bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Grafting Methodology of Nano-Particle Reinforcement on the Performance of Structural Hybrid Composite
Authors: Akinyede Oladapo , Mohan Ram , Kelkar Ajit , Sankar Jag
Published: April 2008

Inclusion of nano-sized alumina by the surface treatment of S2 fiberglass (fiber modification) or ultrasonically exfoliated in epoxy resin system (resin modification) has been shown to provide epoxy-fiberglass hybrid composite systems with changes in their mechanical/ damage behavior under static tensile loading conditions. Integration of alumina nano-particles in epoxy-S2 fiberglass to form hybrid composites has not only shown improvements in the material properties, but also changes in the failure mechanism of the material system. This phenomenon is influenced by the changes in constituent interaction and its load transfer mechanism. In the processing of these hybrids composite systems, alumina nano-particles (sized at 110nm) are functionalized and grafted into epoxy composite material system during material processing via resin solution treatment and fabric surface treatment. These alumina embedding methodologies to form hybrid composites employed are the resin modification and fiber modification in conjunction with the conventional vacuum assisted resin transfer molding (VARTM) process for the manufacture of composite laminates. The chemical bonding and adhesion between the inorganic alumina and the organic resin is also enhanced via the functional treatment of the alumina particles with a coupling agent in the form of tris-2-methyoxyethoxy vinylsilane- T2MEVS (silane coupling agent). Processing methodologies are used to fabricate particulate reinforcement for various (<5%wt) compositions. Performance evaluation is carried to study the effect of the nano-particulate alumina on mechanical properties. Thermo-physical properties changes caused by particulate inclusion in hybrid material matrix phase are studied via Differential Scanning Calorimetry (DSC) and are also discussed.
Numerical Simulation of Direct Metal Laser Sintering of Single-Component Powder on Top of Sintered Layers
Authors: Xiao Bin , Zhang Yuwen
Published: April 2008

A three dimensional model describing melting and resolidification of direct metal laser sintering of loose powders on top of sintered layers with a moving Gaussian laser beam is developed. Natural convection in the liquid pool driven by buoyancy and Marangoni effects is taken into account. A temperature transforming model is employed to model melting and resolidification in the laser sintering process. The continuity, momentum, and energy equations are solved using a finite volume method. Effects of dominant processing parameters including number of the existing sintered layers underneath, laser scanning velocity and initial porosity on the sintering process are investigated.
The Role of Surface Tension Effects During Methanol Droplet Combustion
Authors: Raghavan Vasudevan , Pope Daniel N. , Gogos George
Published: April 2008

A numerical investigation of methanol droplet combustion in a zero-gravity and low-pressure convective environment is presented. Simulations have been carried out using a predictive, transient and axisymmetric model, which includes droplet heating, liquid-phase circulation and water absorption. First, a suspended droplet (constant relative velocity) burning in an ambient of air at 300K is considered. A nearly quiescent environment (initial Reynolds number Re0=0.01) is used to impose a weak gas-phase convective flow, introducing a deviation from spherical symmetry. The resulting weak liquid-phase circulation is greatly enhanced due to surface tension effects, which create a complex, time-varying, multicellular flow pattern within the liquid droplet. The complex flow pattern, which, in the presence of surface tension, results in nearly perfect mixing, causes increased water absorption within the droplet, leading to larger extinction diameters. Surface tension effects are shown to be dominant in causing water absorption, even at initial Reynolds numbers as high as 5. Results for combustion in a nearly quiescent environment (Re0=0.01) with varying initial droplet diameters, (d0 = 0.16 to 1.72 mm), show that predictions of droplet extinction diameters, although they are still below the experimental data, do improve substantially when surface tension effects are included. Next, results for suspended droplets and for moving droplets burning in an ambient of air at 1200K, for a range of initial Reynolds numbers that are of interest in spray combustion (Re0=1-100) are presented. It is shown that, for moving droplets, due to the presence of an envelope flame at some stage during the droplet lifetime, surface tension is important over the entire range of Re0 considered; the extinction diameter decreases with increasing Re0. Extinction is not observed for a moving droplet when surface tension effects are neglected. For suspended droplets, when transition or envelope flame is present, which corresponds to Re0 less than approximately 15, surface tension is important; when an envelope flame is present (Re0 less than approximately 10), the extinction diameter increases with Re0. The variation of droplet lifetime with Re0 is much stronger for suspended droplets than for moving droplets. Depending on the Reynolds number, results on methanol droplet lifetimes and extinction diameters measured through suspended droplet experiments may not be applicable to moving droplets.
Investigation of Hydrogen Transport Related Fracture in Stainless Steels
Authors: Kim Y. , Chao Y. J. , Pechersky M. J. , Morgan M. J.
Published: April 2008

Stress-assisted hydrogen diffusion analysis was performed on arc-shaped tension specimen (C-specimen) fabricated from Type 21-6-9 stainless steel. Two-dimensional finite element method was applied for the determination of elastic-plastic crack front stress fields, which was later coupled with hydrogen diffusion analyses. The extension of Fick's rule was used as the governing equation for the diffusion analysis. The distributions of hydrogen concentration were compared under various Internal Hydrogen Embrittlement (IHE) and Hydrogen Environment Embrittlement (HEE) conditions. Without any external hydrogen pressure in IHE conditions, the increment of hydrogen concentration driven by the gradient of hydrostatic stress was offset by the out-gasing driven by gradient of hydrogen concentration at the crack front region. As the hydrogen pressure increases, the hydrogen concentration at the crack front region becomes dominant and show peak value around the crack tip. Compared with the results of IHE cases, the hydrogen concentrations in HEE conditions could reach the level of steady state in a relatively short time which is attributed to the high solubility and diffusivity of the material at high temperature.
Periodic Motions in the Periodically Forced Oscillator With Multiple Discontinuities
Authors: Luo Albert C. J. , Patel Mehul T.
Published: April 2008

In this paper, the stability and bifurcation of periodic motions in periodically forced oscillator with multiple discontinuities is investigated. The generic mappings are introduced for the analytical prediction of periodic motions. Owing to the multiple discontinuous boundaries, the mapping structures for periodic motions are very complicated, which causes more difficulty to obtain periodic motions in such a dynamical system. The analytical prediction of complex periodic motions is carried out and verified numerically, and the corresponding stability and bifurcation analysis are performed. Due to page limitation, grazing and stick motions and chaos in this system will be investigated further.
The Radiating Annular Fin Problem: A Solution Based on the Green's Function Method
Authors: Jones Matthew R. , Solovjov Vladimir P.
Published: April 2008

Radiating fins are essential elements in the thermal control systems of most spacecraft. The size and weight of the radiating surfaces dominate the design of the thermal control system, so the development of tools useful in the design and optimization of radiating fins is of interest. This paper presents a rigorous new approach for solving the non-linear diffusion problem which results from the analysis of an annular radiating fin. The steady-state, radial temperature profile in the fin is obtained using a Green's function method. The solution method described in this paper results in a single integral equation, whereas solution procedures described in the literature require simultaneous solution of coupled differential and integral equations. The analysis presented in this paper provides new insight into the solution of a classical problem in the thermal management of space vehicles. In addition, the approach outlined in this paper may be applied directly to other types of radiating fins or to other applications governed by non-linear problems.
Enhancement of Natural Convection Heat Transfer in Triangular Channels Using Corona Discharge in Nitrogen Gas
Authors: Molki Majid , Harirchian Tannaz
Published: April 2008

A computational investigation was conducted to determine the effect of nitrogen corona discharge on enhancement of natural convection heat transfer in a triangular channel. The channel side walls were isothermal, the lower wall was adiabatic, and the fluid was nitrogen gas at atmospheric pressure. The electric field was generated by a positive corona discharge from a charged wire electrode located at the center of the channel. The current-voltage characteristics of the corona discharge was measured for nitrogen and used in the computations. The governing equations of the electric and flow fields were solved by a finite-volume technique. Two different meshes, namely structured and unstructured, were used. In the computations, Rayleigh number and the electrode voltage ranged from 3,737 to 37,377 and from 8.25 to 9.5 kV, respectively. At lower values of the applied voltage, the flow pattern was characterized by the presence of six vortices. At higher voltages, however, the flow pattern changed into a single recirculation that covered the entire cross section of the channel. For the applied voltage of 8.5 kV, heat transfer coefficient was enhanced by 18 to 43.6%, while at 9 kV, the enhancement was 53.5% to 87.3%.
Infrared Thermography and Thermoelectrical Study of a Solid Oxide Fuel Cell
Authors: Ju Gang , Reifsnider Kenneth
Published: April 2008

The current interest in power generation industry with more efficient and clean, and more environmentally friendly ways has attracted the research and development in solid oxide fuel cell (SOFC). In SOFC, the chemical energy is converted into electric energy and heat as the by-product. In order to make a thermally self-sustained fuel cell stack, the understanding and management of the heat generation and electric power is a critical issue. Infrared thermography provides a non-destructive way to measure surface temperature. It was used to measure the instantaneous cathode surface temperature response to the current in an operating electrolyte supported planar solid oxide fuel cell (LSCF-6ScSZ-NiO). A numerical model was built to study the coupled electric current and temperature relation by incorporating the temperature dependent material properties, i.e. ohmic resistance and activation resistance, as global functions in the model. The thermal and electric fields were solved simultaneously. The measured and the predicted results agree to each other reasonably well. The cathode polarization overpotential tends to increase with the current at low current densities, but the simulated polarization-current curve exhibited a decreased slope under higher current densities that is ascribed to the local temperature increases due to the high current energy losses.
Integrated Optimization of a Smart Hanger for Garment Inspection Using Multi-Objective Genetic Algorithm
Authors: Yuen C. W. M. , Fung E. H. K. , Wong W. K. , Hau L. C. , Au K. F.
Published: April 2008

This paper presents the formulation and application of Multi-Objective Genetic Algorithm (MOGA) for the design and optimization of a smart hanger, which simulates the manual handling of garments to facilitate the inspection process. Due to the symmetrical nature of clothes, the hanger is expected to expand only half of the clothes. Thus, a four-link robot consisting of three revolute joints and one prismatic joint is employed to model the hanger. With a Proportional and Derivative (PD) controller, the hanger can regulate the link positions by adjusting the applied torques and force. The objective functions are to (1) maximize the link portions within the "effective regions" at final state, (2) minimize the force or torque required to finish the stretching process, and (3) minimize the settling time of the stretching process. In addition to the control gains, the lengths of the four links as well as the desired movements of the joints are the design variables in this optimization problem. The required transient behavior of the system is defined by the constraints on the settling time and the maximum overshoot. Besides, to prevent the clothes from being destroyed by the links when stretching, geometrical constraints are imposed to the motions of the links. MOGA is applied to tackle this integrated optimization problem. The optimization results are presented in the form of Pareto solutions. After analysis, optimal parameters are selected, and numerical simulations are conducted. Results show the feasibility of the hanger.
A New Approach in Finite Element Modeling of Generally Laminated Composite Beams
Authors: Ahmadian M. T. , Jafari-Talookolaei R. A.
Published: April 2008

In this paper, a new finite element model for a generally laminated composite beam (LCB) is presented. Natural frequencies of a generally LCB are derived by developing the stiffness and mass matrices considering the effects of axial force, shear and torsional deformations and rotary inertia. This model includes coupling of bending and torsional modes of deformations which is usually present in LCBs due to ply orientation. The model is designed in such away that it can be used for single and double stepped cross-section. Comparing numerical results for simple cases with analytical solutions and literature indicate high accurate and quick response of the model.
Preliminary Design Considerations for Integrating a Composite Impeller in a Brushless Permanent Magnet Motor
Authors: Mouland Mark H. , Mu¨ller Norbert
Published: April 2008

Traditional turbomachine design is generally characterized by a shaft driven impeller that was created using common manufacturing processes. However, a cutting edge and innovative impeller design involves the manufacturing of the impeller on a winding machine. Through the use of such a machine, a lightweight and high-strength impeller with carbon fibers or other fibers can be prototyped quickly and easily while also produced in large quantities. The impeller will not only be a composite of multiple parts, but a single solid piece. One of the most interesting attributes of this impeller however, is the ability to integrate it as the rotor for a permanent magnet electric motor. Using the concepts of permanent magnet motor design, current can be applied to the housing of the impeller, which would generate forces that would serve the purpose of both rotating the impeller, and securing it into place. This has the advantage of eliminating most of the moving parts in a turbomachine design, but also creating a durable, lightweight and cheap design to prototype and reproduce. Another key advantage to this design is where the torque on the impeller is applied. Traditional turbomachines generally have the torque generated from forces applied from the shaft, which requires higher tangential forces and hence shear stresses due to a much smaller moment arm. But the integration of magnetics into the outer shroud of the impeller allows for the forces to be applied to the outer edge, which requires less force due to a much greater moment arm. Furthermore, this type of motor inherently allows for all of the electrical components to be outside of the fluid flow, which reduces the need for extensive sealing and insulation. In this paper, basic concepts behind the design of electric motors are outlined, as well as how they can be integrated with a rotor impeller, such that together they could act as a turbomachine.
Quantifying Vessel Material Properties Using MRI Under Pressure Condition and MRI-Based FSI Mechanical Analysis for Human Atherosclerotic Plaques
Authors: Yang Chun , Huang Xueying , Zheng Jie , Woodard Pamela K. , Tang Dalin
Published: April 2008

Atherosclerotic plaques may rupture without warning and cause acute cardiovascular syndromes such as heart attack and stroke. Mechanical image analysis using MRI-based models with fluid-structure interactions (FSI) and MRI-determined material properties may improve the accuracy of plaque vulnerability assessment and rupture predictions. A plaque-phantom was set up to acquire plaque MR images under pressurized conditions. The 3D nonlinear modified Mooney-Rivlin (M-R) model was used to describe the material properties with parameters selected to fit the MRI data. The Navier-Stokes equations were used as the governing equations for the flow model. The fully-coupled FSI models were solved by ADINA. Our results indicate that doubling parameter values in the M-R model led to 12.5% decrease in structure maximum principal stress (Stress-P1) and 48% decrease in maximum principal strain (Strain-P1). Flow maximum shear stress (MSS) was almost unchanged. Results from a modified carotid plaque with 70% stenosis severity (by diameter) showed that Stress-P1 at the plaque throat from the wall-only model is 145% higher than that from the FSI model. MSS from a flow-only model is about 40% higher than that from the FSI model. This approach has the potential to develop non-invasive patient screening and diagnosis methods in clinical applications.
Non-Contact Acoustic Techniques for Drug Tablet Monitoring
Authors: Akseki Ilgaz , Libordi Christopher F. , Cetinkaya Cetin
Published: April 2008

Quality assurance monitoring and material characterization is of great importance in the pharmaceutical industry. If the tablet coating and/or core are defective, the desired dose delivery and bioavailability can be compromised. Tablet coatings serve a wide variety of purposes such as regulating controlled release of active ingredients in the body, contributing to the bioavailability of a particular drug or combination of drugs, during certain times and locations within the body, protecting the stomach from high concentrations of active ingredients, extending the shelf life by protecting the ingredients from degradation from moisture and oxygen, and improving the tablet's visual appeal. If a coating layer is non-uniform and/or contains surface or sub-surface defects, the desired dose delivery and bioavailability can be compromised. The Food and Drug Administration has initiated a program named the Process Analytical Technology (PAT) in order to ensure efficient quality monitoring at each stage of the manufacturing process by the integration of analytical systems into the procedure. Improving consistency and predictability of tablet action by improving quality and uniformity of tablets is required. An ideal technique for quality monitoring would be non-invasive, non-destructive, rapid, intrinsically safe and cost-effective. The objective of the current investigation was to develop, non-contact/non-destructive techniques for monitoring and evaluating drug tablets for mechanical defects such as coating layer irregularities, internal cracks and delamination using a laser-acoustic approach. In the proposed system, a pulsed laser is utilized to generate non-contact mechanical excitations and interferometric detection of transient vibrations of the drug tablets. Three novel methods to excite vibration in drug tablets are developed and employed: (i) a vibration plate excited by a pulsed-laser, (ii) pulsed laser-induced plasma expansion, and (iii) an air-coupled acoustic transducer. Nanometer-scale transient surface displacements of the drug tablets are measured using the laser interferometer. Signal processing techniques are then applied to these transient displacement responses to differentiate the defective tablets from the nominal ones. From the analysis of frequency spectra and the time-frequency spectrograms obtained under both mechanisms, it can be concluded that defective tablets can be effectively differentiated from the nominal ones.
Teaching Database Courses to Engineering Students
Authors: Zeid Abe
Published: April 2008

The teaching of databases to engineering students at the undergraduate level has proven challenging for multiple reasons. First, the course is a nontraditional engineering course. Second, the concepts of databases are highly abstract. Third, engineering students prefer the problem-solving, hands-on, and project-based method of learning over the coverage of database design concepts. Fourth, there is a lack of engineering-oriented database textbooks. This paper presents an effective teaching approach that overcomes these challenges. The approach mixes and integrates the database abstract concepts with hands-on and capstone-based learning activities. The approach incorporates engineering students' feedback during the course. The paper discusses the database course objectives, content, project requirements, the skill set students learn, the software tools they use, and assessment tools. Sample projects and students' comments are included. The paper concludes with some observations that can be useful to use in traditional engineering courses to provide a new perspective of teaching in engineering.
Combined Effects of Stress Concentration and Fatigue on the Reliability of Notched Laminates
Authors: Ganesan R. , Arumugam A. K.
Published: April 2008

Composite laminates are used in structural applications such as aircraft wings and tail structures. Drilling holes and making cutouts in these laminates are unavoidable for practical reasons. As a result, stress concentration is introduced near the hole or cutout, and the load-bearing capacity of the structure is reduced. In addition, composite laminates used in aerospace applications are subjected to considerable fatigue loading due to service conditions. In composite laminates, fatigue causes reduction in stiffness and strength. The objective of the present work is to study the combined effect of stress concentration and fatigue on the composite laminate. Since composite laminate displays significant variation in material and strength properties, the stress distribution in the laminate is stochastic in nature. It is more appropriate to analyze the notched composite laminates using a stochastic approach and to design the laminate based on a reliability-based design approach. In the present work, such an approach is developed and the combined effect of stress concentration and fatigue on the reliability of the laminate is investigated.
Rail Geometry and Euler Angles
Authors: Rathod Cheta M. , Shabana Ahmed A.
Published: April 2008

In railroad vehicle dynamics, Euler angles are often used to describe the track geometry (track centerline and rail space curves). The tangent and curvature vectors as well as local geometric properties such as the curvature and torsion can be expressed in terms of Euler angles. Some of the local geometric properties and Euler angles can be related to measured parameters that are often used to define the track geometry. The Euler angles employed, however, define a coordinate system that may differ from the Frenet frame used in the classical differential geometry. The relationship between the track frame used in railroad vehicle dynamics and the Frenet frame used in the theory of curves is developed in this paper and used to shed light on some of the formulas and identities used in the geometric description in railroad vehicle dynamics. The conditions under which the two frames (track and Frenet) become equivalent are presented and used to obtain expressions for the curvature and torsion in terms of Euler angles and their derivatives with respect to the arc length.
Algorithm for the Prediction of Traction Performance of Terrain Vehicles
Authors: Li Lin , Sandu Corina
Published: April 2008

This paper presents the development of an algorithm to estimate the tractive force of an off-road vehicle with uncertainties in the tire stiffness and in the soil moisture content. The algorithm compares the average ground pressure with the critical ground pressure to decide if the tire can be approximated as a rigid wheel, or if it should be modeled as a flexible wheel, and involves using previously developed vehicle and stochastic soil models, and computing along the way the vehicle sinkage, resistance force, tractive force and drawbar pull. The soil modeling focuses on the efficient treatment of poorly known parameters, such as the soil moisture content, and on the impact of these uncertainties on relationships critical in defining the mobility of an off-road vehicle, such as the pressure-sinkage and the shear stress-shear displacement relations. The uncertainties in the tire stiffness and in the soil properties are propagated through the model, and the uncertainty in the output of the vehicle model is analyzed. Such simulations can provide the basis for the study of ride performance, handling, and mobility of the vehicle in off-road conditions. The vehicle model used has seven degrees of freedom. Each of the four suspension systems comprises of a nonlinear spring and a linear viscous damper. The analysis of the dynamic response of the vehicle is performed for two scenarios: a light cargo, and a heavy cargo.
A Paradox of Heat Conduction in Porous Media Subject to Lack of Local Thermal Equilibrium
Authors: Vadasz Peter
Published: April 2008

Based on the traditional formulation of heat transfer in porous media it is demonstrated that Local Thermal Equilibrium (Lotheq) applies generally for any boundary conditions that are a combination of constant temperature and insulation. The resulting consequences raising an apparent paradox are being analyzed and discussed.
Monotonic Growth of Motile Microorganisms
Authors: Vadasz Alisa S. , Vadasz Peter , Leid Jeff G. , Andrade Amanda , Cope Emily , Dobbs Elizabeth , Yong Chen Kiat , Zavodnyik Steven
Published: April 2008

The research results presented here are part of a more extensive effort regarding sustained bioconvection in porous media. Bioconvection is the phenomenon of gravity driven fluid motion due to buoyancy forces resulting from density differences between the fluid and motile micro-organisms suspended in the fluid. While the field of bio-convection in pure fluids emerged substantially over the past decade the corresponding effects of bio-convection in porous media received much less attention, despite the fact that micro-organisms grow naturally in porous environments; soil, food and human tissues serve as basic examples. The research focuses in two major new directions. The first deals with the theoretical and experimental investigation of bio-convection in porous media. The second major new direction is linked to the sustainability of the bio-convection motion. The existing work on bio-convection in both pure fluids and porous media exclude micro-organism growth during the bio-convection because the time scales concerned were very short. However, when the question of the sustainability of this convection over long times arises, microorganism growth has to be accounted for. If sustained bio-convection in porous media is possible it opens the avenue to investigate its impact on microbial proliferation in soil, food and human tissue, an important avenue for application of the theoretical results. Then, if bio-convection enhances microbial proliferation it may be undesirable in some cases, e.g. in food, or it might be desirable if specific micro-organisms that can be used for contaminated soil remediation will be "helped" by the bio-convection process to access contaminated regions in the soil. The theoretical and experimental results presented in this paper reflect the process of monotonic growth of motile microorganisms (e.g. the PAOI strain of Pseudomonas Aeruginosa) to be included in the bioconvection process. A new proposed model is shown to be the appropriate one to better reflect both conceptually as well as practically the microbial growth process.
Dynamic Analysis of a Digital Micromirror Device
Authors: Chaabane G. , Abdel-Rahman E. M. , Nayfeh A. H. , Choura S. , El-Borgi S. , Jammoussi H.
Published: April 2008

We developed a distributed-parameter model (partial differential equations and associated boundary conditions) that describe the coupled torsion and bending motions of the Digital Micromirror Device (DMD) using the extended Hamilton principle. The work done by the electrostatic field is expressed in the form of a potential energy. It is found that coupling between the torsion and bending motions appears in the boundary conditions. The nonlinearity is mainly due to the application of the electrostatic forces and moments. Nonlinear terms appear only in the boundary conditions. The developed model provides a basis for a thorough study of the static and dynamic behaviors of the electromechanical device. The static response of the DMD for different DC loads shows the occurrence of pull-in (snap-down) instability at critical voltage values corresponding to the collapse of the yoke to mechanical stops. Estimates of the voltage, angle, and deflection at pull-in are given. The dynamic behavior of the DMD is analyzed by plotting the natural frequencies versus the applied DC voltage. We conducted a study of the sensitivity of the static and dynamic behaviors of the micromirror to variations in the geometric parameters of the DMD. It is found that the thickness and width of the hinges are the key parameters influencing the occurrence of static pull-in and the values of the voltage, angle, and deflection at pull-in.
Motor Vehicle Exterior Sound Quality Improvement for Indoors
Authors: Ishihama Masao , Sakurai Hiromitsu
Published: April 2008

The objectives of this study are these three items. 1) To find better indices than dB(A) for representing annoyances caused by motor vehicle traffic noise along highways. 2) To find the frequency range of motor vehicle exterior noise that should primarily be controlled to achieve better indoor sound environment along highways. 3) To find suitable vehicle driving conditions for evaluating indoor sound environment. To obtain the desired results psycho-acoustic experiments were conducted. Firstly, sound samples were collected with microphones placed at such locations as on a sidewalk, in front of a small house and at the center of a room inside of the house. The number of test vehicles was fifteen, consisting of six motorcycles and nine passenger cars. The driving conditions were full acceleration and mild acceleration usually found in normal traffic flow. Secondly, semantic differentiation method was used. Ten pairs of adjectives were used to scale the impressions of each sound sample. Finally, physical characters of the sound samples and their subjective evaluations were compared. The results were obtained as follows. 1) Six sound samples got more uncomfortable impression at indoors. These sound samples were collected by vehicles with sport-type mufflers. 2) The samples that indoor sound quality is degraded than outdoor contain high power in low frequency range below 200 Hz. These low frequency components penetrate through the housing walls more easily than higher frequency components. 3) The degradation of comfort impression was found in mild acceleration conditions. The low frequency components of sound samples for mild acceleration are larger than those for full acceleration. Though the throttle is not fully open in mild acceleration, low engine speed generates low frequency components, and eventually increased indoor sound power in the frequency range. The conclusions drawn from these results are, 1) Indoor sound samples should be included for evaluating sound environment along highways. 2) Mild acceleration is a better driving condition for evaluating indoor sound environment along highways. In this condition, very low engine speed causes low frequency component emission that penetrate into housing more than in heavy accelerating conditions. 3) Engine exhaust systems that emit very loud low-frequency components should be focused upon in regulating traffic noise. 4) Extensive collection and analysis of housing sound insulation, absorption and resonance data along highways are necessary for further investigations. 5) Better psycho-acoustic experiment methods should be developed for investigating sound context effects on panelists.
Modeling of the Concurrent Gas-Liquid Trickling Flow Through a Packed-Bed Reactor to Predict Interfacial Area
Authors: Jo Daeseong , Olenik Hayden C. , Revankar S. T.
Published: April 2008

A wavy annular flow model in a packed-bed is developed by introducing the shape of waves in a thin liquid film to predict the local interfacial area. The trickling flow regime in a packed-bed is often approximated by an annular flow through a narrow circular channel in which the continuous gas and liquid are completely separated by a smooth and stable interface. Most of the existing models for the trickling flow utilize balance equations for each phase to predict hydrodynamics parameters: liquid hold-up, interstitial velocities, pressure drop, or void fraction. However, the smooth and stable annular flow may not result in an accurate prediction of the interfacial area between gas-liquid phases in a packed-bed. Therefore, a wavy annular flow model is introduced to predict the more accurate interfacial area. This is important because the transport of mass, momentum, and energy is proportional to the interfacial area between gas and liquid phase. Because of the annular flow model, the ratio of film thickness to the equivalent channel diameter can be expressed as a function of only void fraction. The two-parallel wire probe allowed to measure the local film thickness has been used to obtain the shape of the interface. By integrating the local interfacial areas over a certain time period, the local interfacial area is evaluated. The interfacial areas predicted by the presented model are comparable with the empirical correlations developed in the past decades.
On the Properties of Anisotropic Piezoelectric and Fiber Reinforced Composite Materials
Authors: Gaith Mohamed , Akgoz Cevdet
Published: April 2008

A new procedure based on constructing orthonormal tensor basis using the form-invariant expressions which can easily be extended to any tensor of rank n. A new decomposition, which is not in literature, of the stress tensor is presented. An innovational general form and more explicit physical property of the symmetric fourth rank elastic tensors is presented. The new method allows to measure the stiffness and piezoelectricity in the elastic fiber reinforced composite and piezoelectric ceramic materials, respecively, using a proposed norm concept on the crystal scale. This method will allow to investigate the effects of fiber orientaion, number of plies, material properties of matrix and fibers, and degree of anisotropy on the stiffness of the structure. The results are compared with those available in the literature for semiconductor compounds, piezoelectric ceramics and fiber reinforced composite materials.
Stability of Thermoelectromagnetic Convection
Authors: Houchens Brent C.
Published: April 2008

The role of thermoelectromagnetic convection (TEMC) on the stability of a range of flows is investigated. Here we discuss the general features of TEMC, and describe experiments in which this effect is thought to have significance. The general formulation for TEMC at a solid-liquid interface is presented. Initial results are benchmarked with existing analytical and numerical solutions.
Experimental Study of Nanofluids for Droplet Cooling Applications Using Temperature Microsensors
Authors: Guinn John E. , Banerjee Debjyoti
Published: April 2008

The use of nano-fluids in droplet cooling (boiling) was explored parametrically in this experimental study. The experimental parameters are: nanofluid composition, superheat, liquid subcooling, and spray parameters (nozzle diameter, injection distance, size of droplets, injection pressure, mass flow rate, etc.). Two test fluids were used in the experiments: de-ionized (DI) water and nanofluid. The nano-fluid consists of silica nano-particles with a nominal diameter of 10nm dissolved in water at 2% concentration by weight. An experimental apparatus was fabricated to measure the surface temperature fluctuations during spray cooling of a heated surface. An array of microthermocouples (Thin Film Thermocouples or "TFT") was micro-fabricated on a heated surface to measure the surface temperature fluctuations during spray cooling. The TFT are capable of measuring temperature fluctuations up to a speed of 100 MHz. In the experiments, the exit of the single droplet spray was set a distance of 10 mm away from the surface and was aligned with the location of the TFT array. The spray was produced by pumping test fluid using a syringe pump into a traversing spray head. Silicon wafers with surface micromachined TFT array were clamped on the top of the heater apparatus for measuring temperature changes on the surface of the heater. Wire bead K-Type thermocouples were embedded in the heater apparatus and were used to measure heat flux. The transient temperature data from the TFT were recorded by a data acquisition system connected to a computer. The nano-fluid spray was found to cause fouling of the heater surface due to precipitation of the constituent nano-particles during boiling. This caused the overall heat flux to decrease drastically when compared to spray cooling using water. The nano-fluid spray was found to enhance heat flux by 300% compared to the base heat flux without the spray.
Experimental Identification of Linear and Nonlinear Dynamic Characteristics of a Foam Aircraft Model for Morphing Applications
Authors: Joshua Raymond R. , Adams Douglas E.
Published: April 2008

The genesis of so-called morphing aircraft has been mandated by the need for an expanded flight envelope to fulfill a variety of flight objectives. In order to address the need for expanded flight envelopes, researchers must consider the possibility of dynamic instability due to morphing associated with complex aero-structural interactions during design, development, and flight. The linear and nonlinear dynamic response characteristics of a model aircraft structure are examined in this paper. To identify the linear modal characteristics, impact testing was conducted and the nominal frequency response functions were extracted. Nonlinear characteristics are identified using time-frequency, restoring force, and higher-order frequency response analysis of swept sine response data. The scale-model aircraft with reconfigurable pre-stressed components exhibits strong nonlinearity in the 20-40 Hz frequency range. A cubic stiffness nonlinearity is identified in one portion of the aircraft. In the 40-60 Hz frequency range, stiffness nonlinearities dominate and damping characteristics are primarily linear in nature. Effective characterization of the nonlinearity is a prerequisite for efficient reduced-order models that accurately predict dynamic instability.
Effect of Thin Film Condensation on Thermal Performance of Oscillating Heat Pipes
Authors: Liang S. B. , Xu G. P.
Published: April 2008

Self-sustainable motions of the slug flow in oscillating heat pipes have been investigated in the paper. Thin film condensation in the capillary channels of the condenser of the oscillating heat pipes was studied. Instability of the thin liquid film on the characteristics of heat pipes was analysed. The extra thermal resistance caused by the thickness of the thin liquid film was taken into account for the numerical simulation of the oscillatory motions of the slug flow in the heat pipes. Saturated temperatures and pressures of the working fluid in the condenser were obtained. Thermoacoustic theory was applied to calculate heat transport through the adiabatic section of the heat pipes. Experimental studies were carried out to understand the heat transfer behaviours of heat pipes. One heat pipe with the working fluid of HFC-134a was evaluated. The heat pipe is made of aluminium plate and has the width of 50 mm and thickness of 1.9 mm. Numerical and experimental results relevant to the heat transport capability of the heat pipe were analysed and compared.
Modeling of the Elastic Properties of Contact Between Nominally Flat Rough Surfaces Using a New Multiple Point Asperity Model
Authors: Hariri A. , Zu J. W. , Ben Mrad R.
Published: April 2008

The asperities of rough surfaces have long been considered to be points higher than their immediate neighbors. Based on this concept, theories were developed for quantitatively understanding the nature of contact between rough surfaces. Recently it has been recognized that the above model for asperities is inadequate. Consequently, all the models that have been developed based on that model are inadequate as well. In this paper, based on a newly developed multiple-point asperity model, the elastic contact problem between nominally flat surfaces is reformulated. This leads to finding the deformed area, and load produced by the contact. The model is developed for the general form of isotropic rough surfaces with arbitrary height distribution and autocorrelation function (ACF). The microcontact areas generated by each asperity contact are considered to be circles. The Gaussian distribution of heights and exponential ACF are considered as a benchmark to compare the results of the new model with the existing models. Using results from numerical models developed by other groups, the new model is validated.
Study on Aerostatic Guidance
Authors: Zhao Peng , Satomi Tadaatsu , Nakazawa Tadashi
Published: April 2008

The aerostatic guidance is used as a super precision positioning device in the fields of semiconductor production and measurement machine, and its performance is expected to be improved. Although the study on the small guidance clearance region by which the high positioning precision may be expected is very important, there is almost no research papers published in this area to date. The purpose of this study is to enhance the calculation accuracy in the region of which the guidance clearance is comparatively small in the aerostatic guidance design. This is accomplished by considering the influence of the cutting surface roughness upon the air flow. More specifically, the amount of air flux passing through the orifice which is principal constituent of an aerostatic guidance is calculated in two separated parts. One part is the calculation done on the boundary layer flow whereas the other part on the potential flow. In this case, the calculation of the boundary layer flow is attempted using a theory in which the surface roughness is taken into account. That is, the calculation is done based on a virtual cylinder which has the same area as that of the rough inner surface of the orifice calculated based on the measured result of the surface roughness of an orifice cut surface. The truth inner surface area is calculated from the inspection result of the inner surface roughness measured by using a 3D surface roughness measuring machine. Through this method, the velocity distribution in the boundary layer is made clear where the diameter of the orifice is comparatively small, and a technique for calculating intrarubular flow is newly established. In addition, experimental apparatus to evaluate this theoretical calculation were designed and produced to confirm the flow characteristics and the load characteristic of the squeeze structure used in this study. As a result, the boundary layer velocity in the small diameter orifice which plays an important role in obtaining a high static rigidity and the pressure of the downstream side of the orifice can be calculated with precision. Thus, an attempt is made to improve the calculation precision of static rigidity in the small guidance clearance region where a high positioning precision can be expected. All of these calculation results are in a fairly good agreement with the experimental results.
Precise Measurement and Analysis of Heat Transfer to the Inlet Air Using Intake Port Model: Influence of Intake Valve and Unsteady Effect
Authors: Uchida Keisuke , Suzuki Takashi , Oguri Yasufumi , Yoshida Masatake
Published: April 2008

Temperature measurement experiments with an intake port model and analysis of heat transfer phenomena in the intake port model were carried out, and the influence of the high temperature intake valve to the heat transfer phenomena and the unsteady effect to heat transfer coefficient were investigated. From the results of steady flow experiments with a high temperature intake valve which was heated by a small electric heater, it came to be clear that the change of valve temperatures had little influence to the change of Nusselt number but Nusselt number changed greatly by mass flow rate of gas, and the heat quantity transferred from the heated intake valve was much greater than that from inside wall surface of the intake port model. And the results of unsteady flow experiments, it became clear that the relationship between Nusselt number and Reynolds number was changed by the flow condition of accelerating gas velocity, but this difference was not observed in decelerating gas velocity conditions.
Investigation of Multi-Degree of Freedom Damped Dynamic Absorber Applied to Wheel Noise Control
Authors: Chen Zhaobo , Tu Fengchen , Li Mingzhang , Li Hua , Jiao Yinghou
Published: April 2008

In order to reduce wheel-radiated wideband noise, a new solution that equipped the wheels with multi-degree of freedom (DOF) damped dynamic absorber (DDA) is proposed. The dynamic model of the wheel with absorbers was established. By numerical analysis, the primary structural parameters of the absorber influencing the noise control effect are obtained and optimized. The radiated noise is measured before and after the absorber installed in the laboratory and in the field. The test results show that the wheel-radiated noise could be substantially reduced, especially above 2000Hz. The test results agree well with the theoretical analysis. The parametric analysis provides reference value for the design of multi-DOF DDA
Impact Detection for Plate Based on Time Reversal Processing Using Experimentally Measured Sensor Signals of Surface Bonded PZT Patches
Authors: Adachi Kazuhiko , Sakai Yosuke
Published: April 2008

Time reversal processing for the measured sensor signal can be applied to detect not only structural damage but also impact loading of the structure. Impact identification capability of a time reversal processing using experimentally measured sensor signals is demonstrated in this paper. After measuring the electrical sensor signals corresponding to scattered wave filed of the plate experimentally, time reversal processing is applied to the measured signals in the numerical wave back propagation simulation for localizing the impact loading point on the plate. A time-reversed wave travels back through the plate and is focused on the region around a point where hits by the impact hammer. The illustrative experimental and numerical results demonstrate impact identification capability of the proposed method.