bluuebunny/crossref_metadata_2025 huggingface dataset:
Iconicity in Language Processing and Acquisition: What Signed Languages Reveal
Authors: Thompson Robin L.
Published: September 2011

That linguistic form should be arbitrarily linked to meaning is generally taken as a fundamental feature of language. However, this paper explores the role of iconicity, or non‐arbitrary form‐meaning mappings for both language processing and language acquisition. Evidence from signed language research is presented showing that sign language users exploit iconicity in language processing. Further, iconicity may be at work in language acquisition serving to bridge the gap between conceptual representations and linguistic form. Signed languages are taken as a starting point since they tend to encode a higher degree of iconic form‐meaning mappings than is found for spoken languages, but the findings are more broadly applicable. Specifically, the emerging evidence argues against the dominant view that connections between linguistic form and meaning need be primarily arbitrary. Instead both arbitrariness and iconicity have a role to play in language.
Variation in Sign Languages: Recent Research on ASL and Beyond
Authors: Lucas Ceil , Bayley Robert
Published: September 2011

This article summarizes early approaches to sociolinguistic research and the factors that condition variation in sign languages. The article then examines the methodological issues that arise in the study of sign languages before discussing recent research on variation in several different sign languages and dialects including Black ASL, Australian Sign Language, New Zealand Sign Language, and Italian Sign Language. This research shows that sign languages, like spoken languages, are subject to a wide range of internal and external constraints, some of which are particular to sign languages. We conclude with suggestions for future research.
Use of Murine Bioassay to Resolve Ovine Transmissible Spongiform Encephalopathy Cases Showing a Bovine Spongiform Encephalopathy Molecular Profile
Authors: Beck Katy E. , Sallis Rosemary E. , Lockey Richard , Vickery Christopher M. , Béringue Vincent , Laude Hubert , Holder Thomas M. , Thorne Leigh , Terry Linda A. , Tout Anna C. , Jayasena Dhanushka , Griffiths Peter C. , Cawthraw Saira , Ellis Richard , Balkema‐Buschmann Anne , Groschup Martin H. , Simmons Marion M. , Spiropoulos John
Published: September 2011

Two cases of unusual transmissible spongiform encephalopathy (TSE) were diagnosed on the same farm in ARQ/ARQ PrP sheep showing attributes of both bovine spongiform encephalopathy (BSE) and scrapie. These cases, UK‐1 and UK‐2, were investigated further by transmissions to wild‐type and ovine transgenic mice. Lesion profiles (LP) on primary isolation and subpassage, incubation period (IP) of disease, PrPSc immunohistochemical (IHC) deposition pattern and Western blot profiles were used to characterize the prions causing disease in these sheep. Results showed that both cases were compatible with scrapie. The presence of BSE was contraindicated by the following: LP on primary isolation in RIII and/or MR (modified RIII) mice; IP and LP after serial passage in wild‐type mice; PrPSc deposition pattern in wild‐type mice; and IP and Western blot data in transgenic mice. Furthermore, immunohistochemistry (IHC) revealed that each case generated two distinct PrPSc deposition patterns in both wild‐type and transgenic mice, suggesting that two scrapie strains coexisted in the ovine hosts. Critically, these data confirmed the original differential IHC categorization that these UK‐1 and UK‐2 cases were not compatible with BSE.
NEPHROTIC AND ANTI‐PHOSPHOLIPID SYNDROMES: MULTISYSTEM CONDITIONS ASSOCIATED WITH ACUTE MYOCARDIAL INFARCTION IN YOUNG PATIENTS
Authors: Javaid Muhammad M. , Grigoriou Antigoni , Katsianos Dimitrios , Kon Sui Phin
Published: September 2011

Acute myocardial infarction is relatively uncommon in patients under the age of 40 years. Unlike the older patients where rupture of coronary artery atherosclerotic plaque is the main underlying pathology, the pathogenesis in younger patients can be varied and may require different diagnostic and therapeutic approaches. Hypercoagulable state associated with nephrotic syndrome and antiphospholipid syndrome can lead to the development of occlusive coronary artery thrombus in absence of atherosclerotic coronary artery disease. Acute myocardial infarction in such a setting can sometimes be the first manifestation of an underlying disease. We describe a case of myocardial infarction in a young man with both nephrotic and antiphospho‐lipid syndromes and present a brief literature review.
Interleukin‐6 upregulates expression of ADAMTS‐4 in fibroblast‐like synoviocytes from patients with rheumatoid arthritis
Authors: MIMATA Yoshikuni , KAMATAKI Akihisa , OIKAWA Shinya , MURAKAMI Kenya , UZUKI Miwa , SHIMAMURA Tadashi , SAWAI Takashi
Published: September 2011

Aim:  A disintegrin‐like and metalloproteinase with thrombospondin type 1 motif (ADAMTS)‐4 and ADAMTS‐5 play crucial roles in the cleavage of aggrecan. Several recent studies have demonstrated the effect of cytokines such as interleukin (IL)‐1β, tumor necrosis factor‐α and transforming growth factor‐β on the expression of ADAMTS‐4 and ADAMTS‐5 in fibroblast‐like synoviocytes (FLS). However, the effect of IL‐6 remains unclear. The aim of this study is to investigate the expression of ADAMTS‐4 and ADAMTS‐5 in FLS of rheumatoid arthritis (RA) patients after IL‐6 stimulation.

Method:  Immunohistochemical staining was performed to examine the expression and localization of ADAMTS‐4 and ADAMTS‐5 in RA synovium. FLS isolated from RA patients were stimulated by IL‐6 and soluble IL‐6 receptor (sIL‐6R) in the presence or absence of anti‐IL‐6R antibody, and the expression levels of ADAMTS‐4 and ADAMTS‐5 messenger RNA (mRNA) were assessed using real‐time polymerase chain reaction. Furthermore, the IL‐6 signaling pathway for regulation of ADAMTS‐4 and ADAMTS‐5 was also examined.

Results:  Staining for ADAMTS‐4 and ADAMTS‐5 was mainly observed in the sublining layer of synovial membrane and pannus. The expression of ADAMTS‐4 mRNA was increased by IL‐6/sIL‐6R, whereas that of ADAMTS‐5 was decreased. Anti‐IL‐6R antibody suppressed the effect of IL‐6/sIL‐6R. Mitogen‐activated protein kinase (MAPK)/extracellular signal‐related kinase (ERK) kinase (MEK)1/2 inhibitor U0126 inhibited the effect of IL‐6/sIL‐6R on ADAMTS‐4 mRNA expression in FLS. Signal transducer and activator of transcription 3 (STAT3) inhibitor parthenolide inhibited the effect of IL‐6/sIL‐6R on ADAMTS‐4, and downregulated ADAMTS‐5 expression.

Conclusion:  These results suggest IL‐6 may participate in cartilage destruction in RA as an inducer of ADAMTS‐4 expression from FLS.
Hungry like the wolf: A word‐pattern analysis of the language of psychopaths
Authors: Hancock Jeffrey T. , Woodworth Michael T. , Porter Stephen
Published: September 2011

Purpose.  This study used statistical text analysis to examine the features of crime narratives provided by psychopathic homicide offenders. Psychopathic speech was predicted to reflect an instrumental/predatory world view, unique socioemotional needs, and a poverty of affect.

Methods.  Two text analysis tools were used to examine the crime narratives of 14 psychopathic and 38 non‐psychopathic homicide offenders. Psychopathy was determined using the Psychopathy Checklist‐Revised (PCL‐R). The Wmatrix linguistic analysis tool (Rayson, 2008) was used to examine parts of speech and semantic content while the Dictionary of Affect and Language (DAL) tool (Whissell & Dewson, 1986) was used to examine the emotional characteristics of the narratives.

Results.  Psychopaths (relative to their counterparts) included more rational cause‐and‐effect descriptors (e.g., ‘because’, ‘since’), focused on material needs (food, drink, money), and contained fewer references to social needs (family, religion/spirituality). Psychopaths’ speech contained a higher frequency of disfluencies (‘uh’, ‘um’) indicating that describing such a powerful, ‘emotional’ event to another person was relatively difficult for them. Finally, psychopaths used more past tense and less present tense verbs in their narrative, indicating a greater psychological detachment from the incident, and their language was less emotionally intense and pleasant.

Conclusions. These language differences, presumably beyond conscious control, support the notion that psychopaths operate on a primitive but rational level.
The Flow Between Two Parallel Circular Disks, One of Which is Subject to a Normal Sinusoidal Oscillation
Authors: Terrill R. M.
Published: September 2011

Two parallel circular disks are separated by a viscous fluid; one of the disks oscillates sinusoidally in a direction normal to its plane and the other is at rest. A solution to this problem is presented and compared with previous approximate solutions and experimental results. It is suggested that further experimental results are required.
Experiment and Analysis of a Flat Disk Squeeze-Film Bearing Including Effects of Supported Mass Motion
Authors: Beck J. V. , Holliday W. G. , Strodtman C. L.
Published: September 2011

An experiment is described in which the motion of the supported mass was the main contributor to the generation of the squeeze film. An analysis was performed and a computer program written to predict the motion of the supported mass. Good agreement is shown between the analysis and the computer program and the experiment, except that two of the observed operation points cannot be verified.
Some Characteristics of a Full Journal Bearing Lubricated With Electroconducting Gases
Authors: Korovchinski M. V.
Published: September 2011

The behavior of an infinitely long journal bearing using an ionized gas lubricant in which a magnetic field is applied axially and an electric field is applied transversely to the fluid film is investigated theoretically. It is found that in the absence of an applied electric field the behavior of the bearing with the ionized gas is not much different from that of a bearing using a neutral gas even at large Hartmann numbers. However, by application of the crossed magnetic and electric fields the pressure distribution in the lubricating film can be altered significantly. Various curves showing the effect of the Hartmann, Hughes, and Harrison numbers on the pressure distribution, film load-carrying capacity, and the locus of the journal center in the bearing are presented and discussed.
An Approximate Theoretical Analysis of the Static and Dynamic Characteristics of the Herringbone Grooved, Gas Lubricated Journal Bearing, and Comparison With Experiment
Authors: Foster D. J. , Carow D. , Benson D.
Published: September 2011

An approximate solution for the pressure distribution around a finite length, herringbone grooved journal bearing is derived in analytical form. Some results for the bearing stiffness and attitude angle are presented and compared with experimental results and other theories. The effect of changing the number of grooves is investigated. The validity of the approximate method used is checked by applying it to a simple step slider bearing for which exact solutions are available. The theoretical development is extended to cover the dynamic loading case. Theoretical solutions for the amplitudes of vibration for different frequencies are compared with experimental results.
Mean Free Path Effect in Spiral-Grooved Thrust Bearings
Authors: Hsing F. C. , Malanoski S. B.
Published: September 2011

The objective of this paper is to study the effect of molecular mean free path on the steady-state performance characteristics of a spiral-grooved thrust bearing operating in extremely thin film and/or low ambient pressure environments. Numerical results for the most popular three versions of the spiral-grooved designs are presented. These results reveal that the effect of slip boundary conditions could contribute substantial reduction, in performance. Helium is the worst gas lubricant in this sense because of its high Knudsen number. The slip-flow corrected results check well with recently published experimental data [11].
Design of Pivoted-Pad Journal Bearings
Authors: Elwell R. C. , Findlay J. A.
Published: September 2011

Calculated load capacity and friction for complete pivoted-pad journal bearings are presented, for use in design computations. Dimensionless numerical results are given for the following variations in bearing geometry: 3 and 5 pads, L/D ratios of 1/2 to 1, pivot locations of 40, 50, and 60 percent, on pivot and between pivot loading, and ratios of “assembled” to “ground” clearance of 0.6, 0.8, and 1.0. The numerical results are an extension of the work of Castelli, et al., reference [1],1 and were generated in the same manner i.e., numerical solution of Reynolds’ equation by digital computer. Laminar, incompressible flow, and subambient pressures in diverging portions of the films were assumed. Illustrative numerical examples are included and significant conclusions with respect to major variables (L/D ratio, number of pads, clearances, pivot location, load direction) are drawn from the range of data produced.
Lubrication Review: A Digest of the Literature for 1967
Authors: Rumbarger J. H. , Wu C. C. W. , Heller S. , Stevenson C. H. , Akin L. S. , Roberts W. L. , Barry H. F. , Myers H. , Olszewski W. F. , Schroeder R. J. , Schoeler E. , Liu J. Y.
Published: September 2011

The volume of lubrication literature continued to expand, reflecting the increased experimental and theoretical attention being focused upon this discipline. Special attention is devoted to seals and sealing systems, and the growing importance of this subject is recognized by the addition to the review of a new category for seal technology. Nine categories are summarized by authorities in each particular field.
A Study of Residual Stress Induced During Rolling
Authors: Zaretsky E. V. , Parker R. J. , Anderson W. J.
Published: September 2011

Subsurface residual stress measurements were made on SAE 52100 steel inner races from 207-size deep-groove ball bearings in which ΔH (ball hardness minus race hardness) ranged from −1.1 to 3.5 points Rockwell C. These bearings had been run at an inner-race speed of 2750 rpm and a radial load of 1320 lb producing maximum Hertz stresses of 352,000 and 336,000 psi at the inner and outer races, respectively. The residual stress measurements were made in a circumferential direction at various depths below the inner-race running track surface for a total of 19 of these bearings that had been run for nominally 200, 600 and 1600 hr. The measurements indicated that the maximum compressive residual stresses occur in approximately the same ΔH range for which the maximum fatigue lives were observed. Additionally, no relation between running time and residual stress could be determined from these measurements.
Melt Lubrication of an Annular-Thrust Surface
Authors: Allen C. W. , McKillop A. A.
Published: September 2011

Steady-state melt lubrication of two annular-thrust surfaces is investigated analytically and experimentally. Theoretical analysis shows that complete separation of the solid surfaces is possible and that the coefficients of friction are similar to those obtained in fluid film lubrication. Experimental tests, however, showed that complete separation does not occur and that the coefficients of friction were dependent on the rotational speed but four to six times the theoretical values. An interfacial model is proposed which is consistent with experimental results.
Magnetohydrodynamic Journal Bearing (Report 1)
Authors: Kamiyama S.
Published: September 2011

A theoretical analysis of an infinite full journal bearing is presented for the case of an electrically conducting fluid in the presence of a radial magnetic field. The analysis is based on general external loading conditions. The pressure distribution is obtained under the Reynolds’ boundary conditions in which the cavitation occurrence in the low-pressure region is taken into account. The characteristics of the magnetohydrodynamic journal bearing, namely, load-carrying capacity, altitude angle, and journal driving torque are determined. Furthermore the influence of the wall properties on the load capacity is clearly shown.
Evaluation of Wear Ring Seals for High-Speed, High-Pressure Turbopumps
Authors: Mallaire F. R. , Nelson L. H. , Buckmann P. S.
Published: September 2011

This paper describes a seal evaluation program for application as pump impeller wear rings for high-pressure, high-speed liquid rocket turbopumps. The principal design requirements were to control the leakage to values consistent with efficiency requirements and to eliminate potential explosions resulting from high velocity rubbing at the required clearances. Two approaches were taken: the first allowed rubbing of rotating labyrinth teeth on stationary, soft compatible inserts; the second utilized hydrostatic seals which maintained a fluid film between the stationary seal and the rotating wear ring.
Dynamically Loaded Journal Bearings: Maximum Film Pressure
Authors: Booker J. F.
Published: September 2011

Most analyses of dynamically loaded journal bearings produce only film-thickness information directly; this paper provides a conceptually simple means for calculation of film-pressure information subsequent to (or concurrent with) journal orbit calculations. Though the proposed methods for pressure determination complement previous “mobility” methods for orbit determination (since both involve an observation frame rotating with the load), they are in fact quite independent.
A Helium Face Seal Application In a Liquid Oxygen Pump
Authors: Cieslik Walter J.
Published: September 2011

The object of the work discussed in this paper was to develop a reliable helium gas shaft seal for use in an electric motor-driven, liquid oxygen pump on a space vehicle. The development effort covered tests on two basically different face seal designs, one with an attached carbon face and the other with a floating lap-fitted carbon face. Several bellows vibration damping devices and various seal material combinations were investigated.
Evaluation of Lubricants for High-Temperature Ball Bearing Applications
Authors: Parker R. J. , Bamberger E. N. , Zaretsky E. V.
Published: September 2011

Several lubricants that are considered candidates for ball bearing applications in the temperature range of 500 to 700 deg F were investigated in full-scale ball bearings and in a rolling-contact fatigue rig. Bearing endurance tests indicate that a synthetic paraffinic oil with an antiwear additive can perform beyond catalog rating at temperatures up to 600 deg F in a low oxygen environment. In a rolling-contact fatigue tester, this synthetic paraffinic oil exhibited at least twice the fatigue life at the 10 percent level of a fluorocarbon and a polyphenyl ether. Based on bearing race groove appearance, elasto-hydrodynamic lubrication was apparent at outer-race temperatures up to 700 deg F.
Semi-Implicit Numerical Methods for Treating the Time-Transient Gas-Lubrication Equation
Authors: Castelli V. , Stevenson C. H.
Published: September 2011

This paper presents a numerical method for treating the time-transient Reynolds’ equation which has the numerical stability properties of implicit schemes and the speed of execution of explicit methods. The advantages make this method quite suitable for both steady-state and transient calculations.
Load Support of the Squeeze-Film Journal Bearing of Finite Length
Authors: Beck J. V. , Strodtman C. L.
Published: September 2011

Despite intuition, the squeeze-film bearing of finite dimensions produces much more load support per unit area than is found from a solution based on an infinite bearing. The load support is shown to be made up of two components—that due to the infinite journal plus an additive term due to the axial pressure distribution. Two methods of solution of the governing equation are applied: (a) A small-parameter analysis and (b) a numerical finite-difference technique. In the limit, the infinitely short journal is shown to have a load support 2.5 times that of the infinitely long journal.
Flexible Membrane Hydrostatic Air Bearing
Authors: Levy S. B. , Coogan C. H.
Published: September 2011

The ordinary hydrostatic air bearing requires a very smooth surface upon which to operate. A flexible membrane used as part of the air bearing eliminates this restriction. The membrane shape, pressure distribution, and minimum air gap as functions of bearing load and flow rate are determined by the simultaneous solution of a reduced form of the Navier-Stokes equation and the membrane analogy equation. Experimental measurements verify the approximate mathematical theory.
On Error Torques of Squeeze-Film Cylindrical Journal Bearings
Authors: Pan C. H. T. , Chiang T.
Published: September 2011

The squeeze-film bearing has been considered for the output axis of high performance gyroscopes. Viewing this application, it is important that the parasitic torque of the bearing be very small. In the case of a squeeze-film journal bearing, parasitic torque can result from tolerance effects which disrupt rotational symmetry of the bearing. This problem has been studied by assuming ellipses for the tolerances of the journal and bearing surfaces as well as the squeeze motion, respectively. Each tolerance effect is assumed to be axially uniform. The mathematical problem is linearized with respect to each of the tolerances and the radial displacement of the journal. It was found that the parasitic torques do not depend on the radial displacement of the journal. The parasitic torques result from interactions among the three types of tolerance effects while each of the tolerances alone will not lead to any torque. Numerical estimates based on the geometry of a typical gyroscope and current fabrication practice shows such parasitic torques can seriously impair the accuracy of the gyroscope.
An Experimental Study of Elastohydrodynamic Lubrication of Foil Bearings: Part 1—Displacement in the Central Zone
Authors: Licht L.
Published: September 2011

An elastic foil under tension is wrapped partly around a rotating cylinder and is supported on a thin film of air. Capacitance probes, coincident with the surface of the cylinder, scan the air gap along the arc of wrap. The cylinder can be traversed across the width of the stationary foil, so that the topography of the air gap can be determined from a series of circumferential scans. Experimental results are compared quantitatively with theoretical predictions for the perfectly flexible and for the elastic foil bearing of infinite width [8, 12]. A comparison is also made with theory, for the case when the angle of wrap is small and the entrance and exit transition zones merge [9]. The effect of foil and gap width on side leakage is illustrated. The last part of this study deals with elastic foil bearings of finite width and with the characteristic “edge effect” in particular. The influence of various parameters on the nature of the displacement field of foils is demonstrated and related to recent analyses [13].
Lubrication Review: A Digest of the Literature for 1966
Authors: Harris T. A. , Cocks M. , Wojtowicz W. J. , Kelley B. , Myers H. , Barry H. F. , Schroeder R. J. , Hass H. , Rippel H. C. , McCabe J. T.
Published: September 2011

The volume of lubrication literature continued to expand, reflecting the increased experimental and theoretical attention being given to this discipline; this year’s Digest reviews more than five times the number of papers covered in the first Digest (for 1949).
Compressibility Effects on the Infinitely Wide, Perfectly Flexible Foil Bearing
Authors: Eshel A.
Published: September 2011

The effect of compressibility on foil bearings is found to be characterized by the parameter T∞/par0. Solutions are obtained for various values of this parameter. It is found that, with increasing compressibility, (a) The nominal clearance decreases; (b) the exit undulation decreases in amplitude and increases in wavelength until it completely disappears when T∞/par0 ≥ 2.37.
The Effects of Thermal Expansion in Infinitely Wide Slider Bearings—Free Thermal Expansion
Authors: Hahn E. J. , Kettleborough C. F.
Published: September 2011

The effects of free thermal expansion on the performance of infinitely wide slider bearings are investigated and several numerical examples are computed which show conclusively that thermal expansion is the fundamental cause of hydrodynamic lubrication of radially grooved initially parallel thrust bearings. In addition, thermal expansion is a likely explanation for the performance of centrally pivoted lilting pad thrust bearings.
The One-Dimensional Optimum Hydrodynamic Gas Slider Bearing
Authors: Maday C. J.
Published: September 2011

Bounded variable methods of the calculus of variations are used to determine the optimum or maximum load capacity hydrodynamic one-dimensional gas slider bearing. A lower bound is placed on the minimum film thickness in order to keep the load finite, and also to satisfy the boundary conditions. Using the Weierstrass-Erdmann corner conditions and the Weierstrass E-function it is found that the optimum gas slider bearing is stepped with a convergent leading section and a uniform thickness trailing section. The step location and the leading section film thickness depend upon the bearing number and compression process considered. It is also shown that the bearing contains one and only one step. The difference in the load capacity and maximum film pressure between the isothermal and adiabatic cases increases with increasing bearing number.
An Experimental Study of Taylor Vortices and Turbulence in Flow Between Eccentric Rotating Cylinders
Authors: Vohr J. H.
Published: September 2011

The critical speeds for onset of Taylor vortices inflow between eccentric rotating cylinders are determined by means of torque measurements for various eccentricity ratios and clearance ratios of the cylinders. Results are compared with the theoretical and experimental work of other investigators. Visual studies are made of the flow in both the Taylor vortex and turbulent flow regimes. Friction factor data are obtained for Reynolds numbers up to 40,000.
The Design of Partly Grooved, Externally Pressurized Journal Bearings
Authors: Hirs G. G.
Published: September 2011

The equation for the pressure buildup in these bearings is subjected to a first-order perturbation with respect to parallel as well as skewed displacements of the center lines of journal and bearing. Fluid film forces and their points of application can thus be found. Several configurations of these bearings are discussed. One configuration acts as a simple support, and two others act as a clamped support to the rotatable journal. Promising applications in machines are also discussed.
On the Mechanism of Contact Between Metal Surfaces: Part 2—The Real Area and the Number of the Contact Points
Authors: Tsukizoe T. , Hisakado T.
Published: September 2011

Assuming that the distribution curve obtained from the profile curve of the surface has a normal distribution, the relation between the real contact area and the separation is obtained theoretically in the case of ideal plastic flow of the microcontacts. If the asperities are cones of the same angle which depends on the surface roughness, the three-dimensional number and the distribution of the radii of contact points are also deduced theoretically. The results of the theoretical analyses are compared with the experimental results for the real contact areas and the numbers of the contact points. Results show that over the wide load range the average radii of contact points are almost constant; consequently, the total contact area is increased mainly owing to the increase in the number of the contact points.
The Effects of Geometry and Inertia on Face Seal Performance—Laminar Flow
Authors: Sneck H. J.
Published: September 2011

The “short bearing” equation of lubrication theory, modified to include inertial effects, is used to study the influence of geometric deviations from the ideal. It is found that the centrifugal force could be responsible for hydrodynamic features of the leakage flow which are theoretically unexplainable in the absence of this inertial effect. There is good evidence that the theory and the results are applicable over the entire laminar range of operation, provided the nominal clearance is small compared to the nominal radius.
The Effects of Geometry and Inertia on Face Seal Performance—Turbulent Flow
Authors: Sneck H. J.
Published: September 2011

The “short bearing” equation of lubrication theory, modified to include the inertial effects, is used to study the influence of geometric deviations from the ideal. The turbulent nature of the flow is described by an isotropic apparent viscosity and a power-law velocity distribution. It is found that geometric deviations from the ideal are less influential than in laminar flow.
Microasperity Lubrication
Authors: Anno J. N. , Walowit J. A. , Allen C. M.
Published: September 2011

Large load-supporting capability has been observed between parallel surfaces of a rotary-shaft face-seal when one of the surfaces contains microasperities in the form of circular cylinders with 12 × 10−3-in. dia and 100-microin. height, covering about one third of the surface. A theory is presented in which the load support is attributed to small tills on the tops of the asperities. The experimental data of lubricant film thickness versus applied load are correlated well by this theory assuming an average till of 0.86 microin. for the 12-mil-dia asperities investigated. Torque data obtained by a thermal technique are also correlated by this theory in the form of a plot of coefficient of friction versus Hersey number. Although direct evidence of the presence of small tilts on the asperity tops is lacking, it has been demonstrated that the load support is even further increased when the tops are purposely rounded. It is concluded that the theory developed correlates well the experimental data and, further, that the use of planned microasperities is an effective method for lubricating the parallel surfaces of face seals and thrust-bearing surfaces.
Shaft Geometry—A Major Factor in Oil Seal Performance
Authors: Symons J. D.
Published: September 2011

Five seal variables, viz., flex section thickness, lip length, trim diameter, material, and lip force, and two shaft variables, shaft out-of-round (OOR) and number of lobes, were investigated by means of fractional-factorial experimentation to determine the effects of shaft OOR and number of lobes on seal performance and to determine the interactions between the five seal design factors and the two shaft variables. A 1/4 replicate, 27 fractional-factorial experiment was conducted with leakage as the dependent variable to determine these effects. For the levels of OOR, lobing and shaft speed chosen, the tests indicated that shaft OOR and number of lobes in themselves had no effect. However, they appeared in significant interactions with several seal design factors. Also, at higher speeds, both OOR and lobing are extremely important. Analysis of the interactions and further test work with lobed shafts indicate that due to the interactions between several seal design factors and shaft OOR, the setting of an acceptable shaft OOR tolerance is extremely difficult. However, a general recommendation of 200 microin. maximum shaft OOR, with a minimum number of lobes, is supported by the data and is still valid.
A High Pressure Clearance Seal
Authors: Kamal M. M.
Published: September 2011

A simple method for estimating leakage and friction losses for a high-pressure sleeve type low-clearance metal seal is presented. Elastic deformations in the shaft and seal and the change in viscosity due to the high pressures are accounted for and found to be of major importance.
Oil Seal Quality Control—Important or Imperative
Authors: Brown J. M.
Published: September 2011

In 1957, a research program was initiated for the study of radial lip seals. Results of this study indicated that there was a lack of seal technology concerning the seal lip characteristics and a lack of equipment to measure various design parameters necessary to good sealing practice. From a program of planned experimentation, there emerged a series of controls which, when put into practice, resulted in vastly improved seals being available for assembly and an inherent reduction in the sealing problems.
Contact Elasticity of Seal Elastomers
Authors: Drutowski R. C.
Published: September 2011

The calculation of Young’s modulus of an elastomer is based on the optical measurement of the contact between a transparent spherical indenter and the elastomer. The technique is based on Hertzian contact analysis and agrees with the work done by others on the depth of penetration of indenters. A critical comparison of this method is made with conventional hardness tests. Experimental work establishes the fact that determinations of Young’s modulus based on indentations in thin samples are permissible only if the strains in the elastomer are kept below a calculable limit. The dependence of elastomer modulus on prior strain is described and fluid-elastomer interactions are examined in detail.
Seal Technology Assures Reliability
Authors: Brink R. , Brady J. , Daly R. , Rasmussen W.
Published: September 2011

Oil Seal Engineering has developed sophisticated tools and techniques which enable the end user of the oil seal to expect a high degree of reliability from a very inexpensive product. This paper portrays the development steps necessary to bring a line of oil seals from an idea to the market place. Emphasized are the design considerations, the test methods employed to verify the design parameters, and discussion of the performance characteristics as they relate to applications. The result—a seal design that can be utilized in a variety of applications with a degree of reliability not previously attainable.
Design of Floated Shoe Close Clearance Seals for Supersonic Jet Engine Compressors
Authors: Wilcock D. F. , Bjerklie J. , Cheng H.
Published: September 2011

The increase in engine efficiency to be gained by substituting a floated close running air seal at the high pressure end of large jet engine compressors, in place of the labyrinth seal, has prompted an intensive effort to design such seals for experimental evaluation. This paper describes the design of both a radial and an axial version in which multiple segmental shoes are floated 0.001 in. from the high speed runner surface. In the radial version, the shoes are free to float radially in order to follow runner runout. In the axial version, the shoes track the runner runout by floating axially in a carrier which moves to accommodate 0.4 inch of differential expansion. Floating is achieved through hydrostatic action sustained by the pressure difference across the seal. A shrouded Rayleigh step profile on the primary (high speed rubbing) seal surface provides additional protection. An order of magnitude reduction in leakage rate is predicted.
Behavior of Hydrostatic and Hydrodynamic Noncontacting Face Seals
Authors: Cheng H. S. , Chow C. Y. , Wilcock D. F.
Published: September 2011

In this paper, the pressure generation and static stability of face-type seals are discussed and an expression is developed to estimate the effectiveness of hydrodynamic action in these seals. Some design data are presented for the hydrostatic step seal, hydrostatic-orifice compensated seal, hybrid spiral-groove seal, and the shrouded Rayleigh step seal. These data are applicable to large-diameter seals for compressible fluids. The seal ring distortions due to initial imperfection, pressure, and thermal expansion are discussed. Approaches to estimate and to minimize the effects of these distortions are outlined. Finally, the ability of a face seal to track the vibrations of the runner is also discussed and methods required to determine the dynamic tracking for rigid or flexible seals are described.
The Significant Rheological Characteristics of Lubricants
Authors: Metzner A. B.
Published: September 2011

A substantial body of qualitative information concerning highly viscoelastic materials suggests they may be much superior to Newtonian fluids in some lubrication applications. Contrarily, most quantitative studies have predicted negligible or even adverse effects of the non-Newtonian behavior. This paper is accordingly addressed to a broad consideration of rheological properties and a critical analysis of the validity of common simplifying assumptions, in order to educe major effects which have not been well understood. Largely omitted are those rheological factors which have already been subjected to intensive scientific study. It is seen that the behavior of viscoelastic fluids in elongational deformations and in deformations of short duration are of primary interest; positive effects of two orders of magnitude have been shown in closely related problems. It is shown that the exploitation of these non-Newtonian rheological properties requires favorable geometric and kinematic conditions in a bearing which may differ appreciably from those employed with Newtonian fluids. The conclusions reached are speculative rather than definitive because of the primitive state of the development of this branch of rheology at the present time. They may be helpful, however, and do serve to direct attention to several kinds of lubricant-rheological studies requiring special emphasis.
Normal Stresses at High Shear Rates in a Polymer Solution
Authors: Bernd L. H.
Published: September 2011

Based on an examination of the characteristics of shear viscosity versus shear rate, it was postulated that high tensile and compressive stresses might exist in certain liquids at very high shear rates. If obtainable, these stresses could be important as load-bearing mechanisms in high-speed machine elements, and as a sealing mechanism in radial face seals. Such stresses should be evident in a polymer fortified oil, or in a liquid comprised of molecules possessing an appreciable length to width ratio. Therefore, a jet reaction viscometer reaching 107 sec−1 shear rate was developed to explore this possibility. Tests with polyisobutylene dissolved in a kerosene showed that elastic stresses were dominant with respect to viscous stresses at high shear rates. Tensile stresses up to more thn 1000 psi were obtained. However, the life of the polyisobutylene molecule was short. Hence it is concluded that normal stresses of appreciable magnitude can exist in high-speed machine elements under favorable conditions to affect their operation.
Flow of Greases Under the Action of Complex Shear
Authors: Vinogradov G. V. , Mamakov A. A.
Published: September 2011

Experiments were performed in a coaxial cylinder viscometer in which there were realized separately and simultaneously flows of grease and bright stock (Newtonian fluid) in the axial and peripheral direction. The latter was at uniform shear stress field. The effect of peripheral on axial-flows was a great decrease in resistance toward deformation in the axial direction. This is a very important peculiarity of greases, which are non-Newtonian media, when considering their flow in labyrinth boxes and some other devices. The effect of axial on peripheral flow showed somewhat increased resistance toward the latter. Such behavior was attributed to continuous inflow of fresh grease into the annular space where it did not remain long enough for structural destruction to reach a limiting value.
Pivoted-Pad Journal Gas Bearing Performance in Exploratory Operation of Brayton Cycle Turbocompressor
Authors: Wong R. Y. , Stewart W. L. , Rohlik H. E.
Published: September 2011

This paper describes findings obtained to date in the area of journal gas bearings from an experimental study of a Brayton cycle turbocompressor designed for the requirements of a two-shaft 10-kw space power system. The journal bearing design utilizes three pads pivoted on conforming balls and sockets. Two of the pivots are rigidly mounted to the frame, and the third pivot is mounted to the frame through a low-spring-rate diaphragm. This paper describes the salient package and bearing design features and then presents the principal results obtained from testing the package in both a spin calibration rig and operation at design temperature conditions with an inert gas. The results discussed include (a) the successful use of a pneumatic loading device to vary pad load during operation, (b) the operating characteristics of the bearings as obtained over a range of pad loads and ambient conditions, (c) structural and dynamic behavior of the bearing-support system during design temperature operation and (d) a discussion of the wear characteristics of the conforming ball-and-socket pivot as obtained from the tests made to date.
Application of Gas-Lubricated Bearings to Instruments
Authors: Denhard W. G. , Pan C. H. T.
Published: September 2011

Gas-lubricated bearings, which have been applied to instruments or are actively being applied, are discussed. Bearing types include self-acting, hydrostatic, and squeeze-film. Discussion covers generalized design, materials, dimensional requirements, and theory.
Design Studies of an Opposed-Hemisphere Gyro Spin-Axis Gas Bearing
Authors: Keating W. H. , Pan C. H. T.
Published: September 2011

An extensive analytical study has been carried out on the spiral-grooved, opposed hemisphere, self-acting gas bearing from the point of view of its application in the spin-axis suspension in inertial-grade gyroscopes. An idealized design featuring isoelasticity, zero attitude angle, and minimum compliance is established, resulting in zero compliance torque. Tolerance effects are examined. Limitation on wheel mass, on account of self-excited whirl instability, is determined, and its dependence on bearing clearance is found. Due to dynamic cross-compliance, elliptical orbital motions would be excited by linear simple harmonic forces. The elliptical orbit for a given acceleration level is characterized by its size, ratio of principal axes, orientation of the major axis, and the time phase; all of which are functions of frequency of excitation and are calculated for a range of frequencies for three typical wheel-bearing combinations. Cumulative cross-compliance torques resulting from dynamic excitation are calculated and are found to be of a similar order of magnitude as the tolerance effects.
The Numerical Solution of Linear Elliptic Equations
Authors: Coleman R.
Published: September 2011

A noniterative finite difference method is given for the solutions of linear elliptic equations with linear boundary conditions. This method is applicable to a variety of gas bearing problems. Comparisons are made with other numerical techniques, and an application to the spiral groove thrust plate is given.
Effects of Some Processing Variables on Dimensional Stability
Authors: Maringer R. E. , Imgram A. G.
Published: September 2011

Accuracy and reliability requirements of modern precision devices are, in part, limited by the dimensional instability of the materials from which these devices are constructed. To a large extent, these dimensional instabilities are related to the relaxation of residual stresses introduced during processing. Data are presented which emphasize this relationship, as well as the interrelationships which exist among design, material selection, and processing.
The Rayleigh Step Bearing Applied to a Gas-Lubricated Journal of Finite Length
Authors: Archibald F. R. , Hamrock B. J.
Published: September 2011

A linearization method is employed on the Reynolds equation to obtain the load and friction torque of a Rayleigh step-film scheme applied to a journal bearing of finite length. The analysis is broken into two parts; i.e., the stepped and ridge regions. The film thickness is considered constant in each region thereby simplifying the linearized Reynolds equation. In addition to the usual plain-bearing parameters (the compressibility number, eccentricity ratio, and length-to-diameter ratio), the load and friction force of a stepped bearing depend on the ratio of the stepped clearance to ridge clearance, the ratio of the width of ridge to the width of the pad, and the number of pads. The solution for the load and friction force for a single pad is obtained in the form of a highly convergent series. A number of equal pads are disposed around a journal and the total bearing load is computed for various eccentricities. Computation from the infinite series is lengthy and a digital computer was used in order to carry out the calculational work. This enabled optima to be selected for each system composed of different numbers of pads. The friction torque and hence the bearing power loss were computed for every case.
The Area of Contact Between Rough Surfaces and Flats
Authors: Greenwood J. A.
Published: September 2011

If the real area of contact between surfaces is determined by ideal plastic flow of the microcontacts, then the proportionality between the area of contact and the load follows immediately. If the deformation mode is elastic, or elastic-plastic, or plastic with work-hardening, which will be the usual cases, then the proportionality is harder to explain. However, by considering the statistical distribution of heights of the surface asperities, it can be shown that the average size of a microcontact is almost constant, independent of load; consequently, the fact that the contact pressure at a single micro-contact may vary with contact size becomes irrelevant. If the real origin of the laws of friction is in the statistics of surface roughness and not in a particular mode of deformation, the applicability of the Bowden and Tabor theory of friction to plastics and other nonmetals becomes more readily understandable.
Lubrication Review: A Digest of the Literature for 1965
Authors: Harris T. A. , Barry H. F. , Rowe C. N. , Wojtowicz W. J. , Brown P. F. , Rumbarger J. H. , Hopkins V. , Schroeder R. , Decker O.
Published: September 2011

The volume of lubrication literature continued to expand, reflecting the increased experimental and theoretical attention being given to this discipline; this year’s Digest reviews more than five times the number of papers covered in the first Digest (for 1949).
Stiffness Effects on the Infinitely Wide Foil Bearing
Authors: Eshel A. , Elrod H. G.
Published: September 2011

Numerical solutions are presented for the film thickness of the infinitely wide, self-acting foil bearing for various values of tape stiffness. The solutions indicate that with increasing stiffness there are: (a) a slow reduction in the nearly uniform clearance prevailing under most of the wrap angle; (b) an increase in the peak of the undulations occurring in the region where the tape leaves the spindle; and (c) virtually no change in the trough of these undulations.
On the Role of Contact Stresses in Frictional Damping of Mechanical Oscillation
Authors: Halaunbrenner J. , Sukiennik P.
Published: September 2011

Damping of spinning oscillations of a steel ball on an elastic base has been investigated. These oscillations are excited by the elastic force of a spring and damped by spinning friction. Oscillograms show the decrease of the amplitude to zero and of the period to a constant value, which can be calculated from the “elastic compliance of contact” and the compliance of the spring. Three different phases of oscillations, corresponding to three different kinds of damping can be distinguished. These are caused by: (a) Sliding over the entire contact area; (b) slips over the annular areas, while the internal stuck circle increases with decreasing amplitude; (c) oscillations of the ball, already stuck to the base by adhesion forces over the entire contact circle. The damping arises now from internal damping of base material. The periods of oscillations in two cases have been calculated theoretically.