could be achieved by making specialist studies the core around which are grouped liberal studies which are relevant to those specialist studies. But they must be relevant; the path to culture should be through a man’s specialism, not by-passing it…A student who can weave his technology into the fabric of society can claim to have a liberal education; a student who cannot weave his technology into the fabric of society cannot claim even to be a good technologist.”  Lord Ashby, Technology and the Academics
Turbulent Heat and Mass Transfer Inside Open and Closed Cavities
Authors: S¸eker Deniz , Eg˘rican Nilufer
Published: May 2009

Natural convection inside open and closed cavities provides a suitable benchmarking problem for viscous flow calculations. The necessity of solving the energy equation coupled with momentum equations, the difficulty to determine the boundary conditions on the cavity walls and absence of an appropriate turbulence model for that type of flows remain the problem unsolved.
Enhancement of External Condensation Heat Transfer by Pumping of Liquid Condensate Circumferentially With Electric Conduction Phenomenon
Authors: Yazdani Miad , Seyed-Yagoobi Jamal
Published: May 2009

Electrohydrodynamic (EHD) conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes, generated by the process of dissociation of the neutral electrolytic species and recombination of the generated ions. This paper numerically investigates the effect of EHD conduction pumping of liquid condensate circumferentially on the heat transfer performance of a condensation tube. The local interface profile is determined by the balance of fluid velocity and inter-phase momentum exchange. The conduction mechanism is designated to pump the liquid film from the top portion of the tube where the gravity body force plays minimal role. The interface profile, liquid condensate flow structure, and heat transfer rate under operating of one electrode pair and two electrodes pairs are investigated. The heat transfer performance for various operating conditions is also studied in this paper.
Variable Structure Control of a Ferromagnetic Shape Memory Alloy Actuator
Authors: Tan Honghao , Elahinia Mohammad H.
Published: May 2009

Ferromagnetic Shape Memory Alloys (FSMAs) like Ni-Mn-Ga have attracted significant attention over the last few years. As actuators, these materials offer high energy density, large stroke, and high bandwidth. These properties make FSMAs potential candidates for the new generation of actuators. The preliminary dynamic characterization of Ni-Mn-Ga illustrates nonlinear behaviors including hysteresis, saturation, first cycle effect, and dead zone. In this paper, the positioning control of a FSMA actuator is investigated. To this end, a dynamic model is presented for a Ni-Mn-Ga linear actuator. The actuator model consists of the following subsystems: a field-induced strain model of Ni-Mn-Ga, an elastic deformation model of the Ni-Mn-Ga element, a dynamics/kinematics model, and an electromagnetic dynamics model. The material damping effect is also included in the model by the Kelvin-Voigt model. A Proportional-Integral-Derivative (PID) position control algorithm is developed based on the model. Simulation result indicates poor performance of the PID controller. This is mainly due to nonlinearities in the actuator behavior. To address this problem, a variable structure controller is developed. Simulations with the variable structure controller show that this algorithm can improve the performance of the actuator with respect to rising time and positioning accuracy.
SIFs for Radial Cracks in Annular Discs Under Internal and External Shrinkage Pressure and Constant Angular Velocity
Authors: Sakhaee-Pour A. , Gowhari-Anaraki A. R. , Hardy S. J.
Published: May 2009

Finite element method has been implemented to predict stress intensity factors (SIFs) for radial cracks in annular discs under constant angular velocity. Effects of internal and external uniform pressure on the SIFs have also been considered. Linear elastic fracture mechanics finite element analyses have been performed and results are presented in the form of crack configuration factors for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations. The extensive range of crack configuration factors obtained from the analyses is then used to develop equivalent prediction equations via a statistical multiple non-linear regression model. The accuracy of this model is measured using a multiple coefficient of determination, R2, where 0 ≤ R2 ≤ 1. This coefficient is found to be greater than or equal to 0.98 for all cases considered in this study, demonstrating the quality of the model fit to the data. These equations for the SIFs enable designers to predict fatigue life of the components easily.
Cross Flow Boiling in Micro-Pin Fin Heat Sinks
Authors: Krishnamurthy Santosh , Peles Yoav
Published: May 2009

Flow boiling of water across a bank of circular staggered micro pin fins, 250 μm long and 100 μm diameter with pitch-to-diameter ratio of 1.5, was experimentally studied for mass fluxes ranging from 346 kg/m2s to 794 kg/m2s and surface heat fluxes ranging from 20 W/cm2 to 350 W/cm2. The local two-phase heat transfer coefficients were measured using thermistors located along the flow path of the channel. The flow was visualized and classified as vapor slug and annular flow patterns. Based on the observed flow patterns, the dominant heat transfer mechanism during boiling process was assumed to be convective boiling.
Research Into Durability Prediction Technology Taking Into Account Multiple Plate Clutch Wear Properties
Authors: Saito Toshihiro , Kotegawa Tamotsu , Matsuura Yoshiteru , Tanaka Seiichi , Ohtsuki Kimikazu
Published: May 2009

To increase the durability of multiple-plate clutches used in automatic transmissions, attention was focused on the wear history of the facing material. Measurements have confirmed that correlations can be observed between initial wear and disk contact pressure when the clutch is engaged, and between steady wear and plate temperature. Next, simulation technology was developed to quantify the disk contact pressure and plate temperature. When simulated contact pressure distribution and temperature distribution were used to establish correlations with durability wear, good proportional relationships were found in both cases. It was also found that when clutch specifications and driving conditions were varied, the gradient of the correction also varied, but the correlation remained proportional as long as the same facing material was used. The gradient was ranked as a wear property specific to the facing material. By determining the wear property of the facing material, it was possible for the first time to predict wear condition in a test of the clutch as an independent part.
Body Force Method for Melan Problem With Hole Using Complex Potentials
Authors: Manjunath B. S. , Ramakrishna D. S.
Published: May 2009

The problem of a half plane with concentrated load acting at an interior point is known as melan problem as shown in Fig.1. In the present case melan problem with hole is considered as shown in Fig.2. The body force method is developed for the above case. Body force method is a method based on principle of superposition [1]. In the body force method the actual condition is treated as an imaginary condition i.e. the semi-infinite plate with hole and interior load is treated as a plate without hole; the actual hole is regarded as imaginary on whose periphery boundary forces are applied. The problem is solved by superimposing the stress fields of the boundary forces and concentrated force acting at an arbitrary point to satisfy the prescribed boundary conditions so that the stress condition of the actual plate is approximately equal to that of the imaginary plate [2]. The complex variable method of stress analysis is a versatile technique for stress analysis Problem. The formulas for melan problem are derived and described [3]. Complex potentials are used for stress analysis.
Non-Linear Analysis of Out-of-Phase Instabilities in Advanced Heavy Water Reactor
Authors: Bahga S. S. , Doshi J. B.
Published: May 2009

In this paper we study thermally induced instabilities in Indian Advanced Heavy Water Reactor (AHWR). One dimensional homogeneous equilibrium model has been used to simulate the two-phase flow. The nonlinear mass, momentum and energy conservation equations are solved along the characteristic directions by using implicit finite difference scheme. The virtue of this scheme is that it handles the boundary conditions naturally. This scheme is fast because the time steps can be greater than that given by Courant-Friedrichs-Lewy condition. The numerical scheme is sufficiently general and can handle axially varying heat flux and different combinations of inlet and exit boundary conditions of enthalpy, mass flux and pressure and multiple channels. No assumptions regarding constant properties and in-compressibility have been taken. The one dimensional fuel heat transfer model was then coupled to the thermal-hydraulics model to analyze out-of-phase instabilities in AHWR. Out-of-phase oscillations are studied by considering two parallel boiling channels. Further effects of radial power distribution, inlet orificing and axial power distribution were considered.
The Sustainable House: A Framework for Organization Development for Sustainability (ODFS)
Authors: Marksberry Phillip W.
Published: May 2009

It is agreed that the main factors in sustainability are the environment, economy and the society; however, it is still largely undecided how organizations can best transform themselves to incorporate consideration of these factors. Successful integration of sustainability into the business plan will require an organization-wide effort. A proven technique in organizations for creating systemic change is Organization Development (OD). Unfortunately, OD has not yet been extended to include the key areas of sustainability and organized within a practical framework for implementation. This paper extends OD for Sustainability (ODFS), creating a conceptual model called here “the Sustainable House.” The conceptual model clarifies sustainable organizational characteristics and interdisciplinary interactions. The PDCA (Plan-Do-Check-Act) approach is introduced as a framework for implementing ODFS. It is demonstrated that ODFS requires a substantial support structure and a dynamic learning process for accumulating knowledge. This article identifies key areas of ODFS and provides a conceptual model and a framework for operationalizing sustainability into organizations. Various sustainable tools, methodologies, interacting concepts and gaps in ODFS are also included.
Nanometer Range Closed-Loop Control of a Stepper Micro-Motor for Data Storage
Authors: Patrascu Mihai , Stramigioli Stefano , de Boer Meint , Krijnen Gijs
Published: May 2009

We present a nanometer range, closed-loop control study for MEMS stepper actuators. Although generically applicable to other types of stepper motors, the control design presented here was particularly intended for one dimensional shuffle actuators fabricated by surface micromachining technology. The stepper actuator features 50 nm or smaller step sizes. It can deliver forces up to 5 mN (measured) and has a typical range of about 20 μm. The target application is probe storage, where positioning accuracies of about 10 nm are required. The presence of inherent actuator stiction, load disturbances, and other effects make physical modeling and control studies necessary. Performed experiments include measurements with open- and closed-loop control, where a positioning accuracy in the order of tens of nm or better is obtained from image data of a conventional fire-wire camera at 30 fps.
Parametrical Study of the Flat-Tube and Pin Fin Heat Exchangers
Authors: Pascu Maria , Sahiti Naser , Durst Franz
Published: May 2009

The main objective of the present work was the derivation of heat transfer and pressure drop characteristics for pin fins which could be applied in heat exchangers used in the automobile industry. For this, 34 models of pin fin heat exchangers, characterized by a pin diameter of 0.35 mm, with both inline and staggered arrangements, were numerically investigated. The numerical results were validated through various comparison and validation procedures. The best performing pin fin configuration was determined by employing the performance plot: heat transfer per unit volume (or per unit area, if the pin height is constant) versus the energy input reduced to the same parameter as the heat transfer (volume or area). The heat exchanger performance plot showed that, for the investigated flow length, the staggered pin fin configuration performs better when compared to the inline arrangement. In order to prove the industrial applicability of these results, a louvered fin heat exchanger, commonly used as a car radiator, was experimentally investigated. A comparison of the best performing pin fin heat exchanger with the louvered fin model revealed an enhancement in the heat transfer of the pin fin model of 35%.
Viability of a Eutectic–Thermoelectric Fuel Conditioning System Concept for Diesel Engines
Authors: Schriefer Timothy J. , Bailey Margaret B.
Published: May 2009

Internal combustion engines, which run on hydrocarbon fuels, experience difficulty upon engine start-up in extreme cold weather. As ambient temperature decreases below the fuel cloud point and beyond, paraffin form in the fuel and eventually clog the fuel filter. This problem becomes more pronounced when the engine in question is a Diesel and the fuel utilized is biodiesel. As an alternative fuel source, biodiesel has many advantages; however its cold weather performance is worse than even conventional diesel fuel. As biodiesel becomes more integrated into the world’s energy usage, one of the systems within a Diesel engine requiring further investigation is its fuel conditioning system. This paper describes current research aimed at the development of a fuel conditioning system that utilizes several technologies while decreasing the amount of electrical energy required for operation. The system utilizes a eutectic-thermoelectric (E-TE) combination which consists of a eutectic compound based latent heat storage device with adjacent thermoelectric elements to transfer heat from within the engine into the fuel filter, thus diminishing the amount of electrical energy typically required for the fuel conditioning process. Simulations of the E-TE system are conducted while operating within three different modes (start-up, heat storage, and electrical energy generation), while a supervisory controller distinguishes between desired operational status. The research activities and findings reported within this paper include development of a representative E-TE system model which consists of several components including a set of control laws, and a supervisory system. Model development and preliminary results for the phase one model are discussed herein.
Catalytic Effects of Methane/Air and Propane/Air Mixtures Using a Platinum Catalyst in a Stagnation Point Flow Configuration
Authors: Wiswall James T. , Wooldridge Margaret S. , Im Hong G.
Published: May 2009

A stagnation-point flow burner facility has been developed to provide a canonical framework to study the catalytic surface reactions of premixed combustion systems. The configuration serves as an important platform to investigate the interaction between homogeneous and heterogeneous reactions with an independent control of the characteristic residence time scales. Methane/air, and propane/air mixtures were examined with or without the presence of a platinum catalyst located at the stagnation surface. The effects of oxidizer composition and nitrogen dilution were examined. Depending on the operating conditions, either a stable gas-phase flame is established between the nozzle and the stagnation surface or the unburned reactant mixture directly impinges on the heated surface. In the former case, the extinction limits of the gas-phase flame were measured for various equivalence ratios and flow conditions. In the latter case, the heat release resulting from the surface reaction was quantified by measuring the surface temperature of the stagnation plate. The results are discussed in terms of the relative contributions of the gas-phase and the surface reaction chemistry to the burner performance. Understanding gained from this study will provide insights into the role of catalytic reactions in extending the flammability of compact combustors subjected to excessive surface heat loss.
Oxidation and Volatilization of Silicide Coatings for Refractory Niobium Alloys
Authors: Novak Mark D. , Levi Carlos G.
Published: May 2009

Degradation mechanisms relevant to hypersonic environments have been investigated for silicide-coated niobium alloys. To assess the suitability of silicide coatings for possible leading edge, scramjet combustor, and vehicle acreage applications, tests were conducted over a range of oxygen and water vapor partial pressures. X-ray diffraction was used to characterize the composition of oxide phases. Chemical compositions of both the coatings and resulting oxides have been examined using energy dispersive x-ray analysis. Partial pressures of oxygen and water vapor have been found to influence the oxide composition, which may include silica, chromia, iron niobate, and chromium niobate phases. The formation of volatile oxide and hydroxide species also affects oxidation behavior and coating performance. Thermodynamic models of oxidation and volatilization are used to interpret experimental results.
Generation and Tracking of Sinusoids for Shake Table Control via Extremum Seeking
Authors: Siranosian Antranik A. , Krstic Miroslav , Bement Matt
Published: May 2009

We present the design and implementation of an extremum seeking based shake table controller, where the goal is to generate and track a sinusoid of given amplitude, frequency and phase. Advantages of an extremum seeking based controller over previous shake table controllers are that it is a modular design with respect to linear and nonlinear shaker-specimen dynamics, and with respect to different shaker-specimen combinations. In addition, it can handle time varying dynamics due to possible changes in the specimen during testing. Also, it does not require a plant model to operate, but has the capability to take advantage of minimal knowledge of the plant to improve transient performance.
A Fuzzy Logic Based Decision Making System for Fusing Measurements From an E-Puffer and E-Sniffer Sensing Systems for Detecting Explosives
Authors: Chitikeshi Sanjeevi , Mahajan Ajay , Chu Tsuchin , Don Jarlen
Published: May 2009

This is primarily a concept paper and describes a decision making system that fuses the output from cold plasma based E-Puffer and E-Sniffer sensing systems to reliably detect explosive traces. This paper describes research and development of a novel non-contact method to detect explosive bearing personnel, baggage and vehicles that is based on the integration of a multitude of key technologies, primarily cold/atmospheric plasma and pattern recognition/decision making capabilities. This work will ultimately lead to a viable system that can be installed in doorways of buildings, garages, baggage carousals, etc. that will trigger a positive response when detecting explosive traces on personnel, bags or vehicles going thru a doorway. This paper describes the basic product concept and provides preliminary results of the fusion process from a simulated data set of output measurements from the two orthogonal measurement systems.
Finger Mechanism of a Haptic Glove for Force Feedback in Virtual Environments
Authors: Bullion Conrad , Dazkir Goktug A. , Gurocak Hakan
Published: May 2009

In this paper we present details of a finger mechanism designed as part of an ongoing research on a force feedback glove. The glove will be used in virtual reality applications where it will provide force feedback to the user as he grasps virtual objects. Haptic (touch and force) feedback is an essential component to make the simulated environment feel more realistic to the user. The design employs an innovative mechanism that wraps around each finger. Each mechanism is controlled by one cable. By controlling the tension on the cable and the displacement of the cable, we can control the amount of force applied to the user’s finger at any given position of the mechanism. The glove can provide distributed forces at the bottom surface of each finger while reducing the number of actuators and sensors. First kinematic and force analysis of the mechanism along with experimental verifications are presented. Following description of an experiment to determine grasping forces, we conclude with an overview of the next steps in this research.
Ultrasonic Welding of Aluminum 6111: Reliability and Maintainability Study of Robot Mounted C-Gun Welding System
Authors: Mariam Hasetetsion G. , Baer J. Rick , Scholl David J. , Cooper Ronald P. , Wilkosz Daniel E. , Grima Anthony J. , Reatherford Larry V.
Published: May 2009

Ultrasonic metal welding (USW) is a promising joining method for aluminum automotive body construction applications. During USW, aluminum weldments are joined together by applying high frequency vibrations while holding the parts together with a moderate clamping force. In an effort to further the development of USW for high volume robotic body construction applications, a reliability and maintainability study was performed using a robotic welding cell installed in the Ford Research and Innovation Center. The robot was equipped with a modified Sonobond ultrasonic metal welder, which was mounted on a C-frame. The study consisted of welding fully overlapped 550 mm × 350 mm × 0.9mm thick AA6111-T4 aluminum panels with 330 welds on each panel until 100,000 welds were made. Consistency in welder operation was monitored by welding fully overlapped AA6111-T4 aluminum strips (25mm wide × 550 mm long × 0.9mm thick) at the end of each day’s welding and then tensile testing the strips in a T-peel configuration. There was no statistical difference in average T-peel strength over the course of the 100,000 weld study. There was also no degradation noted in lap shear failure loads between samples welded at the end of the 100,000 weld study and those generated before initiation of the study. Reliability of the USW process during this study was monitored by periodic inspection of the robot and welder joints, attachments, fittings, tip, anvil, clamps, cables, etc. Only very minor wear of the welder tip and anvil contact surfaces were noted after the study was completed. However, during the study, after 82,000 welds a small piece of aluminum was removed from between the tip grooves, even though the weld strength was unaffected by the presence of the aluminum. There were no failures of any mechanical or electrical parts during the study. In addition, primary voltage and current signals of the ultrasonic welder’s power controller were periodically recorded during the weld study and it was determined that there was no change in the electrical behavior of the welder.
Modeling and Experimental Verification of the Contact Resistance of a Novel Anisotropic Conductive Adhesive
Authors: Ramkumar S. Manian , Srihari Krishnaswami
Published: May 2009

The need to eliminate lead-based materials as a means of interconnection has renewed the electronics industry’s interest in using conductive adhesives for component attach, especially Anisotropic Conductive Adhesives (ACA). Typical ACAs require the application of pressure during the curing process, to establish the electrical connection and also to capture a monolayer of conductive particles between the mating surfaces. The novel ACA discussed in this paper uses a magnetic field to align the particles in the Z-axis direction during curing and eliminates the need for pressure. The application of the magnetic field allows for the formation of conductive chains between the mating surfaces, thereby eliminating lateral conductivity. This uniqueness of the novel ACA also accommodates for any coplanarity error and the formation of effective Z-axis conductivity, with a variety of lead and bump shapes. The novel ACA also enables mass curing of the adhesive, eliminating the need for sequential assembly. As part of the study presented in this paper, the conductive chains were modeled as series and parallel resistor networks in an insulating adhesive matrix. The number of particles in the chain and hence the number of interfaces between the particles is found to influence the initial contact resistance of the joints. The interfacial resistance is derived from the experimental run. Area array packages with and without bumps, reveal varying contact resistances as indicated by the model and experiment. This paper will present a model for the conductive chain formation in the novel ACA, and discuss the experimental results obtained to verify the joint contact resistance.
3D Microstructure Reconstructions of Solid Oxide and Proton Exchange Membrane Fuel Cell Electrodes With Applications to Numerical Simulations of Reacting Mixture Flows Using LBM
Authors: Kasula Bhavani V. , Mercado Leslie , Asinari Pietro , von Spakovsky Michael R.
Published: May 2009

Computational modeling of fuel cell electrode-catalyst layers is an important tool in understanding the different electrochemical reactions and transport phenomena occurring within fuel cell electrodes. Proper modeling of this layer is required for an accurate prediction of cell behavior which in turn can be used for the development of more efficient fuel cells. In macroscopic CFD approaches such layers are typically modeled as infinitely thin interfaces populated by sources and sinks or as very thin homogeneous porous layers. However, these layers are neither infinitely thin nor homogeneous and, thus, modeling in this fashion leads to a loss of information about the microstructure and its varying effects on the reacting mixture flows which pass through and into the structure. Thus, the utility of relying only on such macroscopic representations limits the general applicability of these macroscopic models as tools for design and for predicting fuel cell performance over a wide range of conditions. Furthermore, such macroscopic models cannot aid in the design of the electrode-catalyst layer itself. In order to address this latter point, a microscopic/mesoscopic modeling approach can be used, e.g., the Lattice Boltzmann Method (LBM), which models the reacting mixture flow through the porous microstructure of the electrode-catalyst layer. However, to do so requires reconstructing the porous geometry of this layer which can be done by using 2D microscopic images of cross-sections of the layer to generate 3D geometries from, for example, stochastic models which are relatively cost efficient and lead to similar structures with approximately the same characteristics of porosity, catalyst loading, three-phase boundaries, etc. as the original structure. Two such 3D reconstruction methods, i.e. one based on the granulometry law (one-point statistics) and the other on two-point statistics, are applied to a 2D SEM (scanning electron microscope) image of an SOFC electrode-catalyst layer and to the 2D SEM and TEM (transmission electron microscope) images for such a layer in a PEMFC. Results for these reconstructions are presented as are results for reacting mixture flow simulations through the two different reconstructed 3D SOFC structures using a 3D LBM approach. The development and application of a 3D LBM model for two-phase reacting mixture flows in PEMFC electrode-catalyst layer structures is in progress and will be reported in a future paper.
Exergy Methods Applied to the Integrated Mission-Level Analysis and Optimization of Hypersonic Vehicle Concepts
Authors: Markell Kyle C. , Brewer Keith M. , von Spakovsky Michael R.
Published: May 2009

The results of the application of an exergy-based method to highly dynamic, integrated hypersonic vehicle concepts are presented. Conventional aircraft systems and sub-systems traditionally are designed relying heavily on rules of thumb, individual experience, and rather simple, non-integrated tradeoff analyses, which are highly dependent on the evolutionary nature of vehicle development. In contrast, hypersonic vehicles may contain new sub-systems and revolutionary concepts for which there is no existing database to support an evolutionary synthesis/design approach. Thus, a simple tradeoff analysis becomes virtually impossible, particularly in light of the highly integrated, non-linear relationship between hypersonic vehicle sub-systems and the complexity of the missions involved. Therefore, the departure from existing databases and experience levels requires an integrated approach and a common metric for the synthesis/design of hypersonic vehicles to achieve an optimal synthesis/design. To that end, an exergy-based mission integrated methodology is introduced and compared to traditional measures (including a non-integrated approach) by applying these to the synthesis/design and operational optimization of a hypersonic vehicle configuration comprised of an airframe and a propulsion sub-system (consisting of inlet, combustor, and nozzle components). Results of these optimizations are presented and include a quantification of all vehicle losses in terms of exergy lost or destroyed, providing a common metric for the vehicle designer to identify where the largest improvements in vehicle performance can be made. Furthermore, via a number of parametric studies, the impacts of the design and operational decision variables on exergy destruction are discussed.
An Improved Solution of the Transient Response of Convective Radial Fins
Authors: Das S. , Razelos P.
Published: May 2009

This work is devoted to the study of the convective radial fin’s transient response. Although, the steady-state fin analysis has attracted considerable attention for a very long time, the interest in the transient response started in the last quarter of the past century. Several publications have appeared since, either analytical, using the 1-D, and the 2-D conduction models, or experimental. Perusing the pertinent literature, we have observed that, in all previous published papers the authors treat the transient response of extended surfaces, or fins, like regular solids. However, fin endeavors rest on certain fundamental concepts, leading to some simplified assumptions, which we shall briefly discuss in the following sections, which allows using the 1-D conduction model, and their effect on steady-state operation. In addition, the bulk of the previous works refer to longitudinal and pin fins, while very few studies treat radial fins. Therefore, a re-examination and revision of the radial fin analysis is needed. The authors are indeed indebted to the pioneering work by previous researchers on this topic who have opened new avenues in the field of extended surface heat transfer. In this work, we present a new method, developed recently, which employs a new spatial coordinate system. It is also our intention to offer a different point of view to this problem, from those presented in the literature. The solutions presented here, rest on the previously mentioned certain fundamental concepts developed recently. In the following sections we show step by step, how the existing pertinent equations and formulae of the circular fins’ transient response, are transformed to new simpler forms, expressed in terms of certain more appropriate dimensionless parameters, from those presented in previously published papers. We confine our analysis to the constant thickness radial fins subject to specific boundary conditions. For reasons of comparison, the solution of a previous example cited in literature is presented. We also give a logical explanation as to what is meant by “the time required for transient response to attain the steady-state condition”. In addition, roots of the transcendental equation for the transient solution, that were not reported before are presented.