bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of Temperature and Residence Time of Carbon Black Oil Furnace Industrial Reactors
Authors: Javadi A. , Soltanieh M. , Sahebdelfar S. , Bastani D. , Javadi K.
Published: April 2008

In the absence of powerful rigorous models, in this research a simple but practical method for calculating the temperature and residence time and carbon black yield in oil-furnace reactors is proposed. For this purpose an empirical formula of the form CxHy is assumed for the carbon black feedstock based on typical feedstock used in this industry. Based on the prevailing reactor conditions, thermodynamic considerations and available outlet tail gas from the reactor, a few representative reactions are considered to describe the entire reaction network. These include complete combustion for the fuel and, incomplete combustion and pyrolysis for the feedstock. Carbon black yield can be estimated from a mass balance. From the combined mass and heat balance, the reactor temperature as well as the residence time is predicted. The reactions can also be used to obtain the composition of the tail gas. Despite the simplicity of the model, in all cases studied, relatively good agreements were observed between the calculated values and the available industrial data as well as those obtained from computational fluid dynamics (CFD) simulation. An exception was the effects of the air/oil ratio on the reactor mean residence time in the CFD approach. The influences of air/oil ratio and inlet air temperature on reactor mean-temperature were studied. In both cases one observes good agreement between our results and CFD simulation data. They both show an increase in reactor mean-temperature as expected. The effects of process air flow rate on reactor residence time also were studied and a good agreement was observed. However, comparison the effects of the air/oil ratio on reactor residence time showed quite different trends. While the results of CFD simulation predicts insignificant change in reactor residence time versus air/oil ratio, our results show a decline in the residence time in this case. To explain this, prediction of carbon black particle size was considered. Utilizing our predicted residence time results for prediction of particle size showed a good agreement with industrial data, while in contrast the CFD simulation data show opposite trend with the industrial data and our work. Therefore, it can be said that one of the most important reasons caused poor prediction in referred CFD simulation in some cases could be considerable error in prediction of the residence time.
Performance of Spent Fuel Transportation Casks in Severe Tunnel Fires
Authors: Easton Earl P. , Bajwa Christopher S. , Lewis Robert
Published: April 2008

As part of the Nuclear Regulatory Commission's (NRC) overall review of the performance of transportation casks under severe accident conditions, the NRC has undertaken a number of initiatives, including the Package Performance Study (PPS), described in USNRC Package Performance Study Test Protocols, NUREG-1768, which will test full size transportation casks in a severe accident, as well as an examination of the Baltimore tunnel fire of 2001. The final PPS test plan is currently under development by the NRC's Office of Research. The NRC, working with the National Institute of Standards and Technology (NIST), Pacific Northwest National Laboratory (PNNL), and the National Transportation Safety Board (NTSB), performed analyses to predict the response of three different spent fuel transportation cask designs when exposed to a fire similar to that which occurred in the Howard Street railroad tunnel in downtown Baltimore, Maryland on July 18, 2001. NRC Staff evaluated the potential for a release of radioactive material from each of the three transportation casks analyzed for the Baltimore tunnel fire scenario. The results of these analyses are described in detail in Spent Fuel Transportation Package Response to the Baltimore Tunnel Fire Scenario, NUREG/CR-6886, published in draft for comment in November 2005.
Modeling of Gas Turbine Combustor Using Dynamic Neural Network
Authors: Lahroodi Mahmood , Mozafari A. A.
Published: April 2008

This paper presents an Artificial Neural Network (ANN) - based modeling technique for prediction of outlet temperature, pressure and mass flow rate of gas turbine combustor. ANN technique has been developed and used to model temperature, pressure and mass flow rate as a nonlinear function of fuel flow rate to the combustion chamber. Results obtained by present modeling are compared with those obtained by experiment. A quantitative analysis of modeling technique has been carried out using different evaluation indices; namely, Mean-Square-Quantization-Error (MSQE) and actual percentage error. The results show the effectiveness and capability of the proposed modeling technique with reasonable accuracies of about 95 percent.
Combination of Neural Networks and State Vector Feedback Adaptive Control (SVFAC) Technique to Control the Gas Turbine Combustor
Authors: Lahroodi Mahmood , Mozafari A. A.
Published: April 2008

Neural networks have been applied very successfully in the identification and control of dynamic systems. When designing a control system to ensure the safe and automatic operation of the gas turbine combustor, it is necessary to be able to predict temperature and pressure levels and outlet flow rate throughout the gas turbine combustor to use them for selection of control parameters. This paper describes a nonlinear SVFAC controller scheme for gas turbine combustor. In order to achieve the satisfied control performance, we have to consider the affection of nonlinear factors contained in controller. The neural network controller learns to produce the input selected by the optimization process. The controller is adaptively trained to force the plant output to track a reference output. Proposed Adaptive control system configuration uses two neural networks: a controller network and a model network. The model network is used to predict the effect of controller changes on plant output, which allows the updating of controller parameters. This paper presents the new adaptive SFVC controller using neural networks with compensation for nonlinear plants. The control performance of designed controller is compared with inverse control method and results have shown that the proposed method has good performance for nonlinear plants such as gas turbine combustor.
Design, Simulation and Testing of Shape Memory Alloy Actuator for Mixing Two Solutions in High-Pressure Optical Cell for Biophysical Studies
Authors: Xie Hongchun , Zhou Jack , Chong Parkson
Published: April 2008

Window-type high-pressure optical cells (HPOC) such as the one designed by Paladini and Weber [Rev. Sci. Instrum. 52, (1981) p. 419] have provided biophysicists a powerful tool to understand the structure-function relationships of biological molecules. However, the conventional HPOC is only good for single solution testing and does not allow for quick mixing and stirring of additional components while the sample is under pressure. To mix two solutions under pressure, Zhou et al [Rev. Sci. Instrum. 69, (1998) p. 3958] developed a laser activated dual chamber HPOC. However, the expensive laser device and its unavailability in most laboratories make the application difficult. In a later study, Zhou et al. [Rev. Sci. Instrum. 71, (2000) p. 4249] introduced shape memory alloy (SMA) as an actuator to unplug a urethane stopper with a biasing spring for agitation. The drawback is that the biasing spring blocks the observing light beam and creates unwanted reflections. This research is to construct an actuator with concentric SMA spring and compressive biasing spring: an SMA helical tensile spring to pull out the stopper to let two solutions mix; and a helical compressive spring to bias and to agitate solutions, and to leave the lower half cuvette clear for optical observation. Due to the limited space in the cuvette, the alignment of two springs is critical for both motion and heat response to activate each spring separately. This paper discusses the design of SMA actuator, SMA spring testing and mixing testing by the SMA spring actuator. Since SMA (nickel-titanium) spring is not solderable and crimping method is limited due to the space, a conductive adhesive is used not only to fix the alignment between springs and cap, but also to conduct electric current. Spring force testing was done by INSTRON. Mixing testing used flourescein intensity change to trace the mixing process. The bio-compatibility of the nickel-titanium SMA with proteins and phospholipids has also been tested.
Kalman Filter Based Neural Network Methodology for Predictive Maintenance: A Case Study on Steam Turbine Blade Performance Prognostics
Authors: Yan Jihong , Lv Min , Wang Pengxiang , Wang Meiying
Published: April 2008

Predictive maintenance involves condition monitoring, fault detection and prediction of remaining useful life or forthcoming failures. Predictive maintenance systems for steam turbine engines offer detection, classification, and prediction (or prognosis) of potential critical component failures, and ensures substantially reducing the cost of repair and replacement of defective parts, and may even result in saving lives. This paper describes a Kalman filter based neural network approach to provide performance evaluation and residual life prediction with the objectives of improving availability and implementing maintenance before failure occurs by estimating degradation severity and the proper timing for replacement. The approach has been applied to a steam turbine blade fatigue experiment testbed to illustrate the prognostic functionalities of the methodology.
A Fuzzy Lane Tracking System for Driver Assistance
Authors: Milella Annalisa , Reina Giulio
Published: April 2008

In the last few years, driver-assistance systems are increasingly being investigated in automotive field to provide a higher degree of comfort and safety. Lane position determination plays a critical role toward the development of autonomous and computer-aided driving. This paper presents an accurate and robust method for detecting lateral road marking with applications in autonomous vehicles and driver support systems. Much like other lane detection systems, ours is based on computer vision and Hough transform. Our approach, however, is unique in that it combines geometrical and intensity information of the image, based on a fuzzy logic inference system implementing in-depth understanding of different driving and environmental conditions. We call it Fuzzy Logic lane (FLane) tracking system. Details of the main components of the FLane module are presented along with experimental results obtained under varying lighting and road conditions. It is shown that the proposed method is reliable and effective in detecting road border and can be successfully employed for driver assistance.
The Influence of Intercalated Nanoclay Into Nanocomposites Impact Behavior
Authors: Avila A. F. , Neto A. Silva
Published: April 2008

A new nanocomposite is prepared by cold direct mixing. To investigate how this new nanocomposite behaves under low velocity impact loads, a set of plates with 16 layers and 65% fiber volume fraction is manufactured by vacuum assisted wet lay-up. The fibers have a plain-weave configuration, while the epoxy system is ARALDITE M/HY956. The nanoclay is an organically modified montmorillonite ceramic and it is dissolved into the epoxy system in a 1%, 2%, 5% and 10% ratio in weight with respect to the matrix. X-ray diffraction tests indicate that rather than exfoliated, these nanocomposites are mostly in intercalated form, with possible presence of immiscible nano systems at 10% concentration. The impact tests are based on the ASTM D5628-01 standard. For the 20 joules impact energy condition, the energy absorption by delamination increases close to 48%, while for larger energies, i.e. 40 and 60 joules, the average improvement into energy absorption is around 15%. Even for larger energies close to total perforation, i.e. 80 joules, the use of nanoclays leads to an average increase in energy absorption of close to 4%.
Online Prediction of Plate Deformations Under External Forces Using Neural Networks
Authors: Ahmadian M. T. , Mobini A.
Published: April 2008

Recently online prediction of plate deformations in modern systems have been considered by many researchers, common standard methods are highly time consuming and powerful processors are needed for online computation of deformations. Artificial neural networks have capability to develop complex, nonlinear functional relationships between input and output patterns based on limited data. A good trained network could predict output data very fast with acceptable accuracy. This paper describes the application of an artificial neural network to identify deformation pattern of a four-side clamped plate under external loads. In this paper the distributed loads are approximated by a set of concentrated loads. An artificial neural network is designed to predict plate deformation pattern under external forces. Results indicate a well trained artificial neural network reveals an extremely fast convergence and a high degree of accuracy in the process of predicting deformation pattern of plates. Additionally this paper represents application of neural network in inverse problem. This part illustrates the capability of neural networks in identification of plate external loads based on plate deformations. Load identification has many applications in identification of real loads in machineries for design and development.
Laminar Burning Speed Measurements of Premixed JP-8, Oxygen and He Flames
Authors: Parinejad Farzan , Shirk Edwin , Far Kian Eisazadeh , Metghalchi Hameed
Published: April 2008

The focus of this study is the calculation of the laminar burning speed of JP-8, oxygen, and helium mixtures at high temperatures and pressures. Two constant volume combustion vessels were used for the analysis. The spherical vessel was primarily used for the collection of pressure data from which the burning speed was calculated. A cylindrical vessel was also used in conjunction with a shadowgraph system to observe the flame structure and the onset of instability. Observations of JP-8 with both nitrogen and helium as diluents were made in the cylindrical vessel and it was seen that at a temperature of 200° C over the range of 1-8 atmospheres pressure and equivalence ratios of 0.7-1.0 with helium as the diluent, the flame was laminar throughout its combustion. Pressure measurements of JP-8 and oxygen with helium as the diluent were then made in the spherical vessel. Laminar burning speed of JP-8 with oxygen and helium has been calculated using the spherical vessel pressure data for this range of temperatures, pressures and equivalence ratios. Power law correlations for burning speeds have been developed for these results.
A Study on the Effect of Flexible Electrodes and Passive Layers on the Performance of Dielectric Elastomer Membranes
Authors: Fox J. W. , Goulbourne N. C.
Published: April 2008

This paper investigates the effect of flexible electrodes and passive layers on the electromechanical performance of dielectric elastomer membranes. Four compliant electrodes were tested: carbon grease, silver grease, graphite spray, and graphite powder. The test setup consisted of a clamped diaphragm subject to an inflation pressure and an electric field. The electrode experiments show that both silver grease and carbon grease are the most effective electrodes of those tested. Passive layer tests were performed in three groups according to the position of the added layers relative to the actuator: (i) passive layer placed on top of the actuator, (ii) passive layer on the bottom of the actuator, and (iii) passive layers on both the bottom and top of the actuator. For the passive layer tests, the results show that adding elastic layers dramatically changes the mechanical response of the actuator but does not change the electrical response significantly. The ability to use capacitance measurements to determine the membrane's deformation state is investigated. The experiments demonstrate that capacitance measurements can indeed be used for mechanical sensing.
Instrumented Indentation on Intercalated Clay Reinforced Polypropylene Nanocomposites
Authors: Wong Shing-Chung , Qu Shiyue , Lee Hyukjae , Mall Shankar
Published: April 2008

Instrumented indentation techniques were employed to investigate the local stiffness in comparison to the global stiffness in organomodified clay filled maleated polypropylene (MAPP). The morphology of composites was observed under transmission electron microscopy. Both highly intercalated and well exfoliated clay structures were observed in clay filled MAPP system. As a result, the region where indentation load was applied could be considered as the local composite system. Instrumented indentation was performed on three distinct positions: (a) clay intercalated and congregated region supported by MAPP matrix; (b) aggregate-MAPP boundary; and (c) the MAPP alone. The clay aggregated region generally showed higher stiffness as compared to the MAPP matrix. And, the relative increase in indentation stiffness is substantially higher than the relative increase in tensile and compressive stiffnesses. Good linear correlation obtained between the changes in global and local indentation stiffness suggests plausible future application of nanoindentation technique in predicting the mechanical properties of the composite bulk. Furthermore, the highly intercalated morphology clearly provides a local and highly confined nanocomposite system similar to natural materials with optimum stiffening potential.
Solution Rheology of Saline and Polysaccharide Systems
Authors: Almeida Ekmagage Don N. , Rakesh Leela , Hirschi Stanley , Mueller Anja
Published: April 2008

The problem of the characterization of the solution properties of water soluble polymers is long-standing. These polymers tend to form aggregated supramolecular gels that are resistant to molecular dispersion. These materials are being widely used in a variety of industrial applications. Their principle functions are as rheological modifiers, where they thicken or gel solutions in products such as hair-care, detergents, air fresheners and foods; as flocculants for particle separation as applied to water clarification, sewage, and effluent treatment, and as stabilizers to control the properties of concentrated suspension and emulsions, for example in paints, pesticides, dyes, and pharmaceutical industries. Therefore it is important to understand their rheological properties under various operating conditions such as stress, strain, temperature etc, which will induce gelation. The rheological properties of starch gels of high concentration (up to 86% starch) have been investigated before [1]. In this paper we have investigated experimentally the shear viscosity and viscoelasticity properties of saline and polysaccharide suspensions at various low concentrations and pH at different temperatures using controlled stress and strain rheometers (Vilastic-3 and AR 2000). The data were then fitted with the power law and Cross model for low and higher concentrations respectively. The present results show that the viscosity/elasticity does not significantly change for low concentrations at different pH values. The maximum viscosity/elasticity was obtained around pH 5-7.4 at higher concentrations.
Image-Based Modeling for Assessing Thermal Conductivity of Thermal Spray Coatings at Ambient and High Temperature
Authors: Tan Y. , Sharma A. , Longtin J. P. , Sampath S. , Wang H.
Published: April 2008

Thermal spray coatings are used extensively for protection of engineering components and structures in a variety of applications. Due to the nature of thermal spraying process, the coating thermal, mechanical, and electrical properties depend strongly on the coating microstructure, which consists of many individual splats, interfaces between the splats, defects and voids. The coating microstructure, in turn, is determined by the thermal spray process parameters. In order to relate coating process parameters to the final coating performance, then, it is desirable to relate coating microstructure to coating properties. In this work, thermal conductivity is used as the physical parameter of interest. Thermal conductivity of thermal spray coatings is studied by using an image analysis-based approach of typical coating cross sections. Three coating systems, yttria stabilized zirconia (YSZ), molybdenum, and Ni-5wt.%Al are explored in this work. For each material, thermal conductivity is simulated by using a microstructure image-based finite element analysis model. The model is then applied to high temperature conditions (up to 1200 °C) with a hot stage-equipped scanning electron microscope imaging technique to assess thermal conductivity at high temperatures. The coating thermal conductivity of metallic coatings is also experimentally measured by using a high-temperature laser flash technique.
Experimental Investigation of Oxygen Addition to Fuel on Soot Formation in Laminar Coflow Diffusion Flames of Ethylene and Propane
Authors: Liu Fengshan , Thomson Kevin A. , Smallwood Gregory J.
Published: April 2008

Investigation of the effect of oxygen addition to fuel on the visible flame appearance and soot formation characteristics of laminar diffusion flames is important to gain comprehensive understanding of gas-phase combustion chemistry and its interaction with soot chemistry. This paper reports experimental results of oxygen addition to fuel on the visible flame height and soot volume fraction distributions in axisymmetric coflow laminar ethylene and propane diffusion flames at atmospheric flames. The carbon flow rate was maintained constant in all the experiments. Although many experimental studies have been conducted in the literature in this topic, the present investigation aimed at providing spatially resolved soot volume fraction distributions over the entire range of oxygen addition from no oxygen addition up to the point of flashback while keeping the carbon mass flow rate constant. The level of oxygen added to fuel right before flashback is about 45% (the percentage of oxygen addition is always by volume in this study) of the fuel flow rate in the ethylene flame and 300% of the fuel flow rate in the propane flame. As the added oxygen amount to ethylene increases, the visible flame height first increases. When the added oxygen flow rate is about 13% of the fuel flow rate, the flame becomes smoking, i.e., soot escapes from the flame tip. When the oxygen flow rate reaches about 42% of the fuel flow rate, the flame stops smoking. When oxygen was added to propane, the visible flame height linearly decreases with increasing the amount of oxygen. These very different effects of oxygen addition to ethylene and propane indicate that oxygen plays a drastically different role in the chemical pathways leading to soot formation in ethylene and propane flames. Distributions of soot volume fractions in these flames were measured using a 2D light attenuation technique coupled with the Abel inversion. The present study provides valuable experimental data for validating soot models.
Jet Impingement of a Non-Newtonian Fluid
Authors: Zhao Jiangang , Khayat Roger E.
Published: April 2008

The similarity solutions are presented for the wall flow which is formed when a smooth planar jet of power-law fluids impinges vertically on to a horizontal plate, and spreads out in a thin layer bounded by a hydraulic jump. This problem is formulated analogous to radial jet flow problem and the solution procedure is accounted for by means of similarity solution of the boundary-layer equation [1] for Newtonian fluids. For the convenience of analysis, the flow may be divided into three regions, namely a developing boundary-layer region, a fully viscous boundary-layer region, and a hydraulic jump region. The similarity solutions of the film thickness and free surface velocity in fully viscous boundary-layer region include unknown constant L, which is solved numerically and approximately in the developing boundary-layer flow region. Comparison between the numerical and approximate solutions leads generally to good agreement, except for severely shear-thinning fluids. The boundary-layer solution depends on two parameters: power-law index n and α, the dimensionless flow parameters. The effect of α on film thickness and free surface velocity is investigated. The relations between the position of the hydraulic jump and dimensionless flow parameter are obtained and the effect of α on the position of the jump is presented.
Numerical Investigation of Swirling Pipe Flows
Authors: Escue Andrew , Cui Jie
Published: April 2008

Swirling flow is a common phenomenon in engineering applications. It has been shown that swirling flow increases heat and mass transfer, and reduces power requirements in certain engineering applications. A numerical study of the swirling flow inside a straight pipe was carried out in the present work with the aid of the commercial CFD code Fluent. Two-dimensional simulations were performed, and two turbulence models were used, namely, the RNG k-ε model and the Reynolds stress model. Results at various swirling numbers were obtained and compared with available experimental data to determine if the numerical method is valid when modeling swirling flows. It has been shown that the RNG k-ε model is in better agreement with experimental velocity profiles for low swirl, while the Reynolds stress model becomes more appropriate as the swirl is increased. However, both turbulence models predict an unrealistic decay of the turbulence quantities for the flows considered here, indicating the inadequacy of such models in simulating developing pipe flows with swirl.
Wafer-Level, Compliant, Off-Chip Interconnects for Next-Generation Low-K Dielectric/Cu IC’s
Authors: Kacker Karan , Lo George , Sitaraman Suresh K.
Published: April 2008

Demand for off-chip bandwidth has continued to increase. It is projected by the Semiconductor Industry Association in their International Technology Roadmap for Semiconductors (ITRS) that by the year 2015, the chip-to-substrate area-array input-output interconnects will require a pitch of 70 μm. Compliant off-chip interconnects show great potential to address these needs. G-Helix is a lithography-based electroplated compliant interconnect that can be fabricated at the wafer level. G-Helix interconnects exhibit excellent compliance in all three orthogonal directions, and can accommodate the CTE mismatch between the silicon die and the organic substrate without requiring an underfill. Also, these compliant interconnect are less likely to crack or delaminate the low-K dielectric material in current and future ICs. The interconnects are also potentially cost effective as they can be fabricated using conventional wafer fabrication infrastructure. In this paper we present an integrative approach which uses interconnects with varying compliance and thus varying electrical preformance from the center to the edge of the die. Using such a varying geometry from the center to the edge of the die, the system performance can be tailored by balancing electrical requirements against thermo-mechanical reliability concerns. We also discuss the reliability assessment results of helix interconnects assembled on an organic substrate. Results from mechanical characterization experiments are also presented.
Dynamic Progressive Collapse of Closed Cell Aluminum Foam
Authors: Gama Bazle A. , Lopatnikov Sergey L. , Gillespie John W.
Published: April 2008

Progressive collapse behavior of closed cell aluminum foam under multiple-impact loading is presented. A direct impact Hopkinson pressure bar set up is developed to impact aluminum foam cylinders with a striker bar at a constant impact velocity. The total length of the specimen before and after impact is measured. The incident bar response is recorded, and average stress in the specimen is calculated. The incremental plastic strain and maximum strain rate is calculated from basic test parameters. It has been shown that by conducting direct impact experiments at variable impact velocities, it is possible to determine the dynamic behavior of closed cell metal foams at constant strain rates.
Parameterized Regulator Design Method for Switched Linear Systems
Authors: Wu Zhizheng , Ben Amara Foued
Published: April 2008

In this paper, a parameterized regulator design method based on bilinear matrix inequalities (BMIs) is presented for switched linear systems, where it is desired to reject known disturbance signals and/or track known reference inputs. Switching among plant models as well among disturbance and reference signals is defined according to a switching surface. The regulator design approach consists of three steps. The first step consists of constructing a switched observer-based state-feedback central controller for the switched linear system. Switching in the controller is performed according to the same switching rule as in the plant. The second step involves augmenting the switched central-controller to construct a parameterized set of switched controllers. Conditions for internal stability of the resulting switched closed loop system are presented. In the third step, regulation conditions are derived for the switched closed loop system. Based on the regulation conditions, a regulator synthesis approach is proposed based on solving properly formulated BMIs. Finally, a numerical example is presented to illustrate the performance of the proposed regulator.
Three-Dimensional Flow Effects on Convective Heat Transfer From a Window Covered by a Simple Plane Blind With No Top Covering
Authors: Oosthuizen Patrick H.
Published: April 2008

Most studies of convective heat transfer in window-blind systems assume that the flow over the window-blind arrangement is two-dimensional. In some cases, however, three-dimensional flow effects can become important. The present study was undertaken to determine how significant such effects can be for the particular case of a window covered by a simple plane blind. Only convective heat transfer has been considered. The situation considered is only an approximate model of the real window-blind situation. The window is represented by a rectangular vertical isothermal wall section embedded in a large vertical adiabatic plane wall surface and exposed to a large surrounding "room" in which the temperature is lower than the window temperature. The plane blind is represented by a thin vertical wall having the same size as the "window" which offers no resistance to heat transfer across it and in which conductive heat transfer is negligible. The gaps between the blind and the window at the sides and at the top of the window-blind system are assumed to be open. The flow has been assumed to be laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces. The solution has been obtained by numerically solving the three-dimensional governing equations written in dimensionless form. The effects of the dimensionless governing variables on the window Nusselt number have been numerically examined.
The Design and Simulation for a Novel Electroosmotic Micromixer
Authors: Song Hongjun , Yin Xie-Zhen , Bennett Dawn J.
Published: April 2008

The analysis of fluid mixing in microfluidic systems is useful for many biological and chemical applications at the micro scale such as the separation of biological cells, chemical reactions, and drug delivery. The mixing of fluids is a very important factor in chemical reactions and often determines the reaction velocity. However, the mixing of fluids in microfluidics tends to be very slow, and thus the need to improve the mixing effect is a critical challenge for the development of the microfluidic systems. Micromixers can be classified into two types, active micromixers and passive micromixers. Passive micromixers depend on changing the structure and shape of microchannels in order to generate chaotic advection and to increase the mixing area. Thus, the mixing effect is enhanced without any help from external forces. Although passive micromixers have the advantage of being easily fabricated and requiring no external energy, there are also some disadvantages. For example, passive mixers often lack flexibility and power. Passive mixers rely on the geometrical properties of the channel shapes to induce complicated fluid particle trajectories thereby enhancing the mixing effect. On the other hand, active micromixers induce a time-dependent perturbation in the fluid flow. Active micromixers mainly use external forces for mixing including ultrasonic vibration, dielectrophoresis, magnetic force, electrohydrodynamic, and electroosmosis force. However, the complexity of their fabrication limits the application of active micromixers. In this paper we present a novel electroosmotic micromixer using the electroosmotic flow in the cross section to enhance the mixing effect. A DC electric field is applied to a pair of electrodes which are placed at the bottom of the channel. A transverse flow is generated in the cross section due to electroosmotic flow. Numerical simulations are investigated using a commercial software Fluent® which demonstrates how the device enhances the mixing effect. The mixing effect is increased when the magnitude of the electric field increased. The influences of Pe´clet number are also discussed. Finally, a simple fabrication using polymeric materials such as SU-8 and PDMS is presented.
Boiling of Water at Sub-Atmospheric Conditions With Enhanced Structures: Effect of Liquid Fill Volume
Authors: Pal Aniruddha , Joshi Yogendra
Published: April 2008

Liquid cooling with phase change has been demonstrated to be a very efficient technique for thermal management of electronics because it has the potential to achieve high heat transfer coefficients compared to single phase liquid cooling. Previous studies on liquid immersion cooling with fluorocarbons have shown the effectiveness of boiling enhancement structures in lowering boiling incipience, raising the critical heat flux and reducing evaporator size. Two-phase thermosyphons are an alternative to liquid immersion cooling, where phase change liquid cooling can be implemented within a closed loop device. The present study involves a two-phase thermosyphon with boiling enhancement structure in the evaporator, which is subjected to sub-atmospheric pressures for lowering the saturation temperature of the working fluid. The objective of the present research is to provide a detailed understanding of the effect of liquid fill level on boiling of water with enhancement structures at sub-atmospheric pressures. The study will take into account the influence of system pressure and enhancement structure geometry on the boiling heat transfer. Experiments were performed at three different pressures, 9.7 kPa, 15 kPa and 21 kPa using a stacked enhancement structure with three different geometries (1, 4 and 6 layers), corresponding to three different liquid fill levels. The results are compared with a baseline study on sub-atmospheric pressure boiling from a plain surface at similar liquid-fill levels.
Shattered Rim Failure Analysis in Railroad Wheels
Authors: Liu Yongming , Stratman Brant , Liu Liming , Mahadevan Sankaran
Published: April 2008

A general methodology for fatigue reliability degradation of railroad wheels is proposed in this paper. Both fatigue crack initiation and crack propagation life are included in the proposed methodology using previously developed multiaxial fatigue models by the authors. A response surface method in conjunction with design of experiments is used to develop a closed form approximation of the fatigue damage accumulation with respect to the input random variables. The total fatigue life of railroad wheels under stochastic loading is simulated, accounting for the spatial and temporal randomness of the fatigue damage. The field observations of railroad wheel fatigue failures are compared with the numerical predictions using the proposed methodology.
Intelligent Position-Seeking and Methods of Manufacture Based on the Electronic Datum Group Technology
Authors: Xiong Xiang-Wen , Wynn Bear L.
Published: April 2008

Along with more and more fast development of the mechanical engineering, more and more high-tech utilize in the mechanical engineering, caused the mechanical engineering to enter the time of the high intelligence and the high-tech. This is a brand-new, time that comprehensive utilization integrated technology, and the intelligent technology, the robot technology, cross discipline high-tech frequently use in the mechanical engineering. But the modern mechanical engineering as a new technology that development by tradition engineering frequently has some technology of the neck of a bottle of the traditional engineering barrier the further development of the new mechanical technology, even is the high speed development. Therefore, comprehensively eliminates the weak link of the traditional technology in the mechanical engineering, enable the constituent of each technology of mechanical engineering all to obtain the rapid development, is the key to modern mechanical technology. This paper is precisely according to this spirit and the request, in view of Basis weak link of the mechanical engineering–datum, proposed the brand-new electronic datum new technology replace the traditional mechanical datum, causes mechanical engineering again configuring in a new base of datum on, thus thoroughly eliminates the technology of the neck of a bottle of the traditional technology, enable the humanity mechanical engineering to obtain the comprehensive enhancement and the sublimation once again.
Mechanics of Rotating Wound Rolls
Authors: Balaji Raghavan , Mockensturm Eric M.
Published: April 2008

In this paper, we investigate the effect of rotation on the internal loads in a wound roll and the dynamics of a fully wound roll under angular acceleration. Two different types of winding are distinguished: constant transport speed and constant rpm. The original scheme proposed by Benson accounted for large deformation, and used a nonlinear elastic constitutive law; in this paper, the Benson model is first expressed in dimensionless form and extended to account for roll rotation in both cases: constant rpm and constant transport speed. Additionally, tangential dynamics are considered to account for angular acceleration of a fully-wound roll. In general, it is seen that the inclusion of angular velocity in the Benson model alters the lap deformation, interlayer pressure and lap tension profiles compared to the case with no rotation, to an extent determined by the magnitude of angular velocity. A direct consequence of this is that there is now an upper bound on the number of laps that can be safely wound onto the core without loss of contact between the outer-most laps, and this is a function of rotational speed and wrapping tension, among other parameters. A numerical algorithm is then described to account for angular acceleration due to a constant core torque applied after the roll has been completely wound. This allows one to determine the slip profile through the roll at various instants during the motion.
Use of Temporal Irreversibility of Symbolic Time Series for Early Detection of Extinction in Thermal Pulse Combustors
Authors: Datta Subhashis , Mukhopadhyay Achintya , Sanyal Dipankar
Published: April 2008

A nonlinear fourth-order dynamic model of a thermal pulse combustor has been developed. In this work, the time series data generated by solution of the fourth order system is converted into a set of symbols based on the values of pressure variables. The key step to symbolization involves transformation of the original values to a stream of discretised symbols by partitioning the range of observed values into a finite number of regions and then assigning a symbol to each measurement based on the region in which it falls. Once all the measured values are symbolized, a symbol sequence vector consisting of L successive temporal observations is defined and its relative frequency is determined. In this work, the relative frequencies of different symbol sequences are computed by scanning the time series data in forward and reverse directions. The difference between the relative frequencies obtained in forward and reverse scanning is termed as "irreversibility" of the process. It is observed that for given alphabet and word sizes, the "irreversibility" increases as the system approaches extinction. The effects of different choices of alphabet and word sizes are also considered.
On Water Behavior Inside and Around a Void at Polymer Interface
Authors: Jang Changsoo , Park Seungbae
Published: April 2008

As the use of polymeric materials is increasing in microelectronics industry, the failure issues related to moisture are getting more popular. Moisture absorbed into the electronic package causes interfacial delamination through the synergetic effects of hygro-thermo-mechanical stresses and degradation of adhesion strength. It also results in catastrophic crack propagation during reflow process, called pop-coming. Vapor pressure inside preexisting voids at material interfaces is known to be a dominant driving force of this phenomenon. In order to explain vapor pressure generation at high reflow temperature, researchers so far have been presuming two mechanisms: liquid water boiling and quick moisture diffusion. In spite of the importance as a basis of the failure analysis, there has been little focus on the mechanism of liquid water accumulation, more exactly, high vapor pressure generation inside voids. In this study various known mechanisms of liquid water formation inside a void at polymer interface are reviewed. They include condensation, adsorption, capillary, and microfogging. As an alternative possibility, moisture diffusion around the void for a short reflow period is also assessed through numerical analysis.
Transient Analysis of the Thermal and Hydraulic Behavior of a Cooling Fluid in a Bayonet Tube
Authors: Luna J. M. , Hernandez-Guerrero S. , Rubio-Arana C. , Chavez R. H.
Published: April 2008

Analysis of forced convection in transient fluid flows have recently gathered attention due to the development of automatic control devices for precision control of the fluid flow in heat transfer devices of high efficiency. The precise regulation of the fluid flow is very important when the control of heat exchangers has to be assured, thus requiring a better understanding and a precise evaluation of the transient heat behavior. With few exceptions, the calculus methods for the heat exchangers devices are based on the flow patterns using considerations that could be apart from reality and restricted to stationary state conditions. These methods give little information on the possible variations due to the fluid flow changes and temperature distribution that arise due to thermal stresses. This paper deals with the details of a numerical approach to describe the transient hydrodynamic and thermal behavior in a bayonet tube with a fixed geometry using water as the working fluid. The results are reported as a function of the dimensionless Reynolds, Euler and Nusselt numbers. For each zone of the bayonet tube the time required for the fluid flow to be hydro and thermally developed is determined. The effect of the hydrodynamic flow changes on the heat flow local distribution is discussed. For a given Reynolds number a separation vortex is detected in the returning zone and it changes its position as time elapses. It is found that as time approaches the steady state the heat transfer becomes more stable throughout the bayonet.
Microscale Study of the Boiling Process in Low-Surface-Tension Fluids
Authors: Moghaddam Saeed , Kiger Kenneth T.
Published: April 2008

A novel MEMS device has been developed to study some of the fundamental issues surrounding the physics of the nucleation process intrinsic to boiling heat transfer. The device generates bubbles from an artificially generated nucleation site centered within a radially distributed sensor array. The array is fabricated within a Silicon/Benzocyclobutene (BCB) composite wall, with the capability to measure surface temperature with an unprecedented radial resolution of 22-40 μm underneath and around the bubble. The temperature data enabled numerical calculation of the surface heat flux with the same spatial resolution as of the temperature data. The temperature of the sensors and the synchronized images of the bubbles were recorded with a sampling frequency of 8 kHz. The unique data determined in this study were used to address some of the unresolved issues regarding the boiling process including 1) dynamics of bubble growth and associated heat transfer processes and 2) the bubble's role in surface heat transfer during the boiling process.
Anisotropic Thermal Diffusivity Measurements in Nanostructured Samples Using a Photothermoelectric Technique
Authors: Son Youngsuk , Mazumder Monalisa , Borca-Tasciuc Theodorian
Published: April 2008

Knowledge of the thermal transport properties in thin films and nanostructures is critical for a wide range of applications in microelectronics, photonics, micro-electro-mechanical-systems, and thermoelectrics. The last twenty years have seen significant developments in thin-film thermal characterization techniques. Despite these advances, the characterization of the thermal transport properties in low-dimensional systems remains a challenging task. Recently, thermal properties of nanowire/nanotube nanocomposites such as thermoelectric nanowires and aligned carbon nanotubes (CNT) deposited on silicon substrates or in alumina or polymer matrix have attracted a great interest due to their possible applications in high efficiency thermoelectric energy conversion and thermal management applications. However, a major challenge for thermal characterization of nanowire/nanotube composites is their thermal anisotropy. This work presents measurements of anisotropic thermal properties using a photothermoelectric technique.
Experimental and Computational Models for Simulating Sound Propagation and Acoustic Source Localization Within the Lungs
Authors: Acikgoz S. , Ozer M. B. , Royston T. J. , Mansy H. A. , Sandler R. H.
Published: April 2008

An acoustic boundary element (BE) model for porous compliant material like the lung parenchyma is developed and validated theoretically and experimentally. This BE model is coupled with a source localization algorithm to predict the position of an acoustic source within a lung phantom. The BE model is also coupled with a finite element (FE) model to simulate the surrounding shell-like chest wall. Experimental studies validate the BE-based source localization algorithm and show that the same algorithm fails if the BE simulation is replaced with a free field assumption that neglects reflections and standing wave patterns created within the finite-size lung phantom. This research is relevant to the development of advanced auscultatory techniques for lung, vascular and cardiac sounds within the torso that utilize multiple noninvasive sensors to create acoustic images of the sound generation and transmission to identify certain pathologies.
High Atwood Number Effects in Buoyancy Driven Flows
Authors: Andrews Malcolm J. , Jebrail Farzaneh F. , Banerjee Arindam
Published: April 2008

High Atwood number (non-dimensional density difference) effects in buoyancy driven flows are discussed. Buoyancy driven (natural convection) flows may be treated as Boussinesq for small Atwood number, but as Atwood number increases (>0.1, i.e. large temperature differences) the Boussinesq approximation is no longer valid and a distinct "bubble" and "spike" geometry of Rayleigh-Taylor buoyant plumes is formed. Aside from asymmetry in the flow the Atwood number also affects key turbulent mix parameters such as the molecular mix, and heat transfer coefficients. This paper presents recent experimental work being performed in the buoyancy driven mix laboratory at Texas A&M University, using air/helium as mixing components (upto At ~ 0.5). Corresponding numerical simulations of the experiments performed at Los Alamos is also presented, and future directions for the research discussed.