bluuebunny/crossref_metadata_2025 huggingface dataset:
FEM Model for Pipeline Analysis of Ice Scour: A Critical Review
Authors: Konuk Ibrahim , Fredj Abdelfdettah
Published: January 2009

This paper presents results from two different Finite Element (FE) pipeline ice-scour models employing pipe and shell elements that incorporate large deformations and metal plasticity. The main objective of this paper is to investigate the effects and implications of some of the main pipeline design parameters on the response of the pipeline determined by using Winkler models and soil displacements that are based on an empirical scour function commonly used in recent literature. The current model is two dimensional in terms of deformed pipe geometry and incorporates temperature and pressure stiffness effects. A detailed study of the soil displacements underneath and around the scour and a three-dimensional continuum based ice-soil-pipe interaction model is being presented in a different paper. The paper discusses the limitations and implications of the Winkler modeling and compares results obtained using different Winkler spring models. It illustrates the effects of pipe temperature (and pressure), pipe burial depth, and scour width. A comparison of pipe response using shell and pipe elements is also presented. This paper presents results from the FE models for a typical gathering pipeline. The pipe is taken to be a 16 inch diameter and 0.75 inch wall thickness API 5L X65 Specification line pipe.
Innovative Structural Joint Tolerates High Rotational and Shear Overload
Authors: Khonsari S. V. , England G. L. , Parvinnia S. M. H. , Hajialiakbari-Fini E.
Published: January 2009

A new beam-to-column (horizontal brace-to-leg) and bracing-to-frame (diagonal brace-to-horizontal brace/leg) connection was developed. It is a comprehensive package in which the solution to all of the shortcomings and deficiencies of all conventional and/or commonly used connections is provided. The major deficiency of basically all the existing beam-to-column connections is their inability to deliver large rotations. In this devised connection, it has been solved by using a totally different geometry—a geometry which does not restrict the joint from deforming freely in a smooth, uniform and non-violent manner. Such mode of deformation, if delivered by a ductile material, should lead to a high energy dissipation capacity. Especially, if the ductility of the constituting material of the connection is not degraded as a result of fabrication operations, or if so, it is restored through practicing a suitable heat treatment process, e.g. annealing, the energy dissipation capacity should improve substantially. Moreover, in order to attract the damage and prevent it from spreading through the beam (bracing) and the column (leg), whose replacement is formidable, the connection should work in a ‘sacrificial’ capacity. This, together with making it ‘replaceable,’ will reduce the cost of aftermath repair substantially, while replacing the damaged beam or column, if possible, is very costly. In addition to its high rotational (bending) capacity, at least 6 times those of conventional joints (depending on the connection design), its ‘shear deformation capacity’ is quite considerable, absolutely incomparable with those of its conventional counterparts, which are virtually ‘nil.’ This connection is a ‘self-contained separate entity’ which comprises two parallel attachment plates between which two circular, or else, tubes are laid and fixed through welding, though alternatively the whole combination can be produced by extrusion. In the ‘original version’ of the connection, the two plates are laid in a parallel relation with the axis of bending, whereas in its ‘alternate version,’ they are laid in an orthogonal relation with the axis of bending. Tests carried out on specimens of the two distinct versions of the connection proved all its claimed characteristics, both in shear and bending. In particular, those carried out more recently, not reported in previous papers (OMAE’02-28264 & OMAE’03-37292), were quite revealing with regard to the ‘shear strength’ and the ‘shear deformation capacity’ of the original version (horizontally-laid-tube, HLT, version) of the connection—far beyond what was expected by the authors.
Efficient Time-Domain Model for Frequency-Dependent Added Mass and Damping
Authors: Kaasen Karl Erik , Mo Knut
Published: January 2009

In simulation of 1st-order wave-induced motion of vessels it is sometimes necessary to express frequency-dependent added mass and damping in time-domain formulation. One way to do this is to transform the frequency dependence into retardation functions. During simulation these are convolved with the velocity history, which is time-consuming and impractical. To get a more efficient model a method for expressing the retardation function as a linear differential equation has been developed. The method calculates the coefficients of the differential equation from the damping function only, avoiding the uncertain added mass function.
A Numerical Calculation of Hydrodynamic Forces on a Seagoing Ship by 3-D Source Technique With Forward Speed
Authors: Inoue Yoshiyiki , Kamruzzaman Md.
Published: January 2009

In this paper, the hydrodynamic forces of a surface ship advancing in waves at constant forward speed are numerically calculated by using the 3-D source distribution techniques. The paper also deals with the numerical calculations of free surface flow around an advancing ship in calm water as well as in waves. The body boundary condition is linearised about the undisturbed position of the body and the free surface condition is linearised about the mean water surface. The potential is represented by a distribution of sources over the surface of the ship and its waterline. The problem is solved by the method of singularities distributed over the hull surface. Hess & Smith method is used to obtain the density of these singularities. The numerical solution of the surface ship case is approximately obtained by considering the hull as a position of plane polygonal elements, bearing a constant singularity distribution. The velocity potential of any particular point in the free surface around the moving hull is determined by using the 3-D Green function with forward speed which satisfies the boundary conditions for a pulsating source in the fluid. Contours of wave patterns around moving surface ships are calculated from the velocity potential. The numerical accuracy of the computer code is firstly checked by calculating the velocity potential of a translating, pulsating unit source with arbitrary frequency and forward speed. Free surface wave patterns generated by a Wigley hull advancing with steady forward speed are calculated by using this code. Some corresponding hydrodynamic coefficients of heave and pitch modes for the Wigley hull has been calculated. Exciting forces and motion amplitudes are also investigated. The numerical result of this code is validated by comparing the calculated results with the experimental ones and those calculated by other methods. From the comparison, the results predicted by the present calculations are found in fairly good agreement with the experiment. Finally, the effects of motion amplitude on the free surface elevation are analyzed. These will be helpful for the accurate estimation of sea keeping problems for a ship advancing in waves.
A Study on the Weld Bead Characteristics in Pulsed Gas Metal Arc Welding With Rotating Arc
Authors: Rao P. Srinivasa , Gupta O. P. , Murty S. S. N.
Published: January 2009

Pulsed Gas Metal Arc Welding is widely used in industries because of its high productivity. The bead geometry obtained in welding steel is far from ideal and needs to be improved. It is experimentally observed that the beads are either convex or the penetration is deep and narrow. Both these conditions are undesirable. Proper selection of pulse parameters can improve the wetting, but the penetration remains finger type penetration. An arc rotation mechanism is developed which can be adapted to any conventional GMA welding torch. The beads deposited with rotating arc are flat and the penetration is semi-circular. It is observed that the penetration is maximum only at a particular rotating arc speed.
The Phased Array Inspection of Friction Stir Welded Aluminium Plant
Authors: Bird C. R. , Kleiner D.
Published: January 2009

Friction stir welding (FSW) is a relatively new welding process compared to electron beam or arc welding. Unlike most other welding processes there is no liquid state for the weld pool. For this reason the potential defect types present within the weld are quite different from conventional welding defects such as voids or lack of fusion. These can still be present, but defects such as slag or hot tearing due weld pool shrinkage cannot. Other defects more akin to those associated with resistance welding (joint line remnants) are more likely and can be more serious. TWI has run and taken part in a number of projects including the European “Qualistir” project lead by R/D-tech. The object of these projects was to develop a reliable inspection method for determining the quality of FSW in a butt and lap welded configurations. This paper describes the novel method developed by TWI for the detection of the joint line remnant defects. The paper describes the use of back scattered noise analysis for determining whether the weld has been correctly forged and whether the metallurgical structure indicates a good weld. Further to the difficult FSW specific flaws the paper also describes how the inspection procedure detects the more conventional defects.
Comparison of Historical and Deductive Methods for the Calculation of Low-Probability Seastates in the Gulf of Mexico
Authors: Toro Gabriel R. , Cornell C. Allin , Cardone Vincent J. , Driver David B.
Published: January 2009

Historical methods are typically used to determine the 100-year seastates used in traditional design practice. In these methods, one fits a probability distribution to the historical record of Hs and wind speed. With the development of more rational design standards, interest has shifted to rare events-with annual exceedence probabilities of 10−4 or lower. If one uses historical methods to determine the seastates associated with these probabilities, one typically encounters high uncertainties as a result of limited sample size and modeling uncertainty associated with the choice of distribution shape. This paper presents the results from Phase-I of an industry-sponsored project aimed at the development of more reliable methods for the calculation of seastates (particularly Hs) associated with rare probabilities. These methods construct deductive (or physically based) probabilistic models of the storm characteristics and their effects, and then use these models (together with the laws of probability theory) to calculate the probabilities of rare seastates. The objective of this first (exploratory) phase was to develop and apply a deductive model for hurricanes affecting platform sites in the western Gulf of Mexico, compare the predictions of this model to those of the historical approach, investigate and compare the uncertainties in both approaches, and explore other benefits of using the deductive method. For the sake of efficiency and internal consistency, a simple parametric-hindcast method was used for both the deductive and historical approaches. Results from this project indicate that the deductive and historical methods predict identical values of Hs for annual exceedence probabilities of 10−2 per year. For lower probabilities (particularly for 10−4), the predictions by the deductive method are within the range of predictions by the historical method using different assumptions about distribution shape. The statistical uncertainty of the deductive method is comparable to that of the historical method (if the latter uses pooled data coming from the entire static region). If no pooling is performed with the historical method, the uncertainty in the deductive method is lower. In addition, the deductive method shows less sensitivity to distribution-shape assumptions. This paper also summarizes ongoing efforts to adapt the deductive approach to extra-tropical storms in the North Sea — which have more complicated wind fields than hurricanes — and to the entire Gulf of Mexico — with the associated geographical variation in storm rate and characteristics.
Effect of Loading Frequency on Fatigue Performance of Risers in Sour Environment
Authors: Buitrago Jaime , Weir Michael S. , Kan Wan C. , Hudak Stephen J. , McMaster Fraser
Published: January 2009

ExxonMobil requires experimental verification of fatigue performance of fracture-critical risers designed for sour environments. Interaction between the sour environment and cracks in welded risers affects the crack-growth rate and, thus, the fatigue performance of the risers. Therefore, when conducting tests on riser welds in a sour environment, the frequency at which cyclicloads are applied during testing is critical to properly capturing the physio-chemical reactions and diffusion processes at the crack tip. Unfortunately, the load frequencies required to properly capture these effects are much lower than those currently used in cost-effective, resonant fatigue testing in air. Depending on the material, sour environment composition, and loading regime, testing at too high a frequency can eliminate the potential deleterious effects of the environment acting on the riser. Yet, testing at too low a frequency may not be practical. In order to determine the most efficient but technically valid load frequency to be used in a fatigue qualification testing program, a novel experimental screening methodology has been devised and implemented. In this paper, the proposed methodology is discussed and the results of a pilot test program conducted with C-Mn steel in a mildly sour environment are presented. For the particular sour brine, C-Mn steel and loading regime, it was found that the loading frequency could be increased up to about 1Hz, thereby making the fatigue verification tests more practical and cost-effective than the 1/3Hz currently used.
Real-Time Ultrasonic Characterization of Fluids and Slurries: Process Techniques Applicable in the Offshore Environment
Authors: Bamberger Judith Ann , Bond Leonard J. , Greenwood Margaret S.
Published: January 2009

In the harsh environment of the world’s oceans instrumentation must be robust and able to operate unattended for long periods of time. Ultrasonic sensors developed and deployed to characterize physical properties of radioactive waste slurries provide a unique robust method for non-invasively characterizing multiphase pipe flows, such as crude oil extracted in the ocean environment and transported via pipeline to tankers or to shore. Transducers mounted in spool pieces, or for large tanks and vessels mounted on the wall or suspended in the fluid, can be used to measure fluid or slurry density, solids concentration, rheology, viscosity, detect changes in particle size and detect interfaces, such as those between air and oil and oil and water.
Design, Fabrication, Testing, and Fuzzy Modeling of a Large Magnetorheological Damper for Vibration Control in a Railcar
Authors: Atray Vipul S. , Roschke Paul N.
Published: January 2009

This paper presents the procedure used for design, fabrication, testing, and numerical modeling of a magnetorheological (MR) damper that is to be applied for vibration control in a 70-ton railcar. MR dampers are semiactive vibration control devices whose damping characteristics can be modified in real time by varying an applied current. Design parameters for the MR damper are estimated from those exhibited by a linear viscous damper that exerts the necessary force required to limit vertical vibrations of the rail truck within acceptable limits. An MR damper is fabricated by modifying the piston of a standard hydraulic damper to function as a solenoid. The assembled MR damper is tested in a uniaxial testing machine by subjecting it to sinusoidal and random displacements while simultaneously varying the current flowing in the solenoid. A variable magnetic field is applied to the MR fluid that fills the damper cavity and the resisting force exerted by the damper is recorded. Data collected in the laboratory are used to train a fuzzy model of the MR damper that characterizes its behavior. Results indicate that a fuzzy model of the MR damper can predict its behavior with a sufficient degree of accuracy while requiring minimal computational time.
Study of Cubic Splines and Fourier Series as Interpolation Techniques for Filling in Short Periods of Missing Building Energy Use and Weather Data
Authors: Baltazar Juan-Carlos , Claridge David E.
Published: January 2009

A study of cubic splines and Fourier series as interpolation techniques for filling in missing data in energy and meteorological time series is presented. The followed procedure created artificially missing points (pseudo-gaps) in measured data sets and was based on the local behavior of the data set around those pseudo-gaps. Five variants of the cubic spline technique and 12 variants of Fourier series were tested and compared with linear interpolation, for filling in gaps of 1 to 6 hours of data in 20 samples of energy use and weather data. Each of the samples is at least one year in length. The analysis showed that linear interpolation is superior to the spline and Fourier series techniques for filling in 1–6 hour gaps in time series dry bulb and dew point temperature data. For filling 1–6 hour gaps in building cooling and heating use, the Fourier series approach with 24 data points before and after each gap and six constants was found to be the most suitable. In cases where there are insufficient data points for the application of this approach, simple linear interpolation is recommended.
Operational Performance of a 5 kW Solar Chemical Reactor for the Co-Production of Zinc and Syngas
Authors: Kra¨upl Stefan , Steinfeld Aldo
Published: January 2009

We report on the improved operational performance and energy conversion efficiency of a 5 kW solar chemical reactor for the combined ZnO-reduction and CH4-reforming “SynMet” process. The reactor features a pulsed vortex flow of CH4 laden with ZnO particles, which is confined to a cavity-receiver and directly exposed to solar power fluxes exceeding 2000 kW/m2. Reactants were continuously fed at ambient temperature, heated by direct irradiation to above 1350 K, and converted to Zn(g) and syngas during mean residence times of 10 seconds. Typical chemical conversion attained was 100% to Zn and up to 96% to syngas. The thermal efficiency was in the 15–22% range; the exergy efficiency reached up to 7.7% and may be increased by recovering the sensible and latent heat of the products. The Synmet process avoids emissions of greenhouse-gases and other pollutant derived from the traditional fossil-fuel-based production of zinc and syngas, and further converts solar energy into storable and transportable chemical fuels.
Measurement of High Thermodynamic Temperatures in the DLR Solar Furnace by UV-B Detection
Authors: Rohner Nicola , Neumann Andreas
Published: January 2009

The correct selection of the operating wavelength is essential for a precise pyrometric temperature measurement on solar irradiated samples, as the measurement may be disturbed by reflected solar radiation. Atmospheric conditions and particularly the emissivity as basic material property determine the amount of this reflected and the emitted radiation from a sample under investigation. An approach to solve this problem by using a monochromator system for temperature measurement in the UV-B range was developed and experimentally tested. With this system, temperature measurements were possible beginning at 1320°C and ranging up to about 2400°C. Two calculation methods are described and compared. The influence of the calibration temperature on the quality of the temperature measurement is shown. Measurements on a blackbody up to 1500°C were performed for calibration purpose. Temperature measurements on a real solar heated magnesia sample up to 2400°C are presented and discussed. These spectral measurements on hot bodies irradiated in the DLR Solar Furnace led to the final specification of the measurement wavelengths to be in the range from 280 nm to 293 nm.
Solar Chimney Turbine: Part 2 of 2 — Experimental Results
Authors: Gannon Anthony J. , von Backstro¨m Theodore W.
Published: January 2009

An experimental investigation of a solar chimney turbine design is undertaken. The aim of the program is to demonstrate and evaluate a proposed solar chimney turbine design. The measured results of an experimental model turbine are presented and the turbine efficiency calculated. The current turbine design has a total-to-total efficiency of 85–90% and total-to-static efficiency of 77–80% over the design range. Secondary objectives are to compare the measured and predicted results and through investigation of the experimental results suggest improvements to the turbine design.
A Design of Crowning to Reduce Ball Passage Vibrations of a Linear Guideway Type Recirculating Linear Ball Bearing
Authors: Ohta Hiroyuki , Kato Soichiro , Matsumoto Jun , Nakano Kenta
Published: January 2009

This paper deals with a design of crowning to reduce the ball passage vibrations of a linear guideway type recirculating linear ball bearing (linear bearing) with the crowning length LC (1.2s ≤ LC ≤ 1.7s, where s is the distance between the adjacent balls in the load zone). First, a fundamental condition to reduce the ball passage vibrations is provided. Second, a design method of the crowning by applying an approximate curve (an assumed functional formula) to the control points (satisfying the fundamental condition or being the intersection of straight and crowning areas of a raceway) is presented. Third, the design procedure is explained by giving an example. In the design example the power function crowning fits the control point best. In addition, the calculated amplitude for the power function crowning is lower than those for the circular arc crowning and the crowning of the commercial linear bearing. Finally, the validity of the presented design method is confirmed experimentally.
Enhancing Tribological Conditions in Tube Hydroforming by Using Textured Tubes
Authors: Ngaile Gracious , Gariety Mark , Altan Taylan
Published: January 2009

The effects of textured tubes on the tribological performance in Tube Hydroforming (THF) are discussed. Textured surfaces, namely sand blasted, knurled, and as rolled surfaces were tested under various interface pressure and sliding velocity conditions. Sand blasted textured tubes were found to have the best tribological performance. It was also found that the interface pressure has a great influence on the attainment of Micro-Plasto HydroDynamic Lubrication (MPHDL) and Micro-Plasto HydroStatic Lubrication (MPHSL) conditions at the tool-workpiece interface. Preliminary finite element simulations on the deformation behavior of tube surface shows that surface textures can be optimized to enhance tribological performance.
Probabilistic Designs of Air-Bearing Surface on Manufacturing Tolerances
Authors: Yoon Sang-Joon , Choi Dong-Hoon
Published: January 2009

The focus in this paper is to automatically design the air-bearing surface (ABS) considering the randomness of its geometry as an uncertainty of design variables. Designs determined by the conventional optimization could only provide a low level of confidence in practical products due to the existence of uncertainties in either engineering simulations or manufacturing processes. This calls for a reliability-based approach to the design optimization, which increases product or process quality by addressing randomness or stochastic properties of design problems. In this study, a probabilistic design problem is formulated considering the reliability analysis which is employed to estimate how the fabrication tolerances of individual slider parameters affect the final flying attitude tolerances. The proposed approach first solves the deterministic optimization problem. Beginning with this solution, the reliability-based design optimization (RBDO) is continued with the probabilistic constraints affected by the random variables. Probabilistic constraints overriding the constraints of the deterministic optimization attempt to drive the design to a reliability solution with minimum increase in the objective. The simulation results of the probabilistic design are directly compared with the values of the initial design and the results of the deterministic optimum design, respectively. In order to show the effectiveness of the proposed approach, the reliability analyses by the Monte Carlo simulation are carried out. And the results demonstrate how efficient the proposed approach is, considering the enormous computation time of the reliability analysis.
Modeling and Simulation of Elastohydrodynamic Lubrication of Piston Skirts Considering Elastic Deformation in the Initial Engine Start-Up
Authors: Malik M. Afzaal , Rashid Badar , Qasim Syed Adnan , Khushnood Shahab
Published: January 2009

The presence of Elasto-hydrodynamic Lubrication (EHL) film between opposing piston and liner surfaces prevents possible solid-to-solid contact and wear. This enhances engine life manifold as compared to when the EHL film is non-existent in the initial engine startup or breaks down during normal engine operation. Forced dry sliding of piston during engine cranking followed by partial lubrication in the initial engine startup leads to adhesive wear. This research investigates the possibility of an EHL film on such an occasion by considering elastic deformation of opposing piston skirt and liner surfaces due to Elasto-hydrodynamic (EHD) pressures. The geometry of piston skirts is defined and governing equations are applied to determine hydrodynamic pressures. The EHL film thickness profile generated by inverse solution technique and its expression is defined by incorporating contact geometry and EHD pressures in the piezoviscous regime. A computer code is developed and used to simulate the performance parameters and their behavior during initial engine startup. Due to critical factors such as engine speed, redial clearance between piston skirts and liner and lubricant viscosity, a time dependent 2-D EHL film profile is generated. The simulated results indicate that, despite piston eccentricities due to secondary oscillatory motion, EHL film established between the opposing piston skirts and liner surfaces prevented possible solid-to-solid contact in the entire duration of 720-degree crankshaft rotation, which corresponds to four piston strokes.
Thin Oil Film Volatility and Its Mechanism
Authors: Zou Q. , Vijayakumar S.
Published: January 2009

The evaporation loss of lubricating oils is an issue of particular importance in lubrication. It is known that the volatility of oil has a significant effect on oil consumption. Portions of oil can evaporate under high temperature conditions, potentially altering oil properties such as viscosity. In this paper, the volatility of the thin oil films was studied. Different kinds of oils were used for the test. The work was to investigate the effect of the different working conditions on the volatility of lubricating oil. Conditions such as the oil film thickness, contacting surface area and the surface material were studied. Encouraging results were obtained with respect to the effect of working conditions on the volatility of thin oil films. This emphasizes that the working conditions play a significant role in the evaporation rate and an appropriate set hand to be considered to minimize the loss.
The Use of System Identification Methods to Evaluate the Effects of Slider-Disk Contacts and Disk Micro-Waviness on the Flying Height Modulations
Authors: Deoras Saurabh , Talke Frank E.
Published: January 2009

System identification methods have been used to study the response of a magnetic recording slider during contact with a scratch on the disk surface. In addition, the slider response was studied taking into account the effect of disk micro-waviness at various disk rotational speeds. The simulated slider response was compared with the measured slider dynamic behavior. Very good agreement was found between simulated and measured data. The flying height modulation of the slider, due to disk micro-waviness, was found to depend on disk velocity.
Theoretical and Experimental Investigations Into Spacing Characteristics Between Roller and Three Types of Webs With Different Permeabilities
Authors: Hashimoto H. , Okajima M.
Published: January 2009

A new theoretical model for estimating the entrained air film thickness between a web and roller is presented for both impermeable and permeable webs. A simple closed-form formula for estimating the air film thickness, which considers the effects of air leakage from the web edges and air diffusion due to the permeability of web, was obtained based on a large number of simultaneous numerical solutions of the compressible Reynolds equation and the web equilibrium equation. The variation of air film thickness with roller velocity is measured for three typical webs: PET (polyethylene terephthalate), coated paper, and newsprint. The effects of web permeability, web width and web tension on the air film thickness are examined theoretically and experimentally for a wide range of roller velocity. Reasonable agreement is seen both quantatively and qualitatively between the predicted and measured results. The validity of the formula for the first order estimation of web-roller interface problems is verified experimentally.
Nanomechanical and Nanotribological Properties of an Antiwear Tribofilm Produced From Phosphorus-Containing Additives on Boundary-Lubricated Steel Surfaces
Authors: Komvopoulos K. , Do V. , Yamaguchi E. S. , Ryason P. R.
Published: January 2009

Nanoindentation and nanotribological experiments were performed on an antiwear tribofilm produced from a blend consisting of gear base oil and phosphorus-containing additive. Electrical contact resistance measurements were used to determine in situ the formation of the tribofilm on AISI steel surfaces at 100 °C under conditions favoring sliding in the boundary lubrication regime. Nanoindentation experiments were carried out with a surface force microscope on a small sector of a disk specimen that contained part of the wear track. A Berkovich diamond tip with a nominal radius of curvature equal to 100 mm was used to perform indentations on and off the wear track under a normal load between 100 and 600 μN. The phosphate tribofilm exhibited an average hardness of 6.0 GPa and reduced elastic modulus of 122.7 GPa compared to 12.5 GPa and 217.6 GPa of the steel substrate, respectively. In addition to the nanomechanical properties, the nanotribological properties of the tribofilm were evaluated in light of nanofriction tests performed with a 20 μm radius of curvature conical diamond tip under a normal load in the range of 100–200 μN. The original steel surfaces exhibited constant friction, whereas the wear track covered by the phosphate tribofilm, whereas the wear track covered by the phosphate tribofilm revealed a higher and more fluctuating coefficient of friction, which is attributed to the roughness of the wear track and the greater plasticity of the tribofilm than the substrate.
On the Shear Bands and Shear Localizations in EHL Films
Authors: Chang L.
Published: January 2009

Liquid lubricants in elastohydrodynamic lubrication (EHL) are subjected to high pressures of the magnitude of 109 N/m2 (GPa). Under these high pressures, the lubricants in room temperatures are usually in the glassy state behaving as amorphous solids. Similar to the polymers, the lubricants exhibit elastic or visco-elastic behavior under low-shear-stress loading and plastic or visco-plastic behavior with high shear stresses. Recent laboratory experiments have revealed two types of localized shear responses that can take place in the lubricant bulk. The localized shear may be active in the EHL film and may play a significant role in the responses exhibited by the contact conjunction. A typical example is the EHL traction. This paper summarizes the up-to-date research related to the shear localizations.
Application of Optimization Approach to Static FE Analysis of HDD Slider
Authors: Hwang Pyung , Khan Polina V.
Published: January 2009

The objective of the present work is to present the numerical analysis of the computer hard disk slider. The pressure between slider and disk surfaces is calculated using the finite element method for the generalized Reynolds’ equation solution, with application of tabulated data for the flow rate coefficient. The search for the steady state attitude of the slider is formulated in terms of optimization and solved by a combination of the conjugate gradient method, method of feasible directions and quadratic curve fitting. The advantages of the perturbation method in static analysis are considered. The steady state attitude of the femto slider is studied for various radial positions and skew angles. The parameters having effect on the objective function Hessian matrix are studied for the purpose of improvement of the search process convergence rates.
Elastic Contact Stiffness and Contact Resistance for Fractal Profiles
Authors: Ciavarella M. , Barber J. R.
Published: January 2009

A recent theorem due to Barber shows an analogy between conductance and incremental stiffness of a contact, implying bounds on conductance based on peak-to-peak roughness. This shows that even a fractal roughness, with bounded amplitude, has a finite conductance. The analogy also permits a simple interpretation of classical results of rough contact models based on independent asperities such as Greenwood-Williamson and developments. For example, in the GW model with exponential distribution of asperity heights, the conductance is found simply proportional to load, and inversely proportional to a roughness amplitude parameter which does not depend greatly on resolution, contrary to parameters of slopes and curvatures. However, for the Gaussian distribution or for more refined models also considering varying curvature of asperities (such as Bush Gibson and Thomas), there is dependence on sampling interval and the conductance grows unbounded. An alternative choice of asperity definition (Aramaki-Majumdar-Bhushan) is suggested, which builds on the geometrical intersection of the rough surface, with the consequence of a finite contact area, and converging load-separation and load-conductance relationship. A discussion follows, also based on numerical results.
IMPLEMENTING HIRSCHBERG'S PRAM-ALGORITHM FOR CONNECTED COMPONENTS ON A GLOBAL CELLULAR AUTOMATON
Authors: JENDRSCZOK JOHANNES , HOFFMANN ROLF , KELLER JÖRG
Published: January 2009

The GCA (Global Cellular Automata) model consists of a collection of cells which change their states synchronously depending on the states of their neighbors like in the classical CA model. In differentiation to the CA model the neighbors are not fixed and local, they are variable and global. The GCA model is applicable to a wide range of parallel algorithms, and it can be implemented on reconfigurable hardware. We discuss the GCA implementation of PRAM algorithms on reconfigurable hardware (Field Programmable Gate Array, FPGA), exemplified by the algorithm of Hirschberg et al., which determines the connected components of a given undirected graph. We provide two implementations with different numbers of cells: one with maximum parallelism and a compact one. We compare the implementation complexities, i.e. number of FPGA cells of both implementations, and thus present experimental evidence of our claims. The GCA(N) algorithm uses 3n cells with time complexity O(n log n), whereas the GCA(N2) algorithm uses n(n + 1) cells with time complexity O( log 2 n). The GCA(N) algorithm is more economic with respect to resources (logic × execution time) whereas the GCA(N2) algorithm can produce the result faster with a speedup of O((n+m)/ log n). Further insights are that efficient mappings of PRAM algorithms onto GCA exist, and that PRAM and GCA optimality criteria differ because the latter takes memory consumption into account. This makes the GCA a parallel computational model and an implementation platform, thus narrowing the gap between theory and practice.
PROFILE AND EXISTENCE OF SIGN-CHANGING SOLUTIONS TO AN ELLIPTIC SUBCRITICAL EQUATION
Authors: BEN AYED MOHAMED , GHOUDI RABEH
Published: January 2009

In this paper, we study the nonlinear elliptic problem involving nearly critical exponent (Pε) : Δ2 u = |u|(8/(n-4))-εu, in Ω, Δu = u = 0 on ∂Ω, where Ω is a smooth bounded domain in ℝn, n ≥ 5. We characterize the low energy sign-changing solutions (uε) of (Pε). We prove that (uε) are close to two bubbles with different signs and they have to blow up either at two different points with the same speed or at a critical point of the Robin function. Furthermore, we construct families of each kind of these solutions and we prove that the bubble-tower solutions exist in our case.
Family History, Genetic Testing, and Clinical Risk Prediction: Pooled Analysis of CHEK2*1100delC in 1,828 Bilateral Breast Cancers and 7,030 Controls
Authors: Fletcher Olivia , Johnson Nichola , dos Santos Silva Isabel , Kilpivaara Outi , Aittomäki Kristiina , Blomqvist Carl , Nevanlinna Heli , Wasielewski Marijke , Meijers-Heijerboer Hanne , Broeks Annegien , Schmidt Marjanka K. , Van't Veer Laura J. , Bremer Michael , Dörk Thilo , Chekmariova Elena V. , Sokolenko Anna P. , Imyanitov Evgeny N. , Hamann Ute , Rashid Muhammad U. , Brauch Hiltrud , Justenhoven Christina , Ashworth Alan , Peto Julian
Published: January 2009

If breast cancers arise independently in each breast the odds ratio (OR) for bilateral breast cancer for carriers of CHEK2*1100delC should be ∼5.5, the square of the reported OR for a first primary (OR, 2.34). In the subset of bilateral cases with one or more affected relatives, the predicted carrier OR should be ∼9. We have tested these predictions in a pooled set of 1,828 cases with 2 primaries and 7,030 controls from 8 studies. The second primary OR for CHEK2*1100delC carriers was 6.43 (95% confidence interval, 4.33-9.56; P < 0.0001), significantly greater than the published estimate for a first primary (P < 0.001) but consistent with its square. The predicted increase in carrier OR with increasing numbers of affected relatives was seen using bilateral cases from the UK (Ptrend = 0.0003) and Finland (Ptrend = 0.37), although not using those from the Netherlands and Russia (P = 0.001 for heterogeneity between countries). Based on a standard genetic model, we predict lifetime risks for CHEK2*1100delC carrier and noncarrier daughters of bilateral breast cancer cases of 37% and 18%, respectively. Our results imply that clinical management of the daughter of a woman with bilateral breast cancer should depend on her CHEK2*1100delC carrier status. This and other moderate penetrance breast cancer susceptibility alleles, together with family history data, will thus identify increasing numbers of women at potentially very high risk. Before such predictions are accepted by clinical geneticists, however, further population-based evidence is needed on the effect of CHEK2*1100delC and other moderate penetrance alleles in women with a family history of breast cancer. (Cancer Epidemiol Biomarkers Prev 2009;18(1):230–4)
Aldehyde Dehydrogenase 2 and Head and Neck Cancer: A Meta-analysis Implementing a Mendelian Randomization Approach
Authors: Boccia Stefania , Hashibe Mia , Gallì Paola , De Feo Emma , Asakage Takahiro , Hashimoto Tomoko , Hiraki Akio , Katoh Takahiko , Nomura Takeshi , Yokoyama Akira , van Duijn Cornelia M. , Ricciardi Gualtiero , Boffetta Paolo
Published: January 2009

Alcohol drinking at high doses is a risk factor for head and neck cancer, and exposure to acetaldehyde, the principle metabolite of alcohol, is supposed to account for the increased risk. Individuals homozygous for the *2 variant allele of aldehyde dehydrogenase 2 (ALDH2) are unable to metabolize acetaldehyde, which prevents them from alcohol drinking, whereas *1*2 have 6-fold higher blood acetaldehyde concentration postalcohol consumption with respect to *1*1. According to the concept of Mendelian randomization, because this polymorphism is distributed randomly during gamete formation, its association with head and neck cancer should be not confounded by smoking. We carried out a meta-analysis of ALDH2 and head and neck cancer searching for relevant studies on Medline and Embase up to January 31, 2008, and investigated the consistency between the expected odds ratio (OR) among drinkers from the largest pooled analysis among never smokers and the observed OR from this meta-analysis by an interaction test. Six studies were selected (945 cases, 2,917 controls). The OR of head and neck cancer among *2*2 was 0.53 [95% confidence interval (95% CI), 0.28-1.00] relative to *1*1 and 1.83 (95% CI, 1.21-2.77) among *1*2. The expected OR for head and neck cancer due to alcohol intake among *1*1 was 1.38 (95% CI, 0.88-2.17) and the observed OR among *1*1 compared with 2*2 from this meta-analysis was 1.88 (95% CI, 1.00-3.57; P for interaction = 0.43). Besides showing the effectiveness of the Mendelian randomization approach, these findings support the theory that alcohol increases head and neck cancer risk through the carcinogenic action of acetaldehyde. (Cancer Epidemiol Biomarkers Prev 2009;18(1):248–54)
Serum Undercarboxylated Osteocalcin as Biomarker of Vitamin K Intake and Risk of Prostate Cancer: A Nested Case-Control Study in the Heidelberg Cohort of the European Prospective Investigation into Cancer and Nutrition
Authors: Nimptsch Katharina , Rohrmann Sabine , Nieters Alexandra , Linseisen Jakob
Published: January 2009

From cell studies, Vitamin K is known to exert anticancer effects on a variety of cancer cell lines, including prostate cancer cells. Recently, we reported an inverse association between dietary intake of menaquinones (vitamin K2), but not phylloquinone (vitamin K1), and risk of prostate cancer. In this nested case-control study including 250 prostate cancer cases and 494 matched controls, we aimed to confirm this cancer-protective effect using serum undercarboxylated osteocalcin (ucOC), a biomarker of vitamin K status inversely associated with vitamin K intake. In addition, effect modification by a functionally relevant polymorphism in the vitamin K epoxide reductase gene (VKORC1) was assessed. Serum ucOC and intact total osteocalcin (iOC) were analyzed with the use of ELISA tests. Serum ucOC was expressed relative to iOC (i.e., as ucOC/iOC ratio). Conditional logistic regression was used to calculate multivariate adjusted odds ratios (OR) and 95% confidence intervals (95% CI). Serum ucOC/iOC ratio was positively associated with advanced-stage (OR per 0.1 increment, 1.38; 95% CI, 1.03-1.86) and high-grade prostate cancer (OR, 1.21; 95% CI, 1.00-1.46) but not with total prostate cancer. The significant association with advanced-stage prostate cancer was confirmed when serum ucOC/iOC ratio was jointly modeled with menaquinone intake data. There was indication of a lower prostate cancer risk in carriers of the A allele (compared with GG carriers) of the +2255 VKORC1 polymorphism with increasing menaquinone intake (Pinteraction = 0.14) whereas no distinct effect modification was observed for the ucOC/iOC ratio (Pinteraction = 0.37). The increased risks of advanced-stage and high-grade prostate cancer with higher serum ucOC/iOC ratio strengthen the findings for dietary menaquinone intake. (Cancer Epidemiol Biomarkers Prev 2009;18(1):49–56)
Menopausal Hormone Therapy and Risk of Colorectal Cancer
Authors: Johnson Jill R. , Lacey James V. , Lazovich DeAnn , Geller Melissa A. , Schairer Catherine , Schatzkin Arthur , Flood Andrew
Published: January 2009

We evaluated colorectal cancer risk associated with the duration and recency of specific menopausal hormone therapy formulations (i.e., unopposed estrogen versus estrogen plus progestin) and regimens (i.e., sequential versus continuous estrogen plus progestin use) among 56,733 postmenopausal women participating in the Breast Cancer Detection Demonstration Project follow-up study. Hormone therapy use and other risk factors were ascertained through telephone interviews and mailed questionnaires from 1979 to 1998. The final cancer group included 960 women who were identified from self-report, medical records, state registry data, and the National Death Index. Poisson regression was used to generate multivariable rate ratios (RR) and 95% confidence intervals (95% CI). We observed a decreased risk of colorectal cancer among ever users of unopposed estrogen therapy (RR, 0.83; 95% CI, 0.70-0.99). Among estrogen users, the largest reduced risk was observed for current users (RR, 0.75; 95% CI, 0.54-1.05) and users of ≥ten years duration (RR, 0.74; 95% CI, 0.56-0.96). We found a reduced risk among users of estrogen plus progestin therapy (RR, 0.78; 95% CI, 0.60-1.02), with sequential regimen users (progestin <15 days per cycle) having the largest risk reduction (RR, 0.64; 95% CI, 0.43-0.95). Past users of ≥5 years ago (RR, 0.55; 95% CI, 0.32-0.98) had the largest risk reduction. In this study, estrogen plus progestin use, especially sequential regimen use, was associated with the largest overall reduction of colorectal cancer risk. (Cancer Epidemiol Biomarkers Prev 2009;18(1):196–203)
Genetic Polymorphisms ofCYP2E1and Risk of Colorectal Cancer: The Fukuoka Colorectal Cancer Study
Authors: Morita Makiko , Le Marchand Loïc , Kono Suminori , Yin Guang , Toyomura Kengo , Nagano Jun , Mizoue Tetsuya , Mibu Ryuichi , Tanaka Masao , Kakeji Yoshihiro , Maehara Yoshihiko , Okamura Takeshi , Ikejiri Koji , Futami Kitaroh , Maekawa Takafumi , Yasunami Yohichi , Takenaka Kenji , Ichimiya Hitoshi , Imaizumi Nobutoshi
Published: January 2009

Cytochrome P450 2E1 (CYP2E1) is involved in the metabolic activation of a wide variety of potential carcinogens, and functional polymorphisms in the CYP2E1 gene have been investigated in relation to colorectal cancer. We examined the relation of the CYP2E1 RsaI and 96-bp insertion polymorphisms to colorectal cancer risk and the interaction between these polymorphisms and some lifestyle risk factors. Subjects were 685 incident cases of colorectal cancer and 778 community controls. Statistical adjustment was made for alcohol use, body mass index, physical activity, and other factors. The RsaI c2 allele was associated with a decreased risk of rectal cancer [adjusted odds ratio for at least one c2 allele, 0.71; 95% confidence interval (95% CI), 0.53-0.95], and an increased risk of rectal cancer was observed among individuals having one or two 96-bp insertion alleles (adjusted odds ratio, 1.40; 95% CI, 1.06-1.85). Individuals with two 96-bp insertion alleles showed a 2.28-fold increase in colon cancer risk (95% CI, 1.29-4.01). The two polymorphisms were in almost complete linkage disequilibrium (D′ = 0.94). A positive association between alcohol intake and colorectal cancer was observed only in individuals without RsaI c2 allele (Ptrend = 0.03) or in those without 96-bp insertion allele (Ptrend = 0.009). Colon cancer risk was increased in relation to red meat intake only in individuals having one or two 96-bp insertion alleles (Pinteraction = 0.03). The present study suggests that variation in activity and inducibility of CYP2E1, in relation to alcohol or red meat intake, contributes to the development of colorectal cancer. (Cancer Epidemiol Biomarkers Prev 2009;18(1):235–41)