bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of bone morphogenetic proteins and their associated molecules in ameloblastomas and adenomatoid odontogenic tumors
Authors: Kumamoto H , Ooya K
Published: December 2005

Objective:  To further clarify the roles of regulators of embryonic development, bone morphogenetic protein (BMPs) and their associated molecules, in oncogenesis and cytodifferentiation of odontogenic tumors, the expression of these regulator molecules were analyzed in epithelial odontogenic tumors as well as in tooth germs.

Materials and methods:  Tooth germs, ameloblastomas, adenomatoid odontogenic tumors, and malignant ameloblastomas were examined by RT‐PCR and immunohistochemistry for detection of BMP‐2, ‐4, ‐7, BMP receptors I and II (BMPR‐I, BMPR‐II), core‐binding factor α1 (CBFA1), and osterix.

Results:  mRNA expression of BMPs, BMPRs, CBFA1, and osterix was detected in all odontogenic tissues. Immunohistochemical reactivity for BMPs, BMPRs, and CBFA1 was detected in both epithelial and mesenchymal cells of tooth germs and epithelial odontogenic tumors. BMPs and BMPRs were evidently expressed in odontogenic epithelial cells in tooth germs and epithelial odontogenic tumors. Acanthomatous ameloblastomas showed increased BMP‐7 reactivity in keratinizing cells. Nuclear CBFA1 expression was detected scatteredly in odontogenic epithelial cells in normal and neoplastic odontogenic tissues, as well as in some mesenchymal cells in tooth germs and in some stromal cells in epithelial odontogenic tumors. Ameloblastic carcinomas showed low reactivity for BMPs, BMPRs, and CBFA1.

Conclusion:  BMPs and their associated molecules might play a role in cytodifferentiation of normal and neoplastic odontogenic epithelium via epithelial–mesenchymal interactions.
Possible evidence for the ejection of a supermassive black hole from an ongoing merger of galaxies
Authors: Haehnelt Martin G. , Davies Melvyn B. , Rees Martin J.
Published: December 2005

Attempts of Magain et al. to detect the host galaxy of the bright quasi-stellar object (QSO) HE0450–2958 have not been successful. We suggest that the supermassive black hole (SMBH) powering the QSO was ejected from the observed ultraluminous infrared galaxy (ULIRG) at the same redshift and at 1.5 arcsec distance. Ejection could have been caused either by recoil due to gravitational wave emission from a coalescing binary of SMBHs or the gravitational slingshot of three or more SMBHs in the ongoing merger of galaxies which triggered the starburst activity in the ULIRG. We discuss implications for the possible hierarchical build-up of SMBHs from intermediate and/or stellar mass black holes, and for the detection of coalescing supermassive binary black holes by LISA.
The complex velocity distribution of galaxies in Abell 1689: implications for mass modelling
Authors: Łokas E. L. , Prada F. , Wojtak R. , Moles M. , Gottlöber S.
Published: December 2005

The Abell 1689 galaxy cluster has recently become a subject of intensive study. Thanks to its intermediate redshift (z= 0.183), its mass distribution can be reconstructed using numerous methods including gravitational lensing, galaxy kinematics and X-ray imaging. The methods used to yield conflicting mass estimates in the past, and recently the cluster mass distribution has been claimed to be in conflict with standard cold dark matter scenarios due to the rather large concentration and steep mass profile obtained from the detailed studies of Broadhurst et al. using lensing. By studying in detail the kinematics of about 200 galaxies with measured redshifts in the vicinity of the cluster, we show that the cluster is probably surrounded by a few structures, quite distant from each other, but aligned along the line of sight. We support our arguments by referring to cosmological N-body simulations and showing explicitly that distant, non-interacting haloes can produce entangled multi-peak line-of-sight velocity distributions similar to that in Abell 1689. We conclude that it is difficult to estimate the cluster mass reliably from galaxy kinematics, but the value that we obtain after applying a simple cut-off in velocity agrees roughly with the mass estimated from lensing. The complicated mass distribution around the cluster may, however, increase the uncertainty in the determination of the density profile shape obtained with weak lensing.
Peptide, Peptidomimetic and Small‐molecule Drug Discovery Targeting HIV‐1 Host‐cell Attachment and Entry through gp120, gp41, CCR5 and CXCR4†
Authors: Kazmierski Wieslaw M. , Kenakin Terry P. , Gudmundsson Kristjan S.
Published: December 2005

This review highlights selected examples of peptide, peptidomimetic and small‐molecule drug discovery targeting HIV‐1 to advance novel anti‐HIV pharmaceuticals that inhibit initial stages of the viral cycle; namely, attachment and entry. Some of these approaches have culminated in the development of peptide‐based drugs, while other have exploited peptides as enabling tools toward the identification of small‐molecule lead compounds. Both of these conceptually different approaches have facilitated lead optimization of molecules with complementary and often surprising anti‐HIV pharmacological properties, supporting their role in pharmaceutical development. Furthermore, such molecules enabled mechanistic elucidation of viral attachment and entry and provided additional insights toward achieving the desired drug profile.
The Discovery of Small Molecule Inhibitors of Neutral Endopeptidase. Structure–Activity Studies on Functionalized Glutaramides
Authors: Maw Graham N. , Stobie Alan , Planken Simon , Pryde David C. , Sanderson Vivienne , Platts Michelle Y. , Corless Martin , Stacey Peter , Wayman Christopher , Van Der Graaf Piet , Kohl Christopher , Coggon Sara , Beaumont Kevin
Published: December 2005

A series of small molecule glutaramides were synthesized and evaluated for potency against canine and human neutral endopeptidase using target criteria of molecular weight <400 and log P between 2 and 4.5 to maximize the likelihood of achieving good oral absorption. The structure‐activity relationship (SAR) investigations described in this paper led to the identification of an ethyl 1,3,4‐thiadiazole glutaramide which demonstrated good neutral endopeptidase potency, selectivity and excellent oral absorption in the rat.
Stability of Gold Nanoparticle‐Bound DNA toward Biological, Physical, and Chemical Agents
Authors: Han Gang , Martin Craig T. , Rotello Vincent M.
Published: December 2005

Positively charged trimethylammonium‐modified mixed monolayer protected clusters (MMPCs) interact with DNA by complementary electrostatic binding, serving as efficient DNA delivery systems. The stability of gold nanoparticle‐bound DNA toward biological, physical, and chemical agents is investigated. The MMPC‐bound DNA is efficiently protected from DNAse I digestion and experiences nicking/cleavage‐induced morphology changes with higher concentrations of DNAse I. Significant protection of MMPC‐bound DNA was also observed in a physical sonication assay. However, the MMPC‐bound DNA was found to show enhanced cleavage upon exposure to chemically induced radicals. The latter may indicate that bound DNA is bent and wrapped on the surface of the cationic MMPC.
A Chemogenomic Approach to Discovering Target‐Selective Drugs
Authors: Janzen William P. , Hodge C. Nicholas
Published: December 2005

An approach is described for identifying scaffolds with predefined selectivity profiles directly from a high‐quality high‐throughput screening data set, and monitoring that selectivity profile throughout the drug discovery process. This approach results in reduced drug development timelines from ‘hit’ to ‘lead’ stage, and should reduce liabilities for a molecule advancing through the development process.
Mobility of Overconstrained Parallel Mechanisms
Authors: Dai Jian S. , Huang Zhen , Lipkin Harvey
Published: December 2005

The Kutzbach–Grübler mobility criterion calculates the degrees of freedom of a general mechanism. However, the criterion can break down for mechanisms with special geometries, and in particular, the class of so-called overconstrained parallel mechanisms. The problem is that the criterion treats all constraints as active, even redundant constraints, which do not affect the mechanism degrees of freedom. In this paper we reveal a number of screw systems of a parallel mechanism, explore their inter-relationship and develop an original theoretical framework to relate these screw systems to motion and constraints of a parallel mechanism to identify the platform constraints, mechanism constraints and redundant constraints. The screw system characteristics and relationships are investigated for physical properties and a new approach to mobility analysis is proposed based on decompositions of motion and constraint screw systems. New versions of the mobility criterion are thus presented to eliminate the redundant constraints and accurately predict the platform degrees of freedom. Several examples of overconstrained mechanisms from the literature illustrate the results.
Three-Dimensional Assembly Synthesis for Robust Dimensional Integrity Based on Screw Theory
Authors: Lee Byungwoo , Saitou Kazuhiro
Published: December 2005

This paper presents a three-dimensional (3D) extension of our previous work on the synthesis of assemblies whose dimensional integrity is insensitive to the dimensional variations of individual parts. Assuming that assemblies can be built in the reverse sequence of decomposition, the method recursively decomposes a given product geometry into two subassemblies until parts become manufacturable. At each recursion, joints are assigned to the interfaces between two subassemblies to ensure the two criteria for robust dimensional integrity, in-process dimensional adjustability, and proper part constraints. Screw theory is utilized as a unified 3D representation of the two criteria. A case study on an automotive space frame is presented to demonstrate the method.
Decomposition-Based Assembly Synthesis of Space Frame Structures Using Joint Library
Authors: Lyu Naesung , Saitou Kazuhiro
Published: December 2005

This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering structural characteristics, manufacturability, and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined structural frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined frames, associated with their structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multiobjective genetic algorithm using a direct crossover. A case study on an aluminum space frame of a midsize passenger vehicle is discussed.
Analytic Form Solution of the Direct Position Analysis of a Wide Family of Three-Legged Parallel Manipulators
Authors: Di Gregorio Raffaele
Published: December 2005

A wide family of parallel manipulators (PMs) is the one that groups all PMs with three legs where the legs become kinematic chains constituted of a passive spherical pair (S) in series with either a passive prismatic pair (P) or a passive revolute pair (R) when the actuators are locked. The topologies of the structures generated by these manipulators, when the actuators are locked, are ten. Two out of these topologies are the SR-2PS topology (one SR leg and two PS legs) and the SP-2RS topology (one SP leg and two RS legs). This paper presents two algorithms. The first one determines all the assembly modes of the SR-2PS structures. The second one determines all the assembly modes of the SP-2RS structures. The presented algorithms can be applied without changes to solve, in analytical form, the direct position analysis (DPA) of all the parallel manipulators that generate a SR-2PS structure or a SP-2RS structure when the actuators are locked. In particular, the closure equations of two generic structures, one of type SR-2PS and the other of type SP-2RS, are written. The eliminants of the two systems of equations are determined and the solution procedures are presented. Finally, the proposed procedures are applied to real cases. This work demonstrates that (i) the DPA solutions of any PM that becomes a SR-2PS structure are at most eight, and (ii) the DPA solutions of any PM that becomes a SP-2RS structure are at most sixteen.
Use of the FFT to Determine the Subsurface Stresses Locally in Multilayered Elastic Solids Caused by a TEHL Loading
Authors: Riche I. , Villechaise B.
Published: December 2005

This paper presents a numerical two-dimensional model to study a rough thermal elastohydrodyanmic lubrication sliding contact locally and to calculate the stresses in multilayered solids. The model deterministically calculates the pressure and the surface temperature in solving simultaneously the equations that govern the lubrication and the thermoelasticity problem, respectively. The Reynolds equation and a parabolic profile for the temperature makes it possible to treat the lubrication part of the problem. The heat equation and the thermoelasticity equations in the solids are treated using a method based on the integral Fourier transform and solved with a fast Fourier transform algorithm.
Position Analysis of the RRP-3(SS) Multi-Loop Spatial Structure
Authors: Innocenti Carlo , Wenger Philippe
Published: December 2005

The paper presents the position analysis of a spatial structure composed of two platforms mutually connected by one RRP and three SS serial kinematic chains, where R, P, and S stand for revolute, prismatic, and spherical kinematic pair, respectively. A set of three compatibility equations is laid down that, following algebraic elimination, results in a 28th-order univariate algebraic equation, which in turn provides the addressed problem with 28 solutions in the complex domain. Among the applications of the results presented in this paper is the solution to the forward kinematics of the Tricept, a well-known in-parallel-actuated spatial manipulator. Numerical examples show adoption of the proposed method in dealing with two case studies.
Tribological Studies on Oscillating Bronze Bearings Lubricated With Environmentally Adapted Lubricants (EALs)
Authors: Ukonsaari Jan , Kassfeldt Elisabet
Published: December 2005

Different compositions of bronze materials are used for sliding bearings in various applications including those involving oscillatory motion and moderate temperatures. The compatibility of new environmentally adapted synthetic esters with different contacting surface materials helps ensure good tribological performance. The present work deals with tribological studies on oscillatory journal bearings manufactured using three different compositions of bronze materials lubricated with EALs under boundary lubricated conditions. Under certain operating conditions, alloying constituents from the bronze-bearing material dissolute into the synthetic ester lubricant, thereby leading to the formation of a copper enriched bearing surface layer. Tin-bronze with synthetic ester lubricant showed more stable friction values and roughly ten times better wear results than harder aluminium- and manganese-bronze as well as outperforming the mineral oil under the same conditions.
Effect of Intermolecular Forces on the Static and Dynamic Performance of Air Bearing Sliders: Part I—Effect of Initial Excitations and Slider Form Factor on the Stability
Authors: Gupta Vineet , Bogy David B.
Published: December 2005

The mechanical spacing between the slider and the disk has to be reduced to less than 5 nm in order to achieve an areal density of 1Tbit∕in2. Certain physical phenomena, such as those that can be caused by intermolecular and surface forces, which do not have a significant effect at higher flying heights, become more important at such low head-media separations. These forces are attractive for head-media separation as low as 0.5 nm, which causes a reduction in the mechanical spacing as compared to what would be the case without them. Single degree of freedom models have been used in the past to model these forces, and these models have predicted unstable flying in the sub-5-nm flying height range. Changes in the pitch and the roll angles were not accounted for in such models. A 3-DOF air bearing dynamic simulator model is used in this study to investigate the effect of the intermolecular forces on the static and dynamic performance of the air bearing sliders. It is seen that the intermolecular forces increase the level of flying height modulations at low flying heights, which in turn results in dynamic instability of the system similar to what has also been observed in experiments. The effect of initial vertical, pitch, and roll excitations on the static and dynamic flying characteristics of the slider in the presence of the intermolecular forces has also been investigated. A stiffness matrix is defined to characterize the stability in the vertical, pitch, and roll directions. The fly height diagrams are used to examine the multiple equilibriums that exist for low flying heights. Finally, a study was carried out to compare the performance of pico and femto designs based on the hysteresis observed during the touchdown-takeoff simulations.
A Non-Phenomenological Account of Friction/Vibration Interaction in Rotary Systems
Authors: Farhang Kambiz , Lim Aik-Liang
Published: December 2005

Using a nonlinear model of a two disk brake system, coupled equations of motion are found for their frictional interaction. The mathematical formulation relates the tribological events at micron scale and the macroscopic scale vibration response of a two-disk brake system. This is accomplished by a viscoelastic account of interaction at the micron scale, its statistical quantification through the approximate analytical representation of the statistical expectation of contact force and the introduction of the contact force into the macroscale dynamics of the two-disk system. Steady-state analysis of the system establishes the relation between friction torque and speed and supports observed behavior of many mechanical systems with friction. It is shown that, as a result of coupling of the macrosystem’s dynamics and contact, there are combinations of parameters at the micro- and macroscale that yield negative slope in friction torque/sliding speed relation, a well known source of dynamic instability. This results in an effective negative damping that tends to decrease with decrease in the normal load and/or increase in structural damping of the system.
Transient and Steady State Vibration Analysis of a Wavy Thrust Bearing
Authors: Zhao H. , Choy F. K. , Braun M. J.
Published: December 2005

This paper describes a numerical procedure for analyzing the dynamics of transient and steady state vibrations in a wavy thrust bearing. The major effects of the wavy geometry and the operating parameters on the dynamic characteristics of the bearing had been discussed in a previous paper; the present paper thus concentrates on examining the relationships between the development of the transient and steady state vibrations when operating conditions are parametrically varied. Special attention is given to the development of steady state vibrations from initial transients with comparisons and consequences to the overall system stability. Numerical based vibration signature analysis procedures are then used to identify and quantify the transient vibrations. The conclusions provide general indicators for designing wavy thrust bearings that are less susceptible to transients induced by external perturbations.
Unsteady Aerodynamics and Interactions Between a High-Pressure Turbine Vane and Rotor
Authors: Urbassik Ryan M. , Wolff J. Mitch , Polanka Marc D.
Published: December 2005

A set of experimental data is presented investigating the unsteady aerodynamics associated with a high pressure turbine vane (HPV) and rotor blade (HPB). The data was acquired at the Turbine Research Facility (TRF) of the Air Force Research Laboratory. The TRF is a transient, blowdown facility generating several seconds of experimental data on full scale engine hardware at scaled turbine operating conditions simulating an actual engine environment. The pressure ratio and freestream Reynolds number were varied for this investigation. Surface unsteady pressure measurements on the HPV, total pressure traverse measurements downstream of the vane, and surface unsteady pressure measurements for the rotor blade were obtained. The unsteady content of the HPV surface was generated by the rotor potential field. The first harmonic decayed more rapidly than the second harmonic with a movement upstream causing the second harmonic to be most influential at the vane throat. The blade unsteadiness appears to be caused by a combination of shock, potential field, and vane wake interactions between the vane and rotor blade. The revolution averaged data resulted in higher unsteadiness than a passing ensemble average for both vane and rotor indicating a need to understand each passage for high cycle fatigue (HCF) effects.
Predicting Blade Stress Levels Directly From Reduced-Order Vibration Models of Mistuned Bladed Disks
Authors: Lim Sang-Ho , Pierre Christophe , Castanier Matthew P.
Published: December 2005

The forced vibration response of bladed disks can increase dramatically due to blade mistuning, which can cause major durability and reliability problems in turbine engines. To predict the mistuned forced response efficiently, several reduced-order modeling techniques have been developed. However, for mistuned bladed disks, increases in blade amplitude levels do not always correlate well with increases in blade stress levels. The stress levels may be computed by postprocessing the reduced-order model results with finite element analysis, but this is cumbersome and expensive. In this work, three indicators that can be calculated directly from reduced-order models are proposed as a way to estimate blade stress levels in a straightforward, systematic, and inexpensive manner. It is shown that these indicators can be used to predict stress values with good accuracy relative to finite element results, even for a case in which the displacement and stress levels show different frequency response trends.
The Effect of Inlet Guide Vanes Wake Impingement on the Flow Structure and Turbulence Around a Rotor Blade
Authors: Soranna Francesco , Chow Yi-Chih , Uzol Oguz , Katz Joseph
Published: December 2005

The flow structure and turbulence around the leading and trailing edges of a rotor blade operating downstream of a row of inlet guide vanes (IGV) are investigated experimentally. Particle image velocimetry (PIV) measurements are performed in a refractive index matched facility that provides unobstructed view of the entire flow field. Data obtained at several rotor blade phases focus on modification to the flow structure and turbulence in the IGV wake as it propagates along the blade. The phase-averaged velocity distributions demonstrate that wake impingement significantly modifies the wall-parallel velocity component and its gradients along the blade. Due to spatially non-uniform velocity distribution, especially on the suction side, the wake deforms while propagating along the blade, expanding near the leading edge and shrinking near the trailing edge. While being exposed to the nonuniform strain field within the rotor passage, the turbulence within the IGV wake becomes spatially nonuniform and highly anisotropic. Several mechanisms, which are consistent with rapid distortion theory (RDT) and distribution of turbulence production rate, contribute to the observed trends. For example, streamwise (in rotor frame reference) diffusion in the aft part of the rotor passage enhances the streamwise fluctuations. Compression also enhances the turbulence production very near the leading edge. However, along the suction side, rapid changes to the direction of compression and extension cause negative production. The so-called wall blockage effect reduces the wall-normal component.
Local Heat/Mass Transfer Characteristics on a Rotating Blade With Flat Tip in Low-Speed Annular Cascade—Part I: Near-Tip Surface
Authors: Rhee Dong-Ho , Cho Hyung Hee
Published: December 2005

The present study focuses on local heat/mass transfer characteristics on the near-tip region of a rotating blade. To investigate the local heat/mass transfer on the near-tip surface of the rotating turbine blade, detailed measurements of time-averaged mass transfer coefficients on the blade surfaces were conducted using a naphthalene sublimation technique. A low speed wind tunnel with a single stage annular turbine cascade was used. The turbine stage is composed of sixteen guide plates and blades with spacing of 34 mm, and the chord length of the blade is 150 mm. The mean tip clearance is about 2.5% of the blade chord. The tested Reynolds number based on inlet flow velocity and blade chord is 1.5×105 and the rotational speed of blade is 255.8 rpm for the design condition. The result at the design condition was compared with the results for the stationary blade to clarify the rotational effect, and the effects of incoming flow incidence angle were examined for incidence angles ranging from −15 to +7deg. The off-design test condition is obtained by changing the rotational speed maintaining a fixed incoming flow velocity. Complex heat transfer characteristics are observed on the blade surface due to the complicated flow patterns, such as flow acceleration, laminarization, transition, separation bubble and tip leakage flow. The blade rotation causes an increase of the incoming flow turbulence intensity and a reduction of the tip gap flow. At off-design conditions, the heat transfer on the turbine rotor changes significantly due to the flow acceleration/deceleration and the incoming flow angle variation.
Local Heat/Mass Transfer Characteristics on a Rotating Blade With Flat Tip in a Low-Speed Annular Cascade—Part II: Tip and Shroud
Authors: Rhee Dong-Ho , Cho Hyung Hee
Published: December 2005

The local heat/mass transfer characteristics on the tip and shroud were investigated using a low speed rotating turbine annular cascade. Time-averaged mass transfer coefficients on the tip and shroud were measured using a naphthalene sublimation technique. A low speed wind tunnel with a single stage turbine annular cascade was used. The turbine stage is composed of sixteen guide plates and blades. The chord length of blade is 150 mm and the mean tip clearance is about 2.5% of the blade chord. The tested Reynolds number based on inlet flow velocity and blade chord is 1.5×105 and the rotational speed of the blade is 255.8 rpm at design condition. The results were compared with the results for a stationary blade and the effects of incidence angle of incoming flow were examined for incidence angles ranging from −15 to +7deg. The off-design test conditions are obtained by changing the rotational speed with a fixed incoming flow velocity. Flow reattachment on the tip near the pressure side edge dominates the heat transfer on the tip surface. Consequently, the heat/mass transfer coefficients on the blade tip are about 1.7 times as high as those on the blade surface and the shroud. However, the heat transfer on the tip is about 10% lower than that for the stationary case due to reduced leakage flow with the relative motion. The peak regions due to the flow reattachment are reduced and shifted toward the trailing edge and additional peaks are formed near the leading edge region with decreasing incidence angles. But, quite uniform and high values are observed on the tip with positive incidence angles. The time-averaged heat/mass transfer on the shroud surface has a level similar to that of the stationary cases.
Modeling of Film Cooling—Part I: Experimental Study of Flow Structure
Authors: Bernsdorf Stefan , Rose Martin G. , Abhari Reza S.
Published: December 2005

This paper, which is Part I of a two part paper, reports on experimental data taken in a steady flow, flat plate wind tunnel at ETH Zürich, while Part II utilizes this data for calibration and validation purpose of a film cooling model embedded in a 3D CFD code. The facility simulates the film cooling row flow field on the pressure side of a turbine blade. Engine representative nondimensionals are achieved, providing a faithful model at larger scale. Heating the freestream air and strongly cooling the coolant gives the required density ratio between coolant and freestream. The three dimensional velocities are recorded using nonintrusive PIV; seeding is provided for both air streams. Two different cylindrical hole geometries are studied, with different angles. Blowing ratio is varied over a range to simulate pressure side film cooling. The three dimensional flow structures are revealed.
Averaging Nonuniform Flow for a Purpose
Authors: Cumpsty N. A. , Horlock J. H.
Published: December 2005

Averaging nonuniform flow is important for the analysis of measurements in turbomachinery and gas turbines; more recently an important need for averaging arises with results of computational fluid dynamics (CFD). In this paper we show that there is a method for averaging which is “correct,” in the sense of preserving the essential features of the nonuniform flow, but that the type of averaging which is appropriate depends on the application considered. The crucial feature is the decision to retain or conserve those quantities which are most important in the case considered. Examples are given to demonstrate the appropriate methods to average nonuniform flows in the accounting for turbomachinery blade row performance, production of thrust in a nozzle, and mass flow capacity in a choked turbine. It is also shown that the numerical differences for different types of averaging are, in many cases, remarkably small.
Long-to-Short Length-Scale Transition: A Stall Inception Phenomenon in an Axial Compressor With Inlet Distortion
Authors: Lin Feng , Li Meilin , Chen Jingyi
Published: December 2005

A theoretical and experimental study of stall inception processes in a three-stage low-speed axial flow compressor with inlet distortion is presented in this paper. Since inlet distortion provides asymmetric flows imposing onto the compressor, the main goal of this research is to unveil the mechanism of how such flows initiate long and/or short length-scale disturbances and how the compression system reacts to those disturbances. It is found that the initial disturbances are always triggered by the distorted flows, yet the growth of such disturbances depends on system dynamics. While in many cases the stall precursors were the short length-scale spikes, there were some cases where the compressor instability was triggered after the disturbances going through a long-to-short length-scale transition. A Moore-Greitzer-based (system scale) model was proposed to qualitatively explain this phenomenon. It was found that, when the compressor operated in a region where the nonlinearity of the characteristics dominated, long length-scale disturbances induced by the inlet distortion would evolve into short length-scale disturbances before they disappeared or triggered stall. However, the model was not able to predict the fact that many disturbances that were triggered by the distorted sector(s) were completely damped out in the undistorted sector(s). It is thus suggested that in future research of compressor instability, one should consider the flows in blade passage scale, the dynamics in system scale, and their interaction simultaneously.
A Unified Correlation for Slip Factor in Centrifugal Impellers
Authors: von Backström Theodor W.
Published: December 2005

A method that unifies the trusted centrifugal impeller slip factor prediction methods of Busemann, Stodola, Stanitz, Wiesner, Eck, and Csanady in one equation is presented. The simple analytical method derives the slip velocity in terms of a single relative eddy (SRE) centered on the rotor axis instead of the usual multiple (one per blade passage) eddies. It proposes blade solidity (blade length divided by spacing at rotor exit) as the prime variable determining slip. Comparisons with the analytical solution of Busemann and with tried and trusted methods and measured data show that the SRE method is a feasible replacement for the well-known Wiesner prediction method: it is not a mere curve fit, but is based on a fluid dynamic model; it is inherently sensitive to impeller inner-to-outer radius ratio and does not need a separate calculation to find a critical radius ratio; and it contains a constant, F0, that may be adjusted for specifically constructed families of impellers to improve the accuracy of the prediction. Since many of the other factors that contribute to slip are also dependent on solidity, it is recommended that radial turbomachinery investigators and designers investigate the use of solidity to correlate slip factor.
Heat Transfer on Internal Surfaces of a Duct Subjected to Impingement of a Jet Array with Varying Jet Hole-Size and Spacing
Authors: Uysal U. , Li P.-W. , Chyu M. K. , Cunha F. J.
Published: December 2005

One significant issue concerning the impingement heat transfer with a jet array is related to the so-called “crossflow,” where a local jet performance is influenced by the convection of the confluence from the impingement of the jet∕jets placed upstream. As a result, the heat transfer coefficient may vary along the streamwise direction and creates more or less nonuniform cooling over the component, which is undesirable from both the performance and durability standpoints. Described in this paper is an experimental investigation of the heat transfer coefficient on surfaces impinged by an array of six inline circular jets with their diameters increased monotically along the streamwise direction. The local heat transfer distributions on both the target surface and jet-issuing plate are measured using a transient liquid crystal technique. By varying the jet hole-size in a systematic manner, the actual distribution of jet flow rate and momentum within a jet array may be optimally metered and controlled against crossflow. The effects on the heat transfer coefficient distribution due to variations of jet-to-target distance and interjet spacing are investigated. The varying-diameter results are compared with those from a corresponding array of uniform jet diameter.
Combined Three-Dimensional Fluid Dynamics and Mechanical Modeling of Brush Seals
Authors: Lelli Diego , Chew John W. , Cooper Paul
Published: December 2005

Development and application of a combined 3D computational fluid dynamics (CFD) and 3D bristle bending model for brush seals is described. The CFD model is created using commercial CFD mesh generation and solver software. A small gap is assumed between all bristles in the CFD model so as to avoid meshing problems at contact points and allow for imperfections in bristle geometry. The mechanical model is based on linear beam bending theory and allows large numbers of bristles to be modelled with arbitrary bristle-to-bristle contact and imported from the CFD solution. Deformed geometries may be exported directly to the mesh generation software, allowing iterative solution of the coupled aerodynamic/mechanical problem.
Teeth-Number Synthesis of a Multispeed Planetary Transmission Using an Estimation of Distribution Algorithm
Authors: Simionescu P. A. , Beale D. , Dozier G. V.
Published: December 2005

The gear-teeth number synthesis of an automatic planetary transmission used in automobiles is formulated as a constrained optimization problem that is solved with the aid of an Estimation of Distribution Algorithm. The design parameters are the teeth number of each gear, the number of multiple planets and gear module, while the objective function is defined as the departure between the imposed and the actual transmission ratios, constrained by teeth-undercut avoidance, limiting the maximum overall diameter of the transmission and ensuring proper spacing of multiple planets. For the actual case of a 3+1 speed Ravigneaux planetary transmission, the design space of the problem is explored using a newly introduced hyperfunction visualization technique, and the effect of various constraints highlighted. Global optimum results are also presented.
Stiffness of Cable-based Parallel Manipulators With Application to Stability Analysis
Authors: Behzadipour Saeed , Khajepour Amir
Published: December 2005

The stiffness of cable-based robots is studied in this paper. Since antagonistic forces are essential for the operation of cable-based manipulators, their effects on the stiffness should be considered in the design, control, and trajectory planning of these manipulators. This paper studies this issue and derives the conditions under which a cable-based manipulator may become unstable because of the antagonistic forces. For this purpose, a new approach is introduced to calculate the total stiffness matrix. This approach shows that, for a cable-based manipulator with all cables in tension, the root of instability is a rotational stiffness caused by the internal cable forces. A set of sufficient conditions are derived to ensure the manipulator is stabilizable meaning that it never becomes unstable upon increasing the antagonistic forces. Stabilizability of a planar cable-based manipulator is studied as an example to illustrate this approach.
Performance Modeling and Optimization of a Novel Multi-mode Hybrid Powertrain
Authors: Zhang Y. , Lin H. , Zhang B. , Mi C.
Published: December 2005

This paper presents a systematic model for the operation simulation and optimization of a novel multi-mode hybrid powertrain. The hybrid configuration proposed in the paper features a planetary gear train for an electric CVT mode in addition to lay-shaft gears for multiple speed ratios and realizes six operation modes in a simple structure. Detailed component level models were established for the multi-mode hybrid transmission and integrated to the overall vehicle model according to the system configuration using the Simulink/Advisor platform. The vehicle control strategy was then established with the objective to optimize the overall vehicle operation and each hybrid operation mode in terms of fuel economy and emission levels. The performance of the proposed hybrid vehicle system was studied using the developed model under various operation conditions and benchmarked with a current market model with leading performance parameters. The proposed hybrid configuration shows substantial improvements over the benchmark and is validated as a viable hybrid design based on the model simulation.
Spatial Kinematic Analysis of Threaded Fastener Assembly
Authors: Wiedmann Stephen , Sturges Bob
Published: December 2005

Compliant mechanisms for rigid part mating exist for prismatic geometries. A few instances are known of mechanisms to assemble screw threads. A comprehensive solution to this essentially geometric problem comprises at least three parts: parametric equations for nut and bolt contact in the critical starting phase of assembly, the possible space of motions between these parts during this phase, and the design space of compliant devices which accomplish the desired motions in the presence of friction and positional uncertainty. This work concentrates on the second part in which the threaded pair is modeled numerically, and contact tests are automated through software. Tessellated solid models were used during three-dimensional collision analysis to enumerate the approximate location of the initial contact point. The advent of a second contact point presented a more constrained contact state. Thus, the bolt is rotated about a vector defined by the initial two contact points until a third contact location was found. By analyzing the depth of intersection of the bolt into the nut as well as the vertical movement of the origin of the bolt reference frame, we determined that there are three types of contacts states present: unstable two-point, quasi-stable two-point, stable three point. The space of possible motions is bounded by these end conditions which will differ in detail depending upon the starting orientations. We investigated all potential orientations which obtain from a discretization of the roll, pitch, and yaw uncertainties, each of which has its own set of contact points. From this exhaustive examination, a full contact state history was determined, which lays the foundation for the design space of either compliant mechanisms or intelligent sensor-rich controls.
An Experimental Study of Static and Dynamic Characteristics of a 580mm(22.8in.) Diameter Direct Lubrication Tilting Pad Journal Bearing
Authors: Ikeda Kazunori , Hirano Toshio , Yamashita Tatsuo , Mikami Makoto , Sakakida Hitoshi
Published: December 2005

Direct lubrication tilting pad journal bearings (DLTPJ bearings) have rarely been applied to large-scale rotating machinery, such as turbines or generators, whose journal diameters are more than 500mm. In this paper, static and dynamic characteristics of a 580mm(22.8in.) diameter DLTPJ bearing were studied experimentally using a full-scale bearing test rig. In the static test, distribution of metal temperature, oil film pressure, and bearing loss were measured in changing oil flow rate, with mean bearing pressure ranging up to 2.9MPa. The maximum metal temperature of the DLTPJ bearing was compared to that of a conventional flood lubrication bearing, and it was confirmed that the direct lubrication could increase load capacity. In the dynamic test, spring and damping coefficients of oil film were obtained by exciting the bearing casing that was floated by air bellows. These data will be used for analysis and design of steam turbine rotors and their bearing systems. Also, vibration of pads was investigated because metal failure on upper pads due to vibration has been found in some actual machines. In order to generate oil film pressure on the surface of upper pads, a Rayleigh-step was machined there, and it was confirmed that vibration was reduced by the Rayleigh-step.
A New Model of Thermoelastohydrodynamic Lubrication in Dynamically Loaded Journal Bearings
Authors: Fatu Aurelian , Hajjam Mohamed , Bonneau Dominique
Published: December 2005

A comprehensive method of thermoelastohydrodynamic (TEHD) lubrication analysis for dynamically loaded journal bearings is presented. An algorithm for mass conserving cavitation is included, and the effect of viscosity variation with the temperature is taken into account. The Reynolds equation in the film is solved using the finite element (FE) discretization. Thermal distortions as well as the elastic deformation of the bearing surfaces are computed using the FE method. The temperature of the lubrication film is treated as a time-dependent three-dimensional variable with a parabolic variation with respect to the film thickness. In order to compute the temperature of the film and its surrounding solid surfaces, a new heat flux conservation algorithm is proposed. An important element in this analysis is the consideration of thermal boundary layers for solids. It is known that the thermal transients on the film-solid interfaces and the dynamic loading have the same period (one cycle). However, beyond the thermal boundary layers, the time scale for thermal transient in the journal and bushing are several orders of magnitude greater than those for the oil film. The Fourier series approximates the instantaneous temperature fields in the solid boundary layers. In this way, the mean heat flux that passes into the solid can be computed and a steady-state heat conduction equation can be used to obtain thermal fields inside the solids. Finally, solving the complex problem of big-end connecting-rod bearing TEHD lubrication proves the efficiency of the algorithm. Oil film temperatures are found to vary considerably over the time and space.
A Comparison of Flattening and Indentation Approaches for Contact Mechanics Modeling of Single Asperity Contacts
Authors: Jackson Robert L. , Kogut Lior
Published: December 2005

This study compares the flattening and indentation approaches for modeling single asperity contacts in order to reveal quantitatively their different behaviors in terms of the constitutive relationships for the contact parameters and deformation regimes. The comparison is performed with four empirical models recently developed for flattening and indentation based on the finite element method. In the elasto-plastic regime, the classic Hertz solution does not hold and, therefore, different mechanical behavior was obtained for flattening and indentation cases. Consequently, the contact condition and relative strength of mating surfaces should be considered when choosing between indentation or flattening models.
A Comparison of Contact Modeling Utilizing Statistical and Fractal Approaches
Authors: Kogut Lior , Jackson Robert L.
Published: December 2005

Statistical and fractal approaches for characterizing surface topography have been used widely in contact mechanics. In the present study, a comparison is conducted between contact mechanics results obtained with statistical and fractal approaches to characterize surface topography. Specifically, a three-dimensional fractal surface was generated and statistical surface parameters were extracted using different sampling resolutions. Contact mechanics simulations were performed using the simulated fractal surface and statistical surfaces represented by the extracted statistical surface parameters. Purely elastic contact (Hertz) is studied in order to eliminate any possible influence of the individual asperity mechanical response on the obtained results. Therefore, differences in the simulated contact area and load can be related solely to the different approach employed for surface characterization.
Uncertainty Analysis by Dimension Reduction Integration and Saddlepoint Approximations
Authors: Huang Beiqing , Du Xiaoping
Published: December 2005

Uncertainty analysis, which assesses the impact of the uncertainty of input variables on responses, is an indispensable component in engineering design under uncertainty, such as reliability-based design and robust design. However, uncertainty analysis is an unaffordable computational burden in many engineering problems. In this paper, an uncertainty analysis method is proposed with the purpose of accurately and efficiently estimating the cumulative distribution function (CDF), probability density function (PDF), and statistical moments of a response given the distributions of input variables. The bivariate dimension reduction method and numerical integration are used to calculate the moments of the response; then saddlepoint approximations are employed to estimate the CDF and PDF of the response. The proposed method requires neither the derivatives of the response nor the search of the most probable point, which is needed in the commonly used first and second order reliability methods (FORM and SORM) and the recently developed first order saddlepoint approximation. The efficiency and accuracy of the proposed method is illustrated with three example problems. With the same computational cost, this method is more accurate for reliability assessment and much more efficient for estimating the full range of the distribution of a response than FORM and SORM. This method provides results as accurate as Monte Carlo simulation, with significantly reduced computational effort.