bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved Transient Model of Tool Temperatures in Metal Cutting
Authors: Jen Tien-Chien , Anagonye Aloysius U.
Published: July 2002

A model for predicting cutting tool temperatures under transient conditions is presented. The model of Stephenson et al. [10] is extended to include the initial transient response to the tool temperature and nonuniform heat flux distributions. The main goal in this paper is to be able to accurately predict the initial transient tool temperature response, or temperatures in interrupted cutting for cases where the cutting time is short. A method to predict the true transient energy partitioning instead of quasi-steady energy partitioning (Stephenson et al., [10]), without seeking the full numerical analysis, has been developed. In this paper, the transient energy partitioning is obtained through a fixed-point iteration process by modifying the quasi-steady energy partitioning method presented by Loewen and Shaw [11]. The predicted transient tool temperatures are compared quantitatively to the experimental data. Utilizing a semi-empirical correlation for heat flux distribution along the tool-chip interface, the temperature distribution is calculated and compared qualitatively to existing experimental data.
Flow Characteristics Inside Circular Injection Holes Normally Oriented to a Crossflow: Part II—Three-Dimensional Flow Data and Aerodynamic Loss
Authors: Lee Sang Woo , Joo Seong Kuk , Lee Joon Sik
Published: July 2002

Presented are three-dimensional mean velocity components and aerodynamic loss data inside circular injection holes. The holes are normally oriented to a crossflow and each hole has a sharp square-edged inlet. Because of their importance to flow behavior, three different blowing ratios, M=0.5, 1.0, and 2.0, and three hole length-to-diameter ratios, L/D=0.5, 1.0, and 2.0, are investigated. The entry flow is characterized by a separation bubble, and the exit flow is characterized by direct interaction with the crossflow. The uniform oncoming flow at the inlet undergoes a strong acceleration and a subsequent gradual deceleration along a converging–diverging flow passage formed by the inlet separation bubble. After passing the throat of the converging–diverging passage, the potential core flow, which is nearly axisymmetric, decelerates on the windward side, but tends to accelerate on the leeward side. The presence of the crossflow thus reduces the discharge of the injectant on the windward side, but enhances its efflux on the leeward side. This trend is greatly accentuated at M=0.5. In general, there are strong secondary flows in the inlet and exit planes of the injection hole. The secondary flow within the injection hole, on the other hand, is found to be relatively weak. The inlet secondary flow is characterized by a strong inward flow toward the injection-hole center. However, it is not completely directed inward since the crossflow effect is superimposed on it. Past the throat, secondary flow is observed such that the leeward velocity component induced by the crossflow is superimposed on the diverging flow. Short L/D usually results in an exit discharging flow with a steep velocity gradient as well as a strong deceleration on the windward side, as does low M. The aerodynamic loss inside the injection hole originates from the inlet separation bubble, wall friction and interaction of the injectant with the crossflow. The first one is considered as the most dominant source of loss, even in the case of L/D=2.0. At L/D=0.5, the first and third sources are strongly coupled with each other. Regardless of L/D, the mass-averaged aerodynamic loss coefficient has an increasing tendency with increasing M.
A New QFT Design Method for SISO Cascaded-Loop Design
Authors: Wu Wei , Jayasuriya Suhada
Published: July 2002

A new QFT design method for SISO cascaded-loop design, which is different from the conventional inner-outer procedure and the outer-inner procedure, is proposed in this paper. The desired uncertainty of the inner loop after closure is prescribed as a design specification before designing the inner controller, which is done by introducing an appropriate weight function. The inner loop design, therefore, is transferred into a sensitivity reduction problem. Then, the outer-loop design becomes that of a plant with mixed uncertainty which can be carried out as usual. In this method, the weight function is an important design factor, which actually allocates the control burden between the inner and outer controllers. This method not only removes the arbitrariness in the closure of the inner loop in the inner-outer procedure, but also can reduce the number of iterations needed, which therefore could give a significant reduction in the outer controller bandwidth as is demonstrated in two examples.
Heat Rate Predictions in Humid Air-Water Heat Exchangers Using Correlations and Neural Networks
Authors: Pacheco-Vega Arturo , Dı´az Gerardo , Sen Mihir , Yang K. T. , McClain Rodney L.
Published: July 2002

We consider the flow of humid air over fin-tube multi-row multi-column compact heat exchangers with possible condensation. Previously published experimental data are used to show that a regression analysis for the best-fit correlation of a prescribed form does not provide an unique answer, and that there are small but significant differences between the predictions of the different correlations thus obtained. It is also shown that it is more accurate to predict the heat rate directly rather than through intermediate quantities like the j-factors. The artificial neural network technique is offered as an alternative technique. It is trained with experimental values of the humid-air flow rates, dry-bulb and wet-bulb inlet temperatures, fin spacing, and heat transfer rates. The trained network is then used to make predictions of the heat transfer. Comparison of the results demonstrates that the neural network is more accurate than conventional correlations.
Flow Control of Rotating Stall in a Radial Vaneless Diffuser
Authors: Tsurusaki Hiromu , Kinoshita Takahiro
Published: July 2002

The instabilities of a backflow layer on a diffuser wall and the main flow with vorticity have already been shown theoretically to cause the occurrence of rotating stall in a vaneless diffuser. These instabilities, however, have not yet been proven to exist experimentally. This study was carried out to examine the factors contributing to the occurrence of rotating stall using a jet installed in a diffuser. Rotating stall was completely suppressed by a jet that was set in the direction opposite to the vector of the impeller peripheral velocity, and amplified by the jet set in the same direction as that vector. The effects of the jets were confirmed by the experiment using the jets installed at positions other than the neighborhood of the diffuser wall. The results suggest that the instability of the main flow contributes to the onset of rotating stall. The factors contributing to the onset of rotating stall and the effect of the jet on the performance of the impeller-diffuser combination are discussed.
A Numerical Investigation on the Development of an Embedded Streamwise Vortex in a Turbulent Boundary Layer With Spanwise Pressure Gradient
Authors: Lee InSub , Ryou Hong Sun , Lee Seong Hyuk , Hong Ki Bae , Chae Soo
Published: July 2002

It is the aim of this article to investigate numerically the effects of spanwise pressure gradient on an embedded streamwise vortex in a turbulent boundary layer. The governing equations were discretized by the finite volume method and SIMPLE algorithm was used to couple between pressure and velocity. The LRR model for Reynolds stresses was utilized to predict the anisotropy of turbulence effectively. The validation was done for two cases: one is the development of a streamwise vortex embedded in a pressure-driven, three-dimensional turbulent boundary layer. The other involves streamwise vortex pairs embedded in a turbulent boundary layer without the spanwise pressure gradient. In the case of the former, the predicted results were compared with Shizawa and Eaton’s experimental data. In the latter case, the calculated results were compared against the experimental data of Pauley and Eaton. We performed numerical simulations for three cases with different values of spanwise pressure gradient. As a result, the primary streamwise vortex with spanwise pressure gradients decays more rapidly than the case with no pressure gradients, as the spanwise pressure gradient increases. This indicates that the spanwise pressure gradient may play an important role on mean and turbulent structures. In particular, it can be seen that the increase of pressure gradient enhances a level of turbulent normal stresses.
Axial Leakage Flow-Induced Vibration of the Elastic Rod as the Axisymmetric Continuous Flexible Beam
Authors: Fujita Katsuhisa , Shintani Atsuhiko
Published: July 2002

The evaluation methodologies for the flow-induced vibration instability of a long flexible rod due to axial leakage-flow are reported. In the previous papers, the axisymmetric rods are regarded as rigid bodies, not as continuous bodies. In this paper, we deal with the rod as a continuous flexible body. The equations for the fluid and the structure are coupled analytically and the added mass, added damping, and added stiffness are derived by considering unsteady pressure acting on the rod. The relation between the axial velocity and the unstable phenomena is clarified. Concerning the critical flow velocity, the root locus (Argand diagram) is shown. We compared our results with the experimental results which one of the authors reported before.
Analysis of Temporal Shear Stress Gradients During the Onset Phase of Flow Over a Backward-Facing Step
Authors: Haidekker Mark A. , White Charles R. , Frangos John A.
Published: July 2002

Endothelial cells in blood vessels are exposed to blood flow and thus fluid shear stress. In arterial bifurcations and stenoses, disturbed flow causes zones of recirculation and stagnation, which are associated with both spatial and temporal gradients of shear stress. Such gradients have been linked to the generation of atherosclerotic plaques. For in-vitro studies of endothelial cell responses, the sudden-expansion flow chamber has been widely used and described. A two-dimensional numerical simulation of the onset phase of flow through the chamber was performed. The wall shear stress action on the bottom plate was computed as a function of time and distance from the sudden expansion. The results showed that depending on the time for the flow to be established, significant temporal gradients occurred close to the second stagnation point of flow. Slowly ramping the flow over 15 s instead of 200 ms reduces the temporal gradients by a factor of 300, while spatial gradients are reduced by 23 percent. Thus, the effects of spatial and temporal gradients can be observed separately. In experiments on endothelial cells, disturbed flow stimulated cell proliferation only when flow onset was sudden. The spatial patterns of proliferation rate match the exposure to temporal gradients. This study provides information on the dynamics of spatial and temporal gradients to which the cells are exposed in a sudden-expansion flow chamber and relates them to changes in the onset phase of flow.
Nonlinear Dynamic Analysis of a Hydrodynamic Journal Bearing Considering the Effect of a Rotating or Stationary Herringbone Groove
Authors: Jang G. H. , Yoon J. W.
Published: July 2002

This research investigates the dynamic characteristics of a herringbone grooved journal bearing with plain sleeve (GJPS) and a plain journal bearing with herringbone grooved sleeve (PJGS) under static and dynamic load. FEM is used to solve the Reynolds equation in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors of a journal, such as orbit or rotational speed, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. Numerical results are validated by the experimental results of prior researchers. A GJPS produces less friction torque than a PJGS so that the GJPS consumes less input power than the PJGS. Under static load, the PJGS converges to the fixed equilibrium position, but the GJPS has a whirling motion due to the rotating groove even at the steady state, which produces the excitation frequencies corresponding to the integer multiple of the rotor speed multiplied by the number of grooves. The variation of rotational speed of a GJPS is always less than that of a PJGS due to less friction torque. Under the effect of mass unbalance, the excitation frequencies of the reaction force in a GJPS and a PJGS are the rotational frequency due to mass unbalance and its harmonics due to the nonlinear effect of fluid film. However, the GJPS has relatively big amplitude corresponding to the multiples of the number of grooves, in comparison with the amplitudes at the adjacent harmonics.
On the Internal Resonance of a Spinning Disk Under Space-Fixed Pulsating Edge Loads
Authors: Chen Jen-San
Published: July 2002

Internal resonance between a pair of forward and backward modes of a spinning disk under space-fixed pulsating edge loads is investigated by means of multiple scale method. It is found that internal resonance can occur only at certain rotation speeds at which the natural frequency of the forward mode is close to three times the natural frequency of the backward mode and the excitation frequency is close to twice the frequency of the backward mode. For a light damping case the trivial solution can lose stability via both pitchfork as well as Hopf bifurcations when frequency detuning of the edge load is varied. On the other hand, nontrivial solutions experience both saddle-node and Hopf bifurcations. When the damping is increased, the Hopf bifurcations along the trivial solution path disappear. Furthermore, there exists a certain value of damping beyond which no nontrivial solution is possible. Single-mode resonance is also briefly discussed for comparison.
Alternative Models of Turbulence in a Porous Medium, and Related Matters
Authors: Nield D. A.
Published: July 2002

Recently published papers involving two distinct models of turbulence in a porous medium are discussed, together with related matters including inertial effects, lateral momentum transfer and spin-up, nonlinear drag, and the detection of the onset of turbulence.
Numerical Investigation of Tandem-Impeller Designs for a Gas Turbine Compressor
Authors: Roberts Douglas A. , Kacker Suresh C.
Published: July 2002

The tandem-bladed impeller centrifugal compressor, which may offer potential aerodynamic benefits over conventional designs, is rarely employed in production gas turbine applications. Conventional impeller designs are often favored because of concerns for both significant performance losses and increased manufacturing costs associated with tandem configurations. In addition, much of the available literature concerning the characteristics of tandem-impellers is inconclusive, and at times contradictory. Because of the scarcity of tandem-impellers, rules for their design are nearly nonexistent. Also, the effects of inducer/exducer clocking upon tandem-impeller performance and exit flow characteristics are not fully understood. In the present study, a numerical investigation was performed to investigate the aerodynamic characteristics of a tandem-impeller design for the rear stage of a gas turbine compressor (target impeller PRt−t≈3.0). A parametric study of tandem-impeller inducer/exducer clocking was performed in order to explore its effect upon performance and exit flow quality. Because the tandem impeller was designed to be retrofittable for an existing conventional impeller, it was also compared to predictions for the baseline conventional design. Results of the study indicated that the tandem-impeller was less efficient than the conventional design for all clocking configurations studied. Tandem-impeller blade clocking was found to have a significant effect upon predicted pressure ratio, temperature ratio, efficiency, and slip factor; the maximum values for these parameters were predicted for the in-line tandem configuration. The minimum predicted tandem-impeller isentropic efficiency occurred at a clocking fraction of 50 percent, falling 3.8 points below that of the in-line case. Although the tandem-impeller performance was predicted to diminish as blade clocking was increased, significant improvements in the uniformity of impeller exit velocity profiles were observed. Profiles of both total pressure and swirl at impeller exit indicated that the tandem-impeller design may offer both improved diffuser recovery and stalling margin over the conventional design.
Improved Compressor Exit Diffuser for an Industrial Gas Turbine
Authors: Orth U. , Ebbing H. , Krain H. , Weber A. , Hoffmann B.
Published: July 2002

Cycle studies carried out for the medium pressure ratio gas turbine THM 1304 of 10 MW power output manufactured by MAN Turbomaschinen AG GHH BORSIG predicted that the overall efficiency of the multistage compressor, composed of a ten-stage axial and a single-stage centrifugal compressor, would improve by 0.8 percent if the efficiency of the back stage centrifugal unit could be raised by 4 percent. It was expected that this would result in a noticeable improvement of the thermal gas turbine efficiency. The paper describes the aerodynamic design process used for the stage optimization, applying today’s advanced design tools for blade generation and three-dimensional aerodynamic calculation methods. Additionally, it describes the manufacturing procedure for the resulting three-dimensional blades and the experimental verification of the design approach.
A Theoretical Study of Film Condensation in Horizontal Microfin Tubes
Authors: Honda Hiroshi , Wang Huasheng , Nozu Shigeru
Published: July 2002

A stratified flow model of film condensation in helically grooved, horizontal microfin tubes has been developed. The height of stratified condensate was estimated by extending the Taitel and Dukler model for a smooth tube to a microfin tube. For the upper part of the tube exposed to the vapor flow, laminar film condensation due to the combined effects of gravity and surface tension forces was assumed. For the lower part of the tube exposed to the stratified condensate flow, the heat transfer coefficient was estimated by an empirical equation for the internally finned tubes developed by Carnavos. The theoretical predictions of the circumferential average heat transfer coefficient by the present model and previously proposed annular flow model were compared with available experimental data for five tubes and five refrigerants. It was shown that the stratified flow model was applicable to wide ranges of mass velocity and quality as long as the vapor to liquid density ratio was larger than 0.05. Comparison was also made with the predictions of previously proposed empirical equations.
Interaction of Elastic Dilatational and Shear Waves With a Frictional Sliding Interface
Authors: Nosonovsky Mikhail , Adams George G.
Published: July 2002

The refraction and reflection of plane dilatational and shear waves, which are incident upon a sliding frictional interface between two elastic half-spaces, is considered. The contact interface is governed by Coulomb’s friction law with a constant friction coefficient. The incoming waves interact with the interface to form two reflected waves (shear and dilatational) as well as two such refracted waves. The dependency of the reflected and refracted wave amplitudes on the incoming wave angle is investigated. It is shown that the contact normal stress, shear stress and relative sliding velocity are proportional to each other. The interaction of an isolated interfacial rectangular wave pulse, or of a periodic set of pulses, with the frictional interface is then investigated. It is shown that steady motion of the two bodies can result due to the propagation of interface stick-slip waves. This motion can occur in the same direction or in the opposite direction of the remotely applied shear traction, or without an applied shear traction. The velocity of relative motion as a function of material parameters, friction coefficient, remotely applied shear and normal tractions, and parameters of the pulse is presented and discussed. These results may lead to a new form of ultrasonic propulsion which can be utilized for position or velocity control of a sliding body.
Probabilistic Modeling of Flow Over Rough Terrain
Authors: Ghanem Roger , Hayek Bernard
Published: July 2002

This paper presents a method for the propagation of uncertainty, modeled in a probabilistic framework, through a model-based simulation of rainflow on a rough terrain. The adopted model involves a system of conservation equations with associated nonlinear state equations. The topography, surface runoff coefficient, and precipitation data are all modeled as spatially varying random processes. The Karhunen-Loeve expansion is used to represent these processes in terms of a denumerable set of random variables. The predicted state variables in the model are identified with their coordinates with respect to the basis formed by the Polynomial Chaos random variables. A system of linear algebraic deterministic equations are derived for estimating these coordinates.
Single-Passage Analysis of Unsteady Flows Around Vibrating Blades of
a Transonic Fan Under Inlet Distortion
Authors: Li H. D. , He L.
Published: July 2002

Computations of unsteady flows due to inlet distortion driven blade vibrations, characterized by long circumferential wavelengths, typically need to be carried out in multi-passage/whole-annulus domains. In the present work, a single-passage three-dimensional unsteady Navier-Stokes approach has been developed and applied to unsteady flows around vibrating blades of a transonic fan rotor (NASA Rotor-67) with inlet distortions. The phase-shifted periodic condition is applied using a Fourier series based method, “shape-correction,” which enables a single-passage solution to unsteady flows under influences of multiple disturbances with arbitrary interblade phase angles. The computational study of the transonic fan illustrates that unsteady flow response to an inlet distortion varies greatly depending on its circumferential wavelength. The response to a long wavelength (whole-annulus) distortion is strongly nonlinear with a significant departure of its time-averaged flow from the steady state, while that at a short wavelength (two passages) behaves largely in a linear manner. Nevertheless, unsteady pressures due to blade vibration, though noticeably different under different inlet distortions, show a linear behavior. Thus, the nonlinearity of the flow response to inlet distortion appears to influence the aerodynamic damping predominantly by means of changing the time-averaged flow. Good agreements between single-passage solutions and multi-passage solutions are obtained for all the conditions considered, which clearly demonstrates the validity of the phase-shifted periodicity at a transonic nonlinear distorted flow condition. For the present cases, typical CPU time saving by a factor of 5–10 is achieved by the single-passage solutions.
Multiaxial Cyclic Ratcheting in Coiled Tubing—Part I: Theoretical Modeling
Authors: Rolovic Radovan , Tipton Steven M.
Published: July 2002

Coiled tubing is a long, continuous string of steel tubing that is used in the oil well drilling and servicing industry. Bending strains imposed on coiled tubing as it is deployed and retrieved from a well are considerably into the plastic regime and can be as high as 3 percent. Progressive growth of tubing diameter occurs when tubing is cyclically bent-straightened under constant internal pressure, regardless of the fact that the hoop stress imposed by typical pressure levels is well below the material’s yield strength. A new incremental plasticity model is proposed in this study that can predict multiaxial cyclic ratcheting in coiled tubing more accurately than the conventional plasticity models. A new hardening rule is presented based on published experimental observations. The model also implements a new plastic modulus function. The predictions based on the new theory correlate well with experimental results presented in Part II of this paper. Some previously unexpected trends in coiled tubing deformation behavior were observed and correctly predicted using the proposed model. [S0094-4289(00)00402-3]
Effect of Slip Velocity and Heat Transfer on the Condensed Phase Momentum Flux of Supersonic Nozzle Flows
Authors: Sherif S. A. , Lear W. E. , Winowich N. S.
Published: July 2002

One of the methods used for industrial cleansing applications employs a mixture of gaseous nitrogen and liquid water injected upstream of a converging-diverging nozzle located at the end of a straight wand assembly. The idea is to get the mixture to impact the surface at the maximum momentum flux possible in order to maximize the cleansing effectiveness. This paper presents an analysis geared towards this application in which the effects of slip and heat transfer between the gas and liquid phases are present. The model describes the liquid momentum flux (considered a figure of merit for cleansing) under a host of design conditions. While it is recognized that the emulsification mechanism responsible for cleansing is far more complicated than simply being solely dependent on the liquid momentum flux, the analysis presented here should prove useful in providing sufficiently accurate results for nozzle design purposes. [S0098-2202(00)01801-0]
Effects of Vapor Superheat and Condensate Subcooling on Laminar Film Condensation
Authors: Mitrovic J.
Published: July 2002

Nusselt's model is employed to illustrate the effects of vapor superheat and condensate subcooling on laminar film condensation occurring under simultaneous actions of gravity and interfacial shear. The vapor superheat affects the condensation kinetics in cooperation with heat transfer in both phases. Under comparable conditions, the condensate film is thinner and the heat transfer coefficient larger for superheated than for saturated vapor. The heat flux on the cooling surface arising from the sensible heat of condensate increases as the critical point of the condensing substance is approached and, at this point, the Nusselt condensation model gives the single-phase boundary layer solutions. [S0022-1481(00)00701-5]
Fourier Versus Non-Fourier Heat Conduction in Materials With a Nonhomogeneous Inner Structure
Authors: Herwig H. , Beckert K.
Published: July 2002

Distinct non-Fourier behavior in terms of finite propagation velocity and a hyperbolic wave like character of heat conduction has been reported for certain materials in several studies published recently. However, there is some doubt concerning these findings. The objective of this note is to present experimental evidence for a perfectly Fourier-like behavior of heat conduction in those materials with nonhomogeneous inner structure that have been under investigation in the other studies. This controversy needs to be settled in order to understand the physics of heat conduction in these materials. [S0022-1481(00)00102-X]
Critical Structures of Metal Destruction Under the Process of Wear
Authors: Garbar I. I.
Published: July 2002

Resistance to wear is determined by the ability of the metal structure to change in such a way that it can withstand friction stresses. The structure of surface layers which have undergone wear can be identified as a “critical” structure. This is where destruction takes place. To study the surface structure specimens of low-carbon steel, aluminum and copper were subjected to wear tests and then investigated by X-ray. Under certain test conditions it was found that the changes in the surface layer structure, evidenced by the structural broadening of diffraction lines, reach a maximum level. The tests showed that as one progresses from mild wear to harsher friction conditions and correspondingly higher wear intensity, the structural broadening of the diffraction lines is first increased but than reduced. The results show that under low and moderate wear conditions, the structure of the surface layers is changed by the friction process, the surface layers being hardened by fragmentation. The level of metal hardening corresponds to the friction stresses that occur in the surface layers, and reaches a maximum when the fragment dimensions are minimal. As the friction conditions become more severe, the critical structure of the metal approaches the initial conditions, and therefore its strength is less than that of the hardened structure formed under moderate wear conditions. Such results can be explained by the difference in the rates of the plastic deformation and of plastic relaxation processes. Therefore, the critical structure under the process of wear depends on the friction conditions. To put the mechanical properties of the material to best use, one should choose optimal friction and wear conditions so that the metal will be hardened as much as possible. [S0742-4787(00)04801-3]
The Decomposition Mechanisms and Thermal Stability of ZDOL Lubricant on Hydrogenated Carbon Overcoats
Authors: Chen Chao-Yuan , Wei Jianjun , Fong Walton , Bogy David B. , Bhatia C. Singh
Published: July 2002

Tribo-chemical studies of the head/disk interface (HDI) were conducted using hydrogenated CHx carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated Al2O3-TiC sliders and thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. The friction and catalytic decomposition mechanisms as well as the thermal behavior of ZDOL are described, and data demonstrating the chemical reactions of the lubricant and carbon overcoat are also presented. During the sliding at the carbon-coated slider/ZDOL lubricated CHx disk interface, frictional heating is the primary decomposition mechanism of ZDOL. [S0742-4787(00)01902-0]
Calculation of Equilibrium Position and Dynamic Coefficients of a Journal Bearing Using Free Boundary Theory
Authors: Zheng Tiesheng , Hasebe Norio
Published: July 2002

A finite element method, which is based on the variational inequality approach, is introduced to calculate the oil film pressure distribution of a journal bearing. The cavitation zone is found by solving a linear complementary problem. By means of this approach a perturbation can be performed directly on the finite element equation and, consequently, the Jacobian matrices of the oil film forces are obtained concisely. The equilibrium position of the bearing at a given static load is found by the Newton-Raphson method and, as byproducts, dynamic coefficients are obtained simultaneously without any extra computing time. Numerical examples show that the method works satisfactorily. [S0742-4787(00)02302-X]
Three-Dimensional Unsteady Flow for an Oscillating Turbine Blade and the Influence of Tip Leakage
Authors: Bell D. L. , He L.
Published: July 2002

The results of two investigations, concerning the aerodynamic response of a turbine blade oscillating in a three-dimensional bending mode, are presented in this paper. The first is an experimental and computational study, designed to produce detailed three-dimensional test cases for aeroelastic applications and examine the ability of a three-dimensional time-marching Euler method to predict the relevant unsteady aerodynamics. Extensive blade surface unsteady pressure measurements were obtained over a range of reduced frequency from a test facility with clearly defined boundary conditions (Bell and He, 1997, ASME Paper No. 97-GT-105). The test data indicate a significant three-dimensional effect, whereby the amplitude of the unsteady pressure response at different spanwise locations is largely insensitive to the local bending amplitude. The computational results, which are the first to be supported by detailed three-dimensional test data, demonstrate the ability of the inviscid method to capture the three-dimensional behavior exhibited by the experimental measurements and a good level of quantitative agreement is achieved throughout the range of reduced frequency. Additional computational solutions, obtained through application of the strip methodology, reveal inadequacies in the conventional quasi-three-dimensional approach to the prediction of oscillating blade flows. The issue of linearity is also considered, and both experimental and computational results indicate a linear behavior of the unsteady aerodynamics. The second, an experimental investigation, addresses the influence of tip leakage upon the unsteady aerodynamic response of an oscillating turbine blade. Results are provided for three settings of tip clearance. The steady flow measurements show marked increases in the size and strength of the tip leakage vortex for the larger settings of tip clearance and deviations are present in the blade loading toward the tip section. The changes in tip clearance also caused distinct trends in the amplitude of the unsteady pressure at 90 percent span, which are observed to correspond with localized regions where the tip leakage flow had a discernible impact on the steady flow blade loading characteristic. The existence of these trends in the unsteady pressure response warrants further investigation into the influence of tip leakage on the local unsteady flow and aerodynamic damping. [S0889-504X(00)01101-6]
Core Level and Valence Band XPS Spectra of E-120 Pitch-based Carbon Fiber Galvanostatically Oxidized in HNO3 Solution
Authors: Xie Yaoming , Sherwood Peter M. A.
Published: July 2002

Du Pont E-120 high modulus pitch-based carbon fiber was galvanostatically oxidized in HNO3 solution and analyzed with both core level and valence band XPS. Compared to the untreated E-120 fiber, the galvanostatically oxidized fiber had a much higher oxygen content on its surface. Both surface and bulk graphitic structures were severely disordered by the electrochemical treatment as evidenced by both XPS and XRD studies. [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621, (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645, (1992).] However, no nitrogen was found on this pitch-based carbon fiber either before or after the treatment in HNO3 solution. Our previously reported work [Y. Xie and P. M. A Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992)] showed that XPS valence band spectra were more sensitive to chemical environment on the carbon fiber surface than core level spectra and could be well interpreted by X–α calculations with model compounds. In this work, the valence band spectrum, together with the O 1s core level spectrum, showed that there was only one single-type oxygen containing functional group formed on the surface when the fiber was electrochemically oxidized in HNO3 solution. We also reported [see Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 45, 1158 (1991)] that the reproducibility of the galvanostatic treatment was better than that of the potentiostatic treatment, although the galvanostatic oxidation gave a very similar result to that of the potentiostatic oxidation.
Core Level and Valence Band XPS Spectra of E-120 Pitch-based Carbon Fiber Galvanostatically Oxidized in (NH4)2CO3 Solution
Authors: Xie Yaoming , Wang Tiejun , Sherwood Peter M. A.
Published: July 2002

Du Pont E-120 high modulus pitch-based carbon fiber was galvanostatically oxidized in (NH4)2CO3 solution and analyzed with both core level and valence band XPS. Compared to the untreated E-120 fiber, the galvanostatically oxidized fiber had a very much higher oxygen content on its surface. Nitrogen was also found on this carbon fiber sample after the treatment in (NH4)2CO3 solution but no nitrogen was found either before or after the treatment in HNO3 solution. Our previously reported work [see Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992)] showed that XPS valence band spectra were more sensitive to chemical environment on the carbon fiber surface than core level spectra and could be well interpreted by X–α calculations with model compounds. In this work, the valence band spectrum shows that there were three different types of oxygen-containing functional groups formed on the fiber surface when the fiber was electrochemically oxidized in (NH4)2CO3 solution but only one type of oxygen-containing functionality formed after the electrochemical treatment in HNO3 solution. We also reported [see Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 45, 1158 (1991)] that the reproducibility of the galvanostatic treatment was better than that of the potentiostatic treatment, although the results from potentiostatic oxidation and galvanostatic oxidation were very similar.
Iron Carbide Formed by Reacting Surface Hydrocarbons with an Iron Film
Authors: Geib K. M. , Wilmsen C. W.
Published: July 2002

A first derivative C KLL Auger electron spectrum from an Fe film which was heated to react with adventitious surface hydrocarbons is presented as a “finger print” for the identification of an iron–carbon reaction. The iron carbide peak shape is significantly different from that of the adventitious hydrocarbons prior to heating the sample and a subsequent 1 min argon ion sputter at 1 keV or that of bulk graphite [K. M. Geib, C. W. Wilmsen, J. E. Mahan, and M. C. Bost, J. Appl. Phys. 61, 5299 (1987)]. The carbon is probably bonded as Fe3C because this compound is thermodynamically more stable than the other iron carbides and because the carbon is in an iron rich environment.
Sr(NO3)2 by XPS
Authors: Vasquez Richard P.
Published: July 2002

X-ray photoelectron spectroscopy measurements of the principal core levels, including the energy loss regions, for high purity strontium nitrate are presented.
Spin Cast Poly(vinyl isobutyl ether) Film on Glass Substrate by XPS
Authors: Ackeret Michael , Ratner Buddy D.
Published: July 2002

X-ray photoelectron spectroscopy was used to analyze poly(vinyl isobutyl ether), a pure spin cast polymer. This polymer was centrifugally spun cast onto a glass substrate and stored in an UV/ozone cleaned, O-ring sealed aluminum container. The polymer was examined at three different electron takeoff angles to verify homogeneity. Data were collected and atomic compositions calculated with a Hewlett-Packard 5950B ESCA. Measured atomic composition percentages closely matched the expected stoichiometry of the polymer.
Sputter-deposited Cr–Si–O Cermet Films by XPS
Authors: Bertóti Imre , Tóth Andras , Móhai Miklos
Published: July 2002

X-ray photoelectron spectroscopy (XPS) was used to characterize thin film of Cr–Si–O cermet, rf sputter-deposited onto a thermally oxidized Si wafer. Angle dependent spectra (θ=0° and 60°) were acquired on both the as received and the Ar+ ion sputtered states. In the as received state the topmost layer is enriched in Si and O; Si and Cr are present in both oxidized and reduced forms. After sputtering by Ar+ (2.5 keV, 6 × 1016 ions/cm2), Cr becomes reduced to Cr0, and the relative amount of Si0 increases substantially (i.e., up to about 40% of total Si). These reduced states are found to recombine to CrxSi-type silicides. The Cr–Si–O layers are applied as precision thin film resistors of good long-range stability with low temperature coefficient of resistivity. Heat treatment—leading to crystalline silicide phase—is used to consolidate the properties of these layers for device applications. We have shown (apparently for the first time), however, that room temperature ion impact can also create highly dispersed—nondetectable by XRD—silicide clusters, the formation of which has been deduced from the Si Auger parameter, being significantly higher for the silicide (aSi=1716.2–1716.5 eV) than for elemental Si (aSi=1716.0 eV).
Polysaccharide by XPS: Analysis of Maltodextrin
Authors: Gerin Patrick A. , Genet Michel J. , Rouxhet Paul G.
Published: July 2002

Maltodextrin was analyzed as a model compound representative of polysaccharides. A relatively smooth surface was obtained by pressing the maltodextrin powder in a small trough. The C 1s peak component was split into three components with the same FWHM. The main component was found at 286.3 eV and was attributed to carbon involved in the alcohol functions. The component found at 287.8 eV was attributed to carbon in the acetal function; the alcohol to acetal ratio ([C_—OH]/[O—C_—O]) was 0.21, i.e., close to the stoichiometric ratio 0.20. A component found at 284.8 eV indicated the presence of hydrocarbon-like surface contamination. The O 1s peak showed only one component at 532.7 eV; oxygen involved in hydroxyl could not be distinguished from oxygen involved in a acetal function. The surface analysis of model compounds was performed under conditions of practical significance for the analysis of microbial cells and of materials treated by biological fluids. This approach allowed quantification of chemical functions of biosurfaces and modeling of the composition of the latter in terms of classes of biochemical compounds (polysaccharides, proteins, lipids, …)
Characterization of Polystyrene (1 kDa) Functionalized with a Dimethyl- phenylsilane Endgroup by TOF-SIMS: Effect of Post-Ionization Using a Nonresonant Multiphoton Technique
Authors: Belu A. M. , Hunt M. O. , DeSimone J. M. , Linton R. W.
Published: July 2002

TOF-SIMS measurements of 1 kDa polystyrene functionalized with a dimethylphenylsilane endgroup are presented and compared with measurements made by multiphoton ionization sputtered neutral mass spectrometry (MPI-SNMS). Silver cationized intact oligomer signals are obtained by TOF-SIMS and non-silver cationized intact oligomer signals are generated with MPI-SNMS. The Mn values from both methods are in good agreement.
Fuchs-Kliewer HREEL Phonon Spectrum of Single Crystal NiO(100) and of Ni(100)/NiO(111) and Ni(100)/NiO(100) Thin Films
Authors: Carson G. A. , Nassir M. H. , Wulser K. W. , Langell M. A.
Published: July 2002

The high resolution electron energy loss spectrum (HREELS) of an ionic material is generally dominated by inelastic scattering of the electron with Fuchs-Kliewer phonon modes of the lattice surface. The phonon motion, in which the cations and anions vibrate out of phase to each other, yields a substantial dipole moment and thus an intense phonon spectrum along the specular scattering direction. In NiO, the high symmetry of its fcc rocksalt structure produces a single fundamental Fuchs-Kliewer phonon mode. However, the large cross section for phonon excitation results in multiple scattering events and thus a series of losses at integral multiples of the fundamental phonon energy. We report Fuchs-Kliewer phonon spectra for single crystal NiO(100) and for thin films of nickel oxide grown on Ni(100) single crystal substrates. The NiO(100) orientation is nonpolar, with interpenetrating square arrays of cations and anions, and is the thermodynamically most stable nickel oxide surface. The entire phonon spectrum of the thin film is considerably less than that of the NiO(100) single crystal substrate due to the damping effect of the underlying Ni(100) metal. NiO(100) is produced for Ni(100) substrate temperatures <=300 K under comparable oxygen partial pressures. The NiO(100) orientation is metastable and grows to a limiting thickness of three layers. With a single loss energy of 69.6 meV, the Ni(100)/NiO(1111) Fuchs-Kliewer phonon loss is equal to that of NiO(100) but the multiple losses are more poorly developed despite the comparable thicknesses of the two thin films. The poorer definition of the phonon spectrum is believed to result from a greater amount of disorder in the metastable NiO(111) thin film.
Tl2Ba2CuO6+δ by XPS
Authors: Vasquez R. P. , Ren Z. F. , Wang J. H.
Published: July 2002

XPS core level and valence band spectra are presented for chemically etched epitaxial thin films of superconducting Tl2Ba2CuO6+δ on SrTiO3(100) substrates which are as-grown overdoped (superconducting transition temperature [Tc]=11 K) and annealed (Tc=63 K). The core levels measured from the annealed film are shifted to higher binding energies relative to those from the as-grown overdoped film, consistent with a doping-induced change in the chemical potential.
High Resolution Spectra of Poly(cis-isoprene)
Authors: Mähl Sven
Published: July 2002

X-ray photoelectron spectroscopy was used to analyze poly(cis-isoprene). The polymer was centrifugally spin cast on a silicon wafer. We find that the cis spectrum can be described by five Voigt profiles. The parameters of the lines with standard deviations are found by least-square fitting.
TlBa2CaCu2O7−δ by XPS
Authors: Vasquez R. P. , Siegal M. P.
Published: July 2002

XPS core level and valence band spectra are presented for chemically etched epitaxial thin films of superconducting TlBa2CaCu2O7−δ, one of which is as-grown overdoped (superconducting transition temperature [Tc] = 74.5 K) and two which are annealed (Tc = 86.5 K and 87.5 K). The core levels measured from the annealed films are shifted to higher binding energies relative to those from the as-grown overdoped film, consistent with a doping-induced change in the chemical potential.
1,2-Polybutadiene Spin Cast Films by XPS
Authors: Burrell Michael C. , Chera John J.
Published: July 2002

A spin cast film of poly(butadiene) (PBD) was analyzed by XPS using monochromatic Al Kα excitation. The XPS survey spectrum contained only carbon, as expected from the stoichiometry of the polymer. The high resolution spectrum of the C 1s peak is also reported.
Nylon 66 Spin Cast Films by XPS
Authors: Burrell Michael C. , Chera John J.
Published: July 2002

A spin cast film of poly(hexamethylene adipamide) (Nylon 6,6) was analyzed by XPS using monochromatic Al Kα excitation. The measured atomic composition closely matched the expected stoichiometry of the polymer. Peak positions of the individual chemically shifted C 1s, O 1s, and N 1s components are reported. The results are in general agreement with other reported spectra of poly(hexamethylene) polymers: experimental, C 67.1%, O 17.6%, and N 11.1%; theoretical, C 75.0%, O 12.5%, and N 12.5%.
Analysis of a 30% Glass-filled Nylon 6 Polymer by XPS
Authors: Lannon John M. , Meng Qingru
Published: July 2002

We report x-ray photoemission spectra for a 30% glass-filled nylon 6 polymer (PA6). XPS spectra were acquired with a SSI model SSX-100 instrument using monochromated Al Kα x-rays. We present the survey spectrum (binding energy 0–1000 eV) and a narrow spectrum of the C 1s, O 1s, and N 1s photoelectron peaks.
Analysis of a 30% Glass-filled Poly(phenylene ether) and Nylon 6,6 Polymer Blend by XPS
Authors: Lannon John M. , Meng Qingru
Published: July 2002

We report x-ray photoemission spectra for a 30% glass-filled poly(phenylene ether) and nylon 6,6 (PPE+PA66) polymer blend. XPS spectra were acquired with a SSI model SSX-100 instrument using monochromated Al Kα x-rays. We present the survey spectrum (binding energy 0–1000 eV) and a narrow spectrum of the C 1s, O 1s, and N 1s photoelectron peaks.
Low-Temperature Angle-Resolved Photoemission Spectra of the Layered CMR Oxide La1.2Sr1.8Mn2O7
Authors: Dessau D. S. , Saitoh T.
Published: July 2002

We present high resolution (40 meV) angle-resolved photoemission data from cleaved single-crystalline surfaces of the layered colossal magnetoresistive oxide La1.2Sr1.8Mn2O7. The sample was in the low temperature ferromagnetic state at T=10 K, well below the phase transition temperature of T=126 K. Full valence bands containing Mn 3d and O 2p states are shown, as well as blowups of the near EF spectra which are made up of the eg symmetry Mn 3d-O 2p hybrid states. k-vectors span the Brillouin zone center (0,0) to the zone face (π,0).