bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture Analysis of Cracks in Anisotropic Materials Using 3DFAS and ANSYS®
Authors: Ozkan U. , Kaya A. C. , Loghin A. , Ayhan A. O. , Nied H. F.
Published: April 2008

The analysis of two and three dimensional fracture mechanics problems in anisotropic materials using ANSYS finite element software and 3DFAS (Three Dimensional Fracture Analysis System) is examined in this study. The methodology uses analytically derived generalized plane strain crack tip fields in anisotropic materials and is implemented into an ANSYS Macro using ANSYS Parametric Design Language. It is shown that quarter-point finite element approach is still a very effective technique for general three dimensional crack problems in homogeneous anisotropic materials. The expressions of the crack tip asymptotic displacement field are summarized and numerical examples of two and three dimensional crack problems in orthotropic, directionally solidified, and single crystal materials are presented. The stress intensity factors are compared with two-dimensional analytical and numerical solutions available in the literature and with numerical solutions obtained from FRAC3D [1, 2], a three dimensional fracture analysis program using enriched finite elements. Very good agreement is obtained between the different numerical techniques or with the analytical solutions.
A Microfluidic Based High Throughput Resistive Pulse Sensor
Authors: Zhe Jiang , Jagtiani Ashish , Mamun Nazmul , Dutta Prashanta , Hu Jun , Carletta Joan
Published: April 2008

We describe a micromachined. resistive pulse sensor with multiple sensing microchannels. A unique design placing measurement microelectrodes in the center of the microchannels is demonstrated. This design creates isolation resistances among channels and thus circumvents the crosstalk caused by automatic electrical connection among microchannels. When implemented using microscale channels, the design is appropriate for the sensing of microscale particles in deionized water or in very dilute electrolyte solution; using nanoscale channels, the design is appropriate for the sensing of nanoscale particles in electrolyte solutions of any concentration. The design has multiple channels operating in parallel, but integrated with just one sample reservoir and one power source. The results with a four-channel device show that this device is capable of differentiating and counting micro polymethacrylate particles and Juniper pollens rapidly. The throughput is improved significantly in comparison to a single channel device. The concept can be extended to a large number of sensing channels in a single chip for significant improvement in throughput.
Structural Modification of Carbon Nanotube Tip Using Focused Ion Beam
Authors: Han C. S. , Yoon Y. H. , Shin Y. H. , Song J. W.
Published: April 2008

We report the structural modification of carbon nanotube (CNT) tip for Atomic force microscopy (SPM) based on ion beam irradiation. In general, CNT tip assembled by dielectrophoresis would often have non-vertical angle, very crooked shape or too lengthy one. Therefore, these tips should be modified to the appropriate shape to use as an AFM tip. We found that the ion beam could contribute to merge the bundled CNTs, to make the CNT diameter uniform as well as to make the wavy shape of CNT straight. In addition, we could cut the free-standing CNT on a Si tip using focused ion beam (FIB). From the atomic force microscope (AFM) measurement of 15 nm gold particles and DNA molecules, we showed that the CNT tip modified by FIB produced high resolution images as well as little wear by comparing with those of a conventional silicon tip
Discrete Variable Structure Control Based on Optimization by Cultural Differential Evolution Approach
Authors: Coelho Leandro dos Santos , Mariani Viviana Cocco
Published: April 2008

Advanced conceptions to design industrial control systems are, in general, dependent of mathematical models of the controlled process. Also, the task of the controllers is to achieve an optimum performance when facing with various types of disturbances that are, sometimes, unknown in practical applications. An advanced methodology for control design is the variable structure control (VSC) with sliding mode. This paper considers the non-linear control of industrial processes based on self-tuning discrete VSC technique. A novel and systematic VSC design methodology is proposed, which integrates an estimator based on recursive least square algorithm, a discrete quasi-sliding surface and a optimization method. Contrary to the trial and error selection of the variable structure feedback gains reported in the literature, the selection in present work is done using differential evolution (DE) optimization, an evolutionary computation technique, with a new operator based on normative knowledge of cultural algorithms. The proposed design has been applied to a control valve described by a non-linear Wiener model. Numerical simulation results reveal that the new DE approach is applicable and promising for the VSC design.
Simultaneous Detection of Multiple Bioparticles With a High Throughput Resistive Pulse Sensor
Authors: Jagtiani Ashish , Zhe Jiang , Newby Bi-min Zhang
Published: April 2008

We describe an all-electronic, label-free, resistive pulse sensor that utilizes multiple micropores for simultaneous detection and counting of multiple biological particles. Four particle samples were utilized for the sensor testing: 20μm and 40μm polymethacrylate (PM) particles, Juniper pollen and Eastern Cottonwood pollen. Experiments demonstrated that this sensor was able to differentiate and count multiple particle solutions simultaneously through its four micropores fabricated on polymer membranes. Thus the sensing throughput has been improved significantly. Furthermore, the experimental results also proved the feasibility of differentiating various pollens from PM microparticles with the multi-pore resistive pulse sensor, with no need for labeling of samples.
CFD Investigation of Developing and Redeveloping Laminar Flow and Heat Transfer Characteristics in Coiled Tube Systems for Constant Wall Temperature Heating and Cooling: Part II — Spiral Configurations
Authors: Bowman Anthony J. , Park Hyunjae
Published: April 2008

In this paper developing and redeveloping laminar fluid flow and heat transfer performance in spiral coiled tube heat exchanger systems with specified coil-to-tube radius ratios (5 to 45), spiral pitch and inside-to-outside flow are investigated using appropriate numerical modeling techniques in the CFD package (Fluent v6.2). The CFD models employ variable thermo-physical properties in the analysis of uniform wall temperature heating and cooling of common working fluids such as air and water. The CFD models developed in Part I of this investigation are extended to analyze spiral tube configurations. Appropriate dimensionless variables used to describe the (re)developing hydrodynamic and thermal flow for coiled tube systems are defined and discussed. The spiral configuration is unique in that fully developed flow is not attained for the coil-to-tube radius ratios used in this work. In spiral configurations, the centrifugal effects are not constant as the radius of curvature is not constant. Flows within the spiral flow passages are analyzed as re-developing or re-establishing hydrodynamic and thermal flows. As with the helical flow configuration, it has been shown that in addition to the radius ratio and the Dean and Prandtl numbers, the heat transfer performance also depends upon the interactions (expansion and suppression) between the viscous and thermal boundary layers due to secondary flows caused by the centrifugal forces inherent in coiled tube systems. The predictions of the numerical simulations also showed that the local friction factor and heat transfer performance continuously vary along the length of the tube. The results obtained from this work indicate the limits of application of the friction factor and heat transfer correlations reported in the literature.
Prediction of Raceways in a Blast Furnace
Authors: Selvarasu Naresh K. , Huang D. , Chen Zumao , Gu Mingyan , Zhao Yongfu , Chaubal Pinakin , Zhou Chenn Q.
Published: April 2008

In a blast furnace, preheated air and fuel (gas, oil or pulverized coal) are often injected into the lower part of the furnace through tuyeres, forming a raceway in which the injected fuel and some of the coke descending from the top of the furnace are combusted and gasified. The shape and size of the raceway greatly affect the combustion of, the coke and the injected fuel in the blast furnace. In this paper, a three-dimensional (3-D) computational fluid dynamics (CFD) model is developed to investigate the raceway evolution. The furnace geometry and operating conditions are based on the Mittal Steel IH7 blast furnace. The effects of Tuyere-velocity, coke particle size and burden properties are computed. It is found that the raceway depth increases with an increase in the tuyere velocity and a decrease in the coke particle size in the active coke zone. The CFD results are validated using experimental correlations and actual observations. The computational results provide useful insight into the raceway formation and the factors that influence its size and shape.
Measurement and Modeling of MEMS
Authors: Pryputniewicz Ryszard J. (Rich) , Marinis Ryan T. , Klempner Adam R. , Hefti Peter
Published: April 2008

Advances in MEMS, also called microsystems, require the use of computational modeling and simulation with physical measurements, i.e., measurements and modeling (M&M) approach is needed. We believe that successful combination of computer aided design (CAD) and multiphysics/multiscale simulation tools with the state-of-the-art (SOTA) measurement methodology will contribute to reduction of high prototyping costs, minimization of long product development cycles as well as time-to-market pressures while developing MEMS for various applications. In our approach we combine a unique, fully integrated, software environment for multiscale, multiphysics, high fidelity analyses of MEMS with the SOTA optoelectronic laser interferometric microscope (OELIM) methodology. The OELIM methodology allows remote, noninvasive, full-field-of-view measurements of deformations with very high spatial resolution, nanometer accuracy, and in near real-time. In this paper, both, the software environment and the OELIM methodology are described and their applications are illustrated with representative results demonstrating viability of the M&M approach to the development of MEMS. These preliminary results demonstrate capability of the M&M approach to quantitatively determine effects that static and dynamic loads have on the performance of MEMS.
A Unified Microscopic and Macroscopic Thermal Contact Resistance Model
Authors: Prasher Ravi , Phelan Patrick
Published: April 2008

There are two types of thermal contact resistance at the interface of two solids. One of them is due to the constriction of heat flow lines at the interface, commonly known as thermal contact resistance. The other type of constriction resistance is microscopic in nature. If the characteristic dimension of the constriction becomes comparable to the mean free path of the heat carriers then there is a ballistic component to the constriction resistance. For different materials on the two sides, thermal boundary resistance due to acoustic mismatch becomes important. In this paper a unified model is developed which accounts for both microscopic and macroscopic contact resistances.
Photo-Degradation Studies of Zinc Oxide Filled Polypropylene Nanocomposites
Authors: Zhao Hongxia , Li Robert K. Y.
Published: April 2008

With the rapid developments in polymer matrix nanocomposites, there is growing interest in understanding their behaviors under adverse service conditions. A simple literature search will show the tremendous number of publications on montmorillonite (MMT) filled nanocomposites. It is therefore natural to see that the degradation behaviors for MMT filled nanocomposites have also received a number of detailed studies [1–10]. It was observed that by introducing MMT particles into LDPE [5] and PP [6, 7] matrices, the rate of photo-oxidative degradation was much faster than the corresponding unfilled matrixes. Furthermore, the dispersion state of the MMT particles did not seem to have influence on the photo-degradation rate [5].
Effects of Welding Current on Metal Transfer and Weld Pool Dynamics in Gas Metal Arc Welding
Authors: Hu J. , Tsai H. L. , Wang P. C.
Published: April 2008

In gas metal arc welding (GMAW), current is one of the most important factors affecting the mode of metal transfer and subsequently the weld quality. Recently, a new technology using pulsed currents has been employed to achieve the one droplet per pulse (ODPP) metal transfer mode with the advantages of low average currents, a stable and controllable droplet generation, and reduced spatter. In this paper, the comprehensive model recently developed by the authors was used to study the influences of different current profiles on the droplet formation, metal transfer, and weld pool dynamics in GMA, welding. Five types of welding currents were studied, including two constant currents and three waveform currents. In each type, the transient temperature and velocity distributions of the arc plasma and the molten metal, and the shapes of the droplet and the weld pool were calculated. The results showed that a higher electromagnetic force was generated at a higher current and becomes the dominant factor that detaches the droplet from the electrode tip. A smaller droplet size and a higher droplet frequency were obtained for a higher current. The model has demonstrated that a stable ODPP metal transfer mode can be achieved by choosing a current with proper waveform for given welding conditions.
Experimental Studies of Spray Cooling of High Temperature Metals Using High Mass Flux Industrial Nozzles
Authors: Al-Ahmadi Hamed M. , Yao S. C.
Published: April 2008

Systemic experiments were conducted for the spray cooling of high temperature stainless steel using three different types of industrial sprays, full cone and flat hydraulic nozzles and a flat air-mist nozzle. In the present study wide range of mass flux (1.5-30 kg/m2sec) is covered, which has never been thoroughly investigated before. Orientations with respect to gravity and spray angle were also explored. The data have been analyzed and correlated. The results of this study will be important to the product quality control in industries by providing a good estimate of heat flux at different mass flux, spray types and surface temperatures, especially for spray cooling of stainless steel and other metals with similar thermal properties.
Design of Robust Mixed Fuzzy Controller for Gas Metal Arc Welding Process
Authors: Eftekharian Ata Allah , Sayyaadi Hasan , Tadayon Mohammad Amin
Published: April 2008

Welding is an important manufacturing process that can be automated and optimized. In this paper we discuss the Gas Metal Arc Welding (GMAW) control and modeling problem. For modeling the process recently developed highly nonlinear fifth order mathematical model is used, for controlling the GMAW process we use a new Mixed Fuzzy Control (MFC) structure. In this work first a Traditional Fuzzy Controller (TFC) is designed from the viewpoint of a Single-Input Single-Output (SISO) system for controlling each state of GMAW process. Then, an appropriate coupling fuzzy controller is also designed according to the characteristics of gas metal arc welding process and incorporated into a TFC. We then show by simulation that this control strategy can not only improve the tracking performance of the controller, but also can deal with model uncertainty and disturbances.
Monte Carlo Simulation of Phonon Backscattering in a Nanowire
Authors: Saha Sanjoy , Shi Li , Prasher Ravi S.
Published: April 2008

Surface roughness can play a large role in phonon transport in nanoscale devices. Phonon scattering at a surface is often treated to be either specular, diffusive, or partially specular and partially diffuse. The observation of backscattering of gas molecules on a surface has led us to speculate that under certain conditions strong phonon backscattering can occur at a surface. Such backscattering is usually not taken into account in phonon transport simulation. In this work, Monte Carlo simulation of phonon transport is employed to investigate whether phonon backscattering can occur at the surface of a silicon nanowire with V-shaped surface roughness of various sizes.
Multi-Field FE Modeling of Resistive Heating in a 6061-T6511 Aluminum Specimen
Authors: Khalilollahi Amir , Johnson David H. , Roth John
Published: April 2008

Electric current's effect on material mechanical properties has been of interest since it can lessen the mechanical energy associated with deforming/working a material. The objective of this work is to have a representative model of the thermal/structural effects of electricity on a tensile specimen so that the simple effect of temperature can be separated from any mechanical material property changes due to the electric current. The finite element models in this study were generated and their results were compared to experimental data obtained from a representative tensile test. Comparison with the experimental results on material engineering stress-strain curves and transient temperature profiles offers assurance for the further use of FEA as a significant tool in understanding the electrical effects on material properties. A multi-field large deformation finite element model for a cylindrical tensile bar of 6061-T6511 aluminum is developed to evaluate the distribution of temperature within the specimen. The model also evaluates the stress-strain characteristics of the material while the specimen is carrying a large DC current and being deformed. The simulation results are compared to surface infrared temperature measurements in order to verify the FE model first and then to attain more qualitative and possibly quantitative insight into the effects of electric field.
Optimization of Finite Element Modeling Methodology for Projectile Models
Authors: Sridharala Srujanbabu , Trabia Mohamed B. , O'Toole Brendan , Chakka Vinod , Chowdhury Mostafiz
Published: April 2008

Gun-fired projectiles are subjected to severe loads over extremely short duration. There is a need to better understand the effects of these loads on components within a projectile. While experimental data can be helpful in understanding projectile launch phenomena, collecting such data is usually difficult. There are also limitations on the reliability of sensors under these circumstances. Finite element modeling (FEM) can be used to model the projectile launch event. Currently, engineers usually use large number of elements to accurately model the projectile launch event, which results in an extremely long computational time. FEM results in these cases are always subject to questions regarding accuracy of the results and proof of mesh stability This paper presents an expert system that can reduce computational time needed to perform FEM of gun-fired projectiles. The proposed approach can result in reducing computational time while ensuring that accuracy of results is not affected. Recommendations of the expert system are reached through two stages. In the first stage, an equivalent projectile with simple geometry is created to reduce the complexity of the model. In the second stage, parameters controlling mesh density of the equivalent projectile are used as variables in an optimization scheme with the objective of reducing computational time. Accuracy of the acceleration results from an optimized model with respect to a model with an extremely fine mesh is used as an inequality constraint within the optimization search. A projectile model meshed with aspect ratios obtained from the optimization search produces good agreement with the finite element results of the original densely-meshed projectile model while significantly reducing computational time. It is anticipated that this approach can make it easier to conduct parametric analysis or optimization studies for projectile design.
Scaling-Up Issues With a Magnetostrictive-Hydraulic Pump
Authors: Chaudhuri A. , Yoo J.-H. , Wereley N. M. , Nerssessian N.
Published: April 2008

A hybrid magnetostrictive hydraulic actuator capable of applying a prescribed pre-stress on the magnetostrictive driver was designed and built. Performance of the pump was analyzed using a 2" long and a 4" long magnetostrictive Terfenol-D rod to address scaling up issues. The peak in output velocity, under no external loading, of both pumps occurred around 3.5in/sec. The 4" pump had a larger frequency bandwidth while the 2" pump exhibited a large drop in output velocity at much lower driving frequencies. The load line of the 4" pump was slightly more shifted to the right compared to the 2" pump, indicating higher blocked force and free velocity. The relatively low increase in performance moving from the 2" to the 4" pump was attributed to lower stiffness of the longer rod and the larger impedance of the 4" long solenoid that caused amplifier saturation and resulted in lower saturation magnetostriction from the Terfenol-D driver.
In-Situ Carbon Dioxide Generation for Oil Recovery: Experimental Study of Pressure and Temperature Variations During Stoichiometric Reaction
Authors: Bakhtiyarov Sayavur I. , Shakhverdiev Azizaga Kh. , Panakhov Geilani M. , Abbasov Eldar M. , Siginer Dennis
Published: April 2008

Experimental simulation of chemical reaction behavior between gas-forming (GF) and carbonate rock components has been conducted. During the reaction an allocation of carbon dioxide and pressure change in PVT bombe were discovered. In these series of experiments a dynamics of pressure and temperature changes during stoichiometric reaction between GF reactant and a carbonate rock was investigated. The GY component was prepared on fresh water (Shollar). As a carbonate rock samples, Karadag rock deposits (Azerbaijan) were used. Researches were conducted at constant temperature T=293 K and at various volumetric ratios of GY reactant and a carbonate rock The quantity of reacting agents was defined from stoichiometric correlation which provided a full neutralization of the tested rock.
Dynamic Tensile Properties of Carbon Fiber and Carbon Fiber Reinforced Aluminum
Authors: Zhou Uuanxin , Wang Ying , Xia Yuanming , Jeelani Shaik
Published: April 2008

In this study, dynamic and quasi-static tensile behaviors of carbon fiber and unidirectional carbon fiber reinforced aluminum composite have been investigated. The complete stress-strain curves of fiber bundles and the composite at different strain rate were obtained. The experimental results show that carbon fiber is a strain rate insensitive material, but the tensile strength and critical strain of the Cf/Al composite increased with increasing of strain rate because the strain rate strengthening effect of aluminum matrix. Based on experimental results, a fiber bundles model has been combined with Weibull strength distribution function to establish a one-dimensional damage constitutive equation for the Cf/Al composite.
Development of a Performance Rating Standard for Residential Fuel Cell Systems
Authors: Ellis Michael W. , Davis Mark W. , Fanney A. Hunter , Dougherty Brian P. , Doebber Ian
Published: April 2008

Fuel cell systems for residential applications are an emerging technology for which specific consumer-oriented performance standards are not well defined. This paper presents a proposed experimental procedure and rating methodology for evaluating residential fuel cell systems. In the proposed procedure, residential applications are classified as grid independent load following; grid connected constant power; grid connected thermal load following; and grid connected water heating. An experimental apparatus and procedures for steady state and simulated use tests are described for each type of system. A rating methodology is presented that uses data from these experiments in conjunction with standard residential load profiles to quantify the net effect of a fuel cell system on residential utility use. The experiments and rating procedure are illustrated using data obtained from a currently available grid connected thermally load following system.
Damping Enhancement of Hybrid Nanocomposites Embedded With Engineered Carbon Nanopaper
Authors: Gou J. , Sumerlin S. , Gu H. C. , Song G.
Published: April 2008

This paper presents a novel process to manufacture multifunctional and cost-effective hybrid nanocomposites through integrating engineered carbon nanofiber paper into traditional fiber reinforced composites to improve structural damping properties. In this study, carbon nanofibers are vapor grown carbon fibers, which are grown catalytically from gaseous hydrocarbons using metallic catalyst particles. Vapor grown carbon nanofibers are much less costly than single-walled and multi-walled carbon nanotubes. Carbon nanofibers were preformed as a nanopaper which had a porous structure with highly entangled carbon nanofibers and short glass fibers. The vacuum-assisted resin transfer molding (VARTM) process was used to fabricate the nanocomposites by using engineered carbon nanofiber paper as inter-layer or surface layer of traditional composite laminates. To characterize the structural damping properties, the influence of frequency dependence was analyzed through the experiments conducted using the nanocomposite beams. It was found that there is up to 200-700% increase of the damping ratios at higher frequencies. In addition, experiments were also performed to study the interface characteristics between the carbon nanofiber paper and the laminate ply. The study showed a complete penetration of the resin through the carbon nanofiber paper. It was found that the connectivities between carbon nanofibers and short glass fibers within the carbon nanofiber paper were responsible for the significant energy dissipation in the hybrid nanocomposites during the structural vibration applications. The research results confirm the possible advantage of using engineered carbon nanofiber for damping augmentation.
Integrated Optimization for Automated Design of Dynamic Systems
Authors: Wu Zhaohong , Campbell Matthew I. , Ferna´ndez Benito R.
Published: April 2008

This paper introduces research leading to a computer-aided design tool in which engineering designers can test various concepts in an environment equipped to automatically model the dynamics and then optimize the specified components to best meet the specifications of the design problem. The input to the system is a graph of components where the components' design variables are to be determined by a subsequent optimization process. Design goals are often as clearly defined as possible prior to any design effort, which suggests that the objective function can be automatically generated if a system dynamics model is available and the transformation from the system model to objective function can be automated. In this research, automated objective function derivation is demonstrated through automated bond graph modeling and model transformation according to the goals defined by designers. A component (or sub-system) repository is being developed to store not only the component dynamics models, but also various information including typical component design constraints and physical constitutive laws. The paper discusses a systematic approach to automatically prepare a mechatronic design problem for optimization, which can decode and encode proper genotypes of intended design variables, which account for the existing of design constraints and physical constitutive laws. An example of a weighing machine design is used to showcase the approach.
Integration of Vision and Inertial Sensors for a Surgical Tool Tracking
Authors: Parnian N. , Golnaraghi M. F.
Published: April 2008

This paper represents a hybrid Vision/INS system in a microsurgical tool tracking application. Surgical MEMS devices must not only cope with all of the challenges that conventional MEMS devices have, but also address the integration of electronics and signal processing, calibration, reliability, accuracy and testing. A hybrid Vision/INS system with the integration of the Extended Kalman Filter precisely calculates 6D position-orientation of a microsurgical tool during surgery. This configuration guarantees the real-time tracking of the instrument. Ultimately, the vision system supports the IMU to deal with the drift problem but the position error increases dramatically in the absence of the vision system. In this paper, the tool motion modeling is proposed to bind the error in the acceptable range for a short period of missing data. The motion of the tool is modeled and updated at any time that the instrument is in the camera view field. This model is applied to the estimation algorithm whenever the camera is not in line of site and the optical data is missing.
Improved Organizational Behavior Through Strategic Total Productive Maintenance Implementation
Authors: Ahuja Inderpreet Singh , Khamba J. S. , Choudhary Rajesh
Published: April 2008

The manufacturing industry has experienced an unprecedented degree of change in the highly competitive and dynamics manufacturing scenario. Recent competitive trends have been pushing manufacturing executives to reconsider the impact and importance of increasing equipment availability and utilization, maintenance productivity and resource utilization, and increasing quality and responsiveness of maintenance services in meeting overall goals to achieve World Class status. TPM has been envisioned as an effective tool in the quest for achieving the world class status and meeting the ever increasing competition. This paper elaborates the contribution of TPM implementation towards improvement in organizational behavior in the Indian process industry in the quest to attain world-class competitiveness and sustainability efforts. The case study of TPM implementation though team building in Indian process industry has been brought out through the presentation of TPM benefits at the Hot Strip Mill division at a steel manufacturing company. The various aspects of TPM implementation have also been illustrated with the help of a case study.
Flow/Acoustic Characteristics for Flow Over Two Tandem Cylinders
Authors: Zheng Z. Charlie , Yang X. , Zhang N.
Published: April 2008

Flow over two tandem cylinders is simulated using an immersed-boundary method. Cases with different distances between the cylinders are investigated. The flow field is then used to provide information to analyze the pressure fluctuations both in the cylinders (assumed rigid and hollow) and at the far field. The results show that the downstream cylinder pertains higher levels of pressure fluctuations both inside the cylinder and at far field than the upstream cylinder. When the distance between the cylinders increases from the quasi-reattachment flow pattern to the critical regime, the pressure fluctuation levels from the downstream cylinder increase significantly. The spectral analysis reveals only one significant peak at the frequency of twice of the corresponding Strouhal number for the far-field acoustics, but two peaks at the frequencies of both the Strouhal number itself and twice of it for pressure fluctuations inside the cylinders.
Near-Field Radiative Energy Transfer Between Two Spheres
Authors: Narayanaswamy Arvind , Chen Dye-Zone , Chen Gang
Published: April 2008

Radiative energy transfer between closely spaced bodies is known to be significantly larger than that predicted by classical radiative transfer because of tunneling due to evanescent waves. Polar materials like silicon carbide and silica can support surface phonon polaritons due to resonances in the dielectric function of such materials. This leads to an enhanced density of states of electromagnetic surface modes near the surface compared to vacuum and leads to a pronounced increase in energy transfer near the resonance region. Experimental measurements between half-planes of polar materials can be very challenging because of the difficulty in measuring the gap as well as the parallelism between the surfaces. Theoretical investigation of near-field energy transfer on the other hand, is generally restricted to that between two parallel half-planes because of the complications involved in analyzing other configurations such as sphere-sphere or sphere-plane. Sphere-sphere or sphere-plane configurations beyond the dipole approximation have not been attempted. In this work, we analyze numerically the radiative energy transfer between two adjacent non-overlapping spheres.
Bulk Modulus of Air Content Oil in a Hydraulic Cylinder
Authors: Ruan Jian , Burton Richard
Published: April 2008

A model of oil with entrained air content is developed which considers fluid compression and the subsequent dissolving of mixed entrained air. According to the model the mixed entrained air affects the "gross" bulk modulus below some critical pressure, but has no effect above this value due to the complete dissolving of the entrained air into solution. The critical pressure is shown to be proportional to the square root of the amount of the initial mixed entrained air. The temporal pressure gradient has also a substantial effect on the critical pressure value and thus on the bulk modulus. The critical pressure value increases but tends towards an upper value with increasing temporal pressure gradient (a true dynamic condition); the opposite occurs when the pressure gradient decreases as the critical pressure converges to a lower value (essentially a static value). Thus regions of static and dynamic bulk modulus can be established. The model predicts that the upper critical pressure value is some 1.8 times that of the static one. Experiments have been designed to verify the feasibility of the model by measuring the temporal pressure gradient against the variation of compressed oil volume. It is demonstrated that the model is verified not only for the case of positive pressures (above atmospheric pressure) but also for pressures less than atmosphere. Finally a comparison of the proposed model is made with those proposed in the literature. The bulk modulus predicted by the proposed model is a little larger than these given in literature. The reason for such difference is attributed to the result of air being dissolved into oil.
Measurements of Soot Volume Fraction in Pulsed Diffusion Flames by Laser-Induced Incandescence
Authors: Sapmaz H. , Ghenai C.
Published: April 2008

Laser-Induced Incandescence (LII) is used in this study to measure soot volume fractions in steady and flickering ethylene diffusion flames burning at atmospheric pressure. Better understanding of flickering flame behavior also promises to improve understanding of turbulent combustion systems. A very-high-speed solenoid valve is used to force the fuel flow rate with frequencies between 10 Hz and 200 Hz with the same mean fuel flow rate of steady flame. Periodic flame flickers are captured by two-dimensional phase-locked emission and LII images for eight phases (0° - 360°) covering each period. LII spectra scan for minimizing C2 swan band emission and broadband molecular florescence, a calibration procedure using extinction measurements, and corrections for laser extinction and LII signal trapping are carried out towards developing reliable LII for quantitative applications. A comparison between the steady and pulsed flames results and the effect of the oscillation frequency on soot volume fraction for the pulsed flames are presented.
Heat Exchanger Development for Compact Water/LiBr Sorption Systems
Authors: Estiot E. , Natzer S. , Harm M. , Kren C. , Schweigler S.
Published: April 2008

For energy efficient tri-generation, solar cooling or residential heating compact sorption appliances using the working pair water/lithium bromide (LiBr) can be applied. Standard plant technology established in the field of large capacity chillers and heat pumps with conventional tube-and-shell configuration cannot be easily adapted to compact units for economic and operational reasons. For a successful marketing of compact sorption units, major effort is required to achieve tolerable plant dimensions and weight together with affordable first cost and reliable operation. In a research project, the design of all key components, i.e. main heat exchangers - evaporator, absorber, condenser and generator - and the liquid pumps for refrigerant and absorbent solution has been revised. In order to achieve uncomplicated manufacturing and improved vacuum tightness, concepts for standardized heat exchanger modules have been developed. A single effect absorption plant has been erected for the experimental investigation of the newly designed finned heat exchangers and plate heat exchanger configurations as main heat exchangers in an absorption cycle. Concepts for sizing these compact heat exchanger units in compliance with the given thermo-hydraulic conditions of a water/lithium bromide absorption cycle will be presented. Estimations of the wetting of the heat exchangers, the pressure drop in the vapor flow, as well as the achieved heat transfer per heat exchanger volume will be discussed. Experimental results for falling film absorption with compact heat exchangers will be presented.
Film Thickness for Two Phase Flow in a Microchannel
Authors: Grimes Ronan , King Colin , Walsh Edmond
Published: April 2008

The issue of contamination of micro channel surfaces by bio fluids is a significant impediment to the development of many biomedical devices. A solution to this problem is the use of a carrier fluid, which segments the bio fluid and forms a thin film between the bio fluid and the channel wall. A number of issues need to be addressed for the successful implementation of such a solution. Amongst these is the prediction of the thickness of the film of carrier fluid which forms between the bio sample and the channel wall. The Bretherton and Taylor laws relate the capillary number to the thickness of this film. This paper investigates the validity of these laws through an extensive experimental program in which a number of potential carrier fluids were used to segment aqueous droplets over a range of flow rates. The aqueous plugs were imaged using a high speed camera and their velocities were measured. Film thicknesses were calculated from the ratio of the velocity of the carrier fluid to the velocity of the aqueous plug. The paper concludes that significant discrepancies exist between measured film thicknesses and those predicted by the Bretherton and Taylor laws.
An Object-Oriented Systems Engineering Model Design for Integrating Spent Fuel Treatment Facility and Chemical Separation Processes
Authors: Cheng Ming , Hodges Matthew , Kwan Kenny , Hsieh Hsuan-Tsung , Chen Yitung , Vandegrift George , Copple Jackie , Laidler James
Published: April 2008

The mission of the Transmutation Research Program (TRP) at University of Nevada, Las Vegas (UNLV) is to establish a nuclear engineering test bed that can carry out effective transmutation and advanced reactor research and development effort. TRPSEMPro package, developed from previous project period, integrated a chemical separation code from the Argonne National Laboratories (ANL). Current research focus has two folds: development of simulation system processes applied to Spent Fuel Treatment Facility (SFTF) using ASPEN-plus and further interaction of ASPEN+ program from TRPSEMPro interface. More details will be discussed below. ANL has identified three processes simulations using their separation technologies. The first process is to separate aqueous acid streams of acetic acid, nitric acid, water and a variety of fission product nitric salts. Distillation separation method is used to remove the desired components from the streams. The second simulation is to convert plutonium nitrate to plutonium metal. Steps used for the process simulation are precipitation, calcinations, fluorination and reduction. The third process currently under development is vitrification of fission product of raffinate streams. During the process, various waste streams from the plant are mixed and fed to a process that converts them to a solid state glass phase. The vitrification process used by the Hanford and Savannah River facilities was selected as a guideline to develop the prototype simulation process using ASPEN-Plus. Current research is focusing on identifying unit operations required to perform the vitrification of the waste streams. The first two processes are near completion stage. Microsoft Visual Basic (MS VB) has been used to develop the entire system engineering model package, TRPSEMPro. Currently a user friendly interface is under development to facilitate direct execution of ASPEN-plus within TRPSEMPro. The major purpose for the implementation is to create iterative interaction among system engineering modeling, ANL separation model and ASPEN-Plus process that outputs optimized separation/process simulation results. The ASPEN-plus access interface from TRPSEMPro allows users to modify and execute process parameters derived from the ASPEN Plus simulations without navigating through ASPEN-Plus. All ASPEN-plus simulation results can be also accessible by the interface. Such integration provide a single interaction gateway for researchers interested in SFTF process simulation without struggling with complicate data manipulation and joggling among various software packages.
On the Path to World Class Retention
Authors: Hensel Edward , Hortop Amy
Published: April 2008

Retention of students from the first to second year of engineering programs has long been recognized as an important and challenging hurdle. The Mechanical Engineering Department at RIT has implemented several changes to its first year programs and student support services during the preceding five years, which have resulted in a significant increase in one-year retention. During the 2005-06 academic year, additional support services were provided to first year learning communities in combination with course offering logistics modifications. Additional focus was placed on building a firm relationship between each student and their faculty adviser. Six initiatives were studied during the 2005-06 academic year, resulting in a projected first year retention rate of 98% at the institution, and 96% retention within the mechanical engineering department.
Development of Smart Material-Hydraulic Pumps and Actuators
Authors: Sneed Ryan C. , Smith Roland R. , Cash Michael F. , Bales Gregory L. , Anderson Eric H.
Published: April 2008

Smart materials such as piezoelectrics and magnetostrictives produce mechanical power in a form that is improperly matched to many applications. When packaged in typical ways, these stiff materials have excess force but are deficient in displacement. Recent research has suggested that smart materials can be used for the pressurization and pump stage in electrohydrostatic actuators (EHAs). EHAs offer advantages over traditional centralized hydraulic systems by providing local pressurization in a closed fluid system and eliminating the need for distributed, high-pressure fluid lines. Given inherent material power densities, smart material-based EHAs could produce higher power output compared to electromagnetic actuators. High frequency, low displacement smart material actuation, typically operated in the range of 500 Hz, but in some cases much higher, is rectified via fluid flow to produce larger output displacements at lower frequencies. Valve limitations, mechanical compliances, and fluid compressibility account for significant losses in the pumps. Continuing previous research, this paper describes design approaches that address and attempt to minimize losses. Piezoelectric and magnetostrictive devices are compared, and the design and testing of magnetostrictive pumps is described in greater detail, with special considerations given to heat generation and improved efficiency.
Characterizing Slot Film Cooling Through Detailed Experiments
Authors: Cruz Carlos A. , Raffan Fernando , Cadou Christopher , Marshall Andre´ W.
Published: April 2008

With the ever increasing operating temperatures of gas turbine engines, the surface cooling of hot section components remains a primary consideration in propulsion system design. At the same time, numerical tools are being used more extensively for hot-section flow-path design. Recognizing the need for detailed data to help develop and validate these numerical tools, the present study focuses on characterizing near-wall mixing and heat transfer in a canonical 2D slot film cooling configuration. The lack of comprehensive and detailed experimental film cooling data under realistic temperature and blowing ratio conditions has led the authors to develop and implement a unique experimental facility that will allow measuring velocity and temperature profiles as well as surface temperatures and heat transfer at the wall under adiabatic and isothermal conditions. This hot wind tunnel facility provides optical access for Laser Doppler Velocimetry (LDV) near the wall and wall surface temperature distribution with infrared (IR) thermography. In addition to these non-intrusive diagnostics, the gas-phase temperature is measured with a minimally intrusive micro-thermocouple probe with fast response time and high frequency sampling. The performance of selected film cooling effectiveness scaling laws is analyzed. The thermal and momentum mixing of the film described in terms of temperature and velocity profiles and associated statistics. These detailed measurements are hoped to provide guidance and validation for CFD model developers.
Nonlinear Modeling and Experimental Validation of Tire Nonuniformity Induced Tangential Steering Wheel Vibrations
Authors: Ayglon Virgile , Jalili Nader , Haque Imtiaz
Published: April 2008

This paper describes the model integration and validation that followed the development of nonlinear models of a tire with non-uniformities, a double wishbone suspension and rack-and-pinion power steering. These submodels are integrated to investigate the effects of variation of tire, suspension and steering parameters on the transmission of tire forces acting on the wheel spindle to the steering system and vehicle chassis. The tire model is based on a rigid ring model which includes mass imbalance and balancing mass. The suspension is idealized as rigid links with seven degrees-of-freedom and the bushings are represented by spring-damper elements. The equations of motion are derived using the Lagrange multiplier method in Maple, and solved numerically using Matlab DAE solver. The steering system is idealized as a four degree-of-freedom system and considers motion of the rack, rack housing, pinion gear and steering wheel. Nonlinear compliant friction is considered between the pinion gear / rack, and the steering column / chassis interfaces. The analytical model is used to develop a quantitative measure of the relative importance of the parameters such as mass/inertia, suspension bushing stiffness and damping, torsion bar stiffness and damping, rack friction and damping, to the force transmissibility to the vehicle chassis and the steering system. Experimental results include a modal analysis, a shop-testing and road testing, which are used to cross verify the numerical simulations. The testing shows the variation of forces in the steering system due to tire imbalances, emphasizing the nonlinear variation of the nibble phenomenon with vehicle speed and tire imbalance. Results obtained from simulation matches well with the experimental measurements.