bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Dynamics Investigation of Carbon Diffusivity in Metal Nanoparticles During CVD-Based Nanotube Fabrication Process
Authors: Hosseini Mahmoud Reza , Jalili Nader
Published: April 2008

In this paper, molecular dynamics technique is utilized to investigate carbon molecules diffusivity into iron oxide nanoparticles such as FeO and Fe2O3. Such nanoparticles can be used during carbon nanotube (CNT) synthesis process in a chemical vapor deposition (CVD) system. Several simulations are conducted in the atmospheric pressure condition and for different temperatures ranging from 500 to 1100°C, which is common range for multi-walled and single-walled CNT (MWCNT and SWCNT) fabrication. The mean square displacement (MSD) diagrams and their corresponding diffusivity of the carbon molecules into the nanoparticles are then plotted. The results are compared with those obtained after adding silicon molecular structure to the each nanoparticle as substrate. The results From NPT/NVE (pressure constant-temperature constant/velocity constant-energy constant) simulations show that for each nanoparticle, the diffusivity increases as higher temperatures considered in the simulation. However, the corresponding diffusivity rate doesn't necessarily increase. In the diffusivity diagrams, three distinctive temperature regions are observed. In the temperature regions where MWCNT and SWCNT are commonly produced, decreasing in diffusivity rate is observed, while in transition region where CNTs change from multi-walled to single-walled, the diffusivity increases for both simulated metal nanoparticles. Finally, by investigating and comparing diffusivity diagrams of each nanoparticle, before and after adding silicon as substrate, it is observed that the effects of silicon layer decreases the amount of carbon molecules diffusivity. This decrease is more considerable in higher temperatures. The obtained information from this study helps to understand the growth rate and formation mechanism of MWCNT/SWCNT and their relationship with carbon diffusivity in metal nanoparticles in great detail which are important keys in controlling nanotube properties.
A Comprehensive Off-Tuning Analysis of Damping Controlled Tuned Vibration Absorbers
Authors: Koo Jeong-Hoi , Ahmadian Medhi
Published: April 2008

The main purpose of this study is to offer a comprehensive off-tuning analysis of a semi-active tuned vibration absorber. A base-excited, single-degree-of-freedom structure with a tuned vibration absorber (TVA) model is adapted as the baseline model for our analysis. Moreover, a non-model based groundhook control (displacement based on-off control or "On-off DBG") is used to control the damping in the TVA. In order to study the effect of off-tuning, numerical models of the damping controlled TVA along with its equivalent passive TVA were developed. Using these models, the optimal tuning parameters of both TVA models were obtained based on minimization of peak transmissibility. The two optimally tuned models were then "off-tuned" by varying the primary structure's mass, stiffness, and damping. Using the peak transmissibility reduction criteria, the dynamic performances of the off-tuned TVAs were evaluated. The results indicate that the peak transmissibility of the semi-active TVA is about 20% lower than that of passive, implying that the semi-active TVA is more effective in reducing vibration levels. The results further indicate that the semi-active TVA is more robust to changes in primary structure mass and stiffness. In summary, the offtuning analyses of the semi-active TVA revealed the practical benefits of using it over the passive counterpart to structures subjected to changes in system parameters.
Fuzzy Adaptation and Matrix Implementation of Smith Predictor for Dynamic Matrix Control in Continuous Processes With Large Dead Time
Authors: Durango Nestor D. , Sanjuan Marco E.
Published: April 2008

Industrial processes with large and varying dead time are difficult to control and sustain a good controller performance over a wide range of process conditions. Since Dynamic Matrix Control is based on sampled-data model identification, and online inverse calculations are avoided, adaptation of the original model is not performed in commercial solutions. This paper presents an on-line adaptive form of the DMC control based on the Smith Predictor compensation strategy for processes with large dead time that does not require recalculating the inverse of the process matrix. The matrix form of the Smith Predictor was modeled in software and implemented in a lab scale continuously stirred tank reactor, where actual process noise was present. The adaptive algorithm included a Mamdani-type fuzzy inference system to modify the size of the dead time matrix. Implementation results demonstrated the algorithm ability to compensate for large dead time emulating the response of the non-delayed process. At the same time, the controller is able to adjust the size of the delay based on process response.
Determination of Gap Surface Temperature Distribution in Axial Piston Machines
Authors: Ivantysynova Monika , Huang Changchun , Japing Andreas J.
Published: April 2008

The paper presents a new method for determination of gap surface temperature distribution in axial piston machine. A special thermal model has been developed to consider the energy dissipation in the lubricating gap, the heat convection of the fluid and the heat conduction through the rotating group assuming constant case and port temperatures. The energy dissipation in the gap is calculated using gap flow model considering non-isothermal flow, surface deformation and micro motion of parts. The calculated surface temperatures are further used as boundary parameters for the 3D non-isothermal gap flow model. The developed thermal model has been implemented in a new module of the CASPAR simulation software. The program CASPAR has been developed in the research group of the authors (Wieczorek and Ivantysynova 2002, Huang and Ivantysynova 2003). The model will be explained and simulation results will be discussed and compared with measurements. A special single piston test pump has been designed and implemented on a special test rig allowing to measure surface temperature distribution, dynamic pressure field in the gap between piston and cylinder and leakage. The paper will present a comparison of calculated and measured surface temperature fields.
Direct Numerical Simulation of Particle-Laden Turbulent Flows in Two-Way Coupling Using Equilibrium Assumption
Authors: Shotorban Babak , Balachandar S.
Published: April 2008

A two-fluid approach is proposed for direct numerical simulation of particle-laden turbulent flows in two-way coupling through equilibrium assumption that is valid for particles with sufficiently small time constants. Making this assumption, a Eulerian velocity field is calculated for the particle phase through a truncated series expansion in terms of the velocity and acceleration of the fluid phase and the gravity acceleration. The transport equation of the Eulerian concentration field of particles (particle volume fraction) is solved along with the fluid phase equations for which the effect of particles on the fluid phase is taken into account through source terms in the momentum equations. For the assessment purposes, particle-laden isotropic turbulence is simulated. The results obtained through this approach are compared against those obtained by a trajectory approach in which the particle equations are solved in the Lagrangian framework. It is shown that there is a good agreement between the results obtained by the proposed two-fluid model and the trajectory approach by comparing the mean turbulent kinetic energy and its dissipation rate of the fluid phase as well as their spectra.
Tolerance Variation and Passive Alignment in Modular, Polymer Microfluidic Devices
Authors: You Byoung Hee , Park Daniel S. , Mock Christopher W. , Caceres Wilfredo M. , Nikitopoulos Dimitris E. , Soper Steven A. , Murphy Michael C.
Published: April 2008

Simulations and experiments to assess the predictability of dimensional and locational tolerances of passive alignment structures on injection molded microfluidic components were performed. A center-gated disk with microscale assembly features, to aid metrology, was reproduced using injection molding. The feature dimensions were 100, 200, 300, and 400 μ. Dimensions of the features were measured using optical profilometery and optical microscopy. Simulations using a commercial package overestimated replication fidelity. Mold surface temperatures and injection speeds significantly affected the replication fidelity as the ratio of surface area to volume increased. The location of better replication fidelity, at each mold surface temperature, moved from the edge of the mold cavity to the injection point as the mold surface temperature increased from 100°C to 150°C. Therefore, process parameters and the design of a mold have to be considered for successful replication of the features.
Capturing Planer Tire Enveloping Properties Using Static Constraint Modes
Authors: Ferris John B.
Published: April 2008

This work establishes a new method for predicting the deformed shape of a tire with unilateral geometric constraints imposed by the road surface. Specifically, a method is developed for determining the static constraint mode that captures the planer enveloping properties of a tire for uneven road surfaces. This new method uses a recursive algorithm for determining which geometric constraints are active. A simple planer tire model, described by a linear ring on an elastic foundation, is used to demonstrate the method. The result of this method is a set of active geometric constraints on the tire and the static constraint modes that compose the deflection of the tire along its circumference. The success of the method is demonstrated by an example. This work forms the basis for developing nonlinear dynamic tire models that accurately account for active, unilateral, geometric constraints on the tire.
Constructing a Design Knowledge Base Using Natural Language Processing
Authors: Sundararajan V.
Published: April 2008

Mechanical engineering, like other engineering disciplines, has witnessed maturation of various aspects of its domain, obsolescence of some areas and a resurgence of others. With a history of over 200 years of continuous research and development, both in academia and industry, the community has generated enormous amounts of design knowledge in the form of texts, articles and design drawings. With the advent of electronics and computer science, several of the classical mechanisms faced obsolescence, but with the emergence of MEMS and nanotechnology, the same designs are facing a resurrection. Research and development in mechanical engineering would derive enormous benefit from a structured knowledge-base of designs and mechanisms. This paper describes a prototype system that synthesizes a knowledge-base of mechanical designs by the processing of the text in engineering descriptions. The goal is to construct a system that stores and catalogs engineering designs, their sub-assemblies and their super-assemblies for the purposes of archiving, retrieval for launching new designs and for education of engineering design. Engineering texts have a relatively clear discourse structure with fewer ambiguities, less stylistic variations and less use of complex figures of speech. The text is first passed through a part-of-speech tagger. The concept of thematic roles is used to link different parts of the sentence. The discourse structure is then taken into account by anaphora resolution. The knowledge is gradually built up through progressive scanning and analysis of text. References, interconnections and attributes are added or deleted based upon the nature, reliability and strength of the new information. Examples of analysis and resulting knowledge structures are presented.
Modeling and Simulation of a Cold-Engine Test Stand Driveline With Experimental Comparisons
Authors: Gul Kamran A. , Adams Douglas E.
Published: April 2008

There is a need to develop cold-engine test stands for use in diagnosing cylinder faults and measuring gear noise given the new quieter fuel injection systems in modern engines. When engines run hot, these characteristics are not easily measured. By running the unfired cold-engine as a load using an electric motor and driveline, torque measurements can be used to diagnose assembly faults, damage and noise characteristics. In this paper, two cold-engine test stand drivelines are considered. Both stands experience large torsional vibrations excited by the various engine harmonics. Engine fault diagnosis becomes a challenge when these torsional vibrations degrade the measured torque signals. To solve this problem of torsional vibrations, an engine test stand model is developed to understand the system dynamics and analyze the free and forced response characteristics of the system. The model is used to predict the impact of the changes made to the test stand driveline and the trends observed in the simulation results are compared with experimental results for model validation. It is shown that based on model sensitivity analysis the changes made to the driveline parameters help to reduce the amplitude of the driveline resonances considerably. The developed model can be used to design a cold test stand for production diagnostics.
Nanomanipulation Modeling and Simulation
Authors: Mualim Yanto , Ghorbel Fathi H. , Dabney James B.
Published: April 2008

A novel approach to better model nanomanipulation of a nanosphere laying on a stage via a pushing scheme is presented. Besides its amenability to nonlinear analysis and simulation, the proposed model is also effective in reproducing experimental behaviors commonly observed during AFM-type nanomanipulation. The proposed nanomanipulation model consists of integrated subsystems that are identified in a modular fashion. The subsystems consistently define the dynamics of the nanomanipulator tip and nanosphere, interaction forces between the tip and the nanosphere, friction between the nanosphere and the stage, and the contact deformation between the nanomanipulator tip and the nanosphere. The main feature of the proposed nanomanipulation model is the Lund-Grenoble (LuGre) dynamic friction model that reliably represents the stick-slip behavior of atomic friction experienced by the nanosphere. The LuGre friction model introduces a new friction state and has desirable mathematical properties making it a well-posed dynamical model that characterizes friction with fidelity. The proposed nanomanipulation model facilitates further improvement and extension of each subsystem to accommodate other physical phenomena that characterize the physics and mechanics of nanomanipulation. Finally, the versatility and effectiveness of the proposed model is simulated and compared to existing models in the literature.
A Study on the Thermal Behavior of Electrothermal Microactuators Due to Various Voltage Inputs.
Authors: Mayyas Mohammad , Shiakolas Panos
Published: April 2008

The steady state temperature profiles of U- and I-shaped electrothermal microactuators are analytically derived. The temperature profiles could be used to evaluate the performance sensitivity of the microactuator due to various parameter changes. In this work, the analysis assumes an unpackaged silicon microactuator with an air gap between the actuator and substrate and the profiles are evaluated for various input voltage amplitudes. It was found that at low voltage inputs the temperature profile is exponential in nature with the failure being due to thermo-structural stresses and/or structure melting. At voltages larger than a critical value, a combined sinusoidal and exponential temperature profile is observed with the failure being strongly due to structural melting as well. However, higher voltage excitation causes a fully distributed sinusoidal temperature profile. In this mode, failures occur at different locations and due to high localized thermal stresses causing the temperature to exceed the material melting point. The behavior of U- and I-shaped microactuators based on silicon on insulator (SOI) fabrication and femtosecond laser micromachining was experimentally examined with the results corroborating the conclusions drawn from the analysis.
Evaluating the Failure Pressure of Bilayer Lipid Membranes by a Controllable Electromagnetic Test Fixture
Authors: Hopkinson David P. , De Vita Raffaella , Leo Donald J.
Published: April 2008

The motion of plants is the inspiration for a new biomimetic actuator that uses fluid transport across a bilayer lipid membrane (BLM) to create internal pressure and cause displacement in the actuator. In order for the actuator to be viable the BLM must be able to withstand this internal pressure without failing. In a previous study, BLMs were formed over a porous polycarbonate substrate and a hydrostatic pressure was applied to the BLM and gradually increased until failure. This test was performed over different pore sizes to measure the failure pressure of the BLM as a function of pore radius. To improve this series of experiments, a new test fixture has been developed that will allow for a more precise measurement of the failure pressure as well as an expanded range of failure pressures. It is computer controlled, using an electromagnetic actuator to pressurize the BLMs and a pressure transducer to monitor pressure. The design scheme for this test fixture and some preliminary results will be presented.
Robust Design of RF-MEMS Cantilever Switches Using Contact Physics Modeling
Authors: Shalaby Mohammed , Wang Zhongde , Chow Linda L. W. , Jensen Brian D. , Volakis John L. , Kurabayashi Katsuo , Saitou Kazuhiro
Published: April 2008

This paper presents the design optimization of a RF MEMS direct contact cantilever switch for minimum actuation voltage and opening time, and maximum power handling capability. The design variables are the length and thickness of the entire cantilever, the widths of the sections of the cantilever, and the dimple size. The actuation voltage is obtained using a 3D structural-electrostatic FEM model, and the opening time is obtained using the same FEM model and the experimental model of adhesion at the contact surfaces developed in our previous work. Since the precise control of the contact resistance during the micro machining process is practically impossible, the power handling capability is estimated as the ratio of the RMS power of the RF current ("signal") passing through the switch to the contact temperature ("noise") resulting from the possible range of the contact resistance. The resulting robust optimization problem is solved using a Strength Pareto Evolutionary Algorithm, to obtain design alternatives exhibiting different trade-offs among the three objectives. The results show that there exists substantial room for improved designs of RF MEMS direct-contact switches.
Scaling Analysis and a Critical Thickness Criterion for Thermosetting Composites
Authors: Secord Thomas W. , Stelson Kim A. , Mantell Susan C.
Published: April 2008

In composites processing, the combination of thickness, mold temperature, and resin kinetics can lead to temperature overshoot within a part during cure. In this paper, the interplay between these variables was considered to establish a critical thickness separating parts having large overshoots from parts having small overshoots. The one-dimensional heat equation with an autocatalytic relation for curing was used to model the process. The equations were placed in dimensionless form using a scaling analysis. Five dimensionless groups were identified. Two of these groups were found to affect the overshoot of the temperature: the modified Damko¨hler number Da*, which distinguishes thin and thick composites and the dimensionless temperature ramp rate [Equation]trise, which depends on the boundary condition and heat transfer characteristics of the composite. To validate the scaling analysis, a finite difference model was created to calculate part temperatures during cure. The numerical analysis confirms that thin and thick parts, as defined by the relative temperature overshoot, can be predicted by Da* and [Equation]trise.
Numerical Investigation of the Thermal Baking Method for Start-Up Aluminum Electrolytic Cell
Authors: Zhang Li , Pan Liang-Ming , Wu Cheng-Bo
Published: April 2008

k-ε turbulent model and discrete radiant intension method is used to numerical investigate the temperature and flow field of the Thermal Baking Method for start-up aluminum electrolytic cell. Present investigation is based on the assumption of the absorption coefficient of radiation is not affected by turbulent and temperature variation of flue gas which is of up to 1200 °C. The source term of the energy equation is discretized using Discrete Radiation Intension Method, and the controlling equations are solved at SIMPLER algorithm. The results reveal that when the aluminum electrolytic cell is heated at low heat load at the very beginning stage, it would cause relative high temperature gradients (197°C between jets and the edge of cell). At higher heat load, the temperature field becomes more uniform. At the final stage of the thermal baking, the temperature gradient falls to 30 °C/m; it satisfies the start-up technology of aluminum electrolytic cell. The numerical results agreed with industrial experimental results very well.
Feasibility of Using Ultrasound Cavitation to Create Interconnected Porous Structures in Polymer Foams
Authors: Wang Xiaoxi , Li Wei , Kumar Vipin
Published: April 2008

Most of the existing fabrication techniques for tissue engineering scaffolds require the use of organic solvents that may never be fully removed even after long leaching hours. The residues of these organic solvents may reduce the ability of biological cells to form new tissue. In this study, interconnected porous structures were created using solid-state foaming and ultrasound. The interconnectivity was verified with dye test. The pore sizes of the foams ranged from 300 to 500 μm. Permeability measurements were also performed to quantify the interconnectivity using a system developed in house. The achieved average permeability of PLA foams with 300 μm pore size is 3.1×10-12 m2. The bigger the closed pores are, the easier ultrasound can make them open. There is an optimum temperature range in which ultrasound will enhance the interconnectivity of the solid-state foam the most efficiently. An ultrasound cavitation model was proposed as the dominant pore opening mechanism and was used to explain the temperature effects and pore size effects. The combined solidstate foaming and ultrasound processing provides a way to fabricate porous polymer for potential tissue engineering applications.
Europium as a Candidate Staining Material to Determine Polyethylene Wear
Authors: Wimmer Markus A. , Ngai Valentina , Kunze Joachim
Published: April 2008

Current protocols employed to measure wear of ultra-high molecular weight polyethylene (UHMWPE) utilize gravimetric and/or topographic measurement techniques. However, these methods may be subject to error due to creeping and fluid absorption capabilities of polyethylene. A novel process designed to avoid these errors was developed using Europium (Eu) as a tracer material to quantify polyethylene wear. Eu is a rare earth element that does not naturally occur in the human body and can be quantified using ICP-MS. By combining a solution of Eu – stearate with nascent UHMWPE powder, 9.5 mm diameter pins were molded and subjected to pin-on-disk testing. Samples of the testing lubricant were obtained at regulated intervals. These samples were analyzed for Eu quantification, which were then compared with the gravimetric pin measurements.
Preliminary Experimental Study of SMA Knitted Actuation Architectures
Authors: Evans Julianna , Brei Diann , Luntz Jonathan
Published: April 2008

Nature builds an immense set of materials exhibiting a wide range of behaviors using only a small number of basic compounds. The range of materials comes about through architecture, giving functional structure to the basic materials. Analogously, a new genre of actuators can be derived from existing smart materials through architecture. This paper presents a preliminary experimental study of knitted actuation architectures that yield high strains (up to 73%) with moderate forces (tens of Newtons or more) from basic contracting smart material fibers. By different combinations of the two primary knit loops – purl and knit – a variety of behaviors can be achieved including contraction, rolling, spirals, accordions, arching, and any combination of these across the fabric. This paper catalogs several basic knit stitches and their actuated form: garter, stockinette, seed, rib and I-cord. These knitted architectures provide performance tailorability (force, strain, stiffness, and motion) by manipulation of key design parameters such as the material properties of the wire, the geometric parameters (wire diameter, loop size, and gauge), and architectural parameters (stitch type and orientation). This is demonstrated via a quasi-static force-deflection experimental study with several shape memory alloy garter prototypes with varying geometric parameters. While the basic architecture of a knit is simple, it affords a vast array of architectural combinations and control of geometrical and material parameters that generate a myriad of gross motion capabilities beyond that of current day actuation strategies.
The Application of Wireless Sensor Networks for Fault Condition Monitoring in Three-Phase Induction Motors
Authors: Xue Xin , Sundararajan V. , Brithinee Wallace P.
Published: April 2008

A commonly used technique for the detection of faults in large three-phase induction motors is to measure the supply current to the motor and analyze the signal spectrum. This technique is well established and has been shown to be indicative of a faulty condition. However, current signature analysis is usually used by very skilled technicians using expensive equipment. A cost effective condition monitoring technique is needed for smaller motors (those smaller than 200 HP). A motor's heat signature tells more about its quality and condition. For heavy-duty motors, it is very important to detect overheating because hot windings deteriorate rapidly. This paper explores the possibilities of using wireless sensors inside the motor. Wireless sensors are gaining popularity in condition monitoring applications because of their relatively low cost and ease of installation. This paper proposes a system of condition monitoring of the three-phase induction motor using wireless sensor networks (WSN) to measure the temperature and the vibration signals. The sensor nodes are placed on the rotor and the stator. The data acquisition is accomplished at a base station located at a distance of 6 feet. Issues related to electromagnetic interference between the wireless devices and the magnetic fields present within the motor are investigated.
Efficient Nonlinear Vibration Analysis of the Forced Response of Rotating Cracked Blades
Authors: Saito Akira , Castanier Matthew P. , Pierre Christophe
Published: April 2008

The efficient nonlinear vibration analysis of a rotating elastic structure with a crack is examined. In particular, the solution of the forced vibration response of a cracked turbine engine blade is investigated. Starting with a finite element model of the cracked system, the Craig-Bampton method of component mode synthesis is used to generate a reduced-order model that retains the nodes of the crack surfaces as physical DOF. The nonlinearity due to the intermittent contact of the crack surfaces, which is caused by the opening and closing of the crack during each vibration cycle, is modeled with a piecewise linear term in the equations of motion. Then, the efficient solution procedure for solving the resulting nonlinear equations of motion is presented. The approach employed in this study is a multi-harmonic, hybrid frequency/time-domain (HFT) technique, which is an extension of the traditional harmonic balance method. First, a simple beam model is used to perform a numerical validation by comparing the results of the new method to those from transient finite element analysis (FEA) with contact elements. It is found that the new method retains good accuracy relative to FEA while reducing the computational costs by several orders of magnitude. Second, a representative blade model is used to examine the effects of crack length and rotation speed on the resonant frequency response. Several issues related to the rotation are investigated, including geometry changes of the crack and the existence of multiple solutions.
Walking Pattern Filter for Dynamic Biped Robot With SMA Actuators
Authors: Esfahani E. Tarkesh , Elahinia Mohammad
Published: April 2008

In this paper we present a walking pattern filter for Shape Memory Alloy (SMA) actuated biped robots. SMAs are known for their slow response. The actuation speed limitation can potentially lead to stability problems for biped robots. This filter adapts the human motion for a SMA biped in order to have a stable walking pattern. The Zero Moment Point (ZMP) is used as a main criterion of the filter to guarantee the stability of the motion. The SMA actuators are designed based on the dynamic and kinematics data of the motion. The response time of each SMA actuator is modeled in order to estimate the behavior of the actuator in realizing the given trajectory. After applying the delay times to the motion new trajectories are generated and checked by the ZMP criterion. The output of the filter can generate smooth trajectories for the SMA biped robots. The filter furthermore guarantees the stability while mimicking the human motion. The filter provides a practical way to create stable walking patterns using SMA actuators.
Viscous Flow-Induced Bending of Microcantilever Sensors
Authors: Jana Anirban , Tripp Steve , Raman Arvind , Reifenberger Ronald
Published: April 2008

Micro-cantilevers have recently evolved into a key sensor technology. Many of these sensors are deployed in fluid streams, for example, in rapid sensing of trace quantities of chemical or biological species in gaseous or aqueous environments[1,2], or in high resolution, high bandwidth anemometry [3]. Their design needs to consider microcantilever bending caused by the flow. This work presents detailed experimental data on the flowinduced bending of micro-cantilevers, and a simple theoretical model for quantitatively predicting such behavior.
Harmonic Motion Genration in an RSSP Mechanism
Authors: Farhang K. , Kolusu P. , Ghatti V.
Published: April 2008

It is possible to cast a set of dynamic performance requirements of a mechanism as a set of kinematic requirements and perform design at the kinematic synthesis stage. Inadvertently, this process leads to the sythesis of mechanism for function generation in which the output motion is a simple harmonic function of the input angular position. A perturbation technique is used to find approximate simple harmonic functions relating output link angular motion to the input angle. A higher order analysis is performed to obtain more accurate estimate functions relating input and output motions. Several RSSP sythesis cases are exemplified. Error analysis for the range of parameter space is performed showing favorable performance of the mechanisms, accuracy of the approximate equations as well as error estimations.
Rapid Silicon-to-Steel Bonding via Inductive Heating
Authors: Sosnowchik Brian D. , Lin Liwei , Pisano Albert P.
Published: April 2008

In this work, we present a rapid, low temperature process for the bonding of silicon to steel through the use of inductive heating for MEMS sensor applications. The bonding process takes as short as three seconds with a maximum bonding temperature as low as 230°C at the steel surface. The bonding strength is strong, and causes minimal damage to steel. The process has also been shown to work using leaded and leadfree bonding solder with minimal surface preparation to the steel. Four characterization experiments – tensile and compressive 4-point bend, axial extension, and fatigue tests – have been performed to validate the bonding process and materials. As such, this work illustrates the promise of applying inductive heating for the rapid silicon bonding to steel components for MEMS sensing applications.
Comparison Final Velosity Between Sailing Boat With a Rigid Airfoil and Cloth Sail
Authors: Amini H. , Rad M. , Fakhraee A.
Published: April 2008

The powering requirement of a ship is one of the most important aspects of naval architecture. Traditionally, ships have been tested for hull resistance using hydrodynamic tank testing. But it is very time consuming, expensive, and has inherent scaling errors. Because of these reasons, today many vessels are sold on the market without any model testing. Another set of design tools are Computational Fluid Dynamics and parametric prediction. Computational Fluid Dynamics (CFD) codes are not yet wholly proven in its accuracy. Parametric predictions contain acquired data for a specific family of hull forms and use key hull parameters to evaluate a particular design. This tool is absolutely validating. In this work, parametric predictions tool has been used for velocity prediction of sailing boats and experimental equation has been used for hydrodynamic and aerodynamic calculation. However in this work from experimental equation from Delft towing tank has been used for hydrodynamic calculation but it is acceptable for more boats and ships. In this work velocity is predicted for a sailing boat with one rigid airfoil and sailing boat with cloth sailing. Rigid airfoil can control the velocity of boat. The maximum velocity occurred in 70 to 120 degree angle of courses. In Final stage, the velocity of boat is compared between sailing boat with rigid airfoil and cloth sail.
High Temperature Heat Exchangers (HTHX) for Nuclear Applications
Authors: Govern James C. , Herman Cila V. , Nagle Dennis C.
Published: April 2008

Many nuclear engineering applications, current and future, require heat exchangers operating at high temperatures. The operating conditions and performance requirements of these heat exchangers present special design challenges. This paper considers these challenges with respect to a simple heat exchanger design manufactured of a novel carbon material. Heat transfer and effectiveness calculations are performed for several parametric studies regarding heat exchanger parameters. These results are used to better understand the design challenges of high temperature heat exchangers as well as provide a starting point for future optimization work on more complex heat exchanger designs.
Dynamics of Microcantilevers Tapping on Nanostructures in Liquid Environments in the Atomic Force Microscope
Authors: Basak Sudipta , Raman Arvind
Published: April 2008

The Atomic Force Microscope (AFM) has become an indispensable tool in biology because it permits the probing of nanomechanical properties under physiological (liquid environments) conditions. AFM has been used in liquid environments to image, manipulate and probe atoms, living cells, bacteria, viruses, subcellular structures such as microtubules, individual proteins and DNA. Probably the most popular method used for AFM in liquids is the tapping mode wherein a resonant microcantilever is scanned over a sample. Yet very little is known about the dynamics of microcantilevers in liquid environments while interacting with nanostructures. This problem is especially challenging because viscous hydrodynamics couples strongly with cantilever motions, and the contribution from the electric double layer forces, which is not significant in air, must be taken into account. Previous attempts in the analysis and simulation of tapping mode in liquid modeled the tip-sample interaction forces using either a Lennard-Jones potential [1, 2], an exponentially growing force of small duration of the cantilever oscillation cycle [3] without any contact mechanics, or an unrealistic discontinuous interaction force [4]. Moreover, in all these papers the microcantilever was modeled by a point (lumped) mass, and the hydrodynamic effects were not derived rationally from basic hydrodynamic theory. Instead, a low quality factor (Q factor) and an added fluid mass were simply assumed [1–4]. A direct method to systematically deal with the AFM microcantilever using continuous beam theory in liquids governed by the unsteady Stokes equations and experiencing intermittent contact with the sample is not available in the literature.
Implementation of Environmental Friendly Multi Regional Packaging and Logistics Solutions for Semi-Finished Goods
Authors: Villafuerte Jaime
Published: April 2008

In order to take advantage of the global economy, manufacturing companies have developed a complex and an extended supply chain which includes manufacturing components or parts in LCCs (low-cost countries) and shipping them to factories near to their consumer market for final assembly, customization and distribution. These activities involve several different organizations that follow widely different approaches in logistical management. In order to sustain the long shipment distances in different geographic regions, (i.e. China-Mexico-US-Europe), handling & environmental conditions & shipping modes (Air vs Ground vs Sea); suitable, flexible and economical packaging solutions are required. This flow of semi-finished goods usually requires packaging materials such as carriers (i.e. wooden pallets) and moisture inhibitors (i.e. desiccants) to protect the goods. Competitive pressures, environmental consciousness, customer awareness and legislative requirements have driven manufacturers to review business practices and redesign solutions that are environmentally friendly, as well as help reduce costs in the long run. The author of this paper will present an experience where "non-traditional" packaging is used as an economical and environmental friendly solution to globally transport goods between multiple facilities.
An Effective Computational Parametric Appraoch for Optimization of Adhesively Bonded Tubular Joints Subjected to Torsion Loading
Authors: Hosseinzadeh Ramin , Cheraghi Nader , Taheri Farid
Published: April 2008

Due to their low manufacturing cost, low stress concentration and ease of maintenance, adhesively bonded joints are now one of the most commonly and widely used joining systems in various industrial applications. As the use of composites gains popularity in oil and gas industry, the use of such joints for joining composite pipes is also gaining demand. The design and analysis methodologies applied to these joints under different loading conditions are however non-standard and rather controversial. The inherently complicated equations governing the behaviour of these joints have also impeded their use among the design engineers. As stated, however, as the use of composite pipes gains more popularity in oil and gas industry, the need for standardization of the methodology used for designing such joints becomes more essential. This paper discusses the details of 2D axis-symmetric and full-3D finite element models developed using the ABAQUS commercially available FEM software [1] for modeling and characterizing a series of adhesively bonded tubular joints used in isotropic and orthotropic pipes. The parametric script module of ABAQUS was used to systematically investigate the influence of several design parameters (such as the adhesive thickness, joint length, joint diameter, pipe material, and loading conditions), which govern the performance of such joints. The influence of various parameters specific to composite pipes (including the effect of laminate stacking sequence) was also investigated. Generated from the investigations was a set of useful design curves that provide the relationships among the parameters governing the behaviour of the joints. An important feature of the approach is its ability to establish the most optimized and effective joint length. The integrity of the optimization procedure was evaluated by comparing the response of the joints designed based on the developed design curves with those analyzed in detail by the finite element method (FEM).
On Vibrating Traveling Waves Actuation, Sensing, and Tuning in Finite Structures
Authors: Gabay Ran , Bucher Izhak
Published: April 2008

This work is concerned with a method to generate pure traveling vibration waves in finite structures. Using progressing deformations, i.e. waves, is not common when dealing with forced vibration since structures are naturally vibrating in their, naturally occurring, normal modes. Indeed, natural vibration modes can be referred to standing waves. Since a structure does not lend itself to a traveling wave vibration, the generation of traveling waves in a structure becomes a challenging task. The boundary conditions or external forces must be carefully tuned in an iterative process that necessitates measurement and identification of the traveling and standing wave components. In this work, a method to generate and measure traveling waves is presented for one and two-dimensional structures. Both analytical and experimental results are provided here. A traveling wave is a disturbance that propagates away from its source carrying energy along its path. In finite structures, a wave hitting a boundary experiences an impedance change that gives rise to a partial reflection, thus distorting its original form. For a pure traveling wave to occur, the boundary of the structure must be set to match the impedance of the structure, and thus to absorb the disturbance while preventing any reflected wave from the boundaries. Impedance matching can be accomplished by passive or active means. Active impedance matching is obtained by generating a vibrating wave at one end (a source) and 'pumps' it on the other, active absorbing end, often addressed as a sink. Indeed, active impedance matching sometimes referred as the "active sink" method. Special methods must be used to extract the description of the vibrating wave characteristics from the measured vibration efficiently, and possibly in real-time (for control purposes). A parametric method is employed in this work to describe and analyze the wave vibration from measurements. In reality, the theoretical knowledge of how to excite a vibrating traveling wave is not sufficiently accurate to produce traveling waves. Minute manufacturing imperfections, small structural and actuator asymmetry may cause large deviations from pure traveling waves state. It is shown that a tuning process that relies on the measurements but combined with a physical model, should serve as the basis of the practical implementation. Several experiments on a string-like structure are described stressing the physical implications as well as the refined experimental procedure. The actuation techniques, wave identification methods and the tuning procedure of a vibrating traveling wave are described in some detail for the experimental work.
Prediction of Mercury Speciation in Coal-Combustion Systems
Authors: Bhopatkar Neelesh S. , Ban Heng , Gale Thomas K.
Published: April 2008

This study is a part of a comprehensive investigation, to conduct bench-, pilot-, and full-scale experiments and theoretical studies to elucidate the fundamental mechanisms associated with mercury oxidation and capture in coal-fired power plants. The objective was to quantitatively describe the mechanisms governing adsorption, desorption, and oxidation of mercury in coal-fired flue gas carbon, and establish reaction-rate constants based on experimental data. A chemical-kinetic model was developed which consists of homogeneous mercury oxidation reactions as well as heterogeneous mercury adsorption reactions on carbon surfaces. The homogeneous mercury oxidation mechanism has eight reactions for mercury oxidation. The homogeneous mercury oxidation mechanism quantitatively predicts the extent of mercury oxidation for some of datasets obtained from synthetic flue gases. However, the homogeneous mechanism alone consistently under predicts the extent of mercury oxidation in full scale and pilot scale units containing actual flue gas. Heterogeneous reaction mechanisms describe how unburned carbon or activated carbon can effectively remove mercury by adsorbing hydrochloric acid (HCI) to form chlorinated carbon sites, releasing the hydrogen. The elemental mercury may react with chlorinated carbon sites to form sorbed HgCl. Thus mercury is removed from the gas-phase and stays adsorbed on the carbon surface. Predictions using this model have very good agreement with experimental results.
Peeling Mode Capacitive Pressure Sensor for Sub-KPA Pressure Measurements
Authors: Han Jeahyeong , Yang Shunzhou , Shannon Mark A.
Published: April 2008

Capacitive pressure sensors measure changes in pressure typically by the deflection of a flexible conducting membrane towards a fixed electrode. The deflection in the membrane produces a quadratic change in capacitance, which often yields higher sensitivity to changes in pressure compared to piezo-resistive pressure sensors, which measures the resistance changes proportional to the applied pressure. However, residual stresses in the membrane can provide a substantial resistance to deformation compared to the driving force created by the applied pressure, which decreases the sensitivity at low pressures and produces a nonlinear signal. If the membrane is made compliant enough to increase sensivitiy, pull-in of the membrane can occur, reducing the effective pressure range of the capacitive manometer type pressure sensor. Hence, these type of sensors are typically not used to measure very low pressure differences over several hundred Pascals. To overcome this limitation, a capacitive pressure sensor was developed that operates in a peeling mode while under applied electrostatic actuation, which counters the residual stresses. The changes in capacitance can be detected if the pressure is just enough to overcome the interfacial electrostatic pressure. This type of pressure sensor can potentially be used for very low differential pressure differences, well below 100 Pa, over ~ 1 kPa range.
Parametric Study of Heat Sink Performance at High Altitudes With Air Impingement Cooling
Authors: Seidel Robert E. , Rhee Jinny
Published: April 2008

Heat sinks are one of the primary mechanisms today for thermal management of electronics. In the high altitudes reached by modern military aircraft, the capacity for air cooling is reduced due to the rarefied atmosphere. With an increase in altitude there is a subsequent decrease in the density of air. A review of the literature shows a lack of research done on pin-fin heat sinks with impingement flows at low Reynolds number conditions. Experimental testing will determine the thermal resistance of a pin-fin heat sink with impingement flow at low absolute pressures. A test apparatus will be constructed, and experiments will be conducted within a hypobaric chamber. In a hypobaric chamber, it is possible to simulate altitudes up to 30 000 meters by reducing the absolute pressure using a vacuum pump. Temperature is regulated and air is circulated within the chamber. The test apparatus, which is to be completely enclosed within the hypobaric chamber, consists of a centrifugal blower forcing air through a duct. Air is impinged upon a pin-fin heat sink heated with uniform flux on the base. Incident air flow is along the axis of each circular pin-fin, and exhaust from the heat sink will be transverse to the pins. Feedthroughs are available in the chamber wall for supplying electrical power to the blower, for taking temperature measurements with embedded thermocouples, and for measuring blower shaft speed. Temperature measurements are made in the base of the heat sink, in the air, and at other points to characterize other heat losses from the apparatus. Blower speed is monitored with an optical tachometer, and by similarity laws for turbomachinery it will be possible to determine the air flow impinging upon the heat sink. Pressure in the chamber will be varied in several steps up to the equivalent of a 30 000-meter altitude, and at each step a correlation will be made between heat sink thermal resistance and Reynolds number of the impinging air.