bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydraulic Needle Valve Actuator and Its Application to a Camless Engine
Authors: de Ojeda William , Ferna´ndez Jorge
Published: May 2008

The design and operation of a hydraulic actuator that can track precise trajectories under large accelerations and under heavy load conditions is presented. The actuator is based on a master and slave-piston arrangement and compensates for varying temperature and supply pressures without significant deterioration. A slave piston, capable of exercising a large force, tracks faithfully the motion of a needle or master spool. The actuator has been used to provide individual control over the intake and exhaust engine valves in a medium duty engine, replacing the mechanical camshaft. Simulation and test data shows the actuator to have exceptional tracking characteristics for viscosities between 0.02 and 1.5 Ns/m2, and pressures above 5MPa during warm operation. A linear motor is used to prescribe the needle motion. The low inertia of the needle and its electronic interface allows for a highly flexible electronically controlled valve system. The power consumption from the hydraulic and electrical systems is shown to be smaller than its mechanical counterpart.
Free Flexural (or Bending) Vibrations of Orthotropic Composite Mindlin Plates With a Bonded Non-Central (or Eccentric) Lap Joint
Authors: Yuceoglu U. , Gu¨vendik O¨. , O¨zerciyes V.
Published: May 2008

The present study is concerned with the “Free Flexural (or bending) Vibrations of Orthotropic Composite Mindlin Plates with a Bonded Non-Central (or Eccentric) Lap Joint”. The Mindlin plate adherends or panels of dissimilar, orthotropic material are connected by an adhesively bonded non-central (or eccentric) single lap joint. The adhesive layer is considered to be relatively very thin and linearly elastic. The theoretical formulation is based on the combination of the full set of the dynamic plate equations and the adhesive layer stress-displacement equations. Eventually, the system of equations is reduced to a set of the first order governing ordinary differential equations in the “state vector” form. The governing system of the differential equations is numerically integrated by means of the “Modified Transfer Matrix Method (with Interpolation and/or Chebyshev Polynomials)”. The effect of the non-central (or eccentric) location of the bonded lap joint is investigated and presented in detail in terms of natural frequencies and the associated mode shapes. The significant effects of the “hard” or the “soft” adhesive layer constants on the mode shapes and the natural frequencies are also investigated. Some important parametric studies such as the influences of the “Joint Length Ratio”, the “Joint Position Ratio” and the “Bending Rigidity Ratio” on the natural frequencies are computed and presented for the “hard” and the “soft” adhesive cases.
Delamination Failure of Laminated Fabric Composites Under Various Thermal Cycles
Authors: Babu K. S. , Chan W. S. , Dan-Jumbo E.
Published: May 2008

Edge delamination test was often used to screen the material system with unindirectional fiber reinforced composites for damage tolerance structural design. No standard tests were established for fabric composites. One of the objectives of this study was to employ this method to fabric composites and to investigate feasibility of using this method for material screening. Laminates with E-glass 7781 fabric impregnated by three different matrices, namely SI-BUI, SI-ZG-5A, and RS-E9 resins were tested to investigate their delamination and ultimate strength. It was observed that the strain level at the onset of stiffness change decreases as the thermal cycles increase for the laminates with a given matrix system. No significant delamination was observed for all of the coupons except the laminates with SI-BUI matrix under no thermal cycle. However, these laminates give the highest ultimate strength among all of the test coupons. Laminates with RS-E9 resin, cured by electronic beam, have the lowest strength among all of the test coupons. All of the laminates under thermal cycles result in strength reduction. Fracture surfaces of the laminates were also investigated for their failure modes. It is suggested that for fabric composites, this edge delamination test is not a viable material screening method for determining damage tolerance property.
Distributed Journal Bearing Dynamic Coefficients for Structural Finite Element Models
Authors: Campbell Robert L.
Published: May 2008

A physics-based method to circumferentially journal bearing dynamic coefficients is presented. The method is based on the traditional perturbation approach for developing linearized bearing coefficients. The focus of this paper is on the plain and titling pad bearings, but the method is applicable to any bearing model that is developed using the perturbation approach. When used for tilting pad bearings, the method removes the effect of the pad rotational degree of freedom on the computed coefficients, and thus eliminates the need to assume a pad vibration frequency to reduce the coefficients to the usual eight-coefficient representation. A numerical study is performed to show the effect of coefficient distribution for a flexible rotor/stator structure. The results of the study show a significant effect of the distribution method of the bearing coupling characteristics.
A New Criterion for Classification of Flows
Authors: Thompson Roney Leon , de Souza Mendes Paulo Roberto
Published: May 2008

Astarita (1979) proposed a local and objective criterion to classify flows. His criterion is not restricted to MWCSH, and is essentially an attempt to quantify the stress-relieving rotation experiences by the flowing material. Huilgol (1980) analyzed Astarita’s work and showed, through examples, some inconsistencies which rendered it useless as a general flow criterion. The present work revisits Huilgol’s examples and discusses in detaile the underlying physics that mark Astarita’s criterion to fail for certain flows. This analysis leads to a new criterion for flow classification involving the concept of persistence of straining. A key kinematic entity introduced in the proposed criterion is the π-plane, a plane that is normal to the relative-rate-of-rotation vector. For a more comprehensive criterion, other parameters are needed in addition to a persistence-of-straining parameter. One of them is a measure of the deformation rate in the π-plane. Emphasis is given to isochoric motions. The proposed kinematic criterion is local, frame-different and is not restricted to particular classes of flows.
Haptic Remote Guided Exploration of Deformable Objects
Authors: Domi´nguez-Rami´rez Omar A. , Parra-Vega Vicente
Published: May 2008

Perception and interaction with virtual objects through kinesthetic sensation and visual stimuli is the basic issue of a haptic interface. If a real object is located at a remote station and explored (in contact) with a passive device, a haptic interface in a local station can be used to perceive its spatial and surface attributes. This is one type of haptic guidance. This problem has been addressed with undeformable object, and contact force modelled with the penalty-based method. However, this approach yields limited haptic properties of the object, and if the object is deformable, it is difficult to achieve stable contact. However, there exists relevant tasks for exploration of deformable objects, such as exploration of fruits, skin of animals and dermatological procedures. Motivated by these kind of tasks, an approach for guided remote exploration of deformable objects is proposed in this paper. A real object is explored in a remote location and object attributes and properties such as spatial location, shape, texture and roughness are perceived with a constrained Lagrangian-based decentralized force-position controller in the local station. Stable interaction is theoretical proved and experimental results using PHANToM 1.0A validate the approach.
Experimental Evaluation of the Probe Test for Measuring Thin Film Adhesion
Authors: Dillard David A. , Scott Caleb , Mount Kris , Xu Dingying , Wan Kai-Tak , West Robert , Dillard John G.
Published: May 2008

A probe test is proposed to quantify the adhesion of thin films and coatings. Using a micromanipulator, a tungsten probe is advanced into the edge of a polymeric coating. Debonds initiate at the loading point and propagate into semicircular cracks at the interface as the probe slides under the coating. The size of the debond is related to the interfacial fracture energy; poorer adhesion results in larger debonds for a given probe displacement. Approximate closed-form and finite element analyses of the geometry have been conducted, along with a significant number of experiments on as-produced and environmentally-conditioned specimens. The technique is showing considerable promise for characterizing coating adhesion, and has certain advantages over existing techniques for certain application.
Influence of the Cross Sectional Area of a Separation Column Using Structured Packing
Authors: Cha´vez Rosa H. , de J. Guadarrama Javier , Pe´rez Osbaldo , Herna´ndez-Guerrero Abel
Published: May 2008

In order to determine the dimension of a separation column, hydrodynamic and mass transfer models are necessary to evaluate the pressure drop and the height of the global mass transfer unit, respectively. Those parameters are a function of the cross sectional area of the column. The present work evaluates the dependency of the pressure drop and height of the global transfer unit with respect to the cross sectional area of the column, using an absorption column with high efficiency structured packing, in order to recover SO2 in the form of NaHSO3, as an example. An optimization was done applying Two Film model which is based on the number of global mass transfer units of both gas and liquid, involving the separation efficiency in terms of the height of a global transfer unit. Structured packing, geometrically heaped in a separation column, has been achieving wider acceptance in the separation processes due to their geometric characteristics that allow them to have greater efficiency in the separation processes. Three different structured packing were evaluated in this work. The results show how ININ packing is one of the packings does the best work having the highest separation efficiency because it has the lowest height of the global mass transfer unit and Mellapak packing has the largest capacity because it manages the largest liquid and gas flows. An analysis is done with respect to the pressure drop through the system for all packings considered, and a discussion is presented for each hydrodynamic and mass transfer parameter studied.
A Coal-Fired Power Plant With Zero Atmospheric Emissions
Authors: Martinez-Frias Joel , Aceves Salvador M. , Smith J. Ray , Brandt Harry
Published: May 2008

This paper presents the thermodynamic analysis of a coal-based zero-atmospheric emissions electric power plant. The approach involves an oxygen-blown coal gasification unit. The resulting synthetic gas (syngas) is combusted with oxygen in a gas generator to produce the working fluid for the turbines. The combustion produces a gas mixture composed almost entirely of steam and carbon dioxide. These gases drive multiple turbines to produce electricity. The turbine discharge gases pass to a condenser where water is captured. A stream of carbon dioxide then results that can be used for enhanced oil recovery, or for sequestration. This analysis is based on a 400 MW electric power generating plant that uses turbines that are currently under development by a U.S. turbine manufacturer. The power plant has a net thermal efficiency of 42.6%. This efficiency is based on the lower heating value of the coal, and includes the energy necessary for coal gasification, air separation and for carbon dioxide separation and sequestration. The paper also presents an analysis of the cost of electricity (COE) and the cost of conditioning carbon dioxide for sequestration for the 400 MW power plant. Electricity cost is compared for three different gasification processes (Texaco, Shell, and Koppers-Totzek) and two types of coals (Illinois #6 and Wyodak). Cost of electricity ranges from 5.16 ¢/kWhr to 5.42 ¢/kWhr, indicating very little sensitivity to the gasification processes considered and the coal types used.
Mathematical Models and Stability of Linear System in the Presence of Control Saturations
Authors: Guo Shuli , Yan Shaoze , Huang Lin
Published: May 2008

In this paper, a new method for the control system with saturation inputs is given. By defining saturation function, the whole space is divided into 3m intervals and relationships among equilibrium points and intervals are established. The equilibrium points are discussed for the linear system under saturated inputs.
Numerical Modeling of Flow-Induced Suspension Vibrations in Hard Disk Drives
Authors: Kazemi Mohammad , Haj-Hariri Hossein , Humphrey Joseph A. C.
Published: May 2008

The problem of flow-induced vibrations of suspensions in a hard disk drive is studied numerically. The 2D unsteady flow field is calculated by solving the continuity and momentum equations for a fluid with constant physical properties. In addition, a 2D vibration analysis is employed to study the flowinduced oscillations of the suspension. The calculated aerodynamic loads are used to determine the response of the suspension and, consequently, the magnetic head positioning error.
An Algebraic Series Method to Solve Strongly Nonlinear Oscillators
Authors: Rosales Marta B. , Filipich Carlos P.
Published: May 2008

The well-known technique of power series is exploited here to find a recurrence algorithm to solve strongly nonlinear oscillators. A wide variety of nonlinearities may be tackled with this approach. Simple recurrence relationship are obtained after some algebra handling. Three illustrations are analytically developed and numerically solved: a parametrically excited nonlinear oscillator, the differential equation of motion of a moored structure with non-truncated mooring nonlinearities and the classical Lorenz oscillator. In the first illustration a strongly nonlinear parametric oscillator that governs a rotor dynamics problem is solved. The results are depicted as trajectories, phase plots and Poincare´ maps. The second illustrations deals with the dynamic behavior of a simplified model of a small floating structure anchored by chains or cables. This type of structure is sometimes known as Catenary Anchor Leg Mooring (CALM) system. The structure is first modeled as a two DOF oscillator with strongly nonlinear stiffness and subjected to a harmonic wave force. A further simplification is introduced by prescribing the vertical motion as a harmonic oscillation. Then, the resulting equation is stated with a single DOF. Here the use of the power series is twofold: an algebraic recurrence algorithm is employed to obtain a nontruncated differential equation and, as in the first illustration, also used as a time integration scheme. When the forcing frequency is chosen as the bifurcation parameter, the system shows diverse type of solutions: 1-, 3-, multi-period, and quasiperiodic behavior. The third illustration deals with the well-known Lorenz system. The strange attractor is obtained without difficulties.
Summation Resonance of Parametrically Excited Moving Viscoelastic Belts
Authors: Chen Tao , Hou Zhichao
Published: May 2008

The nonlinear dynamic analysis is performed on parametrically excited, viscoelastic moving-belts at summation resonance. The belt material behavior is described by a Voigt-Kelvin model. Closed-form solutions are derived at the first order approximation. Focus is put on the stability of the nontrivial solutions. The explicit expressions on the stability conditions are obtained, and then simplified through numerical simulations. The influences of moving speed and tension fluctuation on the stability of the nontrivial solutions are also demonstrated.
Design, Optimization, and Experiments of Compliant Microgripper
Authors: Oh Young Seok , Lee Woo Ho , Stephanou Harry E. , Skidmore George D.
Published: May 2008

Recent progress of MEMS technology enables the mass production of microdevices with low cost. However, methods for designing microgrippers and microdevice assembly processes have not been studied extensively. This paper presents the design and optimization of compliant microgripper, and snap-fit based microassembly experiments. A key issue of microassembly is to design a microgripper that is capable of handling and manipulating microparts with positional uncertainty and the lack of sensory information. Topology optimization is used to design compliant microgrippers that can produce a large opening at the tip or a gripper, and Finite Element Analysis (FEA) is performed to evaluate the characteristics of grippers. Compliant microgripper driven by the embedded thermal actuator and snap-connectors were fabricated using deep reactive ion etching (DRIE) process with Silicon On Insulator (SOI) wafer. With a fabricated microgripper and several snap-fits, the assembly of a three dimensional microstructure was successfully demonstrated.
Optimization of the Fixed-Geometry Valve for Increased Micropump Performance
Authors: Gamboa Adrian R. , Morris Christopher J. , Forster Fred K.
Published: May 2008

The fixed-geometry valve micropump is a seemingly simple device in which the interaction between mechanical, electrical, and fluidic components produces a maximum pump output near resonance. This type of pump offers advantages such as scalability, durability, and simplicity of fabrication in a variety of materials. Past work has focused on the development of a predictive linear dynamic model for pump design, while little has been done to improve valve shape. Here we present a process to optimize valve shape using 2D computational fluid dynamics in conjunction with an optimization algorithm. The calculated valve diodicity was maximized by manipulating six independent, non-dimensional geometric variables for a Tesla-type valve. The resulting optimally shaped valve had a 25% increase in calculated diodicity averaged over the Reynolds number range [0, 2000] compared to a non-optimized Tesla-type valve. Overall pump design was investigated by sizing the optimized Tesla valve shape in relation to all other parameters in linear dynamic model that was modified to include the effects of cavitation and other limiting factors. Four pump prototypes were fabricated in acrylic and polycarbonate using numerical-control machining techniques and miniature end mills. Testing demonstrated that a pump with the optimal shape produced nearly three times the performance of the same pump with a non-optimized valve.
Reliability of an 1657CCGA (Ceramic Column Grid Array) Package With 95.5Sn3.9Ag0.6Cu Lead-Free Solder Paste on PCBs (Printed Circuit Boards)
Authors: Lau John , Dauksher Walter
Published: May 2008

In many applications such as computers and telecommunications, the IC chip sizes are very big, the on-chip frequency and power dissipation are very high, and the number of chip I/Os is very large. The CCGA (ceramic column grid array) package developed by IBM is one of the best candidates for housing these kinds of chips [1–7]. There are two parts in this study. One is to show that the 2-parameter Weibull life distribution is adequate for modeling the thermal-fatigue life of lead-free solder joints. This is demonstrated by comparing the 2-parameter and 3-parameter Weibull distributions with life test data of an 1657-pin CCGA package with the 95.5wt%Sn3.9wt%Ag0.6wt%Cu lead-free solder paste on lead-free PCBs (printed circuit boards) under thermal cycling conditions. The other part of this study is to determine the time-history creep strain energy density of the 1657-pin CCGA solder column with two different solder paste materials, namely, 95.5wt%Sn3.9wt%Ag0.6wt%Cu and 63wt%Sn37wt%Pb and under three different thermal cycling profiles, namely, 25 ↔ 75°C, 0 ↔ 100°C, and −25 ↔ 125°C. The effects of these solder pastes and temperature conditions on the thermal-fatigue life of the high-lead (10wt%Sn90wt%Pb) solder columns of the CCGA package are provided and discussed.
Metallic Nanowires From Carbon Nanotube Building Blocks: The Effect of Atomic Defects on the Nanotube Influencing Nanowire Growth
Authors: Panchapakesan B. , Sivakumar Kousik , Lu Shaoxin
Published: May 2008

Manipulation and control of matter at the nano- and atomic level are crucial for the success of nano-scale sensors and actuators. The ability to control and synthesize multilayer structures using carbon nanotubes that will enable to build electronic devices within a nanotube is still in its infancy. In this paper, we present results on selective electric field assisted deposition of metals on carbon nanotubes realizing metallic nanowire structures. Silver and platinum nanowires has been fabricated using this approach due to its applications in chemical sensing sensing as catalytic materials to sniff toxic agents and in the area of biomedical nanotechnology for construction of artificial muscles. The electric field assisted technique allows the deposition of metals with high degree of selectivity on carbon nanotubes by manipulating the charges on the surface of the nanotubes. The thickness and the growth of the nanowires was altered by inducing defects on the initial surface of the nanotubes that affected the local current densities and electrochemical reduction of silver and platinum on those defect sites. SEM and TEM investigations revealed silver and platinum nanowires between 10 nm-100 nm in diameter. Relatively higher metal deposition was achieved in defect related sites or places where the nanotubes criss-crossed each other, due to the high current densities in these sites. The present technique is versatile and enables the fabrication of host of different types of metallic and semiconduting nanowires using carbon nanotube templates for nanoelectronics and myriad of sensor applications. Further, nanowires can also serve as model systems for studying quantum size effects in these dimensions.
Modeling Time-Dependent Systems Using Multi-Stage Bayesian Surrogates
Authors: Romero David A. , Amon Cristina , Finger Susan
Published: May 2008

Multi-Stage Bayesian Surrogate Models (MBSM) are meta-models, constructed using data obtained from different sources, which have the ability to integrate information and responses with different levels of accuracy. In applications of surrogate models for time-dependent systems, the data obtained from physical or computational experiments is usually a sequence of response values over time, measured for different combinations of design parameters. For such applications, the traditional MBSM approach is impractical to incorporate all the observed data in a single model of the system, mainly due to the prohibitive computational effort involved. In this paper, we propose a framework for building surrogate models for time-dependent systems, based on the cokriging technique. The proposed framework regards the observations as a set of time-correlated spatial processes, with a stationary, separable cross-covariance structure of known functional form. Results show that for time-dependent systems, the proposed methodology outperforms joint space-time models built with the traditional MBSM approach both in terms of accuracy and computational effort.
Microdevices for Microdialysis and Membrane Separations
Authors: Hsieh Yi-Cheng , Liang Huinan , Zahn Jeffrey D.
Published: May 2008

Microdialysis is a commonly used technique for separating small biomolecules within a complex biological mixture for continuous biochemical monitoring. Microdialysis is based upon controlling the mass transfer rate of small biomolecules diffusing across a semipermeable membrane into a dialysis fluid while excluding larger molecules such as proteins. These small molecules are subsequently sensed using a biosensor. Since many biosensors are extremely susceptible to fouling, their stability and lifetime can be extended if metabolites are filtered through a microdialysis membrane before the dialysis fluid is moved into the sensor. Dialysis is also used commonly in biological laboratories to desalt high ionic strength protein solutions. As biochemical analysis systems become more integrated for μTAS systems there is a need to automate this process. Thus, an on-chip dialysis system is useful for biochemical reaction engineering where very tight control of ionic conditions must be maintained for effective enzymatic activity. This work demonstrates the ability to integrate polymer microdialysis membranes with microfluidic systems. Microchannels are bonded with a regenerated cellulose membrane. After microchannels are produced using standard processing techniques, they are integrated with these membranes. The cellulose is activated in an oxygen plasma followed by a lamination bond to the microchannels at moderate pressure and elevated temperature. Devices were placed in a solution of rhodamine dye, and dialysis fluid was allowed to flow through the microchannels. The outlet dye concentration was measured by fluorescence intensity as a function of flow rate and follows analytically predicted results.
Advances in Fabric and Structural Analyses of Pressure Inflated Structures
Authors: Quigley Claudia J. , Cavallaro Paul V. , Johnson Arthur R. , Sadegh Ali M.
Published: May 2008

Novel methods for analyzing the response of air inflated fabric structures are presented. The first method determines the global structural response of air inflated beam and arch structures. It employs a previously developed specialized finite element. The element was derived by minimizing the strain energy potential for a cylindrical membrane deforming about its pressurized state. Through the use of displacement approximations defining the motion of the beam’s cross section, analogous to classical beam theory, the energy principle is reduced to one dimension. However, the effect of the pressure is included in the formulation. Numerical results compare favorably to experimental data for air beams constructed from Vectran®. The second method is based on the micromechanics of plain-woven fabrics. It employs nonlinear kinematics to predict the load-displacement response of a biaxially loaded fabric. Based on the fabric strip model, this method includes the effects of crimp in nonlinear kinematic material behavior and estimates values of effective material properties in tension and shear.
Full Scale Tank Car Coupler Impact Tests
Authors: Lyons Matthew L. , Riddell William T. , Koch Kevin D.
Published: May 2008

Full scale tests were performed to investigate various aspects of tank car behavior during coupler impacts. A tank car was equipped with 37 accelerometers and an instrumented coupler. Two series of full scale coupler impact tests, comprising 26 impacts, are discussed. In the first series, the tank car was empty. In the second series, the tank car was full. A range of impact speeds was investigated. Accelerometer response and coupler force were measured for each test. Aspects of the tank car response to coupler impacts can be determined by studying the coupler force versus time relationship, Shock Response Spectrum (SRS), and Power Spectral Density (PSD) analyses of accelerations measured on the tank car body. The dominant draft gear load transfer mechanism can be determined from the coupler force vs. time relationship. Accelerations were measured at many locations on the tank car. However, based on preliminary analyses, a single location near the manway was chosen for detailed study. SRS results of accelerations at this location show good correlation with the peak coupler force, although different relationships were observed when the car was empty than when it was full. PSD analyses of empty tank cars have peaks at different frequencies than PSD analyses of full tank cars, so a PSD analysis could be used to determine whether a car is empty or full. Therefore, the combination of SRS and PSD results suggests the possibility of estimating peak coupler forces resulting from yard impacts based on SRS and PSD analyses of accelerations measured at a single location on a tank car.
Simulation of Local Blood Flow in Human Brain Under Altered Gravity
Authors: Kim Chang Sung , Kiris Cetin , Kwak Dochan
Published: May 2008

Blood circulation as well as body fluids distribution undergoes significant adaptation during and after space flight. Much study on physiological changes under weightlessness has been performed since the early days of the space program. In particular, cardiovascular research in conjunction with the space shuttle program has included diverse physiological functions affected by the nervous system such as heart rate, blood pressure, hormone release, and respiration. The altered cardiac output due to adaptation during flight and deconditioning after the flight will impact blood circulation in the human body. Especially, this altered blood supply in the brain and consequent oxygen supply to certain parts of the brain will make non-negligible impact on long-duration flight. To assess the impact of changing gravitational forces on human space flight, it will be essential to quantify the flow characteristics in the brain under varying gravity conditions. Analysis of blood circulation in brain as well as other parts of human body requires the capability to analyze flow in large arteries and capillaries.
Temper Embrittlement Analyses at HAZ in New Generation of 2-1/4Cr-1Mo Steels by CTOD Tests
Authors: Zumpano Petronio , Ferreira Itamar
Published: May 2008

Temper embrittlement susceptibility was analyzed at HAZ of welded joints at room temperature in new generation of 2-1/4Cr-1Mo steels. Assessment was made by fracture toughness parameter CTODm in welded joints at coarse-grain heat affected zone (CGHAZ) and fine-grain heat affected zone (FGHAZ). Microstructural analysis was made before and after CTODm tests to place correctly fatigue pre crack at CGHAZ or at FGHAZ. Temper embrittlement simulation was made by “Step Cooling” treatment. Hardness results and microstructural analysis proved the use of stress associated with “Step Cooling” made the efficacy of this treatment better. The control of impurities content in the steel avoids development of temper embrittlement. This was confirmed by fracture toughness experiments at room temperature. No significant variation on CTODm results of three different situations of treatment and between CGHAZ and FGHAZ were observed. Scanning Electron Microscope analysis indicated fracture mechanism after embrittlement simulation was microvoids coalescence.
CFD Applications for Coal/Air Balancing in Power Plants
Authors: Vijiapurapu Sowjanya , Cui Jie , Munukutla Sastry
Published: May 2008

A new method for balancing coal / air flow to individual burners connected to a mill in a pulverized coal fired unit was proposed. A generalized calculation procedure based on this method was developed for sizing the orifices needed for balancing the coal / air flow. Efficient use of commercially available computational fluid dynamics (CFD) software was suggested for the calculation of the pressure drop in pipes with unclear specifications of geometries. The current industry practice is to balance the clean air flow and accept the resulting imbalance in the coal / air flow. By this new method the clean-air flow would be unbalanced in a tailored manner so that balanced coal / air flow would result. In order to implement this new method the power plants would still have to conduct clean air tests only.
Faceted Design of Microscale Channels for Electrokinetic Flows
Authors: Fiechtner Gregory J. , Cummings Eric B.
Published: May 2008

A novel methodology for designing microfluidic channels for low-dispersion, electrokinetic flows is presented. The technique relies on trigonometric relations that apply for ideal electrokinetic flows, allowing faceted channels to be designed using common drafting software and a hand calculator. Flows are rotated and stretched along the abrupt interface between adjacent regions having differing specific permeability. Two-interface systems are used to eliminate hydrodynamic rotation of bands injected into channels. Regions bounded by interfaces form faceted flow “prisms” with uniform velocity fields that can be combined with other prisms to obtain a wide range of turning angles and expansion ratios. Lengths of faceted prisms can be varied arbitrarily, simplifying chip layout and allowing the ability to select time-of-flight for a given faceted prism. The method is tested using combined experimental and computational demonstrations of flow displacers. Designs are demonstrated using two-dimensional numerical solutions of the Laplace equation. Experimental flow visualization is performed using standard epi-fluorescence microscopy techniques.
Methods for and Benefits of Centrifugal Compressor Design Audits
Authors: McKee Robert J. , Hollingsworth Justin R. , Smalley Anthony J.
Published: May 2008

As gas pipeline and industrial compressors become more powerful and more complex, it has become beneficial to conduct technical audits of these machines in the design stage. Detailed analysis of critical or advanced compressors by independent evaluators have identified operating limitations, resonant responses, potential vibrations, weak components, the onset of stall, and other instabilities, and have recommended ways to eliminate a variety of potential problems before the compressor is placed in operation. The suitability of a compressor and its driver for the planned service should be thoroughly evaluated, so that each component and the system not only satisfy the design conditions, but also extreme operating conditions. This paper presents a description of the tools available for design audits and gives examples of benefits that have resulted from recent audits. The rotordynamics of any large high-speed compressor should be carefully evaluated to identify potential instabilities, high vibration levels, and even destructive responses of the machine. Powerful rotordynamic analysis tools and specific knowledge exists to accurately predict bearing and seal stiffness and damping, lateral critical speeds, and damped forced responses. Some examples of significant results obtained from rotordynamic evaluations are presented, and typical problems that have been identified and eliminated are highlighted. Torsional vibration analyses for compressor trains are an essential aspect of a design audit that have identified vibration problems and weak components. Examples of torsional vibration responses and problems that can be identified and corrected are included in this paper. The aerodynamics of a compressor is a design audit topic to which attention should be paid. Thermophysical properties of the process gas, as it is compressed, are important quantities which can be accurately determined by modern equations of state. The internal velocity distribution and pressure rise per impeller and diffuser can be evaluated to identify areas of excess loss, poor work transfer, or restrictions within a compressor. Flow angles such as at the impeller and diffuser entrances can be predicted and evaluated. The diffuser inlet flow angle is a critical indicator of the onset of rotating stall. This type of aerodynamic analysis also provides important input for performance test planning and evaluation. This paper concludes with a summary of benefits of design audits for pipeline and industrial compressors.
Advances in the Railroad Locomotive Crashworthiness
Authors: Punwani Swamidas , Samavedam Gopal , Kokkins Steve
Published: May 2008

The paper describes locomotive and fuel tank crashworthiness research being conducted by the Federal Railroad Administration for improved safety of the locomotive crew under collision scenarios. The research involves static and dynamic impact strength evaluations of locomotive structural components. These evaluations which are based on full scale tests and simulations using finite element analysis are described in this paper. Correlations between the test and simulation results are also presented in some cases.
High-Pressure Microhydraulic Actuator
Authors: Mosier Bruce P. , Crocker Robert W. , Rognlien Judith L. , Patel Kamlesh D.
Published: May 2008

Actuation forces of 2.1 and 5.3 pounds (9.3 and 24 N) at velocities of 1 and 0.5 mm/s have been demonstrated with compact electrokinetic pumps producing 200 μL/min at 400 psi (2.8 MPa) and 100 μL/min at 1000 psi (6.9 MPa). This output compares favorably with electromechanical actuators (solenoid, piezoelectric, stepper motor) of similar size and is achieved silently and with no moving parts. Electrokinetic pump monoliths based on phase-separated porous methacrylate polymer monoliths and slurry-packed, sintered silica monoliths have been developed that can generate electrokinetic pressures of 3 psi/V (21 kPa/V) and 8 psi/V (6.9 kPa/V), respectively. Corresponding maximum power conversion efficiencies of 1% and 3% have been demonstrated in 10 mM TRIS-HCI at pH 8.5. Gas-bubble-free electrodes have been demonstrated to deliver 2 mA and seal to 1200 psi (8.3 MPa) for microhydraulic actuation.
Reduced-Order P.O.D. Models for Nonlinear Vibrations of Cylindrical Shells
Authors: Amabili M. , Sarkar A. , Pai¨doussis M. P.
Published: May 2008

The nonlinear (large-amplitude) response of perfect and imperfect, simply supported circular cylindrical shells to harmonic excitation in the spectral neighbourhood of some of their lowest natural frequencies is investigated. The shell is assumed to be completely filled with an incompressible and inviscid fluid at rest. Donnell’s nonlinear shallow-shell theory is used, and the solution is obtained by the Galerkin method. The proper orthogonal decomposition (POD) method is used to extract proper orthogonal modes that describe the system behaviour from time-series response data. These time-series have been obtained via the conventional Galerkin approach (using normal modes as a projection basis) with an accurate model involving 16 degrees of freedom, validated in previous studies. The POD method, in conjunction with the Galerkin approach, permits a lower-dimensional model with respect to the conventional Galerkin approach. Different proper orthogonal modes computed from time-series at different excitation frequencies are used and solutions are compared. Some of these modes are capable of describing the system behaviour over the whole frequency range around the fundamental resonance with good accuracy and with only three degrees of freedom. They allow a drastic reduction in the computational effort, as compared to using the 16 degrees-of-freedom model necessary when the conventional Galerkin approach is used.
An Analytical Study of the Optimized Performance of an Impingement Heat Sink
Authors: Sathe S. B. , Sammakia B. G.
Published: May 2008

The results of a study of a new and unique high performance air-cooled impingement heat sink are presented. An extensive numerical investigation of the heat sink performance is conducted and is verified by experimental data. The study is relevant to cooling of high power chips and modules in air-cooled environments and applies to workstations or mainframes. In the study, a rectangular jet impinges on a set of parallel fins and then turns into cross-flow. The effects of the fin thickness and gap nozzle width and fin shape on the heat transfer and pressure drop are investigated. It is found that pressure drop is reduced by cutting the fins in the central impingement zone without sacrificing the heat transfer due to a reduction in the extent of the stagnant zone. A combination of fin thicknesses of the order of 0.5 mm and channel-gaps of 0.8 mm with appropriate central cut-out yielded heat transfer coefficients over 1500 W/m2K at a pressure drop of less than 100 N/m2, as is typically available in high-end workstations. A detailed study of flow-through heat sinks, subject to the same constraints as the impingement heat sink showed that the flow-through heat sink could not achieve the high heat transfer coefficients at a low pressure drop.
Model-Based Shear Stress Gradient in Realistic Vascular Flows and Its Relation to Arterial Macromolecular Permeability
Authors: LaMack Jeffrey A. , Himburg Heather A. , Li Xue-Mei , Friedman Morton H.
Published: May 2008

Evans blue dye (EBD) was injected into the carotid arteries of three anesthetized pigs and allowed to circulate for 90 minutes. At the conclusion of the 90-minute period, the animals were sacrificed and injection casts of the infrarenal aorta and iliac-femoral arteries were prepared. The casts with their surrounding arteries were removed and immersed in fixative. After fixation, the EBD-stained vessels were separated from the casts, which were used to construct computational meshes for simulation of the flow fields and wall shear stress distributions that had existed in the casted regions during the experiments. The inlet flow waves and flow partitions were based on flow measurements performed during each experiment. Based on a conceptual model of the relation between shear stress nonuniformity and permeability increase, the spatial and angular variation of the gradient of the time-average shear stress at the walls of the external iliac arteries was found from the computational fluid dynamic simulations for each experiment. Using affine transformations, the gradient and time-average shear stress results, and the EBD optical density distributions, were mapped to a common template, allowing pixel-by-pixel correlations of the hemodynamic stress parameters and local permeability. The results suggest that both shear stress gradient and time-average shear play a role in determining vascular permeability to macromolecules.
A Madymo Study of Pelvic and Lower Extremity Injury in Frontal Crashes
Authors: Keeley Jason W. , Kim Jong E. , Davidson James , Moore Willard A. , Eberhardt Alan W.
Published: May 2008

Recent studies suggest that there is increased risk to the pelvis and lower extremities for unbelted, front seat occupants when airbags deploy in frontal collisions. Among belted drivers, women and small adults are more likely to experience fractures of the knee-thigh-hip complex and lower leg. The occupant kinematics and impact mechanics for varying sized drivers under belted and unbelted conditions, with a deploying airbag, have not been well-investigated. The present study used occupant kinematic computer software (MADYMO) to investigate injury likelihood for the pelvis, femur and lower leg in simulations of FMVSS 208 test conditions (30 mph, rigid barrier, frontal crash) for a mid-size sedan with airbag deployment. The pelvic force criterion (PFC), femur force criterion (FFC), and Tibia index (TI) were calculated as injury predictors for 50th percentile male and 5th percentile female drivers, belted and unbelted, with variations in instrument panel angle and stiffness as well as hip abduction. The results indicated, most notably, that the unbelted 5th percentile female submarined beneath the airbag and experienced TI values that exceeded the current tolerance in nearly every unbelted simulation. Injury scores for the left leg were generally higher for both dummies, due to leg entrapment and the intruding floor pan. Hip abduction of 20 degrees led to excessive hip forces in the 50th percentile male. Seatbelts were effective at reducing injury measures in both dummies, most notably the TI score of the 5th percentile female.
Overturning Thresholds of a Rocking Block Subjected to Harmonic Excitation: Computer Simulations and Analytical Treatment
Authors: Lenci Stefano , Rega Giuseppe
Published: May 2008

When a rigid block resting on a horizontal rigid foundation is shaken by a periodic excitation it can topples if the excitation amplitude is sufficiently high. This question is addressed in this work by the combined use of numerical and analytical tools. Numerical computations are first performed aimed at understanding the overall overturning behavior, and how it is modified by varying relevant parameters, such as the excitation phase and the coefficient of restitution at impacts. Then the problem is addressed from a theoretical point of view, with the objective of analytically detecting the most relevant features highlighted by previous numerical simulations. We succeed in obtaining closed form and manageable criteria for overturning.
Fluid Flow Bifurcation in Micro-Channels
Authors: Patel S. , Drikakis D.
Published: May 2008

The paper presents a numerical study of incompressible fluid flow through micro-channels. Using a high-resolution numerical method (second-order accurate) in conjunction with a non-linear multigrid algorithm and the pseudo-compressibility approach, we have investigated micro-flows through straight channels, as well as through a sudden contraction-expansion geometry. For the straight channel geometry, the computational results are in reasonable agreement with the experimental data for various low Reynolds numbers. For the contraction-expansion geometry, the results reveal the flow transition to instability. This is manifested in the form of asymmetric separation downstream of the expansion.
Development of an Electrohydrodynamic (EHD) Micro Pump for LN2 Spot Cooling
Authors: Zhao Y. , Lawler J. , Foroughi P. , Ohadi M.
Published: May 2008

Cryogenic cooling systems play increasingly important roles in both military and commercial applications. These systems are essential for the operation of superconducting electronics and sensors. The development of innovative cryogenic cooling solutions to replace the traditionally bulky, complicated, and less efficient devices that rely solely on heat conduction is becoming more and more attractive. Spot cooling is a novel concept for cryogenic cooling systems. However, spot cooling devices require a compact, efficient and reliable pump that can pump cryogenic fluids. This paper presents preliminary efforts on developing a micro pumps for cryogenic cooling of certain specialty electronics, including those of sensor and detector applications. A packaging method compatible with cryogenic applications is proposed. The tested micro pump, fabricated by MEMS techniques, had a saw-tooth emitter and planar collector with 50-μm electrode spacing and 200-μm pair spacing. The pump was tested in sub cooled liquid nitrogen (with about 7 K sub cooling). It was shown by the experimental tests that liquid nitrogen is pumped by the EHD effects if the electrodes of the pumps are properly designed. The tested micro pump pumped liquid nitrogen at a flow rate of 2.3 g/min and had an output pumping head of 5 Pa when 1000 volts were applied across the electrodes.
Rapid and Simple Diagnosis of
Chlamydophila pneumoniae
Pneumonia by an Immunochromatographic Test for Detection of Immunoglobulin M Antibodies
Authors: Miyashita Naoyuki , Ouchi Kazunobu , Kishi Fumio , Tabuchi Mitsuaki , Tsumura Naoki , Bannai Hisaichi , Iwata Satoshi , Tanaka Toshihiro , Oka Mikio
Published: May 2008

To evaluate a newly developed immunochromatographic test (the MySet test) for the detection of
Chlamydophila pneumoniae
-specific immunoglobulin M antibodies, the results obtained by the MySet test were compared with those obtained by two serological tests. The sensitivity and specificity of the MySet test were 100% and 92.9%, respectively. The MySet test is rapid and simple to use and is thought to be a useful tool for the selection of appropriate antibiotic therapy.
Modified Caspase-3 Assay Indicates Correlation of Caspase-3 Activity with Immunity of Nonhuman Primates to
Yersinia pestis
Infection
Authors: Welkos Susan , Norris Sarah , Adamovicz Jeffrey
Published: May 2008

Defined candidate human vaccines for treating infection by
Yersinia pestis
, the agent of plague, have been developed. To facilitate evaluation of the vaccines' efficacy, the in vitro caspase-3 assay for cytotoxicity-neutralizing activity was modified and reevaluated. Immune serum-mediated caspase-3 neutralizing activity correlated with protection against infection in a nonhuman primate vaccine model of plague immunity.