bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Assessment of Multi-Cylinder Engine Using CNG
Authors: Mistry Chetan S. , Gohil Piyush P. , Sharma D. M.
Published: April 2008

The paper reviews the performance test on multi cylinder engine using petrol and CNG as a fuel under variable load and speed conditions, which covers the performance parameters like fuel economy, specific fuel consumption, thermal efficiencies, effect of some operating parameters like exhaust gas temperature and engine friction etc. Finally, the comparative study on performance shows that CNG to be a good alternative fuel, as composition along with the highly desired fuel properties sets the right blend for the number of technical and economical advantages like zero evaporative emission, excellent antiknock property, compatibility with fuel efficient lean burn technology with optimum ignition timing.
First Steps Toward Curricular Integration of Computational Tools
Authors: Hinds T. , Sticklen J. , Urban-Lurain M. , Amey M. , Eskil T.
Published: April 2008

Calls for new paradigms for engineering education are widespread [1-3]. Yet, major curricular change is difficult to accomplish for many reasons, including having the necessary faculty buy-in [4]. Generally, efforts can be classified as either top-down/structural, in which faculty assess an entire program of study and address needs in each component before implementation begins; or bottom-up/individual, a more traditional approach that implements change in one course at a time. Faculty buy-in, consensus, and resources (unit and institutional) needed for the top-down approach make it difficult to accomplish. On the other hand, the bottom-up model is slow; the assumption that curricular reform can be affected by an accumulation of individual course adaptations is unproven, and the change goals need to have a more systemic focus. Unless the curriculum helps students integrate material across their courses, they have difficulty seeing how the material they learn in one course will connect to the next. We have performed a pair of initial studies using an evolutionary approach to curricular reform that capitalized on the strengths of both the top-down and bottom-up models, which was built on the science, technology, engineering, and mathematics (STEM) reform literature. This approach developed a pairwise linkage among strategic courses in the engineering curricula to promote curricular integration and helped students see connections between their first-year courses and subsequent courses. Vertically integrated problem-based learning scenarios that link across courses are crucial to this model. Pre-reform data collected in the first study showed that students taking an introductory computing course did not see the importance of learning a particular software tool (MATLAB), because they did not see connections to their future courses. This had negative impacts on student motivation, learning, and retention. In our recent work, which was our first vertical effort, we focused on MATLAB with integration of the learning of this engineering tool in an introductory computing course with the solution of statics problems in an introductory mechanical engineering course. Our recent study set out to determine if joint team efforts would enhance student perceptions of the set learning goal for the introductory computing students while enhancing learning outcomes for both the introductory computing and introductory mechanical engineering students. The paper outlines this pairwise linkage model, the goals of this project, the framework for evaluating the linkage, and the types of data we collected as part of the evaluation effort. Results from the initial study confirmed that problem-based teamwork enhanced student attitudes towards MATLAB. We also describe how results here will enable us to reach our long-term goal of curricular integration.
Equality Constraints in Multiobjective Robust Design Optimization: Implications and Tradeoffs
Authors: Rangavajhala Sirisha , Mullur Anoop A. , Messac Achille
Published: April 2008

In the present paper, we explore issues in handling equality constraints in multiobjective robust design optimization (RDO) problems. Satisfying an equality constraint exactly under uncertainty can be a challenging task. The challenge of handling equality constraints is compounded in multiobjective RDO problems. Modeling the tradeoffs between the mean of the performance and the variation of the performance for each design objective in a multiobjective RDO problem is a complex task by itself. Equality constraints add to this complexity because of the additional tradeoffs that are introduced between constraint satisfaction under uncertainty and multiobjective performance. Satisfying equality constraints at their mean values, an approach typically followed, could lead to undesirable results. In this paper, we study the implications of equality constraint satisfaction in a multiobjective RDO problem, and provide a new problem formulation approach to resolve the above discussed tradeoffs. We illustrate that the proposed formulation can be used as an effective multiobjective design space exploration tool, with emphasis on equality constraint satisfaction under uncertainty. We present numerical examples to illustrate our theoretical developments.
Simulation of Bioparticle Movement in a Dielectrophoretic Microchannel
Authors: Kamat Mahesh , Noh Hongseok
Published: April 2008

This paper presents an analysis of two of the most significant factors that affect particle movement in a dielectrophoretic microchannel: Drag force and Dielectrophoretic force (Figure 1). We have simulated particle trajectories for 2 and 10 micron diameter polystyrene beads in a dielectrophoretic microchannel under pressure-driven flow and analyzed the effects of fluid drag force and dielectrophoretic force on its trajectory. All particle simulations have been performed for two electrode types, thin film electrodes and dome shaped electrodes. The two electrode configurations are analyzed for their applicability in dielectrophoretic systems based on the extent of their dielectrophoretic effect in the microchannel. The results show that a higher dielectrophoretic effect and near-uniform field gradients along the particle flow path can result by using dome shaped electrodes. We also propose that this technique can be used for the manipulation of bioparticles. The suggested idea of using these results for bioparticles lies in the fact that the Clausius Mossotti factor for a bioparticle which would be based on a multishell model would be equivalent to a certain rigid sphere at the same applied frequency. Thus the simulation design can be used to evaluate the behavior of bioparticles with only the Clausius Mossotti information, without the need to model it into the trajectory tracking program and this can be obtained experimentally using dielectrophoretic techniques.
Joystick Ergonomic Study in Material Handling Using Virtual Humans
Authors: Pen˜a Pitarch Esteban , Yang Jingzhou , Abdel-Malek Karim , Kim Joo , Marler Tim
Published: April 2008

Raw material and product manufacturing are related to material handling. Although there have been great advances in technologies, regulations, methodologies, strategies, and workplace safety, the number of fatalities, the severity of injuries, and the number of lost workdays per accident-incident related to material handling continue keeping high. Some hand injuries occur when the operators repetitively use joysticks to handle materials in manufacturing environment. This paper studies joystick ergonomics used in the material handling equipment and evaluates the design and use of joysticks using a new generation of virtual humans (Santos™). The Denavit-Hartenberg method is implemented to analyze the 25-degree-of-freedom (DOF) hand model of the virtual humans. Human performance measures (joint torques and joint displacements) are criteria for the design of joysticks in the material handling machines.
The Contenur 2400 L Waste Container Product: An Example of CAE in Injection Plastic Design
Authors: Aisa Jorge , Javierre Carlos , Castany Javier , De la Serna Jose Antonio
Published: April 2008

This paper is focused on 2400 liter waste container design, made by Contenur Espan˜a; using computer aided engineering tools (CAE) and T.I.I.P. team experience, (University of Zaragoza, Spain). The goal was to produce a new plastic container concept, including all its elements, indicating assembly operations and selecting the plastic injection machine required for each part. Final cost should be reduced under other company’s prices. Several requisites were established at the beginning of the design stage: material type, European regulations on the product dimensions and testing procedures, an easy assembly, simple storage and low transport fares.... This work exposes several points of view around the complete design and work steps: feasibility analysis, aesthetical and structural design, detail drawing, injection molding definition, service tests, and final assembly. Methodology followed in this big product is described, collecting several fields’ experience. The final result is shown and four patents recognize this wide technical work.
Quantitative Study of Shrinkage and Warpage Behavior for Microcellular and Conventional Injection Molding
Authors: Kramschuster Adam , Cavitt Ryan , Ermer Don , Shen Chris , Chen Zhongbao , Turng Lih-Sheng
Published: April 2008

This research investigated the effects of processing conditions on the shrinkage and warpage (S&W) behavior of a box-shaped, polypropylene part using conventional, microcellular, and microcellular co-injection molding. Three sets of 26-1 fractional factorial design of experiments (DOE) were employed to perform the experiments and proper statistical theory was used to analyze the data. After the injection molding process reached steady state, molded samples were collected and measured using an optical coordinate measurement machine (OCMM), which had been evaluated using a proper repeatability and reproducibility (R&R) measurement study. By analyzing the statistically significant main and two-factor interaction effects, the results show that the supercritical fluid (SCF) content (nitrogen in this case, in terms of SCF dosage time) and the injection speed affect the S&W of microcellular injection and microcellular co-injection molded parts the most, whereas pack/hold pressure and pack/hold time have the most significant effect on the S&W of conventional injection molded parts. Also, this study quantitatively showed that, within the processing range studied, a reduction in the S&W could be achieved with the microcellular injection molding and micro- cellular co-injection molding processes.
Design and Analysis of a Warpage Measurement System to Simulate Convective Reflow
Authors: Powell Reinhard E. , Ume I. Charles
Published: April 2008

In this research, a warpage measurement system to simulate forced convective reflow is designed and developed. In order to design a system to simulate forced convective reflow, the system should be capable of heating a PWB at an average rate of 2 °C/second. This paper will present PWB heating rate results produced by modifying a laboratory oven to enable it to simulate forced convective reflow. The initial modification of the current forced convective reflow oven failed to achieve the desired PWB heating rate. Therefore, a computational fluid dynamics (CFD) analysis was carried out to determine which critical oven parameters could be modified to produce the desired PWB heating rates. The parameters that were chosen for this study were oven system volume, heater surface area and heater power. The CFD model was used to perform a design of simulations (DOS), and regression was used to analyze the DOS results. The regression results will be used to make recommendations on how to improve the PWB heating rate of the forced convective reflow system.
Differential Assessment of the ABET “a-k” Program Outcomes Based on Learning Domains
Authors: Pape D. A.
Published: April 2008

In this paper each of the eleven EC 2000 “a-k” program outcomes are investigated in terms of Bloom’s three domains of learning. It is found that most of the published work in engineering assessment is focused on outcomes related to the cognitive domain. Some difficulties in assessing the outcomes involving the professional skills, which tend to fall in the affective domain, are addressed. Since some outcomes fall in a single domain and others encompass multiple domains, there is a need to use different, and possibly multiple, types of assessment techniques for each outcome. Specific methods for developing assessable performance criteria for these outcomes are described. The result is a clearer picture of assessment needs and methods related to each outcome, and an understanding of remaining work in this area.
Simulation of Solid Cargo-Vehicle Interaction During Braking of a Heavy Vehicle With ABS
Authors: Romero Jose´ A. , Rakheja Subhash , Lozano Alejandro
Published: April 2008

The effect of cargo shifting on the braking efficiency of a freight truck is investigated thorough development and analysis of an analytical model of the cargo-vehicle system together with the tie-down system. Braking efficiency is characterized in terms of the stopping distance, as a function of the cargo securement method (direct and indirect) and deck vibration caused by varying levels of road roughness. The relative movement of the cargo with respect to the deck causes decoupling of the cargo and the vehicle masses. The effective braking forces are thus applied to a reduced total mass. An important phenomenon that influences the cargo-vehicle interaction derives from the decoupling of the cargo and vehicle masses during the shifting of the cargo, leading to a situation in which the braking forces are applied to a reduced mass. The vehicle performance with a rigidly fixed cargo is also evaluated for comparison purposes. Results show that the indirectly restrained cargo produces the minimum stopping distances, irrespective of the road roughness, while the maximum stopping distances are attained for the directly restrained cargo.
Field Determination of Cargo-Deck Friction Coefficients
Authors: Romero Jos A. , Marti´nez Miguel , Lozano Alejandro
Published: April 2008

Friction between cargo and vehicle’s deck has been considered among the supplemental means for securing cargo. Although friction coefficients have been determined as a function of different influencing factors, such measurements have been performed under laboratory controlled conditions that simplify vehicle vibration and cargo-deck stiffness and contact characteristics. In this paper a methodology is proposed to quantify cargo-deck friction coefficients under realistic field conditions throughout the kinematical analysis of the stopping of the cargo-carrying vehicle by effects of dragging the cargo on the vehicle’s platform. The vehicle is located on an inclined road segment while the cargo is lashed to a fixed point on the road, in such a manner that the vehicle can travel a certain distance before the lashing becomes tensioned and the cargo starts stopping the vehicle. While average values for friction coefficients correlated well with those reported in the literature, standard deviations represented up to 33% of such average values.
Hydrodynamic Loading of Vibrating Micro-Cantilevers
Authors: Basak Sudipta , Raman Arvind , Garimella Suresh V.
Published: April 2008

The hydrodynamic loading on silicon microcantilevers vibrating in different fluids close to (finite gap) and away from (infinite gap) a surface is analyzed numerically. Analytical techniques available to predict the hydrodynamic loading are restricted to simple cantilever geometries in fluids of infinite extent and are inaccurate for the higher modes of vibration. In this paper a finite element model developed in ADINA 8.1 (a fluid-structure interaction software, [1]) is used to overcome the shortcomings of the analytical models. Selective modal excitation of the cantilever in a fluid yields the corresponding modal frequency and damping factor. The numerical model benchmarks favorably with previously published experimental and analytical results. Detailed numerical analyses are performed in ADINA for variable gap lengths for a rectangular microcantilever for the first and second bending modes and the first torsional mode. Different cantilever geometries are also investigated. The results expose the physics of dissipation in the surrounding fluid and are expected to be of immediate interest to the Atomic Force Microscopy (AFM) and microcantilever biosensor communities.
Localization and Follow-the-Leader Control of a Heterogeneous Group of Mobile Robots
Authors: Huang Jiangyang , Farritor Shane M. , Qadi Ala’ , Goddard Steve
Published: April 2008

This paper investigates the control and localization of a heterogeneous (different sensor, mechanical, computational capabilities) group of mobile robots. The group considered here has several inexpensive sensor-limited and computationally-limited robots which follow a leader robot in a desired formation over long distances. This situation is similar to a search, de-mining, or planetary exploration situation where there are several deployable/disposable robots led by a more sophisticated leader. Specifically, the robots in this paper are designed for highway safety applications where they automatically deploy and maneuver safety barrels commonly used to control traffic in highway work zones. Complex sensing and computation are performed by the leader while the followers perform simple operations under the leader’s guidance. This architecture allows followers to be simple, inexpensive and have minimal sensors. Theoretical and statistical analysis of a tracking-based localization method is provided. A simple follow-the-leader control method is also presented. Experimental results of localization and follow-the-leader formation-motion are included.
Facilitating Meta-Design via Separation of Problem, Product, and Process Information
Authors: Panchal Jitesh H. , Ferna´ndez Marco Gero , Allen Janet K. , Paredis Christian J. J. , Mistree Farrokh
Published: April 2008

Different products necessitate different design processes. Determining which such process is most appropriate for a particular product, in turn, requires its delineation before the design of the product under consideration. The phase where design processes are composed is called meta-design. Despite its importance, current simulation-based design frameworks such as FIPER, ModelCenter, and iSIGHT do not support meta-design. This oversight can be attributed at least in part to the fact that these frameworks capture information about products, design processes, and the associated tools in a lumped fashion. Processes are captured in terms of the specific tools employed and the product information, associated with their use, thereby restricting the re-utilization (i.e., reuse via adaptation or customization) of instantiated processes for designing different products. This inherent inability to separate product and process information hinders the exploration of different design process options for designing a product at a fundamental level, thereby restricting meta-design. In order to address this challenge, we propose an approach for distinctly capturing and processing three key components of design related information - a) design problem, b) design process, and c)product. We term this approach, rooted in decision-based design, modularity, and separation of declarative and procedural information, 3-P. The modular separation of information associated with problem, product, and process enables designers to utilize existing knowledge, captured in the form of pre-defined process configurations, for more effectively designing a given product. The proposed approach facilitates the efficient exploration and reconfiguration of design processes, furnishing a much needed and essential basis for meta-design.
Complex Impact Response of a Beam and Rigid Body Structure to Harmonic Base Excitation
Authors: Ervin Elizabeth , Wickert Jonathan
Published: April 2008

This paper investigates the forced response dynamics of a clamped-clamped beam to which a rigid body is attached, and in the presence of periodic or non-periodic impacts between the body and a comparatively compliant base structure. The assembly is subjected to base excitation at specified frequency and acceleration, and the potentially complex responses that occur are examined analytically. The two sets of natural frequencies and vibration modes of the beam-rigid body structure (in its in- contact state, and in its not-in-contact state), are used to treat the forced response problem through a series of algebraic mappings among those states. A modal analysis based on extended operators for the (continuous) beam and (discrete) rigid body establishes a piecewise linear state-to-state mapping for transition between the in-contact and not-in-contact conditions. The contact force, impulse, and displacement each exhibit complex response characteristics as a function of the excitation frequency. Periodic responses occurring at the excitation frequency, period-doubling bifurcations, grazing impacts, sub-harmonic regions, fractional harmonic resonances, and apparently chaotic responses each occur at various combinations of damping, excitation frequency, and contact stiffness. Parameter studies are discussed for structural asymmetry and eccentricity of contact point’s location.
Lattice Boltzmann Modeling of the Thermal Response of Silicon-On-Insulator Transistors Under Joule Heating Including Phonon Dispersion
Authors: Escobar Rodrigo A. , Amon Cristina H.
Published: April 2008

Lattice Boltzmann Method (LBM) simulations of phonon transport are performed in a computational model of an Siliconon-Insulator (SOI) transistor to investigate the transient thermal response of the device under Joule heating conditions, which give origin to a non-equilibrium region of high temperature known as hotspot. The gray LBM based on the Debye assumption is compared to a dispersion LBM which incorporates nonlinear dispersion for all phonon branches, including explicit treatment of optical phonons without simplifying assumptions. The simulations cover the effect of hotspot size, heat pulse duration, and source term modeling, as either a constant or frequency-dependent term. Results indicate that hotspot peak temperature levels found by both the dispersion and the gray LBM are higher than Fourier diffusion predictions. Additionally, proper modeling of the source term is found to be critical, in order to accurately predict peak hotspot temperatures.
Fluid Flow Characteristics of a Confined Slot Jet Without or With a Target Surface
Authors: Liu L. K. , Fang C. J. , Wu M. C. , Lee C. Y. , Hung Y. H.
Published: April 2008

A series of experimental investigations with a stringent measurement method on the fluid flow characteristics of slot jet without or with a target surface have been successfully conducted. From all the fluid velocity data measured in the present study, the experimental conditions have been verified to be spanwise-symmetrically maintained and the results have been achieved in a spanwise-symmetric form. Three types of jet configuration without or with target surface are investigated: (A) Confined Slot Jet without Target Surfaces – the fluid flow parameters studied in the present investigation is the jet Reynolds number (ReD). Its ranges are ReD=506-1517. (B) Confined Slot Jet with Smooth Surfaces – the fluid flow parameters studied in the present investigation include the ratio of jet separation distance (H) to nozzle width (W) and the jet Reynolds number (ReD). The ranges of the relevant parameters are H/W=2–10 and ReD=504–1526. (C) Confined Slot Jet with Extended Surfaces – the fluid flow parameters studied include the ratio of jet separation distance (H) to nozzle width (W), the Reynolds number (ReD) and the ratio of extended surface height (Hes) to nozzle width (W). Their ranges are H/W=3–10, Hes/W=0.74-3.40 and ReD=501–1547. The flow characteristics such as the local mean streamwise velocity distribution, mean streamwise velocity decay along jet centerline, local jet turbulence intensity distribution, and turbulence intensities along jet centerline have been presented and discussed in the study.
Virtual Lab for System Identification of an Electromechanical System
Authors: O’Malley Marcia K. , McStravick David
Published: April 2008

A stand-alone virtual instrument (vi) has been developed to augment an experimental system identification laboratory exercise in a required mechanical engineering course on system dynamics. The Virtual Lab (VL) was used productively as a post-lab exercise in conjunction with an existing laboratory experiment for system identification. The VL can be formatted as a standalone file, which the students can download and access at their convenience, without the need for LabVIEW software. The virtual lab presented in this paper used the experimental identification of a transfer function for an xy recorder developed at Rose-Hulman Institute of Technology. In the original Rose-Hulman experiment, students view a video of the acquisition of frequency response data for an X-Y recorder. Then, students complete a detailed optimization procedure using Microsoft Excel in order to determine system parameters for two transfer function models. This paper describes using the Virtual Lab to extend the original lab exercise into an interactive mode. The students complete the Microsoft Excel part of the exercise, but then repeat the optimization using brute force via the LabVIEW based VL developed by the authors, rather than using the optimization toolbox in Excel. With the VL, students can see in real-time the effects of each unknown parameter on the frequency response plot, thus providing additional insight into the relationships between these parameters and the behavior of the electromechanical system. This feature is notably absent in the Microsoft Excel portion of the exercise. Although this exercise uses simple dynamic models, the combination of Excel and LabVIEW approaches provide an insightful introduction to experimental system identification. In this paper, details of the VL are presented, including the functionality of the VL and methodologies for disseminating the VL as a stand-alone piece of software. Finally, some assessment results for the original (Excel version) and VL methods of presenting the laboratory exercise are discussed.
Self Calibrated and High Accuracy Thermal Control in Cavities
Authors: Belo Francisco Antonio , Paz Marcelo Magalha˜es A´vila , Leite Antonio Pralon Ferreira , Nascimento Leonaldo Jose´ Lira do
Published: April 2008

The study of thermal control in different geometry cavities (cylindrical and rectangular), to obtain high accuracy, short and long term stability responses applied to electronic instruments, is presented. Automatic dynamic electrical compensation is achieved by a feedback electronic circuit and low thermal inertia sensors. One sensor element is also employed as an actuator (heat generator) and the other as a reference sensor (resistance of manganine wire). In the rectangular cavity, the transducer (that is sensor and heater) is manufactured directly in the circuit board surface using a CAD/CAM equipment. This architecture allows a high dimensional accuracy of the sensor/actuator with a minimum track thickness, i.e., around 100 μm. In the cylindrical cavity, the transducer is manufactured using a copper wire. For this geometry, low aspect ratios were analyzed. Electronic response equations are derived and coupled to those governing the heat transfer phenomenon in cavities. After several tests, the model is compared to the experimental data. The obtained results seem to confirm the validity of the proposed idea, allowing an accurate temperature control in cavities with a self calibrating feature. At present time, we have obtained for both geometries a precision around of 0.01°C and an accuracy around of 0.1°C.
Prediction of Laminar Flow in a Microchannel With Transverse Ultrahydrophobic Ribs
Authors: Davies J. , Woolford B. , Maynes D. , Webb B. W.
Published: April 2008

One approach recently proposed for reducing the frictional resistance to liquid flow in microchannels is the patterning of micro-ribs and cavities on the channel walls. When treated with a hydrophobic coating, the liquid flowing in the microchannel wets only the surfaces of the ribs, and does not penetrate the cavities, provided the pressure is not too high. The net result is a reduction in the surface contact area between channel walls and the flowing liquid. For micro-ribs and cavities that are aligned normal to the channel axis (principal flow direction), these micro-patterns form a repeating, periodic structure. This paper presents experimental and numerical results of a study exploring the momentum transport in a parallel plate microchannel with such microengineered walls. The liquid-vapor interface (meniscus) in the cavity regions is treated as ideal in the numerical analysis (flat). Two conditions are explored with regard to the cavity region: 1) The liquid flow at the liquid-vapor interface is treated as shear-free (vanishing viscosity in the vapor region), and 2) the liquid flow in the microchannel core and the vapor flow within the cavity are coupled through the velocity and shear stress matching at the interface. Predictions and measurements reveal that significant reductions in the frictional pressure drop can be achieved relative to the classical smooth channel Stokes flow. Reductions in the friction factor are greater as the cavity-to-rib length ratio is increased (increasing shear-free fraction) and as the channel hydraulic diameter is decreased. The results also show that the average friction factor – Reynolds number product exhibits a flow Reynolds dependence. Furthermore, the predictions reveal the impact of the vapor cavity regions on the overall frictional resistance.
System Level Synthesis, Modeling and Roadmapping for Aeronautical SOFC/Gas Turbine Hybrid Systems
Authors: Ma Zhiwen , Haynes Comas , Patel Pinakin
Published: April 2008

Solid oxide fuel cell /gas turbine (SOFC/GT) hybrid power systems have been recognized as having the potential to operate at unprecedented levels of performance (e.g., 50%+ electrical power generation efficiencies with significantly mitigated greenhouse gas, criteria pollutant and noise emissions). Although the emphasis has been upon land applications, there are aeronautical benefits that may be derived as well. Despite these benefits, there have been limited investigations into the technical merit and feasibility of incorporating these hybrid systems onboard aerovehicles. A feasibility investigation has been performed in conjunction with fuel cell system modeling capabilities to conceptually establish auxiliary power system possibilities as well as the viability technology gaps.
Systematic Process for Constructing Spherical Four-Bar Mechanisms
Authors: Turner Michael L. , Perkins David A. , Murray Andrew P. , Larochelle Pierre M.
Published: April 2008

This paper presents a methodology for constructing spherical four-bar mechanisms with an emphasis on utilizing simpler machining processes and part geometries. By building each link out of easily created pieces instead of a single complex shape, a mechanism can be quickly prototyped and tested. The paper discusses the benefits and some of the issues that need to be addressed by this approach. Significant areas of concern include link design and tolerancing issues.
Enhanced Pool Boiling Using Carbon Nanotube Arrays on a Silicon Surface
Authors: Ujereh Sebastine O. , Mudawar Issam , Amama Placidius B. , Fisher Timothy S. , Qu Weilin
Published: April 2008

Progress in integrated circuit technology has caused device density and power dissipation to increase, resulting in significant cooling challenges. Pool boiling is an attractive cooling option because of its unique combination of passive fluid circulation and high heat flux capability. Having no mechanical pumps, pool boiling hardware is less complex, easier to seal, and free of pump-induced fluid pulsations that are present with many alternative approaches. One of the main obstacles for improvements in pool boiling technology is the limiting factor of critical heat flux (CHF), which limits cooling capacity. The present experimental work considers the introduction of carbon nanotube (CNT) arrays on the chip surface to delay CHF and to enhance boiling heat transfer. Pool boiling curves for a smooth silicon surface and a silicon surface coated with CNTs were obtained. Tests were conducted in which power was input in 1 W increments to the respective silicon surfaces immersed in FC-72 fluid. These experiments reveal significant boiling enhancement. Testing reveals a measured CHF of approximately 15 W/cm2 for a CNT-coated silicon wafer and a CHF of approximately 10 W/cm2 for bare silicon wafers. Further, superheat at fully developed boiling is reduced on CNT-coated surfaces by up to 60%, and effective heat transfer coefficients are enhanced by approximately 400% by the presence of CNTs.
Collaborative Behavior for Vehicle Replacement in AUV Formations
Authors: Rajala Andrew G. , Edwards Dean B. , O’Rourke Micheal
Published: April 2008

The Navy would like to use platoons of cooperating Autonomous Underwater Vehicles (AUVs) for large area underwater mine countermeasures (MCM). Collaborative behavior requires a common language, control structure, and logic so the AUVs can coordinate their action through communication. The loss of an AUV (can no longer perform assigned tasks) is a problem the formation is likely to face. The formation must compensate for lost AUVs, or time would be wasted in researching the area. In order to replace a lost AUV, the formation must determine when a vehicle is lost and what to do if a vehicle returns after being declared lost. To address these problems, fuzzy logic was used to determine when an AUV should be replaced, and a logic structure was developed to insert returning AUVs. Computer simulations showed that the logics increased the defined performance index by about 70% over the baseline case.
Modeling of Capillary Dryout and Rewetting for Room-Temperature Heat Pipes
Authors: Brocheny P. , Ochterbeck J. M.
Published: April 2008

An analytical investigation was conducted to examine and predict the capillary dryout and rewetting behaviors occurring at the evaporator section of room-temperature heat pipes during startup. The physical model is based on the displacement of a leading-edge front of a thin liquid layer flowing on finite groove uniformly heated with a constant heat flux. Numerical solutions were obtained by a fully implicit Finite Difference Method, accounting for the movement of the liquid and a known time-variable temperature boundary condition at the liquid front. The velocity and position of the liquid front were found to vary with the applied heat flux, the initial conditions, and the thermophysical properties of the working fluid. The wall temperature distribution in the dried region was also predicted. The working fluid temperature compared well with experimental results. The analysis indicated that a partial or full dryout at the evaporator section may exist for certain heat fluxes.
Towards High Temperature Actuation Using Graphite Intercalation Compounds
Authors: Massey Cameron , Barvosa-Carter William , Liu Ping
Published: April 2008

Electrochemically formed graphite intercalation compounds (GICs) have many intrinsic properties well-suited for compact actuation in applications at high temperatures. GICs using ionic liquids are of interest because of their good thermal stability at elevated temperatures, high ionic conductivity, and low volatility. In this study we observed the potential and strain behavior of highly oriented pyrolytic graphite and 1-ethyl-3-methylimidazolium hexafluorophosphate subjected to a light compressive load and constant current. In situ measurements of the anode during intercalation showed a reversible strain of 2.5% to 4.5% from 100°C up to 250°C.
Influence of the Electrophoretic Motion of Particle Suspensions on the Bulk Electroosmotic Flow of Water Through Fused Silica Capillaries
Authors: Young J. , Maynes D. , Webb B. W.
Published: April 2008

The influence of microparticles on electroosmotic flow was investigated experimentally. Experiments were conducted using four different particle types of varying chemical composition, surface charge and polarity. Each particle type was tested at five different volume fractions ranging from 0.001 – 0.025. With a constant applied electric field, positively charged particles enhanced the electroosmotic flow by as much as 800%. The enhancement depended on particle composition, size and concentration. For negatively charged particles, the bulk electroosmotic flow was retarded with the largest reductions being 35%.
Induced-Charge Electrophoresis in Suspensions of Rodlike Particles: Theory and Simulations
Authors: Saintillan David , Darve Eric , Shaqfeh Eric S. G.
Published: April 2008

Recent developments in microfluidics and analytical chemistry have spurred renewed interest in electrokinetic manipulation of colloidal particles. In this work we investigate the dynamics of a suspension of conducting rods in an applied electric field, in the limit thin electrical double layers. The theory by Bazant and Squires for induced-charge electroosmosis [1, 2] is extended to high-aspect ratio particles to derive a simple model for the induced flow on the particle surfaces. Simulations are performed that include multi-body hydrodynamic interactions, and results are reported for orientation distributions and pair distribution functions. In particular, the pair distribution functions indicate that particle pairing occurs in the suspension as a result of the induced electroosmotic flow. A simple two-particle analytical model is derived for the pairing.
Development of a Robust Controller and Observer for the Control of a Single-Link Flexible Robotic Manipulator
Authors: Chalhoub N. G. , Kfoury G. A. , Bazzi B. A.
Published: April 2008

A fuzzy-sliding mode controller (FSMC) has been developed in this study to control the rigid and flexible motions of a single-link robotic manipulator. Only the angular displacement at the base joint of the beam is assumed to be measured. Therefore, a robust nonlinear observer has been designed, based on the sliding mode methodology, to accurately estimate the state variables in the presence of both structured and unstructured uncertainties. Both the controller and the observer account for the first elastic mode of the beam in their design. The dynamic model, used in assessing the performance of the closed-loop system, considers the first two elastic modes of the beam. The second elastic mode is included in order to investigate the effects of the higher order dynamics on the overall performance of the system. The digital simulations demonstrate the capability of the observer in yielding accurate estimates of the state variables in the presence of modeling inaccuracies. Furthermore, they serve to prove the viability of using the observer to provide on-line estimates of the state variables for the computation of the control signals. The simulation results illustrate robust performances of the controller and the observer in controlling the rigid and flexible motions of the single-link robot in the presence of both structured and unstructured uncertainties.
Enhancement of the Accuracy of the Modified (P–ω) Method Through the Implementation of a Nonlinear Robust Observer
Authors: Kfoury G. A. , Chalhoub N. G. , Henein N. A. , Bryzik W.
Published: April 2008

The original version of the (P–ω) method is a model-based approach developed for determining the instantaneous friction torque in internal combustion engines. This scheme requires measurements of the cylinder gas pressure, the engine load torque, the crankshaft angular displacement and its time derivatives. The effects of the higher order dynamics of the crank-slider mechanism on the measured angular motion of the crankshaft have caused the (P–ω) method to yield erroneous results, especially, at high engine speeds. To alleviate this problem, a nonlinear sliding mode observer has been developed herein to accurately estimate the rigid and flexible motions of the piston-assembly/connecting-rod/crankshaft mechanism of a single cylinder engine. The observer has been designed to yield a robust performance in the presence of disturbances and modeling imprecision. The digital simulation results, generated under transient conditions that represent a decrease in the engine speed, have illustrated the rapid convergence of the estimated state variables to the actual ones in the presence of both structured and unstructured uncertainties. Moreover, this study has proven that the use of the estimated rather than the measured angular displacement of the crankshaft and its time derivatives can significantly improve the accuracy of the (P–ω) method in determining the instantaneous engine friction torque. However, the effects of structural deformations of the crank-slider mechanism have rendered the original version of the (P–ω) method to be inapplicable at high engine speeds. This problem has been addressed herein by modifying the formulation of the (P–ω) method in order to account for the first two elastic modes of the crankshaft torsional vibration. The simulation results confirm the good performance of the modified (P–ω) method in determining the instantaneous friction torque at high engine speeds.
Architecture and Hydraulics of a Lower Extremity Exoskeleton
Authors: Zoss Adam , Kazerooni H.
Published: April 2008

Wheeled vehicles are often incapable of transporting heavy materials over rough terrain or up staircases. Lower extremity exoskeletons supplement human intelligence with the strength and endurance of a pair of wearable robotic legs that support a payload. This paper summarizes the design and analysis of the Berkeley Lower Extremity Exoskeleton (BLEEX). The anthropomorphically-based BLEEX has seven degrees of freedom per leg, four of which are powered by linear hydraulic actuators. The selection of the degrees of freedom, critical hardware design aspects, and initial performance measurements of BLEEX are discussed.
Experimental Study of Effects of Volumetric Porosity and Critical Meniscus Radius on Evaporation/Boiling From Thin Capillary Wicks
Authors: Li Chen , Peterson G. P.
Published: April 2008

The evaporation/boiling heat transfer and critical heat flux (CHF) from surfaces coated with multiple, uniform layers of sintered isotropic copper mesh were studied experimentally in an atmospheric environment. Two series of investigations were conducted: one was designed to study the effects of the critical meniscus radius and effective pore size, which are controlled by the wire diameter and mesh number, with the volumetric porosity and wick thickness are held constant; and a second to study the effects of volumetric porosity for a constant wick thickness and effective pore size. The experimental results indicate that the critical heat flux (CHF) was strongly dependent on the critical meniscus radius and effective pore size, as well as the volumetric porosity; while the evaporation/boiling heat transfer coefficient was significantly affected by critical meniscus radius and effective pore size, but not strongly dependent on the volumetric porosity. The data further illustrate that the menisci at CHF are located in the corner formed by wire and heated wall and between the wires in both the vertical and horizontal directions. The minimum value of these three menisci determined the maximum capillary pressure generated through the capillary wick. Sample structure and fabrication processes as well as the test procedures, are described in detail and discussed. The experimental results and observations are systematically presented and analyzed.
Flutter Analysis of Viscoelastic Sandwich Plate in Supersonic Flow
Authors: Khudayarov B. A.
Published: April 2008

In this work is investigated the flutter of viscoelastic sandwich plate streamlined by gas current. The basic direction of work is consisted in taking into account of viscous-elastic material’s properties at supersonic speeds. The vibration equations relatively of deflection are described by Integro-Differential Equations (IDE) in partial derivatives. By Bubnov-Galerkin methods reduced the problems to investigation of system of ordinary IDE. The IDE are solved by numerical method, which based on using of quadrature formula. Critical speeds for sandwich plate flutter are defined.
Research on the Identification of Nonlinear Internal Damping and Kinematical Joint Damping of Mechanical Systems
Authors: Wu Ziying , Liu Hongzhao , Liu Lilan , Yuan Daning
Published: April 2008

A simultaneous identification method of the nonlinear internal damping of alloy material and the Coulomb friction in the kinematical joints in a mechanical system is put forward in this paper. The free vibration differential equation of a vibration system with these two kinds of damping is established. According to the free vibration response signal, the nonlinear internal damping characteristic curve and the Coulomb friction are got by using the moving rectangle window method. Several types of the nonlinear damping models are investigated in simulations. The validity and accuracy of the proposed method are illustrated by the good simulation results, in which the computing accuracy of the nonlinear internal damping is higher than that of the Coulomb damping in kinematical joints.
Studies on Tantalum Nitride (TaN) Hard Coatings on Turning Tools by DC Magnetron Sputtering Technique
Authors: Aryasomayajula Aditya , Gupta Mohit Kumar , Janarthanaam Santhosh Kumar
Published: April 2008

Tantalum nitride (TaN) thin films were coated at room temperature (30°C) on carbide turning inserts using DC magnetron sputtering technique. The mechanical properties like adhesion and hardness of these coating have been evaluated by Scratch tester; the thickness is estimated by Ball and Crater method. The properties of the films are studied by X-Ray diffraction (XRD) technique. The Optical Emission Spectroscopy (OES) has been employed to analyze the sputtering plasma to understand the reaction kinetics of tantalum nitride formation. The surface of the substrates: tools, glass and single crystal silicon, has been treated with plasma for better adhesion. A 2 μm thick TaN was deposited on the turning inserts. The coated inserts withstood a load of 20 N. The preliminary results reported are quite encouraging.
Multivariable Identification and Controller Validation of a Flight Control System
Authors: Fung E. H. K. , Wong Y. K. , Yau D. T. W.
Published: April 2008

This paper investigates the multivariable identification and controller validation for the longitudinal channel of a Boeing 747 transport. The transfer function matrix of the system are identified using the prediction error (PE) identification method with multivariable ARX model. An ellipsoidal parametric uncertainty set is constructed from the covariance matrix of the identified parameters. It contains the parameters of actual system at a certain probability level. The identified models and the associated uncertainty sets are validated by measuring the worst case v -gap. A PID controller is chosen for the pitch angle control and a H∞ controller is designed for the speed control. Their stability are validated by measuring the stability radius. The performance is further validated by computing the worst case performance criterion function which is obtained by solving a standard convex optimization problem involving linear matrix inequalities (LMI) constraints.