bluuebunny/crossref_metadata_2025 huggingface dataset:
Fretting Wear Mechanisms and Their Effects on Fretting Fatigue
Authors: Berthier Y. , Colombie´ Ch. , Vincent L. , Godet M.
Published: October 2009

Fretting wear and fretting fatigue are governed by the rate of formation of materials (third-bodies) between the initial contact surfaces. Furthermore, the third-bodies must be maintained within the contact. The issue of the race between third-body formation and subsurface damage conditions the effect of fretting on fatigue. That race lasts for only a few hundred or at best a few thousand cycles. Effective third-bodies (or good anti-fretting lubricants) must adhere strongly to the rubbing surfaces, and be able to accommodate at least part of the relative displacement. Great care in the design of test equipment has to be exercised before definitive results on the effect of amplitude and frequency on either fretting fatigue or fretting wear can be obtained for a given contact condition, given materials and given environments.
Effect of High Energy Ion Bombardment on the Tribological Properties of WS2 Sputtered Films
Authors: Hirano Motohisa , Miyake Shojiro
Published: October 2009

An attempt was made to improve the tribological properties of WS2 sputtered film by bombarding the film surface with various inert gaseous ions (He+, Ar+, Kr+, Xe+). The resulting changes in tribological properties were investigated together with related changes in physical properties such as morphology and crystallinity of the films. Bombardment by He+ and Ar+ effectively reduces WS2 film friction, whereas Kr+ – and Xe+ – bombardment increased WS2 film friction. The effect of high-energy ion bombardment is discussed in relation to the crystallinity of WS2 film.
On the Nature of O-Rings in Contact With Rough Surfaces
Authors: Warren W. E. , Curro J. G. , Amos D. E.
Published: October 2009

This work provides a theoretical analysis of the elastic behavior of an O-ring compressed between two rigid plates with irregular surfaces. Relations between deflection, contact force and contact pressure are obtained. The contact pressure, which is of fundamental importance in establishing criteria for effective sealing, is dependent upon both the amplitude and wavelength of the surface irregularity. This analysis suggests that surfaces in contact with O-ring seals should be characterized by the root mean square slope Δq in addition to the usual Ra which depends on amplitude only.
The Friction of Some Polymers and Elastomers at High Values of Pressure X Velocity
Authors: Ettles C. M. , Hardie C. E.
Published: October 2009

Experimental data are given of the friction coefficient of spherically radiused sliders against three polymers and two elastomers. Tests were carried out over a four order of magnitude range of PV, to include friction conditions covering a wide range of interface temperature. The results indicate that an upper bound “friction defined temperature” may be obtained at high PV, which is not exceeded as conditions are made more severe. This is characterized by a reduction of friction with increasing velocity according to μ∝V−1/2.
Collocation Method for Finite Length Squeeze Film Dampers With Variable Clearance
Authors: Arakere N. K. , Nelson H. D.
Published: October 2009

The Collocation method is used to study the characteristics of a finite length Squeeze Film Damper (SFD) with variable clearance. The secant stiffness and damping coefficients of the SFD for centered circular orbits is compured by solving Reynolds equation for a finite bearing, using the collocation method. A significant disadvantage with a conventional SFD is the highly nonlinear variation of secant stiffness and damping coefficients with eccentricity ratio. It is shown in this paper that by suitably varying the parameters α and λ, which control the nature of clearance variation, the secant stiffness and damping coefficient variation with eccentricity; ratio can be altered to better suit specific design needs. Nonlinear transient analysis of a single journal in a finite SFD is carried out, and, periodic journal center orbits due to unbalance response for uncentered finite SFD’s are also obtained. The centered circular orbit response for different unbalance values and speeds is obtained. Results from the Collocation method show excellent agreement with finite difference results. The Collocation method is shown to be an efficient and viable technique that is an order of magnitude computationally faster than the finite difference method, for static and dynamic analysis of finite length SFD’s.
Development of a Method for the Prediction of Pressure-Viscosity Coefficients of Lubricating Oils Based on Free-Volume Theory
Authors: Wu C. S. , Klaus E. E. , Duda J. L.
Published: October 2009

A simple method based on free-volume theory to predict the pressure-viscosity coefficients of liquid lubricants has been developed. The method only requires the viscosity-temperature relationship and the viscosity at the temperature of interest. The method provides good accuracy when it was tested for 162 data points for various fluid types over wide ranges of temperature and viscosity.
Asperity Excited Temperature Field in a Coated Medium With a Random Uniform Coating Thickness
Authors: Liu Jew-Chyi , Ju F. D.
Published: October 2009

The present paper investigates the random temperature response of a coated medium subjected to a fast moving asperity, taking into consideration the randomness of coating thickness. While the coating thickness is uniform for individual specimens, there is a small random variation from one specimen to another in a statistical space. Stochastic responses in coated solid media are investigated by the perturbation method, and the results are presented in terms of the mean value and the standard deviation of the temperature field. The numerical example considers a typical stochastic process. It is noted that even for very small thickness variation, for instances, the coefficient of the variation of coating thickness is 0.1 percent, the temperature at the interface for a thin coating can vary by a coefficient of variation of 18 percent.
Entrance and Stationary Roughness Effects on the Load Carrying Capacity of a Wide Wedge Gas Bearing
Authors: Raad P. E. , White J. W.
Published: October 2009

The objective of this work is the determination of the effects of surface roughness amplitude and inlet conditions on ultra-thin, compressible, isothermal, infinitely-wide gas bearings. The method of study is numerical in nature and consists of a second-order accurate finite difference solution of the Reynolds equation of lubrication without molecular slip for a range of bearing numbers spanning six orders of magnitude. The motivation for this work comes from the magnetic disk drive industry where ever decreasing head flying heights are being sought to increase the recording density. Past studies by these authors of the infinitely-wide air bearing with stationary roughness have shown that, unlike in the case of a smooth bearing, the load peaks at a finite bearing number comparable to that at which current rigid disk drives operate. This suggests that it may be possible to arrange the roughness pattern in such a way as to cause the slider to separate from the hard disk more rapidly, minimizing wear to both surfaces. A wedge bearing with stationary sinusoidal roughness is studied for different roughness amplitudes and two phases. It is shown that for all configurations considered, the load exhibits a peak unlike in the case of the smooth bearing where the load monotonically reaches a peak at an infinite gas bearing number. Two rough sliders with flat tapers smoothly attached to their leading edge are also studied to answer questions regarding the role that the inlet condition plays in the resulting magnitude and behavior of the generated load. The leading taper allows the bearing to dynamically determine the entrained flow rate and maximum pressure as well as to self prescribe the inlet condition at the leading edge of the first roughness wave. The inlet conditions prescribed by the developing flow in the flat taper region still give rise to a peak in the load. The addition of the smooth taper, however, causes an overall decrease (increase) in the load when the roughness waves are entirely above (below) the plane of the taper compared to the results of the rough bearing with no taper. It is demonstrated that all the considered roughness patterns result in a peak load at a finite bearing number. Of special interest are two bearing configurations: one composed of a smooth taper followed by a transversely roughened slider and the other is a rough slider with a transverse roughness pattern whose slope at the inlet of the bearing is negative. Both are shown to achieve a maximum lifting force at low bearing numbers, providing rapid separation while alleviating the narrow rail manufacturing problem.
Compressible Elastohydrodynamic Lubrication of Rough Surfaces
Authors: Sadeghi F. , Sui Ping C.
Published: October 2009

A complete numerical solution of compressible elastohydrodynamic lubrication of rough surfaces has been obtained. The Newton-Raphson technique is used to solve the simultaneous system of modified compressible Reynolds and elasticity equations. The effects of various loads, surface pattern, and roughness parameter have been investigated. Results have been presented for loads ranging from W = 2.0452 × 10−5 to W = 2.3 × 10−4 at the speed of U = 1.0 × 10−11. The results indicate that the compression effects are significant and cannot be neglected.
Contact Temperature and Its Effects in an Oscillatory Sliding Contact
Authors: Kennedy F. E. , Cullen S. C. , Leroy J. M.
Published: October 2009

The relationship between contact temperature, friction coefficient, and wear rate was studied here for the case of dry sliding between pin and flat in small amplitude oscillatory motion. In the first part of the study, infrared radiation pyrometry and finite element analysis techniques were used to measure and model surface temperatures in an oscillatory contact. Good agreement was achieved between model predictions and experimental measurements. The model was then applied to an oscillating contact between an ultra-high molecular weight polyethylene pin and a rough stainless steel flat. Temperature predictions for that case were correlated with measured friction coefficients and wear rates. It was found that the polyethylene wear rate decreased as the contact temperature increased. The uniformity and thickness of the transfer films which formed on both counterface and polymer pin were found to be affected by contact temperature. Transfer film behavior was deemed responsible for the influence of contact temperature on wear rate.
Hydrodynamic Analysis and Fluid-Solid Interaction Effects on the Behavior of a Compliant Wall (Thick) Journal Bearing. Part 2: Results
Authors: Braun M. J. , Dougherty J. D.
Published: October 2009

The second part of this two part paper presents the results of the parametric numerical experiment performed with the compliant bearing model presented in Part 1. The parameters are angular velocity, eccentricity, shaft axial misalignment, linear material and the working fluid. It was found that wall compliance greatly influences the shape and size of the clearance between the rotating shaft and the stationary housing and provides a strong feedback for the changes in the pressure distribution map, the magnitude of the maximum pressure, and the inception of the cavitation point. The effects of misalignment are major with respect of both the axial location of the plane containing the maximum pressure and the resulting skewed pressure map.
Analyses of the Role of Surface Roughness on Contact Stresses Between Elastic Cylinders With and Without Soft Surface Coating
Authors: Merriman T. , Kannel J.
Published: October 2009

The paper presents a theory for contact stresses between a smooth and rough elastic cylinder. Three types of primary surface textures are considered: a peaked surface texture, a normal surface texture, and a grooved surface texture. The predicted contact stresses between a smooth and a rough surface are considerably higher than would be predicted by Hertz theory for smooth contact. In addition, when the rough surface has high peak asperities the contact stresses are higher than when the rough surface is grooved even though the average roughness is the same. A soft layer on the smooth surface can reduce the magnitude of the peak stresses.
An Efficient, Robust, Multi-Level Computational Algorithm for Elastohydrodynamic Lubrication
Authors: Chang L. , Conry T. F. , Cusano C.
Published: October 2009

A new computational algorithm is developed for the numerical analysis of elastohydrodynamic (EHD) lubrication problems. This algorithm combines direct-iteration, Newton-Raphson, and multigrid methods into one working environment. Accurate solutions for a wide range of steady-state, line-contact problems are obtained with a relatively small number of numerical operations. The algorithm can be used to efficiently simulate transient processes in EHD lubrication. It can also be extended to solve point-contact problems with high computational and storage efficiency.
Analysis of Misaligned Journal Bearings Operating in Turbulent Regime
Authors: Safar Z. S. , Elkotb M. M. , Mokhtar D. M.
Published: October 2009

This paper presents an analysis of the performance characteristics for a misaligned full journal bearing operating in turbulent regime. The modified Reynolds equation for turbulent flow is solved taking into consideration that the distribution of the effective viscosity is dependent on local shear stress. It is found that journal misalignment influences bearing behavior especially at lower eccentricity ratios. Also, it is concluded that for the same load carrying capacity misaligned journal bearing consumes more power than an aligned one.
Roughness-Induced Shear- and Squeeze-Film Effects in Magnetic Recording—Part II: Applications
Authors: Bhushan Bharat , To̸nder Kristian
Published: October 2009

Surface roughness-induced hydrodynamic gas lubrication theory including rarefaction effects is used to explain the effects of surface roughness on the magnetic head-medium spacing. Since video-recording operates at h/σ (film thickness/standard deviations of composite roughness) ≤ 3, the spacing increases with the roughness because the head surface remains at the distance on the order of 3σ from the mean of the tape surface. Data processing tapes operate at h/σ ≥ 4, and the increase in spacing with the roughness is found to be due to roughness-induced squeeze films. Squeeze motion can be generated by the isolated high asperities on the tape surface and bearing load variations due to a moving roughness (in shear flow) which are expected to increase with an increase in the surface roughness, and modulations of surfaces from other instabilities. Increase in signal-to-noise ratio and in amplitude variation for a rougher tape is also explained by the surface roughness variations. Influence of surface roughness on the head-disk spacing is also analyzed. Recommendations are made for an optimum roughness orientation and magnitude and whether the roughness should lie on the stationary or moving surfaces.
The Solution of the Elrod Algorithm for a Dynamically Loaded Journal Bearing Using Multigrid Techniques
Authors: Woods C. M. , Brewe D. E.
Published: October 2009

Numerical solution to a theoretical model of vapor cavitation in a dynamically loaded journal bearing is developed, utilizing a multigrid iterative technique. The method is compared with a noniterative approach in terms of computational time and accuracy. The computational model is based on the Elrod algorithm, a control volume approach to the Reynolds equation which mimics the Jakobsson-Floberg and Olsson cavitation theory. Besides accounting for a moving cavitation boundary and conservation of mass at the boundary, it also conserves mass within the cavitated region via a smeared mass or striated flow extending to both surfaces in the film gap. The mixed nature of the equations (parabolic in the full film zone and hyperbolic in the cavitated zone) coupled with the dynamic aspects of the problem create interesting difficulties for the present solution approach. Emphasis is placed on the methods found to eliminate solution instabilities. Excellent results are obtained for both accuracy and reduction of computational time.
Practical Limits to the Performance of Magnetic Bearings: Peak Force, Slew Rate, and Displacement Sensitivity
Authors: Maslen E. , Hermann P. , Scott M. , Humphris R. R.
Published: October 2009

Magnetic bearings are subject to performance limits which are quite different from those of conventional bearings. These are due in part to the inherent nonlinearity of the device and in part to its electrical nature. Three important nonideal behaviors are presented: peak force capacity, force slew rate limitation, and sensitivity to rotor motion at large displacements. The problem of identifying the dynamic requirements of a magnetic bearing when used to support a known structure subject to known loads is discussed in the context of these limits. Several simple design tools result from this investigation.
Effects of Lubricant Rheology and Kinematic Conditions on Micro-Elastohydrodynamic Lubrication
Authors: Chang L. , Cusano C. , Conry T. F.
Published: October 2009

The effects of lubricant rheology and surface kinematic conditions on micro-elastohydrodynamic (EHD) lubrication are analyzed under isothermal line-contact conditions. Micro-EHD lubrication is modeled by introducing a surface irregularity in the form of an asperity or a furrow into the contact zone. Under simple sliding conditions, the pressure generated in the vicinity of the irregularity and the resulting surface deformation depend strongly on the lubricant rheology. The surface kinematic conditions have profound effects on micro-EHD lubrication. In general, a stationary surface irregularity produces a relatively strong downstream effect when it is in the inlet region of the contact, and a moving surface irregularity produces a relatively strong upstream effect after it enters the Hertzian central region. The simulated results agree qualitatively with previous experimental measurements and observations.
Influence of Elastic Deformations of Turbo-Generator Tilting Pad Bearings on the Static Behavior and on the Dynamic Coefficients in Different Designs
Authors: Brugier D. , Pascal M. T.
Published: October 2009

The load on the larger tilting pad bearing can be as high as 106 N. With such high static loads, pad and pivot distortions and thermal effects in the lubricant cannot be neglected. This paper analyzes the influence of the deformation of the pads and pivots on the static and dynamic behavior of typical turbo-generator tilting pad bearings used in actual operating conditions. Thermal and pressure distortions are compared. The hydrodynamic pressures and lubricant temperatures are computed with a three-dimensional model. Thermal and elastic pad and pivot distortions are obtained with a three-dimensional finite element model.
Basic Equations for Fluid Films with Variable Properties
Authors: Booker J. F.
Published: October 2009

Very general relations are derived in compact form for fluid-film lubrication with variable material properties. Rigorous consideration of mechanical work leads to simple (and apparently novel) power dissipation formulas, one of which is particularly appropriate for finite element calculations. Comparison is made to previous results for the particular example of a flooded journal bearing.
Some Aspects of Determining the Flow Factors
Authors: Hu Yuanzhong , Zheng Lingqing
Published: October 2009

The uncertainty in calculated results of the flow factors greatly limits the application of the average flow model [1] which otherwise is an approach with broad prospects for studying the lubrication behavior of rough surfaces. The effects of boundary conditions, grid systems, and surface statistics on the flow factors are discussed in the paper, and the reason why the calculated results for the flow factors obtained by different researchers widely differ from each other is revealed. The research shows that ∂p/∂y over the micro-bearing has an effect on the calculated value of flow factors; the influence of the sideflow arises from the simulation approach itself, in which a micro-bearing is used for determining flow factors; the grid systems and the procedure to generate random surfaces may change the statistics of the surfaces used in calculation and affect the results thereby.
Effects of Lubricant Oil Film Thickness on Seizure Initiation in Cold Extrusion of Aluminium
Authors: Nakamura T.
Published: October 2009

A critical condition for seizure initiation has been investigated under a relatively low extrusion speed using an extrusion-type friction testing machine. To examine the effects of lubricant oil film thickness on seizure initiation, the oil film thicknesses at the tool-workpiece interface were estimated theoretically, and paraffinic mineral oils with three grades of viscosity were tested with various thicknesses of oil film applied, using commercially pure aluminium as the workpiece. The seizure phenomenon was always near the die exit. The lower the viscosity grade of oil used and the thinner the oil film applied, the shorter the critical punch stroke for seizure initiation became. Consequently, it has been clarified that the critical oil film thickness for seizure initiation was about 0.2 μm.
Thermomechanical Behavior of Multilayered Media: Theory
Authors: Leroy J. M. , Floquet A. , Villechaise B.
Published: October 2009

Hard coatings are more and more used to improve the mechanical and tribological behavior of surfaces. Thermomechanical cracking can occur in these coatings when they slide under heavy loads. We present a two-dimensional model of a finite thickness layered medium submitted to a moving heat source. The analytical solution of the temperature and thermoelastic stress fields is obtained using Fourier transforms. The behavior of each layer is described by transfer-matrices and a relation between the displacement- and stress-vectors is given. The originality of the study is the use of a Fast Fourier Transform algorithm. With this method, calculation time is reduced, no singularity problems are met in the inverse transform and each parameter (especially the thickness of the layers) can be studied over a wide range.
Micro-Elastohydrodynamic Lubrication of an Elliptical Contact With Transverse and Three-Dimensional Sinusoidal Roughness
Authors: Kweh C. C. , Evans H. P. , Snidle R. W.
Published: October 2009

The paper describes the results of the analysis of elastohydrodynamic (EHD) lubrication of an elliptical contact between a rough, stationary surface and a smooth, moving surface. Roughness takes the form of sinusoidal grooves aligned in the direction transverse to that of lubricant entrainment. The conditions analyzed are chosen to correspond to the operating conditions of a high speed, high temperature disk machine. The main feature of the results is the almost complete flattening of the roughness that occurs, accompanied by a corresponding ripple in the pressure distribution. A contact with three-dimensional roughness has also been analyzed, and this shows that in comparison with the two-dimensional case, the longitudinal grooves tend to persist.
Viscoplastic Behavior of a Silicone Oil in a Metalforming Inlet Zone
Authors: Wilson W. R. D. , Huang X. B.
Published: October 2009

A metalforming inlet zone analysis is developed for a viscoplastic lubricant that is Newtonian below some critical stress level at which it shears plastically. The analysis includes the effects of variations in the lubricant viscosity and shear strength with pressure, and curvature of the tooling surface. The results of the analysis are compared with experimental measurements of the lubricant film thickness in rolling chemical lead with mineral oil and silicone lubricants.
Thermal Evolution of Hot Spots in Thermally Nonlinear Carbon Graphite Sliders
Authors: Yune Young Gill , Bryant M. D.
Published: October 2009

Frictional heating of a thermal mound (or hot spot) present on the interface between a carbon graphite block sliding against a fast moving conductor is simulated. Heating of this mound due to frictional power dissipation is modeled as a collection of internal heat sources uniformly distributed within a very shallow volume (or layer) located directly beneath the sliding contact interface. The thermal mound, assumed to be motionless on and originating from the carbon graphite block, possesses the extreme temperature dependent thermal conductivity and heat capacity common to carbon graphite materials. Evolution of thermal mound temperatures from cold to hot is studied as a function of the intensity of the internal heat source distribution and the thickness of the heat source layer. For a fast moving conducting body sliding against the graphite block, it is shown that (a) an optimal heat source layer thickness exists, whereby temperatures maximize for this thickness and (b) for a sufficiently high heat source intensity, thermal instability of the mound is possible.
Finite Element Analysis of Dynamically Loaded Flexible Journal Bearings: A Fast Newton-Raphson Method
Authors: McIvor J. D. C. , Fenner D. N.
Published: October 2009

A fast Newton-Raphson method is presented for the finite element analysis of dynamically loaded flexible journal bearings. The method makes use of 8-node isoparametric elements for the lubrication analysis and 20-node isoparametric elements for the structural analysis. Results are presented for the Ruston and Hornsby 6VEB Mk III marine diesel big-end bearing using this method. The computing time required for this analysis is more than two orders of magnitude less than that previously reported for an elastohydrodynamic bearing analysis using a conventional Newton-Raphson method.
On the Rheology of a Traction Fluid
Authors: Ramesh K. T.
Published: October 2009

Results are presented of pressure-shear plate impact experiments performed on a traction fluid. The overall behavior of this material appears to be very similar to that of elastohydrodynamic (EHD) lubricants such as 5P4E: the material exhibits a saturation of the flow stress with strain rate, and a nearly linear dependence of the critical shear stress on the applied pressure. The plate impact results are compared with those of other workers using completely different experimental techniques and operating at lower strain rates and much lower pressures. The results obtained from the various techniques are in general agreement.
Static Characteristics of Gas-Lubricated Slider Bearings Operating in a Helium-Air Mixture
Authors: Ohkubo T. , Fukui S. , Kogure K.
Published: October 2009

This paper outlines experimental investigations of the static characteristics of self-acting gas-lubricated slider bearings operating in a helium-air mixture. The experimental results are compared with numerical results obtained by solving a modified Reynolds equation and a generalized lubrication equation based on an equivalent molecular mean free path (MMFP) and on an equivalent viscosity derived from molecular gas dynamics. At any mole ratio of air α, the values of the equivalent MMFP are generally expected to be smaller than those of the MMFP derived from linear interpolation, whereas the values of equivalent viscosity are expected to be larger. The numerical results agree well with the experimental results within the range of α from 1.0 to 0.6. Lower values of α give a bigger difference between numerical and experimental results, and make the experimental results lower than the numerical results. Moreover, results of a generalized lubrication equation based on the Boltzmann equation give a closer prediction or qualitative tendency to the experimental results than do those based on the modified Reynolds equation.
Effect of Galling on Metal Fracture in Cup Ironing Process
Authors: Saito M. , Saiki H. , Kawai N.
Published: October 2009

The metal fracture mechanism in cup ironing process was investigated, taking into account the effect of the galling. Three types of metal cracking were observed, which are distinguishable from each other in crack appearance. The axial fracture stress measured at the ironed cup wall decreases as the galling becomes heavy, though the tensile strength of the ironed wall metal is scarcely decreased by the surface damage caused by the galling. In such cases, a stress concentration is always caused by the uneven circumferential distribution of the friction at the die-metal interface. The cracking begins at the circumferential position where the axial stress exerted on the ironed cup wall partially reaches the axial tensile strength of the ironed wall metal. The mean axial fracture stress is thus decreased. This also yields the decrease of crack propagation velocity and consequently the difference in crack appearance. The interaction between the tribological phenomena and the metal fracture behavior in the ironing process was clarified.
Two-Sided Texture Effects on Ultra-Thin Wide Wedge Gas Bearings
Authors: Raad Peter E. , Kuria Isaac M.
Published: October 2009

This work seeks to determine the effects of two-sided surface roughness amplitude on ultra-thin, compressible, isothermal, infinitely wide gas bearings. The transient Reynolds equation of lubrication is solved using a finite difference scheme that is second order accurate in space and time. Solutions of the Reynolds equation are presented for bearing numbers spanning seven orders of magnitude, including those experienced in magnetic hard disk recording. The results presented here show that introducing roughness on either bearing surface causes an increase in the load carrying capacity as compared to the smooth bearing case. However, when roughness is introduced on the stationary surface, the gas bearing generates higher loads which also exhibit a peak at finite bearing numbers. The load peaks increase quadratically with increasing stationary roughness amplitude. It is also demonstrated that at very high values of the bearing number, the load becomes dependent on the amplitude of the surface roughness and not its location. This suggests that a closer look at the possibility of roughening the head surface instead of the larger disk surface in order to cause a more rapid separation is warranted. Stiction resistance would still be achieved, but perhaps more economically, and wear to both surfaces would be minimized.
Breaking the Code of DNA Binding Specificity of TAL-Type III Effectors
Authors: Boch Jens , Scholze Heidi , Schornack Sebastian , Landgraf Angelika , Hahn Simone , Kay Sabine , Lahaye Thomas , Nickstadt Anja , Bonas Ulla
Published: October 2009

TAL Order

Xanthomonas
bacteria attack their plant hosts by delivering their own transcription-activator–like (TAL) proteins into the plant cell nucleus and alter the plant's gene regulation (see the Perspective by

Voytas and Joung

).
Moscou and Bogdanove
(p.
1501
, published online 29 October: see the cover) and

Boch
et al.

(p.
1509
, published online 29 October) have now discovered how the similar but not identical repeats in the TAL proteins encode the specificity needed for the proteins to find their targets. Each repeat is specific for one DNA base pair, a specificity encoded by hypervariable amino acid positions. Combining several repeats with different amino acids in the hypervariable positions allowed the production of new effectors that targeted new DNA sites.
Pandemic H1N1 and the 2009 Hajj
Authors: Ebrahim Shahul H. , Memish Ziad A. , Uyeki Timothy M. , Khoja Tawfik A. M. , Marano Nina , McNabb Scott J. N.
Published: October 2009

It will take vigilance, commitment, and action by all global stakeholders to reduce the potential impact of pandemic influenza during the upcoming Hajj pilgrimage.
Agency, duties and the “Ashley treatment”
Authors: Tan N , Brassington I
Published: October 2009

In 2006, a paper in the journalArchives of Pediatric and Adolescent Medicinedescribed a novel case of growth attenuation therapy and other treatments carried out on Ashley, a severely cognitively, neurologically and physically disabled 6-year-old girl. Some of the moral arguments that have sprung up in respect of the so-called “Ashley treatment” are considered, and it is suggested that they all miss something—that the proper treatment of Ashley may have as much to do with doctors’ duties to themselves as with their duties to her. It is suggested that the Ashley treatment may have been in violation of doctors’ self-regarding duties and that this possibility is worthy of further investigation.
Autonomy at the end of life: life-prolonging treatment in nursing homes—relatives’ role in the decision-making process
Authors: Dreyer A , Forde R , Nortvedt P
Published: October 2009

Background:

The increasing number of elderly people in nursing homes with failing competence to give consent represents a great challenge to healthcare staff’s protection of patient autonomy in the issues of life-prolonging treatment, hydration, nutrition and hospitalisation. The lack of national guidelines and internal routines can threaten the protection of patient autonomy.

Objectives:

To place focus on protecting patient autonomy in the decision-making process by studying how relatives experience their role as substitute decision-makers.

Design:

A qualitative descriptive design with analysis of the contents of transcribed in-depth interviews with relatives.

Participants:

Fifteen relatives of 20 patients in 10 nursing homes in Norway.

Results and Interpretations:

The main findings reveal deficient procedures for including relatives in decision-making processes. Relatives have poor knowledge about the end of life, and there is little discussion about their role as substitute decision-makers for patients who are not competent to give consent. Few relatives understand the concept of patient autonomy. In Norway the treating physician is responsible for patient treatment. When relatives are included in discussions on treatment, they perceive themselves as responsible for the decision, which is a burden for them afterwards. This qualitative study describes relatives’ experiences, thus providing important information on the improvement potential with the main objective of safeguarding patient autonomy and caring for relatives.

Conclusion:

The study reveals failing procedures and thus a great potential for improvement. Both ethical and legal aspects must be addressed when considering patient autonomy.
Solo doctors and ethical isolation
Authors: Cooper R J
Published: October 2009

This paper uses the case of solo doctors to explore whether working in relative isolation from one’s peers may be detrimental to ethical decision-making. Drawing upon the relevance of communication and interaction for ethical decision-making in the ethical theories of Habermas, Mead and Gadamer, it is argued that doctors benefit from ethical discussion with their peers and that solo practice may make this more difficult. The paper identifies a paucity of empirical research related to solo practice and ethics but draws upon more general medical ethics research and a study that identified ethical isolation among community pharmacists to support the theoretical claims made. The paper concludes by using the literary analogy of Soderberg’s Doctor Glas to illustrate the issues raised and how ethical decision-making in relative isolation may be problematical.
KO-HOMOLOGY AND TYPE I STRING THEORY
Authors: REIS RUI M. G. , SZABO RICHARD J. , VALENTINO ALESSANDRO
Published: October 2009

We study the classification of D-branes and Ramond–Ramond fields in Type I string theory by developing a geometric description of KO-homology. We define an analytic version of KO-homology using KK-theory of real C*-algebras, and construct explicitly the isomorphism between geometric and analytic KO-homology. The construction involves recasting the C ℓn-index theorem and a certain geometric invariant into a homological framework which is used, along with a definition of the real Chern character in KO-homology, to derive cohomological index formulas. We show that this invariant also naturally assigns torsion charges to non-BPS states in Type I string theory, in the construction of classes of D-branes in terms of topological KO-cycles. The formalism naturally captures the coupling of Ramond–Ramond fields to background D-branes which cancel global anomalies in the string theory path integral. We show that this is related to a physical interpretation of bivariant KK-theory in terms of decay processes on spacetime-filling branes. We also provide a construction of the holonomies of Ramond–Ramond fields in Type II string theory in terms of topological K-chains.
AN UPDATED TIME-OPTIMAL 3RD-ORDER LINEAR SACCADIC EYE PLANT MODEL
Authors: ZHOU WEI , CHEN XINNIAN , ENDERLE JOHN
Published: October 2009

A linear third-order model of the ocular motor plant for horizontal saccadic eye movements is presented consisting of a linear ocular motor plant and a time-optimal saccadic controller based on physiological considerations. The ocular motor plant consists of the eyeball and two extraocular muscles. All parameters and initial conditions are estimated or measured from physiological data. The neural inputs are described by pulse-slide-step waveforms with a post inhibitory rebound burst and based on a time-optimal controller. Model parameters are estimated using the system identification technique. The static and dynamic behaviors of the model are in excellent agreement with the experimental data.
REINFORCEMENT LEARNING IN SUPPLY CHAINS
Authors: VALLURI ANNAPURNA , NORTH MICHAEL J. , MACAL CHARLES M.
Published: October 2009

Effective management of supply chains creates value and can strategically position companies. In practice, human beings have been found to be both surprisingly successful and disappointingly inept at managing supply chains. The related fields of cognitive psychology and artificial intelligence have postulated a variety of potential mechanisms to explain this behavior. One of the leading candidates is reinforcement learning. This paper applies agent-based modeling to investigate the comparative behavioral consequences of three simple reinforcement learning algorithms in a multi-stage supply chain. For the first time, our findings show that the specific algorithm that is employed can have dramatic effects on the results obtained. Reinforcement learning is found to be valuable in multi-stage supply chains with several learning agents, as independent agents can learn to coordinate their behavior. However, learning in multi-stage supply chains using these postulated approaches from cognitive psychology and artificial intelligence take extremely long time periods to achieve stability which raises questions about their ability to explain behavior in real supply chains. The fact that it takes thousands of periods for agents to learn in this simple multi-agent setting provides new evidence that real world decision makers are unlikely to be using strict reinforcement learning in practice.
ONTOLOGY-GUIDED SERVICE-ORIENTED ARCHITECTURE COMPOSITION TO SUPPORT COMPLEX AND TAILORABLE PROCESS DEFINITIONS
Authors: LEE SEOK-WON , GANDHI ROBIN A. , WAGLE SIDDHARTH J.
Published: October 2009

Services as abstractions of functionality have enabled the engineering of systems that support well-defined processes with relative ease. This success leads to aspirations for achieving greater complexity with the service-oriented paradigm. In particular, we address the case where the process definition is tailored differently in each instantiation based on negotiations among stakeholders of a socio-technical context. For such cases the process definition invariably crosscuts the architecture of a process-support system that composes available services. However, use of pre-defined process variations may bias the tailoring effort and thus, act against the original motivation of having a flexible definition. On the other hand, the characteristics of process complexity and tailorability introduce differences between stakeholder understanding of the process activities and their manifestation in tool support. We encounter these issues while developing a service-oriented process-support system for a security Certification and Accreditation (C&A) process. In this paper, we present our approach to effectively separate the C&A process definition from the architecture of its process-support system. We employ ontological modeling techniques to explicitly model the process definition and later expose it as a service to provide weaving rules for dynamically composing the process-support system architecture at runtime. The feasibility of our approach has been demonstrated in the design of a service-oriented architecture for a prototype workbench that supports the Department of Defense Certification and Accreditation Process (DITSCAP).
USING GENETIC ALGORITHM TO SOLVE MULTIPLE SEQUENCE ALIGNMENT PROBLEM
Authors: LAI CHIH-CHIN , WU CHIH-HUNG , HO CHENG-CHEN
Published: October 2009

Multiple sequence alignment (MSA) has become an important issue in computational molecular biology. The purpose of MSA is to infer evolutionary history or discover homologous regions among closely related DNA or protein sequences. A wide variety of approaches has been proposed for the MSA problem; however, some of them need prerequisites to find the best alignment or may suffer from the drawbacks of high computational complexity and huge memory requirement so they can be only applied to cases with a limited number of sequences. In this paper, we view the MSA problem as an optimization problem and resolve it by applying a genetic algorithm. In order to improve the search performance and obtain a better alignment quality, we design a few problem-specific genetic operators. Experimental results on real DNA and protein sequences are given to illustrate the feasibility of the proposed approach.
VERITAS: COMBINING EXPERT OPINIONS WITHOUT LABELED DATA
Authors: CHOLLETI SHARATH R. , GOLDMAN SALLY A. , BLUM AVRIM , POLITTE DAVID G. , DON STEVEN , SMITH KIRK , PRIOR FRED
Published: October 2009

We consider a variation of the problem of combining expert opinions for the situation in which there is no ground truth to use for training. Even though we do not have labeled data, the goal of this work is quite different from an unsupervised learning problem in which the goal is to cluster the data. Our work is motivated by the application of segmenting a lung nodule in a computed tomography (CT) scan of the human chest. The lack of a gold standard of truth is a critical problem in medical imaging. A variety of experts, both human and computer algorithms, are available that can mark which voxels are part of a nodule. The question is, how to combine these expert opinions to estimate the unknown ground truth. We present the Veritas algorithm that predicts the underlying label using the knowledge in the expert opinions even without the benefit of any labeled data for training. We evaluate Veritas using artificial data and real CT images to which synthetic nodules have been added, providing a known ground truth.
ONTOLOGICAL COGNITIVE MAP
Authors: CHAUVIN LIONEL , GENEST DAVID , LOISEAU STÉPHANE
Published: October 2009

A cognitive map model provides a graphical representation of an influence network between concepts. One drawback of this model is that large cognitive maps are difficult to exploit and understand. This paper introduces an ontological cognitive map model that enables the designer to organize concepts in an ontology. On the one hand, this model provides an ontological influence mechanism that shows the influence from any concept of the ontology to any other according to the map. The map is then easier to exploit. On the other hand, the ontology is used for providing a synthetical view of a map. The map is then easier to understand.
e-TOURISM: A TOURIST RECOMMENDATION AND PLANNING APPLICATION
Authors: SEBASTIA LAURA , GARCIA INMA , ONAINDIA EVA , GUZMAN CESAR
Published: October 2009

e-Tourism is a tourist recommendation and planning application to assist users on the organization of a leisure and tourist agenda. First, a recommender system offers the user a list of the city places that are likely of interest to the user. This list takes into account the user demographic classification, the user likes in former trips and the preferences for the current visit. Second, a planning module schedules the list of recommended places according to their temporal characteristics as well as the user restrictions; that is the planning system determines how and when to realize the recommended activities. Having the list of recommended activities organized as an agenda (i.e. an executable plan), is a relevant characteristic that most recommender systems lack.
GENERALIZED LATENT CLASS ANALYSIS BASED ON MODEL DOMINANCE THEORY
Authors: CHEN YIXIN , HUA DONG , LIU FANG
Published: October 2009

Latent class analysis is a popular statistical learning approach. A major challenge for learning generalized latent class is the complexity in searching the huge space of models and parameters. The computational cost is higher when the model topology is more flexible. In this paper, we propose the notion of dominance which can lead to strong pruning of the search space and significant reduction of learning complexity, and apply this notion to the Generalized Latent Class (GLC) models, a class of Bayesian networks for clustering categorical data.

GLC models can address the local dependence problem in latent class analysis by assuming a very general graph structure. However, The flexible topology of GLC leads to large increase of the learning complexity. We first propose the concept of dominance and related theoretical results which is general for all Bayesian networks. Based on dominance, we propose an efficient learning algorithm for GLC. A core technique to prune dominated models is regularization, which can eliminate dominated models, leading to significant pruning of the search space. Significant improvements on the model.
ATOMIC TUNNELING AND ENTANGLEMENT SUDDEN DEATH IN A DISSIPATIVE ATOM-CAVITY SYSTEM
Authors: SHEN J. , CHEN JIAO , WANG W. , YI X. X.
Published: October 2009

In this paper, we study the effect of atom decay on the atomic tunneling and entanglement dynamics in an atom-cavity system. This system consists of an atom trapped in a double-well potential and a cavity that couples to the atom. The population of the atom in the left/right well and the dynamics of entanglement are calculated and discussed. We find that the tunneling behaves as a damping-oscillating function of time, and the entanglement between the internal and external degree of freedom of the atom exhibits entanglement sudden death (ESD).
BOOK REVIEW: "QUIPS, QUOTES AND QUANTA — ANECDOTA, OR A PRIVATE HISTORY OF THE EARLY MODERN PHYSICS", BY A. Z. CAPRI
Authors: TERNO DANIEL R.
Published: October 2009

A review of A. Z. Capri, Quips, quotes and quanta (World Scientific, 2007).
ADAPTIVE FREQUENCY ESTIMATION WITH LOW SAMPLING RATES BASED ON ROBUST CHINESE REMAINDER THEOREM AND IIR NOTCH FILTER
Authors: LIANG HONG , LI XIAOWEI , XIA XIANG-GEN
Published: October 2009

In this paper, based on an adaptive IIR notch filter and a robust Chinese remainder theorem (CRT), we propose an adaptive frequency estimation algorithm from multiple undersampled sinusoidal signals. Our proposed algorithm can significantly reduce the sampling rates and provide more accurate estimates than the method based on adaptive IIR notch filter and sampling rates above the Nyquist rates does. We then present simulation results to verify the performance of our proposed algorithm for both stationary and nonstationary signals.
RECENT MATHEMATICAL DEVELOPMENTS ON EMPIRICAL MODE DECOMPOSITION
Authors: XU YUESHENG , ZHANG HAIZHANG
Published: October 2009

Building the mathematical foundation for the empirical mode decomposition is an important issue in adaptive data analysis. The task of building such a foundation consists of two stages. The first is to construct a large bank of basis functions for the time–frequency analysis of nonlinear and nonstationary signals. The second is to establish a fast adaptive decomposition algorithm. We survey recent mathematical progress on these two stages. Related results on piecewise linear spectral sequences and the Bedrosian identity are also reviewed.