bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Nonlinear Dynamic Behavior of a Typical Jacket Type Platform Under Environmental Loading (Wave and Current) and Blast Overpressure
Authors: Dousti M. , Gharabaghi A. R. M. , Chenaghlou M. R.
Published: January 2009

In this paper the behavior of a jacket platform, which is installed in Persian Gulf under blast overpressure, is evaluated and interaction between blast and operating environmental wave and current loads is studied. Using finite element software the whole parts of platform, which include topside and jacket sections are modeled. The real pressure of blast load is applied for conducting the analyses. The study involves elastic and elasto-plastic analyses, which in the last one (elasto-plastic) the geometry and material nonlinearity have been considered. In the studied platform the results show that the interaction between blast and operating environmental wave and current loads is negligible but the comparison between two models, the one in which the whole parts of platform are modeled and the other one which only topside is modeled indicates that there are appreciable differences between the axial plastic strains.
The Effect of the Reeling Laying Method on the Collapse Pressure of Steel Pipes for Deepwater
Authors: Pasqualino Ilson P. , Silva Silvia L. , Estefen Segen F.
Published: January 2009

This work deals with a numerical and experimental investigation on the effect of the reeling installation process on the collapse pressure of API X steel pipes. A three-dimensional nonlinear finite element model was first developed to simulate the bending and straightening process as it occurs during installation. The model is then used to determine the collapse pressures of both intact and plastically strained pipes. In addition, experimental tests on full-scale models were carried out in order to calibrate the numerical model. Pipe specimens are bent on a rigid circular die and then straightened with the aid of a custom-made test facility. Subsequently, the specimens are tested quasi-statically under external pressure until collapse in a pressure vessel. Unreeled specimens were also tested to complete the database for calibrating the numerical model. The numerical model is finally used to generate collapse envelopes of reeled and unreeled pipes with different geometry and material.
Springing Analysis of Elastic Vessels in Head and Oblique Seas Including Nonlinear Effects Due to Second Order Diffraction Pressures
Authors: He Haiping , Troesch Armin W. , Shin Yung Sup , Kim Boo-Ki
Published: January 2009

The wave-induced vibration of the ship hull, commonly called springing, may not produce extreme stresses, but it is likely to have a direct effect on fatigue-life estimates due to its high frequency content. This research investigates the second order contribution to the springing bending moment from the sum frequency of incident ocean waves in both head and oblique seas. The computer program developed here extends the ABS SSRS (Ship Spring Response System) program to oblique seas using Troesch’s oblique sea linear diffraction theory [1]. The theoretical calculations for forward speed are modified by an empirical factor to correlate more closely with experimental results. An example calculation on a Bulk Carrier was performed for different heading angles. For one such representative sea state, the overall increase to the total bending moment from the nonlinear, sum-frequency excitation is found to be less than 12%. However, the nonlinear springing (RMS) increases the total RMS springing over the linear springing by more than 5 times in some stations, which has significant implications for fatigue studies. A sea state sweep study (using ITTC spectrum) also shows the springing effects are highly sea state dependent. Overall, springing effects decrease as zero crossing periods increase, which indicates springing is important in sea states with short waves and becomes less significant in sea states with long waves.
Stability Criteria and Analysis of a Monocolumn Concept
Authors: de Campos Felipe Cruz Rodrigues , Cueva Marcos , Nishimoto Kazuo , Dos Santos Costa Ana Paula
Published: January 2009

To be classified and approved by a classification society, all offshore structures shall be submitted and analyzed according to standard rules. The stability criteria are based on the IMO–MODU (International Maritime Organization–Mobile Offshore Drilling Units) Code which has reference to almost all types of floating units such as surface, column-stabilized and self elevating, but problems were found when dealing with monocolumn concept due to differences between this concept and those presented by the rules. The monocolumn studied is a floating production system (FPS) platform designed to handle steel catenary risers (SCR) in a depth of 1800 m in Brazilian oil fields. In this project, special concern was given to sea keeping behavior, constructability and security. This paper discusses the last item, focusing on subdivision and stability analysis. In order to overcome difficulties in finding the appropriate criteria, the work was developed using a special criteria, discussed with Det Norske Veritas (DNV) and PETROBRAS, which could be implanted in future classifications for this type of hull.
Predictions and Model Tests of an SCR Undergoing VIV in Flow at Oblique Angles
Authors: Moe Geir , Teigen Torbjo̸rn , Simantiras Paolo , Willis Neil , Lie Halvor
Published: January 2009

The paper describes how an existing computer code, VICoMo, see Moe & Arntsen (2002), has been extended to analyse Vortex Induced Vibrations (VIV) of SCR’s for situations in which the flow is neither in the plane of the riser, nor perpendicular to it. Various strategies were attempted in order to make the solution deal with flows at oblique angles. It was found that the best approach was to assume that the riser motions occurred in plane perpendicular to the flow, while motions in the flow direction were disregarded. One source of uncertainty is associated with the empirical database in VICoMo which is based on tests in which the flow was perpendicular to the riser elements. The timeseries from the experiment showed large temporal variations. Actually the average motions amplitudes at given points may be as low half of the maximum value. Also the largest amplitudes at different points on the experimental envelope on the riser will usually have been reached at quite different times. These features were not included in the theoretical model, and made direct comparisons between predictions and measurements difficult. We ended up comparing the envelopes of motion response. In several of the cases the predictions matched the experiments closely, for frequency, modeshape as well as amplitudes. In other cases the match was somewhat less satisfactory, however.
Effect of Skirt-Tip Geometry on Set-Up Outside Suction Anchors in Soft Clay
Authors: Andersen Knut H. , Andresen Lars , Jostad Hans Petter , Clukey Edward C.
Published: January 2009

An important part of suction anchor design is the determination of the shear strength along the outside skirt wall. Previous work has suggested that when a suction anchor in clay is installed by applying underpressure inside the anchor, the external skin friction may be reduced compared to the skin friction expected for driven piles. The primary reason for this reduction is that the movement of soil at and beneath the caisson tip during installation will be influenced by whether the anchor is penetrated by weight or by underpressure. To further investigate the impact of installation by underpressure, additional finite element analyses have been performed where the skirt installation process has been better followed than in the previous analyses. The movement of soil around the caisson wall was studied for both a flat caisson tip and a tip with a tapered edge of 45° towards the outside of the anchor. The tapering was made to see if it would cause more of the displaced soil to move outside the anchor and thereby increase the mean total stresses and the shear strength along the outside anchor wall. The analyses were made with two separate wall roughness factors for a typical anchor in soft clay.
Industrial Implementation of Risk Based Inspection Planning Lessons Learnt From Experience: Part 1 — The Case of FPSOs
Authors: Goyet Jean , Rouhan Antoine , Faber Michael Havbro
Published: January 2009

This paper is the first part of a report dealing with industrial implementation of Risk Based Inspection planning methods to offshore facilities. The first part deals with FPSO/FSO while the second deals with fixed steel offshore structures. The objective of the report is to convey “lessons learned” from experience using RBI methods. Theses methods aim at establishing inspection planning based on optimization procedures derived from specific risk assessments. Experience of the three authors is based on the last methodological developments in the area of RBI planning for structural components subject to fatigue degradation and on application of these methods to various types of offshore facilities. The main steps of the RBI methodology are summarized in the first paper. General conclusions related to the two types of facilities are given at the end of the second paper.
Estimations of the T-Stress for Small Cracks at Notches
Authors: Wang Xin , Bell Robert , Lambert Steve
Published: January 2009

The T-stress is increasingly being recognized as an important additional stress field characterizing parameter in the analysis of cracked bodies. Using T-stress as the constraint parameter, the framework of failure assessments including the constraint effect has been established; and the effect of T-stress on fatigue crack propagation rate has been investigated by several researchers. In this paper, a simple method for determining the T-stress for small notch-emanating cracks is presented. First, the background on the T-stress calculation using the superposition principle and the similarities between the elastic notch tip stress fields described by two parameters: the stress concentration factor and the notch-tip radius, are summarized. Then, the method of estimating T-stress for both short and long cracks at the notches is presented. The method is used to predict T-stress solutions for edge notched plates under remote tension with cracks emanating from the notches. A wide range of notch and crack geometries are considered and the results are compared to the available T-stresses solutions in the literature. Good agreements have been achieved. The method presented here can be used for a variety of notch crack geometries.
Extended Bayesian Estimation of Directional Wave Spectra
Authors: Iseki Toshio
Published: January 2009

The Bayesian modelling procedure has been extended to estimate time-varying directional wave spectra. In the proposed method, the hull of a ship is regarded as a wave sensor and the time history data of ship motions is analyzed to evaluate cross spectra. In this concept, a special attention should be paid to changes of the directional wave spectrum because the ship is moving and the location at sea is changing continuously. Therefore, the extended Bayesian estimation is based on the cross spectra evaluated at different times and the fluctuation of wave spectrum is taken into account. In order to examine the reliability of the proposed method, data of onboard experiments were analyzed. Comparisons between the results of the proposed method and visual observations show good agreements.
Water Waves and Marine Structure Interaction
Authors: Sado´ Garriga Octavi , Falzarano Jeffrey M.
Published: January 2009

The purpose of this paper is to combine and extend existing potential flow theory in order to analyze the linear free surface problem of an Oscillating Water Column (OWC) device and apply it to moonpool design. Analytical results were obtained implementing the previously derived theories, and later compared to experimental results conducted at the University of New Orleans Towing Tank. The model tests consisted of a study of a cylindrical OWC. The theoretical and experimental results of the free surface for the OWC tests agree for the resonant frequency estimation response but they disagree on the amplitude of the response.
The Impact of the Second Order Vessel Motion on the Fatigue Life of Steel Catenary Risers
Authors: Mansour Ghiath
Published: January 2009

Fatigue is a primary factor in assessing the feasibility of a steel catenary riser solution for production and export of offshore hydrocarbons from floating production systems. The first and second order vessel motion due to wave and wind loading is a major source of fatigue. While the first order motion fatigue can be readily estimated through the vessel response amplitude operators, assessing the impact of the second order motion is time and effort consuming especially in generating the vessel motion time traces, more so for coupled analysis. However, inclusion of the second order motion at early stages of the riser feasibility assessment, when the mooring system design is far from final, is essential in predicting the riser fatigue life. In this article, a simplified approach for estimating the impact of the second order motion at an early stage in the design is presented based on the first order motion analysis and the vessel mean static offsets as obtained from frequency domain analysis.
Collision Safety Comparison of Conventional and Crash Energy Management Passenger Rail Car Designs
Authors: Severson Kristine J. , Tyrell David C. , Perlman A. Benjamin
Published: January 2009

In conjunction with full-scale equipment tests, collision dynamics models of passenger rail cars have been developed to investigate the benefits provided by incorporating energy-absorbing crush zones at the ends of the cars. In a collision, the majority of the structural damage is generally focused at the point of impact for cars of conventional design. In contrast, cars with crush zones, or crash energy management (CEM), can better preserve occupied areas by distributing crush to the ends of cars. Impact tests of conventional equipment have already been conducted, which consisted of a single car and two coupled cars colliding with a rigid wall. Corresponding tests are planned using CEM equipment. This paper presents preliminary predictions of the one- and two-car CEM tests, and compares them to the results of the respective conventional equipment tests. The comparison will focus on loss of occupant volume, secondary impact velocity (SIV), and lateral buckling, as measures of occupant protection. The modeling results indicate that the occupant volume can be preserved in both the one-car and two-car tests of the CEM equipment, while 2 1/2 and 3 feet of occupant volume were crushed in the respective tests of conventional equipment. In the two-car model, the CEM design is able to distribute the crush between both cars, whereas the conventional design incurs nearly all the crush at the point of impact. The CEM design can absorb more energy without crushing the occupied area because it requires a higher average force per foot of crush at the vehicle ends. The trade-off associated with this higher crush force is generally a higher SIV for occupants in the CEM cars. Secondary impact velocity refers to the velocity at which an occupant strikes some part of the interior, in this analysis the back of the seat ahead of the occupant. The greatest SIV penalty is in the impacting car. The difference between the SIV for cars in a conventional and a CEM consist decreases in each trailing car. That is, the SIV generally decreases in each trailing car of a CEM consist, while the SIV remains approximately the same in each trailing car of a conventional consist.
Parametric Study of a Simplified Ice Storage Model Operating Under Conventional and Optimal Control Strategies
Authors: Henze Gregor P.
Published: January 2009

A simplified ice storage system model was developed in which the icemaking mode is reflected by a higher power consumption per unit cooling than in chilled-water mode. The performance of four control strategies for ice storage systems is evaluated. The four control strategies investigated are chiller-priority and constant-proportion as conventional, instantaneous controls, while storage-priority and optimal control represent sophisticated controls employing load forecasting. Six parameters were investigated with respect to their influence on the ice storage system performance: Storage losses, utility rate structures, rate periods, penalty for icemaking, storage capacity, and the impact of load forecasting. Optimal control was determined to provide maximal operating cost savings. The storage-priority control yields operating costs only slightly higher than those of optimal control. Chiller-priority control realized savings that were typically on the order of 50% of what is theoretically possible (optimal control). Constant-proportion control proved to be a simple control strategy yielding higher savings than chiller-priority, yet lower than storage-priority control.
Analyzing Two Federal Building Integrated Photovoltaics Projects Using ENERGY-10 Simulations
Authors: Walker Andy , Weaver Norm , Kiss Gregory , Balcomb Doug , Becker-Humphry Melinda
Published: January 2009

A new version of the ENERGY-10 computer program simulates the performance of photovoltaic systems, in addition to a wide range of opportunities to improve energy efficiency in buildings. This paper describes two test cases in which the beta release of ENERGY-10 version 1.4 was used to evaluate energy efficiency and building-integrated photovoltaics (BIPV) for two Federal building projects: a 16,000-ft2 (1,487 m2) office and laboratory building at the Smithsonian Astrophysical Laboratory in Hilo, Hawaii, and housing for visiting scientists [three 1400-ft2 (130 m2) and three 1564-ft2 (145 m2) houses] at the Smithsonian Environmental Research Center in Edgewater, Maryland. The paper describes the capabilities of the software, the method in which ENERGY-10 was used to assist in the design, and a synopsis of the results. The results indicate that ENERGY-10 is an effective tool for evaluating BIPV options very early in the building design process. By simulating both the building electrical load and simultaneous PV performance for each hour of the year, the ENERGY-10 program facilitates a highly accurate, integrated analysis.
Solar Powered Water Pumps: The Past, the Present — and the Future?
Authors: Short T. D. , Oldach R.
Published: January 2009

Solar (photovoltaic) powered water pumps could be a real instrument for the alleviation of water related deaths and illnesses in developing countries through the provision of clean water. However, despite the benefits that access to sustainable potable water supplies can bring, solar powered water pumps have a long way to go before they even begin to meet the needs of those who could use them. This paper addresses some of the complex, inter-related social and technical issues that have prevented solar powered water pumping from reaching its full potential and shows how future efforts should be directed in order to respond to these issues.
Raceway Curvature Effect Analysis and Optimum Design on Ball Bearing Life Performance
Authors: Qiu Liangheng , Parejko Jim
Published: January 2009

The effect of raceway curvature on ball bearing contact stress and fatigue life is analyzed with both Hertzian theory and FEM. A numerical program and a 3-D FEM model are developed to calculate the contact stress and deformation at the bearing ball and raceway. The simulation results of the contact stress and deformation are discussed. The accuracy is evaluated by contrasting finite element results with analytical solutions from Hertzian theory. The effect of bearing race curvature on the contact maximum stress and area between ball and races is discussed. The results show that the race curvature is very sensitive factor to affect the bearing contact stress. The raceway curvature effect on the bearing thrust load capability and bearing running temperature is analyzed and discussed as well. For the validation, A. B. Jones’ program has been used to calculate bearing life with different raceway curvatures.
Thermal Distortion of an Anisotropic Elastic Half-Plane and Its Application in Contact Problems Including Frictional Heating
Authors: Lin Yuan , Ovaert Timothy C.
Published: January 2009

The thermal surface distortion of an anisotropic elastic half-plane is studied using the extended version of Stroh’s formalism. In general, the curvature of the surface depends both on the local heat flux into the half-plane and the local temperature variation along the surface. However, if the material is orthotropic, the curvature of the surface depends only on the local heat flux into the half-plane. As a direct application, the two-dimensional thermoelastic contact problem of an indenter sliding against an orthotropic half-plane is considered. Two cases, where the indenter has either a flat or a parabolic profile, are studied in detail. Comparisons with other available results in the literature show that the present method is correct and accurate.
Direct Visualization of Molecularly Thin Lubricant Films on Magnetic Disks by Ellipsometric Microscopy With a White Light Source
Authors: Fukuzawa Kenji , Nakada Akira , Mitsuya Yasunaga , Zhang Hedong
Published: January 2009

We demonstrated the direct visualization of molecularly thin lubricant films on magnetic disks with a thickness resolution of 0.1 nm by using an ellipsometric microscope with a white light source. It was able to reduce the optical interference noise that arises in conventional laser-based ellipsometric microscopes, and to provide a large SNR by a factor of about 6 compared to a laser-based ellipsometric microscope. The wavelength width should be given the first priority in designing a white light source ellipsometric microscope, and the width should be determined after considering the required coherence length and thickness resolution. Theoretical calculations indicate that a wavelength width of less than 10 nm can provide a thickness resolution of 0.1 nm. A white light source ellipsometric microscope can provide real-time visualization of a molecularly thin lubricant film with a thickness resolution of 0.1 mm, which is useful in investigating the kinetic behavior of molecularly thin lubricant films on magnetic disks.
Relationship Between Temperature Distribution in EHL Film and Dimple Formation
Authors: Yagi Kazuyuki , Kyogoku Keiji , Nakahara Tsunamitsu
Published: January 2009

This paper describes an experimental study on dimple formations under elastohydrodynamic lubrication (EHL) conditions. The oil film thickness between a ball surface and a sapphire disk was measured using optical interferometry and the temperatures of both the surfaces and of the oil film averaged across it were measured by an improved infrared emission technique. It was found that temperature profile across the oil film varies abruptly along the direction of the oil film thickness and the Couette flow decreases due to the viscosity wedge action as the oil flow is close to the dimple zone. The maximum temperature rise in the dimple zone sometimes reached above 400 K and thus the phase transition of the oil from liquid to glass may not occur.
Adhesive Effects on Dynamic Friction for Unlubricated Rough Planar Surfaces
Authors: Shi Xi , Polycarpou Andreas A.
Published: January 2009

As the size of contacting and sliding tribosystems decrease, intermolecular or adhesive forces become significant partly due to nanometer size surface roughness. The presence of adhesion has a major influence on the interfacial contact and friction forces as well as the microtribosystem dynamics and thus influences the overall dynamic friction behavior. In this paper, a dynamic friction model that explicitly includes adhesion, interfacial damping and the system dynamics for realistic rough surfaces was developed. The results show that the amplitude and mean value of the time varying normal contact and friction forces increase in the presence of adhesion under continuous contact conditions. Also, due to the attractive nature of adhesion, its presence delays or eliminates the occurrence of loss of contact. Furthermore, in the presence of significant adhesion, dynamic friction behavior is significantly more complicated compared to the no adhesion case, and the dynamic friction coefficient predictions may be misleading. Thus, it is more appropriate to discuss dynamic friction force instead of dynamic friction coefficient under dynamic conditions.
A Mesh-Less Method for Solving Air Bearing Problems in Hard Disk Drives
Authors: Li Xuhong , Du Hejun , Liu Bo , Li Jianhua
Published: January 2009

In this paper, a mesh-less method, least square finite difference (LSFD) method, was applied to solve the slider air bearing problems in hard disk drives. The LSFD method derives from weighted least square approximation procedure and a Taylor series expansion of pressure distribution to directly discretize the Reynolds equation. The scheme is able to approximate the second-order derivatives to the second-order accuracy in this study. The mesh-free method does not require maintaining detailed structural information about the computational meshes in the computational domain. Furthermore, adaptive node distribution can prevents pressure oscillatory in the high-pressure gradient regions. In addition, Successive Over Relaxation iteration technique is applied to solve nonlinear system equations. Finally, the static flying attitude of the Taper Flat, Tripad and the Transverse Pressure Contour (TPC) sliders are calculated.
Contact Area as a Critical Determinant in the Tribology of Metal-on-Polyethylene Total Joint Arthroplasty
Authors: Mazzucco Dan , Spector Myron
Published: January 2009

The effects of contact area and contact stress on friction and wear of polyethylene-metal articulation were evaluated using a bi-directional pin-on-disk apparatus. A doubling of the contact area under fixed loading conditions led to a 50% increase in the coefficient of friction and a doubling of the wear rate. There appeared to be a relationship between the increase in wear rate and the increase in the coefficient of friction. A model was developed to explain the mechanism by which engagement of asperities results in the increasing wear rate with increasing contact area despite the decreased stress.
Heat Partition in Rolling/Sliding Elastohydrodynamic Contacts
Authors: Clarke A. , Sharif K. J. , Evans H. P. , Snidle R. W.
Published: January 2009

The paper presents the results of a thermal analysis of a set of disk experiments carried out by Patching et al. to investigate scuffing. The experiments used crowned steel disks at 76 mm centres with maximum Hertzian contact pressures of up to 1.7 GPa. Experimental measurements of contact friction were used as the basis for a thermal analysis of the disks and their associated support shafts. Temperatures measured by embedded thermocouples 3 mm below the running tracks of the disks were used to determine the heat partition between the faster and slower running disks in order to match the experimental with calculated temperatures. This partition was found to vary approximately as a function of the product of sliding speed and surface temperature difference. A transient (flash) temperature analysis of one of the experiments was also carried out. This shows large differences between the disk transient surface temperatures. These surface temperature distributions were compared with those obtained from corresponding elastohydrodynamic lubrication (EHL) analyses using two different non-Newtonian lubricant formulations. The EHL analyses show that the heat partition obtained depends on the form of non-Newtonian behaviour assumed, and that to achieve the same partition as is evident in the experiment a limiting shear stress formulation is necessary. It is suggested that the combination of heat transfer and EHL analysis presented in the paper could be used as a sensitive tool for distinguishing between different non-Newtonian lubricant models under realistic engineering loads and with high sliding speeds.
Impact of a Rigid Sphere on an Elastic Homogeneous Half-Space
Authors: Yang J. , Komvopoulos K.
Published: January 2009

Impact of a rigid sphere moving at constant velocity on elastic homogeneous half-space was analyzed by the finite element method. Frictionless dynamic contact was modeled with special contact elements at the half-space surface. A dimensionless parameter, β, was introduced to study the effect of wave propagation on the deformation behavior. For small surface interference (β), the front of the faster propagating dilatational waves extends up to the contact edge, the real contact area is equal to the truncated area, and the contact pressure distribution is uniform. However, for large surface interference (β ≤ 1), the dilatation wave front extends beyond the contact edge, the real contact area is less than the truncated area, and the contact pressure exhibits a Hertzian-like distribution. The mean contact pressure increases abruptly at the instant of initial contact, remains constant for β ≤ 1, and increases gradually for β > 1. Based on finite element results for the subsurface stress, strain, and velocity fields, and simple theoretical model that yields approximated closed-form relationships for the mean contact pressure and kinetic and strain energies of the half-space was derived for small surface interference (β ≤ 1), and its validity was confirmed by favor comparisons with finite element results.
Investigation of the Contact Zone of Ultrasonic Motors at Different Modes of Exciter Vibrations
Authors: Ostasevicius V. , Palevicius A. , Ragulskis M. , Daugela A. , Janusas G.
Published: January 2009

A polarization vector of the piezoceramic element and location of excitation electrodes on its surface determine the resonance modes of the high frequency vibration exciter. In its turn the modes of vibration play a key role in the functionality of ultrasonic motor. Two different regimes of operation are analyzed — when the contact zone of the resonator performs elliptic and unidirectional motions. Though the mechanical characteristics of the ultrasonic motor in both cases are comparable, detailed analysis of the contact surface shows very different wears. Computational simulation and experimental investigations are used to analyze the contact zone of ultrasonic motor. Laser holography is used to identify and control the regimes of motion. Atomic force microscopy is used for analysis of contact surfaces.
A New Point of View on Rolling Friction Coefficient
Authors: Irimescu Luminita , Diaconescu Emanuel , Berthier Yves
Published: January 2009

The micro-slip developed in contact area points is involved in rolling friction. It occurs in some points whilst in others the surfaces move together. Contact area is divided into micro-slip zones, subjected to opposite shear stresses. These are computed in each point and their values yield the power lost by interface friction and related micro-slip torque. Theoretical results are checked by comparison with published data. The specific power loss, defined as the power lost by friction on a unity of contact area, does not depend on direction of shear and its integral over contact area yields the lost power due to micro-slip. The micro-slip component of rolling friction coefficient is calculated by dividing power losses by the product between normal load and relative angular velocity. Global rolling friction coefficient includes as well hysteresis losses. Experimental evidences confirm well the advanced model.
ANALYSIS OF THE AVERAGE EXECUTION TIME FOR A SELF-STABILIZING LEADER ELECTION ALGORITHM
Authors: FERNÁNDEZ-ZEPEDA JOSÉ ALBERTO , ALVARADO-MAGAÑA JUAN PAULO
Published: January 2009

This paper focuses on the self-stabilizing leader election algorithm of Xu and Srimani [10] that finds a leader in a tree graph. The worst case execution time for this algorithm is O(N4), where N is the number of nodes in the tree. We show that the average execution time for this algorithm, assuming two different scenarios, is much lower than O(N4). In the first scenario, the algorithm assumes an equiprobable daemon and it only privileges a single node at a time. The average execution time for this case is O(N2). For the second case, the algorithm can privilege multiple nodes at a time. We eliminate the daemon from this algorithm by making random choices to avoid interference between neighboring nodes. The execution time for this case is O(N). We also show that for specific tree graphs, these results reduce even more.
MATCHING PRECLUSION FOR ALTERNATING GROUP GRAPHS AND THEIR GENERALIZATIONS
Authors: CHENG EDDIE , LESNIAK LINDA , LIPMAN MARC J. , LIPTÁK LÁSZLÓ
Published: January 2009

The matching preclusion number of a graph is the minimum number of edges whose deletion results in a graph that has neither perfect matchings nor almost-perfect matchings. In this paper, we find this number for the alternating group graphs, Cayley graphs generated by 2-trees and the (n,k)-arrangement graphs. Moreover, we classify all the optimal solutions.
Prenatal Risk Factors for Cutaneous Malignant Melanoma: Follow-up of 2,594,783 Danes Born from 1950 to 2002
Authors: Olesen Anne Vingaard , Parner Erik Thorlund , Mortensen Preben Bo , Sørensen Henrik Toft , Olsen Jørn
Published: January 2009

The incidence of cutaneous malignant melanoma has increased in young adults, specifically in Denmark. In this study, we examined the risk of cutaneous malignant melanoma in relation to prenatal markers of hormone levels and to family-related risk factors. The study was based on a follow-up of 2,594,783 Danes born from 1950 to 2002. Occurrence of possible hormone-related cancers among family members and indicators of abnormal prenatal hormone levels were not associated with cutaneous malignant melanoma risk, whereas family size and mother's age at first birth were significant risk factors for cutaneous malignant melanoma in offspring. (Cancer Epidemiol Biomarkers Prev 2009;18(1):155–61)
Randomized Controlled Trial of Aerobic Exercise on Insulin and Insulin-like Growth Factors in Breast Cancer Survivors: The Yale Exercise and Survivorship Study
Authors: Irwin Melinda L. , Varma Katie , Alvarez-Reeves Marty , Cadmus Lisa , Wiley Andrew , Chung Gina G. , DiPietro Loretta , Mayne Susan T. , Yu Herbert
Published: January 2009

Background: High insulin and insulin-like growth factor-I (IGF-I) levels may be associated with an increased breast cancer risk and/or death. Given the need to identify modifiable factors that decrease insulin, IGF-I, and breast cancer risk and death, we investigated the effects of a 6-month randomized controlled aerobic exercise intervention versus usual care on fasting insulin, IGF-I, and its binding protein (IGFBP-3) in postmenopausal breast cancer survivors.

Methods: Seventy-five postmenopausal breast cancer survivors were identified from the Yale-New Haven Hospital Tumor Registry and randomly assigned to an exercise (n = 37) or usual care (n = 38) group. The exercise group participated in 150 minutes per week of moderate-intensity aerobic exercise. The usual care group was instructed to maintain their current physical activity level. A fasting blood sample was collected on each study participant at baseline and 6 months. Blood levels of insulin and IGF were measured with ELISA.

Results: On average, exercisers increased aerobic exercise by 129 minutes per week compared with 45 minutes per week among usual care participants (P < 0.001). Women randomized to exercise experienced decreases in insulin, IGF-I, and IGFBP-3, whereas women randomized to usual care had increases in these hormones. Between-group differences in insulin, IGF-I, and IGFBP-3 were 20.7% (P = 0.089), 8.9% (P = 0.026), and 7.9% (P = 0.006), respectively.

Conclusions: Moderate-intensity aerobic exercise, such as brisk walking, decreases IGF-I and IGFBP-3. The exercise-induced decreases in IGF may mediate the observed association between higher levels of physical activity and improved survival in women diagnosed with breast cancer. (Cancer Epidemiol Biomarkers Prev 2009;18(1):306–13)
Gynecologic and Breast Cancers in Women After Exposure to Blue Asbestos at Wittenoom
Authors: Reid Alison , Segal Amanda , Heyworth Jane S. , de Klerk Nicholas H. , Musk Arthur W.
Published: January 2009

Introduction: Animal studies have suggested an association between asbestos and ovarian cancer, and asbestos fibers have been detected in human ovaries. Sexual intercourse may introduce asbestos fibers into the vagina and to the cervix and ovaries. Occupational cohorts have reported excess mortality from reproductive cancers, but exposure-response relationships are inconsistent. We examine the incidence and exposure-response relationships of these cancers among 2,968 women and girls exposed to blue asbestos at Wittenoom, Western Australia.

Methods: 2,552 women were residents of the town and 416 worked for the asbestos company (Australian Blue Asbestos). Standardized incidence ratios compared the Wittenoom women with the Western Australian population. A nested case-control design and conditional logistic regression examined exposure-response relationships.

Results: Ovarian (standardized incidence ratio, 1.27), cervical (standardized incidence ratio, 1.44), and uterine cancer (standardized incidence ratio, 1.23) increased but not statistically significantly among the Wittenoom women compared with the Western Australian population. Among the Australian Blue Asbestos workers, cervical cancer was twice that of the Western Australian population (standardized incidence ratio, 2.38), but ovarian cancer was less (standardized incidence ratio, 0.65). Women who first arrived at Wittenoom aged ≥40 years had an odds ratio of 13.9 (95% confidence interval, 2.2-90.2) for cervical cancer compared with those aged <15 years at first arrival. Women who lived with or washed the clothes of an Australian Blue Asbestos worker did not have an increased risk for any of the gynecologic or breast cancers.

Discussion: There is no consistent evidence of an increased risk for gynecologic and breast cancers among the women from Wittenoom. Ovarian cancers and peritoneal mesotheliomas were not misclassified in this cohort. (Cancer Epidemiol Biomarkers Prev 2009;18(1):OF140–8)
Sex Hormone Levels, Breast Cancer Risk, and Cancer Receptor Status in Postmenopausal Women: the ORDET Cohort
Authors: Sieri Sabina , Krogh Vittorio , Bolelli Gianfranco , Abagnato Carlo Alberto , Grioni Sara , Pala Valeria , Evangelista Alberto , Allemani Claudia , Micheli Andrea , Tagliabue Giovanna , Schunemann Holger J. , Menard Sylvie , Berrino Franco , Muti Paola
Published: January 2009

Background: Endogenous sex hormone levels have been associated with increased breast cancer risk in postmenopausal women in several prospective studies. However, it remains unclear to what extent serum hormone-breast cancer associations differ with receptor status.

Methods: Associations between serum sex hormone levels and breast cancer risk were assessed in a nested case-control study on postmenopausal women of the ORDET cohort. After a median follow-up of 13.5 years, 165 women developed breast cancer. Relative risks of developing breast cancer were estimated by conditional logistic regression.

Results: Total and free testosterone levels were directly associated with breast cancer risk [relative risk, 3.28 (95% confidence interval, 1.93-5.55) and 2.86 (95% confidence interval, 1.66-4.94), respectively, for highest versus lowest quartile]. When relations between hormone level and risk of breast cancer expressing various receptor combinations were assessed, high total testosterone was significantly associated with increased risk of estrogen receptor–positive cancers, irrespective of progesterone receptor status. High total testosterone was also associated with increased risk of both human epidermal growth factor receptor 2 (HER2)–negative (HER2−) and HER2+ cancers. High estradiol tended to be associated with increased risk of HER2− cancer and inversely associated with HER2+ cancer, with significant (P = 0.027) heterogeneity between HER2+ and HER2− cancers. However, there were relatively few HER2+ cases.

Conclusions: This study provides further evidence that high levels of circulating testosterone increase the risk of developing breast cancer in postmenopausal women. The cancers that develop are mainly estrogen receptor positive. Although HER2+ and HER2− breast cancers were both associated with high total testosterone, they showed opposing associations with estrogen. (Cancer Epidemiol Biomarkers Prev 2009;18(1):169–76)
Long-term Alcohol Consumption and Risk of Endometrial Cancer Incidence: A Prospective Cohort Study
Authors: Friberg Emilie , Wolk Alicja
Published: January 2009

Alcohol consumption has been hypothesized to increase the risk of endometrial cancer. We used data from the prospective population-based Swedish Mammography Cohort including 61,226 women to examine the association between alcohol and endometrial cancer incidence. Alcohol consumption was assessed with validated food frequency questionnaires at baseline 1987 to 1990 and at follow-up in 1997. During a mean follow-up of 17.6 years, 687 endometrial cancer cases were identified in the Swedish cancer registries. We found no association between alcohol consumption and endometrial cancer risk after adjustment for age, body mass index, and smoking. The multivariable rate ratios (95% confidence intervals) for the three upper categories of long-term alcohol consumption as compared with no consumption were 1.01 (0.84-1.22) for <3.4 g/d, 1.01 (0.80-1.27) for 3.4 to 9.9 g/d, and 1.09 (0.71-1.67) for ≥10 g/d, respectively. The association did not differ by age, body mass index, folic acid intake, or postmenopausal hormone use in stratified analysis. In conclusion, our results suggest that low alcohol consumption (up to one drink per day) is unlikely to substantially influence risk of endometrial cancer. (Cancer Epidemiol Biomarkers Prev 2009;18(1):355–8)
High-Dose Fenretinide in Oral Leukoplakia
Authors: William William N. , Lee J. Jack , Lippman Scott M. , Martin Jack W. , Chakravarti Nitin , Tran Hai T. , Sabichi Anita L. , Kim Edward S. , Feng Lei , Lotan Reuben , Papadimitrakopoulou Vassiliki A.
Published: January 2009

We previously showed that low-dose fenretinide (200 mg/d) had limited activity in retinoid-resistant oral leukoplakia (34% response rate) possibly because serum drug levels were insufficient to induce retinoid receptor–independent apoptosis. Therefore, we designed the single-arm phase II trial reported here to investigate whether higher-dose fenretinide would improve leukoplakia response over that of our previous study. Leukoplakia patients received fenretinide (900 mg/m2 twice daily) in four 3-week cycles (1 week on drug followed by 2 weeks off). At week 12, clinical responses were determined and blood samples were collected for serum drug level assessments. A planned interim futility analysis led to early trial closure after the initial 15 (of 25 planned) patients because only 3 (20%) had a partial response (stopping rule: ≤4 responses in first 16 patients). Fenretinide was well tolerated—only one grade 3 adverse event (diarrhea) occurred. Serum fenretinide levels changed from 0 (baseline) to 0.122 ± 0.093 μmol/L (week 12). In correlative in vitro studies, high-dose fenretinide inhibited the growth of head and neck cancer cells more and oral leukoplakia cells less than did lower doses of fenretinide. This result is consistent with our clinical finding that high-dose fenretinide did not improve on the historical response rate of lower-dose fenretinide in our previous oral leukoplakia trial.
Cyclin D1 and Cancer Development in Laryngeal Premalignancy Patients
Authors: Papadimitrakopoulou Vassiliki , Izzo Julie G. , Liu Diane D. , Myers Jeffrey , Ceron Tania L. , Lewin Jan , William William N. , Atwell Anthea , Lee J. Jack , Gillenwater Ann , El-Naggar Adel , Wu Xifeng , Lippman Scott M. , Hittelman Walter N. , Hong Waun Ki
Published: January 2009

In a previous trial, we found that combined 13-cis-retinoic acid, IFN-α, and α-tocopherol more effectively reversed advanced premalignant lesions of the larynx than of the oral cavity and that cyclin D1 (CD1) G/A870 single nucleotide polymorphism correlated with cancer risk. We conducted the present trial primarily to confirm the clinical activity of the combination in advanced laryngeal premalignancy and to confirm and extend our findings on CD1, both genotype and protein expression, in association with cancer risk in this setting. Twenty-seven moderate-to-severe laryngeal dysplasia patients underwent induction with combined 13-cis-retinoic acid daily, α-IFN twice weekly, and α-tocopherol daily for 1 year; 14 nonprogressing patients then were randomized to maintenance fenretinide or placebo for 2 years. During induction, two patients had pathologic complete responses, six had partial responses (30% overall response rate), and five developed laryngeal cancer. There were no significant differences between maintenance fenretinide and placebo in response or cancer rates. Ten patients developed cancer overall. Twenty-four patients were evaluated for the CD1 G/A870 genotype, and 23 for pretreatment and posttreatment CD1 protein expression. Consistent with our earlier report, shorter cancer-free survival was associated with the CD1 AA/AG genotype (P = 0.05). Extending our earlier work, high CD1 expression was associated with worse cancer-free survival overall (P = 0.04) and within each CD1 genotype group. These findings support CD1 genotype and protein expression as important risk markers for laryngeal cancer and suggest future trials targeting upstream regulators of CD1 transcription.
Transfusion-Associated Iron Overload as an Adverse Risk Factor for Transplantation Outcome in Patients Undergoing Reduced-Intensity Stem Cell Transplantation for Myeloid Malignancies
Authors: Kim Yu Ri , Kim Jin Seok , Cheong June-Won , Song Jae Woo , Min Yoo Hong
Published: January 2009

Transfusion-associated iron overload could be an important risk factor in myeloablative hematopoietic stem cell transplantation. However, few studies have evaluated the effect of iron overload in reduced-intensity stem cell transplantation (RIST). We evaluated 38 patients with myeloid malignancies, 16 with and 22 without iron overload, who received RIST. We used pretransplant serum ferritin as a marker of iron overload. There was a positive correlation between the number of transfused packed red blood cells and pretransplant serum ferritin levels (21.5 units and 1,578.7 μg/l in the iron overload group vs. 12 units and 739.3 μg/l in the iron non-overload group; p <0.01). Engraftment day and chimerism analysis were not affected by iron overload (p = 0.71 and 0.47, respectively). There were no differences in treatment-related mortality (p = 0.94), veno-occlusive disease (p = 0.99), acute and chronic graft versus host disease (p = 0.58 and 0.99, respectively) according to iron overload. There was a significant difference in disease-free and overall survival (35.8 and 27% in the iron overload group vs. 80.6 and 54.6% in the iron non-overload group; p = 0.01 and 0.03, respectively). We conclude that transfusion-associated iron overload is an adverse risk factor in RIST for myeloid malignancies. The clinical outcomes according to iron overload in RIST were different in myeloablative hematopoietic stem cell transplantation. A serial follow-up of serum ferritin level and judicious iron chelation therapy will be needed to manage the side effect of iron overload in RIST and improve transplantation outcomes.